Estimation of transport parameters of a tracer plume dispersion on field experiments from GPR and 3D ERT imaging

Electrical resistivity tomography (ERT) and Ground-Penetrating Radar (GPR) are commons geophysicals methods used to study near surface hydrogeological processes. As resistivity depends on properties such as temperature, saturation or solute concentration, these techniques are now also used to monitor, for instance, saline intrusion, solute transport and contaminated soil remediation. In the recent years, laboratory scale experiments have been performed in order to improve the ability to make and interpret ERT and GPR measurements. The purpose of this study is to quantify experimentally the evolution of dissolved species in porous media from 3D resistivity models and surface GPR. Transport experiments are done at the metric scale by performing flow in fontenaibleau sand. From previous 2D laboratory experiments a post-processing ERT data has been defined to provide quantitative information about transport parameters in porous media such as the dispersivity, the mixing front velocity and the retardation factor associated to the sorption or trapping of the tracers in the pore structure. The present work deals with field data, the dimension of the area study is 1m x 1m x 2m (xyz) and a solute tracer is injected at the top of the investigated zone at constant flow rate with a pump.Compared to the experimental studies the area is not water satured and the saturation rate is about 10%. ERT data are acquire in 4 boreholes with 21 electrodes and GRP data are done with surface profils at the same time. During infiltration two GPR antennas (transmitter and receiver) were recording a trace every second from an offset position on the surface.. ERT and GRP data allows a good description of the temporal variation of the medium and comparison of the temporal evolution of the NaCl concentration distribution estimated from ERT models with GPR analysis are done.