1Assistant Prof., Department of Soil Science, Urmia University, Urmia 57135-165, Iran.
2Assistant Prof., Department of Soil Science, Shahrekord University, Shahrekord 88186/34141, Iran.
Soil contamination with potentially toxic elements (PTEs) in agricultural lands, in part, is responsible for limiting the crop productivity and the food chain contamination. The objective of this study were to asses the limiting of crop productivity by cadmium (Cd) and lead (Pb), the potential transfer and bioaccumulation of these PTEs in plants, and ultimately the food chain contamination to ensure that the pre-established soil threshold concentrations for Cd and Pb are enough to control food chain exposure to them. Therefore, land cress and spinach were grown in some pots containing a sandy loam soil contaminated with increasing concentrations of Pb and Cd. The concentrations of Pb and Cd in land cress and spinach at any level of soil contamination were compared with the threshold concentrations of Pb and Cd in leafy vegetables as established by the Codex Alimentarius Commission (CAC). A bioaccumulation factor was calculated to estimate the potential transfer of Pb and Cd to the food chain. According to the results, Pb was of more phytotoxicity than Cd. The lower limit of the maximum acceptable concentration of Pb in soil was safe enough to ensure the prevention of the food chain contamination to Pb. Results also showed that growing land cress on contaminated soils was of great potential risk of Pb transfer to the human food chain when compared to spinach. The pre-established maximum acceptable concentration of Cd in soil of 1-20 mg kg-1 was not safe to prevent the contamination of food chain. Cd was of a greater potential of entering the human food chain than Pb.