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

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⁻.