Effect of Organic and Inorganic Soil Amendments on Cadmium Immobilization and Bioaccumulation in Chinese Cabbage

Chemical immobilization, as a cost-effective and environmentally friendly technique, has been widely researched in the remediation of cadmium (Cd)-contaminated soil. The key is to find appropriate amendments and optimize their use. In this study, the effects of the application of an inorganic material (phosphorus slag (PS)) and organic materials (biochar (BC) and beer lees (BL)), individually or combinedly on the immobilization of Cd in contaminated soil and subsequent bioaccumulation in Chinese cabbagewere investigated. The results showed that PS and PS+BL were more effective in decreasing exchangeable Cd (EX-Cd) than other treatments, decreased by 91.2% in the PS treatment and by 64.0% in the PS+BL treatment. However, the soil enzyme activity and soil microbial activity decreased in the treatment with PS alone. In contrast, the combination use of PS and BL could increase soil enzyme activity, soil microbial activity, and functional diversity, and decrease EX-Cd as well. Moreover, the PS+BL treatment reduced the accumulation of Cd in Chinese cabbage most effectively, 81.5% in roots and 72.5% in shoots. This treatment could also increase the aboveground height and chlorophyll content of Chinese cabbage while reducing the content of malondialdehyde (MDA). Thus, the PS + BL treatment is highly recommended for Cd immobilization, as it can improve soil quality and reduce Cd accumulation in Chinese cabbage at the same time and hence promote plant growth.