Abstract
This study was conducted to assess the level of heavy metals contamination of soil around oil filling and service stations in the Tamale Metropolis. Soil samples were collected from various oil filling and service stations. Elemental analysis of samples was conducted using atomic absorption spectrometer at Atomic Energy Laboratory, Accra. The metals concentrations ranged from 2.37 to 15.00 mg/kg for Cr; 0.01 to 0.03 mg/kg for Hg; 3.2 to 22.68 mg/kg for Cu; 0.12 to 6.63 mg/kg for Cd and 4.93 to 74.20 mg/kg for Pb. The mathematical models: Index of geoaccumulation (Igeo), enrichment factors (EF), contamination factor and degree of contamination were employed to identify possible levels of pollution from anthropogenic sources. The enrichment factor means places the elements in a decreasing order as Cd > Pb > Cr > Cu > Ni> Fe > Zn > As > Hg > Mn that agreed with others models such as contamination factor, pollution load index and degree of contamination. Elements such as chromium (Cr), copper (Cu), lead (Pb) and manganese (Mg) gave enrichment factor values ranging from 2-5 signifying moderate enrichment. The study revealed that soil contamination by the metals originated from a common anthropogenic source such as the oil filling activities, brake wear, tyres wear and corroded vehicles engine materials since these sources are noted to contribute one or two correlated metals to the natural environment. Hence, pose potential threat to humans and critical environmental media such as water bodies. It is therefore recommended that Environmental Protection Agency (EPA) should regularly monitor the oil filling and service stations to check the levels of heavy metals in the metropolis. Key words: Oil filling, service station soils, enrichment factor, heavy metals, cadmium, Tamale Metropolis.
Highlights
Heavy metals enter the environment by natural and anthropogenic means such as natural weathering of the earth’s crust, mining, soil erosion, industrial discharge, urban runoff, sewage effluents, pest and disease control agents applied to plants, air pollution fallout, oil leaking
Enrichment factor proved to be an effective tool in differentiating a natural origin from anthropogenic source of contamination for the various elements investigated under the study
The mean value of the enrichment factor places the elements in a decreasing order as Cd > Pb >
Summary
Heavy metals are among the more serious pollutants in our natural environment due to their toxicity, persistence and bioaccumulation potential (Caeiro et al, 2005). Following the introduction of heavy metal contaminants. Heavy metals are natural constituents of the earth crust. The main anthropogenic sources of heavy metals are the industrial point sources, the present and former mining activities, foundries, smelters and diffuse sources such as piping, constituents of products, combustion of by products, traffic and human activities (Nilgun et al, 2004). Heavy metals at trace levels present in natural water, air, dusts, soils and sediments play an important role in human life (Isaac et al, 2004). Topsoil and dusts in urban areas are indicators of heavy metal contamination from atmospheric deposition. It has been noted that location close to roads are severally polluted by heavy metals such as Pb, Zn, Cu, Cd among others from traffic (Guvenc et al, 2004; Wilson et al, 2005)
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