“…In-situ geophysical monitoring of subsurface fluid saturation changes and contamination is important for environmental protection and oil industry, for instance (1) leakage at buried waste sites, (2) contaminant remediation in groundwater, and (3) fluid injection for enhanced petroleum recovery. Geophysical monitoring of groundwater contamination has been examined by many methods with geophysical instruments (e.g., Greenhouse and Monier-Williams, 1985;Benson et al, 1997;Buselli and Lu, 2001;McGlashanb et al, 2012). Commonly-used geophysical methods for monitoring groundwater contamination and plume migration include geoelectrical methods (e.g., Mazac et al, 1987;de Lima et al, 1995;Benson et al, 1997;Sauck, 2000;Nwankwo and Emujakporue, 2012;Bellmunt et al, 2016) and ground penetrating radar methods (e.g., Benson, 1995;Daniels et al, 1995).…”