Performance information

• Overview of the Special Issue “Progress of Earth and Data Sciences Research into Tsunami Deposits, and Contribution to Tsunami Disaster Prevention (Part II): Novel Analytical Techniques and Data Processing for Tsunami Deposits”
  Noriyoshi TSUCHIYA; Takeshi KOMAI; Kengo NAKAMURA
  Journal of Geography (Chigaku Zasshi), Volume：132, Number：5, First page：363, Last page：364, Oct. 2023, [Reviewed], [Invited]
  Tokyo Geographical Society, Japanese, Scientific journal
  DOI：https://doi.org/10.5026/jgeography.132.363
  DOI ID：10.5026/jgeography.132.363, ISSN：0022-135X, eISSN：1884-0884
• Statistical Correlation for Geological Layers Using XRF Core Scan Data: Proof of Concept in Application to Tsunami Deposits
  Tatsu KUWATANI; Toshimoto SAKAI; Kengo NAKAMURA; Takeshi KOMAI
  Journal of Geography (Chigaku Zasshi), Volume：132, Number：5, First page：367, Last page：384, Oct. 2023, [Reviewed], [Invited]
  Tokyo Geographical Society, Japanese, Scientific journal
  DOI：https://doi.org/10.5026/jgeography.132.367
  DOI ID：10.5026/jgeography.132.367, ISSN：0022-135X, eISSN：1884-0884
• Estimating Layer Boundaries of Mixed-layer Tsunami Deposits with a XRF Core Scanner
  Kengo NAKAMURA; Tatsu KUWATANI; Takeshi KOMAI
  Journal of Geography (Chigaku Zasshi), Volume：132, Number：5, First page：403, Last page：415, Oct. 2023, [Reviewed], [Invited]
  Tokyo Geographical Society, Japanese, Scientific journal
  DOI：https://doi.org/10.5026/jgeography.132.403
  DOI ID：10.5026/jgeography.132.403, ISSN：0022-135X, eISSN：1884-0884
• Machine Learning-based Geochemical Discrimination Method for Tsunami Deposits and a Simple Determination System
  Shuta SATO; Takeshi KOMAI; Kengo NAKAMURA; Noriaki WATANABE
  Journal of Geography (Chigaku Zasshi), Volume：132, Number：5, First page：385, Last page：402, Oct. 2023, [Reviewed], [Invited]
  Tokyo Geographical Society, Japanese, Scientific journal
  DOI：https://doi.org/10.5026/jgeography.132.385
  DOI ID：10.5026/jgeography.132.385, ISSN：0022-135X, eISSN：1884-0884
• Overview of the Special Issue “Progress of Earth and Data Sciences Research into Tsunami Deposits, and Contribution to Tsunami Disaster Prevention (Part I): Paleoevironmental Analysis and Disaster Prevention Education Using Tsunami Deposits”
  Noriyoshi TSUCHIYA; Takeshi KOMAI; Kengo NAKAMURA
  Journal of Geography (Chigaku Zasshi), Volume：132, Number：4, First page：265, Last page：268, Aug. 2023
  Tokyo Geographical Society, Scientific journal
  DOI：https://doi.org/10.5026/jgeography.132.265
  DOI ID：10.5026/jgeography.132.265, ISSN：0022-135X, eISSN：1884-0884
• CO2 Injection-Induced Shearing and Fracturing in Naturally Fractured Conventional and Superhot Geothermal Environments
  Eko Pramudyo; Ryota Goto; Kiyotoshi Sakaguchi; Kengo Nakamura; Noriaki Watanabe
  Rock Mechanics and Rock Engineering, Mar. 2023, [Reviewed]
  Abstract
  
  This study elucidates the possibility of CO₂ injection-induced formation of a complex cloud-fracture network (CFN) in granite, along with shearing (shear slip) of natural pre-existing fractures under conventional (~ 150–300 °C) and superhot (> ~ 400 °C) geothermal conditions, potentially providing additional connecting flow paths between the stimulated natural fractures. Here, we conduct a set of experiments under triaxial stress states at 150 °C and 450 °C on cylindrical granite samples containing a sawcut (representing a natural fracture) inclined 45° from the sample’s axis. CO₂ injection induced dynamic shear slip on the sawcut, with higher slip velocities at 150 °C owing to the higher elasticity of the rock than that at 450 °C. The lower viscosity of CO₂ also allowed it to more uniformly pressurize the sawcut, resulting in higher slip velocities and slip displacements compared with those based on water injection in the 150 °C experiments. This implies that under conventional geothermal conditions, CO₂ injection can stimulate the same volume of rock as that of water injection at lower injection-well pressures. The CFNs then formed via CO₂ injection at pressures similar to those predicted by the Griffith failure criterion as the sawcut shear slip progressed at both experimental temperatures. The experiments also revealed potential challenges associated with CO₂ injection in naturally fractured geothermal environments, such as narrow aperture CFNs, owing to decreasing differential stress during their formation; all these factors should be addressed in future research.
  Springer Science and Business Media LLC, English, Scientific journal
  DOI：https://doi.org/10.1007/s00603-022-03153-7
  DOI ID：10.1007/s00603-022-03153-7, ISSN：0723-2632, eISSN：1434-453X, ORCID：124624078
• Effectiveness and characteristics of atmospheric CO2 removal in croplands via enhanced weathering of industrial Ca-rich silicate byproducts
  Rina Yoshioka; Kengo Nakamura; Ryota Sekiai; Jiajie Wang; Noriaki Watanabe
  Frontiers in Environmental Science, Volume：10, First page：1068656, Nov. 2022, [Reviewed]
  Enhanced weathering of industrial Ca-rich silicate byproducts in croplands is potentially profitable for large-scale atmospheric CO₂ removal; during the weathering process, CO₂ dissolves to form HCO₃⁻ and CO₃²⁻ in alkaline soil pore water, which eventually flows into the ocean. However, the effectiveness of such systems is still in doubt, owing to the unrealistic models used for prediction and the insufficient consideration of the dynamic influences of soils on fluid chemistry. We determined the effectiveness of such systems for atmospheric CO₂ removal, along with their characteristics, through a set of batch- and flow-through-type laboratory experiments, using andosol and decomposed granite soil as agricultural and non-agricultural soils, respectively, and Portland cement, steelmaking slag, and coal fly ash as industrial byproducts. The results of the batch-type experiments demonstrated that agricultural soils were suitable for CO₂ removal, owing to their moderately high pH and Ca concentrations in pore water that prevented intensive calcium carbonate precipitation. The flow-through experiments demonstrated that a higher Ca-content byproduct can have a large atmospheric CO₂ removal capacity. However, the magnitude of CO₂ removal and its time-dependent behavior were difficult to predict because they were not in conjunction with the changes in the average pH value. This indicated that the diffusive transport of CO₂ from the atmosphere-soil interface to deeper soils was more complex than expected. Maximizing CO₂ removal requires a better understanding of the diffusive transport of CO₂ through gas-filled pore spaces, created by unsteady-state air–water two-phase flow, due to intermittent rainfall.
  Frontiers Media SA, English, Scientific journal
  DOI：https://doi.org/10.3389/fenvs.2022.1068656
  DOI ID：10.3389/fenvs.2022.1068656, eISSN：2296-665X
• Influence of non-uniform flow on toxic elements transport in soil column percolation test　　　　　　　　　　　　　　　
  Kyouhei Tsuchida; Kengo Nakamura; Noriaki Watanabe; Takeshi Komai
  Heliyon, Volume：8, Number：11, First page：e11541, Last page：e11541, Nov. 2022
  Elsevier BV, Scientific journal
  DOI：https://doi.org/10.1016/j.heliyon.2022.e11541
  DOI ID：10.1016/j.heliyon.2022.e11541, ISSN：2405-8440, ORCID：122496674
• Erratum to “CO2 injection-induced complex cloud-fracture networks in granite at conventional and superhot geothermal conditions” [Geothermics 97 (2021) 102265] (Geothermics (2021) 97, (S0375650521002224), (10.1016/j.geothermics.2021.102265))　　　　　　　　　　　　　　　
  Eko Pramudyo; Ryota Goto; Noriaki Watanabe; Kiyotoshi Sakaguchi; Kengo Nakamura; Takeshi Komai
  Geothermics, Volume：101, May 2022
  DOI of original article: 10.1016/j.geothermics.2021.102265 The publisher regrets for using an incorrect mathematical symbol for Eq. (2), incorrect layouts for Tables 1-3, inconsistent citation formats, and made a number of typographic errors. The correct Eq. (2), Tables 1-3, citation formats, and typographies, are as follows. [Formula presented] Introduction section, 4th paragraph: “Goto et al. (Goto et al., 2021) clarified” “according to Eqs (1) and (2)” Section 2.2., 2nd paragraph: “developed by Watanabe et al. (Watanabe et al., 2019; Goto et al., 2021)” Section 3.1, 2nd paragraph: “Watanabe et al. (Watanabe et al., 2017b) suggested” Section 3.2.1., 6th paragraph: “in both Ishida et al. (Ishida et al., 2016) and Isaka et al. (Isaka et al., 2019)” “Ishida et al. (Ishida et al., 2016) oriented” 7th paragraph: “in Isaka et al. (Isaka et al., 2019)” Section 3.3., 1st paragraph: “Goto et al. (Goto et al., 2021) also revealed” 2nd paragraph: “Goto et al. (Goto et al., 2021) indicated” “Cladouhos et al. (Cladouhos et al., 2018) found” 5th paragraph: “Rose et al. (Rose et al., 2010) demonstrated” The publisher would like to apologise for any inconvenience caused. The authors regret that the caption of Fig. 1 is incorrect. 1 “hydraulic fracturing of granite 450 °C” should be replaced with “hydraulic fracturing of granite at 450 °C”.2 “using uncrossed (d–f) polarized, (g–i) crossed polarized, and (j–l) UV light” should be replaced with “using (d, g, j) uncrossed polarized, (e, h, k) crossed polarized, and (f, i, l) UV light”.The publisher would like to apologise for any inconvenience caused.
  Scientific journal
  DOI：https://doi.org/10.1016/j.geothermics.2021.102340
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  DOI ID：10.1016/j.geothermics.2021.102340, ISSN：0375-6505, SCOPUS ID：85124662575
• Potentially toxic elements pose significant and long-term human health risks in river basin districts with abandoned gold mines
  Arie Pujiwati; Kengo Nakamura; Jiajie Wang; Yoshishige Kawabe; Noriaki Watanabe; Takeshi Komai
  Environmental Geochemistry and Health, Volume：44, Number：2, First page：Article 00149R2, Mar. 2022, [Reviewed]
  Gold (Au) mining area is known to be one of the major sources of toxic elements; however, the potential risks of toxic elements from abandoned Au mines to the surrounding river basin districts and human exposure pathways to toxic elements need to be clarified. In this study, the distribution and mobilities of nine toxic elements (As, Cd, Cu, Pb, Sb, Zn, Cr, Ni and V) in Kesennuma City, Tohoku Region in Japan, a typical Au-mining district with several river basins, were studied through a geochemical survey (including element total concentrations and water-/acid-leaching concentrations determinations, as well as GB calculations), and environmental assessment on these elements in soil, river sediment, and river water samples from the study area. The contamination evaluation by index of geo-accumulation (Igeo) and enrichment factor (EF) suggested that As, Cu, Ni and Sb enrichments were greatly observed in the vicinity of the abandoned Au mines; moreover, calculated GB upper values for Cu in the river sediment surpass that of Tohoku Region. It has been found in this study that each element has particular mobility, which eventually influences its exposure pathway to humans. For instance, As in soil and sediment poses adverse non-carcinogenic risks and unacceptable carcinogenic risks to especially children mainly through groundwater ingestion. To minimize the potential risks associated with exposure to toxic elements in Au-mining districts, effective risk management measures should be implemented around river system by Au-mining companies even after their long-time closures, based on the consideration of each element’s mobility.
  Springer Science and Business Media LLC, English, Scientific journal
  DOI：https://doi.org/10.1007/s10653-022-01229-5
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  DOI ID：10.1007/s10653-022-01229-5, ISSN：0269-4042, eISSN：1573-2983, SCOPUS ID：85125899330
• Role of water in unexpectedly large changes in emission flux of volatile organic compounds in soils under dynamic temperature conditions　　　　　　　　　　　　　　　
  Asma Akter Parlin; Monami Kondo; Noriaki Watanabe; Kengo Nakamura; Jiajie Wang; Yasuhide Sakamoto; Takeshi Komai
  Scientific Reports, Volume：12, Number：1, First page：4418, Mar. 2022, [Reviewed]
  Abstract
  
  Understanding the diffusive transport behavior of volatile organic compounds (VOCs) in near-surface soils is important because soil VOC emissions affect atmospheric conditions and climate. Previous studies have suggested that temperature changes affect the transport behavior; however, the effect of these changes are poorly understood. Indeed, under dynamic temperature conditions, the change in VOC flux is much larger than that expected from the temperature dependency of the diffusion coefficient of VOCs in air. However, the mechanism is not well understood, although water in soil has been considered to play an important role. Here, we present the results of experiments for the upward vertical vapor-phase diffusive transport of two VOCs (benzene and tetrachloroethylene) in sandy soil under sinusoidal temperature variations of 20–30 °C, as well as its numerical representation. The results clarify that the unexpectedly large changes in emission flux can occur as a result of changes in the VOC concentration gradient due to VOC release (volatilization) from/trapping (dissolution) into water, and that such flux changes may occur in various environments. This study suggests the importance of a global evaluation of soil VOC emissions by continuous measurements in various soil environments and/or predictions through numerical simulations with thorough consideration of the role of water in dynamic soil environments.
  Springer Science and Business Media LLC, English, Scientific journal
  DOI：https://doi.org/10.1038/s41598-022-08270-5
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  DOI ID：10.1038/s41598-022-08270-5, eISSN：2045-2322, PubMed ID：35292685, SCOPUS ID：85126222541
• A geochemical approach for source apportionment and environmental impact assessment of heavy metals in a Cu–Ni mining region, Botswana　　　　　　　　　　　　　　　
  Fiona Motswaiso; Jiajie Wang; Kengo Nakamura; Noriaki Watanabe; Takeshi Komai
  Environmental Earth Sciences, Volume：81, Number：5, Mar. 2022
  Soil pollution by heavy metals is increasing continuously in developing countries due to industrial activities such as mining. This study addresses the distribution, potential risk to human health, and ecological risk of heavy metals (Cu, Ni, Cr, Co and Zn) taken from the soil in the vicinity of a relinquished Cu–Ni mine in Selibe Phikwe, Botswana. Furthermore, source apportionment of heavy metals was also conducted through Positive Matrix Factorization (PMF). The geochemical analysis results showed that the mean Cu, Ni, Cr, Pb, Co and Zn concentrations in the soil reached 141.65, 132.30, 87.64, 4.30, 8.97 and 37.15 mg/kg, respectively. Although Hazard Quotient (HQ) calculations results suggest that non-cancerous risks of the target heavy metals are low under the present conditions, the Hazard Index (HI) calculation results indicate a potential non-carcinogenic risk of Cr (HI > 1) for children. The mean values for cancer risk (CRtotal) also reached 3.00 × 10–5 in children and 5.59 × 10–5 in adults. The findings also suggested a potential ecological risk resulting from Cu and Ni in the region. The PMF model effectively revealed that Pb, Zn, and Co were mainly geologic, while anthropogenic sources were primarily responsible for the Cr, Ni, and Cu enrichment in soils. This study suggests that inexpensive risk mitigation efforts such as phyto-capping should be implemented, particularly in areas with slag piles and tailings dams.
  Scientific journal
  DOI：https://doi.org/10.1007/s12665-021-10158-y
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  DOI ID：10.1007/s12665-021-10158-y, ISSN：1866-6280, eISSN：1866-6299, SCOPUS ID：85125283727
• Significance of soil moisture on temperature dependence of Hg emission　　　　　　　　　　　　　　　
  S. Zhao; A. Terada; K. Nakamura; M. Nakashima; T. Komai; S. Riya; M. Hosomi; H. Hou
  Journal of Environmental Management, Volume：305, Mar. 2022
  Soil moisture is a key factor for mercury (Hg) emission from soil. Despite its significance for Hg emissions, the effect of soil moisture on Hg flux and fractions has not been thoroughly investigated. The objective of this study was to elucidate the influences of soil moisture and temperature on Hg fluxes from soils and Hg fractions. A kinetic study was performed to measure Hg emission fluxes of six soil samples under different temperature (T) (15 °C, 20 °C, 25 °C, 30 °C, and 35 °C) and moisture conditions (0%, 10%, and 20% added water). The results showed that the Hg fluxes increased with increases in T and soil moisture. A linear correlation was found between ln (Hg emission flux) and 1/T for the six soil samples at different moisture contents (R2 = 0.73–0.99). The range of activation energy (Ea) values was 25.31–57.86 kJ/mol. The Hg fractions in soils of different moisture content were determined by a sequential extraction method. The results demonstrated that soil moisture affected the Hg fractions in soils. The Ea values had different relationships with soil moisture in different soils. There were correlations between Ea and the elemental and mercuric sulfide fractions for air-dried soils. However, for moist soils, Ea was negatively correlated with the water-soluble and acid-soluble fractions. Collectively, the combination of the Hg emission kinetics and Hg fraction measurement of different moist soils indicated that Hg emission was affected by both total Hg concentration and Hg fractions.
