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In this decade, electro‐geophysical methods are widely used in different environmental subjects. Studies on soil remediation when polluted by dense non‐aqueous phase liquids (DNAPLs) has become a certain need for all countries. Geoelectrical methods have shown their potential to facilitate evaluating decontamination processes. Our challenge in this study was to understand how coupled temperature and saturation changes affect electro‐geophysical parameters in a contaminated 2D sample. The primary objective was to evaluate the efficiency and potential of spectral‐induced polarization (SIP) for monitoring the recovery of DNAPLs in contaminated porous media. A set of 2D tank experiments investigated the impacts of temperature and saturation changes on the electrical complex resistivity of a saturated porous medium under non‐isothermal conditions. The measurements were made with a coal‐tar and water fluid pair in a porous medium that has been simulated by 1 mm glass beads. Hot water was circulated around the tank and an immersion heater used to heat the porous medium in the tank at different stages. The SIP technique (also called complex resistivity) was used to measure the complex electrical resistivity of a medium in the frequency domain. The experimental results for a simple drainage case were validated using numerical modelling. The complex electrical resistivity was used to obtain the saturation field before and after imbibition. For this purpose, the generalized Archie's law obtained for the same fluid pair with 1D cells (with a vertical flow) was used. Our results from electrical resistivity measurements for saturation fields are in accordance with 2D tank images and can illustrate the saturation change with pointwise resistivity measurements. The results show that saturation change has the primary role in electrical resistivity variation compared to temperature (5%–7%). We also studied the effects of temperature change on the Cole–Cole parameters, and the results confirm our previous findings with the same variation trend in these parameters. The results from varying electrical complex resistivity from the 2D tank (with vertical and horizontal flow) in the laboratory conditions will help us to understand the coupled temperature and saturation effects on complex resistivity in a real polluted site case. [ABSTRACT FROM AUTHOR]

The effective techniques for remediation of sites polluted by dense non-aqueous phase liquids (DNAPLs) remains a challenge. Among the various technical monitoring methods, there is an increasing interest in studying the geophysical characteristics of contaminated soils, as indicators of the progress in clean-up programs. This work sought to investigate the variation of the electrical complex resistivity and the relative permittivity by analyzing the results obtained from spectral induced polarization (SIP) and time domain reflectometry (TDR). Different series of measurements during drainage and imbibition of DNAPLs in porous media were done to validate the clean-up process on sites polluted by DNAPLs. Therefore, a methodology based on laboratory work was designed and carried out to study the electrical complex resistivity (both in magnitude and phase) in the frequency range 0.183 Hz to 20 kHz, and the relative dielectric permittivity at 70 MHz. The experiments were done on small 1D cells. In these cells, glass beads were used as a porous medium. Two different fluid couples, i.e., coal tar (CT)/water and canola oil (CO)/salty ethanol (SE), were used to produce two-phase flow. Our findings highlight that due to the high resistivity of CO and CT, an increase in water saturation led to decrease in amplitude and phase. Saturation change of SE had the same effect on resistivity but no relationship was found for phase and saturation for the mixture CO and SE. It is also showed that the complex resistivity and relative permittivity measurements were compatible with generalized Archie's law and complete complex refractive index method (CRIM) model as two empirical models for defining the correlation between the electrical resistivity, relative permittivity, and saturation of each phase in the multiphase porous medium. [ABSTRACT FROM AUTHOR]

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While some recent studies have discussed various effects of temperature on the electric and electromagnetic properties of multiphase porous media, the effect of temperature changes in multiphase porous media polluted by dense non-aqueous phase liquids (DNAPLs) has rarely been documented. We attempted to characterize how relative permittivity and electrical resistivity vary with temperature in multiphase porous media. The measurements were carried out using two different column sizes. Glass beads with a 1 mm diameter were used to simulate porous media. Spectral induced polarization (SIP) and time domain reflectometry (TDR) were used to measure complex electrical resistivity and relative permittivity, respectively. We investigated the geophysical characteristics of two DNAPLs, coal tar (CT) and chlorinated solvent (CS), from 20 to 50 °C; ultra-pure water was used as the reference fluid. Experimental data on the relative permittivity and complex resistivity of pure water obey empirical models, validating our experimental setup and protocol. Results demonstrated that the real parts of relative permittivity and electrical resistivity are functions of temperature in the medium with the presence or absence of a solid phase. While we did not study the imaginary part of relative permittivity, our observations in the DNAPL samples indicated that temperature increases decreased the imaginary parts of the complex electrical resistivity of DNAPLs tested, whether in the presence or absence of the solid phase. Temperature dependency of relative permittivity and complex resistivity were also studied in multiphase porous media, after drainage (80% DNAPL and 20% water) and after imbibition (8% DNAPL and 92% water). The effect of temperature increases on complex resistivity has a secondary effect on frequency domain and Cole-Cole parameters. It was found that the relationship between temperature and resistivity is linear; therefore, resistivity temperature coefficients were obtained for water and both DNAPLs with the presence and absence of solid phase. • Effects of temperature on electrical resistivity and relative permittivity. • Using SIP & TDR to monitor evolution of complex resistivity and relative permittivity. • Influence of water and DNAPLs saturations on geophysical parameters. • Cole-Cole parameters are affected by temperature increase. [ABSTRACT FROM AUTHOR]