Title：Distinguishing Summertime Atmospheric Production of Nitrate Across the East Antarctic Ice Sheet
Journal/Publisher：ELSEVIER
Year：2018
Authors：G. Shi, A.M. Buffen, H. Ma, Z. Hu, B. Sun, C. Li, J. Yu, T. Ma, C. An, S. Jiang, Y. Li, M.G. Hastings
Abstract
Surface snow and atmospheric samples collected along a traverse from the coast to the ice sheet summit (Dome A) are used to investigate summertime atmospheric production of nitrate (NO3 – ) across East Antarctica. The strong relationship observed between d15N and d18O of nitrate in the surface snow suggests a large (lesser) extent of nitrate photolysis in the interior (coastal) region. A linear correlation between the oxygen isotopes of nitrate (d18O and D17O) indicates mixing of various oxidants that react with NOx (NOx=NO+NO2) to produce atmospheric nitrate. On the plateau, the isotopes of snow nitrate are best explained by local reoxidation chemistry of NOx, possibly occurring in both condensed and gas phases. Nitrate photolysis results in redistribution of snow nitrate, and the plateau snow is a net exporter of nitrate and its precursors. Our results suggest that while snow-sourced NOx from the plateau due to photolysis is a significant input to the nitrate budget in coastal snow (up to 35%), tropospheric transport from mid-low latitudes dominates (65%) coastal snow nitrate. The linear relationship of d18O vs. D17O of the snow nitrate suggests a predominant role of hydroxyl radical (OH) and ozone (O3) in nitrate production, although a high D17O(O3) is required to explain the observations. Across Antarctica the oxygen isotope composition of OH appears to be dominated by exchange with water vapor, despite the very dry environment. One of the largest uncertainties in quantifying nitrate production pathways is the limited knowledge of atmospheric oxidant isotopic compositions.
Keywords: nitrate, isotopes, snow, atmosphere, east Antarctica
Distinguishing summertime atmospheric production of nitrate across the East Antarctic Ice Sheet.pdf