Abstract：
China\'s lowland rural rivers are facing severe eutrophication problems due to excessive phosphorus (P) from anthropogenic activities. However, quantifying P dynamics in a lowland rural river is challenging due to its complex interaction with surrounding areas. A P dynamic model (River-P) was specifically designed for lowland rural rivers to address this challenge. This model was coupled with the Environmental Fluid Dynamics Code (EFDC) and the Phosphorus Dynamic Model for lowland Polder systems (PDP) to characterize P dynamics under the impact of dredging in a lowland rural river. Based on a two-year (2020-2021) dataset from a representative lowland rural river in the Lake Taihu Basin, China, the coupled model was calibrated and achieved a model performance (R2>0.59, RMSE<0.04 mg/L) for total P (TP) concentrations. Our research in the study river revealed that (1) the time scale for the effectiveness of sediment dredging for P control was ∼300 days, with an increase in P retention capacity by 74.8 kg/year and a decrease in TP concentrations of 23% after dredging. (2) Dredging significantly reduced P release from sediment by 98%, while increased P resuspension and settling capacities by 16% and 46%, respectively. (3) The sediment-water interface (SWI) plays a critical role in P transfer within the river, as resuspension accounts for 16% of TP imports, and settling accounts for 47% of TP exports. Given the large P retention capacity of lowland rural rivers, drainage ditches and ponds with macrophytes are promising approaches to enhance P retention capacity. Our study provides valuable insights for local environmental departments, allowing a comprehensive understanding of P dynamics in lowland rural rivers. This enable the evaluation of the efficacy of sediment dredging in P control and the implementation of corresponding P control measures.
摘要：
由于人为活动造成的磷（P）过多，中国低地农村河流面临着严重的富营养化问题。然而,由于低地农村河流与周边地区的复杂相互作用，量化P动力学具有挑战性。为应对这一挑战，专门为低地农村河流设计了P动态模型（River-P）。该模型与环境流体动力学代码（EFDC）和低地Polder系统（PDP）的磷动力学模型相结合，以表征在低地农村河流疏dr影响下的P动力学。基于太湖流域代表性低地农村河流的两年（2020-2021）数据集，中国,对耦合模型进行了校准，并获得了总P（TP）浓度的模型性能（R2>0.59，RMSE<0.04mg/L）。我们在研究河流中的研究表明，（1）泥沙疏浚控制磷的有效性的时间尺度为300天，疏浚后P保留能力增加74.8kg/年，TP浓度降低23％。(2)疏浚显著降低沉积物磷释放量98%,虽然磷的再悬浮和沉降能力增加了16%和46%，分别。（3）沉积物-水界面（SWI）在河流内部磷的转移中起着至关重要的作用。由于重新暂停占TP进口的16%，结算占TP出口的47%。考虑到低地农村河流的巨大磷保留能力，带有大型植物的排水沟和池塘是提高磷保留能力的有希望的方法。我们的研究为当地环境部门提供了宝贵的见解，全面了解低地农村河流的磷动态。这样就可以评估P控制中沉积物疏浚的有效性并实施相应的P控制措施。
