Marine chemistry in the coastal environment: A special symposium sponsored by the Middle Atlantic Region at the 169th meeting of the American Chemical ... April 8-10, 1975 (ACS symposium series ; 18)

Marine Chemistry in the Coastal Environment Thomas M. Church, EDITOR University of Delaware A special symposium spons...

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Marine Chemistry in the Coastal Environment Thomas M. Church,

EDITOR

University of Delaware

A special symposium sponsored by the Middle Atlantic Region at the 169th Meeting of the American Chemical Society, Philadelphia, Penn., April 8-10,

1975

ACS SYMPOSIUM SERIES

AMERICAN

CHEMICAL

SOCIETY

WASHINGTON, D. C. 1975

In Marine Chemistry in the Coastal Environment; Church, T.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.

18

Library of Congress CIP Data Marine chemistry in the coastal environment. (ACS symposium series; 18. ISSN 0097-6156) Includes bibliographical references and index. 1. Chemical oceanography—Congresses. 2. Coasts— Congresses. 3. Esruarine oceanography—Congresses. 4. Waste disposal in the ocean—Congresses. I. Church, Thomas M., 1942II. American Chemical Society. Middle Atlantic Region. III. Series: American Chemical Society. ACS symposium series; 18. GC111.2.M37 I S B N 0-8412-0300-8

551.4'601

75-28151 A C S M C 8 18 1 - 7 1 0

Copyright © 1975 American Chemical Society All Rights Reserved PRINTED IN THE UNITED STATES OF AMERICA


ACS Symposium Series Robert F. Gould, Series Editor


FOREWORD The A C S SYMPOSIUM SERIES was founded in 1974 to provide a medium for publishin format of the SERIES parallels that of the continuing ADVANCES IN CHEMISTRY SEMES except that in order to save time the papers are not typeset but are reproduced as they are submitted by the authors in camera-ready form.

As a further

means of saving time, the papers are not edited or reviewed except by the symposium chairman, who becomes editor of the book.

Papers published in the A C S SYMPOSIUM SERIES

are original contributions not published elsewhere in whole or major part and include reports of research as well as reviews since symposia may embrace both types of presentation.


PREFACE 'raditionally, marine chemists have followed the descriptive leads of oceanographers in using basic chemical processes to unravel the more simple chemical processes that drive the complex electrolyte called the sea. In the open ocean this approach has been successful because the system is essentially one dimensional, the compositions are temporally invarient, and chemical processes are in rather steady state. In the coastal environment, however, th tages since he is dealing with a multi-dimensional system that includes time and where tidal action drives a system whose dynamic processes are rarely in equilibrium. Compounding these problems are the interactions with fresh water supplies, geological solids, immense biological productivity, and not least, the catabolism of human technocracy. Since the pioneering work of Ketchum and co-workers some 20 years ago, coastal oceanography has suffered an embarrassing gap of knowledge because attentions have been turned largely to the apparently simpler chemical processes of the open and deep sea.

T h e price of this lapse

has now closed in on man who is being forced to rely ever more heavily on the resources of the coastal marine environment. Separate cities located traditionally at the fall line of estuarine river systems have turned into a contiguous sprawl of industrialized metropolises. Estuaries, such as in the Middle Atlantic Region, have become open conduits of raw material import and waste export. As the volumes needed to fuel this technocracy escalated and man became less willing to tolerate spoiling of the land, the coastal environment bore the brunt that today threatens its viable existence. As a result, in this decade, the marine chemist has been called to help devise means to prudently manage and revitalize the coastal marine resource. This symposium is the first attempt to collate some of the most recent advances i n the field of marine chemistry i n the coastal environment. T h e sessions follow a theme which looks beyond simple descriptions to those processes that integrate basic chemistry, tracer techniques, geochemistry, pollutant fates, waste disposal, resource applications, and biological dynamics in the coastal ocean. T h e goal has been to show that instead of merely describing problems, there is greater potential in applying the tools of modern oceanography and chemistry to progressive concepts that give sophisticated insight to help solve these problems. ix In Marine Chemistry in the Coastal Environment; Church, T.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.

T h e papers touch upon several disciplines which a purer chemist might even construe as irrelevant. T h e intended purpose was to demonstrate that sound chemical knowledge is not enough; realistic solutions must consider the coastal regions as geological, biological, and anthropological entities as well.

Hopefully this symposium also reflects the growing

recognition of the chemist for the validity of research in this area. H o w ever, continued federal support must order national priorities to guarantee prudent use and protection of the coastal environment. I would like to gratefully acknowledge the session officers who composed the symposium committee: R. H . W o o d , O . P. Bricker, G . R. Helz, M . G . Gross, R. J. Huggett, and J . H . Sharp. Their energies were largely responsible for successfully collating a distinguished program, and their continuing enthusiasm helped me immeasurably in organizing the symposium and completing thi University of Delaware donated much of its resources, including the secretarial assistance of Sandra Northrup. Lastly, we are all sincerely i n debted to the M i d d l e Atlantic Region of the American Chemical Society for sponsoring this timely forum on marine chemistry in the coastal environment. THOMAS M . CHURCH

University of Delaware Newark, D e l . July 21,

1975

x


1 Chemical Equilibrium in Seawater R. M. PYTKOWICZ, E. ATLAS, and C. H. CULBERSON School of Oceanography, Oregon State University, Corvallis, Ore. 97331

The concept of chemical equilibrium can be applied to the oceans in three ways; trol of the oceanic composition, for fast reactions equilibrium constants are used to calculate the concentrations of species present in seawater, and for slow reactions departures from equilibrium are useful for kinetic studies. Seawater differs from the solutions that are usually examined by chemists because of the large number of solutes and, at times, of suspended particles that are present in the oceans. Also, one must consider the concurrent effects of purely chemical, hydrographic, biological, and geological processes upon the composition of seawater. One must consider as well the gravitational field and pressure, temperature, and compositional gradients that result from the extent and depth of the oceans. The study of the equilibrium chemistry of the oceans is facilitated because the major ions are present in almost constant proportions. This makes seawater an ionic medium which can be characterized by one compositional parameter, the chlorinity or the salinity. The constancy of the relative composition is not always present in estuaries because river water, which mixes with seawater, has its major ions in proportions which differ from those in seawater. Still, it will be shown that equilibrium data obtained for seawater can often be applied to estuarine waters. In this work we will first examine briefly the composition of seawater. Then, we will outline some major aspects of equilibria as applied to the oceans. Next, we will consider to what extent these equilibrium considerations are relevant to estuaries and finally, we will examine some topics on the control of the oceanic composition. We will not attempt a compre1


2

MARINE CHEMISTRY

h e n s i v e c o v e r a g e of the s u b j e c t but w i l l e m p h a s i z e b a s i c c o n cepts a n d methods. T h e C o m p o s i t i o n of S e a w a t e r A l l the n a t u r a l l y o c c u r r i n g e l e m e n t s a n d m a n y of t h e i r c o m p o u n d s f i n d t h e i r w a y i n t o the o c e a n s t h r o u g h r i v e r s , g r o u n d w a t e r s , a e r i a l t r a n s p o r t , a n d s u b m a r i n e v o l c a n i s m . A few m a j o r c o n s t i t u e n t s , shown i n T a b l e I, a c c o u n t f o r o v e r 90% Y weight o f the s o l u t e s present i n seawater ( 1 ) . b

T a b l e I.

M a j o r C o n s t i t u e n t s of S e a w a t e r of 34. 3%o S a l i n i t y (19%o C h l o r i n i t y )

Constituent Cl" Na

so

+

4

2

"

Mg

ppm

Constituent

18,971

Ca

10,555

K

2+

+

2,657

HCO ~

1,268

Br"

Constituent

ppm

403.9

B(OH)

391

Sr

142

F"

2

ppm

25. 6 7.7

+

1. 3

65.9

T h e s e m a j o r constituents a r e p r e s e n t i n a l m o s t constant p r o p o r t i o n s i n the o c e a n s (1_,2) i n d i c a t i n g that the m i x i n g t i m e of the o c e a n s , w h i c h i s of the o r d e r of 1,000

y e a r s , i s fast r e l a t i v e

to the i n p u t r a t e s a n d to the r e a c t i v i t y of the c o n s t i t u e n t s (3.-5). T h e c o n s t a n t r e l a t i v e c o m p o s i t i o n a l s o l e d to the d e f i n i t i o n s of chlorinity and salinity which a r e presented i n standard oceanographic texts,

e. g. , R i l e y a n d C h e s t e r (6).

It i s i m p o r t a n t to

r e a l i z e that the c h l o r i n i t y c a n be u s e d to r e p r e s e n t the extent of m i x i n g of r i v e r w a t e r w i t h s e a w a t e r i n a n e s t u a r y .

The defined

s a l i n i t y l o s e s i t s m e a n i n g , h o w e v e r , w h e n the o c e a n i c p r o p o r tions of the m a j o r i o n s a r e a l t e r e d i n e s t u a r i n e w a t e r s o r i n the p o r e w a t e r s of s u b m a r i n e

sediments.

T h e m i n o r e l e m e n t s v a r y g r e a t l y i n t i m e a n d s p a c e (1_) a n d a r e i n g e n e r a l quite i m p o r t a n t b e c a u s e of t h e i r p a r t i c i p a t i o n i n c h e m i c a l , b i o l o g i c a l , and geological p r o c e s s e s .

These

elements

a r e e x a m i n e d e l s e w h e r e i n this v o l u m e . T h e g e n e r a l g e o c h e m i c a l c o n t r o l of the c h e m i c a l c o m p o s i t i o n of the o c e a n s i n t e r m s of e q u i l i b r i a ,

steady s t a t e s , and

fluxes between n a t u r a l r e s e r v o i r s i s a v i t a l t o p i c .

I t s study

y i e l d s i n s i g h t s i n t o the c h e m i c a l h i s t o r y of s e a w a t e r a n d h e l p s u s u n d e r s t a n d the p o t e n t i a l i m p a c t of m a n - m a d e p e r t u r b a t i o n s


1.

PYTKOWICZ ET AL.

3

Chemical Equilibrium in Seawater

upon the e n v i r o n m e n t ( 5 , 7 - 1 1 ) .

T h i s s u b j e c t w i l l be e x a m i n e d

b r i e f l y at the e n d of t h i s w o r k , a f t e r a c r i t i c a l r e v i e w of the m a i n r e a c t i o n s w h i c h i n f l u e n c e the l o c a l d i s t r i b u t i o n s of c h e m i cal species i n seawater.

T h e f i r s t t o p i c r e l a t e d to l o c a l e q u i -

l i b r i a w i l l be the d i s s o c i a t i o n of w e a k a c i d s . D i s s o c i a t i o n of W e a k A c i d s T h e d i s s o c i a t i o n c o n s t a n t s of w e a k a c i d s a n d b a s e s c a n be u s e d for the c a l c u l a t i o n of the c o n c e n t r a t i o n s of m o l e c u l e s

and

i o n s of o c e a n o g r a p h i c i n t e r e s t b e c a u s e the d i s s o c i a t i o n r e a c t i o n s a r e f a s t r e l a t i v e to c o m p e t i n g b i o l o g i c a l a n d g e o l o g i c a l p r o c e s s e s and r e a c h e q u i l i b r i u m .

C a r b o n i c a c i d is an especially

i m p o r t a n t weak e l e c t r o l y t a n d i n the f o r m a t i o n of l i m e s t o n e s a n d d o l o m i t e s . s e r v e s a s a m o d e l s y s t e m f o r the s t u d y of other w h i c h a r e p r e s e n t i n the

Also,

it

electrolytes

oceans.

T h e u s e of t h e r m o d y n a m i c d i s s o c i a t i o n constants i s not r e c o m m e n d e d for c a r e f u l w o r k in seawater because it r e q u i r e s the e s t i m a t e of the t o t a l a c t i v i t y c o e f f i c i e n t s of s i n g l e i o n s These coefficients are conventional quantities and, their a c c u r a c y i s unknown.

Still,

(12).

therefore,

t h e r m o d y n a m i c constants

may

be a n d a r e often u s e d for f a s t l o w a c c u r a c y e s t i m a t e s b y m a r i n e geochemists

w h e n c o n s t a n t s m e a s u r e d i n a c t u a l s e a w a t e r a r e not

available. B u c h et a l . (13) i n t r o d u c e d to o c e a n o g r a p h y the

so-called

apparent d i s s o c i a t i o n constants m e a s u r e d d i r e c t l y i n seawater. In t h e i r p r e s e n t f o r m , for a g e n e r i c a c i d H A , these a r e defined by

constants

(14) ka (A R

K

=

)

T

(1)

(HA)

P a r e n t h e s e s r e p r e s e n t c o n c e n t r a t i o n s a n d T r e f e r s to t o t a l ( f r e e plus i o n - p a i r e d ) quantities,

apj i s the c o n v e n t i o n a l h y d r o g e n i o n

a c t i v i t y d e f i n e d , for e x a m p l e ,

on the N B S s c a l e ,

k is a constant,

w i t h i n the r e p r o d u c i b i l i t y of p H d a t a , w h i c h i s c a n c e l l e d out between the d e t e r m i n a t i o n a n d the a p p l i c a t i o n of K ' (14).

Thus,

k does not affect the a c c u r a c y w i t h w h i c h ( A " ) ^ » a n d H A c a n be determined.

A p p a r e n t c o n s t a n t s have b e e n shown to be i n v a r i a n t

for m a n y p r o c e s s e s

of o c e a n o g r a p h i c i n t e r e s t

(14).

A n o t h e r d e f i n i t i o n of d i s s o c i a t i o n c o n s t a n t s , f r o m K ' o n l y i n that ( H ) +

T

which differs

i s u s e d i n s t e a d of k a ^ , w a s

proposed


4

MARINE CHEMISTRY

b y H a n s son (15).

(H ) +

T

c a n be d e t e r m i n e d e i t h e r w i t h t r i s

b u f f e r s p r e p a r e d i n s e a w a t e r (16) o r w i t h c o n v e n t i o n a l N B S b u f f e r s (17).

W e w i l l r e t u r n to a l t e r n a t e d e f i n i t i o n s of the p H

later. T h e a p p a r e n t d i s s o c i a t i o n c o n s t a n t s a n d the c o n s t a n t s d e f i n e d b y H a n s son f o r c a r b o n i c a c i d a n d f o r b o r i c a c i d w e r e d e t e r m i n e d i n s e a w a t e r at a t m o s p h e r i c p r e s s u r e b y s e v e r a l workers (13,15,18-20).

D i s t e c h e a n d D i s t e c h e (21),

Culberson

et a l . (22), a n d C u l b e r s o n a n d P y t k o w i c z (23) e x t e n d e d the m e a s u r e m e n t s to the h i g h p r e s s u r e s w h i c h a r e e n c o u n t e r e d i n the deep o c e a n s .

C u l b e r s o n a n d P y t k o w i c z (23) p r o d u c e d c o r r e c t i o n

t a b l e s f o r the i n c r e a s e i n p H that o c c u r s w h e n deep

seawater

s a m p l e s a r e b r o u g h t to s h i p b o a r d . The carbon dioxid four e q u a t i o n s i n s i x unknowns once the a p p a r e n t d i s s o c i a t i o n c o n s t a n t s a r e k n o w n a n d the b o r a t e c o n t r i b u t i o n i s s u b t r a c t e d f r o m the a l k a l i n i t y (24).

One c a n , therefore,

completely

specify

the s y s t e m b y m e a n s of a n y two r e l e v a n t m e a s u r e m e n t s . h a s l e d to a p r o l i f e r a t i o n of m e t h o d s , tages a n d d r a w b a c k s .

This

e a c h w i t h i t s own a d v a n -

O n e c a n m e a s u r e the p H a n d the t i t r a t i o n

a l k a l i n i t y w h i c h c a n be o b t a i n e d a c c u r a t e l y b y a s i n g l e a c i d a d d i t i o n (17).

A l t e r n a t i v e l y one c a n d e t e r m i n e the t i t r a t i o n a l k a l i n i t y

a n d the t o t a l C 0 C0

2

2

b y a G r a n t i t r a t i o n (25), the p C 0

gasometrically,

a n d so on.

2

a n d the t o t a l

T h e c h o i c e of a m e t h o d depends

upon the q u a n t i t y of p r i m a r y i n t e r e s t . In s i t u p H p r o b e s ,

s u c h a s those d e v e l o p e d b y M a n h e i m

(26) a n d b y G r a s s h o f f (27), a r e of s p e c i a l i n t e r e s t f o r t i m e series measurements

i n estuaries.

p r o b i n g p o r e w a t e r s of s e d i m e n t s .

T h e y a r e adaptable f o r This eliminates

possible

shifts i n m i n e r a l - s e a w a t e r e q u i l i b r i a that m a y o c c u r w h e n s e d i m e n t s a r e b r o u g h t to d i f f e r e n t t e m p e r a t u r e s a n d p r e s s u r e s i n the laboratory. T h e a p p a r e n t d i s s o c i a t i o n c o n s t a n t s of p h o s p h o r i c a c i d i n seawater,

n e e d e d f o r the s t u d y of the f o r m a t i o n of a p a t i t e s a n d

p h o s p h o r i t e s , w e r e d e t e r m i n e d b y K e s t e r a n d P y t k o w i c z (28). K ' j f o r h y d r o g e n s u l f i d e w a s m e a s u r e d b y G o l d h a b e r (29).

Cul-

b e r s o n et a l . (17) d e t e r m i n e d the d i s s o c i a t i o n c o n s t a n t s of h y d r o f l u o r i c a c i d a n d of b i s u l f a t e i o n s .

C u l b e r s o n a n d P y t k o w i c z (30)

m e a s u r e d the i o n i z a t i o n of w a t e r i n s e a w a t e r . It s h o u l d be e m p h a s i z e d that t o t a l a c t i v i t y c o e f f i c i e n t s a n d , therefore,

apparent constants,

w h i c h a r e r e l a t e d to t h e r m o d y -

n a m i c ones b y these c o e f f i c i e n t s , c o m p o s i t i o n of the m e d i u m .

d e p e n d upon the m a j o r i o n

T h u s , one s h o u l d u s e these q u a n t i -

t i e s w i t h c a r e i n e s t u a r i e s a n d i n the p o r e w a t e r s of s e d i m e n t s


1.

because

5


PYTKOWICZ ET AL.

the m a j o r i o n c o m p o s i t i o n of these m e d i a m a y d i f f e r

f r o m that of o c e a n i c

waters.

p H of S e a w a t e r It was m e n t i o n e d e a r l i e r that the N B S buffer s c a l e , a p p l i e d to s e a w a t e r ,

y i e l d s a q u a n t i t y ka^j a n d that k i s

out i n p r a c t i c e , w i t h i n the r e p r o d u c i b i l i t y of p H d a t a .

when

cancelled T h u s , it

i s the r e p r o d u c i b i l i t y r a t h e r than the a c c u r a c y of p H data w h i c h i s r e l e v a n t to o c e a n o g r a p h i c m e a s u r e m e n t s . l a b o r a t o r y that c a r e f u l p H m e a s u r e m e n t s

We found i n our

in seawater

are r e p r o -

d u c i b l e to w i t h i n ± 0. 01 p H u n i t s between d i f f e r e n t e l e c t r o d e s

and

that the r e p r o d u c i b i l i t y a p p e a r s to be l i m i t e d b y the l i q u i d j u n c tion p o t e n t i a l s . H a n s son (16) p r o p o s e d a p m H - p s c a l e b a s e d upon b u f f e r s B a t e s a n d M a c a s k i l l (31)

p r e p a r e d i n seawater.

b u f f e r s but d e t e r m i n e d p m H j r i n s t e a d of p m H - p .

also used such (H ),p and +

(H )p +

w h e r e the s u b s c r i p t s F a n d T r e f e r to the f r e e a n d to the t o t a l concentrations,

a r e r e l a t e d by (H ) +

T

T h e N B S , the p m H , T

= (H ) +

F

(17)

+ (HS0 ~) + (HF)

(2)

4

a n d the p m H - p s c a l e s

can be r e l a t e d b y

m e a n s of the data p r e s e n t e d by C u l b e r s o n et a l .

(17).

It i s p o s s i b l e that the u s e of b u f f e r s p r e p a r e d i n m a y r e d u c e the l i q u i d j u n c t i o n p o t e n t i a l a n d , t h e r e f o r e , the r e p r o d u c i b i l i t y of p H data.

seawater, increase

O n the other h a n d , the p r e p a r a -

t i o n of s e a w a t e r b u f f e r s a n d of r e f e r e n c e e l e c t r o d e s b y i n d i v i d u a l investigators may introduce systematic

errors.

W i t h r e g a r d to the g e n e r a l c o n t r o l of the o c e a n i c p H , S i l l e n (7) s u g g e s t e d that c l a y - s e a w a t e r

interactions exert a p r i m a r y

p H - s t a t t i n g r o l e . P y t k o w i c z (5J c o n c l u d e d , h o w e v e r ,

that the

c a r b o n d i o x i d e s y s t e m i s the m a j o r p H b u f f e r i n g agent i n the present

oceans.

S o l u b i l i t i e s of M i n e r a l s The m o s t i n t e n s e l y studied salt i n seawater has been

calci-

u m c a r b o n a t e b e c a u s e of i t s b i o l o g i c a l a n d g e o l o g i c a l i m p o r t a n c e . In a d d i t i o n , w o r k on c a r b o n a t e s h a s y i e l d e d c o n c e p t s a n d t e c h n i q u e s w h i c h a r e a p p l i c a b l e to the i n t e r a c t i o n s of other s a l t s a n d of s o l i d s i n g e n e r a l w i t h Wattenberg

{32)

seawater.

f i r s t d e t e r m i n e d the s o l u b i l i t y of c a l c i t e i n


6

MARINE CHEMISTRY

s e a w a t e r at a t m o s p h e r i c p r e s s u r e .

H e u s e d the s t o i c h i o m e t r i c

solubility product

K'

(3)

SP

w h e r e the s u b s c r i p t S r e f e r s to the c o n c e n t r a t i o n at s a t u r a t i o n . T h e u s e of s t o i c h i o m e t r i c s o l u b i l i t y p r o d u c t s o b v i a t e s the n e e d to e s t i m a t e the a c t i v i t y c o e f f i c i e n t s o f s i n g l e i o n s .

These products

r e m a i n e s s e n t i a l l y c o n s t a n t at a g i v e n s a l i n i t y f o r p r o c e s s e s , s u c h a s the d i s s o l u t i o n a n d the p r e c i p i t a t i o n of c a r b o n a t e s i n the o c e a n s , w h i c h h a v e o n l y a s l i g h t effect u p o n the m a j o r i o n c o m p o s i t i o n of s e a w a t e r .

T h e r e h a v e b e e n m a n y m e a s u r e m e n t s of

the s o l u b i l i t y of c a r b o n a t e s i n c e W a t t e n b e r g (32), the m o s t r e c e n t ones b e i n g those of Mclntire

(33) a n d of Ingle et a l . (34).

P y t k o w i c z a n d c o - w o r k e r s ( 3 5 - 3 9 ) e x t e n d e d the r e s u l t s on c a r b o n a t e s to h i g h p r e s s u r e s b y m e a n s of p o t e n t i o m e t r i c m e a s u r e m e n t s w h i l e B e r n e r (40), M i l l e r o a n d B e r n e r (41), a n d D u e d a l l (42) u s e d the p a r t i a l m o l a l v o l u m e a p p r o a c h . S e v e r a l i n t e r e s t i n g f e a t u r e s e m e r g e d f r o m the study of the s o l u b i l i t y of c a l c i u m c a r b o n a t e i n s e a w a t e r , v a n t to other s o l i d s .

w h i c h m a y be r e l e -

S o m e of these f e a t u r e s a r e ; the m e t a s t a b l e

s u p e r s a t u r a t i o n of n e a r - s u r f a c e w a t e r s ,

the h y s t e r e s i s a n d l a c k

of r e p r o d u c i b i l i t y of s o l u b i l i t y data f o r c a l c i t e , the f a c t o r s that c o n t r o l the c r y s t a l f o r m that p r e c i p i t a t e s f r o m s e a w a t e r a n d the d i a g e n e t i c a l t e r a t i o n of s e d i m e n t s ,

the k i n e t i c b e h a v i o r of c a r -

bonate m a t e r i a l s at d e p t h , the c y c l i n g of c a r b o n a t e s i n n a t u r e , the p H b u f f e r i n g of s e a w a t e r ,

a n d the d i s t r i b u t i o n a n d f l u x e s of

the c a r b o n d i o x i d e s y s t e m i n n a t u r e . T h e m e t a s t a b i l i t y of the c a l c i u m c a r b o n a t e s u p e r s a t u r a t i o n i n n e a r - s u r f a c e w a t e r s r e s u l t s f r o m the i n h i b i t i o n of n u c l e a t i o n a n d g r o w t h b y m a g n e s i u m i o n s , o r g a n i c m a t t e r , a n d phosphate ions (43-46).

T h e r e s u l t s of P y t k o w i c z (43_,45) s h o w e d that the

i n o r g a n i c p r e c i p i t a t i o n of c a r b o n a t e s i n the o c e a n s c a n o n l y o c c u r i n a few s p e c i a l e n v i r o n m e n t s a n d that the r e m o v a l of c a r b o n a t e s f r o m seawater i s p r i m a r i l y biogenic. W e y l (47) o b s e r v e d that the s o l u b i l i t y of c a l c i t e i n s e a w a t e r u n d e r g o e s h y s t e r e s i s - t y p e effects w h i c h w e r e not o b s e r v e d to a n y s i g n i f i c a n t extent f o r a r a g o n i t e .

H e a t t r i b u t e d h i s r e s u l t s to

the a d s o r p t i o n of m a g n e s i u m i n s u r f a c e c o a t i n g s .

H y s t e r e s i s due

to s u r f a c e c o a t i n g s m a y be the c a u s e of the p o o r r e p r o d u c i b i l i t y o b s e r v e d i n c a l c i t e s o l u b i l i t y data.

T h e p r e s e n c e of h y d r a ted

p h a s e s , w h i c h m a y affect the s o l u b i l i t y b e h a v i o r of c a l c i t e , h a s


1.

7


PYTKOWICZ ET AL.

r e c e n t l y b e e n p r o p o s e d (48). T h e o r g a n i c a n d i n o r g a n i c f a c t o r s that c o n t r o l the c r y s t a l f o r m of c a l c i u m c a r b o n a t e that i s p r e c i p i t a t e d i n o r g a n i c a l l y f r o m s e a w a t e r w e r e s t u d i e d b y K i t a n o (49) a n d K i t a n o et a l . (50). A l t h o u g h m o s t of the c a r b o n a t e s e d i m e n t a t i o n i n s e a w a t e r i s b i o g e n i c ( 4 3 , 4 5 ) , these r e s e a r c h e s m a y l e a d to i n s i g h t s i n t o p r o c e s s e s w i t h i n the b o d y f l u i d s of o r g a n i s m s .

T h e f o r m of c a l c i u m

c a r b o n a t e that p r e c i p i t a t e s f r o m n o r m a l s e a w a t e r , to w h i c h a s o l ulbe carbonate s a l t has been, added to supersaturate i t , i s aragon i t e C a l c a r e o u s o r g a n i s m s p r o d u c e p r i m a r i l y a s e r i e s of m a g n e s ian calcites although some aragonite i s a l s o f o r m e d .

The m e c h -

a n i s m s w h i c h c o n t r o l the c r y s t a l f o r m s of c a l c i u m c a r b o n a t e i n the s h e l l s of c a l c a r e o u s o r g a n i s m s have not y e t b e e n e l u c i d a t e d . Aragonite i n sediment stable c a l c i t e (51) a n d m a g n e s i a n c a l c i t e s tend to be d i a g e n e t i c a l l y a l t e r e d to p u r e r c a l c i t e s a n d to d o l o m i t e (52, 53).

C h a v e et a l .

(54) found that the s t a b i l i t y of c a r b o n a t e s i n s e a w a t e r i n the o r d e r ; h i g h m a g n e s i a n c a l c i t e , a r a g o n i t e ,

increases

low magnesian

c a l c i t e , p u r e c a l c i t e , d o l o m i t e , but B e r n e r (46) r e c e n t l y c o n c l u d e d that c a l c i t e s w i t h 2 - 7 % m o l e - f r a c t i o n of M g C O ^ a r e t h e r m o d y n a m i c a l l y stable i n s e a w a t e r . Intermediate

o c e a n i c w a t e r s a r e u n d e r s a t u r a t e d i n the

North Pacific Ocean.

T h i s i s the r e s u l t of the h i g h c o n c e n t r a t i o n

of c a r b o n d i o x i d e p r e s e n t t h e r e b e c a u s e the w a t e r s a r e o l d a n d e x t e n s i v e o x i d a t i o n of o r g a n i c m a t t e r h a s taken p l a c e i n t h e m . A l l deep o c e a n i c w a t e r s a r e u n d e r s a t u r a t e d a s the r e s u l t of the effects of h i g h p r e s s u r e s a n d l o w t e m p e r a t u r e s upon the s o l u b i l i t y of c a l c i u m c a r b o n a t e ( 3 6 - 3 9 ,

55).

D e g r e e of s a t u r a t i o n data i n d i c a t e that c a r b o n a t e

sediments

can p e r s i s t u n t i l b u r i a l w h i l e e x p o s e d to u n d e r s a t u r a t e d w a t e r s (55,56).

T h i s c o n c l u s i o n i s c o n f i r m e d b y the fact that the l y s o -

c l i n e , the depth at w h i c h c a l c a r e o u s t e s t s f i r s t show s i g n s of d i s s o l u t i o n , i s w e l l above the c a r b o n a t e c o m p e n s a t i o n d e p t h , w h i c h m a r k s a sudden d e c r e a s e i n the c a r b o n a t e content of s e d i m e n t s (57, 58).

M o r s e a n d B e r n e r (59) c o n c l u d e d f r o m t h e i r k i n e t i c

r e s u l t s that the l a r g e i n c r e a s e i n d i s s o l u t i o n r a t e at the c o m p e n s a t i o n depth c o r r e s p o n d s to a change i n the m e c h a n i s m of solution. D i s s o l u t i o n of c a r b o n a t e s at depth l e d to s t u d i e s of the c a r bon d i o x i d e - c a r b o n a t e c y c l e s w i t h i n a n d t h r o u g h the o c e a n s a s w e l l a s to s t u d i e s of the f a c t o r s w h i c h c o n t r o l the c a r b o n d i o x i d e c o m p o n e n t s a n d the p H ( 5 , 8 , 9 , 6 0 ) . O t h e r m i n e r a l s w i t h s o l u b i l i t i e s that have b e e n d e t e r m i n e d i n s e a w a t e r a r e c a l c i u m p h o s p h a t e s (61), s i l i c a (62, 63), the l e a s t


8

MARINE CHEMISTRY

s o l u b l e c o m p o u n d s of a s e r i e s of t r a c e m e t a l s (64),

and clays

(65). In s o l u b i l i t y w o r k a s w e l l as i n the c a s e of d i s s o c i a t i o n c o n s t a n t s i t i s i m p o r t a n t , before a p p l y i n g e q u i l i b r i u m data o b t a i n e d i n seawater to e s t u a r i e s and to pore waters to a s c e r t a i n t h a t there have been no l a r g e changes i n the major i o n p r o p o r t i o n s . Ion A s s o c i a t i o n T h i s i s an i m p o r t a n t t o p i c b e c a u s e the f o r m a t i o n of i o n p a i r s , b y a f f e c t i n g the d i s t r i b u t i o n s of solute s i z e s a n d c h a r g e s , m o d i f i e s m o s t p h y s i c o - c h e m i c a l p r o p e r t i e s of s e a w a t e r ,

includ-

ing solubility equilibria. G a r r e l s and Thompso tion of i o n - p a i r s i n s e a w a t e r .

T h e y w e r e f o r c e d to m a k e a l a r g e

n u m b e r of a s s u m p t i o n s b e c a u s e n e e d e d data w a s not a v a i l a b l e to them.

Even so,

s o m e f e a t u r e s of t h e i r r e s u l t s w e r e

by subsequent i n v e s t i g a t i o n s .

confirmed

K e s t e r a n d P y t k o w i c z (67)

and

P y t k o w i c z a n d H a w l e y (68) u s e d p o t e n t i o m e t r i c m e t h o d s to d e t e r m i n e the c o n c e n t r a t i o n s of f r e e i o n s a n d of i o n - p a i r s i n

seawater

a n d w e r e a b l e to a v o i d m o s t of the a s s u m p t i o n s m a d e b y G a r r e l s and T h o m p s o n

(66).

T h e r e s t i l l a r e s o m e c o n t r a d i c t i o n s i n the r e s u l t s of d i f f e r ent i n v e s t i g a t o r s r e g a r d i n g the i n t e r a c t i o n s a m o n g the m a j o r of s e a w a t e r .

ions

In a d d i t i o n , f u r t h e r w o r k i s n e e d e d to c h a r a c t e r i z e

p o s s i b l e t r i p l e i o n s a n d the effects of t e m p e r a t u r e ,

salinity, and

p r e s s u r e upon i o n - p a i r i n g (68). Activity Coefficients W e w i l l d w e l l at s o m e l e n g t h u p o n this t o p i c b e c a u s e

much

of the m a t e r i a l p r e s e n t e d h e r e h a s not b e e n p u b l i s h e d b e f o r e . A c t i v i t y c o e f f i c i e n t s a r e v a l u a b l e b e c a u s e they p r o v i d e i n s i g h t s into solvent-ion and i o n - i o n interactions.

Also,

they a r e u s e f u l

for s t o i c h i o m e t r i c computations made when apparent d i s s o c i a t i o n c o n s t a n t s a n d s t o i c h i o m e t r i c s o l u b i l i t y p r o d u c t s a r e not a v a i l a b l e . One m a y u s e f r e e o r t o t a l m e a n a c t i v i t y c o e f f i c i e n t s free or total single ion activity coefficients, p r o b l e m under consideration. m i n e d i n solutions actions.

and

d e p e n d i n g upon the

F r e e c o e f f i c i e n t s a r e those d e t e r -

w h i c h t h e r e a r e no s p e c i f i c i o n i c i n t e r -

In s e a w a t e r they a r e c o n s t r u c t s w h i c h c o r r e s p o n d to the

f r e e i o n s i f the i o n - p a i r i n g m o d e l i s u s e d (68)

o r to l o n g - r a n g e

i o n i c i n t e r a c t i o n s , of the D e b y e - H u c k e l type (69),

i f the s p e c i f i c

i n t e r a c t i o n m o d e l of B r ^ n s t e d (70) a n d G u g g e n h e i m (71)

is


1.

PYTKOWICZ ET AL.

e m p l o y e d (72).

9


T o t a l a c t i v i t y c o e f f i c i e n t s a r e those o b t a i n e d i n

solutions i n which i o n - p a i r s or s h o r t - r a n g e specific interactions o c c u r a n d a r e r e l a t e d to the f r e e ones b y a = f (F) p

(12)

= f (T)

(4)

T

a i s the a c t i v i t y , f the a c t i v i t y c o e f f i c i e n t , w h i l e ( F ) a n d ( T ) r e p r e s e n t the c o n c e n t r a t i o n of f r e e i o n s a n d the s t o i c h i o m e t r i c (total) c o n c e n t r a t i o n . T h e m e a n f r e e a c t i v i t y c o e f f i c i e n t c a n be o b t a i n e d f r o m data i n c h l o r i d e s o l u t i o n s i f s u c h s o l u t i o n s a r e i n d e e d u n a s s o c i a t e d (67).

T h i s m u s t be done at the s a m e e f f e c t i v e i o n i c s t r e n g t h

a s that of the s e a w a t e r of i n t e r e s t .

The effective i o n i c strength

i n c l u d e s the e f f e c t s of strength p r i n c i p l e for n o n - s p e c i f i c i n t e r a c t i o n s i n m o d e r a t e l y concentrated m u l t i - e l e c t r o l y t e s o l u t i o n s , as was b y P y t k o w i c z a n d K e s t e r (73).

demonstrated

O t h e r s p r e f e r to o b t a i n m e a n

f r e e c o e f f i c i e n t s b y a s s u m i n g that the D e b y e - H i i c k e l e q u a t i o n i s v a l i d at the i o n i c s t r e n g t h of s e a w a t e r , t i o n (74)

with a h y d r a t i o n c o r r e c -

o r without it (72).

T o t a l m e a n a c t i v i t y c o e f f i c i e n t s can be m e a s u r e d d i r e c t l y i n the a s s o c i a t e d s o l u t i o n s of i n t e r e s t o r c a n be c a l c u l a t e d f r o m f r e e c o e f f i c i e n t s c o u p l e d to

i o n - p a i r or specific i n t e r a c t i o n

terms. C o r r e s p o n d i n g f r e e a n d t o t a l a c t i v i t y c o e f f i c i e n t s of s i n g l e i o n s a r e c o n v e n t i o n a l q u a n t i t i e s w h i c h d e p e n d upon n o n - t h e r m o dynamic assumptions and a r e , therefore,

of u n k n o w n a c c u r a c y .

S t i l l , they a r e u s e f u l for m a n y of the o c e a n o g r a p h i c a n d g e o c h e m i c a l c o m p u t a t i o n s w h i c h a r e b a s e d upon t h e r m o d y n a m i c e q u i l i b r i u m constants. N e x t , we w i l l c a l c u l a t e a c t i v i t y c o e f f i c i e n t s b y the m e a n s a l t m e t h o d c o u p l e d to i o n - p a i r m o d e l s a n d w i l l c o m p a r e t h e m to those o b t a i n e d b y other i n v e s t i g a t o r s . T h e f r e e a c t i v i t y c o e f f i c i e n t s of s i n g l e i o n s , T a b l e II, w e r e o b t a i n e d b y u s i n two s t e p s .

First,

shown i n an i n t e r p o l a -

tion e q u a t i o n w a s u s e d to o b t a i n v a l u e s of the m e a n a c t i v i t y c o e f f i c i e n t s i n t e r m e d i a t e to those c o m p i l e d b y H a r n e d a n d O w e n a n d b y R o b i n s o n a n d Stokes (76).

of the s i n g l e i o n s w e r e o b t a i n e d b y the m e a n - s a l t m e t h o d T h i s m e t h o d depends upon the v a l i d i t y of the M a c l n n e s (77) vention, (%)p

(75)

T h e n , the a c t i v i t y c o e f f i c i e n t s (66). con-

= ^Q\» w h i c h i s b a s e d u p o n t r a n s f e r e n c e n u m b e r s .

T h i s c o n v e n t i o n cannot be v e r i f i e d u n a m b i g u o u s l y b e c a u s e a c t i v i t i e s of s i n g l e i o n s cannot be m e a s u r e d .

the

The m e a n salt


10

MARINE CHEMISTRY

T a b l e II.

F r e e A c t i v i t y C o e f f i c i e n t s of P o t a s s i u m , S o d i u m ,

C a l c i u m , M a g n e s i u m a n d C h l o r i d e V e r s u s the I o n i c S t r e n g t h at 25 ° C , Ionic Strength (molal)

K

+

O b t a i n e d b y the M e a n - S a l t M e t h o d

Na

+

0. 00 0. 05

1. 000 0. 816

1. 000 0. 826

0. 10 0. 15

0. 769

0. 20

0.739 0.718

0. 25

0.701

0. 30

0. 68

Ca

2+

Mg

2+

Cl"

1. 000 0. 486

1. 000

0. 473

0. 787 0.765

0. 392

0. 408

0. 351

0. 368

0.750

0. 325

0. 343

0.769 0.739 0.718

0.739

0. 307

0. 326

0. 701

1. 000

0. 816

0. 35

0. 676

0. 726

0. 284

0. 305

0. 676

0. 40

0. 666

0.721

0. 277

0. 298

0. 666

0. 45

0. 657

0. 657

0. 650

0. 271 0. 266

0. 293

0. 50

0.718 0.716

0. 290

0. 650

0. 55

0. 643

0.714

0. 263

0. 288

0. 643 0. 637

0. 60

0. 637

0. 712

0. 260

0. 286

0. 65

0. 631

0.712

0. 258

0. 285

0. 631

0.70 0. 75

0. 626

0.711 0.711

0. 256 0. 255

0. 285

0. 626

0. 286

0. 622

0. 80

0.711

0. 254

0. 286

0. 85

0. 618 0. 614

0. 253

0. 288

0. 618 0. 614

0.90 0.95

0. 610 0. 607

0.711 0.712 0. 712

0. 253 0. 253

1. 00

0. 603

0.713

0. 253

0. 289 0. 291 0. 293

0. 622

0. 610 0. 607 0. 603

m e t h o d s h o u l d not be u s e d f o r a n i o n s u n l e s s they do not a s s o c i ate w i t h p o t a s s i u m i o n s . M e a s u r e d m e a n a c t i v i t y c o e f f i c i e n t s r e f l e c t two types of hydration effects;

the d i r e c t effect of i o n - s o l v e n t i n t e r a c t i o n s

u p o n c h e m i c a l p o t e n t i a l s a n d the c h a n g e s i n c o n c e n t r a t i o n a n d i o n i c s t r e n g t h due to the r e m o v a l of w a t e r of h y d r a t i o n f r o m the bulk solution.

T h e f i r s t effect i s t a k e n i n t o a c c o u n t a u t o m a t i c a l -

l y i n the m e a n - s a l t m e t h o d a s the m e t h o d i s b a s e d upon m e a s u r e d mean coefficients.

W e m a d e a c o r r e c t i o n f o r the s e c o n d

effect b y m e a n s of the e q u a t i o n I

A

= 1(1 + 0. 018h I / n ) A

1^ i s the c o r r e c t e d i o n i c s t r e n g t h , h i s the h y d r a t i o n n u m b e r ,


(5)

1.

11


PYTKOWICZ ET AL.

a n d n i s 1 for 1 -1

s a l t s a n d 3 for 1 -2 s a l t s .

T h e effect of the

change i n the i o n i c s t r e n g t h upon a c t i v i t y c o e f f i c i e n t s w a s

found

to be n e g l i g i b l e . T h e data i n T a b l e II c a n be u s e d for e s t u a r i n e a n d f o r p o r e w a t e r s as f r e e a c t i v i t y c o e f f i c i e n t s

at a g i v e n i o n i c s t r e n g t h a r e

i n s e n s i t i v e to the c o m p o s i t i o n of the s o l u t i o n (67, 6 8 , 7 3 , 7 8 ) . F u r t h e r m o r e , we c a l c u l a t e d f r o m the H a r n e d r u l e of R o b i n s o n a n d B o w e r (79)

coefficients

that the m e a n a c t i v i t y c o e f f i c i e n t s

of

N a C l a n d C a C l 2 , i n g o i n g f r o m a p u r e N a C l to a p u r e C a C ^ s o l u t i o n at 0. 75 i o n i c s t r e n g t h ,

o n l y change b y 1. 8 a n d b y 0.

1%

respectively. B a t e s et a l . (74) u s e d a h y d r a t i o n e q u a t i o n to e s t i m a t e free activity coefficients

of

single

ions.

They

the

assumed

that the D e b y e - H u c k e e f f e c t s of n o n - s p e c i f i c e l e c t r o s t a t i c i n t e r a c t i o n s f o r i o n i c s t r e n g t h s up to I = 6 a n d that c h l o r i d e i o n s a r e not h y d r a t e d . Our results,

shown i n T a b l e II, a n d those of B a t e s et a l .

(74)

d i f f e r b y about 3% for p o t a s s i u m a n d s o d i u m a n d b y up to

16%

f o r c a l c i u m a n d m a g n e s i u m at I = 1. 0.

to

It i s not p o s s i b l e

d e c i d e w h i c h set of r e s u l t s i s m o r e a c c u r a t e b e c a u s e , m e n t i o n e d e a r l i e r , the a c t i v i t y c o e f f i c i e n t s

as

was

of s i n g l e i o n s a r e

conventional. Marine chemists

often n e e d a c t i v i t y c o e f f i c i e n t s

as a f u n c t i o n of the s a l i n i t y .

expressed

T h e c o e f f i c i e n t s i n T a b l e II w e r e

e x p r e s s e d i n t e r m s of the s a l i n i t y , as i s shown i n T a b l e III,

by

m e a n s of the i o n i c s t r e n g t h - s a l i n i t y r e l a t i o n s h i p of L y m a n a n d F l e m i n g (80).

We found that the u s e of the e f f e c t i v e

ionic

s t r e n g t h (73) i n s t e a d of the c o n v e n t i o n a l one h a s a n e g l i g i b l e effect u p o n the a c t i v i t y

coefficients.

The total a c t i v i t y coefficients this w o r k f o r K ,

Na ,

+

+

Ca

2

+

of the s i n g l e i o n s o b t a i n e d i n

and M g

w e r e c a l c u l a t e d f r o m the f r e e o n e s , *T

=

^F^M^),

l e y (68).

a n c

* ^

e

2

+

,

a n d shown i n T a b l e I V ,

E q u a t i o n 4 i n the f o r m

s p e c i a t i o n m o d e l of P y t k o w i c z a n d H a w -

T h e c o e f f i c i e n t of sulfate w a s o b t a i n e d b y the m e t h o d

of K e s t e r a n d P y t k o w i c z (67) w h i l e those of b i c a r b o n a t e a n d c a r bonate i o n s w e r e c a l c u l a t e d f r o m the r a t i o s of the a p p a r e n t d i s s o c i a t i o n constants

of c a r b o n i c a c i d to the t h e r m o d y n a m i c

ones,

the a c t i v i t y c o e f f i c i e n t of c a r b o n i c a c i d , a n d the a c t i v i t y of water i n seawater.

The total mean a c t i v i t y coefficients

were

then c a l c u l a t e d f r o m those for the s i n g l e i o n s a n d a r e shown i n Table V .

T h e r e s u l t s of B e r n e r (81_) a n d of v a n B r e e m e n

(82)

w e r e e s t i m a t e d b y p r o c e d u r e s a k i n to those of G a r r e l s a n d Thompson

(66).

W h i t f i e l d (72)

a s s u m e d that n o n - s p e c i f i c i o n i c i n t e r a c t i o n s


12

MARINE CHEMISTRY

T a b l e III.

F r e e A c t i v i t y Coefficients

of S i n g l e Ions at 25 ° C

V e r s u s the S a l i n i t y S a l i n i t y (%)

K

+

Na*

^ 2+ Ca

Mg

2

+

Cl"

25

0. 648

0.715

0. 265

0.646

0. 714

0. 264

0. 289 0. 288

0. 648

26 27

0. 643

0.714

0. 263

0. 288

0. 643

28

0. 641

0. 260

0. 287 0. 286

0. 641

0.637

0. 713 0. 712

0. 261

29 30

0. 635

0. 712

0. 635

31

0. 633

0. 285

0. 633

32

0. 630

0.712 0.711

0. 259 0. 258 0. 257

0. 286 0. 285

0. 630

33

0. 62 0. 626

0. 646

0. 637

34

0. 626

0.711

0. 256

0. 285

35

0. 625

0.711

0. 255

0. 285

0. 625

36

0. 623

0.711

0. 255

0. 285

0. 623

37

0. 620

0.711

0. 254

0. 286

0. 620

38

0. 618

0.711

0. 254

0. 286

0. 618

39 40

0. 617 0. 615

0. 711

0. 254

0. 287

0. 617

0. 711

0. 254

0. 287

0. 615

Table IV.

T o t a l A c t i v i t y C o e f f i c i e n t s of S i n g l e Ions a t about 35%o S a l i n i t y a n d 25 ° C

Reference

K

Na

+

^ 2+ Ca

+

Mg

CI

*>.*-

This work

0. 618

0. 695

0. 225

0. 254

0. 625

0. 084

(8j_)

0. 624

0.703

0. 237

0. 252

0. 630

0. 068

(82) (72)

0. 620 0. 617

0. 228 0. 203

0. 254 0. 217

0. 630 0. 686

0. 090 0. 122

(83)

0. 630

0. 695 0. 650 0. 680

0. 214

0. 234

0. 658

0. 108

HCG ~

C0

0. 501

0.030

3

This work

3

2

"

can be d e s c r i b e d b y the m o d i f i e d D e b y e - H u c k e l e q u a t i o n w i t h B a = 1. H e d i d not i n t r o d u c e a h y d r a t i o n c o r r e c t i o n e v e n though both h y d r a t i o n e f f e c t s m e n t i o n e d e a r l i e r s h o u l d be taken i n t o consideration. The specific short range interactions were a c c o u n t e d f o r b y a d d i t i v e i n t e r a c t i o n t e r m s between c a t i o n s a n d anions. T h e good a g r e e m e n t b e t w e e n h i s c a l c u l a t e d m e a n c o e f -



(#)

2

2

2

2

2

3

3

4

4

4

3

3

4

3

3

s

2

2

0. 0. 0. 0.

299 323 127 131

0. 627 0. 666 0. 455 0.464

0. 0. 0. 0. 0. 0. 0. 0. 449 465 326 352 143 151

625 662

(82)

0. 0. 0. 0. 0. 0. 0. 0.

650 668 457 467 360 372 157 163

(72)

644 666 453 466 355 368

0. 151

0. 0. 0. 0. 0. 0.

(83)

0.090

0. 378

0. 672

(*)

(87)

(86)

Experimental

s o l u b i l i t y p r o d u c t of c a l c i u m

0. 158

0. 467 0. 345 0. 366

0. 639 0. 669

(84)

at about 35%o S a l i n i t y a n d 25 ° C

O b t a i n e d f r o m the r a t i o of the s t o i c h i o m e t r i c to the t h e r m o d y n a m i c carbonate.

2

0.621

0. 659 0.445 0.463 0.318 0. 343 0.137 0. 146 0. 56 0. 59 0.39 0.40 0.23 0. 24 0.083 0. 087

NaCl CaCl MgCl K S0 Na S0 CaS0 MgS0 KHCO3 NaHC0 Ca(HC0 ) Mg(HCO ) K C0 Na C0 CaC0 MgCQ

(81)

Total Mean A c t i v i t y Coefficients

This work

KC1

Reference Salt

Table V .

MARINE CHEMISTRY

14

f i c i e n t s a n d e x p e r i m e n t a l data i n d i c a t e s that h y d r a t i o n e n t e r s i n a d v e r t e n t l y i n t o the i n t e r a c t i o n t e r m s .

Leyendekkers

i n c l u d e d i n t e r a c t i o n s b e t w e e n i o n s of the s a m e c h a r g e The total a c t i v i t y coefficients methods are i n rough agreement.

(83)

types.

c a l c u l a t e d b y the v a r i o u s A c o m p a r i s o n of T a b l e s I V

a n d V shows that the l o w v a l u e of ( f i N a z S O ^ T o b t a i n e d i n t h i s w o r k r e l a t i v e to that of W h i t f i e l d (72) i s p r i m a r i l y due to the c o n t r i b u t i o n of sulfate i o n s .

O u r v a l u e of ( f s o ^ x

w

a

°°tained

s

without r e s o r t to the m e a n - s a l t m e t h o d a n d i s e s s e n t i a l l y upon p o t e n t i o m e t r i c m e a s u r e m e n t s .

based

T h i s indicates an i n c o m -

p a t i b i l i t y between the e x p e r i m e n t a l r e s u l t of K e s t e r a n d P y t k o w i c z (67)

obtained with glass and ion-exchange electrodes and

that of P l a t f o r d (87) w h i c h w a s m e a s u r e d w i t h a m a l g a m trodes.

elec-

Robinson and

i t y c o e f f i c i e n t s b y a n e x t e n s i o n of the m e t h o d of F r i e d m a n (85). Other E q u i l i b r i a T h e e q u i l i b r i a i n v o l v i n g the c o m p l e x a t i o n of t r a c e

metals

h a v e r e c e n t l y b e e n r e v i e w e d b y S t u m m (88) a n d a r e f u r t h e r e x a m i n e d elsewhere i n this v o l u m e .

K e s t e r (89) p r e s e n t e d a

r e v i e w of g a s - s e a w a t e r i n t e r a c t i o n s .

M a n y other a s p e c t s

of

m a r i n e c h e m i s t r y and g e o c h e m i s t r y have been d e s c r i b e d i n H o m e (90),

R i l e y a n d C h e s t e r (6J,

M a c k e n z i e (91), (5).

We w i l l ,

B r o e c k e r (92),

therefore,

B e r n e r (81),

G a r r e l s and

G o l d b e r g (93), a n d P y t k o w i c z

l i m i t t h i s w o r k to the t o p i c s a l r e a d y

d e s c r i b e d a n d to a l o o k at the e q u i l i b r i u m c h e m i s t r y of e s t u a r i n e w a t e r s f o l l o w e d b y a b r i e f e x a m i n a t i o n of the c o n t r o l of the oceanic composition. Equilibrium in Estuaries L i t t l e a p p e a r s to h a v e b e e n done c o n c e r n i n g e q u i l i b r i a i n estuaries.

We w i l l e x a m i n e ,

t h e r e f o r e , h o w one m a y a s c e r t a i n

whether e q u i l i b r i u m constants m e a s u r e d in seawater a p p l i e d to e s t u a r i e s .

c a n be

T h i s w i l l be i l l u s t r a t e d b y c o n s i d e r i n g the

d i s s o c i a t i o n r e a c t i o n s of c a r b o n i c a c i d . T h e c o m p o s i t i o n of r i v e r s depends upon the g e o l o g i c a l n a t u r e of t h e i r d r a i n a g e b a s i n s (91). we w i l l ,

therefore,

F o r illustrative purposes

d i s c u s s the e f f e c t s of m i x i n g s e a w a t e r w i t h

a h y p o t h e t i c a l r i v e r of a w o r l d - a v e r a g e shown i n T a b l e V I .

composition which is

T h e r e l a t i v e c o m p o s i t i o n of r i v e r w a t e r

d i f f e r s f r o m that of s e a w a t e r a n d t h e i r m i x i n g y i e l d s i n p r i n c i p l e e s t u a r i n e w a t e r s i n w h i c h the p r o p o r t i o n s of the m a j o r

ions


1. PYTKOWICZ ET AL. Table VI.


15

C o n c e n t r a t i o n P a r a m e t e r s f o r M i x t u r e s of R i v e r

Water and Seawater.

The Concentrations a r e E x p r e s s e d

in Molality x 1 0 .

i s the T o t a l I o n i c S t r e n g t h .

3

. 0078

7. 60^ 4

3.80

60

40

20

0

378. 1

281.7

186. 6

92.78

. 274

10. 37

8. 247

6. 157

4. 096

2. 063

. 0588

54. 06

42.98

32. 05

21. 27

10. 65

. 1687

Ca

10. 44

8. 37

Cl"

544.4

440.4

328. 1

217. 3

108. 0

. 2200

28. 68

22. 80

17. 01

11. 30

5. 671

. 1166

2. 122

1.883

1. 646

1.414

1. 184

.9575

.7078

. 5626

.4196

. 2785

. 1393

. 002074

Cl%o

19.0

15. 20

SW%

100

80

476.0

Na K

+

+

Mg

+

2

HCQ 3

][

11.40

d i f f e r f r o m those i n the o c e a n s .

2

T h u s , estuarine waters

to be i o n i c m e d i a of constant c o m p o s i t i o n ,

cease

the s i m p l i f y i n g f e a -

ture which r e n d e r s apparent constants useful. however,

6

Fortunately,

r i v e r w a t e r i s so d i l u t e that e s t u a r i n e w a t e r s t e n d to

r e t a i n the m a j o r i o n p r o p o r t i o n s of s e a w a t e r down to f a i r l y l o w chlorinities. T h e extent of m i x i n g i n a n e s t u a r y depends upon a l a r g e n u m b e r of f a c t o r s s u c h a s the s e a s o n a l l y v a r i a b l e r i v e r f l o w , the t i d a l c y c l e , the w i n d s t a t e ,

the t o p o g r a p h y , a n d the r e l a t i v e

t e m p e r a t u r e s of the r i v e r w a t e r a n d the s e a w a t e r .

One m u s t

a l s o c o n s i d e r i n a c t u a l e s t u a r i e s the i n f l o w of g r o u n d a n d m e l t waters.

T h e c o n v e n t i o n a l s a l i n i t y depends upon the r e l a t i v e

c o m p o s i t i o n of s e a w a t e r a n d , t h e r e f o r e ,

the c h l o r i n i t y a n d the

t o t a l s a l t content a r e b e t t e r c o m p o s i t i o n a l v a r i a b l e s than the s a l i n i t y to a s c e r t a i n the extent of m i x i n g at a n y g i v e n l o c a t i o n . In T a b l e VII we p r e s e n t the r a t i o s of the c o n c e n t r a t i o n s of the m a j o r i o n s i n s e a w a t e r a n d i n e s t u a r i n e w a t e r at the s a m e chlorinities.

It c a n be s e e n that the c o n c e n t r a t i o n s r e m a i n

s i m i l a r i n the two m e d i a down to l o w v a l u e s of the c h l o r i n i t y . N e x t , l e t us c o n s i d e r by how m u c h e q u i l i b r i u m constants d e t e r m i n e d i n s e a w a t e r m a y d i f f e r f r o m those i n e s t u a r i n e w a t e r s at the s a m e c h l o r i n i t i e s .

T h e e x a m p l e w i l l be h y p o t h e t i -

c a l b e c a u s e we a r e c o n s i d e r i n g a w o r l d - a v e r a g e r i v e r a n d


16

MARINE CHEMISTRY

Table VII.

R a t i o s of C o n c e n t r a t i o n s a n d of the I o n i c S t r e n g t h i n

S e a w a t e r to T h o s e i n the E s t u a r i n e W a t e r at the Same C h l o r i n i t y % SW Na K

+

+

Mg Ca

+

+

2

2

Cl" S O / 4 I

100

80

60

1. 00

1.0000

.9999

.9997

.9993

1.00

.9981

.9964

.9919

.9786

1.00

.9993

.9781

. 9958

. 9889

1. 00

.9909

.9742

.9478

. 8721

.9982

.9961

.9897

20

40

1. 00 1.00

2

.999

LOO

T

• 999

b e c a u s e a p p a r e n t d i s s o c i a t i o n c o n s t a n t s have not yet b e e n d e t e r m i n e d at the l o w c h l o r i n i t i e s w h i c h m a y be found n e a r the h e a d s of e s t u a r i e s . A p p a r e n t d i s s o c i a t i o n constants a r e r e l a t e d to the c o r r e s ponding t h e r m o d y n a m i c constants by total a c t i v i t y coefficients. T h e s e c o e f f i c i e n t s i n t u r n a r e r e l a t e d to the f r e e ones b y f*p = f ( F ) / ( T ) w h e r e f p r e f l e c t s the i o n i c s t r e n g t h effect a n d ( F ) / ( T ) F

r e p r e s e n t s the i o n - p a i r

effect.

T h e i o n i c s t r e n g t h effect c a n be c a l c u l a t e d f r o m the data i n T a b l e II a n d f r o m the f r e e a c t i v i t y c o e f f i c i e n t s of b i c a r b o n a t e a n d c a r b o n a t e i o n s (94).

T h e effect of i o n - p a i r i n g c a n be c a l c u -

l a t e d f r o m the e q u a t i o n s of P y t k o w i c z a n d H a w l e y (68) w h i c h r e l a t e a p p a r e n t d i s s o c i a t i o n c o n s t a n t s to s t o i c h i o m e t r i c a s s o c i a tion constants a n d free cation concentrations. example,

F o r K \ , for

the e q u a t i o n s y i e l d

(

K

1>EW

1

+

S

K

= ( K

'l>SW

1

+

S

K

# MHCO, 2 (

M H C 0

3

c+ >F(EW)

M

_ (

M

( 6

)

W)

w h e r e K i s the s t o i c h i o m e t r i c a s s o c i a t i o n c o n s t a n t , M represents c a t i o n s , E W r e f e r s to e s t u a r i n e w a t e r s a n d SW r e f e r s to seawater. T h e r e s u l t s of the c o m b i n e d effects a r e shown i n T a b l e VIII. T h e a s s o c i a t i o n c o n s t a n t s a n d the f r e e i o n c o n c e n t r a t i o n s


1.

PYTKOWICZ ET AL.

Table VIIL

17


R a t i o s of K ' j a n d K ^ , the A p p a r e n t D i s s o c i a t i o n

C o n s t a n t s of C a r b o n i c A c i d ,

i n S e a w a t e r to T h o s e

i n E s t u a r i n e W a t e r s at the S a m e C h l o r i n i t i e s % Seawater 100

< K ' > S W VE W

^

(K^ ^ / ( K ^

/(K

2

1.000

1.000

80

0.9994

0.9981

60

0.9986

0.9943

40

0.9977

0.9877

20

0.9953

0.9670

10

0.9914

0.9290

a r e w e l l known o n l y a the m a x i m u m a n d the m i n i m u m e f f e c t s of c o m p o s i t i o n a l

differ-

e n c e s u p o n the a p p a r e n t d i s s o c i a t i o n c o n s t a n t s b y u s i n g v a l u e s of i n E q u a t i o n 6 at 19%o c h l o r i n i t y a n d at i n f i n i t e d i l u t i o n r e s p e c tively.

T h e a s s o c i a t i o n c o n s t a n t s at i n f i n i t e d i l u t i o n a r e c o n s i d -

e r a b l y l a r g e r than those at 19%o a n d enhance the effect of c o m positional variations.

O n l y the m a x i m u m e f f e c t s a r e shown i n

Table VIIL It c a n be s e e n f r o m the r e s u l t s i n T a b l e VIII that K ^ a n d K ^ determined for oceanic waters

c a n be u s e d i n e s t u a r i e s

by a hypothetical w o r l d - a v e r a g e w h i c h contain only 20% seawater.

r i v e r down to e s t u a r i n e

supplied waters

T h i s c a n be done w i t h a n

e r r o r of l e s s than 4%, w h i c h i s w i t h i n the l i m i t s of u n c e r t a i n t y of m e a s u r e d a p p a r e n t c o n s t a n t s (20). C o n t r o l of the O c e a n i c C o m p o s i t i o n A n u n d e r s t a n d i n g of the c o n t r o l m e c h a n i s m s

f o r the c h e m i -

c a l c o m p o s i t i o n of the o c e a n s i s i m p o r t a n t b e c a u s e i t h e l p s u s u n d e r s t a n d the g e o c h e m i c a l h i s t o r y of the o c e a n s a n d the i m p a c t of p e r t u r b a t i o n s upon the c h e m i c a l n a t u r e of s e a w a t e r .

This

subject w a s e x a m i n e d c r i t i c a l l y b y P y t k o w i c z (5J a n d w i l l o n l y be mentioned briefly here. T h e c o n t r o l of the c o m p o s i t i o n of s e a w a t e r

c a n be approached

f r o m two p o i n t s of v i e w ; that of v a r i a t i o n s i n t i m e a n d s p a c e w i t h i n the o c e a n s a n d the b r o a d g e o c h e m i c a l v i e w i n w h i c h the o c e a n s a r e but one of s e v e r a l l i n k e d r e s e r v o i r s .

The first

a p p r o a c h c o n s i s t s b a s i c a l l y i n d e t e r m i n i n g the p a r a m e t e r s f o r a n d s o l v i n g the e q u a t i o n


18

MARINE CHEMISTRY

dN TT ot

^

d

A.

oN

=) ^ < — £j d i p i

oi

"

-

v

N

>

+

R

7

1 A

i

N i s the c o n c e n t r a t i o n of a non - c o n s e r v a t i v e c o n s t i t u e n t , — the e d d y d i f f u s i o n c o e f f i c i e n t ,

is

a n d V - i s the a d v e c t i v e v e l o c i t y .

R r e p r e s e n t s the e f f e c t s o f s o u r c e s a n d s i n k s s u c h a s uptake b y the b i o t a a n d the s e d i m e n t s a n d g a s e x c h a n g e (95).

Considerable

w o r k h a s b e e n done w i t h v a r i o u s f o r m s of E q u a t i o n 7 i n the open o c e a n a n d i n e s t u a r i e s (5). The g e o c h e m i c a l d e s c r i p t i o n of the o c e a n s i s not a s straightf o r w a r d b e c a u s e of th ing and sedimentation d i s c u s s i o n (5J.

S o m e of the m a i n s i n k s f o r n a t u r a l l y o c c u r r i n g

a n d m a n - p r o d u c e d c h e m i c a l s b r o u g h t i n t o the o c e a n s b y r i v e r s , w i n d s , a n d s u b m a r i n e v o l c a n i s m a r e a d s o r p t i o n a n d exchange r e a c t i o n s on the s u r f a c e of s e t t l i n g d e t r i t a l p a r t i c l e s , p r e c i p i t a t i o n of o x i d e s a n d s u l f i d e s ,

authigenie

d i f f u s i o n i n t o the s e d i m e n t s ,

b i o g e n i c s e t t l i n g , a n d the d i a g e n e t i c a l t e r a t i o n of s e d i m e n t s . One a s p e c t of r e m o v a l m e c h a n i s m s ,

namely,

seawater-clay

i n t e r a c t i o n s , h a s r e c e i v e d c o n s i d e r a b l e a t t e n t i o n be c a u s e S i l l e n (7) p r o p o s e d that the e q u i l i b r i a f o r s u c h i n t e r a c t i o n s m a y c o n t r o l the c o n c e n t r a t i o n s of the m a j o r i o n s a n d the p H of s e a w a t e r . C l a y s p r o b a b l y do e x e r t a m e a s u r e of c o n t r o l b y a d d i n g a n d removing

some seawater ions.

It i s d o u b t f u l , h o w e v e r ,

that

e q u i l i b r i a a r e a c h i e v e d i n the open o c e a n s a n d i t i s l i k e l y that the m a j o r i o n c o m p o s i t i o n of s e a w a t e r ,

w h i c h m a y have

r e m a i n e d s o m e w h a t c o n s t a n t f o r a l o n g t i m e , h a s done so a s the r e s u l t of s t e a d y states r a t h e r than of e q u i l i b r i a ( 5 , 8 - 1 0 ) .

Also,

it h a s b e e n shown that the p r i m a r y c o n t r o l s of the p H a n d of the b u f f e r i n g c a p a c i t y of s e a w a t e r i n the r e c e n t o c e a n s r e s u l t f r o m the a c t i o n of the c a r b o n d i o x i d e s y s t e m .

Still, aluminium s i l i -

c a t e s do p l a y a r o l e b e c a u s e t h e i r w e a t h e r i n g c o n t r i b u t e s about 15% of the p r i m a r y b u f f e r i n g a g e n t ,

b i c a r b o n a t e i o n s , to the

o c e a n s ( 5 , 8 , 9 , 60). T h e r e i s s o m e p o s s i b i l i t y that c l a y - s e a w a t e r

equilibria may

be r e a c h e d w i t h i n the p o r e w a t e r s of s e d i m e n t s (11).

This

s h o u l d l e a d , i f f i r s t order models are used as g u i d e l i n e s f o r thought

( 5 ) , t o s o l u t i o n s o f the type B = (k

A B

/k )A e

+

B

e


(8)

1.

19


PYTKOWICZ ET AL.

A a n d B a r e the contents of a g i v e n c o n s t i t u e n t i n the w e a t h e r i n g a n d i n the o c e a n i c r e s e r v o i r s , B u m , and k ^ B and k

e

e

i s the v a l u e of B at e q u i l i b r i -

r e p r e s e n t the r a t e c o n s t a n t s for the r i v e r

a n d the e x c h a n g e f l u x e s .

It c a n be s e e n f r o m E q u a t i o n 8 that

e q u i l i b r i u m i n p o r e w a t e r s w o u l d l e a d to an e v e n t u a l s t e a d y state B i n the o c e a n s d i f f e r e n t f r o m the e q u i l i b r i u m v a l u e B

e

unless

the r i v e r input w a s m u c h s m a l l e r than the f l u x i n t o the s e d i ments.

It c a n a l s o be seen that the t e r m B

e

w o u l d be a b s e n t i f

the p o r e w a t e r s w e r e not at e q u i l i b r i u m w i t h the s e d i m e n t s . equations governing the removal of p o l l u t a n t s

Thus

could be q u i t e

d i f f e r e n t i n the p r e s e n c e o r i n the a b s e n c e of e q u i l i b r i a . It i s i m p o r t a n t for the m o d e l l i n g of f l u x e s i n the p r e s e n c e of m a n - m a d e p e r t u r b a t i o n s to d e t e r m i n e a n d u s e a c t u a l r a t e l a w s for the t r a n s f e r of c h e m i c a l example,

Donaghay, S m a l l and Pytkowicz (unpublished results)

m a d e p r e l i m i n a r y l a b o r a t o r y s t u d i e s of the t r a n s f e r of i n c r e a s i n g a m o u n t s of c a r b o n d i o x i d e i n s e a w a t e r ton.

to m a r i n e p h y t o p l a n k -

T h i s i s a v i t a l t o p i c b e c a u s e the o c e a n i c b i o t a c a n take up a

c o n s i d e r a b l e f r a c t i o n of the c a r b o n d i o x i d e r e l e a s e d to the a t m o s p h e r e a n d the o c e a n s b y the c o m b u s t i o n of f o s s i l f u e l s a n d , t h u s , attenuate the g r e e n h o u s e

effect.

The experiments were p e r f o r m e d i n chemostats, I s o c h r y s i s galbana c u l t u r e , while bubbling

with an

a i r containing v a r i o u s

a m o u n t s of c a r b o n d i o x i d e t h r o u g h the s y s t e m .

The

biomass

went f r o m 7 m g / 1 f o r a s e a w a t e r w i t h a n o r m a l c a r b o n d i o x i d e content to 16 m g / 1 at f i v e t i m e s n o r m a l to 13 m g / 1 at ten t i m e s n o r m a l carbon dioxide.

T h u s , a tenfold i n c r e a s e i n c a r b o n d i o x -

i d e c a n double the b i o m a s s .

T h e d e c r e a s e f r o m 16 to 13

mg/1

m a y p e r h a p s r e f l e c t the effect of the d e c r e a s i n g p H upon b i o l o g i c a l a c t i v i t y , a h y p o t h e s i s that i s u n d e r study.

B y generalizing

the e q u a t i o n s a n d the e x t r a p o l a t i o n s of P y t k o w i c z (96)

to i n c l u d e

the m a r i n e p h y t o p l a n k t o n , one f i n d s that the a t m o s p h e r i c c a r b o n d i o x i d e m a y i n c r e a s e i n a c e n t u r y b y a f a c t o r of ten i n s t e a d of fourteen, Of c o u r s e ,

the v a l u e o b t a i n e d i n the a b s e n c e of the m a r i n e b i o t a . this i s o n l y a p r e l i m i n a r y r e s u l t

plankton species was u s e d

since a single phyto-

A l s o n u t r i e n t l i m i t a t i o n , the l a n d b i o t a ,

a n d b i o t i c a d a p t a t i o n w e r e not c o n s i d e r e d , a n d the p r e d i c t i o n of the f u t u r e c o n s u m p t i o n of f o s s i l f u e l s (96) w a s p e s s i m i s t i c . illustrates, however,

the i m p o r t a n c e of d e t e r m i n i n g r a t e

It

laws

for the c h e m i c a l f l u x e s i n n a t u r e . A c k n ow l e dg e m e n t T h i s w o r k w a s s u p p o r t e d b y the O c e a n o g r a p h y S e c t i o n of the


20

MARINE CHEMISTRY

National Science Foundation through G r a n t D E S T2-01631 and by the O f f i c e of N a v a l R e s e a r c h C o n t r a c t N 0 0 0 1 4 - 6 7 - A - 0 3 6 9 - 0 0 0 7 under NR083-102.

Abstract Concurrent chemical, biological and geological processes, in addition to the presence of the gravitational potential and of temperature and pressure gradients must be taken into consideration in the study of chemical equilibria in the oceans. A simplifying feature occurs because the approximate constant ratios of the concentrations of th ionic medium of constant relative composition. Estuarine waters differ from normal seawater be cause of time and spacial variations in composition due to the input of river water. The equilibrium chemistry of estuarine waters has not been studied to any significant extent but it will be shown that equilibrium data for open ocean waters are often applicable to estuaries. Literature Cited 1. Pytkowicz, R. M., Kester, D. R., "Oceanogr. Mar. Biol. Ann. Rev., "H. Barnes, ed., Vol. 9, pp. 11-60, Allen and Unwin, London, 1971. 2. Culkin, F., "Chemical Oceanography," J. P. Riley and G. Skirrow, eds., Vol. 1, pp. 121-161, Academic, New York, 1965. 3. Barth, T. F. W . , "Theoretical Petrology," Wiley, New York, 1952. 4. Goldberg, E. D . , "Chemical Oceanography," J. P. Riley and G. Skirrow, eds., Vol. 1, pp. 163-196, Academic, New York, 1965. 5. Pytkowicz, R. M., Earth Sci. Rev., Vol. 11, p. 1, 1975. 6. Riley, J. P., Chester, R . , "Introduction to Marine Chemistry," Academic, New York, 1971. 7. Sillen, L. G., "Oceanography," M . Sears, ed., Am. Assoc. Adv. S c i . , Washington, D. C., 1961. 8. Pytkowicz, R. M., "The Changing Chemistry of the Oceans," D. Dyrssen and D. Jagner, eds., pp. 147 -152, Almqvist and Wiksell, Stockholm, 1972. 9. Pytkowicz, R. M., Schweizer. Zeitsch. Hydrol. (1973) 35, 8. 10. Broecker, W. S., Quatern. Res. (1971) 1, 188. 11. Siever, R., Earth Planet. Sci. Letters (1968) 5, 106.


1.

PYTKOWICZ ET AL.


12.

21

Pytkowicz, R. M., Duedall, I. W . , Connors, D. N., Science (1966) 152, 640. 13. Buch, K . , Harvey, H. W . , Wattenberg, H., Gripenberg, S., Rapp. Cons. Int. Explor. Mer (1932) 79, 1. 14. Pytkowicz, R. M., Ingle, S. E., Mehrbach, C . , Limnol. Oceanogr. (1974) 19, 665. 15. Hansson, I., Deep-Sea Res. (1973) 20, 46. 16. Hansson, I., Deep-Sea Res. (1973) 20, 479. 17. Culberson, C . , Pytkowicz, R. M., Hawley, J. E., J. Mar. Res. (1970) 28, 15. 18. Buch, K . , Acta Acad. Aeboensis Mat. Phys. (1938) 11, 1. 19. Lyman, J . , Ph. D. Dissertation, University of California, Los Angeles, 1956. 20. Mehrbach, C., Culberson wicz, R. M., Limnol. (1973) 18, 897. 21. Disteche, A., Disteche, S., J. Electrochem. Soc. (1967) 114, 330. 22. Culberson, C . , Kester, D. R . , Pytkowicz, R. M., Science (1967) 157, 59. 23. Culberson, C . , Pytkowicz, R. M., Limnol. Oceanogr. (1968) 13, 403. 24. Park, P. K . , Limnol. Oceanogr. (1969) 14, 179. 25. Dyrssen, D . , Sillen, L. G., Tellus (1967) 19, 113. 26. Manheim, F., Stockholm Contrib. Geol. (1961) 8, 27. 27. Grasshoff, K . , Bull. Cons. Int. Explor. Mer (1964) 123, 1. 28. Kester, D. R . , Pytkowicz, R. M., Limnol. Oceanogr. (1967) 12, 246. 29. Goldhaber, M. B . , Ph.D. Dissertation, University of California, Los Angeles, 1974. 30. Culberson, C. H., Pytkowicz, R. M., Mar. Chem. (1973) 1, 309. 31. Bates, R. G., Macaskill, J. B . , "Analytical Methods of Oceanography, " R. F. Gould, ed., American Chemical Society, Washington, D. C., in press. 32. Wattenberg, H., Wiss. Ergebn. Dt. Atlant. Exped. 'Meteor' (1933) 8, 1. 33. Mclntire, W. G., Bull. Res. Bd. Canada No. 200, Ottawa, 1965. 34. Ingle, S. E., Culberson, C. H., Hawley, J. E., Pytkowicz, R. M., Mar. Chem. (1973) 1, 295. 35. Pytkowicz, R. M., Connors, D . N . , Science (1964) 144, 840. 36. Pytkowicz, R. M., Limnol. Oceanogr. (1965) 10, 220. 37. Pytkowicz, R. M., Disteche, A., Disteche, S., Earth Planet. Sci. (1967) 2, 430.


22

MARINE CHEMISTRY

38. Pytkowicz, R. M., Fowler, G. A., Geochem. J. (1967) 1, 169. 39. Hawley, J. E . , Pytkowicz, R. M., Geochim. Cosmochim. Acta (1969) 33, 1557. 40. Berner, R. A., Geochim. Cosmochim. Acta (1965) 29, 947. 41. Millero, F. J., Berner, R. A., Geochim. Cosmochim. Acta (1972) 36, 92. 42. Duedall, I. W., Geochim. Cosmochim. Acta (1972) 36, 729. 43. Pytkowicz, R. M., J. Geol. (1965) 73, 196. 44. Chave, K. E . , Suess, E . , Limnol. Oceanogr. (1970) 15, 633. 45. Pytkowicz, R. M., Am. J. Sci. (1973) 273, 515. 46. Berner, R. A., Geochim 47. Weyl, P. K., Stud. Trop. Oceanogr. Miami (1967) 5, 178. 48. North, N. A., Geochim. Cosmochim. Acta (1974) 38, 1075. 49. Kitano, Y., Bull. Chem. Soc. Japan (1962) 35, 1973. 50. Kitano, Y., Kanamori, N., Tokuyama, A . , Am. Zool. (1969) 9, 681. 51. Bischoff, J. L., Fyfe, W. S., Am. J. Sci. (1968) 266, 65. 52. Peterson, M. N. A., Von Der Borch, C. C., Bien, G. S., Am. J. Sci. (1966) 264, 257. 53. Clayton, R. M., Jones, B. F., Berner, R. A., Geochim. Cosmochim. Acta (1968) 32, 415. 54. Chave, K. E . , Deffeyes, K. S., Weyl, P.K., Garrels, R. M., Thompson, M. E . , Science (1962) 137, 33. 55. Edmond, J. M., Deep-Sea Res. (1974) 21, 455. 56. Pytkowicz, R. M., Geochim. Cosmochim. Acta (1970) 34, 836. 57. Berger, W. H., Mar. Geol. (1970) 8, 111. 58. Heath, G. R., Culberson, C. H., Geol. Soc. Amer. Bull. (1970) 81, 3157. 59. Morse, J. W., Berner, R. A., Am. J. Sci. (1972) 272, 840. 60. Pytkowicz, R. M., Geochim. Cosmochim. Acta (1967) 31, 63. 61. Roberson, C. E . , M.S. Thesis, University of California, San Diego, 1965. 62. Krauskopf, K. B., Geochim. Cosmochim. Acta (1956) 10, 1. 63. Jones, M. M., Pytkowicz, R. M., Bull. Soc. Royale Sci. Liege (1973) 42, 125. 64. Krauskopf, K. B., Geochim. Cosmochim. Acta (1956) 9, 1. 65. Siever, R., Woodford, N., Geochim. Cosmochim. Acta (1973) 37, 1851.


1.

PYTKOWICZ ET AL.


23

66. Garrels, R. M., Thompson, M. E . , Am. J. Sci. (1962) 260, 57. 67. Kester, D. R., Pytkowicz, R. M., Limnol. Oceanogr. (1969) 14, 686. 68. Pytkowicz, R. M., Hawley, J. E., Limnol. Oceanogr. (1974) 19, 223. 69. Debye, P., Hückel, E . , Physik. Z. (1923) 24, 185. 70. Brønsted, J. N., J. Am. Chem. Soc. (1922) 44, 877. 71. Guggenheim, E. A., Philos. Mag. (1935) 19, 588. 72. Whitfield, M . , Mar. Chem. (1973) 1, 251. 73. Pytkowicz, R. M., Kester, D. R., Am. J. Sci. (1969) 267, 217. 74. Bates, R., Staples, B. R., Robinson, R. A., Analyt. Chem. (1970) 42 75. Harned, H. S., Owen, B. B., "The Physical Chemistry of Electrolytic Solutions," Am. Chem. Soc. Monogr. 137, Reinhold, New York, 1958. 76. Robinson, R. A., Stokes, R. H., "Electrolyte Solutions," Butterworths, 2nd ed., London, 1965. 77. MacInnes, D. A., J. Am. Chem. Soc. (1919) 41, 1086. 78. Gieskes, J. M., Z. Physik. Chem. (Frankfurt) (1966) 50, 78. 79. Robinson, R. A., Bower, V. E . , J. Res. NBS (1966) 70A(4), 313. 80. Lyman, J., Fleming, R. H., J. Mar. Res. (1940) 3, 135. 81. Berner, R. A., "Principles of Chemical Sedimentology, " McGraw-Hill, New York, 1971. 82. van Breemen, N., Geochim. Cosmochim. Acta (1973) 37, 101. 83. Leyendekkers, J. V., Mar. Chem. (1973) 1, 75. 84. Robinson, R. A., Wood, R. H., J. Solut. Chem. (1972) 1, 481. 85. Friedman, H. L., "Ionic Solution Theory," Inter science, New York, 1962. 86. Platford, R. F., J. Mar. Res. (1965) 23; 55. 87. Platford, R. F., Dafoe, T., J. Mar. Res. (1965) 23, 63. 88. Stumm, W., "Chemical Oceanography," J. P. Riley and G. Skirrow, eds., 2nd ed., Vol. pp. , Academic New York, 89. Kester, D. R., "Chemical Oceanography," J. P. Riley and G. Skirrow, eds., 2nd ed., Vol. , pp. , Academic, New York, .


24

MARINE CHEMISTRY

90. Horne, R. A., "Marine Chemistry: The Structure of Water and the Chemistry of the Hydrosphere," Inter science, New York, 1969. 91. Garrels, R. M., Mackenzie, F. T., "Evolution of Sedimentary Rocks," Norton, New York, 1971. 92. Broecker, W. S., "Chemical Oceanography," Harcourt Brace Jovanovich, New York, 1974. 93. Goldberg, E. D., ed., "The Sea: Ideas and Observations on Progress in the Study of the Sea," Vol. 5, Interscience, New York, 1974. 94. Walker, A. C., Bray, V. B., Johnston, J., J. Am. Chem. Soc. (1927) 49, 1235. 95. Redfield, A. C., Ketchum, B. H., Richards, F. A., "The Sea: Ideas and Observation the Sea," M.N. Hill, ed., Vol. 2, pp. 26-77, Interscience, New York, 1963. 96. Pytkowicz, R. M., Comments on Earth Sci. : Geophys. (1972) 3, 15.


2 The Physical Chemistry of Estuaries FRANK J. MILLERO Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Fla. 33149

In recent years, there have been a number of major advances made on the interpretatio ponent electrolyte solutions (1-8). A number of chemical models have been developed from these recent studies. The models have been applied to seawater solutions in an attempt to understand how the physical chemical properties of seawater are related to the ion-water and ion-ion interactions of the major constituents of seawater (8-21) and how the medium of seawater affects the state of metal ions in seawater (8,9,22-39). In the present paper these models and methods will be briefly reviewed and applied to river water and estuarine water (mixtures of river and seawater). In the next two sections the application of these methods to seawater will be reviewed. Physical Chemical Properties of Seawater One of the most useful generalizations to be developed for multicomponent electrolyte solutions is Young's rule (40,41) and its modifications by Wood and coworkers (42-44) and Millero (8, 9-19). Young's rule for a multicomponent electrolyte solution is given by • - EE1*1

(1)

where $ is any apparent equivalent property (such as volume, expansibility, compressibility, enthalpy and heat capacity), is the equivalent ionic fraction of species i^ (E^ • e^/e^ where e^ is the equivalent molality of species i, and eT = Z e^) and |i is the apparent equivalent property of species i^ at the ionic strength of the solution. The apparent equivalent property of the solution is related to the measured property (P) of seawater by • - (P - P°)/e T (2) 25 In Marine Chemistry in the Coastal Environment; Church, T.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.

26

MARINE CHEMISTRY

where P° i s the physical property of pure water and e- i s the total equivalents of sea s a l t . (Equation 1) essentially states that as a f i r s t approximation the excess properties of mixing sea salts at a constant ionic strength can be neglected. This relationship i s a very useful f i r s t approximation and has been shown to be applicable to many multicomponent electrolyte solutions. For a solution that contains a number of ionic components i t i s possible to use Young s rule, i n terms of the constituent salts, a number of ways. For example, for the major sea salt ions (Mg , Na , CI and SO^ "), we have 1

2+

+

2

# * ^ a C l *NaCl #

=

E

Na S0 2

#

4

+

( 3 )

^gSO^, *MgS(>

4

*Na S0 2

+

V

4

***gCl

2

( 4 ) 2

E

* NaCl *NaC ^gC^

*MgCl

+

( 5 )

^gSO^, *MgS0

2

4

Wood and Anderson (42) have suggested that (equation 5) i s the better of the forms to use since i t includes a l l the possible plus-minus interaction pairs which make up the major ionic interactions . More recent work by Reilly and Wood (44) has indicated a more general form for Young s rule 1

E

* • ^

( 6 )

X *MX

where E^ i s the equivalent fraction of cation M and E i s the equivalent fraction of anion X. This equation was arrived at by f i r s t mixing a l l the salts of one cation at constant ionic strength i n such a manner as to yield the anion composition of the f i n a l mixture. This step i s repeated for each cation and then a l l of the resulting cation solutions were mixed to give the f i n a l mixture. Millero (8,9) has elaborated on the application of this procedure to seawater. By making the summation for each cation over a l l i t s possible salts, one obtains the equivalent weighted cation contribution x

*(MDC.) -

+

V

a

+

W

Vte

W

^

Vo0

+

3

+

*MC0

+

3

W

E

(

)

^

3

E

M B(OH) *MB(OH) 4

+

4

(7

Wr *MF > The total ionic component for seawater i s given by 1

\

^MX " •
f2

3 / 2 v

+ C Cly

S , C = k k' b.

2

(14)

This equation


28

MARINE CHEMISTRY

predicts the concentration dependence of seawater solutions d i luted with pure water. Since $° i s related to ion-water interactions, S and b are related to ion-ion interactions, any physical property of seawater can be visualized as being equal to P = P° + E ion-water interactions + E ion-ion interactions

(15)

The ion-ion interaction term can be s p l i t up into a theoretical Debye-Htickel limiting law term and a term due to deviations from the limiting law E ion-ion interactions = Debye-Htickel term + E deviations fro (equations 11 to 14) have been shown to be valid for predicting and representing the concent rat ion dependence of the thermodynamic (8-19) and transport (8) properties of seawater. Recently we have applied these methods to lakes (46), rivers (47) and estuaries (47)• The application of these methods to the physical chemical properties of seawater can be demonstrated by examining the dens i t y . The apparent equivalent volume of seawater i s related to the density (d) by $

v

- 1000

(d°-d) / e d° + M/d°

(17)

T

where d° i s the density of water, e i s the normality (equival e n t s / l i t e r ) and M i s the mean equivalent weight of sea s a l t . By combining this equation with the concentration dependence of 0 (equation 11), we obtain (noting that e = 0.0312803 CI and 1^ = 0.0360145 Cly) d - d

0

+ Ay d y

+ ^

C l ^ H" ^

(18)

5

where A^ - (M - d° * °) x 3.12803 x 10" , By - S d° x 5.93621 x KT and C - - byd° x 4.78277 x 10" . The calculations of the #y° and by values for sea salt using the molal volume data given elsewhere (8,48,50) i s demonstrated i n Table I. 6

7

y

TABLE I CALCULATION OF 3> ° AND v

Solute

E. 0.77268 0.17573 0.03390

<j>°(i) - 1.21 -10.59 - 8.93 v

by FOR E -

SEA SALT AT 25 °C 0

±

cj) (i) 0.935 1.861 0.303 v

by 1.078 -0.197 0.242

E b (i) 0.833 -0.035 0.008 ±


v

2.

MILLERO

Physical Chemistry of Estuaries

29

TABLE I continued Solute

h

+

K Sr C1

~2SO, HCO ~ Br B(OH), CO 2B(0H) ~ F~ 3

0.01684 0.00030 0.90078 0.09318 0.00318 0.00139 0.00054 0.00067 0.00014 0.00011

•v°(i). 9.03 - 9.08 17.83 6.99 24.28 24.71 39.22 - 1.89 21.84 - 1.16

Vv°

0.152 - 0.003 16.061 0.651 0.077 0.034 0.021 - 0.001 0.003 - O.OOOj^

Combining these values of $ ° and b 58.034 (51), we obtain the equation v

with

v

E Vi)

( i )

±

1.129 0.569 -1.030 0.134 0.302 -1.107 1.300 -0.780 3.630 -0.538

0.019

o.ooo

9 Z

-0.928 0.013 -0.010 -0.001 0.001 -0.001 0.001

-o.ooo

1

» 2.150 and M •

-3 -5 3/2 d - 0.997075 + 1.38192 x 10 Cly - 1.27255 x 10 Cl J /

y

3

+ 4.82143 x 10" C l

2

(19)

y

The densities calculated from (equation 19) from 5 to 35°/oo s a l i n i t y are compared to the measured values (52) i n Table I I . TABLE II COMPARISON OF THE CALCULATED AND MEASURED DENSITIES OF SEAWATER SOLUTIONS AT 25°C 3 A, ppm Salinity M e a s " ° )io , Calc - 4 5°/oo 2.770 3.769 3.765 10 7.518 - 7 5.561 7.511 15 8.372 - 7 11.254 11.261 20 15.002 15.007 - 5 11.205 25 1 14.058 18.756 18.757 30 22.512 11 16.932 22.523 24 35 26.276 19,827 26.300 mean + 8 (d

d

The agreement i s very good when one considers that the single salt density data at high concentrations i s only good to + 10 x 10" g cm"-*. At present i t i s not possible to state with certainty that the deviations at high concentrations are due to unreliable single salt data or a failure of Young's rule. Further studies are needed to examine the excess volumes of mixing the major sea salts, 6


30

MARINE CHEMISTRY

A¥

m

- [ $ ( e a s ) - § (calc)]/e v

m

v

T

(20)

In the low s a l i n i t y range the estimated d e n s i t i e s are i n e x c e l l e n t agreement w i t h the measured v a l u e s s i n c e the h i g h e r order terms ( B ^ C l y ' and C l ^ ) are not of great importance. 3

2

P r o p e r t i e s of I o n i c Solutes i n Seawater To o b t a i n an understanding of how the medium of seawater or any multicomponent e l e c t r o l y t e a f f e c t s an i o n i c chemical r e a c t i o n A + B

(21)

C + D

i t i s necessary t o examin a c t ant s p e c i e s . This n o n - i d e a amining the a c t i v i t y c o e f f i c i e n t (y ) of the r e a c t a n t s p e c i e s as w e l l as i t s p r e s s u r e V - V ° = RT(91n y / (S) are the apparent equivalent volume at the ionic strength of the mixtures ( I - E I + E I ) . The values of $ (Est) for the estuary determined trom êquation 45) at various weight fractions of seawater are given i n Table X. R

v

V

T

R

g

v


MARINE CHEMISTRY

42

TABLE X THE APPARENT EQUIVALENT VOLUME, MEAN MOLECULAR WEIGHT AND TOTAL NORMALITY OF ESTUARY SALTS AT VARIOUS WEIGHT FRACTIONS OF SEA SALT X

SW

0 0.02 0.04 0.06 0.08 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00

h

* (Est)

0 0.8827 0.9392 0.9594 0.9698 0.9762 0.9893 0.9937 0.9960 0.9973 0.9982 0.9988 0.9993 0.9997 1.0000

19.768 14.866 14.644 14.608 14.617 14.641 14.806

77.446 63.310 59.215 58.822 58.620 58.496 58.242

0.00164 0.01370 0.02576 0.03785 0.04995 0.06207 0.12280

15.217 15.323 15.418 15.508 15.590 15.671

58.086 58.069 58.057 58.047 58.040 58.034

0.30694 0.36895 0.43127 0.49393 0.55689 0.62019

v

i

Also given i n this Table are the mean equivalent weight of the estuary salt "t •

\ \

N

E

+

E

( 4 6 )

M

s s

and t o t a l normality T-

R

N

R

+

E

S

N

(47

S

>

The relative densities of the estuary have been calculated from the $y, M^, and N given i n Table X, using the equation d - d° - (Hj - d° * ) N y

T

(48)

and are given i n Table XI. Also given i n this Table are the densities of seawater diluted with pure water (52) calculated at the same t o t a l solid concentration. Over the entire weight fraction of sea salt the densities calculated from the seawater TABLE XI THE DENSITIES OF ESTUARINE WATERS AT VARIOUS FRACTIONS OF SEA SALT X

S "0 0.02 0.04

g

T 0.127 0.827 1.529

(d — d^)10^ Estuary " ' Seawater 0.095 0.096 0.622 0.622 1.149 1.148

A, ppm - 1 0 1


2.


