长江口悬浮体粒度特征及其季节性差异

1998年11月和1999年5月长江口悬浮体样品的激光粒度仪分析结果表明，长江口悬浮体粒度较细，分选较差，偏态和峰态偏小，粒度组成以粉砂为主；粘土含量次之，基本不含砂或砂含量很小，由陆向海平均粒径有由粗到细的变化趋势。粒度分布呈典型的非正态分布，存在“双峰”和“三峰”两种形式，表层样品以“双峰”分布为主，底层“三峰”或“双峰”并存。标准偏差-粒度曲线上多峰出现，反映了长江口悬浮体组成的复杂性。长江口悬浮体粒度特征有较大的季节变化。悬浮体粒度变化的影响因素包括泥沙来源、底质再悬浮、生物作用和絮凝作用，粒度特征的季节差异是这些因素综合作用的结果。

PARTICLE-SIZE CHARACTERISTICS AND SEASONAL VARIABILITY OF SUSPENDED PARTICULATE MATTERS IN THE CHANGJIANG RIVER ESTUARY

Grain size compositions of 78 samples of suspended particulate matter collected from the Changjiang River estuary during November 1998 and May 1999 were analyzed with a Cilas-940L Laser Grain-size Analyzer.The results show that the suspended sediment consists mainly of fine-grained (silt) materials,relatively poorly sorted,with small skewness and kurtosis values; the grain size decreases in the seaward direction.The particle-size distribution curves show bimodal or multi-modal patterns,and several peaks are present in the curves of the standard deviation versus particle size.The correlation between the SPM concentration and the median particle-size is poor,but it is high between the inorganic particle content and D 50,indicating that the terrigenous detritus content of SPM is an important factor controlling the particle size of the SPM.Further,there is significant seasonal variability of the particle-size characteristics.The main factors affecting the variability include sediment sources,tidally-induced resuspension of bottom sediment,biological activity,and flocculation of fine-grained particles.