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| Titel |
How to improve the air quality over megacities in China: pollution characterization and source analysis in Shanghai before, during, and after the 2010 World Expo |
| VerfasserIn |
K. Huang, G. Zhuang, Y. Lin, Q. Wang, J. S. Fu, Q. Fu, T. Liu, C. Deng |
| 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. 12 ; Nr. 13, no. 12 (2013-06-20), S.5927-5942 |
| Datensatznummer |
250018711
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| Publikation (Nr.) |
 copernicus.org/acp-13-5927-2013.pdf |
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| Zusammenfassung |
| Three field campaigns were conducted before, during, and after the 2010 World
Expo in Shanghai, aiming to understand the response of secondary aerosol
components to both control measures and human activities. In spring,
PM2.5 (particulate matter) averaged 34.5 ± 20.9 μg m−3 with a severe
pollution episode influenced by a floating dust originating from northwestern
China on 26–28 April, right before the opening of the expo. With the
approaching expo a significant increasing trend of SNA (SO42−,
NO3−, and NH4+) concentrations was observed from 22 April to
2 May, attributed to the enhanced human activities. Nitrate had the most
significant daily increasing rate of 1.1 μg m−3d−1 due
to enhanced vehicle emission. In summer, two intensive pollution episodes
were found to be a mixed pollution of SNA with biomass burning due to loose
control of post-harvest straw burning. In the autumn phase of the expo, before
the closing of the expo (20–30 October), the air quality over Shanghai was
much better than ever before. However, the air quality rapidly plummeted as
soon as the expo was announced closed. SNA increased 3–6 fold to be 42.1 and
68.2 μg m−3 on 31 October and 1 November, respectively, as
compared to 20–30 October. Of which, nitrate increased most ~5–8
fold, indicating the serious impact from enhanced vehicle emission. Compared
to the spring and summer of 2009, NO3− increased 12–15% while
SO42− showed reductions of 15–30%. Continuous desulfurization
of SO2 emission from power plants in recent years was responsible for
the lowered SO42−, while increased traffic emission from the
tremendous number of expo visitors was the major contributor to the increased
NO3−. Compared to the autumn of 2009, all the ion components
increased in 2010, owing to the lifting of emission control measures after
the expo. SO42− was found
least increased while NO3− and
Ca2+ had tremendous increases of 150 and 320%, respectively.
The anthropogenic Ca as a tracer from construction dust increased from
2.88 ± 1.85 μg m−3 during the expo to
6.98 ± 3.19 μg m−3 during the post-expo period,
attributed to the resumption of construction works after the expo. The lack
of successive control measures with the loose regulations after the expo were
responsible for this jump of the bad quality. The ratio of
NO3−/SO42− in
PM2.5 over Shanghai had a significant
increasing trend from ~0.3 in the early 2000s to more than 1.0 in 2010,
indicating the increasing role of mobile sources. Reducing NOx
emission will be China's priority in the future in order to improve the air quality
over the megacities. In addition, lowering mineral aerosol components (e.g.,
Ca2+) was also demonstrated to be beneficial for alleviating air
pollution in China. This study demonstrated that stringent emission control
measures aiming at mega-events in China could achieve positive benefits on
improving the air quality in a short term. However, persistent efforts of
curbing the anthropogenic emission remain a long way to go in the future. |
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