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Yamasaki T, Suzuki S, Nishikiori T. Impact evaluation of typhoons and remediation works on spatiotemporal evolution of air dose rate in two riverside parks in Fukushima, Japan after the Dai-ichi nuclear power plant accident. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2023; 332:117311. [PMID: 36724596 DOI: 10.1016/j.jenvman.2023.117311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 01/10/2023] [Accepted: 01/14/2023] [Indexed: 06/18/2023]
Abstract
This study elucidated the impacts of typhoon events and remediation works on the spatiotemporal evolution of the air dose rate in riverside areas frequented by residents. Spatial distribution of the air dose rate and radiocesium concentration in the sediments were measured in two riverside parks located near each other in Fukushima Prefecture, Japan, for 2015-2020. The air dose rates measured by walk surveys were interpolated using ordinary kriging to generate air dose rate maps, to facilitate a comparison between the results at different points in time during the measurement campaigns. After the typhoons that occurred during 2015-2018, the air dose rate near the riverside in one park decreased, but not in the other, because the erosion and sediment deposition patterns differed between them. This could be due to the presence of a dam upstream, which serves a flood mitigation function. However, the extreme event of typhoon Hagibis in 2019 dropped the air dose rates near the riversides in both parks. In contrast to the typhoon events which affected the riverside areas, remediation works such as decontamination undertaken during 2015-2019 reduced the air dose rates around the garden and lawn areas which are frequently used as recreational sites. Modeling the temporal evolutions in the air dose rates for the entire area of the riverside parks revealed that 35% of the reduction was caused by physical decay of radiocesium on average, 14% by vertical migration of radiocesium in the soil through precipitation, and 51% by the three typhoons and remediation works during 2015-2019. The contribution of 20% from the strongest typhoon Hagibis highlights the fact that floods resulting from large typhoons are effective in causing natural attenuation of air dose rates in riverside parks.
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Affiliation(s)
- Takuhei Yamasaki
- Fukushima Prefectural Centre for Environmental Creation, 10-2 Fukasaku, Miharu Town, Fukushima, 963-7700, Japan
| | - Satoshi Suzuki
- Fukushima Prefectural Centre for Environmental Creation, 10-2 Fukasaku, Miharu Town, Fukushima, 963-7700, Japan
| | - Tatsuhiro Nishikiori
- Fukushima Prefectural Centre for Environmental Creation, 10-2 Fukasaku, Miharu Town, Fukushima, 963-7700, Japan; Agricultural Radiation Research Center, Tohoku Agriculture Research Center, National Agriculture and Food Research Organization, 50 Harajukuminami, Arai, Fukushima City, Fukushima 960-2156, Japan.
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Konoplev A, Wakiyama Y, Wada T, Ivanov M, Komissarov M, Nanba K. Reconstruction of time changes in radiocesium concentrations in the river of the Fukushima Dai-ichi NPP contaminated area based on its depth distribution in dam reservoir's bottom sediments. ENVIRONMENTAL RESEARCH 2022; 206:112307. [PMID: 34756914 DOI: 10.1016/j.envres.2021.112307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Revised: 09/20/2021] [Accepted: 10/26/2021] [Indexed: 06/13/2023]
Abstract
Radionuclide depth distribution in bottom sediments in deep-water zones of dam reservoirs, where no sediment mixing occurs, can be used to reconstruct time changes in particulate activity concentrations of radionuclides strongly bound to bottom sediments. This approach was used to analyze the 137Cs concentration profile in a bottom sediment core collected from Ogaki dam reservoir on the Ukedo River in the Fukushima Dai-ichi nuclear power plant contaminated zone in October 2019. The derived 137Cs particulate concentrations provided a basis for estimating the dissolved concentration and its temporal trend in the Ukedo River, using the mean value of the apparent 137Cs distribution coefficient. The reconstructed particulate and dissolved 137Cs concentrations and their temporal trends are consistent with monitoring data. The annual mean particulate and dissolved 137Cs wash-off ratios were also calculated for the period of eight years after the accident. Interestingly, the particulate 137Cs wash-off ratios for the Ukedo River at Ogaki dam were found to be similar to those for the Pripyat River at Chernobyl in the same time period after the accident, while the dissolved 137Cs wash-off ratios in the Ukedo River were an order of magnitude lower than the corresponding values in the Pripyat River. Both the particulate and dissolved 137Cs wash-off ratios in the Ukedo River declined faster during the first eight years after the FDNPP accident than predicted by the diffusional model, most likely, due to greater natural attenuation and, to some extent, remediation measures implemented on the catchments in Fukushima.
