Assessment of some heavy metals in sediment of Lake Bosomtwi in the Ashanti Region of Ghana
Date
NOVEMBER, 2015
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Abstract
It is important to monitor the level of heavy metal contaminants in Lake Bosomtwi, thus, assessing its suitability for domestic and agricultural use. In order to determine this, fifty (50) sampling points were selected using the Global Positioning System (GPS) for the collection of fifty 50 sediments samples from April to June 2012. Physicochemical parameters recorded mean values of 111.3±33.4, 2.4 ± 0.5 and 9.1±0.3 for EC, OM and pH respectively. pH recorded a mean value of 9.1 ± 0.3 indicating that the sediment was basic or alkaline in nature. Zn, Cu, Ni, Pb, and Cd sediments were analyzed by Buck Scientific 210 VGP Atomic Absorption Spectrophotometry (AAS). The heavy metals concentration in the sediment was of the order Ni > Pb > Zn > Cd > Cu, the highest mean concentration of 70.19 ± 27.87 μg/g, 63.80 ± 33.41 μg/g, 43.53 ± 19.18 μg/g, 2.01±4.27 μg/g and 0.93 ± 0.89 μg/g for Ni, Pb, Zn, Cd, Cu respectively. Significant spatial variation in concentration was observed for all metals. Correlation analysis showed that Zn content of sediment was partially controlled by organic matter. Pollution status was evaluated using geo-accumulation index and sediment quality guidelines. Based on geo-accumulation index, lake Bosomtwi sediment can be considered as unpolluted with respect to Zn, Ni, Cu and unpolluted to moderately polluted with respect to Pb and Cd . Mean concentrations of Zn and Cu were below the Continental Average Shale (CAS), Threshold effect level (TEL), Severe effect level (SEL) and Permissible limit (PL). However, the mean concentration of 70.19 μg/g, 63.80 μg/g and 2.01 μg/g for Ni, Pb, and Cd respectively were above the Continental Average Shale (CAS) and Threshold Effect Level (TEL) in the sediment at lake Bosomtwi. This implies that the waste assimilation capacity of the lake is high, a phenomenon that could be ascribed to dilution, sedimentation and continuous water exchange. This is an indication that an urban, domestic and industrial waste discharged into the lake has a significant effect on the ecological balance of the lake, ecosystem and human health.
Description
A thesis submitted to the Department of Theoretical and Applied Biology,
Kwame Nkrumah University of Science and Technology
in partial fulfillment of the requirements
Master of Science degree in Environmental Science.