Ideal versus Nonideal Transport of PFAS in Unsaturated Porous Media

WATER RESEARCH

卷:202

Article

Brusseau, Mark L.^1,2  Guo, Bo²  Huang, Dandan^1,3  Yan, Ni^1,4  Lyu, Ying^1,5,6 

[1] Univ Arizona, Environm Sci Dept, Tucson, AZ 85721 USA

[2] Univ Arizona, Hydrol & Atmospher Sci, Tucson, AZ 85721 USA

[3] China Univ Geosci, Sch Water Resources & Environm, Beijing 100083, Peoples R China

[4] Ocean Univ China, Coll Environm Sci & Engn, Key Lab Marine Environm Sci & Ecol, Qingdao 266100, Peoples R China

[5] Jilin Univ, Jilin Prov Key Lab Water Resources & Environm, Key Lab Groundwater Resources & Environm, Changchun 130026, Peoples R China

[6] Jilin Univ, Inst Water Resources & Environm, Changchun 130026, Peoples R China

关键词: PFOS;    PFOA;    transport;    adsorption;    per-and polyfluoroalkyl substances;   

DOI  :  10.1016/j.watres.2021.117405

来源: Elsevier

【 摘 要 】

Per- and poly-fluoroalkyl substances (PFAS) adsorb at air-water interfaces during transport in unsaturated porous media. This can cause surfactant-induced flow and enhanced retention that is a function of concentration, which complicates characterization and modeling of PFAS transport under unsaturated conditions. The influence of surfactant-induced flow and nonlinear air-water interfacial adsorption (AWIA) on PFAS transport was investigated with a series of miscible-displacement transport experiments conducted with a several-log range in input concentrations. Perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and ammonium perfluoro 2-methyl-3-oxahexanoate (GenX) were used as model PFAS. The results were interpreted in terms of critical reference concentrations associated with PFAS surface activities and their relationship to the relevancy of transport processes such as surfactant-induced flow and nonlinear AWIA for concentration ranges of interest. Analysis of the measured transport behavior of PFAS under unsaturated-flow conditions demonstrated that AWIA was linear when the input concentration was sufficiently below the critical reference concentration. This includes the absence of significant arrival-front self-sharpening and extended elution tailing of the breakthrough curves, as well as the similarity of retardation factors measured for a wide range of input concentrations. Independentlypredicted simulations produced with a comprehensive flow and transport model that accounts for transient variably-saturated flow, surfactant-induced flow, nonlinear rate-limited solid-phase sorption, and nonlinear ratelimited AWIA provided excellent predictions of the measured transport. A series of simulations was conducted with the model to test the specific impact of various processes potentially influencing PFOS transport. The simulation results showed that surfactant-induced flow was negligible and that AWIA was effectively linear when the input concentration was sufficiently below the critical reference concentration. PFAS retention associated with AWIA can be considered to be ideal in such cases, thereby supporting the use of simplified mathematical models. Conversely, apparent nonideal transport behavior was observed for experiments conducted with input concentrations similar to or greater than the critical reference concentration.

【 授权许可】

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