著者

渡久山 章

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.2, pp.i-iii, 2018

著者

友寄 喜貴 棚原 朗 武村 盛久 渡口 輝 平良 初男

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.4, pp.227-233, 1997-12-10 (Released:2016-12-22)

参考文献数

20

被引用文献数

2

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The activities of natural radionuclides, 238U, 234U, 226Ra, 228Ra, 222Rn, 210Pb and 210Po in ground waters collected from Okinawa Island were measured. The 234U/238U activity ratios in most samples showed more or less unity, whereas, relatively high values of 2.0-4.0 were obtained in samples from Motobu area. 222Rn activities in the ground waters were much higher than the other uranium series nuclides. The 222Rn/226Ra activity ratios ranged from 3000 to 29000, and those for 210Po/210Pb were from 0.08 to 0.82. On the whole, activities of the nuclides in the ground waters at the studied points showed higher in the order of 222Rn≫210Pb>234U>238U>226Ra>210Po. In addition to α_recoil dissolution, the selective absorption and/or desorption by some organic or inorganic substances in the aquifer may be happening.

著者

和田 茂樹 アゴスティーニ シルバン

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.4, pp.195-205, 2017-12-25 (Released:2017-12-25)

参考文献数

72

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Surface oceans absorb a part of anthropogenic CO2, and it induces changes in carbonate equilibrium of seawater. The seawater is gradually acidified, and saturation status of calcium carbonate is being lowered. These changes in carbonate chemistry would be serious threats for marine organisms (e.g., calcifying organisms). Ecosystems around submarine CO2 vents; CO2 seep, would be natural analogues of ocean acidification (OA) in coastal area, and ecosystem-level studies have been carried out so far. Drastic changes in species composition of primary producers have been reported in several CO2 seep. Common features are decrease in calcifying organisms such as coral and calcifying algae, and increase in mat-forming turf algae and seagrass. Considering such shift of benthic flora, change in primary production in coastal ecosystem is expected. However, there are limited number of direct measurements for photosynthesis, and their reports had focused on only some species living both in/out of CO2 seep. Therefore, the knowledges are limited to the physiological response of the primary producers to OA. In order to quantify the impact on the primary production at ecosystem level, consideration on the shift of flora and estimation per unit community area will be required.

著者

南 雅代

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.4, pp.244, 1997-12-10 (Released:2016-12-22)

著者

呉 佳紅 西島 好美 佐竹 洋

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.42, no.1, pp.1-11, 2008

参考文献数

37

被引用文献数

1

---

Nitrogen isotope ratio of nitrate ion in precipitation at Toyama was traced from June 2003 to December 2005 to investigate the behavior of nitrate ion inassociation with precipitation. δ¹⁵N value varied from -7.8 to + 1.6%o and showed seasonal variation; i.e., it was higher in winter than in summer. δ¹⁵N value negatively correlated to solar radiation. Negative correlation was also observed between δ¹⁵N value and concentration of atmospheric oxidant, which converted NO₂ to HNO₃. Such correlations suggest that the δ¹⁵N value of nitrate ion decreases with increasing conversion rate from atmospheric NO₂ to HNO₃. Based on an equation obtained from the relationship between the conversion rate and δ¹⁵N value according to the Rayleigh distillation model, 78-98% (av. ±1σ, 90±5%) NO₂ exhausted into the atmosphere were estimated to be converted into HNO₃. The similar seasonal variation was also observed at Nagoya, although the δ¹⁵N values are systematically higher than those of Toyama. The NO₂ concentration at Nagoya istwice as high as the concentration at Toyama, suggesting that the conversion rate from NO₂ to HNO₃ is lower in Nagoya (av. ±1σ, 86±6%) than in Toyama.

