Composition and Surface Tension of Surface-Active Organics in Biomass Burning Aerosol
ARIANA DEEGAN, Chase Glenn, Omar El Hajj, Kruthika Kumar, Anita Anosike, Joseph O'Brien, Rawad Saleh, Amanda Frossard,
University of Georgia Abstract Number: 353
Working Group: Carbonaceous Aerosol
AbstractThe organic fraction of biomass burning aerosol contains humic-like substances (HULIS), some of which have been shown to be surfactant-like. Current work is investigating the surfactant fraction of biomass burning aerosol and its influence on the ability of particles to act as cloud condensation nuclei. In this study, aerosol particles were collected from the Georgia WIldland-fire Simulation Experiment (GWISE). Biomass from three Georgia ecoregions (Piedmont, Coastal, and Blue Ridge) were combusted with two moisture contents (low and high), resembling wildfire and prescribed fire conditions, respectively. A Potential Aerosol Mass Oxidation Flow Reactor (PAM-OFR) was used to replicate photochemical aging. Particles were extracted from filters, and organic compounds were isolated using two solid phase extractions. UV-Vis spectroscopy coupled with colorimetry was used to measure concentrations of anionic and cationic surfactants in the organic extracts. Tensiometry was used to measure surface tension isotherms and surface tension minimums and calculate critical micelle concentrations (CMCs). We show that the relative fraction of surfactants in the aerosol particles and the surface tension minimums of the surfactants vary as a function of biomass fuel type and moisture content. Across all fuels and moisture contents, anionic surfactants were the most prevalent. The Coastal fuel type, under the wildfire conditions, produced aerosol particles with the highest relative concentrations of surfactants. Surface tension minimums ranged from 33 to 46 mN m
- for organics extracted from particles produced across all fuel and moisture types. The aged particles had larger surface tension minimums than the fresh samples, in each experimental pair. The average CMC of the organic extracts was 0.256 mM. The surfactant concentration and surface tension depressions highlight the influence of fuel type, burning conditions, and aging on the composition and physical properties of surface-active organics in biomass burning aerosol.