GEOCHEMICAL JOURNAL
Online ISSN : 1880-5973
Print ISSN : 0016-7002
ISSN-L : 0016-7002
Volume 45, Issue 3
Displaying 1-9 of 9 articles from this issue
  • GYANA RANJAN TRIPATHY, SUNIL KUMAR SINGH, RAVI BHUSHAN, V. RAMASWAMY
    2011 Volume 45 Issue 3 Pages 175-186
    Published: June 20, 2011
    Released on J-STAGE: November 01, 2013
    JOURNAL FREE ACCESS
    A temporal high-resolution analysis of Sr–Nd isotopic composition, Fe, Al and V concentration and magnetic susceptibility (MS) has been carried out in a sediment core from the western Bay of Bengal to trace sediment sources. Significant variations in the Sr and Nd isotopic composition and corresponding MS and elemental Fe/Al and V/Al ratios are observed in the sediment core with depth (time) indicating variable contributions from sources. The observed changes in the sediment provenance correlate well with the climatic record of the region, highlighting the important influence of climate over erosion. Relatively lower 87Sr/86Sr and higher εNd corresponding to the Last Glacial Maximum (LGM) suggests proportionally reduced sediment contribution from the Himalaya. Erosion rate over the Himalaya decreased during LGM due to combined influence of reduced intensity of the southwest monsoon and larger extent of glaciations over the Higher Himalaya, the main source of sediments to the Bay of Bengal.
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  • MASATO IWASHITA, AYAMI SAITO, MIKA ARAI, YOSHIAKI FURUSHO, TADASHI SHI ...
    2011 Volume 45 Issue 3 Pages 187-197
    Published: June 20, 2011
    Released on J-STAGE: November 01, 2013
    JOURNAL FREE ACCESS
    Rare earth element (REE) concentrations were determined in 32 rainfall events collected in suburban Tokyo. Two or more samples were collected for 13 events out of 32 events. A pre-concentration method was applied using a chelate resin solid phase extraction column. Good and uniform recoveries for REEs (Y to Lu, 99~101% at pH = 3.7~4.0) were obtained. Detection limits reached as low as 0.001 ng L–1 (for Tb) with a 30 fold pre-concentration using a conventional Q-pole ICP-MS. Clear La and Gd excesses (definition is in the text) were evident in many cases. Y, Eu, Lu and Yb excesses may also exist in some events. In some events where multiple samplings were performed, crust normalized REE patterns changed during the rainfall events. These are the first evidences of clear REE pattern variations during the same rainfall events. The initial and final stage of some rainfall events may have different origins for the REEs. The correlations among the REEs with respect to logarithmic concentrations indicate that most of the REEs are of natural origin while La and Gd may have common anthropogenic components. We propose that materials for high refractive index and low dispersion optical glass production processes could be potential sources of La and Gd excesses because 1) La and Gd excesses are correlated, 2) other sources such as a cracking catalyst for petroleum refining or a contrast agent of magnetic resonance imaging cannot explain the excesses.
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  • YI DUAN, JINXIAN HE
    2011 Volume 45 Issue 3 Pages 199-207
    Published: June 20, 2011
    Released on J-STAGE: November 01, 2013
    JOURNAL FREE ACCESS
    Molecular composition and compound-specific carbon and hydrogen stable isotope ratios of n-alkanes are presented for leaves of grass, reeds and trees from five regions extending between latitudes 22° and 39°, China. The distribution of n-alkanes ranges from C15 to C35 with a high odd over even predominance and carbon-number maxima at C27, C29 or C31. The carbon preference index (CPI) values are from 3.49 to 17.25, with mean values increasing following tree leaf > reed > grass. The average chain length (ACL) values are between 26.24 and 30.26 and the mean values increase following grass > reed > tree leaf. It is observed that Cmax, CPI and ACL values of n-alkanes in plants from low latitudes are higher than those from high latitudes. The δ13C values of C27 and C29 n-alkanes in plants range from –25.3 to –35.5‰ and the grass has a lighter mean carbon isotopic composition than the reed and tree leaf. The δD values of C27 and C29 n-alkanes in the plants are between –132.1 and –192.6‰ and the mean hydrogen isotopic compositions of C27 and C29 n-alkanes in the grass are lighter than those in the reed and tree leaves. C27 and C29 n-alkanes in the grass and tree leaves from high-latitude and elevation area have relatively lighter hydrogen isotopic composition, indicating that these δD values can be used as excellent indicators of environment and climate.
