Application of wetland waste plant biochar in combination with arbuscular mycorrhizal fungi on immobilization of Cd in contaminated soil

Abstract

Abstract In this study, biochar pyrolyzed from different wetland waste plants (Reed, Typha, Canna) was used to immobilize Cd in contaminated soil. The results showed that biochar could all enhance the residual Cd2+ in soil. Moreover, Ca500 (pyrolyzed at 500 ℃ from Canna) showed the best immobilization capacity due to its larger surface, higher number of pores and its regular, smooth structure. Optimum conditions for Ca-500 immobilization to Cd2+ in soil were: amount 6% (wt%) and contacting time 16 weeks, the exchangeable and the state of bound to carbonates of heavy metals reduced 92.08% and 67.64%, respectively. After combining biochar with arbuscular mycorrhizal, the results showed that the combined system could more effectively reduce the transportable Cd content in soil, increase the proportion of residual Cd, effectively reduce the migration of Cd, improve the biomass and root length of vegetables, reduce Cd absorption by vegetables and the ability of vegetables to transfer Cd from root to the upper part, and reduce the edible safety risk. Simultaneously, biochar with arbuscular mycorrhizal can improve the antioxidant capacity of vegetables and their resistance to heavy metals, optimize the composition of soil microbial community, and improve soil microbial abundance and community β-diversity. It can also significantly change the functional gene expression of soil microorganisms, soil fertility, and the self-healing ability to heavy metals.