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Volume 27 (1993)
- Issue 6 Pages 367-
- Issue 4-5 Pages 181-
- Issue 3 Pages 131-
- Issue 2 Pages 59-
- Issue 1 Pages 1-
Volume 27, Issue 2
Displaying 1-6 of 6 articles from this issue
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Akira Shimoyama, Kazuhide Hayakawa, Kaoru Harada1993 Volume 27 Issue 2 Pages 59-70
Published: 1993
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSOleic acid (cis-9-octadecenoic acid) was converted to monocarboxylic acids and γ- and δ-lactones by heating at 200°C under free oxygen. The monocarboxylic acids showed a C9 acid predominance in the presence of Na-montmorillonite in contrast to a C8 acid predominance in the absence of the clay. The γ-lactones showed a C6 lactone predominance in the former case and C4 and C8 lactone predominances in the latter case. Accordingly, it was postulated that the catalytic cracking of oleic acid in the presence of the clay produced mainly the C9 acid that, in turn, generated the C6 lactone by thermal oxidation. The molecular distribution patterns of the monocarboxylic acids and the γ-lactones in the range of C4 to C12 produced by the heating in the presence of the clay resemble those found in the Neogene Shinjo sediments. Therefore, unsaturated monocarboxylic acids with a C-C double bond at C9 were probably important precursors of the monocarboxylic acids and the γ-lactones found in the sediments.View full abstractDownload PDF (2819K) -
John C. Bailey1993 Volume 27 Issue 2 Pages 71-90
Published: 1993
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSNW Pacific surface sediments are dominantly detrital with lesser amounts of biosiliceous and hydrogenous material. The detrital components change regularly from trench sediments dominated by island-arc volcanoclastic debris to open-ocean sediments with higher REE, Th, Rb, Cs, La/YbN, La/Sc and Th/Hf but lower Eu/Eu*, Co/Th, K/Rb and Rb/Cs. The open-ocean sediments are dominated by upper continental crustal debris. Buried sediments from DSDP holes pass through a three-stage evolution: ocean-ridge basaltic debris and hydrothermal precipitates, abyssal plain sediments characterised by hydrogenous material and upper continental crustal debris, and near-shore island-arc detritus with intermittent air-fall ash. Biogenic and within-plate basaltic/hydrothermal components cause important local deviations from this evolution.View full abstractDownload PDF (5629K) -
Dmitri P. Krylov, Alexander P. Meshick, Yury A. Shukolyukov1993 Volume 27 Issue 2 Pages 91-102
Published: 1993
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe Xe–Xe spectrum dating results are presented for zircons from early Archaean Napier Complex (East Antarctica). Experimental procedure includes measurements of Xe isotopes ratios during stepwise heating (900 to 1800°C, step interval 100°) of samples after preliminary irradiation in a thermal column of a nuclear reactor (fluence 3 × 1016 n/cm2). The most reliable Xe-Xe zircons ages of ca. 3.3–3.9 Ga (gas increments in the range of 1100–1500°C) are similar to the known dates of the crust formation in the region. In turn, the closure temperature (Tc) estimates for the studied zircons mostly agree with the maximum conditions of the “primary” (M1) granulite metamorphism in Napier Complex and exceed those for later processes. The correlation of the derived Xe-ages with M1 demonstrates that the oldest observed regional metamorphism shortly postdated the crust formation. Hence, previously considered tremendous gap (0.5 b.y. or more) between the two events seems doubtful.View full abstractDownload PDF (3443K) -
Kitao Fujiwara, Toshinao Ushiroda, Kazuhiko Takeda, Yu-ichiro Kumamoto ...1993 Volume 27 Issue 2 Pages 103-115
Published: 1993
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSHydrogen peroxide was determined in seawater at the Hiroshima Bay, the Seto Inland Sea under sunny conditions. Concentration of hydrogen peroxide was in accordance with the intensity of the solar radiation. Photochemical production under strong biological activity might be responsible for the profiles of the diurnal and seasonal variation of hydrogen peroxide concentration. The spatial distribution of hydrogen peroxide in the Seto Inland Sea gave a good correlation with salinity, suggesting that the photosensitizer to produce hydrogen peroxide was substances brought from river waters. Hydrated electron as a possible precursor of hydrogen peroxide in the photochemical reaction was generated in seawater collected at the Seto Inland Sea by means of irradiating the third harmonic wave of the YAG laser (355 nm: 60 mJ): The amount generated showed a positive correlation against total organic carbon (TOC) and dissolved organic carbon (DOC) in seawater. This correlation was greately improved by the addition of EDTA. The EDTA treatment suggests the existence of some species obstructed the hydrogen peroxide production. Also, this correlation coefficient was improved when taking fluorescent matter instead of TOC or DOC.View full abstractDownload PDF (3171K) -
Shinya Hashimoto, Hua Yan Sun, Takeshi Nakamura, Yukihiro Nojiri, Akir ...1993 Volume 27 Issue 2 Pages 117-123
Published: 1993
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSSeasonal variations in dissolved nitrous oxide concentrations in Lake Kasumigaura were measured to examine a eutrophic shallow lake without anaerobic layer as one of natural nitrous oxide emission sources. Samples were monthly taken using a Go-Flo sampler at 6 sites including lake center during April, 1991 to March, 1992. Dissolved nitrous oxide in the lake water samples was measured by an automatic analyzer consisting of purge and trap system and GC-ECD detector. The concentrations in surface water at lake center ranged from 9 nM to 21 nM and there was no large vertical difference. On the other hand, those at the inner-most part of Takahamairi Bay, where heavy blooming of cyanobacteria occurs every summer, ranged from 13 nM in summer to 63 nM in autumn. The variation pattern that nitrous oxide concentrations in Takahamairi Bay were high in autumn to winter and low in summer was similar to that of nitrate-nitrogen concentration. The present results show that nitrous oxide concentrations in surface lake waters at all sites in this lake were supersaturated or at least equilibrated, and suggest that nitrous oxide may be being produced in many eutrophic shallow lakes, even though anaerobic layer is not formed in summer, and that they can be one of the natural nitrous oxide emission sources.View full abstractDownload PDF (1816K) -
David M. Pyle1993 Volume 27 Issue 2 Pages 125-129
Published: 1993
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe utility of helium and neon isotopes as tracers of mixing in geothermal systems may be enhanced by employing an appropriate method of graphical analysis. On linear 3He/4He-20Ne/4He diagrams mixing is revealed by straight lines. This is contrary to the current procedure of plotting 3He/4He against 4He/20Ne, where mixing lines are curved. Construction of triangular mixing plots with such data allows an immediate quantitative assessment of the extent to which the measured isotopic ratios reflect those of different endmembers (e.g. atmospheric, radiogenic and magmatic) and allows one to use these plots to compare the sources of rare gases in geothermal systems from different parts of the globe.View full abstractDownload PDF (1599K)
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