Mass-Independent Sulfur Isotope Fractionation in the Photochemical SO2 Processes under the UV Radiation of Different Wave Length

A series of photochemical experiments with sulfur dioxide were carried out using a xenon lamp (λ > 200 nm), a low-pressure mercury lamp (λ = 184.9 and 253.7 nm), and an UP-213 laser system (λ = 213 nm) as light sources. Based on the isotope data obtained for elemental sulfur (the end product of SO2 photolysis), we revealed specifics in correlations between δ34S, ∆33S, and ∆36S values depending on the spectral characteristics of the incident radiation. Our studies showed that the Archean Δ33S/δ34S and Δ36S/Δ33S ratios could be reproduced in the SO2 photolysis experiments by combining spectral composition of the radiation, the intensity of the spectral components, and the partial pressure of SO2. The results of the experiments suggest that the UV radiation with wavelengths less than 200 nm was a determining factor in the production of sulfur isotopic anomalies in the Archean atmosphere.