Temporal and Spatial Characteristics of Surface Sediment Grainsize Distribution in Changjiang Estuary

Key words: 
• Changjiang Estuary /
• surface sediment /
• grain size /
• temporal and spatial distribution

Abstract: Based on 558 surface sediment samples collected in Changjiang Estuary recently, the temporal and spatial characteristics of surface sediment grain size were analyzed, and the distribution of D50 and types were obtained, too. The results showed that few changes of the surface sediment grain size in upper Hengsha Island was showed between flood and dry seasons. The grain size in flood season was coarser than that of dry season in the Turbidity Maximum, and in the mouth of the estuary, the grain size in flood season was finer than that of dry season. The types of surface sediment in upper Hengsha Island and mouth of the estuary were changeless between flood and dry seasons, while in the Turbidity Maximum, it was much more complex and various. Whether in flood season or in dry season, the coarsest surface sediment was in North Channel, then in the North Passage, and the finest surface sediment was in the South Passage. Little difference of surface sediment grain size was showed between spring tide and neap tide, and the difference of mean diameter was about 9.7%. The grain size of different years was changed with the Water discharge and sediment discharge of Datong Station. The grain size of surface sediment in upper North Branch, distributary site of South and North Channels and Turbidity Maximum of South and North Passages were much more changeable in the recent fifteen years. These changes were due to the natural channel processes and human activities. The dynamic sediment environment in Changjiang Estuary was divided by Pejrup triangular diagram, and the grain size characteristics of each sediment environment were discussed. Then, the grain size parameters of surface sediment in Yellow River, Changjiang and Pearl River Estuary were contrasted in this paper.