NEW ESTIMATES OF NITROUS-OXIDE EMISSIONS FROM BIOMASS BURNING

ATMOSPHERIC nitrous oxide is important because of its role in stratospheric ozone destruction 1 and because it is a greenhouse gas. 2,3. Measurements indicate that N2O is increasing in the atmosphere at a rate of approximately 0.2% yr-1 (ref. 4). Fossil-fuel combustion and biomass burning 5,6 have been considered to be significant global sources of N2O, but the recent discovery of an artefact producing increased levels of N2O in combustion gas samples collected and stored in grab bottles before chemical analysis 7,8 has resulted in the downgrading of a fossil-fuel combustion and the questioning of biomass burning as important sources of N2O 9,10. As almost all reported analyses of N2O produced from biomass burning have involved essentially the same collection and analysis protocols as used in the fossil-fuel studies, this source of N2O must also be re-examined. Here we report and compare measurement of N2O made over a large prescribed fire using a near real-time in situ measurement technique with measurements of N2O from simultaneously collected grab-bottle samples. The results from 27 small laboratory biomass test fires also help clarify the validity of earlier assessments. We conclude that biomass burning contributes approximately 7% of atmospheric N2O, as opposed to earlier estimates of several times this value 6.