湖泊沉积物中正构烷烃和碳同位素的分布特征及其环境意义

Distribution Characteristics of n-Alkanes and δ^(13) C in the Lake Sediments and Their Environmental Significance

正构烷烃碳分子及碳同位素的分布特征在环境领域的应用是目前全球变化研究的热点问题之一.本文以湖泊沉积物为研究载体,综述了国内外利用正构烷烃及碳同位素技术在湖泊及其流域内生物源的识别、植被类型的判断及古植被、古气候的恢复和重建等方面的研究进展.并且以石臼湖流域为例,探讨了运用该技术指示湖泊及其周围流域近现代气候与环境变化的可行性.结果表明:(1)石臼湖沉积物中正构烷烃化合物主要分布在nC23～nC31,呈现明显的奇偶优势;(2)从底层至表层,沉积物中高碳数正构烷烃的相对含量有逐渐减少的趋势,而低碳数正构烷烃含量逐渐增加.据此可以初步推断,近百年来石臼湖流域内的陆生高等植被呈现出相对退化的趋势,而菌藻类和其他水生植物则相对增多,水体富营养化问题逐渐突显,生态环境不断恶化.

In recent years, the application of n-alkanes carbon molecules and carbon isotopic distribution has been one of the hot issues in global change research in the field of environment. This paper summarized the achievements of domestic and foreign utilized the n-alkanes and δ^13C in biological input identification, vegetation type judgment and recovery and reconstruction of paleovegetation and paleoclimate. The climate and environment changes in Lake Shijiu were discussed using n-alkanes and δ^13C. The results show that the distribution of n-alkanes compounds in Shijiu Lake sediments is mainly derived from terrestrial higher vegetations, the most abundant components are nC27 - nC31 , which show a signifi- cant odd-even predominance. Besides, from the bottom to surface, the relative content of long chain n-alkanes in the sediments was decreased while the short chain n-alkanes was increased. It can be inferred that terrestrial higher vegetations in this basin were gradually decreased while algae and other maerophytes were gradually increased over the past century. This indicates that eutrophication phenomenon has highlighted and ecological environment is becoming worse in the Basin of Shijiu Lake recently.