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| Titel |
Evaluation of 1,3,5 trimethylbenzene degradation in the detailed tropospheric chemistry mechanism, MCMv3.1, using environmental chamber data |
| VerfasserIn |
A. Metzger, J. Dommen, K. Gaeggeler, J. Duplissy, A. S. H. Prévôt, J. Kleffmann, Y. Elshorbany, A. Wisthaler, U. Baltensperger |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 8, no. 21 ; Nr. 8, no. 21 (2008-11-13), S.6453-6468 |
| Datensatznummer |
250006440
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| Publikation (Nr.) |
 copernicus.org/acp-8-6453-2008.pdf |
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| Zusammenfassung |
The degradation mechanism of 1,3,5-trimethyl- benzene (TMB) as implemented in
the Master Chemical Mechanism version 3.1 (MCM) was evaluated using data
from the environmental chamber at the Paul Scherrer Institute. The results
show that the MCM provides a consistent description of the photo-oxidation
of TMB/NOx mixtures for a range of conditions. In all cases the
agreement between the measurement and the simulation decreases with
decreasing VOC-NOx ratio and in addition with increasing precursor
concentration. A significant underestimation of the decay rate of TMB and
thus underestimation of reactivity in the system, consistent with results
from previous appraisals of the MCM, was observed.
Much higher nitrous acid (HONO) concentrations compared to simulations and
expected from chamber characterization experiments were measured during
these smog chamber experiments. A light induced NO2 to HONO conversion
at the chamber walls is suggested to occur. This photo-enhanced NO2 to
HONO conversion with subsequent HONO photolysis enhances the reactivity of
the system. After the implementation of this reaction in the model it
describes the decay of TMB properly. Nevertheless, the model still
over-predicts ozone at a later stage of the experiment. This can be
attributed to a too slow removal of NO2. It is also shown that this
photo-enhanced HONO formation is not restricted to TMB photo-oxidation but
also occurs in other chemical systems (e.g. α-pinene). However, the
influence of HONO as a source of OH radicals is less important in these more
reactive systems and therefore the importance of the HONO chemistry is less
obvious. |
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