Depth profiling of Pu, 241Am and 137Cs in soils from southern Belarus measured by ICP-MS and ? and ? spectrometry

Abstract

The depth distribution of plutonium, americium, and 137Cs originating from the 1986 accident at the Chernobyl Nuclear Power Plant (NPP) was investigated in several soil profiles in the vicinity from Belarus. The vertical migration of transuranic elements in soils typical of the 30 km relocation area around Chernobyl NPP was studied using inductively coupled plasma mass spectrometry (ICP-MS), alpha spectrometry, and gamma spectrometry. Transuranic concentrations in upper soil layers ranged from 6 x 10(-12) g g(-1) to 6 x 10(-10) g g(-1) for plutonium and from 1.8 x 10(-13) g g(-1) to 1.6 x 10(-11) g g(-1) for americium. These concentrations correspond to specific activities of (239+240)Pu of 24-2400 Bq kg(-1) and specific activity of 241Am of 23-2000 Bq kg(-1), respectively. Transuranics in turf-podzol soil migrate slowly to the deeper soil layers, thus, 80-95%, of radionuclide inventories were present in the 0-3 cm intervals of turf-podzol soils collected in 1994. In peat-marsh soil migration processes occur more rapidly than in turf-podzol and the maximum concentrations are found beneath the soil surface (down to 3-6 cm). The depth distributions of Pu and Am are essentially identical for a given soil profile. (239+240)Pu/137Cs and 241Am/137Cs activity ratios vary by up to a factor of 5 at some sites while smaller variations in these ratios were observed at a site close to Chernobyl, suggesting that 137Cs is dominantly particle associated close to Chernobyl but volatile species of 137Cs are of relatively greater importance at the distant sites.

Comparison of Pu and 137Cs as tracers of soil and sediment transport in a terrestrial environment

“…Many of the reported measurements of the 137 Cs/ 239þ240 Pu ratio have been directed towards studying local effects of accidents (Boulyga et al, 2003), nuclear testing (Yamamoto et al, 2004) or nearby reprocessing plants (Peirson et al, 1982). Measurements that are representative of global fallout are less common.…”

Inductively coupled plasma mass spectrometry (ICP-MS) and laser ablation ICP-MS for isotope analysis of long-lived radionuclides

“…Other mass spectrometric techniques such as resonance ionization mass spectrometry (RIMS) [26][27][28][29] and accelerator mass spectrometry (AMS) [30][31][32] possess high isotope selectivity for an extreme ultratrace and isotope analysis of, in particular, radiotoxic isotopes ( 14 C, 41 Ca, 90 Sr, 99 Tc, 210 Pb, 236 U and plutonium isotopes) in the environment, cosmochemistry, radiodating, nutrition and biomedical research. For example, a minimum detectable isotopic ratio for 129 I/ 127 I of about 10 −12 can be achieved by AMS [33].…”

“…Problems in ICP-MS due to the isobaric interferences of long-lived radioactive nuclides and molecular ions or stable isotopes of other chemical elements can be solved by the application of double-focusing sector field ICP-MS at the required mass resolution, by the application of ICP-MS with collision cell, or by the application of coupling (hyphenated) techniques such as ion chromatography, HPLC and CE with ICP-MS [5,[37][38][39][40]. Because long-lived radionuclides occur at extremely low concentrations, especially in environmental or medical samples, matrix separation and enrichment of the analytes has been proposed for their analysis by several authors [20,[41][42][43]. Trace/matrix separation, which is performed off-line or on-line, is used more and more frequently for isotope ratio measurements of long-lived radionuclides in order to avoid possible isobaric interferences, matrix effects and to reduce the detection limits.…”

Application of isotope-dilution laser ablation ICP?MS for direct determination of Pu concentrations in soils at pg�g?1 levels

“…Note that isotope dilution with 244 Pu and internal standardization with 230 Th were carried out by parallel analyses with corresponding sample aliquots, and thus the results could be influenced by sample inhomogeneity. Results of α-spectrometry and ICP-IDMS after digestion of soil samples with potassium pyrosulfate and plutonium extraction with TEVA resin (trialkyl, methylammonium nitrate) from Eichrom Technologies [20] are given for comparison. Results of LA-ICP-IDMS agreed well with results of α-spectrometry for the Krasnosel'e and Radin samples, and the corresponding data obtained by use of LA-ICP-MS with internal 230 Th standardization coincided, within experimental error, with results from α-spectrometry and ICP-IDMS obtained after sample decomposition and Pu extraction.…”

“…Homogenized soil samples were ashed at 600°C. Details of the sample preparation procedure can be found elsewhere [15,20]. Standard reference materials NIST 1646 Estuarine Sediment and NIST 4357 Ocean Sediment Environmental Radioactivity Standard, the latter consisting of a blend of ocean sediments collected off the coast of Sellafield (British Nuclear Fuels facility), UK, and in the Chesapeake Bay, USA, were obtained from the National Institute of Standards and Technology (Gaithersburg, MD, USA).…”