Radiological and Hyperfine Characterization of soils from the Northeasthern region of the Province of Buenos Aires, Argentina

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

HYPERFINE INTERACTIONS

Springer

Año: 2011 vol. 202 p. 5 - 16

0304-3843

The activity concentrations of both natural (238U and 232Th chains and40K) and anthropogenic (137Cs) radionuclides down along the soil profile have beendetermined in soil samples collected from inland and coastal areas of the LaPlata River, located in the Northeastern region of the Province of Buenos Aires,Argentina. These studies were complemented with 57Fe Mössbauer spectroscopycharacterization, pH, texture and organic carbon content measurements. FromMössbauer results, the sample compositions differ from one area to the other.Spectra from both soil samples are dominated by the Fe3+ paramagnetic signal.For soil samples from the coastal area, the α-Fe2O3 contribution is lower, Fe3O4was not detected, and the relative areas of each spectral contribution are nearlyconstant with depth. For samples from the inland area, the Fe3+ paramagneticfraction increases up to 82%, mainly at the expense of the magnetically orderedphase. The main observed activity originates from the decay of 40K (540–750 Bq/kg),followed by 238U (60–92 Bq/kg) and 232Th (37–46 Bq/kg) chains. The activity of235U was in all the cases lower than the detection limit (LD = 0.02 Bq/kg). The onlydetermined anthropogenic nuclide was 137Cs, arising from the fallout of the SouthernHemisphere nuclear weapon tests. Three of the observed differences in the depthdistributions can be described by the dispersion-convection model. A correlation