Pb, Cu, Zn and Ni concentrations in vegetables in relation to their extractable fractions in soils in suburban areas of Nanjing, China

To investigate the bioavailability and bio-enrichment of metals from soils to vegetables, the concentrationsof Ni, Pb, Zn, and Cu in vegetables and their grown soils sampled from eight suburban areas of Nanjing, China, were determined, and the fractions of these metals in soils was characterized by using the BCR sequential extraction procedure. The results showed that the residual fraction was the dominant proportion for Pb (46%-64% in total), Cu (49%-73% in total) and Ni (40%-61% in total) in soils, whereas Zn was found mainly in the oxidizable fraction (31%-69% in total). The translocation coefficients of metals in leaf/root systems revealed that Cu, Zn and Ni were mainly accumulated in roots, whereas Pb mainly in the leaves of these vegetables. The enrichment coefficients of metals in leaf/root systems indicated that Zn had the strongest capacity of accumulation from soils to vegetables among all four elements. No significant correlations were found among metal concentrations in the vegetables, the metal fractions in corresponding soils, and the enrichment coefficients from soils to plants.