To explore the effects of Fe/P-loaded biochar on neutral Cd-contaminated paddy soils and the potential synergistic effects between biochar and modifying materials, a pot experiment was conducted using neutral paddy soil with a total Cd concentration of 1.10 mg/kg. Ball milling was employed for modified biochar production. Specifically, iron-loaded biochar (PBCFe) and phosphorus-loaded biochar (PBCP) were prepared using Fe2O3 and K3PO4, respectively. Results showed that PBCP significantly increased rice biomass while effectively inhibiting Cd uptake and accumulation in rice grains. Compared to the control (CK), P (K3PO4), and PBC treatments, the Cd content in rice grains under PBCP treatment decreased by 69.20%, 52.13%, and 56.06%, respectively. Moreover, compared with the treatments using single modifiers, PBCP and PBCFe effectively reduced Cd uptake and accumulation in rice tissues, especially in leaves and stems. In contrast, PBCP was more effective than PBCFe in enhancing iron plaque formation and Cd adsorption onto iron plaque. This promoted Fe uptake in rice roots, which might inhibit the upward translocation of Cd from roots to stems. Further analysis with FTIR and XPS results indicated that PBCP might be more compatible in immobilizing Cd in soil by inducing Cd-P co-deposition. Therefore, phosphorus-loaded biochar (PBCP) could be a more promising amendment for remediating Cd-contaminated alkaline rice paddy soils and improving rice quality.
Sui et al. (Sun,) studied this question.