NITROUS-OXIDE FLUX ESTIMATES FOR SOUTH-EASTERN AUSTRALIA

Nitrous oxide (N2O) fluxes for south-eastern Australia have been estim ated using a combination of the in situ N2O and radon (Rn) measurement s made at the Cape Grim Baseline Air Pollution Station, in north-west Tasmania. The average N2O fluxes from the south-eastern mainland of Au stralia and from Tasmania over the nine years of record analysed (1985 -1993) have been found to be 130 +/- 30 kgN km(-2) yr(-1) and 160 +/- 45 kgN km(-2) yr(-1) respectively. These fluxes are larger than expect ed and a significant dependence of the flux on rainfall is observed, w ith greater fluxes in the spring (October-December) and during periods of positive Southern Oscillation Index. A large flux (1, 300 +/- 500 kgN km(-2) yr(-1)) from a nearby island (King Island) was also estimat ed from the data record, indicating a strong source, although the smal l size of the island means that it is not a significant source for Aus tralia.