Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK.
Environ Sci Process Impacts. 2014 Jul;16(7):1637-45. doi: 10.1039/c3em00681f.
Surface water quality in the UK and much of Western Europe has improved in recent decades, in response to better point source controls and the regulation of fertilizer, manure and slurry use. However, diffuse sources of pollution, such as leaching or runoff of nutrients from agricultural fields, and micro-point sources including farmyards, manure heaps and septic tank sewerage systems, particularly systems without soil adsorption beds, are now hypothesised to contribute a significant proportion of the nutrients delivered to surface watercourses. Tackling such sources in an integrated manner is vital, if improvements in freshwater quality are to continue. In this research, we consider the combined effect of constructing small field wetlands and improving a septic tank system on stream water quality within an agricultural catchment in Cumbria, UK. Water quality in the ditch-wetland system was monitored by manual sampling at fortnightly intervals (April-October 2011 and February-October 2012), with the septic tank improvement taking place in February 2012. Reductions in nutrient concentrations were observed through the catchment, by up to 60% when considering total phosphorus (TP) entering and leaving a wetland with a long residence time. Average fluxes of TP, soluble reactive phosphorus (SRP) and ammonium-N (NH4-N) at the head of the ditch system in 2011 (before septic tank improvement) compared to 2012 (after septic tank improvement) were reduced by 28%, 9% and 37% respectively. However, TP concentration data continue to show a clear dilution with increasing flow, indicating that the system remained point source dominated even after the septic tank improvement.
英国和西欧大部分地区的地表水水质在近几十年有所改善，这是由于更好的点源控制和对肥料、粪便和泥浆使用的监管。然而，现在人们假设，农业领域的养分淋溶或径流以及包括农场、粪堆和化粪池污水系统在内的微观点源（特别是没有土壤吸附床的系统）等扩散污染源，对输送到地表水的养分的很大一部分有贡献。如果要继续改善淡水水质，就必须以综合方式解决这些污染源。在这项研究中，我们考虑了在英国坎布里亚郡的一个农业流域内，通过建造小型田间湿地和改进化粪池系统来综合改善地表水水质。通过手动采样，在 2011 年 4 月至 10 月和 2012 年 2 月至 10 月期间，每两周监测一次沟渠-湿地系统的水质，而化粪池的改进则发生在 2012 年 2 月。通过整个流域，观察到养分浓度的降低，当考虑具有长停留时间的湿地进入和离开的总磷（TP）时，降低幅度高达 60%。2011 年（在化粪池改进之前）与 2012 年（在化粪池改进之后）相比，在沟渠系统的头部，TP、可溶解性反应磷（SRP）和铵氮（NH4-N）的平均通量分别减少了 28%、9%和 37%。然而，TP 浓度数据仍显示出随着流量增加而明显稀释的趋势，表明即使在化粪池改进之后，该系统仍以点源为主。
