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Journal Articles

Isotopic signals in fracture-filling calcite showing anaerobic oxidation of methane in a granitic basement

Mizuno, Takashi; Suzuki, Yohei*; Milodowski, A. E.*; Iwatsuki, Teruki

Applied Geochemistry, 150, p.105571_1 - 105571_11, 2023/03

 Times Cited Count:1 Percentile:62.05(Geochemistry & Geophysics)

Anaerobic oxidation of methane (AOM) affects both the redox conditions and carbon cycle in groundwater. However, examples of studies on crystalline rock deep in terrestrial subsurface as well as the potential host rock for geological disposal are few. Therefore, we conducted a paleohydrogeological study on fracture-filling calcite in the Toki Granite. The $$delta$$$$^{18}$$O$$_{VPDB}$$ value (-32.7 to -0.59 permil) revealed that the groundwater that precipitated the calcite was groundwater derived from hydrothermal fluid, freshwater that came from the surface, and seawater that penetrated during marine transgression. On the other hand, $$delta$$$$^{13}$$C$$_{VPDB}$$ (-56.6 to 6.0 permil) was wider than the isotopic range of DIC that originated from hydrothermal, freshwater, and seawater sources (-25 to 2 permil). Calcite with $$delta$$$$^{13}$$C$$_{VPDB}$$ that was lighter than -25 permil was believed to have precipitated DIC, which was provided by AOM. In contrast to previous studies, the Mizunami AOM calcite was precipitated in a freshwater environment, indicating that various processes could have generated AOM in crystalline rocks deep in the terrestrial subsurface.

Journal Articles

Precipitation sequence of fracture-filling calcite in fractured granite and changes in the fractionation process of rare earth elements and yttrium

Mizuno, Takashi; Milodowski, A. E.*; Iwatsuki, Teruki

Chemical Geology, 603, p.120880_1 - 120880_16, 2022/08

 Times Cited Count:3 Percentile:56.2(Geochemistry & Geophysics)

This study has focused on the formation sequence and Rare earth elements with yttrium (REY) of fracture-filling calcite in the Toki Granite in the Mizunami area, central Japan. The morphological, chemical and isotopic characteristics of the calcite and chemistry of fluid inclusions reveal that the calcite in the Toki Granite can be differentiated into four discrete generations: Calcite I (oldest) to Calcite IV (most recent). The precipitation history of calcite reflects the changes in the hydrogeochemical regime of paleo-groundwaters, controlled by the evolution of groundwater by seawater infiltration associated with marine transgression and surface water infiltration associated with marine regression and uplift. The post-Archean average shale-normalized REY patterns in generations of calcite show no significant Ce anomaly, negative Eu anomaly, and light REY (LREY)-depleted pattern in dominates. These features are also common to the Toki Granite. The consistency of the features in each generation of calcite indicates that REY was supplied from the Toki Granite by water-rock interaction. The lack of a Ce anomaly in the calcite demonstrates that groundwaters have maintained reducing conditions during the calcite precipitation. However, the fractionation of LREY and heavy REY (HREY) in each generation of the calcite is more pronounced than in the granite. The fractionation process in the paleo-groundwaters from which each generation of calcite precipitated closely relates to the systematic variation of carbonate complex in REY series and/or pH in palaeo-groundwater. The findings of this study will be necessary for assessing the long-term safety of geological disposal of high-level radioactive waste.

JAEA Reports

Proceedings of debriefing session on JAEA's Underground Research Laboratory Projects, 2020

Shimizu, Mayuko; Amano, Kenji; Mizuno, Takashi; Hama, Katsuhiro

JAEA-Review 2021-004, 92 Pages, 2021/07


Japan Atomic Energy Agency (JAEA) has been conducting research and development (R&D) on geological disposal technology in order to establish a scientific and technological basis for the geological disposal of HLW. "Debriefing Session on JAEA's Underground Research Laboratory" was held online on December 1, 2020 by live stream on YouTube, in order to widely disseminate the results of R&D themes ("Important issues") that we have been focusing on from fiscal year 2015 to 2019 and the plans for 2020 and beyond, and to further enhance the research plan. This document summarizes the overview of the debriefing session and the presentation materials.

Journal Articles

Ecological and genomic profiling of anaerobic methane-oxidizing archaea in a deep granitic environment

Ino, Kohei*; Hernsdorf, A. W.*; Konno, Yuta*; Kozuka, Mariko*; Yanagawa, Katsunori*; Kato, Shingo*; Sunamura, Michinari*; Hirota, Akinari*; Togo, Yoko*; Ito, Kazumasa*; et al.