  Scientific journal
  DOI：https://doi.org/10.1016/j.jenvman.2021.114308
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  DOI ID：10.1016/j.jenvman.2021.114308, ISSN：0301-4797, eISSN：1095-8630, PubMed ID：34953228, SCOPUS ID：85121631119
• Sustainable process for enhanced CO2 mineralization of calcium silicates using a recyclable chelating agent under alkaline conditions　　　　　　　　　　　　　　　
  Jiajie Wang; Noriaki Watanabe; Kosuke Inomoto; Masanobu Kamitakahara; Kengo Nakamura; Takeshi Komai; Noriyoshi Tsuchiya
  Journal of Environmental Chemical Engineering, Volume：10, Number：1, Feb. 2022
  This study explored a key challenge of aqueous indirect CO2 mineralization: the consumption of chemicals for a large pH swing between acidic and alkaline conditions and the production of waste fluid. Herein, we proposed and experimentally examined the technical feasibility of a sustainable process for enhanced CO2 mineralization using a new potentially recyclable alkaline solution of chelating agent [N,N-dicarboxymethyl glutamic acid (GLDA)] at near-room temperatures. This process comprising the following: enhanced Ca extraction from silicates with suppressed formation of silica-rich passivation layer via the combined actions of proton and chelating agent attacks at weakly alkaline conditions; Ca carbonation using sodium carbonate at high pH and temperature; and regeneration of the extraction solution (i.e., a decrease in pH and silicon removal) via CO2 gas dissolution. Ca extraction experiments using representative calcium silicate (CaSiO3) at various GLDA concentrations and initial pHs under 50 °C demonstrated the possibility of enhanced Ca extraction with almost all GLDA molecules combining with Ca (Ca/GLDA≈1) at an optimum condition (0.1 M GLDA and pH 8 in this study). This type of extraction is desirable as it contributes to an efficient Ca carbonation in addition to a decreased stability of the Ca-GLDA complex; indeed, most of the extracted Ca were carbonated to aragonite at 80 °C. Moreover, such extraction with the relatively low pH of 8 was found to be desirable for solution regeneration that involves pH adjustment (reduction) because of low silica solubility at lower pH. It was demonstrated that room-temperature CO2 bubbling removed almost all Si as amorphous SiO2, during which CO2 captured as NaHCO3 was also occurring. The recyclability of extraction solution was also demonstrated in this paper. This study encourages further extensive studies to optimize reaction conditions, particularly for using alkaline solid wastes, to make the process both technically and economically feasible.
  Scientific journal
  DOI：https://doi.org/10.1016/j.jece.2021.107055
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  DOI ID：10.1016/j.jece.2021.107055, eISSN：2213-3437, SCOPUS ID：85121606828
• QUANTITATIVE PREDICTION MODEL OF VOLATILIZATION FLUX GENERATION FROM UNSATURATED SOIL―VERIFICATION BASED ON HISTORY MATCHING PROCESS OF SOIL COLUMN TEST―　　　　　　　　　　　　　　　
  Monami KONDO; Yasuhide SAKAMOTO; Yoshishige KAWABE; Kengo NAKAMURA; Noriaki WATANABE; Takeshi KOMAI
  Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), Volume：78, Number：3, First page：87, Last page：103, 2022
  In recent years, numerical analysis method for quantitatively predicting volatilization flux has been required for soil contamination countermeasures and exposure risk management. In particular, there are few models that take into account transport phenomena and phase changes such as advection, diffusion, and volatilization of volatile chemical substances (VCSs) from unsaturated contaminated soil. In this study, a soil column test was conducted on the constructed model to verify the validity of the calculation results. In the history-matching process, the coefficient of relative permeability, the rate constant, and the molecular dispersion coefficient on the ground surface and inside the soil became important parameters, and the consistency of these various values was confirmed. Since these values could be set to appropriate values even if the tortuosity and hydrodynamic dispersion coefficient were also reasoned, numerical model proved to have validity. A volatilization flux prediction method was precisely established through a parameter matching process used in a numerical analysis model that expresses mass transfer phenomena that take into account the environmental dynamics associated with the volatilization of VCSs.
  Japan Society of Civil Engineers, Japanese, Scientific journal
  DOI：https://doi.org/10.2208/jscejer.78.3_87
  DOI ID：10.2208/jscejer.78.3_87, eISSN：2185-6648
• CO2 injection-induced complex cloud-fracture networks in granite at conventional and superhot geothermal conditions　　　　　　　　　　　　　　　
  Eko Pramudyo; Ryota Goto; Noriaki Watanabe; Kiyotoshi Sakaguchi; Kengo Nakamura; Takeshi Komai
  Geothermics, Volume：97, First page：102265, Last page：102265, Dec. 2021
  Complex cloud-fracture networks, favorable for enhanced geothermal system reservoir development, were shown to be able to be achieved in granite under superhot geothermal conditions, with temperatures of approximately 400-500 degrees C, by injecting low-viscosity water at these temperatures. Nonetheless, water utilization has several drawbacks, such as its reactivity with rock-forming minerals. Carbon dioxide (CO2), which has a low viscosity similar to that of the low-viscosity water under both superhot and lower-temperature conventional geothermal conditions, is a proposed replacement to overcome these challenges. This low viscosity of CO2 motivates its application to create cloud-fracture networks under various geothermal conditions. The present study, for the first time, demonstrated the formation of cloud-fracture networks in granite under both geothermal conditions through a set of CO2 fracturing experiments conducted from 200 to 450 degrees C under conventional and true triaxial stress states. The Griffith failure criterion was shown to be applicable for the formation of a cloud-fracture network in both geothermal conditions because it indicated that the fracture network was formed by the stimulation of pre-existing microfractures. The formation of cloud-fracture networks has potential advantages, such as additional fracturing in the presence of sizable natural fractures and a lower risk of induced seismicity; however, CO2 fracturing has the challenge of narrower fracture apertures under conventional geothermal conditions, which should be addressed in future research.
  Elsevier BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.geothermics.2021.102265
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  DOI ID：10.1016/j.geothermics.2021.102265, ISSN：0375-6505, eISSN：1879-3576, SCOPUS ID：85116557221, Web of Science ID：WOS:000706996700004
• Novel chemical stimulation for geothermal reservoirs by chelating agent driven selective mineral dissolution in fractured rocks　　　　　　　　　　　　　　　
  Noriaki Watanabe; Kaori Takahashi; Ryota Takahashi; Kengo Nakamura; Yusuke Kumano; Kohei Akaku; Tetsuya Tamagawa; Takeshi Komai
  Scientific Reports, Volume：11, Number：1, Dec. 2021
  Improving geothermal systems through hydraulic stimulation to create highly permeable fractured rocks can induce seismicity. Therefore, the technique must be applied at a moderate intensity; this has led to concerns of insufficient permeability enhancement. Adding chemical stimulation can mitigate these issues, but traditional methods using strong mineral acids have challenges in terms of achieving mineral dissolution over long distances and highly variable fluid chemistry. Here, we demonstrate a novel chemical stimulation method for improving the permeability of rock fractures using a chelating agent that substantially enhances the dissolution rate of specific minerals to create voids that are sustained under crustal stress without the challenges associated with the traditional methods. Applying this agent to fractured granite samples under confining stress at 200 °C in conjunction with 20 wt% aqueous solutions of sodium salts of environmentally friendly chelating agents (N-(2-hydroxyethyl)ethylenediamine-N, N′, N′-triacetic acid and N, N-bis(carboxymethyl)-l-glutamic acid) at pH 4 was assessed. A significant permeability enhancement of up to approximately sixfold was observed within 2 h, primarily due to the formation of voids based on the selective dissolution of biotite. These results demonstrate a new approach for chemical stimulation.
  Springer Science and Business Media LLC, English, Scientific journal
  DOI：https://doi.org/10.1038/s41598-021-99511-6
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  DOI ID：10.1038/s41598-021-99511-6, ISSN：2045-2322, eISSN：2045-2322, PubMed ID：34620962, SCOPUS ID：85116572142, Web of Science ID：WOS:000706376200101
• Development of a Model for Predicting the Volatilization Flux from Unsaturated Soil Contaminated by Volatile Chemical Substances
  Monami Kondo; Yasuhide Sakamoto; Yoshishige Kawabe; Kengo Nakamura; Noriaki Watanabe; Takeshi Komai
  Environmental Modeling & Assessment, Volume：27, Number：2, First page：251, Last page：273, Oct. 2021
  This work developed a model for predicting the volatilization flux from the unsaturated soil contaminated by volatile chemical substances (VCSs) such as mercury and benzene. The model considers a series of phenomena under the unsaturated condition such as multi-phase flow consisting of a non-aqueous phase liquid, water, and gases together with the permeation of rainfall into the surface soil, the volatilization/condensation of VCSs, and the adsorption/desorption of VCSs. On this basis, this work clarified a mechanism for the generation of a volatilization flux at the ground surface. In addition, the effects of various transport phenomena in the surface soil on the magnitude and seasonal changes in this flux due to variations in weather factors such as rainfall level, temperature, and air pressure were quantitatively evaluated. This newly developed prediction model can be utilized to estimate dynamic variations in the flux under real-environmental conditions.
  Springer Science and Business Media LLC, Scientific journal
  DOI：https://doi.org/10.1007/s10666-021-09796-0
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  DOI ID：10.1007/s10666-021-09796-0, ISSN：1420-2026, eISSN：1573-2967, ORCID：102003923, SCOPUS ID：85116480166
• Prediction and Remediation of Groundwater Pollution in a Dynamic and Complex Hydrologic Environment of an Illegal Waste Dumping Site　　　　　　　　　　　　　　　
  Thatthep Pongritsakda; Kengo Nakamura; Jiajie Wang; Noriaki Watanabe; Takeshi Komai
  Applied Sciences, Volume：11, Number：19, First page：9229, Last page：9229, Oct. 2021
  The characteristics of groundwater pollution caused by illegal waste dumping and methods for predicting and remediating it are still poorly understood. Serious 1,4-dioxane groundwater pollution—which has multiple sources—has been occurring at an illegal waste dumping site in the Tohoku region of Japan. So far, anti-pollution countermeasures have been taken including the installation of an impermeable wall and the excavation of soils and waste as well as the monitoring of contamination concentrations. The objective of this numerical study was to clarify the possibility of predicting pollutant transport in such dynamic and complex hydrologic environments, and to investigate the characteristics of pollutant transport under both naturally occurring and artificially induced groundwater flow (i.e., pumping for remediation). We first tried to reproduce the changes in 1,4-dioxane concentrations in groundwater observed in monitoring wells using a quasi-3D flow and transport simulation considering the multiple sources and spatiotemporal changes in hydrologic conditions. Consequently, we were able to reproduce the long-term trends of concentration changes in each monitoring well. With the predicted pollutant distribution, we conducted simulations for remediation such as pollutant removal using pumping wells. The results of the prediction and remediation simulations revealed the highly complex nature of 1,4-dioxane transport in the dumping site under both naturally occurring and artificially induced groundwater flows. The present study suggests possibilities for the prediction and remediation of pollution at illegal waste dumping sites, but further extensive studies are encouraged for better prediction and remediation.
  MDPI AG, English, Scientific journal
  DOI：https://doi.org/10.3390/app11199229
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85116595625&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85116595625&origin=inward
  DOI ID：10.3390/app11199229, eISSN：2076-3417, ORCID：100947948, SCOPUS ID：85116595625, Web of Science ID：WOS:000706522500001
• Dynamic evaluation method for planning sustainable landfills using GIS and multi-criteria in areas of urban sprawl with land-use conflicts　　　　　　　　　　　　　　　
  Chelsea Langa; Junko Hara; Jiajie Wang; Kengo Nakamura; Noriaki Watanabe; Takeshi Komai
  PLOS ONE, Volume：16, Number：8, First page：e0254441, Last page：e0254441, Aug. 2021
  Landfill site selection is problematic in many countries, especially developing nations where there is rapid population growth, which leads to high levels of inadequate waste disposal. To find sustainable landfill sites in sprawling cities, this study presents an approach that combines geographic information system (GIS) with multi-criteria (social, environmental and, technical criteria) and the population growth projection. The greater Maputo area in Mozambique was selected as a representative city for the study, which is undergoing rapid urbanization. Six criteria, i.e., land use, transport networks, hydrology, conservation reserve, geology and slope, were considered and overlaid in the GIS using an analytic hierarchy process (AHP). The arithmetic projection of the population trend suggests that the greater Maputo area is experiencing a rapid and uncontrolled population growth, especially in Matola city. These pronounced changes in population then significantly change the landfill placement decision making. Dynamic and static scenarios were created, based on the analysis of multi-criteria and the areas likely to undergo future increased population growth. A comparative evaluation in a scenario of dynamic behavior considering future population showed that suitable areas for landfill sites have been drastically modified due to social and environmental factors affected by population distribution in some regions. The results indicate that some suitable areas can generate land use conflicts due to population growth with unplanned land use expansion. Finally, the western part of Matola city is recognized as the most recommendable landfill site, which can serve both Maputo and Matola city with affordable costs. This study provides an effective landfill placement decision making approach, which is possible to be applied anywhere, especially in developing countries to improve sustainable municipal solid waste management systems.
  Public Library of Science (PLoS), Scientific journal
  DOI：https://doi.org/10.1371/journal.pone.0254441
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85113832855&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85113832855&origin=inward
  DOI ID：10.1371/journal.pone.0254441, eISSN：1932-6203, PubMed ID：34449785, SCOPUS ID：85113832855
• Enhancement of aragonite mineralization with a chelating agent for CO2 storage and utilization at low to moderate temperatures　　　　　　　　　　　　　　　
  Jiajie Wang; Noriaki Watanabe; Kosuke Inomoto; Masanobu Kamitakahara; Kengo Nakamura; Takeshi Komai; Noriyoshi Tsuchiya
  SCIENTIFIC REPORTS, Volume：11, Number：1, Jul. 2021
  Among the CaCO3 polymorphs, aragonite demonstrates a better performance as a filler material in the paper and plastic industries. Despite being ideal from the environmental protection perspective, the production of aragonite particles via CO2 mineralization of rocks is hindered by the difficulty in achieving high production efficiencies and purities, which, however, can be mitigated by exploiting the potential ability of chelating agents on metal ions extraction and carbonation controlling. Herein, chelating agent N,N-dicarboxymethyl glutamic acid (GLDA) was used to enhance the extraction of Ca from calcium silicate and facilitate the production of aragonite particles during the subsequent Ca carbonation. CO2 mineralization was promoted in the presence of 0.01-0.1 M GLDA at <= 80 degrees C, with the maximal CaCO3 production efficiency reached 308 g/kg of calcium silicate in 60 min using 0.03 M GLDA, which is 15.5 times higher than that without GLDA. In addition, GLDA showed excellent effects on promoting aragonite precipitation, e.g., the content of aragonite was only 5.1% in the absence of GLDA at 50 degrees C, whereas highly pure (>90%, increased by a factor of 18) and morphologically uniform aragonite was obtained using >= 0.05 M GLDA under identical conditions. Aragonite particle morphologies could also be controlled by varying the GLDA concentration and carbonation temperature. This study proposed a carbon-negative aragonite production method, demonstrated the possibility of enhanced and controlled aragonite particle production during the CO2 mineralization of calcium silicates in the presence of chelating agents.
  NATURE RESEARCH, English, Scientific journal
  DOI：https://doi.org/10.1038/s41598-021-93550-9
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85109352472&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85109352472&origin=inward
  DOI ID：10.1038/s41598-021-93550-9, ISSN：2045-2322, eISSN：2045-2322, PubMed ID：34230588, SCOPUS ID：85109352472, Web of Science ID：WOS:000672717700036
• Water-Enhanced Flux Changes under Dynamic Temperatures in the Vertical Vapor-Phase Diffusive Transport of Volatile Organic Compounds in Near-Surface Soil Environments　　　　　　　　　　　　　　　
  Asma Akter Parlin; Monami Kondo; Noriaki Watanabe; Kengo Nakamura; Mizuki Yamada; Jiajie Wang; Takeshi Komai
  SUSTAINABILITY, Volume：13, Number：12, Jun. 2021
  The quantitative understanding of the transport behavior of volatile organic compounds (VOCs) in near-surface soils is highly important in light of the potential impacts of soil VOC emissions on the air quality and climate. Previous studies have suggested that temperature changes affect the transport behavior; however, the effects are not well understood. Indeed, much larger changes in the VOC flux under in situ dynamic temperatures than those expected from the temperature dependence of the diffusion coefficients of VOCs in the air have been suggested but rarely investigated experimentally. Here, we present the results of a set of experiments on the upward vertical vapor-phase diffusive transport of benzene and trichloroethylene (TCE) in sandy soils with water contents ranging from an air-dried value to 10 wt% during sinusoidal temperature variation between 20 and 30 degrees C. In all experiments, the flux from the soil surface was correlated with the temperature, as expected. However, the changes in flux under wet conditions were unexpectedly large and increased with increasing water content; they were also larger for TCE, the volatility of which depended more strongly on the temperature. Additionally, the larger flux changes were accompanied by a recently discovered water-induced inverse correlation between temperature and flux into the overlying soil. These results demonstrated that the flux changes of VOCs under dynamic temperatures could be increased by volatilization-dissolution interactions of VOCs with water. Future extensive studies on this newly discovered phenomenon would contribute to a better understanding of the impacts of soil VOC emissions on the air quality and climate.
