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|Title: ||Studies on Levels of Mercury, Cadmium and Zinc in Fish and Sediments from River Offin in Ghana|
|Authors: ||Dwumah-Ankoana, Stephen|
|Issue Date: ||7-Jun-2008|
|Series/Report no.: ||4960;|
|Abstract: ||One hundred and forty eight fish samples covering twelve different species, twenty sediment samples and five soil samples were collected at five locations (Dominase, Nkotumso, Dunkwa-on-Offin, Buabenso, Awisam) along Offin River and analysed for
total mercury, cadmium and zinc. Mercury was determined using the Cold Vapour Atomic Absorption Spectrometry employing an Automatic Mercury Analyzer (HG 5000
model). An Atomic Absorption Spectrometer (Unicam 929 model) was used for the determination of total cadmium and zinc. The fish species included Oreochromis niloticus, Chrysichthys nigrodigitatus, Labeo coubie, Brycinus sp., Hepsetus odoe, Mormyrus sp., Papyrocranus afer, Heterobranchus sp., Tilapia zilli, Synodontis sp., Sarotherodon melanotheron, and Schilbe mystus.
Total mercury concentration in fish ranged from 1.02 to 795.94 ng/g wet weight, from 68.73 to 1066.65 ng/g in sediments and from 44.61 to 137.80 ng/g in soil. Total cadmium concentration in fish ranged from below detection to 0.10 mg/kg wet weight and was below detection in all the sediments and soil sampled whereas total zinc concentration in fish ranged from below detection to 18.16 mg/kg wet weight, from 13.57 to 47.81 mg/kg in sediments and from 8.45 to 81.49 mg/kg in soil. Synodontis sp. recorded the highest concentration (mg/kg, wet weight) of Hg (0.79), Cd (0.10) and Zn (18.16) in all the fish samples analysed. About 37.5% and 18.8% fish species showed positive correlation between muscle tissue mercury concentration and fresh weight, and muscle tissue mercury concentration and total length of fish respectively. Generally, there was an irregular distribution of these metals in fish as the river flows downstream towards river Pra, Analytical results obtained showed that, cadmium and zinc concentrations in fish tissue were generally below the WHO maximum permissible limit; however, 3.4% of the fish samples analysed had tissue mercury concentrations above the WHO limit of 0.5 mg Hg/kg. Though the results of the research indicates that consumption of fish from the Offm River is unlikely to constitute a health threat to consumers, the concentrations of Hg and Zn obtained were of elevated levels compared to those obtained in the year 2000 in River Offiri. Continuous mining along the banks of Offin River coupled with long term bioaccumulation of heavy metals through food chain is of major concern. The study also revealed that Synodontis sp. (locally called Nkontro) has a good Hg, Cd and Zn accumulation potential and may serve as a biomarker for toxicological studies for these metals in the Offin River.|
|Description: ||A Thesis submitted to the Department of Chemistry, Kwame Nkrumah University of Science and
Technology in partial fulfilment of the requirements for the degree of Master of Science (Analytical Chemistry), 2008|
|Appears in Collections:||College of Science|
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