Global analysis of carbon disulfide (CS 2 ) using the 3-D chemistry transport model STOCHEM

Carbon disulfide (CS 2 ), a precursor to the long-lived carbonyl sulphide (OCS) is one of the main contributors to the atmospheric sulfate layer. The annual fluxes from its sources and sinks are investigated using a 3-D chemistry transport model, STOCHEM-CRI. In terms of the flux analysis, the oxidation of CS 2 by OH is found to be the main removal process (76–88% of the total loss) and the dry deposition loss contributes 11–24% to the total loss of CS 2 . The global burden of CS 2 was calculated, varying between 6.1 to 19.2 Tg and the lifetime of CS 2 was determined to be within the range of 2.8–3.4 days. The global distribution of CS 2 found the Northern Hemisphere (NH) continental landmasses to be the areas of concentration maxima with peak concentrations reaching up to 20 ppt during June-July-August (J-J-A) season and 40 ppt during December-January-February (D-J-F) season in anthropogenic source regions. Oceanic regions returned low CS 2 levels of less than 2 ppt. The vertical profile of CS 2 shows higher levels up to 3 ppt at 30°N–45°N during J-J-A and up to 4 ppt at 30°N–55°N during D-J-F. The oxidation of CS 2 by OH can produce a substantial amount (0.58 Tg/yr) of atmospheric OCS and the annual average surface distribution of this flux shows up to 6 Gg/yr OCS formed in the regions with highest anthropogenic pollution (e.g., South east Asia). In general, the model-measurement comparison reveals an underprediction of model CS 2 compared with measured CS 2 for most of the regions. It is likely that the emissions of CS 2 are being underestimated and there are likely much larger emission sources of atmospheric CS 2 than previously suggested.