Mineralogical composition and metals retention in the fine-fraction streambed precipitates of on AMD affected system

Abstract

This work presents data from an abandoned mine (Valdarcas, NW Portugal) that, although submitted to environmental rehabilitation, stills presenting marks of AMD. Water and sediment samples from the riverine system were analyzed for chemical composition and mineralogy. Chemical contents of Fe, As and W in the < 20μm fraction indicate strong enrichment relatively to the water. Proportions of iron oxide-oxyhydroxides and clay minerals vary downstream, acting as mineralogical indicators of mining contamination. Additionally, the observed relation between the mineral proportions and metal concentrations indicates the relevance of each mineral phase to retain metals.