Mechanism of composite passivators to reduce cadmium absorption and accumulation in Chinese cabbage on cadmium-polluted soil

Abstract

Abstract Background The accumulation of heavy metals, including cadmium (Cd), in soil endangers the quality of agricultural products and can harm human health. At present, the application of passivators is a relatively efficient, quick, and economical way to address this problem. In the experimental site of the present study, the effects of different composite passivators (red mud + lime + phosphorite powder, red mud + lime + biochar, lime + humic acid + seafoam, seafoam + biochar + red mud, seafoam + biochar + phosphorite powder) on the physiology and biochemistry of Chinese cabbage were investigated. Results After passivator application, the soil’s effective state Cd content was reduced, and the Cd content, bioconcentration factor (BCF), transfer coefficient (TF), oxidative stress, and antioxidant enzyme activity levels of Chinese cabbage leaves and stalks were reduced to different degrees. The reduction of reactive oxygen species content was mainly owing to passivator application, which reduced the degree of oxidative stress and increased the content of osmotic substances, the activity of antioxidant enzymes, and the ability to scavenge hydroxyl radicals. The soluble protein content of Chinese cabbage was mainly increased by an increase in the content of osmotic substances and non-enzymatic antioxidant substances and a reduction in the inhibition of protein synthesis. Conclusions Our findings suggest that the reduction of reactive oxygen species was the main cause of the reduction of Cd accumulation, transport, and toxicity in leaves. The increase in soluble protein was the main cause of the reduction of Cd accumulation, transport, and toxicity in petioles. Graphical Abstract

Keywords

• Antioxidant system
• Composite passivator
• Moderately to mildly Cd-contaminated soil
• Osmotic regulatory substances
• Path analysis