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Environmental Simulation Chambers: Application to Atmospheric Chemical Processes

NATO Science Series A Series presenting the results of scientific meetings supported under the NATO Science Programme. The Series is published by IOS Press, Amsterdam, and Springer in conjunction with the NATO Scientific Affairs Division

Sub-Series I. II. III. IV.

Life and Behavioural Sciences Mathematics, Physics and Chemistry Computer and Systems Science Earth and Environmental Sciences

IOS Press Springer IOS Press Springer

The NATO Science Series continues the series of books published formerly as the NATO ASI Series. The NATO Science Programme offers support for collaboration in civil science between scientists of countries of the Euro-Atlantic Partnership Council. The types of scientific meeting generally supported are “Advanced Study Institutes” and “Advanced Research Workshops”, and the NATO Science Series collects together the results of these meetings. The meetings are co-organized bij scientists from NATO countries and scientists from NATO’s Partner countries –countries of the CIS and Central and Eastern Europe. Advanced Study Institutes are high-level tutorial courses offering in-depth study of latest advances in a field. Advanced Research Workshops are expert meetings aimed at critical assessment of a field, and identification of directions for future action.

As a consequence of the restructuring of the NATO Science Programme in 1999, the NATO Science Series was re-organized to the four sub-series noted above. Please consult the following web sites for information on previous volumes published in the Series. http://www.nato.int/science http://www.Springer.com http://www.iospress.nl http://www.wtv-books.de/nato-pco.htm

Series IV: Earth and Environmental Series – Vol. 62

Environmental Simulation Chambers: Application to Atmospheric Chemical Processes edited by

Ian Barnes Bergische University Wuppertal, Physical Chemistry Department, Germany and

Krzysztof J. Rudzinski Institute of Physical Chemistry of the PAS, Warsaw, Poland

Published in cooperation with NATO Public Diplomacy Division

Proceedings of the NATO Advanced Research Workshop on Environmental Simulation Chambers: Application to Atmospheric Chemical Processes Zakopane, Poland 1 - 4 October 2004

A C.I.P. Catalogue record for this book is available from the Library of Congress. ISBN-10 ISBN-13 ISBN-10 ISBN-13 ISBN-10 ISBN-13

1-4020-4231-0 (PB) 978-1-4020-4231-7 (PB) 1-4020-4230-2 (HB) 978-1-4020-4230-0 (HB) 1-4020-4232-9 (e-book) 978-1-4020-4232-4 (e-book)

Published by Springer, P.O. Box 17, 3300 AA Dordrecht, The Netherlands.

www.springer.com

Printed on acid-free paper

All Rights Reserved © 2006 Springer No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission from the Publisher, with the exception of any material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work Printed in the Netherlands.

CONTENTS

Preface

ix

Acknowledgements

xiii

Simulation Chamber Facilities Overview on the Development of Chambers for the Study of Atmospheric Chemical Processes Becker, K. H.

1

The UCR EPA Environmental Chamber Carter, W. P. L.

27

Investigations of Secondary Organic Aerosol in the UCR EPA Environmental Chamber Cocker II, D. R. and Song, C.

43

Field Measurement and Modelling Motivated Design of a Programme of Aerosol Chamber Experiments McFiggans, G.

49

Chamber Simulations of Cloud Chemistry: The AIDA Chamber Wagner, R., Bunz, H., Linke, C., Möhler, O., Naumann, K-H., Saathoff, H., Schnaiter, M., and Schurath, U.

67

New on-line Mass Spectrometer for Identification of Reaction Products in the Aqueous Phase: Application to the O H-oxidation of N-methyl-pyrrolidone under Atmospheric Conditions Poulain, L., Monod, A., and Wortham, H.

83

Dynamic Chamber System to Measure Gaseous Compounds Emissions and Atmospheric-Biospheric Interactions Aneja, V. P., Blunden, J., Claiborn, C. S., and Rogers, H. H.

97

Chemical Process Studies Chamber Studies on the Photolysis of Aldehydes Wenger, J. C.

111

Determination of Photolysis Frequencies for Selected Carbonyl Compounds in the EUPHORE Chamber Olariu, R-I., Duncianu, M., Arsene, C., and Wirtz, K.

121

v

vi

Contents

Remote Sensing of Glyoxal by Differential Optical Absorption Spectroscopy (DOAS): Advancements in Simulation Chamber and Field Experiments Volkamer, R., Barnes, I., Platt, U., Molina, L. T., and Molina, M. J.

129

Aromatic Hydrocarbon Oxidation: The Contribution of Chamber Oxidation Studies Bloss, C., Jenkin, M. E., Bloss, W. J., Rickard, A. R., and Pilling, M. J.

143

FT-IR Kinetic Study on the Gas-Phase Reactions of the OH Radical with a Series of Nitroaromatic Compounds Bejan, I., Barnes, I., Olariu, R., Becker, K. H. and Mocanu, R.

155

Atmospheric Fate of Unsaturated Ethers Mellouki, A.

163

Atmospheric Oxidation of the Chlorinated Solvents, 1,1,1-Trichloroethane, Trichloroethene and Tetrachloroethene Nolan, L., Guihur, A-L., Manning, M., and Sidebottom, H.

171

Simulation Chamber Study of the Oxidation of Acetic Acid by OH Radicals: Detection of Reaction Products by CW-CRDS in the Near-Infrared Range Crunaire, S., Fittschen, C., Lemoine, B., Tomas, A., and Coddeville, P.

181

Kinetics, Products and Mechanism of O(3P) Atom Reactions with Alkyl Iodides Barnes, I.

193

Kinetics of the Reaction between CF2O and CH3OH Burgos Paci, M. A. and Argüello, G. A.

207

New Kinetic and Spectroscopic Measurements in the CF3Ox + NOx System Chiappero, M. S., Malanca, F. E., Argüello, G. A., Nishida, S., Takahashi, K., Matsumi, Y., Hurley, M. D., and Wallington, T. J.

213

Kinetic Study of the Temperature Dependence of the OH Initiated Oxidation of Dimethyl Sulphide Albu, M., Barnes, I., and Mocanu, R.

223

Environmental Chamber Studies of Ozone Formation Potentials of Volatile Organic Compounds Carter, W. P. L.

231

Evaluation of the Detailed Tropospheric Chemical Mechanism, MCM v3, Using Environmental Chamber Data: Butane and Its Degradation Products Pinho, P. G., Pio, C. A., and Jenkin, M. E.

241

Studies on Nitrate-Affected SO 2 Oxidation and Their Perspectives Pasiuk-Bronikowska, W. and Bronikowski, T.

253

Contents

vii

Heterogeneous and Aqueous-Phase Transformations of Isoprene Rudzinski, K. J.

261

Investigation of Atmospheric Transformation of Diesel Emissions in the European Photoreactor (EUPHORE) Zielinska, B., Sagebiel, J., Stockwell, W., McDonald, J., Seagrave, J-C., Wiesen, P., and Wirtz, K.

279

Investigation of Real Car Exhaust in Environmental Simulation Chambers: Results from the INFORMATEX and DIFUSO Projects Wiesen, P.

285

The EUROCHAMP Integrated Infrastructure Initiative Wiesen, P.

295

Air Pollution Studies Survey on Atmospheric Chemistry Research in Some New EU Member States and Candidate Countries Batchvarova, E., Spassova, T., Valkov, N., and Iordanova, L.

301

New Measurements of NMVOC Concentrations in the City Air of Wuppertal, Germany: Input Data for Chemical Mass Balance Modelling Niedojadlo, A., Becker, K. H., Kurtenbach, R., and Wiesen, P.

341

Surface and Total Ozone Over Bulgaria Kolev, S. and Grigorieva, V.

351

Heavy Metals Pollution: An Everlasting Problem Mocanu, R., Cucu-Man, S., and Steinnes, E.

359

Atmospheric Wet Deposition Monitoring in Iasi, Romania Arsene, C., Mihalopoulos, N., Olariu, R-I., and Duncianu, M.

369

Problems of Air Quality in Tashkent City Tolkacheva, G. A.

379

Precipitation Quality in Different Zones of the Tashkent Region in Relation to Photo-Chemical Reactions Smirnova, T. and Tolkacheva, G.

393

Influence of Atmospheric Aerosol Contamination on the Regional Climate in Central Asia Chen, B. B. and Lelevkin, V. M.

403

Assessment of Air Pollution and Ecosystem Buffer Capacity in the Industrial Regions of Ukraine Kharytonov, M. M., Anisimova, L. B., Gritsan, N. P. and Babiy, A. P.

415

viii

Contents

Two Neutral Network Methods in Estimation of Air Pollution Time Series Cigizoglu, H. K., Alp, K., and Kömürcü, M.

421

List of Participants

433

Author Index

441

Subject Index

443

PREFACE Atmospheric pollution has many different detrimental impacts on air quality at urban, regional and global scales. Large volume photoreactors (often referred to as smog or simulation chambers) have been used very effectively to investigate and understand many varied aspects of atmospheric chemistry related to air pollution problems. Photochemical smog formation, which was first observed around 1945 in Los Angeles, is now a major environmental problem for all industrialised and densely populated regions of the world. Over the years many different modelling and experimental tools have been developed to analyse and simulate the complex chemical processes associated with tropspheric photooxidant formation. Work in environmental chambers has played a key role in the development of our understanding of the atmospheric chemistry associated with pollution problems on local, regional and global scales. Chamber observations have also been used in connection with environmental policy issues. In general they are used for validation of atmospheric chemical models, studies of chemical reaction mechanisms and as a direct means to test the possible impact of specific chemical compounds on air quality under simulated ambient conditions New large smog chamber installations have been recently developed in the US (Riverside, California), Europe (Jülich, Germany) and Japan, and a large number of smaller scale laboratory chambers are in operation around the world. Over the years there have been numerous new technical developments related to environmental chamber facilities such as the design of the chambers (e.g. outdoor versus indoor chambers), the techniques applied to control the physical and chemical conditions within them and the analytical facilities that are coupled to the chambers. Some chambers are now equipped with technology allowing measurement of highly reactive radicals such as OH HO2 and NO3, that play pivotal roles in atmospheric chemistry. In addition to the technical developments the scientific applications of chambers are being expanded, for example, the current understanding of secondary organic aerosol formation has been developed principally from environmental chamber studies and chambers have been used even more recently to investigate photolysis processes under ”real” atmospheric conditions. Such new scientific applications are often linked to new technical analytical and other technical developments and environmental chambers offer a perfect platform for testing environmental monitors. The many new scientific applications and technical developments of environmental chambers in the last years created a need for an Advanced Research Workshop where scientists who use chambers (experimentalists, analyticlists as well as modellers) could meet to exchange ideas, experiences and results and document advances in the application of chambers to research. With this background a NATO ARW entitled “Environmental Simulation Chambers: Application to Atmospheric Chemical Processes” was organised and held in the Antalowka Hotel (www.polskietatry.pl.) in Zakopane, Poland from Friday 1st October to Monday 4th October 2004. The major goal of the workshop was to review i) the various types of photoreactors currently in use and ii) the considerable diversity of environmental problems to which photoreactors have been used to successfully investigate. The aims were timely since in Europe within the EU 6th Framework programme a project entitled EUROCHAMP was initiated which had the aim of integrating large scale chamber facilities in Europe and also eventually US facilities. Another goal of the meeting was to promote a better awareness of the scientific community, in particular from NATO partner/Mediterranean dialogue countries and the EU ix

x

Preface

countries, of the availability of such facilities and their considerable potential for investigating problems related not just too atmospheric processes but chemical processes in general. It was particularly hoped that the workshop would attract young scientists from NATO partner countries where such facilities are not widely available but with assistance of the expertise from NATO countries basic experimental setups could easily be realized. At the time of the organisation of the workshop the European Union was expanded by 10 New Member States (Cyprus, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia and Slovenia). Blugaria, Romania and Turkey are at the time of writing EU applicant countries. Presently, chamber technology is mainly located in western European countries and the US, therefore, in order to actively integrate scientists from eastern countries into the workshop programme a special section was organized with presentations from invited key speakers from several of these countries which showcased many of the acute environmental problems within these countries. A highlight of this section was overview of the research within Eastern European Countries by Dr. E. Batchvarova (Bulgaria) which was specially commissioned by Joint Research Center, Ispra, Italy. The workshop created a unique forum for scientists to present the new scientific applications of environmental chambers as well as the technical developments of these installations, including the advantages and drawbacks of the different types of smog chambers that are in use. Scientists from eastern European countries had the opportunity to learn firsthand about chamber techniques and dialogue with chamber users helped to identify potential applications of the techniques to their own environmental problems. This book contains contributions which give a broad overview of the different types of chamber facilities available and their major applications. The contents has been arranged along three thematic lines – presentation of simulation chamber facilities, chemical process studies, mostly utilising the chamber facilities, and regional studies, mostly indicating the needs for chamber use. Restrictions in the size of the workshop meant that not all the major chambers users could be invited to the meeting but we hope that sufficient reference has been made within the various contributions to these facilities that will allow easy referencing by the reader. (i) The section on Simulation Chambers Facilities begins with an historical overview of chamber development in USA and Europe, discussion of the advantages and disadvantages of using the chambers, the experimental techniques applied and gives exemplary results obtained from chambers in Bonn (now non-operational), Wuppertal and Valencia [Becker]. Detailed overviews are provided of smog chambers in Riverside [Carter; Cocker, aerosol studies], Bayreuth [Zetsch, investigation on POPs], and Karlsruhe [Wagner]. Two untypical yet interesting microchambers are presented, that are being used for studies of aqueous-phase oxidation of N-methyl pyrrolidone (an industrial solvent) [Monod] and for the measurement of fluxes of gaseous compounds between water and air or earth and air [Aneja]. (ii) The section on Chemical Process Studies carried out in the chambers contains a general discussion on the photolysis of atmospheric trace components [Wenger], as well as studies on the photolysis of small carbonyl compounds [Olariu], the photolysis of nitroaromatic compounds [Bejan] and the photolysis of chloral and dichloroacetyl chloride [Sidebottom]. Further contributions in this section describe oxidation processes investigated in the chambers and include: the OH initiated oxidation of benzene, toluene and p-xylene leading to formation of glyoxal, that was monitored by DOAS both in a chamber and in the

Preface

xi

field [Volkammer], an overview on the oxidation of aromatic hydrocarbons [Pilling], reactions of nitroaromatic compounds with OH that contribute to the formation of aerosols [Bejan], the reaction of acetic acid with OH radicals studied with the Continuous-Wave Cavity Ring Down Spectroscopy [Crunaire], and the oxidation of alkyl iodides by O(3P) atoms [Barnes]. Other contributions discuss VOC reactivity and ozone formation potential [Carter], the atmospheric fate of unsaturated ethers [Mellouki], reactions of oxygenated fluorocarbons with NOx and methanol [Arguello; Arguello], evaluation of the MCM v.3 against chamber data [Pinho], and investigations on vehicle ehaust emissions [Wiesen; Zielinska]. Two contributions report on aqueous and heterogeneous chemistry, namely the influence of nitrate ions on the mechanism of S(IV) autoxidation [Pasiuk-Bronikowska], and the heterogeneous and aqueous-phase reactions of isoprene [Rudzinski]. (iii) The section on Regional Studies refers to the geographical area stretching from Central and Eastern Europe to Southern Europe and to Central Asia. The contributing countries were Bulgaria, Germany, Uzbekistan, Kyrghistan, Romania, Turkey and Ukraine. The section starts with contribution which surveys the state (at the time of writing) of atmospheric chemistry research in the new EU member and candidate countries [Batchvarova]. The section covers several important topics. Air quality and pollution in cities is discussed in terms of the contribution of vehicle traffic and solvent use [Niedojadlo], the monitoring and analysis of wet deposition (pH and insoluble fraction) [Arsene], the influence of ozone, dust, nitrogen oxides, carbon oxide and sulphur dioxide, as well as their transformation [Smirnova; Tolkacheva], and the contamination of aerosols [Lelevkin]. Behaviour and effects of heavy metals in the atmosphere are discussed [Mocanu] as well as their impact on the ecosystems [Kharytonov]. The latter contribution also analyses the capacity of ecosystems to cope with air pollution. Other contributions discuss monitoring of ozone and collecting of reference data during a solar eclipse [Kolev], using neural network approach to properly fill the gaps in monitoring data [Cigizoglu], as well as lidar analysis of long range transport of aerosols and source identification [Lelevkin]. In closing, environmental simulation chambers continue to serve as indispensable tools in atmospheric chemistry research. Laboratory and modelling studies are being more frequently coupled to simulation chamber experiments for verification of ideas and for obtaining a deeper insight and understanding of chemical processes. Noticeably, present uses of chambers are not being restricted to the study of gas phase processes, the need for the study of aqueous-phase and heterogeneous studies within a common chamber forum has been recognised and methods are emerging for the study of multiphase systems. Environmental simulation chambers are located mainly in the USA and Western Europe. It would be good if the existing chambers could be made available to researchers outside these confines possibly through common projects. Possible initiatives to improve the global disparity in distribution with newly built chambers is also an alternative which could be explored. Some support for such actions exist within European projects such as ACCENT, EUROCHAMP and INTROP (ESF), which were briefly introduced at the workshop.

Ian Barnes and Krzysztof J. Rudzinski, June 2005

ACKNOWLEDGEMENTS The NATO Science Committee is very gratefully acknowledged for having faith in the venture and providing the initial basis financial support for the workshop. The additional support which was received from other sponsors is also very gratefully acknowledged. Without the support of all the sponsors it would not have been possible to invite and support the 55 participants at the meeting and make the workshop such an all-round success. Financial support of the workshop was by the following organizations/industries: x NATO Scientific and Environmental Affairs Division, Brussels x Institute for Environmental and Sustainability, JRC x European Science Foundation Programme INTROP x BMW - Bavarian Motor Company Munich

xiii

Overview on the Development of Chambers for the Study of Atmospheric Chemical Processes Karl H. Becker Bergische University Wuppertal, FB C, Physical Chemistry, Gauss Str. 20, 42119 Wuppertal, Germany Key Words: Atmospheric chemistry, Hydroxyl radicals, Ozone, Photoreactors, Photosmog

Introduction Photoreactors have been used for quite some time by scientists to study organic photochemistry (Bayes, Blacet, Calvert, Gunning, Hammond, Heicklen, Leighton, Okabe, Noyes, Steacy, and others mentioned in the text book by Calvert and Pitts, 1966). In industry, the photolytic initiation of product synthesis has been known since the beginning of the last century. A large chamber, known as the “Große Bonner Kugel” (Groth et al., 1972), was built in Bonn between 1966 and 1968; its conception was initiated by Groth and Harteck to study air glow reactions at the low pressures prevailing in the upper atmosphere. Afterwards, the chamber was also used to study reactions of tropospheric interest, but the knowledge of tropospheric chemistry at that time was very basic. Photolytic radical sources could not be applied in this reactor, and the radicals had to be introduced from the exterior using discharge flow techniques. Details of the chamber in Bonn will be discussed later in the article. Shortly after the Second World War, the Los Angeles photosmog became a problem which was investigated using relatively large chambers for the simulation of plant damage and health effects, e.g. eye irritation (Hagen-Smit, 1952). In the mid 70-ties, the Pitts group in Riverside (Finlayson-Pitts and Pitts, 1986; 2000) started to build an indoor chamber with the objective of exploring the processes which lead to photosmog formation, see Figure 1. Advances were slow because appropriate analytical techniques still had to be developed. Following this activity, Akimoto duplicated the chamber in Japan (Akimoto et al., 1979), while Atkinson in the Pitts group started to develop very successfully the procedures to measure OH, O3 and NO3 reaction rate constants, after the importance of OH radical reactions for tropospheric chemistry had been accepted. At the same time, others started to use Teflon bags for studying smog reactions under irradiation by natural sunlight, but their results were very much limited to the conditions prevailing in L.A.. Rather important work began at Ford Motor Company where in the late 60-ties Weinstock (1969) promoted the importance of OH reactions in the troposphere. In this laboratory Niki used a rather small photoreactor to develop the application of FTIR spectroscopy for quantitative investigation of atmospheric reactions in the laboratory (Niki et al., 1972; Wu et al., 1976; Niki et al., 1981). IR absorption spectroscopy was applied quite early to study chemical reactions of atmospheric interest (Stephens, 1958; Hanst, 1971), based mainly on mirror systems which allowed long path light absorption (White, 1942; 1976; Herriott et al., 1964, 1965). However, real progress and success came with the application of modern FTIR spectrometers by Niki et al. (1981) and further work in the Pitts’ group to quantitatively measure rate constants and products in photoreactors by long path FTIR absorption. 1 I. Barnes and K. J. Rudzinski (eds.), Environmental Simulation Chambers: Application to Atmospheric Chemical Processes, 1–26. © 2006 Springer. Printed in the Netherlands.

2

Figure 1.

K . H. Becker

Indoor chamber from Riverside, already employing long path FTIR absorption spectroscopy (Source: Finlayson-Pitts and Pitts, 2000).

In the late 60-ties the understanding of atmospheric reactions took a large step forward when OH radicals were identified as the most important oxidizing agent in the troposphere. The discovery resulted in particular from the analysis of the CO budget (Heicklen et al., 1969; Weinstock, 1969, Stedman et al., 1970; Levy, 1971), though the oxidation of CO by OH had already been measured two years earlier (Greiner, 1967). The built-up of a radical chain was understood 10 years later when the rate constant of the fast reaction HO2 + NO o OH + NO2 was measured by several groups (Howard and Evenson, 1977; Leu, 1979; Howard, 1979; Glaschick-Schimpf et al., 1979; Hack et al., 1980; Howard, 1980; Thrush and Wilkinson, 1981) after Crutzen and Howard (1978) indicated the important role of this reaction in stratospheric ozone chemistry. However, it turned out that OH/HO2 radicals are also the key species in the tropospheric oxidation processes that determine the smog formation. In Europe, studies of tropospheric reactions were started in the 70-ties by a few laboratories, e.g. Becker and coworkers in Bonn and Cox and coworkers in Harwell. The technique of long path FTIR absorption mentioned above was introduced in the early 80-ties by Becker and co-workers in Wuppertal. They used a multiple reflection mirror system in a 420 l photoreactor which can be operated between -50 to 50°C to determine the OH reaction rate constants in combination with product analyses in the ppm range, Somewhat later a 6 m long quartz glass reactor of 1080 l volume was built which enabled measurements to be extended down to the ppbV level. The reaction chambers are illustrated in Figures 12 - 16 later in the text where some examples of selected experimental work carried out in the chambers are also given. More recently, other European laboratories have started to use indoor chambers up to 1000 l volume irradiated by black lamps (Baltensperger et al. in Villigen/Zürich, Carlier and Doussin in Paris, Hjorth et al. in Ispra, Herrmann et al. in Leipzig, Le Bras et al. in Orléans, Treacy et al. in Dublin, Wenger et al. in Cork). Tables 1 and 2 show a, not necessarily complete, list of larger indoor and outdoor reactors.

Overview on the Development of Chambers Tabl e 1.

Indoor chambers without light sources, or irradiated by black lamps or solar simulators.

Year of Laboratories Building 1968 1976 1976

3

Groth et al., Bonn Pitts et al., Riverside Niki et al., Dearborn

Description

Application

dark chamber 220 m3, stainless steel (high vacuum) 6 m3, evacuable, thermostated, FEP coated aluminium 150 l Pyrex

without light sources, for low pressure studies photooxidant and kinetic studies kinetic and mechanistic studies

1979

Akimoto et al., 6 m3 evacuable, thermostated, FEP coated aluminium Tsukuba

photooxidant studies

1980

Winer et al., Los Angeles

6 m3 evacuable, thermostated, FEP coated aluminium


1981

Becker et al., Wuppertal

420 l Duran glass, evacuable, thermostated -50 to +50 ºC

gas phase studies

1982

Joshi et al. (EPA), Research Triangle Park

440 glass reactor


1986

Becker et al., Wuppertal

quartz glass 1080 l, evacuable, thermostated 0 to +25 °C

1986

Evans et al., Australia

4 x 200 l FEP bags

gas phase and aerosol kinetic and mechanistic studies photooxidants studies

1988

Zetzsch et al., ca. 3000 l, Duran glass, Hannover, now thermostated –25 oC to ambient temperature Bayreuth

aerosol studies

1990

Schurath et al., 84 m3, thermostated -90 to +60 ºC, AIDA Karlsruhe

without light source, for aerosol studies

1996

Wahner et al., Jülich.

256 m3, FEP wall cover of a lab room

without light source, for NOY chemistry

1997

Carlier et al., Paris

977 l, glass

gas phase mechanistic studies

1998

Seinfeld et al., Pasadena Carter et al., Riverside

2 × 28 m3, 10 to 40 ºC

aerosol studies

FEP, double wall

low NOx studies

2000

K. H. Becker

4 Table 2.

Outdoor chambers irradiated by sunlight.

Year of Building

Laboratories

Volume, Wall Material

1976

Jeffries et al., Chapel Hill 25 m3, FEP

1981

Lonneman et al.,

15-40 l, FEP bags

1981

Fitz et al.,

40 m3, FEP

1983

Spicer et al.,

17.3 m3, FEP

1985

Kelly et al.,

450-2000 l, FEP bags

1985

Kamens et al., Chapel Hill

25 m3, FEP

1985

Seinfeld et al., Pasadena

65 m3, FEP

1995

Becker et al., Valencia

2 x 200 m3, FEP, EUPHORE

2000

Wahner et al., Jülich

280 m3, FEP, double wall, SAPHIR

In the meantime several large outdoor chambers have been built in the US with support from EPA to study the mechanisms of smog chemistry. One aim was to determine the ozone isopleths under US conditions. These chambers were mainly constructed from bags made of FEP, with volumes up to 25 m3. They brought about a better understanding of smog chemistry, but no results were obtained that could be generalized, because of narrow simulation conditions requested by the US-EPA. In Riverside, Carter and coworkers http://pah.cert.ucr.edu/~carter/bycarter.htm) developed a method to define the ozone ( formation potential of VOC's by determining maximum incremental reactivity (MIR) factors using smog chamber data and chemical modelling. A similar method was introduced by Jeffries in Chapel Hill (http://airsite.unc.edu/), who also used a smog chamber. Other groups injected engine exhausts directly into a smog chambers, and studied the formation of ozone. Collected at very different VOC/NOX ratios, the results from the US could not be generalized and applied to conditions in other countries. In addition, Atkinson and coworkers (http://www.ph.ucla.edu/scpcs/faculty/atkinson.html) refined their method to determine the OH reactivity from chamber measurements, using structure activity relationships to calculate rate constants of OH radical reactions with VOC’s. In the mid 80-ties, Seinfeld (http://www.che.caltech.edu/faculty/seinfeld_j/) in Pasadena, started to use a 65 m3 outdoor chamber made of FEP to study the aerosol formation from the oxidation of aromatic and biogenic hydrocarbons. In the mid 90-ties Becker and co-workers, together with Millán, built in Valencia/Spain the first European large outdoor chamber called EUPHORE (European Photoreactor). Actually, it consists of two chambers made of FEP, each of 200 m3 volume (Becker, 1996). This facility became a centre for European laboratories to carry out mechanistic and kinetic studies. Real exhaust gases from gasoline and Diesel engines were also investigated with respect to ozone formation. The EUPHORE chambers are equipped with all the necessary analytical instrumentation, also for in situ HO2 and OH measurements. In 2000, the group of Ehhalt in Jülich, now guided by Wahner, built a new double wall

Overview on the Development of Chambers

5

outdoor chamber called SAPHIR, of 280 m3 volume, see Figure 2. The double wall made of FEP allows studies of oxidation processes at low NOx concentrations (below 1 ppbV). The Ehhalt group did pioneering work in field measurements of OH and HO2 concentrations, so SAPHIR is fully equipped with the most advanced in situ radical measurement techniques. A smaller double wall indoor chamber (see book contribution) was recently built by Carter in Riverside, to study tropospheric oxidation processes at low NOX concentrations.

Figure 2 .

The double wall outdoor chamber SAPHIR in Jülich, Germany.

Two other chambers were built in Germany, at the same time, for the study of aerosol processes. Already in 1986, Zetzsch and coworkers built in Hannover a 3000 l Duran-glass indoor chamber, covered inside with FEP, and irradiated by solar simulators. This facility has recently been moved to Bayreuth. In 1990, Schurath and co-workers (see contribution in this book) built in Karlsruhe a 84 m3 stainless steel chamber called AIDA, which could be operated between -90 and +60 ºC. EUPHORE will be described later in more detail. Other groups also now operate medium sized chambers: Baltensperger in Zürich, Wenger in Cork, Le Bras in Orleans, Herrmann in Leipzig, Hjorth in Ispra and Doussin in Paris.

6

K. H. Becker

Large static reactors which can be operated at atmospheric pressure Advantages The probability of wall effects relative to gas reactions decreases with the size R of a reactor, K ~ c • 1/R. The large reactor diameter favours the application of long path absorption spectroscopy in the UV, VIS and IR. * Sampling of gas is not limited, and allows the use of a large variety of analytical instruments. * The large volume inside a reactor provides space for in situ analytical equipment,* e.g. cryo-trapping of radicals and LIF. Application of the relative rate method enables the determination of rate constants not influenced by impurities, which is a problem in absolute rate determination. The study of radical reactions with a reactant using the relative rate method is not influenced by radical chains which may develop during the reaction process. A mixture of reactants can be introduced together with air or inert gases as tracers. Studies of aerosol formation, and the chemical composition and physical properties of the particles become possible, provided the temperature gradient in the chamber can be controlled. *) This allows the analysis of reaction mechanisms by measuring intermediate products and operation in the ppbV range, i.e. at nearly ambient concentrations.

Disadvantages With increasing R the volume of the reactor increases by R3 which creates room problems and increases the costs. Low rate constants for radical reactions, below 10-14 cm3/(molecule • s), cannot be measured because the change of the reactant concentration is given by k×[radical] and [radical] is low, e. g. for OH in the order of 107 -108 radicals/cm3. The photolytic radical source in a chamber might be less controllable (e.g. wall source of HONO). Special Problems The light source of indoor chambers may deviate from the sunlight and create different photochemistry. In the outdoor chamber, the solar spectrum varies with cloud cover and solar zenith angle and the distribution of the radiation is difficult to model. Radical Sources The radical source is a crucial point in using reaction chambers for photooxidation studies. At the successful dawn of chamber work, direct radical measurements were not technically possible. Production of OH radicals in systems like NOX + VOC + air + light occurred mainly by uncontrolled surface processes producing HONO which is photolysed.


7

Photolytical OH sources in indoor chambers: x

VOC + NOX + air + hQ (source not controlled, probably includes HONO photolysis)

x

HONO + hQ o OH + NO

x

O3 + H2O + hQ o 2 OH + O2

x

RONO + NO + air + hQ o ....... OH RONO + hQ o RO + NO o R'CHO + HO2 RO + O2 HO2 + NO o OH + NO2

x

H2O2 + hQ o 2 OH

x

HCHO + NO + air + hQ o ..... 2 OH + air HCHO + hQ o H + HCO H + O2 + M o HO2 + M HCO + O2 o HO2 + CO HO2 + NO o OH + NO2 Dark OH sources used in chambers: x HO2NO2 + NO + air o OH + 2 NO2 HO2NO2 + M o HO2 + NO2 + M HO2 + NO o OH + NO2 x

olefins + O3 o .....OH......

x

N2H4 + O3 o ..... OH ......

NO3 radical source used in chambers: x N2O5 + M o NO3 + NO2 + M

x NO2 + O3 o NO3 + O2 RO2-radical rource used in chambers: x Cl2 + RH + O2 + hQ + M o 2 RO2 + 2 HCl + M The above lists shows the reactions which have been used to produce OH radicals under controllable conditions by irradiation with an appropriate light source or in the dark. For the study of NO3 radical reactions, either N2O5 has to be introduced into the chamber or the studies have to be carried in the presence of NO2 + O3. For RO2 radical studies, H atom abstraction by photolytically generated Cl atoms in the presence of O2 was employed. For indoor chambers, a variety of photolysis lamps have been used, either intensive Xe high pressure arc or fluorescent lamps with different spectral transmittances. The reactor walls for indoor chambers had to be made from Duran/Pyrex glass or quartz glass in order to ensure transmittance of photolytically active light for initiation of the radical photooxidation (see Figure 3) or the lamps had to be installed inside the reactor. For simulation studies the radical source should be as similar as possible to the outdoor situation, however, in reality this is never fully achieved. Figure 4 gives spectral thresholds for the production of photolytic radical sources in the troposphere, and Figure 5 shows the diurnal variation of the production rates of the different OH radical sources based on field measurements in Germany 1998 within the BERLIOZ campaign. This shows that different OH sources even during daylight

K. H. Becker

8

are active in the troposphere near the surface. Apart from simulation studies photoreactors of all sizes have been successfully used for a long time to measure reaction rate constants of radicals by employing the relative rate technique.

Figure 3 .

Absorptions spectra of NO2, HONO and CH3ONO.

Figure 4 .

Spectral thresholds of photolytic radical sources in the troposphere and the spectral distribution of sunlight a) above the ozone layer, b) near the surface.


9

Figure 5 . Comparison of the four dominant atmospheric OH radical sources (photolysis of O3, HONO, HCHO, and ozonolysis of VOC’s) for 20th and 21st of July 1998. The difference in the OH production in the early morning hours can be seen easily. After 12:00 on 20th July and 8:00 on 21st July, respectively, the modelled J(HCHO) values were used, because no measurements were available for this time period. The dotted line shows the calculated P(OH) from nitrous acid photolysis during daytime. The data were obtained during the BERLIOZ campaign at the Pabstthum site, northwest from Berlin (Platt et al., 2002).

Relative rate technique The relative rate technique has a few advantages over other methods, i.e. no absolute concentrations have to be measured, impurities do not generally disturb the measurements and the experiments can be carried out in the presence of several reaction partners (Barnes et al., 1982). Also the initiation of radical chains during the reaction process does not distrurb the measurements. However, the rate constant of the reference reaction, k2, has to be known. The following system illustrates the kinetics of the relative rate technique.

10

K. H. Becker X1 + Y Products, k1 (cm3 s-1) X2 + Y Products, k2 X1 and X2: stable species, Y: radical

Reactions:

d [X1] / dt d ln [X1] / dt d [X2] / dt d ln [X2] / dt

= = = =

- k1 [X1] [Y] - k1 [Y] - k2 [X2] [Y] - k2 [Y]

(1/k1) ³d ln [X1]t = - ³[Y]t dt t

t

(1/k2) ³d ln [X2]t = - ³[Y]t dt t

t

(1/k1) ³d ln [X1]t = (1/k2) ³d ln [X2]t t

t

k1 / k2 = ln ([X1]t / [X1]o) / ln ([X2]t / [X2]o)

Selected experimental results from chamber studies "Große Bonner Kugel" The chamber was built between 1966-68 by W. Groth upon the initiative of P. Harteck. The facility was operated by K. H. Becker, E. Fink, D. Kley and U. Schurath (Groth et al., 1972). Properties of the chamber: volume: 221 m3 surface: 177 m2 inner diameter: 7.5 m heatable: Tmax = 350 ºC with 233 KW power for reaching a vacuum of 10-9 Torr. cooling of baffles between pumps and chamber with liquid hydrogen material: stainless steel, 10 mm wall thickness pumping speed: 240 000 l/s with 8 diffusion pumps lowest pressure: 10-9 Torr Major purpose: Studies of O and N atom reactions of aeronomic interest in the upper atmosphere in the pressure range of 0.1-100 mTorr. Major achievements: New results on the recombination reactions of NO + O + (M) (Becker et al., 1972c; 1973), N + N + (M) (Becker et al., 1969; 1971a; 1972b), reactions of O2(1'g) and O2(16+g) with other trace gases (Becker et al., 1971b; 1972a; Penzhorn et al., 1974), reactions of O3 with olefins (Becker et al., 1974a), detection of an energy transfer reaction from O2(1'g) to the HO2 radical and identification of a low lying excited state of HO2 (Becker et al., 1974b; 1975; 1978a). The studies on NO + O and N + N included the quantification of radiative recombination by inverse predissociation which could be clearly


11

identified in the low pressure regime. Unfortunately, at that time dark OH radical sources and the importance of OH reactions were not known. Figures 6 - 8 show the facility installed beside the Institute of Physical Chemistry, Bonn University. The facility was dismantled few years ago.

Figure 6 .

The housing of the “Große Bonner Kugel”.

Figure 7. Cross-section through the spherical reaction chamber.

12

K . H. Becker

Figure 8 . The pipe system by which the chamber could be heated up to 300 °C (top), enormous pumping capacity needed to reach the vacuum of 10-9 Torr (middle), and the platform at which the experiments were prepared and carried out (bottom).


13

Studies on the air glow reaction NO + O + M o NO2 + M + hQ The controversial discussion surrounding this reaction as to the relative contributions of a two-body or three-body mechanism could only be settled by experiments carried out at relatively low total pressure, because nearly all previous studies were performed in flow tubes at about 1 Torr or in flow tubes at lower pressures, with significant wall influences. It was expected that the large reaction chamber offered the best possibility to study the reaction at low pressures. The O atoms were generated by flowing O2 through a discharge before introducing the atoms into the chamber. This could be done from the side or even from the centre of the sphere by means of inserted Teflon tubes. After switching off the discharge, the atoms decayed rapidly by wall reactions. However, the large volume provided about 100 s time during the decay, in which the air glow could be measured during stepwise increase of the total pressure. Figure 9 shows an intensity-time profile of the air glow during the stepwise increase of the total pressure.

Figure 9 . The intensity-time profile of the air glow reaction NO + O + M during the decay of the O atoms and the stepwise increase of the total pressure, M = O2, from 0.1 to 0.8 mTorr (upper part) and from 0.1 to 24.5 mTorr (lower part). As can be seen from Figure 11, below 1 mTorr the air glow rate constant follows a two-body radiative recombination with a rate constant of 4.2 × 10-18 cm3 molecule-1 s-1

14

K . H. Becker

Figure 10. Spectral distribution of the air glow emission at different total pressures (M = O2), absolutely calibrated against the distribution at 1 Torr measured in a flow tube (Fontijn et al., 1964).

Figure 11. The air glow intensity obtained by the integral over the spectral distribution of the chemiluminescence shown in Figure 10, which is plotted as apparent two-body rate constant kM against total pressure (M = O2).


15

whereas above 1 Torr the “high pressure” limit with an apparent two-body rate constant of 6.4 × 10-17 cm3 molecule-1 s-1 has been reached where three-body recombination by M and quenching by M is balanced. From the slope of the plot of kM vs. total pressure a three-body rate constant of 7 × 10-32 cm6 molecule-1 s-1 was determined. As a consequence, the air glowreaction proceeds by a two-body as well as by a three-body reaction. When the air glow rate constant is compared with the total recombination rate of NO + O + M, which also was measured in the chamber, it can be concluded that the air glow rate constant represents within the error limits the total recombination rate constant. Further details are given in the publications Becker et al. (1972c) and (1973). Experiments from Wuppertal Several photoreactors between 420 to 1080 l volumes are in operation in the Physical Chemistry Department of the Bergische University Wuppertal. A thermostated photoreactor of 420 l volume is shown schematically in Figure 12. The reactor consists of an inner Duran glass tube, o.d 0.6 m and length 1.5 m which is concentrically inserted in a wider Duran glass tube of the same length. On both sides the tubes are closed by aluminium flanges covered with Teflon on the inner side. Between the tubes a cooling fluid circulates, and inside the fluid space black lamps/fluorescent lamps in protective Duran covers are installed. The covers are flushed with dry purified air. Figure 13 shows that the whole reactor including the cooling systems is inserted into a rigid optical bench which is part of a White multiple path mirror system coupled to a FTIR spectrometer. In order to minimise light losses of the IR beam, the White mirrors are installed inside the reactor, but can be adjusted to optimal path length from outside. The flanges contain several ports, such as gas inlet/outlet ports and syringe port for taking GC samples, as well as windows for UV/Visible absorption spectroscopy. The optimal path length of several hundred meters enables quantitative concentration measurements in the

Figure 12 . Schematic view of the 420 l reactor in Wuppertal, operating in the temperature range of ± 50 oC.

K . H. Becker

16

ppmV range, while gases with low IR absorption are measured by GC. The spectroscopic measurements require careful recording of reference spectra. The reactor is evacuable down to 1 mTorr, and is operated mostly at atmospheric pressure, filled either with synthetic air or with rare gases. The temperature can be set between –50 to +50 °C. A first version of a

Figure 13.

The suspended double wall reactor of 420 l volume.

Figure 14 .

View of the thermostated and non-thermostated reactors mounted in series.


17

photoreactor of the same size was built with the cooling system, and now it is installed in line with the thermostated reactor, Figure 14.

Figure 15 . View of the 6 m long quartz glass reactor of 1080 l volume.

Figure 16 .

Schematic drawing of the 1080 l reactor setup.

K . H. Becker

18

Figure 15 and 16 show the 1100 l quartz glass reactor consisting of two combined tubes with a combined length of 6.2 m length with an o.d. of 0.47 m. The end flanges contain all the necessary ports for gas inlets, gas sampling and the White mirrors. The path length for FTIR absorption was extended to approximately 500 meters, to achieve a sensitivity for product analysis reaching the low ppbV range. Examples of experimental work using the chambers (i)

Measurement of pressure dependence of the reaction rate constant of C2H4 + OH in the presence of air and argon (Klein et al., 1984),

(ii)

Measurement of the temperature and pressure dependence of the reaction rate constant HO2NO2 + OH (Barnes et al., 1981; 1986),

(iii)

Measurement of thermal decomposition rates of peroxynitrates, RO2NO2 (Zabel et al., 1986; Kirchner et al., 1990; Becker et al., 1993 and Zabel, 1995) as a function of temperature.

(i) Measurements of the pressure dependence of the reaction rate constant k1 for C2H4 + OH +M o products with M = air and Ar A dark source of OH radicals from the thermal decomposition of HO2NO2 in the presence of NO was employed, and the relative rate method was used with reference reactions, n-hexane + OH and n-butane + OH reactions, for which no pressure dependence is

Figure 17. Dependence of C2H4 + OH +M on total pressure at 295 K for M = synthetic air (M = Ar not shown). The solid line through the data points is the calculated falloff curve. The error bar represents the average of 2V errors for all individual data points.


19

known. Figure 17 shows the experimental results and, together with Figure 18, demonstrates the high quality of the measurements.

Figure 18 . Comparison of literature k1 values near room temperature with the calculated falloff curves from this work (solid line M = Ar, broken line M = synthetic air. The data points are presented without error limits to simplify the comparison.

(ii) Studies on the temperature and pressure dependence of the reaction rate constant HO2NO2 + OH. The next example describes the measurements of the reaction rate constant of peroxynitric acid (HO2NO2) with OH radicals as a function of pressure (He) and temperature, details of which can be found in the literature (Barnes et al., 1981; 1986). It is impressive that for a rather complex chemical system no absolute concentration measurements were needed. A relative rate method with reference to the known reaction rate constant kn-butane + OH was used. HO2NO2 was prepared outside the reactor and introduced together with NO, He and the reference substance (n-butane) into the reaction chamber. The OH radicals steadily produced from the thermal decomposition of HO2NO2, caused a decay in n-butane which could be followed by GC analysis, stage I in Figure 19. The decay of HO2NO2 measured by FTIR absorption is due to thermal decomposition, possible wall losses and the HO2NO2 + OH reaction, also shown in Figure 19, stage I. After stage I, the n-butane concentration was rapidly increased, which resulted in a change of the OH concentration because of the faster radical consumption by n-butane. Consequently, the decay of HO2NO2 became slower because of the lower OH concentration. From the different slopes of HO2NO2 and n-butane in stage I and stage II, all measured relatively during the time steps 't in both stages, the

20

K . H. Becker

following equation was derived from which the reaction rate constant kHO2NO2 evaluated:

+ OH

was

kHO2NO2+OH/kn-butane+OH = {('ln[HO2NO2]/'t)stage I ('ln[HO2NO2]/'t)stage II}/ {('ln[n-butane]/'t)stage I ('ln[n-butane]/'t)stage II}

Figure 19. Concentration-time profiles for X = HO2NO2 (o) and X = n-butane (); reaction conditions: T = 278 K, ptotal = 133 mbar, M = He, [NO]o = 2.4 x 1015 molecules/cm3 , [NO2 ]o = 1.0 x 1014 molecules/cm3. (iii) The thermal decomposition rates of peroxynitrates, RO2NO2, as a function of temperature and pressure. The last example deals with measurements of the thermal decay of peroxynitrates, RO2NO2, as a function of pressure and temperature. Details can be found in the publications Zabel et al. (1986), Kirchner et al. (1990), Becker et al. (1993) and Zabel (1995). In the experiments, the peroxynitrates were produced in the presence of O2 and NO2 from R radicals generated by H atom abstraction by Cl atoms from different hydrocarbons (see the reaction scheme in Figure 20).


21

Alkane + Cl2 +O2 + M + hQ

ĺ

RO2 +HCl +M

RO2 + NO

ĺ

RO + NO2 k1

ĺ

RONO2

RO2 + NO2 + M

ĺ

RO2NO2 + M

k2

RO2NO2 + M

ĺ

RO2 + NO2 + M

k3

(+M)

k3(effective) = k3 x {1 + (k2/k1)x[NO2]/[NO]}-1 k3(T, [M]) for [NO] >> [NO2] and (k2/k1) from variation of [NO]

Figure 20. Production and decomposition of peroxynitrates in the presence of Cl2, NO, NO2 and O2 during the photolysis of Cl2.

Figure 21. Decay of RO2NO2, here HO2NO2, at different NO concentrations.

According to the equation in Figure 20, by increasing the concentration of NO, the parameter k3 can be determined as a function of temperature and total pressure. This can be seen in Figure 21 where k3 is derived from the slope of ln(ct/co) a t at higher NO concentration. Table 3 shows the results for different peroxynitrates. It can be seen that a

22

K . H. Becker

carbonyl group beside -O2 stabilizes the peroxynitrate as for peroxyacetylnitrat, CH3C(O)O2NO2, (PAN), in particular at lower temperatures. Table 3 .

Rate constants, Arrhenius parameters and thermal lifetimes of several peroxynitrates (experiments and evaluation are described in Zabel et al. (1986), Kirchner et al. (1990), Becker et al. (1993) and Zabel (1995).

R in RO2NO2 C4H9 C6H13 C8H17 C2H5 CH3C(O)CH2 CH3 C6H5CH2 HOCH2 CH3OCH2 CH3C(O)OCH(CH3) C6H5OCH2 H CH3OC(O) CH3C(O) C6H5C(O) *

k3 (298K)*

Ea

Thermal lifetime, K-1

A

-1

kJ/mol

10 s

25 °C

0 °C

- 20 °C

6.5 5.8 3.7 3.7 2.6 1.65 1.5 1.0 0.44 0.24 0.23 0.083 0.00084 0.00040 0.00031

86.2 86.2 86.2 86.2 85.6 83.8 90.3 85.3 92.2 94.9 95.0 89.2 107.0 112.9 116.4

0.83 0.75 0.48 0.47 0.26 0.08 1.0 0.09 0.64 1 1 0.036 0.48 2.5 7.9

0.15 s 0.17 s 0.27 s 0.27 s 0.38 s 0.61 s 0.67 s 1.00 s 2.27 s 4.17 s 4.35 s 12.05 s 19.8 min 41.7 min 53.8 min

3.7 s 4.1 s 6.5 s 6.6 s 9.2 s 13.5 s 19 s 23.3 s 1.1 min 2.4 min 2.5 min 5.4 min 17.2 h 1.8 days 2.7 days

1.3 min 1.4 min 2.2 min 2.2 min 3.0 min 4.2 min 7.3 min 7.7 min 28.3 min 1.1 h 1.1 h 2.0 h 30 days 94 days 157 days

s

16 -1

k3 (T) = A×exp(-Ea/RT)

EUPHORE: the EUropean PHOtoREactor in Valencia In 1995, at the CEAM Foundation in Valencia, the European photoreactor came into operation. The facility was built by the group of Becker from Wuppertal, and is hosted and operated by CEAM under the direction of Millían and Wirtz. Figures 22 and 23 show photos of the facility, which consists of two half-sphere outdoor chambers made from TEDLAR. Each chamber has a volume of 200 m3. Movable rigid covers protect both chambers against heavy storms, and are used to cut off the solar irradiation during experiments. The chambers are fully equipped with state-of-the-art analytical instrumentation. Besides more conventional methods, FTIR long path absortion and DOAS are employed. In one chamber OH and HO2 radicals can be measured in situ by the LASER fluorescence technique. Regular EUPHORE reports are published which can be obtained from Ian Barnes ([email protected]) or Klaus Wirtz ([email protected]).


Figure 22 . One of the two EUPHORE chambers at CEAM/Valencia.

Figure 23 . Building hosting two EUPHORE chambers, one closed by a metal cover.

23

24

K . H. Becker

Figure 24 . In situ measurements of OH radicals (line) during the oxidation of toluene, for comparison, the points represent OH concentrations that were calculated from the decay rate of toluene (Pilling, M. J. et al., 2003). An example of the good agreement which has been obtained in the EUPHORE chamber between measured OH radical profiles using the FAGE technique (Pilling, M. J. et al., 2003) and the OH radical concentration in the chemical system calculated from the decay of toluene is shown in Figure 24. Outlook Numerous results from kinetic and mechanistic studies using photo-reactors have been obtained which have contributed significantly to an increase in our knowledge on atmospheric chemistry, in particularly in the gas phase. Some open questions still remain, e.g. the mechanisms of the photooxidation of aromatic hydrocarbons and the process of gas-toparticle conversion. More recently also aerosol studies are being carried out in chambers. Some very recent work has led now to a much better understanding of the photochemical wall effects in chambers which produce OH radicals (Rohrer et al., 2005). The state of chemical knowledge has, however, so much advanced that it is quite difficult to propose further innovative work and the interest on additional applications of new results for improving tropospheric models is decreasing. On the other side, interest in exposure experiments using advanced simulation facilities and analytical techniques to study impacts of air pollutants on human health, plant damages and material destruction is on the increase. This could be viewed perhaps as a return to the 50-ties (Hagen-Smit, 1952), however, compared to then present-day approaches are at a much higher level of understanding of the chemical systems and use techniques which enable in situ radical measurements and the monitoring of trace gases in the pptV range. At the time of writing a new EU infrastructure project EUROCHAMP (co-ordinator P. Wiesen < [email protected] >) has as its main goal the integration of all European chamber facilities to improve studies on atmospheric chemical systems and also to open simulation facilities for impact studies.


25

References Akimoto, H., M. Hoshino, G. Inoue, F. Sakamaki, N. Washida and M. Okuda; Environ. Sci. Technol. 13 (1979) 471. Barnes, I., V. Bastian, K.H. Becker, E.H. Fink and F. Zabel; Atmos. Environ. 16 (1982) 545. Barnes, I., V. Bastian, K. H. Becker, E. H. Fink and F. Zabel; Chem. Phys. Lett. 83 (1981) 459. Barnes, I., V. Bastian, K.H. Becker, E.H. Fink and F. Zabel; Chem. Phys. Lett. 123 (1986) 28. Becker, K.H., W. Groth and D. Kley; Z. Naturforschung 24a (1969) 1840. Becker, K.H., A. Elzer, W. Groth and D. Kley; Z. Naturforschung 26a (1971a) 929. Becker, K.H., W. Groth and U. Schurath; Chem. Phys. Lett. 8 (1971b) 259. Becker, K.H., W. Groth and U. Schurath; Chem. Phys. Lett. 14 (1972a) 489. Becker, K.H. E. H. Fink, W. Groth, W. Jud and D. Kley; Faraday Disc., Chem. Soc. 53 (1972b) 35. Becker, K.H., W. Groth and D. Thran; Chem. Phys. Lett. 15 (1972c) 215. Becker, K.H., W. Groth and D. Thran; 14th Symp. (International) on Combustion, Pittsburgh (1973) 353. Becker, K.H., U. Schurath and H. Seitz; Int. J. Chem. Kinet. 6 (1974a) 725. Becker, K.H., E. H. Fink, P. Langen and U. Schurath; J. Chem. Phys. 60 (1974b) 4623. Becker, K.H., E. H. Fink, P. Langen and U. Schurath; 15th Symposium (International) on Combustion, The Combustion Institute, Pittsburgh (1975) 961. Becker, K.H., E. H. Fink, A. Leiss and U. Schurath; Chem. Phys. Lett. 54 (1978a) 191. Becker, K.H., J. Löbel und U. Schurath; Staub-Reinhaltung Luft 38 (1978b) 278. Becker, K.H., F. Kirchner and F. Zabel; in: K.H. Becker and H.Niki (eds), The Tropospheric Chemistry of Ozone in Polar Regions. NATO ASI Series, Vol. 17, Springer Verlag, Berlin Heidelberg (1993) 351. Bridier, I., F. Caralp, H. Loirat, R. Lesclaux, B. Veyret, K. H. Becker, A. Reimer and F. Zabel; J. Phys. Chem. 95 (1991) 3594. Calvert, J.G. and J.N. Pitts, Jr.; Photochemistry, John Wiley & Sons, New York (1966). Crutzen, P.J. and C.J. Howard; Pure Appl. Geophys. 116 (1978) 497. Finlayson-Pitts, B.J. and J.N. Pitts, Jr.; Atmospheric chemistry, John Wiley & Sons, New York (1986). Finlayson-Pitts, B.J. and J.N. Pitts, Jr.; Chemistry of the upper and lower atmosphere, Academic Press, New York (2000). Fontijn, A., C.B. Meyer and H.I. Schiff; J. Chem. Phys. 40 (1964) 64. George, C., R. S. Strekowski, J. Kleffmann, K. Stemmler and M. Ammann; Faraday Discuss. 130 (2005) 1-16. Glaschick-Schimpf, I.,A. Leiss, P.B. Monkhouse, U. Schurath, K.H. Becker and E.H. Fink, Chem. Phys. Lett. 67 (1979) 318. Greiner, N. R.; J. Chem. Phys. 46 (1967) 2795. Groth, W., K. H. Becker, G.H. Comsa, A. Elzer, E. Fink, W. Jud, D. Kley, U. Schurath and D. Thran; Naturwissenschaften 59 (1972) 379. Haagen-Smit; Ind. Eng. Chem. 44 (1952) 1342. Hack, W., A. W. Preuss, F. Temps, H.Gg. Wagner and K. Hoyermann; Int. J. Chem. Kinet. 12 (1980) 851. Hanst, P. L.; Adv. Environ. Sci. Technol. 2 (1971) 91. Heicklen, J., K. Westberg and N. Cohen; Report, Center for Air Environmental Studies, (1969) 115-169. Herriott, D., H. Kogelnik and R. Kompfner; Appl. Opt. 3 (1964) 523. Herriott, D., and H.J. Schulte; Appl. Opt. 4 (1965) 883.

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Howard, C.J., and K.M. Evenson; Geophys. Res. Lett. 4 (1977) 437. Howard, C.J.; J. Chem. Phys. 71 (1979) 2352. Howard, C.J.; J. Am. Chem. Soc. 102 (1980) 6937. Klein, Th., I. Barnes, K.H. Becker, E.H. Fink and F. Zabel; J. Phys. Chem. 88 (1984) 5020. Leu, M.-T.; J. Chem. Phys. 70 (1979) 1662. Levy, H., Science 173 (1971) 141. Niki, H., E.E. Daby and B. Weinstock; Adv. Chem. Ser., Washington, 113 (1972) 16. Niki, H., P.D. Maker, C.M. Savage and L. P. Beitenbach; Chem. Phys. Lett. 80 (1981) 499. Penzhorn, R.D., H. Güsten, U. Schurath and K.H. Becker; Environ. Sci. Technol. 8 (1974) 907. Pilling, M. J. et al. (2003). Effects of the oXidation of Aromatic Compounds in the Troposphere (EXACT, EVK2-CT-1999-00053), Final Report., http://www.chem.leeds.ac.uk/exact Platt, U., B. Alicke, R. Dubois, A. Geyer, A. Hofzumahaus, F. Holland, M. Martinez, D. Mihelcic, T. Klüpfel, B. Lohrmann, W. Pätz, D. Perner, F. Rohrer, J. Schäfer and J. Stutz; J. Atmos. Chem. 42 (2002) 359. Rohrer, F., B. Bohn, T. Brauers, D. Brüning, F.-J. Johnen, A. Wagner, J. Kleffmann, Atmos.Chem. Phys. Discus. 4 (2004) 7881. Stedman, D.H., E.D. Morris, Jr., E.E. Daby, H. Niki and B. Weinstock; 160th National Meeting of Am. Chem. Soc., Chicago (1970). Stephens, E.R.; Soc. Appl. Spectrosc. 12 (1958) 80. Thrush, B.A. and J.P.T. Wilkinson; Chem. Phys. Lett. 81 (1981) 1. Weinstock, B.; Science 166 (1969) 224. White, J.U.; J. Opt. Soc. Am. 32 (1942) 285. White, J.U.; J. Opt. Soc. Am. 66 (1976) 411. Wu, C.H., S.M. Japar and H. Niki; J. Environ. Sci. Health, Environ. Sci. Eng. A11 (1976) 191. Zabel, F.; Z. Physi. Chem. 188 (1995) 119.

The UCR EPA Environmental Chamber William P. L. Carter College of Engineering Center for Environmental Research and Technology, University of California, Riverside, California, 92521, USA Key Words: Environmental chambers, Atmospheric chemical mechanisms, Ozone, Volatile organic compounds, Oxides of nitrogen

Abstract The UCR EPA chamber is a new large indoor environmental chamber constructed at the University of California at Riverside (UCR) under United States EPA funding for the purpose of evaluating gas-phase and secondary aerosol mechanisms for ground-level air pollution. The major characteristics of this chamber, the results of its initial characterization for gas-phase mechanism evaluation, and examples of initial gas-phase mechanism evaluation experiments, are described. It is concluded that the chamber has lower or at most comparable background effects than other chambers previously used for mechanism evaluation, and can provide useful mechanism evaluation data at NOx levels as low as 2 ppb. Future research directions to utilize the capabilities of this chamber are discussed. Background Chemical mechanisms are critical components of airshed models used for predictions of secondary pollutants such as ground-level ozone or secondary organic aerosol. Because many of the chemical reactions are incompletely understood, these mechanisms cannot be relied upon to give accurate predictions of impacts on emissions on air quality until they have been shown to give accurate predictions under realistic but controlled conditions. The most reliable way to test this is to compare their predictions against results of well-characterized environmental chamber experiments that simulate the range of conditions in the atmosphere. If a model cannot accurately predict results of such experiments, it cannot be expected to reliably predict effects of proposed control strategies on ambient air quality. For this reason, environmental chambers are essential to developing predictive mechanism for compounds for which basic mechanistic information are insufficient (as is the cased for aromatics), testing approximations and estimates necessary for modelling the reactions of almost all VOCs under simulated atmospheric conditions, and testing entire mechanisms under varied conditions. However, results of environmental chamber experiments are only useful for testing mechanisms if the conditions of the experiments are sufficiently well characterized so that the characterization uncertainties are less than the uncertainties of the mechanisms being tested. As discussed by Dodge (2000), the chamber data base used to develop and evaluate current mechanisms had a number of limitations and data gaps that could affect their accuracy. Uncertainties exist concerning characterization of chamber conditions that could cause compensating errors in the gas-phase mechanism (Carter and Lurmann, 1990, 1991; Jeffries et al, 1992). Most chamber experiments lack measurement data for important species, limiting the level of detail to which the mechanisms can be evaluated, and the types of air quality impact predictions that can be assessed. Furthermore, because of chamber effects and because of inadequate analytical equipment employed, the current environmental chamber data base is not suitable for evaluating chemical mechanisms under the lower NOx conditions found in 27 I. Barnes and K. J. Rudzinski (eds.), Environmental Simulation Chambers: Application to Atmospheric Chemical Processes, 27–41. © 2006 Springer. Printed in the Netherlands.

W. P. L. Carter

28

rural and urban areas with lower pollutant burdens. Because of this, one cannot necessarily be assured that models developed to simulate urban source areas with high NOx conditions will satisfactorily simulate downwind or cleaner environments where NOx is low. To address the need for improved an improved environmental chamber facility to evaluate mechanism for O3 and PM formation, the College of Engineering, Center for Environmental Research and Technology (CE-CERT) at the University of California at Riverside (UCR) has undertaken a program to develop a “Next Generation” environmental chamber facility for chemical mechanism evaluation and VOC reactivity assessment. The objectives are to develop the environmental chamber facility needed for evaluating gas-phase and gas-to-particle atmospheric reaction mechanisms, for determining secondary aerosol yields, and for measuring VOC reaction products and radical and NOx indicator species under more realistic and varied environmental conditions than previously has been possible. This project resulted in the construction of new “UCR EPA” chamber, which became fully operational in early 2003. The design features and characteristics of this chamber, the results of its initial characterization, and completed and ongoing projects in this chamber are summarized briefly below. Facility Description The indoor facility comprises a 20’x20’x40’ thermally insulated enclosure that is continually flushed with purified air at a rate of 1000 L min-1 and is located on the second floor of a laboratory building specifically designed to house it. Located directly under the enclosure on the first floor is an array of gas-phase continuous and semi-continuous gas-phase monitors. Within the enclosure are two ~90 m3 (6.1 m x 3.1 m x 5.5 m, Surface area to volume = 1.35 m-1) 2 mil FEP Teflon® film reactors, a 200 kW Argon arc lamp, a bank of 72 W 4-ft blacklights, along with the light and aerosol instrumentation. A schematic of the enclosure is provided in Figure 1.

Movable top frame allows reactors to collapse under pressure control

2 Banks of Blacklights This volume kept clear to maintain light uniformity

200 KW Arc Light

Dual Teflon Reactors

20 Two air Handlers ft. are located in the corners on each side of the light (not shown).

Mixing System Under floor of reactors Floor Frame 20 ft.

Temperature controlled room flushed with purified air and with reflective material on all inner surfaces

Figure 1.

20 ft.

Access Door

SEMS (PM) Instrument

Gas sample lines to laboratory below

Schematic of the environmental chamber reactors and enclosure.

The UCR EPA Environmental Chamber

29

Enclosure The interior of the thermally insulated 450 m3 enclosure is lined with reflective Everbrite® (Alcoa, PA) aluminium sheeting to maximize the interior light intensity and homogenize the interior light intensity. A positive pressure is maintained between the enclosure and the surrounding room to reduce contamination of the reactor enclosure by the surrounding building air. The enclosure air is well mixed by the large air handlers that draw in air from inlets around the light and force the air through a false ceiling with perforated reflective aluminium sheets. The enclosure is temperature controlled with a ~30 ton air conditioner capable of producing a temperature range of -5 to 80 C. Teflon Reactors The 2 mil (54 Pm) FEP Teflon® reactors are mounted within the enclosure with a rigid bottom frame and a moveable top frame. The floor of the reactor is lined with Teflon film with openings for reactant mixing within and between reactors and 8 ports ranging in size from ¼” to ½” for sample injection and withdrawal. The moveable top frame is raised/lowered with a motorized pulley system enabling the user to expand (during filling) and contract (during an experiment or for flushing) as necessary. The rate of contraction/expansion is set to maintain a differential pressure of 0.02 in H2O between the inside of the reactor and the enclosure. During experiments, the top frames are slowly lowered to maintain positive pressure as the volume decreases due to sampling, leaks, and permeation. The experiment is terminated when the final reactor volume reaches 1/3 of its maximum value (typically about 10 hours). The elevator system coupled with differential pressure measurements allows for repeatable initial chamber volumes and allows for reactants to be injected with greater than 5% precision. The Teflon reactors are built in-house using a PI-G36 Pac Impulse Sealer (San Rafael, CA) heat sealing device for all major seams and a U-frame mount to the reactor ceiling and floor. Pure Air System An Aadco 737 series (Cleves, Ohio) air purification system produces compressed air at rates up to 1500 L min-1. The air is further purified by passing through canisters of Purafil® and heated Carulite 300® followed by a filter pack to remove all particulate. The purified air within the reactor has no detectable non-methane hydrocarbons (0.99) and 0.049, 0.178, 0.301, 0.008 for high HCo:NOx ratios (R2>0.99). (Song et al., 2005). A plot of the modeled aerosol mass concentrations versus hydrocarbon reacted can be found in Figure 1.

400 HCo:NOx8.0

350

Mo(Pg/m3)

300 250 200 150 100 50 0 0

500

1000

1500

2000

3

HC(Pg/m ) Figure 1.

SOA mass concentrations from m-xylene photooxidation as a function of mxylene consumption. Empirical fit using equation 3 for low NOx (HCo:NOx>8.0) and high NOx (HCo:NOx 1.6 are established by controlled pumping, typically from 1000 to 800 hPa. The mechanical pump can be operated at variable pumping speeds to establish cooling rates which vary by more than an order of magnitude. Figure 5 depicts temperature and pressure profiles for two different pumping scenarios. Using the maximum pumping speed (from 1000 to 800 hPa in less than 4 min) leads to a cooling rate of initially more than 4 K min-1. At slow pumping speeds, cooling rates less than 0.1 K min-1 can be controlled. Note that the cooling rate in AIDA approximately obeys the Poisson equation (4) only at the very beginning of an expansion cooling experiment:

Sice T

T

§ p· T0 ¨ ¸ © p0 ¹

R Cp

(4)

Later on the cooling rate continuously levels off due to the increasing difference between the gas temperature and the wall temperature, which remains almost constant throughout the expansion. This gives rise to an increasing heat flux from the walls into the

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chamber air and limits the maximum supersaturation with respect to ice which can be achieved.

