Design and analysis for an inverse problem arising from an advection-dispersion process

We consider a process of one-dimensional fluid flow through a soil-packed tube in which a contaminant is initially distributed. The contaminant concentration, as a function of location in the tube and time after flushing begins, is classically modeled as the solution of a linear second-order partial differential equation. Here, we consider the related issues of how contaminant concentration measured at some location–time combinations can be used to approximate concentration at other locations and times and how the sampled location–time combinations can be most effectively selected for this purpose (i.e., experimental design). The method is demonstrated for the case in which initial concentrations are approximated based on data collected only at the downstream end of the tube. Finally, the effect of misspecifying one of the model parameters is discussed, and alternative designs are developed for instances in which that parameter must be estimated from the data.