AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Large Contribution of Oxygenated Aromatic Compounds in Biomass Burning Emissions to Secondary Organic Aerosol Formation
ALI AKHERATI, Charles He, Matthew Coggon, Abigail Koss, Carsten Warneke, Joost de Gouw, Christopher Cappa, Jeffrey R. Pierce, Michael Kleeman, Shantanu Jathar, Colorado State University
Abstract Number: 724 Working Group: Biomass Combustion: Emissions, Chemistry, Air Quality, Climate, and Human Health
Abstract Biomass burning is the largest combustion source of organic compounds to the atmosphere. However, there are large uncertainties in how the gas-phase organic compounds chemically react in the light and dark atmosphere to form secondary organic aerosol (SOA). In this work, we used a state-of-the-science model to simulate the chemistry, thermodynamic properties, and microphysics of SOA arising from photochemical aging of biomass burning emissions. The chemistry and thermodynamic properties were modeled using the Statistical Oxidation Model (SOM) and the microphysics was modeled using the TwO-Moment Aerosol Sectional (TOMAS) model. The initial concentrations of the SOA precursors were informed by the detailed speciation performed using a H3O+-chemical ionization mass spectrometer. We developed new sets of parameterizations to represent the SOA formation from oxygenated aromatic (e.g., phenol, guaiacol) and heterocyclic (e.g., furan and substituted furans) compounds since they contribute substantially to high molecular weight emissions from biomass burning. SOM-TOMAS was applied to 9 chamber experiments performed on four different fuels under moderate to high NOX conditions. Traditional SOA precursors such as single-ring aromatics, isoprene, and terpenes accounted for less than 10% of the measured SOA. In contrast, oxygenated aromatic compounds, with major contributions from phenols and substituted phenols, guaiacol, and cresol, were responsible for approximately three-quarters of the observed SOA. Heterocyclic species were not found to be important SOA precursors. Oxygenated aromatic compounds are short-lived species and are likely to play an important role in the near-field evolution of organic aerosol (OA). Ongoing work is focused on using the SOM-TOMAS model (i) to simulate the production of particulate organic nitrates (PONs) in chamber experiments performed with the NO3 radical and (ii) to investigate where laboratory-based parameterizations can help explain the field-observed OA evolution in wildfire plumes.