Journal article
Photo-Oxidation of cis-Pinic Acid in the Aqueous Phase: A Mechanistic Investigation Under Acidic and Basic pH Conditions
Environmental Science: Atmospheres, Vol.1(5), pp.276-287
2021
DOI: 10.1039/D1EA00031D
Abstract
Atmospheric aqueous phases (cloud and fog droplets, aerosol liquid water) are important reaction media for the processing of water-soluble organic acids (OAs). The photochemistry of these species is known to contribute to the formation of aqueous secondary organic aerosols (aqSOA). OAs arising from the gas-phase oxidation of α-pinene, such as cis-pinonic acid (CPA) or pinic acid (PA), are considered relevant aqSOA precursors, as they are oxygenated compounds and expected to be sufficiently water-soluble to undergo cloudwater processing. Although PA is a major oxidation product of α-pinene, the mechanism of its aqueous-phase photo-oxidation has never been studied previously. In this work, we performed the first in-depth investigation for aqueous-phase OH-oxidation of PA. Given that the pH of atmospheric aqueous phases is highly variable, and it has been increasing over the past 40 years, we were particularly interested in the impact of pH on the reaction mechanisms and product yields. Experiments were performed using a combination of offline and online MS techniques to identify PA and monitor the evolution of PA OH-oxidation products. We identified PA as a novel source of important α-pinene SOA tracers, including 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA), and norpinic acid (NPA). Furthermore, we show a drastic difference in the yield of the oxidation products of PA under acidic and basic pH conditions, mainly due to a charge transfer reaction pathway unique to the aqueous-phase. Such impact of pH on the reaction mechanism of OA has never been shown before.
Details
- Title: Subtitle
- Photo-Oxidation of cis-Pinic Acid in the Aqueous Phase: A Mechanistic Investigation Under Acidic and Basic pH Conditions
- Creators
- Jéssica Vejdani AmorimXinyang GuoTania GautamRongyan FangChristian FotangFlorence J WilliamsRan Zhao
- Resource Type
- Journal article
- Publication Details
- Environmental Science: Atmospheres, Vol.1(5), pp.276-287
- DOI
- 10.1039/D1EA00031D
- ISSN
- 2634-3606
- eISSN
- 2634-3606
- Grant note
- DOI: 10.13039/501100000190, name: University of Alberta; DOI: 10.13039/501100000038, name: Natural Sciences and Engineering Research Council of Canada, award: RGPIN-2018-03814; DOI: 10.13039/501100000196, name: Canada Foundation for Innovation, award: 38334
- Language
- English
- Date published
- 2021
- Academic Unit
- Iowa Neuroscience Institute; Chemistry
- Record Identifier
- 9984094982902771
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