海洋におけるホウ素同位体とpH Boron isotopes and pH in the oceans

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The composition of two stable isotopes <sup>10</sup>B (〜20%) and <sup>11</sup>B (〜80%) can vary significantly on the earth and provides important information on the global geochemical cycle. Art Spivack has proposed a simple and elegant idea called "palaeo-pH", that boron isotopes in foraminifera might indicate past oceanic pH values. The mean oceanic residence time of boron is calculated at 1.6×10<sup>7</sup> years. Therefore, the boron concentration (4.5ppm) and isotopic composition (δ<sup>11</sup>B=39〜40‰) in seawater are quite uniform throughout the world's oceans (Tablel). The dominant boron species in seawater is B(OH)<sub>3</sub> and B(OH)<sub>4</sub><sup>-</sup>. There is about 2% difference between the isotopic composition of B (OH)<sub>3</sub> and B(OH)<sub>4</sub><sup>-</sup>, as a result of the isotope fractionation. The <sup>11</sup>B isotope is concentrated into B(OH)<sub>3</sub> in seawater. The relative proportion of the two species is controlled by pH. Boron isotopic composition of B(OH)<sub>3</sub> and B(OH)<sub>4</sub><sup>-</sup> in seawater is shown as a function of pH. If one of each species is incorporated into marine carbonates, the boron isotopes should reflect seawater records of pH in which they have grown. Using the boron isotope "palaeo-pH" method,the Lamont group attempted to estimate surface oceanic pH differences between the last glacial period and the Holocene. Studies on boron isotopes from coral samples clarify some issues on the "palaeo-pH" in aquatic environments. More detailed studies will make progress on the boron isotope pH-meter.

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  • 地球化学

    地球化学 33(2), 115-122, 1999

    一般社団法人日本地球化学会

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各種コード

  • NII論文ID(NAID)
    110008679975
  • NII書誌ID(NCID)
    AN00141280
  • 本文言語コード
    JPN
  • 資料種別
    REV
  • ISSN
    0386-4073
  • NDL 記事登録ID
    4755862
  • NDL 雑誌分類
    ZM41(科学技術--地球科学)
  • NDL 請求記号
    Z15-645
  • データ提供元
    CJP書誌  CJP引用  NDL  NII-ELS  J-STAGE 
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