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1.
两种纯化方法获得脂肪酸的链长及碳同位素分布特征对比   总被引：1，自引：0，他引：1  
饱和脂肪酸及其同位素组成是重建古环境和古气候的重要代用指标,目前存在多种提取及纯化流程。在全球变化研究中,基于不同原理的纯化流程得到的脂肪酸含量及其同位素组成是否一致,直接影响着该指标应用于不同区域重建结果的对比。本文用两种常见的脂肪酸纯化流程提取脂肪酸标准、现生植物和泥炭样品类脂物,通过对比发现:对脂肪酸标准两种流程都可以得到纯净的单体脂肪酸,而且回收率均较高(85%以上),都是较为可靠的脂肪酸纯化流程;然而对于天然样品,虽然高碳数脂肪酸(碳数>C24)的回收率相近,流程1却能够获得相对较多的低碳数饱和脂肪酸,如泥炭样品中该流程获得的n-C22脂肪酸是流程2的3倍;两种流程纯化狗尾草(Setaira viridis)和三叶草(Trifolium repens)得到n-C16脂肪酸的δ13C不同,流程1分别为-21.1‰和-36.2‰;流程2分别为-23.3‰和-34.9‰,表明两个实验流程得到的低碳数脂肪酸的含量、脂肪酸链长分布模式以及碳同位素组成均存在明显的差异。实验结果显示,流程2分离纯化样品可得到几乎全部的游离态脂肪酸,而流程1可提纯样品中游离态和酯态存在的总脂肪酸。由于在沉积物中游离态脂肪酸和酯态脂肪酸可以相互转化,因此使用流程1分析样品中的总脂肪酸更为合适,也可以将类脂物皂化使酯态脂肪酸释放为游离态,然后使用流程2。  相似文献   

2.
Models of peat accumulation assume that peat decomposition occurs mostly above the water table, with little or no decomposition once it enters the deeper, saturated, anoxic zone. Few studies have used molecular biomarkers for tracing post depositional, decomposition-related trends in peat deposits. We studied the major diagenetic changes in the phenolic constituents within a Sphagnum-dominated ombrotrophic bog deposit. The yield of lignin-derived phenols and degree of decomposition, measured using alkaline cupric oxide oxidation of bulk peat samples and their corresponding humic acids, revealed that most of the degradation takes place in the surface layers corresponding to the acrotelm. In fact, total phenolic constituents of peat samples decrease from 36.1 to 21.6 mg g−1 OC (organic carbon) over the first 36 cm, whereas in the deeper anoxic layers, phenolic constituents tend to accumulate, reaching a highest concentration of 71.0 mg g−1 OC. The diagenetic alteration of these phenolic constituents during peat accumulation involves significant demethoxylation and an increasing yield of vanillyl oxidation products despite the low redox potential. Syringyl phenols tend to be particularly resistant to diagenetic alteration and are significantly enriched within the humic acid fraction (twofold) with respect to the bulk peat. This, together with the higher degree of oxidation, suggests that this organic matter fraction is enriched in more resistant, but nonetheless diagenetically altered, phenolic constituents. This suggests that humic acids constitute a refractory pool of organic C with a relatively low turnover rate. Our results confirm that the major processes involved in the variation in phenolic constituents with depth are strongly related to the post depositional environment and that evaluation of diagenetic trends in phenolic constituents may provide molecular-level information on the changes that fresh biomass undergoes during early diagenesis in peatlands.  相似文献   

3.
This study aims to attempt a treatment strategy based on fungi immobilized on silica-alginate (biocomposites) for removal of phenolic compounds in olive oil mill wastewater (OMW), OMW supplemented (OMWS) with phenolic compounds and water supplemented (WS) with phenolic compounds, thus decreasing its potential impact in the receiving waters. Active (alive) or inactive (death by sterilization) Pleurotus sajor caju was encapsulated in alginate beads. Five beads containing active and inactive fungus were placed in a mold and filled with silica hydrogel (biocomposites). The biocomposites were added to batch reactors containing the OMW, OMWS and WS. The treatment of OMW, OMWS and WS by active and inactive biocomposites was performed throughout 28 days at 25 °C. The efficiency of treatment was evaluated by measuring the removal of targeted organic compounds, chemical oxygen demand (COD) and relative absorbance ratio along the time. Active P. sajor caju biocomposites were able to remove 64.6–88.4 % of phenolic compounds from OMW and OMWS and 91.8–97.5 % in water. Furthermore, in the case of OMW there was also a removal of 30.0–38.1 % of fatty acids, 68.7 % of the sterol and 35 % of COD. The silica–alginate–fungi biocomposites showed a high removal of phenolic compounds from OMW and water. Furthermore, in the application of biocomposites to the treatment of OMW it was observed also a decrease on the concentration of fatty acids and sterols as well as a reduction on the COD.  相似文献   

