1. Civil and Environmental Engineering, University of California, Berkeley, California 94720-1710, Environmental HydroGeochemistry, University of Pau, BP 1155, 64013 Pau Cedex, France, Geochemistry Department, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and ANDRA, 1/7 rue Jean Monnet, 92298 Châtenay-Malabry cedex, France