Science.gov

Sample records for organic carbon iron

  1. Selective stabilization of aliphatic organic carbon by iron oxide

    PubMed Central

    Adhikari, Dinesh; Yang, Yu

    2015-01-01

    Stabilization of organic matter in soil is important for natural ecosystem to sequestrate carbon and mitigate greenhouse gas emission. It is largely unknown what factors govern the preservation of organic carbon in soil, casting shadow on predicting the response of soil to climate change. Iron oxide was suggested as an important mineral preserving soil organic carbon. However, ferric minerals are subject to reduction, potentially releasing iron and decreasing the stability of iron-bound organic carbon. Information about the stability of iron-bound organic carbon in the redox reaction is limited. Herein, we investigated the sorptive interactions of organic matter with hematite and reductive release of hematite-bound organic matter. Impacts of organic matter composition and conformation on its sorption by hematite and release during the reduction reaction were analyzed. We found that hematite-bound aliphatic carbon was more resistant to reduction release, although hematite preferred to sorb more aromatic carbon. Resistance to reductive release represents a new mechanism that aliphatic soil organic matter was stabilized by association with iron oxide. Selective stabilization of aliphatic over aromatic carbon can greatly contribute to the widely observed accumulation of aliphatic carbon in soil, which cannot be explained by sorptive interactions between minerals and organic matter. PMID:26061259

  2. Iron-sulfur-carbon relationships in organic-carbon-rich sequences I: Cretaceous Western Interior seaway

    USGS Publications Warehouse

    Dean, W.E.; Arthur, M.A.

    1989-01-01

    Cretaceous marine strata deposited in shallow to intermediate depths in the Western Interior seaway of North America show considerable variation in organic-carbon enrichment and degree of pyrite formation. The extreme range of paleoceanographic and depositional conditions that occurred in this seaway provide a unique opportunity to examine the effects of iron-, carbon-, and sulfur-limitation on pyrite formation in one region over about 30 my. Ternary diagrams of the system Fe-S-OC, together with some measure of the reactivity of organic matter (pyrolysis hydrogen index), provide a rapid means of recognizing iron-, carbon-, and sulfur-limitation on pyrite formation in a series of samples from a single lithologic unit. Iron limitation is indicated by a concentration of data along a line of constant S/Fe ratio on a Fe-S-OC ternary diagram. Carbon limitation is indicated by a concentration of data along a line of constant S/OC ratio. Sulfur-limitation is suggested by the lack of a systematic Fe-S-OC relationship and residual organic matter that is high in abundance and reactivity. -from Authors

  3. Entrapment of ancient and modern organic carbon by iron on the Eurasian Arctic Shelf

    NASA Astrophysics Data System (ADS)

    Salvado, Joan A.; Tesi, Tommaso; Semiletov, Igor P.; Dudarev, Oleg V.; Gustafsson, Örjan

    2015-04-01

    Given the potential for climate-carbon feedbacks in the Siberian-Arctic land-ocean system, there is a need for improved understanding of carbon cycle processes (Vonk et al., 2012). The entrapment of organic carbon in sediments is a key factor to attenuate the outgassing of greenhouse gases to the atmosphere. In this context, there is a pressing need to understand the mechanisms that control preservation and accumulations of organic carbon in marine sediments. Recently, the role of iron oxides in the preservation of organic matter globally has been outlined (Lalonde et al., 2012). In the present study, the composition of organic carbon associated to reactive iron (OC-Fe) on the Eurasian Arctic Shelf is evaluated. For this purpose, sediment cores and grab samples were collected in the shelves of the Kara Sea, Laptev Sea and East Siberian Sea from 9 to 69 m water depth. Experiments were conducted to extract the OC-Fe from the sediments by applying a citrate-dithionite iron reduction method -accurately control corrected- and analyze the δ13C, % OC and Δ14C of the bulk and iron-associated fractions. The results show that 11.0 ± 5.5% of organic carbon in surface-sediments of the Siberian Arctic Shelf is attached to reactive iron. The Δ14C and δ13C signatures presented sharply contrasting offsets between the sedimentary bulk and the OC-Fe. The OC-Fe is much younger than the OC-bulk in the eastern East Siberian Sea and older in the Laptev Sea. The same offsets were observed using a dual-carbon endmember mixing model showing that the iron fraction is mainly composed by young marine plankton organic carbon in the eastern East Siberian Sea and pre-aged thawing permafrost in the Laptev Sea. Overall, it seems that (i) some of this pre-aged organic carbon still remains bound to iron oxides after permafrost thawing and (ii) the iron oxides are transferring dissolved organic carbon to the sediment. This study presents the first analyses of Δ14C ever done in the OC

  4. Effects of iron-aluminium oxides and organic carbon on aggregate stability of bauxite residues.

    PubMed

    Zhu, Feng; Li, Yubing; Xue, Shengguo; Hartley, William; Wu, Hao

    2016-05-01

    In order to successfully establish vegetation on bauxite residue, properties such as aggregate structure and stability require improvement. Spontaneous plant colonization on the deposits in Central China over the last 20 years has revealed that natural processes may improve the physical condition of bauxite residues. Samples from three different stacking ages were selected to determine aggregate formation and stability and its relationship with iron-aluminium oxides and organic carbon. The residue aggregate particles became coarser in both dry and wet sieving processes. The mean weight diameter (MWD) and geometry mean diameter (GMD) increased significantly, and the proportion of aggregate destruction (PAD) decreased. Natural stacking processes could increase aggregate stability and erosion resistant of bauxite residues. Free iron oxides and amorphous aluminium oxides were the major forms in bauxite residues, but there was no significant correlation between the iron-aluminium oxides and aggregate stability. Aromatic-C, alkanes-C, aliphatic-C and alkenes-C were the major functional groups present in the residues. With increasing stacking age, total organic carbon content and aggregate-associated organic carbon both increased. Alkanes-C, aliphatic-C and alkenes-C increased and were mainly distributed in macro-aggregates, whereas aromatic-C was mainly distributed in <0.05-mm aggregates. Organic carbon stability in micro-aggregates was higher than that in macro-aggregates and became more stable. Organic carbon contents in total residues, and within different aggregate sizes, were all negatively correlated with PAD. It indicated that organic materials had a more significant effect on macro-aggregate stability and the effects of iron-aluminium oxides maybe more important for stability of micro-aggregates. PMID:26832865

  5. Enhancing zero valent iron based natural organic matter removal by mixing with dispersed carbon cathodes.

    PubMed

    Liu, Peng; Keller, Jurg; Gernjak, Wolfgang

    2016-04-15

    Former studies have shown that adding granular activated carbon (GAC) cathodes could enhance the overall performance of the zero valent iron (ZVI) process for organics removal. The present study evaluates for the first time the performance of such an enhanced ZVI process to remove natural organic matter (NOM), an important water quality parameter in drinking water. Lab-scale batch tests were conducted with surface reservoir feed water from a drinking water plant. In the GAC enhanced ZVI process dissolved organic carbon (DOC) and UV254 were reduced by 61±3% and 70±2%, respectively, during 24h treatment corresponding to 1.8min empty bed contact time. The process was superior to ZVI alone, particularly during the earlier stages of the process due to the synergistically increased iron dissolution rate. Besides GAC, graphite and anthracite also prove to be suitable and potentially more cost-effective options as cathode materials for the enhanced ZVI process, whereby electrically conductive graphite clearly outperformed anthracite. The dominant mechanisms in terms of NOM removal from surface water were found to be coagulation following iron dissolution and adsorption in the case of employing GAC. Oxidation was also occurring to a lesser degree, converting some non-biodegradable into biodegradable DOC. PMID:26808400

  6. Distinct iron isotope signatures in suspended matter in the northern Baltic Sea; implications for cycling of organic carbon and phosphorus

    NASA Astrophysics Data System (ADS)

    Ingri, Johan; Conrad, Sarah

    2015-04-01

    Two distinct groups of iron isotope signatures can be identified both in river water and in the Bothnian Bay, northern Baltic Sea. Particles and colloids with negative iron isotope signatures (enriched in the light isotope) are mobilised in the riparian zone during high discharge. Due to high concentration of DOC the oxidation of Fe(II) is incomplete, and un-oxidised Fe(II) is associated with Fe(III)-OH and OC (organic carbon), forming Fe(II,III)-OC colloids, and particles, with a negative iron isotope signature. Colloidal iron with a negative signature is a labile fraction that transforms during freshwater transport. Photo reduction of Fe(II,III)-OC particles and colloids will release Fe(II) and reduce Fe(III) to Fe(II), and formed Fe(II) is oxidised forming Fe(III)-OH colloids with a heavy iron isotope signature. Phosphorus and organic carbon are to different extent associated to these two suspended iron complexes during transport and early diagenesis. Flocculation of negative Fe(II,III)-OC colloids produce negative Fe(II,III)-OC particles, without changes in the isotopic composition. Most of the suspended iron is rapidly removed below 1.0 psu, due to flocculation and sedimentation. Negative Fe(II,III)-OC particles may serve as an efficient 'rusty sink' for organic carbon, when deposited in the coastal zone.

  7. Variation in stable carbon isotopes in organic matter from the Gunflint Iron Formation. [Precambrian rock analysis

    NASA Technical Reports Server (NTRS)

    Barghoorn, E. S.; Knoll, A. H.; Dembicki, H., Jr.; Meinschein, W. G.

    1977-01-01

    Results are presented for an isotopic analysis of the kerogen separated from 15 samples of the Gunflint Iron Formation, Ontario, and the conformably overlying Rove Formation. Reasons for which the Gunflint Iron Formation is suitable for such a study of a single Precambrian formation are identified. The general geology of the formation is outlined along with sample selection, description, and preparation. Major conclusions are that the basal Gunflint algal chert and shale facies are depleted in C-13 relative to the chert-carbonate and taconite facies, that differences in the delta C-13 values between Gunflint facies correlate with marked differences in their biological source materials as evidenced by their respective microbiotas, that the anthraxolites are anomalously depleted in C-13 relative to the kerogen of their encompassing cherts and shales, and that the effects of igneous intrusion and concomitant thermal alteration are shown by a marked loss of C-12 at the contact. The demonstration that not all kerogens are isotopically alike stresses the importance of facies data to the interpretation of C-13/C-12 ratios of ancient organic matter.

  8. Biogeochemistry of Two Types of Permeable Reafctive Barriers, Organic Carbon and Iron-bearing Organic Carbon for Mine Drainage treatment: Column experiments

    SciTech Connect

    Guo, Q.; Blowes, D

    2009-01-01

    Permeable reactive barriers (PRBs) are an alternative technology to treat mine drainage containing sulfate and heavy metals. Two column experiments were conducted to assess the suitability of an organic carbon (OC) based reactive mixture and an Fe{sup 0}-bearing organic carbon (FeOC) based reactive mixture, under controlled groundwater flow conditions. The organic carbon mixture contains about 30% (volume) organic carbon (composted leaf mulch) and 70% (volume) sand and gravel. The Fe{sup 0}-bearing organic carbon mixture contains 10% (volume) zero-valent iron, 20% (volume) organic carbon, 10% (volume) limestone, and 60% (volume) sand and gravel. Simulated groundwater containing 380 ppm sulfate, 5 ppm As, and 0.5 ppm Sb was passed through the columns at flow rates of 64 (the OC column) and 62 (the FeOC column) ml d{sup -1}, which are equivalent to 0.79 (the OC column) and 0.78 (the FeOC column) pore volumes (PVs) per week or 0.046 m d{sup -1} for both columns. The OC column showed an initial sulfate reduction rate of 0.4 {mu}mol g (OC){sup -1} d{sup -1} and exhausted its capacity to promote sulfate reduction after 30 PVs, or 9 months of flow. The FeOC column sustained a relatively constant sulfate reduction rate of 0.9 {mu}mol g (OC){sup -1} d{sup -1} for at least 65 PVs (17 months). In the FeOC column, the {delta}34S values increase with the decreasing sulfate concentration. The {delta}34S fractionation follows a Rayleigh fractionation model with an enrichment factor of 21.6%. The performance decline of the OC column was caused by the depletion of substrate or electron donor. The cathodic production of H{sub 2} by anaerobic corrosion of Fe probably sustained a higher level of SRB activity in the FeOC column. These results suggest that zero-valent iron can be used to provide an electron donor in sulfate reducing PRBs. A sharp increase in the {delta}13C value of the dissolved inorganic carbon and a decrease in the concentration of HCO{sub 3}{sup -} indicate that

  9. Sorption of high explosives to water-dispersible clay: influence of organic carbon, aluminosilicate clay, and extractable iron.

    PubMed

    Dontsova, Katerina M; Hayes, Charolett; Pennington, Judith C; Porter, Beth

    2009-01-01

    Explosives in soils can present environmental problems for military installations. Fine, mobile particles represent the most reactive fraction of the soil and, therefore, are expected to adsorb explosives and potentially facilitate their transport. The objective of this study was to determine the relative significance of phyllosilicate clay, organic matter, and two forms of extractable iron in adsorption of 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by the colloidal water-dispersible clay (WDC) fraction of the soil. The WDC fraction of two mineral and one organic soil was separated and then treated to remove organic carbon (OC) and several forms of iron (Fe(o), oxalate extractable, and Fe(d), dithionite-citrate extractable). Adsorption coefficients were determined for whole soils, untreated, and treated WDC. For mineral soils, adsorption of TNT and RDX on the WDC was greater than on the whole soil. The presence of OC increased explosives sorption by WDC. When OC was removed, iron interfered with TNT sorption. In the presence of OC, removal of Fe(o) decreased RDX adsorption and increased TNT adsorption indicating different adsorption mechanisms. Organic carbon was a more significant indicator of explosives adsorption by WDC than clays or iron oxides and hydroxides. Therefore, OC is the most likely medium for facilitated transport of TNT and RDX. PMID:19465721

  10. Distributions of Manganese, Iron, and Manganese-Oxidizing Bacteria In Lake Superior Sediments of Different Organic Carbon Content

    NASA Technical Reports Server (NTRS)

    Richardson, Laurie L.; Nealson, Kenneth H.

    1989-01-01

    Profiles of oxygen, soluble and particulate manganese and iron, organic carbon and nitrogen were examined in Lake Superior sediment cores, along with the distribution and abundance of heterotrophic and manganese oxidizing bacteria. Analyses were performed using cores collected with the submersible Johnson Sea Link II. Three cores, exhibiting a range of organic carbon content, were collected from the deepest basin in Lake Superior and the north and south ends of the Caribou trough, and brought to the surface for immediate analysis. Minielectrode profiles of oxygen concentration of the three cores were carried out using a commercially available minielectrode apparatus. Oxygen depletion to less than 1% occurred within 4 cm of the surface for two of the cores, but not until approximately 15 cm for the core from the south basin of the Caribou trough. The three cores exhibited very different profiles of soluble, as well as leachable, manganese and iron, suggesting different degrees of remobilization of these metals in the sediments. Vertical profiles of viable bacteria and Mn oxidizing bacteria, determined by plating and counting, showed that aerobic (and facultatively aerobic) heterotrophic bacteria were present at the highest concentrations near the surface and decreased steadily with depth, while Mn oxidizing bacteria were concentrations primarily at and above the oxic/anoxic interface. Soluble manganese in the pore waters, along with abundant organic carbon, appeared to enhance the presence of manganese oxidizing bacteria, even below the oxic/anoxic interface. Profiles of solid-phase leachable manganese suggested a microbial role in manganese reprecipitation in these sediments.

  11. Activated carbons impregnated with iron oxide nanoparticles for enhanced removal of bisphenol A and natural organic matter.

    PubMed

    Park, Hak-Soon; Koduru, Janardhan Reddy; Choo, Kwang-Ho; Lee, Byungwhan

    2015-04-01

    The removal of bisphenol A (BPA) is important for the provision of safe drinking water, but its removal in the presence of natural organic matter (NOM) is challenging. Thus, the present study involved the fabrication and characterization of powdered activated carbons impregnated with iron oxide nanoparticles (IONPACs) with respect to the simultaneous removal of BPA and NOM. The number of Fe ions loaded into the PAC pores was optimized in terms of exposure time. Impregnation with iron oxide reduced the surface area and pore volume, but the pore size was maintained. IONPAC adsorbents had considerably greater sorption capabilities for BPA and NOM compared to native, bare PAC particles. The adsorption capacities of BPA and NOM were in the following sequence: bare PACiron oxides (e.g., hydroxyl groups) and organics (e.g., phenolic/carboxyl groups). Iron oxide impregnation enabled the BPA uptake to be maintained in the presence of NOM, indicating that the hybrid adsorbent provided synergistic adsorption characteristics for BPA and NOM. Although the solution pH had a negligible impact on BPA uptake, the ionic strength showed a significant effect, particularly in the presence of divalent Ca ions. PMID:25594935

  12. Organic carbon remobilized from thawing permafrost is resequestered by reactive iron on the Eurasian Arctic Shelf

    NASA Astrophysics Data System (ADS)

    Salvadó, Joan A.; Tesi, Tommaso; Andersson, August; Ingri, Johan; Dudarev, Oleg V.; Semiletov, Igor P.; Gustafsson, Örjan

    2015-10-01

    Given the potential for permafrost carbon (PF/C)-climate feedbacks in the Siberian-Arctic land-ocean system, there is a need for understanding the fate of thawed-out PF/C. Here we show that the sequestration of OC by reactive iron (OC-Fe) ranges between 0.5 and 22% on the Eurasian Arctic Shelf, with higher values in the Kara Sea (KS) (18 ± 6%) and the Laptev Sea (LS) (14 ± 4%). The Δ14C/δ13C signatures of the OC-Fe are substantially older and more terrestrial than the bulk sediment OC in the LS but younger and more dominated by marine plankton sources in the East Siberian Sea (ESS). Statistical source apportionment modeling reveal that reactive iron phases resequestered 15 ± 5% of thawing PF/C in the LS and 6.4 ± 5% in the ESS, derived from both coastal erosion of ice complex deposit and thawing topsoil. This Fe-associated trap of PF/C constitutes a reduction of the degradation/outgassing and thus also an attenuation of the PF/C-climate feedback.

  13. Iron, phytoplankton growth, and the carbon cycle.

    PubMed

    Street, Joseph H; Paytan, Adina

    2005-01-01

    Iron is an essential nutrient for all living organisms. Iron is required for the synthesis of chlorophyll and of several photosynthetic electron transport proteins and for the reduction of CO2, SO4(2-), and NO3(-) during the photosynthetic production of organic compounds. Iron concentrations in vast areas of the ocean are very low (<1 nM) due to the low solubility of iron in oxic seawater. Low iron concentrations have been shown to limit primary production rates, biomass accumulation, and ecosystem structure in a variety of open-ocean environments, including the equatorial Pacific, the subarctic Pacific and the Southern Ocean and even in some coastal areas. Oceanic primary production, the transfer of carbon dioxide into organic carbon by photosynthetic plankton (phytoplankton), is one process by which atmospheric CO2 can be transferred to the deep ocean and sequestered for long periods of time. Accordingly, iron limitation of primary producers likely plays a major role in the global carbon cycle. It has been suggested that variations in oceanic primary productivity, spurred by changes in the deposition of iron in atmospheric dust, control atmospheric CO2 concentrations, and hence global climate, over glacial-interglacial timescales. A contemporary application of this "iron hypothesis" promotes the large-scale iron fertilization of ocean regions as a means of enhancing the ability of the ocean to store anthropogenic CO2 and mitigate 21st century climate change. Recent in situ iron enrichment experiments in the HNLC regions, however, cast doubt on the efficacy and advisability of iron fertilization schemes. The experiments have confirmed the role of iron in regulating primary productivity, but resulted in only small carbon export fluxes to the depths necessary for long-term sequestration. Above all, these experiments and other studies of iron biogeochemistry over the last two decades have begun to illustrate the great complexity of the ocean system. Attempts to

  14. Metal organic frameworks derived porous lithium iron phosphate with continuous nitrogen-doped carbon networks for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Liu, Yuanyuan; Gu, Junjie; Zhang, Jinli; Yu, Feng; Dong, Lutao; Nie, Ning; Li, Wei

    2016-02-01

    Lithium iron phosphate (LiFePO4) nanoparticles embedded in the continuous interconnected nitrogen-doped carbon networks (LFP/N-CNWs) is an optimal architecture to fast electron and Li+ conduction. This paper, for the first time, reports a reasonable design and successful preparation of porous hierarchical LFP/N-CNWs composites using unique Fe-based metal organic framework (MIL-100(Fe)) as both template and starting material of Fe and C. Such nitrogen-doped carbon networks (N-CNWs) surrounding the lithium iron phosphate nanoparticles facilitate the transfer of Li+ and electrons throughout the electrodes, which significantly decreases the internal resistance for the electrodes and results in the efficient utilization of LiFePO4. The synthesized LFP/N-CNWs composites possess a porous structure with an amazing surface area of 129 m2 g-1, considerably enhanced electrical conductivities of 7.58 × 10-2 S cm-1 and Li+ diffusion coefficient of 8.82 × 10-14 cm2 s-1, thereby delivering excellent discharge capacities of 161.5 and 93.6 mAh·g-1 at 0.1C and 20C, respectively.

  15. Iron(III)-reduction in a low-organic-carbon brackish-marine system

    SciTech Connect

    Adams, L.K.; Macquaker, J.H.S.; Marshallf, J.D.

    2006-05-15

    Siderite rhizocretions are generally considered to be an indicator of fresh-water conditions. The presence of siderite rhizocretions with a marine{delta}{sup 18}O isotope signature in the Rutland Formation, Ketton, U.K. seems to contradict this belief. Commonly, in marine settings pyrite is more prevalent than siderite because of the high concentrations of sulfate in seawater. The Rutland Formation is a fine-grained mixed carbonate-clastic succession with interbedded coals that was deposited in marginal marine conditions. Analysis of siderite revealed that it was chemically zoned, predated pyrite, and has an average {delta}{sup 18}O signature of +0.44 parts per thousand. This siderite is interpreted as having precipitated during early diagenesis from brackish to marine porewaters containing low concentrations of bioavailable organic matter. Despite the porewaters being dominantly marine, under conditions of restricted organic-matter quality and/or quantity Fe(III)-reducing bacteria can outcompete sulfate-reducing bacteria for the organic substrate, resulting in the precipitation of siderite at the expense of pyrite.

  16. Reactive-transport modeling of iron diagenesis and associated organic carbon remineralization in a Florida (USA) subterranean estuary

    USGS Publications Warehouse

    Roy, Moutusi; Martin, Jonathan B.; Smith, Christopher G.; Cable, Jaye E.

    2011-01-01

    Iron oxides are important terminal electron acceptors for organic carbon (OC) remineralization in subterranean estuaries, particularly where oxygen and nitrate concentrations are low. In Indian River Lagoon, Florida, USA, terrestrial Fe-oxides dissolve at the seaward edge of the seepage face and flow upward into overlying marine sediments where they precipitate as Fe-sulfides. The dissolved Fe concentrations vary by over three orders of magnitude, but Fe-oxide dissolution rates are similar across the 25-m wide seepage face, averaging around 0.21 mg/cm2/yr. The constant dissolution rate, but differing concentrations, indicate Fe dissolution is controlled by a combination of increasing lability of dissolved organic carbon (DOC) and slower porewater flow velocities with distance offshore. In contrast, the average rate constants of Fe-sulfide precipitation decrease from 21.9 × 10-8 s-1 to 0.64 × 10-8 s-1 from the shoreline to the seaward edge of the seepage face as more oxygenated surface water circulates through the sediment. The amount of OC remineralized by Fe-oxides varies little across the seepage face, averaging 5.34 × 10-2 mg/cm2/yr. These rates suggest about 3.4 kg of marine DOC was remineralized in a 1-m wide, shore-perpendicular strip of the seepage face as the terrestrial sediments were transgressed over the past 280 years. During this time, about 10 times more marine solid organic carbon (SOC) accumulated in marine sediments than were removed from the underlying terrestrial sediments. Indian River Lagoon thus appears to be a net sink for marine OC.

  17. Novel mode of microbial energy metabolism: organic carbon oxidation coupled to dissimilatory reduction of iron or manganese.

    PubMed

    Lovley, D R; Phillips, E J

    1988-06-01

    A dissimilatory Fe(III)- and Mn(IV)-reducing microorganism was isolated from freshwater sediments of the Potomac River, Maryland. The isolate, designated GS-15, grew in defined anaerobic medium with acetate as the sole electron donor and Fe(III), Mn(IV), or nitrate as the sole electron acceptor. GS-15 oxidized acetate to carbon dioxide with the concomitant reduction of amorphic Fe(III) oxide to magnetite (Fe(3)O(4)). When Fe(III) citrate replaced amorphic Fe(III) oxide as the electron acceptor, GS-15 grew faster and reduced all of the added Fe(III) to Fe(II). GS-15 reduced a natural amorphic Fe(III) oxide but did not significantly reduce highly crystalline Fe(III) forms. Fe(III) was reduced optimally at pH 6.7 to 7 and at 30 to 35 degrees C. Ethanol, butyrate, and propionate could also serve as electron donors for Fe(III) reduction. A variety of other organic compounds and hydrogen could not. MnO(2) was completely reduced to Mn(II), which precipitated as rhodochrosite (MnCO(3)). Nitrate was reduced to ammonia. Oxygen could not serve as an electron acceptor, and it inhibited growth with the other electron acceptors. This is the first demonstration that microorganisms can completely oxidize organic compounds with Fe(III) or Mn(IV) as the sole electron acceptor and that oxidation of organic matter coupled to dissimilatory Fe(III) or Mn(IV) reduction can yield energy for microbial growth. GS-15 provides a model for how enzymatically catalyzed reactions can be quantitatively significant mechanisms for the reduction of iron and manganese in anaerobic environments. PMID:16347658

  18. Tropical forest soil microbial communities couple iron and carbon biogeochemistry

    SciTech Connect

    Dubinsky, E.A.; Silver, W.L.; Firestone, M.K.

    2009-10-15

    We report that iron-reducing bacteria are primary mediators of anaerobic carbon oxidation in upland tropical soils spanning a rainfall gradient (3500 - 5000 mm yr-1) in northeast Puerto Rico. The abundant rainfall and high net primary productivity of these tropical forests provide optimal soil habitat for iron-reducing and iron-oxidizing bacteria. Spatially and temporally dynamic redox conditions make iron-transforming microbial communities central to the belowground carbon cycle in these wet tropical forests. The exceedingly high abundance of iron-reducing bacteria (up to 1.2 x 10{sup 9} cells per gram soil) indicated that they possess extensive metabolic capacity to catalyze the reduction of iron minerals. In soils from the higher rainfall sites, measured rates of ferric iron reduction could account for up to 44 % of organic carbon oxidation. Iron reducers appeared to compete with methanogens when labile carbon availability was limited. We found large numbers of bacteria that oxidize reduced iron at sites with high rates of iron reduction and large numbers of iron-reducers. the coexistence of large populations of ironreducing and iron-oxidizing bacteria is evidence for rapid iron cycling between its reduced and oxidized states, and suggests that mutualistic interactions among these bacteria ultimately fuel organic carbon oxidation and inhibit CH4 production in these upland tropical forests.

  19. Variations of iron flux and organic carbon remineralization in a subterranean estuary caused by interannual variations in recharge

    USGS Publications Warehouse

    Roy, Moutusi; Martin, Jonathan B.; Cable, Jaye E.; Smith, Christopher G.

    2013-01-01

    We determine the inter-annual variations in diagenetic reaction rates of sedimentary iron (Fe ) in an east Florida subterranean estuary and evaluate the connection between metal fluxes and recharge to the coastal aquifer. Over the three-year study period (from 2004 to 2007), the amount of Fe-oxides reduced at the study site decreased from 192 g/yr to 153 g/yr and associated organic carbon (OC) remineralization decreased from 48 g/yr to 38 g/yr. These reductions occurred although the Fe-oxide reduction rates remained constant around 1 mg/cm2/yr. These results suggest that changes in flow rates of submarine groundwater discharge (SGD) related to changes in precipitation may be important to fluxes of the diagenetic reaction products. Rainfall at a weather station approximately 5 km from the field area decreased from 12.6 cm/month to 8.4 cm/month from 2004 to 2007. Monthly potential evapotranspiration (PET) calculated from Thornthwaite’s method indicated potential evapotranspiration cycled from about 3 cm/month in the winter to about 15 cm/month in the summer so that net annual recharge to the aquifer decreased from 40 cm in 2004 to -10 cm in 2007. Simultaneously, with the decrease in recharge of groundwater, freshwater SGD decreased by around 20% and caused the originally 25 m wide freshwater seepage face to decrease in width by about 5 m. The smaller seepage face reduced the area under which Fe-oxides were undergoing reductive dissolution. Consequently, the observed decrease in Fe flux is controlled by hydrology of the subterranean estuary. These results point out the need to better understand linkages between temporal variations in diagenetic reactions and changes in flow within subterranean estuaries in order to accurately constrain their contribution to oceanic fluxes of solutes from subterranean estuaries.

  20. Sorption of dissolved organic carbon by hydrous aluminum and iron oxides occurring at the confluence of deer creek with the Snake River, Summit County, Colorado

    USGS Publications Warehouse

    McKnight, Diane M.; Bencala, K.E.; Zellweger, G.W.; Aiken, G.R.; Feder, G.L.; Thorn, K.A.

    1992-01-01

    Organic solute sorption by hydrous iron and aluminum oxides was studied in an acidic, metal-enriched stream (the Snake River) at its confluence with a pristine stream (Deer Creek). From 1979 to 1986, typically 40% of the dissolved organic carbon (DOC) was removed from solution by sorption onto aluminum and iron oxides, which precipitate as the two streamwaters mix. Upstream DOC concentrations, which increase during snowmelt, were identified as the most significant variables in a multiple regression for determining the DOC concentration below the confluence, and the extent of Al and Fe precipitation was much less significant. On hourly timescales, removal of Al and Fe varied erratically but DOC removal was steady, indicating that "sorbable" organic solutes are sorbed either by precipitating oxides or by oxides on the streambed. Characterization of two reactive DOC fractions (fulvic and hydrophilic acids) showed that sorption results in chemical fractionation. Molecules with greater contents of aromatic moieties, carboxylic acid groups, and amino acid residues were preferentially sorbed, which is consistent with the ligand exchange-surface complexation model.

  1. Carbon in iron phases under high pressure

    NASA Astrophysics Data System (ADS)

    Huang, L.; Skorodumova, N. V.; Belonoshko, A. B.; Johansson, B.; Ahuja, R.

    2005-11-01

    The influence of carbon impurities on the properties of iron phases (bcc, hcp, dhcp, fcc) has been studied using the first-principles projector augmented-wave (PAW) method for a wide pressure range. It is shown that the presence of ~6 at. % of interstitial carbon has a little effect on the calculated structural sequence of the iron phases under high pressure. The bcc -> hcp transition both for pure iron and iron containing carbon takes place around 9 GPa. According to the enthalpies comparison, the solubility of carbon into the iron solid is decreased by high pressure. The coexistence of iron carbide (Fe3C) + pure hcp Fe is most stable phase at high pressure compared with other phases. Based on the analysis of the pressure-density dependences for Fe3C and hcp Fe, we suggest that there might be some fraction of iron carbide present in the core.

  2. Promotion and nucleation of carbonate precipitation during microbial iron reduction.

    PubMed

    Zeng, Z; Tice, M M

    2014-07-01

    Iron-bearing early diagenetic carbonate cements are common in sedimentary rocks, where they are thought to be associated with microbial iron reduction. However, little is yet known about how local environments around actively iron-reducing cells affect carbonate mineral precipitation rates and compositions. Precipitation experiments with the iron-reducing bacterium Shewanella oneidensis MR-1 were conducted to examine the potential role of cells in promoting precipitation and to explore the possible range of precipitate compositions generated in varying fluid compositions. Actively iron-reducing cells induced increased carbonate mineral saturation and nucleated precipitation on their poles. However, precipitation only occurred when calcium was present in solution, suggesting that cell surfaces lowered local ferrous iron concentrations by adsorption or intracellular iron oxide precipitation even as they locally raised pH. Resultant precipitates were a range of thermodynamically unstable calcium-rich siderites that would likely act as precursors to siderite, calcite, or even dolomite in nature. By modifying local pH, providing nucleation sites, and altering metal ion concentrations around cell surfaces, iron-reducing micro-organisms could produce a wide range of carbonate cements in natural sediments. PMID:24862734

  3. Impact of Organic Carbon Electron Donors on Microbial Community Development under Iron- and Sulfate-Reducing Conditions

    PubMed Central

    Kwon, Man Jae; O’Loughlin, Edward J.; Boyanov, Maxim I.; Brulc, Jennifer M.; Johnston, Eric R.; Kemner, Kenneth M.; Antonopoulos, Dionysios A.

    2016-01-01

    Although iron- and sulfate-reducing bacteria in subsurface environments have crucial roles in biogeochemical cycling of C, Fe, and S, how specific electron donors impact the compositional structure and activity of native iron- and/or sulfate-reducing communities is largely unknown. To understand this better, we created bicarbonate-buffered batch systems in duplicate with three different electron donors (acetate, lactate, or glucose) paired with ferrihydrite and sulfate as the electron acceptors and inoculated them with subsurface sediment as the microbial inoculum. Sulfate and ferrihydrite reduction occurred simultaneously and were faster with lactate than with acetate. 16S rRNA-based sequence analysis of the communities over time revealed that Desulfotomaculum was the major driver for sulfate reduction coupled with propionate oxidation in lactate-amended incubations. The reduction of sulfate resulted in sulfide production and subsequent abiotic reduction of ferrihydrite. In contrast, glucose promoted faster reduction of ferrihydrite, but without reduction of sulfate. Interestingly, the glucose-amended incubations led to two different biogeochemical trajectories among replicate bottles that resulted in distinct coloration (white and brown). The two outcomes in geochemical evolution might be due to the stochastic evolution of the microbial communities or subtle differences in the initial composition of the fermenting microbial community and its development via the use of different glucose fermentation pathways available within the community. Synchrotron-based x-ray analysis indicated that siderite and amorphous Fe(II) were formed in the replicate bottles with glucose, while ferrous sulfide and vivianite were formed with lactate or acetate. These data sets reveal that use of different C utilization pathways projects significant changes in microbial community composition over time that uniquely impact both the geochemistry and mineralogy of subsurface environments

  4. Impact of Organic Carbon Electron Donors on Microbial Community Development under Iron- and Sulfate-Reducing Conditions.

    PubMed

    Kwon, Man Jae; O'Loughlin, Edward J; Boyanov, Maxim I; Brulc, Jennifer M; Johnston, Eric R; Kemner, Kenneth M; Antonopoulos, Dionysios A

    2016-01-01

    Although iron- and sulfate-reducing bacteria in subsurface environments have crucial roles in biogeochemical cycling of C, Fe, and S, how specific electron donors impact the compositional structure and activity of native iron- and/or sulfate-reducing communities is largely unknown. To understand this better, we created bicarbonate-buffered batch systems in duplicate with three different electron donors (acetate, lactate, or glucose) paired with ferrihydrite and sulfate as the electron acceptors and inoculated them with subsurface sediment as the microbial inoculum. Sulfate and ferrihydrite reduction occurred simultaneously and were faster with lactate than with acetate. 16S rRNA-based sequence analysis of the communities over time revealed that Desulfotomaculum was the major driver for sulfate reduction coupled with propionate oxidation in lactate-amended incubations. The reduction of sulfate resulted in sulfide production and subsequent abiotic reduction of ferrihydrite. In contrast, glucose promoted faster reduction of ferrihydrite, but without reduction of sulfate. Interestingly, the glucose-amended incubations led to two different biogeochemical trajectories among replicate bottles that resulted in distinct coloration (white and brown). The two outcomes in geochemical evolution might be due to the stochastic evolution of the microbial communities or subtle differences in the initial composition of the fermenting microbial community and its development via the use of different glucose fermentation pathways available within the community. Synchrotron-based x-ray analysis indicated that siderite and amorphous Fe(II) were formed in the replicate bottles with glucose, while ferrous sulfide and vivianite were formed with lactate or acetate. These data sets reveal that use of different C utilization pathways projects significant changes in microbial community composition over time that uniquely impact both the geochemistry and mineralogy of subsurface environments

  5. Surface-Plasmon-Enhanced Photodriven CO2 Reduction Catalyzed by Metal-Organic-Framework-Derived Iron Nanoparticles Encapsulated by Ultrathin Carbon Layers.

    PubMed

    Zhang, Huabin; Wang, Tao; Wang, Junjie; Liu, Huimin; Dao, Thang Duy; Li, Mu; Liu, Guigao; Meng, Xianguang; Chang, Kun; Shi, Li; Nagao, Tadaaki; Ye, Jinhua

    2016-05-01

    Highly efficient utilization of solar light with an excellent reduction capacity is achieved for plasmonic Fe@C nanostructures. By carbon layer coating, the optimized catalyst exhibits enhanced selectivity and stability applied to the solar-driven reduction of CO2 into CO. The surface-plasmon effect of iron particles is proposed to excite CO2 molecules, and thereby facilitates the final reaction activity. PMID:27001900

  6. Iron cycling at corroding carbon steel surfaces.

    PubMed

    Lee, Jason S; McBeth, Joyce M; Ray, Richard I; Little, Brenda J; Emerson, David

    2013-01-01

    Surfaces of carbon steel (CS) exposed to mixed cultures of iron-oxidizing bacteria (FeOB) and dissimilatory iron-reducing bacteria (FeRB) in seawater media under aerobic conditions were rougher than surfaces of CS exposed to pure cultures of either type of microorganism. The roughened surface, demonstrated by profilometry, is an indication of loss of metal from the surface. In the presence of CS, aerobically grown FeOB produced tight, twisted helical stalks encrusted with iron oxides. When CS was exposed anaerobically in the presence of FeRB, some surface oxides were removed. However, when the same FeOB and FeRB were grown together in an aerobic medium, FeOB stalks were less encrusted with iron oxides and appeared less tightly coiled. These observations suggest that iron oxides on the stalks were reduced and solubilized by the FeRB. Roughened surfaces of CS and denuded stalks were replicated with culture combinations of different species of FeOB and FeRB under three experimental conditions. Measurements of electrochemical polarization resistance established different rates of corrosion of CS in aerobic and anaerobic media, but could not differentiate rate differences between sterile controls and inoculated exposures for a given bulk concentration of dissolved oxygen. Similarly, total iron in the electrolyte could not be used to differentiate treatments. The experiments demonstrate the potential for iron cycling (oxidation and reduction) on corroding CS in aerobic seawater media. PMID:24093730

  7. Binding of dinitrogen to an iron-sulfur-carbon site

    NASA Astrophysics Data System (ADS)

    Čorić, Ilija; Mercado, Brandon Q.; Bill, Eckhard; Vinyard, David J.; Holland, Patrick L.

    2015-10-01

    Nitrogenases are the enzymes by which certain microorganisms convert atmospheric dinitrogen (N2) to ammonia, thereby providing essential nitrogen atoms for higher organisms. The most common nitrogenases reduce atmospheric N2 at the FeMo cofactor, a sulfur-rich iron-molybdenum cluster (FeMoco). The central iron sites that are coordinated to sulfur and carbon atoms in FeMoco have been proposed to be the substrate binding sites, on the basis of kinetic and spectroscopic studies. In the resting state, the central iron sites each have bonds to three sulfur atoms and one carbon atom. Addition of electrons to the resting state causes the FeMoco to react with N2, but the geometry and bonding environment of N2-bound species remain unknown. Here we describe a synthetic complex with a sulfur-rich coordination sphere that, upon reduction, breaks an Fe-S bond and binds N2. The product is the first synthetic Fe-N2 complex in which iron has bonds to sulfur and carbon atoms, providing a model for N2 coordination in the FeMoco. Our results demonstrate that breaking an Fe-S bond is a chemically reasonable route to N2 binding in the FeMoco, and show structural and spectroscopic details for weakened N2 on a sulfur-rich iron site.

