PHYTOACCUMULATION OF METALS BY AQUATIC MACROPHYTE; Pistia stratiotes L. (WATER LETTUCE)

Abstract

Macrophytes have been used for heavy metal removal from a variety of sources. Aquatic macrophytes such as water lettuce, is one of the most commonly used plants in constructed wetlands because of its fast growth rate and large uptake of nutrients and contaminants. It is generally known that aquatic macrophytes in wetlands can accumulate heavy metals. Therefore, an experiment was designed to check the metal tolerance capacity by using different concentrations i.e., 0 ppm, 2 ppm, 4 ppm and 6 ppm of nutrient cadmium chloride and copper sulphate solutions. Various physico-chemical parameters like pH, ECe and TDS were observed in the concentrations. The high value of pH (8.9), ECe (645 µs cm^-1) and TDS (350 mg L^-1) was found in the highest concentration of nutrient solution (6 ppm). These plants were grown in different concentrations of nutrient solution for 15, 30 and 45 days. Morphological parameters like root length, leave length, dry weight, fresh weight and number of leaves were also observed after 15, 30, 45 days respectively. Best metal uptake was observed in 6 ppm nutrient solution while in control (0 ppm) a reduced amount of uptake of metals was observed. The maximum root and leave length (30 g) were found in case of control concentration (0 ppm) because having no salt. The excess amount of metals reduced the growth parameters. Therefore, minimum growth was observed in 6 ppm nutrient solution. Order of metal uptake was Cd > Cu. Uptake of Cd in roots was higher (134 mg Kg^-1) than Cu (50 mg Kg^-1). Roots accumulated highest amount of heavy metals in 6 ppm nutrient solution, Cd (187 mg Kg^-1) than leaves (98 mg Kg^-1) because it was completely submerged into nutrient solutions. Similarly maximum amount of Cu uptake via roots was observed in 6 ppm nutrient solution (100 mg Kg^-1) than 0 ppm. Translocation factor of Cadmium and Copper was less than 1. The purpose of this study to evaluate the effect of heavy metals on the growth parameters of plant Pistia stratiotes L. in different concentration of nutrient solution as well this present research aims to assess P. stratiotes' (as a phytoremediator plant) capability of cadmium (Cd), copper (Cu), and a translocation factor from wastewaters (effluent).