Measurements of acetone and other gas phase product yields from the OH-initiated oxidation of terpenes by proton-transfer-reaction mass spectrometry (PTR-MS) |
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| Affiliation: | 1. Universität Innsbruck, Institut für Ionenphysik, Technikerstrasse 25, A-6020 Innsbruck, Austria;2. Joint Research Centre, European Commission, Environment Institute, TP 272, I-21020 Ispra (VA), Italy;1. School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA;2. Environmental Control Systems, Boeing Commercial Airplanes, Everett, WA 98203, USA;3. School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China;1. School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA;2. School of Civil Engineering, Purdue University, West Lafayette, IN 47907, USA;3. Tianjin Key Laboratory of Indoor Air Environmental Quality Control, School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China;1. Department of Environmental Engineering, Technical University of Crete, Polytechneioupolis, 73100 Chania, Greece;2. Norwegian Institute for Air Research (NILU), Instituttveien 18, 2007, Kjeller, Norway |
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| Abstract: | The atmospheric oxidation of several terpenes appears to be a potentially relevant source of acetone in the atmosphere. Proton-transfer-reaction mass spectrometry was used as an on-line analytical method in a chamber study to measure acetone and other gas phase products from the oxidation of α- and β-pinene initiated by OH radicals in air and in the presence of NOx.Acetone may be formed promptly, following attack by the OH radical on the terpene, via a series of highly unstable radical intermediates. It can also be formed by slower processes, via degradation of stable non-radical intermediates such as pinonaldehyde and nopinone.Primary acetone and pinonaldehyde molar yields of 11±2% (one σ) and 34±9% (one σ), respectively, were found from the reaction between α-pinene and the OH radical. After all α-pinene had been consumed, an additional formation of acetone due to the degradation of stable non-radical intermediates was observed. The total amount of acetone formed was 15±2% (one σ) of the reacted α-pinene. An upper limit of 12±3% (one σ) for the acetone molar yield from the oxidation of pinonaldehyde was established.From the reaction between β-pinene and the OH radicals, primary acetone and nopinone molar yields of 13±2% (one σ) and 25±3% (one σ), respectively, were observed. Additional amounts of acetone were formed by the further degradation of the primary product, such as the most abundant product nopinone. The total amount of acetone formed was 16±2% (one σ) of the reacted β-pinene. An upper limit of 12±2% (one σ) for the acetone molar yield from the oxidation of nopinone was established.The observed product yields from α- and β-pinene are in good agreement with other studies using mass-spectrometric and gas chromatographic analytical techniques, but differ significantly from previous studies using spectroscopic methods. Possible reasons for the discrepancies are discussed. |
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