American Association for Aerosol Research - Abstract Submission

AAAR 39th Annual Conference
October 18 - October 22, 2021

Virtual Conference

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Secondary Organic Aerosol Formation from the Oxidation of Volatile Organic Compound Mixtures

YUMENG CUI, Kunpeng Chen, Ying-Hsuan Lin, Roya Bahreini, University of California, Riverside

     Abstract Number: 249
     Working Group: Carbonaceous Aerosol

Abstract
Smog chamber experiments have been widely used to simulate the ambient aerosol formation, and to understand the gas-phase and particle-phase chemistry. The chemical and microphysical properties of resultant aerosols formed from chamber experiments are generally applied to atmospheric models to estimate the aerosol formation and its radiative effects. However, most of the chamber studies focus on secondary organic aerosols (SOA) formation from a single volatile organic compound (VOC), while in the ambient atmosphere, VOCs from different sources usually mix after emissions. In this study, we explored the SOA formation and the chemical and optical properties of resulting particles from pure or the mixture of longifolene with 1-methylnaphthalene and phenol using continuous-flow chamber experiments under high-NOx conditions, and single scattering albedo (SSA) and mass absorption coefficient (MAC) of SOA at 375nm were calculated (1-methylnaphthalene SOA: SSA375≈0.85, MAC375≈0.6m2/g; phenol SOA: SSA375≈0.75, MAC375≈3.1m2/g; longifolene SOA: SSA375≈0.99, MAC375<0.1m2/g). Our preliminary results show that the addition of longifolene weakened the absorption of aromatic SOA. In 1-methylnaphthalene and longifolene mixture experiments, the SSA375 increased from 0.85 in the pure system to 0.96, and MAC375 decreased from 0.6m2/g to 0.3m2/g; in phenol and longifolene mixture experiments, the SSA375 increased from 0.75 in the pure system to 0.88, and MAC375 decreased from 3.1m2/g to 1.1m2/g. The aerosol mass spectrometer (AMS) data showed the formation of organonitrate and/or nitroorganic compounds (NOx+org) in SOA, and the ratio of NOx+org concentration to measured organics (RON) varied under different VOC schemes. Time-integrated aerosol samples collected at the end of the experiments will be analyzed with offline instruments (UV-Vis spectrophotometer and liquid chromatography coupled with a diode array detector and a high-resolution time-of-flight mass spectrometer equipped with an electrospray ionization source) for molecular characterization. More details about the aerosol optical properties and chemical composition will be presented to discuss the effects of mixing VOC precursors.