中文摘要：

利用2009～2010年北京城市生态系统地表水10处监测点水环境监测数据,评价了北京城市生态系统地表水硝酸盐污染状况及其空间分布,结合水化学因子相关关系分析了硝酸盐的主要来源.结果表明,北京城市生态系统地表水硝态氮（NO3--N）质量浓度为0.7～7.6 mg.L-1,其中,位于北京市东南部的地表水监测点（东便门和通惠河）水体NO3--N质量浓度为7.0～7.6 mg.L-1,显著高于上游8个监测点NO3--N质量浓度（P〈0.01）;Cl-质量浓度为14.8～86.0 mg.L-1,东便门、通惠河地表水监测点水体Cl-质量浓度为81.5～85.0 mg.L-1,约为上游其他8个监测点的2.3～5.8倍.东便门、通惠河地表水监测点水体电导率（EC）、SO24-质量浓度也表现出同NO3--N、Cl-相似的变化规律,表明东便门、通惠河两处地表水监测点附近存在明显的污染源.相关分析表明,地表水Cl-/Na＋和SO24-/Ca2＋呈明显的线性相关,说明地表水NO3--N污染来源比较单一;水体中NO3--N/Cl-及NO3--N的质量浓度状况说明北京城市生态系统地表水NO3--N污染来源主要是城市污水,包括污水处理厂的废水、垃圾沥出液及生活污水.未来北京市地表水治理应重点关注东便门、通惠河等东南部下游水体污染治理.

英文摘要：

The spatial variation in nitrate-nitrogen（NO-3-N） concentrations in surface water of ten sampling sites in the Beijing urban ecosystem from Kunminghu Lake to Tonghui River were assessed using monitoring data from 2009 to 2010.Nitrogen sources were examined using a hydro-chemical method.The results showed that the average nitrate-N concentrations of surface water in the Beijing urban ecosystem ranged from 0.7-7.6 mg·L-1,with concentrations at all sites affected by human activities to a varying degree.The nitrate-N concentrations in the Dongbianmen and Tonghui River located in the southeastern of Beijing ranged from 7.0-7.6 mg·L-1 and were significantly higher than those in the upper reaches（P〈0.01）.For all sampling sites,the chloride concentrations fell between 14.8-86.0 mg·L-1.The chloride concentrations at the furthest downstream sites,in the Dongbianmen and Tonghui River,ranged from 81.5-85.0 mg·L-1 and were 2.3-5.8 times higher than those in the upper reaches.This indicates that the surface water in Dongbianmen and Tonghui River is clearly affected by human activities and that there are outfalls or pollutant sources near these two sampling sites.Further,the Cl-/Na＋,SO2-4/Ca2＋ ratios showed that the majority of nitrate-N came from a single source.The information given by the nitrate-N concentrations combined with the NO-3-N/Cl-ratio implied that sewage effluent,including industrial waste water,leakage from solid waste disposal and domestic wastewater mainly controlled nitrate distribution in the Beijing urban surface water.The results from this study suggest that surface water management should focus on downstream sites located in the southeastern region of Beijing such as the Dongbianmen and Tonghui River in the future.