Abstract
Artificial radionuclides including radiocesium (134Cs and 137Cs) and radiosilver (110mAg) were released into the environment following the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011. These particle-bound substances deposited on soils of Northeastern Japan located predominantly within a ~3000 km2 radioactive fallout plume and drained by several coastal rivers to the Pacific Ocean. The current dataset that can be accessed at https://doi.pangaea.de/10.1594/PANGAEA.928594 compiles gamma-emitting artificial radionuclide activities measured in 782 sediment samples collected from 27 to 71 locations during 16 fieldwork campaigns conducted in Japan between November 2011 and November 2020 in river catchments draining the main radioactive plume. This database may be useful to evaluate and anticipate the post-accidental redistribution of radionuclides in the environment and for the spatial validation of models simulating the transfer of radiocesium across continental landscapes.
Highlights
The accident that occurred in March 2011 at the Fukushima Dai-ichi nuclear power plant (FDNPP) released large quantities of radionuclides into the environment (Leelossy et al, 2011)
This database compiles radiocesium activities analysed in recent sediment deposits collected following a homogeneous protocol in the coastal catchments draining the main radioactive pollution plume in the Fukushima Prefecture, Japan
These results demonstrate that the radiocesium levels in sediment transiting these rivers decreased by more than 90 % between 2011–2020. This is confirmed by the similar decline (∼ 85 %) in radioactive dose rates observed in the field between 2011–2018
Summary
The accident that occurred in March 2011 at the Fukushima Dai-ichi nuclear power plant (FDNPP) released large quantities of radionuclides into the environment (Leelossy et al, 2011). Among the radioactive substances emitted, two radiocesium isotopes (134Cs and 137Cs) are the most problematic over the medium to long term as they were released in abundant quantities (Shozugawa et al, 2012) They are characterized by relatively long half-lives (2 years for 134Cs and 30 years for 137Cs), which may cause their persistence in the environment (Evrard et al, 2015). Both radiocesium isotopes were released in equivalent proportions during the accident, with initial 134Cs : 137Cs activity ratios close to 1 (Kobayashi et al, 2017). As the soils located in the main radioactive pollution plume are drained by several coastal river systems to the Pacific Ocean, the redistribution of the initial contamination through water erosion and riverine sediment transfer processes was anticipated (Evrard et al, 2015; Onda et al, 2020)
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