长江口南支河槽悬浮颗粒现场粒径特征

The Features of in Situ Particle Size of Suspended Sediment in the South Channels of the Yangtse River Estuary

细颗粒悬浮泥沙的现场粒径特征对于研究沉积物输运有着重要的意义。河口涨落潮槽的水动力有着明显的差异,从而对悬浮泥沙的粒径特征产生重要的影响。2005年3月在长江口南支中部水域利用现场激光粒度仪LISST-100定点连续测量了小潮涨落潮变化过程中表中底部悬浮泥沙的粒径变化,并同时使用ADCP、OBS和观测了水体流速、浊度、盐度和温度,分析了这些因素对表中底部悬浮泥沙的粒径变化的影响。结果表明落潮槽南支主槽内悬沙颗粒粒径高于涨潮槽新桥水道内数值,而悬沙颗粒从表层到底层依次增大。流速基本和粒径呈负相关关系,但在新桥水道由于地形较为复杂,更易产生紊流,使得这里的流速和粒径的关系较为复杂。另外浊度和盐度都会对悬浮颗粒的粒径产生影响,而温度变化的影响不是很明确。总体来说对于长江河口悬浮体颗粒、流速和盐度仍然是最重要的影响因素。

The features of in situ particle size of suspended sedi ment have great significance for researching the movement of sediments. Different hydrodynamic properties exist in flood and ebb-dominated channels and this may cause the different particle size features of suspended sediments. In situ particle sizes of sus- pending sediments are measured using Laser Particle Size Analy- zer （LISST-- 100） in the middle part of South Channel （ebb dominated） of the Changjiang Estuary in March 2005. At the same time, the data of velocity, turbidity, salinity and tempera- ture of water volume were obtained using ADCP, OBS--3A, and CTD respectively. The results show that large current velocity caused small particle sizes of suspended sediments in the ebb channel but these two factors have a complex relationship in the flood channel due to the strong turbulent flow which cause by channel topography. Turbidity, salinity and temperature seem that they play the roles in the size of suspended sediments; how- ever, current velocity and salinity are the most important role in influencing the features of suspended sediments.