巢湖表层沉积物中重金属的分布特征及其污染评价

以巢湖表层沉积物为研究对象,利用BCR连续提取法研究了沉积物中Cr、Co、Ni、Cu、Cd、Zn、V和Pb等8种重金属元素的分布特征,同时运用潜在风险指数法和地累积指数法综合评价了巢湖沉积物中重金属的生态风险。结果表明,巢湖沉积物中的重金属含量在空间上表现出东西高、中间低的分布特征。巢湖表层沉积物中Cr、Co、Ni、V和Cu 5种重金属都主要以残渣态为主,Zn和Cd主要以弱酸提取态为主,Pb以可还原态为主,同时,Co和Cu 2种元素的可交换态及可还原态含量占有较高比例,具有潜在危害性。相关性分析显示,Cr、Cu、Pb、Ni、Zn和Cd 6种重金属元素的来源和分布可能具有相似性,Co和V 2种重金属元素具有相似的地球化学行为且其主要来源可能与其他几种重金属不同。潜在生态风险指数评价结果表明,巢湖表层沉积物中8种重金属元素构成的生态危害顺序为:Cd>Pb>Co>Cu>Ni>Zn>V>Cr,Cd具有高的生态危害等级,其他7种重金属元素均为低生态危害等级。地累积指数法评价结果表明:巢湖沉积物重金属元素的富集程度为Cd>Zn>Pb>Co>Cu>V>Ni>Cr,Cr属于清洁级别,Co、Cu、V和Ni处于轻度污染水平,Zn和Pb处于偏中度污染,Cd达到了重污染水平。

Distribution characteristics and contamination assessment of heavy metals in surface sediments of Chaohu Lake, China

Surface sediment samples were taken from Chaohu Lake and different fractions of eight heavy metals (Cr, Co, Ni, Cu, Cd, Zn, V and Pb) were studied using BCR (European Communities Bureau of Reference) sequential extraction procedure. The pollution levels of eight heavy metals were evaluated by the potential ecological risk index (RI) and geoaccumulation index (I_geo). The heavy metal distribution of surface sediment indicated a higher degree of contamination in the east and west regions of the lake than that in the middle region. The residual fraction was the main contribution for Cr, Co, Ni, V and Cu in the sediments and the soluble fraction was the dominant for Zn and Cd, while Pb was found mainly in the reducible fraction. Meanwhile, Co and Cu were composed of the soluble and reducible fractions indicating potential hazard to aquatic organisms. The results of correlations analysis showed that Cr, Cu, Pb, Ni, Zn and Cd have the similar origin and distribution.However, Co and V possessed the alike geochemical source and their origins likely were different from the other six heavy metals. Potential ecological risk index of eight heavy metals investigated were the rank order: Cd> Pb> Co> Cu> Ni> Zn> V> Cr. Cd had high potential ecological risk and contributed most to potential ecological index compared with the other heavy metals. Based on the geoaccumulation index of heavy metals, the degree of heavy metal pollution decreased in the order of Cd > Zn> Pb> Co> Cu> V> Ni> Cr. The I_geo values suggested the unpolluted for Cr, unpolluted to moderately polluted for Co, Cu, V, and Ni, moderately polluted for Zn and Pb and moderately to heavily polluted for Cd.