Atmospheric pollution 1980, Volume 8: Proceedings of the 14th International Colloquium, UNESCO Building, Paris, France, May 5-8, 1980

ATMOSPHERIC POLLUTION 1980

Studies in Environmental Science Volume 1 Atmospheric Pollution 1978 Proceedings of the 13th International Colloquium, held in Paris, April 25-28,1978 edited by M.M. Benarie Volume 2 Air Pollution Reference Measurement Methods and Systems Proceedings of the International Workshop, held in Bilthoven, December 12-16,1977 edited by T. Schneider, H.W. de Koning and L.J. Brasser Volume 3 Biogeochemical Cycling of Mineral-Forming Elements edited by P.A. Trudinger and D.J. Swaine Volume 4 Potential Industrial Carcinogens and Mutagens by L. Fishbein Volume 5 Industrial Waste Water Management by S.E. Jq5rgensen Volume 6 Trade and Environment: A Theoretical Enquiry by H. Siebert, J. Eichberger, R. Gronych and R. Pethig Volume 7 Field Worker Exposure during Pesticide Application Proceedings of the Fifth InternationalWorkshop of the Scientific Committee on Pesticides of the International Association on Occupational Health, held in The Hague, The Netherlands, October 9-1 1, 1979 edited by W.F. Tordoir and E.A.H. van Heemstra-Lequin

Studies in Environmental Science 8

ATMOSPHERIC POLLUTION 1980 Proceedings of the 14th InternationalColloquium, UNESCO Building, Paris, France, May 5-8,1980 Organised by the lnstitut National de Recherche Chimique AppliquGe, Vert-le-Petit, France, in associationwith the Commission on Atmospheric Environment of the International Union of Pure and Applied Chemistry (IUPAC) edited by

Michel M. Benarie Titular Member of the Commission on Atmowheric Environment of IUPAC

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Library of Congress Cataloging in Publication Data

International Colloquium on Atmospheric Pollution, l b t h , P a r i s , 1980. Atmospheric pollution 1980. (Studies i n environmental science ; 8 ) 1. Air--Pollution--Congesses. I. Benarie, Michel M. 11. Paris. I n s t i t u t national de recherche chimique appliquce. 111. InternatiDnal Union of Pure and Applied Chemistry. Conmission on Atmospheric Euvironment. N, T i t l e . V. Series. TD881.1555 1980 363.7’392 80-12833

ISBN 0-444-41889-x

(U.S. ) (Netherlands)

ISBN C444-41889-X (Val. 8 ) ISBN: 044441696-X (Series) 0 Elsevier Scientific Publishing Company, 1980 All rights reserved. N o part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publisher, Elsevier Scientific Publishing Company, P.O. BOX330, 1000 A H Amsterdam, The Netherlands Printed in The Netherlands

V

PREFACE This volume c o n t a i n s a s e l e c t i o n o f t h e 81 papers presented a t the 14th I n t e r n a t i o n a l Colloquium on Atmospheric P o l l u t i o n h e l d i n P a r i s , UNESCO B u i l d i n g , from t h e 5 t h t o 8 t h May 1980. Organized every second year; o u r Colloquium has t h e aim o f covering a very wide area i n t h e f i e l d o f a i r p o l l u t i o n . We a l r e a d y s t a t e d i n t h e Prefaces o f previous r e p o r t s o f t h i s s e r i e s t h a t t h e volume i s purposedly heterogeneous. We i n t e n d t o show "what i s on" i n a i r p o l l u t i o n , i n a somewhat d i f f e r e n t way than i s usual i n the e s t a b l i s h e d s c i e n t i f i c j o u r n a l s . The purpose o f a colloquium r e p o r t i s d i f f e r e n t . A rough analogy o f t h e d i f f e r e n c e can be given as f o l l o w s . The s c i e n t i f i c j o u r n a l i s e q u i v a l e n t t o t h e s p e c i a l i z e d r e t a i l trade, w i t h i t s e s t a b l i s h e d and guaranteed brands, i t s l e i s u r e l y t i m i n g s , and so on. A colloquium r e p o r t i s modelled on t h e stock exchange, and i t s h e c t i c d e a l i n g i n stocks which a r e n o t a l l n e c e s s a r i l y b l u e . But t h e advantage o f the stock exchange i s t o e s t a b l i s h r a p i d l y t h e worth o f commodity. But l e t us l e a v e t h e f i e l d o f analogies and models and e x p l a i n t h e d i f f e r e n c e s as we see them. The f i r s t d i f f e r e n c e i s t h e quickness o f r e p o r t i n g . From t h e moment o f w r i t i n g t h e l a s t word of a s c i e n t i f i c paper, i t can take on t h e average 12 months i n a good j o u r n a l b e f o r e t h e f i r s t reader becomes aware o f t h e r e s u l t . The conference r e p o r t has shortened t h e i n t e r v a l between the l a s t word w r i t t e n and t h e f i r s t one read t o a mere four months. Therefore i t s nature i s nearer t o l a b o r a t o r y and i n s t i t u t e ( " g r e y " ) r e p o r t s . Here i s our second p o i n t . As s c i e n t i f i c progress advances these days, as views and scopes change, 12 months i s t o o l o n g f o r p u b l i c a t i o n . Therefore, much o f t h e e f f o r t and r e s u l t s o f research teams go i n t o annual r e p o r t s , s p e c i a l r e p o r t s t o t h e sponsoring agencies, and xeroxed t e x t s o f r e s t r i c t e d a v a i l a b i l i t y , i n a c c e s s i b l e t o a f r a c t i o n of t h e s c i e n t i f i c community and inadequately indexed by a b s t r a c t s . Some end up published, o t h e r s n o t . By o f f e r i n g s i m i l a r delays as t h e "grey" c i r c u l a t i o n , b u t a t t h e same time a g r e a t e r d i f f u s i o n , an adequate awareness v i a t h e i n d e x i n g and a b s t r a c t i n g s e r v i c e s and j o u r n a l s , we t h i n k t h e p u b l i c a t i o n should be o f r e a l use t o t h e s c i e n t i f i c community. This s h o r t e n i n g o f t h e delay has been made p o s s i b l e by an increased e d i t o r i a l e f f o r t , aided by a s p e c i a l g o o d w i l l o f t h e team i n charge a t t h e p u b l i s h i n g house and, l a s t l y , by l e s s e d i t o r i a l i n t e r f e r e n c e than i s usual w i t h s c i e n t i f i c j o u r n a l s .Instead o f m a i l i n g o u t t h e t e x t s f o r r e f e r e e i n g , two stages o f s e l e c t i o n have taken p l a c e on panel b a s i s . F i r s t t h e a b s t r a c t s and then the t e x t s were

VI

appraised. B u t the final assessment will be made by the reviewers, by the whole readership of the volume. This i s the t h i r d difference with the s c i e n t i f i c journals, where a f t e r acceptance by two referees, a "good brand" of research i s being offered t o the reader. And here the "stock exchange model" becomes useful. Official financial support, on which so much research nowadays depends, does not necessarily reach the s c i e n t i f i c a l l y most prominent, original , or competent workers. Here we p u t into the limelight pertinent research together with the inconsequential ; the creative together with the more routine report. Thus we hope t o raise the awareness of b o t h concerned parties: t h a t which allocates the funds and t h a t which uses them. In t h i s way we hope t o improve the cost-effectiveness of research funding. The usual weeding out by refereeing i n s c i e n t i f i c journals encourages the strong, b u t a t the same time, overprotects the weak. By not being publicly compared, by leaving the l e s s worthy a c t i v i t y i n the benevolent shade of the internal reports, a l o t of rather below-average research i s l e f t t o thrive on public funds, t h u s depriving others, m r e deserving, from t h i s benefit. In t h i s volume before you, readers are asked t o judge each paper on i t s own merits, independently from the past laurels of the laboratory o r other non-scientific considerations. W e see an added benefit i n the f a c t t h a t some papers rejected by journal referees may nevertheless contain valuable information. If t h i s i s relegated to some obscure "grey" report, the e f f o r t will sometimes be duplicated -t h a t much e f f o r t wasted. The authors have been asked t o keep their papers short. This may be astonishing a t a time when sponsoring agencies often evaluate research reports by t h e i r volume. B u t a well formulated, well executed endeavour can be related adequately i n n o t more than a few pages. Alas, n o t every paper i s equal t o Einstein's essay on general r e l a t i v i t y , which had a mere f i v e pages, b u t this k i n d of result-to-length r a t i o would be the ideal one. Without daring to say t h a t a l l long papers are necessarily bad, we may s t a t e that most of them would g a i n a l o t by being l e s s rambling and d i r e c t l y and clearly reporting the f a c t s . A short paper i s e i t h e r good as i t stands, o r lacks something which could be f o r In the l a t t e r case, the paper example, quality, o r i g i n a l i t y , l u c i d i t y , e t c i s bad, and the shorter i s the time the reader losses while browsing through i t . Unfortunately, t h e production process o f t h i s book makes the compilation of a subject index v i r t u a l l y impossible.

...

Michel Benarie

VII

ACKNOWLEDGEMENTS The enormous administrative work necessary for the organisation o f such a colloquium was t h i s time also expertly executed by Mme Monique Thavard, t o whom thanks are expressed herewith.

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IX

CONTENTS

..................................................................

Preface

V

MODELING Models and Modeling A. C. Stern ...........................................................

3

Modeling t h e t r a n s p o r t and d i f f u s i o n of a i r p o l l u t a n t s using a prognostic mesoscale model

R. T. McNider and R. A. Pielke

........................................

P a r t 1: Overview and t r a n s p o r t a t i o n module R. M. Patterson, P . B. Simmon and W. B. Petersen ......................

9

Commuter exposure modeling.

Commuter exposure modeling.

P a r t 11: Emissions and dispersion modules and

generation o f exposure s t a t i s t i c s P . B. Simmon, R. M. Patterson and W . B. Petersen APT

- A

13

......................

19

computer program f o r the numerical s o l u t i o n o f problems i n

atmospheric dispersion A. J . H. Goddard, A. Ghobadian, A. D. Gosman, C . Harter and G . D. Kaiser

25

The t r a n s p o r t , chemical transformation, and removal of SO2 and s u l f a t e i n t h e Eastern United S t a t e s G. R. Carmichael and L. K. P e t e r s .....................................

31

The atmospheric impacts o f evaporative cooling systems

J . E. Carson

..........................................................

37

Improvement of mathematical models f o r plume r i s e and d r i f t deposition from cooling towers

A. J . P o l i c a s t r o , R. A. Carhart, M. Wastag, S. Ziemer, K. Haake, W. E. Dunn and P. Gavin ...............................................

43

X The simple box model simplified M. M. Benarie

.........................................................

49

GAUSSIAN PLUME

Sensitivity analysis o f the gaussian plume model G. Neumann and G. Halbritter ..........................................

57

Development of a gaussian plume model appropriate t o an urban area

M. Bennett

............................................................

63

AIRFLOW AND DISPERSION

Physical theories o f turbulent diffusion B. E. A. Fisher

.......................................................

Dispersion experiments from the 213 m high meteorological mast a t Cabauw in the Netherlands H. van Duuren and F. T. M. Nieuwstadt

71

.................................

77

.....................................................

91

Dispersion around buildings

P. J . H . Builtjes

A carbon monoxide dispersion experiment in a built-up area H. Kolb, H. Mohnl, U. Pechinger and R. Werner

.........................

97

Real-time prediction of local wind by means of stochastic models C. Bonivento, G. Fronza and A. Tonielli

...............................

Air p o l l u t i o n impact in s t r e e t s with heavy t r a f f i c and the e f f e c t s of the dominant parameters H . Sobottka

...........................................................

105

109

ANALOG MODELING

Wind tunnel modelling of buoyant emissions

A. G. Robins

..........................................................

117

Flue gas dispersion in the vicinity of buildings: wind tunnel simulation and comparison with f i e l d measurements H. Sommers, J . Hoitz and R. Haupt

.....................................

125

XI

Comparison o f wind tunnel and f u l l s c a l e measurements t o i n v e s t i g a t e t h e d i s p e r s i o n o f v e h i c l e exhaust gases

P. Leisen

.............................................................

131

Use o f a water-analog model t o determine t h e optimum l a y o u t o f a highc a p a c i t y power s t a t i o n

J . Rigard and M. M i l h e

................................................

137

POLLUTANT FORMATION, TRANSFORMATION AND l'RANSPORT

Regional s c a l e t r a n s p o r t o f f i n e aersol c o n s t i t u e n t s from urban a i r p o l l u t i o n i n Eastern North America

J . W. Winchester, J . W. Nelson, A. C. D. L e s l i e , M. Darzi, L. C. S. Boueres and S. E. Bauman

.....................................

147

Atmospheric t r a n s p o r t o f p a r t i c u l a t e sulphate and ozone i n t o the Toronto r e g i o n and i t s c o r r e l a t i o n w i t h v i s i b i l i t y

K. G. Anlauf, M. Olson, H. A. Wiebe and M. A. Lusis

...................

153

A study o f t h e t r a n s p o r t o f t r a c e metals and s u l f u r i n t o Scandinavia

H. 0. Lannefors and H. C. Hansson

.....................................

159

Transport o f ozone i n I s r a e l

E. H. Steinberger

.....................................................

165

D i r e c t f o r m a t i o n o f NO2 i n combustion products

W. J . McLean, J. Y. Chen, F. C. Gouldin and M. 3. Oven The r a t e o f NO, C. W. S p i c e r

................

173

r e a c t i o n i n t r a n s p o r t e d urban a i r

..........................................................

181

COMPUTATIONS AND STATISTICAL REPRESENTATIONS

D e s c r i p t i v e a n a l y s i s o f t h e SO2 p o l l u t i o n i n Brussels: seasonal v a r i a t i o n w i t h r e f e r e n c e t o sampling s i t e l o c a t i o n

F. A. S a r t o r

..........................................................

189

The generation o f h o u r l y average wind v e c t o r s u s i n g a Markov process

J . W. Bacon and B. Henderson-Sellers

..................................

195

XI1

An e m p i r i c a l d e s c r i p t i o n o f t h e extreme values o f SO2 c o n c e n t r a t i o n i n an urban area G. Drufuca and M. G i u g l i a n o

..........................................

209

Random sampl ing a g a i n s t continuous m o n i t o r i n g f o r a i r qua1 it y m o n i t o r i n g networks

J . G. Kretzschmar and G. Cosemans

....................................

213

A I R CHEKSTRY AND FORMATION OF PARTICULATE MATTER

Photochemical aerosol f o r m a t i o n i n multi-component system c o n t a i n i n g pre-exi s t i n g p a r t i c l e s

..............................

M. Kasahara, K. Takahashi and S. Tohno

221

I n t e r f a c i a l physicochemical c h a r a c t e r i s t i c s o f a i r b o r n e soot p a r t i c l e s

F. de Wiest and P. M. B r u l l

........................................

227

The e f f e c t o f p a r t i c l e s i z e on t h e e x t e n t o f bromination o f p o l y s t y r e n e 1atex aerosol s

J . A. Spatola and J . W. Gentry

.......................................

233

Aerosol p a r t i c l e s i n a i r w i t h a g r a d i e n t o f h u m i d i t y

H. Straubel

.........................................................

239

Heterogeneous n i t r o g e n o x i d e - p a r t i c l e r e a c t i o n s G. M. Sverdrup and M. R. Kuhlman

....................................

245

P a r t i c u l a t e p o l l u t i o n o f t h e atmosphere due t o l i q u i d hydrocarbon f i r e s Pham Van Dinh and B. Benech

..........................................

249

AEROSOL PHYSICS AND bBASUREMNT CONCERNING THE SUSPENDED PARTICULATE MATTER

Measurement o f p a r t i c l e s i z e d i s t r i b u t i o n s o f f l u e d u s t by means o f cascade impactors

R . Wiedemann

........................................................

Measurement o f aerosols l e s s than 0.01 p m

-

257

a p p l i c a t i o n t o the n u c l e a t i o n

i n t h e atmosphere

M. L. P e r r i n , Y. C. B o u r b i g o t and G. J . Madelaine

....................

267

XI11

On the c o u n t i n g e f f i c i e n c y o f a continuous f l o w condensation n u c l e i counter

Y. Metayer and G. Madelaine R e a l i z a t i o n o f a d u s t tunnel

-

..........................................

273

response o f some a i r sampling instruments

used i n in d u s t r i a1 hygiene

J . F. Fabries and B. Carton

..........................................

279

P r e l i m i n a r y measurements of t h e soot Stokes-Einstein parameters i n an oxygen/acetylene blow-pipe by means o f d i f f u s i o n broadening spectrosCOPY

G. Gouesbet, P. Flament, G. Grehan and M. W e i l l

......................

285

The generation and measurement o f primary soot aerosols between 50 and

400

8, Y. 0. Park, J

C a r o l l a and J . W . Gentry

..............................

291

I n s i t u c h a r a c t e r z a t i o n o f soot aerosols by s c a t t e r i n g and absorption o f a l a s e r beam

J. Lahaye and

G. Prado

...............................................

297

The development o f t h e GCAF i n e r t i a l impactor f o r s e p a r a t i o n o f non-spherical p a r t i c l e s S. L i n , R. Preston and

J. W. Gentry

..................................

303

New i n e r t i a l p a r t i c l e s i z e c l a s s i f i c a t i o n techniques f o r aerosol sampling and measurement K. W i l l e k e , R. E. P a v l i k , W. C. Friedman, S. A. Haberman

J. D. Blanchard and

.......................................................

309

Some s p e c i a l problems concerning asbestos f i b e r p o l l u t i o n i n ambient a i r K. R. Spurny, W.

Stober, G. Weiss and H. Opiela

......................

315

Comprehensive methods f o r r a p i d q u a n t i t a t i v e a n a l y s i s o f a i r b o r n e p a r t i c u l a t e s by o p t i c a l microscopy, SEM and TEM w i t h s p e c i a l reference t o asbestos G. B u r d e t t , J . M. l e Guen, A. P. Rood and 5. J . Rooker

...............

323

Some a p p l i c a t i o n s o f t h e “ J e t i m e t e r ”

J. C. Guichard, A. G a i l l a r d and M. Lamauve

...........................

339

XIV MONITORING NETWORKS AND SURVEY RESULTS

The design of a i r quality monitoring networks u s i n g an information content measure E. E. Pickett and R. G. W h i t i n g ......................................

347

The Canadian a i r and precipitation monitoring network APN L. A. Barrie, H. A. Wiebe, K. Anlauf and P. Fellin ...................

355

Ambient a i r pollution from industrial sources M. J . Suess ..........................................................

361

Measurements of atmospheric e l e c t r i c a l parameters near an industrial plant - influence o f ionized plumes on the e a r t h ’ s e l e c t r i c a l f i e l d 0. Laurent and R. Peyrous ............................................

365

A comparison of v i s i b i l i t i e s in polluted and unpolluted areas H. Horvath

371

Relationship between c i t i z e n complaints of a i r pollution, meteorological data and immission concentrations J . E. Evendijk, P. J . W. M. Miiskens and T. J . R. M. de Jong ..........

