Mine tailing ponds are environmental hazards because of high susceptibility to leaching and erosion by water and wind. Vegetation establishment is an effective technique to reclaim tailing ponds but requires knowledge of the spatial relationship between the structural composition and physical and chemical properties of soils. In this study we have demonstrated the use of electrical resistivity imaging (ERI), combined with soil chemical analyses, to determine the structural and chemical composition of mine tailing ponds to assess efficient measures of environmental protection. We used a Syscal R1 resistivity meter to generate twoand three-dimensional (2-D/3-D) ERI images from El Lirio and Brunita mine tailing ponds. Soil samples were collected at 1-m intervals to a depth of 15 m, and were analyzed for pH, electrical conductivity and cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) contents. Results show that materials in the ponds can be classified into three categories: fine tailings -low ER (,8 Vm), coarse waste rock -intermediate ER (8-150 V-m), and bedrock -high ER (.150 V-m). Our interpretation of the 2-D/3-D ERI images with respect to the historical depositions of materials in the ponds show that at El Lirio, decant water outlet was initially at the center and advanced to the east of the tailing pond as the mining activities progressed. At Brunita, the intermediate ER values on the west side of the pond marked the deposition of coarse waste rock materials released during a pond breakage in 1972. The ERI helped us image the spatial distribution of tailings and its qualitative spatial correlation with chemical properties (i.e., pH, EC, metals content). Low ER values are related to high amounts of Zn, Pb, Cu and Cd. These qualitative relationships underlie the usefulness of the combined geophysical and soil chemical approaches to improve our understanding of the properties of mine tailing ponds in the Sierra Minera (and other parts of the world).

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A large quantity of pig slurry is produced in the Murcia Province, raising serious environmental concern. Monitoring the evolution of the slurry ponds with time in the subsoil is a prime requirement for environmental safety. Our aim was to determine the temporary effects of pig slurry ponds on the subsoil in the Murcia Province to establish the degree of slurry pond infiltration in semi‐arid climates. A non‐destructive, geophysical, 2D electrical tomography technique was used to: 1) monitor the vertical movement of pig slurry into the subsoil and 2) determine the possible depth of this movement. The results of our studies showed that the method works well. Areas affected by pig slurries have, indeed, developed environmental problems over time. The method identified the lithological layers with sufficient resolution in order to study the possible pollution of the soils by the slurry, including salts. The method is also capable of monitoring seasonal changes and the time‐dependent behaviour of the polluting plume within different subsoils in the ponds.