Applicability of for modelling dissolved Cs concentrations in Fukushima river water; Case study of the upstream Ota River

Sakuma, Kazuyuki   ; Tsuji, Hideki*; Hayashi, Seiji*; Funaki, Hironori ; Malins, A.  ; Yoshimura, Kazuya  ; Kurikami, Hiroshi  ; Kitamura, Akihiro   ; Iijima, Kazuki  ; Hosomi, Masaaki*

A study is presented on the applicability of the distribution coefficient () absorption/desorption model to simulate dissolved Cs concentrations in Fukushima river water. The simulation results were in good agreement with the observations on water and suspended sediment fluxes, and on particulate bound Cs concentrations under both ambient and high flow conditions. By contrast the measured concentrations of dissolved Cs in the river water were much harder to reproduce with the simulations. By tuning the values for large particles, it was possible to reproduce the mean dissolved Cs concentrations during base flow periods (observation: 0.32 Bq/L, simulation: 0.36 Bq/L). However neither the seasonal variability in the base flow dissolved Cs concentrations (0.14-0.53 Bq/L), nor the peaks in concentration that occurred during storms (0.18-0.88 Bq/L, mean: 0.55 Bq/L), could be reproduced with realistic simulation parameters.