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| Titel |
Measurements of ozone and its precursors in Beijing during summertime: impact of urban plumes on ozone pollution in downwind rural areas |
| VerfasserIn |
J. Xu, J. Z. Ma, X. L. Zhang, X. B. Xu, X. F. Xu, W. L. Lin, Y. Wang, W. Meng, Z. Q. Ma |
| 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. 23 ; Nr. 11, no. 23 (2011-12-07), S.12241-12252 |
| Datensatznummer |
250010248
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| Publikation (Nr.) |
 copernicus.org/acp-11-12241-2011.pdf |
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| Zusammenfassung |
| Sea-land and mount-valley circulations are the dominant mesoscale synoptic
systems affecting the Beijing area during summertime. Under the influence of
these two circulations, the prevailing wind is southwesterly from afternoon
to midnight, and then changes to northeasterly till forenoon. In this study,
surface ozone (O3), carbon monoxide (CO), nitric oxide (NO), nitrogen
dioxide (NO2), nitrogen oxide (NOx) and non-methane hydrocarbons
(NMHCs) were measured at four sites located along the route of prevailing
wind, including two upwind urban sites (Fengtai "FT" and Baolian "BL"), an
upwind suburban site (Shunyi "SY") and a downwind rural site (Shangdianzi
"SDZ") during 20 June–16 September 2007. The purpose is to improve our
understanding of ozone photochemistry in urban and rural areas of Beijing
and the influence of urban plumes on ozone pollution in downwind rural
areas. It is found that ozone pollution was synchronism in the urban and
rural areas of Beijing, coinciding with the regional-scale synoptic
processes. Due to the high traffic density and local emissions, the average
levels of reactive gases NOx and NMHCs at the non-rural sites were much
higher than those at SDZ. The level of long-lived gas CO at SDZ was
comparable to, though slightly lower than, at the urban sites. We estimate
the photochemical reactivity (LOH and the ozone formation potential
(OFP) in the urban (BL) and rural (SDZ) areas using measured CO and NMHCs.
The OH loss rate coefficient (LOH by total NMHCs at the BL and SDZ
sites are estimated to be 50.7 s-1 and 15.8 s-1, respectively.
While alkenes make a major contribution to the LOH, aromatics dominate
OFP at both urban and rural sites. With respect to the individual species, CO
has the largest ozone formation potential at the rural site, and at the
urban site aromatic species are the leading contributors. While the O3
diurnal variations at the four sites are typical for polluted areas, the
ozone peak values are found to lag behind one site after another along the
route of prevailing wind from SW to NE. Intersection analyses of trace gases
reveal that polluted air masses arriving at SDZ were more aged with both
higher O3 and Ox concentrations than those at BL. The results
indicate that urban plume can transport not only O3 but its precursors,
the latter leading more photochemical O3 production when being mixed
with background atmosphere in the downwind rural area. |
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