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Affiliation(s)
- Alexei Konoplev
- Institute of Environmental Radioactivity, Fukushima University, Kanayagawa 1, Fukushima, 960-1296, Japan.
| | - Yoshifumi Wakiyama
- Institute of Environmental Radioactivity, Fukushima University, Kanayagawa 1, Fukushima, 960-1296, Japan
| | - Toshihiro Wada
- Institute of Environmental Radioactivity, Fukushima University, Kanayagawa 1, Fukushima, 960-1296, Japan
| | - Maxim Ivanov
- Faculty of Geography, Moscow State University, Moscow, 119991, Russia; Institute of Geography, Russian Academy of Science, Russia
| | | | - Kenji Nanba
- Institute of Environmental Radioactivity, Fukushima University, Kanayagawa 1, Fukushima, 960-1296, Japan
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Funaki H, Tsuji H, Nakanishi T, Yoshimura K, Sakuma K, Hayashi S. Remobilisation of radiocaesium from bottom sediments to water column in reservoirs in Fukushima, Japan. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 812:152534. [PMID: 34954177 DOI: 10.1016/j.scitotenv.2021.152534] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2021] [Revised: 11/17/2021] [Accepted: 12/15/2021] [Indexed: 06/14/2023]
Abstract
Reservoir sediments generally act as a sink for radionuclides derived from nuclear accidents, but under anaerobic conditions, several radionuclides remobilise in bioavailable form from sediments to water columns, which may contribute to the long-term contamination of aquatic products. This study systematically investigated the 137Cs activities of sediment-pore water, providing a direct evidence of the remobilisation of bioavailable 137Cs from sediments in two highly contaminated reservoirs affected by the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. We observed that the dissolved 137Cs activity concentration of pore water (3.0-65.8 Bq L-1) was one to two orders of magnitude higher than that of reservoir water. Moreover, the distribution coefficient (Kd) values for the 137Cs of sediment-pore water (2.6-14 × 103 L kg-1) decreased with depth. The Kd values were significantly and negatively correlated with the concentration of the major 137Cs competing cation NH4+. Our results strongly indicate a competitive ion exchange process between 137Cs and NH4+ via a highly selective interaction with the frayed edge sites of phyllosilicate minerals, which is the major reason for the variability of Kd values of sediment-pore water, even in the Fukushima case. Additionally, the sediment accumulation rates were relatively high, and the annual depositional rate of exchangeable 137Cs prevailed over the annual diffusive flux of 137Cs from the sediment to the overlying water. This finding indicates that even after 10 years since the FDNPP accident, the bioavailable 137Cs is still continuously supplied from the catchment covered by mountainous forests, and reservoir sediments are a long-term important source of bioavailable 137Cs in the riverine system. Our findings provide important parameter values for mid- and long-term assessments of the radiation impact of radionuclide discharges to freshwater environments.
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Affiliation(s)
- Hironori Funaki
- Japan Atomic Energy Agency, 45-169, Kaihama-sukakeba, Minamisoma, Fukushima 975-0036, Japan.
