222Rn, 226Ra and hydrochemistry in the Bauru Aquifer System, Sao Jose do Rio Preto (SP), Brazil

In this paper, the Rn-222 and Ra-226 activity concentration was measured in groundwater samples collected from the Bauru Aquifer System, Sao Jose do Rio Preto city, Sao Paulo State, Brazil. The site has been selected for a detailed radiometric survey due to the large number of tubular wells drilled in the aquifer there, which provide water for similar to 70% of the local population. Despite the importance of groundwater for the local water-supply system, there is a lack of both Rn-222 and Ra-226 data in the municipality. Establishment of these data is relevant to assure that the water quality from a radiological point of view, is not health threat. Sao Jose do Rio Preto city is geologically situated in Bauru Group that is located within the Parana sedimentary basin. The monitoring program involved the collection of 50 groundwater samples from deep tubular wells during three field campaigns held from 17th to 19th January 2011, from 2nd to 3rd August 2011 and in 30th November 2011. Temperature and pH readings were realized in the field, whereas Rn-222 and Ra-226 analysis were performed at the laboratory using the Alpha Guard-Aquakit analytical protocol, which allowed us to obtain Rn-222 activity concentration ranging from 0.69 to 14.95 Bq/L. These data indicate that the abundances of Rn-222 and Ra-226 in the groundwater system of Bauru Group is below the WHO guideline limit of 100 Bq/L Chemical analysis has been also realized for major cations and anions in order to better understand the water features in the municipality. (C) 2014 Elsevier Ltd. All rights reserved.