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

This paper is devoted to the grain-size characteristics of the surficial sediments of the Lake Chenpuhai.Combined with the radiocarbon dating data of 210 Pb,environmental evolution of the lake is revealed.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 origin.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(14.1μm)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 dominated the lake sediments.