Insights on the Abiotic/Biotic Interactive Impacts on the Occurrence of PFASs in Municipal Solid Waste Landfill Leachate

Per- and polyfluoroalkyl substances (PFASs) presented in landfill leachate can be transported to groundwater and soil, posing risks to human health in food and water. However, the occurrence characteristics of PFASs in landfill leachate and the influence paths of abiotic and biotic factors have not been fully discussed. Our study found that the detection rate of PFASs in the leachate samples was 100%; ΣPFASs ranged from 1328 ng/L to 37,447 ng/L; and the average ΣPFASs was 9593 ng/L. Most of the physical and chemical indexes in the landfill leachate showed a significant positive correlation with PFASs concentration, with the main physical and chemical factors including TOC, sodium ion, chromium ion, and chloride ion. Moreover, dissolved organic matter had a very important influence on the environmental behavior of PFASs. The degree of dissolved organic matter (DOM) humification promoted the transportation of PFBA and PFBS from the landfill waste to leachate, while microbial DOM inhibited the transportation of ∑13 PFCAs. The microorganisms in the leachate were mainly Firmicutes, Campylobacterota and Proteobacteria, among which there was a negative correlation between PFBS and Proteobacteria, indicating that PFBS was highly toxic to Proteobacteria and would inhibit the growth of Proteobacteria in leachate. Firmicutes and Campylobacterota had little influence on PFASs. However, Synergistota, and Halanaerobiaeota, which had a low abundance, both positively correlated with the various PFASs. This result may imply that these rare microphyla are the main microphyla driving the transformation of PFASs in leachate. Microorganisms in leachate indirectly affected the occurrence of PFASs, mainly by influencing the environmental factors in leachate. Therefore, abiotic factors are important factors affecting PFASs in the landfill leachate. In summary, PFASs pollution management in landfills should be enhanced by regulating abiotic factors to control PFASs in leachate.