Atmospheric Chemistry Program Seminar: Nadine Borduas-Dedekind

Fire, air, and ice: The multifaceted impact of wildfire emissions on atmospheric chemistry (singlet oxygen and selenium) and ice nucleation

Prof. Nadine Borduas-Dedekind, Department of Chemistry, University of British Columbia, Vancouver, Canada

Wildfires have devastating and long-lasting impacts on air quality and climate. In my group, we are interested in 3 consequences of biomass burning organic aerosols (BBOA): (1) their photochemical oxidant production as they age through the atmosphere; (2) their ability to emit selenium and impact its biogeochemical cycle; (3) their ability to cause heterogenous ice nucleation in mixed-phase clouds. I’ll be presenting my group’s efforts towards these 3 research areas. First, I’ll give an overview of BBOA chemical composition and evolution. I’ll then describe how photochemical aging of aqueous droplets of BBOA generates triplet excited states which can subsequently form the first excited state of molecular oxygen (O2): singlet oxygen (1O2*).1–3 This aerosol-phase oxidant can modify the chemical properties of BBOA and their ability to nucleate ice clouds.4,5 Second, we are interested in the biogeochemical cycling of selenium, specifically in the context of selenium pollution in the environment which leads to severe ecotoxicity in fish and selenosis in humans. We’ve been studying the atmospheric transformations of organic selenium species as they are transported through the atmosphere, running chemical kinetic experiments and computational chemistry to support oxidation mechanisms of methylated selenide compounds. Third, these BBOA can induce the heterogeneous ice nucleation of supercooled water droplets, and my group has been interested in studying the mechanism by which macromolecules like lignin in BBOA can cause freezing.6–8 Overall, we’ll discuss how fire impacts air and ice chemistry.