长江河口控制站泥沙絮凝特性研究

Study on flocculation characteristics in the Yangtze Estuary

基于2008-2014年逐月现场激光粒度仪(LISST)在长江口徐六泾的定点观测数据,分析了河口控制站徐六泾的悬沙絮凝特性,研究给出絮团粒径与有效密度及沉速的关系。统计表明絮团平均粒径变化范围20~120μm,比分散颗粒中值粒径(平均5.3μm)大一到两个数量级。絮团的分形维数主要在1.8~2.4,有效密度变化范围70~600kg/m^3,其随絮团增大呈减小趋势。洪枯季对比表明,洪季絮团沉降速度比枯季大18%,平均沉速分别为0.26mm/s和0.22mm/s,比以往估算得到的长江口浑浊带絮团沉速小。由此说明为更好认识流域到河口的泥沙输运过程,有必要针对长江河口不同区域进行分段的研究。

Based on the field observations with LISST from year 2008 till 2014 at Xuliujing,the upper part of Yangtze Estuary,flocculation characteristics in the Yangtze Estuary was studied. It was found that mean floc size at Xuliujing ranged between 20 and 120 μm,which was a few to a few ten times larger than primary particle size. Fractal dimension of floc changed between 1. 8 and 2. 4,and effective density of floc varied from 70 to 600 kg / m^3,it decreased with the increase of floc size. Floc settling velocity was between 0. 05 - 1. 2 mm/s,and the average result in wet season was 18% larger than in dry season. Average settling velocity in wet season and dry season were 0. 26 mm / s and 0. 22 mm / s,respectively. Settling velocity in this study was smaller than that estimated in the turbidity maximum of the Yangtze Estuary before. To further understand sediment transportation in the Yangtze,it is necessary to conduct separate research in different areas of the estuary.