北京市清河水体非点源污染特征

为揭示城市水体非点源污染特征，以北京市清河流域为研究对象，于2013年8月—2014年12月对流域不同河段河水、雨水、降雨前后河水、降雨径流以及不同下垫面（居民区、商业区、绿地、街道、农田）的土壤或降尘中主要污染物进行了采样分析.结果表明:清河水体污染严重，大部分污染物浓度均超过GB 3838—2002《地表水环境质量标准》的V类标准，营养盐浓度甚至超过GB 18918—2002《城镇污水处理厂污染物排放标准》一级A排放标准.河水主要污染物浓度远高于雨水污染物浓度，长期来看，受雨水影响较小.丰水期河水ρ（TDP）（TDP为溶解性总磷）显著高于枯水期和平水期，而丰水期ρ（TDN）（TDN为溶解性总氮）却低于枯水期和平水期（P < 0.05），ρ（COD_Mn）和ρ（NH₄+-N）在3个水期没有显著差异.与降雨前相比，降雨后河水ρ（TDN）显著降低，ρ（TDP）却显著升高（P < 0.05），ρ（COD_Mn）、ρ（NH₄+-N）在降雨前后没有显著差异.研究显示，清河流域的降雨径流增加了河水外源磷输入，磷的初期冲刷效应最为显著，且水体磷的非点源特征明显，而氮主要来源于生活污水排放，受非点源影响较小，清河水体COD_Mn、NH₄+-N则同时受点源和非点源的影响. 

Characteristics of Non-Point Source Pollution of Qinghe River in Beijing City

To explore the characteristics of non-point source pollution in Beijing, the Qinghe River Basin was selected as the study area. During the period from August 2013 to December 2014, samples of the river water at different sections, the river water before and after rainfall, and different land uses (residential, commercial, greenbelt, street, and farmland) soil (or dust) were taken and analyzed. The results showed that the Qinghe River was seriously polluted, and the concentration of most pollutants exceeded the standard of V class in terms of Environmental Quality Standard for Surface Water (GB 3838-2002). The river nutrient concentrations were even higher than the 1A standard of treatment plant of Urban Sewage Treatment Plant Pollutants Dischange Standards(GB 18918-2002). The concentration of major pollutants in river water was much higher than those in the rainwater pollutants, indicating that the river water was less affected by rainwater in the long run. The total dissolved phosphorus (TDP) in the wet season was significantly higher than that in the dry season and the normal water season, while the total dissolved nitrogen (TDN) concentration in the river water was significantly lower in the wet season than that in the dry season and the normal water season(P<0.05). However, no significant difference was observed for COD_Mn and NH₄⁺-N concentrations in the three water periods. Compared with the river water quality before rainfall, TDN decreased significantly and the TDP increased significantly after rainfall (P<0.05). There was also no significant difference of the river water COD_Mn and NH₄⁺-N concentrations before and after rainfall, further indicating the characteristics of non-point source pollution for phosphorus. Since the rainfall-runoff increased the phosphorus input into the river, the initial flushing effect of phosphorus was definitely observed. This work implies that the non-point source pollution of phosphorus was apparent in the Qinghe River. Nitrogen mainly derived from domestic sewage discharges, and was less affected by non-point sources. COD_Mn and NH₄⁺-N were affected by both point source and non-point source pollution.