Spatial variability of perchlorate in East Antarctic surface snow: Implications for atmospheric production

Abstract

Abstract Surface snow along a 1250-km transect from the coast to the East Antarctic ice sheet summit Dome Argus are used to investigate factors influencing spatial variability of perchlorate (ClO4−) production and deposition, and to explore contributions from tropospheric and stratospheric sources to ClO4− in Antarctic snow. The average ClO4− concentration of 104.3 ± 33.3 ng kg−1 is in the range of previously reported ClO4− concentrations in Antarctic snow, and one to two orders of magnitude higher than those in Arctic snow. The transect profile of ClO4− concentration shows relatively small spatial variability and no single consistent trend, with apparently high concentrations at locations with low accumulation rate. In the coastal region, strong correlation between ClO4− and troposphere-produced nitrate (NO3−) is observed. This may indicate that ClO4− in the coastal region is formed predominantly in the troposphere during summer, and the contribution from the stratosphere may be negligibly small. The lack of apparent correlation between ClO4− and NO3− in snow in interior East Antarctica suggests that a significant amount of ClO4− may be of stratospheric origin, with some tropospheric production. No significant correlation is found between sea-salt chloride (Cl−) and ClO4− in the coastal region, suggesting that tropospheric sea-salt Cl− is probably not an important precursor of ClO4− in snow in this region. In the inland Dome A region, part of Cl− might be converted into ClO4−.