Fabio Taioli

Contaminação por chorume e sua detecção por resistividade

Resistivity geophysical techniques were applied closed to the Londrinas county sanitary landfill, allowing the detection and mapping of leachate contamination plume. The study area lies on the Parana Basin which is locally represented by basaltic rocks of the Serra Geral Formation. A correlation between lower resistivity values and the supposed leachate contaminations was stablished, once the electrical conduction, under natural conditions, occurs mainly in an ionic way, which are normally presented in the leachate. The main contamination flows in a general SE direction. An unexpected finding of this work was the detection of another flux direction of contamination plume to SW, which flows trough horizontal fractures or alteration surfaces of basaltic contacts.

Métodos e técnicas geoelétricas rasas na delimitação de área afetada por ruptura em teto de túnel urbano

This paper presents a case study where geophysics was successfully applied to solve a complex problem associated with a tunnel excavation accident in an urban area. It presents and describes the results obtained with geoelectrical methods applied in an emergencial task in a risky urban area in Sao Paulo City. It also compares the techniques and field arrays, ways to present and interpret the data. The employed methods were electroresistivity, induced polarization (IP) and self potential (SP). The objective of the survey was to delineate the extension of a roof failure of an urban tunnel under excavation beneath the Ibirapuera Park in order to orientate the volume of tunnel roof should be treated. Only two days (Saturday and Sunday) were available to carry out the survey and its interpretation. The results were considered satisfactory and brought a significant economy to the final cost of the tunnel. This economy was due to the decreasing of the remediation area from the initial 20 x 20 m (estimated by the engineers) to 3 x 5 m (estimated by the geophysical survey).

Desenvolvimento e testes de mini-sonda Wenner para avaliação de contaminações rasas

The evaluation of soil and groundwater contamination has been an important task in the geosciences field and pushing on the methodological improvement. The contamination extension is normally investigated using geophysical methods or boreholes and chemical analysis. Otherwise, several contamination problems are at low depths (less than 0.5m) allowing the easy access to the contaminated region. Therefore, a low-cost and simple system (mini-probe Wenner) was developed and tested and it is aimed at low depth resistivity measurements. The system is formed by a current source (AC) and a PVC probe which contains a Wenner array with a electrode spacing of 1 cm. Laboratory tests show that the current source works adequately in the resistance range normally associated with contaminated materials while the system tests (including the current source and probe) indicated apparent resistivity values very similar to the resistivity values calculated using the equation proposed by Archie, in the 1.5 to 57 Wm interval. Preliminary field tests showed that the mini-probe is easily applicable in sandy and sand-silty soils while in clayey or hard soils is difficult its introduction. Therefore, interesting applications to the proposed system are the study of agricultural areas or the study of contamination in predominantly sandy lithologies.

Análise integrada de dados de sensoriamento remoto, geologia e geofísica no estudo de aqüífero fraturado, Lindóia - SP

Detecting groundwater in fractured aquifers is always a difficult task. This paper presents the detailed study of a fractured aquifer in Lindoia region, Sao Paulo, Brazil. The study area was selected after a regional study analyzing the favorability for occurrence of groundwater which classified the area as being of excellent groundwater favorability. The study consisted on fractures mapping based on aerial photographs (scale 1:25,000) and geoelectrical survey (vertical electrical sounding and resistivity imaging). The geophysical data was processed, inverted and analyzed by using geological field data, wells data, springs data and fractures mapped using aerial photographs. The results show that it was possible to define favorable locations for the wells and optimize field work.