ISME Journal, 12(1), p.31 - 47, 2018/01

 Times Cited Count:49 Percentile:91.33(Ecology)

In this study, we found the dominance ofanaerobic methane-oxidizing archaea in groundwater enriched in sulfate and methane from a 300-m deep underground borehole in granitic rock.

Journal Articles

Consideration of methodology for estimating hydrochemistry based on results of resistivity logging in deep boreholes

Mizuno, Takashi; Iwatsuki, Teruki; Matsuzaki, Tatsuji*

Oyo Chishitsu, 58(3), p.178 - 187, 2017/08

no abstracts in English

Journal Articles

Determination of dissolved natural thorium and uranium in Horonobe and Mizunami Underground Research Laboratory groundwater and its thermodynamic analysis

Sasaki, Takayuki*; Kokami, Takayuki*; Kobayashi, Taishi*; Kirishima, Akira*; Murakami, Hiroaki; Amano, Yuki; Mizuno, Takashi; Iwatsuki, Teruki; Sasamoto, Hiroshi; Miyakawa, Kazuya

Journal of Nuclear Science and Technology, 54(3), p.373 - 381, 2017/03

Trace amounts of natural thorium and uranium in deep groundwater were investigated at two underground research laboratories situated at Horonobe and Mizunami, Japan. The groundwater was sampled from underground boreholes, and the colloid contribution was checked by in situ two size-fractionated ultrafiltration systems. A decrease in the concentration after in situ filtration suggested the presence of natural colloids and suspended matter that were carriers of a portion of the elements. The result of the Th and U concentrations in groundwater after 10 kDa filtration was analyzed thermodynamically using existing hydrogeological and geochemical data such as the mineral components in the groundwater at a given pH, ionic strength, concentration of co-existing ions, redox potential, and solid phase assumed. A crystalline solid phase made the solubility very low compared with that of the amorphous phase, and the solubility agreed well with the concentrations measured.

Journal Articles

Interaction of rare earth elements and components of the Horonobe deep groundwater

Kirishima, Akira*; Kuno, Atsushi*; Amamiya, Hiroki; Kubota, Takumi*; Kimuro, Shingo*; Amano, Yuki; Miyakawa, Kazuya; Iwatsuki, Teruki; Mizuno, Takashi; Sasaki, Takayuki*; et al.

Chemosphere, 168, p.798 - 806, 2017/02

 Times Cited Count:3 Percentile:10.21(Environmental Sciences)

For better understanding of the migration behavior of minor actinides (MA) in deep groundwater, the interaction of doped rare earth elements (REEs) and components in Horonobe deep groundwater was studied. Appx. 10 ppb of rare earth elements, i.e., Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm and Yb were doped to the sample groundwater collected from a packed sections in borehole drilled from 140 m depth experiment drift of Horonobe underground research laboratory (URL), Hokkaido, Japan. Then, that groundwater was sequentially filtrated by 0.2 micron pore filter, 10 kDa, 3 kDa and 1 kDa of nominal molecular weight limit (NMWL) ultrafilters by keeping inert condition. After that, the filtrate solutions were analyzed by ICP-MS to determine the concentrations of retained REEs at each filtration steps, while the used filters were analyzed by the neutron activation analysis (NAA) and TOF-SIMS element mapping to know the amount and chemical speciation of trapped fraction of the REEs on each filter. A remarkable relation between the retention ratios of REEs in the filtrate solutions and the ionic radius was observed, i.e., smaller rare earth element solves more in liquid phase under the Horonobe groundwater condition. NAA and TOF-SIMS analyses revealed that certain portions of REEs were trapped by 0.2 micron pore filters as rare earth phosphates which corresponded with the predicted predominant species by a chemical equilibrium calculation for the Horonobe groundwater condition, while small portions of colloidal REEs were trapped by 10 kDa and 3 kDa NMWL ultrafilters. The result suggested that phosphate anion plays an important role in the chemical behavior of REEs in saline (seawater based) groundwater, which could be referred for the prediction of migration behavior of trivalent actinide released from the repository of radioactive waste in far future.

