Chemical Modeling of Acid Waters

Thermodynamic Property Evaluation

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Aqueous geochemical codes such as WATEQ4F, MINTEQA2, EQ3/6, and PHREEQC are only as reliable as the input data allows. Our project evaluates the thermodynamic data that is used by these and other programs to improve modeling capabilities. A compilation of high quality data has been done for most major and selected trace element reactions (Nordstrom et al., 1990) and comprehensive evaluations have been done for aluminum and chromium species (Nordstrom and May, 1996; Ball and Nordstrom, 1998). An evaluation of arsenic species is in preparation. Some types of speciation modeling can be tested by analytical measurements (Nordstrom, 1996) and testing of fluoride speciation is in preparation.

Nordstrom, D.K. and Archer, D.G. (2003) Arsenic thermodynamic data and environmental geochemistry, In Arsenic in Ground Water, A.H. Welch and K.G. Stollenwerk, eds., Kluwer Publishers, 1-26.

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