Heavy Metal Phytoremediation by Water Hyacinth at Constructed Wetlands in Taiwan

The ability of water hyacinth ( Eichhornia crassipes Mart. Solms.) to absorb and translocate cadmium (Cd), lead (Pb), copper (Cu), zinc (Zn), and nickel (Ni) was studied in the Erh-Chung wetlands. Translocation ability was defined as the quantity of Cu, Pb, Cd, Ni, and Zn translocated in the plant’s tissues, and was expressed as a root/shoot ratio. The ratio results were in the order of Cu>Pb>Cd>Ni>Zn. Water hyacinth plants had a high bioconcentration of these trace elements when grown in water environments with low concentrations of the five elements. Generally, the concentration of these five elements in the roots was 3 to15 times higher than those in the shoots. The concentrations in the root tissue were found in the order of Cu>Zn>Ni>Pb>Cd. The absorption capacity for water hyacinth was estimated at 0.24 kg/ha for Cd, 5.42 kg/ha for Pb, 21.62 kg/ha for Cu, 26.17 kg/ha for Zn, and 13.46 kg/ha for Ni. This study shows water hyacinth to be a promising candidate for phytoremediation of wastewater polluted with Cu, Pb, Zn, and Cd.