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Science 5 June 2009:
Vol. 324. no. 5932, p. 1288
DOI: 10.1126/science.1170510
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Brevia

Anthropogenic Impacts on Nitrogen Isotopes of Ice-Core Nitrate

M. G. Hastings,1,* J. C. Jarvis,2 E. J. Steig2

A strong, unambiguous negative trend is found in the nitrogen isotopic composition ({delta}15N) of nitrate over the industrial period, on the basis of a 100-meter ice core from Summit, Greenland. This record indicates that ice-core nitrate reflects changes in nitrogen oxide (NOx) source emissions and that anthropogenic emissions of NOx have resulted in a 12 per mil decline in {delta}15N of atmospheric nitrate from preindustrial values to present. Variations in the isotopic composition of nitrate may affect the interpretation of other records of environmental change that are affected by atmospheric nitrate.

1 Department of Geological Sciences and Environmental Change Initiative, Brown University, Providence, RI 02912, USA.
2 Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA.

* To whom correspondence should be addressed. E-mail: meredith_hastings{at}brown.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)