The water area of the South Channel is wide,the volume of the water body is large,thedynamics is strong,and the content of suspended sediments is higher.the sediments consist of fine-grained sediments mostly.The water has high capability of transporting,diluting and clearin.The pollutants of the South Channel are absorded mainly by sediments.They go there and back during empting to the sea.They are circularly transported and transported towards bottom,flats,flood channels,and accumulated at the places between the river and the sea.