Evaluation Of Contamination At A Feedlot In San Pedro, Argentina, By Means Of Electromagnetic Methods

Contamination at a feedlot, enclosure of animals, in San Pedro, Argentina, was investigated using geophysical methods. Results of inversion of time domain electromagnetic (TEM) data resolved three layers at each point of investigation, namely, a surface layer of clayish soil, a second layer comprising partially water saturated clastic sediments and hydrogeological basement that was very conductive, possible clay bearing. Resistivity of sediments is very low, below 10.5 Ohm m. The three layers are characterized by different resistivity range of values. The first layer is very thin, and it is not clearly seen in the profiles. In the corral it is fully contaminated by manure. The resistivity of this layer decreases in corral up to less than 3 Ohm m (the thickness of soil is less than 3 m within the corral increasing to the test site). Resistivity of the second layer is about 9.5-10.5 Ohm m. The resistivity of clay considerably decreases beneath the corral. The identified geo-electrical layers may not always be identified with geological layers. The TEM results showed full agreement with previous results of frequency domain electromagnetic (FDEM) method and electrical resistivity tomography. It was demonstrated that electrical and electromagnetic methods are a very important tools for the evaluation of contamination.