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  

姚鹏  于志刚  赵美训 《中国海洋大学学报(自然科学版)》2011,41(5):71-78

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   

南极罗斯海表层沉积物GDGTs含量 分布及其环境意义          下载免费PDF全文

陈文深  于培松  韩喜彬  赵军  潘建明 《海洋学研究》2019,37(1):30-39

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TEX^L₈₆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TEX^L₈₆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   

南黄海、东海北部陆架区表层沉积物 有机质分布特征     

熊林芳  石学法  邓煜  白亚之 《海洋通报》2013,32(3):281-286

对南黄海和东海北部462个表层沉积物样品进行了有机碳、总氮及粒度测试,以趋探讨表层沉积物有机质的分布规 律及来源。结果表明：南黄海及东海北部陆架区沉积有机碳质量分数分布范围为0.11 豫耀0.82 豫,均值为0.44 豫;总氮质量 分数分布范围为0.01 豫耀0.11 豫,均值为0.06 豫。有机碳及总氮质量分数平面分布特征相似,泥质沉积区质量分数较高,砂 质沉积区较低,最高值位于杭州湾外部。其分布特征明显遵从粒度效应,随着粒度变粗,有机碳、总氮质量分数减小,其中 在粒度>4准的细粒沉积物中,粒度处于6原11准的细粒沉积物更为富集有机碳。沉积物C/N比值显示,南黄海及东海北部大部 分区域沉积有机质为陆地和海洋混合来源,仅在123.5毅E以东、31毅N以南东海中陆架小部分区域为海洋自生来源。  相似文献   

长江口及邻近海域沉积物中四醚脂类的来源及其对底层溶解氧指示作用探究     

王宗月  袁华茂  宋金明  贺志鹏  段丽琴  李学刚 《海洋科学》2023,47(11):24-34

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   

长江、老黄河口及东海陆架沉积有机质物源指标及有机碳的沉积环境   总被引：11，自引：0，他引：11  

朱纯  潘建明  卢冰  扈传昱  刘小涯  叶新荣  薛斌 《海洋学研究》2005,23(3):36-46

利用2002年9月“东方红2号”调查船调查中获得的沉积物样品,定量研究了长江、老黄河口以及东海陆架沉积物中正构烷烃和无环类异戊二烯烷烃(姥鲛烷和植烷)两种天然示踪物,结果表明:(1)各采样站位样品的碳数范围为n-C14~n-C34,主要可分为陆源单峰、双峰和石油污染等3种类型。(2)长江口东南软泥区和浙江沿岸软泥区沉积物样品中高碳正构烷烃n-C27、n-C29和n-C31含量较高,奇碳优势显著,表明其来源以陆源高等植物输入占优势;相反,“东海冷涡”泥质区和黄海中南陆架区沉积物样品中的低碳正构烷烃n-C17、n-C18和n-C19含量较高,奇偶优势不明显,表明其来源主要以浮游生物和细菌为主。冲绳海槽泥质区沉积物样品中高碳与低碳正构烷烃的含量几乎相当,表明其来源为海洋低等生物和陆地高等植物共同输入,其中陆源物质是从东海陆架经底流搬运而来的。(3)有机质的堆积受控于物质供应和沉积环境两大因素。东海中陆架区沉积物中正构烷烃总量和有机碳含量为最低,这是由于台湾暖流的顶托,使黄河和长江两大物质扩散系统对该区的物质供应量减少,沉积速率低,潮流冲刷作用强,沉积物保存有机碳的能力较差;表层沉积物中正构烷烃及有机碳的最高值分别出现在浙江沿岸软泥区(E 5站)和冲绳海槽泥质区(P 4站);“东海冷涡”泥质区沉积环境最为适宜,但是陆源有机质供应则相对较少。  相似文献   

北冰洋沉积物中四醚脂类来源与TEX_(86)指数初步研究     

于晓果  边叶萍  阮小燕  叶黎明  章伟艳  金肖兵  姚旭莹 《海洋地质与第四纪地质》2015,(3):11-22

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   

冲绳海槽中部8.2ka以来GDGTs组成及温度重建*     

刘磊  许兰芳  管红香  孙治雷  王利波  茅晟懿  刘丽华  吴能友 《热带海洋学报》2020,39(6):77-92

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, TEX^H₈₆), 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, TEX^H₈₆ 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; TEX^H₈₆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TEX^H₈₆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   

碳同位素质谱法探讨现代海洋有机沉积物来源     

朱桂海  Jame M.Brooks 《海洋学研究》1986,(2)