379

Building ventilation and indoor a i r quality C. D. Hollowell, J . V. Berk, M. L. Boegel, R. R. Miksch, W. W . Nazaroff and G. W. Traynor

387

Measurement of nitrosamines i n the a i r of Paris by thermal energy analysis B. T. Chuong and M. Benarie ..........................................

397

Performances of a piezoelectric p a r t i c l e mass monitor J . Paulou ............................................................

401

...........................................................

.....................................

EFFECTS: ON MAN AND ON VEGETATION

The exposure of human populations t o a i r pollution R. E. Munn ...........................................................

409

xv Monitoring of the a i r quality by analysis of biological indicators and accumulators R. A. Impens, T. P i r e t , G. Kooken and A. Benko .......................

417

Patterns of fluoride accumulation in Boreal f o r e s t species under perennial exposure t o emissions from a phosphorus plant S. S. Sidhu ..........................................................

425

Contamination of edible parts of seven plant crops and s o i l s by heavy metals in urban area by a i r pollution i n Alexandria d i s t r i c t , Egypt I . H. Elsokkary ......................................................

433

Author index

.............................................................

439

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MODELING

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Atmospheric Pollution 1980, Proceedings of the 14th International Colloquium, Paris, France, May 5--8,1980, M.M. Benarie (Ed.), Studies in Environmental Science, Volume 8 0 Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands

3

MODELS AND MODELING ARTHUR C. STERN U n i v e r s i t y o f N o r t h Carolina, Chapel H i l l , N.C.

USA

ABSTRACT The f i r s t hundred years o f a i r p o l l u t i o n modeling, from 1859 t o 1959, i n t r o duced t h e box model f o r urban p o l l u t i o n c o n c e n t r a t i o n and p o i n t source plume models.

I t ended w i t h t h e i n t r o d u c t i o n o f t h e e l e c t r o n i c d i g i t a l computer t o

modeling.

I n t h e n e x t decade, u n t i l 1969, urban models more s o p h i s t i c a t e d than

t h e box model became o p e r a t i o n a l and p o i n t source models f o r l e v e l t e r r a i n came t o maturity.

I n t h e most r e c e n t decade, t o 1979, new modeling concepts have been

introduced, keeping pace w i t h enhanced computer c a p a b i l i t y and speed; models have been developed f o r complex t e r r a i n and f o r chemical r e a c t i o n s among p o l l u t a n t s , and t h e r e has been i n t e n s i v e o p e r a t i o n a l use o f models.

THE FIRST HUNDRED YEARS

-

1859-1959

Gerald De M a r r a i s ' H i s t o r y o f A i r P o l l u t i o n Meteorology through 1969' t e l l s us t h a t f i r s t computation o f p r e d i c t e d p o l l u t i o n c o n c e n t r a t i o n was most l i k e l y t h a t by R. Angus Smith,2 i n 1859, o f carbon d i o x i d e over Manchester; and t h a t Sutton'

i n 1932 f o r m u l a t e d a t h e o r y o f eddy d i f f u s i o n i n t h e atmosphere a p p l i c a -

b l e t o d i s p e r s i o n from l a r g e p o i n t sources, which, i n 1936, was expressed as exp l i c i t formulae f o r computing concentrations downwind o f continuous p o i n t and 4 l i n e sources by Bosanquet and Pearson. 5 I n t h e 1940's and e a r l y 1950's, Sherlock and S t a l k e r showed how t o compute 6 7 downwash from chimneys; H o l l a n d and Davidson showed how t o compute plume r i s e ; 8 Bosanquet, Carey and H a l t o n gave formulae f o r p r e d i c t i n g dust d e p o s i t i o n from 9 stack plumes; and Strom and H a l i t s k y described t h e i r New York U n i v e r s i t y wind tunnel modeling f a c i l i t i e s t h a t were t o p l a y an important r o l e i n t h e l a t e 1950's and e a r l y 1960's, d u r i n g which t i m e users t r u s t e d wind t u n n e l s more than mathem a t i c a l models. 1955 was a key y e a r i n t h e h i s t o r y o f modeling.

I t saw t h e assignment t o t h e

A i r P o l l u t i o n Research Group a t t h e Robert A. T a f t S a n i t a r y Engineering Center o f t h e U n i t e d S t a t e s P u b l i c H e a l t h Service i n C i n c i n n a t i , Ohio, o f t h e cadre o f U n i t e d States Weather Bureau m e t e o r o l o g i s t s , charged, among o t h e r t h i n g s , w i t h

4

the development of a i r p o l l u t i o n f o r e c a s t i n g and modeling techniques. This cadre, subsequently relocated t o Research Triangle Park, North Carolina, has worked on t h i s t a s k continuously f o r the p a s t twenty-five years. 1955 was a l s o t h e y e a r of the publication of "Meteorology and Atomic Energy"" by the United S t a t e s Atomic Energy Commission--most probably t h e f i r s t book one could turn t o f o r a i r p o l l u t i o n formulae and models. Urban a i r p o l l u t i o n f o r e c a s t s s t a r t e d i n Los Angeles i n 1955," and Frenkiel" described t h e r e s u l t s of h i s mathematical mode l of a i r p o l l u t i o n i n Los Angeles. Although t h i s study did not use the e l e c t r o n i c computer, Frenkiel noted t h e a p p l i c a b i l i t y of computers t o mathematical modeling o f a i r p o l l u t i o n .

I remember 1955 well a s the y e a r t h a t the I n t e r n a t i o n a l Business Machine company s t a r t e d t o aggressively merchandise i t s IBM-650 computer. T h i s was the one with a r o t a t i n g magnetic drum memory which was programed numerically because a l phabetic computer "software" was j u s t being invented. There were t h r e e 6 5 0 ' s in Cincinnati; one a t the telephone company, one a t the University of Cincinnati t o t r a i n the l i k e s of me on i t s use; and one i n a downtown s t o r e f r o n t window of t h e IBM o f f i c e . We, a t t h e T a f t Center, used a l l t h r e e of t h e s e machines t o debug and eventually r u n our f i r s t d i g i t a l computer program f o r the archiving and anal y s i s of a i r q u a l i t y d a t a , including t h e computation of t h e parameters of one of the f i r s t s t a t i s t i c a l models--the log-normal d i s t r i b u t i o n of t h e s e data. TOOLING UP

-

1959-1969

The 1959-1969 decade was ushered in w i t h the development i n C a l i f o r n i a of t h e rollback m 0 d e 1 . l ~ This model was conceived as a r a t i o n a l e f o r s e t t i n g l i m i t s on emission of carbon monoxide and hydrocarbons from automobile exhaust, and l a t e r in t h e decade, was extended t o t h e s e t t i n g of l i m i t s f o r oxidants and oxides of nitrogen from motor v e h i c l e s .

Also during t h i s decade, Pooler14 i n 1961 published

one of t h e f i r s t urban a i r p o l l u t i o n prediction models; the procedures advanced by Pasquill15 and Gifford'' and t h e plume r i s e computation procedures of Briggs 17 were accepted a s the b a s i s f o r most point and l i n e source modeling. These procedures were made widely a v a i l a b l e i n 1967 in Turner's "Workbook of Atmospheric Dispersion Estimates"18 and i t s subsequent e d i t i o n s .

The Workbook a l s o discussed

t h e a p p l i c a t i o n of modeling p r i n c i p l e s t o area sources and the combination of m u l t i p l e p o i n t , line and area sources t h a t would be necessary f o r a m u l t i p l e source urban d i f f u s i o n model, and which were incorporated i n t h e several multiple source urban d i f f u s i o n models published i n t h e l a t e 1960's. I p a r t i c u l a r l y remember 1968 because i t was my l a s t year with t h e U.S. Public Health Service and my f i r s t y e a r a t the University of North Carolina.

The l a s t

chore I did f o r t h e Public Health Service was t o set up the c o n t r a c t s p e c i f i c a t i o n s , review the c o n t r a c t o r s ' proposals, and recomnend t h e c o n t r a c t s f o r what became, when published i n 1969, t h e Air Quality Display Model (AQDM)lg--the work-

5

horse of m u l t i p l e source models i n t h e e a r l y 1970's i n t h e United S t a t e s , where i t was used t o e s t a b l i s h t h e boundaries of the Air Quality Control Regions o f the nation and t o develop i t s S t a t e Implementation Plans. One of t h e f i r s t chores I did a t t h e University of North Carolina was t o organize i n 1968 t h e Symposium on Multiple Source Urban Diffusion Modelsz0 held i n Chapel H i l l , North Carolina, in 1969.

THE MODELING EXPLOSION - 1969-1979 De Marrais' History 1 ends w i t h 1969. However, we a r e f o r t u n a t e t h a t i n 1979, Turnerz1 and the E l e c t r i c Power Research I n s t i t u t e (EPRI)" have brought modeling h i s t o r y u p t o d a t e . Turner's updating was in h i s Air Pollution Control Associat i o n C r i t i c a l Review Paper, "Atmospheric Dispersion Model ing;"21 and t h a t of EPRI i n t h e i r five-volume pub1 i c a t i o n , "Mathematical Models f o r Atmospheric of which t h e f i f t h volume (Appendix 0) i s e n t i t l e d , "Available Air Quality Models." There has been so much ferment i n t h e modeling f i e l d , during t h i s decade, t h a t models have expanded t o include a broad d i v e r s i t y w i t h respect t o time, source, receptor, t e r r a i n and type. W i t h r e s p e c t t o time, t h e r e a r e models whose output i s in terms of hourly, d a i l y o r annual averaging time; and those t h a t t r y t o t e l l u p what w i l l happen next y e a r , o r , a s i n t h e case of t h e build-up of global carbon dioxide, next century. Models a r e classed i n terms of the source c a t e g o r i e s they can represent a s point o r s i n g l e source; l i n e o r highway source, area source, o r m u l t i p l e source. In terms of r e c e p t o r , we have S t r e e t Canyon, Airport, Shopping Center models, e t c . Models of the e a r l i e r decades were only f o r l e v e l t e r r a i n . We now have models f o r v a l l e y s and o t h e r forms of complex t e r r a i n , f o r land/sea and fumigation conditions. The d i v e r s i t y of types i s shown by t h e o u t l i n e below: I . Physical A. Wind Tunnel B. Liquid Flume C. Towing Tank 11. Mathematical A. Empirical - Deterministic 1. Box - Eulerian 2. S t a t i s t i c a l - Rollback B. Semi-Empirical 1. Gaussian Plume - Puff 2. Trajectory - Moving Cell C. Numerical - Reactive 1. Multibox - Lagrangian 2 . Grid - Eulerian - Finite Difference 3 . P a r t i c l e ; P a r t i c l e - i n - C e l l ; Marker and Cell D. Global - Pollution

6

E.

Visibility

F. Dosage - Exposure O f these, I w i l l comment o n l y on t h e l a s t o f these c a t e g o r i e s .

Although Dosage

and Exposure models have been used almost e x c l u s i v e l y t o assess human exposure, H o r i e and t h e author23 p o i n t e d o u t t h e i r p o t e n t i a l f o r much wider a p p l i c a t i o n t o o t h e r p o p u l a t i o n s (e.g.,

vegetation, m a t e r i a l s , s t r u c t u r e s , e t c . ) .

The U n i t e d S t a t e s Clean A i r Amendments o f 197724 have had a profound i n f l u e n c e on modeling.

F i r s t l y , by making t h e Prevention o f S i g n i f i c a n t D e t e r i o r a t i o n (PSD)

o f u n p o l l u t e d areas a l e g a l requirement, i t has f o r c e d t h e p o i n t source modeling o f a l l new major sources as a p r e c o n d i t i o n f o r t h e i r approval.

The d r a f t e r s o f

t h e a c t almost committed t h e a b s u r d i t y o f s p e c i f y i n g t h e model t o be used, b u t were persuaded i n s t e a d t o s u b s t i t u t e t h e f o l l o w i n g language i n t h e a c t : STANDARDIZED A I R QUALITY MODELING Sec. 320. ( a ) Not l a t e r than s i x months a f t e r t h e date o f enactment o f t h e Clean A i r Act Amendments o f 1977, and a t l e a s t every t h r e e years t h e r e a f t e r , t h e A d m i n i s t r a t o r s h a l l conduct a conference on a i r q u a l i t y modeling. I n conducting such conference, s p e c i a l a t t e n t i o n s h a l l be given t o approp r i a t e modeling necessary f o r c a r r y i n g o u t p a r t C o f t i t l e I ( r e l a t i n g t o prevention o f s i g n i f i c a n t deterioration o f a i r q u a l i t y ) . ( b ) The conference conducted under t h i s s e c t i o n s h a l l p r o v i d e f o r p a r t i c i p a t i o n by t h e N a t i o n a l Academy o f Sciences, r e p r e s e n t a t i v e s o f S t a t e and l o c a l a i r p o l l u t i o n c o n t r o l agencies, and a p p r o p r i a t e Federal agencies, i n c l u d i n g t h e N a t i o n a l Science Foundation; t h e N a t i o n a l Oceanic and Atmospheric A d m i n i s t r a t i o n , and t h e N a t i o n a l Bureau o f Standards. ( c ) I n t e r e s t e d persons s h a l l be p e r m i t t e d t o submit w r i t t e n comments and a v e r b a t i m t r a n s c r i p t o f t h e conference proceedings s h a l l be maintained. ( d ) The comments submitted and t h e t r a n s c r i p t maintained pursuant t o subs e c t i o n ( c ) s h a l l be i n c l u d e d i n t h e docket r e q u i r e d t o be e s t a b l i s h e d f o r purposes o f promulgating o r r e v i s i n g any r e g u l a t i o n r e l a t i n g t o a i r q u a l i t y modeli n g under p a r t C o f t i t l e I. Secondly, t h e s e c t i o n s o f t h e a c t on non-attainment areas, i . e . what must be done i n areas where t h e a i r q u a l i t y o f a p o l l u t a n t i s worse than t h e a i r q u a l i t y standard f o r t h a t p o l l u t a n t , i m p l i c i t y r e q u i r e t h e use o f m u l t i p l e source models t o o b t a i n f e d e r a l approval f o r what i s proposed t o be done, p a r t i c u l a r l y i f emission o f f s e t s are required. T h i r d l y , t h e r e a r e s e c t i o n s o f t h e a c t concerned w i t h p r e v e n t i o n o f degradation o f v i s i b i l i t y , which among o t h e r t h i n g s , has prompted our Environmental P r o t e c t i o n Agency t o i s s u e i n 1979, a pub1 i c a t i o n e n t i t l e d , "The Development o f Mathematical Models f o r t h e P r e d i c t i o n of Anthropogenic V i s i b i l i t y Impairment. F o u r t h l y , by o u t l a w i n g t h e use o f supplementary c o n t r o l systems f o r c o a l - f i r e d power p l a n t s , t h e a c t has denied t h e U n i t e d States t h e b e n e f i t o f t h e use o f f o r e c a s t i n g e f f l u e n t d i s p e r s i o n from such p l a n t s . THE MODELING DILEMMA

-

1980

Two decades ago--even one decade ago--we b e l i e v e d t h a t i f o n l y we had t h e programs, t h e program i n p u t s , and t h e computer c a p a b i l i t y t o r u n them, we c o u l d gain

7

understanding o f o u r a i r p o l l u t i o n problems. We b e l i e v e d t h a t modeling c a p a b i l i t y would p u t us i n t h e d r i v e r ' s seat i n o u r t h r u s t t o c o n t r o l p o l l u t i o n . Unfortunatel y , now t h a t we have achieved modeling c a p a b i l i t y , a t l e a s t i n t h e United States

i t has p u t t h e models i n t h e d r i v e r s ' seats and l e f t many o f us asking where they

a r e t a k i n g us. The r o l l b a c k model f o r motor v e h i c l e carbon monoxide as o r i g i n a l l y developed i n C a l i f o r n i a was a r a t i o n a l procedure and used d e f e n s i b l e i n p u t data.

However,

i n t h e two decades s i n c e i t s development, i t s a p p l i c a t i o n t o t h e s e t t i n g o f f e d e r a l motor v e h i c l e emission standards has become i n c r e a s i n g l y i r r a t i o n a l and i t s input data increasingly indefensible.

With t h e r o l l b a c k model i n t h e d r i v e r ' s

seat, i t has d r i v e n us t o expend b i l l i o n s o f d o l l a r s needlessly, and i t s a p p l i c a t i o n t o t h e c o n t r o l o f hydrocarbons and oxides o f n i t r o g e n emissions has n o t accomplished i t s intended o b j e c t i v e o f reducing smog. I n t h e a p p l i c a t i o n o f p o i n t , l i n e and m u l t i p l e source models t h e r e are substant i a l issues t h a t need r e s o l u t i o n . '-8mong them are:

t h e p r o p r i e t y o f modeling o n l y

worst-case s i t u a t i o n s , which would occur r a r e l y , i f ever, i n r e a l l i f e ; t h e use o f models based on s h o r t - t e r m exposure t o e s t a b l i s h compliance w i t h standards

based on long-term exposure; and t h e r e l i a b i l i t y o f i n s t r u m e n t a l measurements and c a l i b r a t i o n s which a r e a t o r c l o s e t o t h e lower l i m i t o f d e t e c t i o n o f such instruments.

Here again, d e c i s i o n s on model i n p u t data can r e s u l t i n costs f a r

exceeding t h e b e n e f i t s achieved.

A w e l l c o n s t r u c t e d model does one t h i n g s u p e r l a t i v e l y w e l l .

It t e l l s us t h e

s i g n and o r d e r o f magnitude o f t h e change i n o u t p u t f o r a g i v e n change i n an i n p u t parameter.

T h i s i s a v e r y u s e f u l t h i n g t o know when s i t i n g a source and de-

s i g n i n g i t s c o n t r o l system; when s i t i n g m o n i t o r i n g s t a t i o n s and i n t e r p r e t i n g t h e i r r e s u l t s ; and when s t u d y i n g atmospheric t r a n s p o r t a t i o n and t r a n s f o r m a t i o n processes. However, when we use a model t o g i v e a go o r no-go d e c i s i o n , we a r e asking t h a t i t p r e c i s e l y t e l l whether t h e ground l e v e l c o n c e n t r a t i o n i s g r e a t e r o r l e s s than

some s p e c i f i c number.

N e i t h e r t h e models n o r t h e i r i n p u t data are t h a t good o r

a r e ever l i k e l y t o be so.

I f we t r y t o use models as go o r no-go d i s c r i m i n a t o r s ,

we a r e f o r c e d t o make them more and more complex t o accommodate a l l p o s s i b l e pert u r b i n g i n f l u e n c e s ; b u t i f we use them t o show t h e magnitude and s i g n o f change, we can r e l y on s i m p l e r models. THE FUTURE

A i r p o l l u t i o n models have come o f age.

They a r e a v a i l a b l e o f f - t h e - s h e l f from

p r i v a t e c o n s u l t a n t s and governmental agencies (e.g., United States).*l

the

UNAMAP models i n t h e

There a r e s t i l l many problems w i t h t h e models themselves, t h e

way t h e y a r e r e q u i r e d t o be used and t h e way t h e y a c t u a l l y a r e used, which i t i s hoped t h i s decade w i l l h e l p r e s o l v e .