MILLERO

43

TABLE XI continued Xg 0.06 0.08 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00

g^ 2.229 2.931 3.631 7.136 10.640 14.144 17.649 21.153 24.657 28.161 31.666 35.170

Estuary

Seawater

A, ppm

1.675 2.200 2.725 5.339 7.951 10.560 13.172 15.788 18.408 21.034 23.66 26.30

1.672 2.197 2.720 5.335 7.947 10.558 13.172 15.789 18.410 21.035

3 3 5 4 4 2 0 - 1 - 2 - 1

mean +1.9 equation of state are i n excellent agreement with the values estimated from (equation 48). Recently, we have made direct measurements on mixtures of a r t i f i c i a l river water and standard seawater (47) and found that the measured values agreed with those calculated from the seawater equation at the same total solid concentration to + 3 x 10"^g cm~3 from 0 to 35°/oo s a l i n i t y . From these comparisons, i t i s clear that the densities (as well as other physical chemical properties) of seawater diluted with pure water can be used i n rivers and estuaries as well as lakes and seas (46). By knowing the river water input of total dissolved solids, the solids of the estuarine salt can be determined from g (Estuary) = g (River) + b S(°/oo) T

T

(49)

where S(°/oo) i s the conductivity s a l i n i t y and the constant b is given by b - [35.170 - g (River)] / 35.000 T

(50)

Recently, we have used these equations to examine the densities of Baltic Sea waters (52). We have found that (see Table XII) TABLE XII COMPARISONS OF THE MEASURED DENSITIES OF THE BALTIC WITH THOSE OF SEAWATER DILUTED WITH PURE WATER Ours-Cox, e t . a l . , 0°C S( /oo) Uncorr Corr 9.579 -53 17 15.541 -45 9 20.130 -51 -10

Ours-Kremling, 0.36°C S(°/oo) Uncorr Corr 15.247 -57 - 2 20.083 -44 - 3 25.013 -38 -10


MARINE CHEMISTRY

44

TABLE XII continued Ours-Cox, e t . a l . , 0°C S( /oo) 20.154 25.439 29.698 35.004 39.232 40.288

Corr

Uncorr -32 -29 -25 - 4 8 9

9 - 2 -10 - 4 - 3 - 5 +

Ours-Kremling, 0.36°C Uncorr -13 - 9 -11 - 4 3 - 3

S(°/oo) 29.839 31.191 31.920 32.319 35.495 39.232

7.7

Corr 1 2 - 3 4 2 -14 + 4.5

the density measurements of Cox, e t . a l . , (69) and Kremling (70) are i n good agreement (+ 7 ppm) with our measurements on seawater diluted with pur This value for the rive the value determined from the composition data of Kremling (71). It i s interesting to note that the e a r l i e r measurements of Knudsen (72) give a value of g (River) = 0.073 g kg" which i s in agreement with earlier composition data of Lyman and Fleming (73). I t , thus, appears that the river input or the evaporation to precipitation has increased i n the Baltic Sea i n the last 60 years. The densities of the Mediterranean and Red Seas were also found (52) to be i n agreement with evaporated seawater at the same g as determined from (equation 49) with g (River) = 0.120 g kg" . Thus, these seas behave as an evaporated estuary, not evaporated seawater. The fact that the densities of rivers, estuaries, lakes, seas and seawater are i n good agreement at the same total dissolved solid concentration, brings up a problem concerning the new definition of s a l i n i t y (74) T

T

1

(51)

S(°/oo) = 1.80655 Cl(°/oo)

This new definition causes a difference between the physical chemical properties of seawater diluted with pure water and d i rect measurements made on natural waters (due to the lack of a river water input term). By using (equation 49) (or i t s equivalent expressed i n chlorinity using (equation 51), or the e a r l i e r definition of s a l i n i t y by Knudsen, these problems could have been avoided. Since the conductivity of seawater diluted with pure water are nearly equivalent to the conductivity of natural water at the same g (52), the redefinition of the conductivity ratio (R-_) i n terms of weight diluted or evaporated seawater w i l l y i e l d weight s a l i n i t i e s S(°/oo) valid for a l l natural waters (52). T


2.

MILLERO

45


S(°/oo)

T

= 27.25860610 R - 27.23834557 R

+ 19.0618570 R ^

15

3

+ 27.09960846 R ^

5

+ 3.01618532 R

1 5

- 14.19791134 R ^

2

6 1 5

4

(52)

Due to the sensitivity of conductivity measurements, the conductivities of estuaries at low s a l i n i t i e s w i l l deviate considerably from seawater diluted with pure water. The equivalent conductivity of solutions unlike the thermodynamic properties approach values at i n f i n i t e dilution that are dependent upon the composition. For example, i f we estimate the i n f i n i t e dilution equivalent conductance (A • 10^ L /e^, where L i s the specif i c conductance) of river salts a n l sea salts ffBm g

g

A we obtain (see Table XIII) A

0

2 —1 —1 = 97.34 and 127.85 cmft"eq

TABLE XIII CALCULATION OF THE INFINITE DILUTION EQUIVALENT CONDUCTANCE OF RIVER AND SEA SALTS AT 25°C River Salt Ion

A°

a 4

i Na

M g

2+ o 2I+

Ca

2 +

Sr Cl~ SO 2HCO," B r

~f 2

CO. " B(0H) " F" NO," 4

50.10 53.05 59.50 73.50 59.47 76.35 80.02 44.50 78.14 69.3 65.0 55.4 71.46

a) From Robinson and Stokes (57). been estimated.

Sea Salt

E. A ° i i

E. A°, i i

8.367 10.896 27.168 2.646

38.711 9.322 2.017 1.238 0.018 68.775 7.457 0.142 0.109 0.047 0.009 0.006

4

10.239 11.363 25.961

0.700 97.340

127.850

The value for B(0H)^ has

respectively, for river and sea salts (using values of A given in reference (57)). If i t i s assumed that (equation 53) i s v a l i d over a wide concentration range, i t i s possible to estimate the A of an estuary formed by mixing river and sea salts. These values of A(Estuary) are shown i n Figure 6 (75). At concentrations of e greater than 0.122 or g = 7.13 g kg" the


MARINE CHEMISTRY

Figure 6. The equivalent conductance of river water, seawater, and estuarine waters as a function of the square root of normality at25°C


MILLERO


Cations

Figure 7.

Anions

The speciation of the major cations and anions of river salt at 25°C

An:;r::i C'.:::iical

In Marine Chemistry in the Coastal Environment; Church, T.; ACS Symposium Series;Society American Chemical LibrarySociety: Washington, DC, 1975.

48

MARINE CHEMISTRY

A(Estuary) i s approximately equal to the A of seawater diluted with pure water. Further experimental conductance studies are needed to see i f these calculations are correct. The Speciation of Major and Minor Ions i n River Waters Since the composition of river waters and seawater are quite different, one might expect chemical reactions i n estuaries to be affected by the mixing of the two waters. One of the easiest ways of examining how the composition of rivers affects the properties of ionic solutes i s to compare the speciation of the ionic solutes i n river waters and seawaters• Since the ionic strength of river water i s very low, i t i s possible to estimate the activity coefficient of free ions and charged ion pairs by using the equation (55-57 log Y

F

=-(0.509) Z

2

[I

1 / 2

/(l + I

1 / 2

) - 0.31]

(54)

This equation yields values of = 0.951 for monovalent ions or ion pairs and 0.817 for divalent ions or ion pairs at I = 2.095 x 10" mol kg" . The stoichiometric association constants determined from thermodynamic association constants (9) for the major river salts are given i n Table XIV. 3

1

TABLE XIV THE STOICHIOMETRIC ASSOCIATION CONSTANTS FOR THE MAJOR RIVER SALTS AT 25°C

V so, "" 2

Na 2+ Mg; 2+

3

4.3 108 137 7.4 78

HC0 ~

OH

3

1.3 13.2 14.5

2.9 1272 5552

0.2„ 1.5c 0.5:

0.2 310 15.2

0.5 54 9.0

The speciation of the major ionic components of river salt are given i n Table XV, and shown i n Figure 7. As i n seawater, the TABLE XV THE SPECIATION OF THE MAJOR CATIONS AND ANIONS IN RIVER WATER AT 25°C Cation — H Na; Mg

+

2+

%M 99.98 99.83 97.54

% M S04

#

0.02 0.05 1.15

%MHC0 3 o

0.12 1.21

%M_C03

% M OH

0.08

0.01

o


2.

MILLERO

49


TABLE XV continued —Cation — Ca ^ K Anion

Zi

+

C1

~2-

HCO3C 0 2NO30H~ 3

F-

%M

%MHCO 3

96.89 99.92

% M SO, 4 1.45 0.08

1.32

0.33

0.01

% X

% Na X

% Mg X

% Ca X

% K X

100.00 93.55 99.23 31.03 99.93 94.64 98.79

0.11 0.04 0.03 0.01 0.01

%MCO

0

1.66 0.21 6.50

0

3

% M OH

0.04

4.64 0.52 62.44 0.06 0.52

4.83

major river cations are predominately i n the free form. The anions with the exception of CO^ are also predominately i n the free ion form. The total activity coefficients for river ions determined from (equations 32 and 33) are given i n Table XVI. TABLE XVI THE TOTAL ACTIVITY COEFFICIENTS OF THE MAJOR RIVER IONS Ion

«

+

% Free 99.98 99.83 97.54 96.89 99.92 100.00 93.55 99.23 31.03 99.93 94.64 98.79

+

Na 2+ Ca2+

Mg

C1

~2-

3iCO no;t

H

c

8

J

0H F"

IF

Z

J

IT 0.951 0.949 0.797 0.792 0.950 0.951 0.764 0.944 0.254 0.950 0.900 0.939

0.951 0.951 0.817 0.817 0.951 0.951 0.817 0.951 0.817 0.951 0.951 0.951

It should be pointed out that values of Y f ° river ions determined from the specific interaction moael are i n good agreement with the values given i n Table XVI. The difference between using values of y and Y for ionic equilibria i n river waters can be demonstrated by examining the value y (CaCO^) = y(Ca) x y(CO^); which can be used to examine the sol-ability of CaC0«. The value of y+ (CaCO^) determined from free ion activity coefficients (0.667) i s 3.3 times larger than the value determined from the total activity coefficients (0.201). The speciation of the heavy metals Cu, Zn, Cd and Pb i n r

t

p

t

+


50

MARINE CHEMISTRY

river waters can also be made by using free ion activity coefficients determined from (equation 54) and the thermodynamic constants tabulated by Zirino and Yamamoto (32). The speciation of these metals i n river and seawater are shown i n Figure 8. The predominate form of a l l the heavy metals i n river waters i s the carbonate complex, while i n seawater hydroxide> chloride and carbonate complexes are important. It i s interesting to note that a greater percentage of free heavy metal ions exist i n seawater than i n river waters. The total activity coefficients of the heavy metals i n river water are given i n Table XVII. TABLE XVII THE TOTAL ACTIVITY COEFFICIENTS OF HEAVY METALS IN RIVER WATERS Metal 2

Cu * Znf " Cd Pb 1

2 +

2 +

% Fre 0.817 0.817 0.817 0.817

0.0197 1.1691 0.9367 0.0077

0.0002 0.0096 0.0077 0.0001

The importance of examining a l l of the interaction parameters for heavy metal ions i s clearly demonstrated by these calculations. The ratio of the free ion activity coefficients for Cu, Zn and Pb i n river and seawaters i s 2.5 to 3.2, while the value for the total activity coefficients i s 0.01 to 0.2. The cadium calculations do not show these effects since the y_ i n seawater determined by using the mean salt method from Y+(CaCl2) i s quite low (0.012). This i s due to the strong interactions between C d and CI" ions. If the y for Cd i n seawater had been e s t i mated from (equation 54) ( y = 0.34 (32)), the results would have been similar [y (River)/ Y (SW) = 2.4 and y (River)/ Y (SW) = 0.9] to the ratios for Cu, Zn and Pb. These results point out the importance of using the same methods to determine y at both low and high concentrations,if one i s going to compare values of y^ or ionic equilibria i n fresh and saline waters. A l though the mean salt method yields more reliable values for y^, at high concentrations, i t cannot easily be used at low concentrations (below 0.1 m) since tabulations of experimental data are not available. These differences occur, however, only for the few metals that form complexes with CI" ions. Since organic ligands of unknown concentrations present i n river waters could also complex these heavy metals, these calculations must be considered as a f i r s t approximation. The calculations do show, however, that large changes i n the state of metal ions can occur at the interface between rivers and seawaters. Further work i s necessary to examine how the state of ionic solutes influences chemical processes (such as s o l u b i l i t y and ion-exchange) that occur i n estuaries. 2 +

F

F

p

T

T

p


2.

§

a*

3

O

§'

K

to

I


52

MARINE CHEMISTRY

Acknowled gemen t The author wishes to acknowledge the support of the Office of Naval Research (Contract ONR - N00014-75-C-0173) and the oceanographic branch of the National Science Foundation (GA-40532) for this study. The author also wishes to thank Mr. Peter Chetirkin for preparing the Figures.

Abstract In recent years a great deal of progress has been made in developing models to examine the physical chemistry of multicomponent electrolyte solutions like seawater. These models have been used to examine the physical chemical properties of seawater and the state of ionic solutes in seawater. In the present paper these models will be briefl The physical chemical properties of estuaries have been estimated by mixing river water with seawater and assuming that the excess properties of the resulting mixture are equal to zero. These calculations demonstrate that at the same total solid concentration the physical chemical properties of estuaries are equal to those of seawater diluted with pure water. The state of metal ions in estuaries have also been examined by using the ion pairing model for ionic interactions. Literature Cited (1) Friedman, H. L., J. Chem. Phys., (1960), 32, 1134. (2) Harned, H. S., Robinson, R. S., "Multicomponent Electrolyte Solutions", Pergamon, Oxford (1968). (3) Scatchard, G., J. Amer. Chem. Soc., (1968), 90, 3124. (4) Wood, R. H., Reilly, P. J., Ann. Rev. Phys. Chem., (1970), 21, 287. (5) Millero, F. J., in "Biophysical Properties of Skin", H. R. Elden, ed., Wiley, New York (1971), p. 329. (6) Scatchard, G., J. Amer. Chem. Soc., (1969), 91, 2410. (7) Anderson, H. L., Wood, R. H., in "Water", F. Franks, ed., Plenum, New York (1974), p. 119. (8) Millero, F. J., in "The Sea" Vol. 5, E. D. Goldberg, ed., Wiley, New York (1974), p. 3. (9) Millero, F. J., Ann. Rev. Earth Planet. Sci., (1974), 2, 101. (10) Lepple, F. K., Millero, F. J., Deep Sea Res., (1971), 18, 1233. (11) Millero, F. J., Deep Sea Res., (1973), 20, 101. (12) Millero, F. J., J. Soln. Chem., (1973), 2, 1. (13) Millero, F. J., Lepple, F. K., Mar. Chem., (1973), 1, 89. (14) Millero, F. J., Perron, G., Desnoyers, J. E., J. Geophys. Res., (1973), 78, 4499.


MiLLERO


53

(15) Millero, F. J., in "Structure of Water and Aqueous Solutions", W. Α. P. Luck, ed., Verlag Chemie, Germany (1973), p. 513. (16) Emmet, R. T., Millero, F. J., J. Geophys. Res., (1974), 79, 3463. (17) Millero, F. J., Naval Rev., (1974), 27, 40. (18) Leung, W. Η., Millero, F. J., J. Chem. Thermodyn., (1975), in press. (19) Millero, F. J., Duer, W., Oglesby, Β., Leung, W. H., J. Soln. Chem., (1975), submitted. (20) Robinson, R. Α., Wood, R. H., J. Soln. Chem., (1972), 1, 481. (21) Whitfield, Μ., Deep Sea Res., (1974), 21, 57. (22) Sillen, L. G., in "Oceanography", M. Sears, éd., A.A.A.S., Washington, D. C., (1961), p. 549. (23) Garrels, R. Μ., Thompson 260, 57. (24) Rester, D. R., Pytkowicz, R. M., Limnol. Oceanogr., (1969), 14, 686. (25) Pytkowicz, R. M., Rester, D. R., Amer. J. Sci., (1969), 267, 217. (26) Lafon, G. Μ., Ph.D. Thesis, Northwestern University, Evanston, Illinois (1969). (27) Rester, D. R., Pytkowicz, R. Μ., Geochim. Cosmochim. Acta, (1970), 34, 1039. (28) Rester, D. R., Byrne, R. Η., Jr., "Ferromanganese Deposits on the Ocean Floor", Lamont, New York (1972), p. 107. (29) Atkinson, G., Dayhoff, M. O., Ebdon, D. W., in "Marine Electrochemistry", J. B. Berkowitz, et.al., ed., The Electrochem. Soc. Inc., Princeton, (1973), p. 124. (30) Morel, F., Morgan, J., Environ. Sci. Tech., (1972), 6,, 58. (31) Dyrssen, D., Wedborg, Μ., in "The Sea" Vol. 5, E. D. Goldberg, ed., Wiley, New York (1974), p. 181. (32) Zirino, Α., Yamamoto, S., Limnol. Oceanogr., (1972), 17, 661. (33) Stumm, W., Brauner, P. Α., in "Chemical Oceanography" Vol. 1, (2nd Ed.), J. P. Riley and G. Skirrow, eds., Academic Press, New York (1975), in press. (34) Millero, F. J., Limnol. Oceanogr., (1969), 14, 376. (35) Millero, F. J., Geochim. Cosmochim. Acta, (1971), 35, 1089. (36) Millero, F. J., Berner, R. Α., Geochim. Cosmochim. Acta, (1972), 36, 92. (37) Millero, F. J., in "The Sea" Vol. 6, E. D. Goldberg, ed., Wiley, New York (1975). (38) Leyendekkers, J. V., Mar. Chem., (1972), 1, 75. (39) Whitfield, Μ., Mar. Chem., (1973), 1, 251. (40) Young, T. F., Rec. Chem. Progr., (1951), 12, 81. (41) Young, T. F., Smith, M. B., J. Phys. Chem., (1954), 58, 716. (42) Wood, R. H., Anderson, H. L., J. Phys. Chem., (1966), 70, 1877.


54

MARINE CHEMISTRY

(43) Reilly, P. J., Wood, R. H., J. Phys. Chem., (1969), 73, 4292. (44) Reilly, P. J., Wood, R. H., Robinson, R. A., J. Phys. Chem. (1971), 75, 1305. (45) Ward, G. K., Millero, F. J., J. Soln. Chem., (1974), 3, 431. (46) Millero, F. J., Earth Planet. Sci. Letters, (1975), in press. (47) Millero, F. J., Lawson, D. R., J. Geophys. Res., (1975), submitted. (48) Millero, F. J., Chem. Rev., (1971), 71, 147. (49) Millero, F. J., in "Water and Aqueous Solutions", R. H. Home, ed., Wiley, New York (1972), p. 519. (50) Millero, F. J., Gonzalez, A., J. Chem. Eng. Data, (1975), to be submitted. (51) Millero, F. J., i Wiley, New York (1975) , in press. (52) Millero, F. J., Gonzalez, A., Ward, G. K., J. Mar. Res., (1975), submitted. (53) Guggenheim, E. A., Phil. Mag., (1935), 19, 588. (54) Scatchard, G., Rush, R. M., Johnson, J. S., J. Phys. Chem., (1970), 74, 3786. (55) Lewis, G. N., Randall, M., "Thermodynamics", (2nd Ed.), revised by K. S. Pitzer and F. Brewer, McGraw-Hill, New York (1961). (56) Harned, H. S., Owen, B. B., "The Physical Chemistry of Electrolyte Solutions", ACS Mono. Ser. No. 137, Reinhold, New York (1958). (57) Robinson, R. A., Stokes, R. H., "Electrolyte Solutions", Butterworths, London (1959). (58) Pitzer, K. S., J. Phys. Chem., (1973), 77, 268. (59) Whitfield, M., personal communication, (1975). (60) Elgquist, B., Wedborg, M., Mar. Chem., (1974), 2, 1. (61) Millero, F. J., Thallasia Yugoslavia, (1975), in press. (62) Watson, M. W., Wood, R. H., Millero, F. J., in this book. (63) Pritchard, D. W., "Estuaries", A.A.A.S. Pub. 83, Washington D. C., (1967), p. 3. (64) Livingstone, D. A., in "Data of Geochemistry", M. Fleisher, ed., Geol. Sur. Prof. Paper 440-G, p. 641. (65) Harned, H. S., Scholes, S. R., Jr., J. Amer. Chem. Soc., (1941), 63, 1706. (66) Chatterjee, B., J. Indian Chem. Soc., (1939), 14, 589. (67) Kell, G. S., J. Chem. Eng. Data, (1967), 12, 66. (68) Brewer, P., Bradshaw, A., J. Mar. Res., (1975), in press. (69) Cox, R. A., McCartney, M. J., Culkin, R., Deep Sea Res., (1970), 17, 679. (70) Kremling, K., Deep Sea Res., (1972), 19, 377. (71) Kremling, K., Kieler Meeresf., (1972), 28, 99. (72) Knudsen, M., "Hydrographische Tabellen", G.E.C., Grod., Copenhagen (1901).


2.

MILLERO


55

(73) Lyman, J., Fleming, R. H., J. Mar. Res., (1940), 3, 134. (74) UNESCO, Second Report on Joint Panel on Oceanography Tables and Standards UNESCO Tech. Rept., Mar. Sci. No. 4, (1966). (75) Thomas, B. D., Thompson, T. G., Utterback, C. L., J. Cons. Int. Explor. Mer., (1934), 9, 28.


3 Redox Reactions and Solution Complexes of Iron in Marine Systems DANA R. KESTER, ROBERT H. BYRNE, JR., and YU-JEAN LIANG Graduate School of Oceanography, University of Rhode Island, Kingston, R.I. 02881

The chemistry of iro i l ha considerabl effect on a variety of unique role in many biological systems due to its abi1ity to form porphyrin molecules which participate in biochemical oxidationreduction react ions. Changes in the oxidation state of iron in response to environmental changes in redox potential is a signif icant factor for geochemical processes such as the formation of pyrite ores and ferro-manganese nodules. The chemical behavior of iron in natural waters is also important because of its prev alent use in structural materials and its subsequent deterioration through corrosion reactions. The tendency of iron to form colloidal and part iculate phases provides a mechanism for the remova1 of dissolved trace elements from natural waters by ad sorption and coprecipitation. Due to this diverse range of chemical processes, it is important to establish a reliable under standing of the redox reactions of iron in marine waters. Analytical measurements of the concentration of iron in natural waters provides a basis for evaluating the significance of this element in various chemical systems. The distinction between dissolved and particulate iron has general1y been made on the basis of filtration using a 0.5 μm pore size filter. This procedure leads to an operationally defined separation of iron into soluble and sol id phases which can be difficult to relate to chemically defined forms such as aqueous ions, solution complexes, and colloidal part icles. 11 is important for this reason to qual? fy analyt ical observat ions accord ing to the separat ion techn iques employed. Table I provides a brief example of the concentrations of iron found in some natural waters. These results do not show the var iabi1ity which occurs in the amount of i ron in natural waters, but they represent the magn itudes which are encountered and they suggest the significance of a remova1 mechan ism for i ron as waters pass from fresh to estuarine to oceanic environments. A second step in def in ing the chemica1 processes involving iron is to distinguish between Fe(ll) and Fe(lll) and to deter56 In Marine Chemistry in the Coastal Environment; Church, T.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.

3.

KESTER ET AL.

Table I .

Iron in Marine Systems

Concentrations

Environment

o f iron

i n some n a t u r a l

waters.

Form

Reference

Iron (mol/kg)

River

1.2 x 1 0 "

Estuarine

5 x 10~

Estuarine (l°/oo S a l i n i t y )

3 x 10"

Estuarine (20%o Salinity)

6 x 1(T

Oceanic

2 x 10"

Oceanic

3 x 10~

57

5

D i s s o l v e d and part i c u l a t e not s p e c i f i e d

(1)

6

Particulate

(2)

6

Dissolved

(3)

Dissolved

(3)

8

Dissolved

(4)

9

Particulate

(5)

m i n e t h e t e n d e n c y o f t h e s e two o x i d a t i o n s t a t e s t o f o r m s o l u t i o n c o m p l e x e s and s o l i d p h a s e s . A t t h e p r e s e n t t i m e t e c h n i q u e s do not e x i s t w h i c h c a n r e v e a l t h e s p e c i f i c c h e m i c a l f o r m s i n a q u e o u s s a m p l e s c o n t a i n i n g l e s s t h a n 10*" m o l / k g i r o n . It i s therefore necessary t o pursue a l e s s d i r e c t approach i n which a chemical model f o r i r o n i n n a t u r a l w a t e r s i s d e v e l o p e d f r o m t h e r m o d y n a m i c and k i n e t i c i n f o r m a t i o n . Some o f t h e g e n e r a l c h a r a c t e r i s t i c s o f c h e m i c a l m o d e l s and t h e i r r e l a t i o n s h i p t o n a t u r a l s y s t e m s w e r e c o n s i d e r e d by Morgan ( 6 ) . Previous considerations o f iron c h e m i s t r y i n m a r i n e s y s t e m s have e x a m i n e d t h e i m p o r t a n c e o f h y d r o x i d e , p h o s p h a t e , and o r g a n i c 1 i g a n d s ( 7 - 1 3 ) . In t h i s p a p e r we w i l l i n c o r p o r a t e d a t a r e c e n t l y o b t a i n e d i n o u r l a b o r a t o r y into a c o n s i d e r a t i o n o f iron i n marine waters g i v i n g p a r t i c u l a r a t t e n t i o n t o t h e e f f e c t s o f s a l i n i t y a n d pH. I t i s p o s s i b l e t o i d e n t i f y f r o m t h i s model t h e most s i g n i f i c a n t f o r m s and r e a c t i o n s o f i r o n , a n d t e c h n i q u e s may t h e n be d e v i s e d t o c h a r a c t e r i z e t h e s e c h e m i c a l s y s t e m s u n d e r n a t u r a l c o n d i t i o n s . A c h e m i c a l model i s l i m i t e d by i t s i n a b i l i t y t o a c c o u n t f o r t h e e f f e c t s o f b i o c h e m i c a l p r o c e s s e s on t h e c h e m i s t r y o f a c o n s t i t u e n t s u c h a s i r o n . N e v e r t h e l e s s , d e v i a t i o n s between t h e p r e d i c t i o n s f r o m c h e m i c a l m o d e l s and t h e e n v i r o n m e n t a l o b s e r v a t i o n s c a n i n d i c a t e t h e e x i s t ence o f a d d i t i o n a l f a c t o r s which r e q u i r e c o n s i d e r a t i o n . T h i s p a p e r p r e s e n t s a c h e m i c a l model f o r i r o n i n m a r i n e s y s t e m s based on t h e r m o d y n a m i c and k i n e t i c i n f o r m a t i o n . Emphasis w i l l be p l a c e d on t h e r e d o x r e a c t i o n s o f i r o n b e c a u s e o f t h e i r 6


58

MARINE CHEMISTRY

1

unique importance i n t h i s metal s e n v i ronmental c h e m i s t r y . An Eh-pH d iagram ( F i g u r e 1) p r o v i d e s a u s e f u l o r i e n t a t i o n f o r t h e m a t e r i a l t o be p r e s e n t e d . The two b r o k e n 1 i n e s d e l i n e a t e t h e s t a b i 1 i t y r a n g e f o r w a t e r m o l e c u l e s r e l a t i v e t o o x y g e n and hydrogen g a s e s ; a l 1 s t a b l e aqueous systems f a l l w i t h i n t h e s e bounds. The r e d o x p o t e n t i a l (Eh) o f mar i n e s y s t e m s a p p e a r s t o be c o n t r o l l e d by e i t h e r o x y g e n o r s u l f i d e . T h e r m o d y n a m i c a l 1 y, t h e o x y g e n - w a t e r r e a c t i o n s h o u l d c o n t r o l t h e Eh o f a e r a t e d s y s t e m s ( 1 i n e ABC i n F i g u r e 1 ) , but due t o k i n e t i c f a c t o r s i t i s p o s s i b l e t h a t t h e o x y g e n - h y d r o g e n p e r o x i d e r e a c t i o n r e g u l a t e s t h e Eh i n t h e s e s y s t e m s ( 1 4 , 15)» F o r mar i n e e n v i r o n m e n t s d e v o i d o f o x y g e n t h e s u l f a t e - s u l f i d e r e a c t i o n ( 1 i n e DEF i n F i g u r e 1) c o n t r o l s t h e Eh. A c h e m i c a l model f o r f e r r o u s i r o n wi11 be d e v e l o p e d w h i c h a p p l i e s a l o n g 1 i n e DEF. A s i m i l a r model f o r f e r r i c i r o n a p p l i c a b l e t o 1 i n e ABC wi11 wi1 s i b l e t o examine t h e redo t i o n s t a t e s , and f i n a l l y oxygenatio n a t u r a l w a t e r s wi11 be c o n s i d e r e d . Solution E q u i 1 i b r i a of Ferrous

Ions

The f i r s t s t e p i n f o r m u l a t i n g a c h e m i c a l model i n n a t u r a l w a t e r s i s t o c o n s i d e r t h e c o m p o s i t i o n o f t h e mediurn and t h e t e n d e n c y f o r t h e s e components t o f o r m m e t a l c o m p l e x e s . T a b l e I I 1 i s t s the m o l a l i t i e s o f the major const i t u e n t s i n r i v e r water ( 0 , o c e a n w a t e r ( 1 6 , 17) and m i x t u r e s o f t h e s e two w a t e r s . This i n f o r m a t i o n may be c o m b i n e d w i t h d a t a on t h e f o r m a t i o n o f s o l u t i o n c o m p l e x e s ( 1 8 , 19) t o o b t a i n a c h e m i c a l model f o r a c o n s t i t uent. The l a c k o f k n o w l e d g e a b o u t t h e o r g a n i c c o n s t i t u e n t s i n mar i n e w a t e r s and o f t h e i r a b i 1 i t y t o f o r m i r o n - o r g a n i c c o m p l e x e s i s a 1 i m i t ing f a c t o r i n d e v e l o p i n g a quant i t a t i v e model. One approach t o t h i s problem i s t o cons i d e r the inorgan ic s p e c i a t ion o f i r o n and t h e n a s s e s s t h e p o s s i b l e s i g n i f i c a n c e o f o r g a n i c 1 i g a n d s r e l a t i v e t o t h e i n o r g a n i c o n e s . T h e r e a r e two a r e a s i n which t h e p r e s e n t knowledge o f i n o r g a n i c i r o n complexes i s i n adequate f o r marine systems: the p o s s i b l e format ion of b i c a r b o n a t e , c a r b o n a t e , and s u l f i d e c o m p l e x e s c a n n o t be i n c o r p o r a t e d i n t o t h e model w i t h e x i s t i n g d a t a ; and t h e p o s s i b l e s i g n i f i c a n c e o f m i x e d 1 i g a n d c o m p l e x e s has n o t been e s t a b l i s h e d . The r o l e o f m i x e d 1 i g a n d c o m p l e x e s s u c h a s c h l o r o - h y d r o x y s p e c i e s i s a chemi c a l problem o f s p e c i a l importance t o multicomponent n a t u r a l w a t e r s w h i c h c h e m i s t s s t u d y i n g s i n g l e s a l t s o l u t i o n s have a v o i d e d . Some c o n s i d e r a t i o n s have i n d i c a t e d t h a t m i x e d 1 i g a n d c o m p l e x e s may be i m p o r t a n t f o r c o p p e r , z i n c , and m e r c u r y i n s e a w a t e r ( 2 0 ) . A c h e m i c a l model f o r i r o n c a n be d e v e l o p e d w i t h i n t h e s e 1 i m i t a tions. S t a b i 1 i t y c o n s t a n t s f o r h y d r o x i d e , c h l o r i d e , and s u l f a t e c o m p l e x e s o f f e r r o u s i r o n were s e l e c t e d i n t h e f o l l o w i n g manner. T h e s e e q u i 1 i b r i u m c o n s t a n t s have been measured i n a v a r i e t y o f i o n i c med i a s u c h a s sod i urn p e r c h l o r a t e s o l u t i o n s w i t h i o n i c


3.

KESTER ET AL.

Table

II.

59


M o l a l i t y o f c o n s t i t u e n t s and i o n i c s t r e n g t h ( i ) parameters i n m i x t u r e s o f s u r f a c e o c e a n i c seawater and w o r l d a v e r a g e r i v e r w a t e r (RW).

Salinity Constituent

Na

+

Mg

2 +

Ca

2 +

K

RW

Woo

IOV00

20°/oo

35°/oo

0.00027

0.05426

0.13731

0.27574

0.48614

0.00017

0.00623

0.01556

0.03110

0.05473

0.00037

0.00151

0.00327

0.00620

0.01065

0.00006

+

c r

0.0106

0.00022 2

SOi, -

0.00011

0.00335

0.00833

0.01664

0.02926

HCO3-

0.00096

0.00113

0.00139

0.00182

0.00247

F"

0.00001

0.00002

0.00003

0.00004

0.00007

I

0.0021

0.0820

0.2051

0.4102

0.7218

0.0434

0.2226

0.3H7

0.3904

0.4593

/F/(i

+ /i)

s t r e n g t h s ( i ) between 0.1 a n d 3.0 m o l a l ( 1 8 , 1 9 ) * In some c a s e s t h e s e e q u i l i b r i u m c o n s t a n t s were e v a l u a t e d a t i n f i n i t e d i l u t i o n or zero ionic strength. A plot o f the logarithm o f the s t a b i l i t y c o n s t a n t f o r e a c h c o m p l e x v e r s u s / f / ( 1 + / i ) was c o n s t r u c t e d i n o r d e r t o examine t h e c o n s i s t e n c y o f t h e v a r i o u s v a l u e s and t o o b t a i n t h e i r i o n i c s t r e n g t h d e p e n d e n c e . The f u n c t i o n a l f o r m /T/(1 + / i ) p r o v i d e s a c o n v e n i e n t means o f i n t e r p o l a t i n g between d i f f e r e n t i o n i c s t r e n g t h s and o f e x t r a p o l a t i n g d a t a t o i n f i n i t e d i l u t i o n (21_, 2 2 ) . The r e s u l t i n g s t a b i l i t y c o n s t a n t s a r e summarized i n T a b l e III. The v a l u e s w h i c h have been r e p o r t e d f o r l o g *&2(^ (^)l) range from -17.6 t o -5.85 f o r 0 < I 1 1. S u c h w i d e d i s c r e p a n c i e s may o c c u r between d i f f e r e n t s t u d i e s when i n o n e c a s e t h e f o r m a t i o n o f r e l a t e d complexes such a s F e 0 H i s taken i n t o a c count w h i l e i n another case these complexes a r e not c o n s i d e r e d and t h e i r e f f e c t s t h u s become a s s o c i a t e d w i t h t h e F e ( 0 H ) 2 ° . A l t e r n a t i v e l y , m e a s u r e m e n t s o f t h i s c o n s t a n t may be p a r t i c u l a r l y d i f f i c u l t due t o t h e tendency o f F e ( l l ) t o o x i d i z e t o F e ( l l l ) w h i c h u n d e r g o e s much more e x t e n s i v e h y d r o l y s i s . The s y s t e m a t i c s e l e c t i o n o f f r e e e n e r g y d a t a by L a n g m u i r (23) p r o v i d e s a c o n s i s t e n t s e t o f v a l u e s f o r hydroxy s p e c i e s a t i n f i n i t e d i l u t i o n . Other d a t a f o r * & 2 ( F e ( 0 H ) 2 ° ) would r e q u i r e t h a t t h i s c o n s t a n t i n c r e a s e by s i x t o t w e l v e o r d e r s o f m a g n i t u d e between 1 = 0 a n d e

+


ACS

In

Marine Symposium

Chemistry Series;

in American

the Chemical

+

+

2

F e

-

S°«t°)

2

BitHSO^ ) =

M

2

B (FeCl °) =

e!(FeCl ) -

2

+

[HSO^-]

+

[Fe2 ] [SO^-]

[FeSO^ ]

0

[Fe2+][Cl-]2

2

[FeC1 °]

[Fe2+][C1"]

+

[Fe2 ]

2

+

[Fe(0H) °][H ]2

[FeCl ]

*e (Fe(0H) °) -

*Bl(FeOH ) =

[FeOH ] [H+]

+

Constant

Table I I I . S t a b i l i t y constants selected waters.

2

x

- -17.6

= - 8 . 3 0 + 3-58

2

- 0.21 - 0.29 / T / ( l + / i )

l o g B i = 1-99 - 1.06 v T / ( l + / i )

l o g @i = 2.12 - 2.1»7 / F / 0 + / i )

tog B

+ /i)

vT/(l + / i )

l o g 6 j = 0.79 - 0.73 / f / ( l

log *$

log *e

Value

2k)

(27-30)

(26)

(25) —

(25) —

(23) —

(23,

Reference

f o r the c a l c u l a t i o n o f f e r r o u s complexes i n n a t u r a l


KESTER ET AL.

3.

61

1, w h i c h i s t o t a l l y c o n t r a r y t o t h e I o n i c s t r e n g t h d e p e n d e n c e w h i c h c a n be a s s o c i a t e d w i t h t h e v a r i o u s s p e c i e s . For example:

9

* B ( F e ( 0 H ) ° , I - 0.7) 2

2

Fe

2 +

- * B ( F e ( 0 H ) ° , I - 0) 2

(1)

2

9

Fe(0H) °

9

2

H

+

where t h e g f a c t o r s r e p r e s e n t t h e f r e e a c t i v i t y c o e f f i c i e n t s o f each s p e c i e s a t I = 0.7. Even t h o u g h a c c u r a t e v a l u e s c a n n o t be a s s i g n e d t o i n d i v i d u a l i o n i c a c t i v i t y c o e f f i c i e n t s , l i m i t s c a n be p l a c e d o n t h e i r v a r i a t i o n w i t h I s u c h t h a t t h e q u o t i e n t o f g - v a l u e s i n e q u a t i o n (1) c a n n o t be e x p e c t e d t o v a r y by s i x o r d e r s o f m a g n i t u d e between 1 * 0 and 1. In f a c t r u l e o f thumb" v a l u e s f o r t h e s *3 (Fe(0H) °) should b I; t h i s r a t i o n a l e y i e l d e d the value f o r t h i s constant selected i n T a b l e I I I . The e q u i l i b r i u m c o n s t a n t s f o r f e r r o u s c h l o r i d e and s u l f a t e c o m p l e x e s w e r e n o t a v a i l a b l e o v e r a r a n g e o f i o n i c s t r e n g t h s , so t h e i r i o n i c s t r e n g t h dependences were e s t i m a t e d a l s o f r o m a r e l a t i o n s h i p a n a l o g o u s t o e q u a t i o n (1) and f r o m i n f o r m a t i o n on t h e t y p i c a l b e h a v i o r o f a c t i v i t y c o e f f i c i e n t v a r i a t i o n s between 1 = 0 a n d 1 ( 3 1 ) . The c a l c u l a t i o n o f f e r r o u s i r o n s p e c i a t i o n i s based o n t h e expression f o r total Fe(ll): M

2

2

T(Fe(ll))

= [Fe ] 2 +

+

0

+ [ F e C l ] + [FeCl °] + [FeSOi, ]

+

2

+

[ F e 0 H ] + [Fe(0H) °]

(2)

2

Due t o t h e l o w c o n c e n t r a t i o n o f i r o n i n n a t u r a l w a t e r s i t i s not n e c e s s a r y t o c o n s i d e r p o l y n u c l e a r c o m p l e x e s o f i r o n . The f r a c t i o n o f F e ( l l ) w h i c h i s u n c o m p l e x e d may be d e r i v e d f r o m e q u a t i o n (2) w i t h t h e d e f i n i t i o n o f s t a b i l i t y c o n s t a n t s c o n tained i n Table I I I : [Fe

2 +

]/T(Fe(ll))

= 1/(1 + B ( F e C l ) [ C I " ] + B ( F e C l ° ) [ C l ~ ] +

x

2

2

2

+ 3 i ( F e S 0 i ) [ S 0 i " ] + * 3 i ( F e 0 H ) / [ H ] + * B ( F e ( 0 H ) ° ) / [ H ] ) (3) o

2

f

+

+

+

+

2

2

2

and s i m i l a r l y t h e f r a c t i o n o f F e ( l l ) w h i c h o c c u r s a s t h e g e n e r i c s p e c i e s F e L i s g i v e n by: n

[FeL ]/T(Fe(ll))

= B (FeL )[L] /(l + Bi(FeCl )[CI"] + n

n

3 (FeCl °)[Cl"] 2

n

+

n

+ BitFeSOi/HSOi, -]

2

2

2

+

+ *Bi (Fe0H )/[H ] + +

+

(k)

2

*& (Fe(0H) °)/[H ] ) 2

The

2

square brackets designate

the m o l a l i t y o f the enclosed


MARINE CHEMISTRY

62

s p e c i e s ( e . g . , u n a s s o c i a t e d o r f r e e 1 i g a n d s ) and t h e s p e c i e s i n parentheses f o l l o w i n g each beta i d e n t i f i e s the p a r t i c u l a r s t a b i l i t y c o n s t a n t a s d e f i n e d i n T a b l e III. The m o l a l i t y o f f r e e 1 i g a n d s was based on an i o n - p a i r i n g model f o r s e a w a t e r i n w h i c h t h e f r e e c h l o r i d e was assumed t o be equal t o the t o t a l c h l o r i d e ( 3 2 ) . The f r e e s u l f a t e was 33% o f t h e t o t a l s u l f a t e a t 3 5 ° / o o s a l i n i t y ( 3 2 ) and t h i s p e r c e n t a g e i n c r e a s e d t o 100% i n r i v e r w a t e r i n p r o p o r t i o n t o t h e d e c r e a s e in s a l I n i t y . The d e c r e a s e i n [SOi* *] a t l o w pH due t o t h e f o r m a t i o n o f HSOi*" was a c c o u n t e d f o r i n t h e c a l c u l a t i o n s . For t h e p u r p o s e o f t h i s c h e m i c a l model o f i r o n a pH s c a l e was u s e d s u c h t h a t pH - - l o g [ H ] so t h a t t h e pH y i e l d s t h e f r e e H directly. T h i s pH s c a l e has a number o f a d v a n t a g e s f o r t r e a t i n g s e a w a t e r e q u i l i b r i a , and i t d e p a r t s f r o m t h e c o n v e n t i o n a l N a t i o n a l Bureau o f S t a n d a r d ( 3 3 , 3J0 . 2

+

+

The r e s u l t s o f t h e s r a n g e o f 3.0 t o 10.0 f o r r i v e r w a t e r , 4 ° / o s a l i n i t y , and 3 5 ° / o o s a l i n i t y s e a w a t e r a r e shown i n F i g u r e 2 . In r i v e r w a t e r b e l o w pH 7 t h e F e ( l l ) e x i s t s p r i m a r i l y a s F e w h e r e a s between pH 7 and 10 t h e h y d r o x i d e c o m p l e x e s o f F e ( l l ) become s i g n i f i c a n t . At 3 5 ° / o o s a l i n i t y c h l o r o - c o m p l e x e s a r e a major form o f F e ( l l ) up t o a pH o f 7 , beyond w h i c h t h e F e 0 H s p e c i e s i s t h e predomi n a n t f o r m . The e f f e c t o f s a l i n i t y on t h e F e ( l l ) s p e c i e s d i s t r i b u t i o n a t pH 8 i s i l l u s t r a t e d i n F i g u r e 3 . T h e r e a r e two f a c t o r s i n v o l v e d i n t h e e f f e c t o f s a l i n i t y on F e ( l l ) : one i s t h e c h a n g e i n c o n c e n t r a t i o n o f t h e c h l o r i d e and s u l f a t e c o m p l e x i n g 1 i g a n d s ; t h e second i s t h e change i n s t a b i 1 i t y c o n s t a n t s w i t h ion i c s t r e n g t h . T a b l e IV p r o v i d e s a more c o n v e n i e n t q u a n t i t a t i v e r e p r e s e n t a t i o n o f t h e n e t e f f e c t o f t h e s e two f a c t o r s a t pH 7 and pH 8. T h e s e r e s u l t s p r o v i d e an i n o r g a n i c c h e m i c a l model f o r i r o n w h i c h i s a p p l i c a b l e t o 1 i n e DEF i n F i g u r e 1 a t various s a l i n i t i e s . pH

0

2 +

+

It i s p o s s i b l e t o e v a l u a t e the p o t e n t i a l s i g n i f i c a n c e o f o r g a n i c 1 i g a n d s i n c o m p l e x i n g f e r r o u s i r o n . Mar i n e w a t e r s t y p i c a l l y c o n t a i n a maximum o f 1 - 5 mg o f d i s s o l v e d o r g a n i c c a r bon (DOC) p e r 1 i t e r (]_, 35_> 3 6 ) • A s s u m i n g a p p r o x i m a t e l y one f u n c t ional group c a p a b l e o f complexing F e p e r s i x c a r b o n atoms and an a v e r a g e DOC c o n c e n t r a t i o n o f 2 mg/1 y i e l d s an e f f e c t i v e c o n c e n t r a t i o n o f 2.8 x 1 0 " m o l a l f o r t h e o r g a n i c 1 i g a n d s . In o r d e r f o r t h e s e 1 i g a n d s t o c o m p l e x 20% o f t h e F e ( l l ) i n 3 5 ° / o o s a l i n i t y s e a w a t e r a t pH 8.0 t h e y must have a s t a b i 1 i t y c o n s t a n t on t h e o r d e r o f 2 . 2 x 1 0 w h e r e a s i n r i v e r w a t e r a t pH 7 an F e ( l l ) - o r g a n i c s t a b i 1 i t y c o n s t a n t o f 9 . 6 x 1 0 w o u l d be s u f f i c i e n t t o c o m p l e x 20% o f t h e F e ( l l ) . S t a b i 1 i t y constants f o r the format ion o f F e complexes w i t h t h e f u n c t i o n a l groups o f amino a c i d s , a c e t a t e , c i t r a t e , and q u i n o l i n e c a r b o x y l a t e a r e g e n e r a l 1y in t h e range 1-6 x 1 0 (18, 19) w h i c h i n d i c a t e s t h a t t h e s e t y p e s o f 1 i g a n d s c o u l d n o t compete w i t h t h e i n o r g a n i c o n e s f o r F e ( l l ) i n s e a w a t e r , but t h e y c o u l d be s i g n i f i c a n t i n r i v e r w a t e r . A second f a c t o r t o cons i d e r i n e v a l u a t i n g t h e e f f e c t i v e n e s s 2 +

5

5

3

2 +

3



3. KESTER ET AL.

Figure 1. Eh—pH diagram for natural waters. Line ABC shows the relationship between Eh and pH when the 0 /H 0 controls the Eh. Line DEF is the relationship for the SOf~/S ~ reaction in marine systems. The intermediate line shows control by the 0 /H 0 reaction. 2

2

2

2

2

2

P CO

100

.^ &v

—^—

4

FeC! LU CD
6 0 ) . T a n n i c a c i d , g a l l i c a c i d , and p y r o g a l l o l p r e v e n t e d t h e o x y g e n a t i o n o f Fe(ll). O t h e r s u b s t a n c e s s u c h as g l u t a m i c a c i d , t a r t a r i c a c i d , and g l u t a m i n e p r o d u c e d a s l o w e r r a t e o f o x y g e n a t i o n t h a n was o b s e r v e d i n NaHC03 s o l u t i o n s a t t h e same pH = 6 . 3 . C i t r i c acid p r o d u c e d an i n i t i a l r a t e w h i c h was g r e a t e r t h a n t h e one i n NaHC0 . Thus d i f f e r e n t o r g a n i c m a t e r i a l s can i n h i b i t , r e t a r d , o r a c c e l e r a t e t h e r a t e o f f e r r o u s o x y g e n a t i o n . T h e i s and S i n g e r (60) a l s o f o u n d t h a t l O " m o l a r c o n c e n t r a t i o n s o f numerous o r g a n i c compounds c o u l d r e d u c e 1 0 " t o 1 0 ~ m o l a r c o n c e n t r a t i o n s o f F e ( l l l ) to F e ( l l ) i n t h e presence o f d i s s o l v e d oxygen. The humic a c i d p o r t i o n o f o r g a n i c m a t e r i a l e x t r a c t e d from f r e s h waters e x h i b i t s some o f t h e same c h a r a c t e r i s t i c s w i t h F e ( l l ) and F e ( l l l ) a s t a n n i c a c i d . These r e s u l t require investigation o marine systems. Some i n i t i a l s t u d i e s o f t h e r a t e o f f e r r o u s o x y g e n a t i o n i n n a t u r a l w a t e r s have been c a r r i e d o u t i n o u r l a b o r a t o r y . Two e x p e r i m e n t a l approaches were used. A d i r e c t m o n i t o r i n g o f t h e F e ( l I I ) p r o d u c t a s a f u n c t i o n o f t i m e was p e r f o r m e d by r e c o r d i n g the a b s o r b a n c e a t 295 nm o f t h e r e a c t i o n s o l u t i o n c o n t a i n e d i n a 10 cm c e l l . A p p r o x i m a t e l y 5 x 1 0 ~ m o l e s o f F e C l was added t o the r e a c t i o n medium w h i c h had a pH between 7*9 and 8 . 3 . The i n c r e a s e i n a b s o r b a n c e a t 295 nm w i t h t i m e i s due t o t h e f o r m a t i o n o f f e r r i c h y d r o x y c o m p l e x e s and t h e s c a t t e r i n g o f l i g h t by c o l l o i d a l and p a r t i c u l a t e h y d r o u s f e r r i c o x i d e . Because t h e a t t e n u a t i o n o f l i g h t i n t e n s i t y due t o a b s o r p t i o n and s c a t t e r i n g may n o t have been d i r e c t l y p r o p o r t i o n a l t o t h e F e ( l l l ) c o n c e n t r a t i o n a s e c o n d t e c h n i q u e was used i n w h i c h s c a t t e r i n g was n o t a factor. Samples w e r e a l l o w e d t o r e a c t f o r v a r i o u s p e r i o d s o f t i m e , and t h e r e a c t i o n was quenched by t h e a d d i t i o n o f 1.1 N HClOi* t o r e d u c e t h e pH t o 2 . 5 . The UV s p e c t r u m o f t h e quenched sample was c h a r a c t e r i s t i c o f F e ( l l l ) c o m p l e x e s o v e r t h e w a v e l e n g t h r a n g e 240-400 nm. The a b s o r b a n c e a t 3 0 3 nm o f t h e quenched samples v a r i e d l i n e a r l y w i t h the f e r r i c c o n c e n t r a t i o n o v e r the r a n g e o f 1 - 8 uM. An e x a m p l e o f t h e r e s u l t s o b t a i n e d by t h e d i r e c t m o n i t o r i n g o f a b s o r b a n c e a t 295 nm i s shown i n F i g u r e 6. For the r e a c t i o n : 3

4

6

5

6

2

Fe(ll) + 0 the

pseudo f i r s t

d

[

d

Fe(lll)

2

o r d e r r a t e l a w may

6

[

H

)

]

=

k

'

{

[Fe(ll)]

be w r i t t e n

o

-

[Fe(lll)]}

(15)

where [ F e ( l l ) ] and [ F e ( l l l ) ] a r e t h e c o n c e n t r a t i o n s o f r e d u c e d and o x i d i z e d i r o n a t t i m e t and [ F e ( l l ) ] i s the i n i t i a l concent r a t i o n of ferrous iron. The r a t e p a r a m e t e r k w i l l be a c o n s t a n t o

1


74

MARINE CHEMISTRY

Figure 5. Variation in the ratio of total Fe(III) to total Fe(II) molality as a function of Eh for three natural water systems. A> Eh control by the 0 /H 0 reaction; Eh control by the 0 /H 0 reaction; the control of Eh by the SOf~/S ~ reaction. 2

2

2

2

2

2

.20 r

u < I2|QD

CC

io .081< .041-

J_ 8

12

o=[Fe(.i)]

_J_ 16 20

24

_L_ 28 32

0

-(a-x)=[Fe(ll)]^[Fe(lll)] °

3

TI M E , m i n

Figure 6. Rate of Fe(II) oxygenation in Narragansett Bay seawater at pH = 8.08. The upper curve shows the continuously recorded absorbance at 295 nm. The lower plot shows the logarithmic fit which is characteristic of a pseudofirstorder rate, the slope of which yields k'.


3.

KESTER ET AL.

75


p r o v i d e d t h a t pH and P a r e c o n s t a n t (compare e q u a t i o n (15) w i t h (10)). The p l o t o f In £ F e ( l l ) ] / ( I F e ( l l ) ] - [Fe(lll)]) versus time y i e l d s a s t r a i g h t l i n e d u r i n g the i n i t i a l p o r t i o n o f the r e a c t i o n ( e . g . , t h e f i r s t 16 min i n F i g u r e 6 ) . D e v i a t i o n s f r o m t h i s l i n e a r e o b s e r v e d o v e r l o n g e r p e r i o d s o f t i m e w h i c h may be due t o d e p a r t u r e s i n a d i r e c t p r o p o r t i o n a l i t y b e t w e e n [ F e ( l l l ) ] and a b s o r b a n c e due t o c o a g u l a t i o n and s c a t t e r i n g e f f e c t s o f t h e h y d r o u s f e r r i c o x i d e . The v a l u e o f k' was o b t a i n e d f r o m t h e i n i t i a l l i n e a r p o r t i o n of the data. T h i s r a t e p a r a m e t e r was i n d i s t i n g u i s h a b l e f r o m t h e v a l u e o b t a i n e d by t h e q u e n c h i n g t e c h n i q u e i n w h i c h s c a t t e r i n g o f t h e l i g h t was n o t a f a c t o r . The r a t e c o n s t a n t k i n e q u a t i o n (10) was c a l c u l a t e d f r o m k , pH, and P. The r e s u l t s o f o u r measurements i n n a t u r a l s e a w a t e r f r o m N a r r a g a n s e t t Bay and s u r f a c e S a r g a s s o S e a w a t e r a r e shown i n T a b l e IX a l o n g w i t h th in sodium b i c a r b o n a t e s o l u t i o n s f o r t h e c o n c e n t r a t i o n o f F e ( l l ) t o be d i m i n i s h e d by a f a c t o r o f two. T h e s e p r e l i m i n a r y r e s u l t s show t h a t t h e r a t e o f t h i s r e a c t i o n i s much s l o w e r i n n a t u r a l m a r i n e w a t e r s t h a n w o u l d be e x p e c t e d on t h e b a s i s o f measurements i n s o d i u m b i c a r b o n a t e s o l u tions. T h i s o b s e r v a t i o n c o u l d r e f l e c t the importance o f o r g a n i c m a t t e r a s p o i n t e d o u t by T h e i s and S i n g e r (60) o r o f o t h e r c o n s t i t u e n t s i n m a r i n e w a t e r s on t h e r a t e o f f e r r o u s o x y g e n a t i o n . 0

0

1

Table

IX.

The r a t e o f f e r r o u s o x y g e n a t i o n i n m a r i n e w a t e r s in sodium b i c a r b o n a t e s o l u t i o n s .

t£ a t P UT

Medium

1

- 0.209 *

Q

pH = 8

pH - 7 (min)

N a H C 0 , pH = 2 - 6

8.0

Narragansett

6 x 10

3

Bay

x 10

1 3

1 1

and

Source

(min)

4

0.04

(57)

550

5.5

T h i s work

330

3.3

T h i s work

S /oo 31.2 /oOf pH = 7 . 9 8.3 =

Sargasso S°/oo

Seawater

10 x

10

1 1

= 36.0°/oo, 8.2

pH -

a: The

units f o r k are

Summary o f

liter

Iron Reactions

2

mol"

2

atm"

1

min

i n Marine Waters

Four a s p e c t s o f the c h e m i s t r y o f

i r o n have been

considered


76

MARINE CHEMISTRY

In t h i s p a p e r . The f o r m a t Ion o f f e r r o u s s o l u t i o n c o m p l e x e s v a r i e s s i g n i f i c a n t l y w i t h s a l i n i t y and pH o v e r t h e r a n g e o f c o n d i t i o n s e n c o u n t e r e d i n c o a s t a l r e g i o n s . C o m p l e x e s o f f e r r i c i ron a r e p r i m a r ? l y h y d r o x i d e s p e c i e s w h i c h depend o n pH and w h i c h a p p e a r not t o v a r y g r e a t l y w i t h s a l i n i t y . T h e r e d o x e q u i 1 i b r i u m between F e ( l l ) and F e ( l l l ) f a v o r s t h e predominance o f F e ( l l l ) i f t h e r e d o x p o t e n t i a l i s s e t by e i t h e r t h e O2/H2O o r O2/H2O2 r e a c t i o n , but F e ( l l ) i s t h e s t a b l e o x i d a t i o n s t a t e when t h e r e d o x p o t e n t i a l i s s e t by t h e S 0 \ " V S ~ r e a c t i o n . T h e r a t e o f o x y g e n a t i o n o f F e ( l l ) i n n a t u r a l w a t e r s depends g r e a t l y on pH, and p r e l i m i n a r y d a t a i n d i c a t e that t h i s r e a c t i o n i s s l o w e r i n marine waters than i n sodiurn b i c a r b o n a t e s o l u t i o n s . Knowledge o f t h e s e t y p e s o f c h e m i c a l p r o c e s s e s under e n v i ronmental c o n d i t i o n s p r o v i d e s a b a s i s f o r p r e d i c t i n g t h e b e h a v i o r o f d i s s o l v e d i ron i n mari ne systems. This analysis o f iro where a d d i t i o n a l i n f o r m a t i o n i s needed. D a t a a r e l a c k i n g f o r e v a l u a t i n g t h e s i g n i f i c a n c e o f b i c a r b o n a t e and c a r b o n a t e s p e c i e s o f i r o n and f o r p o s s i b l e s u l f i d e s p e c i e s o f F e ( l l ) . Equi1ibrium c o n s i d e r a t i o n s i n d i c a t e t h a t i ron o r g a n i c c o m p l e x e s a r e n o t 1 i k e l y t o be s t a b l e i n m a r i n e s y s t e m s , b u t t h i s c o n c l u s i o n s h o u l d be t e s t e d by e x p e r i m e n t a l methods and i t s h o u l d be r e c o g n i z e d t h a t b i o c h e m i c a l l y s y n t h e s i z e d i r o n o r g a n i c s p e c i e s may be k i n e t i c a l l y , i f n o t t h e r m o d y n a m i c a l l y , s t a b l e . Addi t i o n a l work i s r e q u i red t o d e t e r m i ne t h e k i n e t i c s o f f e r r o u s o x y g e n a t i o n i n m a r i ne s y s t e m s . The r o l e o f d i s s o l v e d o r g a n i c m a t t e r a p p e a r s t o be o f c o n s i d e r a b l e importance. O b s e r v a t i o n s by L e w i n and Chen (61) i n d i c a t e t h e presence o f F e ( l l ) in c o a s t a l waters immediately a f t e r sampling and t h e q u a n t i t y o f F e ( l l ) d e c r e a s e s o v e r a p e r i o d o f 30-40 h o u r s upon s t o r a g e . T h e r e may be a s t e a d y s t a t e c o n c e n t r a t i o n o f F e ( l l ) i n m a r i n e w a t e r s due t o a b a l a n c e between i t s r a t e o f p r o d u c t i o n by b i o l o g i c a l s y s t e m s and i t s r a t e o f o x y g e n a t i o n t o F e ( l l l ) . The d e v e l o p m e n t o f a n a l y t i c a l t e c h n i q u e s t o d e t e r m i n e 1 0 " m o l a r c o n c e n t r a t i o n s o f o r g a n i c and i n o r g a n i c forms o f F e ( l l ) and F e ( l l l ) i n m a r i n e w a t e r s w o u l d be a g r e a t a s s e t t o f u r t h e r w o r k on t h e m a r i n e c h e m i s t r y o f i r o n . 2

2

8

Ac know1ed g emen t s We a p p r e c i a t e t h e a s s i s t a n c e o f M a r i 1 y n Ma l e y i n t h e p r e p a r a t i o n o f t h e m a n u s c r i p t . T h i s work was s u p p o r t e d by t h e O f f i c e o f Naval Research C o n t r a c t N00014-68A-0215-0003.

Literature Cited 1. Livingstone, D.A., "Data of Geochemistry, 6th edition, Chapter G," U.S. Geological Survey, Professional Paper 440-G, page G1-G64. U.S. Government Printing Office, Washington, D.C., 1963. 2. Burton, J.D. and Head, P.C., Limnology and Oceanography (1970)


3. KESTER ET AL.


77

15 (1): 164-167. 3. Boyle, E., Collier, R., Dengler, A.T., Edmond, J.M., Ng, A.C. and Stollard, R.F., Geochimica et Cosmochimica Acta (1974) 38 (11): 1719-1728. 4. Chester, R. and Stoner, J.H., Marine Chemistry (1974) 2 (1): 17-32. 5. Betzer, P.R. and Pilson, M.E.Q., Journal of Marine Research (1970) 28 (2): 251-267. 6. Morgan, J.J., "Equilibrium Concepts in Natural Water Systems" R.F. Gould, editor, pages 1-29, American Chemical Society, Washington, D.C., 1967. 7. Cooper, L.H.N., Journal of the Marine Biological Association, United Kingdom (1948) 27 (2): 314-321. 8. Schindler, P.W., "Equilibrium Concepts in Natural Water Systems," R.F 196-221, Chemical Society 9. Duursma, E.K. and Sevenhuysen, W., Netherlands Journal of Sea Research (1966) 3 (1): 95-106. 10. Hem, J.D. and Cropper W.H., "A Survey of Ferrous-Ferric Chemical Equilibria and Redox Potentials," U.S. Geological Survey, Water-Supply Paper No. 1459-A, pages 1-31, U.S. Government Printing Office, Washington, D.C., 1959. 11. Hem, J.D., Bulletin of the Geological Society of America (1972) 83 (2): 443-450. 12. Morel, F., McDuff, R.E., and Morgan, J.J., "Trace Metals and Metal-Organic Interactions in Natural Waters," P.C. Singer, editor, pages 157-200, Ann Arbor Science Publishers, Ann Arbor, Michigan, 1973. 13. Lerman, A. and Childs, C.W., "Trace Metals and Metal-Organic Interactions in Natural Waters," P.C. Singer, editor, pages 201-235, Ann Arbor Science Publishers, Ann Arbor, Michigan, 1973. 14. Breck, W.G., "The Sea: Ideas and Observations on Progress in the Study of the Sea," Vol. 5, E.D. Goldberg, editor, pages 153-179, Wiley-lnterscience, New York, 1974. 15. Parsons, R., "Dahlem Workshop on the Nature of Seawater," E.D. Goldberg, editor, Dahlem Konferenzen, Berlin, 1975, In Press. 16. Pytkowicz, R.M. and Kester, D.R., "Oceanography and Marine Biology: Annual Review," Vol. 9, H. Barnes, editor, pages 11-68, George Allen and Unwin, London, 1971. 17. Carpenter, J.H. and Manella, M.E., Journal of Geophysical Research (1973) 78 (18): 3621-3626. 18. Sillen, L.G. and Martell, A.E., "Stability Constants," Special Publication No. 17, 754 pages, The Chemical Society, London, 1964. 19. Sillen, L.G. and Martell, A.E., "Stability Constants, Supplement No. 1," Special Publication 25, 865 pages, The Chemical Society, London, 1971. 20. Dyrssen, D. and Wedborg, M., "The Sea: Ideas and Observations


78

21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40.

MARINE CHEMISTRY

on Progress in the Study of the Sea," Vol. 5, E.D. Goldberg, editor, pages 181-195, Wiley-lnterscience, New York, 1974. Marshall, W.L., Journal of Physical Chemistry (1967) 73 (11): 3584-3588. Kester, D.R., "Ion Association of Sodium, Magnesium, and Calcium with Sulfate in Aqueous Solution," Ph.D. Thesis, 116 pages, Oregon State University, Corvallis, 1969. Langmuir, D., "The Gibbs Free Energies of Substances in the System Fe-02-H20-C02 at 25°C," U.S. Geological Survey, Professional Paper 650-B, pages B180-B184, U.S. Government Printing Office, Washington, D.C., 1969. Komar, N.P., Uchenye Zapiski Khar'kov Univ. (1963) 133 (Trudy Khim 18). Olerup, H., Dissertation (1944) University of Lund (Cited by reference 18) Wel1s, C.F. and Salam, M.A., Journal of the Chemical Society (1968) No. 2, pages 308-315. Dunsmore, H.S. and Nancollas, G.H., Journal of Physical Chemistry (1964) 68 (6): 1579-1581. Marshall, W.L. and Jones, E.V., Journal of Physical Chemistry (1966) 70 (12): 4028-4040. Helgeson, H.C., Journal of Physical Chemistry (1967) 71 (10): 3121-3136. Daly, F.P., Brown, C.W., and Kester, D.R., Journal of Physical Chemistry (1972) 76 (24): 3664-3668. Kester, D.R., "The Oceans Handbook," R.A. Horne, editor, Marcel Dekker, New York, 1975, In Press. Kester, D.R. and Pytkowicz, R.M., Limnology and Oceanography (1969) 14 (5): 686-692. Bates, R.G., "Dahlem Workshop on the Nature of Seawater," E.D. Goldberg, editor, Dahlem Konferenzen, Berlin, 1975, In Press. Hansson, I., Deep-Sea Research (1973) 20 (5): 479-491. Duursma, E., "Chemical Oceanography," Vol. 1, J.P. Riley and G. Skirrow, editors, pages 433-475, Academic Press, New York, 1965. Wagner, F.S., Contributions in Marine Biology, University of Texas at Port Aransas (1969) 14: 115-153. Stumm, W. and Morgan, J.J., "Aquatic Chemistry," 583 pages, Wiley-lnterscience, New York, 1970. Stumm, W. and Brauner, P.A., "Chemical Oceanography," Vol. 1, 2nd edition, J.P. Riley and G. Skirrow, editors, Academic Press, London, 1975, In Press. Kester, D.R. and Byrne, R.H., Jr., "Ferromanganese Deposits on the Ocean Floor," D.R. Horn, editor, pages 107-116, Columbia University, Palisades, New York, 1972. Byrne, R.H., Jr., "Iron Speciation and Solubi1ity in


3. KESTER ET AL.

41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61.


79

Seawater," Ph.D. Thesis, 205 pages, University of Rhode Island, Kingston, 1974. Byrne, R.H., Jr. and Kester, D.R., "Potentiometric Determination of Ferric Hydroxide Complexes in Aqueous Solutions at 0.7 Ionic Strength," Manuscript in Preparation, 1975. Byrne, R.H., Jr. and Kester, D.R., "Determination of the Solubility of Hydrous Ferric Oxide in Seawater," Manuscript in Preparation, 1975. Kester, D.R., O'Connor, T.P., and Byrne, R.H., Jr., Thallasia Jugoslavica (1975), In Press. Bent, H.E. and French, C.L., Journal of the American Chemical Society (1941) 63:568-572. Rabinowitch, E. and Stockmayer, W.H., Journal of the American Chemical Societ (1942) 64: 335-347. Mattoo, B.N., Zeitschrif (Frankfurt) (1959) 19: 156-167. Willix, R.L.S., Transactions of the Faraday Society (1963) 59 (6): 1315-1324. Paul, A.D., Thesis (1955) University of California at Berkeley, UCRL-2926 (Cited by reference 18). Connick, R.E., Hepler, L.G., Hugus, Z.Z., Jr., Kury, J.W., Latimer, W.M., and Tsao, M., Journal of the American Chemical Society (1956) 78 (9): 1827-1829. Vanderborgh, N.E., Talanta (1963) 15 (10): 1009-1013Ellis, A . J . , Journal of the Chemical Society (1963) No. 9, 4300-4304. Hudis, J. and Wahl, A.C., Journal of the American Chemical Society (1953) 75: 4153-4158. Miller, G.R. and Kester, D.R., Marine Chemistry (1975) In Press. Lengweiller, H., Buser, W., and Feitknecht, W., Helvita Chimica Acta (1961) 44: 796-805. Stumm, W. and Lee, G.F., Industrial and Engineering Chemistry (1961) 53 (2): 143-146. George, P., Journal of the Chemical Society (1954): 4349" 4359. Singer, P.C. and Stumm, W., Science (1970) 167 (3921): 1121-1123. Goto, K., Tamura, H., and Nagayama, M., Inorganic Chemistry (1970) 9 (4): 963-964. Theis, T.L. and Singer, P.C., "Trace Metals and MetalOrganic Interactions in Natural Waters," P.C. Singer, editor, pages 303-320, Ann Arbor Science Publishers, Ann Arbor, Michigan, 1973. Theis, T.L. and Singer, P.C., Environmental Science and Technology (1974) 8 (6): 569-573. Lewin, J. and Chen, C-H., Limnology and Oceanography (1973) 18 (4): 590-596.


4 Minor Element Models in Coastal Waters P E T E R G . B R E W E R and D E R E K W . S P E N C E R Woods Hole Oceanographic Institution, Woods Hole, Mass. 02543

It is now almost twenty years since Richards (1) discussed the state of our knowledg a brief, and somewhat pungent paper he pointed out that by 1956 there had been no valid analyses of deep ocean water for Sb, Ba, Cd, Cs, Ce, Cr, Co, Ga, Ge, La, Pb, Hg, Mo, Ni, Sc, Se, Ag, T1, Th, W, Sn, V, Y and Zr; that the assumption of a single oceanic concentration level for these elements was doubtful, and that computed residence times for these elements were of limited use in assessing their oceanic chemistry. Since then a great deal of work has been carried out. Recently, one of us was obliged to review (2) what is now known of minor element concentrations in sea water. The task set was simply to review the observational data base; discussions of analytical methods, theoretical models, or calculations of chemical speciation were to be kept to a minimum. The result was disturbing, for it was soon apparent that we are still far from having an adequate set of analytical data on which to base extensive theoretical models of minor element chemical processes in the ocean (3, 4, 5). In this paper, we briefly examine what is known of some minor element concentrations in sea water. We ask what chemical processes may be controlling their distribution, and inquire as to under what circumstances these processes may be revealed through direct observation. Analytical Data It is now true that, of the list of elements given above, some reasonable estimate of the deep water concentrations may be given. A listing of these data, and the calculated residence times are given in Table I.How accurate are these data, and what may be inferred from the residence time calculation? An inspection of the recent literature shows that, of the elements listed by Richards 0), we may now be sure of the deep water abundance of Ba, Cs, Mo, Sc (6, 7, 8, 9). Of these elements, Mo and Cs exhibit essentially conservative behavior, 80 In Marine Chemistry in the Coastal Environment; Church, T.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.

Minor Element Models

4. BREWER AND SPENCER

81

though the c o n c e n t r a t i o n o f Mo may be perturbed i n anoxic systems; Sc shows a s m a l l , but s t a t i s t i c a l l y s i g n i f i c a n t , i n crease w i t h depth from 1.42 x l O " M/l above 2000m. to 2.04 x 1 0 " M/l below 2000m; 8a e x h i b i t s a w e l l documented range o f values from c a . 3 x 1 0 " M/l t o c a . 22 x 1 0 " M / l . The covariance o f Ba w i t h Si i s s t r o n g and a good deal may be s a i d o f i t s oceanic d i s t r i b u t i o n and chemistry. For the r e s t , data on Sb, Cd, Ce, C r , Co, Ga, Ge, L a , Pb, Hg, N i , S e , A g , T l , Th, W, S n , V, Y and Zr are p o s s i b l y c o r r e c t to an order o f magnitude. Sampling problems are severe f o r Sb, C d , C r , Co, Pb, Hg, N i , A g , Sn, V, and sample contamination i s probably a l i m i t i n g f a c t o r at the present t i m e . Problems o f d e t e c t i o n l i m i t , and p a r t i c u l a r l y the p r e c i s i o n o f the d e t e r m i n a t i o n , are troublesome f o r Ce, Ga, Ge, L a , Se, T l , Th, W, Y and Z r . The goal o f a t t a i n i n g at l e a s t one, a c c u r a t e , deep water value i s e x t r a o r d i n a r i l y l i m i t e d . A more productiv o f a d e t a i l e d v e r t i c a l p r o f i l e i n a major ocean b a s i n . From t h i s , the c o r r e l a t i o n of the element w i t h w e l l known oceanic v a r i a b l e s (T, S % , 0 , N 0 , POi,, S i ( 0 H K , z C 0 , a l k a l i n i t y ) can be examined. This leads to estimates o f b i o l o g i c a l c y c l i n g , and important i n f o r m a t i o n on s o u r c e s , s i n k s and t r a n s p o r t mechanisms. There i s a general f e e l i n g t h a t t r a c e metal data are "gett i n g l o w e r a l l the time" as sampling and a n a l y t i c a l methods i m prove. Has t h i s i n f a c t occurred? Figure 1 shows data taken from references 2 and 10, f o r s e v e r a l t r a c e elements, p l o t t e d a g a i n s t y e a r o f p u b l i c a t i o n f o r the l a s t 40 o r so y e a r s . It i s by no means c l e a r t h a t a d e f i n i t e trend towards lower concent r a t i o n i s observed. Rather, the data show e r r a t i c v a r i a t i o n s , o f t e n w i t h a f a i r l y wide ( i . e . order o f magnitude) range o f values f o r any one author. This may be taken to mean: ( i ) t h a t the ocean contains i n h e r e n t t r a c e metal v a r i a b i l i t y over s h o r t s c a l e s o f d i s t a n c e o r t i m e , ( i i ) t h a t a n a l y t i c a l problems e x i s t such t h a t the data presented are e s s e n t i a l l y n o i s e , o r ( i i i ) t h a t sampling problems e x i s t to the extent t h a t even the most c a r e f u l a n a l y s i s w i l l see o n l y a s i g n a l dominated by the l a r g e v a r i a t i o n s o f the metal ions coming from, o r t o , the i n d i v i d u a l c o n t a i n e r surfaces. Hypotheses ( i i ) and ( i i i ) must c o n t r i b u t e g r e a t l y to the s c a t t e r apparent i n the d a t a . Not a l l samples have been s t o r e d i n the a c i d i f i e d c o n d i t i o n to minimize a d s o r b t i o n (11) and sample contamination has been shown to e x i s t i n a number o f cases (12, 1 3 ) . F i n a l l y , recent data on c a r e f u l l y taken oceanic samples (14, 15) do show a markedly lower abundance f o r Cu ( 1 - 3 x 10" M/l) andPFor Mn (5 x 1 0 " M/kg) than the mean c o n c e n t r a t i o n reported over the l a s t 40 y e a r s . These d a t a , made p o s s i b l e by the remarkable s e n s i t i v i t y and s p e c i f i c i t y o f g r a p h i t e f u r nace atomic a b s o r p t i o n spectroscopy, provide the most c o n v i n c i n g evidence so f a r of a h i s t o r y of a n a l y t i c a l o r sampling problems over the l a s t few decades. 1 1

1 1

8

0

9

2

8

3

z

1 0


MARINE CHEMISTRY

82

MANGANESE IN SEA WATER

_ \

1930

1940

1950

1960 TIME

1970 1980

CHROMIUM IN SEA WATER

48

is

I

B

20

I

5?

10 •J 1930

1940 1950

1960

TIME

1970

1980

Ok VANADIUM IN SEA WATER

1

C

|,00 i \ i \

I S 50

1930

1940

1950

1960 TIME

1970 1980

Figure 1. Estimates of the concentration of three trace elements in seawater with time. Data taken principally from references 2 and 10. No clear trend is apparent.


4.

BREWER

A N D SPENCER


In s p i t e o f these caveats a s u b s t a n t i a l body o f evidence may be advanced i n f a v o r o f hypothesis ( i ) . I f t h i s i s c o r r e c t then the concept o f a residence t i m e , as given i n Table I, i s not p a r t i c u l a r l y h e l p f u l . A residence time o f 10,000 years corresponds to approximat!ey 10 global oceanic s t i r s , s u f f i c i e n t to smear out a l l observable c o n c e n t r a t i o n g r a d i e n t s . An element w i t h a h a l f - l i f e o f t h i s time s c a l e would be q u a s i - u n i f o r m l y d i s t r i b u t e d . However, small s c a l e r e g i o n a l v a r i a t i o n s have been shown to e x i s t (11) and to be c o r r e l a t e d w i t h hydrographic f e a t u r e s , o r l o c a l b i o l o g i c a l p e r t u r b a t i o n (16) f o r Cu, Zn, Fe and Mn. This demonstrates t h a t chemical o r B i o l o g i c a l c o n t r o l s o f some kind may be o p e r a t i n g on a time s c a l e two o r three orders of magnitude s h o r t e r than the conventional residence time would suggest. MODEL CALCULATIONS How might we, even c r u d e l y , assess t h i s ? In the case o f b i o l o g i c a l e f f e c t s , we can o b t a i n average values f o r primary p r o d u c t i v i t y , and estimates o f the elemental composition o f marine phytoplankton are a v a i l a b l e Q 7 ) . Assuming t h a t primary p r o d u c t i v i t y i s ^ 100 g C/m /yr., the depth o f the euphotic zone i s 100 m, then the growth r a t e i s approximately 2.5 x 10*3 g dry weight of phytoplankton/l/yr. In Table II,we show estimates o f removal times o f some t r a c e elements i n s u r f a c e waters w i t h respect to removal by phytoplankton, assuming e i t h e r complete uptake and removal by s i n k i n g , o r 90% r e c y c l i n g o f the element i n a manner analogous to phosphate. The true r e s u l t probably l i e s somewhere between. The values range from < 1 to ^ 1 0 y e a r s . Some o f the data are m i s l e a d i n g ; f o r i n s t a n c e , the low values f o r Al and Ti are not due to pronounced metabolic a c t i v i t y . They probably r e f l e c t the i n c o r p o r a t i o n o f c l a y p a r t i c l e s i n t o the phytoplankton sample. Let us c o n s i d e r the s i m p l e s t p o s s i b l e c a s e . I t i s i m p l i c i t i n the t r a d i t i o n a l residence time concept t h a t the continents represent a constant s o u r c e , and the oceans a uniform s i n k . We i n c o r p o r a t e a c o a s t a l zone i n t e r f a c e connecting the two v i a h o r i z o n t a l d i f f u s i o n . Given what we know o f c o n c e n t r a t i o n gradients and uptake rates (Table I l h w o u l d non-conservative e f f e c t s be d i s t i n g u i s h a b l e from purely c o n s e r v a t i v e t r a n s p o r t by d i f f u s i o n ? I f we c o n s i d e r a one dimensional model o f the s u r f a c e ocean w i t h d i s t a n c e from the c o a s t , a simple case could be given by 2

5

dc dt

_ "

„ K

(1)

where c i s the c o n c e n t r a t i o n o f a c o n s t i t u e n t , x i s d i s t a n c e from the c o a s t , t i s t i m e , x i s a f i r s t order removal r a t e c o n s t a n t , and K i s the h o r i z o n t a l eddy d i f f u s i v i t y .


MARINE CHEMISTRY

TABLE I The Concentration and Residence Times o f Some Minor Elements i n Sea Water Element

Concentration (M/l)

*Residence Time (Years)

Be

6 x 10"

1 1

? Short

Al

7 x 10"

8

1 x 10

Sc

2 x 10"

1 1

4 x 10*

Ti

2 x 10"

8

1 x 10*

V

5

Cr

6 x 10"

9

6 x 10

3

Mn

5 x lO"

1 0

2 x 10

3

Fe

3 x 10"

8

2 x 10

2

Co

8 x 10"

1 0

3 x 10*

Ni

3 x 10"

Cu

8 x 10"

Zn Ga

2

5 x 10*

8

2 x 10*

9

8 x 10"

8

2 x 10*

4 x 10"

1 0

1 x 10*

Ge

7 x 10"

1 0

As

5 x 10"

8

Se

3 x 10"

9

Rb

1.4 x 1 0 "

Y

1 x 10

Zr

3 x 10"

1 0

1 0

- l u

Nb

1 x 10"

Mo

1 x lO"

Ag

4 x 10"

Cd

1 x 10

Sn

8 x 10"

Sb

2 x 10"

I

5 x 10

7

1 0

5 x 10* 2 x 10* 6

4 x 10

6

? ? ? 2 x 10

5

4 x 10

H

?

- 9

1 1

9

- 7

?

? 7 x 10

3

4 x 10

5




TABLE I (Continued) Element

Concentration (M/1) *Residence Time (Years)

Cs

3 x 10"

Ba

1-3 x 10~

La

2 x 10"

Ce

1 x 10"

1 0

?

Pr

4 x 10"

1 0

?

ND

1.5 x 1 0 "

Sm

3 x 10"

Eu

6

Gd

6 x 10

9

4 x 10*

7

6 x 10

u

1 1

?

4 x 10"

1 2

?

Tb

9 x 10"

1 3

?

Dy

6 x 10"

1 3

?

Ho

1 x 10"

1 2

?

Er

4 x 10"

1 2

1

Tm

8 x 10'

1 3

?

Yb

3 x 10"

1 2

1

?

2

?

1 2

Lu

5

?

Hf

4 x 10"

Ta

1 x 10"

1 1

W

5 x 10"

1 0

Re

4 x 10"

1 1

Au

2 x 10-

1 0

Hg

1.5 x 1 0 "

Tl

5 x 10"

Pb

1 x 10"

1 0

Bi

1 x 10"

1 0

?

Ra

3 x 10"

1 6

?

Th

4 x 10"

U

1 x 10"

?

n

1 0

1 x 10

5

2 x 10

5

8 x 10*

1 1

u

8

4 x 10

2

2 x 10

2

3 x 10

6

* Residence Time ( ) i s defined as T

T

"

A W3i


86

MARINE CHEMISTRY

where A i s the t o t a l amount o f the element d i s s o l v e d i n the ocean, and dA/dt i s the amount introduced t o , o r removed from, the ocean each y e a r . A steady s t a t e i s assumed.

TABLE

II

Concentration o f Some Minor Elements i n Phytoplankton and Estimated Residence Times i n Surface Waters With Respect to B i o l o g i c a l Removal Element

Sr Ba Al Fe Mn TiCr Cu Ni Zn Ag Cd Pb Hg

*Concentratio i n Phytoplankton (ug/g dry A (complete removal) B (90% r e c y c l i n g ) weight) 100 _ 700 20 300 10 400 200 1500 5 15 0 30 5 1 15 1 10 10 100 0.1 1 1 5 0 - 10 0 0.2

-

4 x 10 13 1 0.8 26 t 13 -v 40 27 40 40 4 15 » 40 > 40 3

-

3 x 10 200 40 6 80

-

800 400 400 40 80

4

4 x 10 130 10 8 260 130 400 270 400 400 40 150 > 400 40

4

*Data taken from references 2 , 18 tPrimary p r o d u c t i v i t y = 100 g c/nr/yr. Depth o f euphotic zone = 100 m ^ Growth r a t e = 1 x 10"3 g c/l/yr 2.5 x 1 0 " g dry 6

-

3 x 10 2000 400 60 800

-

8000 4000 4000 400 800

-

5

weight/l/yr.




87

Assuming a steady s t a t e c o n d i t i o n i s achieved then dc and a p a r t i c u l a r s o l u t i o n o f the equation ( 1 ) i s dt given by r C

_ ~ =

C

o

-Mx e

, +

e^-e ^ MXm -MXm e -e

/ (

C

m

~ " °

r m

C

g

=

-MXnu

6

}

where M j r . Co i s a f i x e d c o n c e n t r a t i o n a t X = 0 and Cm i s a f i x e d c o n c e n t r a t i o n a t X = Xm. Figure 2 shows s e v e r a l s o l u t i o n s o f t h i s model where we assume the c o n c e n t r a t i o n a t the c o a s t to be f i x e d at 1 0 u n i t s by r i v e r i n p u t and the c o n c e n t r a t i o n i n the open ocean, a t 2 0 0 km from the s h o r e , f i x e d a t a lower l e v e l o f 0 . 1 u n i t s maintained by a d i f f u s i v e f l u x from below. The f i g u r e shows s o l u t i o n s f o r eddy d i f f u s i v i t i e s (K) o f 1 0 and 1 0 cm s e c ' l and removal r a t e constants g i v i n g residence times o f 0 . 5 1 and 5 y e a r s . With th t r a c e element d e t e r m i n a t i o n s . i t i s apparent t h a t a t eddy d i f f u s i v i t i e s o f 1 0 cm sec"' a residence time o f even 0 . 5 y e a r could hardly be d i s t i n g u i s h e d from the s t r a i g h t d i f f u s i o n model. With a eddy d i f f u s i v i t y o f 1 0 cm sec"' a residence time of one y e a r should be d e t e c t a b l e but i t i s doubtful t h a t a f i v e y e a r residence time could be seen. A somewhat more s o p h i s t i c a t e d model could c o n s i d e r the case o f a c o a s t a l zone i n w h i c h , i n a d d i t i o n to a f i x e d boundary conc e n t r a t i o n maintained by r i v e r i n p u t , there occurs an a d d i t i o n a l i n p u t e i t h e r from an atmospheric f l u x o r f l u x from the bottom sediments. Such a case could be modelled by 6

7

K ^ 4

=

2

2

6

^

7

2

- XC + a = 0

(2)

dx^

a t

where X i s a f i r s t order removal r a t e constant and a i s an i n p u t f u n c t i o n which decreases w i t h d i s t a n c e from the coast according to a =a o

e

-ux

so t h a t the maximum i n p u t i s i n the near c o a s t a l zone. A s o l u t i o n to equation ( 2 ) i s given by o ' , .2 a

C = C

G

e"Jl

e

-yX

.

e

- J X

where, a t i n f i n i t e X, C approaches z e r o . Such a model may be a simple approximation f o r Pb, and o t h e r heavy metals t h a t have a s i g n i f i c a n t atmospheric f l u x , however, we know o f no s t a b l e t r a c e element data s u i t a b l e to t e s t t h i s model. 228 A p o s s i b l e a p p l i c a t i o n i s to the d i s t r i b u t i o n o f Ra Moore and S a c k e t t ( J 8 ) and Moore Q 9 ) have suggested t h a t the


88

MARINE

CHEMISTRY

R 2 2 8 distribution in the surface ocean is strongly influenced by input from the continental shelves. This conclusion has been adopted by Kaufman et a l . ( 2 0 ) who give substantial amounts of surface data for R a , including a horizontal traverse from the near shore of Long Island into the Sargasso Sea. These authors modelled the data of this traverse using the simple f i r s t order decay - diffusive model given by equation ( 1 ) to suggest an eddy diffusion coefficient o f about 2 x 1 0 cnr s e c " . However, of the 3 8 0 km represented by the traverse, about 2 0 0 km is on the continental shelf and one would expect that equation ( 2 ) would be a more appropriate model. Figure 3 shows the R a data from Kaufman et a l . ( 2 0 ) together with three solutions of equation ( 2 ) . The f i r s t solution allows no input from the continental shelf ( i . e . sets a =0 ) . This would model the cas by river input and a reasonabl be obtained with this boundary concentration set at 2 5 dpm/100 kg. The second solution a r b i t r a r i l y sets a = 1 0 0 dpm/100 kg/ y r . and u = 0 . 0 5 . The boundary concentration, Co, necessary for a reasonable f i t to the observed data is about 1 8 dpm/ 1 0 0 kg. The third solution sets the boundary concentration, Co, to zero and, in this case, a reasonable f i t to the data could be obtained with a = 1 3 0 0 e " ° - dpm/100 kg/yr. If Moore ( 2 1 ) i s correct in his statement that the river concentration of R a is extremely low 2 dpm/100 kg) then the third solution is the most appropriate. However, a l l three models give an agreeable f i t to the data and, i f the last is most appropriate, then the flux of R a from the bottom cannot be maintained over the whole shelf but must be restricted to the immeJiate 2 0 - 3 0 mile near shore area. In the shelf region off Long Island the existence of a stable "winter water" cold layer in the outer shelf region at about 5 0 meters depth may establish a sufficiently stable water column that vertical diffusion of the Ra input from the sediments may be essentially restricted to the well mixed near shore zone. It should be pointed out that the f i t to the data given by the three models described above was obtained through the use of a radioactive decay constant appropriate to a h a l f - l i f e of 5 . 7 5 years. This is the value gi ven in recent compilations of isotopic data (e.g. reference ( 2 2 ) ) , but i t differs by about 20% from the older value ( 2 3 ) of 677"years quoted in many papers on the use of R a as a geochemical tracer ( 1 8 , 1 9 , 2 0 , 2 1 ) . It is interesting to see how stable the models are to perturbations of this kind, since i t is certain that trace metal removal rates, as for instance those calculated in Table II, are subject to large errors. A f i t of the third model to the data, using a decay constant of 0 . 1 0 3 (t«j/ = 6 . 7 years) gave a = 8 5 0 - 0 . i x dpm/100 kg/yr., with K = 1 x 1 0 cm /sec. The result is numerically different, requiring a diffusion coefficient of about half the previous value, but the conclusions are substana

2 2 8

6

1

2 2 8

0

0

l x

2 2 8

2 2 8

8

2 2 8

2

6

2

e



BREWER AND SPENCER

Co=10

Figure 2. Simple model of diffusive transport of a nonconservative tracer from a coastal source to an oceanic sink. X is distance from coast. The removal rate is first order, and the concentration gradient Co/Cm = 100. At a diffusion coefficient of 10 cm /sec, a 1 year half-life would produce significant perturbation; at JO env/sec > 5 years half-life could be distinguished. 7

2

6

20

to 10 o I

0

100

200

300

X Figure 3. Application of Equation 2 to the Ra data of Kaufman et al. (20). X is distance from coast. Three solutions fit to the data: Q = Ra data in dpm/100 kg; oa = 0,Co =25 dpm/100 kg; X a = 100 dpm/100 H/yr-> — 0.05, Co = 18; + a = 1300 e-° dpm/100 kg/yr., Co — 0. 228

228

o

0

lx


90

MARINE CHEMISTRY

t i a l l y the same. I f r i v e r i n p u t i s s e t to z e r o , then the f l u x from the sediments i s s i g n i f i c a n t only i n the 2 0 - 3 0 mile near shore a r e a . Removal Processes o f S h o r t e r Time Scale Superimposed upon processes such as a c t i v e b i o l o g i c a l upt a k e , and processes o f a time s c a l e o f months to y e a r s , are many s h o r t term e f f e c t s . P r e c i p i t a t i o n and adsorbtion f a l l i n t o t h i s category. I t i s commonly assumed t h a t these p r o cesses must take p l a c e i n the ocean and probably operate on a time s c a l e o f minutes to days. Under what circumstances could these processes by i n v e s t i g a t e d by d i r e c t observation? We must again c o n s i d e r the r a t e o f the process r e l a t i v e to the r a t e o f d i f f u s i o n . Equation case i n which the d i f f u s i o n c o e f f i c i e n t was h e l d to be c o n s t a n t . T h i s i s v a l i d over d i s t a n c e s o f the o r d e r o f s e v e r a l tens o f k i l o m e t e r s . However, h o r i z o n t a l d i f f u s i o n i n the ocean i s n o n - F i c k i a n ( 2 4 , 2 5 ) and over s h o r t e r d i s t a n c e s t h i s must be taken i n t o account. For F i c k i a n d i f f u s i o n the variance ( c r ) o f the c o n c e n t r a t i o n around a p o i n t source i s p r o p o r t i o n a l to time ( t ) , p e r m i t t i n g the d e f i n i t i o n o f a constant d i f f u s i o n c o efficient. In the ocean the variance i s observed to i n c r e a s e f a s t e r than t ' , the p h y s i c a l reason b e i n g e s s e n t i a l l y t h a t l a r g e eddies c o n t a i n p r o p o r t i o n a t e l y more energy than small ones. Thus, the r a t e o f d i s p e r s i o n increases w i t h t i m e . Okubo ( 2 4 ) has prepared oceanic d i f f u s i o n diagrams, reducing the r e s u l t s o f many experiments, and one o f these i s reproduced i n Figure 4 . The s l o p e o f a l l the p o i n t s i s given by a

2

= 0.018 t 2

3 4

3 Theory would p r e d i c t a dependence on t . The r e l a t i o n s h i p between the apparent d i f f u s i v i t y (Ka) and s c a l e length ( 1 ) , defined as 3 a , i s Ka

= 0.0103

l

1

'

1

5

A g a i n , theory would p r e d i c t a dependence on l ^ . Okubo has shown t h a t the 4 / 3 power law may h o l d l o c a l l y . These data have been obtained from dye experiments, i n which a q u a n t i t y o f Rhodamine B dye i s r e l e a s e d , so as to r e semble as c l o s e l y as p o s s i b l e an instantaneous p o i n t source. The i n i t i a l v a r i a n c e , a , may be represented as 3

Q

2

where P i s a d i f f u s i o n v e l o c i t y (^ 1 cm sec"^) and % i s a c h a r a c t e r i s t i c growth time from a p o i n t source to s i z e o ^ .


