长江口沉积物重金属的分布、来源及潜在生态风险评价

为了解长江口潮滩沉积物中重金属的污染特征,采用电感耦合等离子体发射光谱法(ICP-AES)分析了长江口北支、南支和杭州湾27个表层沉积物中Cu、Pb、Ni、Ag、As、Cd、Zn、Sn、Sb和Hg 10种重金属的含量,并对其分布、来源及生态风险进行了评价.结果表明,沉积物中10种重金属的含量和介于102.9 ～ 326.4 mg· kg-1之间,北支、南支和杭州湾的平均值分别为180.9、244.7和155.6 mg·kg-1.方差分析结果表明,南支与北支、杭州湾平均含量之间均存在显著性差异(p＜0.01),南支因受沿岸工业污水和生活污水的影响污染加重.来源分析表明,沉积物中大多数重金属的来源具有一定的相似性,主要来源于各种工农业废水、船舶运输、农药和化肥污染,而Ag和Hg具有不同的来源.地积累指数评价结果表明,10种重金属的平均污染程度由高到低依次为:Cd＞ Hg＞ Sb＞ Ag＞ As＞ Cu ＞Zn＞ Ni＞ Sn＞ Pb,Hg和Cd在多数采样点分别为中度污染和偏重污染,南支Cd和Ag的污染程度高于北支和杭州湾,而在杭州湾Hg的污染程度高于北支和南支.潜在生态风险系数评价结果表明,长江口沉积物7种重金属潜在生态风险系数从高到低依次为:Cd＞Hg＞As＞Cu ＞Ni＞Pb ＞Zn,长江口沉积物的潜在生态风险主要由Cd和Hg引起,两者的贡献分别为62.6％和34.0％,各采样点7种重金属的潜在生态风险指数(RI)介于565.9～1601之间,均达到极强生态风险.

Distribution, sources and ecological risk assessment of heavy metals in sediments of the Yangtze River estuary

In order to understand the pollution characteristics of heavy metals in surface sediments of north and south branches of the Yangtze River estuary and Hangzhou bay, the concentrations of 10 heavy metals including Cu, Pb, Ni, Ag, As, Cd, Zn, Sn, Sb and Hg in 27 sediment samples were analyzed by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and the potential ecological risks of each heavy metals were evaluated. The total concentrations of 10 metals in the sediment samples ranged from 102.9 mg·kg^-1 to 326.4 mg·kg^-1, the mean concentrations of heavy metals in sediments of north branch, south branch and Hangzhou bay were 180.9, 244.7 and 155.6 mg·kg^-1, respectively. The average concentration of north branch sediments was different significantly from those of south branch and Hangzhou bay (p < 0.01), indicating the pollution extent of south branch of the Yangtze River was aggravated by industrial wastewater and domestic sewage. The source of most heavy metals in sediments were similar, and came mainly from industrial and agricultural wastewater, shipping, and the use of pesticide and chemical fertilizer. The pollution extent of heavy metals in sediments by geo-accumulation index (I_geo) followed the order: Cd >Hg>Sb>Ag>As>Cu>Zn>Ni>Sn>Pb. The pollution extent of Cd and Hg were at class 3 (moderately to heavily polluted) and 4 (heavily polluted) at most sampling sites. The potential ecological risk of 7 heavy metals in sediments by the potential ecological risk factors followed the order: Cd>Hg>As> Cu>Ni>Pb>Zn. Cd and Hg contributed the most to the total potential ecological risk, accounting for 62.6% and 34.0%, respectively. The potential ecological risk indexes (RI) of 7 heavy metals at all sampling sites were in the range of 563.0 and 1431, and posed very high potential ecological risks for the Yangtze River estuary.