The importance of the sediment pathway in the radionuclide dose received by aquatic non-human biota: Reconstruction and mapping of spatiotemporal partitioning in Perch lake sediments over a 40-year period

Environmental Technologies Branch, Atomic Energy of Canada Limited, Chalk River, Ontario K0J 1J0, Canada

Abstract

There is a growing interest in assessing risk to non-human biota following exposure to radionuclides. However, before dose to aquatic biota can be determined, it is critical to have a solid understanding of radionuclide concentrations in key environmental phases due to their importance in determining external and internal dose. Further understanding of a system can be reached by monitoring temporal changes in radionuclide levels in these phases, especially if assessing the success of remediation activities. The current study has focused on estimating inputs of ⁹⁰Sr, ¹³⁷Cs and ⁶⁰Co to the sediments of a small, Canadian Shield lake located downstream of two Waste Management Areas at AECL's, Chalk River Laboratories site over a 40-year period. Overall, it was found that ¹³⁷Cs and ⁶⁰Co inputs have declined in the lake over the last 40 years, which resulted in a net depletion of these radionuclides from the sediments over time. Strontium-90 inputs have remained fairly constant over this time period with ⁹⁰Sr retention in lake sediments of approximately 15%. It is expected that benthic biota will receive approximately a 2- to 6-fold higher radionuclide dose than pelagic organisms, on average, particularly when feeding in the depositional zone of the lake.