BREWER AND

SPENCER

10m


1000

100

10000

/(cm) Deep Sea Research

Figure 4. Oceanic diffusion diagram showing the relationship between apparent diffusivity (Ka) and scale length (I), with the fit of the 4/3 power law locally


92

MARINE CHEMISTRY

R e l i a b l e data on t u r b u l e n t d i f f u s i o n may only be obtained at some c r i t i c a l time > to. A time o f 10 to i s o f t e n chosen. In d e s c r i b i n g dye d i f f u s i o n experiments o f t h i s k i n d i t i s f r e q u e n t l y s t a t e d t h a t they are o f p r a c t i c a l importance i n connection w i t h the d i s p e r s a l o f poi1utants o r chemical t r a c e r s . I f the r a t e o f removal o f a t r a c e r i s f i r s t order ( r a d i o a c t i v e decay, a d s o r b t i o n , p r e c i p i t a t i o n ) then a s o l u t i o n to the d i f f u s i o n equation can be found and, i n p r i n c i p l e , knowing the d i f f u s i o n c o e f f i c i e n t and measuring the d i s p e n s i o n , a removal r a t e may be c a l c u l a t e d from d i r e c t o b s e r v a t i o n . So f a r as we know, t h i s has not been attempted. We can enquire whether i t would be p o s s i b l e t o c o n s t r u c t an experiment i n which the cont r o l l e d r e l e a s e o f a t r a c e m e t a l , or o t h e r t r a c e r s u b s t i t u t e f o r a dye, i n the ocean would provide i n f o r m a t i o n on the l o c a l removal processe analogous to the problems posed by the d i s p e r s a l o f metals from waste water d i s c h a r g e s , o r a c a t a s t r o p h i c p o l l u t i o n event. The problem does not appear to be s i m p l e . F i r s t l y , the inherent s c a t t e r i n the oceanic d i f f u s i o n diagrams i s such t h a t i t would be i m p o s s i b l e to p r e d i c t the l o c a l d i f f u s i o n c o e f f i c i e n t to much b e t t e r than an order o f magnitude. T h i s probably means t h a t measurements o f some c o n s e r v a t i v e t r a c e r , r e l e a s e d s i m u l taneously w i t h the element of i n t e r e s t , would have to be made i n order to provide estimates o f l o c a l t u r b u l e n t d i f f u s i o n . (In f a c t , the measured variance o f a dye patch i s independent o f any f i r s t o r d e r decay, the measure o f removal being given by the change i n peak c o n c e n t r a t i o n and mass b a l a n c e . However, f o r a t r a c e r w i t h a r a p i d removal r a t e , the d i s p e r s i o n would provide an i n f e r i o r estimate o f t u r b u l e n t d i f f u s i o n . ) An obvious candidate f o r such a c o n s e r v a t i v e t r a c e r would be Rhodamine B dye. I t has been w i d e l y used, i s harmless, and may be measured w i t h great s e n s i t i v i t y . U n f o r t u n a t e l y , i t i s not c l e a r whether i t s behavior i s t r u l y c o n s e r v a t i v e . Mass balances o f 50-70% are o f t e n reported ( 2 4 ) , the l o s s being a t t r i b u t e d to photochemical decomposition o r a d s o r b t i o n on to p a r t i c l e s . If the l a t t e r i s a s i g n i f i c a n t f a c t o r then the dye would compete f o r a d s o r b t i o n s i t e s w i t h the element o f i n t e r e s t . Secondly, f o r most mi nor elements i n seawater, there are problems of d e t e c t i o n 1 i m i t and severe problems i n generating a s i g n i f i c a n t c o n c e n t r a t i o n g r a d i e n t . The d e t e c t i o n l i m i t f o r Rhodamine B dye i s approximately 1 0 " g/kg. For convenience i t i s customary to use a v i s u a l l i m i t o f about 10~ g/kg f o r observing the spread o f the dye patch by eye and p l a n n i n g sampling s t r a t e g y . For d i f f u s i o n experiments o f the o r d e r o f one week i n time s c a l e perhaps 50 kg o f dye would be used. In t h i s manner c o n c e n t r a t i o n gradients o f 10-100 from the center o f the dye patch to the edge can be maintained. For many chemical elements t h i s would be i m p o s s i b l e . I t i s true t h a t the c o n c e n t r a t i o n o f mi nor elements i n seawater i s not maintained by 8

5


4.

BREWER

A N D SPENCER


93

e q u i l i b r i u m w i t h t h e i r l e a s t s o l u b l e phase, but the n a t u r a l l e v e l s may o f t e n not be exceeded g r o s s l y before s u p e r s a t u r a t i o n does o c c u r . In Table I I I , we show a comparison o f the n a t u r a l l e v e l o f some t r a c e metals i n seawater w i t h t h e i r l i m i t i n g c o n c e n t r a t i o n w i t h r e s p e c t t o the formation o f a s o l i d phase ( 2 6 ) . The c a l c u l a t e d values f o r Co and Ni would suggest t h a t l o c a l c o n c e n t r a t i o n s c o u l d be r a i s e d d r a s t i c a l l y , but t h a t Cu, Zn and Ba occur n a t u r a l l y w i t h i n a f a c t o r o f 10 o f t h e i r maximum p e r m i s s i b l e c o n c e n t r a t i o n . K i n e t i c f a c t o r s may, o f c o u r s e , i n h i b i t p r e c i p i t a t i o n , as i n the case o f Mn where o x i d a t i o n and p r e c i p i t a t i o n as Mn0 i s slow below pH c a . 8 . 5 Were p r e c i p i t a t i o n t o o c c u r then our d i f f u s i o n experiment would simply reveal the r a t e o f d i s p e r s i o n o f the p a r t i c l e s . For many problems o f p r a c t i c a l importance t h i s would be most v a l u a b l e , and s t u d i e s o f s o l i d phase formation and t r a n s p o r t d u r i n g s e t t l i n g are muc f u s i o n diagram (Figure 3) shows t h a t i f p r e c i p i t a t i o n are s e t t l ing and complete w i t h i n 24 hours, then the v a r i a n c e o f the t r a c e r d i s t r i b u t i o n i n the sediments around the source would be o f the o r d e r o f one k i l o m e t e r . Local advection would elongate the d i s t r i b u t i o n p a t t e r n . The a c t u a l r a t e o f formation o f p a r t i c l e s must take p l a c e on a much s h o r t e r time s c a l e , and may be i m p o s s i b l e t o observe adequately i n s i t u . I f the r a t e o f removal by a d s o r b t i o n i s o f i n t e r e s t then we are l i m i t e d by the q u a n t i t y o f the s o l i d phase n a t u r a l l y p r e s e n t , and our ignorance o f i t s s u r f a c e chemical c h a r a c t e r i s t i c s . The q u a n t i t y o f p a r t i c u l a t e matter i n c o a s t a l waters i s h i g h l y v a r i a b l e ; i t can range from > 1 mg/kg t o c a . 100 ug/kg. The e f f e c t i v e s u r f a c e area o f t h i s m a t e r i a l i s unknown; a value o f 100 m /gram may be an approximate value f o r a c l a y mineral such as i l l i t e ( 2 6 ) . L e t us assume a value o f 50 m /gram f o r marine suspended matter. At a c o n c e n t r a t i o n o f 1 mg/kg we thus have 0.05 m /kg a v a i l a b l e f o r a d s o r b t i o n . The a d s o r b t i o n d e n s i t y o f v a r i o u s ions i n seawater on to marine p a r t i c u l a t e matter i s unknown. Taking Co as an example o f an elemental t r a c e r , then at a c o n c e n t r a t i o n o f 10" M/l i n seawater the a d s o r b t i o n dens i t y on i l l i t e would be 1 0 " moles/m , and on 6-Mn0 5 x 10" moles/m ( 2 6 ) . Using a h y p o t h e t i c a l value o f 1 0 " moles/m f o r the a d s o r b t i o n d e n s i t y on marine p a r t i c u l a t e matter then we have 5 x 1 0 " moles Co adsorbed per kg o f seawater. I f we were t o add 1 kg (17 moles) o f Co t o seawater t o i n i t i a t e a t r a c e r experiment, then under the c o n d i t i o n s d e s c r i b e d above, a patch 1 m deep and approximately 10 km radius would form before complete removal by a d s o r b t i o n c o u l d o c c u r . The l i m i t i n g f a c t o r being the presence o f adsorbing s i t e s . A patch o f t h i s s i z e would form over the time s c a l e o f about one week and would be represented by an e f f e c t i v e d i f f u s i o n c o e f f i c i e n t o f * 1 0 cm s e c " . Reference t o a diagram such as Figure 1, w i t h a p p r o p r i a t e s c a l e f a c t o r s , reveals t h a t w i t h an a n a l y t i c a l 2

2

2

2

2

7

1 0

2

2

7

2

8

2

1 0

5

2

1


94

MARINE CHEMISTRY

TABLE I I I

Natural and L i m i t i n g Minor Element Concentration i n Seawater w i t h Respect t o the Formation o f a S o l i d Phase ( 2 6 ) . Element

N a t u r a l Level (M/l)

Limi t i n g Concentration

S o l i d Phase

x 10"

6

CaC0

8

1.1 x 1 0 "

2

Ni(OH)

8 x 10"

9

3.4 x 1 0

Zn

8 x 10"

8

4.4

x 10"

7

ZnC0

3

Ba

3 x 10"

7

3.5 x 1 0 "

7

BaS0

4

Co

8 x 10"

Ni

3 x 10"

Cu

1 0

8.5

- 7

3

CuO


2



95

p r e c i s i o n of 1% the removal r a t e would be s c a r c e l y d i s t i n g u i s h able from s t r a i g h t d i f f u s i v e t r a n s p o r t o f a conservative t r a c e r . Conclusions In w r i t i n g a simple review paper o f t h i s k i n d , we are f o r c i b l y reminded o f the acute lack o f accurate o b s e r v a t i o n a l data on the ocean, and i n p a r t i c u l a r o f the c o a s t a l zone. The admittedly crude estimates o f uptake rates given here would tend t o suggest t h a t non-conservative e f f e c t s i n t r a c e element chemistry may w e l l be hard t o d i s t i n g u i s h through d i r e c t observat i o n . This should i n no way d e t e r good experimental work. It i s c l e a r t h a t f u r t h e r advances w i l l not come from casual o b s e r v a t i o n , but from c a r e f u l l y planned e x p e d i t i o n s i n a defined oceanographic s e t t i n g w i t may have to reveal through h i s d a t a . Some o f the problems discussed h e r e , the c o a s t a l - t o - o c e a n i c elemental gradients and the a d s o r b t i v e p r o p e r t i e s o f marine p a r t i c u l a t e matter, appear to be o f b a s i c importance and should y i e l d to experimental work. I f t h i s paper can s t i m u l a t e some work i n these f i e l d s , we w i l l count ourselves f o r t u n a t e . Acknowledgements This work was supported by the U. S. Atomic Energy Commission under Contract No. AT ( l l - l ) - 3 5 6 6 , C o n t r i b u t i o n Number 3539 from the Woods Hole Oceanographic I n s t i t u t i o n . Abstract The concept o f a t r a c e element residence time i n the ocean leads to estimates o f c a . 1 0 y e a r s . Were t h i s the only f a c t o r then t r a c e element g r a d i e n t s would be e f f e c t i v e l y e l i m i n a t e d . However, some d a t a , and simple uptake c a l c u l a t i o n s , show t h a t gradients i n s u r f a c e waters do o c c u r . Attempts to evaluate t h i s by a simple d i f f u s i v e model o f t r a n s p o r t o f a non-conservative t r a c e r from a c o n t i n e n t a l source to an oceanic s i n k through a c o a s t a l zone, as i n 4

2

show t h a t a " h a l f - l i f e " o f >> 5 years can probably not be d i s t i n g u i s h e d from t r u l y c o n s e r v a t i v e behavior. The model may be modified t o i n c l u d e an e x p o n e n t i a l l y v a r y i n g i n p u t f u n c t i o n , as from inshore sediments. This model i s a p p l i e d to p u b l i s h e d data on R a ( t 1/2 = 5.75 y e a r s ) as an example. Estimates o f removal processes o f s h o r t e r time s c a l e are g i v e n . We conclude t h a t b a s i c data on c o a s t a l to oceanic elemental g r a d i e n t s , and 2 2 8


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MARINE CHEMISTRY

the adsorptive properties of marine particulate matter, are sadly lacking.

Literature Cited (1) (2)

Richards, F. A. Geochim. Cosmochim. Acta (1956) 10, 241. Brewer, P. G. In "Chemical Oceanography" 2nd ed., Academic Press, London, 1975. (3) Morel, F., Morgan, J. J. Environ. Sci. Techno1. (1972) 6, 58. (4) Craig, H. Earth Planet. Sci. Lett. (1974) 23, 149. (5) Millero, F. J. In "The Sea", Vol. 6, Interscience. In press. (6) Bacon, M. P., Edmond, J. M. Earth Planet. Sci. Lett. (1972) 16, 66. (7) Spencer, D. W., Robertson, D. E . , Turekian, K. K. and Folsom, T. R. J. Geophys. Res. (1970) 75, 7688. (8) Morris, A. W. Deep Sea Res. (1975) 22, 49. (9) Brewer, P. G., Spencer, D. W., Robertson, D. E. Earth Planet. Sci. Lett. (1972) 16, 111. (10) Høgdahl, O. T. "The Trace Elements in the Ocean. A Bibliographic Compilation", Central Institute for Industrial Research, Norway, 1963. (11) Spencer, D. W., Brewer, P. G. Geochim. Cosmochim. Acta (1969) 33, 325. (12) Schutz, D. F., Turekian, K. K. Geochim. Cosmochim. Acta (1965) 29, 259. (13) Robertson, D. E. Geochim. Cosmochim. Acta (1970) 34, 553. (14) Boyle, E . , Edmond, J. M. Nature (1975) 253, 107. (15) Bender, M. Unpublished work. (16) Morris, A. W. Nature (1971) 233, 427. (17) Martin, J. H . , Knauer, G. A. Geochim. Cosmochim. Acta (1973) 37, 1639. (18) Moore, W. S., Sackett, W. M. J. Geophys. Res. (1964) 69, 5401. (19) Moore, W. S. Earth Planet. Sci. Lett. (1969) 6, 437. (20) Kaufman, A . , Trier, R. M., Broecker, W. S., Feely, H. W. J. Geophys. Res. (1973) 78, 8827. (21) Moore, W. S. J. Geophys. Res. (1969) 74, 694. (22) Heath, R. L. In "Handbook of Chemistry and Physics", 53rd ed., The Chemical Rubber Co., Ohio, 1972-1973. (23) Curie, M., Debierne, A . , Eve, A. S., Geiger, H., Hahn, O., Lind, S. C., Meyer, St., Rutherford, E . , Schweidler, E. Revs. Mod. Phys. (1931) 3, 427. (24) Okubo, A. Deep Sea Res. (1971) 18, 789. (25) Csanady, G. T. Turbulent diffusion in the environment, Reidel, 1973. (26) Murray, J. W., Brewer, P. G. In "Marine Manganese Deposits", Elsevier, in press.


5 The Calculation of Chemical Potentials in Natural Waters. Application to Mixed Chloride-Sulfate Solutions G. MICHEL LAFON Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, Md. 21218

A fundamental problem in the study of natural waters is ascertaining the chemica The chemical potentials are of particular interest because they provide the most natural expression of equilibrium between the solution and other phases, their gradients are the driving forces of molecular diffusion, and they also characterize the free energy available for non-equilibrium processes such as the precipitation and dissolution of minerals. Because many of the solid phases in contact with natural waters are reactive over relatively short periods of time, departures from equilibrium are often small. For example, the calcite saturation factor in the deep ocean is about 0.6 to 0.7 and decreases below 0.5 only very rarely (1) . The barium concentrations of sediment pore waters from the eastern Pacific Ocean appear to be controlled by equilibrium with barite (2). To study equilibrium and non-equilibrium processes in natural waters, we need to determine the chemical potentials of dissolved components with an accuracy sufficient to detect these small departures from equilibrium (say, 10 per cent or better). The chemical potentials of dissolved salts can be expressed either in terms of the activities of constituent ions, or more directly in terms of the activities of neutral components.These two approaches have recently been discussed by Leyendekkers (3, 4) and Whitfield (5), and Millero (6) has reviewed their application to sea water. Results for metal ions, chloride and bicarbonate are in good agreement, but there are serious discrepancies for sulfate and carbonate. Ionic activities cannot be measured directly and must instead be estimated using some arbitrary nonthermodynamic assumption.The models used to estimate ionic activities in mixed-electrolyte solutions (e.g. ion-pairing or specific interaction models) fail in some cases where there are strong interactions between ions (7). Thus, the choice of neutral components which can be investigated experimentally appears preferable. Many empirical models of the chemical potentials of neutral components in mixed-electrolyte solutions have been proposed, and they are discussed in some detail by Harned and Owen (8), Robinson 97 In Marine Chemistry in the Coastal Environment; Church, T.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.

98

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and Stokes (9) and Hamed and Robinson (10) . More recently, Friedman (11) has suggested a generalization of Young's (12) Rule, proposing that the excess free energy of a mixed-electrolyte solution be expressed as the sum of the contributions of single-salt solutions at the same ionic strength and of an expansion i n the products of the ionic strength fractions of each electrolyte. Using Friedman's approach, Reilly and Wood (13) and Scatchard and colleagues (14,15) have obtained equations for the free energy of arbitrary mixed-electrolyte solutions which appear to be superior to previous treatments. The purpose of this paper i s to show that the equations of Reilly, Wood and Robinson (16) accurately predict the values of chemical potentials i n mixed-electrolyte solutions where there are strong ion-ion interactions. The additivity of the interaction terms i n the general equation f (16) i demonstrated fo system of the type NaCl-MS0t»-H20 predict chemical potentials natura waters more accurately tha has been possible previously. Chemical Potentials and Interaction Parameters i n mixed-electrolyte solutions. Using Reilly and Wood's (13) expression for the free energy of an arbitrary mixed-electrolyte solution, Reilly, Wood and Robinson (16) have derived expressions for the osmotic coefficient and for the activity coefficients of components i n terms of the experimental properties of single-salt solutions and of interaction parameters. These parameters, denoted here by #(1,J,K) can be obtained from measurements i n electrolyte mixtures with a common ion, IJ-IK. Although the general equations of Reilly,Wood and Robinson (RWR) are cumbersome, their mathematical treatment is simple and easily programmed on a computer. Because relatively few single-salt data and interaction parameters are needed for the computation of a l l the chemical potentials i n any mixed-electrolyte solution, the approach of R e i l l y , Wood and Robinson i s particularly well suited to the study of natural waters, especial l y sea water (17). Scatchard and colleagues (14,15) have presented a very similar treatment, but have chosen to represent the properties of single-salt solutions and the interaction parameters by power series i n the ionic strength. The RWR equations have the advantage that they use experimental quantities directly and that they do not presuppose the functional form of the interaction parameters. Friedman (11) has shown that, for asymmetrically charged mixtures, the interaction parameter approaches In I i n the limit of i n f i n i te dilution, which makes a power function representation highly doubtful at low ionic strength. The RWR expressions for a c t i v i t y coefficients are functions of the interaction parameters and, independently, of their part i a l derivatives with respect to the ionic strength. The


5.

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Chemical Potentials in Natural Waters

99

expression for the osmotic coefficient depends solely on the quantity 8 ( J ^ ) / 3 J which can be conveniently denoted by the symbol w. To achieve a consistent thermodynamic description of mixtures with a common ion, the values of g obtained from a c t i v i t y c o e f f i cients must be related to those of w obtained from the osmotic coefficient. The relation between g and w i s discussed i n detail elsewhere (18). We simply r e c a l l here that, i f w can be represented empirically by some function / over the ionic strength interval: x i < J <X2, then g must be given by:

where C i s a constant to be determined from a c t i v i t y coefficient data. The leading inverse term arises from our ignorance of the behavior of w at ionic strengths below xi and vanishes only when / i s also a good representation of w over the interval ( 0 , X i ) , which i s not generally the case when / i s a power function. It has been shown (16) that the RWR equations accurately predict osmotic and activity coefficients i n mixed chloride solutions and that they provide a good f i r s t approximation of the trace activity coefficient of N(C10i0 2 i n HC1 solutions when the interaction terms are neglected. Before we can apply the general equations to the study of natural waters, i t i s important to establish that the f u l l equations are valid i n the systems of the type MX-NY where marked ion-ion interactions are known to take place. In particular, we wish to test the additive character of the RWR equations which makes i t possible to express the properties of complicated mixed-electrolyte solutions i n terms of those of single-salt solutions and mixtures with a common ion. A convenient way to test these characteristics i s to examine the trace a c t i v i t y coefficients of metal sulfates i n sodium chloride solutions. The trace a c t i v i t y coefficient of MSOi» i n NaCl solutions. The investigation of the s o l u b i l i t y of salts i n electrolyte solutions i s an important and powerful method for the study of the thermodynamic properties of mixed-electrolytes (8,9). In particular, the s o l u b i l i t i e s of sparingly soluble sulfate salts in sodium chloride solutions provide an exacting test of the RWR equations. The equilibrium condition for a s o l i d phase of compos i t i o n MSO^nHaO i s : log K =

2 log m. MSOi*

+

2

l 0

* ^MSO* + n log a

H 2 0


100

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CHEMISTRY

and the a c t i v i t y coefficient of MSOt* i s easily obtained from solub i l i t y data i f we know the a c t i v i t y of H2O and the equilibrium constant. Because we consider sparingly soluble salts only, the fraction of total ionic strength contributed by the sulfate i s very small. Thus, the a c t i v i t y of H 0 does not d i f f e r appreciably from i t s value i n solutions of pure NaCl and the a c t i v i t y c o e f f i cient determined from equilibrium s o l u b i l i t i e s i s a good estimate of the trace a c t i v i t y coefficient of MSOi* i n NaCl solutions. Using the RWR equations, expressions for the trace a c t i v i t y coefficient of MS(H i n sodium chloride solutions, and a c t i v i t y and osmotic coefficients i n NaCl-MCl -H 0 and NaCl-Na S0i»-H 0 have been gathered i n Table I(equations 3 to 9). The trace a c t i v i ty coefficient of MSO^ i n NaCl solutions depends on the properties of pure NaCl, Na S0i and MC1 solutions and on the sum of the interaction parameters gr(Na,Cl,50^ ) d ^(Na,M,Cl) Thus calcu lations based on s o l u b i l i t i e + = "

4

-

5

9

4

^

The equilibrium constant at 25 C was calculated from the s o l u b i l i ty of gypsum i n water and estimates of the activity and osmotic coefficients of CaSOi* i n dilute solutions. Although no data for CaSOi* are available, Harned and Owen (8) have pointed out that the activity and osmotic coefficients of the divalent metal sulfates depend very l i t t l e on the nature of the metal ion at low ionic strength. Therefore, the properties of ZnSOi* solutions were used as good approximations of those of CaSCH solutions. Note that the equilibrium constant i n equation 15 differs markedly from the limiting s o l u b i l i t y extrapolated to zero ionic strength by Marshall and Slusher (24). Their extrapolation requires that the activity coefficient of CaS0t» l i e above the Debye-HUckel limiting slope at low ionic strength f i c i e n t of ZnSOj* approache ductance curves for 2:2 electrolytes are also known to approach the limiting law from below (8), a fact consistent with the widespread assumption of ion-pairing i n these solutions. Thus, the limiting s o l u b i l i t i e s extrapolated by Marshall and Slusher (24) are probably not good estimates of the equilibrium constant for gypsum dissolution. The results derived from the s o l u b i l i t y of gypsum are quite similar to those obtained above from that of barite. Therefore, only sample calculations at 3.0 and 6.0 m are reported here. At these ionic strengths, the logarithms of the molal s o l u b i l i t i e s are -1.240 and -1.305 respectively [equation 6 of reference (24)]. The corresponding values of the trace activity coefficient of CaSO^ are 0.0982 and 0.1341, leading to values of [#(Na,Cl,S0. ) + #(Na,Ca,Cl)] of -0.0692 at 3.0 m and -0.0495 at 6.0 m. Next, we obtain #(Na,Ca,Cl) from the thermodynamic properties of mixed NaCl-CaCl solutions i n a manner similar to that used for ) + ^(Na,Ca,Cl)] calculated from the data for common-ion mixtures are -0.0640 at 3.0 m and -0.0495 at 6.0 m.The corresponding values obtained from the s o l u b i l i t y of gypsum are -0.0692 and -0.0570 respectively. Here, again, the agreement between the two methods i s excellent, especially when we consider the experimental uncertainties involved at each step of the calculations. We conclude that the s o l u b i l i t y of gypsum can be predicted accurately by equation 3 and the interaction parameters given by equations 10 and 17. Conclusions We have shown that the osmotic and a c t i v i t y coefficients i n NaCl-BaCl2-H 0 and NaCl-CaCl -H 0 can be described accurately by the equations of Reilly, Wood and Robinson (16) where the interaction parameters are given by equations 12, 14, 16 and 17. We have further shown that these interaction parameters can be added to the parameter that characterizes NaCl-Na S0i -H 0 to provide accurate estimates of the trace a c t i v i t y coefficients of BaSCKand CaSOif i n sodium chloride solutions. Thus, i t appears that the additive character of the interaction terms i n the general equations of Reilly, Wood and Robinson i s v a l i d even for systems where marked specific interactions between ions are known to exist (in this case, between metal ions and sulfate). This strong ly suggests that the general RWR equations can be used to estimate chemical potentials i n natural waters more accurately than has been possible to date. More s p e c i f i c a l l y , these equations together with appropriate expressions for the interaction parameters are l i k e l y to y i e l d significantly improved estimates of the a c t i v i t y coefficients of sulfate and carbonate components i n sea water and i n continental brines. Finally, the s o l u b i l i t i e s of sparingly soluble sulfate salts i n sodium chloride solutions can be used in conjunction with values of #(Na,Cl,S0O to estimate 2

2

2

2

t

2


5.

LAFON

Chemical Potentials in Natural Waters

111

the interaction parameter ^(Na,M,Cl) in systems for which no direct data are available. Literature Cited (1) Takahashi T., in "Dissolution of Deep-Sea Carbonates",(1975) Cushman Foundation for Foraminiferal Research, Spec. Publ. 13, p. 11, Washington. (2) Church T. M. and Wohlgemuth K., Earth Planet. Sci. Letters (1972) 15, 35. (3) Leyendekkers J. V., Anal. Chem. (1971) 43, 1835. (4)__________________,Marine Chemistry (1973) 1, 75. (5) Whitfield M. , Marine Chemistry (1973) 1, 251. (6) Millero F. J., in "Annual Review of Earth and Planetary Sciences", vol. 2 (7) Lafon G. M. and Truesdell A. H., ms in preparation. (8) Harned H. S. and Owen B. B., "The Physical Chemistry of Electrolytic Solutions", 3rd Edition, xxxiii + 803 p., Reinhold Book Corp., New York (1958). (9) Robinson R. A. and Stokes R. H.,"Electrolyte Solutions", 2nd Edition(revised), xv + 571 p., Butterworths, London,(1970). (10) Harned H. S. and Robinson R. A., "Multicomponent Electrolyte Solutions", xiii + 110 p., Pergamon Press, Oxford, (1968). (11) Friedman H. L., J. Chem. Phys. (1960) 32, 1351. (12) Young T. F. and Smith M. B., J. Phys. Chem. (1954) 58, 716. (13) Reilly P. J. and Wood R.H.,J. Phys. Chem. (1969) 73, 4292. (14) Scatchard G., J. Am. Chem. Soc. (1961) 83, 2636. (15) Scatchard G., Rush R. M. and Johnson J. S., J. Phys. Chem. (1970) 74, 3786. (16) Reilly P. J., Wood R. H. and Robinson R. A., J. Phys. Chem. (1971) 75, 1305. (17) Robinson R. A. and Wood R. H., J. Solution Chem. (1972) 1,481 (18) Lafon G. M., ms in preparation. (19) Templeton C. C., J. Chem. Eng. Data (1960) 5, 514. (20) Rosseinsky D. R., Trans. Faraday Soc. (1958) 54, 116. (21) Robinson R. A. and Bower V. E., J. Res. Nat. Bur. Standards (1965) 69A, 19. (22) Lanier R. D., J. Phys. Chem. (1965) 69, 3992. (23) Christenson P. G., J. Chem. Eng. Data (1973) 18, 286. (24) Marshall W. L. and Slusher R., J. Phys. Chem. (1966) 70, 4015 (25) Robinson R. A. and Bower V. E., J. Res. Nat. Bur. Standards (1966) 70A, 313.


6 The Activity of Trace Metals in Artificial Seawater at 25°C M. W. WATSON and R. H . WOOD Department of Chemistry and College of Marine Studies, University of Delaware, Newark, Del. 19711 FRANK J. MILLERO Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Fla. 33149

Considerable interest has been generated recently in the effects of trace metal and chemical activity of trace metals is determined by the chemical form in which they occur. (1-6) In particular, trace organic chelating agents in seawater play a very important part in changing the effect of trace metals on the environment. (2-4) These chelating agents may solubilize certain trace metals and thus facilitate their transport. If the chelating action is too strong then necessary amounts of trace metals may not be available for use by marine organisms. Conversely, the effect of toxic metals may be reduced by the chelating action. Because of the very small concentrations of both trace metals and chelating agents it is very difficult to learn about the form in which metal ions occur in seawater. For this reason most of the studies have been limited to determining the total concentration of metals in the solution phase. (6) One way of attacking this problem is to make theoretical calculations of the speciation of the various components in seawater. (7-12) However, the calculation of the interaction of a trace metal ion with a complexing agent requires a knowledge of the activity of the free metal ion in order to perform the calculation. (13) Recently Robinson and Wood (14) have shown that it is possible to use the equations of Reilly, Wood and Robinson (15) to calculate the activity coefficients for the major components of artificial seawater. Similar calculations have been made using both the equations of Scatchard, (16) and the BrønsteadGuggenheim equations either alone (9,10) or with the addition of like-charged interactions (8). All of the results are in substantial agreement and agree with the available experimental results. The purpose of this paper is to extend these calculations to the activity coefficients of the chlorides and sulfates of a variety of trace metals in artificial seawater. Thus these results give Taken in part from the M.S. Thesis of Mark W. Watson, University of Delaware June 1975. 112 In Marine Chemistry in the Coastal Environment; Church, T.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.

6.

WATSON E T

AL.

Trace Metals in Artificial Seawater

113

the activity coefficient of that part of the metal that i s uncomplexed by trace inorganic and organic complexing agents. Specifically, the a r t i f i c i a l seawater contains sodium, magnesium, potassium, chloride and sulfate ions so interactions of the trace metals with these ions are the only interactions taken into account in the calculations. Calculation of Activity Coefficients The calculations were done using equation A-9 (15) of Reilly, Wood and Robinson which requires knowing the a c t i v i t y and osmotic coefficients of each salt i n i t s own solution at the ionic strength of the mixture and the interaction parameters for each two salt mixture with one ion in common. The activity and osmotic coefficient taken from Robinson an and Pitzer (19) have re-evaluated the activity and osmotic coefficients of MgSO^ with similar results. The values of Pitzer were used. The new Y±(MgS04) data resulted i n a 2% decrease i n the activity of MgSO^ in seawater and much lower changes in the a c t i v i t i e s of the other s a l t s . The interaction parameters used i n the calculations are given i n Table 1. A l l of the interaction parameters involving transition metals and a few of the interactions between major components are not a v a i l able. The a r t i f i c i a l seawater used for the calculations consisted of a solution of four salts i n the ratio 0.4852 m NaCl, 0.0106 m KC1, 0.0367 m MgCl2 and 0.0293 m MgS04. The resulting solution has a s a l i n i t y of 35% , chlorinity of 19.375% , and a molal ioni c strength of 0.7231. The results of the calculation are given in Table II for the trace salts and the major components. The absence of activity and osmotic coefficients for CaS04 at high concentrations preclude including Ca**"* in the calculation. An examination of the basis of the R e i l l y , Wood and Robinson equation shows that good accuracy i s expected for the calculation of "normal" strong electrolytes. On the other hand, i t i s equally clear that for strongly ion-paired species; for instance, acetic acid (K (association) ^ 10^), the equation w i l l give large errors and an ion-pairing approach using an association constant i s needed. As association constants become larger than those for "normal" strong electrolytes, i t i s not yet clear at what point i t i s best to go over to an ion-pairing approach. For magnesium sulfate with a K of about 200, the equations of R e i l l y , Wood, and Robinson did not work nearly as accurately as they do for "normal" strong electrolytes. On the other hand, ion-pairing calculations are d i f f i c u l t because of the concentration dependence of the stoichiometric association constant (11). For these reasons, we expect that the activity coefficients for the sulfates of divalent cations calculated i n Table II w i l l be somewhat less accurate than the other results. In addition, the very low activity c

c

a

a


114

MARINE

CHEMISTRY

Table I Interaction Parameters Ion Interactions 4

b

1

Na*, Mg*", C l " +

+

+

+

Na , K , C l "

0.0654 -0.0253

Na , H , C l " 44

+

+

44

Mg ", K , C l " Na , Mg ", SO " +

-

-b

o,i

Na , K , S0 " 4

b

0,2

-0.0176

b

0,3

Reference

0.00191

b c

-0.00299

0.0557

d

0.0

e

0.03178 -0.003055

b

-0.0359

0.0076

-0.05821

0.0

f

Mg *, K , S0~ 4

+

=

C l ^ S 0 , Na

+

4

=

Cl", S0 , Mg 4

=

Cl", S0 , K 4

+

+t

0.000439

-0.0368 -0.0542

b b

0.0105

f

a)

The interaction parameter g i n equation (A-6)^ i s given by

b)

8 0,l 0,2 0,3 Wu, Y. C., Rush, R. M., and Scatchard, G., J . Phys. Chem. (1968) 72, 4048; (1969) 73, 2047.

=

b

+ b

I / 2 + b

l 2 / 3

c)

Rush, R. M. and Robinson, R. A., J . Tenn. Acad. S c i . (1968) 43, 22.

d)

Harned, H. S., J . Phys. Chem. (1959) 63, 1299.

e)

Zero used since no data i s available.

f)

Robinson, R. A., Platford, R. F. and Childs, C. W., J . Soln. Chem. (1972) 1, 167.


6.

WATSON

E T A L .

115


Table II Log y± of electrolytes i n A r t i f i c i a l Seawater at 35% Salinity and 25°C c

Salt

log Y±

Y

±

-0.176

0.667

-0.435

0.367

2

-0.330

0.468

MgS0

-0.796

0.160

KC1

-0.196

0.636

-0.629

0.235

*CdSO, 4

-1.245

0.057

CuCl

-0.339

0.458

-0.810

0.155

2

-0.332

0.466

*MhS0

-0.799

0.159

*NiCl

2

-0.330

0.468

4

-0.796

0.160

-0.331

0.467

-0.797

0.160

NaCl Na S0 2

MgCl

4

4

K S0 2

4

*CdCl

2

2

* CuS0 *MnCl

4

4

*NiS0

*ZnCl

2

*ZnSO. 4 *trace component


MARINE

116

CHEMISTRY

coefficient for pure CdCl^, which reflect the strong complex formed between Cd ^ and chloride ions, indicates that the activity coefficients calculated for this salt w i l l not be accurate. For the other s a l t s , good accuracy i s expected; i n fact, Robinson and Wood have shown that the calculated a c t i v i t i e s of both sodium chloride and sodium sulfate are within experimental error of the meûrements that have been made (14). Unlike the calculations for the major components, the calculated activity coefficients for the transition metal ions i n a r t i f i c i a l seawater are not expected to be good representations of the activity coefficients i n actual seawater. This i s because the transition metal ions have very strong interactions with some of the ions excluded from the a r t i f i c i a l seawater (OO^ , HCO ~, OH", and trace organics). Indeed, recent calculations using tne ionpairing model show tha transition metal chloride lower by a factor of 2 to 10 than the values for a r t i f i c i a l seawater l i s t e d i n Table I I . The major reason for these differences are the interactions with ions l e f t out of the a r t i f i c i a l seawater. The best estimates on the a c t i v i t i e s w i l l probably result from using the equations of Reilly, Wood and Robinson to calculate the interactions between the strong electrolytes present i n the solution and combining this with calculations of the association between the ions having large association constants (Ka greater than about 200). In this way each method i s used where i t i s the most accurate. The present results should be useful i n the calibration of specific ion electrodes i n seawater composed of only the major cations and anions. By adding OH" and HCO- (as well as other complexing agents) to these mixtures i t i s possible to study the interactions of trace metals with trace ligands i n seawater. +

58

Calculation of the Freezing Point Robinson and Wood (14) predicted osmotic coefficient (and thus water activity) for seawater at 25°C using the equations of R e i l l y , Wood and Robinson (15). The prediction was within 0.1% of the experimental results (20, 21) even for solutions five times more concentrated than seawater • There are two recent measurements of the freezing point of seawater (22,23). The present calculation was made to see i f the predictions and experiments at both temperatures were consistent with each other. The freezing point of the a r t i f i c i a l seawater described above was calculated from the predicted osmotic coefficient at 25°C (24) and the heat of dilution of seawater measured by Millero, Hansen and Hoff (25). F i r s t the osmotic coefficient at the estimated freezing point i s calculated from the equation (17):


6.

WATSON

E T

AL.


117

where Zm i s the total molality of solute ions, m i s the molality of ion i and the summation i s over a l l the ions, and R i s the gas constant, 1.987 cal K" mol" . Values for L i at 35%.salinity were plotted vs 1/T and graphically integrated to obtain the area under the curve. This i s a small correction since the change i n osmotic coefficient i s small, ( $ -$298^ " The activity of the water at T i s given by the following equation (17): ZmW ±

±

1

1

=

, 0 1 2 2 #

T

f

±

2

3

10 f where W i s the molecular weight of water. The freezing point depression, 0, of the solution i s then calculated from the equation (17): - log a„ n

If necessary the calculation i s repeated with this new estimate of the freezing point. Doherty and Kester (22) report for seawater with 35% s a l i n ity a freezing point of -1.922°C ± .002 while Fujino, Lewis, and Perkin (23) report -1.921 ± .003°C. Our predicted value of -1.927°C agrees to within 0.26% of their result. This agreement i s satisfactory since the 25°C data on which the prediction i s based (17) has an estimated accuracy of 0.1 to 0.2%. The agreement between experimental and prediction at 35% s a l i n i t y means freezing points for more dilute natural waters can be predicted with confidence. Similarly previous results indicate that calculation of the a c t i v i t i e s of the other major components (Na+1, K+ , Mg , C l " , SO,") should be very accurate. For accurate calculations involving trace transition metals the strong complexes with trace ligands (0H-, HCOJ, etc.) w i l l have to be i n cluded i n the calculation. 0

0

1

+2

Acknowledgement. The support of the National Science Foundation (GA-40532 and MPS74-11930), and the office of Naval Research (contract ONR-N00014-75-C-0173) i s gratefully acknowledged. Summary The equations of Reilly, Wood and Robinson were used to c a l culate the trace activity coefficients of the chlorides and s u l fates of cadmium, copper, manganese, nickel and zinc i n a r t i f i c i a l seawater at 25°C. The activity coefficients of the major components of seawater were recalculated using new values for the activi t y of magnesium sulfate. The freezing point of seawater was predicted from the calculated osmotic coefficient at 25°C and the heat of dilution of seawater.


118

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Literature Cited 1 Barber, R. T., Trace Metals and Metal-Organic Interactions in Natural Waters, Ch. 11. Phillip Singer, ed. Ann Arbor Science Pub., Inc. Ann Arbor, Mich., 1973. 2 Davey, E. W., Gentils, J. H., Erickson, S. J. and Betzor, R., Limnol. Oceanogr. (1970) 15, 486. 3 Steeman-Nielson, E. and Wium-Anderson, S., Mar. Biol. (1970) 6, 93. 4 Davey, E. W., Morgan, M. J., Erickson, S. J., Limnol. Oceanogr. (1973) 18, 993. 5 Martin, J. H., Limnol. Oceanogr. (1970) 15, 756. 6 Millero, F. J., The Sea, Vol. 6 (E. D. Goldberg, ed.), Wiley New York (1975) in press. 7 Garrels, R. M. and Thompson, M. E., Amer. J. Science (1962) 260, 57. 8 Leyendekkers, J. V., Marine Chem. (1972) 1, 75. 9 Whitfield, M., Marine Chem. (1973) 1, 251. 10 Pytkowicz, R. M. and Kester, D. R., Amer. J. Science (1969) 267, 217. 11 Kester, D. R. and Pytkowicz, R. M. Limnol. Oceanogr. (1968) 13, 670; (1969) 14, 686. 12 Whitfield, M., Deep Sea Research (1973) 20, 1. 13 Zirino, A. and Yamanoto, S., Limnol. Oceanogr. (1972) 17, 661. 14 Robinson, R. A. and Wood, R. H.,J. Soln. Chem. (1972) 1, 481 15 Reilly, P. J., Wood, R. H. and Robinson, R. A. J. Phys. Chem. (1971) 75, 1305. 16 Scatchard, G., Rush, R. M. and Johnson, J. S., J. Phys. Chem. (1970) 74, 786. 17 Robinson, R. A. and Stokes, R. H., (1970) Electrolyte Solutions, Butterworths, London. 18 Gardner, A. W. and Glueckauf, E., Proc. Roy. Soc. Lond. (1969) A 313, 131. 19 Pitzer, K. S., J. Chem. Soc. Faraday Trans. II (1972) 68, 101. 20 Robinson, R. A. J. Marine Biol. Assoc. U. K. (1954) 33, 449. 21 Rush, R. M. and Johnson, J. S., J. Chem. Eng. Data (1966) 11, 590. 22 Doherty, B. T. and Kester, D. R., J. Marine Res. (1974) 32, 285. 23 Fujino, K., Lewis, E. L. and Perkin, R. G., J. Geophys. Res., (1974) 79, 1792. 24 The change in data for MgSO4 used in the calculation gave a new osmotic coefficient, $ - 0.9061, which is only slightly different from the previous calculation, j - 0.9068. 25 Millero, F. J., Hansen, L. D. and Hoff, E. V., J. Marine Res. (1973) 31, 21.


7 Methane and Radon-222 as Tracers for Mechanisms of Exchange Across the Sediment-Water Interface in the Hudson River Estuary D. E. HAMMOND, H. J. SIMPSON, and G. MATHIEU Lamont-Doherty Geological Observatory of Columbia University, Palisades, N.Y. 10964

One problem in formulating material balances for aquatic systems is predicting th sediment-water and water-atmosphere interfaces. An empirical relationship based on wind speed (1) has been developed to predict the rate of exchange across the upper interface, but exchange across the lower interface is usually calculated by use of reaction-molecular diffusion models. Almost no information exists regarding the accuracy of these models in calculating fluxes. This paper seeks to examine such processes in the Hudson Estuary by examining the distribution of CU4 and Rn222 , two naturally-occurring tracers which are generated primarily in sediments and migrate into the overlying water column. Due to limitations of space, this paper is a brief preliminary summary of research reported by Hammond (2). Future papers will present a more detailed discussion of the results summarized here. Description of the Hudson Estuary The Hudson Estuary is shown in Figure 1 with several regions of interest labelled. The standard mile point (mp) reference system used in the text is indicated. This index represents statute miles north of the southern tip of Manhattan along the river axis. A distinct difference in bedrock geology has resulted in the development of a broad, shallow channel profile through the quaternary deposits of the Tappan Zee region (mean depth « 5.3m) and a narrow, deep profile through the crystalline rocks of the Hudson Highlands (mean depth 12.8m). A summary of the regional geology can be found in Sanders (3) and references he cites. This distinct morphology change is important to the discussion of methane distribution. The Hudson has been classified as a partially-mixed estuary (4). Bottom salinities are typically 20-40% greater than surface salinities. The estuary is tidal from the Narrows (mr> -8) to the Green Island Dam (mp +154), with an amplitude of about one meter throughout. The 0.1°/ o o isohaline penetrates to about mp 25 119 In Marine Chemistry in the Coastal Environment; Church, T.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.

MARINE CHEMISTRY

I 74030*

U 74°00*

i

1 73°30'

Figure 1. Map of lower Hudson Estuary. The mile point reference index is abbreviated as MP. The Tappan Zee region has a broad, shallow channel, and the Hudson Highlands has a narrow, deep channel. Large amounts of sewage from New York and New Jersey are discharged to the Upper Bay.


HAMMOND

7.

Methane and Radon-222 as Tracers

ET AL.

121

during periods of high fresh water discharge (spring) and to about mp 60 during periods of low discharge (late summer). Circulation within the estuary has been discussed in terms of a one-layer advection-diffusion model by a number of authors (see _5 and references cited there) and a two-layer advective model (6). On the basis of s a l i n i t y distribution, the horizontal eddy d i f f u s i v i t y calculated from the f i r s t type of model i s 3-6 x 10 cm /sec (25-50 kra2/day). An estimation of the rate of exchange of dissolved gases across the atmosphere-water interface can be made on the basis of the Lewis and Whitman stagnant film model (7) recently reviewed by Broecker and Peng (8). This model envisions gas flux to be limited by molecular diffusion through a stagnant film of water at the air-water interface. The surface of this film i s in equilibrium with the atmospher same composition as th is a function of wind speed, and the evasive flux of gas C per unit area i s then: 6

2

*c - |

+

X

(

°s

q

-

[2]

where X i s the decay constant of radon. The solution to [2] i s : q

r

(C| - C ) = Me"*!* + ?!e l

x

[3]

s

where r i «y /^s* A

C

s

C

q

C

" s =

s

88

0

^PPly^S

t n e

boundary conditions

at x » «> at x - 0 where C = overlying x*ater concentration w

and differentiating, the flux of radon to the overlying water is: Jsed

(Cf/l - C^)

Measurements of Cg^ were made by making a slurry from a known volume of wet sediment and d i s t i l l e d water. This slurry was sealed in a glass kettle, purged of radon, stored, and the re-growth of radon was measured. For Tappan Zee sediments C§
X

2

^X9 /D . * Applying boundary conditions: in

at x • 0

w

+ ?T

e

83 2

r i x e

r

r

= P ~ 2y + Q 2* e

r

r

at x « d

e

x

r

y

r i ( N l * - Me" l ) - r (O r2y - P "" 2 ) e

2

CgT

" )

=

2 0 0

The flux from

2

atoms/M sec

The model calculated d i f f u s i v i t y w i l l depend on the value of d chosen for the thickness of the mixed zone, but d = 2 cm i s reasonable on the basis of the soupiness c r i t e r i a and indicates D = 7.2 x 10""^ cm /sec. This i s about seven times the molecular d i f f u s i v i t y in the layer below and indicates that substances dissolved in i n t e r s t i t i a l waters may migrate through the upper few centimeters of sediment at rates above their molecular 2

g


MARINE CHEMISTRY

130

38

d i f f u s i v i t i e s . Selection of d ° 5 cm would Indicate Dg 3*0 x 10~5 cm /sec. The source of turbulence for this s t i r r i n g could be small polycheate worms which populate these sediments or i t could be s t i r r i n g by t i d a l currents. Data collected i n winter months, when bioturbation i s minimal, may provide an answer to this question. It should be pointed out that alternative models could explain the "enhanced" flux of radon. One p o s s i b i l i t y i s a sediment-reworking model i n which localized erosion to several centimeters occurs periodically at random locations. The distribution of shortlived radionuclides i n the sediment may be useful i n distinguishing between among possible alternatives. 2

Conclusions 1. Bubbles of methan p a r t i a l l y dissolve as they r i s e through the overlying water column appear to dominate the transport of methane across the sedimentwater interface i n the Hudson Istuary. Thus, methane i s apparently not useful for tracing the process of diffusion through surface sediments i n estuaries. 2. A radon excess of 1.33 + 0.28 dpm/fc exists during summer months i n the waters of the Hudson Estuary between mp 16 and mp 60. Most of this excess i s supported by input from the sediments at a rate which exceeds evasion to the atmosphere. Radioactive decay of radon i n the water column accounts for over half the loss of this sediment input. 3. Summertime radon flux from the sediments i s about twice as great as a molecular diffusion model would predict. The mechanisms controlling the flux cannot be uniquely constrained. A model which can account for the flux envisions the sediments to be composed of two layers. In the upper layer, uniform s t i r r i n g by currents and organisms creates an eddy d i f f u s i v i t y . In the lower layer, molecular diffusion controls transport. Choosing the thickness of the upper layer as 2 cm indicates an eddy d i f f u s i v i t y during summer months approximately seven times greater than molecular d i f f u s i v i t y . Acknowledgements The authors thank J. Goddard, J . Rouen and T. Torgersen for assistance i n sample collection and analysis, P. Biscaye, J. Sarmiento, T. Torgersen and S. Williams for reviewing the manuscript, K. Antlitz for typing i t , and D. Warner for drafting the figures. The research reported here was supported In part by the Environmental Protection Agency, contract No. R803113-01. t


7. HAMMOND ET AL.

Methane and Radon-222 as Tracers

131

Abstract Methane concentrations in Hudson Estuary waters range from ~0.2 μmol/l to ~1 μmol/l. North of mp 20, concentrations are dominated by the balance between input from sediments and evasion to the atmosphere. Seasonal and regional distribution characteristics indicate that transport across the sediment-water interface is dominated by bubbles of methane which are produced in sediment and partially dissolve as they escape and rise through the water column. Radon-222 is a noble gas with a four day half-life. It is produced primarily in sediments and may migrate into overlying waters where it decays or escapes to the atmosphere. Estimates of the rate of the latter process, combined with measurement of the former, indicates that in the Hudson Estuary migration across the sediment-wate predicted by a molecular diffusion model developed by Broecker (20). To account for the observed radon flux, a two-layer model developed by Peng et al. (22) can be applied to sediments. The model employs an upper layer in which uniform stirring by currents and organisms creates an eddy diffusivity about seven times the rate, of molecular diffusivity in the layer below. Literature Cited 1. Emerson, S.R., The Gas Exchange Rate in Small Canadian Shield Lakes, Limnology and Oceanography, (in press), 1975. 2. Hammond, D.E., Dissolved Gases and Kinetic Processes in the Hudson River Estuary, Ph.D. Thesis, Columbia University, 161 pp., 1975. 3. Sanders, J.E., Geomorphology of the Hudson Estuary, in Roels, O.A., cd., Hudson River Colloquium, Annals of theNewYork Academy of Sciences, vol. 250, pp. 5-38, 1974. 4. Pritchard, D.W., Estuarine Circulation Patterns, Proc. Am. Soc. Civil Engrs., 81, pp. 717/1-717/11, 1955. 5. Simpson, H.J., R. Bopp and D. Thurber, Salt Movement Patterns in the Lower Hudson, Third Symposium on HudsonRiverEcology, 1973, Hudson River Environmental Society, New York, 1974. 6. Abood, K.A., Circulation intheHudson Estuary, in Roels, O.A., ed., Hudson River Colloquium, Annals of the New York Academy of Sciences, vol. 250, pp. 39-111, 1974. 7. Lewis, W.K. and W.G. Whitman, Principles of Gas Absorption, Industrial and Engineering Chemistry, 16, pp. 1215-1220, 1924. 8. Broecker, W.S. and T.H. Peng, Gas Exchange Rates Between Air and Sea, Tellus, 26, pp. 21-35, 1974. 9. McCrone, A.W., The Hudson River Estuary: Sedimentary and Geochemical Properties Between Kingston and Haverstraw, New York, J. Sed. Petrol., 37, pp. 475-436, 1967.


132

MARINE CHEMISTRY

10. Claypool, C.E. and I.R. Kaplan, The Origin and Distribution of Methane in Marine Sediments, in Kaplan, I.R., ed., Natural Gases in Marine Sediments, Plenum Press,NewYork, pp. 99-139, 1974. 11. Schubel, J.R., Gas Bubbles and the Acoustically Impenetrable, or Turbid, Character of Some Estuarine Sediments, in, Kaplan, I.R., ed., Natural Gases in Marine Sediments, Plenum Press, New York, pp. 275-298, 1974. 12. Worzel, J.L. and C.L. Drake, Structure Section Across the Hudson River at Nyack, New York, from Seismic Observations, Annals of the New York Academy of Sciences, 80, pp. 1092-1105, 1959. 13. Reeburgh, W.S., Observations of Gases in Chesapeake Bay Sediments, Limnology and Oceanography, 14, pp. 363-375, 1969. 14. Martens, C.S. and R.A. Berner, Methane Production In the Interstitial Waters of Sulfate-deplete 185, pp. 1167-1169, 1974. 15. Sackett, W.M. and J.M. Brooks, Origin and Distribution of Low-molecularWeight Hydrocarbons in Gulf of Mexico Coastal Waters, (this volume). 16. Nissenbaum, A., B.J. Presley and I.R. Kaplar, Early diagenesis in a Reducing Fjiord, Saanich Inlet, British Columbia. I. Chemical and Isotopic Changes in Major Components of Interstitial Water, Geochimica and Cosmochimica Acta, 36, pp. 10071027, 1972. 17. Cappenberg, T.E., Ecological Observations on Heterotrophic, Methane Oxidizing and Sulfate Reducing Bacteria in a Pond, Hydrobiologia, 40, pp. 471-435, 1972. 18. Rudd, J.W.M., R.D. Hamilton and N.E.R. Campbell, Measurement of Microbial Oxidation of Methane in Lake Water, Limnology and Oceanography, 19, pp. 519-524, 1974. 19. Swinnerton, J.W. and V.J. Linnenbom, Gaseous Hydrocarbons in Sea Water: Determination, Science, 156, pp. 1119-1120, 1967. 20. Broecker, W.S., The Application of Natural Radon to Problems in Ocean Circulation, in Ichiye, T., ed., Symposium on Diffusion in Oceans and Fresh Waters, Lamont -Doherty Geological Observatory, Palisades, N.Y., pp. 116-145, 1965. 21. Rona, E., Diffusionsgrösse und Atomdurch-messer der Radiumemanation, Z. Physik Chemie, 92, pp. 213-218, 1917. 22. Peng, T.H., T. Takahashi and W.S. Broecker, Surface radon measurements in the North Pacific Station Papa, Journal of Geophysical Research, 79, pp. 1772-1730, 1974. 23. Li, Y.H. and S. Gregory, Diffusion of ions in sea water and deep-sea sediments, Geochimica and Cosmochimica Acta, 38, pp. 703-714, 1974.


8 Processes Affecting the Transport of Materials from Continents to Oceans B. N. TROUP Department of Earth Sciences, Case Western Reserve University, Cleveland, Ohio 44106 O. P. BRICKER Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, Md. 21218

The major portion of the terrigenous material that reaches the estuarine and shallo continents through weathering processes and transported via river systems. The products of continental weathering and erosion are transported in the form of suspended particulate matter, colloidal material, and dissolved species. The impact that these terrigenous materials have on the shallow water marine environment varies according to the nature and amount of the material and the site of discharge. Some materials introduced by rivers via an estuary may undergo major changes during their residence time in that environment before finally reaching the ocean. Others may be relatively unaffected during transit. The behavior of each material is dictated by its chemical composition and physical properties, and by the chemical, physical, and biological constraints imposed upon it by the estuarine environment. Understanding the chemistry of the estuarine and near-shore marine environment thus entails a knowledge of the chemical inputs into the environment and the nature of the interactions that take place among these materials within the environment. In river waters and in sea water the species Na+, Mg++, ++ Ca , K+, C1-, SO4=, HCO3- and H4SiO4 account for more than 98% of the total dissolved solids. These major elements determine the general chemical character of the waters. The other elements, the trace elements, are present in much smaller quantities, but may nevertheless play important roles in determining the chemical quality of the environment. The sediments carried by rivers to estuaries and the nearshore marine environment are constituted primarily of the elements O, Si, Al, Ca, Mg, K, Na, and Fe with other elements present in trace amounts. The continuum of reactions that occur between the waters and solids during the weathering process, transport through river systems and after sedimentation in the estuarine or coastal marine environment, are major influences on the composition of the aqueous phase and lead ultimately to the mineral assemblages 133


134

MARINE CHEMISTRY

that are preserved i n the sedimentary r e c o r d . It may be i n s t r u c t i v e at t h i s p o i n t to examine some o f the types o f r e a c t i o n s that occur during the sedimentary c y c l e . The m a t e r i a l s o f the e a r t h ' s c r u s t can be separated i n t o two groups on the b a s i s o f chemical composition, the s i l i c a t e s and the carbonates. A t h i r d group, the e v a p o r i t e - d e p o s i t s , i s quant i t a t i v e l y unimportant i n terms o f volume, but can p l a y an important chemical r o l e on a l o c a l s c a l e . Chemical weathering o f the e a r t h ' s c r u s t produces two types o f p r o d u c t s : a) d i s solved s p e c i e s , and b) r e s i d u a l s o l i d s that are more s t a b l e under e a r t h ' s surface c o n d i t i o n s than the o r i g i n a l minerals i n the rocks being weathered. These r e s i d u a l s o l i d s are u s u a l l y a l u m i n o - s i l i c a t e minerals o f the P h y l l o s i l i c a t e group ( c l a y s ) , o r hydrous oxides o f i r o n and manganese. Present information suggests t h a t , once formed i n the weathering environment than s h i f t s i n the exchangeable i o n p o p u l a t i o n u n t i l they are deposited i n the marine environment. S i m i l a r l y , the a l k a l i and a l k a l i n e e a r t h c a t i o n s f r e e d i n weathering r e a c t i o n s undergo few r e a c t i o n s other than minor involvement i n i o n exchange r e a c t i o n s with c l a y minerals and, perhaps with p a r t i c u l a t e organic matter, during t h e i r t r a n s i t to the s e a . In i n t e r s t i t i a l waters o f e s t u a r i n e and marine sediments, however, r e a c t i o n s occur that i n v o l v e these elements. For i n s t a n c e , Drever (1) has reported exchange o f Mg f o r Fe i n c l a y s i n the sediments o f the Rio Ameca basin. The c l a y s take up Mg i n exchange f o r i r o n , and the r e l e a s e d i r o n r e a c t s with s u l f i d e i o n i n the anoxic i n t e r s t i t i a l waters to form i r o n s u l f i d e . D e p l e t i o n o f Mg i n the i n t e r s t i t i a l waters o f deep sea sediments has a l s o been reported (2, 3 ) . The i n t e r s t i t i a l water environment i n the sediments appears to be the l o c a l e i n which s i g n i f i c a n t chemical changes begin to o c c u r . The behavior o f t r a c e elements i n e s t u a r i e s i s i n marked c o n t r a s t to the n e a r l y conservative behavior o f the major i o n s . Trace elements p a r t i c i p a t e i n a v a r i e t y o f biogeochemical r e a c t i o n s , and an understanding o f these r e a c t i o n s i s c r u c i a l to the understanding o f the c y c l i n g o f t r a c e elements between continents and oceans. R i v e r Transport R i v e r input i s the major source o f t r a c e elements to the e s t u a r i n e and near-shore marine environments. The chemical form o f an element i n r i v e r water to a great extent determines the type o f r e a c t i o n i t p a r t i c i p a t e s i n during i t s passage through an e s t u a r y . Trace elements can be t r a n s p o r t e d by r i v e r s i n several different fractions: A. Dissolved 1. Inorganic - i n c l u d e s the " f r e e " hydrated i o n and inorganic ion pairs ( i . e . , F e O H , F e C l ) 2 +

2

+


8.

TKOUP

A N D BRICKER

Transport of Materials

135

2. Organic - composed of trace elements complexed with dissolved organic matter. Trace elements i n the dissolved fraction are highly reactive and readily participate i n a l l types of estuarine processes. B. Particulate 1. Adsorbed on the surface of particles - most suspended particles i n natural waters are negatively charged and cations are attracted to their surfaces. Additionally, trace elements are adsorbed on ion exchange positions of clay minerals and on hydrous oxides of iron and manganese. Both kinds of adsorbed ions are easily desorbed from particles when the chlorinity of surrounding solution changes. 2. Coprecipitated with iron and manganese i n hydrous oxide coatings - durin and immediately precipitate hydrated oxide. This material readily scavenges trace metals either by coprecipitation or sorption. Manganese i n solution commonly coprecipitates with iron. These fine-grained, high surface area hydrous oxides coat d e t r i t a l particles and are transported with them by rivers . The coatings are stable i n highly oxic surface waters, but are unstable under anoxic conditions and quickly dissolve releasing the contained trace metals. 3. Precipitated on the surface of d e t r i t a l particles some trace metals can precipitate i n the form of pure phases on surfaces of clay minerals or other d e t r i t a l particles at low temperatures and pressures ( 5 ) . These precipitates can dissolve under varying conditions of pH and pE. 4. Bound within the crystalline l a t t i c e of sediment particles - these trace metals can only be released to solution under harsh chemical conditions rarely encountered in natural waters. 5. Bound within organic particulates - stable i n oxic environments and unstable i n anoxic waters and sediments. Rate of decomposition and subsequent release of trace metals depends on the composition of the organic matter and the intensity of bacterial activity. The chemical reactivity of trace elements i s different i n each of these fractions; and consequently, the behavior of an element passing through an estuary i s strongly influenced by i t s d i s t r i bution among these fractions. Gibbs (6) investigated the p a r t i tioning of trace metals among some ofTnese fractions i n the Amazon River System. His results i l l u s t r a t e the substantial variation i n the distribution of four elements among these fractions during their transport i n the river (Figure 1). In the Amazon, most of the Fe and Mn are transported as oxide coatings, while most of the Cu and Co reside i n the crystalline l a t t i c e . In addition, large portions of the total Cu and Mn are i n the dissolved state and significant amounts of Fe and Co are bound with organic particulates. Gibbs also reported that the order


136

MARINE

CHEMISTRY

of dominance of the fractions (i.e., Fe: coating > organic > solution) varied l i t t l e between rivers but that the absolute percentage of an element i n each fraction did change. Thus, since the chemical reactivity of elements varies between the fractions, the amount of each trace metal available for different biological and geochemical reactions i n estuaries varies from river to river and must be determined for each element under study. Several workers have found that trace element concentrations vary greatly between different rivers (7, 8 , 9 , 10). This observation i s not unexpected since the concentration i n a river depends on the relative concentration of trace elements being weathered i n the drainage basin and on the rate of weathering of the different minerals containing trace elements. Recent studies have also show vary greatly as a functio time of year. Carpenter et. a l . (11) completed an extensive study of the temporal v a r i a b i l i t y of trace metals transported by the Susquehanna River to the Chesapeake Bay. They sampled the river on a weekly basis for a period of approximately 1% years at a station one mile below the Conowingo Dam. Each sample was separated into three fractions and these fractions were analyzed for trace metals according to the following procedures (11): 1. Settled solids (SS) - 100 l i t e r s of river water were allowed to settle for 10-14 days. The supernatant water was removed and the remaining slurry was digested with 1 M HC1 and 1.5 M HAc for 48 hours at 60°. 2. Filtered solids (FS) - 50 l i t e r s of the supernatant water was f i l t e r e d through acid-washed 0.2 urn cellulose acetate membrane f i l t e r s . The f i l t e r e d solids were then treated ident i c a l l y to the settled solids. The remaining 50 l i t e r s of supernatant water was centrifuged to determine the weight concentration of solids. 3. "Soluble" (SOL) - 50 l i t e r s of the f i l t r a t e from step two was run through a cation exchange resin (Chelex 100 i n acid form). The resin was eluted with 1 M HC1 and the eluate was evaporated to dryness. The residue was oxidized with n i t r i c acid and made to volume with 0.1 M HC1. A l l three fractions were then analyzed for their trace metal content by atomic absorption spectrophotometry preceded by APDC complexation and MIBK extraction. The standard deviation of replicate samples varied between 1.0 and 2.2%. The discharge of water and suspended solids by the Susquehanna River over a 17 month period i n 1965-66 i s depicted i n Figure 2. The most striking feature of the data i s the large variation of both discharges during the year. As we would expect, both discharges are greatest during early spring. In fact 5.1% of the total annual discharge of solids occurred on one day, February 17; and 30% of the total annual solids discharge


8.

TROUP

AND

BRICKER


137 SITE CRYSTAL LATTICE

^

OXIDE COATING

|

AQUEOUS SOLUTION

^

ORGANIC MATERIAL | ^ ION EXCHANGE SITES Q

Fe Gibbs (1973)

Figure 1.

Figure 2.

Mechanisms of metal transport in the Amazon River

Susquehanna River discharge, water, and suspended solids, April 1965-September 1966 (after Carpenter et al. (11))


138

MARINE CHEMISTRY

occurred in one week, February 14-20. Because of these large fluctuations i n discharge rates, we conclude that estimates of total solids and total trace element discharge of rivers computed from concentrations and flow rates determined during periods of low or moderate discharge are not representative of the true total annual discharge. As a f i r s t approximation the trace metal concentration (ug/ kg water) data correlates well with the solids discharge (Figures 3, 4 and 5). The concentrations are highest i n the spring and lowest i n the summer and f a l l . Closer inspection, however, reveals differences i n the patterns of particular elements and total solids. Mn, Ni, Zn and Co exhibit large concentrations i n January, and Cu, Cr and Mn have concentration maxima i n late spring or early summer. The temporal v a r i a b i l i t y of the solids discharge can be eliminate ing the weight concentration tion (mg/kg solids). These data are shown i n Figures 6 and 7. Generally there are peaks i n concentration for a l l the metals during December and January and secondary peaks for Co, Cr, Ni, Cu and Mn i n July. Since decaying organic matter (particulate and dissolved) i s abundant i n the Susquehanna during these two periods, the high concentrations may be the result of binding of the metals to particulate organisms. Figures 8 and 9 i l l u s t r a t e the distributions of Fe, Mn, Cu, Ni and Zn among the three fractions during the 17 month sampling period. Most of the Fe and Zn are associated with the solids throughout the year except during January when a substantial portion of the two metals i s i n the dissolved state. The partitioning of Mn between solution and solids varies throughout the year. There i s a substantial amount of soluble manganese present during January and early spring, but the rest of the year manganese i s associated predominantly with the solids fractions. Large amounts of Ni and Cu are in the dissolved form throughout the year, but the ratio of the soluble to that associated with the solids fraction increases in December and January. We believe that the high concentrations of dissolved trace metals during early winter can be associated with the increased amounts of decaying organic matter i n the river during this period. Further investigation i s needed to confirm this conclusion. The importance of frequent sampling i n the estimation of trace element transport i s pointed out i n Table 1. Turekian s estimates are based on one sampling period during the summer of 1966, and those of Carpenter and Grant are time averages over a 17 month period. The discrepancies between the two sets of data are greater than an order of magnitude for many of the metals. The higher estimates of Turekian may be attributed to the high concentrations of several trace metals i n the solids fractions noted by Carpenter during July, 1966 (Figures 6 and 7). !


8.

TROUP

Figure 3.

AND

BRICKER


139

Concentrations of Cd, Cr, and Co (mg/kg H O) in Susquehanna River discharge, April 1965-September 1966 (after Carpenter et al. (11)) z


140

MARINE

1965 APR MAY JUN JUL

4000-

AUG SEP OCT NOV DEC l JAN FEB

MAR APR

CHEMISTRY

MAY JUN JUL

AUG SEP 1966

NOV DEC JAN FEB MAR APR MAY JUN JUL

AUG SEP 966

Fe

3000-

1965 APR

Figure 5.

MAY JUN

JUL

AUG SEP OCT

1

Concentrations of Fe and Mn (mg/kg H 0) in Susquehanna River discharge, April 1965 to September 1966 (after Carpenter et al. (11)) t

JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL

Figure 6. Concentrations of Ni, Zn, Mn, and Fe (mg/kg solids) in Susquehanna River discharge July 1965-July 1966 (after Carpenter et al. (11))


TROUP

AND


BRICKER

5 JUL AUG

SEP

OCT

Cd

I 24

1 w

• 1

i

™

^

1

Co

Cu

A

I i i AUG SEP OCT

1965 JUL

NOV

l

Ai

1 1 1 .1 1. -J I DEC JAN FEB MAR APR MAY J UN JUL 1966 1

Figure 7. Concentrations of Cd, Cr, Co, and Cu (mg/kg solids) in Susquehanna River discharge July 1965-July 1966 (after Carpenter et al. (11)) 1965 SEP

I

OCT

NOV DEC i JAN I |

FEB

MAR

APR

MAY

JUN

JUL

AUG

1966

450-

4000

1

1

1965 SEP OCT NOV

1

1

DEC

1

JAN FEB

1

1

MAR

APR

1

1

1

1

MAY JUN JUL AUG

1966

Figure 8. Partitioning of Mn and Fe between solutions and solids in Susquehanna River discharge, April 1965-September 1966 (after Carpenter et al. (11))


MARINE

142 Table 1.

CHEMISTRY

Trace metal transport of the Susquehanna River (Tons) Carpenter et a l . (11)

Suspended solids Fe Mn Zn Ni Cu Co Cr Cd Ag Mo

767,000 43,000 5,300 650 215 105 88 53 2

— —

Turekian § Scott (7) 300,000 120,000 3,000 1,500 870 45 97

Although rivers ar entering estuaries, r a i n f a l l and particulate fallout may be important sources i n specific locales, particularly for v o l a t i l e trace metals, such as Se, Hg and Pb. For example Patterson (12) has reported that dry aerosol deposition of Pb i n the Southern California Bight equals more than 75% of the amount of Pb transported by rivers and waste waters. Similarly, i n the Delaware estuary, Biggs (13) has found that the concentration of Cd and Pb i n r a i n f a l l i s higher than the concentrations observed i n unpolluted streams discharging into the estuary. Biogeochemical Processes i n Estuaries Once the rivers have transported trace elements to an estuary, the elements can undergo several kinds of physical, chemical and biological reactions. It i s important to identify these reactions since estuarine processes affect the amount and the form of the trace elements transported to the ocean. On the basis of their behavior i n estuaries, elements can be c l a s s i f i e d as either conservative or non-conservative. Conservative elements display a linear relationship between concentration and chlorinity along the length of an estuary which reflects a simple, physical mixing process between river and sea water. Conservative behavior i s typically exhibited by the major ions and some minor constituents, such as s i l i c a i n the Merrimac estuary (14, and Figure 10). Most trace elements are nonconservative, like iron (Figure 10), and physical mixing processes alone cannot account for their distributions i n an estuary. There are five major categories of reactions which influence trace metal transport i n estuaries: 1. Flocculation and sedimentation - these processes are encouraged by the increased s a l i n i t y of estuarine waters. As a result of the salt-wedge type of circulation commonly observed (Figure 11), sedimentation i s concentrated i n the upper reaches of estuaries. Suspended sediment discharged by rivers i s carried


8.

TROUP

AND

BRICKER

£


143

40-

1965SEP' OCT

Figure 9. Partitioning of Cu, Ni, and Zn between solution and solids in Susquehanna River discharge, April 1965September 1966 (after Carpenter et al. (11))

IO

7

Figure 10. Conservative behavior of silica vs. nonconservative behavior of Fe in the Merrimac River estuary (after Boyle et al. (14))

is to SALINITY %•

X

SALINITY %•

—*-


144

MARINE CHEMISTRY

toward the ocean by the fresh water at the surface of the estuary. As the solid particles settle, they f a l l into the salt wedge layer moving toward the mouth of the river. The particles continue to settle and sedimentation i s concentrated i n the low velocity region near the t i p of the salt wedge. Schubel (pers. comm.) estimates that, i n the Chesapeake Bay 90% of the solids discharge i s deposited i n the northern third of the estuarine system. His argument i s substantiated by the distribution of Fe in sediments along the length of the bay. The time-averaged concentration of Fe i n suspended solids discharged by the Susquehanna River i s about 5-10% (11). The concentration of Fe i n northern Chesapeake Bay sediments averages 5%, while the concentration i n southern bay sediments averages 3%. These data suggest that most of the sediments of the southern bay originate from shoreline erosion 2. Mineral-water i t y , pH and oxygen content of estuarine waters can affect the precipitation or dissolution of minerals (for instance, the dissolution of the hydrous oxide coatings under low O2 conditions in water or sediments). 3. Adsorption/desorption - due to the high concentration of Na and Mg i n seawater, ion exchange reactions occur rapidly i n estuarine waters as sediment particles adsorb the seawater c a t i ons and desorb trace elements. 4. Diagenesis and remobilization of trace metals i n sediments - the decreased pH and strong pE gradient i n sediment i n t e r s t i t i a l waters brought about by the decomposition of organic matter significantly affects the s o l u b i l i t y of trace element solid phases and ion exchange equilibria. Trace metal concentrations i n sediment pore waters are typically orders of magnitude greater than i n the overlying water, and the flux of trace elements across the sediment-water interface may constitute an important mass transfer process i n estuaries. 5. Biological processes - interactions with aquatic organisms may strongly influence the behavior of trace elements during their passage through estuaries. The generally recognized mechanisms are: ingestion of particulate suspended matter containing trace metals, trace metal complexation with organic chelates produced by organisms, trace element uptake i n metabolic processes, and ion exchange and sorption on the surfaces of organisms (15). Most trace elements undoubtedly participate i n a l l these major categories of reactions to some extent, and i t i s important to identify which reactions most strongly influence the transport of each element under study. To this end, our group at Johns Hopkins has concentrated on the effect of sediment-water exchange processes on trace element cycling.


8.

TROUP

AND


BRICKER

145

Desorption of Zn from Estuarine Sediments Bradford (16) investigated the influence of sediments on zinc concentrations i n the overlying water i n Chesapeake Bay. Using anodic stripping voltammetry, he observed large Zn concentrations just above the sediment-water interface i n the northern bay during May. The distribution of total zinc (UV oxidized) and inorganic zinc (raw sample) just above the sedimentwater interface at station 914S i s shown i n Figure 12. During May there i s a large concentration of zinc at this station. The zinc i s t o t a l l y i n the inorganic form because there i s no d i f f e r ence i n concentration between the oxidized and raw samples. The only other major change occurring during May at 914S was a rapid increase i n the chlorinity from less than 0.2 % to greater than 3 °/ (Figure 13) Th larg zin concentratio t b the result of mixing o centration of zinc neve pp at this station. Thus, the large increase i n Zn must have come from sediments. This conclusion i s substantiated by the concentration gradients of Zn at station 914S during A p r i l , May and June (Figure 14). During April Zn varies from 4.5 ppb at 4 m to 5.5 ppb at 1 m above the interface. In May there i s a large vertical concentration gradient which implies a flux of Zn from the interface. In June the Zn concentration i s uniform at this station. We conclude from these data that zinc was desorbed from freshly deposited river sediments at this station as Mg and Ca from the salt wedge were adsorbed. During March and April the Susquehanna discharges a large quantity of suspended solids to the upper reaches of the Chesapeake Bay. These solids form a layer 1-2 cm thick in the northern bay. The ion exchange positions of these solids are i n equilibrium with the river water ratios of the major cations. Once the river discharge subsides the salt wedge begins to move landward again. During May the salt wedge moved across the sediments at 914S, and i n response to the ion exchange equilibria, the sediments adsorbed the major sea water cations and desorbed Zn to the overlying water. This conclusion confirms earlier observations suggesting that Zn rapidly desorbs from surface sediments as the chlorinity increases above 0.4% (17, 18). 0

QO

o

Remobilization of Trace Metals i n Sediment Pore Waters In the highly oxygenated conditions of normal river beds the hydrous Fe and Mn oxide layers coating sediment particles are stable. When the d e t r i t a l particles reach the marine environment and become incorporated into the organic reach bottom sediments of an estuary or marine delta, they encounter very different conditions. Oxygen i s usually depleted within the upper few centimeters of sediment by bacterially mediated oxidation of organic material. In brackish and marine waters, after oxygen i s


146

MARINE CHEMISTRY

UPSTREAM

OCEAN

LOSS

—

OISPERSEO OVERBORNE — » . SEDIMENT

^ , ^ ^ ^

—

/ ^ A PORTION OF

MIXTURE OF NEi RIVERBORNE PARTICLES I RETURNING AGGREGATE! AGGREGATES ^"COLLECT FINE PARTICLES.

SETTLING

J| f

V_ IIWA^TCIRCUUTEV M I I I I I I I J-*«snT />V/ / / / V / / v / / /

>///////f////A///////

HIGHER CONC. LOR BED SHEAR. I CONSOLIDATION

M

M

T

SHEARING Figure 11.

Diagram of an estuarine salt wedge (after Neiheisel (22))


8.

TROUP

AND

BRICKER

Transport of Materials CHLORINITY

Botto

MAR

Figure 13.

APR

MAY MONTH

JUN

147

(%.)

JUL

AUG

SEP

The chlorinity with depth and time at Station 914S in the upper Chesapeake Bay (after Bradford (16))


MARINE

148

CHEMISTRY

depleted, bacteria use sulfate as an electron acceptor to continue the oxidation of organic matter (equation 1): 2

organic matter + S 0 ~ = HC0 ~ + HP0 " + HS" + H 4

3

+

4

(1)

These reactions decrease the sulfate concentration and pH and increase the concentrations of bicarbonate, phosphate and sulfide. Additionally, strongly reducing conditions are produced i n which the oxide coatings on d e t r i t a l particles are chemically unstable. Solution of the oxide coatings produces large concentrations of dissolved iron, manganese and other trace metals i n the inters t i t i a l waters. The vertical distribution of dissolved Fe(II) and Mn i n the i n t e r s t i t i a l waters of the upper meter of sediments at a station i n the northern Chesapeake Bay i s shown i n Figure 15. The concentrations of bot below the sediment wate of the oxide coatings. Below 10 cm, the concentrations decrease rapidly and become nearly constant below 40 cm. We attribute the rapid decreases of the concentrations to the precipitation of authigenie trace metal phases i n the i n t e r s t i t i a l water as phosphate and carbonate increase rapidly with depth. Siderite and vivianite control the dissolved iron concentrations below 10 cm (1£), while rhodocrosite controls the Mn distribution (20). The concentrations of other trace metals which had coprecipitated with Fe and Mn during weathering also increase as the oxide coatings dissolve. In northern Chesapeake Bay pore waters, Cu and Pb mimic the distributions of Fe and Mn (Figure 16). Thus , just below the sediment-water interface there i s a concentrated reservoir of dissolved trace metals which can be transferred across the interface by molecular diffusion, sediment resuspension and bioturbation (21). Because of the magnitude of the trace metal concentrations i n sediment pore waters, very l i t t l e transfer would have to occur to significantly alter the overlying water concentrations, and consequently, to increase trace metal transport to the oceans. Conclusions At the present time we can draw a f a i r l y complete picture of the transport of major ions between continents and oceans, due to their nearly conservative chemical behavior. On the other hand, trace elements are non-conservative species i n estuaries, and extensive spatial and temporal surveys of their distributions are required to delineate the modes of transport of individual elements . Specifically, we need the following kinds of data: 1. River transport data for a l l important trace metal fractions to determine season-to-season and year-to-year variations . 2. Data on the flux of trace elements through biological systems


8.

TROUP

AND

i


BRICKER

,

5

,

1

IO

15

1 r

1

10

1

5

( ) m Figure 15.

149

10

1

15

r 10

ppm

Concentrations of dissolved Fe and Mn as a function of depth beneath the sediment-water interface CBASS m

STAT I ON

10*H

Figure 16. Concentrations of dissolved Pb and Cu as a function of depth beneath the sediment-water interface


150

MARINE CHEMISTRY

3. Quantitative assessment of the role of sediments in trace metal transport. 4. Data on oceanic input of trace elements into estuaries, so that estimates of net transport to the ocean can be calculated. In general we know the kinds of reactions which are important in trace metal transport. However, in many cases we do not know which reaction is most important for a given element, and in almost all cases we do not know the amount of each element participating in the reaction or the rate at which the reaction is occurring. The data that has been collected and that we are now collecting,will help to remedy this situation. Acknowledgements We would like to thank Dr. James H. Carpenter for allowing us to use some data fro Kaerk for providing unpublished data on lead and copper in Chesapeake Bay sediments. Mr. Gerry Matisoff kindly assisted with the preparation of the figures. This work was supported by AEC Contract AT(11-1)-3292. Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

12.

Drever, J. I. Science (1971) 172: 1334-1336. Bischoff, J. L. and T. Ku, Jour. Sedimentary Petrology (1970) 40: 960-972. Bischoff, J. L., R. E. Greer, and A. O. Luistro, Science (1970) 167: 1295-1246. Carroll, D., Geochimica et Cosmochimica Acta (1957) 14: 1-28. Tiller, K. G. and J. G. Pickering, Clays and Clay Minerals (1974) 22: 409-416. Gibbs, R. J., Science (1973) 180: 71-73. Turekian, K. K. and M. R. Scott, Environmental Science and Technology (1967) 1: 940-942. Kharkar, D. P., K. K. Turekian and K. K. Bertine, Geochimica et Cosmochimica Acta (1968) 32: 285-298. Konovalov, G. S. and A. A. Ivanova, Okeanologua (1970) 10: 628-636 (in Russian). Windom, H. L., K. C. Beck and R. Smith, Southeastern Geology (1971) 1971: 1109-1181. Carpenter, J. H., W. L. Bradford and V. E. Grant, "Processes Affecting the Composition of Estuarine Waters (HCO3, Fe, Mn, Zn, Cu, Ni, Cr, Co, Cd)" In Proceedings of the Second International Estuarine Conference, J. H. Carpenter (ed.) (in press). Patterson, C. C. In"Pollutant Transfer to the Marine Environment", R. A. Duce, P. L. Parker, and C. S. Giam (eds.), P. 12, Deliberations and recommendations of the National Science Foundation, International Decade of Ocean Exploration Pollutant Transfer Workshop, January 11-12, 1974.


8. TROUP AND BRICKER 13. 14. 15. 16.

17. 18. 19. 20. 21. 22.


151

Bopp, Frederick III, F. K. Lepple and R. B. Biggs, Trace Metal baseline studies on the Murderkill and St. Jones Rivers, Delaware Coastal Plain. College of Marine Studies, Univ. of Delaware Publication DEL-SG-10-72, 31 pp. (1972). Boyle, E., R. Collier, A. T. Dengler, J. M. Edmond, A. C. Ng and R. F. Stallard, Geochimica et Cosmochimica Acta (1974) 38: 1719-1728. Martin, D. F., "Marine Chemistry", Vol. 2 (New York, Marcel Dekker, 1970). Bradford, W. L., "A Study on the chemical Behavior of Zinc in Chesapeake Bay Water using Anodic stripping Voltammetry", Chesapeake Bay Institute, Johns Hopkins Univ., Tech. Rept. 76 (1972) Reference 72-7, 103 p., Baltimore, Md. 21218 Bachman, R. W., Zn-65 in studies of the water zinc cycle. In Radioecology Proceedings of the First National Symposium on Radioecology, Colorado State University (1961), pp. 485-496. O'Connor, J. T., Civil Engineering Studies, Sanitary Eng. Ser. No. 49 (1968), Dept. of Civil Eng., Univ. of Ill., Urbana. Troup,B.N, O.P. Bricker, J.T. Bray, Nature (1974) 249: 237-39. Holdren, G. R., Ph.D. Dissertation. Johns Hopkins University, Baltimore, Md. 21218 (in preparation). Bricker, O. P. and B. N. Troup, "Sediment-Water Exchange in Chesapeake Bay" In Proceedings of the Second International Estuarine Conference, J. H. Carpenter (ed.) (in press). Neiheisel, J., "Significance of clay minerals in shoaling problems". Comm. Tidal Hydraulics Tech. Bull. No. 10, Corps of Engineers, U. S. Army, Vicksburg, Miss. (1966).


9 A Field Study of Chemical Budgets for a Small Tidal Creek—Charleston Harbor, S.C. J. L. SETTLEMYRE and L. R. GARDNER Department of Geology and Belle W. Baruch Coastal Research Institute, University of South Carolina, Columbia, S.C. 29208

The intertidal marsh is perhaps one of the most reactive geochemical environment due to the combination of intense biological activity, sulfate reduction and H2S production and the presence of reactive fine grained sediment. Marshes are known to be extremely productive environments and to serve as nurseries for many marien organisms. As many chemical pollutants tend to become concentrated in the marine biosphere, it is important to understand the mechanisms by which, and the extent to which various substances accumulate and/or degrade in marshes. Also as a result of their areal extent the accumulation or export of various substances by marshes may affect the quality and productivity of nearby estuaries and coastal waters. Despite these considerations, little attention has been devoted to the interaction of marshlands and estuarine waters with respect to chemical quality, or to exploring the possible uptake or degradation of pollutants by marshes. The present study, therefore, was undertaken to identify the major water quality changes resulting from the interaction of estuarine water with a tidal marsh. The area chosen for this study is the drainage basin of Dill's Creek, a moderate size tidal creek (Figure 1) on the south side of Charleston Harbor, S.C. Dill's Creek was chosen because it has a relatively well defined drainage basin which is isolated from inputs of fresh water and because the adjacent harbor waters are moderately polluted. Chemical and fertilizer industries on the Ashley and Cooper Rivers supply heavy metals and organophosphates to the harbor. Nearby sewerage systems on the Ashley River included the Charleston Municipal Yacht Basin and the outfall of the City of Charleston's Pine Island sewerage treatment plant (Figure 1). This situation thus offered the opportunity of detecting interactions between the marsh and the polluted waters of Charleston Harbor.

152


SETTLEMEYRE

AND

GARDNER

Figure 1.

Chemical Budgets

Location of the study area


154

MARINE CHEMISTRY

Methods Of Study. This study i s based on the comparison of the chemical quality of discharge weighted composite samples of flood versus ebb flow for twenty-five different t i d a l cycles monitored from August 1973 to August 1974. With each cycle, sampling began at slack low water through high tide to the following low tide. Thus, for each cycle the composite ebb sample was sampled from the same mass of seawater as the preceding composite flood sample. Because of l o g i s t i c s , the samples could not be discharge weighted by conventional current meter surveys. Instead we estimated flow into and out of the marsh on the basis of a hypsometric model and tide gage measurements i n a manner similar to that outlined by Ragotskie and Bryson Q ) . The procedure employs aerial photographs to estimate the areas of the marsh and the channel networ It i s assumed that the between low water and bank f u l l stage i s equal to the difference in stage times the average of the bank f u l l and low water channel areas. Between low water and bank f u l l stage i t i s further assumed that the volume increments as a linear function of stage. The same procedure and assumptions are employed to estimate the volume that accumulates between bank f u l l and marsh f u l l (i.e. the stage at which water reaches the perimeter of the basin). The volume that enters between marsh f u l l and high tide i s simply the marsh area times the stage difference. The rating curve obtained by this procedure for D i l l ' s Creek i s shown i n Figure 2. With such a rating curve i t i s possible to select a series of t i d a l stages which mark off equal increments of water volume. Between low tide and bank f u l l stage we sampled so that each 250 ml sample represented 1.25 x 10^ l i t e r s of water according to the tide gage schedule shown i n Figure 2. From bank f u l l to high tide,sample volumes and volume increments were selected as shown in Figure 2. During each cycle water was continuously pumped from the creek through 100 meters of plastic pipe to the edge of the sewerage treatment plant embankment where e l e c t r i c i t y was available for light and instrumentation. The sample intake was located i n mid-channel (Figure 1) 1.3 meters above the bottom. Thus during each cycle the sample intake ranged from about 0.6 meters below the water surface at low tide to about 2.5 meters below the surface at high tide. The pump effluent was monitored at close i n tervals for s a l i n i t y , temperature, and turbidity. A temperature compensated optical refractometer was used for salinity measurements , a calibrated thermistor probe for temperature, and a colorimeter for turbidity. After collection, three aliquots of each composite sample were f i l t e r e d through pre-weighed Millipore 0.45 micron f i l t e r s . The f i l t e r s were washed with d i s t i l l e d water, dried at 105°C and reweighed i n order to determine total suspended sediment (TSS). The organic suspended sediment (OSS) was estimated from the igni-


9.

SETTLEMEYRE AND

GARDNER

Chemical Budgets

155

10

o UJ 3

TIDE G A G E (cm)

Figure 2.

