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| Titel |
Effect of isoprene emissions from major forests on ozone formation in the city of Shanghai, China |
| VerfasserIn |
F. Geng, X. Tie, A. Guenther, G. Li, J. Cao, P. Harley |
| 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 ; 11, no. 20 ; Nr. 11, no. 20 (2011-10-20), S.10449-10459 |
| Datensatznummer |
250010136
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| Publikation (Nr.) |
 copernicus.org/acp-11-10449-2011.pdf |
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| Zusammenfassung |
| Ambient surface level concentrations of isoprene (C5H8) were
measured in the major forest regions located south of Shanghai, China.
Because there is a large coverage of broad-leaved trees in this region, high
concentrations of isoprene were measured, ranging from 1 to 6 ppbv. A
regional dynamical/chemical model (WRF-Chem) is applied for studying the
effect of such high concentrations of isoprene on the ozone production in the
city of Shanghai. The evaluation of the model shows that the calculated
isoprene concentrations agree with the measured concentrations when the
measured isoprene concentrations are lower than 3 ppb, but underestimate the
measurements when the measured values are higher than 3 ppb. Isoprene was
underestimated only at sampling sites near large bamboo plantations, a high
isoprene source, indicating the need to include geospatially resolved bamboo
distributions in the biogenic emission model. The assessment of the impact of
isoprene on ozone formation suggests that the concentrations of peroxy
radicals (RO2) are significantly enhanced due to the oxidation of
isoprene, with a maximum of 30 ppt. However, the enhancement of RO2 is
confined to the forested regions. Because the concentrations of NOx
were low in the forest regions, the ozone production due to the oxidation of
isoprene (C5H8 + OH → → RO2 + NO
→ → O3) is low (less than 2–3 ppb h−1).
The calculation further suggests that the oxidation of isoprene leads to the
enhancement of carbonyls (such as formaldehyde and acetaldehyde) in the
regions downwind of the forests, due to continuous oxidation of isoprene in
the forest air. As a result, the concentrations of HO2 radical are
enhanced, resulting from the photo-disassociation of formaldehyde and
acetaldehyde. Because the enhancement of HO2 radical occurs in
regions downwind of the forests, the enhancement of ozone production
(6–8 ppb h−1) is higher than in the forest region, causing by higher
anthropogenic emissions of NOx. This study suggests that the
biogenic emissions in the major forests to the south of Shanghai have
important impacts on the levels of ozone in the city, mainly due to the
carbonyls produced by the continuous oxidation of isoprene in the forest air. |
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