| | - Hideki Tsuji
- National Institute for Environmental Studies, 10-2 Fukasaku, Miharu, Fukushima 963-7700, Japan
| | - Takahiro Nakanishi
- Japan Atomic Energy Agency, 45-169, Kaihama-sukakeba, Minamisoma, Fukushima 975-0036, Japan
| | - Kazuya Yoshimura
- Japan Atomic Energy Agency, 45-169, Kaihama-sukakeba, Minamisoma, Fukushima 975-0036, Japan
| | - Kazuyuki Sakuma
- Japan Atomic Energy Agency, 45-169, Kaihama-sukakeba, Minamisoma, Fukushima 975-0036, Japan
| | - Seiji Hayashi
- National Institute for Environmental Studies, 10-2 Fukasaku, Miharu, Fukushima 963-7700, Japan
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Funaki H, Sakuma K, Nakanishi T, Yoshimura K, Katengeza EW. Reservoir sediments as a long-term source of dissolved radiocaesium in water system; a mass balance case study of an artificial reservoir in Fukushima, Japan. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 743:140668. [PMID: 32673913 DOI: 10.1016/j.scitotenv.2020.140668] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 06/25/2020] [Accepted: 06/30/2020] [Indexed: 06/11/2023]
Abstract
Because of their large mobility and high bioavailability, it is necessary to elucidate the origins and dynamics of dissolved radionuclides in river and reservoir systems to assess the transfer of those radionuclides from water to crops and aquatic organisms. Elution from contaminated reservoir sediments, a potential source of dissolved radionuclides, presents a long-term concern, particularly for long-lived radionuclides. In this study, we systematically investigated caesium-137 (137Cs) concentrations using a time-series suite of input and output water samples collected from 2014 to 2019 from the Ogaki Dam Reservoir, which has a catchment with a high 137Cs inventory due to the Fukushima Dai-ichi Nuclear Power Plant accident. The results of our study showed that dissolved 137Cs concentration was significantly higher in the output water than that in the main input water, and that the effective ecological half-life of dissolved 137Cs in the output water was longer than in the main input water. We quantitatively evaluated the mass balance of dissolved 137Cs in the reservoir to elucidate how much dissolved 137Cs from the rivers and production from reservoir sediments contribute to 137Cs in the reservoir output. The annual output of dissolved 137Cs was significantly higher than the total input of dissolved 137Cs, with approximately 32%-40% of the dissolved 137Cs in the output water presumably being produced from reservoir sediments. Consequently, the estimated dissolved 137Cs fluxes from reservoir sediments to overlying water were 0.57-1.3 × 104 Bq m-2 y-1. This implies that approximately 0.04%-0.09% of 137Cs accumulated in the sediments was released through elution to the overlying water each year. Reservoir sediments containing high 137Cs levels may thus become even more important as sources of bioavailable dissolved 137Cs in the future.
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Affiliation(s)
- Hironori Funaki
- Japan Atomic Energy Agency, 45-169, kaihama-sukakeba, Minamisoma, Fukushima 975-0036, Japan.
| | - Kazuyuki Sakuma
- Japan Atomic Energy Agency, 45-169, kaihama-sukakeba, Minamisoma, Fukushima 975-0036, Japan
| | - Takahiro Nakanishi
- Japan Atomic Energy Agency, 45-169, kaihama-sukakeba, Minamisoma, Fukushima 975-0036, Japan
| | - Kazuya Yoshimura
- Japan Atomic Energy Agency, 45-169, kaihama-sukakeba, Minamisoma, Fukushima 975-0036, Japan
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Katengeza EW, Sanada Y, Yoshimura K, Ochi K, Iimoto T. The ecological half-life of radiocesium in surficial bottom sediments of five ponds in Fukushima based on in situ measurements with plastic scintillation fibers. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2020; 22:1566-1576. [PMID: 32628231 DOI: 10.1039/d0em00160k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Plastic scintillation fibers (PSFs) have been instrumental in in situ surface contamination surveys post the Fukushima Daichi Nuclear Power Plant accident. Their deployment to monitoring bottom sediments in aquatic environments provides the spatial extent of contamination over wide areas compared to discrete points as provided traditionally by sediment sampling. This study evaluated the wide area ecological half-life (Teco) of radiocesium concentration for surface sediments of five ponds in Fukushima using PSFs, monitoring data generated between 2013 and 2019. The least squares' regression method was employed to evaluate the Teco. Four ponds had a Teco ranging from 3.0 ± 0.3 years to 11.4 ± 2.3 years. A forest-catchment pond exhibited a relatively long Teco of 41.6 ± 55 years. Local variation in the Teco appears to be influenced by sedimentation as we demonstrated larger values for areas showing potential sedimentation in the forest catchment pond. This study demonstrates the importance of wide area in situ monitoring techniques, such as PSF, in providing an overview of the spatial-temporal trends of radiocesium in bottom sediments and confirms the importance of forests as secondary contaminant sources to their drainage.
