Aplicação dos métodos eletromagnéticos indutivo, eletrorresistividade eip domínio do tempo em caracterização geoambiental

Abstract

This project aims characterizing environmental problem generated in Serrana Landfill region, contained in Ribeirao Preto city (SP). In there, due to a huge soil cavity originated from sand extraction used in building site, the disposal of domestic, industrial and hospital residues started in mid 1970s. Nowadays, this landfill is saturated and without activity. However, damages caused by the inadequate residue disposition are still present, and the generated contamination plume still remains. The methodology used in this work consists in the integration of geophysical techniques efficient in the evaluation and characterization of environmental problems. The focus in here is to apply geophysical prospecting methods, such as resistivity, induced polarization related to time domains as well as electromagnetic inductive method, in geotechnical and environmental studies. The project was based on a compilation and reinterpretation of a large amount of pre-existent geophysical data as well as those collected during work conduction associated to surface geology and well data. In such way, with integrated information it attempted to study parameters to evaluate problems associated to tropical soil and groundwater contamination for urban residue landfill. This project accomplishment intends to achieve two main objectives. First of all it was application and interpretation of geoelectrical assays to a better geological characterization from the area. Geophysical data were linked to geological information from existent wells for a better local geology interpretation and definition. The second objective was the environmental problem characterization by using geophysical method and some water chemical analysis available by Ribeirao Preto City hall. In this context, it was also studied a geophysical parameter behavior of chargeability and time constant in digging delimitation filled out with residues from leachate shallow area and contamination plume inside of saturated area (deep area), once two mentioned parameter answers are not well known. This unknowing answer never happens with resistivity (and conductivity) case. The use of results obtained from electrical sounding has interpreted base on information about water monitoring wells and leachate collection, deep tubular wells, auger sounding, and surface geology made possible a better knowledge about landfill geology, which presents complex contact among three different geological units, and two types of aquifer. Since geological model establishment, results of electric profiling (resistivity and induced polarization) can be used in order to understand the association between residues and environment in landfill limits. Results of electromagnetic profile make possible a visualization of environmental impact in landfill zone and its surrounding as well as the establishment of hypothesis about format and way of contamination plume whose existence in the zone is verified by data from groundwater chemical analysis.