GEOCHEMICAL JOURNAL
Online ISSN : 1880-5973
Print ISSN : 0016-7002
ISSN-L : 0016-7002
Volume 55, Issue 4
Displaying 1-9 of 9 articles from this issue
  • Norio Kitadai, Kumiko Nishiuchi, Yuko Nakano
    Article type: research-article
    2021 Volume 55 Issue 4 Pages 193-207
    Published: 2021
    Released on J-STAGE: November 22, 2021
    JOURNAL FREE ACCESS
    Supplementary material
    Selenium (Se) is a micronutrient for human with a very narrow range between deficit and toxic levels. Because selenate (SeO42-) is the most prevalent form of bioavailable Se in agricultural soils, the prediction of selenate adsorption/desorption behaviors on soil constituting minerals is an important step to minimize potential health problems. This article describes a comprehensive predictive model for selenate adsorption on oxide minerals applicable for a wide range of pH, ionic strength, selenate concentration, solid/water ratio, and amorphous and crystalline adsorbents. The principle selenate surface species are a monodentate-mononuclear inner-sphere and a bidentate-binuclear outer-sphere complexes represented by >MOH + SeO42- + H+ → >MOSeO3- + H2O and 2>MOH + SeO42- + 2H+ → (>MOH2+)2_SeO42-, respectively, for all oxides except for ferrihydrite, which requires an additional surface species, 2>MOH + SeO42- + 2H+ → (>MOH2+)(>MOSeO3-) + H2O. With the three reactions formulated in the extended triple layer model, we demonstrate adequate reproduction of a large number of adsorption, surface titration, and proton co-adsorption data for various selenate-oxide systems reported in literature. Calculations with the theoretically derived selenate adsorption constants indicate that, in addition to aqueous condition, crystalline states of Fe and Al oxides significantly influence the surface adsorption affinity for selenate. Thus, our developed model is useful not only for estimating the solid-liquid partitioning of selenate by soil oxide minerals, but also for assessing its response to changing aqueous conditions and ageing processes.
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  • Atsunori Nakamura, Atsuyuki Ohta, Hiroyuki Matsuzaki, Takashi Okai
    Article type: research-article
    2021 Volume 55 Issue 4 Pages 209-222
    Published: 2021
    Released on J-STAGE: November 22, 2021
    JOURNAL FREE ACCESS
    Preparing Be carrier solutions with low 10Be/9Be ratios is essential for the applications of in-situ-produced cosmogenic 10Be in geochronology. This is because commercially available Be carriers are non-negligibly contaminated by 10Be. Recently, in-house Be carriers have been successfully applied to samples that contain small amounts of in-situ-produced 10Be. The first step in preparing in-house Be carriers is selecting suitable Be-bearing minerals that contain less 10Be. Here, we present a simple method for selecting appropriate raw minerals for in-house Be carriers. That is, measuring the 10Be/9Be ratios of Be-bearing minerals by direct Cs sputtering. Analyses of the 10Be/9Be ratios of phenakite (Be2SiO4) and beryl (Be3Al2Si6O18) obtained from a mineral collection at the Geological Survey of Japan indicate that phenakite generally contains more 10B, interfering isobar of 10Be, than beryl. In addition to the necessity of finding raw materials that contain low 10Be, our results indicate that it is preferable to select a starting material with a low B concentration. Fragments of Be-bearing minerals from target samples were directly packed, and showed effective beam currents. Therefore, we anticipate that the direct packing method can also potentially be used to measure 10Be in Be-bearing minerals for geological applications. The measurement background of accelerator mass spectrometry was evaluated using a B-removed Be carrier solution. While B is partly adhered to hydroxide gel, we demonstrate that the hydroxide gel wash reduces B in a Be carrier solution. To highlight the 10Be/9Be ratios of Be-bearing minerals against commercially available Be solutions, we also investigated the 10Be/9Be ratios of commercially available Be solutions.
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  • Motoo Ito, Yoshinori Takano, Yoko Kebukawa, Takuji Ohigashi, Moe Matsu ...
    Article type: research-article
    2021 Volume 55 Issue 4 Pages 223-239
    Published: 2021
    Released on J-STAGE: November 22, 2021
    JOURNAL FREE ACCESS
    We have analyzed the carbonaceous materials generated by the explosion of an High-melting explosive mixture in an Ar atmosphere in a laboratory simulation of the small carry-on impactor experiment. We used both non-destructive and destructive analytical techniques to identify the chemical nature of the materials. From SEM-EDS, we found the materials to be composed mainly of carbon, nitrogen, and oxygen, with a detectable amount of metals. Suitable parameters for identifying these materials are a FTIR peak at 1520 cm-1, low reflectance and gentle red slope of FTIR spectrum compared with the Murchison CM2 chondrite, the Raman D and G bands, and the hydrogen, carbon, and nitrogen isotopic compositions and their spatial distributions. The scanning transmission X-ray microscopy (STXM)-XANES results provided information about the molecular nature of these highly aromatic materials, which was supported by results from TD-GC/MS. These results suggest that it is possible to distinguish Ryugu samples from SCI potential contaminants in a sample container by using proper combinations of analytical techniques. This assessment provides information that will be useful for the analysis of the Ryugu asteroidal samples.