Pressure (hPa)

1 000

950

1 900 850

2

800

Temperature (K)

240 238

1

236 234

4 K/min

2

232

0.1 K/min

230

0

10

5

15

Time (min) Figure 5 .

Time profiles of total pressure (top panel) and mean gas temperature (bottom panel) during two AIDA expansion cooling experiments with largely different pumping speeds.

Expansion cooling experiments are started after coating the walls of the AIDA chamber with a thin ice layer, i.e. at an ice saturation ratio Sice close to unity. The coating is made by filling the chamber with humidified air at some higher temperature and subsequent cooling to a lower temperature. Due to several internal heat sources (mixing fan, heated sampling tubes) the mean gas temperature is always a few tenths of a Kelvin higher than the wall temperature under static conditions, which explains why Sice is slightly less than unity before an expansion is started. As already indicated in the introductory section, very low background aerosol number concentrations of < 0.1 cm-1 can be established by evacuating the chamber to < 0.01 hPa and performing several flushing cycles with particle-free synthetic air. Afterwards, the desired seed aerosol is added to the chamber and characterised by e.g. filter sampling and size distribution measurements. Upon the start of expansion cooling, the calculated saturation water vapour pressure over ice pw,ice(T) in Eq. (3) decreases exponentially with decreasing AIDA gas temperature whereas the actual water vapour pressure pw decreases at most linearly with the total pressure during pumping. This leads to a rapid increase in Sice with a rate dSice/dt of typically 0.3-0.4/min. Note that pw is directly measured in situ with the tuneable diode laser instrument. The rate dSice/dt during expansion cooling is further enhanced by evaporation of ice from the chamber walls as a result of the almost constant wall temperature during pumping. The onset of ice nucleation after exceeding the freezing threshold relative humidity as well as time profiles of the number concentration of the growing ice crystals can be detected by various techniques. In the following, we will demonstrate this interplay of the various AIDA instruments, taking as example two ice

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nucleation experiments with different flame soot aerosol probes from the CAST burner as ice nuclei (Figure 6). This comparison will also illustrate how sensitively the ice nucleation potential depends on the chemical composition of the seed aerosol (Möhler et al., 2004b). Using different air/fuel ratios, two distinctly different samples of CAST soot aerosol with 16% and 40% organic carbon (OC) content, respectively, were generated. The OC fraction was determined by thermographic analysis of the soot aerosols sampled on quartz filters, following a standard protocol as described in the literature (VDI 2465, Blatt 2). To study the influence of the OC fraction of the soot aerosol on its ice nucleation potential, two otherwise identical AIDA expansion experiments were performed using either the 16% OC or the 40% OC soot samples as seed aerosol. The pressure changes during pumping as well as the associated changes in gas temperature for the two experiments are shown in the upper panels of Figure 6 (solid lines: 16% OC, dotted lines: 40% OC). Note the excellent reproducibility of the profiles, whereby the ice nucleation properties of different aerosol types can be directly compared. For the same reason approximately the same soot aerosol number concentrations (about 1000 cm-3) were used in both experiments. Panel 3 shows the relative humidity with respect to ice (RHi) calculated using Eq. (3) from the measured gas temperature and water vapour concentration (circles: 16% OC, triangles: 40% OC). When the onset time of ice nucleation can be determined, the corresponding threshold relative humidity can be directly read off this graph. At first, we will focus on the expansion cooling experiment with the 16% OC soot sample. Here, three independent measurement techniques point to a sharp, well-defined ice nucleation onset after about 100 s, as indicated by the solid vertical line. The optical particle spectrometer (PCS2000) starts to detect a large number of particles larger than 0.5 Pm in diameter, providing clear evidence for the formation and growth of pristine ice crystals (panel 5). At the same time, the infrared spectral signatures also indicate the nucleation of ice particles. The ice crystal number concentrations retrieved from the FTIR spectra (shown as circles in panel 5) turn out to be in excellent agreement with the data from the optical particle counter. Furthermore, the growing ice crystals lead to an increasing back-scattered light intensity, as evidenced in panel 4. From panel 3, we can infer an ice saturation ratio of 1.45 at ice nucleation onset. After reaching a maximum value of about 1.50, Sice starts to decrease as a result of the increasing uptake of water vapour by the growing ice crystals due to their increasing surface area concentration. Ice particle measurements in the expansion experiment with 40% OC soot aerosol markedly differ from the 16% OC sample. Note that the optical particle spectrometer hardly detects any ice particles. Additionally, extinction signatures of ice are barely visible in the infrared spectra and there is only a weak intensity increase of the back-scattered laser light in course of the expansion. The number concentration of ice crystals is less than 10 cm-3, thus < 1% of the seed aerosol particles act as deposition ice nuclei. In contrast to the 16% OC experiment, no precise critical ice saturation ratio can be specified for the 40% OC soot sample. RHi continues to increase to 190% because very little water vapour is lost on the small surface area of the scarce ice crystals. In summary, the comparison of the two expansion experiments provides first evidence that a higher fraction of organic carbon notably suppresses the ice nucleation potential of flame soot particles.

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Figure 6 .

Measured time profiles of pressure, gas temperature, relative humidity with respect to ice, back-scattered laser light intensity, as well as ice particle number concentration for two expansion cooling experiments with different flame soot aerosol samples from the CAST burner as seed aerosol (Möhler et al., 2004b). See text for details.

Concluding remarks Due to the availability of several excellent diagnostic techniques for comprehensive studies of the formation and growth of ice crystals, as exemplified in Figure 6, ice nucleation on various types of aerosol particles will continue to be a focus of AIDA research activities. Future studies are planned to systemically analyse the impact of the chemical composition of soot on its ice nucleation properties. Further experiments will address the impact of coatings on the ice nucleating efficiency of mineral dust particles as well as the role of environmental ice nucleating bacteria. The above diagnostics will soon be supplemented by a new optical device which is presently under construction in our laboratory: it will be designed to measure

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scattering phase functions of ice crystals which are simultaneously imaged by a CCD camera with microscope optics at 2 µm optical resolution. References Arnott, W.P., C. Schmitt, Y.G. Liu and J. Hallett; Droplet size spectra and water-vapor concentration of laboratory water clouds: Inversion of Fourier transform infrared (500-5000 cm-1) optical-depth measurement, Appl. Opt. 36 (1997) 5205-5216. Duft, D. and T. Leisner; Laboratory evidence for volume-dominated nucleation of ice in supercooled water microdroplets, Atmos. Chem. Phys. 4 (2004) 1997-2000. Fuller, K.A., W.C. Malm and S.M. Kreidenweis; Effects of mixing on extinction by carbonaceous particles, J. Geophys. Res. (Atmos.) 104 (1999) 15941-15954. Haag, W., B. Kärcher, S. Schaefers, O. Stetzer, O. Möhler, U. Schurath, M. Krämer and C. Schiller; Numerical simulations of homogeneous freezing processes in the aerosol chamber AIDA, Atmos. Chem. Phys. 3 (2003) 195-210. Jacobson, M.Z.; Strong radiative heating due to the mixing state of black carbon in atmospheric aerosols, Nature 409 (2001) 695-697. Kamm, S., O. Möhler, K.H. Naumann, H. Saathoff and U. Schurath; The heterogeneous reaction of ozone with soot aerosol, Atmos. Env. 33 (1999) 4651-4661. Knopf, D.A., P. Zink, J. Schreiner and K. Mauersberger; Calibration of an aerosol composition mass spectrometer with sulfuric acid water aerosol, Aerosol. Sci. Tech. 35 (2001) 924-928. Koop, T., B.P. Luo, A. Tsias and T. Peter; Water activity as the determinant for homogeneous ice nucleation in aqueous solutions, Nature 406 (2000) 611-614. Mangold, A., R. Wagner, H. Saathoff, U. Schurath, C. Giesemann, V. Ebert, M. Krämer and O. Möhler; Experimental investigation of ice nucleation by different types of aerosols in the aerosol chamber AIDA: implications to microphysics of cirrus clouds, Meteorol. Z. (2004) accepted for publication. Mishchenko, M.I. and L.D. Travis; Capabilities and limitations of a current FORTRAN implementation of the Tmatrix method for randomly oriented, rotationally symmetric scatterers, J. Quant. Spectrosc. Radiat. Transfer 60 (1998) 309-324. Möhler, O., O. Stetzer, S. Schaefers, C. Linke, M. Schnaiter, R. Tiede, H. Saathoff, M. Krämer, A. Mangold, P. Budz, P. Zink, J. Schreiner, K. Mauersberger, W. Haag, B. Kärcher and U. Schurath; Experimental investigation of homogeneous freezing of sulphuric acid particles in the aerosol chamber AIDA, Atmos. Chem. Phys. 3 (2003) 211-223. Möhler, O., S. Büttner, C. Linke, M. Schnaiter, H. Saathoff, O. Stetzer, R. Wagner, M. Krämer, A. Mangold, V. Ebert and U. Schurath; Effect of Sulphuric Acid Coating on Heterogeneous Ice Nucleation by Soot Aerosol Particles, J. Geophys. Res. (Atmos.) (2004a) submitted. Möhler, O., C. Linke, H. Saathoff, M. Schnaiter, R. Wagner and U. Schurath; Ice nucleation on flame soot aerosol of different organic carbon content, Meteorol. Z. (2004b) accepted for publication. Naumann, K.H.; COSIMA - a computer program simulating the dynamics of fractal aerosols, J. Aerosol Sci. 34 (2003) 1371-1397. Niedziela, R.F., M.L. Norman, C.L. DeForest, R.E. Miller and D.R. Worsnop; A temperature- and compositiondependent study of H2SO4 aerosol optical constants using Fourier transform and tunable diode laser infrared spectroscopy, J. Phys. Chem. A 103 (1999) 8030-8040. Norman, M.L., J. Qian, R.E. Miller and D.R. Worsnop; Infrared complex refractive indices of supercooled liquid HNO3/H2O aerosols, J. Geophys. Res. (Atmos.) 104 (1999) 30571-30584. Rothman, L.S., A. Barbe, D.C. Benner, L.R. Brown, C. Camy-Peyret, M.R. Carleer, K. Chance, C. Clerbaux, V. Dana, V.M. Devi, A. Fayt, J.M. Flaud, R.R. Gamache, A. Goldman, D. Jacquemart, K.W. Jucks, W.J. Lafferty, J.Y. Mandin, S.T. Massie, V. Nemtchinov, D.A. Newnham, A. Perrin, C.P. Rinsland, J. Schroeder, K.M. Smith, M.A.H. Smith, K. Tang, R.A. Toth, J. Vander Auwera, P. Varanasi and K. Yoshino; The HITRAN molecular spectroscopic database: edition of 2000 including updates through 2001, J. Quant. Spectrosc. Radiat. Transfer 82 (2003) 5-44.

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Saathoff, H., K.H. Naumann, N. Riemer, S. Kamm, O. Möhler, U. Schurath, H. Vogel and B. Vogel; The loss of NO2, HNO3, NO3/N2O5, and HO2/HOONO2 on soot aerosol: A chamber and modeling study, Geophys. Res. Lett. 28 (2001) 1957-1960. Saathoff, H., O. Möhler, U. Schurath, S. Kamm, B. Dippel and D. Mihelcic; The AIDA soot aerosol characterisation campaign 1999, J. Aerosol Sci. 34 (2003a) 1277-1296. Saathoff, H., K.H. Naumann, M. Schnaiter, W. Schöck, O. Möhler, U. Schurath, E. Weingartner, M. Gysel and U. Baltensperger; Coating of soot and (NH4)2SO4 particles by ozonolysis products of alpha-pinene, J. Aerosol Sci. 34 (2003b) 1297-1321. Schnaiter, M., H. Horvath, O. Möhler, K.H. Naumann, H. Saathoff and O.W. Schöck; UV-VIS-NIR spectral optical properties of soot and soot-containing aerosols, J. Aerosol Sci. 34 (2003) 1421-1444. Schreiner, J., C. Voigt, C. Weisser, A. Kohlmann, K. Mauersberger, T. Deshler, C. Kröger, J. Rosen, N. Kjome, N. Larsen, A. Adriani, F. Cairo, G. Di Donfrancesco, J. Ovarlez, H. Ovarlez and A. Dörnbrack; Chemical, microphysical, and optical properties of polar stratospheric clouds, J. Geophys. Res. 108(D5), 8313 (2003) doi:10.1029/2001JD000825. Seifert, M., R. Tiede, M. Schnaiter, C. Linke, O. Möhler, U. Schurath and J. Ström; Operation and performance of a differential mobility particle sizer and a TSI 3010 condensation particle counter at stratospheric temperatures and pressures, J. Aerosol Sci. 35 (2004) 981-993. Toon, O.B., M.A. Tolbert, B.G. Koehler, A.M. Middlebrook and J. Jordan; Infrared optical constants of H2O ice, amorphous nitric acid solutions, and nitric acid hydrates, J. Geophys. Res. (Atmos.) 99 (1994) 2563125654. Wagner, R., A. Mangold, O. Möhler, H. Saathoff, M. Schnaiter and U. Schurath; A quantitative test of infrared optical constants for supercooled sulphuric and nitric acid droplet aerosols, Atmos. Chem. Phys. 3 (2003) 1147-1164. Wagner, R., O. Möhler, H. Saathoff, O. Stetzer and U. Schurath; Infrared spectrum of nitric acid dihydrate influence of particle shape, J. Phys. Chem. A (2004) submitted. Zasetsky, A.Y., J.J. Sloan, R. Escribano and D. Fernandez; A new method for the quantitative identification of the composition, size and density of stratospheric aerosols from high resolution IR satellite measurements, Geophys. Res. Lett. 29, 2071 (2002) doi:10.1029/2002GL015816. Zink, P., D.A. Knopf, J. Schreiner, K. Mauersberger, O. Möhler, H. Saathoff, M. Seifert, R. Tiede and U. Schurath; Cryo-chamber simulation of stratospheric H2SO4/H2O particles: Composition analysis and model comparison, Geophys. Res. Lett. 29 (2002) 46-49. Zöger, M., A. Afchine, N. Eicke, M.T. Gerhards, E. Klein, D.S. McKenna, U. Mörschel, U. Schmidt, V. Tan, F. Tuitjer, T. Woyke and C. Schiller; Fast in situ stratospheric hygrometers: A new family of balloonborne and airborne Lyman-D photofragment fluorescence hygrometers, J. Geophys. Res. (Atmos.) 104 (1999) 1807-1816.

New On-line Mass Spectrometer for Identification of Reaction Products in the Aqueous Phase: Application to the OH-oxidation of N-methylpyrrolidone under Atmospheric Conditions Laurent Poulain, Anne Monod, and Henri Wortham Laboratoire de Chimie et Environnement, CNRS FRE 2704, Université de Provence case 29, 3 place Victor Hugo, 13 331 Marseille cedex 03, France Key Words : Aqueous phase tropospheric simulation chamber, On-line mass spectrometry, N-methylpyrrolidone, Kinetic rate constants, OH-oxidation, Reaction products, Chemical mechanisms

Introduction The atmosphere is a complex medium where chemicals are released, dispersed by physical processes and oxidized by photochemical reactions initiated by solar radiation. One of the most efficient oxidants is the OH radical produced by complex photochemical processes (Atkinson, 2000). In the past, the studies of Volatile Organic Compounds (VOCs) were focused on the gas phase reactivity. In the 1980s, inter-relations between gas and aqueous phases in the troposphere started to be considered (Graedel and Weschler, 1981). It was recognized that the aqueous phase photochemistry of Water Soluble Organic Compounds (WSOCs) has an impact on the gas phase concentrations of key species such as OH, HO2 and O3 (Lelieveld and Crutzen, 1990; Monod and Carlier, 1999; Herrmann, 2003). More recently, the contribution of WSOC to aerosol hygroscopicity and their ability to act as cloud condensation nuclei was found (Gelencser et al., 2003; Claeys et al., 2004; Ervens et al., 2004). Cloud droplets, which contain numerous chemical species originating both from the gas phase and from the condensation nuclei, are a medium where complex chemistry and photochemistry occur. Several free radicals (e.g. OH, NO3, Cl, Cl2-, SO4-) are formed, which can react with dissolved organic matter. Among these radicals, one of the most efficient oxidizing species is the OH radical (Ervens, et al., 2003, Herrmann, 2003). N-methyl-pyrrolidone (NMP) is used in the industry as a solvent. Its atmospheric lifetime is moderate, 13 h, if [OH] = 106 molecules cm-3 (Aschmann and Atkinson, 1999). However, NMP is a highly soluble compound (KH = 6.4 104 M atm-1, Hine and Moorkerjee, 1975), thus it is likely to enter into tropospheric droplets. The present work was aimed at determining the OH-oxidation rate constant of NMP and the reaction products formed in the aqueous phase under tropospheric conditions. NMP is a medium sized molecule (Table 1), containing 5 carbon atoms, so its OH-oxidation may give rise to a large number of products. This study presents a new on-line technique suitable to identify as many reaction products as possible, during the reaction. Two different kinds of experiments were conducted to determine respectively the kinetics and the reaction products formed. Experimental Reagents. The chemicals used were: H2O2 (not stabilized, Fluka, 30% w); methyl ethyl ketone (MEK) (Fluka, more than 99.5%); methyl-iso-butylketone (MIBK) (Fluka, more than 99%); FeSO4 (Prolabo), acetonitrile (Acros, HPLC grade); methanol (Acros, HPLC grade); succinimide (Sigma Aldrich, 98%), methylamide (Sigma Aldrich, 40%); N-ethylacetamide (Sigma Aldrich, 99%); N-methylsuccinimide (Sigma Aldrich, 99%); N-hydroxymethylpyrrolidone (Sigma Aldrich); acetamide (Sigma Aldrich, 98%), formamide (Sigma 83 I. Barnes and K. J. Rudzinski (eds.), Environmental Simulation Chambers: Application to Atmospheric Chemical Processes, 83–96. © 2006 Springer. Printed in the Netherlands.

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Aldrich, 98%), N-ethylformamide (Sigma Aldrich, 99%), 2-pyrrolidone (Sigma Aldrich, 99%), dimethylacetamide (Sigma Aldrich, 99%). Solutions were prepared using purified water from a Millipore MilliQ system utilising the reverse osmosis, micro-filtration, nucleargrade deionization and activated carbon modules (the resistivity of the purified water was greater than 1.8u 107 : cm-1). Glass cleaning procedure. The work was performed with diluted solutions, in order to avoid any contamination. The reactor and all the sampling vessels were carefully cleaned according to the following procedure: 3 rinses with reverse osmosed water; 1 hour soaking in 2 % DECON detergent diluted with reverse osmosed water; 5 rinses with ultrapure MilliQ water; 2 hours soaking in 2 % HCl diluted with ultrapure MilliQ water; 5 rinses with ultrapure MilliQ water; 15 hours soaking in ultrapure MilliQ water; 3 rinses with ultrapure MilliQ water. Kinetic studies of OH-oxidation of NMP We have shown previously that OH radicals can be generated through the Fenton reaction (1) under specific experimental conditions (Monod, et al., 2005). This technique was used in the dark at pH = 2 for the kinetic study of the OH oxidation of NMP. Fe

2+

H+

+ H2O2

OH

+

Fe(OH)2+

(1)

The kinetic rate constant of the OH oxidation of NMP was determined using the relative kinetic method. The principle of this method is to measure the decay rate of the OHinduced oxidation of the reactant (NMP) relative to that of a reference compound (R) for which the OH oxidation rate constant is well known (reactions 2 and 3). In this study, two reference compounds were chosen: methylethylketone (MEK) and methyl-iso-butylketone (MIBK): NMP + OH

R

+

OH

kX

kR

products

(2)

products

(3)

where kNMP and kR are the rate constants of the OH oxidation of NMP and a reference compound, respectively. The corresponding kinetic equations can be written as follows: § >NMP @ 0 · ¸¸ ln¨¨ © >NMP @ t ¹

§ >R @ 0 · k NMP ¸¸ u ln¨¨ kR © >R @ t ¹

(4)

where [NMP]0, [R]0, [NMP]t, [R]t are respectively the concentrations of NMP and a reference § >NMP @ 0 · § >R @ 0 · ¸¸ versus ln¨¨ ¸¸ yields a linear curve with compound at times 0 and t. Plotting ln¨¨ © >NMP @ t ¹ © >R @ t ¹ a slope of kNMP / kR and an intercept of zero. To obtain kNMP r dkNMP, the median value and

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85

§ >NMP @ 0 · ¸ ln ¨¨ the standard deviation (r2V ) of the ratios © >NMP @ t ¸¹ were calculated and multiplied by kR. § >R @ 0 · ¸¸ ln ¨¨ © >R @ t ¹

To establish the Arrhenius expressions for NMP, the equations given in Monod, et al. (2005) were used for the reference compounds:

ln k MEK (T )

26.2 r 1.0 1600 r 300

(5)

ln k MIBK (T )

25.6 r 1.0 1200 r 300

(6)

T

T

The analyses of NMP were performed using a High Pressure Liquid Chromatograph (HPLC) equipped with a reversed phase C18 column (Alltima, Alltech) and a UV detector working at 212 nm. A binary methanol/water eluent was used (with a gradient from 20%/80% to 90%/10% in 10 min, then maintained so for 5 min), at 1 mL min-1. The analysis of MEK and MIBK was performed by derivatisation with 2,4-dinitrophenylhydrazine (2,4-DNPH), followed by HPLC analysis with a reversed phase C18 column (Alltima, Alltech) and a UV detector working at 360 nm. A tertiary eluent (CH3CN/H2O/CH3OH) was used (isocratic at 20%/40%/40% for 3 min, then a linear gradient to 5%/25%/70% in 10 min, then another linear gradient to 5%/15%/80% in 10 min, then maintained for 6 min). Each sample was prepared by removing an aliquot of 180 µL from the reactor and diluting it with 800 µL of 2,4-DNPH (0.36 mg L-1). These techniques produced sharp peaks in the chromatograms. Before each experiment, a calibration was carried out for each compound in a range covering the concentrations encountered during the experiments.

23

T (K) 276

22.6 22,6

298 308

ln (kOH)

23

322

22.2 22,2

k OH + NMP (10 9 M-1 s -1) relative to MEK relative to MIBK (triangles) (squares) 2.69 r 0.52 2.44 r 0.37 4.63 r 0.51 3.50 r 1.3 4.30 r 0.54

3.45 r 0.31 2.99 r 0.47 3.66 r 0.40

21.8 21,8

21,4 21.4 21 21 3.00 3,00

3.10 3,10

3.20 3,20

3.30 3,30

3.40 3,40

3.50 3,50

3.60 3,60

3.70 3,70

10- 3 / T (K-1 )

Figure 1.

Arrhenius plot and relative rate constants (inset) for the reaction of OH radical with NMP in the aqueous phase.

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The kinetic studies were conducted at four temperatures covering the atmospheric conditions, from 276 to 322 K. The results are presented in Figure 1. Taking into account all the data presented, one obtains the Arrhenius expression (7):

( 24.4 r 1.1)

ln(k OH )

(760 r 320) T

(7)

The results show that the aqueous phase OH oxidation of NMP is fast compared to that of other WSOC, and that temperature has little effect on the kinetics. Assuming that 15% of air contains clouds, and that [OHg] = 106 molec/cm3, [OHaq] = 10-13 M, the presence of clouds can reduce the atmospheric lifetime of NMP by 13 %, from 13 h to 11 h (for the estimation of global atmospheric lifetimes, see Monod et al. (2005). Thus, the aqueous phase OH oxidation has an important impact on the atmospheric behaviour of NMP. Because the kinetics of the reaction is fast, special attention has to be paid to the reaction products formed. Reaction products studies

To study the reaction products the OH oxidation of NMP in the aqueous phase, the continuous photolysis of H2O2 was used to produce OH radicals (reaction 8). H2 O2

+

hX

2 OH

(8)

The Fenton reaction (1) was not used here to avoid any artefacts due to reactions of FeII with any organic acids formed. The reaction took place in an aqueous-phase simulation chamber, which consisted of a 450 mL Pyrex vessel. Unbuffered aqueous solutions were continuously stirred and maintained at 298 r 0.2 K. The light source was a 300 W xenon arc lamp (see Monod, et al. (2005) for further details on the apparatus). The initial concentrations of NMP and H2O2 were 5×10-4 and 1×10-3 mol L-1, respectively. During the reaction, aliquots of the solution were sampled at regular time intervals with an automatic sampler, and stored at 0 °C for further analysis. HPLC analysis

The formation of N-methylsuccinimide (NMS), succinimide and 2-pyrrolidone (2P) (Table 1) was expected by Campbell and Striebig (1999) and Friesen et al. (1999) who performed OH-oxidation of NMP in alkaline solutions and by photocatalysis, respectively. We performed the HPLC analysis using the same C18 column as described above, and a UV detection at 202 nm. A binary eluent (80 %/20 % acetonitrile/water) was used at 1 mL min-1. The results showed that some of the expected reaction products were formed. Figure 2a shows the time profiles of NMP, NMS and succinimide, while Figure 2b shows the corresponding plots of product concentrations versus the concentration of NMP consumed. The latter plots clearly show that NMS was a primary reaction product, whereas succinimide was a secondary one. The carbon balance of NMS production is 55 ± 1 %. This indicates that other primary reaction products have to be formed. Figure 2 shows that one unidentified compound was a primary product. Furthermore, the HPLC chromatograms contained a lot of unidentified and unresolved peaks (Figure 3). Therefore, an on-line mass spectrometer was designed in order to identify more reaction products.


5x10

-4

4x10

-4

3x10

-4

2x10

-4

1x10

-4

0 0 NMP

10000

20000

30000

40000

time (seconds) 2P Succinimide

NMS

50000

2x10

6

2x10

6

1x10

6

5x10

5

0 60000

unidentified compound

[NMS] and [Succinimide] (mol/L)

Fig 2 b

2x10

-4

2x10

-4

1x10

-4

5x10

-5

0 0

1x10 NMS

Figure 2.

-4

2x10

6

2x10

6

1x10

6

5x10

5

unidentified compound (peak areas)

concentration (mol/L)

Fig 2 a

unidentified compound (peak areas)

87

0 -4 -4 -4 -4 2x10 3x10 4x10 5x10 ' [NMP] (mol/L) succinimide unidentified compound

HPLC analysis: (a) time profiles of NMP, two identified reaction products, (NMS and succinimid) and one unidentified reaction product, during the OHoxidation of NMP in the aqueous phase; (b) concentrations of the products (or HPLC signal in arbitrary units, a. u.) as functions of the consumed NMP.

L. Poulain et al.

88

Figure 3.

Example of an HPLC chromatogram during the OH-oxidation of NMP in the aqueous phase at t = 5 h 46 min (20778 seconds).

Design of an on-line mass spectrometer To perform in situ analysis of the solution during the course of the reaction, the simulation chamber was directly connected to a mass spectrometer (MS). The solution was transported to the MS by an HPLC pump. The MS was equipped with an electrospray ionisation (ESI) unit and a triple quadrupole, thus allowing ESI-MS+, ESI-MS-, and ESI-MSMS+ analyses to be performed. The HPLC pump flow was adjusted to 0.1 mL min-1 in order to get a good compromise between maximum analytical sensitivity and minimum volume sampled from the simulation chamber. A 9 minutes delay between sampling from the chamber and the MS analysis was taken into account in the evaluation of results. Over 20 hours of a reaction run, the mass spectrometer was operated continuously, in 48 cycles. Each cycle was 25 minutes long and contained 3 successive modes: ESI-MS+, ESI-MS-MS+ and ESI-MS(Figure 4), in order to identify the time profiles of as many compounds as possible. Each mode was operated with a scan range of 20 – 1000 atomic mass units (amu). The stabilisation times mentioned in Figure 4 were taken into account in the analysis of results. t = 6 min

t=0

ESI-MS positive mode

t = 14 min

ESI-MS-MS positive mode

Argon pressure stabilisation in quadrupole 2

t = 25 min

ESI-MS negative mode

Pressure stabilisation in quadrupole 2

Figure 4. A 25 minute operation cycle of the mass spectrometer directly connected to the simulation chamber during the OH oxidation of NMP in the aqueous phase. The cycle was repeated 48 times, to cover the 20 hours of a reaction run.


89

Results. The experimental protocol allowed us to obtain, for the first time (to our knowledge), the time profiles of a large number of reaction products (around 66 species). The ESI-MS+ scans revealed around 40 products formed, and the ESI-MS- scans around 26 products. Figure 5a (full scale) shows the decrease of the NMP concentration during the reaction, at m/z = 100 amu in the positive mode (henceforward noted as 100+ amu), while Figures 5a (zoom) and 5b (full scale and zoom) show the formation of several oxidation products. Some of the products were formed initially and then destroyed, certainly due to their reaction with OH radicals (for example m/z = 86+, 114+, 130+ and 115-). Up to 300 amu, in both modes, one can observe the formation of compounds those masses are regularly spaced by 'm/z) = 14 to 18 amu (Figure 5a and 5b). This can be the consequence of the increasing oxidation level of the NMP ring, and/or the consequence of the formation of hydrated reaction products. Although the scan was performed up to 1000 amu, no signal was observed above 300 amu. Excellent reproducibility of the mass spectra was observed in three experiments. Discussions on the mass spectra. The identification of the products was performed by comparison with standard solutions (when available) and using ESI-MS+, ESI-MS-, and/or ESI-MS-MS+ scans. The results are shown in Tables 1 and 2. NMP was detected at 100+ amu. Interestingly, its dimer was detected simultaneously at 200 amu. Tests with standard solutions of NMP showed that the dimer was formed in the electrospray unit of the mass spectrometer, and the time-profile of the MS signal at 200+ amu seems to confirm that this dimer was not formed in the photoreactor (Figures 5a and 6). +

The time-profile of the MS signal at 100+ amu (Figure 6) is different from the NMP signal obtained by HPLC (Figure 2). The HPLC shows an exponential decrease in NMP, whereas the MS signal at 100+ amu shows a significant shoulder between 8000 and 22000 seconds, which is also observed in ESI-MS-MS+ scans at 58 amu. The shoulder can be explained by formation of a product of the same mass as NMP. Succinimide produced during the reaction was identified at 100+ amu, and the ESI-MS-MS+ scans of standard solutions revealed the same daughter ions as for NMP, at 58 and 72 (major) amu (Table 1). Fortunately, tests with standard solutions of succinimide showed that this compound and its hydrate can be detected in ESI-MS- scans at m/z = 97- and m/z = 115- (Table 2), and thus can be distinguished from NMP (Figure 6). In the HPLC analysis, N-methylsuccinimide (NMS) was identified as one of the main primary reaction products (Figure 2). Tests with standard solutions showed that NMS is detected in ESI-MS+ scans at m/z = 114+, and its hydrated form is detected in ESI-MS- scans at m/z = 130-. However, an excessive carbon balance (§ 120 %) was obtained with the MS analysis at m/z = 130- (calibrated with standard solutions of NMS), in disagreement with the 55 ± 1 % obtained by HPLC. This can be due to the formation of another product of equal mass. 1-Formyl-2-pyrrolidone (FP) has exactly the same mass as NMS, and was previously identified as an important primary reaction product during the OH oxidation of NMP in the gas phase (Aschmann and Atkinson, 1999). The ESI-MS-MS+ scans of mass 114+ during the experiments show the formation of two daughter ions: one at m/z = 86, which corresponds to NMS, as verified with standard solutions, and one at 72. FP is not available commercially, so we could not perform separate tests for this compound. However, the major fragmentation pathway of FP should include the loss of •CH2-C•(O) and/or •CH2-CH2-CH2•, by analogy with NMP, succinimide and NMS. The fragmentation pathway of FP leads to a major daughter ion at m/z = 72+, thus confirming the formation of FP during the reaction. Furthermore, FP may

90

Figure 5.

L. Poulain et al.

Full scale and zoom 3D plots of the MS signal versus mass and time during the OH-oxidation of NMP in the aqueous phase (scan range 20 to 300 amu), (a) in the positive mode, and (b, facing page) in the negative mode. See Table 1 for the identification of the observed masses.

also be responsible for the unidentified peak in HPLC (Figure 3), which signal shows that it is a primary reaction product (Figure 2). It is known that hydroxyl compounds can be formed in the aqueous phase during OH oxidation processes (Von Sonntag and Schuchmann, 1997), so this pathway was explored. At m/z = 116+ amu, Figures 5a and 6 show the formation of an important reaction product, which can be 5-hydroxy-N-methylpyrrolidone (5-HNMP) and/or Nhydroxymethylpyrrolidone (NHMP) (Table 1). The formation of both compounds was confirmed by ESI-MS-MS+ scans, with two daughter ions produced and detected at m/z = 88 (5-HNMP) and at m/z = 73 (NHMP). This is in good agreement with the major fragmentation pathways of NMP, NMS and succinimide. Furthermore, this was confirmed by tests with standard solutions of NHMP, which also allowed us to observe its hydrated form at m/z = 132- (Table 2). The formation of 2-pyrrolidone (2P) was suggested by Campbell and Striebig (1999) and Friesen et al. (1999). We observed its formation at m/z = 86+ amu (Figures 5a and 6), which was confirmed by ESI-MS-MS+ scans (Table 1). The formation of smaller compounds such as methylamine, formamide, NMF, N-methyl-4-aminobutanoic acid (in ESI-MS+ scans), and butanoic acid (in ESI-MS- scans) was also observed (Tables 1 and 2).


Figure 6.

91

Time-profiles of some ESI-MS+ and ESI-MS- scans during the OH-oxidation of NMP in the aqueous phase.

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Reaction products identified in the positive mode, and unidentified reaction products for which the MS signal was high.

Table 1.

Name

Formula

Methylamine

H3C

(M+H)+ a 32

NH2

m/z (MS-MS)+ b

O

Formamide

H2N

N-methylformamide (NMF)

46

C H O

H N

H3C

60

C H

H3 C

Acetamide

C

NH2

60

O

86

69 - 70

88

57-58

O

H

N

2-pyrrolidone (2P)

CH3

N-ethylacetamide

H2 C

H3C

H N

C

O CH3 CH3

Dimethylacetamide

H3C

N

88

C O

CH3

N

N-methylpyrrolidone (NMP)

100 58 (major) and 72 200 (NMP dimer)

O

H

Succinimide

N

O

O

100

72 (major) and 58

114

86 (major)

114

72 (major) supposed

116

88 (major) and 58

116

73

CH3

O

N-methyl succinimide (NMS)

N

O

H

O

C

1-formyl-2-pyrrolidone (FP)

N

O

CH3

5-hydroxy-N-methylpyrrolidone (5-HNMP)

HO

N

O

HO

CH2

N-hydroxymethylpyrrolidone (NHMP)

N

O

O

N-methyl-4-aminobutanoic acid

118 H3C

N H

OH CH3

N

O

O

2-hydroxy-N-methylsuccinimide

130 HO

Unidentified compound a

+

132 b

+

ESI-MS scans at (M + H); ESI-MS-MS daughter ions.

New On-line Mass Spectrometer for Identification of Reaction Products Table 2.

93

Reaction products identified in the negative mode, and unidentified reaction products for which the MS signal was high. Name

m/z (M – H + (M – H) H2O)- b

Formula

-a

H

N

O

Succinimide

97 c

O

H HO

Hydrated Succinimide

N

115 c

O

HO O

116

N-methyl-4-aminobutanoic acid H3C

N H

OH

CH3

Hydrated N-methyl succinimide (NMS)

HO

N

O

130

HO HO HO

O

C

Hydrated 1-formyl-2pyrrolidone (FP)

H

N

C

H

N

O

130

OH

or

OH

CH2(OH)

Hydrated Nhydroxymethylpyrrolidone (NHMP)

N

132

OH

OH

CH3

Hydrated 5-hydroxy-Nmethylpyrrolidone (5-HNMP)

HO

N

OH

132

OH CH3

HO

Hydrated 2-hydroxy-Nmethylsuccinimide

N

CH3

O

N

O

OH

146 OH

HO HO

or

HO

O

87

Butanoic acid OH

Unidentified compounds a

43 101 148

ESI-MS- scan at (M - H); b ESI-MS- scans of hydrated molecules at (M–H), Succinimide was identified at (M - 2H)- and its hydrate was identified at (M – 2H + H2O) after verification with standard solutions.

c

L. Poulain et al.

94 Chemical mechanisms.

Based on the results, a possible mechanism is suggested here for the OH oxidation of NMP in the aqueous phase under tropospheric conditions. The reaction probably proceeds via three different pathways (Figure 7). - Pathway (a) proceeds via hydrogen atom abstraction by the OH radical from the methyl group of NMP. This leads to the formation of an alkyl radical, which then reacts with dissolved oxygen to form a peroxy radical. By analogy with the aqueous phase behaviour of other peroxy radicals (Von Sonntag and Schuchmann, 1997), it can self-react to form a tetroxide which rapidly decomposes, leading to the formation of FP and NHMP. - Pathway (b) proceeds via hydrogen atom abstraction by OH radicals, from the CH2 group adjacent to the amine group of NMP. This leads to the formation of an alkyl radical which reacts with dissolved O2 to form another peroxy radical. This peroxy radical can also self-react to form a tetroxide, which rapidly decomposes into NMS and 5-HNMP. From the HPLC analysis a value of 55 ± 1 % can be put on the importance of this pathway. - Pathway (c) is more speculative, but it has been previously suggested by Horikoshi, et al., 2001, who investigated the OH oxidation of 2P in the aqueous phase, in the presence of TiO2. This pathway may occur for NMP under real tropospheric conditions. It proceeds via a ring-opening mechanism, leading to the formation of N-methyl-4-aminobutanoic acid. The formation of smaller molecules can be explained by the subsequent reactions of the primary products of the pathways (a), (b) or (c), which may lead to ring-opening mechanisms. CH3

N O

a

+ OH

c

b

O x

CH2

CH3

N

C

•

N

O

O

Cx

H3C

N

•

+

H2O

OH

+ O2

+ O2

C

• OO

CH3

CH2

• N

OO

O

CH2OH

CH3

N

N

FP

Figure 7.

NHMP

O

N-methyl-4aminobutanoic acid

O

N

O

O

N C

CHO

O

H3C

H N

CH3

O

NMS

HO

N O

5-HNMP

Suggested mechanism for the OH oxidation of NMP in the aqueous phase.


95

Summary and conclusions The reactivity of NMP towards OH radicals was studied in the aqueous phase, under tropospheric conditions. The kinetic results show that the OH oxidation of NMP is fast compared to that of other WSOC, and thus should induce modifications of the composition of water droplets, due to the reaction products formed. A new experimental technique was developed to study the aqueous phase OH oxidation of NMP. A mass spectrometer was coupled to an aqueous phase simulation chamber, thus providing an on-line analysis of the solution. The mass spectrometer was equipped with an electrospray ionisation (ESI) unit and a triple quadrupole, which allowed ESI-MS+, ESI-MS-, and ESI-MS-MS+ analysis. The results proved that this experimental technique is highly promising, as it allowed us to detect the formation of 66 reaction products, of which 24 were positively identified. Based on the results obtained, a chemical mechanism has been suggested for the OH oxidation of NMP in the aqueous phase. The developed equipment can be used to study other molecules and other reactions of atmospheric interest. Acknowledgements This study was funded by the European project MOST (EVK2-CT-2001-00114). The authors also thank Séverine Barale, Marie Bonnevialle, Leïla Debiesse, Claire Detruit for their kind help with the experiments and analysis by HPLC. References Aschmann S. M. and R. Atkinson; Atmospheric chemistry of 1-methyl-2-pyrrolidinone, Atmos. Environ., 33 (1999) 591-599. Atkinson R.; Atmospheric chemistry of VOCs and NOx, Atmos. Environ., 34 (2000) 2063-2101. Campbell H. L. and B. A. Striebig; Evaluation of N-Methylpyrrolidone and its oxidation products toxicity utilizing the Microtox assay, Environ. Sci. Technol., 33 (1999) 11, 1926-1930. Claeys M., W. Wang, A. C. Ion, I. Kourtchev, A. Gelencser and W. Maenhaut; Formation of secondary organic aerosols from isoprene and its gas-phase oxidation products through reaction with hydrogen peroxide, Atmos. Environ., 38 (2004) 25, 4093-4098. Ervens B., G. Feingold, S. L. Clegg and S. M. Kreidenweis; A modeling study of aqueous production of dicarboxylic acids: 2. implications for cloud microphysics., J. Geophys. Res. [Atmos.], 109 (2004) D15, D15206/15201-D15206/15212. Ervens B., S. Gligorovski and H. Herrmann; Temperature-dependent rate constants for hydroxyl radical reactions with organic compounds in aqueous phase, Phys. Chem. Chem. Phys., 5 (2003) 1811-1824. Friesen D. A., J. V. Headley and C. H. Langford; The photooxidative degradation of N-Methylpyrrolidone in the presence of Cs3PW12O40 and TiO2 colloid photocatalysts., Environ. Sci. Technol., 33 (1999) 18, 3193 3198. Gelencser A., A. Hoffer, G. Kiss, E. Tombacz, R. Kurdi and L. Bencze; In-situ Formation of Light-Absorbing Organic Matter in Cloud Water, J. Atmos. Chem., 45 (2003) 25-33. Graedel T. E. and C. J. Weschler; Chemistry within aqueous atmospheric aerosols and raindrops, Rev. Geophys. Space Phys. 19 (1981) 505-539. Herrmann H.; Kinetics of aqueous phase reactions relevant for atmospheric chemistry, Chem. Rev. 103 (2003) 4691-4716. Hine J. and P. K. Moorkerjee; Strucural effects on rate and equilibriums. XIX. Intrinsic hydrophobic character of organic compounds. Correlations in terms of structural contributions, J. Org. Chem. 40 (1975) 293 298.

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Horikoshi S., H. Hidaka and N. Serpone; Photocatalyzed degradation of polymers in aqueous semiconductor suspensions: V. Photomineralization of lactam ring-pendant polyvinylpyrrolidone at titania/water interfaces, J. Photochem. Photobiol. A: Chem. 138 (2001) 69-77. Lelieveld J. and P. J. Crutzen; Influence of cloud photochemical processes on tropospheric ozone, Nature, 343 (1990) 227-233. Monod A. and P. Carlier; Impact of clouds on the tropospheric ozone budget: Direct effect of multiphase photochemistry of soluble organic compounds, Atmos. Environ., 33 (1999) 4431-4446. Monod A., L. Poulain, S. Grubert, D. Voisin and H. Wortham; Kinetics of OH-initiated oxidation of oxigenated organic compounds in the aqueous phase: new rate constants, structure-activity relationships and atmospheric implications, Atmos. Environ. (2005) in press. Von Sonntag C. and H.-P. Schuchmann; Peroxyl radicals in aqueous solution, in: Z. Alfassi (ed.), Peroxyl radicals. John Wiley & Sons, Chichester (1997) 173-234.

Dynamic Chamber System to Measure Gaseous Compounds Emissions and Atmospheric-Biospheric Interactions Viney P. Aneja1*, Jessica Blunden1, Candis S. Claiborn2, and Hugo H. Rogers3 1

Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University , Raleigh, NC 27695-8208, U.S.A. 2 Department of Civil and Environmental Engineering, Washington State University, Pullman, Washington 99164-2910, U.S.A. 3 National Soil Dynamics Laboratory, ARS-USDA, Auburn, Alabama 36832, U.S.A.

Key Words: Dynamic chamber, Emissions, Ammonia, Nitrogen oxide, Hydrogen sulphide, Hydrogen peroxide

Abstract The dynamic flow-through chamber system has been developed in response to a need to measure emissions of nitrogen, sulphur, and carbon compounds for a variety of field applications. The cylindrical chamber system is constructed of chemically inert materials and internally lined with 5mil thick transparent fluorinated ethylene polypropylene (FEP) Teflon to reduce chemical reactions and build up of temperature inside the chamber. The chamber (diameter = 27cm, height = 42 cm, volume = 24.05 L) is designed with an open-ended bottom that can penetrate either soil or liquid to a depth of ~6-8 cm, thus creating a completely enclosed system. Carrier gas (e.g. compressed zero-grade air) is pumped at a constant flow rate (~2 to ~5 lpm), depending on the season. The air inside the chamber is well mixed by a variable-speed, motor-driven Teflon impeller (~40 to ~100 rpm). Many different laboratory and field experiments have been conducted using this dynamic chamber system. Oxides of nitrogen (NO, NO2, NOy) emissions have been measured from agricultural soils where nitrogen-rich fertilizers have been applied. Ammonia-nitrogen (NH3-N) and reduced organic sulphur compounds emissions have been measured using this same technique across a gas-liquid interface at swine waste treatment anaerobic storage lagoons, and agricultural fields. Similar chamber systems have also been deployed to measure uptake of nitrogen, sulphur, ozone, and hydrogen peroxide gases by crops and vegetation to examine atmospheric-biospheric interactions. Emissions measurements have been validated by a coupled gas-liquid transfer with chemical reaction model as well as a U.S. Environmental Protection Agency (EPA) WATER 9 model. Introduction The dynamic flow-through chamber system is a technique that has been developed and modified over the past 25 years in an effort to measure earth-atmosphere and water-atmosphere fluxes of various compounds including biogenic sulphur, oxides of nitrogen, ammonia, and methane. Determination of fluxes for these different gaseous compounds is desirable in order to permit accurate assessment of the relative roles of biogenic and anthropogenic sources in contributing to such phenomena as the atmospheric sulphate and nitrate burdens, acidity in

97 I. Barnes and K. J. Rudzinski (eds.), Environmental Simulation Chambers: Application to Atmospheric Chemical Processes, 97–109. © 2006 Springer. Printed in the Netherlands.

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precipitation due to biogenic emissions, and contribution to aerosol formation through atmospheric photochemical processes in localized areas downwind of suspect sources. Similar systems have also been utilized to measure exposure of plants to various air pollutants and to quantify the uptake of trace gases by plants (e.g., Aneja, 1976; Rogers et al., 1979; Heck et al., 1987; Claiborn and Aneja, 1993). Hill et al. (1978) initially developed this technique to measure biogenic sulphur fluxes from a salt marsh in Long Island, New York. More recently, the dynamic flow-through chamber system has also been used to measure ammonia emissions from agricultural and non-agricultural soils (Roelle and Aneja, 2002), hog waste treatment lagoons (Aneja et al., 2000, 2001a,b), and agricultural crop soils over which liquid hog waste has been applied (Roelle and Aneja, 2002), and biogenic nitric oxide emissions from various types of agricultural soils (Li et al., 1999; Roelle et al., 2001) as well as municipal wastewater treatment plant bio-solids-amended soils (Tabachow et al., 2002). Currently, a study by the North Carolina State University Air Quality research group, in coordination with the U.S. Department of Agriculture National Research Initiative, is underway to measure simultaneous emissions of nitric oxide, ammonia and hydrogen sulphide from swine waste treatment lagoons using this same technique. For measuring emissions, the chamber technique has the important advantage of association of a particular emission site and its measurable array of physical, chemical, and microbiological properties with emissions of particular compounds or their reaction products. In addition, gas residence times in the chamber are on the order of minutes so that chemical transformations between emission and analysis may be minimized. The entire chamber system is small, lightweight and easily transportable, thus making a survey of trace gas flux very convenient. Finally, the system is relatively inexpensive and laboratory requirements are low. However, it should be noted that the chamber system cannot completely simulate the ambient environment. The chamber measures over a small area (requires extrapolation) and extrapolation to large scale may be a problem. For measuring fluxes to plants, the dynamic chamber is operated as a well-mixed chamber. Ideally, then, mixing is instantaneous, conditions are uniform throughout the chamber, and exit conditions are representative of internal, well-mixed conditions, thus simplifying calculations of fluxes and mathematical treatment of non-plant surface losses (Aneja, 1976; Claiborne and Aneja, 1993). Dynamic Flow-Through Chamber for Emissions at the Air-Water/Soil Interface In the dynamic emission flux chamber method, a continuously stirred tank reactor (CSTR; Levenspiel, 1962) with an open bottom is placed over an area of interest of soil, mud, or water (Hill et al., 1978). For flux measurements at the air-water interface, a floating platform is used to hold the chamber system above water. A hole is cut in the centre of the platform in which the chamber rests, allowing the bottom of the chamber to penetrate the water surface by 3-4 cm, thus forming a seal between the water surface and the air within the chamber and thereby providing a completely enclosed system in which to measure gaseous fluxes. Figure 1 depicts a schematic of a typical dynamic flow-through chamber system used to measure gaseous emissions from a swine waste treatment lagoon. For soil measurements, the chamber is placed onto a stainless steel ring

Dynamic Chamber System to Measure Gaseous Compounds Emissions

99

which is then inserted into the soil. Flux measurements are taken ~1 hour after the insertion of the ring into the soil to ensure steady-state conditions have been reached within the chamber. Over the years construction of the dynamic chamber has been modified. For studies conducted recently, the chamber is generally constructed as follows. The dynamic flow-through chamber system is cylindrical in nature and built from Plexiglas material. Chamber dimensions may vary but are generally about 23 cm inner diameter (i.d.) and 46 cm. in height. The entire closed system is lined on the inside with 2 mil fluorinated ethylene propylene (FEP) Teflon and stainless steel fittings in order to minimize chemical reactions with sample flow.

Meteorological Tower

Zero Air (no NHx , NOx, or Sx)

Mobile Laboratory

Continuous Duty Motor

Vent Line

Mass Flow Controller

23 cm

Outflow Impeller Stirrer

Inflow

46 cm Floating Platform

pH Probe Lagoon

Temperature Probe #1 Temperature Probe #2

Figure 1.

Schematic of dynamic flow-through chamber system configured to measure emissions from a swine waste treatment lagoon.

A sweep gas such as compressed zero-grade air is passed through a Teflon FEP sample line into the chamber. The in-flowing air is monitored by a mass flow controller and subsequently delivered into the chamber. The air inside the chamber is ideally well-mixed by a variable-speed motor-driven Teflon impeller stirrer (speeds generally range from ~40-100 rpm). The dynamic chamber system, with the continuous stirring provided by the impeller, meets the necessary criteria for performance as a continuously stirred tank reactor (CSTR). For performance as a CSTR, the chamber needs to be “ideally” mixed (Aneja, 1976). In ideal mixing, the composition of any elemental volume within the chamber is assumed to be the same as that of any other volume within the chamber. Tracer experiments (residence time distribution) have been used to test the flow and mixing characteristics of the system. The results of these mixing studies

V. P. Aneja et al

100

indicated that the dynamic chamber behaved as a “perfect” mixer with negligible stagnancy or channelling (Aneja et al., 2000). Johansson and Granat (1984) conducted research on pressure differences between the outside atmosphere and air within a chamber using a tilted water manometer, which indicated that pressure differences were below detectable limits (0.2 mm H2O). Arkinson (2003) conducted research on temperature difference between the outside atmosphere and air within the chamber. The results indicate that temperature differences are d 0.4°C. The out-flowing gas also flows through a Teflon FEP sample line and is directed into a temperature controlled mobile laboratory, which houses the analytical instruments and data acquisition system. Here, the sample is analyzed continuously for content of the gas of interest. A vent line is fitted to the exiting sample line to prevent pressurization and was periodically bubble tested to check for under pressurization and/or leaks in the enclosed system. Sample lines do not exceed 10 meters. Flux Calculations The following mass balance equation may be used for the dynamic flow-through chamber system and applied to any target gaseous substance of known concentration: dC dt where

§ LAw q · § q[Cair ] JA · ¸R ¨ ¸ C ¨ V ¹ V¹ © V © V

C

concentration of gas inside the chamber (ppbV)

Cair

concentration of gas in carrier air (ppbV)

q

flow rate of compressed air through the chamber (lpm)

V

volume of the chamber (L)

A

emission surface area covered by chamber (m2)

Aw

inner surface area of the chamber of inner and upper wall

(1)

surfaces (m2) L

total loss of gas in the chamber per unit area (m min-1) due to reaction with inner and upper walls of the chamber

h

internal height of the chamber (cm)

J

emission flux per unit area (µg [gas] m-2 s-1)

R

gas phase reactions inside the chamber

Since zero-grade air is used as the carrier gas, Cair is equal to zero and gas phase reactions, R, are also assumed to be zero. Since the air inside the chamber is assumed to be well mixed by


101

the impeller stirrer, C is assumed to be constant within the chamber. At steady-state conditions, § dC · the change of concentration with respect to time ¨ ¸ is expected to be zero. Therefore equation © dt ¹ (1) can be simplified as:

J h

§ LAw q · Ceq¨ ¸ V¹ © V

(2)

The loss term, L, is determined experimentally while equilibrium-state gas concentration (Ceq), flow rate (q) and chamber dimensions (V and h) are all measured. Kaplan et al. (1988) has ª Ceq C (t ) º devised a method for calculating loss term by calculating the slope of the plot of ln « » ¬ Ceq Co ¼ versus time (t). For this experiment, Co is the initial equilibrium state gaseous concentration measured by the chamber system at a constant flow rate (lpm). Ceq is the measured gaseous concentration at a second equilibrium state at an increased or reduced flow rate (lpm) into the chamber system. C(t) depicts the gaseous concentration at any time, t, during the transition between the first and second equilibrium states. L is determined by:

L

q ·§ V · § ¨ slope ¸¨ ¸ V ¹© Aw ¹ ©

(3)

Dynamic Flow-Through Chamber for Measuring Trace Gas Uptake by Plants For measuring uptake of gaseous species by plants, and for conducting exposure experiments, it is important to characterize the conditions very near the plant surface under study; thus, assuring well-mixed conditions for such experiments becomes very important. Claiborn and Aneja (1993) constructed a chamber with a 1:1 diameter to height ratio, which is ideal for wellmixed conditions (Uhl and Gray, 1966). The chamber is constructed of a Teflon-coated strap iron frame lined internally with a 5 mil thick Teflon film to allow for maximum light, and even light and temperature distribution. Mixing is provided by a Teflon-coated impeller mounted at the top of the frame, and aided by 3 Teflon-coated baffles. The entire system operates under slight negative pressure, and it is important to assure that there are no leaks into the system, to allow for proper determination of the air flow rate through the system and the initial concentration of the trace gas of interest. The air flow rate through the chamber provides one to two chamber exchange rates per minute. Sample ports are located on the inlet and outlet Teflon pipes. Separate sample manifolds are provided for CO2/water vapour and the trace gas of interest. Air samples from the chamber inlet and outlet are alternated automatically to the analyzers so that concentration differences across the chamber are determined using the same analyzer. In order to determine trace gas uptake, wall losses to the empty chamber surfaces must first be determined. The fraction of the trace gas introduced into the chamber that is lost to the chamber walls during the chamber loss experiment (CL) is determined:

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CL

C Ao ,empty C A,empty C Ao ,empty

(4)

where CA and CAo are the outlet and inlet concentrations, respectively, of trace gas species A, and the subscript empty indicates the concentrations measured for the empty chamber experiment. Total losses (i.e., to both plant surfaces and chamber surfaces) are then measured, and the fractional loss (TL) of the trace gas entering the chamber is similarly determined:

TL

C Ao ,exp C A,exp

(5)

C Ao ,exp

where CA and CAo are, again, the outlet and inlet concentrations, respectively, of trace gas species A, and the subscript exp indicates the concentrations measured for the exposure chamber experiment. Treatment of Wall Losses For trace gases that are not very reactive, it is sufficient to subtract the wall losses from the empty chamber experiment from the total trace gas losses from the plant uptake experiments in order to determine the losses to plant surfaces, alone. In other words, BL = TL-CL

(6)

where BL is the fractional loss of the trace gas to plant biomass surfaces, alone. For very reactive and/or water-soluble species like hydrogen peroxide or nitric acid, however, a more rigorous method of correcting for wall losses must be employed (Claiborn and Aneja, 1993). By treating both wall losses and losses to plant surfaces as two parallel reactions, the fractional loss to the plant biomass surfaces, BL, is calculated from TL and CL,

BL

TL CL 1 CL

(7)

From this equation, it is evident that for species for which the chamber losses are very low, it is acceptable to simply subtract the fractional loss to the walls (CL) from the fractional loss during the exposure chamber (TL). Finally, fluxes to plant surfaces (QA) are calculated from the fractional loss to the plant surfaces (BL), the chamber air flow rate (F), the inlet trace gas concentration, and the plant surface area (AL): QA

BL F C Ao,exp AL

(8)


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Results The graphs in Figure 2 (a,b,c,d) provide results from some field studies undertaken to measure fluxes of selected S, N, and C compounds. Figure 2a (Aneja et al., 2001c) reports the log of hourly averaged ammonia-nitrogen flux from a swine waste treatment lagoon plotted against lagoon aqueous phase surface temperature during four different seasonal measurements. The graph shows an observed exponential (r2 = 0.78) relationship between NH3 and lagoon water temperature measured over the year. Figure 2b demonstrates the effect of soil temperature on NO from an agricultural (soybean) crop soil at four different sites. Figure 2c illustrates the temperature dependence of average H2S emission fluxes from a salt marsh. The emission rate appears to increase semi-logarithmically with increasing temperature within a temperature range of ~0qC to ~40°C. Finally, Figure 2d represents isoprene (hydrocarbon) concentration plotted against temperature during warm months (April through September). Please note that concentrations (ppbV), which are treated as a surrogate for emission (since the concentration measurements are in close proximity to the source), are reported rather than flux calculations. The graph depicts the linear relationship between the logarithm of isoprene concentration and temperature using data from four sites.

a)

(c)

Figure 2 (a,b,c,d).

(b)

(d)

Emissions of NH3 (Aneja et al., 2000), NO (Aneja et al., 2001c), Isoprene (Hagerman et al., 1997), and H2S (Hill et al., 1978), respectively, versus Temperature at various locations.

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The well-mixed chamber was used to measure uptake of gaseous hydrogen peroxide by spruce saplings (coniferous species). Hydrogen peroxide is a highly reactive and water-soluble atmospheric oxidant, for which wall losses are very significant (10-35% for 1-2 air exchanges per minute) and highly variable (standard deviation of 50% for daytime experiments) (Claiborn, 1991). A linear relationship between hydrogen peroxide flux and chamber concentration was apparent for the red spruce saplings (Figure 3). Note that there is no significant difference between daytime and night time fluxes. Average deposition velocities were calculated for these experiments, and ranged from 0.08 to 0.12 cm/s, and 0.08 – 0.12 cm/s for daytime and night time values, respectively. In contrast, similar uptake experiments conducted on bean plants (broad leaf plants) resulted in deposition velocities ranging from 0.8 to 1.4 and 0.5 to 0.6 for days and nights, respectively (Claiborn, 1991). H2O2 uptake by Red Spruce saplings 25

Day Night

Flux, x 10^15 mol/cm2-s

20

15

10

5

0 0

1

2

3

4

5

6

7

Chamber concentration, ppbv

Figure 3 .

Fluxes of gaseous H2O2 to needles of red spruce saplings as measured in wellmixed chamber experiments. Diamonds denote daytime fluxes and squares denote night time fluxes (Claiborn, 1991).

Data Comparisons As with any type of experimental procedure, it is desirable to compare data acquired in field studies with controlled laboratory studies and/or related models. Various comparisons with models, as well as other measurement techniques, have been made with data collected via the dynamic flow-through chamber system. Some results are presented in the following discussion. For model comparisons with the dynamic flow-through chamber system, Aneja et al., (2001d) developed a mass transport model based on the quiescent thin film concept (Danckwerts,


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1970), which takes into account molecular diffusion and chemical reactions. Figure 4 shows seasonal variation comparison of ammonia emissions between modelling results and dynamic chamber system experiments for ammonia emissions from a swine waste treatment lagoon from a field study conducted by Aneja et al. (2000). The coupled mass transfer model simulations corroborated experimental results utilizing the dynamic chamber technique and validated the application to the flux equation. Also, Figure 5 shows how closely the recently developed WATER9 model, based on a set of air emission models that are documented in Air Emissions Models for Waste and Wastewater, U.S. Environmental Protection Agency, (U.S. EPA, 1994), compare with the same set of ammonia emissions data as discussed with the mass transport model previously. Tabachow et al. (2002) conducted and compared the results of nitric oxide (NO) emissions measurements for both in situ field and laboratory experiments from unamended and municipal wastewater treatment plant biosolids-amended soil. Based on matching soil temperatures (within 5ºC) and water filled pore space (WFPS) (± 5%), the ratio of volumetric soil water to total porosity of the soil, five of six scenarios showed no statistically significant difference in the NO flux measurements from the laboratory versus the field studies.

Figure 4 .

Seasonal variation comparison of ammonia emissions between modelling results and dynamic chamber system experiments.

Nitric oxide emissions from soils on a soybean field, measured by the dynamic chamber system (Li et al., 1999), were compared in Figure 6 with NO fluxes calculated at a 5 meter height utilizing the eddy-correlation method (Gao et al., 1996). In spite of differences in flux magnitudes (note the different scales used), the two show qualitatively similar variations and structure with time. The values of NO soil emissions are greater than the NO fluxes at 5 m, which implies that

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some of the NO might have been converted to nitrogen dioxide (NO2) through reactions with ozone and peroxy radicals by the time it reaches the 5-m height level from the source. In a coordinated research effort (Project NOVA), NO emissions were measured from fine sandy loam soil in a corn field using two different (dynamic and static) chamber techniques. One group from North Carolina State University used the dynamic chamber method while a group from NASA Langley Research Center used a closed box flux technique (static chamber), in which NO fluxes were calculated using the mixing ratio of NO (ppbv) versus time. (Anderson and Levine, 1987). Figure 7 depicts a difference plot of the composite averaged fluxes calculated by the dynamic chamber technique and the static chamber technique. Upon, statistical analysis, it was shown that there was no statistically significant difference between NO flux as measured using the two different chamber methods. Chamber experiments on uptake by plants provide useful information for the determination of deposition velocities, however, the deposition velocities over forest canopies will be different to those calculated in the chamber experiments. Deposition velocities take into account not only the resistance to mass transfer due to the plant itself, but also the resistance due to the forest canopy structure, and the turbulence over the canopy.

U.S. EPA WATER9 Model Ammonia Flux Measurements

Figure 5 .

Ammonia flux versus lagoon temperature comparison between WATER9 modelling results and dynamic chamber experimental calculated results.


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Figure 6 .

Inter-comparison of NO fluxes at 5 meter height using eddy-correlation technique with NO soil emissions using dynamic chamber technique.

Figure 7.

Difference of NO flux between two chamber techniques (dynamic chamber flux – static chamber flux) versus time of day. Vertical lines indicate one standard deviation of the NO flux measurements made from both chamber techniques.

Conclusions The dynamic flow-through chamber system has been successfully developed in response to a need to measure emissions of nitrogen, sulphur, and carbon compounds for a variety of field applications. Moreover, similar chamber systems have also been deployed to measure uptake of nitrogen, sulphur, ozone, and hydrogen peroxide gases by crops and vegetation to examine

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atmospheric-biospheric interactions. Experimental results have been effectively validated by independent flux models. Acknowledgements Funding of this research project was provided by the U.S. Department of Agriculture (USDA) as a part of the National Research Initiative (NRI) under Contract No. 2003-05360. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. References Anderson, I.C. and J.S. Levine, Simultaneous field measurements of biogenic emissions of nitric oxide and nitrous oxide, J. Geophys. Res., 92, 965-976, 1987. Aneja, V.P., Dynamic Studies of Ammonia Uptake by selected Plant Species Under Flow Reactor conditions, Ph.D. Thesis, North Carolina State University, Raleigh, N.C., pp. 216, 1976. Aneja, V.P., G.C. Murray, and J. Southerland, Atmospheric nitrogen compounds: Emissions, transport, deposition, and assessment, EM, April 22-25, 1998. Aneja, V.P., J.P. Chauhan, and J.T. Walker, Characterization of atmospheric ammonia emissions from swine waste storage and treatment lagoons, J. Geophys. Res., 105, No. D9, 11535-11545, 2000. Aneja, V.P., B. Bunton, J.T. Walker, and B.P. Malik, Measurement and analysis of atmospheric ammonia emissions from anaerobic lagoons, Atmos. Environ., 35, 1949-1958, 2001a. Aneja, V.P., P.A. Roelle, G.C. Murray, J. Southerland, J.W. Erisman, D. Fowler, W.A.H. Asman, and N. Patni, Atmopheric nitrogen compounds II: emissions, transport, transformation, deposition, and assessment. Atmos. Environ., 35, 1903-1911, 2001b. Aneja, V.P., P.A. Roelle, and Y. Li, Effect of environmental variables on NO emissions from agricultural soils, Phyton (Austria), 4, 29-40, 2001c. Aneja, V.P., B.P. Malik, Q. Tong, D. Kang, and J.H. Overton, Measurement and Modelling of ammonia emissions at waste treatment lagoon-atmospheric interface, Water, Air, and Soil Pollution, 1, 177-188, 2001d. Arkinson, H.L., Measurements, Modeling, and Analysis of Ammonia Flux from Hog Waste treatment technologies, M.S. Thesis, pp.129, 2003. Claiborn, C.S., Atmospheric-Biospheric Interactions of Ambient H2O2: Climatology at Mt. Mitchell, N.C., and Transport into Needles of Red Spruce, Ph.D. Thesis, North Carolina State University, 1991. Claiborn, C. S., and V.P. Aneja. Transport and fate of reactive trace gases in red Spruce needles, part 1: Uptake of gaseous hydrogen peroxide as measured in controlled chamber flux experiments. Environmental Science and Technology 27, 2585-2592, 1993. Danckwerts, P.V., Gas-Liquid Reactions, McGraw-Hill Book Company, New York, 1970. Gao, W., M.L. Wesely, D.R. Cook, and T.J. Martian, Eddy-correlation measurements of NO, NO2 and O3 fluxes, in Proceedings of Measurement of Toxic and Related Air Pollutants, pp. 146-150, Air and Waste Manage. Assoc., Pittsburgh, PA, 1996. Hagerman, L.M., V.P. Aneja, and W.A. Lonneman, Characterization of non-methan hydrocarbons in the rural southeast United States, Atmos. Environ., 31, 4017-4038, 1997.


