Cadmium and lead removal from water by the duckweed. Lemna gibba L. (Lemnaceae)

Abstract

Duckweed was exposed during 7 days to cadmium, and lead, at concentrations ranging from 50 to 300 mg/L in a greenhouse with controled photoperiod and temperature. The Cd and Pb measurements were performed on plants and nutrients solution using Plasma emission spectrometer. These was not correlation between the Cd and Pb content in plants and in the nutrient solution, this is indicative of the fast attainment of plants saturation state and the result of combination of absorption and adsorption phenomena. The effects of Cd and Pb on the growth of Lemna gibba were examinated during 13 days in the same experimental design. In all tests the maximum growth were at the third day then, the toxicity effects were aproached by chlorophyll a, b and total content at the third day of growing. There was more than 50% decrease in chlorophyll content in all tests in relation with control.