北京市中坝河底泥污染特征及生态风险评价

为探索北运河流域污染底泥土地利用的可能性，以中坝河为例开展了底泥污染特征分析及溯源，依据内梅罗污染指数法和潜在生态风险危害指数法分别开展底泥氮磷污染和重金属生态风险评价，给出了中坝河底泥土地利用建议.结果表明，中坝河底泥呈弱碱性，有机质、氮磷均值分别为33.11、759.94和1295.21 mg·kg^-1，变异系数分别为73%、29%和85%，说明有机质和全氮沿河道分布不均匀.8种重金属中除As外均超过北京土壤背景值，说明底泥存在重金属累积.Pearson相关性和主成分分析表明，受周边工业和生活污水影响，污染物在河道中下游存在累积.底泥氮磷污染评价结果显示河道下游氮磷污染最重.重金属潜在生态风险危害系数表明，中坝河底泥Cd为强污染，Hg中等污染，RI值分别为116和46，其他重金属为轻度污染.S4和S5 RI分别为344和374，为强污染，其他点位为中等或轻污染，整条河道RI为170，为中等污染级别.总体而言，中坝河底泥肥力较好，风险可控，建议施用于道路绿化带、工厂附属绿地等有潜在污染源的绿/林地或防护林等与人接触较少的绿/林地.

Pollution characteristics and ecological risk assessment of sediment in Zhongba River, Beijing

In order to investigate the possibility of land use of polluted sediment in North Canal basin, Zhongba River was selected as an example to analyze pollution characteristics and source tracking. To provide technical support for land use, nitrogen and phosphorus pollution status and ecological risk were evaluated using Nemeiro pollution index and potential ecological risk index method, respectively. Results showed that the sediment was weakly alkaline. The average contents of organic matter, total phosphorus and nitrogen were 33.11, 759.94 and 1295.21 mg·kg^-1 respectively, and their variation coefficients were 73%, 29% and 85%, which implying an uneven distribution along the river of organic matter and total nitrogen. Average contents of all 8 heavy metals except arsenic were higher than those of soil background value in Beijing, indicating a widespread heavy metal accumulation. Pearson correlation and principal component analysis showed that pollutants accumulated in the middle and lower reaches of the river due to the influence of surrounding industrial wastewater and domestic sewage. The assessment results of nitrogen and phosphorus pollution status showed that downstream was serious polluted. Ecological risk assessment results showed that RI of Cadmium was at 116, indicating a strong pollution level, while Hg was 46 at medium pollution level. Other heavy metals were at light pollution level. RI values at sampling point S4 and S5 were 344 and 374 respectively, indicating a strong pollution level, while other points were moderately polluted or lightly polluted. The entire river was comprehensively evaluated as a medium pollution level with RI 170. In conclusion, fertility of sediment in Zhongba River was good and its risk was controllable. As a result, the sediment could be applied to green areas with potential pollutant source or less human contact, such as road green belts, green areas attached to factories, woodland, shelter forest, etc.