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Large woody debris -A river restoration panacea for streambed nitrate attenuation?

大型木质碎片 - 河床硝酸盐衰减的河流恢复灵丹妙药？

基本信息

批准号：
NE/L004437/1
负责人：
Mark Trimmer
金额：
$ 34.89万
依托单位：
Queen Mary University of London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2014
资助国家：
英国
起止时间：
2014 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FL004437%2F1
关键词：
Large woody debris river restoration

项目摘要

For centuries, large woody debris has been removed from UK and European rivers to reduce potential flood risks caused by these obstacles and blockage. However, the removal of large woody debris has been shown to severely impact on ecosystem services provided by rivers, including habitat functioning and the potential to reduce nutrient and sediment loading by acting as both a physical and biochemical barriers. This caused detrimental impacts on in-stream and floodplain biota as well as society in the provision of clean drinking water.Recent EU and UK environmental policies (notably the European Water Framework Directive) are promoting a significant shift in management practices, strongly emphasizing the reintroduction of in-stream wood to improve the resilience of lowland river ecosystems to environmental change by increasing their capacity to attenuate excess nitrate pollution. As obstacle in the river, woody debris is expected to increase the down-welling of surface water into the streambed and enhance its contact time in the very reactive streambed zone, resulting in increased chemical turnover and nitrate attenuation. However, the impacts of large woody debris on the main drivers of biogeochemical processes in the streambed, the exchange fluxes between groundwater and surface water as well as the residence time of water in the streambed are poorly understood. To improve design of large woody debris structures to efficiently remove nitrate from the streambed, river basin management and restoration programmes require scientific evidence for the effectiveness of different large woody debris designs for water quality improvement.This project will therefore provide the scientific evidence required for assessing the efficiency of different permanent and mobile designs of large woody debris for enhancing the uptake of nitrogen in lowland rivers. Our research focuses specifically on lowland streams as these represent the majority of UK rivers under threat of critically high nitrate concentrations. The findings of this project will directly inform river restoration practice and decide whether, to what degree and with what design, large woody debris will be deployed in UK lowland streams to reduce critically high nitrate loads.We will combine novel monitoring techniques and environmental tracer technologies with innovative numerical modelling approaches to identify the occurrence of streambed hotspots of increased biogeochemical turnover that are facilitated by large woody debris. We will quantify to what degree excess nitrate concentrations can be reduced in this reactive hotspots and what different designs of large woody debris structures best facilitate this ecosystem service. We will improve sophisticated numerical models to quantify how effective permanent and mobile large woody debris may attenuate excess nitrate from lowland rivers. By developing and simulating a set of scenarios, assuming wider ranges of environmental conditions then observed experimentally, we will predict how efficiently different large woody debris structures in lowland rivers can reduce nitrate pollution under changing environmental conditions. Knowledge of how in-stream wood facilitates the occurrence of biogeochemical hotspots will assist river managers in adopting techniques which deliver benefits to both in-stream biota and water quality for human uses. This project, twinned with the proposed policy advice documents we will develop, will provide an ideal opportunity for the formation of science-based restoration activities which are able to deliver quantitative water quality improvements for little to no additional cost.

几个世纪以来，英国和欧洲河流中的大型木质残骸已被清除，以减少这些障碍和堵塞造成的潜在洪水风险。然而，已表明，清除大型木质残体会严重影响河流提供的生态系统服务，包括生境功能以及作为物理和生物化学屏障减少养分和沉积物负荷的潜力。这对河流和洪泛区生物群以及提供清洁饮用水的社会造成了不利影响。（特别是欧洲水框架指令）正在推动管理实践的重大转变，特别强调重新引入-溪流木材，以提高低地河流生态系统对环境变化的适应能力，污染作为河流中的障碍物，木质残体预计将增加地表水流入河床的下降量，并增加其在非常活跃的河床区的接触时间，从而增加化学周转和硝酸盐衰减。然而，大型木质残体对河床中的生态地球化学过程的主要驱动因素，地下水和地表水之间的交换通量以及水在河床中的停留时间的影响知之甚少。为了改进大型木质残体结构的设计，以有效地从河床中去除硝酸盐，河流流域管理和恢复方案需要科学证据来证明不同的大型木质残体设计对改善水质的有效性。因此，本项目将提供所需的科学证据，以评估不同的永久性和移动的大型木质残体设计对提高低地河流。我们的研究重点特别是低地溪流，因为这些代表了英国大部分河流的威胁下，极高的硝酸盐浓度。该项目的研究结果将直接告知河流恢复实践，并决定是否，在何种程度上，以何种设计，将在英国低地河流中部署大型木质残体，以减少极高的硝酸盐负荷。我们将把联合收割机新的监测技术和环境示踪技术与创新的数值模拟方法相结合，以确定河床热点的出现，这些热点的出现促进了生物地球化学周转的增加。大的木质残体。我们将量化到什么程度过量的硝酸盐浓度可以减少在这个反应热点和什么不同的设计大型木质残体结构最好地促进这种生态系统服务。我们将改进复杂的数值模型，以量化永久性和移动的大型木质残体如何有效地减少低地河流中过量的硝酸盐。通过开发和模拟一组场景，假设更广泛的环境条件，然后观察实验，我们将预测如何有效地不同的大型木质残体结构在低地河流可以减少硝酸盐污染在不断变化的环境条件下。了解河流中的木材如何促进生物地球化学热点的发生，将有助于河流管理人员采用有利于河流生物群和人类用水水质的技术。该项目与我们将制定的拟议政策咨询文件相结合，将为形成以科学为基础的恢复活动提供理想的机会，这些活动能够以很少或没有额外成本的方式提供定量的水质改善。