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 nssSO(4)(2-) concentrations in snow-pit samples was performed to determine the main and secondary sources, transport effects and seasonal pattern of biogenic sulphur compounds. Four snow pits, 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 nssSO(4)(2-) by using MSA as a univocal biogenic marker. The nssSO(4)(2-)/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 nssSO(4)(2-) snow content.