Characterization of agricultural contaminant transport using ground-penetrating radar and electrical data

Abstract

In this on-going study, a combination of Ground Penetrating Radar (GPR) and electrical surveys is used to characterize the physico-chemical properties of soil, in particular those concerning lithology variations, water content, porosity and salinity in agricultural zones. These investigations will be completed by independent chemical analyses of soil and water. The experiments are conducted on fields of intensive corn culture (4 x 2 km) where the water table is 1.5 to 5 m deep, in a geological context of alluvial deposits. Analyses of water from various wells in the study area show high concentrations of nitrate coming from the chemical fertilizers spread on the soil surface. Globally, values increase from south to north and can be explained by the general direction of flow in the water table aquifer. In this on-going study, GPR and electrical data are recorded at two sites located along a north-south line and seasonal variations will be monitored for twelve months. Preliminary results which are presented here, give structural information concerning the subsurface and show vertical flow of mineralized water (from the surface to the aquifer) providing evidence of transport of dissolved contaminants to the water table aquifer. This study demonstrates the potential of non-destructive geophysical methods for providing information on hydric and solute transfer in the ground and monitoring soil contamination.