Impact of measurement uncertainty in chemical quantities on environmental prognosis by geochemical transport modelling

in Germany, geochemical modelling takes a strong position in two aspects of broader public interest. The first aspect is the safety assessment of a nu clear waste repository, the second is remediation of uranium mining areas. In both aspects, the application of geochemical modelling is stipulated by authorities. This situation results from the possibility to model highly co mplex situations by computers. The increase in computing power experienced in recent times now offers techniques to assess the sensitivity of modellin g results to uncertain input data both in the thermodynamic data base and t he site-specific field data. Both aspects are investigated by using Monte C arlo methods in combination with non-parametric statistics. A probabilistic geochemical modelling of uranium mill tailings leaching is demonstrated by application of TReaC modelling code using a simplified site model.