The flux of charcoal to the troposphere during the period of agricultural burning in Panama

Abstract

Although extensive areas of forests and grasslands are burned in the tropics, relatively little scientific attention has been focused on this phenomenon. In order to determine the land area burned and estimate the charcoal (elemental or graphitic carbon) produced, I monitored agricultural burning in a 1145 km 2 area in central Panama during the 1981 dry season. Over 10% of the land surface was burned in that year. Charcoal concentrations in the aerosol were also measured and reached values of 3.1 ~gC/m 3 during the peak in burning. Off-peak values of aerosol charcoal are less than 1 ~tgC/m 3. The high charcoal concentration reflects the massive amounts of vegetational burning occurring in the area.The charcoal advected by the air mass flowing over the area has been estimated using a box model. Assuming an average aerosol concentration of charcoal of 1 ~tgC/m 3 for a three-month burning period, a 2 km atmospheric mixed layer, a 14 km/h wind velocity to the south, and a 150 km wide zone across the western Gulf of Panama watershed, I estimate that, during the dry season, 9 × 10 9 g charcoal are mobilized by the troposphere, if 4.1 × 1012 g phytomass are annually burned in this region, then the charcoal emission factor to the troposphere is 2.2 × 10 -3 .

On uncertainty in the computation of global emissions from biomass burning

“…Though this formula has subsequently been used elsewhere (Andreae et al, 1988;Suman, 1988;Setzer et al, 1988), it is but one of many formulas used by Seiler and Crutzen, and, as discussed in the concluding section, it has some undesirable properties. Other formulations employed for inferring biomass burned from available data are reviewed below.…”

“…Based on personal observation of fires and weak references in the literature, they guessed that 20% of biomass ended up as char. This estimate has been used by other studies (Suman, 1988;Goudriaan and Ketner, 1984;Houghton et al, 1983). Comery's (1981) attempt to measure char formation in long-leaf pine in Florida, and Fearnside et al's (unpublished data) study of char yields in burning associated with forest clearing in the Brazilian Amazon both indicate char yields on the order of 2%.…”

Carbonaceous Aerosols from Prescribed Burning of a Boreal Forest Ecosystem

“…Inthepast, carbonaceous particles found inthesmokeplumes ofcombusted biomass have been evaluated as bulk aerosol components. Two forms of smoke aerosol, organic carbon (OC)andelemental carbon (EC), areradiatively active components; OC particles scatter solar radiation(depending on composition) and EC particles scatter and absorb the same radiation.Total carbon (TC), OC, and EC have been identified in smoke from the tropics (Andreae et al, 1988;Cachier et al, 1989;Suman 1988). Recent estimates of the global emissions ofparticulate organic carbon andelemental carbon duetobiomass burning show major releases to the troposphereof these radiatively important carbonaceous particles (69 Tg/yr for OC; 19 Tg/yr for EC) (Andreae, 1990).…”