Mechanistic study of the formation of ring-retaining and ring-opening products from the oxidation of aromatic compounds under urban atmospheric conditions
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acp-19-15117-2019.pdf
Description
Published version
Size
1.4 MB
Format
Adobe PDF
Checksum (MD5)
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Author(s)
Zaytsev, Alexander
Koss, Abigail R.
Breitenlechner, Martin
Krechmer, Jordan E.
Nihill, Kevin J.
Lim, Christopher Yung-Ta
Rowe, James Clifford.
Cox, Joshua L.
Moss, Joshua Alexandre
Roscioli, Joseph R.
Date Issued
December 2019
Journal
Atmospheric Chemistry and Physics
Publisher
Copernicus GmbH
Citation
Zaytsev, Alexander, et al. "Mechanistic study of the formation of ring-retaining and ring-opening products from the oxidation of aromatic compounds under urban atmospheric conditions." Atmospheric Chemistry and Physics, 19, 23 (December 2019): 1511-15129. © 2019 Author(s).
Version
Final published version
Abstract
Aromatic hydrocarbons make up a large fraction of anthropogenic volatile organic compounds and contribute significantly to the production of tropospheric ozone and secondary organic aerosol (SOA). Four toluene and four 1,2,4-trimethylbenzene (1,2,4-TMB) photooxidation experiments were performed in an environmental chamber under relevant polluted conditions (NOx ~ 10 ppb). An extensive suite of instrumentation including two proton-transferreaction mass spectrometers (PTR-MS) and two chemical ionisation mass spectrometers (NHC 4 CIMS and I- CIMS) allowed for quantification of reactive carbon in multiple generations of hydroxyl radical (OH)-initiated oxidation. Oxidation of both species produces ring-retaining products such as cresols, benzaldehydes, and bicyclic intermediate compounds, as well as ring-scission products such as epoxides and dicarbonyls. We show that the oxidation of bicyclic intermediate products leads to the formation of compounds with high oxygen content (an O V C ratio of up to 1.1). These compounds, previously identified as highly oxygenated molecules (HOMs), are produced by more than one pathway with differing numbers of reaction steps with OH, including both auto-oxidation and phenolic pathways. We report the elemental composition of these compounds formed under relevant urban high-NO conditions. We show that ringretaining products for these two precursors are more diverse and abundant than predicted by current mechanisms. We present the speciated elemental composition of SOA for both precursors and confirm that highly oxygenated products make up a significant fraction of SOA. Ring-scission products are also detected in both the gas and particle phases, and their yields and speciation generally agree with the kinetic model prediction.
MIT Department
Massachusetts Institute of Technology. Department of Civil and Environmental Engineering
Terms of Use
Creative Commons Attribution 4.0 International license
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DOI of Published Version
https://doi.org/10.5194/ACP-19-15117-2019