Hypsometric model, tidal gage rating curve, and composite sample schedule for Dills Creek



DATE 08-03-73F E 08-06-73F E 08-08-73F E 08-20-73F E 08- 22-73F E 09- 30-73F E 11-02-73F E 11- 16-73F E 12- 19-73F E 01-08-74F E 01-18-74F E 01- 31-74F E 02- 01-74F E 02-21-74F E

TEMP °C 22.5 25.4 26.3 25.1 25.8 25.4 27.7 29.6 27.5 27.3 27.0 28.2 19.0 20.0 17.1 18.1 11.0 10.8 14.5 13.7 14.9 14.8 16.3 16.0 17.0 17.3 15.0 14.8

8

TABLE I SAL VOL -EEL 10 1 13.2 3.5 13.3 13.9 3.7 12.0 14.4 4.7 14.0 16.5 5.0 17.0 16.5 6.9 16.5 14.7 6.4 14.8 22.5 3.4 23.0 22.0 3.5 21.5 10.4 3.0 10.2 12.5 5.4 13.5 12.2 1.8 12.0 12.4 2.9 11.7 13.8 2.1 13.4 10.9 3.5 10.6 M

M

f

Characteristics of D l l l s TSS ISS COLI Si02 10^/1 ppm PP PP 15.8 8.4 — 4.80 5.4 2.6 — 4.90 75.0 42.0 — 5.00 116.0 65.0 — 5.65 103.0 67.5 33 4.50 133.0 74.5 9 5.20 14.2 9.0 22 4.45 21.0 13.0 7 4.95 20.5 17.1 32 4.40 37.0 30.3 7 4.90 1.0 0.6 26 5.00 1.8 0.9 7 5.00 2.4 1.1 10 2.97 2.5 1.2 8 3.00 28.0 20.0 3 3.40 20.5 10.1 1 3.05 4.2 3.7 27 4.75 5.2 4.2 10 4.00 80.7 70.0 33 3.65 36.2 30.4 32 3.40 11.9 8.2 57 4.45 10.2 7.9 63 4.35 14.3 10.1 2 4.10 12.7 10.7 3 4.10 12.4 8.7 14 4.40 15.2 11.9 1 3.75 21.1 17.1 45 4.85 21.8 17.2 42 4.65 4

Creek Composite Samples P0 BOD7 SURF Fe Cu ppm J2EE E£2 22k EEt 0.64 — 0.56 4.0 5.0 0.77 — 0.27 10.0 4.3 0.32 — 0.62 — 0.57 — 0.45 — 0.28 — 0.53 0.5 2.1 0.50 — 0.24 0.5 0.1 0.41 4.0 0.55 — 0.62 1.7 0.45 0.54 1.8 0.68 -0.84 2.0 0.55 — 0.26 — 0.40 0.5 11.0 0.37 0.31 2.0 7.0 0.20 — 0.74 0.5 14.0 0.28 0.71 4.0 14.0 0.16 — 0.60 — 0.17 0.67 — 0.14 0.8 0.49 2.0 3.0 0.24 0.6 0.42 44.0 4.0 0.31 2.6 0.26 — 0.26 2.2 0.30 — 0.70 — 0.17 1.7 0.56 — 0.24 1.8 0.15 2.6 0.42 4.0 8.0 0.23 2.0 0.44 6.0 6.0 0.13 2.3 0.40 4.0 8.0 0.14 1.8 0.48 4.0 8.0 0.15 1.6 0.36 2.0 4.0 0.17 1.3 0.40 4.0 6.0 ppb 2.0 1.0

1.0 1.0

13.0 11.0 15.0 15.0

13.0 10.0

0.5 10.0 11.3 3.0 2.0 1.0

4.0 5.0

50.0 27.0 20.0 48.0

45.0 15.0

45.0 42.0 67.0 53.0 31.0 42.0

Pb

ppb 35.0 30.0

Zn

05


88

TSS = ISS = OSS = COLI

DATE 03-17-74F E 03-31-74F E 05-04-74F E 05-05-74F E 05- 29-74F E 06- 10-74F E 06-17-74F E 06- 19-74F E 07- 09-74F E 07-24-74F E 07-25-74F E

8

TABLE 1 SAL VOL 10 1 PPt 13.0 1.0 12.9 16.7 1.2 17.0 16.0 7.1 15.5 15.5 4.3 16.0 16.6 3.8 16.2 17.7 2.1 17.3 21.0 5.0 19.5 19.5 7.8 21.0 17.5 4.7 17.2 11.2 5.3 11.0 10.2 3.6 10.0

(Cont.) TSS ISS -EES ppm 18.2 12.6 23.4 17.7 21.4 17.6 21.0 17.6 77.4 46.0 63.0 36.0 40.0 28.0 41.0 18.0 23.8 19.0 37.4 30.0 20.6 16.0 28.3 13.0 41.0 30.0 59.0 39.0 66.0 54.0 73.0 61.0 37.0 32.0 31.0 23.4 35.0 30.0 44.0 34.0 29.0 24.0 36.0 26.0 COLI 10 II 14 6 21 7 22 1 42 16 2 3 21 17 8 13 1 23 13 100 14 6 0 1

total suspended sediment inorganic suspended sediment organic suspended sediment = TSS coliform bacteria

TEMP °C 16.8 16.9 17.8 18.4 23.7 22.7 21.4 21.8 25.0 25.7 26.3 27.5 28.8 27.3 28.3 27.1 27.2 28.5 28.0 29.5 28.0 28.6

ISS

2

Si0 ppm 3.35 3.15 2.75 2.90 2.75 2.80 2.75 2.85 3.10 3.10 2.35 2.85 1.85 2.65 1.60 2.25 2.80 2.85 3.00 3.10 3.00 3.00 4

P0 ppm 0.33 0.34 0.25 0.28 0.58 0.57 0.33 0.42 0.15 0.15 0.16 0.25 0.25 0.28 0.18 0.23 0.18 0.22 0.16 0.16 0.15 0.16

BOD7 ppm 2.7 2.7 1.9 2.3 3.7 3.3 2.9 2.9 3.0 2.9 2.6 3.4 3.6 2.9 3.5 3.0 1.7 1.8 2.0 2.4 1.6 2.0

SURF ppm 0.36 0.35 0.64 0.60 0.54 0.47 0.50 45 49 47 48 45 0.24 0.15 0.17 0.16 0.27 0.13 0.27 0.21 0.27 0.25 7.2 4.9 4.0 4.9 4.1 4.2 1.0 37.0 5.1 1.0 2.8 5.6 3.1 5.1 9.2 2.5 4.3 3.2 3.9 3.0

Fe ppb

12.6 10.0 0.7 1.6 3.2 4.0 6.7 5.1 4.2 2.6 17.0 5.0 3.5 2.0 6.6 6.9 3.8 5.2 1.9 4.1

14.0 51.6 6.6 46.0 1.2 33.3 4.9 42.2 7.2 43.7 9.0 66.6 7.0 54.0 3.8 45.0 2.6 103.0 0.2 46.7 3.7 65.0 7.6 67.0 3.9 36.0 6.6 83.0 8.5 58.0 5.9 53.0 9.0 55.7 9.6 108.9 8.7 58.0 9.8 94.4

b

Pb PP

Zn ppb.

Cu ppb

158

MARINE

CHEMISTRY

tion loss at 550°C (2). A separate aliquot of each composite sample was f i l t e r e d through Millipore 0.45 micron f i l t e r s and a portion of each f i l trate was sent to Orlando Laboratories, Inc., Orlando, Florida for atomic absorption analysis of dissolved Fe, Cu, Zn and Pb on a contract basis. This laboratory uses the APDC-MIBK extraction procedure (3) and employs high intensity replaceable lamp f i l a ments for high sensitivity (4). The rest of the f i l t r a t e was used for analysis of dissolved s i l i c a , phosphate and surfactants. For these measurements Hach Chemical Company reagents and a calibrated Delta S c i e n t i f i c colorimeter were used. S i l i c a was determined by amino acid reduction-molybdate blue formation, phosphate by stannous chloride reduction-molybdate blue formation, and surfactants by melthylene blue-chloroform extraction (2). For some cycles BO the Pine Island sewerag s i s . Millipore Coli Count water testers were used to obtain estimates of coliform bacteria concentrations i n unfiltered samples. Results. Physical data along with the concentrations of various constituents for ebb and flood composite samples for each cycle are shown i n Table I. Budgets for various parameters for each cycle were calculated by multiplying the concentration d i f ference between flood and ebb composite samples times the volume of the t i d a l prism and dividing by the area of the basin (1.08 km ). The results of these calculations are shown i n Table I I . To evaluate the significance of the derived budgets and to identify factors which may influence water quality parameters of the system the data were analyzed by a variety of s t a t i s t i c a l techniques. The paired " t " test (5) was employed i n order to ascertain whether the mean deviations between flood and ebb concentrations of various water quality parameters are significantly different from zero (Table III). The significance of the number of cycles for which flood concentration exceeded ebb was tested by means of binomial probability theory, the null hypothesis being that the chance of flood concentration exceeding ebb on a particular cycle i s 0.50 (Table IV). Because water temperatures change dramatically between September and November and between March and May the budget results have been classified into those of the winter season (November-March) versus those of summer (May-September} The " t " test (6) was used to ascertain the significance of d i f f e r ences between the mean budgets for the two seasons. The results of the analysis of seasonal effects are shown i n Table V along with the simple and seasonally adjusted mean yearly budgets. Seasonal adjustment i s necessary because the number of summer cycles, 15, substantially exceeds the number of winter cycles, 10. Finally, an attempt was made to ascertain whether day versus night conditions have an impact on any of the budgets. Cycles were c l a s s i fied as day or night cycles according to the time of high tide. If high tide occurred at night or within one hour of sunset or



-33 650 180 -230 0 -55 -160 160 55 -500 38 185 74 93 9 -37 324 -195 139 74 695 -1080 120 93 65

2

SALT mg/m

D= day cycle.

D08-03-73 D08-06-73 D08-08-73 D08-20-73 D08-22-73 D09-30-73 Dll-02-73 Dll-16-73 N12-19-73 N01-08-74 N01-18-74 NOl-31-74 D02-01-74 N02-21-74 D03-17-74 D03-31-74 N05-04-74 N05-05-74 D05-29-74 D06-10-74 D06-17-74 N06-19-74 D07-09-74 D07-24-74 D07-25-74

DATE

f

3.37 -14.04 -13.03 -3.17 -10.55 -0.44 0.00 2.42 -0.28 22.20 0.28 0.44 -0.55 -0.24 -0.48 0.05 9.45 -0.40 -4.77 -1.50 -8.33 -5.05 2.61 -4.40 -2.33

2

TSS g/m 2

-42 -85 -130 -97 -192 -65 -25 -4 -28 25 -12 -21 -2 -6 -1 -3 6 -36 0 -18 -14 -36 -17 0 -4

N= night cycle

-32 -220 -304 -232 -319 0 -10 113 208 125 17 0 126 65 18 -17 -32 -40 0 -97 -370 -469 -21 -49 0

2

19 -20 23 -6 -16 -13 1 7 45 20 7 6 42 7 61 30 6

55 200 -17 161 97 97 0 -44 263 0 35 -150 342 324 -20 -185 -124

93 — 57 — 126 46 1250 83 -128 — 54 — 9

2

?

COLI P0, SURF B0D Si0 106/m mg/m2 mg/mz mg/m mg/m2

1.88 — -7.88 -3.05 10.4 -1.85 6.9 -8.43 16.0 -0.18 11.2 0.6 0.00 3.20 0.7 -0.14 4.7 19.80 0.5 0.05 -1.0 -0.16 -0.3 -0.70 2.5 1.0 -0.04 -0.47 0.7 0.00 1.5 6.57 13.4 3.98 10.3 -3.85 -0.4 0.8 0.58 -4.16 -2.3 -5.05 -15.9 3.74 -38.0 -1.96 3.9 -0.67 -0.3

2

ISS g/m 2 2

0.82 -2.42 -0.65 1.16 0.46 -1.34 -1.95 1.13 -0.30 -0.38

—

0.54 0.00 -0.65

--

0.62 -5.85 -9.15 3.26 10.95 -0.92 -33.90 2.18 -26.00 -12.00

—

0.81 2.72 -3.56

0.29 -0.59 -0.31 0.56 0.31 5.56 1.08 -0.13 -0.69 -0.73

—

-2.54 1.55 0.32

—

0.83 —

8.32

-0.28 — —

1.18 0.00

13.20 -8.85

--

—

0.00

—

0.32

2

Pb mg/m

2.37 0.00

— —

-0.44

—

1.62

2

Zn mg/m

0SS= TSS - ISS

0.26 -0.59 -0.04 -13.00 0.80 -1.30 -1.44 2.96 0.54 0.30

—

-0.54 0.00 -0.65

—

-11.65

-0.88 -1.10

—

—

0.87

0.00 —

—

0.23

Cu mg/m

—

-1.90

Fe mg/m

Table I I . Budgets for D i l l s Creek Water Quality Parameters

MARINE CHEMISTRY

Table III. Paired " t " test results on concentration deviations. Sal 0.15 1.07

D t

TSS -1.29 0.36

ISS -0.12 0.05

OSS -3.17 2.35

COLI 3.48 0.73

Si0 -0.09 1.19

P 0

o

4 -0707 4.27

Pb Fe Zn BOD Cu SURF 0.42 0.19 0.06 -3.28 1.08 -4.65 1.27 3.40 0.51 1.06 0.61 1.53 D == mean deviation. Units for deviation are same as in Tables5 I & I I . t(0.05) = 2.07 (23 d.f) - 2.13 (15d.f . ) .

D t

Table IV. Binomia Sal F<E 8 F>E 16 p 0.08 BOD F<E 6 F>E 10 p 0.23

TSS 16 8 0.08 SURF 5 20 0.01

ISS 15 8 0.11 Fe 11 5 0.11

OSS 16 7 0.05 Cu 8 8 0.60

COLI 7 16 0.05 Zn 9 9 0.60

SiO? 14 . 7 0.09 Pb 6 10 0.23

P0 21 2 0.01 4

Students i i! n results for winter versus summer budgets. Parameter A E F B D C Salinity 0.42 17.0 11.9 50.0 26.5 -8.3 -0.56 -393 -1.16 2.20 TSS -3.50 2.38 280 0.40 ISS 0.05 -1.35 1.71 2.15 -1.21 -0.96 -673 OSS 2.23 0.23 -2.15 760 Coliform 1.08 1.20 1.09 0.03 1.07 -29.0 3.89 -62.0 -146 -41 64.5 Si02 -19.6 P0 -28 -32 2.23 -8 -49 84.5 0.52 120 B0D 124 94 146 22 15.4 3.94 SURF -2 27 46 Fe -1.23 -1.75 -1.21 0.51 -1.57 -2.28 0.00 Cu -0.02 0.00 -0.07 0.23 0.07 -1.69 Zn 0.80 -2.39 0.01 -3.18 -4.78 0.22 Pb 0.31 0.59 0.39 0.07 0.55 A -- simple average, units as given i n Table I I . B -- winter average, units as given i n Table I I . C -- summer average, units as given i n Table I I . D -- " t " s t a t i s t i c for difference of winter versus summer mean E -- seasonally adjusted average, units as given i n Table II. F — yearly tpdget based on E i n gnr^ y r " l or 10 cell m y r ~ l . Table V.

t

4

?

6


9.

SETTLEMEYRE AND

Chemical Budgets

GARDNER

161

sunrise the cycle was considered to be a night or subdued light cycle; otherwise, i t was considered a day or f u l l light cycle. A " t " test was used to ascertain the significance of differences between the mean budgets for night versus day (Table VI). Also the day-night effect was analyzed non-parametrically by means of 2 x 2 hypergeometric contingency tables (7). The hypergeometric probabilities of the observed contingency tables are shown i n Table VII. Table VI.

Student's " t " test results on day versus night budgets. Sal

TSS

ISS

OSS

COLI

Si0

t

1.72

2.34

2.81

1.82

0.17

0.94

t

BOD 0.25

SURF

PO

4

1.35

1.64

t(0.05) = 2.07 Table VII.

2

(23 d.f.) - 2.13

(15 d.f.)

Hypergeometric 2 x 2 contingency probabilities (7) for day versus night effect on budgets. Sal

TSS

ISS

OSS

COLI

p

0.17

0.16

0.30

0.17

0.31

Si02 0.11

p

BOD 0.20

SURF 0.14

Fe 0.08

Cu 0.06

Zn 0.24

Pb 0.32

PO4 0.09

Discussion. In this section we w i l l attempt to analyze the results presented in Tables I-VII i n the light of presently understood physical, chemical and biological processes relevant to the salt marsh environment. This then w i l l be an attempt to evaluate the compatibility of our results with previous related research and to suggest mechanisms which may govern the import and/or export of substances from the marsh. In addition, we wish also to assess the s u i t a b i l i t y and limitations of the method of investigation employed i n this study. Salinity. The primary reason for measuring salinity i s that i t provides a check on the method of composite sample collection. Salinity i n D i l l ' s Creek commonly varies by five to six parts per thousand between low and high tide. On rainless days unbiased composite samples of flood and ebb flow should show identical sal i n i t i e s . Consistently higher composite flood s a l i n i t i e s would suggest that the sampling method results i n sampling more saline waters on flood flow whereas the opposite result would i n dicate over sampling of fresher water on flood flow. The paired " t " test (Table III) indicates that the mean deviation between flood and ebb s a l i n i t i e s i s not significant. Binomial probability


MARINE CHEMISTRY

162

theory, however, indicates that the probability of flood salinity exceeding ebb on 16 out of 24 cycles i s only 0.08 (Table IV). It should be noted, however, that on four cycles (8-3, 8-6, 8-22, 12-19) r a i n f a l l occurred during ebb flow and this might explain the lower ebb s a l i n i t i e s observed on these days. On a seasonal basis s a l i n i t y budgets are negative i n winter and positive in summer but the two seasons are not significantly different (Table V). No day-night effects are present (Tables VI and VII) . These considerations, then, together with the fact that there are no obvious correlations with the budgets of other constituents, suggest that the failure to obtain balanced s a l i n i t i e s on most samples i s due to random errors i n sampling and measurement rather than to systematic errors associated with the sampling procedure. Thus, we have confidence that persistent patterns shown by certain constituents (most notably phosphate procedure but are the result Suspended Sediment. In general the average total suspended sediment (TSS) concentration i n D i l l s Creek i s about 31 ppm.Of this, the v o l a t i l e fraction averages about 29 percent. These figures compare closely with those of the Federal Water Pollution Control Administration (8) which reported an average of 32 ppm and 28 percent v o l a t i l e matter for a surface water station i n the Ashley River near the mouth of D i l l s Creek. The paired " t " test (Table 3) indicates that the mean deviations for total and inorganic suspended sediment (ISS) are not significant whereas the deviation for organic suspended sediment (OSS) i s significant. Binomial probabilities (Table IV) suggest that cycles showing export of suspended sediment tend to occur more frequently than cycles showing import. However, i t should be noted that the average budgets for winter versus summer cycles are significantly different at the 0.05 level for TSS and OSS and at the 0.10 level for ISS (Table V). Thus export of suspended sediment probably occurs preferent i a l l y i n summer whereas i n winter there i s import (TSS and ISS) or balance (OSS). On a seasonally adjusted basis the yearly budget for TSS, ISS and OSS are -393 g m" y r " , +280 g m" y r " and -673 g m" yr respectively. The significance of these budgets w i l l be discussed i n detail i n a future report. For the sake of brevity we w i l l simply note that the theoretical budget for ISS required for v e r t i c a l marsh growth to keep pace with rising sea level, 0.15 cm y r ~ l (9,10), can be shown to be about 570 gm m~ y r ~ l , which i s about twice the observed seasonally adjusted budget. With regard to the budget for OSS i t i s reasonable to assume that the maximum export of OSS should not exceed the yearly above ground production of Spartina which for this region probably f a l l s between 660 and 970 g m"2 y r ~ l (11,12). By comparison our value for OSS, -670 g m~ yr'*, may be somewhat excessive since allowance must be made for the fact that a portion of the annual Spartina production i s either incorporated into the sediment or solubilized during microbial 1

f

2

1

2

1

2

2

2


9.

SETTLEMEYRE

A N D GARDNER

Chemical Budgets

163

decomposition. These figures are set forth here because they have a bearing on the budgets of some of the substances discussed below. As for seasonal effects i t i s of interest to note that Boon (13) i n a study of a small tidal creek i n Virginia also found major export of TSS i n summer with minor import i n winter. S i l i c a and Phosphate. The budgets for dissolved s i l i c a and phosphate indicate that the D i l l ' s Creek marsh i s releasing these substances. Since both are involved i n the growth of phytoplankton their export by marshes could play a role i n the ecology of coastal waters. Release of phosphate occurred on twenty-one out of twenty-five cycles. Both the binomial and paired t test results indicate that the export budget for phosphate i s s t a t i s t i cally significant at the 0.05 level (Tables III and IV). On a seasonally adjusted yearl to about 19.6 gm m~ (Tabl fourteen cycles, uptake on seven cycles and no difference on four cycles. It should be noted, however, that a l l of the uptake cycles occurred during the winter months (November through March) and that persistent release occurred during summer. Thus there i s a s t a t i s t i c a l l y significant seasonal pattern to s i l i c a uptake and release (Table V). On a seasonally adjusted yearly basis the net s i l i c a release averages about 29.0 g m~ . The rate of s i l i c a release based on the data of this study compares favorably with an earlier study of s i l i c a export associated with low tide runoff (14). In that study the discharge and s i l i c a concentration of a number of small t i d a l creeks near North Inlet, S.C. and also i n the D i l l s Creek basin were monitored during low tide exposure. The results indicate that dissolved s i l i c a i n the i n t e r s t i t i a l water system diffuses from the sediment into a thin layer of water l e f t on the marsh surface by the receding tide. Drainage of this water during low tide exposure results i n the export of dissolved s i l i c a at a rate of about 1.9 ug m"2 s e c . Discharge weighted composite sampling of a small creek near North Inlet and of a small creek i n the D i l l ' s Creek basin over seven separate cycles gave an average export rate of 2.3 ug m" sec"l as compared with an export rate of 1.0 ug m~ sec" for the D i l l ' s Creek basin. The general concurrence of these three different scale studies indicates that diffusion of s i l i c a from marsh sediment i s a continuous process (at least during summer), that the average yearly flux of s i l i c a from the sediment i s on the order of 50 g m" and that the method of composite sample collection used i n D i l l ' s Creek yields acceptable estimates for budget studies of certain dissolved substances. The export rate for phosphate can be evaluated by similar comparisons. For low tide runoff with an average discharge of 62.2 l i t e r s sec" km" and an equivalent phosphate concentration of 0.7 ppm (14) the export rate i s 0.044 ug m" sec" . This rate, however, i s based mainly on small creeks i n the North Inlet area. One small creek i n the D i l l ' s Creek basin gave a low tide export lf

ff

2

2

f

- 1

2

2

1

2

1

2

2

1


MARINE CHEMISTRY

164 2

rate of 0.31 ug m"* sec"l. Discharge weighted composite sampling of the same creek over three different cycles gave an average export rate_of 0.47 ug m" sec" as compared with an average rate of 0.62 ug n f sec"l for the entire D i l l ' s Creek basin. Thus there i s better correspondence between the results for D i l l ' s Creek at large and one of i t s small creeks than between D i l l ' s Creek at large and the low tide runoff results for the small creeks i n the North Inlet area. The discrepancy between the phosphate export rates for the low tide runoff from the pristine marshes of the North Inlet area as compared with the D i l l ' s Creek basin may be partly due to the fact that the low tide studies do not measure the effect of phosphate pumping by Spartina from the i n t e r s t i t i a l water reservoir (15). From Reimold's data (15) i t appears that the pumping effect could account at most for 0.13 ug PO4 n f sec" or twenty percent f th observed D i l l ' Creek rate Never theless the difference due to the pumping effec expor D i l l ' s Creek basin i s almost an order of magnitude larger than the low tide export rate for the North Inlet area and i n fact compares more favorably with the D i l l ' s Creek rate based on composite sampling than with the North Inlet low tide export rate. This may indicate that there i s a greater amount of decomposing organic det r i t u s i n the D i l l ' s Creek marsh as compared to the North Inlet area because of greater primary production and/or because of the accumulation and decomposition of sewage. The minimum Spartina production that would have to be solubilized i n order to maintain the D i l l ' s Creek rate of phosphate export can be estimated as follows. Assuming that the phosphorous content of dry Spartina i s 0.1 percent (12) then the decomposition of 100 gm of Spartina should yield about 0.1 gram of P or 0.3 grams of PO4. Thus to maintain a yearly export rate of 19.6 g PO, m"2 would require yearly production and subsequent complete decomposition of about 6500 g Spartina per square meter. This figure i s well beyond the range of Spartina production estimates even i f the production of roots and rhizomes i s taken into account. Because only a portion of the Spartina i s solubilized the total production would have to be substantially greater than 6500 grams. Thus the phosphate export rate may be due chiefly to decomposition of sewerage and/or to dissolution of phosphatic sediment derived from f e r t i l i z e r plants and/or to solubilization of f e r r i c phosphate i n the anoxic sediment followed by diffusion into the surface water. As indicated i n an earlier report (14) the magnitude of the export rates for Si(>2 and PO^ indicates "tEat the total amounts of these substances supplied to coastal waters by South Carolina marshes may equal or exceed the total amounts supplied by the combined runoff from the Pee Dee, Santee, and Savannah River basins. Marshes, therefore, may play an important role i n determining the concentrations of these and perhaps other substances i n nearby estuarine waters. 2

1

2

2

1


9.

SETTLEMEYRE

A N D GARDNER

Chemical Budgets

165

Surfactants. Uptake of surfactants occurred on 20 out of 25 cycles. A l l of the cycles that showed release occurred during the winter season (Table I I ) . Thus, as i n the case of s i l i c a , and to some extent with phosphate, there appears to be a seasonal pattern to the surfactant budget. Strong uptake (degradation) occurs i n summer with balance or slight release i n winter. On the average, yearly uptake appears to be about 15.4 g m~2 (Table V). This uptake rate does not necessarily mean that the marsh actually sequesters surfactants by adsorption on clays or chemical precipitation. More l i k e l y i t simply means that surfactants undergo bacterial degradation while the water resides i n the marsh. The question then i s whether the rate of degradation i n the marsh i s greater tha swer to this question i in the marsh environment. The average ratio of ebb surfactant concentration to flood concentration for the 28 cycles available (including three cycles for a small creek) i s 0.87. Thus there i s , on the average, a 13 percent decrease i n surfactant concentration during residence of the water i n the marsh. On the basis of tide gage-time curves and tide gage-volume curves (Fig. 2) we estimate that the average residence time of water i n the marsh i s 4.5 hours. I f i t i s assumed that surfactants are degraded i n an exponential fashion i n accordance with f i r s t order reaction kinetics and that there i s a 13 percent reduction every 4.5 hours, then the time required to reduce an i n i t i a l concentration by 95% (i.e. the lifetime) i s 4.1 days. Patton (16) states that sodium p-m-decyl benzene sulfonate i s biologically decomposed after four days i n river water whereas alkyl benzene sulfonates have halflives of about fifteen days. Thus the marsh degradation rate only represents significant acceleration i f the surfactants present are dominantly of the ABS type. This i s unlikely because most commerc i a l detergents now contain readily degradable surfactants of the linear alkylate sulfonate type. Trace Metals. Analyses of Fe, Cu, Zn and Pb were obtained for 18 cycles. Nickel and cobalt were measured on several cycles but the results were generally below the limit of detection (0.5 ppb) and study of these elements was abandoned. None of the trace metals show significant mean deviations (Table III) nor are their binomial probabilities (Table IV) significant. Of the metals, Fe shows the greatest and most significant mean deviation and the lowest binomial probability. An ordinary " t " test i n d i cates that the mean flood and ebb concentrations for Fe are significantly different (t = 2.05, d.f. = 48). Thus there i s some suggestion that Fe may be exported at a rate of about 1.0 g m y r " (Table V). None of the metals show seasonal effects (Table V) but there i s an indication (Tables VI and VII) that day-night conditions may affect the budgets of Fe and Cu. 2


1

MARINE

166

CHEMISTRY

Assessment of these results i s d i f f i c u l t because the processes and factors which control the concentrations and migration of trace metals i n aquatic environments are poorly understood. Some of the factors and processes that have been discussed i n recent literature are: interactions between trace metals and hydrous iron and manganese oxides (17); precipitation of metal sulfides (18); uptake and movement of trace metals through biota (19, 20, 21, 22, 23); cation exchange between water and sediment (24, 25); complexing of trace metals by dissolved organic matter (21, 26, 27, 28, 29, 30, 31, 32, 33, 34); diffusion and advection under potential gradients (18, 35, 36). In the following paragraphs we w i l l attempt to evaluate several processes which might play a role i n controlling the budgets for trace metals i n the D i l l ' s Creek basin. Accumulation of trac tide i s supersaturated as f e r r i c hydroxide. Then during residence of the t i d a l prism precipitation might occur resulting i n a positive budget. This possibility can be evaluated by estimating the state of saturation of trace metals i n the flood composite sample with respect to possible solid precipitates. In Table VIII we present estimates of the solubility of various metal hydroxides, carbonates and phosphates i n water with a pH of 8 and 14 ppt s a l i n i t y . Metal sulfides are not considered here because sulfide cannot be detected in D i l l ' s Creek surface water and thus metal sulfide precipitation can only occur after diffusion into the sediment (discussed below). Equilibrium free metal ion a c t i v i t i e s , F, are based on solu b i l i t y products given by Krauskopf (37) and Nriagu (38, 39, 40, 41) and assumed C0^"2 and P0^~3 maximum a c t i v i t i e s of 10"5 and 10 10 respectively. Equilibrium total a c t i v i t i e s are based on ion pair formation constants given by Krauskopf (37) and were calculated by means of the equations at the bottom of TableVIII. The equilibrium total a c t i v i t i e s are compared (Table VIII) with the maximum observed flood trace metal concentrations which represent the most favorable conditions for precipitation and positive budgets. As can be seen Cu and Zn i n D i l l s Creek water are undersaturated with respect to possible known precipitates. Lead may be supersaturated with respect to Pb^ (PO^^ Cl but only on those rare occasions when both lead and phosphate reach unusually high concentrations. Iron i s probably supersaturated with respect to f e r r i c hydroxide unless i t exists predominantly i n the ferrous state or i s highly complexed by dissolved organic matter. However, iron appears to have a negative (i.e. export) budget, as indicated above, and thus i t s tendency to precipitate must be offset by other processes. As indicated above the precipitation of trace metals from D i l l ' s Creek surface water as metal sulfides probably depends on the extent to which the dissolved metals can diffuse from the water column into the s u l f i d i c sediment during residence of the water i n the basin. The rate of diffusion i n turn depends primarily 1


9.

SETTLEMEYRE

Chemical Budgets

A N D GARDNER

167

Table VIII. State of saturation of trace metals i n flood tide composite sample.

15.1 39.1 10.5 36.0 26.4 20.5 33.8 36.9 16.9 10.8 35.3 15.3 13.1 9.9 43.5 81.0

Fe(OH) Fe(OH)« FeC0 Fe«(P0 ) 8H 0 FeP0 .2H20 2

3

4

2

2

4

Cu(OH) Cu (OH) C03 Cu (P0 } 2

2

2

3

4

2

Zn(OH) ZnC0 Zn3(PO4)^4H 0 2

3

2

Pb(0H) PbC0 Pb HP0 Pb (P0 ) 2

3

4

3

4

2

pb (po ) ci 5

4

3

Eqt.

pF

Ref.

pKsp

Solid

(37) (37) (37) (38) (39) (37) (37) (37)

3.1 21.1 5.5 5.3 16.4 8.5 8.4 5.4

(37) (40) (37) (37) (37) (37) (41)

5.8 5.1 4.8 8.1 4.9 7.7 10.0

*

*

10.8

1

*

* *

*

*

* * *

* *

6.1 6.3 6.2

1 2 2

5.8 * 5.4 7.7

3 3 3

*

Max. obs. cone, (-log moles / l ) Fe 6.8

Cu 6.7

Zn 5.8

Pb 7.1

pF= equilibrium free ion activity (-log) pT= equilibrium total activity (-log) * No calculation necessary 11

21

1

2

34

2

4

1- F e ^ F e ^ l - f 10 -' [OH] + 10 ' [OH] + 1 - [OH] + 0

1

5

IO* [ci]j 6

7

1

6

8

2- ( ^ - ( c u + t y l + 10' (OH"] + 10 (cr]+ 10' [C0'J + J ° |C03 "'J ) . ^ - [ p b + j (i + i o ' [OH-] + i o - [OH] + i o - [OH] 107.3 jco -2] + IO ' [CO"] + 10* |C1 "]+ IO' 2

3

2

6

2

1 0

9

2

1 3

3+

9

3

10

6

2

2

1

6

3

[» f)


1

8

MARINE CHEMISTRY

168

on the difference i n trace metal concentration between the surface water and the s u l f i d i c i n t e r s t i t i a l water and the depth to the oxidized-reduced boundary (i.e. the gradient). Probably the most outstanding feature of the work that has been done on the occurrence of dissolved trace metals i n s u l f i d i c marine waters i s the fact that, except for Mn and perhaps Fe, the concentrations observed far exceed those predicted by simple metal sulfide equilibria (18,33,34,42). Reasons suggested for the enhanced solubility of trace metals i n s u l f i d i c waters are equilibration with more soluble solid phases, organometallic complexes and bisulfide or polysulfide complexes (26). A summary of average trace metal concentrations found by various workers i s presented in Table IX. Our values are for four grab samples analyzed on contract by Orlando Laboratories. Table IX.

Average concentration marine waters (ppb). Fe 6 22 40 186 5 54

Reference (34) (34) (32) (42) 35 (18) This study 3. 8

Cu Zn 3 7 6 28 4 30 112 105 1 0.5 4 33

Pb

-

In the case of Cu and Zn,the concentrations of these metals i n sediment pore water and D i l l s Creek surface waters are approximately equal i f we assume pore water values of about 5 ppb Cu and 30 ppb Zn. Thus strong gradients probably do not exist to drive these elements into or out of the sediment by diffusion alone and this i s perhaps the reason for our failure to observe significant uptake or export of these two elements. The concentration of Fe i n s u l f i d i c i n t e r s t i t i a l waters, on the other hand, typically f a l l s i n the range from 20-200 ppb as compared to an average 3.6 ppb for D i l l ' s Creek flood composite samples. Furthermore, observations i n the Black Sea (18) and i n other anoxic water bodies indicate that dissolved iron and manganese both show concentration maxima just below the oxidized-reduced boundary whereas zinc and copper do not. While such concentration maxima have not been clearly detected for s u l f i d i c sediments, many of the pore water profiles described by the workers cited i n Table IX show maximum iron and manganese concentrations i n the uppermost samples even though the concentrations i n the overlying water are much lower. We have measured iron concentrations i n several pore water profiles from Baruch Marsh sediments using the newly developed Ferrozine reagent (44) and found that maximum iron concentrations (200-300 ppb) tend to occur i n the upper 10cm of sediment. Thus for diffusion of iron from marsh sediments the most favorable and at the same time r e a l i s t i c circumstances that 1


9.

SETTLEMEYRE

AND

Chemical Budgets

GARDNER

169

can be envisioned i s a maximum iron concentration of about 300 ppb located just below the oxidized-reduced boundary which genera l l y l i e s 5 to 10 mm below the sediment surface. Location of an iron maximum near this boundary i s consistent with the fact that a pH minimum i s commonly found here (unpublished work i n progress) Assuming then the most favorable configuration (300 ppb Fe at 0.5 cm depth) and assuming a linear concentration gradient to the surface where the concentration i s less than 10 ppb, the flux calculated i n accordance with Ficks f i r s t law of diffusion would be about 1.4 x 10" ug cm" sec" using a value of 3.0 x 10" cm sec" for the diffusion coefficient and a value of 0.80 for the porosity. If more or less steady state conditions prevail during t i d a l submergence and i f , as assumed i n the surfactant calculations above, the average residence time of the t i d a l prism is 4.5 hours (1.6 x 10 the sediment to the surfac ug cm" . For an average t i d a l prism with a volume of 5 x 10 l i t e r s this would produce a change i n iron concentration of +0.5 ug l i t e r - which i s about one seventh of the average change. Thus, i f the conditions outlined above actually prevail i n marsh sediments, then diffusion of iron from the sediment pore water could account for a significant portion of the observed export. Additional transfer of iron could also result from bioturbation. Another possible mode of trace metal migration that can be roughly evaluated i s release from decomposing surface Spartina. Dead Spartina i s reported to contain 5,000 ug Fe and 22 ug Zn per gram dry weight (11) whereas the l i v i n g mature plant contains about 300 ug Fe, 11 ug Zn and 2.5 ug Cu (12). These authors i n dicate that Spartina probably accumulates trace metals mainly from the i n t e r s t i t i a l water of deep sediments but that some absorption from surface water may also occur, especially after death. The dramatic difference i n iron between l i v i n g and dead Spartina may be due to i n f i l t r a t i o n of iron rich sediment into the plant after death as after death the ash content increases from 14 to 28 percent (11). Using the trace metal values for the l i v i n g plant i t cari""oe shown that complete decomposition and solubilization on the marsh surface of the annual Spartina production (660 g dry wt m"2 y r " ) would y i e l d about 210 mg Fe -2 -l i 7.0 mg Zn m"2 yr" . Copper and zinc budgets based solely on this mechanism probably could not be detected whereas for iron the calculated yield i s one f i f t h of the observed export and i s probably the maximum to be expected from this process because a large proportion of the annual Spartina production either i s exported as suspended organic sediment or accumulates in the marsh sediment. The rate of iron release from decomposing Spartina can be further evaluated by assuming that most of the suspended organic sediment i s composed of Spartina detritus and by estimating the release of iron from suspended organic sediment during residence of the t i d a l prism i n the marsh. The c l a s s i c a l approach to the 6

2

1

1

2

1

1

m

v

r

a n
24 h o u r s ) c o u n t i n g times needed f o r r e s o l u t i o n ) , no ESCA Fe 2p3/2 peak was o b s e r v e d (12 hour s c a n n i n g t i m e ; t y p i c a l of a l l these s t u d i e s ) . T h i s probably i n d i c a t e s t h a t the s m a l l amount o f i r o n i n k a o l i n i t e i s p r e s e n t i n the l a t t i c e a t depths g r e a t e r than t h e escape depth f o r the p h o t o e j e c t e d e l e c t r o n s . S i n c e Mossbauer i s a b u l k t e c h n i q u e compared t o the ESCA s u r f a c e t e c h n i q u e , i t i s r e a s o n a b l e t h a t s m a l l amounts o f l a t t i c e i r o n p r e s e n t i n the b u l k would be detected. When kaolinite i s s t i r r e d w i t h 100 ppm F e ( N 0 3 ) s o l u t i o n (pH remained low enough t o p r e v e n t p r e c i p i t a t i o n o f any i r o n h y d r o x i d e s p e c i e s ) , t h e Fe 2P3/2 peak was o b s e r v e d i n t h e XPS spectrum ( F i g . I l l ) . Tne Mossbauer spectrum i n d i c a t e d approximately a three f o l d i n c r e a s e i n the amount o f F e ( I I I ) p r e s e n t . The b i n d i n g energy o f t h i s a d s o r b e d F e ( I I I ) s p e c i e s was found t o be 711.4 eV, 1.2 eV lower than t h a t f o r F e ( I I I ) i n a l a t t i c e s i t e i n the o c t a h e d r a l l a y e r o f a s i l i c a t e m i n e r a l . It i s s u g g e s t e d t h a t the l o w e r i n g o f the Fe 2 p / 2 b i n d i n g energy i s due t o the i n t e r a c t i o n o f F e ( I I l ) w i t h the c l a y s u r f a c e upon a d s o r p t i o n . Cations i n the c l a y s u r f a c e r e g i o n (Stern l a y e r ) are a t t r a c t e d to 3

3


11.

Sorbed Metal Ions on Clay Minerals

KOPPELMAN AND DiLLARD

-P «H •H CO

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ooooo

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CM CM

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co m CM ο ο ο ο

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+ 1+1 ^ σ> m m

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195

MARINE

196

CHLORITE

Fe 2p

NONTRONITE α satellite //Λ b Fe(lll)

/

/ b Λ satellite 0

/ /

\

lattice/ ·*

Fe 2p

\

/ \b Fe(ll) ι lattice

a /α

I

y / \ .

\ V

' /

'

/

*

\;

*

V V \

/

I

τ

\V I

I

713

V

*

\ 716

\

.*

*

_J

\

Λ

\

\ » * *

\

I

1

1

710 713 710 Binding Energy (ev)

707

Figure I. Deconvolution of the photopeaks of the Fe 2p /2 level in nontronite and chlorite 3

a

satellite

b

Fe(lll)

c

satellite

d

/ lattice /

Fe(ll) lattice

S t

\

/

ILLITE

\ .

1

Fe 2 p

3 / 2

//

%

/

.· \ c

/

y 717

χ\ 712

707

Binding Energy (ev) Figure 2. Deconvolution of the photopeak of the Fe 2p level in pure untreated illite s/2


CHEMISTRY

KOPPELMAN


A N D DiLLARD

KAOLINITE

I

720

I

I —

715

710

Binding Energy (ev) Figure 3. Photoelectron spectra for the Fe 2p level in untreated kaolinite and kaolinite treated with 100 ppm Fe(NO ) s/t

s

s


198

MARINE

CHEMISTRY

n e g a t i v e l y c h a r g e d s u r f a c e bonding s i t e s where they experience a negative s i t e p o t e n t i a l . i L The e f f e c t o f a n e g a t i v e b o n d i n g s i t e p o t e n t i a l on i r o n would be t o lower t h e b i n d i n g energy o f t h e a d s o r b e d c a t i o n . In s i m i l a r a d s o r p t i o n s t u d i e s o f F e ( I I I ) on c h l o r i t e * t h e b i n d i n g energy measured f o r i r o n from t h e e x p e r i m e n t a l photopeak i s 711.4 ( s e e T a b l e I I ) . T h i s v a l u e i s g r e a t e r than t h a t measured f o r i r o n i n n a t i v e c h l o r i t e and s i m i l a r t o t h a t d e t e r m i n e d f o r F e ( I I I ) a d s o r b e d on kaolinite. I t was d e t e r m i n e d t h a t t h e composite e x p e r i m e n t a l photopeak c o u l d be d e c o n v o l u t e d i n t o two i r o n peaks ( i n c l u d i n g s a t e l l i t e s t r u c t u r e f o r each peak) w i t h b i n d i n g e n e r g i e s o f 711.4 and 710.3 eV. The i r o n s p e c i e s r e p r e s e n t e d by t h e peak a t a b i n d i n g energy o f 711.4 i s w h i l e t h a t a t 710. chlorite lattice. S i m i l a r l y , t h e composite e x p e r i m e n t a l Fe 2p^/2 peak f o r i l l i t e , o b t a i n e d when t h e c l a y m i n e r a l was s t i r r e d a t pH 1 i n a 100 ppm F e ( N 0 ) s o l u t i o n , c o u l d be d e c o n v o l u t e d i n t o t h r e e i r o n peaks ( i n c l u d i n g s a t e l l i t e s t r u c t u r e f o r each peak) w i t h b i n d i n g e n e r g i e s o f 712.6 eV, 711.5 eV, and 710.4 eV. The i r o n s p e c i e s r e p r e s e n t e d by t h e peak a t 712.6 eV i s a t t r i b u t e d t o l a t t i c e F e ( I I I ) , t h a t a t 711.5 eV t o a d s o r b e d F e ( I I I ) , and t h e peak a t 710.4 eV i s c h a r a c t e r i s t i c of l a t t i c e Fe(II). In a f u r t h e r e f f o r t t o i n v e s t i g a t e t h e e f f e c t o f the n e g a t i v e s u r f a c e p o t e n t i a l upon a d s o r b e d c a t i o n s , C r ( I I I ) a d s o r p t i o n e x p e r i m e n t s onto k a o l i n i t e , c h l o r i t e and i l l i t e were p e r f o r m e d . Uvarovite, i n which C r ( I I I ) i s i n an o c t a h e d r a l l a y e r s i t e , was i n v e s t i g a t e d w i t h XPS t o determine t h e b i n d i n g energy f o r Cr 2p>g/2 e l e c t r o n s f o r t h e l a t t i c e s u b s t i t u e n t Cr( I I I ) . XPS i n v e s t i g a t i o n o f t h e t h r e e u n t r e a t e d c l a y s gave no evidence f o r a Cr 2 p « peak. Upon a d s o r p t i o n o f C r ( I I I ) from 100 ppm C r ( N 0 ) (pH = 1 . 0 ) s o l u t i o n s , the XPS spectrum o f each o f t h e s e c l a y s r e v e a l e d a Cr 2p #2 P©ak, i n d i c a t i n g t h a t chromium had i n d e e d been adsorbed. The b i n d i n g energy d a t a f o r t h e Cr 2 p / e l e c t r o n s f o r a l a t t i c e s u b s t i t u t e d C r ( I I I ) as w e l l as t h e d a t a f o r t h e a d s o r b e d C r s p e c i e s can be f o u n d i n T a b l e I I I . The b i n d i n g energy r e s u l t s f o r t h e a d s o r b e d C r ( I I I ) species r e f l e c t e d a s i m i l a r decrease i n b i n d i n g energy f o r t h e a d s o r b e d c a t i o n , as was found i n the F e ( I I I ) a d s o r p t i o n s t u d y . The n e g a t i v e s u r f a c e p o t e n t i a l a t t h e a d s o r p t i o n s i t e m a n i f e s t s i t s e l f by i n c r e a s i n g t h e e l e c t r o n d e n s i t y on t h e a d s o r b e d m e t a l ion thus lowering the binding energy of the metal. 3

3

/ 2

3

3

3

3

2


11. KOPPELMAN AND DiLLARD

Sorbed Metal Ions on Cfoy Minerals

The differences in binding energy for Cr 2p 3 /2 electrons for a lattice substituted Cr(III) as compared to an adsorbed Cr(III) ranged from 0.8 eV (Cr(III)) on kaolinite) to 1.1 eV (Cr(III) on chlorite). Conclusions The technique of X-ray photoelectron spectroscopy has been shown to be a useful tool in the investigation of adsorbed metal ions on solid surfaces. Not only may i t prove to be an analytical tool for detecting small (ppm level) quantities of adsorbed cations, but may be instrumental in determining the bonding nature of an adsorbed cations. Through further investigations of the adsorption of cations of different oxidation states model for cations adsorbed on mineral surfaces can be developed. Acknowledgements This work has been supported by the NSF (Grant GP-29178 ESCA Spectrometer) and by the VPI Small Projects Fund. We would also like to thank Mrs. N. Crews for assistance with the compilation and interpretation of the Mossbauer data and Drs. J. Craig and C. I. Rich for help in obtaining the minerals used in this study.

Abstract The bonding nature of metal ions sorbed from aqueous solutions by the marine clay minerals kaolinite, i l l i t e , and chlorite has been examined using X-ray Photoelectron Spectroscopy (XPS). Binding energies for lattice elements Si, Al, O, Mg, K, and Ca are reported, and are in good agreement with published values. Significant differences (1.9 eV) in binding energies for the Fe 2 p 3 / 2 level for iron in nontronite and chlorite were observed. This difference in binding energy was attributed to the two different oxidation states of iron, Fe(II) in chlorite and Fe(III) in nontronite. I l l i t e , which contains both Fe(II) and Fe(III) in lattice positions was found to have an unusually broad Fe 2 p 3 / 2 photopeak. This broad peak could be deconvolutea into two peaks whose binding energies were indicative of both Fe(II) and Fe(III) lattice constituents. Fe(III) adsorbed onto kaolinite had an Fe 2p3/2 level binding energy 1.2 eV lower than lattice Fe(III). This lowering of binding energy for the adsorbed iron species as compared to


199

200

MARINE CHEMISTRY

lattice Fe(in) may arise from the negative potential of the electrical double layer at the mineral surface when the cation is adsorbed. Comparison of binding energies of sorbed ions ( F e + 3 , C r + 3 ) and their stoichiometric or mineral lattice counterparts i n d i cate a decrease in binding energy for the sorbed ions. Extent of sorption was determined by monitoring sorbed metal ion species concentrations as well as examining changes in solution pH, dissolved SiOo and concentra tion of stoichiometric lattice elements ( A l + , K + , Mg + 2 , F e + 2 ' + 3 ) . Literature Cited 1. Krauskopf, Κ. Β . , Geochim. Cosmochim. Acta, (1956) 9, 1. 2. Kharkar, D. P., Κ. K. Turekian, and Κ. K. Bertine, Geochim. Cosmochim. Acta, (1968) 32, 285. 3. Stumm, W., and Morgan, J. J . , Aquatic Chemistry, Wiley-Interscience, New York, 1970. 4. Van Olphen, Η., An Introduction to Clay Colloid Chemistry, Wiley-Interscience, New York, 1963. 5. Grim, R. Ε . , Clay Mineralogy, 2nd ed., McGraw-Hill, New York, 1968. 6. Whittig, L. D., Page, A. L . , Soil Sci. Soc. Amer. Proc., (1961), 278. 7. Follett, E. A. C . , J. of Soil Science, (1965) 16, 334 8. Fordham, A. W., Aust. J. Of S o i l . Res., (1969) 7 185. 9. Fordham, A. W., Aust. J. of Soil Res., (1969) 7, 199. 10. Fordham, A. W., Aust. J. of Soil Res., (1969) 8, 107. 11. Blackmore, Α. V . , Aust. J. of Soil Res., (1973) 11, 75. 12. Fordham, A. W., Clays and Clay Minerals, (1973) 21, 175. 13. Lindau, I., Spicer, W. Ε., J. Of Electron Spectros copy and Related Phenomena, (1974) 3, 409. 14. Singleton, J. Η., Vac. Symp. Trans., (1963) 15,267. 15. Personal communication with Dr. Peter Orenski of Union Carbide Corporation. 16. Mullin, J. Β . , Riley, J. P . , Analytica Chimica Acta (1955) 12, 162-176. 17. Fanning, Κ. A . , Pilson, M.E.A., Anal. Chem., (1973) 45, 136. 18. Written by G. W. Dulaney, VPI & SU, 1969 (Presently at Digital Equipment, Corp., Maynard, Mass.)


11.

KOPPELMAN AND

DiLLARD


19. Seals, R. D., Alexander, R., Taylor, L. T . , Dillard, J. G., Inorg. Chem., (1973) 12, 2485. 20. Burness, J. H . , Dillard, J. G., Taylor, L. T . , Inorg. Nucl. Chem. Lett., (1974) 10, 387. 21. Adams, I., Thomas, J. M., Bancroft, G. Μ., Earth and Planetary Science Letters, (1972) 16, 429. 22. Huntress, W. T. J r . , Wilson, L . , Earth and Plane tary Science Letters, (1972) 15, 59. 23. Anderson, P. R., Swartz, W. E. J r . , Inorg. Chem. (1974) 13, 2293. 24. Yin, L. T . , Ghose, S., Adler, I., Science, (1971) 173, 633-635. 25. Schultz, H. D., Vesely, C. J . , Langer, D. W., Appl Spect., (1974) 28, 374. 26. Carver, J. C . , Schweitzer J. of Chem. Phys. 27. Fadley, C. S., Shirley, D. Α., Phys. Rev., A. (1970) 2, 1109. 28. Fadley, C. S., Shirley, D. Α . , Freeman, A. J . , Bagus, P. S., Mallow, J. V . , Phys. Rev. Lett., (1969) 23, 1397. 29. Uvarovite - C a 3 C r 2 ( S i O 4 ) 3 (garnet group) - from Outokumpo, Finlana, sample provided by Dr. J. Craig, Dept. of Geological Sciences, VPI & SU, Chemical composition data may be found in Rock Forming Minerals by W. A. Deer, R. A. Howie, and J. Zussman, Longmans Press, London, 1962.


201

12 The Use of Natural Pb-210 as a Heavy Metal Tracer in the River-Estuarine System LARRY K. BENNINGER, DALE M. LEWIS, and KARL K. TUREKIAN Department of Geology and Geophysics, Yale University, New Haven, Conn. 06520

The naturally occurring radioactive isotope of lead, Pb-210, provides a valuable trace the soil-stream-estuary system. Since i t is continuously produced only as a member of the U-238 decay series, i t is free from the problems of environmental or analytical contamination so often encountered in stable heavy metal studies. In addition, because of its half-life of about 22 years i t is useful not only as a tracer but also as a dating tool to monitor events of the past 100 years in various repositories. Lead-210 can be supplied to the soi 1-stream-estuary system through two pathways: (1) atmospheric--Rn-222 released from soils to the atmosphere decays to Pb-210 which then follows the fate of aerosols, ultimately to be returned to the Earth's surface via atmospheric precipitation; (2) terrigenous--Ra-226 in soils, rocks, streams and groundwater generates Pb-210 which is in some degree subject to mobilization. By following the pathways of Pb-210 from both these sources we can make predictions about the expected behavior of common lead at the Earth's surface. Further, by analogy with lead we can get an idea of the behavior of other trace metals in the Earth's aqueous reservoirs. The Fate of the Atmospherically-Supplied Pb-210 Precipitation, as rain, snow or dry fallout, continually strips the atmosphere of aerosols, including the Pb-210 produced there from Rn-222 decay. It has been estimated that tropospheric aerosols associated with Pb-210 have a mean residence time of a week or less (1). As Pb-210 is deposited i t can fall either on standing bodies of water, the ocean or lakes, or on land. There is sufficient evidence now to indicate that in lakes i t is rapidly removed from the dissolved state to the lake sediments (2, 3^ l i l t is also being removed from the ocean surface. We neecT to know the fate of Pb-210 (and presumably other metals) when i t encounters soil. One of the ways of determining this is to see how the atmospherically-derived Pb-210 is distributed in the soil profile 202


12.

BENNINGER E T A L .

Pb-210 as a Heavy Metal Tracer

203

and how w e l l the t o t a l i n v e n t o r y of a t m o s p h e r i c a l l y - d e r i v e d Pb-210 i n the s o i l p r o f i l e r e f l e c t s the expected f l u x . I f the s o i l c o n t a i n s a l l the Pb-210 t h a t i s d e l i v e r e d t o i t by p r e c i p i t a t i o n , we can be sure t h a t the p r o p e r t i e s o f the s o i l s make them e f f i c i e n t scavengers f o r l e a d and o t h e r t r a c e metals s i m i l a r t o lead i n chemical behavior. Continuous c o l l e c t i o n o f p r e c i p i t a t i o n and dry f a l l o u t and monthly a n a l y s i s f o r Pb-210 content have been c a r r i e d out a t the K l i n e Geology Laboratory a t Y a l e f o r the past y e a r - a n d - a - h a l f . These i n d i c a t e a f l u x o f 1 dpm Pb-210/cm /y i n the New Haven a r e a . I f we assume t h a t t h i s i s an adequate measure o f the Pb210 f l u x f o r the northeastern United S t a t e s , then by assaying s o i l i n v e n t o r i e s we can a r r i v e a t the extent of m o b i l i z a t i o n o f Pb-210 from the s o i l . I f a s o i l i s t o be used i n such a study i t must be i n steady s t a t e w i t h r e s p e c t t o th s o u r c e s ; t h i s r e q u i r e s t h a t the s o i l p r o f i l e be undisturbed by man s a c t i v i t i e s f o r 5 h a l f - l i v e s o f Pb-210 o r around 100 y e a r s . Then the f l u x o f a t m o s p h e r i c a l l y - d e r i v e d Pb-210 to the s o i l i s given by the standing crop o f excess Pb-210 d i v i d e d by the mean l i f e of Pb-210, i f there i s no l o s s from the s o i l p r o f i l e by leaching. Several s o i l p r o f i l e s from the Northeast have now been analysed t o t e s t t h i s . We have s t u d i e d the Cook F o r e s t S t a t e Park i n north c e n t r a l P e n n s y l v a n i a , where there i s a v i r g i n stand o f timber up t o 300 years o l d , and two s i t e s i n c o a s t a l C o n n e c t i c u t , the Farm R i v e r s a l t marsh and an a s s o c i a t e d upland i s l a n d . In a d d i t i o n to our d a t a , Fisenne (5) has reported Ra-226 and Pb-210 data f o r an undisturbed s o i T p r o f i l e from a tobacco-growing r e g i o n of Maryland. Table I shows the i n t e g r a t e d f l u x t o these sample s i t e s compared t o the r a i n f a l l d a t a . W i t h i n the u n c e r t a i n t i e s , s o i l s and s a l t marshes r e t a i n v i r t u a l l y a l l o f the Pb-210 s u p p l i e d from the atmosphere. 2

1

Table I Flux o f Pb-210 to the Eastern U.S.A. location

flux dpm/cnr/yr

New Haven, Conn.

1

p r e c i p . & dry f a l l o u t

East Haven, Conn.

1

s a l t marsh p r o f i l e (6)

East Haven, Conn.

0.8

Cook Forest S t . P a r k , Pa. Maryland soil.

1 1.2

type o f measurement

s o i l p r o f i l e (6) soil

profile

s o i l p r o f i l e (5)

The Pb-210 i s a s s o c i a t e d w i t h the o r g a n i c f r a c t i o n of the T h i s m a t e r i a l has the c a p a c i t y to sequester o t h e r metals


204

MARINE CHEMISTRY

as w e l l , as the data from a s o i l p r o f i l e o f the Hubbard Brook Experimental F o r e s t i n New Hampshire c l e a r l y show (Table I I ) . Thus we conclude t h a t metal s s u p p l i e d t o a s o i l p r o f i l e have a low m o b i l i t y i n the d i s s o l v e d phase probably because o f the strong sequestering properties of s o i l organics. Table

II

Hubbard Brook, N.H. s o i l p r o f i l e (7) soil horizon A

Pb-210 excess dpm/gm

Cu PPm

Zn PPm

Cd PPm

Pb PPm

1.5

0.9

1.1

2.1

organic content

280

l

0

A,

0

Lead-210 i n Ground Waters There a r e three p o s s i b l e sources o f Pb-210 i n ground water: (1) A t m o s p h e r i c a l l y - d e r i v e d Pb-210 which i n f i l t r a t e s the s o i l and e n t e r s the ground water r e s e r v o i r s . We know from the s o i l data t h a t t h i s cannot be a l a r g e f r a c t i o n o f the amount s u p p l i e d t o the s o i l . In most o f the e a s t e r n United S t a t e s the mean annual p r e c i p i t a t i o n i s ^100 cm. However the process o f é v a p o t r a n s p i r a t i o n r e t u r n s about h a l f t h i s water t o the atmosphere, r e s u l t i n g i n a net a d d i t i o n o f 50 cm o f water per y e a r o r about 0.05 A/cm /y. S i n c e the f l u x o f Pb-210 i s 1 dpm/cm2/yr, the c o n c e n t r a t i o n o f Pb-210 i n a n n u a l l y charged a q u i f e r s would then be about 20 dpm/ί, i f no removal occurred d u r i n g i n f i l t r a t i o n . (2) Ra-226 and Rn-222 i n s o l u t i o n i n the ground w a t e r , d e r i v e d from l e a c h i n g o r r e c o i l from r o c k s . Ra-226 i n ground water ranges from 0.2 dpm/jt t o 40 dpm/fc but i n general i s around 10 dpm/i ( 8 ) . (3) Pb-210 d i r e c t l y leached from rock and s o i l during weathering. Holtzman's (8) study o f w e l l waters i n I l l i n o i s shows t h a t the a c t i v i t y o f Pb-210 i s always lower than the Ra-226 a c t i v i t y . The s h a l l o w w e l l s c o n t a i n low amounts o f Ra-226 from rock weathering and the h i g h e s t Pb-210 c o n c e n t r a t i o n s o f the ground waters a n a l y s e d . Consequently, they most d i r e c t l y r e f l e c t the annual p r e c i p i t a t i o n . However, the h i g h e s t value i n these s h a l l o w a q u i f e r s , 0.4 dpm/fc, i s s t i l l much lower than the value expected i n the Northeast from p r e c i p i t a t i o n (20 dpm/fc). Thus, l e s s than 2% o f the Pb-210 s u p p l i e d to a t e r r a i n from the r a i n i s t r a n s m i t t e d t o ground water. I f we c o n s i d e r the deep w e l l s analyzed by Holtzman (8) as tapping a q u i f e r s i n which the water has a r e s i d e n c e time o f about 100 y e a r s , we note t h a t the a c t i v i t y r a t i o s o f Pb-210/Ra-226 a r e so low as t o p r e d i c t a mean r e s i d e n c e time f o r Pb-210 o f about 2


12. BENNiNGER E T A L .

Pb-210 as a Heavy Metal Tracer

205

one month (with d e v i a t i o n s by a f a c t o r o f ten around t h i s v a l u e ) . Such a s h o r t residence time i n dominantly limestone and sandstone a q u i f e r s i m p l i e s t h a t any heavy metals i n j e c t e d i n t o the ground water system w i l l be adsorbed on the rocks c l o s e t o the p o i n t o f i n j e c t i o n , and very l i t t l e can be s u p p l i e d t o the streams d r a i n ing the adjacent ground water r e s e r v o i r . The Fate of Pb-210 i n Streams The p r i n c i p a l sources o f d i s s o l v e d Pb-210 t o streams are d i r e c t p r e c i p i t a t i o n onto the water s u r f a c e and s u r f a c e r u n o f f , although some t e r r i g e n o u s Pb-210 i s s u p p l i e d by ground water d i s c h a r g e . In mining areas a c i d mine waters supply Pb-210 as w e l l . What has been learned about the behavior o f Pb-210 i n normal s o i l p r o f i l e s and i n ground water i n d i c a t e s t h a t very l i t t l e Pb-210 can reach normal weathering c o n d i t i o n s . However, the i n j e c t i o n o f Pb-210 i n t o streams by a c i d mine waters does provide a t e s t o f the behavior o f s o l u b l e Pb-210 i n a normal stream system. The f i r s t study o f Pb-210 i n r i v e r waters impacted by mine drainage was c a r r i e d out on the Colorado R i v e r system ( 9 ) . The source waters were as high as 14 dpm Pb-210/fc because o 7 l e a c h i n g of t a i l i n g s from uranium mining operations i n t h i s s e m i - a r i d r e g i o n . As the r i v e r continued downstream t h i s high value was found to be reduced t o 0.29 dpm/fc. T h i s i n d i c a t e s t h a t processes w i t h i n the Colorado R i v e r remove Pb-210 onto p a r t i c l e s . A d e t a i l e d Pb-210 study of the Susquehanna R i v e r system i n the northeastern U.S. has been done. The West Branch of the Susquehanna R i v e r i s massively a f f e c t e d by mine drainage from coal mining and i s high i n d i s s o l v e d (5 meters) and e v e n t u a l l y may d i f f u s e and bubble upwards i n t o the o v e r l y i n g water column. I n t u i t i v e l y , the magnitude of t h i s p r o c e s s s h o u l d be p r o p o r t i o n a l to the amount of o r g a n i c s u b s t r a t e a v a i l a b l e to methane p r o d u c i n g b a c t e r i a . A n o x i c b a s i n s such as the C a r i a c o Trench a r e env i r o n m e n t s which have h i g h amounts of o r g a n i c carbon (^5% i n sediments)· The minimal exchange of t h e s e b a s i n waters w i t h the open ocean a l l o w s f o r a b u i l d u p of h i g h c o n c e n t r a t i o n s of ^ S , produced i n the s u l f a t e r e d u c i n g zone near the sediment-water i n t e r f a c e , and CH^, produced i n the sediments below the s u l f a t e r e d u c i n g zone. Thus, e x t r e m e l y h i g h methane l e v e l s (up to 0.2 m l g p / l i t e r ) a r e observed i n C a r i a c o Trench B a s i n waters (2) . The f l u x of methane from the few a n o x i c b a s i n s to the open ocean i s seemingly s m a l l compared to the add i t i o n from r i v e r i n e , e s t u a r i n e and c o n t i n e n t a l s h e l f sediment s around the w o r l d . C o a s t a l and e s t u a r i n e sediments u s u a l l y have o n l y moderate amounts of o r g a n i c T


13.

S A C K E T T A N D BROOKS

Low Molecular Weight Hydrocarbons

217

matter and p r o b a b l y become s u l f a t e - f r e e w i t h i n a few meters of the sediment-water i n t e r f a c e . It i s highly l i k e l y t h a t a l l of t h e s e w i d e l y d i s t r i b u t e d sediments a r e s o u r c e s of methane which m a n i f e s t themselves as widespread band of d i f f u s i v e seeps. These may be e i t h e r s m a l l b u b b l i n g seeps or n o n - b u b b l i n g w i t h methane b e i n g exchanged by d i f f u s i v e p r o c e s s e s i n the s e d i ments. In many r e g i o n s of the c o n t i n e n t a l s h e l f s m a l l b u b b l e s w i l l d i s s o l v e i n the o v e r l y i n g water column b e f o r e r e a c h i n g the s u r f a c e . R e g a r d l e s s of whether the seep i s b u b b l i n g or n o n - b u b b l i n g the g r e a t e s t dep o s i t i o n of hydrocarbons w i l l take p l a c e i n near bottom water. A l o n g the n o r t h e r n c o n t i n e n t a l s h e l f of the G u l f of Mexico, over one l o c a t e d by sonar t e c h n i q u e a r e a s s o c i a t e d w i t h f o u r t y p e s of g e o l o g i c a l s e t t i n g s : ( 1 ) s h a l l o w n o n s t r u c t u r e d s e d i m e n t a r y beds, ( 2 ) f a u l t i n g , (3) domes, and ( 4 ) mud mounds ( 2 6 ) . The o n l y two gas samples which have been a n a l y z e d and r e p o r t e d i n the l i t e r a t u r e have m o l e c u l a r ( > 9 9 . 9 % methane) and isotopic (6^^C ^ - 6 0 vs PDB) c o m p o s i t i o n s i n d i c a t i v e of a b i o g e n i c o r i g i n (8)· However, both of t h e s e seep gases were a s s o c i a t e d w i t h banks t h a t a r e not known to be a s s o c i a t e d w i t h s a l t domes or deep f a u l t i n g . A c o n c e n t r a t i o n v e r s u s depth p r o f i l e a t one seep l o c a t i o n ( F i g u r e 2 ) shows h i g h d i s s o l v e d methane c o n c e n t r a t i o n s a t d e p t h , i n d i c a t i n g t h a t a p p r e c i a b l e amounts of the seep gases d i s s o l v e i n the o v e r l y i n g water column. The r e l a t i v e l a c k of higher concentrations of ethane and propane at depth than observed a t the s u r f a c e i s a l s o c h a r a c t e r i s t i c of a b i o g e n i c seep. I t i s h i g h l y l i k e l y , a l t h o u g h not s u b s t a n t i a t e d at the p r e s e n t time to the a u t h o r s s a t i s f a c t i o n , t h a t g e o l o g i c a l f a u l t s and s a l t domes may g i v e r i s e to p e t r o g e n i c gas seeps. As p r e v i o u s l y suggested p e t r o g e n i c seepage would be c h a r a c t e r i z e d by low C-/ i ^ + C o ) r a t i o s and ), the p i s t o n v e l o c i t y or exchange r a t e i s on the o r d e r of one to two meters per day f o r methane w i t h slower r a t e s f o r h i g h e r m o l e c u l a r weight and/or more h y d r o p h i l i c species. By e l i m i n a t i n g a l l a n t h r o p o g e n i c s o u r c e s , i t would take about one-month f o r c o a s t a l waters w i t h an i s o p y c n a l water column s t r u c t u r e , such as found f o r w i n t e r c o n d i t i o n s , to r e t u r n to e q u i l i b r i u m w i t h r e s p e c t to the atmosphere. T h i s e s t i m a t e i s based on a mean depth of about 50 meters. For summer c o n d i t i o n s when a t h e r m o c l i n e d e v e l o p s , t h i s exchange would o n l y take p l a c e r e a d i l y w i t h i n the mixed l a y e r . High h y d r o c a r b o n l e v e l s i n the deeper water such as shown on F i g u r e 2. might w e l l be l a t e r a l l y advected out i n t o the open G u l f , and thereby p r o v i d e a tag f o r s t u d y i n g the m i x i n g dynamics between c o a s t a l and open G u l f w a t e r s .


Figure 6. Relative hydrocarbon concentrations and Ci/(C + C ) ratios in the Mississippi River at the delta for 1900-2400 LMT on 14 May 1974 2

3


13.

S A C K E T T A N D BROOKS

Low Molecular Weight Hydrocarbons

229

Summary Thousands of to d i s s o l v e d hydrocarbon de t e r m i n a t i o n s have been made on water samples from the G u l f of Mexico i n o r d e r to l o c a t e and/or c h a r a c t e r i z e (1) n a t u r a l seeps and (2) man-derived s o u r c e s of pe troleum c o n t a m i n a t i o n . R i s i n g bubbles from over 100 n a t u r a l gas seeps have been l o c a t e d by v a r i o u s groups u s i n g c o n v e n t i o n a l sonar t e c h n i q u e s , but the o n l y bub b l e s a n a l y z e d thus f a r have hydrocarbon (>99% CHi*) and isotopic (20 nm tow net) samples were taken a t each Chesapeake Bay s t a t i o n . S i t e l o c a t i o n s were f i x e d by v i s u a l , r a d a r , and sounding techniques. Standard water parameters, i n c l u d i n g s a l i n i t y , - t e m p e r a t u r e , pH, and d i s s o l v e d oxygen, a t depths of i n t e r e s t i n water, were determined. A g r a v i t y c o r e r was used to o b t a i n sediment samples. These were 6 cm i n diameter and v a r i a b l e i n l e n g t h . Cores were immedia t e l y s e c t i o n e d i n t o 4an frozen (-80°C) on board 4 cm s e c t i o n s o f the f r e s h core were immediately measured f o r pH, Eh, and t o t a l s u l f i d e by s e l e c t i v e e l e c t r o d e . Frozen samples f o r l a t e r l a b o r a t o r y analyses were subsequently thawed a t room temperature and d r i e d to constant weight over several weeks i n a s t i l l oven maintained a t 50°C. D r i e d sediment samples were f i n e l y ground i n an acid-washed p o r c e l a i n mortar and thoroughly blended. T o t a l mercury analyses performed i n accordance w i t h EPA methods f o r mercury i n sediments (61) used c o n t r o l spikes o f methylmercuric c h l o r i d e as an i n d i c a t i o n o f the r e l i a b i l i t y o f the procedure. T y p i c a l l y , s p i k e r e c o v e r i e s were i n the range o f 85-110%. Free s u l f u r and ext r a c t a b l e mercury were determined on samples obtained from 24 hr continuous acetone e x t r a c t i o n o f 20-100 g sediment samples i n a g r e a s e - f r e e Sohxlet apparatus. The t o t a l f r e e s u l f u r was determined i n a l i q u o t s o f the e x t r a c t s o l u t i o n by c o l o r i m e t r i c t i t r a t i o n w i t h cyanide to a bromthymol blue endpoint ( 2 0 ) ; p r e c i s i o n here was b e t t e r than ±0.3%. E x t r a c t a b l e mercury was determined by evaporating a l i q u o t s o f the e x t r a c t s o l u t i o n and performing the t o t a l mercury a n a l y s i s by the EPA sediment method. P o s s i b l e v a p o r i z a t i o n o f mercury-containing components o f high vapor pressure from sediments t r e a t e d i n above manners was q u a n t i t a t i v e l y assessed by comparison w i t h e q u i v a l e n t wet sediment samples subjected to exhaustive pumping under h i g h vacuum. Thus, a g r e a s e - f r e e g l a s s apparatus, open to a Hg-free pumping s t a t i o n , c o n t a i n i n g 46.20 g of wet sediment sample, was pumped f o r 48 h r s . to a steady u l t i m a t e pressure o f 7.5X10" T o r r . A l l condensable v o l a t i l e s removed from the sample were c o l l e c t e d i n a t r a p maintained a t - 1 9 6 ° C ; t h i s was 27.39 g which on t o t a l Hg a n a l y s i s i n d i c a t e d a t o t a l of 9.1 ng of Hg had been t r a n s f e r red. The t o t a l Hg found i n the r e s i d u a l vacuum d r i e d sediment was 2.17 ± 0.02 yg/g. Another sample of the same sediment was oven d r i e d a t 50°C f o r one week to constant weight. Total Hg d e t e r mined i n t h i s m a t e r i a l was 2.09 ± 0.05 yg/g, i n d i c a t i n g t h a t no s i g n i f i c a n t d i f f e r e n c e i n Hg assay r e s u l t e d from the two d i f f e r e n t 5


339

Cycling of Heavy Metals

18. BRiNCKMAN AND IVERSON

methods, and t h a t v o l a t i z e d Hg was 0

i * CORE # 1

2 3 if

10 Figure 16. Spatial variation of reactive ortho-phosphate at Station 853-G. Note lower values than Station 853-C and agreement with ammonium (Figure 13), carbonate alkalinity (Figure 10), and chloride (Figure 4) from the same sta tion.

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358

MARINE CHEMISTRY

decrease i n pH with depth might be expected. Figure 17 shows some of the results of the spatial study. The pH values are good to approximately +_ .2 pH units, with a mean pH of about 7.4. The temporal data are incomplete, and therefore not presented, but they show no systematic variations, a l l having values of approximately 7.4 +. .4. Eh. The platinum ion electrode potentials are interesting even though the specific reactions taking place at the electrode surface cannot be determined. The redox potential (platinum electrode potential) drops dramatically from about +100 m i l l i volts to 0 or to negative values i n the f i r s t few centimeters of the sediment, and usually remains relatively constant below 20 cm. Aside from this similar behavior, the profiles from a l l four stations are very this i s a result of a variatio sulfate. The reason that the oxidation-reduction potential appears to stabilize at the value i t does i s not yet understood. Values of the potential appear to be reproducible within about +. 20 m i l l i v o l t s , as seen i n Figure 18. Troup (22) has demonstrated that the absolute value of Eh i s unimportant i n the reduction of f e r r i c oxides and hydroxides to the more soluble ferrous ion as long as the Eh i s no greater than about 0 mv. Holdren (23) has shown that this i s also true for manganese. Thus, i t can be seen that except for the very top of the core, the sediment i s anoxic, and hence, iron and manganese species are mobile. A slight increase i n the oxidation potential with depth may be due to a subsequent depletion of sulfide by the precipitation of iron sulfides (24). Obviously, any sample to be used for the measurement of tEê redox potential must be protected against oxidation by a i r during sampling. Because Eh data collected before 1973 are not reliable, temporal data for Eh are not given. Iron and Manganese. Weathering processes produce fine grained iron and manganese oxides and hydroxides which are brought into the Bay as colloids or as adsorbed coatings on d e t r i t a l particles. Because of reducing conditions beneath the sediment-water interface, the metals are reduced to lower oxidation states and become more soluble. Sediment sampling procedures that minimize the p o s s i b i l i t y of oxidation have resulted in significantly higher observed concentrations for dissolved metals than did prior sampling techniques. These higher metal concentrât ions are compatable for saturation with phases such as iron carbonates and phosphates. The presence of vivianite i n the sediment has already been shown (2) and i s discussed above in connection with phosphate. Concentrations of trace metals i n i n t e r s t i t i a l waters thus becomes a function not only of pH and Eh, but possibly of various metal-anion mineral equilibria .


19.

MATISOFF ET A L .

Interstitial

Water

Chemistry

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S p a t i a l v a r i a t i o n o f i r o n i s d e p i c t e d i n Figure 19. T h i s s t a t i o n e x h i b i t s the poorest agreement among the cores o f the f o u r s t a t i o n s sampled. The c o n c e n t r a t i o n s measured a t 8 5 3 - E agree t o w i t h i n about +_ 10%. N e v e r t h e l e s s , even a t t h i s s t a t i o n q u a n t i t a t i v e comparison o f the cores i s d i f f i c u l t , although q u a l i t a t i v e l y , there i s e x c e l l e n t agreement. The l a r g e v a r i a t i o n s observed are probably r e l a t e d t o l o c a l e q u i l i b r i u m w i t h v i v i a n i t e (compare the i n v e r s e r e l a t i o n s h i p o f Figures 15 and 19). S o l u b l e manganese d i s t r i b u t i o n shown i n Figure 20 f o r s t a t i o n 853-C a l s o e x h i b i t s t h e l a r g e s t v a r i a t i o n among t h e f o u r s t a t i o n s . Q u a n t i t a t i v e l y , t h e data a r e probably good t o about ± 25%. The manganese d i s t r i b u t i o n i s s i g n i f i c a n t l y d i f f e r e n t from i r o n , suggesting t h a t i t s c o n c e n t r a t i o n i s probably cont r o l l e d by a d i f f e r e n t has suggested an e q u i l i b r i u gives a mathematical model f o r the manganese d i s t r i b u t i o n i n t h e next paper o f t h i s symposium (11). Conclusions A c q u i s i t i o n o f a core from a given s t a t i o n i s s u b j e c t t o two fundamental problems which a f f e c t t h e r e l i a b i l i t y o f the data: 1) n a v i g a t i o n a l accuracy which l i m i t s r e l o c a t i o n o f sample s i t e s t o 100 -500', and 2) v a r i a t i o n s i n temperature, s a l i n i t y , and sediment d e p o s i t i o n r a t e s on seasonal and on other t i m e - s c a l e c y c l e s which can i n f l u e n c e both the b i o l o g i c a l and i n o r g a n i c processes t a k i n g p l a c e w i t h i n the cores. Q u a l i t a t i v e l y , t h e r e l i a b i l i t y o f s p a t i a l data i s e x c e l l e n t f o r most chemical species s t u d i e d . I n g e n e r a l , s p a t i a l v a r i a t i o n s were o n l y s l i g h t l y g r e a t e r than t h e l i m i t s s e t by the a n a l y t i c a l techniques. Some important exceptions e x i s t . Ground water i n f i l t r a t i o n can s e v e r e l y a f f e c t t h e i n t e r s t i t i a l water chemistry and may be an important i n f l u e n c e i n some areas o f the bay. A l s o , t h e d i s t r i b u t i o n o f some chemical species i s c o n t r o l l e d by l o c a l m i n e r a l e q u i l i b r i a , and t h i s decreases t h e reproduci b i l i t y o f s p a t i a l data. Temporal v a r i a t i o n s f a r exceed t h e l i m i t s o f s p a t i a l v a r i a t i o n f o r each chemical species i n v e s t i g a t e d . For parameters which a r e c o n s e r v a t i v e and/or i n f l u e n c e d predominantly by i n o r g a n i c a c t i v i t y , seasonal changes i n s a l i n i t y and temperature c o n t r o l the i n t e r s t i t i a l water p r o f i l e s . Those species which are i n v o l v e d i n the decomposition o f organic matter a l s o show a gross seasonal c o r r e l a t i o n , but other processes must be t a k i n g p l a c e . A d d i t i o n a l work i s needed t o f u l l y understand these temporal v a r i a t i o n s and t h e i r importance i n governing t h e mass f l u x across t h e sediment-water i n t e r f a c e . 1


Interstitial Water Chemistry

MATisoFF ET AL.

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Acknowledgements Most of the temporal data were collected by John Bray, Bruce Troup, Mimi Uhlfelder, and Virginia Grant. The authors thank John Ferguson, David Given, Ruth Braun, and Betsy Daniel for their help i n acquisition of the spatial data. Financial support was provided by AEC grant #AT(11-1)-3292. G. Matisoff i s the recipient of a Baltimore Gas and E l e c t r i c Company Fellow ship. Literature 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

11. 12. 13. 14. 15. 16. 17. 18. 19.

20. 21.

Cited

Reeburgh, W. S., Limnol. Oceanogr. (1967) 12, 163-165. Bray, J. T., Bricker, O. P., and Troup, Β. Ν., Science (1973) 180, 1362-1364. Knudsen, M., "Hydrographi Copenhagen, 1901. Dollman, G. W., Environ. Sci. Technol. (1968) 2, 1027-1029. Murphy, J. and Riley, J. P., Anal. Chim. Acta (1962) 27, 31-36. Harwood, J. Ε., van Steenderen, R. A., and Kuhn, A. L., Water Res. (1969) 3, 417-423. Bray, J. T., Ph.D. dissertation, 149 pp., The Johns Hopkins University, Baltimore, 1973. Sandell, Ε. Β., "Colorimetric determination of traces of metals" 1032 pp., Interscience, New York, 1959. Solórzano, L., Limnol. Oceanogr. (1969) 14, 799-801. Strickland, J. D. H. and Parsons, T. R. "A practical handbook of seawater analysis", 311 pp., Bull. Fisheries Res. Board of Can. no. 167, 1968. Holdren, G. R. Jr., Bricker, O. P. III, Elliott, A. J. and Matisoff, G. (this volume). Mackenzie, F. T., Garrels, R. Μ., Bricker, O. P. and Bickley, F., Science (1967) 155, 1404-1405. Hurd, D. C., Earth Planet. Sci. Lett. (1972) 15, 411-417. Lewin, J. C., Geochim. Cosmochim. Acta (1961) 21, 182-198. Siever, R. and Woodford, Ν., Geochim. Cosmochim. Acta (1973) 37, 1851-1880. Hurd, D. C., Geochim. Cosmochim. Acta (1973) 37, 2257-2282. Fanning, K. A. and Pilson, M. E. Q., Science (1971) 173, 1228-1231. Reeburgh, W. S., Ph.D. dissertation, 94 pp., The Johns Hop kins University, Baltimore, 1967. Richards, F. A., In "Chemical oceanography", vol. 1, J. P. Riley and G. Skirrow (eds.), 611-645, Academic, New York, 1965. Mackenzie, F. T. and Garrels, R. M., Amer. Jour. Sci. (1966) 264, 507-252. Berner, R. A., Scott, M. R. and Thomlinson, C., Limnol. Oceanogr. (1970) 15, 544-549.


19. MATISOFF ET AL. 22. 23. 24.

Interstitial Water Chemistry

363

Troup, Β. N., Ph.D. dissertation, 114 pp., The Johns Hopkins University, Baltimore, 1974. Holdren, G. R. Jr., Ph.D. dissertation (in preparation), The Johns Hopkins University, Baltimore. Nissenbaum, Α., Presley, B. J. and Kaplan, I. R., Geochim. Cosmochim. Acta (1972) 36, 1007-1028.


20 A Model for the Control of Dissolved Manganese i n

the Interstitial Waters of Chesapeake Bay G.R.HOLDREN,JR.,O.P.BRICKER, III, and G. MATISOFF Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore,Md.21218

Recent interest i ferro-manganese deposit tions of the distribution of dissolved manganese i n recent sediments (1-6). Attempts to model the observed manganese distribution have been made by several investigators. Michard (7) devised a model to describe the concentration of manganese as a function of depth i n the sediment by dividing the sediment into three chemically distinct zones and by using a partition coefficient, α, to describe the distribution of manganese between the s o l i d and solution phases. The differential equations were developed independently for each zone, and, then, they were coupled at the boundaries between the different zones in order to maintain continuity i n the calculated profiles. Calvert and Price (8) developed a qualitative model to describe the profiles of manganese in the sediments of Loch Fyne, Scotland. Unfortunately, their sample spacing was too large to delineate the fine structure of the dissolved manganese profile typically found in the top few centimeters of an estuarine sediment. Also, analyses of chemical parameters other than the trace metals were not done, and so, they could only presume that the chemical con trols in Loch Fyne were the same as have been found i n other systems. Robbins and Callendar (9) developed a model, purportedly continuous over the depth of the "sediment column, to describe the diagenesis of manganese in Lake Michigan sediments. This model, however, requires that a point source of manganese exist at some arbitrary depth i n the sediment and that the concentration of dissolved manganese slowly approach equilibrium with some elusive d e t r i t a l manganese phase at greater depths. While a nice quali tative fit is obtained for their f i e l d data, very little i s actually known about the chemical nature of these i n t e r s t i t i a l waters, and, thus, the operative equilibrium controls i n this system are again left to conjecture. Other models have been developed to explain the frequently observed enrichment of manganese i n the solid phases of surface sediments. Bender (10), Anikonchine (11) , and Lynn and Bonatti 364


20.

HOLDREN

ET AL.

Dissolved Manganese in Interstitial Waters

365

(12) have developed diffusion models to describe this phenomona. The emphasis of these works has been to investigate i f upward diffusion of manganese could supply the metal required to explain the observed enrichment. In light of this goal, no attempts were made to describe the specific diagenetic reactions involved i n the control of manganese i n these sediment systems. In this paper, we explore possible chemical and physical mechanisms that may control the distribution of manganese i n the Chesapeake Bay estuarine sediments. I n t e r s t i t i a l waters of the bay sediments contain greater concentrations of dissolved man ganese than have been reported i n any other marine or brackish water sediment system (1-4). It i s not uncommon to find man ganese concentrations that exceed 400 uM (^20 ppm) and concentra tions as high as 950 yM (52.5 ppm) have been observed. Based on these observations and i n t e r s t i t i a l waters, w manganous ion i n the Chesapeake Bay sediments. Field Study and Methods A two phase f i e l d program was i n i t i a t e d to investigate the spatial and temporal v a r i a b i l i t y i n the pore water composition of Chesapeake Bay sediments. Figure 1 shows the location of some of our standard sampling stations. The problems involved i n relo cating at any particular stations i n the bay and the attendant sampling errors have been discussed (13). Temporal changes were investigated by sampling monthly at a mid-bay station for the period June 1971 to August 1972. This station, 858-8, i s located at 38°58 20 N χ 76°23 W, east of the mouth of the Severn River and i s located i n about 33 m of water. Three gravity cores were collected each month using a Benthos gravity corer. The sediment was held i n cellulose-acetatebutyrate plastic coreliners. A plastic butterfly valve was used to retain the sediment during retrieval. The water trapped above the sediment i n the core liners during this operation was siphoned off, f i l t e r e d and saved for chemical analysis. Pre determined sections of the sediment were extruded directly into Reeburgh-type sediment squeezers (14). The pore waters to be used for chemical analysis were expressed through Whatman f i l t e r paper and 0.22 ym Millipore membrane f i l t e r s by 150 p s i pressure exerted by nitrogen gas against a rubber diaphram i n the squeezer. Aliquots of these samples were analyzed for carbonate alka l i n i t y , chloride, ammonia, reactive phosphate, ferrous iron, pH, pS and Eh onboard ship. The remainder of the sample was returned to the lab for analysis of s i l i c a and sulfate. A complete description of both the analytical techniques and the sample handling procedures are found elsewhere i n this symposium (13) . In the second phase of the f i e l d program, the spatial vari a b i l i t y of the pore water composition i n the bay was investigated. ,

f,

f

=


MARINE CHEMISTRY


20.

HOLDREN ET AL.


367

Six cruises conducted between August 1972 and December 1974 allowed us to collect over 700 individual i n t e r s t i t i a l water samples along with the associated sediment. Sampling locations ranged from station 935, located at the mouth of the Susquehanna River near Havre de Grace, Md., to station 724R, located between the York and Rappahannock Rivers i n Virginia. During this phase of the program, a l l sample handling operations were done i n a glove box under an inert nitrogen atmosphere to avoid the loss of trace metals and phosphate (15). Otherwise, a l l onboard and laboratory analytical techniques remained unchanged. In addition to the above analyses, dissolved manganese was determined on acidified subsamples of the pore water collected during this phase of the study by direct aspiration of the sample into an atomic absorption spectrophotometer. Typically, samples were diluted by a factor of the concentration of manganes for our instrument. A detailed description of the techniques i s found elsewhere i n this symposium (13). Results and Discussion Physical Influences on Transport: Chloride Data. The Chesapeake Bay estuary i s a very productive area, biologically. This i s reflected i n the organic content of the sediments i n the estuary which i s typically 2 to 3% on a dry weight basis. A large infaunal benthic community i s supported by these organics. The resulting activity mixes the upper portion of the sediment and enhances the exchange of material between the sediments and the overlying water. To investigate the magnitude of this mixing effect, along with other physical processes such as diffusion, we have studied the time dependent changes that occur i n pore water chloride concentration with depth beneath the sediment/water interface. Chloride i s an ideal tracer to study these effects i n an estuary such as the bay. It i s essentially inert i n terms of chemical reactivity i n the estuarine environment. Thus, only the changing physical environment affects i t s distribution. Because of the seasonal variations i n the fresh water input to the bay, the chloride distribution i n the bottom waters i s con stantly changing. This produces a continually varying concentra tion gradient between bottom waters and i n t e r s t i t i a l waters. By following the response of the chloride p r o f i l e i n the sediment to changes i n the chlorinity of the overlying waters, an estimate of the net rate of transport i n the sediment can be made. Figure 2 shows the results of our study at station 858-8. Easily measurable changes occur i n the chloride p r o f i l e on a month-to-month basis. The surface sediments respond most quickly and, with increasing depth, the magnitude of the changes decreases u n t i l at a depth of about 20 cm, variations are essentially within the analytical limits of the measurements. The mean concentration


368

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L

of chloride i n the upper &J 20 cm of the p r o f i l e i s igo aoo ago 210 considerably more dilute than the concentrations deeper i n the sediment. This i s a result of the year-to-year fluctuations in the mean discharge of the Susquehanna River which supplies between 90 and 97% of the fresh water to this portion Depth of the bay. (cm) 50 Statton 854-e If the primary 1 30-VI-71 mechanism for the trans port of chloride i s d i f 5 2H-XI-71 fus ional i n nature, the 7 22-11-72 S 28-IV-7Z diffusion equation should |11 27-VI-72 adequately describe the 1211-VII-7E 13 22-VI11-7E shapes of the measured profiles. Lateral con centration gradients of chloride i n the sediments are small compared to 1οσthe vertical gradients, and so the situation i s reduced to a one dimen sional diffusion problem. Figure 2. Interstitial water chloride profiles collected Several models for dif at station 856-8 (C) over a one-year period. Only about fusion i n modem sedi half of the profiles are shown here. Sampling date for ments have appeared i n each profile is given in the legend. the recent literature ( 1 6 - 1 9 ) . Only one of these was designed specifically to deal with a boundary condition which i s oscillatory i n nature ( 1 7 ) . However, for our purposes i n this paper, the numerical approach used by Scholl et a l . , i s too involved. One other may be important i n setting up this diffusion model for chloride. Sediment deposition i n the Chesapeake Bay is on the order of 1 cm/yr ( 2 0 ) . The sediment i s derived from both shoreline erosion and suspended sediment discharge from the inflowing rivers and streams. While this probably does not significantly alter the chloride distribution i n the sediment over the period of one year, provisions should be made i n the model to account for any long term effects resulting from the sediment accumulation on the chloride distribution. The equation, incorporating a sedimentation term, is : dCl

D d Cl z

- U dCl

ί Ά Λ


20.


HOLDREN E T A L .

