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1.
WANG Shilu WAN Guojiang State Key Laboratory of Environmental Geochemistry Institute of Geochemistry CAS Guiyang 《《地质学报》英文版》2000,74(2):301-305
The comparison between the carbon isotope and the index of ring width of a pine disc from the Tuomuer Peak region in Xinjiang shows that the effects of climate changes on the tree-ring growth and carbon iso-topic fractionation varies with time. The reason is probably relative to the characters of climate changes and adaptability of the tree-ring growth to climate changes. The relationships between the atmospheric CO2 level and the revised δ13Cair by the tree-ring carbon isotope indicate that the carbon cycle is not in a steady state, but under a stage-change condition in this area. It also can be concluded that the ratio of CO2 from the terrestrial eco-system has increased, and the flux of CO2 exchange between the atmosphere and the biosphere was gradually increasing over the past century. In addition, the results also confirm the validity and superiority of the carbon isotope to the research of the water-use efficiency. 相似文献
2.
Carbon isotope fractionation in phospholipid fatty acid biomarkers of bacteria and fungi native to an acid mine drainage lake 总被引：3，自引：0，他引：3
Benjamin R. Cowie Gregory F. Slater Luc Bernier Lesley A. Warren 《Organic Geochemistry》2009,40(9):956-962
This study identifies isotope signatures associated with autotrophic and heterotrophic microbial communities that may provide a means to determine carbon cycling relationships in situ for acid mine drainage (AMD) sites. Stable carbon isotope ratios (δ13C) of carbon sources, bulk cells, and membrane phospholipids (PLFA) were measured for autotrophic and heterotrophic microbial enrichment cultures from a mine tailings impoundment in northern Ontario, Canada, and for pure strains of the sulfur oxidizing bacteria Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. The autotrophic enrichments had indistinguishable PLFA distributions from the pure cultures, and the PLFA cyc-C19:0 was determined to be a unique biomarker in this system for these sulfur oxidizing bacteria. The PLFA distributions produced by the heterotrophic enrichments were distinct from the autotrophic distributions and the C18:2 PLFA was identified as a biomarker for these heterotrophic enrichments. Genetic analysis (16S, 18S rRNA) of the heterotrophic cultures indicated that these communities were primarily composed of Acremonium fungi.Stable carbon isotope analysis revealed that bulk cellular material in all autotrophic cultures was depleted in δ13C by 5.6–10.9‰ relative to their atmospheric CO2 derived carbon source, suggesting that inorganic carbon fixation in these cultures is carbon limited. Individual PLFA from these autotrophs were further depleted by 8.2–14.6‰ compared to the bulk cell δ13C, which are among the largest biosynthetic isotope fractionation factors between bulk cell and PLFA reported in the literature. In contrast, the heterotrophic bulk cells were not significantly fractionated in δ13C relative to their carbon source and heterotrophic PLFA ranged from 3‰ enriched to 4‰ depleted relative to the isotopic composition of their total biomass. These distinct PLFA biomarkers and isotopic fractionations associated with autotrophic and heterotrophic activity in this laboratory study provide potential biomarkers for delineating autotrophic and heterotrophic carbon cycling in AMD environments. 相似文献
3.
We report an improved method for determining the intramolecular carbon isotopic composition of acetate using direct injection of aqueous samples. The system builds upon prior work that established pyrolytic conditions for online analysis and represents a significant advance in that it requires minimal preparation for samples containing as little as 1 mM sodium acetate in aqueous solution. The technique is applicable for analysis of oilfield brines, culture samples, biological samples and natural porewaters. We demonstrate its accuracy by use of a stable isotope dilution series. We also show that addition of a base and cryogenic preconcentration may induce an isotopic effect on the carboxyl carbon. This isotopic fractionation does not appear to extend to the measured methyl carbon isotope value although it can significantly alter the measured isotopic composition of the whole molecule. Our preconcentration experiments demonstrate that the method is suitable for carbon isotopic measurements of acetate methyl carbon in natural samples at concentrations as low as 90 μM, considerably broadening potential applications. 相似文献
4.