  8. Iron traps terrestrially derived dissolved organic matter at redox interfaces.

    PubMed

    Riedel, Thomas; Zak, Dominik; Biester, Harald; Dittmar, Thorsten

    2013-06-18

    Reactive iron and organic carbon are intimately associated in soils and sediments. However, to date, the organic compounds involved are uncharacterized on the molecular level. At redox interfaces in peatlands, where the biogeochemical cycles of iron and dissolved organic matter (DOM) are coupled, this issue can readily be studied. We found that precipitation of iron hydroxides at the oxic surface layer of two rewetted fens removed a large fraction of DOM via coagulation. On aeration of anoxic fen pore waters, >90% of dissolved iron and 27 ± 7% (mean ± SD) of dissolved organic carbon were rapidly (within 24 h) removed. Using ultra-high-resolution MS, we show that vascular plant-derived aromatic and pyrogenic compounds were preferentially retained, whereas the majority of carboxyl-rich aliphatic acids remained in solution. We propose that redox interfaces, which are ubiquitous in marine and terrestrial settings, are selective yet intermediate barriers that limit the flux of land-derived DOM to oceanic waters. PMID:23733946

  9. Iron traps terrestrially derived dissolved organic matter at redox interfaces

    PubMed Central

    Riedel, Thomas; Zak, Dominik; Biester, Harald; Dittmar, Thorsten

    2013-01-01

    Reactive iron and organic carbon are intimately associated in soils and sediments. However, to date, the organic compounds involved are uncharacterized on the molecular level. At redox interfaces in peatlands, where the biogeochemical cycles of iron and dissolved organic matter (DOM) are coupled, this issue can readily be studied. We found that precipitation of iron hydroxides at the oxic surface layer of two rewetted fens removed a large fraction of DOM via coagulation. On aeration of anoxic fen pore waters, >90% of dissolved iron and 27 ± 7% (mean ± SD) of dissolved organic carbon were rapidly (within 24 h) removed. Using ultra-high-resolution MS, we show that vascular plant-derived aromatic and pyrogenic compounds were preferentially retained, whereas the majority of carboxyl-rich aliphatic acids remained in solution. We propose that redox interfaces, which are ubiquitous in marine and terrestrial settings, are selective yet intermediate barriers that limit the flux of land-derived DOM to oceanic waters. PMID:23733946

  10. Photochemical flocculation of terrestrial dissolved organic matter and iron

    NASA Astrophysics Data System (ADS)

    Helms, John R.; Mao, Jingdong; Schmidt-Rohr, Klaus; Abdulla, Hussain; Mopper, Kenneth

    2013-11-01

    Dissolved organic matter (DOM) rich water samples (Great Dismal Swamp, Virginia) were 0.1-μm filtered and UV-irradiated in a solar simulator for 30 days. During the irradiation, pH increased, particulate organic matter (POM) and particulate iron formed. After 30 days, 7% of the dissolved organic carbon (DOC) was converted to POC while 75% was remineralized. Approximately 87% of the iron was removed from the dissolved phase after 30 days, but iron did not flocculate until a major fraction of DOM was removed by photochemical degradation and flocculation (>10 days); thus, during the initial 10 days, there were sufficient organic ligands present or the pH was low enough to keep iron in solution. Nuclear magnetic resonance and Fourier transform infrared spectroscopies indicated that photochemically flocculated POM was more aliphatic than the residual non-flocculated DOM. Photochemically flocculated POM was also enriched in amide functionality, while carbohydrate-like material was resistant to both photochemical degradation and flocculation. Abiotic photochemical flocculation likely removes a significant fraction of terrestrial DOM from the upper water column between headwaters and the ocean, but has previously been ignored. Preliminary evidence suggests that this process may significantly impact the transport of DOM and POM in ocean margin environments including estuaries.

  11. Soil Iron Content as a Predictor of Carbon and Nutrient Mobilization in Rewetted Fens.

    PubMed

    Emsens, Willem-Jan; Aggenbach, Camiel J S; Schoutens, Ken; Smolders, Alfons J P; Zak, Dominik; van Diggelen, Rudy

    2016-01-01

    Rewetted, previously drained fens often remain sources rather than sinks for carbon and nutrients. To date, it is poorly understood which soil characteristics stimulate carbon and nutrient mobilization upon rewetting. Here, we assess the hypothesis that a large pool of iron in the soil negatively affects fen restoration success, as flooding-induced iron reduction (Fe3+ to Fe2+) causes a disproportionate breakdown of organic matter that is coupled with a release of inorganic compounds. We collected intact soil cores in two iron-poor and two iron-rich drained fens, half of which were subjected to a rewetting treatment while the other half was kept drained. Prolonged drainage led to the mobilization of nitrate (NO3-, > 1 mmol L-1) in all cores, regardless of soil iron content. In the rewetted iron-rich cores, a sharp increase in pore water iron (Fe) concentrations correlated with concentrations of inorganic carbon (TIC, > 13 mmol L-1) and dissolved organic carbon (DOC, > 16 mmol L-1). Additionally, ammonium (NH4+) accumulated up to phytotoxic concentrations of 1 mmol L-1 in the pore water of the rewetted iron-rich cores. Disproportionate mobilization of Fe, TIC, DOC and NH4+ was absent in the rewetted iron-poor cores, indicating a strong interaction between waterlogging and iron-mediated breakdown of organic matter. Concentrations of dissolved phosphorus (P) rose slightly in all cores upon rewetting, but remained low throughout the experiment. Our results suggest that large pools of iron in the top soil of drained fens can hamper the restoration of the fen's sink-service for ammonium and carbon upon rewetting. We argue that negative effects of iron should be most apparent in fens with fluctuating water levels, as temporary oxygenation allows frequent regeneration of Fe3+. We conclude that rewetting of iron-poor fens may be more feasible for restoration. PMID:27050837

  12. Soil Iron Content as a Predictor of Carbon and Nutrient Mobilization in Rewetted Fens

    PubMed Central

    Emsens, Willem-Jan; Aggenbach, Camiel J. S.; Schoutens, Ken; Smolders, Alfons J. P.; Zak, Dominik; van Diggelen, Rudy

    2016-01-01

    Rewetted, previously drained fens often remain sources rather than sinks for carbon and nutrients. To date, it is poorly understood which soil characteristics stimulate carbon and nutrient mobilization upon rewetting. Here, we assess the hypothesis that a large pool of iron in the soil negatively affects fen restoration success, as flooding-induced iron reduction (Fe3+ to Fe2+) causes a disproportionate breakdown of organic matter that is coupled with a release of inorganic compounds. We collected intact soil cores in two iron-poor and two iron-rich drained fens, half of which were subjected to a rewetting treatment while the other half was kept drained. Prolonged drainage led to the mobilization of nitrate (NO3-, > 1 mmol L-1) in all cores, regardless of soil iron content. In the rewetted iron-rich cores, a sharp increase in pore water iron (Fe) concentrations correlated with concentrations of inorganic carbon (TIC, > 13 mmol L-1) and dissolved organic carbon (DOC, > 16 mmol L-1). Additionally, ammonium (NH4+) accumulated up to phytotoxic concentrations of 1 mmol L-1 in the pore water of the rewetted iron-rich cores. Disproportionate mobilization of Fe, TIC, DOC and NH4+ was absent in the rewetted iron-poor cores, indicating a strong interaction between waterlogging and iron-mediated breakdown of organic matter. Concentrations of dissolved phosphorus (P) rose slightly in all cores upon rewetting, but remained low throughout the experiment. Our results suggest that large pools of iron in the top soil of drained fens can hamper the restoration of the fen’s sink-service for ammonium and carbon upon rewetting. We argue that negative effects of iron should be most apparent in fens with fluctuating water levels, as temporary oxygenation allows frequent regeneration of Fe3+. We conclude that rewetting of iron-poor fens may be more feasible for restoration. PMID:27050837

  13. Fabrication of Iron-Containing Carbon Materials From Graphite Fluoride

    NASA Technical Reports Server (NTRS)

    Hung, Ching-cheh

    1996-01-01

    Carbon materials containing iron alloy, iron metal, iron oxide or iron halide were fabricated. Typical samples of these metals were estimated to contain 1 iron atom per 3.5 to 5 carbon atoms. Those carbon materials containing iron alloy, iron metal, and/or Fe3O4 were magnetic. The kinetics of the fabrication process were studied by exposing graphite fluoride (CF(0.68)) to FeCl3 over a 280 to 420 C temperature range. Between 280 and 295 C, FeCl3 quickly entered the structure of CF(0.68), broke the carbon-fluorine bonds, and within 10 to 30 min, completely converted it to carbon made up of graphite planes between which particles of crystalline FeF3 and noncrystalline FeCl3 were located. Longer reaction times (e.g., 28 hr) or higher reaction temperatures (e.g., 420 C) produced materials containing graphite, a FeCl3-graphite intercalation compound, FeCl2(center dot)4H2O, and FeCl2(center dot)2H2O. These products were further heat treated to produce iron-containing carbon materials. When the heating temperature was kept in the 750 to 850 C range, and the oxygen supply was kept at the optimum level, the iron halides in the carbon structure were converted to iron oxides. Raising the heat to temperatures higher than 900 C reduced such iron oxides to iron metal. The kinetics of these reactions were used to suggest processes for fabricating carbon materials containing iron alloy. Such processes were then tested experimentally. In one of the successful trial runs, commercially purchased CF(0.7) powder was used as the reactant, and NiO was added during the final heating to 1200 C as a source of both nickel and oxygen. The product thus obtained was magnetic and was confirmed to be a nickel-iron alloy in carbon.

  14. Preservation of iron(II) by carbon-rich matrices in a hydrothermal plume

    SciTech Connect

    Toner, Brandy M.; Fakra, Sirine C.; Manganini, Steven J.; Santelli, Cara M.; Marcus, Matthew A.; Moffett, James W.; Rouxel, Olivier; German, Christopher R.; Edwards, Katrina J.

    2008-09-20

    Hydrothermal venting associated with mid-ocean ridge volcanism is globally widespread. This venting is responsible for a dissolved iron flux to the ocean that is approximately equal to that associated with continental riverine runoff. For hydrothermal fluxes, it has long been assumed that most of the iron entering the oceans is precipitated in inorganic forms. However, the possibility of globally significant fluxes of iron escaping these mass precipitation events and entering open-ocean cycles is now being debated, and two recent studies suggest that dissolved organic ligands might influence the fate of hydrothermally vented metals. Here we present spectromicroscopic measurements of iron and carbon in hydrothermal plume particles at the East Pacific Rise mid-ocean ridge. We show that organic carbon-rich matrices, containing evenly dispersed iron(II)-rich materials, are pervasive in hydrothermal plume particles. The absence of discrete iron(II) particles suggests that the carbon and iron associate through sorption or complexation. We suggest that these carbon matrices stabilize iron(II) released from hydrothermal vents in the region, preventing its oxidation and/or precipitation as insoluble minerals. Our findings have implications for deep-sea biogeochemical cycling of iron, a widely recognized limiting nutrient in the oceans.

  15. Synthesis and properties of a novel structural binder utilizing the chemistry of iron carbonation.

    PubMed

    Das, Sumanta; Souliman, Beshoy; Stone, David; Neithalath, Narayanan

    2014-06-11

    This paper explores, for the first time, the possibility of carbonating waste metallic iron powder to develop sustainable binder systems for concrete. The fundamental premise of this work is that metallic iron will react with aqueous CO2 under controlled conditions to form complex iron carbonates which have binding capabilities. Chosen additives containing silica and alumina are added to facilitate iron dissolution and to obtain beneficial rheological and later-age properties. Water is generally only a medium for mass transfer in these systems thereby making the common reaction schemes in portland cement concretes inapplicable. The compressive and flexural strengths of the chosen iron-based binder systems increase with carbonation duration and the specimens carbonated for 4 days exhibit mechanical properties that are comparable to those of companion ordinary portland cement systems that are most commonly used as the binder in building and infrastructural construction. The influence of the additives, carbonation duration, and the air curing duration after carbonation are explored in detail. Thermogravimetric analysis demonstrate the presence of an organic carbonate complex (the dissolution agent used to dissolve iron is organic), the amount of which increases with carbonation duration. Thermal analysis also confirms the participation of some amount of limestone powder in the reaction product formation. The viability of this binder type for concrete applications is proved in this study. PMID:24840162

  16. Total organic carbon analyzer

    NASA Technical Reports Server (NTRS)

    Godec, Richard G.; Kosenka, Paul P.; Smith, Brian D.; Hutte, Richard S.; Webb, Johanna V.; Sauer, Richard L.

    1991-01-01

    The development and testing of a breadboard version of a highly sensitive total-organic-carbon (TOC) analyzer are reported. Attention is given to the system components including the CO2 sensor, oxidation reactor, acidification module, and the sample-inlet system. Research is reported for an experimental reagentless oxidation reactor, and good results are reported for linearity, sensitivity, and selectivity in the CO2 sensor. The TOC analyzer is developed with gravity-independent components and is designed for minimal additions of chemical reagents. The reagentless oxidation reactor is based on electrolysis and UV photolysis and is shown to be potentially useful. The stability of the breadboard instrument is shown to be good on a day-to-day basis, and the analyzer is capable of 5 sample analyses per day for a period of about 80 days. The instrument can provide accurate TOC and TIC measurements over a concentration range of 20 ppb to 50 ppm C.

  17. Iron hydroxy carbonate formation in zerovalent iron permeable reactive barriers: Characterization and evaluation of phase stability

    SciTech Connect

    Wilkin, Richard T.; Lee, T.R.

    2010-10-22

    Predicting the long-term potential of permeable reactive barriers for treating contaminated groundwater relies on understanding the endpoints of biogeochemical reactions between influent groundwater and the reactive medium. Iron hydroxy carbonate (chukanovite) is frequently observed as a secondary mineral precipitate in granular iron PRBs. Mineralogical characterization was carried out using X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and X-ray absorption spectroscopy on materials collected from three field-based PRBs in the US (East Helena, MT; Elizabeth City, NC; Denver Federal Center, CO). These PRBs were installed to treat a range of contaminants, including chlorinated organics, hexavalent chromium, and arsenic. Results obtained indicate that chukanovite is a prevalent secondary precipitate in the PRBs. Laboratory experiments on high-purity chukanovite separates were carried out to constrain the room-temperature solubility for this mineral. An estimated Gibbs energy of formation ({Delta}{sub f}G{sup o}) for chukanovite is - 1174.4 {+-} 6 kJ/mol. A mineral stability diagram is consistent with observations from the field. Water chemistry from the three reactive barriers falls inside the predicted stability field for chukanovite, at inorganic carbon concentrations intermediate to the stability fields of siderite and ferrous hydroxide. These new data will aid in developing better predictive models of mineral accumulation in zerovalent iron PRBs.

  18. Iron hydroxy carbonate formation in zerovalent iron permeable reactive barriers: characterization and evaluation of phase stability.

    PubMed

    Lee, Tony R; Wilkin, Richard T

    2010-07-30

    Predicting the long-term potential of permeable reactive barriers for treating contaminated groundwater relies on understanding the endpoints of biogeochemical reactions between influent groundwater and the reactive medium. Iron hydroxy carbonate (chukanovite) is frequently observed as a secondary mineral precipitate in granular iron PRBs. Mineralogical characterization was carried out using X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and X-ray absorption spectroscopy on materials collected from three field-based PRBs in the US (East Helena, MT; Elizabeth City, NC; Denver Federal Center, CO). These PRBs were installed to treat a range of contaminants, including chlorinated organics, hexavalent chromium, and arsenic. Results obtained indicate that chukanovite is a prevalent secondary precipitate in the PRBs. Laboratory experiments on high-purity chukanovite separates were carried out to constrain the room-temperature solubility for this mineral. An estimated Gibbs energy of formation (Delta(f)G degrees) for chukanovite is -1174.4 +/- 6 kJ/mol. A mineral stability diagram is consistent with observations from the field. Water chemistry from the three reactive barriers falls inside the predicted stability field for chukanovite, at inorganic carbon concentrations intermediate to the stability fields of siderite and ferrous hydroxide. These new data will aid in developing better predictive models of mineral accumulation in zerovalent iron PRBs. PMID:20554346

  19. The Iron Metallome in Eukaryotic Organisms

    PubMed Central

    Dlouhy, Adrienne C.; Outten, Caryn E.

    2013-01-01

    This chapter is focused on the iron metallome in eukaryotes at the cellular and subcellular level, including properties, utilization in metalloproteins, trafficking, storage, and regulation of these processes. Studies in the model eukaryote Saccharomyces cerevisiae and mammalian cells will be highlighted. The discussion of iron properties will center on the speciation and localization of intracellular iron as well as the cellular and molecular mechanisms for coping with both low iron bioavailability and iron toxicity. The section on iron metalloproteins will emphasize heme, iron-sulfur cluster, and non-heme iron centers, particularly their cellular roles and mechanisms of assembly. The section on iron uptake, trafficking, and storage will compare methods used by yeast and mammalian cells to import iron, how this iron is brought into various organelles, and types of iron storage proteins. Regulation of these processes will be compared between yeast and mammalian cells at the transcriptional, post-transcriptional, and post-translational levels. PMID:23595675

  20. In-Situ Regeneration of Saturated Granular Activated Carbon by an Iron Oxide Nanocatalyst

    EPA Science Inventory

    Granular activated carbon (GAC) can remove trace organic pollutants and natural organic matter (NOM) from industrial and municipal waters. This paper evaluates an iron nanocatalyst approach, based on Fenton-like oxidation reactions, to regenerate spent GAC within a packed bed con...

  1. Responses of Sugar Beet Roots to Iron Deficiency. Changes in Carbon Assimilation and Oxygen Use1

    PubMed Central

    López-Millán, Ana Flor; Morales, Fermín; Andaluz, Sofía; Gogorcena, Yolanda; Abadía, Anunciación; Rivas, Javier De Las; Abadía, Javier

    2000-01-01

    Different root parts with or without increased iron-reducing activities have been studied in iron-deficient and iron-sufficient control sugar beet (Beta vulgaris L. Monohil hybrid). The distal root parts of iron-deficient plants, 0 to 5 mm from the root apex, were capable to reduce Fe(III)-chelates and contained concentrations of flavins near 700 μm, two characteristics absent in the 5 to 10 mm sections of iron-deficient plants and the whole root of iron-sufficient plants. Flavin-containing root tips had large pools of carboxylic acids and high activities of enzymes involved in organic acid metabolism. In iron-deficient yellow root tips there was a large increase in carbon fixation associated to an increase in phosphoenolpyruvate carboxylase activity. Part of this carbon was used, through an increase in mitochondrial activity, to increase the capacity to produce reducing power, whereas another part was exported via xylem. Root respiration was increased by iron deficiency. In sugar beet iron-deficient roots flavins would provide a suitable link between the increased capacity to produce reduced nucleotides and the plasma membrane associated ferric chelate reductase enzyme(s). Iron-deficient roots had a large oxygen consumption rate in the presence of cyanide and hydroxisalycilic acid, suggesting that the ferric chelate reductase enzyme is able to reduce oxygen in the absence of Fe(III)-chelates. PMID:11027736

  2. Parameterized electronic description of carbon cohesion in iron grain boundaries.

    PubMed

    Hatcher, Nicholas; Madsen, Georg K H; Drautz, Ralf

    2014-04-01

    We employ a recently developed iron-carbon orthogonal tight-binding model in calculations of carbon in iron grain boundaries. We use the model to evaluate the properties of carbon near and on the Σ5 (3 1 0)[0 0 1] symmetric tilt grain boundary (GB) in iron, and calculations show that a carbon atom lowers the GB energy by 0.29 eV/atom in accordance with DFT. Carbon segregation to the GB is analyzed, and we find an energy barrier of 0.92 eV for carbon to segregate to the carbon-free interface while segregation to a fully filled interface is disfavored. Local volume (via Voronoi tessellation), magnetic, and electronic effects are correlated with atomic energy changes, and we isolate two different mechanisms governing carbon's behavior in iron: a volumetric strain which increases the energy of carbon in interstitial α iron and a non-strained local bonding which stabilizes carbon at the GB. PMID:24651649

  3. Synthesis of carbon-encapsulated iron nanoparticles via solid state reduction of iron oxide nanoparticles

    SciTech Connect

    Bystrzejewski, M.

    2011-06-15

    The encapsulation of iron nanoparticles in protective carbon cages leads to unique hybrid core-shell nanomaterials. Recent literature reports suggest that such nanocomposites can be obtained in a relatively simple process involving the solid state carbothermal reduction of iron oxide nanoparticles. This approach is very attractive because it does not require advanced equipment and consumes less energy in comparison to widely used plasma methods. The presented more-in-depth study shows that the carbothermal approach is sensitive to temperature and the process yield strongly depends on the morphology and crystallinity of the carbon material used as a reductant. - Graphical abstract: Reduction of iron oxide nanoparticles by carbon black at 1200 deg. C yields well crystallized carbon-encapsulated iron nanoparticles. Highlights: > Carbon-encapsulated iron nanoparticles were synthesized by carbothermal reduction of iron oxide nanoparticles. > The process has the highest selectivity at 1200 C. > Lower temperatures result in iron oxide nanoparticles wrapped in carbon matrix. > The encapsulation rate of Fe at 1200 deg. C was found to be 15%.

  4. Chemical oxygen demand, total organic carbon and colour reduction in slaughterhouse wastewater by unmodified and iron-modified clinoptilolite-rich tuff.

    PubMed

    Torres-Pérez, J; Solache-Ríos, M; Martínez-Miranda, V

    2014-01-01

    In this study, reduction of chemical oxygen demand (COD), colour, and total organic carbon in effluents from a slaughterhouse in central Mexico was performed using clinoptilolite-rich tuff. The experimental parameters considered were initial concentration of the adsorbate, pH, adsorbent dosage, and contact time. Surface morphology of the materials was tested by using scanning electron microscopy. Specific surface area was analysed by using Brunauer-Emmett-Teller (BET) and phase composition was analysed by using X-ray diffraction. The experimental adsorption data were fitted to the first- and pseudo-second-order kinetic models. The highest COD removal was observed in slightly acidic pH conditions. The maximum reduction efficiency of COD was accomplished with unmodified clinoptilolite-rich tuff at a contact time of 1440 min. In these conditions, the adsorbent was efficient for treating wastewater from a slaughterhouse. Moreover, after several regeneration cycles with Fenton reagent or hydrogen peroxide, the regenerated zeolite with H2O2 (3%) showed the best reduction efficiencies. PMID:24701954

  5. Dynamic behavior of iron forms in rapid reduction of carbon-coated iron ore

    SciTech Connect

    Sugawara, Katsuyasu; Morimoto, Koji; Sugawara, T.; Dranoff, J.S.

    1999-03-01

    As a part of a fundamental study of the kinetics of rapid smelting reduction of iron oxide with solid carbon, particles of carbon-coated iron ore were prepared by heating a mixture of iron ore and phenolphthalein (a model compound of coal tar) at 773 K in a nitrogen stream. The reduction behavior of the carbon-coated iron ore particles during rapid heating was studied using a drop-tube reactor at temperatures from 1,073 to 1,773 K. The reduction extent increased rapidly with the beginning of melting at temperatures over 1,650 K, reaching 60% at 1,773 within 0.7 s. The observed changes in the distribution of iron states in the particles were successfully simulated.

  6. Iron-carbonate interaction at Earth's core-mantle boundary

    NASA Astrophysics Data System (ADS)

    Dorfman, S. M.; Badro, J.; Nabiei, F.; Prakapenka, V.; Gillet, P.

    2015-12-01

    Carbon storage and flux in the deep Earth are moderated by oxygen fugacity and interactions with iron-bearing phases. The amount of carbon stored in Earth's mantle versus the core depends on carbon-iron chemistry at the core-mantle boundary. Oxidized carbonates subducted from Earth's surface to the lowermost mantle may encounter reduced Fe0 metal from disproportionation of Fe2+ in lower mantle silicates or mixing with the core. To understand the fate of carbonates in the lowermost mantle, we have performed experiments on sandwiches of single-crystal (Ca0.6Mg0.4)CO3 dolomite and Fe foil in the laser-heated diamond anvil cell at lower mantle conditions of 49-110 GPa and 1800-2500 K. Syntheses were conducted with in situ synchrotron X-ray diffraction to identify phase assemblages. After quench to ambient conditions, samples were sectioned with a focused Ga+ ion beam for composition analysis with transmission electron microscopy. At the centers of the heated spots, iron melted and reacted completely with the carbonate to form magnesiowüstite, iron carbide, diamond, magnesium-rich carbonate and calcium carbonate. In samples heated at 49 and 64 GPa, the two carbonates exhibit a eutectoid texture. In the sample heated at 110 GPa, the carbonates form rounded ~150-nm-diameter grains with a higher modal proportion of interspersed diamonds. The presence of reduced iron in the deep lower mantle and core-mantle boundary region will promote the formation of diamonds in carbonate-bearing subducted slabs. The complete reaction of metallic iron to oxides and carbides in the presence of mantle carbonate supports the formation of these phases at the Earth's core-mantle boundary and in ultra-low velocity zones.

  7. Iron Hydroxy Carbonate Formation in Zerovalent Iron Permeable Reactive Barriers: Characterization and Evaluation of Phase Stability

    EPA Science Inventory

    Predicting the long-term potential of permeable reactive barriers for treating contaminated groundwater relies on understanding the endpoints of biogeochemical reactions between influent groundwater and the reactive medium. Iron hydroxy carbonate (chukanovite) is frequently obs...

  8. Organics Synthesized Using Iron-Grain Silicates

    NASA Technical Reports Server (NTRS)

    Johnson, N. M.; Cody, G. D.; Nuth, J. A., III

    2003-01-01

    We use Fischer-Tropsch type (FTT) synthesis to produce hydrocarbons by hydrogenating carbon monoxide via catalytic reactions. The products of these reactions have been studied using 'natural' catalysts and calculations of the efficiency of FTT synthesis in the Solar Nebula suggest that these types of reactions could make significant contributions to the composition of material near three AU. We coat Fe-silicate grains with organic material using FTT synthesis to simulate the chemistry in the early Solar Nebula. In our experimental setup, we roughly model a nebular environment where grains are successively transported from hot to cold regions of the nebula. In other words, the starting gases and FTT products are continuously circulated through the grains at high temperature with intervals of cooling. Organics generated in this manner could represent the carbonaceous material incorporated in comets and meteorites. We analyze the resulting organics and present the results.

  9. Iron-carbon compacts and process for making them

    DOEpatents

    Sheinberg, Haskell

    2000-01-01

    The present invention includes iron-carbon compacts and a process for making them. The process includes preparing a slurry comprising iron powder, furfuryl alcohol, and a polymerization catalyst for initiating the polymerization of the furfuryl alcohol into a resin, and heating the slurry to convert the alcohol into the resin. The resulting mixture is pressed into a green body and heated to form the iron-carbon compact. The compact can be used as, or machined into, a magnetic flux concentrator for an induction heating apparatus.

  10. Insight into the Iron-Molybdenum Cofactor of Nitrogenase from Synthetic Iron Complexes with Sulfur, Carbon, and Hydride Ligands.

    PubMed

    Čorić, Ilija; Holland, Patrick L

    2016-06-15

    Nitrogenase enzymes are used by microorganisms for converting atmospheric N2 to ammonia, which provides an essential source of N atoms for higher organisms. The active site of the molybdenum-dependent nitrogenase is the unique carbide-containing iron-sulfur cluster called the iron-molybdenum cofactor (FeMoco). On the FeMoco, N2 binding is suggested to occur at one or more iron atoms, but the structures of the catalytic intermediates are not clear. In order to establish the feasibility of different potential mechanistic steps during biological N2 reduction, chemists have prepared iron complexes that mimic various structural aspects of the iron sites in the FeMoco. This reductionist approach gives mechanistic insight, and also uncovers fundamental principles that could be used more broadly for small-molecule activation. Here, we discuss recent results and highlight directions for future research. In one direction, synthetic iron complexes have now been shown to bind N2, break the N-N triple bond, and produce ammonia catalytically. Carbon- and sulfur-based donors have been incorporated into the ligand spheres of Fe-N2 complexes to show how these atoms may influence the structure and reactivity of the FeMoco. Hydrides have been incorporated into synthetic systems, which can bind N2, reduce some nitrogenase substrates, and/or reductively eliminate H2 to generate reduced iron centers. Though some carbide-containing iron clusters are known, none yet have sulfide bridges or high-spin iron atoms like the FeMoco. PMID:27171599

  11. IRON

    EPA Science Inventory

    The document surveys the effects of organic and inorganic iron that are relevant to humans and their environment. The biology and chemistry of iron are complex and only partially understood. Iron participates in oxidation reduction processes that not only affect its geochemical m...

  12. Iron-mediated stabilization of soil carbon amplifies the benefits of ecological restoration in degraded lands.

    PubMed

    Silva, Lucas C R; Doane, Timothy A; Corrêa, Rodrigo S; Valverde, Vinicius; Pereira, Engil I P; Horwath, William R

    2015-07-01

    Recent observations across a 14-year restoration chronosequence have shown an unexpected accumulation of soil organic carbon in strip-mined areas of central Brazil. This was attributed to the rapid plant colonization that followed the incorporation of biosolids into exposed regoliths, but the specific mechanisms involved in the stabilization of carbon inputs from the vegetation remained unclear. Using isotopic and elemental analyses, we tested the hypothesis that plant-derived carbon accumulation was triggered by the formation of iron-coordinated complexes, stabilized into physically protected (occluded) soil fractions. Confirming this hypothesis, we identified a fast formation of microaggregates shortly after the application of iron-rich biosolids, which was characterized by a strong association between pyrophosphate-extractable iron and plant-derived organic matter. The formation of microaggregates preceded the development of macroaggregates, which drastically increased soil carbon content (-140 Mg C/ha) a few years after restoration. Consistent with previous theoretical work, iron-coordinated organic complexes served as nuclei for aggregate formation, reflecting the synergistic effect of biological, chemical, and physical mechanisms of carbon stabilization in developing soils. Nevertheless, iron was not the only factor affecting soil carbon content. The highest carbon accumulation was observed during the period of highest plant diversity (> 30 species; years 3-6), declining significantly with the exclusion of native species by invasive grasses (years 9-14). Furthermore, the increasing dominance of invasive grasses was associated with a steady decline in the concentration of soil nitrogen and phosphorus per unit of accumulated carbon. These results demonstrate the importance of interdependent ecological and biogeochemical processes, and the role of soil-plant interactions in determining the success of restoration efforts. In contrast with previous but

  13. Hydrogen storage and carbon dioxide capture in an iron-based sodalite-type metal-organic framework (Fe-BTT) discovered via high-throughput methods

    SciTech Connect

    Sumida, Kenji; Horike, Satoshi; Kaye, Steven S; Herm, Zoey R; Queen, Wendy L; Brown, Craig M; Grandjean, Fernande; Long, Gary J; Dailly, Anne; Long, Jeffrey R

    2010-01-01

    Using high-throughput instrumentation to screen conditions, the reaction between FeCl₂ and H₃BTT∙2HCl (BTT3- = 1,3,5-benzenetristetrazolate) in a mixture of DMF and DMSO was found to afford Fe₃[(Fe₄Cl)₃(BTT)₈]₂∙22DMF∙32DMSO∙11H₂O. This compound adopts a porous three-dimensional framework structure consisting of square [Fe₄Cl]7+ units linked via triangular BTT3- bridging ligands to give an anionic 3,8-net. Mössbauer spectroscopy carried out on a DMF-solvated version of the material indicated the framework to contain high-spin Fe2+ with a distribution of local environments and confirmed the presence of extra-framework iron cations. Upon soaking the compound in methanol and heating at 135 °C for 24 h under dynamic vacuum, most of the solvent is removed to yield Fe₃[(Fe₄Cl)₃(BTT)₈(MeOH)₄]₂ (Fe-BTT), a microporous solid with a BET surface area of 2010 m2 g-1 and open Fe2+ coordination sites. Hydrogen adsorption data collected at 77 K show a steep rise in the isotherm, associated with an initial isosteric heat of adsorption of 11.9 kJ mol-1, leading to a total storage capacity of 1.1 wt% and 8.4 g L-1 at 100 bar and 298 K. Powder neutron diffraction experiments performed at 4 K under various D₂ loadings enabled identification of ten different adsorption sites, with the strongest binding site residing just 2.17(5) Å from the framework Fe2+ cation. Inelastic neutron scattering spectra are consistent with the strong rotational hindering of the H₂ molecules at low loadings, and further reveal the catalytic conversion of ortho-H₂ to para-H₂ by the paramagnetic iron centers. The exposed Fe2+ cation sites within Fe-BTT also lead to the selective adsorption of CO₂ over N₂, with isotherms collected at 298 K indicating uptake ratios of 30.7 and 10.8 by weight at 0.1 and 1.0 bar, respectively.

  14. Carbon content of austenite in austempered ductile iron

    SciTech Connect

    Chang, L.C.

    1998-06-05

    The development of austempered ductile iron (ADI) is a major achievement in cast iron technology. The austempering heat treatment enables the ductile cast iron containing mainly strong bainitic ferrite and ductile carbon-enriched austenite, with some martensite transforms from austenite during cooling down to room temperature. A key factor controlling the stability of the retained austenite can be evaluated soundly using the thermodynamics principles. It is the purpose here to demonstrate that the data of ADI from numerous sources have a similar trend.

  15. Kinetics of Carbon Dissolution of Coke in Molten Iron

    NASA Astrophysics Data System (ADS)

    Jang, Dongik; Kim, Yumkyum; Shin, Minsoo; Lee, Joonho

    2012-12-01

    The effect of temperature on the dissolution rate of carbon from coke in molten iron was investigated using a sampling technique in the temperature range of 1723 K to 1923 K (1450 °C to 1650 °C). The dissolution rate of carbon from coke in molten iron increased as the temperature increased. At 1923 K (1650 °C), the rate-determining step was the mass transfer of carbon in the boundary layer adjacent to the metal-carbon interface. At 1723 K (1450 °C), the rate-determining step changed from the mass transfer to the interfacial chemical reaction as the reaction proceeded. At 1823 K (1550 °C), both reaction steps affected the apparent reaction rates. Sulfur dissolution did not affect the carbon dissolution rates in molten iron, so it was considered that the sulfur adsorption at the metal/coke interface was not so significant. The apparent activation energy of the carbon dissolution of coke in molten iron was estimated to be 442 kJ/mol.

  16. Enriched Iron(III)-Reducing Bacterial Communities are Shaped by Carbon Substrate and Iron Oxide Mineralogy

    PubMed Central

    Lentini, Christopher J.; Wankel, Scott D.; Hansel, Colleen M.

    2012-01-01

    Iron (Fe) oxides exist in a spectrum of structures in the environment, with ferrihydrite widely considered the most bioavailable phase. Yet, ferrihydrite is unstable and rapidly transforms to more crystalline Fe(III) oxides (e.g., goethite, hematite), which are poorly reduced by model dissimilatory Fe(III)-reducing microorganisms. This begs the question, what processes and microbial groups are responsible for reduction of crystalline Fe(III) oxides within sedimentary environments? Further, how do changes in Fe mineralogy shape oxide-hosted microbial populations? To address these questions, we conducted a large-scale cultivation effort using various Fe(III) oxides (ferrihydrite, goethite, hematite) and carbon substrates (glucose, lactate, acetate) along a dilution gradient to enrich for microbial populations capable of reducing Fe oxides spanning a wide range of crystallinities and reduction potentials. While carbon source was the most important variable shaping community composition within Fe(III)-reducing enrichments, both Fe oxide type and sediment dilution also had a substantial influence. For instance, with acetate as the carbon source, only ferrihydrite enrichments displayed a significant amount of Fe(III) reduction and the well-known dissimilatory metal reducer Geobacter sp. was the dominant organism enriched. In contrast, when glucose and lactate were provided, all three Fe oxides were reduced and reduction coincided with the presence of fermentative (e.g., Enterobacter spp.) and sulfate-reducing bacteria (e.g., Desulfovibrio spp.). Thus, changes in Fe oxide structure and resource availability may shift Fe(III)-reducing communities between dominantly metal-respiring to fermenting and/or sulfate-reducing organisms which are capable of reducing more recalcitrant Fe phases. These findings highlight the need for further targeted investigations into the composition and activity of speciation-directed metal-reducing populations within natural environments. PMID

  17. Iron-carbon composites for the remediation of chlorinated hydrocarbons

    NASA Astrophysics Data System (ADS)

    Sunkara, Bhanu Kiran

    This research is focused on engineering submicron spherical carbon particles as effective carriers/supports for nanoscale zerovalent iron (NZVI) particles to address the in situ remediation of soil and groundwater chlorinated contaminants. Chlorinated hydrocarbons such as trichloroethylene (TCE) and tetrachloroethylene (PCE) form a class of dense non-aqueous phase liquid (DNAPL) toxic contaminants in soil and groundwater. The in situ injection of NZVI particles to reduce DNAPLs is a potentially simple, cost-effective, and environmentally benign technology that has become a preferred method in the remediation of these compounds. However, unsupported NZVI particles exhibit ferromagnetism leading to particle aggregation and loss in mobility through the subsurface. This work demonstrates two approaches to prepare carbon supported NZVI (iron-carbon composites) particles. The objective is to establish these iron-carbon composites as extremely useful materials for the environmental remediation of chlorinated hydrocarbons and suitable materials for the in situ injection technology. This research also demonstrates that it is possible to vary the placement of iron nanoparticles either on the external surface or within the interior of carbon microspheres using a one-step aerosol-based process. The simple process of modifying iron placement has significant potential applications in heterogeneous catalysis as both the iron and carbon are widely used catalysts and catalyst supports. Furthermore, the aerosol-based process is applied to prepare new class of supported catalytic materials such as carbon-supported palladium nanoparticles for ex situ remediation of contaminated water. The iron-carbon composites developed in this research have multiple functionalities (a) they are reactive and function effectively in reductive dehalogenation (b) they are highly adsorptive thereby bringing the chlorinated compound to the proximity of the reactive sites and also serving as adsorption

  18. The Rusty Sink: Iron Promotes the Preservation of Organic Matter in Sediments

    NASA Astrophysics Data System (ADS)

    Lalonde, K. M.; Mucci, A.; Moritz, A.; Ouellet, A.; Gelinas, Y.

    2011-12-01

    The biogeochemical cycles of iron (Fe) and organic carbon (OC) are strongly interlinked. In oceanic waters, organic ligands have been shown to control the concentration of dissolved Fe [1], whereas in soils, solid Fe phases provide a sheltering and preservative effect for organic matter [2]. Until now however, the role of iron in the preservation of OC in sediments has not been clearly established. Here we show that 21.5 ± 8.6% of the OC in sediments is directly bound to reactive iron phases, which promote the preservation of OC in sediments. Iron-bound OC represents a global mass of 19 to 45 × 10^15 g of OC in surface marine sediments. This pool of OC is different from the rest of sedimentary OC, with 13C and nitrogen-enriched organic matter preferentially bound to Fe which suggests that biochemical fractionation occurs with OC-Fe binding. Preferential binding also affects the recovery of high molecular weight lipid biomarkers and acidic lignin oxidation products, changing the environmental message of proxies derived from these biomarkers. [1] Johnson, K. S., Gordon, R. M. & Coale, K. H. What controls dissolved iron in the world ocean? Marine Chemistry 57, 137-161 (1997). [2] Kaiser, K. & Guggenberger, G. The role of DOM sorption to mineral surfaces in the preservation of organic matter in soils. Organic Geochemistry 31, 711-725 (2000).

  19. Synthetic effect between iron oxide and sulfate mineral on the anaerobic transformation of organic substance.

    PubMed

    Chen, Tian-Hu; Wang, Jin; Zhou, Yue-Fei; Yue, Zheng-Bo; Xie, Qiao-Qin; Pan, Min

    2014-01-01

    Synthetic effect between sulfate minerals (gypsum) and iron oxide (hematite) on the anaerobic transformation of organic substance was investigated in the current study. The results showed that gypsum was completely decomposed while hematite was partially reduced. The mineral phase analysis results showed that FeS and CaCO3 was the major mineralization product. Methane generation process was inhibited and inorganic carbon contents in the precipitates were enhanced compared to the control without hematite and gypsum. The inorganic carbon content increased with the increasing of hematite dosages. Co-addition of sulfate minerals and iron oxide would have a potential application prospect in the carbon sequestration area and reduction of the greenhouse gas release. The results would also reveal the role of inorganic mineral in the global carbon cycle. PMID:24189378

  20. Cold catalytic recovery of loaded activated carbon using iron oxide-based nanoparticles.

    PubMed

    Bach, Altai; Zelmanov, Grigory; Semiat, Raphael

    2008-01-01

    A novel approach for the recovery of spent activated carbon by an advanced oxidation process using iron oxide-based nanocatalysts was proposed and investigated. Model organic contaminants, such as ethylene glycol and phenol, were chosen for this study as water pollutants. It was shown that there are several advantages in using catalytic oxidation recovery of activated carbon with iron oxide-based nanocatalysts: low temperature reactivity of catalytic recovery without heating; and a relatively large number of adsorption-recovery cycles, without a reduction in the adsorptive properties of the virgin activated carbon or without a performance decrease from the first adsorption-recovery cycle of the new modified adsorptive properties of the activated carbon. The catalytic recovery takes place without ultraviolet light or any visible radiation sources. Results show a high efficiency of catalytic recovery of spent activated carbon using iron oxide-based nanocatalysts. A 97-99% efficiency of spent activated carbon catalytic regeneration was achieved under chosen conditions after 15-20 min of reaction. The process may be also considered as cold in situ recovery of active carbon. PMID:17826818

  1. Synthesis of carbon-coated iron nanoparticles by detonation technique

    SciTech Connect

    Sun, Guilei; Li, Xiaojie; Wang, Qiquan; Yan, Honghao

    2010-05-15

    Carbon-coated iron nanoparticles were synthesized by detonating a mixture of ferrocene, naphthalene and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in an explosion vessel under low vacuum conditions (8.1 kPa). The RDX functioned as an energy source for the decomposition of ferrocene and naphthalene. The carbon-coated iron nanoparticles were formed as soot-like deposits on the inner surface of the reactor, which were characterized by XRD, TEM, HRTEM, Raman spectroscopy and vibrating sample magnetometer. And a portion of the detonation soot was treated with hydrochloric acid. The product was carbon-coated nanoparticles in perfect core-shell structures with graphitic shells and bcc-Fe cores. The detonation technique offers an energy-saving route to the synthesis of carbon-coated nanomaterials.

