Ochs, M.*; Dolder, F.*; Tachi, Yukio
Applied Geochemistry, 136, p.105161_1 - 105161_11, 2022/01
Various types of radioactive wastes and environments contain organic substances that can stabilize the aqueous complexes with radionuclides and therefore lead to a decrease of sorption. The present study focuses on testing a methodology to quantify sorption reduction factors (SRFs) in the presence of organic ligands for cement systems. Three approaches for the estimation of SRFs; (1) analogy with solubility enhancement factors, (2) radionuclide speciation based on the thermodynamic calculations, and (3) experimental sorption data in ternary systems, were coupled and tested for the representative organic ligands (ISA and EDTA) and selected key radionuclides (actinides). Our approach allows to critically evaluate the dependence of SRFs for various systems on the chosen method of quantification, in accordance with the data availability for a given systems. The reliable SRFs can only be derived from the sorption measurements in ternary systems. SRF often need to be derived in the absence of such direct evidence, and estimations need to be made based on analogies and speciation information. However, such estimates may be subject to substantial uncertainties.
Mei, H.; Aoyagi, Noboru; Saito, Takumi*; Kozai, Naofumi; Sugiura, Yuki; Tachi, Yukio
Applied Geochemistry, 136, p.105178_1 - 105178_8, 2022/01
Wilson, J.*; Bateman, K.; Tachi, Yukio
Applied Geochemistry, 130, p.104979_1 - 104979_19, 2021/07
The concept of deep geological disposal will include the multiple use of cement-based materials. In the case of argillaceous host rocks, the presence of hyperalkaline cement porefluid results in the destabilization of primary minerals in the argillite, resulting in the development of a zone of alteration at cement-rock interfaces. The process understanding gained from experimental, analogue, and modelling studies has been reviewed, and remaining areas of uncertainty identified. Although there is a reasonably good understanding of the mineral assemblages that are likely to occur due to cement-rock interactions, there are still some areas where a degree of uncertainty remains, in particular: the evolution of cement-argillite interfaces at T 25C; the rates at which secondary minerals form; the extent of pore clogging due to secondary mineral precipitation; the implications of alteration for radionuclide transport.
Watanabe, Takahiro; Tsuchiya, Noriyoshi*; Yamasaki, Shinichi*; Sawai, Yuki*; Hosoda, Norihiro*; Nara, Fumiko*; Nakamura, Toshio*; Komai, Takeshi*
Applied Geochemistry, 118, p.104644_1 - 104644_11, 2020/07
Possible tsunami inundation areas can be predicted from the distribution of paleo tsunami deposits, which are mainly composed of marine-derived sands and muds on land. Such exotic sandy and muddy layers have been identified by multiple approaches. However, there still remain uncertainties and other useful proxies need to be investigated for the identification of tsunami deposits. Here we show the geochemical signatures of modern tsunami deposits from the Pacific coast of Northeast Japan (2011 Tohoku tsunami), as well as those paleo tsunami deposits, which were taken from the Tohoku District (Jogan, ca. 1080 calibrated ages before present [cal BP] and Yayoi, ca. 2000 cal BP). A geochemical ternary diagram (Seawater-Rock-(As+Metals)) enables the weathering trend of tsunami deposits over ca. 2000 years in the Sendai Plain in the Tohoku to be shown. In the paleo tsunami layers from the Tohoku, the Na/Ti atomic ratios markedly increased to 23.4, and the average values were 19.33.0 (Jogan and Yayoi tsunami deposits), which were clearly higher than those of other layers (soil deposits, 10.33.5 on average). These results show that the Na/Ti ratio is a useful indicator of marine incursions in our case. Our rapid and simple method using the Na/Ti ratio can be easily applied to the Tohoku, and it may contribute to the detection of unrecorded muddy tsunami deposits.
Nakata, Kotaro*; Hasegawa, Takuma*; Solomon, D. K.*; Miyakawa, Kazuya; Tomioka, Yuichi*; Ota, Tomoko*; Matsumoto, Takuya*; Hama, Katsuhiro; Iwatsuki, Teruki; Ono, Masahiko*; et al.
Applied Geochemistry, 104, p.60 - 70, 2019/05
no abstracts in English
Tanaka, Kazuya; Kaplan, D. I.*; Onuki, Toshihiko
Applied Geochemistry, 85(Part B), p.119 - 120, 2017/10
We have prepared a special issue for Applied Geochemistry entitled "Transformation and Fate of Natural and Anthropogenic Radionuclides in the Environments". Here, we present 13 peer-reviewed articles on the general theme of natural and anthropogenic radionuclides in different environments. At the same time, these articles cover various topics of field research on the distribution of radionuclides, as well as laboratory experiments on adsorption and redox chemistry of these. The articles have been written by the attendees of the session at the Goldschmidt 2016 held in Yokohama, Japan, and by other authors who submitted their manuscripts to Applied Geochemistry focusing on the theme of the special issue.
