Presenter: Yung-Chieh Chuang
Date: 2016/03/03
Abstract
In contrast to traditional field investigation techniques in hydrogeology, geophysical methods are relatively non-invasive, cost effective and can be performed with a higher spatial sampling. Among such techniques, self-potential method is directly related to the hydrogeophysics mechanism, and electrical resistivity method is sensitive to the resistivity change in vadose zone and aquifer. In this presentation, first of all, the authors show the sources of electrical current can be related to the zones of contaminated areas with relative high DNAPLs concentration. Then, they determine the contaminant with the isosurfaces of the current source at ±12μA. Furthermore, combined with piezometric level data and geochemical measurements, the authors evaluate the streaming potential coupling coefficient (-10.60mV/m) and redox coupling coefficient (0.51, dimensionless) with first-order approximation, and separate the self-potential map into streaming potential component and redox potential component. As a result, they successfully determine the groundwater flow direction and define the redox front at the landfill. Last but not the least, with the fluid conductivity in boreholes, the authors calculate the groundwater conductivity distribution from electrical resistivity results. They show the paleochannels and flow direction at a depth of -3.82m and -5.56m, and attribute the contaminant distribution to the local preferential flow paths.
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