Accumulation of (137)cesium and (90)strontium 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 con taminated area of the Red Forest near the Chornobyl (Ukraine) Reactor 4 to evaluate the uptake rates of Cs-137 and Sr-90 from abiotic, sources. Mice w ere provided with uncontaminated food supplies, ensuring that uptake of rad ionuclides was through soil ingestion, inhalation, or water. Mice were samp led before introduction and were reanalyzed every 10 d for Cs-137 Uptake. L evels of Sr-90 were assessed in subsamples from the native populations and in experimental animals at the termination of the study. Uptake rates in ho use mice were greater than those in voles for both 137Cs and Sr-90. Daily u ptake rates in house mice were estimated at 2.72 X 10(12) unstable atoms pe r gram (whole body) for Cs-137 and 4.04 X 10(10) unstable atoms per gram fo r Sr-90. Comparable rates in voles were 2.26 X 10(11) unstable atoms per gr am for Cs-137 and 1.94 X 1010 unstable atoms per gram for Sr-90. By compari ng values from voles in the enclosures to those from wild voles caught with in 50 m of the enclosures, it was estimated that only 8.5% of Cs-137 was in corporated from abiotic, sources, leaving 91.5% being incorporated by uptak e from biotic materials. The fraction of Sr-90 uptake from abiotic sources was at least 66.7% (and was probably much higher). Accumulated whole-body d oses during the enclosure periods were estimated as 174 mGy from intramuscu lar Cs-137 and 68 mGy by skeletal Sr-90 in house mice over 40 d and 98 mGy from Cs-137 and 19 mGy from Sr-90 in voles over 30 d. Thus, uptake of radio nuclides from abiotic materials in the Red Forest at Chornobyl is an import ant source of internal contamination.