Transformations of Sulfur in the Atmosphere

The most important pathway of sulfur through the atmosphere involves injection as a low oxidation state gas and the removal as oxidation state VI sulfate in rainwater (see Fig. 13-2, paths 1,4,5,6, 7, 8,9,10, 12, and 13). Since this pathway involves a change in chemical oxidation state and physical phase, the lifetime of sulfur in the atmosphere is governed by both the kinetics of the oxidation reactions and the frequency of clouds and rain. We will argue below that the overall process is fast - on the order of days -meaning that the atmospheric sulfur cycle is a regional phenomenon and that the distribution of nearly all sulfur species in the atmosphere is necessarily patchy over the globe. 

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Fig. 13-2 The chemical and physical transformations of sulfur in the atmospheric cycle. Circles are chemical species, the box represents cloud-liquid phase. DMS = CH3SCH3, DMDS = CH3SSCH3, Siv = (S02)aq + HSOi" + SO3 + CH20HS03, and MSA (methane sulfonic acid) = CH3SO3H. The chemical transformations are as... 

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