A Graphing Method of Solute Parameter Estimation for Convection-Dispersion Equation

Abstract

A graphing method is presented in this paper for estimating the parameters of solute transport in soils based on the convection-dispersion equation (CDE). The ratio of flux concentration change with time (dc/dt) is obtained on data of breakthrough curve (BTC) of solute transport in a semi-infinite soil column. Using graphing software, for example, the Microsoft Excel, can draw two curves of t1.5dc/dt and dc/dt respect to time. Each curve has single peak. The two curves are used to estimate the retardation factor and dispersion coefficient in the CDE. Hypothetical examples and displacement experimental data of two soils were used to validate the new graphing method for its accuracy and stability for estimating the two parameters. The stability of parameter estimation is evaluated by the standard deviations of estimation parameters to their average value. The accuracy of the new method is assessed by comparing it with other two most used methods that are the CXTFIT and the slope methods. The results show that the method has both high accuracy and good stability. The new method is particularly good for the estimation of parameter R. The method is a deterministic method and it is simple in terms of calculations. It also has the advantages of uniqueness and no initial guess of the parameters over the CXTFIT method. The new method provides an alternative approach for estimating parameters of solute transport in soils. It is simple, accurate, stable, and saves time.