Impact Models to Assess Regional Acidification

Abstract

ForewordSensitive receptors such as soil and fresh bodies of water are at the end of a long chain of events in the process of regional acidification. This chain begins thousands of kilometers upwind at the emitters of acidifying pollutants. The topics covered in this book are important in the study of regional acidification for two reasons. First, it is important to assess the sensitivity of terrestrial and aquatic ecosystems to the deposition of acidifying pollutants. If the sensitivity of an ecosystem is known, then international control strategies can be developed to reduce deposition in the receptor areas of greatest importance. This is an important factor in designing the most effective strategies because of the very high costs of reducing emissions of acidifying pollutants.Second, it is important to be able to predict changes in ecosystems for decades into the future, whether it be an improvement owing to decreases in acidifying emissions or, alas, a further deterioration because control strategies are nonexistent or inadequate. In either event, it is important to be able to judge the results of our actions.Decision makers tend to be mistrustful of models unless they can judge their reliability. The application and testing of the models in Part III of this book cover, therefore, an important facet of model building.This book is an ideal companion to another book that is forthcoming from the Transboundary Air Pollution Project at IIASA: The RAINS Model of Acidification: Science and Strategies in Europe. The latter book is a description of the development and use of the Regional Acidification INformation and Simulation (RAINS) model, an integrated assessment model for developing and determining control strategies to reduce regional acidification in Europe. Much of the research described in this book forms part of the foundation of the RAINS model. These two books cover a great deal of the present knowledge about assessing and dealing with a very important environmental problem in Europeregional acidification. R. W. Shaw Leader Transboundary Air Pollution Project Introduction Acidification of the EnvironmentAcidification of the environment is, like most recent environmental problems, a consequence of change in the natural cycles of elements. Some chemical substances that during millions of years leaked from the biosphere are again being emitted to the atmosphere. Owing to these anthropogenic emissions, fluxes of acidifying compounds to the soils and waters have increased manyfold since preindustrial times.The whole problem of air pollution is transboundary in nature; its geographic dimensions are difficult to define. Pollution sources are scattered in many countries, the consequences extending far away. Acidifying sulfur and nitrogen oxides can persist in the air up to a few days, long enough to be transported hundreds or even thousands of kilometers from the place they were emitted. During this transit time, gaseous pollutants undergo a complicated chemical conversion into nitric and sulfuric acids, which ar...