Sample records for n2o methane ch4

  1. Microbial CH4 and N2O Consumption in Acidic Wetlands

    PubMed Central

    Kolb, Steffen; Horn, Marcus A.

    2012-01-01

    Acidic wetlands are global sources of the atmospheric greenhouse gases methane (CH4), and nitrous oxide (N2O). Consumption of both atmospheric gases has been observed in various acidic wetlands, but information on the microbial mechanisms underlying these phenomena is scarce. A substantial amount of CH4 is consumed in sub soil by aerobic methanotrophs at anoxic–oxic interfaces (e.g., tissues of Sphagnum mosses, rhizosphere of vascular plant roots). Methylocystis-related species are likely candidates that are involved in the consumption of atmospheric CH4 in acidic wetlands. Oxygen availability regulates the activity of methanotrophs of acidic wetlands. Other parameters impacting on the methanotroph-mediated CH4 consumption have not been systematically evaluated. N2O is produced and consumed by microbial denitrification, thus rendering acidic wetlands as temporary sources or sinks for N2O. Denitrifier communities in such ecosystems are diverse, and largely uncultured and/or new, and environmental factors that control their consumption activity are unresolved. Analyses of the composition of N2O reductase genes in acidic wetlands suggest that acid-tolerant Proteobacteria have the potential to mediate N2O consumption in such soils. Thus, the fragmented current state of knowledge raises open questions concerning methanotrophs and denitrifiers that consume atmospheric CH4 and N2O in acidic wetlands. PMID:22403579

  2. Thermodynamic calculations in the system CH4-H2O and methane hydrate phase equilibria

    USGS Publications Warehouse

    Circone, S.; Kirby, S.H.; Stern, L.A.

    2006-01-01

    Using the Gibbs function of reaction, equilibrium pressure, temperature conditions for the formation of methane clathrate hydrate have been calculated from the thermodynamic properties of phases in the system CH4-H 2O. The thermodynamic model accurately reproduces the published phase-equilibria data to within ??2 K of the observed equilibrium boundaries in the range 0.08-117 MPa and 190-307 K. The model also provides an estimate of the third-law entropy of methane hydrate at 273.15 K, 0.1 MPa of 56.2 J mol-1 K-1 for 1/n CH4??H 2O, where n is the hydrate number. Agreement between the calculated and published phase-equilibria data is optimized when the hydrate composition is fixed and independent of the pressure and temperature for the conditions modeled. ?? 2006 American Chemical Society.

  3. NO(y) Correlation with N2O and CH4 in the Midlatitude Stratosphere

    NASA Technical Reports Server (NTRS)

    Kondo, Y.; Schmidt, U.; Sugita, T.; Engel, A.; Koike, M.; Aimedieu, P.; Gunson, M. R.; Rodriguez, J.

    1996-01-01

    Total reactive nitrogen (NO(y)), nitrous oxide (NO2), methane (CH4), and ozone (03) were measured on board a balloon launched from Aire sur l'Adour (44 deg N, 0 deg W), France on October 12, 1994. Generally, NO(y) was highly anti-correlated with N2O and CH4 at altitudes between 15 and 32 km. The linear NO(y) - N2O and NO(y) - CH4 relationships obtained by the present observations are very similar to those obtained on board ER-2 and DC-8 aircraft previously at altitude below 20 km in the northern hemisphere. They also agree well with the data obtained by the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument at 41 deg N in November 1994. Slight departures from linear correlations occurred around 29 km, where N2O and CH4 mixing ratios were larger than typical midlatitude values, suggesting horizontal transport of tropical airmasses to northern midlatitudes in a confined altitude region.

  4. Climate change reduces the net sink of CH4 and N2O in a semiarid grassland.

    PubMed

    Dijkstra, Feike A; Morgan, Jack A; Follett, Ronald F; Lecain, Daniel R

    2013-06-01

    Atmospheric concentrations of methane (CH4 ) and nitrous oxide (N2 O) have increased over the last 150 years because of human activity. Soils are important sources and sinks of both potent greenhouse gases where their production and consumption are largely regulated by biological processes. Climate change could alter these processes thereby affecting both rate and direction of their exchange with the atmosphere. We examined how a rise in atmospheric CO2 and temperature affected CH4 and N2 O fluxes in a well-drained upland soil (volumetric water content ranging between 6% and 23%) in a semiarid grassland during five growing seasons. We hypothesized that responses of CH4 and N2 O fluxes to elevated CO2 and warming would be driven primarily by treatment effects on soil moisture. Previously we showed that elevated CO2 increased and warming decreased soil moisture in this grassland. We therefore expected that elevated CO2 and warming would have opposing effects on CH4 and N2 O fluxes. Methane was taken up throughout the growing season in all 5 years. A bell-shaped relationship was observed with soil moisture with highest CH4 uptake at intermediate soil moisture. Both N2 O emission and uptake occurred at our site with some years showing cumulative N2 O emission and other years showing cumulative N2 O uptake. Nitrous oxide exchange switched from net uptake to net emission with increasing soil moisture. In contrast to our hypothesis, both elevated CO2 and warming reduced the sink of CH4 and N2 O expressed in CO2 equivalents (across 5 years by 7% and 11% for elevated CO2 and warming respectively) suggesting that soil moisture changes were not solely responsible for this reduction. We conclude that in a future climate this semiarid grassland may become a smaller sink for atmospheric CH4 and N2 O expressed in CO2 -equivalents. © 2013 Blackwell Publishing Ltd.

  5. Experimental study and detailed modeling of toluene degradation in a low-pressure stoichiometric premixed CH4/O2/N2 flame.

    PubMed

    Bakali, A El; Dupont, L; Lefort, B; Lamoureux, N; Pauwels, J F; Montero, M

    2007-05-17

    Temperature and mole fraction profiles have been measured in laminar stoichiometric premixed CH4/O2/N2 and CH4/1.5%C6H5CH3/O2/N2 flames at low pressure (0.0519 bar) by using thermocouple, molecular beam/mass spectrometry (MB/MS), and gas chromatography/mass spectrometry (GC/MS) techniques. The present study completes our previous work performed on the thermal degradation of benzene in CH4/O2/N2 operating at similar conditions. Mole fraction profiles of reactants, final products, and reactive and stable intermediate species have been analyzed. The main intermediate aromatic species analyzed in the methane-toluene flame were benzene, phenol, ethylbenzene, benzylalcohol, styrene, and benzaldehyde. These new experimental results have been modeled with our previous model including submechanisms for aromatics (benzene up to p-xylene) and aliphatic (C1 up to C7) oxidation. Good agreement has been observed for the main species analyzed. The main reaction paths governing the degradation of toluene in the methane flame were identified, and it occurs mainly via the formation of benzene (C6H5CH3 + H = C6H6 + CH3) and benzyl radical (C6H5CH3 + H = C6H5CH2 + H2). Due to the abundance of methyl radicals, it was observed that recombination of benzyl and methyl is responsible for main monosubstitute aromatic species analyzed in the methane-toluene flame. The oxidation of these substitute species led to cyclopentadienyl radical as observed in a methane-benzene flame.

  6. The CH2O column as a possible constraint on methane oxidation

    NASA Astrophysics Data System (ADS)

    Valin, L. C.; Fiore, A. M.; Lin, M.

    2013-12-01

    We explore the potential for space-based measurements of the CH2O column to quantify variations of methane oxidation in the remote atmosphere due to changes in climate (e.g., T, H2O, stratospheric O3) and atmospheric composition (e.g., NOxO, O3, CO, CH4). We investigate the variability of methane oxidation and the formaldehyde column using available global simulations (MOZART-2 chemistry-transport model, GFDL AM3 climate-chemistry model). Over a large region (135° - 175° W; 0° - 16° S), the rate of methane oxidation simulated in the models varies intraseasonally (×10%), seasonally (×20%) and interannually (×5%), and is well correlated with the simulated variability of the CH2O column (R2 = 0.75; ~1x1015 molecules cm-2). The precision of a single space-based measurement is approximately 1×1016 molecules cm-2, an order of magnitude larger than the simulated variability of the CH2O column. However, in a large region such as the tropical Pacific, UV/Vis spectrometers are capable of making thousands of measurements daily, enough sampling to theoretically increase the precision by √N, such that variations on the order of 1×1015 molecules cm-2 should be observable on intraseasonal and interannual timescales.

  7. Greenhouse gas budget (CO2, CH4 and N2O) of intensively managed grassland following restoration.

    PubMed

    Merbold, Lutz; Eugster, Werner; Stieger, Jacqueline; Zahniser, Mark; Nelson, David; Buchmann, Nina

    2014-06-01

    The first full greenhouse gas (GHG) flux budget of an intensively managed grassland in Switzerland (Chamau) is presented. The three major trace gases, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) were measured with the eddy covariance (EC) technique. For CO2 concentrations, an open-path infrared gas analyzer was used, while N2O and CH4 concentrations were measured with a recently developed continuous-wave quantum cascade laser absorption spectrometer (QCLAS). We investigated the magnitude of these trace gas emissions after grassland restoration, including ploughing, harrowing, sowing, and fertilization with inorganic and organic fertilizers in 2012. Large peaks of N2O fluxes (20-50 nmol m(-2) s(-1) compared with a <5 nmol m(-2) s(-1) background) were observed during thawing of the soil after the winter period and after mineral fertilizer application followed by re-sowing in the beginning of the summer season. Nitrous oxide (N2O) fluxes were controlled by nitrogen input, plant productivity, soil water content and temperature. Management activities led to increased variations of N2O fluxes up to 14 days after the management event as compared with background fluxes measured during periods without management (<5 nmol m(-2) s(-1)). Fluxes of CO2 remained small until full plant development in early summer 2012. In contrast, methane emissions showed only minor variations over time. The annual GHG flux budget was dominated by N2O (48% contribution) and CO2 emissions (44%). CH4 flux contribution to the annual budget was only minor (8%). We conclude that recently developed multi-species QCLAS in an EC system open new opportunities to determine the temporal variation of N2O and CH4 fluxes, which further allow to quantify annual emissions. With respect to grassland restoration, our study emphasizes the key role of N2O and CO2 losses after ploughing, changing a permanent grassland from a carbon sink to a significant carbon source. © 2014 John Wiley & Sons Ltd.

  8. Comprehensive effects of a sedge plant on CH4 and N2O emissions in an estuarine marsh

    NASA Astrophysics Data System (ADS)

    Li, Yangjie; Wang, Dongqi; Chen, Zhenlou; Hu, Hong

    2018-05-01

    Although there have been numerous studies focusing on plants' roles in methane (CH4) emissions, the influencing mechanism of wetland plants on nitrous oxide (N2O) emissions has rarely been studied. Here, we test whether wetland plants also play an important role in N2O emissions. Gas fluxes were determined using the in situ static flux chamber technique. We also carried out pore-water extractions, sedge removal experiments and tests of N2O transportation. The brackish marsh acted as a net source of both CH4 and N2O. However, sedge plants played the opposite role in CH4 and N2O emissions. The removal of the sedges led to reduced CH4 emissions and increased accumulation of CH4 inside the sediment. Apart from being a conduit for CH4 transport, the sedges made a greater contribution to CH4 oxidation than CH4 production. The sedges exerted inhibitory effects on the release of N2O. The N2O was barely detectable inside the sediment in both vegetated and vegetation-removed plots. The denitrification measurements and nitrogen addition (the addition rates were equal to 0.028, 0.056 and 0.112 g m-2) experiments suggest that denitrification associated with N2O production occurred mainly in the surface sediment layer. The vascular sedge could transport atmospheric N2O downward into the rhizosphere. The rhizospheric sediment, together with the vascular sedge, became an effective sink of atmospheric N2O.

  9. Combining two complementary micrometeorological methods to measure CH4 and N2O fluxes over pasture

    NASA Astrophysics Data System (ADS)

    Laubach, J.; Barthel, M.; Fraser, A.; Hunt, J. E.; Griffith, D. W. T.

    2015-09-01

    New Zealand's largest industrial sector is pastoral agriculture, giving rise to a large fraction of the country's emissions of methane (CH4) and nitrous oxide (N2O). We designed a system to continuously measure CH4 and N2O fluxes at the field scale on two adjacent pastures that differed with respect to management. At the core of this system was a closed-cell Fourier-transform infrared spectrometer (FTIR), measuring the mole fractions of CH4, N2O and carbon dioxide (CO2) at two heights at each site. In parallel, CO2 fluxes were measured using eddy-covariance instrumentation. We applied two different micrometeorological ratio methods to infer the CH4 and N2O fluxes from their respective mole fractions and the CO2 fluxes. The first is a variant of the flux-gradient method, where it is assumed that the turbulent diffusivities of CH4 and N2O equal that of CO2. This method was reliable when the CO2 mole-fraction difference between heights was at least 4 times greater than the FTIR's resolution of differences. For the second method, the temporal increases of mole fractions in the stable nocturnal boundary layer, which are correlated for concurrently-emitted gases, are used to infer the unknown fluxes of CH4 and N2O from the known flux of CO2. This method was sensitive to "contamination" from trace gas sources other than the pasture of interest and therefore required careful filtering. With both methods combined, estimates of mean daily CH4 and N2O fluxes were obtained for 60 % of days at one site and 77 % at the other. Both methods indicated both sites as net sources of CH4 and N2O. Mean emission rates for one year at the unfertilised, winter-grazed site were 8.2 (± 0.91) nmol CH4 m-2 s-1 and 0.40 (± 0.018) nmol N2O m-2 s-1. During the same year, mean emission rates at the irrigated, fertilised and rotationally-grazed site were 7.0 (± 0.89) nmol CH4 m-2 s-1 and 0.57 (± 0.019) nmol N2O m-2 s-1. At this site, the N2O emissions amounted to 1.19 (± 0.15) % of the

  10. Combining two complementary micrometeorological methods to measure CH4 and N2O fluxes over pasture

    NASA Astrophysics Data System (ADS)

    Laubach, Johannes; Barthel, Matti; Fraser, Anitra; Hunt, John E.; Griffith, David W. T.

    2016-03-01

    New Zealand's largest industrial sector is pastoral agriculture, giving rise to a large fraction of the country's emissions of methane (CH4) and nitrous oxide (N2O). We designed a system to continuously measure CH4 and N2O fluxes at the field scale on two adjacent pastures that differed with respect to management. At the core of this system was a closed-cell Fourier transform infrared (FTIR) spectrometer, which measured the mole fractions of CH4, N2O and carbon dioxide (CO2) at two heights at each site. In parallel, CO2 fluxes were measured using eddy-covariance instrumentation. We applied two different micrometeorological ratio methods to infer the CH4 and N2O fluxes from their respective mole fractions and the CO2 fluxes. The first is a variant of the flux-gradient method, where it is assumed that the turbulent diffusivities of CH4 and N2O equal that of CO2. This method was reliable when the CO2 mole-fraction difference between heights was at least 4 times greater than the FTIR's resolution of differences. For the second method, the temporal increases of mole fractions in the stable nocturnal boundary layer, which are correlated for concurrently emitted gases, are used to infer the unknown fluxes of CH4 and N2O from the known flux of CO2. This method was sensitive to "contamination" from trace gas sources other than the pasture of interest and therefore required careful filtering. With both methods combined, estimates of mean daily CH4 and N2O fluxes were obtained for 56 % of days at one site and 73 % at the other. Both methods indicated both sites as net sources of CH4 and N2O. Mean emission rates for 1 year at the unfertilised, winter-grazed site were 8.9 (±0.79) nmol CH4 m-2 s-1 and 0.38 (±0.018) nmol N2O m-2 s-1. During the same year, mean emission rates at the irrigated, fertilised and rotationally grazed site were 8.9 (±0.79) nmol CH4 m-2 s-1 and 0.58 (±0.020) nmol N2O m-2 s-1. At this site, the N2O emissions amounted to 1.21 (±0.15) % of the nitrogen

  11. Seasonal, inter-annual and decadal changes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in the Scheldt estuary (Belgium, The Netherlands)

    NASA Astrophysics Data System (ADS)

    Borges, Alberto V.; Middelburg, Jack J. B.; Chou, Lei; Kromkamp, Jacco; Houtekamer, Marco; Harlay, Jérôme

    2014-05-01

    We carried out monthly cruises to study the seasonal and spatial variations of the partial pressure of carbon dioxide CO2 (pCO2), methane (CH4) and nitrous oxide (N2O) concentrations in the Scheldt estuary, a strongly human impacted system located in Belgium and the Netherlands. This survey was initiated in 2008 for pCO2, and from 2009 onwards for methane (CH4) and nitrous oxide (N2O). In the lower estuary, pCO2 strongly decreased and oxygen saturation level (%O2) strongly increased during the spring phytoplankton bloom. In the upper estuary, two yearly maxima of pCO2 coinciding with minima of %O2 occurred in spring and fall due to enhanced nitrification and/or net heterotrophy. In the upper estuary, pCO2 decreased in winter due to lower temperature (affecting solubility and inhibiting biological activity). pCO2 also decreased in summer due to increase in primary production and decrease of net heterotrophy. In the upper estuary, maxima of CH4 were observed in winter due to enhanced river inputs (high discharge) while in the lower estuary higher CH4 was observed in summer. This was probably due to inputs of CH4 from inter-tidal areas at the mouth of estuary that increased in summer due to higher temperatures and higher organic matter availability. N2O also showed higher values during winter in the upper estuary, but in summer N2O was low in the lower estuary due to decreased solubility due to higher temperature. During winter 2009, extremely high N2O values were observed in the upper estuary, up to 3257 nM (23738% saturation). This was related to the problems encountered by the Brussels North waste water treatment plant (WWTP) in late 2009. One of the collectors of the station was shut down in 25 November 2009, and by 8 December 2009, the whole WWTP was shut down and the waste-water was delivered directly to the Rupel. Extremely high N2O values were observed in the upper estuary on 7 December 2009, and abnormally high N2O values (compared to other years) persisted

  12. Annual Greenhouse Gas (CO2, CH4, and N2O) Fluxes Via Ebullition from a Temperate Emergent Wetland

    NASA Astrophysics Data System (ADS)

    Mcnicol, G.; Sturtevant, C. S.; Knox, S. H.; Baldocchi, D. D.; Silver, W. L.

    2014-12-01

    Quantifying wetland greenhouse gas exchange is necessary to evaluate their potential for mitigating climate change via carbon sequestration. However measuring greenhouse gas fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in wetlands is difficult due to high spatial and temporal variability, and multiple transport pathways of emission. Transport of biogenic soil gas via highly sporadic ebullition (bubbling) events is often ignored or quantified poorly in wetland greenhouse gas budgets, but can rapidly release large volumes of gas to the atmosphere. To quantify a robust annual ebullition flux we measured rates continuously for a year (2013-2014) using custom-built chambers deployed in a restored emergent wetland located in the Sacramento-San Joaquin Delta, CA. We combined ebullition flux rates with observations of gas concentrations to estimate annual ebullition emissions of CO2, CH4, and N2O and compare flux rates to whole-ecosystem exchange of CO2 and CH4 measured simultaneously by eddy covariance.Mean ebullition flux rates were 18.3 ± 5.6 L m-2 yr-1. Ebullition CH4 concentrations were very high and ranged from 23-76 % with a mean of 47 ± 2.9 %; CO2 concentrations were lower and ranged from 0.7-6.6 % with a mean of 2.8 ± 0.3 %; N2O concentrations were below atmospheric concentrations and ranged from 130-389 ppb(v) with a mean of 257 ± 13 ppb(v). We calculated well-constrained annual ebullition fluxes of: 6.2 ± 1.9 g CH4 m-2 yr-1, 1.0 ± 0.3 g CO2 m-2 yr-1 and 9.3 ± 2.8 mg N2O m-2 yr-1. Methane emissions via ebullition were very large, representing 15-25 % of total wetland CH4 emissions measured at this site, whereas ebullition released only relatively small quantities of CO2 and N2O. Our results demonstrate that large releases of CH4 via ebullition from open water surfaces can be a significant component of restored wetland greenhouse gas budgets.

  13. Annual dynamics of N2O, CH4 and CO2 fluxes from the agricultural irrigation watersheds in southeast China

    NASA Astrophysics Data System (ADS)

    Wu, S.; Zou, J.; Liu, S.; Chen, J.; Kong, D.; Geng, Y.

    2017-12-01

    Agricultural irrigation watershed covers a large area in southeast of China and is a potentially important source of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). However, the flux magnitudes contribution to the overall catchment greenhouse gas (GHGs) fluxes and their drivers of seasonal variability are limited in agricultural irrigation watersheds. An in-situ observation was performed to measure annual CO2, CH4 and N2O fluxes from an agricultural irrigation watershed in southeast of China from September 2014 to September 2016. GHGs fluxes were measured using floating chambers and a gas exchange model was also used to predict CH4 and N2O fluxes. All GHGs showed varied seasonally with highest fluxes in early summer (July) and lowest in winter. Estimated seasonal CH4-C fluxes (11.5-97.6 mg m-2 hr-1) and N2O-N fluxes (2.8-80.8μg m-2 hr-1) were in relative agreement with measured CH4-C fluxes (0.05-74.9mg m-2 hr-1) and N2O-N fluxes (3.9-68.7μg m-2 hr-1) fluxes using floating chambers. Both CH4 and N2O fluxes were positively related to water temperature. The CH4 fluxes were negatively related to water dissolved oxygen (DO) concentration but positively related to sediment dissolved organic carbon (DOC). The N2O fluxes were positively related to water NH4+ and NO3-. The calculated EF5-r value in this study (mean = 0.0016; range = 0.0013-0.0018) was below the current IPCC (2006) default value of 0.0025. This implied that IPCC methodology may over estimates of N2O emissions associated with nitrogen leaching and runoff from agriculture.

  14. Edge effects on N2O, NO and CH4 fluxes in two temperate forests.

    PubMed

    Remy, Elyn; Gasche, Rainer; Kiese, Ralf; Wuyts, Karen; Verheyen, Kris; Boeckx, Pascal

    2017-01-01

    Forest ecosystems may act as sinks or sources of nitrogen (N) and carbon (C) compounds, such as the climate relevant trace gases nitrous oxide (N 2 O), nitric oxide (NO) and methane (CH 4 ). Forest edges, which catch more atmospheric deposition, have become important features in European landscapes and elsewhere. Here, we implemented a fully automated measuring system, comprising static and dynamic measuring chambers determining N 2 O, NO and CH 4 fluxes along an edge-to-interior transect in an oak (Q. robur) and a pine (P. nigra) forest in northern Belgium. Each forest was monitored during a 2-week measurement campaign with continuous measurements every 2h. NO emissions were 9-fold higher than N 2 O emissions. The fluxes of NO and CH 4 differed between forest edge and interior, but not for N 2 O. This edge effect was more pronounced in the oak than in the pine forest. In the oak forest, edges emitted less NO (on average 60%) and took up more CH 4 (on average 177%). This suggests that landscape structure can play a role in the atmospheric budgets of these climate relevant trace gases. Soil moisture variation between forest edge and interior was a key variable explaining the magnitude of NO and CH 4 fluxes in our measurement campaign. To better understand the environmental impact of N and C trace gas fluxes from forest edges, additional and long-term measurements in other forest edges are required. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Harmonisation and diagnostics of MIPAS ESA CH4 and N2O profiles using data assimilation

    NASA Astrophysics Data System (ADS)

    Errera, Quentin; Ceccherini, Simone; Christophe, Yves; Chabrillat, Simon; Hegglin, Michaela I.; Lambert, Alyn; Ménard, Richard; Raspollini, Piera; Skachko, Sergey; van Weele, Michiel; Walker, Kaley A.

    2016-12-01

    This paper discusses assimilation experiments of methane (CH4) and nitrous oxide (N2O) profiles retrieved from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). Here we focus on data versions 6 and 7 provided by the ESA processor. These data sets have been assimilated by the Belgian Assimilation System for Chemical ObsErvations (BASCOE). The CH4 and N2O retrieved profiles can oscillate, especially in the tropical lower stratosphere. Using the averaging kernels of the observations and a background error covariance matrix, which has previously been calibrated, allows the system to partly remedy this issue and provide assimilated fields that are more regular vertically. In general, there is a good agreement between the BASCOE analyses and independent observations from ACE-FTS (CH4 and N2O) and MLS (N2O), demonstrating the general good quality of CH4 and N2O retrievals provided by MIPAS ESA. Nevertheless, this study also identifies two issues in these data sets. First, time series of the observations show unexpected discontinuities due to an abrupt change in the gain of MIPAS band B, generally occurring after the instrument decontamination. Since the calibration is performed weekly, the abrupt change in the gain affects the measurements until the subsequent calibration is performed. Second, the correlations between BASCOE analyses and independent observations are poor in the lower stratosphere, especially in the tropics, probably due to the presence of outliers in the assimilated data. In this region, we recommend using MIPAS CH4 and N2O retrievals with caution.

  16. Long-term measurements of atmospheric trace gases (CO2, CH4, N2O, SF6, CO, H2), O2, and δ13CH4 isotopes at Weybourne Atmospheric Observatory, UK: past, present and future

    NASA Astrophysics Data System (ADS)

    Manning, Andrew C.; Forster, Grant L.; Oram, David E.; Reeves, Claire E.; Pickers, Penelope A.; Barningham, S. Thomas; Sturges, William T.; Bandy, Brian; Nisbet, Euan G.; Lowry, David; Fisher, Rebecca; Fleming, Zoe

    2016-04-01

    The Weybourne Atmospheric Observatory (WAO) is situated on the north Norfolk Coast (52.95°N, 1.13°E) in the United Kingdom and is run by the University of East Anglia (UEA), with support from the UK National Centre for Atmospheric Science (NCAS). In 2016, the WAO became a UK-ICOS (Integrated Carbon Observing System) monitoring station. Since 2008, we have been collecting high-precision long-term in situ measurements of atmospheric carbon dioxide (CO2), oxygen (O2), carbon monoxide (CO) and molecular hydrogen (H2), as well as regular bag sampling for δ13CH4. In early 2013, the measurement of atmospheric methane (CH4) commenced, and nitrous oxide (N2O) and sulphur hexafluoride (SF6) began in 2014. We summarise the CO2, O2, CH4, N2O, SF6, CO, H2 and δ13CH4 measurements made to date and highlight some key features observed (e.g. seasonal cycles, long-term trends, pollution events and deposition events). We summarise how the long-term measurements fit into other broader projects which have helped to support the long term time-series at WAO over the years, and highlight how we contribute to broader global atmospheric observation networks.

  17. Climate change reduces the net sink of CH4 and N2O in a semiarid grassland

    USDA-ARS?s Scientific Manuscript database

    Methane (CH4) and nitrous oxide (N2O) are potent greenhouse gases; their concentrations in the atmosphere have increased because of human activity. Soils are important sources and sinks of both gases where their production and consumption are largely regulated by biological processes. Climate change...

  18. Isotopomer analysis of production and consumption mechanisms of N2O and CH4 in an advanced wastewater treatment system.

    PubMed

    Toyoda, Sakae; Suzuki, Yuuri; Hattori, Shohei; Yamada, Keita; Fujii, Ayako; Yoshida, Naohiro; Kouno, Rina; Murayama, Kouki; Shiomi, Hiroshi

    2011-02-01

    Wastewater treatment processes are believed to be anthropogenic sources of nitrous oxide (N(2)O) and methane (CH(4)). However, few studies have examined the mechanisms and controlling factors in production of these greenhouse gases in complex bacterial systems. To elucidate production and consumption mechanisms of N(2)O and CH(4) in microbial consortia during wastewater treatment and to characterize human waste sources, we measured their concentrations and isotopomer ratios (elemental isotope ratios and site-specific N isotope ratios in asymmetric molecules of NNO) in water and gas samples collected by an advanced treatment system in Tokyo. Although the estimated emissions of N(2)O and CH(4) from the system were found to be lower than those from the typical treatment systems reported before, water in biological reaction tanks was supersaturated with both gases. The concentration of N(2)O, produced mainly by nitrifier-denitrification as indicated by isotopomer ratios, was highest in the oxic tank (ca. 4000% saturation). The dissolved CH(4) concentration was highest in in-flow water (ca. 3000% saturation). It decreased gradually during treatment. Its carbon isotope ratio indicated that the decrease resulted from bacterial CH(4) oxidation and that microbial CH(4) production can occur in anaerobic and settling tanks.

  19. Global Inverse Modeling of CH4 and δ13C-CH4 Measurements to Understand Recent Trends in Methane Emissions

    NASA Astrophysics Data System (ADS)

    Karmakar, S.; Butenhoff, C. L.; Rice, A. L.; Khalil, A. K.

    2017-12-01

    Methane (CH4) is the second most important greenhouse gas with a radiative forcing of 0.97 W/m2 including both direct and indirect effects and a global warming potential of 28 over a 100-year time horizon. After a decades-long period of decline beginning in the 1980s, the methane growth rate rebounded in 2007 for reasons that are of current debate. During this same growth period atmospheric methane became less enriched in the 13CH4 isotope suggesting the recent CH4 growth was caused by an increase in 13CH4-depleted biogenic emissions. Recent papers have attributed this growth to increasing emissions from wetlands, rice agriculture, and ruminants. In this work we provide additional insight into the recent behavior of atmospheric methane and global wetland emissions by performing a three-dimensional Bayesian inversion of surface CH4 and 13CH4/12CH4 ratios using NOAA Global Monitoring Division (GMD) "event-level" CH4 measurements and the GEOS-Chem chemical-transport model (CTM) at a horizontal grid resolution of 2ox2.5o. The spatial pattern of wetland emissions was prescribed using soil moisture and temperature from GEOS-5 meteorology fields and soil carbon pools from the Lund-Potsdam-Jena global vegetation model. In order to reduce the aggregation error caused by a potentially flawed distribution and to account for isotopic measurements that indicate northern high latitude wetlands are isotopically depleted in 13CH4 relative to tropical wetlands we separated our pattern into three latitudinal bands (90-30°N, 30°N-0, 0-90°S). Our preliminary results support previous claims that the recent increase in atmospheric methane is driven by increases in biogenic CH4 emissions. We find that while wetland emissions from northern high latitudes (90-30°N) remained relatively constant during this time, southern hemisphere wetland emissions rebounded from a decade-long decline and began to rise again in 2007 and have remained elevated to the present. Emissions from rice

  20. Factors Related with CH4 and N2O Emissions from a Paddy Field: Clues for Management implications

    PubMed Central

    Wang, Chun; Lai, Derrick Y. F.; Sardans, Jordi; Wang, Weiqi; Zeng, Congsheng; Peñuelas, Josep

    2017-01-01

    Paddy fields are major sources of global atmospheric greenhouse gases, including methane (CH4) and nitrous oxide (N2O). The different phases previous to emission (production, transport, diffusion, dissolution in pore water and ebullition) despite well-established have rarely been measured in field conditions. We examined them and their relationships with temperature, soil traits and plant biomass in a paddy field in Fujian, southeastern China. CH4 emission was positively correlated with CH4 production, plant-mediated transport, ebullition, diffusion, and concentration of dissolved CH4 in porewater and negatively correlated with sulfate concentration, suggesting the potential use of sulfate fertilizers to mitigate CH4 release. Air temperature and humidity, plant stem biomass, and concentrations of soil sulfate, available N, and DOC together accounted for 92% of the variance in CH4 emission, and Eh, pH, and the concentrations of available N and Fe3+, leaf biomass, and air temperature 95% of the N2O emission. Given the positive correlations between CH4 emission and DOC content and plant biomass, reduce the addition of a carbon substrate such as straw and the development of smaller but higher yielding rice genotypes could be viable options for reducing the release of greenhouse gases from paddy fields to the atmosphere. PMID:28081161

  1. Emissions of N2O, CH4 and CO2 from tropical forest soils

    NASA Technical Reports Server (NTRS)

    Keller, Michael; Kaplan, Warren A.; Wofsy, Steven C.

    1986-01-01

    Emissions of nitrous oxide, methane, and carbon dioxide were measured at diverse locations in tropical forests of Brazil, Ecuador, and Puerto Rico using a static open chamber technique. Mean fluxes to the atmosphere were 1.7 x 10 to the 10th, -0.7 x 10 to the 10th, and 1.5 x 10 to the 14th molecules/sq cm per s for N2O, CH4, and CO2, respectively. The data indicate that tropical forests contribute a significant fraction of the global source for atmospheric N2O, about 40 percent of the current source, and possibly 75 percent of the preindustrial source. Methane is consumed by soils on average, but the sink is an insignificant part (less than 5 percent) of the atmospheric cycle for the gas. Emissions of CO2 from forest soils are higher at equatorial sites than at middle or high latitudes, as expected from ecological considerations. Soils emit CO2 at rates more than twice as large as the rate of carbon infall in litter; hence much of the emitted CO2 must arise from root metabolism.

  2. CH4 and N2O emissions from China's beef feedlots with ad libitum and restricted feeding in fall and spring seasons.

    PubMed

    Lin, Zhi; Liao, Wenhua; Yang, Yuanyuan; Gao, Zhiling; Ma, Wenqi; Wang, Dianwu; Cao, Yufeng; Li, Jianguo; Cai, Zhenjiang

    2015-04-01

    Accurately quantifying methane (CH4) and nitrous oxide (N2O) emissions from beef operations in China is necessary to evaluate the contribution of beef cattle to greenhouse gas budgets at the national and global level. Methane and N2O emissions from two intensive beef feedlots in the North China Plain, one with a restricted feeding strategy and high manure collection frequency and the other with an ad libitum feeding strategy and low manure collection frequency, were quantified in the fall and spring seasons using an inverse dispersion technique. The diel pattern of CH4 from the beef feedlot with an ad libitum feed strategy (single peak during a day) differed from that under a restricted feeding condition (multiple peaks during a day), but little difference in the diel pattern of N2O emissions between two feeding strategies was observed. The two-season average CH4 emission rates of the two intensive feedlots were 230 and 198gCH4animal(-1)d(-1) and accounted for 6.7% and 6.8% of the gross energy intake, respectively, indicating little impact of the feeding strategy and manure collection frequency on the CH4 conversion factor at the feedlot level. However, the average N2O emission rates (21.2g N2Oanimal(-1)d(-1)) and conversion factor (8.5%) of the feedlot with low manure collection frequency were approximately 131% and 174% greater, respectively, than the feedlot under high frequency conditions, which had a N2O emission rate and conversion factor of 9.2g N2Oanimal(-1)d(-1) and 3.1%, respectively, indicating that increasing manure collection frequency played an important role in reducing N2O emissions from beef feedlots. In addition, comparison indicated that China's beef and dairy cattle in feedlots appeared to have similar CH4 conversion factors. Copyright © 2015 Elsevier Inc. All rights reserved.

  3. Resolved 12CH2D2 and 13CH3D in CH4 as Sensitive Indicators of Disequilibrium and Equilibrium during Microbial Methane Cycling

    NASA Astrophysics Data System (ADS)

    Ash, J. L.; Egger, M.; Slomp, C. P.; Kohl, I. E.; Treude, T.; Rumble, D.; Young, E. D.

    2016-12-01

    The ability to measure the relative concentrations of at least two doubly-substituted rare isotopologues of gases with biogeochemical relevance provides new constraints on sources and sinks of these gases. In particular, as shown recently for O2, the use of two independent, rare isotopologues allows for detection of thermodynamic intra-species equilibrium and disequilibrium. Here, we report the first measurements of fully resolved 13CH3D and 12CH2D2 from natural samples of microbial methane gas. A suite of sedimentary methane samples from the Bornholm Basin in the Baltic Sea was collected during IODP Exp. 347. Sample depths range from 2-20 meters below seafloor (mbsf). Methane concentrations decrease with depth, and mcrA (a marker for methanogenesis and methanotropy) is present throughout. See Figure. Both Δ13CH3D and Δ12CH2D2 increase with depth as methane concentrations decrease with the shallowest samples exhibiting disequilibrium by up to 2‰ in Δ13CH3D and 13‰ in Δ12CH2D2 while the deepest samples approach isotopic thermodynamic equilibrium (marked by grey bars in Figure). The Fe-mediated anaerobic oxidation of methane (Fe-AOM) has been inferred in these sediments by geochemical modeling . Slow methane cycling by methanogensis and methanotrophy is likely responsible for the approach to isotopic bond order equilibrium in CH4 with depth, consistent with Fe-AOM. While axenic culturing experiments generate methane with large deficits in 12CH2D2 (reported at this meeting), these data from the Baltic Sea demonstrate that isotopic equilibrium can be achieved during microbial recycling of methane. In the absence of Δ12CH2D2, the Δ13CH3D values alone could be misinterpreted as representing gradients in temperature due perhaps to exothermic organic matter degradation. The combination of both mass-18 rare isotopologues of methane provides the means to distinguish equilibrium from disequilibrium and probe microbial methane cycling even where Δ13CH3D suggests

  4. Impact of the heatwave in 2003 on the summer CH4 and N2O budget of a spruce forest ecosystem: A four-year comparison

    NASA Astrophysics Data System (ADS)

    Lamers, M.; Fiedler, S.; Jungkunst, H. F.; Stahr, K.; Streck, T.

