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Volume 46 (2012)
- Issue 4 Pages 189-
- Issue 3 Pages 137-
- Issue 2 Pages 79-
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Volume 46, Issue 3
Displaying 1-5 of 5 articles from this issue
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The Geochemical Society of Japan Award for Young Researcher
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Chisato YOSHIKAWA2012 Volume 46 Issue 3 Pages 137-147
Published: September 05, 2012
Released on J-STAGE: February 20, 2017
JOURNAL FREE ACCESSThe marine nitrogen cycle is known to often control biological activity in the ocean, because nitrogen is an indispensable nutrient for phytoplankton. Understanding the marine nitrogen cycleis very important with respect to marine biological activity. In this study, nitrogen isotopic ratios (δ15N) and marine material cycle models are used to understand the marine nitrogen cycle. Here, our previous studies of nitrogen cycle in the western and central equatorial Pacific and in the Sea of Okhotsk are introduced. In the equatorial Pacific, the distributions of δ15N values of nitraterevealed that surface nutrient sources are atmospheric and/or terrestrial nitrogen in the western and marine nitrogen in the central. Moreover, the time variations of δ15N values in sinking particles reconstructed the transition of surface nutrient sources with transport of the fresh pool. In the Sea of Okhotsk, a marine nitrogen cycle model including nitrogen isotopes wasnewly developed in order to quantitatively understand the observed feature of winter high δ15N values of sinking particles relative to the spring values. The model suggested that the nitrification with large isotopic effects causes the winter high δ15N values of sinking particles. Finally, my future prospects of the nitrogen isotopic modeling are discussed.View full abstractDownload PDF (1338K)
Frontiers in Geochemistry
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Hirochika SUMINO2012 Volume 46 Issue 3 Pages 149-170
Published: September 05, 2012
Released on J-STAGE: February 20, 2017
JOURNAL FREE ACCESSSubduction volcanism generally forms a "subduction barrier" that efficiently recycles water and other volatiles (carbon, nitrogen, sulfur, halogens, and noble gases) contained in subducted slabs back to the Earth's surface. In this contribution, current knowledge of volatile budgets in subduction zones is reviewed. Although most of the bound water in hydrous minerals in subducting altered oceanic crust and sediments is recycled back to the surfaces of subduction zones, the serpentinized slab mantle carries a significant portion of such water into a depth beyond arcs. Carbon and sulfur seem to be subducting to the deep mantle effectively, whereas nitrogen behavior is enigmatic. Recent findings on seawater-like heavy noble gases in the convecting mantle, as well as on the noble gases and halogens of sedimentary pore water origin in exhumed mantle wedge peridotites and slab mantle serpentinites, suggest that surface noble gases and halogens are readily incorporated into hydrous minerals in oceanic lithospheric mantle and that their incomplete removal via subduction zone metamorphism results in further subduction of the volatiles to a great depth into the mantle. Further investigations on volatiles in deep-mantle derived samples and the experimental constraints on the behaviors of trace volatiles during the metamorphism of the subducting slab are necessary to reveal the global volatile budgets in the Earth's interior.View full abstractDownload PDF (2790K)
Review
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Shigeshi FUCHIDA2012 Volume 46 Issue 3 Pages 171-180
Published: September 05, 2012
Released on J-STAGE: February 20, 2017
JOURNAL FREE ACCESSOligomerization of amino acids is an essential process in chemical evolution of precursor of life and would have occurred on the primitive earth. Peptide formation is unfavorable in aqueous solution, since this reaction involves dehydration. However, the peptides are synthesized in aqueous solution at hydrothermal condition. Equilibrium thermodynamic calculation and experiments indicate that the synthesis is promoted at high temperature and pressure conditions such as seafloor hydrothermal systems. However, the amino acids and peptides are rapidly decomposed under the hydrothermal condition. Peptides formation reaction positively occurs by heating and application of pressure without catalysts under dry condition, and the products were remained for a long time. The peptide formation is also promoted via Salt-induced peptide formation (SIPF), in which transition metal ions included in the complexes with amino acids to form peptides. Also, oligomerization of amino acids is accelerated via adsorption on oxide mineral surface. In particular, clay minerals have a high ability of peptide chain elongation, and protect from thermal decomposition of amino acids and proteins. Catalysts such as transition ions and minerals would be important to synthesize primary biopolymer on the primitive earth.View full abstractDownload PDF (1398K)
Original paper
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Shunichiro IGARI2012 Volume 46 Issue 3 Pages 181-185
Published: September 05, 2012
Released on J-STAGE: February 20, 2017
JOURNAL FREE ACCESSThe measuring method of nonmethane hydrocarbons in methane rich gas was improved. Nonmethane hydrocarbons were condensed in a vacant stainless column at liquid nitrogen temperature in the former system (Igari, 1995). However, in the system, recovery rate of nonmethane hydrocarbons dropped as low as 80%, in the case of large volume sample injection, more than 5 ml. To improve the recovery rate, the concentration column was packed with quartz sand and a vacant precolumn was equipped to avoid sample injection shock. By these improvements, recovery rate of nonmethane hydrocarbons became about 100% even in the case of 10 ml sample injection.View full abstractDownload PDF (559K)
Abstract of doctoral thesis
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Riko Iizuka2012 Volume 46 Issue 3 Pages 186-187
Published: September 05, 2012
Released on J-STAGE: February 20, 2017
JOURNAL FREE ACCESSDownload PDF (315K)
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