369

With the boundary conditions: Cl(0,t) = Clo + C l i cos(aht) + C l cos(a)2t)

(2)

2

dCl

dC

= ° X +

(3)

oo

where Cl(X,t) = depth and time dependent chlorinity Clo = long term mean chlorinity C l i , CI2 = short and long term chlorinity variations, respectively ωι, 402 = frequency of the short and long term variations, respectively D = the molecular diffusion coefficient X = depth i n cm below the sediment/water interface and U = sedimentatio Equation (1) i s the standar equation with an advective term (-U dCl/dX) to describe the ef fects of sediment deposition. The boundary conditions are based on the physical observation made for the system. The f i r s t boundary condition describes the chloride concen tration i n the overlying water as a function of time. The f i r s t term on the right hand side of the equation i s the long-term mean chlorinity. The second term accounts for the seasonal fluctua tions i n the chloride concentration. These are the variations ob served i n the month-to-month changes i n the chloride p r o f i l e s . The last term describes the long term changes i n the mean annual chlorinity. It i s this term which accounts for the skewing of the upper portion of the p r o f i l e toward more dilute concentrations relative to the deeper pore waters. The second boundary condition simply states that there i s no net diffusional flux of chloride at great depth i n the sediment. This i s equivalent to saying that the estuary i s "lined" by impermeable bedrock beneath the sediment. For constant D and U the solution to this equation i s found in Carslaw and Jaeger (21): Cl(X,t) = C l + Cl -cos{(0it - Xa ^ s i n ( ^ i ) }-exp 0

r

cos(%(>!)} + Cl -cos{a) t - X a 2

e x p i i g - Xa

a, where a i - {-^

++

- Xa ^

x

h 2

îSjl }}h , 2

Φι = tan^HDaH/U ) ,

2

2 2

x

sin(%f> )}' 2

cos(^f> )}

(4)

2

aa, -- f - ϋ ΐ 2

φ

++

β 2

1 }% 2

2

= tan^HDo^/U )

and a l l other terms as defined above. By picking values for U, 0 , and 0)2(0)1 = 2II/year), theoretical, time dependent chloride profiles can be calculated. The range of


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370

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the values f o r U and 0)2 are a v a i l a b l e from independent sources (20, 22). T h e r e f o r e , an extimate o f the d i f f u s i o n c o e f f i c i e n t t y p i c a l of bay sediments can be made by matching c a l c u l a t e d p r o f i l e s to the f i e l d d a t a . The r e s u l t s o f some r e p r e s e n t a t i v e c a l c u l a t i o n s are shown i n figure 3a-c. A l l three parameters, D, U and ωζ, were v a r i e d i n the c a l c u l a t i o n s to determine the nçt e f f e c t o f each on the p r o files. Results i n d i c a t e that reasonable r a t e s o f sedimentation has very l i t t l e e f f e c t on the c h l o r i d e p r o f i l e s . I t makes l i t t l e d i f f e r e n c e whether U i s 3 x 1 0 " cm/yr o r 3 cm/yr i n the final results. Changes i n ωζ has o n l y a s l i g h t l y greater e f f e c t . 5

Changes i n the d i f f u s i o n c o e f f i c i e n t , D, had the g r e a t e s t e f f e c t o f these three parameters. Comparison o f the c a l c u l a t e d p r o f i l e s t o the f i e j d data i n d i c a t e t h a t the best value f o r a constant D i s 5x10"" c m values that have been r e p o r t e Results o f the model i n d i c a t e that the d i f f u s i o n c o e f f i c i e n t i s not s t r i c t l y a constant with depth. We have a numerical model which c a l c u l a t e s c h l o r i d e c o n c e n t r a t i o n p r o f i l e s through time f o r any a r b i t r a r y f u n c t i o n a l form o f D. However, the purpose here i s not t o generate exact r e p l i c a t e s o f the observed c h l o r i d e p r o f i l e s i n the bay sediments, but r a t h e r i s to o b t a i n a f e e l i n g f o r the magnitude o f the combined e f f e c t s o f d i f f u s i o n , b i o t u r b a t i o n and sedimentation on the d i s t r i b u t i o n o f any d i s s o l v e d component o f the i n t e r s t i t i a l waters. The simple model d e s c r i b e d above accomplishes t h i s g o a l . Manganese: F i e l d Data. The next step i n determining the o v e r a l l d i a g e n e t i c behavior o f d i s s o l v e d manganese i n anoxic pore waters i s to i d e n t i f y which, i f any, s p e c i f i c r e a c t i o n s o r apparent e q u i l i b r i a may be i n v o l v e d i n c o n t r o l l i n g the manganese cycle. To do t h i s i t f i r s t helps to examine the c o n c e n t r a t i o n p r o f i l e s o f manganese. Figure 4 shows some t y p i c a l p r o f i l e s o f d i s s o l v e d manganese f o r s t a t i o n s l o c a t e d along the a x i s o f the bay. These samples were c o l l e c t e d i n the summer o f 1973. Several features o f these p r o f i l e s should be noted. The c o n c e n t r a t i o n o f d i s s o l v e d manganese i n the o v e r l y i n g waters never exceeded 6 μΜ on t h i s c r u i s e . These v a l u e s , which are r e l a t i v e l y concentrated by open water standards, are probably the r e s u l t o f the resuspension and subsequent mixing o f the top few m i l l i m e t e r s o f sediment which occurred during the c o r i n g operation. Within the sediment, concentrations o f d i s s o l v e d manganese i n c r e a s e q u i c k l y below the sediment/water i n t e r f a c e . Commonly, the c o n c e n t r a t i o n i n the top two centimeters o f the sediment column i s the h i g h e s t i n the c o r e . Concentration o f d i s s o l v e d manganese u s u a l l y decreases with depth. Samples c o l l e c t e d at other times o f the year e x h i b i t the same gross f e a t u r e s . However, d u r i n g c o l d e r p e r i o d s , the maximum c o n c e n t r a t i o n i s reached f i v e or ten centimeters below the sediment/water i n t e r face.


20.

moo

U ··

I

tyo.to

%οο. oo

U

Ο cm / yr

tii.oo

6

S-j

cm

2

s

Ϊ Ι » 00

s.oo

»»o.oo

»P»oo

'Ε · 0

0

1 0 cm / yr

D : 5 x ICT cm sec"

sec

2

1

ω 2 = 25 yr

012 = 12 5 yrs

â00.00

CMLflRlMITT wa.oe «f°;»°

wo.oo

6

D = 2 5 « K)"

371


HOLDREN ET AL.

ÎJ0.00

2*5 00

?60.00

?7V 00

[CL*J m e ^ y l 2MO

2fcO

2«0

30O 310

U = 0 cm/yr D = 2 5 « I0" cm/yr 6

CJ2 =25 yr

Figure 3. a-c. Vertical profiles of chloride calculated by the diffusion model. These plots show the effect of varying D, U, and ω2 on the profiles, d. For comparison to the model profiles, the field data is replotted.


372

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CHEMISTRY

To determine whether any heterogeneous equilibrium con straints are being imposed on the concentration of dissolved manganese by the pore water composition, a c t i v i t y calculations were made on each sample. These calculations were checked for possible saturation of a number of common sedimentary manganese minerals including rhodochrosite (MnC0 ), reddingite (Μη (Ρ0ι*)2* 3H20) and albandite (MnS). The calculation used a modified form of the Garrels and Thompson model for sea water (25) to describe the ionic medium and determine ionic strengths. Activity coef ficients were estimated from the extended form of the Debye-Huckel equation. An ion pairing model was then used to calculate a c t i v i ties of manganous ion from the composition of the pore waters. Free energy data used i n calculations were obtained from several sources (26, 27). The results of thes i s the only mineral fo This supersaturation exists at a l l stations and for most levels within the sediments of the bay. In the northern bay, the pore waters are between 1.5 and 2.5 orders of magnitude supersaturated and i n the southern bay, the pore waters are generally i n the range of 0.5 to 1.5 orders of magnitude supersaturated with respect to rhodochrosite. Alabandite i s the only other mineral that even approaches saturation i n the pore water system. This situation occurs i n the southern portion of the bay where pore water sulfide values are generally higher because of the greater sulfate concentrations in the overlying water. To describe manganese profiles i n the bay, the interaction between manganese and carbonate must be further investigated. To this end i t i s helpful to understand the behavior and genesis of bicarbonate i n the pore waters of the bay. 3

3

Carbonate. At pore water pH's, bicarbonate ion concentration is essentially equal to the carbonate alkalinity. Figure 5 shows some profiles of carbonate alkalinity measured at stations located along the axis of the bay. Concentrations of bicarbonate ion i n surface sediments and overlying waters rarely exceed 1.5 meq/1. The concentration generally increases with depth; however, individual profiles can be quite complex. Bicarbonate ion i s a byproduct of bacterial oxidation of organic matter i n the sediment. In an anoxic marine environment, sulfate i s used by the bacteria as an oxygen source. The general equation for this oxidation i s written: (CH O) 6(NH ) (H3PO^) + 53 SOiT = 106 HC0 " + 53 HS~ 2

10

3

+ 16 NH/

l6

3

+ ΗΡΟι» " + 39 H 2

+

(5)

For every equivalent of sulfate reduced, one equivalent of bicarbonate i s generated, along with lesser amounts of ammonia,


20.


HOLDREN ET AL.

373

Mn *x I0" M 2

100 300

100 300

6

100 300

500

100

300

500 700

ι o| 20 30 40 50 60

927

919

856-C

904-Ν

/

° 80 100 300

5 «ο 20 Ά0 40 50607080-

500

700

— ι — | J ι \—ι—ι—ι—r

\ 848 Ε

\

Γ

100 300

100 300

100 300

100 300

'

834 6

L 8I8P

804

I

. 724 R

Figure 4. Profiles of dissolved manganese in the interstitial waters of the sediments obtained along the central axis of the bay. These are typical summer profiles.

Figure 5.

Sulfate and alkalinity data for the interstitial waters along the axis of the bay. These are typical profiles.


374

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phosphate and sulfide. Measured profiles of sulfate i n the bay sediments are shown i n figure 5. The one-to-one correspondence between the amount of sulfate reduced and the amount of bicarbonate generated as predicted by (5) does not hold true. However, as can be seen i n figure 5, a nearly linear relation does exist. Bicarbonate Ion Control of Manganese. The reaction of bicarbonate ion with manganous ion can be expressed as; Mn

2+

+ HC0 " = MnC0 j + H 3

3(g

+

(6)

As indicated by the a c t i v i t y calculations, this i s the reaction which controls the concentration of manganese i n the sediment. The ion activity product (IAP) of the reaction components of ( 6 ) calculated from pore wate thermodynamically derive This occurs for two reasons. F i r s t , one of the assumptions made i n setting up the ion pairing model to calculate manganous ion a c t i v i t i e s was that only inorganic ion pairs need be considered. No attempt was made to account for organic complexes of manganese. The i n t e r s t i t i a l waters of the Chesapeake Bay contain up to 70 ppm dissolved organic carbon. Others (28) have shown that manganese can complex strongly with naturally occurring organics. Because the association constants for reactions of this type are not well known, they cannot be included i n the equilibrium calculations. This exclusion results i n calculated a c t i v i t i e s which are larger than actually occur. The second reason apparent supersaturation exists i n the bay sediments i s that the IAP we calculate i s compared to the solub i l i t y of pure rhodochrosite. It i s highly l i k e l y that the rhodochrosite i n the sediments i s not a pure phase, but a solid solution with an enhanced s o l u b i l i t y compared to that of pure rhodochrosite. To incorporate the effects of these two factors, we calculated an "apparent s t a b i l i t y constant", K£p, to describe the reaction between the dissolved components and the solid sedimentary carbonate phase. pH, alkalinity and manganese data from the deepest sample from each core was used for this purpose. We f e l t that these samples had had the greatest opportunity to attain equilibrium with the s o l i d phase. This calculation yields a Gibbs free energy for the manganese carbonate phase of -193.1 kcal/mole. These combined effects reduce the apparent s t a b i l i t y of the sediment phase by about 2 kcal compared to the free energy of pure rhodochrosite which l i e s i n the range -195.05 (29) to -195.7 kcal/mol (30). If the pH and bicarbonate concentration are known, the concentration of manganese can be determined from the mass action relation for (6).


20.

Μη*-

375


HOLDREN E T AL.

%

=

[ H

]

' * [HC0 "]

(7)

3

Sample by sample adjustments of pH could be made i n applying (7) to the calculated manganese profiles. However, because variations in pH with depth in any one core are generally small, and i n order to maintain continuity, the mean value of the measured pH within a core i s used for a l l depths in that core. Similarly, bicarbonate concentrations on a point by point basis could be used i n the calculation. However, to expedite the computational process and again for sake of continuity i n the p r o f i l e s , we chose to use a simple model to describe the genera tion of bicarbonate. Because of the observed relation between sulfate and bicarbonate modificatio f Berner model fo sulphur diagenesis was use distribution i n the sediment described as a function of depth by the equation: 1

HC0 ' = HC0 " UJ 3

where

3

+

T

T

U

f °° [1 - exp(-KiX/U)] + KiD n

(8)

HC0 ^jj= bicarbonate i n the overlying water 3

U D G Ki

the sedimentation rate the diffusion coefficient for bicarbonate the organic content of surface sediments the f i r s t order rate constant for bicarbonate generation and X = distance below sediment/water interface (cm) There are several assumptions i n this model. U and D must be constants through time and space, respectively. Generation of bicarbonate i s assumed to be a f i r s t order reaction with respect to the amount of available organic material in the sediment. Finally the bicarbonate p r o f i l e i s assumed to have reached steady state. Since we are simply f i t t i n g this model to the bicarbonate data, these assumptions are of l i t t l e concern to us. Estimates for U and D are obtained by independent means. By adjusting the values of Ki and G the model can be f i t to the data. The results of this method of calculating the bicarbonate concentrations are shown in figure 7 for several of our stations. The values of pH, U, Ki, and G used for each station are l i s t e d in table I. By using (8), concentrations of dissolved manganese can be calculated for most of the sediment column. However, the results of the calculation i n the top few centimeters of the sediment are inconsistent with the f i e l d data. This portion of the p r o f i l e must be controlled by some other process. Oxidation and Diffusion of Manganese. The concentration of dissolved manganese i n the waters immediately overlying the sedi ment are generally small. The concentration jumps to as high 0

= = = =

0

0


376

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CHEMISTRY

TABLE I Station

pH

U cm/yr

904D 834G 914Q 84 8F 919T

Ki year""

Go mmoles l "

0.0133 0.0385 0.0345 0.0198 0.0277

0.091 0.265 0.082 0.179 0.105

1

1.0 0.5 1.0 0.5 1.0

7.5 7.65 7.2 7.7 7.0 6

K 1

(Μη0 )ο 2

2

year"

1

0.0173 0.0173 0.0173 0.0173 0.0173

moles 1" 0.010 0.0025 0.012 0.005 0.015

2

D = 3x10" cm /sec. for a l l stations. as 857 μΜ within the top two centimeters of the sediment. To maintain such a large concentratio tance for any length o exist at the sediment/water interface. Manganese i s sensitive to the oxidation potential of the environment. Upon diffusing from' the anoxic mud into a zone containing free molecular oxygen, manganese would precipitate as a hydrous-oxide phase. Then, upon burial, this metal would be available for remobilization. The concentration of dissolved manganese i n the zone immedi ately beneath the oxic layer i s dependent on two factors: 1) how fast the metal i s released from the solid phase, and 2) how quickly i t diffuses away from i t s source. The rate a material is released from a solid depends on many parameters. The surface area of the s o l i d i s one of the major factors (32, 33). The hydrous oxide phase i s present essentially as a two dimensional coating on clay particles. For this reason, the amount of solid manganese i s roughly proportional to the surface area of the solid available for dissolution. I f we assume that the rate of dissolu tion of manganese i s f i r s t order relative to the amount of avail able solid phase, the rate of production w i l l be expressed as

^42fi

(9)

= -K (Mn0 ) 2

2

To apply this expression to bay sediments, we must assume that for any station the supply of solid manganese to the surface sediments i s constant with time. Since this surface zone rarely extends more than about 5 cm into the sediment, representing a maximum period of about 10 years, this i s a reasonable assumption. Finally, the balance between the rate of dissolution and subsequent upward diffusion of the manganous ion must be estab lished. I f we assume the system i s i n steady state, this balance can be written D dm — 2

2+

aX

U d Mn — — —

2+

ν Γ\Λ c\ \ A + K (Mn0 ) = 0 2

2

(10)

aX


20.


HOLDREN E T A L .

377

with the boundary conditions 2+

Mn (0,t) = 0 and

2+

Mn (°°,t) = M n

2+ f

The solution to this equation is Μη * = 2

ϋ

[i

2

U

2

- exp(-K X/ ) ]

(11)

2

+ K2D

υ = the sedimentation rate D = the diffusion coefficient for Mn K2 = the f i r s t order rate constant for the dissolution of the hydrou and (MQO2)0= the amoun sediments. X = distance below sediment/water interface (cm) This solution i s similar to (8). The values of (MnU2)o and K2 are l i s t e d i n table I. The two processes that dominate manganese chemistry have now been described. They must be integrated into a unified model i n order to predict the distribution of dissolved manganese over the whole sediment column. Each reaction i s limiting over that part of the sediment where i t i s dominant. This i s to say, i n the upper part of sediment, there i s only a limited rate at which Mn i s produced. It cannot attain concentrations large enough to become saturated with respect to any mineral because i t simply diffuses to the sediment/water interface too quickly. At greater depths, the amount of dissolved Mn which can be maintained by dissolution i s greater than that which i s allowed by the solu b i l i t y of the manganese carbonate. Precipitation of the carbo nate then becomes the limiting factor i n the observed concentra tion of the metal. Therefore, by calculation the concentration of manganese using both (7) and (11), the observed concentration w i l l be the lesser of the two values at any particular depth. where

2+

2+

2+

Results of Model Calculations. Figure 6 shows the results of our calculations. The second i n each set of graphs shows the concentration of dissolved manganese as a function of depth in the sediment at several northern and mid-bay stations. The solid line i s the concentration of dissolved manganese predicted by the model. Remember that this single line i s the combined result of two competing processes. The portion of the curve increasing with depth i s the result of the dissolution and upward diffusion of manganous ion. The lower portion of the p r o f i l e i s the part controlled by equilibrium with the carbonate phase.


378

MARINE CHEMISTRY

•>·*/!

ΚΓ*Μ

rnaq/i

0 1

I

ΙΟ"· M 300

10"* M

400

1

7 \ -

854 6 CBASS S M n » * ΙΟ"· Μ

§34 6 C.A. mtq/1

1

- 1

1

,1

Figure 6. Plots of the carbonate alkalinity and dissolved manganese profiles atfiveupper and mid-hay stations. The alkalinity plots show thefielddata (φ) and the model repre sentation of that data used in the calculation of the manganese profiles ( ). The sec ond graph in each set contains the dissolved manganese profile at each station (φ). The concentration profiles predicted by our model using the pH and alkalinity data are shown by the line.


20.

HOLDREN E T A L .


379

Conclusion We have developed a model for the prediction of dissolved manganese distribution i n the anoxic pore waters of the sediments of the Chesapeake Bay. The model requires knowledge of the pH of the pore waters, the distribution of bicarbonate ion with depth in the sediment, the amount of manganese oxide i n the surface sediment and the rate of release of manganous ion from those solids. In the calculations presented, a modification of Berner*s model for sulphur diagenesis was used to describe bicarbonate ion distribution. This model was f i t to the observed profiles. Other techniques, however, such as f i t t i n g a power series to the data, could equally serve this purpose. There were severa diffusion coefficient an constant through space and time, respectively. We assumed that steady state had been reached i n the system, and that with depth in the core manganous ion was i n equilibrium with a poorly crystalline carbonate phase. The model was developed from observations on the pore water composition. The model describes the results of two independent competing reactions. Both reactions are continuous over the whole sediment column, and the final calculated concentration of dissolved manganese at any particular depth i s dictated by the process most limiting that concentration at that depth. Agreement between the model and the f i e l d data i s generally good. This suggests that the processes controlling the distribution of dissolved manganese i n the bay sediments are basically understood. The results of the model are qualitatively the same as reported profiles of dissolved manganese i n other marine sediment systems (1, 3, 9). It would be most interesting to see i f the model can describe these i n t e r s t i t i a l water systems with the same accuracy as was obtained i n Chesapeake Bay sediments. Acknowledgements The authors thank John Bray, Robert Mervine, Bruce Troup and Mary Uhlfelder who helped develop most of the f i e l d techniques used i n this work and who conducted the f i r s t phase of the f i e l d program. We also thank Ruth Braun, Betsy Daniel, J e f f Elseroad, John Ferguson, Dave Given, Peter Kaerk and the many others who assisted us i n both the f i e l d and lab. Special thanks goes to Mrs. Virginia Grant who did much of the lab work and to whom we went when the inevitable problems arose i n the lab. This work was supported by AEC contract no. AT(11-1)3292.


380

MARINE CHEMISTRY

Literature 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

14. 15. 16. 17. 18. 19. 20. 21. 22.

23. 24. 25. 26.

Cited

Duchart, Patricia, S. E. Calvert and Ν. B. Price, Limnol. Oceanogr. (1973), 18 (4), 605-610. Bischoff, James L., T-L Ku, J. Sed. Pet. (1971), 41 (4), 1008-1017. Li, Yuan-Hui, J. L. Bischoff and G. Mathieu, Earth Planet. Sci. Letters (1969), 7, 265-270. Presley, B. J., R. R. Brooks and I. R. Kaplan, Science (1967) 158, 906-910. Hartmann, vonMartin, Meyniana (1964), 14, 3-20. Spencer, Derek W. and P. G. Brewer, J. Geophys. Res. (1971), 76 (24), 5877-92. Michard, Gil, J. Geophys. Calvert, S. E. and (1972), 16, 245-249. Robbins, John A. and E. Callendar, Amer. J. Sci. (1975), accepted for publication. Bender, Michael L., J. Geophys. Res. (1971), 76 (18), 42124215. Anikouchine, William H., J. Geophys. Res. (1967), 72 (2), 505-509. Lynn, D. C. and E. Bonatti, Mar. Geol. (1965), 3, 457-474. Matisoff, Gerald, O. P. Bricker, G. R. Holdren Jr. and P. Kaerk, Proc. ACS-MARM Symposium, Mar. Chem. in the Coastal Environment, Philadelphia, Pa. (1975). Reeburgh, William S., Limnol. Oceanogr. (1967) 12, 163-165. Troup, Bruce Ν., O. P. Bricker and J. T. Bray, Nature (1974), 249 (5454), 237-239. Lerman, A. and B. F. Jones, Limnol. Oceanogr. (1973), 18 (1), 72-85. Lerman, A. and R. R. Wei1er, Earth Planet. Sci. Letters (1970), 10, 150-156. Tzur, Y., J. Geophys. Res. (1971), 76 (18), 4208-4211. Scholl, David W. and W. L. Johnson, 7th Int'l. Sedimento logical Congr. (1967), Abstract. Schubel, J. R., Beach and Shore (1968), April. Carslaw, H. S. and J. C. Jaeger, "Conduction of Heat in Solids," 510 pp, Oxford Press, London, 1959. U. S. Dept. of the Interior, Geological Survey, "Estimated Stream Discharge Entering Chesapeake Bay," Monthly Reports 1951- . Manheim, F. T., Earth Planet. Sci. Letters (1970), 9, 307-309 Li, Yuan-Hui, and S. Gregory, Geochim. Cosmochim Acta (1974), 38, 703-714. Garrels, R. M. and M. E. Thompson, Amer. J. Sci. (1962), 260, 57-66. Garrels, R.M. and C. L. Christ, "Solutions, Minerals, and Equilibria," 450 pp., Harper and Row, New York, 1965.


20.

27.

28. 29. Gov't 30. 31. 32. 33.

HOLDREN

ET

AL.


381

Wagman, D. D., W. H. Evans, V. B. Parker, I. Halow, S. M. Bailey, and R. H. Schumm, "Selected Values of Chemical Thermodynamic Properties," NBS-TN-270-4, 141 pp., U. S. Gov't. Printing Office, Washington, D. C., 1969. Crerar, David Α., R. K. Cormick and H. L. Barnes, Acta Mineral. Petrogr. (1972), XX (2), 217-226. Robie, R. A. and D. R. Waldbaum, U.S.G.S. Bull. 1259, U. S. Printing Office, Washington, D. C., 1968. Bricker, O. P. Amer. Mineral. (1965), 50, 1296-1354. Berner, R. Α., Geochim. Cosmochim. Acta (1964), 28, 1497-1503 Hurd, David C., Earth Planet. Sci. Letters (1972), 15, 411417. Rickard, D. T., Amer. J. Sci. (1974), 274, 941-952.


21 Release of Heavy Metals from Sediments: Preliminary Comparison of Laboratory and Field Studies KERILYNC.BURROWS*and MATTHEW H. HULBERT† Center for Marine and Environmental Studies and Department of Chemistry, Lehigh University, Bethlehem, Penn. 18015 The work reported in this paper is the initial portion of a study intended to clarify the rates and mechanisms of heavy metal uptake and release by sediments. Particular reference is made to estuarine sediments lead. The significance detrimental effects on a variety of animals, including man, and plants via interference with certain enzymes. At present the biologically critical levels of various chemical species of the heavy metals are imperfectly known, and these for only a few biological species. Evidence for synergistic and antagonistic effects has been reported, but data is so limited as to be merely tantalizing. Estuarine sediments are of particular interest since the estuaries serve as breeding grounds of many economically important species, and, in the anoxic state, the sediments appear to serve as traps or sinks for heavy metals. (6,7) Anoxic sediments are to be expected in areas where large quantities of organic wastes are discharged into overlying water; heavy metals accompany the organic wastes in industrialized, urban areas. Below Philadelphia such sediment must be dredged to maintain navigation. In the past this sediment has been used to "reclaim" salt marshes, but with the growing recognition of the values of unreclaimed marshland and the increasing political muscle of conservation interests, new methods of disposal have become mandatory. A particularly apt disposal technique is the construction of artificial wildlife habitats including structures designed to form fresh water ponds. But what happens when oxygenated water percolates through these anoxic sediments? Would reversal of the metal-sequestering reactions lead to undesirable water quality in the surroundings? Experimental Reagents. Stock solutions (1 mg/ml) of zinc, cadmium, copper, and lead were prepared by dissolving 100 mg high purity metal (Alfa-Ventron) in a few milliliters Ultra-Pure nitric acid *Present address: The Wetlands Institute, Box 91, Stone Harbor, N.J. 08247 tPresent address: Department of Chemistry, Connecticut College, New London, Conn. 06320 382


21. BURROWS AND HULBERT

383

Heavy Metals from Sediments

(65%, Alfa-Ventron) and diluting to 100 ml with d i s t i l l e d water. These solutions were stored i n polypropylene bottles. Working solutions were prepared daily by serial dilutions of the stock solutions with pH 1.3 HN0_. pH 1.3 n i t r i c acid, which was also used for rinsing glassware, was prepared by adding 750 y l Ultra-Pure HN0 to 1 i dist i l l e d water, and further purified by electrolysis at -1.5 V (vs. SCE) for approximately 24 hours. One M sodium citrate solution was prepared from USP tri-sodium citrate and purified by electrolysis. Hydrofluoric acid (48%, Fisher Reagent Grade) was r e d i s t i l l e d using a sub-boiling Teflon s t i l l (4). A l l other chemicals were reagent grade and used without further p u r i f i c a tion. 3

Sediments. Unpollute from the upper 50 cm o meter of water at low tide i n Jenkins Sound, Stone Harbor, New Jersey. The Sound has a s a l i n i t y of 25 to 30% and i s located about one mile from both major roads and major pleasure boat t r a f f i c . Samples were transported i n covered plastic buckets, under several inches of overlying water. Portions not immediately processed were frozen at -20°C i n polyethylene bags. Polluted samples were collected i n the Schuylkill River i n south Philadelphia, just below the Gulf refinery and Naval Yard, on 3 November 1974 by the University of Delaware's R/V Ariadne, using a modified Foster Anchor Dredge. The upper 10 cm of the bottom sediments were taken, under 1.5 meters of water. Samples were stored i n plastic bags at 0°C for about 16 hours, then frozen to -20°C. o

Sediment Digestion. Sediment samples were dissolved by an adaptation of the method used by Presley.(5) Prior to analysis, the samples were dried at 70°C, ground by hand, and washed by shaking for one minute with equal volumes of d i s t i l l e d water, centrifuged 1.5 minutes at 4100 rpm, and dried again. This was designed to remove excess salts from the sediments. Adsorbed fraction. Two grams of ground, dried sediment were placed i n a 15 ml polypropylene centrifuge tube with 10 ml d i s t i l l e d water, shaken by hand for five minutes, centrifuged at 4100 rpm for five minutes, f i l t e r e d into a 25 ml volumetric flask, and taken to volume with pH 1.3 HNO^. Reducible fraction. The residue remaining i n the centrifuge tube and on the f i l t e r paper was washed into a 125 ml flask with 50 ml of 0.25 M NH 0H.HC1 i n 25% acetic acid, and stirred magnetically for 4 hours at room temperature (23°C). The solution was transferred to the centrifuge tube, centrifuged at 4100 rpm for three minutes, and f i l t e r e d into a 250 ml Teflon beaker. The residue was washed by shaking for one minute with five 10 ml 2


384

MARINE CHEMISTRY

portions of d i s t i l l e d water, centrifuging at 4100 rpm for 30 seconds, and combining the supernatant with the f i l t r a t e . The f i l t r a t e was heated slowly to near dryness on a hot plate. Af ter cooling, one ml HNO and 5 ml HC1 were added. The solution was f i l t e r e d into a 25 ml volumetric flask and taken to volume with pH 1.3 HN0 . 3

Oxidizable fraction. The residue remaining i n the centri fuge tube and on the f i l t e r paper was washed back into the flask with 50 ml d i s t i l l e d water, heated to dryness, and cooled. Twenty-five ml 30% H ^ was added i n 10 ml portions, and the solution l e f t to stand overnight. On the following morning, i t was heated for 30 minutes, cooled, centrifuged at 4100 rpm for three minutes, f i l t e r e d into a Teflon beaker and prepared as for the reducible fraction Residual fraction. Ten ml d i s t i l l e d water was used to wash the residue into the 25 ml Teflon cup of a Parr bomb, and the sample was heated to dryness. After cooling, 10 ml HF and 2.4 ml HNO were added, the solution heated i n the bomb for three hours at I25°C, cooled overnight, and taken to dryness. This process was repeated using another 10 ml of HF and 2.6 ml of HNO3. After cooling, 3 ml HC1 and approximately 15 ml pH 1.3 HNO^ were added and heated for ten minutes, then the solution was transferred to a 50 ml glass flask and boiled to dissolve the remaining solids. The solution was f i l t e r e d , when cool, into a 50 ml volumetric flask and taken to volume with pH 1.3 HNQ^. Total. One-half gram of ground, dried sediment was prepared as for the residual fraction. A l l samples were stored i n two-ounce polypropylene bottles which had been 1eached for a week prior to use with 6 M n i t r i c acid. Leaching Studies. Short term 1eaching studies were con ducted using washed and dried samples of clean and polluted sedi ments i n both d i s t i l l e d and saline waters under atmospheres of a i r and nitrogen. The caps of one l i t e r wide mouth polypropylene bottles were d r i l l e d for gas inlet and outlet tubes, and leached for a week with 6 M n i t r i c acid. Twenty-four hours before use, they were f i l l e d with the 1eaching 1iquid, which was either dis t i l l e d water or fresh sea water f i l t e r e d through a three micron f i l t e r (30%o s a l i n i t y ) . For the studies, this was discarded, replaced with 500 ml of fresh solution, and the bottles connected to a nitrogen tank or a i r pump and purged for one hour at a flow rate of 200 ml/min. Ten grams of polluted sediment or 20 grams of the clean were added, and the systems stirred magnetically for twenty-four hours. After settling for 45 minutes, a 50 ml por tion was pipetted into a two ounce polypropylene bottle and acid i f i e d with 20μ 1 HNOo.


21.

BURROWS AND HULBERT


385

Long-term leaching studies were conducted on clean sediment exposed to the weather. A hole was d r i l l e d i n the bottom of a 20 gallon plastic trash barrel and a plastic drainage plug (11 cm inside diameter) was inserted. The cap of a one l i t e r narrow mouth polypropylene bottle was d r i l l e d to accommodate the plug, and held i n place by a rubber 0 ring. The cans were supported in a wooden frame. Seepage samples were collected i n polypropylene bottles screwed into the cap. A similar system was used for rain- and dust-fall collection. In early June, the barrel was f i l l e d with clean wet sediment. Three bottles of seepage were collected within the next two days; afterwards, the bottles were changed at irregular intervals, generally after rain f a l l s . Samples were preserved by the addition of 0.5 ml HNO^. A surface sample of weathered sediment was taken for analysis i n late January. Instrumentation. Sample analyze , , lead, and copper by d i f f e r e n t i a l pulse anodic stripping voltammetry (DPASV) using a hanging mercury drop electrode (HMDE). The analyses were performed with a Princeton Applied Research model 174 polarographic analyzer, and data recorded on a HewlettPackard 7001 A XY flatbed recorder. The analytical c e l l consisted of 50 ml capacity borosilicate glass bottom (PAR 9301) with p l a s t i c top and f i t t i n g s supplied by PAR. A metro-ohm mercury micro-feeder (model E-410) served as the HMDE; a standard colomel electrode (SCE) isolated by a pH 1.3 HN0 bridge and Pt wire were the reference and counter electrodes, respectively. The instrument was used i n the d i f f e r e n t i a l pulse mode, with a 1.5 V scan range, 25 mV modulation amplitude, and one second drop time; the recorder's X axis was calibrated at 100 mV/inch. A setting of three divisions of the micro-feeder provided a mercury drop with a surface area of 1.8 mm . One analytical cycle consisted of purging with nitrogen and s t i r r i n g at 15 rpm for one minute, plating and s t i r r i n g for one minute, plating for 30 seconds, and scanning. During the analysis the nitrogen flow was directed over the solution. 3

Analysis. Sediment fractions were diluted 1:5 with pH 1.3 HNCL before analysis. A ten ml aliquot of the solution to be analyzed was placed i n the c e l l and purged with nitrogen for 15 minutes. Sodium citrate solution (0.5 ml for rainwater samples, 1.0 ml for seepages, 2.0 ml for sediments and leachates) was added (2), and a preliminary analysis made. This was run from -1.4 V to +0.1 V, at 10 mV/sec from -1.4 V to -0.8 V, 5 mV/ sec from -0.8 V to -0.4 V, and 10 mV/sec from -0.4 V to +0.1 V, at a current range of 10 yA. This scan was used to estimate the peak potentials and current ranges needed for the individual metals. In general -1.4 V served as the i n i t i a l potential for Zn, -0.8 V for Cd, -0.7 V for Pb, and -0.4 V for Cu. Zinc and copper were scanned at 10 mV/sec and cadmium and lead at 5 mV/sec. Once the peak had been scanned, the drop was rapidly scanned to


386

MARINE

CHEMISTRY

+0.1 V ; this portion was not recorded as i t s only purpose was to strip the remaining metals back into solution. Quantitation was accomplished by standard additions; two spikes of 20 to 100 yl and appropriate concentrations were added. Results and Discussion Sediments used i n these studies were selected to represent a relatively unpolluted area and an urban area subjected to i n dustrial pollution. These w i l l be referred to i n tables and figures as "clean" and "dirty" respectively. Both sediments were dark, anoxic, and rich i n organic matter ; the unpolluted sample was characterized as a clayey s i l t , the polluted as s i l t . TABLE I Grain Size Analysis of Sediments Sample %Sand %Silt %Clay CLEAN 16,7 63.0 20.3 DIRTY 9.2 81.1 9.7 Short-term Studies. Short-term leaching experiments were designed to test the effects of oxygen and s a l i n i t y on heavy metal removed from unpolluted and polluted sediments (Figure 1 ) . With respect to zinc, the unpolluted sediments showed very l i t t l e difference with the various treatments, losing approximately 15 yg zinc per gram of dry sediment. Loss from the polluted sediments under salt water was somewhat less, around 5 yg/g. Under fresh water the polluted sediment lost 60 yg Zn/g. Presence or absence of oxygen had no appreciable effect. These variations imply that zinc i s bound i n different ways i n the different sediments. Cadmium studies show a tendency for the sediments to actually remove the metal from fresh water, amounting to an increase of 0.9 yg/g for the unpolluted sample and 1.7 yg/g for the polluted one. In salt water this appears to be affected by the oxygen content. The unpolluted sample releases 3 yg Cd/g i n the absence of oxygen ; release from the polluted sample, 2 yg/g, occurs i n the presence of oxygen. Here a synergistic effect may be taking place, with the organic content of the sea water being of greater importance than the s a l i n i t y . Under fresh water the unpolluted sample shows similar losses of lead, 1 yg/g, regardless of oxygen content. The polluted sample shows a release more than doubled i n the absence of oxygen, 14 yg Pb/g as opposed to 6. Meaningful data i n salt water i s d i f f i c u l t to obtain as a consequence of analytical error, but the lead i s below detection limits when the unpolluted sample is exposed to oxygen, and when the polluted sample i s not. This may also result from a synergistic effect. Sediment Analysis.

Samples of both sediments, as well as


BURROWS


A N D HULBERT

—

ZN

20 PPM OXYGEN No OXYGEN

FRESH C9

SALT

• i

>1—

•

5

1

CD

1 •

SLT

0 X

•

1

Μ OX ι ι — 2 PPM

FR OX

u Ν OX

SLT

~

FR -

IN OX

OX

SLT

4 PPM

PB FR

SLT FR

OX

Ν OX SLT

Metal Released / Gram Sediment Figure 1. Effects of oxygen and salinity on unpolluted and polluted sediments during short-term leaching


388

MARINE CHEMISTRY

unpolluted sediment weathered for six months, were subjected to a four-stage analysis to determine metal distribution. The f i r s t stage, a brief washing with d i s t i l l e d water, was designed to remove labile adsorbed species. This was followed by treatment with hydroxylamine hydrochloride i n acetic acid to dissolve the reducible fraction, consisting of carbonates and iron-manganese oxides. Hydrogen peroxide was employed to dissolve oxidizable species such as sulfides and organic complexes. The final residual portion consists primarily of s i l i c a t e s ; under normal conditions the metals i n this phase are environmentally inert. The summations of the fractional metal analyses are i n generally good agreement with a total dissolution of the sample. Prior to weathering no one fraction of the unpolluted sample can be identified as metal-rich (Figure 2). Zinc i s concentrated in the reducible fraction Cadmium i s detectable below the detection limit i n the total digestion. Roughly half the lead i s adsorbed, and an additional third i s associated with the reducible fraction. After weathering; v i r t u a l l y a l l the cadmium and lead are found i n the residual fraction; about 2% of the latter remains adsorbed. Approximately three-fourths of the zinc i s also residual, but 20% remains associated with the reducible fraction (note added i n proof - Ref · 8). The greatest contrast between the polluted and unpolluted sediment metal distributions i s found with cadmium. The oxidizable fraction of the former contains no detectable amount, over half i s associated with the reducible fraction. This portion also accounts for 40% of the zinc; a l l but 1% of the remainder i s divided evenly between the oxidizable and residual portions. Lead i s undetectable i n the oxidizable fraction ; i t is located primarily i n the residual component with less than 1% adsorbed. Seepage Studies. During the six-month period of natural weathering, seepage and r a i n f a l l were monitored for zinc, cadmium, and lead. The r a i n f a l l averaged 40 ppb, 8 ppb, and 20 ppb in the respective metals; the variation was generally random, with two exceptions, and a l l three metals followed similar patterns. Two marked increases i n metal content were noted, one of roughly ten-fold i n the sample taken over the Fourth of July and one of three-fold i n the sample taken over Labor Day. As these samples were collected i n a resort community, the increases probably result from the influx of land and marine vacationers. Metals i n the seepage from unpolluted sediment over the same period exhibit a gradual but definite increase (Figure 3). Zinc levels range from undetectable to 13 ppm, cadmium from 10 to 130 ppb, and lead from 10 to 90 ppb. Thus, r a i n f a l l appears to be a minor source of metal input to the seepage. Analysis of the sediment at this stage i s ambiguous, showing a slight decrease in zinc content, but increases i n both cadmium and lead. However,



BURROWS AND HULBERT

21.

GLEAN

40

CLEAN

ads red ox res SUM)

η SUM

WEATHERED

389

2

Below D e t e c t i o n Β

Limits

(B)

WEATHERED

40 ads red ox res SUM|

ni 01 res SUM

tit

DIRTY

ads rte IX ris

DIRTY

200 ads red| ox res SUM| tot

-5

SUM

tit

_L PPM

ads red| ox res SUM tot

adsk red| ox res SUM tot

CLEAN

10

WEATHERED

10

I

_L

CD IN SEDIMENT

*.25

Below Detection Limits Β

DIRTY ads red ox res SUM tot

PPM

I N IN SEDIMENT

(B)

100

«2.5

±

PPM

PB IN SEDIMENT

Figure 2. Distribution of Zn, Cd, and Pb among sediment fractions


390

MARINE

CHEMISTRY

Ν

J

150h

lOOh

10H

50h

si J

A

S

Ο

J

A

S

Ο

Ν

D

J

Ν

D

J

J

A

S

Ο

D

150h-

100H

50h

t

t

Figure 3. Loss of Zn, Cd, and Pb from unpolluted sediment during weathering


21.

BURROWS AND HULBERT


391

a distinct change i n metal distribution i s observed, as previously noted. Copper. Under the experimental conditions reported here, the determination of copper was d i f f i c u l t . At analyte levels below 0.5 ppm Cu, the copper peak could not be effectively detected on the shoulder of the mercury oxidation wave. In order to exhibit well-defined peaks, copper levels above 1 ppm were necessary. Such levels are not desirable for simultaneous determination of zinc, due to the formation of a zinc-copper intermetallic which decreases the zinc signal and enhances the copper response (1). Conclusions The three metals unde responses to short-term leachings. Zinc removal i s not i n fluenced by the presence of oxygen, but changes from fresh to saline water do appear to affect removal from the polluted sample. Cadmium responds to the presence or absence of oxygen i n both sediments, but only under salt water. A similar result for lead i s shown only by the polluted sample i n fresh water. Correlations between metal distribution i n the sediment fractions and metal removal have not become apparent. Changes i n sediment zinc content due to weathering and to short-term fresh water leaching are comparable, and the negative short-term result for cadmium may be paralleled by the slight i n crease i n cadmium content of the weathered sediment, but no correlation i s found for lead. However, the seepage shows that a l l three metals are, and continue to be, leached from the unpolluted sediment at appreciable levels. As may be anticipated for natural systems, none of the relatively simple laboratory techniques used seem sufficient to reflect the heavy metal release which actually occurs as sediments are weathered. Total sediment dissolution, i n addition to being time-consuming, provides no distinction between environmentally-active metals and those which may be classed as inert. Results of the various partial digestion procedures employed here are not easily correlated with metal removed. Simple shortterm leaching i s qualitative at best, and even here active elements may be undetected. The key to this question may l i e i n specific portions of the gross sediment fractions, notably hydrous iron and manganese oxides i n the reducible fraction and organics or sulfides i n the oxidizable fraction (3). More selective techniques than those currently employed are called for. Natural weathering of polluted sediment samples i s essential to determine the u t i l i t y of shortterm techniques, although i t appears reasonable to expect higher metal levels than those found i n the seepage from unpolluted sediments. Rates of such release may be expected to depend as


392

MARINE CHEMISTRY

well on the type of pollution*, industrial, essentially metalcontaminated sediments may d i f f e r substantially from urban sources containing significant amounts of organic matter. When several areas are being considered as sediment sources for creation of a r t i f i c i a l habitats, a six-month period of weathering i s impractical as a technique of sample preparation. Rapid, representative methods are essential, both for determination of sediment s u i t a b i l i t y and for estimation of the removal times involved. For example, a sediment with a small but constant metal loss may prove satisfactory i n an open, easily flushed situation, while the construction of a fresh water pond may lead to the accumulation of potentially harmful metal levels. This work has been confined to the effects of geochemical processes. In r e a l i t y biologically induced transformations, such as s o i l oxidation logical transport may prov in heavy metal mobilization. While the construction of phy s i c a l l y suitable w i l d l i f e habitats poses no great d i f f i c u l t i e s , the question of chemical s u i t a b i l i t y i s much more subtle, complex, and v i t a l . Future work i n this laboratory i s directed toward reducing the time required to obtain an environmental1y meaningful sample from raw sediments, and toward improving both the speed and sens i t i v i t y of the analytical technique, particularly with respect to copper. The f i r s t objective involves investigations of both selective sediment digestion and other parameters of short-term leaching, notably organic content. Currently we are investigating the applicability of thin-film mercury electrodes and suppression of intermetallic interferences following the gallium technique proposed by Copeland et a l . (1). Acknow1edgement s. The authors wish to acknowledge the f i nancial support of this work by the Victoria Foundation, and express appreciation for the cooperation of the staff of the Wetlands Institute. Sampling assistance was generously provided by Fred Bopp of the University of Delaware and Mike Criss of the Wetlands Institute, and Joe Kelley of Lehigh University performed the grain size analysis. We are especially grateful to Mark Brindie of Lehigh for his invaluable aid during the early stages of the polarographic work. Abstract Sediments taken from polluted and unpolluted areas were exposed to short-term leaching i n the laboratory, and an unpolluted sample was exposed to natural weathering for six months. The sediments were subjected to fractional digestion. Zinc, cadmium, and lead levels i n leachates, seepage, and sediment were determined by differential pulse anodic stripping voltammetry. The metals continue to be leached during natural


21.

BURROWS AND HULBERT


393

weathering, a process not adequately reflected by short-term studies, and become associated primarily with the residual sedi ment fraction. Implications of these results must be considered in the use of dredge spoils for a r t i f i c i a l habitat construction. Literature

Cited

1.

Copeland, T. R., R. A. Osteryoung, and R. K. Skogerbee, Anal. Chem. (1974) 46, 2093.

2.

Florence, T. M., J. Electroanal.

3.

Jenne, E. A. in "Trace Inorganics in Water," Advances in Chemistry Series No. 73, p. 337, American Chemical Society, Washington, D. C., 1968.

4.

Mattinson, J. Μ., Anal. Chem. (1972) 44, 1715.

5.

Presley, B. J., California.

6.

Presley, B. J., Y. Kolodny, A. Nessenbaum, and R. J. Kaplan, Geochim. Cosmochim. Acta (1972) 36, 1073.

7.

Windom, H., J. Waterways, Harbors, Coastal Engineering Division, Amer. Soc. Civil Eng. (1972) 98, 475.

Chem. (1972) 35, 237.

PhD Thesis (1969), UCLA, Los Angeles,

8. Note: Added in proof: The hydroxyl amine HCl technique is not sufficiently rigerous to dissolve free iron oxides and hydroxides; this may account for the increased amount of heavy metals found in the residual (HF soluble) fraction of the weathered sample (E.A. Jenne, personal communication).


22 Trends in Waste Solid Disposal in U.S. Coastal Waters, 1968-1974 M. G R A N T GROSS Chesapeake Bay Institute, The Johns Hopkins University, Baltimore, Md. 21218

Sources of Waste S o l i d s Large volumes of s o l i d s are transported to sea by barges or seagoing hopper dredges f o r d i s p o s a l i n c o a s t a l waters. These wastes ( l i s t e d i n approximate order of volumes dumped at sea) i n clude sediment d e p o s i t s dredged from waterways, s o l i d s i n waste chemicals, sewage sludges, rubble from b u i l d i n g c o n s t r u c t i o n and d e m o l i t i o n , and f l y ash (1,2). F l o a t a b l e waste s o l i d s such as garbage, r e f u s e , and r u b b i s h as w e l l as e x p l o s i v e s are excluded. Although produced i n l a r g e q u a n t i t i e s i n urban areas, these materi a l s are not now dumped i n c o a s t a l or e s t u a r i n e waters, except from ships ( 3 ) . Riverborne sediments c a r r i e d i n t o harbors by e s t u a r i n e c i r c u l a t i o n i n the adjacent c o a s t a l ocean and by sands moving along beaches (4) must be dredged from harbors. A r t i f i c i a l l y deepened n a v i g a t i o n channels and i r r e g u l a r s h o r e l i n e s formed by s l i p s and basins used f o r s h i p p i n g are e f f e c t i v e sediment t r a p s and must p e r i o d i c a l l y be dredged to m a i n t a i n water depths needed f o r n a v i gation. I f c l e a n g r a v e l s , sands, or coarse s i l t s were the only mater i a l s dredged, there would be l i t t l e problem i n most c o a s t a l urban areas. Dredged m a t e r i a l s have been used f o r l a n d f i l l , e s p e c i a l l y h y d r a u l i c l a n d f i l l s , and f o r other c o n s t r u c t i o n purposes. In u r ban areas, however, dredged m a t e r i a l s must commonly be handled as wastes because the n a t u r a l r i v e r b o r n e sediments have been p o l l u t e d by municipal and i n d u s t r i a l wastes. Moreover, convenient l a n d f i l l s i t e s are u s u a l l y u n a v a i l a b l e at the time when wastes must be disposed o f . In both cases, ocean d i s p o s a l i s an a t t r a c t i v e option. M u n i c i p a l wastes, i n c l u d i n g sewage s o l i d s , are major c o n t r i b utors of m a t e r i a l s dredged from n a v i g a b l e waterways. Untreated ("raw") sewage i s o f t e n discharged to the waterways, which then provide primary treatment through g r a v i t a t i o n a l s e t t l i n g of s o l i d s and secondary treatment through b i o l o g i c a l degradation of organic matter. The s o l i d s s e t t l e out i n the waterways. E f f l u e n t s from 394


22.

GROSS

Waste Solid Disposal

395

sewage treatment plants also carry suspended solids into adjacent waterways, and some of these solids doubtlessly add to the deposi t s that must be removed by dredging. In addition to the human wastes, many urban areas also discharge wastes and debris washed from streets by storm water discharges. Regulation of Ocean Disposal In the united States, prior to 1973, regulation of dredging and disposal of dredged materials was primarily the responsibility of the U.S. Army Corps of Engineers. In most areas, these regulatory functions were conducted under the authority of the Refuse Acts (.5), which prohibited waste disposal i n navigable waters without prior permission of the local Corps of Engineers D i s t r i c t . In New York, Baltimore disposal was regulated unde Act (6). On the Pacific coast, especially i n California, regional and state agencies were also involved i n regulation of waste d i s charges (1). Since A p r i l 1973 waste disposal i n U.S. coastal waters has been regulated through the issuance of permits by the Environment a l Protection Agency (EPA), except for dredged "spoils," under provisions of PL 92-532, The Marine Protection, Research and Sanctuaries Act of 1972. Dredge spoil disposal i s conducted under permits issued by the Corps of Engineers, subject to EPA review. This regulatory program i s directed toward a "no harmful discharge" goal and covers a l l dumping seaward of the baseline from which the t e r r i t o r i a l sea i s measured (7). Waste Disposal Sites Most waste disposal sites are situated i n open estuarine waters or on the continental shelf, relatively close to city or i n dustry generating the wastes. Disposal sites are usually deeper than 20 meters i n the United States except where the materials are used for beach replenishment or construction of a r t i f i c i a l fishing reefs. (In the Gulf of Mexico some sites are located i n waters as shallow as 4 meters.) Beneficial uses of waste solids appear to be the exception rather than the rule. In order to avoid interference with navigation and to remove disposal sites as far as possible from beaches and other public areas, many are located more than 5 kilometers from the nearest land, often i n international waters. Of thirty-one sites along the open Atlantic coast from Maine to Cape Hatteras, North Carol i n a , for which good location data were available i n 1970, seventeen were more than 5 kilometers from the coast and eight were more than 10 kilometers from the coastline. A site used for toxic chemicals i s approximately 190 kilometers from the entrance to New York harbor. Estuarine areas have i n the past received large volumes of


MARINE

396

CHEMISTRY

waste solids. Chesapeake Bay, Long Island Sound, and Puget Sound each have several waste disposal sites (Table 1). A l l were used primarily for disposal of locally dredged wastes except for Long Island Sound, which has received wastes from the New York Metropolitan Region as well as small volumes of waste chemicals dumped in the eastern end. In general, more recently established waste disposal areas are farther offshore than older disposal areas and this trend continues . And use of estuarine disposal sites seems l i k e l y to d i minish further, owing to local opposition from fishing, s h e l l f i s h ing, and conservation interests. In the late 1960s, there were at least 140 waste disposal sites i n U.S. estuarine and coastal ocean waters (Table 1). Along the U.S. Atlantic coast, there were fifty-nine active waste disposal sites (Figures 1 At least twenty sites wer coast, and at least sixty sites were i n use along the U.S. Pacific coast, including Alaska. No data were available on waste disposal operations i n the Hawaiian Islands or U.S. territories or possessions . Although this report does not include the Great Lakes, ninety-five waste disposal sites were reported to be active there in the late 1960s (8). Despite the limitations of the data, i t i s apparent that the number of actively used disposal sites i n U.S. waters has dropped from 140+ i n the late 1960s to 110 i n 1973 (7). Many of the i n shore and estuarine sites have been abandoned or are scheduled to be moved because they are too close to shore or interfere with commercial fishing operations. Natural Sediment Sources Except for the Gulf Coast, most continental shelf areas now receive l i t t l e sediment (9) which might dilute or bury waste deposits. Therefore, i t i s essential to consider the tonnage of sediment brought by rivers to each of the coastal areas i n comparison with the tonnage of wastes deposited there. This permits a crude assessment of potential environmental effects resulting from waste deposits remaining i n contact with overlying waters or with bot torn-dwelling organisms for long periods of time. Waste discharges i n the Canadian Maritime Provinces, the U.S. portion of the Gulf of Maine, Long Island Sound, and the midAtlantic coast areas greatly exceed the probable suspended sediment discharge by rivers in these areas (10). For example, the discharge of riverborne suspended sediment into Long Island Sound is probably about 10 metric tons per year, whereas waste d i s charges prior to 1970, exceeded 10 metric tons per year (11). Furthermore, the sediment comes primarily from the Connecticut River near the eastern end of the Sound. Waste disposal a c t i v i ties were concentrated i n western Long Island Sound because the bulk of the wastes came from nearby densely populated urban areas. 5


22.

GROSS


397

Table I. Location and number of waste disposal sites i n various coastal ocean areas with estimated tonnages of wastes dumped i n each region, 1960s.

Disposal Sites (no. of active sites)

Estimated Tonnage (10 tons/year) 6

Atlantic Coast (61) Gulf of Maine (13) Mid-Atlantic coast (29)* South Atlantic (17) Puerto Rico (2)

14.3

Gulf of Mexico (20+) Eastern Gulf (9) Western Gulf (5+) Mississippi River (6) Pacific Coast (59) California (3) Oregon-Washington (38) Total

10 56.2

* Includes Long Island Sound (12) and Chesapeake Bay (2)(after 11)


398

MARINE CHEMISTRY

Figure 1. Location of waste disposal sites and volumes of dredged wastes (10 m /year) discharged in 1968 6

Figure 2. Locations of waste disposal sites in the New York Metropolitan Region in 1968 and volumes of dredged wastes (10 m / year) discharged in each s


5

3

22.

GROSS

399


Near the mouth of the Mississippi River the river's suspended sediment load (12), about 3.1 * 10 metric tons per year, greatly exceeds the tonnage of wastes dumped there so that wastes are l i k e l y to be buried rather quickly. Similar situations probably prevail near the mouths of other rivers i n the Gulf of Mexico, near the mouth of the Columbia River (13) and i n the Strait of Georgia (14). Elsewhere on the continental shelf, wastes probably accumulate and remain at the water-sediment interface for long periods of time. Based on these rather sketchy data, one can surmise that large volumes of wastes dumped at sea are l i k e l y to have the least effect i n the Gulf of Mexico, and greatest effect on the Atlantic Coast. 8

Impact of Dredged Wast Waste solids pose immediate and potential long-term problems in the coastal ocean. The immediate effects arise i n two ways— from dredging and from waste disposal operations. Wastes and sediments are disturbed during dredging causing increased turbidity and releasing nitrogen compounds, phosphates, and various reduced substances to the water. Increased oxygen demand arising from i n troduction of reduced substances (15) and decomposition of excessive phytoplankton growth (resulting from the phosphate and n i trate enrichment of the waters) deplete dissolved oxygen concentrations i n near-bottom waters (16). Potentially more troublesome i s the long-term exposure of unburied waste deposits on the continental shelf or estuary bottom. Since most waste disposal sites are located i n relatively shallow water, t i d a l currents and wave action may resuspend and move them outside the designated disposal area. Under certain conditions such as upwelling, movement of near-bottom waters i s directed landward, toward the estuary or river mouth. Some resuspended wastes may move toward beaches or back into the harbor from which they were removed. There i s no compelling evidence that large volumes of waste solids have moved from disposal sites to be deposited on beaches. Studies of two waste disposal sites near New York City receiving dredged wastes and sewage sludges indicate that populations of bottom-dwelling organisms i n both waste disposal areas were severely reduced over several tens of square kilometers (16). Factors thought to be responsible include low dissolved oxygen concentrations, i n waters over the disposal s i t e and presence of toxic compounds, or pathogenic organisms i n the wastes. In addition, i t seems l i k e l y that physical factors may also play a role. The bottom was originally hard sand or gravel, but the waste deposits formed a fine-grained soft bottom. Furthermore, rapid accumulation of wastes (ranging from 0.4 to 30 cm/year, assuming that the wastes are spread uniformly throughout the affected areas) may make i t impossible for many bottom-dwelling organisms


400

MARINE

CHEMISTRY

to l i v e i n waste disposal sites (17). And the changed bottom conditions inhibit (or prevent) repopulation of the disposal sites by organisms from nearby unaffected ocean areas. Since 1968, data have become available on the environmental impact of waste solid disposal i n coastal waters ; much of the data come from studies of the New York Bight (18). Enrichments of several metals (including Cu, Pb, Ni$ Zn, and Cr) were substantial, typically 10 to 25 times greater than i n nearby uncontaminated sediment deposits (19). These metal-rich sediments were found nearly 40 km down the axis of Hudson Channel seaward of the designated disposal sites. Studies of the effects of sewage sludge disposal i n the Thames Estuary (20), the Firth of Clyde (21), and Liverpool Bay (22) have not found, i n general, the obvious local effects on bottom-dwelling organism disposal sites. This ma the sludge i n the coastal waters around Great Britain because of strong t i d a l currents there. In this case, the effects of waste disposal operations may eventually be f e l t over a much wider area. Trends i n Ocean Disposal Operations Despite changes i n regulation of disposal operations, coastal ocean areas w i l l probably receive even larger volumes of wastes over the next five to ten years. Coastal urban areas are short of land necessary for the present style of waste disposal operations (23) ; they find ocean disposal to be an attractive solution for existing and foreseeable waste disposal problems. At present there i s no equal-cost alternative to ocean disposal for largevolume wastes. Hence, there w i l l l i k e l y be increasing pressure for new types of wastes to be dumped in ocean waters, at least on an interim basis. It i s useful to consider changes i n tonnages of wastes disposed at sea i n 1968 and 1973 (Table 2). The amounts of indust r i a l wastes, sewage sludges, and construction-demolition debris have increased, at compound rates of +2.9, +3.9 and +14.2% per year, respectively. Ocean discharges of garbage and refuse have been greatly reduced and disposal of explosives at sea has ceased. Tonnages of dredged spoils disposed at sea have apparently decreased from an estimated 62 million tons i n 1968 to 37 million tons i n 1973. (Table 2.) This apparent decrease may well be the result of incomplete data. It i s also instructive to consider trends i n ocean disposal since 1949 (Table 3). These data indicate a compound annual change of +7.7% between 1949 and 1968 i n the amount of waste disposed at sea. (Data i n Tables 2 and 3 are not directly comparable, although each indicate trends in the two periods involved.) It i s too early to judge the impact of the new regulatory procedures, implemented i n 1973, and the use of the ocean for disposal of i n dustrial and municipal wastes. There has, however, been a de-



1

+14.2 + 4.2 - 6.9 - 4.7

1.16 12.0 36.9 48.9

0.57 9.74 52.2 61.9

0 0 9.45 9.45

0 0.98 8.32 9.30

0 1.41 9.01

0 0.70 13.0 13.7

1.16

10.6

18.4

29.0

0.57

8.06

30.9

39.0

Construction and demolition debris

Subtotal

«•

3

2

To calculate tonnages of dredged wastes, a solid content (dry) of 0.9 metric ton per cubic meter of dredged material i s assumed.

Compound increase.

1973 data from (7).

1968 data from (2).

TOTAL

10.4

+ 3.9

5.43

4.48

0

0

0

0

5.43

4.48

Sewage sludges

11

+ 2.9

5.41

4.69

0

0.98

1.41

0.70

4.00

3.01

Industrial wastes

Dredged wastes

(%)

1973

1968

1973

1968

3

Change/year

1973

Total

(in millions of tons).

Pacific Ocean

2

1968

Gulf of Mexico

and 1973

1973

Atlantic Ocean

Ocean disposal of various waste solids, 1968

1968

Waste type

Table II.

402

MARINE

Table I I I .

CHEMISTRY

Ocean waste d i s p o s a l , excluding dredged s p o i l , 194968, i n m i l l i o n s of short tons (2).

Coastal region

1949-53

1954-58

1959-63

Atlantic

8.0

16.0

27.3

Gulf

0.04

0.28

0.86

2.

Pacific

0.49

0.85

0.94

3. 4

Total U.S.

8.53

Average/yr

1.7

1.8

5.8

7. 4

1964- 68

31. 1 6

These data i n c l u d e the tonnage of l i q u i d s discharged as w e l l as waste s o l i d s . They cannot be compared d i r e c t l y w i t h Table 2.


22.

GROSS

403


crease i n dredge spoil disposal in the past five years. It seems most l i k e l y that there w i l l be increasing volumes of dredged wastes i n the future as new port f a c i l i t i e s are prepared for deep-draft vessels, requiring 20 to 25 m of water. In the U.S., channel depths now rarely exceed 15 m; thus extensive dredging w i l l l i k e l y be required to accommodate larger ships. The magnitude of this potential problem can be appreciated by considering that the dredging necessary for maintaining depths exceeding 20 m at the entrances to the Hook of Holland (Rotterdam-Euro port, Netherlands) resulted i n the annual dredged-waste discharges i n creasing from 5.1 x 10 m i n 1957 to 2.2 x 10 m i n 1968, a fortyfold increase i n eleven years, an amount 3.9 times that dredged from New York Harbor i n 1964-68 (18). These figures refer mainly to maintenance dredging. At present the amount of dredged mater i a l i s substantially increase entrance channel for passag increase in dredged waste disposal was experienced at the port of Amsterdam during this same period (Director, Rijkswaterstaat, written communication, January 2, 1970). The total volume of mat e r i a l dredged from these ports was 1.3 x 10 m , about one-third the present annual sediment discharge of the Mississippi River (12). If comparable port developments occur i n Nortil America, the volume of dredged materials w i l l probably increase sharply. Because of the widespread use of ocean disposal sites, their potential long-term effects, and the present inadequate knowledge about the wastes and their effects on the ocean waters and marine organisms, marine scientists face a challenge to apply their research capabilities i n this area. There i s also a chance to contribute toward possible solutions for environmental problems as well as to learn more about coastal ocean processes that are otherwise d i f f i c u l t or impossible to study. Far more studies with more careful experimental design w i l l be needed to determine what i s causing the environmental degradation observed i n the New York Bight and to devise means of dealing with i t . Present studies of such sites can best be described as inclusive rather than discriminating. Virtually every conceivable item i s measured or examined. At best this i s costly and i s l i k e ly to be self-defeating. The recent abandonment of disposal sites raises the issue of rehabilitation of waste deposits. On land, a garbage dump i s closed by covering i t with several feet of earth and landscaping. But for ocean areas we lack even this simple technology. It seems reasonable to expect that a complete ocean waste management program would include efforts to isolate waste deposits i n abandoned sites from possible interactions with the overlying water column or marine l i f e . This i s probably a simple problem but one that merits attention. Another trend to be considered i s the probable increased volume of sewage sludges as the required level of treatment i s raised. And the use of scrubbers to remove S O 2 from power plant 5

3

7

8

3

3


404

MARINE CHEMISTRY

exhausts w i l l also generate large volumes of fine-grained watery wastes which are d i f f i c u l t to dispose of on land, especially i n urban areas. For coastal c i t i e s and industries, ocean disposal i s a convenient and, by conventional economic analysis, a relatively cheap disposal method. Such disposal operations ( i f permitted) pose new challenges to marine scientists to provide the data and insights on the coastal ocean and i t s organisms needed for proper planning and monitoring of the disposal operations. Abstract Estuaries and coastal oceans receive large volumes of waste solids dredged from harbors or removed from sewage treatment plants or industrial plants and placed on the adjacent continental shelf, which often receive sources. Legislation, implemente cant reduction i n the number of sites used; from 140+ i n the late 1960s to 110 i n 1973. Dredged spoil disposal apparently decreased; from 56 million tons i n 1968 to 37 million tons i n 1973. Dumping of industrial wastes, sewage sludges and construction debris has increased at annual rates of +2.9%, +3.9% and +14.2%. The present trend is to operate fewer disposal sites located f a r ther from shore. Literature Cited 1. Brown, R . P . , and Smith, D.D. Marine Pollution Bulletin (1969) 18:12-16. 2. Smith, D.D. and Brown, R.P. "Ocean disposal of barge-delivered liquid and solid wastes from U.S. coastal c i t i e s , " Environmental Protection Agency Publication SW-19c, Washington, D.C. (1971). 3. Cox, G.V. Environmental Science and Technology (1975) 9(2): 108-111. 4. Meade, R.H. Journal of Sedimentary Petrology (1969) 39(1); 222-234. 5. U.S. Congress, 1899. River and Harbor Act, approved March 3 1899 (30 Stat. 1152; 33 U.S.C. 407); River and Harbor Act, approved March 3, 1905 (33 Stat. 1147; 33 U.S.C. 419). 6. U.S. Congress, 1888. Supervisor of Harbor Act, approved June 29, 1888 (33 U.S.C. 441-451), amended July 12, 1952 and August 28, 1958 (Pub. L . 85-802, 72 Stat. 970). 7. EPA. Administration of the ocean dumping permit program: Second Annual Report, Environmental Protection Agency, Washington, D.C. (1974). 8. U.S. Army Corps of Engineers. "Dredging and Water Quality Problems i n the Great Lakes," Buffalo, New York (1969). 9. Emery, K.O. Bulletin of the American Association of Petroleum Geologists (1968) 52:445-464.


port

22.

GROSS


405

10. Dole, R.B. and Stabler, H. U.S. Geological Survey of Water Supply Paper (1909) 234:85. 11. Gross, M.G. Waste-solid disposal in coastal waters of North America, p. 252-260. In W.H. Matthews and others (ed). Man's Impact on Terrestrial and Oceanic Ecosystems. M.I.T. Press, Cambridge, Mass. (1971). 12. Holeman, John N. Water Resources Research (1968) 4(4):737747. 13. Gross, M.G., McManus, D.A. and Ling, Y-Y. Journal of Sedimentary Petrology (1967) 37(3):790-795. 14. Waldichuk, M.W. Fisheries Research Board of Canada, Progress Report (1953) No. 95:59-63. 15. Brown, C.L. and Clark, R. Water Resources Research (1968) 4(6):1381-1384. 16. Pearce, J.B. The communities in the New Marine pollution and sea life. Fishing News (Books) Ltd., London (1972). 17. Gross, M.G. Water Resources Research (1970) 6(3):927-931. 18. Gross, M.G. Geological Society America Bulletin (1972) 83:3163-3176. 19. Carmody, D.J., Pearce, J.B. and Yasso, W.E. Marine Pollution Bulletin (1973) 4(9):132-135. 20. Shelton, R.G.J. Marine Pollution Bulletin (1971) 2:24-27. 21. MacKay, D.W., Halcrow, W. and Thorton, I. Marine Pollution Bulletin (1972) 3(1):7-11. 22. Dept. of the Environment. "Out of Sight, Out of Mind: Reof a Working Party on the Disposal of Sludge in Liverpool Bay", Her Majesty's Stationery Office, London, 3 volumes (1972). 23. Regional Plan Association. Waste management, Regional Plan Association Bulletin, 107 (1968).


23 Industrial Viewpoint on Ocean Disposal L L O Y D L. FALK Engineering Service Division, Engineering Department, Ε. I. du Pont de Nemours & Co., Wilmington,Del.19898

Advocates or opponent d i s p o s a l systems mus adopted must adhere to natural laws. For example, the laws of thermodynamics and of the conservation of mass energy say: "The only thing you get for nothing - i s nothing". Since these laws apply to environmental c o n t r o l problems, we see that some ideas which have formed the basis for Federal water p o l l u t i o n c o n t r o l laws are unattainable. The idea of t o t a l waste recycle or "zero" discharge has magical a p p e a l · The concept, however, f a i l s to consider that i n d u s t r i a l s o c i e t i e s draw upon reser voirs of nonrenewable resources which occur i n the oceans, i n the atmosphere, and i n the ground. If we use these resources, those laws of nature require those materials to be returned eventually to the oceans, to the air, or to the ground whence they came. We may change the nature of the materials and how the deposition i s d i s t r i b u t e d , but we cannot a l t e r the ultimate requirement that deposition take p l a c e . Thus, we see that the idea of t o t a l recycle of mate rials i s a w i l l - o ' - t h e - w i s p unless we ultimately include redeposition i n the environment within our d e f i n i t i o n of t o t a l r e c y c l e . Regardless of how many times a material i s repeatedly cycled through a box we might call "World Society", i t must be returned to the earth from which we extracted it. Furthermore, while recycling can minimize a natural material drain, it i s usually done at the cost of an energy d r a i n . Once we take something from nature and use it, we must eventually return it. The question then becomes: How do we return those materials we have extracted from the world around us i n such a way as to be compatible with the environment we wish to main tain? If we approach t h i s problem wisely, we will 406


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407

r e c o g n i z e the oceans can s e r v e as a r e c e i v e r o f some e x c e s s b y - p r o d u c t s which have no e c o n o m i c a l means o f recycle. Such e x c e s s b y - p r o d u c t s we c a l l "wastes". The term " e c o n o m i c a l means" i n c l u d e s a l l t e c h n i q u e s used f o r r e c y c l i n g w h i l e s t i l l m a i n t a i n i n g economic h e a l t h b o t h w i t h i n the s o c i e t y and i n c o m p e t i t i o n w i t h o t h e r s o c i e t i e s . We must a l s o r e c o g n i z e t h a t the a c t o f r e c y c l i n g i t s e l f can have economic and environmental c o s t s . F o r example, i f we n e u t r a l i z e s u l f u r i c a c i d w i t h h y d r a t e d l i m e t o form a p o t e n t i a l l y r e c y c l a b l e gypsum, we must expend energy t o e x t r a c t l i m e s t o n e from the e a r t h , t r a n s p o r t i t , c a l c i n e i t , t r a n s p o r t i t a g a i n , use i t , and t r a n s p o r t the gypsum. T h i s r e q u i r e s energy, and the p o s s i b i l i t y o f c r e a t i n g o t h e r b y - p r o d u c t s fro recycling entails a is for free. The oceans, the ground, and the a i r a l l have a s s i m i l a t i v e c a p a c i t i e s which our duty, as u s e r s o f resources, r e q u i r e s us t o d e t e r m i n e and use w i s e l y . In the c a s e o f waste d i s p o s a l i n the oceans, i n d u s t r i a l s o c i e t i e s need t o r e g u l a t e how they use t h a t capacity. I want t o mention here t h a t when Congress was c o n s i d e r i n g the passage o f ocean dumping r e g u l a t o r y legislation i n 1972, i n d u s t r y g e n e r a l l y f a v o r e d such r e g u l a t i o n s r a t h e r than see the p r a c t i c e abused. B a r g i n g wastes t o sea has d i s t i n c t i v e advantages o v e r o t h e r ways o f r e c y c l i n g waste p r o d u c t s back i n t o the environment, p r o d u c t s which o f t e n would u l t i m a t e l y r e a c h the ocean anyway. A barge has a m o b i l e d i s charge p o i n t . You have a wide s e l e c t i o n o f l o c a t i o n s to d i s p e r s e wastes. I f wastes, even t r e a t e d , a r e d i s c h a r g e d t o r i v e r s , you cannot d i v e r t mouths o f rivers. Sewer p i p e s d i s c h a r g i n g t o the ocean can be moved o n l y w i t h i n narrow l i m i t s . T h i s means t h a t , by p r o p e r p r i o r e v a l u a t i o n , barge wastes can be d i s p e r s e d i n an a r e a w i t h minimum, o r even no, e n v i r o n m e n t a l impact. The 1972 law Congress passed i s known as the "Marine P r o t e c t i o n , R e s e a r c h , and S a n c t u a r i e s A c t " . E s s e n t i a l l y , t h a t law p r o h i b i t s t r a n s p o r t o f wastes f o r t h e purpose o f dumping them i n t o the ocean w i t h o u t an a p p r o p r i a t e p e r m i t i s s u e d by the E n v i r o n m e n t a l P r o t e c t i o n Agency. Subsequent t o the passage o f the law, EPA adopted a complex s e t o f r e g u l a t i o n s i n 1973. These s p e c i f y the k i n d s o f p e r m i t s t h a t can be obt a i n e d , and e s t a b l i s h e s c r i t e r i a f o r the k i n d s o f wastes which may be d i s c h a r g e d . EPA i s p r e s e n t l y i n the p r o c e s s o f r e v i s i n g i t s e x i s t i n g r e g u l a t i o n s and criteria. I e x p e c t Mr. T. A. W a s t i e r , who follows


408

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CHEMISTRY

l a t e r i n t h i s symposium, w i l l d i s c u s s t h e law and regulations. I t a p p e a r s , however, t h a t EPA maybe moving i n t h e d i r e c t i o n o f making t h e r e g u l a t i o n s more complex, and t h e o b t a i n i n g o f p e r m i t s even more d i f f i c u l t than now. But a s i d e from t h e c o m p l e x i t y o f o b t a i n i n g p e r m i t s , and r e g a r d l e s s o f how t h e r e g u l a t i o n s a r e p h r a s e d , we i n i n d u s t r y d e t e c t t h a t , a t l e a s t on an EPA r e g i o n a l b a s i s , EPA i s moving i n t h e d i r e c t i o n o f e l i m i n a t i n g ocean d i s p o s a l o f wastes t r a n s p o r t e d t o s e a by v e s s e l s . T h i s i s b e i n g done i n s p i t e o f the e x p r e s s e d purpose i n t h e F e d e r a l law t o r e g u l a t e ocean d i s p o s a l , n o t e l i m i n a t e i t . F o r example, even though a waste d i s p o s a l o p e r a t i o n may meet t h e current c r i t e r i a fo S p e c i a l (and renewable f o r a p e r i o d o f t h r e e y e a r s , EPA r e g i o n a l o f f i c e s so f a r have i s s u e d o n l y I n t e r i m p e r m i t s which c a n o n l y l a s t f o r a maximum o f one y e a r and a r e n o t renewable. A d i s c h a r g e r i s t h e n r e q u i r e d t o r e a p p l y f o r a new p e r m i t and undergo a l l o f t h e complex p r o c e s s o f o b t a i n i n g i t . He must do t h i s even though he has s p e c i f i c a l l y i n d i c a t e d t h a t a p a r t i c u l a r d i s p o s a l o p e r a t i o n w i l l be phased o u t w i t h i n two o r t h r e e y e a r s . We b e l i e v e t h e r e g u l a t i o n s on ocean dumping s h o u l d be s i m p l i f i e d , n o t made more complex. F o r example, t h e d r a f t s o f t h e r e v i s e d r e g u l a t i o n s which I have seen go i n t o g r e a t d e t a i l a s t o how d i s p o s a l o p e r a t i o n s a r e t o be m o n i t o r e d and how s t u d i e s o f s i t e s a r e t o be conducted p r i o r t o t h e s t a r t of disposal operations. The r e q u i r e m e n t s f o r such s p e c i f i c s t u d i e s s h o u l d be d e v e l o p e d on a c a s e - b y - c a s e b a s i s depending upon t h e amounts, k i n d s , f r e q u e n c y o f wastes, and where t h e d i s p o s a l o p e r a t i o n i s t o o c c u r . F u r t h e r , t h e EPA Region s h o u l d have g r e a t e r f l e x i b i l i t y i n d e c i d i n g t h e n a t u r e o f such studies. As a r e s u l t o f t h e a p p a r e n t t r e n d toward e l i m i n a t i o n o f ocean d i s p o s a l , o u r s o c i e t y i s b e i n g r e q u i r e d t o seek a l t e r n a t i v e ways o f d i s p o s i n g o f waste p r o d u c t s . These a l t e r n a t i v e s may p r o v e t o be e n v i r o n m e n t a l l y l e s s sound o v e r a l l than would be ocean d i s p o s a l . We b e l i e v e t h a t any r e g u l a t o r y agency s h o u l d n o t c a t e g o r i c a l l y f o r e c l o s e any method o f waste d i s p o s a l . Rather, a l l a l t e r n a t i v e s , i n c l u d i n g ocean d i s p o s a l , s h o u l d be e v a l u a t e d so t h a t t h e l e a s t c o s t l y , c o n s i d e r i n g b o t h t o t a l e n v i r o n m e n t a l as w e l l as economic needs, i s selected. I n s t e a d o f f o r c i n g an end t o any


23.

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Industrial Viewpoint on Ocean Disposal

p a r t i c u l a r waste d i s p o s a l t e c h n o l o g y o r t e c h n i q u e , r e g u l a t o r y a g e n c i e s need t o educate the p u b l i c t h a t t h e r e a r e no c a t e g o r i c a l l y u n u s a b l e t e c h n i q u e s . I would l i k e t o summarize as f o l l o w s : 1. As l o n g as we t a k e nonrenewable r e s o u r c e s from t h e ground, a i r , o r waters o f the e a r t h we must e v e n t u a l l y r e t u r n them. We cannot i g n o r e the laws o f thermodynamics and c o n s e r v a t i o n o f mass-energy. 2 . The ocean can be a s a t i s f a c t o r y p l a c e f o r n o n r e c y c l a b l e by-products or wastes. We need t o a s s e s s i t s a s s i m i l a t i v e c a p a c i t y t o d e t e r m i n e how t o d i s p o s e o f wastes commensurate w i t h m a i n t a i n i n g a s a t i s f a c t o r y ocea c a n n o t hav mize i t . 3 . Regulatory agencies should not c a t e g o r i c a l l y r u l e o u t any s p e c i f i c a l t e r n a t i v e f o r waste d i s p o s a l , i n c l u d i n g ocean d i s p o s a l , s i n c e t h a t a l t e r n a t i v e may. p r o v e , i n c e r t a i n i n s t a n c e s , t o be the most environmentally acceptable o v e r a l l . Other a l t e r n a t i v e d i s p o s a l methods which appear "more a c c e p t a b l e " t o the p u b l i c may u l t i m a t e l y p r o v e t o be e n v i r o n m e n t a l l y more c o s t l y when one c o n s i d e r s the energy r e q u i r e m e n t s as w e l l as the d i s p o s a l o f r e s i d u e s from the waste d i s p o s a l o p e r a t i o n s t h e m s e l v e s . Ocean d i s p o s a l , adeq u a t e l y c o n t r o l l e d and m o n i t o r e d , can o f t e n p r o v i d e the most e c o n o m i c a l , e n v i r o n m e n t a l l y sound a l t e r n a t i v e a v a i l a b l e t o us i n managing waste p r o d u c t s o f i n d u s t r i a l societies. f


409

24 Sludge Disposal and the Coastal Metropolis NORMAN NASH Department of Water Resources, City of New York, Municipal Building, New York, N.Y. 10007

In August 1973 its first year o f administratio program. On the whole, t h i s was an admirable work. However, e a r l y i n the report it mentioned the deaths and i l l n e s s e s a t t r i b u t e d to mercury i n Minamata Bay, Japan, went on to c i t e the f a c t that about 20 percent of the s h e l l f i s h beds i n the United States are closed because of p o l l u t e d waters, and then s a i d , " F i n a l l y , attention i s drawn to the case of the New York Bight, New York C i t y ' s 'dump'." We are inured to such remarks, although we c a n ' t help wincing at each blow, but it is discouraging to hear it from the EPA, which should know b e t t e r . The bight i s not "New York C i t y ' s dump." I t also i s Nassau County's dump, and Westchester County's, and e s p e c i a l l y New J e r s e y ' s . I t i s the dump for a multitude of i n d u s t r i a l wastes, greater i n volume than New York C i t y ' s sludge, and for a v e r i t a b l e mountain of dredge s p o i l , nearly four times the volume of sludge discharged by the C i t y . In 1973 dredge s p o i l constituted 56 percent of the t o t a l volume of dumped wastes; municipal sludges from New York C i t y , New Jersey and Nassau and Westchester Counties amounted to 26 percent, and the remainder, 18 percent, was i n d u s t r i a l wastes, all from New Jersey (Figure 1). Dredge s p o i l has been described by the EPA as "34 percent polluted"; if sludge i s considered to be 100 percent p o l l u t e d , then dredge pollution. That i s , by virtue of its large volume, inspite of its lesser percentage of pollution, the total inpact of dredge spoil discharged at disposal sites cannot be ignored. 410


24.

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Sludge Disposal

411

However, t h e volume o f s p o i l i s so huge, t h e n e c e s s i t y f o r d r e d g i n g i s u s u a l l y so o b v i o u s , and a l t e r n a t i v e s t o ocean d i s p o s a l a r e so n o n - e x i s t e n t , t h a t o p p o s i t i o n t o t h e p r a c t i c e never g o t o f f t h e ground. R e g i o n I I o f EPA i s c o n s i d e r i n g moving t h e dredge s p o i l s i t e f a r t h e r o f f s h o r e , which i s t h e o n l y s o l u t i o n t o t h e problem, i f indeed i t i s a p r o b l e m . The opponents o f ocean d i s p o s a l c o n c e n t r a t e t h e i r f i r e on t h e sewage s l u d g e t h a t i s d i s c h a r g e d a t the s i t e about 12 m i l e s o f f s h o r e . Yes, i t i s t r u e t h a t New Y o r k C i t y i s r e s p o n s i b l e f o r 58 p e r c e n t o f t h e t o t a l volume; New J e r s e y a c c o u n t s f o r 34 p e r c e n t , Nassau County 6 p e r c e n percent. But the p o p u l a t i o s e r v e d by t r e a t m e n t p l a n t s , and thus by t h e d i s p o s a l s i t e , i s j u s t about 58 p e r c e n t o f t h e t o t a l s e r v e d population of a l l areas. T h e r e f o r e , i t m i g h t be s a i d t h a t New Y o r k C i t y d i s c h a r g e s no more t h a n i t s r i g h t f u l share. F u r t h e r m o r e , our s l u d g e i s produced b y secondary t r e a t m e n t , and so i s much l e s s dense and much more voluminous t h a n t h e p r i m a r y s l u d g e d i s c h a r g e d by W e s t c h e s t e r County and by v i r t u a l l y a l l o f t h e New J e r s e y s o u r c e s . I f t h o s e communities p r a c t i c e d secondary t r e a t m e n t , t h e n t h e p e r c e n t a g e s would be r e v e r s e d : New J e r s e y would be t h e major c o n t r i b u t o r , w i t h about 60 p e r c e n t , and New Y o r k C i t y ' s s h a r e would be o n l y about 35 p e r c e n t . Better treatment o f wastes, which i s t h e h e a r t o f our b u s i n e s s , p r o d u c e s more s l u d g e ; c i t i e s which p r a c t i c e secondary t r e a t m e n t s h o u l d be commended f o r t h e i r committment t o h i g h e r t r e a t m e n t , n o t s c o l d e d as ocean p o l l u t e r s . The d i s c h a r g e s o f New Y o r k C i t y and New J e r s e y cannot p r o p e r l y be compared w i t h o u t c o n s i d e r i n g t h e l a r g e volume o f i n d u s t r i a l wastes, a l l from New J e r s e y , t h a t i s d i s c h a r g e d a t t h e dumping s i t e s ( F i g u r e 2 ) . The 281,600 cu f t / d a y o f i n d u s t r i a l wastes, p l u s New J e r s e y ' s m u n i c i p a l s l u d g e volume o f 143,800 cu f t / d a y , make New J e r s e y ' s s h a r e o f t h e t o t a l volume 61 p e r c e n t New Y o r k C i t y ' s share i s reduced t o 35 p e r c e n t , and Nassau's and W e s t c h e s t e r ' s t o o n l y 3 and 1 p e r c e n t . I f t h e p r i m a r y v s . secondary t r e a t m e n t f a c t o r were i n t r o d u c e d i n t o t h i s a c c o u n t i n g , New Y o r k C i t y ' s t r u e s h a r e would be reduced even f u r t h e r , t o o n l y 24 p e r c e n t and New J e r s e y ' s would i n c r e a s e t o 72 p e r c e n t .


412

MARINE


CHEMISTRY

24.

NASH

Sludge Disposal

413

So much f o r t h e r e l a t i v e volumes o f t h e s e v e r a l s o u r c e s ; now f o r some o f t h e c o n s t i t u e n t s o f t h e wastes. The f i n g e r has been p o i n t e d a t heavy m e t a l s as g r a v e dangers t o marine and even t o human l i f e , and so i n F i g u r e s 3 and 4 a r e p r e s e n t e d t h e average d a i l y a d d i t i o n s o f seven m e t a l s and o i l a t the t h r e e dump s i t e s , i n c l u d i n g t h o s e from i n d u s t r i a l w a s t e s . T h i s does n o t mean t h a t we a g r e e t h a t m e t a l s a r e a paramount danger; mighty l i t t l e r e a l e v i d e n c e has been p r e s e n t e d t o j u s t i f y t h e n o i s e and f e a r t h o s e c l a i m s have a r o u s e d . F u r t h e r m o r e , m e t a l s a r e ubiquitous. S u b s t a n t i a l amounts e x i s t even i n p u r e l y r e s i d e n t i a l wastes d onl partl d i th s l u d g e , and i n stor removed. Cadmium, mercury and n i c k e l have been grouped i n F i g u r e 3 , and f o u r o t h e r m e t a l s and o i l i n F i g u r e 4, b e c a u s e t h e l b s / d a y d i s c h a r g e d f o r t h o s e i n each s e t are s i m i l a r . I t can be seen t h a t f o r t h e f i r s t t h r e e m e t a l s , New J e r s e y i s t h e p r i n c i p a l c o n t r i b u t o r . The e l e c t r o p l a t i n g i n d u s t r y i s the l a r g e s t source o f n i c k e l ; some i d e a o f t h e number o f such f i r m s and/or t h e i r degree o f a t t e n t i o n t o h o u s e k e e p i n g p o s s i b l y can be g l e a n e d from t h e d a t a : 125 l b s / d a y from New Y o r k C i t y and 217 from New J e r s e y . (The d a t a f o r Nassau and W e s t c h e s t e r c o u n t i e s a r e n o t shown, e x c e p t f o r W e s t c h e s t e r i n F i g u r e 4, because t h e i r d i s c h a r g e s are insignificant.) New Y o r k C i t y c o n t r i b u t e s more copper and l e a d t h a n does New J e r s e y , b u t l e s s chromium and z i n c . N e a r l y 1.4 t o n s / d a y o f o i l a r e d i s c h a r g e d , 58 p e r c e n t from New Y o r k C i t y , 41 p e r c e n t from New J e r s e y , and 1 p e r c e n t from Nassau and W e s t c h e s t e r . Thus, about 80 b a r r e l s a day a r e d i s c h a r g e d i n s l u d g e and i n d u s t r i a l wastes. So s i n i s n o t c o n f i n e d t o one s i d e o f t h e Hudson R i v e r ; but soon w e ' l l a l l be i n t h e same b o a t , t h e l a g g a r d s w i t h t h e l e a d e r s , a l l c h a i n e d t o 85 p e r c e n t r e m o v a l o f BOD and y e a r - r o u n d d i s i n f e c t i o n , r e g a r d l e s s o f whether we d i s c h a r g e t o a p o t a b l e stream o r t o a t i d a l e s t u a r y . The amount o f s l u d g e t h a t w i l l be produced b y t h e p r e s e n t u s e r s o f t h e s i t e , i n c l u d i n g a l a r g e i n c r e a s e from New Y o r k C i t y ' s new and upgraded p l a n t s , i s an i n c r e d i b l e 1 - m i l l i o n cu f t / d a y . This


MARINE

1000

CHEMISTRY

h

Chromium

Figure 4.

Copper

Lead

Chromium, copper, lead, zinc, and oil from New York City and New Jersey sources, 1973


24.

NASH

415

Sludge Disposal

would f i l l Yankee Stadium 10 f e e t deep, i n c l u d i n g t h e b u l l pen, t o t h e l a s t row o f t h e lower b o x s e a t s . What i s t o b e done w i t h i t ? V e r y l i t t l e c a n b e p l a c e d on t h e l a n d , and none i n New York C i t y , u n l e s s we a r e p r e p a r e d t o l a g o o n i t i n C e n t r a l Park. I t can be burned i n s l u d g e i n c i n e r a t o r s , b u t a t a f e a r f u l c a p i t a l c o s t and a g r e a t c o n t i n u i n g c o s t i n e n e r g y and dollars. Perhaps i t c a n b e consumed i n i n c i n e r a t o r s d e s i g n e d t o b u r n a m i x t u r e o f r e f u s e and s l u d g e , and so s o l v e two p r o b l e m s . And t h e r e i s t h e ocean, a r e s o u r c e which s h o u l d be used w i t h c a r e . O f c o u r s e , t h e ocean s h o u l d n o t be t h e dumping ground f o t r u l toxi be, t o o , t h a t some volume o f s l u d g e d i s p o s e d t h e r e . I t may even b e n e c e s s a r y t o end s l u d g e d i s p o s a l a l t o g e t h e r . B u t whatever d e c i s i o n i s made must b e b a s e d o n s c i e n t i f i c f a c t , n o t o n emotion and s e m i - h y s t e r i a . The ocean i s not a v i r g i n t o b e p r o t e c t e d a g a i n s t a l l c o n t a c t w i t h t h e c o a r s e n e s s o f man; i t i s t h e once and f u t u r e s i n k w i t h a n undoubted c a p a c i t y t o a s s i m i l a t e some volume o f waste. I t i s f o l l y to, without evidence, disregard that capacity and burden the land and the a i r with consequences possibly f a r more serious. L e t u s d i v o r c e emotion and s c a r e t a c t i c s rrom t h i s m a t t e r . Well-meaning b u t i l l - i n f o r m e d c r i t i c i s m must n o t b e a l l o w e d t o d e t e r s c i e n t i s t s and e n g i n e e r s from a d i s c i p l i n e d r e s o l u t i o n o f t h e p r o b l e m t h a t i m p a r t i a l l y c o n s i d e r s t h e t o t a l environment. ABSTRACT When both sludge and i n d u s t r i a l wastes are considered, i t i s evident that New Jersey, not New York C i t y , i s the l a r g e s t c o n t r i b u t o r to the New York b i g h t disposal s i t e s . New Jersey wastes contain more cadmium mercury, n i c k e l , chromium and z i n c than does New York City sludge, but New York discharges more copper, lead and oil. Whatever decisions are made on the future of ocean d i s p o s a l must be based on s c i e n t i f i c f a c t , not on emotion. Without evidence, the ocean should not be ruled out as a disposal site, and the entire burden transferred to the land and the air.


