Samples were collected from rocks, wastes, sediments, groundwater, and soils, and analyzed for As mainly by atomic absorption spectrometry with hydride generation and ICP-AES. Physico-chemical determinations and analyses of other toxic elements were also carried out. Mineralogical (XRD, SEM-EDS, SEM-WDS and IR) and chemical characterization, including sequential extractions, have also been performed in solid materials. Finally, the suitability of indigenous limestone to remove As from polluted solutions (water and acid mine drainage) was assessed through batch and column experiments.