The grain-size characteristics and sediment mixing pattern of surface sediment from the western Bohai Bay, China.

135 samples were collected from the western Bohai Bay, a shallow semi-enclosed embayment in western part of Bohai Sea, to examine the surface sediment in grain-size characteristics. The surface deposits exhibit 4 main sedimentation types, respectively sand, silty sand, sandy silt and clayey silt. From northeast to south along the coast, surface sediment gets finer from sand, silty sand to sandy silt, and to clayey silt. And from northeast to north area, the grain size frequency distribution shows the coarser population decreases in content and changes from single mode to main or second mode gradually and is almost absent in south area. While the finer population changes following an opposite trend. The grain size parameters reveal a variable degree of mixture between coarser- and finer-grained hydrodynamic populations along the seashore. The sediment mixing pattern is probably associated with the two-way sediment transportation, caused by the complete changes of coastal circulation directions in different seasons.