Phytoavailability of heavy metals in tidal flat soils after fresh water leaching

The phytoavailability of Cd, Pb, Cr, Zn, Cu, and Ni, retained in tidal flat soil after fresh water leaching during reclamation was investigated. Two salt-tolerant varieties of tomato (Lycopersicon esculentum) and edible amaranth (Amaranthus mangostanus L.) were planted in soils having eight different desalination levels (from 6.7 to 1.4 g kg−1 salinity) using pot experiments. Soil leaching significantly decreased the uptake of all metals by crop roots except for Ni. The reduction of soil salinity and exchangeable fraction content of Cd and Pb after leaching contributed to the decrease of uptake of metals by roots. All heavy metal concentrations in the edible parts of both crops in the two lowest salinity level treatments were lower than their maximum allowable levels in food. Results suggest that reclamation of tidal flats can reduce the phytoavailability of the heavy metals retained in soil. But the soil heavy metals may still pose health risks in the cultivation of root food crops.

► Reclamation reduced exchangeable fraction content of Cd and Pb in soil.
► Tidal flat soil leaching decreased the soil heavy metal uptake by crop roots.
► Reclamation reduced the phytoavailability of the heavy metals retained in soil.
► Soil heavy metals may still pose health risks in the cultivation of root food crops.