TRACE-METAL BEHAVIOR IN NATURAL GRANITIC WATERS

Alkaline thermal waters were sampled in granitic areas of southern Eur ope. In this study attention is focused on the behaviour of trace elem ents likely to be present in a radioactive waste disposal. We demonstr ate that, in this type of waters: (1) most transition metals are limit ed 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 elem ents (REE), we observe that they are well correlated with Th, with a s lope of 1 in log-log diagrams. These elements are associated with part icles suspended in solution. The different Th to REE or Th to Zr, Hf, etc., ratios are constant in solution and in the particulate fraction.