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  • GÜLTEN YAYLALI-ABANUZ, NECATI TÜYSÜZ
    2011 Volume 45 Issue 3 Pages 209-219
    Published: June 20, 2011
    Released on J-STAGE: November 01, 2013
    JOURNAL FREE ACCESS
    The Akoluk gold mineralization area is located in the southern section of the western Pontide tectonic belt in the northeast of Turkey. The area of interest is intensely vegetated with hazelnut trees grown on a grass covered land. Rock exposures are quite limited, mainly encountered in small valleys. Therefore, soil geochemistry is the only useful tool in delineating the areas of gold mineralization. For this purpose, 375 soil samples were collected from the B-horizon of soil profile which is widely available in the area for a representative sampling. A vein type gold occurrence is confined to the fault zones crossing dacitic tuffs of Upper Cretaceous age. Faults are a conjugate set of a shear system, striking N 45–50 E, and N 55–60 W dipping 80–85 SE and 70–80 NW, respectively. Gold mineralization occurs generally as replacement of dacitic tuffs along the fault planes and less of void fillings. The main ore minerals are electrum, stibnite, zinkenite, pyrite, marcasite, realgar, orpiment, sphalerite, galena, chalcopyrite, malachite, and azurite, and the most common gangue minerals are barite and quartz. The soil is residual and well developed with a thickness ranging from 0.5 m to 1 m. The soil type in the study area is brown podzolic. A total of 375 soil samples were collected on 25 m intervals along N25W trending lines and 50 m apart throughout this study. Elements analyzed and interpreted are the ones which are known to have close association with gold. Ag, Sb, As, Mo, W, and Ba show a single very significant anomaly pattern. Several other small isolated anomalies are also observed due to sampling artifacts. The significant anomaly is circular in shape and has a diameter of approximately 200 m. The anomaly does not reflect the fracture system. This may be due to the fact that the sampling interval is wider than the fault zones. Cluster and factor analyses reveal that Zn, Mo, and W form a different suite which is not related to the same mineralizing system as gold. These elements form the deeper section of the mineralization which is partly exposed in the area. Since their anomalous patterns are coinciding with that of gold, the former appears to be the case.
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  • SAEKO FUJIWARA, KOSHI YAMAMOTO, KOICHI MIMURA
    2011 Volume 45 Issue 3 Pages 221-234
    Published: June 20, 2011
    Released on J-STAGE: November 01, 2013
    JOURNAL FREE ACCESS
    In order to evaluate the dissolution processes of elements from subducting sediments into fluids during early stages of metamorphism (up to oligoclase–biotite zone at about 30 km depth), the chemical composition of Sanbagawa pelitic schists, Sanbagawa Metamorphic Belt, Japan was studied. Samples from different metamorphic grades show similarities in their major element and Rb compositions, suggesting that the Sanbagawa schists experienced insignificant dissolution of these elements. Arsenic, N (as ammonium, NH4+) and Cs contents decrease with increasing metamorphic grade, demonstrating that their dissolution is enhanced under respective metamorphic stages (As: upper–garnet zone, NH4+: chlorite ~ oligoclase–biotite zone, Cs: garnet ~ albite–biotite zone). Dissolution mechanisms proposed are as follows. The NH4+ dissolution accompanies dehydration of the pelitic schists, which may produce fluids with a high potential to dissolve or oxidize NH4+. The thermal structure of the subducted slab is likely to influence the depth of the NH4+ dissolution. The Cs dissolution is caused mainly by fluid flow from underlying meta-mafic rocks and the amount of fluids possibly controls the degree of the Cs dissolution. Heterogeneous dissolution of Cs suggests that the fluid flow from the underlying meta-mafic rocks has a channelized structure. The mechanism of As dissolution is not clearly understood; however, it may be strongly related to graphitization of kerogens in the pelitic schists. Differences in Cs dissolution were observed between the Sanbagawa pelitic schists and other well-studied meta-sedimentary sequences, particularly the Catalina Schist, California and New Caledonia Schistes Lustrés. In the case of the Catalina Schists, Cs was dissolved into fluids more effectively than the Sanbagawa pelitic schists. In contrast, meta-sedimentary rocks of the Schistes Lustrés nappe did not experience any Cs dissolution, although rocks subducted deeper than their dehydration depth. One of the reasons for these differences may be variations in the amount of channelized structures among subduction zones.
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Invited Review
  • KHAN M. G. MOSTOFA, FENGCHANG WU, CONG-QIANG LIU, DAVIDE VIONE, TAKAHI ...
