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_Walter Klopffer Burkhard O. Wagner Atmospheric Degradation of Organic Substances 1807–2007 Knowledge for Generations Each generation has its unique needs and aspirations When Charles Wiley first opened his small printing shop in lower Manhattan in 1807 it was a generation of boundless potential searching for an identity And we were there helping to define a new American literary tradition Over half a century later in the midst of the Second Industrial Revolution it was a generation focused on building the future Once again we were there supplying critical scientific technical and engineering knowledge that helped frame the world Throughout the 20th Century and into the new millennium nations began to reach out beyond their own borders and a new international community was born Wiley was there expanding its operations around the world to enable a global exchange of ideas opinions and know-how_ _For 200 years Wiley has been an integral part of each generation’s journey enabling the flow of information and understanding necessary to meet their needs and fulfill their aspirations Today bold new technologies are changing the way we live and learn Wiley will be there providing you the must-have knowledge you need to imagine new worlds new possibilities and new opportunities_ _Generations come and go but you can always count on Wiley to provide you the knowledge you need when and where you need it! William J. Pesce President and Chief Executive Officer Peter Booth Wiley Chairman of the Board Walter Klopffer Burkhard O. Wagner Atmospheric Degradation of Organic Substances Data for Persistence and Long-range Transport Potential The Authors Prof Dr Walter Klopffer Am Dachsberg 56 E 60435 Frankfurt am Main Germany Dr Burkhard O. Wagner Am Hirschsprung 37 a 14195 Berlin Germany All books published by Wiley-VCH are carefully produced Nevertheless authors editors and publisher do not warrant the information contained in these books including this book to be free of errors Readers are advised to keep in mind that statements data illustrations procedural details or other items may inadvertently be inaccurate_ _Library of Congress Card No applied for British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library Bibliographic information published by the Deutsche Nationalbibliothek The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografe detailed bibliographic data are available in the Internet at http dnb d nb de_ _© 2007 WILEY-VCH Verlag GmbH & Co KGaA Weinheim All rights reserved (including those of translation into other languages) No part of this book may be reproduced in any form by photoprinting microfilm or any other means nor transmitted or translated into a machine language without written permission from the publishers Registered names trademarks etc used in this book even when not specifically marked as such are not to be considered unprotected by law_ _Typesetting Manuela Treindl Laaber Printing Strauss GmbH Mülrenbach Binding Litges & Dopf Buchbinderei GmbH Heppenheim Printed in the Federal Republic of Germany Printed on acid-free paper ISBN 978-3-527-31606-9 V Foreword Who should read a book on photo-degradation Only the few scientists experienced in this very specific area No this book is a storehouse for students risk assessors in administration and industry and other interested people who want to learn why we can still breathe fairly clean air in most parts of the world The book contains a concise and understandable scientific presentation of the various mechanisms that contribute to the photochemical degradation of organic molecules in the troposphere their kinetics and the variables that influence the efficacy of the degradation processes Experimental data on 1081 substances make this book valuable for readers who want to assess chemicals develop simulation models and predict the environmental fate and distribution of pollutants_ _Photochemical oxidation in the atmosphere by hydroxyl and nitrate radicals and by ozone is obviously the most effective mechanism to decompose xenobiotics (and also several natural substances) which partition to air to a certain extent This is why in the 1970s and 1980s numerous scientists began to measure rate constants for photochemical degradation Their experiments were aimed at obtaining a first estimation as to whether atmospheric pollutants would accumulate and subsequently pose a risk The results were encouraging and relieving Most chemicals are attacked by the cleansing agents of the atmosphere oxidized and finally eliminated However some molecules such as the chlorofluorocarbons (CFCs) are recalcitrant and are only slightly or non-reactive_ _By 1991 the German Federal Environment Agency (UBA) had compiled the photo-degradation data of 544 substances in a study that was co-financed by the German Chemical Industry Association (VCI) demonstrating a significant scientific interest in such experimental studies at that time UBA-Texte 51 91 In the intervening years AOP (Atmospheric Oxidation Potential) and other quantitative structure activity relationship programmes (QSAR) have been developed which allow plausible predictions of the photo reactivity of chemical substances This led to a significant decline in experimental interest Calculations were easier cheaper and more rapid than