Accumulation of137Cesium and90Strontium from abiotic and biotic sources in rodents at Chornobyl, Ukraine

Bank voles (Clethrionomys glareolus) and laboratory strains of house mice (Mus musculus BALB and C57BL) were relocated into enclosures in a highly contaminated area of the Red Forest near the Chornobyl (Ukraine) Reactor 4 to evaluate the uptake rates of 137 Cs and Sr from abiotic sources. Mice were provided with uncontaminated food supplies, ensuring that uptake of radionuclides was through soil ingestion, inhalation, or water. Mice were sampled before introduction and were reanalyzed every 10 d for 137 Cs uptake. Levels of 90 Sr were assessed in subsamples from the native populations and in experimental animals at the termination of the study. Uptake rates in house mice were greater than those in voles for both 137 Cs and 90 Sr. Daily uptake rates in house mice were estimated at 2.72 × 10 12 unstable atoms per gram (whole body) for 137 Cs and 4.04 x 10 10 unstable atoms per gram for 90 Sr. Comparable rates in voles were 2.26 x 10 11 unstable atoms per gram for 137 Cs and 1.94 x 10 10 unstable atoms per gram for 90 Sr. By comparing values from voles in the enclosures to those from wild voles caught within 50 m of the enclosures, it was estimated that only 8.5% of 137 Cs was incorporated from abiotic sources, leaving 91.5% being incorporated by uptake from biotic materials. The fraction of 90 Sr uptake from abiotic sources was at least 66.7% (and was probably much higher). Accumulated whole-body doses during the enclosure periods were estimated as 174 mGy from intramuscular 137 Cs and 68 mGy by skeletal 90 Sr in house mice over 40 d and 98 mGy from 137 Cs s and 19 mGy from 90 Sr in voles over 30 d. Thus, uptake of radionuclides from abiotic materials in the Red Forest at Chornobyl is an important source of internal contamination.