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1.
GDGT在全球气候变化研究中的应用进展 总被引：2，自引：0，他引：2
甘油双烷基甘油四醚(Glycerol Dialkyl Glycerol Tetraethers,GDGTs)是古菌和细菌等微生物细胞膜脂的主要组成部分,包括类异戊二烯GDGTs和支链GDGTs两大类。类异戊二烯GDGTs主要来自海洋泉古菌,其分子中环结构的数目随温度变化而变化。描述类异戊二烯GDGTs相对分布的TEX86指标与表层海水温度(SST)和湖泊表面温度(LST)之间存在良好的线性关系,可以用来重建长时间尺度,特别是地质历史高温时期的古海洋和古湖沼温度。支链GDGTs则主要来自土壤中的厌氧细菌,其分子中环数量和碳链中的甲基数目与大气温度和土壤pH相关,由此而建立的MBT/CBT指标可以通过对近海沉积物的研究反演流域气温的历史变化。将支链GDGTs和类异戊二烯GDGTs相结合而形成的BIT指标则可以用来解析近海沉积物中陆源土壤有机质的来源和分布,与上述指标的结合可以提高结果的可靠性。GDGTs及其相关指标正在逐渐成为推动海洋和陆地全球气候变化研究的重要工具。 相似文献
2.
利用中国南极考察获取的沉积物样品,对普里兹湾10个表层沉积物中GDGTs的含量与分布进行分析。结果表明:普里兹湾内GDGTs含量为27.69~900.78 ng/g,其中类异戊二烯GDGTs占比94%~99%,远高于支链GDGTs。类异戊二烯GDGTs与支链GDGTs都呈现东南高、西北低的分布趋势,且与沉积物中有机碳含量显著正相关(R>0.95)。沉积物中类异戊二烯GDGTs来源于水生古菌,而支链GDGTs主要来源于沉积物中的细菌。根据GDGTs不同异构体含量计算得到的指标TEX86和TEXL86都与普里兹湾1月表层海水温度呈现良好的相关性。这表明TEX86和TEXL86指标在普里兹湾海域具有适用性,可以作为重建古海温的替代指标。 相似文献
3.
通过分析罗斯海15个表层沉积物中甘油双烷基甘油四醚(Glycerol Dialkyl Glycerol Tetraethers,GDGTs)的含量与分布,探讨了各种GDGTs来源及TEX86指标的环境意义。结果表明:表层沉积物中GDGTs总含量为93.67~2 663.37 ng/g,其中类异戊二烯GDGTs(IsoGDGTs)占90.33%~98.56%,远高于支链GDGTs(BrGDGTs)。类异戊二烯GDGTs与支链GDGTs具有显著的耦合关系(R2=0.88,p<0.01)。沉积物中的IsoGDGTs主要来源于海洋奇古菌,BrGDGTs主要由海洋水体和沉积物中原位细菌所产生。应用TEXL86公式估算研究区SST,与WOA夏季表层温度呈现较好的线性关系,表明TEXL86指标在罗斯海具有适用性,可作为重建古海洋温度的替代指标。 相似文献
4.
《海洋地质与第四纪地质》2015,(1)
实际的天然气水合物明显不同于冷泉碳酸盐岩样品。南海已有诸多冷泉碳酸盐岩的研究,针对具有水合物实际产出的神狐海域沉积物样品开展了GDGTs分析测试研究,试图为其成因、来源、AOM作用、生源等提供信息。研究结果表明:SH7B站位96.5~225.2m的岩心样品中,传统指标总有机碳的δ13 C值和C/N值对南海神狐海域天然气水合物赋存段的沉积物之生源输入指示效果不明显;GDGTs主要以类异戊二烯GDGTs为主,水合物赋存段(155~177m)较非水合物赋存段,支链GDGTs相对百分含量明显增多,类异戊二烯GDGTs相对百分含量明显减少。BIT值进一步明确说明:水合物赋存段比非水合物赋存段,沉积物的陆源有机质输入明显增多。前人研究表明~6 Ma左右南海北部接受了较强的河流碎屑和季风碎屑输入,此次事件造成水合物赋存段(6.0~6.74 Ma)陆源有机质输入增多,结果导致沉积物颗粒粒度增大,孔隙空间增多。较粗颗粒物的大量注入可以改善储层物性,形成上细下粗的有利储集体系,从而为神狐海域天然气水合物提供良好储集空间。 相似文献
5.
