Geophysical study of the industrial waste land in Mortagne-du-Nord (France) using electrical resistivity.

The industrial waste land in Mortagne-du-Nord (France) has been the site of a zinc smelter unit and a lead smelter unit linked to sulphuric acid production. It has been systematically explored by drillings and pits. Geophysical data have led to the location of mineralized soil and water, and to the identification of water seepage towards the river drain. Various geophysical devices are used for subsurface exploration and for studies with higher spatial resolution. The prospect area covers a surface of 4.5 ha. Data obtained from trenches has been used to calibrate and to validate the geophysical interpretation. It has been found that variations in the depth of the interface between resistive and conductive layers are due to two types of waste: ‘non-active’ (carbonates and oxides) and ‘active’ (sulphides and sulphates) materials. Lower resistivities than expected are due to the presence of mineralized water in all geological formations.