Determinação Eletroquímica de Radioisótopos de Chumbo e Bismuto em Zonas com Falhas Geológicas e sua Correlação

Radon is continuously being emitted in geological fault areas. Because of the geochemical characteristics of radon gas (222Rn decayed from 238U, with a half-life of 3.8 days), its variations of concentrations in the soil and fluid samples are considered a useful tool for earthquake monitoring and prediction in active fault zones [1]. The objective of this study was to identify and relate the total concentration of lead and bismuth in a geological fault area by anodic stripping voltammetry (Model 797 VA, Metrohm) using the hanging mercury drop. The radioisotopes are electroreduzed on the working eletrode during a deposition step, and reoxidized during the stripping step. Samples in the region identified with geological faults were manually obtained at three different depths (15, 30, and 60 cm) using a cup-type auger. Table 1 indicates the values for the concentration of Pb and Bi for each soil profile indifferent horizons depths. According to the data shown in Table 1, the concentrations of Pb and Bi increased with soil depth, with lower concentrations in the shallowest horizons (15cm), compared to the deepest horizons (60cm). This is indicative of the direct influence of radon emissions. The bismuth concentration follows a direct relationship with increasing concentration of lead, demonstrating that the elements are probably the same emission source. The bivariate analyses (Pearson correlation) were applied to determine relationships between lead-bismuth and relation between concentration and the soil depth. The two sets showed significant associations.