对北冰洋海域11个站位的沉积物进行了四醚脂类(GDGTs)生物标志化合物的浓度及分布特征分析,结合沉积物的TOC及TN含量及同位素组成对GDGTs的来源进行了探讨。对比TEX86-SST与WOA数据库资料,研究区内美亚海盆73°N以南站位以及欧亚海盆ARC5-BB06站的TEX86-SST与SST具有很好的符合性。楚科奇海域68~73°N站位样品和全球海洋TEX86-SST模式一致,与年平均SST具有较好的符合性。白令海区及ARC5-BB06站TEX86-SST与夏季平均SST符合性更好,可能与提供GDGT的古菌夏季的生产力更高,在全年生产力中所占比例大有关。 相似文献
6.
异戊二烯类甘油二烷基甘油四醚脂类化合物(isoprenoid Glycerol dialkyl glycerol tetraethers, isoGDGTs)在海洋奇古菌(Thaumarchaeota)中广泛存在, 其结构对温度变化的敏感性使其成为广受欢迎的古气候与古温度重建材料。在北冰洋和西太平洋气候以及黑潮等多种因素的影响下, 冲绳海槽中部成为研究全新世以来古海洋和古气候变化的天然实验室。本文通过研究C14柱状沉积物的GDGTs组成、含量变化特征及其延伸的86个碳原子的四醚指标(tetraether index of tetraethers consisting of 86 carbons, TEXH86), 分析冲绳海槽中部的GDGTs来源, 并定量计算C14柱状沉积物记录的海洋表面温度(sea surface temperature, SST), 从而探讨8.2ka以来冲绳海槽中部古温度变化的驱动机制。通过甲烷指数和支链/异戊二烯类指标等, 我们确认isoGDGTs主要来自于氨氧化古菌, 适用于古温度重建。距今8.2ka以来, TEXH86 SST的变化范围是21.6~27.2℃。冲绳海槽中部SST主要受到西热带太平洋、低纬度冬季日晒量的影响; TEXH86指标记录的温度上升趋势与东亚夏季风强度的减弱不一致。7.4—6.6ka冷事件广泛存在于冲绳海槽的SST记录中, 但只在TEXH86数据中显示较大幅度的降低(~5℃), 我们推测可能受到Kikai-Akahoya火山灰(~7.3ka)的影响。 相似文献
7.
甘油二烷基甘油四醚(glycerol dialkyl glycerol tetraethers,GDGTs)作为一种重要的膜脂化合物,广泛存在于海洋水体和沉积物中。基于GDGTs对温度的敏感性, TEX86(Tetra Etherinde Xoftetraethers consisting of 86 carbons)指标被广泛用于海洋古温度重建。然而,研究表明GDGTs母源生物古菌也会受到环境中溶解氧(DO)变化的影响,进而影响其膜脂组成,但边缘海DO对GDGTs组成的影响仍不清楚。本文研究了夏季长江口及其邻近海域颗粒物与表层沉积物中GDGTs的含量与组成,探讨了表层沉积物中GDGTs的来源及其组成对底层DO的响应。结果表明,长江口及其邻近海域颗粒物GDGTs的含量随水深的增加而增加,同时表层沉积物中的GDGT-2/GDGT-3和GDGT-0/Cren比值均与底层颗粒物相近,表明沉积物中GDGTs主要来源于底层颗粒物的沉降输入。进一步对受陆源有机质输入影响较小的站位研究发现有机质来源BIT(Branched and Isoprenoid Tetractter)指... 相似文献
8.
东海沉积物中微生物标志物GDGTs年代际变化及来源 总被引：2，自引：0，他引：2
甘油双烷基甘油四醚(Glycerol Dialkyl Glycerol Tetraethers,GDGTs)是近几年来新发现的一类生物标志化合物,基于GDGTs的各种指标以其在指示物质来源以及海洋和陆地古温度重建等方面显示出的巨大应用潜力,逐渐成为古海洋学、古湖沼学和古气候学研究的重要工具。对采自东海陆架区的DH5-1站位(29°28.118′N、123°06.639′E,水深63.5m)的柱状沉积物样品进行了总有机质和GDGTs分析,研究了GDGTs化合物在东海陆架区柱状沉积物样品中的含量和沉积通量变化,并利用δ13 C、C/N以及基于GDGTs化合物的BIT指标讨论了该海区近150年来沉积有机质的来源变化。结果显示,近百年来东亚冬季风的增强,加强了冬季闽浙沿岸流对长江口沉积物的搬运,使得该海区陆源输入量呈增加趋势,但20世纪80年代以来,人类活动的加剧导致营养盐输入的增加,使得海洋生产力提高,沉积有机质中陆源有机质比例下降。 相似文献
9.
