Environmental Science and Engineering Seminar

Secondary organic aerosol generated from biomass burning (BB-SOA) significantly influences atmospheric composition, air quality, and climate, yet uncertainties persist regarding its atmospheric lifetime and chemical evolution. Capturing those processes in global climate models is important for constraining organic aerosol mass and correctly predicting both direct and indirect effects of aerosols on climate. Recently Sedlacek et al. have described biomass burning aerosol lifecycle using data from multiple field measurements, showing a fast (first few hours) initial organic coating accumulation through secondary organic aerosol (SOA) formation, followed by a slow (1-10 days) loss of 75% of the organic coating. In this seminar, we present detailed results from recent environmental chamber experiments designed to quantify the photolytic lifetimes of biomass burning-derived SOA produced from common biomass combustion precursors furfural and guaiacol. We use mass spectrometry to monitor the chemical composition and physical properties of SOA over periods of exposure to UV light to elucidate critical photochemical transformation mechanisms and quantify corresponding changes in aerosol mass and optical properties. Additionally, we discuss the implications of environmental variables such as relative humidity and the presence of NOx on the aging processes and atmospheric stability of BB-SOA. Guaiacol- and furfural-derived SOA was found to be non-photolabile compared to biogenically-derived SOA produced from oxidation of isoprene and ɑ-pinene, suggesting longer atmospheric lifetimes, consistent with field campaign data. Complementary field measurements conducted in regions frequently impacted by biomass burning events further contextualize laboratory findings and provide real-world validation. Collectively, these insights enhance our understanding of the lifecycle and atmospheric implications of biomass burning-derived SOA, ultimately improving predictive atmospheric models and informing policy measures aimed at mitigating air pollution and climate impacts.