Variation of participate heavy metals in coastal water over the course of tidal cycle in estuary

Variation characteristics and its mechanism of particulate heavy metals in coastal water over the course of tidal cycle on the eastern coast of Chongming Island in Yangtze Estuary were studied. Concentrations of Cu, Pb, Fe, Mn, Zn, Cr and Al in suspended particles in bottom water were respectively 184%, 99%, 56%, 62%, 147%, 50% and 45% higher than those in surface sediments influenced by particle size. The concentrations of the reducible Cu, Pb, Fe, Mn, Zn and Al in suspended particles of bottom water were also two to three times of those in surface sediments, but percentages of the reducible fraction of the above-mentioned elements in total metal concentrations in suspended particles were similar to those in surface sediments. High concentrations of particulate heavy metals occurred at the beginning of the food-tide, around the slack water and latter of the ebb tide over the course of five tidal cycles, which was mainly caused by the hydrodynamic conditions. When current velocity increased, the particulate heavy metals resuspended from bottom sediments diluted the perpetual suspended particles in water to a large extent. Environmental factors such as salt, dissolved oxygen and pH in water have little influence on the variations of particulate heavy metals over the course of tidal cycle.