Enhanced bio-immobilization of Pb contaminated soil by immobilized bacteria with biochar as carrier

This paper examines the potential value of phosphate-solubilizing bacteria(PSB) in the dissolution of soil phosphorus and in the subsequent immobilization of lead (Pb), both in bacterial growth medium and in soil. In growth medium, Pseudomonas chlororaphis showed both phosphate-solubilizing and Pb-immobilizing capability, the immobilization of Pb was attributed to pyromorphite formation, as indicated by X-ray diffraction analysis. P. chlororaphis cannot multiply in soil in the presence of indigenous soil bacteria; however, when the added content of PSB-immobilized biochar (PIB) was equal to or greater than 800 mg/kg, the PSB could proliferate effective and the NH₄NO₃-extractable Pb concentration was decreased to below 1 mg/kg. Therefore, the inoculation of PIB in soil can be used as an alternative technique to Pb immobilization, thereby avoiding secondary pollution arising from the addition of large amounts of phosphorus as a heavy-metal passivator.