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Geophysical methods have been adopted to characterize a site whose soils and groundwater had been contaminated by nonaqueous-phase liquid (NAPL); the hydrocarbons were found in both residual form and as a free phase above the water table. The geophysical survey was aimed at improving the knowledge of the hydrogeological setting of the site; we wanted to estimate the soil heterogeneity and the hydrogeological parameters (porosity, water content, and hydraulic conductivity). We also wanted to assess the effect of the water table fluctuations on the interaction between the groundwater and the residual NAPL. The geophysical investigation was conducted using geoelectrical, electromagnetic (frequency domain), and georadar methods; data calibration was conducted using borehole geochemical logs.
The presence of residual NAPL in the silty and sandy material was confirmed by a remarkable increase of the attenuation in the georadar energy and by peak of induced polarization response. The hydrocarbons have been detected in concentrations of more than 1000 mg/kg (1000 ppm) at a depth of 5 m (15 ft) and in concentrations of 3000 mg/kg (3000 ppm) at a depth of 6 to 8 m (18–24 ft).
Alberto Godio received his M.S. in mining engineering and Ph.D. in mining geophysics (1993) at Politecnico di Torino. Since 2005, he has been an associate professor at Politecnico di Torino. He worked as a consultant in mining and a civil engineering–related field. He has been employed as an assistant professor at Politecnico di Torino since 1993. His main research interests include GPR and electrical methods for hydrogeophysical survey.
Alessandro Arato obtained his M.S. degree in environment and territory engineering at Politecnico di Torino in 2009. As of January 2010, he is studying for his Ph.D., where his main focus will be on geophysical methods applied to hydrogeological and geochemical processes in contaminated sites.
Stefano Stocco graduated in environment and territory engineering at Politecnico di Torino in 2005. In 2010, he took his Ph.D. in engineering of the territory at University of Cagliari. His research interests involves magnetic and electromagnetic methods in near-surface geophysics and environmental and archeological fields.