MEASUREMENTS OF DIMETHYL SULFIDE, DIMETHYL-SULFOXIDE, DIMETHYL SULFONE, AND AEROSOL IONS AT PALMER STATION, ANTARCTICA

In January and February 1994, measurements of dimethylsulfide (DMS) in air and seawater were conducted at Palmer Station, Antarctica, during project SCATE (Sulfur Chemistry in the Antarctic Troposphere Experime nt). Corresponding values ranged between 6 and 595 pptv (median: 94 pp tv) and 0.7 and 3.7 nM (median: 2 nM), respectively. Atmospheric DMS l evels were significantly enhanced during a storm episode in connection with large-scale low-pressure systems passing through the study area. DMS sea-to-air fluxes ranged between 0.03 and 19 (median: 1.1) mu mol m(-2) d(-1) based on seawater DMS and wind speed measurements. The at mospheric DMS lifetime is estimated to be 9 days based on a 24-hour av eraged OH concentration of 1.1 x 10(5) cm(-3). Atmospheric dimethylsul foxide (DMSO) and dimethylsulfone (DMSO2) mixing ratios varied mostly between <0.2 and 15 pptv. These variations consisted of many short-ter m spikes which may be explained by downward mixing of these compounds from the free troposphere [Davis et al., this issue]. The DMSO photoch emical lifetime with respect to the 24-hour average OH concentration i s approximately 25 hours in the coastal Antarctic troposphere in summe r. However, present calculations show that the dominant sink of both D MSO and DMSO2 could be surface loss, yielding atmospheric lifetimes of a few hours for both compounds [see also Davis et al., this issue]. A good correlation was found between DMSO and DMSO2. Aerosol MSA and ex cess sulfate concentrations also showed a good correlation, with a slo pe of 0.73. However, DMS was not correlated with any of its measured o xidation products, probably because of its long atmospheric residence time over Antarctica.