Carbon Trapping Research Articles

Efficient trapping of organic carbon in sediments on the continental margin with high fluvial sediment input off southwestern Taiwan

Accumulation rates of marine and terrigenous organic carbon in the continental margin sediments off southwestern Taiwan were estimated from the measured concentrations and isotopic compositions of total organic carbon (TOC) and previously reported sedimentation rates. Surficial sediments were collected from the study area spanning from the narrow shelf near the Kaoping River mouth to the deep slope with depths reaching almost 3000 m. The average sediment loading of Kaoping River is 17 Mt/yr, which yields high sediment accumulation rates ranging from 0.08 to 1.44 g cm −2 yr −1 in the continental margin. About half of the discharged sediments were deposited on the margin within 120 km of the river mouth. Carbon isotopic compositions of terrestrial and marine end-members of organic matter were determined, respectively, based on suspended particulate matter (SPM) collected from three major rivers in the southwestern Taiwan and from an offshore station. All samples were analyzed for the TOC content and its isotopic composition ( δ 13C org). The SPM samples were also analyzed for the total nitrogen (TN) content. TOC content in marine sediments ranges from 0.45% to 1.35% with the highest values on the upper slope near the Kaoping River mouth. The TOC/TN ratio of the SPM samples from the offshore station is 6.8±0.6, almost identical to the Redfield ratio, indicating their predominantly marine origin; their δ 13C org values are also typically marine with a mean of −21.5±0.3‰. The riverine SPM samples exhibit typical terrestrial δ 13C org values around −25‰. The δ 13C org values of surficial sediments range from −24.8‰ to −21.2‰, showing a distribution pattern influenced by inputs from the Kaoping River. The relative contributions from marine and terrestrial sources to sedimentary organic carbon were determined by the isotope mixing model with end-member compositions derived from the riverine and marine SPM. High fluvial sediment inputs lead to efficient trapping of organic carbon over a wide range of water depth in this continental margin. The marine organic accumulation rate ranges from 1.6 to 70 g C m −2 yr −1 with an area weighted mean of 4.2 g C m −2 yr −1, which is on a par with the mean terrestrial contribution and accounts for ∼2.3% of mean primary production. The depth-dependent accumulation rate of marine organic carbon can be simulated with a function involving primary productivity and mineral accumulation rate, which may be applicable to other continental margins with high sedimentation rates. Away from the nearshore area, the content of terrigenous organic carbon in surficial sediments decreases with distance from the river mouth, indicating its degradation in marine environments.

Atomic scale observations of bainite transformation in a high carbon high silicon steel

A fine-scale bainitic microstructure with high strength and high toughness has been achieved by transforming austenite at 200 °C. X-ray diffraction analysis showed the carbon concentration of these bainitic ferrite plates to be higher than expected from para-equilibrium. Atom-probe tomography revealed that a substantial quantity of carbon was trapped at dislocations in the vicinity of the ferrite–austenite interface. These results suggest that the carbon trapping at dislocations prevents the decarburization of super-saturated bainitic ferrite and therefore alters the carbide precipitation sequence during low-temperature bainite formation.

In-situ observations of lattice parameter fluctuations in austenite and transformation to bainite

The isothermal transformation of high-carbon austenite-to-bainitic ferrite has been investigated with the in-situ technique of time-resolved X-ray diffraction using synchrotron radiation. The measurements indicate that prior to transformation, the austenite divided into regions with significantly different lattice parameters. It is possible that this is due to the development of carbon-rich and carbon-poor regions in the austenite, as a precursor to transformations including the bainite reaction. The lattice parameter became uniform as transformation progressed and the fraction of carbon-poor austenite decreased. The ferrite itself exhibited a large range of lattice parameters during the early stages of transformation, due to the trapping of carbon.

