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1.
浙江长兴更新世红土中的分子化石及其古环境意义   总被引:9,自引:2,他引:9  
利用GC/MS从浙江长江更新世红土中检测出种类繁多但含量甚微的分子化石,主要包括正构烷烃、长链三环萜、五环三萜、一元正脂肪酸、正脂肪醇、正烷基-2-酮等系列。红土中的这些分子化石,特别是正构烷烃的特征表明本区的红土是在多水的环境下形成的,并且其上发育了以草本植物为主的高等植被。三环萜烷与三萜烷比值(C23/C30)随地层的变化与红土网纹化程度密切相关,可能具有潜在的古气候指示意义。  相似文献   

2.
类脂生物标志物是古环境、古气候研究中一类常用的生物标志物,其稳定碳同位素性质能反映母源先质的来源以及温度、湿度等信息。在中国,类脂生物标志物分子稳定碳同位素对母源体的指示意义的研究大多局限于现代表层土壤中且存在区域限制性,河流中的研究工作较少。本研究以黄河为例,自2011年6月~2013年7月期间采集了黄河下游东营站12个表层悬浮颗粒物样品,利用13 C同位素确证了不同类脂生物标志物来源的指示意义。其中长链正构烷烃的δ13 C值在两年调查研究中均呈现冬、春季相对偏正,夏、秋季偏负的季节性变化趋势,且与长链正构烷烃CPI25~33值呈显著的线性负相关,显示了正构烷烃受到偏正的烃源沉积岩贡献。长链脂肪酸(n-C28、n-C30)的δ13 C值无明显的季节性变化,且CPIΣ24~32较低,范围分别为-31.4‰~-32.1‰和-31.1‰~-32.2‰,表明黄河悬浮颗粒物中脂肪酸主要来源于中国北部以C3植被覆盖为主的黄土土壤有机质的贡献,受季节更替新鲜植被源贡献较少。短链n-C17烷烃的δ13 C值季节变化明显,在夏、秋季显示出了明显的偏负的水生藻类源信号,而短链n-C16、n-C18脂肪酸在很大程度上受到δ13 C偏正的水体异养微生物的贡献。  相似文献   

3.
随着类脂化合物单体碳稳定同位素组成在古气候、古环境方面应用的不断深入,分辨率更高的类脂化合物单体氢稳定同位素组成开始得到重视。近年来,气相色谱热转换同位素比质谱仪分析技术的发展与应用,极大地促进了依据类脂化合物单体中δD值反演古气候和古环境信息方面的探索。国内外的最新研究成果显示,沉积有机质中类脂化合物单体氢稳定同位素组成与温度有很好的相关性,可以恢复水环境的氢同位素组成,记录大气相对湿度变化,重建一个生态系统的蒸发效应,是一种很具潜力的恢复古气候环境的新手段。  相似文献   

4.
利用GC-MS对红原泥炭样品中的分子化石进行了系统检测,获得了一系列正构烯烃,碳数分布范围为C18—C28,主峰碳为C27,次主峰为C23或C25,与同一深度处的正构烷烃分布模式完全不同。泥炭中正构烯烃的轻重组分∑C21-/∑C2 1、正构烯烃与相应碳数的正构烷烃比值呈有意义的阶段性变化。其中∑C21-/∑C21 与正构烷烃L/H的变化趋势大体一致;而C24:1/C24:0和C23:1/C23:0比值却与之相反。这可能与正构烯烃,特别是这些中碳数化合物因气候如温度的变化在厌氧条件下发生微生物的氢化作用有关,很可能记录了青藏高原东北部地区全新世以来的温度信号。(C26 C27 C28)/(C23 C24 C25)正构烯烃比值,与该区植被分布具有一定的对应关系,说明这些正构烯烃可能除了与植被有关外,也与不同植被类型的组织具有不同抗微生物降解能力相关。这些指标记录的气候信息与前期报道的分子化石记录的气候演化基本一致,说明正构烯烃可以作为古气候的替代性指标。  相似文献   

