U- and Th-series radionuclides in snowshoe hare ( Lepus americanus) taken near U mill tailings close to Elliot Lake, Ontario, Canada

Abstract

Snowshoe hare ( Lepus americanus) trapped near U tailings had higher concentrations of 226Ra in their bones (250 ± 94 mBq g −1 dry wt) than those from local control sites 3–15 km from the tailings (20–30 mBq g −1 dry wt) and those from a distant control site 880 km away from the U mining area, which were below the detection limit (DL) (3.7 mBq g −1 dry wt). Most chyme (stomach content) samples contained 226Ra below DL. Concentration ratios of 226Ra from tissues of local plants, considered important in the hare's diet, to bone ranged from 0.22 to 8.60. Concentrations of 210Pb and 210Po (95–245 mBq g −1 dry wt) were not significantly different among tailings and control site populations. Disequilibrium between these isotopes and their precursors was noted. No significant accumulation of U and Th was noted at any site. Higher concentrations of 228Th compared to 232Th are attributed to accumulation of 228Ra in a manner similar to that of 226Ra. Based on bone 226Ra and 210Po contents, the maximum internal dose rates to the skeleton and the maximum life-time dose of hare living near tailings were 3.9 × 10 −5 Gy d −1 and 4.2 × 10 −2 Gy, respectively. These rates were below the threshold required to produce osteosarcoma in other mammals and were considered unlikely to adversely affect hare during their lifetime. Radionuclide uptake by the animals was concluded to have no environmental significance in the transport of radionuclides from tailings to other locations.