Absence of isotope exchange in the reaction of N₂O + O(¹D) and the global Δ¹⁷O budget of nitrous oxide

Abstract

Yung et al. (2004) suggested that N2O exchanges isotopes with O(1 D), analogous to CO2, which would represent an additional contribution to the 17O isotope anomaly of atmospheric N2O. Here we demonstrate by isotope measurements of N2O remaining after partial conversion with O(1 D) that this isotope exchange most likely proceeds a

Sources of the oxygen isotopic anomaly in atmospheric N2O

“…The anomaly is on the order of 50%. To explain the observed 1% oxygen anomaly in N 2 O, the atmospheric source of N 2 O needs to be about 2% of the total source, i.e., a column production of N 2 O $5 Â 10 7 molecules cm À2 s À1 or 0.4 TgN/ year, consistent with the suggestion by Kaiser and Röckmann [2005].…”

“…These processes have been summarized and discussed by McLinden et al [2003] and Kaiser and Röckmann [2005]. In addition to the aforementioned proposals that generate nonzero D 17 O in the atmosphere, it has also been suggested that microbial production of N 2 O in the biosphere [Michalski et al, 2003;Kaiser et al, 2004;Kaiser and Röckmann, 2005] could contribute the observed oxygen anomaly.…”

“…In addition to the aforementioned proposals that generate nonzero D 17 O in the atmosphere, it has also been suggested that microbial production of N 2 O in the biosphere [Michalski et al, 2003;Kaiser et al, 2004;Kaiser and Röckmann, 2005] could contribute the observed oxygen anomaly. A recent calculation by Kaiser and Röckmann [2005] suggests that microbial nitrification and denitrification, O( 1 D) + N 2 , and NH 2 (and N) + NO 2 contribute 0.30, 0.36, and 0.18% to D 17 O, respectively, summing to a total of 0.82 À0.24 +0.30 %. Biomass burning and industrial processes only make a small contribution to D 17 O.…”

“…These processes provide a new source of N 2 O in the atmosphere, contrary to the current belief that the source of N 2 O in the atmosphere is negligible. The mechanism [Kaiser and Röckmann, 2005].…”

Background

“…For example, the atmospheric detection of an Earth-like amount of nitrous oxide (N 2 O) for an Earth-like planet orbiting a sunlike star would constitute a biosignature because according to current knowledge, such a signal could not be produced by anything other than microbes. In other words, the known atmospheric abiotic sources (for an overview see, e.g., Kaiser and Röckmann 2005) for this gas are much too slow to "mimic" life in such a case.…”