Lead (Pb) is a major toxicological concern of the present day that demands immediate attention. The use of aquatic macrophytes with high Pb tolerance and accumulation may be a very convenient and economically viable solution for remediating Pb. We examined the ability of Salvinia cucullata, Alternanthera sessilis, Lemna minor, and Pistia stratiotes to remove 0.12 mM, 0.24 mM, 0.36 mM, and 0.48 mM Pb for 96-h under hydroponic cultivation system. The plants accumulated variable amounts of Pb: S. cucullata > A. sessilis > P. stratiotes > L. minor, with low mobility of Pb from root to shoot. Lead uptake kinetics were monitored up to 96-h. After 96-h, the uptake efficiency for S. cucullata (98-99%), A. sessilis (79-96%), L. minor (45-79%), and P. stratiotes (40-76%) was noted. For S. cucullata and A. sessilis, an extremely high uptake rate was seen within the initial 24-h of trials, followed by slower uptake till 96-h. P. stratiotes and L. minor worked best at 0.12 mM Pb. Pb-Phytotoxicity became prominent at 0.48 mM exposure with biomass loss and morphological changes. The plants had a quick growth rate, extensive root system, high biomass yield, and the ability to tolerate and accumulate Pb that made them suitable for phytoremediation purposes. NOVELTY STATEMENT: Lead phytoremediation potential of four aquatic macrophytes found in Indian waters was evaluated. These macrophytes, often considered as weeds, could be used for phytoremediation purposes that would turn out to be a sustainable means of the utilization of natural resources in developing countries like India. In this study, not only metal accumulation by plants but also the lead uptake kinetics at several time intervals and valuable growth attributes were estimated to establish the suitability of these plants as probable lead phytoremediators. Two of the plant species, Salvinia cucullata, and Alternanthera sessilis, showed excellent Pb accumulation capacities that had not been reported earlier, to the best of our knowledge. The work is all the more significant as there have been needs for identifying Pb-phytoremediators well suited to native climate and growth conditions that could take up large amounts of metal from the substratum.
Keywords: Aquatic plants; lead; phytoextraction; root; uptake kinetics.