著者

渡辺 豊

出版者

一般社団法人日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.50, no.1, pp.01_i-01_iii, 2016-03-25 (Released:2016-03-25)

著者

山本 政儀 坂口 綾

出版者

日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.49, no.4, pp.173-184, 2015-09-25 (Released:2015-12-25)

参考文献数

25

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Huge amounts of radionuclides were released into the atmosphere and ocean from the Fuku shima Dai-ichi Nuclear Power Plant (FDNPP), as a result of the reactor accident after the magnitude 9.0 Great East Japan Earthquake and subsequent gigantic tsunami on March 11, 2011. This paper summarizes our research activities on measurements of actinide elements (236U, 238,239,240,241Pu, 241Am and 242,243,244Cm) in the environmental samples.

著者

丸山 誠史 服部 健太郎 平田 岳史

出版者

日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.48, no.3, pp.187-199, 2014-09-25 (Released:2014-10-10)

参考文献数

41

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Concentrations of uranium and thorium in commercial bottled mineral waters (81 domestic and 11 foreign products) have been analyzed using ICP-MS. Domestic bottled mineral waters exhibit very wide range of the uranium concentrations (0.1–3300 ng/L). However uranium concentrations of most samples were below 100 ng/L. There is no obvious correlation between the values of hardness and the uranium concentrations of the domestic bottled mineral waters. The uranium concentrations of foreign bottled mineral waters tended to be much higher than those of domestic ones (up to 4000 ng/L), and the values of hardness correlate roughly with the uranium concentration. It may be due to interactions between limestone and groundwater. Thorium concentrations of both domestic and foreign bottled mineral waters are typically less than 3.0 ng/L. Concentrations of uranium and thorium in bottled mineral waters were greatly lower than provisional guideline values defined by WHO. Therefore, it can be considered that there is no health risk chemically/radioactively induced by natural uranium and thorium in commercial mineral waters currently available in Japan, especially in Kyoto City.

著者

唐戸 俊一郎

出版者

一般社団法人日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.56, no.4, pp.99-108, 2022-12-25 (Released:2022-12-25)

参考文献数

28

被引用文献数

1

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In order for life to emerge and evolve, ocean must be present on a planet for billions of years. Observed sea-level change shows that the sea-level fluctuates a lot, but on average (over several 100 Mys) it is stable: after a rapid reduction (<100 Mys),the sea-level recovered quickly leading to the stable ocean mass. However, the cause for the stable ocean mass has been unclear because ocean mass is controlled by dynamic equilibrium rather than static equilibrium. A model is developed to explain the stability of the ocean mass considering both degassing and regassing. It is shown that degassing at mid-ocean ridges is too inefficient to stabilize the ocean mass after the reduction of the ocean mass. It is suggested that the deep mantle melting (across the transition zone) provides a key role (i) to maintain the high water content in the transition zone, and (ii) to stabilize the ocean mass via the water leak from transition zone in cold regions. The area of cold regions needed to stabilize the ocean mass is estimated to be ~2×1010 m2 that corresponds to a few volcanoes such as Chanbaishan (this review is based on Karato et al., 2020).

著者

橘 省吾 澤田 弘崇 岡崎 隆司 高野 淑識

出版者

一般社団法人日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.48, no.4, pp.265-278, 2014-12-25 (Released:2015-01-06)

参考文献数

101

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Hayabusa2 is the sample return mission to the near-Earth C-type asteroid (162173) 1999 JU3 (2014–2020). Samples from C-type asteroids, which are abundantly present in the asteroid belt and of which reflectance spectra resemble those of carbonaceous chondrites, may well preserve the information covering the entire history of the Solar System; the epoch prior to the birth of the Sun, planetesimals and planet formation including a behavior of volatiles to terrestrial planets. Moreover, asteroidal surface samples record current surface geological processes and the dynamical evolution of small bodies in the Solar System, which are not recorded in meteoritic samples. The Hayabusa2 spacecraft will launch off in 2014, and arrive at the asteroid 1999 JU3 in mid-2018. Investigations by several remote sensing techniques and sample collections at three different locations will be carried out during its 18-month stay. The spacecraft will return to Earth with asteroidal samples in December 2020. In this article, we describe the outline and cosmochemical rationales of the Hayabusa2 mission with its significance in primitive small body exploration missions.

