Kazuya Yoshimura

Kazuya Yoshimura
Japan Atomic Energy Agency | JAEA · Sector of Fukushima Research and Development

PhD

About

73
Publications
6,195
Reads
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1,239
Citations
Citations since 2017
47 Research Items
1010 Citations
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
Additional affiliations
June 2009 - December 2013
University of Tsukuba
Position
  • Research Associate
Education
April 2005 - May 2009
University of Tsukuba
Field of study
  • Oceanography, Acuatic ecology

Publications

Publications (73)
Article
Full-text available
After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, individual exposure doses to residents have been assessed by many municipalities, governments and research institutes. Various methods including measurements with personal dosimeters and simulations have been used for this evaluation depending on purposes, but the information of asse...
Article
Radioactive cesium-rich microparticles (CsMPs) derived from the Fukushima Daiichi Nnuclear Power Plant accident were detected from soils and river water around Fukushima Prefecture, Japan. Because CsMPs are insoluble and rich in radioactive cesium (RCs), they may cause the overestimation of solid-water distribution coefficient (Kd) for RCs in the w...
Article
Full-text available
The evacuation order areas established due to the accident at the Tokyo Electric Power Company Holdings’ (TEPCO) Fukushima Daiichi Nuclear Power Plant (FDNPP) have been reorganized according to the decrease in ambient dose rates and the decontamination progress. The Japanese government decided to decontaminate the difficult-to-return areas and lift...
Article
Cesium-rich microparticles (CsMPs) with high cesium-137 (137Cs) concentrations were released and deposited in surface soil after the Fukushima Daiichi Nuclear Power Plant accident. Radioactive materials on the soil surface layer enter rivers owing to soil erosion during rainfall. In this study, we investigated CsMPs runoff through the river via soi...
Article
Full-text available
Measurements in forest catchments in Fukushima Prefecture indicate that cesium‐137 (¹³⁷Cs) leaching from forest litter affects dissolved ¹³⁷Cs levels in river water. Existing simulations have been unsuccessful in reproducing this phenomenon due to mechanistic limitations in the models connecting the forest ecosystem and the river system. This paper...
Article
Background: After the Fukushima Daiichi Nuclear Power Station (FDNPS) accident, a model was developed to estimate the external exposure doses for residents who were expected to return to their homes after evacuation orders were lifted. However, the model’s accuracy and uncertainties in parameters used to estimate external doses have not been evalua...
Article
Background: Residential areas have some factors on the external exposure of residents, who usually spend a long time in these areas. Although various survey has been carried out by the government or the research institutions after the Fukushima Daiichi Nuclear Power Plant accident, the mechanism of radiocesium inventory in the terrestrial zone has...
Article
Full-text available
Ambient dose equivalent conversion coefficients (ADCRCs) for converting a radiocaesium inventory to ambient dose equivalent rates (air dose rates) depend on the vertical distribution of radiocaesium in soil. To access the validity of ADCRCs, the air dose rate at 1 m above ground and the vertical distribution of radiocaesium in the soil around the F...
Article
Background: The radionuclides released by the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident 9 years ago are still being monitored by various research teams and the Japanese government. Comparison of different surveys’ results could help evaluate the exposure doses and the mechanism of radiocesium behavior in the urban environment in the ar...
Article
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 s...
Article
The dynamics of radionuclides in terrestrial environments is a crucial consideration for environmental remediation and radiation protection after a severe nuclear disaster. Although the dynamics of radionuclides, especially ¹³⁷Cs, have been intensively studied in diverse environments and reviewed in-depth, studies in urban areas are limited and hav...
Article
An enormous amount of radionuclides was released into the atmosphere following the Fukushima Dai-ichi Nuclear Power Plant accident, with part of it penetrating houses. Information on radionuclide distribution inside and outside houses is useful for indoor external dose assessments. To investigate the radionuclide distribution, we collected both soi...
Article
Full-text available
Abrasion of the brake lining of automobiles is one of the main antimony (Sb) sources on the road. Therefore, the road effluent possibly supplies Sb to the combined sewer collection system. However, Sb in road-sewer systems has attracted little concern, although heavy metals such as copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) in sewer water...
Article
Full-text available
We investigated the radiocaesium content of nine epiphytic foliose lichens species and the adjacent barks of Zelkova serrata (Ulmaceae, "Japanese elm") and Cerasus sp. (Rosaceae, "Cherry tree") at the boundary of the Fukushima Dai-ichi Nuclear Power Station six years after the accident in 2011. Caesium-137 activities per unit area (the 137 Cs-inven...
Article
Full-text available
