Heavy metal enrichments in the Changjiang (Yangtze River) catchment and on the inner shelf of the East China Sea over the last 150 years.

Compositions of heavy metals including Cu, Zn, Cr and Pb in three sediment cores recovered from the lower basin of the Changjiang (Yangtze River) and the inner shelf mud of the East China Sea were analyzed by traditional X-ray florescence (XRF) and XRF Core Scanner. This study aims to investigate the accumulation of heavy metals in the fluvial sediments and to decipher the influence of anthropogenic activities within the large catchment over the last 150 years. The data suggest that the heavy metals, especially Pb and Zn, show obvious enrichments in concentrations since 1950s, and the small and consistent variations of heavy metal concentrations before 1950s can represent geochemical background values. After removing the grain size effect on elemental concentrations, we infer that the sources of heavy metals predominantly come from natural weathering detritus, while human contamination has increased over the last half century. The calculations of both enrichment factor and geoaccumulation index, however, indicate that the pollution of these heavy metals in the fluvial and shelf environments is not significant. The rapid increase in human activities and fast socioeconomic development in the Changjiang catchment and East China over the last five decades accounts for the enrichments of heavy metals in the river and marine sediments. The inner shelf of the East China Sea, as the major sink of the Changjiang-derived fine sediments, provides a high-resolution sediment archive for tracing the anthropogenic impacts on the catchment.