Assessment of Heavy Metal Pollution in Soil from an Automobile Mechanic Workshop in Abuja

Spent oil contaminated soil from a mechanic workshop located in Gwagwalada Area Council of Abuja, FCT of Nigeria, was assessed of heavy metals (Fe, Pb, CD, Cu, Cr, Ni and Zn) concentration. Soil samples were collected from seven points at depth 0- 15 cm, wet digested in duplicates with 2 M HNO3 in a closed system and concentrations of heavy metals analyzed by Atomic Absorption Spectrophotometer. The order of the mean concentration of heavy metal content in the contaminated sample and control soil were Fe> Zn > Cu >Pb > Cr > Ni > Cd and Fe > Cr > Zn > Pb > Cu > Ni > Cd respectively. The range (mg/kg) of the heavy metals in the contaminated soil were: 158.55 for Fe, 0.01 for Cd, 17.14 for Cu, 3.17 for Cr, 1.96 for Ni, 16.40 for Zn and 60.41 for Pb. There was an indication that Ni had the same source in the contaminated soil with Fe and Zn, having shown a correlations at r= 0.69; p = .043 and r= 0.85; p = .008 respectively while total organic matter and Carbonate content (r = - 0.96; p < 0.001), showed inverse correlation. The degrees of contamination, potential ecological risk factor and potential risk index of the heavy metals in all the points of the mechanic workshop were of low grade. The mean geo-accumulation index, Igeo, values for the various metals in the different points were all negative. Therefore, the heavy metals have not caused any harm yet to the mechanic workshop under study. The findings of this study would add to the environmental database of the soil of this mechanic workshop, which in due course, will assist in the monitoring, management and remediation strategies for heavy metal contaminated soil.