Silvia Martín-Velázquez

Application of electrical resistivity tomography to the environmental characterization of abandoned massive sulphide mine ponds (Iberian Pyrite Belt, SW Spain)

Mining activity in the Iberian Pyrite Belt, on the south-west of the Iberian Peninsula, has generated a great amount of mine tailing ponds, which once the extractive activity is finished, are abandoned and become a serious environmental problem. Here we present the results of applying the electrical resistivity tomography (ERT) technique to characterize the abandoned mine ponds in two sites: Monte Romero and Mina Concepcion. ERT has allowed us to determine both the general geometry of the pond’s base and the maximum thickness of the mine tailings. In all cases, the resistivity contrast between the infilling and the bedrock is high enough to clearly define the bottom pond boundary. The low-resistivity values (lower than 5 Ωm) obtained for the infilling are explained by the high concentration of pyrite in the tailings and the occurrence of acid waters. Whereas the Monte Romero mine pond is almost completely saturated with water, in Mina Concepcion it has been possible to identify the presence of inner acid water flows, the outlet of which through the damaged dyke originates a spilling of acid waters to the Odiel River. No low-resistivity water flows through the base of the ponds into the bedrock have been observed, indicating a good isolation of the base of the studied mine ponds.

Mapping of landslide susceptibility of coastal cliffs: the Mont-Roig del Camp case study

The weathered and fractured conglomerate cliffs of Mont Roig del Camp constitute a rock fall hazard for the surrounding pocket beaches and, therefore, for the population that frequent them, especially over the summer. Landslide susceptibility of the cliff has been assessed using the Rock Engineering System method (RES). The determinant and triggering factors considered in this study include: wave exposure, shoreline variations, cliff height, cliff slope, geotechnical quality of the rocky mass, superficial runoff and cliff orientations favoring landslides. Geographic Information Systems (GIS) have been employed to facilitate the information analysis and generate new susceptibility maps. The quality of the rock mass and cliff orientation are the most interactive factors for the stability of the cliff. However, shoreline variations and surface runoff are the most dominant factors in the system. Thus, the quality of the rock mass has been determined to be a basic variable in the cliff characterization because of its high dependence on the variations of the remaining factors. The landslide susceptibility map depicts a predominance of surfaces with moderate degrees of susceptibility concentrated mainly in the headlands, where the combined actions of subaerial and marine processes control the weathering and eroding processes. Therefore, the landslide susceptibility assessment based on this methodology has allowed the identification of hazardous areas that should be considered in future management plans.