巻号一覧
28 巻 (1994)
- 6 号 p. 429-
- 5 号 p. 369-
- 4 号 p. 307-
- 3 号 p. 137-
- 2 号 p. 71-
- 1 号 p. 1-
28 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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Naoki Mita, Akihiko Maruyama, Akira Usui, Takanori Higashihara, Yu Har ...1994 年 28 巻 2 号 p. 71-80
発行日: 1994/04/20
公開日: 2008/04/08
ジャーナル フリーThe formation process of hydrous manganese oxide deposit can hardly be demonstrated in natural environments, namely, hot and cold springs and deep-sea hydrothermal vents. We discovered a unique phenomenum that hydrous manganese oxide is now actively depositing from the hot spring water at the Yuno-taki Falls, Hokkaido, Japan. The chemical and the biological factors that potentially control the actual manganese deposition in the natural environment were examined. Pure manganese oxide deposit (1.1 ton/year calculated as MnO2) is currently being formed from weakly acidic hot spring water by the mediation of microbial consortium consisting of manganese-oxidizing bacteria and filamentous algae. A comparison of the mineral deposition at this location with other terrestrial and oceanic deposits suggests that they were formed in a similar manner.抄録全体を表示PDF形式でダウンロード (2449K) -
Tasuku Akagi, Hiroki Haraguchi1994 年 28 巻 2 号 p. 81-97
発行日: 1994/04/20
公開日: 2008/04/08
ジャーナル フリーThe surface and bulk chemical composition of suspended particles (SP) from the Tamagawa estuary and Tokyo Bay have been studied. X-ray photospectroscopy (XPS) was used for the surface analyses. By comparison with bulk analysis, it was found that there was a surface layer enriched in organic matter and manganese, and that such the particles were coexisting. Silica may also be adsorbed onto the surface, but is depleted relative to the bulk nevertheless. The organic matter in the surface is considered to be humic acids from its chemical composition, and becomes the dominant substance on the surface with increasing depth and distance offshore, overwhelming silicates and oxides. The effect of such particles on dissolved trace metals was investigated by comparing their concentration gradients with the coverage of humic acid, silicates and oxides in the surface. The concentration gradients of dissolved Ni, Cu and Zn correlate better with the surface areas of Al, Fe and Mn than with that of organic matter, suggesting the former are more effective adsorbers of metals than the latter.抄録全体を表示PDF形式でダウンロード (3940K) -
Kazuya Takahashi, Akimasa Masuda1994 年 28 巻 2 号 p. 99-113
発行日: 1994/04/20
公開日: 2008/04/08
ジャーナル フリーLunar meteorites recovered from Antarctica are recognized to have been derived from the lunar highlands. Seventeen samples (rock fragments and clasts) from Yamato-791197 and Yamato-82192 have been analyzed for chemical compositions (rare earth elements and major elements) and Rb-Sr systematics. Those samples show chemical and chronological characteristics resembling the lunar highland samples very much. The lunar highland rocks have been known to show positive Ce anomalies in their REE (rare earth elements) abundance patterns. These anomalies are considered to have formed on the lunar surface, but their genesis has not been discussed definitely. The lunar meteorites, which we analyzed, also show the positive Ce. anomalies. According to our geochemical (major elements and REE abundances) and chronological (Rb-Sr systematics) studies for some lunar meteorites, the Ce anomalies appear to increase with decreasing Al2O3 and CaO contents. Furthermore, the initial 87Sr/86Sr ratios obtained for some samples with ages of around 3.9 Gyr are as low as that for the Juvinas eucrite which has an age of 4.5 Gyr, indicating the removal of radiogenic 87Sr. Samples of a lunar meteorite, which form an isochron with relatively high initial ratio, show smaller positive Ce anomalies than the samples of 2 other lunar meteorites which form isochrons with relatively low initial ratios. As one possibility, these correlations among major element contents, REE abundances, initial 87Sr/86Sr ratios and Ce anomalies suggest that H2O (possibly ice) might have played a role in the alteration having produced the Ce anomalies, and it is suggested that ice may have existed at least locally on the surface of the moon at an early stage of lunar history.抄録全体を表示PDF形式でダウンロード (3000K) -
Akio Makishima, Akimasa Masuda1994 年 28 巻 2 号 p. 115-122
発行日: 1994/04/20
公開日: 2008/04/08
ジャーナル フリーLREE (La, Ce, Nd and Sm) concentrations, and 143Nd/144Nd and 138Ce/142Ce ratios of two powder aliquots from the bulk Allende meteorite (BAM) were measured to investigate p-isotopic anomalies of Ce. Initial Ce isotope ratios of the two aliquots were calculated assuming an age of 4.56 Ga, identical with ages of other chondrites or eucrites. From the data, we conclude that there are no recognizable p-isotopic anomalies in BAM. This suggests that the existence of p-isotopic anomalies of other REE in BAM is unlikely. Our data can not, however, rule out the possibility that this is only caused by averaging of heterogeneous distribution of p-isotopic anomalies.抄録全体を表示PDF形式でダウンロード (2230K) -
Jun Sato, Taeko Doi, Toru Segawa, Shin-ichi Sugawara1994 年 28 巻 2 号 p. 123-129
発行日: 1994/04/20
公開日: 2008/04/08
ジャーナル フリーConcentrations of 210Pb and 7Be in the surface air were measured at Tsukuba Science City (36°03′N, 140°07′E), Japan, during the period of November 1987 to May 1992. The air concentrations of 210Pb and 7Be ranged from 0.2 to 0.8 mBq/m3 and from 1 to 6 mBq/m3, respectively. Seasonal variation of 210Pb concentration was similar to that of 7Be, showing a “two-peak” variation pattern: high concentrations appeared in the spring and the fall. This variation pattern was formed on the 210Pb concentration generated from 222Rn in the surface air. This was interpreted as part of 222Rn emitted from the ground surface may be transported upwards to accumulate long-lived 210Pb in the lower part of the stratosphere. It may then subside into the troposphere with the cosmogenic 7Be through the tropopause break, during the spring, and along the descending currents, including those which accompany the migratory anticyclones passing frequently over Japan during the spring and fall. Unusual and temporal increase in the 210Pb concentration and in the 210Pb/7Be activity ratio observed in the winter months of 1991-1992 may be attributed partly to the 210Pb fallout originating from the 1991 eruption of Pinatubo volcano, Philippines.抄録全体を表示PDF形式でダウンロード (1988K) -
Pradeep Kumar, P. S. Goel1994 年 28 巻 2 号 p. 131-135
発行日: 1994/04/20
公開日: 2008/04/08
ジャーナル フリーUsing RNAA method plus fire-assay technique, the 190Os/184Os ratio has been measured in the carbon-rich (CR) residues of four stone meteorites (prepared by HF-HCl demineralization). The residues percent-weight-recovery is between 3–4 in Allende, Plainview and Rangala and 0.80 in Ambapur Nagla. After neutron activation and Hg distillation (vacuum), the aliquots of residues were fired (at temperature ∼1200°C) separately with the flux containing Ni powder and sulphur to incorporate osmium in Ni-NiS beads. The beads were cleaned, decomposed with H2SO4 in the presence of CrO3 and Os was distilled with conc. HNO3 as OsO4 in thiourea solution (5% in 6M HCl). The CR-residues though contain isotopically anomalous Hg yet the collected Os from these show normal isotopic ratio within ± 10% variations. The Os concentrations are 1 to 2 order of magnitude higher than the bulk values.抄録全体を表示PDF形式でダウンロード (1345K)
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