Radiological and hyperfine characterization of soils from the Northeastern region of the Province of Buenos Aires, Argentina

M. L. MONTES; R. C. MERCADER; M. A. TAYLOR; J. RUNCO; P. IMBELLONE; P. C. RIVAS; J. DESIMONI

HYPERFINE INTERACTIONS

Springer

Año: 2011 vol. 202 p. 5 - 16

0304-3843

Abstract The depth profile activity concentrations of both natural (238U and 232Th chains and 40K) and anthropogenic (137Cs) nuclides have been determined in soil samples collected from inland and coastal areas of the La Plata River, located in the Northeastern region of the Province of Buenos Aires, Argentina. These studies have been complemented with a Mössbauer Effect characterization, pH, texture and organic carbon content measurements. According to the Mössbauer results, the sample compositions differ from one area to the other. The spectra of both soils are dominated by the Fe3+ signal. In the coastal area soils, the -Fe2O3 contribution is lower, Fe3O4 was not detected, and the relative fractions are nearly constant in depth. In the inland area, the Fe3+ fraction increases up to 82%, mainly at the expense of the -Fe2O3 one. The main observed activity resulted originated from the decay of 40K (540 Bq/kg -750 Bq/kg), following in importance those of 238U (60 Bq/kg – 92 Bq/kg) and 232Th (37 Bq/kg - 46 Bq/kg) chains. The activity of 235U was in all the cases lower than the detection limit (LD= 0.02 Bq/kg). The only determined anthropogenic nuclide was 137Cs, arising from the fallout of the South Hemisphere nuclear weapon tests. Three of the observed differences in the depth distributions can be described by the dispersion-convection model. A correlation between the natural nuclide activities and the Mössbauer relative fractions was found, while there is not an apparent correlation between the 137Cs profile and the relative fraction of Fe3O4 or with other iron species.