Heavy metal compositions of suspended sediments in the Changjiang (Yangtze River) estuary: significance of riverine transport to the ocean

Suspended sediments were collected from the Changjiang (Yangtze River) estuary and analysed to determine heavy metal concentrations (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) during four consecutive cruises between 1986 and 1988, which covered both dry (low water) and wet (high water) seasons over the drainage basin. Riverine concentrations of metals vary within 10–20% during each cruise, and normalization of absolute concentrations to aluminium illustrates a somewhat stable distribution of metals in the estuarine mixing zone. It has been estimated that sediment compositions (e.g. grain-size and mineralogy) relative to hydro-dynamic regimes could account for 80–90% of heavy metal variations along with the spread of fresh water effluents from the Changjiang, and terrigenous sediments disperse for a distance of 250–300 km eastwards over East China Sea shelf regions.