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GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L13817, doi:10.1029/2004GL022121, 2005

Isotopic composition of Antarctic Dry Valley nitrate: Implications for NO_y sources and cycling in Antarctica

G. Michalski

Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, Indiana, USA
Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California, USA

J. G. Bockheim

Department of Soil Science, University of Wisconsin-Madison, Madison, Wisconsin, USA

C. Kendall

United States Geological Survey, Menlo Park, California, USA

M. Thiemens

Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California, USA

Abstract

Nitrates minerals from the Dry Valleys of Antarctica have been analyzed for their oxygen and nitrogen isotopic compositions. The ¹⁵N was depleted with δ¹⁵N values ranging from −9.5 to −26.2‰, whereas the ¹⁷O and ¹⁸O isotopes were highly enriched (with excess ¹⁷O) with δ¹⁸O values spanning 62–76‰ and Δ¹⁷O values from 28.9 to 32.7‰. These are the largest ¹⁷O enrichments observed in any known mineral. The oxygen isotopes indicate that nitrate is from a combination of tropospheric transport of photochemically produced HNO₃ and HNO₃ formed in the stratosphere.

Received 30 November 2004; accepted 19 May 2005; published 9 July 2005.

Index Terms: 0426 Biogeosciences: Biosphere/atmosphere interactions (0315); 0444 Biogeosciences: Evolutionary geobiology; 0469 Biogeosciences: Nitrogen cycling; 0486 Biogeosciences: Soils/pedology (1865); 0793 Cryosphere: Biogeochemistry (0412, 0414, 1615, 4805, 4912).

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Citation: Michalski, G., J. G. Bockheim, C. Kendall, and M. Thiemens (2005), Isotopic composition of Antarctic Dry Valley nitrate: Implications for NO_y sources and cycling in Antarctica, Geophys. Res. Lett., 32, L13817, doi:10.1029/2004GL022121.

Copyright 2005 by the American Geophysical Union.