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Heck, W.W.,O.C. Taylor, and D.T. Tingey, Assessment of Crop Loss from Air Pollutants, Elsevier Applied Science, London, U.K. p. 552, 1987. Hill, F.B, V.P. Aneja, and R.M. Felder, Atechnique for measurement of biogenic sulfur emission fluxes, J. Environ. Sci. Health, A13(3), 199-225, 1978. Kim, D.S., V.P. Aneja, and W.P. Robarge, Characterization of nitrogen oxide fluxes from soil of a fallow field in the coastal piedmont of North Carolina, Atmos. Environ., 28, 1129-1137, 1994. Levenspiel, O., Chemical Reaction Engineering, John Wiley &Sons, New York, 1962. Li, Y., V.P. Aneja, S.P. Arya, J. Rickman, J. Brittig, P. Roelle, and D.S. Kim, Nitric oxide emissions from intensively managed agricultural soil in North Carolina, J. Geophys. Res., 104, 26,115-26,123, 1999. Roelle, P.A. and V.P. Aneja, Characterization of ammonia emissions from soils in the upper coastal plain, North Carolina, Atmos. Environ., 36, 1087-1097, 2002. Roelle, P.A., V.P. Aneja, B. Gay, C. Geron, and T. Pierce, Biogenic nitric oxide emissions from cropland soils, Atmos. Environ., 35, 115-124, 2001. Roelle, P.A., V.P. Aneja, J. O’Connor, W. Robarge, D.S. Kim, and J.S. Levine, Measurement of nitrogen oxide emissions from an agricultural soil with a dynamic chamber system, J. Geophys. Res., 104, 1609-1619, 1999. Rogers, H.H., H.E. Jeffries, and A.M. Witherspoon. Measuring air pollutant uptake by plants: nitrogen dioxide. Journal of Environmental Quality 8, 551-557, 1979. Tabachow, R.M., P.A. Roelle, J.J. Pierce, and V.P. Aneja, Soil nitric oxide emissions: lab and field measurements and comparison, Environmental Engineering Science, 19(4), 205-213, 2002. U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC, November 1994, EPA-453/R-94-080A.

Chamber Studies on the Photolysis of Aldehydes John C. Wenger Department of Chemistry and Environmental Research Institute, University College Cork, Ireland Key Words: Photolysis, Aldehydes, Photooxidation

Introduction Aldehydes are emitted directly into the atmosphere from a variety of natural and anthropogenic sources and are also formed in situ from the atmospheric degradation of volatile organic compounds (VOCs). The atmospheric fate of aldehydes is controlled by photolysis and reaction with hydroxyl (OH) or nitrate (NO3) radicals and, in the case of unsaturated compounds, reaction with ozone (Atkinson, 1994). The photolysis of aldehydes is of particular importance because it is a source of free radicals in the troposphere, and thus may significantly influence the oxidizing capacity of the lower atmosphere (Finlayson-Pitts and Pitts, 1986). Aldehydes absorb in the near ultraviolet range and typically exhibit a weak absorption band in the wavelength range 240-360 nm as a result of a symmetry forbidden n-S* transition. The minimum wavelength of sunlight that reaches the troposphere is 290 nm, which is of sufficient energy to cause photolysis of aldehydes. The importance of photolysis relative to other loss processes such as reaction with OH, NO3 or O3 can be determined by comparison of the rates of all the competing degradation pathways. If photolysis is found to be important then the products need to be identified and mechanisms constructed in order to provide a more complete picture of the photolysis process. In this paper an overview of the application of simulation chamber studies to the photolysis of aldehydes is presented and a brief review of the kinetic and mechanistic data currently available is also provided. Finally, results from some of the first studies of the photolysis of aromatic aldehydes in an outdoor simulation chamber are presented and discussed. Determination of Photolysis Rate Coefficients The photolysis of a species X follows first order kinetics; j X + hQ o Products

and is described by the photolysis rate coefficient j. The rate of removal of X by photolysis is thus; -d[X]/dt = j[X] The photolysis rate coefficient (in s-1) depends on the absorption cross-section (ı, base e in cm2 molecule-1), the quantum yield for photolysis (ĳ, in molecule photons-1) and the solar actinic flux (F, in photons cm-2 s-1), all of which are wavelength dependent; j = ı(Ȝ) ĳ(Ȝ) F(Ȝ) 111 I. Barnes and K. J. Rudzinski (eds.), Environmental Simulation Chambers: Application to Atmospheric Chemical Processes, 111–119. © 2006 Springer. Printed in the Netherlands.

(,)

J. C. Wenger

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Under atmospheric conditions where a range of wavelengths at Ȝ > 290 nm are present then the atmospheric photolysis rate coefficient is best described by the following expression; Ȝi

j

¦ ı(Ȝ)M(Ȝ) F (O )

(II)

Ȝ 290 nm

where ı(Ȝ) and ĳ(Ȝ) are averaged over the wavelength interval ǻȜ and F is summed over the same wavelength range. The sum is carried out from 290 nm to some wavelength Ȝi at which either the quantum yield or absorption cross-section becomes negligible (Finlayson-Pitts and Pitts, 1986). Calculation of j requires the values of ı and ĳ to be known. While the experimental determination of absorption cross-sections is fairly straightforward, the measurement of quantum yields is not, mainly due to the rapid secondary reactions of radicals. In fact, there is no quantum yield data available for the vast majority of aldehydes. As a result, calculations of photolysis rates are often carried out in which it is assumed that ĳ(Ȝ) = 1.0. This, of course, only produces a value for the maximum photolysis rate. In addition, because the actinic flux depends on many factors, including geographical location, time and season, photolysis rates are normally calculated for certain conditions; e.g. at noon on a cloudless day at a location 40°N on the Earth’s surface on July 1. The problems associated with calculating photolysis rates can be overcome by the experimental determination of j values in outdoor simulation chambers, such as the European Photoreactor (EUPHORE), in Valencia, Spain (Becker, 1996). The decay of an aldehyde when irradiated by natural sunlight can be measured directly by FTIR spectroscopy or gas chromatography and the j values determined from a simple first order kinetic plot in the form of equation (III); ln[X]0/[X]t = -jt

(,II)

To ensure that photolysis is the only loss process for the aldehyde experiments can be carried out in the presence of an excess concentration of a radical scavenger such as cyclohexane. In cases where the high concentration of a scavenger is undesirable, e.g. because it causes saturation in the infrared absorption spectrum, a tracer compound, such as di-n butyl ether, can be used to correct for the measured decay of the aldehyde in order to obtain the j value. Typical starting concentrations used in photolysis experiments at EUPHORE are [aldehyde] = 0.5-1.5 ppmv, [scavenger] = 10-50 ppmv or [tracer] = 0.1-02. ppmv (Wenger et al., 2004 and Magneron et al., 2002). The experimentally determined value of j is, of course, only measured under one particular set of atmospheric conditions. Since the photolysis rate depends on the intensity and spectral distribution of the sunlight it is useful to quote the photolysis rate coefficient relative to a conventional measure of solar light intensity, such as j(NO2). The value for j(aldehyde)/j(NO2) can be used to calculate the photolysis rate of the aldehyde under a range of atmospheric conditions. Information on the quantum yield for photolysis of the aldehyde by sunlight can de obtained by comparison of the experimentally determined value of j with the maximum theoretical value. The latter is calculated from solar flux intensity measurements during the experiment, known absorption cross-section data and assuming ĳ(Ȝ) = 1.0. The ratio of the

Chamber Studies on the Photolysis of Aldehydes

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measured j value to the calculated value gives the effective quantum yield, ĳeff, over the atmospheric absorption range of the aldehyde. During the last 5 years, the photolysis of over twenty aldehydes has been performed at EUPHORE. Many of these studies were performed as part of the EU-funded research project RADICAL (Moortgat, 2000). A summary of the reported j values and effective quantum yields is provided in Table 1 along with the calculated lifetimes due to photolysis (Ĳphot = 1/jexp) and reaction with OH radicals (ĲOH = 1/kOH[OH]). Table 1.

Summary of photolysis rate coefficients (jexp) measured at EUPHORE. Ĳphot (hr)

ĲOHa (hr)

(2.9 ± 2.7) × 0.06 ± 0.05 10-6

96

17

(1.1 ± 0.1) × 10-5

3.8 × 10-5

0.28 ± 0.04

29

14

Butyraldehyde

(1.0 ± 0.2) × 10-5

5.1 × 10-5

0.20 ± 0.04

29

12

i-Butyraldehyde

(3.7 ± 0.1) × 10-5

5.2 × 10-5

0.71 ± 0.02

7.5

11

n-Pentanal

(1.6 ± 0.2) × 10-5

5.4 × 10-5

0.30 ± 0.02

17

10

-5

-5

0.72 ± 0.03

7.3

12

3-Methylbutyraldehyde

(1.25 ± 0.1) × 10

-5

0.27 ± 0.01

22

12

Pivaldehyde

(1.45 ± 0.1) × 10-5 2.6 × 10-5

0.56 ± 0.05

19

10

n-Hexanal

(1.65 ± 0.3) × 10-5 5.9 × 10-5

0.28 ± 0.05

17

15

n-Nonanal

(1.15 ± 0.2) × 10-5 4.9 × 10-5

0.23 ± 0.03

24

10

Glyoxal

(1.05 ± 0.3) × 10-4 2.7 × 10-3

0.04 ± 0.01

2.6

25

Glycolaldehyde

(1.15 ± 0.3) × 10-5 8.6 × 10-6

Compound

jexp (s-1)

jmax (ĳ = 1) (s-1)

Acetaldehyde

(2.9 ± 2.7) × 10-6

Propionaldehyde

2-Methylbutyraldehyde

Methacrolein

(3.8 ± 0.1) × 10

-5

-6

< × 10

-6

5.2 × 10

4.7 × 10

ĳeff

1.32 ± 0.30

24

28

5.2 × 10

-4

< 0.004

> 144

8

-4

< 0.004

> 144

13 7.4

Acrolein

< × 10

4.3 × 10

trans-Crotonaldehyde

(1.2 ± 0.2) × 10-5

4.0 × 10-4

0.03 ± 0.01

24

Pinonaldehyde

(1.15 ± 0.1) × 10-5 8.0 × 10-5

0.14 ± 0.01

24

3.1 6

a) OH rate coefficients taken from (Atkinson, 1994), lifetime calculated assuming [OH] = 1 × 10 molecule cm-3.

The straight chain C3-C9 aldehydes all have similar photolysis rates and values for ĳeff in the range 0.20-0.30. For these compounds the atmospheric lifetimes for photolysis by sunlight are longer than the lifetimes for reaction with OH radicals. In contrast, the Įbranched aldehydes possess significantly higher values for ĳeff and their photolysis lifetimes are shorter than those for reaction with OH radicals. Interestingly, the ĳeff values for the

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unsaturated aldehydes, methacrolein, acrolein and trans-crotonaldehyde are very small, even though these compounds possess absorption spectra extending towards the visible. In many atmospheric chemistry models quantum yields are assumed to be unity, which, as shown in Table 1, is seldom the case. Thus it appears that the importance of photolysis in the degradation of the aldehydes and their contribution to radical formation in the atmosphere is often over-estimated. However, details concerning the production of radicals from the atmospheric photolysis of aldehydes are best obtained from mechanistic studies. Mechanisms for the Photolysis of Aldehydes There are a number of theoretical reaction pathways in the photolysis of aldehydes, as demonstrated below for n-hexanal (Tadiü et al., 2001); CH3CH2CH2CH2CH2CHO + hȞ ĺ ĺ ĺ ĺ ĺ ĺ

n-C5H11 + HCO (Norrish Type I) n-C5H12 + CO C4H8 + CH2=CHOH (Norrish Type II) C3H7 + CH2CH2CHO C5H10 + HCHO CH3CH2CH2CH2CH2CO + H

(1) (2) (3) (4) (5) (6)

Reactions (1) and (3) are believed to be the most important under atmospheric conditions. The Norrish Type I process results in fragmentation into free radicals, whilst the Norrish Type II process, which is common to molecules with a Ȗ-hydrogen atom, is an intramolecular rearrangement that results in no radical formation. Experiments performed at EUPHORE and in indoor photoreactors as part of the RADICAL project found that the Norris Type I process is dominant for n-butanal and smaller straight chain aldehydes, but the Norrish Type II process is the major pathway for the photolysis of n-pentanal and n-hexanal. Simulation Chamber Studies on the Photolysis of Aromatic Aldehydes Aromatic aldehydes are emitted into the atmosphere as primary pollutants from automobile exhausts and are also formed in situ from the OH radical initiated oxidation of alkyl aromatic compounds. Tolualdehydes and dimethylbenzaldehydes are produced from the gas-phase reaction of OH with xylenes and trimethylbenzenes respectively (Calvert et al., 2002). The subsequent atmospheric fate of these aromatic aldehydes is controlled by reaction with OH and NO3 radicals and photolysis by sunlight. Kinetic studies of the gas-phase reactions of the tolualdehydes and dimethlybenzaldehydes have been recently performed (Thiault et al., 2002 and Clifford, 2004) and preliminary studies of the photolysis of the tolualdehydes have also been reported (Volkamer et al., 2000 and Thiault et al., 2001). In this work the photolysis of the 3 tolualdehydes and 6 dimethylbenzaldehydes (DMBAs) were investigated during July 2003. The measured photolysis rate coefficients have been used to calculate tropospheric lifetimes and provide an assessment of the relative importance of photolysis as an atmospheric loss process for the compounds. Experiments were performed in Chamber B of the EUPHORE facility. Reactants were introduced into the chamber by gently heating a known amount of the compound in a glass impinger and flushing the vapour into the chamber via a stream of purified air. Concentrations ranging from 131 to 511 ppbv of reactant were used during different experiments. The


115

reactant was allowed to mix for approximately one hour and its rate of deposition to the walls of the chamber was measured during this period. Photolysis was then initiated by opening the protective housing and thereby exposing the chamber to sunlight. The solar actinic flux was measured over the range 290-520 nm with a spectral resolution of 1 nm FWHM using a calibrated spectroradiometer (Bentham TM300). A full spectral scan took 420-430 seconds. The duration of photolysis was typically 2-3 hours. The temperature inside the chamber increased slightly as the experiments progressed but was always within the range 296-308 K. Chemical analysis was performed throughout the experiments by in situ FTIR spectroscopy using an optical path length of 553.5 m. Infrared spectra in the range 600-4000 cm-1 were obtained using a Nicolet Magna 550 FTIR spectrometer operated at a resolution of 1 cm-1 using a broad band MCT detector and derived from the co-addition of 270 scans collected over 5 minutes. Additional chemical detection was provided by a gas chromatograph (Fisons 8160) equipped with flame ionisation and photoionisation detectors (FID and PID). The chromatograph was operated using a 30 m DB-624 fused silica capillary column (J&W Scientific, 0.32 mm i.d., 1.8 Pm film). Air was sampled from the chamber into a 3 ml sampling loop and then injected onto the column. The temperature of the column was held isothermal (120º C for tolualdehydes and 150ºC for dimethylbenzaldehydes). The reactants were quantified using calibrated reference infrared spectra and gas chromatographic sensitivity factors obtained by introducing known volumes of pure materials into the chamber. The leak rate from the chamber was determined daily by adding about 20 ppbv of the unreactive tracer gas SF6 and measuring its loss by FTIR spectroscopy. The derived correction factors were applied to determine the amounts of reactants consumed and products formed. Table 2.

Experimental details for the photolysis of 2,4-DMBA at EUPHORE. Date

9th July 2003

Initial Concentration (ppbv) Irradiation time j (NO2)average (s-1) Results k(2,4-DMBA)FTIR (s-1) k(2,6-DMBA)GC-PID (s-1) kSF6 (s-1) kwall (s-1) j(2,4-DMBA)FTIR (s-1) j(2,4-DMBA)GC-PID (s-1) j(2,4-DMBA)average (s-1) j(2,4-DMBA)/j(NO2))

303 2hr 39min (7.47 ± 0.75) × 10-3 (2.14 ± 0.02) × 10-4 (2.43 ± 0.04) × 10-4 (9.19 ± 0.88) × 10-6 (2.44 ± 0.76) × 10-5 (1.90 ± 0.03) × 10-4 (2.19 ± 0.03) × 10-4 (2.05 ± 0.03) × 10-4 (2.74 ± 0.27) × 10-2

Except for j(NO2), quoted errors are twice the standard deviation arising from the least squares fit of the data. For j(NO2) the estimated error is 10%.

A total of eight experiments were performed at EUPHORE in July 2003. The experiments were conducted for at least two hours during the middle of the day. The loss of the aromatic aldehydes was monitored using FTIR spectroscopy and GC-PID. The measured decay rates of the compounds were corrected for wall loss and dilution. Concentration-time

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profiles and kinetic plots were generated for each of experiments. Data for the photolysis of one of the compounds, 2,4-dimethylbenzaldehyde (2,4-DMBA), are shown in Figures 1 and 2, with the associated experimental details listed in Table 2. Similar data were obtained for all the aromatic aldehydes. A summary of the photolysis rate coefficients obtained in the EUPHORE experiments is given in Table 3. The values quoted for j(aldehyde) are the average of the data obtained by FTIR spectroscopy and GC-PID in several experiments. The ratio j(aldehyde)/j(NO2) was also determined and can be used to calculate the photolysis rate of the aromatic aldehydes under different light conditions in the real atmosphere. The effective quantum yields obtained for o-, m- and p-tolualdehyde were determined by comparing the measured j values with the maximum theoretical values. The latter were calculated from solar flux intensity measurements during the experiments, known absorption cross-section data (Thiault et al., 2004) and assuming ĳ(Ȝ) = 1.0. There is no gas-phase absorption cross-section data available for the dimethylbenzaldehydes. However, inspection of the solution phase spectra indicates that the light absorption characteristics will be similar to those of the tolualdehydes. From the measured experimental photolysis rates of 2,3-, 2,4-, 2,5- and 2,6- DMBA it is expected that the effective quantum yields will be similar to that of o-tolualdehyde and will be close to unity. For 3,4- and 3,5DMBA, which did not photolyse at EUPHORE, it is expected that the quantum yields will be similar to m- and p-tolualdehyde, i.e. about 0.03.

350

0.008

Chamber Closed

Chamber Open

0.007

250 0.006 200

0.005

150

0.004

100

FTIR GC-PID j(NO2)

0.003 0.002

50

0.001

0 08:24

j(NO2) (s-1)

2,4-DMBA (ppbv)

300

0.009

0.000 08:52

09:21

09:50

10:19

10:48

11:16

11:45

12:14

Time of day (hh:mm)

Figure 1.

Concentration-time profile and j(NO2) during the photolysis of 2,4-DMBA at EUPHORE on 9th July 2003.

The following compounds were readily photolysed by sunlight; o-tolualdehyde, 2,3-, 2,4-, 2,5- and 2,6-DMBA. The photolysis rate coefficients are all remarkably similar, with values for j(aldehyde) in the range 2.0 – 2.7 × 10-4 s-1. For the compounds that did not undergo photolysis (m- and p-tolualdehyde, 3,4- and 3,5- DMBA), the rate of decay of the compounds is equivalent to the wall loss or dilution rate. The j values determined for these


117

compounds are therefore upper limits. The photolysis rate coefficients obtained for o-, m- and p-tolualdehyde in this study are in good agreement with those previously reported (Volkamer et al., 2000 and Thiault et al., 2001). As this is the first study on the photolysis of the DMBAs, no comparative data exists. 0

ln[2,4-DMBA]0/[2,4-DMBA]t - kwallt

-0.2 -0.4 -0.6 -0.8 -1 -1.2 -1.4 -1.6

FTIR GC-PID

-1.8 -2 0

1000

2000

3000

4000

5000

6000

7000

8000

9000

Photolysis time (s)

Figure 2.

Photolytic loss rate of 2,4-DMBA at EUPHORE on 9th July 2003.

Table 3.

Results obtained for the photolysis of the tolulaldehydes and DMBAs at EUPHORE.

Compound

o-tolualdehyde m-tolualdehyde p-tolualdehyde 2,3-DMBA 2,4-DMBA 2,5-DMBA 2,6-DMBA 3,4-DMBA 3,5-DMBA

j(aldehyde) (s-1)

j(aldehyde)/j(NO2) -4

(2.15 ± 0.06) × 10 (7.43 ± 0.60) × 10-6 (7.43 ± 0.60) × 10-6 (2.28 ± 0.20) × 10-4 (2.05 ± 0.03) × 10-4 (2.36 ± 0.09) × 10-4 (2.31 ± 0.06) × 10-4 (9.36 ± 0.20) × 10-6 (8.27 ± 0.18) × 10-6

-2

(2.66 ± 0.27) × 10 (0.09 ± 0.01) × 10-2 (0.09 ± 0.01) × 10-2 (3.02 ± 0.30) × 10-2 (2.74 ± 0.27) × 10-2 (3.52 ± 0.35) × 10-2 (3.01 ± 0.30) × 10-2 (0.11 ± 0.01) × 10-2 (0.10 ± 0.01) × 10-2

ĳeff

1.19 ± 0.04 < 0.05 < 0.03 1.0* 1.0* 1.0* 1.0* 0.03* 0.03*

* Estimated as no gas-phase data available The photolysis rate coefficients obtained in this work can be used to calculate the tropospheric lifetimes of the aromatic aldehydes with respect to photolysis. The lifetimes listed in Table 4 were calculated from the values of j(aldehyde)/j(NO2) obtained at

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118

EUPHORE and assuming a value of j(NO2) = 1 × 10-2 s-1, which is typical of the maximum photolysis rate at solar noon during summer months. The atmospheric lifetimes due to reaction with OH and NO3 are also shown for comparative purposes. For o-tolualdehyde, 2,3-, 2,4-, 2,5- and 2,6-DMBA, photolysis is clearly the dominant atmospheric loss process, whilst for the remaining aldehydes, gas-phase reaction with OH radicals is the most important degradation pathway. Lifetimes (in hours) of the aromatic aldehydes with respect to the various atmospheric loss processes.

Table 4.

Compound

WOH

WNO3

Wphotolysis

o-tolualdehyde m-tolualdehyde p-tolualdehyde 2,3-DMBA 2,4-DMBA 2,5-DMBA 2,6-DMBA 3,4-DMBA 3,5-DMBA

8.7 8.4 8.5 6.8 6.4 6.3 5.8 7.1 6.2

56.7 58.7 58.7

1.0 30.9 30.9 0.9 1.0 0.8 0.9 25.3 27.8

The OH and NO3 lifetimes were calculated from rate coefficients determined by (Clifford, 2004). No rate coefficients are available for the reaction of NO3 with the DMBAs.

The fact that photolysis only occurs for compounds in which the -CHO group is adjacent (ortho) to a methyl group suggests that some form of intramolecular interaction between these functional groups is a significant component of the photolysis mechanism. This aspect is currently being investigated further and photolysis mechanisms are in development. Acknowledgements This author would like to thank the following co-workers; G.M. Clifford, A. Mellouki, G. Le Bras, A. Munoz, M. Martín-Reviejo and K. Wirtz. This work was supported by the European Commission, through the IALSI project (Contract EVR1-CT-2001-40013), the Irish Higher Education Authority (HEA) and the French Programme National de Chimie Atmosphérique (PNCA). The CEAM Foundation is supported by the Generalitat Valenciana and BANCAIXA. References Atkinson, R; Gas-phase tropospheric chemistry of organic compounds, J. Phys. Chem. Ref. Data, Monograph 2 (1994) 1-216. Becker, K.H. (Ed.); The European Photoreactor EUPHORE, Final Report of the EC Project EV5V-CT92-0059, Wuppertal (1996). Clifford, G.M.; Atmospheric chemistry of aromatic aldehydes, PhD thesis, University College Cork (2004). Finlayson-Pitts, B.J., J.N. Pitts Jr.; Atmospheric Chemistry, John Wiley, New York (1986) Magneron, I., R. Thévenet, A. Mellouki, G. Le Bras, G.K. Moortgat and K. Wirtz; A study of the photolysis and OH-initiated oxidation of acrolein and trans-crotonaldehyde, J. Phys. Chem. A 106 (2002) 2526.


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Moortgat, G.K. (Ed.); Evaluation of radical sources in atmospheric chemistry through chamber and laboratory studies, Final Report of the EC Project ENV4-CT97-0419, Mainz (2000). Tadiü, J., I. Juraniü and G.K. Moortgat; Photoxidation of n-hexanal in air, Molecules, 6 (2001) 287-299. Thiault, G., A. Mellouki, G. Le Bras and K. Wirtz; The photolysis of aromatic aldehydes in The European Photoreactor, EUPHORE, 4th report, (2001), 29. Thiault, G., A. Mellouki , G. Le Bras; Kinetics of gas phase reactions of OH and Cl with aromatic aldehydes; Phys. Chem. Chem. Phys, 4 (2002) 2194 - 2199. Thiault, G., A. Mellouki , G. Le Bras,A. Chakir, N. Sokolowski-Gomez, D. Daumont; UV-absorption cross sections of benzaldehyde, ortho-, meta-, and para-tolualdehyde, J. Photochem. Photobiol. A: Chem. 162 (2004) 273. Volkamer, R., U. Platt and K. Wirtz; OH reaction rate constants and photolysis frequencies of a series of aromatic aldehydes and phenols in The European Photoreactor, EUPHORE, 3rd report, (2000) 1. Wenger, J.C., S. Le Calvé, H.W. Sidebottom, K. Wirtz, M. Martín-Reviejo and J.A. Franklin; Photolysis of chloral under atmospheric conditions, Environ. Sci. Technol. 38 (2004) 831-837.

Determination of Photolysis Frequencies for Selected Carbonyl Compounds in the EUPHORE Chamber Romeo-Iulian Olariu1, Marius Duncianu1, Cecilia Arsene1, and Klaus Wirtz2 1

2

“Al.I. Cuza” University of Iasi, Faculty of Chemistry, Analytical Chemistry Department, 700506 Iasi, Romania. Centro de Estudios Ambientales del Mediterráneo, Parque Tecnológico, C.\ Charles R. Darwin 14, 46980 Paterna, Valencia, Spain Key Words: Photolysis, Actinic flux, Spectroradiometer, Carbonyl compounds

Introduction Small carbonyl compounds are formed during the photochemical oxidation of many volatile organic compounds (VOC’s), in urban as well as in rural areas. Photolysis and reaction with the OH radical are the most important initiation reactions for the atmospheric degradation of these compounds, and lead to the formation of peroxy radicals in the former case and either stable molecules and/or free radicals in the latter case (Finlayson-Pitts and Pitts, 1999). About 580 actinic flux spectra recorded under different meteorological conditions (clear sky, partially cloudy or overcast) in the EUPHORE smog chambers, have been used to calculate the photolysis frequencies for various small carbonyl compounds that are considered to be important from the atmospheric chemistry point of view. The results are presented here. Experimental a) Actinic Flux measurement (F) The actinic flux spectra were recorded under realistic atmospheric conditions in the large scale outdoor EUropean PHOtoREactor (EUPHORE). The EUPHORE chamber is made from PTFE-Teflon foil. It is half spherical in shape with a volume of about 204 m3 and is mounted on aluminium floor panels. The PTFE-Teflon foil is highly transparent even to short wavelength radiation, with transmissions ranging from 85% in the range 500 - 320 nm to > 75% at 290 nm. A detailed description of the experimental set-up is available elsewhere (Becker, 1996). The light intensity was measured using a calibrated spectroradiometer (Bentham DM300). Both direct and reflected beams of the incident light are optically coupled and pass simultaneously but geometrically separated through a double monochromator. The entire set of actinic flux spectra have been recorded in the range of 290 nm to 520 nm. The spectra were recorded every 5 min with a spectral resolution of 1 nm in the range from 290 nm to 360 nm and 5 nm between 360 to 520 nm. The actinic flux spectra were recorded during an entire year, i.e. under different meteorological conditions, clear sky, scattered clouds or overcast etc. b) Photolysis frequencies calculation (Jx) In practice, rather than integrating over the wavelength spectrum to obtain the total rate of photolysis, the sum of product V(O) × I(O) × F(O) over discrete wavelength intervals 'Oҏwas used. The choice of the width of these intervals was usually based on the intervals for which F(O) was measured. Thus, the total photolysis rate was calculated using the equation:


122

R.-I. Olariu et al.

J

Oi

¦O

290

V (O ) u I O u F (O)

(E1)

where V (O ) and I (O ) are the values averaged over a wavelength interval 'O centred at O, and F(O) is actinic flux in photons cm-2 s-1 summed over the wavelength interval'Ocentred at O The numerical sum over the relevant wavelength range in eq. E1 has been performed using a home-produced MS-DOS program. The program contains a data base for the computation of 43 photo-dissociation reactions of 40 different trace gases of atmospheric relevance. For the present study the measured EUPHORE radiation spectra together with published molecular data (Moortgat, 2000) were used for the calculation of the photolysis frequencies of 17 carbonyl compounds.

c ) Calculation of solar zenith angle (T) The solar zenith angle can be calculated in the following manner for any particular location (i.e. latitude and longitude), day of the year and time of the day (Finlayson-Pitts and Pitts, 1999). There are two steps that need to be considered. First, the “local hour angle” (th), which is defined as the angle between the meridian of the observer and that of the sun, in radians, has to be calculated:

th = S[(GMT/12)-1 + (longitude/180)] + EQT

(E2)

where GMT is Greenwich mean time converted from the local time, longitude (in degree, west of the Greenwich meridian are negative) and EQT is the “equation time”, given by: -5

-3

EQT = 7.5 ×10 + 1.868 ×10 cos N -2

–3.2077 ×10 sin N -2

–1.4615 ×10 sin 2N - 4.0849 ×10 -2sin 3N

(E3)

where N (in radian) is defined as:

N= 2Sdn/365

(E4)

The day of the year, dn, is defined as the day number (0 - 364), with 0 corresponding to January 1 and 364 to December 31. The second parameter that is needed for the calculation of the solar zenith angle at a particular time and place is the solar declination, G, defined as the angle between the direction of the sun and the equatorial plain of the earth. The value of G (in radian) can be calculated as follows: -3

G = 6.918 ×10 -0.399912cos N + 0.070257 sin N – -3

-4

- 6.758 ×10 cos 2N + 9.07 ×10 sin 2N -3

-3

–2.697 ×10 cos 3N + 1.480 ×10 sin 3N

(E5)

Determination of Photolysis Frequencies for Selected Carbonyl Compounds

123

with these two parameters the solar zenith angle for any particular time and place can be easily calculated: cos T = sinG ×sin(latitude) + cos G×cos(latitude) ×cos th

(E6)

where Gand th are calculated as already described and latitudes north of the equator (in radian) are positive and south are negative. If all of the input parameters are in radians, T is also obtained in radians and can be converted to degree using 1 rad = 57.2960. For example, at Valencia, Spain, (longitude: 0.50 W, latitude: 39.50 N) on September 1 at noon local time, GMT = 11.0, dn= 243, N = 4.183, EQT = - 0.0016, th = -0.2721 rad, G = 0.149 rad, and cosT = 0.829, giving a solar zenith 0 angle of 0.592 rad, or 33.92 Consequently, the actinic flux data recorded in the EUPHORE chamber during one year will provide useful and complementary data over the range of the zenith angle values pertinent to this local area. Results and discussion The actinic flux spectra were used to calculate the spectral photolysis frequency distributions taking into account the molecular parameters (V(O) x I(O)), which after wavelength integration yield the respective J values. Figure 1 shows typical actinic flux profiles recorded in the EUPHORE chamber at various times of the year. The spectral data have been used to obtain atmospheric photo-dissociation frequencies for several carbonyl compounds. For all the investigated compounds (see Table 1) plots of the calculated photolysis frequencies versus solar zenith angle show a cloud-type distribution of data points. Figure 2 shows an example for acetaldehyde. The strong scattering and lack of a clear linear dependency has probably several causes one of which is likely the variation in the degree of cloudiness over the EUPHORE chamber. Since the photolysis frequency is directly coupled with the solar zenith angle one major objective of the present study was the realization of a relative dependency between the calculated photolysis frequencies and solar zenith angle. To obtain a clear dependency a statistical treatment of all the calculated photolysis frequencies, derived from all the actinic spectra recorded in the EUPHORE chamber has been performed. Figure 3 shows an example of the complete dataset for acetaldehyde. The statistical treatment has allowed a clear dependency between the calculated photolysis frequency and the solar zenith angle to be established. The result obtained for acetaldehyde statistical treatment after is presented graphically in Figure 4. The error bars represent the statistical (1V) error only. Photolysis frequencies have been calculated in the range of 19º to 71.5º solar zenith angles for 17 carbonyl compounds. The calculated photolysis frequencies obtained for the different zenith angles as derived from all the EUPHORE actinic flux spectra measurements are presented in Table 1. Using the data obtained in the present work a simple analytical expression has been derived for Jx(T) which captures more than 75% of all the measurements up to a 71.50 solar zenith angle with an error band of 14%. The general analytical expression obtained is as follows: Jx(T) = [m u exp(-n u sec(T)] s-1 2

E7

The empirical parameters m, n and r obtained from fits of the calculated photolysis frequencies as a function of solar zenith angle are listed in Table 2.

124

R.-I. Olariu et al.

Figure 1.

Actinic flux profiles recorded in the EUPHORE chamber for a 400 zenith angle at the following dates and times: a) on 24.03.2003 at 13:56 h; b) on 20.06.2002 at 16:00 h; c) on 20.03.2001 at 13:09 h; d) 20.03.2002 at 12:55 h.

Figure 2.

Plot of the calculated photolysis frequencies of acetaldehyde from the entire data set against solar zenith angle.


Figure 3.

125

Calculated photolysis frequency profile for one year derived from data recorded using the EUPHORE outdoor chamber.

Photolysis frequenciey of acetaldehyde (s-1)

4.0e-5

3.0e-5

2.0e-5

1.0e-5

0.0 0

Figure 4.

10

20

30 40 50 60 Solar zenith angle (degree)

70

80

90

Plot of the calculated photolysis frequencies of acetaldehyde (obtained after statistical treatment) versus solar zenith angle.

R.-I. Olariu et al.

126 Table 1.

-1

Calculated photolysis frequencies for carbonyl compounds (in s ) at different zenith angles derived from the EUPHORE chamber measurements.

Compound

exp

acetaldehyde CH3CH2CHO n-Butyraldehyde i-Butyraldehyde 3-Methybutyraldehyde Pentanal Pinonalddehyde Pivalaldehyde Glyoxal Glycolaldehyde Acrolein Methacrolein Crotonaldehyde Caronaldehyde 2-Petanone MVK Pyruvic_acid

10 10-5 -5 10 -5 10 -5 10 10-5 10-5 -5 10 -3 10 -6 10 -4 10 -4 10 -4 10 10-5 10-5 -4 10 -4 10

-5

Table 2.

19.10 3.35±0.51 3.76 ±0.58 4.93±0.75 4.98±0.76 4.37±0.68 5.06±0.77 6.70±1.05 2.76±0.43 2.82±0.86 8.27±0.13 4.65±0.73 4.59±0.70 4.40±0.68 3.53±0.57 1.28±0.20 4.55±0.70 2.86±0.45

zenith angle (degree) 32.03 51.83 2.96±0.41 2.09±0.24 3.32±0.46 2.34±0.27 4.31±0.61 3.10±0.36 4.35±0.62 3.12±0.36 3.90±0.57 2.78±0.35 4.44±0.63 3.20±037 5.86±0.83 4.05±0.50 2.47±0.36 1.74±0.22 2.97±0.37 2.58±0.22 7.17±0.10 4.87±0.65 4.48±0.60 3.54±0.30 4.38±0.59 3.42±0.30 4.20±0.56 3.29±0.28 3.07±0.46 2.07±0.28 1.10±0.16 0.74±0.10 4.35±0.58 3.41±0.30 2.79±0.38 2.24±0.19

71.53 0.87±0.14 0.97±0.01 1.31±0.22 1.31±0.22 1.21±0.20 1.37±023 1.62±0.26 7.41±0.12 1.45±0.39 1.87±0.31 1.82±0.32 1.73±0.30 1.67±0.29 7.88±0.12 0.28±0.04 1.73±0.30 1.17±0.21

Empirical parameters m, n and r2 from E7.

2

compound

m

n

r

acetaldehyde CH3CH2CHO n-Butyraldehyde i-Butyraldehyde 3-Methybutyraldehyde Pentanal Pinonalddehyde Pivaldehyde Glyoxal Glycolaldehyde Acrolein Methacrolein Crotonaldehyde Caronaldehyde 2-Petanone MVK Pyruvic_acid

10-4 -4 10 -4 10 -4 10 -4 10 -4 10 -4 2 x 10 -4 10 -4 9 x 10 -4 10 -4 8 x 10 -4 8 x 10 -4 7 x 10 -4 10 -4 10 -4 8 x 10 -4 5 x 10

0.7291 0.760 0.737 0.741 0.758 0.736 0.807 0.779 0.356 0.869 0.484 0.509 0.503 0.889 0.884 0.503 0.457

0.96 0.98 0.98 0.98 0.97 0.98 0.98 0.97 0.98 0.98 0.98 0.98 0.98 0.97 0.98 0.99 0.99


127

In Table 3 the mean of the all calculated photolysis frequencies for the various compounds obtained from the analysis of the actinic flux measurements performed using EUPHORE chamber facilities is compared with results from other similar studies. In the estimates a quantum yield of unity has been assumed. The errors are a combination of the statistical errors and the errors associated with uncertainties in the molecular parameters. The effective quantum yields, Ieff, in Table 3 were determined by division of the measured individual photolysis frequencies (J3) by the photolysis frequencies calculated in this study (J1) assuming a quantum yield of unity. For some of the carbonyl compounds the determined Ieff is significantly below unity. The photolytic lifetimes obtained using the present photolysis frequencies are also presented in Table 3. Table 3.

compound

Photolysis frequencies and effective quantum yield Ieff for some carbonyl compounds as derived from the EUPHORE facilities and found in the literature. exp -5

J1(X), s

-1

estimated this work

Acetaldehyde 10 2.26±0.84 -5 CH3CH2CHO 10 2.53±0.95 -5 3.34±1.23 n-Butyraldehyde 10 -5 3.37±1.25 i-Butyraldehyde 10 -5 2.97±1.19 3-Methyl-butyraldehyde 10 -5 3.44±1.27 Pentanal 10 -5 4.43±1.75 Pinonaldehyde 10 -5 1.86±0.71 Pivaldehyde 10 -3 2.54±0.47 Glyoxal 10 -6 8.52±1.58 Glycolaldehyde 10 -4 3.62±0.97 Acrolein 10 -4 Methacrolein 10 3.51±0.98 -4 Crotonaldehyde 10 3.37±0.93 -6 2-Pentanone 10 8.28±3.46 -4 MVK 10 3.49±0.97 -4 Pyruvic acid 10 2.26±0.58 a b Moortgat, 2000, Wirtz, 1999.

J2(X), s

-1

estimated literature a

4.9 a 3.8 a 5.1 a 5.2 a 4.7 a 5.4 a 8.0 a 2.6 a 2.7 a 8.6 a 4.3 a 5.2 a 4.0 b 8.6 a 5.2 a 2.3

J3(X), s

-1

Ieff

measured values a

0.29±0.27 a 1.10±0.10 a 1.00±0.20 a 3.70±0.10 a 1.25±0.10 a 1.60±0.20 a 1.15±0.10 a 1.45±0.10 a 0.10±0.03 a 11.4±2.5 a 300 nm)

Cl + Cl

Cl +CHCl2C(O)Cl

Cl(O)CCl2 +HCl

ClC(O)CCl2 + O2 + M

ClC(O)CCl2O2 + M

X2

ClC(O)CCl2O ' (C-C) ~90%

ClC(O) + Cl2C(O)

'(C-Cl) ~10%

ClC(O)C(O)Cl + Cl

Cl + CO

Figure 2.

Mechanism for the chlorine atom initiated oxidation of CHCl2C(O)Cl.

The hydroxyl radical initiated oxidations of trichloroethene (50-100 ppm) and tetrachloroethene (50-100 ppm) were investigated in air at 1 atmosphere total pressure and 298 K in the laboratory reactor. Photolysis of hydrogen peroxide (100-500 ppm) at 254 nm was used as the OH radical source. Reactions were carried out both in the absence and presence of dimethyl ether, which was used as a chlorine atom scavenger. The products found from the reactions of OH with CHCl=CCl2 and CCl2=CCl2 in the absence of CH3OCH3 show the presence of CHCl2C(O)Cl and CCl3C(O)Cl respectively, formed in the Cl atom initiated oxidation of the alkenes. Under conditions where sufficient CH3OCH3 had been added to the reaction mixtures so that the yields of acid chlorides were negligible, it was assumed that the Cl atoms generated in the OH reactions were totally scavenged. The major products detected in the OH radical initiated oxidations of CHCl=CCl2 and CCl2=CCl2 for reactions performed in the presence of sufficient CH3OCH3 to sufficiently quench the Cl atom reactions with the chloroalkenes were Cl2C(O) and CO. The yields of Cl2C(O) in both systems were approximately 70% in reasonable agreement with previously reported data (Tuazon et al., 1988). The yield of HClC(O) from the reaction of OH with CHCl=CCl2 was shown to be less than 5%. The OH radical initiated oxidations of the chloroethenes proceed by initial OH addition to the carbon-carbon double bond. All the available evidence suggests that for

L. Nolan et al.

176

unsymmetric alkenes, OH addition to the least substituted carbon atom dominates and hence reaction with CHCl=CCl2 is expected to involve the addition to the =CHCl group (Atkinson, 1994). While it is known at low pressures the hydroxyalkyl radical formed may unimolecularly decay by loss of OH, it is generally assumed that under atmospheric conditions the hydroxyalkyl formed will rapidly add O2 (Atkinson, 1994). Reaction with CHCl=CCl2 and CCl2=CCl2 can potentially lead to a complex series of reactions since the OH radical adds to a carbon atom that is bonded to a chlorine atom. The adduct radical formed by addition of OH to the alkene may eliminate a Cl atom or HCl (Figures 3 and 4).

HOCHCl-CCl2

OH + CHCl=CCl2

' (C-Cl) O / X2

HOCH=CCl2 + Cl

HC(O)CCl2 +HCl

HOCHClCCl2O ' (C-C)

CHCl2C(O)H

O / X2

HC(O)CCl2O

HOCHCl +Cl2C(O) ' (C-C)

O2

HO2 + HClC(O)

HC(O) + Cl2C(O)

' (C-Cl)

HC(O)C(O)Cl +Cl

O2

HO2 + CO

Figure 3.

Mechanism for the hydroxyl radical initiated oxidation of CHCl=CCl2.

Atmospheric Oxidation of the Chlorinated Solvents

177

HOCCl2-CCl2

OH + CCl2=CCl2

' (C-Cl) O / X2

HOCCl=CCl2 + Cl

ClC(O)CCl2 +HCl

HOCHCl2-CCl2O ' (C-C)

CHCl2C(O)Cl

O / X2

ClCC(O)CCl2O

HOCCl2 +Cl2C(O) ' (C-C)

O2

HO2 + Cl2C(O)

ClC(O) + Cl2C(O)

' (C-Cl)

ClC(O)C(O)Cl +Cl

O2

Cl + CO

Figure 4.

Mechanism for the hydroxyl radical initiated oxidation of CCl2=CCl2.

The absence of CHCl2C(O)H and CHCl2C(O)Cl from the reaction products of the OH initiated oxidation of CHCl=CCl2 and CCl2=CCl2 respectively indicates that Cl atom elimination from the OH-chloroalkene adducts is of minor importance in 1 atmosphere of air. Addition of OH radicals to CHCl=CCl2 and CCl2=CCl2 gave Cl2C(O) and CO as the major oxidation products. The relatively low yield of Cl2C(O) in the OH initiated oxidation of CCl2=CCl2 and formation of Cl2C(O) but the absence of HClC(O) in the OH initiated oxidation of CHCl=CCl2 provides evidence that elimination of HCl occurs from the initially formed energy rich adducts in these reactions. Thus, the results are consistent with the formation of HC(O)CCl2 and ClC(O)CCl2 radicals in the reactions of OH with CHCl=CCl2 and CCl2=CCl2 (Figures 3 and 4 respectively). These radicals are identical to the radicals formed by photolysis of chloral and the reaction of Cl atoms with CHCl2C(O)Cl. The absence of HClC(O) and the relatively low yield of Cl2C(O) in the CHCl=CCl2 and CCl2=CCl2 systems suggest that addition of OH to the chloroalkenes leads mainly to loss of HCl rather than addition of the adduct radicals to molecular oxygen.

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Rather interestingly further information on the mechanism for the OH radical initiated oxidation of CHCl=CCl2 comes from studies on the reactions of Cl atoms with 2,2,2trichloroethanol in the presence of O2. Reaction of Cl atoms with CCl3CH2OH involves Hatom abstraction from the –CH2- group to give the CCl3CHOH radical. Reaction of this radical with O2 is expected to yield CCl3C(O)H, Figure 5. Formyl chloride and phosgene were also identified as primary oxidation products and it is suggested that these products arise from a 1,2 chlorine atom rearrangement of CCl3CHOH to give the HOCHClCCl2 radical. Reaction of this radical with molecular oxygen followed by self reaction of the peroxy radicals will generate the ȕ–hydroxy radical HOCHClCCl2O. The initial yields of CCl3C(O)H (~0.5), Cl2C(O) (~0.4) and HClC(O) (~0.4) from reactions carried out in air at 1 atmosphere suggests that under these conditions around 50% of the alkyl radicals CCl3CHOH, formed by H-atom abstraction from the parent alcohol, react with O2 to form CCl3C(O)H while the 1,2 chlorine atom shift process accounts for the balance of the products. As expected the yield of CCl3C(O)H is oxygen dependent, increasing with the oxygen pressure. It is interesting to note that HOCHClCCl2 radicals formed by 1,2 chlorine atom rearrangement are also produced by the addition of OH to CHCl=CCl2. As discussed previously, the energised adduct radical formed by addition of OH to CHCl=CCl2 appears to eliminate HCl leading to the production of Cl2C(O) as the only stable product. However, the major reaction channel for the thermalised HOCHClCCl2O radical generated from the reaction of Cl with CCl3CH2OH appears to be carbon-carbon bond fission, and both HClC(O) and Cl2C(O) are important reaction products. The proposed reaction mechanism for the Cl atom initiated oxidation of CCl3CH2OH is shown in Figure 5. Cl + CCl3CH2OH

CCl3CHOH + HCl

O2

HO2 + CCl3C(O)H

1,2-Cl atom shift

HOCHClCCl2

O2 / X2

HOCHCl + Cl2C(O)

HOCHClCCl2O

O2

HO2 + HClC(O)

Figure 5.

Mechanism for the chlorine atom initiated oxidation of CCl3CH2OH.

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Conclusions and atmospheric implications The major reaction pathway for HC(O)CCl2O and ClC(O)Cl2O radicals, generated from the photolysis of chloral and the Cl-atom initiated of dichloroacetyl chloride respectively is decomposition via C-C bond fission to produce phosgene. These alkoxy radicals are also proposed to be intermediates in the OH radical initiated oxidation of trichloroethene and tetrachloroethene under atmospheric conditions. Thus, the major oxidation product of 1,1,1trichloroethane, trichloroethene and tetrachloroethene is Cl2C(O). Modelling study showed that tropospheric removal of Cl2C(O) is predominantly via wet decomposition with a lifetime of around 70 days (Kindler et al., 1995). Hence Cl2C(O) may provide a small flux of Cl into the stratosphere. References Atkinson R.; Gas-phase tropospheric chemistry of organic compounds, J. Phys. Chem. Ref. Data, Monograph no.2 (1994). Kindler T.P., W.L. Chameides, P.H. Wine, D.M. Cunnold, F.N. Alyea and J.A. Franklin; The fate of atmospheric phosgene and the stratospheric chlorine loadings of its parent compounds: CCl4, C2Cl4, C2HCl3, CH3CCl3 and CHCl3, J. Geophys. Res. 100 (D1) (1995) 1235-1251. Nelson L., I. Shanahan, H.W. Sidebottom, J. Treacy and O.J. Nielsen; Kinetics and mechanism for the oxidation of 1,1,1-trichloroethane, Int. J. Chem. Kinet. 22 (1990) 577-590. Platz J., O.J. Nielsen, J. Sehested and T.J. Wallington; Atmospheric chemistry of 1,1,1-trichloroethane: UV absorption spectra and self-reaction kinetics of CCl3CH2 and CCl3CH2O2 radicals, kinetics of the reactions of the CCl3CH2O2 radicals with NO and NO2 and the fate of the alkoxy radical CCl3CH2O, J. Phys. Chem. 99 (17) (1995) 6570-6579. Sidebottom H., and J. Franklin; The atmospheric fate and impact of hydrofluorocarbons and chlorinated solvents, Pure and Appl. Chem. 68 (1996) 1757-1769. Talukdar R.K., A. Mellouki, J.B. Burkholder, M.K. Gilles, G. Le Bras and A.R. Ravishankara; Quantification of the tropospheric removal of chloral (CCl3CHO): Rate coefficient for the reaction with OH, UVabsorption and quantum yields, J. Phys. Chem. 105 (2001) 5188-5196. Tuazon E.C., R. Atkinson, S.M. Aschmann, M.A. Goodman and A.M. Winer; Atmospheric reactions of chloroethenes with the OH radical, Int. J. Chem. Kinet. 20 (1988) 241-265. Wenger J., S. Le Calvé, H.W. Sidebottom, K. Wirtz, M.M. Reviejo and J.A. Franklin; Photolysis of chloral under atmospheric conditions, Environ. Sci. Technol. 38 (2004) 831-837.

Simulation Chamber Study of the Oxidation of Acetic Acid by OH Radicals: Detection of Reaction Products by CW-CRDS in the Near-Infrared Range Sabine Crunaire1,3, Christa Fittschen1, Bernard Lemoine2, Alexandre Tomas3, and Patrice Coddeville3 1

PC2A, “Physico-Chimie des Processus de Combustion et de l’Atmosph è re”, UMR CNRS 8522 2 PhLAM, “Physique des Lasers, Atomes et Molécules”, UMR CNRS 8523 Université des Sciences et Technologies de Lille 1, 59655 V illeneuve d’A scq Cedex, France 3 Département Chimie-Environnement, École des Mines de Douai, 941 Rue Charles Bourseul, 59508 Douai Cedex, France Key Words: Acetic acid, CW-CRDS, OH radicals, Smog chamber

Abstract The branching ratio for the reaction of OH radicals with CH3COOD was determined at 298 r 2 K and at atmospheric pressure using an indoor smog chamber (300 L) coupled to two different detection systems: (i) Gas Chromatograph (GC) with FTIR detection for determination of [CH3COOD], (ii) Cavity Ring Down Spectroscopy (CRDS) using a telecommunication diode laser as a source for the determination of [HDO] and [H2O]. The reaction CH3COOD + OH occurs via D-atom abstraction with an efficiency of 36 r 20 %. Introduction Although anthropogenic emissions of volatile organic compounds (VOCs) in France seem to have been decreasing for several years, the contribution from oxygenated VOCs remains constant (CITEPA, 2000). Primary emissions of this type of compounds are mainly due to their use in industry (as paints, solvents, etc.). Some are also employed in fuels as substituents for aromatic hydrocarbons. In addition, as the atmospheric oxidation of hydrocarbons generally leads to oxygenated compounds (like carbonyls), secondary emissions are also significant. Among the oxygenated compounds, carboxylic acids have become the subject of growing interest over the past two decades. Low molecular weight carboxylic acids like acetic acid have been recognized as potentially important especially in urban polluted atmospheres where concentrations can exceed 20 µg/m3 (Chebbi and Carlier, 1996). Acetic acid is produced photochemically mainly from reactions of the peroxy acetyl radical (CH3CO3) with other peroxy radicals. For example, the reaction of CH3CO3 with HO2 is known to lead to about 20% CH3C(O)OH (Tyndall et al., 2001). Acetic acid in the gas phase is also produced by reaction of ozone with various olefins like propene, butene or pentene (Atkinson and Arey, 2003). A total photochemical source strength of 120 Tg/year has been reported (Baboukas et al., 2000). The contribution of direct emissions from anthropogenic (biomass combustion, motor exhaust) and biogenic (bacteria metabolisms, emission from soil and vegetation) sources is estimated at 48 Tg/year (Chebbi and Carlier, 1996). Acetic acid is principally removed from the atmosphere by wet deposition. In the atmospheric gas phase, the main loss of CH3C(O)OH is its reaction with OH radicals. 181 I. Barnes and K. J. Rudzinski (eds.), Environmental Simulation Chambers: Application to Atmospheric Chemical Processes, 181–191. © 2006 Springer. Printed in the Netherlands.

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182 OH + CH3C(O)OH o products

(1)

The corresponding reaction rate, k1 = 7.5 x 10-13 cm3.molecule-1.s-1 at T = 298K (Singleton et al., 1989), corresponds to an atmospheric residence time (W k1[OH]) of more than a week (with typical tropospheric OH concentration of 1×106 molecule.cm-3). The photooxidation chain contributes to the production of photooxidants, so that the implications in the atmospheric HOx budget are important (Atkinson and Arey, 2003). However, models usually do not take these effects into account because too little is known about the fate of CH3C(O)OH in the atmosphere. In order to assess its tropospheric impact information on the product distribution of the reaction is needed. Two channels are expected to occur in the OH-initiated oxidation of acetic acid: OH + CH3C(O)OH o CH3 + CO2 + H2O o CH2C(O)OH + H2O

(1a) (1b)

According to Singleton et al. (1989) and Butkovskaya et al. (2004), hydrogen atom abstraction from the carboxyl group (pathway 1a) is the preferred pathway. A branching ratio of (64 r 17) % has been determined between 249 and 300 K (Butkovskaya et al., 2004). We present here the determination of the branching ratio of the products formed in the reaction of partly deuterated acetic acid with hydroxyl radicals under atmospheric conditions (298 K and 760 Torr) in a simulation smog chamber. OH + CH3C(O)OD o CH3 + CO2 + HDO o CH2C(O)OD + H2O

(2a) (2b)

The detection of CO2 was not possible at the time or writing due to a lack of an adequate light source (such studies are planned), however, the formation of HDO and H2O has been investigated. CH3COOH and CH3COOD have the same molecular structure, thus by analogy it is expected that the branching ratios will be fairly similar. The HDO (2a) and H2O (2b) formation rates were measuring by the CW-CRDS technique (Continuous Wave – Cavity Ring Down Spectroscopy). The setup was developed so that it could be coupled to the smog chamber. This is, to our knowledge, the first report of such a coupling and it will be described in detail in the next section. Experimental Section Simulation chamber (Figure 1) Experiments were performed in a Teflon-film bag of about 300 litres placed in a dark box equipped with an irradiation system and a temperature regulation device. The latter consist of 2 fans fixed at the top of the box flushing laboratory air around the bag. The irradiation system consists of 6 Philips TMX 204 LS fluorescent tubes (30 W, Omax = 254 nm) and 6 Philips TMX 200 LS tubes (18 W, Omax = 365 nm), distributed on both chamber sides. Each tube can be operated separately in order to modulate the irradiation flux. In the experiments presented below, only the fluorescent tubes at 365 nm have been used. Organic

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compounds are introduced into the smog chamber using a heated (T ~ 100°C) small glass chamber under vacuum. After vaporization, they are pressed into the bag by a flow of purified air (zero air). purified air

evacuation introduction of organic d

CW-CRDS GC-FTIR

heated glass chamber under vacuum

Teflon film bag

introduction of OH precursors

irradiation system: 6 fluorescent tubes at Omax = 254 nm and 6 tubes at Omax = 365 nm

Figure 1.

Top view of the indoor simulation chamber at the Ecole des Mines.

Chemicals For all the experiments, hydroxyl radicals were produced by the photolysis of methyl nitrite around 365 nm: CH3ONO + hQ (365 nm) o CH3O + NO CH3O + O2 o HO2 + HCHO HO2 + NO o NO2 + OH Methyl nitrite was prepared by slowly adding a dilute solution of H2SO4 to a mixture of NaNO2 and methanol according to the synthesis described by Taylor et al. (1980). Gas samples of about 20 mL of CH3ONO were injected in the chamber through a septum. Partly deuterated acetic acid CH3C(O)OD was obtained commercially (Acros Organics) with a purity higher than 98 % for the D-atom. Purified air was produced by flowing compressed air through a commercial air purification system (Claind AG 2301 HC). Experimental procedure Experiments were carried out at 298 r 2 K and at atmospheric pressure. Acetic acid was introduced in concentrations between 20 and 100 ppm and the bag was filled with purified air. Mixtures were left approximately one hour in the dark for stabilization during which time several samples were taken in order to determine accurately the initial concentration of reactant. The bag was then irradiated for one to four hours and sampling was

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performed at short and regular time intervals (between 15 and 30 minutes). After each run, the mixture was evacuated and the bag was then cleaned by filling it with purified air. This was repeated three times. Two different techniques were used to analyse the reaction mixture. The concentrations of CH3C(O)OD were determined using a GC-FTIR analytical device. The concentrations of reaction products HDO and H2O were measured by the CW-CRDS technique recently developed in our laboratory. Analysis apparatus 1: sample loop-TCT-GC-FTIR Sampling procedure and thermal desorption system (Figure 2) (a) Sample loop filling mode oven 150°C trap tube -190°C

(b) Trap mode oven trap tube

(c) Injection mode oven trap tube

150°C -190°C 30mL/min

50mL/min

150°C 280°C 30mL/min

sample loop

Teflon bag mixture

purified air

purified air

6 ports rotary valve

He

oven

liquid N2

He

He

empty glass tube "transfer line" cold trap tube filled with glass beads

vent

Figure 2.

GC 2 mL/min

30mL/min

GC 2 mL/min

GC 2 mL/min

Schematic diagrams of the device for sampling and thermal desorption.

Gas samples were taken from the bag using a 20 mL loop (4.57 mm i.d. Silcosteel tubing) and a 6-port valve (Valco). Figure 2a shows the loading position of the valve. The gas sample from the chamber is pumped through the heated (T = 100°C) sample-loop at 50 mL/min for 4 min. After switching off the pump, the 6-port valve is turned to the injection position (Figure 2b) and the 20 mL gas sample is conveyed to the cold trap of the TCT Chrompack (Thermal desorption and Cold Trap) device by the carrier gas. It should be noted

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that this system allows several fillings of the sample loop to increase the sampling volume. During the experiments, depending on the concentrations of reactants, injections of one or two loops have been carried out. The cryo-focusing with liquid nitrogen was enhanced for the more volatile compounds by filling the trap (uncoated deactivated fused silica; i.d. = 0.53 mm; length = 40 cm) with glass beads. Finally, Figure 2c shows the injection step. The trap tube was subject to a fast temperature increase (approximately 10°C/s) in order to inject the compounds into the gas chromatograph within a few seconds. GC-FTIR analysis The sample loop-TCT injection unit is coupled to a gas chromatograph (GC) Varian 3300 with detection by a FTIR spectrometer (Nicolet Magna 550) (Figure 3). The chromatographic separation was performed using a capillary column CP SIL 5 CB (50 m x 0.32 mm i.d.). The following temperature program was used for the GC oven: isothermal at 40°C for 5 min, first temperature ramped at 8°C/min to 120°C, second temperature ramped at 15°C/min to 225°C, where it was maintained for 5 min. Helium was used as the carrier gas at an initial pressure of 15 psi (40°C). The column effluent was passed through a fused silica transfer line (0.6m x 0.32mm i.d.) to the light pipe, both maintained at 240°C. The light pipe is a narrow borosilicate tube with a smooth, thin gold coating layer on the inside surface. By reflecting the IR beam through the light pipe via this coating, the path length of the cell is increased by a factor of ten or more with respect to the actual length of the tube (Ragunathan et al., 1999). The infrared beam was focused onto a fast response MCT detector cooled with liquid nitrogen.

TCT

Gas sample loop (20mL – T ~100°C)

Michelson interferometer

FID

capillary column

Teflon bag's sample

lightpipe

IR source

Principal infrared bench

Figure 3.

MCT detector

GC-FTIR interface

Transfer line

TCT-GC-FTIR analytical device.

GC

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Data acquisition was performed using compatible Omnic software (Nicolet). The Gram-Schmitt (total spectral response) chromatogram was constructed from interferograms registered at different times. Spectra were taken in real time between 650 and 4000 cm-1 at a resolution of 16 cm-1 with a scan every 2 s (average of 10 interferograms). Functional group chromatograms were extracted from the Gram-Schmitt chromatogram in the 1600-1900 cm-1 spectral region (C=O band) to carry out the quantitative analysis of acetic acid. Analysis apparatus 2: CW-CRDS Introduction Cavity Ring-Down Spectroscopy was introduced in 1988 by O'Keefe and Deacon as a spectroscopic method for absorption measurements (O'Keefe and Deacon, 1988). It is a versatile high sensitivity absorption technique. One of the most essential advantages of CRDS in contrast to usual absorption methods is that the CRDS signal is not affected by intensity fluctuations of the laser since only the decay time of the signal, which does not depend on the laser intensity, is detected. The setup of O'Keefe and Deacon employed a pulsed, tunable laser, and is known as a "generic pulsed CRDS setup". Since the publication of their article, the method of CRDS has been applied to different absorptions ranging from ~ 200 nm to ~ 10 µm and many variants of excitation and detection schemes have been used. Various methods and applications of CRDS are described in a number of reviews (Wheeler et al., 1998; Berden et al., 2000; Brown, 2003). In 1997, Romanini et al. adapted the use of small, continuous-wave diode lasers to CRDS (Romanini et al., 1997a; Romanini et al., 1997b). In order to perform quantitative analyses of H2O and HDO during oxidation of deuterated acetic acid in the smog chamber, we have developed a similar setup. CRDS principle The principle of CRDS is based upon a measurement of the rate of decay of an optical resonator with a high quality factor, indicating a long lifetime of the photons in the cavity. The principle is schematically illustrated in Figure 4. L

L

laser

laser

.. .

.. . M1

M2

(a) Figure 4.

time

M1

d

(b)

M2

time

Principle of CRD absorption measurements. (a) light decaying in an empty cavity, (b) cell is filled with an absorber.

After coupling the laser light into the cavity, the light intensity decreases with every pass within the resonator because of reflection losses of the mirrors and absorption losses of the medium. Therefore an exponential decay is obtained at the detector (eq.1).

Simulation Chamber Study of the Oxidation of Acetic Acid by OH Radicals § t· It I 0 exp¨ ¸ © W¹

187

(eq.1)

Without absorbing species between the mirrors (Figure 4a), the ring down time of the optically empty cavity is given by (eq.2): W0

L c (1 R )

(eq.2)

where c is the velocity of light and R the reflectivity of the mirrors. The decay time of the cavity filled with an absorbing medium (Figure 4b) is (eq.3): W abs

L c >1 R Dd @

(eq.3)

where Dthe linear absorption coefficient is inversely proportional to the measured decay time of the CRDS signal (eq.4; here L=d).

D

1 § 1 1· ¨¨ ¸¸ c © W abs W 0 ¹

(eq.4)

Using D makes it possible to determine directly the concentration of a trace gas inside the cavity if the absorption cross-section Vabs is known (eq.5).

D

>abs@ V abs

(eq.5)

CW-CRDS setup and data acquisition

The experimental setup (Figure 5) used in this work was very similar to that described by Romanini et al. (1997b). It works with an external cavity diode laser (Sacher Lasertechnik) tunable from 1420 to 1480 nm with an output power of at least 3 mW. For the cavity mirrors, a 1 m radius of curvature and low-loss mirrors by Layertec, covering the range from about 1400 nm to 1550 nm, were used. They were placed at a distance L of 70 cm and sealed the cell. One of them was mounted on a piezoelectric transducer (Physik Instrumente). This device was used to modulate the cavity length in order to let one of the cavity modes oscillate around the laser line. As the beam reflected by the input cavity mirror can strongly perturb the laser, a Faraday isolator (Isowave) was placed in the path to attenuate this effect. The intensity of the light leaving the cavity was measured with a photodiode avalanche. When a predefined threshold was reached, an acoustic-optical modulator (Gooch and Housego) turned off the laser beam and a clean ring-down decay could be measured. The ring-down signals were registered by an InGaAs photodiode (EG&G) and digitised by a 12 bits PC interface card (National Instruments). Using the graphic programming language LabVIEW (National Instruments), the ring-down signals were recorded at a rate of about 100 Hz. The analysis of each ring-down (fitted by an exponential function using a nonlinear Levenberg-Marquardt algorithm) is made separately before averaging the decay time W. With the system described above, a section of the C2H2 overtone spectrum around 1512 nm has been measured, using a distributed feedback diode laser. The noise equivalent absorption coefficient is in the order of 5×10-8 cm-1 or a detection limit of less than 100 ppb

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for C2H2 under the experimental conditions. A summary of the performance characteristics of the setup is given in Table 1.

