Effects of earthworms on metal uptake of heavy metals from polluted mine soils by different crop plants.

A pot experiment was conducted in order to assess the effect of the earthworm Eisenia fetida on the uptake of Pb, Zn, Cd and Cu from soils polluted by mining activities using maize (Zea mays) and barley (Hordeum vulgare). Results from single and sequential extractions showed that the soil chemical partitioning of heavy metals was significantly changed by E. fetida, leading to a higher concentration of metals in the non-residual fractions of the soil. Earthworm activities significantly increased shoot biomass (65% for maize and 73% for barley) and root metal concentration for all the metals under study in both maize and barley. The total accumulation rate values for Cd, Cu, Pb and Zn were significantly higher in the presence of E. fetida for both crop plants. Those latter effects led to an increase in Zn extraction yields of up to 3.7-fold and 2.3-fold for barley and maize, respectively.