Journal Articles

Retention of rare earth elements, thorium and uranium in sedimentary rocks; A Case study in the Horonobe area of Hokkaido, Japan

Murakami, Takuma; Sasamoto, Hiroshi; Mizuno, Takashi

Chikyu Kagaku, 50(4), p.299 - 317, 2016/12

Development of techniques for investigating the long-term migration of elements in deep underground is important with respect to safety assessment for the geological disposal of high-level radioactive waste. As one study of the migration of elements in deep underground, the distribution of REE, Th and U in sedimentary rock of Horonobe area in Hokkaido was investigated, and discussed whether the difference of hydrogeological structure and lithofacies influences on the distributions. As the results, it was considered that REE and Th were mainly retained in minerals originating from terrigenous clastic and secondary mineral occurred in early diagenesis, and their distributions were relatively homogenous in both the Koetoi and Wakkanai formations. Uranium was indicated to be maintained in the sedimentary rock until now after depositing in deep-sea sediment. It was considered that the U deposition was occurred by adsorption on organic matter and reductive precipitation with decomposition of organic matter. In addition, it was confirmed that the distributions of these elements were not influenced by the difference of hydrogeological and lithofacies.

Journal Articles

Deep microbial life in high-quality granitic groundwater from geochemically and geographically distinct underground boreholes

Ino, Kohei*; Konno, Yuta*; Kozuka, Mariko*; Hirota, Akinari*; Togo, Yoko*; Fukuda, Akari*; Komatsu, Daisuke*; Tsunogai, Urumu*; Tanabe, Akifumi*; Yamamoto, Satoshi*; et al.

Environmental Microbiology Reports (Internet), 8(2), p.285 - 294, 2016/04

 Times Cited Count:26 Percentile:68.59(Environmental Sciences)

To understand the subsurface biosphere, borehole investigation was conducted for 300-m deep granitic rocks at the Mizunami underground research laboratory, Japan. The initial biomass was the highest with the flourish of aerobic H$$_{2}$$-oxidizing Hydrogenophaga spp., whereas an uncultivated lineage of the phylum Nitrospirae became predominant after three years with decreasing biomass. The common occurrence of many species of Nitrospirae and Chlorobi phyla at the geographically distinct sites and the exclusive detection of their phylogenetically related environmental sequences from deep groundwaters and terrestrial hot springs, suggest that these bacteria are indigenous and potentially adapted to the deep terrestrial subsurface.

Journal Articles

Formation and geological sequestration of uranium nanoparticles in deep granitic aquifer

Suzuki, Yohei*; Mukai, Hiroki*; Ishimura, Toyoho*; Yokoyama, Takatomi*; Sakata, Shuhei*; Hirata, Takafumi*; Iwatsuki, Teruki; Mizuno, Takashi

Scientific Reports (Internet), 6, p.22701_1 - 22701_6, 2016/03

 Times Cited Count:14 Percentile:49.58(Multidisciplinary Sciences)

The stimulation of bacterial activities that convert hexavalent uranium to tetravalent uranium appears to be feasible for cost-effective remediation of contaminated aquifers. However, U(VI) reduction typically results in the precipitation of U(IV) particles less than 5 nanometers in diameter. Here we show that U(IV) nanoparticles of coffinite formed in fracture-filling calcium carbonate in a granitic aquifer. As the microbiologically induced precipitation of calcium carbonate in aquifer systems worldwide is extremely common, we anticipate simultaneous stimulation of microbial activities for precipitation reactions of calcium carbonate and U(IV) nanoparticles, which leads to long-term sequestration of uranium and other radionuclides in contaminated aquifers and deep geological repositories.

Journal Articles

Preparation and evaluation of an astatine-211-labeled sigma receptor ligand for $$alpha$$ radionuclide therapy

Ogawa, Kazuma*; Mizuno, Yoshiaki*; Washiyama, Koshin*; Shiba, Kazuhiro*; Takahashi, Naruto*; Kozaka, Takashi*; Watanabe, Shigeki; Shinohara, Atsushi*; Odani, Akira*

Nuclear Medicine and Biology, 42(11), p.875 - 879, 2015/11

 Times Cited Count:23 Percentile:70.83(Radiology, Nuclear Medicine & Medical Imaging)

JAEA Reports

Synthesized research report in the second mid-term research phase; Mizunami Underground Research Laboratory Project, Horonobe Underground Research Laboratory Project and Geo-stability Project

Hama, Katsuhiro; Mizuno, Takashi; Sasao, Eiji; Iwatsuki, Teruki; Saegusa, Hiromitsu; Sato, Toshinori; Fujita, Tomoo; Sasamoto, Hiroshi; Matsuoka, Toshiyuki; Yokota, Hideharu; et al.

