Ahmed Dame MBOUP^1,, Alassane THIAM², Abib NDIAYE³

The objective of this study is to evaluate heavy metals and their origins in raw water from the Senegal River Delta, the main source of water for local populations. These metals cause waterborne diseases, particularly bilharzia in humans and liver fluke in animals, despite the fact that the OMVS has begun installing water purification and treatment units to protect the health of users. To carry out this study, two campaigns of in-situ measurements of physical parameters such as temperature (°C), pH, and electrical conductivity (µS/cm), followed by sampling, were conducted on December 22, 2023 (just after the rainy season) at Rawette, Ronkh, and Ross Béthio sites, then on January 9, 2025, at Mboubène bridge, Kassak, and Mboundoum sites. For the first campaign, three (03) surface water samples were taken, one (01) per site, and for the second campaign, three (03) samples were taken, one (01) per site. The six samples were packaged in 500 mL polyethylene bottles and transported in a cooler to the CERES LOCUSTOX laboratory in Dakar for physical and chemical analysis (turbidity, major ions, and heavy metals). The results obtained show values of 127 NTU, in accordance with the (150 NTU) for the Ross Béthio site, and high values of 240 and 320 NTU respectively for Rawette and Ronkh sites. For the second campaign, the turbidity values comply with the above standard (Mboubène 27.74 NTU and Mboundoum 70.28 NTU), except for Kassak site with a value of 164 NTU. For heavy metals, copper (Cu) and arsenic (As) showed minimum concentrations of 0 and maximum concentrations ranging from 0.194 to 0.0162 mg/L, respectively, following a spatio-temporal variation that complied with the values established by the standard. Lead (Pb) was detected in all samples during the two campaigns, with concentrations ranging from 0.029 to 0.317 mg/L, exceeding the threshold values established by the standard. Only cadmium (Cd) and zinc (Zn) were completely absent in both campaigns. These metals probably originate from agro-industrial activities upstream of the study sites and gold panning, motor pump repairs, and runoff during the rainy season. This contamination could be avoided by treating waste in accordance with the waste standards in force in Senegal.

Heavy metals, SEQ, Waterborne diseases, Senegal River Delta