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| Titel |
Atmospheric OH reactivities in the Pearl River Delta – China in summer 2006: measurement and model results |
| VerfasserIn |
S. Lou, F. Holland, F. Rohrer, K. Lu, B. Bohn, T. Brauers, C. C. Chang, H. Fuchs, R. Häseler, K. Kita, Y. Kondo, X. Li, M. Shao, L. Zeng, A. Wahner, Y. Zhang, W. Wang, A. Hofzumahaus |
| 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 ; 10, no. 22 ; Nr. 10, no. 22 (2010-11-30), S.11243-11260 |
| Datensatznummer |
250008919
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| Publikation (Nr.) |
 copernicus.org/acp-10-11243-2010.pdf |
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| Zusammenfassung |
| Total atmospheric OH reactivities (kOH) have been measured as
reciprocal OH lifetimes by a newly developed instrument at a rural site in
the densely populated Pearl River Delta (PRD) in Southern China in summer
2006. The deployed technique, LP-LIF, uses laser flash photolysis (LP) for
artificial OH generation and laser-induced fluorescence (LIF) to measure the
time-dependent OH decay in samples of ambient air. The reactivities observed
at PRD covered a range from 10 s−1 to 120 s−1, indicating a large
load of chemical reactants. On average, kOH exhibited a pronounced
diurnal profile with a mean maximum value of 50 s−1 at daybreak and
a mean minimum value of 20 s−1 at noon. The comparison of reactivities
calculated from measured trace gases with measured kOH reveals a
missing reactivity of about a factor of 2 at day and night. The reactivity explained
by measured trace gases was dominated by anthropogenic pollutants (e.g., CO,
NOx, light alkenes and aromatic hydrocarbons) at night, while it was strongly
influenced by local, biogenic emissions of isoprene during the day.
Box model calculations initialized by measured parameters reproduce the observed
OH reactivity well and suggest that the missing reactivity is contributed by
unmeasured, secondary chemistry products (mainly aldehydes and ketones) that
were photochemically formed by hydrocarbon oxidation. Overall, kOH
was dominated by organic compounds, which had a maximum contribution of 85%
in the afternoon. The paper demonstrates the usefulness of direct reactivity
measurements, emphasizes the need for direct measurements of oxygenated
organic compounds in atmospheric chemistry studies, and discusses uncertainties
of the modelling of OVOC reactivities. |
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