Characterization of soil and sediments from a Mediterranean mining area and its relationships with metal mobility

Resumo

Mobility of heavy metals in soils, waters and sediments have received attentionin last years. In a solid matrix, such as soil and sediment, metal mobility andleaching depends on many physicochemical properties of those, such as chemicalform, reactions, solubility, density, porosity, pH, electrical conductivity, watercontent, electrokinetic, surface thermodynamic... All these properties of thematerials involved can be affecting to the metal mobility and leaching.Regarding this, the research has been focused, first, on the study of the solublemetal concentration, pH, electrical conductivity (EC), and water contentvariation depending on samples depth of different soils and sediment layers in adrill taken in a wades riverbed placed in a Mediterranean mining area. Resultsshow high soluble Al, Pb, Zn and Fe concentration (tens of ppm). Therelationship between pH and depth shows a variation between 2.5 and 6.7, witha minimum placed between 1 and 2 m. On the other hand, EC has a maximumaround 4 mS/cm between 1 and 4 m, and a minimum around 3 mS/cm between0.3 and 3 m. The water content is higher in the interval 2-3 m depth withvalues around 25 % w/w. All these results show the high sensitivity of thesystems to the electrokinetic and surface properties of the involved soil andsediments due to the solid/liquid interfaces of the systems. Since presentcolloidal particles in the can carry adsorbed metals, the work is being completedwith a determination of the electrokinetic and surface thermodynamic propertiesof the samples. This kind of study can provide information on the mobility anddynamics of metals in polluted soils and sediments.