Modeling the Transport of Solutes to Groundwater Using Transfer Functions
- Kurt Roth * and
- William A. Jury
Transport of chemicals through the unsaturated zone into groundwater is in general a highly nonlinear process with a pronounced spatial structure of which only a very limited number of measurements is economically and technically feasible. In most applications, it is thus not practicable to model these processes with high spatial and temporal resolutions. However, in an agricultural environment chemicals are usually applied to large areas, and we are generally interested in their long-term effects on groundwater quality. With these restrictions, the transport processes may be averaged in space and time over sufficiently large regions such that it may be permissible to use a stationary, linear approximation. An efficient way to study such systems exploits that a stationary, linear system is completely determined by its transfer function, that is, by its response to a narrow pulse input. We use a general formalism to represent the transport processes implicitly by the relation between the flux and the resident concentration of a conservative chemical. To model the transport of nonconservative chemicals, this description is coupled, as it was done by (Villermaux, 1981), with a model of the local interactions. We obtain an expression for the transfer function of a linearly adsorbing chemical with linear adsorption kinetics and first-order decay in the water and in the adsorbed phase which is based on the measured transfer function of a conservative tracer. This procedure has the major advantage that parameter estimation and model validation tests can be applied to the chemical reaction processes alone.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © . .