Global analysis of carbon disulfide (CS₂) using the 3-D chemistry transport model STOCHEM

Abstract

Carbon disulfide (CS2), 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 CS2 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 CS2. The global burden of CS2 was calculated, varying between 6.1 to 19.2 Tg and the lifetime of CS2 was determined to be within the range of 2.8–3.4 days. The global distribution of CS2 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 CS2 levels of less than 2 ppt. The vertical profile of CS2 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 CS2 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 CS2 compared with measured CS2 for most of the regions. It is likely that the emissions of CS2 are being underestimated and there are likely much larger emission sources of atmospheric CS2 than previously suggested.

Keywords

• Carbon disulfide
• chemistry transport model
• global budget
• surface distribution
• zonal distribution