keywords: Ecological risk assessment, mechanic workshops, potentially toxic metals
Soil samples from 12 major automobile spare parts sales and car dismantling sites in Lagos and a control sample were analysed for selected potentially toxic metals (PTM): Cd, Cr, Cu, Ni, Pb and Zn. The soil samples were digested with aqua regia and analysed using a flame atomic absorption spectrophotometer. The concentrations (mg/kg) of Cd, Cu, Cr, Ni, Pb, and Zn in the soil samples ranged from 2.73- 19.2, 7.12- 113, 1.3- 77.7, 2.74- 17.7, 0.73- 68.3 and 40.4- 254, respectively. Compared with established limits set for soils in some countries, the values measured in this study were higher than these limits in several cases. Principal component analysis (PCA) was used to examine relationship between the sets of data and two major components were extracted. PC1 had a high loading of Ni, Cr and pH thus suggested to be the result of the contamination from battery charger shop close to the site where the samples were collected, while PC2 had a high loading of Zn, Cd and Cu probably also suggesting anthropogenic influence. The Hakanson ecological risk index revealed that the degree of metals pollution was greatly influenced by Cd and the other metals in the order: E_R(Cd) greater than E_R(Zn) greater than E_R(Cu) greater than E_R(Pb) greater than E_R(Cr) greater than E_R(Ni).
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