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| Titel |
Gaseous pollutants in Beijing urban area during the heating period 2007–2008: variability, sources, meteorological, and chemical impacts |
| VerfasserIn |
W. Lin, X. Xu, B. Ge, X. 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 ; 11, no. 15 ; Nr. 11, no. 15 (2011-08-10), S.8157-8170 |
| Datensatznummer |
250009996
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| Publikation (Nr.) |
 copernicus.org/acp-11-8157-2011.pdf |
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| Zusammenfassung |
| Gaseous pollutants, NOy/NOx, SO2, CO, and O3, were
measured at an urban site in Beijing from 17 November 2007 to 15 March
2008. The average concentrations (with ± 1σ) of NO, NO2,
NOx, NOy, CO, SO2, and O3 were 29.0 ± 2.7 ppb,
33.7 ± 1.4 ppb, 62.7 ± 4.0 ppb, 72.8 ± 4.5 ppb, 1.99 ± 0.13 ppm,
31.9 ± 2.0 ppb, and 11.9 ± 0.8 ppb, respectively, with hourly maxima of
200.7 ppb, 113.5 ppb, 303.9 ppb, 323.2 ppb, 15.06 ppm, 147.3 ppb, and
69.7 ppb, respectively. The concentrations of the pollutants show "saw-toothed"
patterns, which are attributable mainly to changes in wind direction and
speed. The frequency distributions of the hourly mean concentrations of
NOy, SO2, CO, and O3 can all be decomposed in the two Lorentz
curves, with their peak concentrations representing background levels under
different conditions. During the observation period, the average ratio
NOx/NOy was 0.86 ± 0.10, suggesting that the gaseous pollutants
in Beijing in winter are mainly from local emissions. Data of O3,
NOz, and NOx/NOy indicate that photochemistry can take place
in Beijing even in the cold winter period. Based on the measurements of
O3, NOx, and NOy, ozone production efficiency (OPE) is
estimated to be in the range of 0–8.9 (ppb ppb−1) with the mean(± 1σ)
and median values being 1.1(± 1.6) and 0.5 (ppb ppb−1), respectively,
for the winter 2007–2008 in Beijing. This low OPE would cause a
photochemical O3 source of 5 ppb day−1, which is small but significant
for surface O3 in winter in Beijing. Downward transport of O3-rich
air from the free troposphere is the more important factor for the
enhancement of the O3 level in the surface layer, while high NO level
for the destruction of O3. The concentrations of SO2, CO, and
NOx are strongly correlated among each other, indicating that they are
emitted by some common sources. Multiple linear regression analysis is
applied to the concentrations of NOy, SO2, and CO and empirical
equations are obtained for the NOy concentration. Based the
equations, the relative contributions from mobile and point sources to
NOy is estimated to be 66 ± 30 % and 40 ± 16 %, respectively,
suggesting that even in the heating period, mobile sources in Beijing
contribute more to NOy than point sources. |
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