Characterization Of Particulate Matter (PM2.5) Emissions During Prescribed Fires Of The Coconino National Forest

Biomass burning is a major source of carbonaceous particles in the atmosphere. In recent years, prescribed fire has become an increasingly important tool for forest management in the Western United States, in order to reduce the risk of catastrophic wildfire. This has led to concerns about the impact of prescribed fire on local and regional air pollution and on human health and visibility. However, in situ characterizations of wildland or prescribed fires are very rare. This is surprising, given that recent studies suggest that biomass burning, including forest fires, is a major source of particulate matter in the Western U.S. A number of laboratory studies exist; however, such studies reflect only poorly the actual fuel composition and burning regimes of authentic forest fires. We will report results that characterize particulate matter (PM2.5) collected during five prescribed fires of the Coconino National Forest, the largest ponderosa pine forest in North America. Samples were collected in situ during the initial (ignition/flaming) stage of the burns and, occasionally, a day later during the smoldering stage of the fire. Samples were analyzed for total, organic, and elemental carbon by a thermo-optical method. Individual organic species, including polycyclic aromatic hydrocarbons, anhydrosugars, resin acids, and methoxyphenols were quantified by gas chromatography coupled to mass spectrometry (GC/MS) after solvent extraction. We will discuss the concentrations and emission ratios of individual species as a function of burning regime and type of fuel burned. The resulting emission profiles will be compared to common profiles used in source apportionment studies.