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Secondary Organic Aerosol Formation and Chemical Composition from Biogenic Oxygenated Terpenes
FARZANEH KHALAJ, Véronique Perraud, Shan Gu, Celia Faiola, University of California, Irvine
Abstract Number: 71
Working Group: Aerosol Chemistry
Abstract
Biogenic volatile organic compounds (BVOCs) released primarily from terrestrial vegetation contribute up to 90% of total atmospheric volatile organic compounds (VOCs) and up to 50% of the production of secondary organic aerosol (SOA) worldwide. SOA formation and composition influence aerosol climate effects and atmospheric radiative properties, but many BVOCs have not been the subject of previous laboratory SOA studies. For example, oxygenated monoterpenes are commonly emitted from plant species in Southern California’s coastal sage ecosystem, but their SOA chemistry is not well understood. This study investigates SOA formation and composition from oxygenated terpenes that have been identified in sage shrub emissions, such as camphor, eucalyptol, borneol, and bornyl acetate. SOA was generated via photooxidation in an oxidation flow reactor (OFR). Continuous monitoring of ozone and particle size distributions was conducted using an ozone monitor and a scanning mobility particle sizer (SMPS), respectively. For the SOA chemical composition, samples were collected on Teflon filters and analyzed offline 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). VOC samples were collected at the OFR inlet and outlet on absorbent cartridges and analyzed offline with a thermo-desorption gas chromatograph mass spectrometer (TD-GC-MS). SOA mass yield curves, impact of OH exposure on SOA mass yield, and high-resolution chemical composition of the SOA particles generated from these oxygenated terpenes reactions will be compared. This study sheds light on the potential role of these less-studied oxygenated terpenes in SOA formation and will help improve predictions of SOA production in a future climate where sage shrubs are expected to exhibit range expansion.