Abstract
Disposal of dredged sediment contaminated with heavy metals on site or in landfills inevitably causes leaching of metals that generate new environmental problems. In this study, we investigated the effectiveness of stabilizing heavy metal Cd in sediment taken from Dongting Lake, China, using a chitosan-coated zeolite, and assessed the feasibility of reusing the stabilized sediment in river bank soil based on chemical and biological analyses. Results showed that the addition of chitosan-coated zeolite significantly reduced acid-exchangeable Cd by 8% in the dredged sediment and 7% in a sediment–soil mixture. Cadmium leachability was greatly reduced in the amended sediment or sediment–soil mixture. Toxicity bioassay using Eisenia fetida showed the mortality rate of worms reduced by 16% in sediment–soil mixture with a Cd concentration of 550 mg/kg and by 17% under a Cd concentration of 250 mg/kg, both with the addition of modified zeolite. Moreover, assimilation of Cd in the earthworms was decreased by a maximum of 36 mg/kg in the sediment–soil mixture with zeolite amendment. These results indicate that the reuse of Cd-contaminated sediment following chitosan-coated zeolite modification is a feasible option for treating the dredged sediment, and could thus benefit both aquatic and terrestrial systems.
•Dredged sediment contaminated with Cd was stabilized with chitosan-coated zeolite.•Cd leachability in the soil–sediment mixture was reduced upon modified-zeolite addition.•Chitosan-coated zeolite reduced the bioavailable Cd accessed by E. fetida.•The stabilized dredged sediment could be further reused for land application.