本文用NUCLIDE RMS 6-60质谱仪测定了长江口及邻近海区(北纬30°06′至31°15′,东经122°30′至124°30′)表层沉积物中有机碳稳定同位素组成(δ~(13)C为-23.6×10~(-3)—-21.3×10~(-3))、有机碳含量(0.4—0.1％),溶剂可提取有机物浓度及有机C/N比值。结果表明,从有机地球化学角度解释并证实了其他地学家在该区域的研完成果,即东海陆架泥质沉积物主要由陆源悬浮物和海洋浮游生物体混合组成,长江入海物质随着远离长江口而递减,大部分陆源悬浮物向东南运移,并沉积在东经123°以西的长江口区。  相似文献   

过去一百年济州岛西南泥质区有机质来源变化的多参数指标研究     

葛田田  李大伟  赵宗山  陈蔚芳  邢磊  赵美训 《中国海洋大学学报(自然科学版)》2013,(2):40-47

C/N是一种传统的区分海洋沉积有机质来源的指标,基于总有机碳与总有机氮的比值。BIT(Branched andIsoprenoid Tetraether index)和TMBR(Terrestrial and Marine Biomarker Ratio)是近年提出的用于指示陆源有机质相对贡献的新指标,二者具有明确的陆源及海源端元值。BIT指标是基于陆地土壤厌氧细菌生标Branched GDGTs与泉古菌生标Crenarchaeol的比值,TMBR指标是基于陆源高等植物生标和海源藻类生标的比值。本文利用C/N、BIT和TMBR指标,对济州岛西南泥质区DH11站位过去一百年以来陆源有机质和海源有机质的相对贡献进行了定量评估。总有机碳(TOC)、陆源和海源生物标志物的分析结果显示:近50a来,该站位的总有机质、海源有机质和陆源有机质的沉积通量(Mass Accumulation Rates,MARs)一直在增加。C/N指标通过二元混合模型的计算结果显示陆源有机质占总沉积有机质的比例在0.22～0.30之间,BIT与TMBR指示的陆源有机质贡献分别在0.05～0.11,0.08～0.22之间,所得相对贡献的差异主要是由不同指标的指示意义不同造成的。3种指标的结果表明该研究海域海源有机质在沉积有机质中占据主导地位。另外,从1950s开始陆源有机质的相对贡献呈现下降趋势,这说明海源有机质沉积通量增加的比例大于陆源有机质,这可能是由东亚季风、黑潮、河流输入、大气沉降和人类活动等多重因素引起的。  相似文献   

中国边缘海沉积有机质来源及其碳汇意义     

《中国海洋大学学报(自然科学版)》2017,(9)

中国边缘海(本文特指渤海、黄海和东海,不包括南海)是陆源和海源有机质的重要碳汇。总有机质指标和生物标志物的结果显示,表层沉积物中陆源有机质高值集中在近岸尤其是河口附近;海源有机质在陆架海盆处有高值,受控于海洋生产力和沉积环境。利用多参数指标对表层沉积物中不同来源和不同年龄有机质的贡献比例估算的结果显示,我国边缘海的有机碳埋藏量约13 Mt/a,占全球边缘海沉积物有机碳埋藏量(~138 Mt/a)的~10%,其中陆源有机质的碳埋藏量(3.9 Mt/a)占全球边缘海沉积物陆源有机质埋藏量的~7%。若假定陈化土壤有机质和古老有机质主要是陆源物质,则非现代有机质的碳埋藏量为~6Mt/a,占我国边缘海总有机质碳埋藏量的~46%,与全球边缘海沉积物中陆源有机质的平均比例(44%)相当。这些结果表明我国边缘海在全球海洋碳循环中具有重要地位。本文利用已发表的文献数据,总结和归纳了中国边缘海沉积有机质来源及其碳汇意义。  相似文献   

Origin of sedimentary organic matter in the north-western Adriatic Sea   总被引：1，自引：0，他引：1  

M. Giani  D. Berto  F. Rampazzo  F. Savelli  F. Alvisi  P. Giordano  M. Ravaioli  F. Frascari 《Estuarine, Coastal and Shelf Science》2009,84(4):573-583

