Plant uptake and the leaching of metals during the hot EDDS-enhanced phytoextraction process

Using pot experiments, the effect of the application of the biodegradable chelating agent S,S-ethylenediaminedisuccinic acid (EDDS) in hot solutions at 90°C on the uptake of Cu, Pb, Zn, and Cd by corn (Zea mays L. cv. Nongda No. 108) and beans (P vulgaris L. white bean), and the potential leaching of metals from soil, were studied. When EDDS was applied as a hot solution at the rate of 1 mmol kg-1, the concentrations and total phytoextraction of metals in plant shoots exceeded or approximated those in the shoots of plants treated with normal EDDS at the rate of 5 mmol kg-1. On the other hand, the leaching of Cu, Pb, Zn, and Cd after the application of the hot EDDS solution at the rate of 1 mmol kg-1 was reduced by 46%, 21%, 57%, and 35% in comparison with that from the application of normal EDDS at 5 mmol kg-1, respectively. For treatment with 1 mmol kg-1 of EDDS, the leached metals decreased to the levels of the control group (that without EDDS amendment) 14 d after the application of EDDS. The soil amendment with biodegradable EDDS in hot solutions may provide a good alternative to chelate-enhanced phytoextraction in enhancing metal uptake by plants and limiting metals from leaching out of the soil.