内蒙古河套地区陈普海子湖泊沉积物粒度特征及其环境意义

GRAIN-SIZE CHARACTERISTICS AND ITS ENVIRONMENTAL SIGNIFICANCE OF LAKE CHENPUHAI SEDIMENTS IN HETAO PLAIN,INNER MONGOLIA

对河套地区陈普海子湖泊及其流域不同类型表层沉积物的粒度特征进行了分析,并结合放射性同位素210Pb测年,探讨了湖泊的沉积演变过程。通过主成分分析,对沉积物剖面粒度不同粒级组分含量进行了研究,分析了湖泊沉积物的物质来源,得到两个主控因子F1和F2,它们控制了湖泊沉积物近98.68%的粒度变化特征。研究表明,F1代表了以6.18μm为众数粒径的次总体,主要受流水作用控制;而F2为以42.75μm为众数粒径的次总体,主要来源于地表风沙作用。通过粒径-标准偏差方法,提取了湖泊沉积物中不同时期的环境敏感粒度组分,结果表明：在1996AD之前,流水作用所携带的细颗粒（〈14.1μm）决定了沉积物的粒级特征,在1960—1985AD期间表现出风沙活动强烈;1996AD以来,由于人类开展了大规模的沙荒土地开垦,流沙活动强烈,流域风沙活动所携带的粗颗粒（14.1~224.35μm）控制了沉积物的粒度组成。

This paper is devoted to the grain-size characteristics of the surficial sediments of the Lake Chen puhai. Combined with the radiocarbon dating data of 210 Pb, environmental evolution of the lake is re- vealed. Primary components of the sediment are used for study of the source of the lake sediment. Two main controlling factors, which account for 98.68%of the sediment, are picked out by statistic analysis. It shows that coarse fraction of the lake sediment is of fluvial origin in addition to fine fraction of eolian ori- gin. Environmentally sensitive grain-size components were extracted by the variation in grain-size standard deviation. The results indicate that before 1996 AD, the fine particle （〈14. lμm） carried by fluvial water dominated the sediments. Severe sand-dust storm occurred during 1960-1985 AD and had brought great impact to the characteristic of the sediment; since 1996 AD, as a result of the human made large-scale land reclamation and strong sand activities, coarse particle （14.1~224.35μm） carried by sand storms domina- ted the lake sediments.