Submitted to: Ground Water Modeling Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 15, 1995
Publication Date: N/A
Interpretive Summary: While many models have been developed which quantify different physical and chemical processes, most models usually consider only one solute by severely simplifying the different chemical interactions. This paper presents two models on which we demonstrate two approaches which may be used for modeling the transport of multiple ions which undergo a number of simultaneous interactive chemical reactions. The first approach (one-step method) represents more traditional approach as used independently by soil physicists and soil chemists. Examples of the application of both models on transport of nitrogen species and transport of major ions are presented.
Technical Abstract: This paper presents two models typical of two different approaches often used for modeling the convective-dispersive transport of multiple ions in variably-saturated porous media. The first approach assumes that all solute reactions can be incorporated directly into the governing transport equations (the one-step method), while the second approach divides the mathematical solution process into two separate steps: one for transport, and one for most or all chemical reactions (the two-step method). The two approaches are illustrated using the one-step CHAIN 2D code which simulates the nonlinear nonequilibrium transport of solutes involved in sequential first-order decay reactions, and the two-step UNSATCHEM-2D code which considers equilibrium and kinetic non-equilibrium chemistry of major ions.