    2009-04-01

    Both CH4 and N2O reduction and oxidation are highly sensitive to variation in soil moisture. Significant changes of net CH4 and total N2O fluxes from soils can therefore be expected to accompany redistribution for precipitation in the course of climate change where more extreme events are predicted for the future. The extreme summer drought in 2003 offered the unique opportunity to study the impact of such events on the emission of greenhouse gases, such as methane or nitrous oxide, under field conditions. The main objective of the present study was to evaluate the impact of the summer drought in 2003 on the net methane and nitrous oxide budget of a spruce forest ecosystem (South-West Germany) with large variation in soil drainage. During the summers of 2000-2004 we measured net CH4 and N2O fluxes (bi)-weekly using the closed-chamber technique for six different soil types ranging from well-aerated Cambisols to poorly drained Gleysols and a wet Histosol. With regard to CH4 the extreme summer draught (1) did not elevate net CH4-sink function of soils, but (2) highly reduced net CH4-source strength and (3) reversed the net CH4 source of the investigated catchment into a sink. In all four summers investigated, net ecosystem exchange of CH4 was found only in the hydromorphic soils but not in the dominant well-aerated soils. This highlighted the key role of hydromorphic soils for the investigated pedodiverse system. With regard to N2O the summer draught in 2003 significantly reduced N2O emissions at least for the Humic Gleysol and the Sapric Histosol and hence markedly reduced the net N2O source strength of the investigated ecosystem.

  5. A unified equation for calculating methane vapor pressures in the CH4-H2O system with measured Raman shifts

    USGS Publications Warehouse

    Lu, W.; Chou, I.-Ming; Burruss, R.C.; Song, Y.

    2007-01-01

    A unified equation has been derived by using all available data for calculating methane vapor pressures with measured Raman shifts of C-H symmetric stretching band (??1) in the vapor phase of sample fluids near room temperature. This equation eliminates discrepancies among the existing data sets and can be applied at any Raman laboratory. Raman shifts of C-H symmetric stretching band of methane in the vapor phase of CH4-H2O mixtures prepared in a high-pressure optical cell were also measured at temperatures between room temperature and 200 ??C, and pressures up to 37 MPa. The results show that the CH4 ??1 band position shifts to higher wavenumber as temperature increases. We also demonstrated that this Raman band shift is a simple function of methane vapor density, and, therefore, when combined with equation of state of methane, methane vapor pressures in the sample fluids at elevated temperatures can be calculated from measured Raman peak positions. This method can be applied to determine the pressure of CH4-bearing systems, such as methane-rich fluid inclusions from sedimentary basins or experimental fluids in hydrothermal diamond-anvil cell or other types of optical cell. ?? 2007 Elsevier Ltd. All rights reserved.

  6. CO 2 uptake is offset by CH 4 and N 2O emissions in a poplar short-rotation coppice

    DOE PAGES

    Zenone, Terenzio; Zona, Donatella; Gelfand, Ilya; ...

    2015-04-18

    The need for renewable energy sources will lead to a considerable expansion in the planting of dedicated fast-growing biomass crops across Europe. These are commonly cultivated as short-rotation coppice (SRC), and currently poplar ( Populus spp.) is the most widely planted. In this study, we report the greenhouse gas (GHG) fluxes of carbon dioxide (CO 2), methane (CH 4) and nitrous oxide (N 2O) measured using eddy covariance technique in an SRC plantation for bioenergy production. Measurements were made during the period 2010–2013, that is, during the first two rotations of the SRC. The overall GHG balance of the 4more » years of the study was an emission of 1.90 (±1.37) Mg CO 2eq ha -1; this indicated that soil trace gas emissions offset the CO 2 uptake by the plantation. CH 4 and N 2O contributed almost equally to offset the CO 2 uptake of -5.28 (±0.67) Mg CO2eq ha -1 with an overall emission of 3.56 (±0.35) Mg CO 2eq ha -1 of N 2O and of 3.53 (±0.85) Mg CO 2eq ha-1 of CH 4. N 2O emissions mostly occurred during one single peak a few months after the site was converted to SRC; this peak comprised 44% of the total N 2O loss during the two rotations. Accurately capturing emission events proved to be critical for deriving correct estimates of the GHG balance. The nitrogen (N) content of the soil and the water table depth were the two drivers that best explained the variability in N 2O and CH 4, respectively. Here, this study underlines the importance of the ‘non-CO 2 GHGs’ on the overall balance. Further long-term investigations of soil trace gas emissions should monitor the N content and the mineralization rate of the soil, as well as the microbial community, as drivers of the trace gas emissions.« less

  7. The Effects of Flame Structure on Extinction of CH4-O2-N2 Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Du, J.; Axelbaum, R. L.; Gokoglu, S. (Technical Monitor)

    1996-01-01

    The effects of flame structure on the extinction limits of CH4-O2-N2 counterflow diffusion flames were investigated experimentally and numerically by varying the stoichiometric mixture fraction Z(sub st), Z(sub st) was varied by varying free-stream concentrations, while the adiabatic flame temperature T(sub ad) was held fixed by maintaining a fixed amount of nitrogen at the flame. Z(sub st) was varied between 0.055 (methane-air flame) and 0.78 (diluted- methane-oxygen flame). The experimental results yielded an extinction strain rate K(sub ext) of 375/s for the methane-air flame, increasing monotonically to 1042/s for the diluted-methane-oxygen flame. Numerical results with a 58-step Cl mechanism yielded 494/s and 1488/s, respectively. The increase in K(sub ext) with Z(sub st) for a fixed T(sub ad) is explained by the shift in the O2 profile toward the region of maximum temperature and the subsequent increase in rates for chain-branching reactions. The flame temperature at extinction reached a minimum at Z(sub st) = 0.65, where it was 200 C lower than that of the methane-air flame. This significant increase in resistance to extinction is seen to correspond to the condition in which the OH and O production zones are centered on the location of maximum temperature.

  8. Occurrence of greenhouse gases (CO2, N2O and CH4) in groundwater of the Walloon Region (Belgium).

    NASA Astrophysics Data System (ADS)

    Jurado, Anna; Borges, Alberto V.; Pujades, Estanislao; Hakoun, Vivien; Knöller, Kay; Brouyère, Serge

    2017-04-01

    Greenhouse gases (GHGs) are an environmental problem because their concentrations in the atmosphere have continuously risen since the industrial revolution. They can be indirectly transferred to the atmosphere through groundwater discharge into surface water bodies such as rivers. However, their occurrence is poorly evaluated in groundwater. The aim of this work is to identify the hydrogeological contexts (e.g., chalk and limestone aquifers) and the most conductive conditions for the generation of GHGs in groundwater at a regional scale. To this end, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) concentrations, major and minor elements and environmental isotopes were monitored in several groundwater bodies of the Walloon Region (Belgium) from September 2014 to June 2016. The concentrations of GHGs in groundwater ranged from 1769 to 100519 ppm for the partial pressure of CO2 and from 0 to 1064 nmol/L and 1 to 37062 nmol/L for CH4 and N2O respectively. Overall, groundwater was supersaturated in GHGs with respect to atmospheric equilibrium, suggesting that groundwater contribute to the atmospheric GHGs budget. Prior inspection of the data suggested that N2O in groundwater can be produced by denitrification and nitrification. The most suitable conditions for the accumulation of N2O are promoted by intermediate dissolved oxygen concentrations (2.5-3 mg L-1) and the availability of nitrate (NO3-). These observations will be compared with the isotopes of NO3-. CH4 was less detected and at lower concentration than N2O, suggesting that groundwater redox conditions are not reducing enough to promoted the production of CH4. The results will be presented and discussed in detail in the presentation.

  9. The Regulation of CH4 and N2O fluxes by Wetlands at Landscape Level

    NASA Astrophysics Data System (ADS)

    Soosaar, K.; Maddison, M.; Salm, J. O.; Järveoja, J.; Hansen, R.; Mander, Ü.

    2012-04-01

    : median values 4.2, 1.4, 1.1, and 0.9 kg N2O-N ha-1 y-1, respectively. In peatlands, median values of CH4-C were 85.2, 23.7, 0.07 and 0.12 kg ha-1 yr-1, and N2O-N -0.05, -0.01, 0.18 and 0.19 kg ha-1 yr-1, respectively. There were significantly higher emissions of N2O from abandoned and active peat mining areas, whereas CH4 emissions were significantly higher in natural and drained areas. We also found that the buffering capacity of long-term loaded riparian alder forests in agricultural landscapes will decrease over time, which calls for the careful management of these riparian forests. Mitsch, W.J, Zhang, L., Stefanik, K.C., Nahlik, A.M., Anderson, C.J., Bernal, B., Hernandez, M., Song, K. 2012. Creating wetlands: Primary succession, water quality changes, and self-design over 15 years. BioScience in press Zedler, JB. 2003. Wetlands at your service: reducing impacts of agriculture at the watershed scale. Front. Ecol. Environ., 1, pp. 65-72 Teiter, S., Mander, U. 2005. Emission of N2O, N2, CH4, and CO2 from constructed wetlands for wastewater treatment and from riparian buffer zones. Ecol. Eng., 25, pp. 528-541 Thiere, G., Stadmark, J., Weisner, SEB. 2011. Nitrogen retention versus methane emission: Environmental benefits and risks of large-scale wetland creation. Ecol. Eng., 37, pp. 6-15

  10. Background CH4 and N2O fluxes in low-input short rotation coppice

    NASA Astrophysics Data System (ADS)

    Görres, Carolyn-Monika; Zenone, Terenzio; Ceulemans, Reinhart

    2016-04-01

    Extensively managed short rotation coppice systems are characterized by low fluxes of CH4 and N2O. However due to the large global warming potential of these trace gases (GWP100: CH4: 34, N2O: 298), such background fluxes can still significantly contribute to offsetting the CO2 uptake of short rotation coppice systems. Recent technological advances in fast-response CH4 and N2O analysers have improved our capability to capture these background fluxes, but their quantification still remains a challenge. As an example, we present here CH4 and N2O fluxes from a short-rotation bioenergy plantation in Belgium. Poplars have been planted in a double-row system on a loamy sand in 2010 and coppiced in the beginning of 2012 and 2014 (two-year rotation system). In 2013 (June - November) and 2014 (April - August), the plantation's CH4 and N2O fluxes were measured in parallel with an eddy covariance tower (EC) and an automated chamber system (AC). The EC had a detection limit of 13.68 and 0.76 μmol m-2 h-1 for CH4 and N2O, respectively. The median detection limit of the AC was 0.38 and 0.08 μmol m-2 h-1 for CH4 and N2O, respectively. The EC picked up a few high CH4 emission events with daily averages >100 μmol m-2 h-1, but a large proportion of the measured fluxes were within the EC's detection limit. The same was true for the EC-derived N2O fluxes where the daily average flux was often close to the detection limit. Sporadically, some negative (uptake) fluxes of N2O were observed. On the basis of the EC data, no clear link was found between CH4 and N2O fluxes and environmental variables. The problem with fluxes within the EC detection limit is that a significant amount of the values can show the opposite sign, thus "mirroring" the true flux. Subsequently, environmental controls of background trace gas fluxes might be disguised in the analysis. As a next step, it will be tested if potential environmental drivers of background CH4 and N2O fluxes at the plantation can be

  11. CH{sub 4} and N{sub 2}O emissions from China’s beef feedlots with ad libitum and restricted feeding in fall and spring seasons

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lin, Zhi; Liao, Wenhua; Yang, Yuanyuan

    Accurately quantifying methane (CH{sub 4}) and nitrous oxide (N{sub 2}O) emissions from beef operations in China is necessary to evaluate the contribution of beef cattle to greenhouse gas budgets at the national and global level. Methane and N{sub 2}O emissions from two intensive beef feedlots in the North China Plain, one with a restricted feeding strategy and high manure collection frequency and the other with an ad libitum feeding strategy and low manure collection frequency, were quantified in the fall and spring seasons using an inverse dispersion technique. The diel pattern of CH{sub 4} from the beef feedlot with anmore » ad libitum feed strategy (single peak during a day) differed from that under a restricted feeding condition (multiple peaks during a day), but little difference in the diel pattern of N{sub 2}O emissions between two feeding strategies was observed. The two-season average CH{sub 4} emission rates of the two intensive feedlots were 230 and 198 g CH{sub 4} animal{sup −1} d{sup −1} and accounted for 6.7% and 6.8% of the gross energy intake, respectively, indicating little impact of the feeding strategy and manure collection frequency on the CH{sub 4} conversion factor at the feedlot level. However, the average N{sub 2}O emission rates (21.2 g N{sub 2}O animal{sup −1} d{sup −1}) and conversion factor (8.5%) of the feedlot with low manure collection frequency were approximately 131% and 174% greater, respectively, than the feedlot under high frequency conditions, which had a N{sub 2}O emission rate and conversion factor of 9.2 g N{sub 2}O animal{sup −1} d{sup −1} and 3.1%, respectively, indicating that increasing manure collection frequency played an important role in reducing N{sub 2}O emissions from beef feedlots. In addition, comparison indicated that China’s beef and dairy cattle in feedlots appeared to have similar CH{sub 4} conversion factors. - Highlights: • CH{sub 4} and N{sub 2}O emissions from China’s beef feedlots

  12. Fluxes of CO2, CH4 and N2O at two European beech forests: linking soil gas production profiles with soil and stem fluxes

    NASA Astrophysics Data System (ADS)

    Maier, Martin; Machacova, Katerina; Halaburt, Ellen; Haddad, Sally; Urban, Otmar; Lang, Friederike

    2016-04-01

    Soil and plant surfaces are known to exchange greenhouse gases with the atmosphere. Some gases like nitrous oxide (N2O) and methane (CH4) can be produced and re-consumed in different soil depths and soil compartments, so that elevated concentrations of CH4 or N2O in the soil do not necessarily mean a net efflux from the soil into the atmosphere. Soil aeration, and thus the oxygen status can underlay a large spatial variability within the soil on the plot and profile scale, but also within soil aggregates. Thus, conditions suitable for production and consumption of CH4 and N2O can vary on different scales in the soil. Plant surfaces can also emit or take up CH4 and N2O, and these fluxes can significantly contribute to the net ecosystem exchange. Since roots usually have large intercellular spaces or aerenchyma they may represent preferential transport ways for soil gases, linking possibly elevated soil gas concentrations in the subsoil in a "shortcut" to the atmosphere. We tested the hypothesis that the spatial variability of the soil-atmosphere fluxes of CO2, CH4 and N2O is caused by the heterogeneity in soil properties. Therefore, we measured soil-atmosphere gas fluxes, soil gas concentrations and soil diffusivity profiles and did a small scale field assessment of soil profiles on the measurments plots. We further tried to link vertical profiles of soil gas concentrations and diffusivity to derive the production and consumption profiles, and to link these profiles to the stem-atmosphere flux rates of individual trees. Measurements were conducted in two mountain beech forests with different geographical and climatic conditions (White Carpathians, Czech Republic; Black Forest, Germany). Gas fluxes at stem and soil levels were measured simultaneously using static chamber systems and chromatographic and continuous laser analyses. Monitoring simultaneously vertical soil gas profiles allowed to assess the within-soil gas fluxes, and thus to localize the production and

  13. Nitrate loading and CH4 and N2O Flux from headwater streams

    NASA Astrophysics Data System (ADS)

    Sousa, C. H. R. D.; Hilker, T.; Hall, F. G.; Moura, Y. M.; McAdam, E.

    2014-12-01

    Freshwater ecosystems transport and process significant amounts of terrestrial carbon and can be considerable sources of CO2, CH4, and N2O. A great deal of uncertainty, however, remains in both global estimates and our understanding of drivers of freshwater greenhouse gas emissions. Furthermore, small headwater streams have received insufficient attention to date and may contribute disproportionately to global GHG flux. Our objective was to quantify GHG flux and assess the impact of changes in DOC and NO3 concentrations in surface and subsurface water on flux rates in three streams in the Lamprey River watershed in New Hampshire, USA, that contrast in surface water DOC:NO3. We measured DOC, NO3 and dissolved gas concentrations in surface waters of each stream monthly from May 2011 to April 2012. Empirical measurements of reaeration coefficients were used to convert dissolved gas concentrations to fluxes. We found higher GHG concentrations and fluxes in the two streams with high DOC concentrations, particularly gases produced by anaerobic metabolism (CH4, N2O from methanogenesis and denitrification, respectively). The stream with high DOC and high NO3 showed high N2O and low CH4 flux, while the high DOC, low NO3 stream showed high CH4 and low N2O flux. Our results are consistent with a model in which C inputs drive total GHG production, while NO3 input regulates the relative importance of CH4 and N2O by suppressing methanogenesis and stimulating denitrification. The magnitude of GHG fluxes suggests that streams in this region are likely to be small sources of CO2, but potentially important sources of CH4 and N2O. Since CH4 and N2O are many times more powerful than CO2 at trapping heat in the atmosphere, freshwater emissions of these gases have the potential to offset a significant proportion of the climate benefits of the terrestrial carbon sink, a possibility that has not been sufficiently incorporated into climate models.

  14. Nitrate loading and CH4 and N2O Flux from headwater streams

    NASA Astrophysics Data System (ADS)

    Schade, J. D.; Bailio, J.; McDowell, W. H.

    2015-12-01

    Freshwater ecosystems transport and process significant amounts of terrestrial carbon and can be considerable sources of CO2, CH4, and N2O. A great deal of uncertainty, however, remains in both global estimates and our understanding of drivers of freshwater greenhouse gas emissions. Furthermore, small headwater streams have received insufficient attention to date and may contribute disproportionately to global GHG flux. Our objective was to quantify GHG flux and assess the impact of changes in DOC and NO3 concentrations in surface and subsurface water on flux rates in three streams in the Lamprey River watershed in New Hampshire, USA, that contrast in surface water DOC:NO3. We measured DOC, NO3 and dissolved gas concentrations in surface waters of each stream monthly from May 2011 to April 2012. Empirical measurements of reaeration coefficients were used to convert dissolved gas concentrations to fluxes. We found higher GHG concentrations and fluxes in the two streams with high DOC concentrations, particularly gases produced by anaerobic metabolism (CH4, N2O from methanogenesis and denitrification, respectively). The stream with high DOC and high NO3 showed high N2O and low CH4 flux, while the high DOC, low NO3 stream showed high CH4 and low N2O flux. Our results are consistent with a model in which C inputs drive total GHG production, while NO3 input regulates the relative importance of CH4 and N2O by suppressing methanogenesis and stimulating denitrification. The magnitude of GHG fluxes suggests that streams in this region are likely to be small sources of CO2, but potentially important sources of CH4 and N2O. Since CH4 and N2O are many times more powerful than CO2 at trapping heat in the atmosphere, freshwater emissions of these gases have the potential to offset a significant proportion of the climate benefits of the terrestrial carbon sink, a possibility that has not been sufficiently incorporated into climate models.

  15. Aerial Photography Estimation of CH4 and N2O Emissions from Adelie Penguins During 1983-2012 in Victoria Land, Antarctic

    NASA Astrophysics Data System (ADS)

    He, H.; Li, X.; Cheng, X.

    2016-12-01

    Sea animals are the "bio-indicators" of the climate change in the Antarctic. The abundant nutrient components in their excreta such as carbon (C) and nitrogen (N) promote the emissions of greenhouse gases (GHGs) including methane (CH4) and nitrous oxide (N2O). Adélie Penguins are important sea animals, their colonies therefore become the potential "hotspots" of the GHGs emissions. Some field observations have been carried out to study the penguin excreta on CH4 and N2O emissions in the Antarctic peninsula. However, due to the lacking of the penguin population data, the total emissions of GHGs have not been estimated at regional scale. This study aimed to extract penguin information from two period aerial photographs respectively in 1983 and 2012 using object-oriented method in Victoria Land, Antarctic, and then estimate the Adélie penguin populations on Inexpressible Island combined with the shadow analysis. Meanwhile, a GHGs model was developed to estimate CH4 and N2O emissions from Adelie penguins based on the CH4 and N2O fluxes of penguin guanos, the number of penguins, and the fresh weight of penguin guanos and so on. The results indicated that object-oriented method was effective in penguin information extraction from high-resolution images, and there were 17120 and 21183 Adélie penguins respectively in 1983 and 2012, respectively. The main reasons for the increase in penguin populations from 1983 to 2012 might be explained from physical environment and biological environment, such as the rising temperatures and reduced Antarctic toothfishes. And the total CH4 and N2O emissions from penguins on Inexpressible Island during breeding season were 246 kg CH4 and 2.67 kg N2O in 1983, and 304 kg CH4 and 3.31 kg N2O in 2012. Our study aimed to provide important reference value for the estimation of GHG budget in Antarctic.

  16. Removal of NO in NO/N2, NO/N2/O2, NO/CH4/N2, and NO/CH4/O2/N2 systems by flowing microwave discharges.

    PubMed

    Hueso, José L; Gonzalez-Elipe, Agustín R; Cotrino, José; Caballero, Alfonso

    2007-02-15

    In this paper, continuing previous work, we report on experiments carried out to investigate the removal of NO from simulated flue gas in nonthermal plasmas. The plasma-induced decomposition of small concentrations of NO in N2 used as the carrier gas and O2 and CH4 as minority components has been studied in a surface wave discharge induced with a surfatron launcher. The reaction products and efficiency have been monitored by mass spectrometry as a function of the composition of the mixture. NO is effectively decomposed into N2 and O2 even in the presence of O2, provided always that enough CH4 is also present in the mixture. Other majority products of the plasma reactions under these conditions are NH3, CO, and H2. In the absence of O2, decomposition of NO also occurs, although in that case HCN accompanies the other reaction products as a majority component. The plasma for the different reaction mixtures has been characterized by optical emission spectroscopy. Intermediate excited species of NO*, C*, CN*, NH*, and CH* have been monitored depending on the gas mixture. The type of species detected and their evolution with the gas composition are in agreement with the reaction products detected in each case. The observations by mass spectrometry and optical emission spectroscopy are in agreement with the kinetic reaction models available in literature for simple plasma reactions in simple reaction mixtures.

  17. Integrated measurements and modeling of CO2, CH4, and N2O fluxes using soil microsite frequency distributions

    NASA Astrophysics Data System (ADS)

    Davidson, Eric; Sihi, Debjani; Savage, Kathleen

    2017-04-01

    Soil fluxes of greenhouse gases (GHGs) play a significant role as biotic feedbacks to climate change. Production and consumption of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are affected by complex interactions of temperature, moisture, and substrate supply, which are further complicated by spatial heterogeneity of the soil matrix. Models of belowground processes of these GHGs should be internally consistent with respect to the biophysical processes of gaseous production, consumption, and transport within the soil, including the contrasting effects of oxygen (O2) as either substrate or inhibitor. We installed automated chambers to simultaneously measure soil fluxes of CO2 (using LiCor-IRGA), CH4, and N2O (using Aerodyne quantum cascade laser) along soil moisture gradients at the Howland Forest in Maine, USA. Measured fluxes of these GHGs were used to develop and validate a merged model. While originally intended for aerobic respiration, the core structure of the Dual Arrhenius and Michaelis-Menten (DAMM) model was modified by adding M-M and Arrhenius functions for each GHG production and consumption process, and then using the same diffusion functions for each GHG and for O2. The area under a soil chamber was partitioned according to a log-normal probability distribution function, where only a small fraction of microsites had high available-C. The probability distribution of soil C leads to a simulated distribution of heterotrophic respiration, which translates to a distribution of O2 consumption among microsites. Linking microsite consumption of O2 with a diffusion model generates microsite concentrations of O2, which then determine the distribution of microsite production and consumption of CH4 and N2O, and subsequently their microsite concentrations using the same diffusion function. At many moisture values, there are some microsites of production and some of consumption for each gas, and the resulting simulated microsite concentrations of CH4

  18. Emissions of CH4 and N2O under Different Tillage Systems from Double-Cropped Paddy Fields in Southern China

    PubMed Central

    Zhang, Hai-Lin; Bai, Xiao-Lin; Xue, Jian-Fu; Chen, Zhong-Du; Tang, Hai-Ming; Chen, Fu

    2013-01-01

    Understanding greenhouse gases (GHG) emissions is becoming increasingly important with the climate change. Most previous studies have focused on the assessment of soil organic carbon (SOC) sequestration potential and GHG emissions from agriculture. However, specific experiments assessing tillage impacts on GHG emission from double-cropped paddy fields in Southern China are relatively scarce. Therefore, the objective of this study was to assess the effects of tillage systems on methane (CH4) and nitrous oxide (N2O) emission in a double rice (Oryza sativa L.) cropping system. The experiment was established in 2005 in Hunan Province, China. Three tillage treatments were laid out in a randomized complete block design: conventional tillage (CT), rotary tillage (RT) and no-till (NT). Fluxes of CH4 from different tillage treatments followed a similar trend during the two years, with a single peak emission for the early rice season and a double peak emission for the late rice season. Compared with other treatments, NT significantly reduced CH4 emission among the rice growing seasons (P<0.05). However, much higher variations in N2O emission were observed across the rice growing seasons due to the vulnerability of N2O to external influences. The amount of CH4 emission in paddy fields was much higher relative to N2O emission. Conversion of CT to NT significantly reduced the cumulative CH4 emission for both rice seasons compared with other treatments (P<0.05). The mean value of global warming potentials (GWPs) of CH4 and N2O emissions over 100 years was in the order of NT

  19. Emissions of CH4 and N2O under different tillage systems from double-cropped paddy fields in Southern China.

    PubMed

    Zhang, Hai-Lin; Bai, Xiao-Lin; Xue, Jian-Fu; Chen, Zhong-Du; Tang, Hai-Ming; Chen, Fu

    2013-01-01

    Understanding greenhouse gases (GHG) emissions is becoming increasingly important with the climate change. Most previous studies have focused on the assessment of soil organic carbon (SOC) sequestration potential and GHG emissions from agriculture. However, specific experiments assessing tillage impacts on GHG emission from double-cropped paddy fields in Southern China are relatively scarce. Therefore, the objective of this study was to assess the effects of tillage systems on methane (CH4) and nitrous oxide (N2O) emission in a double rice (Oryza sativa L.) cropping system. The experiment was established in 2005 in Hunan Province, China. Three tillage treatments were laid out in a randomized complete block design: conventional tillage (CT), rotary tillage (RT) and no-till (NT). Fluxes of CH4 from different tillage treatments followed a similar trend during the two years, with a single peak emission for the early rice season and a double peak emission for the late rice season. Compared with other treatments, NT significantly reduced CH4 emission among the rice growing seasons (P<0.05). However, much higher variations in N2O emission were observed across the rice growing seasons due to the vulnerability of N2O to external influences. The amount of CH4 emission in paddy fields was much higher relative to N2O emission. Conversion of CT to NT significantly reduced the cumulative CH4 emission for both rice seasons compared with other treatments (P<0.05). The mean value of global warming potentials (GWPs) of CH4 and N2O emissions over 100 years was in the order of NT

  20. Theoretical Investigation of Methane Hydroxylation over Isoelectronic [FeO]2+- and [MnO]+-Exchanged Zeolites Activated by N2O.

    PubMed

    Mahyuddin, M Haris; Shiota, Yoshihito; Staykov, Aleksandar; Yoshizawa, Kazunari

    2017-09-05

    While the most likely structure of the active site in iron-containing zeolites has been recently identified as [FeO] 2+ (Snyder et al. Nature 2016, 536, 317-321), the mechanism for the direct conversion of methane to methanol over this active species is still debatable between the direct-radical-rebound or nonradical (concerted) mechanism. Using density functional theory on periodic systems, we calculated the two reaction mechanisms over two d 4 isoelectronic systems, [FeO] 2+ and [MnO] + zeolites. We found that [FeO] 2+ zeolites favor the direct-radical-rebound mechanism with low CH 4 activation energies, while [MnO] + zeolites prefer the nonradical mechanism with higher CH 4 activation energies. These contrasts, despite their isoelectronic structures, are mainly due to the differences in the metal coordination number and O α (oxo) spin density. Moreover, molecular orbital analyses suggest that the zeolite steric hindrance further degrades the reactivity of [MnO] + zeolites toward methane. Two types of zeolite frameworks, i.e., medium-pore ZSM-5 (MFI framework) and small-pore SSZ-39 (AEI framework) zeolites, were evaluated, but no significant differences in the reactivity were found. The rate-determining reaction step is found to be methanol desorption instead of methane activation. Careful examination of the most stable sites hosting the active species and calculation for N 2 O decomposition over [Fe] 2+ -MFI and -AEI zeolites were also performed.

  1. Beyond the Methanogenic Black-Box: Greenhouse Gas Fluxes (CO2, CH4, N2O) as Evidence for Wetlands as Dynamic Redox Systems

    NASA Astrophysics Data System (ADS)

    Mcnicol, G.; Knox, S. H.; Sturtevant, C. S.; Baldocchi, D. D.; Silver, W. L.

    2015-12-01

    Seminal wetland research in the 1990s demonstrated that annual methane (CH4) fluxes scaled positively with ecosystem production across distinctive wetlands globally. This relationship implies a model of flooded wetland ecosystems as 'methanogenic black-boxes'; poised at a low redox state, and tending to release a fixed fraction of incoming annual productivity as CH4. In contrast, recent studies have reported high ratios of carbon dioxide (CO2) to CH4 emissions, and are adding to a body of evidence suggesting wetlands can vary more widely in their redox state. To explore this apparent incongruence we used principles of redox thermodynamics and laboratory experiments to develop predictions of wetland greenhouse gas (GHG) fluxes under different redox regimes. We then used a field study to test the hypothesis that ecosystem seasonality in gross primary productivity (GPP) and temperature would drive changes in GHG emissions, mediated by a dynamic - as opposed to static - redox regime. We estimated wetland GHG emissions from an emergent marsh in the Sacramento Delta, CA from March 2014-2015. We measured CO2, CH4 and N2O emissions via diffusion and ebullition with manual sampling, and whole-ecosystem fluxes of CO2 and CH4 using eddy-covariance. Ebullition and diffusive CH4 fluxes were strongly seasonal, with minimum rates (0.86 and 0.35 mg C-CH­­4 m-2 yr-1, respectively) during winter, and maximum rates (1.3 and 1.8 g C-CH­­4 m-2 yr-1, respectively) during the summer growing season. In contrast, winter diffusive CO2 fluxes (494 g C-CO2 m-2 yr-1) and fall bubble CO2 concentrations (1.49%) were highest, despite being seasons of lower GPP, temperature, and CH4 flux. Further, diffusive and ebullition fluxes of N2O showed zero net flux only during spring and summer months, whereas the wetland was a significant source of N2O during winter (81.2 ± 24.4 mg N-N2O m-2 yr-1). These seasonal flux dynamics contradict a 'methanogenic black box' model of wetland redox, which

  2. Experimental warming of a mountain tundra increases soil CO2 effluxes and enhances CH4 and N2O uptake at Changbai Mountain, China

    PubMed Central

    Zhou, Yumei; Hagedorn, Frank; Zhou, Chunliang; Jiang, Xiaojie; Wang, Xiuxiu; Li, Mai-He

    2016-01-01

    Climatic warming is expected to particularly alter greenhouse gas (GHG) emissions from soils in cold ecosystems such as tundra. We used 1 m2 open-top chambers (OTCs) during three growing seasons to examine how warming (+0.8–1.2 °C) affects the fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from alpine tundra soils. Results showed that OTC warming increased soil CO2 efflux by 141% in the first growing season and by 45% in the second and third growing season. The mean CH4 flux of the three growing seasons was −27.6 and −16.7 μg CH4-C m−2h−1 in the warmed and control treatment, respectively. Fluxes of N2O switched between net uptake and emission. Warming didn’t significantly affect N2O emission during the first and the second growing season, but stimulated N2O uptake in the third growing season. The global warming potential of GHG was clearly dominated by soil CO2 effluxes (>99%) and was increased by the OTC warming. In conclusion, soil temperature is the main controlling factor for soil respiration in this tundra. Climate warming will lead to higher soil CO2 emissions but also to an enhanced CH4 uptake with an overall increase of the global warming potential for tundra. PMID:26880107

  3. The Molybdenum(V) and Tungsten(VI) Oxoazides [MoO(N3 )3 ], [MoO(N3 )3 ⋅2CH3 CN], [(bipy)MoO(N3 )3 ], [MoO(N3 )5 ](2-) , [WO(N3 )4 ], and [WO(N3 )4CH3 CN].

    PubMed

    Haiges, Ralf; Skotnitzki, Juri; Fang, Zongtang; Dixon, David A; Christe, Karl O

    2015-12-14

    A series of novel molybdenum(V) and tungsten(VI) oxoazides was prepared starting from [MOF4 ] (M=Mo, W) and Me3 SiN3 . While [WO(N3 )4 ] was formed through fluoride-azide exchange in the reaction of Me3 SiN3 with WOF4 in SO2 solution, the reaction with MoOF4 resulted in a reduction of Mo(VI) to Mo(V) and formation of [MoO(N3 )3 ]. Carried out in acetonitrile solution, these reactions resulted in the isolation of the corresponding adducts [MoO(N3 )3 ⋅2CH3 CN] and [WO(N3 )4CH3 CN]. Subsequent reactions of [MoO(N3 )3 ] with 2,2'-bipyridine and [PPh4 ][N3 ] resulted in the formation and isolation of [(bipy)MoO(N3 )3 ] and [PPh4 ]2 [MoO(N3 )5 ], respectively. Most molybdenum(V) and tungsten(VI) oxoazides were fully characterized by their vibrational spectra, impact, friction and thermal sensitivity data and, in the case of [WO(N3 )4CH3 CN], [(bipy)MoO(N3 )3 ], and [PPh4 ]2 [MoO(N3 )5 ], by their X-ray crystal structures. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Geographic Inventory Framework (GiF) for estimating N2O and CH4 emissions from agriculture in the province of Alberta, Canada

    NASA Astrophysics Data System (ADS)

    Dimitrov, D. D.; Wang, J.

    2016-12-01

    A Geographic Information Framework (GiF) has been created to estimate and map agricultural N2O and CH4 emissions of the province of Alberta, Canada. The GiF consists of a modelling component, a GIS component, and application software to communicate between the model, database and census data. For compatibility, GiF follows the IPCC Tier 1 method and contains census data for animal populations, crop areas, and farms for the main IPCC animal and plant types (dairy cows, cattle cows, pigs, sheep, poultry, other animals, grasses, legumes, other crops), and estimated N2O and CH4 emissions from manure management, enteric fermentation, direct soil emissions (with applied manure, synthetic fertilizer, crop residue degradation, biological fixation) and indirect soil emissions (with atmospheric deposition and leaching). Methane emissions from enteric fermentation (609.24 Gg) prevailed over those from manure (44.99 Gg), and nitrous oxide emission from manure (22.01 Gg) prevailed over those from soil (17.73 Gg), with cattle cows emitting most N2O and CH4, followed by plant N2O emissions, and pigs and dairy cows CH4 emissions. The GIS maps showed discernible pattern of N2O and CH4 emissions increasing from North and West to the central Alberta and then slightly declining to South and East, which could be useful to address various mitigation strategies. The framework allows easy replacement of Tier 1 emission factors by Tire 2 or 3 ones from process-based models. Future applying of the latter will allow accounting for CO2 source/sink strength of agricultural ecosystems, hence their complete GHG balance affected by soil, water, and climate.

  5. Formation of a nanobubble and its effect on the structural ordering of water in a CH4-N2-CO2-H2O mixture.

    PubMed

    Kaur, Surinder Pal; Sujith, K S; Ramachandran, C N

    2018-04-04

    The replacement of methane (CH4) from its hydrate by a mixture of nitrogen (N2) and carbon dioxide (CO2) involves the dissociation of methane hydrate leading to the formation of a CH4-N2-CO2-H2O mixture that can significantly influence the subsequent steps of the replacement process. In the present work, we study the evolution of dissolved gas molecules in this mixture by applying classical molecular dynamics simulations. Our study shows that a higher CO2 : N2 ratio in the mixture enhances the formation of nanobubbles composed of N2, CH4 and CO2 molecules. To understand how the CO2 : N2 ratio affects nanobubble nucleation, the distribution of molecules in the bubble formed is examined. It is observed that unlike N2 and CH4, the density of CO2 in the bubble reaches a maximum at the surface of the bubble. The accumulation of CO2 molecules at the surface makes the bubble more stable by decreasing the excess pressure inside the bubble as well as surface tension at its interface with water. It is found that a frequent exchange of gas molecules takes place between the bubble and the surrounding liquid and an increase in concentration of CO2 in the mixture leads to a decrease in the number of such exchanges. The effect of nanobubbles on the structural ordering of water molecules is examined by determining the number of water rings formed per unit volume in the mixture. The role of nanobubbles in water structuring is correlated to the dynamic nature of the bubble arising from the exchange of gas molecules between the bubble and the liquid.

