We investigated smoke emissions from fires in savanna, forest, and agricultural ecosystems by airborne sampling of plumes close to prescribed burns and incidental fires in southern Africa. Aerosol samples were collected on glass fiber filters and on stacked filter units, consisting of a Nuclepore prefilter for particles larger than approximately 1-2 microns and a Teflon second-filter stage for the submicron fraction. The samples were analyzed for soluble ionic components, organic carbon, and black carbon. Onboard the research aircraft, particle number and volume distributions as a function of size were determined with a laser-optical particle counter and the black carbon content of the aerosol with an aethalometer. We determined the emission ratios (relative to CO2 and CO) and emission factors (relative to the amount of biomass burnt) for the various aerosol constituents. The smoke aerosols were rich in organic and black carbon, the latter representing 10-30 percent of the aerosol mass. K(+) and NH4(+) were the dominant cationic species in the smoke of most fires, while Cl(-) and SO4(2-) were the most important anions. The aerosols were unusually rich in Cl(-), probably due to the high Cl content of the semiarid vegetation. (Author)