  2. Carbonates of the Gunflint Banded Iron Formation as Analogs of Martian Carbonates

    NASA Technical Reports Server (NTRS)

    Pun, A.; Papike, J. J.; Shearer, C. K.

    2001-01-01

    Terrestrial iron formations preserve remnants of life on Earth and may serve as analogs for identifying evidence of biologic activity in martian rocks. We report on the petrography, mineralogy and trace-element abundances of carbonates of the Gunflint banded iron formation. Additional information is contained in the original extended abstract.

  3. Stabilization of Organic Matter by Interactions with Iron Oxides: Relative Importance of Sorption vs. Aggregation

    NASA Astrophysics Data System (ADS)

    Jin, L.; Berhe, A. A.

    2015-12-01

    Persistence of organic matter in soil is largely determined by the environmental conditions that organic compounds encounter in the environment. The most important stabilization mechanisms for carbon in soil include chemical and physical association of organic compounds with soil minerals. However, to date, we don't have a complete understanding of the relative contribution of each process to carbon stabilization, especially under different soil conditions. To develop better process-level understanding of these stabilization mechanisms, the relative importance of chemical vs. physical mechanisms of carbon stabilization facilitated by iron oxides at different soil solution conditions using a variety of advanced approaches including electron microscopy and infrared spectroscopy is determined. Our preliminary results suggest that aggregation may be the dominant process in mineral-organic associations. These results improve our understanding of factors that regulate persistence of organic matter in soil system.

  4. Carbonate petrography, kerogen distribution, and carbon and oxygen isotope variations in an early Proterozoic transition from limestone to iron-formation deposition, Transvaal Supergroup, South Africa

    NASA Technical Reports Server (NTRS)

    Beukes, N. J.; Klein, C.; Kaufman, A. J.; Hayes, J. M.

    1990-01-01

    The transition zone comprises Campbellrand microbialaminated (replacing "cryptalgalaminate") limestone and shale, with minor dolomite, conformably overlain by the Kuruman Iron Formation of which the basal part is characterized by siderite-rich microbanded iron-formation with minor magnetite and some hematite-containing units. The iron-formation contains subordinate intraclastic and microbialaminated siderite mesobands and was deposited in deeper water than the limestones. The sequence is virtually unaltered with diagenetic mineral assemblages reflecting a temperature interval of about 110 degrees to 170 degrees C and pressures of 2 kbars. Carbonate minerals in the different rock types are represented by primary micritic precipitates (now recrystallized to microsparite), early precompactional sparry cements and concretions, deep burial limpid euhedral sparites, and spar cements precipitated from metamorphic fluids in close contact with diabase sills. Paragenetic pathways of the carbonate minerals are broadly similar in all lithofacies with kerogen intimately associated with them. Kerogen occurs as pigmentation in carbonate crystals, as reworked organic detritus in clastic-textured carbonate units, and as segregations of kerogen pigment around late diagenetic carbonate crystals. Locally kerogen may also be replaced by carbonate spar. Carbon isotope compositions of the carbonate minerals and kerogen are dependent on their mode of occurrence and on the composition of the dominant carbonate species in a specific lithofacies. Integration of sedimentary, petrographic, geochemical, and isotopic results makes it possible to distinguish between depositional, early diagenetic, deep burial, and metamorphic effects on the isotopic compositions of the carbonate minerals and the kerogen in the sequence. Major conclusions are that deep burial thermal decarboxylation led to 13C depletion in euhedral ferroan sparites and 13C enrichment in kerogen (organic carbon). Metamorphic

  5. Carbonate petrography, kerogen distribution, and carbon and oxygen isotope variations in an early Proterozoic transition from limestone to iron-formation deposition, Transvaal Supergroup, South Africa.

    PubMed

    Beukes, N J; Klein, C; Kaufman, A J; Hayes, J M

    1990-01-01

    The transition zone comprises Campbellrand microbialaminated (replacing "cryptalgalaminate") limestone and shale, with minor dolomite, conformably overlain by the Kuruman Iron Formation of which the basal part is characterized by siderite-rich microbanded iron-formation with minor magnetite and some hematite-containing units. The iron-formation contains subordinate intraclastic and microbialaminated siderite mesobands and was deposited in deeper water than the limestones. The sequence is virtually unaltered with diagenetic mineral assemblages reflecting a temperature interval of about 110 degrees to 170 degrees C and pressures of 2 kbars. Carbonate minerals in the different rock types are represented by primary micritic precipitates (now recrystallized to microsparite), early precompactional sparry cements and concretions, deep burial limpid euhedral sparites, and spar cements precipitated from metamorphic fluids in close contact with diabase sills. Paragenetic pathways of the carbonate minerals are broadly similar in all lithofacies with kerogen intimately associated with them. Kerogen occurs as pigmentation in carbonate crystals, as reworked organic detritus in clastic-textured carbonate units, and as segregations of kerogen pigment around late diagenetic carbonate crystals. Locally kerogen may also be replaced by carbonate spar. Carbon isotope compositions of the carbonate minerals and kerogen are dependent on their mode of occurrence and on the composition of the dominant carbonate species in a specific lithofacies. Integration of sedimentary, petrographic, geochemical, and isotopic results makes it possible to distinguish between depositional, early diagenetic, deep burial, and metamorphic effects on the isotopic compositions of the carbonate minerals and the kerogen in the sequence. Major conclusions are that deep burial thermal decarboxylation led to 13C depletion in euhedral ferroan sparites and 13C enrichment in kerogen (organic carbon). Metamorphic

  6. Formation of magnetite and iron-rich carbonates by thermophilic iron-reducing bacteria

    SciTech Connect

    Zhang, C.; Liu, S.; Roh, Y.; Cole, D.; Phelps, T.; Vali, H.; Kirschvink, J.L.; Onsttot, T.; McKay, D.

    1997-06-01

    Laboratory experiments were performed to study the formation of iron minerals by a thermophilic (45 to 75 C) fermentative iron-reducing bacterial culture (TOR39) obtained from the deep subsurface. Using amorphous Fe(III) oxyhydroxide as an electron acceptor and glucose as an electron donor, TOR39 produced magnetite and iron-rich carbonates at conditions consistent, on a thermodynamic basis, with Eh ({minus}200 mV to {minus}415 mV) and pH (6.2 to 7.7) values determined for these experiments. Analyses of the precipitating solid phases by X-ray diffraction showed that the starting amorphous Fe(III) oxyhydroxide was nearly completely converted to magnetite and Fe-rich carbonate after 20 days of incubation. Increasing bicarbonate concentration in the chemical milieu resulted in increased proportions of siderite relative to magnetite and the addition of MgCl{sub 2} caused the formation of magnesium-rich carbonate in addition to siderite. The results suggest that the TOR39 bacterial culture may have the capacity to form magnetite and iron-rich carbonates in a variety of geochemical conditions. These results may have significant implications for studying the past biogenic activities in the Martian meteorite ALH84001.

  7. Formation of magnetite and iron-rich carbonates by thermophilic iron-reducing bacteria

    NASA Astrophysics Data System (ADS)

    Zhang, Chuanlun; Vali, Hojatollah; Liu, Shi; Roh, Yul; Cole, Dave; Kirschvink, Joseph L.; Onstott, Tullis C.; McKay, David S.; Phelps, Tommy J.

    1997-07-01

    Laboratory experiments were performed to study the formation of iron minerals by a thermophilic (45 - 75 degree(s)C) fermentative iron-reducing bacterial culture (TOR39) obtained from the deep subsurface. Using amorphous Fe(III) oxyhydroxide as an electron acceptor and glucose as an electron donor, TOR39 produced magnetite and iron-rich carbonates at conditions consistent, on a thermodynamic basis, with Eh (-200 mV to -415 mV) and pH (6.2 to 7.7) values determined for these experiments. Analyses of the precipitating solid phases by X-ray diffraction showed that the starting amorphous Fe(III) oxyhydroxide was nearly completely converted to magnetite and Fe-rich carbonate after 20 days of incubation. Increasing bicarbonate concentration in the chemical milieu resulted in increased proportions of siderite relative to magnetite and the addition of MgCl2 caused the formation of magnesium-rich carbonate in addition to siderite. The results suggest that the TOR39 bacterial culture may have the capacity to form magnetite and iron-rich carbonates in a variety of geochemical conditions. These results may have significant implications for studying the past biogenic activities in the Martian meteorite ALH84001.

  8. Deactivation by carbon of iron catalysts for indirect liquefaction

    SciTech Connect

    Bartholomew, C.H.

    1991-01-10

    Although promoted cobalt and iron catalysts for Fischer-Tropsch (FT) synthesis of gasoline feedstock were first developed more than three decades ago, a major technical problem still limiting the commercial use of these catalysts today is carbon deactivation. This report describes recent progress in a fundamental, three-year investigation of carbon formation and its effects on the activity and selectivity of promoted iron catalysts for FT synthesis, the objectives of which are to: determine rates and mechanisms of carbon deactivation of unsupported Fe and Fe/K catalysts during CO hydrogenation over a range of CO concentrations, CO:H{sub 2} ratios, and temperatures; and model the rates of deactivation of the same catalysts in fixed-bed reactors. To accomplish the above objectives, the project is divided into the following tasks: (1) determine the kinetics of reaction and of carbon deactivation during CO hydrogenation on Fe and Fe/K catalysts coated on monolith bodies. (2) Determine the reactivities and types of carbon deposited during reaction on the same catalysts from temperature-programmed-surface-reaction spectroscopy (TPSR) and transmission electron microscopy (TEM). Determine the types of iron carbides formed at various temperatures and H{sub 2}/CO ratios using x-ray diffraction and Moessbauer spectroscopy. (3) Develop mathematical deactivation models which include heat and mass transport contributions for FT synthesis is packed-bed reactors. Progress to date is described. 48 refs., 3 figs., 1 tab.

  9. Synthesis of amorphous carbon nanofibers using iron nanoparticles as catalysts

    NASA Astrophysics Data System (ADS)

    Ali, Mokhtar; Ramana, G. Venkata; Padya, Balaji; Srikanth, V. V. S. S.; Jain, P. K.

    2013-06-01

    Amongst various carbon nanomaterials, carbon nanofibers (CNFs) have lately attracted considerable interest as a promising reinforcement in polymer matrix composites. CNFs are often synthesized using copper nanoparticles as catalysts and by using chemical vapor deposition (CVD). In this work iron (Fe) nanoparticles are used as catalysts to synthesize amorphous carbon nanofibers. This owes significance since Fe nanoparticles often lead to tubes rather than fibers. Fe nanoparticles (size ˜30-60nm) are prepared by first mixing an appropriate quantity of potassium sodium tartrate tetrahydrate salt with iron (II) chloride dehydrate to obtain iron tartrate and then dried and heated in vacuum oven at about 250°C to remove tartrate. In a subsequent step, CNFs are obtained by using CVD. Acetylene was used as the carbon source in the CVD process. Scanning and transmission electron microscopy show the formation of nanofibers whose diameter is dependent on the size of Fe catalysts. Raman scattering from the fibers show that they are made up of carbon and are amorphous.

  10. The elements just beyond iron - Formation during explosive carbon burning

    NASA Technical Reports Server (NTRS)

    Wefel, J. P.; Schramm, D. N.; Blake, J. B.; Pridmore-Brown, D.

    1981-01-01

    It is pointed out that the details of the synthesis of the elements just beyond iron are unclear. Thus, a reexamination of the role played by neutron-capture reactions during explosive carbon burning is indicated. A description is given of calculations of explosive carbon-burning nucleosynthesis using a complete neutron capture (n-process) computer code with a network extending from Cr through Zr and including not only (n,gamma), (gamma,n) reactions and beta-decay but also (p,n), (n,p), (p,gamma), and (p,alpha) reactions. Initial conditions indicative of the composition of a massive star following core helium burning were selected, and a comparison is made with conditions similar to those used by Howard et al. (1972). It is found that neutron reactions during explosive carbon burning are an important source for the elements just beyond iron.

  11. Natural organic matter and iron export from the Tanner Moor, Austria

    PubMed Central

    Jirsa, Franz; Neubauer, Elisabeth; Kittinger, Richard; Hofmann, Thilo; Krachler, Regina; von der Kammer, Frank; Keppler, Bernhard K.

    2013-01-01

    Samples from a pristine raised peat bog runoff in Austria, the Tannermoor creek, were analysed for their iron linked to natural organic matter (NOM) content. Dissolved organic carbon < 0.45 μm (DOC) was 41–64 mg L−1, iron 4.4–5.5 mg L−1. Samples were analysed applying asymmetric field flow fractionation (AsFlFFF) coupled to UV–vis absorption, fluorescence and inductively coupled plasma mass spectrometry (ICP-MS). The samples showed an iron peak associated with the NOM peak, one sample exhibiting a second peak of iron independent from the NOM peak. As highland peat bogs with similar climatic conditions and vegetation to the Tanner Moor are found throughout the world, including areas adjacent to the sea, we examined the behaviour of NOM and iron in samples brought to euhaline (35‰) conditions with artificial sea salt. The enhanced ionic strength reduced NOM by 53% and iron by 82%. Size exclusion chromatography (SEC) of the samples at sea-like salinity revealed two major fractions of NOM associated with different iron concentrations. The larger one, eluting sharply after the upper exclusion limits of 4000–5000 g mol−1, seems to be most important for iron chelating. The results outline the global importance of sub-mountainous and mountainous raised peat bogs as a source of iron chelators to the marine environment at sites where such peat bogs release their run-offs into the sea. PMID:23805012

  12. Iron

    MedlinePlus

    ... organ failure, coma, convulsions, and death. Child-proof packaging and warning labels on iron supplements have greatly ... levodopa that the body absorbs, making it less effective. Levodopa, found in Sinemet® and Stalevo®, is used ...

  13. Uniform yolk-shell iron sulfide-carbon nanospheres for superior sodium-iron sulfide batteries

    NASA Astrophysics Data System (ADS)

    Wang, Yun-Xiao; Yang, Jianping; Chou, Shu-Lei; Liu, Hua Kun; Zhang, Wei-Xian; Zhao, Dongyuan; Dou, Shi Xue

    2015-10-01

    Sodium-metal sulfide battery holds great promise for sustainable and cost-effective applications. Nevertheless, achieving high capacity and cycling stability remains a great challenge. Here, uniform yolk-shell iron sulfide-carbon nanospheres have been synthesized as cathode materials for the emerging sodium sulfide battery to achieve remarkable capacity of ~545 mA h g-1 over 100 cycles at 0.2 C (100 mA g-1), delivering ultrahigh energy density of ~438 Wh kg-1. The proven conversion reaction between sodium and iron sulfide results in high capacity but severe volume changes. Nanostructural design, including of nanosized iron sulfide yolks (~170 nm) with porous carbon shells (~30 nm) and extra void space (~20 nm) in between, has been used to achieve excellent cycling performance without sacrificing capacity. This sustainable sodium-iron sulfide battery is a promising candidate for stationary energy storage. Furthermore, this spatially confined sulfuration strategy offers a general method for other yolk-shell metal sulfide-carbon composites.

  14. Uniform yolk-shell iron sulfide-carbon nanospheres for superior sodium-iron sulfide batteries.

    PubMed

    Wang, Yun-Xiao; Yang, Jianping; Chou, Shu-Lei; Liu, Hua Kun; Zhang, Wei-Xian; Zhao, Dongyuan; Dou, Shi Xue

    2015-01-01

    Sodium-metal sulfide battery holds great promise for sustainable and cost-effective applications. Nevertheless, achieving high capacity and cycling stability remains a great challenge. Here, uniform yolk-shell iron sulfide-carbon nanospheres have been synthesized as cathode materials for the emerging sodium sulfide battery to achieve remarkable capacity of ∼ 545 mA h g(-1) over 100 cycles at 0.2 C (100 mA g(-1)), delivering ultrahigh energy density of ∼ 438 Wh kg(-1). The proven conversion reaction between sodium and iron sulfide results in high capacity but severe volume changes. Nanostructural design, including of nanosized iron sulfide yolks (∼ 170 nm) with porous carbon shells (∼ 30 nm) and extra void space (∼ 20 nm) in between, has been used to achieve excellent cycling performance without sacrificing capacity. This sustainable sodium-iron sulfide battery is a promising candidate for stationary energy storage. Furthermore, this spatially confined sulfuration strategy offers a general method for other yolk-shell metal sulfide-carbon composites. PMID:26507613

  15. Uniform yolk-shell iron sulfide–carbon nanospheres for superior sodium–iron sulfide batteries

    PubMed Central

    Wang, Yun-Xiao; Yang, Jianping; Chou, Shu-Lei; Liu, Hua Kun; Zhang, Wei-xian; Zhao, Dongyuan; Dou, Shi Xue

    2015-01-01

    Sodium–metal sulfide battery holds great promise for sustainable and cost-effective applications. Nevertheless, achieving high capacity and cycling stability remains a great challenge. Here, uniform yolk-shell iron sulfide–carbon nanospheres have been synthesized as cathode materials for the emerging sodium sulfide battery to achieve remarkable capacity of ∼545 mA h g−1 over 100 cycles at 0.2 C (100 mA g−1), delivering ultrahigh energy density of ∼438 Wh kg−1. The proven conversion reaction between sodium and iron sulfide results in high capacity but severe volume changes. Nanostructural design, including of nanosized iron sulfide yolks (∼170 nm) with porous carbon shells (∼30 nm) and extra void space (∼20 nm) in between, has been used to achieve excellent cycling performance without sacrificing capacity. This sustainable sodium–iron sulfide battery is a promising candidate for stationary energy storage. Furthermore, this spatially confined sulfuration strategy offers a general method for other yolk-shell metal sulfide–carbon composites. PMID:26507613

  16. Iron carbonates in the Earth's lower mantle: reality or imagination?

    NASA Astrophysics Data System (ADS)

    Cerantola, V.; McCammon, C. A.; Merlini, M.; Bykova, E.; Kupenko, I.; Ismailova, L.; Chumakov, A. I.; Kantor, I.; Dubrovinsky, L. S.; Prescher, C.

    2015-12-01

    Carbonates play a fundamental role in the recycling of carbon inside our planet due to their presence in oceanic slabs that sink through the Earth's interior. Through this process, iron carbonates are potential stable carbon-bearing minerals in the deep mantle in part due to spin crossover of ferrous iron. Our goal is to identify which minerals may be the dominant carriers of carbon into the deep mantle at the relevant conditions of fO2, P and T. All experiments were performed using synthetic FeCO3 and MgFeCO3 single crystals in laser heated diamond anvil cells up to 100 GPa and 3000 K in order to simulate the conditions prevailing in the Earth's lower mantle. Transformation and decomposition products of the original carbonates were characterized at different synchrotron facilities by means of single-crystal XRD, synchrotron Mössbauer source spectroscopy and XANES techniques. At deep lower mantle conditions, we observed the transformation of FeCO3 to two new HP-carbonate structures, monoclinic Fe22+Fe23+C4O13 and trigonal Fe43+(CO4)3, both characterized by the presence of CO4 tetrahedra with different degrees of polymerization. At shallower depths in the lower mantle where temperatures are lower following the geotherm, Fe-carbonates decompose to different Fe-oxides instead of new HP-carbonates. However, at slab temperatures several hundred degrees lower than the surrounding mantle, carbonates could be stabilized until reaching conditions that trigger their transformation to HP-structures. We postulate that Fe-rich carbonates could exist in regions down to the core-mantle boundary in the proximity of subducting slabs, i.e., a "cold" environment with relatively high fO2.

  17. Effect of carbon content on friction and wear of cast irons

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1977-01-01

    Friction and wear experiments were conducted with cast irons and wrought steels containing various amounts of carbon in the alloy structure in contact with 52100 steel. Gray cast irons were found to exhibit lower friction and wear characteristics than white cast irons. Further, gray cast iron wear was more sensitive to carbon content than was white. Wear with gray cast iron was linearly related to load, and friction was found to be sensitive to relative humidity and carbon content. The form, in which the carbon is present in the alloy, is more important, as the carbon content and no strong relationship seems to exist between hardness of these ferrous alloys and wear.

  18. Iron-Containing Carbon Materials Fabricated

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Development of high-strength, lightweight materials for electromagnetic interference (EMI) shielding at low frequencies may be possible if the carbon fibers used in these composites can be made to have ferromagnetic properties. One way to obtain such fibers is by inserting small ferromagnetic particles into the fiber structure.

  19. Microbial Synthesis of Iron Sulfide (FeS) and Iron Carbonate (FeCO3) Nanoparticles.

    PubMed

    Kim, Yumi; Lee, Yuri; Roh, Yul

    2015-08-01

    This study examined mineral transformations during anoxic bioreduction of iron hydroxide and iron oxyhydroxysulfate found in acid mine drainage (AMD) into iron sulfide (FeS) and siderite (FeCO3) nanoparticles. Glucose (10 mM) was inoculated into AMD to stimulate indigenous bacterial growth for bioreduction of Fe(III)-containing minerals. Changes in microbial, geochemical, and mineralogical characteristics were monitored via 16S rRNA, XRD, SEM-EDX, TEM-EDX, ICP-AES, and IC analyses. The AMD was found to be rich in elements, including Fe, Al, Mn, Na, and S (SO4), and had a pH of 5.2. The mineral contents mainly consisted of Fe(III)-containing minerals, such as schwertmannite [Fe8O8 (OH)8-2x(SO4)x · nH2O] and akaganeite [β-FeO(OH)]. During anoxic bioreduction of AMD, the Fe(III)-containing minerals were transformed by indigenous iron-reducing bacteria (e.g., Geobactersp.) into Fe(II)-containing minerals, such as iron sulfide (FeS) and iron carbonate, siderite (FeCO3), within 3-4 days. The microbially-formed iron sulfide (FeS) and siderite (FeCO3) were of 40-60 nm and 10 nm-3 µm in size, respectively. These results not only show that indigenous iron-reducing bacteria in AMD can aid or accelerate formation of Fe(II)-containing minerals when under anoxic environments, but can also offer a simple method for microbial synthesis of nano-sized Fe(II)-containing minerals that can be used as catalysts for environmental remediation by recycling AMD. PMID:26369153

  20. Tracing iron-fueled microbial carbon production within the hydrothermal plume at the Loihi seamount

    NASA Astrophysics Data System (ADS)

    Bennett, Sarah A.; Hansman, Roberta L.; Sessions, Alex L.; Nakamura, Ko-ichi.; Edwards, Katrina J.

    2011-10-01

    The Loihi hydrothermal plume provides an opportunity to investigate iron (Fe) oxidation and microbial processes in a system that is truly Fe dominated and distinct from mid-ocean ridge spreading centers. The lack of hydrogen sulfide within the Loihi hydrothermal fluids and the presence of an oxygen minimum zone at this submarine volcano's summit, results in a prolonged presence of reduced Fe within the dispersing non-buoyant plume. In this study, we have investigated the potential for microbial carbon fixation within the Loihi plume. We sampled for both particulate and dissolved organic carbon in hydrothermal fluids, microbial mats growing around vents, and the dispersing plume, and carried out stable carbon isotope analysis on the particulate fraction. The δ13C values of the microbial mats ranged from -23‰ to -28‰, and are distinct from those of deep-ocean particulate organic carbon (POC). The mats and hydrothermal fluids were also elevated in dissolved organic carbon (DOC) compared to background seawater. Within the hydrothermal plume, DOC and POC concentrations were elevated and the isotopic composition of POC within the plume suggests mixing between background seawater POC and a 13C-depleted hydrothermal component. The combination of both DOC and POC increasing in the dispersing plume that cannot solely be the result of entrainment and DOC adsorption, provides strong evidence for in-situ microbial productivity by chemolithoautotrophs, including a likelihood for iron-oxidizing microorganisms.

  1. Adsorbent 2D and 3D carbon matrices with protected magnetic iron nanoparticles.

    PubMed

    Carreño, N L V; Escote, M T; Valentini, A; McCafferty, L; Stolojan, V; Beliatis, M; Mills, C A; Rhodes, R; Smith, C T G; Silva, S R P

    2015-11-01

    We report on the synthesis of two and three dimensional carbonaceous sponges produced directly from graphene oxide (GO) into which functionalized iron nanoparticles can be introduced to render it magnetic. This simple, low cost procedure, wherein an iron polymeric resin precursor is introduced into the carbon framework, results in carbon-based materials with specific surface areas of the order of 93 and 66 m(2) g(-1), compared to approx. 4 m(2) g(-1) for graphite, decorated with ferromagnetic iron nanoparticles giving coercivity fields postulated to be 216 and 98 Oe, values typical for ferrite magnets, for 3.2 and 13.5 wt% Fe respectively. The strongly magnetic iron nanoparticles are robustly anchored to the GO sheets by a layer of residual graphite, on the order of 5 nm, formed during the pyrolysis of the precursor material. The applicability of the carbon sponges is demonstrated in their ability to absorb, store and subsequently elute an organic dye, Rhodamine B, from water as required. It is possible to regenerate the carbon-iron hybrid material after adsorption by eluting the dye with a solvent to which it has a high affinity, such as ethanol. The use of a carbon framework opens the hybrid materials to further chemical functionalization, for enhanced chemical uptake of contaminants, or co-decoration with, for example, silver nanoparticles for bactericidal properties. Such analytical properties, combined with the material's magnetic character, offer solutions for environmental decontamination at land and sea, wastewater purification, solvent extraction, and for the concentration of dilute species. PMID:26441224

  2. Adsorbent 2D and 3D carbon matrices with protected magnetic iron nanoparticles

    NASA Astrophysics Data System (ADS)

    Carreño, N. L. V.; Escote, M. T.; Valentini, A.; McCafferty, L.; Stolojan, V.; Beliatis, M.; Mills, C. A.; Rhodes, R.; Smith, C. T. G.; Silva, S. R. P.

    2015-10-01

    We report on the synthesis of two and three dimensional carbonaceous sponges produced directly from graphene oxide (GO) into which functionalized iron nanoparticles can be introduced to render it magnetic. This simple, low cost procedure, wherein an iron polymeric resin precursor is introduced into the carbon framework, results in carbon-based materials with specific surface areas of the order of 93 and 66 m2 g-1, compared to approx. 4 m2 g-1 for graphite, decorated with ferromagnetic iron nanoparticles giving coercivity fields postulated to be 216 and 98 Oe, values typical for ferrite magnets, for 3.2 and 13.5 wt% Fe respectively. The strongly magnetic iron nanoparticles are robustly anchored to the GO sheets by a layer of residual graphite, on the order of 5 nm, formed during the pyrolysis of the precursor material. The applicability of the carbon sponges is demonstrated in their ability to absorb, store and subsequently elute an organic dye, Rhodamine B, from water as required. It is possible to regenerate the carbon-iron hybrid material after adsorption by eluting the dye with a solvent to which it has a high affinity, such as ethanol. The use of a carbon framework opens the hybrid materials to further chemical functionalization, for enhanced chemical uptake of contaminants, or co-decoration with, for example, silver nanoparticles for bactericidal properties. Such analytical properties, combined with the material's magnetic character, offer solutions for environmental decontamination at land and sea, wastewater purification, solvent extraction, and for the concentration of dilute species.

  3. Seasonal variation in soil organic carbon

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Organic carbon in soil is most often measured at a single point in time, under the assumption that the major pools of organic carbon change so slowly that variation over weeks or months will be insignificant. The validity of this assumption has implications for accurate comparison of soil carbon bet...

  4. Role of Iron Oxyhydrates in Accumulation and Stabilization of Soil Organic Matter in Rice Paddy: Case Studies from China

    NASA Astrophysics Data System (ADS)

    Pan, G.; Lu, H.; Sun, J.; Li, L.; Liu, X.; Zheng, J.; Zhang, X.; Cheng, K.

    2014-12-01

    Iron is an important element in soils, often in forms either of crystalline mineral or amorphous colloids upon redox cycling in hydromorphic soils. However, role of iron particularly via oxyhydrates in organic matter dynamics n rice soils has been not yet well assessed. Rice paddy soils of China have been recognized as a unique type of Anthrosols mostly with iron accumulation and dynamic movement in soil profile through long term hydroagric management. Soil organic matter contents of rice soils are shown significantly correlated with the contents of free or amorphous iron oxyhydrates. And organic matter accumulation in young rice soils followed iron oxyhydrate content changes as rice cultivation proceed, which could be often traced by the changes in iron oxyhydrate-bound OC fractions. The importance of association of OC with iron oxyhydrates is known by the fact that organic carbon was not related to total free iron oxyhydrates in wetland but in rice soil shifted from the wetlands, with OC contents much higher in rice soils than in the precedent wetland soil. This could be attributed to the chemical binding of OC to oxyhydrate surface, contributing to the stabilization of newly sequestered OC. This has been again confirmed by lab incubation studies, where total mineralization of OC has been found significantly lower in iron-oxyhrate rich soil than in iron-oxyhrate poor soils. This effect has been further explored in an incubation study with experimental warming that the temperature dependence of OC mineralization of rice soils from a long term fertilizer treated trial was linked to the abundance of iron oxyhydrate content, varying with the long term management practice. Initial carbon sequestration in rice soil subject to new carbon input was promoted by the iron oxyhydrates in the soil, showing a fast increase in iron hydrate-bound OC in the initial stage. The bound OC exerted further stabilization through enhanced humification to form residual OC fraction in long

  5. Adsorption of dissolved natural organic matter by modified activated carbons.

    PubMed

    Cheng, Wei; Dastgheib, Seyed A; Karanfil, Tanju

    2005-06-01

    Adsorption of dissolved natural organic matter (DOM) by virgin and modified granular activated carbons (GACs) was studied. DOM samples were obtained from two water treatment plants before (i.e., raw water) and after coagulation/flocculation/sedimentation processes (i.e., treated water). A granular activated carbon (GAC) was modified by high temperature helium or ammonia treatment, or iron impregnation followed by high temperature ammonia treatment. Two activated carbon fibers (ACFs) were also used, with no modification, to examine the effect of carbon porosity on DOM adsorption. Size exclusion chromatography (SEC) and specific ultraviolet absorbance (SUVA(254)) were employed to characterize the DOMs before and after adsorption. Iron-impregnated (HDFe) and ammonia-treated (HDN) activated carbons showed significantly higher DOM uptakes than the virgin GAC. The enhanced DOM uptake by HDFe was due to the presence of iron species on the carbon surface. The higher uptake of HDN was attributed to the enlarged carbon pores and basic surface created during ammonia treatment. The SEC and SUVA(254) results showed no specific selectivity in the removal of different DOM components as a result of carbon modification. The removal of DOM from both raw and treated waters was negligible by ACF10, having 96% of its surface area in pores smaller than 1 nm. Small molecular weight (MW) DOM components were preferentially removed by ACF20H, having 33% of its surface area in 1--3 nm pores. DOM components with MWs larger than 1600, 2000, and 2700 Da of Charleston raw, Charleston-treated, and Spartanburg-treated waters, respectively, were excluded from the pores of ACF20H. In contrast to carbon fibers, DOM components from entire MW range were removed from waters by virgin and modified GACs. PMID:15927230

  6. Removal of trichloroethylene by zerovalent iron/activated carbon derived from agricultural wastes.

    PubMed

    Su, Yuh-fan; Cheng, Yu-ling; Shih, Yang-hsin

    2013-11-15

    Activated carbon (AC) and zerovalent iron (ZVI) have been widely used in the adsorption and dehalogenation process, respectively, for the removal of organic compounds in environmental treatments. This study aims to prepare ZVI/AC derived from an agricultural waste, coir pith, through simple one-step pyrolysis. The effect of activation temperature and time on the surface area, iron content, and zerovalent iron ratio of ZVI/AC was systemically investigated. The results indicated that the activation of AC by FeSO4 significantly increased surface area of AC and distributed elemental iron over the AC. The X-ray diffraction (XRD), electron spectroscopy for chemical analysis (ESCA), and X-ray absorption near edge structure (XANES) spectra of ZVI/AC revealed that zerovalent iron was present. As compared to AC without FeSO4 activation, ZVI/AC increased the trichloroethylene removal rate constant by 7 times. The dechlorination ability of ZVI/AC was dominated by the zerovalent iron content. We have shown that lab-made ZVI/AC from coir pith can effectively adsorb and dehalogenate the chlorinated compounds in water. PMID:23994578

  7. Sulfur reactions and cryptic cross-linkages to oxygen, iron, and carbon cyclin

    NASA Astrophysics Data System (ADS)

    Druschel, G.; Kafantaris, F. C. A.; Fike, D. A.; Schmitt-Kopplin, P.; Dvorski, S.; Oduro, H.

    2014-12-01

    Sulfur speciation in any setting is controlled by a complex series of redox reactions, polymerization, and complexation reactions that are affected by both biotic and abiotic processes. Additionally there are several crossroads of reactions with oxygen, carbon, and iron in which polysulfide molecules serve as a key reaction component that affects not only sulfur speciation, but the speciation, solubility, and bioavailability of these elements as well. Utilizing a combination of analytical approaches including electrochemistry, spectroscopy, mass spectrometry, and chromatography, we have started to unravel the interconnections between sulfur and other key elements, and how microorganisms may be either direct or indirect contributors to these chemical and mineralogical signatures. In microbial mats, we have observed microbial production of significant hydrogen peroxide under UV-stressed conditions. This peroxide interaction with hydrogen sulfide changes the kinetics and the pathways of abiotic sulfur reactions, potentially affecting the overall bioavailability and isotopic fractionations for specific reactions via a change in the linkage between oxygen and sulfur cycling. In systems containing significant iron, we have observed the production of an electroactive form of ferrous iron and sulfide (FeS(aq)) that is of a size that can be described between a dissolved molecular cluster and a small nanoparticle. This FeS(aq) can be a significant fraction of the dissolved iron or sulfide in a system, and is a key part of both the solubility of iron and sulfur and the pathways potentially important for pyritization reactions. In systems where we investigate the links between sulfur and carbon, laboratory and field experiments indicate a wide range of large and more reduced organic compounds are highly reactive towards polysulfide. Utilizing Fourier-transform ion cyclotron resonance mass spectrometry in conjunction with electrochemistry and chromatography, we are seeing a

  8. Fouling of carbon steel heat exchanger caused by iron bacteria

    SciTech Connect

    Starosvetsky, J.; Armon, R.; Starosvetsky, D. ); Groysman, A.

    1999-01-01

    A carbon steel heat exchanger installed in a reverse osmosis unit failed after 1 1/2 years from start-up as a result of tubes, lids, tube sheets, and connection pipes clogging from rust deposits. Chemical analysis of cooling water and scraped precipitates, as well laboratory screening of the deposits for bacteria, revealed that activity of iron-oxidizing bacteria present in cooling water could lead to heat exchanger blockage.

  9. Comparison of methods for the removal of organic carbon and extraction of chromium, iron and manganese from an estuarine sediment standard and sediment from the Calcasieu River estuary, Louisiana, U.S.A.

    USGS Publications Warehouse

    Simon, N.S.; Hatcher, S.A.; Demas, C.

    1992-01-01

    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. ?? 1992.

  10. Soil organic carbon across scales.

    PubMed

    O'Rourke, Sharon M; Angers, Denis A; Holden, Nicholas M; McBratney, Alex B

    2015-10-01

    Mechanistic understanding of scale effects is important for interpreting the processes that control the global carbon cycle. Greater attention should be given to scale in soil organic carbon (SOC) science so that we can devise better policy to protect/enhance existing SOC stocks and ensure sustainable use of soils. Global issues such as climate change require consideration of SOC stock changes at the global and biosphere scale, but human interaction occurs at the landscape scale, with consequences at the pedon, aggregate and particle scales. This review evaluates our understanding of SOC across all these scales in the context of the processes involved in SOC cycling at each scale and with emphasis on stabilizing SOC. Current synergy between science and policy is explored at each scale to determine how well each is represented in the management of SOC. An outline of how SOC might be integrated into a framework of soil security is examined. We conclude that SOC processes at the biosphere to biome scales are not well understood. Instead, SOC has come to be viewed as a large-scale pool subjects to carbon flux. Better understanding exists for SOC processes operating at the scales of the pedon, aggregate and particle. At the landscape scale, the influence of large- and small-scale processes has the greatest interaction and is exposed to the greatest modification through agricultural management. Policy implemented at regional or national scale tends to focus at the landscape scale without due consideration of the larger scale factors controlling SOC or the impacts of policy for SOC at the smaller SOC scales. What is required is a framework that can be integrated across a continuum of scales to optimize SOC management. PMID:25918852

  11. Iron-Doped Carbon Aerogels: Novel Porous Substrates for Direct Growth of Carbon Nanotubes

    DOE R&D Accomplishments Database

    Steiner, S. A.; Baumann, T. F.; Kong, J.; Satcher, J. H.; Dresselhaus, M. S.

    2007-02-20

    We present the synthesis and characterization of Fe-doped carbon aerogels (CAs) and demonstrate the ability to grow carbon nanotubes directly on monoliths of these materials to afford novel carbon aerogel-carbon nanotube composites. Preparation of the Fe-doped CAs begins with the sol-gel polymerization of the potassium salt of 2,4-dihydroxybenzoic acid with formaldehyde, affording K{sup +}-doped gels that can then be converted to Fe{sup 2+}- or Fe{sup 3+}-doped gels through an ion exchange process, dried with supercritical CO{sub 2} and subsequently carbonized under an inert atmosphere. Analysis of the Fe-doped CAs by TEM, XRD and XPS revealed that the doped iron species are reduced during carbonization to form metallic iron and iron carbide nanoparticles. The sizes and chemical composition of the reduced Fe species were related to pyrolysis temperature as well as the type of iron salt used in the ion exchange process. Raman spectroscopy and XRD analysis further reveal that, despite the presence of the Fe species, the CA framework is not significantly graphitized during pyrolysis. The Fe-doped CAs were subsequently placed in a thermal CVD reactor and exposed to a mixture of CH{sub 4} (1000 sccm), H{sub 2} (500 sccm), and C{sub 2}H{sub 4} (20 sccm) at temperatures ranging from 600 to 800 C for 10 minutes, resulting in direct growth of carbon nanotubes on the aerogel monoliths. Carbon nanotubes grown by this method appear to be multiwalled ({approx}25 nm in diameter and up to 4 mm long) and grow through a tip-growth mechanism that pushes catalytic iron particles out of the aerogel framework. The highest yield of CNTs were grown on Fe-doped CAs pyrolyzed at 800 C treated at CVD temperatures of 700 C.

  12. Iron-Doped Carbon Aerogels: Novel Porous Substrates for Direct Growth of Carbon Nanotubes

    SciTech Connect

    Steiner, S A; Baumann, T F; Kong, J; Satcher, J H; Dresselhaus, M S

    2007-02-15

    We present the synthesis and characterization of Fe-doped carbon aerogels (CAs) and demonstrate the ability to grow carbon nanotubes directly on monoliths of these materials to afford novel carbon aerogel-carbon nanotube composites. Preparation of the Fe-doped CAs begins with the sol-gel polymerization of the potassium salt of 2,4-dihydroxybenzoic acid with formaldehyde, affording K{sup +}-doped gels that can then be converted to Fe{sup 2+}- or Fe{sup 3+}-doped gels through an ion exchange process, dried with supercritical CO{sub 2} and subsequently carbonized under an inert atmosphere. Analysis of the Fe-doped CAs by TEM, XRD and XPS revealed that the doped iron species are reduced during carbonization to form metallic iron and iron carbide nanoparticles. The sizes and chemical composition of the reduced Fe species were related to pyrolysis temperature as well as the type of iron salt used in the ion exchange process. Raman spectroscopy and XRD analysis further reveal that, despite the presence of the Fe species, the CA framework is not significantly graphitized during pyrolysis. The Fe-doped CAs were subsequently placed in a thermal CVD reactor and exposed to a mixture of CH{sub 4} (1000 sccm), H{sub 2} (500 sccm), and C{sub 2}H{sub 4} (20 sccm) at temperatures ranging from 600 to 800 C for 10 minutes, resulting in direct growth of carbon nanotubes on the aerogel monoliths. Carbon nanotubes grown by this method appear to be multiwalled ({approx}25 nm in diameter and up to 4 mm long) and grow through a tip-growth mechanism that pushes catalytic iron particles out of the aerogel framework. The highest yield of CNTs were grown on Fe-doped CAs pyrolyzed at 800 C treated at CVD temperatures of 700 C.

