Minerals and water ーPHREEQC programsー Groundwater and Geochemistry Rinko Koichi MATSUBARA

What is PHREEQC? “PHREEQC is used for simulating a variety of reactions and processes in natural waters or laboratory experiments.” PHREEQC is based on an ion-association aqueous model and has capabilities for (1) speciation and saturation-index calculations (2) batch-reaction and one-dimensional (1D) transport calculations … (3) inverse modeling From abstract of PHREEQC2

What can we do by PHREEQC? Equilibrium Reactions

What can we do by PHREEQC? Ion exchange

What can we do by PHREEQC? Kinetic reaction

What can we do by PHREEQC? Surface complexation Sorption on charged surfaces is calculated with surface complexation models. For example, the sorption of Zn2+ on ferrihydrite (hydrous ferric oxide, or 2-line FeOOH) follows the reaction: Zn2+ + Hfo_sOH ↔ Hfo_sOZn+ + H+

Getting started Download the software from… PHREEQC for Windows version 2.13.05, April 6, 2007 (1.8M) http://www.geo.vu.nl/users/posv/phreeqc/download.html Install the software Click on the PHREEQC icon to start Run example files

Example file 1 Graphs Ca vs F　concentration in equilibrium with fluorite

Keywords SOLUTION_MASTER_SPECIES defines elements and, among other things, their formula weights. SOLUTION The aqueous concentrations in a solution are defined with SOLUTION. The symbols for the elements are listed in the first column of SOLUTION_MASTER_SPECIES in the database. Solution 1 Analysis A -units ppm Ca 10 F 5.5 end Mixing the solutions… Make equilibrium adding reactants.. Make reaction adding reactants… Prepare “solution”

Keywords Mineral Equilibration A solution can be equilibrated with minerals assembled together in EQUILIBRIUM_PHASES, or the initial concentration of a component can be adapted when defining the SOLUTION. equilibrium_phases 1 fluorite 0 gypsum Mineral attained equilibrium Saturation index Reactant (defined as PHASES)

Keywords REACTION The keyword REACTION is used to stepwise add reactants or amounts of minerals to the solution. REACTION H -1 Na 1 25 mmol in 25 steps Reactant relative amount (relative molal)

Keywords USER_GRAPH USER_GRAPH -headings Ca F pH -chart_title "Fluorite Equilibrium" -axis_titles "Ca (mg/L)" "F (mg/L)" "pH" -initial_solutions false -start 10 graph_x tot("Ca")*40.08e3 20 graph_y tot("F")*19e3 30 graph_sy -la("H+") -end

Keywords MIX The effects of mixing of two or more groundwaters on the speciation and saturation state with respect to minerals can be calculated with keyword MIX. This keyword is also useful for simulating laboratory batch experiments.

Keywords EXCHANGE The keyword EXCHANGE is used to define exchange properties and to calculate the composition of the exchanger.

Keywords Surface Complexation The keyword SURFACE is used to define the surface complexation properties of sediments in much the same way as EXCHANGE. OECD/NEA:Using Thermodynamic Sorption Models for Guiding Radioelement distribution Coefficient (Kd) Investigations, A Status Report , 2001

Keywords KINETICS For kinetic calculations a rate equation must be programmed in BASIC using keyword RATES. The rate is called with keyword KINETICS which can also pass parameters to the rate. The BASIC functions are explained under keyword RATES in the PHREEQC manual.

More options… We can see various options from http://www.xs4all.nl/~appt/exmpls/index.html