The Japanese government is beginning to consider radiation protection in the “specific reconstruction reproduction base area” of the Fukushima nuclear power plant, the evacuation order of which will be lifted by 2023. It is essential to grasp the present situation of radiation contamination and evaluate exposure dose in the area to realize the lift...
Article
Full-text available
After the Fukushima Daiichi Nuclear Power Plant accident, atmospheric radiocesium concentration has been monitored by the Nuclear Regulation Authority as a national project to assess its temporal change from August 2011 to November 2017. During the first two years, the atmospheric radiocesium concentration ranged from 10−1–100 Bq m−3, while concent...
Article
In forest ecosystems, forest litter is considered an active medium for radiocesium (¹³⁷Cs). To understand discharge mechanisms of highly bioavailable dissolved ¹³⁷Cs from forests to river systems, we investigated the characteristics of ¹³⁷Cs leaching from forest litter as observed from litterbag experiments. Leaching experiments with conifer needle...
Article
The deposited ¹³⁷Cs is one of the long-lived radionuclides, that was released following the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, has been hydrologically transported as particulates in the terrestrial environment of the Fukushima region. The impact of freeze-thaw processes and subsequent runoff affecting the ¹³⁷Cs flux and concen...
Article
Full-text available
Radiocesium released from the Fukushima Daiichi nuclear power plant (FDNPP) and deposited in the terrestrial environment has been transported to the sea through rivers. To study the long-term effect of riverine transport on the remediation process near the FDNPP, a monitoring project was initiated by the University of Tsukuba. It was commissioned b...
Article
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Article
The 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, Japan, released the largest quantity of radionuclides into the terrestrial environment since the 1986 accident at Chernobyl. This accident resulted in 2.7 PBq of radiocaesium (¹³⁷Cs) contaminated forests, agricultural lands, grasslands and urban areas, which subsequently migrated thro...
Article
Full-text available
The information on the absorbed dose rate which is derived from natural radionuclides is needed to evaluate additional exposure dose. However, there is inadequate positional resolution and precision for such data around Fukushima Dai-ichi Nuclear Power Station (FDNPS). In this study, we created a map of the absorbed dose rate that is derived from n...
Article
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 sedi...
Article
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 radionuclide...
Article
Vertical and horizontal distributions are fundamental for sampling and in-situ gamma spectrum measurement strategies. The distributions of 137Cs were investigated for paved surfaces affected by the Fukusima Dai-ichi Nuclear Power Plant accident. Additionally, the effects of the distributions on the measurement uncertainties of in-situ spectrometry...
Article
Full-text available
In 2011, after the Fukushima Dai-ichi Nuclear Power Plant accident, the initial decrease in the ambient dose equivalent rate (dH*(10) dt⁻¹), an alternative quantity to the effective dose, was studied using monitoring data obtained from March 16, 2011. The dH*(10) dt⁻¹ was normalized by the ¹³⁷Cs activity per unit area (norm-dH*(10) dt⁻¹) to analyze...
Article
Full-text available
The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident released the most significant quantity of radiocesium into the environment since Chernobyl and detailed measurements over the initial 5 years provide new insight into fluvial redistribution of radiocesium. We found that the high initial activity concentration of ¹³⁷Cs-bearing suspended sedi...
Article
Full-text available
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 disch...
Article
Trends of air dose rate decrease after decontamination works and factors which affect them constitute essential information for radiation protection, such as prediction of external exposure to the public and implementation of measures to reduce such exposure. This study investigated the decrease of air dose rate (ambient dose rate at 1 m above the...
Article
Understanding solid 137Cs wash-off in sediment sources is important for predicting radiological risks in zones contaminated by the Fukushima Dai-ichi Nuclear Power Plant accident. Yoshimura et al. (2015) studied solid 137Cs wash-off using soil erosion plots representing different land uses in Fukushima. However, temporal trends of 137Cs activity co...
Article
An autonomous unmanned helicopter (AUH) survey is a useful tool for monitoring the distribution of ambient dose equivalent rates. However, the AUH survey method was developed for plane permeable fields such as agricultural land, and its applicability to urban areas is unclear. In this study, the applicability was investigated by comparing the resul...
Technical Report
Cabinet Office Nuclear Emergency Response Headquarters starts to consider radiation protection in the “specific reconstruction reproduction base area” of which evacuation order will be possibly lifted in 2022-2023. To consider the radiation protection, it is essential to understand the present situations of radiation contamination and evaluate expo...
Article
A study is presented on the applicability of the distribution coefficient (Kd) absorption/desorption model to simulate dissolved ¹³⁷Cs concentrations in Fukushima river water. The upstream Ota River basin was simulated using GEneral-purpose Terrestrial Fluid-flow Simulator (GETFLOWS) for the period 1 January 2014 to 31 December 2015. Good agreement...
