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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-561
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
03 Jul 2017
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
Temperature dependent rate coefficients for the reactions of the hydroxyl radical with the atmospheric biogenics isoprene, α-pinene and Δ-3-carene
Terry J. Dillon1,a, Katrin Dulitz1,b, Christoph M. B. Gross1, and John N. Crowley1 1Department of Air Chemistry, Max Planck Institute for Chemistry, 55124 Mainz, Germany
anow at: Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, YO10 5DD, York, UK
bnow at: Physikalisches Institut, University of Freiburg, Hermann-Herder Str. 3, 79104 Freiburg, Germany
Abstract. Abstract. Pulsed laser methods for OH generation and detection were used to study atmospheric degradation reactions for three important biogenic gases: OH + isoprene (R1); OH + α-pinene (R2); and OH + Δ-3-carene (R3). Gas-phase rate coefficients were characterised by non-Arrhenius kinetics for all three reactions. For (R1), k1 (241–356 K) = (1.93 ± 0.08) × 10−11 exp (466 ± 12)/T cm3 molecule−1 s−1 was determined, with a room temperature value of k1 (297 K) = (9.3 ± 0.4) × 10−11 cm3 molecule−1 s−1, independent of bath-gas pressure (5–200 Torr) and composition (M = N2 or air). Accuracy and precision were enhanced by online optical monitoring of isoprene, with absolute concentrations obtained via an absorption cross-section, σisoprene = (1.28 ± 0.06) × 10−17 cm2 molecule−1 at λ = 184.95 nm, determined in this work. These results indicate that significant discrepancies between previous absolute and relative rate determinations of k1 result in part from σ values used to derive the isoprene concentration.

Similar methods were used to determine rate coefficients (in 10−11 cm3 molecule−1 s−1) for (R2–R3): k2 (238–357 K) = (1.83 ± 0.04) × exp (330 ± 6)/T; and k3 (235–357 K) = (2.48 ± 0.14) × exp (357 ± 17)/T. This is the first temperature-dependent dataset for (R3) and enables the calculation of reliable atmospheric lifetimes with respect to OH removal for e.g. boreal forest springtime conditions. Room temperature values of k2 (296 K) = (5.4 ± 0.2) × 10−11 cm3 molecule−1 s−1 and k3 (297 K) = (8.1 ± 0.3) × 10−11 cm3 molecule−1 s−1 were independent of bath-gas pressure (7–200 Torr, N2 or air), and in good agreement with previously reported values. In the course of this work, 184.95 nm absorption cross-sections were determined: σ = (1.54 ± 0.08) × 10−17cm 2 molecule−1 for α-pinene and (2.40 ± 0.12) × 10−17  cm2 molecule−1 for Δ-3-carene.


Citation: Dillon, T. J., Dulitz, K., Gross, C. M. B., and Crowley, J. N.: Temperature dependent rate coefficients for the reactions of the hydroxyl radical with the atmospheric biogenics isoprene, α-pinene and Δ-3-carene, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-561, in review, 2017.
Terry J. Dillon et al.
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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RC1: 'Review of MS No.: acp-2017-561', Anonymous Referee #1, 16 Jul 2017 Printer-friendly Version Supplement 
 
RC2: 'Review of ACP-2017-561', Anthony Hynes, 06 Aug 2017 Printer-friendly Version Supplement 
 
AC1: 'Final comments from authors', Terry Dillon, 02 Oct 2017 Printer-friendly Version Supplement 
Terry J. Dillon et al.
Terry J. Dillon et al.

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Short summary
A great quantity & variety of organic compounds is released to the atmosphere annually. These organics impact greatly on air chemistry, quality and climate. Laser-based experiments were used to study the atmospheric breakdown of three organics: isoprene; alpha-pinene; & delta-3-carene. Results provided important missing information for low-temperature atmospheric conditions, resolved discrepancies from previous work, and allowed estimation of lifetimes of a few hours for each organic.
A great quantity & variety of organic compounds is released to the atmosphere annually. These...
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