Analysis on application of reclaimed substrate soil in mine ecological restoration of phosphate tailings base

The Kunyang Phosphate Mine is situated within the water quality protection area of Dianchi Lake in Kunming, Yunnan Province. Mine reclamation and ecological restoration hold significant importance for safeguarding the aquatic environment of Dianchi Lake. Utilizing a substantial quantity of phosphate tailings generated from the flotation process of the Kunyang Phosphate Mine, efforts are made to enhance the substrate soil for mine reclamation. Through soil column leaching experiments, effective ecological restoration methodologies have been devised. Subsequently, the feasibility and effectiveness of these methods have been validated during pilot tests, thereby presenting novel concepts and directions for mine reclamation within the basin. During the improvement experiment phase, with phosphate tailings serving as the substrate, black shale, fillers, compost, phosphate-fixing agents, and granulating agents are selected as modifiers. The factors influencing the properties of the substrate soil, such as infiltration rate, pH value, bulk density, and saturated water content, are investigated. The correlations between varying addition amounts of each modifier and the alterations in the aforementioned properties of the substrate soil are also ascertained. Soil column leaching experiments are designed to mimic the rainfall environment and explore the ameliorative impact of the modifiers on the phosphate content of the phosphate tailings. Upon comparing and analyzing the experimental data, it is observed that when the addition amount of filler SZ reaches 15%, compost is 12%, phosphate-fixing agent FP-1 is 0.15%, and granulating agent is 0.02%, the phosphate content in the leachate is merely 0.18 mg/L（in terms of P）. In contrast to the control treatment CK, the phosphate content experiences a significant reduction of 97.8%, the infiltration rate escalates from 7.464 mm/h to 8.508 mm/h, the pH value is adjusted from 6.87 to 7.23, and the EC value diminishes from 2.625 mS/cm to 0.961 mS/cm. In the in-depth implementation stage of the pilot test, an analysis of the physical and chemical properties of the substrate soil is conducted, covering detection indices such as pH value, EC value, organic matter, nutrients, and heavy metals, all of these meet the industry standard of “Soil for Greening and Planting”（CJ/T 340—2016）. Simultaneously, an examination of the leachate water quality is carried out, key detection indicators like pH value, EC value, phosphate, fluoride, and heavy metals all conform to the national standard of “Integrated Wastewater Discharge Standard” （GB 8978—1996）. The growth of plants in each experimental area is in good condition, verifying the effectiveness of the substrate soil and planting plan for the reclamation of phosphorus tailings base mines.