countries accelerating to reach a consensus on the role that atmospheric emissions and acidic precipitation play in the environment, publication of this series is timely. The editors thank the contributors to this volume for their efforts in describing a wide array of atmospheric topics, all of which are important to an understanding of the acidic precipitation issue. Oak Ridge, Tennessee Steven E Lindberg Riverside, California Albert L. Page Orono, Maine Stephen A. Norton Contents Series Preface .................................................... v Preface... ....... ...... ..... ... .. ............................... .. vii Contributors ..................................................... xiii Sources of Acids, Bases, and Their Precursors in the Atmosphere . . . 1 Roger L. Tanner I. Introduction and Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 II. Sources of Acids ............................................... 3 III. Sources of Acid-Neutralizing Substances (Bases) ................... 9 IV. Distribution of Atmospheric Acids and Bases ...................... 10 V. Gas-Aerosol Equilibria and Boundary Layer Mixing ................ 14 VI. Summary of Significant Acid-Formation Pathways.............. . .. . 15 References ................................•................... 17 Aerosol Sulfur Association with Aluminum in Eastern North America: Evidence for Solubilization of Atmospheric Trace Metals before Deposition ......... . . . . . . . . . . 21 . . .

Acid rain was one of the major environmental issues of the 1980s. But while industrialized countries have taken measures to reduce the emissions that lead to acidification, the problems have not gone away. Trees are still dying, lakes are still being made uninhabitable; buildings are still corroding; and human health is still suffering. The most worrying trend is the repetition in the industrializing countries of Asia and Latin America of the problems that have long afflicted Europe and North America. More than 10 years after it was first published, the highly acclaimed Acid Earth still provides the only global view of acidification, and remains the standard text on the subject. Chapters on the causes, effects and growing scientific understanding of acid pollution, and the possible solutions, are followed by detailed studies of the political struggles involved in responding to acid damage in western and eastern Europe, the US and the newly industrializing countries. Written in non-technical language for people interested in the problems of the environment, Acid Earth calls for a renewed sense of public and political will to bring the problems of acid pollution under control. The book also makes valuable reading for specialists and students. Originally published in 1992

Since the beginning of the 1980's, research has continued to clarify and improve our understanding of the problern of the ecological impact of acidic precipitation. From September 15-20, 1985, Canada convened the the Muskoka Symposium on Acidic Precipitation to review progress and help chart the direction of future studies. The Conference was held in central Ontario, Canada, a region of heavy sulphate deposition where aquatic effects are evident. Approximately 700 people attended, over 500 of whom were research scientists. Over 400 papers were presented. Nearly 200 of the papers are included in these proceedings, which tagether give the present state of the art of acid rain research. The Conference focused on atmospheric science and aquatic and terrestrial effects. I have made some general observations on progress in clarifying issues and linkages between these areas of research. Out standing issues which require a great deal more work are identified. These are my views, influenced by personal bias and limited by my expertise. Atmospheric Seiences Three aspects were covered: measurement techniques, the actual measure ments, and source-receptor relationships.