Design, performance, evaluation and modelling of a natural gradient multitracer transport experiment in a contaminated heterogeneous porous aquifer

For the investigation of solute transport within a contaminant plume in a highly heterogeneous porous aquifer with complex boundary conditions, a natural gradient multitracer test was performed. In order to obtain information as detailed as possible from only a single tracer experiment, four individual tracers (fluorescein, eosine, sodium naphthionate, and sodium bromide) were injected simultaneously in four adjacent wells. Tracers could be detected at nine observation wells (including five multilevel wells) over a travel distance of 230 m. Transport parameters such as transport velocity, effective porosity and longitudinal dispersivity, were determined in a first step by fitting a two-dimensional analytic solution to measured breakthrough curves. Using the resulting parameter values, a numerical principle model of the test site was set up to investigate the parameter heterogeneity and the complex boundary conditions in detail.