Tableau input coupled kinetic equilibrium transport (TICKET) model.

TICKET is a general-purpose, multispecies reactive transport model that is based on the tableau structure in MINEQL. The model can be used in solving problems from simple chemical equilibrium calculations for batch systems to complex one-dimensional, reactive transport computations for surface water, groundwater, and water treatment systems. To streamline model input and model formulation, specifications of equilibrium speciation (including homogeneous precipitation, solid solutions, adsorption, and ion exchange) and linear and nonlinear kinetic reactions are defined directly in the tableau. In addition, the burden of accounting for appearing and disappearing solid phases is circumvented by approximating homogeneous precipitation as a solid solution (with an insoluble seed). The solution technique for the model is based on a one-step algorithm and can be applied to both steady-state and fully implicit, time-variable problems. This approach is particularly well-suited in handling chemical speciation-transport problems with fast, nonlinear reaction kinetics and transient chemical intermediates. TICKET model simulations are presented for several test cases to verify the computational scheme. A model application, which examines the effects of sorption and overlying dissolved oxygen concentration on Fe(II) and As(III) oxidation in a sediment column, is also presented to demonstrate the utility of TICKET in examining complex chemical speciation-transport behavior.