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  • M. Tanimizu, N. Sugimoto, T. Hosono, C. Kuribayashi, T. Morimoto, A. I ...
    Article type: research-article
    2021 Volume 55 Issue 4 Pages 241-250
    Published: 2021
    Released on J-STAGE: November 22, 2021
    JOURNAL FREE ACCESS
    In this study, we investigated the detailed processes of hydro-chemical changes in regional groundwater flow systems associated with large earthquakes using stable isotope ratios of dissolved trace elements. A Cl-B-Li ternary diagram, in combination with isotope systematics of δ11B and δ7Li was applied to the groundwater system of Kumamoto, Japan to understand the groundwater disturbances associated with the Kumamoto earthquakes in 2016. Our approach was based on the conservative chemical behavior of these three elements in the groundwater system, and their contrasting concentrations and isotopic signatures of B and Li among seawater, stagnant groundwater, and hydrothermal fluid. A small contribution from the influx of deep hydrothermal fluid into the aquifer was detected in one observation well near the epicenter of the 2016 Kumamoto earthquake, along the Futagawa fault. B-Li isotope systematics are useful isotopic proxies to precisely evaluate hydro-chemical changes in groundwater flow systems, and detect contribution of different sources associated with various tectonic disturbances on a finer scale.
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  • Tian Sun, Yanhua Wang, Yan Chen, Xinggong Kong, Chun Ye
    Article type: research-article
    2021 Volume 55 Issue 4 Pages 251-263
    Published: 2021
    Released on J-STAGE: November 22, 2021
    JOURNAL FREE ACCESS
    Polycyclic aromatic hydrocarbons (PAHs) accumulate and persist ubiquitously in natural environment during Anthropocene. This study was conducted in a heavily industrialized and urbanized Taihu basin of the lower reaches of Yangtze River. The concentrations of 15 priority PAHs were measured in the sediment core (49.5-cm length). Multiple source apportionment methods were used to trace the pollution history and sources, spanning the last ca. 116 years (1902∼2018). The PAHs concentration in the sediment increased from 428.70 to 1486.60 ng·g-1. Three representative periods with characteristics of high PAHs level were divided: the 1952 peak was linked to the beginning of industrial development under the first Five-Year-Plan (1951∼1955); the 1979 peak was closely related to the industrial boom by the application of Reform and Opening policy since 1978. The highest PAHs value in 2008 and then decreased indicated the enhanced pollution treatment after Water Crisis event in Wuxi City (2007). The toxic equivalent quantity (TEQ) value for the PAHs indicated that toxicity in 79% of samples exceeded the environmental standard set from 1980s~2010s. The results of diagnostic ratios and a positive matrix factorization (PMF) model show that the contribution of coal combustion and vehicle emissions to the PAHs compounds account for 41% and 26%, respectively throughout the sedimentary period.
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  • Dongfeng Niu, Yuejun Si, Baosheng Li, Fengnian Wang, Peixian Shu, Xiao ...
    Article type: research-article
    2021 Volume 55 Issue 4 Pages 265-276
    Published: 2021
    Released on J-STAGE: November 22, 2021
    JOURNAL FREE ACCESS
    Supplementary material
    The MGS1 segment of the Milanggouwan stratigraphic section, which is located on the southeastern margin of the Mu Us Desert in China, recorded 11 sedimentary cycles consisting of aeolian dune sands overlapping with fluvio-lacustrine facies or paleosols in the Holocene. Through the analysis of trace elements, gastropods, and sporopollen fossils in some layers of the MGS1, this study presents the monsoon climate fluctuations on the millennial-scale in the Mu Us Desert during the Holocene. The results show that the contents of trace elements (P, Pb, Rb, Nb, Zr, V, Sr, Cu, Ni, As, Ba, and Co) have similar distribution characteristic, their contents are low in the dune sands but are relatively high in the overlying fluvio-lacustrine facies or paleosols showing 11 cycles in alternation of valleys and peaks. The trace elements in the paleo-mobile dune sands of MGS1 are quite consistent with those of modern mobile dune sands in Salawusu River Valley; therefore, paleo-mobile dune sands can be assumed to be a result of the main periods of the prevalence of East Asian winter monsoon. The increased element contents in the overlying fluvio-lacustrine facies or paleosols are mainly due to the prevailing East Asian summer monsoon. In addition, the 11 elements’ cycles represent the climate changes on the millennial-scale in the alternation of East Asian winter and summer monsoons in the Holocene. The paleoecology indicated by gastropods and sporopollen fossils reflects the warm and humid sparse forest grassland environment prevailing in the East Asian summer monsoon when the fluvio-lacustrine facies were deposited; the sporopollen is missing in the dune sands, presumably, it might be dry and windy sandy desert then. The dominant periods of the winter monsoon in these cycles, in terms of time and nature of the climate, could correspond to the cold events in the North Atlantic and lakes, loess, peat and stalagmites in China. It probably indicates that the millennial-scale environmental changes in China’s desert regions may be caused by the changes of solar radiation and the increase in ice volume in the Northern Hemisphere during the Holocene.
