中文摘要：

利用高分辨率激光粒度仪MS2000对安固里淖、三台河以及长江等多个地点湖泊和河流沉积物样品细粒部分的粒度多组分分布特征进行了系统、深入研究。总结了其粒度分布特征及组分间差异并讨论了其成因机制。研究认为：1）湖泊沉积物粒度一般由多个组分叠加构成，表现为多组分粒度分布特征，其受控于水动力强度和搬运方式等因素。2）粒度分布最多可有6个组分（中值粒径范围分别为①〈1μm，②2—10μm，③10—70μm，④70～150μm，⑤150—700μm，⑥〉700μm），其中前4个组分属悬浮组分（③组分是流域内风成作用强弱的判别标志），⑤为跳跃组分，⑥为滚动组分，整体分选性差。3）据粒度分布特征可分为湖滨、过渡和湖心三相，三相间粒度分布特征有明显差异，同时又存在此消彼长的良好过渡关系。湖滨相以④组分为优势组分，该组分含量越高，指示沉积物越靠近湖滨；过渡相④组分含量随距湖心距离靠近而减小，但②组分含量却在逐渐增加；湖心相以②组分占主导优势，该组分含量越高，指示沉积物越靠近湖心。4）湖相沉积物受湖滨拍岸浪和湖心波浪的影响而产生了明显的粒度分异规律。

英文摘要：

By using high-resolution laser grain size instrument Mastersizer 2000, the multimodal characteristics of grain size distribution of sediments from the Angulinao Lake （41° 18＇ - 41°24＇N, 114°20＇ - 114°27＇E ）, Santai River （41°18＇N,114°24＇E） ,Changjiang River（32°07＇N, 118°46＇E）,etc. are measured and carefully analyzed. The standard patterns and their grain size characteristics of various sediments are systemically summarized, the discrepancies of multimodal distribution among lake sediments are concluded and the physical mechanisms of grain size multimodal distribution are also discussed in the paper. Major conclusions include： （1） The multimodal characteristic of grain size distribution is a common feature in all lake sediments and is resulted from properties of transportation medium, dynamic intensity, transportation manner and other factors ; （2） There are 6 modes （ median size are 〈 1μm, 2- 10μm, 10 - 70μm, 70 - 150μm, 150 - 700μm, and 〉 700μm, respectively） in grain size distribution of lake sediments. The former 4 are suspending while the others are saltated and roiling; （3） Lake sediments can be divided into three facies： lake shore facies, transitional facies ,and central lake facies. The grain size distributions of the three facies are distinctly different with clear-cut boundaries. In all modes, the third is a criteria to identify windblown deposition in watershed. In lake shore sediments, suspending particles are dominant, a saltation mode sometimes occurs and the fourth mode is the most important one. In the transitional facies, the percentage of the fourth mode decreases and that of the second mode increases from lake shore to central lake. In the central lake facies, the second mode is dominant. A higher content of the second mode indicates its position more close to the central lake; （4） The formation mechanism of grain size distribution in lake is believed to be caused by comber in lake shore and waves in central lake.