8

REFERENCES

1 G.A. 2 3 4 5 6 7 8 9 10

11

12 13 14 15 16 17 18 19 20 21

22 23 24 25

De M a r r a i s , A H i s t o r y o f A i r P o l l u t i o n M e t e o r o l o g y t h r o u g h 1969, NOAA T e c h n i c a l Memorandum ERL ARL-74, N a t i o n a l Oceanic and Atmospheric A d m i n i s t r a t i o n , S i l v e r S p r i n g , Md., 1979, 78 pp. R. Angus Smith, On t h e A i r o f Towns, Q u a r t . J. Chem. SOC. London, 11(1859), pp. 196-235. O.G. S u t t o n , A Theory o f Eddy D i f f u s i o n i n t h e Atmosphere, Proc. Royal S o c i e t y London A 135(826), pp. 143-165. C.H. Bosanquet and J.L. Pearson, The Spread o f Smoke and Gases f r o m Chimneys, Trans. Faraday SOC., 32(1936), pp. 1249-1263. R.H. S h e r l o c k and E.A. S t a l k e r , A Study o f Flow Phenomena i n t h e Wake o f Smoke Stacks, B u l l e t i n No. 29, Dept. o f E n g i n e e r i n g Research, U n i v e r s i t y o f Michigan, Ann A r b o r , Mich., 1941, 49 pp. J.Z. H o l l a n d , A M e t e o r o l o g i c a l Survey o f t h e Oak Ridge Area, ORO-99, Atomic Energy Commission, Oak Ridge, Tenn., 1953, 584 pp. ( p a r t i c u l a r l y pp. 554-559). W.F. Davidson, The D i s p e r s i o n and S p r e a d i n g o f Gases and Dusts f r o m Chimneys, 38-55. Trans. B u l l . No. 13, 1 4 t h Ann. Mtg., Ind. Hyg. F o u n d a t i o n (1949) p C.H. Bosanquet, W.F. Carey and E.M. H a l t o n , Dust D e p o s i t i o n f r o m C\\mney Stacks, Proc. I n s t . Mech. Eng., 162(1950), pp. 355-367. G.H. Strom and J. H a l i t s k y , I m p o r t a n t C o n s i d e r a t i o n s i n t h e Use o f Wind Tunn e l s f o r P o l l u t i o n S t u d i e s o f Power P l a n t s , A i r R e p a i r 4(1954), pp. 24-30. M e t e o r o l o g y and Atomic Energy, AECU 3066, U.S. Atom. Energy Comm., Washington, D.C., 1955, 169 pp. E.K. Kauper, R.G. Holmes and A.B. S t r e e t , M e t e o r o l o g i c a l V a r i a b l e s and Object i v e F o r e c a s t i n g Techniques R e l a t i n g t o t h e A i r P o l l u t i o n Problem i n Los Angeles, Tech. Paper No. 15, A i r P o l l u t i o n C o n t r o l D i s t r i c t , Los Angeles, C a l i f o r n i a , 1955, 15 pp. F.N. F r e n k i e l , Atmospheric P o l l u t i o n i n Growing Communities, Smithsonian I n s t i t u t e Report f o r 1956, Washington, D.C. (1957), pp. 269-299, ( f i r s t desc r i b e d i n paper b e f o r e A i r P o l l u t i o n C o n t r o l A s s o c i a t i o n i n 1955). J.A. Maga and G.C. Hass, The Development o f M o t o r V e h i c l e Exhaust Emission Standards i n C a l i f o r n i a , J . A i r P o l l . C o n t r o l Assn., 10(1960), pp. 393-396, 414. F. P o o l e r , A P r e d i c t i o n Model o f Mean Urban P o l l u t i o n f o r Use w i t h Standard Wind Roses, I n t . J . A i r Water P o l l . , 4 ( 1 9 6 1 ) , pp. 199-211. F. P a s q u i l l , The E s t i m a t i o n o f t h e D i s p e r s i o n o f Windborne M a t e r i a l , Met. Mag. 90( 1961), pp. 33-49. F.A. G i f f o r d , Jr., Uses o f R o u t i n e M e t e o r o l o g i c a l O b s e r v a t i o n s f o r E s t i m a t i n g Atmospheric D i s p e r s i o n , N u c l e a r S a f e t y , 2(1961), pp. 47-51. G.A. B r i g g s , Plume Rise, U.S. Atomic Energy Comm., Oak Ridge, Tenn., 1969, 8 1 PP. D.B. Turner, Workbook o f Atmospheric D i s p e r s i o n E s t i m a t e s , PHS Pub. No. 999-AP26, U.S. P u b l i c H e a l t h S e r v i c e , C i n c i n n a t i , Ohio, 1967, 84 pp. TRW Systems Group, A i r Q u a l i t y D i s p l a y Model, N a t i o n a l T e c h n i c a l I n f o r m a t i o n S e r v i c e No. PB189-194, (NAPCA C o n t r a c t PH-22-68-60) , U .S. Dept. o f Commerce, Washington, D.C., 1969. Symposium on M u l t i p l e Source Urban D i f f u s i o n Models (A.C. S t e r n , ed.) - AP-86, U.S. E n v i r o n m e n t a l P r o t e c t i o n Agency, Washington, D.C., 1970, 461 pp. D. Bruce T u r n e r , Atmospheric D i s p e r s i o n M o d e l i n g - A C r i t i c a l Review, J. A i r P o l l . C o n t r o l Assn., 29( 1979), pp. 502-525 and 927-941. Mathematical Models f o r Atmospheric P o l l u t a n t s , E P R I EA-1131, (118 p p . ) ; Append i c e s A ( 9 9 pp.); B ( 8 4 pp.); C (254 pp.); D (143 p p . ) , E l e c t r i c Power Research I n s t i t u t e , P a l o A l t o , C a l i f o r n i a , 1979. Y . H o r i e and A.C. S t e r n , " A n a l y s i s o f P o p u l a t i o n Exposure t o A i r P o l l u t i o n i n New York-New J e r s e y - C o n n e c t i c u t T r i - S t a t e Region," EPA-450/3-76-027, U.S. Env i r o n m e n t a l P r o t e c t i o n Agency, Research T r i a n g l e Park, N.C., 1976, 169 pp. P u b l i c Law 95-95, U.S. Government P r i n t i n g O f f i c e , Washington, D.C., 1977. The Development o f Mathematical Models f o r t h e P r e d i c t i o n o f Anthropogenic V i s i b i l i t y Impairment, EPA-450/1-78-110, a.b.c., U.S. Environmental P r o t e c t i o n Agency, Research T r i a n g l e Park, N.C., 1979, 778 pp.

Atmospheric Pollution 198O! Proceedings of the 14th International Colloquium, Paris, France, May 5--8,1980, M.M. Benarie (Ed.), Studies in Environmental Science, Volume 8 0 Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands

9

MODELING THE TRANSPORT AND DIFFUSION OF A I R POLLUTANTS USING A PROGNOSTIC

MESOSCALE MODEL R.T.

McNIDER

Alabama A i r P o l l u t i o n C o n t r o l Commission, Montgomery, AL, USA R.A.

PIELKE

U n i v e r s i t y of V i r g i n i a , C h a r l o t t e s v i l l e , V A , USA

ABSTRACT The u s e o f a t h r e e - d im e n s i o n a l ,

p r i m i t i v e e q u a t i o n , mesoscale model is examined

f o r p r e d i c t i n g t h e t r a n s p o r t and d i f f u s i o n of a i r p o l l u t a n t s i n complex flow s i t u a t i o n s such as sea b r e e z e and mountain v a l l e y c i r c u l a t i o n s .

P o l l u t a n t con-

c e n t r a t i o n s from area s o u r c e s w i t h scales l a r g e r t h an t h e model g r i d sp aci n g can be a d e q u a t e l y modeled u s i n g t h e c o n s e r v a t i o n e q u a t i o n and g r a d i e n t t r a n s f e r theory.

The

modeling o f p o l l u t a n t c o n c e n t r a t i o n s from p o i n t s o u r c e s is, however, d i f f i c u l t i n c o a r s e g r i d mesoscale models because o f n u m e r ical damping and t h e t h e o r e t i c a l inadequacy o f K-theory f o r plumes which are small compared t o t h e t u r b u l e n t scales.

To

model p o i n t s o u r c e s , a s t a t i s t i c a l p a r t i c l e d i s p e r s i o n scheme is ex p l o r ed w i t h i n t h e mesoscale model framework.

INTRODUCTION

In

sea

b r eeze f l o w s o r mountain-valley f l o w s, s t a n d a r d Gaussian d i s p e r s i o n models

are i n a p p r o p r i a t e due t o t h e u n s t e a d y n a t u r e and s p a t i a l inhomogeneity of t h e s e l o c a l

circulations.

A p r o g n o s t i c mesoscale model h a s t h e p o t e n t i a l t o i n c l u d e t h e impor-

t a n t p h y s i c a l mechanisms f o r t h e s e complex c i r c u l a t i o n s and t h u s p r o v i d e a p h y s i c a l l y c o n s i s t e n t flow f i e l d t o examine t h e t r a n s p o r t o f p o l l u t a n t s .

.In t h e f o l l o w i n g

d i s c u s s i o n , t e c h n i q u e s are o u t l i n e d u t i l i z i n g a mesoscale model f o r a i r p o l l u t i o n applications.

DISCUSSION The U n i v e r s i t y of V i r g i n i a Mesoscale Model ( r e f . 1 ) h as been employed t o s i m u l a t e t hr e e - d i m en s i o n al sea b r e e z e and t o p o g r a p h i c c i r c u l a t i o n s .

F i g u r e 1 shows p a r t i c l e

s t r e a k l i n e s i n t h e f l o w f i e l d o v e r t h e S o u t h F l o r i d a P e n i n s u l a d u r i n g a sea breeze event.

P a r t i c l e s have been r e l e a s e d from v a r i o u s p o i n t s o v er t h e p e n i n s u l a ev er y t e n

10 minutes s i n c e t h e beginning of model i n t e g r a t i o n at s u n r i s e .

Although t h e general

s y n o p t i c flow is from t h e S o u t h e a s t , t h e p a r t i c l e s r e l e a s e d on t h e West Coast a r e caught w i t h i n t h e sea breeze flow and a r e a l t e r n a t e l y c a r r i e d i n s h o r e and offshore producing a h e l i c a l p a t t e r n .

F i g u r e 1.

P a r t i c l e s t r e a k l i n e s a t 1900 LST from 300 meter release h e i g h t s .

Although t h e mean wind f i e l d is important f o r determining t r a n s p o r t d i r e c t i o n and f o r producing l a r g e scale meandering of plumes, i n c l u s i o n of t h e t u r b u l e n t s t r u c t u r e

is necessary t o make p r e d i c t i o n s of p o l l u t a n t concentrations.

For l a r g e s c a l e area

s o u r c e s and f o r plumes whose size is large i n comparison t o t h e model g r i d s c a l e and t u r b u l e n t scale, t h e conservation equation, 11, can be u t i l i z e d ;

where K is a t u r b u l e n t exchange c o e f f i c i e n t .

I n t h e c u r r e n t model, t h e advection

component is solved using an upstream s p l i n e i n t e r p o l a t i o n technique which f o r r e s o l v e a b l e s c a l e s is a highly c o n s e r v a t i v e technique.

The v e r t i c a l exchange coef-

f i c i e n t s f o r t h e convective boundary l a y e r needed i n 1 ) a r e based on a cubic polyno-

mial formulation dependent on t h e p l a n e t a r y boundary h e i g h t and s u r f a c e s i m i l i a r i t y theory. F i g u r e 2. shows suspended p a r t i c l e t r a n s p o r t and d i f f u s i o n using t h e conservation equation 1) i n a two-dimensional v e r s i o n of t h e model through a cross-section of the F l o r i d a Peninsula.

An urban s t r i p over t h e East Coast and p a r t i c l e production over

t h e rest of t h e peninsula provide a r e a sources f o r production of p a r t i c l e s i n t o t h e model atmosphere.

A t 1330 l o c a l time, t h e p a r t i c l e s are e s s e n t i a l l y w e l l mixed

w i t h i n t h e model convective boundary l a y e r .

A t n i g h t , t h e upward v e r t i c a l d i f f u s i o n

i s suppressed i n t h e s t a b l e atmosphere; and by 0530 on t h e East Coast, t h e suspended p a r t i c l e s are c a r r i e d out t o sea i n a shallow land breeze.

11

4

3

E2 r4

1

Figure 2.

Contours of p a r t i c l e c o n c e n t r a t i o n s i n a two-dimensional v e r s i o n of t h e m e s o s c a l e model. S y n o p t i c f l o w i s from t h e east ( R ) .

P o i n t s o u r c e s o f p o l l u t i o n cannot be d i r e c t l y handled i n t h e c o a r s e g r i d

mesoscale model u s i n g 1 ) due t o n u m e r i c a l damping and t h e f a c t t h a t plumes small compared t o t h e t u r b u l e n t scale d o n o t d i f f u s e i n a g r a d i e n t f a s h i o n o r a t least r e q u i r e t h e e f f e c t i v e K t o b e a f u n c t i o n of t r a v e l d i s t a n c e .

Because of t h e h i g h l y

s h e a r e d environment and u n s t e a d y c h a r a c t e r of t h e l o c a l c i r c u l a t i o n s , t h e s u b g r i d

scale d i s p e r s i o n cannot be e a s i l y p a r a m e t e r i z e d u s i n g a n a l y t i c a l methods.

An a l t e r -

n a t i v e t h a t w e are c u r r e n t l y u t i l i z i n g is a c o n d i t i o n e d p a r t i c l e d i s p e r s i o n scheme ( r e f . 2 ) based upon T a y l o r s ' 1921 theorem for p a r t i c l e d i s p e r s i o n i n which t h e par-

t i c l e v e l o c i t y , "p is expressed by up

=

u +

u'

2)

where 5 is t h e mesoscale wind, u' is a t u r b u l e n t component g i v e n by u'(t

+ T)

=

u ' ( t ) R(T)

+ U"

3)

and utl is a random component dependent upon t h e t u r b u l e n t energy,U,, and t h e autoc o r r e l a t i o n f u n c t i o n R. The u s e of t h i s scheme r e q u i r e s a n estimate o f a , and R

12 c o n s i s t e n t w i t h t h e model boundary l a y e r .

T h i s is accomplished f o r t h e vertical

component by u s i n g

where A,

is t h e s p e c t r a l peak i n t h e v e r t i c a l component and

d i c t e d exchange c o e f f i c i e n t .

The parameter

A,

I$,,

is t h e model pre-

is r e l a t e d t o h e i g h t and i n t h e l i m i t

t o t h e model p r e d i c t e d boundary l a y e r h e i g h t i n t h e c o n v e c t i v e boundary. F i g u r e 3. shows modeled deduced Ow v a l u e s s c a l e d a p p r o p r i a t e l y f o r comparison with estimates of The results look promising, and it is f e l t t h a t t h e u s e of

from f i e l d o b s e r v a t i o n s .

t h e p a r t i c l e d i s p e r s i o n scheme a l o n g w i t h t h e p r o g n o s t i c mesoscale model c a n be u t i l i z e d t o examine p o l l u t a n t b e h a v i o r i n l o c a l c i r c u l a t i o n s .

Irwin 11919)

Model . Wangara 33 1400 LSl

.I

.5

1.0

WW.

F i g u r e 3.

Model e x t r a c t e d aw f r o m a s i m u l a t i o n of Day 33 of t h e Wangara experiment. W, i s t h e c o n v e c t i v e v e l o c i t y and Zi i s t h e p l a n e t a r y boundary h e i g h t . S o l i d l i n e and dashed l i n e are composites of f i e l d o b s e r v a t i o n s .

ACKNOWLEDGEMENTS The a u t h o r s would l i k e t o thank t h e i r c o l l e a g u e s a t t h e U n i v e r s i t y of V i r g i n i a and Dr. S t e v e n Hanna f o r t h e i r h e l p i n t h i s r e s e a r c h and Ms. Linda Geddie who typed t h e m a n u s c r i p t . T h i s r e s e a r c h sponsored through U.S. Grant No. R80627010.

Environmental P r o t e c t i o n Agency

REFERENCES 1 Mahrer, Y., and R. A. P i e l k e , The effects o f topography on t h e sea and l a n d b r e e z e s i n a two-dimensional n u m e r i c a l model.Mon. Wea. Rev., I&, (1977) 1151-

1162. J. 2 Hanna, S.R., Some s t a t i s t i c s of Lagrangian and E u l e r i a n wind f l u c t u a t i o n s , Appl. Meteor., l8, (1979) 518-531. 3 I r w i n , J.S., E s t i m a t i n g plume d i s p e r s i o n A recommended g e n e r a l i z e d scheme. F o u r t h Symposium on Turbulence, D i f f u s i o n and Air Q u a l i t y , American M e t e r o l o g i c a l S o c i e t y . Reno, Nevada, 1979.

-

AtmosphericPollution 1980, Proceedingsof the 14th International Colloquium,Paris, France, May 5-8,1980, M.M. Benarie (Ed.), Studies in Environmental Science,Volume 8 0 Elsevier Scientific Publishing Company,Amsterdam - Printed in The Netherlands

13

COMMUTER EXPOSURE MODELING PART 11: EMISSIONS AND DISPERSION MODULES AND GENERATION OF EXPOSURE STATISTICS P. B. SIMMON and R. M. PATTERSON SRI International, Menlo Park, CA 94025 (U.S.A.) and W. B. PETERSEN U.S. Environmental Protection Agency, Research Triangle Park, NC

2 7 7 1 1 (U.S.A.)

ABSTRACT A model methodology has been designed to compute commuter exposure statistics

through simulation of the traffic, vehicular emissions, and atmospheric dispersion of roadway-related air pollutants. A detailed description of the emissions and dispersion elements of the commuter exposure modeling methodology and a discussion of the results generated by the model are presented in this paper; the traffic

element of the methodology is discussed in a companion paper. The commuter exposure model's emissions module incorporates two emissions methodologies: a treatment based on average route speed, and one that considers the effects of driving mode changes. Dispersion of pathway emissions is simulated by two separate dispersion treatments, while dispersion from nonpathway sources is computed with the simple Hanna-Gifford model.

The model produces a number of statistics describing annual average or short-term worst-case exposure. INTRODUCTION

This is the second (Paper 11) of two papers describing the development of a computer model of commuter exposure to air pollution. The modeling methodology requires the model user to define the major commute corridors or "pathways" in a metropolitan area. The computer model reads traffic and roadway characteristics of the pathways, general information regarding traffic and emissions on the remainder of the roadway network, and various meteorological data. This information is used by the three major modules of the model to simulate traffic flow, compute vehicular emissions, and calculate the atmospheric dispersion of roadway-related air pollutants. Various statistics describing pathway exposures (concentration integrated with time over the length of the pathway) are the output of the model.

Paper I gives an overview

of the model methodology and describes the computer model's traffic flow computa-

tion module.