著者

菅原 健

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.14, no.2, pp.43-61, 1981-03-30 (Released:2016-11-17)

著者

中村 岳史 野尻 幸宏 大槻 晃 橋本 伸哉

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.28, no.1, pp.47-57, 1994-03-24 (Released:2016-12-13)

被引用文献数

3

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Seasonal changes in the methane concentration of seawater were measured in highly eutrophic, Tokyo Bay. Methane concentrations varied from 27.8 to 1850nM during May 1991 to December 1992 and were always supersaturated with the atmospheric methane. During the spring and summer seasons, when bottom water became anoxic, dissolved methane was observed to accumulate (maximum 929nM). There were inverse correlations between dissolved oxygen and dissolved methane in bottom water, when dissolved oxygen concentrations in the bottom water fluctuated. Throughout the experimental period, fluctuations of methane concentrations at mid-depth were relatively small. Particularly during summer, methane concentrations in surface water frequently increased to the same levels, or became higher than concentrations in bottom water. The source of methane in these surface waters were attributed to lateral transport from the near shore zone. From fall throughout winter, methane concentrations decreased and resulted in uniform distribution through the water column. Methane oxidation activities measured in June and August, 1991 in surface and bottom water were extremely low. The calculated diffusive flux from the bay surface to the atmosphere were 1.5-11mgCH4/m2/d.

著者

杉山 裕子 Hatcher Patrick G. 三田村 緒佐武 片野 俊也 熊谷 哲 中野 伸一 DRUCKER Valentin V. FIALKOV Vladimir A. 杉山 雅人

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.42, no.4, pp.165-177, 2008

被引用文献数

1

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Lake Baikal, located on the north-eastern borders of Central Asia, is the deepest (maximum depth 1,700 m) and one of the largest lakes in the world. To elucidate the chemical composition of dissolved organic matter (DOM) in the Lake Baikal, we applied high resolution fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) to the lake water samples. Water samples were taken at the deepest point of Lake Baikal and its inflowing Barguzin River mouth on August 2005. The sample water was filtrated on board and DOM was extracted using C 18 solid-phase extraction disks (Kim et al., 2003^a). The extracted samples on the disks were analyzed by a 9.4-T FT-ICR mass spectrometer at the National High Magnetic Field Laboratory (Tallahassee, FL, USA) in negative ionization mode with a needle voltage of -2.0 kV. From the FT-ICR mass analysis, 3511, 2862 and 2191 peaks were detected (S/N>3) in river and 5 m- and 945 m- depth lake water samples, and more than 80% of the peaks were assigned within ± 1.0 ppm error. Using van Krevelen Diagrams (van Krevelen, 1950), we found that the main component of L. Baikal DOM was allochthonous lignin-like organic molecule, and that autochthonous lipid- and protein-like molecules were also found in surface water.

著者

金井 豊 井内 美郎 山室 真澄 徳岡 隆夫

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.32, no.2, pp.71-85, 1998-05-20

参考文献数

38

被引用文献数

5

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In order to study sedimentation environments and sedimentation rates in Lake Shinji, Shimane Prefecture, the Pb-210 and Cs-137 radioactivities were measured in 15 cores taken on Oct. in 1994. The sedimentation rates in the lake varied at each location; those in the western area are about 0.25g/cm^2/y, larger than in the eastern area (about 0.1g/cm^2/y), and those in the central area are the lowest (≦0.05g/cm^2/y). This fact indicates that most of the sediments supplied by the Hii river deposited in the western area and little amount was transported to the central area. The inventries of radionuclides that indicate the amount of accumulation were larger in the western area, which is the same tendency as the sedimentation rate. They are in a positive correlation (correlation coefficient (R) is 0.78), and their relationships are different from that observed in offshore sediments of Japan sea. The fluxes of excess Pb-210 and Cs-137 are large in western area, which suggests that much amount of sediment were supplied from the Hii river. The concentrations of excess Pb-210 and Cs-137 in surface sediments are in a good correlation (R=0.76), which indicates that both nuclides in sediment grains may exist in a constant ratio. The sources of radionuclides are supposed to be terrestial fallout and suspended particles carried from river. Although the latter source is not negligible, it is considered that the former is superior and that radionuclides moved and distributed heterogeneously in Lake Shinji.

