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在青海湖不同盐度的四孔近代沉积物岩芯（Ｑ－１６Ａ，ＱＨ，ＱＥ和ＱＧ）（图１）抽提物支链和环烷烃组分中检出了非常丰富的Ｃ２０，Ｃ２５和Ｃ３０高度支链类异戊二烯烯烃（ｈｉｇｈｌｙｂｒａｎｃｈｅｄｉｓｏｐｒｅｎｏｉｄａｌｋｅｎｅｓ），简称ＨＢＩ烯烃。这是在我国近代湖泊沉积物发现这类化合物的首次详细报导。由于Ｃ２０，Ｃ２５和Ｃ３０ＨＢＩ烯烃比正构烷烃具有较强的抵抗生物降解的能力（ＲｏｂｓｏｎａｎｄＲｏｗｌａｎｄ，１９８８ｂ），因此，它们广泛分布于各种近代环境中，如湖泊、海洋和高盐环境的近代沉积物中（ＲｏｗｌａｎｄａｎｄＲｏｂｓｏｎ，１９９０）。并且，具有１～６个双键的Ｃ２０，Ｃ２５和Ｃ３０烯烃经常是现代沉积物中丰富的烃类。最近在印度洋现代沉积物中又发现了一个新的具有７个双键的Ｃ３５ＨＢＩ烯烃（Ｈｏｅｆｓｅｔａｌ，１９９５）。全饱和的Ｃ２０（Ｉ，附图）、Ｃ２５（Ⅱ，附图）和Ｃ３０（Ⅲ，附图）ＨＢＩ烷烃已通过标样的合成确切地确定了它们的结构。在青海湖ＱＧ孔（尕海，咸水）和ＱＥ孔（耳海，淡水）抽提物中发现了Ｃ２０单烯（１号峰，图２ａ）。Ｃ２５烯烃（２号峰，图２ａ、２ｂ）和Ｃ３０烯烃（主要是３号和８号峰，图２ａ、２ｂ）存在?
C20, C25 and C25 were abundantly detected in the branched and naphthenic fractions of four-hole modern sediment cores (Q-16A, QH, QE and QG) C30 highly branched isoprenoid olefins (highlybranchedisoprenoidalkenes), referred to as HBI olefins. This is the first detailed report of the discovery of such compounds in modern lake sediments in our country. Because C20, C25 and C30HBI olefins have stronger resistance to biodegradation than n-alkanes (Robson and Rowland, 1988b), they are widely distributed in various modern environments such as modern sediments of lakes, oceans and high salt environments (Rowland and Robson, 1990). Also, C20, C25 and C30 olefins with 1 to 6 double bonds are often abundant hydrocarbons in modern sediments. Recently a new C35HBI olefin with seven double bonds was found in modern Indian sediments (Hoefsetal, 1995). Fully saturated C20 (I, figure), C25 (II, figure) and C30 (III, figure) HBI alkanes have confirmed their structure by standard synthesis. C20 monoolefins (No. 1 peak, Fig. 2a) were found in QG pore (seawater and salt water) and QE pore (sea and freshwater) extracts from Qinghai Lake. C25 olefins (No.2 peak, Fig. 2a, 2b) and C30 olefins (mainly No.3 and No.8 peaks, Figs.2a, 2b) exist?