Noval porous phosphate-solubilizing bacteria beads loaded with BC/nZVI enhanced the transformation of lead fractions and its microecological regulation mechanism in soil

Soil lead pollution becomes a serious environmental problem. Microbial remediation has received widespread attentions due to high efficiency and no secondary pollution. In this research, a noval porous spherical phosphate-solubilizing bacteria bead loaded with biochar/nZVI (Bio-bead) was used to passivate lead in soil, and the effects and microecological regulation mechanisms of this process were also investigated. The results showed that the pH, OM, and AP of soil in the Bio-bead group were increased and the ORP was decreased over time compared with the blank group. The proportion of stable (oxidizable and residue) fractions of lead in Bio-bead group (45%) was much higher than that of the blank group (35%). In addition, the result of microbial community structure showed that Bio-beads did not change the species of dominant bacterial, excepting the abundance of Pseudomonas increased significantly and the abundance of Sphingomonas reduced during remediation. Redundancy analysis showed that pH, OM, AP and the ratio of residual and oxidizable fractions lead in soil were positively correlated with the abundance of Pseudomonas, while ORP was negatively correlated with the abundance of Pseudomonas. These findings have proved that Bio-bead is a potential strategy for remediation of lead-contaminated soil even in complexed soils.