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| Titel |
Atmospheric photochemistry of aromatic hydrocarbons: OH budgets during SAPHIR chamber experiments |
| VerfasserIn |
S. Nehr, B. Bohn, H.-P. Dorn, H. Fuchs, R. Häseler, A. Hofzumahaus, X. Li, F. Rohrer, R. Tillmann, A. Wahner |
| 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 ; 14, no. 13 ; Nr. 14, no. 13 (2014-07-04), S.6941-6952 |
| Datensatznummer |
250118872
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| Publikation (Nr.) |
 copernicus.org/acp-14-6941-2014.pdf |
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| Zusammenfassung |
| Current photochemical models developed to simulate the atmospheric
degradation of aromatic hydrocarbons tend to underestimate OH radical
concentrations. In order to analyse OH budgets, we performed experiments with
benzene, toluene, p-xylene and 1,3,5-trimethylbenzene in the atmosphere
simulation chamber SAPHIR. Experiments were conducted under low-NO conditions
(typically 0.1–0.2 ppb) and high-NO conditions (typically
7–8 ppb), and starting concentrations of 6–250 ppb of
aromatics, dependent on OH rate constants. For the OH budget analysis a
steady-state approach was applied in which OH production and destruction rates
(POH and DOH) have to be equal. The POH
were determined from measurements of HO2, NO, HONO, and O3
concentrations, considering OH formation by photolysis and recycling from
HO2. The DOH were calculated from measurements of the OH
concentrations and total OH reactivities. The OH budgets were determined from
DOH/POH ratios. The accuracy and reproducibility of the
approach were assessed in several experiments using CO as a reference
compound where an average ratio DOH/POH = 1.13 ± 0.19
was obtained. In experiments with aromatics, these ratios ranged within
1.1–1.6 under low-NO conditions and 0.9–1.2 under high-NO conditions. The
results indicate that OH budgets during photo-oxidation experiments with
aromatics are balanced within experimental accuracies. Inclusion of a
further, recently proposed OH production via HO2 + RO2
reactions led to improvements under low-NO conditions but the differences
were small and insignificant within the experimental errors. |
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