4.
氨基酸、脂肪酸对过渡带气、低熟原油形成的意义   总被引：21，自引：4，他引：21  
对草海盆地泥炭、柴窝堡盆地第四系沉积物以及辽河东部凹陷、胜利东营凹陷、苏北金湖凹陷等第三系烃源岩中氨基酸、脂肪酸进行定性、定量分析，并开展热模拟实验。研究表明氨基酸主要赋存于沥青中，分解后可以生成烃类气体和Ｎ２气，对过渡带气的形成可作出贡献。烃源岩干酪根和沥青中的脂肪酸含量不少，沥青中脂肪酸以一元酸为主，具偶碳优势，干酪根中脂肪酸以二元酸为主，不具偶碳优势。沥青和干酪根中脂肪酸脱羧基后产生烷烃，对过渡带气和低熟油都可作出贡献，沥青中脂肪酸是生成低熟油中具奇碳优势正烷烃的主要物源。  相似文献   

5.
杨渭林  向武  汪亦柳  刘煜 《地球科学》2018,43(11):4056-4065
泥炭沼泽是具有全球意义的湿地类型,研究泥炭沼泽源酚酸对铁有机复合体的溶解作用有助于深入了解铁碳耦合地球化学循环过程.以中国东北金川泥炭沼泽为研究对象,提取了泥炭腐殖质,并实验合成了铁有机复合体及一系列的铁氧化物.选择原儿茶酸、咖啡酸和没食子酸等代表性泥炭沼泽源酚酸对铁有机复合体以及铁氧化物等系统开展了不同条件下的溶解试验.结果表明酚酸对无定型的水铁矿和新合成的铁有机复合溶解能力相对较弱,而对结晶态的赤铁矿、针铁矿和老化后的铁有机复合体的溶解能力较强.pH值、酚酸浓度和铁氧化物自身的结构和组成都对铁矿物的溶解作用产生影响.反映了铁有机复合体在酚酸溶液体系中比无机铁氧化物更稳定,这与泥炭沼泽中有机结合态铁比例较高、而普通矿质土壤中结晶态铁氧化物占比更大的事实相吻合.证明了铁有机复合体是泥炭沼泽中影响铁碳循环耦合的关键载体.泥炭沼泽中铁碳作用十分复杂,既能以铁有机络合物形式向海洋等水生生态系统输出大量的溶解性铁,也能通过铁有机复合体的形成促进泥炭沼泽有机碳的保存,进而影响全球铁碳循环耦合,具有重要的生态环境意义.   相似文献   

6.
不同类型沉积物中脂肪酸的分布、演化和生烃意义   总被引：14，自引：2，他引：14  
对近代海洋沉积物、泥炭、福山凹陷第三系泥岩、茂名盆地第三系油页岩和辽河盆地东部凹陷第三系沉积岩剖面等样品中脂肪酸类型和分布特征进行了分析与研究。结果表明以低等浮游动植物为主的沉积中，二元肪酸丰度相对比一元酸占优势。随深程度增加，沥青中脂肪酸高碳数相对减少，低碳数相对增高，偶碳估势逐渐消失。在辽河盆地东部凹陷埋深２２６６ｍ的泥岩中发现脂肪酸仍具有偶碳优势，证明沉积有机质中偶碳脂肪酸优势可以保存到生油高峰前的较高演化阶段，对低熟原油烷烃的生成和具奇碳优势有重要意义。  相似文献   

7.
利用气相色谱-质谱联用仪(GC-MS)系统地分析了阿萨巴斯卡地区Mildred泥炭柱37个样品的脂类化合物,研究了它们的组成特征及可能来源。结果表明,样品中检出的正构烷烃、正烷酮、正烷醛、正烷醇、脂肪酸和脂肪酸甲酯均由高碳数化合物构成,并具明显的奇碳或偶碳优势,GC-MS质量色谱图中甾类和萜类极性化合物呈现显著的高峰。根据泥炭分子地球化学分析,Mildred泥炭柱沉积有机质主要来源于原地堆积的高等植物,苔藓类、水生植物对泥炭有机质也有一定程度的贡献,其中松柏、杜鹃花科等木本植物、莎草科草本植物以及泥炭藓类是主要的成炭植物。萜类和甾类极性化合物的分布存在明显差异,萜类化合物主要集中于剖面的上部,其形成与泥炭藓类植物存在联系;甾类化合物来源不具专属性,多与高等植物的输入有关,也可能是受微生物的改造作用而形成。  相似文献   