  MDPI, English, Scientific journal
  DOI：https://doi.org/10.3390/su13126570
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85108322716&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85108322716&origin=inward
  DOI ID：10.3390/su13126570, eISSN：2071-1050, SCOPUS ID：85108322716, Web of Science ID：WOS:000666389000001
• Experimental and Numerical Studies on Dissociation of Methane Hydrate by Simultaneous Injection of Nitrogen and Hot Water　　　　　　　　　　　　　　　
  Yasuhide Sakamoto; Yusuke Nakano; Fuyuki Kaneko; Kengo Nakamura; Takeshi Komai
  INTERNATIONAL JOURNAL OF OFFSHORE AND POLAR ENGINEERING, Volume：31, Number：2, First page：186, Last page：198, Jun. 2021
  This study aims to investigate the targeting behavior of a gas phase consisting of multicomponent and gas-water multi-phase flow assumed in an in situ low-temperature oxidation (LTO) process as an enhanced gas recovery from a methane hydrate (MH) reservoir. Experimental and numerical studies on MH dissociation in porous media by simultaneous injection of N-2 and hot water were carried out. It can be confirmed based on experimental results that the equilibrium temperature as a result of the decrease of the molar fraction of methane gas (CH4) in the gas phase with N-2 injection was maintained at a lower level so that dissociated CH4 production was completed earlier. In addition, based on the experimental observation of change of equilibrium temperature, the interfacial model of MH for the estimation of fugacity change was constructed and introduced into the numerical model. The history matching for temperature change, permeability characteristics, and CH4 production during simultaneous injection process was subsequently conducted. Through the optimization of each parameter, it was found that the calculated results could reproduce a series of behaviors quantitatively. As a result, from the viewpoint of the behavior of the gas phase consisting of multicomponents on MH dissociation, the validity of a numerical model developed for an in situ LTO process has been confirmed.
  INT SOC OFFSHORE POLAR ENGINEERS, English, Scientific journal
  DOI：https://doi.org/10.17736/ijope.2021.jc793
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85110269418&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85110269418&origin=inward
  DOI ID：10.17736/ijope.2021.jc793, ISSN：1053-5381, SCOPUS ID：85110269418, Web of Science ID：WOS:000671172200008
• Creating Cloud-Fracture Network by Flow-induced Microfracturing in Superhot Geothermal Environments　　　　　　　　　　　　　　　
  Ryota Goto; Noriaki Watanabe; Kiyotoshi Sakaguchi; Takahiro Miura; Youqing Chen; Takuya Ishibashi; Eko Pramudyo; Francesco Parisio; Keita Yoshioka; Kengo Nakamura; Takeshi Komai; Noriyoshi Tsuchiya
  ROCK MECHANICS AND ROCK ENGINEERING, Volume：54, Number：6, First page：2959, Last page：2974, Jun. 2021
  Superhot geothermal environments with temperatures of approximately 400-500 degrees C at depths of approximately 2-4 km are attracting attention as new kind of geothermal resource. In order to effectively exploit the superhot geothermal resource through the creation of enhanced geothermal systems (superhot EGSs), hydraulic fracturing is a promising technique. Laboratory-scale hydraulic fracturing experiments of granite have recently demonstrated the formation of a dense network of permeable fractures throughout the entire rock body, referred to as a cloud-fracture network, at or near the supercritical temperature for water. Although the process has been presumed to involve continuous infiltration of low-viscosity water into preexisting microfractures followed by creation and merger of the subsequent fractures, a plausible criterion for cloud-fracture network formation is yet to be clarified. The applicability of the Griffith failure criterion is supported by hydraulic fracturing experiments with acoustic emission measurements of granite at 400 degrees C under true triaxial stress and at 450 degrees C under conventional triaxial stress. The present study provides, for the first time, a theoretical basis required to establish the procedure for hydraulic fracturing in the superhot EGS.
  SPRINGER WIEN, English, Scientific journal
  DOI：https://doi.org/10.1007/s00603-021-02416-z
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85103175666&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85103175666&origin=inward
  DOI ID：10.1007/s00603-021-02416-z, ISSN：0723-2632, eISSN：1434-453X, ORCID：91173258, SCOPUS ID：85103175666, Web of Science ID：WOS:000632294700003
• Using data-driven analysis of geochemical environmental information to infer the environmental impact of closed mines　　　　　　　　　　　　　　　
  Kengo Nakamura; Yoshishige Kawabe; Takeshi Komai
  HELIYON, Volume：7, Number：5, May 2021
  River sediments have the effect of aggregating geochemical environmental information, such as that related to geological and artificial pollution resulting from mine closure. This information comprises high-dimensional data and is related to the distribution and quantities of elements in river sediments. However, accessing and interpreting this geochemical information can be difficult. This study employed a data-driven analysis that can be mathematically and statistically reduced in dimension. Using high-dimensional geochemical and environmental information on river sediments, this study evaluated the environmental impact of closed mines. Sample for analysis were collected from three rivers. There are differences in the existence of mines and mine wastewater treatment methods in this river. A total of 33 elements were measured in river sediments. Frequency distribution analysis and Principal component analysis revealed that the elements had unique distribution and frequency characteristics in each river catchment. Four environmental factors could be extracted from the relationship of elements due to lower dimension. PC1 was influenced by the land use in the river area. PC2 captured the geological background. PC3 captured the mixing-diluting effect that occurs in rivers. PC4 effectively captured the effects of domestic wastewater and the effects of closed mines. The effects of the closed mines could be confirmed using the PC4 score for the Okawa River and the Akagawa River. By examining the elemental relationships obtained using these mathematical methods, it is possible to infer the effect of geological features and mines on sediment physiochemistry using existing data on river sediments.
  ELSEVIER SCI LTD, English, Scientific journal
  DOI：https://doi.org/10.1016/j.heliyon.2021.e06927
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85105309735&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85105309735&origin=inward
  DOI ID：10.1016/j.heliyon.2021.e06927, ISSN：2405-8440, eISSN：2405-8440, SCOPUS ID：85105309735, Web of Science ID：WOS:000663597800016
• Water-Induced Inverse Correlation between Temperature and Flux Changes in Vertical Vapor-Phase Diffusive Transport of Volatile Organic Compounds in Near-Surface Soil Environments　　　　　　　　　　　　　　　
  Asma Akter Parlin; Noriaki Watanabe; Kengo Nakamura; Mizuki Yamada; Jiajie Wang; Takeshi Komai
  APPLIED SCIENCES-BASEL, Volume：11, Number：8, Apr. 2021
  Volatile organic compounds (VOCs) in contaminated soils have been investigated in near-surface environments to describe their transport behaviors and the resultant impacts of vapor intrusion into buildings. Prior studies have suggested that temperature changes significantly influence such transport behaviors in near-surface soils; however, the nature of these influences and their mechanisms have remained unclear. This is because an inverse correlation between the in situ temperature and VOC flux changes has been suggested but has not been experimentally investigated or demonstrated. Herein, we show the results of a set of experiments on the vertical and upward vapor-phase diffusive transport of benzene in sandy soils for different sand grain size and water content combinations under sinusoidal temperature changes between 20 and 30 degrees C. Under all experimental conditions, changes in the flux from the soil surface correlated with temperature changes, whereas changes in the flux into the overlying soil showed inverse correlations. Concurrent monitoring of the relative humidity revealed that an inverse correlation was exhibited in response to the condensation and volatilization of water. Moreover, the intensity of the inverse correlation was independent of grain size but was larger at higher water contents. Overall, water in soil may induce an inverse correlation.
  MDPI, English, Scientific journal
  DOI：https://doi.org/10.3390/app11083489
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85104133505&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85104133505&origin=inward
  DOI ID：10.3390/app11083489, eISSN：2076-3417, SCOPUS ID：85104133505, Web of Science ID：WOS:000643977800001
• Leaching of As and Se from coal fly ash: fundamental study for coal fly ash recycling　　　　　　　　　　　　　　　
  Tsugumi Seki; Kengo Nakamura; Yasumasa Ogawa; Chihiro Inoue
  ENVIRONMENTAL MONITORING AND ASSESSMENT, Volume：193, Number：4, Apr. 2021
  Coal fly ash (CFA) is a useful recycled resource for uses such as cement raw material. To manage and evaluate safety for effective utilization of CFA, the leaching concentration and amounts of toxic elements in CFA need to be determined. In this study, 38 types of CFA and aged CFA generated in Japan were used to measure the occurrence and leaching concentration range of As and Se. In addition, the leaching characteristics over the long term were examined using statistical analysis. Leaching concentrations of As and Se from CFAs were in the range of 0.001-0.163 mg/L (average: 0.025 mg/L, median: 0.014 mg/L) and 0.001-0.189 mg/L (average: 0.071 mg/L, median: 0.055 mg/L), respectively. In general, the concentrations of aged CFAs were less than those of the CFAs with a few exceptions. Leaching concentrations of As and Se in the tank leaching test changed with time, and As and Se concentrations in the dispersions increased with stirring time. In contrast, pH of the dispersion decreased with time. The relation between As or Se and CFA factors showed that As or Se and pH or Ca were highly correlated. However, in aged CFAs for long-term use, the correlation coefficient for the relation between As and other factors was low while that for Se-S was high. Considering the effective utilization of CFA as a long-term recyclable resource, the leaching processes of As and Se in CFA would change with time depending on the environmental conditions.
  SPRINGER, English, Scientific journal
  DOI：https://doi.org/10.1007/s10661-021-08954-x
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85103390628&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85103390628&origin=inward
  DOI ID：10.1007/s10661-021-08954-x, ISSN：0167-6369, eISSN：1573-2959, PubMed ID：33768424, SCOPUS ID：85103390628, Web of Science ID：WOS:000634818100002
• Consideration of strength development by three-dimensional visualization of porosity distribution in coal fly ash concrete　　　　　　　　　　　　　　　
  Kengo Nakamura; Yuusuke Inoue; Takeshi Komai
  JOURNAL OF BUILDING ENGINEERING, Volume：35, Mar. 2021
  Coal fly ash mixed with cement is a substitute civil engineering material that can secure the physical properties of concrete solidification. The benefits of this substitute were qualitatively evaluated the porosity distribution and phase change and the compressive strength resulting from chemical reactions. Visualization of the 3D porosity distribution of coal fly ash mixed material concrete with different material moisture ratios by X-ray CT is important for this purpose. The specimens were subjected to a uniaxial compression test and the porosity distribution was measured by X-ray CT after 7, 28, and 120 days. The strength at 120 days was 15-23 MPa for all specimens. Porosity increased 2% in all specimens as they aged. From the results of the 3D porosity distribution, specimens with a moisture ratio of 17 or 19 wt% had a porosity of 47% according to the porosity distribution histogram. These specimens also exhibited a porosity distribution with a layered structure. The other specimens (moisture ratio of 21 wt% with different mixing methods) were observed to have no layered structure and numerous large spherical pores. These results suggest that the porosity structure produced by the moisture ratio is important for the strength development of concrete containing coal fly ash. Moreover, a uniform porosity distribution and structure imparted by the correct moisture ratio appears to contribute to long-term strength development by effective chemical reactions in the specimen.
  ELSEVIER, English, Scientific journal
  DOI：https://doi.org/10.1016/j.jobe.2020.101948
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85097721777&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85097721777&origin=inward
  DOI ID：10.1016/j.jobe.2020.101948, ISSN：2352-7102, eISSN：2352-7102, SCOPUS ID：85097721777, Web of Science ID：WOS:000618129900001
• Formation of amorphous silica nanoparticles and its impact on permeability of fractured granite in superhot geothermal environments　　　　　　　　　　　　　　　
  Noriaki Watanabe; Hikaru Abe; Atsushi Okamoto; Kengo Nakamura; Takeshi Komai
  SCIENTIFIC REPORTS, Volume：11, Number：1, Mar. 2021
  Superhot geothermal environments in granitic crusts of approximately 400-500 degrees C are a frontier of geothermal energy. In the development of such environments, there is a concern of a reduction of permeability of fractured granite due to the formation of fine particles of amorphous silica induced by the phase change from subcritical water to supercritical water or superheated steam. However, the formation of silica particles and a resultant reduction in permeability have not been demonstrated to date. Therefore, experiments were conducted on the formation of amorphous silica particles with various combinations of temperature (430-500 degrees C) and pressure (20-30 MPa), in which the phase change of Si-containing water from liquid to either supercritical fluid or vapor was induced. Amorphous silica nanoparticles occurred under all conditions with smaller particles for higher temperature. The permeability of fractured granite was also observed to decrease significantly within several hours during injection of the particles into rock at 450 degrees C and 30 MPa under a confining stress of 40 MPa, with slower permeability reduction at a smaller number of particles or in the presence of larger aperture fractures. The present study suggests that the nanoparticles are likely to form and destroy the permeability in superhot geothermal environments, against which countermeasures should be investigated.
  NATURE RESEARCH, English, Scientific journal
  DOI：https://doi.org/10.1038/s41598-021-84744-2
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85102209187&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85102209187&origin=inward
  DOI ID：10.1038/s41598-021-84744-2, ISSN：2045-2322, eISSN：2045-2322, PubMed ID：33674693, SCOPUS ID：85102209187, Web of Science ID：WOS:000627411200016
• Process and optimum pH in permeability enhancement of granite by chelating-agent-induced selective mineral dissolution　　　　　　　　　　　　　　　
  高橋亮太; 渡邉則昭; 中村謙吾; 駒井武
  日本地熱学会学術講演会講演要旨集, Volume：2021, 2021
  J-Global ID：202202219406073679
• Chemical characterization of paleo-tsunami deposits by data-driven analysis　　　　　　　　　　　　　　　
  佐藤就太; 中村謙吾; 渡邉則昭; 駒井武
  Proceedings of Symposium on Geo-Environments and Geo-Technics, Volume：31st, 2021
  ISSN：0917-7183, J-Global ID：202202257734391119
• Data-driven analysis for source apportionment and geochemical backgrounds establishment of toxic elements and REEs in the Tohoku region, Japan　　　　　　　　　　　　　　　
  Arie Pujiwati; Jiajie Wang; Kengo Nakamura; Yoshishige Kawabe; Noriaki Watanabe; Takeshi Komai
  CHEMOSPHERE, Volume：263, Jan. 2021
  The Tohoku region of Japan is geologically diverse, with a long agriculture and mining history; however, little information about the origins and distribution mechanisms of elements in this region has been reported. This study aims to provide fundamental insights into the effects of geological features and anthropogenic activities on various elements, including toxic elements and rare-earth elements (REEs), in the Tohoku region. A geochemical database (2007, AIST) consisting of data for 53 elements in 485 river sediment samples from the region was used, and a data-driven method combining principal component analysis (PCA) was applied for analysis. GBs for numerous types of areas, including general areas (GGB), natural environments (NGB), high anthropogenic-influenced areas (AGB) and mineralised areas (MGB) were established; especially, MGB was newly proposed in this study to illuminate the role of ore deposits. Both PCA and GBs comparison results show that geological features (especially igneous rock distribution) were the most important factor affecting elemental distribution, rather than anthropogenic activities. In the PCA, the first principal component showed that REE resources were commonly associated with the distribution of granitic rocks and REE-bearing minerals. Anthropogenic contaminations from mining, urban, and anthropogenic areas played important roles as the origin of some toxic elements (e.g. Ni, Pb, Sb). Comparisons between these GBs effectively elucidated the enrichment of certain toxic elements (e.g., Hg, Sb) in ore deposit areas. This data-driven study not only clarified the origins of toxic elements, but also revealed the location of potential REE mineral resources in the Tohoku region. (C) 2020 Elsevier Ltd. All rights reserved.
  PERGAMON-ELSEVIER SCIENCE LTD, English, Scientific journal
  DOI：https://doi.org/10.1016/j.chemosphere.2020.128268
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85090717471&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85090717471&origin=inward
  DOI ID：10.1016/j.chemosphere.2020.128268, ISSN：0045-6535, eISSN：1879-1298, PubMed ID：33297212, SCOPUS ID：85090717471, Web of Science ID：WOS:000595802200318
• Regional landfill planning for improvement of waste management in Maputo, Mozambique
  Chelsea Langa; Kengo Nakamura; Noriaki Watanabe; Takeshi Komai
  Advances In Natural And Applied Sciences, Volume：14, Number：3, First page：89, Last page：95, Dec. 2020, [Reviewed]
  English, Scientific journal
  DOI：https://doi.org/10.22587/anas.2020.14.3.12
  DOI ID：10.22587/anas.2020.14.3.12
• Numerical Simulation of a Laboratory-scale Experiment for the Hydrate Dissociation Process in Porous Media by Acid Injection　　　　　　　　　　　　　　　
  Yasuhide Sakamoto; Yusuke Nakano; Fuyuki Kaneko; Kengo Nakamura; Takeshi Komai
  INTERNATIONAL JOURNAL OF OFFSHORE AND POLAR ENGINEERING, Volume：30, Number：4, First page：501, Last page：512, Dec. 2020
  In this study, to enhance gas recovery from a methane hydrate reservoir, experimental and numerical studies that considered the acid injection process as a secondary gas recovery process after the depressurization operation were conducted. First, we experimentally analyzed the dissociation behavior of propane hydrate (PGH) in porous media by using acid injection and confirmed that the dissociation condition of PGH was shifted to the sides of low temperature and high pressure. This enabled the dissociation to proceed easily as the concentration of the injected acid increased. Then, on the basis of experimental observation, we conducted history matching for the temperature change and gas production behavior during PGH dissociation by acid injection, by varying the initial hydrate saturation, the reaction rate constant for acid consumption, and the intrinsic dissociation rate constant as the calculation parameters. Through history matching, we confirmed the validity of the developed numerical model targeting the dissociation of hydrates in porous media by acid injection.
