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A variety of plants have been used as phytoremediation materials to remove Cd from polluted soil. However, the disadvantages of using plants for decontamination include low biomass, low uptake, and inefficiency. We conducted experiments to determine the effects of spermidine and activated carbon treatments of Salix integra on Cd removal. The results showed that exogenous spermidine and activated carbon increased plant growth and root development compared with the CK. The increased dry mass (39.65–92.95%) with the combined spermidine and activated carbon treatments was higher than that with either single treatment (14.79–62.80%). The root length, surface area, root volume, and root diameter with the combined spermidine and activated carbon treatments (53.51–189.35%, 113.08–207.62%, 111.71–499.27%, and 32.51–106.62%, respectively) were higher than those of the lone application treatments (19.35–132.23%, 52.33–111.57%, 35.08–297.07%, and 24.22–81.38%, respectively). In addition, spermidine and activated carbon application reduced the toxicity of Cd to S. integra by improving the antioxidant capacity, thereby increasing the accumulation of Cd. The application of spermidine and activated carbon also changed the distribution of Cd in each part of S. integra. There was increased accumulation of Cd in the shoots and better absorption by the S. integra shoots, thereby improving their Cd remediation efficiency. The combined 0.8 mM spermidine and 0.5 g kg−1 activated carbon were most effective on removing Cd from the soil. The Cd removal efficiency was 78.11–120.86% higher than that of the CK. Our results may provide foundational information for understanding the mechanisms for the sustainable remediation of Cd-contaminated soil using a combination of spermidine and activated carbon. [Display omitted] • Effects of spermidine and activated carbon treatment of Salix integra on Cd removal. • Plant growth and development were increased compared with the control. • Cd toxicity to S. integra was reduced as the antioxidant capacity was improved. • Cd removal efficiency was 78.11–120.86% higher than that of the control. • This novel strategy might help understand the mechanisms of sustainable remediation. [ABSTRACT FROM AUTHOR]

The alkaline mineral amendment is a practical means of alleviating Cd concentration in rice grain (Cd R) in the short-term; however, the long-term remediation effect of mineral amendment on the Cd R and the eco-environmental controls remains unknown. Here a mineral (Si–Ca–Mg) amendment, calcined primarily from molybdenum tailings and dolomite, was applied biannually over 6 years (12 seasons) to acidic and moderately Cd-contaminated double-rice cropping ecosystems. This study investigated the inter-annual variation of Cd in the rice-soil ecosystem and the eco-environmental controls in subtropical rice ecosystems. Cd R was reduced by 50%–86% following mineral amendment. The within-year reduction in Cd R was similar between early rice (50%–86%, mean of 68%) and late rice (68%–85%, mean of 74%), leading to Cd R in all early rice and in 83% of late rice samples below the upper limit (0.2 mg kg−1) of the China National Food Safety Standards. In contrast, the inter-annual reduction in Cd R was moderately variable, showing a greater Cd R reduction in the later 3 years (73%–86%) than in the former 3 years (54%–79%). Three years continuous mineral amendment was required to guarantee the safety rice production. The concentrations of DTPA-extractable and exchangeable Cd fractions in soil were reduced, while the concentration of oxides-bound Cd was increased. In addition, the soil pH, concentrations of Olsen-P and exchangeable Ca and Mg were elevated. These imply a lower apparent phytoavailability of Cd in the soil following mineral amendment. An empirical model of the 3-variable using soil DTPA-Cd, soil Olsen-P, and a climatic factor (precipitation) effectively predicted temporal changes in Cd R. Our study demonstrates that Cd phytoavailability in soil (indexed by DTPA-extractable Cd) and climatic factors (e.g., temperature and precipitation) may directly/indirectly control the inter-annual reduction in Cd R following mineral amendment in slightly and moderately Cd-contaminated paddy ecosystems. [Display omitted] • Continuous mineral amendment (MA) in mild Cd-contaminated paddy immobilized Cd. • Three years continuous MA was required to guarantee safety rice production. • Inter-annual reduction of rice Cd (Cd R) was variable in 6-year biannual MA. • Cd R reduction was similar in early and late rice. • Temporal Cd R was effectively predicted by soil DTPA-Cd, Olsen-P, and precipitation. [ABSTRACT FROM AUTHOR]