Analysis of nitrate in the snow and atmosphere at Summit, Greenland: Chemistry and transport

Abstract : As a major sink of atmospheric nitrogen oxides (NOx = NO + NO2), nitrate (NO3-) in polar snow can reflect the long-range transport of NOx and related species (e.g., PAN). On the other hand, because NO3- in snow can be photolyzed, potentially producing gas-phase NOx locally, NO3- in snow (and thus, ice) may reflect local processes. Here we investigate the relationship between local atmospheric composition at Summit, Greenland (72°35’N, 38°25’W) and the isotopic composition of NO3- to determine the degree to which local processes influence atmospheric and snow NO3-. Based on snow and atmospheric observations during May-June 2010 and 2011, we find no connection between the local atmospheric concentrations of a suite of gases (BrO, NO, NOy, HNO3 and nitrite (NO2-)) and the NO3- isotopic composition or concentration in snow. This suggests that 1) the snow NO3- at Summit is primarily derived from long-range transport and 2) this NO3- is largely preserved in the snow. Additionally, three isotopically distinct NO3- sources were found to be contributing to the NO3- in the snow at Summit during both 2010 and 2011. Through the complete isotopic composition of NO3-, we suggest that these sources are local anthropogenic particulate NO3- from station activities (δ15N = 16‰, Δ17O = 4‰ and δ18O = 23‰), NO3- formed from mid-latitude NOx15N = -10‰, Δ17O = 29‰, δ18O = 78‰) and a NO3- source that is possibly influenced or derived from stratospheric ozone NO3-15N = 5‰, Δ17O = 39‰, δ18O = 100‰).
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Submitted on : Tuesday, April 19, 2016 - 4:55:09 PM
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Dorothy L. Fibiger, Jack E. Dibb, Dexian Chen, Jennie L. Thomas, John F. Burkhart, et al.. Analysis of nitrate in the snow and atmosphere at Summit, Greenland: Chemistry and transport. Journal of Geophysical Research: Atmospheres, American Geophysical Union, 2016, 121 (9), pp.5010-5030. ⟨10.1002/2015JD024187⟩. ⟨insu-01304385⟩



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