8.
A detailed study has been made of the solvent extractable monocarboxylic, dicarboxylic and hydroxylated fatty acids and n-alkanes in a surface intertidal sediment, and the distributions compared to microorganisms cultured from the sediment. Diatoms are shown to contribute most of the monocarboxylic acids, particularly the significant amounts of polyunsaturated acids present, and a small proportion of the n-alkanes. Bacteria contribute between 11 and 14% of the monocarboxylic acids and markers for this, including trans-monounsaturated acids, are proposed. Detritus from the sea-grass Zostera muelleri is a major source of the α-hydroxy-, ω-hydroxy and α,ω-dicarboxylic acids in the sediment and a minor contributor of n-alkanes and long-chain fatty acids.  相似文献   

9.
In order to investigate how lipids in cave water respond to seasonal climate change, drip water samples were collected from 2006 to 2008 in Heshang Cave, central China for fatty acid analysis. These lipids are abundant in the drip water. Their compositions are dominated by lower-molecular-weight nC16:0, nC18:0 and nC14:0 acids, together with mono-unsaturated nC18:1, nC16:1 and nC14:1. Analysis of one water sample revealed marked differences between the dissolved and particulate fractions. The dissolved fraction contains total fatty acids one order of magnitude higher than that of the particulate fraction. The distributional patterns of the fatty acids suggest that microbes living in the overlying soils and/or groundwater system contribute most fatty acids to the drip water. This 2-a monitoring experiment reveals that the abundance of mono-unsaturated fatty acids relative to the saturated homologues (nC16:1/nC16:0 and nC18:1/nC18:0) relate inversely to the changes of synchronous external air temperature. Higher values occur under cold conditions (winter/spring), while lower values appear in warm intervals (summer). Further studies are needed to elucidate the dynamic processes by which the external temperature affects fatty acids in drip water and to confirm the potential application of fatty acid ratios such as nC16:1/nC16:0 and nC18:1/nC18:0 in paleotemperature reconstructions.  相似文献   

10.
《Applied Geochemistry》1993,8(2):127-139
Ligand adsorption on δ-Al2O3 at pH 8 was examined for a series of organic ligands (aromatic acids, monochlorophenols and aliphatic acids) including both monodentate and bidentate ligands. Adsorption isotherms for the aromatic acids exhibited saturation at high dissolved ligand concentrations; saturation was not observed (over the concentration range examined) for the chlorophenols. Small, though measurable, amounts of heat were evolved on reaction of the aromatic acids, the monochlorophenols and propionate (but not of the longer chain fatty acids) with the oxide surface; overall ligand adsorption reactions wereexothermic (ΔHobs < O). For adsorption of (partially or fully) protonated ligands, the favorable ΔHobs was due largely to the exothermic proton transfer reaction between phenolic hydroxyl groups of the ligands and hydroxide ions displaced from the oxide surface. The enthalpy corresponding to the ligand-exchange reaction of surface hydroxyl groups for the various ligands (as fully deprotonated species), ΔHcorr, appeared to be related to the ligand structure. The surface ligand-exchange reaction was more exothermic for the dicarboxylic acid phthalate than for the monocarboxylic acids benzoate or propionate or for salicylate and was endothermic for the chlorophenols.  相似文献   

11.
Contributions by bacteria to recent sediments have been recognized as one important source of input for the extractable lipids. It has, however, proved difficult so far to conclusively relate the components identified to the contributing bacteria. This fact is primarily related to the lack of information on both the lipid chemistry of marine bacteria, and of detailed structures of the sedimentary lipids. In this paper a study of the fatty acids from a tropical marine sediment selected because of its high biomass content is reported, and relationships between the sedimentary extracts of the surface layer to fatty acid components of bacteria cultured from the sediment sample are detailed. By selecting specific structural features, a group of fatty acids have been identified as valid markers for bacteria in this environment: these include iso- and anteiso-branched chain acids; 10-methylpalmitic acid; cyclopropyl 17:0 and 19:0 acids of which ▽19:0 (11,12) is unique to bacteria; cis-vaccenic acid; and the 15:1, 17:1 ω6 and ω8 isomers especially when these occur in pairs; iso Δ7–15: 1 and iso Δ9–17:1 are branched unsaturated acids apparently unique to bacteria. Trans-monoene fatty acids are likely to be a direct bacterial input, and the hydroxy acids identified are probably of bacterial cell wall origin. This study, whilst emphasizing the necessity for detailed structural information on fatty acids in order to use them validly as biological markers, considerably extends the range of fatty acids as markers of bacterial input to contemporary sediments.  相似文献   

