Assessment of radionuclides activities and heavy metals contamination in sediments, water and fish in Lake Bosomtwi and Bui dam

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Concentration of heavy metals and natural radioactivity were measured in water, sediment and fish samples from Lake Bosomtwi and Bui dam. The concentrations of the heavy metals in sediments were found to decrease in the sequence, Fe > Mn > Ni > Zn > Cr > Cu > Co > As > Hg for Lake Bosomtwi and Fe > Mn > Ni > As > Cr > Zn > Cd > Cu for Bui dam. Heavy metal concentration in water was in the order: Fe > Pb > Mn > Zn = As > Cd = Cr in Lake Bosomtwi and Fe > As > Pb > Mn > Cd = Zn > Cr for Bui dam whilst metal concentration in fish samples was in the order: Fe > Zn > Mn > Cu > Ni > Pb > Cr > Cd > Hg for Lake Bosomtwi and Fe > Mn > Zn > Cu > Ni > Pb > Cr > Cd > Hg for Bui dam. The study indicated a general absence of serious pollution in the two reservoirs with respect to heavy metals. The activity concentration due to 238U, 232Th and 40K determined with the - spectrometer indicated that the surface water radioactivity concentration of 238U, 232Th and 40K were ranging from 0.20±0.07 to 0.98±0.24, 0.03±0.08 to 0.82±0.13 and 0.02±0.67 to 3.32±0.77 Bq/L respectively for Lake Bosomtwi and from 0.13±0.08 to 0.42±0.01, 0.07±0.14 to 0.82±0.14 and 0.78±0.73 to 2.42±0.75 Bq/L respectively for Bui Dam. The average annual effective dose due to ingestion of radionuclide in water ranged from 20.5 to 156 and 26.5 to 162 μSv/year for Lake Bosomtwi and Bui Dam respectively. The average activity concentration of 238U, 232Th and 40K in the sediment from the two reservoirs was 7.90, 7.83 and 169.73 Bq/kg respectively for Lake Bosomtwi and 7.56, 8.11 and 49.0 Bq/kg respectively for Bui Dam which is lower than world averages. The determined absorbed dose rate and annual effective dose for the sediments ranged from 12.41 to 18.74 nGy/year and 15.2 to 23.0 S/year respectively for Lake Bosomtwi and 8.68 to 11.47 nGy/year and 10.6 to 14.1S/year respectively for Bui Dam which are within worldwide recommended average of 59 nGy/year and 100 S/year. None of the radioactivity is expected to cause significant health problems to human beings through ingestion of water, consumption of fish or use of sediments for building purposes. Keywords: Lake Bosomtwi; Bui dam; Heavy metals; Radioactivity; Hazard indices; Absorbed dose rate; Annual effective dose.
A Thesis submitted to the Department of Chemistry of the Kwame Nkrumah University of Science and Technology, in partial fulfilment of the requirements for the degree of Master of Philosophy (Analytical Chemistry).