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Iwatsuki, Teruki; Kato, Toshihiro; Nakata, Kotaro*; Hasegawa, Takuma*
no journal, ,
Water chemistry, isotopes and chlorofluorocarbons in groundwater down to a depth of 500 m were monitored in the Mizunami Underground Research Laboratory (MIU), Japan. The monitoring of water chemistry for more than 10 years shows the increase of shallow water infiltration in UHFD at depths between 200 - 400 m. Based on 3H and CFCs concentrations the mixing proportion of shallow groundwater was estimated up to about 50 %. On the other hand groundwater in LSFD at the depth of 500 m was identified relatively isolated condition from the hydraulic disturbance by the facility construction. The residence time of the isolated groundwater was estimated 18 - 25 ka by C.
Otosaka, Shigeyoshi; Kobayashi, Takuya
no journal, ,
The Cs abundance in surface sediment in the coast off Fukushima decreased at the rate of about 30%/year. In this study, we assessed the three processes, (1) vertical mixing of sediment, (2) offshore transport of
Cs bound particles, and (3) desorption of
Cs from sediment, that may affect the decrease in the
Cs abundance. The process (1) was assessed by applying time-series data of vertical distribution of sedimentary
Cs into a pulse input sediment mixing model. The model estimated up to 70% of
Cs in the coastal sediment was efficiently transported to the lower sedimentary layers in the first 5 years after accident. In conclusion, we consider that the primary process decreasing the
Cs abundance in surface sediment is vertical mixing of sediment due to bioturbation or storm events.
Sueoka, Shigeru; Shimada, Koji; Ishimaru, Tsuneari; Niwa, Masakazu; Yasue, Kenichi; Umeda, Koji; Danhara, Toru*; Iwano, Hideki*
no journal, ,
no abstracts in English
Sasamoto, Hiroshi; Ohara, Shigeru*
no journal, ,
In the present study, a non-destructive technique using Particle Tracking Analysis (PTA) has been tested to determine size distribution and concentration of colloids in groundwater. The groundwaters were sampled from water-rings (4 samples) located in the vertical shafts and boreholes (6 samples) drilled in the drifts of the Horonobe URL. Results suggest that colloid particle concentrations range from 9.110
to 7.8
10
particle/mL (pt/mL) and the estimated colloid mass concentrations range from 3.4
10
to 4.2 mg/L for the diameter of 1 to 1000 nm, respectively. Colloid concentrations of groundwater sampled from water-rings are generally higher than those sampled from boreholes due to differences in groundwater sampling conditions. For sizes
100 nm of particles, colloid stability was evaluated on the basis of DLVO theory. DLVO theory predicts that particle sizes
100 nm would be unstable (i.e., coagulation could occur). Particle and mass colloid concentrations in the groundwater were therefore reevaluated to obtain the reliable colloid particle concentrations range from 5.8
10
to 3.0
10
pt/mL and colloid mass concentrations range from 2.0
10
to 1.3
10
mg/L for the diameter range
100 nm, respectively. Furthermore, the reevaluated results indicate a negative correlation between colloid concentrations and IS of groundwater.
Tamura, Hajimu; Kokubu, Yoko; Umeda, Koji
no journal, ,
JAEA installed an IsotopX NGX noble gas mass spectrometer with an water sample oriented preparation system in Tono Geoscience Center to measure helium accumulation age and neon isotope ratio of ground water for estimation of ground water stability on long term geological stability survay on geological disposal of nuclear waste. High precision isotope analysis by multi-collector mass spectrometer is neccessary tool for neon isotope analysis of young ground water due to small isotopic variation of neon for nucleogenic reaction or mixing of volcanic fluids in ground water. NGX-004 was configured for simultanous measurement of neon isotopes with 2 faradays for Ne and
Ne, and 1 SEM for
Ne spaced out 1 m/z each other. 10.084
0.002 of
Ne/
Ne and 0.02598
0.00004 of
Ne/
Ne were obtained by
ohm faraday and
ohm faraday, and ion count and
ohm faraday, which is able to resolve 0.2% difference.
