新疆博斯腾湖表层沉积物粒度空间分布特征

Spatial Distribution of Grain Size Composition of Surface Sediment in the Bosten Lake Region,Xinjiang

结合数理统计学方法,通过对新疆博斯腾湖表层沉积物的粒度组成、粒度参数、粒度频率曲线等粒度特征的分析,探讨湖泊表层沉积物的粒度空间特征及其影响因素。结果表明：在博斯腾湖表层沉积物粒度组分中,细粉沙质（4~16μm）组分为优势粒级,含量为19.2%~62.1%,平均值为40.1%。粒度组成空间特征总体表现为：以湖泊西北角为中心的环状分布,表明受清水河、黄水沟等的影响以及顺反时针环流的影响,由西北部向西南部和东南部延伸,细颗粒组分含量逐渐增加,粗颗粒组分含量逐渐减少,南岸堆积大量黏土组分。沉积物样品可分为两类,指示不同湖区的沉积环境：（1）开阔湖区：沉积物粒度频率曲线虽以多峰为主,但是形状大体一致,存在显著的众数粒径为6~20μm的主峰,在500μm和1μm左右各有一个低峰,为负偏态,表明沉积物处于悬移搬运作用为主的静水低能沉积环境;（2）河口区：沉积物粒度频率曲线为多峰型,表现为众数粒径为70~100μm的主峰,部分还存在2~10μm的次峰,以及在500μm和1μm左右各有一个低峰,表明此区处于滨岸湖浪和河流混合作用的高能沉积环境。通过分析粒度特征的空间分布,揭示不同湖区的现代沉积环境和水动力条件的差异,为进一步研究湖泊污染物输入、扩散等反映现代生态环境的研究提供科学参考。

In this paper,the spatial distribution characteristics of grain size and its affecting factors were discussed by using the mathematical and statistical methods and analyzing the characteristics of the composition,parameters and frequency curves of grain size of surface sediment in the Bosten Lake region,Xinjiang. The results revealed that the fine silt composition was dominant in surface sediment in the lake region,and its content varied in a range of19. 2%-62. 1% with an average of 40. 1%. The surface sediment was holistically in a concentric-ring distribution centered on the northwest area,and extended from the northwest area to the southwest and east areas under the effects of the Qingshui River,Huangshui Stream and clockwise or counterclockwise circulating flow. With the increase of distance from the circle center,the content of fine particles increased but that of coarse particles decreased,gradually,and much clay deposited on the south bank. The results of cluster analysis showed that the sediment samples could be divided into two classes,indicating the different deposition environment：（1） In the broad lake region,the grain size frequency curves of surface sediment were mostly multimodel,but their shape was similar,the high peak was dominated by the particles with moderate diameter of 6-20 μm,and the low peaks were dominated by the particles of 500 μm and about 1 μm respectively,and they were in a negative skewness,showing a hydrostatic and low-energy depositional environment in the suspended transportation of the particle;（2） In the estuary area,the grain size frequency curves of surface sediment were multimodel,the high peak was dominated by the particles with diameter of 70-100 μm,and even there was a secondary peak dominated by the particles with diameter of 2-10 μm,suggesting a high-energy deposition environment under the mixing effect of lake wave and river water.Through analyzing the spatial distribution of grain size of surface sediment and its affecting factors,the modern sediment environment and the hydropower conditions in the different lake areas were revealed,and the results could be referred for researching the ecological environment in the lake region.