Nitrates minerals from the Dry Valleys of Antarctica have been analyzed for their oxygen and nitrogen isotopic compositions. The 15N was depleted with ??15N values ranging from -9.5 to -26.2???, whereas the 17O and 18O isotopes were highly enriched (with excess 17O) with ?? 18O values spanning 62-76??? and ?? 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.
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Isotopic composition of Antarctic Dry Valley nitrate: Implications for NOy sources and cycling in Antarctica