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

Abstract

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 90 Sr, 137 Cs and 60 Co 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 137 Cs and 60 Co 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 90 Sr 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.

An international model validation exercise on radionuclide transfer and doses to freshwater biota

“…Historic and contemporary radionuclide activity concentration data were collated for environmental media (sediment and water) and a range of aquatic biota; fishes, primary producers (including unrooted, free-floating; rooted, floating-leafed; rooted, submergent; and emergent species), invertebrates, herpetofauna (amphibians and reptiles) and mammals. The data were obtained from samples collected in Perch Lake in the mid-1960s to late-1990s (e.g., Yankovich and Cornett 2001, 2004 and historical data on temporal changes in 60 Co, 90 Sr, 3 H (determined as HTO) and 137 Cs activity concentrations in lake water and sediment (Yankovich 2002.…”