珠江口磨刀门泥沙絮凝特征

本文利用激光粒度仪实测得到珠江口磨刀门河口2013年夏季悬浮泥沙现场絮凝及絮凝体特征,同时对比悬沙分散粒径和含沙量,研究表明:悬沙分散粒径平均值为27.9μm,现场实测絮团粒径平均值为91.6μm,表明磨刀门口外的悬浮泥沙絮凝现象显著;实测絮团平均粒径变化范围为13.0~273.8μm,小潮期间絮团粒径平均值为131.5μm,大于大潮平均值76.9μm;絮凝体粒径在垂向上的变化表现为由表及底先变大再变小。絮团体积浓度、沉速与粒径的关系在不同情况下有差异,体积浓度和絮团粒径在表层和中层有明显正相关关系,絮团沉速在大潮时刻随着粒径的增大而增大。综合分析影响絮凝的因素,得知在珠江口盐度对于絮团大小影响不明显;而流速大小的差异是影响大小潮之间絮团大小不同的主要因素。研究结果有助于了解珠江口细颗粒泥沙输移特性和相关生物化学过程。

Observations of in situ flocs characteristic in the Modaomen Estuary of the Pearl River

The Laser In Situ Scattering and Transmissometry-100(LISST-100)was used to the field observation in the Modaomen Estuary of the Pearl River during the July 2013(flood season). Based on the in situ data,we get some flocculation information: the dispersion of suspended sediment particle size is about 27.9 μm,the measured floccules mean diameter is about 91.6 μm,it indicated that suspended sediment flocculation phenomenon significantly. The in situ mean diameter of floc varied from 13.0 to 273.8 μm,the neap tidal floc was larger than spring tide. The variation of floc particle size was decreases at first,and then increases. The relationship between floc diameter and volume concentration,settling velocity were vary from case to case. The volume concentration and particle size of the floccules had positive correlation in surface and middle layer,floccules settling velocity increases with the increase of particle size in spring time. Comprehensive analysis of the factors affecting flocculation,the results show that the salinity have no significant relationship with floccules size,the influence of velocity to floccules had two kinds of circumstances,large flow motion will hinder the development of the floc size. These knowledge will contributes to a further understanding of fine sediment transport characteristics and biochemical process in the Pearl River Estuary.