The complex effect of DOM on PFOA and PFOS transport: Considering the interference of solution ionic strength and cation type

The transport behavior of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in porous media controls their final environmental fate and risk. Current work used column experiments and a two-site kinetic retention model to reveal the effect of dissolved organic matter (DOM) on their migration under the interference of solution ionic strength and cation type. Results showed the migration of PFOA and PFOS was inhibited by 1 mg/L DOM but promoted by 10 mg/L DOM. Compared with the presence of 1 mg/L DOM, increasing ionic strength (1–10 mM) and changing cation type (Na+ to Ca2+) had a stronger inhibitory effect on PFOS transport. However, the opposite is true for PFOA due to its different molecular structure and adsorption behavior from PFOS. Ca2+ was more tended to interact with PFOS (owing to its sulfonate group) than with PFOA, and PFOS had a higher affinity with Ca2+ than with DOM. Cation bridging and increasing ionic strength could promote the inhibition of PFOA and PFOS transport by 1 mg/L DOM. The influence of DOM on PFASs transport could be very complex in the natural environment due to the variable solution chemistry conditions of pore water and physico-chemical properties of PFASs. The results of this work have scientific significance for better evaluating and managing the environmental risk of soil PFASs.