Arsenic, Cadmium, Copper and Lead Accumulation in Water, Sediments and Fish Species of Oueme River in Bonou

In order to evaluate the level of contamination of Oueme river with heavy metals and raise awareness of the local population regarding heavy metals pollution and its risks for health, assessment of toxic metals (cadmium, lead, copper and arsenic) was carried out in water, sediments and fish species samples of Oueme River in Bonou municipality located in the south of Benin. The study was carried out in 2011. Except for water, sediments and fish samples were mineralized before the analysis with atomic absorption spectrophotometer. Mean concentrations of heavy metals in water rose from ND to 1.0 mg/L in the case of lead and 4.41 to 10.23 mg/L for arsenic. In water, copper showed low concentrations in all locations and most of the values of cadmium were below the detectable limits. The mean concentrations in the sediments were: Cd (0.01 to 22.07 mg/Kg); Pb (2.73 to 20.12 mg/Kg); Cu (7.84 to 58.96 mg/Kg) and As (0.01 to 870.03 mg/Kg). In fish, the concentrations were expressed in mg/Kg. Clarias gariepinus is the most polluted species with high levels in Cd, Pb, Cu and As (2.31±1.44; 2.09±1.29; 15.10±6.34; 13.90±7.88), respectively. The mean concentrations of heavy metals recorded in Parachanna obstura are 1.34±0.65; 1.17±0.79; 2.72±2.19; 4.11±3.56, respectively for Cd, Pb, Cu and As, respectively. In Tilapia guineensis were recorded Cd: 1.53±0.97; Pb: 1.56±1.27; Cu: 0.91±0.58 and As: 7.56±2.41. The implication of this finding is that the consumption of water and fishes of Oueme River by man could lead to health hazards induced by heavy metals.