Model validation and analyses of parameter sensitivity and uncertainty for modeling long-term retention and leaching of PFAS in the vadose zone
Model validation and analyses of parameter sensitivity and uncertainty for modeling long-term retention and leaching of PFAS in the vadose zone
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DOI：
10.1016/j.jhydrol.2021.127172
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发表时间：
2021-11
影响因子：
6.4
通讯作者：
J. Zeng;M. Brusseau;B. Guo
中科院分区：
文献类型：
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作者：
J. Zeng;M. Brusseau;B. Guo
PFAS是广泛存在于环境中的新兴污染物。PFAS是一种表面活性剂，易于在渗透带的固水界面和空气-水界面积聚，可能对地下水造成长期威胁。控制PFAS在血管渗透区的长期滞留的主要因素仍然知之甚少。为了解决这一知识差距，我们首先使用来自输移实验的多个数据集来验证最先进的数学模型，该模型包含瞬态可变饱和流动、表面活性剂诱导流动、限速和非线性固相和空气-水界面吸附。然后，我们利用验证的模型模拟和分析了控制PFAS在一个模型防火训练区渗透区的保留和浸出的主要过程和参数。我们的模拟表明，在固水和空气-水界面处的吸附导致PFAS在渗透区有很强的保留。随着PFAS链长和孔水离子强度的增加，截留强度增加，而随着PFAS浓度的增加，由于非线性吸附，截留强度降低。综合参数敏感性分析表明，当空气-水界面吸附（AWIA）比固相吸附（SPA）更重要时，模型预测对空气-水界面面积和PFAS界面性质相关参数最敏感。由于输入参数的不确定性，预测的PFAS浸出率变化很大，但长链PFAS的不确定性范围远大于短链PFAS。模拟的地下水到达时间服从对数正态分布。最后，模型复杂性分析表明，在本研究中广泛的现场条件下，AWIA、动力学SPA和动力学AWIA的非线性对PFAS的长期保留影响很小。
PFAS are emerging contaminants widespread in the environment. As surfactants, PFAS tend to accumulate at solid–water and air–water interfaces in the vadose zone, which may pose long-term threats to groundwater. The primary factors that control the long-term retention of PFAS in the vadose zone remain poorly understood. To address this knowledge gap, we first use multiple datasets from transport experiments to validate a state-of-the-art mathematical model that incorporates transient variably saturated flow, surfactant-induced flow, and rate-limited and nonlinear solid-phase and air–water interfacial adsorption. We then employ the validated model to simulate and analyze the primary processes and parameters controlling the retention and leaching of PFAS in the vadose zone at a model fire-training-area site. Our simulations show that adsorption at solid–water and air–water interfaces leads to strong retention of PFAS in the vadose zone. The strength of retention increases with PFAS chain length and porewater ionic strength, while it decreases at greater PFAS concentrations due to nonlinear adsorption. Comprehensive parameter sensitivity analyses reveal that model predictions are most sensitive to parameters related to the air–water interfacial area and PFAS interfacial properties when air–water interfacial adsorption (AWIA) is more important than solid-phase adsorption (SPA). Predicted PFAS leaching rates vary by a wide range resulting from uncertainties in the input parameters, but the uncertainty range is much greater for longer-chain PFAS than that of their shorter-chain counterparts. The simulated arrival times to groundwater were found to follow log-normal distributions. Finally, model complexity analysis reveals that nonlinearity in AWIA and kinetic SPA and kinetic AWIA have a minimal impact on the long-term retention of PFAS under the wide range of field conditions examined in the present study.