Limitations in recovering the history of a groundwater contaminant plume

Groundwater contaminant transport is a dispersive process and consequently there are limits to what may be learned about a contaminantʹs origins (history) from measurements of its present spatial distribution. The extent of these limitations in a particular case depends on a number of factors, including the dispersive properties of the transport medium, the accuracy of the measured plume, and the interval of time over which the plume has evolved. We propose to characterize the limitations that will be encountered in a given transport medium by performing numerical simulations that assess our ability to recover various ‘test functionsʹ, i.e., hypothetical contaminant release functions that are designed to provide insight into the effect that a transport mediumʹs dispersive properties have on the recoverability of a plume history. Knowing our ability to recover test functions that differ, for example, in the time span over which the release occurs or in the amount of mass released allows us to make inferences about our ability to recover the history of an arbitrary plume in a transport medium with dispersive properties similar to those used in the simulations. Our ability to recover a test function is quantified using a Monte Carlo methodology. The method is demonstrated for the case of Gaussian test functions.