Francisco Yukio Hiodo

Investigações geofísicas de superfície e de poço no sítio controlado de geofísica rasa do IAG-USP

This paper presents the results obtained from surface and borehole geophysical investigations carried out at the Shallow Geophysical Test Site of IAG-USP. The main objective was to characterize the sediments and the top of basement. The area is constituted by sandy-clay sediments of Sao Paulo Basin (Sao Paulo and Resend Formations) on the granite-gneiss basement with different degrees of weathering. In the area of studies, three boreholes were drilled for geological and geophysical research purposes (pioneer in Brazil). These boreholes were used to verify the stratigraphy, to collect the sample for laboratory measurements, to calibrate the results of surface geophysics and to carry out well logging. The surface methods used were: seismic (reflection and refraction), electric-resistivity (profiling and vertical electric sounding) and GPR-Ground Penetrating Radar. The integration of results show excellent agreement and allow constructing a geological-geophysical model for the site which is at the border of Sao Paulo sedimentary basin. Moreover, the various geophysics methods, commonly used in geological, geotechnical and environmental researches, have been tested under controlled conditions.

O sítio controlado de geofísica rasa do IAG/USP: instalação e resultados GPR 2D-3D

The data interpretation from shallow geophysical survey can be complex because the uncertainty about subsurface targets. To reduce the ambiguity and help in the interpretation of geophysical data, the Shallow Geophysical Test Site of IAG-USP (Sitio Controlado de Geofisica Rasa-SCGR do IAG-USP) was installed inside the campus at USP. Different targets at various depths were installed along seven lines. The targets buried in the Test Site simulate targets found in geotechnical, archaeological, and environmental studies. In this article, the construction methodology of the Test Site and some GPR results along a line characterized by empty metallic tanks are presented. The geophysical characterization in controlled field condition allowed the calibration of geophysical responses due to known targets, such as, metallic tanks. 250 MHz GPR profile showed an excellent agreement with a GPR 2D model determined by finite difference in time domain method. Fk-migration improved the resolution and the spatial position of the metallic tanks. GPR 3D results, such as 3D cube, fence diagrams, and depth slices, were very important to improve the characterization of the targets in subsurface. SCGR-IAG revealed itself as important tool for teaching, research and extension activities in university related to Geophysics, and it will be very important to our community. With the installation of this Test Site, an important step was done in searching the State of Art in Shallow Geophysics in Brazil, were the development of news equipment, modeling and inversion software could be tested and its response calibrated.

Investigações GPR nos distritos mineiros de Santa Bárbara e Bom Futuro: Província Estanífera de Rondônia

Investigacoes GPR - Ground Penetrating Radar foram realizadas nos distritos mineiros de Santa Barbara e Bom Futuro (Provincia Estanifera de Rondonia), visando averiguar a aplicabilidade do metodo para localizacao de depositos estaniferos primarios e secundarios, bem como otimizar os custos envolvidos na etapa de prospeccao. Os perfis de reflexao GPR foram adquiridos com antenas de 25, 50 e 100 MHz, o que permitiu investigar a subsuperficie ate 30 metros de profundidade. Em relacao aos depositos primarios das minas de Santa Barbara e de Bom Futuro, o metodo GPR permitiu identificar zonas com predominância de corpos de greisens. No deposito secundario aluvionar da mina de Bom Futuro, o metodo GPR permitiu localizar uma estrutura de paleocanal na base do sistema deposicional sedimentar. Os resultados obtidos apresentaram uma excelente concordância com as informacoes geologicas provenientes das sondagens, demonstrando essa nova aplicabilidade do metodo GPR para a exploracao mineral, na qual podera ser extendida para ambientes similares do Craton Amazonico. Alem disso, os custos envolvidos no processo exploratorio poderao ser otimizados, caso as investigacoes GPR sejam realizadas antes da execucao de sondagens.

Aplicação de ensaios elétricos e eletromagnéticos em problema de poluição ambiental

This work aims at the detection of the contamination caused by a waste disposal area, through the electric geophysical methods of resistivity, induced electromagnetics. Field measurements had been carried out in Ribeirao Preto, Sao Paulo, Brazil, in a deactivated waste disposal area. The obtained data had been dealt with appropriate softwares that enabled the distinction of the anomalies which help the characterization of the environmental pollution problem.

