Metal distribution and bioavailability in surface sediments from the Huaihe River, Anhui, China

This study presents the total concentrations and chemical fractionations of metals (Cu, Pb, Zn, Ni, Fe, and Mn) in 54 surface sediment samples collected from the Huaihe River (Anhui Province) in eastern China. Compared with the average shale values, Zn and Pb exhibited the most substantial anthropogenic enrichment, especially in Fengtai and Huainan areas, the main industrial districts along the Huaihe River (Anhui Province). Low levels of Cu and Ni were observed in the sediments. Based on risk assessment code (RAC), the metals associated with weak acid soluble (F1) in the Huaihe River sediments followed the order: Mn > Zn > Cu > Pb > Ni > Fe. Manganese presented the most potential for releasing into the aqueous environment and can easily enter the food chain. Copper, zinc, nickel, and iron were found dominant in the residual fraction, implying that these four metals were strongly bound to the sediments. Lead showed a different partitioning pattern from that of other metals studied, with a large percentage in Fe-Mn oxide fraction, indicating that slight redox potential changes may make significant influence on the removability of Pb. Moreover, Cu in oxidizable (F3) and residual (F4) fractions presented high positive correlation with organic matter, which can explain the high percentage of Cu in these two fractions.