西菲律宾海作为西太平洋暖池的一部分,重建其在地质历史时期的热力学变化、陆源输入变化,对于理解西太平洋暖池在全球地质时间尺度上的作用具有重要意义.利用古菌与细菌的细胞膜质甘油二烷基甘油四醚(glycerol dialkyl glycerol tetraethers,GDGTs)对西菲律宾海XT-47孔沉积物的陆源输入及其... 相似文献
10.
珠江口表层水体颗粒物中古菌四醚类脂物的分布特征 总被引：1，自引：0，他引：1
类异戊二烯甘油二烷基甘油四醚类化合物（isoGDGTs）是古菌微生物的特征脂类标志物,由这组化合物构造出的TEX86温标在海水古温度重建中得到了广泛应用。本文调查了珠江口及近岸海域（水深小于30 m）4个季节水体悬浮颗粒物（SPM）的isoGDGTs分布情况。结果显示:虎门上游河流水体中的isoGDGTs主要来自原地生产的甲烷古菌输入,进入河口水体后,主要来自原地奇古菌和广古菌的输入。陆源古菌的输入在5月份和8月份,对河流水体产生一定的影响,但对河口水体的影响相对较小。珠江口水体isoGDGTs中的GDGT-2与GDGT-3比值（GDGT-[2]/[3]）和GDGT-Cren'的丰度百分比（Cren'%）分别小于4和4%,与南海深水沉积物明显不同,表明珠江口与南海深水沉积物中isoGDGTs的古菌来源存在差异,这也可能是引起珠江口水体TEX86温度（基于全球标定公式）偏离水体实际温度的原因。珠江口表层水体isoGDGTs中的GDGT-2和GDGT-3的丰度百分比与南海表层水体存在差异,这可能与GroupⅠ奇古菌和GroupⅡ广古菌相对比例空间变化有关。珠江口表层水体isoGDGTs的TEX86温度在2月份明显高于原地表层水体温,而其他月份都低于原地表层水体温度,可能与Group Ⅰ奇古菌和Group Ⅱ广古菌相对比例的季节变化有关。几个月份中11月份isoGDGTs绝对含量最高,8月份较低,表明11月份和8月份分别是原地古菌生产量较大和较小时期。统计分析的结果显示,水体铵根离子含量、水体温度,以及溶解氧水平可能是控制珠江口水体isoGDGTs分布的主要环境因素。 相似文献
11.
将盐藻在［Ｎ］／［Ｐ］（氮磷浓度比）为０．５至６０．０的培养液中进行培养,测定了不同实验条件下［Ｎ］／［Ｐ］比值对盐藻生长、培养液中甘油和叶绿素含量以及β－胡萝卜素累积的影响,并初步建立了盐藻在不同［Ｎ］／［Ｐ］比值下的生长动力学模式。研究结果表明,在［Ｎ］／［Ｐ］为２５时,盐藻的生长最佳。［Ｎ］／［Ｐ］比值变化对甘油含量的影响不大。［Ｎ］／［Ｐ］比值小于１５时,叶绿素含量随［Ｎ］／［Ｐ］比值的增加而增加;比值大于１５时,叶绿素含量基本不受［Ｎ］／［Ｐ］比值变化的影响．单细胞β－胡萝卜素含量随［Ｎ］／［Ｐ］比值的增加而减少,而培养液中β－胡萝卜素含量在［Ｎ］／［Ｐ］比值小于１５时基本不受影响,比值大于１５时含量呈下降趋势。 相似文献
12.
Chandralata Raghukumar G. Sheelu P. A. Loka Bharathi Shanta Nair C. Mohandass 《Marine Georesources & Geotechnology》2001,19(1):1-16
In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance. 相似文献
13.
Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths. 相似文献
14.
海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。 相似文献
15.
Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification
An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm. 相似文献
16.
Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
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Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations. 相似文献
19.
The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
20.