Diffusive gradients in thin films (DGT) for the prediction of bioavailability of heavy metals in contaminated soils to earthworm (Eisenia foetida) and oral bioavailable concentrations

The applicability of diffusive gradients in thin-films (DGT) as a biomimic surrogate was investigated to determine the bioavailable heavy metal concentrations to earthworm (Eisenia foetida). The relationships between the amount of DGT and earthworm uptake; DGT uptake and the bioavailable concentrations of heavy metals in soils were evaluated. The one-compartment model for the dynamic uptake of heavy metals in the soil fitted well to both the earthworm (R ²=0.641-0.990) and DGT (R ²=0.473-0.998) uptake data. DGT uptake was linearly correlated with the total heavy metal concentrations in the soil (aqua regia), the bioavailable heavy metal concentrations estimated by fractions I+II of the standard measurements and testing (SM&T) and physiologically based extraction test (PBET, stomach+intestine). The coefficients of determination (R ²) of DGT uptake vs. aqua regia were 0.433, 0.929 and 0.723; vs. SM&T fractions (I+II) were 0.901, 0.882 and 0.713 and vs. PBET (stomach+intestine) were 0.913, 0.850 and 0.649 for Pb, Zn and Cu, respectively. These results imply that DGT can be used as a biomimic surrogate for the earthworm uptake of heavy metals in contaminated soils as well as predict bioavailable concentrations of heavy metals estimated by SM&T (I+II) and PBET as a human oral bioavailable concentrations of heavy metals.