Preliminary tests of an electrokinetic barrier to prevent heavy metal pollution of soils

Sardinia has to deal with significant environmental problems related to heavy-metal contamination, mainly located at its abandoned mining districts. In particular, acid mine drainage management and groundwater pollution are typical problems associated with mining activities which constitute a serious threat to human health. To prevent contaminant spread over the adjacent environment, it is of great interest to consider using an electric field as a containment fence to counteract pollutant transport. In this application, contaminant transport due to a hydraulic gradient driving force is prevented by the combined effect of electro-osmosis and electro-migration. Although there are other alternative containment technologies, the electrokinetic fence offers many advantages, as it is easy to operate, there is a minimal exposure to the operating personnel and it is likely to be effective for a wide range of contaminants. In this work, both one-dimensional (1D) and two-dimensional (2D) tests have been carried out. In the 1D tests, the efficiency of an electrokinetic barrier to prevent cadmium from polluting an uncontaminated sample was investigated; soil pH, metal concentration and current intensity have been monitored; results indicate that the barrier can prevent or significantly reduce heavy-metal contamination from spreading against a hydraulic gradient of 7. In 2D tests, two rows of electrodes inserted in a horizontally flat soil tank were used to generate an electric field. It was found that an electric field of 125 V m−1 was sufficient to prevent significant copper incursion from a contaminant flow under a hydraulic gradient of 1.3.