Sources of the oxygen isotopic anomaly in atmospheric N2O

[1] One-dimensional and two-dimensional models are used to investigate the isotopic composition of atmospheric N2O. The sources of N2O in the atmosphere are based on recent laboratory measurements of the N2O quantum yield in the mixture of O3/O2/N2 (Estupiñán et al., 2002). Two recently proposed pathways (Estupiñán et al., 2002; Prasad, 2005) are evaluated in the model. We find that the new atmospheric sources constitute a few percent of the total N2O source, but can account for 50–100 % of the D17O anomaly observed in N2O. The essence of the mechanism is to transfer a heavy oxygen atom originally in O3 to N2O. The magnitude of D 17O in N2O is a linear function of the strength of these new N2O sources. Laboratory and atmospheric measurements are proposed to confirm the chemical pathways. The potential of D17O in N2O for providing a new tool to probe ozone levels in paleoatmospheres is discussed