By analyzing the content of the heavy metals Zn

Cu

Cr and Pb in the sediment of tide flats with sewage outfall and the control point which has no sewage outfall

some conclusions are arrived. The concentrations of heavy metals in the sediments of all sampling sites including the control point are higher than the environment background values of tidal flat

and the average concentrations of heavy metals are two to three times to the environment background values; The heavy metal concentrations in the sediments of tide flats near the sewage outfalls are higher than those of the control point. The content of heavy metals in the core sediment of each sites changes with the depth regularly to some extent. And also the content of heavy metals in superficial sediment decrease with the distance to the sewage outfall in the LaoGang landfill tide flat. Through the correlation analysis of the heavy metal contents in each sampling site

it is found that the heavy metals of each sites have different sources: the heavy metals in the sediment of tideland with sewage outfall mainly come from the discharge of sewage from sewage outfalls

while the heavy metals in the sediment of the control point mainly come from the input of the natural background or the exterior source transported by the sea water.