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| Titel |
Traffic restrictions in Beijing during the Sino-African Summit 2006: aerosol size distribution and visibility compared to long-term in situ observations |
| VerfasserIn |
Y. F. Cheng, J. Heintzenberg, B. Wehner, Z. J. Wu, H. Su, M. Hu, J. T. Mao |
| 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 ; 8, no. 24 ; Nr. 8, no. 24 (2008-12-17), S.7583-7594 |
| Datensatznummer |
250006520
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| Publikation (Nr.) |
 copernicus.org/acp-8-7583-2008.pdf |
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| Zusammenfassung |
| Based on the long-term in-situ observations of aerosol particle number size
distributions and meteorological parameters, the measures of traffic
restriction during the Sino-African Summit (4–6 November 2006) in Beijing,
China have been found to be efficient in reducing the number concentration
of aerosol particles, in particular Aitken and accumulation mode particles,
and in improving the visibility when local emissions dominated. The
influence of traffic restrictions on the particle concentrations differed
for different particle sizes. More significant effects on fine particles
with diameters ranging from 40 to 500 nm have been found. Based on
statistical analysis of long-term observations, under comparable weather
conditions, the number concentrations of the particles in Aitken and
accumulation modes seemingly were reduced by 20–60% when the traffic
restrictions were in place. This change may be mainly due to the reduction
of secondary particle contributions. However, it is worth to notice that the reduction of 60% might overestimate the effect of the measures of traffic control, due to the inherent data shortage with very high wind speeds in the comparison data population.
Our size-dependent aerosol data also
indicate that measures led to reductions in particulate air pollution in the
optically most important diameter range, whereas further vehicle restriction
measures might lead to an increase in ultrafine particle formation if the
condensational sink further decreased. Assuming that there were no traffic
restrictions and with normal levels of the vehicle emissions, the
visibilities during the Summit would have been lower by about 20–45%. The
fact that over 95% cases with visibility range lower than 5 km during
2004 to 2007 occurred when the local wind speed was lower than 3 m s−1
may suggest that the importance of the emission restrictions is highest when
the wind speed is lower than 3 m s−1, concerning the improvement of
serious low visibility situations in Beijing. |
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