Optical Properties\nof Biomass Burning Aerosols from\nSimulated Wildfires and Prescribed Fires with Representative Fuel\nBeds from the Southeast United States

We report measurements\nof the absorption Ångström exponent\n(AAE) and single scattering albedo (SSA) of biomass burning aerosol\nfrom the combustion of fuel beds representing three eco-regions of\nthe Southeast U.S. (Piedmont, Coastal Plain, and Blue Ridge Mountains)\nwith moisture content representative of wildfires and prescribed fires.\nWe find a strong correlation between the AAE and SSA for both simulated\nwildfires (low fuel moisture) and prescribed fires (higher fuel moisture).\nFor wildfires, the AAE and SSA are strongly dependent on the eco-region\nof the fuel bed and span a much wider range (AAE = 1.3–4.2,\nSSA = 0.75–0.97) than they do for prescribed fires (AAE = 2.4–3.1,\nSSA = 0.88–0.96). The AAE and SSA are also found to be correlated\nwith the fraction of total carbon that is elemental carbon (<i>f</i><sub>EC</sub>) for both wildfires and prescribed fires,\nbut the range of <i>f</i><sub>EC</sub> observed (0.02–0.14)\nfrom the fuel beds is much smaller than that reported previously from\nlaboratory studies using individual fuels. The observations from the\npresent study suggest that fuel-bed composition and moisture content\nare significant factors in determining the relative amount of organic\nmaterial in biomass burning aerosols and, consequentially, their optical\nproperties.