Determination of gross alpha and beta radioactivity by liquid scintillation counting in drinking water consumed in the cities of Paraná-Brazil

Abstract

The liquid scintillation counting (LSC) is a technique in which the sample is mixed to a chemical organic liquid, forming a scintillation solution, capable to convert the kinetic energy of nuclear emissions into light energy photons. The aim of this study was to quantify the concentration of gross alpha and beta radioactivity in drinking water using the LSC. The water samples were collected in the Paraná cities: Telêmaco Borba, Castro, Tibagi, Reserva, Curiúva, Ponta Grossa, Imbaú and Curitiba. They have free access sources of drinking water to the public. The initial step of the methodology was standardizing the pre-concentration of the water samples by heating on a hot plate from 1 L to a final volume of 50 mL, at maximum temperature of 80°C. An aliquot of 5 mL of the final solution was mixed with 15 mL of the scintillation solution (Hisafe 3) in a vial and measured on a LSC. The equipment used for the measurement of gross alpha and beta activities was a 1220 Quantulus™ Ultra Low Level Liquid Scintillation Spectrometer. The activity concentration of gross alpha varied from <0.10 to 0.20 Bq L-1 and gross beta varied from <0.18 to 0.23 Bq L-1. The results of gross alpha and beta concentration obtained in the samples are below the maximum limits adopted by Ministry of Health in Brazil.