Sulfur-containing species (sulfate and methanesulfonate) in coastal Antarctic aerosol and precipitation

The concentrations of sulfur-containing species (sulfate and methanesulfonate (MSA)) of aerosols collected at three coastal Antarctic sites (Neumayer, Dumont d'Urville, and Halley) have been studied in order to investigate the natural sulfur cycle at high southern latitudes. The multiple-year data sets indicate annual mean concentrations of MSA and non-sea-salt (nss) sulfate of 38 and 151 ng m(-3) at Neumayer (1983-1995) and 20 and 147 ng m(-3) at Dumont d'Urville (1991-1995). On the basis of the study of a more limited time period (1991 and 1992), the Halley data set indicates significantly lower MSA and nss sulfate concentrations, 15 and 50 ng m(-3), respectiveley. The concentrations of both species exhibit a consistent and strong seasonal cycle with maxima from December to March and minima from May to September (from 2 to 4 and from 17 to 50 ng m(-3), for MSA and nss sulfate, respectively). These data, together with radionuclide studies (Pb-210 and Be-10), indicate that the marine biogenic source dominates the sulfur budget of the boundary layer of these regions throughout the year. The contribution of other sources, such as the long-range transported sulfur from continents and to a lesser extent the stratospheric sulfate reservoir, remains weak when averaged over the year. Differences in the seasonal pattern of the two sulfur-containing species, as well as intersite differences in the summer concentrations, are compared to several factors, mainly the spatial and temporal variations of the chlorophyll content of the surface ocean water and the seasonality of the sea ice cover. This permits investigation of the respective influence of marine regions emitting dimethylsulfide located either near the Antarctic continent (south of 60 degrees S) or at more temperate latitudes. A strong correlation is found between the chlorophyll content of the Antarctic ocean and the level of total nss sulfur. Furthermore, nss sulfate and MSA deposition fluxes determined from firn and ice cores extracted at sites located at various distances from the ocean and various altitudes allow assessment of the spatial variation of the marine biogenic sulfur input in Antarctica.