南极典型地区湖泊沉积物中脂类生物标志物及同位素地球化学研究

发布时间：2018-08-30 12:03

【摘要】：南极地区是研究气候变化和生态环境响应的重要场所。湖泊沉积物由于具有相对高的分辨率和良好的年代序列被认为是重建气候和生态环境变化的可靠载体。生物标志物和单体碳同位素等有机地球化学指标在南极古环境研究中应用广泛。南极地区湖泊沉积物中生物标志化合物的种类、含量、分布特征以及碳同位素组成特征可以很好地指示环境中有机质输入状况和沉积环境的变化,同时也可以重建研究地区生态环境演化历史。本研究主要选取东南极罗斯海地区生物粪土沉积物、西南极菲尔德斯半岛和东南极拉斯曼丘陵湖泊近表层沉积物,以及保存较好的生物残体和一些环境介质样品,通过有机生物标志物和碳、氮同位素地球化学等方法,从历史的角度探讨南极典型地区湖泊沉积物中脂类生物标志物和碳、氮同位素地球化学分布特征及其所反映的气候和生态环境变化信息。涉及的主要研究内容和得到的主要研究结果如下:1.南极湖泊沉积物长链烷基脂质有机地球化学分析湖泊沉积物中一般存在具有较强奇偶优势的长链(C24)烷烃和较强偶碳优势的长链烷酸,传统观点认为长链烷基脂质主要来源于陆地维管植物,是植物叶蜡的主要组成部分。由于全球大部分环境中都存在高等植物,许多科学研究很难发现沉积物中非维管植物的脂质来源。南极地区气候环境恶劣且缺乏维管植物,因此可以成为研究非维管植物脂质来源的有利场所。通过对东南极大明湖和南极半岛长湖湖泊沉积物中脂类化合物及其单体碳同位素分析,并与南极各种环境样品的脂质分布及其单体碳同位素特征开展了对比分析,研究结果发现两个湖泊沉积物样品(大明湖和长湖)中都存在大量的长链烷基脂质,南极半岛长湖沉积物长链烷基脂质主要来源于苔藓和地衣的贡献,但大明湖周围苔藓地衣分布稀少,因此该湖泊沉积物中检测到的长链脂质可能有其它来源。样品的单体碳同位素值也证明了大明湖沉积物中长链烷基脂质主要来源于水生环境,最有可能是源于水体中的微生物(真菌和细菌)或者是微生物对湖藻来源的有机化合物产生改造作用的结果,而维管植物对在高纬度的东南极湖泊环境的长链烷基脂质的贡献可以忽略不计。2.东南极蒲福岛地区粪土层脂类生物标志物特征对罗斯海蒲福岛地区粪土沉积物开展了脂肪酸和甾醇等有机地球化学分析,结果表明BI沉积剖面中脂肪酸以短链C16和C18为主峰,短链主要来源于湖泊藻类和生物粪便输入。醇类以粪便甾醇为主,将胆甾烷醇和异构粪甾醇含量分别作为企鹅和海豹数量的替代性指标,重建了历史时期企鹅和海豹的数量变化,结果表明在1680-1770 AD和1860 AD-至今两个时期企鹅和海豹的数量都有所增加,而海豹的数量变化相对而言更为剧烈。植物甾醇和叶绿素a在深度剖面上的变化趋势与企鹅和海豹种群数量变化相似,表明采样点周围生物活动与湖泊水生生态系统的发育具有密切关联。生物粪的输入为水生藻类的生长提供营养物质,促进藻类进一步生长。3.东南极难言岛湖泊沉积物有机碳同位素特征及其生态环境意义我们对东南极难言岛两个沉积柱IIL9和IIL1以及水生藻类等环境介质样品进行了总有机碳(TOC)、总氮(TN)和有机碳同位素(δ13Corg)分析,结果表明IIL9沉积物δ13Corg值在-14.6%～-11.6‰之间变化,平均值为-13.4‰(n=48),明显高于IIL1沉积物有机碳同位素值(-23.2‰20.4%‰,平均值为-21.8‰)(n=55),表明两根沉积柱的有机质来源不同。因此,有机碳同位素可以有效区分难言岛地区水系沉积物的有机质来源。将IIL9和IIL1沉积物δ13Corg值与南北极不同来源的有机质和湖泊沉积物δ13Corg数据进行比较,结果表明IIL9沉积物的有机质主要来源于藻类,而IIL1沉积物中低δ13Corg值表明了沉积物受企鹅粪便输入的影响较大。根据有关文献报道,并结合研究区的自然环境背景,我们认为IIL9沉积物中高δ13Corg值可能是由于水生生态系统中光合作用效率高而在水体中形成二氧化碳扩散限制环境,导致更多的13C被藻类同化吸收。IIL9沉积剖面中δ13Corg与TOC和TN的变化呈显著正相关,初步推断IIL9沉积物中的δ13Corg值与湖泊初级生产力的变化相关,较高的δ13Corg对应于更多的水生藻类生长,因此δ13Corg值可以用作指示初级生产力的变化。4.东南极罗斯岛Cape Bird地区生物粪土沉积物中脂类生物标志物及其单体碳同位素地球化学特征南极企鹅和海豹对气候变化的响应具有一定的差异性。我们对罗斯岛Cape Bird地区沉积物中保存的古海豹毛进行了形态学统计分析,发现在采样点附近活动的海豹种属主要是象海豹。通过对Cape Bird地区古海豹毛和粪甾醇的分析表明在1280-1660 AD时期,海豹曾生活在此处,该时期是海豹生存的适宜期晚期。同时发现在维多利亚地南部Marble Point地区在约2.7 Ka BP存在象海豹适宜期早期。Cape Bird地区生物粪土沉积物中脂肪酸的分布特征以短链C16和C18为主峰,推测研究的沉积剖面中有机质主要来源于生物粪便和藻类等植物残体的输入。脂肪酸单体碳同位素值范围在-34.7～-28.5‰之间,在深度剖面上短链脂肪酸单体同位素值与生物粪的输入量具有一定的关联,表明单体碳同位素不仅可以明确地指示沉积物有机质来源,而且有可能应用于古生态变化记录的重建。
[Abstract]:Antarctica is an important place for studying climate change and ecological environment response. Lacustrine sediments are considered as reliable carriers for reconstructing climate and ecological environment because of their high resolution and good chronological sequence. Application of organic geochemical indicators such as biomarkers and carbon isotopes in Antarctic paleoenvironment research The types, contents, distributions and carbon isotope compositions of biomarkers in lake sediments in Antarctica can indicate the changes of organic matter input and sedimentary environment, and reconstruct the evolutionary history of the ecological environment in the study area. Sediments from dung soil, near-surface sediments from the Fields Peninsula in the southwest Antarctica and lakes in the Rasmann Hills in the Southeast Antarctica, as well as better preserved bioremnants and some environmental media samples, were used to study lipids in lake sediments from a historical perspective by using organic biomarkers and carbon and nitrogen isotope geochemistry. Geochemical distribution characteristics of biomarkers and carbon and nitrogen isotopes and their climatic and ecological environmental changes. The main research contents and results are as follows: 1. Organic geochemical analysis of long-chain alkyl lipids in Antarctic Lake sediments. 4) Alkanes and long-chain alkanes with strong carboxylic predominance. Traditionally, long-chain alkyl lipids are believed to originate mainly from terrestrial vascular plants and are a major component of plant wax. Lipids and their monomers in sediments from Minghu Lake and Changhu Lake in the Antarctic Peninsula were analyzed and compared with lipid distribution and monomer carbon isotope characteristics of various environmental samples in Antarctica. The results showed that there were a lot of long-chain alkyl lipids in the sediments of both lakes (Daming Lake and Changhu Lake). The long-chain alkyl lipids in the sediments of the Antarctic