Arnscheidt J, Jordan P, Li S, McCormick S, McFaul R, McGrogan H J, Neal M, Sims J T
School of Environmental Sciences, University of Ulster, Coleraine, BT52 1SA, Northern Ireland, UK.
Sci Total Environ. 2007 Aug 15;382(1):1-13. doi: 10.1016/j.scitotenv.2007.03.036. Epub 2007 May 21.
Nutrient transfers from the land to rivers have the potential to cause persistent eutrophic impacts at low flows even though the transfers may constitute a minor percentage of total annual fluxes. In rural catchments, the contribution from agricultural soils during storm events can be particularly large and untangling the relative contributions from multiple sources that vary in time and space is especially problematic. In this study, the potential for domestic septic tank system pollution during low flows was investigated in 3 small catchments (3 to 5 km(2)) using an integrated series of methods. These included septic system surveys, continuous (10 min) total phosphorus (TP) monitoring at the outlet of each catchment, repeated low-flow water quality surveys in sub-catchments upstream of the catchment outlets and single day river-walk water quality surveys. A series of faecal matter and grey-water fingerprinting techniques were also employed. These included determining sterol ratios in stream sediments, monitoring the presence of proteins, E. coli and enterococci bacterial signatures and boron. The total density and density of poorly maintained septic systems mirrored the magnitude of frequent TP concentrations in the catchments although this relationship was less apparent in the nested sub-catchments. The exception was possibly related to the simple hydraulics in one particular catchment and indicated temporary effluent attenuation in the other catchments. Repeated low-flow and river-walk water quality surveys highlighted discrete areas and reaches where stepped changes in nutrient concentration occurred. Bio-chemical fingerprinting showed that between 7% and 27% of sediments were contaminated with human faecal material and correlation matrices indicated that, at least during low flows, P fractions were positively correlated with some markers of faecal and grey-water contamination.
尽管从陆地到河流的养分转移可能仅占年总通量的一小部分，但在低流量情况下仍有可能造成持续的富营养化影响。在农村集水区，暴雨期间农业土壤的贡献可能特别大，而理清多个时空变化源的相对贡献尤其困难。在本研究中，采用一系列综合方法，对3个小集水区（3至5平方公里）低流量期间生活化粪池系统的污染潜力进行了调查。这些方法包括化粪池系统调查、在每个集水区出口连续（10分钟）监测总磷（TP）、在集水区出口上游的子集水区重复进行低流量水质调查以及单日河流徒步水质调查。还采用了一系列粪便物质和灰水指纹识别技术。这些技术包括测定河流沉积物中的甾醇比率、监测蛋白质、大肠杆菌和肠球菌细菌特征以及硼的存在情况。维护不善的化粪池系统的总密度和密度反映了集水区中频繁出现的总磷浓度的大小，尽管这种关系在嵌套子集水区中不太明显。这一例外情况可能与一个特定集水区的简单水力学有关，并表明其他集水区存在临时的污水衰减。重复进行的低流量和河流徒步水质调查突出了养分浓度出现阶梯式变化的离散区域和河段。生物化学指纹识别表明，7%至27%的沉积物受到人类粪便物质的污染，相关矩阵表明，至少在低流量期间，磷组分与粪便和灰水污染的一些标志物呈正相关。
