A combined mixing cell/analytical model to describe two‐dimensional reactive solute transport for unidirectional groundwater flow

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Abstract
A combined two‐dimensional mixing cell/analytical solution is presented which describes multiple reactive solute transport in unidirectional groundwater flow regimes. The model uses a two‐step solving routine which separates chemical equilibria computations (ion exchange and mineral precipitation/dissolution) from calculations of advection/dispersion. Before running the model for a particular grid configuration, an isochemical flow situation is run first to calibrate the model. The calibration technique adjusts for mass losses or gains to and from cells, which occurs when using mixing cell models. Computational time for calculating chemical equilibria in each mixing cell is markedly reduced by the use of a single‐equation solution to solve for multi‐ion exchange equilibria and a rapid iterative technique to solve for calcite equilibria. The application of the model to simulate a solution injection experiment into an unconsolidated sand deposit yielded results in reasonable agreement with field observations.