piChem

piChem, developed for DHI by Laurin Wissmeier, is a plug-in for FEFLOW for the calculation of advanced geochemical reactions together with aqueous phase flow and transport. piChem employs the interface version of PHREEQC as a reaction engine, which enhances FEFLOW’s built-in reaction capabilities with the full set of geochemical reactions provided by PHREEQC.

The reaction capabilities of piChem include

• Activity corrected solution speciation (using various activity corrections, as well as the Pitzer or SIT ion association models),

• Mineral dissolution/precipitation reactions,

• Solid solution reactions,

• Ion exchange reactions,

• Surface complexation reactions with optional diffuse double layer calculations (Dzombak & Morel DDL and CD_MUSIC),

• Gas phase exchange reactions,

• Temperature and pressure dependent reactions,

• Advanced calculations of solution density from ion composition, and

• Kinetic reactions with possible dependency on solution speciation using PHREEQC’s scripting capabilities and rate integrators.

Immediate access to comprehensive geochemical databases is provided. Functionality to extend these databases with user-defined components and reactions is an integral part of PHREEQC.

piChem defines geochemical reactions through PHREEQC input scripts. These can be produced using one of PHREEQC’s graphical user interfaces or a text editor.

User-defined geochemical output is imported into FEFLOW for graphical display using FEFLOW’s integrated visualization tools. In addition, PHREEQC output is saved with the DAC/DAR-files for later post-processing.

Please contact DHI for obtaining a license for the piChem plug-in.