Characterization of grain size distribution of sediments and transport trend analysis in Caofeidian sea area, Bohai Bay

A total of 161 surface sediment samples were collected in the Caofeidian sea area of Bohai Bay and classified, the grain size fractions and parameters were analyzed, the depositional dynamic environments were partitioned using Pejrup's triangular projection map. The Gao-Collins model was used to simulate sediment transport trends. Results indicate that the surface sediments in the study area included sand, silty sand, sandy mud, muddy sand, silt, and clay, of which silt was the most widely distributed, followed by silty sand. The grain size showed a gradient from coarser to finer from northeast to southwest with increased sorting. Two distinct depositional centers were recognized, each with unique sediment transport patterns. The eastern center showed offshore transport in the northern side and onshore transport in the southern side, while the western center exhibited transport to the southwest, west, and north. The material source, topography, and hydrodynamic conditions were the primary factors controlling the materials transport. The depositional dynamic environment in the study area could be divided into three zones on the Pejrup triangle diagram according to the surrounding engineering environmental factors, seabed topography, ocean current and geological background. Material transport was primarily governed by tidal currents, waves, and the Bohai Bay circulation. This study unveiled the modern sedimentary and hydrodynamic characteristics in the southern Caofeidian area, and provided foundational data for research into the changes in the depositional environment after land reclamation in the area.