长江口表层沉积物分布特征及动力响应

Characteristics of Surface Sediment Distribution and Its Hydrodynamic Responses in the Yangtze River Estuary

基于长江口2003年2月采集的58个表层沉积物样品及以同步水动力资料的分析表明,表层沉积物中值粒径自江阴—口外逐渐变细,由江阴附近的217.8!m减少到南槽口外的12.1"m;浑浊带海域表层沉积物中值粒径北港最大,平均为126.2#m,北槽其次,平均为48.4$m,南槽最小,平均为14.2%m;口外海域则北槽最大,为22.4&m,北港其次,为16.5’m,南槽最小,为12.1(m。沉积物分选性大多为中等—很差,中值粒径越大,分选系数越小;沉积物偏度大多是近对称—极正偏;峭度表现为中等峭度—很窄尖。横沙以上区域表层沉积物类型以砂为主,口外海域沉积物类型以粘土质粉砂为主,浑浊带海域表层沉积物类型复杂多样。长江口主槽表层沉积物中值粒径与落潮历时、Ve/Vf值和余流值等动力参数呈正相关关系,落潮动力条件是决定长江口表层沉积物中值粒径大小的主要动力因素。

The analysis results of 58 surface showed that the median diameter of surface sediment samples collected in February 2003 sediment （D50） was decreased gradually from Jiangyin to the mouth of the Yangtze River Estuary, and the value decreased from 217.8 μm of Jiangyin to 12.1 μm of the mouth of South Passage. In Turbidity Maximum, the coarsest surface sediment was in North Channel, and the average median diameter was 126.2 μm. The coarser surface sediment was in North Passage, and the average median diameter was 48.4 μm. The finest surface sediment was in South Passage, and the average median diameter was 14.2 μm. While in the mouth of the estuary, the coarsest surface sediment was in North Passage, then in North Channel, and the finest surface sediment was in South Passage. The median diameter of the mouth of North Passage was 22.4 μm, and that of North Channel 16.5 μm, and South Passage 12.1 μm. The sorting of surface sediment was mainly moderately sorted to very poorly sorted, and the greater the median diameter, the smaller the sorting coefficient. The skewness was mainly nearly symmetrical to very positive. The kurtosis was mesokurtic to extremely leptokurtic. The composition of surface sediment in upper Hengsha island was mainly sand, while in the mouth of the estuary was mainly clayey silt. In Turbidity Maximum, it was much more complex and variational. There was positive relationship between the D50 of surface sediment and the ebb tidal duration, value of Ve/Vf and residual current speed in channel of the Yangtze River Estuary, and the ebb current condition was the main dynamic factor to determine D50.