Influence of humic acids on the accumulation of copper and cadmium in Vallisneria spiralis L. from sediment

Physiological responses and metal accumulation in Vallisneria spiralis L. exposed to copper and cadmium contaminated sediment were examined at different metal concentrations and the influence of humic acids on copper and cadmium accumulation was also studied. The plants of V. spiralis accumulated high amount of copper and cadmium. The maximum accumulation of 396 and 114 mg kg−1 DW copper were found in the roots and shoots, respectively, at 614 mg kg−1 DW after 21 days’ copper exposure; they were 63.8 and 48.0 mg kg−1 DW for cadmium at 88.69 mg kg−1 DW. The plants showed decrease in chlorophyll content with the increasing concentration of copper/cadmium in sediment. With addition of humic acids from 3.09 to 7.89 g kg−1 DW, both copper and cadmium accumulation in V. spiralis were significantly inhibited (p < 0.01). The cadmium concentrations of roots and shoots of plant decreased 26.4–50.3 and 14.3–33.0% under cadmium treatments, respectively; copper accumulation decreased much more with 44.0–77.0 and 35.0–62.7%, respectively. It was concluded that V. spiralis appeared to be an ideal candidate for the phytoremediation of copper and cadmium polluted sediments, and humic acids had an important role in regulating copper and cadmium bioavailability and toxicity in sediments.