TRACE GAS EMISSIONS FROM BIOMASS BURNING IN TROPICAL AUSTRALIAN SAVANNAS

During the 1991 and 1992 dry seasons (April to October), we collected and analyzed over 100 samples of smoke from savanna fires at the Kapal ga Research Station (12-degrees-S, 132-degrees-E) in Kakadu National P ark, Northern Territory, Australia. Samples collected from the ground and from a light aircraft flying at 50-700 m above the fires were anal yzed for CO2, CO, CH4, C2H2, C6H6, CH2O, CH3CHO, NO(X) (=NO+NO2), NH3, HCN, and CH3CN using gas phase Fourier transform infrared (FTIR) spec troscopy, matrix isolation FTIR spectroscopy, and chemiluminescence te chniques. In addition, we made detailed analyses of the mass, carbon, and nitrogen loads of the prefire fuel and the postfire ash residue. M olar emission ratios relative to emitted CO2 and CO, and emission fact ors relative to the fuel carbon or nitrogen burned were determined for the measured trace gases. Over 96% of the fuel carbon burned was rele ased to the atmosphere, predominantly as CO2 (87+/-3% of fuel C) and C O (7.8+/-2.3%). The mean DELTACO/ACO2 emission ratio of 9.0+/-2.6% ind icates efficient combustion in these fires of grasses and other light fuels. The main nitrogen-based emissions we measured were NO(X) (21+/- 8% of fuel N) and NH3 (23+/-13%). The combined emissions of NO(X), NH3 , N2O, CH3CN, and HCN accounted for only 51+/-17% of the fuel N releas ed to the atmosphere during combustion. We use these measurements to e stimate the annual emissions of several important trace gases from sav anna burning in Australia.