Bioaccumulation of Zinc and Cadmium by two aquatic plants: Eichhornia crassipes (Mart.) Solms and Pistia stratiotes L. under nursery conditions

This study investigated the bioaccumulation abilities of Eichhornia crassipes and Pistia stratiotes for zinc and cadmium under nursery conditions.The plants were grown in tap water medium spiked with varying concentrations of 5 mg l -1 , 10 mg l -1 and 20 mg l -1 of zinc and cadmium salts while the control experiments was not spiked with any of the metallic salts.The biomass of each plant species was harvested after six weeks and separated into leaves, stems and roots and the metal concentrations in their tissues were determined according to various treatments.It was observed that both the fresh weight and dry weight decreased serially with the increase in the concentration of the metals.In Pistia stratiotes, the Bioconcentration factor (BCF) was higher for cadmium than zinc; on the other hand, the BCF was higher for zinc than cadmium in Eichhornia crassipes.Significant differences occurred between the control and the treatment (P ≤0.05) in the tissues of both plant species for zinc and cadmium contents which shows that the plants were able to bioaccumulate the metals.Comparing the two species based on the total amount of metals accumulated by the plants, Pistia stratiotes showed better bioaccumulation values for both cadmium and zinc than Eichhornia crassipes.Overall, the study revealed that the two aquatic macrophytes are potential bioaccumulators of cadmium and zinc and thus may be considered as candidate species for the phytoremediation of water bodies contaminated with heavy metals.