Effect of the algal growth in the estuary on enhance of the settlement of suspended particles

研制了水下微视频测定仪，用于测量絮体沉降速度，并将其应用于赤果河河口悬浮物絮体。成功地测定了絮凝体的有效密度。从絮体沉降速度和粒径出发，提出了絮体密度分布函数。絮体密度分布函数随潮汐变化而变化。退潮时，浮体密度小于涨潮时。这说明涨潮时的絮凝体主要由从河床上悬浮下来的泥沙组成。计算了质量沉降通量。当悬浮沉积物中含有藻类或藻类残留物时，沉降速度较低。另一方面，含有高浓度的胞外聚合物（EPS）使得沉降速度高。

Under water micro video scope was developed to measure floc settling velocity and applied to the suspended sediment floc in the Chikugo River estuary. The effective densities of the flocs were measured successfully. The floc density distribution function was proposed from the floc settling speed and their diameters. The floc density distribution function varied with tide. In ebb tide, floc densites were smaller than in flood tide. This fact shows that the flocs in flood tide mainly consists of the mud which was suspended from the river bed. Mass settling flux was also calculated. When suspended sediment contains algae or algal residuals, the settling velocity showed lower value. On the other hand, containing high concentration of extracellular polymeric substances(EPS) made settlement velocity high.