This article shows the interesting results of a pioneer effort by IAG/USP researchers to use ground-penetrating radar (GPR) for humanitarian purposes, guiding the rescue of victims in the tragedy of Brumadinho. The tailings Dam I at the Córrego do Feijão iron ore mine, located in the Brumadinho complex, Minas Gerais State, Brazil, collapsed on 25 January 2019. About 11.7 million m3 of mining mud was spilled from the dam, burying bodies, equipment, structural buildings, buses, and cars along a length of 8.5 km up to the Paraopeba River. Additionally, the contaminated mud traveled more than 300 km along the bed of the Paraopeba River toward the São Francisco River. This work shows the results of a geophysical investigation using the GPR method 17 days after the event. To carry out the geophysical survey, an excavator was used for soil compaction. The data acquisition was performed on the tracks left by the excavator chain using SIR-4000 equipment and antennas of 200 and 270 MHz (GSSI). The GPR studies aimed to map bodies, structural buildings, and equipment buried in the mud. The location of the profiles followed preferably the edge of the slope due to the higher probability of finding buried bodies and objects. The GPR results allowed the detection of subsoil structures, such as concentrations of iron ore and accumulations of sand from the dam filter. The GPR was effective because the iron ore sludge in the mixing process became porous and the pores were filled with air, which provided penetration and reflection of the GPR electromagnetic waves up to a depth of 3.5 m. The results were surprising. Although no bodies or underground equipment were found, the results of this research served to eliminate the studied areas from future excavations, thus redirecting the rescue teams and optimizing the search process. These important results can serve as an additional motivation for the use of GPR in future humanitarian work in areas of tragedies.
The accident involving oil spill that occurred on the Brazilian coast in 2019 reached 2,880 km in extension, and more than 200 tons of oily material was removed from coastal environments in the northeast of the country in about five months. In the impact on beach environment there may still be non-visible residues and its by-products in subsurface, so that geophysical prospecting can be the suitable to evaluate the presence of remaining material. The evolution of environmental studies has required new research technologies. Geophysical methods have shown to be efficient in environmentalstudies, with the use of relatively new methods in Brazil that provide results with excellent coverage in the area and quickly. Among these methods stands out the Capacitive Resistivity Method. Environmental research work with this method has been reported with good results, but it is necessary to take into account the operational physical bases of the method so that the data is reliable. This work presents the results of tests carried out in a beach environment that was affected by oil. This environment is characterized by a medium of high conductivity, where data acquisition with equipment configured with smaller dipolar cables results in extremely noisy data. On the other hand, the configuration with larger dipolar cables allowed the transmission of higher electrical current to the ground resulting in the acquisition of good quality data. The results showed that there are no more indications of oil residues on the beach studied.
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