GAIN SIZE VARIATION AND ITS INFLUENCING FACTORS IN THE SEDIMENT CORES OF YALU RIVER ESTUARY

The gain size parameters and sensitive components of the core sediments in the Yalu river estuary were analyzed in order to reveal the depositional characteristics under changing dynamic environment. The depositional characteristics in the estuary areas are influenced by both the nature and human activities. ²¹⁰Pb was used for dating the cores. The sediments in the west Yalu River channel are dominated by mud and sand under the action of tidal current, and the vertical variation of gain size parameters is small. The cores in western tidal flat of the estuary, controlled by tide and wave, contained shell fragments, and the' gains became coarser from certain depth to the surface. The variation of the sediments characteristics in the Yalu river estuary was mainly affected by the variations of water and sediment discharges induced by human activities in recent decades. The wavy characteristics of the core sediments indicate the unstable feature of the river before 1941. Due to the decrease in both the sediment and water discharges, the sandy sediment had been decreasing and instead silt component increasing during the period from 1941 to 1970(1980). The grain composition and sensitive components remained stable during the period of 1970(1980) and 1990 since the sediment and water flux had little change. However, with the further decreasing of the sediment flux, the trend of sediment coarsening upwards have been recorded near the Yalu River mouth after 1990.