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Volume 28 (1994)
- Issue 2 Pages 93-
- Issue 1 Pages 1-
Volume 28, Issue 2
Displaying 1-5 of 5 articles from this issue
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Original Papers
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Yuichi KOIKE, Yuzuru NAKAGUCHI, Kazuyoshi UMEUCHI, Keizo HIRAKI1994 Volume 28 Issue 2 Pages 93-99
Published: September 10, 1994
Released on J-STAGE: December 14, 2016
JOURNAL FREE ACCESSOrganic-metal compound are enriched in the euphotic and bottom layers, relative to the intermediate layer. It has been suggested that these compounds within the euphotic layer are supplied by biological activities such as excretion from plankton. However, these compounds in the bottom layer may be supplied by means of not only plankton excretion but also dissolution from sediments under the anoxic conditions. Then the dissolution of organic-metal compounds from sediments is investgated. Distilled water was added to sediment sample and repeat leaching operation by means of the irradiation of ultrasonic waves was carried out. Organic-metal compounds was divided into amino acid, organic acid, carbohydrate and marine humus fractions, respectively. The greater part of organic-metal compounds was removed from sediment to the aqueous phase by the first leaching operation. Then, copper was detected in organic acid fraction, manganese in amino acid fraction and selenium in all fractions. In addition, the dissolution experiment for reducing sediment under the aerated condition was carried out. Organic copper, manganese and selenium compounds were leached in the same fractions as well as the ultrasonic irradiation experiment. However, the amount of dissolution account for only 5 to 10% of the case for the ultrasonic irradiation.View full abstractDownload PDF (715K) -
Masaaki MUSASHI, Takanobu ISHIDA1994 Volume 28 Issue 2 Pages 101-112
Published: September 10, 1994
Released on J-STAGE: December 14, 2016
JOURNAL FREE ACCESSIn order to develop a theoretical basis useful in discussing the boron isotope geochemistry, it is first necessary to establish a reliable correlation between the molecular structures and molecular forces of boron compounds found in nature. With a goal to facilitate such basis by obtaining the reduced partition function ratios (RPFR) of all important boron compounds, we have first examined B2O3 . The geometrical parameters and spectroscopic data of B2O3 in literature have been critically reviewed, and a new force field for B2O3 has been computed on the basis of a planar V-shaped (C2v structure of B2O3 . The concept of the Urey-Bradley force field has been used by defining a B...B nonbonded stretching coordinate rather than a B-O-B angle bending. The eigenvalues and eigenvectors obtained by the present normal coordinate analysis agree reasonably well with the spectral data observed by Sommer et al. (1963). The RPFR of 19 pairs of isotopic B2O3 molecules have been computed, and implications of the results have been discussed.View full abstractDownload PDF (1148K) -
Reiko SUZUKI, Yukiko SAKAI, Masae KIKUCHI1994 Volume 28 Issue 2 Pages 113-122
Published: September 10, 1994
Released on J-STAGE: December 14, 2016
JOURNAL FREE ACCESSThe occurrence of nontronite as hot-spring deposit is first described from Ikaho Hot-springs, Gunma Prefecture, Japan. The hot-spring water, issuing from the No. 6 drilled well (Temp.=65.9℃, pH=6.65) is introduced into a concrete tank, where yellow-green deposit is precipitating with a rate of 1cm /year. The deposit has been identified as nontronite by chemical analysis, thermal analyses (DTA and TG), infrared spectra, and X-ray diffractometry. A typical nontronite sample (No. 6-1-G), with a composition of {Na0.02K0.01Ca0.10} (Fe3+1.45Mn0.02Mg0.08)[Si3.37Al0.13Fe3+0.50]O10(OH)1.86. nH2O. has been revealed by scanning electron microscopy to be an aggregate of small particles with a diameter less than 1〜2μm, and by transmisson electron micrograph to be feathery. This sample is slightly higher in iron content than the idealized formula of nontronite. Moessbauer spectroscopy showed that Fe in the sample is mostly in trivalent state. The genetic condition of this mineral is also discussed.View full abstractDownload PDF (1052K)
Review
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Hodaka KAWAHATA1994 Volume 28 Issue 2 Pages 123-142
Published: September 10, 1994
Released on J-STAGE: December 14, 2016
JOURNAL FREE ACCESSCarbonate has played an important role on global carbon cycle. The fossil carbonate component of deep-sea sediments provides much of our knowledge of its fluctuation as well as paleoclimatic change. The compiled data on the distribution, preservation, and accumulation of carbonate on the seafloor indicate that depth of sedimentary lysocline has fluctuated markedly in conjunction with late Quaternary climate cycles and that carbonate sedimentation is much affected by the fluctuation of the abyssal carbonate ion concentration. Also it is suggested that the fluctuations of the dissolution are largely controlled by changes in the global mass balance of carbonate and ocean circulation, which have a close relationship with climatic conditions.View full abstractDownload PDF (1899K)
Achievement for Geochemical Society Award
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Hiroshi HIDAKA1994 Volume 28 Issue 2 Pages 143-154
Published: September 10, 1994
Released on J-STAGE: December 14, 2016
JOURNAL FREE ACCESSThe Oklo uranium ore in the Republic of Gabon is an ideal natural analogue for radioactive waste disposal in geosphere, because it has preserved abudant fissiogenic nuclides for 2 Ga. Isotopic studies of the Oklo fission reactor zones have been carried out to estimate the geochemical behavior of fissiogenic nuclides and to evaluate some nuclear parameneters for the reactor characterization. In a few years, new type of fission reactor zones has been found in the Oklo ore, and interesting information on the behavior of long-lived radionuclides such as 90Sr, 99Tc, 135Cs and 137Cs has been obtained. Cooperative isotopic measurements by whole rock analysis (with TIMS and ICP-MS) and by in-situ observation (with SIMS) make possible to clarify the retention and /or migration processes of fissiogenic nuclides over the wide range from μm to m. In this paper, recent studies and perspectives in near future on the behavior of radionuclides expected from Oklo study are reviewed.View full abstractDownload PDF (1177K)
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