著者

本多 真紀

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.176-192, 2021-12-25 (Released:2021-12-25)

参考文献数

82

---

Iodine 129 (129I) is a radionuclide that decays to 129Xe with a half-life of 15.7 million years. The analysis of 129I in the environment has played an important role not only in the fields of planetary science and earth science, but also in the nuclear field in recent years. Particularly, in the case of the Fukushima Dai-ichi Nuclear Power Plant accident in March, 2011, the scientists estimated the distribution and soil deposition of 131I over a wide area, and contributed to the assessment of internal exposure doses in the early stage of the accident. This is one of the most significant achievements in recent 129I-related studies. Future studies are expected to be conducted to elucidate the transport mechanism of 129I from land to river and sea, and to investigate the possible accumulation of 129I in aquatic organisms. The mobility of 129I in the soil studied by the author during the 10-years since the accident has been mainly reviewed in this manuscript.

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

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.

著者

淵田 茂司

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.247-259, 2015-09-25 (Released:2015-12-25)

参考文献数

87

---

Amino acids, necessary to form life body, are present in greater abundances in natural seafloor hydrothermal fluids over 200℃ than in ambient seawater, although these are unstable and decomposed rapidly under simulated hydrothermal conditions. Serine and aspartic acid, which are thermally labile amino acids, are detected in the high temperature fluids. Inorganic matters such as metal ions and minerals could protect these labile amino acids in the fluids. Most of the dissolved amino acids are combined form and L form, suggesting that these are derived from organisms around hydrothermal vents. In addition, low levels of non-protein amino acids content indicate that amino acids are fresh and not experienced thermal alteration for long time. Amino acids are important as common sources of carbon and nitrogen for heterotrophic marine microbes. The release of biogenic amino acids along circulation paths of hydrothermal fluids could be effective for the development of hydrothermal vent fauna. In this paper, I review the origins and characteristics of dissolved amino acids in the natural hydrothermal fluids and implicates importance of the biogeochemical cycle of nitrogen and carbon around hydrothermal venting in detail.

著者

柳川 弘志 小林 憲正

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.22, no.1, pp.96-105, 1988-06-30 (Released:2016-12-01)

被引用文献数

1

著者

南 武志 河野 摩耶 古川 登 高橋 和也 武内 章記 今津 節生

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.47, no.4, pp.237-243, 2013-12-31 (Released:2017-02-24)

---

Vermilion was collected from powerful people's mounds of places of Japan Sea coast depending on the period from the decline of the Yayoi to Kofun and was measured sulfur isotope ratio (δ34S value), and compared the value obtained from cinnabar ores of three Japanese mines, Niu, Yamato-suigin, and Sui, and two Chinese mines, Wanshan and Xunyang, which were selected from old records. The vermilion of the late Yayoi period, the 1st to 2nd century A.D., was from China, and the vermilion of the early Kofun period, from the late 3rd century A.D., was from Japan. During the late Yayoi and early Kofun periods, the 3rd century A.D., the vermilion showed the middle of the shift of Japanese cinnabar. It is concluded that the measurement of sulfur isotope of vermilion is an effective method for the determination of original sources of vermilion.

著者

古川 善博

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.1-9, 2016-03-25 (Released:2016-03-25)

参考文献数

60

被引用文献数

1

---

Emergence of life's building blocks on the prebiotic Earth should be the fundamental step to the origins of life. Geological evidences suggest that such organic compounds accumulated at some point in the time between 4.4 to 3.8 billion years ago. During this period, the flux of extraterrestrial objects was significantly higher than the subsequent periods. Such extraterrestrial objects might have provided substantial amounts of metallic iron to the surface of the Earth. Shock-recovery experiments simulating the impact-induced reactions of such iron-bearing objects suggest that hypervelocity oceanic impacts of meteorites form nucleobases and various amino acids as well as amines and carboxylic acids. High annual mass flux of such large objects suggests that the impact-induced formation was not negligible as a source of organic compounds on the early Earth. Further investigations on the impact-induced reactions and the nature of extraterrestrial objects would elucidate the fundamental step to the origin of life.

著者

木村 純一 土谷 信高 佐野 栄 中馬 教允 吉田 武義

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.31, no.3, pp.133-151, 1997-08-04 (Released:2016-12-21)

