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

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 δ 18O values spanning 62-76‰ and Δ 17O 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. Copyrigbt 2005 by the American Geophysical Union.