Production of hydrogen by thermal methane splitting in a nozzle-type laboratory-scale solar reactor

A high-temperature solar reactor has been developed for co-producing hydrogen-rich gas and high-grade carbon black (CB) from concentrated solar energy and methane. The approach is based on a single-step thermal decomposition (pyrolysis) of methane without catalysts and without emitting carbon dioxide since solid carbon is sequestered. In the tested reactor, a graphite nozzle absorbs concentrated solar radiation provided by a solar furnace. The heat is then transferred to the reactive flow. The experimental setup, first test results, and effect of operating conditions are described in this paper. The conversion of methane was strongly dependant on the solar furnace power input, on the geometry of the graphite nozzle, on gas flow rates, and on the ratio of inert gas-to-reactive gas. CB was recovered in the carbon trap, and maximum chemical conversion of methane-to-hydrogen and CB was 95%, but typical conversion was in the range 30–90%.

Effect of phosphorus on the formation of titanium carbide in 17% Cr ferritic steels stabilized with titanium

The trapping of carbon by titanium in ferritic stainless steels with low interstitial contents depends on the presence of other non metallic elements such as phosphorus. The decrease of phosphorus content in the steels promotes the segregation of carbon at the grain boundaries and prevents the formation of the titanium carbonitrides. In fact, the formation of these precipitates depends on the quantity of remaining carbon in the matrix after the segregation of this element at the grain boundaries. Thus, this quantity could be sufficient to allow the formation of Ti(C, N) compounds by reduction of their solubility as the tempering temperature is decreased.

Synthesis of the cis diastereoisomer of 5-diethoxyphosphoryl-5-methyl-3-phenyl-1-pyrroline N-oxide (DEPMPPO c) and ESR study of its superoxide spin adduct

The cis and trans diastereoisomers of 5-diethoxyphosphoryl-5-methyl-3-phenyl-1-pyrroline N-oxide (DEPMPPO), the C(3)-phenyl analogue of DEPMPO, were prepared in three steps from phenylacetaldehyde and used in ESR-spin trapping of various carbon-, oxygen- and sulfur-centred radicals. In the case of the cis-isomer, the presence of the phenyl group cancels the alternating line width phenomenon observed for the DEPMPO–OOR (R = H, Bu t ) spin adducts. The ESR spectra of the DEPMPPO c–OOR spin adducts exhibit more straightforward patterns and are more easily assignable.

85Kr Extraction from Water Samples

A system for extracting krypton from a sample of natural water preextracted under field conditions is described. A carbon trap at –76°C is used to precipitate inert gases. The β radiation of 85Kr is detected using a 3.5-liter multiwire proportional counter, placed on the ground and in a gallery at a depth of 500 m water equivalent in a low-background counter. The background of the counter enclosed in shielding with a built-in anticoincidence ring in the 85Kr β-particle energy range is 0.8 counts/min on the surface and 2 counts/h in the underground laboratory. Various schemes for degassing and removing krypton from water samples are examined – heating, bubbling, and vacuum degassing. The extraction coefficients for dissolved gases are as follows: 88 ± 2% for extraction by heating water, 95 ± 3% for bubbling, and 70 ± 10% for vacuum degassing. Preliminary measurements show that the 85Kr concentration in different natural waters in Krasnodarsk krai is 130–1080 decays/min·mmole.

Chemical Behaviors of Energetic Deuterium Implanted into Boron Coatings

To study chemical behaviors of energetic deuterium implanted into boron coating deposited by boronization in fusion devices, two types of boron coating film deposited on silicon and IG-430U were prepared by Plasma Chemical Vapor Deposition (PCVD) technique. Boron polycrystal was used as the reference sample. The chemical behavior of deuterium was investigated by XPS (X-ray photoelectron spectroscopy) and TDS (Thermal adsorption spectroscopy).The 1.0 keV D2+ ions were implanted into the samples and the deuterium desorption behavior was studied by TDS. The TDS spectra showed that there were two deuterium release peaks at around 550 and 750 K, which were attributed to the release from deuterium trapped by boron and carbon, respectively. It was also found that most of implanted deuterium was trapped in carbon trapping site compared with boron one.In XPS measurements, the chemical shift of B-1s towards positive side was observed in the film on IG-430U after D2+ ion implantation. However, no chemical shifts were found in the film on silicon and boron polycrystal. In highly concentrated boron materials, even if deuterium was implanted into the boron materials, the amount of B-D bond was too low to be measured by XPS. This suggests that deuterium implanted into highly pure boron materials wasn’t almost trapped, so that the retention of deuterium in the boron materials would be reduced, compared that in carbon materials.