Article
The time and size dependencies of particulate ¹³⁷Cs concentrations in a reservoir were investigated to evaluate the dynamics of ¹³⁷Cs pollution from a mountainous forested catchment. Sediment and sinking particle samples were collected using a vibracorer and a sediment trap at the Ogaki Dam Reservoir in Fukushima, which is located in the heavily co...
Article
The influence of buildings, trees and paved surfaces on outdoor ambient dose equivalent rates (H˙∗(10)) in suburban areas near to the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) was investigated with Monte Carlo simulations. Simulation models of three un-decontaminated sites in Okuma and Tomioka were created with representations of individual bu...
Article
Contamination of agricultural products by resuspended matter remains a concern in the highly contaminated areas. Radiocesium concentration of spinach cultivated with non-contaminated soil was low in the decontaminated areas, but high in the contaminated areas. The washed plants had relatively lower radiocesium concentration than the unwashed plants...
Article
The time and size dependencies of particulate137Cs concentrations in a reservoir were investigated to evaluate the dynamics of137Cs pollution from a mountainous forested catchment. Sediment and sinking particle samples were collected using a vibracorer and a sediment trap at the Ogaki Dam Reservoir in Fukushima, which is located in the heavily cont...
Article
A study is presented on the applicability of the distribution coefficient (Kd) absorption/desorption model to simulate dissolved 137Cs concentrations in Fukushima river water. The upstream Ota River basin was simulated using GEneral-purpose Terrestrial Fluid-flow Simulator (GETFLOWS) for the period 1 January 2014 to 31 December 2015. Good agreement...
Article
Distribution of ¹³⁷Cs on components in urban areas such as roofs and roads is crucial for evaluating the behavior of radiocesium and ambient dose rates in the area. This study evaluated relative ¹³⁷Cs inventories, which are defined as the relative values of ¹³⁷Cs inventory on each component to that on a nearby permeable plane field, for 11 building...
Article
A wide area of paddy fields was contaminated by radiocesium derived from the Fukushima nuclear accident. Implement of agricultural countermeasures is one of the principle methods to reduce the contamination of rice plants. In this study, the effect of topsoil removal measure and fertilizer application on radiocesium uptake by rice plants was invest...
Article
The Fukushima nuclear accident in 2011 resulted in (137)Cs contamination of large areas in northeast Japan. A watershed-scale (137)Cs transport model was developed and applied to a forested catchment in Fukushima area. This model considers (137)Cs wash-off from vegetation, movement through soils, and transport of dissolved and particulate (137)Cs a...
Conference Paper
Full-text available
The Fukushima Daiichi Nuclear Power Plant accident has released massive amount of radiocesium into the terrestrial environment, and the radiocesium (Cs-137) transfer and flux through river network is important to understand the redistribution of radiocesium in terrestrial environment, which is essential for assessing the external and internal radio...
Article
Full-text available
It is crucial to monitor light environments in large lakes using satellite remote-sensing data. Many studies have proposed prediction schemes of transparency information, but most of them were site-specific. Here, we applied semi-analytical retrieval procedures of inherent optical properties from in situ-measured remote-sensing reflectance and then...
Article
The concentration of particulate (137)Cs in paddy fields, which can be a major source of (137)Cs entering the water system, was studied following the Fukushima Daiichi Nuclear Power Plant accident. To parameterize the concentration and to estimate the time dependence, paddy fields covering various levels of (137)Cs deposition were investigated over...
Article
About half of the total paddy field area, which is the dominant agricultural land in Fukushima Prefecture, was contaminated by radiocesium released by the Fukushima Daiichi Nuclear Power Plant accident. In this study, we investigated the temporal changes of radiocesium in soil, irrigation water, and rice plant in two adjacent rice paddies, with and...
Article
The chlorophyll-a (Chl-a) concentration is one of the most important parameters for evaluating the state of water environments, which often vary markedly across both time and space. Here we propose a hybrid algorithm for retrieving the Chl-a values from in situ remote sensing data. This hybrid algorithm contains three individual Chl-a estimation al...
Article
Euphotic zone depth (${Z_{{rm{eu}}}}$), defined as the depth where photosynthetic available radiation (PAR) is 1% of its surface value, is of great importance in studies of water biogeochemical processes. Satellite remote sensing is a powerful technique to obtain ${Z_{{rm{eu}}}}$, as it can cover large areas at very frequent intervals. Several remo...
Article
An extensive investigation of particulate radiocaesium in suspended solids and dissolved radiocaesium in river water was undertaken at 30 sites in Fukushima and Miyagi Prefectures in December 2012, and their relationships with catchment inventory and the solid/liquid distribution coefficient (Kd) were evaluated. Rivers located in the coastal region...
Article
