Radionuclides in bats using a contaminated pond on the Nevada National Security Site, USA

• Bats uptake radionuclides from a contaminated pond.
• Tritium had highest concentrations but 137Cs gave highest dose.
• Tritium concentrations in bats are approximately one-twentieth of that in the pond.
• Population level effects are not expected based on RESRAD-Biota dose estimates.
• It may be more appropriate to model the bats as riparian animals in RESRAD-Biota.

Perched groundwater percolating through radionuclide contamination in the E Tunnel Complex on the Nevada National Security Site, formerly the Nevada Test Site, emerges and is stored in a series of ponds making it available to wildlife, including bats. Since many bat species using the ponds are considered sensitive or protected/regulated and little information is available on dose to bats from radioactive water sources, bats were sampled to determine if the dose they were receiving exceeded the United States Department of Energy dose limit of 1.0E-3 Gy/day. Radionuclide concentrations in water, sediment, and flying insects were also measured as input parameters to the dose rate model and to examine trophic level relationships. The RESRAD-Biota model was used to calculate dose rates to bats using different screening levels. Efficacy of RESRAD-Biota and suggested improvements are discussed. Dose to bats foraging and drinking at these ponds is well below the dose limit set to protect terrestrial biota populations.