Photochemical oxidation of reduced sulfur compounds in an urban location based on short time monitoring data

This study examines the oxidation of reduced sulfur compounds (RSCs) in urban ambient air. The photochemical conversions of RSC (such as DMS, CS2, H2S, DMDS, and CH3SH) to a further oxidized form (e.g., SO2, MSA, and H2SO4) were assessed using a photochemical box model. For our model simulation of RSC oxidation, measurements were taken at an urban monitoring station in Seoul, Korea (37.6° N, 127° E) during three separate time periods (e.g., Sept. 17–18, Oct. 23, and Oct. 27–28, 2003). The results indicate that DMS and H2S were the dominant RSCs with concentrations of 370 ± 140 and 110 ± 60 pptv, respectively. The photochemical conversion of DMDS to SO2 was found to occur more efficiently than other RSCs. The overall results of our study suggest that photochemical conversion of RSCs accounted for less than 15% of the observed SO2 during the measurement period. The SO2 production from DMS oxidation (mainly by the reaction with OH) was found to be affected primarily by the abstraction channel due to high NOx levels during the experimental conditions.