AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Chemical Characterization of Secondary Organic Aerosol Formed from the Photoreactions of Guaiacyl Acetone in an Aqueous Particle Extract
WENQING JIANG, Richie Kaur, Martin Brüggemann, Hartmut Herrmann, Cort Anastasio, Qi Zhang, University of California, Davis
Abstract Number: 296 Working Group: Aerosol Chemistry
Abstract Guaiacyl acetone (GA) is a typical phenol emitted in significant quantities from biomass burning through lignin pyrolysis. With a high Henry’s law constant, GA readily partitions into atmospheric aqueous phases, where it reacts to produce secondary organic aerosol (SOA). In addition to fog and cloud waters, these aqueous reactions can also take place in particle-bound water, which is ubiquitous and persistent in the atmosphere despite low liquid water contents. In addition, recent studies have shown the concentrations of some photooxidants in particle water to be higher than in fog waters (Kaur et al., ACPD, 2018). Also, the high concentrations of organics, salts and metals in particle water could affect aqueous photooxidation reactions. In this study, we use high resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS) and Orbitrap mass spectrometry coupled to liquid chromatography (LC-Orbitrap MS) to investigate the chemical composition of the SOA formed from photoreactions of GA in an aqueous extract of wintertime particulate matter (PM extract) collected in a residential area with significant wood burning. GA oligomers and their derivatives are observed in the irradiated GA-PM extract solution by LC-Orbitrap MS and AMS. The AMS analysis further shows that ion signals representative of GA oligomers (e.g., C20H22O6+ and C18H19O5+) increase at the beginning of irradiation and then decrease. It suggests that oligomerization of GA is more important early in the reactions, but fragmentation becomes more important in later periods. In addition, the nitrogen-to-carbon ratio of the GA-PM extract solution increases from 0.37 to 0.44, and the contribution of CxHyNp+ and CxHyOzNp+ signals in the AMS mass spectra increases from 7.3% to 9.0% during irradiation, indicating the formation of N-containing organic compounds. A large number of N-containing compounds formed in the photooxidation of GA are identified by LC-Orbitrap MS.