Abstract:

Riverine sediment cores of the Hanjiang River tributaries and corresponding river mouths in the upper reach of the Danjiangkou Reservoir were taken to analyze the sedimentary heavy metal contents at vertical profile,then environmental risk of those metals was assessed by using both effects limits (the standard of New York state department of environmental conservation,NYSDEC) and Lars Hkanson potential ecological risk index.The results showed that contents of Cd,Cr,Cu,and Zn in the sediment cores from the river mouth were 186,2712,9991 and 4783 mg/kg,respectively,which were at least 2 times than those in the Hanjiang River tributaries.According to NYSDEC guidlines,contents of Pb in the surface sediments (010 cm) were below LEL (Lowest Effect Level) value,and it was between LEL and SEL (Severe Effect Level) value for Cd,as well as for Ni.However,contents of Cr,Cu and Zn in certain layer of surface sediments exceeded their respective SEL values,indicating severely sedimentary pollution. Enrichment factors for Cd,Cr,Cu and Zn in surface sediments were 712,180,163 and 284,respectively.Correlation analysis revealed that Ni and Pb were originated from natural sources,while Cd,Cr,Cu and Zn were mainly influenced by anthropogenic activities.Compared to the background values of the Danjiangkou Reservoir,the studied heavy metals in the surface sediments had a high ecological risk in sequence as follow Cd ＞ Cu ＞Cr＞Zn＞Pb