[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 x 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.