Measurement of multioxygen isotopic (δ¹⁸O and δ¹⁷O) fractionation factors in the stratospheric sink reactions of nitrous oxide

Abstract

Nitrous oxide is an important component in the Earth's atmosphere with a global budget that shows significant imbalance between known sources and sinks. A recent isotopic analysis of atmospheric nitrous oxide has suggested that back fluxing from the stratosphere could be an important source of N 2 O to the troposphere. To quantitatively determine the potential magnitude of this process, the relevant isotopic fractionations must be known. We have measured the isotopic fractionation factors associated with the two known stratospheric sink reactions of N 2 O: photolysis and photooxidation. It is observed that nitrous oxide photolysis produces no fractionation in δ 18 O and δ 17 O, while photooxidation produces a small mass‐dependent enrichment in 18 O and 17 O in the residual N 2 O.