巻号一覧
33 巻 (1999)
- 4 号 p. 207-
- 3 号 p. 141-
- 2 号 p. 67-
- 1 号 p. 1-
33 巻, 2 号
選択された号の論文の6件中1～6を表示しています
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企画総説「地球化学の新方法」
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鈴木 勝彦1999 年 33 巻 2 号 p. 67-102
発行日: 1999/06/01
公開日: 2016/12/28
ジャーナル フリーNegative thermal ionization mass spectrometry (N-TIMS) has been recently developed as a precise and accurate method in mass spectrometry to determine isotope ratios of some elements, which cannot be measured by positive thermal ionization mass spectrometry (P-TIMS) easily. In N-TIMS, isotopic compositions of elements, such as halogens, chalcogens, boron and platinum group elements with high ionization potentials, are determined as negative atomic ions M-, oxide ions MOx- (x=1-4) or fluoride ions MFx- (x=4). Recent interesting developments in geochemistry is the determinations of rhenium-osmium systematics, redetermination of the relative atomic masses of elements by more precise and more accurate isotope ratio measurements, the determination of isotope variations in geological and cosmic samples and the analysis of trace and ultra-trace amounts of elements in the environment. In this paper, after theory and characteristics of N-TIMS are mentioned, some recent applications of N-TIMS is summarized in the field of geochemistry and environmental chemistry. Among recent topics, (1) application to rhenium-osmium systematics, (2) precise boron isotope analysis and its application to environmental chemistry, and (3) precise iron isotope analysis and its application to biological and medical use are described. Problems involved in N-TIMS are also discussed.抄録全体を表示PDF形式でダウンロード (3602K)
1997年度日本地球化学会奨励賞受賞記念論文
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木多 紀子1999 年 33 巻 2 号 p. 103-114
発行日: 1999/06/01
公開日: 2016/12/28
ジャーナル フリーThis paper summarizes the chronological studies on enstatite chondrites and ureilites, both of which are special groups of meteorites with unknown origins. Two unequilibrated enstatite chondrites, Qingzhen and Yamato 6901 (E3), showed the highly disturbed Rb-Sr system, while their silicate fractions yielded the 2.1 Ga isochron. The thermally metamorphosed enstatite chondrite Khairpur (E6) showed the older Rb-Sr age of 4.50 Ga. The parent body of E3 chondrites experienceda late thermal event at low temperature, which broke down alkali-bearing sulfides in E3. The observed Rb-Sr data are consistent with the mobilization of Rb from alkali-sulfide to silicate phases. Ureilites show highly depleted trace elements abundance which makes it difficult to determine the age of the formation. The U-Pb and Sm-Nd age determination of low-Ca ureilite Goalpara showed that the Pb and Nd isotopes are heavily contaminated with terrestrial components. The acid residues of high-Ca ureilite MET-78008 were free of contamination and defined the old U-Pb age of 4.563 ± 0.006 Ga. The early formation of ureilites supports their formation through the collisional destruction of the parent body. Including the ureilite date, many evolved meteorites formed within the first 10 million years of the solar system history. Future studies on meteorite chronology with the purpose of understanding the early history of the solar system should focus on the fine time resolution through the precise U-Pb age determination or the relative age determination using the extinct nuclides with half lives less than 10 million years.抄録全体を表示PDF形式でダウンロード (1317K)
総説
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大出 茂, ZULEGER Evelyn1999 年 33 巻 2 号 p. 115-122
発行日: 1999/06/01
公開日: 2016/12/28
ジャーナル フリーThe composition of two stable isotopes 10B (〜20%) and 11B (〜80%) can vary significantly on the earth and provides important information on the global geochemical cycle. Art Spivack has proposed a simple and elegant idea called "palaeo-pH", that boron isotopes in foraminifera might indicate past oceanic pH values. The mean oceanic residence time of boron is calculated at 1.6×107 years. Therefore, the boron concentration (4.5ppm) and isotopic composition (δ11B=39〜40‰) in seawater are quite uniform throughout the world's oceans (Tablel). The dominant boron species in seawater is B(OH)3 and B(OH)4-. There is about 2% difference between the isotopic composition of B (OH)3 and B(OH)4-, as a result of the isotope fractionation. The 11B isotope is concentrated into B(OH)3 in seawater. The relative proportion of the two species is controlled by pH. Boron isotopic composition of B(OH)3 and B(OH)4- in seawater is shown as a function of pH. If one of each species is incorporated into marine carbonates, the boron isotopes should reflect seawater records of pH in which they have grown. Using the boron isotope "palaeo-pH" method,the Lamont group attempted to estimate surface oceanic pH differences between the last glacial period and the Holocene. Studies on boron isotopes from coral samples clarify some issues on the "palaeo-pH" in aquatic environments. More detailed studies will make progress on the boron isotope pH-meter.抄録全体を表示PDF形式でダウンロード (782K)
報文
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真田 幸尚, 佐藤 太, 熊田 英峰, 高田 秀重, 山本 愛, 加藤 義久, 上野 隆1999 年 33 巻 2 号 p. 123-138
発行日: 1999/06/01
公開日: 2016/12/28
ジャーナル フリーTo estimate the sedimentation rate and to understand the sedimentation processes in Tokyo Bay, vertical distributions of 210Pb and 137Cs were determined for two sediment cores (F-2 and F-5) from Tokyo Bay and one from the moat of Imperial Palace for the Tokyo. Molecular stratigraphy was applied to one of the Tokyo Bay sediment cores using polychlorinated biphenyls (PCBs) and linear and tetrapropylene-based alkylbenzenes (LABs and TABs). 210Pb showed exponential downcore decrease with substantial fluctuation. In the sediment core of the bay (F-2), radiocesium maximum, corresponding to the atmospheric deposition maximum at 1963, was observed. Good agreement between the deposition date estimated using radionuclides (137Cs and 210Pb) and the vertical distributions of PCBs, LABs and TABs, suggests the utility of multiple markers approach for sediment stratigraphy. In the Tokyo Bay sediments, only slight or negligible decrease in 137Cs activity was observed toward the surface layer where significant amounts of 137Cs was detected, whereas a sharp peak of 137Cs were observed for the Moat which has no inflowing rivers. PCBs and TABs, whose productions and usage ceased by early 1970s, decreased gradually to the sediment-water interface in the Tokyo Bay and were found significantly in the surficial sediments. All these markers suggest that riverine and estuarine sediments play a role of a reservoir of the pollutants, that is, particle-reactive pollutants are temporally deposited and stored in riverine and estuarine sediments which are intermittently supplied to Tokyo Bay during flood events with resuspension.抄録全体を表示PDF形式でダウンロード (1624K)
博士論文抄録
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笹木 圭子1999 年 33 巻 2 号 p. 139-
発行日: 1999/06/01
公開日: 2016/12/28
ジャーナル フリーPDF形式でダウンロード (189K) -
山中 寿朗1999 年 33 巻 2 号 p. 140-
発行日: 1999/06/01
公開日: 2016/12/28
ジャーナル フリーPDF形式でダウンロード (185K)
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