中文摘要：

2003年7月中小潮期间使用Midas-400型边界层探测仪在江苏大丰潮滩的细砂滩上对悬沙浓度进行了六层位垂向同步观测，根据实测资料分析了悬沙粒径组成和悬沙浓度的时空分布特征。结果表明，Midas-400型边界层探测仪在测量悬沙浓度时具有较高精度，浊度计的平均测量误差介于±7％。观测期间悬沙粒径组成十分稳定，时空变化很小，悬沙物质来源是影响悬沙粒径组成的主要因素。悬沙颗粒细，粉砂和粘土是悬沙的主要成分，两者含量之和大于99％。悬沙颗粒在垂向上混合充分，Rouse公式能够比较准确的模拟各水层的悬沙浓度。悬沙沉降速度为悬沙中值粒径静水沉降可能速度的22—28倍，絮凝沉降可能是影响悬沙总体沉降速度和悬沙浓度垂向分布的决定性因素。悬沙浓度的垂向分布也可用对数形式表达，根据两个水层的悬沙浓度具有的对数分布关系可以比较准确的模拟其他水层的悬沙浓度。

英文摘要：

A Midas - 400 system for boundary layer data collection was deployed at a site on the lower tidalflat of Dafeng, northern Jiangsu, in July 2003, to measure suspended sediment concentrations at 6 levels above the seabed. For in-situ calibration, water samples were collected at the site of measurements. The results show that the instrument is suitable for high resolution measurements for suspended sediment concentrations, with an average measurement error of ± 7 %. During the period of measurements, spatial and temporal variations in grain size distributions of suspended sediment were small, which were related mainly to the source characteristics of the suspended material. The content of silt and clay accounted for 〉 99 %. Suspended particles were well mixed within the water column. In addition, the suspended sediment concentration can be derived accurately on the bases of the Rouse equation. The settling velocity of suspended sediment is around 22 - 28 times of the values calculated using the Stokes equation. The flocculation was the major factor affecting the settling of the bulk sediment and the vertical distribution pattems of the concentration. Further, the suspended sediment concentration profile can be expressed by a logarithmic equation. Based upon the logarithmic relationship established using suspended sediment concentration data of two different levels, the concentration of other levels above the bed can be estimated with a moderate accuracy.