End-member characteristics of sediment grain size of modern Yellow River Delta sediments and their response to channel shifts and human activities

Yellow River Delta sediments record environmental changes in the Yellow River basin at long time scales, and respond sensitively to natural and human activities such as river diversions and reservoir construction in the basin. We analyzed the grain size distribution of core YDC from onshore delta since 1976 near the river mouth were analyzed using a parametric end-member analysis model. Results show that EM1 and EM2 are composed of fine-grained clay and fine powder sand, deposited under weak hydrodynamic conditions for long distance transport in the Yellow River, while EM3 and EM4 are coarse powder sand fractions, deposited by wave and tidal action under stronger dynamic conditions. By comparing the data on channel alteration and human activities, and combining data from previous studies on sedimentation rates in the Yellow River estuary, we found that significant changes in grain size characteristics could be used as reference points for sediment age determination. The grain size parameters and end element data reflect the natural and human activities since 1976, such as the diversion of the Yellow River from Qingshuigou to the sea, the construction of the Longyangxia Reservoir, and the diversion of the Yellow River from Qingbacha to the sea. This study provide a reference for the management of the Yellow River Delta estuary and coastal engineering construction, and a scientific basis for ecological protection and high-quality development of the Yellow River basin.