INFEWS N/P/H20: Nitrogen and Phosphorus Dynamics in Restored Floodplains of Intensively Managed Watersheds

1706612（McMillan）。接收沃茨（溪流、河流、湖泊等）中过量的氮和磷与高营养素输入有关（例如，农业和城市用途的流域管理不可持续和密集，因此，这些流域的农业和城市用途受到严重影响（例如，化肥、食物和动物废物、污水溢出）。可持续地恢复洪泛区显示出改善水质和多种生态系统（例如，洪泛区土壤）服务，但是，一个明确的理解和量化的氮和磷动态淹没的累积效应是迫切需要的。因此，本研究的目标是确定营养素源和汇之间存在的功能关系（例如，反硝化作用，磷释放）和自然系统驱动因素（例如，水动力学和地球化学）。为了实现这一目标，本项目试图（1）量化河流洪泛区系统中水文连通性在空间和时间尺度上的变化，（2）描述水动力与生态地球化学过程对洪泛区土壤中氮和磷输入、去除和释放速率的相对作用，（3）确定河流-洪泛区系统尺度上氮磷滞留或释放的累积效应。该研究将包括三个主要组成部分，以连接恢复河流洪泛平原的氮和磷动态的物理和生态地球化学控制。第一个组成部分将应用Wabash-Tippecanoe河汇流的二维模型，预测淹没的时间和横向范围以及地表流速和地下水流的大小和方向，以量化水力停留时间和横向水通量。第二个组成部分将量化的关键过程，负责营养素通量在河漫滩系统，包括通过反硝化，磷的吸收/释放，氮的去除和土壤特性，可以帮助预测这些过程。氮和磷的响应变量和潜在的预测变量将在第三个组成部分，以确定控制过程中使用的多元统计方法。系统分析方法将用于将这些关系应用于月尺度的总通量，并确定净洪泛区函数（例如，源/宿行为）。通过这项研究，将提供可持续恢复洪泛区生态系统所需的关键信息，最大限度地改善氮和磷的水质。这项研究的影响可能是深远的，因为社区和监管机构投资于缓解项目，以减少富营养化影响发生的下游湖泊和沿海地区的营养负荷。

1706612 (McMillan). Excess nitrogen and phosphorus in receiving waters (streams, rivers, lakes, etc.) is associated with high nutrient inputs (e.g., fertilizer, food and animal waste, sewage overflows) in watersheds that are unsustainably and intensively managed for agriculture and urban uses. Sustainably restoring floodplains shows great promise to improve water quality and multiple ecosystem (e.g., floodplain soils) services, however a clear understanding and quantification of the cumulative effects of inundation on nitrogen and phosphorus dynamics is critically needed. Therefore, the goal of this research is to determine the functional relationships that exist between sources and sinks of nutrients (e.g., denitrification, phosphorus release) and natural system drivers (e.g., hydrodynamic and biogeochemical). To achieve this goal, this project seeks to (1) quantify how hydrologic connectivity varies across spatial and temporal scales in a river floodplain system, (2) characterize the relative role of hydrodynamic versus biogeochemical processes on the rates of nitrogen and phosphorus inputs, removal and release in floodplain soils, and (3) determine the cumulative effect on the retention or release of nitrogen and phosphorus at the river-floodplain system scale. The research will consist of three major components to link physical and biogeochemical controls of nitrogen and phosphorus dynamics in restored riverine floodplains. The first component will apply a 2-dimensional model of the Wabash-Tippecanoe River confluence to predict the time and lateral extent of inundation as well as magnitude and direction of surface velocity and groundwater flow to quantify hydraulic residence time and lateral water flux. The second component will quantify key processes responsible for nutrient flux in the floodplain system, including nitrogen removal via denitrification, phosphorus uptake/release, and the soil properties that could help predict these processes. Nitrogen and phosphorus response variables and potential predictors variables will be linked in the third component to identify the controls on processes using a multivariate statistical approach. A systems analysis approach will be used to apply these relationships to aggregate fluxes at the monthly scale and determine net floodplain function (e.g., source/sink behavior). Through this research, critical information will be provided that is needed to sustainably restore floodplain ecosystems that maximize water quality improvements for both nitrogen and phosphorus. Impacts of this research are potentially far-reaching as communities and regulatory agencies invest in mitigation projects to reduce nutrient loads to downstream lakes and coastal zones where eutrophication impacts are occurring.