Assessment of Heavy Metals in Surface Water of the Ikpoba Reservoir, Benin City, Nigeria

The present study was carried out to determine the impact of some heavy metals namely, Cd, Mn, Cu, Fe, Pb, Ni, Zn and Cr on the water quality of the Ikpoba reservoir Benin City, Nigeria, with a view to safeguard public health. Water samples were randomly collected from four stations within the Reservoir from August 2005 to December 2005 and were analyzed for heavy metal concentrations using Atomic Absorption Spectrometric technique. The mean concentration of these metals were, Cd, (0.02mg/l), Mn(0.026mg/l), Cu(0.24mg/l), Fe(5.60mg/l), Pb(0.07mg/l), Ni(0.03mg/l), Zn(116.59mg/l) and Cr(0.033mg/l). The mean concentrations of Cd, Fe, Pb, Ni and Zn, exceeded the World Health Organization (WHO) maximum permissible level for drinking water.Keywords: water quality, heavy metals, Ikpoba reservoi

Trace metals in some benthic fishes of the Ikpoba river dam, Benin City, Nigeria

The concentration of iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), nickel (Ni), cadmuim (Cd), chromium (Cr) and lead (Pb) in two benthic fish species (Mormyrops deliciosus and Mormyrus macrophthalmus netted from two locations (Okhoro and Low lift pump sites) on the Ikpoba River Dam, Benin City, Nigeria were determined using atomic absorption spectrometric technique. Sediment and water samples were also analysed for their trace metal concentrations. The range of trace metal concentrations (μg/g) in the fishes which is the focus of the study were as follows: Fe = 39.60 - 41.07 μg/g, Cu = 5.04 - 8.04 μg/g, Mn = 0.38 - 1.34 μg/g, Zn = 17.01 - 23.16μg/g, Ni = 0.24 - 0.48 μg/g, Cd = 0.79 - 0.98 μg/g, Cr = 0.38-0.91 μg/g, and Pb = 2.67-3.53 μg/g. Results show that relatively, higher metal levels were recorded in M. deliciosus than M. macrophthalmus. No significant differences (P > 0.05) were recorded between the concentrations of Fe, Mn, Zn and Pb in the two fish species. Significant differences (P < 0.05) were however, recorded between the concentrations of Cu, Ni, Cd and Cr in the fishes. The levels of Pb in the fish species exceeded the limit recommended in fish and fishery products by the Food and Agricultural Organization (FAO) of the United Nations. Also, the levels of Fe and Cd in the water exceeded the levels recommended for portable drinking water by the World Health Organization (WHO).Keywords: Trace metals, benthic fishes, Ikpoba dam, Benin City, Nigeri

The use of the mangrove oyster (Crossostrea gasar) as a bio-indicator for chemical element contamination in the Niger Delta

The study evaluated the concentrations of some chemical elements namely Copper (Cu), Manganese (Mn), Zinc (Zn), Chromium (Cr), Nickel (Ni) and Lead (Pb) in the mangrove oyster (Crossostrea gasar) and water from Golubo creek in the Niger Delta region of Nigeria, to ascertain the impact of these metals on the investigated ecosystem. The evaluation was carried out using Atomic Absorption spectroscopy technique. The mean  concentrations of the aforementioned elements in C.gasar were 1.06 mg/kg, 0.38 mg/kg, 50.13 mg/kg, 0.14 mg/kg, 0.39 mg/kg and 1.55 mg/kg, respectively while the mean concentrations of the elements in water were 0.65 mg/l, 0.04 mg/l, 16.47 mg/l, 0.86 mg/l, 0.85 mg/l and 1.50 mg/l, respectively. Copper, Manganese, Zinc and Lead were  bioaccumulated by C.gasar while the estimated daily intake of these elements ranged from 0.0056 mg/person/day for Chromium to 2.01 mg/person/day for Zinc. The Maximum Acceptable Risk values for Copper, Manganese, Zinc, Chromium, Nickel and Lead in C. gasar were 0.79, 0.05, 24.67, 0.94, 1.08 and 1.94, respectively. The Toxicity Quotient values for the chemical elements in C.gasar ranged from 0.66 for Zinc to 0.93 for Chromium while in the case of water, the range was from 0.65 for Copper to 1.5 for Lead. With regard to health risk to man, the mean concentrations of the chemical elements in the oysters, did not exceed the Federal Environmental Protection Agency (FEPA) maximum allowable limit for chemical elements in food. The mean concentrations of these metals in the bivalve were, therefore, within health limits and therefore do not present an immediate health threat to consumers. It was observed that the mean concentrations of the chemical elements in water were generally below the FEPA maximum allowable limits for chemical elements in drinking water with the exception of Lead. The study, thus, revealed that there is a potential health risk to man as a result of consuming Pb-contaminated water. Based on the findings from this study, it is advocated that the creek be closely monitored for toxic metals in order to avert the occurrence of episodic ecological accidents.Key words: Chemical elements, Oyster, Niger Delt