This paper continues the discussion with a description of the emission

14 rate computation module, the dispersion module, and the methodology used to generate exposure statistics. EMISSION RATE COMPUTATIONS Emission rates for each pathway segment and grid square are computed using one of two types of emission treatments:

a treatment based on the average route speed

and one that considers the effects of driving mode changes on emissions. The first treatment is the EPA methodology based on the Federal Test Procedure (FTP) (ref. 1). The second treatment is the "Automobile Exhaust Emission Modal Analysis Model," (ref. 2) or modal model.

Emissions modeling along pathways requires both treat-

ments; FTP-based emissions estimates are suitable for nonpathway sources. Emission rates (Q) for pathway segments that are freeways, expressways, or arterials outside the central business district (CBD) are found by multiplying an emission density, E, computed using the FTP methodology and chosen according to the average route speed on the segment, by the demand volume (V) on the segment. To compute the average emission rate over a segment having congested flow, it is convenient to break the emissions into two components:

those occurring during

normal flow, E, and the excess over normal flow emissions that occur during congested flow, E'-E,

where E' represents the emissions during congested flow. The

component of total emissions due to uncongested flow is given by Q, with E chosen according to the average route speed on the uncongested portion of the segment. The average emission rate over the pathway segment is the sum of the components due to uncongested (Q) and congested (Q')

flow, as given by:

where E' corresponds to an average route speed of 20 mi/h,

i is the number of

vehicles affected by the backup, L = segment length (m), Lq = backup length (m), and

+

is the duration (seconds) of the backup.

Travel on arterials within the CBD is characterized by interrupted flow and low speeds, and a modal emissions treatment should be used.

This is available

through an adaptation of EPA's modal model. The modal model determines an instantaneous emission rate, e(t>, which is a function of vehicle speed, v, and acceleration, a. Acceleration to or from a given speed is assumed to be a perturbation to the steady-state emission rate. For the commuter exposure model, simulation of the effects of modal emissions is facilitated through the introduction of the concept of excess modal emissions. Excess modal emissions are those that occur over and above those that would have

15 occurred had the vehicle not stopped. The total excess emissions, EE(g/m/s),

the

sum of idle emissions, and the acceleration and deceleration parts of the excess emission, Em, may be expressed as

Where N = number of vehicles in the backup; b10 = constant (g/s), D = delay

(s),

P = proportion of vehicles stopped for the signal, and Cy = signal cycle length

(s)

The cruise emissions that would have occurred had the vehicle not stopped are found by integrating the modal model expression for the steady-speed emission rate over 4 T. The cruise emissions component may be calculated by E = C

6 V/3600 v 1609.344/3600

(G

)

(3)

where 1609.344 is the number of meters in a mile. Once emissions are calculated with the modal treatment, they are averaged for each pathway segment. DISPERSION MODELING Dispersion of Pathway Emissions For the purpose of computing the dispersion of vehicular emissions on commute pathways, limited-access and nonlimited-access pathway segments are distinguished from segments located in a street canyon. The dispersion of pollutants emitted by vehicles on both limited-access and nonlimited-access roadways is computed using a technique taken from the CALINE 2 (ref. 3) dispersion model. The model formulation is based on the treatment of pollution dispersion as the vector sum of two components: dispersion occurring along the horizontal wind component oriented perpendicular to the roadway, and dispersion along the horizontal wind component parallel to the roadway. The parallel wind model assumes that the roadway is divided into a series of square area sources as wide as the roadway. The concentration downwind of the area source is computed as if the emissions originated from a virtual source located upwind of the area source, at a distance that forces the model to assume a uniform concentration within a mixing cell over the roadway. The equation used to compute the concentration from each area source is:

3 where X = concentration from parallel dispersion (g/m ) , U = wind speed (m/s), P Q k = line-source emission rate (g/m/s), W = roadway width (m), 8 = angle between

16

wind direction and roadway, y = perpendicular distance between receptor and roadway edge plus an initial dispersion parameter (m), z above grade-level (m),

0

Y

=

height of the receptor

= horizontal dispersion function (m), and o

= vertical

dispersion function (m). The concentrations from each area source are summed to give the parallel component, which is then corrected by a stability-dependent factor. The cross-wind or normal component of concentration is given by

xn

=

O

iexp [- (31I $

U

(5)

3

where X = concentration from normal dispersion (g/m ) n

.

The parallel and crosswind components are summed to give the total concentration when

€Iis

non-zero.

Dispersion on a roadway with tall buildings on both sides is greatly influenced by the presence of the buildings.

The street-canyon dispersion treatment used in

the commuter exposure model is based on the empirical street-canyon model developed by Johnson et al. (ref. 4 ) and modified by Ludwig et al. (ref. 5 ) .

For the commuter

exposure model, the concentration on the roadway (X) was assumed to be the average of the expressions for the concentrations on the windward and leeward sides of the street, as given by KQk

x=

2(U+0.5)

where Q,

=

(h

+

$)

line-source emission rate (g/m/s), K

=

empirically derived nondimensional

constant =2 m, and W = street width (m). Segment pollutant concentrations are summed for each pathway and integrated over travel time to yield pathway exposures. Dispersion of Nonpathway Source Emissions It is expected that the portion of the total pathway integrated concentration (exposure) that results from nonpathway sources will be small in comparison to the portion resulting from traffic on the commuter pathways themselves. Therefore, a very simple emissions and dispersion treatment is used. The line-source emissions on nonpathways have been aggregated into area-source emissions from grid squares. For each pathway segment a concentration is computed, according to the so-called Hanna-Gifford (ref. 6 ) dispersion treatment, at receptors

17 located at the endpoints and the midpoint of the segment. These concentrations

(X) are given by

where C

=

$ $&

;

Qo= emission rate of the grid square in which the receptor is located (g/m2 /s),

U

=

wind speed (m/s), D

=

city size, and a and b are stability-dependent constants.

The normalized integrated concentration over the segment (the exposure E) is found by performing a stepwise integration over travel time from one endpoint to the midpoint and the midpoint to the other endpoint of the segment. The model computes exposures for all segments of a pathway and sums the results to yield the pathway exposure resulting from nonpathway sources. On-Roadway/In-Vehicle Concentration Relationship The little information that exists about the relationship between the concentration on the roadway and the concentration within a vehicle indicates that concentrations of CO inside a vehicle are about equal to that on the outside. Therefore, the commuter exposure model assumes the concentrations at the two locations are identical. Generation of Commuter Exposure Statistics Exposures are computed for each pathway according to the meteorological conditions of the mode of model operation chosen by the model user.

If the short-term

mode is chosen, one exposure is computed for each pathway, for the input meteorological conditions and traffic information. If the model is operating in the annual mode, morning and evening exposures are computed for each pathway for 576 sets of meteorological conditions (each combination of 6 wind speeds, 16 wind directions, and 6 atmospheric stability classes).

These exposures are weighted according to

the frequency of occurrence of each set of conditions and summed for each pathway. I n ad-ditinr!to the exposures, the model stores the total travel time or times on

each pathway and the average number of commuters using the pathway. When the model is run in the short-term mode, the output includes a list of the exposure on each pathway for the input worst-case meteorological and traffic conditions and the average and standard deviation of pathway exposure. When the model is in the annual mode it lists the annual average exposure on each pathway and over the modeled region. For either mode, the model produces data for two histograms. For the short-term mode the data pertain to a single commute; for the annual mode, the data are representative of annual variations. First, the range of exposures

18 found on all pathways is divided into several classes. Then for each class, two parameters are listed:

the percentage of the commuting population (commuting

vehicles multiplied by the average number of commuters per vehicle) treated by the model that experience exposure levels in the class, and the probability of experiencing the exposure levels in the class (i.e., the percentage of time commuters are exposed to the levels of the exposure class). may be output at the user's discretion.

Subsets of these statistics

Finally, the model user may call for

model output in grahical form. For a summary of model output, the reader is referred to Part I, Overview. ACKNOWLEDGEMENTS This work was supported by the U . S .

Environmental Protection Agency under

Contract No. 68-02-2754. REFERENCES 1 Mobile Source Emission Factors, Final Document, Environmental Protection Agency, Office of Transportation and Land Use Policy, Washington, D.C., 1978. 2 Modal Program Guide, an update to Automobile Exhaust Emission Modal Analysis Model, U.S. EPA Report No. EPA-46013-74-005, 1974. 3 K.E. Noll, T.L. Miller, and M. Claggett, A Comparative Analysis of EPA HIWAY, California, and CALINE 2 Line-Source Dispersion Models, submitted to Transportation Research Board, Washington, D.C., 1976. 4 W.B. Johnson, W.F. Dabberdt, F.L. Ludwig, and R.J. Allen, Field Study for Initial Evaluation of an Urban Diffusion Model for Carbon Monoxide, Comprehensive Report, CRC and Environmental Protection Agency (EPA) Contract CAF'A-3-68 (1-69), SRI International, Menlo Park, CA, 1971. 5 F.L. Ludwig and W.F. Dabberdt, Evaluation of the APRAC-1A Urban Diffusion Model for Carbon Monoxide, Final Report, CRC and EPA Contract CAPA-3-68 (1-69), SRI International, Menlo Park, CA, 1972. 6 S.R. Hanna, A Simple Method of Calculating Dispersion from Urban Area Sources, J. Air Pollution Control Assoc. 21, pp. 774-777, 1971.

Atmospheric Pollution 1980, Proceedings of the 14th InternationalColloquium,Pans, France, May 5-8,1980,M.M. Benarie (Ed.),Studies in Environmental Science, Volume 8 0 Elsevier Scientific PublishingCompany,Amsterdam - Printed in The Netherlands

19

COMMUTER EXPOSURE MODELING PART I: OVERVIEW AND TRANSPORTATION MODULE

R. M. PATTERSON and P. B. SIMMON SRI International, Menlo Park, CA

94025 (U.S.A.)

and

W. B. PETERSEN U.S. Environmental Protection Agency, Research Triangle Park, NC

27711 (U.S.A.)

ABSTRACT Recent concern over commuter exposure to high levels of roadway-related air pollutants, the projected increase in the number of diesel-powered passenger vehicles, and the demonstrated inadequacy of fixed monitoring stations in replicating commuter exposure have prompted research in this area. This paper presents the development of new methodological tools for identifying, predicting, and analyzing commuter exposure to motor vehicle generated air pollutants.

Commuter exposure modeling is

of interest to those involved in regulation, monitoring, planning, and health effects research. The approach was to build a methodology based on three distinct modules treating traffic flow, emissions, and dispersion.

This paper deals in

detail with the first module; the second two are discussed in "Part 11:

Emissions

and Dispersion Modules and Generation of Exposure Statistics."

INTRODUCTION This is the first (Paper I) of two papers describing the development of a computer model of commuter exposure to air pollution.

Those concerned with air qualit:

assessment are increasingly recognizing the inadequacy of fixed point monitoring data for characterizing the pollutant exposure of various population groups. The spatial variation of concentrations over short distances is recognized to be sufficiently great for some pollutants that concentration measurements made at fixed locations are not necessarily representative of the concentrations to which people, as moving receptors, are exposed.

Since the objective of air quality

regulation in general is to protect the health of people, the air quality assessment community has realized that simulation modeling should be directed toward modeling pollutant concentrations at the locations where people spend time, and considering the amount of time spent at each location. Thus, it is being

recognized that the quantity of real concern is not concentration, but rather exposure, which implies the interaction of a concentration and a (human) receptor, and that the population group experiencing the highest potential exposure to automobile-related pollutants is commuters.

To assess commuter exposures, the

U.S. Environmental Protection Agency commissioned a study (ref. 1) to develop methodologies for modeling commuter exposure using both computer and manual techniques.

The result was a recommendation for a modularized treatment of traffic,

emissions, and dispersion that reflected the current state of the art, but which also lent itself to relatively easy revision as modeling sophistication advanced in each of the three modules. The key element was the computer model; the manual model would be based on the computer model and consist of a series of nomographs.

This paper, which presents

the computer modeling methodology, provides an overview of the commuter exposure model and a discussion of the traffic flow module.

The emissions and dispersion

modules are presented in a second, companion paper. OVERVIEW The commuter exposure model has been designed in a modular format to facilitate the understanding of the code, to reduce the possibility of coding error and ease debugging, and to make modification relatively easy for the user.

However, the

crux of the commuter exposure modeling problem is defining the modeling area, and the most critical aspect in defining the modeling area is choosing the appropriate commuter pathways.

The commuter exposures that are calculated and the statistics

that are derived all depend directly on the pathways that are defined.

Choosing

the pathways might then be considered as a fourth module of the commuter exposure model, and it is the first to be exercised. For the problem to be manageable, a reasonable number of major commuting routes or pathways must be defined.

The commuter exposure model is designed to accommodate

up to 25 pathways having the highest numbers of vehicle miles of travel (VMT) by commuters. While it is recognized that these pathways will not carry all commuters, they will include the commuters at risk of experiencing high exposures. Most of the extensive commuting will be done along the defined pathways, both i n time and distance, and the pathways will by definition carry high volumes of traffic. A l though their total number may be close to that on the pathways, the commuters "missed" will, on the average, be traveling shorter times and distances on less heavily traveled roads.

They are not considered to be at risk to high pollutant

exposures during their commute. Commuting trips are not begun (for a morning commute) on the commute pathways as defined here, but rather on local surface streets and "collectors."

To handle

21 t h e exposure d u r i n g t h e approach t o and d e p a r t u r e from t h e pathway, minor pathways a r e used t h a t a r e r e p r e s e n t a t i v e of t h e t r a v e l t o and from t h e r o u t e .

Likewise,

a t t h e end of a (morning) commute, ending r o u t e s a r e s p e c i f i e d t h a t a r e r e p r e s e n t a The p r o c e s s i s r e v e r s e d

t i v e of t r a v e l from t h e major pathways t o work l o c a t i o n s . f o r t h e evening commute.

T r a f f i c on roadways o t h e r t h a n pathways i s t r e a t e d by a l l o c a t i n g VMT on a g r i d square b a s i s ( r e f . 2).

T h i s approximation i s made because t h e major c o n t r i b u t i o n

t o p o l l u t a n t c o n c e n t r a t i o n s on a pathway i s made by t h e v e h i c l e s t r a v e l i n g on t h e pathway i t s e l f .

The g r i d d e d street network i s d i v i d e d i n t o t h e primary network,

which i n c l u d e s roadways f o r which t r a f f i c volume i s a v a i l a b l e , and t h e secondary network, which i n c l u d e s t h e remaining roadways.

The VMT on t h e secondary network

a r e assumed t o b e a f u n c t i o n of t h e primary network t r a f f i c and l o c a l e .

The

gridded t r a f f i c d a t a a r e s u p p l i e d by t h e u s e r . The model i s designed t o be used i n a s h o r t - t e r m mode s i m u l a t i n g a s i n g l e commute p e r i o d , and i n a n a n n u a l mode t h a t s i m u l a t e s a n a v e r a g e commute over a y e a r .

A number of d a t a a r e g e n e r a t e d f o r each mode of o p e r a t i o n .

For t h e short-term

mode t h e s e a r e A l i s t of exposures on each pathway.

The a v e r a g e and s t a n d a r d d e v i a t i o n of exposures on pathways i n t h e modeling region. The p e r c e n t a g e of commuters i n each of s e v e r a l exposure c l a s s e s . For t h e a n n u a l mode t h e y a r e The p e r c e n t a g e of commuters i n each of s e v e r a l exposure c l a s s e s f o r each pathway and f o r a l l pathways. The p r o b a b i l i t y of e x p e r i e n c i n g exposure l e v e l s i n each of s e v e r a l exposure c l a s s e s f o r each pathway and f o r a l l pathways. The pathway c o n c e n t r a t i o n a s a f u n c t i o n of m e t e o r o l o g i c a l c o n d i t i o n s . Pollution roses. The exposure on each pathway and o v e r modeled r e g i o n .

TRAFFIC MODULE The t r a f f i c module of t h e commuter exposure model h a n d l e s two s e p a r a t e t r a f f i c flow regimes:

u n i n t e r r u p t e d f l o w and i n t e r r u p t e d flow.

T r a v e l on expressways i s

g e n e r a l l y u n i n t e r r u p t e d , a l t h o u g h d u r i n g a backup t h e flow can become s e v e r e l y c o n s t r a i n e d t o t h e p o i n t of becoming " s t o p and go."

I n t e r r u p t e d flow d e s c r i b e s

t r a v e l on a r t e r i a l s w i t h t r a f f i c s i g n a l s a t t h e i n t e r s e c t i o n s .

(Intersections that

have s t o p s i g n s a r e n o t c o n s i d e r e d , s i n c e t h e y w i l l n o t b e p r e s e n t f o r t h e main t r a f f i c flow on a n a r t e r i a l , commuter pathway.) t h o s e elements t h a t d e s c r i b e t h e t r a f f i c flow.

The f o l l o w i n g d i s c u s s i o n d e t a i l s

22 U n i n t e r r u p t e d Flow The c h a r a c t e r i s t i c s of u n i n t e r r u p t e d f l o w can b e o b t a i n e d from two parameters: demand volume (V) and f r e e - f l o w c a p a c i t y (C) of t h e road segment. some form are r e q u i r e d i n p u t s .

Volume d a t a i n

Data i n t h e form of a v e r a g e d a i l y t r a f f i c (ADT) o r

a n n u a l a v e r a g e d a i l y t r a f f i c (AADT) are converted t o h o u r l y v a l u e s through d i u r n a l and s e a s o n a l d i s t r i b u t i o n s , which may b e s u p p l i e d by t h e u s e r o r obtained through d e f a u l t v a l u e s i n t h e model.

Capacity d a t a may a l s o b e u s e r - s u p p l i e d ,

otherwise

t h e model assumes d e f a u l t v a l u e s a p p r o p r i a t e t o t h e v a r i o u s t y p e s of roadways. T r a v e l speed i s i m p o r t a n t f o r e s t i m a t i n g v e h i c l e p o l l u t a n t emissions along t h e pathways and f o r c a l c u l a t i n g t r a v e l t i m e , which i s t h e n used i n t h e exposure and dose c a l c u l a t i o n s .

Again, speed may b e i n p u t by t h e u s e r .

I f i t i s n o t , t h e model

c a l c u l a t e s speed on each pathway segment a s a f u n c t i o n of volume, c a p a c i t y , and t h e t y p e of roadway. Freeway Backup When demand exceeds c a p a c i t y , a t r a f f i c backup may o c c u r .

For t h e purposes of

commuter exposure modeling, a simple model was developed t o e s t i m a t e t h e s i z e of a backup and t h e a v e r a g e d e l a y t h a t i t would c a u s e .

The s t a r t i n g p o i n t i s an

e x p r e s s i o n s t a t i n g t h a t t h e r a t e of growth of t h e backup e q u a l s t h e d i f f e r e n c e i n demand minus c a p a c i t y :

where n i s t h e number of v e h i c l e s i n t h e backup, t i s t i m e , and q and s a r e t h e demand and c a p a c i t y i n v e h i c l e s p e r u n i t t i m e .