5.
本文对白令海北部陆坡B2-9站位沉积物岩芯开展了高分辨率的生物标志物分析,获得了研究区近一万年来陆源长链正构烷烃(简写为烷烃)的输入及其源区植被结构的变化等相关记录。结果表明,nC27是烷烃中最高的主碳峰,对烷烃总量的贡献也最大,这可能与源区木本植物的丰度及其分布有关;nC23的含量也较高,可能主要是来源于北半球沿海地区广泛分布的一类沉水植物。全新世期间,烷烃总量分别在7.8 ka B.P.,6.7 ka B.P.和5.4 ka B.P.经历了三次阶梯状的下降过程,呈现出四个相对稳定的阶段,可能主要受控于早全新世海平面上升以及源区气候环境和植被分布的变化。烷烃的分子组合特征各参数(如CPI、ACL以及nC31/nC27等)的变化则表明,烷烃主要来自陆生高等植物,且全新世期间植被结构较为稳定,木本植物占据优势。此外,在几个较短的时期内,烷烃总量及其分子组合特征等参数的变化具有同步性,表明在这些时期特殊的气候条件下,源区木本植物烷烃对烷烃总量的贡献率的增加可能低于草本植物烷烃和化石烷烃。  相似文献   

6.
泸沽湖沉积物正构烷烃分布特征及其古植被意义   总被引:1,自引:0,他引:1  
利用气相色谱-质谱联用仪从泸沽湖沉积物中检测出丰富的正构烷烃系列分子化石,泸沽湖沉积物正构烷烃分布特征可归纳为双峰前峰型和双峰后峰型,说明泸沽湖沉积有机质母质来源为混源。较高丰度的中等长度正构烷烃及Paq和(C15+C17+C19)/(C27+C29+C31)比值等指标指示挺水植物及沉水/漂浮植物等水生植物贡献量较大,同时,也说明较大的内源输入可能是泸沽湖TOC含量较高的原因之一。主峰碳及正构烷烃代用指标(C27+C29)/(C31+C33)比值和ACL指示泸沽湖沉积有机质木本植物输入量占优势,这与现今泸沽湖流域植被类型特征相符。纵向上,(C27+C29)/(C31+C33)比值和ACL没有明显的阶段性和趋势性变化,反映出正构烷烃记录的泸沽湖流域草本植被与木本植被相对变化不明显。不同沉积时期正构烷烃分布特征有所不同。3万年以来泸沽湖流域植被演化特征可以分为3个阶段:30~20cal.kaBP气候偏干冷,沉积有机质母质主要为低等水生生物和藻类,沉水和漂浮植物也有较大贡献;20~5cal.kaBP为相对暖湿的气候环境,陆源高等植被对泸沽湖沉积有机质的贡献增加;5~0cal.kaBP(对应剖面205~0cm)气候有变冷干的趋势,沉积有机质物源以低等水生生物和藻类为主,同时,具有较多高等植物和沉水/漂浮植物输入。泸沽湖流域12kaBP为干冷气候时期,这在时间与气候特征上与YD事件相符,可能是西南季风对YD事件的响应。  相似文献   

7.
北极沉积物中正构烷烃的组合特征及古沉积环境的研究   总被引:8,自引:2,他引:6  
报道了北极楚科奇海和白令海沉积物中正构烷烃的含量和分布类型,并通过因子分析方法对正构烷烃的来源和古沉积环境加以初步探讨.研究结果表明,正构烷烃碳数分布范围多数在nC15~nC33之间,分布类型有两种,第1种高分子碳范围,MH为nC25~nC27,CPI大于1,奇偶优势显著.第2种低分子碳范围,MH为nC17~nC20,奇偶优势不明显.以上特征指示了正构烷烃来源于陆源高等植物和海洋内生两个部分,并且以陆源贡献最大.楚科奇海和白令海大部分测站的Pr/Ph小于1,指示了缺氧还原沉积环境.因子分析结果与样品中正构烷烃不同分子组成特征相互对应.  相似文献   

8.
通过气相色谱-质谱联用仪(GC-MS)和气相色谱-同位素质谱仪(GC-IRMS),分别分析了冲绳海槽南部唐印和第四与那国热液区热液硫化物与热液沉积物中烷烃含量和正烷烃单体碳同位素组成特征。热液产物样品中正烷烃显示出明显的双峰分布,高分子正烷烃显示出明显的奇数碳优势,其丰度最大值位于C31处;低分子正烷烃显示出偶数碳优势,其丰度最大值位于C18处。正烷烃的分布特征以及正烷烃碳同位素组成表明,样品中正烷烃主要来源于热液微生物代谢活动和陆源高等植物的输入,其中,低分子的正烷烃主要来源于热液微生物代谢活动,而高分子的正烷烃主要来源于陆源高等植物。热液硫化物样品中低分子正烷烃含量和比重都高于热液沉积物,表明热液硫化物中热液微生物活动可能更加繁盛。热液硫化物中正烷烃单体的δ13C表现出随碳原子个数增加,同位素值减小的趋势,暗示该区非生物合成有机质的贡献可能不能忽略。  相似文献   

