Effect of EDTA,Phosphate,pH and Metal Species on Cadmium and Nickel Uptake by Aquatic Macrophyte Spirodela Polyrhiza

Abstract

The phytoremediation potential of an aquatic macrophyte, Spirodela polyrhiza for cadmium (Cd) and nickel (Ni) removal was studied. Effect of different concentrations (1–10 mg/L) of Cd and Ni on multiplication rate and photosynthetic pigments were determined to evaluate the tolerance of the plants and the toxicity of Cd and Ni. Presence of EDTA (ethylene diamine tetraacetic acid) exerted a remarkable inhibition on the uptake of both Cd and Ni by the plants. Phosphate in the medium was found to favour the growth of the plants. However, the uptake Cd and Ni by the plant decreased significantly on the addition of phosphate. Spirodela exhibited a pH dependent phenomenon of metal accumulation. As compared to uptake at pH 7, Cd and Ni uptake was increased by 29% and 60% at pH 5. However, decline in Cd and Ni uptake was observed at alkaline pH 9 and pH 11. Accumulation of Cd and Ni by plants in the presence of single metal and combination of metal species (Cd+Ni+Zn+Cu) at different concentrations was evaluated. In the presence of other metal species, Cd and Ni uptake was reduced by 21–35% and 21–27%, respectively, as compared to plants exposed to Cd or Ni singly.