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Atmospheric Evolution of Emissions from a Boreal Forest Fire: The Formation of Highly- Functionalized Oxygen-, Nitrogen-, and Sulfur-Containing Compounds
JENNA DITTO, Megan He, Tori Hass-Mitchell, Samar Moussa, Katherine Hayden, Shao-Meng Li, John Liggio, Amy Leithead, Patrick Lee, Michael Wheeler, Jeremy Wentzell, Drew Gentner, Yale University
Abstract Number: 203
Working Group: Aerosol Chemistry
Abstract
Forest fires are major contributors of reactive gas- and particle-phase organic compounds to the atmosphere. We used high resolution tandem mass spectrometry to perform a molecular-level speciation of evolving gas- and particle-phase compounds sampled via aircraft from a boreal forest fire in Saskatchewan, Canada. We observed diverse multifunctional compounds containing oxygen, nitrogen, and sulfur (CHONS), whose structure, formation, and impacts are understudied. The abundance of particle-phase CHONS species increased with smoke plume age, from 19% to 40% of the relative abundance of observed functionalized organic aerosol (OA) over the first 4 hours of downwind transport. The relative contribution of particle-phase sulfide functional groups increased with age from 4% to 40% of observed OA abundance, and were present in up to 75% of CHONS compounds. The increases in sulfides were accompanied by increases in ring-bound nitrogen, and both rose together with CHONS prevalence. A complex mixture of intermediate- and semi-volatile gas-phase organic sulfur species was emitted from the fire and depleted downwind, representing potential precursors to particle-phase CHONS compounds. We discuss potential reactions that formed these CHONS species, and origins of the reduced sulfur-precursors. Together, these results demonstrate CHONS formation from nitrogen/oxygen-containing biomass burning emissions in the presence of reduced sulfur species, and highlight chemical pathways that may also be relevant in situations with elevated levels of nitrogen and sulfur emissions from residential biomass burning and fossil fuel use (e.g. coal), respectively.