PHREEQC application examples

PHREEQC APPLICATION EXAMPLES

Most of these examples stem from Appelo and Postma, 2005. Geochemistry, groundwater and pollution, 2nd ed. The examples can be easily run and plotted with Vincent Post's PHREEQC for windows interface.

Equilibrium Reactions
- Ca²⁺ / F^- in equilibrium with fluorite ( CaF₂ ) explains high F^- concentration in African Rift Valley waters.
- Dissolution of calcite ( CaCO₃ ) depends on the CO₂ pressure. Mixing causes subsaturation which explains cave formation in karst areas and coastal zones.
- The Al concentration in water depends on Gibbsite ( Al(OH)₃ ) equilibrium.
- Both at low and high pH, the Al concentration may exceed the drinking water limit.
- Ca and SO₄ concentrations diverge when gypsum (CaSO₄.2H₂O) precipitates from an evaporating brine.
- The series of salts that precipitate from evaporating seawater can be computed using Pitzer equations for calculating activities.
Ion exchange
- Find exchangeable cations on soil in a sea-/fresh water mixture.
  Details: Rothmund-Kornfeld and active fraction models.
- CaCl₂ solution displaces (Na, K)NO₃ pore water in a series of column experiments:
  1. Basic model with chromatographic displacement of Na⁺ and K⁺ by Ca²⁺.
  2. Chromatographic displacement with stagnant zones.
  3. Chromatographic displacement with kinetic exchange.
- Two classical field examples of chromatography in aquifers:
  1. The Aquia aquifer (Maryland, USA).
  2. Valocchi's fresh water injection in a brackish aquifer.
Surface complexation
- Zn sorption edge, % Zn sorbed as function of pH and the Zn concentration.
- CO₂ sorption on oxy-hydroxides is important in natural systems and must be included in the Dzombak and Morel database.
Kinetic reactions
- Kinetic dissolution of quartz.
- Biodegradation of phenol with Monod kinetics.
- Biodegradation of xylene coupled with biomass growth.
Application examples
- In situ iron removal, principles of removing iron from groundwater by injecting oxygenated water.
- In situ iron removal, a specific case showing kinetic effects.
- Retardation of U(6) and Zn from acid mine drainage.
- Oxidation of pyrite in a column experiment.
Modeling isotope fractionation
- Rayleigh fractionation and ¹³C fractionation
Specific Conductance
- How to calculate the specific conductance of a solution with PHREEQC

NEW in PHREEQC version 2.13 (consult PHREEQC Help for details, unblock this file)

Multicomponent diffusion
- Multicomponent diffusion can be upgradient, contrary to Fick's laws, as explained in a column example.
- PHREEQC's multicomponent module can be checked by calculating CaCl₂ diffusion profiles:
  1. Compare with the Nernst equation which gives the diffusion coefficent of a salt from its constituent ions. Charge on the tracer, or diffusion in a concentrated solution give different results!
  2. Compare with classic PHREEQC, which calculates with one and the same diffusion coefficient for all species.
- Multicomponent diffusion of seawater in a fresh water sediment is different for cations and anions.
- Multicomponent diffusion of tracers in clays is a function of the tracer diffusion coefficient and diffuse double layer effects such as anion exclusion and enhancement of cation transport.
Diffuse Double Layer calculations
- The membrane properties of clays depend on the extent of the diffuse double layer.
Colloid transport
- Ferrihydrite, with sorbed Uranium, can be transported as colloid through a column.

NEW in PHREEQC version 2.16 (consult PHREEQC Help)

Surface/interlayer diffusion of cations
- Surface or interlayer diffusion can be significant for strongly sorbed cations such as Cs⁺.
Solution density calculations
- Density of evaporating seawater .
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PHREEQC APPLICATION EXAMPLES Most of these examples stem from Appelo and Postma, 2005. Geochemistry, groundwater and pollution, 2nd ed. The examples can be easily run and plotted with Vincent Post's PHREEQC for windows interface.

PHREEQC APPLICATION EXAMPLES

NEW in PHREEQC version 2.13 (consult PHREEQC Help for details, unblock this file)

NEW in PHREEQC version 2.16 (consult PHREEQC Help)

«—

PHREEQC APPLICATION EXAMPLES

Most of these examples stem from Appelo and Postma, 2005. Geochemistry, groundwater and pollution, 2nd ed. The examples can be easily run and plotted with Vincent Post's PHREEQC for windows interface.