Photolysis of SO2 in the Modern Atmosphere

FIGURE 5.7 Model delta-values and S-MIF signatures for atmospheric column densities of SO2 and SO relative to initial SO2. Isotope fractionation occurs during SO2 dissociation from 190 to 220 nm using a present-day solar flux. The model assumes pCOi = 0.02 and initial pSO = 

10 ppb. The arrows show the direction of the time evolution of the delta values and S-MIF signature. As a greater fraction of SO2 is photolyzed the magnitude of the delta values of residual SO2 (labeled as SO2) increase and those of SO decrease. The locations at which initial SO2 has been reduced by 10% is indicated by vertical bars, (a) Model and values for SO and residual SO2, and the mass-dependent curves (MD). (b) Model and S values for SO and residual SO2. The line labeled ice core has a slope of —3.3 and was determined from measurement of Antarctic ice core sulfates derived from the Agung eruption [17]. The Archean line has a slope of —0.9 and was determined from measurement of Archean and Paleoproterozoic sulfides and sulfates [4]. 

FIGURE 5.8 of the column density of photolysis product SO that corresponds to a 10% 

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