The tropical forest and fire emissions experiment: laboratory fire measurements and synthesis of campaign data

[摘要] As part of the Tropical Forest and Fire EmissionsExperiment (TROFFEE), tropical forest fuels were burned in a large,biomass-fire simulation facility and the smoke was characterized withopen-path Fourier transform infrared spectroscopy (FTIR), proton-transferreaction mass spectrometry (PTR-MS), gas chromatography (GC), GC/PTR-MS, andfilter sampling of the particles. In most cases, about one-third of the fuelchlorine ended up in the particles and about one-half remained in the ash.About 50% of the mass of non-methane organic compounds (NMOC) emitted bythese fires could be identified with the available instrumentation. The labfire emission factors (EF, g compound emitted per kg dry fuel burned) werecoupled with EF obtained during the TROFFEE airborne and ground-based fieldcampaigns. This revealed several types of EF dependence on parameters suchas the ratio of flaming to smoldering combustion and fuel characteristics.The synthesis of data from the different TROFFEE platforms was also used toderive EF for all the measured species for both primary deforestation firesand pasture maintenance fires – the two main types of biomass burning inthe Amazon. Many of the EF are larger than those in widely-used earlierwork. This is mostly due to the inclusion of newly-available, large EF forthe initially-unlofted smoldering emissions from residual logs in pasturesand the assumption that these emissions make a significant contribution(~40%) to the total emissions from pasture fires. The TROFFEE EFfor particles with aerodynamic diameter <2.5 microns (EFPM_2.5) is 14.8 g/kgfor primary deforestation fires and 18.7 g/kg for pasture maintenancefires. These EFPM_2.5 are significantly larger than a previous recommendation(9.1 g/kg) and lead to an estimated pyrogenic primary PM_2.5 source for theAmazon that is 84% larger. New regional budgets for biogenic andpyrogenic emissions were roughly estimated. Coupled with an estimate ofsecondary aerosol formation in the Amazon and source apportionment studies,the regional budgets suggest that ~5% of the total mass of theregionally generated NMOC end up as secondary organic aerosol within theAmazonian boundary layer within 1–3 days. New global budgets confirm thatbiogenic emissions and biomass burning are the two largest global sources ofNMOC with an estimated production of approximately 1000 (770–1400) and 500(250–630) Tg/yr, respectively. It follows that plants and fires may also bethe two main global sources of secondary organic aerosol. A limited set ofemission ratios (ER) is given for sugar cane burning, which may helpestimate the air quality impacts of burning this major crop, which is oftengrown in densely populated areas.

[学科分类] 大气科学