Effects of the nuclear disaster on marine products in Fukushima: An update after five years

Abstract

Original data (Cs and Cs, and sampling location) of marine products in Fukushima Prefecture monitored during 2011-2015 (n = 32,492) were analyzed to present an updated detailed description of radiocesium contamination after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident and to examine taxon/habitat-specific decreasing trends in different areas. Furthermore, marine species data presented by the Tokyo Electric Power Company (TEPCO) during 2012-2015 (n = 5458) were analyzed to evaluate the decreasing trends ofCs inside and outside (within a 20 km radius) of the FDNPP port. Monitoring results by Fukushima Prefecture show that percentages of samples higher than the Japanese regulatory limit of 100 Bq kg-wet (>RL%) were higher, whereas those below the detection limit (<DL%) (mean 8.3 and 7.4 Bq kg-wet for Cs andCs, respectively) were lower in demersal fishes than in pelagic fish or other taxa. However, >RL% and <DL% of demersal fish respectively decreased dramatically and increased gradually to 0.06% and 86.3% in 2015, although slightly elevated radiocesium concentrations were still observed in shallow areas south of the FDNPP. The drastic decrease in radioactivity was supported by the spatiotemporal distribution of radiocesium concentrations in demersal fish, in which higher concentrations that were frequently observed in 2011 and 2012 were rarely detected in 2015, even within the 20 km radius area (maximum 220 Bq kg-wet in Japanese rockfish Sebastes cheni). Statistical analyses of TEPCO data revealed that Cs concentrations both inside and outside of the FDNPP port decreased exponentially with time: The respective geometric mean days of ecological half-lives were 218 d and 386 d. These results show clearly that the contamination level of marine products in Fukushima Prefecture, even within the 20 km radius area, has decreased drastically during the five years after the FDNPP accident, althoughCs concentrations higher than 10 kBq kg-wet were still detected in some specimens of sedentary rockfishes (S. cheni, Sebastes oblongus, and Sebastes pachycephalus) in the FDNPP port. Fishing operations started on a trial basis in June 2012 have gradually expanded the target areas and species. Careful monitoring should be continued to accelerate the restoration of coastal fisheries in Fukushima Prefecture.

Marine radioecology after the Fukushima Dai-ichi nuclear accident: Are we better positioned to understand the impact of radionuclides in marine ecosystems?

“…This is compatible with differences in TB½s for these radionuclides and in agreement with other studies (Sohtome et al, 2014;Wada et al, 2016;Wada et al, 2013). There was a high variability in the…”

Food safety hazards in the European seaweed chain

“…Data from Asia describing high radionuclide concentrations in seaweeds right after the Fukushima accidents showed a clear decrease over time toward low, stable concentrations within 0.5 to 5 years, clearly below the regulatory limit for radiocesium of 600 Bq/kg (Kawai et al., ; Wada et al., ; Wada et al., ). Data from Canada and Sweden also showed reasonably low concentrations of 129 I (44 to 575 × 10 9 atoms/g and 137 Cs [2 to 21 Bq/kg]) in F. vesiculosus samples (Gómez‐Guzmán et al., ).…”

A dual pathways transfer model to account for changes in the radioactive caesium level in demersal and pelagic fish after the Fukushima Daï-ichi nuclear power plant accident

“…Slow depuration was also observed in sedentary demersal fish in the near field [4, 8] and the hypothesis of an influence by sediment contamination levels naturally emerged [13], although it was reported that transfer between sediment radioactive Cs contamination and biota is minor [14]. However, we used the DPTM to test the potential effect of a transfer route influenced by sediment.…”