25 Chemical Needs for the Regulation of Ocean Disposal T.A.WASTLER and C. K. OFFUTT O i l and Special Materials Control Division, Environmental Protection Agency, Washington, D.C. 20460

Shortly after the Control A c t Amendment of the Marine Protection, Research, and Sanctuaries A c t of 1972, often known as the Ocean Dumping A c t , which p r o hibits the disposal in ocean waters of certain materials and which provides a permit system to regulate a l l other forms of ocean disposal. A l s o included in the A c t are provisions for r e s e a r c h to determine effects of disposal on the marine environment and authorization to establish specified areas as marine sanctuaries for recreational, conservational, and ecological purposes. The legislation was initiated by the Administration following the release by the Council on Environmental Quality in 1970 of the report "Ocean Dumping -- A National Policy" which surveyed current and past ocean disposal activities. Both the Senate and House versions of this Bill reflected the concern that pollutants, which were previously discharged into the nation's waters or air and are now restricted by the F W P C A and the Clean A i r A c t , not cause unreasonable degradation of the marine environment. The A c t prohibits, except by permit, disposal in any ocean waters of materials which have been transported from U . S . ports or from any port in U . S . flag vessels. It also prohibits disposal without a permit by any ship in U . S . t e r r i t o r i a l waters and contiguous zone. No permit may be issued for disposal of radiological, biological, and chemical warfare agents and high-level radioactive wastes. The Administrator of E P A is authorized to establish r e g ulations under which permits w i l l be issued and c r i t e r i a by which to evaluate permit applications considering the need for the proposed dumping, the effects of dumping on the marine environment, alternative methods of disposal, and alternate uses of the oceans. E P A is also authorized to designate disposal sites. These regulations have been issued and are contained in Title 40 of the Code of F e d e r a l R e g 416


25.

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Regulation of Ocean Disposal

u l a t i o n s at S e c t i o n s 2 2 0 - 2 2 7 . T h e r e g u l a t i o n s e s t a b l i s h c a t e g o r i e s of p e r m i t s w h i c h m a y be i s s u e d a n d a l s o d e s i g n a t e disposal sites i n which dumping may o c c u r . C o n c u r r e n t w i t h the d e v e l o p m e n t of d o m e s t i c l e g i s l a t i o n to s t r i c t l y r e g u l a t e o c e a n d i s p o s a l , the I n t e r n a t i o n a l C o n v e n t i o n o n the P r e v e n t i o n of M a r i n e P o l l u t i o n b y D u m p i n g of W a s t e s a n d O t h e r M a t t e r w a s n e g o t i a t e d i n 1972 at a c o n ference attended b y 92 n a t i o n s . In F e b r u a r y , 1973, the P r e s i d e n t s u b m i t t e d the C o n v e n t i o n to the Senate f o r r a t ification, which was a c c o m p l i s h e d i n August, 1973. The Convention w i l l b e c o m e e f f e c t i v e after r a t i f i c a t i o n b y 15 n a t i o n s , at w h i c h t i m e the o c e a n d u m p i n g l a w b e c o m e s the e n a b l i n g d o m e s t i c l e g i s l a t i o n f o r the t r e a t y . A t the p r e s e n t t i m e n i n e n a t i o n s h a v e r a t i f i e d the C o n v e n t i o n , a n d i t i s a n t i c i p a t e d that it w i l l c o m e into f o r c e b y the end of 1975. E P A i n i t i a t e d the tions for i s s u i n g p e r m i t s for ocean d i s p o s a l , c r i t e r i a c o n s i s t e n t w i t h both the A c t a n d the C o n v e n t i o n u n d e r w h i c h to e v a l u a t e w a s t e s , and e n f o r c e m e n t p r o g r a m s to i n s u r e c o m p l i a n c e . O n A p r i l 23, 1973, the p r o g r a m b e c a m e o p erational a n d u n p e r m i t t e d o c e a n d i s p o s a l w a s no l o n g e r a l l o w e d . B y J u l y , 1973, 47 p e r m i t s h a d b e e n i s s u e d u n d e r i n t e r i m r e g u l a t i o n s . F i n a l regulations were promulgated on O c t o b e r 15, 1973, a n d to date 106 p e r m i t s i n c l u d i n g r e n e w a l s a n d r e a p p l i c a t i o n s have b e e n i s s u e d u n d e r the f i n a l r e g u l a t i o n s f o r s t r i c t l y r e g u l a t e d o c e a n d i s p o s a l of w a s t e s . E P A i s c u r r e n t l y r e v i s i n g the o c e a n d u m p i n g r e g u l a t i o n s b a s e d on our o p e r a t i n g e x p e r i e n c e a n d , i n c o m p l i a n c e with the N a t i o n a l E n v i r o n m e n t a l P o l i c y A c t ( Ν Ε Ρ Α ) , i s b e g i n n i n g s t u d i e s f o r the p r e p a r a t i o n o f e n v i r o n m e n t a l i m p a c t s t a t e m e n t s o n the d i s p o s a l s i t e s . T h e c r i t e r i a for evaluating each p e r m i t application a r e i n S e c t i o n 227 o f T i t l e 40 of the C o d e of F e d e r a l R e g u l a t i o n s . It i s u s e f u l to u n d e r s t a n d that the the c r i t e r i a a r e b a s e d o n s p e c i f i c r e q u i r e m e n t s of the I n t e r n a t i o n a l O c e a n D u m p i n g c o n v e n t i o n a s w e l l a s the s t a t u t o r y r e q u i r e m e n t s i n the O c e a n D u m p i n g A c t . In a d d i t i o n to the p r o h i b i t i o n s on d u m p i n g b i o l o g i c a l , c h e m i c a l , a n d r a d i o l o g i c a l w a r f a r e agents a n d h i g h - l e v e l r a d i o a c t i v e w a s t e s , the c o n v e n t i o n p r o h i b i t s the d u m p i n g of w a s t e s c o n t a i n i n g m e r c u r y , c a d m i u m , o r g a n o halogens, p e r s i s t e n t p l a s t i c s , and p e t r o l e u m o i l s , as other than t r a c e c o n t a m i n a n t s . T h e C o n v e n t i o n , h o w e v e r , d o e s not define " t r a c e c o n t a m i n a n t s " ; a n d , t h e r e f o r e , e a c h c o u n t r y m u s t m a k e i t s own i n t e r p r e t a t i o n of what a " t r a c e c o n t a m i n a n t " i s , a n d what l e v e l s c a n be p e r m i t t e d i n w a s t e s to b e ocean dumped. T h e E P A c r i t e r i a reflect these prohibitions a n d go one step f u r t h e r b y a l s o p r o h i b i t i n g the d i s p o s a l of materials i n s u f f i c i e n t l y d e s c r i b e d to p e r m i t e v a l u a t i o n of t h e i r i m p a c t o n the m a r i n e e n v i r o n m e n t , w h i c h i s one of the r e a s o n s why c h e m i c a l a n a l y s i s of the w a s t e s i s s o i m -


417

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CHEMISTRY

portant. A technical e v a l u a t i o n m u s t be m a d e o n e a c h a p p l i c a t i o n , not o n l y a s to the c o m p l i a n c e w i t h t h e s e c r i t e r i a , but a l s o a s to the n e e d f o r the d u m p i n g , the a v a i l a b i l i t y of a l t e r n a t i v e s , a n d f e a s i b i l i t y of t r e a t m e n t . T h e b a s i c d e c i s i o n to i s s u e a p e r m i t f o r o c e a n d u m p i n g depends o n the d e t e r m i n a t i o n by the A d m i n i s t r a t o r that the " d u m p i n g w i l l not u n r e a s o n a b l y d e g r a d e o r e n d a n g e r h u m a n h e a l t h , w e l f a r e , o r a m e n i t i e s , o r the m a r i n e e n v i r o n m e n t , ecological systems, or economic potentialities. Such d e c i s i o n s a r e d i f f i c u l t to m a k e i n a r e g u l a t o r y p r o g r a m without adequate c r i t e r i a , a n d without s t r o n g t e c h n i c a l c a p a b i l i t y f o r e v a l u a t i n g p e r m i t s a n d f o r u n d e r s t a n d i n g the effects of p o l l u t a n t s o n the m a r i n e e n v i r o n m e n t . T h e t e c h n i c a l n e e d s f o r the r e g u l a t i o n of o c e a n d i s p o s a l i n v o l v e the a b i l i t y : (1) to d e v e l o p c r i t e r i i m p a c t of w a s t e m a t e r i a l s o n the m a r i n e e n v i r o n ment; (2) to c h a r a c t e r i z e f u l l y w a s t e m a t e r i a l s p r o p o s e d f o r ocean disposal; (?) to a c c u r a t e l y a s s e s s the e x i s t i n g c o n d i t i o n s at a disposal site; and (4) to a c c u r a t e l y d e t e c t any e f f e c t s of the d u m p i n g a c t i v i t i e s o n the d i s p o s a l s i t e . It m u s t be u n d e r s t o o d c l e a r l y that what we a r e r e a l l y c o n c e r n e d about i n t e r m s of the i m p a c t of p o l l u t a n t s o n the m a r i n e e n v i r o n m e n t i s t h e i r u l t i m a t e i m p a c t on the l i v i n g organisms of the o c e a n a n d o n t h e i r i n t e r r e l a t i o n s h i p s . R e c o g n i t i o n of t h i s b a s i c c o n c e r n f r e q u e n t l y tends to put the c h e m i c a l a s p e c t s of m a r i n e p o l l u t i o n c o n t r o l p u r e l y i n the p o s i t i o n of a t e c h n i c a l s u p p o r t r e q u i r e m e n t f o r the l a r g e r e c o l o g i c a l c o n c e r n s r a t h e r than a s the b a s i c t e c h n i q u e a n d approach t h r o u g h w h i c h s i t u a t i o n s of p o t e n t i a l e c o l o g i c a l c o n c e r n c a n be i d e n t i f i e d and m e c h a n i s m s f o r t h e i r c o r r e c tion developed. In d i s c u s s i n g the r o l e of the c h e m i s t and of c h e m i s t r y i n s e c u r i n g data f o r s u p p o r t i n g r e g u l a t o r y p r o g r a m s f o r the m a r i n e e n v i r o n m e n t , w e w i l l e m p h a s i z e not s o m u c h s p e c i f i c problems that p r e s e n t l y e x i s t , but r a t h e r the t y p e s of a p p r o a c h e s we f e e l w o u l d be m o s t r e w a r d i n g i n a s s e s s i n g the i m p a c t of p o l l u t a n t s o n m a r i n e e c o s y s t e m s . T h e s e c a n be g r o u p e d r o u g h l y into t h r e e g e n e r a l c a t e g o r i e s of i n v e s t i g a t i o n , w h i c h we w o u l d l i k e to c h a r a c t e r i z e b r i e f l y , a n d then r e l a t e to e a c h of the r e g u l a t o r y n e e d s a l r e a d y m e n t i o n e d . F i r s t , there is sheer analytical capability. This may a p p e a r to be p e r f e c t l y s t r a i g h t f o r w a r d , but c o n s i d e r that i n the p a r t i c u l a r r e g u l a t o r y s i t u a t i o n that c o n c e r n s u s , we a r e interested first i n d e t e c t i n g a c h e m i c a l c o n s t i t u e n t (an element, i o n , o r specific compound) i n " t r a c e " quantities i n a waste m a t e r i a l containing many s i m i l a r c h e m i c a l species; 1 1


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t h e n , after i t i s d u m p e d , we want to be a b l e to detect i t at s e v e r a l o r d e r s of m a g n i t u d e s m a l l e r c o n c e n t r a t i o n s - not i n a p u r e s o l u t i o n i n d i s t i l l e d w a t e r but i n a t h r e e p e r c e n t s a l t s o l u t i o n of v a r i a b l e c o m p o s i t i o n — a n d w i t h s u f f i c i e n t a c c u r a c y that we c a n d e t e r m i n e i f t h e r e i s any p r o g r e s s i v e b u i l d u p i n c o n c e n t r a t i o n a t t r i b u t a b l e to the d i s c h a r g e of the c o n s t i t u e n t f r o m the w a s t e i n w h i c h it w a s o r i g i n a l l y i d e n t i f i e d a s a " t r a c e " c o n t a m i n a n t . W e w o u l d , of c o u r s e , l i k e to be a b l e to p e r f o r m the n e c e s s a r y a n a l y s e s o n a r o u t i n e b a s i s with m i n i m a l l y t r a i n e d technicians u s i n g f o o l - p r o o f m e t h o d s of a n a l y s i s w h i c h r e q u i r e i n e x p e n s i v e e q u i p m e n t . H o w e v e r , i t i s not enough to s i m p l y be a b l e to m e a s u r e c o n c e n t r a t i o n s of s p e c i f i c c o n s t i t u e n t s u n d e r h i g h l y v a r i a b l e c o n d i t i o n s . W e a l s o n e e d to know the k i n e t i c s of t h e i r t r a n s f o r m a t i o n s i n the m a r i n e e n v i r o n m e n t . T h i s i s the s e c o n d of the m a j o r c a t e g o r i e a b l y i n t o the t h i r d , w h i c h i s the c o n s i d e r a t i o n of s y n e r g i s m a n d a n a t a g o n i s m a m o n g v a r i o u s w a s t e c o n s t i t u e n t s when a w a s t e m a t e r i a l of one c o m p o s i t i o n i s d u m p e d s u d d e n l y a n d without p r e p a r a t i o n i n t o a m e d i u m of s o m e w h a t d i f f e r e n t c h a r a c t e r is tic s. T h e point we w i s h to b r i n g to y o u r attention i s s i m p l e to s t a t e , but i s e x t r e m e l y c o m p l e x w h e n a p p l i e d to the r e a l world. T o use a s i m p l e e x a m p l e , i f y o u know what the k i n e t i c s of t h e m e t h y l a t i o n of m e r c u r y a r e i n a p u r e s o l u t i o n , c a n y o u e x t r a p o l a t e t h i s a c c u r a t e l y to the m e t h y l a t i o n of m e r c u r y i n s e w a g e s l u d g e o r i n the m a r i n e e n v i r o n m e n t ? In a r e g u l a t o r y p r o g r a m , we a r e m i l d l y i n t e r e s t e d i n the " p u r e s o l u t i o n " c a s e , but we a r e v i t a l l y i n t e r e s t e d i n the l a t t e r two c a s e s a n d t h e i r r e l a t i o n s h i p . T h e r e f o r e , k i n e t i c s , s y n e r g i s m , a n a t a g o n i s m , and what h a p p e n s i n a t h r e e p e r cent s a l t s o l u t i o n to affect any o r a l l of t h e s e t y p e s of r e a c t i o n s of a w a s t e c o n s t i t u e n t a r e the b a s i c i n f o r m a t i o n upon which an environmentally r e s p o n s i b l e r e g u l a t o r y p r o g r a m m u s t r e s t , a n d it i s i n t h i s context i n w h i c h we w o u l d l i k e to d i s c u s s what we f e e l i s n e e d e d i n e a c h of the f o u r t y p e s of t e c h n i c a l r e q u i r e m e n t s o u t l i n e d e a r l i e r . Criteria

Development

T h e r e a r e c e r t a i n a s p e c t s of the o c e a n d i s p o s a l c r i t e r i a w h i c h a r e n o w , a n d w i l l p r o b a b l y r e m a i n , a m a t t e r of j u d g m e n t on the p a r t of E P A a s to what i s a c c e p t a b l e a n d what i s not. T h e s e i n c l u d e the a m o u n t s of i n e r t m a t e r i a l s a n d the a m o u n t s of a c i d i c , b a s i c , o r o x y g e n - c o n s u m i n g m a t e r i a l s w h i c h c a n be d u m p e d without u n r e a s o n a b l e d e g r a d a t i o n i n any p a r t i c u l a r c a s e . M o r e s p e c i f i c than t h e s e a r e the o v e r a l l t o x i c i t y c r i t e r i a d e t e r m i n e d b y a b i o a s s a y a c c o r d i n g to s p e c i f i e d a p p r o v e d p r o c e d u r e s w h i c h s e t s l i m i t s on how t o x i c w a s t e s c a n be d i s p o s e d of i n the m a r i n e e n -


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v i r o n m e n t . B e y o n d t h i s a r e d e f i n i t e l i m i t s set o n the a m o u n t s of c e r t a i n s p e c i f i c w a s t e c o n s t i t u e n t s p r o h i b i t e d a s o t h e r t h a n "trace contaminants. T h e p r o b l e m s a s s o c i a t e d with setting r a t i o n a l l i m i t s on s u c h c o n s t i t u e n t s m a y be i l l u s t r a t e d b y the p r o b l e m s s u r r o u n d i n g the s e t t i n g of r e a s o n a b l e l i m i t s o n the d i s c h a r g e of m e r c u r y to the m a r i n e e n v i r o n m e n t . T h e e x i s t i n g c r i t e r i a a r e b a s e d o n a l l o w i n g , w i t h i n the m i x i n g z o n e , a n i n c r e a s e of 50 p e r c e n t a b o v e a v e r a g e a m b i e n t l e v e l s f o r m e r c u r y i n the w a t e r c o l u m n o r i n the s e d i m e n t s . R e c e n t i n f o r m a t i o n s e t s a n a c u t e t o x i c i t y l e v e l f o r m e r c u r y i n s e a w a t e r of 50 p p b , a n d a c h r o n i c l e v e l of 0 . 1 0 p p b , w h i c h i s i n the r a n g e of n o r m a l a m b i e n t l e v e l s f o r m e r c u r y i n s e a w a t e r . T h e r e a r e s e v e r a l p r o b l e m s that a p p e a r i n r e l a t i n g the k n o w n t o x i c v a l u e s f o r m e r c u r y i n the e n v i r o n m e n t to t h o s e which a r e p e r m i s s i b l l i k e to r e l a t e t h e s e to the c o n c e p t s of k i n e t i c s , s y n e r g i s m , and a n t a g o i s m d i s c u s s e d e a r l i e r . M e r c u r y i s g e n e r a l l y r e ported a s t o t a l m e r c u r y , w h e r e a s the b i o l o g i c a l l y a c t i v e s p e c i e s i s o r g a n i c m e r c u r y . T h u s , we m u s t f i r s t d e t e r m i n e how m u c h of the t o t a l m e r c u r y b e c o m e s b i o l o g i c a l l y a c t i v e a n d at what r a t e ; second, hm i s the r a t e o f conversion to o r g a n i c m e r c u r y r e l a t e d to the a m o u n t of s e w a g e s l u d g e o r other waste p r e s e n t and its o r g a n i c content; a n d , t h i r d , i f one p u t s t h i s c o m p l e x m i x t u r e i n t o a t h r e e p e r c e n t s a l t s o l u t i o n , how d o e s t h i s affect the c o n v e r s i o n of i n o r g a n i c m e r c u r y to the b i o l o g i c a l l y a c t i v e m e t h y l a t e d m e r c u r y ? T o answer such questions r e q u i r e s an integrated, cohesive a p p r o a c h t o w a r d d e t e r m i n i n g the k i n e t i c s of M e r c u r y r e actions in s e a w a t e r a n d the s y n e r g i s t i c o r a n t a g o n i s t i c e f f e c t s o f m e r c u r y i n the e n v i r o n m e n t , a n d the d e v e l o p m e n t of f i n a l c r i t e r i a f o r m e r c u r y d i s c h a r g e s m u s t d e p e n d u p o n the c h e m i c a l r e s e a r c h to i d e n t i f y t h e s e r e l a t i o n s h i p s . 1 1

Waste Characterization Complete analysis of w a s t e m a t e r i a l s i s e s s e n t i a l to i d e n t i f y the c o n s t i t u e n t s , t h e i r n a t u r e a n d t h e i r c o n c e n t r a t i o n . R e f e r e n c e c a n be m a d e to data a v a i l a b l e i n the l i t e r ature on t o x i c o l o g i c a l effects, and a p r e d i c t i o n c a n be m a d e o n the b e h a v i o r of the c o n s t i t u e n t s i n the m a r i n e e n v i r o n m e n t - whether a m a t e r i a l w i l l be completely soluble, concentrate i n a s u r f a c e s l i c k , o r a d s o r b onto b o t t o m s e d i m e n t s . F r o m a r e g u l a t o r y s t a n d p o i n t , we h a v e r e a s o n a b l y good c a p a b i l i t y i n b e i n g a b l e to d e t e r m i n e the c o n s t i t u e n t s of w a s t e m a t e r i a l s t h e m s e l v e s . T h e t h i r t e e n t h e d i t i o n of S t a n d a r d Methods f o r the E x a m i n a t i o n of W a t e r a n d W a s t e w a t e r , p r e p a r e d a n d p u b l i s h e d j o i n t l y b y the A m e r i c a n P u b l i c H e a l t h Association ( A P H A ) , A m e r i c a n Water Works Association, and W a t e r P o l l u t i o n C o n t r o l F e d e r a t i o n , i s c u r r e n t l y a v a i l -


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able and is revised and updated p e r i o d i c a l l y . Another c o m m o n r e f e r e n c e i s the A n n u a l B o o k o f A S T M S t a n d a r d s a n d s p e c i f i c a l l y P a r t 23 f o r W a t e r . S e c t i o n 304(g) o f the F e d e r a l W a t e r P o l l u t i o n C o n t r o l A c t A m e n d m e n t s of 1972 r e q u i r e s that E P A p r o m u l g a t e g u i d e l i n e s e s t a b l i s h i n g t e s t p r o c e d u r e s f o r the a n a l y s i s of p o l l u t a n t s S u c h t e s t p r o c e d u r e s a r e to b e u s e d b y p e r m i t a p p l i c a n t s to d e m o n s t r a t e that effluent d i s c h a r g e s m e e t a p p l i c a b l e p o l l u t a n t d i s c h a r g e l i m i t a t i o n s , a n d b y the States a n d o t h e r e n f o r c e m e n t a c t i v i t i e s i n m o n i t o r i n g of effluents to v e r i f y effectiveness of pollution c o n t r o l m e a s u r e s . In r e s p o n s e to that l e g i s l a t i v e r e q u i r e m e n t E P A p u b l i s h e d g u i d e l i n e s f o r t e s t p r o c e d u r e s i n the F e d e r a l R e g i s t e r of O c t o b e r 16, 1973 (40 C F R 136). A s p a r t of that effort E P A has c o m p i l e d i n the r e c e n t e d i t i o n o f " M e t h o d s f o r Chemical Analysis o a n a l y t i c a l p r o c e d u r e s u s e d b y i t s l a b o r a t o r i e s f o r the e x a m ination of ground and surface w a t e r s , domestic and i n d u s t r i a l waste effluents, and treatment p r o c e s s s a m p l e s . Except w h e r e noted the m e t h o d s a r e a p p l i c a b l e to both w a t e r a n d w a s t e w a t e r s , a n d both f r e s h a n d s a l i n e w a t e r s a m p l e s . A l though o t h e r t e s t p r o c e d u r e s m a y b e u s e d , a s p r o v i d e d i n the O c t o b e r 16, 1973, F e d e r a l R e g i s t e r i s s u e , the m e t h o d s d e s c r i b e d i n the m a n u a l w i l l b e u s e d b y E P A i n d e t e r m i n i n g compliance w i t h a p p l i c a b l e w a t e r a n d effluent s t a n d a r d s e s t a b l i s h e d b y the A g e n c y . M o s t of the E P A m e t h o d s a r e d i r e c t m o d i f i c a t i o n s o r c l a r i f i c a t i o n s o f the A P H A o r A S T M m e t h o d s , s o m e of w h i c h h a v e b e e n a d a p t e d to i n s t r u m e n t a l m e t h o d s i n p r e f e r a n c e to m a n u a l p r o c e d u r e s b e c a u s e o f the improved speed, a c c u r a c y , and p r e c i s i o n . In d e v e l o p i n g t e s t p r o c e d u r e s f o r the i m p l e m e n t a t i o n o f the O c e a n D i s p o s a l P e r m i t P r o g r a m . T h e m e t h o d s that w e r e d e v e l o p e d i n r e s p o n s e to S e c t i o n 304(g) o f the F W P C A , w e r e adopted f o r a n a l y z i n g wastes p r o p o s e d f o r ocean d i s p o s a l . A s s e s s m e n t of D i s p o s a l Site C o n d i t i o n s In o r d e r to e v a l u a t e i m p a c t o f d u m p i n g o n the m a r i n e environment, an accurate r e p r e s e n t a t i o n of the e x i s t i n g conditions i s n e c e s s a r y . T h e s e disposal site evaluations n e e d to i n c l u d e e x a m i n a t i o n o f the w a t e r c o l u m n a n d b e n t h i c r e g i o n s w i t h r e s p e c t to w a t e r q u a l i t y , b i o t a , a n d s e d i m e n t s . B u t t h e r e a r e a n u m b e r of c o m p l i c a t i n g f a c t o r s . A n y s a m p l i n g i s o c c u r r i n g i n a d y n a m i c s y s t e m . E v e n the s a m p l i n g t e c h n i q u e s t h e m s e l v e s a r e not s t a n d a r d i z e d . T h e ambient c o n c e n t r a t i o n o f m a n y c o n s t i t u e n t s o f i n t e r e s t a r e o n the range of p a r t s per million and parts p e r billion, and although p r e c o n c e n t r a t i o n t e c h n i q u e s a r e a v a i l a b l e , they do i n t r o d u c e c h a n c e of e r r o r . T h e v e r y n a t u r e o f the s e a water causes analytical p r o b l e m s with saline i n t e r f e r e n c e s .


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The objective i n making baseline assessments i s not only to determine the ambient concentrations of particular constituents, but also to understand the variation of levels in time and space, to provide information statistical variability and the range of values. Here, again, we must face the problems of kinetics, synergism, and antagonism, because in the initial baseline assessment of a particular disposal site, attention must be directed toward the rates at which certain reactions occur, and the factors which tend to stimulate or suppress certain reactions. It i s only through a thorough understanding of the processes which are most significant at a particular location that the fundamental rate processes which occur at a disposal site can be understood to the extent that effective control can be exerted over the site to reduce adverse effects and to enhanc The major goal o y regulatory progra is to find out what forms of waste disposal have unacceptable adverse effects on the environment and to eliminate, or at least reduce the unacceptable adverse impact. In the marine environment this i s very difficult to achieve for a number of reasons. F i r s t , the existing baseline data are poor simply because no agency has ever had the mandate to conduct the extensive surveys necessary to establish baselines adequate for regulatory purposes. Second, the major portion of the existing chemical r e s e a r c h efforts during the past has been directed toward how to improve our analytical capability, which i s of course an essential precursor to finding out what analytical results mean i n terms of environmental protection, but which does not contribute directly toward an understanding of the effects of specific pollutants on the marine environment. Third, the volumes of water involved in ocean disposal are so great that many v e r y c r i t i c a l pollutants, such as trace metals and organohalogens become diluted v e r y rapidly, so that the measurements that are needed to detect pollutants and their impacts require techniques that are so sensitive that contamination of samples by the sampling equipment itself becomes a c r i t i c a l problem in some cases. Fourth, many ocean sediments contain potentially toxic trace metals, but in forms which are not available to the ecosystem under normal ambient conditions in the oceans. Certain materials, even in s m a l l quantities, might upset this balance and cause the release into the seawater of toxic materials from natural sediments. Conversely, toxic materials which might be a problem in a fresh water ecosystem could become non -toxic in seawater or be adsorbed onto or absorbed into some natural sediments and be permanently removed f r o m the ecosystem. This i s m e r e l y a listing of some of the types of chemical


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problems we face in implementing a regulatory program to protect the marine environment. It i s not intended to be exhaustive, but just to indicate the scope of the chemical problems which need to be attacked and solved so that we can deal with pollution problems i n the marine environment with the same degree of certainity that we have i n the fresh water environment. Problems associated with marine pollution have been highlighted by the national concern about the effect of ocean dumping of toxic materials on the marine environment which culminated in the passage of the Ocean Dumping Act. It i s well to remember, however, that the vast majority of p o l lutants reaching the ocean enter the marine environment through ocean outfalls or by way of r i v e r s and estuaries, and that the needs an well to pollutants f r o The problem of ocean pollution is not a temporary one. In the United States the rate of both population and industrial growth i s greater in the coastal area than i n the interior; i n addition, we are entering an era of greater exploitation of offshore marine resources and the development of deepwater ports near shore. These activities and this growth w i l l undoubtedly result in greater direct stress on the marine environment and greater pressure for increased waste d i s posal into ocean waters. It is possible that the ocean may be the most environmentally acceptable place to put some types of wastes after they have been adequately treated. Before we can accept this, however, we must know much more about the marine environment and how pollutants behave i n it. I hope that our comments here have served to focus your attention on what some of that "much more" might be as far as chemistry is concerned.


26 Pollutant Inputs and Distributions off Southern California D. R. YOUNG, D. J. M c D E R M O T T , T. C. HEESEN, andT.K.JAN Southern California Coastal Water Research Project, El Segundo, Calif. 90245

The c o a s t a l p l a i habited by approximatel percent of the Nation's population. A wide v a r i e t y of a c t i v i t i e s i n t h i s region generate waste products that may contribute pollutants to the adjacent marine environment, which is known as the Southern California Bight. Most of the freshwater that enters the Bight i s municipal wastewater discharged from four submarine o u t f a l l systems l y i n g o f f the c i t i e s of Los Angeles, Santa Ana, and San Diego (Figure 1). These systems carry approximately 95 percent of the more than 1 billion gallons of wastewater released d a i l y o f f southern C a l i f o r n i a . In a d d i t i o n , surface runoff contributes, on the average, the equivalent of 400 m i l l i o n gallons per day (mgd) of freshwater through 15 major channels d i s t r i b u t e d fairly evenly along the coast. However, about 80 percent of t h i s flow r e s u l t s from a few storms, which generally occur during the fall and winter seasons. Another p o t e n t i a l source of p o l l u t i o n i s industrial waste discharged d i r e c t l y into the marine environment. A great number of these discharges enter the Los Angeles/Long Beach Harbor i n San Pedro Bay, the largest harbor i n the Bight. This harbor also receives the greatest v a r i e t y of i n d u s t r i a l wastes. The 14 major harbors or marinas along the southern C a l i f o r n i a coast provide anchorage for approximately 40,000 r e c r e a t i o n a l c r a f t , i n addition to numerous commercial and naval v e s s e l s . The r e l a t i v e l y large q u a n t i t i e s of a n t i f o u l i n g and other bottom paints applied annually at these anchorages represent another p o t e n t i a l source of marine p o l l u t a n t s , particularly trace metals and synthetic organic compounds. A f i f t h route by which man-made contaminants may 424


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r e a c h t h e c o a s t a l environment i s aerial precipitation. In v i e w o f t h e s e v e r e a i r p o l l u t i o n problems i n s o u t h e r n C a l i f o r n i a , one would e x p e c t a e r i a l f a l l o u t t o be a s i g n i f i c a n t f a c t o r i n marine p o l l u t i o n i n the area. A t present, we have relatively l i t t l e information on the precipitation of trace elements; however, we recently established the importance of this input route for chlorinated hydrocarbons such as DDT and polychlorinated biphenyls (PCB). The B i g h t i s r o u g h l y d e f i n e d on t h e west b y the e a s t e r n edge o f t h e C a l i f o r n i a C u r r e n t , w h i c h g e n e r a l l y c a r r i e s l a r g e q u a n t i t i e s o f t r a c e m a t e r i a l s (1). Ihus, i t i s i n s t r u c t i v e , f o r comparative purposes, t o estimate the q u a n t i t y of a given m a t e r i a l that f l u x e s through the s u r f a c e l a y e r s current advection. I n t h e p a s t 4 y e a r s , t h e C o a s t a l Water R e s e a r c h P r o j e c t has i n v e s t i g a t e d t h e i n p u t s and d i s t r i b u t i o n s o f more t h a n a dozen p o t e n t i a l l y h a r m f u l t r a c e elements (1, 2, 3^ 4, 5) . Here we summarize our r e s u l t s on one o f t h e s e elements, mercury, as an example o f our f i n d ings to date. D u r i n g Water Year 1971-72, we sampled storm r u n o f f from f o u r major c h a n n e l s i n t h e urban and a g r i c u l t u r a l r e g i o n s of the southern C a l i f o r n i a c o a s t a l p l a i n and anal y z e d the samples f o r t r a c e m e t a l s and c h l o r i n a t e d h y d r o c a r b o n s . We o f t e n o b s e r v e d a c o r r e l a t i o n between f l o w r a t e and c o n c e n t r a t i o n o f suspended sediments and t r a c e c o n s t i t u e n t s ( F i g u r e 2 ) . D u r i n g 1972-73, we r e p e a t e d our s u r v e y o f c h l o r i n a t e d h y d r o c a r b o n s i n Los A n g e l e s R i v e r storm r u n o f f and o b t a i n e d f l o w - w e i g h t e d mean c o n c e n t r a t i o n s v e r y s i m i l a r t o t h o s e o f t h e p r e vious year. T h e r e f o r e , we have e x t r a p o l a t e d our d a t a t o unsampled c h a n n e l s and time p e r i o d s t o o b t a i n B i g h t wide e m i s s i o n e s t i m a t e s f o r Water Y e a r 1972-73. The f l o w - w e i g h t e d mean c o n c e n t r a t i o n s o f t o t a l mercury found i n storm r u n o f f from t h e f o u r c h a n n e l s ranged from 400 t o 1030 ng/L. To o b t a i n an i n i t i a l i n d i c a t i o n o f t h e importance o f d i r e c t i n d u s t r i a l waste d i s c h a r g e s , d u r i n g 1973, we sampled e f f l u e n t s from a number o f d i f f e r e n t k i n d s o f i n d u s t r i e s l o c a t e d i n Los A n g e l e s Harbor. Our r e s u l t s f o r t o t a l mercury a r e summarized i n T a b l e 1. The h i g h e s t c o n c e n t r a t i o n we o b s e r v e d (240 ng/L) o c c u r r e d i n wastewater from a f i s h cannery; however, t h i s v a l u e was o n l y e i g h t times t h e average l e v e l s (30 ng/L) we have measured i n seawater c o l l e c t e d o f f s o u t h e r n California. Most o f the c o n c e n t r a t i o n s o b s e r v e d were lower t h a n t h e cannery waste v a l u e and do n o t s u g g e s t s i g n i f i c a n t mercury c o n t a m i n a t i o n v i a t h i s r o u t e .


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121°W

120 W e

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117°W

Figure 1. The Southern California Bight Outfall systems are: (1) Oxnard City, (2) Hyperion, Los Angeles City, (3) Whites Point, Los Angeles County, (4) Orange County, and (5) San Diego City.

0000

Figure 2.

0800 1600 22 DEC 1971

0000

0800 1600 23 DEC 1971

Total mercury in Los Angeles River storm runoff, 22-23 December 1971


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427

D u r i n g 1972-73, we o b t a i n e d s e v e r a l 1-week comp o s i t e s o f f i n a l e f f l u e n t from t h e f i v e major m u n i c i p a l wastewater t r e a t m e n t p l a n t s a l o n g t h e c o a s t o f the Bight. S e v e r a l grab samples per day were c o l l e c t e d and f r o z e n . At the end o f t h e week, r e p l i c a t e composi t e s were o b t a i n e d and f i l t e r e d , and t h e f i l t r a t e s and r e s i d u e s were a n a l y z e d f o r t o t a l mercury. Average r e s u l t s a r e l i s t e d i n T a b l e 2. These d a t a i n d i c a t e t h a t the m u n i c i p a l e f f l u e n t s c o n t a i n c o n c e n t r a t i o n s o f mercury an o r d e r - o f - m a g n i t u d e g r e a t e r t h a n t h o s e found i n d i r e c t i n d u s t r i a l d i s c h a r g e s t o Los Angeles Harbor. I n a d d i t i o n , the wastewater p a r t i c u l a t e s have r e l a t i v e l y h i g h mercury c o n c e n t r a t i o n s : T y p i c a l l e v e l s are a t l e a s t 100 times t h e average c o n c e n t r a t i o n (0.04 mg/dry kg) we c o a s t a l marine sediments In T a b l e 3, we have summarized our v a l u e s f o r annual mass e m i s s i o n r a t e s o f t o t a l mercury to the B i g h t v i a t h e t h r e e t y p e s o f wastewater d i s c u s s e d above. The t a b l e a l s o c o n t a i n s an e s t i m a t e o f t h e amount o f mercury f l o w i n g through t h e B i g h t v i a ocean c u r r e n t a d v e c t i o n , b a s e d on an average seawater c o n c e n t r a t i o n o f 30 ng/L measured d u r i n g s e v e r a l s u r v e y s sponsored by t h e P r o j e c t , and on océanographie assumptions o u t l i n e d by Young (2). These r e s u l t s i n d i c a t e t h a t m u n i c i p a l wastewaters a r e t h e dominant f l u v i a l s o u r c e o f mercury t o the B i g h t . The i n p u t o f mercury v i a m u n i c i p a l wastewaters would be u n d e t e c t a b l e i f i t were w e l l mixed w i t h t h e a d v e c t i n g seawater. However, t h i s i s n o t always t h e c a s e , as i s i l l u s t r a t e d by t h e d a t a o f F i g u r e 3. This f i g u r e summarizes t h e r e s u l t s o f a 1973 s u r v e y o f mercury i n s u r f a c e sediments around t h e JWPCPl submarine o u t f a l l system o f f Whites P o i n t on t h e P a l o s Verdes P e n i n s u l a . As w i t h e f f l u e n t p a r t i c u l a t e v a l u e s l i s t e d i n T a b l e 2, c o n t a m i n a t i o n l e v e l s i n t h e s e d i ments a r e two o r d e r s o f magnitude above c o n c e n t r a t i o n s i n c o a s t a l c o n t r o l areas. V e r t i c a l p r o f i l e s o f mercury i n box c o r e s c o l l e c t e d a t S t a t i o n s B18 t h r o u g h B21 a r e i l l u s t r a t e d i n F i g u r e 4. These r e s u l t s i n d i c a t e t h a t the i n f l u e n c e of the o u t f a l l s extends t o approximately 30 cm below the sediment s u r f a c e a t t h e d i s c h a r g e d e p t h o f about 60 m. On t h e b a s i s o f numerous v e r t i c a l p r o f i l e s o b t a i n e d a t t h e m o n i t o r i n g s t a t i o n s shown i n F i g u r e 3, we e s t i m a t e t h a t r o u g h l y 4 m e t r i c t o n s o f a n t h r o p o g e n i c mercury a r e c o n t a i n e d i n t h e s e sediments. 1. J o i n t Water P o l l u t i o n C o n t r o l P l a n t o f t h e County S a n i t a t i o n D i s t r i c t s o f Los Angeles County.


428

MARINE

Table 1.

CHEMISTRY

Concentrations of t o t a l mercury i n i n d u s t r i a l e f f l u e n t s discharged d i r e c t l y to the Los Angeles Harbor, 1973.

Type of Discharge

Flow (mgd)

Mercury (ng/L)

F i s h Cannery Waste No. 1 Waste No. 2 Retort Discharge Condensor Water

5.55 3.20 0.12 1.94

240 140 81 120

Shipyard Cooling Water No Cooling Water No. 2 O i l Tanker Cleandown Ship B a l l a s t No. 1 Ship B a l l a s t No. 2

0.43 0.25 0.04 0.29

86 120 95 150

0.02

48

O i l Refinery Cooling Water Power Plant Cooling Water Chemical Plant Combined Processes Average Seawater

257

38

5.51

79 30

Table 2.

Concentrations of t o t a l mercury i n municipal wastewater discharged o f f southern C a l i f o r n i a , 1972-73. Wet Dry Discharger Flow (mgd) (mg/L) (mg/dry kg) Oxnard C i t y

10

0.0005

3.3

Los Angeles C i t y Effluent Sludge

330 5

0.0005 0.05

5.2 8.4

Los Angeles County

360

0.001

4.0

Orange County San Diego C i t y

150

0.001

100

0.001

6.7 6.0


26.

YOUNG

ET

AL.


Figure 4. Vertical profiles of total mercury concentrations in box core sediments collected northwest of the Whites Point outfall system, July 1971. Stations shown on Figure 3.

15

20 25 DEPTH (CM)


429

430

MARINE CHEMISTRY

w i t h a p p r o x i m a t e l y 20 p e r c e n t o f t h i s q u a n t i t y l o c a t e d i n t h e u p p e r 5 cm. A number o f o t h e r t r a c e e l e m e n t s a l s o a r e h i g h l y c o n c e n t r a t e d above n a t u r a l l e v e l s i n the Whites P o i n t discharge area. T a b l e 4 summarizes t y p i c a l sediment contamination f a c t o r s observed i n a bottom t r a w l i n g zone between Whites P o i n t and P o i n t V i c e n t e , "downstream" of the o u t f a l l d i f f u s e r s . Also l i s t e d are average concentrations of these t r a c e elements i n l i v e r s o f r e s i d e n t f l a t f i s h , the Dover s o l e ( M i c r o stomus p a c i f i c u s ) , t r a w l e d from t h e s e c o n t a m i n a t e d sediments and from an uncontaminated r e g i o n o f f Santa Catalina Island. These i n v e s t i g a t i o n s were c o n d u c t e d i n c o l l a b o r a t i o n with J . Galloway (University of C a l i f o r n i a , San Diego) and V . G u i n n and J . de G o e i j (University of California The most s t r i k i n g r e s u l t from the Dover s o l e study i s the f a c t t h a t the o u t f a l l specimens (known b y t h e i r h i g h DDT c o n c e n t r a t i o n s a n d f r e q u e n t l y e r o d e d f i n s t o have o c c u p i e d the contaminated region) d i d not e x h i b i t increased concentrations of the contaminant elements. The o n l y s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e s observed were r e d u c e d l i v e r c o n c e n t r a t i o n s o f a r s e n i c , cadmium, and s e l e n i u m i n t h e f i s h c o l l e c t e d near t h e d i s c h a r g e s . Subsequent s t u d i e s s t i l l i n progress have confirmed t h i s l a c k o f g e n e r a l enhancement of elemental concent r a t i o n s i n t h i s s p e c i e s on the P a l o s Verdes shelf. With t h e support o f the U . S. Environmental P r o t e c t i o n Agency we have i n v e s t i g a t e d i n p u t s o f c h l o r i n a t e d h y d r o carbons t o t h e waters o f the B i g h t v i a s i x d i f f e r e n t routes d u r i n g t h e p a s t two y e a r s . The m u n i c i p a l , i n d u s t r i a l , s u r face r u n o f f , and a d v e c t i o n i n p u t s t u d i e s g e n e r a l l y f o l l o w e d the p a t t e r n s o u t l i n e d above f o r mercury. D e t a i l e d surveys o f a n t i f o u l i n g p a i n t usage were conducted a t t h r e e major southern C a l i f o r n i a h a r b o r s , and a n a l y s i s o f approximately t h i r t y major brands o f p a i n t were made (2^· In addition, u s i n g a technique developed by V . McClure , we have c o n ducted e x t e n s i v e s t u d i e s o f d r y a e r i a l p r e c i p i t a t i o n o f c h l o r i n a t e d hydrocarbons throughout the B i g h t d u r i n g t h r e e d i f f e r e n t seasons. The r e s u l t s o b t a i n e d t o date from the c h l o r i n a t e d hydrocarbon s t u d i e s are sunroarized i n T a b l e 5. The p r i n c i p a l c h l o r i n a t e d hydrocarbons observed were DDT and PCB compounds. Major c o a s t a l sources d u r i n g 1973-74 were m u n i c i p a l wastewater and a e r i a l dry p r e c i p i t a t i o n .

2.

N a t i o n a l Marine F i s h e r i e s S e r v i c e , L a J o l l a , California.


26.

YOUNG ET A L .

T a b l e 3.


431

I n p u t s o f t o t a l mercury t o the S o u t h e r n C a l i f o r n i a B i g h t , 1972-73. E s t i m a t e d Flow (mgd)

Route M u n i c i p a l Wastewater*

Mercury MER (metric tons/yr)

950

Direct Industrial**

2.5-1

1,300

Storm R u n o f f

0.04

400

0.4 7

Ocean C u r r e n t s

1 χ 10

600

*

f

concentration

Estimate based o o b t a i n e d by SCCWR

** San Pedro Harbor o n l y , MER e s t i m a t e e x c l u d e s the natural mercury i n seawater used for cooling.

T a b l e 4.

T r a c e elements i n f l a t f i s h c o l l e c t e d o f f Los A n g e l e s d u r i n g 1971 and 1972. O u t f a l l specimens were t r a w l e d o f f P a l o s Verdes P e n i n s u l a ; c o n t r o l , o f f Santa Catalina Island.*

Trace Element

Sediments Outfall/Control

Antimony

Flatfish Liverst (mg/wet kg) Outfall

Control

13

0.003

0.003

Arsenic

15

1.3

3.1

Cadmium

160

0.19

0.58

Copper

23

2.0

2.2

Mercury

85

0.11

0.11

Selenium

14

0.65

1.2

1.8**

2.2**

Silver Zinc

3 17

26

27

* Sediment d a t a a f t e r G a l l o w a y (6); f l a t f i s h v a l u e s a f t e r de G o e i j e t a l . , (5) . ** A r b i t r a r y u n i t s . t A r s e n i c , cadmium and s e l e n i u m v a l u e s s i g n i f i c a n t l y d i f f e r e n t a t t h e 95 p e r c e n t c o n f i d e n c e l e v e l .


432

MARINE

CHEMISTRY

S u r f a c e r u n o f f i n p u t s were o f secondary importance, and c o n t r i b u t i o n s from d i r e c t i n d u s t r i a l d i s c h a r g e s and a n t i f o u l i n g p a i n t s c u r r e n t l y i n use appear t o b e insignificant. However, a few d r i e d samples o f o l d a n t i f o u l i n g p a i n t showed e x t r e m e l y h i g h PCB c o n c e n t r a t i o n s ( a p p r o x i m a t e l y 10 p e r c e n t on a d r y w e i g h t b a s i s ) ; t h i s s u g g e s t s t h a t p a s t c o n t r i b u t i o n s from v e s s e l p a i n t s may have been on t h e o r d e r o f s e v e r a l m e t r i c tons per year. By f a r t h e l a r g e s t i n p u t o f c h l o r i n a t e d h y d r o c a r b o n s t o t h e Southern C a l i f o r n i a B i g h t h a s b e e n t h e r e l e a s e o f hundreds o f t o n s o f DDT wastes v i a t h e JWPCP o u t f a l l s o f f P a l o s Verdes P e n i n s u l a . T h i s i n p u t t o t h e sewer system was t r a c e d t o a l a r g e m a n u f a c t u r e r of t h e p e s t i c i d e i t a m i n a t e d sediment t o be c a r r i e d i n JWPCP e f f l u e n t , and d u r i n g 1971, an e s t i m a t e d 20 m e t r i c t o n s o f DDT wastes were d i s c h a r g e d o f f Whites P o i n t . We r e c e n t l y i n v e n t o r i e d a p p r o x i m a t e l y 200 m e t r i c t o n s o f t h e s e w a s t e s i n t h e upper 30 cm o f b o t t o m sediments i n a 50-sq-km r e g i o n on t h e P a l o s Verdes s h e l f : Seventy p e r c e n t o f t h i s t o t a l l i e s i n t h e f i r s t 12 cm o f sediment, t h e l a y e r most a v a i l a b l e t o b e n t h i c organisms ( 8 ) . F i g u r e 5 i l l u s t r a t e s t h e s u r f a c e sediment c o n c e n t r a t i o n s we measured i n 1972 c o l l e c t i o n s from t h e d i s c h a r g e r e g i o n . A subsequent s u r v e y (summer 1973) d i d n o t r e v e a l any d e c r e a s e i n s u r f a c e sediment c o n c e n t r a t i o n s . The i n p u t o f DDT wastes v i a t h e JWPCP system has r e s u l t e d i n extensive contamination o f the b i o t a l i v i n g o f f s o u t h e r n C a l i f o r n i a (9, 10, 1 1 ) . D u r i n g 1971, we examined i n t e r t i d a l m u s s e l s ( M y t i l u s c a l i f o r n i a n u s ) from s t a t i o n s t h r o u g h o u t t h e B i g h t and o b s e r v e d e n hanced c o n c e n t r a t i o n s i n specimens c o l l e c t e d more than 100 km from t h e JWPCP o u t f a l l s (12). We a l s o found s i m i l a r g r a d i e n t s o f t o t a l DDT i n f l e s h o f b e n t h i c f i s h and c r a b s . As shown i n F i g u r e 6, Dover s o l e t h a t were c o l l e c t e d around t h e o u t f a l l s i n 1971 and 1972 o f t e n c o n t a i n e d c o n c e n t r a t i o n s 100 times t h o s e i n specimens from t h e i s l a n d c o n t r o l a r e a s . During t h i s p e r i o d , a p p r o x i m a t e l y t w o - t h i r d s o f t h e Dover s o l e c o l l e c t e d o f f P a l o s Verdes h a d DDT c o n c e n t r a t i o n s i n f l e s h t h a t exceeded t h e 5-ppm F e d e r a l g u i d e l i n e f o r DDT r e s i d u e s i n s e a f o o d . I n 1973, specimens o f two p o p u l a r s p o r t f i s h , b l a c k p e r c h and k e l p b a s s , were c o l l e c t e d i n t h i s a r e a ; 65 p e r c e n t o f t h e p e r c h anal y z e d , and 45 p e r c e n t o f t h e b a s s , a l s o exceeded t h e F e d e r a l DDT l i m i t . However, lower DDT v a l u e s were found i n y e l l o w market c r a b s (Cancer a n t h o n y i ) t a k e n near t h e o u t f a l l s i n 1971 and 1972, l e v e l s ranging from


26.

YOUNG


ET AL.

T a b l e 5.

433

C h l o r i n a t e d hydrocarbon inputs t o the Southern C a l i f o r n i a B i g h t , 1973-74. M e t r i c Tons/Year

Route Municipal Direct

Total

Wastewater

Industrial

Antifouling

Paint

Surface Runoff Aerial

PCB

6.5

0.02

0.05

0.001

0.001 200 m deep) such as the Wilkinson Basin (Gulf of Maine) with somewhat restricted flushing, has lower values (4 to 5 ml/1) (19). A continental slope site might have values around 7 ml/1 (20). The pH of the bale water w i l l i n i t i a l l y drop, probably due to food acids, formation of metal hydroxides, and release of carbon dioxide. Loder et»al. (13) found an average pH drop to 6.5 while Pratt et.al. (12) reported a drop to pH of 6.0 within a day after immersion. The pH i n our experimental bales rose to between 8 and 9 after over three months of immersion. It has remained this high for over two years for most of the bales, although some bales have pH values of between 6.5 and 7.0 (13). The pH of these systems i s controlled by complex reactions i n volving carbon dioxide, organic acids, sulfides, and ammonia (23). The pH can have an important effect on biological activity, metals solubility, and the forms of sulfides present i n the bale. There w i l l be some phosphorous i n the waste, i n a quantity 1

1


472

M A R I N E CHEMISTRY

Table I I .

R e s u l t s of oxygen consumption experiments on b a l e d s o l i d wastes immersed i n seawater.

Experiment d e s c r i p t i o n (Ref.) Temperature (°C)

Oxygen consumption (ml 02/m^-hr^)* "Ave. (//values)Range

Laboratory Test b l o c k s (12) 2 months immersion 5 months immersion 7 months immersion

3.2-7.5 8-9 16-17

39 (6) 26 (4) 83 (2)

23-55 16.6-30.6 70-90

Whole, exper. b a l e s (30-40 kg) i n 15 m water a t I s l e Shoals, N.H. a f t e r 1 months (13)

8-10

16 (4)

10.5-17.4

Whole, exper. b a l e s (10-20 kg) i n l a b o r a t o r y a f t e r 12-18 months (21).

3-5 15 14-17

25 (2) 22 (1) 76 (2)

23-28

Commercial s i z e d b a l e s i n 15 m water at WHOI (22)

21.7

* (ml 0 /m 2

46-106 30-126

- h r ~ ) χ (0.0248) - micro-moles oxygen (0)/mr - s e c " x

1

of probably w e l l l e s s than one percent of the o r g a n i c matter present. The phosphorous w i l l be o x i d i z e d to phosphate and w i l l i n i t i a l l y adsorb to the metal oxy-hydroxides i n the waste, or form f e r r i c phosphate. T h i s phosphate w i l l be r e l e a s e d as the b a l e system goes anoxic (24)· In s e v e r a l experiments on s o l i d waste, phosphate reached l e v e l s o f 20-30 μΜ and then dropped o f f r a p i d l y a f t e r 3 t o 4 months (12, 13). I t appears t h a t the g r e a t e s t amounts of phos phate w i l l be r e l e a s e d d u r i n g the f i r s t few months of decomposi tion. Most n i t r o g e n i n the b a l e s w i l l be converted to ammonia which then may d i f f u s e from the b a l e system. Concentrations of ammonia reached a l i t t l e over 400 μΜ i n c l o s e d s o l i d waste-seawater systems ( 1 2 ) , w h i l e ammonia i n e x p e r i m e n t a l b a l e s a t sea averaged between 12 t o 35 μΜ w i t h h i g h e s t v a l u e s around 100-150 μΜ (13). The ammonia d i f f u s e d from a s h a l l o w waste dumpsite could have an impact on p r o d u c t i v i t y i n inshore waters where n i t r o g e n i s o f t e n the l i m i t i n g n u t r i e n t (25). I n a deep water dumpsite the impact would be s m a l l . S i n c e the r e l a t i v e amount of n i t r o g e n to carbon i s v e r y low as a r e s u l t of the h i g h c e l l u l o s e content of t r a s h (Table I ) , the b a c t e r i a w i l l depend on n i t r a t e d i f f u s e d i n t o the b a l e s as a n i t r o g e n source once the


29.

LODER

Baled Solid Waste Disposal

473

nitrogen within the original bale i s u t i l i z e d . Dissolved organic matter concentrations within the bale w i l l rise to 2 to 3 orders of magnitude greater than the surrounding water. Pratt et«al (12) reported concentrations as high as 1200 mg dissolved organic carbon (D0C)/1 after about three months, while I found concentrations of 50 to several 100 mg DOC/1 after two years of immersion for our experimental bales. Since normal ocean concentrations of DOC range from about 0.5 to several mg DOC/1, there w i l l be a diffusional flux of dissolved organic matter out of the bale, which could contribute to the bale decom position or solution at a rate 1 to 2 orders of magnitude faster than sulfide reduction rates predict. A diffusion equation (Table IV) can be used to calculate the rate of loss of organic materials where Φ « 0.6; Οχΐ» 1 mg C / l ; C - 100 mg C/Ι· and x coefficient (D ) i s d i f f i c u l t the molecular value for simple ions ( 10~* cm^/sec); consequent ly D = 10-6 was used i n this example. The resultant loss rate then i s 5 μ-moles DOC/m^-sec."". This could be an order of mag nitude slower or faster depending on how r e a l i s t i c the diffusion rates are and whether or not the organic matter w i l l continue to be solubilized at the same rate after the f i r s t few years of immersion. At the above rate a 3000-pound bale would "dissolve" in about 30 years. Trace metals i n solid wastes have been determined by analysis of incinerator wastes (3), and reactions of some of these metals have been discussed by Pratt et» a l . (12). Many of the trace metals w i l l form relatively insoluble sulfides, preci pitate, and remain within the bale. However, some of the metals may form soluble polysulfide complexes or dissolved organic com plexes due to the relatively high amount of dissolved organic matter i n the bales, This may mobilize the metals and allow them to diffuse out of the bale. It i s not possible to estimate the proportions of each metal that w i l l remain or diffuse out of a bale at this time. This important area of research needs more work. Hydrogen sulfide i s produced within the bales as a result of the reduction of sulfate i n seawater through a complex series of microbiological reactions, which decompose the organic matter within the bale releasing carbon dioxide, ammonia, hydrogen s u l fide and phosphate. Pratt (12) reported the release of hydrogen and methane early after solid waste materials i n seawater had gone anoxic, but found only H S was produced after about 5 months. The rate of production of hydrogen sulfide i s a function of the temperature and pressure affecting the microbiological activity with the limiting rate a function of the diffusion rate of sulfate into the bale. Once formed, the hydrogen sulfide may be bound within the system by metal sulfide precipitation, or may leave the system by volatization or diffusion. Once i t reaches the surface of the bale, i t may be oxidized to sulfur by e

Q

s

s

1

2


474


s u l f u r - o x i d i z i n g b a c t e r i a such as the Beggiatoa, sp. and T h i o t h r i x , sp, ( F i g s . 2 and 3) commonly found on the s o l i d waste b a l e s (ÎQ, 12, 13, 26). I t may undergo chemical o x i d a t i o n to t h i o s u l f a t e , s u l f i t e , or s u l f a t e w i t h most a l l of i t ending up as s u l f a t e a f t e r 30 to 40 hours i n seawater (27)» The maximum r a t e of p r o d u c t i o n of s u l f i d e s w i t h i n s o l i d waste m a t e r i a l s appears to roughly be about 0.1 μ-moles/l-day" (0.0012 μ-moles/l-sec-l) (12, 13). T h i s i s s e v e r a l times h i g h e r than a value of 0.04 μ-moles/l-day estimated f o r some anoxic sediments (28). Every μ-mole of H2S produced w i l l use up f i v e μ-moles of oxygen i f t o t a l l y o x i d i z e d . I f we assume the amount of s u l f i d e l o s t from a b a l e equals the p r o d u c t i o n r a t e , then f o r a 3000-pound b a l e w i t h 60 percent v o i d space and a 5.8 meter s u r face a r e a , we can c a l c u l a t e an e q u i v a l e n t oxygen consumption r a t e of 0.78 μ-moles oxygen the maximum r a t e , i t represent consumption by a b a l e s u r f a c e as measured (Table I I ) w i t h the r e s t being due to r e s p i r a t i o n by b a c t e r i a and organisms on the o u t s i d e of a b a l e . Using the maximum r a t e of s u l f i d e p r o d u c t i o n one can c a l c u l a t e the maximum r a t e of decomposition o r o x i d a t i o n of the o r ganic matter i n a b a l e . I t i s g e n e r a l l y assumed t h a t two moles of o r g a n i c carbon are o x i d i z e d to carbon d i o x i d e per mole of s u l f a t e reduced (28, 29). I f the maximum s u l f i d e p r o d u c t i o n r a t e i s about 0.1 m-mole/ 1-day" then 0.2 m-moles of o r g a n i c carbon would be o x i d i z e d . Thus a 3000-pound b a l e of s o l i d waste w i t h a 60 percent p o r o s i t y and 25 percent carbon w i l l take a minimum of about 500 years to decompose. T h i s time i s s u b s t a n t i a l l y longer than p r e d i c t e d based on d i s s o l v e d o r g a n i c carbon d i f f u s i o n l o s s . Since t h i s s u l f i d e p r o d u c t i o n r a t e i s the maximum estimated r a t e , the b a l e decomposition could take an order of magnitude longer i f decom p o s i t i o n r a t e s are an order of magnitude too h i g h . T h i s might be the case f o r the deep sea. I t i s not s u r p r i s i n g then t h a t newspaper removed from our submerged b a l e s a f t e r s e v e r a l years i s e a s i l y readable. I t i s d i f f i c u l t to p r e d i c t what w i l l happen to a s i n g l e b a l e or group of b a l e s (a dump) over an extended time p e r i o d because the b i o c h e m i c a l and b i o l o g i c a l degradation r a t e s w i l l change. The e a s i l y s o l u b i l i z e d and o x i d i z e d m a t e r i a l s w i l l be removed f i r s t , l e a v i n g more r e s i s t a n t m a t e r i a l s , r e s u l t i n g i n slower de g r a d a t i o n rates» As a b a l e becomes covered w i t h sediment, the d i f f u s i o n r a t e s w i l l a l s o slow. However, as the b i o c h e m i c a l processes slow, the b a l e s should become more a t t r a c t i v e to en c r u s t i n g organisms. D e s t r u c t i o n by b o r i n g organisms such as v a r i o u s s p e c i e s of polychaetes o r isopods has been shown ( F i g . 4 ) . B o r i n g shipworms ( T e r e d i n i d s ) may a l s o a t t a c h and c o l o n i z e i n these b a l e s (30). I f b o r i n g organisms do c o l o n i z e the b a l e s i n l a r g e numbers the degradation r a t e of a b a l e could decrease to s e v e r a l decades from the 500 year estimate based only on s u l f i d e 1

1


LODER


Figure 3. Close-up of a mat of sulfur-oxidizing bacteria on a food waste bale immersed at 15 m. Both genera Beggiotoa and Thiothrix of the order Beggiatoales are present. (For scale reference the mesh openings are about one-quarter inch (6.3 mm).)

Figure 4. Photograph of newspaper from the outside 10 cm of an experimental waste bale immersed for 13 months at 15 m. The burrows on the left were found in the outside 2-A cm and were made by a bunowing isopod Limnora ligorum. The dark areas are due to precipitation of iron sulfides.


476


rates. Since most of the volume of a bale i s paper-type material , there w i l l be a large volume decrease of a bale as this material i s removed. In the end there would remain a p i l e of carbon-rich relatively inert materials consisting of glass, plastics, stone, dirt and some metals. These remaining materials w i l l be either scattered by organisms and currents or buried depending on their quantity and dump s i t e conditions. A l l the above parameters w i l l probably result i n different overall rates for a continental shelf dump vs. a deep water dump. Overall rates w i l l probably be slower at a deep water s i t e , but whether they w i l l be significantly slower i s not known and d i f f i c u l t to estimate. Input to Dump Model In the following sectio that w i l l affect the f i n a l size and chemical changes at a hypothesized dumpsite located either on the continental shelf or on the continental slope. Some of the input data can be stated quite accurately such as the size and density of the bales. For other data one i s forced to choose a most-likely estimate and give i t a range of an order of magnitude or more. Some of these estimated values are s i t e specific, such as currents, and could be better known prior to an actual dump. Other values such as the diffusion rates are only estimates based on limited measurements and poorly known diffusion coefficients. The parameters chosen are summarized i n Table III. The weight of commercial-sized bales that have been used i n experimental work and l a n d f i l l has been about 3000 lbs (1360 kg) (10, 31). Generally one dimension i s variable while 2 directions remained fixed as a function of the size of the f i n a l compressing chamber. Although the San Diego bales were rectangular i n shape (31), i t i s assumed that for this model the bale shape i s a cube with dimensions such as to contain a given weight at a given density. A nearly cubic bale of about 3000 lbs (1360 kg; 1.08 m on a side) i s easy to handle i n terms of strapping, wrapping, and shipping, and i s commercially feasible to manufacture (32). Bale density should be greater than that of seawater (about 63.9 lbs/ft.3 - 1.024 g/cc) so they w i l l sink as soon as they enter the water. It i s possible to make bales of shredded waste to densities of slightly over 70 l b s / f t . (1.121 g/cc) although a density of slightly under that would be more l i k e l y . A bale must be strapped together prior to dumping. This may be done using No. 6 to 10 carbon steel wire (possibly vinyl coated) or polypropylene strapping with metal or p l a s t i c c l i p s . Uncoated steel wire lasts at least 2 to 3 years i n shallow seawater (22); however, plastic strapping would last substantially longer. Encapsulation may be done to prevent i n i t i a l loss of floatables and shredded material, but w i l l reduce the rate of interchange with the water. This could range from a plastic 3


29.

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477

Table III. Summary of ranges and average or most-likely values for input variables to model.

Variable Name

Estimated Average Range

Units

Symbol

W

3000

1.

Bale weight

(lbs)

2.

Bale density

(lbs/ft )

β$

68

3.

Dumping rate of Input

(tons/day)

I

2000

4.

Bottom coverage density

5.

Bottom currents (a) shallow and mid-depth (b) deep

(cm/sec)

ν

6.

Thickness of mixed layer above bottom

(m)

7.

Concentration of X in bottom water (a) oxygen (b) sulfides (c) carbon (DOC) (d) ammonia

(μ-moles/l) [x]

8.

3

2800-3500 64-72 1000-6000

5-40

10

h

2

0.5-5

2

1-5

540 0 80 0.5

350-700 0 40-160 0-2.0

±

Diffusion rate of X (μ-moles/m^-sec"^-) (a) (b) (c) (d)

0.74 0.1 5 0.1

oxygen uptake sulfide release* carbon (DOC) release** ammonia release***

0.37-1.5 0.01-0.2 1-50 0.01-0.5

*

Based on about maximum sulfide production and steady-state release. ** Based on diffusion equation and estimated Ds (see text) ***Based on diffusion equation with D - 3.5 χ 10 cm^/sec. (18) (see text) 6

s


478

MARINE

CHEMISTRY

mesh allowing total chemical interchange (13) to polyethylene sheeting (6 mil) with a few holes punched to release gases (10). The dumping rate for this model was chosen as 2000 tonsTday. A rate below 1000 tons/day would not be economically feasible, while 5000 tons/day represents almost the entire output from a f a i r l y large city such as Boston (32). The percent of the bottom actually covered by dumped bales would depend on an environmental decision whether to spread a low-level input over a large area or to have a higher level input in a more local area. The less dense the dumping, the less the impact on benthic fauna and bottom water quality. I t would also depend on whether the deposit was i n shallow water and was used as an a r t i f i c i a l reef (hence high percent of coverage) or deep water where spreading out might be necessary to reduce impact. The amount of scatter i how they were dumped an coverage might range from a few percent up to nearly 100 percent. A barge dumping bales over a 5-minute period while d r i f t i n g at one knot would end up with localized coverage of about 20 percent assuming a dump path of about 33 m and a constant dump rate with l i t t l e water movement. Repeated dumping i n the same spot would increase the coverage, however, 20 percent coverage w i l l be considered most l i k e l y with an approximate range of 5 to 50 percent. Because the bales are represented as cubes with five sides exposed to the water, each bale increases the effective surface area of the bottom by 5-fold. As coverage i s increased the effective area of bale surfaces would increase, but the exposure of a bale surface to water currents would start to decrease as more bales inhibited the free flow of bottom water past the sides of the bales and only the tops had access to free current flow. Consequently, the actual situation i n a real dump would be far more complex than described. Choosing average values for bottom currents at a dumpsite i s very d i f f i c u l t because the current regimes can be very s i t e specific. Most data available has been for short durations and , consequently,long term seasonal as well as storm driven currents variations are not well known. In addition, most current measurements have been made well above the bottom to eliminate benthic boundary layer effects which result from bottom f r i c t i o n and slow the currents down just along the bottom (33). A further consideration i s that the currents are often t i d a l i n nature even on the continental slope, and thus may change direction on a diurnal basis. I t i s conceivable that a parcel of water could o s c i l l a t e over a dumpsite several times before being carried out of the dumpsite area, however, only undirectional flow i s considered i n this model. The rate of dumping (I) and bottom coverage (C) should be partly dependent on the currents at the dump s i t e , because the currents w i l l renew oxygen and remove degradation products. It i s assumed that a dumpsite would not be chosen unless i t had reasonable currents.


29.

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479

At a shallow water site on the continental shelf (30 to 200m) current speeds tend to show greater variation of both speed and direction and could be strongly affected by storms at some shallow depths up to 50 to 100 m. Current speeds range from nearly zero to about 100 cm/sec. with average currents of 5 to 40 cm/sec. (0.1 to 0.8 knots). Bottom d r i f t e r movements give an estimate of very minimum current speeds which can range from 0.5 to 4 cm/ sec. on some shelf areas (34, 35). There i s less data available for deeper water off the con tinental shelf. Schmitz (36) reported near-bottom currents averaging 2.7 cm/sec (range 1.5 to 3.7), 2 to 3 m off the bottom in water 943 to 993 m deep i n an area just east of Block Canyon. I have chosen to calculate the effects of a dump on the con centrations of oxygen, hydrogen sulfide, dissolved organic carbon and ammonia i n the botto values used for oxygen ar bon from (37) while for ammonia and hydrogen sulfide they are estimated. The diffusion rates for these parameters were e s t i mated from various sources discussed i n the previous section. Using this data and the following assumptions, the concentration of each parameter [x| t i s determined for bottom water that just passed through the dumpsite after one year of dumping. Assumptions made to simplify the model are: 1. Bales are of uniform density and size and are cubic i n shape. 2. The bales are placed on the bottom i n a uniform grid covering a given percent area of the bottom. 3. A water parcel surrounds each bale and remains around each bale for a given time determined by the bottom current speed. During this time period a calculated amount of material i s added to i t or removed as i n the case of oxygen. 4. The volume of a water parcel i s calculated using equation (8) in which (h) i s the height above bottom to which complete mixing occurs (Fig. 5 ) . The value for h would increase down stream at a real bale s i t e , but here i s assumed to remain constant. This value (h) i s a complex function of current speed (ν), turbulence induced by the bales and benthic boundary layer effects, a l l of which affect the v e r t i c a l eddy d i f f u s i v i t y , and a l l of which are d i f f i c u l t to determine without actual f i e l d measurements. A value of 2 m (about 1.5 χ the bale height off the bottom) was estimated for h. 5. Concentrations for each component (x]t are calculated using equations (2-10) i n Table IV and are given i n Table Vb. There are nine input variables and each one can vary, but to sim p l i f y I have chosen only three combinations whose inputs and re sults are l i s t e d i n Table Vb. Results of Dump Model Table Va summarizes the physical parameters describing the bales and dumpsite after one year of dumping at a rate of 2000


480


D Figure 5. Cross-sectional schematic of bale dump model for calculating the chemical effect of bale decom position on bottom water quality just downstream of the dumpsite where: ν = current; hDV = height, side, and volume at the mixed water parcel; [XL =- initial con centration at component Χ; [X] =finalconcentration of component X at downstream edge of dumpsite; A — area of bale side; X /Bale = amount of X diffused from bale per unit time. Equations for calculations are listed in Table IV. w

t

B

D


LODER

29.

481


Table IV·

Equations used i n model.*

J

x

= (-D )

(Φ) (C . - C ) (10*)

J

x

• mass diffusing from bale i n (y-moles/m^-sec" ) (38)

s

x

(1)

G

1

where

D

• diffusion coefficient (molecular diffusion about 10"^ cm /sec) Φ = porosity of the bale (assumed value 0.6) Οχΐ» concentration of component χ i n water outside bale (μ-moles/l) C • concentratio x = distance ove occur (assumed 10 cm) s

2

Q

f

β

2

V

B

S

B

- VB /

A

B

- V /

3

(W#>e) (2.8317 χ 10" ) » Volume of bale (m )* 1

2

3

(2)

- side dimension of bale (m)

3

(3)

2

- side area of bale (m )

B

(4)

5

Ν

- (I) (7.3 χ 10 )/w * bales per year

Κ

- (1 χ 10~ ) (N) (A )/(c) » area bottom covered (km /yr)

(6)

D

- (100 A /C)^ - water parcel side for one bale (m)

(7)

V

4

(5) 2

B

B

2

w

• [(D ) (h) - VjH 1000 * water parcel volume for one bale (liters)

X /Bale - (A ) (5) (Χβ) bale/sec. D

[x]

B

t

=

X

±

V

w

β

(8)

amount of material diffusing out of

+^ (100) (D)

(9) (X /bale)j (Nt)** n

— * Symbol definition and units are given i n Tables 3 and 5, unless given above.


(10)

482

MARINE

CHEMISTRY

tons p e r day. The dumpsite covers a r e l a t i v e l y s m a l l area o f the ocean bottom a t 20 percent coverage (2.8 km o r 1.09 m i ) . The values o f Δ X (Table Vb) g i v e an estimate o f the amount of change i n the c o n c e n t r a t i o n o f the f o u r chemical components considered. The r e s u l t s are c a l c u l a t e d f o r both a shallow o r s h e l f s i t e as w e l l as a deep s i t e . The impact f o r a l l parameters i s g r e a t e r a t the deep s i t e example, because the c u r r e n t s were estimated a t o n e - f i f t h the v e l o c i t y o f those a t the shallow s i t e . The r e l a t i v e impact o f the Δ X i s a f u n c t i o n o f the concentra t i o n of the component i n the bottom water. F o r example, s i n c e there i s e f f e c t i v e l y no s u l f i d e i n oxygenated ocean water, the [x) represents a l l the s u l f i d e added. S u l f i d e i s o x i d i z e d i n the water (a r a t i o o f 1 mole s u l f i d e t o 5 moles o f oxygen) and the oxygen content r e d u c t i o n as a r e s u l t o f t h i s s u l f i d e oxygen demand can be e a s i l y c a l c u l a t e d s i t e ) would t h i s reduc a l l the other s i t u a t i o n s the a d d i t i o n a l s u l f i d e oxygen demand l e s s than doubles the Δ X f o r oxygen. The amount o f o r g a n i c carbon r e l e a s e d i s s u b s t a n t i a l and w i l l exert an oxygen demand on the water column. The time neces sary to o x i d i z e i t a l l could range from weeks t o years, during which time there w i l l be s u b s t a n t i a l d i l u t i o n and the end e f f e c t on the oxygen c o n c e n t r a t i o n should be s m a l l . The same i s a l s o true f o r ammonia because i t takes s e v e r a l months f o r ammonia to be n i t r i f i e d (39). F o r the worst case (deep s i t e ) the concentra t i o n o f ammonia could reach l e v e l s a t which i t becomes t o x i c to c e r t a i n f i s h types (12). A l l o f these values a r e a t the end o f one year. A t longer p e r i o d s o f time, the c o n c e n t r a t i o n (Δ X ) i n c r e a s e s by a f a c t o r of 1.4 f o r every doubling o f amount o f m a t e r i a l o r y e a r s . The e f f e c t o f doubling other input v a r i a b l e s i s shown i n Table V I . For example, i t would take about 60 years o f dumping a t 2000 tons per day to reduce the oxygen c o n c e n t r a t i o n to zero a t the down stream edge o f the b a l e s i t e f o r the deep s i t e i f only oxygen consumption f o r the average case i s considered. 2

2

t

Conclusions Thus i t appears on the b a s i s o f t h i s simple model, u s i n g only short-term-based decomposition r a t e s , that dumping o f b a l e d s o l i d waste would not be harmful t o the water q u a l i t y f o r the parameters examined and over the short term. T h i s suggests that an experimental dump o f compacted b a l e d s o l i d waste could be undertaken. The p h y s i c a l , b i o l o g i c a l , and chemical c h a r a c t e r i s t i c s o f the s i t e must be c a r e f u l l y considered p r i o r to i t s s e l e c t i o n . For example, an area w i t h very low oxygen c o n c e n t r a t i o n and low c u r r e n t s should not be chosen. Once a s i t e i s chosen and an experimental dump i s begun, c a r e f u l monitoring o f the s i t e area must be maintained. This monitoring w i l l provide a c t u a l f i e l d data which w i l l enable


29.

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483

Table Va. Calculated results for input data given i n Table 3 using equations i n Table 4.

Variable name

Units

1.

Side dimension of bale

(m)

2.

Area of bale side

(m )

3.

Volume of a bale

4.

Number of bales at a given time (1 year

5.

Area of bottom covered

6.

Side of water parcel around bale

Symbol Average

B

1.077

B

1.159

v

1.249

S

2

(#)

A

B

Nt

(km /yr) Κ 2

(m)

7. Volume of water parcel (liters) ( l i t e r s ) around bale

4.87 χ 10

5

2.82

D

2.41

V

1.04 χ 10* w

Table Vb. Concentrations of X and ΔΧ i n μ-moles/l just down stream of dump at time (t) for deep (D) and shallow (S) sites when t i s one year.

Average

Wt Oxygen

S D

Δ

Η

Worst*

M

t

533 505

-7 -35

322 68

Sulfide S D

0.94 4.7

—

3.77 37.7

Carbon

127 315

47 235

S D

Ammonia S D

1.44 5.21

.94 4.71

981 9,450 9.41 94

*M -23 -282

Best*

Mt 699 693

Δ

Μ -1 -7

1.07 0.19 971 9,410 9.41 94

162 179 2.02 0.19

2 19 0.02 0.19

* For both worst and best cases Ν,^/Ορ, I, C, and h were held at average estimates. For |~χ] ^ and v, worst was low range value; best was high range value. For (X) worst was high range value, best was low-range value. D


484


Table VI. The effect on ΔΧ after one year by doubling variables.

Variable

Change ΔΧ by factor of:

Double bale weight

GO

0.92

Double bale input/yr.

(I)

1.4

Double percent coverage

(C)

1.6

Double height of mixing (t)

0.5

Double current speed

(v)

0.5

(t)

1.4

Double diffusion rate Double time

scientists to modify and update the dumping impact predictions. It must also be possible f o r the dumping scheme to be altered or stopped anytime the monitoring shows rapid deleterious effects to the area. Any dumping program should remain on an experimen t a l basis since ocean dumping should be considered only as an interim solution to the s o l i d waste problem. At least p a r t i a l resource recovery w i l l ultimately be of more benefit both to man and the oceans rather than ocean disposal of the entire solid waste problem, i n spite of the fact that everything ultimately ends up i n the oceans.

Abstract Compacted experimental bales of municipal solid waste (trash) have been immersed in seawater for several years and monitored for chemical, biological and physical changes. This experimental data is used to develop a descriptive and simple mathematical model for a commercial-sized disposal operation on the continental shelf or deep water off the shelf, handling the needs of a medium-sized coastal city. Factors considered in the model include: bale size; quantity per unit time; bale composi tion; packaging; areal extent of dump; depth; biota; current regime; decomposition rates; and the effects on water quality such as oxygen consumption, dissolved organics, nutrients, and hydrogen sulfide. The effects of a dumpsite on bottom water quality at the end of one year are calculated for a shallow and deep site for the "average-most likely" dump and plausible ex tremes of the above variables.


29.

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Literature Cited 1. 2. 3.

4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27.

ES & Τ Special Report, Environ. Sci. Technol. (1970) 4: 384. Smith, D.D., Brown, R.P., Ocean disposal of barge-delivered liquid and solid wastes from U.S. coastal cities. EPA Solid Waste Management Series (SW-19c), 119 p, 1971. First, M.W. (Ed.) Municipal Waste Disposal by shipboard in cineration and sea disposal of residues. Final Rept. on EPA Grant #UI-00557. Harvard University School of Public Health, 1972. Dunlea, J.V., Jr., U.S. Patent 3,330,088, July 11, 1967. Devanney, J.W., Livanos, V., Patell, J., Massachusetts Institute of Technology Rept. No. MITSG 71-2, 124 p, 1970. Bostrom, R.C., Sherif, M.A. Nature (1970) 228: 154-156. Stone, R.B., R/V Challenger Pearce, J.B., Mar. Stone, R.B., Mar. Poll. Bull. (1972) 3: 27-28. Loder, T.C., Rowe, G.T., Clifford, C.H., Rept. in "Proc. Inter. Artificial Reef Conf.", Houston, March, 1974 (in press) 1975. Bogost, M.S., Mar. Tech. Soc. Jour. (1973)7:34-37. Pratt, S.D., Saila, S.B., Gaines, A.G., Krout, J.E., Mar. Tech. Rept. Series No. 9, University of Rhode Island, 53 p, 1973. Loder, T.C., Anderson, F.E., Shevenell, T.C., Sea Grant Rept. UNHSG-118, University of New Hampshire, 107 p, 1973. Loder, T.C., Culliney, J., Turner, R., Univ. of New Hampshire, Harvard, (1974) Unpublished reports. American Chemical Society, "Cleaning Our Environment, The Chemical Basis for Action", Washington, D.C., 167 p, 1969. Jannasch, H.W., Eimhjellen, Κ., Wirsen, C.O., Farmanfarmaian, Science (1971) 171: 672-675. Torrest, R.S., Loder, T.C., Univ. of New Hampshire, (1974) Unpublished report. Berner, R.A., "The Sea, Vol. 5: Marine Chemistry", p. 427450, John Wiley and Sons, New York, 1974. Colton, J.B., Jr., Marak, R.R., Nickerson, S., Stoddard, R.E., Bur. Comm. Fish., U.S.F.W.S. Data Rept. No. 23, 190 p, 1968. Smith, K.L., Jr., Teal, J.M., Science (1973) 179: 282-283. Loder, T.C., Eppig, P., University of New Hampshire, (1973) Unpublished report. Rowe, G., WHOI, (1974) Unpublished report. BenYaakov, S., Limnol. Oceanogr. (1973) 18: 88-95. Stumm, W., Morgan, J.J., "Aquatic Chemistry", Wiley Interscience, New York, 583 p, 1970. Ryther, J.H., Dunston, W.M., Science (1971) 171: 1008-1013. Behan, R.W., Burton, S.D., Loder, T.C., Abs. in Proc. Amer. Assoc. Microbiologists Ann. Mtg., 1974. Cline, J.D., Richards, F.A., Environ. Sci. Technol. (1969) 3: 838-843.


486 28. 29. 30. 31. 32. 33.

34. 35. 36. 37. 38. 39. 40.


Orr, W.L., Gaines, A.G., "Advances in Organic Geochemistry", p. 791-812, Editions Technip, Paris, 1973. Richards, F.A., In J.P. Riley and G. Skirrow, "Chemical Oceanography 1", p. 611-645, Academic Press, New York, 1965. Turner, R., Harvard (1975), Pers. Comm. Anonymous, Solid Wastes Management/RRJ (1971), Oct., p. 2-3. Dunlea, J., Seadun, Inc. (1975), Pers. Comm. Wimbush, Μ., Munk, W., "The Sea, Vol. 4, New concepts of sea floor evolution, Part I", p. 731-758, John Wiley and Sons, New York, 1970. Gross, M.G., Morse, B.A., and Barnes, C.A., J. Geophys. Res. (1969) 74: 7044-7047. Bumpus, D.F., Prog. in Oceanogr. (1973) 6: 111-157. Schmitz, W.J., Jr., Jour. Mar. Res. (1974) 32: 233-251. Loder, T.C. (1971), Rept. R71-15, 236 Berner, R.A., "Principles of chemical sedimentology", 240 p., McGraw-Hill, New York, 1971. Harvey, H.W., "The chemistry and fertility of sea water", 224 p., Cambridge University Press, London, 1955. Acknowledgments. This research has been supported by the New England Regional Commission, UNH Contract No. 10230372 and the UNH Coherent Area Sea Grant Program 2-35244. I would like to thank Dr. Wendell Brown, UNH and Mr. Robert Stewart, MIT for discussions about the model and Drs. Gilbert Rowe, WHOI; Franz Anderson and Henri Gaudette, UNH; and M. Grant Gross, Johns Hopkins for discussions and review of the manuscript.


30 Pioneering the New Industry of Shrimp Farming PAUL F. BENTE, JR. Marifarms, Inc., P.O. Box 2239, Panama City, Fla. 32401

In the l a t e 1 9 3 0 (Hudinaga) working a t A i o , Japan r e p r o d u c t i o n o f kuruma shrimp (Penaeus j a p o n i c u s ) caught c o m m e r c i a l l y i n t h e S e t o I n l a n d Sea. H i s c l a s s i c paper ( 1 ) , c o n t a i n i n g d e t a i l e d drawings and d e s c r i p t i o n s of"~the many l a r v a l t r a n s f o r m a t i o n s and complete b i o l o g i c a l development o f t h i s shrimp, was r e c e i v e d f o r p u b l i c a t i o n ( i n t h e E n g l i s h language) one week b e f o r e P e a r l Harbor day. Such r e s e a r c h , i n t e r r u p t e d b y t h e war, was resumed i n t h e 1950's. H a t c h i n g and r a i s i n g shrimp c o m m e r c i a l l y g o t underway i n t h e I960*s. The Japanese government a l s o i n s t a l l e d s e v e r a l large hatcheries with the goal o f h a t c h i n g baby shrimp i n o r d e r t o r e s t o c k t h e S e t o I n l a n d Sea t o improve commercial s h r i m p i n g . H a t c h i n g and growing shrimp became t h e most advanced o f some two-dozen m a r i c u l t u r e o p e r a t i o n s t h a t were under intense study i n Japan. Kuruma shrimp a r e now c u l t i v a t e d c o m m e r c i a l l y i n Japan i n many s m a l l farms, w h i c h have growing ponds t h a t g e n e r a l l y a r e from 2 t o 20 a c r e s i n s i z e . To h a r v e s t a c r o p , a pond i s d r a i n e d , and t h e shrimp a r e c o l l e c t e d b y hand, c h i l l e d , packed i n sawdust, s h i p p e d b y a i r , t r u c k o r t r a i n , and d e l i v e r e d a l i v e , t o tempura r e s t a u r a n t s . T h i s s p e c i a l t y market has grown t o about 700,000 l b s . p e r y e a r . I t s p r i c e s a r e s e v e r a l times h i g h e r t h a n t h o s e charged f o r p r o c e s s e d f r o z e n o r canned shrimp s o l d i n t h e w o r l d m a r k e t s . E f f o r t s were n o t made t o d e v e l o p t h e know-how i n t o l a r g e s c a l e f a r m i n g t o s u p p l y w o r l d markets, p r i m a r i l y b e c a u s e t h e r e were no s u i t a b l e , l a r g e , 487


MARINE

488

CHEMISTRY

unused c o a s t a l areas a v a i l a b l e f o r such o p e r a t i o n s . Water p o l l u t i o n and u n f a v o r a b l y low temperatures f o r much o f the y e a r were o t h e r d e t e r r i n g f a c t o r s . M a r i f a r m s , I n c o r p o r a t e d , was formed t o u n d e r t a k e such a v e n t u r e i n the U n i t e d S t a t e s , s t a r t i n g i n F l o r i d a . With a p p r o v a l o f the Japanese government, M a r i f a r m s a c q u i r e d shrimp m a r i c u l t u r e r i g h t s and know-how from the T a i y o F i s h i n g Co., L t d . , o f Tokyo, J a p a n . To b e g i n e x p l o r a t o r y t e s t s i n 1968, Dr. M . Miyamura, t h e n p r e s i d e n t o f T a i y o s s u b s i d a r y engaged i n shrimp f a r m i n g a t Takematsu, came t o Panama C i t y , F l o r i d a , w i t h f o u r e x p e r i e n c e d t e c h n i c i a n s . Americans were a l s o employed t o u n d e r s t u d y and t o h e l p . As o p e r a t i o n o f 14 Japanese were employed a t one time o r another, b u t g r a d u a l l y a l l r e t u r n e d t o Japan, e x c e p t f o r Dr. Miyamura who s t i l l s e r v e s on the company s Board o f Directors. 1

1

I n t h i s p i o n e e r i n g work M a r i f a r m s encountered a f o r m i d a b l e a r r a y o f problems — b u s i n e s s , f i n a n c i a l , public relations, socio-cultural, technical, etc. T h i s paper d e s c r i b e s a few o f the many s i g n i f i c a n t t e c h n i c a l advances t h a t the company made i n w r e s t l i n g w i t h t h e p r o b l e m o f making l a r g e s c a l e o p e r a t i o n s viable. Hatching A l t h o u g h the Japanese team was v e r y e x p e r i e n c e d i n h a t c h i n g the kuruma shrimp, o f c o u r s e , i t had never worked w i t h the t h r e e commercial v a r i e t i e s found i n t h e G u l f o f Mexico — t h e brown (Penaeus a z t e c u s ) , the w h i t e (Penaeus s e t i f e r u s ) , and the p i n k (Penaeus duorarum) shrimp. Moreover, t h e r e was no a v a i l a b l e h a t c h i n g e x p e r i e n c e i n U.S. l a b o r a t o r i e s comparable t o t h a t i n Japan, and no e x p e r i e n c e i n c a t c h i n g l a r g e numbers o f shrimp, ready t o spawn. Hence, h a t c h i n g became the f i r s t o r d e r o f b u s i n e s s . H a t c h i n g i s f i r s t d e s c r i b e d and t h e r e a f t e r mother s h r i m p i n g , t h a t i s , p r o c u r i n g shrimp f o r spawning t o begin hatching. Three c o n c r e t e , 28,000 g a l l o n t a n k s , a p p r o x i m a t e l y 30 f t . b y 30 f t . by 6 f t . deep, the l a r g e s t s i z e t h a t had been used s u c c e s s f u l l y i n Japan, were


30.

BENTE

Shrimp Farming

489

i n s t a l l e d f o r t h e h a t c h i n g t e s t s . A f t e r a few a b o r t i v e s t a r t s i n t h e summer o f 1968, the h a t c h e r y t u r n e d o u t 7.5 m i l l i o n baby shrimp o f the p i n k variety. I n 1969, about 14 m i l l i o n w h i t e , 5 m i l l i o n p i n k , and 70 thousand brown shrimp were h a t c h e d . F o r t u n a t e l y , the h a t c h i n g o f each v a r i e t y s u f f i c i e n t l y resembled t h e p r o c e s s f o r the kuruma shrimp t h a t the t e c h n i c i a n s were a b l e t o adapt p r o c e d u r e s t o a c h i e v e good y i e l d s . On t h e s t r e n g t h o f t h i s p r o g r e s s , 32 more o f these tanks were c o n s t r u c t e d f o r commercial work. D u r i n g t h e 1970-74 seasons i t t u r n e d o u t a t o t a l o f about 1.5 b i l l i o n bab shrimp Each 20 m i l l i o were s t o c k e d i n p u b l i were p r o v i d e d t o s e v e r a l r e s e a r c h c e n t e r s . The h a t c h i n g o f baby shrimp i s shown b y T a b l e I . Table I C h a r a c t e r i s t i c s of Hatching Time i n Form Indicated (days)

Form

Egg Larva Nauplius (Stages I-V) Zoea (Stages I - I I I ) Mysis (Stages I - I I I ) Shrimp Baby (suspended i n water) Baby (bottom dwelling)

Cycle Size at Close of Period (mm.)

Common Food

0.25

1

0.5

2

egg

4

phytoplankton (5-10 μ i n s i z e ) zooplankton, artemia, yeast

2.2

artemia, p e l l e t feed

7.5

3

6

14

yolk

marine l i f e i n c l . benthic, p e l l e t feed

* Weight a t t h i s s i z e i s about 0.02

5.0

20.0*

gms.