The t o t a l number of v e h i c l e s a f -

fected is then

where N’

i s t h e t o t a l number a f f e c t e d w h i l e demand exceeds c a p a c i t y , and t h e expres

s i o n i s e v a l u a t e d a f t e r demand f a l l s below c a p a c i t y .

The a v e r a g e d e l a y i s c a l c u l a t

by D = - k NeL v N

(3)

where k i s t h e d i s t a n c e between v e h i c l e s , v i s t h e t r a v e l s p e e d , and k / v i s t h e time headway.

23 I n t e r r u p t e d Flow I n t e r r u p t e d f l o w p e r t a i n s t o t r a f f i c c o n d i t i o n s when movement i s r o u t i n e l y s t o p p e d , o r i n t e r r u p t e d , f o r a f i n i t e p e r i o d of t i m e .

For t h e commuter exposure

model, o n l y two c a u s e s of i n t e r r u p t e d f l o w need b e c o n s i d e r e d :

signalized inter-

s e c t i o n s and t o l l b o o t h s , where t r a f f i c goes through mode changes from c r u i s e t o d e c e l e r a t i o n , i d l e , a c c e l e r a t i o n , and back t o c r u i s e .

Emissions, and hence con-

c e n t r a t i o n s , and t i m e s of e x p o s u r e are i n f l u e n c e d by t h e s e mode changes. Because of v e h i c l e e m i s s i o n c h a r a c t e r i s t i c s , t h e a v e r a g e r o u t e speed methodology used f o r freeways i s u s e d f o r a r t e r i a l s o u t s i d e of t h e c e n t r a l b u s i n e s s d i s t r i c t (CBD)

.

A more thorough a n a l y s i s i s w a r r a n t e d f o r CBD pathway segments.

Calculations

must be made o f d r i v i n g mode c h a n g e s , t h e p r o p o r t i o n of v e h i c l e s changing modes, and t h e l e n g t h of t i m e s p e n t i n t h e d i f f e r e n t modes.

Basically, t h i s requires a

c a l c u l a t i o n of queue l e n g t h s and d e l a y a t i n t e r s e c t i o n s .

The p a r a m e t e r s r e q u i r e d

are demand volume, c a p a c i t y , and t h e t r a f f i c s i g n a l p a r a m e t e r s of c y c l e l e n g t h and l e n g t h of t h e g r e e n (go) p h a s e . o r have t h e model c a l c u l a t e them.

The u s e r may choose t o i n p u t t h e s i g n a l parameters Queue l e n g t h and d e l a y d a t a can t h e n be used t o

c a l c u l a t e modal e m i s s i o n s . Once c a p a c i t y , volume, and t h e s i g n a l p a r a m e t e r s a r e known, t h e p r o p o r t i o n of v e h i c l e s t h a t s t o p f o r a s i g n a l i s g i v e n by

P =

1-GICy l-V/Cs

(4)

where G i s t h e l e n g t h of t h e g r e e n p h a s e , Cy i s t h e s i g n a l c y c l e l e n g t h , V i s t h e h o u r l y demand volume, and C s i s t h e c a p a c i t y service volume p e r hour of green. The number (N) of v e h i c l e s s u b j e c t t o queueing d e l a y i s

N =

P

v cy 3600

(5)

w h i l e t h e maximum l e n g t h of t h e queue (Lq, meters) i s

where 8 i s t h e d i s t a n c e ( m e t e r s ) occupied by e a c h queued v e h i c l e and M i s t h e number of l a n e s i n t h e approach.

On t h e a v e r a g e , a s t o p p e d v e h i c l e w a i t s one-half

the

l e n g t h of the r e d ( s t o p ) p h a s e , s o t h e a v e r a g e d e l a y t o t h e s e v e h i c l e s i s

D = 0.5 (Cy-G)

.

(7 1

24

For toll booths, the methodology is different because and wait to be served.

vehicles must stop

The average number of vehicles waiting to leave a toll

booth is computed from classical queueing theory as

The queue length in meters is Lq

=

8N M

(9)

’

The average delay for vehicles at a toll booth is the queue length (vehicles) multiplied by the average service rate, or the inverse of capacity: N D = - 3600 . C

(10)

The methodology presented here has been demonstrated for air pollution work in a number of studies (refs. 3,4).

While there are other more complicated methods

of handling traffic flow modeling, the present approach has been found to be quite suitable for air pollution work.

The basic outputs of the traffic module--speed,

volume, travel time, and modal behavior--are those required by the emissions and dispersion modules to calculate commuter exposure. ACKNOWLEDGEMENT This work was supported by the U.S. Environmental Protection Agency under contract No. 68-02-2754. REFERENCES

1 P.B. Simmon and R.M. Patterson, Commuter Exposure Modeling Methodologies, Report No. EPA-600/4-79-010, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, February 1979. 2 F.L. Ludwig et al., Users Manual for the APRAC-2 Emissions and Dispersion Model, Final Report, EPA Contract No. 68-01-3807, SRI International, Menlo Park, CA 94025, 1977. 3 R.M. Patterson and F . A . Record, Monitoring and Analysis of Traffic and Carbon Monoxide Concentrations at Oakbrook, Report No. EPA-450/3-74-058, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, 1974. 4 R.M. Patterson, Air Quality Modeling at Signalized Intersections, Conference on State of the Art of Assessing Transportation-Related Air Quality Impacts, Transportation Research Board, National Academy of Sciences, Washington, D.C., October 22-24, 1975.

Atmospheric Pollution 1980, Proceedings of the 14th International Colloquium, Paris, France, May 5-8,1980, M.M. Benaxie (Ed.), Studies in Environmental Science, Volume 8 0 Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands

APT

-

25

A COMPUTER PROGRAM FOR THE NUMERICAL SOLUTION OF PROBLEMS IN ATMOSPHERIC

DISPERSION

A J H GODDARD, A GHOBADIAN, AND A D GOSMAN, Mechanical Engineering Department, Imperial College, London. C HARTER AND G D KAISER, UK Atomic Energy Authority Safety and Reliability Directorate

ABSTRACT APT (Atmospheric rollution Transport) is a computer program for predicting the dispersal of non-buoyant plumes emanating from point or line sources in a two-dimensional turbulent boundary layer.

The governing partial differential

conservation equations are sblved by means of a marching finite-difference procedure and incorporate a second-order closure turbulence model, with allowance for anisotropy and thermal-stratification effects.

The methods adopted

are briefly described in this paper, as is the application of the code to an example problem involving dispersal over terrain with downwind changes in surface roughness and heat flux.

INTRODUCTION The Safety and Reliability Directorate of the United Kingdom Atomic Energy Authority has sponsored the Mechanical Engineering Depalrtment at Imperial College to develop and assess a method for the prediction of the atmospheric dispersion of radioactive material downstream of the source, using numerical schemes and physical models that had previously proved successful in several engineering applications.

This work has now been completed (ref.1) and it is felt that it

is appropriate to report on the present state of the project, including details of the method used, the applications and possible future improvements. The dispersion method has been incorporated into a computer program, APT (Atmospheric Pollution Transport), which may be used to predict the dispersal of passive plumes emanating from point or line sources in a two-dimensional turbulent boundary layer.

The method solves the governing time-averaged partial

conServation equations by means of a marching finite-difference procedure with the effects of turbulence simulated by way of a second-order closure turbulence model, which also allows for anisotropy and thermal-stratification effects on

26

on both the flow and concentration fields. The formulation of the equations is outlined as is the numerical finite-difference procedure for solving them. It is intended that APT should be used in nuelear safety studies in some circumstances in which it is not appropriate to employ a simplified Gaussian model such as is found in consequence modelling codes(ref.2).€n

particular APT can allowwind

speed, surface roughness and heat flux to change as a function of distance downwind and carries no restriction on the initial source height.

The code also contains pro-

vision for simulating deposition via a source depletion model, but this aspect will not be described in the present paper.

An example of these capabilities is given in

the form of a prediction of the release of a plume into a stably-stratified atmosphere over open countryside and its subsequent behaviour as it crosses increasingly rougher and hotter surburban, and then urban, terrain. In conclusion, a brief summary of the paper is given and other areas of application and possible further improvements are indicated.

OUTLINE OF METHOD Basic assumptions and restrictions In the interests of economy, two key assumptions were made at the outset of the development of the APT method, one being that the flow and dispersal processes are amenable to the usual time-averaging employed in turbulence theory, and the other that the flow behaves as a two-dimensional boundary layer.

The former assumption (which is

inherent in Gaussian models) allows direct calculation of the time-averaged behaviour and thereby reduces the computational burden: however, as discussed later it does imply the need for special practices to allow for long-term meteorological effects such as changes in mean wind direction.

As for the second assumption, this too considerabl)

reduces the computer requirements from what would otherwise be a three-dimensional flow calculation, but also at a price: thus, for example buoyant plumes cannot be represented in this context (although overall thermal stratification effects may,and are).

It should be emphasised however that neither assumption is essential and indeed

the consideration of buoyant plumes is already underway as part of a separate study.

Governing Equations Within the present framework the dispersion problem may be represented mathematically in terms of the governing equations of motion and thermal energy for a steady two-dimensional fully-turbulent boundary layer, viz:

a (,Pu~T) /ax, + a ( P U ~ T /ax3 )

=

-a (

P ~ T/ax3 )

(3)

27

and the conservation equation f o r the three-dimensional field of plume material: + a(Pu3c)/ ax3 =

a(Pu1c)/

- a ( P u i i ) /ax2 - a (PUT) / ax3

(4)

where: U,T and C stand for time-average values of velocity, temperature and plume concentration respectively and the lower-case versions represent fluctuations about these averages; subscripts 1,2 and 3 refer in turn to the downwind, lateral and vertical directions; p is the static pressure and p the air density; and the overbar denotes time averaging, A key feature of the method is the manner of determining the additional unknowns pu73,pu3T,pu3C and

prc 2

arising from the time-averaging process: these represent, re-

spectively, the turbulent fluxes of momentum, thermal energy and plume material in the vertical direction, and the counterpart of the latter in the lateral direction.

Un-

fortunately space does not permit details to be given here of tkdevelopment of the equations for these, nor can they be quoted, for they are lengthy.

All that can be

said is that the fluxes are deduced from mathematical models (refs 3-5) of the turbulent transport processes, which under the present circumstances, allow them to be calculated from solution of two additional differential transport equations of the general form of (3) above for the time-averaged turbulence energy k and its dissipation rate

E,

together with algebraic relations connecting the fluxes to these and

other dependent variables of the set (I) to (4).

An important aspect of the equations

is that the anisotropies of the turbulent diffusivities emerge naturally, as do likewise influences of thermal stratification. the cited references (ref.1)

Complete details are available in one of

.

Numerical Solution Procedure Since under the boundary-layer assumptions Ul is everywhere positive and diffusion in the windward direction is negligible by comparison with convection (the relevant diffusion terms therefore having been omitted from the foregoing equations) the system of equations to be solved is parabolic in the x i direction and consequently amenable to a downwind-marching finite-difference method of solution, which is the approach adopted in APT, With such methods, the differential equations are transformed by finite-difference analysis into algebraic versions which link the values of the dependent variables at the nodal points of a computational grid, of the kind shown in Fig.1, the resulting equations being typically of the form: D aCQC =zan+nD + + s

(5)

all n where

+

stands for any of the variables U1,U2, T I C, k and

E;

the superscripts D and

U respectively refer to a particular Downstream cross-sectional plane of nodes and its

Upstream neighbours; the -

subscript

C

stands for the Central node of a typical cluster

in either plane and the summation C is over its nearest neighbours; and the a’s and S contain the combined effects of convection, diffusion and internal sources. Given a

28

starting field of

$u's, the sets of simultaneous equations (5) written for each vari-

able at all nodes are easily solved for the

$ J ~ ' S ,and

the resulting solution is then

available as the 'upstream' field for the next forward step in the x1 direction; and

so on. The foregoing entirely conventional practices are followed in APT, as is also the,,practiceof adjusting the dimensions of the grids in the cross-stream plane during the marching process so as just to encompass the region of significant gradients in the $Is.

An

important novelty (ref.1) is however the use of a separate smaller embed-

ded grid for the plume concentration calculations, as indicated in Fig.1.

Thisis done

out of recognition that the plume dimensions are often significantly smaller than those of the atmospheric boundary layer, thus entailing quite different grid spacings for optimum accuracy and economy.

Interpolation is employed to transfer velocity and dif-

fusivity information from the large grid onto the smaller one. APPLICATION Example problem The example that has been chosen to illustrate some of the useful features ofthe

APT program is that of the transport of a radioactive plume over consecutive regions of rural, suburban and urban terrain, each exhibiting different characteristic values of meteorological roughness and ground sensible heat flux, This use of the code in this context serves to demonstrate the capability to simulate varying surface conditions and the importance of doing this is reinforced by a second calculation in which the rural conditions are imposed throughout, as might be done in the equivalent conventional Gaussian plume representation. The specific conditions imposed are as follows: the notional radioactive pollutant,is assumed not to decay and is released at a constant rate from a 100 m elevated source into a nominal 8 m/s wind which has developed from an initially neutral 1 km deep atmospheric layer (this specification providing the starting conditions for the calculations) over a 20 km upstream fetch of rural terrain with a ground heat flux of

-

lo W/m2 and roughness length of 0 . h .

These conditions give a stably-stratified

atmosphere corresponding to Pasquill weather category E, according to the curves derived by Smith (ref.6).

The surface conditions remain at the rural levels for a fur-

ther 2 km downstream of the source, at which point a 2 km stretch of suburban terrain is encounter.,d. Data for- typical UK cities (ref.7) show that appropriate levels for sensible heat flux and surface roughness over such terrain are 10 W/m2 and 0.5 m respectively.

Following on from this the levels are further increased, in accordance with

the same data source, to values of 40 W/m2 and 1.0 m appropriate to urban conditions and the calculations are terminated after proceeding a final 2 km. Results The solid curves of Fig. 2 show the predicted variations with downstream distance the heighth, of the location of concentration Cmax in the cross-section; the relative value of the ground level concentration maximum Cground/Cmax; and the locations of the

of,

29 upper (1,) Cma,:

and lower A(),

plume boundaries, defined as the locations where C is 50%

The dashed lines depict the same information for uniformly-rural conditions,

and show the plume developing in the manner characteristic of Gaussian models of elevated releases, with the centreline running roughly parallel with the ground and no dramatic change in rate of spread with downstream distance. By contrast.,the full rural/suburban/urban simulation shows the plume as being initially deflected upwards as it passes over the suburban region and then the lower boundary plummeting downwards shortly after the urban zone is encountered, a manifestation of the expected 'fumigation' effect.

Inspection of the detailed output of the

calculations reveals the initial upwards motion as being due to the upwards velocities provoked by the sudden retardation of the near-ground wind by the increased roughness, an effect which occurs again at the start of the urban zone.but is masked by other processes there.

However the increase in roughness and positive heat flux also pro-

mote the growth of an internal layer of high turbulence which propagates upwards and eventually causes fumigation to occur when it reaches the main plume, through both the augmentation of the diffusivities and the downwards velocities resulting from the consequent thinning of the boundary layer.

As can be seen, the full simulation therefore

produces significantly higher ground level concentrations once fumigation occurs than does the representation based on uniform meteorological conditions.

Side Elevation Figure 1 Illustration of the flow grid and the embedded plume grid, showing their adjustment during the marching process.

30 I

I I

I I

+

-

+

-

+

RURAL TERRAIN THROUGHOUT

I

I I I

b

I I

DOWNSTREAM DISTANCE (m)

heat flux and (below) position of plume centreline, 50% boundaries and relative ground level concentrations. ACKNOWLEDGEMENTS The important contributions made to the development of APT by Professor B.E.

Launder,notably in the area of turbulence,are hereby acknowledged.

REFERENCES 1 S. El Tahry, Turbulent Plume Dispersal, PhD Thesis, Imperial College, London, 1979. 2 L.S. Fryer and G.D.Kaiser, TIRION 4, a Computer Code for use in Nuclear Safety Studies, UKAEA Rep. SRD R/34 (1978). 3 B.E. Launder, G.J. Reece, and W. Rodi, Journal of Fluid Mechanics, (1975) 68, 537. 4 B.E. Launder, Heat and Mass Transport, Chapter 6 in Topics in Applied Physics (1976), Volume 12, Springer, Edited by P. Bradshaw. 5 M.M. Gibson and B.E. Launder, Ground effects on pressure fluctuations in the atmospheric boundary layer, Journal of Fluid Mechanics (1978), 86,491. 6 F.B.Smith, A Scheme for Estimating the Vertical Dispersion of a Plume from a source near Ground Level, Proc. 3rd Mtg. on Air Pollution Modelling, NATO/CCMS, 14, Brussels (1972), unpublished UK Meteorologiaal Office Report. 7 R.H. Clarke, National Radiological Protection Board Report, NRPB-R91, (1979). 8 S. El Tahry, A.D.Gosman and B.E. Launder,The Two-and-Three-Dimensional Dispersal Of a Passive Scalar in a Turbulent Boundary Layer. Imperial College, Mechanical Engineering Department Report (1979). To appear in 1nt.J. Heat Mass Transfer.

Atmospheric Pollution 1980,Proceedings of the 14th International Colloquium, Paris, France, May 5--8,1980, M.M. Benarie (Ed.), Studies in Environmental Science, Volume 8 0 Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands

31

THE TRANSPORT, CHEMICAL TRANSFORMATION, AND REMOVAL OF SO2 AND SULFATE I N THE EASTERN UNITED STATES

GREGORY R . CARMICHAEL and LEONARD K. PETERS U n i v e r s i t y o f Iowa, Iowa City, I A and U n i v e r s i t y o f Kentucky, Lexington, KY (U.S.A.)

ABSTRACT

A r e g i o n a l model o f SOE and s u l f a t e t h a t includes a d v e c t i v e and d i f f u s i v e t r a n s p o r t , homogeneous and heterogeneous o x i d a t i o n , and d r y d e p o s i t i o n o f both species i s described. and wind f i e l d .

The model i n c o r p o r a t e s t e m p o r a l l y and s p a t i a l l y v a r y i n g m i x i n g l a y e r Studies on the dynamic response o f an e l e v a t e d plume t o daytime

v a r i a t i o n s i n v e r t i c a l m i x i n g show the s h i f t toward t h e surface o f the plume c e n t e r l i n e , t h e e x i s t e n c e o f a double maxima i n ground l e v e l concentration, and the t r a p p i n g o f p o l l u t a n t s i n t h e e a r l y evening.

INTRODUCTION S u l f u r d i o x i d e has l o n g been known t o be a major p o l l u t a n t , b u t s t u d i e s now i n d i c a t e t h a t t h e o x i d a t i o n product, s u l f a t e , may present a g r e a t e r h e a l t h hazard and produce a number o f adverse e c o l o g i c a l e f f e c t s ( r e f . 1 ) .

