TRACE-METAL BEHAVIOR IN NATURAL GRANITIC WATERS

Alkaline thermal waters were sampled in granitic areas of southern Europe. In this study attention is focused on the behaviour of trace elements likely to be present in a radioactive waste disposal. We demonstrate that, in this type of waters: (1) most transition metals are limited to very low concentrations probably by sulfide minerals (CoS, MoS3, ZnS, Sb2S3); (2) uranium is limited in solution by uraninite; (3) for tri- and tetravalent metals such as Zr, Hf, etc., and rare-earth elements (REE), we observe that they are well correlated with Th, with a slope of 1 in log-log diagrams. These elements are associated with particles suspended in solution. The different Th to REE or Th to Zr, Hf, etc., ratios are constant in solution and in the particulate fraction.