9.
长江三角洲的CM和HM孔揭示了冰后期以来的河床相、河漫滩—河口湾相、浅海相和三角洲相的沉积环境。钻孔的有机碳、总氮和有机碳同位素δ13C以及碳酸盐组成在不同沉积相中变化规律不一致,基本上落在现代长江主要支流和干流的沉积有机质组成范围内,而偏离河口地区的表层沉积有机质组成,反映长江流域的高等植被是三角洲冰后期沉积有机质的主要来源,而水生生物有机质的贡献较少。冰后期早期河床相和晚期三角洲相的沉积有机质组成变化要大于中间的河漫滩、河口湾到浅海相沉积。冰后期沉积有机质和碳酸盐组成基本上可以反映冰后期长江流域的古气候变化特征,主要的古气候波动变化与孢粉研究结果相似;但全新世大暖期和古洪水等气候变化事件在沉积有机质组成上的反映不显著。显然,河口三角洲地区由于陆海相互作用强烈,沉积地层不连续,且沉积有机质来源比较复杂和沉积环境变化大,运用全岩有机元素和有机碳同位素以及CaCO3组成指示古环境有相当的难度和多解性,需要寻找更敏感与可靠的古气候与古环境的替代指标。  相似文献   

10.
单体分子放射性碳同位素分析(CSRA)是近十几年来发展起来的一项新兴的分析手段,将所需的单体分子(生物标志物)从复杂的环境样品基质中分离并富集,再进行加速质谱仪(AMS)的放射性碳(14C)测定。这种分子水平的放射性碳同位素测定技术能够揭示出总有机质同位素组成的异质性,为解释有机碳的来源、迁移和转化等提供了新型的手段。在海洋科学研究中,单体分子放射性碳同位素分析已应用于计算碳在全球各储库的逗留时间并揭示和定量估算化石源有机碳的输入、指示沉积物的搬运过程、示踪微生物的代谢途径、改进沉积物年代学等;在环境科学研究中,单体分子放射性碳同位素分析可用于有毒物质(如多环芳烃)的源解析,示踪有机污染环境中微生物的代谢途径等。伴随着单体分子分离技术的改进及AMS灵敏度的提高,CSRA技术的应用会更加广泛。  相似文献   

11.
末次盛冰期(Last Glacial Maximum,LGM)全球低海平面时,巽他陆架大面积暴露,其上的植被类型对于生物多样性演化和全球陆地碳储库有重要影响。但目前植被重建结果仍存在很大争议:一种观点认为LGM时巽他陆架主要分布稀树草原植被,雨林只零星存在于少数区域;而一些数值模拟结果和沉积记录显示巽他陆架上不存在大面积跨赤道的稀树草原,雨林植被仍占主导。LGM时巽他大陆北部可靠的植被记录十分有限。本研究依据靠近巽他陆架北部古河流入海口的沉积物岩芯,利用叶蜡烷烃含量和正构烷烃平均链长指标重建LGM时北巽他大陆的植被信息,结果显示平均链长在22~14.5 kaBP期间出现最大值,推测相对于全新世,冰期时巽他大陆北部草本成分增加。海平面降低使得冰期太平洋沃克环流减弱,呈现类厄尔尼诺状态,导致巽他大陆地区干旱加重,特别是赤道外围区域(南北纬7°以外)降水季节性增强,这种气候状态可能是草本植被成分增多的主要因素。  相似文献   

12.
Ocean Science Journal - The carbon isotopic compositions (δ13C) of n-alkanes in various environmental samples have been previously proposed as suitable fingerprints for assessing the origin of...  相似文献   

