Abstract View
Characterizing the Physical and Chemical Evolution of Organic Aerosol in Biomass Burning Smoke using Gas- and Particle-phase Molecular Tracers from Laboratory and FIREX-AQ Observations
MELINDA SCHUENEMAN, Douglas Day, Demetrios Pagonis, Seonsik Yun, Olivia Jenks, Pedro Campuzano-Jost, Hongyu Guo, Benjamin A. Nault, Wyatt Brown, Julia Lee-Taylor, Joost de Gouw, Jose-Luis Jimenez, CIRES, University of Colorado, Boulder
Abstract Number: 404
Working Group: Wildfire Aerosols
Abstract
Fire plumes introduce large amounts of diverse gas- and particle-phase species into the atmosphere, which have been shown to negatively impact human health and the environment. This diversity makes characterizing fire impacts challenging. The abundant emissions of volatile organic compounds (VOCs), particles, and NOx suggest that substantial organic aerosol (OA) formation should occur downwind of fires. However, typically no enhancement of total OA is observed in most cases. One explanation that we are exploring is that primary OA (POA) evaporation is balanced by the condensation of less-volatile oxidized VOCs from VOC precursors onto existing aerosols (forming SOA). During the NASA/NOAA FIREX-AQ mission, for the first time, an Extractive Electrospray Soft Ionization Time-of-Flight Mass Spectrometer (EESI) was used to perform an extensive study of the OA composition in fire plumes. While the identity of some key molecules is clear based on previous literature and other evidence, most of the hundreds of OA species detected in the fire plume are not yet identified. These species hold essential information needed to understand the overall chemical evolution of OA. A suite of laboratory chamber experiments using the EESI and Vocus-PTR-ToF were conducted, targeting known and suspected biomass burning SOA precursors (e.g., phenol, catechol, and styrene). Catechol, nitrophenol, nitrocatechol, 5-nitro-1,2,3-benzenetriol, dinitrocatechol, and two ring-opened products were identified in the particle phase. Many of those species were also identified in the gas phase with the Vocus PTR-ToF-MS. A box model was constructed to represent these experiments, along with selected wildfire plumes from FIREX-AQ, to aid us in interpreting and chemically quantifying the evolution of aerosols in biomass burning plumes. Both the chamber and field models match measured nitrocatechol well. Chemical budgets were created using the direct measurements from the field and chamber studies.