A146-0005
Investigation of α-Pinene atmospheric oxidation using ambient perturbation experiments

Monday, 14 December 2020
Poster
Jean Rivera-Rios, Georgia Institute of Technology Main Campus, School of Chemical and Biomolecular Engineering, Atlanta, GA, United States, Adam T Wright, Georgia Institute of Technology Main Campus, Atlanta, United States, Zijing Zhang, Peking University, Beijing, China, Jennifer Kaiser, Georgia Institute of Technology Main Campus, School of Civil and Environmental Engineering, School of Earth and Atmospheric Sciences, Atlanta, GA, United States and Nga Lee Ng, Georgia Institute of Technology Main Campus, School of Chemical and Biomolecular Engineering, School of Civil and Environmental Engineering, School of Earth and Atmospheric Sciences, Atlanta, GA, United States
Abstract:
Secondary pollutants such as ozone (O3) and secondary organic aerosol (SOA) are formed from the oxidation of volatile organic compounds (VOCs). Laboratory chamber experiments are typically used to study the oxidation of VOCs under carefully controlled conditions to determine their products and influence on O3 and SOA. On the other hand, perturbation experiments introduce ambient air into an outdoor chamber and induce slight changes to investigate atmospheric oxidation as it occurs under natural conditions. Possible perturbations include adding additional oxidants such as O3 or H2O2 (OH), adding nitrogen oxides (NOX) to change oxidation pathways or injecting VOCs. Using VOCs during perturbation experiments allows us to investigate their oxidation as it happens in ambient environments. This includes how product distributions respond to changes in atmospheric conditions such as sunlight, NOX concentrations, presence of other VOCs, and temperature. We performed perturbation experiments using α-Pinene in downtown Atlanta, GA in the summer of 2019. We monitored gas and particle-phase products using a variety of instruments including a Proton Transfer Reaction Mass Spectrometer (PTR-MS), Iodide adduct Chemical Ionization Mass Spectrometer (I--CIMS), Aerosol Mass Spectrometer (AMS), and Scanning Mobility Particle Sizer (SMPS). The CIMS was equipped with a Filter Inlet for Gases and Aerosols (FIGAERO) enabling measurements of speciated gas- and particle-phase components at the molecular level. Our results show large variations in product yields depending on temperature, light intensity, NOX, and O3 concentrations. Positive matrix factorization (PMF) analysis was performed on the SOA formed in these experiments to understand the response of the resolved OA factors to ambient conditions. We resolve known OA factors including an isoprene factor, less-oxidized oxygenated organic aerosol (LO-OOA) and more-oxidized oxygenated organic aerosol (MO-OOA). Oxidation of α-Pinene enhances, primarily, LO-OOA with the yield depending on NOX and O3 concentrations. MO-OOA was found to be both consumed and directly produced depending on NOX levels and temperature/sunlight. Correlations between these OA factors and similarly influenced products as measured by the I-CIMS will be evaluated and discussed.
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