Gamma emitter activity determinations in groundwater of the province of Buenos Aires- Argentina

M.L. MONTES; A. ZAPOROJECTS; M.A. TAYLOR; J. RUNCO; P.C. RIVAS; J. DESIMONI

Mérida

Congreso; 4Th International Congress on Energy and Environment Engineering and management; 2011

Universidad de Extremadura

Introduction ? When analyzing the total annual effective dose from natural sources to human population the dose received by ingestion of long-lived natural radionuclides needs consideration. Doses by ingestion are mainly due to 40K and to the 238U and 232Th series radionuclides present in food and drinking water. In South America the human water-supply is based in networks and domestic wells that use water from aquifers, consequently more than the 60% of the population drinks untreated water. In this frame, we present here the results of a systematic study of the gamma emitter content of drinking water samples consumed at the Province of Buenos Aires- Argentina. Experimental - Ten liters of water obtained from domestic wells were dried at 80 °C up to obtain a solid residue. The gamma spectra of the residue were taken inside an EG&G Ortec low-background chamber in the range of 30 keV to 1.8 MeV, using a GMX10 gamma EG&G Ortec detector with a standard electronic chain and 8192 channels multichannel. Results and Discussion ?The measured activity corresponds mainly to 40K (110 mBq/L - 570 mBq/L) and to the 238U chain (80 mBq/L - 570 mBq/L). These wide variations are depending on the geological characteristics. The 238U measured concentrations neither exceed the radiological reference values accepted for drinking water (1000Bq/L)nor the 100microg/L of U established by the argentine national legislation but, in some cases, exceed other reference values such as the provincial limit of 20μg/l. The annual committed effective dose by intake can be calculated putting together the calculated age-dependent committed effective dose coefficients for the members of public, the water intake (0.75 L/day, 1L/day and 2L/day for infant, children and adults, respectively and the nuclide activities. Afterward, the annual committed effective dose per unit intake of 40K has been estimated The net radiological impact due to water intake is lower than the reports of the worldwide average exposure (170 Sv) due to 40K. The 238U doses were also estimated. Conclusions -A systematic study of domestic well water is presented. All samples presented natural activities lower the reference limits as well as the annual committed effective dose per unit intake of 238U, however in some places the toxicity regional limits are overcome.