Advances on Effects and Mechanisms of Biochar on Chemical Forms of Heavy Metals in Contaminated Soil

As a new type of environmental remediation material with its special structural characteristics, biochar can be used to directly adsorb and fix soil heavy metals through electrostatic adsorption, ion exchange, functional group complexation, and precipitation. Biochar can also indirectly affect soil physical and chemical properties, such as soil pH, organic matter, redox potential, etc., which can also affect the forms of heavy metals in the soil. The form of heavy metals can have great influence on their biological activities and lead to different environmental effects. Based on the relevant domestic and foreign literature, this paper summarizes the impacts of different types of biochar on the chemical form of heavy metals in soil. The influences of physical, chemical and microbial mechanisms of biochar on the chemical forms of heavy metals were discussed. Further studies are needed to explore the interaction between biochar and microorganism and the impacts of its microbial mechanisms on the form of heavy metals through omics approaches.