Application of Geophysical Methods to Waste Disposal Studies

POMPOSIELLO, MARIA CRISTINA; DAPEÑA, CRISTINA; FAVETTO, ALICIA; BOUJON, PAMELA

InTech - Municipal and Industrial Waste Disposal

InTech - Open Access Publisher

Lugar: Rijeka; Año: 2011; p. 3 - 26

Geophysical methods provide information on the distribution of certain physical parametersin the sub-surface, which can be linked to the direct observations. Thus it is called anindirect observation method and it does not provide a "photo" of the sub-surface but itsuggests a model of the underground derived from interpreting the distribution of thesephysical parameters. Clay and granite, for example, have different densities, acousticvelocities, elastic parameters, electrical conductivities, magnetic susceptibilities, anddielectric constants. So, geophysical methods are designed to exploit some of the physicalproperties of a target feature that is in contrast with its host environment, e.g., the lowdensity nature of a void is in contrast to the high density nature of surrounding bedrock, etc.Geophysics should never be a stand-alone tool, but complementary to direct observations,which provide geological/hydrogeological background information (such as some of thosemethods seen in Table 1).There are two general types of geophysical methods: 1) active, which measure the subsurfaceresponse to electromagnetic, electrical, and seismic energy generated by artificialsources; and 2) passive, which measure the earth´s ambient magnetic, electrical, andgravitational fields. Geophysical instruments are designed to map spatial variations in thephysical properties of the Earth. A gravimeter, for example, is designed to measure spatialvariations in the strength of Earth?s gravitational field.Sanitary landfill is the most common way to eliminate solid urban wastes. They have aheterogeneous structure due to random origin of the disposed waste. Geophysical methodsare particularly valuable because they are non-destructive and non-invasive. An importantproblem associated with this practice is leachate production and the related groundwatercontamination. Leachate electrical conductivity is often much higher than that of naturalgroundwater and it is this large contrast that enables contamination plumes to be detectedusing geophysical methods.Ground Penetrating Radar (GPR) and Electrical methods such as Electrical Tomography(ET) and Vertical Electrical Sounding (VES) have been found to be especially useful for thesekinds of environmental studies, due to the conductive nature of most contaminants, andthey can be important tools for the detection and mapping of landfills, trenches, buriedwastes and drums, or other underground structures.