Concentrations, speciation, and ecological risk of heavy metals in the sediment of the Songhua River in an urban area with petrochemical industries.

In this study, the pollution status and the ecological risks of heavy metals (Cu, Zn, Pb, Ni and Cr) in the sediments of the Songhua River in an urban area with petrochemical industries were assessed. The highest mean concentration of total heavy metals occurred in the freezing period, and the highest total heavy metal concentrations were observed near the petrochemical industrial area. The geo-accumulation index indicated that Cu was the most contaminated heavy metal. The potential ecological risk index suggested that the total and individual heavy metal concentrations in the sediment were associated with low ecological risk. The speciation and risk assessment code results indicated that these heavy metals in the sediment had potentially low mobility and bioavailability, with non-residual fractions of 35.2% for Cu, 37.46% for Zn, 33.83% for Pb, 24.59% for Ni and 36.04% for Cr based on the total concentrations. These heavy metals in the sediment were exposed to no to medium ecological risks. The principal component analysis results showed that industrial emissions and discharges, vehicular exhaust emissions and residential waste were the primary pollution sources.