Applied Geochemistry | 2019
Chemical mobility of inorganic elements in stream sediments of a semiarid zone impacted by ancient mine residues
Abstract Water availability is a worldwide issue, particularly in semiarid zones. Therefore, it is necessary to know the geochemical processes involved in the mobility of contaminant sources to ensure adequate quality for this resource. Some mining areas of Mexico are of economic importance; however, they are also the sources of large quantities of mine residues, such as the site included in this study. As an important aspect of understanding contaminant mobility in sediments and water, a thorough mineralogical characterization is paramount to identify sources and sinks for relevant elements, in this case, potentially toxic elements (PTEs) such as arsenic (As), lead (Pb) and cadmium (Cd); hence, scanning electron microscopy (SEM), X-ray diffraction (XRD) and chemical analysis were used. The total geochemical distribution was established by means of a modified selective sequential extraction procedure. The results showed that sediments constitute an effective attenuation substrate for mobilized PTEs to groundwater. Hence, arsenic and cadmium were stabilized in the sediments and/or the vadose zone, and although Pb and Zn were identified in groundwater with concentrations above the background values, they were below drinking water standards. Sulfate and total hardness concentrations in the groundwater confirmed the impact of acid mine drainage (AMD) infiltration. Considering that similar sites in Mexico are found along the Sierra Madre Oriental, the methodology of this study could be applied to understand the mobility of PTEs in the sediments and waters of semiarid environments.