Geochemical models generally use thermodynamics to predict the fundamental geochemical processes which affect the fate and transport of inorganic and organic chemicals in terrestrial and aquatic environments. These models can provide a quantitative description of the processes which affect rock-water interactions, biogeochemical cycling and pollutant bioavailability, remediation and ecotoxicology. Important geochemical models include PHREEQ, Aquachem, and Geochemist's Workbench.

Landsat image centered around St. Louis, MO of the 1993 Mississippi flood. Photograph courtesy of FEMA.

Many biogeochemical studies create large, complex data sets which require information technology tools to visualize spatial and temporal patterns. One of the dominat tools to use is geographic information systems to visualize geospatial data. The dominant GIS tool are developed by the Earth Science Research Institute (ESRI) including ArcGIS and ArcView.

• Speciation Modeling Review
• Validation of Earth Science Models
• Metal Speciation
• GIS Review

PHREEQC

• USGS PHREEQ V. 2
• USGS Toxic Substances Hydrology Program

MINTEQA2

• Download from Old Dominion University Civil Engineering (DOS)
• Visual MINTEQ (Windows 95)
• USEPA Exposure Assessment Tools and Models

MINTEQA2 Manuals

• User Manual
• Supplmental manual 1
• Supplemental Manual 2
• Installation Guide

Other Models

• Various geochemical models
• Other models from Old Dominion

Thermodynamic databases

• UIC-TRL Home Page. The Thermodynamic Research Laboratory of the University of Illinois at Chicago maintains an exhaustive list of websites concerning thermodynamic data and thermodynamic or geochemical calculation tools.
• NEA Thermodynamical Data Base Project (TDB) This project aims at making available a comprehensive, internally consistent, internationally recognised and quality-assured chemical thermodynamic database of selected chemical elements. Thermodynamic data is available for Am, U, Np, Pu and Tc. The NEA is mirrored at http://www.oecdnea.org.
• JESS Thermodynamic database. This site provides access to 215,000 thermodynamic reaction constants for some 70,000 species, in a fully interactive manner. Reactions can be expressed in any form. Any number of equilibrium constants, enthalpy, entropy and Gibbs energy values can be associated with a reaction.