13.
The quantitative characterization of carbon isotopes of n-alkanes is commonly carried out in organic geochemical studies. Possible controls on carbon isotopes include source organic matter, maturity, fractionation during oil expulsion and migration, and the mixing of different oils. In this study of the origin of crude oils in the western Pearl River Mouth Basin, the influences of all of these factors have been considered in reaching a conclusion. Carbon isotopes of n-alkanes in the crude oils, and the extracts of the two effective source rocks (the Wenchang and Enping formations) in the basin, exhibit clear differences. The Wenchang source rocks have heavy δ13C values that remain almost constant or become slightly heavier with increasing carbon number. The Enping source rocks have light δ13C values that become lighter with increasing carbon number. Two groups of oils in this area were identified based on the carbon isotopes of the n-alkanes; groupIoils are similar to extracts of the Wenchang source rocks. However, the groupIIoils are different from both the Wenchang and Enping source rocks and the carbon isotopic profiles of their n-alkanes exhibit a “V” feature with increasing carbon number. The results of artificial thermal maturation experiments indicate that, from the early stage to the peak stage of oil generation (with EasyRo between 0.64% and 1.02%), the δ13C values of n-alkanes in the pyrolysis oils become heavier by about 3‰ with increasing thermal maturity, but the shape of the carbon isotopic profiles are not significantly changed. Calculated δ13C values of n-alkanes in “mixed” artificial pyrolysis oils indicate that the mixture of oils generated from the same source rocks with different maturities could not change the carbon isotopic profile of the n-alkanes, however, a mixing of the Wenchang and Enping oils could give the “V” feature in the profiles, similar to the groupIIoils in this area. The groupIIoils appear to be mixed Wenchang and Enping oils, the latter being the dominant component in the mixture. We conclude that the source organic matter and the degree of mixing are the main factors controlling the carbon isotopic characteristics of n-alkanes in crude oils in the western Pearl River Mouth Basin.  相似文献   

14.
本利用长链不饱和酮分子及分子同位素δ^13C来恢复古气候、古溶解CO2浓度和古盐度;说明有机地球化学在全球变化研究中的应用前景。  相似文献   

15.
The East Asian marginal seas are important sinks of terrigenous materials transported by large rivers. In this study two cores from the Changjiang (Yangtze River) and Zhujiang (Pearl River) estuaries and one core from the inner shelf off of Hong Kong were investigated to examine the burial of organic matter during the postglacial period and its possible links with paleoenvironmental changes. Based on a simple two end-member mixing model, the terrestrial organic matter supplied primarily from the Zhujiang and Changjiang dominates the estuarine areas while marine organic matter contributes more to the inner-mid shelf. The competing contributions of terrestrial and marine organic matter are responsible for the downcore variations of organic elemental compositions. The overall decreasing shifts of total organic carbon concentrations and total organic carbon to total nitrogen ratios in the Zhujiang estuarine sediments since 6.5 kaBP seems to support the notion that depth profiles of organic matter compositions deposited in the Zhujiang Estuary can aid in the reconstruction of monsoon history in the Holocene. Nevertheless, organic matter compositions in the Changjiang Estuary and inner shelf off of southeastern Hong Kong respond in a different and more complex way to freshwater discharges or precipitation changes (monsoon variability) in the catchments, owing to complex controls of deposition and preservation of organic matter in these estuarine and shelf environments. Caution is therefore needed in using organic elemental and isotopic compositions to decipher paleoenvironmental changes in East Asian continental shelves where intense river–sea interactions occur and sedimentary environments change drastically.  相似文献   

16.
崂山湾潮间带食物网结构的碳稳定同位素初步研究   总被引:17,自引:3,他引:14  
通过对1993年8月和1994年2和5月在崂山湾潮间带采集的底栖生物碳稳定同位素组成(δ13C值)的分析,发现该区底栖动物的主要食物来源以δ13C值大致可划分为4类:水体中的颗粒有机质(POM)、底栖硅藻、大型底栖藻类和底泥中的有机物质(SOM).研究结果表明,底栖动物的碳稳定同位素组成与其所摄食的食物的碳稳定同位素组成有密切的关系,因此,底栖动物的碳稳定同位素组成可以用于研究其食物来源.碳稳定同位素数据证实,双壳类等滤食性动物的食物来源主要是POM;甲壳动物的δ13C值的范围较大,证明其食物来源的多样性;底栖硅藻是多数腹足类食物来源的相当重要组成部分.用碳稳定同位素示踪剂对该区底栖-水体耦合作用的初步研究表明,水体中的POM是底栖动物的重要食物来源,但底泥中有机质和底栖硅藻也是许多底栖动物食物来源的相当重要的组成部分.  相似文献   

17.
Long-chain n-alkanols and n-alkanes in core sediments from the northern South China Sea (SCS) were measured to make a comparison during terrestrial vegetation reconstruction from ~42 ka to ~7 ka. The results showed that terrestrial vegetation record from long-chain n-alkanes matched well with previous studies in nearby cores, showing that more C4 plants developed during the Last Glacial Maximum (LGM) and C3 plants dominated in the interglacial period. However, these scenarios were not revealed by terrestrial vegetation reconstruction using long-chain n-alkanols, which showed C3 plant expansion during the LGM. The discrepancy during the interglacial period could be attributed to the aerobic degradation of functionalized long-chain n-alkanols in the oxygen-rich bottom water, resulting in poor preservation of terrestrial vegetation signals. On the other hand, the different advantages of functionalized n-alkanols and non-functional n-alkanes to record local and distal vegetation signals, respectively, may offer a potential explanation for the contradiction during the LGM when the SCS was characterized by low-oxygen deep water. Nevertheless, large variations on n-alkyl lipid compositions in C3/C4 plants could play a part in modulating sedimentary long-chain n-alkanols and n-alkanes toward different vegetation signals, thereby suggesting that caution must be taken in respect to the terrestrial vegetation reconstruction using long-chain n-alkanes and long-chain n-alkanols.  相似文献   

