The ITM conference series has always had a strong spirit of cooperation under the NATO/CCMS umbrella, and with the considerable interest fram Partner countries to participate in the ITM conferences, it provides an excellent opportunity to create ties between scientists. Whereas all previous ITM conferences have taken place in NATO countries, the 23rd ITM takes place in a Cooperative Partner country, Bulgaria, and is hosted by the National Institute of Meteorology and Hydrology, Bulgarian Academy of Sciences. This fact reflects a general wish for a closer connection and collaboration among scientists fram Partner and NATO countries. This volume contains the papers from the 23rd NATO/CCMS International Technical Meetings on Air Pollution Modelling and Its Application, being held September 28 - October 2, 1998, at Riviera Holiday Club, Varna, Bulgaria. It was attended by 120 participants from 30 countries. Thanks are due to all who made it possible to plan, carry through, and follow up the meeting, and to the participants who made the conference so successful. Special thanks are due to the sponsoring institutions: ATO/CCMS EURASAP RIS0 BAS 3M NATO/CCMS - Committee on the Challenges of Modem Society EURASAP - European Association for the Science of Air Pollution RIS0 - Ris0 National Laboratory, Denmark NIMH - National Institute of Meteorology and Hydralogy, Bulgaria BAS - Bulgarian Academy of Sciences 3M Representation office, Bulgaria Prestige Business Ltd. , Bulgaria The excellent collaboration with CIM (Company for International Meetings Ltd.

The chemical enigma that is both a pollutant and anantipollutant--and environmental science's newest causecelebre.oxidants Responsible for chemical reactions both harmfuland benign, oxidants represent the sort of chemical puzzle thathave scientists both concerned and fascinated. Implicated in deadlysmog episodes and arteriosclerosis, oxidants have also played amajor role in treating polluted waters and in certain anticancerdrugs. A broad-based, up-to-date examination of the environmentalchemistry and toxicology of oxidants, Environmental Oxidants is acompendium of the latest research being done in the field. Bringingtogether the work of noted researches, the book contains a detailedlook at: * Evolution, production, distribution, and fate of oxidants in theatmosphere, hydrosphere, and biosphere * Influence of human activities on oxidative processes in theatmosphere * Oxidative stress at the cellular, systemic, and ecosystemlevels * Use of oxidants in wastewater treatment processes A selective and incisive look at the current state of research onoxidants, Environmental Oxidants provides environmental scientistsand engineers with an informative, detailed discussion of just howand why oxidants have emerged as a key issue in human health andenvironmental integrity.

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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.