著者

川口 慎介

出版者

一般社団法人日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.49, no.2, pp.79-97, 2015-06-25 (Released:2015-06-25)

参考文献数

175

被引用文献数

1

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I am very honored to receive Young Scientist Award 2012 from Geochemical Society of Japan. This article overviews advance of continuous flow-isotope ratio mass spectrometry and novel isotopic tracers and then shows achievement and perspective of geochemical studies for deep-sea hydrothermal system. I regard molecular hydrogen and methane as key molecules to discuss limit of biosphere on the Earth and habitability of other planets and moons. This article propounds possibilities of geo-engineering activities and geochemical cell biology.

著者

大野 剛 村松 康行

出版者

日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.49, no.4, pp.239-246, 2015-09-25 (Released:2015-12-25)

参考文献数

26

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Inductively coupled plasma (ICP) is characterized by high ionization efficiency for almost all elements. Recently, a triple quadrupole ICP-MS (ICP-MS/MS) has been applied to the measurements of isotope ratios for ultra-low level radioisotopes. The ICP-MS/MS features an additional quadrupole mass filter situated in front of the octopole reaction cell and quadrupole mass filter, which allows only the analyte ion to enter the cell by rejecting all the other ions. In this manuscript, we review recent studies on environmental radioactivity in Fukushima achieved by ICP-MS/MS techniques.

著者

飯島 和毅

出版者

日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.49, no.4, pp.203-215, 2015-09-25 (Released:2015-12-25)

参考文献数

59

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The Fukushima Dai-ichi Nuclear Power Plant accident led to the release of various and huge amount of radionuclides into the environment, and contamination of wide area of eastern Japan, mainly Fukushima prefecture. More than 70% of radioactive cesium, which dominates the exposure dose, was deposited in forest far from our living sphere and is considered to be remobilized with time by water flow and strong wind caused by natural events such as typhoons. Numerous researches on the behavior of radionuclides in the environment have been performed not only by observation in the contaminated regions but also by model analysis so far. This paper overviewed results of understanding and modeling of transport behavior of radiocesium from forests through river systems.

著者

小暮 敏博 向井 広樹 甕 聡子

出版者

日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.49, no.4, pp.195-201, 2015-09-25 (Released:2015-12-25)

参考文献数

13

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Mineral species that really retain radioactive cesium in Fukushima soil have been investigated by analyzing actual contaminated soil samples in Fukushima using IP autoradiography, electron microscopy and X-ray diffraction. Weathered biotite originated from granitic body in Fukushima was frequently found as radioactive fine particles. The weathered biotite is mineralogically a biotite-vermiculite mixed-layer mineral. Besides, smectite-like clay mineral was identified in biotite-free particles using X-ray diffraction. A new cesium-sorption experiment was conducted, in which various clay minerals were immersed together in dilute 137Cs radioisotope solutions and the amount of 137Cs adsorbed in each mineral was measured by IP autoradiography to reproduce the sorption at actual concentration level in the radioactive particles. It was found that 137Cs was sorbed predominantly by the weathered biotite collected in Fuku shima, confirming the results from the investigation of the actual contaminated soil mentioned above.

