Analysis of particulate pollution (PM10 and PM2.5 in the dry season in Abidjan and Korhogo (Cote d’Ivoire)

For the first time to our knowledge, the aim of this study is to investigate the spatial variation of atmospheric particulate matter concentrations in Abidjan and Korhogo (Cote d’Ivoire), as well as the relative contribution of PM2.5 to PM10 concentrations from measurement campaigns conducted in dry season in Abidjan and Korhogo. During these campaigns, twenty and fourteen sites were sampled respectively in Abidjan and Korhogo during two working days and one week-end day using portable active analysers. Spatial variations obtained by the IDW interpolation method show that PM10 concentrations are the highest in neighbourhoods without paved roads both in Abidjan and Korhogo whereas the highest PM2.5 concentrations are measured at sites influenced by traffic or wood in domestic fires. PM10 is composed of more than 50% PM2.5 particles in Abidjan, but less than 40% in Korhogo. These proportions are partly due to desert dust and road dust resuspension, which are higher in Korhogo than in Abidjan. The results also show the link between particulate concentrations and living standards in the neighbourhoods. Mean daily profiles of PM10 and PM2.5 concentrations are generally similar in Abidjan and Korhogo from site to site, with peaks in morning and in afternoon. However, in Abidjan, some sites have higher morning peaks than evening peaks, while in Korhogo, all concentration peaks are of the same amplitude. In Abidjan, such a difference may be explained by the fact that road traffic intensity is less spread out in the morning than in the evening. In Korhogo, both the use of firewood and dust resuspension increases aerosol concentrations, especially in the evening. In those conditions, a serious public health problem may be expected in both cities, an impact that we have evaluated by measuring PM2.5 oxidative capacity from DTT (Dithiothreitol) analyses in a few sites.