  6. Inverse Modeling of Surface CH4 and δ13C-CH4 Measurements to Understand Recent Trends in Global Methane Emissions

    NASA Astrophysics Data System (ADS)

    Karmakar, S.; Butenhoff, C. L.; Rice, A. L.; Lofdahl, D. B.; Khalil, A. K.

    2016-12-01

    Methane (CH4) is the second most important greenhouse gas with a radiative forcing of 0.97 W/m2 including both direct and indirect effects and a global warming potential of 28 over a 100-year time horizon. Unlike CO2 whose rate of growth in the atmosphere has remained positive and increased in recent decades, the behavior of atmospheric methane is considerably more complex and is much less understood on account of the spatiotemporal variability of its emissions which include biogenic (e.g. wetlands, ruminants, rice agriculture), thermogenic (fossil fuels), and pyrogenic (i.e. biomass burning) sources. After sustained growth during most of the 20th century, the CH4 growth rate declined falling from 15 ppbv/yr during the 1980s to 6 ppbv/yr in the 1990s to near-zero and even negative values in the early 2000s. With some surprise however, the growth rate rebounded in 2007 and has been on average 6 ppbv/yr during the past 10 years. During this same period the 13CH4/12CH4 ratio of atmospheric CH4 also declined suggesting the recent CH4 growth was caused by an increase in 13CH4-depleted biogenic emissions. Here, we provide additional insight into the recent behavior of atmospheric methane by performing a global three-dimensional Bayesian inversion of surface CH4 and 13CH4/12CH4 ratios over the period 1985-2015 using NOAA Global Monitoring Division (GMD) CH4 measurements and the GEOS-Chem chemical-transport model (CTM) at a horizontal grid resolution of 2ox2.5o. The use of the 3-D model allows us to exploit spatial patterns in the global CH4 and 13CH4/12CH4 fields that provide additional constraints on the retrieval of the time-dependent CH4 fluxes. This work follows up on our previous CH4 inversion where we used a 4ox5o horizontal grid for GEOS-Chem to retrieve fluxes from 1985 to 2009. At higher resolution more information is extracted from the observations due to improved model skill and a smaller number of stations aggregated within model grid cells. This increases the

  7. Seasonal changes of CO(2), CH(4) and N(2)O fluxes in relation to land-use change in tropical peatlands located in coastal area of South Kalimantan.

    PubMed

    Inubushi, K; Furukawa, Y; Hadi, A; Purnomo, E; Tsuruta, H

    2003-07-01

    Tropical peatland could be a source of greenhouse gases emission because it contains large amounts of soil carbon and nitrogen. However these emissions are strongly influenced by soil moisture conditions. Tropical climate is characterized typically by wet and dry seasons. Seasonal changes in the emission of carbon dioxide (CO(2)), methane (CH(4)) and nitrous oxide (N(2)O) were investigated over a year at three sites (secondary forest, paddy field and upland field) in the tropical peatland in South Kalimantan, Indonesia. The amount of these gases emitted from the fields varied widely according to the seasonal pattern of precipitation, especially methane emission rates were positively correlated with precipitation. Converting from secondary forest peatland to paddy field tended to increase annual emissions of CO(2) and CH(4) to the atmosphere (from 1.2 to 1.5 kg CO(2)-C m(-2)y(-1) and from 1.2 to 1.9 g CH(4)-C m(-2)y(-1)), while changing land-use from secondary forest to upland tended to decrease these gases emissions (from 1.2 to 1.0 kg CO(2)-C m(-2)y(-1) and from 1.2 to 0.6 g CH(4)-C m(-2)y(-1)), but no clear trend was observed for N(2)O which kept negative value as annual rates at three sites.

  8. Laboratory-scale measurements of N2O and CH4 emissions from hybrid poplars (Populus deltoides x Populus nigra).

    PubMed

    McBain, M C; Warland, J S; McBride, R A; Wagner-Riddle, C

    2004-12-01

    The purpose of this study was to determine whether or not young hybrid poplar (Populus deltoides x Populus nigra) could transport landfill biogas internally from the root zone to the atmosphere, thereby acting as conduits for landfill gas release. Fluxes of methane (CH4) and nitrous oxide (N2O) from the seedlings to the atmosphere were measured under controlled conditions using dynamic flux chambers and a tunable diode laser trace gas analyser (TDLTGA). Nitrous oxide was emitted from the seedlings, but only when extremely high soil N2O concentrations were applied to the root zone. In contrast, no detectable emissions of CH4 were measured in a similar experimental trial. Visible plant morphological responses, characteristic of flood-tolerant trees attempting to cope with the negative effects of soil hypoxia, were observed during the CH4 experiments. Leaf chlorosis, leaf abscission and adventitious roots were all visible plant responses. In addition, seedling survival was observed to be highest in the biogas 'hot spot' areas of a local municipal solid waste landfill involved in this study. Based on the available literature, these observations suggest that CH4 can be transported internally by Populus deltoides x Populus nigra seedlings in trace amounts, although future research is required to fully test this hypothesis.

  9. Theoretical study on the reaction mechanism of CH 4 with CaO

    NASA Astrophysics Data System (ADS)

    Yang, Hua-Qing; Hu, Chang-Wei; Qin, Song

    2006-11-01

    The reaction pathways and energetics for the reaction of methane with CaO are discussed on the singlet spin state potential energy surface at the B3LYP/6-311+G(2df,2p) and QCISD/6-311++G(3df,3pd)//B3LYP/6-311+G(2df,2p) levels of theory. The reaction of methane with CaO is proposed to proceed in the following reaction pathways: CaO + CH 4 → CaOCH 4 → [TS] → CaOH + CH 3, CaO + CH 4 → OCaCH 4 → [TS] → HOCaCH 3 → CaOH + CH 3 or [TS] → CaCH 3OH → Ca + CH 3OH, and OCaCH 4 → [TS] → HCaOCH 3 → CaOCH 3 + H or [TS] → CaCH 3OH → Ca + CH 3OH. The gas-phase methane-methanol conversion by CaO is suggested to proceed via two kinds of important reaction intermediates, HOCaCH 3 and HCaOCH 3, and the reaction pathway via the hydroxy intermediate (HOCaCH 3) is energetically more favorable than the other one via the methoxy intermediate (HCaOCH 3). The hydroxy intermediate HOCaCH 3 is predicted to be the energetically most preferred configuration in the reaction of CaO + CH 4. Meanwhile, these three product channels (CaOH + CH 3, CaOCH 3 + H and Ca + CH 3OH) are expected to compete with each other, and the formation of methyl radical is the most preferable pathway energetically. On the other hand, the intermediates HCaOCH 3 and HOCaCH 3 are predicted to be the energetically preferred configuration in the reaction of Ca + CH 3OH, which is precisely the reverse reaction of methane hydroxylation.

  10. Photo-induced CO2 reduction by CH4/H2O to fuels over Cu-modified g-C3N4 nanorods under simulated solar energy

    NASA Astrophysics Data System (ADS)

    Tahir, Beenish; Tahir, Muhammad; Amin, Nor Aishah Saidina

    2017-10-01

    Copper modified polymeric graphitic carbon nitride (Cu/g-C3N4) nanorods for photo-induced CO2 conversion with methane (CH4) and water (H2O) as reducing system under simulated solar energy has been investigated. The nanocatalysts, synthesized by pyrolysis and sonication, were characterized by XRD, FTIR, Raman analysis, XPS, SEM, N2 adsorption-desorption and PL spectroscopy. The presence of Cu2+ ions over the g-C3N4 structure inhibited charge carriers recombination process. The results indicated that photo-activity and selectivity of Cu/g-C3N4 photo-catalyst for CO2 reduction greatly dependent on the type of CO2-reduction system. CO2 was efficiently converted to CH4 and CH3OH with traces of C2H4 and C2H6 hydrocarbons in the CO2-water system. The yield of the main product, CH4 over 3 wt.% Cu/g-C3N4 was 109 μmole g-cata.-1 h-1 under visible light irradiation, significantly higher than the pure g-C3N4 catalyst (60 μmole/g.cat). In photo-induced CO2-CH4 reaction, CO and H2 were detected as the main products with smaller amount of hydrocarbons. The highest efficiency was detected over 3 wt.%Cu-loading of g-C3N4 and at optimal CH4/CO2 feed ratio of 1.0. The maximum yield of CO and H2 detected were 142 and 76 μmole g-catal.-1 h-1, respectively at selectivity 66.6% and 32.5%, respectively. Significantly enhanced CO2/CH4 reduction over Cu/g-C3N4 was attributed to its polymeric structure with efficient charge transfer property and inhibited charges recombination rate. A proposed photo-induced reaction mechanism, corroborated with the experimental data, was also deliberated.

  11. Affect of dairy cow manure, urine, and slurry on N<2>O, CO<2>, and CH<4> emissions from Pasture

    NASA Astrophysics Data System (ADS)

    Dorich, C.; Varner, R. K.; Contosta, A.; Li, C.

    2012-12-01

    Agriculture is responsible for roughly 25% of total anthropogenic emission of greenhouse gases (GHG) globally. These agricultural emissions are primarily in the form of methane (CH<4>) and nitrous oxide (N<2>O) where they account for roughly 40 and 80 percent of anthropogenic emissions of their gas, respectively. Measuring and modeling of these gases has remained difficult however as management varies between farms and N<2>O fluxes have been difficult to link to climate and site conditions. Most of these N<2>O fluxes occur during soil freeze-thaw and wetting-drying cycles as well as fertilizer addition moments, all of which are difficult to measure and harder yet to model. Thus the N<2>O flux remains poorly understood and may be underestimated in literature. This provides a problem in agriculture emissions as N use efficiency has been suggested as a proxy for farm scale emissions. On a farm scale these large fluxes of N<2>O from soil "hot moments" can account for up to 60% of the total GHG emissions and thus it is essential to capture the full flux. At the University of New Hampshire Agriculture Experiment Station's (NHAES) organic dairy farm a manure fertilizer experiment was conducted. Manure, urine, and slurry from the UNH dairy farms were collected, analyzed, and applied to pasture plots in May 2012 in order to examine N<2>O flux hot moments. Sites were measured at least bi-weekly with manual static flux chambers taken with soil temperature and moisture along with measurements for soil inorganic N, soil C:N, plant biomass and C:N, and soil pH. Gas samples were analyzed for CO<2>, CH<4>, and N<2>O. Emissions were compared with other fluxes from the farm ecosystem including; corn silage, free stall bedding, composting and solid manure, and a manure slurry tank.

  12. Disproportionation and thermochemical sulfate reduction reactions in S-H20-Ch4 and S-D2O-CH4 systems from 200 to 340 °C at elevated pressures

    USGS Publications Warehouse

    Yuan, Shunda; Chou, I-Ming; Burruss, Robert A.

    2013-01-01

    Elemental sulfur, as a transient intermediate compound, by-product, or catalyst, plays significant roles in thermochemical sulfate reduction (TSR) reactions. However, the mechanisms of the reactions in S-H2O-hydrocarbons systems are not clear. To improve our understanding of reaction mechanisms, we conducted a series of experiments between 200 and 340 °C for S-H2O-CH4, S-D2O-CH4, and S-CH4-1m ZnBr2 systems in fused silica capillary capsules (FSCC). After a heating period ranging from 24 to 2160 hours (hrs), the quenched samples were analyzed by Raman spectroscopy. Combined with the in situ Raman spectra collected at high temperatures and pressures in the S-H2O and S-H2O-CH4 systems, our results showed that (1) the disproportionation of sulfur in the S-H2O-CH4 system occurred at temperatures above 200 °C and produced H2S, SO42-, and possibly trace amount of HSO4-; (2) sulfate (and bisulfate), in the presence of sulfur, can be reduced by methane between 250 and 340 °C to produce CO2 and H2S, and these TSR temperatures are much closer to those of the natural system (2O-CH4 system may take place simultaneously, with TSR being favored at higher temperatures; and (4) in the system S-D2O-CH4, both TSR and the competitive disproportionation reactions occurred simultaneously at temperatures above 300 °C, but these reactions were very slow at lower temperatures. Our observation of methane reaction at 250 °C in a laboratory time scale suggests that, in a geologic time scale, methane may be destroyed by TSR reactions at temperatures > 200 °C that can be reached by deep drilling for hydrocarbon resources.

  13. Molecular dynamic simulations of selective self-diffusion of CH4/CO2/H2O/N2 in coal

    NASA Astrophysics Data System (ADS)

    Song, Y.; Jiang, B.; Li, F. L.

    2017-06-01

    The self-diffusion coefficients (D) of CH4/CO2/H2O/N2 at a relatively broad range of temperatures(298.15∼ 458.15K)and pressures (1∼6MPa) under the NPT, NPH, NVE, and NVT ensembles were obtained after the calculations of molecular mechanics(MM), annealing kinetics(AK), giant canonical Monte Carlo(GCMC), and molecular dynamics (MD) based on Wiser bituminous coal model (WM). The Ds of the adsorbates at the saturated adsorption configurations are D CH422ON2(NPT, 298.15K, 0.1MPa). The diffusion activation energy (E) is E H2O (1.07kJ/mol)N2(1.82kJ/mol)2 (2.94kJ/mol)CH4(10.88kJ/mol), indicating that CH4 diffusion requires to overcome the highest adsorption energy barrier and N2 and H2O to the lowest. The order of different ensembles is D N2 (NVE)< D N2 (NVT)≈D N2 (NPH)≈D N2 (NPT) (T<418K) and D N2 (NVE) is remarkable higher than other ensembles when T>418K. The average swelling ratios manifest as H2O (14.7∼35.18%)>CO2 (13.38∼32.25%)>CH4 (15.35∼23.71%)> N2 (11.47∼22.14%) (NPH, 1∼6MPa). There exits differences in D, swelling ratios and E among various ensembles, indicating that the selection of ensembles has an important influence on the MD calculations for self-diffusion coefficients.

  14. Soil-atmospheric exchange of CO2, CH4, and N2O in three subtropical forest ecosystems in southern China

    USGS Publications Warehouse

    Tang, X.; Liu, S.; Zhou, G.; Zhang, Dongxiao; Zhou, C.

    2006-01-01

    The magnitude, temporal, and spatial patterns of soil-atmospheric greenhouse gas (hereafter referred to as GHG) exchanges in forests near the Tropic of Cancer are still highly uncertain. To contribute towards an improvement of actual estimates, soil-atmospheric CO2, CH4, and N2O fluxes were measured in three successional subtropical forests at the Dinghushan Nature Reserve (hereafter referred to as DNR) in southern China. Soils in DNR forests behaved as N2O sources and CH4 sinks. Annual mean CO2, N2O, and CH4 fluxes (mean ?? SD) were 7.7 ?? 4.6MgCO2-Cha-1 yr-1, 3.2 ?? 1.2 kg N2ONha-1 yr-1, and 3.4 ?? 0.9 kgCH4-Cha-1 yr-1, respectively. The climate was warm and wet from April through September 2003 (the hot-humid season) and became cool and dry from October 2003 through March 2004 (the cool-dry season). The seasonality of soil CO2 emission coincided with the seasonal climate pattern, with high CO2 emission rates in the hot-humid season and low rates in the cool-dry season. In contrast, seasonal patterns of CH4 and N2O fluxes were not clear, although higher CH4 uptake rates were often observed in the cool-dry season and higher N2O emission rates were often observed in the hot-humid season. GHG fluxes measured at these three sites showed a clear increasing trend with the progressive succession. If this trend is representative at the regional scale, CO2 and N2O emissions and CH4 uptake in southern China may increase in the future in light of the projected change in forest age structure. Removal of surface litter reduced soil CO2 effluxes by 17-44% in the three forests but had no significant effect on CH4 absorption and N2O emission rates. This suggests that microbial CH4 uptake and N2O production was mainly related to the mineral soil rather than in the surface litter layer. ?? 2006 Blackwell Publishing Ltd.

  15. Characterizing CH4 and N2O emissions from an intensive dairy operation in summer and fall in China

    NASA Astrophysics Data System (ADS)

    Zhu, Gaodi; Ma, Xiaoyuan; Gao, Zhiling; Ma, Wenqi; Li, Jianguo; Cai, Zhenjiang

    2014-02-01

    Evaluation of the global warming potential of the dairy industry both in China and globally necessitates reliable characterization of CH4 and N2O emissions. However, CH4 and N2O emissions from dairy operations differ with feeds, herd structures and manure management practices, and the lack of N2O and CH4 emission measurements for China, especially for intensive dairy operations, causes substantial uncertainty in accounting for GHGs from dairy operation both in China and globally. In this study, CH4 and N2O emissions during summer to fall period from an intensive feedlot in China were characterized to fill the data gap. The diurnal CH4 emission patterns for milking cows and heifers were driven by the feeding activities and the diurnal N2O patterns by the diurnal changes in temperature. The CH4 emission rates of 397 g head-1 d-1 (23.63 L CH4 kg-1 milk) (in summer) and 279 g head-1 d-1 (in fall) for milking cows and heifers accounted for 5.17% and 7.68% of their daily gross energy intakes, whereas the N2O emission rates of 36.7 g head-1 d-1 (0.85 L N2O kg-1 milk) for milking cows and 24.2 g head-1 d-1 for heifers accounted for 4.25% and 6.86% of the daily feed N intake. The CH4 conversion factor and CH4 emission intensity in the measurement season for intensive dairy operations in China are lower than those for collective operations in China, and the CH4 emission intensity is similar to those in developed countries.

  16. Characterizing CH4, CO2 and N2O emission from barn feeding Tibetan sheep in Tibetan alpine pastoral area in cold season

    NASA Astrophysics Data System (ADS)

    Xu, Tianwei; Zhao, Na; Hu, Linyong; Xu, Shixiao; Liu, Hongjin; Ma, Li; Zhao, Xinquan

    2017-05-01

    Herein, methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) emission from different aged barn feeding Tibetan sheep were characterized using a respiration chamber in combination with gas chromatograph method in cold season of 2013. This work was based on measuring the increase of gas concentration inside respiration chamber by the means of gas chromatograph. Results indicated that diurnal CH4 emission patterns for barn feeding Tibetan sheep were driven by feeding schedule, diurnal CO2 emission patterns were relatively stable with two slight emission peaks, diurnal N2O emission patterns were driven by the variation of temperature inside chamber. Diurnal CH4 emission rates were 17.65, 19.49 and 21.06 g sheep-1 d-1 for yearling, two-year and three-year barn feeding Tibetan sheep, account for 6.15%, 5.76% and 5.45% of their daily gross energy intakes, respectively. Diurnal CO2 emission rates were 526.88, 588.43 and 640.66 g sheep-1 d-1 for yearling, two-year and three-year barn feeding Tibetan sheep, respectively. Diurnal N2O emission rates were 1.64, 1.25 and 1.05 mg sheep-1 d-1 for yearling, two-year and three-year barn feeding Tibetan sheep, respectively. Three-year barn feeding Tibetan sheep released more CO2-eq on per unit BW and BW0.75 gain basis.

  17. Diurnal variation of CO2, CH4, and N2O emission fluxes continuously monitored in-situ in three environmental habitats in a subtropical estuarine wetland.

    PubMed

    Yang, Wen-Bin; Yuan, Chung-Shin; Tong, Chuan; Yang, Pin; Yang, Lei; Huang, Bang-Qin

    2017-06-15

    Wetlands play a crucial role in modulating atmospheric concentrations of greenhouse gases (GHGs) such as carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O). The key factors controlling GHG emission from subtropical estuarine wetlands were investigated in this study, which continuously monitored the uptake/emission of GHGs (CO 2 , CH 4 , and N 2 O) by/from a subtropical estuarine wetland located in the Minjiang estuary in the coastal region of southeastern China. A self-designed floating chamber was used to collect air samples on-site at three environmental habitats (Phragmites australis marsh, mudflats, and river water). The CO 2 , CH 4 , and N 2 O concentrations were then measured using an automated nondispersive infrared analyzer. The magnitudes of the CO 2 and N 2 O emission fluxes at the three habitats were ordered as river water>P. australis>mudflats. P. australis emitted GHGs through photosynthesis and respiration processes. Emissions of CH 4 from P. australis and the mudflats were revealed to be slightly higher than those from the river water. The total GHG emission fluxes at the three environmental habitats were quite similar (4.68-4.78gm -2 h -1 ). However, when the total carbon dioxide equivalent fluxes (CO 2 -e) were considered, the river water was discovered to emit the most CO 2 -e compared with P. australis and the mudflats. Based on its potential to increase global warming, N 2 O was the main contributor to the total GHG emission, with that emitted from the river water being the most considerable. Tidal water carried onto the marsh had its own GHG content and thus has acted as a source or sink of GHGs. However, water quality had a large effect on GHG emissions from the river water whereas the tidal water height did not. Both high salinity and large amounts of sulfates in the wetlands explicitly inhibited the activity of CH 4 -producing bacteria, particularly at nighttime. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Version 1.3 AIM SOFIE measured methane (CH4): Validation and seasonal climatology

    NASA Astrophysics Data System (ADS)

    Rong, P. P.; Russell, J. M.; Marshall, B. T.; Siskind, D. E.; Hervig, M. E.; Gordley, L. L.; Bernath, P. F.; Walker, K. A.

    2016-11-01

    The V1.3 methane (CH4) measured by the Aeronomy of Ice in the Mesosphere (AIM) Solar Occultation for Ice Experiment (SOFIE) instrument is validated in the vertical range of 25-70 km. The random error for SOFIE CH4 is 0.1-1% up to 50 km and degrades to 9% at ˜ 70 km. The systematic error remains at 4% throughout the stratosphere and lower mesosphere. Comparisons with CH4 data taken by the SCISAT Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) and the Envisat Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) show an agreement within 15% in the altitude range 30-60 km. Below 25 km SOFIE CH4 is systematically higher (≥20%), while above 65 km it is lower by a similar percentage. The sign change from the positive to negative bias occurs between 55 km and 60 km (or 40 km and 45 km) in the Northern (or Southern) Hemisphere. Methane, H2O, and 2CH4 + H2O yearly differences from their values in 2009 are examined using SOFIE and MIPAS CH4 and the Aura Microwave Limb Sounder (MLS) measured H2O. It is concluded that 2CH4 + H2O is conserved with altitude up to an upper limit between 35 km and 50 km depending on the season. In summer this altitude is higher. In the Northern Hemisphere the difference relative to 2009 is the largest in late spring and the established difference prevails throughout summer and fall, suggesting that summer and fall are dynamically quiet. In both hemispheres during winter there are disturbances (with a period of 1 month) that travel downward throughout the stratosphere with a speed similar to the winter descent.

  19. Solid state coordination chemistry: structural consequences of variations in tether length in the oxovanadium-copper-bisterpy-[O3P(CH2)nPO3]4- system, n= 1-6 (bisterpy = 2,2':4',4'':2'',2'''-quarterpyridyl-6',6''-di-2-pyridine).

    PubMed

    Ouellette, Wayne; Koo, Bon-Kweon; Burkholder, Eric; Golub, Vladimir; O'Connor, C J; Zubieta, Jon

    2004-05-21

    Hydrothermal reactions of Na3VO4, an appropriate Cu(II) source, bisterpy and an organodiphosphonate, H2O3P(CH2)nPO3H2 (n = 1-6) yielded a family of materials of the type [Cu2(bisterpy)]4+/VxOy(n-)/[O3P(CH2)nPO3]4-. This family of bimetallic oxides is characterized by an unusual structural diversity. The oxides [[Cu2(bisterpy)]V2O4[O3PCH2PO3H]2] (1), [[Cu2(bisterpy)(H2O)]VO2[O3P(CH2)3PO3][HO3P(CH2)3PO3H2

  20. Differences in CH4 and N2O emissions between rice nurseries in Chinese major rice cropping areas

    NASA Astrophysics Data System (ADS)

    Zhang, Yi; Li, Zhijie; Feng, Jinfei; Zhang, Xin; Jiang, Yu; Chen, Jin; Zhang, Mingqian; Deng, Aixing; Zhang, Weijian

    2014-10-01

    Studies on greenhouse gas (GHG) emissions from paddy field have primarily focused on the post-transplanting period, however, recent researches raise new concerns about GHGs emission from rice nursery. In this study, CH4 and N2O fluxes were determined from different nurseries under major rice cropping systems in China. The tested nurseries included flooded nursery (FN), moist nursery (MN) and dry nursery (DN). Methane emissions from FN were significantly higher than those from MN and DN under all the rice cropping systems. When comparing with FN, MN decreased total CH4 emissions by 74.2%, 72.1% and 49.6% under the rice-upland rotation cropping system (RUR), and the double rice cropping system for the early rice (EDR) and the late rice (LDR), respectively. DN decreased CH4 emissions by 99.2%, 92.0%, 99.0% and 78.6% compared to FN under the single rice cropping system (SR), RUR, EDR and LDR, respectively. When comparing with FN, MN and DN increased N2O emissions by 58.1-134.1% and 28.2-332.7%, respectively. Ultimately, compared with FN across the cropping systems, MN and DN decreased net global warming potentials (GWPs) of CH4 and N2O by 33-68% and 43-86%, respectively. The mitigating effect of MN and DN on total GWPs varied greatly across the systems, ranging from 30.8% in the LDR to 86.5% in the SR. Chinese actual emission from rice nurseries was reduced to 956.66 × 103 t CO2 eq from the theoretical estimate of 2242.59 × 103 t CO2 eq if under the flooded nursery scenario in 2012. Taking into account the large rice nursery area (2032.52 × 103 ha) in China, the results of this study clearly indicate the importance to estimate and mitigate GHGs emission from flooded rice nursery. Being effective to reduce GHG emissions and increase rice yield, dry nursery technique is a promising candidate for climate smart rice cropping.

  1. Effects of coastal marsh conversion to shrimp aquaculture ponds on CH4 and N2O emissions

    NASA Astrophysics Data System (ADS)

    Yang, P.; Bastviken, D.; Lai, D. Y. F.; Jin, B. S.; Mou, X. J.; Tong, C.; Yao, Y. C.

    2017-12-01

    In this study, we compared the CH4 and N2O fluxes from a tidal brackish Cyperus malaccensis marsh ecosystem and nearby shrimp ponds, converted from C. malaccensis marsh in the last 3-4 years, in the Min River estuary of southeast China over the aquaculture period of the year. Significant differences in CH4 and N2O fluxes were observed in space (between brackish marsh and shrimp ponds) and in time (between sampling occasions that were distributed over the aquaculture period). CH4 fluxes from the shrimp ponds were on an average 10-fold higher than from the brackish marsh. N2O emissions, on the other hand, were lower from the shrimp pond (25% of the emissions from the brackish marsh). Accessory data indicates that these patterns were primarily linked to water level variability and temperature (all fluxes), sediment porewater sulfate concentrations (CH4 flux) and total nitrogen concentrations (N2O flux). Our research demonstrates that the coastal marsh ecosystem converted to aquaculture ponds considerably alter emissions of CH4 and N2O and provides input to the global discussion on how to account for emissions from various types of flooded land in greenhouse gas inventories.

  2. Methanesulfonates of high-valent metals: syntheses and structural features of MoO2(CH3SO3)2, UO2(CH3SO3)2, ReO3(CH3SO3), VO(CH3SO3)2, and V2O3(CH3SO3)4 and their thermal decomposition under N2 and O2 atmosphere.

    PubMed

    Betke, Ulf; Neuschulz, Kai; Wickleder, Mathias S

    2011-11-04

    Oxide methanesulfonates of Mo, U, Re, and V have been prepared by reaction of MoO(3), UO(2)(CH(3)COO)(22H(2)O, Re(2)O(7)(H(2)O)(2), and V(2)O(5) with CH(3)SO(3)H or mixtures thereof with its anhydride. These compounds are the first examples of solvent-free oxide methanesulfonates of these elements. MoO(2)(CH(3)SO(3))(2) (Pbca, a=1487.05(4), b=752.55(2), c=1549.61(5) pm, V=1.73414(9) nm(3), Z=8) contains [MoO(2)] moieties connected by [CH(3)SO(3)] ions to form layers parallel to (100). UO(2)(CH(3)SO(3))(2) (P2(1)/c, a=1320.4(1), b=1014.41(6), c=1533.7(1) pm, β=112.80(1)°, V=1.8937(3) nm(3), Z=8) consists of linear UO(2)(2+) ions coordinated by five [CH(3)SO(3)] ions, forming a layer structure. VO(CH(3)SO(3))(2) (P2(1)/c, a=1136.5(1), b=869.87(7), c=915.5(1) pm, β=113.66(1)°, V=0.8290(2) nm(3), Z=4) contains [VO] units connected by methanesulfonate anions to form corrugated layers parallel to (100). In ReO(3)(CH(3)SO(3)) (P1, a=574.0(1), b=1279.6(3), c=1641.9(3) pm, α=102.08(2), β=96.11(2), γ=99.04(2)°, V=1.1523(4) nm(3), Z=8) a chain structure exhibiting infinite O-[ReO(2)]-O-[ReO(2)]-O chains is formed. Each [ReO(2)]-O-[ReO(2)] unit is coordinated by two bidentate [CH(3)SO(3)] ions. V(2)O(3)(CH(3)SO(3))(4) (I2/a, a=1645.2(3), b=583.1(1), c=1670.2(3) pm, β=102.58(3), V=1.5637(5) pm(3), Z=4) adopts a chain structure, too, but contains discrete [VO]-O-[VO] moieties, each coordinated by two bidentate [CH(3)SO(3)] ligands. Additional methanesulfonate ions connect the [V(2)O(3)] groups along [001]. Thermal decomposition of the compounds was monitored under N(2) and O(2) atmosphere by thermogravimetric/differential thermal analysis and XRD measurements. Under N(2) the decomposition proceeds with reduction of the metal leading to the oxides MoO(2), U(3)O(7), V(4)O(7), and VO(2); for MoO(2)(CH(3)SO(3))(2), a small amount of MoS(2) is formed. If the thermal decomposition is carried out in a atmosphere of O(2) the oxides MoO(3) and V(2)O(5) are formed. Copyright

  3. In Situ Measurements of N2O and CH4 During SOLVE on the ER-2 Using a New Tunable Diode Laser Instrument

    NASA Technical Reports Server (NTRS)

    Jost, Hansjurg

    2002-01-01

    This report is the final report for Cooperative Agreement NCC2-1105: 'In Situ Measurements of N2O and CH4 during SOLVE on the ER-2 using a new tunable diode laser instrument.' The tasks outlined in the proposal are listed below with a brief comment. The publications and the conference presentations are listed. Finally the important publications are attached. The Cooperative Agreement made possible a research effort to produce high precision and high accuracy in situ measurements of methane and nitrous oxide on the ER-2 during the SOLVE field campaign and to analyze these measurements. These measurements of CH4 and N2O were of utmost importance to studies of the ozone losses in the Arctic winter and spring. The concentrations measured over a large spatial and temporal range allowed the separation of the dynamical and chemical ozone loss. The most important results of the SOLVE program were contained in two scientific papers. This Cooperative Agreement allowed the participation of the Argus instrument in the program and the analysis of the data.

  4. In situ stratospheric measurements of CH4, (C-13)H4, N2O, and OC(O-18) using the BLISS tunable diode laser spectrometer

    NASA Technical Reports Server (NTRS)

    Webster, Christopher R.; May, Randy D.

    1992-01-01

    Simultaneous in situ measurements of stratospheric CH4, (C-13)H4, N2O, OC(O-18), pressure, and temperature have been made from Palestine, Texas (32 deg N) in September 1988 with the JPL Balloon-borne Laser In Situ Sensor. Measurements of CH4 and N2O in the altitude range 30-35 km agree well with other measurements, except for an anomalously high value for the N2O at 31 km. Measurements of CH4 support earlier observations of fold in the vertical profile. A ratio for stratospheric (C-13)H4/CH4 of 0.0105 +/- 0.0010 implies an enrichment of delta(C-13) = -45 +/- 92 parts per thousand over the PDB value, in agreement with previous measurements in the troposphere. A large mixing ratio of 1.9 +/- 0.2 ppmv for OC(O-18) is measured, corresponding to an enrichment of delta(O-18) = 280 +/- 50 parts per thousand for the (O-18) isotopic species over the SMOW value.

  5. Infrared spectroscopy of solid normal hydrogen doped with CH3F and O2 at 4.2 K: CH3F:O2 complex and CH3F migration

    NASA Astrophysics Data System (ADS)

    Abouaf-Marguin, L.; Vasserot, A.-M.

    2011-04-01

    Double doping of solid normal hydrogen with CH3F and O2 at about 4.2 K gives evidence of (ortho-H2)n:CH3F clusters and of O2:CH3F complex formation. FTIR analysis of the time evolution of the spectra in the region of the v3 C-F stretching mode indicates that these clusters behave very differently from (ortho-H2)n:H2O clusters. The main point is the observed migration of CH3F molecules in solid para-H2 at 4.2 K which differs from that of H2O under identical experimental conditions. This is confirmed by an increase over time of the integrated intensity of the CH3F:O2 complex with a rate constant K = 2.7(2) . 10-4 s-1.

  6. Stratospheric N2O5, CH4, and N2O profiles from IR solar occultation spectra

    NASA Technical Reports Server (NTRS)

    Camy-Peyret, C.; Flaud, J.-M.; Perrin, A.; Rinsland, C. P.; Goldman, A.; Murcray, F. J.

    1993-01-01

    Stratospheric volume mixing ratio profiles of N2O5, CH4, and N2O have been retrieved from a set of 0.052/cm resolution (FWHM) solar occultation spectra recorded at sunrise during a balloon flight from Aire sur l'Adour, France (44 N latitude) on 12 October 1990. The N2O5 results have been derived from measurements of the integrated absorption by the 1246/cm band. Assuming a total intensity of 4.32 x 10 exp -17 cm/molecule/sq cm independent of temperature, the retrieved N2O5 volume mixing ratios in ppbv, interpolated to 2 km height spacings, are 1.64 +/- 0.49 at 37.5 km, 1.92 +/- 0.56 at 35.5 km, 2.06 +/- 0.47 at 33.5 km, 1.95 +/- 0.42 at 31.5 km, 1.60 +/- 0.33 at 29.5 km, 1.26 +/- 0.28 at 27.5 km, and 0.85 +/- 0.20 at 25.5 km. Error bars indicate the estimated 1-sigma uncertainty including the error in the total band intensity. The retrieved profiles are compared with previous measurements and photochemical model results.

  7. [Emission of CH4, N2O and NH3 from vegetable field applied with animal manure composts].

    PubMed

    Wan, He-Feng; Zhao, Chen-Yang; Zhong, Jia; Ge, Zhen; Wei, Yuan-Song; Zheng, Jia-Xi; Wu, Yu-Long; Han, Sheng-Hui; Zheng, Bo-Fu; Li, Hong-Mei

    2014-03-01

    Greenhouse gas (GHG) emission from vegetable land is of great concern recently because agriculture land is one of the major sources contributing to global GHG emission. In this study, an experiment of Lactuca sativa L. land applied with different animal manure composts was carried out in a greenhouse vegetable land located in the surburb of Beijing to monitor the emission of GHG (CH4 and N2O) and ammonia in situ, and to analyze the affecting factors of GHG and ammonia emission. Results showed that the emission factors (EFs) of CH4 from Treatment NRM, RM and CF were 0.2%, 0.027% and 0.004%, respectively,the EFs of N2O from these three treatments were 0.18%, 0.63% and 0.74%, respectively, and the EFs of ammonia were 2.00%, 3.98% and 2.53%, respectively. CH4 emission flux was significantly affected by soil temperature and humidity, while N2O emission flux was related to soil temperature, surface temperature and humidity. The emission fluxes of CH4, N2O and NH3 were significantly affected by soil moisture, but there was little relation between CH4, N2O and NH3 emissions and the ambient temperature in the greenhouse.

  8. Subtask 1.22 - Microbial Cycling of CH4, CO2, and N2O in a Wetlands Environment

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dingyi Ye; Bethany Kurz; Marc Kurz

    Soil microbial metabolic activities play an important role in determining CO{sub 2}, CH{sub 4}, and N{sub 2}O fluxes from terrestrial ecosystems. To verify and evaluate CO{sub 2} sequestration potential by wetland restoration in the Prairie Pothole Region (PPR), as well as to address concern over restoration effects on CH{sub 4} and N{sub 2}O emissions, laboratory and in situ microcosm studies on microbial cycling of CO{sub 2}, CH{sub 4}, and N{sub 2}O were initiated. In addition, to evaluate the feasibility of the use of remote sensing to detect soil gas flux from wetlands, a remote-sensing investigation was also conducted. Results ofmore » the laboratory microcosm study unequivocally proved that restoration of PPR wetlands does sequester atmospheric CO{sub 2}. Under the experimental conditions, the simulated restored wetlands did not promote neither N{sub 2}O nor CH{sub 4} fluxes. Application of ammonia enhanced both N{sub 2}O and CH{sub 4} emission, indicating that restoration of PPR wetlands may reduce both N{sub 2}O and CH{sub 4} emission by cutting N-fertilizer input. Enhancement of CO{sub 2} emission by the N-fertilizer was observed, and this observation revealed an overlooked fact that application of N-fertilizer may potentially increase CO{sub 2} emission. In addition, the CO{sub 2} results also demonstrate that wetland restoration sequesters atmospheric carbon not only by turning soil conditions from aerobic to anoxic, but also by cutting N-fertilizer input that may enhance CO{sub 2} flux. The investigation on microbial community structure and population dynamics showed that under the experimental conditions restoration of the PPR wetlands would not dramatically increase population sizes of those microorganisms that produce N{sub 2}O and CH{sub 4}. Results of the in situ study proved that restoration of the PPR wetland significantly reduced CO{sub 2} flux. Ammonia enhanced the greenhouse gas emission and linearly correlated to the CO{sub 2} flux within

  9. Effects of the fungicides mancozeb and chlorothalonil on fluxes of CO2, N2O, and CH4 in a fertilized Colorado grassland soil

    USGS Publications Warehouse

    Kinney, C.A.; Mosier, A.R.; Ferrer, I.; Furlong, E.T.; Mandernack, K.W.