干酪根中不同结构和官能团具有不同的碳同位素组成,这种差异可以用有机质碳同位素热力学同位素因子（β因子）进行预测。煤岩模拟实验产物中,δ13CCO2相对烃类气体而言明显偏重,这与干酪根中羧基的β13C较大有关。含水实验产物的δ13CCO2轻于无水实验产物的δ13CCO2是由于含水实验中所增加CO2的碳同位素组成相对较轻造成的,含水实验增加的CO2产率是由β13C相对较小的部分亚甲基碳通过断裂、氢转移、以及与水反应转变而来。模拟实验低温阶段（≤300℃）,甲氧基中的甲基断裂可能的甲烷形成的主要方式。而甲氧基的β13C大于甲基,所以低温阶段出现了甲烷碳同位素组成先较重后变轻的现象。 相似文献
5.
利用多年冻土区湖相沉积物中埋藏植物稳定碳同位素组成重建大气CO2浓度 总被引：5，自引：5，他引：5
沉水植物碳同位素分馏同水中溶解无机碳浓度有一定的关系，因而可以通过青藏高原多年冻土区的湖相沉积物中埋藏沉水植物－－龙须眼子菜（Potamogeton pectinatus)植物屑的碳同位素组成重建该地大气CO2浓度的变化情形，研究结果表明，该地在9．17－6．77ka BP间，大气CO2浓度是整个研究时间段中最低的，其后在6．77－4．56ka BP时期大气CO2浓度增加，在4．56－2．17ka BP之间，大气CO2浓度是整个研究时间内CO2浓度最高的阶段，植物屑的碳同位素组成反映了溶解无机碳浓度的变化，从而可用以重建大气CO2浓度的变化情况。 相似文献
6.
Biogeochemical processes involving acetate in sub-seafloor sediments from the Bering Sea shelf break
Biogeochemical processes involving acetate in sub-seafloor sediments from piston core PC23B from the Bering Sea shelf break were inferred by examining the stable carbon isotopic relationships between acetate and other relevant carbon compounds: total organic carbon (TOC) in the sediment solid phase, and dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in pore water. Throughout the core, the isotopic composition of acetate (δ13Cacetate), from −31‰ to −29‰, was 13C-depleted by ca. 7‰ vs. DOC (δ13CDOC) and its depth profile approximately paralleled that of δ13CDOC, suggesting that the principal process producing acetate was fermentation of dissolved organic compounds. However, the 13C depletion in δ13Cacetate indicates some contribution of acetogenesis to total acetate production, because acetogenesis results in 13C depletion of the acetate produced. The relative contribution of acetogenesis via the H2/CO2 reaction, calculated by using a two source isotope mixing model, increased with depth in the sulfate reduction zone from 10% to 15% and was constant at 19% in the methanogenic zone. The acetogenic contribution to acetate production in the methanogenic zone underlying the sulfate reduction zone is consistent with reported observations, whereas the occurrence of acetogenesis in the sulfate reduction zone may be related to the contribution of terrestrial organic matter (OM) to the sedimentary OM in that depth interval, because the terrestrial component likely includes precursors that favor organoautotrophic acetogenesis. The high acetate concentration (up to 81 μM) and TOC content (up to 1.4%) at the same depth (<200 cmbsf) suggest that some relationship exists between acetate production rate and TOC content, or that a temperature increase during core storage at room temperature might stimulate acetate-producing microbial activity in the high TOC sediment. 相似文献
7.
