Electrokinetic Enhancement on Phytoremediation in Zinc Contaminated Soil by Ruzi Grass

摘要

The use of Ruzi grass (Brachiaria ruziziensis) for electrokinetic (EK)-phytoremedial and phytoremedial removal of zinc ions (Zn2+) from contaminated soil was demonstrated in a laboratory-scale experiment. After 15 d of germination, Ruzi grass seedlings were transferred to experimental soil pots that were supplemented to 0, 300, 400 and 500 mg Zn2+/kg soil. After 15 d growth, the Zn2+ concentration that allowed the highest survival rate and biomass of Ruzi grass was selected to sequentially determine the optimum applied voltage (from 0, 1, 2 and 4 V/cm) and then the duration of the selected applied voltage (0, 2, 4 and 6 h/d). An applied voltage of 2 V/cm for 2 h/d was found to be the most optimal for Zn accumulation in the Ruzi grass, and this was then used to treat soil contaminated with a high concentration of Zn2+ (1000 mg Zn2+/kg soil) in comparison with and without the applied electric field (phytoremediation) over a 15 d treatment. The EK-phytoremediation significantly increased the accumulation of zinc (Zn) in Ruzi grass roots (but not shoots) and decreased the residual Zn levels in the soil compared to that with phytoremediation only. The plant Zn concentration following EK-phytoremediation (393.8 ± 19.7 mg/kg) was almost 4.4-fold higher than that in the phytoremediation system (89.9 ± 4.5 mg/kg).