THEREDA - One Database for thermodynamic and sorption data

For geochemical modeling of scenarios for the disposal of radioactive and (chemo)toxic waste, comprehensive and internally consistent thermodynamic data are required as well as sorption data for the surrounding host rocks. The use of different databases renders it difficult to compare results of geochemical modeling, due to incompleteness, inconsistencies, resticted ranges of variation (temperature, density, pressure), limitations in solution composition (ionic strength) and last but not least missing sorption data.
THEREDA (THErmodynamic REference DAtabase, www.thereda.de) is a project adressing these issues through high quality standards: full documentation and thus transparency of all data, internal consistency, quality assurance measures, different interaction models, comprehensiveness. It shall imporve geochemical modelling for various environmental applications, namely radiochemical waste disposal assessment.
THEREDA contains data for the three ion-ion interaction models: extendend Debye-Hückel, Specific Ion Interaction Theory, and Pitzer model. Tailored parameter files for various geochemical modeling codes are provided (PhreeqC, ChemApp, EQ3/6, Geochemist‘s Workbench). Documented benchmark calculations allow comparisons with other databases as well as between the different geochemical codes. All data, documentation and references are freely accessible via the projects homepage. Additionally, a user forum allows direct contact with the THEREDA members.
A holistic view of geochemical processes in the context of a safety analysis requires the inclusion of sorption calculations. A thermodynamically consistent treatment of these processes is only possible with surface complexation modelling (SCM). Existing SCM data from the RES³T (Rossendorf expert system for surface and sorption thermodynamics, www.hzdr.de/res3t) database is currently subjected to critical evaluation and will be included in THEREDA.