大清河水系河流表层沉积物重金属污染特征

沉积物中重金属污染是影响河流水生态系统健康的重要因素.本文采集大清河水系河流表层沉积物,分析了沉积物粒径分布、沉积物中有机质及6种重金属的含量,并采用富集系数法和生态危害指数法进行了重金属的来源解析和风险评价.结果表明:大清河水系河流表层沉积物粒径分布以粉砂为主,占51.27%,砂、黏土所占比例较低,分别为38.56%和10.17%;沉积物中有机质平均含量达到3.94%,且平原/滨海段含量较高;6种重金属Cd、Cr、Cu、Ni、Pb和Zn的含量均值分别为0.68、110.28、73.91、34.74、32.01和227.88 mg·kg-1,均超出背景值.Cd、Cu和Zn的富集系数分别为5.90、2.69和2.15,以人为来源为主;潜在生态危害指数大小顺序为Cd(217.38)Cu(16.05)Pb(7.45)Ni(5.64)Cr(3.23)Zn(2.91),其中Cd呈很强生态危害;重金属综合潜在生态危害表明,大清河水系河流表层沉积物整体处于中度生态危害(RI=253.56).此外,随沉积物中有机质含量增加,Cu和Zn含量增加;随沉积物粒径中值增大,Cd含量增加.

Heavy metal pollution of the surface sediments in Daqing River System, Haihe Basin

Heavy metal pollution in the sediment is an important factor affecting river ecosystem. The surface sediments were collected from Daqing River System (DRS) to study the particle size, organic matter (OM), and heavy metal pollution. The results showed that the size distribution were 51.27% silt, 38.56% sand, and 10.17% clay, respectively. The average content of OM in the sediments reached 3.94%, and the mean contents of Cd, Cr, Cu, Ni, Pb, and Zn were 0.68, 110.28, 73.91, 34.74, 32.01, and 227.88 mg·kg^-1, respectively. Most of heavy metal contents were higher than the soil background values. Enrichment factor (EF) values revealed that Cd, Cu and Zn in the whole DRS (EF=5.90, 2.69 and 2.15, respectively) were mainly from anthropogenic sources. Potential ecological risk (PER) indexes of individual elements (E_rⁱ) and comprehensively (RI) were calculated, and the orders of the average E_rⁱ for the studied metals were Cd (217.38)> Cu (16.05)> Pb (7.45)> Ni (5.64)> Cr (3.23)> Zn (2.91). Although Cd posed higher PER, the mean RI values showed low PER to the local ecosystem in the whole DRS (RI=253.56). In addition, with the increasing of OM content in the sediment samples, Cu and Zn contents increased, while with the increasing of particle size, Cd content increased.