Chemical fate and transport is a concept now familiar to you: how chemicals move in the environment and change into other chemicals. You have seen pollutants that travel hundreds or thousands of miles and those that end up in unexpected places. Now, follow the story of acid deposition (acid rain). The precursors of acid rain are gases, sulfur dioxide and nitrogen oxides. But these gases are converted into aerosols, and it is these that actually deposit onto, and acidify, soil and water. And that is not the end of their journey.

In this chapter, Section I identifies the major acid precursors that lead to acid deposition, and overviews a major study carried out in the United States, and still ongoing to better understand acid deposition. Section II examines the adverse effects of acid deposition on aquatic life, and on forests and their soils. Section III looks at the emission sources of acid-forming pollutants, and reducing those emissions. It points out that emissions, although lowered are not eliminated; thus, consequences linger. Section IV examines the partial recovery of systems as emissions are reduced. Section V moves on to acid deposition in the international scene.