[Ecological risk assessment of heavy metals in surface sediments in the southern and central Haihe River Basin].

Several heavy metals, including Cu, Zn, Cr, Ni, Pb, and Cd, were investigated at 80 sampling sites in the southern and central areas of Haihe River Basin. The spatial patterns and potential anthropogenic impacts of heavy metals were evaluated by several methods, such as the potential ecological risk index and enrichment factors (EFs). Results showed that, (1) The concentrations of heavy metals in the sediments were higher than the background values in most sites except for Cr, Ni. The concentration of Cd was 2.64 times higher than its background value. Based on the potential ecological risk index for single heavy metal, Cd in river sediments showed a high potential ecological risk while the other elements showed a slight potential ecological risk at most sampling sites. Generally, the decreasing order of the heavy metals was Cd > Cu > Pb > Ni > Cr > Zn. (2) The concentration of heavy metals in surface sediment varied in different regions. The concentration of heavy metals and the potential ecological risks were higher in the Ziya river (RI = 155. 64) and Daqing river (RI = 111.84) than those in the other rivers. For example, slight pollution of heavy metals was found in the Tuhai, Majia river (RI = 69. 54) and Heilonggang river (RI = 84. 50) due to a relatively low level of industrialization. (3) Cd, Pb, Zn, Cr were positively correlated with each other and might be derived from similar sources. The increasing order of anthropogenic impacts on heavy metals was Ni < Cr < Cu < Zn < Pb < Cd according to the calculated EFs. The anthropogenic impacts differed in different rivers. For example, strong impacts were found in the Ziya, Daqing, Yongding and Zhangwei rivers whereas weak impacts were showed in Tuhai, Majia and Heilonggang rivers.