The physical properties of black carbon and other light-absorbing material emitted from prescribed fires in the US

We measured black carbon properties over several prescribed fires in the western and southeastern US as well as black carbon and other related chemical components in laboratory fires for a number of commonly consumed North American fuels. We obtained consistent BC emission factors for the laboratory and aircraft measurements when controlling for combustion conditions, which will be helpful in improving existing prescribed fire emission inventories for the US. We also examined the relationship between the BC properties and the resulting aerosol optical properties. BC played a major role in determining the optical properties of the fire emissions. When BC was absent, as was the case for fires dominated by smoldering-phase combustion, the emissions had a strong wavelength dependence of absorption, with large absorption in the near-UV. When BC was a major component of the emitted aerosol, the resulting aerosol bulk optical properties were consistent with values previously reported in urban settings. Accurate estimates of the optical properties of biomass burning emissions are therefore highly sensitive to the amount of BC emitted.