著者

杉谷 健一郎

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.45, no.4, pp.265-279, 2011-12-25 (Released:2017-02-16)

参考文献数

111

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Early to Middle Archean fossil-like carbonaceous and pyritic microstructures from the Pilbara Craton, Western Australia were reviewed, referring to origins and depositional environments of host rocks. While their biogenicity is not always widely accepted but even controversial, it is plausible that Early to Middle Archean microorganisms were significantly diverse (filamentous, lenticular, spheroidal, film-like) and adapted to wide ranges of environments including deep-sea hydrothermal area, shallow sea and even hyper-saline lake. Hence, these records of microfossil and stromatolites reported from contemporaneous strata could not provide direct information about origin of life and its very early evolution. On the other hand, recently accumulated data of large microfossils (>20μm in major dimension), some of which are morphologically similar to cyanbacteria and eukaria, could provide new framework for studies on the early evolution of life.

著者

丸山 茂穂

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.47, no.3, pp.155-157, 2013

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To understand the origin and evolution of life and to predict the future of life is the ultimate goal of geochemistry that we need to reach. Here, I will show the history of geochemistry and future outlook on the Earth, the universe and Astrobiology.

著者

新村 龍也 沢田 健

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.1, pp.17-29, 2010

被引用文献数

2

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Dietary preferences of archaeological and paleontological animals have been investigated based on stable carbon isotope ratios (δ¹³C) of collagen and non-collagenous proteins in fossil bones. The δ¹³C of individual compound in lipids from fossil bones were recently applied to the reconstruction of palaeodietary of animals. In the present study, we analyze the concentrations, class distributions, and δ¹³C values of fatty acids and steroids in the Pleistocene to Pliocene fossil whale and the Miocene fossil sea cow (<i>Dusisiren</i> sp.) bones, and evaluate their applicability as indicators of palaeodietary and fossil diagenesis. Biosynthetic steroids as cholesterol are detected in the Pleistocene whale bones, while the sterols are very poor in the older Pliocene whale samples, of which major steroids are their diagenetic compounds such as cholestanes and cholestenes. However, a large amount of cholesterol characterizes the Miocene fossil sea cow bone. We also can identify labile unsaturated fatty acids from all fossil whale and sea cow bones. It is suggested that the relative abundances of unsaturated to saturated fatty acids can be useful indicator for estimating diagenetic stage of fossil bones and checking contamination. The δ¹³C values of fatty acids in the fossil whale and sea cow bones range widely from -25.7 to -16‰, and there are differences of 1 to 4‰ between several fatty acid homologues within the same sample. Thus, the δ¹³C analyses of fatty acids in fossil bones may be less applicable for reconstructing palaeodietary. On the other hand, the δ¹³C values of steroidal compounds within the same sample are almost similar, although these values vary ranging between -29.6‰ and -24.4‰ among the different whale samples. Furthermore, the steroidal δ¹³C value in the sea cow sample is -20.5‰, which is concordant with that of food in sea cow. From these results, the δ¹³C value of steroid in fossil bone can be strongly useful tool for reconstructing palaeodietary of paleontological animal.

著者

小路 翔子 笹木 康平 上田 晃 中本 利正

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.2, pp.97-114, 2016-06-20 (Released:2016-06-20)

参考文献数

38

被引用文献数

1

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Chemical and isotopic (δD and δ18O) compositions of 30 hot spring waters and 5 river waters in Okuhida Hot Springs, Gifu, were investigated to examine the geochemical characteristics and geothermal resources. Most hot springs were of meteoric origin and of Na+–Cl-・HCO3- and Na+–HCO3- types with low salinity (less than 30 meq/L). In the study area, meteoric water infiltrates into ground and is heated by magmatic source and enriched in Ca2+and HCO3- during interaction with underlying carbonate rocks. A part of the hot spring is enriched in CO2 due to contribution of CO2-rich volcanic fluid. The estimated underground temperatures by several geothermometers are 150 to 200℃ at the depth of ca. 1 km. The total geothermal resources in the study area are estimated to be ca. 400 MWe for producing the electricity. In the study area, most hot springs have been provided for bathing in hotels and a part of them (60℃, 3,000 L/min) has not been used. We provide this unused geothermal energy to apply for snow melting on road and room heating. For the safety use of geothermal resources in the study area, scaling problem was considered. On the basis of the saturation index of several minerals from the observed chemical compositions of hot spring waters, calcite scale is expected to be precipitated in the reservoir and in the production wells and should be considered to prohibit the precipitation.

