GROUNDWATER SOLUTE TRANSPORT WITH HYDROGEOCHEMICAL REACTIONS

Chemical contamination of ground water is typically associated with mu lticomponent solutions of reactive substances, the mobility of which i s affected by their reactivity. In predicting geochemical transport, i t is therefore important that the liquid and solid phase reactions be modeled, along with the flow-controlled processes. This demanding task is typically carried out on powerful computers. Frequently, however, field data are available for a limited number of species, or, a small number of species suffices to characterize ground-water quality. In su ch cases it is desirable to be able to model the transport on a widely available class of inexpensive computers. We report on the developmen t of a 2-D model for the transport of reactive species that runs effic iently on PCs. The model follows a modified one-step procedure that ad opts total (aqueous and adsorbed) concentrations and aqueous concentra tions of components, and accounts for aqueous complexation and for com petitive sorption via isotherms or selectivity coefficients. The use o f principal directions of transport coordinates, dimensional splitting , and a specialized algorithm for handling advection-dominated transpo rt render it compact and efficient. Mass conservation is satisfied wit h high accuracy.