GEOCHEMICAL JOURNAL
Online ISSN : 1880-5973
Print ISSN : 0016-7002
ISSN-L : 0016-7002
最新号
選択された号の論文の4件中1~4を表示しています
  • Roman Cieśliński, Maciej Major, Łukasz Pietruszyński
    原稿種別: research-article
    2020 年 54 巻 2 号 p. 43-56
    発行日: 2020年
    公開日: 2020/04/15
    ジャーナル 認証あり

    Kettle holes are commonly found in areas embraced by the last Pleistocene glaciations. They are a natural element of the landscape; together with their closed drainage basins they occupy a large proportion of the area. There are many natural conditions that determine their salinity, those listed most often including alimentation, morphometric features, the dynamics of processes taking place in a drainage basin, paths of water supply, the land-use pattern, agricultural pollution, primary production, and the kind of soil cover. The primary goal of this paper is to determine the level of salinity of kettle holes located in the area of young glacial accumulation on the basis of variations in the chemical composition of their waters. An additional goal is to establish factors, including differences in the hydrographic network and the use and development of land, affecting their salinity. The research was conducted in 6 kettle holes in the Parsęta catchment and in 10 depressions in the Borucinka drainage basin in northern Poland. Laboratory analyses concerned primarily the concentrations of ions determining the hydrogeochemical types of water. The examined kettle holes have lower electrolytic conductance than the water of lakes in the study area. This may be indicative of the dominant role of atmospheric alimentation of their waters. The ions dominating in the chemical composition of water in both drainage basins were HCO3 and Ca2+, with elevated levels of Cl, Na+, Mg2+, SO42−, and sporadically of K+. The land-use pattern was found to have a significant effect on the level and range of concentrations of the ions under study. The highest average concentrations and their fluctuations were noted in basins located near farms.

  • Sandeep Singh, Munendra Singh
    原稿種別: research-article
    2020 年 54 巻 2 号 p. 57-70
    発行日: 2020年
    公開日: 2020/04/15
    ジャーナル 認証あり

    The continuous increase of the 87Sr/86Sr isotopic ratio in the seawater since last 40 Ma has been correlated with the rise of the Himalaya. The Ganga-Brahmputra Fluvial System drains the Himalaya along with the Ganga Alluvial Plain (GAP) and the northern Indian Craton regions. Under the humid subtropical climatic condition, the rivers of the alluvial plain contribute a significant (~50%) in the water discharge. Previous studies have identified the Himalayan Rivers as a potential source for the steady increase of marine Sr budget; overlooking the contribution of alluvial rivers. We attempt to constrain the role of GAP as a source for Sr. The Gomati River, a 900 km-long tributary of the Ganga River, drains about 30,437 km2 of the GAP with 7,390 × 106 m3/a water discharge and provides an ideal opportunity to understand the role of GAP in contribution of the global 87Sr budget. A total of 44 river water, 33 groundwater, 6 rainwater, 3 lake water, and 13 alluvial sediment samples were analyzed for 87Sr/86Sr isotopic ratio to determine sources and mixing relationships of the rainwater, groundwater and river water within the GAP. In the Gomati River Basin, the average Sr isotopic ratio of the river water (0.7292) is higher than that of the average Ganga River water (0.7246) and much higher than that of world seawater (0.7119) and modern seawater (0.7092). The average Sr isotopic ratio of the shallow groundwater and rainwater was 0.7242 and 0.7139, respectively. The Gomati River drains the GAP having alluvial sediments with more radiogenic Sr isotopic ratio ranging from 0.7655 to 0.7244. Due to this, the river water displays strong seasonal variability with lower Sr isotopic ratio than groundwater during the monsoon season (0.7184). Our data indicate that the high water discharge contribution with reasonably higher Sr isotopic values from GAP river water makes it an important additional source of high radiogenic Sr in addition to the Himalayan source. The chemical weathering of alluvial sediments in GAP under the monsoon-controlled climatic condition is likely to make significant contributions to the evolution and budget of Sr isotope in the global sea.

