Development of a reduced speciated VOC degradation mechanism for use in ozone models |
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| Affiliation: | 1. Department of Environmental Science and Technology, Imperial College, Silwood Park, Ascot, Berkshire SL5 7PY, UK;2. School of Chemistry, University of Leeds, Leeds LS2 9JT, UK;3. Climate Research Division, Meteorological Office, Bracknell, Berkshire RG12 2SZ, UK;1. Environmental Research Lab, Department of Chemistry, St. Andrew''s College, Gorakhpur, India;2. Department of Chemistry, Dr. BhimRaoAmbedkar University, Agra, India;3. Environment Response Team, United States Environment Protection Agency, New Jersey, USA;1. Instrumental Analytical Chemistry, Faculty of Chemistry, University of Duisburg-Essen, Universitätsstr. 5, Essen, Germany;2. Department of Civil and Environmental Engineering Sciences, Technische Universität Darmstadt, Karolinenpl. 5, 64289 Darmstadt, Germany;3. Institut für Energie, und Umwelttechnik e. V. (IUTA, Institute of Energy and Environmental Technology), Bliersheimer Str. 58-60, 47229 Duisburg, Germany;4. Centre for Water and Environmental Research (ZWU), Universitätsstraße 5, 45141 Essen, Germany;5. IWW Water Centre, Moritzstraße 26, 45476 Mülheim an der Ruhr, Germany;1. Institute for Advanced Sustainability Studies (IASS), Berliner Straße 130, D-14467, Potsdam, Germany;2. Geography Department, Humbold University, Unter den Linden 6, D-10099, Berlin, Germany;3. Karlsruhe Institute of Technologies (KIT), Institute of Meteorology and Climate Research, Department of Atmospheric Environmental Research (IMK-IFU), Division of Regional Climate Systems, Campus Alpin, Kreuzeckbahnstr. 19, D-82467, Garmisch-Partenkirchen, Germany;4. IEK-8, Research Centre Jülich, D-52425, Jülich, Germany;5. Senate Department for Urban Development and the Environment, Brückenstraße 6, D-10179, Berlin, Germany;6. Chair of Forestry Economics and Forest Planning, Albert Ludwig University, Tennenbacher Str. 4, D-79106, Freiburg i. Br., Germany;7. Qatar Environment and Energy Research Institute (QEERI), Hamad Bin Khalifa University, Qatar Foundation, Doha, Qatar;1. Department of Chemistry and Biochemistry, University of Maryland College Park, College Park, MD 20742, USA;2. Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, MD 21250, USA;3. Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA;4. Department of Atmospheric and Oceanic Science, University of Maryland College Park, College Park, MD 20742, USA;5. Earth System Science Interdisciplinary Center, University of Maryland College Park, College Park, MD 20742, USA;6. School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA;7. Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA;8. Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80309, USA;9. Chemical Sciences Division, NOAA Earth System Research Laboratory, Boulder, CO 80305, USA;10. Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA;11. Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523, USA |
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| Abstract: | A reduced mechanism to describe the formation of ozone from VOC oxidation has been developed, using the master chemical mechanism (MCM v2) as a reference benchmark. The ‘common representative intermediates’ (CRI) mechanism treats the degradation of methane and 120 VOC using ca. 570 reactions of ca. 250 species (i.e. the emitted VOC plus an average of about one additional species per VOC). It thus contains only ca. 5% of the number of reactions and ca. 7% of the number of chemical species in MCM v2, providing a computationally economical alternative. The CRI mechanism contains a series of generic intermediate radicals and products, which mediate the breakdown of larger VOC into smaller fragments (e.g., formaldehyde), the chemistry of which is treated explicitly. A key assumption in the mechanism construction methodology is that the potential for ozone formation from a given VOC is related to the number of reactive (i.e., C–C and C–H) bonds it contains, and it is this quantity which forms the basis of the generic intermediate groupings. Following a small degree of optimisation, the CRI mechanism is shown to generate levels of ozone, OH, peroxy radicals, NO and NO2 which are in excellent agreement with those calculated using MCM v2, in simulations using a photochemical trajectory model applied previously to simulation of episodic ozone formation. The same model is used to calculate photochemical ozone creation potentials for 63 alkanes, alkenes, carbonyls and alcohols using both mechanisms. Those determined with the CRI mechanism show a variation from compound to compound which is remarkably consistent with that calculated with the detailed chemistry in MCM v2. This suggests that the CRI mechanism construction methodology is able to capture both the salient features of the ozone formation process in general, and how this varies from one VOC to another. |
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