GAW Report No. 205 - IGAC Project

CHAPTER 2 - AFRICAparticles [Lamarque et al., 2010]. In 2005 and 2030, mean OC estimates are higher by at least afactor 2 in the regional inventory versus ACCMIP/RCP inventories. Such investigations still needfurther development. Indeed, a study on traffic intensity in Burkina Faso for the period 2001 to2020 has shown that vehicle inventories (cars and motorbikes) are evolving very rapidly from 2001to 2005 (Figure 4). In Lagos (Nigeria) also, more information is now available for roadtransportation with details on gasoline and diesel consumption by types of vehicles (motorcycles,light duty trucks, cars and heavy duty trucks). Such examples underline the urgent need to fullycollect regional fuel data in every West-African country.Figure 4 - Evolution of the number and composition of the pool motor vehicles in Burkina FasoThis work has also shown that all sources present in West Africa are not well characterized.That is the case for air transport and the small industries sector in Nigeria and, more importantlyand generally, in West Africa, emissions from unpaved roads, waste management and burning(such as electronic wastes) and processing of used lead batteries.2.2.3 Atmospheric pollutionUnexpected high pollutionUnexpected high pollution levels have been recently measured at traffic sites in WestAfrican megacities in the frame of IGAC DEBITS in Africa (IDAF) and Pollution des CapitalesAfricaines (POLCA) programmes. NO 2 and PM 2.5 concentrations have been found to be particularlyhigh in many cities (Figure 5 and 6), much higher than WHO norms [Liousse and Galy-Lacaux,2010; Doumbia et al., 2012]. This has been confirmed with more details in Dakar and Bamako. Forexample, Figure 7 shows the annual NO 2 , HNO 3 and SO 2 concentrations in Dakar and Bamako,which are much higher than at the rural site of Katibougou (Mali) [Yoboué et al., 2012]. Anotherexample given in Table 2 shows that black carbon pollution measured in West Africa is of thesame order of the rest of the world. Note that the high PM 2.5 concentrations reported in Doumbia etal. [2012] were also obtained in Guerreiro et al., [2005] and Dieme et al. [2012] in Dakar. Finally,studies in Ouagadougou in December 2007 and April 2010 and in Abidjan in January 2008 byLinden et al. [2012] and Kouassi et al. [2010] show urban centers, urban residential, suburbanresidential and industrial sites have exceptionally high concentrations of gases and particles. PM 10mass concentrations found in Ouagadougou, for example, also largely exceed WHO 2006 airquality guideline.33