1 meter

Wavemeter

1468.584 nm

0.75 meter

Fiber optic optic Fiber L

ECDL

AOS

OI

Trigger system Gate generator

1st order

L

L

L PZT

Glass cell APD T, P L

MC

M CC

P

PC

N2 or He

Threshold detector

gas or or smog smog Standard gas chamber's sample sample chamber's

A/D Converter working with LabVIEW 6.1TM

ECDL: External Cavity Diode Laser; OI: Optical Isolator; L: Lens; AOS: Acousto-Optic Switch; PZT: Piezo-Electric actuator; MC: Cavity mirror; APD: Avalanche Photodiode; PC: Pressure Controller; P: Pump

Figure 5.

Scheme of the CW-CRDS setup

Table 1.

Summary of the performance characteristics of the CW-CRDS setup.

coarse tunability of the ECDL fine tunability of the ECDL cavity length cavity mirrors

between 1420 and 1490 nm on 1 nm using the grating piezo control input 70 cm with actual cell RC = 1 m; R ~ 99.99 % o W0 = 25 µs

~ 7 km without absorbing species frequency of cavity length > 200 Hz o one ringmodulation down event every 2.5 ms spectral resolution > 0.01 cm-1 effective path length

sensitivity of the system

5.10-8 cm-1

Determination of [HDO] and [H2O] during smog chamber experiments For quantitative determination of the HDO and H2O concentrations before and during oxidation of CH3COOD by OH in the smog chamber, the reaction mixture was pumped with a flow rate of 70 mL/min through the cavity. During a measurement, the cavity pressure is held constant at 50 Torr to reduce the broadening of the two spectral lines and thus increase the selectivity. Figure 6 shows a CW-CRDS spectrum of characteristic spectral lines of H2O and HDO near 6776 cm-1 (without any averaging). From this measurement, the corresponding concentrations are calculated using the database HITRAN 2004 (Rothman et al., 2005). It takes approximately one minute to measure a spectrum as presented in Figure 6, however, for real-time detection it is sufficient to measure the absorption at only a few wavelengths. Thus

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the concentrations can be determined within a few seconds. Note that quantitative analysis does not require any calibration, CW-CRDS leads directly to absolute concentrations, if the absorption cross section of the measured spectral line is known (from HITRAN 2004 or GEISA databases for example).

+ experimental points Gaussian fit

HDO

H2 O

Figure 6.

CW-CRDS spectrum obtained at 50 Torr from a smog chamber mixture.

Preliminary Results and Discussion The study of the reaction OH + CH3COOD was conducted in an excess of CH3ONO over CH3COOD. The branching ratio of channel (2a) was determined as the ratio of the concentration of HDO produced to the concentration of CH3COOD consumed in reaction 2: R

k 2a k 2a k 2b

k 2a k2

d [ HDO ] d [ CH 3 COOD ]

>HDO @formed [ CH 3 COOD ] reacted

Figure 7 shows an example of a plot of the formation of HDO and H2O versus the loss of CH3COOD for one experiment. The accuracy of the measured CH3COOD concentration was determined from the statistic error (2V) of the calibration curve, obtained by liquid injections. It was estimated to be 5 %. Uncertainties in the HDO and H2O concentrations arise mainly from errors in the measured absorbance and from the accuracy in the absorptions cross sections. They were estimated to be 10 %. The slopes of the above lines give directly the branching ratios R2a and R2b. At first, the branching fraction R2a = (36 r 20) % indicates that channel 2a would be the minor oxidation channel for the OH + CH3COOD reaction. However, this result can't be easily compared with the one of Butkovskaya et al. (2004) because too little is known about the

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isotope effect in the reaction of CH3COOD and OH. On the one hand, the yield of formation of H2O is too high (R2b > 1) and other sources of production must be taken into account. Principally, the interactions between H2O molecules and the walls of the chamber can be responsible for a large perturbation in the H2O absorption signal. Furthermore, the reactions of OH with other species like CH3ONO, HCHO (product of CH3ONO photolysis) or CH3OH (impurity in the CH3ONO synthesized) can be supplementary sources of H2O.

3 '[HDO] and '[H2O] (molecules/cm )

4,5E+15 4E+15

HDO

3,5E+15

H2O

y = 2,2763x R2 = 0,983

3E+15 2,5E+15 2E+15 1,5E+15

y = 0,3627x

1E+15

R2 = 0,6895

5E+14 0 0

2E+14

4E+14

6E+14

8E+14

1E+15

1,2E+15 1,4E+15 1,6E+15 1,8E+15

-'[CH3COOH] (molecules/cm3)

Figure 7.

Formation of HDO (crosses) and H2O (open circles) versus loss of CH3COOD following irradiation of a CH3COOD (~ 3,5×1015 molecules/cm3) + CH3ONO (~ 4×1018 molecules/cm3) mixture with zero air as diluent at 298 r 2 K and atmospheric pressure. The solid lines are linear regressions of the two data sets.

Conclusions The present study reports the first coupling between a smog chamber and a CW-CRDS setup. After a successful evaluation the CW-CRDS setup in the laboratory (spectroscopic study of C2H2 around 1512 nm), this new analytical device permits us to follow the production of small molecules (CO, CO2, C2H2, HCOOH, etc.) and also of isotopic compounds (HDO, H218O for example) almost in "real time" during experiments on VOC degradation (oxidation or photolysis) in a simulation chamber. For the first experiments carried out on the oxidation of CH3COOD by OH radicals, a branching ratio of (36 r 20) % has been determined for the D-atom abstraction channel. These experiments have revealed several difficulties in the analysis of the results and comparison with literature data because of the unknown reaction mechanisms and kinetics involving deuterated compounds. Additional experiments are necessary to resolve these difficulties. Determination of the branching ratio for the product channels in reaction of CH3COOH with OH radicals in a smog chamber under atmospheric conditions by measuring the CO2 formation yield (CW-CRDS using a distributed feedback diode laser at 1570 nm) is in progress.

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Acknowledgments The authors gratefully acknowledge the help of T. Leonardis (Ecole des Mines – Douai) and Dr. D. Romanini (Laboratoire de Spectrométrie Physique – Grenoble) for their technical assistance. Moreover, this work has been achieved with the supports of the CPER (Contrat de Plan Etat Région) Nord-Pas de Calais "air quality", the CNRS (Centre National de la Recherche Scientifique), the CERLA (Centre d'Etudes et de Recherches Lasers et Applications) and the FEDER (Fonds Européen de DEveloppement Régional). References Atkinson R. and J. Arey; Atmospheric degradation of volatile organic compounds, Chem. Rev. 103 (2003) 46054638. Baboukas E. D., M. Kanakidou and N. Mihalopoulos; Carboxylic acids in gas and particulate phase above the Atlantic Ocean, J. Geophys. Res. 105 (2000) 14459-14471. Berden G., R. Peeters and G. Meijer; Cavity ring-down spectroscopy: Experimental schemes and applications, Int. Rev. in Phys. Chem. 19 (2000) 565-607. Brown S. S.; Absorption spectroscopy in high-finesse cavities for atmospheric studies, Chem. Rev. 103 (2003) 5219-5238. Butkovskaya N. I., A. Kukui and N. Pouvesle, G. Le Bras; Rate constant and mechanism of the reaction of OH radicals with acetic acid in the temperature range of 229-300 K, J. Phys. Chem. A 108 (2004) 7021-7026. Chebbi A. and P. Carlier; Carboxylic acids in the troposphere, occurrence, sources, and sinks: a review, Atmos. Environ. 30 (1996) 4233-4249. CITEPA : Emissions dans l’air en France, comparaisons de données d'émissions de la France et d'autres pays, URI: 'http://www.citepa.org/emissions/france_autres/Comparaisons.pdf' (2000). HITRAN 2004; URI: 'http://www.hitran.com'. O'Keefe A. and D. A. G. Deacon; Cavity ring-down optical spectrometer for absorption measurements using pulsed laser sources, Rev. Sci. Instrum. 59 (1988) 5244-2551. Ragunathan N., K. A. Krock, C. Klawun, T. A. Sasaki and C. L. Wilkins; Gas chromatography with spectroscopic detectors, J. Chromatogr. A 856 (1999) 349-397. Romanini D., A. A. Kachanov, N. Sadeghi and F. Stoeckel; CW cavity ring down spectroscopy, Chem. Phys. Lett. 264 (1997a) 316-322. Romanini D., A. A. Kachanov and F. Stoeckel; Diode laser cavity ring down spectroscopy, Chem. Phys. Lett. 270 (1997b) 538-545. Rothman L.S., D. Jacquemart, A. Barbe, D. Chris Benner, M. Birk, L.R. Brown, M.R. Carleer, C. Chackerian Jr., K. Chance, V. Dana, V.M. Devi, J.-M. Flaud, R.R. Gamache, A. Goldman, J.-M. Hartmann, K.W. Jucks, A.G. Maki, J.-Y. Mandin, S.T. Massie, J. Orphal, A. Perrin, C.P. Rinsland, M.A.H. Smith, J. Tennyson, R.N. Tolchenov, R.A. Toth, J. Vander Auwera, P. Varanasi, and G. Wagner; The HITRAN 2004 Molecular Spectroscopic Database, JQSRT, Preprint version, 2005. Singleton D. L., G. Paraskevopoulos and R. S. Irwin; Rates and mechanism of the reactions of hydroxyl radicals with acetic, deuterated acetic, and propionic acids in the gas phase, J. Am. Chem. Soc. 111 (1989) 52485251. Taylor W. D., T. D. Allston, M. J. Moscato, G. B. Fazekas, R. Kozlowski and G. A. Takacs; Atmospheric photodissociation lifetimes for nitromethane, methyl nitrite and methyl nitrate, Int. J. Chem. Kinet. 12 (1980) 231-240. Tyndall G. S., R. A. Cox, C. Granier, R. Lescaux, G. K. Moortgat, M. J. Pilling, A. R. Ravishankara and T. J. Wallington; Atmospheric chemistry of small organic peroxy radicals, J. Geophys. Research. 106 (2001) 12157-12182. Wheeler M. D., S. M. Newman, A. J. Orr-Ewing and M. N. R. Ashfold; Cavity ring-down spectroscopy, J. Chem. Soc., Faraday Trans. 94 (1998) 337-351.

Kinetics, Products and Mechanism of O(3P) Atom Reactions with Alkyl Iodides Ian Barnes Bergische Universität Wuppertal, Fachbereich C - Physikalische Chemie, Gauß Straße 20, D-42119 Wuppertal, Germany

Key Words: Alkyl iodides, Halogens, Oxygen atoms, Relative kinetic, Reaction mechanisms

Introduction Alkyl halides (RX: X = Cl, I) are an important source of halogens in the atmosphere. The major tropospheric sinks of these compounds are photolysis (RBr, RI) and reaction with OH radicals. In the case of alkyl iodides (RI) relative kinetic studies of their OH reactions in photoreactors are complicated by fast reactions with the O(3P) atoms generated by the photochemical OH radical sources. Figure 1 below shows a ln-ln plot of the kinetic data from an experiment performed in a large photoreactor to determine the OH rate coefficient for the reaction OH + CH3CH2CH2I relative to OH + ethene using the photolysis of methyl nitrite (CH3ONO) as the OH radical source. A recent example of the implementation of the relative kinetic technique for the determination of OH radical rate coefficients in a photoreactor can be found in Olariu et al. (2000).

ln((Io/I) propyl iodide

0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 0.00

0.10

0.20

0.30

0.40

0.50

0.60

ln(Io/I) ethene

Figure 1.

Plot of the kinetic data obtained from the irradiation of a propyliodide, ethene, CH3ONO, and synthetic air reaction mixture in a 420 l photoreactor.

The non-linearity with increasing reaction time in the plot in Figure 1 is due to very fast reactions of RI with O(3P). An analysis of the initial slope yields a rate coefficient for the reaction of OH with 1-propyliodide which is in reasonable agreement with the recommended literature value for the reaction of OH with 1-propyliodide (Carl and Crowley, 2001; Cotter et al., 2003) while the slope at extended reaction time yields a rate coefficient in reasonable agreement with literature values for the reaction of O(3P) with 1-propyliodide (Gilles et al., 1996; Terual et al., 2004). Luo et al. (1995) have successfully employed the relative kinetic technique in a 500 l Teflon chamber to measure rate coefficients for the reactions of O(3P) with a series of alkenes 193 I. Barnes and K. J. Rudzinski (eds.), Environmental Simulation Chambers: Application to Atmospheric Chemical Processes, 193–205. © 2006 Springer. Printed in the Netherlands.

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I. Barnes

and terpenes at ambient temperature and atmospheric pressure. The experiments were performed in N2 bath gas and an excess of both NO2 and NO to optimise the concentration of O(3P) and depress possible interferences by reactions of OH and NO3 radicals and O3 with the compounds under investigation. The few rate coefficients for the reactions of O(3P) reactions with alkyl iodides, which have been measured, have been found to be extremely rapid (Gilles et al., 1996; Terual et al., 2004; and references therein). The measured rate coefficients are much faster than those for O(3P) with the chlorine and bromine analogs and are also much faster than those for OH radicals with the alkyl iodides (Carl and Crowley, 2001; Cotter et al., 2001). This has been explained by invoking the initial formation of a R–I–O complex. IO elimination is the most important product channel for the small iodoalkanes such as CH3I and CF3I, however, for longer chain iodoalkanes the presence of a C–H bond in the E-position to the I-atom enables the intramolecular abstraction of an H-atom via a five-membered ring transition state to eliminate HOI and form an alkene (Klaassen et al., 1996; Loomis et al., 1997). As discussed above the kinetic database for the reactions of O(3P) with alkyl iodides is relatively limited. The higher reactivity of alkyl iodides to O(3P) atoms compared to OH radicals suggests that the application of the relative kinetic technique in a photoreactor, as applied by Luo et al. (1996) for the determination of O + alkene/terpene rate coefficients, should also be applicable for the determination of rate coefficients for O + alkyl iodides. Because of the much higher rate coefficients for O(3P) with the alkyl iodides compared to OH, inference by any OH radicals produced in the system will be minimal. Reactions with O3 and NO3 radicals are too slow to be of any importance. In the present work the relative kinetic technique has been applied in large and small photoreactors to measure rate coefficients for the reaction of O(3P) atoms with a series of alkyl iodides at room temperature and atmospheric pressure. The products formed in N2 have also been investigated. Experimental Product and kinetic experiments have been performed on the reaction of O(3P) with a series of mono- and disubstituted alkyl halides. The compounds investigated are listed in Table 1 in the Results section. The product studies were all carried out in either a 1080 1 quartz glass chamber (Mihalopoulos et al., 1992) or a 480 l cylindrical Duran glass chamber (Barnes et al., 1993). Schematic outlines of the 1080 land 480 l chambers are shown in Figures 2 and 3, respectively. In the 1080 lchamber an internally mounted White type multiple reflection mirror system operated at a total optical path length of (484.7 r 0.8) m coupled to an FTIR spectrometer was used for reactant and reference monitoring. IR spectra were recorded at a spectral resolution of 1 cm-1 using a Nicolet NEXUS FT-IR spectrometer equipped with a MCT detector. The 480 l chamber is also equipped with 3 built-in White mirror systems for long path (51.6 m) FTIR (Nicolet Magna 520, MCT detector, 1 cm-1 resolution), VIS (28.8 m) and UV (28.0 m) in situ monitoring of reactants and products. The majority of the kinetic experiments have been carried out in a simple 20 l reactor using GC-FID for the analysis; Hewlett Packard 5890 Series II with HP 3395 integrator, separation on a RESTEX RTX-1301 column (30 m long, 0.53 mm inner diameter and 0.25 Pm film thickness). This reactor is shown in Figure 4. Samples were taken using a 1 ml gas-

Kinetics, Products and Mechanism of O( 3P) Atom Reactions with Alkyl Iodides

195

tight syringe and injected into the GC system. For some of the larger alkyl iodides control experiments were also performed in the 480 l chamber using FT-IR absorption spectroscopy for the kinetic analysis.

Figure 2.

Schematic outline of a 1080 l quartz glass photoreactor equipped with an internally mounted White type mirror system for FTIR in situ monitoring of reactants and products. The chamber can be temperature regulated in the range 303 to 283 K. The chamber is surrounded by 32 super actinic fluorescent lamps (Philips TL 05/40 W: 320 < O < 480, Omax = 360 nm) and 32 low pressure mercury lamps (Philips TUV 40 W: Omax = 254 nm) mounted evenly around the reactor. Other types of lamps can be easily mounted.

All experiments were performed at 1013 mbar total pressure of N2 at 298 ± 2 K using the photolysis of NO2 with fluorescent lamps (Philips TL 40W/05, 320 < O < 450 nm) as the O(3P) atom source: NO2 + hv • NO + O Rate coefficients for the reaction of O(3P) with selected alkyl iodides were determined using the relative kinetic technique as outlined by Luo et al. (1996). 2-Iodopropane (CH3CH(I)CH3) was used as the reference compound: O + RI o products; k1 O + 2-iodopropane o products; k2

I. Barnes

196

Providing that RI and 2-iodopropane are removed solely by reaction with O atoms the following rate law holds: [ RI]t 0 ½ ln ® ¾ ¯ [RI]t ¿

k1 [2 - iodopropane ]t 0 ½ ln ® ¾ k 2 ¯ [2 - iodopropane ]t ¿

(eq 1)

where [RI]to and [2-iodopropane]to are the concentrations of the alkyl iodide under test and reference alkyl iodide, respectively, at time to, [RI]t and [2-iodopropane]t are the corresponding concentrations at time t, and k1 and k2 are the rate coefficients of the alkyl iodide and reference compound with O(3P), respectively. Plots of ln([RI]to/[RI]t) against ln([2iodopropane]to/[2-iodopropane]t) should straight lines with a slope of k1/k2 and zero intercept. The rate coefficients for the reactions of O(3P) with the various alkyl iodides were placed on an absolute basis using a rate coefficient value of k = 4.97 × 10-11 cm3 molecule-1 s-1 from Teruel et al. (2004) for the reaction of O(3P) with 2-iodopropane. This value is in good agreement with the other reported value by Gilles et al. (1996).

Figure 3.

Schematic outline of a 480 Aquartz glass photoreactor equipped with an internally mounted White type mirror systems for FTIR, VIS and UV in situ monitoring of reactants and products. The chamber is surrounded by 20 super actinic fluorescent lamps (Philips TL 05/40 W: 320 < O < 480, Omax = 360 nm) and 12 gold fluorescent lamps (Philips TLD 16/36 W: 500 < O < 700 nm).

The approximate initial reactant concentrations in both reactors (in ppmv units) were as follows: NO2, 50-100; alkyl iodide 10-30 and 2-iodopropane 10-30 (1 ppmV = 2.46 u 1014 molecule cm-3 at 298 K and atmospheric pressure). The concentration-time behaviour of the alkyl iodides were monitored over a 15-30 min irradiation period in both the kinetic and product studies.


197

Figure 4. Schematic outline of a 20 l glass reactor with a metal top flange for inlet and outlet ports. The reactor is equipped with 4 fluorescent lamps (Philips TL05/40 W) and can be evaluated to 0.01 mbar with a simple rotary pump.

Figure 5. Photograph of the simple 20 l glass reactor with GC analysis system shown schematically in figure 4.

Figure 5. Photograph of the simple 20 l glass reactor with a GC analysis system shown schematically in Figure 4.

Results and Discussion Kinetics O + RI To test the relative kinetic method in the small 20 l reactor the rate constant ratio for the reaction of O(3P) with 1-iodopropane relative to 2-iodopropane was determined. The kinetic data from a typical experiment plotted according to equation (1) are shown in Figure 6. A good linear correlation with zero intercept was obtained. The value of the rate coefficient obtained for the reaction of O(3P) with 1-iodopropane is in excellent agreement with the absolute value obtained by Teruel et al. (2004) using pulsed laser photolysis-resonance Fluorescence (PLP-RF) which demonstrates the validity of the applied method for the determination of rate coefficients for the reactions of O(3P) with alkyl iodides.

I. Barnes

198 0.70

Figure 6. Plot of the kinetic data according to eq. (1) for measurements on the reaction of O(3P) with 1iodopropane relative to that with 2-iodopropane.

ln(Io/I) 1-iodopropane

0.60 0.50 0.40 0.30 0.20 0.10 0.00 0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

ln(Io/I) 2-iodopropane

Examples of the kinetic data for some of the alkyl iodides investigated plotted according to eq. (1) are shown in Figure 7. In the main good straight line correlations were obtained with zero intercepts. The rate coefficients obtained for the alkyl iodides investigated are listed in Table 1 where they are compared with the available literature data. The rate coefficients determined in this work are estimated to have a total error of ± 15% 3.50

ln(Io/I) alkyl iodide

3.00 2.50 2.00

iodocyclopentane 1,4-diiodobutane 2-iodo-2-methylpropane 1-iodo-2-methylpropane 1,3-diiodopropane iodocyclohexane Linear (1,4-diiodobutane) Linear (iodocyclopentane) Linear (2-iodo-2-methylpropane) Linear (1-iodo-2-methylpropane) Linear (iodocyclohexane) Linear (1,3-diiodopropane)

Figure 7. Examples of plots of the kinetic data according to eq (1) for measurements on the reaction of O(3P) with several alkyl iodides relative to that with 2iodopropane.

1.50 1.00 0.50 0.00 0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

ln(Io/) 2-iodopropane

Rate coefficients have been determined for the reaction of O(3P) with 17 alkyl iodides 12 of which are first-time measurements. As can be seen from Table 1 there is good agreement between the rate coefficients reported in the literature for the C1 to C4 alkyl monoiodides (Gilles et al., 1996; Teruel et al., 2004) and those determined in this work. This good agreement adds further weight to the soundness of the applied experimental approach. The present work has considerably expanded the number and type of alkyl iodides investigated. The reactivity trends for the reactions of O(3P) with RI have been discussed in detail by Teruel et al. (2004) and Gilles et al. (1996). Teruel et al. (2004) have also made comparisons with the analogous reactions with OH radicals and Cl atoms. Therefore, only salient features of the reactivity trends and supplementary information will be presented here.


199

As in the other studies a gradual increase in the rate coefficient is observed in progressing from CH3I to CH3CH2I to CH3CH2CH2I. It has been observed in this study that introducing a fourth carbon to the linear chain results in a further small increase in the rate coefficient, however, extensions of the chain to C5 and C6 have no further influence on the rate coefficient. In agreement with Teruel et al. (2004) it is found that the rate coefficient for the reaction of O(3P) with 2-iodopropane is greater than that for 1-iodopropane. It has also been found in the present work that the rate coefficient for the reaction of O(3P) with 2-iodobutane is higher than that for 1-butane. This behaviour is reconcilable in terms of the proposed main reaction mechanism mentioned in the Introduction, i.e. the secondary iodides have a larger number of E H-atoms that can be internally abstracted via a five-membered ring R-I-O complex transition state. For the C5 compounds 1-iodo-2-methylbutane and 1-iodopentane the rate coefficient for O(3P) with 1-iodo-2-methylbutane is higher than that for 1-iodopentane, presumably for similar reasons. The highest rate coefficient has been found for the reaction of O(3P) with 2-iodo-2-methylpropane which has the highest possible number abstractable E Hatoms. A number of di-iodo compounds have been investigated. In general the rate coefficients for the di-iodo compounds with chain lengths of C2 are about a factor of 2 higher than the corresponding mono-iodo compounds. In the case of CH3I and CH2I2 the difference reported by Teruel et al. (2004) for the rate coefficients is nearly 4. The rate coefficient for the reaction of O(3P) with neopentyl iodide ((CH3)3CCH2I) is slightly higher than that for CH3I. Neopentyl iodide does not possess any E H-atoms and the mechanism is, as in the case of CH3I, an overall I abstraction mechanism to form IO. This conclusion is supported by the observations in the product studies. The rate coefficients for the reaction of cyclopentane and cyclohexane with O(3P) are larger than those for the corresponding linear chain 1-iodo-alkanes, which probably reflects the lower C-H bond strength in the cyclic compounds compared to the straight chain analogues. The measured rate coefficient for the reaction of O(3P) with cyclopentane in this work is, however, around 30% higher than that for cyclohexane despite the C-H bond energy in cyclohexane (399.6 kJ mol-1) being somewhat lower than that in cyclopentane (403.5 kJ mol-1). Stereo factors may possibly play a role in determining the rate of the reaction; cyclohexane has a chair conformation with zero ring strain whereas cyclopentane has an envelope conformation. This is, however, presently only conjecture, independent conformation of the rate coefficients for the two substances by another method is required before any positive conclusions can be drawn. The room temperature rate coefficients for O(3P) with fluorinated alkyl iodides (Gilles et al., 1996) and selected alkyl iodides (Teruel et al., 2004) and have found to show a linear correlation with the ionisation potential (IP) of the compounds. Table 2 lists the ionization potentials (IP) for a series of alkyl iodides taken from the NIST Chemistry WebBook (http://webbook.nist.gov/chemistry/) and their corresponding rate coefficients for reaction with O(3P) as measured in this study and taken from other available literature sources. The natural logarithm of the 298 K rate coefficients for– the compounds listed in Table 2 are plotted as a function of ionisation potential in Figure 8. The numbers on the plot refer to the correspondingly numbered compounds in Table 2. The points for compounds 3 and 9 overlap on the diagram.

I. Barnes

200 Table 1.

Summary of the product and kinetic data from studies on the reactions of O(3P) with alkyl halides at 1000 mbar total pressure of N2 and 298 ± 2K. The rate coefficients determined in this work (column (a)) have an estimated overall uncertainty of ± 15%. The alkene yields have an uncertainty of approximately ± 20%. k(O + RI) x 1011

Compound

Products

(cm3 molecule-1 s-1)

(a)

(b)

(c)

Alkenes (d) / (% mol yield)

Alkanes/other

iodomethane

CH3I

1.82 2.01

-

-

ethane

iodoethane

CH3CH2I

3.19 3.51

-

ethene / 100

-

1,2-diiodoethane

ICH2CH2I

6.25

-

Iodoethane / (f)

?

-

ethene / 42 1-iodopropane

CH3CH2CH2I

3.88 3.79

-

2-iodopropane

(CH3)2CHI

ref

1,3-diodopropane

ICH2CH2CH2I

11.5

-

-

allyliodide / 100

allyliodide

CH2=CHCH2I

10.2

-

-

1,5-hexadiene / (f)

3-iodopropylene oxide

1-iodobutane

CH3CH2CH2CH2I

4.83

-

-

1-butene / 70

n-octane

2-iodobutane

CH3CH2CHICH3

6.64

-

-

1-butene / 46

3,4-dimethylhexane

4.97 5.18

propene / 80

n-hexane

propene / 68

2,3-dimethylbutane

trans-2-butene / Sc@ Nitrate as a catalyst of SO2 autoxidation to sulphuric acid Sea aerosols initially have an ionic composition of sea water but quickly loose water to attain equilibrium with water vapour in the surrounding air, simultaneously cumulating reactive trace gases and undergoing chemical reactions (Pszenny et al., 1998). Also cloud droplets may undergo dehydration, depending on air humidity. The concentration of nitrate may reach very high values, a mole per dm3 and over, when droplets evaporate almost to dryness. High concentrations of nitrate should also be expected in the case when initially dry or humidified solid NaCl aerosols are reacted with nitric radicals, NO3, or chlorine nitrate, ClONO2, reactions recently discussed, for instance, by Gershenzon et al. (2002). Our recent study on the effect of nitrate at high concentrations led to the results which give ground for inferring that the intervention of nitrates may be also at the level of chain propagation (Pasiuk-Bronikowska et al., 2004). Then, the rate of S(IV) autoxidation substantially exceeds that attained in the absence of nitrate. This is illustrated in Figure 2. When the concentration of nitrate attains a sufficiently high level, the reaction rate, r, starts to grow above the value for the uninhibited reaction. Such an acceleration of S(VI) formation in the presence of high amounts of nitrate indicates that the latter compound must react in the rate determining step. As in this part of our experiments the excess of nitrate with respect to S(IV) was immense, it seemed reasonable to explain the observed changes in the S(IV) autoxidation kinetics assuming that:

Studies on Nitrate-Affected SO2 Oxidation and Their Perspectives

257

Ɣ the presence of sulphate radicals in the reacting system is negligible, Ɣ the hydrogen sulphite anions in the rate controlling step, suitable in the case of low concentrations of nitrate, are replaced by nitrate anions.

Effect of nitrates (concentration region extended) on the rate of S(IV) autoxidation.

Figure 2.

As shown in Table 3, nitrate anions consumed in the rate controlling step are reformed in the next step involving nitric radicals and S(IV). This is a sort of a catalytic cycle, where Interference of nitrates (high concentration).

Table 3. initiation:

-

propagation: SO3 + O2

I

MIII + HSO3–

-

MII + •SO3 – + H+

k’i

SO k (rate controlling step) SO - + NO SO - + NO NO + HSO - NO - + SO - + H k nonradical S(IV) oxidation: SO - + HSO 2SO - + H k I I I

•–

5

p1

–

5

3

– 3

2– 5

– 3

I

3

5

– 3

•

2– 4

3

+

3

+

p

p5

termination: 2SO5 S 2O82 + O2 (nonradical products )

I

-

-

I

2–

kt

W. Pasiuk-Bronikowska and T. Bronikowski

258

nitrate anions play a role of a catalyst. The location of point 4 (white spot in Figure 2) is evidence for the nitrate catalysis. These surprising results shed light on the possible important role of nitrate in the atmospheric autoxidation of SO2 by molecular oxygen. In a certain sense they coincide with the conclusions derived by Leriche et al. (2000) who reported on a multiphase box model for a remote region of the troposphere applied to a set of field measurements in France. It is commonly believed that the main oxidant at low pH is H2O2. To account for the observed conversion of S(IV) to S(VI) at very low concentrations of H2O2 Leriche et al. postulated the decisive role of peroxy nitric acid, HNO4. These authors included in their model of Nchemistry in droplets the following reaction: NO2 + HO2/O2Ǧ ĺ HNO4/ NO4Ǧ According to Amels et al. (1996), the S(IV) oxidation by peroxy nitric acid can proceed very rapidly with the simultaneous formation of nitrate: HNO4 + HSO3Ǧ ĺ NO3Ǧ + SO42Ǧ + 2H+ Both oxidation pathways, the NO3Ǧ catalysed oxidation of S(IV) by molecular oxygen and the oxidation of S(IV) by peroxy nitric acid lead to the formation of sulphate anions and further studies are required to decide, which of the two pathways is the mot important (or perhaps both) under real atmospheric conditions. A chamber reactor as a tool for scaling up A variety of reactor types are known which may be roughly divided into two categories: homogeneous and heterogeneous ones, depending on whether the studied reaction involves reactants present in a single phase or whether they must be drawn from two or more phases. The autoxidation of SO2 is an instructive example of a reaction which leads to different kinetic observations depending on the way it investigated in a particular reactor. In the case of a single-phase laboratory reactor, shown schematically in Table 4, the reactor volume is totally occupied by liquid. The autoxidation of SO2 occurs between reactants, including oxygen, pre-dissolved in the liquid. Thus, the only reaction rate limitations come from the properties of a measuring device (Clark-type electrode) and from the exhaustion of reactants. In a two-phase reactor, with liquid as a continuous phase, the reaction may be observed for a longer time, as the gas reactant is continuously replenished. Here, the intrinsic reaction rate limitation becomes the rate of oxygen supply across the oxygen/water interface (including that of gas bubbles). In a three-phase reactor, also with liquid as a continuous phase, the oxygen/water (slurry) interface is planar, what allows the determination of the rate of oxygen diffusion. A solid suspension is a source of the reacting solute supplied by dissolution. Usually, in a chamber reactor (see the bottom row in Table 4) the complex chemical systems existing in the atmosphere gas phase are approximated. Especially advantageous for studying gas reactions are the two characteristic features of a chamber reactor: a relatively large volume and rather insignificant wall effects. Examples of effectively studied tropospheric reactions in chamber reactors are: photo-dissociation and oxidation of a selection of organic compounds, the latter reactions with such oxidants as ozone, OH and NO3. In many

Studies on Nitrate-Affected SO2 Oxidation and Their Perspectives

259

instances, the studies were focused on gas-phase reaction mechanisms and, to a lesser extent, on the gas-phase reaction kinetics. With the introduction of water droplets or wet aerosol particles into the interior of a chamber, mass transfer in the sense of microphysics emerges as a coordinate part of the problem of the proper approximation of chemical transformations in such a system. To quantitatively describe the mass transfer/chemical reaction interplay is not a trivial task. It requires a set of data on gas-side and liquid-side diffusion to be collected and included in existing models.

Applicability of some typical reactors.

Table 4.

TYPE

REACTOR SCHEME oxygen sensor

liquid-phase (single-phase reactor)

oxygen inlet

gas-liquid (two-phase reactor)

gas-liquid-solid (multiphase reactor)

pH sens or or oxygen probe

air inle t outle t conductometric probe

solid suspension

gas-phase

instrume ntation instrumentation

gas-liquid gas-liquid-solid

instrumentation

REACTOR CHARACTERISTICS • volume: 4x10-3 dm3; • reaction time: several sec; • gas reactant predissolved; • formation of secondary products avoided; • serves to determine kinetic laws and rate constants; • volume: 0.10 dm3; • reaction time: tens of min; • gas reactant supplied by diffusion; • formation of secondary products avoided; • serves to determine kinetic laws and rate constants;

• volume: 0.15 dm3; • reaction time: tens of min; • gas reactant supplied by diffusion; • solute reactant supplied by solid dissolution; • formation of secondary products avoided; • serves to determine kinetic laws and rate constants;

• volume: up to ca. 2x10 5 dm3 (200 m3); • reaction time: hours to days; • formation of secondary products allowed; • serves the determination of chemical composition changes in time (product identification and distribution); • influence of mass transfer (convection/diffusion)

?

We would like to raise the question of the inconveniency resulting from the complexity of cloud chemistry models, at least when taking into account the required computing power and time. To simplify the model approach we suggest treating a cloud not as an aqueous phase volume, but as a system of mixed phases, working as a whole. It would require confining a cloud in a chamber reactor and determining new kinetic parameters as if it were a somewhat modified gas-phase. Conclusions The widely held view that reactions of relatively low rate constants may be safely neglected in the modelling of aqueous phase chemistry should be verified. As shown for the cross-activation of S(IV) and nitrate, the neglected reactions may accelerate, possibly by orders of magnitude, due to an increase of the concentration of inorganic components in desiccating aerosols.

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The use of a chamber reactor for “confining a cloud in a cage” and treating it as a modified gas phase is suggested, here, as an approach to reasonably simplified modelling of chemical composition changes in real clouds. A comparison between the results obtained using a large volume chamber reactor and those calculated from the aqueous phase model, based on data collected using small laboratory reactors, should shed light on the importance of gas-side and liquid-side resistances to mass transfer. Acknowledgements This work, being the contribution to the ESF programme INTROP, is a logical continuation of our study developed within the frames of he EUREKA project, EUROTRAC2. The financial support from the Scientific Committee for Research in Poland is gratefully acknowledged. References Amels, P., H. Elias, U. Goetz, U. Steingens and K. J. Wannowius; Kinetic investigation of the stability of peroxonitric acid and of its reaction with sulphur(IV) in aqueous solution, in: P. Warneck (ed.), Heterogeneous and Liquid-Phase Processes, Springer, Berlin (1996) 77-88. Barker, J. R.; A brief introduction to atmospheric chemistry, in: J. R. Barker (ed.), Progress and Problems in Atmospheric Chemistry, World Scientific, London (1995) 1-33. Crutzen, P. J.; Overview of tropospheric chemistry: developments during the past quater century and a look ahead, Faraday Discuss., 100 (1995) 1-21. Decesari, S., M. C. Facchini, E. Matta, M. Mircea, S. Fuzzi and J.-P. Putaud; Organic and inorganic solutes in atmospheric aerosol: a full characterisation approach, in: P.M.Midgley, M.J.Reuter, M.Williams (eds), Proc. EUROTRAC-2 Symposium 2000 “Transport and Chemical Transformation in the Troposphere”, Springer, Berlin (2001) 274-277. Gershenzon, M. Yu., V. M. Grigorieva, S. D. Il’in, R. G. Remorov, D. V. Shestakov, V. V. Zelenov, E. A .Aparina and M. Yu. Gershenzon; Heterogeneous reactions affecting chlorine activation in the troposphere, in: I. Barnes (ed.), Global Atmospheric Change and its Impact on Regional Air Quality, Kluwer Academic Publishers, Dordrecht (2002) 109-113. Herrmann, H., H.-W. Jacobi, G. Raabe, A. Reese, Th. Umschlag and R. Zellner; Free radical reactions in the tropospheric aqueous phase, in: B. Larsen, B. Versino, G. Angeletti, (eds), The Oxidizing Capacity of the Troposphere, Report EUR 17482 (1997) 503-512. Laj, P., S. Fuzzi, L. Ricci, A. Berner, D. Schell, M. Wendisch, W. Wobrock, G. Frank and B. Martinssonn; Chemical inhomogeneities in fog droplets during the 1994 CHEMDROP experiment, in: B. Larsen, B. Versino, G. Angeletti (eds), The Oxidizing Capacity of the Troposphere, Report EUR 17482 (1997) 513521. Karakas, D. and S. G. Tuncel; Long-range transport of aerosols to Turkish western Black Sea region, in: P.M.Midgley, M.J.Reuter, M.Williams (eds), Proc. EUROTRAC-2 Symposium 2000 “Transport and Chemical Transformation in the Troposphere”, Springer, Berlin (2001) 290-293. Leriche, M., D. Voisin, N. Chaumerliac, A. Monod and B. Aumont; A model for tropospheric multiphase chemistry: application to one cloudy event during the CIME experiment, Atmos. Environ., 34 (2000) 5015-5036. Pasiuk-Bronikowska, W., T. Bronikowski and M. Ulejczyk; Intervention of inorganic radical scavengers during the autoxidation of S(IV), Environ. Sci. Technol., submitted for publication. Pszenny, A., W. Keene, C. O’Dowd and M. Smith; Sea salt aerosols, tropospheric sulfur cycling, and climate forcing, IGACtivities Newsletter (11) (1998) 6-12. Thiemens, M., G. M. Michalski, A. Romero and J. R. McCabe; Mass independent oxygen and sulfur isotopic compositions of environmental sulfate and nitrate. A new probe of atmospheric, hydrospheric and geological processes, Geophys. Res. Abstracts 5 (2003) no. 04359. Waengberg, I., I. Barnes and K.-H. Becker; NO3 radical initiated oxidation of Į-pinene, in: B. Larsen, B. Versino, G. Angeletti (eds), The Oxidizing Capacity of the Troposphere, Report EUR 17482 (1997) 104-108.

Heterogeneous and Aqueous-Phase Transformations of Isoprene Krzysztof J. Rudzinski Institute of Physical Chemistry of the PAS, Kasprzaka 44/52, 01-224 Warsaw, Poland Key Words: Isoprene, Troposphere, Feedback, Sulphate Radical, Oxidation

Introduction Isoprene is a conjugated diene (2-methyl-buta-1,3-diene), volatile and hardly soluble in water; under normal pressure it boils at 34 oC (Merck, 1999) and dissolves up to 1.47×10-2 M at 21.5 oC, with a Henry’s constant of 0.027 mole kg-1 atm-1 at 25 oC (NIST, 2001). Isoprene is a metabolite in plants, microbes, animals and humans, and a major biogenic trace compound emitted to the atmosphere. It is very reactive towards atmospheric gas-phase oxidants such as hydroxyl and nitrate radicals or ozone. At higher concentrations, 220 – 7000 ppm, it is carcinogenic to rodents and possibly carcinogenic to humans (Melnick and Sills, 2001). Terrestrial vegetation produces most of the emitted isoprene – 500 Tg C per year (Guenther et al., 1995). The emitting plants synthesise isoprene in plastids (chloroplasts) from pyruvate and glyceraldehyde-3-phosphate, most probably to better resist the thermal stress (Harley et al., 1999; Kesselmeier and Staudt, 1999; Logan et al., 2000; RodriquezConcepcion and Boronat, 2002). However, many plants do not synthesise isoprene at all. Other natural sources of isoprene include sea phytoplankton (1 Tg C per year, Matsunaga et al., 2002), microbes (Wagner et al., 1999; Fall and Copley, 2000), animals and humans (Fenske and Paulson, 1999; Diskin et al., 2003). In humans, the synthesis of isoprene takes a mevalonate path that is related to the synthesis of cholesterol (Karl et al., 2001). Isoprene exhaled by humans totals roughly 4 Tg C per year. Anthropogenic sources of isoprene, which generally are poorly quantified, include combustion and evaporation of fuels (Broderick and Marnane, 2002; Borbon et al. 2003a, 2003b), cigarette smoking (Pouli et al., 2003; Baek and Jenkins, 2004), biomass burning (Andreae and Merlet, 2001), garden waste (Wilkins and Larsen, 1996) and chemical technology (Leber, 2001). Potential health risks induced the research interest in emissions of isoprene with vehicle exhaust and with cigarette smoke, as well as from facilities manufacturing natural and synthetic rubber, where concentrations of isoprene in ambient air are relatively high. Isoprene is not stored by organisms or in the environment; it encounters sinks wherever it is synthesised or transported, if only reactants are available. Endogenous isoprene may react with oxidants in the intracellular and extracellular fluids, or at walls and membranes in living organisms (Wannaz et al., 2003). The plausible reactants are oxidative species, such as free radicals or radical ions, or ozone. Expelled through the leaf stomata, or with human or animal breath, isoprene may react at the interface or in the volume of fluid films covering the body surfaces; leaves, membranes or skin. Unreacted isoprene is transported to the atmosphere and consumed in several gas-phase reactions (Atkinson and Arey, 2003, 2003a). These reactions are considered a main sink for isoprene in the environment. The possibility of heterogeneous reactions of isoprene on airborne aerosols and of multiphase reactions in atmospheric waters is discussed in this overview. Isoprene may also react in seawater, where 261 I. Barnes and K. J. Rudzinski (eds.), Environmental Simulation Chambers: Application to Atmospheric Chemical Processes, 261–277. © 2006 Springer. Printed in the Netherlands.

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it is produced, or at the sea/air interface. Up to now, only the concentration of isoprene in seawater and the fluxes of isoprene desorbing from the sea to the atmosphere have been measured, while the possibility of aqueous-phase reactions has only been suggested (Milne et al., 1995; Matsunaga et al., 2002). Little is known on the chemistry of isoprene in soils, which naturally provide opportunities for gas-phase, heterogeneous and multiphase reactions. Some soil microbes are a well-quantified sink for isoprene with recognised biochemistry (Boyd et al., 2000), while other microbes produce isoprene (Wagner et al., 1999). The overall balance of isoprene exchange with soils has been estimated at 20.4 Tg C y-1, in favour of deposition (Cleveland and Yavitt, 1997). Gas-phase transformations of isoprene The gas-phase chemistry of isoprene is beyond the scope of this overview, but a short summary is given for completeness, and because many of the gas-phase descendants of isoprene can condense, dissolve in water or react on surfaces under atmospheric conditions.

OH

•

+ O2

OH

+

NO3

•

ONO2 O3

Figure 1.

OO • OH

+ O2

OO •

ONO2

O O O

Gas-phase reactions of isoprene with atmospheric radicals and ozone (for simplicity, only one isomer of each product is shown).

Isoprene does not photolyse in the atmosphere, but reacts with hydroxyl or nitrate radicals and, successively, with molecular oxygen, or with ozone (Figure 1). A hydroxyl radical adds to either of two double bonds in the isoprene molecule to give a hydroxyalkyl radical (four isomers are possible). Hydroxyalkyl radicals react with molecular oxygen to give hydroxyalkyl peroxy radicals in seven isomeric forms. Nitrate radicals react in a similar manner to yield nitrooxyalkyl and nitrooxyalkyl peroxy radicals, each in eight isomeric forms. Ozone adds to either of double bonds of isoprene yielding two isomeric ozonides. Peroxy radicals can react with other radicals, such as NO, HO2 or RO2. A broad spectrum of possible products comprises hydroxy hydroperoxides, diols, hydroxycarbonyls, methyl vinyl ketone, methacrolein, 3-methylfuran, various nitrates (nitroxy peroxy-, hydroxy- and carbonyl-), unsaturated dinitrates, methyl glyoxal, glyoxal, glycol aldehyde, peroxyacetyl nitrate (PAN) and methacrolyl nitrate (MPAN). Ozonides decompose into Criegee radicals and formaldehyde, methyl vinyl ketone or methacrolein. The ultimate products of gas-phase transformation of isoprene in the atmosphere are carbon monoxide and carbon dioxide. Extensive summaries of the gas-phase chemistry of isoprene can be found in the Master Chemical Mechanism (Saunders et al., 2003; http://www.chem.leeds.ac.uk/Atmospheric/

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MCM/ mcmproj.html), or in several reviews (Le Bras et al., 1997; Atkinson, 2000; Atkinson and Arey, 2003, 2003a; Fan and Zhang, 2004). Heterogeneous transformations of isoprene The research interest in heterogeneous transformations of isoprene developed recently, in response to the discovery of humic-like substances (HULIS) in atmospheric aerosols from rural and urban regions (Havers et al., 1998). HULIS are macromolecular or polymeric substances that have dark yellow to brown colour and strongly absorb UV and VIS light (Limbeck et al., 2003; Feng and Möller, 2004). They dissolve in water and contain polysaccharidic and aliphatic substructures (Havers et al., 1998), as well as mono-, di- and polycarboxylic acids (Decesari et al., 2002; Chan and Chan, 2003; Gelenceser et al., 2003; Kiss et al., 2003). Originally, no gas-phase mechanisms could explain the formation of HULIS in the atmosphere, so researchers turned to the heterogeneous transformations of isoprene as a possible explanation. Furthermore, the modellers suggested looking for heterogeneous sinks for isoprene, because the global balance of isoprene did not close in their models (von Kuhlmann et al., 2004). Limbeck et al. (2003) tested the “heterogeneous” hypothesis in a simple laboratory experiment. They passed a stream of synthetic air containing 200 – 2000 ppbv of isoprene through a quartz-fibre bed impregnated with sulphuric acid (50 – 3600 ng). The gas flow rate was 400 dm3 h–1 and the average residence time of isoprene in the bed was 10 ms. The authors varied the acidity of the quartz bed by replacing part of H2SO4 with (NH4)2SO4. In further experiments, they added ozone to the gas stream as a competitive gas-phase reactant. The yellowish products formed on the quartz bed were in part analysed by a thermogravimetric method, and in part extracted with water and, subsequently, with methanol for further analysis. The thermograms indicated the presence of low volatile products, while the water-extracts strongly absorbed the UV light. Methanol extracts were purified by solid phase extraction, from inorganic and polar organic compounds and dried to orange coloured residues. Diffusion reflectance infrared Fourier transform (DRIFT) spectra of these residues revealed the carboxylic, hydroxyl and carbonyl functionalities present. The formation rate of the products decreased with decreasing acidity of the bed, or when ozone was added to the inlet gas stream. Based on these results, Limbeck et al. (2003) suggested that the polymeric substances were formed in a heterogeneous reaction of isoprene with sulphuric acid. Moreover, they showed that the DRIFT spectra of the water-insoluble fractions of their products were extremely similar to spectra of the reference NIST dust. Czoschke et al. (2003) used two large Teflon bags (500 dm3 each) to study the formation of secondary aerosols from isoprene in the presence of ozone, at 22 – 27 oC. They filled the bags with clean, dry air containing 0.57 – 0.59 ppm of O3, and added 5 – 50 µg m–3 of seed aerosol prepared by mixing in various proportions and drying the 6.7 mM solution of (NH4)2SO4 and 5 mM solution of H2SO4. Then, they introduced gaseous isoprene or isoprenealcohol (nonanol or decanol) mixtures into the bags and measured the concentration and size distribution of particles forming, as well as the post-reaction concentrations of ozone. The authors calculated the aerosol yield as the ratio of the volume concentration of aerosol produced to the volume of reactive organic gas consumed. The latter value was estimated from the amount of ozone available to the system and the amount of OH radicals that would be produced in the isoprene-ozone reaction. Table 1 shows the initial concentrations of reactants and the calculated yields of aerosol. The amount of seed aerosol never exceeded

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0.02 to 0.5 % of the total aerosol formed. The yields were higher for acidic seed aerosol and in the presence of alcohols. Table 1. Aerosol yields in seeded ozone-isoprene-alcohol systems (Czoschke et al., 2003). Initial concentrations, ppm: Ozone Isoprene Alcohol Temperature, oC Seed aerosol Aerosol yield, %

3.7 no 24 neutral acidic 0.2 0.6

0.57-0.59 3.1 3.6 (nonanol) 27 neutral acidic 0.4 1.1

4.4 1.4 (decanol) 22 neutral acidic 0.7 1.6

The FTIR spectra showed that the aerosols formed contained hydrates, polymeric forms, acetals and hemiacetals. Several peaks in these spectra closely corresponded to peaks in FTIR spectra of aerosols collected in the Smoky Mountains (Jang et al. 2002). Czoschke et al. (2003) concluded, that in their experiments, isoprene had been oxidised to aldehydes by ozone in the gas phase, and the aldehydes had been converted to the observed products in heterogeneous, acid-catalysed reactions. However, the presented analysis of aerosol yields was very approximate, and did not exclude the possibility of heterogeneous reactions of isoprene in the discussed experiments. All the differences in reactors and techniques given, in the experiments by Limbeck et al. (2003) ozone reacted with isoprene in the gas phase, but decreased the amount of polymers formed. Thus, the heterogeneous reactions of isoprene can be a source of several components of atmospheric aerosols. The evidence is limited, however, and has to be supported by further experimental work. Other work has shown that the formation of polymeric compounds is also possible in non-acid or unseeded gas-phase experiments. Aqueous-phase transformations of isoprene Interest in the aqueous-phase reactions of isoprene first stemmed from attempts to clean the effluents from the natural rubber industry. Elkanzi and Bee Kheng (2000) studied the oxidation of isoprene in a small, stirred photoreactor (0.25 dm–3 volume, maximal lightsource intensity of 2.25 W m–2 at 254 nm and 75 mm distance). They irradiated aqueous solutions containing 1.47 mM of isoprene and 0 – 9 mM of H2O2 (pH = 6.8), for 1 to 3 hours, at 24 oC. The concentrations of isoprene and H2O2 in the reacting solutions were followed offline, using UV spectrophotometry (254 nm) and classical wet-chemical analysis methods. The rate of isoprene degradation was evaluated and best described by Equation 1:

d >isoprene@ dt

k1>isoprene@ k 2 >isoprene@ >H2O2 @

(1)

The rate constants k1 = 3.67×10 – 4 s – 1 and k2 = 4.77×10 – 2 M – 1 s – 1 depended, in an unresolved way, on the intensity of irradiating light. To determine the reaction products, the authors extracted a few samples of the reacting solutions with ethyl acetate, acidified and dried the extracts, and analysed them with GC/MS. At short reaction times, they observed peaks corresponding to isoprene, formaldehyde and methyl vinyl ketone. In experiments with the highest initial ratio of H2O2 to isoprene, these peaks disappeared after 2 hours.


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Pedersen and Sehested (2001) investigated the kinetics of the reaction of isoprene with ozone, being inspired by the smell of wet linen drying in the sun that was commonly attributed to ozone, but might originate from dilute products of isoprene oxidation – methacrolein and methyl vinyl ketone. These authors used a stopped-flow apparatus to mix the 47.1 µM aqueous solution of isoprene with a 6 µM solution of O3, at 5 – 30 oC and pH = 2 (the solution pHs were adjusted with HClO4, for stabilisation of ozone). They followed the extent of reaction in time by measuring the absorption of UV light by ozone, at 260 nm. Similar experiments were carried out for reactions of methacrolein or methyl vinyl ketone with ozone (initial concentrations were 59.5 µM and 57.8 µM, respectively). The reactions were first order with respect to ozone and first order with respect to the organic reactant. The rate constants and energies of activation determined by Pedersen and Sehested (2001) are shown in Table 2. Based on the low-resolution UV spectra of the reacting isoprene-ozone mixtures, these authors suggested a rapid formation of an intermediate, which could be a stabilised carbonyl oxide (Criegee radical) known from the mechanism of the gas-phase ozonolysis of isoprene. Table 2.

Second-order rate constants for reactions of isoprene, methyl vinyl ketone (MVK) and methacrolein (MACR) with ozone, determined by Pedersen and Sehested (2001).

Isoprene + ozone MACR + ozone MVK + ozone

Energy of activation

Rate constant

Reaction

M

–1

s

–1

kJ mol – 1

5 oC

30 oC

25 oC

5 – 30 oC

2.23×105 1.17×104 2.6×104

4.64×105 2.94×104 5×104

(4.2±0.2)×105 (2.4±0.1)×104 (4.4±0.2)×104

19.9±0.5 23.9±0.5 18.0±0.5

Very recently, Claeys et al. (2004, 2004a) discovered two isomers of 2-methyl-butane1,2,3,4-tetraols in aerosol samples collected over the Amazon rain forest and over the continental K-Puszta forest in Hungary. The samples also contained carboxylic acids and polysaccharidic compounds, such as malic acid, oleic acid, palmitic acid, stearic acid, arabitol, mannitol, glucose and levoglucosan. Originally, the authors suggested that tetraols were formed in a series of gas-phase reactions starting from the oxidation of isoprene by OH and O2 radicals, and just condensed to aerosols (Claeys et al., 2004). Such a mechanism required low NOx conditions, but in subsequent field campaigns, more tetraols were found at high NOx conditions (Claeys et al., 2004a). Thus, the authors hypothesised that tetraols were formed in acid-catalysed reaction of isoprene with hydrogen peroxide, presumably heterogeneously or in the aqueous-phase. They carried out simple, experiments at room temperature, in which they mixed vigorously 50 µl of isoprene, 50 µl of 50% aqueous solution of H2O2 and 25 µl of 0.1 M aqueous solution of H2SO4. The mixtures were acidic, with pH = 2. After two hours, the solutions were analysed by GC/MS, using trimethylsilyl derivatisation.. The only products found were the erythro and threo isomers of 2-methyl-butane-1,2,3,4-tetraol. The tetraols peaks were identified in GC/MS chromatograms obtained from aerosols collected in the field campaigns and processed in the same way as the laboratory samples. In addition, Claeys et al. (2004a) carried out similar experiments in which they replaced isoprene with methacrolein or methacrylic acid, the products of the gas-phase oxidation of isoprene. In both cases 2,3-

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dihydroxymethacrylic acid was produced, as well as some precipitate that has not been analysed yet.

1.0

initial concentration of isoprene, mM:

[O2] [O2]o

0.0319 0.0200 0.0040 0

0.5

(a) 0.0

0

1

2

3

4

5

-3

time × 10 , s

1.0

0.0814 0.0407 0.0235 0.0118 0.0061 0.0024 0

initial concentration of isoprene, mM:

[O2] [O2]o 0.5

(b) 0.0 0

2

4

6

8

-3

time × 10 , s

Figure 2.

Decay of oxygen during autoxidation of Na2SO3 initiated by thermal decomposition of K2S2O8 (a) or by Mn(III) (b), and inhibited by isoprene. Initial concentrations of reactants were: K2S2O8 1 mM or MnSO4 0.01 mM; Na2SO3 1.02 mM; O2 0.22-0.25 mM; for isoprene –

Our own interest in the aqueous-phase chemistry of isoprene stemmed from the research on the inhibition of autoxidation of SO2 and its possible impact on the long-range transport of this pollutant (Pasiuk-Bronikowska et al., 2000). Addition of dissolved isoprene slowed down the homogeneous autoxidation of sodium sulphite solutions initiated by thermal decomposition of K2S2O8 (Rudzinski and Pasiuk-Bronikowska, 2001) or catalysed by MnSO4 (Rudzinski et al., 2000). The experiments were performed in a stirred tank reactor operated in a batch manner, at 25 oC. The reactor contained no gas phase and was sealed to prevent any gas-liquid mass exchange. The reacting solutions were slightly alkaline, with pH = 8.0 – 8.5.


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We followed the extent of autoxidation by measuring the concentration of dissolved oxygen versus the reaction time (Figure 2). The plots and the formulas approximating the rates of autoxidation (Eqs 2, 3) clearly show the inhibiting role played by isoprene.

d >O 2 @ k1 >O 2 @ k a1 >O 2 @ dt 1 k >isoprene @0

(for K2S2O8 experiments)

(2)

d >O 2 @ ka 0 dt

(for MnSO4 experiments)

(3)

k0 1 k c >isoprene @0

Further experiments were carried out to explain the kinetics of isoprene degradation during the autoxidation of S(IV) (Rudzinski, 2004). The reactor was equipped with a closed sampling loop for recording the UV spectra of reacting solutions in time. The spectra were decomposed to the component spectra of isoprene, Na2SO3 and K2S2O8, and the time traces of the reactant concentrations were determined (Figure 3). The results were analysed using the chain mechanism of S(IV) autoxidation to which a reaction of isoprene with SO4• – radicals was added:

CH 2 C(CH 3 )CHCH 2 SO x4 o products,

k 2,iso

(I)

The lower limit of the rate constant k2,iso for reaction (I) was estimated under a few quantitative approximations, and the upper limit required the pseudo-stationary-state approximation for SO4• – radicals and SO52 – ions (Egn 4). (7 .07 r 1 .22 ) u 10 8 M1s 1 d k 2, iso d (2 .12 r 0 .37 ) u 10 9 M1s 1

(4)

The real value of k2,iso was anticipated close to the upper limit. The errors given in (4) are just standard errors and do not reflect the errors that could originate from the assumption that isoprene reacted exclusively with sulphate radicals. Approximate analysis showed that if isoprene reacted also with sulphite radicals, the upper limit in (4) is overestimated by a few percent, and if isoprene reacted also with peroxymonosulphate radicals as well, the upper limit is overestimated by not more than 30%. The tentative mechanism of isoprene transformation accompanying the autoxidation of S(IV) was suggested, which started with the addition of a sulphate radical to a double bond in isoprene, followed by addition of oxygen and formation of a peroxy radical. The peroxy radical reacted with sulphite ion to the alkoxy radical, which in turn reacted either with oxygen or with a sulphite ion to give respectively trans-3-methyl-4-sulphoxy-2-buten-1-al or trans-3-methyl-4-sulphoxy-2-buten-1-ol (Rudzinski et al., 2002; Rudzinski, 2004).

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1.0

[iso] [iso]o 0.5

0.0 0

1

2 -3

time × 10 , s

1.0

[S(IV)] [S(IV)]o 0.5

0.0

0

1

2 -3

time × 10 , s

Figure 3. Decay of S(IV) and isoprene during autoxidation of Na2SO3 at 25 oC and pH = 8.0 – 8.5, initiated by thermal decomposition of K2S2O8: 1 mM ( ), 0.2 mM ( ) and 0.1 mM ( ), or catalysed by 0.01 mM MnSO4 ( ). Atmospheric significance of isoprene transformations Heterogeneous formation of HULIS and secondary aerosols from isoprene, as well as the aqueous-phase formation of tetraols were demonstrated only in simple laboratory experiments. Similarities in spectra and chromatograms of the laboratory samples and of the real-life aerosols collected in the field campaigns strongly support the hypothesis that the heterogeneous and multiphase chemistry influence the atmospheric transformation and global balance of isoprene, as well as formation of atmospheric aerosols. The hypothesis, however, requires further proof and a quantitative assessment, which would take into account the competition from other highly reactive organic components of the atmosphere. Such goals can


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only be achieved through concerted efforts of analytical, atmospheric and organic chemists, as well as modellers. Pedersen and Sehested (2002) showed that the aqueous-phase reaction of isoprene with ozone was insignificant for the processing of isoprene in the atmosphere. They estimated the overall and individual lifetimes of isoprene due to reactions with ozone and the hydroxyl radical, at 25 oC and typical in-cloud conditions. The results (Table 3) indicate that clouds generally should not contribute much to the processing of isoprene in the atmosphere. Only in the aqueous phase, were the lifetimes of isoprene due to reactions with ozone and with OH radicals comparable. Similar conclusions were drawn for methyl vinyl ketone, while for methacrolein the clouds could reduce the overall atmospheric lifetime by 50 %. Table 3.

Individual and overall lifetimes of isoprene in the atmosphere, due to reactions with 0.01 pptv OH radicals and 30 ppbv O3, at 25 oC (Pedersen and Sehested, 2001).

Liquid water content Lifetime (OH), h Lifetime (O3), h Lifetime (OH + O3), h

Gas-phase 0 1.12 29.4 -

10-7 28.6 1.08

Cloud 10-6 28.6 1.08

10-5 28.6 1.08

Aqueous phase 1 1 2.05 -

Rudzinski (2004) compared the rates of the aqueous-phase reaction of isoprene with sulphate radicals against the rates of the gas- and the aqueous-phase reactions of isoprene with OH radicals, NO3 radicals and ozone. The rates were evaluated for 25 oC, typical atmospheric concentrations of reactants (Herrmann et al., 2000), and a LWC of 10-5 and 10-4. The partitioning of reactants between phases was described using Henry’s Law. The results, shown in part in Table 4, indicated that the aqueous-phase reaction of isoprene with sulphate radicals was competitive against other reactions only in the aqueous phase and at very high values of liquid water content (LWC =10–4). Table 4. Reactant X

Concentration in the gas-phase

rX,g /(rSO4,aq LWC)* (LWC = 10-4)

rX,aq /rSO4,aq * aqueous phase

OH

0.04 pptv 0.0004 pptv 0.33 pptv 0.0017 pptv 90 ppbv 30 ppbv

684.0 68.4 38.3 0.19 196 65.4

1.89 0.02 0.2 0.001 0.2 0.066

NO3 O3 *

Relative rates of isoprene reactions with OH, NO3, O3 and SO4•in the gas phase (rX,g) and in the aqueous phase (rX,aq) at 25 oC.

concentration of SO4•- radicals in the aqueous phase was 10-12 M

The analysis presented here of the atmospheric significance of the reactions has ignored several important factors such as chemical nonlinearity of the reacting systems, microphysical redistribution of reactants in real atmospheric processes, the kinetic character

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of uptake processes and the influence of chemical reactions on the solubility and the uptake of reactants. For instance, chemical reactions coupled with the mass transfer processes to and in the droplets can significantly alter the Henry’s Law partitioning of reactants based on the bulk-phase concentrations. Nonlinearities of the coupled processes can induce instabilities and oscillations already observed in simple laboratory systems (Pasiuk-Bronikowska et al., 2000a, 2003). Furthermore, the coalescence and break-up of droplets can change the concentrations of reactants inferred from the mass transfer and chemical reaction considerations. Thus, the presented conclusions may be biased and should be re-examined using a more thorough modelling procedure. There are also general reasons that justify further research on the heterogeneous and the aqueous-phase transformations of isoprene. Several reviews on atmospheric processes reflect a common awareness of a general importance of heterogeneous and multiphase reactions (Fuzzi and Ebel, 2000; Herrmann, 2003; Ravishankara, 2003). As already mentioned, von Kuhlmann et al. (2003) showed by modelling that the global balance of isoprene did not close, and called for research on heterogeneous sinks for isoprene. Moreover, the heterogeneous and the aqueous-phase chemistry of isoprene may play a role in local air quality and health problems, that occur close to the sources of isoprene – in the cities, forests, offices and habitats, transport facilities and vehicles, and in the industry. For example, isoprene or products of isoprene reaction with ozone cause eye and airways irritation (Wilkins et al., 2001; Wolkoff and Nielsen, 2001, Rohr et al., 2002). Isoprene health risks in the rubber industry have also been studied (Bird et al., 2001). The possible heterogeneous and multiphase reaction sites in living organisms, seawater and soils were referenced in the Introduction section. partial gas-phase oxidation

ozonides, peroxides

organic compounds

submicron particles heat balance

emission to atmosphere

feeding

soil, water

blue haze

growth

larger particles

plants

Figure 4.

condensation and agglomeration

deposition, rain and snow

color white => grey => => brown => black

Feedbacks in a vegetation - atmosphere system described by Went (1960).

Last but not least come the environmental feedbacks that link atmospheric chemistry, the biosphere and climate change. Isoprene is a major biogenic trace component of the atmosphere. It was more than 40 years ago when Went (1960) discussed a specific relation between plant emissions and a blue haze observed above the countryside vegetation on sunny


271

days. He postulated a cycle that started with plants and the organic compounds they emitted, that were oxidised in the atmospheric gas-phase to compounds that condensed to minute particles that caused the blue haze, and also influenced the heat balance of the ecosystem (and consequently the growth of plants and the emissions). The minute particles grew or agglomerated to larger particles that deposited with rain and snow to build up and possibly fertilise the soil, which influenced plants and the emission of organic compounds (Figure 4). This was a beautiful example of feedback relations that might involve isoprene.

? light CO2

forest growth

T

terpenoid emission

?

heterogeneous and aqueousphase reactions biodiversity

leaf physiology, membranes, damage

?

Figure 5.

aerosol formation

gas-phase reactions

SO2, NOx, NOy, O3, OH, NO3 SO2 LRT, radical scavenging

LRT NOx, NOy

Atmosphere-biosphere-climate feedbacks induced by increased temperature and contents of CO2 (details and references are given in the text).

