Contextualizing Wetlands Within a River Network to Assess Nitrate Removal and Inform Watershed Management
Contextualizing Wetlands Within a River Network to Assess Nitrate Removal and Inform Watershed Management
复制标题
DOI：
10.1002/2017wr021859
复制
发表时间：
2018-02-01
影响因子：
5.4
通讯作者：
Finlay, Jacques C.
中科院分区：
文献类型：
--
作者：
Czuba, Jonathan A.;Hansen, Amy T.;Finlay, Jacques C.
水生硝酸盐的去除取决于湖泊、湿地和河道相互关联的网络中的相互作用。在此，我们提出了一个基于网络的模型，通过湿地-河流网络量化硝酸盐氮和有机碳浓度，并估计流域的硝酸盐出口。该模型动态地考虑了硝酸盐去除的多种竞争限制，明确地将湿地纳入网络中，并捕获了分层网络效应和空间相互作用。我们将该模型应用于明尼苏达州南部数据丰富的 Le Sueur 盆地，面积为 2,880 km(2) 的农业景观，并使用 2013-2015 年 6 月份的天气现场测量来验证该模型。使用该模型，我们表明，通过反硝化对硝酸盐去除率的总体限制在硝酸盐浓度、有机碳可用性和停留时间之间变化，具体取决于排放、水体特征和网络中的位置。我们的模型结果表明，湿地恢复的空间背景是一个重要但经常被忽视的因素，因为系统中的非线性（例如，由于资源限制对反硝化率的转换而产生）可能会导致下游生物地球化学发生意外的变化。我们的结果表明，通过增加水停留时间（通过减慢流速）而不是通过增加有机碳浓度（这可能会限制反硝化），可以最有效地减少勒苏尔盆地的流域规模硝酸盐浓度和下游负荷。该框架可用于评估在何处以及如何恢复湿地，以减少农业流域的硝酸盐浓度和负荷。
Aquatic nitrate removal depends on interactions throughout an interconnected network of lakes, wetlands, and river channels. Herein, we present a network-based model that quantifies nitrate-nitrogen and organic carbon concentrations through a wetland-river network and estimates nitrate export from the watershed. This model dynamically accounts for multiple competing limitations on nitrate removal, explicitly incorporates wetlands in the network, and captures hierarchical network effects and spatial interactions. We apply the model to the Le Sueur Basin, a data-rich 2,880 km(2) agricultural landscape in southern Minnesota and validate the model using synoptic field measurements during June for years 2013-2015. Using the model, we show that the overall limits to nitrate removal rate via denitrification shift between nitrate concentration, organic carbon availability, and residence time depending on discharge, characteristics of the waterbody, and location in the network. Our model results show that the spatial context of wetland restorations is an important but often overlooked factor because nonlinearities in the system, e.g., deriving from switching of resource limitation on denitrification rate, can lead to unexpected changes in downstream biogeochemistry. Our results demonstrate that reduction of watershed-scale nitrate concentrations and downstream loads in the Le Sueur Basin can be most effectively achieved by increasing water residence time (by slowing the flow) rather than by increasing organic carbon concentrations (which may limit denitrification). This framework can be used toward assessing where and how to restore wetlands for reducing nitrate concentrations and loads from agricultural watersheds.