Assessment of heavy metal contamination of road deposited sediments and river sediments in the Kumasi Metropolis, Ghana

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2015-11-03
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Abstract
This study was conducted to determine the levels of five (5) heavy metals (arsenic, cadmium, lead, copper and zinc) in and the effect of seasons on road-deposited sediments and river/ stream sediments of five major roads and adjacent water bodies in the Kumasi Metropolis. Samples were collected over two sampling periods that coincided with the rainy and dry seasons for heavy metal analysis. Road sediments along the sampled highways and major roads in Kumasi were highly contaminated with the studied heavy metals compared to background values, signifying an anthropogenic input most likely from the road-traffic environment. The ranges of the recorded heavy metal concentrations in the road-deposited sediments over the study period across the study sites were as follows; arsenic (3.30-87.80 mgkg -1 ), cadmium (0.20-0.60 mgkg -1 ), copper (0.16-630.10 mgkg -1 ), lead (11.93-121.90 mgkg -1 ) and zinc (11.80-160.30 mgkg -1 ). The heavy metal concentrations in the river/stream sediments over the study period across the study sites were as follows; arsenic (46.73-298.40 mgkg -1 ), cadmium (0.20-1.80 mgkg -1 ), copper (11.80-1052.60 mgkg -1 ), lead (0.20-620.20 mgkg -1 ) and zinc (109.30-1045.10 mgkg -1 ). The variations across the sites appear to be primarily due to site-specific attributes with the sites having higher traffic densities generally recording higher levels of the studied metals. The measured heavy metal levels of the road-deposited sediments and sediments from nearby rivers and streams showed a general trend; the concentrations were significantly higher (p<0.05) in the river / stream sediments than in the road deposits. In terms of seasonality, higher metal concentrations were generally viii recorded during the dry season than in the wet season. The calculated pollution load indices were generally indicative of sites with deteriorated quality as far as the studied metals are concerned. Frequent monitoring of road deposits and river sediments are necessary in order to detect and prevent cumulative consequences of heavy metal pollutants.
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A thesis submitted to the Department of Fisheries and Watershed Management, Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirements for the award of the degree of Master of Philosophy (MPHIL) in Aquatic Resource Management,
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