    2011 Volume 45 Issue 3 Pages 235-254
    Published: June 20, 2011
    Released on J-STAGE: November 01, 2013
    JOURNAL FREE ACCESS
    Chemical properties and reactivity of fluorescent dissolved organic matter (FDOM) are examined in this paper. They are key issues to understand the biogeochemical processes in the aquatic environments. Typically, FDOM undergoes photochemical transformation and is recalcitrant to microbial degradation, except for the aromatic amino acids that are microbiologically degraded under dark conditions. Experimental results demonstrate that the fluorescence intensity of various FDOM components is depleted upon irradiation (in the hours to 70 days time scale), approximately by 20–85% for fulvic acid, by 12–95% for fluorescent whitening agents (FWAs) or commercial detergents, and by 5–60% for trytophan. Microbial degradation is able to decompose the amino acid tryptophan and similar compounds, by approximately 13–24% in unfiltered river waters, 67% in unfiltered sewerage samples, and 11% in filtered river samples. The photoreactivity of FDOM is greatly decreased when passing from freshwater (river and lakes) to marine waters, but deep waters in lakes or marine environments are often more sensitive to photodegradation processes than surface waters. The high reactivity of FDOM toward photodegradation could be understood on the basis of its (however complex) chemical structure, considering that many FDOM components can undergo photoionization or otherwise photosensitized oxidation under sunlight. The controlling factors to the photochemical and microbial degradation of FDOM for a variety of waters are extensively discussed. One of the important functions of FDOM is the formation of complexes with transition metals in the aquatic environments, and this review discusses the mechanisms by which FDOM interacts with metals. Further investigations on FDOM, namely the identification of still unknown FDOM components, the metal-FDOM interactions as well as the photochemical and microbial reactivity will give invaluable information on the DOM dynamics in the aquatic environments.
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Note
  • SEIGO OOKI, KAZUHIRO KATO, FUMIO KITAJIMA, TASUKU AKAGI
    2011 Volume 45 Issue 3 Pages 255-261
    Published: June 20, 2011
    Released on J-STAGE: November 01, 2013
    JOURNAL FREE ACCESS
    To determine the accuracy and precision limits associated with carbon stable isotope ratio (δ13C) measurements of cellulose and lignin from plant samples, experiments were performed using differing extents of treatment for separating these two components. Laboratory reagent lignin and cellulose were used, together with model mixtures of both components. The resulting data were fitted to empirical functions. It was found that the δ13C of cellulose could be determined with higher accuracy (<0.1‰) than that of lignin (<0.25‰). The corresponding precision values were better than 0.04‰ and 0.08‰, respectively. Longer treatment times do not always result in better accuracy of the isotope data for either component.
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Express Letters
  • JIANJIN CAO
    2011 Volume 45 Issue 3 Pages e9-e13
    Published: June 20, 2011
    Released on J-STAGE: November 01, 2013
    JOURNAL FREE ACCESS
    Several studies have shown that gas flows (namely “geogas”) ascending from the Earth’s interior can, while passing through concelead orebodies, assimilate ore nanoparticles and carry them to the surface. The orebodies might be detected by measuring nanoparticle contents in soil gas or in the atmosphere. However, the mechanism by which geogas carries gold nanoparticles from orebodies to the surface is not well understood. To investigate these migration mechanisms, suspended particles from deep gas in the Hetai gold ore district in southern China were collected, gold nanoparticles artificially added, and the distribution of the gold nanoparticles studied using a transmission electron microscope. This study showed that gold nanoparticles migrate by 1) adsorption onto other particles suspended in the geogas, including needle, spherical and flower-like shaped iron-bearing particles, spherical aluminous particles, and calcite; and 2) in aggregated form.
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  • TOMOKI MOCHIZUKI, YUKIKO ENDO, SOU MATSUNAGA, JIE CHANG, YING GE, CHEN ...
    2011 Volume 45 Issue 3 Pages e15-e22
    Published: June 20, 2011
    Released on J-STAGE: November 01, 2013
    JOURNAL FREE ACCESS
    Monoterpenes are major compounds emitted by plants and contribute to the formation of photochemical oxidants and secondary organic aerosols in the troposphere. We measured monoterpene emissions from Chamaecyparis obtusa, a major coniferous tree species in Japan, in both the field and the laboratory. Short-term monoterpene emission from C. obtusa was typically dependent on temperature but barely dependent on light intensity. We calculated the basal emission rate Es assuming β = 0.09 in the G93 model. Three individual trees showed similar, but large seasonal variations in Es; e.g., 0.21–5.42 μg gDW–1h–1 for a tree showing the highest emission rate. The emission rate was much higher in winter and autumn. Although Es values averaged over 4 seasons indicated that C. obtusa is an intermediate emitter among coniferous trees, our results suggest that the large seasonal variation in Es should be considered in estimating annual monoterpene emission from this species. Furthermore, we found a significant effect of branch-to-branch touching by vibration on monoterpene emission from this species, suggesting that wind effect should be considered in the future for more precise emission estimation.
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