Pathways to Highly Oxidized Products in the Δ3-Carene + OH System
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Oxidation of the monoterpene Δ3-carene (C10H16) is a potentially important and understudied source of atmospheric secondary organic aerosol (SOA). We present chamber-based measurements of speciated gas and particle phases during photochemical oxidation of Δ3-carene. We find evidence of highly oxidized organic molecules (HOMs) in the gas phase and relatively low-volatility SOA dominated by C7-C10 species. We then use computational methods to develop the first stages of a Δ3-carene photochemical oxidation mechanism and explain some of our measured compositions. We find that alkoxy bond scission of the cyclohexyl ring likely leads to efficient HOM formation, in line with previous studies. We also find a surprising role for the abstraction of primary hydrogens from methyl groups, which has been calculated to be rapid in the α-pinene system, and suggest more research is required to determine if this is more general to other systems and a feature of autoxidation. This work develops a more comprehensive view of Δ3-carene photochemical oxidation products via measurements and lays out a suggested mechanism of oxidation via computationally derived rate coefficients.
| Original language | English |
|---|---|
| Journal | Environmental Science and Technology |
| Volume | 56 |
| Issue number | 4 |
| Pages (from-to) | 2213-2224 |
| Number of pages | 12 |
| ISSN | 0013-936X |
| DOIs | |
| Publication status | Published - 15 Feb 2022 |
Bibliographical note
Funding Information:
This research was supported by funding from the Academy of Finland, the Independent Research Fund Denmark (9040-00142B), the High-Performance Computing Center at the University of Copenhagen, and a grant to J.A.T. from the U.S. National Science Foundation (CHE-1807204). Chamber measurements were supported in part by a grant from the U.S. Department of Energy DE-SC0018221. ELD was supported by the National Science Foundation Graduate Research Fellowship under grant no. DGE-1256082 and a GROW travel grant. PNNL authors were supported by the U.S. Department of Energy, Office of Biological and Environmental Research, as part of the ASR program. Pacific Northwest National Laboratory is operated for DOE by Battelle Memorial Institute under contract DE-AC05-76RL01830. The authors thank the CSC-IT Center for Science in Espoo, Finland, for computational resources. The authors thank Havala Pye, Ivan Piletic, Donna Schwede, and Kiran Alapaty of the EPA for reviewing the manuscript. The views expressed in this article are those of the authors and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency. It has been subjected to Agency administrative review and approved for publication.
Publisher Copyright:
© 2022 American Chemical Society
- atmospheric chemistry, autoxidation, highly oxidized organic molecules (HOMs), monoterpene oxidation, secondary organic aerosol (SOA)
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