Modeling Groundwater Chemistry with PHREEQC, PHAST and Python

This course will provide practical instruction in the use of PHREEQC and PHAST, two public-domain models available for download from the United States Geological Survey, to simulate aqueous geochemical processes and reactive transport in groundwater systems. After the key concepts for understanding and running both models are covered, techniques for extending the applicability of both packages using Python will also be explored.

At the conclusion of the course, students will be able to:

Construct PHREEQC simulations for a variety of situations, including water-rock and water-gas systems, reactions involving mineral surfaces (ion exchange, surface complexation), and oxidation-reduction processes. Students will also understand how to apply more complex features, such as using solid-solution formulations for variable-composition mineral phases, and how to implement reaction kinetic expressions in a model.
Construct PHAST simulations of multispecies reactive transport in groundwater, including systems entailing hydrologic as well as geochemical/mineralogical heterogeneities.
Use Python scientific programming tools, together with PHREEQC and/or PHAST, to address additional problems; examples will include reactive transport through partially-saturated porous media and conducting sensitivity analyses to parameter values. Also, Python scripts to process model input (e.g., specifying mineral assemblages) and output (e.g., Stiff diagrams) will be developed.
The course will be presented through the use of multimedia explanatory exercises, instructional videos, and a webinar involving working through a specific PHAST application for an environmental remediation example problem.

This course is aimed at hydrogeologists as well as environmental engineers and scientists with some previous exposure to water chemistry concepts (e.g., familiarity with major cations and anions typically measured in groundwater, alkalinity, pH, redox) and a general understanding of the mineralogy encountered in various types of aquifer environments. Knowledge of basic flow and transport concepts for saturated and partially-saturated porous media is assumed. The course will also require some familiarity or experience with numerical groundwater models (e.g., MODFLOW/MT3D) as well as Python scripting. Access to visualization software (e.g., commercial packages such as Surfer, or open-source equivalents) would be helpful, but not required.