A COMPARISON OF POSSIBLE MODEL AND PARAMETER ERRORS ASSOCIATED WITH SOLUTE RETARDATION IN GROUNDWATER TRANSPORT

Groundwater solute transport models were developed which compared line ar to one type of non-linear adsorption. Most traditional transport si mulations rely upon linear adsorption in the form of solute retardance . While generally held to be appropriate at low solute concentrations, linear approximations are inadequate for some other applications. The subject work addressed this model uncertainty by comparing simulation s completed assuming that Freundlich adsorption was appropriate with t hose developed under linear assumptions. A non-linear retardance equat ion was derived. Solute concentration is an equation variable rather t han a constant and its estimation becomes critical in accurately defin ing transport times and distances. Errors associated with the selectio n of linear adsorption when non-linear retardation more appropriatedly applied ranged to 18.5 percent at low solute concentrations with vari ations in the Freundlich exponent. Error values approaching 13 percent were associated with solute concentration variation, while uncertaint y in selecting the partition coefficient accounted for less than 7 per cent.