Secondary Organic Aerosol Formation from Photooxidation of Oxygenated Monoterpenes in Simple and Complex Chemical Systems
CELIA FAIOLA, Farzaneh Khalaj, Shan Gu, Véronique Perraud, Leah Williams, Jordan Krechmer, Andrew Lambe,
University of California, Irvine Abstract Number: 110
Working Group: Aerosol Chemistry
AbstractBiogenic volatile organic compounds (BVOCs) from vegetation are major contributors to secondary organic aerosol (SOA) production worldwide. Oxygenated monoterpenes are commonly observed in many plant emission profiles with relatively low contribution to the total emissions, but they dominate emissions from some plant types, including shrub species in southern California’s coastal sage scrub ecosystem. Very few studies have systematically characterized SOA production and composition from these BVOCs. This presents a gap in our ability to predict SOA production in a future climate where drought-tolerant shrubs will likely experience large range expansion into new areas. This study investigated SOA formation and composition from the major oxygenated terpenes that have been observed in plant emissions across the globe: camphor, 1,8-cineole, borneol, and bornyl acetate. In these experiments, 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 (2B Technologies) and a custom-built scanning mobility particle sizer (SMPS), respectively. SOA composition was characterized offline using a high-resolution Q Exactive Orbitrap mass spectrometer (ThermoScientific) using SOA samples collected on Teflon filters. We also compared composition measured with an aerosol mass spectrometer (HR-ToF-AMS, Aerodyne) for SOA generated from real coastal sage shrub emissions versus oxygenated and aliphatic monoterpene standards. SOA mass yields of oxygenated monoterpenes were compared to alpha-pinene as a reference system. Calculated yields from lowest to highest were bornyl acetate < alpha-pinene < 1,8-cineole/borneol < camphor. Hierarchical clustering of the AMS data demonstrated that the real shrub SOA (dominated by oxygenated monoterpenes) was equally dissimilar from SOA formed from standards of oxygenated and aliphatic monoterpenes. This study sheds light on SOA formed from oxygenated terpenes in both simple and complex chemical systems, and will help improve predictions of SOA production in a future climate.