490


T h i s i s a f a s c i n a t i n g , complex p r o c e s s i n v o l v i n g 12 t r a n s f o r m a t i o n s a f t e r t h e s p a w n e d e g g s h a v e b e e n fertilized. T h e l i t e r a t u r e i s now r e p l e t e w i t h b i o l o g i c a l d e t a i l s o f these changes. Excellent descript i o n s a r e g i v e n i n t w o U.S. P a t e n t s (2) ( 3 ) , w h i c h have been d e d i c a t e d t o t h e p u b l i c . ~" ~~ T h i s paper i s concerned o n l y w i t h a few o f the procedures i n which m o d i f i c a t i o n s of commercial s i g n i f i c a n c e h a v e b e e n made. I n g e n e r a l , t h e h a t c h i n g w a t e r must be g e n t l y a e r a t e d . I t s h o u l d be a t 25°-28°C. a n d h a v e a s a l i n i t y o f a t l e a s t 14 p a r t s per thousand. I f s a l i n i t y i s low, i t can be i n c r e a s e d by a d d i t i o n o f rock s a l t r a t h e r than sea s a l t a s i m p l e r , cheaper procedur o p e d a s f l e x i b i l i t y i n o p e r a t i n g p r o c e d u r e s was explored. The z o e a d o e s n o t swim and must b e k e p t suspended i n w a t e r and f e d b y h a v i n g i t s mouth c o l l i d e w i t h p h y t o p l a n k t o n . The o r i g i n a l p r o c e s s involved culturing special phytoplankton (chlorella and Skeletonema costaturn) b y a d d i n g n u t r i e n t s , i n c l u d i n g r e s i d u e s o b t a i n e d from the manufacture o f soy sauce. One may j u d g e w h a t t h i s h a t c h i n g w a t e r l o o k e d l i k e from the f a c t t h a t the Japanese c a l l e d the m i x t u r e " b l a c k t e a . " T h i s p r o c e d u r e was g r a d u a l l y modified to culturing naturally occurring phytoplankt o n b y a d d i n g c h e m i c a l f e r t i l i z e r s as n u t r i e n t s t o enhance t h e i r m u l t i p l i c a t i o n . Y e a s t was a l s o a d d e d as a f o o d . T h e raysis s w i m s a f t e r i t s f o o d a n d l i v e s o n z o o p l a n k t o n and o t h e r m e a t . The o r i g i n a l p r o c e s s added v a r i o u s forms o f s u p p l e m e n t a l meat, s u c h as f i n e l y g r o u n d up c l a m s . T h i s was m o d i f i e d t o g r o u n d f i s h , a n d t h a t was l a t e r d i s p l a c e d b y a d d i t i o n s o f a l i v e f o o d , i n t h e f o r m o f h a t c h e d a r t e m i a , commonly c a l l e d b r i n e shrimp. These procedures s i m p l i f i e d o p e r a t i o n s , r e d u c e d l a b o r , and i m p r o v e d y i e l d s . In t h i s process the c a p a c i t y o f the h a t c h i n g tanks i s governed c h i e f l y by the t o t a l weight of l i v i n g shrimp (biomass) a t the time the shrimp are f i n a l l y moved t o t h e g r o w i n g a r e a s o f t h e f a r m . This v a r i e s f o r each v a r i e t y of shrimp. White shrimp can t o l e r a t e a much h i g h e r d e n s i t y t h a n b r o w n o r p i n k shrimp. Time f o r t h e f u l l h a t c h i n g c y c l e a l s o v a r i e s


30. BENTE

Shrimp Farming

491

and i s a n o t h e r l i m i t a t i o n on p r o d u c t i v i t y . are g i v e n i n Table I I .

Details

Table I I P r o d u c t i v i t y L i m i t s o f 28,000 G a l l o n H a t c h e r y Tanks Kind o f Shrimp

Brown White Pink

Avg. L i m i t i n g Population*

1,250,000 4,000,000 2,000,00

S i z e o f Shrimp a t End o f C y c l e (mg.) 5-10 3-6

Duration o f T o t a l Cycle (days) 35-40 22

* O c c a s i o n a l l y under i d e a l c o n d i t i o n s d e n s i t i e s 2.5 times t h i s h i g h have been o b t a i n e d . The l i m i t i n g o r maximum number o f eggs o r l a r v a e t o s t a r t t h e p r o c e s s i s thus d e t e r m i n e d b y t h e s e f a c t s , t a k i n g i n t o a c c o u n t m o r t a l i t y e x p e c t e d as t h e l a r v a e move t h r o u g h t h e i r many t r a n s f o r m a t i o n s . To i n c r e a s e c a p a c i t y , t h e p r o c e s s has b e e n d i v i d e d i n t o two s t e p s , i n v o l v i n g s c a l e - u p o f an e x p l o r a t o r y l a b o r a t o r y r e s e a r c h p r o c e d u r e used b y C o r n e l i u s Mock and coworkers o f t h e U.S. G a l v e s t o n Laboratory. The f i r s t s t e p i s conducted i n a c y l i n d r i c a l , open t o p , 7000 g a l l o n , f i b e r - g l a s s tank s t a n d i n g on l e g s i n one c o r n e r o f the 28,000 g a l l o n concrete tank. I t i s p a r t i a l l y submerged i n t h e water o f t h e b i g t a n k . Water i n t h e c y l i n d r i c a l tank i s g e n t l y c i r c u l a t e d — b y b e i n g removed from t h e bottom i n t o an a i r l i f t p i p e which d i s c h a r g e s i t a t the t o p so as t o cause a s l o w r o t a r y s t i r r i n g m o t i o n o f the water column. T h i s o p e r a t i o n accomplishes s e v e r a l t h i n g s . The c i r c u l a t i o n p r e v e n t s the shrimp l a r v a e , food p a r t i c l e s , and g e n e r a l d e b r i s , s u c h as egg s h e l l s , from s e t t l i n g t o t h e bottom, a s i t u a t i o n which g e n e r a l l y k i l l s o f f a large proportion of a hatching i f i t i s allowed to p e r s i s t . To a v o i d t h a t i n t h e 28,000 g a l l o n t a n k s , t e c h n i c i a n s o c c a s i o n a l l y had t o swim about w i t h f l i p p e r s t o s t i r up t h e s e t t l i n g s accumul a t i n g on t h e bottom o f t h e tank d e s p i t e v i g o r o u s a i r


492

MARINE

CHEMISTRY

agitation. The p r o c e d u r e a l s o a l l o w s t h e f i r s t p a r t o f t h e p r o c e s s t o b e d o n e i n much h i g h e r d e n s i t y , thus enhancing the larvae's capture o f the food p a r t i c l e s and t h e r e b y r e d u c i n g t h e t o t a l amount o f e x t r a feed required. I t turns out that this also increases t h e s u r v i v a l o f t h e l a r v a e as t h e y pass t h r o u g h t h e transformations. A t t h e a p p r o p r i a t e t i m e t h e 7000 g a l l o n t a n k i s d r a i n e d i n t o t h e 28,000 g a l l o n t a n k w h i c h c o n t a i n s water prepared f o r the second s t e p o f t h e h a t c h i n g c y c l e when t h e s h r i m p a r e i n t h e p o s t l a r v a l f o r m . While t h i s step i s being c a r r i e d out, i f desired, the f i r s t step o f the next hatchin d concurrently. Thus t h e number o f c y c l e s t h a t c a n b e t u r n e d o u t i s e s s e n t i a l l y doubled. S i n c e s u r v i v a l i s i n c r e a s e d , t h e new p r o c e d u r e i s c a p a b l e o f e s s e n t i a l l y d o u b l i n g and a t times even t r i p l i n g p r o d u c t i o n r a t e , w h i l e s i m u l t a n e o u s l y r e d u c i n g t h e amount o f f o o d u s e d p e r g i v e n number o f s h r i m p h a t c h e d . Though e v e r y t a n k i s g e n e r a l l y o p e r a t i n g i n a d i f f e r e n t s t a g e o f t h e comp l e x h a t c h i n g p r o c e s s , a l l t h i s i s done b y f o u r b i o l o g i s t s a n d t w o h e l p e r s who a r e d e p l o y e d t o o t h e r o p e r a t i o n s w h e n t h e h a t c h e r y i s s h u t down. With t h i s overview of the hatching process i n m i n d c o n s i d e r now some o f t h e d e v e l o p m e n t s i n p r o c u r i n g g r a v i d shrimp needed b y t h e h a t c h e r y . Mother

Shrimping

A f t e r h a t c h i n g was d e m o n s t r a t e d , t h e c o m p a n y made many e x p l o r a t o r y t r i p s , c h a r t e r i n g c o m m e r c i a l t r a w l e r s , t o l e a r n w h e r e i n t h e G u l f and when d u r i n g the calendar year each v a r i e t y o f shrimp i n the g r a v i d c o n d i t i o n c o u l d b e c a u g h t i n s u f f i c i e n t numbers t o operate commercially. G r a v i d shrimp are females c a r r y i n g roe s u f f i c i e n t l y developed so t h a t spawning can be induced i n a hatchery. F i s h i n g i s good when 5 p e r c e n t o r more o f a n o r m a l c a t c h a r e gravid. T h o u g h many s i t e s w e r e f o u n d w h e r e m o t h e r s h r i m p i n g c a n b e done s u c c e s s f u l l y , t h o s e most s u i t e d t o t h e company's l o c a t i o n a r e t h e w a t e r s o f f M o b i l e d u r i n g February through A p r i l f o r brown shrimp,


30. BENTE

Shrimp Farming

493

A p p a l a c h i c o l a d u r i n g May and June f o r w h i t e shrimp, and b o t h l o c a t i o n s d u r i n g J u l y t h r o u g h September f o r p i n k shrimp. D u r i n g t h e seasons o f 1970 t h r o u g h 1974, the company p r o c u r e d a t o t a l o f 154,000 mother shrimp, e q u i v a l e n t t o about 13,000 pounds, heads on b a s i s . Mother s h r i m p i n g i n i t s e l f i s a h i g h l y t e c h n i c a l o p e r a t i o n , f o r which t h e crew must be s p e c i a l l y t r a i n e d and t h e t r a w l e r s p e c i a l l y equipped t o h o l d the shrimp a l i v e i n a e r a t e d , c h i l l e d water, and t h e n t o package and s h i p them s u c c e s s f u l l y t o t h e h a t c h e r y by c h a r t e r e d p l a n e o r , i f t h e r u n i s s h o r t , b y company truck. H a n d l i n g w h i t mothe shrim special problem. The sack shrimp d u r i n g c o p u l a t i o n i s c a r r i e d o u t s i d e t h e s h e l l . (Pink and brown mother shrimp c a r r y i t i n s i d e t h e shell.) I f t h e g r a v i d w h i t e shrimp becomes a g i t a t e d enough t o snap i t s t a i l , as i t does i n t r y i n g t o escape, i t g e n e r a l l y l o s e s t h e spermatophore making f e r t i l i z a t i o n o f t h e s u b s e q u e n t l y spawned eggs impossible. D e s p i t e such odds, b y c a r e f u l h a n d l i n g , t h e h a t c h i n g o f w h i t e shrimp was q u i t e s u c c e s s f u l . These odds were f i n a l l y r e d u c e d b y p l a c i n g each mother shrimp, as soon as i t was caught, i n t o a p e r f o r a t e d c y l i n d e r , capped on each end, and o f a d i a m e t e r t h a t p r e v e n t e d each shrimp from f l i p p i n g i t s t a i l . After t r a n s p o r t a t i o n t h e shrimp was r e l e a s e d s a f e l y i n t h e hatching tank. When a g r a v i d shrimp i s p l a c e d i n t h e h a t c h i n g tank, spawning a l m o s t i n v a r i a b l y t a k e s p l a c e d u r i n g the next n i g h t . S i n c e t h i s happens i n t h e d a r k , no one sees what goes on. By s p e c i a l t e c h n i q u e s , t h e Japanese government has c a p t u r e d t h e spawning p r o c e s s on movie f i l m . T h i s shows t h a t as t h e mother shrimp swims around i t r e l e a s e s a s t r e a m o f r o e t h a t i s d i s p e r s e d i n t h e water b y t h e g e n t l e p a d d l i n g a c t i o n o f i t s 10 swimmerets. The spawning a l s o r u p t u r e s t h e spermatophore s o t h a t t h e r e l e a s e d eggs a r e f e r t i l i z e d i n the sea water. F e e d i n g Shrimp

i n Growing

Areas

In Japan l i t t l e space was a v a i l a b l e f o r use as shrimp farms. T h e r e f o r e , t h e p a t t e r n o f development


494

MARINE

CHEMISTRY

t h e r e was t o c u l t i v a t e w h a t s p a c e was a v a i l a b l e a s i n t e n s i v e l y as p o s s i b l e . B e n t h i c foods, on which shrimp n o r m a l l y f e e d , d i d n o t grow n a t u r a l l y i n t h e bottoms o f t h e ponds t h a t were c o n s t r u c t e d , f o r t h e s e were g e n e r a l l y on a hard pan t h a t had been used i n t h e f o r m e r p r a c t i c e o f e v a p o r a t i n g s e a w a t e r t o manufacture salt. I n f a c t , sand u s u a l l y had t o be h a u l e d i n , i n order t o p r o v i d e a bottom i n which the shrimp c o u l d submerge t h e m s e l v e s . A t t h e t i m e M a r i f a r m s a c q u i r e d i t s know-how i t was common p r a c t i c e t o f e e d the shrimp c r u s h e d clams. M a r i f a r m s s e l e c t e d s i t e s where space p e r m i t t e d extensive operations A 2500 embayment w i t h t i d a l exchange o f wate F l o r i d a a n d t w o 3 0 0 a c r e m a r i n e l a k e s w i t h pumped w a t e r exchange were c o n s t r u c t e d on uplands l e a s e d f r o m a p r i v a t e owner t o compare f a r m i n g i n e a c h t y p e of area. B o t h t y p e s o f farms had bottoms w h i c h were t y p i c a l l y s o f t and sandy and i n w h i c h b e n t h i c o r g a n isms abound. I t was i n t e n d e d t h a t t h e s h r i m p f e e d p a r t i a l l y on n a t u r a l l y o c c u r r i n g marine l i f e which w o u l d p r o v i d e s u f f i c i e n t g r o w t h s t i m u l a n t s and n u t r i e n t s t h a t they c o u l d be f e d a lower grade supp l e m e n t o f g r o u n d up t r a s h f i s h , s i n c e a h i g h e r q u a l i t y r a t i o n o f c l a m s was n o t a v a i l a b l e . L a b o r a t o r y t e s t s showed t h a t c o n v e r s i o n r a t i o s f o r a r a t i o n o f f i s h o n l y were v e r y h i g h , and t h a t o v e r a l l g r o w t h was s l o w a n d w o u l d p r o b a b l y n e v e r r e a c h f u l l p o t e n t i a l , r e g a r d l e s s o f how l o n g s h r i m p were f e d such a r a t i o n . B u t f i s h m e a t f e d i n comb i n a t i o n w i t h n a t u r a l l i v e food, or w i t h hatched a r t e m i a , g a v e much b e t t e r r e s u l t s . The company i n s t a l l e d a n i n s u l a t e d r e f r i g e r a t e d barge t o hold a supply o f f i s h . Pogy f i s h i n g b o a t s d e l i v e r e d l o a d s o f f i s h e v e r y week o r two, pumping as much a s 90 t o n s a t a t i m e i n t o t h e b a r g e . The f i s h w e r e pumped o u t a s n e e d e d , p a s s e d t h r o u g h a g r i n d e r t o make a s l u r r y t h a t was t r a n s p o r t e d t o t h e g r o w i n g a r e a s and d i s c h a r g e d i n t o t h e p r o p wash t o f e e d t h e s h r i m p as t h e f e e d - b o a t t o u r e d t h e s h r i m p f a r m i n a cross-grid pattern. D u r i n g 1 9 7 0 , t h e company f e d a t o t a l o f 800,000 l b s . o f raw f i s h . Because weather i n t e r f e r r e d w i t h f i s h i n g and d e l i v e r y when n e e d e d ,


30.

BENTE

Shrimp Farming

495

i t was d i f f i c u l t t o m a i n t a i n s t e a d y o p e r a t i o n s . F u r t h e r , i t was a messy, malodorous o p e r a t i o n , c o n d u c t e d under the t h r e a t o f b e i n g o v e r t a k e n by spoilage. T h e r e f o r e , the company sought a b e t t e r and more r e l i a b l e s u p p l e m e n t a l f e e d and abandoned the f e e d i n g o f raw f i s h i n 1971 when i t s e x p e r i m e n t a l work w i t h d r y feeds showed p r o m i s e . Many d r y feeds were t e s t e d , made from v a r i o u s c o m b i n a t i o n s o f i n g r e d i e n t s , u s i n g v a r i o u s b i n d e r s i n the c o n v e n t i o n a l method o f f e e d p r e p a r a t i o n by p r e s s i n g the m i x t u r e i n t o a mold. I n g e n e r a l the formula f o r p e l l e t i z e d shrimp f e e d , on a weight b a s i s , i s o r c r a b meal o r c o m b i n a t i o n 20% meat s c r a p s , 2% whey, 2% v i t a m i n mix, and 2% b i n d e r such as Durabond. A l o c a l f e e d m i l l produced f o u r m i l l i o n pounds o f such p e l l e t s f o r o p e r a t i o n s d u r i n g 1971-73, b u t a l l f o r m u l a t i o n s had the d i s a d v a n t a g e o f d i s i n t e g r a t i n g i n sea water i n s e v e r a l m i n u t e s . T h i s o b s t a c l e was f i n a l l y overcome by R a l s t o n - P u r i n a by u s i n g the cooking-extrusion process. Their proprietary pellets had much b e t t e r c o h e s i v e p r o p e r t i e s ; a f t e r b e i n g dropped i n t o water t h e y d i d not d i s i n t e g r a t e f o r 20 t o 24 h o u r s , a l l o w i n g t h e shrimp adequate time t o f i n d and e a t the p e l l e t s . I n 1974, 2.2 m i l l i o n pounds o f t h e s e p e l l e t s were u s e d . L a s t y e a r , i n two 300 a c r e p r o d u c t i o n u n i t s y i e l d i n g h a r v e s t s o f 300 and 200 thousand pounds o f shrimp, r e s p e c t i v e l y , the c o n v e r s i o n r a t i o u s i n g t h i s p e l l e t f e e d was 1.8 and 1.9 pounds (dry weight) f e d p e r pound o f whole shrimp l a n d e d . I n d i c a t i o n s are t h a t c o n v e r s i o n r a t i o s as low as 1.4 w i l l be p o s s i b l e i n r a i s i n g shrimp o f a s i z e a v e r a g i n g 50 p e r pound, heads on b a s i s . I t i s i n t e r e s t i n g t o note t h a t i n J a p a n p r o p r i e t a r y d r y p e l l e t feeds o f a d i f f e r e n t c o m p o s i t i o n were s i m u l t a n e o u s l y and i n d e p e n d e n t l y d e v e l o p e d and adopted as s t a n d a r d p r o c e d u r e . The i n d u s t r y was d r i v e n t o t h i s by the growing s h o r t a g e and r i s i n g p r i c e s o f c l a m s . The p e l l e t s d e v e l o p e d i n J a p a n were b a s e d on h i g h e r q u a l i t y i n g r e d i e n t s , s i n c e the r a t i o n had t o p r o v i d e a l l the growth s t i m u l a n t s i n v i e w o f the f a c t t h a t n a t u r a l foods d i d not o c c u r i n the ponds


496

MARINE

CHEMISTRY

used i n Japan. Consequently, the c o s t o f such feed was v e r y much h i g h e r . N e v e r t h e l e s s , M a r i f a r m s p u r chased a l a r g e l o t o f t h i s f e e d and e v a l u a t e d i t . Used under M a r i f a r m s c o n d i t i o n s o f h a v i n g a p a r t i a l s u p p l y o f n a t u r a l f o o d a v a i l a b l e , t h e r e s u l t s were about the same as t h o s e o b t a i n e d u s i n g the f e e d d e v e l o p e d a t M a r i f a r m s , b u t , o f c o u r s e , the expense was f a r g r e a t e r . 1

C o n f i n i n g Shrimp t o the Growing A r e a s In f a r m i n g t i d a l w a t e r s , t h e baby shrimp were i n i t i a l l y planted i c i r c u l a enclosed b fin mesh n y l o n n e t s h a v i n window s c r e e n i n g . A c h a i n f a s t e n e d t o one edge o f t h e n e t s e a l e d o f f the bottom, w h i l e a l i n e o f c o r k f l o a t s a t t h e o t h e r edge h e l d the n e t t o t h e s u r f a c e . S i n c e s m a l l shrimp move about much as do suspended p a r t i c l e s i n r i l e d water, i n rough weather t h e shrimp would sometimes be washed o u t w i t h waves b r e a k i n g o v e r t h e t o p o f the pens. Though s t i l l on the farm, t h e s e l i b e r a t e d shrimp were i n an a r e a where p r e d a t o r s had not b e e n removed and where f e e d was n o t added. T h e r e f o r e , s u r v i v a l was low, and growth somewhat s l o w e r a t l e a s t u n t i l t h e shrimp grew l a r g e enough t o move about i n s e a r c h o f f o o d . Such d i f f i c u l t i e s were n o t e x p e r i e n c e d i n the marine l a k e s . Moreover, growth o f n a t u r a l foods i n c l o s e d systems c o u l d be s t i m u l a t e d by f e r t i l i z i n g the waters. Hence, o p e r a t i o n s i n the bay were improved b y c o n s t r u c t i n g s t a r t i n g ponds on the a d j a c e n t s h o r e . The p r o c e d u r e s used t o e n r i c h t h e n a t u r a l foods i n t h e s e pond w a t e r s , w h i l e a t the same time s u p p r e s s i n g u n d e s i r a b l e organisms, a r e t h o s e d e v e l o p e d b y Texas P a r k s W i l d l i f e Department ( 4 ) . I n a d d i t i o n a s u p p l e ment o f powdered p e l l e t f e e d i s s p r e a d on t h e waters f o r t h e baby shrimp. M a r i f a r m s conducted many t e s t s t o determine the s i z e t h a t shrimp must be t o be r e t a i n e d by n e t s o f v a r i o u s mesh s i z e s — o r s t r e t c h , as openings a r e termed by the f i s h i n g i n d u s t r y . M a r i f a r m s has found i t most p r o d u c t i v e t o r e t a i n baby shrimp b e h i n d pen n e t s o r w i t h i n d i k e d ponds u n t i l t h e y a r e a t l e a s t 0.3 gm i n s i z e . P o p u l a t i o n has t o be a d j u s t e d a t the


30.

BENTE

Shrimp Farming

497

o u t s e t so t h a t the shrimp do n o t exceed t h e p e r m i s s i b l e b i o - d e n s i t y under t h e o p e r a t i n g c o n d i t i o n s t h a t are e n c o u n t e r e d ( r a t e o f water exchange, temperature, oxygen s u p p l y , k i n d o f shrimp, c o n d i t i o n o f the bottoms, e t c . ) . When t h e shrimp become 0.3 gm i n s i z e t h e y a r e r e l e a s e d i n t o a much l a r g e r n u r s e r y e n c l o s e d b y a c o a r s e r n e t d e s i g n e d t o r e s t r a i n shrimp o f t h a t s i z e . Openings i n t h i s n e t a r e a p p r o x i m a t e l y 1/4" χ 1/4" (or 1/2" nominal s t r e t c h ) . By t h e time t h e shrimp exceed 0.8 gm i n s i z e , t h e y a r e r e l e a s e d i n t o s t i l l l a r g e r a d j a c e n t growing a r e a s c o n f i n e d b y a s t i l l c o a r s e r net s i z e d t hold back thes shrimp Thi net has o p e n i n g s o s t r e t c h ) . A f t e r the shrimp r e a c h 3.0 gm i n s i z e t h e y are r e l e a s e d i n t o the f i n a l growing a r e a which i s e n c l o s e d b y a n e t w i t h openings 7/16" χ 7/16" (or 7/8" nominal s t r e t c h ) . Shrimp behave v e r y d i f f e r e n t l y i n l a r g e growing a r e a s t h a n i n s m a l l e x p e r i m e n t a l ponds o f b u t a few a c r e s . White shrimp m i g r a t e i n s c h o o l s ? whereas brown and p i n k do n o t . Shrimp a l s o move t o f i n d n a t u r a l f e e d i n g g r o u n d s . As shrimp grow l a r g e r t h e y seek deeper water, b u t t h e y f r e q u e n t l y move back i n t o warm s h a l l o w waters t o f e e d on n a t u r a l foods t h a t seem t o abound where more s u n l i g h t r e a c h e s the bottoms. They g e n e r a l l y do not seek t o escape u n t i l t h e y a r e young a d u l t s , a t which time t h e y would norm a l l y move out t o sea w i t h t h e t i d e s . T h i s tendency o c c u r s j u s t p r i o r t o and d u r i n g h a r v e s t p e r i o d s . At s u c h times M a r i f a r m s a t t a c h e s a s p e c i a l l y d e s i g n e d supplementary c o l l a r o f f l o a t s t o the top o f i t s nets i n o r d e r t o s t o p t h e shrimp from swimming o v e r the top d u r i n g rough weather. M a r i f a r m s uses some 15 m i l e s o f n e t s . The h y d r o dynamics o f c o n s t r u c t i o n may be compared t o c o n s t r u c t i n g a suspension cable that i s subjected to f l u c t u a t i n g heavy l o a d s , i . e . , t i d e s moving back and forth. To h o l d t h e n e t s down on t h e bottom, a heavy c h a i n i s l a s h e d t o t h e n e t . V a r i o u s head r o p e s on which f l o a t s were p l a c e d have been t r i e d t o h o l d the net up t o the s u r f a c e . A l l t h e p l a s t i c t y p e r o p e s have caused t r o u b l e , b e c a u s e t h e y g r a d u a l l y e l o n g a t e permanently w i t h repeated s t r e t c h i n g by the t i d e s .


498

MARINE CHEMISTRY

The r e s u l t i s t h a t t h e n e t a t t h e top i s g r a d u a l l y s t r e t c h e d o u t , though not a t the bottom, u n t i l i t f i n a l l y t e a r s from top t o bottom. T h i s d i f f i c u l t y has now been overcome by u s i n g p l a s t i c c o a t e d g a l v a n i z e d s t e e l c a b l e s i n p l a c e o f head r o p e s . Nets o f t e n used i n t h e f i s h i n g i n d u s t r y do n o t have a b a l a n c e d c o n s t r u c t i o n — that i s a heavier n y l o n c o r d i s used i n one d i r e c t i o n t h a n i n t h e other. In Marifarms use when such n e t s t e a r , t h e y p a r t as i f b e i n g u n z i p p e r e d , b r e a k i n g the weaker s t r a n d s progrès s i v e l y and r a p i d l y . M a r i f a r m s has had i t s n e t s s p e c i a l l y made i n a b a l a n c e d c o n s t r u c t i o n . No m a t t e r what s i z opening used th has found, t h a t t o have a t l e a s t a pound o f n y l o n f o r e v e r y 25-30 s q . f t . of net. Nets a r e d i p p e d i n a p r o p r i e t a r y a n t i f o u l i n g m i x t u r e t o r e d u c e t h e i r p i c k i n g up b a r n a c l e s , h y d r o i d s , and o t h e r marine g r o w t h s . The d i p i s made up o f 84% copper o x i d e , 8% t r i b u t y l t i n , and 8% t r i p h e n y l t i n dispersed i n petroleum d i s t i l l a t e . I n a d d i t i o n n e t s must be washed e v e r y few days b y pumping many heavy j e t s o f water, under water, onto each s i d e o f t h e n e t . Equipment f o r d o i n g t h i s i s suspended from a b a r g e on w h i c h a r e l o c a t e d two pumps. T h i s i s one o f t h e " t r a c t o r s " o f the farm which had t o be d e v e l o p e d . I t t r a v e r s e s the n e t s from one end t o t h e o t h e r . A n o t h e r " t r a c t o r " o f the farm i s equipped w i t h a p a i r o f l a r g e r o t a t i n g n y l o n b r i s t l e b r u s h e s w h i c h can s c r u b t h e n e t s c l e a n i f more v i g o r o u s a c t i o n i s n e c e s s a r y . I n appearance t h e s e b r u s h e s l o o k l i k e t h e ones you see i n a c a r wash l i n e , b u t t h e y a r e much s t i f f e r . Without p e r i o d i c c l e a n i n g , t h e openings o f the n e t become so p l u g g e d t h a t the n e t s b r e a k under the s t r a i n o f heavy tides. A n o t h e r b a r g e t r a c t o r has b e e n d e v e l o p e d t o d e p l o y n e t s t o e n c l o s e a r e a s f o r shrimp f a r m i n g o p e r a t i o n s and t o s e t up o u t e r n e t s t o keep o u t f i s h . T h i s t r a c t o r can p u t o u t a m i l e o f n e t i n one day. The same b a r g e can remove the n e t s and t h e c h a i n w h i c h h o l d s the n e t s t o t h e b o t t o m . E v e r y w i n t e r a f t e r h a r v e s t i n g has been completed, t h e s e removal o p e r a t i o n s a r e done i n two s e p a r a t e s t e p s , f i r s t 1


30. BENTE

Shrimp Farming

499

removing f l o a t s and n e t , and t h e n c h a i n which has been c u t f r e e . The n e t s a r e c l e a n e d , r e p a i r e d , c o a t e d w i t h a n t i f o u l i n g agents, r e b u i l t w i t h c h a i n and f l o a t l i n e , and p u t o u t f o r use a g a i n i n t h e spring. With p r o p e r c a r e , a n e t c a n be used f o r three years. Multiple

Cropping

M a r i f a r m s has l e a r n e d enough about t h e a v a i l a b i l i t y o f mother shrimp and t h e h a t c h i n g and growing p a t t e r n s t o make i t p r a c t i c a l t o grow two c o n s e c u t i v e c r o p s o f shrimp i t h Th first c r o p i s brown shrimp and March, p l a n t e d i n t h e s t a r t i n g a r e a s i n A p r i l and May, moved p r o g r e s s i v e l y t h r o u g h t h e n u r s e r y and i n t o the grow-out a r e a s , and h a r v e s t e d i n June t o A u g u s t . The h a t c h e r y meanwhile s h i f t s t o w h i t e shrimp, w h i c h a r e hatched i n t h e May and June p e r i o d . These move p r o g r e s s i v e l y through t h e same a r e a s a r r i v i n g i n the grow-out a r e a s a f t e r the summer h a r v e s t o f brown shrimp has been completed. The w h i t e shrimp a r e t h e n h a r v e s t e d i n t h e O c t o b e r - December p e r i o d . While i t i s t h e o r e t i c a l l y p o s s i b l e t o r u n a t h i r d c r o p o f p i n k shrimp t h r o u g h t h e system, h a t c h i n g t h e s e i n July-August-September period, holding t h r o u g h t h e w i n t e r i n j u v e n i l e form w h i l e i t i s t o o c o l d f o r growth t o c o n t i n u e , and s u b s e q u e n t l y cont i n u i n g growth i n t h e s p r i n g and h a r v e s t i n g them t o g e t h e r w i t h t h e brown c r o p d u r i n g t h e next summer, t e s t s show t h a t w i n t e r i n g o v e r o p e r a t i o n s s h o u l d have f a i r l y deep h o l d i n g a r e a s so t h a t t h e water d o e s n ' t c o o l down as much as i t does i n s h a l l o w e r a r e a s d u r i n g c o l d snaps. S u r v i v a l i n t h e s h a l l o w pond a r e a s i n p a r t i c u l a r i s t o o low t o j u s t i f y such e f f o r t s . When water temp e r a t u r e drops below 1 0 C , s u r v i v a l f a l l s o f f markedly. A t 4°C. the e f f e c t i s l e t h a l . Operations f u r t h e r s o u t h ought t o make a t h i r d c r o p f e a s i b l e . Ô

Harvesting Procedures In hand.

for Quality

Product

shrimping a t sea, the c a t c h i s manipulated by Sometimes as l i t t l e as 10 p e r c e n t o f what i s


500

MARINE

CHEMISTRY

caught a r e shrimp. F i r s t o f a l l , the t r a s h f i s h and o t h e r marine l i f e a r e s o r t e d out by hand and thrown o v e r b o a r d . Then w h i l e t r a w l i n g c o n t i n u e s , the crew members squeeze t h e heads o f f the shrimp b y hand, p l a c e the t a i l s i n w i r e b a s k e t s , and f i n a l l y s t o r e t h e s e w i t h i c e below deck. When a l o a d i s accumul a t e d , the t r a w l e r r e t u r n s t o p o r t t o u n l o a d and s t o c k up on p r o v i s i o n s , and t h e n r e t u r n s t o f i s h i n g a t s e a . S h i p s s t a y o u t a week o r more a t a t i m e . By c o n t r a s t , M a r i f a r m s uses s i m i l a r t r a w l e r s , b u t s i n c e t h e farmed b a y waters c o n t a i n l i t t l e b u t shrimp, t h e r e i s no need t o s o r t the c a t c h by hand on deck. The c a t c h i s dropped on deck spread out and l a y e r e d w i t h shave catch i s g e n e r a l l y kep y few hours o f t r a w l i n g , the b o a t has a l o a d o f s e v e r a l thousand pounds on i t s s t e r n deck. Then t h e b o a t r e t u r n s t o a dock a t s h o r e on the farm where the c a t c h i s unloaded b y a vacuum l i f t w i t h the a i d o f a heavy s t r e a m o f w a t e r . In t h e p r o c e d u r e used i n h a r v e s t i n g t h e farmed marine l a k e s , as t h e y a r e caught, the shrimp a r e p l a c e d i n t o a t r a n s f e r n e t on the s p e c i a l s k i f f used f o r the t r a w l i n g . E v e r y hour o r so t h e s k i f f s t o p s a t a d o c k i n g p o i n t so t h a t t h e t r a n s f e r n e t can be l i f t e d out and i m m e d i a t e l y emptied i n t o a tank o f i c e water mounted on a t r a i l e r . E v e r y few hours t h i s i s h a u l e d t o a vacuum l i f t f o r f i n a l u n l o a d i n g . The shrimp a r e d i s c h a r g e d from the l i f t i n t o a l a r g e a g i t a t e d tank o f i c e water from which t h e y a r e removed b y a m e t a l c h a i n l i n k t y p e conveyor b e l t . The shrimp on t h e conveyor p a s s a c r o s s an i n s p e c t i o n t a b l e where d e b r i s , and the r e l a t i v e l y few f i s h , c r a b s , e t c . , a r e removed by hand. (The c r a b s a r e accumulated and s o l d as a b y - p r o d u c t . Crab y i e l d i n 1974 was about 20,000 l b s . , l i v e weight.) A t t h e end o f the conveyor the shrimp a r e weighed i n t o s t a n d a r d f i s h boxes h o l d i n g 100 pounds e a c h . They a r e k e p t c h i l l e d b y p l a c i n g a l a y e r o f i c e on t h e bottom, i n the m i d d l e , and on the t o p o f each box o f shrimp. These boxes a r e l o a d e d i n t o a t r a c t o r t r a i l e r , and l o a d s o f 20,000 t o 30,000 pounds a r e h a u l e d o f f t o nearby p r o c e s s i n g p l a n t s w i t h i n a day o f b e i n g caught.


30. BENTE

Shrimp Farming

501

The shrimp a r e d e l i v e r e d untouched b y human hands. C o n s e q u e n t l y , t h e b a c t e r i a count i s low. The shrimp do n o t g i v e o f f a s t r o n g f i s h y s m e l l when cooked. They have a sweet t a s t e , d e v o i d o f t h e i o d i n e - l i k e f l a v o r o f t e n e n c o u n t e r e d i n o t h e r shrimp. Thus, t h e q u a l i t y o f the c u l t i v a t e d shrimp produced by M a r i f a r m s i s s u p e r i o r t o t h e s t a n d a r d p r o d u c t o f the market p l a c e . Outlook S i n c e 1970, t h e w o r l d c a t c h o f f i s h has declined. Despit equipment and l a r g e c a t c h o f shrimp seems t o be r e a c h i n g a p l a t e a u . I n t h i s p e r i o d o f mounting c o n c e r n f o r p r o d u c i n g h i g h q u a l i t y , n u t r i t i o u s foods w h i l e a t t h e same time c o n s e r v i n g f u e l , i t i s i m p o r t a n t t o c o n s i d e r where shrimp m a r i c u l t u r e f i t s i n t o t h e p i c t u r e as food and f u e l consumption a r e compared f o r p r o d u c i n g v a r i o u s animals f o r f o o d . As T a b l e I I I shows, c u l t i v a t i n g shrimp uses much l e s s f e e d t h a n does r a i s i n g c a t t l e f o r b e e f . I t i s a l s o c o n s i d e r a b l y lower than f e e d consumed i n r a i s i n g hogs o r t u r k e y s , and i n f a c t i t f a l l s s l i g h t l y below t h a t needed t o r a i s e c h i c k e n s . The p e r c e n t a g e o f meat o b t a i n e d from whole shrimp i s a l s o h i g h e r t h a n t h a t o b t a i n e d from many a n i m a l s r a i s e d f o r f o o d . I t i s a l s o worth n o t i n g t h a t i n t h e c a s e o f r a i s i n g b e e f i t t a k e s about 960 days from s u c c e s s f u l f e r t i l i z a t i o n t o f i n a l s l a u g h t e r and i n t h e case o f p r o d u c i n g p o r k i t t a k e s 240 d a y s . However, i n t h e c a s e o f c u l t i v a t i n g shrimp, depending on v a r i e t y and season, i t t a k e s o n l y 120 t o 180 days, from day o f spawning t o day o f h a r v e s t . The d i r e c t and i n d i r e c t consumption o f f u e l i n shrimp m a r i c u l t u r e i s p r e s e n t l y about e q u a l t o t h a t f o r b e e f p r o d u c t i o n . However, when t h e m a r i c u l t u r e o p e r a t i o n s r e a c h normal c a p a c i t y , f u e l consumption w i l l f a l l t o h a l f t h a t needed t o r a i s e b e e f , and t o l e s s t h a n one f o u r t h t h a t needed t o c a t c h an e q u i v a l e n t amount o f shrimp a t s e a . Hence, development o f shrimp m a r i c u l t u r e i s i n k e e p i n g w i t h t h e demands and c o n c e r n s o f t h e time f o r c o n s e r v a t i o n i n the use o f


502

MARINE

CHEMISTRY

f u e l and f o r more e f f i c i e n t use o f g r a i n s i n produci n g meat f o r human consumption. Table I I I Consumption o f C o m p e t i t i v e Feeds i n R a i s i n g A n i m a l s f o r Meat L b s . Feed Consumed Per Animal 2,625 (a)

Cattle Swine Turkey Chicken Shrimp i n 1974 Shrimp projected

840 70 8 550,000 ( i )

L b s . Raw Lean Meat Produced

Conversion Ratio C o l 2/Col 3

b

7.75< )

340 ( ) 85 l (f) (g) 2

2 < 1

152,500

c

9.9 5.8 3.8 3.55 2.8

(a) I n a d d i t i o n t o 10,875 l b s . o f f o r a g e . (b) S l a u g h t e r w e i g h t = 1050 l b s . Grade i s " h i g h good" t o " l o w - c h o i c e " . " C h o i c e " and "prime" r e q u i r e f e e d i n g more g r a i n . (c) F o r a g e e x c l u d e d from c a l c u l a t i o n . F o r a g e above a c c o u n t s f o r 2 72 l b s . o f l e a n meat, g i v i n g a c o n v e r s i o n r a t i o o f 40 t o 1. (d) G r a i n a l o n e a c c o u n t s f o r 68 l b s . o f l e a n meat, g i v i n g c o n v e r s i o n r a t i o o f 38.6 t o 1. (e) S l a u g h t e r w e i g h t = 240 l b s . (f) S l a u g h t e r weight = 20 l b s . (g) S l a u g h t e r weight = 4 l b s . (h) Gross weight o f c r o p = 305,000 l b s . , heads on. ( i ) I n the c a s e o f shrimp, t h i s f e e d s u p p l i e d f o r a m a r i c u l t u r e c r o p o f 21 m i l l i o n shrimp, a v e r a g i n g about 70 p e r pound, heads on b a s i s . I n a l l , M a r i f a r m s has expended o v e r 310 man y e a r s o f e f f o r t i n p i o n e e r i n g shrimp f a r m i n g . To d a t e , t h e company has h a r v e s t e d 2 m i l l i o n pounds o f shrimp (about 140 m i l l i o n s h r i m p ) , 825,000 pounds (65 m i l l i o n ) o f t h i s l a s t y e a r . The g o a l s a r e t o


30. BENTE

Shrimp Farming

503

more t h a n double t h i s i n 1975. The c a p a c i t y o f t h e farm i s e x p e c t e d t o b e about 5 m i l l i o n pounds p e r y e a r , based on two c r o p s p e r y e a r r a i s e d d u r i n g an 8-month p e r i o d . Marifarms c o n s i d e r s t h i s o n l y t h e beginning. I n another decade shrimp f a r m i n g has t h e p r o s p e c t o f i n c r e a s i n g about 100 f o l d . I t can spread t o d e v e l o p i n g c o u n t r i e s where a new s o u r c e o f food and a c a s h c r o p s h o u l d b e welcome. I n t e c h n i q u e s , m a r i c u l t u r e o f shrimp s t a n d s a t t h e t h r e s h o l d where a g r i c u l t u r e was one o r two g e n e r a t i o n s ago. B u t m a r i c u l t u r e o f shrimp w i l l grow r a p i d l y w i t h t h e advantages o f today's know-how i n marine b i o l o g y coupled with a v a i l a b i l i t t e c h n o l o g y , and e n g i n e e r i n g

Abstract Commercial scale procedures are described which have been developed in pioneering the new industry of hatching, growing and harvesting shrimp in netted off tidal areas and in diked marine lakes with pumped water exchange. The technology described is a fusion of Japanese and U.S. developments in marine biology extended by a 7-year (310 man year) endeavor to commercialize shrimp farming. To date, harvests at the Panama City, Florida, farm have landed approximately 140 million shrimp, weighing nearly 2 million pounds, heads-on basis. Sequential steps in the hatching and growing operations are reviewed. Development of pelleted, dry feeds to supplement live food naturally available in the sea water is discussed, and conversion ratios are given. Unique harvesting procedures are also described which result in a product that is superior in quality to that generally available in commercial quantities. Literature

Cited

1.

Hudinaga, M. (No. 2), pp.

Japanese 305-393.

Journal

of Zoology

2.

Miyamura, M. U.S. Patent No. 3,473,509, to Marifarms, Incorporated, dedicated to public. (October 21, 1969).

(1942),

assigned the


504

MARINE CHEMISTRY

3.

Motosaku, M. U.S. Patent No. 3,477,406, to Marifarms, Incorporated, dedicated to public. (November 11, 1969).

4.

Texas Parks Wildlife Dept. Research, Project 2-169-R,

assigned the

Salt Water Pond Austin, Texas.

Acknowledgement The author extends credit for the progress reported in this paper to all the employees of Marifarms. Their combined, sustained efforts in the face of many unexpected difficulties made this pioneering accomplishment possible.


31 Renatured Chitin Fibrils, Films, and Filaments C. J. BRINE and PAUL R. AUSTIN College of Marine Studies, University of Delaware, Newark, Del. 19711

A resurgence of interes i c h i t i ha bee stimulated b the NOAA-Sea Grant marin and recognition of the important, though l i t t l e understood, role of mucopolysaccharides i n accelerating wound healing and a l l e v i ating inflamations of the skin ( 3 , 4_). Research on the problems of c e l l wall structure and composition i n both fungi and animal tissue ( 5 , 6) has broadened the scope of c h i t i n studies. Very recently, c h i t i n i t s e l f has been shown to be an essential nutrient of the crawfish diet (_7, 2 6 ) , c e l l wall c h i t i n microfibrils have been prepared i n v i t r o with a c h i t i n synthetase (8) and the present authors have purified and crystallized c h i t i n from solution i n f i b r i l l a r and film form for the f i r s t time i n i t s natural or renatured state Ç9, 1 1 ) , showing characteristic spherulitic structures. In nature, c h i t i n not only exists i n well-recognized crystalline forms, but i n tendons and other stress-bearing fibrous portions of marine animals, i t i s even more highly organized into oriented molecular structures showing typical fiber orientation characteristic of man-made fibers such as nylon and polyethylene terephthalate ( 1 2 - 1 6 ) .

It i s the purpose of this report to extend and amplify the earlier disclosures of techniques of c h i t i n f i b r i l and film preparations, and to describe an improved method for the casting of films and extrusion of filaments of c h i t i n with high molecular organization. These renatured structures may be cold drawn to more than twice their original length, which induces fiber orientation and an increase i n tensile strength equal to or surpassing that of natural c h i t i n filaments. It i s recognized that this research i s s t i l l at an early stage and that much refinement of technique and data are required to confirm and enlarge upon these findings. Nevertheless the implications for developing applications for c h i t i n as continuous film and filaments, as well as for a better understanding of c h i t i n properties and functions i n such diverse areas as fungi, insect physiology and marine l i f e has prompted this 505


506

MARINE

CHEMISTRY

progress r e p o r t . Natural C h i t i n As background, s e v e r a l samples of n a t u r a l c h i t i n were obtained and examined by scanning e l e c t r o n microscopy (SEM), p o l a r i z i n g microscopy and x-ray d i f f r a c t i o n techniques. Red crab c h i t i n , used f o r most of our s t u d i e s , occurs as both f l a k e s and s m a l l f i b r i l s as shown by SEM i n F i g u r e s 1 and 2. The ordered l a y e r s or bundled s t r u c t u r e s are s t r i k i n g . With the p o l a r i z i n g microscope, the presence of s p h e r u l i t e s i n n a t u r a l c h i t i n i s i n d i c a t e d by the t y p i c a l Maltese Cross p a t t e r n s , F i g u r e 3. This evidence of c r y s t a l l i n e ordered s t r u c t u r e i s confirmed by x-ray d i f f r a c t o g r a m s w i t h t h e i r w e l l d e f i n e d c o n c e n t r i c Deby I n some c h i t i n p r e p a r a t i o n s Dungeness and King c r a b s , the f i b r o u s m a t e r i a l b a l l s up i n a sample b o t t l e and may c o n t a i n f i l a m e n t s as long as 0.7 cm. Some of these f i l a m e n t s , apparently a r i s i n g from tendons or s t r e s s bearing p o r t i o n s of the c r a b , were found to have s t r o n g f i b e r o r i e n t a t i o n , as evidenced by t h e i r c h a r a c t e r i s t i c nodal x-ray p a t t e r n s , F i g u r e s 5 and 6. Comparison of d-spacings from these d i f f r a c t o g r a m s w i t h l i t e r a t u r e v a l u e s f o r c h i t i n (12, 17), Table I , showed good conformity c o n s i d e r i n g the l i k e l y v a r i a t i o n s i n sample h i s t o r y , moisture content and morphology. Renatured C h i t i n F i l m s Because of i t s i n t r a c t a b i l i t y , c h i t i n i s normally prepared by removing calcareous and proteinaceous m a t e r i a l s from crab s h e l l s , f o r example, by s u c c e s s i v e treatment w i t h d i l u t e a c i d s and a l k a l i e s . The i n s o l u b l e r e s i d u e i s c h i t i n . Although i t i s s o l u b l e i n concentrated m i n e r a l a c i d s and c e r t a i n s a l t s o l u t i o n s , these agents cause degradation or are inconvenient f o r p u r i f i c a t i o n and subsequent h a n d l i n g of the c h i t i n . I n our p r i o r work ( 9 - 1 1 ) i t was shown t h a t c h i t i n could be d i s s o l v e d w i t h reasonable f a c i l i t y i n t r i c h l o r o a c e t i c a c i d (TCA) systems, which permitted f i l t r a t i o n , and then c o u l d be renatured by p r e c i p i t a t i o n w i t h acetone or other anhydrous non-solvent. In t h i s way, amorphous and f i b r i l l a r forms and unsupported f i l m s of c h i t i n were obtained w i t h v a r y i n g degrees of s p h e r u l i t i c c r y s t a l l i n i t y . The new s o l v e n t system c o n t r i b u t e d advantages of reduced r a t e of degradation as w e l l as a g r e a t e r tendency to r e p r e c i p i t a t e ordered s t r u c t u r e s . These s t r u c t u r a l f e a t u r e s were confirmed by comparisons w i t h n a t u r a l c h i t i n : F i g u r e 7, showing f i b r i l s imbedded i n a renatured f i l m , u s i n g p o l a r i z i n g micrography; F i g u r e 8, w i t h s p h e r u l i t e s i n renatured f i l m , i n d i c a t e d by Maltese Crosses; F i g u r e 9, w i t h c o n c e n t r i c Debye r i n g s i n renatured f i l m , which e s t a b l i s h e s i t s c r y s t a l l i n e ordered c h i t i n s t r u c t u r e ; and


BRINE

AND

Chitin

AUSTIN

Fibrils,

Figures 1-6.

Figure

1.

Red Crab 340X

flake,

Films,

and

Filaments

507

Natural chitin studies

SEM

Figure

2.

Red Crab 340X

fibril,

SEM

Figure 3. Red Crab flake; spherulites; polar, microgr. 17 OX

Figure 4. Red Crab fake; x-ray shows crystalline structure

Figure 5. Dungeness Crab filament; x-ray shows orientation

Figure 6.

King Crab filament; x-ray shews orientation


508

MARINE

CHEMISTRY

TABLE I - NATURAL CHITINS, d-SPACINGS (A) Red Crab (Rings) a

Shrimp (Rings)

a

King Crab (Nodes)

Dungeness Crab (Nodes)

Lobster (Nodes) (13, 17) 0

b

11.08 11.00 10.34

7.86 6.81 5.38 5.08 4.87

— 10.15

10.83 — 9.16 8.85

7.33

7.82

— — 4.81

D

v

4.30 3.89

3.79 b

3.51

L

5.68 5.0

3.54

—

9.84 9.26

9.65 9.56

7.30 5.36

7.62 6.96 5.65

4.20 3.96 3.74 3.56 2.71

4.25 3.81 3.38 2.57

b

Flake, s p h e r u l i t i c region of f i b r i l l a r samples, °high intensity group Supplemental Notes to Table I. The x-ray diffraction analyses were performed throughout with the Jarell-Ash Microfocus x-ray Generator #80-000 and the P h i l l i p s Microcamera #56055 for the x-ray photographs. By referring to the geometry of the film and specimen loading i n the microcamera and making the appropriate measurements of the diffraction positions on the film, the characteristic angles, Θ, for the reflections can be derived. The d-spacings can then be calculated using the Bragg relation, where the wavelength of the x-radiation used i s 1.542A for CuKa radiation and specimen to film distance i s 15.0 mm. A l l samples were dried over night at ambient temperature i n a vacuum desic cator over Drierite. Crustacean chitins used i n this study were Opilio chionectes - Japanese Red Crab (Eastman Kodak Co.), Pendalis borealis - Alaskan Pink Shrimp, Paralithodes camtschatica Alaskan King Crab and Cancer magister - Pacific Dungeness Crab (Food, Chemical and Research Laboratories).


BRINE

AND

AUSTIN

Figures 7-12.

Figure 7.

Figure

Chitin

Fibrils,

Films,

and

Filaments

Renatured Red Crab chitin products

Fibrils in Film B1I; polar. microgr. I70X

9. Film BII; x-ray shows crystalline structure

Figure 11. Drawn Film Bill A; x-ray shows orientation

Figure

8. Film BII; spherulites; polar, microgr. 170X

Figure 10.

Figure

Fibrils in Film III; SEM 475X

12. Drawn Filament x-ray shows orientation


VI;

510

MARINE

CHEMISTRY

Figure 10, SEM, renatured c h i t i n film showing the presence of f i b r i l l a r c h i t i n i n the matrix, responsible for the crystalline manifestations. Oriented Chitin Films. With the stage thus set, we appeared to be at the threshold of achieving our long-range goal, that of orienting renatured c h i t i n by cold drawing to enhance i t s properties and to approximate the structure of natural fibrous chitin. Indeed, we found out somewhat laboriously that to obtain c h i t i n films of sufficiently high quality to be cast, coagulated and renatured i n crystalline form, and sufficiently ordered to be coId-drawn to high tenacity products, several c r i t e r i a must be met simultaneously: 1.

An anhydrous solven chloride was bes as a c r i t i c a l component.

2.

High molecular weight polymer ; achieved by short solution time, usually an hour or less, with the resultant solution to be as concentrated and as viscous as possible.

3.

Immersion of the film i n an anhydrous non-solvent, preferably acetone.

4.

Neutralization with anhydrous a l k a l i such as potassium hydroxide i n 2-propanol.

5.

Cold drawing of cut film from a few to over a hundred percent, and

6.

Extraction and/or decomposition of residual solvents to reduce them to a low level.

Again, x-ray diffraction was used to demonstrate the fibertype orientation realized: Figure 11 i s the renatured cold-drawn chitin film (BIIIA), nodal pattern. Although not as distinct a pattern as that of the natural product, there can be no doubt that the desired c h i t i n polymer orientation has been accomplished. Some of the experiments that established the c r i t i c a l factors for the preparation of high quality films are outlined i n Table II, Renatured Chitin Films. For example, i n the f i r s t line (A-105B) a reasonably good film was obtained, as judged by i t s tensile strength, p l i a b i l i t y and toughness, but the c h i t i n had been kept i n acid solvent for four hours, probably too long to maintain i t s molecular weight, and i t was neutralized i n an aqueous system. The film contained very few or no spherulites and i t could not be cold drawn. Note that even with a l k a l i extraction, not a l l the TCA was removed.


31.

BRINE

AND

AUSTIN

Chitin

Fibrils,

Films,

and

Filaments

511

TABLE II - RENATURED CHITIN FILMS Film No.

Film Preparation

Spherulites

Anal. N,% Cl,%

A105B

40% TCA i n CH2CI9, 4 hours"

6.52

0.58

BII

As above, 0.5 houre

6.52

0.58

Bill

Standard (chloral)

5.71

10.06

BIIIA

Standard (chloral)

BIIIA Drawn

Above, ext. 12 hrs. with acetone CH C1

5.03

9.45

Standard (chloral)

5.19

8.88 '

2

BIV

Cold Draw

—

No

-H-

a

Path Diff

15%

25, 125

Sharp rings

100125

Sharp rings

Rings; Nodal after draw

a

+++

100%

b

+++

85%

125

100%

—

2

a

C

+++

"Extracted 4-12 hrs. with CH C1 before analysis 2

2

b

Treating film further with b. 1% NaOH i n 2-propanol then gave N, 6.56; CI, 0.68

c

Treating film further with b. 1% NaOH i n 2-propanol then gave CI, 1.16.

^Film coagulated with two 20 min. acetone washes; neutralized with aqueous sodium hydroxide. e

F i l m coagulated with four 15 minute acetone washes; neutralized with aqueous sodium hydroxide.

^Relative birefringence; path differences obtained with f i r s t order red plate and imbibing f l u i d with refractive index of 1.552; values i n nm.


512

MARINE

CHEMISTRY

An important advance was made with the use of chloral hydrate i n the TCA-methylene chloride system ( B i l l and BIIIA). This mixture speeded solution and dissolved more c h i t i n , up to about 2-3 percent. It also aided the cold drawing operation, but contributed markedly to the chlorine content of the film. The retention of chloral undoubtedly affected the properties of the film, but the x-ray patterns nevertheless appear very similar to those of natural unoriented chitins as shown previously; comparisons of d-values of drawn film (Table III) bears this out. TABLE III - RENATURED CHITIN, DRAWN FILM AND FILAMENT, d-SPACINGS (A) Drawn Film BIIIA >c a

11.63 9.64 7.13 5.93 5.30 3.82

a c

Drawn F i l . VI 12.22 11.00 8.95 7.20 5.66 5.54 4.07 3.63

Lobster

9.56 6.96 5.65 5.13 3.81 3.38 b

N, 5.03%; CI, 9.45%; high intensity group; a l l spacings are close to calculated best f i t values, orthorhombic system

The chlorine compounds i n the film were very d i f f i c u l t to remove and confirm the strong a f f i n i t y of chitin for acids and other organic compounds (18). Simple solvent extraction with methylene chloride or a mixture of i t with acetone s t i l l l e f t a substantial amount of chloral or TCA i n the film. Most of i t could be removed, however, by treatment with hot alcoholic a l k a l i ; i t i s decomposed apparently by the haloform reaction. On the basis of crystallographic evidence, Rudall (14) indicated that approximately one i n every six acetyl groups i n chitin i s deacetylated. If this i s true, one might speculate that chloral may react with the acetamide residues (19) or the free amine groups to form an aldehyde ammonia or S c h i f f s base type of structure, which would account for the d i f f i c u l t y of removing halogenated impurities. Since chloral contains 72 percent of chlorine, a small amount has a significant effect on the composition as a whole. It i s of interest that microscopic indication of f i b r i l l a r structure and spherulites i n the film correlates well with a b i l i t y of the film to be cold drawn, that i s , a high degree of molecular order i n the film i s a prerequisite for f i b e r - l i k e orientation ( B i l l and BIIIA vs. A105B). Both c l o r a i and water f


31.

BRINE

AND

AUSTIN

Chitin

Fibrils,

Films,

and

Filaments

513

have plasticizing effects that f a c i l i t a t e cold drawing. Finally, the tensile strength of the films i s strikingly improved by cold drawing (A105B vs. BIIIA), as brought out with comparisons from the literature i n Table IV. Here i t i s seen that our renatured c h i t i n films, when they have a good degree of crystalline order or are oriented by cold drawing, are far superior to those prepared by the viscose process and equal or surpass the best values for natural, oriented c h i t i n fibers. TABLE IV - CHITIN FILMS Ten. Str. kg/sq mm

Film Natural (oriented fiber Regenerated (xanthate) Renatured (A105B)a Renatured (BIIIA) a

Renatured (BIIIA)

a

Elong., %

32.5 52-58

11 125

75-95

4

Ref. & Comments

Non-crystalline Crystalline; extracted Pre-oriented by p a r t i a l cold drawing

Conditioned at 60% R. Η., room temperature. Method of Preparation. The biological source of c h i t i n is the Japanese red crab, Opilio chionectes, obtained through the Eastman Kodak Company. It i s pulverized dry i n a blender to pass a 24 mesh screen. Two parts by weight of chitin are dissolved in 87 parts by weight of a solvent mixture comprising 40 percent chloral hydrate and 20 percent methylene chloride, with gentle warming and mechanical s t i r r i n g for 30-45 minutes; methylene chloride i s added to replace that lost by evaporation. The very viscous solution i s f i l t e r e d through wool f e l t and/or a glass fiber mat. It i s immediately cast upon glass and doctored with a glass rod to an even thickness, usually about one-sixteenth inch. The glass plate and film i s immersed i n four successive washes of dry acetone, each wash lasting 15 minutes. The films become free from the glass during the acetone washing and are subsequently treated several times with 1-5 percent potassium hydroxide i n 2-propanol. The films are then washed with deionized water u n t i l neutral. The dry films are clear, pliable and strong. Renatured Chitin Filaments As soon as the technique for preparing good c h i t i n films was found, i t was adapted to the preparation of filaments by extrusion of the chitin solution through a syringe and hypodermic needle or by laying a ribbon filament down on glass. Solution


514

MARINE

CHEMISTRY

preparation, f i l t r a t i o n , acetone renaturing and washing were carried out as for films. In several cases the same parent solution was used for the preparation of both films and f i l a ments. Either a sodium hydroxide-potassium hydroxide mixture or potassium hydroxide i n 2-propanol was used for neutralization and the filaments were then washed with deionized water u n t i l neutral. When filaments were extruded into acetone, they were allowed to range freely; nevertheless, strain birefringence from extrusion was noted i n some cases. The filaments contained much crystalline material, as indicated by their birefringence and x-ray d i f f r a c t i o n patterns. They could be cold drawn with necking down and the drawn f i l a ments had good knot strength. The results of these experiments are summarized i n Table V, Renatured Chitin Filaments. TABLE V -

No. F-II

Preparation 3

Standard , Syringe and needle ,a,b Standard" § Syringe and and needle ,a,b Standard" Ribbon on glass 1

VI

Cold Draw

Drawn Fil.

Path D i f f . , nm

Film Ref. No.

200300%

Knotted

175-200

Bill

Fair

Coherent

175-200

BIIIA

Good, Necks down

Good knot strength

175

BIIIA

Standard solution i n TCA, chloral hydrate, CH2CI2; coag. acetone; neut. KOH i n 2-propanol, wash with water. Ext. and anal, as for Film Ref. W i t . with NaOH-KOH i n 2-propanol. With polarizing microscopy, the observations paralleled those of the films. Undrawn filaments showed the Maltese Crosses indicative of the presence of spherulites and upon drawing showed strong birefringence. Using the polarizing technique for birefringence, relative path differences were i n the range of 175-200 nm for cold drawn fibers as compared with 125-150 nm for red and Dungeness crab f i b r i l s and filaments. In x-ray studies, unoriented filaments gave patterns of crystalline materials with f a i r l y sharp, concentric Debye rings, whereas the cold drawn, oriented filaments gave the beautiful nodal patterns as shown i n Figure 12 (VI). The close similarity to natural c h i t i n , Figures 5 and 6, i s apparent. To characterize the nodal x-ray patterns of renatured,


31.

BRINE

AND

AUSTIN

Chitin

Fibrils,

Films,

and

515

Filaments

oriented c h i t i n filaments, the d-spacings were determined and compared with those cold drawn film (BIIIA) and literature values of the lobster (13, 17), Table III. Although crustacean chitins have i n general the same alpha-chitin structure (14, 15, 17, 25), the x-ray diffractograms may d i f f e r slightly because of sample history, thickness, degree of order or c r y s t a l l i n i t y , impurities and polymorphism as i s known with cellulose (21). In spite of these variables, i t was found that the d-spacings of our oriented c h i t i n filaments, even with residual chlorine-containing components, showed reasonable agreement with the literature and those of other oriented c h i t i n filaments determined concurrently (Table I ) . The renatured filaments appear to have the established natural c h i t i n structure. Finally, the contribution of cold drawing and orienting to the strength chitin filament Chitin Filament Properties c h i t i n fibers and a regenerated product, taken from the l i t e r a ture, are compared with our cold drawn filaments. The value for viscose rayon i s cited from the same reference. It i s seen that our renatured c h i t i n filaments are equal or superior to natural c h i t i n fibers, even when calculated on the original fiber dimensions. When calculated on their break dimensions, as i f a cold drawn product were being measured, the higher values are indicated. The small amount of filament available precluded obtaining data directly on the oriented filaments. TABLE VI - ORIENTED CHITIN FILAMENT PROPERTIES Ten. Str. kg/sq mm

Filament Natural (lobster) Regenerated from sulfuric acid (Viscose rayon) Renatured, as extruded Calcd. on dimension at break Renatured, as extruded Calcd. on dimension at break

Elong. %

Reference

58

—

(13)

35 25 56

— — 13

(22) (22) V

44

VI

63

0

a

72

104 Instron TT-CM Tensile Testing machine; conditioned at 60% R.H., room temperature.

b

Cross section 0.08 χ 0.10 mm,

c

Cross section 0.014

Τ at break 0.44

χ 0.740 mm,

kg.

Τ at break 0.75

kg.


516

MARINE

CHEMISTRY

Perspective With the establishment of the principle that c h i t i n can be renatured, even into highly oriented form, attention is focused on the need for a superior solvent system to avoid c h i t i n degradation, provide more concentrated solutions, avoid solvent retention in the filaments and films, and f a c i l i t a t e wet or dry spinning, or casting, of such structures. Studies in this direction are continuing. Considering the modest potential supply of c h i t i n (50-100 million pounds per year i n the U. S.) and the high cost of i n i t i a l manufacture of both c h i t i n and the proposed filaments and films, applications have been hypothesized that involve high value-inuse. Examples include surgical sutures and other hospital supplies, taking advantag sewing thread and decorativ softening point and unusual dye receptivity (23, 24); and oven and other food wrap, based on i t s e d i b i l i t y and temperature stability. It i s noteworthy that there are only a handful of commercial fibers oriented by cold drawing; with the leads developed in this study, perhaps in time c h i t i n can be added to that l i s t . Abstract A method has been developed for the solution and subsequent precipitation of c h i t i n that renatures i t in highly ordered, crystalline form closely similar to native c h i t i n . C r i t i c a l factors include the use of a high molecular weight, soluble c h i t i n and an anhydrous precipitation and neutralization system. A mixture of chloral hydrate, trichloroacetic acid and methylene chloride is an effective solvent, although some solvent residue is retained by the c h i t i n . Acetone i s preferred for renaturing. Filaments and films with a good degree of order and c r y s t a l l i n i t y can be cold drawn to more than double their original length to enhance their properties; tough, pliable films and high strength filaments have been prepared in this way. Acknowledgements The assistance of Dr. Jerold M. Schultz of the Department of Chemical Engineering on the x-ray studies and Dr. Peter B. Leavens of the Department of Geology on the polarizing and scanning electron microscopy is greatly appreciated. The c h i t i n investigation was sponsored in part by NOAA, Office of Sea Grant, Department of Commerce, under Grant No. 02-3-158-30. Literature Cited 1.

Pariser, E . R. and Bock, S., "Chitin and Chitin


31.

BRINE

A N D AUSTIN

Chitin

Fibrils,

Films,

and

Filaments

517

Derivatives, Bibliography 1965-1971," 199 pp. M.I.T. Sea Grant Report 72-3, Cambridge, Mass. 02139 (1972). 2. Pacific Northwest Sea, Oceanographic Inst. of Washington, Seattle, WA 98109, (1973), 6-12, 6 (No. 1). 3. Prudden, John F.; Migel, Peter; Hanson, Paul; Friedrich, Louis and Balassa, L e s l i e , The Am. J. Surgery (1970), 119, 560564. 4. Prudden, John F. and Balassa, L . L., Seminars i n A r t h r i t i s and Rheumatism, (1974), 3, 287-321. 5. Ballou, B . , Sundharadas, G. and Bach, Marilyn L., Science, (1974), 185, 531-533. 6. Brimacombe, J . S. and Webber, J. Μ., "Mucopolysacchar ides", Elsevier, New York, (1964). 7. Meyers, S. P . , Aquanotes, La. State Univ., (1974), 3, 5. 8. Ruiz-Herrera (1974), 186, 357-359. 9. Brine, C. J. and Austin, Paul R . , "Utilization of Chitin, a Cellulose Derivative from Crab and Shrimp Waste," Sea Grant Report DEL-SG-19-74, 12 pp., University of Delaware, Newark, DE 19711 (1974). 10. Austin, Paul R . , 1973, U.S. Patent Application No. 418,441. 11. Brine, C. J., "The Chemistry of Renatured Chitin as a New Marine Resource," M.S. Thesis, 88 pp. (1974), University of Delaware, Newark, DE 19711. 12. Ramakrishnan, C. and Prasad, Ν . , Biochim. Biophys. Acta, (1972), 261(1), 123-135. 13. Clark, G. L . and Smith, A. F., J. Phys. Chem., (1936), 40, 863. 14. Rudall, Κ. Μ., "Advances in Insect Physiology," (1963), 1., 257-311, Academic Press, Ν. Y. 15. Bittiger, H . , Husemann, E . and Kuppel, Α . , J. Pol. S c i . , (1969), Part C, p. 45-56, Polymer Symposia, Proc. 6th Cellulose Conf., Interscience, John Wiley, New York. 16. Dweltz, Ν. E . and Colvin, J. R . , Can. J. Chem. (1968), 46 (6), 1513. 17. Carlstrom, D . , J. Biophys. Biochem. C y t o l . , (1957), 3, 669-683. 18. Giles, C. Η . , Hassan, A. S. Α . , Laidlaw, M. and Subramanian, R. V. R . , Soc. Dyers and Colorists, (1958), 74, 653. 19. Rodd, Ε. H., "Chem. of Carbon Compounds," p. 545, 600, Elsevier, New York, 1951. 20. Thor, C. J. B. and Henderson, W. F., Am. Dyestuff Reporter, (1940), 29, 489. 21. A t a l l a , R. H. and Nagel, S. C . , Science, (1974), 185, 522. 22. Kunike, G . , Soc. Dyers and Colorists, (1926), 42, 318. 23. Hackman, R. H. and Goldberg, Μ., Aust. J. B i o l . Sci., (1965), 18, 935-946. 24. Knecht, E . and Hibbert, Ε . , Soc. Dyers and Colorists,


518

MARINE

CHEMISTRY

(1926), 42, 343. 25. Okafor, Ν . , Biochim. Biophys. A c t a , (1965), 101 ( 2 ) , 193-200. 26. Hood, M. A . and Meyers, S. P., Gulf and Caribbean Fisheries Institute, Proceedings, (1973), 81-92.


32 Seawater Desalination by Reverse Osmosis N. W A L T E R

ROSENBLATT

Ε . I. D u Pont de Nemours & Co., Inc., Wilmington, Del. 19898

In reverse osmosis acts as a molecular pure water ("permeate") from the saline feed stream by pressure driven transport. The process is today established in the desalination of brackish water, where bidding and selling plants of one million gpd* and more on the basis of specified water quality data is an accepted practice in the trade. The published performance record of some plants installed over the last five years is available as realistic evidence to back the warranties given by manufacturers. Research in seawater RO - supported to a large measure by the U.S. Department of the Interior (Office of Water Research and Technology)has now reached the point where reverse osmosis is moving also in this field from the R&D phase into the commercial arena. Process

Principles

The phenomenon of n a t u r a l osmosis takes p l a c e when a d i l u t e s o l u t i o n and a c o n c e n t r a t e d s o l u t i o n are s e p a r a t e d by a semipermeable membrane, the s o l v e n t m i g r a t i n g from the d i l u t e to the c o n c e n t r a t e d compart ment ( F i g u r e 1 ) . The p r o c e s s i s r e v e r s i b l e and under a h y d r a u l i c p r e s s u r e i n excess o f the osmotic p r e s s u r e , s o l v e n t (water) w i l l flow i n t o the d i l u t e compartment. C o n s i d e r a b l e work of a fundamental n a t u r e was c a r r i e d out i n the l a t e 19th and e a r l y 20th c e n t u r i e s as p a r t of the s t u d i e s on c o l l i g a t i v e p r o p e r t i e s of s o l u t i o n s , but the f i e l d was dormant

* g a l l o n s per day

519


520

MARINE

CHEMISTRY

by t h e l a t e 1 9 2 0 ' s . I n t e r e s t was r e k i n d l e d i n t h e 1950 s w i t h the i n t e n s i f i e d s e a r c h f o r e c o n o m i c a l m e t h o d s t o d e s a l t b r a c k i s h and s e a w a t e r . The t h e r m o dynamic e f f i c i e n c y of r e v e r s e osmosis appealed to p h y s i c a l c h e m i s t s a c t i v e i n t h e f i e l d and t h e s e a r c h f o r membranes w i t h s e m i p e r m e a b i l i t y b e g a n . The g o a l s were h i g h r e j e c t i o n of the s o l u t e , i . e . s a l t s , h i g h s o l v e n t o r w a t e r f l u x and i n a d d i t i o n , l i k e w i t h so many o t h e r g o o d t h i n g s i n n a t u r e - l o n g l i f e . The f i r s t i m p o r t a n t l e a d was t h e d i s c o v e r y by R e i d and Breton t h a t c e l l u l o s e a c e t a t e f i l m s have semipermea b i l i t y t o w a r d s s a l t s o l u t i o n s and a c t i v i t i e s i n t h i s f i e l d s u b s e q u e n t l y g a t h e r e d momentum when L o e b and S o u r i r a j a n invented asymmetric c e l l u l o s e acetate membranes. In thes l a y e r s e v e r a l hundre a t h i c k e r b u t more p o r o u s s u b s t r a t e t h a t h a s little r e s i s t a n c e t o w a t e r f l o w ( F i g u r e 2) (1). With asymmetry w a t e r f l u x c o u l d be i n c r e a s e d by one"" t o two o r d e r s o f magnitude without l o s i n g r e j e c t i o n . From t h a t t i m e on, t h e p a c e q u i c k e n e d a t t h e U n i v e r s i t y o f C a l i f o r n i a and a t o t h e r p l a c e s . The f i r s t a t t e m p t s t o d e s a l t s e a w a t e r w e r e more a c r e d i t a b l e d e m o n s t r a t i o n o f p i o n e e r i n g s p i r i t than a t e c h n i c a l accomplishment. The r e a s o n s w e r e i n p a r t t h a t c e l l u l o s e d i a c e t a t e membranes d i d n o t h a v e t h e c h e m i c a l p r o p e r t i e s f o r prolonged s t a b l e performance i n d e s a l t i n g seawater on t o p o f a l l t h e o t h e r f o r m i d a b l e c h a l l e n g e s o f the marine environment. S i n c e then e f f o r t s were l a r g e l y turned towards b r a c k i s h water d e s a l t i n g , w h e r e RO h a s e s t a b l i s h e d a w e l l r e c o g n i z e d p o s i t i o n . S e v e r a l c o m p r e h e n s i v e t e x t s on t h e s t a t e o f t h e a r t i n r e v e r s e osmosis t e c h n o l o g y have been p u b l i s h e d (2, 3, 4, 5 ) . L e t ' s now t u r n t o t h e p r o b l e m s we f a c e w i t h s e a w a t e r RO: TABLE I 1

SALT CONCENTRATION AND IN SEAWATER

OSMOTIC PRESSURE RO

Salt Concentration

Osmotic Pressure (25°C)

Feed

3.45%

369

psia

Concentrate or Reject (30% r e c o v e r y of p r o duct water)

5.15%

567

psia

Average

4.3%

460

psia


ROSENBLATT

Seawater

Figure 1.

Figure 2.

Desalination

Reverse osmosis (RO) principles

Skin structure of asymmetric cellulose acetate membrane (1)


522

MARINE

CHEMISTRY

Standard seawater w i t h a c o n c e n t r a t i o n o f 3·45% s a l t has an osmotic p r e s s u r e of more than 350 p s i . Assuming t h a t 30% of the incoming feed water i s r e covered as product w a t e r , t h e c o n c e n t r a t e stream l e a v i n g the module has a c o n c e n t r a t i o n of 5.15% s a l t and mo re than 550 p s i osmotic p r e s s u r e . In r e a l i t y the t r u e salt concentration at the membrane s u r f a c e i s h i g h e r as a r e s u l t of a phenomenon c a l l e d c o n c e n t r a t i o n p o l a r i z a t i o n ( F i g u r e 3 ) . S a l t and water m i g r a t e to the membrane s u r f a c e , the water passes and the s a l t i s r e j e c t e d and accumulates. U l t i m a t e l y the s a l t r e t u r n s from the boundary to the main strearn as a r e s u l t of the c o n c e n t r a t i o n d i f f e r e n c e . The h i g h e r the membrane f l u x the l a r g e r the accumulât i o n p r o blem . T u r b u l e n t flo i n a laminar flow c o n f i g u r a t i o the boundary l a y e r . The adverse e f f e c t s of conc e n t r a t i o n p o l a r i z a t i o n or a c c u m u l a t i o n of s a l t i n the boundary l a y e r are : © h i g h e r osmotic p r e s s u r e l e a d i n g to reduced water f l u x , © higher s a l t concentration d i f f e r e n c e a c r o s s the membrane between the b r i n e s i d e and t h e product s i d e l e a d i n g to i n c r e a s e d trans-membrane m i g r a t i o n of s a l t , ® i n c r e a s e d r i s k of p r e c i p i t a t i n g sparingly soluble salts. To a c h i e v e r e a l i s t i c f l u x l e v e l s and p r o d u c t i v i t i e s i n seawater RO, the a p p l i e d p r e s s u r e s a c r o s s the membrane a r e 800-1500 p s i . The problems of c o n c e n t r a t i o n p o l a r i z a t i o n were r e c o g n i z e d e a r l y and w e l l u n d e r s t o o d from t h e o r e t i c a l a n a l y s e s of membrane p e r m e a b i l l t y . Another problem encountered i n RO p r a c t i c e was a p p r e c i a t e d f u l l y o n l y when more f i e l d e x p e r i e n c e was g a i n e d . Any s u r f a c e i n a marine environment i s r a p i d l y covered w i t h d e p o s i t s t h a t w i l l i n t e r f e r w i t h water t r a n s p o r t a c r o s s the membrane and w i t h the e f f e c t i v e removal of the accumulated s a l t s from the membrane s u r f a c e . Sources of these d e p o s i t s a r e 1) b i o l o g i c a l , 2) p a r t i c u l a t e matter i n the seawater,or 3) c o r r o s i o n p r o d u c t s generated by the metals used i n the cons t r u c t i o n of the RO p l a n t .


32.

ROSENBLATT

Seawater

Desalination

523

E x p e r i e n c e has shown t h a t the d e c r e a s e i n membrane p r o d u c t i v i t y w i t h time from f o u l i n g and other causes can be c o r r e l a t e d on a l o g / l o g p l o t . The p r o d u c t i v i t y l o s s w i t h time f o r s e v e r a l l e v e l s of l o g a r i t h m i c f l u x d e c l i n e rate are i l l u s t r a t e d i n F i g u r e 4 and the importance of e f f e c t i v e f o u l i n g cont r o l i s evident. We have seen cases where membrane p r o d u c t i v i t y dropped at a r a t e c o r r e s p o n d i n g to 20% r e s i d u a l p r o d u c t i v i t y a f t e r one y e a r . E f f e c t i v e f o u l i n g c o n t r o l can m a i n t a i n a l o g a r i t h m i c f l u x dec l i n e r a t e b e t t e r than 0.05, c o r r e s p o n d i n g to 75% of the i n i t i a l p r o d u c t i v i t y a f t e r the f i r s t year and 70% a f t e r t h r e e years and we b e l i e v e based on our experience that t h i s i s a r e a l i s t i c goal. Interestingly, f o u l i n g i n seawater j e c t i o n than w i t h p r o d u c t i v i t y The p r o d u c t water (permeate) from a d e s a l t i n g p l a n t i s expected to conform w i t h U.S. P u b l i c H e a l t h S t a n d a r d s , i . e . to c o n t a i n not more than 500 ppm t o t a l d i s s o l v e d s o l i d s (TDS). The l i m i t f o r c h l o r i d e i o n s i s 250 ppm. These water q u a l i t y s p e c i f i c a t i o n s c a l l f o r a s a l t r e j e c t i o n c a p a b i l i t y above 98.5%. In p r a c t i c e the r e j e c t i o n has to be b e t t e r than 99% to compensate f o r the i n c r e a s e d s a l t c o n c e n t r a t i o n r e s u l t i n g from product water r e c o v e r y and from concentration polarization. As much as RO appeals t h e r m o d y n a m i c a l l y , the p r o c e s s poses a c o s t e f f i c i e n c y problem because i t i s a r e l a t i v e l y slow r a t e p r o c e s s . F o r example, the water g e n e r a t i n g c a p a c i t y of good f i l m membranes f o r seawater d e s a l i n a t i o n i s 10-15 g a l l o n / s q . f t . / d a y . In comparison a w e l l e n g i n e e r e d e v a p o r a t o r w i t h a heat t r a n s f e r c o e f f i c i e n t of 1000 BTU / ( h r . ) ( s q . f t . ) (°F) g e n e r a t e s 24 l b s . or 3 g a l l o n s o f water per square f o o t per day per °F or 30 g a l l o n s a t a 10°F driving force. Since seawater RO has to be conducted i n s i d e a p r e s s u r i z e d space d e s i g n e d f o r 800 to 1500 p s i o p e r a t i o n , an o b v i o u s g o a l i s to package as much membrane area as p o s s i b l e i n t o a p r e s s u r e v e s s e l . Engineering

of Membrane D e v i c e s

We can now compile a l i s t of the problems t h a t have to be c o n s i d e r e d i n the development of RO d e v i c e s f o r seawater d e s a l t i n g : 1.

Support of the t h i n f r a g i l e membrane a g a i n s t the d i f f e r e n t i a l p r e s s u r e of 800 to 1500 p s i i n the case of seawater.


524

MARINE

CHEMISTRY

MEMBRANE

BULK AQUEOUS

WATER

SALT SOLUTION

REMOVAL

BULK CONC

Figure 3.

Ί

,

,

-j-

,

,

,

, ,

Concentration

,

,

,

polarization

,

1·

I ϊ

ι

1

τ

1 1I i

TIME , days

Figure 4.

Effect of fouling control on productivity


I I

32.

ROSENBLATT

Seawater

525

Desalination

2.

Compactness - h i g h p r o d u c t i v i t y per u n i t volume.

3.

Low c o n c e n t r a t i o n

4.

Fouling control. P r e v e n t i o n and f o u l a n t removal by cleaning.

5.

E f f e c t i v e s e a l i n g of the membrane to prevent b y - p a s s i n g of feed i n t o p r o d u c t .

polarization.

A compact, h i g h p r e s s u r e mass exchange d e v i c e accommodating a l l these requirements was indeed a n o v e l and f o r m i d a b l engineering. Three proposed a t one time or another remained as the p r i n c i p a l c a n d i d a t e s : the t u b u l a r , the s p i r a l , and the h o l l o w f i b e r concept l i s t e d here i n i n c r e a s i n g order of compactness, i . e . s p e c i f i c s u r f a c e a r e a per u n i t volume: 2

3

tubular device

100 f t / f t

s p i r a l device

300

"

"

hollow f i b e r device 3300 " " The e a r l i e s t concept was the p e r f o r a t e d or porous t u b u l a r c o n f i g u r a t i o n , u s u a l l y 0.5 i n c h ID w i t h a membrane c o n t a i n e d i n s i d e the tube and supported on a l i n e r from f a b r i c , paper or non-woven m a t e r i a l s . Feed water under p r e s s u r e flows through the bore and the product water permeates through the membrane and l e a v e s v i a the p e r f o r a t i o n s (.4). T u b u l a r d e v i c e s , b e i n g r e l a t i v e l y s i m p l e , saw the most d i v e r s e e f f o r t to o p t i m i z e them t e c h n i c a l l y and e c o n o m i c a l l y by: • j u d i c i o u s s e l e c t i o n of m a t e r i a l s , e.g. sand l o g s , porous f i b e r g l a s s tubes, • compact packaging, e.g. h e l i c a l c o i l configuration, • advanced f a b r i c a t i o n t e c h n o l o g y , e.g. l a s e r d r i l l i n g of p e r f o r a t i o n s .


526

MARINE

CHEMISTRY

Another approach to a c h i e v e l a r g e s p e c i f i c areas i s the s p i r a l wound d e v i c e , wherein a f l a t membrane envelope i s formed around a f a b r i c spacer and c l o s e d on t h r e e s i d e s ( F i g u r e 5 ) . The open s i d e t e r m i n a t e s at a porous o r p e r f o r a t e d p r o d u c t water tube. The envelope or l e a f t o g e t h e r w i t h an e x t e r n a l s p a c e r f o r the feed water stream i s r o l l e d s p i r a l l y around the p r o d u c t tube and i s then i n s t a l l e d i n a p r e s s u r e vessel. The f e e d stream flows a x i a l l y through the c h a n n e l s between the s p i r a l w i n d i n g s . Water permeates through the membrane and flows r a d i a l l y i n s i d e the l e a f towards the product tube. T h i s membrane conf i g u r a t i o n i s p r e d o m i n a n t l y the r e s u l t o f work done by the Roga D i v i s i o n of G e n e r a l Atomics (now owned by U n i v e r s a l O i l Products O f f i c e of S a l i n e Wate and Technology) i n the U.S. Department of the I n t e r i o r . The most compact membrane d e v i c e s developed so f a r a r e h o l l o w f i b e r permeators. Du P o n t s h o l l o w f i b e r membranes have t h e t h i c k n e s s of a human h a i r . The f i b e r i s asymmetric w i t h a r e j ec t i n g s k i n on the o u t s i d e supported on an i n n e r porous l a y e r ( F i g u r e 6 ) . P r e s s u r i z e d s a l i n e water flows around the o u t s i d e of the f i b e r and the water permeates through the s k i n and the porous support and l e a v e s v i a the bore. The OD i s twice the ID and the f i b e r has the m e c h a n i c a l c h a r a c t e r i s t i c s of a t h i c k - w a l l e d p r e s s u r e v e s s e l and the membrane i s s e l f - s u p p o r t i n g . The f i b e r bundle c o n s i s t i n g o f s e v e r a l hundred thousand up to a few m i l l i o n f i b e r s i s s i m i l a r to a U-tube heat exchanger. The open end i s encased i n an epoxy tube sheet which s e p a r a t e s the s a l i n e water from the permeate. The feed stream e n t e r s through a c e n t r a l d i s t r i b u t o r p i p e , flows r a d i a l l y outward through the bundle and i s removed v i a the a n n u l a r flow s c r e e n a t the v e s s e l w a l l ( F i g u r e 7 ) . D e t a i l s on the c o n s t r u c t i o n and h i s t o r y of the Permasep permeator were p u b l i s h e d elsewhere (J5) . T a b l e I I summarizes the c h a r a c t e r i s t i c s of the d i f f e r e n t designs. More r e c e n t l y a new e n t r y , the " s p a g h e t t i " module h a v i n g the membrane on the o u t s i d e of a p o l y p r o p y l e n e rod w i t h l o n g i t u d i n a l grooves was announced by the U n i t e d Kingdom Atomic Energy E s t a b l i s h m e n t (JO ; but l i t t l e i s known on i t s performance i n seawater desalting. 1


32.

ROSENBLATT

Seawater

Desalination

Figure 5. Spiral wound membrane configuration, (a) spiral element, (b) partially unrolled.

Figure 6.

Skin structure of asymmetric hollow fiber membrane

(1)



1000-1500

Tolerant

Operating Pressure, p s i (seawater)

Particulate Tolerance

Fiber

Chemical

Economical

Expensive

Cost

Sens i t i v e

800

Self-Supporting

3300

Hollow

Mechanical Chemical

Moderate

1000-1500

Supported

300

Spiral

Cleaning

Matter

Supported

100

Membrane Support

Compactness f12 membrane/ft^ v o l .

Tubular

CHARACTERISTICS OF PRINCIPAL RO DEVICES

TABLE I I

32.

ROSENBLATT

Plant

Seawater

Desalination

529

Engineering

The e s s e n t i a l elements o f an RO p l a n t a r e i n t a k e f a c i l i t i e s , p r e t r e a t m e n t equipment to c o n t r o l membrane fouling, a h i g h p r e s s u r e pump to p r o v i d e the d r i v i n g f o r c e and of course membrane modules ( F i g u r e 8 ) . The two p r i n c i p a l system concepts under c o n s i d e r a t i o n f o r seawater d e s a l t i n g were the one-pass and the two-pass p r o c e s s e s i l l u s t r a t e d i n F i g u r e 9. The two-pass approach w i t h two s t a g e s of s a l t i n t e r c e p t i o n appealed as the t e c h n i c a l l y more r e l i a b l e r o u t e , but the membranes i n the two-pass RO p l a n t s h o u l d have a t l e a s t twice the f l u x of one-pass membranes to be e c o n o m i c a l l y competitive. F i e l d t e s t s w i t h l i v e seawater to develop know-how o out a t Ocean C i t y , Ne the Ocean C i t y Research C o r p o r a t i o n . The seawater was d i l u t e d w i t h r u n - o f f water from the areas b o r d e r i n g the bay, a r e p r e s e n t a t i v e c o n c e n t r a t i o n b e i n g 2.7% TDS. The seawater c o n t a i n e d r e l a t i v e l y l a r g e q u a n t i t i e s of suspended matter c o m p l i c a t i n g the cont r o l of membrane f o u l i n g . In 1968 we had l a b t e s t e d w i t h s y n t h e t i c s e a water an asymmetric p o l y a m i d e h y d r a z i d e f i l m membrane (DP-1) which produced 10-12 g f d * (>99% r e j e c t i o n ) at 1000 p s i ( F i g u r e 10) ( 8 ) . Soon t h e r e a f t e r t h i s f i l m membrane was m o d i f i e d f o r two-pass o p e r a t i o n to p r o duce more than 30 g f d * at 1000 p s i and rejection l e v e l s of 90%. Experiments were c a r r i e d out at Ocean C i t y w i t h f l a t t e s t c e l l s ( F i g u r e 11) (9) to c l a r i f y the r e l a t i v e m e r i t s o f one-pass v e r s u s twopass d e s a l i n a t i o n and to l e a r n enough about f i e l d o p e r a t i o n and f o u l i n g c o n t r o l to move towards p i l o t plant t r i a l s . The two major c l a s s e s of membrane f o u l a n t s a r e p a r t i c u l a t e matter and b i o l o g i c a l l y a c t i v e s p e c i e s which form f o u l a n t l a y e r s on the membrane. The f i r s t c a t e g o r y i s b e s t i n t e r c e p t e d by combining c o a g u l a t i o n w i t h f i l t r a t i o n through sand and/or diatomaceous earth f i l t e r s . The b i o l o g i c a l f o u l a n t s a r e conv e n i e n t l y rendered i n a c t i v e by c h l o r i n a t i o n which i s performed more e f f e c t i v e l y below the normal pH 8 of n a t u r a l seawater. S i n c e f r e e c h l o r i n e i s h a r m f u l to p o l y a m i d e h y d r a z i d e and polyamide membranes i t has to be removed c h e m i c a l l y o r w i t h a carbon treatment.

*gallon/sq. ft.-day


MARINE

Figure 7.

Cutaway drawing of Permasep permeator

SALINE WATER INTAKE Figure 8.

Schematic of RO plant

ONE-PASS PROCESS SEAWATER FEED , RO PLANT 3.5% TDS

PERMEATE

pi

CO

578

MARINE CHEMISTRY

and i n sterile and unsterile systems. In dark and s t e r i l e conditions, this compound i s relatively stable with approximately 75% remaining after 16 days. Light and the presence of microorganisms catalyze the disappearance of 1-naphbhol in sea water. This observation i s frequently the situation where synthetic organic compounds are concerned. Apparently, biological systems can supply the activation energy that i s necessary to degrade these compounds. Wauchope and Hague (11) reported upon the kinetics of hydrolysis of carbaryl (sevin) that was somewhat i n disagreement with Aly and El-Dib (7). For example, at pH value of 10.0 and 25°C., Wauchope and Hague reported a t ^ value of 20 minutes whereas Aly and El-Dib reported a value of 15 minutes at the same pH value and at 20°C. The temperature difference does not account for the disagreement which b du t analytical techniques. The hydrolysis of zectra (4-dimethylamino-3.5 xylylmethyl carbamate) i n alkaline water was reported by Hosier (12). The h a l f - l i f e value at a pH value of 9.5 was approximately two days whereas at pH 7.4, the h a l f - l i f e i s approximately 2 weeks at 12-13°C. No order of reaction rates was suggested. Also, Hosier reported a purple colored water solution of zectran under alkaline condtlons (pH9-9.5) when exposed to l i g h t . This was ascribed to the rapid formation of "xylenol" from hydrolysis which i s converted to i t s "xylenoxide" ionic form that i s , i n turn, "very sensitive to photooxidation." No proof was offered to substantiate this mechanism. However, Mathews and Faust (13) have made a similar observation. 0. Miscellaneous Compounds. An examination of the hydrolysis of three explosives i n sea water was reported by Hoffsommer and Rosen (14). These explosives were: TNT (2,4,6-trinitrotoluene), RDX (1,3,5-trlazocyclohexane), and t e t r y l (N-methy1-N-nitro-2,4,6-triazocyclohexane)· Results at 25°Care summarized below: Compound TUT RDX Tetryl

Time-days

Hydrolysis-%

108 112 101

0 11·6 88.

It appears that disposal of these compounds (tetryl excepted) at sea i s not feasible. In an attempt to simulate natural conditions, Bailey, et a l . (15) studied the hydrolysis of the propylene glycol butyl ether ester of 2-(2,4,5)TP (silvex) i n three pond waters. There was an apparent rapid decay of this ester as seen by the tj^ values :


35.