Five years later Rasmussen and Went (1965) conducted the first systematic study of bVOC (isoprene included) contents in the air over forests, meadows and prairies at several locations in the US. Now, at the turn of the century, each year brings at least one significant review on bVOC and isoprene or isoprene alone – Kesselmeier and Staud (1999), Fuentes et al. (2000), Sharkey and Yeh (2001), Monson (2002), Penuelas and Llusia (2001, 2003), Lerdau and Gray (2003). New feedbacks involving isoprene are often discussed (Shallcross and Monks, 2000; Fuentes et al., 2001; Kulmala et al., 2003, 2004). The role of isoprene in formation of aerosols was discussed in a review on atmospheric aerosols that was published almost simultaneously with the beginning of this Workshop (Kanakidou et al., 2004).

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The biosphere-atmosphere-climate feedbacks are quite complicated. A simplified scheme in Figure 5 shows what can happen in the atmosphere and biosphere when temperature and the CO2 concentration increase. Such conditions are expected to promote the growth of plants and, consequently, the emission of terpenoids (including isoprene), which are converted to a larger amount of aerosols that shade the Earth, also by cloud formation, to reduce the temperature (Kulmala et al., 2003, 2004). This relatively simple feedback action is complicated by several factors. Rises in temperature increase the emission of bVOC directly, but within limits determined by such factors as enzyme degradation and physiological response (Clark et al., 2003; Penuelas and Llusia, 2003). Thus, excessive heating may reduce the emissions. Direct influence of CO2 on bVOC emission is species specific – for instance the production of isoprene increases in some plants, but decreases in others (Loreto et al., 2001; Penuelas and Llusia, 2001). Increased production of aerosols and cloud formation or coating of vegetation with particles may limit the amount of light available to the plants and hence decrease the plant growth (Graham et al., 2003; Grantz et al., 2003). Fuentes et al. (2001) described a multilevel mechanism by which VOC and aerosols can increase the nocturnal temperatures of the atmosphere. The mechanism employed absorption of terrestrial radiation by VOC, the release of latent heat during condensation of water vapour on aerosols and thermal stabilisation of the atmosphere. On a long time scale, the mechanism would induce the successful expansion of neotropical plants, which produce more VOC (not shown in Figure 5). The gas-phase reactions of terpenoids with other trace compounds present in the atmosphere may result in formation of substances that are harmful to plants (Cape, 2003; Wannaz et al., 2003). Good condition of plant leaves is critical for emission of bVOC and photosynthesis, so degradation of plants translates into reduced growth and emissions. On the other hand, the long-range transport of nitrogen stored in such gas-phase products as PAN and MPAN may contribute to remote fertilization and growth enhancement (Shallcross and Monks, 2000; Fuentes et al., 2001). Many pollutants deposit on vegetation, and hence can enter and destroy plant tissues either directly or after transformation to even more harmful substances (Erisman and van Pul, 1997; Kesselmeier et al., 1997; Wannaz et al., 2003). Heterogeneous and aqueous-phase reactions of bVOC may produce unknown harmful substances as well, but also may protect the plants by scavenging and destroying the harmful oxidants. Actually, isoprene is considered one of the most effective antioxidants in plants (Loreto et al., 2001a; Loreto and Velikova, 2001; Affek and Yakir, 2002). Degradation and protection of plant ecosystems influences directly the level of CO2 in the atmosphere and the patterns of bVOC emissions. The scheme presented here is incomplete, and does not contain several important factors like water stress or land use (Lerdau and Gray, 2003; Penuelas and Llusia, 2003). Although limited, the scheme in Figure 5 demonstrates well the complexity and nonlinearity of atmosphere-biosphere-climate interactions. Successful modelling and quantifying of this interaction requires a careful and thorough understanding of possible feedbacks, and teams and projects still more multidisciplinary than they are presently are needed to tackle it. Condensation nuclei of such cooperations already exist within several European and global initiatives such as two ESF programs – INTROP and VOCBAS, two EU networks – ACCENT and EUROCHAMP and two global networks – IGAC and IGBP. Chamber experiments with isoprene Dodge (2000) wrote an extensive review on large and small simulation chambers. Gasphase reactions of isoprene were investigated in virtually all facilities – SAPHIR in Jülich (formerly TASK, 370 m3), EUPHORE in Valencia (200 m3), UNC (University of North


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Carolina, 150 m3), TVA (Tennessee Valley Authority, 28 m3), CSIRO (Commonwealth Scientific and Industrial Research Organization in Australia, 20 m3), EPA (US Environment Protection Agency, 9 m3), UCR (University of Carolina at Riverside, 3.5-5.8 m3), General Motors (0.7 m3) and Wuppertal reactors (0.45 – 0.6 m3). Further research on isoprene was done by Geiger et al. (2002) in EUPHORE and Karl et al. (2004) in SAPHIR. All these studies made contributions to our understanding of the gas-phase chemistry of isoprene. Chambers were also used in the research on heterogeneous reactions of isoprene and of other atmospheric trace compounds. As already discussed, Czoschke et al. (2003) studied the formation of SOA from products of isoprene oxidation in 500 dm3 Teflon-bag chambers at UNC. Folkers et al. (2003a,b,c) studied the partitioning and influence of dicarboxylic acids on aerosol formation in Aerosol Chamber in Jülich. Shantz et al. (2003) investigated the growth of aqueous organic particles and cloud condensation nuclei in the CALSPAN chamber. Iinuma et al. (2004; paper submitted to this book) studied the reaction of Į-pinene with ozone on acidic particles in the Leipzig tent-chamber (9 m3). I am not aware of any aqueous-phase studies in chambers, with the exception of a chamber described by Monod et al. (submitted to this book), which actually is similar to the reactor we have been using for the isoprene studies (Rudzinski, 2004). Thus, the field is open for attempts to introduce clouds, fogs, rains and haze into the chambers and to investigate the multiphase and heterogeneous processes therein. Many technical ideas and solutions can be borrowed for this purpose from chemical engineering. References Affek H.P. and D. Yakir; Protection by isoprene against singlet oxygen in leaves, Plant Physiol. 129 (2002) 269– 277. Andreae M. O. and P. Merlet; Emission of trace gases and aerosols from biomass burning, Global Biogeochem. Cycles 15 (2001) 955-966. Atkinson R.; Atmospheric chemistry of VOCs and NOx, Atmos. Environ. 34 (2000) 2063-2101. Atkinson R. and J. Arey; Gas-phase tropospheric chemistry of biogenic volatile organic compounds: a review, Atmos. Environ. 37 (2003) 197-219. Atkinson R. and J. Arey; Atmospheric degradation of volatile organic compounds, Chem. Rev. 103 (2003a) 4605-4638. Baek S.-O. and R.A. Jenkins; Characterization of trace organic compounds associated with aged and diluted sidestream tobacco smoke in a controlled atmosphere-volatile organic compounds and polycyclic aromatic hydrocarbons, Atmos. Environ. 38 (2004) 6583-6599. Bird M.G., J.M. Rice and J.A. Bond; Evaluation of 1,3-butadiene, isoprene and chloroprene health risks, Chem.Biol. Interact. 135–136 (2001) 1–7. Borbon A., H. Fontaine, N. Locoge, M. Veillerot and J.C. Galloo; Developing receptor-oriented methods for non-methane hydrocarbon characterisation in urban air – Part I: source identification, Atmos. Environ. 37 (2003) 4051-4064. Borbon A., H. Fontaine, N. Locoge, M. Veillerot and J.C. Galloo; Developing receptor-oriented methods for non-methane hydrocarbon characterisation in urban air – Part II: source apportionment, Atmos. Environ. 37 (2003a) 4065-4076. Broderick B.M. and I.S. Marnane; A comparison of the C2 - C9 hydrocarbon composition of vehicle fuels and urban air in Dublin, Ireland, Atmos. Environ. 36 (2002) 975-986. Boyd D.R., D. Clarke, M.C. Cleij, J.T.G. Hamilton and G.N. Sheldrake; Bacterial biotransformation of isoprene and related dienes, Monatsh. Chem. 131 (2000) 673-685. Cape J.N.; Effects of airborne volatile organic compounds on plants, Environ. Pollut. 122 (2003) 145-157.

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Investigation of Atmospheric Transformations of Diesel Emissions in the European Photoreactor (EUPHORE) Barbara Zielinska1, John Sagebiel1, William Stockwell1, Jake McDonald2, JeanClare Seagrave2, Peter Wiesen3, and Klaus Wirtz 4 1

Desert Research Institute, 2215 Raggio Parkway, Reno, Nevada 89512, USA; 2Lovelace Respiratory Research Institute, Albuquerque, NM, USA; 3University of Wuppertal, Germany; 4Fundacion Centro de Estudios Ambientales del Mediterraneo, Valencia, Spain Key Words: Diesel exhaust, Emissions, Particles, Photoreator, PAHs, Toxicity

Introduction Once released into the atmosphere, primary diesel emissions (or any other direct emissions) are subject to dispersion and transport and, at the same time, to various physical and chemical processes, which determine their ultimate environmental fate. To elucidate potential health effects of diesel exhaust, it is insufficient to characterize only the primary pollutants that are directly emitted from diesel vehicles. Secondary compounds, formed during the transport of emissions through the atmosphere, may also affect human health. As primary diesel emissions are a very complex mixture containing thousands of organic and inorganic constituents in the gas and particulate phases that have different chemical reactivities, the rates and mechanisms of their atmospheric transformation processes ultimately determine the atmospheric lifetimes of the initially emitted species as well as the chemical nature and biological activities of the resulting secondary pollutants. The more reactive compounds with short lifetimes will be removed from the atmosphere relatively quickly, whereas more stable pollutants (including atmospheric transformation products) can be transported over greater distances. Some of the gaseous species, by a series of chemical transformations, are converted into particles, forming secondary aerosols. Sulfates and nitrates are the most common secondary particles, though a fraction of particulate organic carbon also results from volatile organic compounds (VOC) via atmospheric reactions with reactive gaseous species such as HO radicals, NO3 radicals, or O3. Clearly, knowledge of the atmospheric loss processes, transformation products, and lifetimes for automotive emissions is important, because these factors determine the biological activities and geographic extent of the influence of these emissions. This paper describes a project that was designed to study the products from sunlight, ozone, HO radical, and NO3 radical-initiated reactions (the latest in the dark) of diesel emissions with the aid of an environmental simulation chamber, under realistic ambient conditions (dilution in the range of 1:300 – 1: 400). The European Photoreactor in Valencia, Spain, (EUPHORE) which is currently one of the largest (approximately 200 m3) and best equipped outdoor simulation chambers in the world, is employed for this study. Experimental The EUPHORE chambers in Valencia, Spain, are described in detail elsewhere (Becker, 1996). Briefly, there are two chambers, each consisting of a half-spherical Teflon bag with a volume of about 204 m3 (see Figure 1). The chambers are protected against atmospheric influences by two half spherically shaped protective housings. The inlet and 279 I. Barnes and K. J. Rudzinski (eds.), Environmental Simulation Chambers: Application to Atmospheric Chemical Processes, 279–284. © 2006 Springer. Printed in the Netherlands.

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outlet ports and other accessories, such as mixing fans, analytical systems, and mechanical excess pressure valves, are located on the floor so that the chamber spherical surface remains unobstructed. Integrated into the flanges are ports for the input of reactants and the sampling lines for different analytical instruments. To mix the reactants, two mixing fans with an air throughput of 4000 m3/h each are installed in each chamber. White mirror systems for in situ FTIR spectrometer measurements are situated in the chamber. Numerous analytical instruments, such as NO/NOx/NO2 analyzers, GC, HPLC, GC-MS-system, SMPS and an ozone analyzer are mounted on a platform under the chamber floor. The sampling lines for these instruments are connected directly to the chamber.

Figure 1.

The European Photoreactor EUPHORE in Valencia/Spain.

Diesel exhaust is generated on-site using a light-duty diesel engine and dynamometer, which is equipped with a Horiba gas analyzer allowing for the continuous monitoring of engine-out gaseous emissions of CO, CO2, NOx, total hydrocarbons (THC) and O2. A modern diesel engine (i.e. with a common rail direct injection, turbocharged, intercooled engine) was obtained from Ford Motor Company (Lynx V277 90 PS Ford Focus engine) and has been mounted on the dynamometer. The engine test rig is situated below the EUPHORE chamber; Figure 2 shows the position of the engine in relation to the chamber. The exhaust is guided in heated tubes under the chamber and is introduced into the chamber by means of a three-way valve, which can tolerate temperatures up to 200oC. If desired, a separate, smaller line can be used that allows approximately 20% of the total exhaust from the engine into the chamber, the rest is vented. Inside the EUPHORE chamber very fast dilution is obtained by mixing the exhaust gas with the clean air with help of a powerful fan. This prevents the agglomeration of particles and the condensation of water. The diesel engine is operated under a load of 60 Nm (Newton-meters) that represents approximately 50% of total engine power. Prior to introduction of exhaust to the chamber, the engine is warmed up for approximately 30 min to reach steady-state conditions. A diesel fuel that most closely matches what is currently used (or will be used in the near future) in most of

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the United States is employed (47 ppm sulfur and 15% aromatic content). The exhaust is introduced to the chamber over approximately 2 min and 6 min to obtain sufficient material for chemical analyses and toxicity testing, respectively.

Figure 2.

Set-up of the engine test rig at the EUPHORE chamber.

Results and Discussion The test matrix that will be carried out in the EUPHORE chamber is shown in Tables 1 and 2. These series of tests provide experiments that will examine the effects of aging, photolysis, HO, O3 and the NO3 radical (in the dark) on the composition of diesel exhaust. The experiments are divided into dark (Table 1) and light (Table 2) exposures test matrixes. The dark experiments D-1, D-2, and D-5 provide baselines for other experiments. Experiment D-3 investigates the effects of O3 on diesel exhaust in the dark and experiment D-4 allows the effect of the NO3 radical on diesel exhaust to be studied. Dinitrogen pentoxide is used as a source of NO3 radicals. N2O5 is prepared by reacting ozone with NO2 directly in the chamber. Toxicity testing requires relatively large samples (on the order of 50 mg). Therefore, experiments D-5 through D-7 are made to duplicate the first experiments but without significant amounts of sample extraction for chemical analyses, although other continuous monitoring is performed. The light exposure test matrix includes six core experiments. L-1 is a baseline experiment for the light exposure series; it examines the effects of photolysis reactions on the exhaust composition. Experiment L-2 examines the effect of HO reactions on exhaust composition at relatively high NOx. Experiment L-3 is proposed to examine the effect of the

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reactions of HO on exhaust composition at lower NOx by addition of H2O2. Hydrogen peroxide photolyses to produce HO but no additional NOx will be added to the chamber when H2O2 is added. Toxicity testing is also proposed for the light experiments. Therefore experiments L-4 through L-6 are made to duplicate the first experiments but without significant amounts of sample extraction for chemical analyses, although other continuous monitoring is performed. Chamber contents will be collected for toxicity testing at the end of experiments L-4 through L-6. Table 1.

Dark Exposure Test Matrix.

Run D-1

Composition Diesel Exhaust Only

D-2 D-3

HONO + Diesel Exhaust O3 + Diesel Exhaust

D-4

N2O5 + Diesel Exhaust

D-5

Diesel Exhaust Only

D-6

O3 + Diesel Exhaust

D-7

N2O5 + Diesel Exhaust

Purpose Determine changes in exhaust composition due to aging in chamber. Provide baseline for HO experiment, L-2. Study reactions of ozone with diesel exhaust in the dark. Investigate effects of NO3 on diesel exhaust composition. N2O5 decomposes to form NO2 and NO3. Duplicate run of D-1 for collection of samples for toxicity testing. Duplicate run of D-3 for collection of samples for toxicity testing. Duplicate run of D-4 for collection of samples for toxicity testing.

The initial series of dark experiments was carried out in January 2005 in the EUPHORE chamber. However, it became apparent during these experiments that our modern diesel engine equipped with an oxidation catalyst had a very low diesel particulate matter (PM) emission rate (especially with the low sulfur, low aromatic fuel, we used), and relatively high NOx emissions under load. In order to obtain the required diesel PM concentrations in the chamber, a longer delivery time of the raw exhaust was necessary (on the order of 2 to 6 minutes). This resulted in unrealistically high concentrations of NOx in the chamber. For example, 2-min introduction of diesel exhaust to the chamber produced approximately 30 µg/m3 of diesel PM and nearly 1 ppm of NOx (30% of NOx as NO2). Because of the high NOx concentrations in the chamber, it was not possible to carry out certain exposure scenarios, for example dark ozone exposures. Thus, we are in the process of developing a new NOx denuder that will be able to decrease significantly high NOx concentrations and are planning to deploy it for the next EUPHORE series of experiments, planned for May 2005. The denuder uses cobalt oxide as an efficient sorption material for the capture of nitrogen oxides (NO, NO2, and HNO3) from exhaust streams (Braman et al., 1986; Ammann 2001; Arens et al., 2001). This denuder will need to be scaled to handle the concentration (up to 400 ppm) and flow rate (180 liters per minute) of the exhaust flow. The experiments carried out during the January 2005 EUPHORE campaign consisted mostly of D-1, D4, D-5 and D-7 runs (Table 1). To determine the particle size, number and volume concentrations the Scanning Mobility Particle Analyzer (SMPS) was used and the particle mass was continuously monitored using TEOM. NOx and NOy species were monitored using chemiluminescence and Fourier Transfer Infrared (FTIR) instruments. After several hours of exposure, the samples for semivolatile organic compound’s (SVOC) analysis

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were collected using a polystyrene-divinylbenzene resin (XAD)-coated annular denuder (Gundel et al., 1995) followed by a 90 mm Teflon-impregnated glass fiber (TIGF) filter and an XAD cartridge. The flow rate of 100 L/min was used. The samples for toxicity evaluation were collected using 8x10-inch Teflon filters followed by two XAD cartridges, with flow rate of 200 L/min. In addition, canister samples were collected for volatile organic compounds (VOC) analysis; dinitrophenylhydrazine (DNPH) impregnated cartridges for carbonyl compound analysis, and diesel particles on quartz fiber filters for organic and elemental carbon (OC/EC) analysis. Table 2.

Light Exposure Test Matrix.

Run Composition L-1 Diesel Exhaust Only L-2

L-3

HONO + NOx + Diesel Exhaust H2O2 + Diesel Exhaust

L-4

Diesel Exhaust Only

L-5

HONO + NOx + Diesel Exhaust H2O2 + Diesel Exhaust

L-6

Purpose Examine effects of photolysis reactions on exhaust composition. Investigate effects of HO on diesel exhaust under conditions of high NOx. Investigate effects of HO on diesel exhaust under conditions of lower NOx. Duplicate run of L-1 for collection of samples for toxicity testing. Duplicate run of L-2 for collection of samples for toxicity testing. Duplicate run of L-3 for collection of samples for toxicity testing.

The SVOC collected on each denuder-filter- XAD cartridge sampling train are currently being extracted and analyzed by high resolution capillary gas chromatography-mass spectrometry (GC/MS), as described previously (Zielinska et al., 2004). The samples are analyzed for polycyclic aromatic hydrocarbons (PAH), oxy-PAH, nitro-PAH, organic acids and diacids and other polar organics (potential transformation products), using a Varian 1200 triple quadrupole GC/MS/MS. Samples collected for toxicity testing are extracted by sonication/agitation (filters) and accelerated solvent extraction (XAD) in acetone. The toxicity of combined PM + SVOC extracts will be ranked by comparison of dose-response curves for several endpoints achieved by either in-vitro (macrophages/Salmonella) or in-vivo (instillation in rat lung) assessments broadly classified as: Genotoxicity; Cytotoxicity; Inflammation; Structural/Functional and Oxidative Stress. The results of these analyses will be reported in subsequent papers. Acknowledgement Financial support for this project is provided by the Health Effects Institute, USA. References Ammann, M., (2001): Using 13N as Tracer in Heterogeneous Atmospheric Chemistry Experiments. Radiochim. Acta, 89, 831-838 . Arens, F., L. Gutzwiller, U. Baltensperger, H. W. Gaggeler and M. Amman, (2001):Heterogeneous Reaction of NO2 on Diesel Soot Particles. Environ. Sci. Technol., 35, 2191-2199. Becker, K.H. (1996). Design and Technical Development of the European Photoreactor and First Experimental Results, Final Report of the EC-Project (EV5V-CT92-0059), Wuppertal, 1996.

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Braman, R.S. and M.A. de la Centera, (1986): Sequential, Selective Hollow Tube Preconcentration and Chemiluminescence Analysis System for Nitrogen Oxide Compounds in Air, Anal. Chem., 58, 15371541. Gundel, L.A., V.C. Lee, K.R.R. Mahanama, R.K. Stevens, and J.M. Daisey (1995). Direct Determination of the Phase Distributions of Semi-Volatile Polycyclic Aromatic Hydrocarbons Using Annular Denuders. Atmos. Environ., 29, 1719-1995. Zielinska, B., J. Sagebiel, W.P. Arnott, C.F. Rogers, K.E. Kelly, D.A. Wagner, J.S. Lightly, A.F. Sarofim, G. Palmer (2004). Phase and Size Distribution of Polycyclic Aromatic Hydrocarbons in Diesel and Gasoline Vehicle Emissions. Environ. Sci. Technol. 38, 2557-2567.

Investigation of Real Car Exhaust in Environmental Simulation Chambers: Results from the INFORMATEX and DIFUSO Projects Peter Wiesen Bergische Universität Wuppertal, Phys. Chemie / Fachbereich C, D-42097 Wuppertal, Germany Key Words: Car Exhaust, Diesel, Gasoline, Modelling, Ozone, Particles, Photoreactors

Introduction Emissions from the combustion of fossil fuels, especially road traffic emissions, are major contributors to air pollution. Though exhaust-cleaning techniques for vehicles have been significantly improved during the last years and the averaged fuel consumption per single vehicle has significantly decreased, the contribution of road traffic emissions to tropospheric photosmog formation is still high, due to the increasing total number of vehicles. For the future, an increase in the number of diesel engines is anticipated. Since this engine type consumes less fuel than a comparable gasoline engine, the replacement of gasoline-powered vehicles by diesel-fuelled cars would reduce CO2 emissions and therefore global warming and save natural resources. In contrast, possible negative influences of the relatively high number of particles emitted by diesel-powered vehicles in comparison to gasoline-fuelled cars on tropospheric chemistry is a matter of grave health and environmental concern. At present, the effect fuel composition on the related change of a long-term exchange of the fuel type from gasoline to diesel on air quality is not clear. It is well known that gasoline exhaust is characterised by relatively high concentrations of volatile organic compounds (VOC) and low NOx concentrations, whereas the VOC/NOx ratio of diesel exhaust is extremely low, due to very low concentrations of unburned fuel (Marshall and Owen, 1995, Balek et al., 1997). An effective replacement of gasoline by diesel as the major fuel used in road traffic might therefore significantly influence the photochemistry of the troposphere, e.g. ozone formation. Atmospheric simulation chambers offer the unique possibility for studying the impact of real car exhaust under almost real-world conditions on tropospheric photosmog formation. Within two EC projects, namely INFORMATEX (Becker, 1998) and DIFUSO (Wiesen, 2000) the ozone formation generated by the photooxidation of the exhaust of a gasoline- and diesel-powered engine has been investigated for different fuel formulations. The findings of these projects are summarised in the present paper with focus on the DIFUSO project. More detailed information can be found in recent papers by Geiger et al. (2002 and 2003). Eperimental The experiments presented here were carried out in the outdoor simulation chamber EUPHORE in Valencia, Spain. This facility and the analytical equipment used for the measurement of selected trace gases are described in detail by Becker (1996) as also Barnes and Wenger (1998). 285 I. Barnes and K. J. Rudzinski (eds.), Environmental Simulation Chambers: Application to Atmospheric Chemical Processes, 285–294. © 2006 Springer. Printed in the Netherlands.

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Within the measurement campaign, several smog experiments were carried out. Two reference experiments (base mixture I and II) were focused on a VOC "only" mixture containing n-butane, ethene and toluene in the presence of NO, representing the polluted troposphere. Both experiments differed in the initial NO/NO2 ratio, while the total amount of initial NOx was more or less similar (about 200 ppb). For each of the 5 diesel fuels investigated, a smog experiment was performed, where diesel exhaust was injected into the chamber up to a constant NOx level. After exhaust injection, about 1 ppm of the VOC mixture was added and the chamber was opened for irradiation. Diesel exhaust was generated by a diesel engine (1.8 l, 44kW) mounted on a test bed including an eddy current brake. For all smog chamber runs, similar test cycle conditions were used (see Wiesen (2000) for details). Five diesel fuels with different formulations were tested, a commercial diesel (“standard” diesel) available at European gas stations, biodiesel (rape oil methyl ester) and three sulphur-reduced diesel fuels containing defined amounts of aromatic hydrocarbons (see Table 1). Table 1.

Contents of aromatic hydrocarbons and sulphur for the 5 Diesel fuels used in the present study (Wiesen, 2000).

Fuel

Aromatic HC (weight%)

Sulphur (weight%)

29.3

0.0425

0

0.0030

3 (< 5% aromatic HC)

4.3

0.0043


14.2

0.0045


24.4

0.0046

1 (standard Diesel) 2 (Biodiesel)

Detailed information about the analytical equipment applied is given in Wiesen (2000). All studies were performed at atmospheric pressure. A dilution factor was obtained from the decay of inert SF6, added to the reaction mixtures as a chamber leak dilution tracer. Computer simulations The chemical simulations of the smog systems were performed using a simple chemical box model based on the Regional Atmospheric Chemistry Mechanism (RACM) by Stockwell et al. (1997). This condensed reaction scheme includes a fairly complete set of reactions for inorganic chemistry. Organic species are aggregated according to their chemical structure and reactivity into 32 stable organic species and 24 organic intermediates, except methane, ethane, ethene and isoprene, whose chemistry is treated explicitly. In total, the mechanism comprises of 237 reactions including 23 photochemical reactions. Each experiment was modelled using the box model described below, except that for diesel fuel no. 5. All computer simulations and sensitivity analyses were carried out using the box model SBOX (Seefeld, 1997, Seefeld and Stockwell 1999). This FORTRAN program incorporating the Gear algorithm (Gear, 1971) was operated on an SGI OCTANE workstation (Silicon Graphics) running under IRIX 6.5. The program uses the public domain library VODE (Brown et al., 1989) to integrate the ordinary differential equations.

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From the measured spectral radiant meter data, photolysis frequencies, j, were calculated for several species (Wiesen, 2000). Since the box model SBOX requires photolysis frequencies in a fixed table format, the j values obtained from the radiant meter data were transformed into a suitable matrix. For the calculation of the photolysis frequencies of the 9 photosensitive “lumped” species of the RACM scheme, the program “photoRACM” (Seefeld, 1997, Seefeld and Stockwell 1999) was used. This program generates photolysis frequencies according to Madronich (1987). Since the experiments were carried out using simple VOC mixtures containing only nbutane, ethene and toluene, a few modifications of the original RACM code were necessary for better performance of the calculations. n-Butane is grouped in RACM into the surrogate species HC3, which represents the class of “low” reactive alkanes, whereas toluene is grouped into the aromatic class TOL, indicating aromatic compounds with OH reactivities equal or lower than toluene. For the present calculations, the rate coefficients for the reactions of OH radicals with HC3 (2.20 u 10-12 cm3 s-1) and TOL (5.96 u 10-12 cm3 s-1) were replaced by the explicit literature values for OH + n-butane (2.2 u 10-12 cm3 s-1 (Atkinson, 1994)) and toluene (6.6 u 10-12 cm3 s-1 (Becker, 1994)), respectively. No modifications were necessary with respect to ethene, since this hydrocarbon is explicitly treated in RACM. Results and discussion General observations The diesel exhaust added to the chamber in each experiment mainly contained CO, NOx, HCHO and higher aldehydes, SO2 and soot. The fraction of hydrocarbons, e.g. from unburned fuel, was negligible (Wiesen et al., 2000). In all experiments performed, significant formation of ozone was observed. Table 2 compares for all runs both the ozone formation rates and the values for d([O3]-[NO])/dt, which provides a measure for the ozone formation potential, derived from the experimental data 2 h after opening the chamber. Both rates are significantly smaller for the base mixture experiments than for the exhaust runs. Table 2. Comparison of d[O 3]/dt and d([O 3]-[NO])/dt derived from the experimental data 2 h after opening of the smog chamber. experiment Base Mixture I Base Mixture II Standard Diesel (fuel 1) Biodiesel (fuel 2) Diesel containing 5% Aromatic HC (fuel 3) Diesel containing 15% Aromatic HC (fuel 4) Diesel containing 25% Aromatic HC (fuel 5)

d[O3]/dt (ppb h-1) 6.2 13.1 66.9 82.7 48.8 52.8 46.0

d([O3]-[NO])/dt (ppb h-1) 48.5 46.2 116.6 106.9 108.2 58.1 74.3

The mean OH concentration, which can be estimated from the experimental 6 -3 hydrocarbon degradation, was in the range (1 –3) u 10 cm for all chamber runs performed. All exhaust/VOC studies have been compared to the base mixture I experiment, since they were carried out at an initial NO/NO2 ratio very similar to the first reference run. The ozone

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formation rates for all other runs with diesel exhaust added were in the range 46 – 83 ppb h -1, which is a factor of about 7 –13 higher than observed in the base mixture I experiment. Due to significant deviations in the initial conditions of each experiment, such as concentrations of NO, NO2, aldehydes, etc. as well as different photolytic parameters caused by the weather conditions, a direct interpretation of the ozone data was not possible. Therefore, in order to analyse the data the smog chamber experiments were simulated using the chemical box model described above. At first it was checked whether the differences between the reference system and the exhaust system could generally account for the significant increase in ozone formation observed for the exhaust/VOC experiments. The exhaust runs were characterised by the presence of particles (soot) and relatively high initial concentrations of nitrous acid, formaldehyde and higher aldehydes. It is expected that the initial concentrations of HONO and aldehydes lead to higher ozone concentrations in the exhaust experiments, due to fast photolysis and generation of radicals. In order to check this possibility, a series of simulations with the initial concentrations of base mixture I plus several initial concentrations of nitrous acid or formaldehyde was carried out and the peak ozone concentration was calculated. The results exhibit a strong increase of peak ozone with increasing initial concentrations of HONO or HCHO, which supports the expectation that the strong ozone formation in the exhaust/VOC experiments is due to photolysis of initial nitrous acid and formaldehyde. This is also confirmed by modelling the ozone profiles of the exhaust experiments. As an example, Figure 1 illustrates the experimental ozone concentration for the standard diesel run together with calculated data.

Figure 1.

Experimental () and simulated ozone profiles for different initial concentrations of nitrous acid and formaldehyde for the smog chamber run using fuel 1.

For either [HONO]0 = 0 or [HCHO]0 = 0, the calculations yield significantly lower ozone concentrations than measured. If both initial values are set to zero, the ozone formation is decreased by a factor of about 10.


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Chemical modelling of the experiments For all runs modelled, a systematic overestimation of NO2 by the model was observed, even when the calculated concentrations of other species were excellently fitted to the measured data. The disparity occurred only for reaction times t 2 hours and further increased with increasing time. Since the measured NO2 data were corrected with respect to PAN and HNO3 interferences (Wiesen, 2000), this observation must be explained by a general lack of mechanistic information about the tropospheric degradation of toluene. It is well known that the OH-initiated degradation of aromatic hydrocarbons in smog chambers leads to a significant loss of NOx in the reaction system (see e.g. Calvert et al., 2000), which at present cannot be explained by current chemical models. Also the RACM mechanism used for the present investigations does not account for this NOx loss. Accordingly, the simulation of a reaction system including significant amounts of toluene must lead to an overestimation of NOx, as observed in each calculation performed in the present study. In the following sections the results of the chemical modelling of selected smog chamber runs are presented. Base mixture I Figure 2 illustrates the comparison of experimental and calculated concentration-time profiles for VOC, HCHO, NO, NO2 and ozone for the experiment performed with the base VOC mixture in the presence of NOx (NO/NO2 ratio = 8.8). All data (except NO2, see above) are in excellent agreement within the experimental errors, which are in the range of ±5% – ±15% for the different species. The good modelling results indicate that the RACM mechanism describes the system with sufficient accuracy.

Figure 2.

Comparison of simulated () and experimental concentrations of (left hand side) n-butane (●), ethene (), toluene u 3 (),and (right hand side) NO (●), NO 2 (), ozone (c) and formaldehyde (▲) for the smog chamber run with base mixture I.

Standard diesel (fuel 1) Figure 3 shows a comparison of experimental and calculated concentration-time profiles for NO, NO2 and ozone for the experiment performed with exhaust from the standard diesel fuel together with the base VOC mixture in the presence of NOx. Only the initial formaldehyde concentration was measured. Time-resolved data for HCHO were not available

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for this run. Calculated and experimental concentration-time profiles are in good agreement and the system is well described by the model.

Figure 3.

Comparison of simulated () and experimental concentrations of NO (), NO2 () and ozone (c) for the smog chamber run with fuel 1.

Biodiesel (fuel 2) Figure 4 shows a comparison of experimental and calculated concentration-time profiles for HCHO, NO, NO2 and ozone for the experiment performed with exhaust from the biodiesel fuel together with the base VOC mixture in the presence of NOx. The concentration of formaldehyde is slightly underestimated by the model for reaction times after 13:00 GMT. However, this deviation reaches only a few ppb and is within the experimental error of the HCHO concentration (typically ± 20%). In total, the calculated and experimental concentration-time profiles are in good agreement. From Table 2 it is evident that the ozone formation rate of 82.7 ppb h-1 in the biodiesel experiment is the highest value of all runs. It should be pointed out that this is not specific for the combustion of biodiesel. The observation of Palm and Krüger (1998, 1999) that the combustion of biodiesel leads to higher formaldehyde emissions than the burning of a conventional diesel was not confirmed within the DIFUSO project (Wiesen 2000). The formaldehyde concentrations measured in the biodiesel exhaust were not higher than for all other diesel fuels tested. Accordingly, the high ozone formation observed in the biodiesel experiment from Nov. 18, 1999 was due to the experimental conditions. The photolysis intensity here was the highest of all the days of the campaign and the NO/NO2 ratio is the smallest of all the exhaust experiments performed. Both factors promote ozone formation in the system and are obviously the reason for the remarkably high ozone formation observed.


Figure 4.

291

Comparison of simulated () and experimental concentrations of NO (), NO2 () ozone (E) and formaldehyde (c) for the smog chamber run with fuel 2.

Sensitivity analysis with respect to ozone formation In order to identify the most important steps in the initial phase of the smog chamber runs leading to ozone formation and for further interpretation of the results, sensitivity analyses were carried out using the direct decoupled method of Dunker (1984). The sensitivities of ozone towards all rate coefficients of the chemical mechanism were calculated. For that purpose, rate parameter sensitivity coefficients, SK, were calculated as described by Stockwell et al. (1995). These rate parameter sensitivity coefficients depend on the concentrations of all reactants and, therefore, on reaction time. Thus time-dependent relative sensitivities can be calculated from the SK values. Figure 5 shows the relative sensitivities at t = 30 min (representing the initial phase of each experiment) of ozone towards selected reaction rate coefficients. These 9 reactions are the most sensitive for ozone formation and account for • 90% of the total sensitivity in the initial phase of each run. A positive sensitivity indicates that an increase of the rate coefficient will cause an increase of the ozone concentration, while increasing the rate constants with a negative sensitivity will lead to a smaller concentration of ozone. The plot illustrates the typical situation for a smog system: The photolysis of NO2 is the most important reaction leading to ozone formation, whereas the reaction of O3 with NO is the most significant sink for ozone in the system. Figure 5 clearly indicates that compared to the base mixture I experiment the formation of ozone in the exhaust studies is significantly promoted by the photolysis of the initial concentrations of nitrous acid and formaldehyde. For all diesel experiments, the relative sensitivities for these reactions are about a factor of 2 higher, whereas the importance of the NO2 photolysis and the reaction O3 + NO is lowered by a factor of about 2. The photolysis of higher aldehydes is of minor importance with respect to ozone formation.

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It is remarkable that for all the reactions displayed in Figure 5, the corresponding sensitivities for the diesel exhaust runs are more or less equal, demonstrating that the different but significant higher ozone formation rates observed in comparison to the reference experiment are not specific for the diesel fuel formulation. They are clearly the result of more or less different initial parameters such as start concentrations or photolysis frequencies during the single experiments.

Figure 5.

Relative sensitivities of ozone towards the rate coefficients of selected elementary reactions of the chemical mechanism used at t = 30 min. The results for all diesel exhaust experiments are shown in comparison with those for the reference experiment with base mixture I. DCB = unsaturated dicarbonyls. For the calculation of the total fraction for the other reactions, the signs of the single sensitivities were not considered.

Summary and conclusions It has been demonstrated that atmospheric simulation chambers offer the unique possibility for studying the impact of real car exhaust under almost real-world conditions on tropospheric photosmog formation. The experiments performed in the EUPHORE smog chamber were simulated using a simple box model, including gas-phase chemistry only. The model described all experiments with high accuracy. Sensitivity analyses were carried out in order to explain the observations. The addition of diesel exhaust to a well-defined simple VOC mixture caused a significant increase of the ozone formation after irradiation, in comparison to smog experiments with a similar VOC/NOx ratio in the absence of exhaust gas. The increase of


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ozone observed in the exhaust runs was mainly caused by the high initial concentrations of nitrous acid and formaldehyde emitted by the diesel engine. Higher aldehydes were of minor importance. The ozone formation was not dependent on the formulation of the diesel fuel. Differences in ozone formation rates for the single experiments were due to deviations in initial start concentrations as well as photolysis conditions. Further studies within the DIFUSO project studies exhibited that the influence of diesel soot on the ozone formation is negligible under the conditions of the smog chamber experiments performed. The present simulations using a simple gas-phase model leading to good agreement of experimental and calculated data confirmed this observation. For the future, detailed measurements of NOx, HONO and aldehydes in diesel exhaust for typical motor conditions should be considered. The use of such data as input parameters for the calculation of ozone formation potentials (e.g. incremental reactivities by the method of Carter et al. 1995) can contribute to a better estimation of the influence of diesel exhaust on tropospheric ozone formation. Acknowledgements Financial Support of this work by the European Commission, contracts N° ENV4CT95-0015 (INFORMATEX) and N° EV4V-CT97-0390 (DIFUSO), is gratefully acknowledged. The authors are deeply indebted to K. Wirtz, CEAM, Valencia (Spain), for kindly providing the experimental data, which were used for the model calculations performed in this study. References Atkinson, R.; Gas-phase tropospheric chemistry of organic compounds, J. Phys. Chem. Ref. Data, Monograph No. 2. (1994). Balek, S., R. Heck and S. Roth, S. (eds.).; Diesel engine combustion processes and emission control technologies, Society of Automotive Engineers, Inc., SAE Paper SP-1246, ISBN 1-56091-958-2, Warrendale (1997). Barnes, I. and J. Wenger (eds.); EUPHORE Report 1997, University of Wuppertal, Wuppertal (1998). Becker, K.H. (ed.); Influence of fuel formulation on atmospheric reactivity of exhaust gases (INFORMATEX), final report of the EC project, contract N° ENV4-CT95-0015, Wuppertal (1998) (see also: http://www.physchem.uni-wuppertal.de/PC-WWW_Site/Publications/Publications.html). Becker, K.H. (ed.); The European photoreactor EUPHORE, Final report of the EC project, contract N° EV5VCT92-0059, Wuppertal (1996) (see also: http://www.physchem.uni-wuppertal.de/PCWWW_Site/Publications/Publications.html). Becker, K.H.; The atmospheric oxidation of aromatic hydrocarbons and its impact on photooxidant chemistry, in: Borrell, P.M., P. Borrell, C. Cvitas, W. Seiler, Proc. EUROTRAC Symp. ’94, SPB Academic Publ., The Hague (1994) 67-74. Brown, P.N., G.D. Byrne andA.C. Hindmarsh; VODE: A variable-coefficient ODE solver, Journal of Science, Statistics and Computers 20 (1989) 1038-1051. Calvert, J., R. Atkinson, K.H. Becker, R.M. Kamens, J.H. Seinfeld, T.J. Wallington and G. Yarwood; Mechanisms of atmospheric oxidation of aromatic hydrocarbons, Oxford University Press, Oxford (2000). Dunker, A.; The decoupled direct method for calculating sensitivity coefficients in chemical kinetics, J. Chem. Phys. 81 (1984) 2385-2393. Gear, C.W.; Numerical initial value problems in ordinary differential equations, Prentice-Hall series in automatic computation, Vol. 17, Prentice-Hall, Englewood Cliffs (1971). Geiger, H., J. Kleffmann and P. Wiesen; Smog Chamber Studies on the Influence of Diesel Exhaust on Photosmog Formation, Atmos. Environ. 36 (2002) 1737 –1747. Geiger, H., K.H. Becker and P. Wiesen; Effect of Gasoline Formulation on the Formation of Photosmog: A Box Model Study, J. Air & Waste Manag. Assoc. 53 (2003) 425 –433.

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Madronich, S.; Photodissociation in the atmosphere: 1. Actinic flux and the effects of ground reflections and clouds. J. Geophys. Res. 92 (1987) 9740-9752. Marshall, E.L. and K. Owen (eds.); Motor gasoline, Critical reviews on applied chemistry, Vol. 34, The Royal Society of Chemistry, Cambridge (1995). Palm, W.U. and H.U. Krüger; Comparison of ozone formation from diesel exhaust and rapeoil-methylester (RME): First results of smog chamber experiments, in: Borrell, P.M., P. Borrell, Proceedings of the EUROTRAC-2 Sympposium ’98, WIT Press, Southamptom (1999) 199-204. Palm, W.U. and H.U. Krüger (eds.); Experimentelle Untersuchungen des Ozonbildungspotentials von Motorabgasen bei Verwendung von Dieselkraftstoff und Rapsölmethylester, final report of the project "Ozonbildungspotential", sub-project 2, contract N° 95NR126-F, Fraunhofer Institute for Toxicology and Aerosol Research, Hannover (1998). Seefeld, S.; Laboratory kinetic and atmospheric modelling studies of the role of peroxyacyl nitrates in tropospheric photooxidant formation, Ph.D. thesis, Swiss Federal Institute of Technology, Zürich (1997) Seefeld, S. and W.R. Stockwell; First-order sensitivity analysis of models with time-dependent parameters: An application to PAN and ozone, Atmos. Environ. 33 (1999) 2941-2953. Stockwell, W.R., F. Kirchner, M. Kuhn and S. Seefeld; A new mechanism for regional atmospheric chemistry modelling, J. Geophys. Res. 102 (1997) 25847-25879. Stockwell, W.R., J.B. Milford, D. Gao and Y.J. Yang; The effect of acetyl peroxy-peroxy radical reactions on peroxyacetyl nitrate and ozone concentrations, Atmos. Environ. 29 (1995) 1591-1599. Wiesen, P. (ed.); Diesel fuel and soot: Fuel formulation and its atmospheric applications (DIFUSO), final report of the EC project, contract N° EV4V-CT97-0390, Wuppertal (2000) (see also: http://www.physchem.uni-wuppertal.de/PC-WWW_Site/Publications/Publications.html).

The EUROCHAMP Integrated Infrastructure Initiative Peter Wiesen Bergische Universität Wuppertal, Phys. Chemie / Fachbereich C, D-42097 Wuppertal, Germany Key Words: Atmospheric processes, Infrastructure, Environmental chambers

Introduction The ability of Europe’s research teams to remain at the forefront of all fields of science and technology depends on their being supported by state-of-the-art infrastructures. The term “research infrastructures” refers to facilities and resources that provide essential services to the research community in both academic and/or industrial domains. In this context the European Commission in Brussels is supporting research infrastructures in the framework 6 specific programme on structuring the European research area. The overall objective of this activity is to promote the development of a fabric of research infrastructures of the highest quality and performance in Europe, and their optimum use on a European scale based on the needs expressed by the research community. Specifically this will aim at: – ensuring that European researchers may have access to the infrastructures they require to conduct their research, irrespective of the location of the infrastructure; – providing support for a European approach for the development of new research infrastructures, also at the regional and transregional level, and for the operation and enhancement of existing infrastructures, including where appropriate facilities of worldwide relevance not existing in Europe. Five schemes for support are available under the Research Infrastructures action: 1. 2. 3. 4. 5.

Transnational Access, Integrating Activities, Communication Network Development, Design Studies, and Construction of New Infrastructures.

The objective of the Integrating Activities scheme is to support the integrated provision of infrastructure related services to the research community at a European level. It is also intended to have a structuring effect on the fabric of European research by promoting the coherent use and development of infrastructures in the fields it covers. To that end, the main characteristic of Integrating Activities will be their capacity to mobilise a large number of stakeholders in a given class of infrastructure. The ambition of such Integrating Activity should be to induce a long-term integrating effect on the way research infrastructures operate, evolve and interact with similar infrastructures and with their users, thereby contributing to structure the European Research Area: x Operators of similar infrastructures in a given class should for instance find it easier, through an Integrating Activity, to develop synergies and complementary capabilities in such a way as to offer an improved access to researchers. 295 I. Barnes and K. J. Rudzinski (eds.), Environmental Simulation Chambers: Application to Atmospheric Chemical Processes, 295–299. © 2006 Springer. Printed in the Netherlands.

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x Likewise, infrastructure operators and users should be in a better position to tackle new or unexpected developments in their field, for instance in relation to state-of-the-art instrumentation, with a more co-ordinated approach. x More generally, a closer interaction between a large number of scientists active in and around a number of infrastructures will facilitate cross-disciplinary fertilisations and a wider sharing of knowledge and related technologies across fields and between academia and industry. This scheme is to be implemented primarily through so-called Integrated Infrastructure Initiatives such as the new EUROCHAMP project, which is presented here. The project The EUROCHAMP project integrates the most important environmental reaction chambers in Europe for studying atmospheric processes into a Europe-wide infrastructure. These facilities were created by multinational initiatives to study the impact of atmospheric processes on regional photochemistry, global change, as well as cultural heritage and human health effects under most realistic conditions. Although initial advances in the application of large chambers occurred in the United States, Europe now leads the world in the use of large, highly instrumented chambers for atmospheric model development and evaluation. Smaller chambers that were designed for specific purposes and are operated by experts in their fields excellently support such chambers. The integration of all these environmental chamber facilities within the framework of the EUROCHAMP infrastructure promotes retention of Europe's international position of excellence in this area and is unique in its kind worldwide. The mobilisation of a large number of stakeholders dealing with environmental chamber techniques provides an infrastructure to the research community at a European level that offers a maximum support for a broad community of researchers from different disciplines. The EUROCHAMP project initiates a currently not existing structuring effect of atmospheric chemistry activities performed in European environmental chambers, since it offers the full availability of corresponding facilities for the whole European scientific community. The consortium of partners, which is described below, provides their expertise and experience in atmospheric chemistry to researchers of different disciplines, policy and industry and offers an infrastructure that can be used by interested parties for solving a large variety of problems related to atmospheric science. Grid of partners and associated user groups Besides the 12 partner institutions, a number of selected associated user groups with a high grade of expertise in the different fields of interest provide their experience either as advisers to special topics or as potential users of the infrastructure. The partners and associates institutions are widely distributed over Europe. Two associated user groups are located in the United States of America. Figure 1 shows a map in which the locations of each participant are shown.

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Figure 1.

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Institute locations of the partners and associated user groups of the EUROCHAMP infrastructure. For explanation of the abbreviations please refer to http://www.eurochamp.org.

EUROCHAMP objectives and activities Three networking activities and two joint research activities are formulated and crosslinked in the EUROCHAMP project. Networking activities The major objective of the networking activities within the EUROCAHMP project is the initiation of an effective interdisciplinary collaboration between the community of

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atmospheric scientists and colleagues from other disciplines that are closely related to it. This will be achieved through the three networking activities of EUROCHAMP. Networking activity N1 The objective of networking activity N1 is the generation and application of standardised rules as a method of quality assurance for raw data analyses of the experiments in each facility. For this purpose a number of inter-comparison studies applying analytical devices in reference experiments will be carried in the different chambers, which provides an indirect measure of the infrastructures' excellence. Networking activity N2 In order to make the results of experiments performed in the partners’ facilities most transparent and accessible to the scientific community, a standardised data protocol for chamber studies will be defined. This standardised form will be the basis for the central database of environmental chamber studies to be constructed within the project. This WWWbased database will be made accessible to the whole scientific community, leading to a very effective dissemination of the results. Networking activity N3 Within networking activity N3 four larger international conferences/workshops on infrastructure-related topics will be organised. In order to reach a maximum of success, internationally established experts on the corresponding topics will be invited to join these conferences. The results will be published in suitable proceedings for dissemination to the scientific community. Joint research activities The major objective of the joint research activities within the EUROCHAMP project is the optimisation and further development of the infrastructures' performance. In order to meet these goals, two corresponding research activities are defined in the EUROCHAMP work programme, namely the development and refinement of analytical equipment and the development of chemical modelling techniques. Joint research activity JRA1 The development of novel and the refinement of existing analytical devices of environmental chambers in order to successfully detect atmospheric trace species or to characterise aerosol particles is an essential task to be followed over the whole lifetime of the EUROCHAMP research facilities. The increasing demands for more comprehensive analytical techniques caused by the more and more complex scientific questions to be answered, requires a continuous improvement of the technical possibilities of a chamber. Accordingly, the project includes a number of research activities focused on this topic: x characterisation of oxygenated volatile organic compounds (OVOCs), x radical measurements (OH, HO2, RO2), x nitric acid measurements, x characterisation of aerosols. Besides the optimisation of existing devices, a number of analytical devices will be completely newly designed and introduced for the first time in an environmental chamber. The highly specific equipment will be developed in a mobile form, so that such instruments may be transported to a chamber of choice and used in selected experiments independent of

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localisation. This philosophy strengthens the idea of a real grid of environmental chambers forming a powerful infrastructure. In addition, the instruments to be developed will be of great use for future field campaigns for which sophisticated, improved analytical instrumentation is urgently required. Joint research activity JRA2 The field of chemical modelling is directly coupled to each type of environmental chamber studies. The analysis of chamber experiments without any model application is mostly not possible. Accordingly, model activities are urgently necessary and a permanent companion of each experimental task. 1. Since the quality of simulation studies strongly depends on the question how exactly the chemical behaviour of the chamber itself is characterised, sensitive parameters urgently st required for simulations have to be determined for each facility of the infrastructure (1 objective). The dissemination of each result from such studies serves for a better interpretability of environmental chamber studies as a whole. 2.

The second objective for model applications is the test of complex chemical mechanisms used for multi-phase model applications related to chamber experiments. An established chemical code for interpretation of chamber studies that can be applied to all facilities increases the quality of the whole infrastructure and offers new possibilities for solving open questions of interest for the European researchers’ community.

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Furthermore, chemical models to be developed can be applied in the EUROCHAMP network for the solution of specific problems in atmospheric chemistry, e.g. development and validation of degradation mechanisms of organic pollutants that are of paramount importance, the investigation of atmospheric reactivity as an overall property under various conditions or the influence of alternative fuels or solvents as well as bio rd fuels on tropospheric chemistry (3 objective).

In conclusion, the EUROCHAMP project strengthens the idea of a real grid of environmental chambers as powerful tool for system analysis increasing the value of the whole chambers infrastructure for the European research community. Detailed information, e.g. description of the partner institution, the available environmental chambers and their analytical equipment, events such as meetings and workshops etc. can be found under http://www.eurochamp.org.

Survey on Atmospheric Chemistry Research in Some New EU Member States and Candidate Countries Ekaterina Batchvarova, Tatiana Spassova, Nedialko Valkov, and Liliana Iordanova National Institute of Meteorology and Hydrology, Blvd Tzarigradsko Chaussee No. 66, 1784 Sofia, Bulgaria [email protected] Key Words: Atmospheric chemistry, Air quality monitoring, Air pollution modelling, Atmospheric aerosol, Ozone

Introduction Historically, some of the new EU Member States and the Candidate Countries have experienced high levels of pollution in the past. Enhanced management measures were and are needed to improve their air quality. A survey was recently conducted (Batchvarova et al., 2005) to list the current research activities on atmospheric chemistry in these counties, as well as the groups and institutions involved in it. Air chemistry is an essential element of air quality, climate change modelling, industrial energy planning, and health risk assessments. Atmospheric chemistry research is also related to air quality monitoring. Therefore, the survey has also retrieved information on air quality monitoring networks and their management of those countries involved. Some information on air pollution modelling research is also discussed. The ongoing research (field, laboratory and modelling) in the field of chemical transformation of trace compounds in the atmosphere is discussed here and parallels are drawn among 10 of the new EU Member States and Candidate Countries, namely Bulgaria, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania, the Slovak Republic and Slovenia. Laboratory studies traditionally lay emphasis on rate and equilibrium processes. Field studies are based on aircraft and surface measurements of reaction chemistry, advective influences on the chemical composition of the atmosphere, and air-surface exchange processes. Both field and laboratory experimental studies on atmospheric chemistry are very demanding on equipment and resources. Therefore, most of the funding for these studies is coming from international projects (EC, ESF, NATO, etc.). Modelling efforts address both chemistry and dynamics on regional and global scales. The analysis of research activities in these fields is made with regard to current EU (European Union) practice and the historical frameworks in the ten countries of interest. The unique traditions and achievements in atmospheric chemistry research in these countries are highlighted. The participation of research teams in different projects and initiatives over the last 5-10 years of integration of these countries within the European Framework Programmes is surveyed. Since the 1990s, a number of surveys on environmental quality and management were prepared as part of different PHARE missions and tasks, as part of the European Environmental Agency (EEA) activities and as pre-accession twinning projects under the Twinning Programme of the EC (European Commission). Yet, the research activities within the 10 countries were not discussed. Through the FP4, FP5 and FP6 (Framework Programmes) of the EC the research communities of these countries had the possibility to participate in European-wide scientific projects. There were collaborative achievements, but much less than expected and desired as pointed out in analyzes of the FP4 and FP5 results. The investigations on air pollution modelling


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and the atmospheric chemistry are closely connected to environmental management, but did not get special attention from national funding. The present survey places emphasises on the atmospheric chemistry research in the 10 countries named above. It also describes the air quality monitoring systems and air pollution modelling studies in these countries. The aim is to gather information and make it available in condensed form in order to facilitate collaboration with other nations and also strengthen the research within the countries. Research on atmospheric chemistry is not an essential part of the overall chemical research in almost all of the 10 countries. Only a few groups from the Czech Republic, Poland, Estonia, Slovenia, Latvia, Lithuania and Hungary are dealing with aerosol studies and chemical processes in the atmosphere. The rest of the chemical research is in other fields and only partly concerns the atmosphere. The survey is structured in detailed discussions arranged by country and topics. Most abbreviations are introduced and explained in the text. The parallels, analysis and synthesis of the information are given separately. Air quality monitoring was started in all 10 countries (Bulgaria, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania, the Slovak Republic and Slovenia) in the 1950s. Initially, the radioactivity in the air and dry and wet fallout were considered. The task was given to Atomic Agencies, Institutes of Hygiene and Meteorological services to organize monitoring networks. In the 1970s chemical air pollution monitoring was started as well. Typically, the Hygiene Institutions belong to Ministries of Health and the Meteorological services are attached to different structures. For decades the monitoring networks were developed separately in the different institutions with some differences in observation programmes that reflect the different scopes of their activities and objectives. The meteorological services have a climatological and synoptic monitoring approach, while the hygiene institutes are interested in non-regular sampling for air quality in residential and industrial areas. During the late 1970s state agencies (committees) were established to deal with the environmental protection by controlling industrial emissions. Gradually, in some countries these agencies also developed air quality monitoring networks and were authorized to gather all the information and issue Bulletins (monthly, quarterly or yearly). The atmospheric chemistry research, such as development of sampling and analysis methods, was concentrated in the air pollution monitoring laboratories. Chemical research in a broader sense was concentrated in the chemical institutes in the Academies of Sciences and in universities. Typically, very limited communication and collaboration among the different institutes was established. The reason was probably that the financing system of research was separate for the different institutions. Most of the common activities were due to personal contacts between scientists. The economical and political changes in all these countries since 1989-1990 have lead to transformation of their air quality monitoring networks in different ways. Finally, as all countries join the European Union, the result in terms of air quality monitoring principles is and will be very similar. The organization of science has also changed differently. In Bulgaria, Romania, Poland, Hungary and the Czech Republic the Academies of Sciences were retained but reorganized. In Estonia, Latvia, Lithuania, Slovenia and the Slovak Republic, the situation was different due to their former associations with a larger system and also to the size of the countries and population.

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The parallels that can be drawn among the countries are to be found in the historical development of all the 10 countries during the last 50 years. Future requirements will be harmonized being based on the European Union environmental legislation and also on the wide international collaborations necessary in the field. Overview of Air Pollution Monitoring, Modelling and Atmospheric Chemistry Research by Country The surveys by country include an overview of Air quality monitoring, Atmospheric Chemistry research and Air pollution modelling. For all topics, Institutions and groups involved, Historical aspects, Current projects and studies performed in the last 5 years, National strategies, Achievements, and Publications are discussed. An analysis of problems and the identification of needs is made collectively for all the countries. Bulgaria Ambient Air Quality Monitoring Network Air quality monitoring in Bulgaria started in 1975 (Parvanova, 2002) and was performed by the Institute of Hygiene at the Ministry of Health, the National Institute of Meteorology and Hydrology (NIMH) at the Bulgarian Academy of Sciences and the newly established, at that time, Committee on Environmental issues at the Government. The ambient air radioactivity measurements started at NIMH in the 1950s. In the 1970s significant transformations and changes were made in the institutional structure of the monitoring system. Along with the need for emissions’ control a governmental body was needed information wise, although the environmental information was not publicly available. After 1995 the network was supplied with sophisticated sampling and laboratory equipment through the EC PHARE programme, all concentrated at the Ministry of Environment and Waters (MEW). The air quality monitoring and the emission inventory are financially guaranteed mainly by the state budget and partially by the National Fund at MEW. Because of economic difficulties, the allocated finances from the budget for air quality monitoring are limited, which has resulted in a decrease in the number of manual stations since 1995. The lack of funding is more severe at institutions outside the MEW, like NIMH. A database information system was started in January 1986. Monthly averaged data had been received from the institutions, responsible for the monitoring. At NIMH the data are available in electronic format since 1982 and they are a part of the WMO Green House Gases Database in Tokyo, Japan. Presently, the air quality data management is the responsibility of the EAE (Executive Agency on Environment). There, a new database was created in 1991. Input data are collected from the Regional Environmental Inspectorates (REIs), EAE, NIMH and the Hygienic Inspections. The network consists of 68 stationary stations - 16 automated (on-line) and 52 with manual sampling and chemical analysis, as well as 6 mobile automated stations. The stations are located in 37 settlements spread over the country - urban, residential, high traffic and industrial areas. All the manual stations operate in a unified sampling regime and standardized analytical procedures in accordance with Bulgarian National Standard “Basic rules for air quality sampling”. The sampling frequency is 4 times per day, 5 days per week. The basic measured parameters are: TSP, Pb, aerosols, SO2, NO2, and H2S. In relation with specific industrial

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activities, additional pollutants are also measured, such as: NH3, phenol, arsenic aerosols, HCl, Cl2, HF and fluorides. There is one National Background Station that is part of the GEMS system of UNEP, WMO and UNESCO. It is located on Rojen mount, one of the highest mountain peaks in Bulgaria. The station works on a limited measurement programme due to a lack of governmental funding to equip it. Six OPSIS systems operating continuously are situated in the most affected industrial areas in the country. In addition another seven OPSIS systems are working in the Danube area, mainly in relation with trans-boundary air pollution between Bulgaria and Romania. The establishment of a network along the river Danube was partly financed by a PHARE project. In the air quality laboratories of EAE and REI chemical analyses are performed in accordance with standardized analytical methods. A Quality Handbook, which is periodically updated, is also available. Control of the measurement accuracy is performed (calibration curve settings, verification with standard samples prepared in the laboratory). Comparative assessment of the results of the chemical analyses from different measuring devices is performed. The laboratories of EAE are accredited by the Bulgarian Accreditation Body. Air quality data management is another responsibility of EAE. Raw and aggregated data are stored in local databases of all REIs. The data from REIs are sent to the national database at EAE. NIMH participates in the air quality network with 5 stations, where 24-hour data are gathered in connection with synoptic measurements and thus relevant 24-hour means are delivered to the WMO Data Base for greenhouse and reactive gases. The Air Quality Framework Directive (96/62/EC) provides a comprehensive strategy for the management of air quality in EC Member States linking controls on emissions with the attachment of the air quality objectives. This Directive is progressively taking effect as its daughter Directives are adopted and enter into force. It is transposed into Bulgarian legislation mainly through Regulation N7 on ambient air quality assessment and management. The Bulgarian air quality standard legislation is drafted with the aim of transposing forthcoming EU legislation. Regulation N9 on limit values for sulphur dioxide, nitrogen dioxide, particulate matter and lead in ambient air should fully transpose the first daughter Directive to the Air Quality Framework Directive. The air quality standards are well covered by Bulgarian Legislation, and no additional instruments are needed. It can be noted that some of the air quality standards before 1990 were stricter than those of the EC. Directive 92/72/EEC on tropospheric ozone pollution is also fully transposed into Bulgarian legislation. The main instrument is Regulation N8 on ambient air quality limit values for ozone. The Bulgarian requirements for the ozone-monitoring network comply well with the provisions of the Directive. Atmospheric Chemistry Research At the University of Chemical Technology and Metallurgy (UCTM), the Faculty of Ecology and environmental protection, among the issues for education and research are - the industrial waste utilization and natural resources and their protection monitoring. There is a close co-operation between the UCTM’s Scientific Research Centre and all Bulgarian scientific


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institutions, as well as with related Universities in Europe, Asia and America. UCTM takes an active part in nearly all European scientific programmes – ERASMUS, COPERNICUS, COST, 5th and 6th Framework Programmes, etc. The University of Plovdiv “Paisii Hilendarski”, Faculty of Chemistry is dealing with development and application of new analytical methods for environmental research. At the Sofia University “Sv. Kliment Ohridski”, Faculty of Chemistry, Department of Analytical Chemistry the group of Prof. Vasil D. Simeonov is performing research in analytical chemistry, chemometrics, environmetrics, multivariate calibration; classification, interpretation and modelling of environmental data sets; evaluation and optimization of analytical procedures; potentiometry with ion selective electrodes; atmospheric and marine chemistry. A very wide network of international collaboration is associated with the group. At the Bulgarian Academy of Sciences (BAS) there are a number of research institutes on chemistry. Among them the Institute of Physical Chemistry, the Institute of Catalysis, and the Institute of General and Inorganic Chemistry work on topics close to atmospheric chemistry, but no specific projects were recently undertaken in this field. Air Pollution Modelling and Other Topics Experienced teams of air pollution modellers are working at the National Institute of Meteorology and Hydrology (NIMH) and at the Geophysical Institute (GPhI). Both institutes belong to the Bulgarian Academy of Science. Several advanced national air pollution models, including 3D Eulerian local-to-regional model, are available. Additionally, the pre-processing possibilities are relatively good, e.g. a 3D hydrostatic prognostic model was implemented and a tradition in boundary-layer meteorology has been established. The most significant current project is BULAIR, an EU FP5 Project EVK2-CT-200280024 (BULAIR, 2002). Institutions involved are NIMH and GPhI. Specialists from other BAS institutes as well as experts from the Ministry of Environment and Waters, National Statistical Institute, etc. are involved as well. The scope and objectives of the project are the creation of a database - collection, evaluation and organization of data; Comprehensive review of existing modelling tools, choice of the most relevant for use in the project; Staff training; Increased networking and twinning activities with EU centres. The BULAIR project is the tool to bring the air pollution modelling studies, which started in the 1970s, to an up-to-date technology level. Also the concentration of efforts and collaboration of institutions within Bulgaria and in Europe are an important part of BULAIR. NIMH and GPhI participated in a number of other European projects starting with the EC FP4. MEDCAPHOT-TRACE (EV5V-CT93-0312) was a Mediterranean campaign of photochemical tracers – transport and chemical evolution, which was a comprehensive field experiment study in Athens in 1994. ETEX (The European Tracer Experiment) and RTMOD (the Real-Time Modelling) gathered the modelling efforts of a number of European groups. Scientists from NIMH are participating in the FP5 ENSEMBLE and MERLIN and the FP6 ACCENT and QANTIFY projects. A number of NATO Science for Peace scientific and linkage grants as well as extensive participation in COST 715 were also part of the activities. In urban boundary-layer meteorology a Swiss-Bulgarian bilateral Institutional partnership took place in 2001-2003.

