排污河沉积物中重金属污染的生态风险评价

Ecological risk assessment of heavy metals in polluted sediments of sewage river

以天津市某排污河河道沉积物为研究对象,分析了底泥中Zn、Cu、Cr、Pb、Ni、Cd和Mn的质量比,并用潜在生态风险指数法和地累积指数法对7种重金属的污染状况和生态风险进行了评价。结果表明,Zn的质量比水平最高,平均达1 061.2 mg/kg;而Cd质量比水平最低,均值为4.8 mg/kg。以海滦河流域沉积物背景值为参考值,河道底泥重金属污染严重,其中Cu、Zn、Cd的质量比远远超过背景值,为主要污染风险因子。Cd和Cu在6个采样点都呈现出极大的污染风险,Pb的污染风险则较低。

The object of this paper is to analyze the ecological risk of heavy metals, such as Zn, Cu, Cr, Pb and Ni in the sediments of a sewage river in Tianjin. As we know, heavy metals are often regarded as important parameters that reflect the sediment quality, and, needless to say that the river sediment is an essential component of water environment. The sediment samples were taken and collected from a total of 6 loci of the river from the original source to the downstream, and the concentrations of heavy metals were analyzed by using AAS. Hakanson Potential Ecological Risk Index and Geo-accumulation Index were used to evaluate pollution levels and ecological risk of heavy metals in the sediments. According to the background values of the sediments of Haihe river basin and Luanhe river basin, the results prove that the sediments were severely polluted by the heavy metals. As the result of our investigation, the concentrations of Cu, Zn and Cd turned out much higher than the background values with their major pollution factors reaching the hazard degree. Among the seven heavy metals, the concentration of Zn proves to be the highest （1 061.2 mg/kg） whereas that of Cd was the lowest （4.8 mg/kg）. The results of our study indicate that the contamination hazards of Cu and Cd are very great in all the six samples after being tested by I geo and RI index. According to the assessment of the heavy metal contamination hazards, there is a little difference between the two methods. Such difference can be ascribed to different foci and means of calculation in the two evaluating methods, though they seem to be coincided on the whole. And, perhaps, the application of the two evaluation methods are likely to be able to compensate for the disadvantages of each method. In conclusion, heavy metal contamination risk can be well evaluated by Hakanson Potential Ecological Risk Index and Geo-accumulation Index, which can be used to obtain accurate results in assessing the heavy metal pollution risks in a variety of ways.