Abstract
Airborne measurements of trace gases and particles over and downwind of two prescribed savanna fires in Zambia are described. The measurements include profiles through the smoke plumes of condensation nucleus concentrations and normalized excess mixing ratios of particles and gases, emission factors for 42 trace gases and seven particulate species, and vertical profiles of ambient conditions. The fires were ignited in plots of miombo woodland savanna, the most prevalent savanna type in southern Africa, and dambo grassland savanna, an important enclave of miombo woodland ecosystems. Emission factors for the two fires are combined with measurements of fuel loading, combustion factors, and burned area (derived from satellite burn scar retrievals) to estimate the emissions of trace gases and particles from woodland and grassland savanna fires in Zambia and southern Africa during the dry season (May–October) of 2000. It is estimated that the emissions of CO2, CO, total hydrocarbons, nitrogen oxides (NOx as NO), sulfur dioxide (SO2), formaldehyde, methyl bromide, total particulate matter, and black carbon from woodland and grassland savanna fires during the dry season of 2000 in southern Africa contributed 12.3%, 12.6%, 5.9%, 10.3%, 7.5%, 24.2%, 2.8%, 17.5%, and 11.1%, respectively, of the average annual emissions from all types of savanna fires worldwide. In 2000 the average annual emissions of methane, ethane, ethene, acetylene, propene, formaldehyde, methanol, and acetic acid from the use of biofuels in Zambia were comparable to or exceeded dry season emissions of these species from woodland and grassland savanna fires in Zambia.
Highlights
[Hao and Liu, 1994]
Savanna burning is a source of a wide variety of compounds that are important in atmospheric chemistry, including carbon monoxide (CO), nitrogen oxides (NOx), sulfur dioxide (SO2), nonmethane organic compounds (NMOC), halocarbons, and particles [Crutzen and Andreae, 1990; Sinha et al, 2003a]
Emission factors are given for these species, and they are combined with measurements of fuel loading, combustion factors, and area burned to estimate their emissions from woodland and grassland savanna fires in Zambia and southern Africa during the dry season of 2000
Summary
[2] Biomass burning is the primary source of atmospheric pollution in the tropics [Crutzen and Andreae, 1990], and it affects large areas of the world through long-range transport [Fishman et al, 1991]. Emission factors are given for these species, and they are combined with measurements of fuel loading, combustion factors, and area burned to estimate their emissions from woodland and grassland savanna fires in Zambia and southern Africa during the dry season of 2000. Black carbon (BC) concentrations were measured with an optical transmission technique similar to that described by Rosen and Novakov [1983] This method compares the attenuation of white light through a loaded filter relative to that of a blank filter. A value of 20 m2 gÀ1 was used for the mass absorption cross section [Gundel et al, 1984], which is consistent with the calibration factor of a commercial aethalometer that employs the same optical transmission method for measuring BC concentrations [Bodhaine, 1995] Further discussion of this optical transmission method, including uncertainties and comparison with other methods, is given by Kirchstetter et al [2003] and Sinha et al [2003b].
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