Abstract: Perfluorooctanoic acid (PFOA) and its salts are a group of emerging persistent organic pollutants with both hydrophobic and oleophobic properties. Their widespread presence in soil and groundwater threatens human health and ecological safety. In this study, we investigated the effects of solution ionic strength, pH, dissolved organic matter (DOM), and cation type on the migration of PFOA through saturated column experiments. The breakthrough curves were fitted by the convection-diffusion equation, and the key mechanisms were discussed. Results showed that PFOA had a high mobility. When the background electrolyte was NaCl, the ionic strength and pH of the solution did not affect the maximum relative concentration (C/C_0max) of PFOA, and its breakthrough rate remained at about 100%. However, the electrostatic repulsion between PFOA and the porous media was weakened, leading to a slow migration velocity under acidic conditions. When the background electrolyte was CaCl₂, the migration characteristics of PFOA significantly changed. The increase in ionic strength and the decrease in pH reduced the breakthrough rate of PFOA by 8.3% and 23.4%, respectively. In addition, DOM had the ability to inhibit the migration of PFOA, which was enhanced by Ca²⁺. Multivalent cations in the pore solution could alter the interaction between PFOA and the pore medium by bridging. This alteration could change the response of PFOA transport behavior to variations in solution chemical conditions and play a crucial role in its migration. These results provide an important scientific basis for predicting the environmental transport behavior and managing the migration risk associated with PFOA.

Key words: perfluorinated compound, transport, solution chemical condition, dissolved organic matter, multivalent cation