The Pb capture mechanism of soil prophylactic agents prepared from phosphorus tailings and the influence of phosphorus speciation on its slow-release mechanism.

This research activated phosphorus tailings to prepare a high‑phosphorus core (HPC) for multi-species composite slow-release heavy metal soil prophylactic agents (MCP), aiming to extend the slow-release period of MCP and enhance the efficiency of Pb stabilization. During the preparation of HPC, the proportion of non-apatitic inorganic phosphorus (NAIP) and apatite phosphorus (AP) continuously decreased with increasing polymerization temperature. At 400 °C, polyphosphates (PP) began to form, reaching 74.26 % at 600 °C. Initially, the rapidly soluble NAIP remained the major component of HPC, but the proportion of AP increased with higher polymerization temperatures, reaching 40.8 % at 600 °C. After 120 days of cultivation with four MCPs (MCP 300-21, MCP 400-12, MCP 500-14, MCP 600-14), the total soil phosphorus (TSP), soil organic matter (SOM), and Pb stabilization capacity of the cultivated soil showed significant improvements, reaching maximum values of 2.39 mg/g, 38.16 mg/g, and 45.4 mg/g, respectively, which are 9.9, 4.4, and 5.9 times higher than those of the CK soil. KEGG (Kyoto Encyclopedia of Genes and Genomes) functional prediction analysis indicated that MCPs contribute directly or indirectly to the forms and chemical stability of Pb by stimulating soil physiological and biochemical processes. This research proposes a novel approach for using phosphates in soil heavy metal management strategies and provides new insights into the mechanisms of heavy metal stabilization in soil using environmental functional materials.