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1.
Rock fragments from the deepest parts of a buried hydrothermal system belonging to the Mesozoic Tethys Ocean entered as xenoliths in a Miocenic diatreme,hence brought to the surface,in the Hyblean Plateau(Sicily).Some xenoliths consist of strongly serpentinized ultramafic rocks bearing blebs of abiotic organic matter,where clusters of amorphous carbon nanoparticles,including nanodiamonds,are immersed.Such an occurrence conjures up established hypotheses that diamond surfaces are suitable catalytic platforms stimulating the assemblage of complex bio-organic molecules relevant to the emergence of life on Earth.The appearance of bio-organic molecules under primitive Earth conditions is one of the major unsolved questions on the origin of life.Here we report new micro-Raman spectra on blebs of abiotic organic matter from a selected xenolith.Diamond bands were related to hydrogenated nanocrystalline diamonds,with size of nearly 1-1.6 nm,formed from organics at low pressures and temperatures.In particular,diamond surfaces can give rise to crystalline interfacial water layers that may have played a fundamental role in the early biosphere evolution as a good medium for rapidly transporting positive charges in the form of hydrated protons.Nowadays,proton gradients in alkaline hydrothermal vents along oceanic ridges are generally viewed as key pre-biotic factors.In general,serpentinites span the entire geological record,including prebiotic times.These hydrous ultramafic rocks often display evidence of abiotic carbon species,both organic and inorganic,including nanodiamonds,being also capable to give rise to chemiosmotic processes and proton gradients necessary to the organisms,such as the"Last Universal Common Ancestor"(LUCA),in the prebiotic Earth. 相似文献
2.
Analysis of noble gas proportions and their release kinetics during stepped pyrolysis and oxidation of meteoritic nanodiamonds,
as well as their core-shell structure led to the following conclusions: (1) Noble gases of HL component with anomalous isotopic
composition were presumably formed prior to implantation in the nanodiamonds owing to mixing of nucleosynthetic products of
p- and r- process associated with explosion of type-II supernova with noble gases having “normal” isotopic composition; (2) isotopically
normal P3 noble gases in the nanodiamonds grains are confined to the nondiamond (for instance, graphite-like) phase in the
surface layer. The “layer” structure of nanodiamonds grains resulted from heating up to 800–900°C. Observed increase in contents
of P3 noble gases with increasing grain sizes of meteoritic nanodiamonds is caused by the dependence of the degree of graphitization
of the superfical layer at given temperature on the grain size and surface defect density; (3) bimodal release of noble gases
during pyrolysis of the meteoritic nanodiamonds from weakly metamorphosed meteorites was caused by P3 and HL components, which
are comparable in abundance but sharply differ in their release temperature. 相似文献
3.
Xenon isotopic data were acquired by high resolution step pyrolysis and combined step pyrolysis/combustion of aliquots of size separated nanodiamonds. 129Xe excess (129Xe*) from in situ decay of 129I is preferentially associated with the larger grain size separates. This observation rules out trapping by recoil from surrounding material. The releases of Xe-P3 and 129Xe occur in the same low temperature pyrolysis steps and exhibit similar distributions among the size separates. These observations imply a common site for the components and, in consequence, suggest a common incorporation event.Whether one component or two, our observations require that 129Xe* and Xe-P3 were incorporated into a subpopulation of nanodiamonds before nanodiamonds were mixed and incorporated into parent bodies. Their susceptibilities to loss during heating in the laboratory are similar, but the ratio of 129Xe* to Xe-P3 varies among nanodiamond separates from different meteorites (literature data). We conclude that the 129Xe* we observe today was present as 129I during parent body processing. Furthermore, the range of 129Xe*/132XeP3 ratios across all the separates requires that even nanodiamonds from CI chondrites were at least 5-10× more rich in Xe-P3 during 129I decay than they are today.We present a simple model involving one degassing event per parent body between incorporation of nanodiamonds and final decay of 129I. The observed variations among parent bodies require degassing events separated by several 129I half lives (∼50Ma), consistent with low-temperature processing on parent bodies but longer than expected for nebular processing. In this model, nanodiamonds from ALHA77307 degassed at an unusually early stage, suggesting they alone may retain the signature of processing in the nebula in their P3 and 129Xe* abundances.The isotopic signature associated with Xe-P6 is also found only in the larger size separates. Concentration of Xe-HL increases with increasing grain size, but its relative abundance with respect to Xe-P3 and P6 is higher in smaller grain-size fractions. We argue that Xe-P6 is best seen as a variant of Xe-HL, and that they are both mixtures of a “normal” component akin to solar xenon and a slightly variable exotic component. We show that both current models of Xe-H formation can account for the observed variability, and propose a scenario according to which Xe-HL and P6 were implanted into separate diamond populations before incorporation of Xe-P3 and 129I. 相似文献
4.