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Czech Republic Ambient Air Quality Monitoring Network The main services that carry out air quality monitoring are the National Institute of Public Health (NIPH) and the Czech Hydrometeorological Institute (CHMI). In addition a number of companies and institutions contribute to the national network with a few stations each. The National Institute of Public Health, Department of Air Hygiene supports an Expert Group for Ambient Air Hygiene. The activities comprise the processing of expert opinions, health risk assessments, legislative activities, tuition, and consulting. In 2003, urban air pollution was monitored at 76 stations (44 and 32 operated by the Ministry of Health and the Ministry of the Environment, respectively) located in 27 cities involved in the Monitoring System (SZU, 2004). In 2003, sulphur dioxide (SO2), nitrogen oxides (NO/NO2/NOx), particulate matter (TSP and/or suspended PM10 fractions), and mass concentrations of selected metals (arsenic, chromium, cadmium, manganese, nickel and lead) in particulate matter samples were monitored in all the cities of the Monitoring System except for MČlník. The SO2 measurements in the Public Health Service network were terminated at all the manual stations in the cities with CHMI stations; in the cities without a CHMI station, measurements are made during the heating season only). Concentrations of carbon oxide, ozone, polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) continue to be monitored selectively in a number of the monitored cities. The Czech Hydrometeorological Institute (CHMI) takes care of the national ambient air monitoring system. The charter of CHMI was amended in June 1994 and in August 1995 pursuant to a decision adopted by the Minister of the Environment of the Czech Republic (MoE CR). The amendment defines the aim, object, and functions of the Institute. The Czech Hydrometeorological Institute is a central State institute of the Czech Republic in the fields of air quality, hydrology, water quality, climatology, and meteorology. The objectives of CHMI's activities include: i) the integration of the performance of public service in a rational, efficient and economical manner, ii) the establishment and operation of monitoring stations with the aid of a telecommunications network (national networks for monitoring the atmosphere and hydrosphere both qualitatively and quantitatively and for establishing the reasons underlying their pollution or damage), iii) processing in an expert manner the results of observations, measurements and monitoring, iv) the creation and maintenance of data bases, and v) the provision of information on conditions, characteristics and regimes. The monitoring system of the CHMI consists of 97 automatic stations. The measured pollutants are SO2, NO, NO2, PM10. In some stations O3, CO, organic species such as benzene and toluene are measured. Measurements by airplane L410 Turbulent have been performed since 1979. In the last 10 years the programme has been focused mainly on tropospheric ozone. The measurements include SO2, NO, NO2, NOx, O3 concentrations and temperature at levels from 150 m above ground to 3500 m above sea level.


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Detailed graphical and other information about the Czech air pollution-monitoring network is provided by CHMI, 2004. Two stations, Svratouch and Kosetice, are the Czech contribution to the EMEP monitoring network. They work on a full programme of measurements for precipitation (sulphate, nitrate, ammonium, magnesium, sodium, chloride, calcium, potassium, conductivity, pH), air (sulphur dioxide, nitrogen dioxide, nitric acid, ammonia, ozone, sulphate, nitrate, ammonium, sum of nitric acid and nitrate, sum of ammonia and ammonium). Atmospheric Chemistry Research The Institute of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic hosts the leading Aerosol Laboratory in the country. The main effort is aimed at experimental study of individual parts of the condensation process (nucleation, condensation and evaporation, heat and mass transfer) as well as at more complex phenomena such as gas-phase synthesis of nano-particles, and combustion or atmospheric aerosols. The Institute has experience regarding the development of measurement methodology for air pollution: the pre-concentration of pollutants, measurements of NH3, SO2, NO2, HNO2, HNO3 and O3 determination in ambient air. The group has extensive long-term experience in field measurements and in pollutant monitoring campaigns. The department owns: unique analyzers for monitoring ozone, nitrogen dioxide and nitrous and nitric acids. The fields of research are: particulate emissions from combustion processes; composition and size of atmospheric aerosols; indoor/outdoor aerosols; nucleation phenomena; synthesis of nano-particles via aerosol processes; heat and mass transfer in aerosol systems; and interaction of aerosols with electromagnetic radiation. Some research projects are supported by the EC (“Sub grid scale investigations of factors determining the occurrence of ozone and fine particles” - grant No. EVK2-CT-199900052 SUB-AERO; “Characterization of urban air quality – indoor/outdoor particulate matter chemical characteristics and source-to-inhaled dose relationships” - grant No. EVK4-CT-00018 URBAN-AEROSOL; “Integrated exposure management tool characterizing air pollution-relevant human exposure in urban environment” - grant No. EVK4-CT-2002-00090 URBANEXPOSURE). Other studies are funded by the National Grant Agency or Ministry of Education (“Composite nano-particle synthesis by the CVD method in a hot-wall tube flow reactor” - grant No. 104/02/1079; “Aerosol particle growth in presence of foreign gas and problem of foreign molecule trapping” - No. IAA4072205; “Development of experimental methods for measurement of nucleation rates in mixtures present in clean and polluted atmospheres” - grant No. 2076203; “Comprehensive size resolved characterization of atmospheric particulate matter in Prague” grant No. 205/03/1560; “Nucleation studies using diffusion chambers. Atmospheric aerosol measurements - instruments inter comparison” - grant No. ME699, program KONTAKT; “Indoor aerosol deposition: an experimental study” - grant No. 101/04/1190, 2004-2006 [6318]; “Composition and mode of occurrence of the mineral constituents in brown coal and their behaviour during fluidised bed combustion”; “Reduction of heavy metal emissions from fluidised bed coal combustion using sorbents”; “Physicochemical properties of urban atmospheric aerosol. Source apportionment and impact on air quality”). The research of the groups at the J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Department of Molecular Simulations of

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Atmospheric Aerosols, is in atmospheric reactivity of sea-salt aerosols and urban air pollution control. Measurements of pollutants, physical and chemical modelling of secondary pollutants production and propagation in the urban and rural areas are performed. The main research activities of the J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Department of Chemical Physics, partly concerning atmospheric chemistry are within Gas Phase Ion Chemistry (experimental and theoretical studies of the dynamics and kinetics of processes involving singly- and multiplycharged ions; dynamics of ion-surface collisions; studies of ion-molecule reaction kinetics relevant to medicine-related microanalysis; application of mass spectrometry to structural studies of organic, bioorganic and organo-metallic compounds, and of mechanisms of ionization and fragmentation processes). Research of fog and rime water chemistry and physics is performed at the Institute of Atmospheric Physics, Academy of Sciences of the Czech Republic. The Czech Aerosol Society (CSA) was formed in 1999 from the former Working Group on Aerosol Research of the Czech Society of Chemical Engineering at the occasion of the European Aerosol Conference held in Prague in 1999. As given in its constitution the Society maintains a forum of researchers from various Czech institutions and universities in order to promote collaboration in all areas of aerosol research, to promote by means of meetings and publications the spread of information between the members and the public, to support education in aerosol related fields at all levels, and to support international co-operation. At the Research Centre of Environmental Chemistry and Ecotoxicology (RECETOX) - Air Sampling Group (AIRSAG), research is performed by staff of the centre as well as co-workers from TOCOEN Ltd. and M.Sc. and Ph.D students. Some recent projects: x EcoRA - Ecological Risk Assessment; x UNIDO Project - Implementation of Stockholm POPs convention in the Czech Republic Project objective is preparation of bases for ratification of Stockholm Convention; x National Inventory of POPs in the Czech Republic; x GEF UNEP POPs Project - Regional Report from Region III – Europe; x ELICC – Dioxins & PCBs: Environmental Levels and Human Exposure in Candidate Countries European Commission, Brussels REFERENCE: ENV.C.2/SER/2002/0085 x Transformation of Air Polluting Compounds (Project No. VaV/740/2/01, In Czech); x PBTs Project OCOEN REPORT No.150: Persistent, Bioaccumulative and Toxic Chemicals in Central and Eastern European Countries (State-of-the-art Report prepared under R-T&A by Ivan Holoubek, Anton Koþan, Irena Holoubková, JiĜí Kohoutek, Jerzy Falandysz); x Project Košetice TOCOEN REPORT No.194: Middle European Monitoring of PBT Compounds in Košetice Observatory, South Bohemia by Ivan Holoubek et al. The Project objective is long-term regular monitoring of selected POPs in air and in other environmental compartments in Košetice Observatory of CHMI.


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Air pollution modelling and other topics The most severe urban air pollution problem in the Czech Republic is the traffic air pollution in large cities, particularly in Prague. The Gaussian model developed at the Czech Hydrometeorological Institute (CHMI) is frequently used in urban air pollution studies. A Lagrangian photochemical model SMOG, with simple chemistry, was developed at the Charles University of Prague. An advanced 3D street canyon research model is being developed at the Technical University of Brno. The French modelling system Fluidyn Panache is tested at the Technical University of Ostrava. The US NOAA model HYSPLIT was recently implemented at CHMI. Prague participates in the international project HEAVEN, the main objective being the development of a system for traffic air pollution management in several large European cities. The Swedish modelling system AIRVIRO is to be used in the project. Recent implementation of the French limited area meteorological prognostic model ALADIN - LACE substantially increased pre-processing possibilities in the Czech Republic (e.g. 8 grid points in the territory of Prague). A relatively high quality emission database is available for the Czech Republic, particularly for Prague. Theoretical work and wind tunnel experimental work on boundary-layer theory is carried out at the Institute of Thermodynamics of the ASCR. Estonia Ambient Air Quality Monitoring Network At present, all the monitoring sites in Estonia are operated by the National Monitoring Centre at the Environmental Research Centre. Here the maintenance of the stations as well as a central calibration of the instruments is carried out. It is planned that regional authorities, like the town government of Tallinn, will have on-line access to the data of the monitoring sites of particular interest to them. According to the Final Report of a twinning Estonian-German project (Twinning, 2000) on assessment of the Estonian air quality monitoring system some additional monitoring sites were suggested mainly in the southern rural areas of the country. These stations could collect information on trans-boundary air pollution imported from the neighbouring countries. The Estonian air quality monitoring network would then consist of 14 monitoring sites. The information is published in the Estonian National Environmental Strategy (NES), Atmospheric Air, 2000. The Estonian National Monitoring Centre (NMC) is installed within the Estonian Environmental Research Centre (ERC) in Tallinn. All measuring results from monitoring sites are collected and processed at NMC using a software product of an Austrian company, as a part of a PHARE investment project. On this basis, experts of NMC prepare monthly and yearly reports on air quality and reports concerning certain evaluations of a specific interest. On-line presentation of information to the public is provided via the INTERNET. Within Estonia all monitoring of air pollution is carried out at the Estonian Environmental Research Centre. The Environment Information Centre (EIC) has two main tasks. It collects, processes, issues and stores environmental data. EIC transfers data and information to several Baltic, Nordic and European partners. It acts as the counterpart to the European Environmental Agency (EEA)

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and reports, e.g., the emission data of the stationary sources. EIC prepares information and monitoring related acts, such as: The Environmental Register Act; Legal act on applying the Århus Convention; Regulation by the Minister of Environment on the Procedure of Implementing state environmental monitoring sub-programs. Formerly, EIC co-ordinated the state environmental monitoring programme, make the main contracts with different monitoring bodies and managed and processed collected data. Since September 1999, the University of Tartu was appointed to co-ordinate the National Monitoring Programme (with 16 sub programmes). This includes analyses of statistical data, production of trends and publication of data on the Internet. Atmospheric Chemistry research At the National Institute of Chemical Physics and Biophysics (NICPB), Laboratory of Chemical Physics the research activities range from studying fundamental aspects to applications. Strong emphasis is given to the deployment of modern physical methods in chemistry and biochemistry, which include: principles of mass-spectroscopy and ion-cyclotron resonance; environmental analyses; and theoretical and experimental particle physics. The Centre of Excellence of Analytical Spectrometry was formed in 2001 on the basis of six research groups of the Laboratory of chemical physics of NICPB and one biology-related research group. The laboratory also provides services as a reference laboratory, performs environmental monitoring and general chemical analyses. In addition, the facilities are used for advanced degree studies. Among several groups within the centre, those on Mass-Spectrometry and Catalysis and Environmental Chemistry work in the field of atmospheric chemistry. Experimental studies of oil shale combustion fly ash aerosol under simulated day-time and night-time atmospheric-like conditions were performed at NICPB in a 190m3 outdoor Teflon film chamber. Continuous monitoring of particle size distributions is performed with various optical and electrical devices. The respiration fraction of particles, which contributes most to the health effects of the aerosols, is studied quantitatively. NICPB works in close collaboration with institutions in Estonia, such as the University of Tartu, Institute of Environmental Physics; The Tallinn Technical University; The Estonian Environmental Research Centre and the Geological Survey of Estonia. Among the international partners are the European Science Foundation program INTROP (Interdisciplinary Tropospheric Research: from the Laboratory to Global Change, 2004 – 2008), German, Norwegian and USA institutions. An Electrical Aerosol Spectrometer (EAS) was developed in the Institute of Environmental Physics of the University of Tartu as a result of the 20-year research and developing work. The latest version of EAS has been built by AIREL Ltd. Tartu University, Institute of Technology is a multidisciplinary research institution. Several groups are working on atmospheric pollution topics, such as The Aerosol Research Group; the Atmosphere Dynamics Work Group; the Environment Technology Work Group; the Environmental and Occupational Health Work Group and the Environmental Radioactivity Work Group.


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Air pollution modelling and other topics Decreasing SO2 concentrations and increasing NOx and CO concentrations are observed in Estonian towns. Such trends, which are typical for many East European towns, result from the increasing traffic and from the increasing consumption of natural gas. The urban air pollution model AEROPOL (based on the Gaussian concept) was developed at the University of Tartu, Institute of Environmental Physics of the University of Tartu. The model has been used to estimate urban air pollution in several Estonian towns. The AEROPOL model was tested against a Norwegian (Lillestrom) data set. Recently, the Swedish model system AIRVIRO was implemented in Tallinn. Parameterization of dry deposition processes is among the most recent study activities. Hungary Ambient Air Quality Monitoring Network The organizations, which are currently involved in air quality monitoring, are the Ministry of Health and Social Welfare and the National Meteorological Service. The Ministry for Health and Social Welfare has the responsibility for measuring ambient air quality throughout Hungary. In order to accomplish this task, nitrous oxides, sulphur oxides and particle sedimentation are regularly monitored at 100 stations. The National Meteorological Service maintains the background monitoring network consisting of 4 stations (K-pusta, Farkasfa, Nyírjes and Hortobágy) in accordance with the recommendations and quality requirements of the EMEP. Measurements of the gases (sulphur dioxide, nitrogen dioxide, ozone, ammonia, nitric acid), aerosol particles (sulphate, nitrate, ammonium, sodium, potassium, calcium) and precipitation (pH, conductivity, sulphate, nitrate, chloride, ammonium, sodium, potassium, calcium) are performed. In addition, methodological guidance is provided for the operation of two further stations run by the local Environmental Protectorates: Fertoujlak and Majlatpuszta. Wet deposition of nitrogen and phosphorus over Lake Balaton is estimated by means of precipitation samples collected at Siofok and Keszthely. Sampling and laboratory analyses are performed on the basis of EMEP and WMO GAW Technical Manuals. Besides the operative activities, experts are involved in several national and international projects such as: evaluation and replacement of National Standards for atmospheric transmission; development of accidental (nuclear) dispersion models; deposition of nitrogen and phosphorus over Lake Balaton; three EUREKA/EUROTRAC-2 Projects (BIATEX-2, SATURN, TOR-2) and COST 615 and 715. Atmospheric Chemistry research At the Eötvös Loránd University - Department of Chemical Technology and Environmental Chemistry, a coupled Eulerian photochemical reaction–transport model and a detailed ozone dry-deposition model for the investigation of ozone fluxes over Hungary have been developed and are used in collaboration with Leeds University of the UK. As part of a research project with Ghent University, aerosol samples were collected using several filter-based devices (Nuclepore polycarbonate membrane, Teflon membrane and quartz fibre filters) over

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separate daylight periods and nights, and on-line aerosol measurements were performed by TEOM and aethalometer. The study was carried out in an urban canyon and also at a near-city background site in Budapest, Hungary from 23 April–5 May 2002. The main activities of the Air Chemistry Group in the Hungarian Academy of Science, University Vezsprem are concentrated on the measurement and analyzes of the chemical composition of aerosol. The mass concentrations of inorganic ions, water-soluble organic carbon, water-insoluble organic carbon and black carbon in atmospheric aerosol collected at three European background sites: (i) the Jungfraujoch, Switzerland (high-alpine, PM2.5 aerosol); (ii) K-puszta, Hungary (rural, PM1.0 aerosol); (iii) Mace Head, Ireland (marine, total particulate matter) are determined in collaboration with the Paul Scherer Institute, Villigen, Switzerland. A box model is applied to estimate the direct climate forcing of aerosol particles for rural air in Central Europe during summertime. Data from satellite observations and other surface measurements are used as input parameters for the model. Rural fine aerosol collected in Hungary is analyzed with different techniques to estimate the average molecular weight (AMW) of humiclike substances (HULIS). Air Pollution Modelling and Other Topics The capital of Hungary, Budapest, is the largest city in the 10 countries. The occurrence of winter and summer high air pollution episodes is typical for the city. Therefore, the main effort in Hungary is oriented towards air pollution problems in Budapest. The founders of air chemistry research and air pollution modelling in Hungary Prof. Meszaros and Dr. Szepesi are well known specialists in the international air pollution community. National standard models (Gaussian types) were developed in the seventies. They are routinely used for regulatory purposes in Hungarian towns. Several foreign models were implemented in Hungary in the last decade (US EPA ISC3, Norwegian model KILDER, etc). Hungary has participated in several international modelling projects, e.g. EUROTRAC, COST CITAIR, COST 710 and COST 715. The Hungarian Meteorological Service is a consortium partner of PHARE Topic Link on Air Quality. The main objectives of the current air pollution research in Budapest are: to investigate the urban photochemical processes inside the city and in the urban plume, the origin of toxic elements in atmospheric aerosols and to improve ozone prediction for Budapest. Combination of a statistical model and a causal model (US OZIPR) is being tested. The Aerosol Association of Hungary is a part of the European Aerosol Federation. Latvia Ambient Air Quality Monitoring Network The Ministry of Environmental Protection and Regional Development is responsible for the co-ordination of environmental monitoring in Latvia and the Latvian Hydrometeorological Agency (LHMA) for implementation of the governmental policy in environment quality (water, air, and precipitation). The Latvian Environmental Consulting and Monitoring Centre (LECMC) as reference centre for monitoring activities, and the Latvian State Statistics Bureau (LSSB) as reference centre for environmental statistics are involved in


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air quality monitoring (Latvia, 1999). The first two institutions are subordinated to the Ministry of Environmental Protection and Regional Development. There is one National Air Quality Network in Latvia. During 1997 air monitoring systems running semi-manual air sampling (at 8 posts, 6 cities) were replaced by automatic air quality OPSIS DOAS stations. Since 1998 the network has consisted of six stationary city stations in three towns and two villages. Two stationary city stations (Riga) are included in the EUROAIRNET. The background air quality monitoring includes two stations. Station Rucava was established in 1985, station Zoseni in 1994. SO2, NO2, major ions, heavy metals and other components are measured at both stations; O3 is measured at one station. Both stations are involved in international activities (regional GAW/EMEP/ICP-IM) and are included also in the EUROAIRNET. On-site data are collected on paper charts. Data are available in the form of paper sheets and reports from 1986 (Background Network) and since 1969 (National Air Quality Observation Network - NAQON). From 1991 the data are available in electronic form. Since 1998 raw data from NAQON (excluding background stations) are received via modem line at LHMA. For data analysis the reporter of the OPSIS "EnviMan" management system is used. There is no uniform central database for all the measured data in Latvia (Latvia, 1999). For EUROAIRNET, Latvia has selected two stations in urban areas (in the capital of Latvia – Riga) and two stations have been selected in rural areas. The information is submitted through the Data Exchange Module. The site classification of selected stations and the Quality Assurance and Quality Control (QA/QC) issues have been elucidated. The chemical analyses of manual samples are performed in LHMA's laboratory, which passed accreditation and received certification in January 1998. The calibration of DOAS OPSIS monitors is performed on a regular basis. Regarding the establishment of an ambient air monitoring system in Latvia (Latvia, 2000) compliant with EC directives a number of EU regulations were adopted, namely, the Council Directive 96/62/EC of 26 September 1996 on ambient air quality assessment and management, the Council Directive 92/72/EEC on air pollution by ozone (Information and data exchange Formats (April 96)), the Council Directive 99/30/EC of 22 April 1999 relating to limit values for sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter and lead in ambient air, and the Council Decision 97/101/EC of 27 January 1997 establishing a reciprocal exchange of information and data from networks and individual stations measuring ambient air pollution within the Member States. Atmospheric Chemistry Research Latvian tradition in chemistry research goes back in the 19th and 20th century with Wilhelm Ostwald born in Riga in 1853, who was awarded the Nobel Prize for Chemistry in 1909. Ostwald and Arrhenius (who worked in Riga in 1886) became founders of classical physical chemistry.

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The Institute of Atomic Physics and Spectroscopy (IAPS), University of Latvia has planned a contribution to ACCENT-TROPOSAT-2, Task Group 3 for the period 2004-2008. Within the framework of the TROPOSAT programme the Institute will continue atmosphere chemistry research through laboratory and field experiments (Starnet, 2005). A MAXDOAS Ground validation station for the GOME (Global Ozone Monitoring Experiment) will be built, including a SCIAMACHY (Scanning Imaging Absorption spectrometer for Atmospheric CHartographY). Intense cooperation with colleagues from the University of Bremen is expected. The participation of the institute in laboratory experiments of troposphere and stratosphere chemistry is also a part of ACCENT-TROPOSAT-2 activities. Funding agencies might be the Latvian Science Council, the Ministry of Education and Science, University of Latvia, EU Structural funds, Other EU projects. Within the EUROTRAC-2 Subproject TRAP45, a team from IAPS has analyzed little used data sources on the air pollution history of Lativia. The influence of the transition from a centralized and unified administration under the Soviet Union to a national administration on air quality is elucidated in Übelis and Bergmanis (2000). Studies on size distribution and composition of airborne particles are performed at the University of Latvia, Department of Analytical Chemistry. Air Pollution Modelling and Other Topics The former USSR standard OND-86 (description of the model was included in ETC AQ Model Documentation System) is still in use in Latvia for regulatory purposes. The Swedish model system AIRVIRO was implemented in Riga in 1996 and also in Ventspils. No national air pollution models are being developed in Latvia at the present time. The advanced air pollution monitoring system OPSIS (14 monitoring stations, including 4 stations in Riga) has recently commenced operations. All the monitoring stations are connected to a reciprocal information exchange network and are being gradually connected to EUROAIRNET. Lithuania Ambient Air Quality Monitoring Network The air quality monitoring in Lithuania is managed by the Ministry of Environment (MoE) and is a sub-program of the National Monitoring Programme (NMP) (Lithuania 2001). For most tasks connected with NMP's coordination, the Joint Research Centre (JRC) performs management, data processing and reporting. JRC together with 8 Regional Departments (RD) of MoE deals with monitoring air quality, air emission, and surface water and ground water quality. Ambient air quality monitoring is carried out in 5 RDs, where stationary AQ control stations are located. Regional Departments are responsible for sampling and analyses in their local areas. JRC is responsible for data gathering, data processing and reporting. One part of the air quality monitoring, the background stations, are under the control of the Institute of Physics, which acts in this field as a subcontractor of JRC. Based on the type of impact, regional and local air pollution levels are discernible in Lithuania. Regional air monitoring is carried out at sites remote from industrial enterprises


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(Aukstaitija, Zemaitija, Dzukija, Preila) and is considered as a part of integrated monitoring. Aukstaitija and Dzukija National Parks stations started operation in 1993 (however, in the middle of 1999 the Dzukija station was closed), Zemaitija National Park in 1995. The monitoring station in Preila was opened in 1980 and is operating under international EMEP and EUROTARC programmes. All these stations allow the control of long-range trans-boundary air pollution brought to Lithuania from neighbouring and distant countries. Sampling in these stations is conducted daily (duration 24 hours) or weekly employing the method of air filtration using fibre filters. The measurement programme covers: NO2, SO2, SO4, NO3+HNO3, NH4+NH3, O3. Local monitoring is conducted in zones where point pollution sources or their complexes (cities and industrial centres) are significant, i.e. where the anthropogenic impact both on nature and human health is the most prominent. Air monitoring activity was initiated in Lithuania in 1967 and is basically restricted to a local level. Up to 2000 it consisted of 26 stationary air quality control stations (3 of them automatic) located in the biggest cities and industrial centres. Sampling of the main pollutants is carried out for 30 minutes three times per day (at 7 a.m., 1 p.m. and 7 p.m.). Main measured components are: TSP, SO2, NO2, CO, SO4, NO, H2S, NH3, HF, CH2O (formaldehyde) and phenol. Ozone and PM10 are established in automatic stations, located in Vilnius, as well as SO2, NO2, NO, CO. According to the Air Monitoring Strategy adopted by the MoE authorities and requirements of EU Directives, a new Lithuanian local air-monitoring network is being developed. After the implementation issues listed in the strategy and installation of equipment (supported by PHARE project), there are 5 stations in Vilnius, 1 in Kaunas, 2 in Klaipeda and 1 in Siauliai, Panevezys, Mazeikiai, Kedainiai, Jonava, and N.Akmene. The requirements of EU Council Directive 1999/30/EC for limit values of SO2, NOx, PM10 and lead have been adopted in the statement law of Lithuania as well as the requirements of the Framework Directive. The sampling procedures and the analytical methods are unified through the whole monitoring network. All chemical laboratories perform internal and external inter-calibrations. Quality Assurance procedures apply in these laboratories according to the national standards and norms. Regional Department laboratories carry out internal control based on a programme performed by JRC. JRC organises external control for all RD laboratories a minimum 2 times per year. All controls include the use of calibration standards, calibration curves, check of precision, frequent processing of blank samples, replicate analyses. Accreditation has not yet been implemented. All raw data are collected in the laboratories on paper and in electronic format. The Regional Departments and the Institute of Physics (which is responsible for background station data) send the data in digital form every month to JRC, where the data are processed and stored. Quarterly reports "State of Environment in Lithuania" and "Air Quality Annual Report" are issued. Information from specialised structures of the EoM (including Regional Departments, JRC, and Divisions of EoM) is supplied for different organisations and institutions. Atmospheric Chemistry Research The Institute of Physics is a state scientific research institute of Lithuania. It merges scientists and laboratories for basic and applied research in chemical physics and biophysics,

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modern laser spectroscopy and nonlinear optics, nuclear physics, physics of atmosphere and some other related areas of physics. In addition to the scientific research, the Institute is engaged in educational activities via stringent connection links with several universities of Lithuania. The researchers from the Institute are expected to give professional advice on issues connected with environmental pollution, nuclear energy, etc. In some of the mentioned activities the Institute of Physics is the main or even the only research institution in Lithuania. The Institute of Physics formerly belonged to the Lithuanian Academy of Sciences. Due to reforms in the scientific research organisations carried out in 1991, when the independence of Lithuania was restored, the status of the Institute was changed. The transformations of pollutants in the atmosphere are investigated at the Institute of Physics, Environmental Physics and Chemistry Laboratory (EPCL, IP). Such studies are needed, as the development of cost-effective strategies for the control of pollutant emissions requires accurate assessment of deposition fluxes. It is important to understand the mechanisms of predominant chemical reactions in the atmosphere, to evaluate the rates of gas-to-particle conversion, and to include the information obtained in parameterised form in deposition models. Information about mechanisms of chemical reactions predominant in gas-to-particle conversion processes is obtained by comparing the experimentally determined data with the theoretically predicted particle diameter growth. It has been shown that during summer-months condensation of low-pressure vapour formed by gas phase homogeneous chemical reactions is a predominant mechanism of the continental aerosol particle growth. In winter, the growth of a sub micrometer continental aerosol particle is frequently governed by two competing processes: condensation of low-pressure vapour and heterogeneous oxidation of aerosol precursor gases inside the liquid droplet. Ozone is found to be an active oxidant in the heterogeneous aqueous phase chemical reactions. A number of atmospheric chemistry studies (Long-range transport of gases and particles; cycles of sulphuric and nitrogen compounds in the atmosphere; dynamics of organic compounds in the environment atmosphere, hydrosphere, and soil; variations and changes of total ozone; mechanisms of gas-to-particle conversion in the atmosphere; hygroscopic properties of atmospheric aerosols; evaluation of dry and wet fluxes of atmospheric pollutants to various ecosystems; exchange of chemical and biological constituents at the air/sea interface; seasonal variations of composition and concentrations of airborne fungi in Lithuania; and modelling of the exceedences of critical loads of sulphur and nitrogen for various ecosystems) are performed at EPCL, IP. Extensive international cooperation takes place at the institute with the following major activities: EC project BASYS (Baltic Sea System Study); NATO project on Relationship between Air and Waterborne Micro-organisms in Baltic Waters with the University of Cincinnati, Cincinnati, USA; EUROTRAC-2, subprojects BIATEX-2 (Atmosphere/Biosphere Exchange of Pollutants), AEROSOL (Aerosol Balance in Europe), SATURN (Studying Atmospheric Pollution in Urban Areas), TOR-2 (Photochemical Oxidants over Europe), and MEPOP (Interdisciplinary Research on Mercury and POPs); WMO (World Meteorological Organization) GOOS (Global Ozone Observing System) programme; ICP/IM (International Co-operative Programme on Integrated Monitoring of Air Pollution Effects on Ecosystems) programme; EMEP (European Monitoring and Evaluation) programme; HELCOM (Baltic Marine Environment Protection,


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Helsinki Commission) programme; COST (European Cooperation on Scientific and Technical Research) programme (COST-319- Transport and Air Pollution). Air Pollution Modelling and Other Topics Detailed urban air pollution studies are continuously carried out for the two biggest Lithuanian cities, Vilnius and Kaunas. Both monitoring and modelling tools are applied. Until the year 1998 the only approved air pollution regulatory model in Lithuania was OND-86. The advanced Swedish modelling system AIRVIRO was installed in Vilnius in 1996, and in Kaunas in 2000. For routine regulatory purposes the US EPA models ISC3 and SCREEN3 were recently implemented. The main limitations of urban modelling in Lithuania are: unsatisfactory traffic input data, absence of upper air meteorological measurements and limited information about international air quality modelling projects. Advanced techniques linking numerical models and observation data are under development at The Institute of Physics, Atmospheric Pollution Research Laboratory (APRL, IP). These are used to determine the complex interactions between the sources, the concentrations and deposition fluxes of trace substances having impact on the environment. Recent work has concentrated on the study of the dynamics of gaseous (NH3, HNO3, SO2, NOX, O3, CO2, H2S, etc.) as well as particulate (SO42-, NO3-, Cl-, NH4+, Na+, Ca+, K+, B(a)P, etc) pollutants in the atmosphere and on the evaluation of biosphere/atmosphere exchange fluxes of photo-oxidants, acidifying substances, heavy metals and persistent organic pollutants. Furthermore, the migration of heavy metals and persistent organic pollutants in the terrestrial and aquatic ecosystems has been studied. The serious pollution episodes in the urban environment are not generally caused by the sudden increase in the emission of pollutants, but are rather a result of short-term unfavourable meteorological conditions. A cost-effective way to prevent the occurrence of high air pollution episodes might be the temporal reduction in emissions that is based on the meteorological and air pollution forecast. The main fields of research at the institute include: transformation, migration and bioaccumulation of trace metals in the environment; mercury cycling in the environment, identifying mercury sources and sinks; influence of meteorological parameters on the urban air pollution and its forecast; manufacture of portable Mercury Vapour Analyzers Model GARDIS-5; development of new sampling and analytical methods, developing automated Air Pollution and Meteorological Monitoring Systems. International collaboration is achieved through projects like BASYS (Baltic Sea System Study); EUROTRAC (European Experiment on the Transport and Transformation of Environmentally Relevant Trace Constituents in the Troposphere over Europe); EMEP (Cooperative Programme for the Monitoring and Evaluation of long range Air Pollutants in Europe); HELCOM (Baltic Marine Environment Protection Commission); ECOSLIT (Ecological Sustainability of Lithuania); NORD (Atmospheric Heavy Metal Deposition); collaboration with Lund University, Sweden; co-operation project with Stockholm University; research collaboration with Gothenburg University in Mercury compounds determination; collaboration with EPA in Chicago, USA; collaboration with Tronheim University, Norway.

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Poland Ambient Air Quality Monitoring Network Air quality monitoring in Poland is performed by The State Inspectorate for Environmental Protection SIEP (within the structure of the Ministry of Environmental Protection, Natural Resources and Forestry) with its provincial (voivodship) branches VIEPs; The State Sanitary Inspectorate SSI (subordinated to the Ministry of Health and Social Welfare) with its provincial branches VSIs; industrial plants or companies and research institutes, foundations, etc. In accordance with the Statute of the State Inspectorate for Environmental Protection (SIEP), the Chief Inspector of SIEP plays the co-coordinative role within the State Environmental Monitoring Programme. The State Sanitary Inspectorate (SSI) is responsible for air quality assessment from the viewpoint of health and hygiene requirements. The authority responsible for official data on national emissions into air is the Department of Environmental Protection in the Ministry of Environmental Protection, Natural Resources and Forestry (MoE). Air quality monitoring data are used at national, voivodship (provincial) and local levels. At the national level, the General Monitoring Network of air quality (GMN), established in 1985, is the largest one. It is subordinated to the SSI and operated by its provincial (or local) branches. Its main purpose is to supply information on population exposure to air pollutants for the needs of the National Health Programme. Data are also used for environmental policy purposes. Stations belonging to the network are also a part of lower level monitoring systems - the collected data are used both at the local and voivodship level. In 1997 the network consisted of 506 stations, located in cities above 20 thousand inhabitants and in health resorts. The basic monitored pollutants are SO2, NO2, black smoke and TSP. In total, 37 pollutants (from 1 to 19 compounds at each station) were monitored in 1997. Almost exclusively manual 24-hr measurements are carried out at the stations. The network is supervised by the Nofer Institute of Occupational Medicine (since 1992 till 1999), which is responsible for QA/QC, data collection, assessment and reporting. National Network of Basic Stations (NNBS), established in 1991, is subordinated to the SIEP. The network consists of selected monitoring stations belonging to Voivodship Inspectorates for Environmental Protection (VIEPs), to SSI (i.e. selected stations of GMN), research institutes and industrial plants. Stations incorporated into the network also work (or supply data) for other monitoring systems (local, provincial, regional and international programmes). The NNBS is a regulatory and general assessment network for air pollution and its trends in Poland. In 1998 there were 95 monitoring stations in NNBS, located both in urban and rural areas. The measurement programme comprises 24-hr concentrations of SO2, NO2, suspended particles (PM10/TSP/BS) measured at almost all of the stations, and 30-min concentrations of ozone and traffic-related pollutants at some of the stations. In 2001 the NNBS consisted of 106 air quality monitoring stations, 95 urban and 11 rural, including 4 EMEP stations. Concentrations of SO2 and NO2 were measured at about 100 sites, O3 at 23 sites. The network is operated under the supervision of the Institute of Environmental Protection (IEP), which is responsible for data collection, assessment and reporting and, to some extent, for QA/QC. At the voivodship level the most comprehensive and broad set of monitoring data is used. The monitoring data (operated by different institutions) are


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collected in voivodship databases and are used by provincial authorities and Voivodship Inspectorates of Environmental Protection VIEPs. The Air Quality Monitoring (AQM) data are used mainly to support environmental policy and strategy planning at a voivodship level (which seems the crucial level from the point of view of environmental planning in Poland), and to assess its effectiveness. Regional AQM networks provide information on air quality in a given region to support environmental and economic policy making. The extent, density and measurement programmes of the networks depend on the air pollution problems in a given region. The most advanced, fully automated, regional networks exist in the Black Triangle region and the Silesia agglomeration. Some regional networks have a warning function, providing up-to date information on existing and/or predicted levels of pollutants dangerous to health (e.g. the Automated Network in the Silesia agglomeration). Data from the regional networks are used at the voivodship and local level. Some of the stations are included in the national networks. Local AQM networks cover the area of a city or the area potentially influenced by a specific industrial plant. The networks are established by or with participation of local governments. In the case of the networks owned by industrial plants, the networks are established and operated by the plants/companies on the basis of administrative decisions. Their task is to provide information on the local air quality, local compliance with pollution standards and to evaluate pollution abatement programmes prepared by the industrial plants. In many cases the local networks are planned to serve emergency/warning purposes. Data from selected stations belonging to the local networks are used for air pollution assessment at a higher level. Again, the extent, density and measurement programmes of the local networks depend on the air pollution problems in a given city or the air pollution caused by the industrial plants. In 1998 there were about a dozen automated local networks, 8 of them operated by industrial plants/companies. Poland participates in a number of international programmes like GAW/WMO, HELCOM, EMEP and GEMS/AIR. The monitoring stations (MSs) included in the international programmes are located over the whole area of Poland and are elements of the national monitoring networks. The EMEP, GAW/WMO network includes four background stations. One of these MSs works additionally also for HELCOM. All of the stations belong to NNBS. Six urban stations (3 in Warsaw, 3 in Wroclaw) operated by the State Sanitary Inspection (SSI) and belonging to GMN contribute to the GEMS/AIR international Programme. NNBS prepares monthly and yearly reports for the SIEP. GMN prepares yearly reports. At the Voivodship level daily reports for mass media, yearly (in some voivodships daily and weekly and monthly) reports are released. The local networks data are used by industrial managers and made available to the local authorities and Voivodship Inspectorates for Environmental Protection (VIEP), and in some cases presented to the public. At the EMEP, GAW/WMO stations the standards and recommendations concerning data reporting are kept. Data are sent to the co-ordinating centre at NILU in Norway. At the GEMS/AIR stations the data reports are sent to the GEMS/AIR Centre in Geneva once a year. At all stations and laboratories the QA/QC procedures are systematically implemented, such as EU standards, inter-calibration, external audits, validation and verification. At EMEP,

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GAW/WMO and GEMS/AIR stations the standards and recommendations of the programmes are kept. Basic measured parameters are SO2, NO2, NOx, and PM10/TSP/BS. Additionally, O3, CO, VOC, THC, F2, C12, HCl, NH3, phenol, HCHO, H2S, PAH, PAN, meteo data, turbidity, Cd and Pb in dust fall (monthly samples), and other heavy metals in 24-hour samples are measured at some stations. Atmospheric Chemistry Research The Central Chemical Laboratory (CLCh) is the primary analytical facility of the Polish Geological Institute (PIG) and carries out practically all the chemical analysis at PIG. CLCh took part in the INCO-COPERNICUS Project: “Development of Analytical Procedures to Guarantee Quality Assurance in International Environmental Monitoring”. CLCh participated in numerous international inter-laboratory comparisons as well as organized various inter-laboratory comparatives and proficiency testing studies for laboratories of Provincial Environment Protection Inspectorates. In March 2000, CLCh was granted the Certificate of Testing Laboratory Accreditation, with respect to physical and chemical analyses of water. The Institute for Meteorology and Water Management (IMGW) was founded in 1919. In 1972 IMGW was re-established by merging the Polish Institute of Hydrology and Meteorology (PIHM) with Institute for Water Management (IGW). IMGW is the responsibility of the Ministry of Environment. It has several Regional Branches in Bialystok, Kraków, Gdynia, Katowice, Poznan, Slupsk, Warsaw, and Wroclaw. The Institute has managed scientific and research studies in many fields related to the meteorological, hydrological and environmental problems, including atmospheric chemistry. Two laboratories of IMGW perform analytical measurements for natural water and air. The Laboratory of Atmospheric Chemistry performs analytical measurements for rainwater and precipitations. It participates in inter-comparison of analytical methods within EMEP and other programmes. The Institute for Environmental Protection (IOS) was founded in 1973. In April 1986, it was reactivated as an independent State Unit for scientific research operating under its own statute and subordinated to the Minister of Environmental Protection. Apart from the main centre in Warsaw, the Institute of Environmental Protection has two regional branches in Gdansk and Wroclaw. The Institute has a special entitlement from the Ministry of Environmental Protection to provide expert opinions. The Institute has chemical and biological laboratories, which provide the chemical and biological data. At the Institute of Environmental Engineering (IEE), Zabrze, Polish Academy of Sciences (IEE PAN) research is performed on: mechanics and physico-chemistry of pollutant generation and identification of its origin; transport and transformation of pollutants in the environment; methods of particulate matter and gaseous air pollutants' emission control; studies of environmental contamination and many other topics. The scientific equipment at IEE is of a high standard and modern. The Department of Air Protection at IEE deals with: theory and technology fundamentals of the removal of SO2 and NOx from flue gases; kinetics of homogenous and heterogeneous reactions; study and modelling of the emission from low and unorganized industrial and transport


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sources with methods of FTIR – spectroscopy; application of spectroscopic methods for the study of the air condition in the surroundings of industrial and transport sources; theoretical fundaments and management instruments of the air quality in urbanized areas etc. The Laboratory of Applied Analytical Chemistry at the Warsaw University, Chemistry Department works on environmental analytical chemistry, development of analytical methods for determination of trace metals in environmental samples and speciation analysis as a modern tool for environmental risk assessment. User groups of the EUROCHAMP infrastructure from Poland are the Technical University Wroclaw with the investigation of atmospheric chemical processes, automatic manual and passive monitoring, temporal and spatial modelling of air pollution with advanced statistical tools and the Institute of Meteorology & Water Management, Wroclaw with ambient air monitoring of air pollutants, aerosols, ozone, radioactive compounds as well as background air pollution monitoring (according to EMEP standards), measurements of pollutant loads incoming with precipitation. The Institute for Ecology of Industrial Areas (IETU) has two research (monitoring) stations. The Katowice Research Station operates within the National Atmospheric Pollution Monitoring Network which is part of the National Environmental Monitoring System. Since 1989 the station conducts regular monitoring of air pollution and precipitation quality. In 1999 it was incorporated into the European Monitoring Network of Air Quality EUROAIRNET of the European Environmental Agency. The Brenna Station has been established as a unit of the integrated environmental monitoring, performed within the framework of the Geneva Convention on Long-Range Trans-boundary Air Pollution. At present, the station is operated as an experimental facility to conduct studies on the impact of elevated ozone and UV-B concentrations on the genetic structure of plant populations. IETU’s research and development activities are aimed at formulating the scientific basis for policies and strategies addressing the protection of the natural environment of industrialised and urbanised areas. The main projects are related to characterisation of sites contaminated with organic and inorganic pollutants, impact of pollutant re-suspension on the air quality, secondary air pollution as a source of human exposure, monitoring of air pollution, etc. Among the research areas of the Institute of Physical Chemistry (ICHF), Polish Academy of Sciences (PAS) (ICHF, 2005) are photophysics and photochemistry of organic molecules, involving spectrally and time resolved laser techniques and kinetics and mechanism of chain reactions in homogeneous/heterogeneous systems, as related to sulphur dioxide transformations in the environment: physico-chemical fundamentals of desulphurization processes; atmosphere chemistry including impacts of organic and inorganic scavengers of sulphoxy radicals; interaction between these radicals and bioorganic compounds. As a contribution to a subproject of CMD of EUROTRAC-2, scientists from ICHF studied experimentally the effect of D-pinene and cis-verbenol on the rate of S(IV) oxidation catalyzed by Fe, as well as the ozone-affected autoxidation of aqueous SO2 in the presence of calcium. The investigations were aimed at clarifying the mechanism of the aqueous phase oxidation of SO(IV) simultaneously by O3 and O2, calcium acting as condensation nuclei. Inhibition of the S(IV) autoxidation in the atmosphere by secondary terpenic compounds was also studied

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experimentally. A method was proposed for quantification of the inhibiting effect. All laboratory experiments at ICHF were carried out in a batch, perfectly mixed reactor, which had no gas space, in order to investigate the degradation of isoprene in the presence of sulphoxy radical anions. The aqueous-phase oxidation of isoprene can produce secondary pollutants, and influence transformation and the long-range transport of SO2 in the atmosphere. A team of scientists from the Chemical Faculty, Technical University of Gdansk, Poland and the Department of Chemistry, University of Waterloo, Canada presented monitoring results and an environmental pollution assessment for the Gdask-Sopot-Gdynia Tricity (Poland), based on an analysis of precipitation. Precipitation samples were collected over a period of 12 months (January–December 1998) at ten locations in the Tricity. An attempt was made to explain the co-occurrences of certain ions and the significance of their mutual effects. The use of magnetometry as a fast and cost-effective proxy method for screening and monitoring of anthropogenic pollution over central Europe is proposed within the FP5 MAGPROX (MAGnetic PROXies) project (2000-2003). The project is focused on a large area affected by industrial activities, spanning Germany, Austria, Czech Republic and Poland. The method can be also used for high resolution mapping of pre-selected sites showing anomalous geochemical patterns in order to allow a proper sampling for obtaining additional information. The Air-Sea Interaction Laboratory, Institute of Oceanology, PAS, Sopot conducts research on: mass, energy, momentum and radiation fluxes across the sea surface; the concentration and size distribution of marine aerosol in the boundary layer over the sea surface and in coastal zones; air-sea interaction phenomena, including sea-atmosphere chemistry. Research into aerosol production and its properties in the marine boundary layer was made during the AREX campaigns of 2000-2003 in the open Baltic Sea. Results of cloud water and air chemistry field measurements at Mt. Szrenica in Poland have been reported by scientists from Brandenburg Technical University Cottbus and the Technical University Wroclaw, Institute of Environmental Protection Engineering. Aircraft, large and small balloons, ground-based instruments and satellites are being used to measure ozone and other atmospheric gases and particles. The combined activities aim to improve the understanding of Arctic ozone depletion and upgrade satellite observations of the ozone layer. The joint initiative involves over 400 scientists from the European Union, Canada, Iceland, Japan, Norway, Poland, Russia, Switzerland and the United States. Several institutions in Poland participated in human health-oriented international projects related to atmospheric chemistry. The Institute of Occupational Medicine and Environmental Health (IOMEH), Sosnowiec analyzed measurements of PM10 and PM2.5 at Warsaw and their impact on human health within the frame of the CESAR study (1995-1996). The (National Institute of Hygiene (NIH), Warsaw (as a contributing member of the APHEIS group) made an health impact assessment of air pollution in Krakow (2001). The Institute for Ecology of Industrial Areas (IETU), Katowice and IOMEH were involved in the EMECAP project, with main objective being the improvement of the tools for Regulatory Bodies to plan actions to safeguard citizen’s health from mercury pollution.


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Air Pollution Modelling and Other Topics Poland is the largest country among the 10. The origins of air pollution modelling may be traced to the seventies, when the first simple models, both statistical and Gaussian, were introduced. The Gaussian model is chosen by the Ministry of Environment as a guideline for dispersion calculations from point sources. Several improved versions of the Gaussian model are still widely used in Poland (e.g. EK100W from ATMOTERM Ltd. Opole, which is included in ETC/AQ MDS). From the beginning of the eighties the main effort was put into adaptation and development of numerical models. Currently, there are numerous institutions engaged in this research: universities, state research institutes, local government institutions and private companies. The basic limitations of such activities at present are: shortage of funds available for research and lack of co-ordination on a country scale. Some advanced foreign urban models were implemented in Poland. Several top Polish specialists are working in EMEP MSC-W in Norway (Bartnicki, Olendrzynski, Pacyna). Only two years ago the first mesoscale meteorological prognostic model (Unified Model from the UK Meteorology Office) was put into operation at the Interdisciplinary Centre for Computer and Mathematical Modelling of Warsaw University. Also, at the Institute of Meteorology and Water Management the newest non-hydrostatic mesoscale model from the German Weather Service is being implemented. Poland´s capital city, Warsaw, is situated in flat terrain and this, combined with a high average wind speed leads to relatively good dispersion conditions. The air quality data from Warsaw suggest that maximum sulphur dioxide city background levels do not exceed WHO-AQG. The meteorological summer smog potential is also not high. The improvements of urban air quality in Poland can be illustrated by the city Krakow, where a three-fold decrease in sulphur dioxide and suspended particulate concentrations has been observed over the last decade. The new automatic monitoring devices were installed in 1991. The collection and analyses of data in a central database facilitates forecasting of pollution episodes based on the USA EPA modelling system. Romania Ambient Air Quality Monitoring Network In Romania, the monitoring of air quality is organized under the authority of the Ministry of Waters, Forests and Environmental Protection (MWFEP) and the Ministry of Health. There are four mobile laboratories for air quality measurements, three of them at units subordinated to MWFEP (Bucharest Environmental Protection Agency, Bacau Environmental Protection Agency, Institute for Research and Environmental Engineering) and one at Bucharest Town Hall. The mobile laboratories are equipped with automatic analysers. The National Air Quality Network, subordinated to MWFEP, is one of the subsystems of the National Environmental Monitoring System. It is developed according to the Master Plan elaborated within the PHARE Programme. Air quality monitoring carried out at the international level is concentrated in background pollution stations as part of BAPMoN and EMEP networks. Also the local trans-boundary pollution along the Danube River is monitored in several stations. At the local level, common pollutants (SO2, NO2, NH3, suspended powders) are measured at all stations and specific

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pollutants (HCl, phenols, aldehydes, Cl2, H2S, CS2, F, H2SO4, heavy metals: Pb, Cd) in industrial zones in relation with different activities. At most stations manual 24-hour sampling is applied. At a few sites, semi-automatic systems with 30 minutes sampling at 3-hour intervals are installed. The collection of sediment particles is performed via monthly sampling. The analysis of gases is based on chemical methods, spectrophotometry UV-VIS; of particles on gravimetry; of heavy metals on atomic absorption spectrophotometry. The National Network for Precipitation Quality Monitoring includes approximately 90 stations located in rural and urban zones. A brief description of this network includes 3 main items: sampling – weekly; analysis - pH, conductivity, acidity/alkalinity, concentrations of the main anions and cations (Na+, K+, Mg2+, SO42-, NO3-, Cl-) currently at the background stations and soon in the whole national network; and methods - spectrophotometry. The inter comparison and calibration procedures of Air Quality Monitoring in Romania are strictly followed. Atmospheric Chemistry Research Within the frame of the subproject GPP of EUROTRAC-2, scientists from the Faculty of Chemistry, Al. I. Cuza University Iasi (FC,UI) together with scientists from the Bergische University Wuppertal, Germany studied experimentally the OH -initiated oxidation of dimethyl sulphide (DMS) at sub-zero temperatures using a quartz glass reactor. Chemical transformations of DMS due to its reactions with OH radicals during the day and NO3 radicals during the night lead to the formation of sulphur containing species, both inorganic and organic in nature, which may significantly contribute to the acidity of the atmosphere. Under Romanian-German-Spanish collaboration, experimental investigations of the gasphase reactions of the NO3 radical with a series of benzenediol compounds were performed. The experiments were carried out in two chamber systems with in situ FT-IR (Fourier Transform – Infrared Spectroscopy) detection of reactants: a 1080 l quartz glass reactor at the Bergische University Wuppertal and in the EUPHORE outdoor smog chamber facility in Valencia/Spain. The kinetics of the reaction of NO3 radicals with three benzenediols using a relative kinetic technique have been investigated. As a contribution to the subproject CMD-GPP of EUROTRAC-2, experimental studies on the kinetics, products and aerosol formation from the reaction of O3 with 3 benzenediols were carried out in a smog chamber under controlled conditions. Within the frame of the EU EXACT project (Romania, Germany, France and Spain), studies of the mechanisms of Secondary Organic Aerosol (SOA) formation from the photooxidation of aromatic hydrocarbon systems were performed. Experiments were carried out in the EUPHORE chamber facility. Under collaboration between FC, UI and the Bergische University Wuppertal, experimental studies of the atmospheric chemistry of C3 to C5 alkyl iodides have been performed in the EUPHORE outdoor chamber in Valencia, Spain. The kinetics and mechanism of the reactions of O atoms with alkyl halides have also been investigated.


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A contribution to the subproject Chemical Mechanisms Development - Gas Phase Processes (CMD-GPP) of EUROTRAC-2 was also the study on “Development of Oxidation Mechanisms for Aromatic Hydrocarbons and their Unsaturated Difunctional Products”, made with German and Japanese (National Institute for Environmental Studies, Atmospheric Environment Division, Tsukuba) scientists. All the above mentioned activities are the result of fruitful collaboration between the following institutions: Bergische Universität Wuppertal, Germany; "Al.I.Cuza" University of Iasi, Department of Analytical Chemistry, Faculty of Chemistry, Romania; Ecole des Mines de Douai, Département Chimie et Environnement, France; Fundación Centro de Estudios Ambientales del Mediterráneo, Paterna, Valencia, Spain; National Institute for Environmental Studies, Atmospheric Environment Division, Tsukuba, Ibaraki, Japan. The University of Iasi participates in the user groups of the EUROCHAMP infrastructure with the following fields of excellence: Mechanistic and kinetic indoor and outdoor photo-reactor studies in the gas-phase; Studies on the aerosol formation under simulated atmospheric condition using several reactions chamber facilities; Monitoring of air pollutants, aerosols. Many investigations made by Romanian scientists are dedicated to the interrelations between chemical reactions in the atmosphere and specific meteorological conditions. The National Institute of Meteorology and Hydrology, Bucharest is closely involved in the study of the effects of increasing the CO2 concentration on the extreme temperatures and drought episodes in Europe, as well as ozone depletion related studies. The International Association of Meteorology and Atmospheric Sciences (IAMAS) Organization for Romania, as a Section of the Romanian National IUGG Committee was constituted at the National Institute of Meteorology and Hydrology (NIMH), Bucharest, in cooperation with the Faculty of Physics, Department of Atmosphere Physics of the University of Bucharest. Many research laboratories in the field of air and water pollution monitoring are presently at the Institute of Environment Research and Engineering (IERE). Studies related to upper air are being performed especially at the Astronomical Institute and Romanian Civil Authority for Aeronautics (ROMATSA). The main activities of IAMAS include monitoring of the ozone layer, data processing and instrument maintenance. Long term monitoring has been carried out in Bucharest since January 1980 using a Dobson spectrophotometer. The research activities are focused mainly on ozone climatology related with meteorological conditions on a local scale, total ozone with respect to changes in atmospheric circulation, evolution of the ozone layer on a regional scale. Some attempts of total ozone forecast are made based on improvement of the forecast model ALADIN. The Bucharest station (part of the Global Atmospheric Watch (GAW) Ozone Network as "associated station") fulfils the interaction with other programs and activities. Romania is a permanent participant in the WMO/GAW - GOOS and some European Union Programmes concerning the monitoring of the ozone layer. The research orientation of IAMAS is also related to a development (in the NIMH) of an operational Air Pollution Forecast System. Its goal is to produce 3-day air pollution forecasts of the most important air pollution species on different

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scales. In NIMH, “A pilot system for Urban Environmental Impact Assessment in relation with Urban Planned Land-Use, using Open-GIS technology and pollution levels estimation procedures - ASSURE (ASsessment System for URban Environment )” has been developed. Between November 1995 and October 1996, particulate matter concentrations (PM10 and PM2.5) were measured in 25 study areas in six Central and Eastern European countries: Bulgaria, Czech Republic, Hungary, Poland, Romania and Slovak Republic (CESAR study under PHARE). As a contributing member of the APHEIS group, Romania (Institute of Public Health, Bucharest, Romania) participated in the study concerning the health impact assessment of air pollution in 26 cities (Bucharest) in 12 European countries during 2001. Six European countries are involved in the EMECAP project (2001-2004): Italy, Norway, Slovenia, Sweden, Poland and Romania (University of Bucharest – Bucharest). The objective of the EMECAP Project was to improve the tools at the disposal of Regulatory Bodies to plan actions to safeguard citizens’ health from mercury pollution. Other Romanian institutions partially related to the atmospheric chemistry research are the National Research and Development Institute for Environmental Protection, Bucuresti; Politehnica University of Timisoara; Faculty of Geology and Geophysics, Bucharest; Romanian Academy, State Institute of Physical Chemistry, Supramolecular Chemistry and Interphase Processes Laboratory, Bucharest; Institute of Atomic Physics, Romania; National Research Institute of Cryogenics and Isotopic Technologies; Institute of Environment Research and Engineering; National Institute of Research and Development for Nuclear Physics and Engineering "Horia Hulubei"; Institute of Agrometeorology and Environmental Analysis of Agriculture, FMA- Applied Met. Foundation; Polytechnical Institute in Bucharest. Air Pollution Modelling and Other Topics The leading institution in urban air pollution modelling in Romania is the National Institute of Meteorology and Hydrology and Water Management. Several urban dispersion experiments were completed during the eighties (Bucharest, Baia-Mare, Copsa-Mica, Hunedoara). The main goals of this effort were to test urban dispersion models, plume rise models and the methods for determination of dispersion categories. Currently a climatological dispersion model (CDM) and a Lagrangian puff model (INPUF-U) are used in urban modelling studies. Descriptions of both the models are already included in ETC/AQ MDS. A meteorological pre-processor of wind field and dispersion parameters (OML scheme) is available. The French limited area prognostic model ALADIN version SELAM putting in operation. The capital of Romania, Bucharest, is situated on a flat plain, which will favour dispersion, but this is countered by the generally low wind speed (average wind speed below 2 ms-1).


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Slovak Republic Ambient Air Quality Monitoring Network The Hydrometeorological Institute (SHMI) is the main organization having responsibility with respect to air pollution monitoring in Slovakia (SHMI, 2004). The air monitoring system consists of 35 automatic stations in the whole country with measurements of SO2, NOx, PM10, PM2,5, O3, CO, benzene, H2S. At 22 stations heavy metals Pb, Cd, Ni, and As are measured manually. Additionally, there are 10 monitoring stations of different industrial manufacturers and 18 ozone stations. Monitoring of the regional air and precipitation quality in the Slovak Republic has been performed at SHMI since 1977. The first station, Chopok, was established in 1977. This station was included from the beginning in two international programs, GAW WMO and EMEP UN ECE. Up to 1993 a network of seven regional stations was gradually made operational. At present, the regional network consists of five stations, all are EMEP stations: Chopok, Topo níky, Liesek, Stará Lesná and Starina. The automatic urban air quality monitoring network in the Slovak Republic was put into operation in 1992/1993. At the same time the Slovak regional stations (EMEP) started to be equipped with ozone analysers. Sampling of volatile organic compounds, VOCs C2-C6, or the socalled light hydrocarbons, was started in autumn 1994 at the Starina station. The VOC measurements in Slovakia were implemented under the assistance of the Norwegian Institute for Air Research (NILU). The Starina station is one of the small numbers of European stations, included into EMEP network with regular sampling of volatile organic compounds. They are measured and assessed according to the EMEP method elaborated by NILU. Measurements of identical samples carried out in the Slovak Hydrometeorological Institute and in NILU showed a high degree of agreement. The Slovak Hydrometeorological Institute participated in the AMOHA (Accurate Measurements of Hydrocarbons in the Atmosphere) project. This project was carried out under the leadership of the National Physical Laboratory in United Kingdom and the Fraunhofer Institute in Germany. The aim of this project was to elaborate the European Directive for optimum sampling, measurement and evaluation of hydrocarbons in ambient air. The annual amount of precipitation depends on location and altitude. Concentrations of all chemical substances dissolved in rainwater are spatially rather conservative. Chemical composition of precipitation over the industrial continents is controlled by regional in-cloud processes. Below-cloud scavenging of gases is an ineffective process in most cases. It means that concentrations should reflect the large-scale distribution and trends of emissions. Therefore, pronounced horizontal and vertical concentration gradients should not be expected. It can be noted that the gradual replacement of bulk with wet only samplers in Slovakia caused problems in the trend analysis. The only significant decrease of sulphate concentrations and corresponding increase of pH values were observed at all Slovak regional stations. A QA/QC programme has been partly implemented, but further improvement is needed. Accreditation of network and laboratories is ongoing. Development of standard operation procedures is in progress. Unfortunately present budgetary and capacity limitations do not allow

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its full implementation. The quality of analysis in the laboratory is very good and tested annually via GAW and EMEP inter-comparison measurements. The EMEP model overestimates the measurements for the territory of Slovakia, possibly due to the very complex topography. The correlation of calculated and measured concentrations decreases with altitude. In 1998, there were 7 monitoring stations for regional air pollution monitoring, characterized as pollution of a rural type. The measurement programme includes SO2, NO2 and heavy metal concentrations in atmospheric aerosol PM, Pb, Mn, Cu, Cd, Zn, Ni, V, Cr. Within the framework of the project “Co-operation programme between Flanders and candidate member states in the central and eastern Europe” monitoring of air pollution and audit of Quality System was fulfilled (SHMI, 2004a). Atmospheric Chemistry Research The Department of Analytical Chemistry, Faculty of Natural Sciences, Comenius University performs a number of studies related to atmospheric chemistry (ANALYTIKA, 2004). Among the research projects on the topic funded by different grants are “Analysis and characterization of humic substances in air particulates sampled by filter media for air monitoring by both RP-HPLC and gel chromatography methods”, “New Methods of Air Sampling and Analysis of Chemical Compounds in Air” and “Trace and ultra trace analysis of pyrethoides in air samples by HPLC”. At the Departament of Environment Sciences, Faculty of Chemical Technology, Slovak Technical University, Laboratory of Air Protection Technology (CHTF, 2004), studies on air pollution transport and kinetics of coal combustion in the atmosphere of carbon dioxide are performed. Health effects of air pollution are studied at the Institute of Preventive and Clinical Medicine. Air Pollution Modelling and Other Topics The Czech Republic and the Slovak Republic have a common history of air pollution modelling. The Slovak Republic was established in January 1, 1993. The old guidelines used for regulatory purposes were replaced in 1994. The US EPA ISC model was adapted to Slovak conditions (model MODIM). Additionally, the Slovak model AUTOMOD is recommended by the Ministry of Environment as the standard model for traffic pollution studies. Both models were included in the ETC/AQ MDS. Extensive urban air pollution studies were conducted within the framework of the project PHARE EU/93/AIR22. The very complex terrain of Slovakia limits to a great extent the application of simple dispersion models. The other current air pollution problem in Slovakia is the occurrence of ozone episodes. Implementation of 3D photochemical transport and dispersion model is desirable. Recently, the French mesoscale prognostic model ALADINversion Slovakia was put into operation at the Slovak Hydrometeorological Institute in Bratislava. It increased the potential of air pollution modelling in the Slovak Republic. A


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comprehensive review on the status of the atmospheric chemistry modelling in the Czech Republic and Slovak Republic is given in Zavodski et al (2000). Slovenia Ambient Air Quality Monitoring Network At the Environment Agency of the Republic of Slovenia (ARSO), within the Water Quality Section of the Monitoring Office there is a Chemical Analysis Laboratory (CAL), which performs physical and chemical analyses on samples from the environment (water, precipitation and air) as part of the national and international monitoring of water and air quality. CAL performs analyses of precipitation and air samples as part of the EMEP international air quality monitoring and the GAW/WMO. The analyses involve daily samples of aerosols and gases, and sampling at the Iskrba EMEP station at Koþevska Reka. CAL performs physical and chemical analyses (pH, electrical conductivity, main anions and cations) of daily and weekly precipitation samples taken by the Agency at ten measuring points in Slovenia. In 2003 the CAL successfully completed the accreditation procedure for the area of chemical testing of samples from the environment (water and precipitation) in line with the SIST EN ISO/IEC 17025 standard. In 2001, a project, financed by EU PHARE program and competed by the Slovenian company AMES d.o.o., replaced the existing (since the 1980s) network with a new, up-to date air pollution monitoring system. The Environmental Agency of the Republic of Slovenia (in Slovenian - ARSO) is a body within the Ministry of the Environment, Spatial Planning and Energy (ARSO, 2005). Through its mission and vision, the Environment Agency of the Republic of Slovenia is in step with the European Environment Agency, which functions as a consortium of several countries on an expert level and covers five integral sectors: air and climate change, water, nature and biodiversity, the terrestrial environment, waste and the material cycle. Since environmental information is important for the more successful formulation of environmental policy and monitoring of its implementation, they are joining the European network for transferring environmental information and are setting up a complementary system on the national level, which will allow them to establish links within Slovenia and in international circles, and will ease the processing, analysis, synthesis and comparison of data. Apart from the stations in the network of the Environment Agency, there are other automatic air quality monitoring networks, owned by major Slovenian Power plants, factories and local communities. Most of them are built by AMES. Major networks of this type belong to the Thermal Power Plant Šoštanj (10 stations with meteorological and gases measurements, one station also gamma dose rate measurements, emission stations on three stacks, hydrological station on Paka river), the Thermal Power Plant Trbovlje (6 stations with meteorological and gases measurements, emission stations on the stack, hydrological station on Sava river), the Thermal Power Plant Brestanica (one station with meteorological and gases measurements, one meteorological station, emission stations on the stack, hydrological station), the City of Celje,

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local community (one station with meteorological and gases measurements and two central units), the Cinkarna d.d. Celje (several small stations, SO2 and PM10 and meteorological measurements), and the Nuclear power plant Krško (4 meteorological stations, one has SO2 monitor added, all have gamma dose rate measurements, plus additional 9 stations only for gamma dose rate measurements). AMES d.o.o. is a private high technological and research company. Its fields of work are: meteorological sensors design, development and production; design and production of automatic measuring stations (ambient, emission, hydrological, meteorological, agrological, airport meteorology, radiological); design and production of automatic measuring systems for the environment; research in air pollution modelling (forecasting models based on neural networks, neural networks based solar radiation modelling, air pollution dispersion modelling). Atmospheric Chemistry Research Jozef Stefan Institute, Dept. of Environmental Sciences, Ljubljana, Slovenia (IJS, 2005). The Department of Environmental Sciences is an interdisciplinary group of researchers specializing in the fields of environmental analytical chemistry, radioecology, biogeochemical cycling and metabolism of trace elements in biological systems, bio monitoring, evaluation of nutritional values of food and feedstuffs, environmental modelling, and impact assessments. The Centre for Mass Spectrometry and management of an Ecological Laboratory with a mobile unit also form an important part of the work of the Department. At the division of Environmental Analytical Chemistry, some of the topics are: determination of persistent and/or toxic organic pollutants (aliphatic and aromatic hydrocarbons, chlorinated compounds, phenols, and pesticides) in different environmental matrixes (water samples, sediments, soil, biological materials); qualitative and quantitative analysis of gas samples by mass spectrometry, etc. The Environmental modelling and assessment group works on environmental modelling and assessment. Such modelling includes integrated mass transfer, migration and accumulation of pollutants in/through environmental media. Special emphasis is made on uncertainty and validity of the modelling. Other sides of the work concerns environmental impact assessment and development of expert systems and evaluation procedures for most complex environmental issues in the country, environmental policy development, and support of decision-making, as well as strategic environmental assessments. Among the user groups of the EUROCHAMP infrastructure is the National Institute of Chemistry, Ljubljana, Slovenia, with the main research field “Reactivity of aerosols under haze conditions and chemical characterisation of aerosol particles”. Participation of Slovenia in projects: x As a contributing member of the APHEIS group, Slovenia (Institute of Public Health, Ljubljana) participated in the study concerning the health impact assessment of air pollution in 26 cities (Ljubljana) in 12 European countries during 2001. x Six European countries are involved in the EMECAP project: Italy, Norway, Slovenia (Jozef Stefan Institute, Ljubljana), Sweden, Poland and Romania (April, 2001 - March, 2004). The objective of the EMECAP Project is to improve the tools of Regulatory Bodies to plan the actions to safeguard citizens’ health from mercury pollution.