  INT SOC OFFSHORE POLAR ENGINEERS, English, Scientific journal
  DOI：https://doi.org/10.17736/ijope.2020.jc790
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85098889430&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85098889430&origin=inward
  DOI ID：10.17736/ijope.2020.jc790, ISSN：1053-5381, SCOPUS ID：85098889430, Web of Science ID：WOS:000599526300015
• Numerical Study on the Application of In situ Low-temperature Oxidation for Enhanced Recovery from Methane Hydrate Reservoir　　　　　　　　　　　　　　　
  Yasuhide Sakamoto; Fuyuki Kaneko; Yusuke Nakano; Kengo Nakamura; Takeshi Komai
  INTERNATIONAL JOURNAL OF OFFSHORE AND POLAR ENGINEERING, Volume：30, Number：2, First page：228, Last page：239, Jun. 2020, [Reviewed]
  In this study, a new in situ low-temperature oxidation (LTO) process was developed under the concept of effective utilization of heat generation, resulting from LTO of the injected organic substance (IOS), for the promotion of in situ dissociation of methane hydrate (MH) and the enhancement of gas recovery. When water containing the IOS component and air as an oxidant are injected into the MH reservoir, a high-temperature zone by heat generation is formed under the in situ condition. From this process, in addition to MH dissociation, a numerical model considering multicomponent flow in porous media with LTO reaction was constructed. From the calculation results, it was found that the high-temperature zone formed as a result of heat generation extended to the side of the production well, which promoted MH dissociation. In addition, gas recovery as high as 80% to 100% could be obtained through depressurization and in situ LTO process.
  INT SOC OFFSHORE POLAR ENGINEERS, English, Scientific journal
  DOI：https://doi.org/10.17736/ijope.2020.jc760
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85086769140&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85086769140&origin=inward
  DOI ID：10.17736/ijope.2020.jc760, ISSN：1053-5381, SCOPUS ID：85086769140, Web of Science ID：WOS:000538614200012
• Characteristics of hydrogen production with carbon storage by CO2-rich hydrothermal alteration of olivine in the presence of Mg-Al spinel　　　　　　　　　　　　　　　
  Jiajie Wang; Noriaki Watanabe; Atsushi Okamoto; Kengo Nakamura; Takeshi Komai
  INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Volume：45, Number：24, First page：13163, Last page：13175, May 2020, [Reviewed]
  Artificial control of olivine alteration has potential applications for both H-2 production and CO2 reduction (by mineralization and hydrogenation). To explore methods to overcome the still-constrained olivine alteration problem, olivine + spinel alteration experiments were performed with the addition of Mg-Al spinel in CO2-rich (0.5 M NaHCO3) solution under hydrothermal conditions (300 degrees C and 10 MPa). Mg-Al spinel enhanced olivine serpentinization significantly (more than 2 times), and generation of both H-2 and CO2 hydrogenation products was accelerated (up to 3 times) with >= 10 wt% Mg-Al spinel especially at the latter stage of the 72 h reaction.Mineral measurements revealed that more Al released from Mg-Al spinel was incorporated into Al-serpentine by the replacement of Fe with higher Mg-Al spinel content. Both Al and Fe incorporated into Al-serpentine were released as the reaction proceeded. Thus, H-2 production was elevated with the presence of a large amount Mg-Al spinel at the latter stage of the reaction. HCO3 played an important role in the promotion of Mg-Al spinel dissolution with the release of Al, which was stored in magnesite after being utilized. This study also suggests that the presence of Mg-Al spinel (5-20 wt%) in the starting mineral does not have significant influence on the total H-2 yield from olivine alteration over the entire operation period. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
  PERGAMON-ELSEVIER SCIENCE LTD, English, Scientific journal
  DOI：https://doi.org/10.1016/j.ijhydene.2020.03.032
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85082514577&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85082514577&origin=inward
  DOI ID：10.1016/j.ijhydene.2020.03.032, ISSN：0360-3199, eISSN：1879-3487, SCOPUS ID：85082514577, Web of Science ID：WOS:000528271900004
• Stabilizing and enhancing permeability for sustainable and profitable energy extraction from superhot geothermal environments　　　　　　　　　　　　　　　
  Noriaki Watanabe; Kohei Saito; Atsushi Okamoto; Kengo Nakamura; Takuya Ishibashi; Hanae Saishu; Takeshi Komai; Noriyoshi Tsuchiya
  APPLIED ENERGY, Volume：260, First page：114306, Feb. 2020, [Reviewed]
  Superhot geothermal environments in granitic crusts of ca. 400-500 degrees C and depths of 2-4 km are recognized as a frontier of geothermal energy. In developing such environments, hydraulic fracturing is a promising way to create or recreate permeable fracture networks to effectively access the energy through enhanced geothermal systems (EGS). However, there is a concern about the possibility of stabilizing or enhancing the permeability created by hydraulic fracturing, required for sustainable and profitable energy production, because pressure solution of the fracture surfaces may reduce permeability. On the other hand, permeability may be enhanced by free-face dissolution of the fracture surfaces even if pressure solution occurs. However, the rates of permeability reduction and enhancement are not fully understood, and the possibility of stabilizing/enhancing permeability is therefore unclear. We have conducted hydrothermal flow-through experiments on 400 degrees C fractured granite samples to clarify the influences of stress level and plasticity of the fracture on the rate of permeability reduction by pressure solution and the influences of pore water pressure and corresponding mineral solubility on the rate of permeability enhancement by free-face dissolution. Results suggest that permeability may be either stabilized or enhanced in superhot EGS even when pressure solution can occur by keeping the difference between the concentration of the pore water and the solubility of quartz higher than the stress-dependent permeability stabilization criterion.
  ELSEVIER SCI LTD, English, Scientific journal
  DOI：https://doi.org/10.1016/j.apenergy.2019.114306
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85076292713&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85076292713&origin=inward
  DOI ID：10.1016/j.apenergy.2019.114306, ISSN：0306-2619, eISSN：1872-9118, SCOPUS ID：85076292713, Web of Science ID：WOS:000515108700105
• Pyroxene control of H-2 production and carbon storage during water-peridotite-CO2 hydrothermal reactions　　　　　　　　　　　　　　　
  Jiajie Wang; Noriaki Watanabe; Atsushi Okamoto; Kengo Nakamura; Takeshi Komai
  INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Volume：44, Number：49, First page：26835, Last page：26847, Oct. 2019, [Reviewed]
  Strategies of H-2 production and CO2 mineralization were combined through olivine [(Mg,Fe)(2)SiO4] serpentinization and carbonation in a CO2-rich hydrothermal system. However, natural mantle peridotites commonly contain not only olivine but also orthopyroxene and/or clinopyroxene, which have effects that are not well understood. The present study investigated the reactions in H2O-olivine/orthopyroxene-CO2 systems by performing hydrothermal experiments in 0.5 M NaHCO3 solutions at 300 degrees C and 10 MPa.The yields of H-2 and HCOOH initially were first suppressed in the presence of orthopyroxene; however, after orthopyroxene consumption, the rate of H-2 production increased significantly. H-2 yield increased to 348.3 mmol/kg(mineral) in 120 h with the presence of 20 wt % orthopyroxene at the beginning of the reaction. The initial suppression of H-2 generation was due to incorporation of more Fe(II) into serpentine [(Mg,Fe)(3)Si2O5(OH)(4)] in the high SiO2(aq) concentration system. The presence of orthopyroxene also dramatically accelerated serpentine formation. In contrast, magnesite [(Mg,Fe)CO3] formation was inhibited upon addition of orthopyroxene, which also contributed to the release of Fe(II). Therefore, peridotite containing <= 20 wt% of pyroxenes is more suitable for long-term H-2 production than pure olivine. When considering the reaction output of a water-peridotite-CO2 system, controlling the percentage of pyroxenes in the starting mineral may be more important than expected. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
  PERGAMON-ELSEVIER SCIENCE LTD, English, Scientific journal
  DOI：https://doi.org/10.1016/j.ijhydene.2019.08.161
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85071969068&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85071969068&origin=inward
  DOI ID：10.1016/j.ijhydene.2019.08.161, ISSN：0360-3199, eISSN：1879-3487, SCOPUS ID：85071969068, Web of Science ID：WOS:000491622900010
• Numerical Study on Enhanced Gas Recovery from Methane Hydrate Reservoir During In-situ Heating Process by Acid Injection　　　　　　　　　　　　　　　
  Yasuhide Sakamoto; Fuyuki Kaneko; Yusuke Nakano; Kengo Nakamura; Takeshi Komai
  INTERNATIONAL JOURNAL OF OFFSHORE AND POLAR ENGINEERING, Volume：29, Number：3, First page：347, Last page：358, Sep. 2019, [Reviewed]
  In this study, under the concept of effective utilization of heat generation resulting from mineral dissolution via acid injection for the promotion of in-situ dissociation of methane hydrate (MH) and the enhancement of gas recovery, we conducted a series of numerical analyses of the acid injection process as a secondary gas recovery from an MH reservoir after the depressurization operation. For the numerical analysis, based on the assumption that the charge balance in the injected acid solution after the contact with the solid matrix becomes neutral as a result of mineral dissolution into the water phase, two acid components before and after the contact with the solid matrix were defined. In addition, the kinetic parameters and heat of mineral dissolution during the acid injection were obtained through laboratory column tests and differential scanning calorimetry (DSC) analysis, respectively, and introduced into the developed numerical model. From the calculation results, it was found that the high-temperature zone formed because of heat generation resulting from mineral dissolution extended to the side of the production well promoting MH dissociation, and the total gas recovery through depressurization and acid injection was estimated at approximately 90%.
  INT SOC OFFSHORE POLAR ENGINEERS, English, Scientific journal
  DOI：https://doi.org/10.17736/ijope.2019.jc744
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85075674608&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85075674608&origin=inward
  DOI ID：10.17736/ijope.2019.jc744, ISSN：1053-5381, SCOPUS ID：85075674608, Web of Science ID：WOS:000499717400013
• Construction of a conceptual model for confined groundwater flow in the Gunii Khooloi Basin, Southern Gobi Region, Mongolia　　　　　　　　　　　　　　　
  Batdemberel Bayanzul; Kengo Nakamura; Isao Machida; Noriaki Watanabe; Takeshi Komai
  HYDROGEOLOGY JOURNAL, Volume：27, Number：5, First page：1581, Last page：1596, Aug. 2019, [Reviewed]
  Groundwater plays a vital role in the arid Southern Gobi Region (SGR) of Mongolia. It is the only source of water supply and is largely utilized for mining operations, such as those at Oyu Tolgoi Mine. The area is expected to face severe water shortages for mining and drinking water, which may be related to changes in groundwater recharge due to climate change. Understanding the geochemical evolution of groundwater and recharge mechanisms is thus paramount for water resource management. In this study, for the first time, chemical and isotopic approaches have been used to characterize the groundwater origin and its associated recharge processes in the Gunii Khooloi basin, which is located in the SGR. Shallow groundwater is mainly characterized by Na(HCO3) and NaCl type; however, Gunii Khooloi aquifer is classified as NaCl type with high electrical conductivity. The stable isotope composition of the water in the deep Cretaceous confined aquifer shows depletion in H-2 and O-18 relative to modern rainfall and the Quaternary shallow aquifer, which indicates a weak interaction between the two aquifers. Modern groundwater was identified in the shallow streambed aquifer, probably due to the direct infiltration of rainfall. On the other hand, C-14 ages in the deep groundwater range from 2,800 to 33,500 years, which suggests that this is paleowater that was recharged during the glacial age. The results indicate that there is a need for strategic groundwater management in the Gunii Khooloi basin.
  SPRINGER, English, Scientific journal
  DOI：https://doi.org/10.1007/s10040-019-01955-8
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85062991881&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85062991881&origin=inward
  DOI ID：10.1007/s10040-019-01955-8, ISSN：1431-2174, eISSN：1435-0157, SCOPUS ID：85062991881, Web of Science ID：WOS:000475982700004
• Geochemical Investigation of Metals and Trace Elements around the Abandoned Cu-Ni Mine Site in Selibe Phikwe, Botswana　　　　　　　　　　　　　　　
  Fiona S. Motswaiso; Kengo Nakamura; Noriaki Watanabe; Takeshi Komai
  Journal of Geoscience and Environment Protection, Volume：7, Number：5, First page：275, Last page：293, Jun. 2019, [Reviewed]
  English, Scientific journal
  DOI：https://doi.org/10.4236/gep.2019.75020
  DOI ID：10.4236/gep.2019.75020
• NaHCO3-promoted olivine weathering with H2 generation and CO2 sequestration in alkaline hydrothermal system　　　　　　　　　　　　　　　
  J. Wang; K. Nakamura; N. Watanabe; A. Okamoto; T. Komai
  IOP Conference Series: Earth and Environmental Science, Volume：257, Number：1, May 2019, [Reviewed]
  Hydration of Fe(II) bearing minerals, such as olivine ((Mg,Fe)SiO4), potentially generate hydrogen (H2). However, because of the low Fe(II) dissolution rate, the H2 production rate is usually low. We have recently proposed a novel system to promote H2 production and simultaneous CO2 storage in hydrothermal conditions via NaHCO3-enhanced olivine weathering. The present study reports the role of NaHCO3 on both H2 production from olivine hydration and on minerals generations on laboratory experiments in CO2-rich (0.5 mol/L NaHCO3) and CO2-free hydrothermal conditions at pH range of 8-11. The highest H2, HCOOH yields and carbonation rate reached at the CO2-rich experiment with lower alkaline pH at 8.25. The addition of high concentration NaHCO3 decreased pH from 10.92 to 8.25, whereas olivine and brucite dissolutions were accelerated. Thus, more Fe(II) was released from olivine and brucite, and H2 production was accelerated. At higher pH range, olivine dissolution was promoted, but brucite dissolution was suppressed in both CO2-rich and CO2-free conditions. This study suggests H2 production was promoted with the presence of HCO3-, but not the pH variation. The consumption of Fe(II)-bearing brucite was important in enhancing H2 production during olivine hydration process.
  English, International conference proceedings
  DOI：https://doi.org/10.1088/1755-1315/257/1/012017
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85068260865&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85068260865&origin=inward
  DOI ID：10.1088/1755-1315/257/1/012017, ISSN：1755-1307, eISSN：1755-1315, SCOPUS ID：85068260865
• Enhanced hydrogen production with carbon storage by olivine alteration in CO2-rich hydrothermal environments　　　　　　　　　　　　　　　
  Jiajie Wang; Noriaki Watanabe; Atsushi Okamoto; Kengo Nakamura; Takeshi Komai
  JOURNAL OF CO2 UTILIZATION, Volume：30, First page：205, Last page：213, Mar. 2019, [Reviewed]
  Here we report a novel experimental study on simultaneous hydrogen (H-2) production and CO2 storage. A high concentration of NaHCO3 (source of CO2) is utilized to promote H-2 generation from olivine (Mg, Fe)(2)SiO4) hydration, and then CO2 is reduced to formic acid (HCOOH) or sequestrated in magnesite (MgCO3) in a hydrothermal system. The effects of NaHCO3 concentration (0-1.0 mol/L) and initial pH (8-11) on H-2 production and CO2 storage were experimentally lab-scale tested at 300 degrees C. Both reaction pathways and reaction rates changed with variation of the reaction conditions. Under CO2-rich conditions, olivine consumption was promoted with the absence of Fe(II)-bearing brucite (Mg, Fe(OH)(2)), by which more Mg and Fe ions were released. Thus, the production of H-2 and carbonation processes were significantly accelerated. The highest H-2 generation rate reached 3.13 mmol/kg(olivine).h, which is more than 15 times higher than previously reported. The HCOOH yield was 129.1 mmol/kgolivine and magnesite ((Mg, Fe)CO3) generation reached a maximum of 19.2 wt% in 72 h. The enhancement of H-2 production at lower pH is primarily attributed to the presence of HCO3-, rather than the pH changes caused by NaHCO3 addition. The system proposed here has significant potential to be applied at the field-scale.
