Stable carbon kinetic isotope effects for the production of methacrolein and methyl vinyl ketone from the gas-phase reactions of isoprene with ozone and hydroxyl radicals |
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| Authors: | Richard Iannone Ralf Koppmann Jochen Rudolph |
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| Institution: | 1. Centre for Atmospheric Chemistry, Department of Chemistry, York University, 4700 Keele St., M3J 1P3 Toronto, Ontario, Canada;2. Institut für Chemie und Dynamik der Geosphäre, ICG-II: Troposphäre, Forschungszentrum Jülich, Germany;3. Fachbereich C – Mathematik und Naturwissenschaften, Atmosphärenphysik, Bergische Universität Wuppertal, Germany;1. Jülich Supercomputing Centre (JSC), Forschungszentrum Jülich GmbH, 52428 Jülich, Germany;2. Institute for Meteorology and Climate Research – Atmospheric Trace Gases and Remote Sensing (IMK-ASF), Karlsruher Institut für Technologie, Postfach 3640, 76021 Karlsruhe, Germany;3. Institute of Energy and Climate Research – Stratosphere (IEK-7), Forschungszentrum Jülich GmbH, 52428 Jülich, Germany;1. University of Wuppertal, Germany;2. DLR Oberpfaffenhofen, Germany;3. GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany;4. MPI Meteorology, Hamburg, Germany;5. DWD, Hohenpeißenberg Observatory, Germany;1. Department of Chemistry, Portland State University, Portland, OR 97207, USA;2. Department of Civil & Environmental Engineering, Portland State University, Portland, OR 97207, USA;1. The New Zealand Institute for Plant & Food Research Limited, Private Bag 3230, Waikato Mail Centre, Hamilton 3240, New Zealand;2. The New Zealand Institute for Plant & Food Research Limited, 121 Keri Downs Road, RD 1, Kerikeri 0294, New Zealand;3. The New Zealand Institute for Plant & Food Research Limited, 412 No. 1 Road, RD 2, Te Puke 3182, New Zealand;4. Scion, Private Bag 3020, Rotorua 3046, New Zealand;1. Department of Nuclear Research, Center for Physical Sciences and Technology, Vilnius, Lithuania;2. Department of Environmental Technology, Kaunas University of Technology, Kaunas, Lithuania;3. Faculty of Mechanical Engineering and Mechatronics, Kaunas University of Technology, Kaunas, Lithuania;4. School of Physics & Centre for Climate and Air Pollution Studies, Ryan Institute, National University of Ireland Galway, University Road, Galway, Ireland;1. Instituto de Astronomía y Física del Espacio, CONICET-UBA, Buenos Aires, Argentina;2. Birkeland Centre of Space Science, University Centre in Svalbard, Longyearbyen, Norway;3. Geophysical Institute, University of Alaska Fairbanks, USA;4. Deutsches Zentrum für Luft- und Raumfahrt (DLR), Oberpfaffenhofen, Germany;5. Institute of Cosmophysical Research and Aeronomy SB RAS, Yakutsk, Russia;6. Meteorologiska Institutionen, Stockholms Universitet, Sweden;7. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Moscow, Russia;8. Physics Department, University of Wuppertal, Germany;9. Solar-Terrestrial Environment Laboratory, Nagoya University, Japan;10. University of Western Ontario, London, Ontario, Canada;11. Instituto de Astrofísica de Andalucía, CSIC, Granada, Spain;12. Center for Atmospheric and Space Sciences, Utah State University, USA;13. Unidade Acadêmica de Física, Universidade Federal de Campina Grande, Paraíba, Brazil;14. Norges Teknisk-Naturvitenskapelige Universitet, Trondheim, and Birkeland Centre for Space Science, Bergen, Norway;15. Australian Antarctic Division, Kingston, Tasmania, Australia;p. Institut für Umweltphysik, Universität Bremen, Bremen, Germany;q. Institut für Physik, Ernst-Moritz-Arndt Universität, Greifswald, Germany |
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| Abstract: | The stable-carbon kinetic isotope effects (KIEs) associated with the production of methacrolein (MACR) and methyl vinyl ketone (MVK) from the reactions of isoprene with ozone and OH radicals were studied in a 25 L reaction chamber at (298±2) K and ambient pressure. The time dependence of both the stable-carbon isotope ratios and the concentrations was determined using a gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) system. The average yields of 13C-containing MACR and MVK generated from the ozone reaction of 13C-containing isoprene differed by ?3.6‰ and ?4.5‰, respectively, from the yields for MACR and MVK containing only 12C. For MACR and MVK generated from the OH-radical oxidation of isoprene the corresponding values were ?3.8‰ and ?2.2‰, respectively. These values indicate a significant depletion in the 13C abundance of MACR and MVK upon their formation relative to isoprene’s pre-reaction 13C/12C ratio, which is supported by theoretical interpretations of the oxidation mechanism of isoprene and its 13C-substituted isotopomers. Numerical model calculations of the isoprene + O3 reaction predicted a similar depletion in 13C for both reaction products upon production. Furthermore, the model predicts mixing ratios and stable carbon delta values for isoprene, MACR, and MVK that were in agreement with the experimental results. The combined knowledge of isotope enrichment values with KIEs will reduce uncertainties in determinations of the photochemical histories of isoprene, MACR, and MVK in the troposphere. The studies presented here were conducted with using isoprene without any artificial isotope enrichment or depletion and it is therefore very likely that these results are directly applicable to the interpretation of studies of isoprene oxidation using stable carbon isotope ratio measurements. |
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