Key Laboratory of Surficial Geochemistry of Ministry of Education, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China.
Key Laboratory of Surficial Geochemistry of Ministry of Education, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China.
J Contam Hydrol. 2020 Mar;230:103603. doi: 10.1016/j.jconhyd.2020.103603. Epub 2020 Jan 15.
The widespread presence of entrapped dense non-aqueous phase liquid (DNAPL) in the subsurface poses a continuing challenge to groundwater remediation. Cost-effective and high-resolution subsurface characterization is a critical issue for further DNAPL recovery due to the complexity of DNAPL source zone architecture (SZA). Geophysical techniques provide a noninvasive, spatially continuous and cost-effective way for monitoring the DNAPL remediation process. In particular, the spectral induced polarization (SIP) method has shown great potential in environmental problems. In this study, we performed real-time SIP measurements on DNAPL contaminated soil in columns to quantitatively assess the ability of SIP method for monitoring surfactant-enhanced DNAPL remediation process. Chemical data was simultaneously collected during the remediation process to verify the results obtained by SIP method. Taking account into the variations of subsurface environment, we conducted a series of column flushing experiments under different flow rate, surfactant concentrations and fluid salinities. The results highlight that SIP method is able to effectively monitor the DNAPL remediation process, as well as to evaluate the remediation efficiency under different conditions. The variations in the flow rate, the concentration of surfactant and the salinity of pore water not only affect remediation effectiveness, but also have an impact on the SIP signatures. This study shows that SIP performs better for monitoring DNAPL remediation at a relatively low flow rate of ~ 0.4 m/d, low surfactant concentration of 5000 mg/L and high salinity of 1.0 S/m, with an error of saturation estimation (RMSE) <0.1.
地下环境中广泛存在的被捕获的致密非水相液体（DNAPL）给地下水修复带来了持续的挑战。由于 DNAPL 源区结构（SZA）的复杂性，进行具有成本效益且高分辨率的地下特征描述是进一步回收 DNAPL 的关键问题。地球物理技术为监测 DNAPL 修复过程提供了一种非侵入性、空间连续且具有成本效益的方法。特别是，光谱感应极化（SIP）方法在环境问题中显示出巨大的潜力。在这项研究中，我们在柱状物中对受 DNAPL 污染的土壤进行了实时 SIP 测量，以定量评估 SIP 方法监测表面活性剂增强型 DNAPL 修复过程的能力。在修复过程中同时收集了化学数据，以验证 SIP 方法获得的结果。考虑到地下环境的变化，我们在不同流速、表面活性剂浓度和流体盐度下进行了一系列柱状物冲洗实验。结果表明，SIP 方法能够有效地监测 DNAPL 修复过程，并评估不同条件下的修复效率。流速、表面活性剂浓度和孔隙水盐度的变化不仅影响修复效果，而且对 SIP 特征也有影响。本研究表明，SIP 在相对较低的流速（~0.4 m/d）、5000 mg/L 的低表面活性剂浓度和 1.0 S/m 的高盐度下监测 DNAPL 修复效果更好，饱和度估计误差（RMSE）<0.1。
