Monitoring of Atmospheric Pollutant Concentrations in the City of Dakar, Senegal

Abstract

The lack of data on air quality monitoring and neglected and overlooked pol-lutant emissions in the transportation and industrial sectors are motives for the government of Senegal to set up, in 2009, an air quality management cen-ter, the CGQA (Centre de Gestion de la Qualité de l’Air). Air quality moni-toring at CGQA deals with mainly six pollutants: carbon monoxide (CO), ni-trogen oxides (NOx) (with nitrogen dioxide (NO2) and nitrogen monoxide (NO)), sulfur dioxide (SO2), ground-level ozone (O3), Benzene-Toluene-Xylenes (BTX), and particulate matters (PM) with diameters less than 10 µm (PM10) and 2.5 µm (PM2.5). The concentration levels of gaseous pollutants (CO, O3, NO2 and SO2) in the city generally remain below the limit value set by the WHO (World Health Organization). However, particulate matters (PM10 and PM2.5) are the most important pollutants observed in Dakar, they far exceed the annual thresholds set by the WHO and the national standard (NS 05-062). This situation results in an Air Quality Index (AQI) around bad and very bad during the dry season (November to May) and good to moderate during the rainy season (June to October). The concentrations of PM10 and PM2.5 vary respectively from 120 to 180 µg∙m−3 and from 25 to 48 µg∙m−3. The average concentrations of pollutants therefore vary from one area to another and depending on the location of the air quality monitoring station (near industrial sites, traffic, etc.).