Brusseau Mark L, Guo Bo
Environmental Science Department, The University of Arizona, Tucson, AZ 85721.
Hydrology and Atmospheric Sciences Department, The University of Arizona, Tucson, AZ 85721.
J Hazard Mater Lett. 2023 Nov;4. doi: 10.1016/j.hazl.2023.100077. Epub 2023 Mar 20.
Per and polyfluoroalkyl substances (PFAS) have been shown to be ubiquitous in the environment, and one issue of critical concern is the leaching of PFAS from soil to groundwater. The risk posed by contaminants present in soil is often assessed in terms of the anticipated impact to groundwater through the determination of soil screening levels (SSLs). The U.S. Environmental Protection Agency (EPA) established a soil screening model for determining SSLs. However, the model does not consider the unique retention properties of PFAS and, consequently, the SSLs established with the model may not represent the actual levels that are protective of groundwater quality. The objective of this work is to revise the standard EPA SSL model to reflect the unique properties and associated retention behavior of PFAS. Specifically, the distribution parameter used to convert soil porewater concentrations to soil concentrations is revised to account for adsorption at the air-water interface. Example calculations conducted for PFOS and PFOA illustrate the contrasting SSLs obtained with the revised and standard models. A comparison of distribution parameters calculated for a series of PFAS of different chain length shows that the significance of air-water interfacial adsorption can vary greatly as a function of the specific PFAS. Therefore, the difference between SSLs calculated with the revised versus standard models will vary as a function of the specific PFAS, with greater differences typically observed for longer-chain PFAS. It is anticipated that this revised model will be useful for developing improved SSLs that can be used to enhance site investigations and management for PFAS-impacted sites.
全氟和多氟烷基物质（PFAS）已被证明在环境中无处不在，一个备受关注的关键问题是PFAS从土壤中淋滤到地下水中。土壤中存在的污染物所带来的风险通常通过确定土壤筛选水平（SSLs）来评估对地下水的预期影响。美国环境保护局（EPA）建立了一个用于确定SSLs的土壤筛选模型。然而，该模型没有考虑PFAS独特的保留特性，因此，用该模型建立的SSLs可能无法代表保护地下水质量的实际水平。这项工作的目的是修订标准的EPA SSL模型，以反映PFAS的独特特性和相关的保留行为。具体来说，用于将土壤孔隙水浓度转换为土壤浓度的分布参数被修订，以考虑气 - 水界面的吸附作用。对全氟辛烷磺酸（PFOS）和全氟辛酸（PFOA）进行的示例计算说明了使用修订模型和标准模型获得的不同SSLs。对一系列不同链长的PFAS计算得到的分布参数进行比较表明，气 - 水界面吸附的重要性会因特定的PFAS而有很大差异。因此，用修订模型和标准模型计算出的SSLs之间的差异将因特定的PFAS而有所不同，通常对于长链PFAS观察到的差异更大。预计这个修订后的模型将有助于开发改进的SSLs，可用于加强对受PFAS影响场地的现场调查和管理。
