Thermoddem: A geochemical database focused on low temperature water/rock interactions and waste materials

► Thermodynamic database for geochemical calculations. ► Mineralogical information as a help for modellers. ► Guide lines for thermodynamic data selection. ► FeII–H2O and FeIII–H2O chemical system refinement. The development of Thermoddem, a thermodynamic database devoted to geochemical modelling for environmental studies in general and, more specifically, to chemical systems involving waste materials, is discussed here. Concerns are also focused on taking into account some specific needs for modellers by proposing different output formats and some important information concerning the solid phases, the transformation path, paragenesis and insights into crystallographic details. This additional information aims to avoid considering phases that may not be “active” under current environmental conditions. The database is especially devoted to environmental applications, ranging from waste material management to pollutant behaviour, including the context of deep underground disposal. Selection rules and conventions are illustrated through the example of the Fe-water system, while a second example details the relationships between low and high ionic strength media, from the point of view of thermodynamic databases. Technical aspects concerning the development of a management information system for Thermoddem and its availability on the web (http://thermoddem.brgm.fr) are also provided.