Hyperfine and radiological characterization of soils of the province of Buenos Aires, Argentina

Abstract

The depth profile concentration of both natural and anthropogenic gamma-ray-emitter nuclides were determined in soil samples collected in an area located at 34° 54.452′ S, 58° 8.365′ W, down to 50 cm in depth, using an hyper-pure Ge spectrometer. The soil samples were also characterized by means of Mössbauer spectrometry and X-ray diffraction. The activities of <SUP>238</SUP>U and <SUP>232</SUP>Th natural chains remain constant in depth at 41 Bq/kg and 46 Bq/kg, respectively, while the <SUP>40</SUP>K activity increases from 531 Bq/kg to 618 Bq/kg between 2.5 cm y 25.5 cm of depth. The only anthropogenic detected nuclide is <SUP>137</SUP>Cs, whose activity changes form 1.4 Bq/kg to values lower than the detection limit (L<SUB>D</SUB>) for depths below 25 cm, exhibiting a maximum at 10 cm beneath the surface. The Mössbauer spectra show two magnetic sextets associated with α-Fe<SUB>2</SUB>O<SUB>3</SUB> and Fe<SUB>3</SUB>O<SUB>4</SUB>, as well as two Fe<SUP>+3</SUP> Fe<SUP>+2</SUP> doublets, probably originated in octahedral and tetrahedral sites of paramagnetic phases. The Fe<SUP>3+</SUP> paramagnetic signal relative fraction increases up to 82% at the expense of the α-Fe<SUB>2</SUB>O<SUB>3</SUB> one when de depth increases. No correlation between Fe<SUB>3</SUB>O<SUB>4</SUB> and the <SUP>137</SUP>Cs was identificated.