    2004-01-01

    Management of agricultural soil plays an important role in present and future atmospheric concentrations of the greenhouse gases carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). Pesticides are used as management tools in crop production, but little is known about their effects on soil-atmosphere exchange of CO2, N2O, and CH4. Field studies described in this paper determined the effect of two commonly used fungicides, mancozeb and chlorothalonil, on trace gas exchange. Separate experimental plots, 1 m2, were established in nitrogen fertilized no-tilled native grassland and tilled soils with and without fungicide application. Two studies were conducted. The first study was initiated in June 1999 and lasted for 1 year with monthly flux measurements from tilled and no-till soils. The second study commenced in August 2001 with twelve weekly measurements from tilled soils only. From both studies mancozeb suppressed emissions of CO2 and N2O in the tilled soil by an average of 28% and 47%, respectively. This suppression corresponded with efficacy periods of 14-29 and 56-77 days, respectively. From the no-till soils mancozeb decreased CO2 and N2O emissions by 33% and 80% for periods of 29 and 94 days, respectively. Mancozeb inhibited CH4 consumption in the first study by 46% and 71% in the tilled and no-till soil for periods of 8 and 29 days, respectively, but had no effect in the second study. From both studies chlorothalonil initially suppressed CO2 and N2O emissions and enhanced CH4 uptake in the tilled soil by an average of 37%, 40%, and 115%, respectively. These effects corresponded with efficacy periods of 14-29, 21-56, and 1-14 days, respectively. In the no-till soil chlorothalonil inhibited CO2 and N2O emissions and enhanced CH4 uptake by 29%, 48%, and 86% for periods of 29, 56, and 56 days, respectively. Following the initial period of suppression, chlorothalonil subsequently enhanced N2O emissions in the tilled soil by an average of 51% and in the no

  10. Inter-seasonal and spatial distribution of ground-level greenhouse gases (CO2, CH4N2O) over Nagpur in India and their management roadmap.

    PubMed

    Majumdar, Deepanjan; Rao, Padma; Maske, Nilam

    2017-03-01

    Ground-level concentrations of carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) were monitored over three seasons, i.e., post-monsoon (September-October), winter (January-February), and summer (May-June) for 1 year during 2013-2014 in Nagpur City in India. The selected gases had moderate to high variation both spatially (residential, commercial, traffic intersections, residential cum commercial sites) and temporally (at 7:00, 13:00, 18:00, and 23:00 hours in all three seasons). Concentrations of gases were randomly distributed diurnally over city in all seasons, and there was no specific increasing or decreasing trend with time in a day. Average CO 2 and N 2 O concentrations in winter were higher over post-monsoon and summer while CH 4 had highest average concentration in summer. Observed concentrations of CO 2 were predominantly above global average of 400 ppmv while N 2 O and CH 4 concentrations frequently dropped down below global average of 327 ppbv and 1.8 ppmv, respectively. Two-tailed Student's t test indicated that post-monsoon CO 2 concentrations were statistically different from summer but not so from winter, while difference between summer and winter concentrations was statistically significant (P < 0.05). CH 4 concentrations in all seasons were statistically at par to each other. In case of N 2 O, concentrations in post-monsoon were statistically different from summer but not so from winter, while difference between summer and winter concentrations was statistically significant (P < 0.05). Average ground-level concentrations of the gases calculated for three seasons together were higher in commercial areas. Environmental management priorities vis a vis greenhouse gas emissions in the city are also discussed.

  11. Stratospheric N2O5, CH4, and N2O Profiles from IR Solar Occultation Spectra

    NASA Technical Reports Server (NTRS)

    Peyeret, C. Camy; Flaud, J.-M.; Perrin, A.; Rinsland, C. P.; Goldman, A.; Murcray, F. J.

    1993-01-01

    Stratospheric volume mixing ratio profiles of N2O5, CH4, and N2O have been retrieved from a set of 0.052/ cm resolution (FWHM) solar occultation spectra recorded at sunrise during a balloon flight from Aire sur I'Adour, France (44 deg N latitude) on 12 October 1990. The N2O5 results have been derived from measurements of the integrated absorption by the 1246/ cm band. Assuming a total intensity of 4.32 x 10(exp 17)cm(exp -1) molecule sq cm(exp -2) independent of temperature, the retrieved N2O5 volume mixing ratios in ppbv (parts per billion by volume, 10(exp -9)), interpolated to 2 km height spacings, are 1.64 +/- 0.49 at 37.5 km, 1.92 +/- 0.56 at 35.5 km, 2.06 +/- 0.47 at 33.5 km, 1.95 +/- 0.42 at 31.5 km, 1.60 +/- 0.33 at 29.5 km, 1.26 +/- 0.28 at 27.5 km, and 0.85 +/- 0.20 at 25.5 km. Error bars indicate the estimated I-sigma uncertainty including the error in the total band intensity (+/- 20% has been assumed). The retrieved profiles are compared with previous measurements and photochemical model results.

  12. A vacuum ultraviolet laser pulsed field ionization-photoion study of methane (CH 4): Determination of the appearance energy of methylium from methane with unprecedented precision and the resulting impact on the bond dissociation energies of CH 4 and CH 4 +

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chang, Yih -Chung; Xiong, Bo; Bross, David H.

    Here, we report on the successful implementation of a high-resolution vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) detection method for the study of unimolecular dissociation of quantum-state- or energy-selected molecular ions. As a test case, we have determined the 0 K appearance energy (AE 0) for the formation of methylium, CH 3 +, from methane, CH 4, as AE 0 (CH 3 +/CH 4) = 14.32271 ± 0.00013 eV. This value has a significantly smaller error limit, but is otherwise consistent with previous laboratory and/or synchrotron-based studies of this dissociative photoionization onset. Furthermore, the sum of the VUV lasermore » PFI-PI spectra obtained for the parent CH 4 + ion and the fragment CH 3 + ions of methane is found to agree with the earlier VUV pulsed field ionization-photoelectron (VUV-PFI-PE) spectrum of methane, providing unambiguous validation of the previous interpretation that the sharp VUV-PFI-PE step observed at the AE 0 (CH 3 +/CH 4) threshold ensues because of higher PFI detection efficiency for fragment CH 3 + than for parent CH 4 +. This, in turn, is a consequence of the underlying high- n Rydberg dissociation mechanism for the dissociative photoionization of CH 4, which was proposed in previous synchrotron-based VUV-PFI-PE and VUV-PFI-PEPICO studies of CH 4. The present highly accurate 0 K dissociative ionization threshold for CH 4 can be utilized to derive accurate values for the bond dissociation energies of methane and methane cation. For methane, the straightforward application of sequential thermochemistry via the positive ion cycle leads to some ambiguity because of two competing VUV-PFI-PE literature values for the ionization energy of methyl radical. The ambiguity is successfully resolved by applying the Active Thermochemical Tables (ATcT) approach, resulting in D 0 (H-CH 3) = 432.463 ± 0.027 kJ/mol and D 0(H-CH 3 +) = 164.701 ± 0.038 kJ/mol.« less

  13. A vacuum ultraviolet laser pulsed field ionization-photoion study of methane (CH 4): Determination of the appearance energy of methylium from methane with unprecedented precision and the resulting impact on the bond dissociation energies of CH 4 and CH 4 +

    DOE PAGES

    Chang, Yih -Chung; Xiong, Bo; Bross, David H.; ...

    2017-03-27

    Here, we report on the successful implementation of a high-resolution vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) detection method for the study of unimolecular dissociation of quantum-state- or energy-selected molecular ions. As a test case, we have determined the 0 K appearance energy (AE 0) for the formation of methylium, CH 3 +, from methane, CH 4, as AE 0 (CH 3 +/CH 4) = 14.32271 ± 0.00013 eV. This value has a significantly smaller error limit, but is otherwise consistent with previous laboratory and/or synchrotron-based studies of this dissociative photoionization onset. Furthermore, the sum of the VUV lasermore » PFI-PI spectra obtained for the parent CH 4 + ion and the fragment CH 3 + ions of methane is found to agree with the earlier VUV pulsed field ionization-photoelectron (VUV-PFI-PE) spectrum of methane, providing unambiguous validation of the previous interpretation that the sharp VUV-PFI-PE step observed at the AE 0 (CH 3 +/CH 4) threshold ensues because of higher PFI detection efficiency for fragment CH 3 + than for parent CH 4 +. This, in turn, is a consequence of the underlying high- n Rydberg dissociation mechanism for the dissociative photoionization of CH 4, which was proposed in previous synchrotron-based VUV-PFI-PE and VUV-PFI-PEPICO studies of CH 4. The present highly accurate 0 K dissociative ionization threshold for CH 4 can be utilized to derive accurate values for the bond dissociation energies of methane and methane cation. For methane, the straightforward application of sequential thermochemistry via the positive ion cycle leads to some ambiguity because of two competing VUV-PFI-PE literature values for the ionization energy of methyl radical. The ambiguity is successfully resolved by applying the Active Thermochemical Tables (ATcT) approach, resulting in D 0 (H-CH 3) = 432.463 ± 0.027 kJ/mol and D 0(H-CH 3 +) = 164.701 ± 0.038 kJ/mol.« less

  14. N2O and CH4 emissions from N-fertilized rice paddy soil can be mitigated by wood vinegar application at an appropriate rate

    NASA Astrophysics Data System (ADS)

    Sun, Haijun; Feng, Yanfang; Ji, Yang; Shi, Weiming; Yang, Linzhang; Xing, Baoshan

    2018-07-01

    To understand the impacts of wood vinegar (WV), a by-product of biochar production, on N2O and CH4 emissions and their total global warming potential (GWPt) from N-fertilized rice paddy soil, a soil column experiment was conducted using three treatments: 240 kg urea-N ha-1 accompanied with 0, 5, and 10 t WV ha-1, respectively. Results showed that N2O and CH4 emission flux patterns were dominated by water regime of rice growth cycle, which was independent with WV application. The total N2O, CH4 emission loads and GWPt over rice season of three N received treatments were 6.41-8.85 kg ha-1, 127.7-405.0 kg ha-1, and 5.24-12.03 t CO2-e ha-1, respectively. Rice seasonal N2O and CH4 emissions were synchronously mitigated by 22.4% and 36.4%, respectively, when WV was applied at 5 t ha-1. Consequently, 5 t ha-1 WV treatment reduced 31.5% of GWPt compared with the urea treatment. In addition, 10 t ha-1 WV treatment exerted a more positive effect on suppressing N2O with 27.6% reduction. However, it increased GWPt by 57.2% because its CH4 emission load was increased by 101.8%. In conclusion, WV amendment applied at an appropriate rate (5 t ha-1) or combination with other CH4 control technologies were suggested to reduce both N2O and CH4 emissions and thereby the GWPt in N-fertilized rice paddy soil.

  15. Simulated nitrogen deposition reduces CH4 uptake and increases N2O emission from a subtropical plantation forest soil in southern China.

    PubMed

    Wang, Yongsheng; Cheng, Shulan; Fang, Huajun; Yu, Guirui; Xu, Minjie; Dang, Xusheng; Li, Linsen; Wang, Lei

    2014-01-01

    To date, few studies are conducted to quantify the effects of reduced ammonium (NH4+) and oxidized nitrate (NO3-) on soil CH4 uptake and N2O emission in the subtropical forests. In this study, NH4Cl and NaNO3 fertilizers were applied at three rates: 0, 40 and 120 kg N ha(-1) yr(-1). Soil CH4 and N2O fluxes were determined twice a week using the static chamber technique and gas chromatography. Soil temperature and moisture were simultaneously measured. Soil dissolved N concentration in 0-20 cm depth was measured weekly to examine the regulation to soil CH4 and N2O fluxes. Our results showed that one year of N addition did not affect soil temperature, soil moisture, soil total dissolved N (TDN) and NH4+-N concentrations, but high levels of applied NH4Cl and NaNO3 fertilizers significantly increased soil NO3(-)-N concentration by 124% and 157%, respectively. Nitrogen addition tended to inhibit soil CH4 uptake, but significantly promoted soil N2O emission by 403% to 762%. Furthermore, NH4+-N fertilizer application had a stronger inhibition to soil CH4 uptake and a stronger promotion to soil N2O emission than NO3(-)-N application. Also, both soil CH4 and N2O fluxes were driven by soil temperature and moisture, but soil inorganic N availability was a key integrator of soil CH4 uptake and N2O emission. These results suggest that the subtropical plantation soil sensitively responses to atmospheric N deposition, and inorganic N rather than organic N is the regulator to soil CH4 uptake and N2O emission.

  16. Biogenic CH4 and N2O emissions overwhelm land CO2 sink in Asia: Toward a full GHG budget

    NASA Astrophysics Data System (ADS)

    Tian, H.

    2017-12-01

    The recent global assessment indicates the terrestrial biosphere as a net source of greenhouse gases to the atmosphere (Tian et al Nature 2016). The fluxes of greenhouse gases (GHG) vary by region. Both TD and BU approaches indicate that human-caused biogenic fluxes of CO2, CH4 and N2O in the biosphere of Southern Asia led to a large net climate warming effect, because the 100-year cumulative effects of CH4 and N2O emissions together exceed that of the terrestrial CO2 sink. Southern Asia has about 90% of the global rice fields and represents more than 60% of the world's nitrogen fertilizer consumption, with 64%-81% of CH4 emissions and 36%-52% of N2O emissions derived from the agriculture and waste sectors. Given the large footprint of agriculture in Southern Asia, improved fertilizer use efficiency, rice management and animal diets could substantially reduce global agricultural N2O and CH4 emissions. This study highlights the importance of including all three major GHGs in regional climate impact assessments, mitigation option and climate policy development.

  17. [Effect of carbon substrate concentration on N2, N2O, NO, CO2, and CH4 emissions from a paddy soil in anaerobic condition].

    PubMed

    Chen, Nuo; Liao, Ting-ting; Wang, Rui; Zheng, Xun-hua; Hu, Rong-gui; Butterbach-Bahl, Klaus

    2014-09-01

    Understanding the effects of carbon and nitrogen substrates concentrations on the emissions of denitrification gases including nitrogen (N2) , nitrous oxide (N2O) and nitric oxide (NO), carbon dioxide (CO2) and methane (CH4) from anaerobic paddy soils is believed to be helpful for development of greenhouse gas mitigation strategies. Moreover, understanding the quantitative dependence of denitrification products compositions on carbon substrate concentration could provide some key parameters or parameterization scheme for developing process-oriented model(s) of nitrogen transformation. Using a silt loam soil collected from a paddy field, we investigated the influence of carbon substrate concentration on the emissions of the denitrification gases, CO2 and CH4 from anaerobically incubated soils by setting two treatments: control (CK) with initial soil nitrate and dissolved organic carbon (DOC) concentrations of ~ 50 mg.kg-1 and -28 mg kg-1 , respectively; and DOC added (C + ) with initial soil nitrate and DOC concentrations of ~50 mg.kg-1 and ~300 mg.kg-1 , respectively. The emissions of denitrification gases, CO2 and CH4, as well as concentrations of carbon and nitrogen substrates for each treatment were dynamically measured, using the gas-flow-soil-core technique and a paralleling substrate monitoring system. The results showed that CH4 emission was not observed in CK treatment while observed in C treatment. Aggregate emission of greenhouse gases for C + treatment was significantly higher comparing with the CK treatment (P <0. 01). The mass fractions of NO, N20 and N2 emissions in total nitrogen gases emissions were approximately 9% , 35% and 56% for CK treatment, respectively; and approximately 31% , 50% and 19% for C+ treatment, respectively, with significant differences between these two treatments (P < 0.01). The results indicated that carbon substrate concentrations can significantly change the composition of nitrogen gas emissions. The results also implicated

  18. A 4 U Laser Heterodyne Radiometer for Methane (CH4) and Carbon Dioxide (CO2) Measurements from an Occultation-Viewing CubSat

    NASA Technical Reports Server (NTRS)

    Wilson, Emily L.; DiGregorio, A. J.; Riot, Vincent J.; Ammons, Mark S.; Bruner, WIlliam W.; Carter, Darrell; Mao, Jianping; Ramanathan, Anand; Strahan, Susan E.; Oman, Luke D.; hide

    2017-01-01

    We present a design for a 4 U (20 cm 20 cm 10 cm) occultation-viewing laser heterodyne radiometer (LHR) that measures methane (CH4), carbon dioxide (CO2) and water vapor(H2O) in the limb that is designed for deployment on a 6 U CubeSat. The LHR design collects sunlight that has undergone absorption by the trace gas and mixes it with a distributive feedback (DFB) laser centered at 1640 nm that scans across CO2, CH4, and H2O absorption features. Upper troposphere lower stratosphere measurements of these gases provide key inputs to stratospheric circulation models: measuring stratospheric circulation and its variability is essential for projecting how climate change will affect stratospheric ozone.

  19. Automated CO2, CH4 and N2O Fluxes from Tree Stems and Soils: Magnitudes, Temporal Patterns and Drivers

    NASA Astrophysics Data System (ADS)

    Barba, J.; Poyatos, R.; Vargas, R.

    2017-12-01

    The emissions of the main greenhouse gases (GHG; CO2, CH4 and N2O) through tree stems are still an uncertain component of the total GHG balance of forests. Despite that stem CO2 emissions have been studied for several decades, it is still unclear the drivers and spatiotemporal patterns of CH4 and N2O stem emissions. Additionally, it is unknown how stem emissions could be related to soil physiological processes or environmental conditions. We measured CO2, CH4 and N2O emissions hourly from April to July 2017 at two different heights (75 [LStem] and 150cm [HStem]) of bitternut hickory (Carya cordiformis) trees and adjacent soil locations in a forested area in the Mid Atlantic of the USA. We designed an automated system to continuously measure the three greenhouse gases (GHG) in stems and soils. Stem and soil CO2 emissions showed similar seasonal patterns with an average of 6.56±0.09 (soil), 3.72±0.05 (LStem) and 2.47±0.04 µmols m-2 s-1 (HStem) (mean±95% CI). Soil temperature controlled CO2 fluxes at both daily and seasonal scales (R2>0.5 for all cases), but there was no clear effect of soil moisture. The stems were a clear CH4 source with emissions decreasing with height (0.35±0.02 and 0.25±0.01 nmols m-2 s-1 for LStem and HStem, respectively) with no apparent seasonal pattern, and no clear relationship with environmental drivers (e.g., temperature, moisture). In contrast, soil was a CH4 sink throughout the experiment (-0.55±0.02 nmols m-2 s-1) and its seasonal pattern responded to moisture changes. Despite soil and stem N2O emissions did not show a seasonal pattern or apparent dependency on temperature or moisture, they showed net N2O emissions with a decrease in emissions with stem height (0.29±0.05 for soil, 0.38±0.06 for LStem and 0.28±0.05 nmols m-2 s-1 for HStem). The three GHG emissions decreased with stem height at similar rates (33%, 28% and 27% for CO2, CH4 and N2O, respectively). These results suggest that the gases were not produced in the stem

  20. Effects of Different Vegetation Zones on CH4 and N2O Emissions in Coastal Wetlands: A Model Case Study

    PubMed Central

    Liu, Yuhong; Wang, Lixin; Bao, Shumei; Liu, Huamin; Yu, Junbao; Wang, Yu; Shao, Hongbo; Ouyang, Yan; An, Shuqing

    2014-01-01

    The coastal wetland ecosystems are important in the global carbon and nitrogen cycle and global climate change. For higher fragility of coastal wetlands induced by human activities, the roles of coastal wetland ecosystems in CH4 and N2O emissions are becoming more important. This study used a DNDC model to simulate current and future CH4 and N2O emissions of coastal wetlands in four sites along the latitude in China. The simulation results showed that different vegetation zones, including bare beach, Spartina beach, and Phragmites beach, produced different emissions of CH4 and N2O in the same latitude region. Correlation analysis indicated that vegetation types, water level, temperature, and soil organic carbon content are the main factors affecting emissions of CH4 and N2O in coastal wetlands. PMID:24892044

  1. Estimating Landfill Methane Oxidation Using the Information of CO2/CH4 Fluxes Measured By the Eddy Covariance Method

    NASA Astrophysics Data System (ADS)

    Xu, L.; McDermitt, D. K.; Li, J.; Green, R. B.

    2016-12-01

    Methane plays a critical role in the radiation balance and chemistry of the atmosphere. Globally, landfill methane emission contributes about 10-19% of the anthropogenic methane burden into the atmosphere. In the United States, 18% of annual anthropogenic methane emissions come from landfills, which represent the third largest source of anthropogenic methane emissions, behind enteric fermentation and natural gas and oil production. One uncertainty in estimating landfill methane emissions is the fraction of methane oxidized when methane produced under anaerobic conditions passes through the cover soil. We developed a simple stoichiometric model to estimate the landfill methane oxidation fraction when the anaerobic CO2/CH4 production ratio is known. The model predicts a linear relationship between CO2 emission rates and CH4 emission rates, where the slope depends on anaerobic CO2/CH4 production ratio and the fraction of methane oxidized, and the intercept depends on non-methane-dependent oxidation processes. The model was tested with eddy covariance CO2 and CH4 emission rates at Bluff Road Landfill in Lincoln Nebraska. It predicted zero oxidation rate in the northern portion of this landfill where a membrane and vents were present. The zero oxidation rate was expected because there would be little opportunity for methane to encounter oxidizing conditions before leaving the vents. We also applied the model at the Turkey Run Landfill in Georgia to estimate the CH4 oxidation rate over a one year period. In contrast to Bluff Road Landfill, the Turkey Run Landfill did not have a membrane or vents. Instead, methane produced in the landfill had to diffuse through a 0.5 m soil cap before release to the atmosphere. We observed evidence for methane oxidation ranging from about 18% to above 60% depending upon the age of deposited waste material. The model will be briefly described, and results from the two contrasting landfills will be discussed in this presentation.

  2. Straw enhanced CO2 and CH4 but decreased N2O emissions from flooded paddy soils: Changes in microbial community compositions

    NASA Astrophysics Data System (ADS)

    Wang, Ning; Yu, Jian-Guang; Zhao, Ya-Hui; Chang, Zhi-Zhou; Shi, Xiao-Xia; Ma, Lena Q.; Li, Hong-Bo

    2018-02-01

    To explore microbial mechanisms of straw-induced changes in CO2, CH4, and N2O emissions from paddy field, wheat straw was amended to two paddy soils from Taizhou (TZ) and Yixing (YX), China for 60 d under flooded condition. Illumia sequencing was used to characterize shift in bacterial community compositions. Compared to control, 1-5% straw amendment significantly elevated CO2 and CH4 emissions with higher increase at higher application rates, mainly due to increased soil DOC concentrations. In contrast, straw amendment decreased N2O emission. Considering CO2, CH4, and N2O emissions as a whole, an overall increase in global warming potential was observed with straw amendment. Total CO2 and CH4 emissions from straw-amended soils were significantly higher for YX than TZ soil, suggesting that straw-induced greenhouse gas emissions depended on soil characteristics. The abundance of C-turnover bacteria Firmicutes increased from 28-41% to 54-77% with straw amendment, thereby increasing CO2 and CH4 emissions. However, straw amendment reduced the abundance of denitrifying bacteria Proteobacteria from 18% to 7.2-13% or increased the abundance of N2O reducing bacteria Clostridium from 7.6-11% to 13-30%, thereby decreasing N2O emission. The results suggested straw amendment strongly influenced greenhouse gas emissions via alerting soil properties and bacterial community compositions. Future field application is needed to ascertain the effects of straw return on greenhouse gas emissions.

  3. A 4 U laser heterodyne radiometer for methane (CH4) and carbon dioxide (CO2) measurements from an occultation-viewing CubeSat

    NASA Astrophysics Data System (ADS)

    Wilson, Emily L.; DiGregorio, A. J.; Riot, Vincent J.; Ammons, Mark S.; Bruner, William W.; Carter, Darrell; Mao, Jianping; Ramanathan, Anand; Strahan, Susan E.; Oman, Luke D.; Hoffman, Christine; Garner, Richard M.

    2017-03-01

    We present a design for a 4 U (20 cm  ×  20 cm  ×  10 cm) occultation-viewing laser heterodyne radiometer (LHR) that measures methane (CH4), carbon dioxide (CO2) and water vapor (H2O) in the limb that is designed for deployment on a 6 U CubeSat. The LHR design collects sunlight that has undergone absorption by the trace gas and mixes it with a distributive feedback (DFB) laser centered at 1640 nm that scans across CO2, CH4, and H2O absorption features. Upper troposphere/lower stratosphere measurements of these gases provide key inputs to stratospheric circulation models: measuring stratospheric circulation and its variability is essential for projecting how climate change will affect stratospheric ozone.

  4. New High-Frequency Measurements of CH4, N2O and SF6 from a High-Altitude Station in the Eastern Himalayas of India and Derived Emissions Estimates

    NASA Astrophysics Data System (ADS)

    Ganesan, A. L.; Chatterjee, A.; Salameh, P.; Harth, C. M.; Rigby, M.; Manning, A. J.; Hall, B. D.; Ghosh, S. K.; Muhle, J.; Meredith, L. K.; Mandal, T. K.; Weiss, R. F.; Prinn, R. G.

    2012-12-01

    We present new in situ measurements from a station in Darjeeling, India (27.03°N, 88.26°E, 2200 m above sea level). These measurements comprise the first high-frequency dataset of methane (CH4), nitrous oxide (N2O) and sulfur hexafluoride (SF6) collected in India. Measurements are made with a gas chromatographic system, using a flame ionization detector (GC-FID) for CH4 and an electron capture detector (GC-ECD) for N2O and SF6. Measurements have been linked to calibration scales used in the Advanced Global Atmospheric Gases Experiment (AGAGE, Tohoku University for CH4 and Scripps institution of Oceanography 1998 and 2005, for N2O and SF6, respectively). Preliminary results show a significant diurnal cycle for CH4, consistent with upslope flows bringing local emissions from the town and valley to the site during the day and downslope flows bringing cleaner air at night. This nighttime decrease in mixing ratio could be attributed to a variety of factors, including reduced local emissions or sampling of cleaner, free tropospheric air from aloft. Underlying this local signal is a much larger regional influence, which is driven by the large-scale meteorology that governs which upwind regions contribute to the measured mole fractions at the site. We also investigate local influences on N2O and SF6, which are much smaller than CH4 or negligible, because of their comparatively weaker nearby sources. We present emissions estimates for India using the high-resolution UK Met Office Lagrangian particle dispersion model, the Numerical Atmospheric dispersion Modeling Environment (NAME). Air histories generated using NAME reveal that the site regularly intercepts air from important rice-growing and biomass burning regions of Northern India. This unique dataset allows further constraints to be placed on "top-down" estimates of emissions from these CH4 sources. Further constraints will also be possible for regional agricultural sources of N2O and South-Asian SF6, both of which

  5. Electronic spectroscopy and photodissociation dynamics of Co(2+)-methanol clusters: Co2+ (CH3OH)n (n = 4-7).

    PubMed

    Thompson, Christopher J; Faherty, Kieron P; Stringer, Kay L; Metz, Ricardo B

    2005-03-07

    Solvated cluster ions Co2+ (CH3OH)n (n = 4-7) have been produced by electrospray and studied using photofragment spectroscopy. There are notable differences between the photodissociation spectra of these complexes and the analogous water complexes. Co2+ (CH3OH)6 absorbs significantly more strongly than Co2+ (H2O)6. The photodissociation spectra of Co2+ (CH3OH)n (n = 4, 5 and 6) are very similar, which suggests that they share the Co2+ (CH3OH)4 chromophore, with additional solvent molecules in the second shell. In contrast, our earlier studies indicate that Co2+ (H2O)6 is six coordinate, and its spectrum is significantly different from that of Co2+ (H2O)4. The larger clusters Co2+ (CH3OH)n (n = 5-7) dissociate by simple loss of one or more solvent molecules. Larger clusters tend to lose more solvent molecules, especially at higher photon energies. As with the corresponding water cluster, Co2+ (CH3OH)4 photodissociates by proton transfer through a salt-bridge intermediate. This is accompanied by a modest kinetic energy release of 170 kJ mol(-1) and occurs with a lifetime of 145 ns.

  6. X-ray diffraction analysis of 4- and 4'-substituted C n H2 n + 1O-C6H3(OH)-CH=N-C6H4-C m H2 m + 1 ( n/ m = 2/1 and 3/4) salicylideneanilines

    NASA Astrophysics Data System (ADS)

    Kuz'mina, L. G.; Navasardyan, M. A.; Mikhailov, A. A.

    2017-11-01

    X-ray diffraction study of two crystalline modifications of C2H5O-C6H3(OH)-CH=N-C6H4-CH3 ( 1a, sp. gr. P21/ n, and 1b, sp. gr. C2/c) and C3H7O-C6H3(OH)-CH=N-C6H4-C4H9 ( 2, sp. gr. P212121) has been performed. The 1a crystal structure contains two independent molecules. The molecules are conformationally nonrigid with respect to the mutual rotation of benzene rings; the dihedral angles between their planes are 29.19° and 26.00° in the independent molecules of 1a, 18.72° in the molecule of 1b, and 50.35° in the molecule of 2. The crystal packing of the compounds is discussed.

  7. [Effects of biochar application three-years ago on global warming potentials of CH4 and N2O in a rice-wheat rotation system.

    PubMed

    Wu, Zhen; Dong, Yu Bing; Xiong, Zheng Qin

    2018-01-01

    To evaluate the long-term effects of biochar amendment on greenhouse gas emissions (GHGs), a field experiment was conducted to examine the effects of 3-year field-aged biochar (B 3 ) and fresh biochar (B 0 ) on global warming potential (GWP) and greenhouse gas intensity (GHGI) of methane (CH 4 ) and nitrous oxide (N 2 O) in a typical rice-wheat rotation system. Four treatments were established as control without nitrogen fertilizer (CK), urea without biochar (N), urea with fresh biochar amended in 2015 (NB 0 ), and urea with 3-year field-aged biochar amended in 2012 (NB 3 ). Results showed that both the NB 0 and NB 3 treatments obviously increased soil pH, soil organic carbon (SOC), total nitrogen (TN) and influenced the potential activity of functional microorganisms related to GHGs compared to the N treatment. Relative to the N treatment, the NB 3 treatment significantly improved crop yield by 14.1% while reduced the CH 4 and N 2 O emissions by 9.0% and 34.0%, respectively. In addition, the NB 0 treatment significantly improved crop yield by 9.3%, while reduced the N 2 O emission by 38.6% though increased the CH 4 emissions by 4.7% relative to the N treatment. Moreover, both the NB 0 and NB 3 treatments could significantly reduce both GWP and GHGI, with NB 3 being more effective in simultaneously mitigating the GHGs emissions and enhancing crop yield. Since field-aged biochar showed obvious effects on GHGs mitigation and carbon sequestration after 3 years, biochar incorporations had long-term effect on GHGs mitigation and crop production in the rice-wheat rotation system.

  8. H2O-CH4 and H2S-CH4 complexes: a direct comparison through molecular beam experiments and ab initio calculations.

    PubMed

    Cappelletti, David; Bartocci, Alessio; Frati, Federica; Roncaratti, Luiz F; Belpassi, Leonardo; Tarantelli, Francesco; Lakshmi, Prabha Aiswarya; Arunan, Elangannan; Pirani, Fernando

    2015-11-11

    New molecular beam scattering experiments have been performed to measure the total (elastic plus inelastic) cross sections as a function of the velocity in collisions between water and hydrogen sulfide projectile molecules and the methane target. Measured data have been exploited to characterize the range and strength of the intermolecular interaction in such systems, which are of relevance as they drive the gas phase molecular dynamics and the clathrate formation. Complementary information has been obtained by rotational spectra, recorded for the hydrogen sulfide-methane complex, with a pulsed nozzle Fourier transform microwave spectrometer. Extensive ab initio calculations have been performed to rationalize all the experimental findings. The combination of experimental and theoretical information has established the ground for the understanding of the nature of the interaction and allows for its basic components to be modelled, including charge transfer, in these weakly bound systems. The intermolecular potential for H2S-CH4 is significantly less anisotropic than for H2O-CH4, although both of them have potential minima that can be characterized as 'hydrogen bonded'.

  9. Methane Provenance Determined by CH2D2 and 13CH3D Abundances

    NASA Astrophysics Data System (ADS)

    Kohl, I. E.; Giunta, T.; Warr, O.; Ash, J. L.; Ruffine, L.; Sherwood Lollar, B.; Young, E. D.

    2017-12-01

    Determining the provenance of naturally occurring methane gases is of major interest to energy companies and atmospheric climate modelers, among others. Bulk isotopic compositions and other geochemical tracers sometimes fail to provide definitive determinations of sources of methane due to complications from mixing and complicated chemical pathways of origin. Recent measurements of doubly-substituted isotopologues of methane, CH2D2 (UCLA) and 13CH3D (UCLA, CalTech, and MIT) have allowed for major improvements in sourcing natural methane gases. Early work has focused on formation temperatures obtained when the relative abundances of both doubly-substituted mass-18 species are consistent with internal equilibrium. When methane gases do not plot on the thermodynamic equilibrium curve in D12CH2D2 vs D13CH3D space, temperatures determined from D13CH3D values alone are usually spurious, even when appearing reasonable. We find that the equilibrium case is actually rare and almost exclusive to thermogenic gases produced at temperatures exceeding 100°C. All other relevant methane production processes appear to generate gases that are not in isotopologue-temperature equilibrium. When gases show departures from equilibrium as determined by the relationship between CH2D2 and 13CH3D abundances, data fall within empirically defined fields representing formation pathways. These fields are thus far consistent between different geological settings and and between lab experiments and natural samples. We have now defined fields for thermogenic gas production, microbial methanogenesis, low temperature abiotic (Sabatier) synthesis and higher temperature FTT synthesis. The majority of our natural methane data can be explained by mixing between end members originating within these production fields. Mixing can appear complex, resulting in both hyper-clumped and anti-clumped isotopologue abundances. In systems where mixtures dominate and end-members are difficult to sample, mixing models

  10. Two methanes are better than one: a density functional theory study of the reactions of Mo2Oy- (y = 2-5) with methane.

    PubMed

    Mayhall, Nicholas J; Raghavachari, Krishnan

    2007-08-23

    The mechanisms of chemical reactions of molybdenum suboxide clusters Mo(2)O(n)- (n = 2-5) with methane are investigated using B3LYP hybrid density functional theory and polarized basis sets. In particular, we focus on the reactions of the most stable structural isomers of Mo(2)O(2,3,4,5)- that lead to single molybdenum species such as HMoO(2)CH(3)-, as seen in the recent experimental study of Jarrold and co-workers. We find that, while all experimentally observed products are unfavorable due to the high amount of energy required to cleave the metal oxide, the formation of HMoO(2)CH(3)- is least endothermic. Even in this case, the thermodynamics of these reactions is very unfavorable when a single methane is reacted with the metal oxide. However, we find that the sequential addition of two methanes produces HMoO(2)CH(3)- (and another neutral molecule whose identity depends on the number of oxygens in the metal oxide) at a much lower thermodynamic cost. Further, the overall reaction barriers are much lower when the second methane adds prior to the Mo(2)O(2,3,4,5)- cleavage. The methane addition at each metal center oxidizes the metals to produce a species that is then stable enough to afford the Mo-Mo cleavage.