摘要：四川盆地中南部地区寒武系洗象池群碳酸盐岩的碳、氧同位素组成受后期成岩作用影响较小,基本保留了原始海洋的同位素组成,根据该地区采集的88个碳、氧同位素数据,研究、讨论了中上寒武统碳酸盐岩不同尺度沉积旋回中的碳氧同位素组成、演化及地质意义。研究表明,四川盆地寒武系洗象池群由下至上的地层序列中,碳、氧同位素具有明显的旋回性演化特征：其δ13C值变化于－56‰～3247‰之间,均值为-0979‰,绝大多数的样品都在-2‰～2‰的区间震荡,δ18O值分布于-111‰～-52‰之间,均值为-6934‰,主要集中在－9‰～-6‰的范围内波动。通过对不同尺度沉积旋回碳、氧同位素数据分析研究,认为在体系域尺度沉积旋回中控制碳氧同位素组成特征的主因是海平面变化,在米级旋回中主要受高频海平面变化、古气候、古构造等多方面叠加的影响;通过对碳、氧同位素数据分析研究,首次明确了该地区芙蓉统的底界,为地层的划分对比提供了有力证据;洗象池群早期和中期经历了短暂而快速的海侵后进入缓慢的海退,在晚期缓慢海侵后的快速海退,碳同位素组成反映的海平面变化趋势与沉积相演化一致。 相似文献
8.
Reports of the 13C content of marine particulate organic carbon are compiled and on the basis of GEOSECS data and temperatures, concentrations, and isotopic compositions of dissolved CO2 in the waters in which the related phytoplankton grew are estimated. In this way, the fractionation of carbon isotopes during photosynthetic fixation of CO2 is found to be significantly correlated with concentrations of dissolved CO2. Because ancient carbon isotopic fractionations have been determined from analyses of sedimentary porphyrins [Popp et al., 1989], the relationship between isotopic fractionation and concentrations of dissolved CO2 developed here can be employed to estimate concentrations of CO2 dissolved in ancient oceans and, in turn, partial pressures of CO2 in ancient atmospheres. The calculations take into account the temperature dependence of chemical and isotopic equilibria in the dissolved-inorganic-carbon system and of air-sea equilibria. Paleoenvironmental temperatures for each sample are estimated from reconstructions of paleogeography, latitudinal temperature gradients, and secular changes in low-latitude sea surface temperature. It is estimated that atmospheric partial pressures of CO2 were over 1000 micro atm 160 - 100 Ma ago, then declined to values near 300 micro atm during the next 100 Ma. Analysis of a high-resolution record of carbon isotopic fractionation at the Cenomanian-Turonian boundary suggests that the partial pressure of CO2 in the atmosphere was drawn down from values near 840 micro atm to values near 700 micro atm during the anoxic event. 相似文献
9.
A low-mature coal (Ro=0.4%, from the Manjia'er depression, Tarim Basin, China) was subjected to closed system pyrolysis, in sealed gold tubes,
under isothermal temperature conditions. The carbon isotopic compositions of the pyrolyst fractions (hydrocarbon, CO2, CO, etc.) at two temperature points (350°C and 550°C) were measured. The results showed that {ie359-1} value is generally
heavier at 350°C than that at 550°C, because the high abundance of CO generated at low temperature would greatly influence
{ie359-2} value, and the retention time of CO in gas chromatograph is close to that of CH4. But CO is formed through chemical reaction of the oxygen-containing functional group −C=O, e.g. lactones, ketones, ether,
etc. at low temperature, while CO2 comes mainly from decarboxylization.
The carbon isotopic composition of coal gas from Lanzhou Coal Gas Works was definitely different from that of thermally pyrolysed
products from coal. The {ie359-3} value of coal gas was abnormally heavier than {ie359-4}. At the same time, the reversed
sequence ({ie359-5}) of {ie359-6} and {ie359-7} happened. The bond energy of free ions generally decides the sequence of generation
of hydrocarbon fractions according to the chemical structure, whereas the stability of pyrolysate fractions and their carbon
isotope fractionation are affected by the C−C bond energy.
This study was supported by the National Basic Research (973) Program of China (No. 2001CB209102). 相似文献
10.
