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根据准同步观测的悬浮泥沙及表层沉积物粒度、流速、含沙量资料,分析了长江口及临近海域悬浮泥沙在河口的混合过程。长江河口—陆架系统悬浮泥沙中值粒径呈现“细—粗—细”的变化规律,河口上段悬浮泥沙中值粒径为8.9μm,拦门沙海域为10.5μm,陆架区为4.5μm,北支为9.9μm,杭州湾口为5.6μm,泥沙类型为粘土质粉砂。河口上段和陆架区悬浮泥沙与表层沉积物的垂向混合作用较弱,拦门沙区域二者发生强烈的混合和交换,悬浮泥沙在由长江河口向陆架系统输移过程中仅有表层泥沙保留了流域输入的泥沙粒度特征。长江口悬浮泥沙中值粒径与含沙量呈良好的正相关关系,水流的剪切作用是引起拦门沙海域泥沙再悬浮、近底高含沙量和悬浮泥沙粒径增加的主要原因,悬浮泥沙粒径和含沙量的增加主要由粉砂组分的增加引起。2007年长江河口区范围内悬浮泥沙中值粒径比2003年普遍减小11%,含沙量比2003年减小22%,河口上段含沙量对流域来沙减少的响应最为敏感,而拦门沙区的泥沙粒径对流域来沙减少的响应最敏感。在长江流域来沙量减少的背景下,河口拦门沙区域仍能维持较高的含沙量,主要缘于河口系统内部的供沙。
According to the quasi-synchronous observation of suspended sediment and surface sediment particle size, velocity and sediment concentration data, the Yangtze River estuary and the adjacent sea suspended sediment in the estuary mixing process. The median diameter of suspended sediment in the Yangtze River estuary-shelf system showed a variation of “fine-coarse-fine”. The median diameter of suspended sediment in the upper estuary of the estuary was 8.9μm, that of the estuary sand was 10.5μm, 4.5μm, the north branch is 9.9μm, Hangzhou bayou is 5.6μm, the sediment type is clayey silt. The vertical mixing effect of suspended sediment and surface sediment in the upper estuary and shelf area of the estuary is weak, and both of them are mixed and exchanged strongly. Only the surface layer of suspended sediment in the process of transporting from the Yangtze estuary to the shelf system Sediment reserves the sediment particle size characteristics of the watershed. The median diameter of suspended sediment in the Yangtze River Estuary has a good positive correlation with the sediment concentration. The shearing effect of the water flow is caused by sediment resuspension in the estuarine sand area, high sediment concentration in the near bottom and particle size of suspended sediment The main reason is that the increase of suspended sediment particle size and sediment concentration is mainly caused by the increase of silt components. In 2007, the median particle size of suspended sediment in the Yangtze River estuary area was generally 11% lower than that in 2003 and the sediment concentration decreased by 22% over 2003. The sediment concentration in the upper estuary was the most sensitive to the sediment reduction in the river basin The sediment particle size in the barren area is the most sensitive to the decrease of sediment in the basin. Under the background of the decrease of sediment in the Yangtze River Basin, the sediment concentration in the estuary can still maintain a relatively high sediment concentration, mainly due to the supply of sand inside the estuary system.