Assessment of metal bioavailability in smelter-contaminated soil before and after lime amendment

In this study, changes in bioavailable concentrations of Pb, Zn, Cu and As in former smelter site soils (J1 and J2) were investigated before and after lime amendment. The immobilization efficiencies of metal(loid)s were evaluated by Toxicity Characteristic Leaching Procedure (TCLP). Their bioavailable concentrations in the soils were evaluated by the acid-extractable and -reducible fractions in Standard Measurement and Testing Program (i.e., SM&T(I+II)), in vitro physiologically based extraction test (PBET) and diffusive gradients in thin-films (DGT). The results showed that the bioavailable concentrations remarkably decreased after lime amendment in both J1 and J2 soils. DGT uptake and resupply (R) of Zn, Cu and As from soil to soil solution increased but that of Pb decreased. This pattern was consistent with SM&T(I+II)- and PBET-extractable concentrations after lime amendment. This indicates that lime amendment is highly effective for the immobilization of Zn, Cu and As, but not for Pb. Our results implicate that DGT can be used to estimate bioavailability of metal(loid)s in soils and further extended to estimate risk reduction after soil remediation.

► Lime amendment is highly effective in immobilization of Zn, Cu and As, not Pb.
► PBET, SM&T(I+II) and DGT worked well to estimate bioavailable metal concentrations.
► Bioavailability of Zn, Cu and As, except for Pb, decreased after lime amendment.
► Resupply of metals from soil to soil solution can be measured by DGT.
► DGT can be used as a good biomimic surrogate to probe bioavailability of metal(loid)s in soil.