H. Strauss 《Geochimica et cosmochimica acta》1986,50(12):2653-2662
Carbon and sulfur isotope ratios have been determined for more than 200 samples of Precambrian graphitic and sulfidic metasediments from the Superior and Churchill Provinces of Canada. The sediments were deposited in small sedimentary basins related to various Canadian greenstone belts. The age of the Archean samples is approximately 2.7 Ga., the Proterozoic samples about 1.8 Ga.,
The Archean organic material shows C isotope values between −47 and −15%. vs. PDB. The Proterozoic metasediments show a smaller range, with δ13C between −30 and −17%.,
A few carbonate samples yielded C isotopic compositions between −5.9 and −4.7%.,
Associated iron sulfides have δ34S-values ranging from −6 to +8%., which are consistent with isotopic fractionation effects either by inorganic or bacterial reactions in the sedimentary sulfur cycle.
The great variability of organic C isotopic composition, especially in the late Archean, although affected by extensive postdepositional alteration, might indicate differences in the environmental conditions and/or the organic content of these sedimentary basins. Some extremely 13C-depleted organic carbon values support a global occurrence of environments likely dominated by methanotrophic organisms at the end of the Archean. 相似文献
11.
稳定碳同位素在第四纪古环境研究中的应用 总被引：26，自引：8，他引：26
文章对陆相沉积物、湖沼相沉积物以及脊椎动物牙齿中的δ13C研究作了系统的综述,特别对存在的问题提出了一些看法,认为黄土-古土壤序列中有机质δ13C与碳酸盐δ13C变化趋势相反的原因是CO2与碳酸盐交换平衡时的分馏系数在古土壤堆积时和黄土发育时不一致造成的;陆相沉积物的有机质δ13C较碳酸盐δ13C能更加直接地反映沉积时地表植被状况,陆相沉积物的碳酸盐δ13C在古生态中的应用还有待于对它的形成机制和形成过程进行进一步的研究;我国黄土高原末次冰期的气候不利于C4的生长.文章强调古环境、古生态研究应该从现代过程入手,了解现代植物δ13C与气候参数的关系以及现代C4植物的分布规律.同时还认为分子化石的稳定同位素研究这一新研究手段将会给第四纪研究带来更新的活力. 相似文献
12.
天然气水合物是一种新型的洁净能源。甲烷天然气水合物是储量最丰富的一种类型,常出现在深海中或极地大陆上,其生成的过程中会发生同位素的分馏效应。通过实验室模拟水合物生成的过程,利用天然海水与甲烷或二氧化碳气体反应,以及更接近实际生成环境的甲烷-海水-沉积物动态聚散实验,对甲烷水合物和二氧化碳水合物生成前后δ13C值进行测定,研究水合物生成过程中δ13C的变化情况。实验证明,水合物反应中碳同位素分馏是存在的,其变化程度明显小于氧同位素和氢同位素。甲烷水合物碳同位素的分馏系数αC的值为1000 3~1000 9。二氧化碳水合物生成反应后气相的碳、氧同位素变轻,重同位素趋向于进入水合物中,二氧化碳水合物碳同位素的分馏系数αC的值为1000 7~1001 2。海水中溶解的CO2气体在甲烷水合物形成过程中会被水合物捕获,从而使得δ13CDIC值变小,重的碳同位素趋于进入水合物中,而较轻的碳同位素留在海水中。但由于海水中含有的溶解CO2气体有限,经过多轮水合物动态聚散后δ13CDIC值的变化幅度会越来越小。 相似文献
13.
祁连山冻土区天然气水合物分解气碳氢同位素组成特征 总被引：4，自引：0，他引：4
开展祁连山冻土区天然气水合物气体同位素研究,是解决其气体成因、来源等科学问题的一个重要手段。本研究采集祁连山南麓多年冻土区水合物科学钻探DK2和DK3孔共8个含水合物的岩芯样品,采用真空顶空法收集样品中水合物的分解气,分别用气相色谱(GC)、气相色谱同位素比值质谱(GC-IRMS)测定其气体成分和同位素组成,测试结果表明:祁连山冻土区天然气水合物样品的气体碳氢同位素变化较大,甲烷、乙烷和丙烷的碳同位素(δ13C)变化范围分别为-52.6‰～-48.1‰、-38.6‰～-30.7‰和-34.7‰～-21.2‰,而二氧化碳的碳同位素(δ13C)最低为-27.9‰,最高为16.7‰;甲烷、乙烷和丙烷的氢同位素(δD)变化范围分别为-285‰～-227‰、-276‰～-236‰和-247‰～-198‰。通过对这些碳氢同位素进行综合研究,包括气体分子组成与同位素的关系分析、甲烷的碳氢同位素之间的关系判断等,结果表明研究区天然气水合物的气体主要来源于热解气,而且是在淡水环境中形成的有机成因气。 相似文献
14.