  ELSEVIER SCI LTD, English, Scientific journal
  DOI：https://doi.org/10.1016/j.jcou.2019.02.008
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85062172842&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85062172842&origin=inward
  DOI ID：10.1016/j.jcou.2019.02.008, ISSN：2212-9820, eISSN：2212-9839, SCOPUS ID：85062172842, Web of Science ID：WOS:000461436500019
• Creation of advanced discrimination method of paleo-tsunami deposits based on ITRAX geochemical analysis　　　　　　　　　　　　　　　
  山藤靖一朗; 中村謙吾; 駒井武
  Proceedings of Symposium on Geo-Environments and Geo-Technics, Volume：29th, 2019
  ISSN：0917-7183, J-Global ID：202202261331712412
• Exposure assessment of mercury by means of multi-media transport analysis in Artisanal Small-Scale Gold Mining (ASGM)　　　　　　　　　　　　　　　
  木下陽仁; 中村謙吾; 駒井武; 児玉谷仁; 冨安卓滋; 丸本幸治; 愛澤秀信; 野田和俊
  Proceedings of Symposium on Geo-Environments and Geo-Technics, Volume：29th, 2019
  ISSN：0917-7183, J-Global ID：202202275642899762
• Integrated Happiness Indices Based on Intentional Investigation of SDGs in the Research Fields of Environmental Earth Sciences　　　　　　　　　　　　　　　
  駒井武; 栗田満瑠; 中村謙吾; 保高徹生
  Proceedings of Symposium on Geo-Environments and Geo-Technics, Volume：29th, 2019
  ISSN：0917-7183, J-Global ID：202202286906106687
• Development of the Mercury Sensor using Quartz Crystal Microbalance in Artisanal and Small‐scale Gold Mining　　　　　　　　　　　　　　　
  野田和俊; 丸本幸治; 冨安卓滋; 児玉谷仁; 駒井武; 中村謙吾; 丸本倍美; 愛澤秀信
  Proceedings of Symposium on Geo-Environments and Geo-Technics, Volume：28th, First page：99‐102, Dec. 2018
  Japanese
  ISSN：0917-7183, J-Global ID：201902251623250135
• Hydrogeological Investigation on Shallow and Deep Groundwater in the Southern Gobi Desert, Mongolia
  BAYANZUL Batdemberel; BAYANZUL Batdemberel; MACHIDA Isao; NAKAMURA Kengo; WATANABE Noriaki; KOMAI Takeshi
  Proceedings of Symposium on Geo-Environments and Geo-Technics, Volume：28th, First page：71‐76, Dec. 2018
  English
  ISSN：0917-7183, J-Global ID：201902287038148568
• Application of multivariate analysis to investigate the trace element contamination in top soil of coal mining district in Jorong, South Kalimantan, Indonesia　　　　　　　　　　　　　　　
  Arie Pujiwati; K. Nakamura; N. Watanabe; T. Komai
  IOP Conference Series: Earth and Environmental Science, Volume：118, Number：1, Feb. 2018, [Reviewed]
  Multivariate analysis is applied to investigate geochemistry of several trace elements in top soils and their relation with the contamination source as the influence of coal mines in Jorong, South Kalimantan. Total concentration of Cd, V, Co, Ni, Cr, Zn, As, Pb, Sb, Cu and Ba was determined in 20 soil samples by the bulk analysis. Pearson correlation is applied to specify the linear correlation among the elements. Principal Component Analysis (PCA) and Cluster Analysis (CA) were applied to observe the classification of trace elements and contamination sources. The results suggest that contamination loading is contributed by Cr, Cu, Ni, Zn, As, and Pb. The elemental loading mostly affects the non-coal mining area, for instances the area near settlement and agricultural land use. Moreover, the contamination source is classified into the areas that are influenced by the coal mining activity, the agricultural types, and the river mixing zone. Multivariate analysis could elucidate the elemental loading and the contamination sources of trace elements in the vicinity of coal mine area.
  Institute of Physics Publishing, English, International conference proceedings
  DOI：https://doi.org/10.1088/1755-1315/118/1/012062
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85043283508&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85043283508&origin=inward
  DOI ID：10.1088/1755-1315/118/1/012062, ISSN：1755-1307, eISSN：1755-1315, SCOPUS ID：85043283508
• Numerical Simulation of Gas Hydrate Bearing Sediments for Enhanced Recovery Using Partial Oxidation method　　　　　　　　　　　　　　　
  Takeshi Komai; Yasuhide Sakamoto; Kengo Nakamura; Noriaki Watanabe
  Proceedings of 25th International Symposium of Offshore and Polar Engineering, Volume：25, First page：1, 2018, [Reviewed]
• STUDY ON PARTITIONING AND DISTRIBUTION IN SOIL-WATER PHASES FOR 1,4-DIOXANE IN GEO-ENVIRONMENT　　　　　　　　　　　　　　　
  NAKAMURA Kengo; ITO Haruki; KAWABE Yoshishige; KOMAI Takeshi
  Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), Volume：74, Number：2, First page：59, Last page：66, 2018, [Reviewed]
   1,4-dioxane is a toxic chemical substance which means to be difficult to take on-site soil investigation, compared with VOCs, because it has not been elucidated scientifically on geo-environmental behaviors. This study focuses on the partitioning and the distribution of 1,4-dioxane in soil, water and gas phases for inorganic soil and organic soils. The equilibrium concentrations in soil interlarded by 1,4-dioxane have been obtained under various conditions (pH, moisture content and water retention). The results showed that the distribution ratio of 1,4-dioxane to soil was 0.1 ~ 5.0%. However, under alkaline condition (pH 13), 1,4-dioxane could be distributed in the soil by an amount as much as 20%. The phrase soil water retention ability, 1,4-dioxane concentration largely changed due to the dilution of pore water in the soil with low organic content. Thus, it can be concluded that the majority of released 1,4-dioxane into the environment migrates to pore water in soil structure or into groundwater, unless it changed to a distinctive environmental conditions of high alkali and/or low water retention.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.2208/jscejer.74.59
  DOI ID：10.2208/jscejer.74.59, CiNii Articles ID：130006742999
• Extraction of Surface Soil Geochemical Characteristics of Element Concertation by Principal Component Analysis　　　　　　　　　　　　　　　
  NAKAMURA Kengo; KUWATANI Tatsu; KOMAI Takeshi; YAMASAKI Shin-ichi
  Journal of MMIJ, Volume：134, Number：2, First page：13, Last page：21, 2018, [Reviewed]
  

  Understanding the geochemical characteristics of various soils is significant for revealing the mechanisms occurring under natural conditions, assessing the environmental risks and managing the land use. However these various soils have complex forming mechanisms. This study examined geochemical characteristics of surface soils using statistical analysis. Principal component analysis (PCA), a very commonly used multivariate technique that can extract hidden structures and patterns from high-dimensional data, was applied to 633 classified soil samples. Soil samples collected in the Miyagi and Ibaraki prefectures were analyzed for major elements (Si, Ti, Al, Fe, Mg, Mn, Ca, Na and K) and heavy metals (Cr, Cu, Zn, As and Pb). Major elements showed most distinctive relationships with an inverse correlation between Si and Ti, Fe and Al. Heavy metals did not exhibit clear correlations with each other. However, background concentrations could be estimated using the frequency distribution and log-normal distribution curves. The background concentration of Cr, Cu, Zn, As and Pb were 50 ～150 mg/kg, 75 ～150 mg/kg, 200 ～300 mg/kg, 25 ～50 mg/kg and 30 ～60 mg/kg, respectively. Results of PCA clarified four common factors controlling major elements and heavy metals in the soil samples. They are 'Physicochemical formation', 'Soil components',' Vegetation effect' and 'Adsorption and desorption'. Soils are formed by leaching reactions from rain and groundwater and mixed organic matter from different vegetation types. Therefore, major elements and heavy metals in soil are affected by these processes, which are common to most soil types.

  
  The Mining and Materials Processing Institute of Japan, Japanese
  DOI：https://doi.org/10.2473/journalofmmij.134.13
  DOI ID：10.2473/journalofmmij.134.13, ISSN：1881-6118, J-Global ID：201802234278393755, CiNii Articles ID：130006351472, CiNii Books ID：AA12188381
• Behaviors of 1,4-Dioxane in soil and groundwater and its on-site detection method　　　　　　　　　　　　　　　
  Takeshi KOMAI; Kengo NAKAMURA
  The 14th International Conference on Sustainable Water Environmen, Volume：14, First page：102, Last page：111, 2018, [Reviewed], [Invited]
• Simultaneous olivine alteration and carbonation in CO2-rich geological condition　　　　　　　　　　　　　　　
  Jiajie Wang; Kengo Nakamura; Noriaki Watanabe; Takeshi Komai
  Proceedings of the International Offshore and Polar Engineering Conference, Volume：2018-June, First page：244, Last page：250, 2018, [Reviewed]
  To investigate the mineral change and energy output of the olivine hydration and carbonation processes in carbon rich hydrothermal system, we monitored a reaction between olivine and NaHCO3 fluid at 300oC and 10 MPa. The study showed the addition of NaHCO3 can promote both the olivine alteration and carbonation process. H2 and HCOOH were regarded as the energy output, with the highest yield of 1.13 mmol and 6.45 mmol/L achieved at 1.0 mol/L of NaHCO3 solution in 72 h. Addition of NaOH promotes brucite generation. The whole process was simulated by kinetic pseudo-second-order model.
  International conference proceedings
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85053467696&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85053467696&origin=inward
  ISSN：1098-6189, eISSN：1555-1792, SCOPUS ID：85053467696
• Experimental study on acid injection for enhanced gas recovery from gas hydrate reservoir　　　　　　　　　　　　　　　
  Yusuke Nakano; Fuyuki Kaneko; Kengo Nakamura; Yasuhide Sakamoto; Takeshi Komai
  Proceedings of the International Offshore and Polar Engineering Conference, Volume：2018-June, First page：199, Last page：204, 2018, [Reviewed]
  In-situ dissociation process of gas hydrate by Partial-oxidation and heating through acid or oxidant injection into the reservoir has been proposed. However, it was only evaluated by simulator based on the calorific value of acid. In this study, we carried out gas hydrate dissociation experiments in laboratory scale, by acid injection for the evaluation of this process. From the results, we clarified that the equilibrium temperature shifts to low temperature. In the case of acid injection, the equilibrium temperature decreased from 6.6 °C to 3.5 °C. The gas production rate was enhanced to more than twice due to the effects of exothermic reaction and inhibitor.
  International conference proceedings
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85053447190&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85053447190&origin=inward
  ISSN：1098-6189, eISSN：1555-1792, SCOPUS ID：85053447190
• Experimental investigation on changes in mechanical properties of volcanic sandstones under CO2 geological storage conditions　　　　　　　　　　　　　　　
  Koki Hattori; Noriaki Watanabe; Atsushi Okamoto; Kengo Nakamura; Takeshi Komai; Tetsuya Tamagawa
  ISRM International Symposium - 10th Asian Rock Mechanics Symposium, ARMS 2018, 2018, [Reviewed]
  In CO2 geological storage, CO2/brine/rock chemical interactions may lead to changes in mechanical properties of rocks. These changes can have impacts on performance and integrity in storage depending on their intensities. In case of sandstones consisting mainly of quartz and feldspar grains, there may be little changes in the properties because of low reactivities of the minerals. On the other hand, significant changes may occur in case of volcanic sandstones because they contain high-reactivity volcanic glasses. However, influences of the chemical interactions on the properties of volcanic sandstones have not been investigated so far. Thus, we have conducted triaxial compression experiments on two cylindrical volcanic sandstone samples consisting mainly of andesite/basalt and scoria grains (porosity: ca. 33%) at a confining/axial pressure of 30 MPa, pore pressure of 15 MPa, CO2 saturation of 50% or 77% and 60oC for several weeks. Bulk modulus, Young’s modulus and Poisson’s ratio were measured intermittently. Before and after the experiment, porosity and permeability were also measured on each sample, and initial and final brine chemistries were analyzed. Additionally, X-ray CT was conducted on the samples before and after the experiment. Changes in bulk modulus and Young’s modulus were qualitatively similar whereas Poisson’s ratio was almost constant. In case of one of the sample that contained relatively large scoria grains of high porosities, bulk modulus first decreased, then recovered partially, and finally became constant. In case of the other sample, bulk modulus first increased and then became constant. The decrease and increase in bulk modulus may have been caused respectively by dissolution-induced collapse of the relatively large scoria grains and by precipitations of some minerals such as silica minerals. Permeability of one of the samples increased while permeability of the other sample decreased, although porosity decreased for both samples.
  English, International conference proceedings
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85067526778&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85067526778&origin=inward
  SCOPUS ID：85067526778
• Development of a predictive model for lead, cadmium and fluorine soil-water partition coefficients using sparse multiple linear regression analysis　　　　　　　　　　　　　　　
  Kengo Nakamura; Tetsuo Yasutaka; Tatsu Kuwatani; Takeshi Komai
  CHEMOSPHERE, Volume：186, First page：501, Last page：509, Nov. 2017, [Reviewed]
  In this study, we applied sparse multiple linear regression (SMLR) analysis to clarify the relationships between soil properties and adsorption characteristics for a range of soils across Japan and identify easily-obtained physical and chemical soil properties that could be used to predict K and n values of cadmium, lead and fluorine. A model was first constructed that can easily predict the K and n values from nine soil parameters (pH, cation exchange capacity, specific surface area, total carbon, soil organic matter from loss on ignition and water holding capacity, the ratio of sand, silt and clay). The K and n values of cadmium, lead and fluorine of 17 soil samples were used to verify the SMLR models by the root mean square error values obtained from 512 combinations of soil parameters. The SMLR analysis indicated that fluorine adsorption to soil may be associated with organic matter, whereas cadmium or lead adsorption to soil is more likely to be influenced by soil pH, IL We found that an accurate K value can be predicted from more than three soil parameters for most soils. Approximately 65% of the predicted values were between 33 and 300% of their measured values for the K value; 76% of the predicted values were within +/- 30% of their measured values for the n value. Our findings suggest that adsorption properties of lead, cadmium and fluorine to soil can be predicted from the soil physical and chemical properties using the presented models. (C) 2017 Elsevier Ltd. All rights reserved.
  PERGAMON-ELSEVIER SCIENCE LTD, English, Scientific journal
  DOI：https://doi.org/10.1016/j.chemosphere.2017.07.131
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85028751186&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85028751186&origin=inward
  DOI ID：10.1016/j.chemosphere.2017.07.131, ISSN：0045-6535, eISSN：1879-1298, PubMed ID：28806679, SCOPUS ID：85028751186, Web of Science ID：WOS:000411846900059
• Total and Leachable Concentration of Trace Elements in Soil towards Human Health Risk, Related with Coal Mine in Jorong, South Kalimantan, Indonesia　　　　　　　　　　　　　　　
  Arie Pujiwati; Kengo Nakamura; Noriaki Watanabe; Takeshi Komai
  International Journal of Environmental, Chemical, Ecological, Geological and Geophysical Engineering, Volume：11, Number：10, First page：820, Last page：828, Sep. 2017, [Reviewed]
  English, Scientific journal
• Health Risk Assessment Model of 1,4-Dioxane Based on Physical and Chemical Properties of Soils　　　　　　　　　　　　　　　
  Takeshi Komai; Haruki Ito; Kengo Nakamura
  the 14th International Symposium on Persistent Toxic Substances, Volume：14, First page：241, Last page：248, 2017, [Reviewed], [Invited]
• The effect of reaction heat by acid injection for enhanced gas recovery from methane hydrate reservoir　　　　　　　　　　　　　　　
  Fuyuki Kaneko; Kengo Nakamura; Yasuhide Sakamoto; Noriaki Watanabe; Takeshi Komai
  23rd Formation Evaluation Symposium of Japan 2017, 2017, [Reviewed]
  Natural gas production from methane hydrate reservoir requires supplying heat. However, it is necessary to decrease energy consumption, and some new ways for enhanced gas production are investigated. One of them is partial-oxidation and heating process, which is proposed newly by us. This process is injecting acid or oxidant into the reservoir, which makes several effects for enhanced gas production. One of them is heat effect which comes from mineral dissolution by acid injection. In this study, we evaluated this with simulation. In order to carry out this calculation, we extended conventional numerical simulation model, and some parameters were needed. These parameters were about the dissolution rate and the heat. Therefore, we made the flow experiment with a column and measured the heat of mineral dissolution with a differential scanning calorimetry. In this experiment, Toyoura sand as a sediment and hydrochloric acid were used. In based on those experimental results, we determined constants. We carried out three types of numerical analyses about injecting acid into the reservoir. The first of them was the calculation about the reservoir which has no methane hydrate. The next was about the methane hydrate reservoir. The last was also about the methane hydrate reservoir, but injected acid temperatures were changed. In these calculations about the methane hydrate reservoir, the initial saturation of methane hydrate is 20 % on the assumption that this process as the secondary recovery follows the depressurization. The results show that injecting acid whose concentration is 0.50 mol/L heats the reservoir by approximately 30 ℃ from the initial temperature of methane hydrate reservoir. Hence, the total gas production in that case is comparable with that in hot water injection at 50 ℃ . Additionally, the lower the temperature of injected acid is, the higher the effect of reaction heat of mineral dissolution is. In conclusion, acid injection to methane hydrate reservoir will be the effective way of enhanced natural gas production.
