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Estimating the Contribution of Significant Volatile Organic Compounds to Secondary Organic Aerosol from Biomass Cookstove Emissions
Citation:
Sinha, A., I. George, M. Hays, AND A. Grieshop. Estimating the Contribution of Significant Volatile Organic Compounds to Secondary Organic Aerosol from Biomass Cookstove Emissions. American Association for Aerosol Research Annual Meeting, Portland, Oregon, October 14 - 18, 2019.
Impact/Purpose:
One of the major challenges in air quality modeling science is the ability to accurately predict the formation of secondary organic aerosol. Generally, these models have been underpredicting the amount of these organic particles that are produced through atmospheric reactions of primary emissions. One of the major reasons for these discrepancies is the lack of accurate measurements gas-phase organic components of biomass burning emissions. In this work, speciated VOCs in cookstove emissions were characterized and their contributions towards SOA formation was assessed. This work will improve air quality modeling predictions of SOA formation from biomass burning emissions.
Description:
Almost 3 billion people use biomass cookstoves with emissions resulting in adverse impacts on both health and climate. Emissions from these cookstoves include volatile organic compounds (VOCs), which include hazardous pollutants and various precursors to secondary organic aerosol (SOA). However, the identity and extent to which individual VOCs from biomass stove emissions contribute to SOA production is poorly understood. To better constrain VOC identity and quantity for a range of stoves and fuels, we analyzed whole air samples (WAS) of fresh and photochemically-aged emissions using EPA method (TO-15). Using literature yields, we estimate their contribution to SOA observed in an oxidation flow reactor and quantify mass closure in SOA. Preliminary results indicate that Benzene, Naphthalene and Toluene, were capable of explaining up to ∼65% of the SOA observed in tests of the most efficient stove, but in other cases only ∼10% of SOA formed were explained by these VOCs. On an emission factor basis, the lower combustion efficiency stoves resulted in higher VOCs. SOA contributions from benzene and naphthalene were similar and higher than those from toluene across all conditions. Current work will identify compounds not targeted by the TO-15 protocol, like phenol and derivatives identified as significant SOA precursors, using deconvolution algorithms (‘unknowns’ analysis) on existing sample analyses. We hypothesize that with the incorporation of VOCs from both targeted and semi-quantitatively estimated non-targeted compounds, we can bridge the gap in unaccounted observed SOA mass. We also explore an alternative approach to explaining the SOA by projecting the VOC measurements from canister sampling, and separate measurements of semi- and intermediate-volatility organic compounds (S/IVOCs) from thermal desorption analysis of collected filters in a volatility basis set (VBS) framework. We will investigate how SOA formation from detailed VOC speciation data compares to estimates applying this VBS framework in explaining observed SOA from cookstove emissions.