The homogeneous chemistry of atmospheric sulfur

Sulfur is present in the atmosphere as a constituent of more than 15 compounds and in valence states ranging from −2 to +6. Nearly all of the compounds have both natural and anthropogenic sources. This paper reviews the present information on the reactions of these compounds and their products with typical atmospheric species. It is shown that atmospheric sulfur chemistry proceeds monotonically in the direction of increasing sulfur oxidation and that the gas phase transformation of reduced sulfur compounds to sulfate aerosol in all ambient atmospheres can be described by a common chain consisting of five chemical steps followed by a heterogeneous loss process.