Lysimeter study to identify GPR response under different contaminant level in groundwater

Abstract

Potentials of groundwater contamination due to different pollutant loads can be assessed using different technologies available through quality detection, mapping extend of the contaminant plume and migration of the plume. Real field situation is very complex and application of some techniques might be a challenging task especially with respect to data interpretation. Creating of controlled condition which represents the real field situation is very much important to understand the field situation and applicability of such techniques. Among the available geophysical methods, ground penetrating radar (GPR) technique is suitable for studying the subsurface features. A lysimeter (4.0 m x 1.0 m x 1.5 m (L x W x D)) study was conducted at the Meewathura farm of the Department of Agricultural Engineering, University of Peradeniya to verify the applicability of the GPR technique in detecting contamination level in groundwater. The lysimeter was filled with sand as a media and two iron bars (with a diameter of 5 cm) were placed at 1.0 m and 3.0 m length intervals at 0.2 m above from bottom of the lysimeter. GPR reflection surveys were carried out on lysimeter at different level of contamination. GPR wave response was studied under each situation and analyzed the reflected waves from bottom of the lysimeter and iron bars. 2D GPR wave simulations were carried out using GPRMAX2D for the same lysimeter conditions. For this purpose, a contamination plume with different EC values (to obtain different contaminant levels) in groundwater was introduced to the model domain. Both modeling result and lysimeter study were revealed that the energy of reflected wave attenuated and disappear the reflected event with increasing contaminant level (increasing EC).