Hydride phase formation in carbon supported palladium nanoparticle electrodes investigated using in situ EXAFS and XRD

In situ EXAFS (extended X-ray absorption fine structure), in situ XRD (X-ray diffraction) and electrochemical studies have been used to investigate the palladium hydride phases of carbon supported palladium nanoparticles as a function of applied potential. Electrochemical investigations showed an increase in the hydrogen to palladium ratio with an increasingly negative potential. The H/Pd ratio could be divided into four distinct regions, which described the palladium hydride phase present; the α-phase, a mixture of the α- and β-phases, the β-phase, and a hyperstoichiometric region. The β-hydride phase stoichiometry obtained from the electrochemical data corresponded to PdH. However, the composition obtained from the lattice expansions observed from the in situ EXAFS and XRD, 3.3% and 3.8%, correspond to compositions of PdH0.59 to PdH0.68. The excess hydrogen and hyperstoichiometric amounts found at more negative potentials are attributed to either spillover on to the carbon support or trapping and subsequent reoxidation of H2 in the porous electrode structure.

Fluid transfers at the basement/cover interface: Part I. Subsurface recycling of trace carbonate from granitoid basement rocks (France)

Basement rocks usually contain trace amounts of disseminated carbonate minerals and sometimes also fractures/veins filled with carbonates which may have a variety of origins. Extensive drilling has been performed of a granitoid body (Vienne, western part of the French Massif Central) overlain by a carbonate sedimentary sequence, a situation which is representative of most of the Variscan basement in western Europe. These unique samples provide the opportunity to investigate the behaviour of basement trace carbonate across the basin/basement interface and the mass transfers throughout a series of fluid migration ranging from high (ca. 450 °C) to low (down to 50 °C) temperature conditions. Study of quartz and carbonate found in fracture infillings reveals three major stages of fluid circulation, namely: (1) high to medium temperature late Hercynian fluids which circulated in fractures developed during basement uplift; (2) medium temperature Mesozoic basinal brines migration laterally along the basement/cover contact; (3) late infiltration of diagenetic/marine waters in the upper part of the granitoid body. A majority of analyzed vein carbonates from the three stages displayed a rather restricted range of C isotopic compositions ( δ 13C between −14‰ and −9‰/PDB) whatever the stage in which they were deposited and despite large variations of O isotopic ratios ( δ 18O in the range +3‰ to +30‰/SMOW). Carbon in pervasively altered rocks displays the same features and is distributed among the two broad groups defined using O isotopic ratios in veins and fluid inclusions data, namely the Hercynian and the Mesozoic carbonates. Isotopic data argue that carbon was introduced as carbonates in the early stages of the retrograde Hercynian metamorphism and was systematically reworked by subsequent fluids without any significant carbon introduction from external sources. The only exception corresponds to the stage III calcite veins which are located in the upper sections of the cores, at depths lower than 350 m beneath the basement/cover boundary and are the only witnesses of element transfer from the sediments towards the basement. The present data show that trapping of carbon by Ca-rich plutonic rocks during their cooling history confers on these rocks an efficient self-sealing capacity during later fracturing and fluid flow because carbonates possess high solubility and rapid dissolution/precipitation kinetics. Fluid circulation occurred not only in the macroscopic system of fractures but also within some volumes of the granitic “matrix” in order to scavenge and redistribute the early granitic trace carbonate. In the event of poly-cyclic carbonate redistribution, the use of carbon isotopic composition to unravel the fluid origins must be exercised with caution, as early C could be easily redistributed during later fluid migration episodes.

