@article{1026,
  author = {M.G. Hastings and E.J. Steig and D.M. Sigman},
  title = {Seasonal variations in N and O isotopes of nitrate in snow at Summit, Greenland: Implications for the study of nitrate in snow and ice cores},
  abstract = {<p>Nitrogen and oxygen isotopes of NO3- have been measured in snow and firn from Summit, Greenland. The 15N/ 14N and 18O/16O ratios of NO 3- in recently fallen snow are similar to those of surface snow. Diurnal variation is observed in 15N/ 14N of NO3-, and possibly 18O/16O, suggesting fractionating loss of NO3- from snow during the day, which is subsequently recovered at night. A larger seasonal variation is observed, with higher 15N/14N and lower 18O/16O of NO3- in summer than winter, which cannot be explained by postdepositional fractionation. The generally high 18O/16O of NO 3- in Greenland snow (δ18O versus VSMOW = 65.2 to 79.6{\textperthousand}) indicates that oxygen atoms from ozone have been incorporated into NOx that was subsequently deposited as HNO3. The lower mean δ180 of NO3- in summer snow relative to winter (68.9{\textperthousand} in summer 2000 and 70.5{\textperthousand} in summer 2001 versus 77.5{\textperthousand} in winter 2000-01) is a result of summertime HNO 3 production via NO2 reaction with hydroxyl radical (OH), which dilutes the high δ18O imparted on NO2 from ozone. The higher mean 15N/14N of NO3- observed in snow from spring (δ 15N versus air N2 = +5.9{\textperthousand} in 2000 and -1.4{\textperthousand} in 2001) and summer (+0.1{\textperthousand} in 2000 and -0.8{\textperthousand} in 2001) than fall (-9.2{\textperthousand} in 2000) and winter (-10.0{\textperthousand} in 2000-01) is more difficult to explain with seasonal photochemistry, given current knowledge. The seasonal 15N/14N change may reflect NOx sources, with a greater fall and wintertime contribution from fossil fuel emissions relative to other inputs of NOx (i.e., biogenic soil emissions, biomass burning, and lightning). Copyright 2004 by the American Geophysical Union.</p>},
  year = {2004},
  journal = {Journal of Geophysical Research D: Atmospheres},
  volume = {109},
  number = {20},
  pages = {1-11},
  url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-11844277592\&doi=10.1029\%2f2004JD004991\&partnerID=40\&md5=ced7a4fe4f9e44d9c66d95d7b9704567},
  doi = {10.1029/2004JD004991},
  note = {ps_limited_html},
}