Mechanisms of Manganese–Selenium Synergistic Mitigation of Arsenic–Cadmium Cotoxicity in Rice (Oryza sativa L.)

Cadmium (Cd) and arsenic (As) cocontamination threatens rice safety. In this study, the dual advantage of trace nutrient elements to enhance rice nutrition while reducing toxic metals was utilized, and coapplication of manganese (Mn) and selenium (Se) was proposed as a new strategy to address Cd–As cocontamination in rice. The experiment showed that the synergistic reduction of Cd and As in brown rice was superior to a single treatment. The mechanisms include (1) regulation of Cd and As transport proteins and enhancement of the antagonistic effects of beneficial elements; (2) enhancement of antioxidant defenses and key metabolic pathways; and (3) mobilization of rhizosphere sulfur-oxidizing bacteria and metal-fixing taxa to drive sulfide precipitation to immobilize contaminants. This approach combines agronomic intensification with environmental remediation by utilizing micronutrient interactions to provide a sustainable solution for Cd–As cocontamination of rice fields.