Chikyukagaku
Online ISSN : 2188-5923
Print ISSN : 0386-4073
ISSN-L : 0386-4073
Volume 30, Issue 1
Displaying 1-5 of 5 articles from this issue
The Geochemical Society of Japan Award for Young Researchers
  • George IGARASHI
    1996 Volume 30 Issue 1 Pages 1-16
    Published: April 15, 1996
    Released on J-STAGE: December 17, 2016
    JOURNAL FREE ACCESS
    Some characteristics of groundwater behavior related to earthquakes are discussed with examples recently observed by continuous monitoring of well water level and radon concentration in groundwater. By calibrating strain sensitivity using tidal responses, well water level can be used as a sensitive strain meter. It should be noted, however, that local inhomogeneity near an aquifer system affects the behavior of well water level at shallow wells significantly. Not only crustal activities directly related to earthquakes, various aseismic crustal activities are also likely to cause well water level changes. An exmple is water level changes observed at three wells about one day before an M 5.9 earthquake that occurred deep beneath the Tokyo Bay on February 2, 1992, which may be attributed to a large slow slip that released strain energy even larger than the main shock of the M 5.9 earthquake. Groundwater radon concentration observed at a "suitable" site shows sensitive responses to earthquakes. More than ten of coseismic changes were observed at a radon monitoring station located in the eastern part of Fukushima Prefecture from 1984 to 1987. However, it has turned out that, over longer time scale, the response characteristics of groundwater radon to earthquakes is time variable. It is likely that the nature of groundwater responses to tectonic events is largely affected by tectonic events themselves such as occurrences of nearby large earthquakes. At a well located in the region where people suffered a miserable disaster from the southern Hyogo Prefecture earthquake on January 17, 1995, remarkable increases in groundwater radon concentration began to be observed several months before the earthquake. These precursory radon changes suggest that groundwater movement and pore presure changes in aquifer systems play important roles in the generation process of inland large earthquakes.
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  • Hiroshi NAGASAWA, Masana MORIOKA
    1996 Volume 30 Issue 1 Pages 17-25
    Published: April 15, 1996
    Released on J-STAGE: December 17, 2016
    JOURNAL FREE ACCESS
    Double-layered single crystals of olivine, (Mg, Ni)2SiO4-and (Mg, Co)2SiO4-Mg2SiO4, were synthesized for the purpose of measuring cation inter-diffusivities in olivine. The olivine solid solution layers were epitaxially overgrown on the surface of forsterite seed crystals in Li2O-MoO3-V2O5 flux systems at temperatures below, 1,000℃. Diffusion annealing was performed at 1,050〜1,450℃ for 5 hours to 81 days. Diffusion coefficients observed showed relations D=D0exp (-ED/kT), where D0 for Co-Mg and Ni-Mg are 68.6 and 15.1 cm2/sec, respectively and ED for both Co-Mg and Ni-Mg are 407 kJ/mol. The observed D's are nearly an order of magnitude lower than those previously observed by Morioka (1980;1981), although ED's agree with the previous values. The observed discrepanceies in D's were discussed in terms of diffusion mechanism.
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  • Mutsumi NISHIKIORI, Kimitaka KAWAMURA, Masahiko HAYASHI, Yoshiyuki FUJ ...
    1996 Volume 30 Issue 1 Pages 27-34
    Published: April 15, 1996
    Released on J-STAGE: December 17, 2016
    JOURNAL FREE ACCESS
    Antarctic aerosol samples collected from Syowa Station were studied for the molecular distributions of saturated and unsaturated monocarboxylic acids, α, ω-dicarboxylic acids and oxocarboxylic acids using a capillary gas chromatography (GC) and GC/mass spectrometry (GC/MS). Distributions of normal saturated monocarboxylic acids (C8-C28 ; 3.4-8.1 ngm-3) showed a maximum at C16 with an even carbon number predominance, except for C9 which was more abundant than C8 and C10. Their distribution is dominated by the lower molecular weight (C12-C19) monocarboxylic acids, suggesting that the Antarctic aerosols are mostly derived from marine organisms through sea-to-air emissions. However, unsaturated monocarboxylic acids (C16:1, C18:1; 0.40-0.91 ngm-3), which are more abundant than saturated ones in marine algae, were detected at relatively low concentrations. Depletion of unsaturated acids in the aerosols can be explained by a photochemical oxidation of the acids at their double bond. This is consistent with the abundant presence of C9 α, ω-dicarboxylic acid (azelaic acid) in the Antarctic aerosols, a specific photo-oxidation product of unsaturated fatty acid where a double bond exists predominantly at C-9 position. Relative abundance of azelaic acid carbon content in total aerosol carbon content (TC) was found to be positively correlated with solar radiation. Mid-chain oxocarboxylic acids (4-oxooctanoic and 4-oxononanoic acids; 0.4-1.0 ngm-3) were also detected in the Antarctic aerosols. The 4-oxocarboxylic acids are possible precursors to the production of low molecular weight diacids such as succinic acid (C4).
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  • Shigeo MORINAGA, Ryoshi ISHIWATARI, Tsutomu MACHIHARA
    1996 Volume 30 Issue 1 Pages 35-45
    Published: April 15, 1996
    Released on J-STAGE: December 17, 2016
    JOURNAL FREE ACCESS
    Insoluble macromolecules (kerogen) were isolated from 7 marine and 10 lacustrine sediment samples and subjected to alkaline KMnO4 oxidation, followed by analysis of organic acids in the oxidation products. The major compounds consist of aliphatic C4-C15α, ω-dicarboxylic acids, n-C7-C28 monocarboxylic acids and benzene mono-to-polycarboxylic acids. The α, ω-dicarboxylic acids from lacustrine kerogens have a maximum at C8 or C9. Whereas those from marine ones show a shoulder in this carbon range, have a maximum at C4 and decrease with increasing carbon number. This difference in the relative abundance of C4 and C8, C9 α, ω-dicarboxylic acids may be due to different precursory materials in the different environments. This result is in accordance with our previous findindg, suggesting strongly that a portion of the chemical structures of kerogens from marine and lake environments is generally different from each other. A mathematical expression was proposed to visualize the feature of molecular distribution of α, ω- dicarboxylic acids from kerogens. In addition, it is shown by both alkaline CuO oxidation and KMnO4 experiments that polymerized structure of polyhydroxy acids can be one of the precursors for α, ω-dicarboxylic acids from kerogens.
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  • Shunichiro IGARI
    1996 Volume 30 Issue 1 Pages 47-54
    Published: April 15, 1996
    Released on J-STAGE: December 17, 2016
    JOURNAL FREE ACCESS
    All C1-C5 alkanes of natural gases from several gas deposits and gas signs in Japan were measured. Logalisms of ethane/propane, neopentane/isopentane and isobutane/neopentane ratios show correlations. These correlations can be explained as decompostion process of these hydrocarbons by OH radical. Further, it is presumed that decomposition process of the hydrocarbons is a major controlling factor for the hydrocarbon composition of natural gas samples used in this study.
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