Synergistic mitigation of lead accumulation in celery by magnesium polypeptide and microbially induced calcite precipitation in phosphate mining wasteland soils.

Lead (Pb) contamination in phosphate mining wasteland soils severely inhibits plant growth and compromises ecological safety, thereby necessitating long-term remediation strategies to restore ecosystem functions. Pot experiments were conducted to evaluate the synergistic effects of microbially induced carbonate precipitation (MICP) and magnesium polypeptide (MP) amendments on celery growth and the restructuring of rhizosphere microbial communities. Under Pb stress (200 mg/kg), Pb accumulation in celery was significantly reduced by the combined MICP-MP treatment, with concentrations decreasing to 4.49, 0.26, and 1.93 mg/kg in roots, stems, and leaves, respectively; concurrently, plant growth and development were promoted. Correlation analysis revealed that the remediation-induced enhancement of soil physicochemical properties acted as a primary environmental driver, showing a significant negative correlation with exchangeable Pb content. The transformation of Pb from high-risk, bioavailable exchangeable forms to low-risk, stable fractions, such as carbonate-bound and Fe/Mn oxide-bound forms, was successfully promoted by the treatment, concomitant with enhanced soil physicochemical properties and biological activity. Furthermore, rigorous compositional analysis demonstrated that the MICP-MP treatment significantly enriched beneficial bacterial taxa, such as Nocardiopsis and Planococcus. These shifts in community composition played a key role in enhancing the soil bacterial community's adaptation to Pb stress. In summary, Pb-induced phytotoxicity was alleviated, and rhizosphere microbial stability and assembly were modulated by the MICP-peptide combination, providing new insights into plant-microbe interactions under heavy metal stress.