Estimación de la concentración de actividad específica de radionucleidos en el suelo de la provincia de Tungurahua

Abstract

The objective of this research was to estimate the specific activity concentration levels of the radionuclides; Potassium-40 (K-40), Radium-226 (Ra-226) and Thorium-232 (Th-232) in a total of 44 soil samples collected in the province of Tungurahua. The soil samples were collected at a depth of 15 to 20 centimetres and were monitored in situ with Ludlum equipment for gamma radiation at the locations from which the samples were extracted, followed by a process of drying, crushing and sieving, and then sent to the Subsecretaría de Control y Aplicaciones Nucleares where measurements were made by gamma spectrometry with the Hyper Pure Germanium (HPGe) detector and reports were received on the specific activity of all the samples. The statistical analysis yielded specific activity averages of K-40 at 445.36 Bq/kg, Ra-226 at 123,83 Bq/kg and Th-232 at 33,71 Bq/kg, in addition, the external gamma radiation dose rate was calculated to be 62,46 nGy/hr and the annual terrestrial effective dose equivalent rate was 0.08 mSv/yr, the measurements performed with the Ludlum equipment estimated the absorbed dose rate at 0,093 +/- 0,006 µSv/hr and the annual terrestrial effective dose equivalent at 0,114 +/- 0,007 mSv/yr. Subsequently, specific activity maps were created for K-40, Ra-226, Th-232 and annual terrestrial effective dose equivalent using geostatistical interpolation techniques. In conclusion, high values of external exposure due to ground radiation were obtained in the Chinintahua and Río Negro sectors, in addition to being higher in Ra-226 than in all the samples analysed, which exceeded the reference value recommended by the United Nations Scientific Committee on the Effects of Atomic Radiation. It is recommended to study neighbouring sectors in the north-eastern part of the province of Tungurahua.