Bioconcentration of fallout 137Cs by fungi and red-backed voles (Clethrionomys gapperi)

Cesium-137 and 40K concentrations were measured in vegetation and in red-backed voles (Clethrionomys gapperi) in southeastern Manitoba, Canada, following the Chernobyl accident in 1986. Voles from wet coniferous habitats contained concentrations of 137Cs twenty- to fiftyfold higher than voles from deciduous habitats. Maximum 137Cs values were observed in autumn. Voles captured in a spruce bog at this time contained an average body burden of about 11 Bq. Concentrations in vegetation samples were similar to those found by other researchers. Overall, there was only minimal evidence of contamination attributable to Chernobyl in either vegetation or voles. The primary source of 137Cs in voles appeared to be dietary, particularly mushrooms that contained up to 74 Bq g-1 ash. Based on physiological constraints, mushrooms were the only plausible source of 137Cs in autumn diets. Elevated values at other times in coniferous areas may have been related to the consumption of epiphytic lichens. These findings suggest that fungi, or the animals that consume them, can serve as sensitive indicators of 137Cs contamination in the environment.