Iwatsuki, Teruki; Munemoto, Takashi*; Kubota, Mitsuru*; Hayashida, Kazuki; Kato, Toshihiro*
Applied Geochemistry, 82, p.134 - 145, 2017/05
This study investigated the behavior of rare earth elements (REEs) associated with suspended particles in deep granitic groundwater and in a sealed drift at a depth of 500 m in the Mizunami Underground Research Laboratory (URL) in Japan. Approximately 10%60% of REEs in groundwater are associated with suspended particles. Carbonate particles in groundwater are most likely derived from in situ precipitation of supersaturated carbonate minerals such as calcite. Thermodynamic calculations show that the dissolved REE carbonate complexes in the closed drift decreased in the drift closure period. These complexes may have been absorbed or co-precipitated within the shotcrete on the drift wall. The usage of cement based materials would generate environmental conditions in which REEs are fundamentally immobile in and around the underground facilities.
Yamasaki, Shinya*; Tanaka, Kazuya; Kozai, Naofumi; Onuki, Toshihiko
Applied Geochemistry, 78, p.279 - 286, 2017/03
This study examined the rate constant for the U(VI) reduction process by three flavin analogues, which are redox-active biomolecules secreted from anaerobic bacteria, to elucidate their substituent group effect on the U(VI) reduction rate by electrochemical methods. The formation of the U(IV) was monitored by UV-vis spectrometry in the presence of the flavins. The rate constant for the U(VI) reduction by the flavins was determined. The apparent reduction potential of U(VI) increased about 0.2 V in the presence of the mediators, which strongly suggests that the biological electron mediator makes the U(VI) reduction possible even under more oxidative conditions.
Miyakawa, Kazuya; Ishii, Eiichi; Hirota, Akinari*; Komatsu, Daisuke*; Ikeya, Kosuke*; Tsunogai, Urumu*
Applied Geochemistry, 76, p.218 - 231, 2017/01
no abstracts in English
Umeda, Koji; Asamori, Koichi; Kusano, Tomohiro
Applied Geochemistry, 37, p.134 - 141, 2013/10
This study was undertaken to elucidate spatial and temporal changes of He/He ratios around a source region before and after an inland earthquake using both new and existing helium isotope data from hot spring and drinking water wells. Most gas samples near the seismic source region are characterized by increase in postseismic He/He ratios. In contrast, the postseismic ratios decrease by up to about 30% away from the seismic source region. Episodic faulting could release accumulated radiogenic helium from host rocks, or enhance the transfer of mantle volatiles through permeable fault zones, such that subsequent fluid flow proximal to the source region could then explain the spatio-temporal variations in He/He ratios.
Sasamoto, Hiroshi; Arthur, R. C.*; Hama, Katsuhiro
Applied Geochemistry, 26(8), p.1464 - 1477, 2011/08
It is important to evaluate the undisturbed hydrochemical conditions in deep underground for considering the initial geochemical setting of performance assessment of high level radioactive waste. In the present study, groundwater data obtained thorough the initial surface-based investigation at the Horonobe URL were used to check the correlation and reliability of data based on empirical, geostatistical and geochemical modeling techniques. Applicability of these techniques were discussed in the present study and the representative undisturbed hydrochemical conditions were estimated.
Savage, D.*; Soler, J. M.*; Yamaguchi, Kohei; Walker, C.; Honda, Akira; Inagaki, Manabu; Watson, C.*; Wilson, J.*; Benbow, S.*; Gaus, I.*; et al.
Applied Geochemistry, 26(7), p.1138 - 1152, 2011/07
The use of cement and concrete as fracture grouting or as tunnel seals in a geological disposal facility for rad wastes creates potential issues concerning chemical reactivity. From a long term safety perspective, it is desirable to be able model these interactions and changes quantitatively. As part of the LCS (Long-term Cement Studies) project programme, a modelling inter-comparison has been conducted, involving the modelling of two experiments describing cement hadration and cement-rock reaction, with teams representing the NDA (UK), Posiva (Finland), and JAEA. This modelling exercise showed that the dominant reaction pathways in the two experiments are fairly well understood and are consistent between the different modelling teams, although significant differences existed amongst the precise parameterisation. Future modelling exercises of this type should focus on a suitable natural or industrial analogue that might aid assessing mineral-fluid reactions at these longer timescales.
