Residual Hydrocarbons in a Water-Saturated Medium: A Detection Strategy Using Ground Penetrating Radar

Q2 Earth and Planetary Sciences
Changryol Kim, Jeffrey J. Daniels, Erich D. Guy, Stanley J. Radzevicius, Jennifer Holt
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引用次数: 26

Abstract

The focus of this article is to demonstrate through physical model experimentation a potential means for identifying contaminated areas where a light non-aqueous phase liquid (LNAPL) hydrocarbon has been redistributed by a rising water table in a previously hydrocarbon residual–free vadose zone using ground-penetrating radar (GPR). Analogies of the experimentation conducted in this study are situations where a rise of the water table follows leakage from a tank or pipe at depth or where an LNAPL hydrocarbon plume has migrated laterally from a surface source along the top of the saturated zone and a subsequent rise of the water table occurs. Research to date has provided insight into mechanisms that may offer the potential for LNAPL detection under certain field conditions; however, no studies have specifically focused on developing a potential detection strategy for a case in which residual hydrocarbon is present in a water-saturated medium.

A tank model filled with gravel and sand was designed to allow GPR measurements to be made on the surface before, during, and after water and gasoline injections and fluctuations within the tank. Background GPR measurements were made initially with only water being raised and lowered in the model, and the water table was then raised and lowered beneath a volume of 219 liters of gasoline that was injected into the bottom of the tank. Measurements from the initial raising and lowering of the water with no gasoline present demonstrate the sensitivity of GPR for monitoring changes in subsurface water content and minor fluctuations of the water table. Measurements made during the raising and lowering of the water table with gasoline in the model show differences from the measurements made when only water was raised and lowered, and a comparison of the data show that reflections in GPR data can be enhanced when residual gasoline is present in a water-saturated system because there is less attenuation of the radar signal. Differences in travel times to subsurface reflections between the two stages of the experiment are also caused by the residual gasoline present in the water-saturated medium. Results of this study provide the basis for a strategy that has the potential for successful detection and delineation of LNAPL hydrocarbon–contaminated areas at field sites where the conditions are similar to those modeled through this experimentation.

饱和水介质中残余碳氢化合物:一种探地雷达探测策略
本文的重点是通过物理模型实验证明,利用探地雷达(GPR)识别污染区域的一种潜在方法,在这些污染区域,轻的非水相液体(LNAPL)碳氢化合物已经在以前无残留碳氢化合物的渗透带中随着地下水位的上升而重新分布。与本研究中进行的实验类似的情况是,地下水位上升是由于深层储罐或管道泄漏引起的,或者LNAPL碳氢化合物羽流从地表源沿饱和区顶部横向迁移,随后地下水位上升。迄今为止的研究已经深入了解了在某些现场条件下可能提供LNAPL检测潜力的机制;然而,目前还没有研究专门针对饱和水介质中残余碳氢化合物的潜在检测策略。设计了一个充满砾石和沙子的储罐模型,以便在注入水和汽油之前、期间和之后在地面进行探地雷达测量,以及储罐内的波动。背景探地雷达测量最初只在模型中升高和降低水的情况下进行,然后将地下水位升高和降低到注入油箱底部的219升汽油以下。在不含汽油的情况下,对水的初始升高和降低进行的测量表明,探地雷达对于监测地下水含量的变化和地下水位的微小波动非常敏感。模型中使用汽油升高和降低地下水位时的测量结果与仅升高和降低水位时的测量结果有所不同,数据的比较表明,在饱和水系统中存在残余汽油时,雷达信号的衰减较小,因此GPR数据中的反射可以增强。在实验的两个阶段之间,到地下反射的旅行时间的差异也是由存在于水饱和介质中的残余汽油引起的。本研究的结果为一种策略提供了基础,该策略有可能在条件与本实验模拟的相似的现场成功检测和描绘LNAPL烃类污染区域。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Environmental Geosciences
Environmental Geosciences Earth and Planetary Sciences-Earth and Planetary Sciences (all)
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