Application of induced polarization and resistivity to the environmental investigation of an old waste disposal area

Abstract Waste disposal in dumpsites, or even in sanitary landfills, can generate contamination plumes in the subsurface. The detection and delineation of the shape of the contaminant plume can be assessed using monitoring systems or different site investigation methods, including geophysical methods. This paper presents the results of a geophysical survey conducted to map the soil contamination produced by a waste disposal site located at a geological vulnerable area, characterized by a trench that resulted from the collapse of sandy soils due to erosion. This paper aims to show the improvement in mapping a waste deposit and the contamination produced in sandy soils by integrating resistivity and induced polarization methods. The results of three survey lines performed to map the site are presented—two across the deposit and one external to it; and resistivity, chargeability and normalized chargeability sections were generated. The geoelectrical sections interpretation was integrated with information from monitoring wells to help the characterization of the waste area and to evaluate soil and groundwater contamination. The results show that resistivity identifies the wastes, the contaminated soil and the contamination plume, but it does not distinguish these zones. Normalized chargeability, on the other hand, is more effective in distinguishing the areas with wastes from the areas impacted by the contamination plume.

Ionizing Radiation Dose Due to the Use of Agricultural Fertilizers

The transference of radionuclides from the fertilizers to/and from soils to the foodstuffs can represent an increment in the internal dose when the vegetables are consumed by the human beings. This work evaluates the contribution of fertilizers to the increase of radiation level in the environment and of dose to the people. Samples of fertilizers, soils and vegetables produced in farms located in the neighbourhood of Sao Paulo city in the State of Sao Paulo, Brazil were analysed through gamma spectroscopy. The values of specific activity of 40K, 238U and 232Th show that there is no significant transference of natural radionuclides from fertilizers to the final product of the food chain. The annual committed effective dose due to the ingestion of 40K contained in the group of consumed vegetables analysed in this work resulted in the very low value of 0.882 μSv.

Mapeamento tridimensional de pluma de contaminação através de resistividade elétrica

This work aims at the detection of the contamination caused by a waste disposal area, by the electrical geophysic method of resistivity. Field measurements had been carried out in Mococa, Sao Paulo, Brazil, in a deactivated waste disposal area. The obtained data had been dealt with appropriate softwares that enabled the distinction of the anomalies which help the characterization of the environmental pollution problem. Introducao O objetivo deste trabalho foi delinear a pluma de contaminacao gerada por um lixao desativado, e servir como suporte no Projeto de Recuperacao do mesmo. O local de estudo possui uma area de aproximadamente 150.000 m 2 . A area de estudo localiza-se no municipio de Mococa-SP. Para alcancar este objetivo foi utilizada a metodologia geofisica de eletrorresistividade, com arranjo dipolodipolo com 5 niveis de investigacao e abertura entre eletrodos de 10 metros. Foram adquiridas 6 linhas distribuidas pela area, orientadas perpendicularmente ao local de disposicao de residuos. Para visualizar a dispersao da pluma de contaminacao foi elaborado um mapa tridimensional de

Projeto de um sistema semi-automatizado de medidas de potencial elétrico natural ou induzido do solo para aplicações geoelétricas

The devices were developed to realize spontaneous and induce voltage measurement on the ground. In both case we used a multiwire cable with multiple voltage inputs along the length that becomes possible to conect it in six stainless electrodes fixed in the ground at same time. An automatic sequence digital system controlled by pushbutton touch allows to couple electrodes sequentially to a electronic DC voltmeter with autozeroing circuit based in PID servocontrol circuit. A 60 Hz notch filter and a roll-off low pass filter with time constant of 1s are used to minimize line and spheric noises. Electronic control system becomes too possible to couple cable with receiver datalogger of SYSCAL R-2 in dipole- dipole sounding array.

Investigações geofísicas em rochas graníticas no município de Itu, São Paulo - Brasil

Geophysical investigations was realized on the Granitic Suite of Itu, located near to Itu City, State of Sao Paulo - Brazil, with the objective to find fractures zones in granitic rocks and determine the depth of top of fresh rock, through of integration of GPR - Ground Penetrating Radar and Resistivity Methods. The geophysical profiles were realized on a same line for a comparative study between these two methodologies, inside of philosophy of integrated interpretation. One GPR profile of 80m was acquired with 50, 100 and 200MHz antennas and two electric profiles with dipole of 2 and 10m. Analysis of geophysical profiles allowed to identify two strong dip reflectors: one about 10m depth, interpreted as fractures filled with water and the other between 12 and 17m depth that correspond to one resistive region dipping after of 15m depth, interpreted as the top of granitic fresh rock. Besides, two anomalous regions were identified: one about 50m and the other about 80m. In GPR profiles, these regions are characterized for one shadow zone, because the high attenuation of electromagnetic waves. In electric profiles, these regions correspond to the conductive regions that can be related with the presence of one sub-vertical fracture zone.