Mobility indices and doses from 210Po and 210Pb activity concentrations data in Brazilian spas groundwaters

Abstract

Po and Pb activity concentrations in spas groundwaters occurring at São Paulo (SP) and Minas Gerais (MG) states, Brazil, have been reported in this paper with a dual purpose: to compare different indices for evaluating the radionuclides mobility into waters and to evaluate the drinking water quality from dose calculations. The waters (75 sampling points) are extensively used for drinking in public places, bottling and bathing purposes, among other. The samples were taken from springs and wells drilled at different aquifer systems inserted in Paraná and Southeastern Shield hydrogeological provinces. The WHO guideline reference value forPb and Po of 0.1 Bq/L in drinking water was not reached forPb but the Po levels were equal or above it in four spas groundwaters from MG State. The maximum WHO guidance dose level of 0.1 mSv/yr was also reached or surpassed in them. ThePb "mobility index" taking into account the ratio of the weight of the dissolved Pb per unit volume of solution to its weight per unit weight of the rock matrix yielded values in the range of 0.01-5.2 kg/m. Another "mobility index" (Preference Ratio) expressing the ratio of Pb andU in the waters divided by the ratio of Pb andU in the rock matrices provided values between 0.004 and 7994. The Pb/U activity ratios of some spas groundwaters suggested preferential U transport relative toPb into the liquid phase, whereas the ratio of the Pb toU mobility indices indicated the opposite. Such finding showed a better usefulness of the mobility indices for evaluating processes affecting the radionuclides release into the liquid phase during the water/rock interactions.

Gross alpha/beta radioactivity and radiation dose in thermal and non-thermal spas groundwaters

“…The groundwater samples (75) in this study were taken from the same springs and pumped tubular wells reported by Bonotto (2014, 2015, 2016, 2017) and Bonotto and Oliveira (2017). The water sources occur in different geological contexts associated to distinct aquifer systems in the Paraná and Southeastern Shield hydrogeological provinces (Mente, 2008) at the following spas in SP and MG states: Águas de São Pedro (3), Águas da Prata (7), Águas de Lindóia (7), Serra Negra (8), Lindóia (2), Termas de Ibirá (5), Águas de Santa Bárbara (1), Lambari (6), São Lourenço (8), Cambuquira (6), Caxambu (10), Poços de Caldas (6), Pocinhos do Rio Verde (4) and Araxá (2).…”

“…The water sources occur in different geological contexts associated to distinct aquifer systems in the Paraná and Southeastern Shield hydrogeological provinces (Mente, 2008) at the following spas in SP and MG states: Águas de São Pedro (3), Águas da Prata (7), Águas de Lindóia (7), Serra Negra (8), Lindóia (2), Termas de Ibirá (5), Águas de Santa Bárbara (1), Lambari (6), São Lourenço (8), Cambuquira (6), Caxambu (10), Poços de Caldas (6), Pocinhos do Rio Verde (4) and Araxá (2). The codes adopted by Bonotto (2014, 2015, 2016, 2017) and Bonotto and Oliveira (2017) for their identification will be also used in this paper. The hydrochemical database is very suitable for the purpose of this paper as there is a wide range of values for pH (4.2–9.6), redox potential Eh (−159 to +112 mV), electrical conductivity (20–6390 μS/cm), and Total Dissolved Solids (11–2898 mg/L) (Bonotto, 2016).…”

“…Different methods were used for characterizing the dissolved 222 Rn, 226 Ra, 228 Ra, 238 U, 234 U, 210 Pb and 210 Po in the same water sources as reported by Bonotto (2014, 2015, 2016, 2017) and Bonotto and Oliveira (2017). The radon dissolved in water was analyzed on site using RAD7 alpha particles detector coupled to accessory RADH 2 O from Durridge Co.…”

“…Different aliquots of the same groundwater samples were subjected to several radiochemical steps for analysis of 238 U, 234 U, 210 Pb and 210 Po, which involved co-precipitation with Fe(OH) 3 , Fe 3+ removal, ion exchange in a strong chloride anion exchanger (Dowex 1-X8 resin), 210 Po deposition onto copper discs suspended in hydroxylamine hydrochloride + sodium citrate solution placed on hot plate magnetic stirrer, or U-isotopes electrodeposition on stainless steel planchets after 3 hours in a Teflon cell at a current density of 1 Acm −2 . Alpha spectrometry with four EG&G ORTEC Model BU-020-450-AS ULTRA-AS Ion-Implanted Detectors with B-Mount allowed quantifying the activity concentration of 238 U, 234 U, 210 Pb and 210 Po (Bonotto, 2017; Bonotto and Oliveira, 2017).…”

“…This paper describes a novel gross alpha/beta database for groundwaters exploited by thermal and non-thermal spas used for therapeutic and leisure purposes in the Brazilian states of São Paulo (SP) and Minas Gerais (MG). Radiation dose calculation has been also done taking into account the 40 K, 228 Ra, 238 U, 234 U, 226 Ra, 210 Pb, and 210 Po activity concentration data obtained from previous studies held by Bonotto (2014, 2015, 2016, 2017) and Bonotto and Oliveira (2017). The acquired gross alpha/beta and Committed Effective Dose (CED) databases in the sedimentary/fractured rock aquifers allowed perform a comparative evaluation of the performance of both indices for assuring the radiological quality of the waters.…”