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<article language="en">
	<journal>
		<journal_title>Atmospheric Chemistry and Physics Discussions</journal_title>
		<journal_url>www.atmos-chem-phys-discuss.net</journal_url>
		<issn>1680-7367</issn>
		<eissn>1680-7375</eissn>
		<volume_number>9</volume_number>
		<issue_number>5</issue_number>
		<publication_year>2009</publication_year>
	</journal>
	<doi>10.5194/acpd-9-21011-2009</doi>
	<article_url>http://www.atmos-chem-phys-discuss.net/9/21011/2009/</article_url>
	<abstract_html>http://www.atmos-chem-phys-discuss.net/9/21011/2009/acpd-9-21011-2009.html</abstract_html>
	<fulltext_pdf>http://www.atmos-chem-phys-discuss.net/9/21011/2009/acpd-9-21011-2009.pdf</fulltext_pdf>
	<start_page>21011</start_page>
	<end_page>21039</end_page>
	<publication_date>2009-10-06</publication_date>
	<article_title content_type="html">What caused extreme ozone concentrations over Cotonou in December 2005?</article_title>
	<authors>
		<author numeration="1" affiliations="1,2,3">
			<name>A. Minga</name>
		</author>
		<author numeration="2" affiliations="1,2">
			<name>V. Thouret</name>
			<email>valerie.thouret@aero.obs-mip.fr</email>
		</author>
		<author numeration="3" affiliations="1,2">
			<name>M. Saunois</name>
		</author>
		<author numeration="4" affiliations="1,2">
			<name>C. Delon</name>
		</author>
		<author numeration="5" affiliations="1,2">
			<name>D. Serça</name>
		</author>
		<author numeration="6" affiliations="1,2">
			<name>C. Mari</name>
		</author>
		<author numeration="7" affiliations="1,2">
			<name>B. Sauvage</name>
		</author>
		<author numeration="8" affiliations="1,2,4">
			<name>A. Mariscal</name>
		</author>
		<author numeration="9" affiliations="1,2">
			<name>M. Leriche</name>
		</author>
		<author numeration="10" affiliations="1,2">
			<name>B. Cros</name>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">Université de Toulouse, UPS, LA (Laboratoire d&apos;Aérologie), 14 avenue Edouard Belin, 31400, Toulouse, France</affiliation>
		<affiliation numeration="2" content_type="html">CNRS, LA (Laboratoire d&apos;Aérologie), 31400 Toulouse, France</affiliation>
		<affiliation numeration="3" content_type="html">Faculté des Sciences, Université Marien NGouabi, BP 2702 Brazzaville, Congo</affiliation>
		<affiliation numeration="4" content_type="html">now at: LGIT (Laboratoire de Géophysique Interne et Technophysique) , BP 53, 38 041 Grenoble,  Cedex 09, France</affiliation>
	</affiliations>
	<abstract content_type="html">This paper reports the first record of extreme ozone measurement 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 ppbv at 1 km
      altitude. Retroplumes from the Flexpart model show that the air masses
      sampled at 1 km over Cotonou on this day come from the burning
      area situated north-east of Cotonou and pass 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.
&lt;br&gt;&lt;br&gt;
      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 ppbv 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 ppbv of VOCs combined with 35–80 ppb of
      NO&lt;sub&gt;x&lt;/sub&gt; 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 explains the 295 ppbv ozone maximum measured over
      Cotonou, downwind of Lagos.</abstract>
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