Spatial distribution and seasonal pattern of biogenic sulphur compounds in snow from Northern Victoria Land (Antarctica).

A study of the spatial and temporal distribution of methane sulphonic acid (MSA) and nssSO42- concentrations in snow-pit samples was performed to determine the main and secondary sources, transport effects and seasonal pattern of biogenic sulphur compounds. Four snowpits, about 3 m deep, excavated at the same time at different altitudes (870-2960 m a.s.l.) in Northern Victoria Land, Antarctica, gave coherent information about the effect of altitude and seasonality on the snow chemical composition. A progressive, well-defined decreasing concentration trend is shown as altitude increases, with the biggest effect in the first 1000 m a.s.l. At higher altitudes, biogenic sources make the most important contribution to the total sulphate balance with respect to sea-spray input- Particular attention was paid to the relationship between MSA and nssSO42- by using MSA as a univocal biogenic marker. The nssSO42-/MSA ratio was evaluated with respect to altitude and seasonality to determine the effect of transport mechanisms (such as long-range transport and fractionation) or non-dimethyl sulphide sources on nssSO42- snow content