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Affiliation(s)
- Estiner Walusungu Katengeza
- Department of Environment Systems, Graduate School of Frontier Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan.
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Thiry Y, Tanaka T, Dvornik AA, Dvornik AM. TRIPS 2.0: Toward more comprehensive modeling of radiocaesium cycling in forest. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2020; 214-215:106171. [PMID: 32063289 DOI: 10.1016/j.jenvrad.2020.106171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 01/14/2020] [Accepted: 01/14/2020] [Indexed: 06/10/2023]
Abstract
Because internal transfers can play a key role in radiocaesium persistence in trees, a reliable representation of radiocaesium recycling between tree organs in forest models is important for long-term simulations after radioactive fallout in Chernobyl and Fukushima. We developed an upgraded 2.0 version of the initial TRIPS ("Transfer of Radionuclides In Perennial vegetation System") model involving explicit differentiation between tree organs (i.e., foliage, branches, stemwood and bark). The quality of TRIPS 2.0 was evaluated by testing model outputs against independent datasets for pine stands in Belarus and Ukraine. Scenarios involving "hot particle" deposits in forest remained challenging, but in all other scenarios generally positive verification results for soil and tree compartments indicated that the TRIPS 2.0 model adequately combines the major relevant processes. Interestingly, the response of stemwood contamination to changes in radiocaesium availability in soil, as determined by soil conditions, was shown to be more sensitive than for other tree compartments. We recommend the conceptual tree discretization of TRIPS 2.0 for generic forest modeling for two reasons: 1) regardless of different soil conditions, there was concurrent good agreement between simulations and data for individual tree compartments (foliage, branches, stemwood and bark), and 2) the measurements necessary to estimate internal tree transfers are easily accessible to usual field monitoring in forest biogeochemistry (for details, see Goor, F. & Thiry, Y., 2004. Science of the total environment, 325(1-3), 163-180).
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Affiliation(s)
- Y Thiry
- French National Radioactive Waste Management Agency (Andra) - Research and Development Division, 92298, Chatenay-Malabry, France.
| | - T Tanaka
- EDF R&D, LNHE, 6 Quai Watier, 78400, Chatou, France.
| | - A A Dvornik
- Institute of Radiobiology of National Academy of Sciences of Belarus, 4, Fedjuninskogo Str., 246007, Gomel, Belarus.
| | - A M Dvornik
- Gomel State University, Sovetskaya St.104, 246019, Gomel, Belarus.
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Saito K, Mikami S, Andoh M, Matsuda N, Kinase S, Tsuda S, Yoshida T, Sato T, Seki A, Yamamoto H, Sanada Y, Wainwright-Murakami H, Takemiya H. Summary of temporal changes in air dose rates and radionuclide deposition densities in the 80 km zone over five years after the Fukushima Nuclear Power Plant accident. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2019; 210:105878. [PMID: 30638788 DOI: 10.1016/j.jenvrad.2018.12.020] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 12/13/2018] [Accepted: 12/16/2018] [Indexed: 06/09/2023]
Abstract
We summarized temporal changes in air dose rates and radionuclide deposition densities over five years in the 80 km zone based on large-scale environmental monitoring data obtained continuously after the Fukushima Nuclear Power Plant (NPP) accident, including those already reported in the present and previous special issues. After the accident, multiple radionuclides deposited on the ground were detected over a wide area; radiocesium was found to be predominantly important from the viewpoint of long-term exposure. The relatively short physical half-life of 134Cs (2.06 y) has led to considerable reductions in air dose rates. The reduction in air dose rates owing to the radioactive decay of radiocesium was more than 60% over five years. Furthermore, the air dose rates in environments associated with human lives decreased at a considerably faster rate than expected for radioactive decay. The average air dose rate originating from the radiocesium deposited in the 80 km zone was lower than that predicted from radioactive decay by a factor of 2-3 at five years after the accident. Vertical penetration of radiocesium into the ground contributed greatly to the reduction in air dose rate because of an increase in the shielding of gamma rays; the estimated average reduction in air dose rate was approximately 25% with penetration compared to that without penetration. The average air dose rate measured in undisturbed fields in the 80 km zone was estimated to be reduced owing to decontamination by approximately 20% compared to that without decontamination. The average deposition density of radiocesium in undisturbed