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

摘要

Po-210 and (210)pb activity concentrations in spas groundwaters occurring at Sao 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 Parana and Southeastern Shield hydrogeological provinces. The WHO guideline reference value for Pb-210 and Po-210 of 0.1 Bq/L in drinking water was not reached for Pb-210 but the Po-210 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. The Pb-210 "mobility index" taking into account the ratio of the weight of the dissolved Pb-210 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(3). Another "mobility index" (Preference Ratio) expressing the ratio of Pb-210 and U-238 in the waters divided by the ratio of Pb-210 and U-238 in the rock matrices provided values between 0.004 and 7994. The (210)pb-/U-238 activity ratios of some spas groundwaters suggested preferential U-238 transport relative to Pb-210 into the liquid phase, whereas the ratio of the Pb-210 to U-238 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. (C) 2017 Elsevier Ltd. All rights reserved.