The Assessment of Forms and Bioavailability of Copper, Chromium, and Cadmium in Soils of Automobile Workshops using Sequential Extraction Procedure

The quantification the exact dimension of heavy metals pollution in soils requires more data than the total contents of metals in soils. The determination of different fractions (speciation) is necessary to understand the mobility and bio-availability of the metals in soils. This paper presents results of speciation of copper (Cu), chromium (Cr), and cadmium (Cd) in soils of ten automobile workshops in Sapele, Nigeria. Composite soils samples were taken from depth 0 – 60cm, and geochemical forms and total concentrations of the metals (Cu, Cr & Cd) in soils were determined by sequential extraction procedures and atomic absorption spectrometry. The total concentrations range of: 39.10 – 129.80mg/kgCu, 11.55 – 40.10mg/kgCr, and 3.15 – 6.28mg/kgCd obtained for the soils in the vicinities of the automobile workshops were distinctly higher than that of the control indicating enrichment of these metals in these soils. Speciation revealed that 20 – 33% Cu, 19 – 27% Cr and 25 – 45% Cd, were potentially mobile and bio-available. Keywords: sequential extraction, bio-availability, heavy metals, soils, automobile workshop