Heterogeneity of 90 Sr radioactive contamination at the head part of the East Ural radioactive trace (EURT).

1: We measured90 Sr concentrations and beta particle flux density (BPFD) in 44 soil samples collected from four soil profiles across a central transect on the head of the East Ural Radioactive Trace (EURT). The relationship between BPFD and90 Sr concentration of each soil sample can be characterised by a linear regression model;90 Sr concentration in the upper 12 cm soil layer can thus be assessed by measuring BPFD in the soil surface. 2: The BPFD on the soil surface was measured at 969 points at seven sites with linear dimensions ranging from 140 × 20 m to 140 × 320 m. The correspondence of90 Sr concentration in the 12 cm soil layer with its BPFD value was calculated for each of these seven sites. Eighty (80) % of90 Sr concentration measurements in the 12 cm soil layer in each model site differed by a factor of 2.0-5. The variability of90 Sr concentration increased significantly in the 12 cm upper soil layer over territories with visual features of landscape disturbance (pits, trenches). The ratio of maximum to minimum concentration of90 Sr varied from 6.1 to 6.6 in the 12 cm soil layer over territories without visual features of anthropogenic soil disturbance. 3: The90 Sr concentration was measured in the skeletons of 34 juvenile Microtus oeconomus individuals weighing less than 12.5 g and trapped at the four model sites in July. The assessment of90 Sr concentration in the 12 cm soil layer was conducted for each point where an animal was trapped. The relationship between90 Sr concentration in soil and in the skeleton was characterised by a linear regression model with a determination coefficient of 0.51. 4: The concentration ratio for90 Sr from soil to skeleton (CRskeleton-soil ) was 2.0 ± 0.1 for M. oeconomus over the territory of the EURT, which is consistent with the minimum value of the same CRskeleton-soil for M. oeconomus from the Chernobyl area (Chesser et al., 2000).