AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Enhancements in Secondary Organic Aerosol Formation in the Presence of Ambient or Directly Emitted Organic Particles
JIANHUAI YE, Paul Van Rooy, Cullen Adam H., David R. Cocker III, Arthur Chan, University of Toronto
Abstract Number: 232 Working Group: Aerosol Chemistry
Abstract Secondary organic aerosol (SOA) produced from atmospheric oxidation of organic vapors, comprises a large fraction of ambient particulate matter. Currently, SOA modeling typically assumes that all organic species form a well-mixed phase. Oxidation products are assumed to partition into primary organic aerosol (POA) similarly as into SOA; and it follows that SOA yields (mass of SOA formed per mass of hydrocarbon reacted) must be enhanced in the presence of preexisting organic aerosol. Recently, our study showed that yield enhancements of alpha-pinene SOA were only observed with selected organic aerosol surrogates, such as hexadecanol and tetraethylene glycol. The miscibility of organic species is not ideal, but can be predicted by measures of intermolecular forces, such as Hansen Solubility Parameters.
In this work, the validity of “single phase” assumption is further examined with representative ambient organic aerosol. The enhancements of SOA yields from alpha-pinene ozonolysis are investigated in the presence of organic aerosol collected from emission sources, such as meat cooking, biomass burning and vehicle exhaust, and ambient urban organic aerosol. Hansen Solubility Parameters are used to predict organic miscibility and SOA yield enhancements. Contribution of SOA enhancements from different POA sources will also be discussed. In conclusion, there is a strict mixing criterion for organic aerosol in the atmosphere. Our results will help to provide a better understanding of aerosol mixing and better parameterize SOA formation yields in the atmosphere.