Watanabe, Takahiro; Nara, Fumiko*; Matsunaka, Tetsuya*; Minoura, Koji*; Kakegawa, Takeshi*; Yamasaki, Shinichi*; Tsuchiya, Noriyoshi*; Nakamura, Toshio*; Junbo, W.*; Liping, Z.*
no journal, ,
Understanding of past environmental and geochemical changes is significant issues to estimate global climate variation. Therefore, these changes have been studied by continuous terrestrial sediments. The high-time resolution past environmental changes, especially monsoon fluctuations, have been reported in previous studies using geochemical signatures in stalagmites from Asian caves. However, continuous climate records in Tibetan plateau have not yet been cleared, which a key area to understand mechanism of monsoon fluctuations. In this study, mean grain size and geochemical proxies from lake sediment cores from south Tibetan plateau were used for estimation of past monsoon changes during Holocene. Spectral analysis of the mean grain size in the Tibetan lake indicated 1000-1500 years climate cycles, which might be caused by the changes in solar activities. These monsoon fluctuations based on the mean grain size were also supported by geochemical proxies in this study.
Nara, Fumiko*; Yamasaki, Shinichi*; Watanabe, Takahiro; Tsuchiya, Noriyoshi*; Miyahara, Hiroko*; Kato, Takenori*; Minoura, Koji*; Kakegawa, Takeshi*
no journal, ,
High-time resolution measurements of the major and trace inorganic elements, such as Rb and Sr, from the Lake Baikal sediment core was carried out to estimate the weathering response and the material provenance in the lake watershed. The fluctuations of the Rb/Sr ratio and mean grain size (MGS) during the Holocene were corresponding with each other. The similar profiles between the Rb/Sr ratio and the MGS from loess sediment in China have been observed in previous study. These results imply that the Rb/Sr ratio can be used as the proxy to estimate the East Asian winter monsoon intensity.
Walker, C.; Arthur, R. C.*; Wakiya, Arata; Suto, Shunkichi; Sasamoto, Hiroshi; Oda, Chie; Mihara, Morihiro; Honda, Akira
no journal, ,
The JAEA thermodynamic database for reactions between groundwater, cement, clay, zeolite and/or rock forming minerals Summary: Reactions between groundwaters, cement, clay, zeolite and/or rock forming minerals will control the geochemical evolution of a repository built for the geological disposal of radioactive waste in Japan. JAEA has therefore developed a thermodynamic database (TDB) to simulate and assess the impact of these different reactions on the safety and performance of the repository. The thermodynamic properties of all relevant items have been written into formats supporting the geochemical computer programs SUPCRT92, Geochemists Workbenchtextregistered and PHREEQC.
Miyakawa, Kazuya; Ishii, Eiichi; Mizuno, Takashi; Hirota, Akinari*; Komatsu, Daisuke*; Ikeya, Kosuke*; Tsunogai, Urumu*
no journal, ,
no abstracts in English
Yokoyama, Tatsunori; Kokubu, Yoko; Murakami, Hiroaki; Watanabe, Takahiro; Hirata, Takafumi*; Sakata, Shuhei*; Danhara, Toru*; Iwano, Hideki*; Maruyama, Seiji*; Miyazaki, Takashi*; et al.
no journal, ,
Chronological and geochemical studies of carbonates, which are commonly found as fracture filling minerals in rocks, can provide information about geochemical conditions present during formation including in deep subsurface environments. A dating technique for the carbonates using laser ablation-multiple collector-inductively coupled plasma mass spectrometry (LA-MC-ICPMS) is still immature partly because of a lack of a consensus international carbonate standard for the in-situ dating technique. In this study, we performed a survey on the carbonate standard materials that may be suitable for high precision U-Th-Pb dating using LA-MC-ICPMS. We examined carbonate standard materials JCp-1 and JCt-1 issued by the Geological Survey of Japan (GSJ). Based on solution-based bulk analysis using MC-ICP-MS, heterogeneities in Pb isotope compositions were confirmed. Nevertheless, the 206Pb-based isotopic compositions were all within 1.2 per mill variations acceptable for a standard used for age determination using LA-MC-ICPMS. Additional tests on the heterogenities in U-Th-Pb compositions of the carbonate standards along with determinations of other trace elements using a 2D imaging LA-ICP-MS are ongoing. Examinations on both natural standards and synthetic standards are ongoing for further efforts in determination of the standard suitable for U-Th-Pb dating of carbonates.
Ishii, Yasuo; Watanabe, Takayoshi; Oyama, Takuya; Sasaki, Yoshito; Abe, Hironobu; Mitachi, Katsuaki; Niizato, Tadafumi
no journal, ,
Mountainous forest is currently one of the most important sources of radioactive cesium released from the Fukushima Daiichi Nuclear Power Plant accident in Fukushima prefecture, which was covered approximately 70% of the land area by the forest. This study reports the changes in concentrations of radioactive cesium in sediments outflowed from the steep mountainous forest of the Abukuma Mountains, Fukushima, during September - December 2015.
