geochemical speciation model based on equilibrium thermodynamics which can calculate the equilibrium composition of dilute aqueous systems amongst soluble, solid, adsorbed and gas phases.  Calculations can be performed to take into account varied environmental conditions such as pH, ionic strength, temperature and redox conditions. The program also includes an extensive database which includes thermody<namic data for the soluble complex, mineral solubilities, gas solubilities and redox couples. In addition more recent updates contain a database of metal surface complexation constants and complexation constants for metal complexation with dissolved organic matter.