  International conference proceedings
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85051703990&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85051703990&origin=inward
  SCOPUS ID：85051703990
• 東日本大震災より発生した津波堆積物中の金属類の解析及びヒ素の形態分析による健康リスク評価
  中臺大幾; 楡井久; 駒井武; 中村謙吾; 川辺能成
  Proceedings of Symposium on Geo-Environments and Geo-Technics, Volume：26th, First page：141‐146, Nov. 2016, [Reviewed]
  Japanese
  ISSN：0917-7183, J-Global ID：201702276937202777
• 原位置発熱によるメタンハイドレート分解促進に向けた酸化加熱法適用可能性の評価
  金子冬生; 中村謙吾; 坂本靖英; 駒井武
  石油技術協会誌, Volume：81, Number：4, First page：332‐333, Jul. 2016, [Reviewed]
  Japanese
  ISSN：0370-9868, J-Global ID：201602234175180352
• Discrimination of tsunami deposits by sparse modeling technique : An application to the estimation of tsunami inundation　　　　　　　　　　　　　　　
  Takeshi Komai; Kengo Nakamura; Noriyoshi Tsuchiya; Tatsu Kuwatani
  Journal of the Institute of Electronics, Information and Communication Engineers, Volume：99, Number：5, First page：418, Last page：423, May 2016, [Reviewed], [Invited]
  電子情報通信学会, Japanese, Scientific journal
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84991494219&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84991494219&origin=inward
  ISSN：0913-5693, CiNii Articles ID：40020842579, CiNii Books ID：AN1001339X, SCOPUS ID：84991494219
• Extraction of heavy metals characteristics of the 2011 Tohoku tsunami deposits using multiple classification analysis　　　　　　　　　　　　　　　
  Kengo Nakamura; Tatsu Kuwatani; Yoshishige Kawabe; Takeshi Komai
  CHEMOSPHERE, Volume：144, First page：1241, Last page：1248, Feb. 2016, [Reviewed]
  Tsunami deposits accumulated on the Tohoku coastal area in Japan due to the impact of the Tohokuold earthquake. In the study reported in this paper, we applied principal component analysis (PCA) and cluster analysis (CA) to determine the concentrations of heavy metals in tsunami deposits that had been diluted with water or digested using 1 M HCl. The results suggest that the environmental risk is relatively low, evidenced by the following geometric mean concentrations: Pb, 16 mg kg(-1) and 0.003 ml L-1; As, 1.8 mg kg(-1) and 0.004 ml L-1; and Cd, 0.17 mg kg(-1) and 0.0001 ml L. CA was performed after outliers were excluded using PCA. The analysis grouped the concentrations of heavy metals for leaching in water and acid. For the acid case, the first cluster contained Ni, Fe, Cd, Cu, Al, Cr, Zn, and Mn; while the second contained Pb, Sb, As, and Mo. For water, the first cluster contained Ni, Fe, Al, and Cr; and the second cluster contained Mo, Sb, As, Cu, Zn, Pb, and Mn. Statistical analysis revealed that the typical toxic elements, As, Pb, and Cd have steady correlations for acid leaching but are relatively sparse for water leaching. Pb and As from the tsunami deposits seemed to reveal a kind of redox elution mechanism using 1 M HCl. (C) 2015 The Authors. Published by Elsevier Ltd.
  PERGAMON-ELSEVIER SCIENCE LTD, English, Scientific journal
  DOI：https://doi.org/10.1016/j.chemosphere.2015.09.078
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84953790469&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84953790469&origin=inward
  DOI ID：10.1016/j.chemosphere.2015.09.078, ISSN：0045-6535, eISSN：1879-1298, PubMed ID：26469936, SCOPUS ID：84953790469, Web of Science ID：WOS:000367774400155
• EVALUATION OF POROSITY DISTRIBUTIONS WITHIN PACKED SOIL COLUMNS WITH X-RAY CT BASED 3-D VISUALIZATION　　　　　　　　　　　　　　　
  NAKAMURA Kengo; AOKI Tsubasa; WATANABE Noriaki; KOMAI Takeshi
  Journal of Japan Society of Civil Engineers, Ser. C (Geosphere Engineering), Volume：72, Number：2, First page：190, Last page：195, 2016, [Reviewed]
   The purpose of this paper is to examine the soil structure and flow path in order to standardize an upflow column test using an X-ray CT based numerical analysis. The soil structure and flow path are visualized of a porosity distribution by the X-ray CT. Methods of filling sample to the inside column were used ‘Free fall method’ and ‘Water tightening method’. Porosity of the Water tightening method, sample was maintained 35%-40% before and after in wet condition. And the porosity distribution is confirmed that uniforms and not to change removable with water flow. It is suggested that fluid flux in porosity distributions is stabile in the column. On the other hand, Porosity of the Free fall method, sample was observed that is increased 5% before and after water flow and the chap is occurred before water flow between layers. The porosity distribution is confirmed unevenness forms which have layers and part of large and small pores in the column. These unequal porosity distribution are thought that fluid flux has become spiro-flow and changed flow variation with time. It is revealed that the porosity distribution is significantly different due to differences in the soil filling method even same soil sample. It is considered that most important for standardization and generalization of column test methods and results is understood phenomenon (fluid flux, transport and response) resulting due to porosity distribution and consolidated reproducible test method for radical soil porosity distribute in the column.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.2208/jscejge.72.190
  DOI ID：10.2208/jscejge.72.190, ISSN：2185-6516, J-Global ID：201602229217673979, CiNii Articles ID：130005158091
• A Mathematical Statistical Approach to Assess and Research Heavy Metals in Natori River, Sendai Plain　　　　　　　　　　　　　　　
  NAKAMURA Kengo; Sato Kairi; KAWABE Yoshishige; KUWATANI Tatsu; KOMAI Takeshi
  Journal of MMIJ, Volume：132, Number：1, First page：22, Last page：30, 2016, [Reviewed]
  It is important to understand the distribution mechanism of heavy metal elements in environmental systems, because the toxicities of various metals and metalloids significantly affect health risks. The heavy metals concentrations are controlled by a wide of variety environmental factors. This study aims to clarify main influence factors on the heavy metal distribution in sediment, soil, river in the Natori River, Sendai City. We firstly produced geochemical maps for heavy metal concentrations (As, Pb and Cr) of river sediment, neighboring soil (bulk component, soluble component in 1N HCl and in pure water) and river water. The heavy metals concentrations in river water increase from upper stream to down stream, whereas heavy metal concentrations in river sediments and soil vary little from upper stream to downstream. There are no anomalous distributions of heavy metals in the studied area, although many anthropogenic materials are found in sediment, soil and river water. The correspondence analysis was applied to investigate relationships of heavy-metal concentrations between sediment, soil and river water. The results indicate that the heavy metals (As, Pb Cr and Zn) in sediment, soil and river water are dominantly controlled by natural sedimentary processes, such as denudation and sedimentation. The proposed method could be further applied for other pollutants in various environment systems. From a viewpoint of risk assessment of heavy metals, it is suggested by the presence of closer relationship of heavy metals that contains the risk information of heavy metals.
  The Mining and Materials Processing Institute of Japan, Japanese
  DOI：https://doi.org/10.2473/journalofmmij.132.22
  DOI ID：10.2473/journalofmmij.132.22, ISSN：1881-6118, J-Global ID：201702244773587680, CiNii Articles ID：130005123152, CiNii Books ID：AA12188381
• ネパール・テライ低地における地下水汚染の地球化学的特徴と数理統計解析
  駒井武; 中村謙吾; 大岡健三; 成澤昇; 中村圭三
  Proc Symp Geo-Environ Geo-Tech, Volume：25th, First page：77, Last page：82, Nov. 2015, [Reviewed]
  Japanese
  ISSN：0917-7183, J-Global ID：201502200366010024
• ネパール・テライ低地における地下水汚染の地球化学的特徴と数理統計解析　　　　　　　　　　　　　　　
  駒井 武; 中村謙吾; 大岡健三; 成澤 昇; 中村圭三
  環境地質学論文集, Volume：25, First page：78, Last page：83, Nov. 2015, [Reviewed]
  Japanese, Scientific journal
  ISSN：0917-7183, J-Global ID：201502200366010024
• LONG-TERM LEACHING BEHAVIOR OF HEAVY METALS FROM A MIXTURE OF STEEL SLAG AND HUMIC ACID　　　　　　　　　　　　　　　
  NAKAMURA Kengo; SAKANAKURA Hirohumi; KAWABE Yoshishige; KOMAI Takeshi
  Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), Volume：71, Number：1, First page：39, Last page：48, 2015, [Reviewed]
   Beneficial utilization of steel slag as an environmental remediation material of seawater damages by mixing with humic acid has been expected. To achieve it, environmental impact of the slag is required interms of leaching behavior of heavy metals.
   This research applied a seawater leaching test by shaking and immersing the slag with humic acid. Furthermore, based on the concept of environmental safety quality required in the sea-area utilization, applicability of the slag is discussed. Experimental results showed that by the interaction of steel slag and humic acid, concentration of Cd, Pb, Cr and B decreased and could meet the environmental safety quality criteria. In conclusion, the possibility that the mixture of steel slag and humic acid cause sea-environment pollution proved to be significantly low.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.2208/jscejer.71.39
  DOI ID：10.2208/jscejer.71.39, ISSN：2185-6648, J-Global ID：201502256253094552, CiNii Articles ID：130004962673
• Toward Standardization of a Percolation Test for Environmental Safety of Soil Materials　　　　　　　　　　　　　　　
  Sakanakura Hirofumi; Yasutaka Tetsuo; Inoba Seiji; Watanabe Yasutaka; Nakamura Kengo; Fujikawa Takuro
  地盤工学会誌 : 土と基礎, Volume：63, Number：1, First page：18, Last page：21, Jan. 2015, [Reviewed]
  地盤工学会, Japanese
  ISSN：1882-7276, CiNii Articles ID：110009899598, CiNii Books ID：AA12312210
• 多変量解析を用いた2011年東北沖津波堆積物の重金属類の特性抽出
  中村謙吾; 桑谷立; 川辺能成; 駒井武
  Proceedings of Symposium on Geo-Environments and Geo-Technics, Volume：24th, First page：79, Last page：84, Nov. 2014, [Reviewed]
  Japanese
  ISSN：0917-7183, J-Global ID：201502209827237422
• ネパール・テライ低地におけるヒ素の地下水汚染に関する地質環境
  駒井武; 中村謙吾; 桑谷立; 原淳子; 大岡健三; 濱田浩美; 中村圭三
  日本地下水学会講演会講演要旨, Volume：2014, First page：18, Last page：23, 2014, [Reviewed]
  Japanese
  J-Global ID：201402251898227213
• Up-flow column tests to evaluate heavy metal leaching for standardization　　　　　　　　　　　　　　　
  NAKAMURA Kengo; YASUTAKA Tetsuo; FUJIKAWA Takuro; TAKEO Miyuki; SATO Kenichi; WATANABE Yasutaka; INOBA Seiji; TAMOTO Shuichi; SAKANAKURA Hirofumi
  Japanese Geotechnical Journal, Volume：9, Number：4, First page：697, Last page：706, 2014, [Reviewed]
  In order to standardize an upward style column examination, which is one of evaluation methods on leaching behavior of heavy metal from contaminated soil, nine different conditions examined in this study were based on an ISO/CEN standard and applied to the columns set up in three different organizations. Data on the accuracy of the column and shortening test time were collected. Results showed that maximum concentration rates, integrated elution accounts and shapes of breakthrough curve (BTC) of fluoride, arsenic, calcium, magnesium, sodium, and potassium, with higher concentrations and lower Kd, were obtained with high reproducibility under the same condition in different organization. Moreover, by packing the column with half of the sample, shape of BTC and integrated elution quantity were confirmed with high accuracy. This study also found that the samples under wet or air-dried states had little influence on the results.
  The Japanese Geotechnical Society, Japanese
  DOI：https://doi.org/10.3208/jgs.9.697
  DOI ID：10.3208/jgs.9.697, ISSN：1880-6341, J-Global ID：201502264827661070, CiNii Articles ID：130004944102
• Estimating Grain Size and pH Effects on Steel Slag Dissolution Mechanisms　　　　　　　　　　　　　　　
  Nakamura Kengo; Yoneda Minoru
  Journal of the Japan Society of Material Cycles and Waste Management, Volume：25, Number：0, First page：25, Last page：35, 2014, [Reviewed]
  Steel slag produced by fluoric dissolution trends was examined in this study according to pH and temperature changes of the solvent. Steel slag dissolution amounts depending on grain size were examined under identical conditions. Results of dissolution test, it was suggested that the solvent pH affected the fluorine dissolution amount. Small grain sample showed the difference between estimated and measured data increased. The differences in grain sizes of 0-45 μm, became 100-1000 times on dissolution concentration. Compared with uniformity estimated and the measured data, sample sizes of 1.625-2 mm and 0.425-0.5 mm showed 0.1-10 times difference for each element. Sample sizes of 0-45 μm showed dissolution rates became 1/1000-1/10000 by produced gels. Results imply that the 0-45 μm sample size did not contribute to the dissolution amount, and suggest that 1%-0.1% of surface components are affected by the steel slag dissolution.
  Japan Society of Material Cycles and Waste Management, Japanese
  DOI：https://doi.org/10.3985/jjsmcwm.25.25
  DOI ID：10.3985/jjsmcwm.25.25, ISSN：1883-5856, J-Global ID：201402204016266015, CiNii Articles ID：130003395336, CiNii Books ID：AA12384878
• Evaluation of Geochemical Characteristics of Tsunami Deposits by the 2011 off the Pacific Cost of Tohoku Earthquake Using Dimensionality Reduction with a Principal Component Analysis　　　　　　　　　　　　　　　
  KUWATANI Tatsu; NAKAMURA Kengo; WATANABE Takahiro; OGAWA Yasumasa; KOMAI Takeshi
  Journal of Geography (Chigaku Zasshi), Volume：123, Number：6, First page：923, Last page：935, 2014, [Reviewed]
   Understanding the geochemical characteristics of tsunami deposits assists in revealing the mechanisms of tsunami inundation, assessing environmental risks, and using tsunami deposits industrially. Understanding geochemical characteristics is complex because geochemical compositions result from an accumulation of various known and unknown processes, such as original compositions of the hinterland, weathering, and transport. This study applies the principal component analysis (PCA) to the bulk chemistry of tsunami deposits generated by the 2011 off the Pacific coast of Tohoku Earthquake sampled from coastal areas ranging from Iwate prefecture to Fukushima prefecture. The PCA creates a set of uncorrelated synthetic variables called principal components (PCs) from a set of correlated observational data using an orthogonal transformation. By ignoring principal components that have small statistical variances, an important low-dimensional subspace can be extracted from a high-dimensional dataset. In addition, synthetic variables that have large statistical variances are considered to reflect important factors that control variations of datasets. The PCA was performed on whole-rock compositions of 18 major elements and heavy-metal elements. The first principal component (PC1) shows a clear inverse correlation between Si and other elements, which is considered to reflect the amount of sand composed of quartz and other silicate minerals. The second principal component (PC2) is characterized by a clear inverse correlation between minor elements such as lithophile and siderophile elements and chalcophile elements. The PC2 is considered to reflect the degree of enrichment of chalcophile elements caused by the interaction between original sediments and seawater. The third principal component (PC3) is characterized by an inverse correlation between Na and other major elements. The PC3 is considered to reflect the interaction between original sediments and seawater. Geological implications are not identified for other minor PCs, which have small variances (< 10%), probably due to observational noise and a combination of several known and unknown factors. The above three factors—amount of sand (PC1), enrichment of the chalcophile elements (PC2), and interaction of seawater (PC3) —are important processes that contribute to chemical variations of tsunami deposits generated by the 2011 off the Pacific coast of Tohoku Earthquake. These results and other geological evidence might be useful for understanding the mechanisms of tsunami inundation.
