Proprietes electriques des sols contamines par des hydrocarbures petroliers: Etude en laboratoire

In many worldwide cities, urban development has reached the fringes of old industrial areas, whereas industrial downsizing has produced a significant number of Brownfield. These are often orphan sites contaminated with various pollutants which still remain undeveloped even after several decades of abandonment. In recent years, urban Brownfield started to be considered as been beneficial occasions for urban land redevelopment, however, it was recognized that their remediation and reuse slows down urban sprawl as well as their environmental impacts. Hence, there is a growing need to assess the environmental quality of these sites. The environmental assessment of urban Brownfield is difficult due to their large physical and chemical heterogeneity. One of the most promising methods to characterize these urban sites (heterogeneous fill) that are often contaminated by pollutants after more than a century of industrialization is the induced polarization (IP).;The electrical resistivity and chargeability are in principle susceptible to the soil mineral composition, grain size, water content, pore fluid chemistry, metal content and the degree of hydrocarbons presence. Finally it will be possible to assess the IP sensitivity to hydrocarbon concentration (detection level) and in general the effectiveness of the induced polarization method to evaluate the electrical, physical and chemical behaviour of the urban fills (heterogeneous).;Electrical measurements were performed in the laboratory on soils relatively simple compounds either sand or till. Three containers of sand and two containers of till were putted to various degrees of water saturation and conductivity of the pore water. They were also putted to various concentrations of fresh oil. In parallel to these measures, the conductivity of pore water, saturation (Sw) and the concentration of hydrocarbons (motor oil) and other physical properties of soil such as permeability and porosity were evaluated.;The X-ray diffraction analyses on materials were allowed to determine the mineralogical composition. Water samples taken from piezometers were analyzed repeatedly to monitor the salinity of the water with the dissolution of the elements. Also, particle size and hydraulic conductivity analysis were performed to determine the distribution of grain size and permeability of the soil before filling the containers.;In this project, the potential of this method to detect contaminated soil with fresh oil is investigated by doing laboratory measurements. During the first phase of this project, an exhaustive study is conducted on the different geophysical auscultation methods to characterize heterogeneous fill. This study includes the method of electrical resistivity and induced polarization to characterize the contaminated soil. After the study is completed, these methods analyze the electrical properties such as resistivity and chargeability. The chemical and physical properties will be tested on laboratory samples (sand and till) obtained from a Montreal urban Brownfield.;Electrical measurements were carried out using IP field equipments (ABEM SAS4000 and Syscal Junior). Data quality was evaluated by monitoring the standard deviation of measurements during the acquisition and by realizing tests of reciprocity. Other measured parameters are the soil bulk dielectric constant and water content (using TDR), temperature and pH.;Finally, the data of resistivity were performed by using 3D inversion software BERT. The 3D space distribution of electrical properties for each experiment allowed the monitoring the changes in the properties of soils in different conditions of soil.;Both electrical resistivities and chargeabilities decrease with increase in water salinity for uncontaminated till. This decrease in chargeability can be caused by the growth of salinity which influences the decrease in the thickness of double layer (EDL).;For the uncontaminated sand, electrical resistivities increase with decreasing water saturation. In parallel, electrical chargeabilities increase with decreasing water saturation. But by continuing drainage, chargeability decreases. This decrease in chargeability can be caused by the decrease in cell polarization in a capillary system of soil.;For oil contaminated soils (sand and till), resistivities increase but chargeabilities decrease with increasing hydrocarbon saturation ( SH-sand=11%, 15%, SH-till=15%, 40%).