Reactions Cards (-RG)

There are two Reactions Cards that can be used with the ECKEChem Reactive Transport module. Both Equilibrium and Kinetic Reactions can be defined, though neither card is a requirement for executing a simulation with ECKEChem. However, if an equilibrium equation or kinetic equation is defined, then a corresponding Equilibrium Reactions Card and Kinetic Reactions Card is also required. Since unique equation names are required, the equation names must match between the Equilibrium Equations Card and Equilibrium Reactions Card, as well as the Kinetic Equations Card and Kinetic Reactions Card. If the toEcke pre-processor is used, then the equilibrium equations will be named numerically as EqRc-1...EqRc-n, and the kinetic equations will be named in the same manner as, KnRc-1...KnRc-n.

The only information input into the Equilibrium Reactions Card are parameters used to specify temperature-dependence on equilibrium constants. These parameters must be obtained from a geochemical database and refer to the following equation

Symbols
	equilibrium constant
	temperature, K
	equilibrium constant coefficient
	equilibrium constant coefficient
	equilibrium constant coefficient
	equilibrium constant coefficient
	equilibrium constant coefficient

If these parameters are unknown or no temperature-dependence is required, then zeros can be used. This information is also required the temperature-dependence for the Kinetic Reactions Card, if precipitation-dissolution kinetics is specified (e.g., TST), but it is not required for all kinetic reactions. The information required for kinetic reactions is dependent on the reaction type selected. For example, the types of information that may be required on this card include information on the reactants and their stoichiometry, kinetic rates and decay coefficients. If the toEcke pre-processor is used, a TST formulation is assumed by default and the kinetic reaction will be written for this kinetic reaction type. Users may need to modify the thermodynamic database to accommodate reactions and species not present in the database. The pre-processor assumes that the database is written in a Geochemist Workbench format, which can be downloaded at (http://www.gwb.com/thermo.php).