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x As a contribution to the subproject TOR-2 of EUROTRAC-2, at the Faculty of Chemistry and Chemical Technology, University of Ljubljana, Hydrometeorological Institute, ECOSENSE, Ljubljana in cooperation with Fraunhofer Institute, Germany, an analysis of the ozone spring maximum at the Krvavec was performed. x The Project METROPOLIS covers 17 countries and brings together 38 participants from organisations and research institutes dealing with metrology and environmental monitoring in Europe. Leader from Slovenian part is the Jozef Stefan Institute. The METROPOLIS thematic network pursues three main objectives in environmental metrology: to improve the performance of environmental measurement systems and their harmonisation at EU level; to foster the dialogue between those who provide measurement methods and associated services, and the users of measurement results; to prepare the ground for further integration of research expertise and resources in environmental monitoring across Europe. x At the National Institute of Chemistry (NIC), in the frame of CMD subproject of EUROTRAC-2, experimental studies of the role of soluble constituents of atmospheric aerosols in the aqueous–phase autoxidation mechanisms of S(IV) was studied. The research focused on atmospheric water droplets (clouds, fog), where soluble constituents of atmospheric particles may be important in aqueous SO2 oxidation under non-photochemical conditions. In the frame of CMD project laboratory experiments in a semi-batch continuous stirred tank reactor under controlled conditions (T, air flow rate, stirring), were made in order to study the autoxidation of S(IV)-oxides catalyzed by transition metal ions (Fe(III), Fe(II), Co(II), Cu(II), Ni(II), Mn(II)). These studies were carried out at the National Institute of Chemistry. x At NIC, as a contribution to subproject AEROSOL, EUROTRAC-2, laboratory experiments with a continuous flow of some trace gases under controlled conditions, were performed in a reactor chamber. The preliminary results of SO2 oxidation in synthetic solutions containing various catalytically active metal ions were discussed. A laboratory model study of the role of aerosols composition in the process of formation of secondary acidic species from gaseous and particulate precursors was performed. x MERCYMS: An Integrated Approach to Assess the Mercury Cycling in the Mediterranean Basin x BIOMERCURY: Worldwide remediation of mercury hazards through biotechnology x Certification of trace elements: Several projects with JRC, IRMM- International Measurement Evaluation Programme; Geel, Belgium In the period 2004-2005 there are a number of bilateral projects between Slovenia and Austria: x Heterogeneous reactions of atmospheric aerosols under controlled experimental conditions typical for haze (Kemijski inštitut, Ljubljana); x Development of equations of state for humid gases based on speed-of-sound data (Univerza v Mariboru Fakulteta za strojništvo, Maribor); x Nitrate natural background assesment and pollution sources in groundwater (Univerza v Ljubljani Biotehniška fakulteta, Ljubljana); x Investigation of photochemical properties of molecules important for atmospheric chemistry, especially bromine and nitrogen containing compounds (Institut Jožef Stefan, Ljubljana).

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E. Batchvarova et al. Air pollution modelling and other topics

Because of very complex terrain the application of simple dispersion models is very limited in Slovenia. Traffic pollution and the high level of surface ozone are the main current air pollution problems in the country. No official standard model for regulatory purposes has been accepted in Slovenia up to present. The US EPA model ISC3 is used for routine dispersion calculations from point sources. Some other imported models were tested in Slovenia but only on research basis. A neural network forecasting model was developed for the Sostanj thermal power plant. No urban air pollution studies are reported from Slovenia. Air pollution modelling is performed at the Jozef Stefan Institute, Dept. of Environmental Sciences, Ljubljana, Slovenia (IJS, 2005), AMES d.o.o. and the Hydrometeorological service. Comparative and General Comments, Identified Needs and Problems Air Pollution Monitoring All countries have adopted the EU environmental legislation. The manual stations are being rapidly changed to automatic firstly in Czech Republic, Poland and Hungary, then in Estonia, Latvia, Lithuania and Slovenia and lastly in the Slovak Republic, Romania and Bulgaria. In the different countries the inter-institutional communication problem exists to different extents after the economical changes and the enlargement of the EU. The Ministries of Health and Ministries of Environment keep separate networks, and participate in different international cooperation. In some countries (Czech and Slovak Republic) the Ministries of Environment have delegated the ambient air monitoring to the meteorological services, which has kept and further developed the expertise within the country. In other countries (Bulgaria, Slovenia) the Ministries of Environment enlarged their monitoring activities based on the PHARE programme and other European funding and reduced the monitoring programmes of the meteorological services. In this way, the groups with expertise and tradition suffered a lack of funding and the newly established units suffered a lack of expertise and tradition. There is no easy solution to such problems and they also exist in the Western European Countries as well. What the Ministries of Environment can do is to allocate greater funding for research based on monitoring data (as in Germany, for example). The environmental data have to be easier accessible for research, than they presently are (for example in Bulgaria). As governmental bodies, the Ministries of Environment are the competent authority for the majority of activities related to environmental issues such as trans-boundary air and water pollution, troposphere ozone and climate change, for instance. The main task of a ministry on these issues is therefore to elaborate and implement the environment policy. As it is nearly everywhere within the Member States of the European Union, the ministries carry out only a few studies and analysis by themselves, but a lot of routine work is allocated to different administrations or institutions. This approach was not followed in some countries of the 10 and the research and international collaboration on different environmental programmes suffered for a


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long time. Another problem with the ministries during the period of changes was hidden in the change of staff, which has lead to losses of expertise. Atmospheric Chemistry Research In all countries there are research institutes and departments of universities, where atmospheric chemistry research is performed. The groups from the Czech Republic, Poland, Hungary, Slovenia, Estonia and Lithuania are more active. The groups from Romania, Bulgaria and Latvia have worked mainly within international projects, using facilities in different European countries. In the countries where the scientific structure was not changed with the start of economic changes in 1990s, namely where the academies of sciences and their institutes on physics and chemistry were kept, one can see the most successful groups (Aerosol Laboratory, Institute of Chemical Process Fundamentals, Prague, Academy of Sciences of the Czech Republic for example). These groups kept the expertise and were able to join and substantially contribute to European collaborations. In the small countries, like Slovenia and the Slovak Republic, new institutions with new objectives were formed and some of the expertise has been diluted. The system of financing science only by projects has lead to a reduction of the facilities. There are even cases where within a big project new equipment has been purchased but due to the lack of further funding further use of the equipment has been impossible. Such demerits of the project funding system are also seen in Western European countries. The project funding system stimulates competitiveness, but when institutional funding is available in addition, the effect is better. Air Pollution Modelling As pointed in Zavodski et al (2000) a little effort has been made in all countries towards urban chemistry modelling. A photochemical module using the EMEP chemical reaction scheme was developed and tested in the Slovak Hydrometeorological Institute. At the Charles University in Prague a photochemical urban scale model SMOG was developed. A simple chemical scheme (21 reactions) was implemented in the model. The US EPA model OZIPR (Ozone Isopleth Plotting Package, R-research version), including EKMA resp. CBM schemes, was implemented in the Institute for Atmospheric Physics in Budapest. A combination of the causal model and a statistical model is being tested for forecasting of high ozone concentrations in Budapest. Several stochastic models, based on mutli-parametric regression, artificial neural networks, Kalman filter and other statistical techniques, were implemented for short-term forecast of air pollution episodes, namely high ozone concentrations (Czech Republic, Hungary, Poland, Slovenia). The new generation of 3D urban photochemical transport and dispersion models are not in use in East European countries mainly for two reasons, i.e. shortage of funds available for research programmes and the absence of appropriate emission and meteorological input data. The existing computational facilities were not sufficient and thus the advanced meteorological preprocessors were not usable. The situation is gradually changing due to the advances in computer development, which made them accessible. However, concerning the meteorological pre-

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processing the situation is different. Limited area meteorological prognostic models were put into operation in some of the countries. French limited area hydrostatic models ALADIN (version Central Europe - LACE and version Southeast Europe - SELAM) are available at the meteorological services of Bulgaria, the Czech Republic, Hungary, Romania, Slovakia and Slovenia. The German Weather Service non-hydrostatic mesoscale meteorological model is implemented in Bulgaria and Poland. Recently the Atmosphere Research Programme was launched at Warsaw University in Poland, a common effort of the Interdisciplinary Centre for Computer and Mathematical Modelling (equipped with CRAY T3D) and the Institute of Geophysics. Some sophisticated research air pollution models of various scales are being put in operation. Generally, because of the limited support of science in the all countries in the last decade, efforts to develop dispersion models at a national level are diminishing. The tendency to implement the well-established foreign models was clearly identified. The intensive research in air pollution modelling during the last years in some of the 10 countries is due to the fact that it was concentrated at the Meteorological Services and where the structure and expertise was retained and further developed (Bulgaria, Romania). Another factor for further developments in the modelling studies is the existence of international structures like WMO and EMEP where all 10 countries participate. Participation in International Projects, Overview for all 10 Countries Framework Programme 4 of the EC The participation of the 10 countries in FP4 was under a separate budget and special conditions. The connections among the researchers was poorer than in the period of FP5. The 10 countries participated in only a few research projects. Framework Programme 5 of the EC Under the environment calls in the Energy, Environment and Sustainable Development section 267 projects were funded. About 150 of them were related with atmospheric research. Among those about 50 consortiums include one or more countries of the 10, including the accompanying measures projects such as conferences, centres of excellence and institutional projects. Most successful in the accompanying measures (8 projects) were the teams from Poland (Batchvarova et al., 2005). Bulgaria and the Czech Republic coordinated one project each. Considering the 35 multi-national research consortiums, German groups coordinated 12, English groups 7 and French groups 4 of them. Framework Programme 6 of the EC The database of FP6 is under development and therefore it is difficult to collect data on the participation of the 10 countries in atmospheric chemistry related projects. EC Twinning Programme All countries participated in twinning projects, but on different issues of the accession activities. Most active in such collaborations were the German institutions and groups.


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EUROTRAC-2 Almost all of the 10 countries participated in EUROTRAC-2 projects or subprojects. The EUROTRAC-2 Conferences were supporting participation of those countries, so presentations of groups not involved in specific EUROTRAC-2 projects were often given and thus the collaboration in the field of atmospheric chemistry enlarged. EMEP All 10 countries are members and participate in EMEP activities on Environmental quality measurements and modelling. WMO All 10 countries are members and participate in a number of programmes and activities on Environmental quality measurements and modelling, climate, weather forecast and others. The Meteorological services represent the countries in this collaboration. WHO All countries are members of the WHO and the Public Health services represent them. All participate in Environmental quality assessments, epidemiological studies and others. PHARE All countries were covered by the EC PHARE programme. The studies, projects and reviews were mainly orientated towards air quality monitoring networks. Conferences The research communities in all countries are very active in participating and organising international workshops, meeting, conferences, and congresses. Several Air Pollution Conferences were hosted in Bulgaria, Czech Republic, Poland, Hungary, and Slovenia. The Last European Aerosol Conference was held in Budapest, Hungary in 2004. A number of WMO and WHO meetings were organized by groups in these countries during the last 5-10 years. Synthesis of the Information and Identification of General Needs All countries have adopted national environmental strategies by the end of 2004, which are in line with the EU legislation and practice. In all countries the environmental legislation is in line with that of the European Union. In most of the countries the atmospheric chemistry process studies with appropriate facilities are limited. In the Czech Republic, Poland, Estonia and Slovenia such research is performed by only a few groups. In all the countries there are needs for greater research funding within the countries in order to be able to prevent the young scientists from emigrating. In all countries there is expertise and the senior scientists are aware of all the European and worldwide achievements in their fields. The modest national funding and existing facilities do not allow up-to-date atmospheric chemistry research, even such connected to monitoring. This brings the situation that individual researchers join European scientific projects and visit facilities. Rarely can these researchers provide comparable equipment which would allow them to participate within European projects on an equal basis. In addition, the national (in many cases modest) funding of research is now

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organized on a project basis. This does not support the establishment of long-term modern facilities which are needed for contemporary research. The wide exchange of people and knowledge within Europe is extremely useful, stimulating and necessary. There is still more to do in order to bring researchers back to their country of origin. This need has been recognized in the last years with the new funding form Marie Curie or other fellowships granted to returning scientists. Still, there is much more to do within the countries, where the research groups are trying to keep the knowledge and to participate in international projects. Project funding has the disadvantage of short term, which makes difficult the support of expensive equipment. Even if some equipment is bought for a project, after the end of this project it is hardly used and there is no means to pay consumables and support personnel. The same problem exists in Western European countries as well. Although the aim of the survey was not to go into personal contacts with all groups, for some countries comments were requested from national experts (Slovenia, Hungary, Bulgaria, Czech Republic and Estonia). Also, discussions at conferences and workshops were used to form the conclusions and identify difficulties and gaps. Some of the identified difficulties, such as difficulties in communication among institutions within the countries, shortcomings of the project-funding research system and others, are observed in the Western European countries as well. Acknowledgements The survey was performed under contract 22382-2004-09 F1ED ISP BG between the EC JRC Ispra, Italy and NIMH, Sofia, Bulgaria. The authors, all from the Department of Composition of the Atmosphere and Hydrosphere at the National Institute of Meteorology and Hydrology, are thankful to Krasimira Lazarova from the same department for the technical help during the project. Colleagues from different countries were asked to comment on the survey of their country. The authors are grateful to them for their prompt response. References ANALYTIKA, 2004 - http://www.analytika.sk ARSO, 2005 - http://www.arso.gov.si/english/ Batchvarova E., T. Spassova, N. Valkov and L. Yordanova, 2004, Survey on atmospheric chemistry research in some new EU Member states and Candidate countries, Report on Contract 22382-2004-09 F1ED ISP BG between the EC JRC Ispra, Italy and NIMH, Sofia, Bulgaria. 99 p. Berlyand, M. (Ed.) 1981, Proceedings of the International Conference on Air Pollution held in 1977 in Leningrad, USSR, Leningrad, Gidrometeoizdat. BULAIR, 2002 - www.meteo.bg/BULAIR CHMI, 2004 - http://www.chmi.cz/uoco/isko/tab_roc/1997_enh/ENG/kap_02/kap_02_top.html CHTF, 2004 - http://www.chtf.stuba.sk/ EDXRS, 2002 http://iapf.physik.tu-berlin.de/EDXRS2002/sessions/postersessionii.htm


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EMEP, 2002 - http://www.emep.int/assessment/Part2/183-196_Part2-utan.pdf Estonian National Environmental Strategy (NES), Atmospheric Air, 2000 by Natalja Kohv, Valentina Laius, Siiri Liiv, Ott Roots, Reet Talkop Fiala, J. and J. Ostatnická (eds.), 2003, Air Pollution in the Czech Republic in 2002, Czech Hydrometeorological Institute, 158 p, ISBN 80-86690-07-5, www.chmi.cz/indexe.html. ICHF, 2005 - http://ichf.edu.pl/ IJS, 2005 – www.ijs.si Latvia, 1999, Report from Phare Country Visit- www.chmi.cz/uoco/isko/ptl/99ptl/qpr7-ann3.html Latvia, 2000, Report from Phare Country Visit - http://www.chmi.cz/uoco/isko/ptl/ qpr5ive.html Lithuania, 2001, Phare Country Visit Lithuania, Latvia and Estonia, 5-13 February 2001, Fifth Quarterly Progress Report, Annex IV.C, PTL/AQ - http://www.chmi.cz/uoco/isko/ptl/ Parvanova, M. 2003, Present conditions and problems of air pollution in Bulgaria, WHO Collaborating Centre for Air Quality Management and Air Pollution Control, Berlin, NL 30, http://www.umweltbundesamt.de/whocc/titel/ Puklová, V, P. Denková (eds.), 2003, Environmental Health Monitoring System in the Czech Republic – Report 2002 National Institute of Public Health, Prague 2003, 134 pages, ISBN 80-7071-215-5, www.szu.cz/chzpa/sumrep.htm REC, 1990, Regional Environmental Centre for Eastern and South-eastern Europe - www.rec.org/REC/ SHMI, 2004 - http://www.shmu.sk/ SHMI, 2004a - http://fsp.shmu.sk/document/MinutesBE12-16May.pdf Starnet, 2005 - http://starnet.rta.nato.int/results.asp?node=6&topic=38 SZU, 2004 - http://www.szu.cz/chzp/rep03/szu_03an/ka04_04.htm/ Twinning, 2000 - www.umweltdaten.de/luft/immissionen Ubelis, A. and V. Bergmanis, 2000, Insight in the history of point source air pollutant emission inventory in Latvia. In: Transport and Chemical Transformation in the Troposphere. Munich: EUROTRAC-2, 2000, TRAP-2. Zavodsky D, G Baranka, L Cernikovsky and Ken Stevenson, 2000, Review of urban air pollution models in PHARE accession countries for the support of CAFE October 2000 - http://www.chmi.cz/uoco/isko/ptl/

Appendix I. Addresses of Institutions Bulgaria Institution National Centre of Hygiene National Institute of Meteorology and Hydrology (NIMH), Bulgarian Academy of Sciences (BAS) Ministry of Environment and Waters (MEW) Geophysical Institute, BAS Faculty of Chemistry, Sofia University Faculty of Physics, Sofia University, Executive Agency on Environment, Ministry of

Address Blvd Dimitar Nestorov 15, 1431 Sofia, Bulgaria Blvd Tsarigradsko chaussee 66, 1784 Sofia, Bulgaria, http://www.meteo.bg Address: 1000 Sofia, 67 William Gladstone str., http://www2.moew.government.bg/ Acad. Bonchev Str., Block 3, 1113 Sofia, Bulgaria, www.geophys.bas.bg 1 Blvd James Baucher, 1126 Sofia, Bulgaria, www.chem.uni-sofia.bg 5 Blvd James Baucher, 1126 Sofia, Bulgaria, www.phys.uni-sofia.bg 136 Tzar Boris III blvd., P.O. Box 251

338 Environment and Waters University of Chemical Technology and Metallurgy (UCTM) University of Plovdiv “Paisii Hilendarski”, Faculty of Chemistry The Southwest University “Neofit Rilski” Institute of Physical Chemistry, Bulgarian Academy of Sciences (BAS) Institute of Catalysis, BAS Institute of General and Inorganic Chemistry, BAS

E. Batchvarova et al. 1618 Sofia, Bulgaria 8 St. Kliment Ohridski blvd..1756 Sofia, Bulgaria, www.uctm.edu 24 Tzar Assen St, 4000 Plovdiv, Bulgaria www.uni-plovdiv.bg 66 Ivan Mihailov str., 2700 Blagoevgrad, Bulgaria, www.swu.bg Acad. G. Bonchev Str., Block 11, Sofia 1113, http://www.ipc.bas.bg Acad. G. Bonchev St., Bldg.11, Sofia 1113, Bulgaria, http://ic.bas.bg Acad. G. Bonchev str. Block 11, 1113 Sofia Bulgaria, http://www.igic.bas.bg

Czech Republic Institution Charles University, Department of Meteorology and Environmental Protection The National Institute of Public Health, Department of Air Hygiene The Czech Hydrometeorological Institute (CHMI) Aerosol Laboratory, Institute of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic Institute of Atmospheric Physics, Academy of Sciences of the Czech Republic The Czech Aerosol Society (CSA) Research centre of environmental chemistry and ecotoxicology (RECETOX) - Air Sampling Group (AIRSAG) Institute of Thermomechanics, Academy of Sciences of the Czech Republic

Address V. Holesovickach 2, 18000 Praque 8, Czech Republic, www.cuni.cz Srobarova st 48, 10042 Prague 10, Czech Republic, http://www.szu.cz/ Na Sabatce 17, 14306 Prague 4 – Komorany, Czech Republic, http://www.chmi.cz/indexe.html Rozvojova 2, CZ-165 02 Prague 6 – Suchdol, Czech Republic, http://www.icpf.cas.cz/aero/ Dolejškova 3, 182 23 Prague 8, Czech Republic, http://www.jh-inst.cas.cz Boþní II 1401, 141 31 Praha 4, Czech Republic, http://limail.ufa.cas.cz/en/info.html. Rozvojová 135, 165 02 Praha 6, Czech Republic, http://cas.icpf.cas.cz/index.php RECETOX - TOCOEN&Associates, Kamenice 126/3 625 00 Brno, Czech Republic, http://recetox.chemi.muni.cz/ Dolejkova 5, 182 00 Praha 8, Czech Republic, www.it.cas.cz

Estonia Institution National Institute of Chemical Physics and Biophysics Tartu University, Institute of Physical Chemistry Tartu University, Institute of Thechnology

Address 23 Akadeemia Rd., Tallinn 12618, Estonia, http://www.kbfi.ee/ 2 Jakobi St., Tartu 51014, Estonia http://www.ut.ee/index.aw/ Vanemuise 21, Tartu 51014, Estonia, http://www.tuit.ut.ee/

Hungary Institution The Ministry for Health and Social Welfare

Address Arany János u. 6-8, Budapest H-1051, Hungary, http://www.eum.hu/eum/eum_angol.main.page

Survey on Atmospheric Chemistry Research in Some New EU Member States The National Meteorological Service

Eötvös Loránd University – Dept. of Chemical Technology and Environmental Chemistry Eötvös University, Budapest, Department of Physical Chemistry Air Chemistry Group in the Hungarian Academy of Science, University Vezsprem Aerosol Association of Hungary

1024 Budapest, Kitaibel Pál u. 1. , Postal address:1525 Budapest, Pf. 38, Hungary, http://omsz.met.hu/english/kfo/l Pázmány P. s. 1/A, 1117 Budapest, Hungary, http://teo.elte.hu/fs/ chembase.html). Mail address: 1518 Budapest 112, P.O.Box 32. Hungary, http://www-phch.chem.elte.hu/, H-8201 Veszprém, P.O.Box 158, Hungary, http://www.mta.hu/index). 1085 Budapest, Rigo u. 3

Latvia Institution Ministry of Environmental Protection and Regional Development State Hydrometeorological Agency, Latvia Environmental Quality Division Latvian Environment Agency (under supervision of the Ministry of Environmental Protection and Regional Development) National Environmental Health Center (under supervision of Ministry of Welfare) University of Latvia, Institute of Atomic Physics and Spectroscopy Univ. of Latvia, Dept. of Analytical Chemistry

Address Peldu Str. 25, 1494 Riga, Latvia, www.gov.lv Tel: (371-7) 026-400, Fax: (371-7) 820-442 Maskavas Str. 165, 1019 Riga, Latvia Tel: (371-7) 144-390, Fax: (371-7) 145-154 Straumes str. 2, 2015 Jurmala, Latvia (371-7) 811-492, www.vdc.lv Klijanu Str. 7, 1012 Riga, Latvia Tel: (371-7) 379-231, Fax: (371-7) 339-006 19 Rainis Blvd., LV-1586 Riga, Latvia Tel./Fax.: +371 7229727; http://home.lanet.lv/~asi/ Riga, Latvia

Lithuania Institution Institute of Physics Ministry of Environment, Joint Research Centre, Environmental Quality Assessment Division

Address Savanoriu Pr. 231, 2053 Vilnius, Lithuania, www.fi.lt A. Juozapaviciaus 9, 2600 Vilnius, Lithuania

Poland Institution Institute of Physical Chemistry, Polish Academy of Sciences (PAS) Chemical Faculty, Technical University of Gdask Institute of Oceanology, PAS Environmental Sciences University of Mining and Metallurgy Voivodship Inspectorate of Environmental Protection - Slupsk Inst. of Occupat. Medicine and Environm. Health National Institute of Hygiene Institute for Ecology of Industrial Areas Wroclaw University of Technology Warsaw University of Technology Institute of Nuclear Chemistry and Technology

Address Kasprzaka 44/52, 01-224 Warsaw, Poland 80-952 Gdansk, Poland ul. Powstancow Warszawy 55, 81 712 Sopot, Poland Al. Mickiewicza 30, 30-059 Cracow, Poland Kniaziewicza 30, 76-200 Slupsk, Poland 13 Koscienla Street, 41-200 Sosnowiec, Poland 24 Chocimska, 00 791 Warszawa, Poland Ul. Kossutha 6, 40 833 Katowice, Poland ul. Smoluchowskiego 25, 50372 Wroclaw, Poland Nowowiejska 21/25, 00 005 Warszawa, Poland 16 ul. Dorodna, 03 195 Warszawa, Poland

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340 Institute of Coal Chemistry, PAS The Inst. of Ecological Chemistry and Engineering Technical University of Gdansk

E. Batchvarova et al. Sowinskiego 5, 44 121 Gliwice, Poland Chlodnicza 4, 45 315 Opole, Poland G.Narutowicza Street 11-12 , P.O.Box 612 80 952 Gdansk, Poland

Romania Institution Institute of Hygiene, Public Health, Health Services and Management “Alexandru Ioan Cuza“ University of Iasi, Faculty of Chemistry University of Ploiesti PETROLEUM-GAS National Institute of Meteorology, Hydrology and Water Management National Institute for Marine Research and Development “Grigore Antipa”

Address Leonte str. 1-3, 76256 Bucharest, Romania Carol I Boulevard, 11, Iasi 6600, Romania. Bd. Bucuresti 39, 2000 Ploiesti, Romania Sos. Bucuresti-Ploiesti 97 71552 Bucuresti, Romania Mamaia Boulevard 300 8700 Constantza, Romania

Slovak Republic Institution The Hydrometeorological Institute (SHMU) Slovak Technical Univ., Dept. of environmental sciences, Faculty of Chemical and Food Technology Institute of Preventive and Clinical Medicine Department of Analytical Chemistry, Faculty of Natural Sciences, Comenius University

Address Jeséniova 17, 833 15 Bratislava http://www.shmu.sk/ Radlinského 9, 81238 Bratislava, Slovak Republic, http://www.chtf.stuba.sk/kei/indexe.php Limbová 14, 833 01 Bratislava, Slovak Republic, http://www.upkm.sk/, Mlynska Dolina 15, 1842 Bratislava, Slovakia, http://www.analytika.sk

Slovenia Institution University of Ljubljana, Faculty for Chemistry and Chemical Technology ECOSENSE Inst. of Public Health of the Republic of Slovenia Nova Gorica Polytechnic Josef Stefan Institute University of Ljubjana National Institute of Chemistry (NIC) Ministry of Environment and Spatial Planning, Environmental Agency of Slovenia AMES d.o.o.

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New Measurements of NMVOC Concentrations in the City Air of Wuppertal, Germany: Input Data for Chemical Mass Balance Modelling Anita Niedojadlo, Karl Heinz Becker, Ralf Kurtenbach, and Peter Wiesen Department of Physical Chemistry, University of Wuppertal Gaußstr. 20, 42097 Wuppertal, Germany Key Words: NMVOCs, Oxygenated compounds, Emission profiles, CMB modelling, Source apportionment

Abstract Non-methane volatile organic compounds (NMVOC) were measured at various sites representing different areas and different emission sources in the city of Wuppertal, Germany. The measurements covered volatile hydrocarbons in the range of C2-C10 and oxygenated hydrocarbons such as alcohols, ketones and esters. Samples were collected using Carbotrap and Carbosieve SIII solid adsorption tubes and analysed off-line by thermal desorption and GC-FID analysis. Measurement results were used to create the input data for the source apportionment analysis with the Chemical Mass Balance Modelling technique. Emission profiles for traffic and solvent use were calculated. Introduction With respect to the European scale, road traffic and solvent use are by far the most important source categories of anthropogenic non-methane volatile organic compounds (NMVOC) emissions. Whereas NMVOC emissions from combustion processes contain predominantly pure hydrocarbons (alkanes, alkenes and aromatics), organic solvents and their vapours also contribute large quantities of oxygenated hydrocarbons such as alcohols, ketones, esters, glycol derivatives, ethers and halogenated hydrocarbons (Ullmann's Encyclopedia, 2001). Up to now, data from different German cities could only establish that road traffic represents the dominant source of shorter chain (C2-C9) hydrocarbons (Thijsse et al., 1999; Slemr et al., 2002; Gomes, 2002). On the other hand German NMVOC emission inventories show that solvent use is the main source of NMVOC emissions (Theloke et al., 2001; Umweltbundesamt, 2003). However, the relative importance of these two source categories is still afflicted with a large uncertainty mainly due to the lack of specific measurements of larger hydrocarbons and oxygenated species. In this work atmospheric concentrations of a large number of non-methane volatile organic compounds (NMVOCs) emitted by different anthropogenic sources, in particular from traffic exhaust and solvent use, have been investigated. The results from the studies should provide more information about the relative importance of road traffic and solvent use to the total NMVOC emission in Europe. Investigated compounds For better characterisation of both selected sources, namely traffic and solvent use, in addition to pure hydrocarbons also oxygenated species were included to the group of 341 I. Barnes and K. J. Rudzinski (eds.), Environmental Simulation Chambers: Application to Atmospheric Chemical Processes, 341–350. © 2006 Springer. Printed in the Netherlands.

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investigated compounds. The source category of solvent use is characterised not only by a large variety of solvent-containing products but also by a broad range of applications in industrial production as well as in commercial and private use (Ullmann’s Encyclopedia, 2001). Among a large number of oxygenated species contained in solvents and solvent related products, the most common oxygenated compounds were targeted for the investigation. The choice was based on the known composition of products used in: water-based architectural coatings, consumer products, paint applications, printing industry, dry cleaning (McInnes, 1996; Friedrich and Obermeier, 1999; Ullmann’s Encyclopedia, 2001; EMEP/Corinair, 2003), automotive performance coatings (DuPont, 2001). The most abundant compounds were tested with respect to the capability of their qualification and quantification with the selected analytical method. The list of oxygenated compounds was additionally enhanced by methyl tert-butyl ether, a typical species added to gasoline as an octane enhancer in order to reduce emissions when gasoline is burned in engines (European Fuel Oxygenated Association, 2003). Finally, 18 oxygenated species were selected for investigation. Measurement procedure The measurements of non-oxygenated hydrocarbons and oxygenated species were performed according to the United States Environmental Protection Agency Compendium Method TO-17 entitled “Determination of Volatile Organic Compounds in Ambient Air Using Active Sampling Onto Sorbent Tubes” (Woolfenden and McClenny, 1999). The procedure was as follows: x x x x

ambient air collection by active sampling on glass tubes packed with adsorption materials, thermal desorption of sampled tubes, sample pre-concentration with a cryo trap, gas chromatography-flame ionisation detection analysis.

During the city air measurements sampling collection was performed for four air samples in parallel. Two samples were used for the analysis of non-oxygenated hydrocarbons and two for oxygenated hydrocarbons. For non-oxygenated hydrocarbons mulit-bed tubes packed with Carbotrap graphitized carbon and Carbosieve SIII carbon molecular sieve separated by glass wool were selected. For oxygenated hydrocarbons a combination of two adsorbent tubes with different characteristics was used, namely a tube packed with Carbotrap and a tube with Carbosieve SIII. Constructions of the adsorbent tubes are presented by Figure 1 and 2.

Figure 1. Construction of adsorbent tubes used for the sampling of non-oxygenated hydrocarbons.

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Figure 2. Construction of adsorbent tubes used for sampling of oxygenated hydrocarbons. The main characteristic of employed Carbotrap and Carbosieve SIII sorbents are presented in Table 1. Characteristics of the adsorption materials used for VOC sampling (Woolfenden and McClenny, 1999). hydrophobicity adsorbent max. temp (°C) specific area (m2/g) Carbotrap >400 100 yes Carbosieve SIII 400 800 no

Table 1.

After sampling the adsorption tubes were tightly capped and transported to the laboratory. Until the time of analysis the tubes were stored in a clean container placed in a refrigerator. Sampled tubes were analysed through a sequence of analytical steps. The analysis of non-oxygenated hydrocarbons and oxygenated species were performed separately. There were some variations in the manner of treatment of non-oxygenated and oxygenated compounds, however, the main steps were the same, namely a dry purge of the sampled adsorption tubes, thermal desorption of sampled tubes, analyte refocusing on a secondary trap and followed by GC-FID analysis. A schematic scheme of the analytical steps involved in the sample analysis is shown in Figure 3.

heated line

water trap

cryo trap

Preconcentrator 7100 Entech Instruments

capillary column

GC 6890 / GC 5840A Hewlett Packard

FID tube purge

tube desorption

focus

heated line

Thermal Desorption Unit 890 Supelco

outlet

carrier gas

Figure 3. Schematic overview of the sample analysis steps. The main difference in the way of analysis of non-oxygenated hydrocarbons and oxygenated species was the employment of 2 different gas chromatographs. The nonoxygenated hydrocarbons were analysed using a Hewlett Packard GC 6890 equipped with a 90 m HP-1 (100% dimethylpolysiloxane, nonpolar) capillary column. The oxygenated species were analysed with a Hewlett Packard GC 5840A using a 60 m DB-WAX (CARBOWAX,


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polar) capillary column. The temperature programs for both columns were optimised in order to obtain the best resolution. The FID’s parameters were also set to those giving the best sensitivity of detection. The parameters finally selected for the GC systems are presented in Table 2. Table 2.

Parameters of the GC-FID process.

Parameters capillary column x film material x column length x column diameter x film thickness carrier gas inlet temperature column pressure (setpoint) oven parameters during GC run: x start temperature x ramp x end temperature x total GC run x column back flashing detector (FID) parameters: x detector temperature x hydrogen flow x synthetic air flow x helium flow (make-up gas)

HP GC 6890 HP-1 (nonpolar) dimethylpolysiloxane 90 m (3 x 30 m) 0.32 mm 3.00 Pm helium 100°C 2 bar

HP GC 5840A DB-WAX (polar) carbowax 60 m 0.25 mm 0.25 Pm helium 100°C 2 bar

- 50°C over 10 min 5°C/min up to 200°C 200°C over 20 min 80 min on after 64 min

30°C over 30 min 5°C/min up to 200°C 200°C over 6 min 70 min -

300°C 40 ml/min 350 ml/min 30 ml/min

300°C 24 ml/min 340 ml/min 30 ml/min

The calibration procedure of non-oxygenated hydrocarbons was performed with a NPL (National Physical Laboratory) standard gas mixture containing 30 C2-C9 compounds. For oxygenated compounds, calibration was performed using pure liquid substances supplied by Aldrich, Lancaster or Merck. The calibration procedure involved: x substrate preparation in a 405 L reaction chamber under atmospheric conditions, i.e. 298 K and 760 Torr total pressure, x

determination of the substrate concentration by FTIR spectroscopy (Nicolet Magna 550),

x

active sampling onto adsorption tubes,

x

thermal desorption and GC-FID analysis.

This procedure allowed the calibration of the whole measurement system from the sampling tubes to the gas chromatograph. Measurement sites During three measurement campaigns performed in September 2001, August/September 2002 and October 2003, non-methane volatile organic compounds concentrations were measured at different city areas in Wuppertal near relevant sources of NMVOCs. The


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measurements were carried out using a car equipped with a hydrocarbon sampling system and automatic analysers for detection of carbon monoxide, carbon dioxide, nitrogen oxides, sulphur hexafluoride and a small met-station for meteorological parameters. In order to create the NMVOC emission profiles for road traffic, measurements were performed at areas representative for all major traffic conditions. Sampling was carried out in: x

a traffic tunnel (Kiesberg tunnel),

x

a down-town street intersection,

x

during drives in the city centre of Wuppertal and on the freeways.

It was assumed that the concentrations measured at the above sampling points and driving situations were dominated by emissions from traffic. For the NMVOC profiles of solvents emission measurements were performed around various solvent factories and workshops in Wuppertal. The following emitters were considered: x

DuPont Performance Coatings GmbH,

x

PPG Industries Lacke GmbH,

x

Bayer AG,

x

Dr. Alfred Conrads Lackfabrik Nachf. KG,

x

Karosseriebau Gorn GmbH.

To obtain the local ambient NMVOC concentrations sampling was performed at different points located in Wuppertal. The sampling sites represented residential, industrial, mixed settings and areas down-wind from the city centre. Chemical Mass Balance Modelling For the assessment of the contribution of the emission categories to the observed NMVOC concentrations the Chemical Mass Balance (CMB) modelling technique, version 8 from United States Environmental Protection Agency (Watson et al., 1998; Watson et al., 2001) was selected. The method uses source specific ratios between the emission rates of certain set of compounds and aims to recognise these fingerprints, or source profiles, in the profile measured at the receptor point. As a result the CMB model delivers contributions from each source type to the total ambient NMVOC and individual hydrocarbon species at receptor points and their uncertainties. The fundamental principle of the receptor models is that mass conservation can be assumed and the composition of source emissions are constant over the ambient and source sampling period. Therefore, the ratios between the components emitted by a single source are identical to the ratios between the resulting concentrations on the receptor location. Other assumptions required by the model are: x

the chemical species do not react with each other,

x

all sources which may significantly contribute to the receptor have been identified and their emissions characterised,

x

the number of source categories is less than or equal to the number of chemical species,


346 x x

source profiles are linearly independent, i.e. sufficiently different from one another, measurement errors are random, uncorrelated and normally distributed.

These assumptions are fairly restrictive and difficult to fulfil in practice. However, the CMB model tolerates some deviations, which increase the final uncertainties of the source contribution estimation (Watson et al., 1998). The CMB calculations based on the input data presented below are the subject of a separate paper, which will be published elsewhere (Niedojadlo et al., 2005). Input data for the Wuppertal study As a model input to the CMB model serves: x

NMVOCs emission source profiles, so-called source fingerprints, which are the fractional amount of chemical species in the NMVOCs emissions from each source type,

x

receptor (ambient) NMVOCs concentrations, for which the contributions of emission categories are to be estimated,

x

realistic uncertainties for source and receptor values which are used to weight the relative importance of input data to model solutions and to estimate the uncertainty of the source contributions.

Because the purpose of this study was to provide more information about the relative importance of road traffic and solvent use to the total NMVOC emission only these two source categories were included in the CMB analysis. The fingerprints of NMVOC emission sources prepared for the CMB are those obtained from the source measurements. All fingerprints contain contribution from 105 species (95 varied concentrations, 9 pairs of co-eluted compounds). From about 190 hydrocarbons peaks detected in the GC-FID signals, the following compounds were selected for further investigation and CMB analysis: x

68 non-oxygenated hydrocarbons in the range C2-C10 from the hydrocarbon groups: alkanes, alkenes, alkynes, and aromatics,

x

18 oxygenated hydrocarbons in the range C1-C6 including alcohols, ketones and esters and also methyl tertiary butyl ether (MTBE),

x

19 hydrocarbon compounds with known carbon number but unidentified structure, these species were selected on the basis of their abundance and variation (compounds with an average concentration above 0.3 Pg/m3 and significant variation) and because of high significance to the source profiles diversification.

In this work the convention has been used that the fingerprints are normalised to unity. Results and discussion Traffic emission source profiles The measurements on the source profiles of traffic emission were carried out in a traffic tunnel (Kiesberg Tunnel), a downtown street intersection and during drives in the city centre of Wuppertal and on the freeways. Profiles of each of these measurements have been


347

compared in order to establish whether they can be considered identical. Figure 4 presents the distribution of all the analysed compounds for all the traffic relevant measurements.

Figure 4. Emission profiles for road traffic; the mass distribution of 105 compounds. All the measured traffic profiles were found to be very similar. The same distribution could be observed for tunnel, intersection and street and freeway driving measurements. The highest contribution was from toluene, about 20%, with major contributions also from benzene, meta- and para-xylene, 2-methylpentane, isopentene, 1-butene and isobutene. Because of the good agreement between these profiles, they have been averaged to obtain a single traffic emission profile. This profile is considered characteristic of the traffic conditions and was used in the CMB analysis. The traffic fingerprint is presented on Figure 5.

Figure 5. Average emission profile of road traffic.

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Solvent use emission profiles To obtain solvent relevant emission profiles, measurements were performed around various solvent factories and workshops in Wuppertal. Due to the fact that the emission of solvent plants is not restricted only to the point emitters and is more like a surface emission, direct measurements of the emissions were not possible. Because of this, to determine the emission profile of particular factories the measurements of down-wind sources and background NMVOCs concentrations were performed. The solvent use fingerprints thus obtained are presented in Figure 6.

Figure 6. Emission profiles for solvent use; mass distribution of 105 compounds. As observed from a comparison of Figure 5 and 6, the solvent use fingerprints contain much higher contributions of oxygenated hydrocarbons than in the case for traffic. For example, for the measurements performed close to the DuPont factory (measurements on 18.09.01) the contribution of butyl acetate was about 80%. Also 2-butanol and acetone contribute significantly to the total mass. For non-oxygenated hydrocarbons xylenes and also toluene are important markers for the solvents emission. However, the solvent profiles obtained from the measurements differ significantly from one another. For different measurements different mass distributions were found, thus, no average solvent emission profile could be constructed. Receptors To perform the source apportionment the Chemical Mass Balance model applies the emission profiles from traffic and solvent use to the NMVOCs concentrations measured at the different receptors point in Wuppertal. Measurements were performed down-wind from the city centre, in areas close to the factories and workshop producing or using solvents, in dense traffic areas and in residential areas. The characteristics of the receptor points are presented in Table 2.

New Measurements of NMVOC Concentrations in the City Air of Wuppertal, Germany Table 2.

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Receptor points for CMB analysis. 6 NMVOC measured

receptor sites

characteristic

sampling time

Blücher Str.

Hatzfelder Str.

Industrial area, close to PPG solvents factory, down-wind from the object Industrial area, close to DuPont solvents factory Down-wind from the city centre of Wuppertal Down-wind from the city centre of Wuppertal City centre of Wuppertal, dense traffic intersection City centre of Wuppertal, dense traffic intersection Residential area outside from the city centre Residential area outside from the city centre Industrial area, close to DuPont solvents factory Industrial area, close to DuPont solvents factory

Simon Str.

Bissing Str.

(Pg/m3)

r

18.09.01 13:20-14:20

53.809

2.694

18.09.01 15:20-16:20

515.607

7.590

19.09.01 11:10-12:10

29.775

2.629

22.08.02 15:06-16:06

31.083

2.422

26.08.02 15:35-16:35

58.344

2.167

26.08.02 16:40-17:40

42.527

3.235

27.08.02 15:55-17:05

30.610

1.524

27.08.02 17:12-18:24

23.827

1.190

29.08.02 13:06-14:10

18.408

3.061

29.08.02 14:55-15:55

45.064

2.842

Industrial area, close to Bayer factory

03.09.02 10:35-11:40

26.104

3.071

Industrial area, close to PPG solvents factory Industrial area, close to PPG solvents factory Industrial area, close to Conrads solvents factory Industrial area, close to PPG solvents factory, up-wind from the object Industrial area, close to PPG solvents factory, down-wind from the object

03.09.02 12:52-13:52

36.890

4.112

04.09.02 14:29-15:30

23.233

1.398

04.09.02 16:17-17:17

46.234

2.377

13.10.03 13:06-14:06

21.895

1.930

13.10.03 13:06-14:06

27.548

2.145

Märkische Str.

Close to free way 46

15.10.03 13:08-14:08

72.789

8.992

Hatzfelder Str.

Industrial area, close to DuPont solvents factory Industrial area, close to Gorn solvents workshop Industrial area, close to Gorn solvents workshop

15.10.03 12:55-14:00

61.431

5.503

17.10.03 09:45-10:45

115.315

11.772

17.10.03 09:45-10:55

75.803

10.048

Hatzfelder Str.

Girardet Str. Uni

Bundesallee Bundesallee Im Johannistal, Im Johannistal, Wilkhaus Str.

Lützow Str.

Viehhof Str. Yorck Str. Bissing Str.

Simon Str. Simon Str.

Conclusions NMVOC profiles for traffic emissions were measured in a traffic tunnel, a down-town intersection, during city and freeway drives. All the profiles obtained showed very similar mass distributions of the measured compounds. Hence, one single averaged traffic emission profile representing all traffic conditions was created. Solvent emission profiles were measured in the vicinity of several solvent factories and workshops in Wuppertal. Contrary to the emissions from traffic, the solvent fingerprints obtained from different measurements indicate significant differences between the emissions of different solvent relevant sources. According, it was not possible to create one average solvent use source profile and particular solvent emitters were considered separately. Significant differences between the major compound concentrations for traffic and solvent use emission profiles could be observed. Compared to the traffic fingerprints the

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emission profiles representing solvent use had much higher contributions of oxygenated compounds and toluene and xylenes. Further measurements and calculations are necessary in order to improve the emission profiles of solvent use and to include additional emission sources such as evaporative losses of motor fuel, natural gas leakage, stationary fuel combustion and biogenic emissions to the CMB apportion analysis. Acknowledgements The financial support by the Deutsche Bundesstiftung Umwelt (German Environment Foundation - DBU) is gratefully acknowledged. References DuPont Performance Coatings GmbH, personal communication (2001). European Environmental Agency; Emission inventory guidebook, 3rd Edition, Copenhagen (2003). European Fuel Oxygenates Association; MTBE resource guide (2003). Friedrich, R., A. Obermeier; Antropogenic emissions of volatile organic compounds, in: C. N. Hewitt (eds), Reactive hydrocarbons in the atmosphere. Academic Press, San Diego (1999) 2-38. Gomes J.A.G.; Impact of road traffic emissions on the ozone formation in Germany, PhD thesis of University of Wuppertal, Wuppertal (2002). McInnes, G. (eds); Joint EMEP/CORINAIR atmospheric emission inventory guidebook, European Environmental Agency, Copenhagen (1996). Niedojadlo, A., K.H. Becker, R. Kurtenbach, P. Wiesen; New measurements of NMVOC concentrations in the city air of Wuppertal: Source apportionment by Chemical Mass Balance Modelling, Atmos. Environ. manuscript in preparation (2005). Slemr, F., G. Baumbach, P. Blank, U. Corsmeier, F. Feidler, R. Friedrich, M. Habram, N. Kalthoff, D. Klemp, J. Kühlwein, K. Mannschreck, M. Möllmann-Coers, K. Nester, H.J. Panitz, P. Rabl, J. Slemr, U. Vogt, B. Wickert; Evaluation of modelled spatially and temporarily highly resolved emission inventories of photosmog precursors for the city of Augsburg: The experiment EVA and its major results, J. Atmos. Chem. 42 (2002) 207-233. Theloke, J., A. Obermaier, R. Friedrich; Abschätzung der Emissionen von Lösemitteln in Deutschland, Gefahrstoffe Reinhaltung der Luft 61 (2001) 105-112. Thijsse, Th.R., R.F. Van Oss, P. Lenschow; Determination of source contributions to ambient volatile organic compound concentrations in Berlin, J. Air and Waste Manage. Assoc. 49 (1999) 1394-1404. Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, Electronic Release (2001). Umweltbundesamt; Umweltdaten Deutschland Online (2003). Watson, J.G., J.C. Chow, E.M. Fujita; Review of volatile organic compound source apportionment by chemical mass balance, Atmos. Environ. 35 (2001) 1567-1584. Watson, J.G., N.F. Robinson, E.M. Fujita, J.C. Chow, T.G. Pace, Ch. Lewis, Th. Coulter; CMB8 applications and validation protocol for PM2.5 and VOCs, Desert Research Institute Document No. 1808.2D1, U.S. Environmental Protection Agency (1998). Woolfenden E.A., W.A. McClenny; Determination of volatile organic compounds in ambient air using active sampling onto sorbent tubes, Compendium Method TO-17, Center of Environmental Research Information, U.S. Environmental Protection Agency EPA/625/R-96/010b, Cincinnati (1999).

Surface and Total Ozone Over Bulgaria Staytcho Kolev and Vera Grigorieva National Institute of Meteorology and Hydrology, Bulgarian Academy of Sciences, 66 Tzarigradsko Chaussee, 1784 Sofia, Bulgaria Key Words: Stratospheric intrusion, Solar eclipse, Photochemical O3 formation

Introduction The ozone problems (stratospheric, tropospheric and surface O3) are an important part of atmospheric air pollution problems. One of the goals, outlined in the Recommendations of the meetings of the Ozone Research Managers (under World Meteorological Organization – WMO) was: the conducting of systematic measurements, which provide the basis for understanding the ozone regime and its trends. Total ozone In Bulgaria, the first total ozone measurements with a Dobson ozone spectrophotometer started only in the early 1960s in Sofia, and were carried on for about 5 years. Then, after a few years break, the Bulgarian National Institute of Meteorology and Hydrology (NIMH) in Sofia started to use Russian filter ozonometers. In 1998, two Russian ozonometers M-124 were renovated and calibrated at the Main Geophysical Observatory in St.Petersburg, with financial support from the WMO. All collected data are sent every month to the WMO World Ozone and UV Data Center in Toronto. Figure 1 shows the typical monthly variation of total ozone over Sofia, and compares the O3 behaviour over Sofia to that over Potsdam and over Rome. Since the beginning of the last decade, total ozone observations have also been carried out in Stara Zagora town. Vertical ozone sounding In the period 1983-1992, balloon ozone soundings were released weekly at the NIMHSofia. For that purpose were used ozonesondes, manufactured in Eastern Germany. The activities were interrupted largely due to financial difficulties resulting from the transition to a market economy. Tropospheric ozone is a major atmospheric pollutant, which plays a key role in atmospheric chemistry, and at heightened levels causes damage to human health, forest ecosystems, agricultural crops and materials. In Europe, the systematic long-term observations of surface ozone have been carried out at latitudes higher that 45o, while comparatively less is known about the ozone behaviour near the ground in Southern and South-Eastern Europe (Lindskog et al., 2003). Initial investigations of the surface ozone in Sofia, Bulgaria, started in 1994. The following main goal was pursued – to study the surface ozone behaviour and the processes that define this behaviour. This paper presents the most interesting results on the surface ozone behaviour in Sofia.


S. Kolev and V. Grigorieva

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Figure 1.

Monthly mean values of total ozone over Sofia in 2000 and 2001 (top), and the comparison of monthly mean values of total ozone over Rome, Potsdam and Sofia (bottom).

Site and instrument description The measurements were performed in Sofia (42q39c N, 23q23c E, ca 588 m a.s.l.), which is located in the western part of Bulgaria. The observation site is situated about 7 km to the southeast of the city centre, and has a fairly good vegetative ground cover. At 100 m away from the site there is a road with considerable car traffic. The ozone recorder was installed about 10 m above the ground level. A Teflon pipe was used for air sampling. The measurements were performed mostly during daylight hours, and less regularly in twenty-four hours period.

Surface and Total Ozone Over Bulgaria

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The ozone detector used in the investigations was a chemiluminescent ozone analyzer, model 3-02P1, by OPTEC Inc. (Russia). The measuring principle was that the sensor, consisting of an organic dye on the solid-state support, developed chemiluminescence in the presence of ozone. It must be noted that the chemiluminescence ozone measurements are considerably more free from interferences from other atmospheric components than are the ultra-violet (UV) optical absorption measurements. The UV optical absorption technique of surface ozone detection, which was tested with clean calibration mixtures under laboratory conditions, can give a positive offset in polluted air measurements (Grigorieva and Mihalev, 2003a). The ozone analyzer used in our observations had the response time of not more than 1 s, and the sensitivity of about 2 Pg/m3. Periodically, the analyzer was calibrated against an external O3 generator. Results and discussion Ozone variations and meteorological conditions The pattern of diurnal variations of the surface ozone concentrations is strongly influenced by meteorological conditions. The pronounced O3 maximum in the daytime, which is explained in terms of vertical mixing process and photochemical ozone production, occurred on clear windless afternoons. During the fine windy weather the dilution of the atmospheric pollutants takes place. So the decreased ozone concentrations are detected and the ozone level is approximately constant throughout the day. However, in the cases when vertical exchange is limited (autumn-winter period, nocturnal inversions) the wind enhances the vertical mixing (longrange transport of the polluted air mass also can takes place) and increases the ozone content near the ground. The cloudiness strongly decreases the ozone concentrations near the ground, but when it is foggy the ozone content is very low, often zero. So the ozone concentrations sensitively reflect the meteorological conditions under which measurements are performed. It is very like that more realistic information about temporal and spatial ozone variations may be obtained if ozone data recorded under similar meteorological situations are analyzed. Ozone pollution in Sofia The annual surface ozone behaviour clearly shows a seasonal variation with a summer maximum, which usually varies between ca 60 and 100 µg/m3, depending on the meteorological circumstances. The minimal ozone concentrations (20-35 Pg/m3) were detected during the winter period. The episodes with high O3 concentrations, up to 140 µg/m3, are sometimes observed in summer periods. The recorded seasonal pattern of ozone concentrations is similar to that observed at northern mid-latitudes. The collected data show, that the surface ozone concentrations in Sofia do not exceed the European Union standard hourly average of 180 Pg/m3. It is interesting to compare these results to ozone pollution in some other cities of the Balkan Peninsula, for which data are available. For example, in a big Romanian city Timisoara the maximum ozone concentrations during summer months of 1994-1996 reached only 116-122 µg/m3 (Lorinczi et al., 1999). In western Croatia, the summer ozone pollution in 19961997 rarely exceeded 120 µg/m3 (Butkovic et al., 1999). In Thessalonica (northern Greece), the maximum 8-hours concentration of O3 in 1995 was 90 µg/m3 – the lowest value among a number of large European cities (EEA, 1999). The results are consistent with model calculations, which show that although the efficiency of the photochemical ozone production (the number O3 molecules per NOx molecule) is higher in southern Europe than in western Europe, the chemical


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ozone formation per unit area is more intensive in the western part of the continent, due to the high concentrations of ozone precursors (Roemer et al., 1997). In a general case, it is very difficult to evaluate the role of individual processes, such as long-range transport of the polluted air, local photochemical ozone formation and direct stratospheric intrusions of ozone rich air, in episodes with high ozone pollution. Thus, each particular case was analysed in detail, to identify possible sources of the heightened ozone pollution in Sofia. Long-range transport Ozone pollution on June 3rd 1994, with maximum hourly O3 concentration up to 140 µg/m , was investigated (Grigorieva and Mihalev, 2003b). The event was studied taking into account the ozone data base over Europe during the last week of May 1994. The highest ozone concentrations in Europe in 1994 – 490 µg/m3 (hourly average) – were measured in Italy on May 24th (EEA, 1996). The analysis of air flow at our site showed that in the end of May the prevailing wind direction was from the west sector, i.e. from Italy, (Figure 3b). Just on June 3rd, the meteorological conditions (sunny day, windless until 17:00 LT) were favourable for observation of the variations of ozone concentration, which had a distinct maximum (Figure 2b), was associated with the well-mixed layer and contained information about the ozone concentration in the upper part of the boundary layer, in which the long-range transport occurs. For comparison, Figure 2a shows the behaviour of surface ozone on May 17th, a day with similar meteorological conditions but different wind directions to preceding days (Figure 3a). So there are reasons to assume that the episodes with elevated ozone concentrations in Sofia may be associated with the long-range transport of polluted air masses form the west and the south-west sectors. It should be noted that the highest ozone concentrations observed in Croatia, Slovenia and Hungary are also associated with western, south-western and north-western winds (Hov, 1997). 3

Stratospheric intrusions Initial investigation of the possible role of the direct stratospheric intrusions of the ozonerich air during the high O3 episodes observed near the ground was performed (Grigorieva et al., in press). The origins of high ozone concentrations (year extremes) registered in Sofia during summer 1998 were analyzed, taking into account the information on stratospheric intrusions. The O3 content in the atmospheric air reached values of up to 125 µg/m3 on July 27th, and up to 157 µg/m3 on August 5th. It must be noted, that there was a cold wind on first ten days of August, which normally are warm. Analysis of the data showed that during the same periods, the year extreme ozone concentrations were registered in a large part of Europe. Stations located close to Sofia registeres the following values: K-Puszta, Hungary – the year maximum of 255 µg/m3 on August 4th; Krvavec, Slovenia – high values up to 187 µg/m3 on July 27th-31st, and up to 150 µg/m3 on August 3rd-4th; Kovk, Slovenia – a maximum of 138 µg/m3 on August 3rd. The Mt. Cimone station in Italy showed maximums on July 24th (232 µg/m3) and on August 10th (250 µg/m3). Most of the mentioned values were the absolute year maximums. Taking into account the information about the intensity of stratospheric intrusions during this period (Bonasoni, 2001), one can assume that the large scale stratospheric intrusion events, several days long and covering a vast territorial range, took place over Europe during the considered period.


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a

Figure 2.

Daytime variation of the surface ozone concentration, wind speed and temperature on May 17th 1994 (a) and June 3rd 1994 (b).

a

Figure 3.

b

b

The wind roses in the days before May 17th 1994 (a) and June 3rd 1994 (b). The lengths of the cuts are proportional to the frequency of the wind occurrence in the given direction.


356 Photochemical ozone formation in-situ

The rapid and regular changes of sunlight radiation during a solar eclipse are a rare opportunity to study under real atmospheric conditions the specific behaviour of ozone and, in particular, the ozone production in fast photochemicl reactions proceeding in the boundary layer. The strong influence of meteorological conditions, not only cloudiness but also wind, on the O3 variation near the ground appears to explain why only a few well time-resolved observations of the surface ozone variation during solar eclipse are available up to now (see Grigorieva and Gogosheva, 2003). The meteorological situation that took place in Sofia, Bulgaria during the 94% solar eclipse on 11th August 1999 occurs extremely rarely: x practically clear sky over the day, x practically no wind over the day, x time of the solar eclipse coincided with the main period of photochemical ozone formation.

Figure 4.

Behaviour of the surface ozone concentration during the 94% solar eclipse in Sofia on August 11th 1999 (curve B) and on August 18th 1999, a control day with close meteorological conditions (curve A).

Figure 4 shows the surface ozone behaviour in Sofia during solar eclipse (curve B) and compares it to that observed on 18th August 1999, a control day with close meteorological conditions (curve A). It is clear that O3 distribution is strongly affected by the solar eclipse. The curves representing the variation of surface ozone concentration and the solar radiation during the eclipse are very similar in shape (Figures 4 and 5, respectively). A short time after


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first eclipse contact, the surface ozone concentration still does not "feel" the solar eclipse. The further fall of the sunlight intensity decreases the efficiency of the photochemical ozone formation in-situ, so fast diminution of ozone content in the atmosphere near the ground is observed. The maximum decrease of O3 concentration – from ca 90 µg/m3 to ca 55 µg/m3 – was detected approximately 10 minutes after the totality. This lag is related to the loss rate of ozone (including O3 destruction by NO) and to the photochemical production rate after the maximum phase. The unique high-quality recording of surface ozone variations during a solar eclipse allows the visualization of the dynamics of ozone production and destruction in the boundary layer, and an estimatation the amount of ozone formed due to fast in-situ photochemistry. The opportunity to observe both processes under real atmospheric conditions is extremely rare.

Figure 5.

Variations in UV solar radiation observed in Stara Zagora (about 200 km away from Sofia) during solar eclipse on August 11th 1999.

Conclusions x In the polluted atmosphere, the ultra-violet optical absorption technique (UV-photometer) does not always provides quality ozone data. A possible influence of various interferences on the measuring procedure can be responsible for this. The chemiluminescence method of O3 detection is considerably freer from interferences. x The unique, highly time-resolved variations of the surface ozone concentration during a solar eclipse were recorded, which demonstrate the occurrence of fast photochemical reactions in the boundary layer. The efficiency and the rate of the photochemical ozone production in-situ


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under real atmospheric conditions was clearly demonstrated. These observations show that at our site during summer (under ordinary pollution and meteorological conditions, that are favourable for photochemical ozone production) ca 40% of the measured ozone is produced photochemically in-situ. The O3 concentrations which exceed ca 100 - 110 µg/m3 can be attributed to long-range transport of polluted air masses or to stratospheric intrusions. x Stratospheric intrusions of ozone-rich air can be registered not only by high-altitude mountain stations, but also by stations at low elevations (including the sub-urban locations). x During the analysis of summer episodes of high ozone concentrations, it must be kept in mind that they can have not only photochemical origin, as it is often assumed, but also stratospheric origin. Acknowledgements This work was supported by the Bulgarian Ministry of Education and Science, under contract number NZ-1406. References Bonasoni, P.; Study of tropospheric ozone at Mt. Cimone, in: A. Lindskog (ed), Tropospheric ozone research. Annual Report 1999, EUROTRAC-2 ISS, Munich (2001) 54-58. Butkovic, V., T. Cvitas, N. Kezele, L. Klasinc and S. Vidic; Boundary layer ozone levels in the Adriatic region, in: P.M. Borrell, P.Borrell (eds), Proc. EUROTRAC Symposium’98, WIT Press, Southampton (1999) 281-285. EEA (European Environment Agency); Air quality in Europe, 1993 – a pilot report, Topic Report No 25. EEA, Copenhagen (1996). EEA (European Environment Agency); Environment in the European Union at the turn of the century, Environment Assessment Report No 2. EEA, Copenhagen (1999) 139. Grigorieva, V. and M. Mihalev; The possible uncertainties over quality of the surface ozone data, Proc. SPIE Int. Soc. Opt. Eng. 5226 (2003a) 285-289. Grigorieva, V. and M. Mihalev; Studies of surface ozone over Sofia, Bulgaria, Izvestiya RAN, Atmospheric and Oceanic Physics, 39, Suppl.1 (2003b) S51-S55. Grigorieva, V. and T.Gogosheva; Variations in surface ozone concentration during the solar eclipse August 11, 1999, Izvestiya RAN, Atmospheric and Oceanic Physics, 39, Suppl.1 (2003) S47-S50. Grigorieva, V., S.Kolev and M.Mihalev; Investigation of correlations between the high surface ozone episodes and the stratospheric intrusion events, Proc. SPIE Int. Soc. Opt. Eng. (in press). Hov, O. (ed); Tropospheric ozone research, Springer, Heidelberg (1997) 222, 271, 317. Lindskog, A., M. Beekmann, P. Monks, M. Roemer, E. Schuepbach and S. Solberg; Tropospheric ozone reseaech, in: P. Midgley, M.Reuther (eds), Towards cleaner air for Europe – science, tools and applications. Part 2. Overviews from the final reports of the EUROTRAC-2 subprojects. Margraf Verlag, Weikersheim: (2003) 251-270. Lorinczi, E.A., M. Lorinczi and E. Peter; Monitoring surface ozone at Timisoara, Romania, in: P.M. Borrell, P. Borrell (eds), Proc. EUROTRAC Symposium'98, WIT Press, Southampton (1999) 911-914. Roemer, M.G.M., R. Bosman, T. Thijsse, P.J.H. Builtjes, J.P. Beck, M. Vosbeek and P. Esser; Budget of ozone and precursors over Europe, in: O. Hov (ed), Tropospheric ozone research. Springer, Heidelberg (1997) 461-467.

Heavy Metals Pollution: An Everlasting Problem Raluca Mocanu, Simona Cucu-Man, and Eiliv Steinnes Department of Analytical Chemistry, Faculty of Chemistry, ‘Al. I. Cuza’ University, Iasi, Blvd. Carol I, no. 11, 700506 Romania Key Words: Bio-accumulation, Biomonitoring, Heavy metals, Moss types

Introduction The “heavy metal in the environment” collocation refers to any metallic chemical element and some metalloids (e.g. arsenic) that are toxic or poisonous for living organisms even at low concentration, e.g. Pb, Cd, Hg, As, Tl, Cr. They originate in the Earth’s crust as well as in the majority of wastes resulting from anthropogenic activities. Toxic effects of other heavy metals (Cr, Mo, Ni, As, Se etc.) have to be considered separately from the effects of biologic doses in which they exert their vital role. The danger represented by heavy metals lies in three aspects of their behaviour once the reach organisms: 1. they cannot be degraded or transformed into harmless products; 2. they cannot be destroyed and 3. they are bio-accumulative leading to an increase of their own concentration in a living body (animal, plant, human) over time. Thus, accumulated compounds in living organisms are stored faster than they are metabolised and excreted. The four most dangerous metals and metalloids, not occurring naturally and having no known function in biochemistry and physiology of living organisms are: Pb, Cd, As, Hg. Several examples of the health risks due to the penetration of these heavy metals into a living organism are listed below: Effects of Cadmium (Cd): its chemical similarity to zinc (an essential micronutrient for animals, plants and humans) leads to its toxicological properties. Cd once absorbed by an organism remains stocked for many decades. This bio-persistence generates lung diseases, bone defects, renal dysfunction, increases blood pressure etc. Effects of Lead (Pb): it is one out of four metals that have the most dangerous effects on living organisms. It can enter the human body via air, water and in most of all through uptake via food. In humans Pb can be associated with kidney and brain damages, a rise in blood pressure, disruptive child behaviour and learning abilities etc. Effects of Mercury (Hg): it is toxic by inhalation, ingestion and skin absorption. The effects of long-term exposure to Hg include: increase of blood pressure, hallucinations, memory loss etc. Hg does not have a known function in living organisms. th

Effects of Arsenic (As): known as far back as the 13 century, As is a poison as well as a cure for some diseases or metal for glass, laser, semiconductors. Routes of attack are ingestion, inhalation, skin and eye contact. The targeted organs are: digestive, respiratory, reproductive and central nervous systems, skin, liver, kidneys etc. 359 I. Barnes and K. J. Rudzinski (eds.), Environmental Simulation Chambers: Application to Atmospheric Chemical Processes, 359–368. © 2006 Springer. Printed in the Netherlands.