The release kinetics of Xe of the isotopically normal component of noble gases (P3 component) from the coarse-grained fraction of nanodiamonds from the Orgueil (CI) meteorite and the kinetics of 4He release from lunar soil were studied by means of a numerical simulation. It is demonstrated that the release of these gases as a peak with a single pronounced maximum may not correspond to the diffusion model with a single activation energy and can in fact be controlled by a spectrum of activation energies with a number of peaks a number of peaks remaining unresolved at stepped pyrolysis. In particular, the amount of Xe-P3 preserved in nanodiamonds during thermal metamorphism of the Orgueil meteorite calculated using parameters of the diffusion process (activation energy and frequency factor) that were determined in the model with a single activation energy indicates that practically all Xe should be lost during a very short time. These losses are inconsistent with both the duration of thermal metamorphism of the meteorite parent bodies and the Xe-P3 concentrations measured in these meteorites. A much higher preservation of Xe-P3 during thermal metamorphism lasting for hundreds of years follows from calculations based on diffusion with a spectrum of activation energiesa for Xe release. The results of isothermal pyrolysis of a nanodiamonds fraction from Orgueil confirms a presence of several activation energies for Xe-P3 release from the nanodiamonds. The application of the diffusion model with a spectrum of activation energies to He release from lunar soil samples also shows that He can be retained in these samples at 20°C during a much longer time than it follows from the model with a single activation energy (Anufriev, 2010). 相似文献
5.
NMR studies of chemical structural variation of insoluble organic matter from different carbonaceous chondrite groups 总被引：1，自引：0，他引：1
Solid-state 1H and 13C Nuclear Magnetic Resonance (NMR) spectroscopic experiments have been performed on isolated meteoritic Insoluble Organic Matter (IOM) spanning four different carbonaceous chondrite meteorite groups; a CR2 (EET92042), a CI1 (Orgueil), a CM2 (Murchison), and the unique C2 meteorite, Tagish Lake. These solid state NMR experiments reveal considerable variation in bulk organic composition across the different meteorite group’s IOM. The fraction of aromatic carbon increases as CR2 < CI1 < CM2 < Tagish Lake. The increases in aromatic carbon are offset by reductions in aliphatic (sp3) carbon moieties, e.g., “CHx,” and “CHx(O,N).” Oxidized sp2 bonded carbon, e.g., carboxyls and ketones grouped as “CO,” are largely conservative across these meteorite groups. Single pulse (SP) 13C magic angle spinning (MAS) NMR experiments reveal the presence of nanodiamonds with an apparent concentration ranking in the IOM of CR2 < CI1 < CM2 < Tagish Lake. A pair of independent NMR experiments reveals that, on average, the aromatic moieties in the IOM of all four meteoritic IOM fractions are highly substituted. Fast spinning SP 1H MAS NMR spectral data combined with other NMR experimental data reveal that the average hydrogen content of sp3 bonded carbon functional groups is low, requiring a high degree of aliphatic chain branching in each IOM fraction. The variation in chemistry across the meteorite groups is consistent with alteration by low temperature chemical oxidation. It is concluded that such chemistry principally affected the aliphatic moieties whereas the aromatic moieties and nanodiamonds may have been largely unaffected. 相似文献
6.
The analysis of excess 129Xe in meteoritic nanodiamonds and the kinetics of its release during stepwise pyrolysis allow to suggest that (1) in the solar nebula 129I atoms were adsorbed onto nanodiamond grains and (or) chemisorbed by forming covalent bonds with carbon atoms. Most 129I atoms existed in a surface connected state, but a minor amount of them was in nanopores of the grains. At radioactive decay of 129I the formed 129Xe (129Xe∗) was trapped by diamond grains due to nuclear recoil. (2) During thermal metamorphism or aqueous alteration, the surface-sited 129I atoms were basically lost. On the basis of these assumptions and calculated concentrations of 129Xe∗ in meteoritic nanodiamonds it is shown that the minimum closing time of the I-Xe system for meteorites of different chemical classes and low petrologic types may be about one million years relative to the minimally thermally metamorphized CO3 meteorite ALHA 77307. With increasing metamorphic grade the closing time of the I-Xe system increases and can range up to several ten millions years. This tendency is in agreement with an onion-shell model of structure and cooling history of meteorite parent bodies where the temperature increases in the direction from surface to center of the asteroids. 相似文献
7.
