Temperature dependence of the kinetic isotope effect in ß-pinene ozonolysis

Gensch, I.; Stein, O.; Wahner, A.; Kammer, B.; Hohaus, T.; Wegener, R.; Kiendler-Scharr, A.; Saathoff, H.; Laumer, W.

doi:10.1029/2011JD016084

Journal Article

Temperature dependence of the kinetic isotope effect in ß-pinene ozonolysis

Gensch, I.FZJ* ; Laumer, W.FZJ* ; Stein, O.FZJ* ; Kammer, B.FZJ* ; Hohaus, T.FZJ* ; Saathoff, H. ; Wegener, R.FZJ* ; Wahner, A.FZJ* ; Kiendler-Scharr, A.FZJ*

2011
Union Washington, DC

Journal of Geophysical Research 116, D20301 (2011) [10.1029/2011JD016084]

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Please use a persistent id in citations: http://hdl.handle.net/2128/20918 doi:10.1029/2011JD016084

Abstract: The temperature dependence of the kinetic isotope effect (KIE) of beta-pinene ozonolysis was investigated experimentally at 258, 273 and 303 K in the AIDA atmospheric simulation chamber. Compound specific carbon isotopic analysis of gas phase samples was performed off-line with a Thermo Desorption-Gas Chromatography-Isotope Ratio Mass Spectrometry (TD-GC-IRMS) system. From the temporal behavior of the delta C-13 of beta-pinene a KIE of 1.00358 +/- 0.00013 was derived at 303 K, in agreement with literature data. Furthermore, KIE values of 1.00380 +/- 0.00014 at 273 K and 1.00539 +/- 0.00012 at 258 K were determined, showing an increasing KIE with decreasing temperature. A parameterization of the observed KIE temperature dependence was deduced and used in a sensitivity study carried out with the global chemistry transport model MOZART-3. Two scenarios were compared, the first neglecting, the second implementing the KIE temperature dependence in the simulations. beta-Pinene stable carbon isotope ratio and concentration were computed, with emphasis on boreal zones. For early spring it is shown that when neglecting the temperature dependence of KIE, the calculated average age of beta-pinene in the atmosphere can be up to two times over-or underestimated. The evolution of the isotopic composition of the major beta-pinene oxidation product, nopinone, was examined using Master Chemical Mechanism (MCM) simulations. The tested hypothesis that formation of nopinone and its associated KIE are the determining factors for the observed delta C-13 values of nopinone is supported at high beta-pinene conversion levels.

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Meteorology & Atmospheric Sciences

Note: We thank Jochen Rudolph (York University, Toronto) for fruitful discussions and valuable suggestions. We also gratefully acknowledge the AIDA scientific team for constant advice and assistance during the measurement campaign. This work was supported by the EU within the EUROCHAMP project. We thank Angelika Heil for providing us with IGBP Moderate resolution Imaging Spectroradiometer (MODIS) Land Cover data.

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