Electrical Resistivity and Induced Polarization Methods for Environmental Investigations: an Overview

Contamination of soils and groundwater is one of the most serious environmental problems. The sources of contamination are several and include, among others (i) landfills and industrial waste disposal sites, (ii) saline intrusion, (iii) accidental spills of chemical products or hydrocarbon such as diesel or gasoline, and (iv) pollutants of agricultural origin. Electrical resistivity and induced polarization (IP) methods have been widely used in diagnosis and monitoring of polluted areas since the electrical properties of contaminated formations are distinct from the surrounding medium. This review paper, based on many resistivity/IP surveys performed over the last two decades, presents (i) the basic principles of both methods, (ii) objectives of the surveys carried out, (iii) data acquisition methodologies used in the different surveys, (iv) complementary geophysical methods as well as other types of data (hydrogeological, physicochemical, petrological, geotechnical and others) used in order to validate and calibrate the resistivity/IP data, and (v) significant and representative results obtained both in the field and in the laboratory. Advantages and limitations of these methods are analyzed, and future challenges are also pointed out. The overview shows the suitability of the resistivity/IP methods for imaging contaminated areas, monitoring the behavior of contamination, assessing the risk of groundwater pollution, characterizing the geometry of landfills body and defining the geological structure of coastal aquifer systems. These methods can also help to monitor microbial activity, but it is not yet possible to fully understand the biogeochemical processes involved and their impact on electrical signatures. The SIP technique can play a key role in this field.