12.
Lipid biomarkers from a peat plateau profile from the Northeast European Russian Arctic were analyzed. The peat originated as a wet fen ca. 9 ka BP and developed into a peat bog after the onset of permafrost ca. 2.5 ka BP. The distributions and abundances of n-alkanols, n-alkanoic acids, n-alkanes, n-alkan-2-ones and sterols were determined to study the effect of degradation on their paleoclimate proxy information. Plant macrofossil analysis was also used in combination with the lipid distributions. The n-alkanol and n-alkanoic acid distributions in the upper part of the sequence generally correspond to compositions expected from plant macrofossil assemblages. Their carbon preference index (CPI) values increase with depth and age, whereas those of the n-alkanes decrease. The different CPI patterns suggest that n-alkanoic acids and n-alkanols deeper in the sequence may be produced during humification through alteration of other lipids. Excursions in the n-alkanoic acid content also suggest an important contribution of invasive roots to the lipid biomarker composition. The CPIs associated with these compounds show that under permafrost conditions organic material from Sphagnum is better preserved than material from vascular plants. Increasing stanol/stenol ratio values and decreasing n-alkane CPI values indicate progressive degradation of organic matter (OM) with depth. The n-alkan-2-one/n-alkane and n-alkan-2-one/n-alkanoic acid ratios were shown to be useful proxies that can reflect the degree of OM preservation and suggest that both microbial oxidation of n-alkanes and decarboxylation of n-alkanoic acids produce n-alkan-2-ones in this peat sequence.  相似文献   

13.
Free fatty acids make up the bulk (50–84% wt/wt) of lipid materials recovered from artificial gypsum precipitates and crystals collected from sea salt evaporation pans. Both the fatty acids and hydrocarbons associated with artificial gypsum tend to be of longer mean chain length than organic materials dissolved in the mother liquor. Increased specific adsorption of n-fatty acids at Ca2+ sites on gypsum surfaces is positively correlated with alkyl chain length. Neutral lipids were not significantly enriched in either type of gypsum precipitates. The fatty acids associated with gypsum from sea salt evaporation pans are branched fatty acids in contrast to the predominantly normal acids associated with artificial gypsum samples. Differences in the two adsorbed acid distributions are attributed to the unique lipids of hypersaline biota.  相似文献   

14.
We report hydrogen isotopic fractionations between water and fatty acids of the sulfate-reducing bacterium Desulfobacterium autotrophicum. Pure cultures were grown in waters with deuterium (D) contents that were systematically varied near the level of natural abundance (−37‰ ? δD ? 993‰). H2 of constant hydrogen isotope (D/H) ratio was supplied to the cultures. The D/H ratios of water, H2, and specific fatty acids were measured by isotope-ratio mass spectrometry. The results demonstrate that D. autotrophicum catalyzes hydrogen isotopic exchange between water and H2, and this reaction is conclusively shown to approach isotopic equilibrium. In addition, variation in the D/H ratio of growth water accounts for all variation in the hydrogen isotopic composition of fatty acids. The D/H ratios of fatty acids from cultures grown on H2/CO2 are compared with those from a separate set of cultures grown on D-enriched formate, an alternative electron donor. This comparison rules out H2 as a significant source of fatty acid hydrogen. Grown on either H2/CO2 or formate, D. autotrophicum produces fatty acids in which all hydrogen originates from water. For specific fatty acids, biosynthetic fractionation factors are mostly in the range 0.60 ? αFA-water ? 0.70; the 18:0 fatty acid exhibits a lower fractionation factor of 0.52. The data show that αFA-water generally increases with length of the carbon chain from C14 to C17 among both saturated and unsaturated fatty acids. These results indicate a net fractionation associated with fatty acid biosynthesis in D. autotrophicum that is slightly smaller than in another H2-consuming bacterium (Sporomusa sp.), but much greater than in most photoautotrophs.  相似文献   

