Properties of Biomass Burning Organic Aerosol from Fuel Species in the Southern Great Plains

ELIJAH SCHNITZLER, Katrina Betz, Colton Calvert, Elevia Bruce, Troye Jirka, Nathan Huskins, Oklahoma State University

     Abstract Number: 537
     Working Group: Carbonaceous Aerosol

Abstract
The incidence of severe wildfires in the southern Great Plains, USA, has steadily increased in the last 25 years. The Rhea Fire in 2018, for example, burned roughly 300 000 acres of tallgrass prairie in western Oklahoma. Biomass burning organic aerosol (BBOA) from these grassfires has significant but uncertain effects on climate, as there are many remaining questions regarding its interactions with solar radiation and cloud processes. Using experimental and computational techniques, we are working to contribute insights into the light-absorption and hygroscopicity of BBOA from regionally relevant fuel species, including native tallgrasses collected in summer and winter as well as non-native eastern redcedar, which is associated with higher wildfire risks. BBOA in the absence of elemental carbon is generated by smoldering fuel in a tube furnace. The light-absorption of the BBOA is characterized in terms of the mass absorption coefficient (MAC) using UV-vis spectroscopy, and the dependence on fuel species is explored. The effects of concentration and temperature on absorbance are investigated to probe charge-transfer complexes. The distribution of absorbance, mass, and in turn MAC values across a range of polarity fractions is determined using octanol-water partitioning. The hygroscopicity of the BBOA is measured using a tandem differential mobility analyzer. Furthermore, the evolution of absorption with aging in the aqueous phase is monitored using a photo-reactor. Together, these results will help to better understand the fate and impact of BBOA from wildfires in the southern Great Plains.