Distribution and potential ecological risk assessment of heavy metals in sediments of Zhalong Wetland

This study investigated the concentrations of heavy metals in the sediments of the Zhalong Wetland using ICP-MS,analyzed their spatial distributions,evaluated the potential ecological risk,and explored the pollution sources and environmental influencing factors.The results can be summarized as the followings: ①The concentrations of Hg,Cd,As,Cu,Pb,Zn and Cr were 0.065,0.155,10.26,18.20,21.35,52.08 and 46.47 mg·kg-1,respectively,which were all above the soil background values of the Songnen Plain.Their spatial distributions were distinctly different.The concentration of heavy metals in the north was higher than that in the south,and the east was higher than the west.Particularly in the eastern region,the concentrations of Hg and Cd were 20.8 and 32.4 times the minimum values of the whole area.And in the core zone,the concentration was relatively low.②The sequence of the potential ecological risk posed by the metals was HgCdAsPbCuCrZn.The average potential ecological risk index(RI) of the Zhalong Wetland was 171.9(ranged from 76.9-473.5),suggesting a moderate ecological risk.However,the potential ecological risk was extremely high in the east which should be treated as the major heavy metal pollution prevention site in the future.③Except for Hg and Pb,the concentrations of all heavy metals were significantly correlated to each other,indicating that those heavy metals had homology.④Organic matter was the major environmental influencing factor.However,the trend of land salinization in the Zhalong Wetland has been intensified,indicating a higher risk of heavy metal releasing from the sediments,to which the local authorities should pay enough attention.