An evaluation of possible mechanisms for conversion of sulfur dioxide to sulfuric acid and sulfate aerosols in the troposphere

Abstract

The mechanisms and rates of conversion of sulfur dioxide to sulfur trioxide, sulfuric acid, and other "sulfate" aerosol precursors are considered in view of current knowledge related to atmospheric reactions and chemical kinetics. Several heterogeneous pathways exist for SO₂ oxidation promoted on solid catalyst particles and in aqueous aerosol solutions in ambient air. The rates of these processes are of questionable significance in SO₂-containing gases which are well removed from pollutant sources and highly diluted through turbulent diffusion and transport mechanisms. Computer simulations of the rates of SO₂ removal reactions show that several homogeneous pathways for SO₂ conversion to acid precursor are expected to be important in atmospheres containing even low levels of NO, NO₂, and oxidizable organic matter. Mechanistic considerations allow some reasonable speculation about the nature of the initial products of the SO₂ reactions which lead ultimately to acids and various sulfate salts.

Parent Publication

• Proceedings of the first international symposium on acid precipitation and the forest ecosystem

Citation

Calvert, Jack G. 1976. An evaluation of possible mechanisms for conversion of sulfur dioxide to sulfuric acid and sulfate aerosols in the troposphere. In: Dochinger, L. S.; Seliga, T. A., eds. Proceedings of the first international symposium on acid precipitation and the forest ecosystem; Gen. Tech. Rep. NE-23. Upper Darby, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. p.55