Withers P J A, Jarvie H P
Environment Group, ADAS UK Limited, Nottinghamshire, United Kingdom.
Sci Total Environ. 2008 Aug 1;400(1-3):379-95. doi: 10.1016/j.scitotenv.2008.08.002. Epub 2008 Sep 19.
Phosphorus (P) supply (concentration and flux) is an important driver for biological activity in flowing waters and needs to be managed to avoid eutrophication impacts associated with urbanisation and agricultural intensification. This paper examines the role of in-stream retention and cycling in regulating river P concentrations in order to better understand the links between P sources and their ecological impacts. In terms of their composition (solubility and concentration), patterns of delivery (mode and timing) and therefore ecological relevance, P sources entering rivers are best grouped into wastewater discharges > runoff from impervious surfaces (roads, farmyards) > runoff from pervious surfaces (forestry, cultivated land and pasture). The localized impacts of soluble P discharges during ecologically sensitive periods can be distinguished from the downstream impacts associated with particulate P discharges under high flows due to the different processes by which these sources are retained, transformed and assimilated within the river channel. The range of physico-chemical processes involved in P cycling and the variable importance of these processes in different river environments according to stream size, stream geomorphology and anthropogenic pressures are summarised. It is concluded that the capacity to retain (process) P within the river channel, and hence regulate the downstream delivery of P without stressing the aquatic communities present, is considerable, especially in headwaters. To help achieve good water quality, there is scope to better manage this ecosystem service through regulation of P supply whilst optimising in-stream P retention according to subsidy-stress theory. Further research is needed to develop in-stream management options for maximising P subsidies and to demonstrate that regulation of downstream P delivery will reduce the incidence of eutrophication in connected waterbodies.
磷（P）供应（浓度和通量）是流动水体中生物活动的重要驱动因素，需要进行管理以避免与城市化和农业集约化相关的富营养化影响。本文研究了河道内磷的滞留和循环在调节河流磷浓度中的作用，以便更好地理解磷源与其生态影响之间的联系。就其组成（溶解度和浓度）、输送模式（方式和时间）以及生态相关性而言，进入河流的磷源最好分为废水排放＞不透水表面（道路、农家院）的径流＞透水表面（林业、耕地和牧场）的径流。由于这些磷源在河道内的滞留、转化和同化过程不同，在生态敏感时期可溶性磷排放的局部影响可与高流量下颗粒态磷排放的下游影响区分开来。总结了磷循环中涉及的一系列物理化学过程，以及根据溪流大小、溪流地貌和人为压力，这些过程在不同河流环境中的不同重要性。得出的结论是，河道内滞留（处理）磷的能力，即调节下游磷的输送而不影响现有水生生物群落的能力相当可观，尤其是在源头地区。为了实现良好的水质，有空间通过调节磷供应来更好地管理这一生态系统服务，同时根据补贴-压力理论优化河道内的磷滞留。需要进一步研究，以制定河道内管理方案，以最大限度地增加磷补贴，并证明调节下游磷的输送将减少相连水体中富营养化的发生率。
