Use of radon isotopes, gamma radiation and dye tracers to study water interactions in a small stream in Brazil

In this study, natural (Rn-222) and fluorescent (uranin) tracers were used to investigate the interactions between surface and subsurface waters in a small hydrographical basin located in the southeast region of Brazil. Levels of Rn-222 were measured in 117 water samples with the use of an alpha solid-state detector. After the identification of the probable discharge sections along the stream, a measurement of the natural flows, upstream and downstream of these sections, was done with the use of a fluorimeter and fluorescent tracers. Also, scanning was done to verify a correlation between the natural gamma radiation and the Rn-222 in the areas where its activity was higher. The results showed some sections where the Rn-222 activity is more significant and contributed to the growth of the flows along the stream. It was possible to confirm a correlation between the discharge sections and the natural gamma radiation, what can be used as a preliminary approach to finding these sections in scenarios similar to the one studied here.