Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2016-1016
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
17 Nov 2016
Review status
A revision of this discussion paper was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
Investigation of the β-pinene photooxidation by OH in the atmosphere simulation chamber SAPHIR
Martin Kaminski1,a, Hendrik Fuchs1, Ismail-Hakki Acir1,b, Birger Bohn1, Theo Brauers1,†, Hans-Peter Dorn1, Rolf Häseler1, Andreas Hofzumahaus1, Xin Li1,c, Anna Lutz2, Sascha Nehr1,d, Franz Rohrer1, Ralf Tillmann1, Luc Vereecken1, Robert Wegener1, and Andreas Wahner1 1Institute of Energy and Climate Research, IEK-8: Troposphere, Forschungszentrum Jülich GmbH, Jülich, Germany
2Department of Chemistry and Molecular Biology, University of Gothenburg , Gothenburg, Sweden
anow at: Bundesamt für Verbraucherschutz, Abteilung 5 – Methodenstandardisierung, Referenzlaboratorien und Antibiotikaresistenz, Berlin, Germany
bnow at: Institute of Nutrition and Food Sciences, Food Chemistry, University of Bonn, Bonn, Germany
cnow at: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China
dnow at: Verein Deutscher Ingenieure e.V., Kommission Reinhaltung der Luft, Düsseldorf, Germany
deceased
Abstract. Beside isoprene, monoterpenes are the non-methane volatile organic compounds (VOC) with the highest global emission rates. Due to their high reactivity towards OH, monoterpenes can dominate the radical chemistry of the atmosphere in forested areas. In the present study the photochemical degradation mechanism of β-pinene was investigated in the Jülich atmosphere simulation chamber SAPHIR. The focus of this study is on the OH budget in the degradation process. Therefore the SAPHIR chamber was equipped with instrumentation to measure radicals (OH, HO2, RO2), the total OH reactivity, important OH precursors (O3, HONO, HCHO), the parent VOC beta-pinene, its main oxidation products, acetone and nopinone, and photolysis frequencies. All experiments were carried out under low NOx conditions (≤ 2 ppb) and at atmospheric beta-pinene concentrations (≤ 5 ppb) with and without addition of ozone. For the investigation of the OH budget, the OH production and destruction rates were calculated from measured quantities. Within the limits of accuracy of the instruments, the OH budget was balanced in all β-pinene oxidation experiments. However, even though the OH budget was closed, simulation results from the Master Chemical Mechanism 3.2 showed that the OH production and destruction rates were underestimated by the model. The measured OH and HO2 concentrations were underestimated by up to a factor of two whereas the total OH reactivity was slightly overestimated because of the poor reproduction of the measured nopinone by the model by up to a factor of three. A new, theory-derived first-generation product distribution by Vereecken and Peeters was able to reproduce the measured nopinone time series and the total OH reactivity. Nevertheless the measured OH and HO2 concentrations remained underestimated by the numerical simulations. These observations together with the fact that the measured OH budget was closed suggest the existence of unaccounted sources of HO2.

Citation: Kaminski, M., Fuchs, H., Acir, I.-H., Bohn, B., Brauers, T., Dorn, H.-P., Häseler, R., Hofzumahaus, A., Li, X., Lutz, A., Nehr, S., Rohrer, F., Tillmann, R., Vereecken, L., Wegener, R., and Wahner, A.: Investigation of the β-pinene photooxidation by OH in the atmosphere simulation chamber SAPHIR, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1016, in review, 2016.
Martin Kaminski et al.
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version      Supplement - Supplement
 
RC1: 'Review', Anonymous Referee #1, 17 Dec 2016 Printer-friendly Version Supplement 
AC1: 'Responses to the comments of reviewer #1', Robert Wegener, 06 Apr 2017 Printer-friendly Version 
 
RC2: 'Reviewer Comment ACP 2016-1016', Anonymous Referee #2, 23 Dec 2016 Printer-friendly Version 
AC2: 'Responses to the comments of reviewer #2', Robert Wegener, 06 Apr 2017 Printer-friendly Version 
Martin Kaminski et al.
Martin Kaminski et al.

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Short summary
Monoterpenes emitted by trees are among the volatile organic compounds with highest global emission rates. In forests monoterpenes dominate radical chemistry. The atmospheric degradation of the monoterpene beta-pinene was investigated in the atmosphere simulation chamber SAPHIR in Jülich under low NOx and atmospheric beta-pinene concentrations. While the budget of OH was balanced, both OH and HO2 concentrations were underestimated in simulation results.
Monoterpenes emitted by trees are among the volatile organic compounds with highest global...
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