ABSTRACT
Acid deposition, popularly known as acid rain, has long been suspected of damaging lakes, streams, forests, and soils, decreasing visibility, corroding monuments and tombstones, and potentially threatening human health in North America and Europe. The National Academy of Sciences and other leading scientific bodies first gave credence to these concerns in the early 1980s when they suggested that emissions of sulfur dioxide from electric power plants were being carried hundreds of miles by prevailing winds, being converted in the atmosphere into sulfuric acid, falling into pristine lakes, and killing off aquatic life. The process of acid deposition also begins with emissions of nitrogen oxides (primarily from motor vehicles and coal-burning power plants). These pollutants interact with sunlight and water vapor in the upper atmosphere to form acidic compounds. During a storm, these compounds fall to earth as acid rain or snow; the compounds also may join dust or other dry airborne particles and fall as "dry deposition" [1]. Regulations have been passed concerning the amount of SO2 and NO x , (oxides of nitrogen) emitted in the air. These regulations have caused the power industries to find ways to cut their emissions. The three ways of lowering emissions—before combustion, during combustion, and after combustion—will be discussed.