著者

北台 紀夫 青野 真士 大野 克嗣

出版者

一般社団法人日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.50, no.3, pp.155-176, 2016-09-25 (Released:2016-09-25)

参考文献数

156

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The origin of life must be studied through addressing a problem of the emergence of a free-energetically open complex system, rather than a problem of abiotic syntheses of various building blocks of life (Aono et al., 2015). One of the key aspects of the origin question is the origin of metabolism, since no (genetic) information may be preserved without ample and ordered materials supply. Thus, from the perspective of the origin of ‘proto-metabolism' we critically review currently prevailing approaches to the origin problem. Then, referring to the latest biological and geochemical findings, we will describe a scenario of the electrochemically driven emergence of ‘proto-metabolism' together with experimental proposals.

著者

足立 光司

出版者

日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.49, no.4, pp.185-193, 2015-09-25 (Released:2015-12-25)

参考文献数

27

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Water-insoluble radioactive materials emitted during an early stage of the Fukushima Dai-ichi Nuclear Power Plant accident in 2011 were identified, and their chemical and physical properties were characterized as particulate matters. In this report, studies on radioactive particles collected from filter samples in Tsukuba on March 14–15, 2011 are summarized. Their compositions, chemical states, sizes, shapes, crystallinity, and hygroscopicity were analyzed using microscopic analyses such as electron microscopy and synchrotron with a micro-beam. The results indicate that they include Cs, Fe, and Zn as well as elements from fission products and are water insoluble, spherical-glassy particles with ca. 2 micrometer in size. Understanding of their detailed properties is significant to improve the numerical models during the accident and to understand their occurrences in soil as well as the accident itself. In addition to the water-insoluble radioactive materials, water-soluble radioactive materials, which were likely emitted in different events during the accident, should be investigated to have comprehensive understanding of the accident and its environmental effects. More samples from various environments such as soil will be needed, and more detailed chemical and physical analyses will help to understand their formation process, influences on human health, and long term decrements in ambient conditions.

著者

石村 豊穂

出版者

一般社団法人日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.55, no.3, pp.63-86, 2021-09-25 (Released:2021-09-25)

参考文献数

75

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Stable carbon and oxygen isotopic compositions (δ13C, δ18O) of carbonates, especially calcium carbonate (CaCO3), have been utilized in geochemical research for more than 60 years because the isotopic values record environmental history at the time of formation. In particular, the stable isotopic compositions of biogenic carbonate record the δ18O (salinity variation and global ice volume) and temperature history of ambient seawater, as well as the δ13C of dissolved inorganic carbon (DIC), which is important as basic information for elucidating carbon cycles and mechanism of environmental changes. In recent years, isotopic analysis of carbonate has been expected to improve the sensitivity for high-resolution environmental analysis, but the progress of analytical techniques has been limited. In such a situation, improvements in the sample preparation and introduction system for stable isotope ratio mass spectrometry (IRMS) have made it possible to determine the stable isotopic composition of carbonate less than 1/100 of the sample amount required by previously reported systems (MICAL: Ishimura et al., 2004, 2008b).In this paper, I described the current progress and problems of stable isotopic analysis of carbonate, then explain the details of the development of analytical method for carbonate in ultra-micro scale, and the applications to various research fields.

著者

南川 雅男 和田 英太郎

出版者

一般社団法人日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.19, no.1-2, pp.39-52, 1985-10-15 (Released:2016-11-26)

被引用文献数

1

著者

本多 牧生

出版者

日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.49, no.4, pp.227-238, 2015-09-25 (Released:2015-12-25)

参考文献数

27

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Settling particle collector, sediment trap, has played an important role in the study of spatiotemporal variability in biogeochemical particles' cycle in the ocean. This report reviews the observational study of behavior (such as dispersion, distribution and existence form) of particulate artificial radionuclides in the ocean emitted from severe accidents of two nuclear power plants (Chernobyl NPP and Tokyo Electric Power Corporation Fukushima Dai-ichi NPP) by using time-series sediment trap.

