The adsorption of PFAS at the air-water interface is a topic of current interest that affects several aspects of PFAS transport and remediation. Numerous studies over the past several years have investigated the air-water interfacial adsorption (AWIA) of PFAS, with a subset focusing on quantifying the magnitudes of adsorption and assessing the linearity of adsorption at low concentrations. Different methods have been used in these studies to measure AWIA, and there has been to date limited evaluation of the consistency of results across the methods. Furthermore, differing outcomes have been reported regarding AWIA linearity. To address these knowledge gaps, measured AWIA data sets were compiled from the literature for both PFAS and hydrocarbon surfactants, and subjected to detailed comparative analyses. The data sets represent all three primary approaches for quantifying AWIA, specifically advanced surface-science methods, molecular-modeling simulations, and various physical-based methods, and comprise more than 70 studies in total. With the exception of four studies, measured adsorbed concentrations and K_aw values were consistent across the different methods for a given surfactant, indicating good correspondence among the methods. The aggregated data from these studies clearly demonstrate that K_aw attains a constant, maximum value at concentrations below the critical reference concentration for both PFAS and hydrocarbon surfactants. This behavior is consistent with linear AWIA at low concentrations. In addition, the results demonstrate that the Langmuir isotherm provides an excellent description of AWIA and that the Freundlich isotherm does not. The observation of such consistency across all of the different methods, which vary greatly in approach, is a compelling outcome. Factors that may affect the robustness of measurements and cause potential deviations are discussed. It is anticipated that these results will be useful for planning laboratory and field studies, conducting risk assessments, and implementing modeling-based investigations.

中文翻译：

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量化 PFAS 和碳氢化合物表面活性剂在空气-水界面的吸附：表面科学测量、分子建模模拟和环境应用结果的系统评价和荟萃分析

PFAS 在空气-水界面的吸附是当前关注的一个话题，它影响 PFAS 运输和修复的多个方面。过去几年的大量研究调查了 PFAS 的空气-水界面吸附 （AWIA），其中一部分侧重于量化吸附的大小和评估低浓度下吸附的线性。这些研究中使用了不同的方法来测量 AWIA，迄今为止，对不同方法结果一致性的评估有限。此外，关于 AWIA 线性度的结局也不同。为了解决这些知识差距，根据 PFAS 和碳氢化合物表面活性剂的文献汇编了测得的 AWIA 数据集，并进行了详细的比较分析。这些数据集代表了量化 AWIA 的所有三种主要方法，特别是先进的表面科学方法、分子建模模拟和各种基于物理的方法，总共包括 70 多项研究。除 4 项研究外，对于给定表面活性剂，在不同方法中测得的吸附浓度和 K_aw 值是一致的，表明方法之间具有良好的对应性。这些研究的汇总数据清楚地表明，当浓度低于 PFAS 和烃类表面活性剂的临界参考浓度时，K_aw 会达到恒定的最大值。这种行为与低浓度下的线性 AWIA 一致。此外，结果表明，Langmuir 等温线提供了对 AWIA 的极好描述，而 Freundlich 等温线则没有。 在所有不同方法（方法差异很大）中观察到这种一致性是一个令人信服的结果。讨论了可能影响测量稳健性并导致潜在偏差的因素。预计这些结果将有助于规划实验室和实地研究、进行风险评估和实施基于建模的调查。