EMISSIONS OF TRACE GASES AND AEROSOL-PARTICLES DUE TO VEGETATION BURNING IN SOUTHERN-HEMISPHERE AFRICA

The emissions of trace gases and particles resulting from extensive ve getation fires in southern and central Africa are estimated from the a mount of fuel consumed and emission factors determined during the Sout hern Africa Fire-Atmosphere Research Initiative (SAFARI-92) field camp aign. The fuel consumption estimates are from the modeling approach of Scholes et al. [this issue]. The emission factors are a function of t he ''combustion efficiency,'' a measure of the oxygenation state of th e fire. Combustion efficiency is in turn related to the types of fuel consumed. Most of the burning in southern Africa takes place in savann as during the dry season. The main fuel is dry grass, which burns with high efficiency and produces relatively low emissions of methane, car bon monoxide, and aerosols per unit mass of fuel consumed. The combina tion of the reduced estimates of amount of biomass burned and the low emission factors results in subcontinental emission estimates for CH4, CO, NOx, and aerosols which are substantially lower than previous est imates. The estimates for the nominal year 1989 are 14.9 Tg CO, 0.500 Tg CH4, 1.06 Tg NOx, and 1.08 Tg particles (<2.5 mu m). Approximately 324 Tg CO2 is released by vegetation fires and, in the absence of evid ence to the contrary, is assumed to be reabsorbed by subsequent regrow th. The pyrogenic emissions are concentrated in the area between 5 deg rees and 20 degrees S and in the months between June and October, with a peak in August.