Analysis Of Pyrolysis Products In The Sediments Of Lake Yiheshariwusu,Inner Mongolia,and Paleoclimatic Relations In The Last 2000

In recent years,paleoclimatologists have used various methods to extract paleoenvironment and climate change information from different geological carriers,providing background for predicting future environmental and climate changes.Closed inland lakes in Inner Mongolia of China provide a good vehicle for studying the evolution of high-resolution paleoclimate.The molecular markers in lake sediments can provide more accurate information for recording the sources and changes of biological wood,and they can be stored for a long time in the degradation of organic matter,providing a powerful tool for studying the evolution of paleoclimate.Conventional gas chromatography can only analyze small-molecule compounds that are dissolved in organic solvents.Through the combination of thermal cracking technology and gas chromatography/mass spectrometry,the samples extracted by organic solvents can be passed through a transient high temperature to make natural lignin,cellulose,etc.The molecular compounds are cleaved into lower molecular weight compounds suitable for analysis while also releasing bonded lipids.Analysis of core sediments(after extraction of organic solvents)in lakes of Yihe and Saiwusu in Inner Mongolia by thermal cracking-gas chromatography/mass spectrometry.The main cracking products include n-alkanes,olefins,phenolic compounds,aromatic compounds,cesium,and methyl groups.Ketones,etc.In this dissertation,we studied the characteristics of the distribution of n-alkanes and1-alkenes with time and depth by investigating the sediment samples from Lake Izu and Lake Wusu in Inner Mongolia.The obtained data were analyzed by factors,and the results of factor analysis were compared with previous studies.Comparing the results,it was found that the four factors that contributed the most could indicate dust weather,plant input,temperature,dry and wet climate factors,respectively.Using the obtained indicators to reconstruct the climate change in Inner Mongolia in the past 2000 years.Combining the climatic significance of biomarkers,the local palaeoclimate was reconstructed:from 2000 to 1460,the frequency of dust-falling events changed greatly,but overall it showed a decreasing trend.The overall temperature did not change significantly,and the wet and dry changes drastically.The cold and dry climate may be around 1950-1750;the dust-falling and warm-wet climates have basically stabilized and have not changed much since 1460-700 years ago, and the temperature is low around 1460--700 years or so higher;700-100 years ago,dust events increased slightly,but not obvious,the temperature is low,dry cold-warm and humid climate change is not.This result corresponds well to several major climate change events in northern China: Drak ages,the medieval warm period,and the Little Ice Age in the Ming and Qing Dynasties.