三门峡库区河流湿地沉积物重金属赋存形态和风险评价

调查三门峡库区河流型湿地沉积物中重金属含量和赋存形态,通过污染指数评价沉积物生态潜在风险、表层重金属可交换态与碳酸盐结合态的质量分数评价其释放风险.结果表明,沉积物中重金属Cr、Ni、Cu、Zn、Cd和Pb含量分别为25.8～68.5、12.1～36.7、3.25～48.74、33.5～472.4、0.16～0.69和9.04～90.74 mg.kg-1.从三门峡库区上游至大坝坝前,沉积物重金属含量呈显著增加趋势.库区最大支流渭河入黄口下游沉积物中重金属Ni、Cu、Zn、Cd和Pb含量高于上游.典型污染支流宏农涧河河口沉积物重金属累积明显,极有可能是该区域矿业发展的工业废水排放所致.沉积物污染指数(SPI)平均值为3.11,介于1.83～7.39之间,渭河入黄口下游沉积物重金属污染程度明显增加,宏农涧河河口沉积物SPI=6.33,处于中度风险.污染河口表层沉积物重金属碳酸盐结合态和交换态所占金属总量的质量分数分别为Cd 63.8%～85.7%,Cu 6.58%～22.62%,Pb 10.6%～28.9%,Ni 1.56%～3.02%.支流污染物排放引起重金属累积,三门峡流域下游沉积物生态风险增加,河口表层重金属释放风险由大到小为Cd>Pb>Cu>Ni.此调查可为河流沉积物污染治理和原位修复提供了参考和依据.

Heavy Metals Distribution and Risk Assessment of Sediments in the Riverine Wetland of Sanmenxia Reservoir

The survey for contents and fractions of heavy metal in sediments of riverine wetland in Sanmenxia Reservoir were carried out. Sediment pollution index was applied to assess the potential ecological risk and mass fraction of heavy metal in surface sediment was conducted for release risk assessment. The results showed that the total concentrations of Cr, Ni, Cu, Zn, Cd and Pb ranged in 25.8-68.5, 12.1-36.7, 3.25-48.74, 33.5-472.4, 0.16-0.69 and 9.04-90.74 mg·kg^-1, respectively. The heavy metal contents in the sediments increased obviously from the upper reaches of reservoir to Sanmenxia dam. The concentrations of Ni, Cu, Zn, Cd, Pb in sediments were higher in lower reach located after Weihe River than those of the upstream. The Weihe River was the biggest branch of Yellow River, and heavy metals accumulated obviously in the sediments of typical polluted branch (Hongnongjian River), which might be attributed to the long-term discharge of industrial wastewater. The sediment pollution index (SPI) of Sanmenxia Reservoir ranged from 1.83 to 7.39, with an average value for 3.11. Sediment pollution aggravated in the downstream after Weihe River flowed in, and SPI reached 6.33 in Hongnongjian River mouth for medium risk. The exchangeable and carbonates fraction of Cd, Cu and Pb mass fractions in surface sediments accounted for 63.8%-85.7%, 6.58%-22.62% and 10.6%-28.9%, respectively. The pollutants discharge in branches caused heavy metal accumulation, ecological risk aggravation in lower reach of Sanmenxia basin. And the release risk followed the sequence Cd>Pb>Cu>Ni in surface sediment. The conclusions of this article supplied reference and basis for sediment pollution treatment and in situ remediation.