参考文献数

99

被引用文献数

2

---

Recent advances in inductively coupled plasma source-mass spectrometry (ICP-MS) has enabled us to determine trace and ultra-trace elements contained in various geochemical samples. Due to the high sensitivity and rapid mass scanning features of ICP-MS, multiple element analysis for trace elements can be performed without any pre-concentration procedure. The high sensitivity also permits direct spot analysis of solid geochemicl samples using laser ablation (LA) or laser probe (LP) sampling techniques. Spatial resolution as fine as 5-15μm has been achieved in the LP system. However, despite the great analytical ability of ICP-MS, some care should be taken in quantitative analyses. Spectroscopic interferences such as oxide molecular ions (MO+), doubly charged ions (M++), and polyatomic ions (i. e., ArX+) affect the accuracy of measurements for the certain elements.Non-spectroscopic interferences, known as the matrix effect, also affect the analytical accuracy. There are two causes of the matrix effect: one originates in the plasma equilibrium and the other is the mass discrimination effect in an ion beam known as the "space charge effect". Differences in both the major chemical composition and introduction volume of analyte shift the aspect of the matrix effect. In order to attain high precision and accuracy in the analysis, optimization of the facility setting and analytical procedure is required to minimize those interferences. The problem in LA analysis is elemental fractionation mainly due to thermal heating of the sampling site during the laser ablation. This paper presents the facilities, functions, and analytical techniques of ICP-MS. Actual examples of terrestrial water analysis, rock analysis using solution samples, and micro analysis of minerals and bulk-rock analysis using LA-ICP-MS are also presented in this paper.

著者

田中 万也 高橋 嘉夫 福士 圭介 宇都宮 聡

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.169-171, 2015-09-25 (Released:2015-12-25)

---

Many studies have been carried out since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Here, we would like to introduce the special issue on the FDNPP accident which includes contributions from various fields covering aerosols, soil, forest, river, ocean and application of new analytical technique to samples collected in Fukushima.

著者

癸生川 陽子

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.50, no.3, pp.211-225, 2016-09-25 (Released:2016-09-25)

参考文献数

105

---

I have been studying origin and evolution of extraterrestrial organic matter on the basis of experimental kinetic approaches that enable us to predict changes in its molecular structure and chemistry during parent body processes. Here I summarize experimental studies of organic solid formations starting from formaldehyde and ammonia with the presence of liquid water, and decreasing in aliphatic C–H bonds as observed in infrared spectra with heating experiments of Murchison meteorite. The related works are also reviewed and the applications for deciphering thermal histories of asteroids are discussed.

著者

石渡 良志 内田 邦子 長坂 洋光 塚本 すみ子

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.44, no.3, pp.69-76, 2010

---

A 90 cm sediment core (HAR 99A) from Lake Haruna, Gumma Prefecture, Japan was dated by tephrochronology, lead-210 and cesium-137 methods and was compared stratigraphically with the cores obtained in 1966 (HAR 96B) and 1971 (HAR 71). For the HAR 99A core, the 24-26 cm depth layer was estimated to be AD 1963 by ¹³⁷Cs. The tephra layer in 62-66 cm depth was identified to be volcanic ashes from Asama volcano eruption (Asama-A tephra: As-A) in AD 1783. Average mass sedimentation rate (AMSR) for 1963 to 1999 (0-26 cm depth) is 0.050 g cm^-2yr^-1 and that for 1783 to 1963 (25-62 cm depth) is 0.033 g cm^-2yr^-1. AMSR for the 0-62 cm depth obtained by ²¹⁰Pb ranges between 0.052 and 0.058 g cm^-2yr^-1. In addition, it is proposed that the previous assignment of As-B (AD 1108) for a tephra layer at 40-50 cm depth of the HAR 71 core should be changed to As-A tephra (AD 1783).

著者

加戸 裕也 上田 晃 中本 利正

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.4, pp.279-298, 2016-12-25 (Released:2016-12-25)

参考文献数

49

---

Chemical compositions previously obtained from 333 hot springs in Ishikawa Prefecture were firstly examined for the geochemical characteristic. The Cl- concentration varies from 9 to 17,490 mg/L. Two geothermometers (Na+/K+ratio and SiO2 concentration) have been applied to estimate the subsurface temperatures with the chemical data and show that there are several high temperature areas (>150℃).Secondly, 29 hot springs and three river waters were newly collected from selected areas and analyzed for their hydrogen and oxygen isotopic compositions to also examine the source. The chemical and isotopic compositions indicate that the hot spring waters are a mixture of meteoric water, sea water (fossil sea water in a Green Tuff region) and volcanic fluid. The high temperature geothermal resources on the basis of the estimated subsurface temperature (ca. 200℃) may exist in the Hakusan area, the southern part of Ishikawa. The estimated geothermal resources in this area are ca. 60 MW. During geothermal power generation in this area, calcite is expected to precipitate in the reservoir and production wells according to the saturation indices for the hot spring waters and should be prohibited the precipitation.

著者

野津 憲治

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.47, no.3, pp.105-115, 2013-09-05 (Released:2017-02-23)

---

It is often documented that geochemistry has been established in the West in early 1920s. Since the same period or earlier, books and literatures on the developing geochemistry have been imported to Japan. Jun-ichi Takahashi, who met Vernadsky in Paris in 1924 and later translated his textbook "La Géochimie" to Japanese language in 1933, has studied such imported publications and has used "Chikagaku" as a Japanese equivalent for "Geochimistry" since early 1920s. Separately, Yuji Shibata, who is respected as a founder of Japanese geochemistry, was inspired by Vernadsky's "La Géochimie" (1924) and contributed an article introducing geochemistry as a promising new discipline to a newspaper "Kokumin-Shinbun" in 1926. In this article, he coined "Chikyukagaku" as a Japanese equivalent for "Geochemistry". Since then, the term "Chikyukagaku" became popular in Japanese scientific community. Although Takahashi claimed that the Japanese equivalent for "Geochemistry" was not "Chikyukagaku" but "Chikagaku" in his review paper in 1929, it was too late. Finally, Takahashi had to change his mind to use "Chikyukagaku" on the title of the Japanese translation version (1933) of Vernadsky's "La Géochimie".