In order to evaluate the origin and the transformation of organic matter on the shallow shelf of the NW Adriatic Sea, organic carbon, total nitrogen and stable isotope ratios of organic carbon were analysed in riverine suspended matter and sediments as well as in marine suspended and sedimentary organic matter, in marine phytoplankton and zooplankton.The deposition of organic matter is influenced by fine sediment concentration. Surface sediments were characterised by highly variable biogeochemical conditions on the sea floor, whereas sub-surface sediments showed a more homogeneous hypoxic/anoxic environment.Low C_org/N ratio and high organic carbon and nitrogen concentrations in riverine suspended organic matter indicate an important contribution of freshwater phytoplankton within rivers, particularly during low flow regimes, which adds to the marine phyto- and zooplankton at shelf locations.In order to evaluate the importance of terrestrial, riverine and marine sources of OM in shelf sediments, a three end-member mixing model was applied to shelf surface sediments using ¹³C/¹²C values for organic matter and N/C ratios. The model showed an elevated contribution of terrestrial organic substances at intermediate depths (10–15 m), mostly corresponding to an area of coarser grain-size, whereas the riverine and marine organic fractions were mainly accumulating near the coast and offshore, respectively.  相似文献   

Metal binding by humic acids in recent sediments from the SW Iberian coastal area     

J.M. De la Rosa  M. SantosM.F. Araújo 《Estuarine, Coastal and Shelf Science》2011

The concentrations of Cu, Zn, Cr, Ni, Pb, As, Mn and Co were determined by Inductively Coupled Plasma–Mass Spectrometry both in recent sediments from different locations of the Huelva littoral (SW Iberian Peninsula) and in their humic acid (HA) fractions in order to evaluate distribution and binding capacity of those trace elements to HAs. In addition, elemental composition (C, N, S) and δ¹³C values were determined to appraise the sources of organic matter in the area. This study involved the comparison of selected samples taken from different environments including the estuary of the Guadiana River, the main fluvial system of the region, the Tinto and Odiel estuary system and the proximal shelf. Significant positive correlations were found among Cu, Zn, As and Pb in bulk sediments, suggesting a common origin of all of those elements: the mining activities and pyrite deposits located hinterland. On the other hand, results for Cr, Co and Ni pointed to the basic rocks from the low basin of the Guadiana River as their main source. Elemental (C, N) and isotopic (δ¹³C) composition of sediments indicated a significant contribution of autochthonous plankton in coastal shelf sediments, whereas estuarine and riverine sediments showed a major contribution of terrestrial biomass. Geochemical values for their corresponding HAs suggested a greater terrestrial contribution in the sedimentary OM of the coastal shelf sediments than in bulk sediments, which evidenced the influence of coastal currents and sediment fluxes. Humic acids sequester considerable amounts of Cu and Zn contributing to reduce the bioavailability of these contaminants.  相似文献   

应用木质素示踪楚科奇海表层沉积物中有机碳的来源和降解程度     

王心怡  李中乔  金海燕  郑豪  陈建芳 《海洋学报》2017,39(10):19-31

埋藏在海洋沉积物中的有机碳是大气二氧化碳的净汇,而埋藏过程主要发生在陆架区。北冰洋拥有全球最大的陆架,接收大量来自河流和沿岸侵蚀输运的陆源有机碳,楚科奇海作为北冰洋的边缘海,是有机碳埋藏的重要海区之一。本研究选用楚科奇海和海台的表层沉积物（陆架区33~82.69 m,陆坡区164.63~3 763 m）,通过木质素,结合粒度、比表面积、有机碳百分含量（OC%）、有机碳稳定同位素（δ13C）等指标来示踪楚科奇海沉积物有机碳的来源和降解程度。结果表明,有机碳载荷从陆架到陆坡有明显的降低趋势;δ13C的范围指示有机碳可能来自苔藓、草本裸子植被、浮游植物和冰藻等;木质素丁香基酚（S）与香草基酚（V）的比值（S/V）和肉桂基酚（C）与香草基酚（V）的比值（C/V）表明裸子植物的草本组织贡献了更多的陆源有机碳;此外,较高含量的C9DA二酸（干酪根氧化产物）表明干酪根也可能是楚科奇海表层沉积物中有机质来源的重要组成。指示降解的参数[（Ad/Al） s、（Ad/Al） v、（Ad/Al） p、3,5-Bd/V]在陆架和陆坡沉积物中的差异表明陆坡沉积物中有机质的降解过程受到水动力分选以及原位降解等因素的影响更为明显。  相似文献   

