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| Titel |
Depletion of gaseous polycyclic aromatic hydrocarbons by a forest canopy |
| VerfasserIn |
S.-D. Choi, R. M. Staebler, H. Li, Y. Su, B. Gevao, T. Harner, F. Wania |
| 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. 14 ; Nr. 8, no. 14 (2008-07-31), S.4105-4113 |
| Datensatznummer |
250006309
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| Publikation (Nr.) |
 copernicus.org/acp-8-4105-2008.pdf |
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| Zusammenfassung |
| Rapid uptake of gaseous polycyclic aromatic hydrocarbons (PAHs) by a forest
canopy was observed at Borden in Southern Ontario, Canada during bud break
in early spring 2003. High volume air samples were taken on 12 individual
days at three different heights (44.4, 29.1, and 16.7 m) on a scaffolding
tower and on the forest floor below the canopy (1.5 m). Concentrations of
PAHs were positively correlated to ambient temperature, resulting from
relatively warm and polluted air masses passing over the Eastern United
States and Toronto prior to arriving at the sampling site. An analysis of
vertical profiles and gas/particle partitioning of the PAHs showed that
gaseous PAHs established a concentration gradient with height, whereas
levels of particulate PAHs were relatively uniform, implying that only the
uptake of gaseous PAHs by the forest canopy was sufficiently rapid to be
observed. Specifically, the gaseous concentrations of intermediate PAHs,
such as phenanthrene, anthracene, and pyrene, during budburst and leaf
emergence were reduced within and above the canopy. When a gradient was
observed, the percentage of PAHs on particles increased at the elevations
experiencing a decrease in gas phase concentrations. The uptake of
intermediate PAHs by the canopy also led to significant differences in
gaseous PAH composition with height. These results are the most direct
evidence yet of the filter effect of forest canopies for gaseous PAHs in
early spring. PAH deposition fluxes and dry gaseous deposition velocities to
the forest canopy were estimated from the concentration gradients. |
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