  13. Iron-doped carbon aerogels: novel porous substrates for direct growth of carbon nanotubes.

    PubMed

    Steiner, Stephen A; Baumann, Theodore F; Kong, Jing; Satcher, Joe H; Dresselhaus, Mildred S

    2007-04-24

    We present the synthesis and characterization of Fe-doped carbon aerogels (CAs) and demonstrate the ability to grow carbon nanotubes directly on monoliths of these materials to afford novel carbon aerogel-carbon nanotube composites. Preparation of the Fe-doped CAs begins with the sol-gel polymerization of the potassium salt of 2,4-dihydroxybenzoic acid with formaldehyde, affording K+-doped gels that can then be converted to Fe2+- or Fe3+-doped gels through an ion exchange process, dried with supercritical CO2, and subsequently carbonized under an inert atmosphere. Analysis of the Fe-doped CAs by TEM, XRD, and XPS revealed that the doped iron species are reduced during carbonization to form metallic iron and iron carbide nanoparticles. The sizes and chemical composition of the reduced Fe species were related to pyrolysis temperature as well as the type of iron salt used in the ion exchange process. Raman spectroscopy and XRD analysis further reveal that, despite the presence of the Fe species, the CA framework is not significantly graphitized during pyrolysis. The Fe-doped CAs were subsequently placed in a thermal CVD reactor and exposed to a mixture of CH4 (1000 sccm), H2 (500 sccm), and C2H4 (20 sccm) at temperatures ranging from 600 to 800 degrees C for 10 min, resulting in direct growth of carbon nanotubes on the aerogel monoliths. Carbon nanotubes grown by this method appear to be multiwalled (approximately 25 nm in diameter and up to 4 microm long) and grow through a tip-growth mechanism that pushes catalytic iron particles out of the aerogel framework. The highest yield of CNTs was grown on Fe-doped CAs pyrolyzed at 800 degrees C treated at CVD temperatures of 700 degrees C. PMID:17381146

  14. Pulsed Plasma Synthesis of Iron and Nickel Nanoparticles Coated by Carbon for Medical Applications

    NASA Astrophysics Data System (ADS)

    Abdullaeva, Zhypargul; Omurzak, Emil; Iwamoto, Chihiro; Ihara, Hirotaka; Subban Ganapathy, Hullathy; Sulaimankulova, Saadat; Koinuma, Michio; Mashimo, Tsutomu

    2013-01-01

    Fe and Ni magnetic nanoparticles coated by carbon were synthesized between the Fe-Fe and Ni-Ni metal electrodes, submerged in ethanol using pulsed plasma in a liquid method. Iron coated carbon (Fe@C) nanoparticles have an average size of 32 nm, and Ni@C nanoparticles are 40 nm. Obtained samples exhibit a well-defined crystalline structure of the inner Fe and Ni cores, encapsulated in the graphitic carbon coatings. Cytotoxicity studies performed on the MCF-7 (breast cancer) cell line showed small toxicity about 88-74% at 50 µg/mL of Fe@C and Ni@C nanoparticles, which can be significant criteria for use them in medical cancer treatment. In addition, appropriate sizes, good magnetic properties and well-organized graphitic carbon coatings are highlight merits of Fe@C and Ni@C nanoparticles synthesized by pulsed plasma.

  15. Photochemical Flocculation of Terrestrial Dissolved Organic Matter (tDOM) and Iron: Mechanisms and Geochemical Implications

    NASA Astrophysics Data System (ADS)

    Mopper, K.; Helms, J. R.; Mao, J.; Abdulla, H. A.; Schmidt-Rohr, K.

    2013-12-01

    Photoflocculation of DOM has received relatively little attention. No previous studies have examined the chemical composition of the flocs nor investigated the coagulation mechanisms. We observed that, after 30 days of simulated solar UV irradiation of 0.1-um filtered Great Dismal Swamp (Virginia) water, 7.1% of the DOC was converted to POC while 75% was remineralized. Approximately 87% of the iron was removed from the dissolved phase after 30 days, but iron did not flocculate until a major fraction of DOM was removed by photochemical degradation and flocculation (>10 days); thus, during the initial 10 days, there were sufficient organic ligands present and/or the pH was low enough to keep iron in solution. Although photoflocculation of iron did eventually occur, it is not clear if iron is required for the initial flocculation of DOM. Using NMR and FT-IR techniques, we found that photochemically flocculated POM was enriched in aliphatics and amide functionality relative to the residual non-flocculated DOM, while carbohydrate-like material was neither photochemical degraded nor flocculated. Based on this spectroscopic evidence, we propose several mechanisms for the formation of the flocs during irradiation. We also speculate that abiotic photochemical flocculation may remove a significant fraction of tDOM and iron from the upper water column between headwaters and the ocean, including estuaries. Fig. 1. Concentrations of dissolved (gray), particulate (black), and adsorbed (white) material as a function of irradiation time: (a) organic carbon, (b) absorption at 300 nm, (c) total iron by atomic absorption, and (d) total nitrogen. Error bars represent the combined standard deviations of the 'total,' 'dissolved,' and 'adsorbed' terms from which the 'particulate' term was calculated. Total nitrogen was not determined for the 'adsorbed' material

  16. Surface Reactivity of Core Shell Iron-Iron Oxide Nanoclusters towards Breakdown of Carbon Tetrachloride

    NASA Astrophysics Data System (ADS)

    Tarsem S., Maninder K.; Qiang, You; Kim, Hongseok; Amonette, James E.; Baer, Donald R.

    2012-02-01

    Zero-valent iron (ZVI) is one of the technologies for groundwater remediation to reduce contaminants by removal of mobile chlorinated hydrocarbons. Iron-Iron oxide (Fe/Fe3O4) nanoclusters (NCs) made in our laboratory using cluster deposition technique have enhanced reactivity towards targeted contaminants due to the presence of ZVI protected by a passivated oxide shell. Here, we investigate the effectiveness of the Fe/Fe3O4 NCs in reducing carbon tetrachloride (CT) under laboratory conditions. The reactivity of the NCs was investigated by conducting unbuffered aqueous batch experiments to reduce CT at room temperature. Initial results show that 80% of the degradation of CT resulted in the formation of dichloromethane (DCM) and chloroform (CF); the remainder likely followed a competing pathway to yield nonhazardous products such as CO. The production of undesirable hydrogenated products such as DCM and CF suggests that the dominant reaction pathway occurs through hydrogen (H) atom transfer via H atoms generated by corrosion of the iron. Comparative experiments with ZVI NCs prepared by other methods are underway and the results will be reported. Future work is to analyze and understand factors that control the reaction pathways between desirable and undesirable products.

  17. Electrochemistry of Simple Organometallic Models of Iron-Iron Hydrogenases in Organic Solvent and Water.

    PubMed

    Gloaguen, Frederic

    2016-01-19

    Synthetic models of the active site of iron-iron hydrogenases are currently the subjects of numerous studies aimed at developing H2-production catalysts based on cheap and abundant materials. In this context, the present report offers an electrochemist's view of the catalysis of proton reduction by simple binuclear iron(I) thiolate complexes. Although these complexes probably do not follow a biocatalytic pathway, we analyze and discuss the interplay between the reduction potential and basicity and how these antagonist properties impact the mechanisms of proton-coupled electron transfer to the metal centers. This question is central to any consideration of the activity at the molecular level of hydrogenases and related enzymes. In a second part, special attention is paid to iron thiolate complexes holding rigid and unsaturated bridging ligands. The complexes that enjoy mild reduction potentials and stabilized reduced forms are promising iron-based catalysts for the photodriven evolution of H2 in organic solvents and, more importantly, in water. PMID:26641526

  18. Soil Organic Carbon Input from Urban Turfgrasses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Turfgrass is a major vegetation type in the urban and suburban environment. Management practices such as species selection, irrigation, and mowing may affect carbon (C) input and storage in these systems. Research was conducted to determine the rate of soil organic carbon (SOC) changes, soil carbon ...

  19. Soil Organic Carbon Input from Urban Turfgrasses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Turfgrass is a major vegetation type in the urban and suburban environment. Management practices such as species selection, irrigation, and mowing may affect carbon input and storage in these systems. Research was conducted to determine the rate of soil organic carbon (SOC) changes, soil carbon sequ...

  20. Voronoi analysis of the short–range atomic structure in iron and iron–carbon melts

    SciTech Connect

    Sobolev, Andrey; Mirzoev, Alexander

    2015-08-17

    In this work, we simulated the atomic structure of liquid iron and iron–carbon alloys by means of ab initio molecular dynamics. Voronoi analysis was used to highlight changes in the close environments of Fe atoms as carbon concentration in the melt increases. We have found, that even high concentrations of carbon do not affect short–range atomic order of iron atoms — it remains effectively the same as in pure iron melts.

  1. Iron nanoparticles embedded in carbon films: structural and optical properties

    NASA Astrophysics Data System (ADS)

    Mashayekhi, Fatemeh; Shafiekhani, Azizollah; Sebt, Seyed Ali

    2016-06-01

    In the present work amorphous hydrogenated carbon films with sputtered iron nanoparticles (Fe NPs @ a-C:H) were deposited by co-deposition of RF-sputtering and RF-plasma enhanced chemical vapor deposition methods using acetylene gas and iron target on quartz and silicon substrates. Samples were prepared in different initial pressures and during constant deposition time. The crystalline structure of Fe NPs @ a-C:H was studied using X-ray diffraction and selected area electron diffraction patterns. The X-ray photoelectron spectroscopy analysis presents that increasing the initial pressure decreases the atomic ratio of Fe/C and the sp3-hybridized carbon content in prepared samples. The transmission electron microscope image shows the encapsulated Fe NPs in carbon films. The optical properties and localized surface plasmon resonance (LSPR) of samples were studied using UV-visible spectrophotometry, which is shown that increasing of Fe content decreases the intensity of LSPR peak and increases the optical band gap.

  2. Iron Catalyst Chemistry in High Pressure Carbon Monoxide Nanotube Reactor

    NASA Technical Reports Server (NTRS)

    Scott, Carl D.; Povitsky, Alexander; Dateo, Christopher; Gokcen, Tahir; Smalley, Richard E.

    2001-01-01

    The high-pressure carbon monoxide (HiPco) technique for producing single wall carbon nanotubes (SWNT) is analyzed using a chemical reaction model coupled with properties calculated along streamlines. Streamline properties for mixing jets are calculated by the FLUENT code using the k-e turbulent model for pure carbon monixide. The HiPco process introduces cold iron pentacarbonyl diluted in CO, or alternatively nitrogen, at high pressure, ca. 30 atmospheres into a conical mixing zone. Hot CO is also introduced via three jets at angles with respect to the axis of the reactor. Hot CO decomposes the Fe(CO)5 to release atomic Fe. Cluster reaction rates are from Krestinin, et aI., based on shock tube measurements. Another model is from classical cluster theory given by Girshick's team. The calculations are performed on streamlines that assume that a cold mixture of Fe(CO)5 in CO is introduced along the reactor axis. Then iron forms clusters that catalyze the formation of SWNTs from the Boudouard reaction on Fe-containing clusters by reaction with CO. To simulate the chemical process along streamlines that were calculated by the fluid dynamics code FLUENT, a time history of temperature and dilution are determined along streamlines. Alternative catalyst injection schemes are also evaluated.

  3. Microstructure and properties of pure iron/copper composite cladding layers on carbon steel

    NASA Astrophysics Data System (ADS)

    Wan, Long; Huang, Yong-xian; Lü, Shi-xiong; Huang, Ti-fang; Lü, Zong-liang

    2016-08-01

    In the present study, pure iron/copper composite metal cladding was deposited onto carbon steel by tungsten inert gas welding. The study focused on interfacial morphological, microstructural, and mechanical analyses of the composite cladding layers. Iron liquid-solid-phase zones were formed at copper/steel and iron interfaces because of the melting of the steel substrate and iron. Iron concentrated in the copper cladding layer was observed to exhibit belt, globule, and dendrite morphologies. The appearance of iron-rich globules indicated the occurrence of liquid phase separation (LPS) prior to solidification, and iron-rich dendrites crystallized without the occurrence of LPS. The maximum microhardness of the iron/steel interface was lower than that of the copper/steel interface because of the diffusion of elemental carbon. All samples fractured in the cladding layers. Because of a relatively lower strength of the copper layer, a short plateau region appeared when shear movement was from copper to iron.

  4. Resistive switching in iron-oxide-filled carbon nanotubes.

    PubMed

    Cava, Carlos E; Persson, Clas; Zarbin, Aldo J G; Roman, Lucimara S

    2014-01-01

    Iron-oxide-filled carbon nanotubes exhibit an intriguing charge bipolarization behavior which allows the material to be applied in resistive memory devices. Raman analysis conducted with an electric field applied in situ shows the Kohn anomalies and a strong modification of the electronic properties related to the applied voltage intensity. In addition, the I(D)/I(G) ratio indicated the reversibility of this process. The electrical characterization indicated an electronic transport governed by two main kinds of charge hopping, one between the filling and the nanotube and the other between the nanotube shells. PMID:24201829

  5. Development of carbon composite iron ore micropellets by using the microfines of iron ore and carbon-bearing materials in iron making

    NASA Astrophysics Data System (ADS)

    Pal, Jagannath; Ghorai, Satadal; Das, Avimanyu

    2015-02-01

    Iron ore microfines and concentrate have very limited uses in sintering processes. They are used in pelletization; however, this process is cost intensive. Furthermore, the microfines of non-coking coal and other carbon-bearing materials, e.g., blast-furnace flue dust (BFD) and coke fines, are not used extensively in the metallurgical industry because of operational difficulties and handling problems. In the present work, to utilize these microfines, coal composite iron oxide micropellets (2-6 mm in size) were produced through an innovative technique in which lime and molasses were used as binding materials in the micropellets. The micropellets were subsequently treated with CO2 or the industrial waste gas to induce the chemical bond formation. The results show that, at a very high carbon level of 22wt% (38wt% coal), the cold crushing strength and abrasion index of the micropellets are 2.5-3 kg/cm2 and 5wt%-9wt%, respectively; these values indicate that the pellets are suitable for cold handling. The developed micropellets have strong potential as a heat source in smelting reduction in iron making and sintering to reduce coke breeze. The micropellets produced with BFD and coke fines (8wt%-12wt%) were used in iron ore sintering and were observed to reduce the coke breeze consumption by 3%-4%. The quality of the produced sinter was at par with that of the conventional blast-furnace sinter.

  6. Nitrogen controlled iron catalyst phase during carbon nanotube growth

    SciTech Connect

    Bayer, Bernhard C.; Baehtz, Carsten; Kidambi, Piran R.; Weatherup, Robert S.; Caneva, Sabina; Cabrero-Vilatela, Andrea; Hofmann, Stephan; Mangler, Clemens; Kotakoski, Jani; Meyer, Jannik C.; Goddard, Caroline J. L.

    2014-10-06

    Close control over the active catalyst phase and hence carbon nanotube structure remains challenging in catalytic chemical vapor deposition since multiple competing active catalyst phases typically co-exist under realistic synthesis conditions. Here, using in-situ X-ray diffractometry, we show that the phase of supported iron catalyst particles can be reliably controlled via the addition of NH{sub 3} during nanotube synthesis. Unlike polydisperse catalyst phase mixtures during H{sub 2} diluted nanotube growth, nitrogen addition controllably leads to phase-pure γ-Fe during pre-treatment and to phase-pure Fe{sub 3}C during growth. We rationalize these findings in the context of ternary Fe-C-N phase diagram calculations and, thus, highlight the use of pre-treatment- and add-gases as a key parameter towards controlled carbon nanotube growth.

  7. Mobility of organic carbon from incineration residues

    SciTech Connect

    Ecke, Holger Svensson, Malin

    2008-07-01

    Dissolved organic carbon (DOC) may affect the transport of pollutants from incineration residues when landfilled or used in geotechnical construction. The leaching of dissolved organic carbon (DOC) from municipal solid waste incineration (MSWI) bottom ash and air pollution control residue (APC) from the incineration of waste wood was investigated. Factors affecting the mobility of DOC were studied in a reduced 2{sup 6-1} experimental design. Controlled factors were treatment with ultrasonic radiation, full carbonation (addition of CO{sub 2} until the pH was stable for 2.5 h), liquid-to-solid (L/S) ratio, pH, leaching temperature and time. Full carbonation, pH and the L/S ratio were the main factors controlling the mobility of DOC in the bottom ash. Approximately 60 weight-% of the total organic carbon (TOC) in the bottom ash was available for leaching in aqueous solutions. The L/S ratio and pH mainly controlled the mobilization of DOC from the APC residue. About 93 weight-% of TOC in the APC residue was, however, not mobilized at all, which might be due to a high content of elemental carbon. Using the European standard EN 13 137 for determination of total organic carbon (TOC) in MSWI residues is inappropriate. The results might be biased due to elemental carbon. It is recommended to develop a TOC method distinguishing between organic and elemental carbon.

  8. Missing Iron-Oxidizing Acidophiles Highly Sensitive to Organic Compounds

    PubMed Central

    Ueoka, Nagayoshi; Kouzuma, Atsushi; Watanabe, Kazuya

    2016-01-01

    The genus Acidithiobacillus includes iron-oxidizing lithoautotrophs that thrive in acidic mine environments. Acidithiobacillus ferrooxidans is a representative species and has been extensively studied for its application to the bioleaching of precious metals. In our attempts to cultivate the type strain of A. ferrooxidans (ATCC 23270T), repeated transfers to fresh inorganic media resulted in the emergence of cultures with improved growth traits. Strains were isolated from the resultant culture by forming colonies on inorganic silica-gel plates. A representative isolate (strain NU-1) was unable to form colonies on agarose plates and was more sensitive to organics, such as glucose, than the type strain of A. ferrooxidans. Strain NU-1 exhibited superior growth traits in inorganic iron media to those of other iron-oxidizing acidithiobacilli, suggesting its potential for industrial applications. A draft genome of NU-1 uncovered unique features in catabolic enzymes, indicating that this strain is not a mutant of the A. ferrooxidans type strain. Our results indicate that the use of inorganic silica-gel plates facilitates the isolation of as-yet-unexamined iron-oxidizing acidithiobacilli from environmental samples and enrichment cultures. PMID:27356527

  9. CARBON MONOXIDE REVERSIBLY DISRUPTS IRON HOMEOSTATIS AND RESPIRATORY EPITHELIAL CELLS FUNCTION

    EPA Science Inventory

    Iron dissociation from heme is a major factor in iron metabolism and cellular concentrations of the metal correlate inversely with the expression of heme oxygenase (HO). We tested the hypothesis that 1) exposure to a product of HO, carbon monoxide (CO), disturbs iron homeostas...

  10. Mossbauer effect in the ion-implanted iron-carbon alloys

    NASA Technical Reports Server (NTRS)

    Han, K. S.

    1976-01-01

    The concentration dependence of Mossbauer effect in four carbon ion-implanted iron absorbers, which contain carbon as the solute atoms, has been investigated over the range of concentration 0.05 through 1 atomic percent. The specimens were prepared by implanting carbon atoms on each reference iron foil with four different bombarding energies of 250 keV, 160 keV, 140 keV and 80 keV, respectively. Thus, the specimen contains a uniform dosage of carbon atoms which penetrated up to 3,000 A depth of the reference iron. In the measurement of Mossbauer spectra, the backscattering conversion electron counting geometry was used. Typical results of Mossbauer parameters of iron-carbon alloys show that the isomer shift, quadrupole shift, the effective hyperfine splitting of Fe-57, and the intensity ratio exhibit a large variation with the increase of carbon concentration in the environment of iron atoms.

  11. Resistive switching in iron-oxide-filled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Cava, Carlos E.; Persson, Clas; Zarbin, Aldo J. G.; Roman, Lucimara S.

    2013-12-01

    Iron-oxide-filled carbon nanotubes exhibit an intriguing charge bipolarization behavior which allows the material to be applied in resistive memory devices. Raman analysis conducted with an electric field applied in situ shows the Kohn anomalies and a strong modification of the electronic properties related to the applied voltage intensity. In addition, the ID/IG ratio indicated the reversibility of this process. The electrical characterization indicated an electronic transport governed by two main kinds of charge hopping, one between the filling and the nanotube and the other between the nanotube shells.Iron-oxide-filled carbon nanotubes exhibit an intriguing charge bipolarization behavior which allows the material to be applied in resistive memory devices. Raman analysis conducted with an electric field applied in situ shows the Kohn anomalies and a strong modification of the electronic properties related to the applied voltage intensity. In addition, the ID/IG ratio indicated the reversibility of this process. The electrical characterization indicated an electronic transport governed by two main kinds of charge hopping, one between the filling and the nanotube and the other between the nanotube shells. Electronic supplementary information (ESI) available: See DOI: 10.1039/c3nr04320g

  12. Degradation of carbon tetrachloride in the presence of zero-valent iron.

    SciTech Connect

    Alvarado, J. S.; Rose, C.; LaFreniere, L.; Environmental Science Division

    2010-01-01

    Efforts to achieve the decomposition of carbon tetrachloride through anaerobic and aerobic bioremediation and chemical transformation have met with limited success because of the conditions required and the formation of hazardous intermediates. Recently, particles of zero-valent iron (ZVI) have been used with limited success for in situ remediation of carbon tetrachloride. We studied a modified microparticulate product that combines controlled-release carbon with ZVI for stimulation of in situ chemical reduction of persistent organic compounds in groundwater. With this product, a number of physical, chemical, and microbiological processes were combined to create very strongly reducing conditions that stimulate rapid, complete dechlorination of organic solvents. In principle, the organic component of ZVI microparticles is nutrient rich and hydrophilic and has high surface area capable of supporting the growth of bacteria in the groundwater environment. In our experiments, we found that as the bacteria grew, oxygen was consumed, and the redox potential decreased to values reaching -600 mV. The small modified ZVI particles provide substantial reactive surface area that, in these conditions, directly stimulates chemical dechlorination and cleanup of the contaminated area without accumulation of undesirable breakdown products. The objective of this work was to evaluate the effectiveness of ZVI microparticles in reducing carbon tetrachloride under laboratory and field conditions. Changes in concentrations and in chemical and physical parameters were monitored to determine the role of the organic products in the reductive dechlorination reaction. Laboratory and field studies are presented.

  13. Closed system Fischer-Tropsch synthesis over meteoritic iron, iron ore and nickel-iron alloy. [deuterium-carbon monoxide reaction catalysis

    NASA Technical Reports Server (NTRS)

    Nooner, D. W.; Gibert, J. M.; Gelpi, E.; Oro, J.

    1976-01-01

    Experiments were performed in which meteoritic iron, iron ore and nickel-iron alloy were used to catalyze (in Fischer-Tropsch synthesis) the reaction of deuterium and carbon monoxide in a closed vessel. Normal alkanes and alkenes and their monomethyl substituted isomers and aromatic hydrocarbons were synthesized. Iron oxide and oxidized-reduced Canyon Diablo used as Fischer-Tropsch catalysts were found to produce aromatic hydrocarbons in distributions having many of the features of those observed in carbonaceous chondrites, but only at temperatures and reaction times well above 300 C and 6-8 h.

  14. Carbon-depleted outer core revealed by sound velocity measurements of liquid iron-carbon alloy.

    PubMed

    Nakajima, Yoichi; Imada, Saori; Hirose, Kei; Komabayashi, Tetsuya; Ozawa, Haruka; Tateno, Shigehiko; Tsutsui, Satoshi; Kuwayama, Yasuhiro; Baron, Alfred Q R

    2015-01-01

    The relative abundance of light elements in the Earth's core has long been controversial. Recently, the presence of carbon in the core has been emphasized, because the density and sound velocities of the inner core may be consistent with solid Fe7C3. Here we report the longitudinal wave velocity of liquid Fe84C16 up to 70 GPa based on inelastic X-ray scattering measurements. We find the velocity to be substantially slower than that of solid iron and Fe3C and to be faster than that of liquid iron. The thermodynamic equation of state for liquid Fe84C16 is also obtained from the velocity data combined with previous density measurements at 1 bar. The longitudinal velocity of the outer core, about 4% faster than that of liquid iron, is consistent with the presence of 4-5 at.% carbon. However, that amount of carbon is too small to account for the outer core density deficit, suggesting that carbon cannot be a predominant light element in the core. PMID:26596912

  15. A carbon budget for a naturally iron fertilized bloom in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Morris, Paul J.; Sanders, Richard

    2011-09-01

    Subantarctic islands in the high-nutrient, low-chlorophyll (HNLC) Southern Ocean are natural sources of iron and stimulate blooms in their proximity, such as the one observed close to the Crozet Islands (52°E, 46°S). During 2004/2005, particulate organic carbon (POC) export was measured using the 234Th technique in the Crozet bloom and compared with an HNLC control region. Initial results showed that iron release had no effect on daily POC export rates, thus any iron-driven enhancement in POC export was due to a longer export phase in the bloom region when compared to the control region. The duration of the export event was empirically estimated by closing the silicon budget, thus allowing seasonal POC export to be calculated by applying the export duration to the daily rates of POC export. This yields a seasonal estimate of POC export that is 3.6 times larger (range 1.9-7.1) in the iron-fertilized region than in the HNLC control region. These estimates of POC export were then compared to independent estimates of organic matter storage in the upper ocean, which are significant in both the HNLC and control regions. Overall, integrated POC export was significantly (approximately 50%) lower than estimated seasonal new production, the fraction of production that is supported by inputs of new nutrients. Finally, the sequestration efficiency, the numerical relationship between the supply of the limiting nutrient, iron, and the key ecosystem function of POC export at 100 m, is estimated to be 16,790 mol:mol.

  16. Luminescence turn-on/off sensing of biological iron by carbon dots in transferrin.

    PubMed

    Bhattacharya, Arpan; Chatterjee, Surajit; Khorwal, Vijaykant; Mukherjee, Tushar Kanti

    2016-02-21

    Iron is a key nutrient as well as a potential toxin for almost all living organisms. In mammalian cells, serum transferrin (Tf) is responsible for iron transport and its iron overload/deficiency causes various diseases. Therefore, closely regulated iron homeostasis is extremely essential for cellular metabolism. In the present article we report the pH-dependent luminescence turn-on/off sensing of bound Fe(3+) ions of serum Tf by carbon dots (CDs) with the help of photoluminescence (PL) spectroscopy, FTIR spectroscopy, dynamic light scattering (DLS), circular dichroism (CD) and PL imaging techniques. At physiological pH (7.4), the intrinsic luminescence of CDs gets quenched in the presence of Tf as a consequence of ground-state association, which is driven by favorable electrostatic interactions between negatively charged CDs (-25.45 ± 1.23 mV) and positively charged Fe(3+) ions of Tf. The estimated detection limit of Tf by CDs at physiological pH is found to be 1.82 μM (signal-to-noise ratio of 3), which is much lower than the in vivo plasma concentration of Tf (∼25-35 μM). Various thermodynamic parameters have been evaluated by using the van't Hoff equation. Importantly, the secondary structure of Tf remains unaltered upon association with CDs. However, at pH 3.5, no such luminescence quenching of CDs has been observed in the presence of Tf due to the lack of ground-state interactions between positively charged (+17.63 ± 0.84 mV) CDs and Tf. Furthermore, the results from UV-Vis and far-UV CD measurements revealed a significant conformational change of Tf at pH 3.5 relative to pH 7.4, which triggers the subsequent release of bound iron from Tf. PL microscopy of individual CD revealed significant luminescence quenching at the single particle level, which further supports the non-emissive ground-state complexation at pH 7.4. Our present results show that these chemically synthesized water-dispersed CDs have the ability to selectively sense the bound iron from

  17. Iron-catalysed cross-coupling of organolithium compounds with organic halides

    PubMed Central

    Jia, Zhenhua; Liu, Qiang; Peng, Xiao-Shui; Wong, Henry N. C.

    2016-01-01

    In past decades, catalytic cross-coupling reactions between organic halides and organometallic reagents to construct carbon–carbon bond have achieved a tremendous progress. However, organolithium reagents have rarely been used in cross-coupling reactions, due mainly to their high reactivity. Another limitation of this transformation using organolithium reagents is how to control reactivity with excellent selectivity. Although palladium catalysis has been applied in this field recently, the development of an approach to replace catalytic systems of noble metals with nonprecious metals is currently in high demand. Herein, we report an efficient synthetic protocol involving iron-catalysed cross-coupling reactions employing organolithium compounds as key coupling partners to unite aryl, alkyl and benzyl fragments and also disclose an efficient iron-catalysed release-capture ethylene coupling with isopropyllithium. PMID:26847602

  18. Carbon nanotube electrodes in organic transistors.

    PubMed

    Valitova, Irina; Amato, Michele; Mahvash, Farzaneh; Cantele, Giovanni; Maffucci, Antonio; Santato, Clara; Martel, Richard; Cicoira, Fabio

    2013-06-01

    The scope of this Minireview is to provide an overview of the recent progress on carbon nanotube electrodes applied to organic thin film transistors. After an introduction on the general aspects of the charge injection processes at various electrode-semiconductor interfaces, we discuss the great potential of carbon nanotube electrodes for organic thin film transistors and the recent achievements in the field. PMID:23639944

  19. Magnetorheological characteristics of carbon nanotube wrapped carbonyl iron particles

    NASA Astrophysics Data System (ADS)

    Fang, Fei Fei; Choi, Byung Il; Choi, Hyoung Jin

    2009-02-01

    Carbonyl iron (CI) based magnetorheological (MR) fluid exhibits serious dispersion defect in general due to large density mismatch between CI particles and continuous medium, which restricts further MR application. Thus, various strategies were explored either to reduce the density or to prevent CI particle aggregation. Among them, polymer coating technology becomes more prevalent due to favorable morphology obtained and effective decrease in density by introducing polymeric shell; nevertheless, coating polymer on the surface of CI particles is always influenced by the selected grafting agent, mole ratio of reactant or the temperature of reaction. In this work, considering self-assembling trend of carbon nanotube (CNT) which exhibits similar density with polymer but better magnetic property due to the iron catalyst, we constructed a dense nest composed of CNT on the surface of CI particles by using 4-aminobenzoic acid (PABA) as a grafting agent under sonication. Thickness and morphology of the CNT nest were found to be related with sonication duration via SEM/TEM images. MR performances (yield stress behavior, shear viscosity) of the CI/CNT particles based MR fluid were investigated via controlled shear rate and controlled shear stress methods. Finally, sedimentation observation was checked to be improved.

  20. Effect of natural iron fertilization on carbon sequestration in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Blain, Stéphane; Quéguiner, Bernard; Armand, Leanne; Belviso, Sauveur; Bombled, Bruno; Bopp, Laurent; Bowie, Andrew; Brunet, Christian; Brussaard, Corina; Carlotti, François; Christaki, Urania; Corbière, Antoine; Durand, Isabelle; Ebersbach, Frederike; Fuda, Jean-Luc; Garcia, Nicole; Gerringa, Loes; Griffiths, Brian; Guigue, Catherine; Guillerm, Christophe; Jacquet, Stéphanie; Jeandel, Catherine; Laan, Patrick; Lefèvre, Dominique; Lo Monaco, Claire; Malits, Andrea; Mosseri, Julie; Obernosterer, Ingrid; Park, Young-Hyang; Picheral, Marc; Pondaven, Philippe; Remenyi, Thomas; Sandroni, Valérie; Sarthou, Géraldine; Savoye, Nicolas; Scouarnec, Lionel; Souhaut, Marc; Thuiller, Doris; Timmermans, Klaas; Trull, Thomas; Uitz, Julia; van Beek, Pieter; Veldhuis, Marcel; Vincent, Dorothée; Viollier, Eric; Vong, Lilita; Wagener, Thibaut

    2007-04-01

    The availability of iron limits primary productivity and the associated uptake of carbon over large areas of the ocean. Iron thus plays an important role in the carbon cycle, and changes in its supply to the surface ocean may have had a significant effect on atmospheric carbon dioxide concentrations over glacial-interglacial cycles. To date, the role of iron in carbon cycling has largely been assessed using short-term iron-addition experiments. It is difficult, however, to reliably assess the magnitude of carbon export to the ocean interior using such methods, and the short observational periods preclude extrapolation of the results to longer timescales. Here we report observations of a phytoplankton bloom induced by natural iron fertilization-an approach that offers the opportunity to overcome some of the limitations of short-term experiments. We found that a large phytoplankton bloom over the Kerguelen plateau in the Southern Ocean was sustained by the supply of iron and major nutrients to surface waters from iron-rich deep water below. The efficiency of fertilization, defined as the ratio of the carbon export to the amount of iron supplied, was at least ten times higher than previous estimates from short-term blooms induced by iron-addition experiments. This result sheds new light on the effect of long-term fertilization by iron and macronutrients on carbon sequestration, suggesting that changes in iron supply from below-as invoked in some palaeoclimatic and future climate change scenarios-may have a more significant effect on atmospheric carbon dioxide concentrations than previously thought.

  1. Effect of natural iron fertilization on carbon sequestration in the Southern Ocean.

    PubMed

    Blain, Stéphane; Quéguiner, Bernard; Armand, Leanne; Belviso, Sauveur; Bombled, Bruno; Bopp, Laurent; Bowie, Andrew; Brunet, Christian; Brussaard, Corina; Carlotti, François; Christaki, Urania; Corbière, Antoine; Durand, Isabelle; Ebersbach, Frederike; Fuda, Jean-Luc; Garcia, Nicole; Gerringa, Loes; Griffiths, Brian; Guigue, Catherine; Guillerm, Christophe; Jacquet, Stéphanie; Jeandel, Catherine; Laan, Patrick; Lefèvre, Dominique; Lo Monaco, Claire; Malits, Andrea; Mosseri, Julie; Obernosterer, Ingrid; Park, Young-Hyang; Picheral, Marc; Pondaven, Philippe; Remenyi, Thomas; Sandroni, Valérie; Sarthou, Géraldine; Savoye, Nicolas; Scouarnec, Lionel; Souhaut, Marc; Thuiller, Doris; Timmermans, Klaas; Trull, Thomas; Uitz, Julia; van Beek, Pieter; Veldhuis, Marcel; Vincent, Dorothée; Viollier, Eric; Vong, Lilita; Wagener, Thibaut

    2007-04-26

    The availability of iron limits primary productivity and the associated uptake of carbon over large areas of the ocean. Iron thus plays an important role in the carbon cycle, and changes in its supply to the surface ocean may have had a significant effect on atmospheric carbon dioxide concentrations over glacial-interglacial cycles. To date, the role of iron in carbon cycling has largely been assessed using short-term iron-addition experiments. It is difficult, however, to reliably assess the magnitude of carbon export to the ocean interior using such methods, and the short observational periods preclude extrapolation of the results to longer timescales. Here we report observations of a phytoplankton bloom induced by natural iron fertilization--an approach that offers the opportunity to overcome some of the limitations of short-term experiments. We found that a large phytoplankton bloom over the Kerguelen plateau in the Southern Ocean was sustained by the supply of iron and major nutrients to surface waters from iron-rich deep water below. The efficiency of fertilization, defined as the ratio of the carbon export to the amount of iron supplied, was at least ten times higher than previous estimates from short-term blooms induced by iron-addition experiments. This result sheds new light on the effect of long-term fertilization by iron and macronutrients on carbon sequestration, suggesting that changes in iron supply from below--as invoked in some palaeoclimatic and future climate change scenarios--may have a more significant effect on atmospheric carbon dioxide concentrations than previously thought. PMID:17460670

  2. Worldwide organic soil carbon and nitrogen data

    SciTech Connect

    Zinke, P.J.; Stangenberger, A.G.; Post, W.M.; Emanual, W.R.; Olson, J.S.

    1986-09-01

    The objective of the research presented in this package was to identify data that could be used to estimate the size of the soil organic carbon pool under relatively undisturbed soil conditions. A subset of the data can be used to estimate amounts of soil carbon storage at equilibrium with natural soil-forming factors. The magnitude of soil properties so defined is a resulting nonequilibrium values for carbon storage. Variation in these values is due to differences in local and geographic soil-forming factors. Therefore, information is included on location, soil nitrogen content, climate, and vegetation along with carbon density and variation.

  3. The role of iron and reactive oxygen in the degradation of dissolved organic matter draining permafrost soils (Invited)

    NASA Astrophysics Data System (ADS)

    Cory, R. M.; Page, S. E.; Kling, G. W.; Sander, M.; Harrold, K. H.; McNeill, K.

    2013-12-01

    As the permafrost boundary deepens from climate warming it will create conditions for redox reactions between soil-derived dissolved organic matter (DOM) and iron where those conditions did not previously exist. These new conditions will facilitate the transformation of DOM, and the overarching question is whether the pathway to CO2 released to the atmosphere or the export of DOM to coastal oceans will be favored. Our findings suggest that in either dark soils or sunlit surface waters, the presence of iron promotes the degradation of DOM to CO2. Evidence in support of iron-mediated oxidation of DOM to CO2 includes (1) strong positive correlations between iron and formation of hydroxyl radical (●OH), a highly reactive oxygen species implicated in DOM mineralization, (2) complete oxidation of DOM in the presence of high iron concentrations, and (3) loss of permafrost-derived DOM and iron from a thermokarst-impacted lake over time. For example, iron and DOM-rich soils or surface waters had the highest dark or photochemical ●OH formation respectively, both consistent with a dark or light Fenton source of ●OH and subsequent oxidation of DOM by ●OH. Photo-oxidation of DOM to CO2 was favored over partial photo-oxidation in surface waters characterized by high DOM and dissolved iron concentrations, consistent with photochemical reactions mediated by iron. Changes in DOM quality and quantity over time in a lake receiving permafrost carbon via a landslide (thermokarst slump) were also consistent with iron-mediated photodegradation of DOM. Given differences in DOM degradation across tundra ecosystems varying in iron, along with the abundance of water-logged soils supplying reduced iron to soil water or shallow streams, preliminary calculations at the landscape scale indicate that iron-mediated mineralization of DOM in soils and surface waters may be at least as important to carbon cycling as is bacterial respiration of DOM in the water column of streams and lakes

  4. Organic solvent regeneration of granular activated carbon

    NASA Astrophysics Data System (ADS)

    Cross, W. H.; Suidan, M. T.; Roller, M. A.; Kim, B. R.; Gould, J. P.

    1982-09-01

    The use of activated carbon for the treatment of industrial waste-streams was shown to be an effective treatment. The high costs associated with the replacement or thermal regeneration of the carbon have prohibited the economic feasibility of this process. The in situ solvent regeneration of activated carbon by means of organic solvent extraction was suggested as an economically alternative to thermal regeneration. The important aspects of the solvent regeneration process include: the physical and chemical characteristics of the adsorbent, the pore size distribution and energy of adsorption associated with the activated carbon; the degree of solubility of the adsorbate in the organic solvent; the miscibility of the organic solvent in water; and the temperature at which the generation is performed.

  5. Iron encapsulated in boron and nitrogen codoped carbon nanotubes as synergistic catalysts for Fenton-like reaction.

    PubMed

    Yao, Yunjin; Chen, Hao; Qin, Jiacheng; Wu, Guodong; Lian, Chao; Zhang, Jie; Wang, Shaobin

    2016-09-15

    Iron nanoparticles (NPs) encapsulated in B, N-codoped carbon nanotubes (Fe@C-BN) as heterogeneous Fenton-like catalysts were obtained by a simple and scalable pyrolysis method, and their performances were examined in the oxidative degradation of various organics in the presence of the different oxidants. The results showed that organic dyes can be effectively degraded by Fe@C-BN in the presence of peroxymonosulfate. Calcination temperature and mass of iron salt significantly affected the structures and performances of the catalysts. The effects of several reaction conditions, such as initial dye concentration, oxidant type (peroxymonosulfate, peroxydisulfate, and H2O2) and dosage, initial pH, inorganic anions, reaction temperature and dye types on oxidation as well as the stability of the composite were extensively evaluated in view of the practical applications. Through the investigation of reaction processes, HO(·) and SO4(·-) radicals were identified using quenching experiments. Owing to the synergistic effects between the iron NPs and B, N-doped carbon, Fe@C-BN catalysts intrinsically display an excellent catalytic activity for Fenton-like reaction. This study gives new insights into the design and preparation of iron NPs encapsulated in B, N-codoped carbon nanotubes as an effective strategy to enhance the overall catalytic activity. PMID:27267476

  6. Quantum oscillations and ferromagnetic hysteresis observed in iron filled multiwall carbon nanotubes.

    PubMed

    Barzola-Quiquia, J; Klingner, N; Krüger, J; Molle, A; Esquinazi, P; Leonhardt, A; Martínez, M T

    2012-01-13

    We report on the electrical transport properties of single multiwall carbon nanotubes with and without an iron filling as a function of temperature and magnetic field. For the iron filled nanotubes the magnetoresistance shows a magnetic behavior induced by iron, which can be explained by taking into account a contribution of s-d hybridization. In particular, ferromagnetic-like hysteresis loops were observed up to 50 K for the iron filled multiwall carbon nanotubes. The magnetoresistance shows quantum interference phenomena such as universal conductance fluctuations and weak localization effects. PMID:22155967

  7. Fe, C, and O isotope compositions of banded iron formation carbonates demonstrate a major role for dissimilatory iron reduction in ~2.5 Ga marine environments

    NASA Astrophysics Data System (ADS)

    Heimann, Adriana; Johnson, Clark M.; Beard, Brian L.; Valley, John W.; Roden, Eric E.; Spicuzza, Michael J.; Beukes, Nicolas J.