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Besides the above there are some elements whose presence, if the concentration exceeds the permitted limits, can be considered as pollutants and can become toxic. Effects of Copper (Cu): known to the ancients and most often used as an electrical conductor, in art, industry, and coins. Cu enters the human body via skin or/and eye contact, inhalation, and ingestion. It causes damage to the following target organs: skin, eyes, liver, kidneys and the respiratory system. Copper deficiency causes anaemia, growth inhibition etc. Effects of Zinc (Zn): it plays a remarkable role in the metabolic cycles of human and animals and it is an essential element for plant growth. No toxic effects of Zn are known. It helps copper uptake in human and animal organisms. In addition to the above-mentioned metals, essential or not for human life, mention should also be made of toxic metals like chromium, silver, selenium, barium, aluminium (if their concentration goes beyond the permissible exposure limit). Heavy metals are usually available in the structure of the Lithosphere. Together with those originating from human activities they can enter living organisms through water, air and the food chain (Figure 1). Atmospheric input Continental air Oceanic air

Litosphere and ocean

Aquatic input Running waters Stagnant waters Sediments (sink) (streams, rivers) (lakes, swamps, pools)

Figure 1.

Heavy metals’ cycle in the environment.

A UN-ECE Protocol of heavy metal atmospheric emissions control was signed in 1998. This document designated cadmium (Cd), mercury (Hg) and lead (Pb) as first priority toxic elements. In point of fact the Protocol, in contrast to others as far as the water, soil or sediment pollution with heavy metal is concerned, is the unique “screen” of atmosphere protection. Legislation does not yet exist for other elements with respect to defining the atmospheric pollution by heavy metals. It is left to each country to respect and to protect the atmosphere from pollution through heavy metals.

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Prut River’s basin (Romania). A possible source of trans-boundary pollution with heavy metals Prut River is a first-order tributary of the Danube River; it is the last major tributary before the Danube enters its delta. The total length of the Prut River is 983 km. The uppermost 241 km are on Ukrainian territory, for the next 31 km the river forms the border between Romania and Ukraine, and for the lower 711 km it forms the border between Romania and the Republic of Moldova. The Prut River catchment is bordered in the South and West by the Siret catchment, situated on Romanian territory, and in the North and East by the Nistru catchment, situated on Ukrainian and Moldovan territory. Temporal and spatial information on trace metal (Cd, Cu, Pb and Zn) variation in different environmental compartments of the catchment were obtained by analysing samples collected from nine sites along the Romanian bank line (Figure 2b) during three years (20002002). 1. Description of site 1. Physical-geographical conditions: combination of steppe and forest-steppe. The climate is temperate continental: in winter the mean monthly air temperature is about 10 degrees below zero, in summer it is about 20 degrees above zero. Snow cover is extensive and reaches 30 – 50 cm. The relief is partially plane, partially covered with hills. The highest points are about 800 - 900 m above the sea level. The average duration of positive temperature period comprises 200 - 250 days a year. 2. Soils: the soil layer is represented by chernozem and chestnut soils with humus contents. Vegetation: agricultural crops, vineyards, orchards, meadows. 3. Hydrology: water system includes the Prut River with tributaries as well as freshwater lakes. 4. Industry: several cities, the main being Iasi.

a Figure 2.

b Monitoring sites along the Prut River.

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362 2. Water and sediment pollution with metals

Three very well known forms of pollution can affect water, one of the main sources of life: physical, chemical and biological pollution. The main sources of pollution with heavy metals are: 1. Natural sources –minerals, rocks. 2. Agricultural sources: pesticides, fertilizers that contain heavy metals. 3. Industrial sources: metal ore processing industries, leather, paint, textiles and paper factories etc. 4. Domestic wastewater. 5. Mine wastewater. Heavy metal contamination belongs to the chemical pollution category of persistent (slow or non-degradable) substances. The most dangerous chemical pollution is represented by waste chemical and agricultural drainage systems. Data from 2001 were selected so as to present typical concentration levels of the four metals along the Prut River (Figure 3). For Cu the variation along the river is rather small, but there is a tendency to higher values at sites 6 and 7 than at the other sites. In the case of Zn the variability of its concentration is greater between sites. Levels increase markedly at site 6 relative to the above sites. This is most probably due to input from one of the river tributaries, which receives the wastewater discharge from Iasi, the largest city within the Prut River catchment. Pb shows only moderate variation along the river course. There is a tendency to lower values at sites 8 and 9 compared to the upstream sites. This trend, which is not observed to a similar extent for the other metals, is probably related to a higher removal of Pb from the water column by sedimentation than for the other elements. For sediments, except for a few single samples, the distribution of metals is rather uniform along the river. The tendency to higher values at site 6 and below as observed for the water data is not clearly evident in the sediments (Figure 4). These trends indicate that the Prut River sediment generally is not heavily polluted with the four heavy metals.

Concentration of heavy metals in water Cu samples

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Annual mean concentrations of elements in the Prut River in 2001 (µg·L ).


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Concentrations of heavy metals in sediment samples Concentration (mg/kg)

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Metal concentrations in Prut River sediments collected in 2001 (mg·kg ).

3. Atmospheric pollution with heavy metals and their biomonitoring Surveys of air quality are progressively extending to areas at substantial distances from industrial and urban centres. In these areas the air pollution, frequently qualified as background pollution, is generally connected with the dispersion of pollutants on a large scale of time and space. Among the pollutants of interest, heavy metals are a special category considering the risks that they represent for human health and the danger caused by their accumulation in ecosystems. This preoccupation has lead the countries member of the Geneve Convention (trans-boundary pollution at long distance) to engage themselves for reducing the emissions of some of these metals and to encourage the survey of their deposition and the level of contamination in different compartments of the environment. Surveys of this type of pollution are under the influence of specific constraints because these compounds are present in trace concentrations. These constraints have led many countries to use bio-accumulating organisms, in which the pollutants are quantified. This biosurvey approach permits the evaluation of contamination levels and the exposure of living organisms to the effect of pollutants. Thus, starting with the beginning of 90s, a great number of countries are participating in a survey network of the atmospheric depositions of metals based on their dosage in terrestrial mosses, collected (where possible) in areas far from industrial pollution sources and far from the main circulation axes. Although the acute and chronic effects of heavy metals on humans may be well known, knowledge on the sanitary risks connected to their dispersion by aerial routes is still fragmentary. In the vicinity of some industrial emissions of heavy metals in the air (Pb, Hg and Cd) several studies have made evident a risk for the population in the close vicinity of these sources (Donisa et al., 2000). This risk is generally calculated on the basis of the available exposure data by modelling, considering the inhalation and the contamination of soils and water, which is transferred to humans through the food chain. For the long-range transport of pollutants, besides the possibility of calculating the risk, there are observations on their accumulation in the environment compartments and on the potential exposure of population in terms of remanence and their bioaccumulation.

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Heavy metals are non-degradable compounds and therefore they have the tendency to be accumulated in the biosphere. This is obvious, especially in north and central Europe where on a regional scale the contamination problems of some environmental compartments (forest humus, lakes and arable fields) arise from metal depositions as a consequence of long range atmospheric transport. The forest soils have a surface layer rich in organic matter. This type of soils seems to retain efficiently the atmospheric deposition of heavy metals. These soils are frequent in north and central Europe, where there are high concentrations of lead, cadmium, copper and zinc in the surface layer. Some authors estimate that these concentrations affect the biology of the soil, especially the decomposition of the organic matter, and that they have a baneful effect on the recycling of certain nutritive elements (Johansson and Sliggers, 1997). In several European regions the atmospheric contribution is significant for the contamination of agricultural soils (70 % of the Hg in The Netherlands, more than 90 % of Pb in the United Kingdom, 50 % of Cd in Sweden) (Johansson and Sliggers, 1997). The long range atmospheric contributions of several heavy metals during the last century, has led to the enrichment (by a factor of 5 to 50) of their concentration in the sediments of lakes in the north-eastern United States, southern Canada and southern Scandinavia. For Hg, for example, in southern Scandinavia and the northern United States this contribution has resulted in high concentrations in fish that are dangerous for human health and for fish and marine mammals (Johansson and Sliggers, 1997). Information on atmospheric heavy metals can be obtained by modelling and by measurements of actual atmospheric occurrences and/or deposition. Biomonitoring can be an efficient supplement and even replacement for these types of investigations, and also permits larger scale multiple sites programs, as has been shown by the running series of NORDIC moss survey (Rühling, 1994; Rühling and Steinnes, 1998). Biomonitoring may be defined as the use of bio-organisms/materials to obtain information on certain characteristics of the biosphere. With proper selection of organisms, the advantage of the biomonitoring approach is related primarily to the permanent and common occurrence of organisms in the field, even in remote areas, the ease of sampling, and the absence of any necessary expensive technical equipment. Mosses may be considered as the most commonly used biomonitor organisms. - Mosses do not have a well-developed root system and conducting system; the major source of the supply for essential nutrients (but not only) remains atmospheric deposition. - Mosses have a high capacity to retain many elements by surface sorption or by intracellular uptake. - Mosses retain and concentrate trace heavy metals. - Moss samples are easy to collect and also to analyze compared to precipitation samples. Mosses can be used for surveys of atmospheric depositions within a large as well as a smaller area. - They occur in almost all terrestrial ecosystems. - They have the ability to tolerate long periods of desiccation. This makes them able to colonize areas from north to south, with extreme environmental conditions. The main sources and mechanisms other than air pollution that influence the heavy metal content in mosses are: - Contributions from long-range atmospheric transport (Pb, As, Cd).

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Contributions from local sources (Cu, Cd, Co, Ni). Elements associated with local soil dust (Al, Cr, Fe, Sc). Transfer from soil via higher plants (Zn, Mo, Rb). Contributions from the marine environment (Mg, Mn, Na).

When considering the use of mosses as biomonitors, the active and the passive technique could be employed. The selection of one of these techniques depends mainly on the moss species, with respect to abundance, tolerance and their capacity for accumulating chemical elements. Extension of moss monitoring from the northern European countries (the starting areas for this technique) to more southerly areas, imposed the necessity of using epiphytic species instead of the epigeic ones. Another convenient alternative is to introduce active monitoring using moss transplants, in order to evaluate the exposure to contaminants and to calibrate the results obtained by monitoring with native moss species. This is the situation in lowland sites of Romania, where is difficult to find the classically known species for this purpose. In the eastern part of Romania (province of Moldavia) the most frequently found moss species is the epiphytic Hypnum cupressiforme. To investigate the compatibility of the two methods, passive and active monitoring, the epigeic moss Hylocomium splendens was used in transplants in parallel with epiphytically growing Hypnum cupressiforme employed for passive biomonitoring. The moss technique using the epiphytic Hypnum cupressiforme may be considered as a valuable method for estimating the atmospheric deposition of heavy metals in the catchment of River Prut (Cucu-Man et al., 2004). The data for atmospheric heavy metal deposition biomonitoring of the Prut River basin show rather uniform levels over the entire region, slightly higher in the same middle area of the river catchment (Figure 5), a similar trend as for water and sediments. Cd

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Metal concentration in mosses collected in 2001 in Prut River catchment (mg·kg-1).

Considering the contribution of atmospheric deposition to the metal pollution of Prut River two ways of supply are possible: I. Direct deposition on the water surface. II. Deposition on land and supply to the river by surface runoff and snow melting.

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While the estimate of the latter needs information on factors such as surface soil enrichment of metal erosion rates, the former can be estimated roughly from the monitoring data. In order to use the information from the moss monitoring to estimate the atmospheric deposition in the area of concern the following assumptions have been made: a) Hypnum cupressiforme is structurally quite similar to Hylocomium splendens, therefore they may collect heavy metals to the same extent. The results obtained for the two species collected from the same sites show a significant correlation between the concentrations of typical pollutants (for example Pb, Figure 6). b) The calibration of metal concentration in Hylocomium splendens against bulk deposition from Norway (Berg et al., 1995) are valid also for the region concerned in the present study.

y = 2.1576x - 8.8584

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Lead concentrations (mg·kg ) in Hypnum cupressiforme versus Hylocomium splendens.

Over the stretch of Prut River the Stânca Coste ti reservoir represents a major part of the total water surface (Figure 2a). Therefore the estimation was limited to the direct atmospheric 2 contribution to the surface of this reservoir, which is about 60 km . The values of heavy metal -1 concentrations in Hypnum cupressiforme (mg·kg ) moss samples from Stefanesti (the site closed to the Stânca reservoir) were selected. The yearly deposition values (mg·m -2·y-1) were calculated. Assuming the mean depth of the reservoir to be 12.5 m, the total volume is of the 8 3 order of 7,5u10 m . The annual atmospheric addition of metals to the reservoir were calculated from the estimated deposition rates. If diluted over the whole volume, and given that the residence time of water in the reservoir is about 4 month, the increments to the metal concentrations in water are estimated Comparing the obtained values with those from the monitoring data of the Prut River water shows that the contribution from direct atmospheric deposition to the reservoir is less than 5 %, and hence small compared to contributions from other sources.


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Concentration in Hypnum cupressiforme (mg·kg-1)

Cu – 11.8 Zn – 28.9 Cd – 0.42 Pb – 14.4

Yearly deposition values -2 -1 (mg·m ·y )

Cu – 3.0 Zn – 9.0 Cd – 0.17 Pb – 4.5

Annual atmospheric addition of metals to the reservoir (kg)

Cu – 200 Zn – 500 Cd – 10 Pb – 300

Atmospheric contribution to the concentrations in water (µg·L-1)

Cu – 0.09 Zn – 0.22 Cd – 0.005 Pb – 0.15

Contribution from direct atmospheric deposition to the reservoir (%)

Concentrations in water (µg·L-1)

Cu – 10 Zn – 20 Cd – 0.5 Pb – 3

Cu – 1 Zn – 1 Cd – 1 Pb – 5

The obtained values for atmospheric deposition in the Prut River catchment are lower than those obtained in Transilvania (Stan et al., 2001), similar to those obtained in the Eastern Carpathians and higher compared to the Republic Moldova (Figure 7). This supports the conclusion that no trans-boundary pollution of the investigated elements from Romania to the Republic of Moldova could be considered. Conclusion The above results lead to the conclusion as far as the heavy metals behavior and transport are concerned that Romania is still an importer and an interjacent of pollution but is not an important producer itself (Figure 7).

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Pb Concentration (mg/kg)


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Figure 7.

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Heavy metal concentrations (mg·kg-1) in mosses collected in Transilvania, Eastern Romania, Prut River catchment and Republic of Moldova.

References Berg, T., O. Røyset and E. Steinnes; Moss ( Hylocomium splendens) used as biomonitor of atmospheric trace element deposition: estimation of uptake efficiencies, Atmos. Environ. 29 (3) (1995) 353-360. Cucu-Man, S., R. Mocanu, O. Culicov, E. Steinnes and M. Frontasyeva; Atmospheric deposition of metals in Romania studied by biomonitoring using the epiphytic moss Hypnum Cupressiforme, Int. J. Env. Anal. Chem. 84 (11) (2004) 845-854. Donisa, C., R. Mocanu and E. Steinnes; Heavy metals pollution by atmospheric transport in natural soils from North Eastern Carpathians, Water Air Soil Pollut. 120 (2000) 347-358. Johansson, K. and J. Sliggers; Overview –Effects of heavy metals, Workshop on critical limits and effects based approaches for heavy metals and persistent organic pollutants, Bad Harzburg, Germany (1997). Rühling, Å. (Ed.); Atmospheric heavy metal deposition in Europe. Estimations based on moss analysis, NORD 1994:9, Nordic Council of Ministers, Copenhagen (1994). Rühling, Å. and E. Steinnes (Eds.); Atmospheric heavy metal deposition in Northern Europe. 1995-1996, NORD 1998:15, Nordic Council of Ministers, Copenhagen (1998). Stan, O., A. Lucaciu, M.V. Frontasyeva and E. Steinnes, New results from air pollution studies in Romania, Proc. NATO Advanced Research Workshop on Monitoring and Man-Made Radionuclides and Heavy Metals Waste in Environment, Kluwer Academic (2001) 179-190.

Atmospheric Wet Deposition Monitoring in Iasi, Romania Cecilia Arsene1, Nikos Mihalopoulos2, Romeo-Iulian Olariu1, and Marius Duncianu1 1

“Al.I. Cuza” University of Iasi, Faculty of Chemistry, Analytical Chemistry Department, 700506 Iasi, Romania 2 Environmental Chemical Process Laboratory, Department of Chemistry, University of Crete, 71409 Heraklion, Greece Key Words: Wet Deposition, Monitoring, Environment, Precipitation, Fluxes, Iasi

Introduction The degradation of environmental quality in many regions of the world has accelerated during the past decades especially due to the industrial development, which has led to important changes in different compartments of the environment. Important atmospheric species are considered to be responsible for wide spread environmental effects including, changes in pH deposition, corrosion of buildings material etc. Deposition of air pollutants is an important loss process for most of the species present in the atmosphere that can cause severe damage to ecosystems. Air pollutants are deposited to the earth’s surface especially through wet and dry processes. Deposition rates are determined in order to estimate the impact of these pollutants on ecological systems. Deposition of pollutants by wet processes is relatively easy to determine through analysis of precipitation samples. However, it is well recognised that less is known about dry deposition, which is much more difficult to measure (estimated using measured air concentration and the deposition velocity concept) and which appears to predominate near strong emission sources with wet deposition predominating further downwind (Whelpdale et al., 1997). Direct measurement of pollutants deposition by dry processes is more difficult and requires extensive instrumentation and technical resources. A combination of modelling and measurement activities has been developed in order to achieve effective emission reductions or in order to monitor the progress in terms of deposition (Erisman et al., 2001). While in America and Western Europe the measurement of air pollution has become practically a routine matter for Eastern European countries this is a present-day task. There are many observations in the literature that refer to the importance of wet deposition analysis, in most of Europe, North America and Asia, for obtaining information on the contribution of industrial activities to atmospheric deposition (Agrawal and Singh, 2001; Gao et al., 2001; Nilles and Conley, 2001). Within the last decades, due to intense research studies, acid deposition is now a reasonably well-understood environmental phenomenon. Many researchers blame acid precipitation for much of the damage done to trees and buildings as well as the rising number of people suffering from respiratory problems. Many data concerning acid deposition phenomenon in several regions of the world have been published but a summary for the whole globe does not exist. It has been shown that regions with the highest precipitation concentrations and deposition fluxes of sulphate and nitrate coincide closely with regions having the highest density of SO2 and NOx (NO + NO2) precursor emissions and that this is occurring primarily in the regions where a large fraction of the world’s fossil fuel is consumed (Whelpdale et al., 1997). Presently it is well established that the chemical composition of wet precipitation is strongly affected by the chemical composition of the atmosphere, and is especially affected by the source zone traversed by the cloud system. Particles and gases either incorporated directly 369 I. Barnes and K. J. Rudzinski (eds.), Environmental Simulation Chambers: Application to Atmospheric Chemical Processes, 369–377. © 2006 Springer. Printed in the Netherlands.

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in the cloud (rainout), or/and washed out by the rain droplets below the cloud (washout) are directly responsible for the chemical species identified in rain. It is considered that exchanges between the two phases, rain and aerosol, account for the diversity observed in rain composition. These effects depend on the meteorological, as well as the microphysical conditions (Choularton and Bower, 2001; Samara and Tsitouridou, 2000 and references therein). Although in most regions of the world increased attention has been given to atmospheric deposition in order to elucidate the effect of different types of emission both on dry and wet deposition, for Romania this is a new and contemporary task. The present study, which is a first step in a larger monitoring program meant to be developed in the future in Romania, is focussed on determining the elemental composition of wet deposition and in evaluating the influence of different sources of pollution types on the rainwater pH. In order to assess the main task of the study, wet depositions were collected over a year from May 2003 to May 2004, in Iasi, the biggest city in the Moldavian region and one of the largest cities in Romania with approximately 350,000 inhabitants. The city lies in the Northeast part of Romania and is surrounded by seven hills. As for the climate, due to the geographical location, Iasi city is characterised by a o excessive continental climate with high differences of temperature from winter (-20 –0 C) to o the summer season (20 – 35 C). Unfortunately the sampling site is located in a region that may be potentially largely affected by urban or industrial emissions. Therefore, the deposition values can be perceived as upper limits of what might be considered as regionally representative values. This will be an advantage at a later stage when an enlargement of the database is expected, i.e. a database containing also results from less polluted regions (rural or remote areas). Over a year, however, the precipitation height was about 40 cm. The measured pH values of the rainwater varied in the range of 5.0 to 7.0 for most of the samples. During the winter only January 2004 and partially February 2004 were mostly characterised by snow events, and the pH values of the melted snow water varied in the range of 4.5 to 5.0. The obtained data, however, allow us to make a classification of the rain events in different categories according to their origin, to develop a climatology of air masses associated with rain events, to establish a dependence of pH on the air mass origins, to study the insoluble + fraction as a function of pH and air mass origin, and also to estimate the fluxes of [H ] and the insoluble fraction. Chemical characterisation of both the soluble and insoluble fractions is underway. Data collection Geographical and meteorological characteristics of the sampling site The monitored site lies between 47°20'' northern latitude and 27°60'' eastern longitude (Figure 1). At this latitude incident solar zenith angles between the solar radiation and the Earth’s surface of about 19°23' during the winter and 66°17' during the summer, at midday, are reached with a variation of about 47°. The warmest month of the year is July with a mean monthly temperature of about 24 °C whereas January is the coldest with a mean monthly temperature of about 3 °C. An annual o mean temperature variation of about 28 C is estimated, which classifies Iasi as a region with very a high thermic amplitude corresponding to a severe continental climate. During winter and summer a small difference of the air temperature is observed from one month to another

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within the same season and during spring and autumn this difference can be as high as 10 °C. Usually, at the end of autumn and the beginning of spring within a time range of 12 hours a large difference in the air temperature may occur with important negative consequences for population, agriculture and buildings. Due to its location Iasi city is directly exposed to winds coming from a wide range of directions and hence to the corresponding atmospheric fronts. Winds from the west (W), southwest (SW), southeast (SE) often prevail in the area. There are also situations when the wind direction is from the east (E), northeast (NE) and northwest (NW). During north-easterly winds the sampling site can be regarded as representative of the transfrontalier atmosphere (air fronts coming from the former Soviet Union) while during westerly and south-westerly winds it can be regarded as representative of the urban atmosphere (including industrial activities, agriculture land activities).

Figure 1.

Sampling location and Iasi region.

The topography of the city is dominated by the presence of an important number of hills due to which a local dynamics of the atmospheric air fronts is observed. The difference o in the temperature values measured at the bottom and tops of the hills (at least 1 or 2 C colder at the top of the hill) is also responsible for the appearance of this phenomenon. Method for sampling wet deposition The sampling point was located on the roof of the University building (approximately 20 m from the ground) which is beside the emerging top of the Copou hill of Iasi city. The sampling system was raised 2 m above the roof before precipitation events started. Generally, precautions were taken in order to avoid exposure of the funnel to dry contamination. Rainwater samples were collected on an event basis by using a simple self-developed sampling system (Figure 2). Where possible, rainwater sampling system parts made of polyethylene, polypropylene and 5 litre capacity containers made also of polyethylene terephtalate were used for sampling. The materials employed during the sampling procedure (funnels, 5 liter capacity containers, additional vessels used to measure the volume) were well washed each

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time with liquid cleaning soap, rinsed with a solution of nitric acid and than washed often with deionised water. Dry contamination on the collector funnels was minimized by rinsing funnels with distilled water, as close as possible to the start of rainfall. When rainfall began in the middle of the night the exposure of the funnel to dry contamination may have been for a longer time. The regular cleaning procedures and the nature of the site meant that contamination from insects or birds was not a significant problem. Precipitation samples were collected from the field site as soon as possible after the cessation of rainfall and filtered through Whatman no 41 filter paper. A fraction of the rain samples was preserved immediately with chloroform (CHCl3) o and refrigerated at 4 C for later chemical composition analysis. The pH was measured with a pH meter OP-401/2, Radelkis, using a glass electrode, standardised with pH = 6 buffer solution. The hydrogen ion concentration was calculated from the measured pH. Presently the samples have not yet been completely analysed from the chemical composition point of view. Although the equivalent conductivities of the major ions were not measured it is known that these are roughly equal (with the exception of hydrogen). In fact conductivity can be used to estimate the total amount of dissolved ionizable material incorporated by scavenging processes. For further samples conductivity will be measured and as it varies with temperature the obtained results will be corrected for a standard temperature. Figure 2.

The own developed sampling system.

The pH of a solution is defined in terms of the negative logarithm (to base 10) of the hydrogen ion activity (aH) by the following expression: pH = -log10 (aH) For rainwater, the hydrogen ion activity is a good approximation of the hydrogen ion + + concentration, [H ], therefore it is possible to estimate [H ] from pH measurements by the expression: +

[H ] = 10

-pH

×10 6 (Peq L-1)

A parameter used to characterize rainwater is OH+ that represents the equivalent conductivity of H+ estimated to be 0.350 (PS cm-1)/(Peq L-1). The major soluble component of the atmosphere is CO2 but this is only weakly ionized in solution and the carbonic acid (H2CO3) generated defines a lower limit for background pH of 5.6 at 15 oC (Beverland et al., 1997 and references therein). As Beverland et al (1997) show, although a pH increase of 0.061, due to


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decreasing Henry’s Law constant, can be expected between 5 and 25 oC for carbonic acid alone, changes of CO2 equilibrium cannot be responsible for the observed discrepancies of rain samples collected within the pH range 3.9 to 4.9. The major species which contribute to an increased acidification of rainwater are SO2 and sulphuric (H2SO4), nitric (HNO3) and hydrochloric (HCl) acids. Results and discussion Information (not fully complete) regarding a real assignment of wind direction is available for the previous year. Dependence between rain and air mass climatologies has been followed and it illustrates a highly uncertain trend. However, a northwesterly prevalent direction of air mass trajectories for almost all wind directions has been observed (Figure 3). A view of the pH and temperature trends over the year is presented in Figure 4. However, in the analysis of the data seasonal trends were closely followed and this allowed us to decide if meaningful changes in the observed parameters from one season to another occurred. The observed difference in the values of pH, with smaller values especially during the winter season, probably originates from combustion sources that include a considerable seasonal contribution from heating. The study further of pH indicates that for the summer and + autumn of 2003 rainfalls were more alkaline with less H ions, but as these seasons preceded + precipitation showed lower pH and higher H ion concentrations (Figure 5). Probably in this period the particulate load in the atmosphere declined substantially and hence aerosol rich in + basic ions declined leading to an increase in the H ion concentration and a subsequent lowering of rainfall pH.

Figure 3.

Prevalent direction of air masses trajectories for almost all wind directions.

As it was previously shown most of the rainwater has a pH of 5.6 to 5.8 due to the presence of carbonic acid (H2CO3) formed from dissolved atmospheric CO2 gas and H2O. Precipitations with values of pH below 5.6 or so are considered acid rains, while those with values above are basic rains. The data on mean monthly pH values of wet deposition indicate that rainwater in the Iasi area is to some extend acid, basic or normal accordingly to some remarks made by a specialist with respect as to what represents neutral rainwater. When water vapour reaches the atmosphere values for a non-acidic system is available (pH 7) but, however, in the atmosphere due to a lot of both natural and non-natural sources of materials deviation from the neutral value (5.6 - 5.8) of the rain pH can occur.

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374 305

8.00

40

8.00

300 7.00

7.00

295

275

4.00

) -1

6.00 20 5.00

[H+] ( P echiv L

280

Units of pH

Units of pH

285 5.00

Temperature (K)

30 290

6.00

10

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4.00

3.00 265 2.00 29-Apr- 18-Jun- 07-Aug- 26-Sep- 15-Nov- 04-Jan- 23-Feb- 13-Apr03 03 03 03 03 04 04 04

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Day of the year (DD:MM:YYYY)

3.00 29-Apr- 18-Jun- 07-Aug- 26-Sep- 15-Nov- 04-Jan- 23-Feb- 13-Apr03 03 03 03 03 04 04 04 Day of the year (DD:MM:YYYY)

0

Figure 4. Variation of pH and temperature over the Figure 5. Variation of pH and H+ ion concenyear at the monitored site (open symbols tration over the year at the monitored + – pH and full symbols – temperature). site (circle –pH and square –[H ]).

Table 1. Number of the precipitation events over the year, monthly mean values of the + pH, H ion concentrations and the total monthly amount of rainfall. No. of precipitation Year Months events rain snow I E May II N-W 2 I W 2 June II N 2 I N-W 7 July II E 4 I N-W 2 August II W 2 2003 I E 3 September II S-W I N 2 October II N 4 I E 2 November II E 1 I W 2 December II S-W 1 1 I W 1 3 January II S-W 2 I N 2 1 February II S-W 1 2004 I W 1 1 March II N-W 2 I N-E 1 April II W I –first decade (beginning till middle of the month) II –second decade (middle till end of the month). Trajectory wind direction

Total monthly amount of rain

+

pH

[H ] -1

5.47 5.72 6.20 6.15 6.27 5.42 6.20 5.85 5.70 5.73 4.87 5.55 5.30 5.55 4.77 5.02 5.08 5.43 6.22 6.90 6.65 -

(Peq L ) 3.35 2.14 0.64 0.91 0.66 4.06 0.64 1.30 2.11 2.29 20.12 2.81 6.72 4.22 19.21 9.45 10.41 3.54 0.67 0.13 0.22 -

(mm) 28.88 15.77

32.51

36.39 38.62

84.89

5.67 25.13

32.35

24.26 38.56 23.83

The total number of the precipitations over the year was 52, with 43 rain events and 9 snow events. A total rain column of 405 mm from May 2003 to May 2004 was measured. The + monthly mean values of the pH and H concentrations of rain given by a mean of the number of rain events are presented in Table 1.


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Air masses trajectories were obtained using HYSPLIT: On-line Transport and Dispersion Model (Draxler and Rolph, 2003; Rolph, 2003). An example of the calculated air front trajectories is shown in Figure 6. Rain events were classified in different categories according to their origin, as derived from 120 h air back mass trajectories based on 1000 and 3000 m as for the altitude. From the analysis of these trajectories westerly air fronts appear to be the most frequent (Figure 7). The inset in Figure 7 shows the percentage of precipitation events associated with the air masses fronts. Northwesterly and westerly air fronts appear to induce the most abundant precipitation events over the year, especially during summer and winter. Figure 6. Example of the calculated backward air mass trajectories.

Figure 8 shows the distribution of pH as a function of the air mass origin. From the observed behaviour in Figure 8 it is clear that there are only a few precipitation events with pH values between 4 and 5 while for the others the pH values are in the range of 5 –6 or 6 –7 (about half).

Figure 7. Percentage of air masses trajectories over the year and of the precipitation events.

Figure 8. Distribution of pH as a function of the air mass origin.

From the distribution of the insoluble fraction masses versus pH it is observed that a dependence exists but with a low correlation coefficient (Figure 9). However, a better correlation coefficient is obtained when the mass concentration of the insoluble fraction is plotted as a function of pH (Figure 10). A statistical treatment of the data over a 0.5 unit of pH range leads even to a better correlation coefficient for the dependence of the insoluble fraction mass concentration and pH (0.88 compared to 0.57).

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Figure 9. Distribution of insoluble part masses versus pH.

Figure 10. Insoluble part mass concentration as a function of pH.

From an analysis of the data in Figures 8 and 9 it appears that the pH values increase with increases of the insoluble fraction. It is well known that the pH of the aqueous environment is one key property that defines the nature of the chemical species. Thus, the increase in the insoluble mass fraction with increase of the pH rain droplets could indicate that the insoluble matter may contain in its chemical composition significant amounts of terrigenic elements (e.g. iron oxides) that become more insoluble in rain droplets as the pH values increase. It might be as well that compounds are present whose solubility increases with decreasing pH. The concentration of the insoluble fraction is variable for most of the air masses with more intense variations for north-westerly and northerly trajectories (Figure 11).

Figure 11.

Concentration ranges of the insoluble part at the monitored site as a function of the air mass origin.

Fluxes either of the H+ ion concentration or of the insoluble fraction were calculated from their concentration and the volume of the rainfall during the sampling at the monitored + site. Both H and insoluble fraction fluxes follow almost the same trend over the year with small values up to the end of 2003 and with higher values at the beginning of 2004. Observations In 2003, a wet-deposition collection site was established in Iasi, northeast Romania, to monitor the quantity and chemical quality of atmospheric wet deposition. Monitoring was carried out from May 2003 to May 2004. During the first phase of sampling 52 wetdeposition samples were collected. A second phase of sampling began in May 2004 and is


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still on-going. Wet-deposition samples collected during the first phase of sampling were first analyzed for pH. Meteorological aspects were also closely followed. Presently no chemical speciation concerning the chemical composition of the wet deposition is available. Precipitation caused by air masses originating in west and northwest Europe (48% of total rain events) were characterised by the highest concentration of the insoluble fraction. However, after a complete analysis of the samples from the chemical composition point of view, closely followed by a careful analysis of the meteorological parameters, attempts will be made to obtain full information regarding the behaviour of all the measured pollutants in the atmosphere. Although the presented activity has already begun to produce useful information, its real benefit will be realized after it has been in operational mode for several years. This will enable the examination of the trends of deposition and atmospheric acidity, in particular in relation to the emissions of regulated pollutants by national and international laws. Acknowledgment Financial support from NATO EST.ARW 980164 action for travel funding is gratefully acknowledged. The authors gratefully acknowledge the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model and/or READY website (http://www.arl.noaa.gov/ready.html) used in this publication. References Agrawal, M. and R.K. Singh; Effect of industrial emission on atmospheric wet deposition, Water, Air, and Soil Pollut., 130 (2001) 481-486. Beverland, I.J., M.R. Heal, J.M. Crowther and M.S.N. Srinivas; Real time measurement and interpretation of the conductivity and pH of precipitation samples, Water, Air, and Soil Pollut., 98 (1997) 325-344. Choularton, T.W. and K.N. Bower; The role of clouds processing in the relationship between wet deposited sulphur and sulphur dioxide emissions, Water, Air, and Soil Pollut.: Focus, 1 (2001), 365-372. Draxler, R.R. and Rolph, G.D., 2003. HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory) Model access via NOAA ARL READY Website (http://www.arl.noaa.gov/ready/hysplit4.html). NOAA Air Resources Laboratory, Silver Spring, MD. Erisman, J.W., A. Hensen, D. Fowler, C.R. Flechard, A. Gruner, G. Spindler, J.H. Duyzer, H. Weststrate, F. Romer, A.W. Vonk and H.V. Jaarsveld; Dry deposition monitoring in Europe, Water, Air and Soil Pollut.: Focus, 1 (2001) 17-27. Gao, S., K. Sakamoto, D. Zhao, D. Zhang, X. Dong, S. Hatakeyama; Studies on atmospheric pollution, acid rain and emission control for their precursors in Chongqing, China, Water, Air, and Soil Pollut., 130 (2001) 247-252. Nilles, M.A. and B.E. Conley; Changes in the chemistry of precipitation in the United States, 1981-1998, Water, Air, and Soil Pollut., 130 (2001) 409-414. Rolph, G.D., 2003. Real-time Environmental Applications and Display sYstem (READY) Website (http://www.arl.noaa.gov/ready/hysplit4.html). NOAA Air Resources Laboratory, Silver Spring, MD. Samara,C. and R. Tsitouridou; Fine and coarse ionic aerosol components in relation to wet and dry deposition, Water, Air, and Soil Pollut., 120 (2000) 71-78. Whelpdale, D.M., P.W. Summers and E. Sanhueza; A global overview of atmospheric acid deposition fluxes, Environ. Monit. Assess., 48 (1997) 217-247.

Problems of Air Quality in Tashkent City G. A. Tolkacheva Research Hydrometeorological Institute, Uzbekistan, Tashkent, K. Makhsumov st., 72 Key Words: Air pollution, Carbon dioxide, Metals, Ozone, Precipitation (wet and dry), Sulphur dioxide, Toxicity

Introduction During last years the negative effects of anthropogenic pollution on the environment has intensified. The effects are observed on the regional and local levels in the change of the environment quality, as well as on the global level as in the change of the planet climate. Urban agglomerations play an important role in these processes. The interconnection between the problems of environment, economical development and demographical processes is sensed in urban agglomerations to the highest extent. In a big city, a specific natural technogenic ecosystem is formed, with new trends in biological processes of exchanging the energy and chemical substances. These processes determine, to a certain extent, the urban environment quality. Atmospheric air is the most agile component of the environment. It is subject to the impact of emissions; under their effect various chemical processes occur in the atmosphere, which result in formation of secondary, often more toxic trace components. In this regard, the assessment of the air quality in big industrial urban areas is a very timely and actual task. Tashkent city is the capital of the Republic of Uzbekistan, and is the largest city in Central Asia. The city area covers 259.39 km2 with a population of 2121 thousand. The city is situated in the western part of Central Asia, on a wide foothill plain on the right-hand bank of the Chirchik river, at 440-480 m a.s.l. The eastern part of the city is slightly hilly while the western part is located on a plain. The climate of this territory is extremely continental and dry, with hot summers and relatively cold winters. The area has a high climatic potential for atmosphere pollution. The following aims and tasks for studies in Tashkent city as an exemplary case have been untertaken: x

Assessment of the present state of the atmospheric pollution in Tashkent with the data from systematic observations;

x

Derivation of the relationship between the levels of atmospheric pollution and industrial emissions;

x

Evaluation of the role of chemical composition of the atmospheric fallouts (dry precipitation) as the indicators of atmospheric pollution;

x

Simulation of the effect of atmospheric phytotoxic components on the land vegetation; 379

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Derivation of the criteria for the evaluation of the effect of the polluted air on vegetation, and of the effect of atmospheric precipitation on the environment;

x

Definition of the main directions for the improvement of the air quality system.

Objects and Methodology of Studies Objects such as atmospheric air, atmospheric fallouts (dry and wet precipitation) and land vegetation in Tashkent were chosen for the studies. Systematic observations of the quality of atmospheric air in Tashkent are carried out at 13 stationary observation points conforming to the RD 52.04.186-89 standard (Figure 1).

Figure 1.

Map of Tashkent city.

Samples are taken at least 4 times a day. The data from measurements of the main trace components are compared by the MAɋone time and MACav.daily for the detection of causes and peculiar features. In urban air pollution, the information about climatic conditions determining the transfer and dissipation of trace components in the atmosphere is used along with the

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information about the amount of harmful substances emissions from industrial plants and traffic. Measurements of the concentrations of suspended substances, sulphur dioxide, nitrogen oxides and carbon oxide in the urban atmosphere are obligatory. The index of atmospheric pollution (IAP) is used for estimation of the integrated atmospheric pollution by an array of pollutants: Ji

¦( i 6

qi )c i MACav.daily

where: qi is the mean annual concentration of the i-th substance, MACi is the mean daily maximum admissible concentration (MAC) of the i-th substance and ci is the factor describing the degree of harmfulness of the pollutant (0.85-1.5). Observations of the chemical composition of atmospheric fallouts (dry precipitation) have been carried out in Tashkent since the 80s of the last century, in accordance with standardization procedures worked out at SANIGMI. Chemical analyses of the atmospheric air samples and atmospheric fallouts were made using the methods of atomic adsorption, ion chromatography, photo-colorimetry, etc. The methodology of studying the effects of trace components in simulation chambers was developed for the assessment of the impact of phytotoxins on land vegetation. On the basis of the experimental studies in chambers and of the field studies, ecological standards have been formulated for the effect of atmospheric air pollution on land vegetation. Discussion of Results and Evaluation of the Current State of the Atmospheric Air Pollution in Tashkent city Table 1 presents the dynamics of the atmospheric air pollution as established from the data on systematic observations of the main pollutants in MAC units. It was established that in general, the mean long-term levels of air pollutions exceed the admissible values for the following trace components: dust, nitrogen oxides and ozone. This are a number of factors responsible for this. Ɍɚble 1. Pollutant Ozone Dust Nitrogen dioxide Carbon oxide (II) Nitrogen oxide Sulphur dioxide

Dynamics of the atmospheric air pollution according to the main pollutants in measured in MAC units. 91 92 93 0.8 2 2 1.33 1.33 1.33

94 2 2.0

Years (1991-2002) 95 96 97 98 1.3 2.3 1.3 1.3 2.67 2.0 2.0 2.0

99 00 1.3 2.53 1.33 1.33

01 0.67 2.0

02 1.06 2.0

1.5

1.0

1.0

1.0

1.0

1.0

1.0

1.5

1.75

1.75

1.5

2.0

1.0

1.33

1.0

1.0

1.0

1.0

1.0

0.66

0.66

0.33

0.33

0.66

0.83

0.5

0.5

0.5

0.3

0.5

0.5

1.0

1.0

0.83

0.66

0.83

0.2

0.16

0.2

0.2

0.2

0.12

0.34

0.26

0.2

0.2

0.2

0.24

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The pollution with dust is caused by emissions from industrial plants and traffic, as well as by high emissions from natural sources of dust. The main emission sources of nitrogen oxides are mainly the mobile ones such as motor vehicles. The relatively high level of pollution by ozone is determined by photo-chemical reactions in the atmosphere under the influence of solar radiation and the high level of ozone precursor compounds. Figure 2 presents the zones most strongly affected by the emissions from industrial plants and the local zones with increased atmospheric pollution. It is evident that the field of concentration of pollutants over the city is formed by the emissions. The analysis of the dynamics of the emissions from stationary sources in Tashkent during the last years is shown in Figure 3. The graph of the dynamics of emissions from stationary sources during the last 10 years has also been plotted to reveal possible relationships.

Figure 2.

Industrial zones in Tashkent and local zones of increased atmospheric pollution.


Figure 3.

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The dynamics of emissions from stationary sources in Tashkent for 1992-2001.

Figure 3 shows that during the last ten years the emission of pollutants from stationary sources in the city has been significantly reduced. Carbon oxide accounts for more than half of the overall pollutant emissions. Components such as nitrogen oxides, solid substances and hydrocarbons make a significant contribution to the overall emissions. During the last 10 years the share of hydrocarbons in the emissions has increased significantly. The increase in the average concentrations of dust and nitrogen oxides in the urban air can result from the motor-transport emissions, which account for about 90% of the total emission of the pollutants. Analysis of the seasonal dynamics of the change in the long-term values of the pollutant concentrations sampled at different sampling points has revealed the local peculiar features of the air pollution by the different trace components. Figure 4 presents mean long-term seasonal trend of the change in dust concentrations. The highest concentration values were recorded at the measurement point located in the area subjected to the solid emissions from the Tashkent heat-producing power station. In this case an increase in the dust concentration during summer and autumn months is observed.

Figure 4.

Annual trend of dust concentration (mg/m3) at individual measurement points (average values for 1991-2000).

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The concentrations of nitrogen dioxide in the air measured at all sampling points were almost the same, so the annual trend is negligible (Figure 5).

Figure 5.

Annual trend of nitrogen dioxide concentrations (mg/m3) at individual measurement points (average for 1991-2000).

The situation is more complicated with respect to the levels of carbon oxide (II) and its annual dynamics observed at individual points (Figure 6). A spread of concentrations is observed depending on the season and on the location of each measuring point.

Figure 6.

Annual trend of carbon oxide concentrations (mg/m3) at individual measurement points (average for 1991-2000).

The dynamics of the seasonal variation of the ozone concentrations is presented in Figure 7, for 10 years of observations. It has been established that, during almost all the years of observations, the maximum concentrations were measured in summer months: June, July, and August. When comparing the observed values of the ozone concentration in the surface atmosphere layer recorded in Tashkent and Central Europe, it was revealed that the concentration ranges are very similar and fall in the range of 0.015 – 0.085 mg/m3. A complex analysis of the systematic data on atmospheric air pollution in Tashkent and of the development in the industrial structure and traffic has made it possible to assess in general the spread of the technological stress over the city territory (Figures 1, 2).


Figure 7.

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Dynamics of change of the surface ozone concentrations in Tashkent by months (1990-1999).

Assessment of the Role of Chemical Composition of Atmospheric Fallouts (dry precipitation) as an Indicator of Atmospheric Pollution In big industrial urban agglomerations, such as Tashkent in particular, an important factor concerning the effect of atmospheric pollution on the environment is the mechanism of removal of trace components from the active biological cycles. They are subdivided into classes where the following mechanisms and processes are involved: x

Chemical mechanism of transformation determined by the reactions of oxidation, hydrolysis and photochemical conversion;

x

Biological decomposition which is largely determined by intermediate microbiological reactions which take place in soil, water sediments and atmospheric aerosols;

x

Physical mechanisms, dissolution, agglomeration and gravitational deposition (sinking).

The main mechanisms of the removal of suspended particles and gases from the atmosphere are physical ones: dry and wet deposition or fallout in the form of dry and wet precipitation. Wet atmospheric precipitation comprises rain, snow and hail. Dry atmospheric fallout is the gravitational deposition (sinking) of dust particles and gas ingredients which are deposited on and adsorbed by the objects comprising the environmental surface. Dry fallout is the main mechanism of the removal of particles from troposphere below 100 m. It includes two processes: gravitational deposition and particle accumulation on surfaces of objects (buildings, plants, soil, etc.). The effect of the removal of particles from

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the atmosphere is closely related to physical changes of aerosol particles (increase of particle size with time, coagulation and other processes). The effect of deposition of gas components is determined by their reactivity, by the concentration of polluting components, solar radiation intensity and the oxidizing potential of the atmosphere. Under the conditions of the dry arid climate of Tashkent, the dry deposition of pollutants prevails over wet deposition during the entire year. Information about dry atmospheric fallouts (DAF) is used for the estimation of integral characteristics of urban atmosphere pollution, in order to reveal the ways of transformation of trace components released from the emission sources. Based on the results of the long-term systematic observations of the density of DAFflows, a chart-plot was constructed for the Republic of Uzbekistan. The map thus produced shows that Tashkent is located within the zone where the overall density of DAF-flow is 500 – 1000 kg/ha. Certain chemical transformations take place in the atmosphere as the result of interaction between oxygen, moisture, solar radiation and sulphur dioxide, nitrogen oxides and carbon oxide as follows: hQ SO 2 2 OH o H 2SO 4 SO 2 H 2 O o SO 2 H 2 O SO 2 H 2 O o HSO 3- H NO 2 OH M o HNO 3 M N 2 O 5 H 2 O o 2 HNO 3 NO 2 NO 3 M o N 2 O 5 M N 2 O 5 H 2 O o 2 HNO 3 PhOH NO 3 o PhOH HNO 3 CO O o CO 2 CO CO 2 HOH H 2 CO 3 o ® 2 ¯H 2O

End products of these transformations are sulphates, nitrates, carbonates and hydrocarbonates. These components can deposit on the surface of aerosol particles, and contribute to DAF composition and impact. Figure 8 presents pie diagrams of the averaged data on the mineral composition of the liquid extracts from the dry atmospheric fallouts sampled at Tashkent meteostation in the centre of the city, at Almalyk meteostation in the outskirts of the town and, for comparison, similar data from the meteostations “Chatkal Nature Reservation” and “Abramov glacier”. It is necessary to note that the composition of dry fallouts sampled in Chatkal with the northwestern wind direction (which prevails in that area) can be influenced by the transfer of sulphur dioxide and other components from Almalyk town which is the major source of anthropogenic pollution in Tashkent province. The possibility of such atmospheric transfer has also been confirmed by model calculations.


Figure 8.

387

Relationships between the water-soluble mineral components in dry atmospheric fallouts at various sampling points.

Figure 8 shows that each sampling point is characterized by a certain relationship between water-soluble components and their content in a liquid extract. The lowest mineralization was detected in samples taken from dry fallouts at the meteostation “Abramov glacier”, while the highest was detected in dry fallouts sampled at the Almalyk meteostation. In all samples, except those from the Abramov glacier, the prevalence of hydrocarbonates was observed, as they are, firstly, the main soil component, and secondly, the product of carbon oxide (which is the main emission from traffic) transformation into hydrocarbonates. The highest content of sulphides is typical for the anthropogenic aerosol. The maximum sulphide concentrations were recorded in Almalyk.

Figure 9.

Concentration of solid particles in the atmospheres of towns with population of more than 100 000 people (data from the Hydrometeorological service).

G. A. Tolkacheva

388

Figure 10.

Total content of PAH in atmospheric air of industrial towns in Uzbekistan.

Figure 9 presents data on the dynamics of the dust concentration in the atmosphere of several urban areas, including Tashkent. Figure 10 presents the data on the total concentration of the polyaromatic hydrocarbons (PAH) in the atmosphere of several industrial towns, including Tashkent. It is known that stable organic substances, including PAH, are concentrated in the atmosphere on fine-disperse dust particles. The results of these studies have confirmed this fact. Atmospheric Precipitation – Indicator of the Assessment of Climatic and Chemical Relationships The chemical content of the monthly total precipitation is the integral characteristic reflecting the pollution of the surface atmospheric layer through which the precipitation passes. The dynamics of change of this characteristic throws light on the effect of the general atmospheric circulation on the dispersion of green-house gases and aerosols over a certain territory. It is interesting to investigate the content of hydrocarbonates in precipitation, as the indicator of atmospheric pollution by carbon oxide (a green-house gas). Table 2 shows the relationship between HCO3- content and the ɪɇ of the liquid-phase media.

Table 2. Species

Speciation of carbonic acid in aqueous solutions of various ɪɇ (molar %). ɪɇ 4

5

6

7

8

9

10

11

[H2CO3 ]

99.7

97.0

76.7

24.9

3.22

0.32

0.02

[HCO3- ]

0.3

3.0

23.3

74.98

96.7

98.84

71.43

20.0

[CO32- ]

0.03

0.08

3.84

28.55

80.0

As part of the studies we have determined the dynamics of the change in the chemical composition of precipitation measured at some stations (Tashkent – Observatory, Kaunchi), by applying the commonly used indices (ɪɇ, electric conductivity, total ions, SO42-, NO3-, HCO3-, Cl-, Ca2+, Mg2+, NH4+, Na+, K+). Appropriate trends were revealed.


Figure 11.

389

Correlation between the water-soluble components in precipitation.

Possible relationships between the levels of precipitation pollution by green-house gases species and aerosols (HCO3-, NO3-, Ca2+, Mg2+) and by masses of emissions over the investigated territory have been studied. After analyzing the data on the chemical composition of the atmospheric precipitation measured over the territory of Tashkent city and Tashkent province, it was found that the local sources of atmospheric pollution have a certain effect on the chemical composition of precipitation (Figure 11). Simulation of the Effect of Atmospheric Phytotoxic Trace Components on Land Vegetation The study of the effect of individual atmospheric pollutants on plants under simulated fumigation conditions in chambers is a compulsory element for the assessment of the effect of atmosphere pollution on land vegetation. The concentrations at which atmospheric pollutants cause irreversible changes in the vegetal cell after 30 minutes and 4 hours of exposure were estimated experimentally. Fresh leaves of laboratory plants were used to study the relationships between the concentration of individual pollutants in the fumigation chamber and the peroxide activity, the intensity of peroxidation of lipids and the content of photo-synthetic pigments in the vegetal cell.

G. A. Tolkacheva

390

Based on the output of the conducted experiments, regional ecological standards for the quality of the atmosphere, with respect to the major air pollutants were developed, taking into account the risk for the land vegetation (trees and agricultural crops and plants) (Ɍɚble 3). Maximum admissible concentrations (MAC) of major atmospheric pollutants for humans and for vegetation.

Table 3.

One-time MAC for humans mg/m3 0.5 0.16 0.2 0.02 0.085

Pollutant SO2 O3 NH3 HF NO2

One-time MAC for vegetation mg/m3 0.3 0.061 0.091 0.0096 0.04

Average daily MAC for humans mg/m3 0.05 0.03 0.04 0.005 0.04

Average daily MAC for vegetation mg/m3 0.029 0.029 0.04 0.0033 0.015

As was noted before, the index of atmosphere pollution (IAP) is used in the overall state system of atmosphere monitoring and evaluation of air quality, for the estimation of the degree of air pollution. MACs for ecology were determined for the evaluation of atmospheric air quality in industrial agglomerations, which take into account the harmfulness of pollutants for land vegetation. Thus, new IAPs were developed for vegetation which differ from IAPs estimated on the basis of sanitary-and-hygienic MACs. Examples are shown in Figures 12, 13, and 14.

0,4 0,35 0,3 0,25

for plant

0,2 0,15 0,1 0,05 0 I

Figure 12.

II

III

IV

V

VI

VII

VIII

IX

X

XI

XII

Dynamics of the index of atmospheric pollution by SO2, Tashkent, 2001.


391

7 6 5 4 3 2 1 0 I

II

III

IV

V

VI

VII

VIII

IX

X

XI

XII

Dynamics of the index of atmospheric pollution by NO2, Tashkent, 2001.

Figure 13. 3,5 3 2,5 2 1,5 1 0,5 0 I

Figure 14.

II

III

IV

V

VI

VII

VIII

IX

X

XI

XII

Dynamics of the index of atmospheric pollution by NO2, Angren, 2001.

In our opinion, it is evident that the indices of the atmospheric pollution calculated with the use of ecological standards of quality, present more fairly the impact of individual pollutants on the ecosystem. The conducted experimental studies let us propose four levels characterizing the degree of atmospheric pollution by a given pollutant (i): admissible (Ji 1)

the pollutant concentration is not harmful for vegetation

increased (1 <Ji < 3) substantial (3 < Ji 5) high (Ji > 5)

the pollutant concentration is dangerous for vegetation

An IAP is usually estimated by mean-annual concentrations of harmful trace components, as follows: cj

§ q · ¦ ¨¨ i ¸¸ . i 1 © MPC ¹ m

Jm

G. A. Tolkacheva

392

7,87

Angren

8,98 7,72

Almalyk

10,75 8,67

Tashkent

7,91

0

2

4

2001

Figure 15.

6

8

(J) 10

12

2002

Integral atmospheric pollution (for 5 main pollutants) in several Uzbekistan towns, in 2001 and 2002.

Here, it is recommended to calculate the partial index values for each pollutant, and then to calculate the total index as a sum of the five highest values. Thus, we estimated the integral pollution of the atmospheric air as a sum of IAPs of each pollutant in a given year for five main atmosphere pollutants posing risk for vegetation. Mean annual indices of integral pollution of the atmospheric air were calculated for the big industrial centres of Uzbekistan. Some of them are presented on Figure 15. Following the specification for individual pollutants, four levels characterizing the degree of the integral atmospheric pollution can be considered for five main pollutants: admissible (J 5)

the concentration of the pollutants is harmful for vegetation

increased (5 < J < 8) substantial (8 < J 11)

the concentrations of the pollutants are dangerous for vegetation

high (J > 11)

Figure 15 shows that in all investigated towns of Uzbekistan an increased (5 < J < 8) or substantial (8 < J < 11) level of atmospheric pollution was observed in 2001 and 2002. Conclusion Analysis of the current state of the pollution of the atmospheric air in Tashkent city and of the system of the air quality monitoring has revealed the following: ¾ It is necessary to develop a united information system consisting of automated stations for air quality control; ¾ There is not any system of measuring the dust particles, which is important for the population health; ¾ It is necessary to develop the models of pollutant transfer and transformation for the conditions of the urban environment, taking into account the meteorological parameters. Acknowledgment I thank Mr. A.A. Azizov, Chief of Ecological Program of the State Committee on Science and Technology of the Republic of Uzbekistan, and Ms. N.G. Verechagina, Chief of the Laboratory of NIGMI for financial support of this work. I thank L. Shardakova, Y. Kovalevskaya, T. Smirnova, N. Rahmatova, L. Usmanova and N. Akinshina for their assistance with carrying out this work.

Precipitation Quality in Different Zones of the Tashkent Region in Relation to Photo-Chemical Reactions Tatyana Smirnova and Galina Tolkacheva Hydrometeorological Research Institute Uzhydrome of the Republic of Uzbekistan, 700052 Tashkent, K. Makhsymov, 72 Key Words: Photochemical reactions, Oxidative capacity, Local sources, Mineralization, Underlying surface

Introduction Since many years there has been increased interest in the investigation of chemical processes taking place in the polluted atmosphere. Definite relationships exist between chemical reactions which occur in the atmosphere in the gas, liquid and solid phases under stationary conditions. It is interesting to study comprehensively the relationships and the nature of the processes taking place in a liquid phase and in aerosols, as well as the role of chemical atmospheric processes in the formation of secondary aerosols. The increase of the secondary aerosol concentration in the atmosphere causes a decrease in visibility and the formation of acid rains which have a negative effect on human health, vegetation, soil, buildings and constructions (Ravinskii and Egorov, 1990). Tashkent province was selected for the investigations. This area is known for its typically extreme continental climate, abundance of days with sunshine during the year which means a high solar radiation, high mean-annual air temperature and complex orography. Large industrial enterprises are located in this area. The main emissions of these plants into the atmosphere are: dust (with an abundance of heavy metals), oxides of nitrogen, sulphur and carbon, and other compounds of nitrogen, sulphur and fluorine. It is known that pollutants fall from the atmosphere to the ground surface due to various processes including the dry absorption of gases, humid fallout with precipitation and gravitational deposition of suspended solid particles. The processes which influence the chemical composition of atmospheric precipitation can be investigated using the chemical reactions taking place in atmosphere. It is interesting to follow the possible ways of formation of different compounds in the atmosphere in the selected area in relation to the composition of the emissions of harmful substances into the atmosphere. Objects and Methods of Investigations In this section we describe the methodology used to study the effect of emissions from the local sources of atmospheric pollution on the processes of secondary aerosol formation. The basic admixtures selected as the main objects of investigations were: dust and oxides of sulphur and nitrogen which are the main components of the emissions from the industrial plants in Tashkent province. 393 I. Barnes and K. J. Rudzinski (eds.), Environmental Simulation Chambers: Application to Atmospheric Chemical Processes, 393–402. © 2006 Springer. Printed in the Netherlands.

T. Smirnova and G. Tolkacheva

394

In the first stage of the studies an assessment of the dynamics of the main emissions from the industrial plants and the contents of each component was performed, based on the data from statistical reports (Glavgidromet, 2001). At the same time, the changes of the chemical composition of the gas phase, atmospheric aerosols, and precipitation during the same period were analyzed, and possible impacts of atmospheric fallouts on the environment were assessed. The effect of emissions on the chemical composition of atmospheric precipitation was investigated taking Almalyk town as an example. A lot of industrial objects are located in Almalyk town: construction enterprises and chemical plants; Almalyk mining and smelting plant. Based on the methodical guideliness formulated in the Main Geophysical Observatory and SANIGMI (Gidrometeoizdat, 1991; SANIGMI, 1993a), sampling of precipitation was conducted for 14 years. Sampling and analysis of sulphur and oxygen oxides in atmosphere were performed using a standard technique (Andreani-Aksogoglu, 1996; SANIGMI, 1993b). The chemical composition of atmospheric precipitation was analyzed by the methods of ion chromatography, atomic adsorption, photo-colorimetry and other techniques, in accordance with documented methodical guidelines (Brimblecombe, 1988; SANIGMI, 1993b; Gidrometeoizdat, 1996; Isidorov, 2001). Outcomes and Their Consideration As was mentioned above, at the first stage of the investigations we assessed the dynamics of the emissions of sulphur and nitrogen dioxides and of dust which pollute the atmosphere in Almalyk, the levels of atmospheric pollution of these components and their content in humid and dry atmospheric fallouts. The town of Almalyk was chosen as a model for the investigation of the chemical reactions in the atmosphere causing the formation of nitrates and sulphates in precipitation. Total annual emissions and annual mean concentrations of each component were also calculated. The results obtained are presented in Table 1 (for 2 years).

Table 1.

Emissions and concentrations of atmospheric pollutants in air, precipitation and dry atmospheric fallouts (DAF).

Pollutant Sulphur dioxide Nitrogen oxides Nitrates (water-soluble) Sulphates (water-soluble) Suspended substances Lead , t/y Arsenic, t/y

Emissions into atmosphere 1000 t/year 1999 88.9 1.02

2000 87.7 1.01

Mean concentration in air mg/m3 1999 2000 0.04 0.04 0.05 0.05

0.04

0.03

3.81

3.8

0.2

0.2

1.93 17.6

2.64 33.0

0.12

0.12

in precipitation mg/dm3 1999 2000

DAF mg/dm3 1999 2000

8.09

7.99

5.81

0.913

41.27

34.51

49.71

14.06

Precipitation Quality in Different Zones of Tashkent Region

395

After calculations using the experimental method it was found that in 1999 in Almalyk the total SO42- deposition with liquid precipitation was 151.12 kg/ha/y (monthly average – 12.6 kg/ha) and the total SO42- deposition with dry fallout (DAF) was 139.2 kg/ha/y, (monthly average – 11.6 kg/ha). Figure 1 presents the dynamics of the changes in atmospheric pollution by sulphur and nitrogen oxides and dust.

Figure 1.

Changes in the average levels of atmosphere pollution in Almalyk town.

The industrial enterprises of Almalyk, heating and production of electric energy are the main sources of sulphur dioxide emission into the atmosphere (90% of all emissions). The main source of emission of nitrogen oxides is traffic. During the last years a small increase of sulphur dioxide and dust concentrations in atmosphere was recorded. Correlation factors between the pollutant emissions into the atmosphere and their concentration in atmospheric precipitation have been calculated. Table 2 lists the values obtained. The correlation factors indicate the presence of a certain relationship between the pollutant emissions into the atmosphere and their concentration in atmospheric precipitation.

Table 2.

Correlation factors between pollutant emissions into the atmosphere and concentrations of these substances in atmospheric precipitation.

Pollutants in the atmosphere

Dust (1000 t)

Pollutants in atmospheric precipitation Ion sum mg/dm3

Correlation factor - 0.485

SO2 (1000 t)

SO4 - mg/dm3

0.56

3

0.64

NOx (1000 t)

-

NO3 mg/dm

Nitrogen and simultaneously formed non-organic (ɇ2Ɉ2) and organic (ROOH) peroxides and peroxyacylnitrates are the strongest photo- and phyto oxidants. The increase of the concentration of these secondary pollutants in the atmosphere causes a decrease in bio-

T. Smirnova and G. Tolkacheva

396

productivity and the degradation of a natural vegetation cover over vast territories (Mazin and Krichian, 1988) and, consequently, has a negative effect on the assimilation of one of the main green-house gases, carbon dioxide. The positive trend in the troposphere ozone concentrations is most likely determined by the increase of emissions of the ozone precursors, nitrogen oxides and volatile organic compounds (VOC) from anthropogenic sources. Photo-chemical reactions taking place during the action of intensive solar radiation, high temperature and humidity on the air mass containing pollutants are the main source of the formation of ozone in atmosphere. The formation of ozone in the polluted atmosphere proceeds as follows: under the effect of radiation (wavelength range 310 - 1180 nm), ozone is decomposed with the formation of atomic oxygen in the ground state (Ɉ(3P)). O3+hȞ o Ɉ(3P)+Ɉ2 The oxygen atoms recombine with oxygen to ozone: Ɉ(3P)+O2+Ɇ o Ɉ3+Ɇ* where Ɇ is a molecule of nitrogen or oxygen which obtains excessive vibrational energy from the intermediate complex (Ɉ2 … Ɉ). During the absorption of quanta by ozone in the nearest UV band in the 290 - 310 nm range, the following reaction takes place in the atmosphere: O3+hȞ o Ɉ(1D)+Ɉ2(1'd) The major part of the unstable oxygen being formed in the troposphere is deactivated through collision with molecules of nitrogen or oxygen: Ɉ(1D)+Ɇ o Ɉ(3P)+Ɇ* Ɉ+Ɉ2+Ɇ o Ɉ3+Ɇ A fraction of the unstable oxygen reacts with water vapour to produce hydroxyl radicals: Ɉ(1D)+ɇ2Ɉ o 2ɇɈ+120.5 kJ (Shreier, 1986) Hydroxyl radicals are very reactive, and take part in reactions with many pollutants to make the atmosphere “cleaner”. It should be taken into account that the concentrations of trace gases in the polluted atmosphere can be much higher than in the clean one, so the rates of second order reactions increase significantly. It is most likely that ozone formation in the polluted atmosphere takes place during the oxidation of nitrogen oxides to nitrogen dioxide. Under certain radiation conditions, a pseudobalance between nitrogen oxide and dioxide is maintained. In such cases, the increase of the ozone level in the atmosphere is the evidence for the decrease of the nitrogen oxide concentration therein. Consideration of other reactions of organic components possible in the polluted atmosphere confirms the statement that the main source of ozone in the troposphere is the photolysis of nitrogen oxides: NO2+hȞ (Ȝ

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