Pollutant scavenging from plumes: A modeling case study from the ASARCO smelter

Abstract Rainfall pollutant-concentration data collected around the ASARCO copper smelter plume in Tacoma, Washington, were examined with a Gaussian plume scavenging model employing multicomponent reaction kinetics. The plume model includes below-cloud scavenging and chemical reactions. From the model results, several important pathways for pollutant transfer and reaction in this plume environment were identified. The relative importance of the various mechanisms depends on factors such as distance from the source, height, and raindrop size. At distances where the SO 2 concentration in the air is the greatest, rapid oxidation by hydrogen peroxide was predicted to occur, followed by significant depletion of the aqueous H 2 O 2 . For raindrops in which the aqueous H 2 O 2 was depleted, oxidation by ozone was predicted to be an important SO 2 oxidation mechanism. The trace metal catalyzed oxidation of SO 2 was also determined to have possible significance in this environment.