  11. Spatial variability of nitrous oxide and methane emissions from an MBT landfill in operation: Strong N{sub 2}O hotspots at the working face

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Harborth, Peter, E-mail: p.harborth@tu-bs.de; Fuß, Roland; Münnich, Kai

    Highlights: ► First measurements of N{sub 2}O and CH{sub 4} emissions from an MBT landfill. ► High N{sub 2}O emissions from recently deposited material. ► N{sub 2}O emissions associated with aeration and the occurrence of nitrite and nitrate. ► Strong negative correlation between CH{sub 4} and N{sub 2}O production activity. - Abstract: Mechanical biological treatment (MBT) is an effective technique, which removes organic carbon from municipal solid waste (MSW) prior to deposition. Thereby, methane (CH{sub 4}) production in the landfill is strongly mitigated. However, direct measurements of greenhouse gas emissions from full-scale MBT landfills have not been conducted so far.more » Thus, CH{sub 4} and nitrous oxide (N{sub 2}O) emissions from a German MBT landfill in operation as well as their concentrations in the landfill gas (LFG) were measured. High N{sub 2}O emissions of 20–200 g CO{sub 2} eq. m{sup −2} h{sup −1} magnitude (up to 428 mg N m{sup −2} h{sup −1}) were observed within 20 m of the working face. CH{sub 4} emissions were highest at the landfill zone located at a distance of 30–40 m from the working face, where they reached about 10 g CO{sub 2} eq. m{sup −2} h{sup −1}. The MBT material in this area has been deposited several weeks earlier. Maximum LFG concentration for N{sub 2}O was 24.000 ppmv in material below the emission hotspot. At a depth of 50 cm from the landfill surface a strong negative correlation between N{sub 2}O and CH{sub 4} concentrations was observed. From this and from the distribution pattern of extractable ammonium, nitrite, and nitrate it has been concluded that strong N{sub 2}O production is associated with nitrification activity and the occurrence of nitrite and nitrate, which is initiated by oxygen input during waste deposition. Therefore, CH{sub 4} mitigation measures, which often employ aeration, could result in a net increase of GHG emissions due to increased N{sub 2}O emissions, especially at MBT

  12. Impacts of feedlot floor condition, deposition frequency, and inhibitors on N2O and CH4 emissions from feedlot dung and urine patches.

    PubMed

    Liao, Wenhua; Liu, Chunjing; Gao, Zhiling

    2018-04-09

    Patches of dung and urine are major contributors to the feedlot gas emissions. This study investigated the impacts of dung deposition frequency (partly reflecting animal stocking density of a feedlot), dairy feedlot floor conditions (old floor indicated with the presence of consolidated manure pad [CMP] vs. new floor with the absence of consolidated manure pad [CMPn]), and application of dicyandiamide (DCD) and hydroquinone (HQ) on nitrous oxide (N 2 O) and methane (CH 4 ) emissions from patches in the laboratory, and the integrative impacts were expressed in terms of global warming potential (CO 2 -equivalent). Dung deposition frequency, feedlot floor condition, and application of inhibitors showed inverse impacts on N 2 O and CH 4 emissions from patches. Greenhouse gas (GHG) emissions from the dung, urine, and dung+urine patches on the CMP feedlot surface were approximately 7.48, 87.35, and 7.10 times those on the CMPn feedlot surface (P < 0.05). Meanwhile, GHG emissions from CMP and CMPn feedlot surfaces under high deposition frequency condition were approximately 10 and 1.7 times those under low-frequency condition. Moreover, application of HQ slightly reduced the GHG emission from urine patches, by 14.9% (P > 0.05), while applying DCD or DCD+HQ significantly reduced the GHG, by 60.3% and 65.0%, respectively (P < 0.05). Overall, it is necessary to include feedlot management such as animal stocking density and feedlot floor condition to the process of determining emission factors for feedlots. In the future, field measurements to quantitatively evaluate the relative contribution of nitrification and denitrification to the N 2 O emissions of feedlot surfaces are highly required for effective N 2 O control. This study shows that feedlot CH 4 and N 2 O emissions inversely respond to the dicyandiamide (DCD) application. Applying DCD significantly reduces GHG emissions of feedlot urine patches. Feedlot floor condition and stocking density strongly impact

  13. The δ15N and δ18O values of N2O produced during the co-oxidation of ammonia by methanotrophic bacteria

    USGS Publications Warehouse

    Mandernack, Kevin W.; Mills, Christopher T.; Johnson, Craig A.; Rahn, Thomas; Kinney, Chad

    2009-01-01

    In order to determine if the δ15N and δ18O values of N2O produced during co-oxidation of NH4+ by methanotrophic (methane oxidizing) bacteria can be isotopically distinguished from N2O produced either by autotrophic nitrifying or denitrifying bacteria, we conducted laboratory incubation experiments with pure cultures of methanotrophic bacteria that were provided NH4Cl as an oxidation substrate. The N2O produced during NH4+ oxidation by methanotrophic bacteria showed nitrogen isotope fractionation between NH4+ and N2ON2O–NH4+) of − 48 and − 55‰ for Methylomonas methanica and Methylosinus trichosporium, OB3b respectively. These large fractionations are similar to those previously measured for autotrophic nitrifying bacteria and consistent with N2O formation by multiple rate limiting steps that include NH4+oxidation by the methane monooxygenase enzyme and reduction of NO2− to N2O. Consequently, N2O formed by NH4+ oxidation via methanotrophic or autotrophic nitrifying bacteria might generally be characterized by lower δ15NN2O values than that formed by denitrificaiton, although this also depends on the variability of δ15N of available nitrogen sources (e.g., NH4+, NO3−, NO2−). Additional incubations with M. trichosporium OB3b at high and low CH4 conditions in waters of different δ18O values revealed that 19–27% of the oxygen in N2O was derived from O2 with the remainder from water. The biochemical mechanisms that could explain this amount of O2 incorporation are discussed. The δ18O of N2O formed under high CH4 conditions was ~ + 15‰ more positive than that formed under lower CH4 conditions. This enrichment resulted in part from the incorporation of O2 into N2O that was enriched in 18O due to an isotope fractionation effect of − 16.1 ± 2.0‰ and − 17.5 ± 5.4‰ associated with O2 consumption during the high and low methane concentration incubations, respectively. Therefore, N2O formed by NH4+

  14. Comparison of Landfill Methane Oxidation Measured Using Stable Isotope Analysis and CO2/CH4 Fluxes Measured by the Eddy Covariance Method

    NASA Astrophysics Data System (ADS)

    Xu, L.; Chanton, J.; McDermitt, D. K.; Li, J.; Green, R. B.

    2015-12-01

    Methane plays a critical role in the radiation balance and chemistry of the atmosphere. Globally, landfill methane emission contributes about 10-19% of the anthropogenic methane burden into the atmosphere. In the United States, 18% of annual anthropogenic methane emissions come from landfills, which represent the third largest source of anthropogenic methane emissions, behind enteric fermentation and natural gas and oil production. One uncertainty in estimating landfill methane emissions is the fraction of methane oxidized when methane produced under anaerobic conditions passes through the cover soil. We developed a simple stoichiometric model to estimate methane oxidation fraction when the anaerobic CO2 / CH4 production ratio is known, or can be estimated. The model predicts a linear relationship between CO2 emission rates and CH4 emission rates, where the slope depends on anaerobic CO2 / CH4 production ratio and the fraction of methane oxidized, and the intercept depends on non-methane-dependent oxidation processes. The model was tested using carbon dioxide emission rates (fluxes) and methane emission rates (fluxes) measured using the eddy covariance method over a one year period at the Turkey Run landfill in Georgia, USA. The CO2 / CH4 production ratio was estimated by measuring CO2 and CH4 concentrations in air sampled under anaerobic conditions deep inside the landfill. We also used a mass balance approach to independently estimate fractional oxidation based on stable isotope measurements (δ13C of methane) of gas samples taken from deep inside the landfill and just above the landfill surface. Results from the two independent methods agree well. The model will be described and methane oxidation will be discussed in relation to wind direction, location at the landfill, and age of the deposited refuse.

  15. CW EC-QCL-based sensor for simultaneous detection of H 2O, HDO, N 2O and CH 4 using multi-pass absorption spectroscopy

    DOE PAGES

    Yu, Yajun; Sanchez, Nancy P.; Griffin, Robert J.; ...

    2016-05-03

    A sensor system based on a continuous wave, external-cavity quantum-cascade laser (CW EC-QCL) was demonstrated for simultaneous detection of atmospheric H 2O, HDO, N 2O and CH 4 using a compact, dense pattern multi-pass gas cell with an effective path-length of 57.6 m. The EC-QCL with a mode-hop-free spectral range of 1225-1285 cm -1 operating at similar to 7.8 mu m was scanned covering four neighboring absorption lines, for H 2O at 1281.161 cm -1, HDO at 1281.455 cm -1, N 2O at 1281.53 cm -1 and CH 4 at 1281.61 cm -1. A first-harmonic-normalized wavelength modulation spectroscopy with second-harmonicmore » detection (WMS-2f/1f) strategy was employed for data processing. An Allan-Werle deviation analysis indicated that minimum detection limits of 1.77 ppmv for H 2O, 3.92 ppbv for HDO, 1.43 ppbv for N 2O, and 2.2 ppbv for CH 4 were achieved with integration times of 50-s, 50-s, 100-s and 129-s, respectively. In conclusion, experimental measurements of ambient air are also reported.« less

  16. Reactions of CH3SH and CH3SSCH3 with gas-phase hydrated radical anions (H2O)n(•-), CO2(•-)(H2O)n, and O2(•-)(H2O)n.

    PubMed

    Höckendorf, Robert F; Hao, Qiang; Sun, Zheng; Fox-Beyer, Brigitte S; Cao, Yali; Balaj, O Petru; Bondybey, Vladimir E; Siu, Chi-Kit; Beyer, Martin K

    2012-04-19

    The chemistry of (H(2)O)(n)(•-), CO(2)(•-)(H(2)O)(n), and O(2)(•-)(H(2)O)(n) with small sulfur-containing molecules was studied in the gas phase by Fourier transform ion cyclotron resonance mass spectrometry. With hydrated electrons and hydrated carbon dioxide radical anions, two reactions with relevance for biological radiation damage were observed, cleavage of the disulfide bond of CH(3)SSCH(3) and activation of the thiol group of CH(3)SH. No reactions were observed with CH(3)SCH(3). The hydrated superoxide radical anion, usually viewed as major source of oxidative stress, did not react with any of the compounds. Nanocalorimetry and quantum chemical calculations give a consistent picture of the reaction mechanism. The results indicate that the conversion of e(-) and CO(2)(•-) to O(2)(•-) deactivates highly reactive species and may actually reduce oxidative stress. For reactions of (H(2)O)(n)(•-) with CH(3)SH as well as CO(2)(•-)(H(2)O)(n) with CH(3)SSCH(3), the reaction products in the gas phase are different from those reported in the literature from pulse radiolysis studies. This observation is rationalized with the reduced cage effect in reactions of gas-phase clusters. © 2012 American Chemical Society

  17. Crystal and molecular structure of the first dibino non-geminal macrocyclic dicyclophosphazene, & {;N 3P 3Cl 4[HN(CH 2) 3O(CH 2) 2O(CH 2) 3NH]&}; 2

    NASA Astrophysics Data System (ADS)

    Enjalbert, Renée; Galy, Jean; Sournies, François; Labarre, Jean-François

    1990-04-01

    Reaction of N 3P 3Cl 6 with the 4,7-dioxadecane-1,10-diamine (coded as 3O2O3) using an Et 2O/Na 2CO 3 water interface process leads to the DIBINO non-geminal 30-membered macrocyclic dicyclophosphazene &{;N 3P 3Cl 4[HN(CH 2) 3O(CH 2) 2O(CH 2) 3NH]&}; 2. This 30-crown-ether-like architecture crystallizes in the triclinic system, P1, a=9.019(6), b=9.224(5), c=11.542(8) Å, α=94.87(4), β=95.97(4), γ=99.68(3)°, V=936(1) Å 3, Dx=1.599 Mg m -3, R=0.049 for 2862 unique reflections and 199 variable parameters. The structure exhibits a spatial arrangement of two N 3P 3Cl 4 with two [HN(CH 2) 3O(CH 2) 3O(CH 2) 3NH] as bridges on different P atoms of N 3P 3 rings. Moreover, the two N 3P 3 rings are trans to the average plane of the 30-membered macrocycle ("chair" conformation).

  18. Impact of raw pig slurry and pig farming practices on physicochemical parameters and on atmospheric N2O and CH 4 emissions of tropical soils, Uvéa Island (South Pacific).

    PubMed

    Roth, E; Gunkel-Grillon, P; Joly, L; Thomas, X; Decarpenterie, T; Mappe-Fogaing, I; Laporte-Magoni, C; Dumelié, N; Durry, G

    2014-09-01

    Emissions of CH4 and N2O related to private pig farming under a tropical climate in Uvéa Island were studied in this paper. Physicochemical soil parameters such as nitrate, nitrite, ammonium, Kjeldahl nitrogen, total organic carbon, pH and moisture were measured. Gaseous soil emissions as well as physicochemical parameters were compared in two private pig farming strategies encountered on this island on two different soils (calcareous and ferralitic) in order to determine the best pig farming management: in small concrete pens or in large land pens. Ammonium levels were higher in control areas while nitrate and nitrite levels were higher in soils with pig slurry inputs, indicating that nitrification was the predominant process related to N2O emissions. Nitrate contents in soils near concrete pens were important (≥ 55 μg N/g) and can thus be a threat for the groundwater. For both pig farming strategies, N2O and CH4 fluxes can reach high levels up to 1 mg N/m(2)/h and 1 mg C/m(2)/h, respectively. CH4 emissions near concrete pens were very high (≥ 10.4 mg C/m(2)/h). Former land pens converted into agricultural land recover low N2O emission rates (≤ 0.03 mg N/m(2)/h), and methane uptake dominates. N2O emissions were related to nitrate content whereas CH4 emissions were found to be moisture dependent. As a result relating to the physicochemical parameters as well as to the gaseous emissions, we demonstrate that pig farming in large land pens is the best strategy for sustainable family pig breeding in Uvéa Islands and therefore in similar small tropical islands.

  19. Carbon dioxide induced bubble formation in a CH4-CO2-H2O ternary system: a molecular dynamics simulation study.

    PubMed

    Sujith, K S; Ramachandran, C N

    2016-02-07

    The extraction of methane from its hydrates using carbon dioxide involves the decomposition of the hydrate resulting in a CH4-CO2-H2O ternary solution. Using classical molecular dynamics simulations, we investigate the evolution of dissolved gas molecules in the ternary system at different concentrations of CO2. Various compositions considered in the present study resemble the solution formed during the decomposition of methane hydrates at the initial stages of the extraction process. We find that the presence of CO2 aids the formation of CH4 bubbles by causing its early nucleation. Elucidation of the composition of the bubble revealed that in ternary solutions with high concentration of CO2, mixed gas bubbles composed of CO2 and CH4 are formed. To understand the role of CO2 in the nucleation of CH4 bubbles, the structure of the bubble formed was analyzed, which revealed that there is an accumulation of CO2 at the interface of the bubble and the surrounding water. The aggregation of CO2 at the bubble-water interface occurs predominantly when the concentration of CO2 is high. Radial distribution function for the CH4-CO2 pair indicates that there is an increasingly favorable direct contact between dissolved CH4 and CO2 molecules in the bubble-water interface. It is also observed that the presence of CO2 at the interface results in the decrease in surface tension. Thus, CO2 leads to greater stability of the bubble-water interface thereby bringing down the critical size of the bubble nuclei. The results suggest that a rise in concentration of CO2 helps in the removal of dissolved CH4 thereby preventing the accumulation of methane in the liquid phase. Thus, the presence of CO2 is predicted to assist the decomposition of methane hydrates in the initial stages of the replacement process.

  20. Greenhouse gas fluxes (CO2, CH4, N2O) of a short-rotation poplar plantation after conversion from agriculture

    NASA Astrophysics Data System (ADS)

    Zona, D.; Janssens, I.; Aubinet, M.; Ceulemans, R.

    2012-12-01

    The increasing demand for renewable energy may lead to the conversion of millions of hectares into bioenergy plantations with a possible substantial transitory carbon (C) loss. Here we report on the greenhouse gas fluxes (CO2, CH4, and N2O) measured using eddy covariance of a short-rotation bioenergy poplar plantation converted from agricultural fields. The first six months after the establishment of the plantation (June-Dec 2010) presented substantial CO2, CH4, and N2O emissions (a total of 5.36 ± 0.52 Mg CO2eq ha-1 in terms of CO2 equivalents). Nitrous oxide loss mostly occurred during a week-long peak emission after an unusually large rainfall. This week-long N2O emission represented 52% of the entire N2O loss during one and an half years of measurements. As most of the N2O loss occurred in just this week-long period, accurately capturing these emission events are critical to accurate estimates of the GHG balance of bioenergy. While initial establishment (Jun-Dec 2010) of the plantation resulted in a net CO2 loss into the atmosphere (2.76 ± 0.16 Mg CO2eq ha-1), in the second year (2011) the plantation presented a substantial net CO2 uptake (-4.82 ± 0.47 Mg CO2eq ha-1). During the entire measurement period, CH4 was a source to the atmosphere (0.63 ± 0.05 Mg CO2eq ha-1 in 2010, and 0.49 ± 0.05 Mg CO2eq ha-1 in 2011), and was controlled by water table depth. Importantly, over the entire measurement period, the sum of the CH4 and N2O losses was almost double (3.51 ± 0.52 Mg CO2eq ha-1) than the magnitude of net CO2 uptake (-2.06 ± 0.50 Mg CO2eq ha-1). As water availability was an important control on the GHG emission of the plantation, expected climate change and altered rainfall pattern could increase the negative environmental impacts of bioenergy.

  1. Evaluation of CH4 and N2O Budget of Natural Ecosystems and Croplands in Asia with a Process-based Model

    NASA Astrophysics Data System (ADS)

    Ito, A.

    2017-12-01

    Terrestrial ecosystems are important sink of carbon dioxide (CO2) but significant sources of other greenhouse gases such as methane (CH4) and nitrous oxide (N2O). To resolve the role of terrestrial biosphere in the climate system, we need to quantify total greenhouse gas budget with an adequate accuracy. In addition to top-down evaluation on the basis of atmospheric measurements, model-based approach is required for integration and up-scaling of filed data and for prediction under changing environment and different management practices. Since the early 2000s, we have developed a process-based model of terrestrial biogeochemical cycles focusing on atmosphere-ecosystem exchange of trace gases: Vegetation Integrated SImulator for Trace gases (VISIT). The model includes simple and comprehensive schemes of carbon and nitrogen cycles in terrestrial ecosystems, allowing us to capture dynamic nature of greenhouse gas budget. Beginning from natural ecosystems such as temperate and tropical forests, the models is now applicable to croplands by including agricultural practices such as planting, harvest, and fertilizer input. Global simulation results have been published from several papers, but model validation and benchmarking using up-to-date observations are remained for works. The model is now applied to several practical issues such as evaluation of N2O emission from bio-fuel croplands, which are expected to accomplish the mitigation target of the Paris Agreement. We also show several topics about basic model development such as revised CH4 emission affected by dynamic water-table and refined N2O emission from nitrification.

  2. Argus: a new instrument for the measurement of the stratospheric dynamical tracers, N2O and CH4

    NASA Technical Reports Server (NTRS)

    Loewenstein, Max; Jost, H.; Grose, J.; Eilers, J.; Lynch, D.; Jensen, S.; Marmie, J.

    2002-01-01

    We describe here a new instrument for the simultaneous, in situ measurement of the stratospheric tracer molecules, nitrous oxide (N2O) and methane (CH4). Argus is unique in its small size making it well suited for limited payload atmospheric research platforms. Argus employs second harmonic spectroscopy using tunable lead-salt diode lasers emitting in the mid-infrared. We first explain the Argus design philosophy followed by detailed descriptions of the instrument's optical, mechanical, and thermal sub-systems. Argus employs an in-flight calibration system providing real time calibrations and tightly constrained uncertainty estimates of the returned data. Data analysis is carried out using non-linear least-squares model fits to the acquired second harmonic spectra. A sampling of Argus data acquired on a recent stratospheric research campaign in the Arctic winter is presented.

  3. Spatial variability of nitrous oxide and methane emissions from an MBT landfill in operation: strong N2O hotspots at the working face.

    PubMed

    Harborth, Peter; Fuss, Roland; Münnich, Kai; Flessa, Heinz; Fricke, Klaus

    2013-10-01

    Mechanical biological treatment (MBT) is an effective technique, which removes organic carbon from municipal solid waste (MSW) prior to deposition. Thereby, methane (CH4) production in the landfill is strongly mitigated. However, direct measurements of greenhouse gas emissions from full-scale MBT landfills have not been conducted so far. Thus, CH4 and nitrous oxide (N2O) emissions from a German MBT landfill in operation as well as their concentrations in the landfill gas (LFG) were measured. High N2O emissions of 20-200gCO2eq.m(-2)h(-1) magnitude (up to 428mgNm(-2)h(-1)) were observed within 20m of the working face. CH4 emissions were highest at the landfill zone located at a distance of 30-40m from the working face, where they reached about 10gCO2eq.m(-2)h(-1). The MBT material in this area has been deposited several weeks earlier. Maximum LFG concentration for N2O was 24.000ppmv in material below the emission hotspot. At a depth of 50cm from the landfill surface a strong negative correlation between N2O and CH4 concentrations was observed. From this and from the distribution pattern of extractable ammonium, nitrite, and nitrate it has been concluded that strong N2O production is associated with nitrification activity and the occurrence of nitrite and nitrate, which is initiated by oxygen input during waste deposition. Therefore, CH4 mitigation measures, which often employ aeration, could result in a net increase of GHG emissions due to increased N2O emissions, especially at MBT landfills. Copyright © 2013 Elsevier Ltd. All rights reserved.

  4. A comparison of CH4, N2O and CO2 emissions from three different cover types in a municipal solid waste landfill.

    PubMed

    Wang, Xiaojun; Jia, Mingsheng; Lin, Xiangyu; Xu, Ying; Ye, Xin; Kao, Chih Ming; Chen, Shaohua

    2017-04-01

    High-density polyethylene (HDPE) membranes are commonly used as a cover component in sanitary landfills, although only limited evaluations of its effect on greenhouse gas (GHG) emissions have been completed. In this study, field GHG emission were investigated at the Dongbu landfill, using three different cover systems: HDPE covering; no covering, on the working face; and a novel material-Oreezyme Waste Cover (OWC) material as a trial material. Results showed that the HDPE membrane achieved a high CH 4 retention, 99.8% (CH 4 mean flux of 12 mg C m -2 h -1 ) compared with the air-permeable OWC surface (CH4 mean flux of 5933 mg C m -2 h -1 ) of the same landfill age. Fresh waste at the working face emitted a large fraction of N 2 O, with average fluxes of 10 mg N m -2 h -2 , while N 2 O emissions were small at both the HDPE and the OWC sections. At the OWC section, CH 4 emissions were elevated under high air temperatures but decreased as landfill age increased. N 2 O emissions from the working face had a significant negative correlation with air temperature, with peak values in winter. A massive presence of CO 2 was observed at both the working face and the OWC sections. Most importantly, the annual GHG emissions were 4.9 Gg yr -1 in CO 2 equivalents for the landfill site, of which the OWC-covered section contributed the most CH 4 (41.9%), while the working face contributed the most N 2 O (97.2%). HDPE membrane is therefore, a recommended cover material for GHG control. Monitoring of GHG emissions at three different cover types in a municipal solid waste landfill during a 1-year period showed that the working face was a hotspot of N 2 O, which should draw attention. High CH 4 fluxes occurred on the permeable surface covering a 1- to 2-year-old landfill. In contrast, the high-density polyethylene (HDPE) membrane achieved high CH 4 retention, and therefore is a recommended cover material for GHG control.

  5. Separating methane emissions from agricultural sources and natural gas: direct measurements of excess columns of CH4, C2H6 and NH3 in the Colorado Front Range

    NASA Astrophysics Data System (ADS)

    Kille, N.; Chiu, R.; Frey, M.; Hase, F.; Kumar Sha, M.; Blumenstock, T.; Hannigan, J. W.; Volkamer, R. M.

    2017-12-01

    Methane (CH4) is a major greenhouse gas emitted from biogenic, thermogenic, and pyrogenic sources. Here we demonstrate a novel approach to separate sources of CH4 emissions based on a network of small portable sensors performing column measurements in the Northern Colorado Front Range (NCFR). In the study area CH4 is emitted from biogenic sources such as concentrated animal feeding operations (CAFOs) and natural gas production and storage. In March 2015 we deployed a network of five Fourier Transform Spectrometers (FTS) to characterize the regional scale methane dome in Colorado's Denver-Julesburg Basin based on excess vertical column measurements (the column enhancement inside the dome over background). Three EM27sun FTS measured CH4, oxygen (O2) and water vapor (H2O) columns at Eaton, CO (inside the dome) and at two boundary sites; the CU mobile SOF (Solar Occultation Flux) measured ethane (C2H6), ammonia (NH3), and H2O at Eaton, CO. The column averaged dry air mole fractions XCH4, XC2H6, and XNH3 were determined using O2 columns for air mass factor normalization, and background column was subtracted to derive excess vertical columns of DXCH4, DXC2H6, DXNH3 at Eaton, CO. Eaton is located both near CAFOs and at the northern edge of oil and natural gas production wells. Our approach for source apportioning methane employs a linear regression analysis that explains DXCH4 in terms of DXC2H6 as tracer for natural gas sources, and DXNH3 as tracer for CAFO emissions. The results of the source apportionment are compared with literature values of the NH3/CH4 and C2H6/CH4 ratio to evaluate the method of excess columns, which is independent of boundary layer height.

  6. Ozone perturbations by enhanced levels of CFCs, N2O, and CH4 A two-dimensional diabatic circulation study including uncertainty estimates

    NASA Technical Reports Server (NTRS)

    Isaksen, I. S. A.; Stordal, F.

    1986-01-01

    Observations made over the last few years suggest that the tropospheric concentrations of N2O, CH4, and O3 are increasing. Increases in the concentration of chlorofluorocarbons (CFCs) have been observed for some time. The present study is concerned with combined scenarios of future releases of N2O, CH4, and CFCs, which can affect the height profiles of ozone, while changes in latitudinal gradients of ozone may also be expected. Ozone perturbation calculations performed in the two-dimensional transport-chemistry model described by Stordal et al. (1985) are also presented, and the effects of increased levels of CFCs, N2O, and CH4 are examined. It is found that CH4 may be the most important ozone-perturbing trace species in connection with future tropospheric climatic impacts. A substantial increase in the tropospheric abundancy of CH4 could lead to large future ozone enhancements throughout the troposphere and lower stratosphere at middle and low latitudes.

  7. Mitigating effects of ex situ application of rice straw on CH4 and N2O emissions from paddy-upland coexisting system

    PubMed Central

    Wang, Wei; Wu, Xiaohong; Chen, Anlei; Xie, Xiaoli; Wang, Yunqiu; Yin, Chunmei

    2016-01-01

    The in situ application of rice straw enhances CH4 emissions by a large margin. The ex situ application of rice straw in uplands, however, may mitigate total global warming potential (GWP) of CH4 and N2O emissions from paddy-upland coexisting systems. To evaluate the efficiency of this practice, two field trials were conducted in rice-rice-fallow and maize-rape cropping systems, respectively. Year-round measurements of CH4 and N2O emissions were conducted to evaluate the system-scaled GWP. The results showed that CH4 accounted for more than 98% of GWP in paddy. Straw removal from paddy decreased 44.7% (302.1 kg ha−1 yr−1) of CH4 emissions and 51.2% (0.31 kg ha−1 yr−1) of N2O emissions, thus decreased 44.8% (7693 kg CO2-eqv ha−1 yr−1) of annual GWP. N2O accounted for almost 100% of GWP in upland. Straw application in upland had insignificant effects on CH4 and N2O emissions, which increased GWP only by 91 kg CO2-eqv ha−1 yr−1. So, the transfer of straw from paddy to upland could decrease GWP by 7602 kg CO2-eqv ha−1 yr−1. Moreover, straw retention during late rice season contributed to 88.2% of annual GWP increment. It is recommended to transfer early rice straw to upland considering GWP mitigation, nutrient recycling and labor cost. PMID:27869209

  8. Mitigating effects of ex situ application of rice straw on CH4 and N2O emissions from paddy-upland coexisting system

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Wu, Xiaohong; Chen, Anlei; Xie, Xiaoli; Wang, Yunqiu; Yin, Chunmei

    2016-11-01

    The in situ application of rice straw enhances CH4 emissions by a large margin. The ex situ application of rice straw in uplands, however, may mitigate total global warming potential (GWP) of CH4 and N2O emissions from paddy-upland coexisting systems. To evaluate the efficiency of this practice, two field trials were conducted in rice-rice-fallow and maize-rape cropping systems, respectively. Year-round measurements of CH4 and N2O emissions were conducted to evaluate the system-scaled GWP. The results showed that CH4 accounted for more than 98% of GWP in paddy. Straw removal from paddy decreased 44.7% (302.1 kg ha-1 yr-1) of CH4 emissions and 51.2% (0.31 kg ha-1 yr-1) of N2O emissions, thus decreased 44.8% (7693 kg CO2-eqv ha-1 yr-1) of annual GWP. N2O accounted for almost 100% of GWP in upland. Straw application in upland had insignificant effects on CH4 and N2O emissions, which increased GWP only by 91 kg CO2-eqv ha-1 yr-1. So, the transfer of straw from paddy to upland could decrease GWP by 7602 kg CO2-eqv ha-1 yr-1. Moreover, straw retention during late rice season contributed to 88.2% of annual GWP increment. It is recommended to transfer early rice straw to upland considering GWP mitigation, nutrient recycling and labor cost.

  9. Diagnostic studies of H2 Ar N2 microwave plasmas containing methane or methanol using tunable infrared diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Hempel, F.; Davies, P. B.; Loffhagen, D.; Mechold, L.; Röpcke, J.

    2003-11-01

    Tunable infrared diode laser absorption spectroscopy has been used to detect the methyl radical and nine stable molecules, CH4, CH3OH, C2H2, C2H4, C2H6, NH3, HCN, CH2O and C2N2, in H2-Ar-N2 microwave plasmas containing up to 7% of methane or methanol, under both flowing and static conditions. The degree of dissociation of the hydrocarbon precursor molecules varied between 20% and 97%. The methyl radical concentration was found to be in the range 1012-1013 molecules cm-3. By analysing the temporal development of the molecular concentrations under static conditions it was found that HCN and NH3 are the final products of plasma chemical conversion. The fragmentation rates of methane and methanol (RF(CH4) = (2-7) × 1015 molecules J-1, RF(CH3OH) = (6-9) × 1015 molecules J-1) and the respective conversion rates to methane, hydrogen cyanide and ammonia (RCmax(CH4) = 1.2 × 1015 molecules J-1, RCmax(HCN) = 1.3 × 1015 molecules J-1, RCmax(NH3) = 1 × 1014 molecules J-1) have been determined for different hydrogen to nitrogen concentration ratios. An extensive model of the chemical reactions involved in the H2-N2-Ar-CH4 plasma has been developed. Model calculations were performed by including 22 species, 145 chemical reactions and appropriate electron impact dissociation rate coefficients. The results of the model calculations showed satisfactory agreement between calculated and measured concentrations. The most likely main chemical pathways involved in these plasmas are discussed and an appropriate reaction scheme is proposed.

  10. CH4 and N2O emissions embodied in international trade of meat

    NASA Astrophysics Data System (ADS)

    Caro, Dario; LoPresti, Anna; Davis, Steven J.; Bastianoni, Simone; Caldeira, Ken

    2014-11-01

    Although previous studies have quantified carbon dioxide emissions embodied in products traded internationally, there has been limited attention to other greenhouse gases such as methane (CH4) and nitrous oxide (N2O). Following IPCC guidelines, we estimate non-CO2 emissions from beef, pork and chicken produced in 237 countries over the period 1990-2010, and assign these emissions to the country where the meat is ultimately consumed. We find that, between 1990 and 2010, an average of 32.8 Mt CO2-eq emissions (using 100 year global warming potentials) are embodied in beef, pork and chicken traded internationally. Further, over the 20 year period, the quantity of CO2-eq emissions embodied in traded meat increased by 19%. The largest trade flows of emissions embodied in meat were from Brazil and Argentina to Russia (2.8 and 1.4 Mt of CO2-eq, respectively). Trade flows within the European region are also substantial: beef and pork exported from France embodied 3.3 Mt and 0.4 Mt of CO2-eq, respectively. Emissions factor of meat production (i.e. CO2-eq emissions per kg of meat) produced depend on ambient temperature, development level, livestock category (e.g. cattle, pork, and chicken) and livestock management practices. Thus, trade may result in an overall increase of GHG emissions when meat-consuming countries import meat from countries with a greater emissions intensity of meat production rather than producing the meat domestically. Comparing the emissions intensity of meat production of trading partners, we assess trade flows according to whether they tend to reduce or increase global emissions from meat production.

  11. Continuous multi-plot measurements of CO2, CH4, N2O and H2O in a managed boreal forest - The importance of accounting for all greenhouse gases

    NASA Astrophysics Data System (ADS)

    Vestin, P.; Mölder, M.; Sundqvist, E.; Båth, A.; Lehner, I.; Weslien, P.; Klemedtsson, L.; Lindroth, A.

    2015-12-01

    In order to assess the effects of different management practices on the exchange of greenhouse gases (GHG), it is desirable to perform repeated and parallel measurements on both experimental and control plots. Here we demonstrate how a system system combining eddy covariance and gradient techniques can be used to perform this assessment in a managed forest ecosystem.The net effects of clear-cutting and stump harvesting on GHG fluxes were studied at the ICOS site Norunda, Sweden. Micrometeorological measurements (i.e., flux-gradient measurements in 3 m tall towers) allowed for quantification of CO2, CH4 and H2O fluxes (from May 2010) as well as N2O and H2O fluxes (from June 2011) at two stump harvested plots and two control plots. There was one wetter and one drier plot of each treatment. Air was continuously sampled at two heights in the towers and gas concentrations were analyzed for CH4, CO2, H2O (LGR DLT-100, Los Gatos Research) and N2O, H2O (QCL Mini Monitor, Aerodyne Research). Friction velocities and sensible heat fluxes were measured by sonic anemometers (Gill Windmaster, Gill Instruments Ltd). Automatic chamber measurements (CO2, CH4, H2O) were carried out in the adjacent forest stand and at the clear-cut during 2010.Average CO2 emissions for the first year ranged between 14.4-20.2 ton CO2 ha-1 yr-1. The clear-cut became waterlogged after harvest and a comparison of flux-gradient data and chamber data (from the adjacent forest stand) indicated a switch from a weak CH4 sink to a significant source at all plots. The CH4 emissions ranged between 0.8-4.5 ton CO2-eq. ha-1 yr-1. N2O emissions ranged between 0.4-2.6 ton CO2-eq. ha-1 yr-1. Enhanced N2O emission on the drier stump harvested plot was the only clear treatment effect on GHG fluxes that was observed. Mean CH4 and N2O emissions for the first year of measurements amounted up to 29% and 20% of the mean annual CO2 emissions, respectively. This highlights the importance of including all GHGs

  12. Selective photocatalytic reduction of CO2 by H2O/H2 to CH4 and CH3OH over Cu-promoted In2O3/TiO2 nanocatalyst

    NASA Astrophysics Data System (ADS)

    Tahir, Muhammad; Tahir, Beenish; Saidina Amin, Nor Aishah; Alias, Hajar

    2016-12-01

    Photocatalytic CO2 reduction by H2O and/or H2 reductant to selective fuels over Cu-promoted In2O3/TiO2 photocatalyst has been investigated. The samples, prepared via a simple and direct sol-gel method, were characterized by XRD, SEM, TEM, XPS, N2 adsorption-desorption, UV-vis diffuse reflectance, Raman and PL spectroscopy. Cu and In loaded into TiO2, oxidized as Cu2+ and In3+, promoted efficient separation of photo-generated electron/hole pairs (e-/h+). The results indicate that the reduction rate of CO2 by H2O to CH4 approached to 181 μmol g-1 h-1 using 0.5% Cu-3% In2O3/TiO2 catalyst, a 1.53 fold higher than the production rate over the 3% In2O3/TiO2 and 5 times the amount produced over the pure TiO2. In addition, Cu was found to promote efficient production of CH3OH and yield rate reached to 68 μmol g-1 h-1 over 1% Cu-3% In2O3/TiO2 catalyst. This improvement was attributed to charge transfer property and suppressed recombination rate by Cu-metal. More importantly, H2 reductant was less favorable for CH4 production, yet a significant amount of CH4 and CH3OH were obtained using a mixture of H2O/H2 reductant. Therefore, Cu-loaded In2O3/TiO2 catalyst has shown to be capable for methanol production, whereas product selectivity was greatly depending on the amount of Cu-loading and the type of reductant. A photocatalytic reaction mechanism was proposed to understand the experimental results over the Cu-loaded In2O3/TiO2 catalyst.

  13. Chemical and isotopic equilibrium between CO 2 and CH 4 in fumarolic gas discharges: Generation of CH 4 in arc magmatic-hydrothermal systems

    NASA Astrophysics Data System (ADS)

    Fiebig, Jens; Chiodini, Giovanni; Caliro, Stefano; Rizzo, Andrea; Spangenberg, Jorge; Hunziker, Johannes C.

