Assessment of some heavy metal (Pb, Zn, Mn, Cu, Fe) Concentrations in Raw Water, Sediments and Aquatic Macrophytes at the Barekese Reservoir

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In this study, the concentrations of five heavy metals (Pb, Zn, Mn, Cu and Fe) were determined in raw water, sediments and aquatic macrophytes from selected sites at the Barekese reservoir in Ghana over a 6 month period. The obtained results revealed that the mean concentration ranges for lead (0.04-0.25 mg/L) and iron (0.49-0.89 mg/L) in water samples exceeded the WHO (2008) guidelines for drinking water. The reservoir water is therefore unfit for drinking except after adequate treatment. To assess metal contamination in sediments several indices of contamination (contamination factor, degree of contamination and PLI) and the Numerical Sediment Quality Guidelines (SQGs) were applied. Based on comparison with Numerical SQGs values, the sediment samples at the reservoirs intake were classified as heavily polluted with Pb and Cu. The values of the concentration factor (>1) confirmed the tremendous capacity of sediments to accumulate higher concentration of heavy metals as compared to water samples. Good information was also provided by analysis of whole plants and organs of passive aquatic macrophytes represented by four species: Typha domingensis, Ceratophyllum demersum, Pistia stratiotes and Lemna paucicostata. Metals in all the species were higher in their roots than their shoots. The Biological Accumulation Factor (the ratio of heavy metal content of the plant/water) for all plant species decreased in the order: Fe (279) > Cu (268) > Pb (259) > Mn (206) > Zn (143). The obtained values have elaborated the usefulness of aquatic macrophytes in biological monitoring of heavy metal contamination in water bodies. The overall concentration of the heavy metals in in the sediments was higher than those in the aquatic macrophytes. The raw water samples recorded the least concentration of heavy metals. The mean heavy metal concentrations in all the samples were however observed in the sequence; Fe > Cu > Mn > Pb > Zn.
A Thesis Submitted to the Department of Theoretical and Applied Biology, College of Science, Kwame Nkrumah University of Science and Technology, Kumasi, In Partial Fulfilment of the Requirements for the Award of the Degree of Master of Science (Environmental Science)