Spatial variability and possible sources of acetate and formate in the surface snow of East Antarctica

Abstract

Spatial trends of acetate (Ac^-) and formate (Fo^-) were determined in surface snow samples along a coastal-inland transect (180 km) in the ice cap region at Princess Elizabeth Land and along a coastal transect in the Amery Ice Shelf (130 km), East Antarctica. Variations in both Ac^- and Fo^- seem to be unrelated to the acidity of snow. Ionic balance determined for the snow samples indicate the availability of HNO3 that could undergo photolysis to produce hydroxyl radical (radical dotOH), one of the major reactants involved in oxidation reactions with organic matter. The strong positive correlations between Ac^- and NO₃^- in snow from both regions indicate that NO₃^- mediated radical dotOH-oxidation of organic compounds in snow could be an important source of Ac^- within the snowpack. On the other hand, negative correlation between Fo^- and NO₃^- might indicate that sources other than radical dotOH-oxidation of organic matter may be dominant in the case of Fo^-. Higher Ac^- concentrations in the ice cap compared to the ice shelf correspond with long-range transport of biomass burning emissions to the ice cap region. Interaction of Ac^- and Fo^- with alkaline minerals could lead to their stability in the snowpack and minimize their loss from the snow surface. Resident microbial communities could also influence the budget of the carboxylic acids in snow.