Comparison of heavy metal distribution and bioavailability in surficial sediments collected in the Songhua River, northeast of China

Five elements (iron, manganese, copper, zinc and lead) in three surficial sediments (SSs) and three natural surface coating samples (NSCSs) from the Songhua River, northeast of China were analyzed with the modified sequential extraction procedure (MSEP) to compare the metal distribution and bioavailability in the two solid phases. The results indicated that Cu was present mainly in the bound to organic matter fraction; Zn and Pb appeared in the bound to Fe oxides dominantly. The dominant proportion of Fe was in the residual fraction, while Mn was significantly in the non-residual fractions. Bound to Fe oxides, bound to Mn oxides were relatively dominating fractions compared with bound to organic matter fraction for the metals of Cu, Zn and Pb. There were much more levels of metals in the non-residual fractions and more bioavailable speciation in NSCSs compared with SSs. The distributions of Cu, Zn and Pb in the residual fraction, Zn and Pb in the bound to organic matter fraction were found significant correlation with TOC, and Pb in the bound to carbonates fraction may be affected by TOC. High positive correlations between the total amounts of Fe/Mn oxides and Cu and Zn in the bound to Fe/Mn oxides fractions, and Cu in the bound to carbonates fraction were also greatly affected by Fe/Mn oxides.