河川の物質循環における硝酸態窒素に着目した環境流量の放流効果に関する研究  [in Japanese] THE EFFECT OF ENVIRONMENTAL FLOW FOCUSED ON NITRATE-NITROGEN IN MATERIAL CIRCULATION OF TAMA RIVER  [in Japanese]

Access this Article

Author(s)

Abstract

<p> 硝酸態窒素に着目し,多摩川における環境流量放流による水質改善効果を調べた.計算は河川の物質量と生物量の相互作用を考慮した統合解析モデルを用いた.季節による違いをみるため2017年5月,8月,11月,2018年2月を対象に検討した.計算の結果,下水処理場からの放流を踏まえた縦断方向の物質濃度が概ね再現できているとともに,気温と流量により影響を受けている季節の差も反映できていた.環境流量を0.7m<sup>3</sup>/sと1.5m<sup>3</sup>/sの2パターンで放流した結果,1.5m<sup>3</sup>/s放流した場合にNO<sub>3</sub>濃度の低減効果が大きかったが,NO<sub>3</sub>の取り込み濃度減少に寄与する付着藻類量について流量による差異は見られなかった.また下水処理場の放流点を変えた場合,上流よりも下流に放流した方がNO<sub>3</sub>濃度の低下に繋がることが分かった.</p>

<p> Using integrated model of material cycle and ecosystem along a river, three calculations are conducted in Tama river; reproductive calculation, discharge of Environmental Flow (EF), and displacement of discharge point of treated wastewater. Density of NO<sub>3</sub> was focused with amount of related ecosystems. Four days in 2017 of each season were chosen for the first calculation. As a result, increase of density due to sewage was shown and water temperature and flow contributed seasonal difference.</p><p> 0.7m<sup>3</sup>/s and 1.5m<sup>3</sup>/s of EF were discharged from upstream. NO<sub>3</sub> was decreased in the case of 1.5m<sup>3</sup>/s compared to that of 0.7m<sup>3</sup>/s, however, amount of attached algae was almost the same. Discharge point of wastewater should be downstream of river for NO<sub>3</sub> decrease, not upstream which NO<sub>3</sub> is taken mainly by attached algae. It is largely influenced by discharge of wastewater, thus the point and EF should be considered for desirable condition of ecosystem.</p>

Journal

  • Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering)

    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 74(5), I_469-I_474, 2018

    Japan Society of Civil Engineers

Codes

Page Top