Migration processes of radioactive cesium in the Fukushima nearshore area: Impacts of riverine input and resuspension

Temporal evolution of plutonium concentrations and isotopic ratios in the Ukedo - Takase Rivers draining the Difficult-To-Return zone in Fukushima, Japan (2013–2020)

“…Lower plutonium activity concentrations are observed in the marine environment, probably due to the dilution of particles induced by the strong Kuroshio current (Buesseler et al, 2015;Men et al, 2018). In these studies, a similar decrease and dilution effect of 137 Cs from the Ukedo River and Takase River was observed in the marine environment, and it was found that the total contribution of the 137 Cs from these rivers represented only 7 % of the total annual inventory supplied to seabed sediments (Misonou et al, 2022). Therefore, it is expected that a similar contribution of plutonium may be supplied by these rivers to marine environments but its source is not necessarily identical to the cesium one because a strong contribution from global fallout is observed.…”

Behavior of Radiocesium (137Cs) on the Coastal Seafloor near the Fukushima Daiichi Nuclear Power Plant Inferred from Radiocesium Distributions in Long Cores

“…However, these vertical distributions would be temporary because the occasional impacts significantly disturb them. Misonou et al (2022) observed the shear stress exceeding 0.15 N m −2 several times a year at a water depth of 16 m. Such a disturbance might update the vertical distribution of the 137 Cs concentrations and the median grain size in the sediment cores.…”

“…At a water depth of 10 m near sampling point No. 21 in 2017, Misonou et al (2022) observed annual bottom shear stress (0.088 ± 0.15 N m −2 ) and wave shear stress (0.52 ± 1.6 N m −2 ). That is, at the onshore zone on the Fukushima coast, many stress periods higher than the critical bed shear stress of the sand fraction exist (0.15 N m −2 from Kamidaira et al, 2021), indicating constant vertical mixing.…”

Discussion on the development of nuclear energy and nuclear power plants

“…For instance, after the happened of Fukushima nuclear accident large amount of cesium, which is radioactive, was released into the sea areas as sediments. However, since winds and waves cause resuspension, food chains and the effect of river currents, would send cesium back off offshore [15].…”