Characterization of aged hydrocarbon-contaminated sites is often a challenge due to the heterogeneity of subsurface conditions. Geoelectrical methods can aid in the characterization of such sites due to their non-invasive nature, but need to be supported by geochemical and microbiological data. In this study, a combination of respective methods was used to characterize an aged light non-aqueous phase liquid-contaminated site, which was the scene of a crude oil blow-out in 1994. As a consequence, a significant amount of crude oil was released into the subsurface. Complex resistivity has been acquired, both along single boreholes and in cross-hole configuration, in a two-borehole test site addressed with electrodes, to observe the electrical behaviour at the site over a two-year period (2010-2011). Geoelectrical response has been compared to results of the analysis of hydrocarbon contamination in soil and groundwater samples. Geochemical parameters of groundwater have been observed by collecting samples in a continuous multi-channel tubing (CMT) piezometer system. We have also performed a biological characterization on soil samples by drilling new boreholes close to the monitoring wells. Particular attention has been given to the characterization of the smear zone that is the sub-soil zone affected by the seasonal groundwater fluctuations. In the smear zone, trapped hydrocarbons were present, serving as organic substrate for chemical and biological degradation, as was indicated by an increase of microbial biomass and activity as well as ferrogenic-sulfidogenic conditions in the smear zone. The results show a good agreement between the intense electrical anomaly and the peaks of total organic matter and degradation by-products, particularly enhanced in the smear zone.

A Borehole Thermal Energy Storage living lab was built up nearby Torino (Northern Italy). This living lab aims at testing the ability of the alluvial deposits of the northwestern Po Plain to store the thermal energy collected by solar thermal panels and the efficiency of energy storage systems in this climatic context. Different monitoring approaches have been tested and analyzed since the start of the thermal injection in April 2014. Underground temperature monitoring is constantly undertaken by means of several temperature sensors located along the borehole heat exchangers and within the hydraulic circuit. Nevertheless, this can provide only pointwise information about underground temperature distribution. For this reason, a geophysical approach is proposed in order to image the thermally affected zone (TAZ) caused by the heat injection: surface electrical resistivity measurements were carried out with this purpose. In the present paper, results of time-lapse daily acquisitions are reported with the aim of imaging the thermal plume evolution within the subsoil. Resistivity data, calibrated on local temperature measurements, have shown their potentiality in imaging the heated plume of the system and depicting its evolution within the day. Different types of data processing were adopted in order to face issues mainly related to a highly urbanized environment. The use of apparent resistivity proved to be in valid agreement with the results of different inversion approaches. The inversion processes did not significantly improve the qualitative and quantitative TAZ imaging in comparison to the pseudo-sections. This suggested the usefulness of apparent resistivity data alone for a rough monitoring of TAZ in this kind of applications.

Non-destructive geophysical prospecting methods are increasingly used for the investigation of archaeological sites, where a detailed physical and geometrical reconstruction of structures is required prior to any excavation work. small area had been selected to test the integration of magnetic, ground-penetrating radar, and electrical resistivity tomography techniques.The magnetic data were acquired as the vertical gradient of the total magnetic field and were inverted by minimizing an L-2 norm. The ground-penetrating radar data were acquired as singleoffset measurements on a regular grid and processed to obtain time slices of reflection amplitude. The electrical resistivity tomography data were acquired with dipole-dipole array along parallel profiles in both east-west and north-south directions.In this work, we reprocessed the data collected in 1996 performing a three-dimensional inversion of electrical resistivity tomography data using ground-penetrating radar data and three-dimensional inversion results of the magnetic data. We inverted electrical resistivity tomography data according to L2 and L1 norm minimization. Both the mean apparent resistivity and different resistivity distributions derived from processed ground-penetrating radar and three-dimensional inversion of the vertical gradient of the total magnetic field data were used as a starting model.The results were then compared in the volume under the surveyed area: merits and shortcomings of the different techniques are pointed out and analyzed.From the results of the different applied techniques, it comes that both electrical resistivity tomography and vertical gradient of the total magnetic field locate the searched tomb as a volume, whereas ground-penetrating radar mainly identified the ceiling of the tomb. Vertical gradient of the total magnetic field data inversion obtained from minimization of the L2 norm properly locates both the chamber and the corridor but produces smeared overestimated volumes. Three-dimensional inversions of electrical resistivity tomography data with a priori information give an accurate picture of the chamber and delineates the corridor, even if the resistivity values are underestimated if compared with the expected resistivity of void. Results are compared with the archaeological findings as the area was unearthed and verified in 2001.tures built with the same material of the surrounding ground, as well as soil inhomogeneity and other environmental disturbances, can sometimes yield low signal-to-noise (S/N) ratios on geophysical data. This hinders the definition of the spatial position and extent of the buried structures.During the last decades, many approaches (Brizzolari et al.

The Bio.Lea.R project aims to demonstrate the performance of a landfill for less reactive, biologically treated waste (pretreated organic wastes) compared to a conventionally managed landfill, with regard to both environmental (biogas and leachate production) and economic aspects. The objective is to control the pretreated biodegradable waste through a liquid injection in order to achieve the same biogas quantity in a shorter time than in conventional landfill. Laboratory and full scale monitoring were performed in order to check the efficiency of the landfill acting as bioreactor. A smallscale lysimeter was set up to simulate in laboratory the biological processes that happen at a bioreactor landfill. The lysimeter consists of a cylindrical reactor filled with waste. The monitoring activity of the geophysical parameters of the landfill is based on network of geophysical sensors to detect the changes in time and space of the electrical conductivity at different depth in the landfill. Electrical conductivity is potentially a good indicator of spatial and temporal changes of liquid content of the waste within, as results of the infiltration process. Results of the lysimeter experiment have proved the faster production of biogas, with the Methane Potential Yield at 900 days. The current modeling of leachate infiltration is influenced by availability of experimental data which in this case are provided by time lapse monitoring of geophysical parameters. The combination of time-lapse geophysical monitoring, advanced inversion technique and traditional waste sampling techniques provides robust data to evaluate the infiltration process and degradation of waste.

In the context of shallow geothermal applications, geophysics can be applied as design and monitoring tool. In the last decades mainly electrical resistivity measurements have been adopted both for the characterization and to image spatial and temporal distribution of temperature within the ground. This paper is therefore focusing on the use of electrical resistivity in this context with a devoted look to Italians state of art. A brief literature review of thermal characteristics influencing the resistivity value and example applications of Electric Resistivity Tomography (ERT) data is reported. Two example case histories, in very different hydrogeological contexts, in northern Italy are also briefly commented.