To explore the behavior of radionuclides released after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in March 2011, and the distribution of radiocesium in paddy fields, we monitored radiocesium (Cs) and suspended sediment (SS) discharge from paddy fields. We proposed a rating scale for measuring the effectiveness of surface soil remo...
Article
Radiocaesium wash-off associated with soil erosion in different land use was monitored using USLE plots in Kawamata, Fukushima Prefecture, Japan after the Fukushima Dai-ichi Nuclear Power Plant accident. Parameters and factors relating to soil erosion and (137)Cs concentration in the eroded soil were evaluated based on the field monitoring and pres...
Article
Remote estimation of the vertically averaged diffuse attenuation coefficient over a water layer $overline{K}_{d}(lambda)$ is of great importance in understanding and modeling the physical, chemical, and biological processes in water bodies. A semianalytical algorithm was previously proposed to remotely estimate $overline{K}_{d}( lambda)$ based on t...
Conference Paper
Soil erosion is the initial process which drives radiocesium into the aquatic systems and therefore the quantifi-cation of radiocesium wash-off associated with soil erosion is indispensable for mitigating the risks. This study presents two year's observation of soil erosion and radiocesium wash-off to quantify differences in radiocesium behavior in...
Article
Full-text available
This study used particle size analysis to investigate the initial accumulation and trap efficiency of radiocesium ((137)Cs) in four irrigation ponds, ~4-5 months after the Fukushima Dai-ichi nuclear power plant (DNPP) accident. Trap efficiency, represented by the inventory of (137)Cs in pond sediment to the inventory of radiocesium in soil surround...
Article
Full-text available
This study aimed to quantify the flux of radiocesium in the Abukuma Basin (5,172 km(2)), the largest river system affected by fallout from the Fukushima Daiichi Nuclear Power Plant (FDNPP) event. In the period from 10 August 2011 to 11 May 2012 an estimated 84 to 92% of the total radiocesium transported in the basin's fluvial system was carried in...
Conference Paper
Full-text available
Radioactive materials are generally associated with soil particles in terrestrial environment and therefore the better understanding soil erosion processes is expected to improve the mitigation of radioactive risks. Spatial variability in soil erosion has been one of critical issues for soil erosion management. This study attempts to track soil par...
Article
Full-text available
Surface soils, under various land uses, were contaminated by radionuclides that were released by the Fukushima Daiichi Nuclear Power Plant accident. Because paddy fields are one of the main land uses in Japan, we investigated the spatial distribution of radiocesium and the influence of irrigation water in a paddy field during cultivation. Soil core...
Article
Remote estimation of inherent optical properties (IOPs) for water bodies cannot only provide indicators of water quality, but also be used in the study on biological and biogeochemical processes of waters. The quasi-analytical algorithm (QAA) is a simple and effective method to retrieve IOPs from remote-sensing reflectance (Rrs). The QAA has been w...
Conference Paper
Previous experiences such as Chernobyl Nuclear Power Plant accident have confirmed that fallout radionuclides on the ground surface migrate through natural environment including soils and rivers. Therefore, in order to estimate future changes in radionuclide deposition, migration process of radionuclides in forests, soils, ground water, rivers shou...
Conference Paper
Radioactive contamination has been detected in Fukushima due to the nuclear accident at Fukushima Daiichi Nuclear Power Plant (NPP) following the earthquake and tsunami on 11 March 2011. Following comprehensive investigation (FMWSE project funded by MEXT, Japan; http://fmwse.suiri.tsukuba.ac.jp/) was conducted to confirm migration of radionuclides...
Article
Full-text available
Light environment variability was investigated in the two Japanese lakes Biwa and Kasumigaura, which offer a broad range of optical conditions in the water bodies due to their diverse morphometries and limnological characteristics. To elucidate their light environments, Secchi depths (SDs) were related to long-term monitored datasets of concentrati...
Article
The chlorophyll a-specific absorption coefficient () in a highly eutrophic lake can show characteristics distinct from that in the ocean due to the differences in the structure and composition of phytoplankton. In this study, investigated the variation of in Lake Kasumigaura, a highly eutrophic lake in Japan, in association with the package effect...
Article
A degradation experiment with zooplankton was carried out to investigate the diagenesis of zooplanktonic organic matter, lipids, and lipid classes. In addition, reactivities and the quantitative relation between bulk organic carbon and waxes (which are the biomarkers of zooplankton) were compared during the experiment to evaluate the possibility of...
Article
Natural phytoplankton populations were incubated with NaH13CO3 under light for 1 day, followed by incubation in the dark for 29 days to examine the degradation and dissolution of photosynthetically-produced organic carbon and lipid materials during early diagenesis. Organic matter obtained in this study was divided into two particulate fractions (0...

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