Phosphorus dynamics in groundwater-fed rivers

减少扩散的营养物污染是改善英国河流环境状况的措施的首要重点。在地下水补给的河流中，在地下水位带(HZ)中运行的过程及其与地表水的交换是河流生态健康的关键驱动因素。HZ是西南体下方或邻近的地下区域，在那里与地下水(GW)发生混合。该带具有复杂的水文、地球化学和微生物特征。沉积物-水界面存在较大的氧化还原驱动浓度梯度。由此产生的在进入流床的10-100厘米的低渗透流道中完全消耗溶解氧的潜力创造了厌氧微生物主导微生物活动的区域，这反过来又控制了氧化还原敏感元素的生物有效性，如氮(N)和间接地，磷(P)。通过HZ流和河内过程之间的相互作用来保留/释放P可能特别重要，因为P浓度的升高与河流中植物生长速度的增加、物种组成的变化以及浮游、附生和附生藻类的繁殖有关。这类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。只有当我们了解控制河流生态健康的过程时，这些措施才能成功。该项目旨在解开这些与地下水供水河流中磷动态有关的控制，重点在于了解地下水供水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.