Geophysical Exploration of Mining Ponds – An Effective Tool for Their Geochemical Characterization

In the Murcia Province, there are eighty five mining silt ponds resulting from the treatment and exploitation of ancient metallic sulphur mines. These silt ponds are the potential focus of environmental pollution. The Technical University of Cartagena (Murcia, Spain) and Análisis y Gestión del Subsuelo Company (for geophysics) have been carrying out an integral study of these structures from the year 2003 to the present. In this work, studies from the Brunita and El Lirio mining silt ponds (La Union, Murcia) are described. These have allowed the characterization of different horizons, combining the results obtained through geochemical analysis with data derived from electrical tomography (2D and 3D) techniques. Geochemistry has demonstrated that oxidation and salinization processes are more active in the sediment surface layers than in deeper layers. Acidification has also been found to be more active in upper layers, with analyses showing pH values slightly less acidic, combined with high concentrations of Zn. The results were analyzed with the different electrical profiles, and correlated and corroborated with the geochemical sampling analysis.