Adsorption and fate of per- and polyfluoroalkyl substances from landfill leachate onto aquifer media under the influence of dissolved organic matter

As a primary solid waste treatment method, landfills risk groundwater pollution via leachate leakage, which aids pollutant transport through aquifer media. However, research on the adsorption mechanisms of emerging pollutants in aquifer media and Dissolved Organic Matter (DOM)’s impact on per - and polyfluoroalkyl substances (PFASs) adsorption remains limited. This study investigated four short-chain PFASs in three landfills of different ages (AD > SY > ZT) via adsorption equilibrium experiments, examining the effects of leachate DOM (ultrafiltered into <5, 5–10, >10 kDa fractions) and typical coexisting ions (Cl − -Mg 2+ , SO 4 2− -Mg 2+ , SO 4 2− -Na + ) on PFAS migration, with key factors identified via spectral analysis. Results showed leachate DOM and coexisting ions significantly affected PFAS adsorption capacity: <5 kDa DOM increased adsorption by 32 % on average (vs. 8 %–12 % for 5–10 kDa DOM); Cl − -Mg 2+ had a 1.6-fold stronger synergistic effect than SO 4 2− -Na + . Adsorption equilibrium took 24 h (pure water) vs. 20 h (leachate). AD landfill DOM (SUVA 254 : 4.1 L/(mg·m)) had 51.9 % higher aromaticity than ZT (2.7 L/(mg·m)), regulating PFAS adsorption better. These results confirm adsorption mode is linked to DOM molecular weight and ion type, which determine PFAS adsorption efficiency. Additionally, leachate DOM promotes adsorption via hydrophobic interactions/complexation (regulatory effect depends on its molecular weight); aquifer media adsorption efficiency improves in leachate, highlighting DOM's role in pollutant migration. DOM composition changes with landfill age also affect PFAS adsorption. • Landfill leachate DOM and typical coexisting ions affect PFASs adsorption by aquifer media. • Different molecular weight DOM affects PFASs adsorption differently. • Leachate DOM humic components are affected by adsorption. • PFASs adsorption research conclusions aid landfill pollution prevention and control.