SOA Formation from Toluene Oxidation in the Presence of Inorganic Aerosols Public Deposited

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  • March 20, 2019
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  • Cao, Gang
    • Affiliation: Gillings School of Global Public Health, Department of Environmental Sciences and Engineering
Abstract
  • Recent studies have shown that particle acidity increases SOA yields from biogenic precursors (e.g. isoprene and terpenes). This dissertation is a first attempt to investigate systematically impacts of particle acidity on aromatic SOA formation via heterogeneous reactions. A large number of toluene SOA yield experiments have been conducted in a 2 m3 indoor Teflon photoirradiation chamber under various experimental conditions (e.g. light conditions, NOx concentrations, humidity, inorganic seed compositions). In Chapter II and III, significant increase in toluene SOA yields by the presence of acidic sulfate have been observed under most of our experimental conditions, except at high NOx levels that are however not usual in the real atmosphere. The observations of our yield studies stimulate the further investigation into the impacts of heterogeneous chemistry on partitioning of semivolatile organic compounds on aromatic SOA and also motivate the exploration of a SOA model including partitioning and heterogeneous chemistry for toluene SOA prediction. In Chapter IV, a newly developed approach using deutrated alkanes has been employed to semiempirically determine the model structure of oligomer species of the toluene SOA. The resulting SOA compositions containing oligomeric species are used to estimate absorptive partitioning coefficients of toluene oxygenated products. The results show a considerable discrepancy between calculated and experimental partitioning coefficients of SOA products, suggesting that heterogeneous chemistry in aromatic SOA significantly impacts the gas particle partitioning of organic compounds. In Chapter V, a predictive model for SOA formation through both partitioning and heterogeneous reactions is further explored for SOA produced from toluene oxidation. The SOA model performance is evaluated using a variety of SOA experiments in terms of the ozone formation, the NO to NO2 conversion and the decay of toluene in the gas phase as well as the production of SOA mass. The model allows us to estimate the relative importance of partitioning and heterogeneous chemistry for SOA formation. Finally, Chapter VI summarizes the key findings of the dissertation research and provides the recommendations for future studies.
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  • In Copyright
Advisor
  • Jang, Myoseon
  • Leith, David
  • Sexton, Kenneth
  • Kim, Chong
  • Luecken, Deborah
  • Jeffries, H. E.
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2008
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