Search results for "Anaerobic oxidation of methane"

2015

Iron reduction in subseafloor sulfate-depleted and methane-rich marine sediments is currently a subject of interest in subsurface geomicrobiology. While iron reduction and microorganisms involved have been well studied in marine surface sediments, little is known about microorganisms responsible for iron reduction in deep methanic sediments. Here, we used quantitative PCR (Q-PCR)-based 16S rRNA gene copy numbers and pyrosequencing-based relative abundances of bacteria and archaea to investigate covariance between distinct microbial populations and specific geochemical profiles in the top 5 m of sediment cores from the Helgoland mud area, North Sea. We found that gene copy numbers of bacteri…

2016

AbstractAuthigenic carbonate build-ups develop at seafloor methane-seeps, where microbially mediated sulphate-dependent anaerobic oxidation of methane facilitates carbonate precipitation. Despite being valuable recorders of past methane seepage events, their role as archives of atmospheric processes has not been examined. Here we show that cyclic sedimentation pulses related to the Indian monsoon in concert with authigenic precipitation of methane-derived aragonite gave rise to a well-laminated carbonate build-up within the oxygen minimum zone off Pakistan (northern Arabian Sea). U–Th dating indicates that the build-up grew during past ~1,130 years, creating an exceptional high-resolution a…

Combined CO/CH4 oxidation tests over Pd/Co3O4 monolitic catalyst: effects of high reaction temperature and SO2 exposure on the deactivation process

2007

Abstract CO and CH 4 combined oxidation tests were performed over a Pd (70 g/ft 3 )/Co 3 O 4 monolithic catalyst in conditions of GHSV = 100,000 h −1 and feed composition close to that of emission from bi-fuel vehicles. The effect of SO 2 (5 ppm) on CO and CH 4 oxidation activity under lean condition ( λ  = 2) was investigated. The presence of sulphur strongly deactivated the catalyst towards methane oxidation, while the poisoning effect was less drastic in the oxidation of CO. Saturation of the Pd/Co 3 O 4 catalytic sites via chemisorbed SO 3 and/or sulphates occurred upon exposure to SO 2 . A treatment of regeneration to remove sulphate species was attempted by performing a heating/coolin…

Co3O4/CeO2 composite oxides for methane emissions abatement: Relationship between Co3O4–CeO2 interaction and catalytic activity

2006

Abstract Co 3 O 4 /CeO 2 composite oxides with different cobalt loading (5, 15, 30, 50, 70 wt.% as Co 3 O 4 ) were prepared by co-precipitation method and investigated for the oxidation of methane under stoichiometric conditions. Pure oxides, Co 3 O 4 and CeO 2 were used as reference. Characterization studies by X-ray diffraction (XRD), BET, temperature programmed reduction/oxidation (TPR/TPO) and X-ray photoelectron spectroscopy (XPS) were carried out. An improvement of the catalytic activity and thermal stability of the composite oxides was observed with respect to pure Co 3 O 4 in correspondence of Co 3 O 4 –CeO 2 containing 30% by weight of Co 3 O 4 . The combined effect of cobalt oxide…

Responses of methane oxidation to temperature and water content in cover soil of a boreal landfill

2007

Abstract Methane oxidation in a cover soil of a landfill located in a boreal climate was studied at temperatures ranging from 1–19 °C and with water content of 7–34% of dry weight (dw), corresponding to 17–81% of water-holding capacity (WHC) in order to better understand the factors regulating CH 4 oxidation at low temperatures. CH 4 consumption was detected at all the temperatures studied (1–19 °C) and an increase in CH 4 consumption rate in consecutive incubations was obtained even at 1 °C, indicating activation or increase in enzymes and/or microorganisms responsible for CH 4 oxidation. CH 4 consumption was reduced with low water content (17%WHC) at all temperatures. The response of CH 4…

Methane-derived carbonate conduits from the late Aptian of Salinac (Marne Bleues, Vocontian Basin, France): Petrology and biosignatures

2015

Abstract Peculiar carbonate bodies occur in distinct marl layers of the Marnes Bleues Formation (Aptian–Albian, Vocontian Basin, Southern France). The carbonate conduits exhibit pipe- or sausage-like forms and a central channel. Their sizes range between 30 and 60 cm in length and 5–10 cm in diameter. The conduit carbonates consist of automicrite authigenically formed within the sediment. Millimeter-sized aggregates of framboidal pyrite are abundant within the conduit automicrites, probably representing former colonies of sulfate reducing bacteria. The central channel reflects former pathways of reduced fluids in the carbonate conduit. Ni-enrichments at the margins of the central cavity are…

Methane oxidation at a surface-sealed boreal landfill.

2009

Abstract Methane oxidation was studied at a closed boreal landfill (area 3.9 ha, amount of deposited waste 200,000 tonnes) equipped with a passive gas collection and distribution system and a methane oxidative top soil cover integrated in a European Union landfill directive-compliant, multilayer final cover. Gas wells and distribution pipes with valves were installed to direct landfill gas through the water impermeable layer into the top soil cover. Mean methane emissions at the 25 measuring points at four measurement times (October 2005–June 2006) were 0.86–6.2 m 3  ha −1  h −1 . Conservative estimates indicated that at least 25% of the methane flux entering the soil cover at the measuring…

Support effect on the catalytic performance of Au/Co3O4–CeO2 catalysts for CO and CH4 oxidation

2008

Gold-based catalysts supported on Co3O4, on CeO2 and on mixed Co3O4-CeO2 oxides were prepared by co-precipitation. They were tested in the catalytic oxidation of CO and CH4, in separate tests, and their activities were compared with that of the bare oxides. Tests of CH4 oxidation were performed in two consecutive runs in order to evaluate the catalysts stability. The effect of SO2 in the reactant mixture was investigated. The fresh and spent catalysts were analsed by XRD, BET, TPR and XPS techniques. Among the fresh catalysts, Au supported on CeO2 was the most active in CO oxidation whereas Au supported on Co3O4 was the most active for methane total oxidation. Synergy between the two oxides…

Recycling and fluxes of carbon gases in a stratified boreal lake following experimental carbon addition

2014

Partly anoxic stratified humic lakes are important sources of methane (CH4) and carbon dioxide (CO2) to the atmosphere. We followed the fate of CH4 and CO2 in a small boreal stratified lake, Alinen Mustajärvi, during 2007–2009. In 2008 and 2009 the lake received additions of dissolved organic carbon (DOC) with stable carbon isotope ratio (δ13C) around 16‰ higher than that of local allochthonous DOC. Carbon transformations in the water column were studied by measurements of δ13C of CH4 and of the dissolved inorganic carbon (DIC). Furthermore, CH4 and CO2 production, consumption and emissions were estimated. Methane oxidation was estimated by a diffusion gradient method. The amount, lo…

The analysis of methods for measurement of methane oxidation in landfills

2003

Landfills and dumps are important sources of atmospheric methane. There is no generally accepted estimate of the influence of methane oxidation on landfill methane emissions. The present work aimed to analyse different methods for the investigation of methane emission and oxidation in methane-producing environments (wetlands, landfills, sludge checks), and to develop the precise procedure for the landfills. The combination of geochemical and microbiological methods to estimate and monitor the oxidation and emission of methane in landfills during different seasons is proposed. It includes the measurements, both on the surface and at different depths (up to 1 m) of landfill ground of the foll…