阳宗海湖滨湿地表层沉积物重金属污染特征及生态风险评估

Pollution characteristics and ecological risk assessment of heavy metals in the surface layer sediments of Yangzonghai lakeside wetland

以阳宗海湖滨湿地表层沉积物为研究对象,分析不同湖岸沉积物中8种重金属(As、Zn、Cu、Cr、Ni、Pb、Co、Mn)的含量水平.采用内梅罗污染指数法评价湖滨湿地沉积物中重金属的污染特征,甄别主要污染物,同时采用基于总量的潜在生态风险指数法和基于形态的风险评估指数法来评价沉积物中重金属总量及不同形态的生态风险.研究结果表明:(1)阳宗海湖滨湿地表层沉积物中不同重金属元素在4个湖岸空间分布上存在差异,其中Cu、Ni和Co的最高值出现在北岸,Zn、Mn、Pb、Cr和As的最高值出现在东岸;(2)阳宗海不同湖岸湖滨湿地表层沉积物中重金属污染程度大致呈现东岸湖滨湿地受重金属重度污染,南岸和北岸湖滨湿地受重金属轻度污染;西岸湖滨湿地重金属污染程度处于警戒水平,且不同重金属在不同湖岸的污染程度存在差异;(3)阳宗海湖滨湿地表层沉积物中重金属总体呈现低生态风险,不同湖岸RI值呈东岸>北岸>南岸>西岸,其中As、Co和Cu为主要的风险污染物;(4)阳宗海湖滨湿地沉积物中不同重金属主要赋存形态存在差异,主要以还原态和残余态为主,RAC风险评估指数法表明8种重金属具有中等程度以下的生态风险.

The occurrence and accumulation of 8 heavy metals, As, Zn, Cu, Cr, Ni, Pb, Co and Mn in the sediments collected from main tributaries in the Yangzonghai were analyzed. Nemerow pollution index method was used to evaluate the pollution characteristics of heavy metals in the lakeside wetland sediment, the main pollutants were identified based on the total amount of potential ecological risk index and the total amount of heavy metals in sediments and different forms of ecological risk were evaluated based on the form of the risk assessment index methods.The results showed that：（1） Different heavy metal elements in the Yangzonghai lake shore wetland sur- face sediment are different in spatial distribution of four lake shores, including the highest values of Cu, Ni and Co appears in North shore, the highest values of Zn, Mn, Pb, Cr and As appeared in the East coast.（2） The heavy met- als pollution degree were different, the east side of the lake wetlands was heavily polluted, the southern and the northern shore were slightly polluted, and the pollution level of western shore reached alert level, and the degree of pollution differs in different heavy metasl in different locations of the shore.（3） The heavy metals showed an o- verall low ecological risk,RI values were as follow：East shore〉North shore〉South shore〉West shore,where As, Co and Cu were the main risk pollutants.（4） Different heavy metals mainly occurs in Yangzonghai lake wetland sediment morphological differences, mainly in the reduced form and residual state, RAC risk assessment index method showed that 8 kinds of heavy metals were under the moderate or less ecological risk.