1. U.S. Geological Survey, Building 95, MS 408, Federal Center, Denver, CO 80225
2. Laboratoire de Chimie de l Environment, UPRESA CNRS 6008, Ecole Supérieure d'Ingenieurs de Poitiers, Université de Poitiers, 86022 Poitiers Cedex, France
3. Department of Civil Engineering, MS FX 10, University of Washington, Seattle, WA 98195-2700
4. Metropolitan Water District of Southern California, 700 Moreno Avenue, La Verne, CA 91750-3399
5. Suez Lyonnaise des Eaux, CIRSEE, France
6. U.S. Geological Survey, Boulder, CO 80303