Oxygenated Aromatic Compounds Contribute Substantially to Secondary Organic Aerosol Formation from Photooxidation of Wildfire Emissions
Abstract
Biomass burning is the largest combustion source of organic compounds to the atmosphere. However, there are large uncertainties in how these gas-phase organic compounds chemically react in the atmosphere to form secondary organic aerosol (SOA). In this work, we use a state-of-the-science model that simulates the chemistry, thermodynamic properties, and microphysics of organic aerosol to study the SOA formation in photooxidation experiments performed at the Fire Sciences Laboratory in Missoula, MT during FIREX-2016. 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 an H 3 O + -chemical ionization mass spectrometer. Because oxygenated aromatic (e.g., phenols and methoxyphenols) and heterocyclic (e.g., furan and substituted furans) compounds contribute substantially to high molecular weight emissions from wildfires, we developed new sets of parameterizations to represent their SOA formation using historical chamber data. The 'SOM-TOMAS' model was applied to eleven chamber experiments performed on six different fuels under moderate to high NO X conditions. Traditional SOA precursors such as single-ring aromatics, isoprene, and terpenes accounted for about 10% of the measured SOA. In contrast, oxygenated aromatic compounds, with major contributions from phenol, cresol, guaiacol, and catechol (in increasing order of their contribution to SOA), were responsible for most of the observed SOA mass and changes in the elemental composition (e.g., O:C ratio) of organic aerosol. Heterocyclic species that included furanic species contributed to less than 10% of the total SOA. Oxygenated aromatic compounds are short-lived species and are likely to play an important role in the near-field evolution of organic aerosol in wildfire plumes. 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 NO 3 radical and (ii) to investigate whether the SOM-TOMAS model can help explain the OA evolution reported in wildfire-focused aircraft campaigns (e.g., BBOP, WE-CAN, FIREX-AQ).
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A21C..06J
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0322 Constituent sources and sinks;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE