Division of Soil and Water Management, Department of Earth and Environmental Sciences, KU Leuven, Kasteelpark Arenberg 20 bus 2459, 3001 Leuven, Belgium.
Division of Soil and Water Management, Department of Earth and Environmental Sciences, KU Leuven, Kasteelpark Arenberg 20 bus 2459, 3001 Leuven, Belgium.
Water Res. 2021 Jun 15;198:117160. doi: 10.1016/j.watres.2021.117160. Epub 2021 Apr 18.
Many lowland regions are afflicted with high phosphorus (P) peaks in rivers during the summer months. Static incubations of sediments have shown that reductive dissolution of ferric iron (Fe(III)) minerals in the sediment explain these P peaks. This study was set up to identify if that mechanism also dominates in a dynamic system, thereby testing the roles of water flow velocity and sediment Fe/P ratio. Decreasing flow velocity was suspected to lower the flux of dissolved oxygen (DO) towards the sediment. The role of the Fe(III)/P ratio was tested by amending iron-rich glauconite sand (GS) to the sediment, in this manner testing possible remediation techniques. Eight flumes (1.80 m long) were constructed with duplicates of four treatments of two laminar flow velocities over the sediment (0.05 m s or 0.15 m s) that was either or not amended with GS (10% w/w). In all flumes a daily dose of sodium glutamate was added as a carbon source to mimic wastewater with high BOD, the flumes were operated for 28 days. A decreased velocity lowered the steady-state DO concentration and enhanced the sediment-water release of P by a factor 3. Sediment amendment with GS reduced solution P by factors 3 (low flow velocity) and 2 (high flow velocity). This effect is related to a combination of increasing binding sites for P and of lowering the DO consumption. These experimental data suggest that previously unexplained summer peaks of P in lowland rivers are related to low flow events that limit the DO flux. The internal loading of P requires management of DO in water and can be mitigated by enhancing sediment Fe.
许多低地地区在夏季河流中存在高磷（P）峰值。沉积物的静态培养表明，沉积物中三价铁（Fe(III)）矿物的还原溶解解释了这些 P 峰值。本研究旨在确定该机制是否也在动态系统中占主导地位，从而检验水速和沉积物 Fe/P 比的作用。流速降低被怀疑会降低溶解氧（DO）向沉积物的通量。通过向沉积物添加富含铁的海绿石砂（GS）来测试 Fe(III)/P 比的作用，从而测试可能的修复技术。构建了八个水槽（1.80 米长），每个水槽都有两个层流流速（0.05 米/秒或 0.15 米/秒）的沉积物的四个处理的两个重复，其中一个处理的沉积物添加了或未添加 GS（10%w/w）。在所有水槽中，每天添加谷氨酸钠作为碳源以模拟 BOD 较高的废水，水槽运行 28 天。流速降低会降低稳定状态下的 DO 浓度，并使 P 通过沉积物-水释放增加 3 倍。GS 的沉积物添加使溶液 P 降低了 3 倍（低流速）和 2 倍（高流速）。这种效果与增加 P 的结合位点和降低 DO 消耗的组合有关。这些实验数据表明，以前未解释的低地河流夏季 P 峰值与限制 DO 通量的低流速事件有关。P 的内部负荷需要管理水的 DO，并可以通过增强沉积物 Fe 来减轻。