生物气碳、氢同位素组成是探讨其形成途径和成藏特征的基本手段,研究基于我国10个生物气气藏31个气样的碳、氢同位素组成资料探讨了这些气藏的形成途径和成藏特征。研究表明:这些气藏的氢同位素组成可以分为三个区间,即δDCH4>-200‰;δDCH4值在-250‰～-200‰之间和δDCH4<-250‰。前人认为在陆相淡水条件下生物气的形成途径主要是乙酸发酵作用,我国10个气藏31个气样碳、氢同位素研究表明,海相及盐湖相条件下生物气形成途径为典型的CO2还原途径,具有重的氢同位素组成,其δDCH4>-200‰,而陆相条件下成藏的生物气也主要为CO2还原途径,但氢同位素组成较典型海相成因生物气轻,其δDCH4值在-250‰～-200‰之间。其值可能与古湖泊水介质的咸化程度有关。从柴达木的资料来看,随水介质咸度增大,生物甲烷氢同位素组成也具有相应增大趋势。陆相条件下有处于CO2还原和乙酸发酵两种作用过渡区形成的生物气气藏,其形成可能与古水介质无咸化过程和地温梯度较高有关,如保山盆地。该区形成的生物气具有轻的氢同位素组成,δDCH4<-250‰,碳同位素组成则相对较重,其碳、氢同位素组成之间具有较好的负相关。生物气碳、氢同位素组成的成气机理及途径有可能成为判识自然界采集的生物气气样是否具有工业意义,一般而言,乙酸发酵途径形成的生物气不利于成藏。 相似文献
15.
Data on abundance and isotopic composition of porewater and sedimentary sulfur species are reported for relatively uncontaminated and highly contaminated fine-grained anoxic sediments of St. Andrew Bay, Florida. A strong contrast in amount and composition of sedimentary organic matter at the two sites allows a comparative study of the historical effects of increased organic loading on sulfur cycling and sulfur isotopic fractionation. In the contaminated sediments, an increase in organic loading caused increased sedimentary carbon/sulfur ratios and resulted in higher rates of bacterial sulfate reduction, but a lower efficiency of sulfide oxidation. These differences are well reflected in the isotopic composition of dissolved sulfate, sulfide, and sedimentary pyrite. Concentration and isotopic profiles of dissolved sulfate, organic carbon, and total sulfur suggest that the anaerobic decomposition of organic matter is most active in the upper 8cm but proceeds at very slow rates below this depth. The rapid formation of more than 90% of pyrite in the uppermost 2 cm which corresponds to about 3 years of sediment deposition allows the use of pyrite isotopic composition for tracing changing diagenetic conditions. Sediment profiles of the sulfur isotopic composition of pyrite reflect present-day higher rates of bacterial sulfate reduction and lower rates of sulfide oxidation, and record a profound change in the diagenetic cycling of sulfur in the contaminated sediments coincident with urban and industrial development of the St. Andrew Bay area. 相似文献
16.
Carbon isotopic compositions were determined for individual hydrocarbons in water column and sediment samples from the Cariaco Trench and Black Sea. In order to identify hydrocarbons derived from phytoplankton, the isotopic compositions expected for biomass of autotrophic organisms living in surface waters of both localities were calculated based on the concentrations of CO2(aq) and the isotopic compositions of dissolved inorganic carbon. These calculated values are compared to measured delta values for particulate organic carbon and for individual hydrocarbon compounds. Specifically, we find that lycopane is probably derived from phytoplankton and that diploptene is derived from the lipids of chemoautotrophs living above the oxic/anoxic boundary. Three acyclic isoprenoids that have been considered markers for methanogens, pentamethyleicosane and two hydrogenated squalenes, have different delta values and apparently do not derive from a common source. Based on the concentration profiles and isotopic compositions, the C31 and C33 n-alkanes and n-alkenes have a similar source, and both may have a planktonic origin. If so, previously assigned terrestrial origins of organic matter in some Black Sea sediments may be erroneous. 相似文献
17.