著者

藤﨑 渉

出版者

一般社団法人日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.57, no.1, pp.13-29, 2023-03-25 (Released:2023-03-25)

参考文献数

107

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The biodiversity crisis across the Triassic–Jurassic boundary (TJB; ca. 201 Ma) is characterized by one of the largest mass extinctions in the Phanerozoic. Significant increases in the extinction rate of marine fauna, and major turnovers in terrestrial vegetation and vertebrate groups, have been well documented across the TJB. In addition to the extinction, several unique geological events around the TJB were recognized; i.e., the emplacement of the Central Atlantic Magmatic Provinces (CAMP) which is associated with the breakup of Pangea, meteorite impact, carbon cycle perturbations, widespread ocean anoxia, and ocean acidification. In the last decade, based on of the numerous data-set obtained from the peri-Pangean shelf sequences, major advances have been made in our understanding of the TJB biotic crisis, related environmental changes, and the CAMP volcanism. However, the casual relationships between the CAMP volcanism and extinction-related environmental changes of global context still remain unclear due to the lack of data from pelagic domains. Here, I introduce my recent studies about the mid-superocean Panthalassa, which occupied major portion of the global ocean during the Triassic-Jurassic transition, and discuss the future prospects at the end of the paper.

著者

木村 純一

出版者

一般社団法人日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.52, no.1, pp.29-53, 2018-03-25 (Released:2018-03-25)

参考文献数

129

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Earth's mantle formed at 4.6 Ga and evolved through the Hadean magma ocean stage and subsequent plate tectonics stage since 3.5 Ga. Mantle convection driven by the internal heat is the major driving force of the plate tectonics with considerable tectonic roles of both oceanic and continental plates formed at mid-ocean ridges (MOR) and subduction zones (SZ), respectively. The MOR and SZ regions are the places of plate formations by intensive magma geneses where significant element fractionations between solids and melts are taking place. The MOR and SZ regions are the major factories of tectonic and geochemical mantle evolutions because their products of plates and residual mantles are mixed back into the mantle by stirring or isolated almost permanently. The geochemical fractionations in the MOR and SZ magmatism are modelled based on petrochemical mass balance and elemental and isotopic growths of the magmas and the residues are examined. These combined to enable depicting the thermal, chemical, and isotopic evolutions of the Earth's mantle over 3.5 Gyr. The present-day mantle appears to be geochemically heterogeneous and forms large mantle domains in both deep and shallow portions by Mesoproterozoic (1.7 Ga). These suggest relatively sluggish mantle convection after Mesoproterozoic due to mantle cooling.

著者

野崎 義行

出版者

一般社団法人日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.34, no.3, pp.161-167, 2000-08-23 (Released:2017-01-02)

参考文献数

12

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This article briefly reviews the recent advances in research on the concentration and distribution of the elements in the ocean. Since the last compilation of North Pacific vertical profiles of elements on a periodic table (Nozaki, EOS 78, 221,1997), new data have become available for Nb, Ta, and Os in the literature. Those are shown graphically, and the conservativeness of Os in seawter is examined. We have still lack of knowledge on the fluxes to and out of the ocean for many elements including the above. Chemical speciation and relative importance of complexation with organic ligands in seawater are very obscure as yet for many trace metals. Iron, which plays an important role in the oceanic biogeochemistry of plankton growth and carbon cycling, is not an exemption. Coupling of radionuclide tracers which can provide time-scales and the spatial variations of concentration reflected by the strength of sources and sinks with an isotopic "finger print" should help solve some of the issues generated on the dynamic aspects of elements in the ocean. A case study for Nd by Amakawa et al. (2000) is also briefly outlined.

