磷石膏中特征污染物溶出的原位控制及浸提液对苜蓿萌发的影响OA

Total phosphorus(TP)and fluoride(F−),as characteristic pollutants in phosphogypsum(PG)stockpile leachates,are continuously released through rainfall and surface runoff erosion.Together with hydrogen ions(H+),they form highly acidic and toxic effluent,which significantly contributes to the environmental degradation of PG stockpiles and surrounding ecosystems.Achieving in-situ control of pollutant release while simultaneously improving plant growth conditions has become an urgent challenge in PG stockpile remediation.This study investigated a typical large-scale open-air PG stockpile in Guizhou Province,employing two calcium-based inorganic passivation combinations(CaCO3/Ca(OH)2 and CaCl2/Ca(OH)2)combined with organic amendment(brewing sludge)at low addition rates(1%～3%w/w).The systems were evaluated for in-situ control efficiency of characteristic pollutants in leachates,and effects on pioneer plant(Medicago sativa L.)seed germination and seedling antioxidant enzyme activities.Results demonstrated that minimal amendment addition significantly suppressed TP(99%reduction)and F−(93%～95%reduction)release(P<0.05),while stabilizing leachate pH at 6～9.Treated leachates enhanced alfalfa germination parameters(GR,GE,GI,SVI)and antioxidant enzyme activities(SOD,POD,CAT).Sequential extraction revealed transformation mechanisms:water-extractable P(42%)and bioavailable F(50%)were converted into Ca-bound P(65%～80%)and residual F(76%～88%)through excess Ca2+availability.This speciation shift effectively immobilized pollutants within PG matrix,reducing phytotoxicity.The findings provide theoretical support for in-situ contaminant immobilization and soilless ecological restoration of open-air PG stockpiles.