Grain-size Characteristic And Its Environmental Significance Extracted By The Core Sediments In Chaiwopu Lake, Xinjiang

Chaiwopu Lake Basin is selected as the research object. Environmental sensitive grain-size components were extracted by the variations of the grain-size standard deviation and end-member model method to reveal hundred years history of sand activities and environmental changes,which is not only very important to protect and construct Chaiwopu region environment, but also to predict future climate change and dust weather provided the basic data.The conclusions are as follows:(1)Grain-size of a sediment core DC01 is divided into three components by the variation of the grain-sizestandarddeviation,namely:group1(<13.18μm),group2(13.18μm-275.42μm),g roup3(>275.42μm).The average content of the three components is 63.55%, 36.37%, 0.08%respectively.Wherein group1 represent the action of water, group 2 represent the action of wind.According to the content of the two components in the sediments, environmental change can be divided into four phases. The first phase is 2005-2012(0cm-5cm), in which the flow effect is weak and sandstorms activities is frequent. The second phase is 1951-2005(5cm-45cm), in which the fluctuation range of the two components is relatively small and stable.The third stage is the 1917-1951(45cm-70cm), in which the content of group 2 was significantly increased, indicating that this phase is extremely strong sandstorm activity. The fourth stage is the 1901-1917(70cm after), with the content of group 2 decreasing,the dust activities gradually had decreased, while the action of water plays a leading role at this stage.(2) End-member model method results show that:Grain-size of a sediment core DC01 can be reproduced by four end-members(EM1, EM2, EM3, EM4).The EM1, EM2, EM3 represent the sandstorm process, EM4 represent the action of water process. EM1 + EM2 + EM3 can indicate sand active process.And according to content of EM1 + EM2 + EM3 and EM4 in sediment, climate change can also be divided into four stages.The first stage is 2005-2012(0cm-5cm), in which the action of water is weak and sandstorm is frequent.The second stage is 1949-2005(5cm-46cm), in which EM1 + EM2 + EM3 and EM4 content fluctuate more frequent, and there is a tendency among some layers bits. The third phase is 1908-1949(46cm-77cm), EM1 + EM2 + EM3 were significantly increased, indicating a very strong activity in the sand during this period. The fourth stage is 1901-1908(77cm after), in which dust activity decreased, while the action of waterstrengthen.Analysis showed that sand activities recorded by sediment core and historical data are consistent in time. And comparison of two methods to extract environmental information, find that environmental change can be divided into four stages and the various stages is consistency in time. So these two methods to explore the history of environmental change and the sand activities have been verified each other.(3) According to historical periods of climate change and instrumental data on climate in recent 50 years, combined with the strength of the various periods of human activity, explore the mechanism of dust weather occurrence recorded by Chaiwopu lake sediment cores. Considered the first phase of intense sandstorm activity is the result of interaction of climate and human activities. This stage is characterized by warm and dry climate, and the human activities are intense. The second phase of the sand activity showed some fluctuations. The dust weather before the twentieth century 80’s is mainly due to the dry weather conditions, and the sand dust weather in the late 80’s is the interaction result of climate and human activities. The third phase of intense sandstorm activity is mainly due to dry weather.This stage is characterized by warm and dry weather. And there is a good corresponding relationship between the tree-ring reconstruction of the Xinjiang regional climate change and historical records of climate change.And this stage Chaiwopu lake basin is basically no human disturbance. The fourth stage is cold and wet weather, virtually no human interference, sand activities are weak.(4) The results of the regional climate contrast show that: the precipitation and temperature in Xinjiang has a certain intrinsic link,basically havesynchronization. And Chaiwopu region corresponding period of climate change and regions of Xinjiang climate change has consistency, and thus explains the mechanism of dust weather in different periods Chaiwopu region is different.