长江口水域悬沙浓度时空变化与泥沙再悬浮

Temporal and Spatial Changes of Suspended Sediment Concentration and Resuspension in the Yangtze River Estuary and Its Adjacent Waters

根据近年来长江河口及其邻近水域8个测站1年的表层悬沙浓度逐日观测资料,并结合水动力状况,对悬沙浓度的时空变化进行了分析。结果发现,长江口自徐六泾以下悬沙浓度不断增高,并呈现口内夏高冬低,而口外冬高夏低,且量值为口外大于口内,杭州湾大于长江口。表明长江入海泥沙在海洋动力作用下强烈再悬浮;悬沙浓度在时间上呈现明显的大小潮周期和季节性变化。进一步分析认为,海洋动力(风浪和潮流) 是泥沙再悬浮的主导因素,制约悬沙浓度的年内变化,其中潮流控制悬沙浓度的大小潮周期变化,风浪引起悬沙浓度的季节性变化,河流径流和海洋动力的对比制约悬沙浓度的空间分布。

The detailed analysis of suspended sediment concentration variations over a year period is presented from eight observation stations within the Yangtze River estuary and its adjacent waters, combined with hydrodynamic regime of the estuary. Spatially, the suspended sediment concentration from Xuliujing downward to Hangzhou Bay increases constantly, and the suspended sediment in the inner estuary shows higher concentration during summer than during winter, while in the outer estuary it shows higher concentration during winter than during summer, and the magnitude is greater in the outer estuary than in the inner estuary, and greater in the Hangzhou Bay than in the Yangtze Estuary. The sediments from the Yangtze River are resuspended due to marine dynamic actions including tidal current and wind wave. Temporally, the suspended sediment concentrations show a neap-spring tidal cycle and seasonal fluctuations. Furthermore, it is concluded that wind waves and tidal currents are the two predominant factors related to sediment resuspension and control of the changes of suspended sediment concentration, in which tidal currents control the neap-spring tidal cycle, and wind waves control the seasonal fluctuation. The river water discharge and marine dynamics control spatial distribution of suspended sediment concentrations.