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| Titel |
Variations of ground-level O3 and its precursors in Beijing in summertime between 2005 and 2011 |
| VerfasserIn |
Q. Zhang, B. Yuan, M. Shao, X. Wang, S. Lu, K. Lu, M. Wang, L. Chen, C.-C. Chang, S. C. Liu |
| 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 ; 14, no. 12 ; Nr. 14, no. 12 (2014-06-20), S.6089-6101 |
| Datensatznummer |
250118822
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| Publikation (Nr.) |
 copernicus.org/acp-14-6089-2014.pdf |
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| Zusammenfassung |
| Elevated ground-level ozone (O3), reflecting
atmospheric oxidative capacity, are of increasing concern. High levels of
total oxidants (Ox= O3 + NO2) have been persistently
observed as a feature of Beijing's air pollution. Beijing is a well-known
megacity requiring the enforcement of stringent air quality controls as
rapid economic growth continues. To evaluate the effect of air quality
controls in recent years, ground-based on-line measurements at an urban site
were conducted in summer and the variations in O3 with simultaneous
changes in NOx and volatile organic compounds (VOCs) between 2005 and
2011 were analyzed. Both NOx and total VOCs in Beijing decreased over
the study period, 1.4 ppbv yr−1 and 1.6 ppbv yr−1, respectively. However, VOCs
reactivity, in terms of OH loss rate, showed an indistinct statistical trend
due to unsteady variations from naturally emitted isoprene, though some
anthropogenic species showed decreasing trends, such as pentane, benzene
and toluene. Meanwhile, daytime average O3 increased rapidly at an
annual rate of 2.6 ppbv yr−1, around 5% yr−1 between 2005 and 2011.
Considering the influence of NO titration effect and elevated regional ozone
background in the North China Plain (NCP), the main reason for such an
increase in oxidants was subject to "local" photochemistry. A simplified
model was used to evaluate the effect of changes in the levels of ozone
precursors on ozone production. We found that between 2001 and 2006, the
production rate of total oxidants, P(Ox) increased rapidly due to
increased VOC levels and decreasing NO2, while from 2006 to 2011
P(Ox) remained high, though decreased slightly as a consequence of the
decrease in both VOC reactivity (−5% yr−1) and NOx (−4% yr−1).
Observations have shown that Beijing's efforts to control air pollution were
somehow effective in cutting ozone precursors, but still left higher
ground-level ozone. We surmised that it resulted from potential
contributions from OVOCs and regional transport near Beijing. Therefore,
Beijing needs deeper cooperation with adjacent provinces to control ozone
pollution together. To impel this kind of joint prevention and control
program, ground-level ozone should become a mandatory index for air quality
management, and a faster reduction of VOCs, especially reactive VOCs, in
urban areas, should coordinate with national NOx emission control
programs. |
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