著者

飯塚 毅

出版者

一般社団法人日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.50, no.3, pp.121-133, 2016-09-25 (Released:2016-09-25)

参考文献数

120

被引用文献数

1

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The presence of oceans and continents is one of the Earth's unique features among the planets in our Solar System. Here I discuss the formation and origin of Earth's oceans and continents by combining the results of geological, geochemical and geophysical studies. The geological and geochemical data provide evidence for the presence of Earth's oceans by ca. 3.8 Ga and probably ca. 4.3 Ga. Yet, oceans could be formed even earlier, possibly soon after the solidification of the magma ocean, especially if the Earth had gained water before the Moon-forming Giant Impact. The hydrogen isotope data for meteorites and mantle-derived terrestrial samples suggest that proto-planets and planetesimals, that accreted to form the Earth, could acquire water from solar nebular and water-rich materials delivered from outer Solar System, respectively. Furthermore, the hafnium isotope systematics of Hadean zircon constrain the timing of magma ocean solidification to as early as 4.5 Ga. The infant solid Earth would be characterized by the stagnant-lid convection regime. Meanwhile, radiogenic heat generation induced vigorous mantle plumes and stagnant plates had been cooled and hydrated. Eventually, the hydrated proto-plates were subducted beneath buoyant oceanic plateaus generated by the mantle plumes, resulting in the onset of plate tectonics. Although there is evidence that granitic rocks were locally formed on the Hadean Earth, the geochemical compositions of sedimentary rocks indicate that the emergence and growth of continents occurred during Middle and Late Archean times. This implies that the time interval from the magma ocean solidification to the onset of global plate tectonics is ~1 Gyr.

著者

内田 悦生 中野 孝教

出版者

一般社団法人日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.52, no.4, pp.149-169, 2018-12-25 (Released:2018-12-25)

参考文献数

46

被引用文献数

2

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Skarns are rocks consisting mainly of calc-silicate minerals (skarn minerals) such as clinopyroxene and garnet, formed by hydrothermal metasomatism along the contact zone typically between limestone and granitic rock. They are sometimes associated with economical Pb–Zn, Mo, Cu, Fe, Sn, and W mineralization (skarn deposits). Skarns consist mainly of one or two skarn minerals, and often show a zonation. In case of skarns (endoskarns) derived from Al-rich rocks such as granitic rocks and sedimentary rocks, in addition to temperature and pressure, the supply of Ca from limestone controls the zonation. On the other hand, in case of skarns (exoskarns) derived from limestone, the supply of Si, Al, Fe and Mg from related granitic rock and other rocks, degassing of CO2, and redox state govern the zonation. The mineralized metal species in skarn deposits are determined by the granitic rock related to the skarn formation. Isotope analyses revealed that magmatic water supplied from the related granitic rock is greatly involved in the early stage of skarn formation, and influence of meteoric water tends to increase in the later stage.

著者

和田 敏裕

出版者

一般社団法人日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.55, no.4, pp.159-175, 2021-12-25 (Released:2021-12-25)

参考文献数

94

被引用文献数

2

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This review is an exposition of published reports describing radioactive contamination of marine and freshwater fish, collectively revealing radiocesium contamination mechanisms. Radiocesium concentrations in marine fish caught in the waters off Fukushima have decreased drastically during the decade following the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, mainly because of the area’s open and diffusive marine environments leading to lower radiocesium concentrations in seawater, sediments, and prey items, and because of the low physiological capability of retaining radiocesium in fish. Nevertheless, careful attention must be devoted to marine fish in the FDNPP port because some fish samples collected from the port have exceeded the Japanese regulatory limit of 100 Bq/kg-wet. Long-term monitoring of marine fish and surrounding environments is necessary because coastal waters around FDNPP have not reached an equilibrium state. Radiocesium contamination of freshwater fish has continued in rivers and lakes within areas with high degrees of deposition, although overall contamination levels have decreased considerably. Radiocesium contamination will be particularly persistent in lakes and ponds where dissolved radiocesium leaching from sediments can become a continuing source of contamination for biological magnification through the food web. In riverine environments, continuing supplies of contaminated prey items (e.g., insects) from riparian environments can be expected to engender persistent radiocesium contamination of freshwater fish (e.g., salmonid fish in forest rivers).