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Secondary Organic Aerosol Formation from Photooxidation of Acyclic Terpenes in an Oxidation Flow Reactor
SHAN GU, Farzaneh Khalaj, Véronique Perraud, Celia Faiola, University of California, Irvine
Abstract Number: 156
Working Group: Aerosol Chemistry
Abstract
One challenge in predicting secondary organic aerosol (SOA) formation is an incomplete representation of biogenic volatile organic compounds (BVOCs) emitted by plants, particularly those that are emitted in response to plant stressors. Plant emissions of acyclic monoterpenes, such as β-ocimene and β-myrcene, and acyclic sesquiterpenes, such as α-farnesene, are commonly induced or present at elevated concentrations under stress conditions (e.g. water, ozone, and herbivores stress) – conditions that are becoming more frequent in a rapidly changing climate. In this study, we investigated SOA formation from the photooxidation of acyclic terpene standards in an oxidation flow reactor (OFR). VOC concentrations were measured at the OFR inlet and outlet by sampling the air stream onto multi-bed adsorbent cartridges composed of Tenax TA and Carbopack. The cartridges were analyzed offline with a thermo-desorption gas chromatograph mass spectrometer (TD-GC-MS). At the outlet of the OFR, continuous monitoring of ozone, particle size distributions, and particle bulk composition was conducted using an ozone monitor, custom-built scanning mobility particle sizer (SMPS), and time-of-flight aerosol chemical speciation monitor (TOF-ACSM), respectively. SOA particles were also collected on Teflon filters and analyzed offline for detailed SOA chemical composition using an ultra high performance liquid chromatography system equipped with a heated electrospray ionization source and a high resolution Q Exactive Plus orbitrap mass analyzer (UPLC-HESI-HRMS). SOA chemical composition and mass yields will be compared across acyclic terpene systems, and will also be compared to the more typically studied, α-pinene SOA system.