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| Titel |
Sources and photochemistry of volatile organic compounds in the remote atmosphere of western China: results from the Mt. Waliguan Observatory |
| VerfasserIn |
L. K. Xue, T. Wang, H. Guo, D. R. Blake, J. Tang, X. C. Zhang, S. M. Saunders, W. X. Wang |
| 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 ; 13, no. 17 ; Nr. 13, no. 17 (2013-09-02), S.8551-8567 |
| Datensatznummer |
250085658
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| Publikation (Nr.) |
 copernicus.org/acp-13-8551-2013.pdf |
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| Zusammenfassung |
| The chemistry of the natural atmosphere and the influence by long-range
transport of air pollution are key issues in the atmospheric sciences. Here
we present two intensive field measurements of volatile organic compounds
(VOCs) in late spring and summer of 2003 at Mt. Waliguan (WLG,
36.28° N, 100.90° E, 3816 m a.s.l.), a baseline station
in the northeast part of the Qinghai-Tibetan Plateau. Most VOC species exhibited
higher concentrations in late spring than in summer. A typical diurnal
variation was observed with higher nighttime levels, in contrast to results
from other mountainous sites. Five different air masses were identified from
backward trajectory analysis showing distinct VOC speciation. Air masses
originating from the central Eurasian continent contained the lowest VOC
levels compared to the others that were impacted by anthropogenic emissions
from China and the Indian subcontinent. A photochemical box model based on
the Master Chemical Mechanism (version 3.2) and constrained by a full suite
of measurements was developed to probe the photochemistry of atmosphere at
WLG. Our results show net ozone production from in situ photochemistry during
both late spring and summer. Oxidation of nitric oxide (NO) by the
hydroperoxyl radical (HO2) dominates the ozone production relative to
the oxidation by the organic peroxy radicals (RO2), and the ozone is
primarily destroyed by photolysis and reactions with the HOx
(HOx = OH + HO2) radicals. Ozone photolysis is the
predominant primary source of radicals (ROx = OH + HO2 + RO2), followed by the photolysis of secondary
oxygenated VOCs and hydrogen peroxides. The radical losses are governed by
the self and cross reactions among the radicals. Overall, the findings of the
present study provide insights into the background chemistry and the impacts
of pollution transport on the pristine atmosphere over the Eurasian
continent. |
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