Vertical distribution of trace elements in the sediment cores from major rivers in east China and its implication on geochemical background and anthropogenic effects

In this study, the overbank and floodplain sediment cores were collected from the lower part of 26 large rivers in east China; 353 samples were obtained from these sediment cores; and the concentrations of 21 trace and major elements were measured for each sample. The vertical distributions of the elements exhibit the following patterns: (1) upper part enrichment; (2) complex distribution; (3) deep layer enrichment; and (4) uniform distribution. The heavy metal concentrations in the upper layer of the majority of the rivers are higher than those in the deep layer. The strong positive correlations between the heavy metals and major chemical components (Al2O3, Fe2O3, and organic carbon) indicate that the heavy metal concentrations are partly determined by sediment properties. The heavy metal concentrations and the Me/Fe values both in the upper and deep sediment layers show regional patterns. The high concentrations of As, Cd, Hg, Mn, Mo, Pb, and Zn in most of the south rivers indicate the importance of natural controlling factors from geological setting and mineralization. Significant enrichment of the heavy metals in the upper layer indicates an anthropogenic impact, particularly in some south China rivers.