van Dael Toon, Vermeiren Charlotte, Smolders Erik
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.
Sci Total Environ. 2024 Feb 20;912:168912. doi: 10.1016/j.scitotenv.2023.168912. Epub 2023 Nov 26.
The reaction of phosphorus (P) between sediments and water in streams strongly affects the surface water P concentrations. A new reactive transport model (SWEMP: Sediment-Water Exchange Model for Phosphorus) was developed to describe redox dependent P sorption in the sediment and vertical diffusive transport of solutes to the overlying stream. The model parameters were independently obtained to first predict P release in ten different sediment-water batch systems and in two flumes. Input parameters are the degree of P saturation of the sediment, its organic matter content, dissolved oxygen (DO) concentration and temperature. The dissolved P concentrations in the overlying waters ranged from 0.02 to 1.2 mg P L in these systems and were correctly predicted by the model within, on average, a factor 1.3 (batch) or 1.1 (flume). The P flux from the sediment towards the overlying water increased with increasing sediment P:Fe ratio and respiration rates, and with decreasing DO and water pH. After validation of the model with experimental data, it was used to predict monthly P concentrations in Flemish rivers using the total P emission data, total discharge, average sediment properties and the monthly averaged water temperatures, DO concentrations and electric conductivity. The monthly average P concentrations oscillate annually between 0.24 and 0.73 mg P L and predictions matched the long-term monitoring data within 10 % using only one adjustable parameter for the entire water system (N > 250,000). The model predicts that summer peaks in P are related to internal loading from the sediment under anoxic conditions rather than to emission-dilution effects, i.e. external input of P and/or its concentration at lower flow rates. This suggests that, surface water P concentrations can be lowered by enhanced DO in the water, the addition of Fe and Al rich binding agents to the sediments and by reducing P emissions.
溪流沉积物与水中磷（P）的反应强烈影响地表水的磷浓度。开发了一种新的反应性输运模型（SWEMP：沉积物-水磷交换模型）来描述沉积物中氧化还原相关的磷吸附以及溶质向上覆溪流的垂直扩散输运。模型参数通过独立获取，首先用于预测十个不同沉积物-水批次系统和两个水槽中的磷释放。输入参数包括沉积物的磷饱和度、有机质含量、溶解氧（DO）浓度和温度。在这些系统中，上覆水中溶解磷浓度范围为0.02至1.2毫克P/升，模型预测值平均在1.3倍（批次）或1.1倍（水槽）范围内与实测值相符。从沉积物向上覆水的磷通量随沉积物磷铁比和呼吸速率增加以及溶解氧和水pH值降低而增加。用实验数据对模型进行验证后，利用总磷排放数据、总流量、平均沉积物特性以及月平均水温、溶解氧浓度和电导率来预测佛兰德河流的月磷浓度。月平均磷浓度每年在0.24至0.73毫克P/升之间波动，仅用一个可调参数对整个水系（N>250,000）进行预测时，预测值与长期监测数据的偏差在10%以内。该模型预测，夏季磷峰值与缺氧条件下沉积物的内部负荷有关，而非排放稀释效应，即磷的外部输入和/或低流量时的浓度。这表明，提高水中溶解氧、向沉积物中添加富含铁和铝的结合剂以及减少磷排放可降低地表水的磷浓度。
