Assessment of Metal Availability in a Contaminated Soil by Sequential Extraction

A contaminated soil from Pieve Vergonte (Piedmont, Italy) has been investigated in order to point out the availability and extractability of a series of metal ions and consequently their potential release into other environmental compartments. A sequential extraction procedure has been adopted in order to subdivide total concentrations into five operational fractions with different potential toxicity. A chemometric analysis has been used for the characterization of similarities or differences of behaviour. High concentrations of the main pollutants, namely Cu, Pb and Zn, were extracted into the exchangeable, carbonate-bound/specifically adsorbed and Fe-Mn oxide bound fractions, showing the risk of release of these metals into the environment. A remobilization of Cr, Mn and Ni could also take place, but to a lesser extent. The other investigated metals (Al, Fe, La, Sc, V, Ti and Y) were mainly bound to the residual and, in some samples, to the Fe-Mn oxide bound fractions. The high availability of several potentially toxic metals shows that the soil needs remediation.