Contamination by heavy metals in soils in the neighbourhood of a scrapyard of discarded vehicles

Here we consider the total content of several heavy metals (Fe, Mn, Cd, Co, Cr, Cu, Ni, Pb and Zn) and their more bioavailable fractions, corresponding to the soluble and exchangeable forms, in soils surrounding a vehicles scrapyard, compared with a control soil which is not affected. We observed that there is a significative increase in the total contents of Pb, Cd, Cr, Cu, Ni and Zn and also in Fe and Mn oxides, mainly amorphous, in the soils closer to the source, which clearly decrease with distance. The upper level of these soils (0–2 cm) contains the highest content of heavy metals and Fe and Mn oxides, which decrease with depth. Nevertheless, the extractable contents (extracted with ammonium acetate of pH 7) are considerably lower than the total contents, which confirms the high retention capacity of these soils, based upon their calcareous nature, their moderately basic pH (range 7.72–8.09), their significant content of iron oxides (soil constituents of variable charge) and the possible formation of insoluble heavy metals oxides and hydroxides.