RESUMEN
Groundwater contamination by arsenic was studied in the area of a former larger zinc refinery in France. Maximum contamination was observed under the former sulfuric acid factory, while the overall waste storage area was less contaminated. Arsenic concentrations there were controlled by the solubility of 3:2 calcium arsenate mineral Ca3(AsO4)2 (s) and probably a gypsum/calcium arsenate CaSO4 (s)/Ca3(AsO4)2 (s) solid solution. The speciation of As below the former sulfuric acid factory indicates an overall predominance of As(III) species. The sorption by the clay aquitard was complete for As(V), but limited to approximately 30% for As(III) under our experimental conditions. A potential risk exists, although very limited in area, of contamination of the underlying sandy aquifer and drinking water wells.