15.
A rank series of lignites and coals of low to moderate maturation levels (vitrinite reflectance (R0): 0.27–0.8%) from the New Zealand Coal Band were investigated using alkaline ester cleavage experiments to reveal compositional changes of ester bound components (fatty acids and alcohols) during increasing maturation. Ester bound alcohols are found to be present in highest amounts in the very immature lignite samples (R0: 0.27–0.29%), but show a rapid decrease during early diagenesis. Ester bound fatty acids also show an initial exponential decrease during diagenesis, but reveal an intermittent increase during early catagenesis before decreasing again during main catagenesis. This intermittent increase was related to the short chain fatty acids. To obtain a maturity related signal and to eliminate facies related scattering in the amounts of fatty acids in the coal samples, the carbon preference index of fatty acids (CPIFA) parameter is introduced here. For the long chain fatty acids (C20–C32) originating from terrigenous plant debris, the CPIFA decreases with increasing maturity, showing a strong maturation related signal. During diagenesis, the same trend can be observed for the short chain fatty acids, but the intermittent increase in the amounts of short chain fatty acids is also accompanied by high CPIFA values. This indicates less altered organic biomass at this advanced maturation level and is in contrast to the mature CPIFA signal of the long chain fatty acids of the same samples. One possible reason for this discrepancy could be extremely different amounts of short and long chain fatty acids in the original source organic matter of these samples. However, another intriguing explanation could be the incorporation of immature bacterial biomass from deep microbial communities containing C16 and C18 fatty acids as main cell membrane components. Deep microbial life might be stimulated at this interval by the increasing release of thermally generated potential substrates from the organic matrix during early catagenesis. In contrast to the fatty acids, the high amounts of alcohols in the immature lignite samples are also visible in the alkene distribution from the open system pyrolysis experiments of the organic matrix before and after saponification.  相似文献   

16.
Fatty acids and isoprenoid alcohols were analyzed in river, estuarine, and coastal sediment cores: (1) to investigate the distribution of these lipids among the unbound phase. those bound or closely associated with humic substances, and those bound or closely associated with the huminkerogen and clay mineral matrix. (2) to investigate the diagenetic changes of these lipids with depth in the sediments. and (3) to obtain information on the use of these compounds as organic tracers in marine sediments.Results confirm earlier observations that fatty acids are rapidly altered in marine sediments Both the total and the individual fatty acids decrease in concentration with depth in the sediments: unsaturated acids decrease faster than saturated acids and unbound acids decrease faster than bound acids Approximately 8–62% of the fatty acids were unbound. 2–22% were associated with humic substances. and 38–86% were associated with the residual organic-mineral matrix. Qualitative differences also exist between the fatty acids associated with the unbound, humic, and residual fractions. The ratio of trans/cis geometric isomers of the fatty acids generally increases downcore. with no rearrangement of the double bond positions within the molecules. Either the cis isomer is being preferentially degraded with depth in the sediments, or there is a low temperature, clay catalyzed conversion of the cis isomers to the trans isomers occurring down the cores.Phytol was the major alcohol present in the sediments and does not appear to be altered as rapidly as the fatty acids. Less than 10% of the total phytol (PHY) plus dihydrophytol (DHP) was present as DHP and no trend could be discerned between PHY and DHP with depth or with unbound, humic, and residual material in the cores. All of the isolated DHP appeared to be present as the RRR stereoisomer. Along with the absence of phytane in the cores, this observation suggests that the reduction of phytol to dihydrophytol is microbially mediated in the upper layer of the sediment.  相似文献   

17.
We examined stable carbon isotope fractionation in biosynthesis of fatty acids of a piezophilic bacterium Moritella japonica strain DSK1. The bacterium was grown to stationary phase at pressures of 0.1, 10, 20, and 50 MPa in media prepared using sterile-filtered natural seawater supplied with glucose as the sole carbon source. Strain DSK1 synthesized typical bacterial fatty acids (C14-19 saturated, monounsaturated, and cyclopropane fatty acids) as well as long-chain polyunsaturated fatty acids (PUFA) (20:6ω3). Bacterial cell biomass and individual fatty acids exhibited consistent pressure-dependent carbon isotope fractionations relative to glucose. The observed ΔδFA-glucose (−1.0‰ to −11.9‰) at 0.1 MPa was comparable to or slightly higher than fractionations reported in surface bacteria. However, bulk biomass and fatty acids became more depleted in 13C with pressure. Average carbon isotope fractionation (ΔδFA-glucose) at high pressures was much higher than that for surface bacteria: −15.7‰, −15.3‰, and −18.3‰ at 10, 20, and 50 MPa, respectively. PUFA were more 13C depleted than saturated and monounsaturated fatty acids at all pressures. The observed isotope effects may be ascribed to the kinetics of enzymatic reactions that are affected by hydrostatic pressure and to biosynthetic pathways that are different for short-chain and long-chain fatty acids. A simple quantitative calculation suggests that in situ piezophilic bacterial contribution of polyunsaturated fatty acids to marine sediments is nearly two orders of magnitude higher than that of marine phytoplankton and that the carbon isotope imprint of piezophilic bacteria can override that of surface phytoplankton. Our results have important implications for marine biogeochemistry. Depleted fatty acids reported in marine sediments and the water column may be derived simply from piezophilic bacteria resynthesis of organic matter, not from bacterial utilization of a 13C-depleted carbon source (i.e., methane). The interpretation of carbon isotope signatures of marine lipids must be based on principles derived from piezophilic bacteria.  相似文献   

