A reassessment of the global isotopic budget of atmospheric nitrous oxide

A simple box model is developed which accounts for the natural and anthropo genic sources and sinks of tropospheric nitrous oxide. Stable isotopic term s are included as well to investigate what additional insight they might pr ovide concerning the overall picture of the global nitrous oxide budget. It is seen that fractionation associated with ultraviolet photolysis in the s tratosphere plays a key role in balancing the isotopic budget. it is also n oted that increased production due to human influence should have a unique isotopic signature which should provide observable differences between prei ndustrial air trapped in polar firn or ice and modern air. This build-up of isotopically light, anthropogenic nitrous oxide can be thought of as an N2 O "Suess effect" and should be observable in time series measurements of cl ean baseline atmospheric samples. High-precision records of such changes co uld lead to a better estimate of the preindustrial N2O isotopic signature a s well as provide insight into the pathways of the anthropogenic sources.