EUROTRAC is the EUREKA environmental project studying the transport and chemical transformation of pollutants in the troposphere over Europe. At its inception in 1988 it had three aims: * to increase the basic understanding of atmospheric science; * to promote the technological development of sensitive, specific, fast-response instrumentation for environmental research and monitoring; and * to improve the scientific basis for taking future political decisions on environmental management within Europe. It was clear at an early stage, as the fourteen subprojects were formed and more than two hundred research groups in twenty-four countries were incorporated, that the first aim would readily be achieved. An ample demonstration that the early indications were correct is provided in the other volumes in this series which describe the scientific progress made. Substantial progress was also made towards achieving the second aim although some problems were encountered, mainly due to the high cost of the technological development required.

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.

EUROTRAC is the EUREKA environmental project studying the transport and chemical transformation of pollutants in the troposphere over Europe. At its inception in 1988 it had three aims: * to increase the basic understanding of atmospheric science; * to promote the technological development of sensitive, specific, fast-response instrumentation for environmental research and monitoring; and * to improve the scientific basis for taking future political decisions on environmental management within Europe. It was clear at an early stage, as the fourteen subprojects were formed and more than two hundred research groups in twenty-four countries were incorporated, that the first aim would readily be achieved. An ample demonstration that the early indications were correct is provided in the other volumes in this series which describe the scientific progress made. Substantial progress was also made towards achieving the second aim although some problems were encountered, mainly due to the high cost of the technological development required.

Presenting the first continental-scale assessment of reactive nitrogen in the environment, this book sets the related environmental problems in context by providing a multidisciplinary introduction to the nitrogen cycle processes. Issues of upscaling from farm plot and city to national and continental scales are addressed in detail with emphasis on opportunities for better management at local to global levels. The five key societal threats posed by reactive nitrogen are assessed, providing a framework for joined-up management of the nitrogen cycle in Europe, including the first cost-benefit analysis for different reactive nitrogen forms and future scenarios. Incorporating comprehensive maps, a handy technical synopsis and a summary for policy makers, this landmark volume is an essential reference for academic researchers across a wide range of disciplines, as well as stakeholders and policy makers. It is also a valuable tool in communicating the key environmental issues and future challenges to the wider public.