Delineation of contaminant zone through electrical imaging technique

Electrical imaging technique has been found to be a powerful tool to delineate sub-surface contaminated zone, when there is sufficient resistivity contrast. Electrical tomography (imaging) involves measuring a series of constant separation traverses with the electrode spacing being increased with each successive traverse. Since increasing separation leads to information from greater depths, the measured apparent resistivities have been used to construct a pseudo-section displaying the variation of resistivities, both laterally and vertically over the section. Normally, the pseudosection contains geometrical effects, geological noise and the distorting effects of near-surface lateral changes in resistivities, which occur close to the electrodes (electrode effects). In order to remove geometrical effects as well as to produce an image of true depths and true formation resistivities, the inversion technique is used. This technique was successfully demonstrated near Dindigul town, where groundwater was contaminated due to untreated tannery effluents.