为揭示长江流域泥沙淤积规律和污染物分布特征，基于已有文献资料与三峡库区—长江口原位现场絮凝实测数据，分析了絮团时空变化特征及主要影响因子。絮团时空变化特征观测和分析结果表明：①从三峡库区—长江口均观测到明显的细颗粒泥沙絮凝现象，三峡库区、长江中下游干流、长江口絮团粒径范围分别为22.0~58.0、25.4~101.4、32.6~179.0 μm，洪季絮团粒径从三峡库区—长江口沿程呈现先减小后增大的趋势，枯季长江中下游干流各站（城陵矶—大通）絮团粒径均值大于长江口；不同区域絮团在水体垂线方向的分布存在差异性，汉口站、湖口站粒径从表层到底层逐渐增大。②洪季各区域絮团有效密度差异不大，枯季长江口絮团有效密度大于中下游干流絮团有效密度。③三峡库区、长江中下游干流、长江口絮团沉速范围分别为0.13~0.61、0.30~0.68、0.46~2.32 mm/s，徐六泾絮团沉速从表层到底层逐渐增大。絮团时空变化特征的主要影响因子分析结果表明：对于三峡库区—长江口门而言，较弱的水动力条件、较小的原始分散颗粒、较高的含沙量更有利于絮团形成、发育；盐度对泥沙絮凝的促进作用在长江口较为显著；长江中下游干流部分区域絮凝程度的加深受到有机质的影响。研究成果不仅可以揭示黏性泥沙基本理论和运动规律，而且对长江流域内航道、湖库淤积治理，污染物分布特征及迁移转化探索具有借鉴意义。

[Objective] This study aims to clarify the laws of sediment deposition and the distribution characteristics of pollutants in the Yangtze River Basin. To fill the research gap regarding the spatio-temporal evolution of flocs and their driving factors along the mainstream from the Three Gorges Reservoir （TGR） Area to the Yangtze River estuary， this research systematically explores the variation rules of flocs and identifies their key influencing factors， so as to provide theoretical and practical support for sediment regulation and pollutant research in the basin. [Methods] Combining published literature and in-situ field measurement data of sediment flocculation collected from the TGR Area to the Yangtze River estuary，this paper conducts a comprehensive analysis on the spatio-temporal variation characteristics of sediment flocs.Field observations and statistical analyses are adopted to quantify the particle size，effective density and settling velocity of flocs in different river sections，different seasons and different water depths. Meanwhile，the correlations between floc properties and hydrodynamic conditions， sediment concentration， salinity and organic matter are further discussed to determine the dominant factors affecting floc formation and development. [Results] Obvious flocculation of fine-grained sediment was observed throughout the reach from the TGR Area to the Yangtze River estuary.The floc particle size ranged from 22.0 μm to 58.0 μm in the TGR Area， 25.4 μm to 101.4 μm in the middle and lower mainstream of the Yangtze River， and 32.6 μm to 179.0 μm in the Yangtze River estuary. During the flood season， the floc particle size first decreased and then increased along the river from the TGR Area to the estuary. In the dry season， the average floc particle size at each monitoring station from Chenglingji to Datong in the middle and lower mainstream was larger than that in the estuary. Vertical distribution of floc size varied across regions： at Hankou and Hukou stations， floc particle size gradually increased from the water surface to the bottom layer. There was no significant difference in the effective density of flocs among different regions in the flood season. In the dry season， the effective density of flocs in the estuary was notably higher than that in the middle and lower mainstream. In terms of settling velocity， the ranges were 0.13~0.61 mm/s for the TGR Area， 0.30~0.68 mm/s for the middle and lower mainstream， and 0.46~2.32 mm/s for the estuary. At Xuliujing station， the settling velocity of flocs presented an upward trend from the surface layer to the bottom layer. Weak hydrodynamic conditions， fine primary sediment particles and high sediment concentration were conducive to the formation and growth of flocs along the entire study reach. Salinity exerted a prominent promoting effect on sediment flocculation in the estuary area， while organic matter was a vital factor that intensified flocculation in partial sections of the middle and lower mainstream. [Conclusions] This study quantitatively reveals the spatio-temporal distribution patterns and vertical stratification features of floc particle size， effective density and settling velocity along the Yangtze River from the TGR to the estuary， and clarifies the differentiated controlling mechanisms of multiple environmental factors on flocculation in different river segments. The findings improve the basic theoretical system of cohesive sediment movement in large river basins. Practically， the research results offer important references for the prevention and control of waterway， lake and reservoir sedimentation in the Yangtze River Basin， as well as the investigation on distribution， migration and transformation of pollutants. Furthermore， the differentiated influence rules of hydrodynamic force， salinity and organic matter summarized in this paper can provide a new research perspective for follow-up studies on river sediment dynamics and pollutant migration in similar large river systems.