First measurements and modeling of Delta O-17 in atmospheric nitrate

Abstract

[1] Atmospheric nitrate is anomalously enriched in both the O-18/O-16 and O-17/O-16 isotopic ratios, with Delta(17)O = 20 - 30.8parts per thousand (Delta(17)O = delta(17)O - .52 x delta(18)O). We have modeled the seasonal variation in Delta(17)O by utilizing the transfer of Delta(17)O from ozone to HNO3 during NOx oxidation reactions and by evaluating the relative source strengths of heterogeneous and homogenous HNO3 production. The implications for new insights into the global nitrogen cycle, N2O production and paleoclimate studies are discussed.