Atmospheric Oxidation of SO2 in Coal-Burning Power Plant Plumes

Sampling equipment and procedures applicable for use in a helicopter were devised for collecting the separate SO2 and SO3 components in progressive plume cross sections at a large coal-burning power plant. Samples were collected during a variety of meteorological conditions with particular attention to a wide range of relative humidity. During periods of low humidity, data reveal that oxidation of SO2 is relatively slow, increasing from 2% at one mile (12 minutes) to 3% at 6 miles (60 minutes). With moderately high humidity, oxidation was initially rapid, 22% at one mile (12 minutes), increasing to 32% at 8 miles (96 minutes). The highest total oxidation, 55%, was observed in a slight mist at 9 miles (108 minutes).