Residues and potential ecological risk assessment of metal in sediments from lower reaches and estuary of Pearl River

In order to investigate the heavy metal concentrations and their potential ecological risks in surface sediments of lower reaches and estuary of Pearl River,21 bottom sediment samples were collected from lower reaches and estuary of Pearl River.Total contents of Cr,Mn,Fe,Co,Ni,Cu,Zn,As,Se,Cd,Sb,Pb and Hg in these samples were measured by the inductively coupled plasma mass spectrometry(ICP-MS) and the atomic fluorescence spectrometry(AFS) and using the index of geoaccumulation and the potential ecological risk index to evaluate the pollution degree of heavy metals in the sediments.Results indicated that the concentration of total Fe and total Mn were 41 658.73 and 1 104.73 mg·kg-1 respectively and toxic trace metals,such as Cr、Co,Ni,Cu,Zn,As,Se,Cd,Sb,Pb and Hg were 86.62,18.18,54.10,80.20,543.60,119.55,4.28,10.60,20.26,104.58 and 0.520 mg·kg-1.The descending order of pollution degree of various metals is: Cd As≈ZnHgPb≈ Cu≈Cr,while the single potential ecological risk followed the order: CdHgAsCuPbZnCr.The pollution extent and potential ecological risk of Cd were the most serious among all heavy metals.The distribution pattern of Cd individual potential ecological risk indices is exactly the same as that of general potential ecological risk indices for all heavy metals.Clustering analysis indicates that the sampling stations may be classified into five groups which basically reflected the characteristics of the heavy metal contamination and sedimentation environments along the different river reaches in lower reaches and estuary of Pearl Rive.In general,the serious heavy metal pollution and the high potential ecological risk existed in three river reaches: Chengcun-Shawan,Chengcun-Shundegang and Waihai-Hutiaomen.The pollution degree and potential ecological risk are higher in related river reaches of Beijiang than that in other lower reaches and estuary of Pearl River.