I t i s g e n e r a l l y accepted

t h a t most s u l f a t e i s formed i n t h e atmosphere by chemical conversion from SO2. Long range t r a n s p o r t models can be used t o t r a c e the sources o f SO2 and t o t e s t t h e o r i e s o f t r a n s p o r t , t r a n s f o r m a t i o n , and removal by comparing model p r e d i c t i o n s w i t h measurements from m o n i t o r i n g networks ( r e f . 2-7). I n a p r e v i o u s paper ( r e f . 8 ) , we presented a combined transport/chemistry/surface removal model t o d e s c r i b e t h e r e g i o n a l d i s t r i b u t i o n o f s u l f u r d i o x i d e and s u l f a t e w i t h i n t h e lower troposphere.

I n t h i s paper, we w i l l summarize t h a t development and

study t h e dynamic response o f an e l e v a t e d plume t o daytime v a r i a t i o n s i n v e r t i c a l m i x i n g u s i n g a subset o f t h e model. MODEL DESCRIPTION The r e g i o n a l t r a n s p o r t o f SO2 and s u l f a t e i s modeled w i t h i n an E u l e r i a n framework. The g r i d model i n c o r p o r a t e s chemical transformation,

dry deposition, spatial varia-

t i o n o f topography, and s p a t i a l and temporal v a r i a t i o n s o f m i x i n g l a y e r h e i g h t , wind f i e l d , eddy d i f f u s i v i t y , d e p o s i t i o n v e l o c i t i e s , and temperature and water vapor concentration profiles.

A photochemical SO2 o x i d a t i o n mechanism i s i n c o r p o r a t e d i n t o

32

t h e t r a n s p o r t model w i t h t h e r a t e p a r a m e t e r i z e d u s i n g d i u r n a l l y v a r y i n g r a d i c a l s p e c i e s c o n c e n t r a t i o n s and a f i x e d heterogeneous r a t e c o n s t a n t . The matheniatical a n a l y s i s i s based on t h e coupled, t h r e e - d i m e n s i o n a l a d v e c t i ond i f f u s i o n equations f o r ac

ack+ at

k= Lax.[ K

U J. ax.

J

SO2 and s u l f a t e

(71

j j ax.

J

+ Rk + Sk

(11,

where c k i s t h e c o n c e n t r a t i o n o f s p e c i e s k, u . i s t h e v e l o c i t y v e c t o r , K is the J jj eddy d i f f u s i v i t y t e n s o r (K. .=O f o r i f j has been assumed), Rk i s t h e r a t e o f forma1J

t i o n o r l o s s b y chemical r e a c t i o n , and Sk i s t h e e m i s s i o n r a t e . V a r i a b l e t o p o g r a p h y i s h a n d l e d by mapping t h e i r r e g u l a r v e r t i c a l r e g i o n i n t o a d i m e n s i o n l e s s r e c t a n g u l a r r e g i o n w i t h t h e t o p s e t a t 3000 m e t e r s .

There a r e t e n

v e r t i c a l g r i d s w i t h h i g h e r r e s o l u t i o n between t h e s u r f a c e and 450 meters which p e r m i t s s i m u l a t i o n o f t r a n s p o r t i n s t a b l e l a y e r s a l o f t and i t s subsequent r e - e n t r a i n ment i n t o t h e m i x i n g l a y e r . The dynamic model uses a G a l e r k i n method f o r t h e n u m e r i c a l s o l u t i o n o f t h e p a r t i a l d i f f e r e n t i a l equations ( r e f . 9).

A t t h e b o u n d a r i e s , two cases a r e i m p o r t a n t .

m a t e r i a l t r a n s p o r t i n t o t h e model r e g i o n , and t h e second i s o u t f l o w .

One i s

I n b o t h cases,

t h e b e s t estimate o f t h e f l u x i s obtained from t h e concentration gradient a t the previous time step. CHEMISTRY OF SO2 AND SULFATE

SO2 o x i d a t i o n mechanism i n c o r p o r a t e d i n t o t h e model i s i n s u f f i c i e n t d e t a i l t o p r e d i c t a r e a l i s t i c o x i d a t i o n r a t e o f SO2 w i t h i n an a c c e p t a b l e c o m p u t a t i o n t i m e . The

Furthermore, b o t h homogeneous and heterogeneous processes a r e i n c l u d e d i n conversion t o sulfate. Homogeneous gas phase c h e m i s t r y A homogeneous gas phase mechanism f o r

SO2 o x i d a t i o n was developed by e v a l u a t i n g

t h e r a t e s o f i n d i v i d u a l r e a c t i o n s f r o m a d e t a i l e d k i n e t i c m o d e l i n g of two smog chamb e r s t u d i e s ( r e f . 10, 1 1 ) .

The r e s u l t s from t h e d e t a i l e d model were t h e n used t o c o n -

s t r u c t a s i m p l i f i e d scheme.

T h i s d e t a i l e d mechanism i n c l u d e d 72 r e a c t i o n s , and a com-

p l e t e d e s c r i p t i o n can be f o u n d elsewhere ( r e f . 7 2 ) .

The o v e r a l l r e s u l t s o f t h a t

s t u d y showed t h a t t h e d e t a i l e d k i n e t i c mechanism s i m u l a t e d w e l l t h e

SO2 o x i d a t i o n

r a t e s o b t a i n e d i n t h e two s t u d i e s . Based on t h e r e s u l t s , t h e most i m p o r t a n t r e a c t i o n s were r e t a i n e d . degree o f accuracy, t h e

To a h i g h

SO2 r a t e e x p r e s s i o n can be s i m p l i f i e d t o

The c o n c e n t r a t i o n s o f OH and H02 show d i u r n a l v a r i a t i o n s . The r a t e e x p r e s s i o n f o r SO2 i s uncoupled f r o m t h o s e f o r

OH and H02 by u s i n g t h e

33

SO2 c o n c e n t r a t i o n a t t h e p r e v i o u s t i m e s t e p i n t h e c a l c u l a t i o n o f OH and H o p .

This

approach agrees w e l l w i t h t h e e x p e r i m e n t a l d a t a and t h e v a l u e s p r e d i c t e d b y t h e det a i l e d model.

The r e l a t i v e c o m p u t a t i o n t i m e s f o r t h e d e t a i l e d and s i m p l i f i e d m o d e l s

a r e a p p r o x i m a t e l y 40: 1. Heterogeneous c h e m i s t r y

I n t h e atmosphere, t h e heterogeneous o x i d a t i o n o f SO2 occurs v i a o x i d a t i o n by i n t h e absence o f c a t a l y s t , c a t a l y t i c o x i d a t i o n by 02, and o x i d a t i o n by 0 3 . p o r t e d r a t e c o n s t a n t s f o r t h e u n c a t a l y z e d o x i d a t i o n by d i s s o l v e d

O2

O2

The r e -

v a r y b y two o r -

d e r s o f magnitude, w i t h most r e p o r t s on t h e l o w end i n d i c a t i n g t h a t t h i s r e a c t i o n i s n o t e x t r e m e l y i m p o r t a n t i n t h e atmosphere.

The c a t a l y z e d o x i d a t i o n o f

SO2 i s most

i m p o r t a n t i n urban a r e a s and s t a c k plumes under c o n d i t i o n s of h i g h h u m i d i t y and h i g h c a t a l y s t concentrations;

i t i s u n l i k e l y t o be s i g n i f i c a n t i n r u r a l areas.

Recent

measurements o f t h e r a t e o f o x i d a t i o n o f SO2 b y d i s s o l v e d O3 a l s o d i f f e r by two o r d e r s o f magnitude.

I f t h e h i g h e r r a t e c o n s t a n t i s c o r r e c t , t h e n t h e o x i d a t i o n by

O3 i s i m p o r t a n t even a t a t m o s p h e r i c background ozone c o n c e n t r a t i o n s . Assuming o x i d a t i o n by d i s s o l v e d 0 3 ,

02,and m e t a l c a t a l y s t s o c c u r s i m u l t a n e o u s l y ,

t h e combined heterogeneous r a t e e x p r e s s i o n can be w r i t t e n as d [SO,2-]

h K = -1.5

dt

d[SO,] -

60 KIHv*

dt

[H'I

( h K P '3 '3 '3

+ - 02 [Hf]

+

kcatK2[M+I)Cso21

(3) >

i s i n ppm min-', [SO2] i n ppm, H i s H e n r y ' s l a w c o n s t a n t , v* i s t h e 5 aqueous volume p e r volume o f a i r , ho =1x10 -3.3x105L m o l - l s - ' , K - 2 . 2 ~ 1 0 - ~ m o l L - ~ a t m - ~

where d[S04'-]/dt

O3-8 L 2mol - 2 s -1, [M+] Po3 i s t h e O3 p a r t i a l p r e s s u r e , ho =36 ~ 1 O - ~ s -fl o r 3\

I I

/

\

\

'-'

/

0.05

\

I

* -\

/

'

I'

0.02 0.01

0.02

-

n0

-

0.01 a

I

I

I

6

12

18

n

I

24 - 0

6

b I

I

I

12

18

24

L.S.T (hours) Fig.2 Diurnal ozone variation i n J e r u s a l e m on selected days. (a) No transport ( b ) Evidence of t r a n s p o r t

Frequently, however, a different p a t t e r n is found, ( F i p . 2., (b). H e r e two maxima c a n be observed; t h e f i r s t one between 1 2

-

1 3 h L. S. T . , and the second one,

which is usually considerably higher, two t o t h r e e hours l a t e r .

The sudden

i n c r e a s e in ozone concentrations i n the e a r l y afternoon is accompanied by a s i m i l a r s h a r p r i s e in the w a t e r vapor mixing ratio, w, thus indicating the a r r i v a l of a distinct air m a s s f r o m t h e coast.

Lastly, recent wind observations in

J e r u s a l e m have shown, that wind s p e e d s i n c r e a s e d and wind directions acquired

a w e s t e r l y component a l s o a t about 14 h.

These f a c t s indicate that the appearance

of ozone peaks in the e a r l y afternoon c a n be attributed to transport of polluted air f r o m the c o a s t a l a r e a . The relationship between ozone levels in J e r u s a l e m and T e l Aviv and the variation of w i n J e r u s a l e m a r e shown in Fig. 3 f o r a typical "transport day". -1 and wind On this day wind speed in J e r u s a l e m increased f r o m 8 to 18 k m h direction changed f r o m 120° (Em)to 300" (WNW) a t 14 h.

168

Tel Aviv

A Jerusalem 0 0 3 IJerusalem)

0.10

17.4. I977 /

\

#

0 3 Tel Aviv

0.08

‘,w, Jerusalerr

I 0.07 h

d 0.06

d v

m 0.05

0 0.04

0.03

b\

0.02

b

10

12

14

16

18

L . S . T (hours) Fig. 3. Ozone concentrations in J e r u s a l e m and T e l Aviv and w in Jerusalem on 17. 4.1977. The frequent incidence of transport phenomena is demonstrated in Fig. 4 where the average monthly diurnal ozone variation is given f o r July 1977, July 1978 and September 1978. It can be s e e n that the maximum ozone concentration occured in a l l c a s e s between 14 - 15 h.

Due to the high incidence of transport

days and to the large impact of the p r o c e s s of the pollution levels in Jerusalem, the meteorological conditions enhancing transport f r o m the coast w e r e investigated. During the 3 y e a r s studied 244 transport days occured. The highest incidence of transport w a s in July (71% of all days), the lowest in April (10% of all days).

The dependence of the daily maximum ozone concentration on selected meteorological variables w a s examined.

It was found that the mcs t important factors

w e r e wind direction and inversion height.

It has been shown previously (Halevy

and Steinberger, 1974), that low-level inversions occur on 87% of a l l summer

169

a July 1978 0

Sepi 1978

0.05

I

I

I

6

12

18

I 24

L .S .T ( hours ) Fig. 4.

Average monthly diurnal ozone variation f o r July 1977, 1978 and September 1978 days and the inversion layer penetrates inland to at least 50 km.

Due to the

r i s i n g t e r r a i n (to 800 m elevation) the base of the inversion above J e r u s a l e m is about the same a s on the coast,

This conclusion was recently reconfirmed

by a s e r i e s of simultaneous upper-air soundings in Jerusalem and in Beit Dagan. It should be noted that ozone transport c a n occur a l s o in the absence of inversions, but the ozone maxima w e r e lower and the frequency of occurrence smaller.

(Fig. 5. )

The dependence of ozone concentration on wind direction is shown in Fig. 5. It is s e e n that the largest concentrations w e r e measured for

6

= 320".

This

result is the direct consequence of the relative location of J e r u s a l e m and T e l Aviv.

(Fig. 1. 1. A linear correlation was found between ozone maxima and wind

direction, with a correlation coefficient r = 0. 90. The connection between ozone maxima and inversion base height, H, is shown in Fir?.. 6 . It c a n be s e e n that the highest ozone levels occur for the lowest inversion bases.

This behaviour c a n be explained by noting that when low

inversions a r e present, the vertical mixing in the atmosphere is inhibited,

170

ooo

inversion

00.

No inversion

40

doys 0

.' 0.

O

060

L *

A

050

30-

h

V

i

.

c

4

a Y

040

m

0

I

,030

180

210

240

Wind

270

330

330

360

direction , 8

Fig. 5. Frequency distribution of transport day by wind direction and the average ozone maximum f o r each direction.

'I"

It

0,. 480.5 1 (IOOO/H YZ6' r = 0.86

\o

.08-

E

-2

.06-

n

0 .04 0

,021

500

1000

H (m) Fig. 6 . Ozone maxima vs. inversion base height.

1500

2000

171 leading to i n c r e a s e d pollutant concentrations under the inversion l a y e r .

The

Gaussian dispersion models also p r e d i c t a s i m i l a r dependence of concentrations on H. Various r e g r e s s i o n equations w e r e t r i e d to r e p r e s e n t the data and t h e best f i t w a s obtained by using the equation:

0 3 = 0.047

1000

o*286

with a c o r r e l a t i o n coefficient r = 0. 75.

CONCLUSION

It has been shown that t r a n s p o r t of pollutants f r o m the coast is a r a t h e r frequent p r o c e s s in I s r a e l during the s u m m e r months.

Transport will be facilitated when

low-level inversions a r e present.

REFERENCES' 1 P.E. Coffeyand W.N. Stasiuk, Environ. Sci. Tech., 9, (1975) 59-61. 2 R.A. Cox, F.J. Eggleton, R.G. Derwent, J.E. Lovelock and D.H. Pack, Nature (London), 255 (1975), 118-121. 3 G. Halevy and E. H, Steinberger, I s r a e l J. E a r t h Sci. 23, (1974), 47-54. 4 E. Ganor, E. H. Steinberger a n d A. Donagi, P r o c . 8th Sci. Conf., I s r a e l Ecol. SOC., (1977), 230-241. 5 Z . Naveh, E. H. Steinberger and S. Chaim, Environ. Poll. 1 6 , (1978),249-262. 6 E. H. Steinberger and Y. Balmor, Nature (London), 241, (1973), 341 -342.

This Page Intentionally Left Blank

Atmospheric Pollution 1980, hoceedings of the 14th International Colloquium,Paris, France, May 5-8,1980, M.M. Benarie (Ed.), Studies in EnvironmentalScience, Volume 8 0 Elsevier Scientific Publishing Company, Amsterdam -Printed in The Netherlands

173

DIRECT FORMATION OF NO2 IN COMBUSTION PRODUCTS

W. J. McLEAN Sandia Laboratories, Livermore, California (USA)

J. Y. CHEN, F. C. GOULDIN, and M. J. OVEN Cornell University, Ithaca, New York (USA)

ABSTRACT It is noted that combustion devices may, under some operating conditions, produce NOX emissions containing a rather large fraction of NO2. A detailed chemical kinetic mechanism for such NO2 formation is presented, and the results of measurements on a laboratory combustor are described. It is concluded that NOz forms via the reaction NO + H02 + NO2 + OH in regions where combustion processes are rapidly quenched by mixing with excess air.

INTRODUCTION The oxides of nitrogen (NOX) represent one of the principal classes of primary pollutants of concern in urban environments. The term NOx is used to designate the sum of the concentrations of the two oxides of concern, nitric oxide (NO) and nitrogen dioxide (NO2). Nearly all NOx in urban atmospheres is produced in high temperature combustion devices, where small quantities of atmospheric nitrogen or the trace quantities of organic nitrogen in the fuel may be oxidized to NO. Nitrogen dioxide, the atmospheric end product of NOx emissions, is of concern both because its photochemical reaction products lead to ozone formation, and because health effects are associated with exposure to low levels of NO2. It has also been recently noted that NO2 can play a role in atmospheric reactions which form mutagenic nitro derivatives from polycyclic aromatic hydrocarbons (ref. 1). Although NO2 is the oxide of nitrogen of concern in the polluted atmosphere, combustion sources operating under most conditions usually emit most of their NOx as NO. Subsequent reactions and dispersion in the atmosphere detenine the ambient levels of NOz. The chemical dynamics of NO to NO2 conversion in the atmosphere are complex, but by now reasonably well understood (ref. 2). Ambient concentrations of ozone (03), the primary noxious atmospheric oxidant, are

174

established by a relatively rapid photochemical cycle involving NO2, NO, and 0 3 , which results in O3 concentrations proportional to the ratio of the concentrations of NOz to NO. The high NO2 to NO ratios necessary for attaining ozone levels typical of polluted atmospheres result from photochemically induced reactions of NO, NO2 and hydrocarbons. In brief, oxygen atoms produced by photolysis of NO2 react with hydrocarbons present in polluted atmospheres to produce organic peroxy radicals. These radicals in turn accelerate the required oxidation of NO to NOz. Such processes typically take several hours in urban atmospheres, so that peak ozone levels are usually observed sometime after peak NO emissions. The time interval between the peaks represents the time required for conversion of NO to NO2.

It has recently come to our attention that a number of different types of combustion systems, both practical devices and experimental laboratory combustors, produce NOx containing a large fraction of NO2 under some operating conditions. Although the regimes of high NOz/NOx fractions are in general associated with relatively low total NOx emissions, such direct NO2 emissions to the atmosphere are of concern. Atmospheric reaction cycles on small geographic scales could possibly be perturbed by such emissions. Also, plume visibility and health effects due to short term NO2 exposure would be increased by locally high NOz emission sources. It is also possible that the efficacy of exhaust treatment processes may depend upon the form of the oxide of nitrogen in the exhaust. The purpose of the present study is to summarize those conditions which lead to direct formation of NO2 in combustion systems and to elucidate the causes of such direct NO2 formation. The results of a detailed chemical reaction theory as well as measurements on a laboratory prototype gas turbine combustor are discussed. NOz EMISSIONS FROM COMBUSTION SYSTEMS In this section recent literature regarding measured NOz emissions from various combustion devices is briefly summarized. It should be noted that extreme care must be exercised in sampling and transfer of combustion products if reliable N02/NOx ratios are to be obtained. If samples are obtained near the combustion zone itself, conversion of NO to NOz during cooling in the sampling probe is almost unavoidable (refs. 3,4,5). Care must also be taken to avoid both transformation by heterogeneous reactions in sampling lines and dissolution of NO2 into condensed water vapor (refs. 6 , 7 ) . The measurements cited below were all taken at the exhaust of the combustion devices where reliable probe sampling could be assured. Samples were also carefully handled and conditioned to avoid transformation in sampling lines. Gas turbines are in widespread use both in aircraft engines and in various types of stationary power plants. In both applications gas turbine combustors

175

have been shown t o produce substantial fractions of t h e i r NOx emissions as NO2 under l i g h t load conditions (ref. 7 ) . Such d i r e c t NO2 emissions from large stationary gas turbines may have a d i r e c t influence on plume v i s i b i l i t y (ref.8), while a i r c r a f t emissions may contribute t o locally high NO2 levels which are of concern near a i r p o r t s (ref. 9 ) . NO, emission measurements on a gas turbine power s t a t i o n obtained by Johnson and Smith (ref. 10) perhaps typify gas turbine behavior. Their data are s m a r i z e d i n Fig. 1 where NO and NO2 emissions and the r a t i o N02/NOx is shown as a function of turbine load. Total NOx emissions decrease with load but the NO2 fraction rapidly increases.

