Phytoremediation of cadmium-, lead- and nickel-contaminated water by Phragmites australis in hydroponic systems

This study was carried out to investigate the phytoremediation ability of Phragmites australis to remove cadmium (Cd), lead (Pb) and nickel (Ni) from contaminated water, to study the effect of pH and salinity on the removal of cadmium, lead, and nickel, and to estimate the pattern of accumulation of these metals in the roots, shoots, and leaves of the plant. The experiments were carried out in a deep-water hydroponic system and 5 mg/L was used as a concentration of each of the heavy metals. The results of the study showed that P. australis had a residual of 7% (93% removal) of cadmium, 5% (95% removal) of lead and 16% (84% removal) of nickel over a 6-week period. In the control experiment, there was a residual of 96% (4% removal) for both cadmium and lead and 89% (11% removal) for nickel over a 6-week period. There was no major effect of pH on the removal of cadmium except at pH10, which led to a slightly reduced removal of cadmium (89% removal). Also, there was no major effect of pH on the removal of lead, however, there was the enhanced removal of nickel at pH10 (93% removal). The major mechanisms employed by the plant were probably phytostabilization on the basis of the calculated Biological Concentration Factor (BCF) – metal concentration ratio of plant root to soil; and Translocation Factor (TF) – metal concentration ratio of plants shoots to roots.