    2004-05-01

    The chemical and isotopic composition of fumarolic gases emitted from Nisyros Volcano, Greece, and of a single gas sample from Vesuvio, Italy, was investigated in order to determine the origin of methane (CH 4) within two subduction-related magmatic-hydrothermal environments. Apparent temperatures derived from carbon isotope partitioning between CH 4 and CO 2 of around 340°C for Nisyros and 470°C for Vesuvio correlate well with aquifer temperatures as measured directly and/or inferred from compositional data using the H 2O-H 2-CO 2-CO-CH 4 geothermometer. Thermodynamic modeling reveals chemical equilibrium between CH 4, CO 2 and H 2O implying that carbon isotope partitioning between CO 2 and CH 4 in both systems is controlled by aquifer temperature. N 2/ 3He and CH 4/ 3He ratios of Nisyros fumarolic gases are unusually low for subduction zone gases and correspond to those of midoceanic ridge environments. Accordingly, CH 4 may have been primarily generated through the reduction of CO 2 by H 2 in the absence of any organic matter following a Fischer-Tropsch-type reaction. However, primary occurrence of minor amounts of thermogenic CH 4 and subsequent re-equilibration with co-existing CO 2 cannot be ruled out entirely. CO 2/ 3He ratios and δ 13C CO 2 values imply that the evolved CO 2 either derives from a metasomatized mantle or is a mixture between two components, one outgassing from an unaltered mantle and the other released by thermal breakdown of marine carbonates. The latter may contain traces of organic matter possibly decomposing to CH 4 during thermometamorphism.

  14. Measurements and Modeling of Nitric Oxide Formation in Counterflow, Premixed CH4/O2/N2 Flames

    NASA Technical Reports Server (NTRS)

    Thomsen, D. Douglas; Laurendeau, Normand M.

    2000-01-01

    Laser-induced fluorescence (LIF) measurements of NO concentration in a variety of CH4/O2/N2 flames are used to evaluate the chemical kinetics of NO formation. The analysis begins with previous measurements in flat, laminar, premixed CH4/O2/N2 flames stabilized on a water-cooled McKenna burner at pressures ranging from 1 to 14.6 atm, equivalence ratios from 0.5 to 1.6, and volumetric nitrogen/oxygen dilution ratios of 2.2, 3.1 and 3.76. These measured results are compared to predictions to determine the capabilities and limitations of the comprehensive kinetic mechanism developed by the Gas Research Institute (GRI), version 2.11. The model is shown to predict well the qualitative trends of NO formation in lean-premixed flames, while quantitatively underpredicting NO concentration by 30-50%. For rich flames, the model is unable to even qualitatively match the experimental results. These flames were found to be limited by low temperatures and an inability to separate the flame from the burner surface. In response to these limitations, a counterflow burner was designed for use in opposed premixed flame studies. A new LIF calibration technique was developed and applied to obtain quantitative measurements of NO concentration in laminar, counterflow premixed, CH4/O2/N2 flames at pressures ranging from 1 to 5.1 atm, equivalence ratios of 0.6 to 1.5, and an N2/O2 dilution ratio of 3.76. The counterflow premixed flame measurements are combined with measurements in burner-stabilized premixed flames and counterflow diffusion flames to build a comprehensive database for analysis of the GRI kinetic mechanism. Pathways, quantitative reaction path and sensitivity analyses are applied to the GRI mechanism for these flame conditions. The prompt NO mechanism is found to severely underpredict the amount of NO formed in rich premixed and nitrogen-diluted diffusion flames. This underprediction is traced to uncertainties in the CH kinetics as well as in the nitrogen oxidation chemistry

  15. Potential for negative emissions of greenhouse gases (CO2, CH4 and N2O) through coastal peatland re-establishment: Novel insights from high frequency flux data at meter and kilometer scales

    NASA Astrophysics Data System (ADS)

    Windham-Myers, Lisamarie; Bergamaschi, Brian; Anderson, Frank; Knox, Sara; Miller, Robin; Fujii, Roger

    2018-04-01

    High productivity temperate wetlands that accrete peat via belowground biomass (peatlands) may be managed for climate mitigation benefits due to their global distribution and notably negative emissions of atmospheric carbon dioxide (CO2) through rapid storage of carbon (C) in anoxic soils. Net emissions of additional greenhouse gases (GHG)—methane (CH4) and nitrous oxide (N2O)—are more difficult to predict and monitor due to fine-scale temporal and spatial variability, but can potentially reverse the climate mitigation benefits resulting from CO2 uptake. To support management decisions and modeling, we collected continuous 96 hour high frequency GHG flux data for CO2, CH4 and N2O at multiple scales—static chambers (1 Hz) and eddy covariance (10 Hz)—during peak productivity in a well-studied, impounded coastal peatland in California’s Sacramento Delta with high annual rates of C fluxes, sequestering 2065 ± 150 g CO2 m‑2 y‑1 and emitting 64.5 ± 2.4 g CH4 m‑2 y‑1. Chambers (n = 6) showed strong spatial variability along a hydrologic gradient from inlet to interior plots. Daily (24 hour) net CO2 uptake (NEE) was highest near inlet locations and fell dramatically along the flowpath (‑25 to ‑3.8 to +2.64 g CO2 m‑2 d‑1). In contrast, daily net CH4 flux increased along the flowpath (0.39 to 0.62 to 0.88 g CH4 m‑2 d‑1), such that sites of high daily CO2 uptake were sites of low CH4 emission. Distributed, continuous chamber data exposed five novel insights, and at least two important datagaps for wetland GHG management, including: (1) increasing dominance of CH4 ebullition fluxes (15%–32% of total) along the flowpath and (2) net negative N2O flux across all sites as measured during a 4 day period of peak biomass (‑1.7 mg N2O m‑2 d‑1 0.51 g CO2 eq m‑2 d‑1). The net negative emissions of re-established peat-accreting wetlands are notably high, but may be poorly estimated by

  16. Influence of aeration on CH4, N2O and NH3 emissions during aerobic composting of a chicken manure and high C/N waste mixture.

    PubMed

    Shen, Yujun; Ren, Limei; Li, Guoxue; Chen, Tongbin; Guo, Rui

    2011-01-01

    Co-composting of chicken manure, straw and dry grasses was investigated in a forced aeration system to estimate the effect of aeration rates on NH(3), CH(4) and N(2)O emissions and compost quality. Continuous measurements of gas emissions were carried out and detailed gas emission patterns were obtained using an intermittent-aeration of 30 min on/30 min off at rates of 0.01 (A1), 0.1 (A2) and 0.2 (A3) m(3)min(-1)m(-3). Concentrations of CH(4) and N(2)O at the low aeration rate (A1) were significantly greater than those at the other two rates, but there was no significant difference between the A2 and A3 treatments. CH(4) and N(2)O emissions for this mixture could be controlled when the composting process was aerobic and ammonia emissions were reduced at a lower aeration rate. Comparison of CH(4), N(2)O, NH(3) emissions and compost quality showed that the aeration rate of the A2 treatment was superior to the other two aeration rates. Copyright © 2010 Elsevier Ltd. All rights reserved.

  17. Intramolecular chalcogen-tin interactions in [(o-MeE-C6H4)CH2]2SnPh2-nCln; E = S, O, CH2, n = 0, 1, 2 and intermolecular chlorine-tin interactions in the meta and para-methoxy isomers

    PubMed Central

    Vargas-Pineda, Diana Gabriela; Guardado, Tanya; Cervantes-Lee, Francisco; Metta-Magana, Alejandro J.

    2010-01-01

    Organotin(IV) compounds of the type [(o-MeE-C6H4)CH2]2SnPh2-nCln were synthesized, E = O, n = 0 (1), n = 1 (2), n = 2 (3), E = S, n = 0 (4), n = 1 (5), n = 2 (6) and E = CH2, n = 0 (7), n = 1 (8), n = 2 (9). The dichloro compounds 3 and 6 have been investigated by single crystal X-ray diffraction and exhibit bi-capped tetrahedral geometry at the tin atom as a consequence of significant intramolecular Sn⋯O (3) and Sn⋯S (6) secondary bonding, in monomolecular units. Compound 3 when crystallized from a hexane/thf solvent mixture shows two different conformers, 3′ and 3″, in the crystal structure, 3′ has two equivalent Sn⋯O interactions, while 3″ has two non-equivalent Sn⋯O interactions. Upon recrystallization of 3 from hexane only a single structural form is observed, 3′. The Sn⋯E distances in 3′, 3″, and 6 are 71.3; 73.5, 72.9; and 76.3% of the ΣvdW radii, respectively. The meta and para-substituted isomers of 3 (10, 11) exhibit a distortion at the tin atom due to self-association via intermolecular Sn⋯Cl interactions resulting in polymeric structures. 119Sn NMR spectroscopy suggests that the intramolecular Sn⋯E interactions persist in solution for the dichloride compounds 3 and 6. PMID:20047301

  18. Drainage and tillage practices in the winter fallow season mitigate CH4 and N2O emissions from a double-rice field in China

    NASA Astrophysics Data System (ADS)

    Zhang, Guangbin; Yu, Haiyang; Fan, Xianfang; Yang, Yuting; Ma, Jing; Xu, Hua

    2016-09-01

    Traditional land management (no tillage, no drainage, NTND) during the winter fallow season results in substantial CH4 and N2O emissions from double-rice fields in China. A field experiment was conducted to investigate the effects of drainage and tillage during the winter fallow season on CH4 and N2O emissions and to develop mitigation options. The experiment had four treatments: NTND, NTD (drainage but no tillage), TND (tillage but no drainage), and TD (both drainage and tillage). The study was conducted from 2010 to 2014 in a Chinese double-rice field. During winter, total precipitation and mean daily temperature significantly affected CH4 emission. Compared to NTND, drainage and tillage decreased annual CH4 emissions in early- and late-rice seasons by 54 and 33 kg CH4 ha-1 yr-1, respectively. Drainage and tillage increased N2O emissions in the winter fallow season but reduced it in early- and late-rice seasons, resulting in no annual change in N2O emission. Global warming potentials of CH4 and N2O emissions were decreased by 1.49 and 0.92 t CO2 eq. ha-1 yr-1, respectively, and were reduced more by combining drainage with tillage, providing a mitigation potential of 1.96 t CO2 eq. ha-1 yr-1. A low total C content and high C / N ratio in rice residues showed that tillage in the winter fallow season reduced CH4 and N2O emissions in both early- and late-rice seasons. Drainage and tillage significantly decreased the abundance of methanogens in paddy soil, and this may explain the decrease of CH4 emissions. Greenhouse gas intensity was significantly decreased by drainage and tillage separately, and the reduction was greater by combining drainage with tillage, resulting in a reduction of 0.17 t CO2 eq. t-1. The results indicate that drainage combined with tillage during the winter fallow season is an effective strategy for mitigating greenhouse gas releases from double-rice fields.

  19. Measurement of N2O and CH4 soil fluxes from garden, agricultural and natural soils using both closed and open chamber systems coupled with high-precision CRDS analyzer

    NASA Astrophysics Data System (ADS)

    He, Yonggang; Jacobson, Gloria; Alexander, Chris; Fleck, Derek; Hoffnagel, John; Del Campo, Bernardo; Rella, Chris

    2013-04-01

    Studying the emission and uptake of greenhouse gases from soil is essential for understanding, adapting to and ultimately mitigating the effects of climate change. To-date, majority of such studies have been focused on carbon dioxide (CO2 ) , however, in 2006 the EPA estimated that "Agricultural activities currently generate the largest share, 63 percent, of the world's anthropogenic non-carbon dioxide (non-CO2) emissions (84 percent of nitrous oxide [N2O] and 52 percent of methane[CH4]), and make up roughly 15 percent of all anthropogenic greenhouse gas emissions" (Prentice et al., 2001). Therefore, enabling accurate N2O and CH4 flux measurements in the field are clearly critical to our ability to better constrain carbon and nitrogen budgets, characterize soil sensitivities, agricultural practices, and microbial processes like denitrification and nitrification. To aide in these studies, Picarro has developed a new analyzer based on its proven, NIR technology platform, which is capable of measuring both N2O and CH4 down to ppb levels in a single, field-deployable analyzer. This analyzer measures N2O with a 1-sigma, precision of 3.5 ppb and CH4 with a 1-sigma precision of 3ppb on a 5 minute average. The instrument also has extremely low drift to enable accurate measurements with infrequent calibrations. The data rate of the analyzer is on the order of 5 seconds in order to capture fast, episodic emission events. One of the keys to making accurate CRDS measurements is to thoroughly characterize and correct for spectral interfering species. This is especially important for closed system soil chambers used on agricultural soils where a variety of soil amendments may be applied and gases not usually present in ambient air could concentrate to high levels. In this work, we present the results of analyzer interference testing and corrections completed for the interference of carbon dioxide, methane, ammonia, ethane, ethylene, acetylene, and water on N2O. In addition, we

  20. Kinetics of OH- and Cl-initiated oxidation of CH2dbnd CHC(O)O(CH2)2CH3 and CH2dbnd CHCH2C(O)O(CH2)2CH3 and fate of the alkoxy radicals formed

    NASA Astrophysics Data System (ADS)

    Rivela, Cynthia; Blanco, María B.; Teruel, Mariano A.

    2016-05-01

    Rate coefficients of the reactions of OH and Cl radicals with vinyl and allyl butyrate were determined for the first time at 298 K and 1 atm using the relative method to be (in cm3 molecule-1 s-1): k1(OH + CH2dbnd CHC(O)O(CH2)2CH3) = (2.61 ± 0.31) × 10-11, k2(Cl + CH2dbnd CHC(O)O(CH2)2CH3) = (2.48 ± 0.89) × 10-10, k3(OH + CH2dbnd CHCH2C(O)O(CH2)2CH3) = (2.89 ± 0.31) × 10-11, and k4(Cl + CH2dbnd CHCH2C(O)O(CH2)2CH3) = (2.25 ± 0.96) × 10-10. Reactivity trends and atmospheric lifetimes of esters are presented. Additionally, a product study shown butyric acid and polifunctional products for the reactions of vinyl and allyl butyrate, respectively and general mechanism is proposed.

  1. Growing season CH4 and N2O fluxes from a subarctic landscape in northern Finland; from chamber to landscape scale

    NASA Astrophysics Data System (ADS)

    Dinsmore, Kerry J.; Drewer, Julia; Levy, Peter E.; George, Charles; Lohila, Annalea; Aurela, Mika; Skiba, Ute M.

    2017-02-01

    Subarctic and boreal emissions of CH4 are important contributors to the atmospheric greenhouse gas (GHG) balance and subsequently the global radiative forcing. Whilst N2O emissions may be lower, the much greater radiative forcing they produce justifies their inclusion in GHG studies. In addition to the quantification of flux magnitude, it is essential that we understand the drivers of emissions to be able to accurately predict climate-driven changes and potential feedback mechanisms. Hence this study aims to increase our understanding of what drives fluxes of CH4 and N2O in a subarctic forest/wetland landscape during peak summer conditions and into the shoulder season, exploring both spatial and temporal variability, and uses satellite-derived spectral data to extrapolate from chamber-scale fluxes to a 2 km × 2 km landscape area.From static chamber measurements made during summer and autumn campaigns in 2012 in the Sodankylä region of northern Finland, we concluded that wetlands represent a significant source of CH4 (3.35 ± 0.44 mg C m-2 h-1 during the summer campaign and 0.62 ± 0.09 mg C m-2 h-1 during the autumn campaign), whilst the surrounding forests represent a small sink (-0.06 ± < 0.01 mg C m-2 h-1 during the summer campaign and -0.03 ± < 0.01 mg C m-2 h-1 during the autumn campaign). N2O fluxes were near-zero across both ecosystems.We found a weak negative relationship between CH4 emissions and water table depth in the wetland, with emissions decreasing as the water table approached and flooded the soil surface and a positive relationship between CH4 emissions and the presence of Sphagnum mosses. Temperature was also an important driver of CH4 with emissions increasing to a peak at approximately 12 °C. Little could be determined about the drivers of N2O emissions given the small magnitude of the fluxes.A multiple regression modelling approach was used to describe CH4 emissions based on spectral data from PLEIADES PA1 satellite imagery across a 2 km

  2. Simulating CH4 and N2O emissions from direct-seeded rice systems using the DeNitrification DeComposition (DNDC) model

    NASA Astrophysics Data System (ADS)

    Simmonds, M.; Li, C.; Lee, J.; Six, J.; Van Kessel, C.; Linquist, B.

    2015-12-01

    Process-based modeling of CH4 and N2O emissions from rice fields is a practical tool for conducting greenhouse gas inventories and estimating mitigation potentials of alternative practices at the scales of management and policy-making. However, few studies have evaluated site-level model performance in side-by-side field trials of various management practices during both the growing season and fallow periods. We empirically evaluated the DeNitrification-DeComposition (DNDC) model for estimating CH4 and N2O fluxes in California rice systems under varying management (N fertilizer application rate, type of seeding system, fallow period straw and water management), soil environments, and weather conditions. Five and nine site-year combinations were used for calibration and validation, respectively. The model was parameterized for two cultivars, M206 and Koshihikari, and able to simulate 30% and 78% of the measured variation in yields, respectively. A major strength of DNDC was in estimating general site-level seasonal CH4 emissions (R2 = 0.85). However, a major limitation was in simulating finer resolution of differences in CH4 emissions (or lack thereof) among side-by-side management treatments (range of 0.2-465% relative absolute deviation). Additionally, DNDC did not satisfactorily simulate fallow period CH4 emissions, or seasonal and fallow period N2O emissions across all sites with the exception of a few cases. Specifically, simulated CH4 emissions were oversensitive to fertilizer N rates, but lacked sensitivity to the type of seeding system and prior fallow period straw management. Additionally, N2O emissions were oversensitive to fertilizer N rates and field drainage. Sensitivity analysis showed that CH4 emissions were highly sensitive to changes in the root to total plant biomass ratio. Overall, uncertainty in model predictions was attributed to uncertainty in both the input parameters due to in-field spatiotemporal variability of soil properties, and in the

  3. Responses of CH(4), CO(2) and N(2)O fluxes to increasing nitrogen deposition in alpine grassland of the Tianshan Mountains.

    PubMed

    Li, Kaihui; Gong, Yanming; Song, Wei; He, Guixiang; Hu, Yukun; Tian, Changyan; Liu, Xuejun

    2012-06-01

    To assess the effects of nitrogen (N) deposition on greenhouse gas (GHG) fluxes in alpine grassland of the Tianshan Mountains in central Asia, CH(4), CO(2) and N(2)O fluxes were measured from June 2010 to May 2011. Nitrogen deposition tended to significantly increase CH(4) uptake, CO(2) and N(2)O emissions at sites receiving N addition compared with those at site without N addition during the growing season, but no significant differences were found for all sites outside the growing season. Air temperature, soil temperature and water content were the important factors that influence CO(2) and N(2)O emissions at year-round scale, indicating that increased temperature and precipitation in the future will exert greater impacts on CO(2) and N(2)O emissions in the alpine grassland. In addition, plant coverage in July was also positively correlated with CO(2) and N(2)O emissions under elevated N deposition rates. The present study will deepen our understanding of N deposition impacts on GHG balance in the alpine grassland ecosystem, and help us assess the global N effects, parameterize Earth System models and inform decision makers. Copyright © 2012 Elsevier Ltd. All rights reserved.

  4. 40 CFR Table Aa-2 to Subpart Aa of... - Kraft Lime Kiln and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Kraft Lime Kiln and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O AA Table AA-2 to Subpart AA of Part 98 Protection of Environment... and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O Fuel Fossil fuel-based emissions...

  5. 40 CFR Table Aa-2 to Subpart Aa of... - Kraft Lime Kiln and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Kraft Lime Kiln and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O AA Table AA-2 to Subpart AA of Part 98 Protection of Environment... and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O Fuel Fossil fuel-based emissions...

  6. 40 CFR Table Aa-2 to Subpart Aa of... - Kraft Lime Kiln and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Kraft Lime Kiln and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O AA Table AA-2 to Subpart AA of Part 98 Protection of Environment... and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O Fuel Fossil fuel-based emissions...

  7. Effects of the herbicides prosulfuron and metolachlor on fluxes of CO2, N2O, and CH4 in a fertilized Colorado grassland soil

    USGS Publications Warehouse

    Kinney, C.A.; Mosier, A.R.; Ferrer, I.; Furlong, E.T.; Mandernack, K.W.

    2004-01-01

    The effect that pesticides have on trace gas production and consumption in agricultural soils is often overlooked. Independent field and laboratory experiments were used to measure the effects that the commonly used herbicides prosulfuron and metolachlor have on trace gas fluxes (CO2, N2O, and CH4) from fertilized soil of the Colorado shortgrass steppe. Separate sample plots (1 m2) on tilled and no-till soil at the sites included the following treatments: 1) a control without fertilizer or herbicide, 2) a fertilized (NH4NO3 equivalent to 244 kg ha-1) control without herbicide, 3) and fertilized plots amended with an herbicide (prosulfuron equivalent to 0.46 kg ha-1 57% by weight active ingredient or metolachlor equivalent to 5.7 L ha-1, 82.4% by weight active ingredient). During an initial study of one year duration, measurement of gas exchange revealed that prosulfuron-amendment stimulated N2O emissions and CH4 consumption by as much as 1600% and 1300% during a single measurement, respectively. During a second set of flux measurements beginning in August 2001, more frequent weekly measurements were made during a twelve week period. From this second study an increased N2O efflux and CH4 uptake occurred after a 7-week lag period that persisted for about 5 weeks. These changes in gas flux amounted to an overall increase of 41% and 30% for N2O emission and CH4 consumption, respectively. The co-occurrence of stimulated N2O and CH4 fluxes suggests a similar cause that is related to prosulfuron degradation. Evidence suggested that prosulfuron degradation stimulated microbial activity responsible for trace gas flux. Ultimately, prosulfuron-amendment led to an ???50% reduction in the global warming potential from N2O and CH4 fluxes at this field site, which is equivalent to a reduction of the global warming potential of 0.18 mols CO2 m-2 d-1 from these gases. Metolachlor application did not significantly affect the trace gas fluxes measured. These results demonstrate the

  8. Flux and distribution of methane (CH4) in the Gunsan Basin of the southeastern Yellow Sea, off the Western Korea.

    PubMed

    Lee, Jun-Ho; Woo, Han Jun; Son, Seung-Kyu; Kim, Moonkoo; Lee, Dong-Hun; Tsunogai, Urumu; Jeong, Kap-Sik

    2018-04-16

    The flux and distribution of methane (CH 4 ) was investigated in the seawater column at 14 stations in the Gunsan Basin, the southeastern part of Yellow Sea from 2013 to 2015. Here CH 4 is concentrated 2.4-4.7 (3.4 ± 0.7) nM in the surface and 2.5-7.4 (5.2 ± 1.7) nM in the bottom layer. The CH 4 saturation ratios ranged from 65.5% to 295.5% (162.6 ± 68.7), comprising the mean sea-to-air CH 4 flux of 3.8 to 25.3 (15.6 ± 5.5) µM m -2 d -1 . Methane concentration was largely different in the upper and the lower seawater layers that is separated by the thermocline of which depth is variable (20-60 m) depending on the time of sampling. The concentration of seawater dissolved CH 4 is high between the bottom surface of the thermocline layer and the sea floor. Generally it tends to decrease from the south-westernmost part of the basin toward the west coast of Korea. This distribution pattern of CH 4 seems to result from the CH 4 supply by decomposition of organic matters produced in the upper seawater layer that is superimposed by the larger supply from the underlying sediment layer especially beneath the thermocline. The latter is manifested by ubiquitous CH 4 seeps from the seafloor sediments.

  9. Field Tests of a Gas-Filter Imaging Radiometer for Methane, CH4,: A Prototype for Geostationary Remote Infrared Pollution Sounder, GRIPS

    NASA Astrophysics Data System (ADS)

    Dickerson, R. R.; Fish, C. S.; Brent, L. C.; Burrows, J. P.; Fuentes, J. D.; Gordley, L. L.; Jacob, D. J.; Schoeberl, M. R.; Salawitch, R. J.; Ren, X.; Thompson, A. M.

    2013-12-01

    Gas filter radiometry is a powerful tool for measuring infrared active trace gases. Methane (CH4) is the second most important greenhouse gas and is more potent molecule for molecule than carbon dioxide (CO2). Unconventional natural gas recovery has the potential to show great environmental benefits relative to coal, but only if fugitive leakage is held below 3% and leak rates remain highly uncertain. We present design specifications and initial field/aircraft test results for an imaging remote sensing device to measure column content of methane. The instrument is compared to in situ altitude profiles measured with cavity ring-down. This device is an airborne prototype for the Geostationary Remote Infrared Pollution Sounder, GRIPS, a satellite instrument designed to monitor CH4, CO2, CO, N2O and AOD from geostationary orbit, with capabilities for great advances in air quality and climate research. GRIPS: The Geostationary Remote Infrared Pollution Sounder

  10. Fluxes of N2O and CH4 from forest and grassland lysimeter soils in response to simulated climate change

    NASA Astrophysics Data System (ADS)

    Weymann, Daniel; Brueggemann, Nicolas; Puetz, Thomas; Vereecken, Harry

    2015-04-01

    Central Europe is expected to be exposed to altered temperature and hydrological conditions, which will affect the vulnerability of nitrogen and carbon cycling in soils and thus production and fluxes of climate relevant trace gases. However, knowledge of the response of greenhouse gas fluxes to climate change is limited so far, but will be an important basis for future climate projections. Here we present preliminary results of an ongoing lysimeter field study which aims to assess the impact of simulated climate change on N2O and CH4 fluxes from a forest and a fertilized grassland soil. The lysimeters are part of the Germany-wide research infrastructure TERENO, which investigates feedbacks of climate change to the pedosphere on a long-term scale. Lysimeters (A = 1m2) were established in 2010 at high elevated sites (HE, 500 and 600 m.a.s.l.) and subsequently transferred along an altitudinal gradient to a low elevated site (LE, 100 m.a.s.l.) within the Eifel / Lower Rhine Valley Observatory in Western Germany, thereby resulting in a temperature increase of 2.3 K whereas precipitation decreased by 160 mm during the present study period. Systematic monitoring of soil-atmosphere exchange of N2O and CH4 based on weekly manual closed chamber measurements at HE and LE sites has started in August 2013. Furthermore, we routinely determine dissolved N2O and CH4 concentrations in the seepage water using a headspace equilibration technique and record water discharge in order to quantify leaching losses of both greenhouse gases. Cumulative N2O fluxes clearly responded to simulated climate change conditions and increased by 250 % and 600 % for the forest and the grassland soil, respectively. This difference between the HE and LE sites was mainly caused by an exceptionally heavy precipitation event in July 2014 which turned the LE site sustainably to a consistently higher emission level. Nonetheless, emissions remained rather small and ranged between 20 and 40 μg m-2 h-1. In

  11. EMISSIONS AND COST ESTIMATES FOR GLOBALLY SIGNIFICANT ANTHROPOGENIC COMBUSTION SOURCES OF NOX, N2O, CH4, CO AND CO2

    EPA Science Inventory

    The report discusses the development of emission factors for CO2, CO, CH4, NOx, and N2O for about 80 globally significant combustion sources in seven source categories: utility, industrial, fuel production, transportation, residential, commercial, and kilns/ovens/dryers. ecause o...

  12. Multi-Scale Approach for Measuring N2O and CH4 Emissions in Drainage Water Managed Corn-Soybean System

    NASA Astrophysics Data System (ADS)

    Hagedorn, J.; Zhu, Q.; Davidson, E. A.; Castro, M.

    2017-12-01

    Managing resources wisely while reducing environmental impact is the backbone of agricultural sustainability. Agricultural practices must develop strategies to effectively reduce nutrient runoff from farmed lands. Preliminary research suggests that one such strategy is drainage water management by which water levels are intentionally elevated following fertilization to favor subsoil denitrification and thereby reduce nitrogen leaching into groundwater and streams. Despite documented success in nitrate reduction, this best management practice (BMP) has not been widely adopted in part because users are not aware of the potential. But before extension agencies begin promoting this practice, evaluation of unintentional consequences must be studied. There is a risk that by elevating water levels for the purpose of creating suitable conditions for denitrification, more potent greenhouse gases such as nitrous oxide (N2O) and methane (CH4) could be produced, in which case the practice would be swapping one form of pollution for another. A multi-scale experimental design, using soil chambers and a tower-based gradient method, was implemented in a drainage water managed corn-soybean system on the Eastern Shore of Maryland. Emissions, soil moisture content, and soil nitrate measurements have been collected and analyzed to evaluate for differences between treatment and control plots as standard farm management practices, such as fertilization, occur. Preliminary results based on monthly sampling of transects of stationary soil chambers characterize the spatial heterogeneity of the fields and reveal that there are detectable differences in N2O and CH4 emissions between fields. There are also significant relationships between soil moisture, soil nitrate content and N2O emissions. The tower-based gradient method with micrometerological measurements provides high temporal resolution at the full field scale that complements the soil chamber work. This multi-scale resolution balance

  13. Fundamental Understanding of Methane-Carbon Dioxide-Water (CH 4-CO 2-H 2O) Interactions in Shale Nanopores under Reservoir Conditions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Yifeng

    2016-04-29

    Shale is characterized by the predominant presence of nanometer-scale (1-100 nm) pores. The behavior of fluids in those pores directly controls shale gas storage and release in shale matrix and ultimately the wellbore production in unconventional reservoirs. Recently, it has been recognized that a fluid confined in nanopores can behave dramatically differently from the corresponding bulk phase due to nanopore confinement (Wang, 2014). CO 2 and H 2O, either preexisting or introduced, are two major components that coexist with shale gas (predominately CH 4) during hydrofracturing and gas extraction. Note that liquid or supercritical CO 2 has been suggested asmore » an alternative fluid for subsurface fracturing such that CO 2 enhanced gas recovery can also serve as a CO 2 sequestration process. Limited data indicate that CO 2 may preferentially adsorb in nanopores (particularly those in kerogen) and therefore displace CH 4 in shale. Similarly, the presence of water moisture seems able to displace or trap CH 4 in shale matrix. Therefore, fundamental understanding of CH 4-CO 2-H 2O behavior and their interactions in shale nanopores is of great importance for gas production and the related CO 2 sequestration. This project focuses on the systematic study of CH 4-CO 2-H 2O interactions in shale nanopores under high-pressure and high temperature reservoir conditions. The proposed work will help to develop new stimulation strategies to enable efficient resource recovery from fewer and less environmentally impactful wells.« less

  14. Fundamental Understanding of Methane-Carbon Dioxide-Water (CH4-CO2-H2O) Interactions in Shale Nanopores under Reservoir Conditions.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Yifeng

    Shale is characterized by the predominant presence of nanometer-scale (1-100 nm) pores. The behavior of fluids in those pores directly controls shale gas storage and release in shale matrix and ultimately the wellbore production in unconventional reservoirs. Recently, it has been recognized that a fluid confined in nanopores can behave dramatically differently from the corresponding bulk phase due to nanopore confinement (Wang, 2014). CO 2 and H 2O, either preexisting or introduced, are two major components that coexist with shale gas (predominately CH 4) during hydrofracturing and gas extraction. Note that liquid or supercritical CO 2 has been suggested asmore » an alternative fluid for subsurface fracturing such that CO 2 enhanced gas recovery can also serve as a CO 2 sequestration process. Limited data indicate that CO 2 may preferentially adsorb in nanopores (particularly those in kerogen) and therefore displace CH4 in shale. Similarly, the presence of water moisture seems able to displace or trap CH 4 in shale matrix. Therefore, fundamental understanding of CH 4-CO 2-H 2O behavior and their interactions in shale nanopores is of great importance for gas production and the related CO 2 sequestration. This project focuses on the systematic study of CH 4-CO 2-H 2O interactions in shale nanopores under high-pressure and high temperature reservoir conditions. The proposed work will help to develop new stimulation strategies to enable efficient resource recovery from fewer and less environmentally impactful wells.« less

  15. Factors affecting the process of CO2 replacement of CH4 from methane hydrate in sediments - Constrained from experimental results

    NASA Astrophysics Data System (ADS)

    Lu, H.; Hu, G.; Vanderveen, J.; Liu, C.; Ratcliffe, C.; Ripmeester, J.

    2011-12-01

    CO2 replacement of CH4 from methane hydrate has been proposed as a method to produce gas from natural gas hydrate by taking advantage of both the production of natural gas and the sequestration of CO2. To examine the validity of this method DOE/Conoco-Philips is considering having a field test in Alaska. The reaction of CO2 replacing CH4 from methane hydrate has been confirmed to be thermodynamically feasible, but concern is always raised about the reaction kinetics. Some kinetic studies in the system of methane hydrate and liquid or gaseous CO2 have found that the reaction proceeds at a very low rate. Natural gas hydrate occurs in sediments with multi-components and complex structure, so matters will be even more complicated. Up to now, few investigations have been carried out concerning the factors affecting the reaction process of CO2 replacing CH4 from methane hydrate. Experiments were implemented with sands, which were recovered from Mallik 5L-38 well, Mackenzie Delta, Northwest Territory, Canada, sediment that previously contained hydrate although it had been dried completely before our experiments. The water-saturated sands were tightly charged into a plastic bottle (90 mm deep and 60 mm wide), and then this test specimen was sealed in a pressure cell. After methane hydrate was synthesized in the test specimen for 108 days under a pressure of 11 to 8 MPa and a temperature of 3 degrees Celsius, liquid CO2 was introduced into the pressure cell. The conditions under which CO2 was reacted with methane hydrate were ~5.3 MPa and 5 degrees Celsius. After reacting for 15 days, the test specimen was recovered. The test specimen was cut into ~10 mm thick discs, and sub-samples were further taken from each of the discs. In addition to the determination of hydrate saturation and the gas composition, Raman spectroscopic studies were carried out for the sub-samples obtained. The results revealed: 1) less CO2 replacement in the bottom disc of the test specimen as compared

  16. Low-temperature conversion of methane to methanol on CeO x/Cu 2O catalysts: Water controlled activation of the C–H Bond

    DOE PAGES

    Zuo, Zhijun; Ramírez, Pedro J.; Senanayake, Sanjaya D.; ...

    2016-10-10

    Here, an inverse CeO 2/Cu 2O/Cu(111) catalyst is able to activate methane at room temperature producing C, CH x fragments and CO x species on the oxide surface. The addition of water to the system leads to a drastic change in the selectivity of methane activation yielding only adsorbed CH x fragments. At a temperature of 450 K, in the presence of water, a CH 4CH 3OH catalytic transformation occurs with a high selectivity. OH groups formed by the dissociation of water saturate the catalyst surface, removing sites that could decompose CH x fragments, and generating centers onmore » which methane can directly interact to yield methanol.« less

  17. Sub-arctic Wetland Greenhouse Gases (CO2, CH4 & N2O) Emissions are Driven by Interactions of Environmental Controls and Herbivore Grazers

    NASA Astrophysics Data System (ADS)

    Kelsey, K.; Leffler, A. J.; Beard, K. H.; Choi, R. T.; Welker, J. M.

