Abstract:
Wildfires are a major source of organic aerosols in the atmosphere, referred to as biomass burning organic aerosol (BBOA). Understanding the viscosity and phase state of wildfire-derived BBOA is crucial for predicting its effects on air quality, atmospheric chemistry, and climate. We measured BBOA viscosity using the poke-flow technique and fluorescence recovery after photobleaching. Four types of BBOA were studied: primary BBOA, aged primary BBOA, secondary BBOA, and a mixture of aged primary and secondary BBOA. Our results show that unaged primary BBOA from burning pine wood has a low viscosity and exists in a semisolid state. In contrast, atmospheric aging can increase viscosity by six or more orders of magnitude, transforming BBOA into a glassy state. We also show that UV-aging and OH-aging can generate highly viscous BBOA after 30 and 5 days of atmospheric aging, respectively. Implications for ice nucleation, gas-particle equilibration timescales, and brown carbon lifetimes will be discussed.
Bio:
Allan Bertram is a Professor of Chemistry and Distinguished University Scholar at the University of British Columbia. He earned his BSc from the University of Prince Edward Island, his PhD from the University of Waterloo, and completed a postdoctoral fellowship at the Massachusetts Institute of Technology. His research group investigates the chemical and physical properties of atmospheric aerosols and their effects on air quality, atmospheric chemistry, and climate. Current research topics include the properties of wildfire smoke and microplastics, and their impacts on the atmosphere and environment.