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根据2011年长江口浑浊带枯季悬沙粒度的实测数据分析,发现浑浊带悬沙粒度分布存在明显的时空差异,同时探讨了近20年的粒度变化过程。浑浊带粒度受动力驱动,大潮垂向分布差异显著且粒径较大,中值粒径表层在7μm左右,中层在10~20μm之间,底层在10~25μm之间;小潮期间垂线分布比较均匀且粒径较小,表中底三层中值粒径分布均在3~6μm之间,中值粒径沿水深的垂向分布梯度很小。浑浊带粒度的空间分布特征表现在:浑浊带核心区域,大潮悬沙粒度中约含有30%黏土,70%粉砂,砂含量较少,砂比例垂向上呈增加趋势;核心区悬沙粒度三组分沿水深的分布在大小潮两个时段变化幅度较大,而浑浊带外缘粒度随潮动力的变化幅度不明显。近20~30年间,浑浊带区域的悬沙粒度中值粒径经历了“小-大-小”的变化过程,三组分也同样经历了一个先粗化再细化的过程。
According to the measured data of the suspended sediment particle size in the turbidity zone in the Changjiang Estuary in 2011, it is found that there is a significant spatial-temporal difference in the particle size distribution of the suspended sediment in the turbid zone. Meanwhile, the grain-size change in the past 20 years is also discussed. Turbidity of the turbidity zone was driven by dynamic force. The tidal vertical distribution of the tidal range was significant and the particle size was large. The median surface area was about 7μm, the middle layer was between 10μm and 20μm, and the bottom was between 10μm and 25μm. Uniform and smaller particle size, median bottom three median particle size distribution in the table are 3 ~ 6μm, median particle size along the vertical distribution of water depth gradient is very small. The spatial distribution characteristics of turbidity zone particle size are as follows: the core area of turbidity zone contains about 30% of clay and 70% of silt, the content of sand is small and the proportion of sand is increasing vertically; The distribution of components along the depth of water changed greatly in two periods of large and small tide, while the change of particle size of turbid zone with tidal dynamic was not obvious. In the past 20 ~ 30 years, the median particle size of suspended sediment in the turbid zone experienced a “small - big - small” change process, the three components also experienced a first coarsening and re - refining process.