    2015-12-01

    Climate change is increasing temperatures, altering precipitation regimes and causing earlier growing seasons, particularly at northern latitudes. Such changes in local environmental conditions have the potential to affect biogeochemical cycling including the exchange of greenhouses gases between the atmosphere and the terrestrial biosphere. In addition to the effects of these environmental controls, animals such as migratory geese also influence biogeochemical cycles through grazing, trampling and delivering nutrient-rich fecal matter. In this work we aimed to quantify how local environmental conditions and the presence of grazing interact as drivers of emissions of three key greenhouse gases, CO2, CH4 and N2O, in coastal wetlands of the Yukon Kuskokwim Delta. We explored the magnitude of emissions across gradients of soil temperature and water table depth, and across vegetation types related to the presence of grazing, ranging from no vegetation through grazed and ungrazed vegetation. We also investigated emissions from grazed areas using experimental manipulations of the timing of grazing and advancement of the growing season. We found that local environmental conditions and use by grazers exert interacting controls on emissions of CO2, CH4 and N2O. Emissions of CO2 and CH4 were positively related to soil temperature and CH4 emissions were inversely related to water table depth, but the relationship varied by vegetation type. Net emissions of CO2 were greatest in ungrazed vegetation types (6.62 umols CO2 m-2 sec-1; p=0.0007) whereas CH4 emissions were greatest in the grazed vegetation (122.56 nmols CH4 m-2 sec-1; p=0.037). Flux of N2O was less than 1 nmol N2O m-2 sec-1 across all landscape positions under typical grazing and temperature conditions, but emissions were stimulated to over 10 nmols m-2 sec-1 when grazing occurred early relative to a typical season. Our results indicate that environmental conditions and the presence of migratory herbivores are both

  18. Distribution of dissolved green-house gases (CO2, CH4, N2O) in Lakes Edward and George: Results from the first field cruise of the HIPE project

    NASA Astrophysics Data System (ADS)

    Borges, Alberto V.; Morana, Cédric D. T.; Lambert, Thibault; Okello, William; Bouillon, Steven

    2017-04-01

    Inland waters (streams, rivers, lakes, reservoirs) are quantitatively important components of the global budgets of atmospheric emissions of long-lived greenhouse gases (GHGs) (CO2, CH4, N2O). Available data indicate that a very large fraction of CO2 and CH4 emissions from rivers and reservoirs occurs at tropical latitudes. Data on GHGs at tropical latitudes from lakes however are much more scarse, and the relative importance of emissions, in particular in Africa, remains to be determined. Large tropical lakes are net autotrophic (hence potentially sinks for atmospheric CO2) due generally low dissolved organic carbon concentrations, seasonally near constant light and temperature conditions, and generally deep water columns favourable for export of organic matter to depth. This sharply contrasts with their much better documented temperate and boreal counterparts, usually considered as CO2 sources to the atmosphere sustained by net heterotrophy. Here, we report a data-set of dissolved CO2, CH4, N2O obtained in October 2016 in Lakes Edward and George and adjacent streams and crater lakes in the frame of Belgian Science Policy (BELSPO) HIPE (Human impacts on ecosystem health and resources of Lake Edward, http://www.co2.ulg.ac.be/hipe/) project. Lake George and part of Lake Edward were sinks for atmospheric CO2 and N2O due to high primary production and denitrification in sediments, respectively, and modest sources of CH4 to the atmosphere. Sampled rivers and streams were oversaturated in CO2 and CH4 and close to atmospheric equilibrium with regards to N2O. Spatial variations within rivers and streams were related to elevation and vegetation characteristics on the catchments (savannah versus forest). Levels of CO2, CH4, and N2O were within the range of those we reported in other African rivers. Crater lakes acted as sinks for atmospheric CO2 and N2O but were extremely over-saturated in CH4, due to intense primary production sustained by cyanobacteria. These CH4 levels

  19. The relative abundances of resolved l2CH2D2 and 13CH3D and mechanisms controlling isotopic bond ordering in abiotic and biotic methane gases

    NASA Astrophysics Data System (ADS)

    Young, E. D.; Kohl, I. E.; Lollar, B. Sherwood; Etiope, G.; Rumble, D.; Li, S.; Haghnegahdar, M. A.; Schauble, E. A.; McCain, K. A.; Foustoukos, D. I.; Sutclife, C.; Warr, O.; Ballentine, C. J.; Onstott, T. C.; Hosgormez, H.; Neubeck, A.; Marques, J. M.; Pérez-Rodríguez, I.; Rowe, A. R.; LaRowe, D. E.; Magnabosco, C.; Yeung, L. Y.; Ash, J. L.; Bryndzia, L. T.

    2017-04-01

    We report measurements of resolved 12CH2D2 and 13CH3D at natural abundances in a variety of methane gases produced naturally and in the laboratory. The ability to resolve 12CH2D2 from 13CH3D provides unprecedented insights into the origin and evolution of CH4. The results identify conditions under which either isotopic bond order disequilibrium or equilibrium are expected. Where equilibrium obtains, concordant Δ12CH2D2 and Δ13CH3D temperatures can be used reliably for thermometry. We find that concordant temperatures do not always match previous hypotheses based on indirect estimates of temperature of formation nor temperatures derived from CH4/H2 D/H exchange, underscoring the importance of reliable thermometry based on the CH4 molecules themselves. Where Δ12CH2D2 and Δ13CH3D values are inconsistent with thermodynamic equilibrium, temperatures of formation derived from these species are spurious. In such situations, while formation temperatures are unavailable, disequilibrium isotopologue ratios nonetheless provide novel information about the formation mechanism of the gas and the presence or absence of multiple sources or sinks. In particular, disequilibrium isotopologue ratios may provide the means for differentiating between methane produced by abiotic synthesis vs. biological processes. Deficits in 12CH2D2 compared with equilibrium values in CH4 gas made by surface-catalyzed abiotic reactions are so large as to point towards a quantum tunneling origin. Tunneling also accounts for the more moderate depletions in 13CH3D that accompany the low 12CH2D2 abundances produced by abiotic reactions. The tunneling signature may prove to be an important tracer of abiotic methane formation, especially where it is preserved by dissolution of gas in cool hydrothermal systems (e.g., Mars). Isotopologue signatures of abiotic methane production can be erased by infiltration of microbial communities, and Δ12CH2D2 values are a key tracer of microbial recycling.

  20. Investigation of Wyoming Bentonite Hydration in Dry to Water-Saturated Supercritical CH4 and CH4/CO2 Mixtures: Implications for CO2-Enhanced Gas Production

    NASA Astrophysics Data System (ADS)

    Loring, J.

    2015-12-01

    Injection of CO2 into low permeability shale formations leads to additional gas recovery and reduces the flux of CO2 into the atmosphere, thus combining a strong economic incentive with a permanent storage option for CO2. Reduced formation transmissivity due to clay swelling is a concern in CO2-enhanced gas production. Clay minerals partly determine the physical (i.e. permeability, brittleness) and certain chemical properties (i.e. wetting ability, gas adsorption) of shales, and montmorillonites are of particular interest because they swell by the uptake of species in their interlayer. In this study, the hydration and expansion of Na-, Cs-, and NH4+-saturated montmorillonite (Na-, Cs-, and NH4-SWy-2) in high-pressure (90 bar) and moderate temperature (50 °C) methane, carbon dioxide, and CO2/CH4 mixtures (3 and 25 mole% CO2) were investigated using in situ IR spectroscopic titrations, in situ XRD, in situ MAS-NMR, and ab initio electronic structure calculations. The overarching goal was to better understand the hydration/expansion behavior of Na-SWy-2 in CO2/CH4 fluid mixtures by comparison to Cs-, and NH4+-saturated clays. Specific aims were to (1) determine if CH4 intercalates the clays, (2) probe the effects of increasing dissolved CO2 and H2O concentrations, and (3) understand the role of cation solvation by H2O and/or CO2. In pure CH4, no evidence of CH4 intercalation was detected by IR for any of the clays. Similarly, no measurable changes to the basal spacing were observed by XRD in the presence of pure CH4. However, when dry Cs- and NH4-SWy-2 were exposed to dry fluids containing CO2, IR showed maximum CO2 penetrated the interlayer, XRD indicated the clays expanded, and NMR showed evidence for cation solvation by CO2, in line with theoretical predictions. IR titration of these clays with water showed sorbed H2O concentrations decreased with increasing dissolved CO2, suggesting competition for interlayer residency by CO2 and H2O. For Na-SWy-2, on the other

  1. Tidal variability in methane and nitrous oxide emissions along a subtropical estuarine gradient

    NASA Astrophysics Data System (ADS)

    Sturm, Katrin; Werner, Ursula; Grinham, Alistair; Yuan, Zhiguo

    2017-06-01

    This study investigates the tidal variability in methane (CH4) and nitrous oxide (N2O) emissions along a gradient of the subtropical Brisbane River estuary. Sampling was conducted at the upper, middle and lower reaches over two tidal cycles in 2013 and 2014. Methane and N2O emissions varied significantly over tidal cycles at all sites. Methane and N2O emissions measured at all locations and in both campaigns varied substantially in time, with the maximum to minimum flux ratio in a cycle varying between 2.5 - 9 and 1.7-4.7 times, respectively. Methane emissions peaked just before or at slack tides. In comparison, no clear patterns were observed between the N2O emissions and the tidal cycle despite there being large variations in N2O emissions in some cases. Methane concentrations were elevated during low tides whereas N2O concentrations showed no clear pattern over the tidal cycle. Surface water concentrations and tidal currents played important roles in CH4 and N2O emissions, but wind did not. Our findings show that measurements at a single point in time and site would result in significant errors in CH4 and N2O emission estimates. An adequate and careful sampling scheme is required to capture spatial and temporal variations of CH4 and N2O emissions and surface water concentrations which should cover at least one tidal cycle in different estuarine sections.

  2. CLAES CH4, N2O and CCL2F2 (F12) global data. [Cryogenic Array Etalon Spectrometer

    NASA Technical Reports Server (NTRS)

    Kumer, J. B.; Mergenthaler, J. L.; Roche, A. E.

    1993-01-01

    Zonal mean comparisons of CH4 (for altitude regions above the 1.35 ppmv contour), of N2O (above the 210 ppbv contour), and of F12 (above the 360 pptv contour) with UARS prelaunch climatology and with recent models shows reasonable agreement, and some interesting differences in the details of equatorial uplift and descent near the winter poles, including apparent north-south differences. Prominent features such as the double peaked uplift structure in the April-May SAMS data are clearly evident in all three CLAES tracers. Contours of SAMS CH4 and N2O occur mostly at higher pressures than in the CLAES data, presumably due in part to increased tropospheric content of these gases, and/or perhaps some dynamic difference associated with the 15 years time difference between the data sets. The CLAES F12 are the first long time base global data sets. These show more tropical uplift than climatology or models. This might suggest a somewhat shorter lifetime of F12 in the stratosphere than is currently accepted.

  3. Methane concentration and isotopic composition (δ13C-CH4) in the Nerja Cave system (South Spain)

    NASA Astrophysics Data System (ADS)

    Vadillo, Iñaki; Etiope, Giuseppe; Benavente, José; Ojeda, Lucia; Liñán, Cristina; Carrasco, Francisco

    2016-04-01

    Air in underground caves often has methane (CH4) concentrations below the atmospheric level, due to methanotrophic or other unkown CH4 consuming processes. Caves are thus considered a potential sink for atmospheric methane. If globally important, this underground CH4 oxidation should be taken into account in the atmospheric methane budget, in addition to the known soil methanotrophy and tropospheric/stratospheric sinks. A large set of data is however necessary to understand how and how much methane from external atmospheric air is consumed in the caves. While methane concentration data are available for several caves worldwide, its isotopic composition and variations in space and time are poorly documented. We measured methane concentration and stable C isotope composition (δ13C) in the Nerja cave (Southern Spain) air during two surveys in March and April 2015. CH4 concentration decreases progressively from the more external cave rooms, with atmospheric levels of 1.9 ppmv, to the more internal and isolated rooms down to 0.5 ppmv. δ13C increases correspondingly from -47 ‰ to -41 ‰ (VPDB). CH4 is systematically 13C-enriched (δ13C > -45) in areas of the cave where the concentration is below 1.4 ppmv. This combination of concentration decrease and 13C-enrichment towards the more internal and isolated zones of the cave confirms the importance of CH4 oxidation, likely driven by methanotrophic bacteria. Further data, including stable H isotope composition of sub-atmospheric CH4 concentrations, CO2 and microbial analyses, shall be acquired over time to assess the actual role of methanotrophic bacteria and seasonal controls in the CH4 consumption process.

  4. A neutral molecular-based layered magnet [Fe(C2O4)(CH3OH)]n exhibiting magnetic ordering at TN approximately 23 K.

    PubMed

    Zhang, Bin; Zhang, Yan; Zhang, Jinbiao; Li, Junchao; Zhu, Daoben

    2008-10-07

    Solvothermal synthesis of FeCl(2).4H2O and H2C2O(4).2H2O in methanol at 120 degrees C yielded yellow plate-like crystals of [Fe(C2O4)(CH3OH)]n. Each iron atom is in a distorted octahedral environment, being bonded to four oxygen atoms from two bisbidentate oxalate anions, one O atom of a chelating oxalate anion and one O atom from a methanol molecule as an oxalate group bridging ligand in a five-coordination mode. The neutral layer of [Fe(C2O4)(CH3OH)]n with a [4,4] net along the ac plane. There is no interaction between layers. A long range magnetic ordering with spin canting at TN approximately 23 K was observed and confirmed by AC susceptibility measurements.

  5. Investigation of Wyoming Bentonite Hydration in Dry to Water-Saturated Supercritical CH4 and CH4/CO2 Mixtures: Implications for CO2-Enhanced Gas Production

    NASA Astrophysics Data System (ADS)

    Loring, J.; Thompson, C.; Ilton, E. S.; McGrail, B. P.; Schaef, T.

    2014-12-01

    Injection of CO2 into low permeability shale formations leads to additional gas recovery and reduces the flux of CO2 into the atmosphere, thus combining a strong economic incentive with a permanent storage option for CO2. Reduced formation transmissivity due to clay swelling is a concern in CO2 -enhanced gas production. Clay minerals partly determine the physical (i.e. permeability, brittleness) and certain chemical properties (i.e. wetting ability, gas adsorption) of shales, and montmorillonites are of particular interest because they swell by the uptake of species in their interlayer. In this study, the hydration and expansion of a Na-saturated montmorillonite (Na-SWy-2) in high-pressure (90 bar) and moderate temperature (50 °C) methane and mixtures of methane and carbon dioxide were investigated usingCH4 IR spectroscopic titrations andCH4 XRD. The goals were to (1) determine if the hydration/expansion behavior of the clay in supercritical methane is different than in supercritical CO2, (2) determine if methane intercalates the clay, and (3) probe the effects of increasing CO2 concentrations. IR spectra were collected as Na-SWy-2 was titrated with water under several fluid exposures: pure methane, 25, 50, and 75 mole% CO2 in methane, and pure CO2. ComplementaryCH4 XRD experiments were conducted in the same fluids at discrete dissolved water concentrations to measure the d001 values of the clay and thus its volume change on hydration and CH4 and/or CO2 intercalation. In pure methane, no direct evidence of CH4 intercalation was detected in CH bending or stretching regions of the IR spectra. Similarly, in situ XRD indicated the montmorillonite structure was stable in the presence of CH4 and no measurable changes to the basal spacing were observed. However, under low water conditions where the montmorillonite structure was partially expanded (~sub 1W), the IR data indicated a rapid intercalation of CO2 into the interlayer, even with fluid mixtures containing the

  6. Sources and sinks of methane in the African Savanna. CH4 emissions from biomass burning

    NASA Astrophysics Data System (ADS)

    Delmas, R. A.; Marenco, A.; Tathy, J. P.; Cros, B.; Baudet, J. G. R.

    1991-04-01

    Sources and sinks of atmospheric methane are studied in savanna regions of west and central Africa. Flux measured over dry savanna soils, using static chambers, is always negative the average uptake rate being 2×1010 molecules/cm2/s. In these regions, sources are linked to biomass burning. Methane and CO2 emission from combustion of savanna plants and wood is studied by both field experiments and laboratory experiments using a combustion chamber. For savanna plants most of the carbon (85%) contained in the biomaterial is volatilized as CO2 and 0.1 to 0.25% as methane. For graminaceous plants like loudetia simplex the ratio C-CH4/C-CO2 is 0.11%; it is 0.28% for hyparrhenia the other main type of savanna plants and it attains 1.4% for the combustion of wood. In natural fire plumes this ratio is around 0.26% for savanna fires and 0.56 to 2.22% for forest fires. These results show that methane release is highly dependent on the type of combustion. Methane to CO2 ratios are also studied in vertical profiles in the troposphere taken during the TROPOZ I campaign, an aerial research expedition carried out over west Africa during the bushfire period. Within polluted layers, the average ratio of CH4 to CO2 excess over ambient air concentration is 0.34%. These results show that biomass burning in tropical Africa constitutes an important source of atmospheric methane estimated to about 9.2×106 T(CH4)/yr.

  7. New family of lanthanide-based inorganic-organic hybrid frameworks: Ln2(OH)4[O3S(CH2)nSO3]·2H2O (Ln = La, Ce, Pr, Nd, Sm; n = 3, 4) and their derivatives.

    PubMed

    Liang, Jianbo; Ma, Renzhi; Ebina, Yasuo; Geng, Fengxia; Sasaki, Takayoshi

    2013-02-18

    We report the synthesis and structure characterization of a new family of lanthanide-based inorganic-organic hybrid frameworks, Ln(2)(OH)(4)[O(3)S(CH(2))(n)SO(3)]·2H(2)O (Ln = La, Ce, Pr, Nd, Sm; n = 3, 4), and their oxide derivatives. Highly crystallized samples were synthesized by homogeneous precipitation of Ln(3+) ions from a solution containing α,ω-organodisulfonate salts promoted by slow hydrolysis of hexamethylenetetramine. The crystal structure solved from powder X-ray diffraction data revealed that this material comprises two-dimensional cationic lanthanide hydroxide {[Ln(OH)(2)(H(2)O)](+)}(∞) layers, which are cross-linked by α,ω-organodisulfonate ligands into a three-dimensional pillared framework. This hybrid framework can be regarded as a derivative of UCl(3)-type Ln(OH)(3) involving penetration of organic chains into two {LnO(9)} polyhedra. Substitutional modification of the lanthanide coordination promotes a 2D arrangement of the {LnO(9)} polyhedra. A new hybrid oxide, Ln(2)O(2)[O(3)S(CH(2))(n)SO(3)], which is supposed to consist of alternating {[Ln(2)O(2)](2+)}(∞) layers and α,ω-organodisulfonate ligands, can be derived from the hydroxide form upon dehydration/dehydroxylation. These hybrid frameworks provide new opportunities to engineer the interlayer chemistry of layered structures and achieve advanced functionalities coupled with the advantages of lanthanide elements.

  8. The Relative Abundances of Resolved 12CH2D2 and 13CH3D and Mechanisms Controlling Isotopic Bond Ordering in Abiotic and Biotic Methane Gases

    NASA Astrophysics Data System (ADS)

    Young, E. D.; Kohl, I. E.; Sherwood Lollar, B.; Etiope, G.; Rumble, D.; Li, S.; Haghnegahdar, M. A.; Schauble, E. A.; McCain, K.; Foustoukos, D.; Sutcliffe, C. N.; Warr, O.; Ballentine, C. J.; Onstott, T. C.; Hosgormez, H.; Neubeck, A.; Marques, J. M.; Perez-Rodriguez, I. M.; Rowe, A. R.; LaRowe, D.; Magnabosco, C.; Bryndzia, T.

    2016-12-01

    We report measurements of resolved 12CH2D2 and 13CH3D at natural abundances in a variety of methane gases produced naturally and in the laboratory. The ability to resolve 12CH2D2 from 13CH3D provides unprecedented insights into the origin and evolution of CH4. The results identify conditions under which either isotopic bond order disequilibrium or equilibrium are expected. Where equilibrium obtains, concordant Δ12CH2D2 and Δ13CH3D temperatures can be used reliably for thermometry. We find that concordant temperatures do not always match previous hypotheses based on indirect estimates of temperature of formation nor temperatures derived from CH4/H2 D/H exchange, underscoring the importance of reliable thermometry based on the CH4 molecules themselves. Where Δ12CH2D2 and Δ13CH3D values are inconsistent with thermodynamic equilibrium, temperatures of formation derived from these species are spurious. In such situations, while formation temperatures are unavailable, disequilibrium isotopologue ratios nonetheless provide important information about the formation mechanism of the gas and the presence or absence of multiple sources or sinks. In particular, disequilibrium isotopologue ratios may provide the means for differentiating between methane produced by abiotic synthesis versus biological processes. Deficits in 12CH2D2 compared with equilibrium values in CH4 gas made by surface-catalyzed abiotic reactions are so large as to point towards a quantum tunneling origin. Tunneling also accounts for the more moderate depletions in 13CH3D that accompany the low 12CH2D2 abundances produced by abiotic reactions. The tunneling signature of abiotic CH4 formation may prove to be an important tracer of abiotic methane formation, especially where it is preserved by dissolution of gas in cool hydrothermal systems (e.g., Mars). Isotopologue signatures of abiotic methane production can be erased by infiltration of microbial communities, and Δ12CH2D2 values are a key tracer of

  9. Soil CO2 CH4 and N2O fluxes from an afforested lowland raised peatbog in Scotland: implications for drainage and restoration

    NASA Astrophysics Data System (ADS)

    Yamulki, S.; Anderson, R.; Peace, A.; Morison, J. I. L.

    2013-02-01

    The effect of tree (lodgepole pine) planting with and without intensive drainage on soil greenhouse gas (GHG) fluxes was assessed after 45 yr at a raised peatbog in West Flanders Moss, central Scotland. Fluxes of CO2 CH4 and N2O from the soil were monitored over a 2-yr period every 2 to 4 weeks using the static opaque chamber method in a randomised experimental block trial with the following treatments: drained and planted (DP), undrained and planted (uDP), undrained and unplanted (uDuP) and for reference also from an adjoining near-pristine area of bog at East Flanders Moss (n-pris). There was a strong seasonal pattern in both CO2 and CH4 effluxes which were significantly higher in late spring and summer months because of warmer temperatures. Effluxes of N2O were low and no significant differences were observed between the treatments. Annual CH4 emissions increased with the proximity of the water table to the soil surface across treatments in the order: DP < uDP < uDuP < n-pris with mean annual effluxes over the 2-yr monitoring period of 0.15, 0.64, 7.70 and 22.63 g CH4 m-2 yr-1, respectively. For CO2, effluxes increased in the order uDP < DP< n-pris < uDuP, with mean annual effluxes of 1.23, 1.66, 1.82 and 2.55 kg CO2 m-2 yr-1, respectively. CO2 effluxes dominated the total net GHG emission, calculated using the global warming potential (GWP) of the three GHGs for each treatment (76-98%), and only in the n-pris site was CH4 a substantial contribution (23%). Based on soil effluxes only, the near pristine (n-pris) peatbog had 43% higher total net GHG emission compared with the DP treatment because of high CH4 effluxes and the DP treatment had 33% higher total net emission compared with the uDP because drainage increased CO2 effluxes. Restoration is likely to increase CH4 emissions, but reduce CO2 effluxes. Our study suggests that if estimates of CO2 uptake by vegetation from similar peatbog sites were included, the total net GHG emission of restored peatbog would

  10. Synthesis of Fe3O4@SiO2@OSi(CH2)3NHRN(CH2PPh2)2PdCl2 type nanocomposite complexes: Highly efficient and magnetically-recoverable catalysts in vitamin K3 synthesis.

    PubMed

    Uruş, Serhan

    2016-12-15

    The synthesis of aminomethylphosphine-metal complexes have opened a new perspective to the catalytic applications of organic compounds. Magnetic Fe3O4 nano-core was synthesized using the closed quartz tube with Teflon cover and microwaved 200°C for 1h with power controlled instrument set to max. 600W. Novel nano-composite supported; Fe3O4@SiO2(CH2)3NHArN(CH2PPh2)2 and Fe3O4@SiO2(CH2)3N(CH2PPh2)2 type bis(diphenylphosphinomethyl)amino ligands and their Pd(II) complexes have been synthesized and characterized with FT-IR, SEM, EDX, TEM, UV-Visible, XRD and TG/DTA techniques. All the complexes were used as heterogeneous catalysts in the oxidation of 2-methyl naphthalene (2MN) to 2-methyl-1, 4-naphthoquinone (vitamin K3, menadione, 2MNQ) in the presence of hydrogen peroxide and acetic acid. Selectivity reached about 55-60% with a conversion of 90-96% using the nano-magnetite supported aminomethylphosphine-Pd(II) complexes. The complexes were very active in three times in the catalytic recycling experiments in five catalytic cycles. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Tree species influence soil-atmosphere fluxes of the greenhouse gases CO2, CH4 and N2O

    NASA Astrophysics Data System (ADS)

    Steffens, Christina; Vesterdal, Lars; Pfeiffer, Eva-Maria

    2016-04-01

    In the temperate zone, forests are the greatest terrestrial sink for atmospheric CO2, and tree species affect soil C stocks and soil CO2 emissions. When considering the total greenhouse gas (GHG) balance of the forest soil, the relevant GHGs CH4 and N2O should also be considered as they have a higher global warming potential than CO2. The presented data are first results from a field study in a common garden site in Denmark where tree species with ectomycorrhizal colonization (beech - Fagus sylvatica, oak - Quercus robur) and with arbuscular mycorrhizal colonization (maple - Acer pseudoplatanus, ash - Fraxinus excelsior) have been planted in monocultures in adjacent blocks of about 0.25 ha in the year 1973 on former arable land. The soil-atmosphere fluxes of all three gases were measured every second week since August 2015. The hypothesis is that the total GHG efflux from forest soil would differ between species, and that these differences could be related to the type of mycorrhizal association and leaf litter quality. Preliminary results (August to December 2015) indicate that tree species influence the fluxes (converted to CO2-eq) of the three GHGs. Total soil CO2 efflux was in the low end of the range reported for temperate broadleaved forests but similar to the measurements at the same site approximately ten years ago. It was highest under oak (9.6±2.4 g CO2 m-2 d-1) and lowest under maple (5.2±1.6 g CO2 m-2 d-1). In contrast, soil under oak was a small but significant sink for CH4(-0.005±0.003 g CO2-eq m-2 d-1), while there were almost no detectable CH4 fluxes in maple. Emissions of N2O were highest under beech (0.6±0.6 g CO2-eq m-2 d-1) and oak (0.2±0.09 g CO2-eq m-2 d-1) and lowest under ash (0.03±0.04 g CO2-eq m-2 d-1). In the total GHG balance, soil CH4 uptake was negligible (≤0.1% of total emissions). Emissions of N2O (converted to CO2-eq) contributed <1% (ash) to 8% (beech) to total GHG emissions. Summing up all GHG emissions, the tree species

  12. SAPO-34 Membranes for N-2/CH4 separation: Preparation, characterization, separation performance and economic evaluation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Li, SG; Zong, ZW; Zhou, SJ

    2015-08-01

    SAPO-34 membranes were synthesized by several routes towards N-2/CH4 separation. Membrane synthesis parameters including water content in the gel, crystallization time, support pore size, and aluminum source were investigated. High performance N-2-selective membranes were obtained on 100-nm-pore alumina tubes by using Al(i-C3H7O)(3) as aluminum source with a crystallization time of 6 h. These membranes separated N-2 from CH, with N-2 permeance as high as 500 GPU with separation selectivity of 8 at 24 degrees C. for a 50/50 N-2/CH4 mixture. Nitrogen and CH, adsorption isotherms were measured on SAPO-34 crystals. The N-2 and CH, heats of adsorption were 11 andmore » 15 kJ/mol, respectively, which lead to a preferential adsorption of CE-H-4 over N-2 in the N-2/CH4 mixture. Despite this, the SAPO-34 membranes were selective for N-2 over CH4 in the mixture because N-2 diffuses much faster than CH4 and differences in diffusivity played a more critical role than the competitive adsorption. Preliminary economic evaluation indicates that the required N-2/CH4 selectivity would be 15 in order to maintain a CH4 loss below 10%. For small nitrogen-contaminated gas wells, our current SAPO-34 membranes have potential to compete with the benchmark technology cryogenic distillation for N-2 rejection. (C) 2015 Elsevier B.V. All rights reserved,« less

  13. Synthesis, structure and reactivity of rare-earth metallacarborane alkyls [η(1):η(5)-O(CH2)2C2B9H9]Ln(σ:η(1)-CH2C6H4-o-NMe2)(THF)2.

    PubMed

    Yang, Jingying; Xie, Zuowei

    2015-04-14

    Rare-earth metallacarborane alkyls can be stabilized by the incorporation of a functional sidearm into both π and σ ligands. Reaction of [Me3NH][7,8-O(CH2)2-7,8-C2B9H10] with one equiv. of Ln(CH2C6H4-o-NMe2)3 gave metallacarborane alkyls [η(1):η(5)-O(CH2)2C2B9H9]Ln(σ:η(1)-CH2C6H4-o-NMe2)(THF)2 (Ln = Y (), Gd (), Er ()) via alkane elimination. They represent the first examples of rare-earth metallacarborane alkyls. Treatment of with RN[double bond, length as m-dash]C[double bond, length as m-dash]NR (R = Cy, (i)Pr) or 2-benzoylpyridine afforded the corresponding mono-insertion products [η(1):η(5)-O(CH2)2C2B9H9]Y[η(2)-(RN)2C(CH2C6H4-o-NMe2)](DME) (R = Cy (), (i)Pr ()) or [η(1):η(5)-O(CH2)2C2B9H9]Y[C5H4NC(Ph)(CH2C6H4-o-NMe2)O](THF)2 (), respectively. Complex also reacted with ArNCO or ArNC (Ar = 2,6-diisopropylphenyl, 2,6-dimethylphenyl) to give di-insertion products [η(1):η(5)-O(CH2)2C2B9H9]Y[OC([double bond, length as m-dash]NC6H3Me2)N(C6H3Me2)C(CH2C6H4-o-NMe2)O](THF)2 () or [η(1):η(5)-O(CH2)2C2B9H9]Y[C([double bond, length as m-dash]NC6H3(i)Pr2)C([double bond, length as m-dash]NC6H3(i)Pr2)(CH2C6H4-o-NMe2)](DME) (). These results showed that the reactivity pattern of the Ln-C σ bond in rare-earth metallacarborane alkyls was dependent on the nature of the unsaturated organic molecules. New complexes were characterized by various spectroscopic techniques and elemental analysis. Some were further confirmed by single-crystal X-ray analysis.

  14. Effect of air composition (N2, O2, Ar, and H2O) on CO2 and CH4 measurement by wavelength-scanned cavity ring-down spectroscopy: calibration and measurement strategy

    NASA Astrophysics Data System (ADS)

    Nara, H.; Tanimoto, H.; Tohjima, Y.; Mukai, H.; Nojiri, Y.; Katsumata, K.; Rella, C. W.

    2012-11-01

    We examined potential interferences from water vapor and atmospheric background gases (N2, O2, and Ar), and biases by isotopologues of target species, on accurate measurement of atmospheric CO2 and CH4 by means of wavelength-scanned cavity ring-down spectroscopy (WS-CRDS). Changes of the background gas mole fractions in the sample air substantially impacted the CO2 and CH4 measurements: variation of CO2 and CH4 due to relative increase of each background gas increased as Ar < O2 < N2, suggesting similar relation for the pressure-broadening effects (PBEs) among the background gas. The pressure-broadening coefficients due to variations in O2 and Ar for CO2 and CH4 are empirically determined from these experimental results. Calculated PBEs using the pressure-broadening coefficients are linearly correlated with the differences between the mole fractions of O2 and Ar and their ambient abundances. Although the PBEs calculation showed that impact of natural variation of O2 is negligible on the CO2 and CH4 measurements, significant bias was inferred for the measurement of synthetic standard gases. For gas standards balanced with purified air, the PBEs were estimated to be marginal (up to 0.05 ppm for CO2 and 0.01 ppb for CH4) although the PBEs were substantial (up to 0.87 ppm for CO2 and 1.4 ppb for CH4) for standards balanced with synthetic air. For isotopic biases on CO2 measurements, we compared experimental results and theoretical calculations, which showed excellent agreement within their uncertainty. We derived instrument-specific water correction functions empirically for three WS-CRDS instruments (Picarro EnviroSense 3000i, G-1301, and G-2301), and evaluated the transferability of the water correction function from G-1301 among these instruments. Although the transferability was not proven, no significant difference was found in the water vapor correction function for the investigated WS-CRDS instruments as well as the instruments reported in the past studies

  15. The NASA Langley High Altitude Lidar Observatory (HALO) - Advancements in Airborne DIAL Measurements of CH4 and H2O

    NASA Astrophysics Data System (ADS)

    Nehrir, A. R.; Hair, J. W.; Ferrare, R. A.; Hostetler, C. A.; Notari, A.; Collins, J. E., Jr.; Hare, R. J.; Harper, D. B.; Antill, C.; Cook, A. L.; Young, J.; Chuang, T.; Welch, W.

    2016-12-01

    Atmospheric methane (CH4) has the second largest radiative forcing of the long-lived greenhouse gasses (GHG) after carbon dioxide. However, methane's much shorter atmospheric lifetime and much stronger warming potential make its radiative forcing equivalent to that for CO2 over a 20-year time horizon which makes CH4 a particularly attractive target for mitigation strategies. Similar to CH4, water vapor (H2O) is the most dominant of the short-lived GHG in the atmosphere and plays a key role in many atmospheric processes. Atmospheric H2O concentrations span over four orders of magnitude from the planetary boundary layer where high impact weather initiates to lower levels in the upper troposphere and lower stratosphere where water vapor has significant and long term impacts on the Earth's radiation budget. Active remote sensing employing the differential absorption lidar (DIAL) technique enables scientific assessments of both natural and anthropogenic sources and sinks of CH4 with high accuracy and precision as well as and its impacts on the climate. The DIAL technique also allows for profiling of tropospheric water vapor for weather and climate applications with unprecedented spatial and temporal resolution. NASA Langley is developing the High Altitude Lidar Observatory (HALO) lidar system to address the observational needs of NASA's weather, climate, carbon cycle, and atmospheric composition focus areas. HALO is a multi-function airborne lidar being developed to measure atmospheric H2O and CH4 mixing ratios and aerosol and cloud optical properties using the DIAL and High Spectral Resolution Lidar (HSRL) techniques, respectively. HALO is designed as an airborne simulator for future space based DIAL missions and will serve as test bed for risk reduction of key technologies required of future space based GHG DIAL missions. A system level overview and up-to-date progress of the HALO lidar will be presented. Simulations on the expected accuracy and precision of HALO CH4

  16. A new metal-organic framework for separation of C2H2/CH4 and CO2/CH4 at room temperature

    NASA Astrophysics Data System (ADS)

    Duan, Xing; Zhou, You; Lv, Ran; Yu, Ben; Chen, Haodong; Ji, Zhenguo; Cui, Yuanjing; Yang, Yu; Qian, Guodong

    2018-04-01

    A 3D microporous metal-organic framework with open Cu2+ sites and suitable pore space, [Cu2(L)(H2O)2]·(H2O)4(DMF)8 (ZJU-15, H4L = 5,5‧-(9H-carbazole-2,7-diyl)diisophthalic acid; DMF = N,N-dimethylformamide; ZJU = Zhejiang University), has been constructed and characterized. The activated ZJU-15a has three different types of cages and exhibits BET surface area of 1660 m2 g-1, and can separate gas mixture of C2H2/CH4 and CO2/CH4 at room temperature.

  17. Comparison of the frequencies of NH3, CO2, H2O, N2O, CO, and CH4 as infrared calibration standards

    NASA Technical Reports Server (NTRS)

    Brown, L. R.; Toth, R. A.

    1985-01-01

    The absolute accuracies of infrared calibration standards for the line positions have been investigated using a 0.0056-kayser-resolution (unapodized) Fourier-transform spectrum recorded from 550 to 5000 kayser. The spectrum has been obtained using a multicell arrangement containing the various molecular species. Detailed comoparisons reveal that standards for CO2, CH4, and N2O obtained from laser research and NH3 from Fourier-transform spectrometer research are consistent within the accuracies of the present data (+ or 0.0001 kayser). However, certain N2O, H2O, and CO values in the 1100-to 2300 kayser region are systematically high by 0.0001 to 0.0004 kayser. Correction factors for the H2O and CO standards are obtained to bring these into agreement with the laser values. In addition, corrected values for the 2nu-2 and nu-1 bands of N2O at 9 microns are reported.

  18. High temperature infrared absorption cross sections of methane near 3.4 µm in Ar and CO 2 mixtures

    DOE PAGES

    Koroglu, Batikan; Neupane, Sneha; Pryor, Owen; ...

    2017-11-04

    In this study, the absorption cross-sections of CH 4 at two wavelengths in the mid-IR region: λ peak = 3403.4 nm and λ valley = 3403.7 nm were measured. Data were taken using three different compositions of non-reactive gas mixtures comprising CH 4/Ar/CO 2 between 700 < T < 2000 K and 0.1 < P < 1.5 atm in a shock tube utilizing a continuous-wave distributed-feedback quantum cascade laser. Also, broadband room temperature methane cross section measurements were performed using a Fourier transform infrared spectrometer and the cascade laser to gain a better insight into the changes of the linemore » shapes in various bath gasses (Ar, CO 2, and N 2). An application of the high-temperature cross-section data was demonstrated to determine the concentration of methane during oxy-methane combustion in a mixture of CO 2, O 2, and Ar. Lastly, current measurements will be valuable addition to the spectroscopy database for methane- an important fuel used for power generation and heating around the world.« less

  19. High temperature infrared absorption cross sections of methane near 3.4 µm in Ar and CO 2 mixtures

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Koroglu, Batikan; Neupane, Sneha; Pryor, Owen

    In this study, the absorption cross-sections of CH 4 at two wavelengths in the mid-IR region: λ peak = 3403.4 nm and λ valley = 3403.7 nm were measured. Data were taken using three different compositions of non-reactive gas mixtures comprising CH 4/Ar/CO 2 between 700 < T < 2000 K and 0.1 < P < 1.5 atm in a shock tube utilizing a continuous-wave distributed-feedback quantum cascade laser. Also, broadband room temperature methane cross section measurements were performed using a Fourier transform infrared spectrometer and the cascade laser to gain a better insight into the changes of the linemore » shapes in various bath gasses (Ar, CO 2, and N 2). An application of the high-temperature cross-section data was demonstrated to determine the concentration of methane during oxy-methane combustion in a mixture of CO 2, O 2, and Ar. Lastly, current measurements will be valuable addition to the spectroscopy database for methane- an important fuel used for power generation and heating around the world.« less

  20. High temperature infrared absorption cross sections of methane near 3.4 μm in Ar and CO2 mixtures

    NASA Astrophysics Data System (ADS)

    Koroglu, Batikan; Neupane, Sneha; Pryor, Owen; Peale, Robert E.; Vasu, Subith S.