1

Hilliard and Wheeler (ref. 11) have recently reported results of careful NO and NO2 measurements i n reciprocating piston engine exhausts. In spark

80-

ignition engines, the NO2 i s

P c

0

only about 1%of the t o t a l NO, over a wide range of operating conditions. However, i n the diesel engine the combustion process i s different and considerable NO2 i s found i n the exhaust.

60-

c w

20

40

60

8o

TURBINE LOAD (% FULL LOAD)

F i g . 1. NO and NO emissions from a gas turbine power plan$ as given i n r e f . 10.

loo

Here, as i n the gas turbine system, the peak NO2 values are attained under l i g h t load conditions, while the NO and t o t a l NOx increase as load increases. The percentage of NO2 i n t o t a l NOx is about 2 5 % a t l i g h t loads

and decreases t o l e s s than 5% a t one-half maximum load.

Concentrations of NO,

arein general about an order of magnitude higher i n diesel exhaust than i n gas turbine exhaust. MECHANISM FOR NO2 FORMATION The r e s u l t s c i t e d above indicate t h a t the formation of NO2 is somehow intimately related t o processes i n the combustion chamber, and not simply due t o NO oxidation i n the exhaust system. Otherwise it would be expected t h a t NO2 would follow trends similar to NO. I t i s generally agreed t h a t any NO2 observed is derived from NO i n i t i a l l y formed i n the high temperature primary combustion zone. I t i s also accepted t h a t the t e m l e c u l a r reaction 2NO + O2 + 2 NO2 is too slow t o account f o r the observed NO2 levels. NO2 formation i n practical systems and i n laboratory combustors (ref. 11) i s strongly associated with those operating

176

regimes where hot, NO containing products of partially complete combustion are cooled and chemically quenched by rapid mixing with surrounding excess air. Both gas turbines and diesels operating at light loads exhibit this type of combustion condition, because the low fueling rates produce smaller, less intense Combustion zones which quickly mix with large quantities of surrounding air. Evidently, under these conditions NO is formed in the primary combustion zone and subsequently oxidized to NO2 by chemical reactions which are enhanced by the quenching process. We have constructed a detailed elementary chemical reaction mechanism to help explain our observations of NO2 in a laboratory prototype gas turbine combustor, in which intense shear between co-flowing jets causes rapid quenching of the combustion process. The history of NO to NO2 transformation in combustion products has been calculated during a simulated quenching process. The details of the mechanism and the simulation analysis are reported elsewhere (ref. 3); the principal features are summarized here. The continued oxidation of partially burnt combustion products during the quenching process is simulated by the multistep methane oxidation mechanism represented by the first 43 reactions in Table I. Because it was of interest to examine processes taking place at moderate temperatures, this mechanism contains a number of reactions involving H02 and H202 which are not important during high temperature oxidation. Reactions 44-50 in Table I determine NO and NO2 concentrations, with reaction 48 governing oxidation of NO to NO2. Application of the mechanism of Table I to quenching conditions typical of those found in our laboratory combustor have been carried out, and the details have been reported elsewhere (ref. 3). In brief, combustion products containing 30 ppm NO are assumed to be mixed with unbumt reactants and cooled from 1900K to 700K in Sms. These conditions are determined from analysis of the composition, temperature, and velocity measurements made inside the combustor (ref. 1 2 ) . The results of applying the reaction mechanism under these conditions are shown in Fig. 2 where the species concentrations and temperature are shown as functions of time. The increasing CH4 mole fraction in Fig, 2 is due to the fact that, in this combustor, quenching results from mixing of hot burnt products with cold unburnt reactants containing CH4. With respect to NO and NO2, a detailed analysis of the calculations used to construct Fig. 2 indicates that NO is rapidly oxidized to NO2 by H02, which is produced during quenching by reaction 10. With unbumt CH4 present, sufficient H02 is produced to convert all the NO to NO2. If unburnt CH4 is not present during the quenching process, a much smaller increase in the H02 concentration is obtained, and only about 25% of the NO is oxidized to NO2. EXPER1ME.NP.L RESULTS As part of a continuing experimental program on gas turbine combustion, we have made NO and NO2 measurements in the exhaust plane of a laboratory prototype gas

177

100 80

60 V

40

a

L

20

0

OHxlO-l

1

2

3

4

5

TIME (ms)

Fig. 2.

Calculated species mole fractions during a simulated combustion quenching process.

BvANE SWIRLER

,-INTERJETSHEAR

LAYER

Fig. 3. Schematic drawing of swirl stabilized laboratory combustor.

178

turbine combustor. The experiments are fully described elsewhere (ref. 1 2 ) , and only briefly smarized here. A schematic of the swirl stabilized laboratory combustor is shown in Fig. 3. The combustor is composed of two confined coaxial jets, each having swirl. The inner jet contains premixed methane-air with swirl obtained by tangential air injection. Secondary air is supplied in the outer jet with swirl regulated by variable angle vanes. Both co - and counter - swirl conditions are possible. Combustion is stabilized by the recirculation zone formed immediately downstream of the jet entrance by the fluid dynamic phenemonon hown as vortex breakdown. Samples obtained from the exhaust plane of the combustor by a water cooled probe were analyzed for NO and NO2 by a chemiluminescent analyzer equipped with a stainless steel converter for differentiating between NO and NO2. Additionally a dual beam optical technique based on ultraviolet absorption in the y (0,0) band of NO was used to confirm concentration measurements. The relative difference between the NO mole fractions determined by the two instments was generally less than 10%. The NOx measurements were analyzed for NO2 formation in the cooling region of the probe by the reaction mechanism of Table I. It was concluded that in the exhaust plane temperatures below 1400K prevented significant NO to NO2 conversion during sampling under most conditions (ref. 3). I

I

I

1100

-80

- 'O -5

- 6o -

0,

-3 70

5 80

0

90 %

10 Pm Porticle Diometer dp

100

Fig. 3. Power plant A : stone coal-fired; comparison of the particle size distribution of flue dust out o f the crude exhaust gaq, the pre-cleaner, the final cleaner and the purified exhaust gas.

Yo 100

Od

1

10 Pm Particle Diometer dp ‘pp 1.0 g/cm3 1

100

Fig. 4. Power plant A: lignite-fired, evaluation without preimpactor mass.

265

0 10

3

0

1 Day

Axis 3

20

30 LO 0

4 50 3 LX 60

-

V

9Ar-r 100

L

0.l

1

10 Pm Partide Diameter dp

-

100

I Q =~i.0g/cm31

Fig. 5. Power plant B: lignite-fired, measurements in the purified exhaust gas.

0 POWER PLANT E

10

20

0 1 Day

V

0

Lignite

Axis 3

ZDay 3Day

30

3 LO 2 u)

a"

50

060

> .c

5 70 E

5 80 90 VO

100

0.1

1

10 Pm Particle Diameter dp

0

(pP = l . ~ g / c r n ~ ) Fig. 6. Power plant B: lignite-fired, evaluation without preimpactor mass.

266

3. CONCLUSION

For measurements of particle size distributions of flue dust a cascade impactor is very suitable if no great strain is put on high accuracy. The results of impactor measurements represent a time-averaged value. The application of a pre-separator if particles larger than 10 microns are expected is highly recommended. The impactor should not be used to determine the total dust concentration in an exhaust duct.

REFERENCES

1

Marple, V. A.: A fundamental study of inertial impactors. Diss. Univ. of Minnesota

Atmospheric Pollution 1980, Proceedings of the 14th International Colloquium, Paris, France, May 5-8,1980, M.M. Benarie (Ed.), Studies in Environmental Science, Volume 8 0 Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands

MEASUREMENT OF AEROSOLS LESS THAN 0.01 pm

-

267

APPLICATION TO THE NUCLEATION I N THE

ATMOSPHERE M.L. PERRIN, Y.C. Commissariat DPr/STEP/SPT,

a

BOURBIGOT, 6.3. MADELAINE

1'Energie Atomique, I n s t i t u t de P r o t e c t i o n e t de Sirrete Nucleaire, CEN/FAR B.P. 6, 92260 FONTENAY-aux-ROSES, FRANCE.

ABSTRACT

IJe use a d i f f u s i o n b a t t e r y coupled w i t h a condensation n u c l e i counter t o d e t e r mine the f i n e p a r t o f t h e urban atmospheric aerosol s i z e d i s t r i b u t i o n . The e s t i mation o f t h e n u c l e a t i o n r a t e s i n two cases a l l o w s t o j u s t i f y the presence, o r not, o f a " n u c l e a t i o n " mode which comprises p a r t i c l e s w i t h a diameter l e s s than 0.008 pm.

INTRODUCTION

The d i f f u s i o n b a t t e r y method (1) allowed us t o go deeply i n t o the knowledge o f f i n e p a r t i c l e s , and p a r t i c u l a r l y p a r t i c l e s w i t h a diameter l e s s than lo-'

pm.

Smog-chamber experiments showed t h e d i f f e r e n t process which govern the e v o l u t i o n o f f i n e aerosols, e i t h e r i n s t a n t a n e o u s l y , o r c o n t i n u o u s l y produced ( 2 ) . A f i r s t approach o f the r e a l phenomena was obtained.

Then, i t seemed i n t e r e s t i n g t o make

" i n s i t u " measurements. This paper concerns urban atmospheric measurements. One can o b t a i n several forms o f s i z e - d i s t r i b u t i o n s ,

according t o the time when sam-

p l i n g i s made, m e t e o r o l o g i c a l c o n d i t i o n s , s o l a r a c t i v i t y , e t c . . .The t r i m o d a l d i s t r i b u t i o n g i v e n by WHITBY ( 3 ) seems t o be c o r r e c t t o d e s c r i b e the p h y s i c a l nature o f the atmospheric a e r o s o l . With a d i f f u s i o n b a t t e r y , our study i s more s p e c i a l l y l i m i t e d t o p a r t i c l e s w i t h a diameter between 3.10-3 Um and 2.10-1

pm.

The d i f f u -

s i o n b a t t e r y i s e s t a b l i s h e d as u n a v a i l a b l e beyond t h i s s i z e . On the o t h e r hand, we take advantage o f r e c e n t developements i n t h i s method (1) t o j u s t i f y the presence, o r n o t , of the " n u c l e a t i o n " mode ( 3 ) (Comprised o f p a r t i c l e s w i t h diameter > 1000 pg/m 3 ) may produce coughing, constriction i n the chest, and a sense of pressure i n the head. There is concern t h a t formaldehyde may have serious long-term health e f f e c t s . Several countries are moving rapidly t o establish standards for formaldehyde concentrations i n indoor a i r . In July 1978, the Netherlands established a standard of 120 pg/m 3 as the maximum permissible indoor concentrationlo and Denmark, Sweden, the United States and West Germany a r e considering similar action. Indoor measurements of formaldehyde levels reported from Denmark, Sweden, West Germany and the U.S. were frequently found i n excess of the recommended indoor s t a n dards of 120 pg/m 3 and, i n several cases, exceeded the Threshold Limit Value (2430 3 pg/m ) f o r workroom a i r . In general, these studies showed t h a t several recently constructed residential buildings and mobile homes w i t h air exchange rates less t h a n 3 0.3 ach exhibited h i g h formaldehyde concentrations (>120 pg/m ) . Formaldehyde and total a l i p h a t i c aldehydes (formaldehyde plus other aliphatic aldehydes) have been measured by LBL a t several energy-efficient research houses a t Figure 1 shows a histogram of frequency of various geographic locations i n the U.S. occurrenceof concentrations of formaldehyde and t o t a l a l i p h a t i c aldehydes measured a t an energy-efficient house w i t h an a i r exchange r a t e of 0.2 ach. Data taken a t an energy-efficient house i n Mission Viejo, California, a r e shown i n Table 3. As shown,

392 Concentration ( DDb)

~ n u 7

i

Indoor,

1

HCHO

’7

I

ii

i 60

0

I20 Concentration (pg/m 3 1

I80

240

XBL795-14SIA

F i g . 1. Histogram of i n d o o r and outdoor formaldehyde and t o t a l a l i p h a t i c aldehyde c o n c e n t r a t i o n s measured a t an energy research house i n Maryland d u r i n g March and A p r i l 1979. The a i r exchange r a t e o f t h e house i s about 0.2 ach.

TABLE 3 Indoor/Outdoor Formaldehyde And Aliphatic Aldehyde Concentrations Measured at The Med-ll Residence August 1979

Number of Measurements

Condition

Sampling Time

Formaldehyde Aliphatic ( ~ g / m ~ ) ~ Aldehydes ( ~ g / m ’ ) ~

Unoccupied, without furniture

3

12

80f 9%

Unoccupied, with furniture

3

24

223f 7%

294f 4%

Occupied, dayC

9

12

261 ? 10%

2 7 7 t 15%

Occupied, nightd

9

12

140 f 31%

178 f 29%

a Determined using pararosaniline method (120 pg/m3 < 10 pg/rn3.

= 100 ppb).

90 i 16%

All outside concentrations

b Determined using MBTH method, expressed as equivalents of formaldehyde. All outside concentrations 20 pglrn3.




Y

---

EQUATION 0.99 034X

+

0.96 0.99 0.96

+

44.04X

z 5 G

900

2.0

3.0

UNITS O F X 4 0 F/dml/30 days

000

40

Y r

5.0

6.0

8.0

7.0

--

EQUATION 0 6 6 X - 4.71 099

700

0

2

600

0 500-

e

400-

b

k

500 400

300

”z

200

0

100

Y

0 0 AV

200

400

(ZYRSI

F-CONC

800

600 IN AIR

-

*gF/dm2/30

1000 do*

Fig. 4 . Relationship between average F-concentrations in a i r and accumulation levels of fluoride i n foliage of balsam f i r a f t e r 1 and 2 con ecutive years of exposure to f l u 0 ide emissions from a phosphorus plant - p g F/m 3 values were derived from pg F/dm /30 days by equation reported e a r l i e r ( r e f . 13).

5

Solving f o r X, when Y1 year = Y2 years from regression equations in Fig. 4, one can conclude t h a t no significant difference i s expected in f o l i a r levels a f t e r exposure periods of one and two years a t an average a i r concentration of 2 3 18 p g F/dm /30 days ( = 0.15 pg F/m ) . A t this average F-concentration i n a i r , fluoride levels in f o l i a g e will remain a t levels comparable t o those in foliage from control samples, 7-8 ppm. Foliar fluoride levels have been variously related to v i s i b l e symptoms, a i r concentrations (dose), F-levels in urine, safe levels i n feed f o r c a t t l e and w i l d l i f e and defoliation i n plants ( r e f s . 2, 4, 5, 6 , 8, 10, 11, 15). Predicted values of F-concentrations i n a i r are given i n Table 1 f o r 3 f o l i a r fluoride levels recommended t o be safe f o r plants, f o r F-levels i n urine of c a t t l e and other e f f e c t s on consuming animals by various authors ( r e f s . 4, 5, 6 and 8 ) . Average F-levels of 20 and 35 ppm will accumulate in foliage of balsam f i r and

431

TABLE 1 Predicted values of f l u o r i d e concentrations i n a i r for three reported s a f e levels of f o l i a r F-accumulations.

Exposure Measure of period levels i n a i r

Predicted avg. a i r F-concentrations (+ C.L.)&’ f o r 3 s a f e levels!!/ of f o l i a r F-accumuTations 20 ppm 35 ppm 40 ppm

1 year

55.91 f.40.26

pg F/dm2/30 days 119 F/m3

2 years

pg F/dm2/30 days ug F/m3

0.43 f 0.31 37.44 t 2 3 . 6 8 0.29 2 0.18

100.03 f. 43.42 0.77

2

114.72 f 42.11

0.33

0.89 f 0.32

60.17 5 22.37 0.46 f 0.17

67.74 23.68 0.52 f 0.18

a ) C.L. = Confidence l i m i t s b) Based on references 4, 5, 6, and 8 o t h e r boreal c o n i f e r s f o r a 2-year exposure t o predicted a i r concentrations of 2 3 2 3 37.4 pg F/cbn /30 days ( = 0.29 pg F/m ) and 60.17 pg F/ch /30 days ( = 0.46 pg F/m ) r e s p e c t i v e l y (Table 1 ) . A d e t a i l e d examination of 2-year f i e l d data from pe‘rmanent monitoring s t a t i o n s with average concentrations of 5 0.29 pg F/m 3 revealed t h a t f l u o r i d e accumulations i n 2 years old balsam f i r needles were 5 20 ppm in f o l i a g e sample from 72% of these s t a t i o n s and between 20-35 ppm i n samples from the other 28% of s t a t i o n s . Considering a l l the s t a t i o n s where the f o l i a r F-accumulation 0.46 pg F/m 3 . levels were ( 3 5 ppm, average a i r concentrations were > 0.29 Results of a short-term (4-6 weeks) a i r and vegetation monitoring over 120 s t a t i o n s over an extensive f o r e s t area showed t h a t f o l i a r F-accumulations of 20, 35, and 40 ppm i n balsam f i r occurred a t F-concentrations i n a i r of 0.35, 0.95 and 1.15 3 pg F/m respectively. These values were considerably higher than those based on 2-year averages i n Table 1 and reminds us of the shortcomings and dangers of basing a i r q u a l i t y standards on short-term s t u d i e s . A t average F-concentrations of 37.4 pg F/m 3 ( = 0.29 ug F/m 3 ) f o r a 2-year exposure i n Table 1 , probably very l i g h t or no v i s i b l e F-damage symptoms will occur t o c o n i f e r s a s well a s deciduous boreal species. Average a i r concentrations a t 3 which no visual symptoms of F-damage occurred, were determined t o be 0.20 ug F/m for c o n i f e r s and 0.40 pg F/m 3 f o r deciduous species in an e a r l i e r study ( r e f . 8 ) . 3 The recommended Air Quality Standards of 0.20 pg HF/m f o r 70 days in Canada ( r e f . 15) and 0.30 pg HF/m3 f o r one year by IUFRO ( r e f . 16) compare well w i t h the predicted level of 0.29 pg F/m 3 ( = 0.30 pg HF/m 3 ) f o r 20 ppm of F-accumulation i n f o l i a g e f o r a 2-year exposure (Table 1 ) . These recommended l e v e l s a r e reasonably safe f o r the health and growth of plants and animals based on the information a v a i l a b l e a t this time.