The paper presents a new physicochemical model of the formation of nanosized diamonds from an OHC fluid system under low temperature
and pressure conditions corresponding to the graphite stability area. This model in general explains the specific features
of the composition of gas mixtures for CVD and hydrothermal synthesis in terms of diamond growth and formation under metastable
conditions. It also explains the origin of nanodiamonds and microdiamonds in metamorphic rocks of the Earth’s crust and the
genesis of nanodiamonds in outer space at low temperatures and pressures. 相似文献
8.
The results of spectroscopic and structural studies of phase composition and defects in nanodiamonds from Efremovka (CV3) and Orgueil (CI) chondrites indicate that nitrogen atomic environment in meteoritic nanodiamonds (MND) is similar to that observed in synthetic counterparts produced by detonation and by the Chemical Vapor Deposition (CVD)-process. Most of the nitrogen in MND appears to be confined to lattice imperfections, such as crystallite/twin boundaries and other extended defects, while the concentration of nitrogen in the MND lattice is low. It is suggested that the N-rich sub-population of MND grains may have been formed with high growth rates in environments rich in accessible N (i.e., N in atomic form or as weakly bonded compounds). For the first time the silicon-vacancy complex (the “silicon” defect) is observed in MND by photoluminescence spectroscopy. 相似文献
9.
We observe a 1.3 kg C/net GJ variation of carbon emissions due to inertinite abundance in some commercially available bituminous coal. An additional 0.9 kg C/net GJ variation of carbon emissions is expected due to the extent of coalification through the bituminous rank stages. Each percentage of sulfur in bituminous coal reduces carbon emissions by about 0.08 kg C/net GJ. Other factors, such as mineral content, liptinite abundance and individual macerals, also influence carbon emissions, but their quantitative effect is less certain.The large range of carbon emissions within the bituminous rank class suggests that rank-specific carbon emission factors are provincial rather than global. Although carbon emission factors that better account for this provincial variation might be calculated, we show that the data used for this calculation may vary according to the methods used to sample and analyze coal. Provincial variation of carbon emissions and the use of different coal sampling and analytical methods complicate the verification of national greenhouse gas inventories. 相似文献
10.
Elemental carbon was extracted from sediments by chemical oxidation and identified by Raman spectroscopy. The experimental
results indicate that elemental carbon, defined by processing, is a continuum ranging from single crystal graphite to amorphous
carbon. Chemical oxidation is a feasible method to extract elemental carbon from sediments, and when experimental condition
and time are properly controlled, it can remove organic carbon without any loss of elemental carbon. However, due to the differences
in experimental conditions and methods, different results have been obtained. Therefore, we believe that the determination
of standard sample and its concentration as well as the unification of the experimental method are of great importance. Also,
the unification and definition of all these carbon particulates can facilitate transect comparison and further research in
related fields. In profile research, elemental carbon was extracted and determined by using the same method. The elemental
carbon curve tends to change with other climatic proxies, indicating elemental carbon can provide another new proxy for climatic
and environmental changes. Based on the analysis, we deduce that the elemental carbon record has different implications for
climate and environmental changes on different time-scales.
__________
Translated from Acta Sedimentologica Sinica, 2007, 25(5): 745–752 [译自: 沉积学报] 相似文献
11.
陆地生态系统的碳收支是全球气候变化和碳循环研究的核心内容之一.准确估算陆地生态系统的碳储量及其收支状况,对正确评价陆地生态系统在全球碳循环中的作用有重要意义.本文总结了近10年来各国研究者利用不同方法对陆地碳储量变化的研究进展,并对估算陆地碳储量的不确定性进行评价.同时,对陆地生态系统碳储量变化研究结果的分析表明,末次间冰期以来,全球陆地生态系统碳储量存在较大幅度的变化.在末次间冰期5e阶段、末次盛冰期和全新世中期,陆地生态系统碳储量分别为现在的l30～150%、50～85%和105～130%.并且,陆地生态系统碳储量与气候变化有显著的正相关性,但不同区域的生态系统碳储量随气候变化并非具有相同的变化规律. 相似文献
12.