    2010-05-01

    Combined Fe, C, and O isotope measurements of ~ 2.5 Ga banded iron formation (BIF) carbonates from the Kuruman Iron Formation and underlying BIF and platform Ca-Mg carbonates of the Gamohaan Formation, South Africa, constrain the biologic and abiologic formation pathways in these extensive BIF deposits. Vertical intervals of up to 100 m were sampled in three cores that cover a lateral extent of ~ 250 km. BIF Fe carbonates have significant Fe isotope variability ( δ56Fe = + 1 to - 1‰) and relatively low δ13C (down to - 12‰) and δ18O values ( δ18O ~ + 21‰). In contrast, Gamohaan and stratigraphically-equivalent Campbellrand Ca-Mg carbonates have near-zero δ13C values and higher δ18O values. These findings argue against siderite precipitation from seawater as the origin of BIF Fe-rich carbonates. Instead, the C, O, and Fe isotope compositions of BIF Fe carbonates reflect authigenic pathways of formation in the sedimentary pile prior to lithification, where microbial dissimilatory iron reduction (DIR) was the major process that controlled the C, O, and Fe isotope compositions of siderite. Isotope mass-balance reactions indicate that the low- δ13C and low- δ18O values of BIF siderite, relative to those expected for precipitation from seawater, reflect inheritance of C and O isotope compositions of precursor organic carbon and ferric hydroxide that were generated in the photic zone and deposited on the seafloor. Carbon-Fe isotope relations suggest that BIF Fe carbonates formed through two end-member pathways: low- δ13C, low- δ56Fe Fe carbonates formed from remobilized, low- δ56Fe aqueous Fe 2+ produced by partial DIR of iron oxide, whereas low- δ13C, high- δ56Fe Fe carbonates formed by near-complete DIR of high- δ56Fe iron oxides that were residual from prior partial DIR. An important observation is the common occurrence of iron oxide inclusions in the high- δ56Fe siderite, supporting a model where such compositions reflect DIR "in place" in the soft

  8. Influence of Carbon Sources and Electron Shuttles on Ferric Iron Reduction by Cellulomonas sp. Strain ES6

    SciTech Connect

    Dr Robin Gerlach; Erin K. Field; Sridhar Viamajala; Brent M. Peyton; William A. Apel; Al B. Cunningham

    2011-09-01

    Microbially reduced iron minerals can reductively transform a variety of contaminants including heavy metals, radionuclides, chlorinated aliphatics, and nitroaromatics. A number of Cellulomonas spp. strains, including strain ES6, isolated from aquifer samples obtained at the U.S. Department of Energy's Hanford site in Washington, have been shown to be capable of reducing Cr(VI), TNT, natural organic matter, and soluble ferric iron [Fe(III)]. This research investigated the ability of Cellulomonas sp. strain ES6 to reduce solid phase and dissolved Fe(III) utilizing different carbon sources and various electron shuttling compounds. Results suggest that Fe(III) reduction by and growth of strain ES6 was dependent upon the type of electron donor, the form of iron present, and the presence of synthetic or natural organic matter, such as anthraquinone-2,6-disulfonate (AQDS) or humic substances. This research suggests that Cellulomonas sp. strain ES6 could play a significant role in metal reduction in the Hanford subsurface and that the choice of carbon source and organic matter addition can allow for independent control of growth and iron reduction activity.

  9. A carbonyl iron/carbon fiber material for electromagnetic wave absorption.

    PubMed

    Youh, Meng-Jey; Wu, Hung-Chih; Lin, Wang-Hua; Chiu, Sheng-Cheng; Huang, Chien-Fa; Yu, Hsin-Chih; Hsu, Jen-Sung; Li, Yuan-Yao

    2011-03-01

    A carbonyl iron/carbon fiber material consisting of carbon fibers grown on micrometer-sized carbonyl iron sphere, was synthesized by chemical vapor deposition using a mixture of C2H2 and H2. The hollow-core carbon fibers (outer diameter: 140 nm and inner diameter: 40 nm) were composed of well-ordered graphene layers which were almost parallel to the long axis of the fibers. A composite (2 mm thick) consisting of the carbonyl iron/carbon fibers and epoxy resin demonstrated excellent electromagnetic (EM) wave absorption. Minimum reflection losses of -36 dB (99.95% of EM wave absorption) at 7.6 GHz and -32 dB (99.92% of EM wave absorption) at 34.1 GHz were achieved. The well-dispersed and network-like carbon fibers in the resin matrix affected the dielectric loss of the EM wave while the carbonyl iron affected the magnetic loss. PMID:21449387

  10. The Organization of Controller Motifs Leading to Robust Plant Iron Homeostasis

    PubMed Central

    Agafonov, Oleg; Selstø, Christina Helen; Thorsen, Kristian; Xu, Xiang Ming; Drengstig, Tormod; Ruoff, Peter

    2016-01-01

    Iron is an essential element needed by all organisms for growth and development. Because iron becomes toxic at higher concentrations iron is under homeostatic control. Plants face also the problem that iron in the soil is tightly bound to oxygen and difficult to access. Plants have therefore developed special mechanisms for iron uptake and regulation. During the last years key components of plant iron regulation have been identified. How these components integrate and maintain robust iron homeostasis is presently not well understood. Here we use a computational approach to identify mechanisms for robust iron homeostasis in non-graminaceous plants. In comparison with experimental results certain control arrangements can be eliminated, among them that iron homeostasis is solely based on an iron-dependent degradation of the transporter IRT1. Recent IRT1 overexpression experiments suggested that IRT1-degradation is iron-independent. This suggestion appears to be misleading. We show that iron signaling pathways under IRT1 overexpression conditions become saturated, leading to a breakdown in iron regulation and to the observed iron-independent degradation of IRT1. A model, which complies with experimental data places the regulation of cytosolic iron at the transcript level of the transcription factor FIT. Including the experimental observation that FIT induces inhibition of IRT1 turnover we found a significant improvement in the system’s response time, suggesting a functional role for the FIT-mediated inhibition of IRT1 degradation. By combining iron uptake with storage and remobilization mechanisms a model is obtained which in a concerted manner integrates iron uptake, storage and remobilization. In agreement with experiments the model does not store iron during its high-affinity uptake. As an iron biofortification approach we discuss the possibility how iron can be accumulated even during high-affinity uptake. PMID:26800438

  11. Organic carbon biostimulates rapid rhizodegradation of perchlorate.

    PubMed

    Yifru, Dawit D; Nzengung, Valentine A

    2008-12-01

    Previous hydroponics and field studies identified phytodegradation and rhizodegradation as the two main mechanisms by which plants metabolize perchlorate. Plant uptake and phytodegradation of perchlorate is a slower and undesired process that poses ecological risks resulting from phytoaccumulation of some fraction of the perchlorate. Meanwhile, rhizodegradation is a more rapid and favored process involving perchlorate-degrading bacteria utilizing dissolved organic carbon (DOC) as a carbon and energy (electron) source to rapidly degrade perchlorate to innocuous chloride. In the present study, rhizodegradation of perchlorate by willow trees (Salix nigra) was biostimulated using electron sources obtained from natural and artificial carbon sources. In bioreactors provided with carbon sources as 500 mg/L DOC, 25 to 40 mg/L of initial perchlorate concentrations were removed to below the ion chromatography method detection limit of 2 microg/L in approximately 9 d. For planted controls provided with no electron donors, the time required for the complete removal of the same doses of perchlorate was up to 70 d. Enhancement of rhizodegradation by organic carbon reduced the phytoaccumulated fraction of perchlorate by an order of magnitude from approximately 430 to 20 mg/kg. The implication of the present study is that the high fraction uptake and phytoaccumulation of perchlorate in agricultural products and the recycling of perchlorate into the ecosystem can be significantly curtailed by supplying electron donors derived from organic carbon sources to the root zone of plants. PMID:18593217

  12. Geochemical modeling of iron, sulfur, oxygen and carbon in a coastal plain aquifer

    USGS Publications Warehouse

    Brown, C.J.; Schoonen, M.A.A.; Candela, J.L.

    2000-01-01

    Fe(III) reduction in the Magothy aquifer of Long Island, NY, results in high dissolved-iron concentrations that degrade water quality. Geochemical modeling was used to constrain iron-related geochemical processes and redox zonation along a flow path. The observed increase in dissolved inorganic carbon is consistent with the oxidation of sedimentary organic matter coupled to the reduction of O2 and SO4/2- in the aerobic zone, and to the reduction of SO4/2- in the anaerobic zone; estimated rates of CO2 production through reduction of Fe(III) were relatively minor by comparison. The rates of CO2 production calculated from dissolved inorganic carbon mass transfer (2.55 x 10-4 to 48.6 x 10-4 mmol 1-1 yr-1) generally were comparable to the calculated rates of CO2 production by the combined reduction of O2, Fe(III) and SO4/2- (1.31 x 10-4 to 15 x 10-4 mmol 1-1 yr-1). The overall increase in SO4/2- concentrations along the flow path, together with the results of mass-balance calculations, and variations in ??34S values along the flow path indicate that SO4/2- loss through microbial reduction is exceeded by SO4/2- gain through diffusion from sediments and through the oxidation of FeS2. Geochemichal and microbial data on cores indicate that Fe(III) oxyhydroxide coatings on sediment grains in local, organic carbon- and SO4/2- -rich zones have localized SO4/2- -reducing zones in which the formation of iron disulfides been depleted by microbial reduction and resulted in decreases dissolved iron concentrations. These localized zones of SO4/2- reduction, which are important for assessing zones of low dissolved iron for water-supply development, could be overlooked by aquifer studies that rely only on groundwater data from well-water samples for geochemical modeling. (C) 2000 Elsevier Science B.V.Fe(III) reduction in the Magothy aquifer of Long Island, NY, results in high dissolved-iron concentrations that degrade water quality. Geochemical modeling was used to constrain iron

  13. Susceptibility of Permafrost Soil Organic Carbon under Warming Climate

    NASA Astrophysics Data System (ADS)

    Yang, Z.; Wullschleger, S. D.; Liang, L.; Graham, D. E.; Gu, B.

    2015-12-01

    Degradation of soil organic carbon (SOC) that has been stored in permafrost is a key concern under warming climate because it could provide a positive feedback. Studies and conceptual models suggest that SOC degradation is largely controlled by the decomposability of SOC, but it is unclear exactly what portions of SOC are susceptible to rapid breakdown and what mechanisms may be involved in SOC degradation. Using a suite of analytical techniques, we examined the dynamic consumption and production of labile SOC compounds, including sugars, alcohols, and small molecular weight organic acids in incubation experiments (up to 240 days at either -2 or 8 °C) with a tundra soil under anoxic conditions, where SOC respiration and iron(III) reduction were monitored. We observe that sugars and alcohols are main components in SOC accounting for initial rapid release of CO2 and CH4 through anaerobic fermentation, whereas the fermentation products such as acetate and formate are subsequently utilized as primary substrates for methanogenesis. Iron(III) reduction is correlated to acetate production and methanogenesis, suggesting its important roles as an electron acceptor in tundra SOC respiration. These observations corroborate strongly with the glucose addition during incubation, in which rapid CO2 and CH4 production is observed concurrently with rapid production and consumption of organics such as acetate. Thus, the biogeochemical processes we document here are pertinent to understanding the accelerated SOC decomposition with temperature and could provide basis for model predicting feedbacks to climate warming in the Arctic.

  14. Functionalized single-walled carbon nanotubes containing traces of iron as new negative MRI contrast agents for in vivo imaging.

    PubMed

    Doan, Bich-Thuy; Seguin, Johanne; Breton, Marie; Le Beherec, Ronan; Bessodes, Michel; Rodríguez-Manzo, Julio A; Banhart, Florian; Beloeil, Jean-Claude; Scherman, Daniel; Richard, Cyrille

    2012-01-01

    Single-walled carbon nanotubes (SWCNTs) containing traces of iron oxide were functionalized by noncovalent lipid-PEG or covalent carboxylic acid function to supply new efficient MRI contrast agents for in vitro and in vivo applications. Longitudinal (r(1)) and transversal (r(2)) water proton relaxivities were measured at 300 MHz, showing a stronger T(2) feature as an MRI contrast agent (r(2)/r(1)  = 190 for CO(2) H functionalisation). The r(2) relaxivity was demonstrated to be correlated to the presence of iron oxide in the SWNT-carboxylic function COOH, in comparison to iron-free ones. Biodistribution studies on mice after a systemic injection showed a negative MRI contrast in liver, suggesting the presence of the nanotubes in this organ until 48 h after i.v. injection. The presence of carbon nanotubes in liver was confirmed after ex vivo carbon extraction. Finally, cytotoxicity studies showed no apparent effect owing to the presence of the carbon nanotubes. The functionalized carbon nanotubes were well tolerated by the animals at the dose of 10 µg g(-1) body weight. PMID:22434627

  15. Fertilization increases paddy soil organic carbon density*

    PubMed Central

    Wang, Shao-xian; Liang, Xin-qiang; Luo, Qi-xiang; Fan, Fang; Chen, Ying-xu; Li, Zu-zhang; Sun, Huo-xi; Dai, Tian-fang; Wan, Jun-nan; Li, Xiao-jun

    2012-01-01

    Field experiments provide an opportunity to study the effects of fertilization on soil organic carbon (SOC) sequestration. We sampled soils from a long-term (25 years) paddy experiment in subtropical China. The experiment included eight treatments: (1) check, (2) PK, (3) NP, (4) NK, (5) NPK, (6) 7F:3M (N, P, K inorganic fertilizers+30% organic N), (7) 5F:5M (N, P, K inorganic fertilizers+50% organic N), (8) 3F:7M (N, P, K inorganic fertilizers+70% organic N). Fertilization increased SOC content in the plow layers compared to the non-fertilized check treatment. The SOC density in the top 100 cm of soil ranged from 73.12 to 91.36 Mg/ha. The SOC densities of all fertilizer treatments were greater than that of the check. Those treatments that combined inorganic fertilizers and organic amendments had greater SOC densities than those receiving only inorganic fertilizers. The SOC density was closely correlated to the sum of the soil carbon converted from organic amendments and rice residues. Carbon sequestration in paddy soils could be achieved by balanced and combined fertilization. Fertilization combining both inorganic fertilizers and organic amendments is an effective sustainable practice to sequestrate SOC. PMID:22467369

  16. Synthesis of lithium iron phosphate/carbon microspheres by using polyacrylic acid coated iron phosphate nanoparticles derived from iron(III) acrylate.

    PubMed

    Xu, Dongwei; He, Yan-Bing; Chu, Xiaodong; Ding, Zhaojun; Li, Baohua; He, Jianfu; Du, Hongda; Qin, Xianying; Kang, Feiyu

    2015-03-01

    Lithium iron phosphate/carbon (LiFePO4 /C) microspheres with high rate and cycling performance are synthesized from iron phosphate/polyacrylic acid (FePO4 /PAA) nanoparticles. Iron(III) acrylate is used as a precursor for both the iron and carbon sources. FePO4 nanoparticles are first produced by a coprecipitation reaction. The byproduct, acrylic acid ions, is polymerized in situ to form a uniform PAA layer on the surface of the FePO4 nanoparticles. The as-prepared LiFePO4 /C microspheres are composed of primary nanoparticles with sizes of 40-50 nm. The nanoparticles are fully coated with a thin, uniform carbon layer derived from the decomposition of the PAA layer. The uniform carbon-coating layer cooperates with interstitial and boundary carbon derived from sucrose successfully to construct an excellent interconnecting conductive network in the microspheres. As a result of the unique structure, the as-prepared LiFePO4 /C microspheres display both high electronic and ionic conductivities, which contribute to their high rate performance (162.9 mAh g(-1) at 0.1C and 126.1 mAh g(-1) at 5C) and excellent cycling stability (97.1% of capacity retention after 500 cycles at 5C/5C). PMID:25469674

  17. Correlation between carbon activity and carbon content in α-iron in liquid sodium negative electrode of liquid metal battery

    NASA Astrophysics Data System (ADS)

    Shin, Sang Hun; Lee, Jeong Hyeon; Lee, Jung Ki; Kim, Ji Hyun

    2015-11-01

    Non-metallic elements such as carbon, oxygen, and nitrogen in liquid sodium exert a significant effect on the material behaviour of cell construction materials in liquid metal battery systems. Austenitic Fe-18%Cr-8%Ni foil and α-iron foil are equilibrated at 550 °C in sodium, and, subsequently, the concentration of carbon in the foils is analysed. A new relationship has been obtained between carbon activity and carbon concentration in α-iron foil, and is compared with the previously developed ones involving 304 SS foil reference samples. An equilibrium method has been developed to measure the activity of carbon in liquid sodium by using α-iron with this new expression. The results show similar values to those obtained with the 304 SS foil reference samples.

  18. Magnetorheology of iron associated magnetic metal-organic framework nanoparticle

    NASA Astrophysics Data System (ADS)

    Quan, Xue Mei; Liu, Ying Dan; Choi, Hyoung Jin

    2015-05-01

    Metal-organic frameworks (MOFs) with zeolite-like structured materials have interesting characteristics because of their high surface areas and pore volumes. Among the various MOFs reported thus far, Fe-BTC was chosen as an additive to improve the dispersion stability of soft-magnetic carbonyl iron particle-based magnetorheological (MR) fluids. The morphology of the Fe-BTC additive was examined by TEM, and the behavior of the MR particles dispersed in silicone oil was examined using a rotational rheometer. With a typical magnetic property, the Fe-BTC additive added MR fluid showed similar MR behavior with that of the CI based MR fluid while its improved dispersion stability was observed.

  19. Magnetic graphene-carbon nanotube iron nanocomposites as adsorbents and antibacterial agents for water purification.

    PubMed

    Sharma, Virender K; McDonald, Thomas J; Kim, Hyunook; Garg, Vijayendra K

    2015-11-01

    One of the biggest challenges of the 21st century is to provide clean and affordable water through protecting source and purifying polluted waters. This review presents advances made in the synthesis of carbon- and iron-based nanomaterials, graphene-carbon nanotubes-iron oxides, which can remove pollutants and inactivate virus and bacteria efficiently in water. The three-dimensional graphene and graphene oxide based nanostructures exhibit large surface area and sorption sites that provide higher adsorption capacity to remove pollutants than two-dimensional graphene-based adsorbents and other conventional adsorbents. Examples are presented to demonstrate removal of metals (e.g., Cu, Pb, Cr(VI), and As) and organics (e.g., dyes and oil) by grapheme-based nanostructures. Inactivation of Gram-positive and Gram-negative bacterial species (e.g., Escherichia coli and Staphylococcus aureus) is also shown. A mechanism involving the interaction of adsorbents and pollutants is briefly discussed. Magnetic graphene-based nanomaterials can easily be separated from the treated water using an external magnet; however, there are challenges in implementing the graphene-based nanotechnology in treating real water. PMID:26498500

  20. Comparison of Carbon XANES Spectra from an Iron Sulfide from Comet Wild 2 with an Iron Sulfide Interplanetary Dust Particle

    NASA Technical Reports Server (NTRS)

    Wirick, S.; Flynn, G. J.; Keller, L. P.; Sanford, S. A.; Zolensky, M. E.; Messenger, Nakamura K.; Jacobsen, C.

    2008-01-01

    Among one of the first particles removed from the aerogel collector from the Stardust sample return mission was an approx. 5 micron sized iron sulfide. The majority of the spectra from 5 different sections of this particle suggests the presence of aliphatic compounds. Due to the heat of capture in the aerogel we initially assumed these aliphatic compounds were not cometary but after comparing these results to a heated iron sulfide interplanetary dust particle (IDP) we believe our initial interpretation of these spectra was not correct. It has been suggested that ice coating on iron sulfides leads to aqueous alteration in IDP clusters which can then lead to the formation of complex organic compounds from unprocessed organics in the IDPs similar to unprocessed organics found in comets [1]. Iron sulfides have been demonstrated to not only transform halogenated aliphatic hydrocarbons but also enhance the bonding of rubber to steel [2,3]. Bromfield and Coville (1997) demonstrated using Xray photoelectron spectroscopy that "the surface enhancement of segregated sulfur to the surface of sulfided precipitated iron catalysts facilitates the formation of a low-dimensional structure of extraordinary properties" [4]. It may be that the iron sulfide acts in some way to protect aliphatic compounds from alteration due to heat.

  1. The placenta: the forgotten essential organ of iron transport.

    PubMed

    Cao, Chang; Fleming, Mark D

    2016-07-01

    Optimal iron nutrition in utero is essential for development of the fetus and helps establish birth iron stores adequate to sustain growth in early infancy. In species with hemochorial placentas, such as humans and rodents, iron in the maternal circulation is transferred to the fetus by directly contacting placental syncytiotrophoblasts. Early kinetic studies provided valuable data on the initial uptake of maternal transferrin, an iron-binding protein, by the placenta. However, the remaining steps of iron trafficking across syncytiotrophoblasts and through the fetal endothelium into the fetal blood remain poorly characterized. Over the last 20 years, identification of transmembrane iron transporters and the iron regulatory hormone hepcidin has greatly expanded the knowledge of cellular iron transport and its regulation by systemic iron status. In addition, emerging human and animal data demonstrating comprised fetal iron stores in severe maternal iron deficiency challenge the classic dogma of exclusive fetal control over the transfer process and indicate that maternal and local signals may play a role in regulating this process. This review compiles current data on the kinetic, molecular, and regulatory aspects of placental iron transport and considers new questions and knowledge gaps raised by these advances. PMID:27261274

  2. Iron

    MedlinePlus

    Iron is a mineral that our bodies need for many functions. For example, iron is part of hemoglobin, a protein which carries ... It helps our muscles store and use oxygen. Iron is also part of many other proteins and ...

  3. How to Enhance Soil Organic Carbon Sequestration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optimizing crop yields and reducing soil erosion can enhance soil organic carbon (SOC) sequestration. The influence of management practices on crop residue C and N inputs to the soil, SOC sequestration, and NO3-N leaching potential under irrigated, continuous crop production in northern Texas was e...

  4. CARBON ADSORPTION ISOTHERMS FOR TOXIC ORGANICS

    EPA Science Inventory

    An experimental protocol for measuring the activated carbon adsorption isotherm was developed and applied to a wide range of organic compounds. Methods for treatment of the isotherm data and a standard format for presentation of results are shown. In the early phase of the study ...

  5. Subduction of Organic Carbon into the Earth

    NASA Astrophysics Data System (ADS)

    Plank, T. A.; Malinverno, A.

    2015-12-01

    Seafloor sediments approach active subduction zones with small amounts (generally < 1 dry weight %) of organic carbon, but this small concentration nonetheless constitutes a significant flux over geological time with respect to the size, isotopic composition and electron balance of the carbosphere. In order to quantify the flux of organic carbon into subduction zones, we have examined carbon concentration and density measurements provided by successive drilling programs (DSDP, ODP, IODP) for cores that sample complete sediment sections to basement near deep sea trenches. An interpolation scheme compensates for sparse or non-uniform analyses, and a weighted bulk concentration is calculated for organic carbon (OC) and inorganic carbonate (IC) for each site. When multiplied by the sediment thickness, the trench length and the convergence velocity, a subducted mass flux can be obtained. Sites with the greatest concentration of OC include those that pass beneath regions of high biological productivity (such as the Eastern Equatorial Pacific) and those that receive terrigenous turbidites (e.g., Indus and Begal Fans, Gulf of Alaska, Cascadia, etc). Together, terrigenous turbidites make up about 60% of the global subducted sediment (GLOSS), and thus have a strong control on the concentration of OC in GLOSS. Sites dominated by terrigenous turbidites have 0.4 wt% OC on average (1sd = 0.1 wt%), and GLOSS is very similar, yielding about 6 MtC/yr OC subducted globally. This flux is enough to subduct the entire surface pool of OC every 2.6 Ga, which if not returned, or returned in a more oxidized form, could contribute to a significant rise in oxygen at the surface of the Earth. Seemingly fortuitously, the OC/total carbon fraction in GLOSS is 20%, very near the long term average required to maintain the isotopic composition of marine carbonates at ~ 0 per mil d13C over much of Earth history.

  6. Microwave-assisted combustion synthesis of nano iron oxide/iron-coated activated carbon, anthracite, cellulose fiber, and silica, with arsenic adsorption studies

    EPA Science Inventory

    Combustion synthesis of iron oxide/iron coated carbons such as activated carbon, anthracite, cellulose fiber and silica is described. The reactions were carried out in alumina crucibles using a Panasonic kitchen microwave with inverter technology, and the reaction process was com...

  7. Organic matter mineralization with reduction of ferric iron in anaerobic sediments

    SciTech Connect

    Lovley, D.R.; Phillips, E.J.P.

    1986-04-01

    The potential for ferric iron reduction with fermentable substrates, fermentation products, and complex organic matter as electron donors was investigated with sediments from freshwater and brackish water sites in the Potomac River Estuary. In enrichments with glucose and hematite, iron reduction was a minor pathway for electron flow, and fermentation products accumulated. The substitution of amorphous ferric oxyhydroxide for hematite in glucose enrichments increased iron reduction 50-fold because the fermentation products could also be metabolized with concomitant iron reduction. Acetate, hydrogen, propionate, butyrate, ethanol, methanol, and trimethylamine stimulated the reduction of amorphous ferric oxyhydroxide in enrichments inoculated with sediments but not in uninoculated or heat-killed controls. The addition of ferric iron inhibited methane production in sediments. The degree of inhibition of methane production by various forms of ferric iron was related to the effectiveness of these ferric compounds as electron acceptors for the metabolism of acetate. The addition of acetate or hydrogen relieved the inhibition of methane production by ferric iron. The decrease of electron equivalents proceeding to methane in sediments supplemented with amorphous ferric oxyhydroxides was compensated for by a corresponding increase of electron equivalents in ferrous iron. These results indicate that iron reduction can out compete methanogenic food chains for sediment organic matter. Thus, when amorphous ferric oxyhydroxides are available in anaerobic sediments, the transfer of electrons from organic matter to ferric iron can be a major pathway for organic matter decomposition.

  8. Organic matter mineralization with reduction of ferric iron in anaerobic sediments.

    PubMed

    Lovley, D R; Phillips, E J

    1986-04-01

    The potential for ferric iron reduction with fermentable substrates, fermentation products, and complex organic matter as electron donors was investigated with sediments from freshwater and brackish water sites in the Potomac River Estuary. In enrichments with glucose and hematite, iron reduction was a minor pathway for electron flow, and fermentation products accumulated. The substitution of amorphous ferric oxyhydroxide for hematite in glucose enrichments increased iron reduction 50-fold because the fermentation products could also be metabolized with concomitant iron reduction. Acetate, hydrogen, propionate, butyrate, ethanol, methanol, and trimethylamine stimulated the reduction of amorphous ferric oxyhydroxide in enrichments inoculated with sediments but not in uninoculated or heat-killed controls. The addition of ferric iron inhibited methane production in sediments. The degree of inhibition of methane production by various forms of ferric iron was related to the effectiveness of these ferric compounds as electron acceptors for the metabolism of acetate. The addition of acetate or hydrogen relieved the inhibition of methane production by ferric iron. The decrease of electron equivalents proceeding to methane in sediments supplemented with amorphous ferric oxyhydroxides was compensated for by a corresponding increase of electron equivalents in ferrous iron. These results indicate that iron reduction can outcompete methanogenic food chains for sediment organic matter. Thus, when amorphous ferric oxyhydroxides are available in anaerobic sediments, the transfer of electrons from organic matter to ferric iron can be a major pathway for organic matter decomposition. PMID:16347032

  9. Organic Matter Mineralization with Reduction of Ferric Iron in Anaerobic Sediments

    PubMed Central

    Lovley, Derek R.; Phillips, Elizabeth J. P.

    1986-01-01

    The potential for ferric iron reduction with fermentable substrates, fermentation products, and complex organic matter as electron donors was investigated with sediments from freshwater and brackish water sites in the Potomac River Estuary. In enrichments with glucose and hematite, iron reduction was a minor pathway for electron flow, and fermentation products accumulated. The substitution of amorphous ferric oxyhydroxide for hematite in glucose enrichments increased iron reduction 50-fold because the fermentation products could also be metabolized with concomitant iron reduction. Acetate, hydrogen, propionate, butyrate, ethanol, methanol, and trimethylamine stimulated the reduction of amorphous ferric oxyhydroxide in enrichments inoculated with sediments but not in uninoculated or heat-killed controls. The addition of ferric iron inhibited methane production in sediments. The degree of inhibition of methane production by various forms of ferric iron was related to the effectiveness of these ferric compounds as electron acceptors for the metabolism of acetate. The addition of acetate or hydrogen relieved the inhibition of methane production by ferric iron. The decrease of electron equivalents proceeding to methane in sediments supplemented with amorphous ferric oxyhydroxides was compensated for by a corresponding increase of electron equivalents in ferrous iron. These results indicate that iron reduction can outcompete methanogenic food chains for sediment organic matter. Thus, when amorphous ferric oxyhydroxides are available in anaerobic sediments, the transfer of electrons from organic matter to ferric iron can be a major pathway for organic matter decomposition. PMID:16347032

  10. Thick-shelled, grazer-protected diatoms decouple ocean carbon and silicon cycles in the iron-limited Antarctic Circumpolar Current.

    PubMed

    Assmy, Philipp; Smetacek, Victor; Montresor, Marina; Klaas, Christine; Henjes, Joachim; Strass, Volker H; Arrieta, Jesús M; Bathmann, Ulrich; Berg, Gry M; Breitbarth, Eike; Cisewski, Boris; Friedrichs, Lars; Fuchs, Nike; Herndl, Gerhard J; Jansen, Sandra; Krägefsky, Sören; Latasa, Mikel; Peeken, Ilka; Röttgers, Rüdiger; Scharek, Renate; Schüller, Susanne E; Steigenberger, Sebastian; Webb, Adrian; Wolf-Gladrow, Dieter

    2013-12-17

    Diatoms of the iron-replete continental margins and North Atlantic are key exporters of organic carbon. In contrast, diatoms of the iron-limited Antarctic Circumpolar Current sequester silicon, but comparatively little carbon, in the underlying deep ocean and sediments. Because the Southern Ocean is the major hub of oceanic nutrient distribution, selective silicon sequestration there limits diatom blooms elsewhere and consequently the biotic carbon sequestration potential of the entire ocean. We investigated this paradox in an in situ iron fertilization experiment by comparing accumulation and sinking of diatom populations inside and outside the iron-fertilized patch over 5 wk. A bloom comprising various thin- and thick-shelled diatom species developed inside the patch despite the presence of large grazer populations. After the third week, most of the thinner-shelled diatom species underwent mass mortality, formed large, mucous aggregates, and sank out en masse (carbon sinkers). In contrast, thicker-shelled species, in particular Fragilariopsis kerguelensis, persisted in the surface layers, sank mainly empty shells continuously, and reduced silicate concentrations to similar levels both inside and outside the patch (silica sinkers). These patterns imply that thick-shelled, hence grazer-protected, diatom species evolved in response to heavy copepod grazing pressure in the presence of an abundant silicate supply. The ecology of these silica-sinking species decouples silicon and carbon cycles in the iron-limited Southern Ocean, whereas carbon-sinking species, when stimulated by iron fertilization, export more carbon per silicon. Our results suggest that large-scale iron fertilization of the silicate-rich Southern Ocean will not change silicon sequestration but will add carbon to the sinking silica flux. PMID:24248337

  11. Thick-shelled, grazer-protected diatoms decouple ocean carbon and silicon cycles in the iron-limited Antarctic Circumpolar Current

    PubMed Central

    Assmy, Philipp; Smetacek, Victor; Montresor, Marina; Klaas, Christine; Henjes, Joachim; Strass, Volker H.; Arrieta, Jesús M.; Bathmann, Ulrich; Berg, Gry M.; Breitbarth, Eike; Cisewski, Boris; Friedrichs, Lars; Fuchs, Nike; Herndl, Gerhard J.; Jansen, Sandra; Krägefsky, Sören; Latasa, Mikel; Peeken, Ilka; Röttgers, Rüdiger; Scharek, Renate; Schüller, Susanne E.; Steigenberger, Sebastian; Webb, Adrian; Wolf-Gladrow, Dieter

    2013-01-01

    Diatoms of the iron-replete continental margins and North Atlantic are key exporters of organic carbon. In contrast, diatoms of the iron-limited Antarctic Circumpolar Current sequester silicon, but comparatively little carbon, in the underlying deep ocean and sediments. Because the Southern Ocean is the major hub of oceanic nutrient distribution, selective silicon sequestration there limits diatom blooms elsewhere and consequently the biotic carbon sequestration potential of the entire ocean. We investigated this paradox in an in situ iron fertilization experiment by comparing accumulation and sinking of diatom populations inside and outside the iron-fertilized patch over 5 wk. A bloom comprising various thin- and thick-shelled diatom species developed inside the patch despite the presence of large grazer populations. After the third week, most of the thinner-shelled diatom species underwent mass mortality, formed large, mucous aggregates, and sank out en masse (carbon sinkers). In contrast, thicker-shelled species, in particular Fragilariopsis kerguelensis, persisted in the surface layers, sank mainly empty shells continuously, and reduced silicate concentrations to similar levels both inside and outside the patch (silica sinkers). These patterns imply that thick-shelled, hence grazer-protected, diatom species evolved in response to heavy copepod grazing pressure in the presence of an abundant silicate supply. The ecology of these silica-sinking species decouples silicon and carbon cycles in the iron-limited Southern Ocean, whereas carbon-sinking species, when stimulated by iron fertilization, export more carbon per silicon. Our results suggest that large-scale iron fertilization of the silicate-rich Southern Ocean will not change silicon sequestration but will add carbon to the sinking silica flux. PMID:24248337

  12. The Quest for Organic Carbon on Mars

    NASA Technical Reports Server (NTRS)

    Eigenbrode, Jennifer

    2011-01-01

    We are entering an era of Mars exploration in which organic carbon detection, characterization, and structural identification will be key to addressing some of the outstanding science objectives of the Mars Exploration Program. Success of these missions will depend on technical, scientific, and strategic elements--all of which are strongly determined based on terrestrial experience and knowledge of organic matter formation, concentration, and preservation. Analog studies including Precambrian sediments, modern endolithic communities, and experiments help us fine-tune these approaches, but we also need to expect the unexpected. This presentation will provide perspective on the challenges of detecting organic carbon on Mars, how we may achieve such detections with the in situ instruments, such as the SAM (Science Analysis at Mars) instrument suite onboard Curiosity, the rover for the 2011 Mars Science Laboratory mission.

  13. Carbonate-Iron Interaction: Kinetic Approach for Carbonate Subduction Down to the Mantle Transition Zone

    NASA Astrophysics Data System (ADS)

    Martirosyan, N.; Yoshino, T.; Shatskiy, A.; Litasov, K. D.; Chanyshev, A.

    2015-12-01

    One of the principal redox exchange reactions at the slab-mantle interface during subduction is CaCO3-Fe0 interaction. Using uniaxial press multianvil apparatus, we investigate this reaction at temperatures from 650 to 1400 °C, and pressures from 4 to 16 GPa. These conditions are representative for the PT path of the slab from the surface to the mantle transition zone. Based on our results, redox reaction can be written as: 3 CaCO3 (aragonite) + 13 Fe0 (metal) = Fe7C3 (carbide) + 3 CaFe2O3 (Ca-wüstite). It is a diffusion-controlled process with the reaction rate constant (k) being log-linear in 1/T. The experimental results allow to calculate the length scale over which the reaction kinetics between aragonite and metallic iron is likely effective. Using relatively simple relationship between the characteristic distance of diffusion as a function of k and duration of the process, we estimate the length scale of the reaction for time scales 4-16 Myr, which corresponds to subduction rates of 2-8 cm/year from 250 km (metal-saturation boundary) to 470 km, for different slab PT-profiles. Assuming that carbonates are in a direct contact with iron, the maximum degree of carbonate reduction can be evaluated using the results of our study and the data on CO2 distribution in altered oceanic basalts. The estimates suggest that up to 0.5, 12, and 20 vol. % of carbonates can be reduced in such case during subduction down to the mantle transition zone at the conditions of cold, medium and hot geotherms, respectively. The sluggish kinetics of established CaCO3-Fe0 interaction suggests that even over the entire history of the Earth, carbonates could survive during subduction from metal saturation boundary near 250 km depth, down to the transition zone, and presumably to the lower mantle.

  14. Catalytic effect of different forms of iron in purification of single-walled carbon nanotubes.

    PubMed

    Suzuki, Tomoko; Inoue, Sakae; Ando, Yoshinori

    2010-06-01

    In the arc plasma jet (APJ) method, a large amount of soot including single wall carbon nanotubes (SWNTs) can be produced in a short time. However, as-grown soot contains a lot of impurities, such as metallic particles used as catalyst and amorphous carbon. Hence it is necessary to purify the soot to obtain pure SWNTs. The biggest problem in purifying APJ-SWNTs is how to remove the thick amorphous carbon covering the catalyst metal particles. By refluxing APJ-SWNTs in hydrogen peroxide using iron particle as catalyst, it can be purified. The added fine particle of pure iron is found to be effective. Then, we examine whether SWNTs can be purified more effectively by adding solution containing the Fe ion instead of the iron particle. We used iron (III) nitrate nonahydrate, hydrogen peroxide decomposing agent which contains catalase and ammonium iron (II) sulfate hexahydrate. In the case of iron (III) nitrate and catalase, purification effect is not obvious. Under these conditions hydrogen peroxide was decomposed into H2O and O2, and the hydroxyl radical was not generated. On the other hand, ammonium iron (II) sulfate is effective. Because of existence of Fe2+ in solution Fenton's reaction takes place. Reaction rate is increased at high temperature. Therefore, APJ-SWNT is purified more effectively if refluxed in hydrogen peroxide using ammonium iron (II) sulfate as catalyst. PMID:20355392

  15. Evidence for Localization of Reaction Upon Reduction of Carbon Tetrachloride by Granular Iron

    SciTech Connect

    Gaspar, Daniel J.; Lea, Alan S.; Engelhard, Mark H.; Baer, Donald R.; Miehr, R.; Tratnyek, Paul G.

    2002-10-01

    The distribution of reaction sites on iron particles exposed to water containing carbon tetrachloride has been examined by measuring the locations of reaction products. The uniformity or localization of reaction sites has implications for understanding and modeling the reduction of environmental contaminants by iron in ground water systems. Granular iron surfaces similar to those being used for environmental remediation applications were studied using surfaces analysis techniques to develop an understanding of the physical and chemical structure of the surface and oxide films. Scanning Auger microscopy and imaging time-of-flight secondary ion mass spectrometry revealed that granular iron exposed to carbon tetrachloride-saturated water exhibits chloride-enriched regions occurred at pits rather than on the passive oxide film on the metal. Understanding the nature of the local solute reduction sites will play an important role in modeling the kinetics of reaction at passive iron oxide films in environmental systems.

  16. Organically complexed iron enhances bioavailability of antimony to maize (Zea mays) seedlings in organic soils.

    PubMed

    Ptak, Corey; McBride, Murray

    2015-12-01

    Antimony (Sb) is a metalloid belonging to group 15 of the periodic table. Chemical similarities between arsenic (As) and Sb produce concerns about potential health effects of Sb and enrichment in the environment. Antimony is found in oxic environments predominately as an oxyanionic species, antimonite (Sb[OH](6-)). As a result of its net negative charge, Sb[OH](6-) was not initially predicted to have strong interactions with natural organic matter. Oxyanionic species could bind the negatively charged organic matter via a ternary complexation mechanism, in which cationic metals mediate the strong association between organic matter functional groups and oxyanions. However, these interactions are poorly understood in how they influence the bioavailability of oxyanionic contaminants to plants. Iron (Fe) additions to organic soils have been found to increase the number of organically complexed Fe sites suitable for Sb exchange, resulting in a reduced bioavailable fraction of Sb. The bioavailability of Sb to maize seedlings as a function of organically complexed Fe was examined using a greenhouse study. A significant increase in plant tissue Sb was observed as organically complexed Fe increased, which was not predicted by methods commonly used to assess bioavailable Sb. Extraction of soils with organic acids common to the maize rhizosphere suggested that organic acid exudation can readily mobilize Sb bound by organic Fe complexes. PMID:26076768

  17. Organic carbon transport in the Columbia River

    NASA Astrophysics Data System (ADS)

    Dahm, Clifford N.; Gregory, Stanley V.; Kilho Park, P.

