Indigenous Sporosarcina pasteurii-driven carbonate mineralization couples lead immobilization with erosion control in contaminated slopes.

Lead (Pb) contamination in erosion-prone soils presents a dual environmental issue because it causes concurrent pollution and soil degradation. We developed a sustainable bioremediation technique utilizing microbially induced calcium carbonate precipitation (MICP) with the indigenous Pb-tolerant ureolytic bacterium Sporosarcina pasteurii, isolated from the biological soil crusts of the Qinghai-Tibet Plateau. The strain exhibited considerable urease activity and consistent growth under extreme lead stress (2000 mg/L) and effectively facilitated carbonate mineralization. The MICP treatment resulted in the formation of a continuous CaCO3 layer within the soil profile, significantly enhancing mechanical stability and decreasing sediment yield by 77.6-92.5% across different slopes (45° and 70°) and rainfall intensities (6 and 18 mm). Simultaneously, MICP significantly altered Pb migration dynamics by retaining Pb in the upper soil layer and restricting the transport of dissolved and particulate Pb via runoff and erosion. BCR sequential extraction demonstrated a shift of Pb from the mobile weak-acid extractable and reducible fractions to the more stable residual and oxidizable fractions. Pb immobilization was associated with MICP-induced carbonate mineralization, crystal bridging, particle encapsulation, and pore filling, and incorporation into Pb-bearing mineral phases. Subsequent multivariate analysis revealed that Pb retention and erosion resistance were mostly governed by CaCO3 accumulation and soil stabilization. This study proposes a multiscale mechanism of self-reinforcing physical reinforcement-chemical fixation synergy and demonstrates the potential of MICP as a nature-based solution for remediating heavy metal-contaminated, erosion-prone slopes in cold and ecologically fragile regions.