Potential of a novel modified gangue amendment to reduce cadmium uptake in lettuce (Lactuca sativa L.)

Highlights: • Gangue was modified with KOH successfully. • Modified gangue can reduce bioavailable Cd in soil. • The enzymes activities of soil and plants changed significantly after treatment. • Remediation mechanisms were ion-exchange, precipitation and adsorption. In this study, the modified gangue (GE) was prepared by calcination at lower temperatures using potassium hydroxide (KOH) as the activating agent. The field emission scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray fluorescence (XRF) methods were employed to analyze the physicochemical characteristics of GE before and after the modification. Besides, the GE and commercial zeolite (ZE) were compared in the remediation of Cd-contaminated soil in field experiments. The results showed that both the GE and ZE had positive effects on the stabilization of Cd, decreasing the available Cd by 21.2–33.9% and 22.1–28.2%, respectively, while no significant difference was observed between the two amendments, indicating that the modification of GE was successful. Moreover, the application of GE decreased the Cd mobilization and uptake in lettuce shoot and root by 54.9–61.5% and 9.3–13.2%, respectively, and at the same time, the bio-available Cd decreased by 20.9–34.5%. Moreover, with the addition of GE, activities of urease and alkaline phosphatase increased in soil, while the peroxidase and superoxide dismutase activities were notably reduced in plants. Therefore, GE could be used as an effective amendment for the alleviation of Cd accumulation and toxicity, and thereby improve food safety.