Yoshida, Hidekazu; Metcalfe, R.*; Yamamoto, Koshi*; Amano, Yuki; Hoshii, Daisuke*; Kanekiyo, Akiko*; Naganuma, Takeshi*; Hayashi, Toru*
Applied Geochemistry, 23(8), p.2364 - 2381, 2008/08
Subsurface redox fronts control the mobilization and fixation of many trace elements. Any safety assessment for a deep geological repository for radioactive wastes needs to take into account adequately the long-term redox processes in the geosphere surrounding the repository. The water-rock-microbe interactions can be considered analogous to the processes occurring in the redox fronts that would develop around geological repositories for radioactive waste. Once formed, the Fe-ooxyhydroxides within such a front would be preserved even after reducing conditions resume following repository closure.
Atarashi-Andoh, Mariko; Schnabel, C.*; Cook, G.*; MacKenzie, A. B.*; Dougans, A.*; Ellam, R. M.*; Freeman, S.*; Maden, C.*; Olive, V.*; Synal, H.-A.*; et al.
Applied Geochemistry, 22(3), p.628 - 636, 2007/03
Accelerator Mass Spectrometry (AMS) was used to measure I/I ratios in surface sea, lake and river water samples collected in 2004 and 2005 from the English Lake District and from South west Scotland, areas which are in relatively close proximity to the Sellafield nuclear fuel reprocessing plant in north west England. The I/I ratios in surface water collected from the shore of the Irish Sea were in the range 2.810 to 8.210. These ratios are one order of magnitude higher than that of seawater collected from the Irish Sea in 1992, correlating with the increase in I content of the Sellafield liquid effluent discharge over the last decade. The I/I ratios in lakes in the Lake District were in the range 0.710 to 6.410 and decreased exponentially as a function of distance from Sellafield.
Schnabel, C.*; Olive, V.*; Atarashi-Andoh, Mariko; Dougans, A.*; Ellam, R. M.*; Freeman, S.*; Maden, C.*; Stocker, M.*; Synal, H.-A.*; Wacker, L.*; et al.
Applied Geochemistry, 22(3), p.619 - 627, 2007/03
The present work constitutes the first survey of iodine isotope ratios for Scottish seawater, including the first data for the west of Scotland. I/I ratios in the south-west Scotland reached 310 in 2004. Iodine isotope ratios increased by about a factor of 6 from 1992 to 2003 in the north-east of Scotland, in agreement with the increase of liquid I emissions from Sellafield over that time period.
Iwatsuki, Teruki; Furue, Ryoji; Mie, Hideki; Ioka, Seiichiro; Mizuno, Takashi
Applied Geochemistry, 20(12), p.2283 - 2302, 2005/12
Hydrochemical conditions up to 1000m below ground level around the Mizunami Underground Research Laboratory were investigated to construct a baseline condition model descriving the undisturbed condition.
Matsunaga, Takeshi; Nagao, Seiya*; Ueno, Takashi; Takeda, Seiji; Amano, Hikaru; Tkachenko, Y.*
Applied Geochemistry, 19(10), p.1581 - 1599, 2004/10
The association of dissolved Sr, Pu and Am with natural colloids was investigated in surface waters in the Chernobyl nuclear accident area by means of ultrafiltration. Results suggest that Pu and Am isotopes were preferentially associated with dissolved humic substances (HS) of high molecular size. A model calculation of the complexation of Pu and Am with HS also supported the above. This study has expanded our understanding of the general role of natural organic colloids in dictating the chemical form of actinides in the surface aquatic environment.
Bros, R.; Kamei, Gento; Hidaka, Hiroshi*; Onuki, Toshihiko*
Applied Geochemistry, 18(12), p.1807 - 1824, 2003/12
Fukushi, Keisuke*; Sasaki, Miwa*; Sato, Tsutomu*; Yanase, Nobuyuki; Amano, Hikaru; Ikeda, Hodaka*
Applied Geochemistry, 18(8), p.1267 - 1278, 2003/08
At Nishinomaki abandoned mine district, the water is acidic and contains much amounts of arsenic. However, arsenic concentration decreases downward without any artificial treatment. To understand the mechanism of the natural attenuation, the acid mine drainage and the ochreous precipitates were collected. The samples were analyzed by XRD, IR, ICP-MS and ion-chromatograph. The precipitates were investigated by selective extraction procedure. These results were interpreted with those calculated by the geochemical code. The contamination of water has been result from oxidation of pyrite and realgar and subsequent release of iron. The released ferrous iron transforms to ferric form by bacterial oxidation and then schwertmannite forms immediately. While the arsenic concentrations in the stream are lowered to background level at downstream, these in the ochreous precipitates are up to 60 mg/g. The iron hydroxide has been known to exhibit the high sorption affinity to arsenate. Hence, arsenic is effectively removed by the schwertmannite from the contaminated water and attenuated naturally.
; ; Metcalf; Yoshida, Hidekazu;
Applied Geochemistry, 17(9), p.1241 - 1257, 2002/00