Leaching and uptake of heavy metals by ten different species of plants during an EDTA-assisted phytoextraction process

In a pot experiment, the potential use of 10 plant species, including six dicotyledon species and four monocotyledon species, was investigated for the EDTA-enhanced phytoextraction of Pb from contaminated soil. Mung bean and buckwheat had a higher sensitivity to the EDTA treatment in soils. In the 2.5 and 5.0 mmol kg-1EDTA treatments, the Pb concentrations in the shoots of the six dicotyledon species ranged from 1000 to 3000 mg kg-1of dry matter, which were higher than those of the monocotyledon species. The highest amount of phytoextracted Pb (2.9 mg Pb pot-1) was achieved in sunflowers, due to the high concentration of Pb in their shoots and large biomass, followed by corns (1.8 mg Pb pot-1) and peas (1.1 mg Pb pot-1). The leaching behavior of heavy metals as a result of applying EDTA to the surface of the soil was also investigated using short soil-leaching columns (9.0-cm diameter, 20-cm height) by the percolation of artificial rainfall. About 3.5%, 15.8%, 13.7% and 20.6% of soil Pb, Cu, Zn and Cd, respectively, were leached from the soil columns after the application of 5.0 mmol kg-1of EDTA. The growth of sunflowers in the soil columns had little effect on the amount of metals that were leached out. This was probably due to the shallowness of the layer of soil, the short time-span of the uptake of metals by the plant and the plant's simple root systems.