Immobilization of Pb and Cd by two strains and their bioremediation effect to an iron tailings soil

Abstract

Soil quality of the iron tailings mining was worrying and there are many kinds of heavy metals exceeding the standard. For tailing soil remediation, two strains (C2-Z and P2-Z) were isolated from iron tailing soil in Northwest China based on their Cd and Pb immobilizing potential, respectively. Biosorption capacity of the two strains were 51.90 mg/g and 109.73 mg/g, respectively. Changes of surface morphology and functional groups of C2-Z and P2-Z cells were observed after exposed to Cd2+ and Pb2+ by SEM-EDS and FTIR. Strain C2-Z and P2-Z achieved the immobilization of Cd and Pb respectively through bioprecipitation (25.9 %, 47.07 %), extracellular biosorption (24.5 %, 46.98 %) and intracellular accumulation (1.4 %, 1.95 %). Medium-scale ecosystem experiments revealed that the bacterial consortia CP could reduce acid-soluble Pb (5.72 %) and Cd (16.72 %) in the tailing soil, and increased urease activities (from 0.11–28.5 ng NH4-N/g), acid phosphatase activities (from 0.001–64.02 ug pNP/g) and sucrase activities (from 0.001–50.99 mg Glc/g). Thus, the isolated strain C2-Z and P2-Z could serve as potential candidate for the remediation of Cd and Pb contaminated soil due to their significant Cd and Pb removal efficiency and immobilizing capability.