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对青藏高原西南部-南部3个不同气候区9个湖泊的表层沉积物正构烷烃及其单体氢同位素分布特征进行了分析,并与流域植被的正构烷烃和气候要素进行了对比.结果表明,湖泊表层沉积物的n-C23主要来自水生植物,n-C27~n-C33来自陆生高等植物.湖泊表层沉积物正构烷烃n-C27~n-C33平均碳链长度(ACL27~33)与年均降水量正相关.陆生植物来源的高碳链n-C29和n-C31氢同位素比值分布范围分别为-169‰~-214‰和-185‰~-226‰,与年均降水量反相关,但与大气降水的年均-D变化一致,且n-C31的-D值与生长季节(5~9月)大气降水平均-D值相关性较强(R2=0.74).水生植物来源的n-C23的-D值较陆生n-C31偏高(平均约27‰),体现了青藏高原西南部-南部干旱-半干旱地区湖水由于强蒸发作用引起的较大气降水富集-D值的特点.-n-C25~31/p(高碳链表观分馏)平均值为-95‰,较欧洲湿润地区明显偏高(-128‰),其中εn-C31/p约为-116‰(SD=9较恒定,进一步说明湖泊表层沉积物n-C31对于环境变化具有较好的指示作用.
The distribution characteristics of n-alkanes and their monomeric hydrogen isotopes in surface sediments of 9 lakes in three different climatic zones in the southwestern part of the Tibetan Plateau were analyzed and compared with the n-alkanes and climatic elements in the watershed. The results showed that the n-C23 of lake sediments mainly came from aquatic plants, n-C27 ~ n-C33 came from higher terrestrial plants.The mean carbon chain length of n-C27 ~ n-C33 ) Were positively correlated with annual precipitation.The distribution of hydrogen isotope ratios of high-carbon chain n-C29 and n-C31 from terrestrial plants were -169 ‰ -214 ‰ and -185 ‰ ~ -226 ‰, respectively, But inversely correlated with the annual mean-D of precipitation, and the correlation between -D of n-C31 and the mean-D of atmospheric precipitation in the growing season (May-September) was stronger (R2 = 0.74). The D value of n-C23 derived from aquatic plants is higher than that of terrestrial n-C31 (average about 27 ‰), which shows that the water in the southwestern Tibetan Plateau-southern arid-semiarid region is more abundant than the normal precipitation due to strong evaporation Set-D value.-N-C25 ~ 31 / p (high carbon chain apparent fractionation) average of -95 ‰, significantly higher than the wet areas of Europe (-128 ‰), where εn-C31 / p about -116 ‰ (SD = 9 relatively constant, lake further explained in surface sediments having a n-C31 as good indicators of changes in the environment.