Investigação geoelétrica no aterro controlado da Vila do Segredo, município de Caçapava do Sul – RS

Abstract

Currently one of the concerns of nations is the pollution of soil and groundwater, which poses a great risk to the health of the population. One of the factors responsible for this pollution is the improper disposal of large amounts of waste in socalled dumps. Population growth, followed by household income growth that stimulates consumption, causes a significant increase in waste production. The city of Caçapava do Sul generates 414 tons of waste per month, which represents a waste amount of 13.8 tons per day. This amount represents a generation of 0.543 kg / inhab / day, which is the Brazilian average for cities with up to 30 thousand inhabitants. The current controlled landfill is located in the Vila do Segredo neighborhood, which was used as a dump from December 1997 to December 2005. The large amount of garbage deposited there underwent a process of decomposition of organic matter, generating the presence of leachate (slurry), and that by gravitational action, percolated through the ground and reached the local water table, causing contamination. In this study, the electroresistivity geophysical method was applied to investigate possible aquifer contamination in the transhipment area and around the controlled landfill. The electric walking technique (EC) was used with the dipole-dipole and wenner-schlumberger arrangements. With an average depth of investigation of 20 and 40 meters, respectively. Five parallel profiles of electric walk (CE) were performed, with electrode spacing of 5 meters and total length of 180 meters each one. These profiles are positioned in the N-S direction and perpendicular to the preferred direction of fractures in the region. A total of 3419 points of apparent subsurface resistivity readings were obtained. These fieldacquired data were processed and resistivity values were obtained by 2D mathematical inversion technique which were presented in the form of geometry distribution section sections along the profiles. Interpretation of these sections indicates that anomalies with low resistivity values are associated with the presence of leachate contamination plume. Possible contamination zones have been identified at a depth of up to 15 meters, under the landfill, related to the possible contamination zones associated with the low resistivity presented in the geophysical profiles.