2011 Fukushima Dai-ichi nuclear power plant accident: Summary of regional radioactive deposition monitoring results

Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyodaku, Tokyo 102-8554, Japan.
Journal of Environmental Radioactivity (Impact Factor: 2.48). 11/2011; 111:13-7. DOI: 10.1016/j.jenvrad.2011.09.003
Source: PubMed


After the Great East Japan Earthquake and resulting Tsunami on March 11, 2011, serious accident of the Fukushima Dai-ichi Nuclear Power Plant has been occurred. Huge amounts of radionuclides were released in atmosphere and ocean. Japanese prefectural governments have carried out environmental radioactivity monitoring; external dose rate, radioactivity measurements in environmental samples and others. Since March 18, 2011, daily and monthly deposition samples were collected in 45 stations covering Japanese Islands and radionuclides in the deposition samples were determined. We summarize radioactive deposition data reported by Japanese Government and study the depositional behaviors of the Fukushima-derived radionuclides. The results revealed that Fukushima-derived radioactive cloud dominantly affected in the central and eastern part of Honshu-Island, although it affected all of Japanese land area and also western North Pacific. The temporal change of the Fukushima-derived (137)Cs revealed that the apparent atmospheric residence time of the Fukushima-derived (137)Cs in sites within 300 km from the Fukushima Dai-ichi NPPis about 10 d.

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Available from: Katsumi Hirose, Oct 01, 2015
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    • "March. On 21 March, high deposition of 137 Cs was reported (13 kBq m -2 d -1 ) at Hitachinaka in Ibaraki Prefecture (Hirose, 2012 "
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    ABSTRACT: The Fukushima Daiichi Nuclear Power Plant accident in 2011 resulted in releases of enormous amounts of radio­nuclides into the atmosphere. The radionuclides were deposited over a large forested area in the Tohoku and Kanto regions. There were few reports about the initial depositions of radionuclides on forest ecosystems during the main emission period. We investigated the initial radiocesium deposition at various forest sites. The deposition of radiocesium by bulk precipitation during the initial few months (approximately until the end of May just after the accident) ranged from 4.4-42.1 kBq m-2 while that by throughfall ranged from 2.1-36.6 kBq m-2. The ratio of radiocesium deposition by throughfall to that by bulk precipitation (DTF /DBP) ranged from 0.13-0.66 during the first sampling period (approximately until the end of March just after the accident). In the following sampling periods, the radiocesium input by bulk precipitation decreased rapidly and became undetectable. The DTF /DBP ratios in these periods increased and then generally exceeded 1.0, meaning that the forest canopies gradually released the entrapped radiocesium. Atmospheric radio­cesium inputs to forest ecosystems were strongly influenced by the forest canopy interception and temporal retention.
    Hydrological Research Letters 01/2015; 9(1):1-7. DOI:10.3178/hrl.9.1
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    • "Ayu ingest silt while grazing on algae attached to the stones in riverbeds, thereby resulting in exposure to the radionuclides from contaminated sediments, including the silt component. Aerosol-bound Cs was transported from the atmosphere to the surface soil by dry or wet deposition within 2 months after the Fukuhsima disaster (Masson et al., 2011; Hirose, 2012; Yasunari et al., 2011). Subsequently, the rivers in the Fukushima Prefecture received radionuclides-contaminated soil originating from inland mountain ranges (Evrard et al., 2013). "
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    ABSTRACT: Ayu Plecoglossus altivelis, a herbivorous fish, is an important fishery resource and key component of the foodweb in many Japanese streams. Radionuclide contamination of this species is likely transferred to higher trophic levels, include humans, in the food chain. After the Fukushima accident in March 2011, ayu were exposed to highly contaminated silt while feeding on algae attached to the riverbed stones. To understand the route by which herbivorous fish are exposed to radionuclides, the activity concentrations of sum of (134)Cs and (137)Cs (radiocesium) were analyzed in riverbed samples (algae and silt) and in the internal organs and the muscle of ayu in five river systems in the Fukushima Prefecture between summer 2011 and autumn 2013. Although there was a positive correlation between the radiocesium activity concentrations in the muscle and the internal organs of ayu, the median activity concentration in the muscle was much lower than those in the internal organs. The activity concentrations of radiocesium in the riverbed samples and the internal organs and the muscle of ayu were correlated with contamination levels in soil samples taken from the watershed upstream of the sample sites. The results of the generalized linear mixed models suggest that the activity concentrations in both the internal organs and the muscle of ayu declined over time. Additionally, the activity concentrations in the internal organs were correlated with those in the riverbed samples that were collected around the same time as the ayu. The activity concentrations in the muscle were correlated with ayu body size. Our results suggest that ayu ingest (134)Cs and (137)Cs while grazing silt and algae from the riverbed, and a part of the (134)Cs and (137)Cs is assimilated into the muscle of the fish. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Journal of Environmental Radioactivity 12/2014; 141C:32-37. DOI:10.1016/j.jenvrad.2014.11.012 · 2.48 Impact Factor
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    • "The Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident occurred after the Great East Japan Earthquake on March 11, 2011, releasing high concentrations of radionuclides into the atmosphere (e.g., Hirose, 2012; Takemura et al., 2011). The released radionuclides , such as 137 Cs, 134 Cs, and 131 I, were widely deposited on soil surfaces, causing high dose rates and subsequent contamination of the land. "
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    ABSTRACT: The Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident resulted in extensive radioactive contamination of the environment via deposited radionuclides such as radiocesium and (131)I. Evaluating the extent and level of environmental contamination is critical to protecting citizens in affected areas and to planning decontamination efforts. However, a standardized soil sampling protocol is needed in such emergencies to facilitate the collection of large, tractable samples for measuring gamma-emitting radionuclides. In this study, we developed an emergency soil sampling protocol based on preliminary sampling from the FDNPP accident-affected area. We also present the results of a preliminary experiment aimed to evaluate the influence of various procedures (e.g., mixing, number of samples) on measured radioactivity. Results show that sample mixing strongly affects measured radioactivity in soil samples. Furthermore, for homogenization, shaking the plastic sample container at least 150 times or disaggregating soil by hand-rolling in a disposable plastic bag is required. Finally, we determined that five soil samples within a 3 m × 3-m area are the minimum number required for reducing measurement uncertainty in the emergency soil sampling protocol proposed here.
    Journal of Environmental Radioactivity 06/2014; 139. DOI:10.1016/j.jenvrad.2014.06.002 · 2.48 Impact Factor
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