Understanding the aqueous phase ozonolysis of isoprene: distinct product distribution and mechanism from the gas phase reaction
- Creators
- Wang, H. L.
- Huang, D.
- Zhang, X.
- Zhao, Y.
- Chen, Z. M.
Abstract
The aqueous phase reaction of volatile organic compounds (VOCs) has not been considered in most analyses of atmospheric chemical processes. However, some experimental evidence has shown that, compared to the corresponding gas phase reaction, the aqueous chemical processes of VOCs in the bulk solutions and surfaces of ambient wet particles (cloud, fog, and wet aerosols) may potentially contribute to the products and formation of secondary organic aerosol (SOA). In the present study, we performed a laboratory experiment of the aqueous ozonolysis of isoprene at different pHs (3–7) and temperatures (4–25 °C). We detected three important kinds of products, including carbonyl compounds, peroxide compounds, and organic acids. Our results showed that the molar yields of these products were nearly independent of the investigated pHs and temperatures, those were (1) carbonyls: 56.7 ± 3.7 % formaldehyde, 42.8 ± 2.5 % methacrolein (MAC), and 57.7 ± 3.4 % methyl vinyl ketone (MVK); (2) peroxides: 53.4 ± 4.1 % hydrogen peroxide (H₂O₂) and 15.1 ± 3.1 % hydroxylmethyl hydroperoxide (HMHP); and (3) organic acids: undetectable (<1 % estimated by the detection limit). Based on the amounts of products formed and the isoprene consumed, the total carbon yield was estimated to be 94.8 ± 4.1 %. This implied that most of the products in the reaction system were detected. The combined yields of both MAC + MVK and H₂O₂ + HMHP in the aqueous isoprene ozonolysis were much higher than those observed in the corresponding gas phase reaction. We suggest that these unexpected high yields of carbonyls and peroxides are related to the greater capability of condensed water, compared to water vapor, to stabilize energy-rich Criegee radicals. This aqueous ozonolysis of isoprene (and possibly other biogenic VOCs) could potentially occur on the surfaces of ambient wet particles and plants. Moreover, the high-yield carbonyl and peroxide products might provide a considerable source of aqueous phase oxidants and SOA precursors.
Additional Information
© Author(s) 2012. This work is distributed under the Creative Commons Attribution 3.0 License. Received: 16 Feb 2012 – Discussion started: 01 Mar 2012 – Revised: 18 Jul 2012 – Accepted: 30 Jul 2012 – Published: 07 Aug 2012. The authors gratefully thank the National Natural Science Foundation of China (grants 21077003 and 40875072) and the State Key Laboratory of Environmental Simulation and Pollution Control (special fund 10Z03ESPCP) for financial support. Edited by: R. McLaren.Attached Files
Published - acp-12-7187-2012.pdf
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Additional details
- Eprint ID
- 103569
- Resolver ID
- CaltechAUTHORS:20200529-093435045
- 21077003
- National Natural Science Foundation of China
- 40875072
- National Natural Science Foundation of China
- 10Z03ESPCP
- State Key Laboratory of Environmental Simulation and Pollution Control
- Created
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2020-05-29Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field