中文摘要：

长江口外海滨地区是陆海相互作用显著的区域，该区域复杂的水流等动力因素和地形条件决定了悬沙分布和扩散的特点。本文利用大量实测资料，对口外海滨地区悬沙的分布特征进行了综合分析，研究结果表明，平面分布不均，西高东低，南高北低，高低相差悬殊是长江口外水域悬沙平面分布的主要特点。枯季自西向东含沙量均匀减小，等值线分布较为稀疏。垂向涨落潮含沙量也表现出不同的分布特征，在口外的中西部水域垂向扩散系数较大，水体垂向混合程度均匀；垂向混合程度加强，水体含沙量也随之显著增加，这也造就了口外的南北两个高含沙区。

英文摘要：

The Changjiang estuary located in the coastal area of East China is the largest estuary of the country. The offshore area is the main place where sediments spread and pile up in the Changjiang estuary, and is also the remarkable area of land-ocean interaction. This paper takes the offshore area of the Changjiang estuary as a study area, utilizes the abundant in-situ data to study the characteristic of suspended sediment under the different water conditions and calculates the vertical diffusion coefficients. The difference of suspended sediment concentration is very remarkable in this area, the transient suspended sediment concentration is low, ranging from less than 0. 1kg/m^3 to over 8 kg/m^3, the different runoff, tidal current, salinity and topography determine the complexity of the spatio-temporal distribution of the sediment concentration. The study result shows that the main features of the suspended sediment are in an asymmetric distribution which presents high concentration in the west and south and low in the east and north. This pattern of the suspended sediment concentration distribution proves that the suspended sediment spreading course is obviously influenced by the runoff and ocean dynamics, the topography of relative function and restriction in the study area. The difference in longitudinal distribution is very remarkable in the offshore area of the Changjiang estuary, the sediment concentration reduces gradually from the west to the east, and it is obviously higher in the spring tide than in the neap tide. Salinity is greater than the density of the silt-contained water, as the diluted water from the upper reaches float above the high-density salt water, and fine sediment deposits in the mouth of the salt wedging. Generally, the suspended sediment concentration increases gradually from surface to bed, because of asymmetric distribution and fluctuation of tidal current velocity, the vertical instantaneous velocity is always changing. So it is very difficult to divide various kinds of vertical d