以柴达木盆地北缘不同构造带代表性原油作为研究对象,采用GC-TC-IRMS技术对原油中正构烷烃单体碳、氢同位素进行测定。利用样品正构烷烃单体碳、氢同位素组成特征及分布模式,进行原油成因类型划分和对比分析。研究结果表明,正构烷烃可溶有机质的δ13C分布在-36‰～-25‰,δD分布在-180‰～-110‰。对比发现,不同构造带原油中正构烷烃单体碳、氢同位素组成特征上存在着比较明显的差别。以-30‰（δ13C）和 -140‰（δD）作为分界,结合同位素曲线的分布型式,可以划分为不同的分布模式判识生烃母质和沉积环境。 相似文献
18.
煤岩及其主显微组份热解气碳同位素组成的演化 总被引：13，自引：2，他引：13
模拟实验是有机地球化学研究的重要组成部分 ,也是油气地球化学研究的重要手段。本文通过煤岩及其主要显微组分的热解成气模拟实验产物的组分和同位素组成分析 ,补充和完善了前人对煤岩热解气同位素组成分布的一些认识。同时 ,对比研究了煤型气与煤岩热解气的碳同位素分馏特征 ,结果表明两者具有良好的一致性 ,认为可以通过精细的热解模拟来提供不同含煤沉积盆地煤型气的判识指标 ,而模拟气与天然气碳同位素组成的对比 ,关键是对同位素分析资料的处理。在模拟系列产物碳同位素分析基础上 ,获得了单一成因来源天然气甲烷、乙烷碳同位素组成与演化程度之间的关系式以及演化过程中甲烷碳同位素之间的关系式 ,这些结果会对混源气的判识有重要意义。 相似文献
19.
土壤发生性碳酸盐碳稳定性同位素模型及其应用 总被引：5，自引：0，他引：5
干旱、半干旱地区土壤无机碳库比有机碳库大2~5倍,无机碳库及其周转在该地区土壤碳平衡中具有重要意义。土壤发生性碳酸盐是土壤发育过程的产物,与岩生性碳酸盐溶解/沉积平衡、土壤有机碳分解CO2的再转化密切相关。发生性碳酸盐碳稳定性同位素主要由土壤CO2的碳同位素组成决定,可以用描述不饱和层气体质量传递的扩散—生成模型模拟。在土壤碳酸盐体系（土壤CO2(g)、碳酸盐和土壤溶液）处于同位素平衡状态时,根据生物过程产生的分子扩散以及碳酸盐化学平衡反应的分馏模型,发生性碳酸盐δ13C值比有机质δ13C值大14‰~16‰。扩散—生成模型和/或分馏模型可以用于鉴定和定量化分散态发生性碳酸盐组分、区分土壤碳酸盐悬膜上发生性碳酸盐的比例,并可用于定量评价土地利用管理措施对碳酸盐溶解/沉积平衡的影响,这在全球碳循环研究中具有重要意义。 相似文献
20.
黄土沉积物中碳酸盐同位素组成的研究方法 总被引：3，自引：0，他引：3
利用逐段加热法获得的黄土沉积物中碳酸盐的碳、氧同位素组成表明，黄土沉积物中的碳酸盐是不同来源和成因的碳酸盐的混合物。不同来源和成因的碳酸盐具有不同的碳、氧同位素组成，其示踪意义也不同，７００～８００℃的δ１３Ｃ比用磷酸法获得的δ１３Ｃ更灵敏于古气候的变化。因此，采用磷酸法研究黄土沉积物碳酸盐的同位素组成是不适宜的。 相似文献