Synergistic Remediation of Cadmium-Pyrene Co-Contaminated Soil Using the Chelating Surfactant LED3A and Ryegrass

Pot experiments were conducted to investigate the effects and mechanisms of LED3A-enhanced ryegrass remediation of cadmium （Cd）, pyrene （Pyr）, and Cd-Pyr contaminated soils. The effects of different LED3A concentrations on plant growth （height, fresh weight, and antioxidant responses） and soil properties （enzyme activities and microbial activity） were assessed, along with the pathways and dynamics of contaminant removal in the LED3A–rygrass system. The results showed that LED3A was non-toxic to ryegrass and promoted root development, modulated antioxidant enzymes to reduce MDA concentration, enhancing soil enzyme activities and microbial functions, and thereby facilitating synergistic contaminant removal by plants and microbes. At the optimal LED3A concentration （800 mg/kg）, Cd extraction efficiency increased by 85.29% in single-contaminated soil and by 55.41% in co-contaminated soil, while Pyr extraction efficiency increased by 1.66-fold and 8.64-fold, respectively. Additionally, rhizosphere degradation of Pyr was increased by 7.95% and 10.15%. These results demonstrate that LED3A improves the bioavailability of pollutants through its dual chelation-solubilization properties, and enhances the plant-rhizosphere-microorganism system to achieve simultaneous removal of Cd and Pyr.