Desenvolvimento de mini sonda para avaliações ambientais a pequenas profundidades

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 Ω.m 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 litologies.