Absence of isotope exchange in the reaction of N2O+O(1D) and the global Δ17O budget of nitrous oxide -: art. no. L15808

Yung et al. ( 2004) suggested that N2O exchanges isotopes with O(D-1), analogous to CO2, which would represent an additional contribution to the O-17 isotope anomaly of atmospheric N2O. Here we demonstrate by isotope measurements of N2O remaining after partial conversion with O(D-1) that this isotope exchange most likely proceeds at <1% of the total N2O + O(D-1) reaction rate. It can therefore be neglected as a source of the O-17 anomaly of atmospheric N2O, corroborating arguments based on previous indirect experimental evidence of the absence of such isotope exchange (Rockmann and Kaiser, 2005). In addition, we present a balanced budget of the O-17 anomaly of atmospheric N2O, based on N2O sources at Earth's surface and in the atmosphere: the reactions of N-2 + O(D-1) + M, NH2 + NO2, and N + NO2, industrial processes, biomass burning, and the numerical'' source from microbial nitrogen conversion reactions ( Kaiser et al., 2004b).