  Tokyo Geographical Society, Japanese
  DOI：https://doi.org/10.5026/jgeography.123.923
  DOI ID：10.5026/jgeography.123.923, ISSN：0022-135X, J-Global ID：201502248096427507, CiNii Articles ID：130004813834, CiNii Books ID：AN00322536
• Upgrade of up-flow percolation test ISO/TS 21268-3 - Japan’s intention and possible contributions -　　　　　　　　　　　　　　　
  Tetsuo Yasutaka; Hirofumi Sakanakura; Shuichi Tamoto; Seiji Inoba; Yasutaka Watanabe; Kenichi Sato; Takuro Fujikawa; Kengo Nakamura; Naka angelica; Miyuki Takeo
  ISO-TC190, 2014, [Reviewed]
• Principle component analysis for geochemical data of the 2011 Tohoku-oki Tsunami Deposits　　　　　　　　　　　　　　　
  Kengo Nakamura; Tatsu Kuwatani; Takeshi Komai; Takahiro Watanabe; Yasumasa Ogawa; Noriyoshi Tsuchiya
  ISME-13, First page：75, Last page：80, 2014, [Reviewed]
• EVALUATION OF FLUORINE STANDARD VALUE IN STEEL SLAG FORWARD THE DIFFERENCE IN RISK ASSESSMENT SCENARIOS　　　　　　　　　　　　　　　
  NAKAMURA Kengo; YONEDA Minoru
  Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), Volume：69, Number：2, First page：55, Last page：66, 2013, [Reviewed]
   Environmental application of recycled products is indispensable to recycling-oriented society. For historical reasons, recycled products and soil have been discriminated. In fact, many cases to reuse recycle products have adopted the same criteria as the Soil Concentration Countermeasures Law. As long as recycled products and soil to be distinguished, risk assessment should be made for recycled products instead of applying a similar soil contamination risk assessment. In this study, for risk assessment of recycle products the application of clearance level scenario was examined. Products to apply clearance levels are commercial ones under controlled. Steel slag are also controlled. It is considered that Steel slag can be applied clearance levels scenario from usage. In order to reduce energy consumption in steel slag production, fluorine is added to enhance the fluidity of the slag and lower the temperature. It is also has possibility to reduce the CO₂ emission during the process. Results of the review showed that reference value of Soil Contamination Countermeasures Law have become excessive risk assessment for the use of Steel slag. When applying clearance level scenarios, intake amount of fluorine from steel slag to local residents is 1/10~1/100 by comparison amount of intake the Soil Concentration Countermeasures Law. Excessive risk assessment may impede the industrial development. From the selection of clearance levels as shown in this study, it is necessary to implement a reasonable risk assessment. The recycled products is also possible to use 10 times larger criteria of that of Soil Contamination Countermeasures Law.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.2208/jscejer.69.55
  DOI ID：10.2208/jscejer.69.55, ISSN：2185-6648, J-Global ID：201402273927117230, CiNii Articles ID：130004962475
• Estimates of the chemical form of fluorine in steel slag by the application of saturated column test　　　　　　　　　　　　　　　
  Kengo Nakamura; Minoru Yoneda; Yasuto Matsui; Aki Nakayama
  WASCON2012 Conference proceeding, First page：1, Last page：9, 2012, [Reviewed]
• Problems and future issues about steel slag to be recycled　　　　　　　　　　　　　　　
  中村 謙吾
  Volume：25, Number：2, First page：46, Last page：49, 2011, [Reviewed]
• Study on the method of reducing fluorine dissolution through the process of steel slag aging as recycling material　　　　　　　　　　　　　　　
  Kengo Nakamura; Minoru Yoneda
  2011, [Reviewed]

• ケイ酸塩型土壌改良材の加速風化作用を用いた農地でのCO2除去技術　　　　　　　　　　　　　　　
  中村謙吾
  Volume：37, 2024, [Lead]

• Relationship between the formation of flow paths and elution behavior with water flow through the soil column　　　　　　　　　　　　　　　
  土田恭平; 中村謙吾; 近藤萌波; 渡邉則昭; 駒井武
  地下水・土壌汚染とその防止対策に関する研究集会講演集(Web), 2021
  2021 - 2021
• Visualization of pores and predominant flow paths in undisturbed viscous soil and organic matter soil　　　　　　　　　　　　　　　
  中村謙吾; 土田恭平; 渡邉則昭; 駒井武
  地下水・土壌汚染とその防止対策に関する研究集会講演集(Web), 2021
  2021 - 2021
• Discrimination of Tsunami Deposits using Machine Leaning and its Database Development in Eastern Japan　　　　　　　　　　　　　　　
  駒井武; 栗田満瑠; 中村謙吾; 桑谷立
  Proceedings of Symposium on Geo-Environments and Geo-Technics, 2020
  2020 - 2020
• Geochemical Discrimination of Tsunami Deposits using High-dimensional Data-driven Analysis　　　　　　　　　　　　　　　
  駒井武; 中村謙吾; 桑谷立
  資源・素材(Web), 2020
  2020 - 2020
• 土壌カラム内に形成される流路と溶出挙動との関係　　　　　　　　　　　　　　　
  土田恭平; 中村謙吾; 近藤萌波; 渡邉則昭; 駒井武
  2020
  2020 - 2020
• Visualization of flow path in soil column by X-ray CT　　　　　　　　　　　　　　　
  土田恭平; 中村謙吾; 近藤萌波; 渡邉則昭; 駒井武
  資源・素材(Web), 2020
  2020 - 2020
• Advanced discrimination of paleo-tsunami deposits using data-driven geochemical analysis　　　　　　　　　　　　　　　
  駒井武; 山藤靖一郎; 中村謙吾
  日本地球惑星科学連合大会予稿集(Web), 2020
  2020 - 2020
• Characteristics of factors that release mercury from soil and prediction of mercury flux emission　　　　　　　　　　　　　　　
  近藤萌波; 中村謙吾; 土田恭平; 渡邉則昭; 駒井武
  資源・素材(Web), 2020
  2020 - 2020
• Compositional data analysis for surface soils in Ibaraki Prefecture, Japan　　　　　　　　　　　　　　　
  桑谷立; 中村謙吾; 赤穂昭太郎; 駒井武
  資源・素材(Web), 2020
  2020 - 2020
• Formation of amorphous silica particles and its influences on permeability of granite fractures in supercritical geothermal environments　　　　　　　　　　　　　　　
  阿部光; 渡邉則昭; 中村謙吾; 岡本敦; 駒井武
  日本地熱学会学術講演会講演要旨集, 2020
  2020 - 2020
• A new chemical stimulation: Selective mineral dissolution in fractures by chelating agent flooding　　　　　　　　　　　　　　　
  高橋香於里; 渡邉則昭; 中村謙吾; 駒井武; 熊野裕介; 赤工浩平; 玉川哲也
  日本地熱学会学術講演会講演要旨集, 2020
  2020 - 2020
• 数理統計解析による鉱山の自然回帰のための地球科学的指標　　　　　　　　　　　　　　　
  中村謙吾; 駒井武
  2019
  2019 - 2019
• 吸着材選定のためのデータ駆動解析を用いた土壌へのヒ素吸着機構の推定　　　　　　　　　　　　　　　
  中村謙吾; 駒井武
  2019
  2019 - 2019
• 不飽和汚染土壌からの揮発フラックス予測モデルの構築　　　　　　　　　　　　　　　
  坂本靖英; 川辺能成; 中村謙吾; 駒井武
  2019
  2019 - 2019
• 水銀個人ばく露測定システムの高感度化とその応用　　　　　　　　　　　　　　　
  野田和俊; 愛澤秀信; 丸本幸治; 丸本倍美; 冨安卓滋; 児玉谷仁; 駒井武; 中村謙吾
  2019
  2019 - 2019
• 揮発性化学物質による汚染土壌からの揮発フラックス予測のための数値解析モデル　　　　　　　　　　　　　　　
  坂本靖英; 川辺能成; 中村謙吾; 駒井武
  2019
  2019 - 2019
• 小規模金採掘現場における水銀の個人ばく露の現状と課題　　　　　　　　　　　　　　　
  野田和俊; 愛澤秀信; 丸本幸治; 丸本倍美; 冨安卓滋; 児玉谷仁; 駒井武; 中村謙吾
  Sep. 2018, [Domestic conference]
  Japanese, Oral presentation
• CO₂地中貯留条件下における火山性砂岩の力学特性変化　　　　　　　　　　　　　　　
  服部晃己; 渡邉則昭; 岡本敦; 中村謙吾; 駒井武; 玉川哲也
  石油技術協会誌, Jul. 2018
  Jul. 2018 - Jul. 2018, Japanese
• 2-2-1 Evaluation on Enhanced Recovery of gas hydrates using oxidation heating method　　　　　　　　　　　　　　　
  Komai Takeshi; nakano Yushuke; Nakamura Kengo
  Proc. Annual Conf. J.I.E., Jul. 2018
  

  In order to improve the gas recovery rate from the gas hydrate reservoir, secondary recovery by thermal stimulation method aimed at recovering the temperature inside the reservoir is being considered. The heating method by acidic water injection is a new heat stimulation method proposed by us and enhances dissociation of hydrate by utilizing the heat generation by mineral dissolution in the reservoir due to acidic water injection. In the hydrate dissociation experiment by acidic water injection, the production enhancement effect by the inhibitor effect is clarified. Moreover, the influence of the heat generation effect was confirmed.

• 1,4‐ジオキサンの土壌間隙水中の分配挙動に関する考察　　　　　　　　　　　　　　　
  中村謙吾; 伊東玄樹; 駒井武
  日本水環境学会年会講演集, Mar. 2018
  Japanese
• 地盤中卓越流路を考慮した重金属類溶出・移動性の評価手法の開発　　　　　　　　　　　　　　　
  中村謙吾
  環境助成研究成果 概要集 第36回・2015年度分:3件 第37回・2016度分:24件 平成30年, 2018
  2018 - 2018, Japanese
• Evaluation of the effect of enhanced gas recovery from a methane hydrate reservoir through the utilization of in-situ heat generation by acid injection　　　　　　　　　　　　　　　
  Nakano Yusuke; Nakamura Kengo; Sakamoto Yasuhide; Komai Takeshi
  Journal of the Japanese Association for Petroleum Technology, 2018, The Japanese Association for Petroleum Technology
  2018 - 2018, Japanese
  

  In this study, for the purpose of enhanced gas recovery from an methane hydrate （MH） reservoir, we conducted experimental and numerical study for acid injection process as a secondary gas recovery after the depressurization operation. This process is based on the concept of effective utilization of heat generation resulting from mineral dissolution via acid injection for the promotion of in-situ dissociation of MH. For the numerical analysis for the acid injection process, based on the assumption that the charge balance in the injected acidic solution after the contact with the solid matrix becomes neutral due to mineral dissolution into the water phase, we defined two acid components before/after the contact with the solid matrix. In addition, the kinetic parameters and heat of mineral dissolution during the acid injection were obtained through laboratory column tests and DSC analysis, respectively, and introduced into the developed numerical model. Using this numerical model, we conducted a series of numerical analyses for the acid injection process after the depressurization operation. From the calculation results, it was found that a high-temperature zone formed by in-situ heat generation resulting from mineral dissolution extended to the side of the production well to promote MH dissociation. Based on the total amount of methane gas trapped in MH at the initial stage, total gas recovery using depressurization and acid injection was estimated to be approximately 90% and we confirmed that the acid injection process is very effective as a secondary gas recovery targeting the MH reservoir under low-temperature and low-pressure condition after the depressurization operation.

• 1,4-ジオキサンの土壌汚染調査方法についての検討　　　　　　　　　　　　　　　
  中島誠; 日高レイ; 中村謙吾; 駒井武
  2018
  2018 - 2018
• 酸化加熱法によるガスハイドレートの増進回収に関する基礎的研究　　　　　　　　　　　　　　　
  駒井武; 中野裕介; 中村謙吾; 金子冬生
  2018
  2018 - 2018
• 1,4-ジオキサンによる土壌汚染の調査方法に関する検討　　　　　　　　　　　　　　　
  中島誠; 日高レイ; 中村謙吾; 駒井武
  2018
  2018 - 2018
• Extraction of Surface Soil Geochemical Characteristics of Element Concertation by Principal Component Analysis　　　　　　　　　　　　　　　
  中村謙吾; 桑谷立; 駒井武; 山崎慎一
  Journal of MMIJ (Web), 2018
  2018 - 2018
• 1,4-ジオキサンの土壌間隙水中の分配挙動に関する考察　　　　　　　　　　　　　　　
  中村謙吾; 伊東玄樹; 駒井武
  2018
  2018 - 2018
• 1,4‐ジオキサンによる土壌汚染の調査方法に関する検討　　　　　　　　　　　　　　　
  中島誠; 日高レイ; 中村謙吾; 駒井武
  日本地下水学会講演会講演予稿, 2018
  Japanese
• Research of VOC (1,4-Dioxane, Benzene and 1,1,1-Trichlorethylene) diffusion and distribution in soil using Two-dimensional soil bath　　　　　　　　　　　　　　　
  中村 謙吾; 伊東 玄樹; 駒井 武
  地下水・土壌汚染とその防止対策に関する研究集会講演集, Nov. 2017
  Japanese
• Gas-Solid separation and Health Risk Assessment of 1,4-Dioxane　　　　　　　　　　　　　　　
  伊東 玄樹; 中村 謙吾; 駒井 武
  地下水・土壌汚染とその防止対策に関する研究集会講演集, Nov. 2017
  Japanese
• Study on contamination status of soil and groundwater by 1,4-dioxane　　　　　　　　　　　　　　　
  日高 レイ; 中島 誠; 駒井 武; 中村 謙吾; 中村 公亮
  地下水・土壌汚染とその防止対策に関する研究集会講演集, Nov. 2017
  Japanese
• Data driven analysis for a prediction method of arsenic adsorption to soils　　　　　　　　　　　　　　　
  黒澤 孝太; 中村 謙吾; 駒井 武
  地下水・土壌汚染とその防止対策に関する研究集会講演集, Nov. 2017
  Japanese
• Development of the Personal exposure monitoring system for mercury work environment in Artificial Small-scale and Gold Mining　　　　　　　　　　　　　　　
  野田和俊; 愛澤秀信; 丸本幸治; 丸本倍美; 冨安卓滋; 児玉谷仁; 駒井武; 中村謙吾
  センサ・マイクロマシンと応用システムシンポジウム(CD-ROM), Oct. 2017, Institute of Electrical Engineers of Japan
  Oct. 2017 - Oct. 2017, Japanese
• 小規模金採掘地域での水銀使用作業環境個人ばく露測定システムの開発　　　　　　　　　　　　　　　
  野田和俊; 愛澤秀信; 丸本幸治; 丸本倍美; 冨安卓滋; 児玉谷仁; 駒井武; 中村謙吾
  センサ・マイクロマシンと応用システムシンポジウム(CD-ROM), Oct. 2017
  Japanese
• 土壌特性に着目した1,4‐ジオキサンの分配に関する考察　　　　　　　　　　　　　　　
  中村謙吾; 伊東玄樹; 駒井武
  日本水環境学会年会講演集, Mar. 2017
  Japanese
• 若手研究者＆技術者　　　　　　　　　　　　　　　
  中村 謙吾
  2017, [Invited]
  2017 - 2017
• 日本国内に見られる飽和の無機土壌および有機土壌における1,4-ジオキサン,トリクロロエチレン,ベンゼンの二次元的な移動特性の解明　　　　　　　　　　　　　　　
  中村公亮; 中村謙吾; 駒井武
  2017
  2017 - 2017
• 土壌の加熱に伴う1,4-ジオキサンの除去率の検討　　　　　　　　　　　　　　　
  伊東玄樹; 中村謙吾; 駒井武
  2017
  2017 - 2017
• 土壌特性に着目した1,4-ジオキサンの分配に関する考察　　　　　　　　　　　　　　　
  中村謙吾; 伊東玄樹; 駒井武
  2017
  2017 - 2017
• 不飽和層における物質移行特性に着目した汚染土壌の重金属等によるリスク評価法の検討　　　　　　　　　　　　　　　
  保高徹生; ZHANG Hong; 井本由香利; 中村謙吾; 勝見武
  地盤工学研究発表会発表講演集(CD-ROM), 2017
  Japanese
• 日本国内に見られる飽和の無機土壌および有機土壌における1,4‐ジオキサン,トリクロロエチレン,ベンゼンの二次元的な移動特性の解明　　　　　　　　　　　　　　　
  中村公亮; 中村謙吾; 駒井武
  資源・素材学会春季大会(Web), 2017
  Japanese
• 土壌の加熱に伴う1,4‐ジオキサンの除去率の検討　　　　　　　　　　　　　　　
  伊東玄樹; 中村謙吾; 駒井武
  資源・素材(Web), 2017
  Japanese
• 水晶振動子を利用した水銀作業環境個人ばく露測定システムの検知特性　　　　　　　　　　　　　　　
  野田和俊; 愛澤秀信; 丸本幸治; 丸本倍美; 冨安卓滋; 児玉谷仁; 駒井武; 中村謙吾
  資源・素材(Web), 2017
  Japanese
• フライアッシュコンクリートの強度発現における間隙分布の関係性の考察　　　　　　　　　　　　　　　
  中村謙吾; 井上陽介; 駒井武
  資源・素材(Web), 2017
  Japanese
• データ駆動型解析を用いた歴史大津波堆積物の判別　　　　　　　　　　　　　　　
  遠藤玲紗; 中村謙吾; 駒井武
  資源・素材(Web), 2017
  Japanese
• Study on movement of 1,4-dioxane in saturated soil　　　　　　　　　　　　　　　
  Nakamura Kousuke; Nakamura Kengo; Takeshi Komai
  Proceedings of the Annual Conference of Japan Society of Material Cycles and Waste Management, 2017
  Japanese
  1,4-ジオキサン(DXA)は発癌性を有する揮発性有機化合物(VOC)である。既存のスクリーニング技術では，DXAを土壌ガスから検出できなかった。DXAは帯水層に移行しやすく，他のVOCと混和する。本研究では，帯水層において，他のVOCとしてベンゼン(Bn)およびトリクロロエチレン(TCE)と混在したDXAの移動と残留について，DXA濃度分布の経時変化とDXA，Bn，TCEの残留量の比較により検討した。室内実験では，帯水層を土槽と飽和土により模擬した。間隙水にDXA，Bn，TCEを与えた。土壌を採取して溶出試験を行った。結果より，BnとTCEが5%未満だけ残留する条件でも，DXAは77%以上が残留することが分かった。また，DXAは流水に伴い移動するだけでなく，静水中でも移動することが分かった。水における高い残留性から，スクリーニングでは土壌または間隙水の採取が効果的と予想された。
• 2-1-2 Acid Injection in Heating Process by Oxidation for Enhanced Natural Gas Production from Methane Hydrate　　　　　　　　　　　　　　　
  KOMAI Takeshi; NAKANO Yuusuke; KANEKO Huyuki; NAKAMURA Kengo
  Proceedings of the Annual Conference of The Japan Institute of Energy, 2017
  Japanese
  

  In this study, we evaluated the effect of acid injection for enhanced natural gas production. To evaluate it with numerical analysis, we got the parameter about the calorific value in dissolution of Toyoura sand to three acids (Nitric acid, Hydrochloric acid and Sulfuric acid) and the reaction rate of the dissolution. Based on those results, we carried out simulations of the behavior in the MH reservoir in heating process by acid injection. The injection water (50 deg, °C) contained each acid (0.010 mol/L, 0.050 mol/L, 0.10 mol/L, 0.50 mol/L, 1.0 mol/L and no acid). As a result, MH reservoir was more heated in each acid injection than only hot water injection. The total gas production in the 3.0 years from starting the operation is enhanced by 17.2 percent at a maximum. In conclusion, the acid injection to MH reservoir is the good way of enhanced gas production from MH reservoir.