On-line coupling of supercritical fluid extraction with high-performance liquid chromatography for the determination of explosives in vapour phases

An analytical method for determining nitroaromatic explosives in vapour phases is presented. Samples were collected by pumping air through glass fibre filters and polyurethane foam adsorbents, and an on-line extraction system combining supercritical fluid extraction (SFE) and high-performance liquid chromatography (HPLC) was developed. This allows analytes to be transferred from the adsorbent to the HPLC system via a porous graphitic carbon trap. When using gradient elution with a suitable mobile phase, most of the nitroaromatic isomers tested were separated. The proposed method is fully automated, allows a complete analysis to be processed in less than 30 min, and it is compatible with most of the organic solvents commonly used as SFE modifiers or additives. The method has been applied to the analysis of real samples obtained from headspace sampling of military-grade 2,4,6-trinitrotoluene and has been shown to constitute a promising alternative for assessing whether areas are mined in landmine-clearing operations.

ABSTRACT: Modeling the Structural and Deformational Architecture of Complex Hydrocarbon Traps by HCA Numerical Techniques

Kinematic and geometric models have been proved to be very useful for the interpretation and balancing of fault-related folds. A major limitation of geometric models is that they are fully constrained by geometrical rules that do not take into account the rheology of the deforming rocks, the mechanical balance of the growing structures, and their interaction with surface processes. On the other hand, finite element numerical models are strongly dependent on the architecture of the undeformed mesh and on remeshing algorithms. We approached the modelling of fault-related folds by developing a set of self-determining algorithms that successfully reproduce the behaviour of natural rock multilayers undergoing faulting and folding. The rheology and thickness of each layer (both pre-growth and growth strata) are specified, with no geometrical constraints apart from initial layering and the shape of the faults. The shape of the fault and the mechanical behaviour of the deforming material then determine the shape of the folded hangingwall. A great variety of both compressional and extensional fault-fold kinematics can be modelled, including synchronous faulting and re-faulting of deformed structures. Deformation intensity is computed during each iteration and can be displayed as a model output. In this work we apply our modelling technique to the evolution of field analogues of typical carbonate trap structures in the Apennines.

Carbon Dispersion and Morphology in Carbon–Mineral Adsorbents

Carbon–mineral composite adsorbents prepared by deposition of carbon on various mineral supports have been studied extensively by a new textural approach. The evidence of significant influence of both organization of initial mineral support porous space and mobility of carbon precursors over the surface of mineral support on carbon localization has been obtained. Restricted mobility of carbon precursors leads to homogeneous distribution of carbon clusters over the support surface despite the presence of narrow mesopores in the structure of the support if the entire support surface is equiaccessible. Unrestricted mobility over the smooth surface of the mineral support without narrow mesopores leads to the similar resulting carbon distribution. However, unrestricted mobility of carbon precursors in densely packed porous materials seems to be the reason for carbon pulling and deposition in narrow mesopores. These peculiarities of carbon deposition influence the carbon/mineral (hydrophobic/hydrophilic) composition of the composite surface. Trapping of carbon in narrow mesopores leads to a decrease and, in contrast, homogeneous dispersion of carbon over the whole support surface leads to an increase in the part of the composite surface, which can be appropriated to carbon.

Structure of laser remelted surface of cast irons

Grey and white cast irons were surface remelted using a high power CO2 laser with a scanning velocity in the range 0·5–200 mm s-1 and the resulting surface structures were investigated using optical microscopy and X-ray diffraction. The remelted surface of the white iron was composed of austenite dendrites, which decompose to pearlite at low cooling rates and martensite at medium cooling rates. The maximum volume fraction of martensite was obtained at 10 mm s-1. The lattice parameter of the austenite increased with increasing solidification velocity owing to solute trapping of carbon. The remelted surface of the grey iron was composed of cellular ledeburite and X-ray diffraction analyses of the grey specimen indicated the presence of austenite, martensite, graphite, cementite, and ɛ phases. The initial austenite partially transformed to martensite at high cooling rates and to ɛ phase at low cooling rates. The appearance of the ɛ phase is therefore linked to the decomposition of supersaturated austenite.