432 REFERENCES 1 R.J. Thompson, T.B. McMullen and G.B. Morgan, J. A i r P o l l u t . Control Assoc., 2 1( 1 971 ) 484 -487. 2 L.H. Weinstein, 3. Occup. Med., 19(1977)49-78. 3 U.S. Nat. Acad. Sci., F l u o r i d e s , Comm. B i o l . E f f e c t s Atmos. P o l l u t . Div. Pled. Sci., Nat. Res. Council, Washington, 1971, 295 pp. 4 G.W. I s r a e l , Atmos. Environ., 8(1974)167-181. 5 J.W. S u t t i e , J. A i r P o l l u t . Control ASSOC., 19(1969)239-242. 6 Dyson Rose and J.R. Marier, Nat. Res. Council, Canada Publ. No. NRCC 16081(1977), 151 pp. 7 K.N. Burns i n C.F. M i l l s (Ed.), Trace Element Metabolism i n Animals, Proc. WAA/IBP I n t e r n a t . Symp. 1969, Scotland. Publ. by E. and S. Livingstone, London pp. 490-492. 8 S.S. Sidhu, Proc. 71st Ann. Meeting A i r P o l l u t . Control Assoc., June 25-30, 1978, Houston, Texas, Paper No. 78-24.7, p. 1-16. 9 S.S. Sidhu, Proc. 7 0 t h Ann. Meeting A i r P o l l u t . Control ASSOC., June 20-24, 1978, Toronto, Canada, Paper No. 30.2, p. 1-16. 10 J.S. Rowe. F o r e s t Regions o f Canada. Environ. Canada, Can. For. Serv., Publ. No. 1300, Ottawa, Canada. 1972. 11 L.K. Thompson, S.S. Sidhu and B.A. Roberts. Environ. P o l l u t . 18(1979)221-234. 12 S.S. Sidhu and B.A. Roberts, Environ. Canada, Can. For. Serv., Bi-Monthly Res. Notes, 32( 1976)29-31. 13 S.S. Sidhu, Environ. Canada, Can. For. Serv., Bi-Monthly Res. Notes 35( 1979) 10-1 1 14 R.M. Cooper, N.E. Cook, Jacques P i l o n and E.H. R e i l l y . A D i g e s t o f Environmental P o l l u t i o n L e g i s l a t i o n i n Canada, Canadian I n d u s t r i e s Ltd., Montreal, Canada, 1973. 15 Environment Canada, Canada Gazette Announcements - Clean A i r Act, Proposed N a t i o n a l Ambient A i r Q u a l i t y Objectives, P a r t I , Environ. Canada, Environ. P r o t e c t i o n Service, Ottawa, Canada, August 7, 1976. 16 IUFRO ( I n t . Union Forest. Res. Organizations), IUFRO NEWS 25(3/1979) supplement, S u b j e c t Group S2.09-00 R e s o l u t i o n on A i r Q u a l i t y Standards f o r t h e P r o t e c t i o n of Forests, IUFRO-Secretariat, Vienna, A u s t r i a .

.

Atmospheric Pollution 1980, Proceedings of the 14th International Colloquium, Paris, France, May 5-8,1980, M.M. Benarie (Ed.), Studies in Environmental Science, Volume 8 0 Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands

433

CONTAMINATION OF EDIBLE PARTS OF SEVEN PLAET CROPS ANI) SOILS BY HEAVY METALS IN URBAN AREA BY A I R POLLUTION IN ALEXANDRIA DISTRICT, EGYPT

I.H. ELSOKKARY Soil & Water Sci. Dept., Faculty of Agric. Alexandria Univ.,Egypt.

ABSTRACT Contamination of the edible parts of wheat grains, roquette, radish, pepper, cabbage, parsley and jew's mallow grown in four soil site8 in Alexandria were investigated. The results showed high contamination of these plants and soils with Zn, Pb, Cd, Co and Hg. The sources of contamination are the vehicle exhaustes which acted along distance of 50 meter from roadside, and the industry fallout which was effective beyond 10 km from the source. Significat portions of these metals particulates were subject t o washing out from plants surfaces by water.

INTRODUCTION Work in recent years suggested marked accumulation of Cd, Ni, Pb and Zn in plants grown in soils close to heavily traffic highways (Ref. 2). That work drew the attention to the possibility of contamination of the environment with other heavy metals. The present work attempts a systematic investigation of the contamination of plants and soils by heavy metals at various cultivated sites in Alexandria district, Egypt. MATERIALS AND EYlETHGDS Plants and soils Alexandria district (Triticum sativum), (Raphanus sativus),

samples were taken from various sites in (Fig. 1). These plants included: wheat grains leaves of both roquette (Eruca sativa), radish cabbage (Brassica oleracea var capitata),

434

parsley (Petroselinum hortense) and Jew's mallow (Corchorus o l i t o r i u s ) and the fruit of pepper (Capsicum f r u t e s c e n s ) , Before a n a l y s i s , half of each plant sample was s i m p l y washed with tap water, then the two h a l f s were then separately dried a t 3 5 O C and digested w i t h HN03-HC104 acids mixture, Fe, Mn, Zn, Cu, Cd, Pb and Co were measured i n t h i s e x t r a c t by atomic absorption (Ref, 4). Hg was measured i n the HNO e x t r a c t by flameless atomic absorption. 3 Se w a s measured c o l o r i m e t r i c a l l y (Ref. 1). The DTPA-extractable metale from s o i l s were measured and defined as the available t o plants.

MEDITERRANEAN

SE

-

SCALE

0

1

1:lOO,OOO

-3 2

4-5km

Fig. 1- Location of the c u l t i v a t e d s i t e s i n Alexandria d i s t r i c t . RESULTS AND DISCUSSION

The mean values of metals i n the edible p a r t s of t h e plants grown i n s i t e 1 i n d i c a t e high l e v e l s of contamination by Zn, Pb, Cd, Co and H g and t o some extent w i t h Se (Table 1). The unwashed plants contained r e l a t i v e l y high l e v e l s of metals than those washed. Since a l l these p l a n t s a r e grown i n the same area, the data i n Table 1 give an idea about the effectiveness of t h e vehicle particul a t e deposition, which i s t h e main source of pollution i n s i t e 1,

435

on the c o n cen t ra t i o n of metals i n the various p l an t species. I n t h i s c as e , t h e s e p l a n t s showed d i f f e r e n t s u s c e p t i b i l i t y f o r metals abs o r p ti o n through t h e i r l e a v e s and consequently d i f f e r e n t r a t e s of metals accumulation c a p a c i t i e s. TABLE 1 The mean values of metals i n the p l a n t s ppm, a s influenced by ve hi cle exhaust ( S i t e 1).

P l a n t s p e c i e s and number of samples Metal

A

(9 )

cu

uw W uw W uw

zn

uw

Fe Mn

Pb Cd CO

W

W

uw W uw w uw W

-

31.4

27.3

20.2

0.9 0.19 0.38

10.3

Hg

uw W

0.023

Se

uw w

0.42

A: wheat g r a i n s

-

D: pepper G: Jew's mallow

D (12)

B (8)

C (7)

3650.0 1150.0 185.0 150.0

1350.0

260.0

1000.0

180.0

67.0 55.0 23.5 19.5 88.5 71.5 22.5 10.5 0.5

27.5 22.5 17.0 19.0 34.5 27.5 1.6

18.0

15.0 65.0 51.5 12.5 7.2 0.70

0.55 4 *3 1.6

-

-

B:

1.5

1.5

0.8

0.036 0.25

0.2

1.0 0.2 0.1

-

0.060

-0.12

ro q u e t t e

E: cabbage

UW: unwashed

E (10)

0.8

0.10

0.015

F

G

(12)

(20)

650.0 1750.0 180.0 55.0 45.0 65.0 35.0 47.5 13.8 19.0 17.0 8.8 52.0 80.0 65.0 36.5 14.5 38.0 8.0 19-0 0.65 0.35 0.20 0.45 0.4 1.9 1.3 0.1

460.0 400.0 78.0 69.0

0.15

0.020

-

0.055

-

0.28

22.0

20.5 35.0 32.0 10.5 6.0 0.25

0.10 1.1 0.5

0.25

0.060

C: r a d i s h F: p a r s l e y W: washed

The d a ta i n Table 2 suggest t h a t contamination of p l a n t s and s o i l s by Zn, Pb and Cd occur beyond a d i s t a n c e o f 50 meters from t h e highway ( s i t e 2 ) . Nearly 20-30!% of t h e deposited metals p a r t i c u l a t e s could be washed out from r a d i s h l eav es surfaces by water. Also, about 30-50$ of t h e s e metal p a r t i c u l a t e s a r e subjected t o washing from jew's mallow l e a v e s surfaces . Mostly, t h i s p o rt i o n i s h i g h i n p l a n t s grown a t d i s t a n c e c lo s e t o t h e roadside. Since these s o i l s a r e a l k a l i n e , i t i s expected t h a t t h e l e v e l s of a v a i l a b l e metals a r e below t h e adequate range req u i red by p l a n t s

436

(Ref. 3 ) . The d a t a i n Table 2 showed high l e v e l s of a v a i l a b l e a, Pb and Cd e s p e c i a l l y in soils c l o s e t o t h e roadside. This suggests t h a t t h e s e deposited metals p a r t i c u l a t e s on s o i l s u r f a c e could considered as a r e s e r v o i r for supplying p l a n t s w i t h metals even a t t h a t a l k a l i n e s o i l reaction. TABLE 2

The mean metal content i n t h e p l a n t s and DTPA-extratable-metala from t h e c u l t i v a t e d s o i l s i n r e l a t i o n t o t h e d i s t a n c e from roadside. Distance from road meters

S o i l DTPA-Metals PPm

Metals p l a n t c o n t e n t , ppm.

zn

uw

Pb

w

Cd

uw

w

uw

w

zn

Pb

Cd

32.0 30.0

24.0 20.0 19.5

0.80 0.60 0.50 0.52

0.55 0.50 0.40

0.25 0.12

0.07 0.06

0.11 0.06

0.03 0.01

14.5

0.45

2.8 2.7 1.4 0.6 0.5

0.05

0.01

18.0

0.65

0.20

16.5

0.40

10.4 11.0

0.40 0.35 0.30

0.05 0.05 0.04 0.01 0.01 0.01

Radish l e a v e s 100.0 100.0

5

10 20

88.5

77.5 75.0

30 40

82.5 81.0 80.0

71.0

72.0

22.5 16.5 14.5

14.5

0.45 0.35

Jew's mallow l e a v e s 5

125.0 121.5 85.0 72.0 60.0

10 20

30 40

57.0

50

85.4 85.0

80.6 68.0

5705 55.2

26.5 22.8 16.5 18.0

13.5 10.4

~--

17.0

17.5

0.45 0.35 0.30 0.40 0.20 0.25

0.45

3 .0 2.8 1.0

0.5 0.4 0.4

0.15 0.10 0.05 0.05 0.04 ~~

~~

I n t h e i n d u s t r i a l a r e a a t s i t e 3 (Table 31, a l l t h e jew's mallow Nearly samples a r e h i g h l y contaminated w i t h Zn, Fb, Cd and Co. 2O-3O% of metals p a r t i c u l a t e s a r e s u b j e c t e d t o washing out by water from jew's mallow l e a v e s surfaces. TABLE 3 The mean values of m e t a l s contents, ppm, i n 23 jew's mallow washed l e a v e s samples grown arround the i n d u s t r i a l c e n t e r i n s i t e 3.

zn -

UW W

57.5 43.0

- 99.8 - 81.5

Pb 12.5

9.0

- 47.5 - 32.0

co

Cd

0.35 0.15

- 0.80 - 0.65

0.90

0.75

-

-~

2.15

- 1.80

The d a t a i n Table 4 suggest t h a t contamination of p a r s l e y leaves w i t h Zn, Pb, Cd and Co could occur beyond a d i s t a n c e of about 10 lsm

437

from t h e e l e c t r i c power s t a t i o n . These metals a r e probably dispersed a s a e r o s o l s and are p o t e n t i a l l y capable of being transported over a g r e a t distance. High p o r t i o n of these metals p a r t i c u l a t e s a r e s u b j e c t t o washing o u t by water from p a r s e l y l e a v e s s u r f a c e s ( 40-6%)

.

TABLE 4

Metal c o n t e n t s , ppm, i n p a r s l e y p l a n t l e a v e s grown proximity an e l e c t r i c power s t a t i o n s a t s i t e 4 a s a f u n c t i o n of distance.

zn

Km

from E.P.S. 1

2

5 10

UW

86.0 90.0 76.5 84.5 60.0 72.0 52.0 48.0

Pb

co

Cd

W

uw

w

uw

w

uw

w

45.0

39.0 48.5

60.0 70.0 47.5

0.6 0.7 0.25 0.20 0.15 0.15 0.15 0.20

4.6 5.2 3.6 3.2 1.8 2.6 2.1 2.1

1.8

31.5 32.5 24.0

14.0 13.0 20.0

0.1

43.0

45.0 38.5 40.5

30.5 10.5 8.5

17.0 9.0 10.5 5.0 3.6

0.1 0.15 0.15 0.05 0.15

0.10 0.10

1.6 1.2 1.2 1.4 1.0 0.6 0.8

Generally, t h e r e s u l t s r e p o r t e d i n t h i s work show a marked accumulation of Zn, Pb, Cd, Co and Hg and t o some e x t e n t Se i n t o x i c l e v e l s t o p l a n t s (Ref. 3 ) . I n s p i t e of t h a t Fe, bfn, Zn and Cu d e f i c i e n c i e s i n p l a n t s grown i n s i m i l a r s o i l s a r e most common (Ref. 3 ) , air-borne p a r t i c u l a t e s from v e h i c l e o r i n d u s t r y could be considered r i c h s o u r c e s of some o r a l l of t h e s e metals. While t h e s e l a t e r f o u r metals are w e l l known t o be e s s e n t i a l f o r p l a n t s and human being, t h e o t h e r s : Pb, Cd, Coy Hg and Se a r e not known t o be e s s e n t i a l f o r most of l i v i n g organisms. Because these l a t e r metals a r e h e a l t h hazardous f o r human being, more s t u d i e s should be conducted. For example, t h e bread i s the most p r i n c i p l e food i n Egypt. Wheat grain6 c o n t a i n on t h e average 0.2 ppm Cd. A d a i l y d i e t of 500 gram wheat f l o u r could c o n t a i n n e a r l y 100 p g Cd. This r a t e of C d i n t a k e i n combination with those taken from o t h e r C d sources, i.e. vegetables, w i l l account f o r g r e a t e r d a i l y i n t a k e than the average (50 p g Cd p e r day) f o r i n d i v i d u a l s i n uncontaminated areas.

438

ACKNOWLEDGEMENTS The author wishes to express his thanks to Prof. Dr. S. LLg for his valuable suggestions and to the Norwegian Agency for International Development (NORAD) for the financial support of this work. REFERENCES 1. Elsokkary, I.H.

and A. Idien., Acta. Agric. Scand. 27 (1977)

2 85-288.

2. Elsokkary, I.H. Studies in Environ. Sci. Vol. 1. Atmos. Poll., 1.1. Benarie (Ed.), Proc., 13th, Inter. Collog., Paris. France,

April 25-28, 1978 Elsevier pp. 25-28. 3 . Elsokkary, I.H. and J. Llg. Beitrage Zur Trop. Landw. und Veterinarmedizin, In press (1979). 4. Oien, A. and K. Gjerdingen. Acta. Agric. Scand. 27 (1977) 67-70.

439 AUTHOR Anlauf K.G. Bacon J.K. B a r r i e L.A. Bauman S .E. Benarie M.M. Benech B. Benko A. Bennett M. Berk J.V. Blanchard J.D. Boegel M.L. Bonivento C. Boueres L.C.S. B o u r b i g o t Y.C. B r u l l P.M. B u i l t j e s P.J.H. B u r d e t t G. Carha rt R .A. Carmichael R.G. C a r o l l a J. Carson J.E. Carton B. Chen J.Y. Chuong B.T. Cosemans G. Darzi M. De Jong T.J.R.M. De Wiest F. Drufuca G. Dunn W.E. Elsokkary I . H . Evendi j k J. E. Fabries J.F. F e l l i n P. F i s h e r B.E.A. Flament P. Friedman W.C. Fronza G. G a i l l a r d A. Gavin P. Gentry J.W. Ghobadian A. G i u g l i a n o M. Goddard A.J.H. Gosman A.D. Gauesba t G. Gouldin F.C. Grehan G. Gui chard J. C. Haake K. Haberman S.A. Hal b r i t t e r G. Hansson H.C. H a r t e r C. Haup t R

.

Page 153,355 195 355 147 49,397 249 417 63 387 309 387 105 147 26 7 227 91 323 43 31 291 37 279 173 39 7 2 13 147 379 227 209 43 433 379 279 355 71 285 309 105 339 43 233,291,303 25 209 25 25 285 173 285 339 43 309 57 159 25

125

INDEX Page Henderson-Sel l e r s B. H o i t z J. H o l l o w e l l C.D. Horvath H. Impens R.A. K a i s e r G.D. Kasahara M. Kolb H. Kooken G. Kretzschmar J G. Kuhlman M.R. Lahaye J. Lamauve M. Lannefors H.O. Laurent D. Le Guen J.M. Leisen P. L e s l i e A.C.D. L i n S. Lusis M.A. Madelaine G. McLean W.J. McNider R.T. Metayer Y. Miksch R.R. M i l h e M. Mohnl H. Munn R.E. Muskens P.J.W.M. N a z a r o f f W .W. Nelson J.W. Neumann G. Nieuwstadt F.T.M. Olson M. Opiela H. Oven M.J. Park Y.O. Patterson R.M. Paulou J. P a v l i k R.E. Pechinger U. P e r r i n M.L. Peters K.L. Peyrous R. Petersen W.B. Pham Van Dinh P i c k e t t E.E. P i e l k e R.A. P i r e t T. P o l i c a s t r o A.J. Prado G. Preston R. Rigard J. Robins A.G. Rood A.P. Rooker S.J.

.

195 125 387 371 417 25 221 97 417 213 245 297 339 159 365 323 131 147 303 153 267,273 173 9 273 387 137 97 409 379 387 147 57 77 153 315 173 291 13,19 401 309 97 267 31 365 13,19 249 347 9 417 43 297 303 137 117 323 323

440

S a r t o r F.A. Sidhu S.S. Simmon P.B. Sobottka H. Sommers H. Spatola J.A. S p i c e r C.W. Spurny K.R. Steinberger E.H. S t e r n A.C. Stober W. Staubel H. Suess M.J. Sverdrup G.M. Takahashi K.

Page 189 425 13,19 109 125 233 181 315 165 3 315 239 361 245 221

Page Tohno S. T o n i e l l i A. Traynor G.W. Van Duuren H. Wastag M. W e i l l M. Weiss G. Werner R. Whiting R.G. Wiebe H.A. Wiedemann R. W i l l e k e K. Winchester J.W. Ziemer S.

221 105 387 77 43 285 315 97 347 153,355 257 309 147 43