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
13.
M. Salmasi S. Fatemi M. Doroudian Rad F. Jadidi 《International Journal of Environmental Science and Technology》2013,10(5):1067-1074
Carbon dioxide is known as a hazardous material with acidic property that can be found as impurity in natural gas reservoirs with a broad range of 2 up to 40 %. Therefore, many efforts have been directed to remove and separate carbon dioxide from methane to prevent corrosion problems as well as improving the natural gas energy content. In this study, two molecular sieves, silicoaluminophosphate-34 (SAPO-34) zeotype and T-type zeolite, were synthesized by the hydrothermal method for the comparative study of adsorptive separation of carbon dioxide from methane. The synthesized adsorbents were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and Brunner–Emmett–Teller techniques. These characterization tests confirmed formation of both materials with acceptable crystallinity. Both adsorbents were tested in equilibrium adsorption experiments in order to evaluate maximum capacity and adsorption affinity. Adsorption capacity of carbon dioxide and methane on SAPO-34 and zeolite T were measured in a pressure range of 0.1–2.0 MPa and temperature of 288, 298, and 308 K and fitted with the Sips and Langmuir isotherm models. The ideal selectivity of CO2/CH4 was determined for SAPO-34 and zeolite T at the studied pressures and temperatures, indicating that the molecular sieves can be properly used for CO2–CH4 separation or CO2 capturing from natural gas. 相似文献
14.
2015年8月,在人工温室培养环境下,以蛋白核小球藻为实验材料,通过向培养液中添加两种标记δ13C的碳酸氢钠来培养微藻,每天定时监测培养液的无机碳稳定同位素组成和微藻生物量,并测定最终获得的微藻藻体的有机碳稳定同位素组成,运用双同位素示踪模型,通过无机碳稳定同位素和有机碳稳定同位素两种方法,分别成功计算出了微藻利用不同碳源的份额,实验结果分别为:添加5.0 mmol/L碳酸氢钠条件下是0.19、添加10.0 mmol/L条件下是0.37、而添加20.0 mmol/L条件下是0.57。并对这两种算法进行了分析。定量计算微藻对不同无机碳源的利用份额,在岩溶湖泊碳循环研究领域具有重要意义。 相似文献
15.
Stephan Pötter Arndt Schmitz Andreas Lücke Philipp Schulte Igor Obreht Michael Zech Holger Wissel Slobodan B. Marković Frank Lehmkuhl 《Boreas: An International Journal of Quaternary Research》2021,50(1):184-204
Stable organic carbon and nitrogen isotopes can be used to interpret past vegetation patterns and ecosystem qualities. Here we present these proxies for two loess-palaeosol sequences from the southern Carpathian Basin to reconstruct the palaeoenvironment during the past 350 ka and establish regional commonalities and differences. Before now, isotopic studies on loess sequences from this region were only conducted on deposits from the last glacial cycle. We conducted methodological tests involving the complete decalcification of the samples prior to stable isotope analyses. Two decalcification methods (fumigation method and wet chemical acidification), different treatment times, and the reproducibility of carbon isotope analyses were tested. Obtained results indicate that the choice of the decalcification method is important for organic carbon stable isotope analyses of loess-palaeosol sequences because ratios vary by more than 10‰ between the wet chemical and fumigation methods, due to incomplete carbonate removal by the latter. Therefore, we suggest avoiding the fumigation method for studies on loess-palaeosol sequences. In addition, our data show that samples with TOC content <0.2% bear increased potential for misinterpretation of their carbon isotope ratios. For our sites, C3-vegetation is predominant and no palaeoenvironmental shifts leading to a change of the dominant photosynthesis pathway can be detected during the Middle to Late Pleistocene. Furthermore, the importance of further stable nitrogen isotope studies is highlighted, since this proxy seems to reflect past precipitation patterns and reveals favourable conditions in the southern Carpathian Basin, especially during interstadials. 相似文献
16.
