Maumee River Basin

莫美河流域
  • 文章类型: Journal Article
    地表水养分污染,富营养化的主要原因,尽管政府间努力调节营养源,但仍然是伊利湖西部的主要环境问题。莫美河流域一直是最大的营养贡献者。两种主要的营养来源是施用于农田的无机肥料和牲畜粪便,后来通过径流和土壤侵蚀被带到溪流中。先前对营养源归属的研究集中在年度时间尺度上的大型流域或县。在更精细的时空尺度上进行来源归因,这使得更有效的营养管理,仍然是一个巨大的挑战。本研究旨在通过在分水岭尺度(12位水文单位代码)上开发用于磷源归属的通用贝叶斯网络模型来解决这一挑战。由于磷的释放是不确定的,我们结合了来自肥料和肥料施用的过量磷和作物吸收数据,SWAT模型模拟的流量信息,并使用近似贝叶斯计算对河流中的水质进行测量,以得出将磷的贡献归因于亚流域的后验。我们的结果表明,亚分水岭规模的磷释放存在显着差异,而粗尺度的归因却失去了磷。归因于小流域的磷贡献平均低于环境机构目前采用的养分平衡方法估计的过量磷。肥料比粪肥贡献更多的可溶性活性磷,而粪肥贡献了大部分的非活性磷。虽然是针对莫美河流域的特定背景而开发的,我们的轻量级和可推广的模型框架可以适应其他地区和污染物,并有助于为有针对性的环境监管和执法提供信息。
    Surface water nutrient pollution, the primary cause of eutrophication, remains a major environmental concern in Western Lake Erie despite intergovernmental efforts to regulate nutrient sources. The Maumee River Basin has been the largest nutrient contributor. The two primary nutrient sources are inorganic fertilizer and livestock manure applied to croplands, which are later carried to the streams via runoff and soil erosion. Prior studies of nutrient source attribution have focused on large watersheds or counties at annual time scales. Source attribution at finer spatiotemporal scales, which enables more effective nutrient management, remains a substantial challenge. This study aims to address this challenge by developing a generalizable Bayesian network model for phosphorus source attribution at the subwatershed scale (12-digit Hydrologic Unit Code). Since phosphorus release is uncertain, we combine excess phosphorus derived from manure and fertilizer application and crop uptake data, flow information simulated by the SWAT model, and in-stream water quality measurements using Approximate Bayesian Computation to derive a posterior that attributes phosphorus contributions to subwatersheds. Our results show significant variability in subwatershed-scale phosphorus release that is lost in coarse-scale attribution. Phosphorus contributions attributed to the subwatersheds are on average lower than the excess phosphorus estimated by the nutrient balance approach currently adopted by environmental agencies. Fertilizer contributes more soluble reactive phosphorus than manure, while manure contributes most of the unreactive phosphorus. While developed for the specific context of Maumee River Basin, our lightweight and generalizable model framework could be adapted to other regions and pollutants and could help inform targeted environmental regulation and enforcement.
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  • 文章类型: Journal Article
    降低水生生态系统中的磷(P)浓度,改善水质和减少有害蓝藻水华的发生是必要的。管理减少磷需要有关河流在从陆地到下游水体的磷运输中发挥的作用的信息,但是我们对河流系统何时何地是P源或汇的理解很差。在2019年和2021年的夏季,我们对Maumee河网(伊利湖的主要P负荷来源)的78个地点的河床沉积物进行了采样,重点是零平衡P浓度(EPC0),沉积物既不吸附也不解吸P的可溶性活性磷(SRP)浓度。我们使用结构方程模型来确定EPC0的直接和间接驱动因素。2019年和2021年,溪流沉积物是P汇,分别占站点的40%和67%。在这两年间,EPC0的空间变化由溪水SRP浓度决定,沉积物P饱和度,和沉积物的物理化学特征。反过来,SRP浓度和沉积物P饱和度(PSR)受农业土地利用和河流大小的影响。河流大小的影响因年份而异,河流大小对2019年的SRP和2021年的PSR的影响更大。河床沉积物目前是夏季Maumee河网采样地点的净P汇,但是这些地方的沉积物,尤其是在源头水流中的地方,如果溪水SRP浓度降低,则可能成为P源。我们的研究结果提高了对EPC0的水量和范围控制的理解,但也表明需要进一步研究由于实施保护管理而导致的SRP浓度变化如何影响河床沉积物在磷向伊利湖迁移中的作用。
    Reducing phosphorus (P) concentrations in aquatic ecosystems, is necessary to improve water quality and reduce the occurrence of harmful cyanobacterial algal blooms. Managing P reduction requires information on the role rivers play in P transport from land to downstream water bodies, but we have a poor understanding of when and where river systems are P sources or sinks. During the summers of 2019 and 2021, we sampled streambed sediment at 78 sites throughout the Maumee River network (a major source of P loads to Lake Erie) focusing on the zero equilibrium P concentration (EPC0), the soluble reactive phosphorus (SRP) concentration at which sediment neither sorbs nor desorbs P. We used structural equation modeling to identify direct and indirect drivers of EPC0. Stream sediment was a P sink at 40 % and 67 % of sites in 2019 and 2021, respectively. During both years, spatial variation in EPC0 was shaped by stream water SRP concentrations, sediment P saturation, and sediment physicochemical characteristics. In turn, SRP concentrations and sediment P saturation (PSR) were influenced by agricultural land use and stream size. Effect of stream size differed among years with stream size having a greater effect on SRP in 2019 and on PSR in 2021. Streambed sediment is currently a net P sink across the sites sampled in the Maumee River network during summer, but sediment at these locations, especially sites in headwater streams, may become a P source if stream water SRP concentrations decrease. Our results improve the understanding of watershed- and reach-scale controls on EPC0 but also indicate the need for further research on how changes in SRP concentration as a result of conservation management implementation influences the role of streambed sediment in P transport to Lake Erie.
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