河川浸透層の硝化能力に対する流速と水質の影響 Effects of Seepage Flow Velocity and Water Quality on the Nitrification Capacity of Hyporheic Layer in a Natural River

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河川浸透層における硝化能力を評価するため, 硝化細菌の活性に浸透水の物理・化学的性質が与える影響の解明を試みた.現地河岸で採取した浸透層砂礫を充填した円筒形カラムに, 試水を供給することで河川浸透流を再現した.浸透流速と浸透水質を変えた実験結果から, 浸透水の水質と流速が無機態窒素の酸化過程におよぼす影響を考察した。この結果, 砂礫層中に一方向に卓越した浸透水の流れが存在することが硝化細菌の活性を高める, ということが明らかとなった。カラム内の砂礫による単位時間の硝化量は浸透流速に強く影響されていた.浸透水の窒素濃度が高いとき, 浸透層では硝化細菌の増殖モデルより推算される硝化量の1~3倍程度の窒素が酸化されていた.浸透水の窒素濃度が低く, 硝化細菌がほとんど増殖できないと評価される場合でも, 浸透流速が約3m/hのとき, 増殖モデルから推算される最大硝化量の約70%の窒素量が酸化されることがわかった.

Effect of the physical and chemical conditions of the seepage flow on the bacterial nitrification were discussed in order to determine the nitrification within the hyporheric zone in a natural river. Several kinds of liquid medium were supplied into the cylindrical columns filled with the river sand gravel at different velocities, and the characteristics of the nitrifying capacity varying with both the flow velocity and the inorganic nitrogen concentration were clarified in detail.<BR>In batch incubation experiments, more bacterial growth and nitrification were observed in the unidirectional, less turbulent seepage flow condition such as usually seen in the hyporheic zone than in the well-mixed condition generated by the bubble aeration. The nitrified nitrogen within the sand gravel column in unit time was strongly affected by the flow velocity. In the rich nitrogen conditions, the high nitrification was observed which was several times as large as the maximum values estimated by the logarithmic growth model using the corresponding bacterial density. Furthermore, in low concentration conditions, wherelittle bacterial growth was expected by the model, nearly the maximum oxidation, approximately 70% of that, was achieved under the seepage flow speed 3 meters/hour.

収録刊行物

  • 農業土木学会論文集

    農業土木学会論文集 69(4), 479-487, 2001-08-25

    The Japanese Society of Irrigation, Drainage and Rural Engineering

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各種コード

  • NII論文ID(NAID)
    10012330458
  • NII書誌ID(NCID)
    AN00201203
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    03872335
  • NDL 記事登録ID
    5902731
  • NDL 雑誌分類
    ZR7(科学技術--農林水産--農産)
  • NDL 請求記号
    Z18-365
  • データ提供元
    CJP書誌  NDL  J-STAGE 
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