胶州湾沉积物中氨基酸对有机质降解及细菌源贡献的指示作用解析   总被引：2，自引：2，他引：0  

周卜  袁华茂  宋金明  李学刚  李宁  段丽琴  任成喆 《海洋学报》2018,40(8):29-41

基于对胶州湾表层沉积物中总可水解氨基酸（THAA）的含量、组成、构型及分布特征的系统研究，通过氨基酸碳氮归一化产率（THAA-C%，THAA-N%）、降解因子DI、反应活性指数RI以及D型氨基酸占比（D-AA%，摩尔百分比）等指标结合碳氮比（TOC/TN）、碳稳定同位素（δ13C）探析了胶州湾沉积物中有机质的来源与降解状态，利用细菌源有机质及胞外肽酶活性（EEA）探讨了微生物在有机质迁移转化过程中的作用与贡献。结果表明，胶州湾表层沉积物中氨基酸平均含量为（7.60±3.64）μmol/g，在陆源与海源混合影响下，其水平分布呈现湾内高于湾外、湾内东部高于西部的特点，表明湾内东部陆源输入对沉积物THAA具有较高贡献。THAA-C%、THAA-N%、DI、RI以及D-AA%等指示因子均显示胶州湾表层沉积物中有机质的降解程度呈现湾外高于湾内、湾内东部高于西部的变化趋势，有机质来源、微生物活性与上覆水水深共同影响了有机质的降解程度。胶州湾表层沉积物中细菌源有机碳的贡献率为（29.35±18.73）%，其水平分布显示出湾内西部与湾外相近且高于湾内东部的特点。细菌胞外肽酶活性（EEA）平均为（0.81±1.31）nmol/（g·h）（以MCA计），整体分布趋势与细菌贡献率相反，呈现湾内东部高于湾内西部和湾外的特性。沉积物中有机质的不同海源、陆源占比决定了有机质的可降解性，而有机质的降解程度进一步影响了细菌源有机质的贡献与胞外肽酶活性。  相似文献   

Fluxes,source and transport of organic matter in the western Sea of Okhotsk: Stable carbon isotopic ratios of n-alkanes and total organic carbon     

《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(2):253-270

Settling particles and surface sediments collected from the western region of the Sea of Okhotsk were analyzed for total organic carbon (TOC), long-chain n-alkanes and their stable carbon isotope ratio (δ¹³C) to investigate sources and transport of total and terrestrial organic matter in the western region of the sea. The δ¹³C measurements of TOC in time-series sediment traps indicate lateral transport of resuspended organic matter from the northwestern continental shelf to the area off Sakhalin via the dense shelf water (DSW) flow at intermediate depth. The n-alkanes in the surface sediments showed strong odd carbon number predominance with relatively lighter δ¹³C values (from −33‰ to −30‰). They fall within the typical values of C3-angiosperms, which is the main vegetation in east Russia, including the Amur River basin. On the other hand, the molecular distributions and δ¹³C values of n-alkanes in the settling particles clearly showed two different sources: terrestrial plant and petroleum in the Sea of Okhotsk. We reconstructed seasonal change in the fluxes of terrestrial n-alkanes in settling particles using the mixing model proposed by Lichtfouse and Eglinton [1995. ¹³C and ¹⁴C evidence of a soil by fossil fuel and reconstruction of the composition of the pollutant. Organic Geochemistry 23, 969–973]. Results of the terrestrial n-alkane fluxes indicate that there are two transport pathways of terrestrial plant n-alkanes to sediments off Sakhalin, the Sea of Okhotsk. One is lateral transport of resuspended particles with lithogenic material from the northwestern continental shelf by the DSW flow. Another is the vertical transport of terrestrial plant n-alkanes, which is independent of transport of lithogenic material. The latter may include dry/wet deposition of aerosol particles derived from terrestrial higher plants possibly associated with forest fires in Siberia.  相似文献   

Trace element and molecular markers of organic carbon dynamics along a shelf–basin continuum in sediments of the western Arctic Ocean     

Laura L. Belicka  Robie W. Macdonald  H. Rodger Harvey 《Marine Chemistry》2009,115(1-2):72-85

Molecular organic biomarkers together with trace element composition were investigated in sediments east of Barrow Canyon in the western Arctic Ocean to determine sources and recycling of organic carbon in a continuum from the shelf to the basin. Algal biomarkers (polyunsaturated and short-chain saturated fatty acids, 24-methylcholesta-5,24(28)-dien-3β-ol, dinosterol) highlight the substantial contribution of organic matter from water column and sea-ice primary productivity in shelf environments, while redox markers such as acid volatile sulfide (AVS), Mn, and Re indicate intense metabolism of this material leading to sediment anoxia. Shelf sediments also receive considerable inputs from terrestrial organic carbon, with biomarker composition suggesting the presence of multiple pools of terrestrial organic matter segregated by age/lability or hydrodynamic sorting. Sedimentary metabolism was not as intense in slope sediments as on the shelf; however, sufficient labile organic matter is present to create suboxic and anoxic conditions, at least intermittently, as organic matter is focused towards the slope. Basin sediments also showed evidence for episodic delivery of labile organic carbon inputs despite the strong physical controls of water depth and sea-ice cover. Principal components analysis of the lipid biomarker data was used to estimate fractions of preserved recalcitrant (of terrestrial origin) and labile (of marine origin) organic matter in the sediments, with ranges of 12–79%, 14–45%, and 37–66% found for the shelf, slope, and basin cores, respectively. On average, the relative preserved terrestrial organic matter in basin sediments was 56%, suggesting exchange of organic carbon between nearshore and basin environments in the western Arctic.  相似文献   

