The use of electro-geophysical methods for groundwater pollution and soil salinity problems

Abstract

Over the past five years, the use of the transient electromagnetic (TEM) method for both lateral and vertical profiling of polluted groundwater and saline soil has been investigated, and the results have been compared with dc sounding and frequency domain methods. In the groundwater pollution studies, it has been found that with either two-layer or three-layer inversions of the TEM data a subtle low-resistivity feature which correlates with the presence of a pollution plume in the aquifer near a landfill site can be detected. Data obtained since 1985 at approximately six-month intervals have shown a continuing development of the resistivity low. In the soil salinity studies, investigations have concentrated on the use of TEM and dc sounding methods to determine the thickness and resistivity of the surface leached layer and of salt accumulations. Modelling of the response obtained with a ground-based TEM system shows that measurements at delay times earlier than 1 ms are required to resolve the relevant parameters of a layered-earth model used to approximate a saline soil environment.