GAW Report No. 205 - IGAC Project

CHAPTER 2 - AFRICAFigure 7 - Mean annual concentrations of NO2, HNO3 and SO2 at Dakar and Bamako traffic sites. Values for Katibougou(IDAF rural site) are added for comparison (Mali, 2008-2010), (Yoboué et al., 2013, in prep.)Table 2 - Black carbon concentrations at urban sites (adapted from Table 1 in Doumbia et al., 2012)Location Period BC (µg m -3 ) ReferencesDakar. Senegal June 08-July 09 5.7-15.4 Doumbia et al., 2012Bamako. Mali April 2008 19.2 ± 8.9 Doumbia et al., 2012Cotonou. Benin May 2005 4.9 ± 3.9 Doumbia et al., 2012Yaounde. Cameroon June-July 2004 2.4 ± 0.8Ouafo, Personal Com.August 2010 5.7 ± 2.3Paris. France Aug.-Oct. 97 10-20 Ruellan et Cachier, 2001Singapore. Asie Jan.-Dec. 00 3-14 Balasubranmanian et al., 2003Kanpur. India December 04 12.3 Tripathi et al., 2005Karachi. Pakistan Apr. 06-Apr. 07 2-15 Vincent et al., 2009Beijing. Chine Jan. 03- Aug. 04 1.2-16.3 Guinot et al., 2007Xi’an. Chine Sept 03-April 04 16.5 ± 9.8 Li et al., 2004Marylebone. Londres Oct-Dec 06 12.2 Green, 2007Spatial and temporal variability of gases and particulate concentrations in West AfricancitiesIn West-African cities, concentrations are spatially highly variable : this was observed forexample in Cotonou (Benin) and Bamako (Mali) during AMMA and POLCA programmesrespectively, from real time measurements of BC and CO in a taxi [Doumbia et al., 2012]. It wasalso noticed in Dakar (Sénégal) and in Bamako (Mali) with passive samplers for NO 2 and SO 2gases in the frame of POLCA [Yoboué et al., 2012]. Doumbia et al. [2012] show that differences bya factor of 5 may be found between different BC measurements downtown in Bamako, withmaximum and minimum levels respectively located near the markets and the Niger river. InBurkina Faso, Linden et al. [2012], Boman et al. [2009], Eliasson et al. [2009] and Arku et al.[2008] have observed high variability in PM concentrations at street level, in downtownOuagadougou, with maximum values near unpaved roads and vegetated areas. Also in this study,it is underlined that PM 1 and combustion pollutant concentrations are much higher at traffic sitesthan in suburban areas, whereas PM 10 concentrations are much higher in suburban zones, due tothe important relative impact of household fuel use in such areas.35