Carbon influence on γ-irradiation induced defects in n-type CZ Si

The study of irradiation effect of γ rays for 60Co source on n-type carbon-free and carbon-rich Czochralski silicon single crystals is presented, based on deep level transient spectroscopy technique. It is shown that generation of vacancy-related defects is significantly enhanced in carbon-rich silicon in respect to carbon-free samples. Divacancy and multivacancy-related defects were particularly enhanced. The observed behavior is discussed and related to the carbon presence in the bulk. Carbon trapping of self-interstitials significantly enhanced vacancy concentration that further caused observed behavior.

Novel synthesis of heterocyclic aryl amidines

We have developed a novel amidine synthesis that allows the preparation of heterocyclic amidines that were previously unknown and difficult to prepare by published methods. The route involves the lithiation of heterocycles by the action of n-BuLi followed by reaction with carbon disulfide and trapping with methyl iodide, yielding a dithioate ester. The latter, when heated in 20% methanolic ammonia at 80°C in a sealed tube provides the heterocyclic amidines directly, in good yield. The products are isolated by crystallization of the respective hydrochloride salts.

The birth of the Earth's atmosphere: the behaviour and fate of its major elements

Abstract The accretion of the major volatiles of the Earth is described in the frame of the integral Enstatite Chondrite model [Javoy, M., 1995. The integral Enstatite Chondrite model of the Earth. G.R. Lett., 22, 2219–2222.]. The accretion of the Earth–Moon system takes place inside an inner solar system dominated by EH type material, at temperatures ≥1000°C. A late evolution of that system brings back some unmodified CI material at the end of the accretion on the edge of the inner zone where the Earth resides. This is the cause of a late veneer deposit weighing ∼1.4 per mil of the Earth mass. Following this model the upper and lower mantle are decoupled and the volatile evolution concerns essentially the Upper Earth (UE) (upper mantle+crust+ocean–atmosphere) with negligible contributions from the lower mantle. The main features are the following: (a) the bulk of the primary reduced material, constituting more than 99.8% of the total mass of the planet brought an isotopically light component corresponding to 6% of the hydrogen, 48% of the carbon and 70% of the nitrogen of the UE. (b) the late veneer (7.5 per mil of the UE's, 1.4 per mil of the bulk Earth's mass) of CI (or cometary) composition supplied an isotopically heavy component of H and N corresponding to 94% of the hydrogen, 52% of the carbon and 30% of the nitrogen. (c) the availability of oxygen in the UE results first from the partial reduction of silicon during the upper mantle–lower mantle–core differentiation (Javoy, 1995) bringing ∼7.5% FeO in the upper mantle. Then, the extra oxidizing reservoir due to the CI veneer creates the right proportion of FeIII in that primarily FeII system and explains the current 2.5% Fe3+/Fe2+ presently observed in the upper mantle. (d) atmospheric radiogenic argon is derived essentially from the outgassing of the UE which contains ∼450 ppm of potassium. The present distribution of the major volatiles in the UE corresponds to a negligible supply from the lower mantle. Measured in units of the superficial reservoirs (oceans, atmosphere, crustal carbon), the contents of the upper mantle are the following: water: 0.21 ocean masses, nitrogen: ∼10 atmosphere masses, carbon: 5.4 crustal carbon masses. This corresponds to a very significant trapping of carbon and nitrogen by the mantle during the Earth's history, whereas water repartition stayed about unchanged and strongly favoured the superficial reservoir. That difference between carbon and water is due to the fact that the major part of subducted water from oceanic crust escapes via arc volcanism. There is another very significant difference between carbon and nitrogen; the present outgassing and subducting fluxes of carbon are both mass- and isotopically-equilibrated, whereas there is still a gross isotopic disequilibrium for nitrogen, with the large, isotopically-heavy, subducted flux still outweighing the small, isotopically-light, outgassed flux. This is due to the fact that while carbon and water are essentially incompatible components, nitrogen is a compatible element because of the presence of very stable mantle nitrides (probably osbornite) or of nitride ions substituting oxygen in silicates.

