Acid Deposition -- Copyright -- Preface -- Contents -- Summary -- STATUS OF SCIENTIFIC KNOWLEDGE -- Data -- Meteorological Processes -- Models -- ISSUES -- Applicability of Models To Decisions On Control Strategy -- Nonlinearity -- Influences of Local and Distant Sources -- IMPLICATIONS FOR EMISSION-CONTROL STRATEGIES -- RESEARCH NEEDS -- 1 Introduction -- DEPOSITION ACIDITY -- ENVIRONMENTAL EFFECTS -- Physical and Chemical States of Deposited Materials -- Reversibility and Irreversibility -- OTHER RELATED REGIONAL AIR POLLUTION PHENOMENA -- PURPOSE OF THE STUDY -- ORGANIZATION OF THE REPORT -- NOTES -- REFERENCES -- 2 Atmospheric Processes -- TRANSPORT AND MIXING -- CHEMICAL TRANSFORMATION -- Homogeneous Gas-Phase Reactions -- Homogeneous Aqueous-Phase Reactions -- Relative Roles of Gaseous- and Aqueous-Phase Chemistry -- DEPOSITION -- Dry Deposition -- Wet Deposition -- Attachment Processes -- REFERENCES -- 3 Theoretical Models of Regional Air Quality -- MATERIAL BALANCE -- DETERMINISTIC MODELS -- Treatment of Transport and Mixing -- Treatment of Transformation Chemistry -- Treatment of Dry and Wet Deposition -- Linearity or Nonlinearity in Theoretical Models -- Physical Processes -- Chemical Processes -- FINDINGS AND CONCLUSIONS -- REFERENCES -- 4 Empirical Observations and Source-Receptor Relationships -- AEROMETRIC DATA AND THEIR LIMITATIONS -- RELATIONSHIPS AMONG AEROMETRIC PARAMETERS -- THE INFLUENCE OF METEOROLOGICAL CONDITIONS -- Classification of Meteorological Conditions -- Air-Mass Trajectories -- STATISTICAL METHODS OF ANALYSIS -- Regression on Principal Components -- Empirical Orthogonal-Function Analysis -- Elemental-Tracer Analysis -- ANALYSIS OF HISTORICAL TRENDS -- ANALYSIS OF RELATIVE BEHAVIOR OF SULFUR AND NITROGEN EMISSIONS -- FINDINGS AND CONCLUSIONS -- Nonlinearity -- Influence of Local and Distant Sources -- REFERENCES.

5 Research Needs -- FIELD STUDIES -- Cloud Processes -- Studies of Chemical Mechanisms -- Dry Deposition -- Tracers -- Meteorological Studies -- LABORATORY STUDIES -- DEVELOPMENT OF THEORETICAL MODELS -- Appendix A The Chemistry of Acid Formation -- GAS-PHASE REACTIONS LEADING TO GENERATION OF ACID IN THE TROPOSPHERE -- Oxidation By Stable Atmospheric Molecules -- Reactive Transient Species in the Troposphere -- Atmospheric Oxidation of SO2 by Reactive Transient Species -- Atmospheric Oxidation of NO2 by Reactive Transient Species -- Theoretical Rates of SO2 and NO2 Conversion To H2SO4 and HONO2 Through Gas-Phase Reactions in the Troposphere -- THE SOLUTION-PHASE OXIDATION OF SO2 IN THE TROPOSPHERE -- Aqueous-Phase Oxidation of SO2 -- Comparison of Reaction Pathways For Solution-Phase Oxidation of SO2 -- Solution-Phase Generation of Nitric and Nitrous Acids in the Troposphere -- SUMMARY -- REFERENCES -- Appendix B Transport and Dispersion Processes -- CLASSIFICATION OF TRANSPORT PHENOMENA -- LOCAL AND MESOSCALE TRANSPORT -- SYNOPTIC-OR CONTINENTAL-SCALE TRANSPORT -- HEMISPHERIC OR GLOBAL TRANSPORT -- CONCLUSIONS -- ACKNOWLEDGMENTS -- REFERENCES -- Appendix C Atmospheric Deposition Processes -- 1. INTRODUCTION -- 2. DRY-DEPOSITION PROCESSES -- 2.1 Mechanisms of Dry Deposition -- 2.1.1 Introduction -- 2.1.2 Aerodynamic Factors -- 2.1.3 the Quasi-Laminar Layer -- 2.1.4 Phoretic Effects and Stefan Flow -- 2.1.5 Surface Adhesion -- 2.1.6 Surface Biological Effects -- 2.1.7 Deposition to Liquid-Water Surfaces -- 2.1.8 Deposition to Mineral Surfaces -- 2.1.9. Fog and Dewfall -- 2.1.10 Resuspension and Surface Emission -- 2.1.11 The Resistance Analog -- 2.2 Methods for Measuring Dry Deposition -- 2.2.1 Direct Measurement -- 2.2.2 Laboratory Studies -- 2.2.3 Micrometeorological Measurement Methods -- 2.3 Field Investigations of Dry Deposition.

2.3.1 Gaseous Pollutants -- 2.3.2 Particulate Pollutants -- 2.4 Micrometeorological Models of the Dry-Deposition Process -- 2.4.1 Gases -- 2.4.2 Particles -- 2.5 Conclusions to Section 2 -- 2.6 References -- 3. PRECIPITATION SCAVENGING PROCESSES -- 3.1 Steps in the Scavenging Sequence -- 3.1.1 Introduction -- 3.1.2 Intermixing of Pollutant and Condensed Water (Step 1-2) -- 3.1.3 Attachment of Pollutant to Condensed-Water Elements (Step 2-3) -- 3.1.4 Aqueous-Phase Reactions (Step 3-4) -- 3.1.5 Deposition of Pollutant with Precipitation (Steps 3-5 and 4-5) -- 3.1.6 Combined Processes and the Problem of Scavenging Calculations -- 3.2 Storm Systems and Storm Climatology -- 3.2.1 Introduction -- 3.2.2 Frontal-Storm Systems -- Cold-Front Storms -- Occluded-Front Storms -- 3.2.3 Convective-Storm Systems -- 3.2.4 Additional Storm Types: Nonideal Frontal Storms, Orographic Storms, and Lake-Effect Storms -- 3.2.5 Storm and Precipitation Climatology -- Precipitation Climatology -- Storm Tracks -- Storm-Duration Statistics -- 3.3 Summary of Precipitation-Scavenging Field Investigations -- 3.4 Predictive and Interpretive Models of Scavenging -- 3.4.1 Introduction -- 3.4.2 Elements of an Scavenging Model -- 3.4.2.1 Material Balances -- Energy Balances -- Momentum Balances -- 3.4.3 Definitions of Scavenging Parameters -- 3.4.4 Formulation of Scavenging Models: Simple Examples of Microscopic and Macroscopic Approaches -- 3.4.5 Systematic Selection of Scavenging Models: an Flow-Chart Approach -- 3.5 Practical Aspects of Scavenging Models: Uncertainty Levels and Sources of Error -- 3.5 Conclusions to Section 3 -- 3.7 References -- Appendix D Biographical Sketches of Committee Members.