Aggravation of licensing procedures by doubtful thermodynamic data.

Environmental prognosis by geochemical modelling is a scientific approach to several open questions of general public interest. Two prominent fields where geochemical modelling holds an important share are the remediation of contaminated former uranium mining areas and safety assessment of radioactive waste repositories in the geosphere. In both fields, application of geochemical modelling is stipulated by public authorities. The enormous complexity of models that can be handled by computers rises the awareness on the meaningfulness of a modelling result and demands for provision of an estimate of the dependability of a calculation output by the computers. It is obvious that bias, over- and underestimation of uncertainty in input data reduces the relevance of the calculation output. Chemistry contributes important data to geochemical modelling, both from field analysis and in the fundamental physico-chemical quantities enclosed into the thermodynamic data base. Some examples will be given where progress in quality assessment of chemical data may further the predictive power of geochemical modelling.