Heavy metal concentration in the Owere River at Konongo

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The Owere River located in the Asante Akyem Central Municipality of Ghana is one of the major sources of water for household and farming purposes in the municipality. In recent times there has been indiscriminate small-scale gold mining activity in and around the river which has led to pollution of the river. The study was thus carried out to assess the levels of heavy metals and some physico- chemical parameters in the Owere River at Konongo in the Asante Akyem Central municipality of Ghana. Water samples from the Owere River were collected from upstream, midstream and downstream sites of the river and analyzed for some heavy metals: Arsenic, Cadmium, Iron, Lead and Mercury. pH, temperature, electrical conductivity (EC), alkalinity and turbidity were also determined Results indicated that the mean levels of Arsenic from upstream, midstream and downstream were 0.022± 0.024 (mg/L), 0.007± 0.002 (mg/L) and 0.012± 0.008 mg/L respectively. There was no significant difference in the Arsenic levels between and within the sites. The level in the upstream was above the WHO permissible limit of 0.01mg/L. The mean levels of Cadmium from the sites ranged between 0.027± 0.011 mg/L to 0.066±0.094 mg/L and were above the WHO permissible limit of 0.003 mg/L. The levels of Lead in the midstream and downstream were above the WHO permissible limit of 0.01 mg/L. The mean levels of iron from upstream, midstream and downstream were 4.907± 1.063 mg/L, 1.785± 0.350 mg/L and 2.015± 0.438 mg/L respectively. These levels were high compared to the WHO permissible limit of 1.0 mg/L for drinking water. There was a significant difference between the upstream and midstream water samples. There were no significant differences in the levels of mercury recorded at the three sites and were above WHO permissible limit of 0.001 mg/L except in the upstream where it was below instrument detectable limit. pH was within the range of 6.23± 0.316 to 6.78± 0.588. However the upstream water samples recorded the highest mean temperature of 25.9± 1.152°C. This was within the WHO acceptable limit of 25 to 28 °C for drinking water sample. Mean conductivity for the water samples ranged between 262.5± 80.328 µS/cm to 298.0 ± 14.508 µS/cm. Alkalinity levels were below WHO limit of 700mg/L. The levels recorded ranged between 74.3±0.424 to 107.2± 0.282 mg/L. Turbidity levels at all sites were high and above the WHO limit of 5NTU ranging between 55.5± 8.602 – 62.5± 6.390 NTU. The total dissolved solids levels at all the sites were within the WHO permissible limit of 1000 mg/L in drinking water. There was significant difference in the levels recorded at the sites. It is evident that the activities of the small-scale miners are affecting the quality of the water and thus the need for action to mitigate the effect of mining on the water body.
A thesis submitted to the Department of Theoretical and Applied Biology in partial fulfillment of the requirement for the degree of Master of Science