著者

長尾 誠也

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.217-226, 2015-09-25 (Released:2015-12-25)

参考文献数

43

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This paper reviewed the transport behavior of 137Cs in river systems of Fukushima Prefecture, Japan after the Fukushima Dai-ichi Nuclear Power Plant accident during 2011–2014. Total radioactivity of 137Cs in water samples from the Abukuma River and small watershed river systems in eastern Fukushima, Hama-dori region, decreases exponentially with increasing time after the accident at normal flow condition. Higher radioactivity was found at higher flow condition caused by rain events. Particulate phase of 137Cs in river waters ranged from 60 to 99% to total radioactivity. Apparent distribution coefficient (Kd value) of 137Cs was 102 to 103 l g-1. The annual export of 137Cs from land to coastal ocean was estimated as 1010 to 1013 Bq in the river basins on the basis of field research data. These results indicate that major part of 137Cs is exported as particulate forms associated with suspended solids in the river waters.

著者

高地 吉一 折橋 裕二 小原 北士 藤本 辰弥 春田 泰宏 山本 鋼志

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.1, pp.19-35, 2015-03-25 (Released:2015-03-30)

参考文献数

44

被引用文献数

1

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We carried out an optimization of analytical parameters for U–Pb zircon dating by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) using a NIST SRM 610 glass. As a result, we obtained the following optimum analytical parameters: laser energy: 11.7 J/cm2, repetition rate: 10 Hz, pre-ablation time: 8 sec, integration time: 10 sec and crater diameter: 25 μm. The average 206Pb/238U ratio of the NIST SRM 610 glass normalized by a 91500 zircon standard under the conditions mentioned above was 0.2236±0.0044 (1σ, N : 87). The median value of this result matches with that of the literature value within range of the analytical precision. Furthermore, the 206Pb/238U weighted mean ages of the Plešovice, OD-3 and Fish Canyon Tuff zircons, having the proposed 206Pb/238U ages of 335.48±0.95 Ma (95% conf., N : 38, MSWD : 1.1), 33.25±0.38 Ma (95% conf., N : 23, MSWD : 1.5), 28.56±0.49 Ma (95% conf., N : 34, MSWD : 5.1), respectively, were measured, normalized by the NIST SRM 610 glass standard. The results were consistent within 1% error range of the recommended values. These results suggest that the matrix effect can be reduced to less than analytical precision on materials with different physical properties under well-optimized analytical conditions.

著者

南 秀樹 加藤 義久 和田 秀樹 岡部 史郎

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.29, no.2, pp.85-97, 1995

被引用文献数

7

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Four cores, which penetrated into the Holocene, were collected in 1985-1986 from the center to mouth of Lake Hamana, Japan. Sediments were analyzed for the concentrations of organic C, total N, biogenic SiO₂, Mg, Al, Fe, Mn, V and P. The age of the sediment near the bottom part of each core, which exhibited a higher C/N mole ratio, changed from 11,000 yr B. P. at the mouth to 7,000 yr B. P. at the center part of the lake. This indicated a higher sedimentation of land plants enriched in carbon, which probably took place during a period of high sealevel. After 4,000 yr B. P. in the inner part of the lake there were some distinctive changes in the distributions of elements, as related to their ¹⁴C ages : (1) higher content and large fluctuations in both the sediment, organic carbon and biogenic SiO₂, and (2) an excess organic carbon over biogenic SiO₂. Yet, in contrast, the C/N mole ratio&ap;12 remained constant. These observations suggested that an eutrophic and productive lake was formed when the seawater exchange was restricted. The contents of Fe and Mg also increased remarkably after 4,000 yr B. P. These changes are due to increasing of the transport ation of particles, originating from ultra-basic rocks carried by the Miyakoda River in the northern part of the lake. Before this period marine silt was predominantly transported from the Pacific sea side.

