Risk of arsenic transfer to a semi-confined aquifer and the effect of water level fluctuation in North Mortagne, France at a former industrial site

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 Ca3ŽAsO4.2Žs. and probably a gypsum calcium arsenate CaSO4 Žs. Ca3ŽAsO4.2 Žs. solid solution. The speciation of As below the former sulfuric acid factory indicates an overall predominance of AsŽIII. species. The sorption by the clay aquitard was complete for AsŽV., but limited to approximately 30% for AsŽIII. under our experimental conditions. A potential risk exists, although very limited in area, of contamination of the underlying sandy aquifer and drinking water wells.