The Characteristic And Ecological Risk Assessment Of Heavy Metal In Sediments From Urban Water System

The paper was focused on the heavy metal pollution in surface sediment from urban lakes and streams within Guangzhou City.The concentrations,distribution and speciation of heavy metals were analyzed to understand the heavy metal geochemical characteristics of sediments under the urbanization background,and their pollution degree and ecological risk were evaluated.Based on above research,the relationship between urban development and environment change of urban water body was explored,aiming to provide basis and reference for preventing water pollution and helping ecological protection and restoration of Guangzhou City.?1?The average organic matter level of lake sediments in Guangzhou ranged from 4.67%to17.00%.The average concentration of organic matter in the sediments of Tianhe Lake was the highest,followed by Luhu and Xiaogang Lake.In contrast,the lowest level of organic matter was recorded in Huadu Lake.As for streams running through Guangzhou City,the average concentration of organic matter in sediments ranged from 2.50%to 12.00%with the highest level recorded in Dajiao river.In contrast,its lowest level was found in Chigang river.?2?The concentrations of Cd,Co,Cr,Cu,Mn,Ni,Pb,Zn in sediments of lakes within Guangzhou City have a range of 0.50?7.55,2.00?22.60,36.00?548.6,30.60?783.4,122.3?2320.0,16.40?167.9,32.50?201.0,71.83?1677.5 mg·kg^-1,respectively,exceeding the background values of soil in Guangdong Province.The values of heavy metals in the sediments of Baiyun Lake,Dongshan Lake,Guangfo River and Jiangwei River were higher.The spatial distribution characteristics showed that the distribution characteristics of heavy metals in water sediments in Guangzhou were related to the distribution of industrial enterprises,while the distribution of heavy metals in sediments depended on the distribution of pollution sources.?3?The BCR sequential extraction procedure was applied to examine the speciation of heavy metals in sediments of Guangzhou.The results showed that the mass fraction of Co,Mn,Ni,Zn,Cr,Pb mainly existed in weak acid soluble fraction,followed by residual fraction.Cu existed in oxidizable and residual fraction,and Cd mainly existed in weak acid soluble fraction.?4?The evaluation results of heavy metal pollution in sediments of Guangzhou indicated that the Pollution of Cd was the most serious,followed by Cu and Zn.Based on the potential ecological risk index,the potential ecological risk index of heavy metals in sediments was more than 600,which was at the serious ecological risk.Among them,Baiyun Lake,Dongshan Lake,Xiaogang Lake,Liwan river,Ma river,Haizhu river,Huangpu river,Guangfo river,Chigang river,Dajiao river and Jiangwei river were all at the extremely serious ecological risk.?5?The results of multivariate statistical analysis showed that the sources of heavy metals in the sediments from lakes and streams within Guangzhou city were mainly contributed from human activities.Cd and Ni were derived mainly from industrial and agricultural activities.Co,Zn,Cr and Pb were mainly from industrial activities and automobile emissions.Cu was mainly derived from Agricultural activities and domestic sewage.