Spatial distribution and partitioning of actinides in Yenisey river floodplain soils and bottom sediments

Prolonged activity of Krasnoyarsk Mining and Chemical Combine (MCC) resulted in contamination of the adjacent environment by trace amounts of man-made radionuclides including actinides. The local microanalyses together with sequential extraction data could forecast migration fate of actinides in this region. Vertical profiles of man-made radionuclides in soil and sediment cores collected at Tarygin Island (flood plain soils) and near Atamanovo village (bottom sediments) were analyzed. Actinide-bearing microparticles were located using track radiography (alpha- and fission track analyses, ATA and FTA) and the major element composition of these particles was determined using scanning electron microscopy with energy dispersed X-ray spectrometry (SEM-EDX). Samples were thinly spread on plastic support. In order to localize actinide bearing particles the SEM finder grid with electrodeposited 239Pu was used. The SEM finder grid was placed on the top of the soil sample and then covered by solid-state nuclear track detector (SSNTD). 239Pu from finder grid produced the grid-like track image on both SSNTD used for ATA and FTA. This technique allowed finding single particles of interest for further analysis using SEM-EDX. The morphology, size and major element distribution in selected particles were studied using SEM-EDX technique. The backscattered electron method was used to trace the distribution of actinides within the particle since the image contrast is proportional to the atomic number of the scattering atom. Information on size and morphology of particles was obtained using secondary electron image while major element composition was determined by EDX. The degree of binding of actinides to substrate particles was determined using sequential extraction technique. (author)