Determination of selected actinides (U, Pu and Am) in Belarus soils using high resolution inductively coupled plasma mass and gamma spectrometry

Abstract

Depth distributions are presented for actinides and 137 Cs in soils in agricultural areas of SE Belarus, where Chernobyl fallout levels of 90 Sr and 137 Cs in the soil have led to the land being taken out of habitation and agricultural use. Both gamma spectroscopy and high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) are used to provide absolute values of soil activity concentrations of U, Pu and Am isotopes, and also to provide isotope ratios. At our selected far-field locations (over 150 km from Chernobyl) the Chernobyl 137 Cs fission product contamination levels are comparable (at c . 10 5 Bq kg −1 ) to those at our exclusion zone sampling site at 15 km from Chernobyl. The levels of transuranium isotopes at the far-field locations are, however, significantly lower, at below 2% of those observed in the exclusion zone site, whilst the levels of anthropogenic 235 U are less than 10% of those naturally present. Our exclusion zone site, in October 2001, had a residual total surface deposition level of 239+240 Pu of 23,780 Bq m −2 , whilst the two far-field sites had 239+240 Pu at levels of 190 Bq m −2 and 41 Bq m −2 . The inhomogeneity of the transuranic isotope concentrations in these areas, and the decay of 241 Pu to 241 Am, may result in certain far-field locations with a long-term significant radiological hazard.