Spectroscopic measurements of trace gas emissions from globally significant biomass fires.

摘要

Biomass burning is a major source of trace gases and particles in the global atmosphere. Fourier transform infrared (FTIR) spectroscopy was used to quantify nearly all the major reactive and stable trace gas compounds in biomass burning plumes. These include O₃ (formed photochemically in smoke), CO₂, CO, CH₄, C₂H₂, C₂H₄, C₂H₆, C₃H ₆, NO_x, HCN, NH₃, HCHO, HCOOH, CH₃COOH, C₆H₅OH, HOCH₂COH, and C₄H ₄O. The oxygenated organic species were emitted from biomass burning at higher levels than previously thought and they have been shown to play an important role in tropospheric photochemistry. The first emission factors (EF) for a globally significant combustion phenomenon called “residual smoldering combustion” (RSC) were measured in a series of laboratory fires and in Zambia. EF are reported for both aerosols and the major trace gases as measured by open-path FTIR spectroscopy. Large changes were found due to RSC in estimates of biomass fire emissions, which can be as large as a factor of 2.5, even when RSC accounts for only 10% of fuel consumption.; About 80% of biomass burning is thought to occur in the tropics due to land management practices and domestic fuel use. As part of SAFARI 2000, OP-FTIR was used in Central African villages to measure the trace gas emissions from the production and use of biofuels (the second most prevalent type of biomass burning). Spot measurements were made of the emissions from an earthen charcoal kiln and from several open wood and charcoal fires. Results show much higher emission factors for CH₄, CH₃OH, CH ₃COOH, HCHO, C₂H₄, and NH₃ from domestic biofuel production and use than from savanna fires in Zambia. Additionally, an airborne FTIR (AFTIR) was deployed between 14 August and 14 September 2000 and obtained the first broad overview of African savanna fire trace gas emissions with detailed measurements on ten fires.{09}On average, the initial emissions of oxygenated species make up the majority of nonmethane organic species in “fresh” smoke. These oxygenated compounds have a large, but poorly understood influence on the chemistry of the tropical troposphere.