A Comparative Study of Methods for Determining the Concentration of Radon-222 in Spring Waters in Poços de Caldas Plateau, Brazil

Résumé

This study is a comparison of methodologies to determine the concentration of radon (²²²Rn) found in natural water sources used by the population of the cities of Poços de Caldas and Águas da Prata in the Poços de Caldas Plateau, in southeastern Brazil. The plateau is located in an area affected by the reactivation of volcanic processes that occurred during its formation. This is the largest alkaline complex in Brazil and the greatest stratum-alkaline volcano of Poços de Caldas is a volcanic caldera of about 30km-diameter, consisting of plutonic igneous rocks, where uranium and thorium anomalies are found. Sampling of spring water was carried out throughout the cities and ²²²Rn concentration in waters was determined in Becquerel per liter. Radiation levels found in natural sources were interpreted in accordance to the limits for total doses absorbed by an individual and the standards of radiological protection of the World Health Organization (WHO). Determination of the concentration of ²²²Rn found in the waters was possible through the capture of alpha particles emitted by the decay of the element, accomplished with the use of the Radon Professional Monitor (AlphaGUARD) and were also measured through the Liquid Scintillation Counting method,  equipment brand Camberra PACKARD. The highest value reached was 657.2 Bq.L^-1, measured by the AlphaGUARD, and 513.2 Bq.L^-1, measured through the liquid scintillation method.