The end result of policy-related experimental and theoretical scientific work on the abatement of atmospheric emissions is a hierarchy of computer models that can be used to analyse and predict the behaviour of pollutants on urban, local regional and global scales. Such models are required to simulate an extremely complex natural situation in which a non-linear chemistry must be included together with the vagaries of the meteorology and the terrain. This book describes recent advances in the development and application of models on all scales, and in the techniques for the estimation and verification of emissions. It includes reviews of recent work together with detailed results and provides a useful picture of the field in a European context.

The acidification problem is still an area of great concern. Many areas in the world are subject to large, in some cases increased, deposition ofacidifying substances. Scientific research has played a crucial role in the discovery and exploration of the problems as well as a basis for the development ofcontrol strategies for the more than 25 years that have passed since Svante Oden first presented his results. Even today scientific research is important as a tool for policy, most clearly observed in the effect-oriented second sulphur protocol under the Convention on Long-range Transboundary Air Pollution signed in Oslo 1994. Without a close international scientific cooperation this protocol would have never been able to develop. The 5th Conference on Acidic Deposition Acid Reign '95? should be seen in the context ofthe ongoing process to strengthen the scientific background for policy. It was therefore a great pleasure for Sweden to host the conference. It became a success in many respects. First the number ofscientists and presentations made this conference the most comprehensive ever on acidic deposition. From the organizers, we were extremely pleased to see the number of participants and contributions from countries outside Western Europe and North America. These participants turned the focus to areas showing signs ofan increased acidification problem and areas still under heavy pressure from acidic deposition. An excursion to the Czech republic prior to the conference underpinned this interest.

Viewed from space, the Earth appears as a globe without a beginning or an end. Encompassing the globe is the atmosphere with its three phases- gaseous, liquid, and solid--moving in directions influenced by sunlight, gravity, and rotation. The chemical compositions of these phases are determined by biogeochemical cycles. Over the past hundred years, the processes governing the rates and reactions in the atmospheric biogeochemical cycles have typically been studied in regions where scientists lived. Hence, as time has gone by, the advances in our knowledge of atmospheric chemical cycles in remote areas have lagged substantially behind those for more populated areas. Not only are the data less abundant, they are also scattered. Therefore, we felt a workshop would be an excellent mechanism to assess the state of-knowledge of the atmospheric cycles of sulfur and nitrogen in remote areas and to make recommendations for future research. Thus, a NATO Advanced Research Workshop ' he Biogeochemical Cycling of Sulfur and Nitrogen in the Remote Atmosphere" was held at the Bermuda Biological Station, St. Georges, Bermuda, from 8-12 October 1984. The workshop was attended by 24 international scientists known for their work in atmospheric cycling in remote areas. This volume contains the back ground papers and the discussions resulting from that workshop. The workshop was organized along the lines of the atmospheric cycle. There were working groups on emission, transport, transformation, and deposi tion."

The end result of policy-related experimental and theoretical scientific work on the abatement of atmospheric emissions is a hierarchy of computer models that can be used to analyse and predict the behaviour of pollutants on urban, local regional and global scales. Such models are required to simulate an extremely complex natural situation in which a non-linear chemistry must be included together with the vagaries of the meteorology and the terrain. This book describes recent advances in the development and application of models on all scales, and in the techniques for the estimation and verification of emissions. It includes reviews of recent work together with detailed results and provides a useful picture of the field in a European context.