铜陵市惠溪河滨岸带土壤重金属形态分布及风险评估

为揭示惠溪河滨岸带土壤重金属(Pb、Cu、Zn、Ni、Cr、Cd和As)形态分布和生态风险状况,沿河采集12个采样点的土壤样品,采用改进的Tessier五步连续提取法开展形态分析,并以Hkanson潜在生态危害指数法进行生态风险评估. 结果表明:①As和Cr以残渣态占绝对优势,Zn、Pb和Ni以残渣态和Fe-Mn氧化物结合态为主,Cu则以残渣态和有机结合态为主,Cd具有形态多样的分布特征；②7种重金属污染程度排序为As＞Cd＞Zn＞Cu＞Pb＞Ni＞Cr,潜在生态风险大小排序为Cd＞As＞Cu＞Pb＞Ni＞Zn＞Cr,其中Cd和As属极高风险等级,Cu为中等风险等级,其他4种元素则为轻微风险等级；③根据潜在生态风险指数,小倪村、狼尾湖右岸和大倪村采样点属于高风险等级,其他9个采样点均属于很高风险等级；④由综合污染及潜在生态风险贡献率水平,初步判定As和Cd为惠溪河滨岸土壤重金属污染治理和修复的优先控制对象. 

Fraction Distribution and Ecological Risk Assessment of Soil Heavy Metals in the Riparian Zone of Huixi Stream in Tongling City

To investigate chemical forms and the ecological risk of soil heavy metals in riparian zones, twelve soil samples were collected along the Huixi creek, Tongling City, China. Morphological distribution of heavy metals including Pb, Cu, Zn, Ni, Cr, Cd and As were determined by five steps of sequential extraction Tessier methods and ecological risk assessments were conducted by using the potential ecological risk index proposed by Hkanson. The results indicated that:① As and Cr were absolutely dominated by residual fractions, Zn, Pb and Ni were mainly composed of the residual and Fe-Mn oxide-bound, Cu with the residual and organic-bound, while Cd was controlled by various fractions. ②The order of pollution of the seven heavy metals was:As＞Cd＞Zn＞Cu＞Pb＞Ni＞Cr, while the order of the single potential ecological risk was as:Cd＞As＞Cu＞Pb＞Ni＞Zn＞Cr. The pollution extent and potential ecological risk of Cd and As were the most serious among all heavy metals. The ecological risk level of Cd and As belonged to extremely strong degree, Cu belonged to medium degree, while others belonged to slight degree. ③ According to the values of potential ecological risk index of different sampling sites, the Xiaoni village, the Langwei lake and the Dani village were at the level of the strong risk, while other nine sites were at the level of very strong risk. ④ In view of the contribution of each heavy metal to integrate pollution index and potential ecological risk index, it was suggested that both As and Cd were the priority metals in the metals-contaminated riparian zones along the Huixi creek.