  • Hui Yan, David L. Dettman, Jie Chen, Ningjuan Shen
    原稿種別: research-article
    2020 年 54 巻 2 号 p. 71-79
    発行日: 2020年
    公開日: 2020/04/15
    ジャーナル 認証あり

    Stable isotope ratio measurements of dissolved inorganic carbon (δ13CDIC) provide a useful indication of carbon sources, sinks and fluxes in river ecosystems. Because of the incorporation of dissolved inorganic carbonate during shell growth, shells of aquatic mollusks have the potential to record DIC information and to be a proxy for δ13CDIC in this environment. In our study, specimens of the bivalve mollusk Corbicula fluminea (the Asian freshwater clam) were reared under laboratory conditions and δ13Cshell and δ13CDIC values were measured. It was found that the δ13Cshell values of C. fluminea reared in three tanks which were provided with isotopically distinct foods differed significantly and that all values were more negative than would be obtained under equilibrium fractionation conditions; this is probably because of metabolic effects. In order to estimate the percentage of metabolically-derived carbon in the shell carbonate (CM), δ13Cfood was used as a proxy for the δ13C of metabolic carbon. CM values in the three different tanks were 35%, 49% and 44%, respectively. These proportions are larger than those reported in previous studies. We suggest that the most probable cause is the auto-correlation between δ13Cfood and δ13CDIC. Despite the significant incorporation of metabolic carbon into shell carbonate, our experimental results showed that δ13Cshell was highly correlated with δ13CDIC, following this relationship: δ13CDIC = 0.86 δ13Cshell + 1.57 (R2 = 0.99). A shell collected in 2007 from a river monitored for δ13CDIC shows good agreement between back-calculated and measured δ13CDIC values for the summer of 2006. We suggest that the δ13Cshell of Corbicula fluminea is a promising qualitative proxy of large-scale variations in δ13CDIC in the river environment.

  • Norikatsu Akizawa, Akira Ishikawa, Tetsu Kogiso
    原稿種別: research-article
    2020 年 54 巻 2 号 p. 81-90
    発行日: 2020年
    公開日: 2020/04/15
    ジャーナル 認証あり

    A simple analytical procedure for determination of whole-rock major- and trace-element composition by micro-X-ray fluorescence (μXRF) spectrometer and inductively coupled plasma-mass spectrometer (ICP-MS) using fused-glass bead (sample + lithium tetraborate) is presented. In the case of peridotites, chromian spinel (Cr-spinel) is one of the minerals resistant to acids and interferes with accurate and reproducible determination of whole-rock composition. Such resistant minerals were not observed in the fused-glass beads prepared here, suggesting complete digestion of the samples including Cr-spinels. The μXRF spectrometer was employed to determine SiO2, MgO, and total Fe2O3 contents with the fused-glass beads. They were subsequently dissolved into a nitric acid solution to analyze thirty seven elements, Na, Al, P, K, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Rb, Sr, Y, Zr, Nb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, Pb, Th, and U with sector magnetic field ICP-MS (ICP-SFMS) and Q-pole mass filter ICP-MS (ICP-QMS). The analytical procedures were optimized and evaluated with geological reference materials of JP-1 and BIR-1a, and applied to various mantle xenoliths (lherzolite, harzburgite, dunite, wehrlite, olivine clinopyroxenite, and orthopyroxenite) from Tahiti and Moorea islands (Society Archipelago). Since only fused-glass beads are required as an analytical target to determine whole-rock major- and trace-element compositions, the sample amount consumed through the series of analytical procedure can be constrained to a minute amount (e.g., <0.4 g). The analytical procedures presented here are considered appropriate for tiny and/or precious samples, such as mantle xenoliths and rocks collected by dredging, diving, and drilling from the world’s ocean basins.

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