AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Atmospheric Chemistry of Volatile Chemical Products
REINA BUENCONSEJO, Sophia Charan, Christopher Kenseth, Paul Wennberg, John Seinfeld, California Institute of Technology
Abstract Number: 398 Working Group: Aerosol Chemistry
Abstract Recent work has indicated the growing importance of volatile chemical products (VCPs), particularly as air pollution regulations drive down the contribution of vehicular-based emissions. Thus, it is important to characterize the effects of VCP on atmospheric secondary organic aerosol (SOA) and its formation in order to better resolve discrepancies between SOA observations and models. This work looks at specific chemical mechanisms that lead to SOA formation and growth from VCP precursors. Compounds such as benzyl alcohol, n-butyl acetate, ethylene glycol butyl ether, and D5-siloxane were selected based on consultation with the California Air Resources Board (CARB). Analysis of these compounds is two-fold. First, molecular composition of the samples taken within the first 5 hours and after 5 hours of aerosol growth facilitated by aerosol seed are analyzed by an ultra-performance liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometer (UPLC/ESI-Q-TOF-MS). This analysis determines the oxidation products that result in SOA formation. Secondly, oxidation of the VCP compounds in the absence of aerosol seed is studied via custom-built gas chromatography-chemical ionization mass spectrometer (GC-CIMS) to identify oxidation products. Both classes of experiments are carried out at different NOx conditions so that an intercomparison of the different compounds can be made to better understand how NOx and VCP structure affect the oxidation mechanisms.