1. Joint Research Centre of the European Commission; Inst. for Environment and Sustainability; Soil and Waste Unit; TP 460 21020 Ispra VA Italy
2. Cemagref Rennes; URE Gere; 17 avenue de Cucillé 35044 Rennes Cedex France
3. Laboratory of Applied Geology; Univ. of Paris 6; T.26-0 E.5 case 123, 4, place Jussieu 75252 Paris Cedex 05 France