fields has decreased owing to radioactive decay, indicating that the migration of radiocesium in the horizontal direction has generally been slow. Nevertheless, in human living environments, horizontal radiocesium movement is considered to contribute significantly to the reduction in air dose rate. The contribution of horizontal radiocesium movement to the decrease in air dose rate was estimated to vary by up to 30% on average. Massive amounts of environmental data were used in extended analyses, such as the development of a predictive model or integrated air dose rate maps according to different measurement results, which facilitated clearer characterization of the contamination conditions. Ecological half-lives were evaluated in several studies by using a bi-exponential model. Short-term ecological half-lives were shorter than one year in most cases, while long-term ecological half-lives were different across the studies. Even though the general tendency of decrease in air dose rates and deposition densities in the 80 km zone were elucidated as summarized above, their trend was found to vary significantly according to location. Therefore, site-specific analysis is an important task in the future.
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Affiliation(s)
- Kimiaki Saito
- Japan Atomic Energy Agency, 178-4-4 Wakashiba, Kashiwa, Chiba, 227-0871, Japan.
| | - Satoshi Mikami
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki, 319-1206, Japan
| | - Masaki Andoh
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki, 319-1206, Japan
| | - Norihiro Matsuda
- Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Ibaraki, 319-1195, Japan
| | - Sakae Kinase
- Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Ibaraki, 319-1195, Japan
| | - Shuichi Tsuda
- OECD Nuclear Energy Agency, 46, quai Alphonse Le Gallo, 92100, Boulogne-Billancourt, France
| | - Tadayoshi Yoshida
- Japan Atomic Energy Agency, 4-33 Muramatsu, Tokai-mura, Ibaraki, 319-1194, Japan
| | - Tetsuro Sato
- Hitachi Solutions East Japan Ltd., 2-16-10 Honcho, Aoba-ku, Sendai, 980-0014, Japan; Japan Atomic Energy Agency, 45-169 Sukakeba, Kaihama, Haramachi-ku, Minamisoma, 975-0036, Japan
| | - Akiyuki Seki
- Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Ibaraki, 319-1195, Japan
| | - Hideaki Yamamoto
- Japan Atomic Energy Agency, 178-4-4 Wakashiba, Kashiwa, Chiba, 227-0871, Japan
| | - Yukihisa Sanada
- Japan Atomic Energy Agency, 45-169 Sukakeba, Kaihama, Haramachi-ku, Minamisoma, 975-0036, Japan
| | | | - Hiroshi Takemiya
- Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Ibaraki, 319-1195, Japan
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Sakuma K, Nakanishi T, Yoshimura K, Kurikami H, Nanba K, Zheleznyak M. A modeling approach to estimate the 137Cs discharge in rivers from immediately after the Fukushima accident until 2017. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2019; 208-209:106041. [PMID: 31494389 DOI: 10.1016/j.jenvrad.2019.106041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 08/15/2019] [Accepted: 08/27/2019] [Indexed: 06/10/2023]
Abstract
We developed a simple model to evaluate and predict the 137Cs discharge from catchments using a tank model and the L-Q equation. Using this model, the 137Cs discharge and discharge ratio from the Abukuma River and 13 other rivers in the Fukushima coastal region were estimated from immediately after the Fukushima accident up to 2017. The 137Cs discharge (and discharge ratio to the deposition inventory in the catchment) of the Abukuma River and 13 other rivers in the Fukushima coastal region during the initial six months after the accident were estimated to be 18 TBq (3.1%) and 11 TBq (0.79%), respectively. These values of 137Cs discharge ratio were 1-2 orders of magnitude higher than those observed after June 2011 in previous studies (Ueda et al., 2013; Tsuji et al., 2016; Iwagami et al., 2017a), indicating that the initial 137Cs discharge from the catchments through the rivers was significant. The simulated initial 137Cs discharge rates for the initial six months after the Fukushima accident were about 9-30 times larger in each catchment than those after that point until 2017, though initial 137Cs concentration in river water was derived from an extrapolation of data based on a two exponentially decreasing fitting. However, it was found that the impact on the ocean from the initial 137Cs discharge through the rivers can be limited because the 137Cs discharge from the Abukuma River and the 13 other rivers in the Fukushima coastal region (29 TBq) was two orders of magnitude smaller than the direct release from Fukushima Dai-ichi Nuclear Power Plant (FDNPP) into the ocean (3.5 PBq) and from atmospheric deposition into the ocean (7.6 PBq) (Kobayashi et al., 2013). This model is expected to be useful to evaluate and predict 137Cs discharge from catchments in future water management and in the estimation of 137Cs discharge into reservoirs and the ocean.
