Application of electrical resistivity prospecting for geo-environmental investigation

Abstract

Among geophysical exploration techniques, the application of the electrical resistivity method has recently increased for geo-environmental investigation such as in the detection of soil and groundwater contamination. The electrical resistivity method is used to identify permeable soil layers that are possible channels of contaminant transport. Geo-environmental investigation deals with important social issues and is a growing field of innovation. This paper describes the present state of soil and groundwater contamination in Japan and the application of the electrical resistivity method to the identification of permeability structures that are possible channels of pollutants. Two field studies were carried out: an analysis of the infiltration of saline water and a measurement of the movement of saline water masses by resistivity monitoring. The results are summarized as follows: (1) determination of the state of saline water infiltration by resistivity is effective in preventing contamination by saline water and in determining appropriate sites to bore wells where fresh groundwater is available, and (2) combination with the indirect method of resistivity monitoring, which roughly estimates the positions of saline water masses, sharply improves the efficiency of the salt tracer method. Therefore, the two methods should be combined to understand accurately the flow mechanisms of groundwater in contaminated districts.