漳河上游流域沉积物中重金属生态风险评价

Ecological risk assessment of heavy metals in sediments of the upper reaches of Zhanghe River

海河流域人口密集,大中城市众多,在我国政治经济中具有重要地位.漳河,属海河流域漳卫南运河水系,是漳卫河的一大支流.本研究以漳河上游流域表层沉积物为研究对象,采用相对累积频率法和归一化法建立了4种重金属(Cr、Ni、Cu、Pb)的区域地球化学基线.根据区域地球化学基线值定量计算了漳河上游流域沉积物中重金属污染的人为贡献率.根据不同背景参考值(土壤背景值、重金属浓度中值和区域地球化学基线值)采用地质累积指数和潜在生态风险指数对沉积物中重金属的污染水平和生态风险进行评价.沉积物中Cr、Ni、Cu、Pb的平均含量分别为91.51、43.33、21.93、18.30 mg·kg^(−1),接近中国土壤背景值.计算的区域地球化学基线值略低于沉积物中重金属的平均含量.Cr、Ni、Cu、Pb的平均人为贡献率为17.14%、11.16%、50.92%、29.35%,表明人为影响较小.此外,I_(geo)和EI结果表明,沉积物重金属处于无污染至轻度污染状态,具有较低的生态风险.

Haihe River Basin plays an important role in China's politics and economy.Zhanghe River is the largest tributary of Zhangwei River,which belongs to Zhangweinan Canal in Haihe River Basin.In this study,the regional geochemical baselines of four heavy metals(Cr,Ni,Cu,Pb)were established by relative cumulative frequency and normalization methods.The anthropogenic contribution rate of sediment in the upper reaches of Zhanghe River was quantitatively calculated by using the baseline value of regional geochemistry.The geological accumulation index(I_(geo))and potential ecological risk index(EI)were used to evaluate the pollution level and ecological risk of heavy metals in sediments according to different background reference values(soil background value,median concentration of heavy metals and regional geochemical baseline value).The average contents of Cr,Ni,Cu and Pb in sediments are 91.51 mg·kg^(−1),43.33 mg·kg^(−1),21.93 mg·kg^(−1)and 18.30 mg·kg^(−1),respectively,which are close to the background values of soil in China.The calculated regional geochemical baseline value is slightly lower than the average content of heavy metals in sediments.The average anthropogenic contribution rates of Cr,Ni,Cu and Pb are 17.14%,11.16%,50.92%and 29.35%,indicating that the anthropogenic influence is relatively small.In addition,the results of I_(geo)and EI show that heavy metals in sediments are in a state of no pollution to slight pollution,and the ecological risk is low.