Short Course 1


Thermodynamic Databases and Geochemical Modelling


Dr. Kirk Nordstrom
Hydrogeochemist, University of Colorado, USA


This course takes an in-depth look at thermodynamic data that is used for geochemical modelling of water-rock interactions. It describes the historical development of thermodynamic data, defines “internal consistency,” compares and contrasts the databases available in PHREEQC, summarizes the current status of electrolyte theory, and reviews strengths and limitations with respect to specific applications. An overview of “critical data evaluation” is also presented.

Geochemical modelling is only as good as the input data available which ranges from excellent to non-existent for thermodynamic data. This course provides the basic knowledge of thermodynamic databases that one needs to know for more successful modelling applications. It will be helpful for scientists, engineers, consultants, and students who wish to learn about thermodynamic data. It should also be helpful for anyone thinking of evaluating data.

The course outline will cover

  • a brief review of the most important thermodynamic relationships
  • the historical development of thermodynamic databases
  • a review of electrolyte theory
  • demonstrate the effect of different databases for calculating mineral solubilities
  • examples of critically evaluated systems will include gypsum-water, calcite-water, aqueous arsenic reactions, and sulfide reactions
  • specific examples on acid mine drainage will be included and the difficulties of Fe(III) minerals
  • when the equilibrium assumption is warranted

Participants will have insight into the differences among databases, what their limitations are, and how to choose them. It should be helpful in evaluating uncertainties based on thermodynamic data. All participants will need to download PHREEQC and digital course notes will be made available.