    1981-12-01

    Total organic carbon (TOC) levels in the Columbia River measured monthly from May 1973 to December 1974 ranged from a maximum of 270 μmol l -1 during late spring and early summer to a minimum of 150 μmol l -1 during late autumn. Sampling locations were directly behind the spillway at the Bonneville Dam, 230 km upstream, and at Kalama, Washington, 128km upstream from the river mouth. The average annual TOC contribution from the Columbia River drainage to the north-eastern Pacific is 4·9×10 10 mol with an average concentration of approximately 195μmol l -1. Of this TOC annual export, 89% is dissolved organic carbon (DOC) and 11% is particulate organic carbon (OOC). The TOC and DOC levels were most highly correlated with increased oxygen saturation and dischange, while POC correlated more closely to high instream primary productivy as indicated by higher pH and oxygen supersaturation. Variability of DOC in the main channel of the Columbia River from Portland, Oregon, to the estuary during a June 1974 cruise was minimal. The DOC concentrations ranged from 221-260 μmol l -1 with no significant upstream or downstream gradients. Diel variation also was slight, varying randomly during 24h between 235-257 μmol l -1. The relative annual constancy of the DOC is indicative of the refractory nature of a significant proportion of the dissolved organic load of the Columbia River.

  18. Pore- and micro-structural characterization of a novel structural binder based on iron carbonation

    SciTech Connect

    Das, Sumanta; Stone, David; Convey, Diana; Neithalath, Narayanan

    2014-12-15

    The pore- and micro-structural features of a novel binding material based on the carbonation of waste metallic iron powder are reported in this paper. The binder contains metallic iron powder as the major ingredient, followed by additives containing silica and alumina to facilitate favorable reaction product formation. Compressive strengths sufficient for a majority of concrete applications are attained. The material pore structure is investigated primarily through mercury intrusion porosimetry whereas electron microscopy is used for microstructural characterization. Reduction in the overall porosity and the average pore size with an increase in carbonation duration from 1 day to 4 days is noticed. The pore structure features are used in predictive models for gas and moisture transport (water vapor diffusivity and moisture permeability) through the porous medium which dictates its long-term durability when used in structural applications. Comparisons of the pore structure with those of a Portland cement paste are also provided. The morphology of the reaction products in the iron-based binder, and the distribution of constituent elements in the microstructure are also reported. - Highlights: • Carbonation of iron produces a dense microstructure. • Pore volume in iron carbonate lower, critical size higher than those in OPC pastes • Reaction product contains iron, carbon, silicon, aluminum and calcium. • Power-law for porosity-moisture permeability relationship was established.

  19. Worldwide organic soil carbon and nitrogen data

    SciTech Connect

    Zinke, P.J.; Stangenberger, A.G.; Post, W.M.; Emanuel, W.R.; Olson, J.S.

    1984-05-01

    A compilation of soil carbon and nitrogen storage data for more than 3500 soil profiles from under natural vegetation or relatively undisturbed sites is presented in this report. A summary table of the carbon and nitrogen storage in a pedon of surface cubic meter for each soil profile, as well as location, elevation, climate, parent material, and vegetation information, are presented. The data were used to determine average carbon and nitrogen storage on land surfaces of the world. Calculations were also made of storage related to climatic classifications, ecosystem clasifications, and latitudinal increments from the equator to 75/sup 0/. Carbon (kg.m/sup -3/) varies from 2 in hot dry climates, through 10 in many cold dry or seasonally moist (warm or hot) climates, to more than 30 in wet alpine or subpolar climates. Nitrogen storage, an order of magnitude smaller than carbon storage in soils, shows broad parallels but exceeds 1600 g.m/sup -3/ for subtropical/tropical premontane or lower montane soils, as well as alpine or subpolar wet soils. Such limiting conditions, defined by a balance of income and loss rates for mature soil profiles, also explain much of the variation among major ecosystem complexes whose soils are partly disturbed, incompletely recovered, or imperfectly known regarding their maturity and stability. Classifying profiles into Holdridge life zones and using appropriate life zone areas, we estimate 1309 x 10/sup 15/ g carbon and 92 x 10/sup 15/ g nitrogen in the world's soils. Alternatively, using average organic carbon and nitrogen densities from one degree latitude bands multiplied by the earth's surface area in the respective bands, we arrive at 1728 x 10/sup 15/ g of carbon and 117 x 10/sup 15/ g of nitrogen. Inadequacies that lead to the disparate estimates are discussed. 123 references, 5 figures, 7 tables.

  20. Binding of Iron(III) to Organic Soils: Exafs Spectroscopy And Chemical Equilibrium Modeling

    SciTech Connect

    Gustafsson, J.P.; Persson, I.; Kleja, D.B.; Schaik, J.W.J.van

    2007-07-09

    The complexation of iron(III) to soil organic matter is important for the binding of trace metals in natural environments because of competition effects. In this study, we used extended X-ray absorption fine structure (EXAFS) spectroscopy to characterize the binding mode for iron(III) in two soil samples from organic mor layers, one of which was also treated with iron(III). In most cases the EXAFS spectra had three significant contributions, inner-core Fe-O/N interactions at about 2.02(2) angstroms, Fe-C interactions in the second scattering shell at 3.00(4) angstroms, and a mean Fe-Fe distance at 3.37(3) angstroms. One untreated sample showed features typical for iron (hydr)oxides; however, after treatment of iron(III) the EXAFS spectrum was dominated by organically complexed iron. The presence of a Fe-Fe distance in all samples showed that the major part of the organically complexed iron was hydrolyzed, most likely in a mixture of complexes with an inner core of (O{sub 5}Fe){sub 2}O and (O{sub 5}Fe){sub 3}O. These results were used to constrain a model for metal-humic complexation, the Stockholm Humic Model (SHM). The model was able to describe iron(III) binding very well at low pH considering only one dimeric iron(III)-humic complex. The competition effect on trace metals was also well described.

  1. Inhibition of catecholamine secretion by iron-rich and iron-deprived multiwalled carbon nanotubes in chromaffin cells.

    PubMed

    Gavello, Daniela; Fenoglio, Ivana; Fubini, Bice; Cesano, Federico; Premoselli, Federica; Renna, Annamaria; Carbone, Emilio; Carabelli, Valentina

    2013-12-01

    The assay of the toxic effects of carbon nanotubes (CNTs) on human health is a stringent need in view of their expected increasing exploitation in industrial and biomedical applications. Most studies so far have been focused on lung toxicity, as the respiratory tract is the main entry of airborne particulate, but there is also recent evidence on the existence of toxic effects of multiwalled carbon nanotubes (MWCNTs) on neuronal and neuroendocrine cells (Belyanskaya et al., 2009; Xu et al., 2009; Gavello et al., 2012). Commercial MWCNTs often contain large amounts of metals deriving from the catalyst used during their synthesis. Since metals, particularly iron, may contribute to the toxicity of MWCNTs, we compared here the effects of two short MWCNTs samples (<5μm length), differing only in their iron content (0.5 versus 0.05% w/w) on the secretory responses of neurotransmitters in mouse chromaffin cells. We found that both iron-rich (MWCNT+Fe) and iron-deprived (MWCNT-Fe) samples enter chromaffin cells after 24h exposure, even though incorporation was attenuated in the latter case (40% versus 78% of cells). As a consequence of MWCNT+Fe or MWCNT-Fe exposure (50-263μg/ml, 24h), catecholamine secretion of chromaffin cells is drastically impaired because of the decreased Ca(2+)-dependence of exocytosis, reduced size of ready-releasable pool and lowered rate of vesicle release. On the contrary, both MWCNTs were ineffective in changing the kinetics of neurotransmitter release of single chromaffin granules and their quantal content. Overall, our data indicate that both MWCNT samples dramatically impair secretion in chromaffin cells, thus uncovering a true depressive action of CNTs mainly associated to their structure and degree of aggregation. This cellular "loss-of-function" is only partially attenuated in iron-deprived samples, suggesting a minor role of iron impurities on MWCNTs toxicity in chromaffin cells exocytosis. PMID:23999117

  2. Properties and effects of remaining carbon from waste plastics gasifying on iron scale reduction.

    PubMed

    Zhang, Chongmin; Chen, Shuwen; Miao, Xincheng; Yuan, Hao

    2011-06-01

    The carbonous activities of three kinds of carbon-bearing materials gasified from plastics were tested with coal coke as reference. The results showed that the carbonous activities of these remaining carbon-bearing materials were higher than that of coal-coke. Besides, the fractal analyses showed that the porosities of remaining carbon-bearing materials were higher than that of coal-coke. It revealed that these kinds of remaining carbon-bearing materials are conducive to improve the kinetics conditions of gas-solid phase reaction in iron scale reduction. PMID:25084574

  3. [Effects of different fertilizer application on soil active organic carbon].

    PubMed

    Zhang, Rui; Zhang, Gui-Long; Ji, Yan-Yan; Li, Gang; Chang, Hong; Yang, Dian-Lin

    2013-01-01

    The variation characteristics of the content and components of soil active organic carbon under different fertilizer application were investigated in samples of calcareous fluvo-aquic soil from a field experiment growing winter wheat and summer maize in rotation in the North China Plain. The results showed that RF (recommended fertilization), CF (conventional fertilization) and NPK (mineral fertilizer alone) significantly increased the content of soil dissolved organic carbon and easily oxidized organic carbon by 24.92-38.63 mg x kg(-1) and 0.94-0.58 mg x kg(-1) respectively compared to CK (unfertilized control). The soil dissolved organic carbon content under OM (organic manure) increased greater than those under NPK and single fertilization, soil easily oxidized organic carbon content under OM and NPK increased greater than that under single chemical fertilization. OM and NPK showed no significant role in promoting the soil microbial biomass carbon, but combined application of OM and NPK significantly increased the soil microbial biomass carbon content by 36.06% and 20.69%, respectively. Soil easily oxidized organic carbon, dissolved organic carbon and microbial biomass carbon accounted for 8.41% - 14.83%, 0.47% - 0.70% and 0.89% - 1.20% of the total organic carbon (TOC), respectively. According to the results, the fertilizer application significantly increased the proportion of soil dissolved organic carbon and easily oxidized organic carbon, but there was no significant difference in the increasing extent of dissolved organic carbon. The RF and CF increased the proportion of soil easily oxidized organic carbon greater than OM or NPK, and significantly increased the proportion of microbial biomass carbon. OM or RF had no significant effect on the proportion of microbial biomass carbon. Therefore, in the field experiment, appropriate application of organic manure and chemical fertilizers played an important role for the increase of soil active organic carbon

  4. Temporal fluctuations in grain size, organic materials and iron concentrations in intertidal surface sediment of San Francisco Bay

    USGS Publications Warehouse

    Thomson-Becker, E. A.; Luoma, S.N.

    1985-01-01

    The physical and chemical characteristics of the oxidized surface sediment in an estuary fluctuate temporally in response to physical forces and apparently-fluctuating inputs. These characteristics, which include grain size and concentrations of organic materials and iron, will influence both trace-metal geochemistry and bioavailability. Temporal trends in the abundance of fine particles, total organic carbon content (TOC), absorbance of extractable organic material (EOM), and concentration of extractable iron in the sediment of San Francisco Bay were assessed using data sets containing approximately monthly samples for periods of two to seven years. Changes in wind velocity and runoff result in monthly changes in the abundance of fine particles in the intertidal zone. Fine-grained particles are most abundant in the late fall/early winter when runoff is elevated and wind velocities are low; particles are coarser in the summer when runoff is low and wind velocities are consistently high. Throughout the bay, TOC is linearly related to fine particle abundance (r = 0.61). Temporal variability occurs in this relationship, as particles are poor in TOC relative to percent of fine particles in the early rainy season. Iron-poor particles also appear to enter the estuary during high runoff periods; while iron is enriched on particle surfaces in the summer. Concentrations of extractable iron and absorbance of EOM vary strongly from year to year. Highest absorbances of EOM occurred in the first year following the drought in 1976-77, and in 1982 and 1983 when river discharge was unusually high. Extractable-iron concentrations were also highest in 1976-77, but were very low in 1982 and 1983. ?? 1985 Dr W. Junk Publishers.

  5. Trace-Element Analyses of Carbonate Minerals in the Gunflint Banded Iron Formation

    NASA Technical Reports Server (NTRS)

    Pun, Aurora; Papike, James J.; Shearer, C. K.

    2002-01-01

    We report on the petrography, mineralogy and trace-element abundances of individual carbonate grains in the Early Proterozoic Gunflint BIF (Banded Iron Formation). Trace-element data may be used as environmental recorders of the fluid evolution from which the various carbonate phases precipitated. Additional information is contained in the original extended abstract.

  6. Methylation of secondary amines with dialkyl carbonates and hydrosilanes catalysed by iron complexes.

    PubMed

    Zheng, Jianxia; Darcel, Christophe; Sortais, Jean-Baptiste

    2014-11-25

    Methylation of secondary amines was achieved using dimethyl carbonate or diethyl carbonate as the C1 source under the catalysis of well-defined half-sandwich iron complexes bearing an N-heterocyclic carbene ligand. The reaction proceeded under mild conditions in the presence of hydrosilanes as the reductants, and the amines were obtained with good to excellent isolated yields. PMID:25285339

  7. Natural organic matter enhanced mobility of nano zerovalent iron.

    PubMed

    Johnson, Richard L; Johnson, Graham O'Brien; Nurmi, James T; Tratnyek, Paul G

    2009-07-15

    Column studies showed that the mobility of nanometer-sized zerovalent iron (nZVI) through granular media is greatly increased in the presence of natural organic matter (NOM). At NOM concentrations of 20 mg/L or greater, the nZVI was highly mobile during transport experiments in 0.15-m long columns packed with medium sand. Below 20 mg/L NOM, mobility of the nZVI was less; however, even at 2 mg/L the nZVI showed significantly increased mobility compared to the no-NOM case. Spectrophotometric and aggregation studies of nZVI suspensions in the presence of NOM suggest that sorption of the NOM onto the nZVI, resulting in a reduced sticking coefficient, may be the primary mechanism of enhanced mobility. Modeling the mobility of nZVI in porous media with filtration theory is challenging, but calibration of a simple model with experimental results from the column experiments reported here allows simulation of transport distances during injection. The simulation results show that the increased mobility due to NOM combined with the decrease in mobility due to decreased velocity with distance from an injection well could produce an injection zone that is wide enough to be useful for remediation but small enough to avoid reaching unwanted receptors. PMID:19708381

  8. Environmental Controls of Soil Organic Carbon in Soils Across Amazonia

    NASA Astrophysics Data System (ADS)

    Quesada, Carlos Alberto; Paz, Claudia; Phillips, Oliver; Nonato Araujo Filho, Raimundo; Lloyd, Jon

    2015-04-01

    (kaolinitic) and thus the clay plus silt fraction was the best correlate for SOC but with crystalline iron oxides (dithionite-citrate minus ammonium oxalate - oxalic acid extractable iron) being also correlated to SOC in these soils (R2 = 0.74). Most of SOC in these soils was found on the clay+silt fraction and in stable, clay rich aggregates. However, SOC of high activity clays and other less weathered soils such as Alisols, Cambisols and Plinthosols showed no correlation with particle size or iron oxides, being mostly stabilized by aluminium complexes. We found SOC of these soils to be better explained by a three way interaction among soil pH, carbon quality and dithionite-citrate extractable Al (R2 = 0.85). Consistent with this observation, SOC in the less weathered soils was mostly found in the colloidal fraction (75%). SOC of Podzols and Arenosols on the other hand had only a small but significant influence from their clay plus silt fraction (R2 = 0.31), with particulate organic matter accounting for most of its SOC.

  9. Iron silicide root formation in carbon nanotubes grown by microwave PECVD.

    PubMed

    AuBuchon, Joseph F; Daraio, Chiara; Chen, Li-Han; Gapin, Andrew I; Jin, Sungho

    2005-12-29

    Aligned carbon nanotubes have been grown using microwave plasma enhanced chemical vapor deposition (PECVD). The carbon nanotubes are nucleated from iron catalyst particles which, during growth, remain adherent to the silicon substrates. By analysis with high-resolution electron microscopy, we observe iron silicide roots penetrating into the silicon substrate at the interface of the catalyst particles and the substrate, thus providing strong adhesion of the carbon nanotubes onto the substrate. The iron silicide roots assist in the attachment of the catalyst particles to the substrate and play a role in the evolution of the catalyst particle morphology and resulting base growth mode. Carbon nanotubes grown by microwave PECVD could exhibit superior electrical and thermal transport properties over other PECVD processes, so an understanding of the growth mechanism is important for utilization in device applications. PMID:16375415

  10. Enhanced terrestrial carbon preservation promoted by reactive iron in deltaic sediments

    NASA Astrophysics Data System (ADS)

    Shields, Michael R.; Bianchi, Thomas S.; Gélinas, Yves; Allison, Mead A.; Twilley, Robert R.

    2016-02-01

    We examined the role of reactive iron (FeR) in preserving organic carbon (OC) across a subaerial chronosequence of the Wax Lake Delta, a prograding delta within the Mississippi River Delta complex. We found that ~15.0% of the OC was bound to FeR, and the dominant binding mechanisms varied from adsorption in the youngest subaerial region to coprecipitation at the older, vegetated sites. The δ13C of the iron-associated OC was more negative than the total OC (mean = -2.6‰), indicating greater preference for terrestrial material and/or compounds with more negative δ13C values. However, only the adsorbed OC displayed preferential binding of lignin phenols. We estimate that ~8% of the OC initially deposited in deltaic systems is bound to FeR (equivalent to 6 × 1012 gC yr-1), and this percentage increases postdepositionally, as coprecipitation of FeR and OC allows for an even greater amount of OC to be bound to FeR.

  11. Dispersion and separation of nanostructured carbon in organic solvents

    NASA Technical Reports Server (NTRS)

    Landi, Brian J. (Inventor); Raffaelle, Ryne P. (Inventor); Ruf, Herbert J. (Inventor); Evans, Christopher M. (Inventor)

    2011-01-01

    The present invention relates to dispersions of nanostructured carbon in organic solvents containing alkyl amide compounds and/or diamide compounds. The invention also relates to methods of dispersing nanostructured carbon in organic solvents and methods of mobilizing nanostructured carbon. Also disclosed are methods of determining the purity of nanostructured carbon.

  12. Origin and fate of particulate and dissolved organic matter in a naturally iron-fertilized region of the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Tremblay, L.; Caparros, J.; Leblanc, K.; Obernosterer, I.

    2014-10-01

    Natural iron fertilization of high-nutrient low-chlorophyll (HNLC) waters induces annually occurring spring phytoplankton blooms off Kerguelen Islands (Southern Ocean). To examine the origin and fate of particulate and dissolved organic matter (POM and DOM), D- and L-amino acids (AA) were quantified at bloom and HNLC stations. Total hydrolysable AA accounted for 21-25% of surface particulate organic carbon (%POCAA) at the bloom sites, but for 10% at the HNLC site. A marked decrease in %POCAA with depth was observed at the most productive stations leading to values between 3 and 5% below 300 m depth. AA contributed to only 0.9-4.4% of dissolved organic carbon (%DOCAA) at all stations. The only consistent vertical trend was observed at the most productive station (A3-2) where %DOCAA decreased from ∼2% in the surface waters to 0.9% near 300 m. These AA yields and other markers revealed that POM and DOM were more rapidly altered or mineralized at the bloom sites compared to the HNLC site. Different molecular markers indicated that POM mostly originated from diatoms and bacteria. The estimated average proportion of POM from intact phytoplankton cells in surface waters was 45% at the bloom station A3-2, but 14% at the HNLC site. Estimates based on D-AA yields indicated that ∼15% of POM and ∼30% of DOM was of bacterial origin (cells and cell fragments) at all stations. Surprisingly, the DOM in HNLC waters appeared less altered than the DOM from the bloom, had slightly higher dissolved AA concentrations, and showed no sign of alteration within the water column. Unfavorable conditions for bacterial degradation in HNLC regions can explain these findings. In contrast, large inputs of labile organic molecules and iron, likely stimulate the degradation of organic matter (priming effect) and the production of more recalcitrant DOM (microbial carbon pump) during iron-fertilized blooms.

  13. Linking carbon and iron cycles by investigating transport, fate and mineralogy of iron-bearing colloids from peat-draining rivers - Scotland as model for high-latitude rivers

    NASA Astrophysics Data System (ADS)

    Wood, Deborah; Crocket, Kirsty; Brand, Tim; Stutter, Marc; Wilson, Clare; Schröder, Christian

    2016-04-01

    Linking carbon and iron cycles by investigating transport, fate and mineralogy of iron-bearing colloids from peat-draining rivers - Scotland as model for high-latitude rivers Wood, D.A¹, Crocket, K², Brand, T², Stutter, M³, Wilson, C¹ & Schröder, C¹ ¹Biological and Environmental Sciences, University of Stirling, Stirling, FK9 4LA ²Scottish Association for Marine Science, University of the Highlands and Islands, Dunbeg, Oban, PA37 1QA ³James Hutton Institute, Craigiebuckler, Aberdeen, AB15 8QH The biogeochemical iron cycle exerts significant control on the carbon cycle¹. Iron is a limiting nutrient in large areas of the world's oceans and its bioavailability controls CO2 uptake by marine photosynthesizing microorganisms. While atmospheric iron inputs to the open ocean have been extensively measured, global river inputs have likely been underestimated because most major world rivers exhibit extensive iron removal by flocculation and sedimentation during seawater mixing. Iron minerals and organic matter mutually stabilise each other², which results in a 'rusty carbon sink' in sediments³ on the one hand but may also enhance transport beyond the salinity gradient on the other. Humic-rich, high latitude rivers have a higher iron-carrying capacity⁴‑⁶ but are underrepresented in iron flux calculations. The West Coast sea lochs in Scotland are fed by predominantly peatland drainage catchments, and the rivers entering the sea lochs carry a high load of organic matter. The short distance between many of these catchments and the coastal ocean facilitates source-to-sea research investigating transport, fate and mineralogy of iron-bearing colloids providing a good analogue for similar high latitude fjordic systems. We use SeaFAST+ICP-MS and Mössbauer spectroscopy to survey trace metal concentrations, with emphasis on iron concentrations, speciation and mineralogy, across salinity gradients. In combination with ultra-filtration techniques, this allows

  14. Versatile and Biomass Synthesis of Iron-based Nanoparticles Supported on Carbon Matrix with High Iron Content and Tunable Reactivity

    SciTech Connect

    Zhang, Dongmao; Shi, Sheldon Q; Jiang, Dongping; Che, Wen; Gai, Zheng; Howe, Jane Y; More, Karren Leslie; Arockiasamy, Antonyraj

    2012-01-01

    Iron-based nanoparticles supported on carbon (FeNPs{at}C) have enormous potential for environmental applications. Reported is a biomass-based method for FeNP{at}C synthesis that involves pyrolysis of bleached wood fiber pre-mixed with Fe{sub 3}O{sub 4} nanoparticles. This method allows synthesis of iron-based nanoparticles with tunable chemical reactivity by changing the pyrolysis temperature. The FeNP{at}C synthesized at a pyrolysis temperature of 500 C (FeNP{at}C-500) reacts violently (pyrophoric) when exposed to air, while FeNP{at}C prepared at 800 C (FeNP{at}C-800) remains stable in ambient condition for at least 3 months. The FeNPs in FeNP{at}C-800 are mostly below 50 nm in diameter and are surrounded by carbon. The immediate carbon layer (within 5-15 nm radius) on the FeNPs is graphitized. Proof-of-concept environmental applications of FeNPs{at}C-800 were demonstrated by Rhodamine 6G and arsenate (V) removal from water. This biomass-based method provides an effective way for iron-based nanoparticle fabrication and biomass utilization.

  15. Black Carbon Contribution to Organic Carbon Stocks in Urban Soil.

    PubMed

    Edmondson, Jill L; Stott, Iain; Potter, Jonathan; Lopez-Capel, Elisa; Manning, David A C; Gaston, Kevin J; Leake, Jonathan R

    2015-07-21

    Soil holds 75% of the total organic carbon (TOC) stock in terrestrial ecosystems. This comprises ecosystem-derived organic carbon (OC) and black carbon (BC), a recalcitrant product of the incomplete combustion of fossil fuels and biomass. Urban topsoils are often enriched in BC from historical emissions of soot and have high TOC concentrations, but the contribution of BC to TOC throughout the urban soil profile, at a regional scale is unknown. We sampled 55 urban soil profiles across the North East of England, a region with a history of coal burning and heavy industry. Through combined elemental and thermogravimetic analyses, we found very large total soil OC stocks (31-65 kg m(-2) to 1 m), exceeding typical values reported for UK woodland soils. BC contributed 28-39% of the TOC stocks, up to 23 kg C m(-2) to 1 m, and was affected by soil texture. The proportional contribution of the BC-rich fraction to TOC increased with soil depth, and was enriched in topsoil under trees when compared to grassland. Our findings establish the importance of urban ecosystems in storing large amounts of OC in soils and that these soils also capture a large proportion of BC particulates emitted within urban areas. PMID:26114917

  16. Initial Characterization of Carbon Metabolism in Iron Oxidizing Microbial Communities of Acidic Hot Springs in Norris Geyser Basin, Yellowstone National Park

    NASA Astrophysics Data System (ADS)

    Kreuzer, H. W.; Jennings, R. D.; Whitmore, L.; Inskeep, W. P.; Moran, J.

    2012-12-01

    Norris Geyser Basin in Yellowstone National Park is home to several acidic, sulfidic hot springs. Visual inspection of the springs reveals distinct geochemical regions starting with a sulfur deposition zone followed by a transition to iron oxide deposition downstream. The microbial communities in the iron oxidation zones are dominated by Archaea, including several members that appear to define previously unrecognized taxa. Abiotic iron oxidation rates are very slow at these temperatures (typically ~ 65-70 oC) and pH's (typically ~3). Therefore, the relatively rapid iron oxide deposition rate strongly suggests the process is microbially mediated, and an organism previously isolated from these springs, Metallosphaera yellowstonensis, has been shown to oxide iron in culture. M. yellowstonensis has been observed in the all microbial communities analyzed in the iron oxidizing zones of these springs, though metagenomic profiling suggests it constitutes only ~20% of the community membership. When we began our studies of C flow in the iron-oxidizing community, no C source had been demonstrated. Observed potential carbon sources in the springs include dissolved inorganic carbon, dissolved organic carbon, and methane, as well as random inputs of heterotrophic carbon in the forms of insect carcasses, pine needles, and animal scat. The temperatures in the iron oxidation zones are above the photosynthetic upper temperature limit, thus precluding photosynthetic-based autotrophy within the community itself. We are employing geochemical and stable isotope techniques to assess carbon inventories in the system. We have demonstrated that M. yellowstonensis as well as excised samples of iron oxide mat communities can fix CO2, and our estimated isotopic fractionation factor is consistent with the 3-hydroxypropionate 4-hydroxybutyrate pathway. Genes of this pathway have been identified in the M. yellowstonensis genome. We have tentatively identified small amounts of organic compounds

  17. Kinetics of iron import into developing mouse organs determined by a pup-swapping method.

    PubMed

    Chakrabarti, Mrinmoy; Barlas, Mirza Nofil; McCormick, Sean P; Lindahl, Lora S; Lindahl, Paul A

    2015-01-01

    The kinetics of dietary iron import into various organs of mice were evaluated using a novel pup-swapping approach. Newborn pups whose bodies primarily contained (56)Fe or (57)Fe were swapped at birth such that each nursed on milk containing the opposite isotope. A pup from each litter was euthanized weekly over a 7-week period. Blood plasma was obtained, and organs were isolated typically after flushing with Ringer's buffer. (56)Fe and (57)Fe concentrations were determined for organs and plasma; organ volumes were also determined. Mössbauer spectra of equivalent (57)Fe-enriched samples were used to quantify residual blood in organs; this fraction was excluded from later analysis. Rates of import into brain, spleen, heart, and kidneys were highest during the first 2 weeks of life. In contrast, half of iron in the newborn liver exited during that time, and influx peaked later. Two mathematical models were developed to analyze the import kinetics. The only model that simulated the data adequately assumed that an iron-containing species enters the plasma and converts into a second species and that both are independently imported into organs. Consistent with this, liquid chromatography with an on-line ICP-MS detector revealed numerous iron species in plasma besides transferrin. Model fitting required that the first species, assigned to non-transferrin-bound iron, imports faster into organs than the second, assigned to transferrin-bound-iron. Non-transferrin-bound iron rather than transferrin-bound-iron appears to play the dominant role in importing iron into organs during early development of healthy mice. PMID:25371212

  18. PHOTOCHEICAL PRODUCTION OF HYDROXYL RADICAL IN NATURAL WATER - THE ROLE OF IRON AND DISSOLVED ORGANIC MATTER

    EPA Science Inventory

    Photochemical hydroxyl radical (OH) production was measured in several natural waters to investigate the importance of colored dissolved organic matter (CDOM) and iron-CDOM complexes as sources of OH. High rates of OH photoproduction in highly colored, iron-rich, acidic waters a...

  19. ORGANIC EMISSIONS FROM IRON ORE SINTERING PLANTS: DETERMINATION OF CAUSES AND METHODS OF ABATEMENT

    EPA Science Inventory

    The report gives results of a laboratory study to develop basic information on the emission of organics from iron ore sinter beds. Samples of sinter bed mix components (including several types of iron ore fines, blast furnace flue dust, rolling mill scale, anthracite coal, and li...

  20. The reduction of iron oxides by volatiles in a rotary hearth furnace process: Part II. The reduction of iron oxide/carbon composites

    SciTech Connect

    Sohn, I.; Fruehan, R.J.

    2006-04-15

    The reduction of iron oxide/carbon composite pellets with hydrogen at 900{sup o}C to 1000{sup o}C was studied. Compared to hydrogen, the reduction by carbon was negligible at 900 degrees C and below. However, significant carbon oxidation of the iron oxide/graphite pellets by H{sub 2O generated from the reduction of Fe{sub 2}O{sub 3} by H-2 was observed. At higher temperatures, reduction by carbon complicates the overall reduction mechanism, with the iron oxide/graphite composite pellet found to be more reactive than the iron oxide/char composite pellet. From the scanning electron micrographs, partially reduced composite pellets showed a typical topochemical interface with an intermediate region between an oxygen-rich unreacted core and an iron-rich outer shell. To determine the possibility of reduction by volatiles, a layer of iron oxide powders was spread on top of a high volatile containing bituminous coal and heated inside a reactor using infra-red radiation. By separating the individual reactions involved for an iron oxide/coal mixture where a complex set of reactions occur simultaneously, it was possible to determine the sole effect of volatile reduction. It was found that the light reducing gases evolve initially and react with the iron oxide, with complex hydrocarbons evolving at the later stages. The volatiles caused about 20 to 50% reduction of the iron oxide.

  1. The reduction of iron oxides by volatiles in a rotary hearth furnace process: Part II. The reduction of iron oxide/carbon composites

    NASA Astrophysics Data System (ADS)

    Sohn, I.; Fruehan, R. J.

    2006-04-01

    The reduction of iron oxide/carbon composite pellets with hydrogen at 900 °C to 1000 °C was studied. Compared to hydrogen, the reduction by carbon was negligible at 900 °C and below. However, significant carbon oxidation of the iron oxide/graphite pellets by H2O generated from the reduction of Fe2O3 by H2 was observed. At higher temperatures, reduction by carbon complicates the overall reduction mechanism, with the iron oxide/graphite composite pellet found to be more reactive than the iron oxide/char composite pellet. From the scanning electron micrographs, partially reduced composite pellets showed a typical topochemical interface with an intermediate region between an oxygen-rich unreacted core and an iron-rich outer shell. To determine the possibility of reduction by volatiles, a layer of iron oxide powders was spread on top of a high volatile containing bituminous coal and heated inside a reactor using infra-red radiation. By separating the individual reactions involved for an iron oxide/coal mixture where a complex set of reactions occur simultaneously, it was possible to determine the sole effect of volatile reduction. It was found that the light reducing gases evolve initially and react with the iron oxide, with complex hydrocarbons evolving at the later stages. The volatiles caused about 20 to 50 pct reduction of the iron oxide.

  2. Upgrading and dephosphorization of Western Australian iron ore using reduction roasting by adding sodium carbonate

    NASA Astrophysics Data System (ADS)

    Zhu, De-qing; Chun, Tie-jun; Pan, Jian; Lu, Li-ming; He, Zhen

    2013-06-01

    The technology of direct reduction by adding sodium carbonate (Na2CO3) and magnetic separation was developed to treat Western Australian high phosphorus iron ore. The iron ore and reduced product were investigated by optical microscopy and scanning electron microscopy. It is found that phosphorus exists within limonite in the form of solid solution, which cannot be removed through traditional ways. During reduction roasting, Na2CO3 reacts with gangue minerals (SiO2 and Al2O3), forming aluminum silicate-containing phosphorus and damaging the ore structure, which promotes the separation between iron and phosphorus during magnetic separation. Meanwhile, Na2CO3 also improves the growth of iron grains, increasing the iron grade and iron recovery. The iron concentrate, assaying 94.12wt% Fe and 0.07wt% P at the iron recovery of 96.83% and the dephosphorization rate of 74.08%, is obtained under the optimum conditions. The final product (metal iron powder) after briquetting can be used as the burden for steelmaking by an electric arc furnace to replace scrap steel.

  3. Site-Specific Carbon Isotopes in Organics

    NASA Astrophysics Data System (ADS)

    Piasecki, A.; Eiler, J. M.

    2012-12-01

    Natural organic molecules exhibit a wide range of internal site-specific isotope variation (i.e., molecules with same isotopic substitution type but different site). Such variations are generally unconstrained by bulk isotopic measurements. If known, site-specific variations might constrain temperatures of equilibrium, mechanisms of formation or consumption reactions, and possibly other details. For example, lipids can exhibit carbon isotope differences of up to 30‰ between adjacent carbon sites as a result of fractionations arising during decarboxylation of pyruvate and other steps in lipid biosynthesis(1). We present a method for site-specific carbon isotope analysis of propane, based on high-resolution, multi-collector gas source mass spectrometry, using a novel prototype instrument - the Thermo MAT 253 Ultra. This machine has an inlet system and electron bombardment ion source resembling those in conventional stable isotope gas source mass spectrometers, and the energy filter, magnet, and detector array resembling those in multi-collector ICPMS and TIMS. The detector array has 7 detector positions, 6 of which are movable, and each of which can collect ions with either a faraday cup (read through amplifiers ranging from 107-1012 ohms) or an SEM. High mass resolving power (up to 27,000, MRP = M/dM definition) is achieved through a narrow entrance slit, adjustable from 250 to 5 μm. Such resolution can cleanly separate isobaric interferences between isotopologues of organic molecules having the same cardinal mass (e.g., 13CH3 and 12CH2D). We use this technology to analyze the isotopologues and fragments of propane, and use such data to solve for the site-specific carbon isotope fractionation. By measuring isotopologues of both the one-carbon (13CH3) and the two-carbon (13C12CH4) fragment ion, we can solve for both bulk δ13C and the difference in δ13C between the terminal and central carbon position. We tested this method by analyzing mixtures between natural

  4. Epitaxial Approaches to Carbon Nanotube Organization

    NASA Astrophysics Data System (ADS)

    Ismach, Ariel

    Carbon nanotubes have unique electronic, mechanical, optical and thermal properties, which make them ideal candidates as building blocks in nano-electronic and electromechanical systems. However, their organization into well-defined geometries and arrays on surfaces remains a critical challenge for their integration into functional nanosystems. In my PhD, we developed a new approach for the organization of carbon nanotubes directed by crystal surfaces. The principle relies on the guided growth of single-wall carbon nanotubes (SWNTs) by atomic features presented on anisotropic substrates. We identified three different modes of surface-directed growth (or 'nanotube epitaxy'), in which the growth of carbon nanotubes is directed by crystal substrates: We first observed the nanotube unidirectional growth along atomic steps ('ledge-directed epitaxy') and nanofacets ('graphoepitaxy') on the surface of miscut C-plane sapphire and quartz. The orientation along crystallographic directions ('lattice-directed epitaxy') was subsequently observed by other groups on different crystals. We have proposed a "wake growth" mechanism for the nanotube alignment along atomic steps and nanofacets. In this mechanism, the catalyst nanoparticle slides along the step or facet, leaving the nanotube behind as a wake. In addition, we showed that the combination of surface-directed growth with external forces, such as electric-field and gas flow, can lead to the simultaneous formation of complex nanotube structures, such as grids and serpentines. The "wake growth" model, which explained the growth of aligned nanotubes, could not explain the formation of nanotube serpentines. For the latter, we proposed a "falling spaghetti" mechanism, in which the nanotube first grows by a free-standing process, aligned in the direction of the gas flow, then followed by absorption on the stepped surface in an oscillatory manner, due to the competition between the drag force caused by the gas flow on the suspended

  5. Urban Tree Effects on Soil Organic Carbon

    PubMed Central

    Edmondson, Jill L.; O'Sullivan, Odhran S.; Inger, Richard; Potter, Jonathan; McHugh, Nicola; Gaston, Kevin J.; Leake, Jonathan R.

    2014-01-01

    Urban trees sequester carbon into biomass and provide many ecosystem service benefits aboveground leading to worldwide tree planting schemes. Since soils hold ∼75% of ecosystem organic carbon, understanding the effect of urban trees on soil organic carbon (SOC) and soil properties that underpin belowground ecosystem services is vital. We use an observational study to investigate effects of three important tree genera and mixed-species woodlands on soil properties (to 1 m depth) compared to adjacent urban grasslands. Aboveground biomass and belowground ecosystem service provision by urban trees are found not to be directly coupled. Indeed, SOC enhancement relative to urban grasslands is genus-specific being highest under Fraxinus excelsior and Acer spp., but similar to grasslands under Quercus robur and mixed woodland. Tree cover type does not influence soil bulk density or C∶N ratio, properties which indicate the ability of soils to provide regulating ecosystem services such as nutrient cycling and flood mitigation. The trends observed in this study suggest that genus selection is important to maximise long-term SOC storage under urban trees, but emerging threats from genus-specific pathogens must also be considered. PMID:25003872

  6. Urban tree effects on soil organic carbon.

    PubMed

    Edmondson, Jill L; O'Sullivan, Odhran S; Inger, Richard; Potter, Jonathan; McHugh, Nicola; Gaston, Kevin J; Leake, Jonathan R

    2014-01-01

    Urban trees sequester carbon into biomass and provide many ecosystem service benefits aboveground leading to worldwide tree planting schemes. Since soils hold ∼75% of ecosystem organic carbon, understanding the effect of urban trees on soil organic carbon (SOC) and soil properties that underpin belowground ecosystem services is vital. We use an observational study to investigate effects of three important tree genera and mixed-species woodlands on soil properties (to 1 m depth) compared to adjacent urban grasslands. Aboveground biomass and belowground ecosystem service provision by urban trees are found not to be directly coupled. Indeed, SOC enhancement relative to urban grasslands is genus-specific being highest under Fraxinus excelsior and Acer spp., but similar to grasslands under Quercus robur and mixed woodland. Tree cover type does not influence soil bulk density or C∶N ratio, properties which indicate the ability of soils to provide regulating ecosystem services such as nutrient cycling and flood mitigation. The trends observed in this study suggest that genus selection is important to maximise long-term SOC storage under urban trees, but emerging threats from genus-specific pathogens must also be considered. PMID:25003872

  7. Recent Applications of Acyclic (Diene)iron Complexes and (Dienyl)iron Cations in Organic Synthesis

    PubMed Central

    Chaudhury, Subhabrata

    2009-01-01

    Complexation of (tricarbonyl)iron to an acyclic diene serves to protect the ligand against oxidation, reduction and cycloaddition reactions while the steric bulk of this adjunct serves to direct the approach reagents to unsaturated groups attached to the diene onto the face opposite to iron. Furthermore, the Fe(CO)3 moiety can serve to stabilize carbocation centers adjacent to the diene (i.e. pentadienyl-iron cations). Recent applications of these reactivities to the synthesis of polyene, cyclopropane, cycloheptadiene and cyclohexenone containing natural products or analogs will be presented. PMID:21709767

  8. Transport and cycling of iron and hydrogen peroxide in a freshwater stream: Influence of organic acids

    USGS Publications Warehouse

    Scott, D.T.; Runkel, R.L.; McKnight, Diane M.; Voelker, B.M.; Kimball, B.A.; Carraway, E.R.

    2003-01-01

    An in-stream injection of two dissolved organic acids (phthalic and aspartic acids) was performed in an acidic mountain stream to assess the effects of organic acids on Fe photoreduction and H2O2 cycling. Results indicate that the fate of Fe is dependent on a net balance of oxidative and reductive processes, which can vary over a distance of several meters due to changes in incident light and other factors. Solution phase photoreduction rates were high in sunlit reaches and were enhanced by the organic acid addition but were also limited by the amount of ferric iron present in the water column. Fe oxide photoreduction from the streambed and colloids within the water column resulted in an increase in the diurnal load of total filterable Fe within the experimental reach, which also responded to increases in light and organic acids. Our results also suggest that Fe(II) oxidation increased in response to the organic acids, with the result of offsetting the increase in Fe(II) from photoreductive processes. Fe(II) was rapidly oxidized to Fe(III) after sunset and during the day within a well-shaded reach, presumably through microbial oxidation. H2O 2, a product of dissolved organic matter photolysis, increased downstream to maximum concentrations of 0.25 ??M midday. Kinetic calculations show that the buildup of H2O2 is controlled by reaction with Fe(III), but this has only a small effect on Fe(II) because of the small formation rates of H2O2 compared to those of Fe(II). The results demonstrate the importance of incorporating the effects of light and dissolved organic carbon into Fe reactive transport models to further our understanding of the fate of Fe in streams and lakes.

