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 la rger 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 solubili ty of 3:2 calcium arsenate mineral Ca-3(AsO4)(2)(s) and probably a gypsum/c alcium arsenate CaSO4 (s)/Ca-3(AsO4)(2)(s) solid solution. The speciation o f As below the former sulfuric acid factory indicates an overall predominan ce of As(III) species. The sorption by the clay aquitard was complete for A s(V), but limited to approximately 30% for (AsIII) under our experimental c onditions. A potential risk exists, although very limited in area, of conta mination of the underlying sandy aquifer and drinking water wells. (C) 2001 Elsevier Science B.V. All rights reserved.