Mizuno, Takashi
no journal, ,
Sakuma, Kazuyuki; Malins, A.; Machida, Masahiko; Kitamura, Akihiro
no journal, ,
Amano, Kenji; Alexander, W. R.*
no journal, ,
For the purpose of improving the reliability of geological environment models, we have developed newly modelling methods that to be able to evaluate groundwater flow regime affected by natural events and processes. In addition to that, some approaches for reduction uncertainties in long-term groundwater flow simulations are proposed by the actual hydrochemical data obtained from the boreholes in the Horonobe Town, Hokkaido.
Malins, A.; Sakuma, Kazuyuki; Nakanishi, Takahiro; Machida, Masahiko; Kitamura, Akihiro
no journal, ,
Wakiyama, Yoshifumi*; Manome, Ryo*; Onda, Yuichi*; Yoshimura, Kazuya
no journal, ,
Sanial, V.*; Buesseler, K. O.*; Charette, M.*; Casacuberta, N.*; Castrillejo, M.*; Henderson, P.*; Juan Diaz, X.*; Kanda, Jota*; Masque, P.*; Nagao, Seiya*; et al.
no journal, ,
Radiocesium activities in the coastal ocean off Fukushima dropped by orders of magnitude within one year after the accident of Fukushima Dai-ichi Nuclear Power Plant (FDNPP), but have remained relatively constant over the past 5 years exceeding background values. We investigated distribution of radiocesium in surface seawater and submarine groundwater along the Fukushima coast in October 2015. Our highest radiocesium activities were not found in the ocean, but in groundwater samples underlying coastal beaches 35 km south from the FDNPP. This may be due to sorption of the extremely contaminated waters on to beach sands/clays early after the accident and subsequent desorption back in to the ocean. Submarine groundwater discharge, which is widely recognized to be an important vector for the transport of chemicals from land to ocean, is thus a non-negligible path for transport of Fukushima-derived radionuclides to the ocean.
Kozai, Naofumi; Sakamoto, Fuminori; Tanaka, Kazuya; Sato, Takahiro; Kamiya, Tomihiro
no journal, ,
When living Paramecium cells were exposed to a U(VI) aqueous solution, U was hardly detected in the cells, while U was clearly detected in the Paramecium cells that were pre-killed with a fixative before exposure to the U aqueous solution. The U in the liquid phase after the experiment was found to bound to a large soluble glycoprotein to form pseudocolloid. We discuss the relation between these results and the soluble glycoprotein covering the cell surface of Paramecium.
Kato, Tomoaki; Onuki, Toshihiko; Yu, Q.
no journal, ,
Various radionuclides were released into seawater by the accident of the Fukushima Daiichi Nuclear Power Plant. We need to establish techniques to eliminate such radionuclides from the contaminated seawater. Mn oxides are known to sorb various metal ions. Mn oxides can be produced by reduction of MnO using biomass (biomass-MnOX) although there is little information on metal uptake mechanisms during the formation of biomass-MnOX. In this research, we investigated the uptake of Sr
during the formation of biomass-MnOX produced by reduction of KMnO
with cells of Pseudomonas fluorescens. After inoculating the cells into the Mn(VII) and Sr
containing solution, blackish precipitates were formed in the bottom. EXAFS analysis of Sr
in the precipitates showed that the presence of Mn around Sr, indicating that Sr was formed inner-sphere complex with Mn during coprecipitation.
Tanaka, Kazuya; Tani, Yukinori*; Onuki, Toshihiko*
no journal, ,
We investigated sorption of rare earth elements (REEs) and actinides on biogenic Mn oxide. Sorption experiments of REEs showed a negative Ce anomaly under circumneutral conditions. SEC-HPLC-ICP-MS analysis confirmed that Ce was complexed with organic ligands in solution. A line of data indicates that the negative Ce anomaly under circumneutral pH conditions arose from Ce(III) oxidation on biogenic Mn oxide and subsequent complexation of Ce(IV) with biomolecules. Th(IV) was sorbed, and then desorbed from biogenic Mn oxide with time. The desorption of Th(IV) is possibly attributed to organic ligands released from fungal cells as observed in the Ce sorption. In contrast, sorption of Pu(IV) increased with time, which was similar to that of U(VI). Plutonium(IV) was possible to be oxidized to Pu(VI) by Mn oxide. Sterilized biogenic Mn oxide did not show the desorption behavior of Th(IV), indicating that living cells would release organic ligands strongly complexed with Th(IV).
Okumura, Masahiko; Nakamura, Hiroki; Machida, Masahiko
no journal, ,
no abstracts in English