Based on the field observations in April 2012 in the North Passage of the Changjiang Estuary ,as well as the data measured with scanning electron microscope ,the characteristics of flow and sediment ,the micromorphology and size of floccules and the main influence factors in the North Passage were investigated in this paper .The re‐sults show that the tidal current velocity ,the salinity ,the suspended sediment concentration and the sediment parti‐cle size in the North Passage are very suitable for flocculation .There are varied forms of floccules ,mainly including loose floccules ,porous floccules and dense floccules .They are mainly composed of fine silts and clays ,with rough surfaces ,loose or dense structures .The variations of floccule size are highly related to the flood -ebb process , showing periodic features .The floccule size is big during slacks ,but small during peak currents .Usually ,the floc‐cule size during high water slacks is bigger than that during low water slacks;the floccule size during neap tides is bigger than that during spring tides .Additionally ,the floccule size is gradually increased from the surface to the bottom .The tidal current velocity controls the variations of floccule size .The flocculation of suspended sediment is one of the main reasons for the siltation in the navigation channel of North Passage .%利用多种先进室内外测量仪器进行河口现场观测和室内电镜扫描获得相关资料，对长江河口北槽河道细颗粒泥沙絮凝的水沙环境、絮团的微观形态结构、絮团的粒径组成及其主要影响因素进行了综合分析和讨论。结果表明，北槽河道具有非常适宜细颗粒泥沙絮凝的潮流、盐度、含沙量和悬沙颗粒粒径等基本环境条件。北槽河道悬沙絮团形态多样，主要包括松散状絮团、蜂窝状絮团和密实状絮团。絮团主要由细粉砂和黏土类细颗粒泥沙组成，表面多粗糙不平，结构或密或疏。絮团粒径变化与潮周期动力过程密切相关，具有周期性变化特征。涨、落憩时絮团粒径较大，涨、落急时絮团粒径较小。絮团粒径涨憩大于落憩，小潮大于大潮。垂向上，絮团粒径由表层至底层逐渐增大。周期性潮流流速对北槽河道悬沙絮团粒径变化起到了控制作用。北槽细颗粒泥沙絮凝作用，是导致疏浚航道发生回淤的主要原因之一。
展开▼
