Understanding subsurface transport of perfluoroalkylated substances (PFASs) is of critical importance for the benign use and risk management of PFASs. As the most commonly found PFASs, perfluorooctanoic acid (PFOA) is used as a representative PFAS and water-saturated column experiments were conducted to investigate the effect of Al/Fe oxyhydroxide coating and ionic strength on its transport at an environmentally relevant PFOA concentration (6.8 μg L⁻¹). Our results showed a clear increase in PFOA retardation in Al/Fe oxyhydroxide coated sand (retardation factor: Al: 1.87–5.58, Fe: 1.28–4.05) than those in uncoated sand (1.00–1.05), due to the stronger electrostatic attraction between anionic PFOA and Al/Fe oxyhydroxide coated sand surface. Notably, Al oxyhydroxide have a more profound effect on PFOA retention and retardation than Fe oxyhydroxide. Besides, higher ionic strength significantly inhabited PFOA retention and retardation in positively charged sand, and the considerable retention of PFOA (∼90%) in deionized water than those in 1.5 mM and 30.0 mM NaCl (<10%) clearly proves the role of competitive adsorption of Cl⁻ on PFOA transport in positively charged sand. In contrast, higher ionic strength (0 mM–30 mM NaCl) slightly increased PFOA retardation in negatively charged sand, illustrating the dominance of electrostatic interaction. Our findings advance current knowledge to understand PFOA transport in natural media with different surface charge property under environmental PFOA concentrations.

了解全氟烷基化物质（PFAS）的地下运输对于PFAS的良性使用和风险管理至关重要。作为最常见的PFAS，以全氟辛酸（PFOA）为代表的PFAS，并进行了水饱和柱实验，以研究Al / Fe羟基氧化物涂层和离子强度对其在与环境相关的PFOA浓度下的迁移的影响（6.8微克L ^-1）。我们的结果表明，铝/铁羟基氧化物涂层砂（延迟因子：Al：1.87–5.58，Fe：1.28–4.05）的PFOA延迟明显高于未涂层砂（1.00–1.05），这是因为阴离子PFOA和Al / Fe羟基氧化物涂层的砂表面。值得注意的是，羟基氧化铝比羟基氧化铁对PFOA的保留和延迟有更深远的影响。此外，较高的离子强度显着地影响了带正电的砂中PFOA的保留和阻滞，并且与1.5 mM和30.0 mM NaCl（<10％）相比，去离子水中PFOA的保留率高（约90％），这清楚地证明了竞争的作用。氯的吸附^-在带正电的沙子中进行PFOA运输。相反，较高的离子强度（0 mM–30 mM NaCl）在带负电的沙子中略微增加了PFOA阻滞作用，说明了静电相互作用的优势。我们的发现提高了当前的知识，以了解在环境PFOA浓度下具有不同表面电荷特性的天然介质中PFOA的运输。