Transport and control factors of suspended sediment in Penglai offshore area in summer

Based on the hydrological and sediment observation data in spring tide period in Penglai coastal waters in Bohai Sea in June 2019, we studied the temporal and spatial distribution characteristics of ocean current, temperature, salinity, and suspended sediment, and discussed the transport mechanism and control factors of suspended sediment by using wavelet analysis, single width flux mechanism decomposition, and the Richardson number. Results show that the concentration of suspended sediment in the study area is characterized by a gradual horizontal decrease from Dengzhou shoal to the surrounding sea area, and a gradual vertical increase from the surface layer to the bottom layer. There is a good positive correlation between suspended sediment concentration change and tidal current change with a time lag of 1～2 h. The net sediment transport rate per unit width is 7.84～43.12 g/(s·m). Advection transport plays a dominant role in suspended sediment transport in the study area, followed by vertical net circulation transport. Tidal current is the main driving force of suspended sediment transport. The net transport direction of suspended sediment is consistent with the residual current direction. The suspended sediment in the south of Dengzhou waterway is transported from west to east, while that in the middle of the waterway is transported from east to west, and those on both sides of Nanchangshan Island is transported to the waterway. The stratification phenomenon of some water bodies in the study area is obvious, the mixing of water bodies is suppressed, and the distribution and transportation of suspended sediment are controlled by the tide, the mixing of water bodies, and the topography.