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

1706612(麦克米兰)。接受水(溪流、河流、湖泊等)中氮和磷超标与农业和城市用途不可持续和集约化管理的流域的高养分投入(如化肥、食物和动物粪便、污水溢出)有关。可持续地恢复洪泛区显示出改善水质和多种生态系统(如洪泛区土壤)服务的巨大希望，然而，迫切需要清楚地了解和量化洪水对氮和磷动态的累积影响。因此，这项研究的目标是确定营养源和汇(如反硝化、磷释放)和自然系统驱动因素(如水动力和生物地球化学)之间存在的功能关系。为实现这一目标，该项目力求(1)量化河流泛滥平原系统中水文连通性在空间和时间尺度上的变化，(2)描述水动力过程与生物地球化学过程对泛滥平原土壤中氮和磷的输入、去除和释放速率的相对作用，以及(3)确定河流泛滥平原系统尺度上对氮和磷的保留或释放的累积影响。这项研究将由三个主要部分组成，将恢复的河流泛滥平原氮磷动态的物理和生物地球化学控制联系起来。第一部分将应用Wabash-Tippecanoe河交汇处的二维模型来预测洪水泛滥的时间和横向程度，以及地表速度和地下水流动的大小和方向，以量化水力停留时间和横向水流量。第二部分将量化河滩系统养分通量的关键过程，包括通过反硝化去除氮、磷吸收/释放，以及有助于预测这些过程的土壤性质。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中联系起来，以使用多变量统计方法确定对过程的控制。将使用系统分析方法将这些关系应用于在月尺度上聚集通量，并确定净洪泛区功能(例如，源/汇行为)。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，以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，以减少下游湖泊和沿海地区的营养负荷，这些地区正在发生富营养化影响。

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.