Peninsula were mainly derived from the contribution of mosses and lichens, but the distribution of lichens around Daming Lake was scarce. The carbon isotope values of the samples also show that the long-chain alkyl lipids in the sediments of Daming Lake are mainly derived from the aquatic environment, most likely from the microorganisms (fungi and bacteria) in the water or the microorganisms modifying the organic compounds derived from the lake algae, while the vascular plants modifying the organic compounds derived from the lake algae algae at high latitudes. The contribution of long-chain alkyl lipids to the lake environment in Antarctica can be neglected. 2. Organic geochemical analysis of fatty acids and sterols in fecal sediments from the Pufo Island area, Ross Sea, by the characteristics of lipids biomarkers in the fecal soil layer shows that short-chain C16 and C18 are the main peaks of fatty acids in BI sediment profiles. Alcohols are mainly fecal sterols. Cholesterol and iso-fecal sterols are used as alternative indicators of penguin and seal populations to reconstruct the changes of penguin and seal populations in historical periods. The results show that penguin and seal populations were observed in 1680-1770 AD and 1860 AD-to-date. The changes of phytosterol and chlorophyll a in depth profiles were similar to those in penguin and seal populations, indicating that the biological activities around the sampling sites were closely related to the development of the aquatic ecosystem of the lake. Characteristics of organic carbon isotopes in lake sediments and their ecological and environmental implications in the Antarctic Islands. Total organic carbon (TOC), total nitrogen (TN) and organic carbon isotopes (delta 13 Corg) of two sedimentary columns IIL9 and IIL1 and aquatic algae in the Antarctic Islands were analyzed. The results show that the values of delta 13 Corg in IIL9 sediments vary from - 14.6% to - 11.6, with an average value of - 13.4 (n = 48), which is significantly higher than that in IIL1 sediments (- 23.2 20.4, with an average value of - 21.8) (n = 55), indicating that the organic matter sources of the two sediment columns are different. Comparing the delta 13Corg values of IIL9 and IIL1 sediments with the delta 13Corg data of different sources of organic matter and lake sediments from the Arctic and Arctic, the results show that the organic matter of IIL9 sediments is mainly from algae, while the low delta 13Corg values of IIL1 sediments indicate that the sediments are greatly affected by Penguin manure input. According to the literatures and the natural environment background of the study area, we think that the high value of There is a significant positive correlation. It is preliminarily deduced that the variation of primary productivity is related to the delta 13 Corg value in IIL9 sediments. Higher delta 13 Corg value corresponds to more aquatic algae growth. Therefore, the delta 13 Corg value can be used to indicate the change of primary productivity. The response of Antarctic penguins and seals to climate change is somewhat different. Morphological analysis of the ancient seal hairs preserved in the sediments of Cape Bird area of Ross Island shows that the species of seals living near the sampling sites are mainly elephant seals. Analysis of leopard hair and faecal sterols showed that seals lived here during the 1280-1660 AD period, which was the late optimum period for seals to survive. Simultaneously, about 2.7 Ka BP was found in the Marble Point area of southern Victoria, similar to the early optimum period for seals. The distribution of fatty acids in bio-faecal sediments in Cape Bird area was characterized by short-chain C16. The carbon isotope values of fatty acid monomers ranged from -34.7 to -28.5 and the isotope values of short-chain fatty acid monomers correlated with the input of bio-manure in the depth profile, indicating that the carbon isotope values of monomers were mainly derived from the input of bio-manure and other plant residues. It can not only clearly indicate the source of organic matter in sediments, but also be used to reconstruct paleo-ecological records.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X524

【参考文献】