Evaluation of the Impact of Heavy Metal Pollution on the Environment of Dunkwa- On-Offin From Gold Mining Activities

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2011-06-14
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All heavy metals are potentially harmful to organisms at higher levels of exposure. Concentrations of Hg, Co, Cr, Cu, Ni, Zn, Cd, As and Pb were determined by atomic absorption spectrophotometry in three fish species (Chrysichthys gariepinus, Clarias nigrodigitatus and Heterobranchus bidorsalis), sediments and water from Offin River, soils and terrestrial animals (Futa jallon, Capra hircus and Rattus rattus) sampled from Dunkwa township. The mean concentration of As in the water (17.91 ± 6.60 µg/l) was above the WHO guidelines value of 10 µg/L for drinking water. The mean concentration of As in the sediment samples (62.52 ± 19.69 mg/kg dry-wt) was the highest among the metals analyzed whiles in the soil samples, Zn that recorded a mean concentration of 25.37 ± 19.83 mg/kg, dry-wt was the highest. In the fish species, the gills, livers and muscles were analyzed whiles the livers, kidneys, lungs, brains, small intestines, colons, tongues and hearts were analysed in the Futa jallon and Capra hircus samples. In Rattus rattus, lung, liver, kidney and brain samples were analysed. The mean concentration of As in the water (17.91 ± 6.60 µg/l) was above the WHO guidelines value of 10 µg/L for drinking water. The mean concentration of As in the sediment samples (62.52 ± 19.69 mg/kg dry-wt) was the highest among the metals analyzed whiles in the soil samples, Zn that recorded a mean concentration of 25.37 ± 19.83 mg/kg, dry-wt was the highest. Among the three fish species, muscles and livers had mean Hg concentrations above the WHO permissible limit of 0.5 mg/kg. Chrysichthys nigrodigitatus, Heterobranchus bidorsalis and Clarias gariepinus had Hg concentrations of 1.04 ± 1.23 mg/kg, 0.98 ± 0.91 mg/kg and 1.08 ± 2.07 mg/g in their livers and 1.15 ± 1.27 mg/kg, 0.57 ± 0.11 mg/kg and 0.77 ± 0.99 mg/kg in their muscles respectively. All the mean concentrations of Zn in the organs of sheep (Futa jallon) samples were above the safety limit of 50 mg/kg set by USDA. In goat (Capra hircus) samples, almost all the tissues that were analyzed had their Zn concentrations exceeding the permissible limit for human consumption except that of brain and 50% of the colon samples. Among the terrestrial animals, wild rats (Rattus rattus) had the highest concentrations of As in their tissues. It could be concluded from this study that consumption of water and fish from the Offin river could pose a health hazard due to the high levels of As and Hg in the biota.
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A thesis submitted to the Department of Chemistry, Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirements for the Degree of MASTER OF SCIENCE (ANALYTICAL CHEMISTRY) July 2011
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