Toxicity and accumulation of cadmium and zinc in hydrocotyle umbellata

Abstract

The aquatic plant, Hydrocotyle umbellata, was tested for toxicity and accumulation of Cd and Zn under laboratory conditions. H. umbellata were cultured in modified 10% Hoagland solution supplemented with 0.2, 0.4, 0.6, 0.8 and 1 mg/L Cd and 2, 4, 6, 8, 10 and 50 mg/L Zn and were separately harvested after 3, 6, 9 and 12 days. The toxicity symptoms of H. umbellata exposed to Cd and Zn at different concentrations and exposure times were stunted growth and chlorosis in leaves. Finally, some plants died at higher concentrations of metals. The symptoms were more severe at higher metal concentrations. Cd and Zn caused significant decreases in biomass productivity and chlorophyll content when the exposure times and concentrations of both metals were increased. There were significant increases in metal levels in plant tissues when the exposure times and metal concentrations were increased. Both metals accumulated in roots more than in shoots. The high values of bioconcentration factor (BCF) of Cd (7173, at 0.2 mg/L) and Zn (1717, at 2 mg/L) on day 9 of exposure suggested that H. umbellata is a good candidate for removal of Cd and Zn from contaminated water.