北运河流域沙河水库沉积物重金属分布及生态风险评估

以北运河流域沙河水库为研究对象，选择19个点采集表层（0~20 cm）沉积物，并选择其中3个点采集沉积物柱芯，分析沉积物中As、Cd、Cu、Mn、Ni、Pb、Zn共7种重金属的空间分布特征，采用地累积指数法、潜在生态风险指数法和风险评价编码法对重金属污染进行评价，结合表层沉积物的重金属形态分析其潜在生态风险.结果表明，各区域重金属与北京土壤背景值相比富集倍数均值排序依次为点源污染区 > 库心区 > 库下游 > 南沙河 > 库上游 > 北沙河，分别为2.57倍、2.06倍、1.97倍、1.95倍、1.87倍、1.85倍；库心区和北沙河入库口的柱状样呈现随深度变化先增加后减少的趋势.污染评价结果显示，As为中度或偏中污染，其余重金属无污染或污染较轻，所有采样点的潜在生态风险指数均小于150，为轻度生态危害.As、Cr、Cu的形态多为残渣态，生物有效性低，Mn、Zn虽含量较低，但生物有效性高.通过相关性分析和主成分分析推测沉积物中各种重金属污染来源相似，主要由外源混合废水输入，并且沉积物中重金属与营养盐及有机质呈显著相关，表明其可能均来自点源污染排放.

Distribution and ecological risk assessment of heavy metals in sediments of Shahe Reservoir in Northern Canal Basin

Shahe Reservoir of Northern Canal Basin was selected as the study area. Nineteen surface (0~20 cm) sediment samples and three sediment core samples were collected to analyze the spatial distribution characteristics of As, Cd, Cu, Mn, Ni, Pb and Zn in the sediments. The geo-accumulation index, potential ecological risk index and risk assessment code were used to evaluate heavy metal pollution, as well as its potential risk was analyzed according to the speciation of heavy metals. Results showed that the average enrichment factors of heavy metals compared to the background value in soil of Beijing were ranked at the order as the point source pollution area > the central area of the reservoir > the downstream area of the reservoir > the Nansha River > the upstream area of the reservoir > the Beisha River, namely, 2.57 times, 2.06 times, 1.97 times, 1.95 times, 1.87 times and 1.85 times, respectively. The sediment core samples in the central area of the reservoir and the inlet of the Beisha River showed a trend of increasing firstly and then decreasing with the change of depth. Pollution assessment results showed that As was moderately contaminated or moderately to strongly contaminated, but the other heavy metals were not polluted or lightly polluted. The potential ecological risk index of all sampling sites was less than 150, showing a low ecological risk. As, Cr, and Cu were mainly in the speciation of residues, with low bioavailability. Although the content of Mn and Zn were low, they showed high bioavailability. Based on correlation analysis and principal component analysis, it was speculated that the sources of various heavy metal pollution in the sediment were similar, which were possibly input from the external wastewater. The heavy metals in sediment were positively related to nutrients and organic matter, indicating that all of them were mostly from the same point polluted sources.