JAEA-Research 2015-007, 269 Pages, 2015/08


We have synthesised the research results from Mizunami/Horonobe URLs and geo-stability projects in the second mid-term research phase. It could be used as technical bases for NUMO/Regulator in each decision point from sitting to beginning of disposal (Principal Investigation to Detailed Investigation Phase). High quality construction techniques and field investigation methods have been developed and implemented and these will be directly applicable to the National Disposal Program (along with general assessments of hazardous natural events and processes). It will be crucial to acquire technical knowledge on decisions of partial backfilling and final closure by actual field experiments in Mizunami/Horonobe URLs as main themes for the next phases.

Journal Articles

Proton order-disorder phenomena in a hydrogen-bonded rhodium-$$eta$$$$^{5}$$-semiquinone complex; A Possible dielectric response mechanism

Mitsumi, Minoru*; Ezaki, Kazunari*; Komatsu, Yuki*; Toriumi, Koshiro*; Miyato, Tatsuya*; Mizuno, Motohiro*; Azuma, Nobuaki*; Miyazaki, Yuji*; Nakano, Motohiro*; Kitagawa, Yasutaka*; et al.

Chemistry; A European Journal, 21(27), p.9682 - 9696, 2015/06

 Times Cited Count:7 Percentile:25.07(Chemistry, Multidisciplinary)

Journal Articles

Comparative study of granitic and sedimentary groundwater colloids by flow-field flow fractionation coupled with ICP-MS

Saito, Takumi; Hamamoto, Takafumi*; Mizuno, Takashi; Iwatsuki, Teruki; Tanaka, Satoru*

Journal of Analytical Atomic Spectrometry, 30(6), p.1229 - 1236, 2015/06

 Times Cited Count:13 Percentile:60.95(Chemistry, Analytical)

Size distribution and elemental compositions of colloids in granitic and sedimentary deep groundwater was determined by flow field flow fractionation (Fl-FFF) combined with ICP-MS. In the granitic groundwater organic colloids and various inorganic elements were found in limited size ranges ($$<$$10 nm and $$>$$140 nm). The presence of different types of organic colloids was suggested in this groundwater. Most of the inorganic elements exhibited similar size distributions at $$<$$10 nm, which were largely overlapped with organic colloids rich in fluorophores. In the sedimentary groundwater small organic and probably inorganic colloids were found at $$<$$5 nm together with relatively large inorganic colloids. Organic colloids in this groundwater were homogeneous in terms of their sizes and the compositions of chromohores and fluorophores. The size distribution of inorganic elements depended on their types, indicating the presence of different host colloidal phases for them.

JAEA Reports

Data of groundwater chemistry obtained in the Horonobe Underground Research Laboratory Project (2011-2013)

Sasamoto, Hiroshi; Yamamoto, Nobuyuki; Miyakawa, Kazuya; Mizuno, Takashi

JAEA-Data/Code 2014-033, 43 Pages, 2015/03


Development of technologies to investigate properties (conditions) of deep geological environment and models development of geological environment have been pursued in "Geoscientific Research" in the Horonobe underground research laboratory (Horonobe URL) project. A geochemical model of groundwater evolution which is a part of geological environment model requires the data of groundwater chemistry around the Horonobe URL for the development. This report summarizes the data obtained for 3 years (i.e., from the fiscal year 2011 to 2013), especially for the results for measurement of physico-chemical parameters and analysis of groundwater chemistry, in the Horonobe URL project.

Journal Articles

Biogeochemical signals from deep microbial life in terrestrial crust

Suzuki, Yohei*; Konno, Yuta*; Fukuda, Akari*; Komatsu, Daisuke*; Hirota, Akinari*; Watanabe, Katsuaki*; Togo, Yoko*; Morikawa, Noritoshi*; Hagiwara, Hiroki; Aosai, Daisuke*; et al.

PLOS ONE (Internet), 9(12), p.e113063_1 - e113063_20, 2014/12

 Times Cited Count:12 Percentile:34.33(Multidisciplinary Sciences)

We present multi-isotopic evidence of microbially mediated sulfate reduction in a granitic aquifer, a representative of the terrestrial crust habitat. Deep groundwater of meteoric origin was collected from underground boreholes drilled into the Cretaceous Toki granite, central Japan. A large sulfur isotopic fractionation of 20-60 permil diagnostic to microbial sulfate reduction is associated with the investigated groundwater containing sulfate below 0.2 mM. In contrast, a small carbon isotopic fractionation ($$<$$ 30 permil) is not indicative of methanogenesis. Our results demonstrate that the deep biosphere in the terrestrial crust is metabolically active and playing a crucial role in the formation of reducing groundwater even under low energy fluxes.

