Determination of Heavy Metals in Water and Some Selected Fish Species in River Ofin, Ado-Ekiti

Abstract

This study investigates the physico-chemical parameters of water and quantification of heavy metals (zinc, copper, lead, chromium and cadmium) in the gill, liver and flesh of Oreochromis niloticus, Hemichromis fasciatus, Sarotherodon galilaeus and Oreochromis aureus in River Ofin, fortnightly at two sampling points (Point 1- upper stream and Point 2- downstream) from October to December, 2019, using Atomic Absorption Spectrophotometer by the calibration plot method. Three processes were involved; standard preparation, equipment calibration and sample analysis Mean values of the parameters were; Temperature; 27.18±0.15°C, pH; 7.06±0.10, Turbidity; 9.0±0.94 Ntu, Conductivity; 236.10±0.53 µs/cm, DO; 6.67±0.16 mg/l and BOD; 6.87±0.81 mg/l.  Mean values of the concentration of the heavy metals in the water were; Zn; 0.31±0.01 mg/l, Cu; 0.26±0.01 mg/l, Pb; 0.13±0.01 mg/l, (Pb in water was higher than the highest value 0.12±0.003 (P≤0.05) recorded in fish) Cr; 0.12±0.01 mg/l and Cd; 0.002±0.001 mg/l while the concentration of heavy metals in fish varies from species to species as it displayed species differences.  Heavy metal concentration in water is in this order: Zn>Cu>Pb>Cr>Cd. The presence of Zn, Cu, Pb, Cr and Cd were confirmed in all the fish species expect Cd that was discovered only in the gill of S. galilaeus. Metals in fish gills is in the order of Zn>Cu>Pb>Cr>Cd for the four species, for liver and flesh/muscle in O. niloticus and H fasciatus it is Cu>Zn>Cr.  Pb was detected only in the gill of O. niloticus, the liver and flesh lack Pb. Other fish species parts showed different Pb concentrations with the highest value (0.12±0.003) recorded in the gill of O. aureus. This study showed that Cd, Cr, Zn, and Cu were in the maximum acceptable limit range (Cr; 0.44, Zn; 5.04, Cu; 1.37 and Cd; 0.20) while Pb in water and fish was slightly above the maximum acceptable limit range (Pb; 0.04) by FAO/WHO. Lead poisoning is ranked among the most common environmental health hazard even at low levels. Periodic monitoring by relevant regulatory authorities is recommended to ensure safety of the water and fish consuming populace.