Speciation and risk assessment of Cd, Zn, Pb, Cu and Ni in surface sediments of Dongdagou stream, Baiyin, China

Dongdagou stream accepted treated or untreated domestic wastewater and industrial sewage of baiyin city, which is an important base producing non-ferrous metals in China. Speciation and risk assessment of heavy metals in surface sediments of Dongdagou stream have been investigated based on sediment samples collected from eight locations. Average metal concentrations in sediments decrease in the order Zn>;Pb>;Cu>;Cd>;Ni. Total concentrations of Cd, Pb, Zn and Cu in sediments are much higher than US EPA PEC and EC PEL, indicating that Dongdagou stream is contaminated severely by these metals. Cu, Cd and Zn were mainly controlled by organic fraction, while carbonate fraction were dominant geochemical scavengers for Pb. Ni was mainly controlled by residual fraction. Risk assessment code (RAC) values suggested sediments of Dongdagou stream had high and very high risks to the environment for Cd and Pb in most samples, but with a medium risk associated with Cd at S-4. Sediments are posing low and medium risks for Zn, Cu and Ni, except for Cu at S-8, which has a high risk. Sediments of Dongdagou contaminated by heavy metals need be remedied.