The impact of snow nitrate photolysis on boundary layer chemistry and the recycling and redistribution of reactive nitrogen across Antarctica and Greenland in a global chemical transport model

The formation and recycling of reactive nitrogen (NO, NO 2 , HONO) at the air–snow interface has implications for air quality and the oxidation capacity of the atmosphere in snow-covered regions. Nitrate (NO 3 − ) photolysis in snow provides a source of oxidants (e.g., hydroxyl radical) and oxidant...

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Bibliographic Details
Published in:Atmospheric Chemistry and Physics
Main Authors: M. Zatko, L. Geng, B. Alexander, E. Sofen, K. Klein
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus Publications 2016
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Online Access:https://doi.org/10.5194/acp-16-2819-2016
https://doaj.org/article/f39509afcb48466f9522efd063516054
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Summary:The formation and recycling of reactive nitrogen (NO, NO 2 , HONO) at the air–snow interface has implications for air quality and the oxidation capacity of the atmosphere in snow-covered regions. Nitrate (NO 3 − ) photolysis in snow provides a source of oxidants (e.g., hydroxyl radical) and oxidant precursors (e.g., nitrogen oxides) to the overlying boundary layer, and alters the concentration and isotopic (e.g., δ 15 N) signature of NO 3 − preserved in ice cores. We have incorporated an idealized snowpack with a NO 3 − photolysis parameterization into a global chemical transport model (Goddard Earth Observing System (GEOS) Chemistry model, GEOS-Chem) to examine the implications of snow NO 3 − photolysis for boundary layer chemistry, the recycling and redistribution of reactive nitrogen, and the preservation of ice-core NO 3 − in ice cores across Antarctica and Greenland, where observations of these parameters over large spatial scales are difficult to obtain. A major goal of this study is to examine the influence of meteorological parameters and chemical, optical, and physical snow properties on the magnitudes and spatial patterns of snow-sourced NO x fluxes and the recycling and redistribution of reactive nitrogen across Antarctica and Greenland. Snow-sourced NO x fluxes are most influenced by temperature-dependent quantum yields of NO 3 − photolysis, photolabile NO 3 − concentrations in snow, and concentrations of light-absorbing impurities (LAIs) in snow. Despite very different assumptions about snowpack properties, the range of model-calculated snow-sourced NO x fluxes are similar in Greenland (0.5–11 × 10 8 molec cm −2 s −1 ) and Antarctica (0.01–6.4 × 10 8 molec cm −2 s −1 ) due to the opposing effects of higher concentrations of both photolabile NO 3 − and LAIs in Greenland compared to Antarctica. Despite the similarity in snow-sourced NO x fluxes, these fluxes lead to smaller factor increases in mean austral summer boundary layer mixing ratios of total nitrate (HNO 3 + NO 3 − ), NO x , OH, and O 3 in ...