Phytoaccumulation of trace elements by wetland plants: II. Water hyacinth.

Wetland plants are being used successfully for the phytoremediation of trace elements in natural and constructed wetlands. This study demonstrates the potential of water hyacinth (Eichhornia crassipes), an aquatic floating plant, for the phytoremediation of six trace elements. The ability of water hyacinth to take up and translocate six trace elements-As(V), Cd(II), Cr(VI), Cu(II), Ni(II), and Se(VI)-was studied under controlled conditions. Water hyacinth accumulated Cd and Cr best, Se and Cu at moderate levels, and was a poor accumulator of As and Ni. The highest levels of Cd found in shoots and roots were 371 and 6103 mg kg -1 dry wt., respectively, and those of Cr were 119 and 3951 mg kg ' dry wt., respectively. Cadmium, Cr, Cu, Ni, and As were more highly accumulated in roots than in shoots. In contrast, Se was accumulated more in shoots than in roots at most external concentrations. Water hyacinth had high trace element bio-concentration factors when supplied with low external concentrations of all six elements, particularly Cd (highest BCF = 2150), Cr (1823), and Cu (595). Therefore, water hyacinth will be very efficient at phytoextracting trace elements from wastewater containing low concentrations of these elements. We conclude that water hyacinth is a promising candidate for phytoremediation of wastewater polluted with Cd, Cr, Cu, and Se.