Hygroscopicity of Black-Carbon-Containing Aerosol in Wildfire Plumes
Thursday, 17 December 2015: 11:20
3004 (Moscone West)
Water uptake by black carbon (BC) containing aerosol has been quantified in wildfire plumes of varying age (from 1 to ~40 hr old) sampled in North America during the NASA SEAC4RS mission of 2013. Measurements were made in flight using parallel single-particle soot photometers (SP2) that simultaneously detected the BC component of the ambient aerosol ensemble under contrasting humidity conditions. The hygroscopicity parameter, κ, of material internally mixed with BC derived from this data set is consistent with previous estimates of bulk aerosol hygroscopicity from biomass burning sources. We explore the temporal evolution of κ during aging of the Yosemite Rim Fire plume to constrain the rate of conversion of BC-containing aerosol from hydrophobic to hydrophilic modes in these emissions. We also investigate the relationship between κ values for BC-containing particles and the oxidation state and hygroscopicity of the bulk aerosol. These observations have implications for BC transport and removal in biomass burning plumes and provide important constraints on model treatment of BC optical and microphysical properties from wildfire sources in ambient conditions.