Effects of the different types of conditioners on remediation and microbial community in Cd-contaminated soil

【Objective】To explore the effects of soil conditioner on the remediation and microbial community composition of cadmium(Cd) -contaminated soil, so as to provide a scientific basis for in-situ remediation and management of Cd-contaminated farmland soils using conditioners with different soil active components.【Method】Field experiments were carried out in Cd-polluted farmland in eastern Guangdong, and blank controls were set to study the effects of different soil active component modifiers(mineral type, organic type and microbial type) on soil basic physical and chemical properties, Cd availability and microbial community structure.【Result】The results showed that the application of soil conditioner significantly increased soil pH(0.11-0.24) (P<0.05, the same below), increased organic carbon content(21%-47%), decreased soil available Cd (13%-48%) and brown rice Cd content (26%-42%). Mineral and microbial conditioners led to the largest decrease of Cd content in brown rice. In general, the application of conditioner improved the soil micro domain environment. The results of high-throughput sequencing showed that adding conditioner could maintain the diversity and richness of normal microbial community in polluted soil and significantly change the composition and soil microbial community structure, in which the relative abundance of Desulfobacterota and Bacteroidota decreased. Mineral and organic conditioners increased the relative abundance of Actinobacteriota and Gemmatimonadota in soil, while microbial conditioners increased that of Acidobacteriota. Further, for fungal communities, mineral conditioner significantly increased the relative abundance of Basidiomycota and decreased that of Ascomycota. Organic conditioner significantly increased the relative abundance of Mortierellomycota and decreased that of Rozellomycota. Microbial conditioner significantly increased the relative abundance of Ascomycota and decreased that of Rozellomycota. Obviously, the microbial conditioner could significantly improve the level of dominant populations of bacteria and fungi. Correlation analysis showed that brown rice Cd content and microbial community were significantly positively correlated with Proteobacteria, Desulfobacterota and Bacteroidota. In addition, redundancy analysis and Monte Carlo test showed that the total phosphorus content in soil was an important environmental factor affecting the community structure of soil bacteria and fungi.【Conclusion】In terms of reducing the content of available Cd in soil and Cd in brown rice and its impact on soil microbial structure, microbial soil conditioner has the best remediation effect, which can reduce the Cd in brown rice and improve the structure of soil flora.