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| Titel |
What caused extreme ozone concentrations over Cotonou in December 2005? |
| VerfasserIn |
A. Minga, V. Thouret, M. Saunois, C. Delon, D. Serça, C. Mari, B. Sauvage, A. Mariscal, M. Leriche, B. Cros |
| 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 ; 10, no. 3 ; Nr. 10, no. 3 (2010-02-01), S.895-907 |
| Datensatznummer |
250008019
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| Publikation (Nr.) |
 copernicus.org/acp-10-895-2010.pdf |
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| Zusammenfassung |
This paper reports the first record of extreme ozone measurements in
Africa. As part of the AMMA program, the ozone vertical profile
recorded on 20 December over Cotonou presents exceptionally high ozone
concentrations with up to 295 ppb at 1 km
altitude. Retroplumes from the Flexpart model show that the air masses
sampled at 1 km over Cotonou on this day came from the burning
area situated north-east of Cotonou and passed over Lagos, Nigeria,
which is highly impacted by urban pollution. We used the Master
Mechanism box model to simulate the chemical composition of the plume
during its transit.
We find that neither the biomass burning emissions of ozone precursors
nor additional urban emissions from Lagos are high enough to simulate
more than 120–150 ppb of ozone. The only way to reach almost
300 ppb of ozone within a few hours is to feed the air mass
with large amounts of reactive VOCs as those recorded in the vicinity
of petrochemical area. Sensitivity tests show that
250–600 ppb of VOCs combined with 35–80 ppb of
NOx allow the ozone concentrations to be higher than
250 ppb. Nigeria is the first African country with gas
extraction and petrochemical industries, and petrochemical explosions
frequently happen in the vicinity of Lagos. The hypothesis of
a petrochemical explosion in this area is the most likely scenario
which could explain the 295 ppb ozone maximum measured over
Cotonou, downwind of Lagos. |
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