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AGU: Geophysical Research Letters

 

Keywords

  • nitrate isotopes
  • photochemistry
  • Greenland

Index Terms

  • Biogeosciences: Nitrogen cycling
  • Atmospheric Composition and Structure: Troposphere: composition and chemistry
  • Biogeosciences: Isotopic composition and chemistry
  • Cryosphere: Biogeochemistry

Abstract

Influence of local photochemistry on isotopes of nitrate in Greenland snow

Julia C. Jarvis

Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA

Eric J. Steig

Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA

Meredith G. Hastings

Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, Seattle, Washington, USA

Shelley A. Kunasek

Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA

To explore the seasonality in δ 15N and δ 18O of nitrate in Greenland snow, we describe a simple box model of local photochemistry. Isotope ratios of HNO3 are controlled by the nitrogen isotope fractionation between NO and NO2, the ratio of NO2 to NO, and seasonal variations in HNO3 production. The observed seasonal range in δ 15N requires either a large net fractionation (∼70‰) associated with NOx cycling or a seasonal change in the δ 15N of NOx sources. The observed range in δ 18O of nitrate is smaller than that calculated from HNO3 production pathways, suggesting that seasonal transport may also be required to explain the seasonality in nitrate δ 18O.

Received 31 July 2008; accepted 8 October 2008; published 7 November 2008.

Citation: Jarvis, J. C., E. J. Steig, M. G. Hastings, and S. A. Kunasek (2008), Influence of local photochemistry on isotopes of nitrate in Greenland snow, Geophys. Res. Lett., 35, L21804, doi:10.1029/2008GL035551.

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