Soil, Water, and Environmental Science Department, School of Earth and Environmental Sciences, University of Arizona, Tucson, AZ, 85721, USA; Hydrology and Atmospheric Sciences Department, School of Earth and Environmental Sciences, University of Arizona, Tucson, AZ, 85721, USA.
Water Res. 2019 Apr 1;152:148-158. doi: 10.1016/j.watres.2018.12.057. Epub 2019 Jan 11.
Per- and poly-fluoroalkyl substances (PFAS) are emerging contaminants of critical concern for human health risk. Assessing exposure risk requires a thorough understanding of the transport and fate behavior of PFAS in the environment. Adsorption to fluid-fluid interfaces, which include air-water, OIL-water, and air-OIL interfaces (where OIL represents organic immiscible liquid), is a potentially significant retention process for PFAS transport. Fluid-fluid interfacial adsorption coefficients (K) are required for use in transport modeling and risk characterization, yet these data are currently not available for the vast majority of PFAS. Surface-tension and interfacial-tension data sets collected from the literature were used to determine interfacial adsorption coefficients for 42 individual PFAS. The PFAS evaluated comprise homologous series of perfluorocarboxylates and perfluorosulfonates, branched perfluoroalkyls, polyfluoroalkyls, alcohol PFAS, and nonionic PFAS. The K values vary across eight orders of magnitude, and are a function of molecular structure. The results of quantitative-structure/property-relationship (QSPR) analysis demonstrate that a model employing molar volume (V) as a descriptor provides robust predictions of log K values for air-water interfacial adsorption of the wide range of PFAS. The model also produced good predictions for a limited set of data for OIL-water interfacial adsorption. The predictive capability of the QSPR model for a wide range of PFAS with greatly varying structures reflects the fact that molar volume provides a reasonable representation of the influence of molecular size on cavity formation/destruction in solution, and thus the hydrophobic-interaction driving force for interfacial adsorption. The QSPR model presented herein provides a means to incorporate the fluid-fluid interfacial adsorption process into transport characterization and risk assessment of PFAS in the environment. This will be particularly relevant for determining PFAS mass flux in the atmosphere, in the vadose zone, in source zones containing organic immiscible liquids, and in water/wastewater treatment systems.
全氟和多氟烷基物质（PFAS）是对人类健康风险具有重要关注的新兴污染物。评估暴露风险需要深入了解 PFAS 在环境中的迁移和归宿行为。吸附到流体-流体界面（包括气-水、油-水和气-油界面，其中 OIL 代表有机不混溶液体）是 PFAS 迁移的一个潜在重要保留过程。流体-流体界面吸附系数（K）是用于运输建模和风险特征描述的必需参数，但目前绝大多数 PFAS 都没有这些数据。本文从文献中收集的表面张力和界面张力数据集用于确定 42 种单个 PFAS 的界面吸附系数。评估的 PFAS 包括全氟羧酸和全氟磺酸的同系物、支链全氟烷基、多氟烷基、醇类 PFAS 和非离子型 PFAS。K 值跨越八个数量级变化，是分子结构的函数。定量结构/性质关系（QSPR）分析的结果表明，采用摩尔体积（V）作为描述符的模型能够为广泛的 PFAS 气-水界面吸附提供稳健的 log K 值预测。该模型还为有限的油-水界面吸附数据提供了良好的预测。该 QSPR 模型对具有极大结构差异的广泛 PFAS 的预测能力反映了这样一个事实，即摩尔体积为分子尺寸对溶液中腔形成/破坏的影响提供了合理的表示，从而为界面吸附提供了疏水相互作用驱动力。本文提出的 QSPR 模型为将流体-流体界面吸附过程纳入 PFAS 在环境中的迁移特征和风险评估提供了一种手段。这对于确定大气中、包气带中、含有有机不混溶液体的源区中和水/废水处理系统中的 PFAS 质量通量尤其重要。
