Oxidation of CS2 and COS - sources for atmospheric SO2

The oxidation of COS and CS2 by reaction with hydroxyl radicals is investigated as a possible source of atmospheric SO2 in remote marine regions. Calculations of the vertical profiles of SO2 were performed based on a one-dimensional photochemical model of the formation and destruction of SO2 by various processes for observed O3, CO, CH4 and H2O profiles at 15 deg S. Variations in the rate of SO2 destruction, the chosen deposition velocity and the loss due to aerosols are shown to lead to similar SO2 profiles, which indicate higher mixing ratios at high altitude, while the oxidation of dimethyl sulfide or hydrogen sulfide can not account for the profiles observed. Possible diffuse sources of CS2 and COS are indicated, and it is concluded that the oxidation of COS and possibly CS2 may provide an explanation for the existence of a uniform background level of SO2.