碳中和愿景下,加强森林的固碳增汇功能是抵消和吸纳碳排放最经济和最有效的途径。精准评估森林碳汇和预估森林固碳潜力,有助于量化森林在应对气候变化和实现碳中和愿景中的贡献。然而,森林分布的广泛性、森林生态系统结构的复杂性以及评估数据的代表性不够和方法学的差异性,造成森林碳汇评估的结果普遍存在精度低、不确定性高的问题。在界定森林碳储量、碳汇和固碳潜力等基本概念后,从森林定义、评估时空尺度、碳库选择及其基本方法等方面阐述了森林碳汇评估的方法,分析各类方法的主要特征、主要问题、优势和不足; 基于面积和生长假设情景,回顾了森林固碳潜力预估方法,重点分析了近10 a中国森林固碳潜力研究成果,预估到2030年和2060年,中国森林植被的年固碳潜力分别可达1.69亿t/a和1.48亿t/a左右的水平。最后,探讨了森林碳汇评估方法和固碳潜力预估的未来发展趋势,为不同时空尺度下森林碳汇评估和固碳潜力预估提供参考。 相似文献
17.
Janina Szaran 《Chemical Geology》1998,150(3-4):331-337
Fractionation of the stable carbon isotopes between dissolved and gaseous carbon dioxide has been measured at temperature 25°C by two methods. In the first method the open system conditions and different methods of CO2 sampling were arranged. In the second method—the closed system conditions and CO2 gas extraction were used. The results obtained by these methods are very consistent. Gaseous CO2 is enriched in heavy isotope
by 1.03±0.02 permil in comparison to dissolved carbon dioxide. 相似文献
18.
19.
研究岩性差异对溶蚀速率的影响有助于提高溶蚀试片法估算岩溶碳汇强度的精确度。本文以贵州省普定县为研究区,将埋放地的主要基岩类型（石灰岩与白云岩）制成标准尺寸的试片,并将其埋设于不同土地利用类型和土壤深度下,经过4个水文年的监测后将估算的结果与前人在同一区域使用标准溶蚀试片的研究结果进行对比分析,结果表明:（1）在相同气候和土壤环境条件下,岩性对溶蚀试片的溶蚀速率有显著影响,且溶蚀速率与岩石中CaO含量呈正相关关系,与MgO含量呈负相关关系;（2）石灰岩与白云岩试片溶蚀速率的差异程度受土地利用及埋放深度的调控,整体上石灰岩溶蚀速率比白云岩溶蚀速率大14%;（3）不同岩性试片估算的岩溶碳汇强度相差较大,标准溶蚀试片估算的结果比埋放地基岩试片估算的结果高。故使用溶蚀试片法估算区域岩溶碳通量时应考虑埋放地基岩的岩性,或者对基于标准溶蚀试片的估算结果进行校正,才能准确反映区域尺度真实的岩溶碳通量大小。 相似文献
20.
U.S. National Bureau of Standards (NBS) estuarine sediment 1646 from the Chesapeake Bay, Maryland, and surface sediment collected at two sites in the Calcasieu River estuary, Louisiana, were used to evaluate the dilute hydrochloric acid extraction of Cr, Fe and Mn from air-dried and freeze-dried samples that had been treated by one of three methods to remove organic carbon. The three methods for the oxidation and removal of organic carbon were: (1) 30% hydrogen peroxide; (2) 30% hydrogen peroxide plus 0.25 mM pyrophosphate; and (3) plasma oxidation (low-temperature ashing). There was no statistically significant difference at the 95% confidence level between air- and freeze-dried samples with respect to the percent of organic carbon removed by the three methods. Generally, there was no statistically significant difference at the 95% confidence level between air- and freeze-dried samples with respect to the concentration of Cr, Fe and Mn that was extracted, regardless of the extraction technique that was used. Hydrogen peroxide plus pyrophosphate removed the most organic carbon from sediment collected at the site in the Calcasieu River that was upstream from industrial outfalls. Plasma oxidation removed the most organic carbon from the sediment collected at a site in the Calcasieu River close to industrial outfalls and from the NBS estuarine sediment sample. Plasma oxidation merits further study as a treatment for removal of organic carbon. Operational parameters can be chosen to limit the plasma oxidation of pyrite which, unlike other Fe species, will not be dissolved by dilute hydrochloric acid. Preservation of pyrite allows the positive identification of Fe present as pyrite in sediments. 相似文献