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

Snowshoe hare (Lepus americanus) trapped near U tailings had higher concentrations of Ra-226 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 Ra-226 below DL. Concentration ratios of Ra-226 from tissues Of local plants, considered important in the hare's diet, to bone ranged from 0.22 to 8.60. Concentrations of Pb-210 and Po-210 (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 Th-228 compared to Th-232 aye attributed to accumulation of Ra-228 in a manner similar to that of Ra-226. Based on bone Ra-226 and Po-210 contents, the maximum internal dose rates to the skeleton and the maximum lifetime dose of hare living near tailings were 3.9 x 10(-5) Gy d(-1) and 4.2 x 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. (C) 1997 Elsevier Science Ltd.