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

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

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
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

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

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

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

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

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

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

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

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
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

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
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

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

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
大野 剛
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.54, no.4, pp.209-217, 2020-12-25 (Released:2020-12-25)
参考文献数
32
被引用文献数
2

The accident at the Fukushima Daiichi Nuclear Power Plant resulted in a substantial release of radionuclides including Iodine-131, Cesium-134, and Cesium-137 to the atmosphere, and caused significant contamination of the environment. Most parts of the eastern Japan were subjected to the radioactive contamination, especially in Fukushima Prefecture. An effective dose estimation of released 131I is important but difficult due to lack of data on the deposition of 131I. The long-lived radioiodine isotope 129I (half-life: 1.57×107 y) is one of the important radionuclides released from nuclear fuel reprocessing plants and nuclear accidents into the environment. This radionuclide has provided useful information on the behavior of radioiodines, whose half-lives are very short, in the environment. In particular, 129I has been used as a tool to reconstruct the initial distribution of 131I (half-life: 8 days) at nuclear accidents. Therefore the determination of 129I in soils in Fukushima is needed to reconstruct the distribution of 131I in the environment. In this article, I review recent studies on radioactive iodine in Fukushima.
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

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
窪田 薫
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.54, no.2, pp.61-78, 2020-06-25 (Released:2020-06-25)
参考文献数
122

Biogenic calcium carbonate (coral skeleton, foraminifera shell, bivalve shell, otolith, etc.) is one of the best archives of the past changes of aquatic environment that includes ocean, river, and lake. I have dedicated myself to the development and application of the environmental proxies such as trace element, stable isotope, and radiogenic isotope in calcium carbonate of marine organisms to study paleoclimate, paleoceanography, marine carbon cycle, and calcification processes of them. In this manuscript, I focus on boron isotope proxy of skeleton of marine calcifiers, coral and foraminifera, that are often used in paleoclimatology. Boron isotopes can record pH of the seawater, from which atmospheric carbon dioxide concentration can be estimated, thus it has been recognized as a holy grail in marine carbon cycle study. First, I review the mechanism of boron isotope as seawater pH proxy, history in technical development in the isotope measurement, issues with regard to fractionation factor between boric acid and borate ion in seawater, reconsideration of the boron incorporation mechanism into calcium carbonate skeleton, and recent findings. Then I overview my recent marine carbon cycle studies using boron isotope proxy in different timescales, since the Industrial Revolution (since 1750 C.E.) and since the last glacial period (since ~20,000 years ago).The boron isotopic composition was determined in high precision and accuracy by using thermal ionization mass spectrometry and multi-collector inductively-coupled plasma mass spectrometry in Japan Agency for Marine–Earth Science and Technology.
著者
赤沼 哲史
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.199-210, 2016-09-25 (Released:2016-09-25)
参考文献数
54

Understanding the origin and early evolution of life is fundamental to improve our knowledge on ancient living systems and their environments. Information about the environment of early Earth is sometimes obtained from fossil records. However, no fossil records of ancient organisms that lived more than 3,500 million years ago have been found. Instead, we can now predict the sequences of ancient genes and proteins by comparing extant genome sequences accumulated by the genome project of various organisms. A number of computational studies have focused on ancestral base contents of ribosomal RNAs and the amino acid compositions of ancestral proteins, estimating the environmental temperatures of early life with conflicting conclusions. On the other hand, we experimentally resurrected inferred ancestral amino acid sequences of nucleoside diphosphate kinase that might have existed 3,500–3,800 million years ago. The resurrected proteins are stable around 100℃, being consistent with the thermophilic ancestry of life. Our experimental data do not exclusively indicate the thermophilic origin of life; rather, our conclusion is compatible with the idea that the hyperthermophilic ancestor was selected for increased environmental temperatures of early Earth probably caused by meteorite impacts.
著者
圦本 尚義
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.51, no.2, pp.49-59, 2017-06-25 (Released:2017-06-25)
参考文献数
44

Oxygen is the third most abundant element in the Universe and the most abundant element of the terrestrial planets. The presence of oxygen in gaseous, ice and dust phases makes oxygen isotopes important tracers of various fractionation processes to form a protoplanetary accretion disk, which are essential for understanding the evolution of building blocks for planet formation. Photodissociation of CO isotopologues in cold interstellar environments forms H2O ice with depletion of 16O component relative to the interstellar CO, but with heritage 17O/18O ratio from the interstellar CO. Dynamic evolution of protoplanetary disk generates H2O enrichments inside snowline of the disk to change from 16O-rich to 16O-poor gaseous environments. Thermodynamics during heating processes reset oxygen isotopic compositions of dust in the disk to the gaseous oxygen isotope values. Therefore, building blocks of planet show oxygen isotope variations with variable 16O component, but with similar 17O/18O ratio each other. Oxygen isotopic compositions of outer planets would be 16O-poor in order of increasing distance from the Sun if outer planet formation started from icy planetesimal accretion.