10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Secondary Aerosol from Gas Emissions of Sage (SAGES): Characterizing SOA Production from Coastal Sage Scrub Plant Emissions under High and Low NOx Conditions
CELIA FAIOLA, Chinmoy Sarkar, Jordan Krechmer, Archit Mehra, Leah Williams, Fatemeh Khalaj, Manjula Canagaratna, Alex Guenther, Dasa Gu, Arin Boghoz, Angelo Calinga, John Jayne, Douglas Worsnop, Andrew Lambe, University of California Irvine
Abstract Number: 553 Working Group: Oxidation Flow Reactor: Development, Characterization, and Application to Aerosols
Abstract Plants emit more than 1,700 different volatile compounds, but very few of these compounds have been the subject of systematic SOA laboratory studies. It is unclear if a complex mixture of plant volatiles will generate SOA in a predictable way based on a linear combination of the individual components. Furthermore, it is unclear if the handful of proxy compounds that have been used in most SOA lab studies adequately represent the SOA chemistry of real plant emissions containing unique compounds that have not been studied previously. Thus, there are two major gaps in SOA studies: 1) investigations of realistic complex VOC mixtures and 2) investigations of plant volatiles that have not been the subject of previous lab studies. We addressed these two critical gaps by exposure of Salvia mellifera (black sage) and Artemisia californica (california sagebrush) emissions to O3, OH, and NO3 in the Aerodyne Potential Aerosol Mass oxidation flow reactor. These plants are keystone species in the Southern California coastal sage scrub ecosystem. SOA production was observed via OH exposure under low- and high-NO conditions, but not via O3 or NO3 exposure. The plant emissions and ensuing SOA formation were dominated by compounds that have not been targeted in previous SOA studies, including oxygenated monoterpenes such as camphor, 1,8-cineole, and alpha-thujone. For comparison to the mixture, these three compounds that dominated emissions from black sage were individually exposed to OH radicals. Gas-phase emissions were characterized with GC-ToF-MS and a Vocus PTR-MS, which also measured oxidized products. Particle size distributions and composition were characterized with a scanning mobility particle sizer and an HR-LToF-AMS. An overview of the experiments will be presented including detailed plant emission profiles, SOA yields, and SOA composition.