STUDY ON THE ECOLOGICAL RISK OF HEAVY METALS IN THE SURFACE SEDIMENTS IN GUANGZHOU SECTION OF THE PEARL RIVER

The internal pollution sources are going to be the main factors to influence the water quality of river,with the implementation of interception project,which had effective control of exotic pollution sources in Guangzhou section of the Pearl River.We investigated Cu,Pb,Zn,Cr,Ni,Cd,Hg and As contents,distribution characteristics and potential ecological risk in the surface sediments in Guangzhou section of the Pearl River.The results showed that heavy metal appeared inverted "W" on longitudinal distribution characteristics in the trunk stream.Huadi Stream is the highest,Wu Stream is the lowest,and other streams are in the middle,for heavy metal contents in sediments in creeks.The space distribution characteristics of these heavy metals are generally in similar pattern.There is a positive correlation among heavy metals(except Hg-Cd,Hg-Cr,Hg-As),especially between Cr-Cd,Cu-Cd,Cr-Cu and Cr-Ni,which shows heavy metals have the same distribution tendency in surface sediments.The potential ecological risk of heavy metals in the surface sediments decreased in the following order:Hg>Cd>Cu>As>Pb>Zn>Cr,indicating Hg is the most important ecological risk factor.According to the analysis of potential ecological risk factor(Eir) and the potential ecological risk index(RI) of heavy metals,it can be concluded that 5#(Huangqi),6#(Huangsha),16#(The north exit of the Huadi Stream),7#(Hengjiao) and 14#(The bridge of Zengbu)are the most polluted sites.