Phosphorus dynamics in groundwater-fed rivers

减少扩散性营养物污染是改善英国河流环境状况措施的主要重点。在地下水补给的河流中，在潜流带（HZ）中运行的过程及其与地表沃茨（SW）的交换是河流生态健康的关键驱动因素。HZ是SW体下方或附近的地下区域，在该区域与地下水（GW）发生混合。该区域水文、地球化学和微生物复杂。大的氧化还原驱动的浓度梯度存在于整个沉积物-水界面。在进入河床10-100 cm的低流流动路径中，溶解氧完全消耗的可能性产生了厌氧微生物占主导地位的微生物活性区域，这反过来又控制了氧化还原敏感元素如氮（N）和间接磷（P）的生物利用度。通过HZ流量和在河（SW）过程之间的相互作用的P的保留/释放可能是特别重要的，因为P浓度升高已被链接到植物生长的速度增加，物种组成的变化和增殖的水生和附生和底栖藻类在河流中。这些河流往往达不到欧盟《水框架指令》的标准，因此必须采取昂贵的缓解措施。只有了解控制河流生态健康的过程，这些措施才能取得成功。该项目旨在解开这些控制地下水补给河流中的磷动态。重点是了解地下水补给河流中营养过程的时间变化。

Reducing diffuse nutrient pollution is a prime focus of measures to improve the environmental status of UK rivers. In groundwater-fed rivers, processes operating in the hyporheic zone (HZ) and its interchange with surface waters (SW) are key drivers of the ecological health of the river. The HZ is the subsurface region beneath, or adjacent to, a SW body where mixing occurs with groundwater (GW). This zone is hydrologically, geochemically and microbiologically complex. Large redox-driven concentration gradients exist across the sediment-water interface. The resulting potential for complete consumption of dissolved oxygen in hyporheic flowpaths 10-100 cm into the streambed creates areas where anaerobic microorganisms dominate microbial activity, which in turn control the bioavailability of redox-sensitive elements such as nitrogen (N) and, indirectly, phosphorus (P). The retention/release of P through interaction between HZ flows and in-river (SW) processes may be particularly important because elevated P concentrations have been linked to increased rates of plant growth, changes in species composition and proliferation of planktonic and epiphytic and epibenthic algae in rivers. Such rivers often fail to meet the standards of the EU Water Framework Directive necessitating the introduction of expensive mitigation measures. These measures can only succeed if we understand the processes controlling the ecological health of the river. This project seeks to unravel these controls in relation to P dynamics in groundwater-fed rivers.The focus in on understanding of the temporal variation in nutrient processes in groundwater-fed rivers.