著者

井上 睦夫 小村 和久

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.35, no.1, pp.13-25, 2001-03-20 (Released:2017-01-04)

参考文献数

65

---

Activities of cosmogenic nuclides have been numerously reported for extraterrestrial material, meteorites (especially chondrites). In addition to noble gases, cosmogenic radionuclides (e.g., 22Na, 26Al, 46Sc, 53Mn, 54Mn and 60Co) have also kept important records of their history during last ten million years. For example, low 60Co activity observed in most chondrites (<30 dpm/kg) suggests that their preatmospheric radii are less than 〜30 cm, and activities of 22Na and 26Al reflect various irradiation conditions by cosmic-ray such as shielding effect, exposure age and cosmic-ray flux with time and space. Terrestrial age (Antarctic meteorites; H group, <0.4×106y; L, LL,<106y estimated from 26Al, 36Cl and 14C activities) as well as exposure age (H, 3 -40×106y; L, LL, 3 -50×106y) shows different distributions between H- and L-, LL-group chondrites, which have possibly preserved the information about breakage of parent body and so on. The combined data of exposure age and activities of cosmogenic nuclides also give constraints on the complex history of chondrites (e.g., multi-stage irradiation as a result of fragmentation) until the collision with the Earth. Recently, with the progress of nondestructive γ-ray techniques, activities of relatively short-lived nuclides such as 46Sc, 22Na implied the irradiation conditions just before fall to the Earth. In this paper, "the evolution history of chondrites after separation from the parent body" is represented from activities of cosmogenic radionuclides in meteorites including recently fallen ones.

著者

大河内 直彦

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.3, pp.135-152, 2017-09-25 (Released:2017-09-28)

参考文献数

113

---

This paper reviews the principles and applications of the compound-specific radiocarbon dating developed mainly during the last two decades. This methodology requires two technical challenges: 1) purification of target compounds from natural samples, and 2) small-scale radiocarbon dating with accelerator mass spectrometry. Since its establishment, the compound-specific radiocarbon dating has been successfully applied not only to geochronology of marine and lacustrine sediments, but also to various fields including biogeochemistry, environmental science, and archaeology. Here I describe some of these applications of this approach that provided unique information and revolutionized our knowledge. Variable ages of the organic compounds from the marine sediments have clearly suggested that the transport and deposition processes of the organic matter in the ocean are more complex than that had been expected. Source apportionment has also successfully conducted for organic pollutants from various environmental samples. I end this review with a call for continued efforts including technical improvements for evaluating the purity of the target compounds and extension of the target compounds to variable compounds like amino acids.

著者

松尾 禎士

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.24, no.2, pp.i-iii, 1991-03-20 (Released:2016-12-06)

著者

奥村 大河

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.1, pp.31-40, 2021-03-25 (Released:2021-03-25)

参考文献数

30

被引用文献数

2

---

Radiocesium-bearing microparticles (CsMPs) were emitted from the damaged reactors to the environment during the Fukushima Daiichi Nuclear Power Plant accident. This review summarizes current knowledge with respect to the inner structures and physicochemical characteristics of CsMPs. CsMPs are composed of micron-sized spherical silicate glass with Na, Cl, K, Fe, Zn, Rb, Sn, and Cs as major constituent elements. Besides, CsMPs frequently contain nanocrystals such as Cr-rich oxides and chalcogenides. Thermal and dissolution properties of CsMPs have also been elucidated recently. Radiocesium is released from CsMPs to the atmosphere if they were heated at a high temperature. The aqueous dissolution rate of CsMPs depends on pH and dissolved species in solutions, which is similar to that of silica glass. Estimation of the amount and spatial distribution of CsMPs in the environment is also progressing. These findings will lead to the comprehensive elucidation of the dynamics of CsMPs in the environment.

著者

中村 仁美 岩森 光

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.76-86, 2022-12-25 (Released:2022-12-25)

参考文献数

66

---

Arima-type hot spring waters that exhibit unique geochemical characteristics and their formation are reviewed based on subduction-zone-scale perspectives and studies concerning fluid circulation. Arima-type hot spring waters produced in non-volcanic regions exhibit properties similar to those of volcanic fluids. In order to clarify the formation mechanism, we first review the definition of volcanic/non-volcanic regions and their essential differences. Then we discuss the dehydration reactions in the subducting plates, the resulting distribution and geochemical characteristics of slab fluids, and present evidences of their ascent into the Japanese crust and their role in the global material cycling. In addition, the characteristics and causes of the recently discovered Arima-like hot spring water in the Eurasian continent are reported, and the extent of the material circulation in the wide subduction zone is discussed.