Journal Articles

Size and composition analyses of colloids in deep granitic groundwater using microfiltration/ultrafiltration while maintaining in situ hydrochemical conditions

Aosai, Daisuke*; Yamamoto, Yuhei*; Mizuno, Takashi; Ishigami, Toru*; Matsuyama, Hideto*

Colloids and Surfaces A; Physicochemical and Engineering Aspects, 461, p.279 - 286, 2014/11


 Times Cited Count:10 Percentile:25(Chemistry, Physical)

In studies of colloids in deep groundwater, a serious problem exists because the properties of the colloids are influenced by changes in the chemistry of groundwater upon exposure to the atmosphere and pressure release during sampling. Then, ultrafiltration technique, while maintaining in situ hydrochemical conditions was developed. As the result of the investigation using the method at the Mizunami underground Research Laboratory (MIU), different types of colloids consisting of inorganic and organic substances were observed and complex formation between the colloids and REEs was suggested. Furthermore, characteristic partitioning of REEs depending on colloids size was observed in complex natural environments without chemical disturbance. The current findings are useful for understanding migration of radionuclides.

JAEA Reports

Study of hydrogeology in the Mizunami Underground Research Laboratory Project; Hydrogeological modeling and groundwater flow simulation based on data of hydraulic and hydrochemical impacts during the construction of the MIU facilities; FY 2011

Onoe, Hironori; Maemura, Tsuneyuki*; Kimura, Hitoshi*; Hishiya, Tomoyuki*; Mizuno, Takashi; Takeuchi, Ryuji; Iwatsuki, Teruki

JAEA-Research 2014-010, 35 Pages, 2014/06


In this study, groundwater flow modeling based on the hydrogeological conceptual model was carried out using data of hydraulic responses and groundwater chemistry changes until 500m depth of MIU excavation. As a result of this study, trend of inflow rate into the MIU facilities and hydraulic and geochemical impacts around the MIU Construction Site caused by the MIU construction were reproduced in groundwater flow simulation. In addition, validation of the hydrogeological conceptual model was confirmed.

JAEA Reports

Study of hydrogeology in the Mizunami Underground Research Laboratory Project; Hydrogeological modeling and groundwater flow simulation based on data of hydraulic and geochemical impacts during the construction of the MIU facilities; FY 2010

Hishiya, Tomoyuki*; Maemura, Tsuneyuki*; Kimura, Hitoshi*; Onoe, Hironori; Saegusa, Hiromitsu; Mizuno, Takashi

JAEA-Research 2013-023, 84 Pages, 2013/11


In this study, hydrogeological modeling and groundwater flow simulations have been carried out in order to construct site descriptive model using data of hydraulic responses and groundwater chemistry changes until 460 m depth of MIU excavation. As a result of this study, the effect of hydraulic conductivity and flow porosity of hydrogeological structure to hydraulic and geochemical impacts due to the MIU excavation were confirmed. In addition, trend of inflow rate into the MIU facilities and hydraulic and geochemical impacts around the MIU Construction Site caused by the MIU construction could be reproduced.

Journal Articles

Sorption of Eu(III) on granite; EPMA, LA-ICP-MS, batch and modeling studies

Fukushi, Keisuke*; Hasegawa, Yusuke*; Maeda, Koshi*; Aoi, Yusuke*; Tamura, Akihiro*; Arai, Shoji*; Yamamoto, Yuhei*; Aosai, Daisuke*; Mizuno, Takashi

Environmental Science & Technology, 47(22), p.12811 - 12818, 2013/11

 Times Cited Count:27 Percentile:58.19(Engineering, Environmental)

Eu(III) sorption on granite was examined by the combined microscopic and macroscopic approaches. Polished thin sections of the granite were reacted with solutions containing 10 $$mu$$M of Eu(III) and analyzed using EPMA and LA-ICP-MS. The Eu enrichment up to 6 wt.% was observed on most of the biotite grains. The Eu-enriched parts commonly lose K, which is the interlayer cation of biotite, indicating that the sorption mode is cation exchange in the interlayer. Batch Eu(III) sorption experiments on granite and biotite powders were conducted. The macroscopic sorption behavior of biotite was consistent with that of granite. The obtained sorption edges can be reproduced reasonably by the modeling considering single-site cation exchange reactions. Granite is complex mineral assemblages. However, the combined microscopic and macroscopic approaches revealed that elementary reactions by single phase can be representative for the bulk sorption reaction in complex mineral assemblages.

276 (Records 1-20 displayed on this page)