Annealing behaviour and ranges of implanted ions in III–V and II–VI compound semiconductor materials

Annealing behaviour and ranges of 15–40 keV (doses of 10 15–10 16 cm −2) 13C + and 19F + ions implanted in InP, 13C +, 15N + and 30Si + in GaAs and 15N + in ZnSSe have been investigated. Ion distributions were measured by the nuclear resonance broadening technique by taking advantage of narrow resonances in (p,γ) and (p,αγ) reactions. Annealing of samples was carried out both in Ar atmosphere and in vacuum at temperatures from 300°C to 950°C. Trapping of carbon in InP and GaAs and of nitrogen in GaAs was observed. Surface enrichment was observed in case of silicon implanted GaAs and nitrogen in ZnSSe. Loss of fluorine in InP was found at temperatures above 350°C in 30 min annealings. Range parameters from the deconvoluted depth profiles were determined and compared with semiempirical calculations.

Development of microbial mercury detoxification processes using mercury-hyperresistant strain ofPseudomonas aeruginosa PU21

A mercury-hyperresistant strain of Pseudomonas aeruginosa PU21 harboring plasmid Rip64 was utilized to develop bioprocesses able to detoxify and recover soluble mercuric ions in aquatic systems. The kinetics of mercury detoxification was investigated to determine the parameters needed for the design of the bioprocesses. Batch, fed-batch, and continuous bioreactors were utilized to evaluate the efficiency and feasibility of each mode of operation. The results showed that the specific mercury detoxification rate was dependent on cell growth phases, as well as the initial mercury concentrations. Cells at the lag growth phase exhibited the best specific detoxification rate of approximately 1.1 x 10(-6) microg Hg/cell/h, and the rate was optimal at an initial mercury concentration of 8 mg/L. In batch operations with initial mercuric ions ranging from 2 to 10 mg/L, the mercuric ions added were rapidly volatilized from the media in less than 2-3 h. With periodic feeding of 3 or 5 mg Hg/L at fixed time intervals, the fed-batch processes had mercury removal efficiencies of 2.9 and 3.3 mg Hg/h/L, respectively. For continuous operations, the effluent cell concentration (Xe) was essentially invariant at 527 and 523 mg/L with the dilution rates (D) of 0.18 and 0.325 h-1, respectively. The increase in mercury feeding concentrations (Hgf) from 1.0 to 6.15 mg Hg2+/L did not affect the steady-state cell concentration (Xe) but forced the effluent mercury concentration (Hge) to increase. The decrease in the dilution rate, however, resulted in lower Hge values. It was also found that sequential mercury vapor absorption columns recovered over 80% of the Hg degrees released from the bioreactor while the residual mercury vapor was subsequently immobilized by an activated carbon trap in the down stream of the absorption column.

Simple laboratory-made system for the determination of C2–C7 hydrocarbons relevant to photochemical smog pollution

A simple gas chromatographic system suitable for determining volatile organic compounds from C2 to C7 in air is described. It consists of a capillary cold trap filled with graphitic carbon, a thermodesorbing device, a capillary gas chromatograph equipped with an alumina column and a flame ionization detector. Dry, as well as humid, air samples can be analysed with our system. Up to 2-l samples of air can be enriched on our trapping device by using Nafion membranes for removing water. Direct analysis of air samples is possible by enriching 250 ml on the carbon trap. The recovery, sensitivity and linearity of our system have been checked with standard mixtures and real samples. The performances have been compared with those afforded by a commercially available instrument exploiting a different enrichment procedure. The results obtained show that our analyser can be successfully applied to determinations of C2 to C7 hydrocarbons present in air samples at levels of 0.01 ppb (v/v).