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Katata, Genki; Chino, Masamichi; Terada, Hiroaki; Kobayashi, Takuya; Ota, Masakazu; Nagai, Haruyasu; Kajino, Mizuo*
no journal, ,
We estimated a detailed time trend of atmospheric releases of radionuclides during the accident by using environmental monitoring data and coupling atmospheric and oceanic dispersion simulations by WSPEEDI-II and SEA-GEARN. New schemes for wet, dry, and fog depositions of the radioactive iodine gas and other particles were incorporated into WSPEEDI-II. The source term at the FNPP1 was estimated by the reverse estimation method based on the comparisons between calculations by the coupling models assuming unit release rate (1 Bq h
) and environmental data. The results suggested that the major release of radionuclides from the FNPP1 occurred in the following periods during March 2011: afternoon on the 12th when the venting and hydrogen explosion occurred at Unit 1, morning on the 13th after the venting event at Unit 3, midnight on the 14th when several openings of SRV were conducted at Unit 2, morning and night on the 15th, and morning on the 16th.
Katata, Genki; Held, A.*; Mauder, M.*
no journal, ,
The leaf wetness was monitored using electrical sensors directly clipped to living leaf surfaces of thin and broad-leaved grasses. The measurements were carried out at the pre-alpine grassland site in Germany from September 20 to November 8, 2013. Numerical simulations of a multi-layer atmosphere-SOiL-VEGetation model (SOLVEG) were carried out for analyzing the data. The model reproduced well the observed leaf wetness, surface fluxes and temperature, and soil temperature and moisture. In rain-free days, a typical diurnal cycle as a decrease and increase during the day- and night-time, respectively, was observed in leaf wetness data. The high wetness level was always monitored under rain, fog, and snowcover conditions. Leaf wetness was also often high in the early morning due to thawing of leaf surface water frozen during a cold night.
Katata, Genki; Mauder, M.*
no journal, ,
An existing multi-layer atmosphere-SOiL-VEGetation model (SOLVEG) developed by the authors was modified to simulate snow and frozen soil processes. The schemes of a multi-layer snow structure for heat and liquid water transports in snow and freeze-thaw processes of soil moisture were incorporated into the model. The performance of the modified model was tested at the pre-alpine grassland site in Germany. The modified model overall reproduced the temporal changes in observations of surface energy fluxes, albedo, snow depth and surface temperature, and soil temperature and moisture. The measured increases of soil water content due to infiltration of melted snow to the soil were simulated by the modified model. The observed large negative sensible and positive latent heat fluxes associated with the typical south foehn, a warm and dry downslope wind of the Alps, were also reproduced in the simulation.
Kitamura, Akihiro; Yamaguchi, Masaaki; Sato, Haruo; Yui, Mikazu
no journal, ,
Sediment and cesium 137 discharged into dams and reservoirs and accumulated onto onto dam and reservoir beds in eastern Fukushima prefecture after the Fukushima Dai-ichi accident are simulated by a simple and fast simulation model which we developed by the universal soil loss equation and the geographical information system. Modeling of soil erosion, transport and deposition, and cesium 137 dispersion were implemented. Annual soil loss from each dam basin, annual soil inflow into each dam, annual soil deposition in each dam, and annual soil discharge from each dam are simulated.
Sato, Haruo; Niizato, Tadafumi; Tanaka, Shingo*; Abe, Hironobu; Aoki, Kazuhiro
no journal, ,
This work was conducted as one of the researches relating to distribution maps of radiation dose rate etc. which the government has promoted as one of the counter-measures to the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011, and the 2nd investigation on the depth distribution of radionuclides (RNs) in soil was conducted after about 1 year from the accident, succeedingly to the 1st investigation which was conducted after about 3 months from the accident. Soil core samples to about 50 cm deep were taken at 11 locations in Kawamata-town and Namie-town. Sorption-desorption experiments of Cs-137 and I-131, CEC and AEC measurements and mineralogical analyses by XRD were conducted for 3 types of soils (sandy, clayey, organic) and those elutriated components (clay, silt, sand). Radiocaesium (Cs-134 and Cs-137) and Ag-110m were detected at all locations investigated and only at locations where radiation dose rate is high (east side than Akogi, Namie-town), respectively. Radiocaesium more than 95% and 99% of the inventory distributed within 5 cm and 10 cm deep in soil in the surface layer (mainly sandy soil), respectively. Whilst, radiocaesium more than 95% and 99% of the inventory distributed within 16 cm and 20 cm deep in organic soil and soil at locations where are supposed to have been used as farmland, respectively. Radiocaesium tended to extend to deeper parts in soil that organic and clayey soils are the support layer, particularly in organic soil, compared with the 1st investigation. Distribution coefficients of Cs-137 onto organic soil and its elutriated components were also lower than that onto other soils. This is consistent with trend of penetration profile.
Yamada, Susumu; Itakura, Mitsuhiro; Okumura, Masahiko; Machida, Masahiko; Kitamura, Akihiro
no journal, ,
no abstracts in English
Okumura, Masahiko; Nakamura, Hiroki; Machida, Masahiko
no journal, ,
no abstracts in English
Machida, Masahiko; Yamada, Susumu; Itakura, Mitsuhiro; Okumura, Masahiko; Kitamura, Akihiro
no journal, ,
Radioactive Cs recontamination brought about by deposition of silt and clay on river beds has been a central issue of environmental recovery problems in Fukushima prefecture after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. In fact, the river-side sediment monitored by using remote controlled helicopters and direct sampling measurements has been confirmed to be highly contaminated compared to the other areas, which just naturally decay. Such contamination transportation is especially remarkable in a few rivers in coastal areas of Fukushima prefecture, because their water and sediment are supplied from the highly contaminated area along the northwest direction from FDNPPs. Thus, we numerically study the sediment transportation in rivers by using 2D river simulation framework named iRIC developed by Shimizu et al. Consequently, we find that flood brought about by typhoon is mainly required for the massive transport and the sediment deposition in the flood plain is efficiently promoted by plants naturally grown on the plain. In this presentation, we reveal when and where the sediment deposition occurs in the event of floods through direct numerical simulations. We believe that the results are suggestive for the next planning issue related with decontamination in highly-contaminated evacuated districts.
Onuki, Toshihiko; Sakamoto, Fuminori; Kozai, Naofumi; Yamasaki, Shinya*; Yu, Q.
no journal, ,
In the present study, accumulation and chemical states change of Cs by unicellular fungus of Saccharomyces cerevisiae have been studied to elucidate the role of microorganisms in the migration of radiocesium in the environment. The accumulation experiments of radiocesium was carried out by using the agar medium containing 
Cs and a minerals. The order of accumulation of Cs in the cells was nearly the same as the inverse of distribution coefficient of mineral for Cs in the medium solution. These results indicate that the fungus accumulates radiocesium by competitively with minerals in the soils.