Evaluation of particulate 137Cs discharge from a mountainous forested catchment using reservoir sediments and sinking particles

Abstract The time and size dependencies of particulate 137 Cs concentrations in a reservoir were investigated to evaluate the dynamics of 137 Cs pollution from a mountainous forested catchment. Sediment and sinking particle samples were collected using a vibracorer and a sediment trap at the Ogaki Dam Reservoir in Fukushima, which is located in the heavily contaminated area that formed as a result of the Fukushima Dai-ichi Nuclear Power Plant accident of 2011. The inventory of 137 Cs discharged into the reservoir during the post-accident period (965 days) was estimated to be approximately 3.0 × 10 12 –3.9 × 10 12 Bq, which is equivalent to 1.1%–1.4% of the initial estimated catchment inventory. The particulate 137 Cs concentration showed a decline with time, but the exponent value between the specific surface area and the 137 Cs concentration for the fine-sized ( 137 Cs in reservoir sediments and sinking particles have important implications for the evaluation of 137 Cs dynamics in mountainous forested catchments.