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Notes
  • Takahiro Watanabe, Natsuko Fujita, Akihiro Matsubara, Masayasu Miyake, ...
    Article type: research-article
    2021 Volume 55 Issue 4 Pages 277-281
    Published: 2021
    Released on J-STAGE: November 22, 2021
    JOURNAL FREE ACCESS
    Supplementary material
    Radiocarbon (14C) measurements on samples containing less than 0.1 mg of carbon have been performed via accelerator mass spectrometry and manual sample preparation techniques relying on vacuum glass lines. Since geological samples are often limited in size with respect to 14C dating, sample preparation techniques should be improved for small samples. In this study, the small-mass graphitization of international standard reference materials (∼0.1 mg and ∼0.05 mg of carbon) was evaluated as a technique for 14C dating using an elemental analyzer and third-generation automated graphitization equipment (EA-AGE3; IonPlus AG). This paper also presents the first data for small-sample graphitization for the IAEA standards by EA-AGE3. The preliminary results are encouraging, indicating that the pMC values (without background correction) for the small-mass international standard reference materials containing ∼0.1-0.05 mg carbon are close to their consensus values.
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  • Noriyuki Kawasaki, Changkun Park, Shigeyuki Wakaki, Hwayoung Kim, Suny ...
    Article type: research-article
    2021 Volume 55 Issue 4 Pages 283-287
    Published: 2021
    Released on J-STAGE: November 22, 2021
    JOURNAL FREE ACCESS
    Supplementary material
    Instrumental mass fractionation of Mg-isotopes and the relative sensitivity factor (RSF) for 27Al/24Mg ratios for in situ analysis by secondary ion mass spectrometry were investigated for minerals in Ca-Al-rich inclusions (CAIs) of meteorites, to verify systematic errors in Al-Mg chronological systematics of CAIs. We synthesized seventeen glasses with different chemical compositions that imitate those for CAI minerals and measured their Al-Mg isotopic compositions. In particular, the variation range of RSFs for six melilite glasses almost covering chemical compositions of CAI melilite is 2.0 ± 0.3%, indicating that systematic error for 27Al/24Mg for melilite is less than 2.0 ± 0.3% and likely corresponds to that of an 26Al-26Mg relative age of ∼0.01 Myr for melilite-rich CAIs. Our data strongly support the robustness of variations in initial 26Al/27Al ratios among CAIs, corresponding to a formation age spread of ∼0.4 Myr at the very beginning of the Solar System formation.
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Express Letters
  • Seung-Gu Lee, Tsuyoshi Tanaka
    Article type: research-article
    2021 Volume 55 Issue 4 Pages e9-e17
    Published: 2021
    Released on J-STAGE: November 22, 2021
    JOURNAL FREE ACCESS
    Supplementary material
    One of peculiar geochemical characteristics in the chondrite-normalized REE patterns from highly fractionated granites and high silica rhyolite is extremely large negative Eu anomaly (Eu/Eu* < 0.10) due to very low concentration of Eu. Particularly, Eu provides a valuable information for evolution processes of the earth and planetary materials. Eu has only two isotopes, 151Eu and 153Eu. In this study, Eu isotope ratios from highly fractionated igneous rocks curated GSJ and USGS and some highly fractionated granites with extremely large Eu negative anomaly were determined by MC-ICP-MS using Sm internal standardization methods. The degree of Eu isotope fractionation (δ153/151Eu) was calculated on the basis of NIST3117a Eu standard. All of highly fractionated igneous rocks in this study showed that their 153Eu/151Eu values are higher than NIST3117a Eu standard, indicating that 151Eu isotope was enriched in the felsic magma. Our results suggest that a study for Eu isotope fractionation from highly fractionated granites and high silica rhyolite will provide a valuable key for understanding geochemical processes related with magmatic differentiation processes.
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