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Affiliation(s)
- Kazuyuki Sakuma
- Fukushima Environmental Safety Center, Japan Atomic Energy Agency, Fukushima, 963-7700, Japan.
| | - Takahiro Nakanishi
- Fukushima Environmental Safety Center, Japan Atomic Energy Agency, Fukushima, 963-7700, Japan
| | - Kazuya Yoshimura
- Fukushima Environmental Safety Center, Japan Atomic Energy Agency, Fukushima, 963-7700, Japan
| | - Hiroshi Kurikami
- Fukushima Environmental Safety Center, Japan Atomic Energy Agency, Fukushima, 963-7700, Japan
| | - Kenji Nanba
- Institute of Environmental Radioactivity, Fukushima University, Fukushima, 960-1296, Japan
| | - Mark Zheleznyak
- Institute of Environmental Radioactivity, Fukushima University, Fukushima, 960-1296, Japan
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Ochi K, Urabe Y, Yamada T, Sanada Y. Development of an Analytical Method for Estimating Three-Dimensional Distribution of Sediment-Associated Radiocesium at a Reservoir Bottom. Anal Chem 2018; 90:10795-10802. [PMID: 30114906 DOI: 10.1021/acs.analchem.8b01746] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
After the Fukushima Daiichi Nuclear Power Station accident, the distributions of sediment-associated radiocesium were investigated to evaluate the dispersion and accumulation of radiocesium in the reservoir field. To develop an analytical method for measuring the horizontal and vertical distributions of radiocesium on a wide scale, we obtained 253 gamma-ray spectra at the bottoms of 64 ponds in Fukushima during 2014-2016 by using a NaI(Tl) scintillation detector. For visualizing horizontal distribution, the correlation between detector counting rate and radiocesium concentration of the bottom sediment was confirmed. In estimating vertical distribution, the depth profile of sediment-associated radiocesium was found to be correlated to the intensities of scattered and photo peaks. Good agreement was observed between the results of in situ spectrometry and core sampling. These results indicate that the developed method is suitable for understanding the behavior of radiocesium and determining whether decontamination of reservoirs is required.
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Affiliation(s)
- Kotaro Ochi
- Fukushima Environmental Safety Center , Japan Atomic Energy Agency , 45-169, Sukakeba, Kaibama-aza, Haramachi , Minamisoma , Fukushima 975-0036 , Japan
| | - Yoshimi Urabe
- NESI Inc. , 38, Shinko-cho , Hitachinaka , Ibaraki 312-0005 , Japan
| | - Tsutomu Yamada
- Japan Radiation Engineering Co., Ltd , 1-5-20, Sakuragawa-cho , Hitachi , Ibaraki 316-0002 , Japan
| | - Yukihisa Sanada
- Fukushima Environmental Safety Center , Japan Atomic Energy Agency , 45-169, Sukakeba, Kaibama-aza, Haramachi , Minamisoma , Fukushima 975-0036 , Japan
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