Sea-spray and marine biogenic seasonal contribution to snow composition at Terra Nova Bay, Antarctica

Abstract

Primary and secondary marine aerosol contributions to snow composition in Terra Nova Bay, Antarctica, were evaluated by chemical analysis of surface and snow-pit samples. A seasonal pattern of marine inputs, very clear for secondary aerosol (mainly constituted by nssSO42- and methanesulphonic acid (MSA) coming from phytoplanktonic activity) and less evident for sea spray (Na+, Cl-, Mg2+), was shown by snowpit samples. Altitude and distance from the coast were found to be the main parameters affecting seasonal change in the composition of snow collected within about a 200 km radius of the Terra Nova Bay Italian base. Using Na+ as a sea-spray indicator and MSA as a biogenic marker, fractionating aerosol effects (which are altitude-induced) as well as source contributions for Cl- and nssSO42- were found. A nssSO42-/MSA ratio of 2.7 (w/w), indicating their distribution from the common source dimethylsulphide, was calculated from analysis of fresh summer snow collected in horizontal and vertical transects in northern Victoria Land.