The Evolution of Brown Carbon within Wildfire Smoke

Biomass combustion is known to produce substantial amounts of black carbon (BC) and particulate organic matter (POM). The light absorbing nature of POM from biomass sources has recently been explored and shows stronger visible light absorption from 'brown carbon' (BrC) than seen from other sources. The smoke from a 2010 summer wildfire near Boulder, Colorado was sampled using aerosol optical techniques (multi-wavelength extinction and absorption). The evolution of the light absorption contribution of BC, BrC and coating absorption enhancement within the smoke plume was tracked over a 24 period. The POM was shown to be non-absorbing at 532nm, while the fraction of total aerosol absorption at 405nm attributed to BrC was highly variable and was calculated to be up to 40%. This analysis will present a unique methodology for observing the evolution of the optical impact of both clear and brown carbon aerosol.