18.
Organic matter in cobalt-rich crust(CRC) from the Marcus–Wake Seamounts of the western Pacific Ocean, Sample CM1D03, has been analyzed to understand the source, geochemistry and mineralization of organic matter, and the mineralization environment. Biomarkers, including n-alkanes, isoprenoids, terpanes and sterols, have been detected in various layers of the CRC sample, using gas chromatography(GC) and gas chromatography–mass spectrometry(GC–MS). The content of organic carbon(OC) and its stable isotope(δ13C), and the combined features of the biomarkers show that the mineralized organic matter in CM1D03 CRC was mainly derived from microorganisms and lower plankton(e.g., bacteria and algae, respectively) from marine surface water, with some terrestrial higher plant components. The ratio of chloroform bitumen "A": OC was high in the CRC, between 10.51 and 20.66, showing significant migration characteristics of n-alkanes. Four mineralization categories of organic matter were recognized based on GC chromatograms of n-alkane molecules:(1) primitive type(bacteria and algae), which is characterized by moderately mature of n-alkanes preserving the original characteristics of the organic matter from microorganisms and lower plankton;(2) microbial degradation type, which is characterized by low contents of n-alkanes and rising baseline in the chromatogram, with the "bulge" being the products of organic matter by biodegradation;(3) organic matter migration type, which is characterized by low carbon number of n-alkanes with n C18 as the main peak carbon, without odd even predominance, and low concentrations of isoprenoids and hydrocarbons with high carbon number; and(4) organic matter hydrothermal type, which is characterized by relatively low concentration of small molecular weight n-alkanes, pristane, and phytane, accompanied by higher concentration of n-alkanes with carbon number greater than n C18. This study shows that biomarkers can record controlling factors of mineralization and their variation.  相似文献   

19.
By analyses of carbon isotopic composition(δ13C values) of the benthos collected in the Laoshan Bay in August 1993 and February and May 1994, it is found that the main food sources of the benthos can be divided into four groups in terms of carbon isotope composition: Particulate Organic Matter (POM),benthic diatoms, benthic macroalgae and the organic matter in sediments.The results show that the carbon isotopic composition of the benthic animals has a close relation with that of the food they take in.The carbon isotopic compositions of benthos may be useful in elucidating their food sources.The carbon isotopic data have confirmed that POM is the main food source of the benthic filter feeders such as bivalves; crustaceans have a wide range of δ13C values, showing their food source has diversity; benthic diatoms are an important fraction of the food for most of gastropods.A preliminary investigation of the benthic-pelagic coupling in that region using the stable carbon isotopic tracers has confirmed the importance of POM as a food source for benthos in this region,but the organic matter in sediments and benthic diatoms are also relatively important for a lot of benthic animals.The benthic-pelagic coupling in the Laoshan Bay temperate ecosystem is not so tight as that in ecosystems at higher latitudes such as north-eastern water polynya.  相似文献   

20.
冲绳海槽浮岩中碳、氢同位素组成特征   总被引:4,自引:1,他引:3  
利用分阶段热解释放气体质谱分析法研究了冲绳海槽浮岩热解释放气中CO2和H2O的碳、氢同位素组成,结果显示:浮岩中原生CO2和H2O主要释放于400~1 000℃,CO2的碳同位素组成介于-6.7×10-3~-22.7×10-3,H2O的氢同位素组成从-45×10-3变到-71×10-3,均落入幔源火山岩的变化范围,而且浮岩的氢同位素组成与海槽区玄武岩的氢同位素组成非常接近,这表明冲绳海槽浮岩与玄武岩之间具有密切的成因联系,浮岩岩浆和玄武岩岩浆是同源岩浆不同程度结晶分异的产物.另外,这些浮岩较洋中脊玄武岩要贫13C,并富集D,同时具有从洋中脊玄武岩向岛弧玄武岩变化的趋势,这表明浮岩岩浆在形成或上升过程中可能受到俯冲板块释放流体的影响.  相似文献   

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