【摘要】 利用正构烷烃及其碳同位素的分布特征重建古气候环境是目前全球变化研究的热点问题.对采集于石臼湖的沉积物样品进行210Pb定年.采用正构烷烃及单体碳同位素的分布特征示踪沉积物中有机质的来源,探讨湖区近现代生态环境演变与人类活动的关系.结果表明,正构烷烃碳分子组合特征以C29为主峰碳,C25、C27和C31为次主峰,具有显著的奇偶优势,据此推断沉积物中有机质主要来源于大型水生植物及陆生高等植物.对C27、C29和C31长链正构烷烃进行单体碳同位素测定,利用二元模式估算出湖区植被类型以C3植物为主.正构烷烃及单体碳同位素的分布特征揭示了不同时期人类活动对湖区生态环境的影响:1862～1970年,总有机碳(TOC)、总氮(TN)及中低奇数碳正构烷烃(C17～C25)相对含量较低,长链正构烷烃单体碳同位素(δ13C25～31)值偏轻,说明人类活动对湖区环境影响较小,生态环境相对稳定;1970～1983年,TOC、TN及C17～C25相对含量显著增加,δ13C25～31值明显偏重,指示此时期内围湖造田、化肥农药滥用及废水排放等人类活动造成湖区陆生高等植物退化,水体中藻类暴发,湖泊富营养化程度显著提高,生态环境急剧恶化;1983～2010年,TOC、TN及C17～C25相对含量仍处于高值范畴,湖泊富营养化问题没有得到有效控制,湖区生态环境整体呈现相对退化趋势.更多还原

【Abstract】 The study of global changes has focused on the reconstruction of paleovegetation and paleoclimate by n-alkanes and δ13 C.210 Pb contents were measured for dating.The distribution characteristics of n-alkanes and δ13 C were used to indicate the source of the organic matter in the sediments of Shijiu Lake.The relationship between modern eco-environmental evolution and human behaviors was discussed in this paper.The combination characteristics of n-alkanes showed a significant odd-even predominance in high-carbon number and main peak at C29,suggesting that the organic matter in the sediments were mainly derived from macrophytes and terrestrial higher plants.The δ13 C contents of C27,C29 and C31 n-alkanes were analyzed.Results indicated that C3 plants are the dominant species.The distribution characteristics of n-alkanes and δ13 C in different periods revealed the impact of human behaviors on Shijiu Lake.From 1862 to 1970,the low relative content of TOC,TN,C17-C25 and the light δ13 C25-31 values showed that there were less human behaviors effects on Shijiu Lake and the eco-environment around the lake was stable.From 1970 to 1983,the relative content of TOC,TN and C17-C25 increased significantly,the δ13 C25-31values became weight.In this period,large areas of Shijiu Lake turned into farmland;pollution by fertilizers and pesticides was serious;large amounts of industrial and domestic wastewater were discharged into the lake.All these human behaviors resulted in the degradation of terrestrial higher plants around the lake.Meanwhile,the eutrophication levels were significantly increased.From 1983 to 2010,the relative contents of TOC,TN and C17-C25 were still in high-value ranges,the problem of eutrophication was not effectively controlled and the eco-environment of Shijiu Lake was relatively degradated.更多还原