Air-water interfacial areas relevant for transport of per and poly-fluoroalkyl substances.
Air-water interfacial areas relevant for transport of per and poly-fluoroalkyl substances.
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DOI：
10.1016/j.watres.2021.117785
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发表时间：
2021-12-01
期刊：
影响因子：
12.8
通讯作者：
Guo B
中科院分区：
文献类型：
--
作者：
Brusseau ML;Guo B
土壤中存在的PER和多氟烷基物质(PFAS)对地下水构成长期威胁。对全氟辛烷磺酸在非饱和体系中的保留和传输进行稳健的表征和建模需要准确地确定空气-水界面面积(AWIA)的大小。测量或估算气-水界面面积的方法有多种，包括X射线显微层析成像(XMT)、各种水相和气相界面示踪测试(ITT)方法以及基于热力学的估算方法。用不同的方法测定的AWIA可能有很大的差异。因此，确定哪些测量方法适用于全氟辛烷磺酸的保留和传输是至关重要的。这是通过使用不同方法确定的AWIA来模拟文献中报道的全氟辛酸(PFOA)在不饱和石英砂中传输的混相置换实验结果来实现的。用水相ITT方法测得的AWIA值成功地预测了测得的全氟辛酸的穿透曲线。相反，用XMT方法测量的AWIA和用热力学方法估计的AWIA低估了延迟的大小，并且不能成功地模拟测量的输运数据。这些结果表明，ITT方法似乎为非饱和系统中PFAS输运的稳健表征和建模提供了最合适的AWIA值。在一个典型的AFFF应用场景中，模拟了采用不同的AWIA值对包气带全氟辛酸淋溶的长期影响。全氟辛酸向地下水迁移的预测时间范围从3年到6年到20年不等，这取决于模拟中使用的是哪种AWIA。这些相对较大的差异将导致显著不同的风险评估结果。这些结果表明，采用最具代表性的全氟辛烷磺酸保留量的AWIA来准确预测全氟辛烷磺酸在包气带中的淋溶是至关重要的。
Per and polyfluoroalkyl substances (PFAS) present in the soil pose a long-term threat to groundwater. Robust characterization and modeling of PFAS retention and transport in unsaturated systems requires an accurate determination of the magnitude of air-water interfacial area (AWIA). Multiple methods are available for measuring or estimating air-water interfacial area, including x-ray microtomography (XMT), various aqueous and gas-phase interfacial tracer-test (ITT) methods, and thermodynamic-based estimation methods. AWIAs determined with the different methods can vary significantly. Therefore, it is critical to determine which measurement methods are relevant for application to PFAS retention and transport. This is achieved by employing AWIAs determined with different methods to simulate the results of miscible-displacement experiments reported in the literature for the transport of perfluorooctanoic acid (PFOA) in an unsaturated quartz sand. Measured PFOA breakthrough curves were successfully predicted using AWIA values measured by aqueous ITT methods. Conversely, AWIAs measured with the XMT method and estimated with the thermodynamic method under-predicted the magnitude of retardation and could not successfully simulate the measured transport data. These results indicate that the ITT method appears to provide the most appropriate AWIA values for robust characterization and modeling of PFAS transport in unsaturated systems. The long-term impact of employing different AWIA values on PFOA leaching in the vadose zone was simulated for a representative AFFF application scenario. The predicted timeframes for PFOA migration to groundwater varied from 3 to 6 to 20 years depending on which AWIA was used in the simulation. These relatively large differences would result in significantly different risk-assessment outcomes. These results illustrate that it is critical to employ the AWIA that is most representative of PFAS retention for accurate predictions of PFAS leaching in the vadose zone.
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