  9. Preparation and properties of a novel iron-coated carbon fiber

    NASA Astrophysics Data System (ADS)

    Yang, Yi; Zhang, Baoshan; Xu, Weidong; Shi, Yingbing; Jiang, Zhengsheng; Zhou, Ningsheng; Gu, Benxing; Lu, Huaixian

    2003-01-01

    A novel iron-coated carbon fiber has been fabricated by electrochemical method. Magnetic properties, complex permeability, and complex permitivity have been measured. It is found that the sample has a low coercive force. By doping a few fibers to general absorbers (carbonyl iron), the complex permeability and permitivity of composites achieved a rise without the obvious increase of filling density. This result shows that the doping of fibers to general absorber will effectively decrease the thickness of the microwave absorption layer.

  10. Carbon-14 dating of an iron bloom associated with the voyages of Sir Martin Frobisher

    SciTech Connect

    Sayre, E.V.; Harbottle, G.; Stoenner, R.W. Washburn, W.; Olin, J.S.; Fitzhugh, W.

    1982-01-01

    This paper recounts the history of the iron bloom associated with the English Elizabethan explorer Sir Martin Frobisher who made 3 voyages to the North American mainland in the 1570's. Specifically the paper deals with the use of proportional counters in carbon-14 dating of the Frobisher iron bloom which is located at the Smithsonian Institution. The procedures for preparing the samples for counting are described. (KRM)

  11. Green Carbon, Black Carbon, White Carbon: Simultaneous Differentiation Between Soil Organic Matter, Pyrogenic Carbon and Carbonates Using Thermal Analysis Techniques

    NASA Astrophysics Data System (ADS)

    Plante, A. F.; Peltre, C.; Chan, J.; Baumgartl, T.; Erskine, P.; Apesteguía, M.; Virto, I.

    2014-12-01

    Quantification of soil carbon stocks and fluxes continues to be an important endeavor in assessments of soil quality, and more broadly in assessments of ecosystem functioning. The quantification of soil carbon in alkaline, carbonate-containing soils, such as those found in Mediterranean areas, is complicated by the need to differentiate between organic carbon (OC) and inorganic carbon (IC), which continues to present methodological challenges. Acidification is frequently used to eliminate carbonates prior to soil OC quantification, but when performed in the liquid phase, can promote the dissolution and loss of a portion of the OC. Acid fumigation (AF) is increasingly preferred for carbonate removal, but its effectiveness is difficult to assess using conventional elemental and isotopic analyses. The two-step approach is time, labor and cost intensive, and generates additional uncertainties from the calculations. Quantification of the actively cycling pool of soil organic C (SOC) in many soils is further complicated by the potential presence of more recalcitrant/stable forms such as pyrogenic or black carbon (BC) derived from incomplete combustion of vegetation, or even geogenic carbon such as coal. The wide spectrum of materials currently considered BC makes its quantification challenging. The chemical method using benzene polycarboxylic acids (BPCAs) as markers of condensed aromatic structures indicative of pyrogenic C is highly time, labor and cost intensive, and can generate artifacts. Several research groups are now developing method for the simultaneous identification and quantification of these various forms of soil carbon using thermal analysis techniques such as thermogravimetry, differential scanning calorimetry and evolved gas analysis. The objective of this presentation is to provide a general overview and specific examples of the current progress and technical challenges in this evolving methodology.

  12. Methods development for total organic carbon accountability

    NASA Technical Reports Server (NTRS)

    Benson, Brian L.; Kilgore, Melvin V., Jr.

    1991-01-01

    This report describes the efforts completed during the contract period beginning November 1, 1990 and ending April 30, 1991. Samples of product hygiene and potable water from WRT 3A were supplied by NASA/MSFC prior to contract award on July 24, 1990. Humidity condensate samples were supplied on August 3, 1990. During the course of this contract chemical analyses were performed on these samples to qualitatively determine specific components comprising, the measured organic carbon concentration. In addition, these samples and known standard solutions were used to identify and develop methodology useful to future comprehensive characterization of similar samples. Standard analyses including pH, conductivity, and total organic carbon (TOC) were conducted. Colorimetric and enzyme linked assays for total protein, bile acid, B-hydroxybutyric acid, methylene blue active substances (MBAS), urea nitrogen, ammonia, and glucose were also performed. Gas chromatographic procedures for non-volatile fatty acids and EPA priority pollutants were also performed. Liquid chromatography was used to screen for non-volatile, water soluble compounds not amenable to GC techniques. Methods development efforts were initiated to separate and quantitate certain chemical classes not classically analyzed in water and wastewater samples. These included carbohydrates, organic acids, and amino acids. Finally, efforts were initiated to identify useful concentration techniques to enhance detection limits and recovery of non-volatile, water soluble compounds.

  13. Recovery of iron from zinc leaching residue by selective reduction roasting with carbon.

    PubMed

    Li, Mi; Peng, Bing; Chai, Liyuan; Peng, Ning; Yan, Huan; Hou, Dongke

    2012-10-30

    The recovery of iron from zinc leaching residue by selective reduction roasting with carbon was studied. The effects of roasting temperature, duration time and mass ratio of carbon to residue on decomposition of ZnFe(2)O(4), iron recovery and iron grade were investigated based on thermodynamic calculation and phase composition analysis of zinc leaching residue. 58.6% of iron grade in magnetic concentrate and 68.4% of iron recovery were achieved after the residue roasted at 750°C for 1h under carbon to residue mass ratio of 4%. The phase composition of roasted residue indicated that the ZnFe(2)O(4) decomposed in four stages: reduction of ZnFe(2)O(4) to ZnO and Fe(3)O(4), reduction of Fe(3)O(4) to FeO, formation of Fe(0.85-x)Zn(x)O and reduction of FeO to Fe. A technological process for simultaneously recovering iron and zinc from zinc leaching residue is proposed. PMID:22975260

  14. Computational studies of small carbon and iron-carbon systems relevant to carbon nanotube growth.

    PubMed

    Duan, Haiming; Rosén, Arne; Harutyunyan, Avetik; Curtarolo, Stefano; Bolton, Kim

    2008-11-01

    Density functional theory (DFT) calculations show that dimers and longer carbon strings are more stable than individual atoms on Fe(111) surfaces. It is therefore necessary to consider the formation of these species on the metal surfaces and their effect on the mechanism of single-walled nanotube (SWNT) growth. The good agreement between the trends (energies and structures) obtained using DFT and those based on the Brenner and AIREBO models indicate that these analytic models provide adequate descriptions of the supported carbon systems needed for valid molecular dynamics simulations of SWNT growth. In contrast, the AIREBO model provides a better description of the relative energies for isolated carbon species, and this model is preferred over the Brenner potential when simulating SWNT growth in the absence of metal particles. However, the PM3 semiempirical model appears to provide an even better description for these systems and, given sufficient computer resources, direct dynamics methods based on this model may be preferred. PMID:19198360

  15. Variability of organic and elemental carbon, water soluble organic carbon, and isotopes in Hong Kong

    NASA Astrophysics Data System (ADS)

    Ho, K. F.; Lee, S. C.; Cao, J. J.; Li, Y. S.; Chow, J. C.; Watson, J. G.; Fung, K.

    2006-10-01

    To determine the levels and variations of carbonaceous aerosol in Hong Kong, PM2.5 and PM10 samples were collected by high volume (Hi-vol) samplers at three monitoring stations (representing middle-scale roadside, urban-, and regional-scale environments) during winter (November 2000 to February 2001) and summer (June 2001 to August 2001) periods. The highest concentrations of organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC) were found at the middle-scale roadside site with the lowest at the regional-scale site. The percentages of WSOC in total carbon at these sites were inversely correlated with their concentrations (i.e., the highest percentages of WSOC were observed at the regional-scale site). A high WSOC fraction may be associated with aged aerosol because of the secondary formation by photochemical oxidation of organic precursors of anthropogenic pollutants during transport. The annual average of isotope abundances (δ13C) of OC and EC were -26.9±0.5‰ and -25.6±0.1‰, respectively. There were no notable differences for seasonal distributions of carbon isotopic composition, consistent with motor vehicle emissions being the main source contributors of carbonaceous aerosol in Hong Kong. OC 13C abundances at the regional-scale site were higher than those at the middle-scale roadside and urban sites, consistent with secondary organic aerosols of biogenic origin.

  16. Variability of organic and elemental carbon, water soluble organic carbon, and isotopes in Hong Kong

    NASA Astrophysics Data System (ADS)

    Ho, K. F.; Lee, S. C.; Cao, J. J.; Li, Y. S.; Chow, J. C.; Watson, J. G.; Fung, K.

    2006-06-01

    To determine the levels and variations of carbonaceous aerosol in Hong Kong, PM2.5 and PM10 samples were collected by high volume (Hi-vol) samplers at three monitoring stations (representing middle-scale roadside, urban-, and regional-scale environments) during winter (November 2000 to February 2001) and summer (June 2001 to August 2001) periods. The highest concentrations of organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC) were found at the middle-scale roadside site with the lowest at the regional-scale site. The percentages of WSOC in total carbon at these sites were inversely correlated with their concentrations (i.e., the highest percentages of WSOC were observed at the regional-scale site). A high WSOC fraction may be associated with aged aerosol because of the secondary formation by photochemical oxidation of organic precursors of anthropogenic pollutants during transport. The annual average of isotope abundances (δ13C) of OC and EC were -26.9±0.5 and -25.6±0.1, respectively. There were no notable differences for seasonal distributions of carbon isotopic composition, consistent with motor vehicle emissions being the main source contributors of carbonaceous aerosol in Hong Kong. OC 13C abundances at the regional-scale site were higher than those at the middle-scale roadside and urban sites, consistent with secondary organic aerosols of biogenic origin.

  17. Nitrogen-doped carbon-supported cobalt-iron oxygen reduction catalyst

    DOEpatents

    Zelenay, Piotr; Wu, Gang

    2014-04-29

    A Fe--Co hybrid catalyst for oxygen reaction reduction was prepared by a two part process. The first part involves reacting an ethyleneamine with a cobalt-containing precursor to form a cobalt-containing complex, combining the cobalt-containing complex with an electroconductive carbon supporting material, heating the cobalt-containing complex and carbon supporting material under conditions suitable to convert the cobalt-containing complex and carbon supporting material into a cobalt-containing catalyst support. The second part of the process involves polymerizing an aniline in the presence of said cobalt-containing catalyst support and an iron-containing compound under conditions suitable to form a supported, cobalt-containing, iron-bound polyaniline species, and subjecting said supported, cobalt-containing, iron bound polyaniline species to conditions suitable for producing a Fe--Co hybrid catalyst.

  18. Energy of interaction between carbon impurities in paramagnetic γ-iron

    SciTech Connect

    Ponomareva, A. V.; Gornostyrev, Yu. N.; Abrikosov, I. A.

    2015-04-15

    The energies of interaction between carbon impurity atoms in paramagnetic fcc iron (austenite) are calculated using electron density functional theory. Point defects in the paramagnetic matrix are described using a statistical approach that takes into account local magnetic fluctuations and atomic relaxation in the environment of impurity atoms. It is shown that, in addition to local deformations, magnetism significantly contributes to the energies of dissolution and interaction of carbon atoms. The values of the carbon-carbon interaction energy are indicative of a significant repulsion between these atoms in the first and second coordination spheres. The results of calculations are consistent with estimates obtained from experimental data on the activity of carbon impurity atoms in iron.

  19. Transport of carbon colloid supported nanoscale zero-valent iron in saturated porous media

    NASA Astrophysics Data System (ADS)

    Busch, Jan; Meißner, Tobias; Potthoff, Annegret; Oswald, Sascha E.

    2014-08-01

    Injection of nanoscale zero-valent iron (nZVI) has recently gained great interest as emerging technology for in-situ remediation of chlorinated organic compounds from groundwater systems. Zero-valent iron (ZVI) is able to reduce organic compounds and to render it to less harmful substances. The use of nanoscale particles instead of granular or microscale particles can increase dechlorination rates by orders of magnitude due to its high surface area. However, classical nZVI appears to be hampered in its environmental application by its limited mobility. One approach is colloid supported transport of nZVI, where the nZVI gets transported by a mobile colloid. In this study transport properties of activated carbon colloid supported nZVI (c-nZVI; d50 = 2.4 μm) are investigated in column tests using columns of 40 cm length, which were filled with porous media. A suspension was pumped through the column under different physicochemical conditions (addition of a polyanionic stabilizer and changes in pH and ionic strength). Highest observed breakthrough was 62% of the injected concentration in glass beads with addition of stabilizer. Addition of mono- and bivalent salt, e.g. more than 0.5 mM/L CaCl2, can decrease mobility and changes in pH to values below six can inhibit mobility at all. Measurements of colloid sizes and zeta potentials show changes in the mean particle size by a factor of ten and an increase of zeta potential from - 62 mV to - 80 mV during the transport experiment. However, results suggest potential applicability of c-nZVI under field conditions.

  20. The Speciation of Particulate Iron and Carbon in the East Pacific Rise 15oS Near-field Hydrothermal Plume and Underlying Sediments

    NASA Astrophysics Data System (ADS)

    Toner, B. M.; Lam, P. J.; Nicholas, S. L.; Ohnemus, D.; Hoffman, C. L.; Fitzsimmons, J. N.; Sherrell, R. M.; German, C. R.

    2014-12-01

    Particulate iron and carbon speciation were measured for water column and sediment samples collected at the East Pacific Rise ridge axis (15oS; Station 18) and approximately 80 km down-current (Station 20) during the US GEOTRACES Eastern Pacific Zonal Transect cruise. Water column particles were collected by in situ filtration (0.2 micron, polycarbonate) from above, within, and below the hydrothermal plume. Water column samples were handled in an anaerobic chamber and stored frozen under inert gas shipboard, and protected from ambient oxygen during analysis. The flocculant, top-layer of the sediments was sampled shipboard under ambient conditions and stored frozen until analysis. Iron and carbon speciation were measured using X-ray microprobe (10.3.2) and scanning transmission X-ray microscopy (STXM) instruments at the Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, USA. Iron (1s and 2p) and carbon (1s) X-ray absorption near edge structure (XANES) spectroscopy and imaging for particles revealed that: (1) in comparison to the above plume sample, organic carbon is abundant in particles within and below the plume, as well as in surface sediments; (2) iron sulfides are not detectable in any water column sample investigated so far; (3) the fraction of non-sulfide reduced iron is highest in the below plume samples; and (4) the below plume sample is rich in free-living microbial cells.

  1. Cu Binding to Iron Oxide-Organic Matter Coprecipitates in Solid and Dissolved Phases

    NASA Astrophysics Data System (ADS)

    Vadas, T. M.; Koenigsmark, F.

    2015-12-01

    Recent studies indicate that Cu is released from wetlands following storm events. Assymetrical field flow field fractionation (AF4) analyses as well as total and dissolved metal concentration measurements suggest iron oxide-organic matter complexes control Cu retention and release. Coprecipitation products of Fe oxide and organic matter were prepared under conditions similar to the wetland to assess Cu partitioning to and availability from solid phases that settle from solution as well as phases remaining suspended. Cu coprecipitation and sorption to organomineral precipitation solids formed at different Fe:organic carbon (OC) ratios were compared for net Cu removal and extractability. As more humic acid was present during precipitation of Fe, TEM images indicated smaller Fe oxide particles formed within an organic matrix as expected. In coprecipitation reactions, as the ratio of Fe:OC decreased, more Cu was removed from solution at pH 5.5 and below. However, in sorption reactions, there was an inhibition of Cu removal at low OC concentrations. As the pH increased from 5.5 to 7 and as solution phase OC concentration increased, more Cu remained dissolved in both coprecipitation and sorption reactions. The addition of Ca2+, glycine, histidine and citric acid or lowering the pH resulted in more extractable Cu from the coprecipitation compared with the sorption reactions. The variations in Cu extraction were likely due to a combination of a more amorphous structure in CPT products, and the relative abundance of available Fe oxide or OC binding sites. Suspended Fe oxide-organic matter coprecipitates were assessed using AF4 coupled to online TOC analysis and ICP-MS. In laboratory prepared samples, Cu was observed in a mixture of small 1-5 nm colloids of Fe oxide-organic matter precipitates, but the majority was observed in larger organic matter colloids and were not UV absorbing, suggesting more aliphatic carbon materials. In field samples, up to 60% of the dissolved Cu

  2. High rates of organic carbon burial in fjord sediments globally

    NASA Astrophysics Data System (ADS)

    Smith, Richard W.; Bianchi, Thomas S.; Allison, Mead; Savage, Candida; Galy, Valier

    2015-06-01

    The deposition and long-term burial of organic carbon in marine sediments has played a key role in controlling atmospheric O2 and CO2 concentrations over the past 500 million years. Marine carbon burial represents the dominant natural mechanism of long-term organic carbon sequestration. Fjords--deep, glacially carved estuaries at high latitudes--have been hypothesized to be hotspots of organic carbon burial, because they receive high rates of organic material fluxes from the watershed. Here we compile organic carbon concentrations from 573 fjord surface sediment samples and 124 sediment cores from nearly all fjord systems globally. We use sediment organic carbon content and sediment delivery rates to calculate rates of organic carbon burial in fjord systems across the globe. We estimate that about 18 Mt of organic carbon are buried in fjord sediments each year, equivalent to 11% of annual marine carbon burial globally. Per unit area, fjord organic carbon burial rates are one hundred times as large as the global ocean average, and fjord sediments contain twice as much organic carbon as biogenous sediments underlying the upwelling regions of the ocean. We conclude that fjords may play an important role in climate regulation on glacial-interglacial timescales.

  3. Carbon- and Nitrogen-Based Organic Frameworks.

    PubMed

    Sakaushi, Ken; Antonietti, Markus

    2015-06-16

    This Account provides an overview of organic, covalent, porous frameworks and solid-state materials mainly composed of the elements carbon and nitrogen. The structures under consideration are rather diverse and cover a wide spectrum. This Account will summarize current works on the synthetic concepts leading toward those systems and cover the application side where emphasis is set on the exploration of those systems as candidates for unusual high-performance catalysis, electrocatalysis, electrochemical energy storage, and artificial photosynthesis. These issues are motivated by the new global energy cycles and the fact that sustainable technologies should not be based on rare and expensive resources. We therefore present the strategic design of functionality in cost-effective, affordable artificial materials starting from a spectrum of simple synthetic options to end up with carbon- and nitrogen-based porous frameworks. Following the synthetic strategies, we demonstrate how the electronic structure of polymeric frameworks can be tuned and how this can modify property profiles in a very unexpected fashion. Covalent triazine-based frameworks (CTFs), for instance, showed both enormously high energy and high power density in lithium and sodium battery systems. Other C,N-based organic frameworks, such as triazine-based graphitic carbon nitride, are suggested to show promising band gaps for many (photo)electrochemical reactions. Nitrogen-rich carbonaceous frameworks, which are developed from C,N-based organic framework strategies, are highlighted in order to address their promising electrocatalytic properties, such as in the hydrogen evolution reaction, oxygen reduction reaction (ORR), and oxygen evolution reaction (OER). With careful design, those materials can be multifunctional catalysts, such as a bifunctional ORR/OER electrocatalyst. Although the majority of new C,N-based materials are still not competitive with the best (usually nonsustainable candidates) for each

  4. Relative contribution of iron reduction to sediments organic matter mineralization in contrasting habitats of a shallow eutrophic freshwater lake.

    PubMed

    Chen, Mo; Jiang, He-Long

    2016-06-01

    Iron reduction is one of the important organic matter (OM) mineralization pathway in sediments. Here we investigated the rates and the relative contribution of iron reduction to OM mineralization in Zhushan bay (ZSB, cyanobacterial bloom biomass (CBB)-dominated habitats) and East Taihu Lake (ETL, submerged macrophypes (SM)-dominated habitats) of Lake Taihu, China. Anaerobic microcosm incubation revealed that the rate of iron reduction at ZSB (4.42 μmol cm(-3) d(-1)) in summer was almost 1.5 times higher than at ETL (3.13 μmol cm(-3) d(-1)). Iron reduction accounted for 66.5% (ZSB) and 31.8% (ETL) of total anaerobic carbon mineralization, respectively. No detectable methanogenesis was found at ZSB, while methanogenesis was responsible for 16.7% of total anaerobic respiration in sediments of ETL. Geochemical analysis of solid phase constituents indicated that ZSB surface sediments experienced highly oxidizing conditions with much higher amorphous Fe(III) (71 mmol m(-2)) than ETL (11 mmol m(-2)). Conversely, AVS inventories at ETL (38 mmol m(-2)) were up to 30 times higher than at ZSB (1.27 mmol m(-2)), indicating significant sulfate reduction in sediments of ETL. Overall results suggested that varying carbon sources and distinct geochemical characterizations of the sediments in contrasting habitats significantly influenced the rate of iron reduction and the pathway of C mineralization in a large freshwater lake. PMID:27038578

  5. Understanding drivers of the export of dissolved organic carbon from a German headwater catchment using Generalised Additive Models

    NASA Astrophysics Data System (ADS)

    Selle, Benny; Musolff, Andreas; Tittel, Jörg

    2016-04-01

    In the literature, several causes of recently increasing concentrations of dissolved organic carbon (DOC) in headwaters across eastern North America and northern and central Europe have been debated. One likely driver of the widespread increase of DOC concentrations since the early 1990s are decreasing depositions of acid rain resulting in an increased solubility of organic carbon compounds including humic acids. Here, we tested the hypothesis if the reduced availability of nitrate stimulated the microbial reduction of ferric iron soil minerals and the mobilisation of DOC. Forested catchments are relatively unaffected by agricultural and urban nitrate inputs. In these catchments, decreasing depositions often resulted in a reduced availability of nitrate, which are preferred electron acceptors in microbial decomposition processes. As ferric iron minerals act as efficient sorbents of organic compounds in soils its reduction may cause a release of humic substances and hence an export of DOC. To test this hypothesis, time series of DOC, dissolved iron and nitrate from a forested headwater catchment in Germany were examined using Generalised Additive Models. We found that rising DOC concentrations most likely resulted from a reductive dissolution of iron(III) minerals in soils and the associated mobilisation of adsorbed organic carbon. Phosphate, which can trigger undesired algal growth and is also known to be adsorbed by particulate iron(III), was released as well.

  6. Storage of Organic and Inorganic Carbon in Human Settlements

    NASA Astrophysics Data System (ADS)

    Churkina, G.

    2009-12-01

    It has been shown that urban areas have carbon density comparable with tropical forest. Carbon density of urban areas may be even higher, because the density of organic carbon only was taking into account. Human settlements store carbon in two forms such as organic and inorganic. Carbon is stored in organic form in living biomass such as trees, grasses or in artifacts derived from biomass such as wooden furniture, building structures, paper, clothes and shoes made from natural materials. Inorganic carbon or fossil carbon, meanwhile, is primarily stored in objects fabricated by people like concrete, plastic, asphalt, and bricks. The key difference between organic and inorganic forms of carbon is how they return to the gaseous state. Organic carbon can be returned to the atmosphere without applying additional artificial energy through decomposition of organic matter, whereas energy input such as burning is needed to release inorganic carbon. In this study I compare inorganic with organic carbon storage, discuss their carbon residence time, decomposition rates, and possible implications for carbon emissions.

  7. OCoc- from Ocean Colour to Organic Carbon

    NASA Astrophysics Data System (ADS)

    Heim, B.; Overduin, P. P.; Schirrmeister, L.; Lantuit, H.; Doerffer, R.

    2009-12-01

    Enhanced permafrost warming and increased arctic river discharges have heightened concern about the input of terrigenous matter into Arctic coastal waters. The ‘OCoc-from Ocean Colour to Organic Carbon’ project (IPY-project 1176), funded by the German Research Foundation (DFG), is an Ocean Colour study joined with the Arctic Coastal Dynamics ACD network and Arctic Circum-polar Coastal Observatory Network ACCO-Net (IPY-project 90). OCoc uses Ocean Colour satellite data for synoptical monitoring of organic matter fluxes from fluvial and coastal sources. Initial results from German-Russian expeditions at the southeastern Laptev Sea Coast (Arctic Siberia, Russia) in August 2008 and August 2009 are presented. Large parts of this coastal zone are characterized by highly erosive organic-rich material. Ocean Colour MERIS Reduced Resolution (RR)-LIB data of the have been processed towards optical aquatic parameters using Beam-Visat4.2 and the MERIS case2 regional processor for coastal application (C2R). Calculated aquatic parameters are absorption and backscattering coefficients, apparent optical properties such as the first attenuation depth (‘Z90’) and calculated concentrations of chlorophyll, total suspended matter and coloured dissolved organic matter absorption from the water leaving reflectances. Initial comparisons with expedition data (Secchi depths, cDOM) show that the MERIS-C2R optical parameters ’total absorption’ and the first attenuation depth, ’Z90’, seem adequately to represent true conditions. High attenuation values in the spectral blue wavelength range may serve as tracer for the organic-rich terrigenous input. The synoptic information of Ocean Colour products will provide valuable spatial and dynamical information on the Organic Carbon and sediment fluxes from the Siberian permafrost coast.

  8. The catalytic activity of the iron-coated pumice particles used as heterogeneous catalysts in the oxidation of natural organic matter by H2O2.

    PubMed

    Alver, Alper; Karaarslan, Mihrican; Kılıç, Ahmet

    2016-08-01

    The oxidative removal of natural organic matter (NOM) from waters was investigated by hydrogen peroxide (H2O2) and iron-coated pumice particles in heterogeneous catalytic oxidation process (HCOP). Removal of trihalomethane (THM) precursors, which is formed THM by the reacts with chloride, was performed with the hydroxyl radicals. Coating the original pumice particles with iron oxides significantly enhanced the removal of NOM with peroxide. The studies were carried out in two sections: (1) decomposition of hydrogen peroxide in pure water with iron-coated pumice and (2) oxidation of THM Precursor (NOM) by hydrogen peroxide with iron-coated pumice. The monitored parameters in this study include dissolved organic carbon and trihalomethanes formation potential. The results show that iron-coated pumice catalyst significantly increased the removal efficiency of NOM in the HCOP. The results show that iron-coated pumice catalyst significantly increased the removal efficiency of NOM in the HCOP. Results show that the oxidation of NOM and remaining NOM with H2O2 is improved by the addition of iron-coated pumice particles which activate the H2O2 molecule, leading to the formation of hydroxyl radicals in a Fenton-like process. PMID:26881482

  9. Fate of Organic Micropollutants during Hydrothermal Carbonization

    NASA Astrophysics Data System (ADS)

    Weiner, B.; Baskyr, I.; Pörschmann, J.; Kopinke, F.-D.

    2012-04-01

    The hydrothermal carbonization (HTC) is an exothermic process, in which biomass in an aqueous suspension is transformed into a bituminous coal-like material (hydrochar) at temperatures between 180-250°C and under moderate pressure. With these process conditions, little gas is generated (1-5%), and a fraction of the organic carbon is dissolved in the aqueous phase (10-30%) but the largest part is obtained as solid char. The respective yields and the molecular composition depend on the choice of educts and the process conditions, such as temperature, pH-value, and reaction time. Various biomass-educts have recently been studied, such as waste materials from agriculture, brewer's spent grains, sewage sludge, as well as wood and paper materials. Besides their use for energy generation, the hydrochars have also been investigated as soil amendments. Prior to addition of the chars to soil, these should be free of toxic components that could be released into the environment as harmful organic pollutants. Herein, the potential for the degradation of trace organic pollutants, such as pesticides and pharmaceuticals, under typical HTC conditions will be presented. The degradation of selected organic pollutants with different polarity and hydrophobicity was investigated. Scope and limitations of the degradation potential of the HTC are discussed on examples of micro pollutants such as hormones, residues of pharmaceuticals and personal care products including their metabolites, and pesticides. We will show that the target analytes are partially and in some cases completely degraded. The degree of degradation depends on the HTC process conditions such as reaction temperature and time, the solution pH value, the presence of catalysts or additional reagents. The biotic and abiotic degradation of chlorinated organic compounds, in particular chlorinated aromatics, has been a well-known environmental problem and remains a challenging issue for the development of a HTC process for

  10. Dissolved organic carbon in rainwater: Glassware decontamination and sample preservation and volatile organic carbon

    NASA Astrophysics Data System (ADS)

    Campos, M. L. A. M.; Nogueira, R. F. P.; Dametto, P. R.; Francisco, J. G.; Coelho, C. H.

    The efficiency of different methods for the decontamination of glassware used for the analysis of dissolved organic carbon (DOC) was tested using reported procedures as well as new ones proposed in this work. A Fenton solution bath (1.0 mmol L -1 Fe 2+ and 100 mmol L -1 H 2O 2) for 1 h or for 30 min employing UV irradiation showed to combine simplicity, low cost and high efficiency. Using the optimized cleaning procedure, the DOC for stored UV-irradiated ultra-pure water reached concentrations below the limit of detection (0.19 μmol C L -1). Filtered (0.7 μm) rain samples maintained the DOC integrity for at least 7 days when stored at 4 °C. The volatile organic carbon (VOC) fraction in the rain samples collected at two sites in São Paulo state (Brazil) ranged from 0% to 56% of their total DOC content. Although these high-VOC concentrations may be derived from the large use of ethanol fuel in Brazil, our results showed that when using the high-temperature catalytic oxidation technique, it is essential to measure DOC rather than non-purgeble organic carbon to estimate organic carbon, since rainwater composition can be quite variable, both geographically and temporally.

  11. Organic carbon-14 in the Amazon River system

    SciTech Connect

    Hedges, J.I.; Ertel, J.R.; Quay, P.D.; Grootes, P.M.; Richey, J.E.; Devol, A.H.; Farwell, G.W.; Schmidt, F.W.; Salati, E.

    1986-03-07

    Coarse and fine suspended particulate organic materials and dissolved humic and fulvic acids transported by the Amazon River all contain bomb-produced carbon-14, indicating relatively rapid turnover of the parent carbon pools. However, the carbon-14 contents of these coexisting carbon forms are measurably different and may reflect varying degrees of retention by soils in the drainage basin. 20 references, 1 table.

  12. Oxygen, carbon, and sulfur segregation in annealed and unannealed zerovalent iron substrates.

    PubMed

    Papastavros, Efthimia; Shea, Patrick J; Langell, Marjorie A

    2004-12-21

    Finely ground and pretreated iron substrates known as "zerovalent iron" or "Fe0" are used as reductants in the environmental remediation of halogenated hydrocarbons, and the composition of their surfaces significantly affects their reactivity. Samples of unannealed and annealed (heat-treated under H2/N2) zerovalent iron were analyzed using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Surface concentration of the iron and of the impurities observed by XPS and AES, carbon, chlorine, sulfur, and oxygen, were measured before and after soaking in trichloroethylene (TCE) and in water saturated with TCE (H2O/TCE) to simulate chlorocarbon remediation conditions. Samples pretreated by annealing at high temperature under H2 contained less iron carbide. The carbide contaminant was evident in both iron and carbon XPS spectra, with binding energies of 709.0 and 283.3 eV for the Fe 2p3/2 and C 1s, respectively. The annealed Fe0 surface also contained more sulfur. The carbide concentration was essentially unchanged by TCE and H2O/TCE exposure, whereas the sulfur decreased in proportion to chlorine adsorption following the dechlorination reaction. While oxygen concentration is initially lower on the annealed substrate surface, it rapidly increased during the model TCE remediative treatment process and thus does not represent a significant effect of the annealing process on surface reactivity. PMID:15595777

  13. Understanding and assessing the feasibility of ocean iron fertilization to reduce atmospheric carbon dioxide

    NASA Astrophysics Data System (ADS)

    Buesseler, K.; Lampitt, R. S.; de Baar, H. J.; Blain, S.; Chai, F.; Coale, K. H.; Dai, M.; Karl, D. M.; Leinen, M.; Lohan, M. C.; Rothstein, L.; Trull, T. W.; Whaley, D.; Wuebbles, D. J.; Zhou, M.

    2011-12-01

    Regardless of the strategy for fossil fuel use, atmospheric CO2 is predicted to increase and then decrease such that after 10,000 years, levels will still be much higher than pre-industrial. The objectives of geoengineering CO2 reduction techniques are to reduce the rate of CO2 increase and the height of the CO2 peak. Because the oceans represent such a large reservoir of carbon, small perturbations of the system could cause large changes to carbon flows. The objective of ocean carbon sequestration would be to encourage the oceans to take up carbon at a faster rate than they currently do but with predictable and acceptable consequences. From iron addition experiments in the laboratory and in the open ocean and from studies where there are natural additions of iron to the ocean several conclusions can be drawn. Relief of iron stress increases the biomass of marine phytoplankton and as a consequence reduces surface water CO2. This leads to increased export of carbon from the upper ocean and probably enhanced sequestration in the deep ocean. However, the experiments were not planned from the perspective of geoengineering and conclusions about the potential of this approach as a means of reducing atmospheric CO2 have large uncertainties. In addition, few experiments have addressed the unintended consequences of deliberate additions. This has been a major focus of recent discussion of a risk assessment framework for experimentation by the London Convention and London Protocol. Given the uncertainties, there is an urgent requirement to carry out more studies on ocean iron fertilization with three clear objectives 1: To develop coupled global scale computation models so that predictions can become more reliable and so that in situ experiments are effective. 2: To carry out experiments on a sufficiently large scale and duration to determine the extent, efficiencies and time scales of carbon sequestration. 3: To explore the consequences of ocean iron fertilization, and not

  14. Melting Behavior and Chemical Properties of the Iron-Carbon System

    NASA Astrophysics Data System (ADS)

    Prakapenka, V.; Kantor, I.; Kubo, A.; Kuznetsov, A.; Dera, P.; Rivers, M.; Sutton, S.

    2008-12-01

    One of the most challenging experiments related to the laser heating technique in the diamond anvil cell (DAC) is an unambiguous x-ray based detection of melting by recording high quality diffuse x-ray scattering from molten materials at high pressure. Employing a newly developed, advanced, flat top laser heating system at GSECARS, we were able to perform on-line melting experiments at pressures up to 60 GPa. The capability to maintain the molten sample in the DAC for a relatively long time (at least 60 s) allowed us to collect high quality x-ray scattering data suitable for structure analysis even from low-Z molten materials, such as Si, Ge, Fe, Fe3C, Fe7C3 etc. In this work, we focused on the melting behavior and chemical properties of the iron-carbon system at pressures up to ~170 GPa studied with on-line micro x-ray diffraction in a double sided laser heated DAC at GSECARS (Sector 13, APS). Iron carbides (Fe3C, Fe7C3) were synthesized in- situ in the DAC from various mixtures of Fe and C powders with different atomic ratios. We have found that the chemical reaction between iron and carbon takes place independent of the structure of starting phases of iron (fcc or hcp) and carbon (graphite or diamond). The reaction temperature increased gradually from ~1000 K to ~1700 K as pressure increased from 6 GPa to 155 GPa. The melting temperature of iron carbide was found to be systematically lower than for iron by ~300-400 degrees in the pressure range 20-60 GPa. The experimentally measured structure factor and related pair distribution function of iron carbide melt were analyzed and compared with pure iron data at related pressures. High- pressure, high-temperature stability of iron carbide phases at the relevant Earth's mantle-core conditions and physical/chemical properties of iron-carbon melts provide important constraints on models of the formation of D" layer and interactions at the core mantle boundary. Implications of these results for the composition and

  15. Ocean iron cycle

    NASA Astrophysics Data System (ADS)

    Boyd, Philip W.

    Interest in the biogeochemical cycle of iron has grown rapidly over the last two decades, due to the potential role of this element in modulating global climate in the geological past and ocean productivity in the present day. This trace metal has a disproportionately large effect (1 × 105 C:Fe) on photosynthetic carbon fixation by phytoplankton. In around one third of the open ocean, so-called high-nitrate low-chlorophyll (HNLC) regions, the resident phytoplankton have low growth rates despite an abundance of plant nutrients. This is due to the low supply of iron. Iron is present in the ocean in three phases, dissolved, colloidal, and particulate (biogenic and lithogenic). However, iron chemistry is complex with interactions between chemistry and biology such as the production of iron-binding siderophores by oceanic bacteria. This results in the interplay of inorganic chemistry, photochemistry, and organic complexation. Sources of new iron include dust deposition, upwelling of iron-rich deep waters, and the resuspension and lateral transport of sediments. Sinks for iron are mainly biological as evidenced by the vertical nutrient-like profile for dissolved iron in the ocean. Iron is rapidly recycled by the upper ocean biota within a so-called "ferrous wheel." The fe ratio [(new iron)/(new + regenerated iron)] provides an index of the relative supply of iron to the biota by new versus recycled iron. Over the last 15 years, interest in the potential role of iron in shaping climate in the geological past resulted in some of the most ambitious experiments in oceanography: large-scale (i.e., 50-1000 km2) iron enrichment of HNLC waters. They have provided valuable insights into how iron supply influences the biogeochemical cycles of elements such as carbon, sulfur, silicon, nitrogen, and phosphate.

  16. Effect of carbon on stress corrosion cracking and anodic oxidation of iron in NaOH solutions

    SciTech Connect

    Flis, J.; Ziomek-Moroz, Margaret

    2008-06-01

    Anodic behaviour of decarburised iron and of quenched Fe–C materials with up to 0.875 wt% C was examined in 8.5 M NaOH at 100 °C to explain the role of carbon in caustic stress corrosion cracking (SCC) of plain steels. Removal of carbon from Armco iron strongly reduced its intergranular SCC. Slip steps on grains did not initiate cracks. It has been shown that carbon at low contents deteriorates the passivation of iron, whereas at high contents it promotes the formation of magnetite. High resistance to SCC of high carbon steels can be explained by an intense formation of magnetite on these steels.

  17. Carbon supported Nano-Iron for environmental remediation: Transport observations using column tests, magnet resonance imaging and synchrotron tomography.

    NASA Astrophysics Data System (ADS)

    Busch, J.; Oswald, S. E.; Mackenzie, K.

    2012-04-01

    The use of nano-zerovalent iron (nZVI) for environmental remediation is a promising new technique for in situ remediation of contaminated groundwater. Due to its high surface area and high reactivity, nZVI is able to dechlorinate organic contaminants and render them harmless. Limited mobility, however, due to fast aggregation and sedimentation of nZVI, restricts the practical applicability for source and plume remediation. Carbo-Iron is a newly developed composite material consisting of activated carbon particles (d50 about 500 nm) that act as carrier for nZVI particles. Together with a polyanionic stabilizer (CMC) Carbo-Iron is able to form a stable injectable suspension. These particles are designed to combine the mobility of activated carbon and the reactivity of nZVI. Various methods were used to observe and describe transport properties, with a focus on column tests and tomographic methods: Column tests were performed in chromatography columns of 40 and 60 cm length, filled with sand grains or glass beads. Results indicate high mobility and breakthrough after addition of CMC, but changing transport properties at different pH and ionic strength. Magnet Resonance Imaging (MRI) and Synchrotron Imaging are technologies of growing interest in observing flow and transport in porous media. Even though both methods are based on different physical principles, both are sensible to iron loads in colloids and allow two- and three-dimensional reconstruction and visualization. Therefore both methods may principally be suitable for observing Carbo-Iron in porous media and might give information complementary to other experimental investigations. A suitable MRI method was developed using a medical MRI. The method based on T1 weighted measurement with short repetition time (TR = 7.0 ms) and echo time (TE = 2.95 ms) can detect different particle concentrations in a porous medium. The synchrotron tomography method used an energy rich (13 keV) parallel X-ray beam to collect

  18. A method for quantifying bioavailable organic carbon in aquifer sediments

    USGS Publications Warehouse

    Rectanus, H.V.; Widdowson, M.; Novak, J.; Chapelle, F.

    2005-01-01

    The fact that naturally occurring microorganisms can biodegrade PCE and TCE allows the use of monitored natural attenuation (MNA) as a remediation strategy at chlorinated solvent-contaminated sites. Research at numerous chlorinated solvent sites indicates an active dechlorinating microbial population coupled with an ample supply of organic carbon are conditions needed to sustain reductive dechlorination. A series of extraction experiments was used to compare the ability of the different extractants to remove organic carbon from aquifer sediments. The different extractants included pyrophosphate, sodium hydroxide, and polished water. Pyrophosphate served as a mild extractant that minimally alters the organic structure of the extracted material. Three concentrations (0.1, 0.5, and 1%) of pyrophosphate extracted 18.8, 24.9, and 30.8% of sediment organic carbon, respectively. Under alkali conditions (0.5 N NaOH), which provided the harshest extractant, 30.7% of the sediment organic carbon was recovered. Amorphous organic carbon, measured by potassium persulfate oxidization, consisted of 44.6% of the sediment organic carbon and served as a baseline control for maximum carbon removal. Conversely, highly purified water provided a minimal extraction control and extracted 5.7% of the sediment organic carbon. The removal of organic carbon was quantified by aqueous TOC in the extract and residual sediment organic carbon content. Characterization of the organic carbon extracts by compositional analysis prior and after exposure to the mixed culture might indicate the type organic carbon and functional groups used and/or generated by the organisms. This is an abstract of a paper presented at the 8th International In Situ and On-Site Bioremediation Symposium (Baltimore, MD 6/6-9/2005).

