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 . . .