Chemical Characteristics of Acid Mine Drainage from an As-W Mineralized Zone in Western Spain

Mine drainage from La Parrilla mine affects a stream located in Extremadura Autonomous Community (W Spain) and is the subject of this investigation. A comprehensive analysis of the chemical characteristics of the stream water along its course was performed to understand the dominant processes that control the behavior of contaminant elements. The water in the stream shows low pH values (2.5 to 5), and high sulfate contents (indicating the effect of mining pollution) in the first stages (upstream), resulting in the precipitation of Fe(III) minerals at the bottom of the stream. These precipitates adsorb trace elements from the water, which together with the dilution process that takes place in the stream, reduce the concentration of contaminant elements in the downstream water.