Howden Nicholas J K, Bowes Michael J, Clark Alistair D J, Humphries Neil, Neal Colin
National Soil Resources Institute, Natural Resources Department, School of Applied Sciences, Cranfield University, Cranfield, Bedfordshire MK430AL, United Kingdom.
Sci Total Environ. 2009 Apr 1;407(8):2966-79. doi: 10.1016/j.scitotenv.2008.12.040. Epub 2009 Feb 12.
The water quality of 13 rivers in the lowland, agricultural county of Suffolk is investigated using routine monitoring data for the period 1981 to 2006 collected by the Environment Agency of England and Wales (EA), and its predecessors, with particular emphasis on phosphorus (as total reactive phosphorus, TRP) and total (dissolved and particulate) oxidised nitrogen (TOxN--predominantly nitrate NO3). Major ion and flow data are used to outline fundamental hydrochemical characteristics related to the groundwater provenance of base-flow waters. Relative load contributions from point and diffuse sources are approximated using Load Apportionment Modelling for both TRP and TOxN where concurrent flow and concentration data are available. Analyses indicate a mixture of point and diffuse sources of TRP, with the former being dominant during low flow periods, while for TOxN diffuse sources dominate. Out of 59 sites considered, 53 (90%) were found to have annual average TRP concentrations greater than 0.05 mg P l(-1), and 36 (61%) had average concentrations over 0.120 mg P l(-1), the upper thresholds for 'High' and 'Good' ecological status, respectively. Correspondingly, for TOxN, most of the rivers are already within 70% of the 11.3 mg N l(-1) threshold, with two rivers (Wang and Ore) being consistently greater than this. It is suggested that the major challenge is to characterise and control point-source TRP inputs which, being predominant during the late spring and summer low-flow period, coincide with the peak of primary biological production, thus presenting the major challenge to achieving 'good' ecological status under the Water Framework Directive. Results show that considerable effort is still required to ensure appropriate management and develop tools for decision-support.
利用英格兰和威尔士环境署（EA）及其前身在1981年至2006年期间收集的常规监测数据，对萨福克郡这个低地农业县的13条河流的水质进行了调查，特别关注磷（以总活性磷，TRP计）和总（溶解态和颗粒态）氧化态氮（TOxN，主要为硝酸盐NO3）。主要离子和流量数据用于勾勒与基流水的地下水来源相关的基本水化学特征。在有同时期流量和浓度数据的情况下，使用负荷分配模型估算点源和非点源对TRP和TOxN的相对负荷贡献。分析表明，TRP的点源和非点源混合存在，前者在低流量期占主导，而对于TOxN，非点源占主导。在所考虑的59个站点中，发现53个（90%）的年平均TRP浓度大于0.05 mg P l(-1)，36个（61%）的平均浓度超过0.120 mg P l(-1)，这分别是“高”和“良好”生态状况的上限阈值。相应地，对于TOxN，大多数河流已经在11.3 mg N l(-1)阈值的70%以内，有两条河流（王河和奥勒河）一直高于此值。研究表明，主要挑战在于表征和控制点源TRP输入，在春末和夏末低流量期，点源TRP输入占主导，这与初级生物生产的高峰期重合，因此对根据《水框架指令》实现“良好”生态状况构成了主要挑战。结果表明，仍需要付出巨大努力来确保进行适当管理并开发决策支持工具。
