CHARACTERIZATION OF AMD SEDIMENTS IN THE DISCHARGE OF THE TINTO SANTA ROSA MINE (IBERIAN PYRITIC BELT, SW SPAIN)

The acidic discharge of the Tinto Santa Rosa mine in the Iberian Pyritic Belt (SW, Spain) transports high concentrations of acidity, sulfate and metal(loid)s (e.g., Fe, As, Co, Ni, Cu, Pb, and Mn). This study deals with the mobility of As in this stream, which appears to be associated with the sediments and precipitates of the stream floor. Characterization of the precipitates and sediments from the stream bed was performed by X-ray diffraction (XRD), X-ray-fluorescence (XRF), scanning electron microscopy (SEM) and X-ray absorption spectroscopy (XAS). The aqueous concentration of arsenic and iron decreases markedly from the adit mouth to 300 m downstream due to precipitation of iron oxides and iron oxyhydroxysulfates, which can retain trace elements by coprecipitation and/or sorption processes. The stability of these secondary minerals, which contain high levels of As is of great importance to our understanding of the natural metal(loid) attenuation mechanisms operating in this system.