Contrasting chemical and isotopic compositions of organic matter in Changjiang (Yangtze River) estuarine and East China Sea shelf sediments     

Xu-Chen Wang  Ming-Yi Sun  An-Chun Li 《Journal of Oceanography》2008,64(2):311-321

To examine the source and preservation of organic matter in the shelf sediments of the East China Sea (ECS), we measured bulk C/N and isotopes, organic biomarkers (n-alkanes and fatty acids) and compound-specific (fatty acids) stable carbon isotope ratios in three sediment cores collected from two sites near the Changjiang Estuary and one in the ECS shelf. Contrasting chemical and isotopic compositions of organic matter were observed between the estuarine and shelf sediments. The concentrations of total n-alkanes and fatty acids in the shelf surface sediments (0–2 cm) were 5–10 times higher than those in estuarine surface sediments but they all decreased rapidly to comparable levels below the surface layer. The compositions of n-alkanes in the estuarine sediments were dominated by C₂₆-C₃₃ long-chain n-alkanes with a strong odd-to-even carbon number predominance. In contrast, the composition of n-alkanes in the shelf sediment was dominated by nC₁₅ to nC₂₂ compounds. Long-chain (>C₂₀) fatty acids (terrestrial biomarkers) accounted for a significantly higher fraction in the estuarine sediments compared to that in the shelf sediment, while short-chain (<C₂₀) saturated and unsaturated fatty acids were more abundant in the shelf surface sediments than in the estuarine sediments. Stable carbon isotopic ratios of individual fatty acids showed a general positive shift from estuarine to shelf sediments, consistent with the variations in bulk δ ¹³C_TOCTOC. These contrasts between the estuarine and shelf sediments indicate that terrestrial organic matter was mainly deposited within the Changjiang Estuary and inner shelf of ECS. Post-depositional diagenetic processes in the surface sediments rapidly altered the chemical compositions and control the preservation of organic matter in the region.  相似文献   

Characterizing the depositional settings for sedimentary organic matter distributions in the Lower Yangtze River-East China Sea Shelf System   总被引：2，自引：0，他引：2  

Chun Zhu  Zhang-Hua Wang  Bin Xue  Pei-Song Yu  Jian-Ming Pan  Thomas Wagner  Richard D. Pancost 《Estuarine, Coastal and Shelf Science》2011

Grain-size distributions, total organic carbon (TOC) and total nitrogen (TN) concentrations, and TOC/TN ratios (C/N) were analysed for surface sediments from the Lower Yangtze River-East China Sea (ECS) shelf system. Hierarchical cluster analysis of grain-size parameters (mode, mean, sorting, skewness and kurtosis) has been employed to characterize grain-size compositions. The results suggest there are five grain-size compositional types (type-I–V) that fingerprint distinct depositional conditions. In areas with high sedimentation rates, hydrological sorting preferentially enriches the fraction coarser than 6.4ø (12 μm) in shallow seafloor sediments (water depth<30 m) by transporting the finer fraction to the deeper seafloor (water depth>30 m), and thus forms grain-size compositional type-I (shallow) and type-II (deep). In the open shelf, where modern sediment supply is very limited, grain-size types-III–V are identified according to different winnowing intensity. Overall TOC contents significantly correlate with mud proportions, suggesting muddy sediments are the primary control on OM accumulation. However, de-association of terrestrial OM from fine sediments in the Estuary and the occurrence of presumably relict OM in the open shelf exert additional controls on OM dispersal and carbon cycling in the ECS. By considering geography, oceanography, sediment source, and the relation between sedimentation conditions and sedimentary OM distributions, we define six depositional settings: the lower river, the estuary, the coast, the offshore upwelling area, the erosional area, and the open shelf. These settings describe the sediment dispersal and associated organic matter cycling in the Lower Yangtze River-ECS shelf system.  相似文献