Preliminary evidence of a biomass-burning event from a 60 year-old firn core from Antarctica by ion chromatographic determination of carboxylic acids

Abstract

An ion chromatographic method for the determination of fluoride and some organic anions (lactate, acetate, glycolate, propionate, formate, methane sulphonate and pyruvate) at sub-μg l-1 concentration levels is applied to a 22 m (63 years) firn core drilled at Hercules Neve, northern Victoria Land, Antarctica. The first effective distribution data of acetate, propionate and formate for this region are reported here. Mean values of 9.9, 7.7 and 2.4 μg l-1 were calculated for acetate, formate and propionate, respectively, in the absence of particular events (background values). The temporal (1928-82) concentration/depth profiles of these components showed a probable long-term biomass-burning event in the 1930s that can be related back to processes in the Southern Hemisphere. Such burning events may be demonstrated from the simultaneous concentration increase of carboxylic acid, potassium, ammonium and fluoride and from a very high dust content. Similar increasing trends in the same time period are not shown by other snow components usually considered as source indicators (methane sulphonic acid: biogenic marker; nssSO42-: biogenic and volcanic indicator; Na+ and Cl-: sea-spray contribution; Ca2+: crustal input), so it was possible to exclude such alternative explanations.