Efficient Formation of Secondary Organic Aerosols from the Aqueous Oxidation of Terpenoic 1,2-Diols by OH

Abstract

Aqueous oxidation of pinanediol (PND) and camphanediol (CND) by hydroxyl radical (OH) was investigated using gas and liquid chromatography coupled with mass spectrometry. The yields of the products formed were measured with authentic and surrogate standards. This approach quantified >97% of the products for both reactions under investigation. For the first time, the formation of 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA) and other terpenoic acids (TAs) from the aqueous OH reaction with PND was confirmed with authentic standards. Based on the data acquired, mechanisms of OH oxidation of PND and CND were proposed. The yields of aq SOAs were evaluated by combining kinetic and air−water partitioning models developed for the the precursors, PND and CND, and for the first-generation products: cis-pinonic and camphoric acids. Modeled yields of aq SOAs ranged from 0.05 to 2.5. At liquid water content (LWC) from 1 × 10 −4 to 4 × 10 −3 (g × m −3 , haze, and fogs), oxidized TAs were the major components of aq SOAs. In clouds with LWC > 0.06 (g × m −3 ), the contribution of nonacidic products to the mass of aq SOAs became dominant. Aqueous OH reaction with PND can produce up to 0.3 (Tg × yr −1 ) of aq SOA, assuming the average flux of the precursor at 0.5 (Tg × yr −1 ).