Rhizobacteria effect on bioaccumulation and biotransformation of arsenic and heavy metal compounds in the technogenous soils

This study aimed to disclose migration and transformation of heavy metal and arsenic compounds in the soil-microorganisms-plant system. Plants have been grown on soil inoculated with experimental rhizobacteria Azotobacter and Bacillus. In our experiment, soil samples were collected close to the industrial site of the former Angarsk Metallurgical Plant (AMP) used to produce arsenic (Svirsk town, Eastern Siberia) and from background site. High As, Pb and Cd abundances, dozens and hundreds of times exceeding the Maximum Permissible Concentrations (MPC), were found in the soil around the former plant. Each soil sample was divided into control soil and soil inoculated with rhizobacteria used for plant growing. Concentrations of chemical elements were analyzed in easily exchangeable, carbonate, organic, and Fe hydroxide-associated fractions and chelate forms. Rhizobacteria initiate arsenic and heavy metals immobilization in organic fraction. The highest element abundances were found in the chelate form in soil inoculated by rhizobacteria. The intensity of As and heavy metals accumulation in the plants grown on the inoculated soil is markedly low, owing to biological adsorption of elements by the cells of rhizobacteria capable of creating a barrier for their supply into plants. The study of As and heavy metals behavior under the influence of rhizobacteria is of great importance in developing new biotechnologies related to soil remediation and crop production.