Multidimensional simulation of PFAS transport and leaching in the vadose zone: Impact of surfactant-induced flow and subsurface heterogeneities
Multidimensional simulation of PFAS transport and leaching in the vadose zone: Impact of surfactant-induced flow and subsurface heterogeneities
复制标题
DOI：
10.1016/j.advwatres.2021.104015
复制
发表时间：
2021-09
影响因子：
4.7
通讯作者：
J. Zeng;B. Guo
中科院分区：
文献类型：
--
作者：
J. Zeng;B. Guo
PFAS是一种新兴的污染物，其在环境中的归宿和迁移仍然知之甚少。作为表面活性剂，PFAS在土壤中的气-水界面和固-水界面的吸附使其在包气带中的滞留和淋溶变得复杂。最近的建模研究占PFAS特定的非线性吸附过程预测，大多数长链PFAS仍然在浅包气带几十年后，污染停止与许多现场测量的协议。然而，一些现场调查表明，长链PFAS已经迁移到地面以下几十到一百米。这些差异可能是由于模型简化，如一维（1D）均匀表示的包气带。另一个潜在的关键过程，还没有得到充分研究的一维模型是如何表面诱导流（SIF）影响PFAS浸出多维。我们开发了一个新的三维模型，将PFAS特定的流动和运输过程，以量化的SIF和地下的非均质性的影响。我们的模拟和分析得出结论：1）SIF对PFAS在包气带中的长期浸出影响极小，2）地下非均质性产生的优先流动通道导致PFAS的早期到达和加速浸出。（特别是长链）PFAS，3）PFAS在高水环境中的淋溶加速作用;由于空气-水界面的破坏，在毛细屏障上方的内容物优先路径或停留水比常规污染物更显著，地下不均匀性是预测PFAS在包气带中淋溶和滞留的主要不确定性来源。
PFAS are emergent contaminants of which the fate and transport in the environment remain poorly understood. As surfactants, adsorption at air–water and solid–water interfaces in soils complicates the retention and leaching of PFAS in the vadose zone. Recent modeling studies accounting for the PFAS-specific nonlinear adsorption processes predicted that the majority of long-chain PFAS remain in the shallow vadose zone decades after contamination ceases—in agreement with many field measurements. However, some field investigations show that long-chain PFAS have migrated to tens to a hundred meters below ground surface. These discrepancies may be attributed to model simplifications such as a one-dimensional (1D) homogeneous representation of the vadose zone. Another potentially critical process that has not been fully examined by the 1D models is how surfactant-induced flow (SIF) influences PFAS leaching in multidimensions. We develop a new three-dimensional model incorporating the PFAS-specific flow and transport processes to quantify the impact of SIF and subsurface heterogeneities. Our simulations and analyses conclude that 1) SIF has a minimal impact on the long-term leaching of PFAS in the vadose zone, 2) preferential flow pathways generated by subsurface heterogeneities lead to early arrival and accelerated leaching of (especially long-chain) PFAS, 3) the acceleration of PFAS leaching in high water-content preferential pathways or perched water above capillary barriers is more prominent than conventional contaminants due to the destruction of air–water interfaces, and 4) subsurface heterogeneities are among the primary sources of uncertainty for predicting PFAS leaching and retention in the vadose zone.