1. Department for Isotope Biogeochemistry; Helmholtz-Centre for Environmental Research (UFZ); Permoserstrasse 15 D-04318 Leipzig Germany
2. Max-Planck-Institute for Biogeochemistry; Beutenberg Campus, P.O. Box 100164 D-07701 Jena Germany
3. U.S. Geological Survey; 431 National Center Reston VA 20192 USA
4. Isodetect GmbH; Deutscher Platz 5b D-04103 Leipzig Germany
5. Department of Geological Sciences; Indiana University; Bloomington IN 47405-1405 USA