| Popis: |
The numerical representation of flow and solute transport is often intimidating to the introductory student. Quantifying the results of simple demonstrations in chemical movement is a valuable introduction to transport modeling and parameter estimation. A solution of the convection-dispersion equation (CDE) is used to describe the solute breakthrough curves generated in the demonstrations suggested in the companion paper. Estimation of the best fit model parameters (solute velocity, dispersion, and retardation) is illustrated step-by-step using the method of moments for an example data set. In addition to the model fitting exercise, the predictive merits of the CDE are demonstrated by employing secondary measurements o estimate the parameters. The most important of these supportive measurements is characterization of the soil-dye adsorption isotherm. The blue dye displays linear adsorption in the sand and clay loam (Ko of 0.25 m 3 Mg -t and 2.19 m3 Mg -~, respectively) while the yellow dye is nonadsorbed. It is found that the CDE predicts the dye movement fairly well in a sand, but performs poorly in a clay loam with organic matter. The poor prediction in the clay loam is attributed to the idealized nature of the isotherm measurement and shuttling of the dye with mobile organic material. |
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