• Health Risk Assessment Model Considering Adsorptive Property of 1,4-Dioxane　　　　　　　　　　　　　　　
  伊東 玄樹; 中村 謙吾; 駒井 武
  地下水・土壌汚染とその防止対策に関する研究集会講演集, Jun. 2016
  Japanese
• 3D visualization of preferential flow path in soil for Up-flow column test　　　　　　　　　　　　　　　
  青木 飛翔; 中村 謙吾; 渡邉 則昭; 駒井 武
  地下水・土壌汚染とその防止対策に関する研究集会講演集, Jun. 2016
  Japanese
• Research of 1,4-Dioxane environment dynamics and distribution in Japan　　　　　　　　　　　　　　　
  中村 謙吾; 伊東 玄樹; 駒井 武
  地下水・土壌汚染とその防止対策に関する研究集会講演集, Jun. 2016
  Japanese
• 1,4‐ジオキサンの土壌吸着特性の把握と健康リスク評価　　　　　　　　　　　　　　　
  中村謙吾; 伊東玄樹; 駒井武
  日本水環境学会年会講演集, Mar. 2016
  Japanese
• 日本国内に多く見られる土壌への吸着特性を考慮した1,4-ジオキサンの健康リスク評価　　　　　　　　　　　　　　　
  伊東玄樹; 中村謙吾; 駒井武
  2016
  2016 - 2016
• 土壌環境を考慮した1,4-ジオキサンの分配特性に関する考察　　　　　　　　　　　　　　　
  中村謙吾; 伊東玄樹; 榊原健人; 駒井武
  2016
  2016 - 2016
• 1,4-ジオキサンの分配特性に基づく環境動態および土壌調査法の検討　　　　　　　　　　　　　　　
  駒井武; 中村謙吾; 伊東玄樹; 中島誠
  2016
  2016 - 2016
• 1,4-ジオキサンの土壌吸着特性の把握と健康リスク評価　　　　　　　　　　　　　　　
  中村謙吾; 伊東玄樹; 駒井武
  2016
  2016 - 2016
• 蔵王火山で過去100年間に見られた活発化と現在の状況　　　　　　　　　　　　　　　
  後藤章夫; 土屋範芳; 平野伸夫; 渡邊隆広; 松中哲也; 久利美和; 宇野正起; 岡本敦; 中村謙吾; 町澄秋
  日本地球惑星科学連合大会予稿集(Web), 2016
  Japanese
• 1,4‐ジオキサンの分配特性に基づく環境動態および土壌調査法の検討　　　　　　　　　　　　　　　
  駒井武; 中村謙吾; 伊東玄樹; 中島誠
  資源・素材(Web), 2016
  Japanese
• X線CTを用いたカラム内部流路の可視化による卓越流路の粒径依存特性の評価　　　　　　　　　　　　　　　
  青木飛翔; 中村謙吾; 渡邉則昭; 駒井武
  資源・素材(Web), 2016
  Japanese
• 日本国内に多く見られる土壌への吸着特性を考慮した1,4‐ジオキサンの健康リスク評価　　　　　　　　　　　　　　　
  伊東玄樹; 中村謙吾; 駒井武
  資源・素材(Web), 2016
  Japanese
• 「水銀に関する水俣条約」に対応したオンサイト測定システムの開発　　　　　　　　　　　　　　　
  野田和俊; 丸本幸治; 愛澤秀信; 駒井武; 中村謙吾
  資源・素材(Web), 2016
  Japanese
• 1,4‐ジオキサンの移流特性と微生物分解による浄化効果に関する数値解析　　　　　　　　　　　　　　　
  坂本靖英; 川辺能成; 伊東玄樹; 中村謙吾; 駒井武
  資源・素材(Web), 2016
  Japanese
• 土壌環境を考慮した1,4‐ジオキサンの分配特性に関する考察　　　　　　　　　　　　　　　
  中村謙吾; 伊東玄樹; 榊原健人; 駒井武
  資源・素材(Web), 2016
  Japanese
• 1,4-ジオキサンの環境動態の把握と健康リスク評価　　　　　　　　　　　　　　　
  伊東玄樹; 中村謙吾; 駒井武
  2015
  2015 - 2015
• 主成分分析を用いた重金属類の含有量から見た土壌多様性の考察　　　　　　　　　　　　　　　
  中村謙吾; 桑谷立; 駒井武
  地下水・土壌汚染とその防止対策に関する研究集会講演集(CD-ROM), 2015
  Japanese
• 1,4‐ジオキサンの土壌・地下水中の環境動態およびリスク評価　　　　　　　　　　　　　　　
  駒井武; 中村謙吾; 伊東玄樹; 中島誠; 坂本靖英; 川辺能成
  日本地下水学会講演会講演要旨, 2015
  Japanese
• 名取川流域における地殻表層の元素挙動の解明―次元圧縮を用いた地球化学的特徴抽出―　　　　　　　　　　　　　　　
  佐藤海里; 中村謙吾; 桑谷立; 川辺能成; 駒井武
  資源・素材学会春季大会(Web), 2015
  Japanese
• データ駆動を用いた土壌中成分間の関係性の標準化　　　　　　　　　　　　　　　
  中村謙吾; 川辺成能; 桑谷立; 駒井武
  資源・素材(Web), 2015
  Japanese
• 地圏環境リスク評価システム(GERAS)による1,4‐ジオキサンの土壌・地下水環境中で拡散予測とリスク評価　　　　　　　　　　　　　　　
  坂本靖英; 中村謙吾; 伊東玄樹; 川辺能成; 駒井武
  資源・素材(Web), 2015
  Japanese
• 1,4‐ジオキサンの環境動態の把握と健康リスク評価　　　　　　　　　　　　　　　
  伊東玄樹; 中村謙吾; 駒井武
  資源・素材(Web), 2015
  Japanese
• Comparison of the leaching characteristics of heavy metals from contaminated soil　　　　　　　　　　　　　　　
  保高 徹生; 中村 謙吾; 星 純也
  地下水・土壌汚染とその防止対策に関する研究集会講演集, Jun. 2014
  Japanese
• 上向流カラム試験方法が溶出特性評価に与える影響の検討　　　　　　　　　　　　　　　
  中村謙吾; 保高徹生; 肴倉宏史; 藤川拓朗; 竹尾美幸
  地盤工学研究発表会発表講演集(CD-ROM), 2014
  Japanese
• 実汚染土壌を用いた土壌中重金属類の長期溶出特性の検討　　　　　　　　　　　　　　　
  星純也; 高橋真子; 酒井良枝; 中村謙吾; 保高徹生
  地下水・土壌汚染とその防止対策に関する研究集会講演集(CD-ROM), 2014
  Japanese
• 吸着層工法の適用におけるサイト概念モデルを用いたリスク評価―自然由来ヒ素含有土壌を事例として―　　　　　　　　　　　　　　　
  中村謙吾; 保高徹生; 三浦俊彦; 井出一貴; 鈴木和明; 西田憲司
  地下水・土壌汚染とその防止対策に関する研究集会講演集(CD-ROM), 2014
  Japanese
• 硬質粘土の性状を考慮した吸着層工法の検討　　　　　　　　　　　　　　　
  三浦俊彦; 井出一貴; 西田憲司; 山田祐樹; 保高徹生; 中村謙吾
  地盤工学研究発表会発表講演集(CD-ROM), 2014
  Japanese
• 硬質粘土の砒素溶出特性の検討　　　　　　　　　　　　　　　
  井出一貴; 三浦俊彦; 西田憲司; 鈴木和明; 保高徹生; 中村謙吾
  地盤工学研究発表会発表講演集(CD-ROM), 2014
  Japanese
• 重金属汚染土壌の溶出特性評価―カラム試験と各種溶出試験による累積溶出量の比較―　　　　　　　　　　　　　　　
  保高徹生; 中村謙吾; 星純也; 高橋真子; 三浦俊彦; 井出一貴; 肴倉宏史
  地盤工学研究発表会発表講演集(CD-ROM), 2014
  Japanese
• 上向流カラム通水試験による溶出挙動評価法の基準化に向けた検討　　　　　　　　　　　　　　　
  竹尾美幸; 松尾典映; 佐藤研一; 藤川拓朗; 古賀千佳嗣; 肴倉宏史; 井野場誠治; 渡邊保貴; 保高徹生; 中村謙吾
  地盤工学研究発表会発表講演集(CD-ROM), 2014
  Japanese
• Evaluation of Long-term Leaching characteristics of Arsenic from Soil with Naturally- Derived Arsenic　　　　　　　　　　　　　　　
  Nakamura Kengo; Yasutaka Tetsuo; Miura Toshihiko; Ide Kazuki; Nishida Kenzi
  Proceedings of the Annual Conference of Japan Society of Material Cycles and Waste Management, 2013
  Japanese
  建設現場で発生する自然由来の重金属を含有する土壌の取り扱いは汚染土壌の処理や建設発生土の有効利用の観点から社会的に大きな課題である。重金属類を含有する土壌を適切に管理するためには、土壌からの重金属類の長期的な溶出特性の把握が必要である。本研究では、堆積層の硬質粘土中のヒ素を対象として、粒径別にシリアルバッチ試験、酸/アルカリ溶出試験及び逐次抽出試験を適用し、一般環境下において溶出しうるヒ素の最大量（以下、可能最大溶出量という）を推定した。 シリアルバッチ試験の結果、液j固比10でのヒ素の溶出量は粒径に大きく依存し、1回の溶出量は液固比の増加に伴い漸減することが確認された。また、各種溶出試験から推定された可能最大溶出率から、当該土壌からのヒ素の可能最大溶出量は、粒径31.5-50.0mmの試料で最大2.1%程度、粒径<2mmの試料で最大10.5%程度であることが確認された。
• 製鋼スラグ環境利用におけるフッ素溶出量の検討　　　　　　　　　　　　　　　
  中村謙吾; 米田稔; 松井康人
  地下水・土壌汚染とその防止対策に関する研究集会講演集(CD-ROM), 2012
  Japanese
• 電気炉スラグ環境影響処理によるフッ素溶出量変化の検討　　　　　　　　　　　　　　　
  中村謙吾; 米田稔
  廃棄物資源循環学会研究発表会(CD-ROM), 2012
  Japanese
• 産業廃棄物不法投棄現場周辺における環境水中の重金属濃度　　　　　　　　　　　　　　　
  颯田尚哉; 中村謙吾; 福谷哲; 立石貴浩
  地下水・土壌汚染とその防止対策に関する研究集会講演集(CD-ROM), 2009
  Japanese

• 津波堆積物の地球化学的判別に基づく全国津波データベースの構築　　　　　　　　　　　　　　　
  2021 - 2023
  Principal investigator
• Fluid flow process in soil using a three-dimensional channel formation model　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Early-Career Scientists, 01 Apr. 2019 - 31 Mar. 2022
  Nakamura Kengo, Tohoku University
  Grant amount(Total)：4030000, Direct funding：3100000, Indirect funding：930000
  In this study, we visualized the pore structure of real environments (disturbed and undisturbed soils) by establishing a flow channel formation model that can accommodate soil heterogeneity. The flow paths in the soil were predicted for permeability from fluid flow simulations. We then evaluated the permeability in the real environment, which is the true value, and discussed the dominant factors of pore structure and fluid flow characteristics in the soil. Based on the results of various tests, an excellence channel is formed according to the flow path in the soil. It was also suggested that the leaching process of the constituents in the soil changes significantly depending on the shape of the formed excellence flow paths.
  Grant number：19K15082
• Innovative study on new energy development with carbon storage using reaction field in super-critical geothermal reservoir　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Research (Exploratory), Grant-in-Aid for Challenging Research (Exploratory), 28 Jun. 2019 - 31 Mar. 2021
  Komai Takeshi, Tohoku University
  Grant amount(Total)：6240000, Direct funding：4800000, Indirect funding：1440000
  A novel reaction process that enables the generation of hydrogen and hydrocarbons as well as a CO2 reduction mechanism by utilizing a georeactor (underground reactor) that utilizes the high temperature and high pressure reaction field of supercritical geothermal water was theoretically and experimentally investigated. Theoretical support was provided to derive new breakthroughs in the energy and environmental fields by fabricating a reactor that assumes a sophisticated and high-performance georeactor. Experimental results using a wide variety of minerals and catalysts showed that natural minerals such as olivine, pyroxene, and spinel can produce high concentrations of hydrogen when reacted under CO2-rich environmental conditions. Furthermore, since carbonate minerals were produced as reaction products, CO2 sequestration could be achieved at the same time.
  Grant number：19K22150
• High precision discrimination of paleo-tsunami deposits using high dimensional data driven analysis　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (A), 01 Apr. 2018 - 31 Mar. 2021
  Takeshi Komai, Tohoku University
  Grant amount(Total)：38740000, Direct funding：29800000, Indirect funding：8940000
  To accurately discriminate tsunami deposits by past giant tsunamis that occurred along the coast of Japan, we conducted a geochemical survey to obtain high-dimensional data and statistical and mathematical analysis of tsunami sediments. We surveyed and sampled tsunami deposits mainly in the eastern Japan area, geochemically analyzed the deposit samples at an unprecedentedly high density and analyzed the high-dimensional data obtained by integrating them with geological data using a newly developed sparse modeling method. With this novel technology, a comprehensive framework was developed to discriminate sediments deposited by historical giant tsunamis with high accuracy by mathematically and statistically differentiating various other types of events and historical events. Furthermore, the frequency of seismic tsunami events and the accuracy of identifying the inundation area along the Japanese coast were improved by enhancing the generalization performance of the new developed method.
  Grant number：18H03820
• Earth Process Model Development by Data Driven Analysis based on Sparse Modeling　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), 28 Jun. 2013 - 31 Mar. 2018
  Komai Takeshi; TSUCHIYA Noriyoshi; NAKAMURA Kengo; YOSHIDA Kenta, Tohoku University
  Grant amount(Total)：68380000, Direct funding：52600000, Indirect funding：15780000
  The development of comprehensive framework to extract intrinsic physico-chemical processes hidden in multi-dimensional huge data has been conducted, by introducing the original sparse modeling techniques in the field of earth science. The research areas are the discrimination of tsunami deposits faced on the disaster prevention and the application to basic understanding in solid-earth science and geology, in order to bring fusional approach in the field of big data analysis in earth sciences. For the specific research targets, we have conducted the following three topics for the implementation of data driven analysis. 1) The application to tsunami deposits discrimination method by geochemical data analysis, 2) The risk assessment and behaviors of toxic metals in tsunami deposits, and 3) The introduction of developed sparse modeling to the soli-earth scientific problems.
  Grant number：25120005
• Visualization of water flow in column based on measurement of porosity distribution and impact assessment of harmful matter elution　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Research Activity Start-up, Grant-in-Aid for Research Activity Start-up, 28 Aug. 2015 - 31 Mar. 2017
  Nakamura Kengo; WATANABE Noriaki, Tohoku University
  Grant amount(Total)：1430000, Direct funding：1100000, Indirect funding：330000
  This study is visualized soil structure of porosity distribution and water flow inside of ISO/CEN column test by using the X-ray CT using 3 types soil samples. It is discussed that forming pathway and dissolution mechanisms in column. Water flow in column is made difference of each soil. Toyoura Sand and Decomposed Granite were formed excellence flow path in the vicinity of the tube center. On the hand, Kanto Loam was caused a excellence flow path in the vicinity of the tube wall. The conventional column test is suggested that water flow is different by soil to be used. Thus, it is possible that each column test are caused different the liquid-solid ratio and dispersion in column to filled soil by Physico-chemical characteristics of the soil.
  Grant number：15H06027
• 製鋼スラグ製品のリスク評価とリスク低減策に関する研究　　　　　　　　　　　　　　　
  2010 - 2012
  Grant amount(Total)：2100000, Direct funding：2100000
  Grant number：10J56392