  19. Evidence for 13-carbon enrichment in oxalic acid via iron catalyzed photolysis in aqueous phase

    NASA Astrophysics Data System (ADS)

    Pavuluri, Chandra Mouli; Kawamura, Kimitaka

    2012-02-01

    To investigate the effect of photochemical aging on the stable carbon isotopic ratio (δ13C) of oxalic acid (OxA), a dominant organic species in atmospheric aerosols, we conducted a laboratory photolysis of OxA under H2O2-Fe3+(Fe2+)-UV system in aqueous phase and measured δ13C of remaining OxA. Our results showed that a significant photolysis of OxA occurred with OH radical but the isotopic fractionation of OxA was insignificant. In contrast, in the presence of Fe3+ (Fe2+), we found a significant enrichment of 13C in remaining OxA. We also found that kinetic isotope effect (KIE) of OxA largely depends on photochemical age (irradiation time) and concentration ratios of OxA to iron; 3.20 ± 0.49‰ (2.18 ± 1.18‰) and 21.62 ± 5.41‰ in 90 min and 180 min irradiation, in which OxA and Fe3+ (Fe2+) ratios were 50:1 and 200:1, respectively. The enrichment of 13C in remaining OxA was more significant during the photolysis catalyzed by Fe3+ (7‰) than by Fe2+ (3‰) in 90 min irradiation when OxA and iron ratios are the same (50:1). This study provides a laboratory evidence for the isotopic enrichment of 13C in OxA with photochemical aging. This approach is useful for better interpretation of atmospheric isotopic measurements in terms of the extent of atmospheric processing of aerosols.

  20. Effects of calcium carbonate and hydroxyapatite on zinc and iron retention in postmenopausal women

    SciTech Connect

    Dawson-Hughes, B.; Seligson, F.H.; Hughes, V.A.

    1986-07-01

    We measured the effect of calcium carbonate and hydroxyapatite on whole-body retention of zinc-65 in 11 and iron-59 in 13 healthy, postmenopausal women. In a single-blind, controlled, crossover study, each subject, on three occasions, ingested a standard test meal supplemented with iron-59 or zinc-65 and capsules containing placebo or 500 mg elemental calcium as calcium carbonate or hydroxyapatite. Whole-body countings were performed prior to, 30 min after, and 2 wk after each meal. Mean (SEM) zinc retention was 18.1 +/- 1.0% with placebo (control) and did not vary significantly with calcium carbonate (110.0 +/- 8.6% of control) or hydroxyapatite (106.0 +/- 7.9% of control). Iron retention, 6.3 +/- 2.0% with placebo, was significantly reduced with both calcium carbonate (43.3 +/- 8.8% of control, p = 0.002) and hydroxyapatite (45.9 +/- 10.0% of control, p = 0.003). Iron absorption may be significantly reduced when calcium supplements are taken with meals.

  1. Iron Amendment and Fenton Oxidation of MTBE-Spent Granular Activated Carbon

    EPA Science Inventory

    Fenton-driven regeneration of Methyl tert-butyl ether (MTBE)-spent granular activated carbon (GAC) involves Fe amendment to the GAC to catalyze H2O2 reactions and to enhance the rate of MTBE oxidation and GAC regeneration. Four forms of iron (ferric sulfate, ferric chloride, fer...

  2. Oxygen and carbon isotope geochemistry of the Krivoy rog iron formation, Ukranian SSR

    NASA Astrophysics Data System (ADS)

    Perry, E. C.; Ahmad, S. N.

    1981-04-01

    Oxygen and carbon isotope analyses of samples from three mines in the Krivoy Rog iron formation, Ukranian SSR, are reported here. Maximum and minimum quartz-magnetite fractionation values ( Δ QM) and inferred temperature range in degrees centrigrade for each mine are:

  3. Computer simulation of cascade damage in -iron with carbon in solution

    SciTech Connect

    Calder, Andrew F; Bacon, David J; Barashev, Aleksandr; Osetsky, Nickolai

    2008-01-01

    Computer simulation of cascade damage in -iron with carbon in solution Original Research Article Journal of Nuclear Materials, Volume 382, Issues 2 3, 1 December 2008, Pages 91-95 Andrew F. Calder, David J. Bacon, Alexander V. Barashev, Yuri N. Osetsky

  4. Cobalt and iron oxides dispersed onto activated carbons: The size effect

    NASA Astrophysics Data System (ADS)

    Pankina, G. V.; Chernavskii, P. A.; Kazak, V. O.; Lunin, V. V.

    2015-06-01

    The effect the nature of activated carbons prepared from natural renewable resources has on the metal particle size in cobalt- and iron-containing systems that can be used as catalysts in Fischer-Tropsch synthesis (FTS) is studied. The highest dispersity is observed for the Co3O4-WS (wood sawdust) system. The average particle size is 9.5 nm.

  5. Reduction of iron-oxide-carbon composites: part I. Estimation of the rate constants

    SciTech Connect

    Halder, S.; Fruehan, R.J.

    2008-12-15

    A new ironmaking concept using iron-oxide-carbon composite pellets has been proposed, which involves the combination of a rotary hearth furnace (RHF) and an iron bath smelter. This part of the research focuses on studying the two primary chemical kinetic steps. Efforts have been made to experimentally measure the kinetics of the carbon gasification by CO{sub 2} and wustite reduction by CO by isolating them from the influence of heat- and mass-transport steps. A combined reaction model was used to interpret the experimental data and determine the rate constants. Results showed that the reduction is likely to be influenced by the chemical kinetics of both carbon oxidation and wustite reduction at the temperatures of interest. Devolatilized wood-charcoal was observed to be a far more reactive form of carbon in comparison to coal-char. Sintering of the iron-oxide at the high temperatures of interest was found to exert a considerable influence on the reactivity of wustite by virtue of altering the internal pore surface area available for the reaction. Sintering was found to be predominant for highly porous oxides and less of an influence on the denser ores. It was found using an indirect measurement technique that the rate constants for wustite reduction were higher for the porous iron-oxide than dense hematite ore at higher temperatures (> 1423 K). Such an indirect mode of measurement was used to minimize the influence of sintering of the porous oxide at these temperatures.

  6. Soil Organic Carbon Degradation, Barrow, 2013-2014

    DOE Data Explorer

    Gu, Baohua; Yang, Ziming

    2015-03-30

    This dataset provides information about soil organic carbon decomposition in Barrow soil incubation studies. The soil cores were collected from low-center polygon (Area A) and were incubated in the laboratory at different temperatures for up to 60 days. Transformations of soil organic carbon were characterized by UV and FT-IR, and small organic acids in water-soluble carbons were quantified by ion chromatography during the incubation

  7. Removal of 2-ClBP from soil-water system using activated carbon supported nanoscale zerovalent iron.

    PubMed

    Zhang, Wei; Yu, Tian; Han, Xiaolin; Ying, Weichi

    2016-09-01

    We explored the feasibility and removal mechanism of removing 2-chlorobiphenyl (2-ClBP) from soil-water system using granular activated carbon (GAC) impregnated with nanoscale zerovalent iron (reactive activated carbon or RAC). The RAC samples were successfully synthesized by the liquid precipitation method. The mesoporous GAC based RAC with low iron content (1.32%) exhibited higher 2-ClBP removal efficiency (54.6%) in the water phase. The result of Langmuir-Hinshelwood kinetic model implied that the different molecular structures between 2-ClBP and trichloroethylene (TCE) resulted in more difference in dechlorination reaction rates on RAC than adsorption capacities. Compared to removing 2-ClBP in the water phase, RAC removed the 2-ClBP more slowly in the soil phase due to the significant external mass transfer resistance. However, in the soil phase, a better removal capacity of RAC was observed than its base GAC because the chemical dechlorination played a more important role in total removal process for 2-ClBP. This important result verified the effectiveness of RAC for removing 2-ClBP in the soil phase. Although reducing the total RAC removal rate of 2-ClBP, soil organic matter (SOM), especially the soft carbon, also served as an electron transfer medium to promote the dechlorination of 2-ClBP in the long term. PMID:27593281

  8. Study of Organic and Inorganic Binders on Strength of Iron Oxide Pellets

    NASA Astrophysics Data System (ADS)

    Srivastava, Urvashi; Kawatra, S. Komar; Eisele, Timothy C.

    2013-08-01

    Bentonite is a predominant binder used in iron ore pelletization. However, the presence of a high content of silica and alumina in bentonite is considered undesirable for ironmaking operations. The objective of this study was to identify the alternatives of bentonite for iron ore pelletization. To achieve this goal, different types of organic and inorganic binders were utilized to produce iron oxide pellets. The quality of these iron oxide pellets was compared with pellets made using bentonite. All pellets were tested for physical strength at different stages of pelletization to determine their ability to survive during shipping and handling. The results show that organic binders such as lactose monohydrate, hemicellulose, and sodium lignosulfonate can provide sufficient strength to indurated pellets.

  9. Carbon and iron ion radiation-induced cytotoxicity and transformation in vitro

    PubMed Central

    Zhou, Zhaozong; Ware, Jeffrey H.; Kennedy, Ann R.

    2011-01-01

    The present study was undertaken to characterize carbon and iron ion radiation-induced adverse biological effects in terms of toxicity and transformation in vitro. HTori-3 human thyroid epithelial cells were irradiated with 0.3-GeV/n (13.6 KeV/µm) carbon ions and 1-GeV/n (150 KeV/µm) iron ions, both of which represent high-mass, high atomic number (Z) and high-energy particles known as HZE particles, as well as γ-rays. The survival of the irradiated cells was determined by a clonogenic survival assay. The yield of colonies growing in soft agar was used as a surrogate endpoint biomarker for transformation in vitro. The results showed that HZE particles and γ-ray radiations are effective in increasing the yield of anchorage-independent colonies. Based on the relative biological effectiveness (RBE) values in the clonogenic survival assays, 0.3-GeV/n carbon ions and 1-GeV/n iron ions were 2.9 and 2.4 times, respectively, as effective as γ-rays at killing the irradiated HTori-3 cells. At a dose of 200 cGy, 0.3-GeV/n carbon ions and 1-GeV/n iron ions were found to be 3.5 and 7.3 times, respectively, as effective as γ-rays at inducing anchorage-independent growth. These results suggest that the carcinogenic potential of 0.3-GeV/n carbon ions, as represented by the ability to induce anchorage-independent growth, may be lower than that of 1-GeV/n iron ions. PMID:22866150

  10. Visible-light-driven photocatalytic water oxidation catalysed by iron-based metal-organic frameworks.

    PubMed

    Horiuchi, Yu; Toyao, Takashi; Miyahara, Kenta; Zakary, Lionet; Van, Dang Do; Kamata, Yusuke; Kim, Tae-Ho; Lee, Soo Wohn; Matsuoka, Masaya

    2016-04-14

    An iron-based metal-organic framework, MIL-101(Fe), promotes photocatalytic water oxidation to produce oxygen from aqueous silver nitrate solution under visible-light irradiation. The finely dispersed iron-oxo clusters embedded as nodes of the porous framework would contribute importantly to the efficient promotion of the reaction as compared to bulk hematite (α-Fe2O3). PMID:26996996

  11. A field investigation on transport of carbon-supported nanoscale zero-valent iron (nZVI) in groundwater.

    PubMed

    Busch, J; Meißner, T; Potthoff, A; Bleyl, S; Georgi, A; Mackenzie, K; Trabitzsch, R; Werban, U; Oswald, S E

    2015-10-01

    The application of nanoscale zero-valent iron (nZVI) for subsurface remediation of groundwater contaminants is a promising new technology, which can be understood as alternative to the permeable reactive barrier technique using granular iron. Dechlorination of organic contaminants by zero-valent iron seems promising. Currently, one limitation to widespread deployment is the fast agglomeration and sedimentation of nZVI in colloidal suspensions, even more so when in soils and sediments, which limits the applicability for the treatment of sources and plumes of contamination. Colloid-supported nZVI shows promising characteristics to overcome these limitations. Mobility of Carbo-Iron Colloids (CIC) - a newly developed composite material based on finely ground activated carbon as a carrier for nZVI - was tested in a field application: In this study, a horizontal dipole flow field was established between two wells separated by 5.3m in a confined, natural aquifer. The injection/extraction rate was 500L/h. Approximately 1.2kg of CIC was suspended with the polyanionic stabilizer carboxymethyl cellulose. The suspension was introduced into the aquifer at the injection well. Breakthrough of CIC was observed visually and based on total particle and iron concentrations detected in samples from the extraction well. Filtration of water samples revealed a particle breakthrough of about 12% of the amount introduced. This demonstrates high mobility of CIC particles and we suggest that nZVI carried on CIC can be used for contaminant plume remediation by in-situ formation of reactive barriers. PMID:25864966

  12. The structural-phase state of iron-carbon coatings formed by the ultradispersed particles

    NASA Astrophysics Data System (ADS)

    Manakova, Irina A.; Ozernoy, Alexey N.; Tuleushev, Yuriy Zh.; Vereshchak, Mikhail F.; Volodin, Valeriy N.; Zhakanbayev, Yeldar A.

    2014-10-01

    The methods of nuclear gamma-resonance spectroscopy, elemental microanalysis, and X-ray diffraction were used to study nanoscale coatings. The samples were prepared by magnetron sputtering of carbon and iron particles. They alternately were deposited on monocrystalline silicon or polycrystalline corundum substrate moving relative to the plasma flows in the form of sublayers with a thickness of less than 0.6 nm up to the total thickness of 150-500 nm. Solid solutions with the carbon concentrations of up to 7.5, 12.0, 17.6, and 23.9 at% were produced by co-precipitation of ultradispersed particles of iron and carbon. Using method of conversion electron Mössbauer spectroscopy, we detected the anisotropy of orientation of magnetic moments of iron atoms due to texturing of the formed coatings. The deviation of the crystallite orientation from the average value depends on the degree of carbonization. At 550°C, the pearlite eutectic α- Fe ( C )+ Fe3C is formed from the amorphous structure without formation of intermediate carbides. The relative content of cementite correlates with the amount of carbon in the coating. The formation of the solid solutions-alloys directly during the deposition process confirms the theory of thermal-fluctuation melting of small particles.

  13. The structural-phase state of iron-carbon coatings formed by the ultradispersed particles

    SciTech Connect

    Manakova, Irina A. Ozernoy, Alexey N. Tuleushev, Yuriy Zh. Vereshchak, Mikhail F. Volodin, Valeriy N. Zhakanbayev, Yeldar A.

    2014-10-27

    The methods of nuclear gamma-resonance spectroscopy, elemental microanalysis, and X-ray diffraction were used to study nanoscale coatings. The samples were prepared by magnetron sputtering of carbon and iron particles. They alternately were deposited on monocrystalline silicon or polycrystalline corundum substrate moving relative to the plasma flows in the form of sublayers with a thickness of less than 0.6 nm up to the total thickness of 150-500 nm. Solid solutions with the carbon concentrations of up to 7.5, 12.0, 17.6, and 23.9 at% were produced by co-precipitation of ultradispersed particles of iron and carbon. Using method of conversion electron Mössbauer spectroscopy, we detected the anisotropy of orientation of magnetic moments of iron atoms due to texturing of the formed coatings. The deviation of the crystallite orientation from the average value depends on the degree of carbonization. At 550°C, the pearlite eutectic α‐Fe(C)+Fe{sub 3}C is formed from the amorphous structure without formation of intermediate carbides. The relative content of cementite correlates with the amount of carbon in the coating. The formation of the solid solutions-alloys directly during the deposition process confirms the theory of thermal-fluctuation melting of small particles.

  14. [Organic Carbon and Elemental Carbon in Forest Biomass Burning Smoke].

    PubMed

    Huang, Ke; Liu, Gang; Zhou, Li-min; Li, Jiu-hai; Xu, Hui; Wu, Dan; Hong, Lei; Chen, Hui-yu; Yang, Wei-zong

    2015-06-01

    Ten kinds of trees were selected for preparing dry and wet stick samples. Concentrations of organic carbon (OC), elemental carbon (EC) in particular matter produced by sticks samples in the flaming and smoldering were analyzed through the Thermal Optical Carbon Analyzer (Model 2001A). The results showed that mean values of OC (EF(OC)), EC (EF(EC)), PM (EF(PM)) emission factors were 6.8, 2.1, 16.5 g x kg(-1) in the dry stick flaming smoke, 57.5, 11.1, 130.9 g x kg(-1) in the dry stick smoldering smoke, 13.6, 3.3, 30.5 g x kg(-1) in the wet stick flaming smoke, 57.6, 9.6, 125.6 g x kg(-1) in the wet stick smoldering smoke. Compared to the flaming condition, EF(OC), EF(EC), EF(PM), were much higher in the smoldering condition. In the flaming condition, EF(OC), EF(EC), EF(PM) had positive correlations with the moisture content. The mean values of OC/PM, EC/PM, TC/PM (TC = OC + EC) were 45%, 10%, 55%, and the mass fractions of OC was much higher in smoldering condition than those in flaming condition, but the mass fractions of EC was lower in the smoldering condition. Compared to dry sticks, the smoke of wet sticks combustion had higher mass fractions of OC and lower mass fractions of EC. The mean value of OC/EC was 3.3 (2.5-5.2) in the dry stick flaming smoke, and was 5.2 (4.3-6.3) in the dry stick smoldering smoke, in the wet stick flaming smoke was 4.1 (3.1-5.3), and was 6.2 (4.2-8.4) in the wet stick smoldering smoke. Compared to the flaming condition, the mean value of OC/EC was higher in the smoldering condition, and the mean value of OC/EC was much higher in high moisture content stick combustion smoke. The correlation coefficient between OC and EC was 0.985 in dry stick combustions, and was 0.915 in wet stick combustions. So, based on the flaming and smoldering condition, the correlation between OC and EC was significant in different moisture contents of sticks. PMID:26387300

  15. Transient Dissolved Organic Carbon Through Soils

    NASA Astrophysics Data System (ADS)

    Mei, Y.; Hornberger, G. M.; Kaplan, L. A.; Newbold, J. D.; Aufdenkampe, A. K.; Tsang, Y.

    2009-12-01

    Dissolved organic carbon (DOC) is an important constituent of soil solution that plays a role in many chemical and biological processes in soils; it is also an important energy source for bacteria in the soil ecosystem. Hydrology has a significant control on the transport and fate of dissolved organic carbon in the soil but mechanisms that affect said transport are not well understood. In particular, dynamic information on DOC transport through forest soils on short time scales (one or two precipitation event) is lacking at present. DOC is a very complex mix of organic compounds. A key to quantifying DOC dynamics is to establish useful approximations for behavior of this complex mixture. Biodegradable dissolved organic carbon (BDOC) is an important part of DOC. It is reported that between 12 and 44% of DOC released from the forest floor can be decomposed in solutions by indigenous microbes. In our study, we considered how DOC, BDOC, and flow interact in soil columns. In-situ soil cores with two different lengths were installed under a mixed deciduous canopy. The effects of artificial rain on DOC and BDOC transport were examined by dripping nano pure water amended with bromide on the top of soil cores and sampling the water collected at the bottom of the cores for DOC and BDOC. We used plug-flow biofilm reactors to measure the BDOC concentration. It is likely that reduced rates of decomposition in dry soils will cause microbial products of DOC to accumulate; hence DOC concentration should be high at the first flush of rain and decline as the event proceeds. The experimental results show the expected pattern, that is, the first samples we collected always had the highest DOC and BDOC concentrations. The concentrations tend to decline through the simulated precipitation event. Application of a second “storm” forty minutes after the cessation of the first application of water resulted in effluent DOC concentration increasing a small amount initially and then

  16. Temperature Dependence of Photodegradation of Dissolved Organic Matter to Dissolved Inorganic Carbon and Particulate Organic Carbon

    PubMed Central

    Porcal, Petr; Dillon, Peter J.; Molot, Lewis A.

    2015-01-01

    Photochemical transformation of dissolved organic matter (DOM) has been studied for more than two decades. Usually, laboratory or “in-situ” experiments are used to determine photodegradation variables. A common problem with these experiments is that the photodegradation experiments are done at higher than ambient temperature. Five laboratory experiments were done to determine the effect of temperature on photochemical degradation of DOM. Experimental results showed strong dependence of photodegradation on temperature. Mathematical modeling of processes revealed that two different pathways engaged in photochemical transformation of DOM to dissolved inorganic carbon (DIC) strongly depend on temperature. Direct oxidation of DOM to DIC dominated at low temperatures while conversion of DOM to intermediate particulate organic carbon (POC) prior to oxidation to DIC dominated at high temperatures. It is necessary to consider this strong dependence when the results of laboratory experiments are interpreted in regard to natural processes. Photodegradation experiments done at higher than ambient temperature will necessitate correction of rate constants. PMID:26106898

  17. Aligned carbon nanotubes catalytically grown on iron-based nanoparticles obtained by laser-induced CVD

    NASA Astrophysics Data System (ADS)

    Le Normand, F.; Cojocaru, C. S.; Ersen, O.; Legagneux, P.; Gangloff, L.; Fleaca, C.; Alexandrescu, R.; Dumitrache, F.; Morjan, I.

    2007-12-01

    Iron-based nanoparticles are prepared by a laser-induced chemical vapor deposition (CVD) process. They are characterized as body-centered Fe and Fe 2O 3 (maghemite/magnetite) particles with sizes ≤5 and 10 nm, respectively. The Fe particles are embedded in a protective carbon matrix. Both kind of particles are dispersed by spin-coating on SiO 2/Si(1 0 0) flat substrates. They are used as catalyst to grow carbon nanotubes by a plasma- and filaments-assisted catalytic CVD process (PE-HF-CCVD). Vertically oriented and thin carbon nanotubes (CNTs) were grown with few differences between the two samples, except the diameter in relation to the initial size of the iron particles, and the density. The electron field emission of these samples exhibit quite interesting behavior with a low turn-on voltage at around 1 V/μm.

  18. Mercury remediation in wetland sediment using zero-valent iron and granular activated carbon

    USGS Publications Warehouse

    Lewis, Ariel S.; Huntington, Thomas G.; Marvin-DiPasquale, Mark C.; Amirbahman, Aria

    2016-01-01

    Wetlands are hotspots for production of toxic methylmercury (MeHg) that can bioaccumulate in the food web. The objective of this study was to determine whether the application of zero-valent iron (ZVI) or granular activated carbon (GAC) to wetland sediment could reduce MeHg production and bioavailability to benthic organisms. Field mesocosms were installed in a wetland fringing Hodgdon Pond (Maine, USA), and ZVI and GAC were applied. Pore-water MeHg concentrations were lower in treated compared with untreated mesocosms; however, sediment MeHg, as well as total Hg (THg), concentrations were not significantly different between treated and untreated mesocosms, suggesting that smaller pore-water MeHg concentrations in treated sediment were likely due to adsorption to ZVI and GAC, rather than inhibition of MeHg production. In laboratory experiments with intact vegetated sediment clumps, amendments did not significantly change sediment THg and MeHg concentrations; however, the mean pore-water MeHg and MeHg:THg ratios were lower in the amended sediment than the control. In the laboratory microcosms, snails (Lymnaea stagnalis) accumulated less MeHg in sediment treated with ZVI or GAC. The study results suggest that both GAC and ZVI have potential for reducing MeHg bioaccumulation in wetland sediment.

  19. Mercury remediation in wetland sediment using zero-valent iron and granular activated carbon.

    PubMed

    Lewis, Ariel S; Huntington, Thomas G; Marvin-DiPasquale, Mark C; Amirbahman, Aria

    2016-05-01

    Wetlands are hotspots for production of toxic methylmercury (MeHg) that can bioaccumulate in the food web. The objective of this study was to determine whether the application of zero-valent iron (ZVI) or granular activated carbon (GAC) to wetland sediment could reduce MeHg production and bioavailability to benthic organisms. Field mesocosms were installed in a wetland fringing Hodgdon Pond (Maine, USA), and ZVI and GAC were applied. Pore-water MeHg concentrations were lower in treated compared with untreated mesocosms; however, sediment MeHg, as well as total Hg (THg), concentrations were not significantly different between treated and untreated mesocosms, suggesting that smaller pore-water MeHg concentrations in treated sediment were likely due to adsorption to ZVI and GAC, rather than inhibition of MeHg production. In laboratory experiments with intact vegetated sediment clumps, amendments did not significantly change sediment THg and MeHg concentrations; however, the mean pore-water MeHg and MeHg:THg ratios were lower in the amended sediment than the control. In the laboratory microcosms, snails (Lymnaea stagnalis) accumulated less MeHg in sediment treated with ZVI or GAC. The study results suggest that both GAC and ZVI have potential for reducing MeHg bioaccumulation in wetland sediment. PMID:26874318

  20. Magnetically anisotropic additive for scalable manufacturing of polymer nanocomposite: iron-coated carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Yamamoto, Namiko; Manohara, Harish; Platzman, Ellen

    2016-02-01

    Novel nanoparticles additives for polymer nanocomposites were prepared by coating carbon nanotubes (CNTs) with ferromagnetic iron (Fe) layers, so that their micro-structures can be bulk-controlled by external magnetic field application. Application of magnetic fields is a promising, scalable method to deliver bulk amount of nanocomposites while maintaining organized nanoparticle assembly throughout the uncured polymer matrix. In this work, Fe layers (˜18 nm thick) were deposited on CNTs (˜38 nm diameter and ˜50 μm length) to form thin films with high aspect ratio, resulting in a dominance of shape anisotropy and thus high coercivity of ˜50-100 Oe. The Fe-coated CNTs were suspended in water and applied with a weak magnetic field of ˜75 G, and yet preliminary magnetic assembly was confirmed. Our results demonstrate that the fabricated Fe-coated CNTs are magnetically anisotropic and effectively respond to magnetic fields that are ˜103 times smaller than other existing work (˜105 G). We anticipate this work will pave the way for effective property enhancement and bulk application of CNT-polymer nanocomposites, through controlled micro-structure and scalable manufacturing.

  1. Does Iron Fertilization Lead to Enhanced Carbon Sequestration? A Synthesis of Polar Star Results.

    SciTech Connect

    Buesseler, K.O.

    2002-12-01

    This research synthesized activities related to work conducted as part of the Southern Ocean Iron Experiment (SOFeX) which investigated the effects of iron fertilization on enhanced carbon sequestration. The primary interest was in the fate of sinking particles which carry carbon to the deep ocean, where it can be sequestered from the atmosphere for >100-1000 year time scales. This was accomplished through direct measurements of thorium-234, a naturally occurring particle reactive radionuclide that traces shallow particle export; SF6 measurements to track the position of the Fe fertilized region; and the collection of ancillary data and samples to augment the study of major C, nutrient and elemental budgets as well as appropriate samples for biological study. Results of this work show a small, but progressively increasing flux of particulate organic C to depth as a consequence of Fe fertilization. This is the first data set to show any effect of Fe fertilization on C sequestration in the Southern Ocean. The changes in particle export during SOFeX are significant, but only possible to detect given what is arguably the largest 234Th data set ever collected as part of an oceanographic experiment. Most prior 234Th studies, simply use a steady-state approximation and ignore advective and diffusive fluxes in the calculation of 234Th fluxes. High resolution time-series of average 0-50m 234Th activities in and out of the Southern patch find a clear steady decrease in 234Th flux that is slightly larger in vs. out of the Fe fertilized patch. This decrease must be included in the full 234Th flux calculation and the deliberate tagging of this water mass with SF6 combined with time-series sampling allowed for a careful evaluation of this non-steady state (NSS) term. Likewise, the addition of SF6 allows for the evaluation of vertical exchange (via the gradient of SF6 below the patch) and dilution effects (after correction for atmospheric losses). In most set tings these physical

  2. Biological carbon precursor to diagenetic siderite with spherical structures in iron formations.

    PubMed

    Köhler, Inga; Konhauser, Kurt O; Papineau, Dominic; Bekker, Andrey; Kappler, Andreas

    2013-01-01

    During deposition of Precambrian iron formation, the combined sedimentation of ferrihydrite and phytoplankton biomass should have facilitated Fe(III) reduction during diagenesis. However, the only evidence for this reaction in iron formations is the iron and carbon isotope values preserved in the authigenic ferrous iron-containing minerals. Here we show experimentally that spheroidal siderite, which is preserved in many iron formation and could have been precursor to rhombohedral or massive siderite, forms by reacting ferrihydrite with glucose (a proxy for microbial biomass) at pressure and temperature conditions typical of diagenesis (170 °C and 1.2 kbar). Depending on the abundance of siderite, we found that it is also possible to draw conclusions about the Fe(III):C ratio of the initial ferrihydrite-biomass sediment. Our results suggest that spherical to rhombohedral siderite structures in deep-water, Fe-oxide iron formation can be used as a biosignature for photoferrotrophy, whereas massive siderite reflects high cyanobacterial biomass loading in highly productive shallow-waters. PMID:23612282

  3. Low-carbon transition of iron and steel industry in China: carbon intensity, economic growth and policy intervention.

    PubMed

    Yu, Bing; Li, Xiao; Qiao, Yuanbo; Shi, Lei

    2015-02-01

    As the biggest iron and steel producer in the world and one of the highest CO2 emission sectors, China's iron and steel industry is undergoing a low-carbon transition accompanied by remarkable technological progress and investment adjustment, in response to the macroeconomic climate and policy intervention. Many drivers of the CO2 emissions of the iron and steel industry have been explored, but the relationships between CO2 abatement, investment and technological expenditure, and their connections with the economic growth and governmental policies in China, have not been conjointly and empirically examined. We proposed a concise conceptual model and an econometric model to investigate this crucial question. The results of regression, Granger causality test and impulse response analysis indicated that technological expenditure can significantly reduce CO2 emissions, and that investment expansion showed a negative impact on CO2 emission reduction. It was also argued with empirical evidence that a good economic situation favored CO2 abatement in China's iron and steel industry, while achieving CO2 emission reduction in this industrial sector did not necessarily threaten economic growth. This shed light on the dispute over balancing emission cutting and economic growth. Regarding the policy aspects, the year 2000 was found to be an important turning point for policy evolution and the development of the iron and steel industry in China. The subsequent command and control policies had a significant, positive effect on CO2 abatement. PMID:25662248

  4. Synthesis, structure, and magnetic properties of iron and nickel nanoparticles encapsulated into carbon

    NASA Astrophysics Data System (ADS)

    Tsurin, V. A.; Yermakov, A. Ye.; Uimin, M. A.; Mysik, A. A.; Shchegoleva, N. N.; Gaviko, V. S.; Maikov, V. V.

    2014-02-01

    Nanocomposites based on iron and nickel particles encapsulated into carbon (Fe@C and Ni@C), with an average size of the metal core in the range from 5 to 20 nm and a carbon shell thickness of approximately 2 nm, have been prepared by the gas-phase synthesis method in a mixture of argon and butane. It has been found using X-ray diffraction, transmission electron microscopy, and Mössbauer spectroscopy that iron nanocomposites prepared in butane, apart from the carbon shell, contain the following phases: iron carbide (cementite), α-Fe, and γ-Fe. The phase composition of the Fe@C nanocomposite correlates with the magnetization of approximately 100 emu/g at room temperature. The replacement of butane by methane as a carbon source leads to another state of nanoparticles: no carbon coating is formed, and upon subsequent contact with air, the Fe3O4 oxide shell is formed on the surface of nanoparticles. Nickel-based nanocomposites prepared in butane, apart from pure nickel in the metal core, contain the supersaturated metastable solid solution Ni(C) and carbon coating. The Ni(C) solid solution can decompose both during the synthesis and upon the subsequent annealing. The completeness and degree of decomposition depend on the synthesis regime and the size of nickel nanoparticles: the smaller is the size of nanoparticles, the higher is the degree of decomposition into pure nickel and carbon. The magnetization of the Ni@C nanocomposites is determined by several contributions, for example, the contribution of the magnetic solid solution Ni(C) and the contribution of the nonmagnetic carbon coating; moreover, some contribution to the magnetization can be caused by the superparamagnetic behavior of nanoparticles.

  5. Formation and transformation of a short range ordered iron carbonate precursor

    NASA Astrophysics Data System (ADS)

    Dideriksen, Knud; Frandsen, Cathrine; Bovet, Nicolas; Wallace, Adam F.; Sel, Ozlem; Arbour, Tyler; Navrotsky, Alexandra; De Yoreo, James J.; Banfield, Jillian F.

    2015-09-01

    Fe(II)-carbonates, such as siderite, form in environments where O2 is scarce, e.g., during marine sediment diagenesis, corrosion and possibly CO2 sequestration, but little is known about their formation pathways. We show that early precipitates from carbonate solutions containing 0.1 M Fe(II) with varying pH produced broad peaks in X-ray diffraction and contained dominantly Fe and CO3 when probed with X-ray photoelectron spectroscopy. Reduced pair distribution function (PDF) analysis shows only peaks corresponding to interatomic distances below 15 Å, reflecting a material with no long range structural order. Moreover, PDF peak positions differ from those for known iron carbonates and hydroxides. Mössbauer spectra also deviate from those expected for known iron carbonates and suggest a less crystalline structure. These data show that a previously unidentified iron carbonate precursor phase formed. Its coherent scattering domains determined from PDF analysis are slightly larger than for amorphous calcium carbonate, suggesting that the precursor could be nanocrystalline. Replica exchange molecular dynamics simulations of Fe-carbonate polynuclear complexes yield PDF peak positions that agree well with those from experiments, offering the possibility that the material is a condensate of such complexes, assembled in a relatively unorganised fashion. If this is the case, the material could be nearly amorphous, rather than being composed of well defined nanocrystals. PDF measurements of samples ageing in solution coupled with refinement with the software PDFgui show that the material transforms to siderite or siderite/chukanovite mixtures within hours and that the transformation rate depends on pH. The identified Fe-carbonate precursor may potentially form during anaerobic corrosion or bacterial Fe reduction.

  6. Carbon accumulation in arid croplands of northwest China: pedogenic carbonate exceeding organic carbon

    PubMed Central

    Wang, Xiujun; Wang, Jiaping; Xu, Minggang; Zhang, Wenju; Fan, Tinglu; Zhang, Juan

    2015-01-01

    Soil carbonate (SIC) exceeds organic carbon (SOC) greatly in arid lands, thus may be important for carbon sequestration. However, field data for quantifying carbonate accumulation have been lacking. This study aims to improve our understanding of SIC dynamics and its role in carbon sequestration. We analyzed two datasets of SOC and SIC and their 13C compositions , one with over 100 soil samples collected recently from various land uses in the Yanqi Basin, Xinjiang, and the other with 18 archived soil samples from a long-term experiment (LTE) in Pingliang, Gansu. The data from the Yanqi Basin showed that SOC had a significant relationship with SIC and pedogenic carbonate (PIC); converting shrub land to cropland increased PIC stock by 5.2 kg C m−2, which was 3.6 times of that in SOC stock. The data from the LTE showed greater accumulation of PIC (21–49 g C m−2 year−1) than SOC (10–39 g C m−2 year−1) over 0–20 cm. Our study points out that intensive cropping in the arid and semi-arid regions leads to an increase in both SOC and PIC. Increasing SOC through straw organic amendments enhances PIC accumulation in the arid cropland of northwestern China. PMID:26091554

  7. Carbon accumulation in arid croplands of northwest China: pedogenic carbonate exceeding organic carbon

    NASA Astrophysics Data System (ADS)

    Wang, Xiujun; Wang, Jiaping; Xu, Minggang; Zhang, Wenju; Fan, Tinglu; Zhang, Juan

    2015-06-01

    Soil carbonate (SIC) exceeds organic carbon (SOC) greatly in arid lands, thus may be important for carbon sequestration. However, field data for quantifying carbonate accumulation have been lacking. This study aims to improve our understanding of SIC dynamics and its role in carbon sequestration. We analyzed two datasets of SOC and SIC and their 13C compositions , one with over 100 soil samples collected recently from various land uses in the Yanqi Basin, Xinjiang, and the other with 18 archived soil samples from a long-term experiment (LTE) in Pingliang, Gansu. The data from the Yanqi Basin showed that SOC had a significant relationship with SIC and pedogenic carbonate (PIC); converting shrub land to cropland increased PIC stock by 5.2 kg C m-2, which was 3.6 times of that in SOC stock. The data from the LTE showed greater accumulation of PIC (21-49 g C m-2 year-1) than SOC (10-39 g C m-2 year-1) over 0-20 cm. Our study points out that intensive cropping in the arid and semi-arid regions leads to an increase in both SOC and PIC. Increasing SOC through straw organic amendments enhances PIC accumulation in the arid cropland of northwestern China.

  8. Carbon accumulation in arid croplands of northwest China: pedogenic carbonate exceeding organic carbon.

    PubMed

    Wang, Xiujun; Wang, Jiaping; Xu, Minggang; Zhang, Wenju; Fan, Tinglu; Zhang, Juan

    2015-01-01

    Soil carbonate (SIC) exceeds organic carbon (SOC) greatly in arid lands, thus may be important for carbon sequestration. However, field data for quantifying carbonate accumulation have been lacking. This study aims to improve our understanding of SIC dynamics and its role in carbon sequestration. We analyzed two datasets of SOC and SIC and their (13)C compositions , one with over 100 soil samples collected recently from various land uses in the Yanqi Basin, Xinjiang, and the other with 18 archived soil samples from a long-term experiment (LTE) in Pingliang, Gansu. The data from the Yanqi Basin showed that SOC had a significant relationship with SIC and pedogenic carbonate (PIC); converting shrub land to cropland increased PIC stock by 5.2 kg C m(-2), which was 3.6 times of that in SOC stock. The data from the LTE showed greater accumulation of PIC (21-49 g C m(-2) year(-1)) than SOC (10-39 g C m(-2) year(-1)) over 0-20 cm. Our study points out that intensive cropping in the arid and semi-arid regions leads to an increase in both SOC and PIC. Increasing SOC through straw organic amendments enhances PIC accumulation in the arid cropland of northwestern China. PMID:26091554

  9. Carbon diffusion in solid iron as function of pressure and temperature

    NASA Astrophysics Data System (ADS)

    Stagno, V.; Crispin, K. L.; Fei, Y.

    2012-12-01

    The knowledge of carbon diffusion in metallic iron is of importance for both industrial and geological applications. In industry the diffusion properties of carbon apply to the massive production of steel through carburizing and galvanization processes at high temperature with the aim to improve the hardness and rust resistance of such materials. In geoscience the diffusion of carbon in metallic phases at high pressure and temperature is important for determining the rate of reactions and crystal growth of carbide phases likely coexisting with mantle silicates. Due to a small atomic radius, carbon is expected to dissolve by interstitial diffusion in solid metals. However, to date there are no experimental data available to understand the role that pressure plays on the mobilization of carbon through solid iron. Further, for light elements such as carbon or sulfur the activation energy is assumed to be lower than in case of lattice diffusion. However, with increasing pressure the activation volume must be taken into account to better understand diffusion processes at the atomic scale. We performed experiments using multianvil and piston cylinder devices at pressures between 1.5 and 6 GPa and temperature of 700-1200°C. Experiments were carried out using cylindrical glassy carbon sandwiched between layers of pure iron rods of known thickness enclosed in MgO capsule. Analytical techniques included FE-SEM for textural observation and accurate analyses of the interface between layers, while concentration profiles were measured using the electron microprobe with an optimized standardization procedure. Concentration profiles of carbon in iron were computed to determine the diffusion coefficients based on Fick's second law formulation assuming isotropic one dimension diffusion. Preliminary results confirm the positive temperature dependence of the diffusion coefficient for carbon widely discussed in literature. However, our results also show that a significant increase in

  10. Serum albumin forms a lactoferrin-like soluble iron-binding complex in presence of hydrogen carbonate ions.

    PubMed

    Ueno, Hiroshi M; Urazono, Hiroshi; Kobayashi, Toshiya

    2014-02-15

    The iron-lactoferrin complex is a common food ingredient because of its iron-solubilizing capability in the presence of hydrogen carbonate ions. However, it is unclear whether the formation of a stable iron-binding complex is limited to lactoferrin. In this study, we investigated the effects of bovine serum albumin (BSA) on iron solubility and iron-catalyzed lipid oxidation in the presence of hydrogen carbonate ions. BSA could solubilize >100-fold molar equivalents of iron at neutral pH, exceeding the specific metal-binding property of BSA. This iron-solubilizing capability of BSA was impaired by thermally denaturing BSA at ≥ 70 °C for 10 min at pH 8.5. The resulting iron-BSA complex inhibited iron-catalyzed oxidation of soybean oil in a water-in-oil emulsion measured using the Rancimat test. Our study is the first to show that BSA, like lactoferrin, forms a soluble iron-binding complex in the presence of hydrogen carbonate ions. PMID:24128453