Biogenic sulfur compounds in seawater and the atmosphere of the Antarctic region

ABSTRACT Shipboard measurements of dimethyl sulfide (DMS), carbonyl sulfide (COS) and carbon disulfide (CS2) in seawater and the marine boundary layer were performed during a cruise between Punta Arenas (Chile) and Cape Town (South Africa) through the Weddell Sea in November/December 1990. The DMS concentrations in seawater averaged to 71 ngS/l, atmospheric DMS mixing ratios showed a range between 2 and 1048 pptv. In the Weddell Sea where DMS mixing ratios as low as 24 pptv on the average were observed, the extensive ice cover seemed to minimize the gas exchange between seawater and the overlying atmosphere. The COS levels in seawater showed a mean of 3.5 ngS/l with minor variability. Atmospheric COS mixing ratios measured over the Weddell Sea averaged to 453 ± 43 pptv. In contrast, COS concentrations during advection processes of continental air masses over the Drake Passage were evidently higher with a mean of 628 ± 42 pptv. The concentrations of CS2 in the remote marine boundary layer were below the detection limit of 7 pptv, with enhanced concentrations of about 35 pptv observed in air masses influenced by continental inputs. CS2 values in surface seawater were mostly below the detection limit of 0.43 ngS/l with few exceptions revealing CS2 values between 0.48 and 1.43 ngS/l. In 91% of all seawater samples taken during this cruise CS2 were not found in detectable concentrations.