Department of Civil Engineering , McGill University , Montréal , Québec H3A 0C3 , Canada.
Environ Sci Technol. 2020 Feb 4;54(3):1513-1521. doi: 10.1021/acs.est.9b04989. Epub 2020 Jan 24.
Zwitterionic, cationic, and anionic per- and polyfluoroalkyl substances (PFASs) are identified in aqueous film-forming foam (AFFF) concentrates and AFFF-impacted sites. However, the mobility potential of zwitterionic and cationic PFASs is poorly understood, preventing reliable site assessment. The study aimed to elucidate the mobility behaviors of PFASs of various charge states in saturated soil-water systems and assess critical influencing factors. Five anionic, three zwitterionic, and one cationic PFASs were investigated in five soils through batch sorption experiments. Pairwise comparison revealed that the quaternary ammonium group imparted a strong affinity of cationic perfluorooctaneamide ammonium compound (PFOAAmS) for soils. The influence of the quaternary ammonium group is mitigated in polyfluoroalkyl betaines, yet perfluorooctane sulfonamidoalkyl betaine (PFOSB) showed strong sorption in selected soils. Two soil bulk properties showed some correlations with the soil-water distribution coefficient (). A positive correlation with the fraction of soil organic carbon was found only for anionic PFASs, whereas cation exchange capacity had an approximate positive correlation with only for PFOAAmS. Water chemistry (Ca and pH) influences the sorption of nonanionic PFASs in very distinct fashions or even in opposite trends to what was known for anionic PFASs. Sorption was insensitive to pH changes except for PFOSB; PFOSB underwent profound sorption reduction because its speciation occurs around neutral pH, while the two other betaines and PFOAAmS have p values that are outside of the environmentally relevant range. The lack of correlations suggests that the transport potential of PFASs is probably highly site-specific. It remains a challenge in deciphering PFAS sorption mechanisms and predicting how AFFF plumes migrate.
两性离子、阳离子和阴离子全氟和多氟烷基物质 (PFAS) 已在水成膜泡沫 (AFFF) 浓缩物和受 AFFF 影响的地点中被识别出来。然而，两性离子和阳离子 PFAS 的迁移潜力了解甚少，这阻碍了可靠的现场评估。本研究旨在阐明各种电荷状态的 PFAS 在饱和土壤-水系统中的迁移行为，并评估关键影响因素。通过批量吸附实验，在五种土壤中研究了五种阴离子、三种两性离子和一种阳离子 PFAS。成对比较表明，季铵基团赋予阳离子全氟辛烷酰胺铵化合物 (PFOAAmS) 对土壤的强烈亲和力。在多氟烷基甜菜碱中，季铵基团的影响会减弱，但全氟辛烷磺酰胺基烷基甜菜碱 (PFOSB) 在选定的土壤中表现出强烈的吸附。两种土壤总体性质与土壤-水分配系数 (Kd) 显示出一些相关性。仅发现阴离子 PFAS 与土壤有机碳分数呈正相关，而阳离子交换容量与 PFOAAmS 的 Kd 呈近似正相关。水化学（Ca 和 pH）以非常不同的方式影响非阴离子 PFAS 的吸附，甚至与阴离子 PFAS 的情况相反。除了 PFOSB 外，吸附对 pH 变化不敏感；由于其形态发生在中性 pH 左右，PFOSB 经历了深刻的吸附减少，而另外两种甜菜碱和 PFOAAmS 的 p 值超出了环境相关范围。缺乏相关性表明，PFAS 的迁移潜力可能高度取决于地点。在解释 PFAS 吸附机制和预测 AFFF 羽流如何迁移方面仍然存在挑战。
