AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Effect of OH Induced Aging on the Volatility of alpha-Pinene Ozonolysis Secondary Organic Aerosol Particles
KEI SATO, Satoshi Inomata, Yuji Fujitani, Yu Morino, Kiyoshi Tanabe, National Institute for Environmental Studies
Abstract Number: 659 Working Group: Aerosol Chemistry
Abstract In order to study the changes in product chemical composition and particle volatility during OH induced aging of secondary organic aerosol (SOA), we conducted a series of laboratory chamber experiments of alpha-pinene ozonolysis and exposed SOA particles to OH radicals. OH radicals were produced by the photolysis of methyl nitrite. We investigated the chemical composition of gas and particle products and the volatility of SOA particles before and after OH exposure. The OH exposure of present laboratory experiments corresponded to 1.7-4.2 day exposure at an ambient OH level. The mass fraction remaining (MFR) against to the mass at 298 K was measured for SOA particles by thermodenuder-AMS between 323 and 473 K. Slight increase in MFR was observed after OH exposure at 373 and 423 K, and no significant increase after OH exposure was observed at 323 and 473 K. Particle chemical composition was analyzed by offline liquid chromatography/mass spectrometry. The fractions of pinic acid, pinonic acid, and ester dimers to total SOA signal decreased after OH exposure, whereas those of 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA) and C10H14O6 product to tatal SOA signal increased after OH exposure. The average carbon oxidation state of particle products increased after OH exposure, whereas the average number of carbon atom included in particle product molecules decreased after OH exposure; these results of offline analysis suggest that functionalization and fragmentation are competitive during OH induced aging.