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| Titel |
The transport of atmospheric NOx and HNO3 over Cape Town |
| VerfasserIn |
B. J. Abiodun, A. M. Ojumu, S. Jenner, T. V. Ojumu |
| 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. 2 ; Nr. 14, no. 2 (2014-01-20), S.559-575 |
| Datensatznummer |
250118292
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| Publikation (Nr.) |
 copernicus.org/acp-14-559-2014.pdf |
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| Zusammenfassung |
Cape Town, the most popular tourist city in Africa, usually experiences air
pollution with unpleasant odour in winter. Previous studies have associated
the pollution with local emission of pollutants within the city. The present
study examines the transport of atmospheric pollutants (NOx and
HNO3) over South Africa and shows how the transport of pollutants from
the Mpumalanga Highveld, a major South African industrial area, may
contribute to the pollution in Cape Town. The study analysed observation data
(2001–2008) from the Cape Town air-quality network and simulation data
(2001–2004) from a regional climate model (RegCM) over southern Africa. The
simulation accounts for the influence of complex topography, atmospheric
conditions, and atmospheric chemistry on emission and transport of pollutants
over southern Africa. Flux budget analysis was used to examine whether Cape
Town is a source or sink for NOx and HNO3 during the extreme
pollution events.
The results show that extreme pollution events in Cape Town are associated
with the lower level (surface – 850 hPa) transport of NOx from
the Mpumalanga Highveld to Cape Town, and with a tongue of high concentration
of HNO3 that extends from the Mpumalanga Highveld to Cape Town along the
south coast of South Africa. The prevailing atmospheric conditions during the
extreme pollution events feature an upper-level (700 hPa) anticyclone over
South Africa and a lower-level col over Cape Town. The anticyclone induces a
strong subsidence motion, which prevents vertical mixing of the pollutants
and caps high concentration of pollutants close to the surface as they are
transported from the Mpumalanga Highveld toward Cape Town. The col
accumulates the pollutants over the city. This study shows that Cape Town can
be a sink for the NOx and HNO3 during extreme pollution
events and suggests that the accumulation of pollutants transported from
other areas (e.g. the Mpumalanga Highveld) may contribute to the air
pollution in Cape Town. |
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