著者

鶴田 治雄 中島 映至

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.46, no.2, pp.99-111, 2012

被引用文献数

1

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Massive radioactive materials were released into the atmosphere after the accident of the Fukushima Daiichi Nuclear Power Plant (FD1NPP) caused by the Tohoku Earthquake and Tsunami on 11 March 2011, and transported and deposited to the land surface in a regional scale. A large amount of dataset has been opened such as the routine monitoring of radiation dose, fallout, and the regional map of radionuclides deposited to the surface soils by an intensive field measurement and aircraft monitoring by MEXT. In contrast, continual field measurements for atmospheric radioactivity were made only at seven stations in the Kanto area, while they are necessary to evaluate the initial radiation exposure, to validate results of atmospheric transport models, and to estimate the emission inventory of radionuclides. In this review, the following five points are introduced. (1) Summary of release rate estimation from the FD1NPP by the combination of WSPEEDI-II with atmospheric radioactivity of ¹³¹I and ¹³⁷Cs and radiation dose. (2) The possible mechanisms of many peaks of radiation dose during 11-16 March 2011 which were measured at the monitoring posts near the FD1NPP. (3) Possible mechanism of regional transport and the surface deposition of radionuclides. (4) Summary of atmospheric ¹³¹I in aerosols and gases, and ¹³¹I/¹³⁷Cs in the atmospheric radioactivity. (5) An intensive one-year field measurement of atmospheric radioactivity of ¹³⁷Cs at Fukushima and Koriyama since May 2011.

著者

遠嶋 康徳

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.77-93, 2010

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Observation of the change in atmospheric O₂ concentration, combined with atmospheric CO₂ observation, provides complementary information about the global carbon cycle. This is based on the fact that O₂ and CO₂ fluxes are tightly coupled during terrestrial photosynthesis, respiration, and fossil fuel and biomass burning, but are less or decoupled during the sea-air gas exchanges. Especially, the long-term O₂ changes can be used to partition the sequestration of fossil fuel CO₂ release between ocean and terrestrial biosphere. In this review, we examine the parameters used for the partitioning calculation, including - O₂: C exchange ratios for the terrestrial photosynthesis/respiration and fossil fuel burning. In early atmospheric O₂ studies, the net oceanic O₂ flux was assumed to be zero because of the low solubility of O₂ in seawater in comparison with that of CO₂. However, recent studies have suggested that the upper-ocean warming, reducing the solubility of O₂ and the oceanic ventilation, causes net oceanic O₂ outgassing. We also review approaches to estimate the net oceanic O₂ fluxes. Finally, using the updated fossil CO₂ emission estimates and recently reported warming rates of the global upper ocean, we recalculate the ocean and terrestrial carbon sinks based on the previously reported atmospheric O₂ observations.

著者

中澤 高清

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.16, no.2, pp.63-77, 1982

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In view of the importance of the global increase in atmospheric CO₂ for climatic change, extensive studies have been made on the concentration of atmospheric CO₂. In this paper, the results obtained from these studies are summarized together with those of our own measurements. Methods for measurement of the atmospheric CO₂ concentration by infrared absorption techniques are also described.

著者

北野 康

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.16, no.2, pp.59-62, 1982

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It was reported that since 1850 human activities have increased the CO₂ content of the terrestrial atmosphere from 290 ppm to slightly more than 330 ppm. It is thought that the CO₂ content would reach twice the current CO₂ content by the year 2020 and at that time there will have been a rise in the average air temperature of about 2℃. This has produced a serious fear that a climatic change will occur and reduce some of the present granary regions to rather arid areas. Thus atmospheric CO₂ studies should be one of the most urgent research subjects internationally. Y. Kitano has organized the research group on "The cycle of carbon dioxide through the phases of the atmosphere, hydrosphere and biosphere" in connection with the atmospheric CO₂ problem, sponsored by the Ministry of Education in Japan as a Special Project Research on Environmental Sciences. It is happy to show the results obtained by some members of the research group here.