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| Titel |
Investigation of aromatic compound degradation under atmospheric conditions in the outdoor simulation chamber SAPHIR |
| VerfasserIn |
Sascha Nehr, Birger Bohn, Franz Rohrer, Ralf Tillmann, Robert Wegener, Hans-Peter Dorn, Rolf Häseler, Theo Brauers, Andreas Wahner |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250042160
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| Zusammenfassung |
| Ozone is produced in the lower troposphere by the OH-initiated photooxidation of volatile
organic compounds in the presence of NOx. Aromatic hydrocarbons from anthropogenic
sources are a major contributor to the OH-reactivity and thus to ozone formation in urban
areas [1]. Moreover, their degradation leads to formation of secondary organic aerosol.
Aromatic compounds are therefore important trace constituents with regard to air
quality.
We will present the results of photooxidation experiments which were conducted in the
atmospheric simulation chamber SAPHIR at Forschungszentrum Jülich. The experiments
were designed to investigate the degradation mechanisms of benzene and p-xylene, which are
among the most abundant aromatics in urban air samples. Benzene and p-xylene were
selected because they have high structural symmetry which limits the number of
potential isomers of secondary products. The experiments were performed under
low-NOx-conditions (-¤ 2 ppb). SAPHIR was equipped with instruments for the
measurement of the parent aromatics and their major oxidation products, OH radicals,
important radical precursors (O3, HONO, HCHO), photolysis frequencies and particulate
matter.
As shown in previous studies, simulation chamber data from the photooxidation of aromatics
cannot be explained satisfactorily with current photochemistry mechanisms. For example the
MCMv3.1 tends to overestimate the ozone-concentration and to underestimate the
OH-concentration [2]. In this study, we will contrast model calculations with experimental
results to check if similar discrepancies can be observed in SAPHIR and how they
can be resolved. Based on the results of this preparatory study, further simulation
chamber experiments with special emphasis on the radical budget are scheduled in
2010.
References:
[1] J. G. Calvert, R. Atkinson, K.H. Becker, R.M. Kamens, J.H. Seinfeld, T.J. Wallington, G.
Yarwood: The mechanisms of atmospheric oxidation of aromatic hydrocarbons, Oxford
University Press, 2002
[2] C. Bloss, V. Wagner, M.E. Jenkin, R. Volkamer, W.J. Bloss, J.D. Lee, D.E. Heard, K.
Wirtz, M. Martin-Reviejo, G. Rea, J.C. Wenger, M.J. Pilling: Development of a detailed
chemical mechanism (MCMv3.1) for the atmospheric oxidation of aromatic hydrocarbons,
Atmos. Chem. Phys., 5, 641-664, 2005 |
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