The U-isotopes modeling in aquifers from Poços de Caldas plateau, Brazil

Hydro(radio)chemical relationships in the giant Guarani aquifer, Brazil

“…When these data are taken into account, it is possible to find a U-modeled age of 45 ka, and if a higher porosity value of 20% is adopted, then, a longer groundwater residence time (61 ka) is estimated. Thus, the residence time increases if the porosity also increases, as already discussed Bonotto (2005) in a fractured aquifer system at the Poços de Caldas plateau, Brazil.…”

A comparative evaluation of the CF:CS and CRS models in 210Pb chronological studies applied to hydrographic basins in Brazil

“…For larger quantities (15-100 g), measurements of equivalent uranium, eU ( 214 Bi¼ 226 Ra), were performed by γ-ray spectrometry through a 2" Â 2" NaI(Tl) scintillation detector and a 2048-channels multichannel analyzer provided by Ortec Ace 2K hardware controlled by MAESTRO software. For smaller portions of material ($ 1 g), measurements of 238 U content were done by α-spectrometry after several radiochemical steps that started with addition of a known amount of 232 U-228 Th spike at the beginning of each digestion process (Bonotto, 2010). 238 U was electrodeposited on stainless-steel planchets for assay by α-spectrometry using the same Si(Au) detectors utilized for 210 Po measurements.…”

The dissolved uranium concentration and 234U/238U activity ratio in groundwaters from spas of southeastern Brazil

“…The results are compatible with the field evidences in each area. For instance, Bonotto (2005) recognized that the ternary plot in Fig. 3 at the city of Poços de Caldas (MG) comprised the following components: mean of the colder waters (coded FRA and QUI), mean of the hotter waters (coded PEB and MAC), and water exhibiting intermediate temperature value (coded NOV).…”