Chemical profiles from snow pits and shallow firn cores and snow accumulation on Campbell Glacier (Northern Victoria Land, Antarctica)

Abstract

The chemical composition of snow and firn samples from the Campbell Glacier (Northern Victoria Land) was studied to evaluate the accumulation rate of snow and to investigate the chemical contribution from some different emission sources (marine biogenic activity, sea and crustal). Snow and firn were collected from snow pits and by coring at three sites (74°41’ S-164°30° E; 74° 15° $-164°04’ E and 73 45’ $-163° 20 E), located respectively at 50 m (on the floating glacier tonguc), 800 m and 1560 m a.s.l., during the 1994-95 Italian Antarctic Expedition. Analyses of Na⁺, K⁺, Mg⁺⁺, Ca⁺⁺, CH₃SO₃^- (Msa), CI^-, NO₃^-, SO₄^- were performed by ion chromatography (Dionex 2020i). The separations were obtained with ion-exchange columns Dionex AS5 (NaOH 5 10^-4 N and NaOH 3 10^-2 N eluents) and Dionex CS12 (methane sulfonic acid 20 mM eluent) for anions and cations respectively. H₂0₂, was analyzed by an electrochemical detector (Antec mod. «Decade). Samples from the Campbell Glacier Tongue are characterized by a high level of sea salt and in the upper part of the firn layer a high concentration of nss SO^4- is present. The concentration of sea salt decreases with increasing distance from the coast and with altitude. The differences in the chemical composition of firn at the sites at 800 m and 1560 m altitude could be explained by coupling fractionation of chemical species and air masses of different origin. Msa, H₂0₂, nss SO₄^-, NO₃^-, and nss Ca⁺⁺ profiles show fairly good seasonal cycles. 10-11 and 14-17 years have been identified at the sites of 800 m and 1560 m altitude respectively, The accumulation rate ranges between 150-170 kg m^-2 y^-1 and 150-180 kg m^-2 y^-1 at the first and the second of these two sites.