Organic

FAUST

579

Pesticides

PGBE of 2-(2,4,5) TPs

values i n pond waters: Pond A 5 hrs. Pond B 7 hrs. Pond C 8 hrs.

three natural 1 y-occurring (pH*6.25) (pH»6.09) (pH«6.07)

D

» Comment. Hydrolysis i s , indeed, an important variable af fecting the fate of the appropriate organic pesticide i n aquatic environments. The rate at which hydrolysis occurs i s , of course, unique to the individual compound and i s dependent, also, upon such environmental factors as (H3O) and tempera ture (6). Hydrolytic s t a b i l i t y should be viewed with con cern afeout the length of the time period required for com plete hydrolysis and about the products that may or may not be more toxic than th III.

Chemical Systems

A. Thermodynamic S t a b i l i t y . A natural water i n e q u i l i brium with the atmosphere should be saturated with dissolved oxy gen (neglecting for the moment aerobic biological transforma tions of organic matter). In this situation, this water has a well-defined redox potential of approximately + 800 mv (PO2 0 . 2 1 atm, pH - 7 . 0 , 25°G). A simple equilibrium calcu lation shows that, at this E value, a l l organic carbon should be present as C(+IV) or as G 0 , HCO3, or C 0 ~ , Sand Ν should occur i n the form of S 0 ^ 2 - and NO3, respectively. That or ganic compounds are unstable i n aquatic environments may be shown from a simple thermodynamic model: s

n

2

CH 0 + H 0 2

3

=

2

C 0 ( ) + 4H+ + 4e 2

°2(g) + 4H+ + 4 e -

2H 0

CH 0 + 0

C0

2

2

(

g

)

2

g

2

*

2 ( g )

+

H0 2

The free energy change of this reaction i s - 117.99 Kcal mole" which gives a E g value of 1.28 volts. Under the Euro pean sign convention, a negative ΔG° reaction value and a positive Eg values denotes that the l e f t to right reaction i s feasible. A similar model may be calculated for the organic herbicide 2,4-D i n an oxygenated environment^ CgH,03 C l + 2(g) 2 ( f i ) 4H++4C1 + 4 H 0 . The free energy change for this reaction (25°0) i s -1600.78 Kcal mole" which i n d i cates that i t i s feasible for the carbon i n 2,4-D to be o x i dized to C0 (g) with 0 (g)ae an electron acceptor. This model does not, however, indicate the reaction knetics or immea surably, the reaction w i l l even occur. Only laboratory ex perimentation w i l l answer these two points. More and de t a i l e d information on the thermodynamic s t a b i l i t y of organic pesticides i n aquatic systems i s given by Gomaa and Faust (16). 1

2

1 5 0

β

1 6

c o

+

2

1

2

2


MARINE

580

CHEMISTRY

Β. A r t i f i c i a l Systems. There are numerous electron ac ceptors available for oxidation of organic pesticides i n ar t i f i c i a l l y created environments. However, where the natural environment i s concerned, the oxidative reactions are extremely slow and are incomplete, i n the sense, that toxic r e a c t i o n products may be formed. I t i s extremely deslreable to effect "complete" degradation to CQ , HÔ, etc. Historically, KMnO^, C10 , C I , and 0^ have been em ployed for the oxidation of organic compounds at water treat ment plants. Consequently, these oxidants have been investi gated for their capacity to degrade organic pesticides (16, 17, 18, 19» 20). Several basic concepts have evolved from these five studies for the oxidation of organic compounds. 2

2

2

1. Stoichiometry ment plants, for example quate stoichiometries, i.e., chemical dosages are employed. Gomma and Faust (16) proposed the exact stoichiometric r e l a tionship for several organic pesticides and inorganic oxidants. For example, parathlon and KMnO^ gave: C H O NSM0ifaO^+l4H =20îftiO H0CO +SO^+PO^14H O • MO3 +

10

l4

5

2

2

2

3C H O NSP+50MnO4=50îO +15C o|" -f ^3+3SO|-+3K) | +20H 0^2 0H ?

3L0

14

5

2

-

2

2

These two reaction models suggest rather complex molar ratios of oxidant to compound. The f i r s t reaction represents acidic conditions i n which the ftinO^/parathion molar ratio i s 20:1. In the second reaction, the molar ratio under alkaline conditions is 16.67:1. In order to write these two reactions and others (16), several assumptions were made for the products: a. b. c. d.

H1O4" goes to Mn0 / \ and not to Mn organic C goes to u L i n acid conditions (C+IV) organic C goes to C u,2~ i n alkaline conditions (C+III) _ nitro group goes to N0g~, Ρ group goes to 4 " » and S group goes to SO^ ". 2+

2

2

P0

3

2

That there i s some credibility to the proposed reactions i s seen in Table IV where the moles of KfâiO^ consumed per mole of compound i s i n good agreement with the calculated values. 2. Reaction Kinetics. Well-designed kinetic experiments yield data from chemical oxidation systems that w i l l : a.

confirm thermodynamic reactions models with respect to feasibility and stoichiometry

b.

determine the order of the disappearance reaction


35.

Organic

FAUST

Pesticides

581

c. determine the rate and reaction times required to process design Table IV.

POTASSIUM PERMANGANATE CONSUMED BY THE OXIDATION OF PARATHION, PARAOXON, AND p-NITROPHENOL (16)*

Compound

£2

Parathion Paraoxon p-Nitrophenol Parathion Paraoxon p-Nitrophenol

3.1 3.1 3.1 9.0 9.0 9.0

(a)

Mole MnO^/Mole Comp.

Contact Time (Hours)

Ratio

Experimental Calc.

120 120 96 48

0.386 0.364 0.404 0.392

19.48 16.69 9.10 17.08

20.00 17.33 9.33 16.66

Temperature * 20° + 0.2°C.

Determination of the order of the reactions may be accomplished by f i t t i n g the data into several rate equations. These r e actions are, of course, extremely complex and an exact order i s not expected over the entire course of events. Intermediate oxidation products w i l l compete with the parent molecule for the oxidant. Nontheless, Gomma and Faust (21) found that an integrated form of a second-order expression provided reasonably constant rate constants for the KMnO* oxidation of two d i pyridylium quarternary herbicides - Diquat and Paraquat. This expression was: 2

aC

·

3

0

l

b

°ox "

N

r

u

(

4

)

where S% i s o b t a i n e d from e q u a t i o n ( 2 ) . Thus i n a r e a l i s t i c s i t u a t i o n any c o n c e n t r a t i o n o f a n o n - c o n s e r v a t i v e p r o p e r t y (N ) w i l l be d e t e r m i n e d by f r e s h and o c e a n i c c o n t r i b u t i o n s and b i o l o g i c a l uptake, hence : Q

N and combining

N

0

=

(N

+ Nf) - N

s

with equation

°

=

fïïô

20 μΜ ( 8 ) ) . The a b s o l u t e l o a d i n g r a t e o f phosphate t o the Hudson E s t u a r y i s s u b s t a n t i a l l y h i g h e r than f o r e i t h e r the Potomac R i v e r o r Chesapeake Bay, but the removal r a t e by p h y s i c a l t r a n s p o r t i s more r a p i d than f o r those two e s t u a r i n e systems. The c u r r e n t d i r e c t i o n of phosphate management i n North America i n c l u d e s r e d u c t i o n o r removal o f phosphate from detergents on a short-term b a s i s , and the i n t r o d u c t i o n of t e r t i a r y sewage treatment f o r phosphate removal over the l o n g e r term. These p o l i c i e s are based on the g e n e r a l l y - a c c e p t e d premise that the s t a t e of eutrophy of most f r e s h water l a k e s can be c l e a r l y r e l a t e d to the l o a d i n g r a t e o f phosphorus (9)· Observations of a l g a l standing crop and primary p r o d u c t i v i t y r a t e s i n the Potomac E s t u a r y i n d i c a t e t h a t s i m i l a r c o n s i d e r a t i o n s are probably important f o r n u t r i e n t management f o r some e s t u a r i e s ( 8 ) . However, simple e x t e n s i o n of these p o l i c i e s f o r management o f l a k e s t o a l l e s t u a r i e s may not be j u s t i f i e d . A comparison between Lake E r i e and the Hudson i l l u s t r a t e s t h i s p o i n t . Both systems r e c e i v e sewage e f f l u e n t from about 10? people. The phosphorus l o a d i n g r a t e s are comparable, although Lake E r i e has a somewhat g r e a t e r r a t e per c a p i t a due to a g r i c u l t u r a l a c t i v i t i e s and the e x i s t e n c e o f a detergent ban i n New York S t a t e . The budgets f o r phosphorus are summarized i n Table I . One of the major water q u a l i t y problems i n Lake E r i e i s the e x i s t e n c e of nuisance l e v e l s of a l g a l standing crops. The h i g h e f f i c i e n c y o f


38.

SIMPSON

E T A L .

Nutrient Budgets

631

Comparison of Phosphate Behavior i n the Lower Hudson Estuary and Lake Erie

Hudson

Lake Erie

Volume

0.6 km (l)

Area

60 km

25,000 km

Residence Time

2 days

1000 days

Basin Population

10 (2)

3

2

500

3

km

2

Mean Depth

Σ Ρ Loading Rate

7

-

107 26 mole/sec (3)

Ρθ|- Loading Rate

6 mole/sec

13 mole/sec(4)

Predicted P0^~ (5)

2 pmole/A

2.5 umole/Jl

Measured P0$~

2 umole/£(l)

.03-0.6 iimole/£(6)

Measured Σ Ρ

2.7 pg- atom/il

0.6-1.2 ug-atom/A (7)

Measured Ρθ£~ χ 100% Predicted P0^~ χ 100%

100%

1-25%(6)

(1) High flow conditions (see Figure 7) (2) Only populations discharging above the Narrows and not to the upper East River i s included (^ 65% of total i n basin). (3) See reference 10. (4) Assuming Ρθ|~ « 50% of Σ Ρ loading rate. (5) Assuming conservative behavior for P0$"~. (6) Summer epilimnion near the lower value, winter epilimnion near the upper value. See reference 11. (7) See reference 11.


632

MARINE CHEMISTRY

phosphorus uptake by algae indicates that reduction of the rate of sewage phosphorus loading i s a reasonable way to attack this problem. In the Hudson, algal populations are not usually considered to be a nuisance, and the efficiency of phosphorus removal by algae i s quite low (Table I)» despite the rather high primary productivity rates ( 1 - 2 grams C/M -day) which are observed during low-flow, late-summer periods (T. Malone, personal communication). The cause of the low removal efficiency of phosphate i s poorly understood, but the rate of primary productivity i s clearly not phosphate limited i n the Hudson Estuary at the present time. High concentrations of sewage-derived nitrogen i n the estuary indicate that this nutrient also does not currently limit productivity. Malone (personal communication) has suggested that the standing algal crop light penetration throug algal c e l l s by rapid flushing of the estuary. Control of productivity by these factors does not imply that sewage nutrients have not enhanced productivity nor that the Hudson i n i t s pristine state was not nutrient limited by either Ν or P. Analysis of the current situation does, however, indicate that introduction of phosphate removal to sewage treatment processes i n the lower Hudson should probably not be given f i r s t priority at the present time. There are water quality problems i n the. Hudson which could be expected to respond immediately to improved sewage treatment. Dissolved oxygen levels are less than 40% of saturation i n Upper New York Bay during summer months, and organic detritus contributes to a major s i l t a t i o n problem within the harbor and to the turbid appearance of the water. The most obvious current unresolved sewage treatment problem i n the lower Hudson (aside from the raw sewage discharge from Manhattan which w i l l cease during dry weather conditions when present construction projects are completed near the end of the decade) i s discharge from the Passaic Valley of New Jersey. This large sewage volume has only very crude primary treatment, and constitutes the largest singlesource impact on the oxygen budget of the lower Hudson Estuary. There i s the p o s s i b i l i t y that completion of secondary treat ment plants w i l l reduce suspended particulate levels sufficiently to enhance algal productivity to nuisance levels. I f such a situation develops, construction of nutrient removal f a c i l i t i e s should then be given serious cons iderat ion. Considering the major investments of public funds required, the most reasonable policy would seem to be to complete a l l major secondary treatment plants and then re-examine the c r i t i c a l factors controlling water quality i n the lower Hudson Estuary. In any case, phosphate concentration i n the present Hudson Estuary i s nearly conservative, in distinct contrast to Lake Erie or the Potomac. A second major conclusion of this paper concerns the observations of s i l i c a t e behavior. The removal of s i l i c a t e within 2


38.

SIMPSON

E T A L .

Nutrient

Budgets

633

the t i d a l Hudson is apparently dominated by biological uptake. Because of the long residence time of water upstream of the salt intrusion, organisms can significantly reduce the ambient s i l i c a t e levels during low-flow periods. Thus, nonconservative behavior of s i l i c a t e in the Hudson is most clearly related to the length of water transport time and the biological removal rate, and appears to have no significant relationship to ambient s a l i n i t y . Another unusual feature of s i l i c a t e distribution in the Hudson is the importance of a source term within the waters of New York Harbor, which may be due to high sewage s i l i c a t e levels. Analytical Methods Molybdate-reactive phosphate was determined by the method of Murphy and Riley (12), wit et a l . (13). Samples wer f i l t e r s and were usually stored at 2 C prior to analysis. Particulate phosphate was measured by f i r i n g glass fiber f i l t e r s at 700°C for 1/2 hour, followed by leaching with HC1 at 104 C, neutralizing with NaOH, and analysis for molybdatereactive phosphate. Molybdate-reactive s i l i c a t e was determined by the method of Strickland and Parsons (14). e

Abstract The dominant source of dissolved inorganic phosphate to the lower Hudson Estuary is sewage from the New York City area. Essentially linear phosphate-salinity relationships are observed over tens of miles both upstream and downstream of the major sewage loading, indicating conservative phosphate behavior on the time scale of removal from the system, which is a few days during high fresh water flow and a week or more during low flow. Additional phosphate sources and sinks, including release of phosphate from particulates and net phytoplankton uptake, are minor compared with direct sewage discharge. L i t t l e immediate improvement i n water quality would be expected from the introduction to currently operating secondary plants of tertiary sewage treatment for phosphate removal. Silicate distributions in the Hudson are also quite unusual, showing substantial s i l i c a t e removal during low flow in the t i d a l fresh water Hudson. This suggests that biological uptake rather than a change in ionic strength is primarily responsible for negative deviations from conservative behavior in some estuaries. S i l i c a t e - r i c h sewage may produce a positive deviation from a conservative mixing line on a plot of s i l i c a t e vs. salinity during some periods in the lower Hudson Estuary.


634

MARINE CHEMISTRY

Literature 1.

2.

3.

4.

5.

6. 7.

8.

9. 10. 11. 12.

13. 14.

15.

Cited

Simpson, H.J, R. Bopp, and D. Thurber, "Salt Movement Patterns in the Lower Hudson", in Third Symposium on Hudson River Ecology, ed. G.P, Howells and G.J. Lauer, Hudson River Environmental Society, New York, 1974. Ketchum, B.H., "Eutrophication of Estuaries", in Eutrophication Causes, Consequences, Correctives, pp. 197-209, National Academy of Sciences, Washington, B.C., 1969. Hammond, D.E., "Dissolved Gases and Kinetic Processes in the Hudson River Estuary", Ph.D. Thesis, Columbia University, New York, New York, 1975. Boyle, Ε., R. Collier, A.T. Dengler, J.M. Edmond, A.G. Ng, and R.F. Stallard, Geochim. Cosmochim. Acta, (1974), 38, 1719-1728. Peterson, D.H., T.J. Recent Advances in Estuarine Research, (to be published in 1975). Howells, G.P., T.J. Kneipe, and M. Eisenbud, Environmental Science and Technology, (1970), 4, 26-35. Carpenter, J.H., D.W. Pritchard, and R.C. Whaley, "Observations of Eutrophication and Nutrient Cycles in Some Coastal Plain Estuaries", in Eutrophication: Causes, Consequences, Correctives, pp. 210-221, National Academy of Sciences, Washington, D.C., 1969. Jaworski, N.A., D.W. Lear, Jr., and O. Villa, Jr., "Nutrient Management in the Potomac Estuary", in Nutrients and Eutrophication, ed. G.E. Likens, Special Symposia, vol. 1, pp. 246-273, American Society of Limnology and Oceanography, 1972. Vollenweider, R.A., Organization for Economic Cooperation and Development (Paris), technical report DAS/CSI 68.27, 1968. Vollenweider, R.A., A. Munawar, and P. Stadelmann, J. Fish. Res. Bd. Can., (1974), 31, 739-762. Dobson, R.F.H., M. Gilbertson, and P. Gisly, J. Fish. Res. Res. Bd. Can., (1974), 31, 731-733. Sirois, D.L., "Community Metabolism and Water Quality in the Lower Hudson River Estuary", Third Symposium on Hudson River Ecology, ed. G.P. Howells and G.J. Lauer, Hudson River Environmental Society, New York, 1974. Murphy, J., and J.P. Riley, Anal. Chim. Acta, (1962), 27, 31-36. Stainton, M.P., M.J. Capel, and F.A.J. Armstrong, "The Chemical Analysis of Fresh Water", Miscellaneous Special Publication, No. 25, Fisheries Research Board of Canada, Ottawa, 1974. Strickland, J.D.H., and T.R. Parsons, "A Practical Handbook of Seawater Analysis", pp. 65-70, Fisheries Research Board of Canada, Ottawa, 1968.


38.

SIMPSON

E T A L .

Nutrient

Budgets

635

Acknowledgements A number of ambiguities and inaccuracies x*ere excised from earlier drafts as the result of careful reviewing by R. Bopp, W. Broecker, D. Schindler and T. Takahahsi. Any mistakes and questionable opinions which remain are due to the stubbornness of, the authors and approval by the above reviewers i s not implied. Ship time for collection of samples during March and A p r i l of 1974 was provided by J. Chute of the University Institute of Oceanography of the City University of New York. Sample collection for the January 1975 tributary s i l i c a t e survey was made by R. Bopp. Financial support for the latter stages of this study was provided by the Environmental Protection Agency under contract number R803113-01.


39 The Seasonal Variation in Sources, Concentrations, and Impacts of Ammonium in the New York Bight Apex HAROLD B. O'CONNORS and IVER W. D U E D A L L Marine Sciences Research Center, State University of New York, Stony Brook, N.Y.

11794

The f l u x a n d c o n c e n t r a t i o n o f p l a n t n u t r i e n t s a r e important f a c t o r s i n c o n t r o l l i n g the p r o d u c t i v i t y of m a r i n e w a t e r s (_1, 2^, 3 ) . E v i d e n c e f r o m bo t h l a b o r a t o r y a n d f i e I d meas u r e m e n t s h a v e i n d i c a t e d t h a t , w h i l e NH^ , u r e a , N(>3~, a n d N O 2 " n i t r o g e n may a l l be utili z e d b y phy t o p l a n k t o n f o r u p t a k e a n d g r o w t h , NH^"*" h a s g e n e r a l l y b e e n f o u n d t o be t h e p r e f e r r e d f o r m a n d may i n h i b i t phy t o p l a n k t o n up t a k e o f N O 3 " when p r è s en t i n c o n c e n t r a t i o n s a b o v e t r a c e a m o u n t s ( 1 , 2). Because o f t h e p o t e n t i a l i m p a c t o f a d d e d NH4"*" on phy t o p l a n k t o n p r o d u c t i o n , s t a n d i n g c r o p s p a t i a l d i s t r i b u t i o n , and s p e c i e s abundance, i t i s désirable t h a t i n f o r m a t i o n be ob t a i n e d on i t s r a t e s ο f i n p u t a n d c o n c e n t r a t i o n s i n coas t a l w a t e r s . +

I n t h i s p a p e r we f o c u s on t h e i n p u t o f NH4"*" i n t o t h e New Y o r k B i g h t a p e x ( F i g . 1 ) . Two s o u r c e s o f NH4"*" i n p u t have been i d e n t i f i e d : (1) sewage e f f l u e n t w h i c h i s cont i n u o u s l y d i s charged i n l a r g e volûmes i n t o the r e c e i v i n g w a t e r s w h i c h s u r r o u n d t h e New Y o r k m e t r o p o l i t a n r e g i o n and (2) sewage s l u d g e w h i c h i s t r a n s p o r t e d t o s e a i n b a r g e s a n d dumped a t a l o c a t i o n ab o u t 25 km f r o m t h e e n t r a n c e t o New Y o r k H a r b o r . These was t e s i n t r o d u c e N H ^ t o the apex a t a combined rate t h a t g r e a t l y exceeds the NH^ i n p u t from the Hudson River. +

+

C o n t r i b u t i o n 12 3 o f t h e M a r i n e S c i e n c e s R e s e a r c h C e n t e r (MSRC) o f t h e S t a t e U n i v e r s i t y o f New Y o r k a t S t o n y B r o o k .

636


39.

OCONNORS

NH4+ Input

AND

due

DUEDALL

Impacts of Ammonium

to A d v e c t i v e

637

Processes

Sewage E f f l u e n t . A l a r g e number of sewage t r e a t ment p l a n t s ( F i g . 2) are s i t u a t e d throughout the e n t i r e New York m e t r o p o l i t a n r e g i o n . Combined, they d i s c h a r g e about 50 m^ sec" - of primary and secondary t r e a t e d sewage e f f l u e n t (.A). In a d d i t i o n , about 13 m^ see"* of raw sewage, f o r which no treatment facilities are a v a i l a b l e , i s d i r e c t l y d i s c h a r g e d i n t o r e c e i v i n g waters (T. G l e n n , p e r s o n a l communication). Table I summarizes the mean c o n c e n t r a t i o n s and r a t e s of i n p u t s of sewage d e r i v e d n u t r i e n t s , i n c l u d i n g o r g a n i c n i t r o g e n These c o n c e n t r a t i o n s and i n p u t r a t e s may show s h o r t term v a r i a b i l i t y because the combined s a n i t a r y sewer and s t o r m - d r a i throughout the m e t r o p o l i t a s i z a b l e amounts of u n t r e a t e d sewage to bypass t r e a t ment p l a n t s d u r i n g p e r i o d s of heavy r a i n f a l l . Under these c o n d i t i o n s , the raw sewage i s d i s c h a r g e d d i r e c t l y i n t o the l o c a l r e c e i v i n g waters C5). It i s l i k e l y , however, t h a t these r a i n - c a u s e d e p i s o d e s do not introduce much v a r i a t i o n i n the mean c o n c e n t r a t i o n of NH4 or the volume of flow from the sewage system f o r p e r i o d s l o n g e r than s e v e r a l months (see N u t r i e n t R e l a t i o n s , page 4 ) . A l a r g e but unknown f r a c t i o n of sewage d e r i v e d n u t r i e n t s may r e a c h the New York B i g h t apex ( F i g . 1) i n a matter of days. The e f f e c t s of the Hudson R i v e r discharge, t i d a l o s c i l l a t i o n s , v a r i a b l e coastal c i r c u l a t i o n p a t t e r n s , b i o l o g i c a l p r o c e s s e s , and the p o s s i b i l i t y of v a r i a t i o n s i n r a t e s of i n p u t , combine to cont r o l the r e l a t i v e c o m p o s i t i o n and r a t e of f l u x of n u t r i e n t s i n t o the B i g h t apex. To o b t a i n the n e c e s s a r y data needed to e s t i m a t e the a d v e c t i v e f l u x of NH4+ and o t h e r n u t r i e n t s i n t o the apex, we (6) investigated the s e a s o n a l and t i d a l v a r i a t i o n of n u t r i e n t s and o t h e r océanographie v a r i a b l e s at s e v e r a l s t a t i o n s on a t r a n s e c t (see F i g . 3) between Sandy Hook, New J e r s e y , and Rockaway P o i n t y New York. The c r u i s e s were conducted on November 5, 1973 J a n u a r y 22, March 11, A p r i l 20, and June 5, 1974. The f l u x e s of N H , N0 ", N0 ~, PO4 ", and Si(0H)4 were computed f o r the June c r u i s e u s i n g p r e v i o u s l y o b t a i n e d c u r r e n t data (J) . Reported here a r e o n l y those r e s u l t s t h a t are p e r t i n e n t to NH4"**, i t s i n p u t and f a t e i n the apex. 3

+

+

4

2

3

T e m p e r a t u r e - S a l i n i t y R e l a t i o n s h i p s . The s t r o n g l y l i n e a r t e m p e r a t u r e - s a l i n i t y (T-S) * r e l a t i o n s h i p s (see F i g . 4a and b) demonstrate t h a t the water i n the t r a n s e c t ( F i g . 3) i s a m i x t u r e of p r i m a r i l y two water k


638

MARINE

CHEMISTRY

Figure 2. The New York Bight and its


39.

O'CONNORS A N D DUEDALL

Impacts of

Ammonium


639


I

Η

I

1

1

- * — * .

f

ψα

1

«y

1

1

,

1

1

Η*—I

^

- * — * — £ — i n

H

Η

Η

4

s

- à — * — — i n SALINITY (%.)

1

H

1

APRIL

1

1 Η

1

,

,

— 7fll; # —

- * — i s

I m; - f = 4 m ; *

-*——&—in

Η

Seasonal variation of temperature, NH \ NOf, and NO ~ with salinity. X = 10 m; • = bottom.

4

"4

1

- * — i s

Figure 4a.

s 3 «... i ....

Ε..4

NOVEMBER


Figure 4b.

IT Έ I

"5Î

Q. (A

ui

I

1*

Seasonal variation of POf',

a

4\

NOVEMBER

SALINITY (%c)

H

Η

1

1

I* 1

1

-*—is——in

Η

Si(OE) suspended matter (SS)and chlorophyll a with salinity. 4m;* =7 m; # = 10 m; • = bottom. h

4

——is——*.

V

St

•-

X

642

MARINE

CHEMISTRY

Τ a b 1 e I . A n n u a l mean c o n c e n t r a t i o n s (C) a n d a n n u a l mean i n p u t r a t e s ( F ) o f s e w a g e e f f l u e n t c o n t a i n e d n u t r i e n t s discharged through a h y p o t h e t i c a l o u t f a l l i n t o New Y o r k H a r b o r i ' . Computed f o r t h e p e r i o d J u l y 1973 t o J u l y 1 9 7 4 . C Concentrationk/ in Sewage E f f l u e n t (μΜ)

Sewage Component Organic-N NH

+ 4

(+

NH ) 3

F Input Ratek/ ( m o l e sec"^-)

646

63

726

71

N0 ~ 2

N0 ~

27

2. 6

P0 3-

62

6. 1

3

4

1*7 Mos t o f t h e s e w a g e e f f l u e n t d i s c h a r g e d f r o m t h e New Jersey shore of the harbor has undergone only p r i m a r y t r e a t m e n t f o r w h i c h o n l y d a t a on mean f l o w s a r e a v a i l a b l e (.4). T h e r e f o r e , t h e v a l u e s f o r c ^ s ( s e e f o o t n o t e b ) f o r New J e r s e y e f f l u e n t s w e r e c a l c u l a t e d by a s s u m i n g t h e i r c o n c e n t r a t i o n s w e r e s i m i l a r t o t h e P o r t Richmond p r i m a r y treatment p l a n t on S t a t e n I s l a n d . C a l c u l a t i o n s exclude e f f l u e n t s f r o m o u t f a l l s i n Long I s l a n d Sound and on t h e s o u t h shore of Long I s l a n d . k ^ T h e c o n c e n t r a t i o n s C a r e w e i g h t e d means c a l c u l a t e d f r o m t r e a t m e n t p l a n t a n n u a l mean d i s c h a r g e s ( 4 ) a n d t h e mean o f m o n t h l y c o n c e n t r a t i o n s c o v e r i n g t h e p e r i o d J u l y 1 9 7 3 t o J u l y 19 74. C was c a l c u l a t e d using the equation: C =

• Zf

±

w h e r e c ^ ~ a n n u a l mean c o n c e n t r a t i o n a n d f ^ « a n n u a l mean d i s c h a r g e f o r t h e i treatment p l a n t . The i n p u t r a t e F was c a l c u l a t e d u s i n g t h e e q u a t i o n : F = Σ ( c ^ x f jf ) . The o r i g i n a l s e w a g e d a t a u s e d i n o u r c a l c u l a t i o n s w e r e t a k e n f r o m t h e r e c o r d s o f sewage a n a l y s e s c o n d u c t e d by t h e E n v i r o n m e n t a l P r o t e c t i o n A d m i n i s t r a t i o n o f t h e C i t y o f New Y o r k . These r e c o r d s were k i n d l y p r o v i d e d t o us b y D r . Seymour K i r s chner, D i r e c t o r o f the Water P o l l u t i o n C o n t r o l L a b o r a t o r i e s o f t h e C i t y o f New Y o r k . t

n


39.

OCONNORS

AND

DUEDALL

Impacts of

Ammonium

643

types whose temperatures and s a l i n i t i e s show pronounc ed s e a s o n a l changes. D u r i n g the November c r u i s e , the water mass i n the t r a n s e c t was a m i x t u r e of two water types: (1) r e l a t i v e l y f r e s h e r and c o l d e r r i v e r water and (2) r e l a t i v e l y more s a l i n e , warmer B i g h t water. Temperature and s a l i n i t y ranges were 12-14°C and 24-32°/oo, r e s p e c t i v e l y . D u r i n g the January c r u i s e , a s i m i l a r two-component T-S r e l a t i o n was observed e x c e p t t h a t the water was much c o l d e r (3-7°C) and had a w i d e r range of s a l i n i t i e s (22-32°/oo). In March the water temperature was n e a r l y u n i f o r m at about 5°C and the s a l i n i t y v a l u e s (21-32°/oo) had i n c r e a s e d s l i g h t l y from those o b s e r v e d i n J a n u a r y . In A p r i l the f r e s h e r e s t u a r i n e water was warmer than the more s a l i n e B i g h t water o c c u r r i n g at s l o p e of the T-S diagram e x h i b i t e d the w i d e s t range d u r i n g the e n t i r e s t u d y . In June, water temperatures and s a l i n i t y were b o t h changed s u b s t a n t i a l l y from t h e i r p r e c e d i n g w i n t e r and s p r i n g v a l u e s ; temperatures ranged between 13 and 18°C and s a l i n i t i e s ranged between 23 and 32°/oo. The wide range of s a l i n i t i e s observed i n March and i n A p r i l demonstrates the s t r o n g i n f l u e n c e of the s p r i n g f r e s h w a t e r d i s c h a r g e . S a l i n i t i e s were more v a r i a b l e near Sandy Hook where the f r e s h w a t e r d i s charge had the g r e a t e s t e f f e c t on water p r o p e r t i e s . The most s a l i n e water i n the t r a n s e c t was always s i t u a t e d near Rockaway P o i n t , due to a s t r o n g nont i d a l t r a n s p o r t of B i g h t water i n t o the h a r b o r . N u t r i e n t R e l a t i o n s . The a p p r o x i m a t e l y l i n e a r n u t r i e n t - s a l i n i t y (Nutr-S) r e l a t i o n s h i p s (see F i g s . 4a and b) a l s o demonstrate t h a t the water i n the t r a n s e c t i s a two-component system comprised of n u t r i e n t i m p o v e r i s h e d B i g h t water and n u t r i e n t r i c h e s t u a r i n e water. The n u t r i e n t c o m p o s i t i o n i s v a r i a b l e depending on the season and on whether the p a r t i c u l a r n u t r i e n t s p e c i e s o r i g i n a t e d (1) from sewage e f f l u e n t or (2) was d e r i v e d mainly from the f r e s h w a t e r d i s c h a r g e of the Hudson R i v e r or a l e s s e r e x t e n t , (3) was d e r i v e d from the d i s c h a r g e of the R a r i t a n and P a s s a i c Rivers . Most of the NO3" measured i n the t r a n s e c t comes from Hudson R i v e r d i s c h a r g e and not from sewage effluent. E x t r a p o l a t i o n of the N03~-S r e s u l t s i n F i g . 4a to zero s a l i n i t y g i v e s Ν Ο β " c o n c e n t r a t i o n s t h a t range between 45 and 90 pM. These v a l u e s a r e i n good agreement w i t h the annual range of 50 to 140 μΜ r e p o r t e d (8) f o r N O 3 " i n water samples c o l l e c t e d from the Hudson and R a r i t a n R i v e r s upstream from the


644

MARINE

CHEMISTRY

i n f l u e n c e o f t h e New Y o r k m e t r o p o l i t a n r e g i o n . Sewage e f f l u e n t ( T a b l e I ) i s a p r i n c i p a l source o f N H , N02~, and Ρ Ο ^ ' . For November, e x t r a p o l a t i o n o f t h e NH4+-S, d i a g r a m ( s e e F i g . 4a) t o 15°/oo s a l i n i t y g i v e s a c o n c e n t r a t i o n o f NH4"*", t h a t c o m p a r e t o some E a s t R i v e r v a l u e s (9) and i s a b o u t an o r d e r o f magnitude g r e a t e r than what i s found i n Hudson R i v e r waters upstream from the m e t r o p o l i t a n r e g i o n . During the s p r i n g f r e s h e t , which occurs i n A p r i l , NH4"*", NC>2~ and PO4 c o n c e n t r a t i o n s due t o s e w a g e d i s c h a r g e w o u l d be e x p e c t e d t o u n d e r g o a g r e a t e r d i l u t i o n , w i t h the i n c r e a s e d volume of r i v e r w a t e r i n the e s t u a r y , than i n the e a r l i e r w i n t e r months. This assumes a r e l a t i v e l y c o n s t a n t sewage i n p u t o f t h e s e nutrients. In fact Protection Administratio ( S . K i r s c h n e r , p e r s o n a l c o m m u n i c a t i o n ) show t h a t t h e v a r i a b i l i t y o f t h e f l o w o f s e w a g e e f f l u e n t and i t s n u t r i e n t c o n c e n t r a t i o n i s r e l a t i v e l y s m a l l compared t o t h e amount o f d i l u t i o n . For example, the average c o e f f i c i e n t s of v a r i a t i o n [V% « ( s x l O O ) / X ] f o r the mean e f f l u e n t N H ^ c o n c e n t r a t i o n and f l o w v o l u m e f o r t w e l v e New Y o r k C i t y t r e a t m e n t p l a n t s f o r t h e p e r i o d N o v e m b e r 1973 t o J u n e 1974 w e r e 1 9 . 5 % and 1 0 . 7 % , respectively. The A p r i l f r e s h w a t e r i n p u t f r o m t h e Hudson R i v e r measures a b o u t t h r e e - f o l d o v e r t h a t of November ( 1 0 ) . The c o n c e n t r a t i o n s o f NO3" i n t h e t r a n s e c t i s p r i m a r i l y a f u n c t i o n of the c o n c e n t r a t i o n of r i v e r w a t e r i t s e l f a n d , t h e r e f o r e , may i n c r e a s e o r decrease, depending upon w h e t h e r augmented r u n o f f i n c r e a s e s its c o n c e n t r a t i o n i n the r i v e r water or not. The i n c r e a s e d d i l u t i o n o f NH4" *, N 0 " , and P O 4 " t a k e s p l a c e a t a b o u t t h e same t i m e as t h e s p r i n g p h y t o p l a n k t o n b l o o m , as e v i d e n c e d by t h e r e m a r k a b l e i n c r e a s e s i n t h e c o n c e n t r a t i o n o f c h l o r o p h y l l a_ i n t h e t r a n s e c t , e s p e c i a l l y n e a r S a n d y Hook ( F i g . 4 b ) . T h e r e f o r e , the s e a s o n a l v a r i a t i o n i n the s l o p e s of t h e NH4+-S, N 0 " - S and P Û 4 " - S d i a g r a m s ( F i g . 4a and b) w i l l n o t be s o l e l y a f u n c t i o n o f c h a n g e s i n f r e s h w a t e r d i s c h a r g e , but a l s o i n c l u d e the e f f e c t of the b i o l o g i c a l u t i l i z a t i o n of these c h e m i c a l s p e c i e s . F o r e x a m p l e , a s s u m i n g t h a t no o t h e r processes i n f l u e n c e t h e NH4"*" c o n c e n t r a t i o n , t h e r e l a t i v e e f f e c t s of (1) p h y t o p l a n k t o n u p t a k e d u r i n g the s p r i n g b l o o m and ( 2 ) d i l u t i o n by r i v e r w a t e r on t h e ammonium c o n c e n t r a t i o n i n t h e t r a n s e c t c a n be e s t i m a t e d . This c a n be a c c o m p l i s h e d by c o m p a r i n g ( 1 ) t h e m e a s u r e d NH^ " c o n c e n t r a t i o n v a l u e s w i t h (2) the e x p e c t e d N H 4 c o n c e n t r a t i o n v a l u e s b a s e d s o l e l y on d i l u t i o n . In +

4

+

1

J

2

3

2

4

+


39.

OCONNORS

AND

DUEDALL

Impacts of

Ammonium

645

November, f r e s h w a t e r d i s c h a r g e i n the Hudson e s t u a r y i s g e n e r a l l y about t h r e e times l e s s than i n A p r i l ( 1 0 ) . T h e r e f o r e , i t c o u l d be expected t h a t d i l u t i o n would reduce the ammonium c o n c e n t r a t i o n s i n the t r a n s e c t i n A p r i l to about o n e - t h i r d of the November v a l u e s . In F i g u r e 4a, i t can be seen t h a t at s a l i n i t y of 26°/oo, f o r example, i n November the c o n c e n t r a t i o n of N H was about 40 μΜ. In A p r i l , however, the measured NH c o n c e n t r a t i o n at the same s a l i n i t y ranged from about 5 yM to c o n c e n t r a t i o n s below d e t e c t i o n , which i s about 8 to 13 μΜ l e s s than the c o n c e n t r a t i o n which might be expected from d i l u t i o n a l o n e . I t would appear, t h e r e f o r e , t h a t i n A p r i l , N H was b e i n g r a p i d l y u t i l i z e d by the p h y t o p l a n k t o n i n comparison to November and thu t i o n s i n the t r a n s e c caused by d i l u t i o n due to the i n c r e a s e d f r e s h w a t e r d i s charge. +

4

+

4

+

4

C r o s s - S e c t i o n s i n the T r a n s e c t . Contoured s e c t i o n s of v a r i a b l e s showing the d i s t r i b u t i o n of water p r o p e r t i e s i n the t r a n s e c t were p r e p a r e d u s i n g tidally averaged c o n c e n t r a t i o n s (JS) . P r e s e n t e d h e r e ( F i g s . 5-7) are s e c t i o n s f o r s a l i n i t y , N H , and c h l o r o p h y l l a_. Two f e a t u r e s shown i n these s e c t i o n s are the p r e s e n c e of (1) h i g h s a l i n i t y - l o w N H water near Rockaway P o i n t and (2) low s a l i n i t y - N H r i c h water near Sandy Hook. A s s o c i a t e d w i t h the low s a l i n i t y water d u r i n g A p r i l were h i g h c o n c e n t r a t i o n s of c h l o r o p h y l l a (see F i g . 7a through d ) . Most of the low s a l i n i t y - N H r i c h water p r o b a b l y o r i g i n a t e s i n R a r i t a n Bay where l a r g e s t a n d i n g s t o c k s of phytop l a n k t o n have been r e p o r t e d (11., 12,)· The p r e s e n c e of a l a r g e but slow moving c o u n t e r c l o c k w i s e gy ^ i n R a r i t a n Bay may act to delay some of the n u t r i e n t r i c h Upper Bay water ( F i g . 2) t h a t was advected towards the apex but through R a r i t a n Bay by r i v e r flow and t i d a l action. T h i s delay may p r o v i d e a s u f f i c i e n t amount of time f o r the development of h i g h c h l o r o p h y l l a_ s t a n d i n g crops i n R a r i t a n Bay. T i d a l current charts (13) show t h a t d u r i n g ebb t i d e R a r i t a n Bay waters flow around Sandy Hook i n t o the apex. These low s a l i n i t y R a r i t a n Bay waters c o u l d , d u r i n g p e r i o d s of decreased p h y t o p l a n k t o n p r o d u c t i o n i n the w i n t e r , c o n t a i n e l e v a t e d c o n c e n t r a t i o n s of N H and o t h e r nutrients. However, d u r i n g the s p r i n g when p h y t o p l a n k t o n growth i s at i t s maximum i n R a r i t a n Bay, the low s a l i n i t y water f l o w i n g from R a r i t a n Bay would +

4

+

4

+

4

+

4

r

+

4


646

MARINE

STATION G

DEPTH

F

M

SALINITY SANDY 11

PPT

HOOK

-

ROCKAWAY

POINT

TRANSECT

NOVEMBE

OISTANCE

FROM

SANOY

HOOK/KM

c

OEPTH

CHEMISTRY

β

M

SALINITY SANDY 22

PPT

HOOK

-

JANUARY

ROCKAWAY

DISTANCE STATION Μ

POINT

TRANSECT

1974

FROM

0

SANDY E

HOOK/KM C

Β

y DEPTH

M

SALINITY SANDY

PPT

HOOK

1 1 MARCH

-

ROCKAWAY

POINT

TRANSECT

1974

DISTANCE

FROM

SANDY

HOOK/KM


ο

CONNORS

Impacts of

A N D DUEDALL

Ammonium

0

STATION Η

DEPTH M

SALINITY PPT SANDY 20

HOOK

-

ROCKAWAY

POINT

TRANSECT

APRI

DISTANCE STATION H

C

FROM

F

SANDY E

HOOK/KM C

Β

ι ΟΕΡΤΗ Μ

SALINITY PPT SANDY 5

HOOK

-

ROCKAWAY

3

DISTANCE

Figure Sa-e.

POINT

TRANSECT

JUNE 1974

4

FROM

5

SANDY

6

HOOK/KM

Tidally-averaged salinity distribution in the transect


MARINE

AMMONIUM SANDY 11

μΜ

HOOK

MARCH

CHEMISTRY

-

ROCKAWAY

POINT

TRANSECT

1974

S «ΝΟΥ HOOK DISTANCE

FROM

SANDY

HOOK/KM

Figure 6a-d.

Tidally-averaged


39.

O'CONNORS

AND

Impacts of Ammonium

DUEDALL

STATION H

649

Ψ

O

À DEPTH M

AMMONIU SANOY HOOK - ROCKAWAY P O I N T 20 A P R I L 1974

TRANSECT ROCKMMV POINT

2

STATION Η

DISTANCE

0

FROM SRNDY

HOOK/KM

F

J DEPTH M

AMMONIUM uM SANDY HOOK 5

ROCKAWAY P O I N T

TRANSECT

JUNE 1974 2

3

DISTANCE

4

5

FROM SANDY

6

7

HOOK/KM

ammonium distribution in the transect


650

MARINE

STATION 0

F

DEPTH H

9

CHLOROPHYLL A (MGM) SANDY HOOK - ROCKAWAY POINT 11 NOVEMBER 1973

TRANSECT

DISTANCE FROM SANOY E

C

HOOK/KM Β

DEPTH M

CHLOROPHYLL A (MGwft SANDY HOOK - ROCKAWAY POINT 11 MARCH 1974

TRANSECT

DISTANCE FROM SANOY

HOOK/KM

DEPTH M

/CHLOROPHYLL A {MG*ft SANDY HOOK - ROCKAWAY POINT 20 A P R I L " ! 9 7 4

TRANSECT

DISTANCE FROM SANDY

HOOK/KM


CHEMISTRY

OCONNORS

Impacts of

A N D DUEDALL

STATION H

Ammonium E

G

C

Β

-

^••0

DEPTH M

CHLOROPHYLL SANDY 5

HOOK

JUNE

STATION · !

(MGW) ROCKAWAY

POINT

TRRNSECT

197

*

Figure la-à,

A -

DISTANCE

FROM SANDY

HOOK/KM

Tidally-averaged chlorophyll a distribution in the transect

·2

DEPTH/M

NON-Τ I D A L SANDY 2-7

VELOCITIES

HOOK

JUNE

-

CM P E R S E C

ROCKAWAY

POINT

TRANSECT

1952

3

4

DISTANCE

FROM

5

SANDY

6

HOOK/KM

Current Structure in Sandy Hook Rockaway Point Transect

Figure 8.

Nontidal current velocities in the transect (7). Negative-sign veloci ties are into the harbor.


652

MARINE

CHEMISTRY

c o n t a i n h i g h c o n c e n t r a t i o n s o f c h l o r o p h y l l a_ but low concentrations of n u t r i e n t s . This i s c o n s i s t e n t with the f e a t u r e s o b s e r v e d i n a l l the n u t r i e n t and c h l o r o p h y l l c r o s s - s e c t i o n s [see F i g s . 5, 6, and 7 and a l s o (6)]. The p e r s i s t e n c e o f h i g h e r s a l i n i t y water near Rockaway P o i n t i s m a i n l y due to s t r o n g n o n - t i d a l c u r r e n t s t h a t t r a n s p o r t seawater from t h e apex t o t h e harbor. F i g u r e 8 i s a c r o s s - s e c t i o n showing the d i s t r i b u t i o n of n o n - t i d a l c u r r e n t v e l o c i t i e s normal to the t r a n s e c t d u r i n g June, 1952 (6_) . Negative-sign v e l o c i t i e s i n d i c a t e c u r r e n t s moving towards the h a r b o r . C l e a r l y , Rockaway P o i n t i s a r e g i o n where b o t h s u r f a c e and deep waters a r e t r a n s p o r t e d i n t o the h a r b o r from the apex. Earlier investigator the New York B i g h t ape the e x i s t e n c e of a n o n - t i d a l d r i f t near Rockaway P o i n t which moves towards the h a r b o r . The v e l o c i t y c o n t o u r s i n F i g u r e 8 g i v e the f i r s t p u b l i s h e d q u a n t i t a t i v e e v i d e n c e f o r the p r e s e n c e of t h i s f e a t u r e . The r e s u l t s of a r e c e n t completed seabed d r i f t e r study i n the apex shows near bottom n o n - t i d a l v e l o c i t i e s v e r y s i m i l a r to those i n F i g u r e 8 ( 1 6 ) . At o t h e r l o c a t i o n s , a l o n g the t r a n s e c t , n o n - t i d a l s u r f a c e c u r r e n t s move towards the apex, which i s con s i s t e n t w i t h the p r e s e n c e of low s a l i n i t y - n u t r i e n t r i c h water south of Ambrose c h a n n e l (see F i g s . 5 and 6). A d v e c t i v e N u t r i e n t F l u x e s i n the T r a n s e c t . To o b t a i n e s t i m a t e s of n u t r i e n t i n p u t to t h e apex, the a d v e c t i v e f l u x e s of NH4 , NO2", NO3", P O 4 " , and S i ( O H ) 4 were c a l c u l a t e d u s i n g t h e June 5, 1974 n u t r i e n t c o n t o u r s [see (6)] and the June 2-8, 1952 v e l o c i t y p r o f i l e ( F i g . 8 ) . In the c a l c u l a t i o n s , i t was assumed t h a t the n o n - t i d a l v e l o c i t y s t r u c t u r e i n the t r a n s e c t was s i m i l a r f o r the two p e r i o d s , June 2-8, 1952 and June 5, 1974. Storms t h a t might a l t e r n o n - t i d a l c i r c u l a t i o n i n the apex a r e i n f r e q u e n t i n June. The n o n - t i d a l c u r r e n t s t r u c t u r e s f o r May 21-25, 1958, and August 12-16, 1959 a r e very s i m i l a r to the n o n - t i d a l c u r r e n t s t r u c t u r e f o r June 2-8, 1952 (R. W i l s o n , p e r s o n a l communication). Advective n u t r i e n t f l u x e s were c a l c u l a t e d from t h e e x p r e s s i o n Σ ( ο ± ν ± σ ± ) . The C £ and v^ a r e the t i d a l l y averaged n u t r i e n t c o n c e n t r a t i o n s and n o n - t i d a l c u r r e n t v e l o c i t i e s i n t e r p o l a t e d to a g r i d and c o n t o u r e d i n F i g u r e s 6 and 8, respectively. o^ a r e the areas of d i f f e r e n t g r i d elements. T a b l e I I summarizes our e s t i m a t e s of n u t r i e n t f l u x e s through the t r a n s e c t . +

3


OCONNORS AND

39.

Nutrient

+

(a) I n t o the Harbor

FLUX (moles s e c " ^ ) (b) Out o f the Harbor

14

4

51

1.6

N0 ~ 2

NO3-

4. 6 37

11

653

PO4 "

C(b)-(a)] Bight-ward

37 3 26 3 7

2.5

3

Si(OH)

Ammonium

C a l c u l a t e d N u t r i e n t F l u x e s i n the T r a n s e c t .

Table I I .

NH

Impacts ? of

DUEDALL

10

4

1

NH^"" Inputs

due to Sludge

Dumping

Sewage s l u d g e , which i s dumped i n l a r g e volumes a t sea about 25 km from the e n t r a n c e to New York Harbor, i s a l s o a s o u r c e of NH^ i n the apex. F o r the p e r i o d 1965 to 1970, i t has been e s t i m a t e d t h a t t h e average annual volume o f sludge to the apex i s about 3.2xl0 m (17). The c o n t i n u e d c o n s t r u c t i o n of l a r g e sewage treatment p l a n t s i n the m e t r o p o l i t a n a r e a , i n c l u d i n g the south shore o f Long I s l a n d w i l l ensure an i n c r e a s i n g i n p u t of s l u d g e to the B i g h t i n the f u t u r e i f a l t e r n a t e d i s p o s a l or r e c y c l i n g schemes a r e not developed and implemented. To determine the e f f e c t o f s l u d g e dumping on the d i s t r i b u t i o n of Ν Η ^ i n apex w a t e r s , we conducted a c r u i s e w i t h i n the s l u d g e dumping grounds d u r i n g the p e r i o d J u l y 30-31, 1973 (.18). T a b l e I I I shows t h a t n i n e dumps of s l u d g e o c c u r r e d d u r i n g t h e p e r i o d of s tudy. A r a p i d sampling g r i d ( F i g . 9) was used i n and near the dump s i t e to a s s e s s the s p a t i a l e x t e n t o f NH from s l u d g e dumping. The g r i d c o n s i s t e d of s t a t i o n s spaced around the p e r i m e t e r o f a 9.4 km r a d i u s c i r c l e , c e n t e r e d near the d e s i g n a t e d dump a r e a ( s e e F i g . 9 ) . S u r f a c e , ~10m, and bottom water samples were o b t a i n e d by u s i n g a s u b m e r s i b l e pump and then a n a l y s e d f o r NH^"" onboard the r e s e a r c h v e s s e l . I n a d d i t i o n , an attempt was made to t r a c e the d i s p e r s i o n o f r e c e n t l y dumped sludge by f o l l o w i n g , w i t h a d d i t i o n a l water s a m p l i n g , two parachute drogues s e t a t 4 and 8 m ( F i g . 9). D e t a i l s of the methods used a r e r e p o r t e d +

6

3

+

+

4

1


654

MARINE

CHEMISTRY

Ocean Dumping in the N.Y. Bight

Figure 9. Stations occupied and times of drogue release and location (18). Dashed circle near center of perimeter represents the area (3.3 km ) and location (40° 20' N, 73° 45' W) of the interim sludge dump area established by the U.S. Environmental Protection Agency. 2


39.

OCONNORS

Impacts of

A N D DUEDALL

Ammonium

655

Τ ab1e I I I . Volumes of sewage s l u d g e (wet) dumped i n the New York B i g h t apex d u r i n g the p e r i o d J u l y 30-31, 1973. Data o b t a i n e d from 1973 Ocean Dumping Logs, Marine E n v i r o n m e n t a l Branch, U. S. Coast Guard, Governors I s l a n d , New York. [ T h i s t a b u l a t i o n taken from (18.).]

Date

Estimated Time of Arrival (EDT)

30 J u l y

1055

"Newtown

Creek"

2,860

1126

"Bowery Bay" (New York C i t y )

1,820

0550

"Judson K. Stiékle" (South Amboy, N.J.)

1105

"Newtown Creek" (New York C i t y )

2,860

1111


1,8 70

1700

"Ocean D i s p o s a l " (Passaic Valley Sewage A u t h o r i t y , New J e r s e y )

1729

"Newtown Creek" (New York C i t y )

2,860

1740

"Coney I s l a n d " (New York C i t y )

1,200

1900


1,890

31 J u l y

Sludge V e s s e l & Source of Sludge

Volume—' > Jl' of Sludge m3

1521/

155^/

— ^ O r i g i n a l l o g s r e p o r t volume of wet s l u d g e i n u n i t s of c u b i c f e e t . ^

The d e n s i t y of wet s l u d g e i s about 1 g cm" (this may be low s i n c e some components of s l u d g e s i n k ) ; at t h i s density 1 m equals 1 metric ton. 3

3

— ^ O r i g i n a l data given i n short tons.


656

MARINE

CHEMISTRY

elsewhere (18). The h i g h s u r f a c e and m i d - d e p t h NH4"*" c o n c e n t r a t i o n s ( F i g , 10) a t s t a t i o n 112 c o n f i r m e d an e a r l i e r v i s u a l i n d i c a t i o n of a s l u d g e patch at t h a t s t a t i o n , but the c o n c e n t r a t i o n s o b t a i n e d from the sampling sequence a l o n g the t r a j e c t o r i e s of the drogues are c o n f u s e d . F o r e x a m p l e , s t a t i o n s 114, 1 1 6 , a n d 1 1 7 , w h i c h w e r e s a m p l e d s u b s e q u e n t t o s t a t i o n 112, showed s u r f a c e NH4+ v a l u e s s i m i l a r t o t h o s e m e a s u r e d a t s t a t i o n s away f r o m t h e i m m e d i a t e dump a r e a . I t was n o t u n t i l s t a t i o n 119 was s a m p l e d t h a t s u r f a c e and 10 m NH4"*" c o n c e n t r a t i o n s s i m i l a r to those measured at s t a t i o n 112 w e r e f o u n d . E x t r e m e l y h i g h ammonium c o n c e n t r a t i o n s (^200 t o 500 μΜ) w e r e o b s e r v e d a t s t a t i o n 128 a t 1930 e a s t e r n d a y l i g h judged t h i s observatio r e c e n t s l u d g e dump, as e v i d e n c e d by t h e 1800 EDT s i g h t i n g of a s l u d g e t r a n s p o r t v e s s e l i n the v i c i n i t y t h a t was r e t u r n i n g t o New Y o r k H a r b o r (Ιδ.). I t w o u l d s e e m , t h e r e f o r e , t h a t t h e s l u d g e dump s i t e i s c h a r a c t e r i z e d by p e r s i s t i n g s i g n a t u r e s f r o m p r e v i o u s d u m p i n g a c t i v i t y w h i c h l e a d s t o a v e r y non-homogeneous s p a t i a l d i s t r i b u t i o n o f NH4+ ( F i g . 1 0 ) . The p r e s e n c e o f a pycnocline ( F i g . 11) w o u l d i n h i b i t v e r t i c a l m i x i n g o f t h e s u r f a c e and b o t t o m w a t e r s . However, the data o b t a i n e d a t s t a t i o n 128 d i d show t h a t t h e e f f e c t s o f d u m p i n g c a n , i n some i n s t a n c e s , m a n i f e s t t h e m s e l v e s t h r o u g h o u t the w a t e r column w i t h i n a very s h o r t t i m e . The c o n c e n t r a t i o n o f NH4 * i n s e w a g e s l u d g e i s variable. Some u n p u b l i s h e d a n a l y s e s p e r f o r m e d by t h e New Y o r k C i t y E n v i r o n m e n t a l P r o t e c t i o n A d m i n i s t r a t i o n (S. K i r s c h n e r , p e r s o n a l c o m m u n i c a t i o n ) i n November and D e c e m b e r , 1 9 7 3 , show t h a t the NH4 concentration i n New Y o r k C i t y s l u d g e s r a n g e s f r o m 17 t o 160 m i l l i M , w i t h a mean v a l u e o f 70 m i l l i M . U s i n g t h i s mean c o n c e n t r a t i o n a n d t h e i n p u t s i n T a b l e I I I , we c a l c u l a t e t h e d a i l y i n p u t o f N H 4 t o t h e a p e x f r o m s l u d g e dumped d u r i n g o u r c r u i s e t o be 0 . 3 - 0 . 7 x 1 0 ^ m o l e s , w h i c h i s about o n e - f i f t h to o n e - t e n t h of the i n p u t from the a d v e c t i v e p r o c e s s e s i n the t r a n s e c t . However, u n l i k e the Hudson R i v e r ' s low s a l i n i t y plume, s l u d g e dumping a t sea can p r o d u c e l o c a l l y h i g h c o n c e n t r a t i o n s of NH4**" t h a t may be r a p i d l y d i s p e r s e d b y m i x i n g . Further r e s e a r c h i s needed to determine the s p a t i a l d i s t r i b u t i o n , p e r s i s t e n c e and l o c a l b i o l o g i c a l e f f e c t s o f t h e s e e l e v a t e d NH c o n c e n t r a t i o n s caused by dumped sludge. 4

+

+

+

4


ocoNNORS

Impacts

A N D DUEDALL

DATA NEAR

OR

PROM WITHIN

of

Ammonium

STATIONS THE

DUMP

BACKGROUND SITE

STATIONS

NH4* ( μ Μ ) 12

3 4

5 6 7 8 9

STATION (isoo) July 3 0

III

NH4* ( μ Μ )

2 3 4 5 6 7 8 9

STATION 122 (OMt) July 31

"STATION 123

(0930)

July 31

2

3 4 5 6

7 8 9 0

STATION 113

(!·!·) July30

STATION 115 (2040) July 3 0

STATION 118 (OU5) July 31

STATION 121 (OZOl) July 31

STATION 124 (lOSO) July 31

STATION 126 (I520) July 31

Ocean Dumping in the N.Y. Bight

Figure 10. Observed ammonium concentrations near or within the dump site and at background stations on the indicated perim eter (18). The number in brackets represents the time (EDT) of arrival on station.


658

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39.

OCONNORS

AND

DUEDALL

D i s c u s s i o n and

Impacts of

659

Ammonium

Conclusion

The r e s u l t s of our i n v e s t i g a t i o n s suggest t h a t (1) i n June the net a d v e c t i v e f l u x of N H 4 * from New York Harbor to the New York B i g h t apex p r o b a b l y exceeds the r a t e of i n p u t of N H from s l u d g e dumping i n the B i g h t apex and (2) the e f f e c t s of p h y t o p l a n k t o n uptake and f r e s h w a t e r d i l u t i o n are about the same on NH4+ c o n c e n t r a t i o n s i n the t r a n s e c t d u r i n g the s p r i n g phytop l a n k t o n bloom. T a b l e IV l i s t s (1) the combined mean d a i l y i n p u t s of n u t r i e n t s from sewage d i s c h a r g e and r i v e r d i s c h a r g e and (2) the f l u x of n u t r i e n t s through the t r a n s e c t f o r June 5, 1974. The r e l a t i v e l y l a r g e d i f f e r e n c e s between the r i v e r p l u s sewag t r a n s e c t ( T a b l e IV, Si(0H>4 suggest that these n u t r i e n t s p e c i e s are b e i n g u t i l i z e d by the p h y t o p l a n k t o n at r a t e s about o n e - h a l f the n u t r i e n t i n p u t r a t e . The s m a l l e r d i f f e r e n c e s f o r ΝΟβ" and Νθ£~ suggest t h a t these s p e c i e s may behave as q a u s i - c o n s e r v a t i v e c o n s t i t u e n t s i n these e u t r o p h i c waters. I t has been s u g g e s t e d t h a t N O 3 " i s u t i l i z e d by p h y t o p l a n k t o n only i n the v i r t u a l absence of NH4 ( l , 2). the N H , P O 4 - , and Si(0H>4 u t i l i z a t i o n p r o b a b l y takes p l a c e i n R a r i t a n Bay where l a r g e s t a n d i n g s t o c k s of p h y t o p l a n k t o n have been r e corded (.11, 12) . We emphasize, however, t h a t the r e s u l t s i n T a b l e IV are only a p p r o x i m a t i o n s and, t h e r e f o r e , have very l i m i t e d use i n any n u t r i e n t m a t e r i a l - b a l a n c e c a l c u l a t i o n because (1) June, 1952 c u r r e n t v e l o c i t i e s were used to c a l c u l a t e June 1974 n u t r i e n t f l u x e s i n the t r a n s e c t , (2) n u t r i e n t s may be consumed and r e c y c l e d b e f o r e they reach the t r a n s e c t , p r o c e s s e s about which we have no d i r e c t knowledge. A l s o , i t has been c a l c u l a t e d t h a t about 70 per cent of the sewage d i s c h a r g e d from the f o u r l a r g e s t sewage treatment p l a n t s on the E a s t R i v e r ( F i g . 1) i s t r a n s p o r t e d to Long I s l a n d Sound (20). Furthermore, v i r t u a l l y n o t h i n g i s known about the f a t e of the l a r g e amount of o r g a n i c n i t r o g e n ( T a b l e I) which i n some cases may s e r v e as n i t r o g e n sources f o r growth of phy t o p l a n k t o n (.21, 2)· +

4

+

M

o

s

t

o f

+

3

4

The Hudson R i v e r Plume and C h l o r o p h y l l 3 . Input to the Apex. The t r a n s e c t study has demonstrated the Hudson R i v e r plume's s p a t i a l d i s t r i b u t i o n and tem p o r a l permanence a c r o s s the apex. The plume was most w e l l - d e v e l o p e d i n the t r a n s e c t between Sandy Hook and Ambrose Channel. Of p a r t i c u l a r i n t e r e s t are the h i g h c o n c e n t r a t i o n s of c h l o r o p h y l l & i n the plume and t h e i r


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T a b l e IV. C a l c u l a t e d d a i l y r i v e r and sewage n u t r i e n t i n p u t and Bight-ward n u t r i e n t f l u x through the t r a n s e c t , June 5, 1974.

(xlO Nutrient

NH

+

(a) Sewage*' and R i v e r l / Input

6

moles) (b) Bight-ward Flux

6.5

4

N0 "

3.2

.08

2

[(b)-( )] a

-3.3

.24

.16

N0 ~ 3

P0 34

Si(0H)

4

0.6

0.3

-0.3

4.9

1.8

-3.1

C a l c u l a t e d from T a b l e I. Si(OH) inputs have been n e g l e c t e d f o r l a c k of d a t a . 4

i n sewage

— ^ C a l c u l a t e d from May, June and J u l y c o n c e n t r a t i o n s from 1972 Water Year data at C h e l s e a s t a t i o n (J3) on the Hudson R i v e r . V a l u e s adj usted upward by 10% to a p p r o x i m a t e l y account f o r R a r i t a n R i v e r . P a s s a i c R i v e r input not included.


39.

OCONNORS

A N D DUEDALL

Impacts of Ammonium

661

a f f e c t i n the apex. U s i n g the June 1952 c u r r e n t v e l o c i t i e s ( F i g . 8) and June 1974, c h l o r o p h y l l a c o n c e n t r a t i o n s , we c a l c u l a t e t h a t about 1.9 m e t r i c tons per day of c h l o r o p h y l l a i s t r a n s p o r t e d to the B i g h t apex through the t r a n s e c t . During spring l a r g e r d a i l y t r a n s p o r t s would e x i s t due to development of a more i n t e n s e p h y t o p l a n k t o n bloom (see F i g . 7b, c and d ) . T h i s s e a s o n a l i n p u t of l a r g e abundances of p h y t o p l a n k t o n would be c o n f i n e d to the Hudson plume. The plume, a c c o r d i n g to p r e v i o u s i n v e s t i g a t o r s , remains near to the New J e r s e y c o a s t (14, 15). These h i g h p h y t o p l a n k t o n c o n c e n t r a t i o n s undoubtedly r e p r e s e n t an i m p o r t a n t and r e l a t i v e l y c o n t i n u o u s but s e a s o n a l l y v a r i a b l e s u p p l y of p a r t i c u l a t e food f o r z o o p l a n k t o n herbivores associate remains to be l e a r n e g r a p h i c c h a r a c t e r i s t i c s of the plume. Research s h o u l d be d i r e c t e d toward d e v e l o p i n g an adequate u n d e r s t a n d i n g of the b i o l o g i c a l , c h e m i c a l and p h y s i c a l p r o c e s s e s i n the plume and to determine what impact the plume has on the r e g i o n encompassed by the New York B i g h t . Acknowledgement We g r a t e f u l l y acknowledge the generous and c h e e r f u l a s s i s t a n c e of M r . C h r i s Stuebe, C a p t a i n of the R/V Mic Mac, M r . J e f f P a r k e r , p a r t y c h i e f , Mr. W i l l i a m M i l o s k i , seawater a n a l y s t , M r . G l e n H u l s e , i n s t r u m e n t a t i o n s p e c i a l i s t , and Ms.Sue Oakley and Mr. A l a n Robbins f o r d a t a r e d u c t i o n and computer p l o t t i n g . We thank M r s . J a c q u e l i n e R e s t i v o f o r h e r generous a s s i s t a n c e d u r i n g the m a n u s c r i p t p r e p a r a t i o n . The c r u i s e work would not have been p o s s i b l e w i t h out the l a b o r s of many graduate s t u d e n t s at MSRC, i n c l u d i n g M r . Mike W h i t e , Ms. C y n t h i a M a r k s , and M r . Robert O l s o n . Much of the r e p o r t e d work was s u p p o r t e d by a g r a n t (No. 04-4-158-19) from the NOAA/MESA New York B i g h t P r o j e c t . We thank M r . H . S t a n f o r d f o r h i s assis t a n c e · Abstract +

Two sources of NH4 input to the New York Bight have been identified: (1) Hudson River-Raritan Bay discharge into the apex of the Bight through the Rockaway Point, New York-Sandy Hook, New Jersey, transect and (2) barge-dumped sewage sludge from the greater New York metropolitan region. The Bight-ward flux of ammonium through the transect has been calculated for one 24-hour period in


MARINE

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CHEMISTRY

June and was found to be 5 to 10 times greater than the ammonium input from barge-dumped sludge from a typical two-day period in July. During the April bloom, the rate of phytoplankton uptake and the effect of fresh water dilution were found to decrease the NH4 concen tration a similar amount in the transect. The Hudson River plume was observed to be a persis tent year-round feature near the New Jersey shore and was responsible for the advection of large amounts of chlorophyll a into the Bight. +

Literature

Cited

(1) Pomeroy, L. R., Annual Review of Ecology and Systematics, (1970) (2) Stewart, W. D. Biochemistry," University of California Press, Berkeley, California, 1974. (3) Ryther, J. H., Dunstan, W. Μ., Science, (1971) 171 1008-1013. (4) Interstate Sanitation Commission, "1974 Annual Report," 10 Columbus Circle, New York, New York, 1975. (5) Interstate Sanitation Commission, "Combined Sewer Overflow Study for the Hudson River," 10 Columbus Circle, New York, New York, 1972. (6) Duedall, I. W., O'Connors, Η. Β., Parker, J. Η., Wilson, R., Robbins, Α., "The Seasonal and Tidal Distribution of Nutrients and their Fluxes in the New York Bight Apex," Manuscript in Preparation. (7) Kao, A., "A Study of the Current Structure in the Sandy Hook-Rockaway Point Transect," M. S. Research Paper, Marine Sciences Research Center, State University of New York, Stony Brook, New York, In Preparation. (8) Water Resources Data for New York, "Part 2. Water Quality Records," U. S. Geological Survey, Albany, New York, 1972. (9) Duedall, I. W., Unpublished data. (10) Giese, G. L., Barr, J. W., "The Hudson River Estuary," Bulletin 61, Conservation Department, Water Resources Commission, Albany, New York, 1967. (11) Jeffries, H. P., Limnology and Oceanography, (1962) 7 21-31. (12) Patten, B. C., "The Diversity of Species in Net Phytoplankton of the Raritan Estuary," Ph.D. Thesis, Rutgers University, New Brunswick, New Jersey, 1959.


39.

OCONNORS

AND

DUEDALL

Impacts of Ammonium

663

(13) U. S. Coast and Geodetic Survey, "Tidal Current Charts, New York Harbor," 7th Edition, ESSA, Rockville, Maryland, 1956. (14) Ketchum, B. H., Redfield, A. C., Ayers, J. C., "The Oceanography of the New York Bight," Papers in Physical Oceanography and Meteorology, Mass achusetts Institute of Technology and the Woods Hole Oceanographic Institution, Cambridge and Woods Hole, Massachusetts, 1951. (15) Redfield, A. C., Walford, L. Α., "A Study of the Disposal of Chemical Waste at Sea," National Academy of Sciences-National Research Council, Washington, D. C., 1951. (16) Baylor, E. R., Hardy, C. D., Moskowitz, P., "Bottom Drift over New York Bight," (17) Pararas-Carayannis, G., "Ocean Dumping in the New York Bight: An Assessment of Environmental Studies," Technical Memorandum No. 39, Coastal Engineering Research Center, U. S. Army Corps of Engineers, Fort Belvoir, Virginia, 1973. (18) Duedall, I. W., Bowman, M. J., O'Connors, H. B., Estuarine and Coastal Marine Science, In Press. (19) Ocean Dumping Criteria, Federal Register No. 94, (1973), 38 12872-12877. (20) Bowman, M. J., "Pollution Prediction Model of Long Island Sound," Ocean Engineering III, American Society of Civil Engineers Specialty Conference, Newark, Delaware, June 9-12, 1975. In press. (21) Goering, J. J., "The Role of Nitrogen in Eutrophic Processes," In: Water Pollution Microbiology, ed., R. Mitchel, John Wiley and Sons, Inc., New York, New York, 1972.


40 The Dynamics of Nitrogen and Phosphorus Cycling in the Open Waters of the Chesapeake Bay J A M E S J. M C C A R T H Y

Department of Biology, Harvard University, Cambridge, Mass. 02138 W. ROWLAND TAYLOR and JAY L. TAFT Chesapeake Bay Institute, The Johns Hopkins University, Baltimore, Md. 21218 The use of radioisotopes investigations of plankton is now widely practiced. The introduction of the C technique to measure phytoplankton photosynthesis (1) revolutionized the study of aquatic primary productivity. The use of P in plankton studies has received less attention (2,3,4), and more recently N has proven to be a useful tool (5,6). The literature of the last two decades which includes various applications of these isotopes in studies of aquatic biology is heavily burdened by discussions of problems in experimental design and data interpretation (7,8,9,10). in general the application of such techniques to aquatic biology has progressed more slowly than in other fields of study, and ecologists have been criticized (11) for their naive and often erroneous use of isotopes in studies of transfer processes within aquatic ecosystems. Recently, innovative applications of isotope tracer studies to plankton nutrition have included tritiated substrates in the study of heterotrophy (12) and Si (13) and Ge (14)in the study of the silicious nutrition of diatoms. D i r e c t and i n d i r e c t evidence supports t h e c o n t e n t i o n t h a t n i t r o g e n i s o f t e n the element most l i k e l y t o l i m i t p l a n t prod u c t i v i t y i n the sea (15,16,17). I n a d d i t i o n , s t u d i e s o f t h e nitrogenous n u t r i t i o n o f plankton a r e a t t r a c t i v e i n t h a t n i t r o gen provides perhaps the s i m p l e s t p e r s p e c t i v e from which t o view a m a t e r i a l balance i n a p l a n k t o n i c ecosystem. Whereas c e l l u l a r n i t r o g e n i s p r i m a r i l y bound i n s t r u c t u r a l m a t e r i a l , b o t h carbon and phosphorus a r e l a r g e l y i n v o l v e d i n c e l l u l a r metabolic a c t i v i ties i naddition to their structural roles. Blue-green algae capable o f f i x i n g gaseous n i t r o g e n a r e c o n s i d e r a b l y more common i n fresh-water than i n t h e sea and p a r t i a l l y because of t h i s , the a v a i l a b i l i t y o f n i t r o g e n i s considerably less l i k e l y to regulate plant productivity i n freshwater. Phosphorous i s f r e q u e n t l y looked t o as the most important n u t r i e n t i n both the r e g u l a t i o n o f p r o d u c t i v i t y and l i m i t a t i o n o f biomass i n fresh-water and the open waters o f e s t u a r i e s 32

15

29

68

664


40.

M C C A R T H Y

ET

AL.

Nitrogen

and

Phosphorus

Cycling

665

(18) . In most natural waters dissolved combined nitrogen i s present i n more than a single form. Concentrations of nitrate, n i t r i t e , and ammonium i n the sea vary temporally and spatially (19) and recently, urea has been reported from a l l areas which have been investigated (20,21,22^,23). Amino acids are usually detected (24,25), and although the concentrations are always low, they may at times contribute to phytoplankton nitrogenous nutrition (26,27). Although we know what forms of combined inorganic nitrogen do and do not commonly exist i n the sea, we are largely ignorant of the identity, origin, and fate of a sizeable pool of dissolved organic nitrogen. This material i s temporally and spat i a l l y ubiquitous (27,28,29) and the implication i s that the bulk of i t i s highly refractor gal nitrogenous nutritio The a v a i l a b i l i t y of labeled forms of the plant nutrients thought to be of greatest importance, enables one to assess the relative significance of several forms of nitrogen i n the n u t r i tion of natural plankton assemblages. A few océanographie laboratories i n this country now have the capacity to rapidly process plankton samples for 1 % enrichment, and the recent a v a i l a b i l i t y of optical emission spectrometers may greatly extend the use of N i n plankton studies. Shipboard studies with large volume cultures established by enriching natural seawater with nutrients have demonstrated that estimates of phytoplankton assimilation derived from short interval measurements of 15

15H

uptake agree closely with measurements of both the decrease i n dissolved nitrogenous nutrient and increase i n particulate nitrogen (30). Field studies of nitrogen fixation have also employed " Ν (5), but the acetylene reduction assay for nitrogenase a c t i v i t y (31) i s far more convenient and i t has become widely accepted as the method of choice. Because of the low natural concentrations of some of the phosphorous and nitrogenous forms of interest, experiments must be initiated quickly. In most cases phytoplankton activity i s measured after removal of the zooplankton; such removal certainly reduces the natural supply of the rapidly recycled forms of both phosphorus and nitrogen to the captured phytoplankton. With zooplankton inclusion, phytoplankton are consumed during the experiment, animal metabolites are released, and the inter pretation of data i s immensely complicated. Since ambient sub strate levels should be determined before the i n i t i a t i o n of an experiment, there has been much interest i n improving the capa city to quantitate phosphorous and nitrogenous nutrients with specific, accurate, precise, and convenient methodology. Most of the techniques of choice are described in both manual and automated forms by Strickland and Parsons (1972) (32). We have streamlined these manual methods to permit us to rapidly process 5ml samples with both precision and sensitivity which exceeds


666

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those o f the automated methods. A small number o f samples can be r o u t i n e l y analyzed by a s i n g l e a n a l y s t f o r n i t r a t e , n i t r i t e , ammonium, urea, and s o l u b l e r e a c t i v e phosphate w i t h i n one h a l f hour a f t e r sample c o l l e c t i o n . In the study o f plankton n u t r i t i o n one has to s e l e c t an i n c u b a t i o n technique which best s u i t s the p a r t i c u l a r problem under i n v e s t i g a t i o n . An i n s i t u i n c u b a t i o n i n v o l v e s the c o l l e c t i o n o f a water sample, enclosure i n a s u i t a b l e b o t t l e , a d d i t i o n of isotope t r a c e r m a t e r i a l , and resuspension o f the b o t t l e to the depth from which the sample was c o l l e c t e d . The o b j e c t i v e i s t o execute the i n c u b a t i o n a t near n a t u r a l l i g h t and temperat u r e . C a r e f u l and r a p i d handling a r e r e q u i r e d to minimize physiol o g i c a l shock which may r e s u l t from exposure o f deep water samples to both f u l l i n c i d e n t s o l a r i r r a d i a t i o n and great changes i n temperature. Any p o t e n t i a t i a l s a r e u s u a l l y ignored f e c t e d with a s i n g l e u n i t which captures, i n o c u l a t e s with materi a l o f choice (e.g. isotope s t o c k s ) , and serves as an i n c u b a t i o n chamber (33). A f t e r the completion o f the i n c u b a t i o n the chamber i s brought to the s u r f a c e and the sample i s processed. Advantages of such a system a r e obvious, but the disadvantages a r e p r i m a r i l y that f o r n u t r i e n t a s s i m i l a t i o n s t u d i e s one must make isotope t r a cer a d d i t i o n s without s p e c i f i c knowledge o f the ambient n u t r i e n t levels. A l s o , zooplankton which consume phytoplankton and r e l e a s e p l a n t a s s i m i l a b l e forms o f n i t r o g e n and phosphorus cannot be excluded from the i n c u b a t i o n chamber. Because major sea-going v e s s e l s u s u a l l y cannot remain on s t a t i o n s f o r extended p e r i o d s , and there may not be an opportunity to r e t u r n t o a buoy, b i o l o g i c a l oceanographers f r e q u e n t l y use simulated i n s i t u i n c u b a t i o n s . A deckboard incubator i s f i t t e d with o p t i c a l f i l t e r s to simulate l i g h t a t depth o f sampling, and flowing seawater c o n t r o l s temperature. Some o f the problems a s s o c i a t e d with measuring l i g h t and s e l e c t i n g appropriate f i l t e r s have been i n v e s t i g a t e d and discussed (34). The Chesapeake Bay i s a h i g h l y productive c o a s t a l p l a i n estuary with a w e l l defined two-layer c i r c u l a t i o n (35). I t i s approximately 300 km i n l e n g t h and i t i s p r i m a r i l y an estuary o f the Susquehana R i v e r . The n u t r i e n t l o a d i n g r e s u l t i n g from both the Susquehana R i v e r drainage from western Pennsylvania and c e n t r a l New York and the m e t r o p o l i t a n discharges o f the D i s t r i c t of Columbia and Baltimore, Maryland, a r e p o t e n t i a l l y l a r g e . I t i s indeed i n t e r e s t i n g to note i n the data presented by Carpenter, P r i t c h a r d , and Whaley (1969) (36), that the e f f e c t o f n u t r i e n t l o a d i n g from the adjacent m e t r o p o l i t a n areas i s v i r t u a l l y undet e c t a b l e as d i s s o l v e d i n o r g a n i c n u t r i e n t i n the Bay proper below both Baltimore and the j u n c t i o n o f the Potomac River w i t h the Bay. I t has been demonstrated that the heavy w i n t e r - s p r i n g r u n o f f from the Susquehana River i s the primary source o f n i t r a t e i n the Bay, but no p o i n t sources f o r e i t h e r ammonium o r phosphate can be i d e n tified.


40.

M C C A R T H Y

ET

AL.

Nitrogen

and

Phosphorus

Cycling

667

Data from some coastal regions, such as for Buzzards Bay, Massachusetts, suggest that transport of nitrogen remineralized in the sediment i n t e r s t i t i a l water to the overlying water may contribute significantly to the phytoplankton nitrogen requirement (37). In another study, v e r t i c a l transport from the sand bottom off La J o l l a , California, was shown to provide an insignificant portion of the nitrogen u t i l i z e d by the phytoplankton in the overlying water (38). Carpenter, Pritchard, and Whaley (1969) (36) concluded from calculated v e r t i c a l exchange rates for spring and summer that the transport of dissolved nitrogen and phosphorus from the sediments into the euphotic zone was insufficient to account for more than a few per cent of the approximated rates of phytoplankton nutrient utilization.More recently, Bray, Bricker, and Troup (1973) (39) calculated that upward diffusive flux acros the Chesapeake Bay woul the total orthophosphate in the water column. This i s considerably less than the rate at which phytoplankton remove phosphorus from the euphotic zone of the Bay (40). It can be seen, therefore, that the observations relating to nutrient a v a i l a b i l i t y and plankton biomass i n the Chesapeake Bay are apparently paradoxical: High phytoplankton standing stocks and high phytoplankton productivity persist i n the presence of low ambient levels of dissolved inorganic nitrogen and phosphorus throughout much of the year. The short-term temporal s t a b i l i t y in these patterns suggests an equilibrium i n the biological and chemical processes, and Carpenter, Pritchard, and Whaley (1969) (36) hypothesized that the productivity of the open waters of the Chesapeake Bay i s regulated largely by a dynamic nutrientphytoplankton-zooplankton-nutrient cycle. Our i n i t i a l efforts to stimulate primary productivity by enriching natural water samples from various locations within the Chesapeake Bay were unsuccessful. The results clearly demonstrated the unsuitability of the nutrient enrichmentincubation technique i n the investigation of a highly dynamic planktonic ecosystem, and supported the hypothesis that only through short-term isotope tracer experiments could one come to an understanding of the plankton nutrition i n this estuary. The phytoplankton may grow at rates sufficient to double their biomass i n one or two days and yet such increases i n biomass are rarely observed i n the Bay. In fact, with the exception of localized blooms, the phytoplankton standing stock varies only by approximately a factor of 5 in the entire main body of the Bay throughout an annual cycle. Consider further a summer condition of nearly constant low levels of plant nutrients i n waters containing a population of small herbivorous zooplankters capable of ingesting 2 to 3 times their body mass daily, and one can begin to appreciate both the dynamic nature of estuarine planktonic communities and the great effort required to investigate their nutrition.


668

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CHEMISTRY

What f o l l o w s i s a d e s c r i p t i o n of our recent e f f o r t to study the plankton n u t r i t i o n i n the Chesapeake Bay w i t h i s o t o p e t r a c e r techniques. This program remains i n progress, and most of our r e s u l t s to date are e i t h e r i n press or i n a s t a t e of p r e p a r a t i o n . Our i n t e n t i o n here i s to demonstrate through a preview of some of our data the u t i l i t y of i s o t o p e t r a c e r s i n developing a dynamic image of plankton n u t r i t i o n which permits i n s i g h t i n t o the mech anisms by which p l a n k t o n i c p r o d u c t i v i t y i s r e g u l a t e d . We conducted a s e r i e s of 7 c r u i s e s of 2 weeks d u r a t i o n and a t 6 week i n t e r v a l s to sample and study 8 g e o g r a p h i c a l l y f i x e d s t a t i o n s i n the open waters of the Chesapeake Bay and one s t a t i o n on the adjacent c o n t i n e n t a l s h e l f (Figure 1 ) . N u t r i e n t measure ments were made and experiments were i n i t i a t e d to q u a n t i t a t e pbytoplankton i n c o r p o r a t i o n r a t e s f o r carbon, n i t r o g e n , and phos phorus. Numerous othe measurements were made f o r a d d i t i o n a l experiments. Each s t a t i o n r e q u i r e d a f u l l day of e f f o r t . With the exception of the p r e v i o u s l y mentioned modi f i c a t i o n s , a l l shipboard a n a l y t i c a l methods f o l l o w e d the proce dures o u t l i n e d by S t r i c k l a n d and Parsons (1972) (32). A l l n u t r i e n t , biomass, and n u t r i e n t uptake r a t e measurements which w i l l be reported are averages of two samples from d i f f e r e n t depths i n the euphotic zone, and they are considered to be r e p r e s e n t a t i v e of the upper l a y e r of the estuary. The near constancy of c h o r o p h y l l a_ c o n c e n t r a t i o n s ( h e r e a f t e r r e f e r r e d t o as c h l o r o p h y l l ) w i t h depth i n the p r o f i l e s throughout the upper l a y e r supports the n o t i o n t h a t t h i s l a y e r , and l i k e w i s e the euphotic zone, i s w e l l mixed. In order to minimize the e f f e c t o f any s m a l l s c a l e inhomogeneities, a l l i n d i v i d u a l measurements were made w i t h m a t e r i a l c o l l e c t e d i n a composite sample (the contents of 6 Van Dorn b o t t l e s which were c a s t to the same depth were mixed and a l i q u o t s were withdrawn). C l a b e l e d carbonate, 32p l a b e l e d phosphoric a c i d , and l^N l a b e l e d n i t r a t e , n i t r i t e , ammonium, and urea were added to separ ate b o t t l e s and each was incubated on the deck of the s h i p under simulated i n s i t u c o n d i t i o n s . At the t e r m i n a t i o n of the e x p e r i ments |jje p a r t i c u l a t e m a t e r i a l was analyzed f o r i s o t o p i c e n r i c h ment. C and Ρ were determined by l i q u i d s c i n t i l l a t i o n spectro metry and Ν by mass spectrometry. The d i s s o l v e d organic phos phorus and d i s s o l v e d polyphosphate were a l s o examined f o r e n r i c h ment, and s i m i l a r measurements f o r d i s s o l v e d organic carbon and n i t r o g e n are p a r t of our c o n t i n u i n g program. Because of the frequent c o n d i t i o n of low n u t r i e n t s , h i g h biomass, and hence r a p i d turnover of a v a i l a b l e n u t r i e n t , i n c u b a t i o n s were of o n l y a few hr d u r a t i o n a t midday and e x t r a p o l a t i o n s to d a i l y r a t e s were made using o c c a s i o n a l 24 h r sequences of short i n c u b a t i o n s . The d i s t r i b u t i o n of p l a n t biomass, as c h l o r o p h y l l , i s r a t h e r s u r p r i s i n g l y uniform i n the main body of the Chesapeake Bay (Figure 2 ) . In A p r i l and June higher biomass was observed i n the v i c i n i t y of the Potomac R i v e r discharge, and i n June and


Figure 1.

Location of the Chesapeake Bay and station positions


670

MARINE

CHEMISTRY

August higher biomass was observed below Baltimore. But i n general, there i s l i t t l e temporal or spatial heterogenity: > 50% of the chlorophyll values were between 10 and 20 /ig*liter , and 90% were between 5 and 25 ug«liter*" . The cause of the increased biomass below Baltimore may be the result of greater nutrient a v a i l a b i l i t y , but there i s not evidence for this i n either the nitrogen or phosphorus data throughout most of the year. There i s sufficient nitrogen i n this region to support a greater plant biomass than i s observed and, as demonstrated by Taft, Taylor, and McCarthy (1975) (40), there i s no apparent relationship between plant biomass and soluble reactive phosphorus. The same conclusions with respect to nitrogen and phosphorus apply to the area immediately below the Potomac River i n August when compared to the stations further north. There are numerou association of higher plan the discharges of Baltimore and D i s t r i c t of Columbia, and some of the more obvious include: greater a v a i l a b i l i t y of minor nutrients; unidentified stimulating material associated with the discharge of the metropolitan wastes; less herbivorous grazing potential which may or may not be related to the discharges; and reduced thickness of the near surface mixed layer. We have no data to permit evaluation of hypotheses concerning minor nutrients and other stimulating materials. It would be exceedingly d i f f i c u l t to detect the small reduction in herbivorous grazing potential which could within a few days result i n plant biomass increases comparable to those observed. The pycnocline was quite shallow below Baltimore i n August, and we are further evaluating the relationship of both phytoplankton biomass and phytoplankton productivity on a volume basis to thickness of both the upper mixed layer and the euphotic zone. McCarthy, Taylor and Loftus (1974) (41) demonstrated that throughout the Chesapeake Bay and over an annual cycle,approximately 90% of both the biomass and the productivity of the phytoplankton community i s found in the unicellular forms which pass 35 pm mesh. There are well documented occurences of algal blooms of moderate proportions i n the Chesapeake Bay. During our study a major v i s i b l e bloom was never identified on our regular stations. Loftus, Subba Rao, and Seliger (1972) (42) followed the development and dissipation of a bloom which appeared i n the open Bay near the Severn River following an intensive rain storm. Their data demonstrate that for the portion of the bloom i n the Bay proper there was never adequate nitrogenous nutrient available to permit more than a fractional doubling of plant biomass (1-13%). Therefore,with nutrient limited growth, the bloom was either doomed to dissipate through physical forces or sufficient nutrient had to be delivered through rapid recycling processes within the bloom. Oxytoxum sp. was the dominant phytoplankter and the dominant herbivore, a r o t i f e r (Euchlanis sp.), reached densities of 10^ individuals- l i t e r . They - 1

1

- 1


40.

M C CARTHY

ET

AL.

Nitrogen

and

Phosphorus

Cycling

671

demonstrated that this density of Euchlanis sp. could almost totally^consume maximum observed bloom phytoplankton densities (4 χ 10 /ig c h l o r o p h y l l ' l i t e r " ) in 12 hr. A r o t i f e r of similar size (Brachionus sp.) ingests 3 times i t s mass per day (43), and i t can be concluded that the high metabolic rate per unit biomass for such small zooplankters would result i n considerable return of ingested nitrogen and phosphorus to the water i n dissolved forms. Time permits the consideration of only a single cruise i n any detail, and we have chosen to discuss PROCON 10 of June 1973. It represents an extreme in chlorophyll variations along the major axis of the Bay, and i t demonstrates the preferential algal u t i l i z a t i o n of the more reduced and rapidly recycled forms of nitrogen i n the presence of high concentrations of NO^. Time course measurement incubation of a few hour occurred i n i t i a l l y at a rapid rate which could not, from compari sons with photosynthesis as measured by fixation, be equated with net uptake associated with growth (40). The subsequent phase of reduced uptake can however, with a few exceptions be shown to approximate phytoplankton synthesis of new cellular material. Table I and Figure 3 demonstrate this phenomenon. 1

TABLE I.

ATOMIC RATIO OF CARBON TO PHOSPHORUS UPTAKE (40) Initial Subsequent Station Phase Phase 834G 818P 744 724R 7070 0707V

0.16 0.001 0.001 0.002 0.015 0.45

44 28 60 88 410 6

From the laboratory culture data of Parsons, Stephens, and Strickland (1961) (44), one can calculate atomic ratios for carbon to phosphorus composition of marine phytoplankton which were grown in a phosphorus sufficient medium. For 8 phytoplankters the values ranged from 28 to 102 and had a median of 81. A phosphorus deficient natural phytoplankton population existing in a medium which contains a low constant level of orthophosphate (and no alternate source of phosphorus) would be expected to have less intracellular phosphorus than phytoplankton i n a phosph orus sufficient medium (45). The well documented phytoplankton "luxury uptake" of orthophosphate (46) complicates efforts to make meaningful extrapolation from short-term rate measurements. That i s to say, that even after taking into consideration the above mentioned dual phase uptake, rate measurements for the second phase may s t i l l suggest greater net uptake per unit time than can be reasonably anticipated from independent estimates of



Η

Chlorophyll g /zg-literH

I , 1

Figure 2. Chlorophyll concentration in the Chesa peake Bay from December 1972-December 1973

0707V

707 0

724 R

744

804 C

818 Ρ Η

Θ34 G

854 F

904 Ν

JL__J

8-

0

ÎOÔ

J

200

32

300 ' 400 ' 500 TIME, MINUTES

« L

1973

I—'—Γ

STATION 724 R, JUNE

' 600

' 70C

Figure 3. Uptake of P orthophosphate into the particulate fraction with time, after Ref. 40.

2

g α 2 ρ

È 61

2

10

20

τ—·—Γ

40.

M C C A R T H Y

ET

AL.

Nitrogen and Phosphorus Cycling

673

phytoplankton growth. If the algae are phosphorus stressed as a result of lengthy exposure to medium with lower than usual levels of orthophosphate, and sufficient phosphorus suddenly be comes available, an extremely rapid uptake would be expected i n the second phase. Such a stress would result i n a low carbon to phosphorus uptake value such as that observed at station 0707V (Table 1). Conversely, ample intracellular stores of phosphorus could support high rates of algal carbon fixation concurrent with very slow phosphorus uptake resulting i n a high carbon to phosph orus uptake ratio such as that observed at station 7070 . Stations 7070 and 0707Vwere anomalous in other respects as well. The high specific activity of 32p preparations permits one to make estimates of uptake without measurably increasing the orthophosphate i n the medium (radioactive isotope additions con tributed

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