长江河口细颗粒泥沙絮凝体粒径的谱分析

SPECTRUM ANALYSIS OF FLOCS DIAMETER IN THE CHANGJIANG ESTUARY

2003年6月利用现场激光粒度仪(LISST-100)在不扰动的情况下,获取了长江口徐六泾处悬浮细颗粒泥沙絮凝体的现场粒径系列资料,应用谱分析方法研究了絮凝体粒径在大小潮、表底层的变化规律。分析表明,长江口徐六泾处细颗粒泥沙絮凝体粒径存在着明显的变化周期:大潮表层存在7.86h,3.93h和2.95h的变化周期;小潮表层存在8.38h和3.14h的变化周期;大潮底层存在3.33h和1.19h的变化周期。研究认为长江口涨落潮的周期性变化对徐六泾的絮凝体粒径有影响。涨落潮的周期性变化导致流速的周期性变化,流速的周期性变化引起水流紊动剪切力的周期性变化,周期性变化的水流紊动剪切力作用于絮凝体,从而导致絮凝体粒径的变化周期和涨落潮流历时的周期相近。

The temporal change in flocs size of fine suspended sediments was measured in Xuliujin of the Changjiang Estuary in June of 2003, by using an in situ laser diffraction particle sizer, the laser in situ scattering and transmissomerty-100(LISST-100). The spectrum analysis was applied to analyze the fluctu- ation of flocs diameter during the spring tide and the neap tide. The results showed that the quasi-period of flocs diameter in the surface water during the spring tide included 7.86 h, 3.93 h and 2.95 h; those in the same water during the neap tide included 8.38 h and 3.14 h; those in the bottom water during the spring tide included 3.33 h and 1.19 h. The analysis of the quasi-periods of flocs diameter showed that flocs diam- eter was responded to the period of the current velocity, which was fluctuating through the tidal periods. The periodical varying current velocity resulted in turbulent shear changing periodically, which was gener- ated by the current velocity. The periodical turbulent shear changing affected the flocs diameter, so the quasi-periods of flocs diameter was close to that of current velocity.