18.
将超临界CO2萃取技术应用于泥炭纤维素中有机脂类物质的提纯工作,并对萃取物进行色—质联用分析。结果表明,在萃取物中检出了一系列甲酯类、乙酯类、少量有机酸及正构烷烃组分。首次检出的脂肪酸乙酯系列化合物多数呈高碳数分布,具偶碳优势。长链正构烷烃主峰碳为nC33或nC31,具有明显的奇碳优势,这在一定程度上反映了泥炭生成过程的气候条件,记录了气候变化的信息。同时也显示出超临界CO2萃取技术能够很好地完成除去纤维素中有机脂类这一重要环节,有利于提高泥炭纤维素δ13C值检测的准确度,为超临界流体萃取技术在地学中的应用开辟了一个新途径。  相似文献   

19.
Sparry calcite fracture fills and concretion body cements in concretions from the Flodigarry Shale Member of the Staffin Shale Formation, Isle of Skye, Scotland, entrap and preserve mineral and organic materials of sedimentary and diagenetic origin. Fatty acids are a major component of the lipids recovered by decarbonation and comprise mainly n-alkanoic and α-ω dicarboxylic acids. Two generations of fracture-fill calcite (early brown and later yellow) and the concretion body microspar yield significantly different fatty acid profiles. Early brown calcites yield mainly medium-chain n-alkanoic acids with strong even predominance; later yellow calcites are dominated by α-ω dicarboxylic acids with no even predominance. Both fracture fills lack the long-chain n-alkanoic and α-ω dicarboxylic acids additionally recovered from the concretion bodies. The absence of longer chain acids in the calcite spar fracture fills is inferred to result from the transport of fatty acids by septarian mineralising fluids whereby low-aqueous solubility of longer chain acids or their salts accounts for their relative immobility.Comparative experiments have been carried out using conventional solvent extraction on the concretion body and associated shales, both decarbonated and untreated. Extracted lipid yields are higher, but the fatty acids probably derive from mixed locations in the rock including both kerogen- and carbonate-associated lipid pools. Only experiments involving decarbonation yielded α-ω dicarboxylic acids in molecular distributions probably controlled mainly by fluid transport. Alkane biomarker ratios indicate very low thermal maturity has been experienced by the concretions and their host sediments. Septarian cracks lined by brown calcite formed during early burial. Microbial CO2 from sulphate-reducing bacteria was probably the main source of mineralising carbonate. Emplacement of the later septarian fills probably involved at least one episode of fluid invasion.  相似文献   

20.
Samples of Sphagnum palustre and peat from the Erxianyan peatland, central China, were analyzed for lipids and their carbon isotopes to investigate how lipid distributions respond to hydrological change and to evaluate the importance of the contribution of microbial lipids to the peat moss. The lipids in samples collected from different hydrological settings in and around a pond and in the central part of the bog show clear variation along the hydrological gradient, with higher n-C23/n-C25 alkane ratio values and lower ACL (average chain length) values of long chain n-alkanes, n-fatty alcohols and n-fatty acids at the wetter sites. Although the relationship between the S. palustre lipids and the hydrological conditions can be partially overprinted in peat by an input from vascular plants, lipid ratios such as Paq and ACL can provide useful qualitative information about Sphagnum contributions. In addition, lipid composition and carbon isotope values provide information about microbial activity associated with S. palustre. The occurrence of a high abundance of 7-methylheptadecane in submerged S. palustre is an indication of cyanobacteria in the living peat moss. The relatively 13C-depleted carbon isotope values of the n-C23 alkane could result from the influence of symbiotic methanotrophs on the carbon available for assimilation by S. palustre.  相似文献   

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