experimental determinations but sometimes the limitations of the models were neglected Since then the number of substances that have been examined experimentally for their photo-degradation kinetics has only doubled However this broadening of the data basis which is documented in this book is the reason for compiling the data again and may_ _Atmospheric Degradation of Organic Substances W Klopffer and B O Wagner Copyright © 2007 Wiley-VCH Verlag GmbH & Co KGaA Weinheim ISBN 978-3-527-31606-9 VI Foreword give rise to refinements and modifications to the existing models for calculating the rate constants_ _This book does not simply list and explain various rate constants but discusses the importance of these data generated by environmental scientists for environmental policy and regulation This makes it fascinating reading for risk assessors in administration and industry For many years discussion on environmental risks of chemicals was focused on their toxicological and ecotoxicological properties Only in the last ten years has persistence been given increased attention and become important in environmental risk assessment Substances that are not degradable may accumulate in environmental media and biota irreversibly thus posing a long-term risk that is not predictable The cornerstones of this discussion are the POP Protocol (1998) and the Stockholm Convention (2001) (POP Persistent Organic Pollutant) which prohibit certain extremely persistent and hazardous chemicals worldwide or at least minimize their use and emissions Another branch of regulatory discussions of persistence were the marine conventions OSPAR and HELCOM because the marine environment represents a sink for chemicals discharged into the sea by rivers atmospheric deposition or human activities offshore OSPAR was the first international entity which proposed an assessment scheme for PBT (persistent bioaccumulating and toxic) substances in order to identify and prohibit those substances followed by inclusion of this PBT assessment in the technical guidance document (TGD) for assessing the risks of new and existing chemicals at a European level This was taken up by REACH the new European Chemicals Legislation which will come into force in 2007 Most experts today accord that chemicals which are very persistent and have a great potential to accumulate in biota pose a risk and their consumer use and release into the environment should be restricted or even prohibited even in those cases where toxic or ecotoxic effects are (still) not known Chemicals exhibiting these characteristics are not inherently sustainable_ _Most assessment and regulatory schemes for persistent substances focus on (biotic) degradation in water sediment and soil however abiotic degradation in the atmosphere has attracted little attention Looking at REACH atmospheric lifetimes are missing in the basic data set This is clearly a deficiency because atmospheric degradation is an important mechanism not only for gases and volatile substances but also for all chemicals with a vapour pressure > 10–6 Pa which could vaporize and spread via the atmosphere to a significant extent_ _The atmosphere is not only a wash-house for photo-degradable substances but also the most important medium for long-range transport of persistent substances Most POPs are predominantly transported via air in remote regions They are semi-volatile i e in cold climate zones they may condense and be deposited on soil or water where organisms can take them up When they volatise again this effect is known as the grasshopper effect which explains why concentrations in polar regions are often higher than in the temperate and tropical latitudes where they are emitted Therefore Annex D of the Stockholm Convention lists environmental long-range transport as one of four criteria for identifying POPs_ _Foreword VII The semi-volatility makes experimental determination of the atmospheric lifetime difficult because a significant proportion of the POPs in the atmosphere are not free gaseous molecules but adsorbed onto particles In this state the attack of oxidising reactive species is hindered and this is why many calculations of atmospheric stability of semi-volatile compounds underestimate the lifetime This is a topic where the initial experimental findings resulted in interesting insights However more research is necessary_ _The Stockholm Convention is discussing persistence in the various e_ Ключевые слова: sci, trans, polychlorinated dibenzo-p-dioxins, processes, und, dimethyl ether, multimedia models, kr?ger, constants photo-degradation, science, direct, oecd, phase, organic compounds, abiotic degradation, parent structure, surface, ea, der, carbonyl compounds, sci technol, zenith angle, unintended occurrence, series, photo-degradation processes, chem kinet, atmosphere, ha, photolysis, condensed phase, dimethyl sulfoxide, method, chemicals, tetraalkyllead compounds, lett, reaction, european union, carbon monoxide, inter-system crossing, smog, atmospheric trends, gas, ring strain, photo, temperature, umweltbundesamt, uv, nm, eds methods, int chem, quantum efciency, rate coefcients, radicals, priority setting, nitrated phenols, ester, kl?pffer, organic matter, penetration depth, berlin, von, quantum, nitrate, rate constants, data, water, kerr, 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