1. BRGM; LAB/ISO; 3 avenue Claude Guillemin, BP 36009 F-45060 Orléans cedex 2 France
2. Instrumental Analytical Chemistry; University Duisburg-Essen; Universitätsstr. 5 D-45141 Essen Germany
3. Center for Applied Geoscience (ZAG); Eberhard Karls University Tübingen; Hölderlinstr. 12 D-72076 Tübingen Germany