Two dimensional electrical imaging for detection of hydrocarbon contaminants

The effects of a long-term diesel oil pollution due to leakage from buried tanks have been investigated using electrical resistivity tomography. The reliability of 2D electrical resistivity imaging of the subsoil was assessed using a numerical modelling approach that simulated the different behaviour of the contaminated zone. The effects of inversion parameters, such as the damping factor and smoothing matrix, have been studied in order to evaluate the optimal parameters to process real data. The results of the field test indicated that highly conductive anomalies can be related to the biological degradation of hydrocarbons: geochemical analysis performed on several groundwater samples confirmed the presence of biodegradation activity. Chemical analysis pointed out an anomalous concentration of iron and manganese cations dissolved in the groundwater. Very low values of resistivity can be associated with a marked modification of the cation exchange capacity of the soil mixture due to degradation of these hydrocarbons. Chemical and physical interactions due to hydrocarbon pollution affect the electrical properties of soils and groundwater.