长江口枯季悬沙粒度与浓度之间的关系

Relationship Between Suspended Sediment Grain Size and Concentration in the Changjiang Estuary Area During Dry Season

2003和2004年枯季在长江口采集水样并作水文观测,对所获水样进行过滤和粒度分析,以计算悬沙浓度和悬沙粒度分布。结果表明,2003年11月小潮期间,悬沙中值粒径与悬沙浓度存在着显著的指数关系,在大潮期间没有显著关系;在2004年2月小潮期间,两者之间没有显著关系,但在大潮期间存在着显著的指数关系。枯季水体悬沙以粉砂组份为主,并且随着向口外的推移,细颗粒组份逐渐增加,但在拦门沙最大浑浊带附近,由于絮凝作用,沉积物粒度变幅较大,可产生粒径粗化的现象。小潮期间,砂含量较低,但与悬沙浓度之间有显著相关关系;大潮期间,悬沙粒径粗化,但砂含量与悬沙浓度之间的关系不显著。上述分布趋势与沉积物来源、当地的水动力条件和絮凝作用等因素有密切关系。

Water sample collections and hydrographical surveys were made in the Changjiang estuary area in the dry seasons of 2003 and 2004 for obtaining the suspended sediment concentration and grain size distributions. It is shown from the calculation results that there was a significant relationship between suspended sediment median grain size and concentration during the neap tide in November 2003, but there was not a significant relationship between the two during the spring tide; there was not a significant relationship between the two during the neap tide in February 2004, but there was a significant relationship during the spring tide. The main suspended sediment component during the dry seasons was silt, the fine-grained components increased gradually towards the outer of Changjiang estuary , but the variation range of sediment grain size in the turbidity maximum zone near the mouth bar was large due to the flocculation, which made the sediment grain size coarser in the zone. During the neap tide, the sand content was low, and there was a significant relationship between suspended sediment concentration and sand content; during the spring tide, the suspended sediment grain size became coarser, and there was not a significant relationship between the two. The above-mentioned suspended sediment distribution patterns are closely related to the sediment source, local hydrodynamics and flocculation.