Title: | OH-Radical Oxidation of Surface-Active cis-Pinonic Acid at the Air-Water Interface |
Address: | "The Hakubi Center for Advanced Research, Kyoto University , Kyoto 606-8302, Japan. Research Institute for Sustainable Humanosphere, Kyoto University , Uji 611-0011, Japan. PRESTO, Japan Science and Technology Agency , Kawaguchi 332-0012, Japan. Graduate School of Human and Environmental Studies, Kyoto University , Kyoto, 606-8316, Japan. Graduate School of Global Environmental Studies, Kyoto University , Kyoto, 606-8501, Japan" |
ISSN/ISBN: | 1520-5215 (Electronic) 1089-5639 (Linking) |
Abstract: | "Gaseous biogenic volatile organic compounds (BVOCs) are immediately oxidized by gaseous oxidants to form BVOC-acids that rapidly condense onto aqueous aerosol phase and thus contribute to the growth of atmospheric particles. Because BVOC-acids are highly hydrophobic and hence surface-active in nature, it seems critical to study the oxidation by gaseous hydroxyl radical (.OH(g)) at the air-water interface. Here we report on the fast (=10 mus) oxidation of aqueous cis-pinonic acid (C10H16O3, CPA, cis-pinonate anion's m/z = 183), a representative BVOC-acid, by .OH(g) at the air-water interface for the first time. We find that cis-pinonate anion is more enriched at the air-water interface by approximately 4 and approximately 14 times than n-octanoate anion at 10 and 100 muM, respectively, as revealed by an interface-specific mass spectrometry of the equimolar mixture of microjets. Exposure of aqueous CPA microjets to .OH(g) pulses from the 266 nm laser photolysis of O3(g)/O2(g)/H2O(g)/N2(g) mixtures yields pinonic peroxyl radicals (m/z = 214) that lead to the functionalization products carbonyls (m/z = 197), alcohols (m/z = 199), and pinonic hydroperoxides (m/z = 215) in addition to smaller-mass products including carbonyls (m/z = 155 and 157). We confirmed the formation of the corresponding alcohols, aldehydes, and hydroperoxides in experiments performed in D2O solvent. The analysis of total mass balance implies a significant amount (>70%) of products would be emitted into the gas-phase during the heterogeneous .OH-oxidations. Our results suggest .OH-oxidations of amphiphilic BVOC-acids at the air-water interface may play a far more significant role in photochemical aging process of aqueous aerosols than previously assumed" |
Notes: | "PubMed-not-MEDLINEEnami, Shinichi Sakamoto, Yosuke eng 2016/04/22 J Phys Chem A. 2016 May 26; 120(20):3578-87. doi: 10.1021/acs.jpca.6b01261. Epub 2016 May 9" |