    2018-02-01

    The absorption cross-sections of CH4 at two wavelengths in the mid-IR region: λpeak = 3403.4 nm and λvalley = 3403.7 nm were measured. Data were taken using three different compositions of non-reactive gas mixtures comprising CH4/Ar/CO2 between 700 < T < 2000 K and 0.1 < P < 1.5 atm in a shock tube utilizing a continuous-wave distributed-feedback quantum cascade laser. Also, broadband room temperature methane cross section measurements were performed using a Fourier transform infrared spectrometer and the cascade laser to gain a better insight into the changes of the line shapes in various bath gasses (Ar, CO2, and N2). An application of the high-temperature cross-section data was demonstrated to determine the concentration of methane during oxy-methane combustion in a mixture of CO2, O2, and Ar. Current measurements will be valuable addition to the spectroscopy database for methane- an important fuel used for power generation and heating around the world.

  1. Formation of doubly and triply bonded unsaturated compounds HCN, HNC, and CH2NH via N + CH4 low-temperature solid state reaction: from molecular clouds to solar system objects

    NASA Astrophysics Data System (ADS)

    Mencos, Alejandro; Krim, Lahouari

    2018-06-01

    We show in the current study carried out in solid phase at cryogenic temperatures that methane (CH4) ice exposed to nitrogen atoms is a source of two acids HCN, HNC, and their corresponding hydrogenated unsaturated species CH2NH, in addition to CH3, C2H6, CN-, and three nitrogen hydrides NH, NH2, and NH3. The solid state N + CH4 reaction taken in the ground state seems to be strongly temperature dependent. While at temperatures lower than 10 K only CH3, NH, NH2, and NH3 species formation is promoted due to CH bond dissociation and NH bond formation, stable compounds with CN bonds are formed at temperatures ranged between 10 and 40 K. Many of these reaction products, resulting from CH4 + N reaction, have already been observed in N2-rich regions such as the atmospheres of Titan, Kuiper belt objects, and molecular clouds of the interstellar medium. Our results show the power of the solid state N-atom chemistry in the transformation of simple astrochemical relevant species, such as CH4 molecules and N atoms into complex organic molecules which are also potentially prebiotic species.

  2. Molecular simulation of CH4/CO2/H2O competitive adsorption on low rank coal vitrinite.

    PubMed

    Yu, Song; Bo, Jiang; Wu, Li

    2017-07-21

    The competitive adsorptions of CH 4 /CO 2 /H 2 O on coal vitrinite (DV-8, C 214 H 180 O 24 N 2 ) were computed based on density function theory (DFT) and grand canonical Monte Carlo (GCMC). The adsorption process reaches the saturation state after adsorbing 17 CH 4 s, 22 CO 2 s, and 35 H 2 Os per C 214 H 180 O 24 N 2 respectively. The optimal configurations of CH 4 -vitrinite, CO 2 -vitrinite, and H 2 O-vitrinite respectively manifest as aromatic 1 /T 2 /rT 3 (1 adsorption location, 2 adsorption sites and T here represents sites above the carbon atom and the heteroatom, 3 adsorption orientation and rT here means the orientations of three hydrogen atoms pointing to vitrinite), aromatic/T/v (v represents the orientations perpendicular to the plane of vitrinite), and aromatic/rV/T (rV represents an oxygen atom pointing to the vitrinite surface). The GCMC results show that high temperature is not conducive to the vitrinite's adsorption of adsorbates and the adsorption capacity order is H 2 O > CO 2 > CH 4 (263-363 K) in the one-component, binary, and ternary adsorbate systems. The optimal configurations of vitrinite are similar to graphite/graphene, while ΔE is significantly lower than graphite/graphene. Simulation data are in good agreement with the experimental results.

  3. Electron Irradiation of Kuiper Belt Surface Ices: Ternary N2-CH4-CO Mixtures as a Case Study

    NASA Astrophysics Data System (ADS)

    Kim, Y. S.; Kaiser, R. I.

    2012-10-01

    The space weathering of icy Kuiper Belt Objects was investigated in this case study by exposing methane (CH4) and carbon monoxide (CO) doped nitrogen (N2) ices at 10 K to ionizing radiation in the form of energetic electrons. Online and in situ Fourier transform infrared spectroscopy was utilized to monitor the radiation-induced chemical processing of these ices. Along with isocyanic acid (HNCO), the products could be mainly derived from those formed in irradiated binary ices of the N2-CH4 and CO-CH4 systems: nitrogen-bearing products were found in the form of hydrogen cyanide (HCN), hydrogen isocyanide (HNC), diazomethane (CH2N2), and its radical fragment (HCN2); oxygen-bearing products were of acetaldehyde (CH3CHO), formyl radical (HCO), and formaldehyde (H2CO). As in the pure ices, the methyl radical (CH3) and ethane (C2H6) were also detected, as were carbon dioxide (CO2) and the azide radical (N3). Based on the temporal evolution of the newly formed products, kinetic reaction schemes were then developed to fit the temporal profiles of the newly formed species, resulting in numerical sets of rate constants. The current study highlights important constraints on the preferential formation of isocyanic acid (HNCO) over hydrogen cyanide (HCN) and hydrogen isocyanide (HNC), thus guiding the astrobiological and chemical evolution of those distant bodies.

  4. Distinct transport properties of O2 and CH4 across a carbon nanotube

    NASA Astrophysics Data System (ADS)

    Meng, Xianwen; Wang, Yu; Zhao, Yanjiao; Huang, Jiping

    2013-04-01

    It is of fundamental importance to investigate either O2 or CH4 molecules across nanochannels in many areas such as breathing or separation. Thus, many researches have focused on such a single type of molecules across nanochannels. However, O2 and CH4 can often appear together and crucially affect human life, say, in a mine. On the basis of molecular dynamics simulations, here we attempt to investigate the mixture of O2 and CH4, in order to identify their different transport properties in a nanochannel. We take a single-walled carbon nanotube (SWCNT) as a model nanochannel, and find that their transport properties are distinctly different. As the concentration of O2 increases up to a high value of 0.8, it is always faster for CH4 molecules to transport across the SWCNT, and the total number of gas molecules transporting across the SWCNT is decreased. Meanwhile, CH4 molecules are always dominant in the SWCNT, and the total number of O2 or CH4 inside the SWCNT is a constant. By calculating the van der Waals interaction between the SWCNT and O2 or CH4, we find that the net interaction between CH4 and the SWCNT is much stronger. Our findings may offer some hints on how to separate CH4 from O2, and/or store CH4 efficiently.

  5. Effects of elevated ozone concentration on CH4 and N2O emission from paddy soil under fully open-air field conditions.

    PubMed

    Tang, Haoye; Liu, Gang; Zhu, Jianguo; Kobayashi, Kazuhiko

    2015-04-01

    We investigated the effects of elevated ozone concentration (E-O3) on CH4 and N2O emission from paddies with two rice cultivars: an inbred Indica cultivar Yangdao 6 (YD6) and a hybrid one II-you 084 (IIY084), under fully open-air field conditions in China. A mean 26.7% enhancement of ozone concentration above the ambient level (A-O3) significantly reduced CH4 emission at tillering and flowering stages leading to a reduction of seasonal integral CH4 emission by 29.6% on average across the two cultivars. The reduced CH4 emission is associated with O3-induced reduction in the whole-plant biomass (-13.2%), root biomass (-34.7%), and maximum tiller number (-10.3%), all of which curbed the carbon supply for belowground CH4 production and its release from submerged soil to atmosphere. Although no significant difference was detected between the cultivars in the CH4 emission response to E-O3, a larger decrease in CH4 emission with IIY084 (-33.2%) than that with YD6 (-7.0%) was observed at tillering stage, which may be due to the larger reduction in tiller number in IIY084 by E-O3. Additionally, E-O3 reduced seasonal mean NOx flux by 5.7% and 11.8% with IIY084 and YD6, respectively, but the effects were not significant statistically. We found that the relative response of CH4 emission to E-O3 was not significantly different from those reported in open-top chamber experiments. This study has thus confirmed that increasing ozone concentration would mitigate the global warming potential of CH4 and suggested consideration of the feedback mechanism between ozone and its precursor emission into the projection of future ozone effects on terrestrial ecosystem. © 2014 John Wiley & Sons Ltd.

  6. Highly efficient alkane oxidation catalyzed by [Mn(V)(N)(CN)4](2-). Evidence for [Mn(VII)(N)(O)(CN)4](2-) as an active intermediate.

    PubMed

    Ma, Li; Pan, Yi; Man, Wai-Lun; Kwong, Hoi-Ki; Lam, William W Y; Chen, Gui; Lau, Kai-Chung; Lau, Tai-Chu

    2014-05-28

    The oxidation of various alkanes catalyzed by [Mn(V)(N)(CN)4](2-) using various terminal oxidants at room temperature has been investigated. Excellent yields of alcohols and ketones (>95%) are obtained using H2O2 as oxidant and CF3CH2OH as solvent. Good yields (>80%) are also obtained using (NH4)2[Ce(NO3)6] in CF3CH2OH/H2O. Kinetic isotope effects (KIEs) are determined by using an equimolar mixture of cyclohexane (c-C6H12) and cyclohexane-d12 (c-C6D12) as substrate. The KIEs are 3.1 ± 0.3 and 3.6 ± 0.2 for oxidation by H2O2 and Ce(IV), respectively. On the other hand, the rate constants for the formation of products using c-C6H12 or c-C6D12 as single substrate are the same. These results are consistent with initial rate-limiting formation of an active intermediate between [Mn(N)(CN)4](2-) and H2O2 or Ce(IV), followed by H-atom abstraction from cyclohexane by the active intermediate. When PhCH2C(CH3)2OOH (MPPH) is used as oxidant for the oxidation of c-C6H12, the major products are c-C6H11OH, c-C6H10O, and PhCH2C(CH3)2OH (MPPOH), suggesting heterolytic cleavage of MPPH to generate a Mn═O intermediate. In the reaction of H2O2 with [Mn(N)(CN)4](2-) in CF3CH2OH, a peak at m/z 628.1 was observed in the electrospray ionization mass spectrometry, which is assigned to the solvated manganese nitrido oxo species, (PPh4)[Mn(N)(O)(CN)4](-)·CF3CH2OH. On the basis of the experimental results the proposed mechanism for catalytic alkane oxidation by [Mn(V)(N)(CN)4](2-)/ROOH involves initial rate-limiting O-atom transfer from ROOH to [Mn(N)(CN)4](2-) to generate a manganese(VII) nitrido oxo active species, [Mn(VII)(N)(O)(CN)4](2-), which then oxidizes alkanes (R'H) via a H-atom abstraction/O-rebound mechanism. The proposed mechanism is also supported by density functional theory calculations.

  7. [Effects of Water and Nitrogenous Fertilizer Coupling on CH4 and N2O Emission from Double-Season Rice Paddy Field].

    PubMed

    Fu, Zhi-qiang; Long, Pan; Liu, Yi-yi; Zhong, Juan; Long, Wen-fei

    2015-09-01

    To provide support for the efficient use of water and fertilizer technology to double-season rice cultivation, water and fertilizer coupling mode was applied in this research, including two irrigation methods and four N levels. The irrigation methods were flood irrigation and intermittent irrigation, while four N levels were high-N, middle-N, low-N and none-N. Field experiment was conducted to study the effect of water and fertilizer coupling mode on CH4 and N2O emission. The results showed that the accumulated CH4 emissions were significantly reduced by intermittent irrigation, in comparison with flood irrigation, the reduction in early rice season were from 13. 18 kg.hm-2 to 87. 90 kg.hm-2, and were from 74. 48 kg.hm-2 to 131. 07 kg.hm-2 in late rice season, with a rate of 24. 4% -67. 4% and 42. 5% -65. 5% respectively; whereas the accumulated N20 emissions were increased, the increment were from 0. 03 kg.hm-2 to 0. 24 kg.hm-2 in early rice season and from 0. 35 kg.hm-2 to 1. 53 kg.hm-2 in late rice season when compared flood irrigation, increased by 6.2% -18. 3% and 40.2% - 80.9% respectively. On the whole, intermittent irrigation reduces the warming potential of greenhouse gases (GWP), which were decreased by 18. 8% to 58. 6% in early rice season and by 34. 4% to 60. 1% in late rice season, and the reduction of total GWP were from 2 388 to 4 151 kg. hm-2 (CO2 eq), with a rate of 41% -54% . Through correlation analysis it found that CH4 emissions from soil were significantly related with soil solution Eh and solution CH4 concentration. In comparison with the flood irrigation, the application of intermittent irrigation in double-season rice cultivation was conducive to CH4 reduction, though the increase came in N2O, but the GWPs were significantly reduced. Comprehensively, intermittent irrigation matching with middle-N is more benefit to double-season rice cultivation.

  8. Fluxes of the greenhouse gases (CO2, CH4 and N2O) above a short-rotation poplar plantation after conversion from agricultural land

    NASA Astrophysics Data System (ADS)

    Zona, Donatella; Ceulemans, Reinhart

    2013-04-01

    The increasing demand for renewable energy may lead to the conversion of millions of hectares into bioenergy plantations with a possible substantial transitory carbon (C) loss. In this study we report on the greenhouse gas fluxes (CO2, CH4, and N2O) measured using eddy covariance of a short-rotation bioenergy poplar plantation converted from agricultural fields. During the first six months after the establishment of the plantation (June-Dec 2010) there were substantial CO2, CH4, and N2O emissions (a total of 5.36 ± 0.52 Mg CO2eq ha-1 in terms of CO2 equivalents). Nitrous oxide loss mostly occurred during a week-long peak emission after an unusually large rainfall. This week-long N2O emission represented 52% of the entire N2O loss during one and an half years of measurements. As most of the N2O loss occurred in just this week-long period, accurately capturing these emission events are critical to accurate estimates of the GHG balance of bioenergy. While initial establishment (Jun-Dec 2010) of the plantation resulted in a net CO2 loss into the atmosphere (2.76 ± 0.16 Mg CO2eq ha-1), in the second year (2011) there was substantial net CO2 uptake (-3.51 ± 0.56 Mg CO2eq ha-1). During the entire measurement period, CH4 was a source to the atmosphere (0.63 ± 0.05 Mg CO2eq ha-1 in 2010, and 0.49 ± 0.05 Mg CO2eq ha-1 in 2011), and was controlled by water table depth. Importantly, over the entire measurement period, the sum of the CH4 and N2O losses was much higher (3.51 ± 0.52 Mg CO2eq ha-1) than the net CO2 uptake (-0.76 ± 0.58 Mg CO2eq ha-1). As water availability was an important control on the GHG emission of the plantation, expected climate change and altered rainfall pattern could increase the negative environmental impacts of bioenergy.

  9. Regional Variation of CH4 and N2 Production Processes in the Deep Aquifers of an Accretionary Prism

    PubMed Central

    Matsushita, Makoto; Ishikawa, Shugo; Nagai, Kazushige; Hirata, Yuichiro; Ozawa, Kunio; Mitsunobu, Satoshi; Kimura, Hiroyuki

    2016-01-01

    Accretionary prisms are mainly composed of ancient marine sediment scraped from the subducting oceanic plate at a convergent plate boundary. Large amounts of anaerobic groundwater and natural gas, mainly methane (CH4) and nitrogen gas (N2), are present in the deep aquifers associated with an accretionary prism; however, the origins of these gases are poorly understood. We herein revealed regional variations in CH4 and N2 production processes in deep aquifers in the accretionary prism in Southwest Japan, known as the Shimanto Belt. Stable carbon isotopic and microbiological analyses suggested that CH4 is produced through the non-biological thermal decomposition of organic matter in the deep aquifers in the coastal area near the convergent plate boundary, whereas a syntrophic consortium of hydrogen (H2)-producing fermentative bacteria and H2-utilizing methanogens contributes to the significant production of CH4 observed in deep aquifers in midland and mountainous areas associated with the accretionary prism. Our results also demonstrated that N2 production through the anaerobic oxidation of organic matter by denitrifying bacteria is particularly prevalent in deep aquifers in mountainous areas in which groundwater is affected by rainfall. PMID:27592518

  10. Regional Variation of CH4 and N2 Production Processes in the Deep Aquifers of an Accretionary Prism.

    PubMed

    Matsushita, Makoto; Ishikawa, Shugo; Nagai, Kazushige; Hirata, Yuichiro; Ozawa, Kunio; Mitsunobu, Satoshi; Kimura, Hiroyuki

    2016-09-29

    Accretionary prisms are mainly composed of ancient marine sediment scraped from the subducting oceanic plate at a convergent plate boundary. Large amounts of anaerobic groundwater and natural gas, mainly methane (CH4) and nitrogen gas (N2), are present in the deep aquifers associated with an accretionary prism; however, the origins of these gases are poorly understood. We herein revealed regional variations in CH4 and N2 production processes in deep aquifers in the accretionary prism in Southwest Japan, known as the Shimanto Belt. Stable carbon isotopic and microbiological analyses suggested that CH4 is produced through the non-biological thermal decomposition of organic matter in the deep aquifers in the coastal area near the convergent plate boundary, whereas a syntrophic consortium of hydrogen (H2)-producing fermentative bacteria and H2-utilizing methanogens contributes to the significant production of CH4 observed in deep aquifers in midland and mountainous areas associated with the accretionary prism. Our results also demonstrated that N2 production through the anaerobic oxidation of organic matter by denitrifying bacteria is particularly prevalent in deep aquifers in mountainous areas in which groundwater is affected by rainfall.

  11. Spatial distribution of CH3 and CH2 radicals in a methane rf discharge

    NASA Astrophysics Data System (ADS)

    Sugai, H.; Kojima, H.; Ishida, A.; Toyoda, H.

    1990-06-01

    Spatial distributions of neutral radicals CH3 and CH2 in a capacitively coupled rf glow discharge of methane were measured by threshold ionization mass spectrometry. A strong asymmetry of the density profile was found for the CH2 radical in the high-pressure (˜100 mTorr) discharge. In addition, comprehensive measurements of electron energy distribution, ionic composition, and radical sticking coefficient were made to use as inputs to theoretical modeling of radicals in the methane plasma. The model predictions agree substantially with the measured radical distributions.

  12. High Power and Frequency-Agile Optical Parametric Oscillators for Airborne DIAL Measurements of CH4 and H2O

    NASA Astrophysics Data System (ADS)

    Nehrir, A. R.; Shuman, T.; Chuang, T.; Hair, J. W.; Refaat, T. F.; Ismail, S.; Kooi, S. A.; Notari, A.

    2014-12-01

    Atmospheric methane (CH4) has the second largest radiative forcing of the long-lived greenhouse gasses (GHG) after carbon dioxide. However, methane's much shorter atmospheric lifetime and much stronger warming potential make its radiative forcing equivalent to that for CO2 over a 20-year time horizon which makes CH4 a particularly attractive target for mitigation strategies. Similar to CH4, water vapor (H2O) is the most dominant of the short-lived GHG in the atmosphere and plays a key role in many atmospheric processes. Atmospheric H2O concentrations span over four orders of magnitude from the planetary boundary layer where high impact weather initiates to lower levels in the upper troposphere and lower stratosphere (UTLS) where water vapor has significant and long term impacts on the Earth's radiation budget. NASA Langley has fostered the technology development with Fibertek, Inc. to develop frequency agile and high power (> 3 W) pulsed lasers using similar architectures in the 1645 nm and 935 nm spectral bands for DIAL measurements of CH4 and H2O, respectively. Both systems utilize high power 1 kHz pulse repetition frequency Nd:YAG lasers to generate high power laser emission at the desired wavelength via optical parametric oscillators (OPO). The CH4 OPO, currently in its final build stage in a SBIR Phase II program has demonstrated >2 W average power with injection seeding from a distributed feedback (DFB) laser during risk reduction experiments. The H2O OPO has demonstrated high power operation (>2 W) during the SBIR Phase I program while being injection seeded with a DFB laser, and is currently funded via an SBIR Phase II to build a robust system for future integration into an airborne water vapor DIAL system capable of profiling from the boundary layer up to the UTLS. Both systems have demonstrated operation with active OPO wavelength control to allow for optimization of the DIAL measurements for operation at different altitudes and geographic regions. An

  13. 40 CFR Table C-2 to Subpart C - Default CH4 and N2O Emission Factors for Various Types of Fuel

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... for Various Types of Fuel C Table C-2 to Subpart C Protection of Environment ENVIRONMENTAL PROTECTION... Combustion Sources Pt. 98, Subpt. C, Table C-2 Table C-2 to Subpart C—Default CH4 and N2O Emission Factors... factor (kg N2O/mmBtu) Coal and Coke (All fuel types in Table C-1) 1.1 × 10−02 1.6 × 10−03 Natural Gas 1.0...

  14. 40 CFR Table C-2 to Subpart C - Default CH4 and N2O Emission Factors for Various Types of Fuel

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... for Various Types of Fuel C Table C-2 to Subpart C Protection of Environment ENVIRONMENTAL PROTECTION... Combustion Sources Pt. 98, Subpt. C, Table C-2 Table C-2 to Subpart C—Default CH4 and N2O Emission Factors... factor (kg N2O/mmBtu) Coal and Coke (All fuel types in Table C-1) 1.1 × 10−02 1.6 × 10−03 Natural Gas 1.0...

  15. Insights into the structure of mixed CO 2/CH 4 in gas hydrates

    DOE PAGES

    Everett, S. Michelle; Rawn, Claudia J.; Chakoumakos, Bryan C.; ...

    2015-05-12

    The exchange of carbon dioxide for methane in natural gas hydrates is an attractive approach to harvesting CH 4 for energy production while simultaneously sequestering CO 2. In addition to the energy and environmental implications, the solid solution of clathrate hydrate (CH 4) 1-x(CO 2) x·5.75H 2O provides a model system to study how the distinct bonding and shapes of CH 4 and CO 2 influence the structure and properties of the compound. In this paper, high-resolution neutron diffraction was used to examine mixed CO 2/CH 4 gas hydrates. CO 2-rich hydrates had smaller lattice parameters, which were attributed tomore » the higher affinity of the CO 2 molecule interacting with H 2O molecules that form the surrounding cages, and resulted in a reduction in the unit-cell volume. Experimental nuclear scattering densities illustrate how the cage occupants and energy landscape change with composition. Finally, these results provide important insights on the impact and mechanisms for the structure of mixed CH 4/CO 2 gas hydrate.« less

  16. Soil-atmosphere fluxes of the greenhouse gases N2O, CO2 and CH4 from a long term compost experiment in Austria.

    NASA Astrophysics Data System (ADS)

    Spann, Caroline; Spiegel, Heide; Kitzler, Barbara

    2016-04-01

    The application of composts as fertilizers is becoming increasingly important to achieve a closed-loop economy. However, greenhouse gas (GHG) emissions, especially N2O, from agricultural fields may increase as well. In this study different compost types and N amounts were investigated, especially in terms of their GHG fluxes. We used the closed chamber method to estimate GHG flux rates over one vegetation period from an agricultural soil fertilized with different compost types. The study was conducted on a long term compost experiment site near Linz (Austria) with a crop rotation. The soil is a loamy silt and in 2015 maize was planted. Six different compost treatments were investigated. Organic waste compost (OWC) and farmyard manure compost (FMC) was applied with nitrogen concentrations of 175 (OWC1, FYC1) and 525 kg N ha-1 (OWC3, FYC3). Two compost treatments were fertilized additionally with 80 kg N ha.1 mineral fertilizer (OWC2, FYC2). One treatment (TN) was fertilized only with mineral fertilizer (120 kg N ha-1) and one treatment was not fertilized at all (C). Additionally to the GHG flux rates, ammonium and nitrate content, microbial biomass C and N and different enzyme activities were analysed in the top soil. Nitrous oxide (N2O) was emitted over the entire vegetation period with highest fluxes from April until June, until the plants have been established sufficiently. Overall, at the FMC treatments (FYC2, FYC3) highest fluxes were measured. Compared to FMC, lower N2O emissions were measured from the OWC treatments. The combination of compost and mineral N fertilization resulted in the highest N2O emissions, especially after precipitation events. The treatments OWC1 and FYC1 were not different from the control. Methane (CH4) was mainly taken up at all treatments, but uptake rates were lower at the high N input sites (OWC3, FYC3) with no differences between the compost types. No significant differences were found in the soil respiration rates.

  17. Exotic Spartina alterniflora invasion alters ecosystem-atmosphere exchange of CH4 and N2O and carbon sequestration in a coastal salt marsh in China.

    PubMed

    Yuan, Junji; Ding, Weixin; Liu, Deyan; Kang, Hojeong; Freeman, Chris; Xiang, Jian; Lin, Yongxin

    2015-04-01

    Coastal salt marshes are sensitive to global climate change and may play an important role in mitigating global warming. To evaluate the impacts of Spartina alterniflora invasion on global warming potential (GWP) in Chinese coastal areas, we measured CH4 and N2O fluxes and soil organic carbon sequestration rates along a transect of coastal wetlands in Jiangsu province, China, including open water; bare tidal flat; and invasive S. alterniflora, native Suaeda salsa, and Phragmites australis marshes. Annual CH4 emissions were estimated as 2.81, 4.16, 4.88, 10.79, and 16.98 kg CH4 ha(-1) for open water, bare tidal flat, and P. australis, S. salsa, and S. alterniflora marshes, respectively, indicating that S. alterniflora invasion increased CH4 emissions by 57-505%. In contrast, negative N2O fluxes were found to be significantly and negatively correlated (P < 0.001) with net ecosystem CO2 exchange during the growing season in S. alterniflora and P. australis marshes. Annual N2O emissions were 0.24, 0.38, and 0.56 kg N2O ha(-1) in open water, bare tidal flat and S. salsa marsh, respectively, compared with -0.51 kg N2O ha(-1) for S. alterniflora marsh and -0.25 kg N2O ha(-1) for P. australis marsh. The carbon sequestration rate of S. alterniflora marsh amounted to 3.16 Mg C ha(-1) yr(-1) in the top 100 cm soil profile, a value that was 2.63- to 8.78-fold higher than in native plant marshes. The estimated GWP was 1.78, -0.60, -4.09, and -1.14 Mg CO2 eq ha(-1) yr(-1) in open water, bare tidal flat, P. australis marsh and S. salsa marsh, respectively, but dropped to -11.30 Mg CO2 eq ha(-1) yr(-1) in S. alterniflora marsh. Our results indicate that although S. alterniflora invasion stimulates CH4 emissions, it can efficiently mitigate increases in atmospheric CO2 and N2O along the coast of China. © 2014 John Wiley & Sons Ltd.

  18. Fundamental Understanding of Methane-Carbon Dioxide-Water (CH4-CO2-H2O) Interactions in Shale Nanopores under Reservoir Conditions: Quarterly Report.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Yifeng

    Shale is characterized by the predominant presence of nanometer-scale (1-100 nm) pores. The behavior of fluids in those pores directly controls shale gas storage and release in shale matrix and ultimately the wellbore production in unconventional reservoirs. Recently, it has been recognized that a fluid confined in nanopores can behave dramatically differently from the corresponding bulk phase due to nanopore confinement (Wang, 2014). CO 2 and H 2O, either preexisting or introduced, are two major components that coexist with shale gas (predominately CH 4) during hydrofracturing and gas extraction. Note that liquid or supercritical CO 2 has been suggested asmore » an alternative fluid for subsurface fracturing such that CO 2 enhanced gas recovery can also serve as a CO 2 sequestration process. Limited data indicate that CO 2 may preferentially adsorb in nanopores (particularly those in kerogen) and therefore displace CH 4 in shale. Similarly, the presence of water moisture seems able to displace or trap CH 4 in shale matrix. Therefore, fundamental understanding of CH 4-CO 2-H 2O behavior and their interactions in shale nanopores is of great importance for gas production and the related CO 2 sequestration. This project focuses on the systematic study of CH 4-CO 2-H 2O interactions in shale nanopores under high-pressure and high temperature reservoir conditions. The proposed work will help to develop new stimulation strategies to enable efficient resource recovery from fewer and less environmentally impactful wells.« less

  19. Investigation of Seasonal Cycles of CO, CH4, N2O, and O3 in the High Arctic at Eureka, Canada and Barrow, Alaska using Infrared Emission Spectroscopy

    NASA Astrophysics Data System (ADS)

    Tran, S.; Mariani, Z.; Conway, S. A.; Lutsch, E.; Rowe, P. M.; Kasai, Y.; Strong, K.

    2015-12-01

    The High Arctic experiences prolonged periods of total darkness in the winter and continuous daylight in the summer, influencing the atmosphere and its composition in ways that are still not fully understood. Making atmospheric measurements in this remote region is challenging, particularly during polar night when solar-viewing instruments are not operational. By using infrared emission spectroscopy, which is independent of sunlight, we are able to document year-round the total column abundances of carbon monoxide (CO), methane (CH4), nitrous oxide (N2O), and ozone (O3). Measurements made at two Arctic sites are presented in this study: the Polar Environment Atmospheric Research Laboratory (PEARL, Eureka, Nunavut, Canada, 80.05°N, 86.42°W) and the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) facility on the North Slope of Alaska (NSA, Barrow, Alaska, 71.19°N, 156.36°W). At both sites, Extended-range Atmospheric Emitted Radiance Interferometers (E-AERIs), are used to measure the absolute downwelling infrared emission from the atmosphere between 400 and 3000 cm-1. The E-AERI has a moderate resolution of 1 cm-1 and provides information about trace gases columns with high sensitivity to the lower troposphere. At PEARL, the instrument was installed in October 2008. In addition, a similar instrument, the University of Idaho's Polar AERI (P-AERI) was installed at PEARL from March 2006 to June 2009. At NSA, the E-AERI has been operating since February 1998. Total columns of CO, CH4, N2O and O3 have been retrieved from 2006 to 2015 at PEARL and from 1998 to 2014 at NSA using the SFIT4 algorithm. These two datasets will be compared along with measurements made by high-resolution solar-viewing infrared spectrometers located at PEARL and at Poker Flat, Alaska (65.12°N, 147.47°W) to validate our results. These measurements will be used to present the annual, seasonal and diurnal variabilities of trace gases in the high Arctic at two different

  20. Pasture age effects on N[sub 2]O, NO and CH[sub 4] emissions in the Atlantic Lowlands of Costa Rica

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Keller, M.; Reiners, W.A.; Veldkamp, E.

    A study conducted in Brazil indicated that N[sub 2]O emissions increased following forest conversion to pasture. Our first study in Costa Rica indicated the reverse. To explore this contradiction, we measured N[sub 2]O, NO, and CH[sub 4] emissions in a chronosequence of 8 sites comprising forest and derive pastures of ayes 2 to 25 years, all on the same soil type in the Atlantic Lowlands of Costa Rica. We found large differences through the chronosequence in the fluxes of these three gases. Flux changes were related to changes in available nitrogen, organic matter, moisture content, and bulk density in themore » soil. N[sub 2]O emissions from the 2-year pasture were much greater than from the forest. Emissions declined with pasture age so that 25-year pasture had much smaller emissions than the forest. NO emissions from young pastures were similar to forest emissions, then declined sharply with pasture age. Forest soils consumed CH[sub 4]. Pasture soils mainly produced CH[sub 4]. Prediction of the effects of land use change on trace gas fluxes in the tropics will require an assessment of the history and soil condition of individual land units.« less

  1. Ice core measurements of 14CH4 show no evidence of methane release to atmosphere from methane hydrates during a large warming event 11,600 years ago

    NASA Astrophysics Data System (ADS)

    Petrenko, V. V.; Severinghaus, J. P.; Smith, A.; Riedel, K.; Brook, E.; Schaefer, H.; Baggenstos, D.; Harth, C. M.; Hua, Q.; Buizert, C.; Schilt, A.; Fain, X.; Mitchell, L.; Bauska, T. K.; Orsi, A. J.; Weiss, R. F.

    2016-12-01

    Marine methane hydrate destabilization has been proposed as a potentially large source of methane to the atmosphere in response to both past and future warming. We present new measurements of 14C of paleoatmospheric methane (CH4) over the Younger Dryas - Preboreal (YD - PB) abrupt warming event (≈11,600 years ago) from ancient ice outcropping at Taylor Glacier, Antarctica. The YD - PB abrupt warming was centered in the North Atlantic, occurred partway through the global warming of last deglaciation and was associated with a ≈ 50% increase in atmospheric CH4 concentrations. 14C can unambiguously identify CH4 emissions from "old carbon" sources, such as CH4 hydrates. All samples from before, during and after the abrupt warming and associated CH4 increase yielded 14CH4 values that are consistent with 14C of atmospheric CO2 at that time, indicating a purely contemporaneous methane source. Our results show that neither the abrupt regional warming nor the gradual global warming that preceded it resulted in detectable CH4 release to the atmosphere from CH4 hydrates during the YD - PB transition. Our results are thus consistent with the hypothesis that the vast majority of CH4 that is released from dissociating hydrates or other old-carbon seafloor CH4 sources is oxidized prior to reaching the atmosphere.

  2. Reducing CH4 emission from rice paddy fields by altering water management

    NASA Astrophysics Data System (ADS)

    Sudo, S.; Itoh, M.

    2010-12-01

    Percentage of atmospheric methane emitted form rice paddy is estimated at 60Tg/yr (20 - 100Tg/yr) which is near 10% of total global methane emission of 535Tg/yr (410 - 660Tg) (IPCC(1995), and which is near 30% of anthropogenic CH4 emission. Thus, mitigation of CH4 emission is urgently required. CH4 in paddy soil is emanated by the activities of anaerobic bacteria which is called methane producer through reduction of CO2 or decomposition of acetic acid, and it is transported to atmosphere through soil or paddy water surface. It is effective to control methane emission from rice paddy that period is extended on intermittent drainage, composted rice straw is incorporated as fertilizer instead of flesh one, or other. However, empirical approach of these kinds of experiments had not been sufficient because such a kind of experiment required significant times and efforts. In this study, we conducted demonstrative experiments to verify the effects of water management method differences in order to reduce CH4 emission from rice paddy at 9 experimental sites in 8 prefectures. In this, we used new gas analyzer which can measure CH4, CO2 and N2O at once developed by National Institute for Agro-Environmental Sciences (NIAES), Japan. In this report, we show the results in two years of this study. 'Nakaboshi' (mid-season-drainage) is one of cultivation methods in rice paddy that surface water in paddy field is once drained for about 10 days and the field is maintained like upland field to give adequate stress to rice plant for better harvest qualities and yields. Our targeted evaluation was dependencies of Nakaboshi periods lengths and Nakaboshi periods to CH4 emission reduction amounts for total cultivation periods within harvest yield maintained. The longer length of Nakaboshi period was extended, the lesser CH4 emitted even after when Nakaboshi period lasted, as a whole. In some cases, for example in Kagoshima, exceptional phenomena of that significant high emission were

  3. CW EC-QCL-based sensor for simultaneous detection of H2O, HDO, N2O and CH4 using multi-pass absorption spectroscopy.

    PubMed

    Yu, Yajun; Sanchez, Nancy P; Griffin, Robert J; Tittel, Frank K

    2016-05-16

    A sensor system based on a continuous wave, external-cavity quantum-cascade laser (CW EC-QCL) was demonstrated for simultaneous detection of atmospheric H2O, HDO, N2O and CH4 using a compact, dense pattern multi-pass gas cell with an effective path-length of 57.6 m. The EC-QCL with a mode-hop-free spectral range of 1225-1285 cm-1 operating at ~7.8 µm was scanned covering four neighboring absorption lines, for H2O at 1281.161 cm-1, HDO at 1281.455 cm-1, N2O at 1281.53 cm-1 and CH4 at 1281.61 cm-1. A first-harmonic-normalized wavelength modulation spectroscopy with second-harmonic detection (WMS-2f/1f) strategy was employed for data processing. An Allan-Werle deviation analysis indicated that minimum detection limits of 1.77 ppmv for H2O, 3.92 ppbv for HDO, 1.43 ppbv for N2O, and 2.2 ppbv for CH4 were achieved with integration times of 50-s, 50-s, 100-s and 129-s, respectively. Experimental measurements of ambient air are also reported.

  4. Vertical Transport Rates in the Stratosphere in 1993 from Observations of CO2, N2O and CH4

    NASA Technical Reports Server (NTRS)

    Wofsy, Steven C.; Boering, Kristie A.; Daube, Bruce C., Jr.; McElroy, Michael B.; Loewenstein, Max; Podolske, James R.; Elkins, James W.; Dutton, Geoffrey S.; Fahey, David W.

    1994-01-01

    Measurements of CO2, N2O and CH4 are analyzed to define hemispheric average vertical exchange rates in the lower stratosphere from November 1992 to October 1993. Effective vertical diffusion coefficients were small in summer, less than or equal to 1 m(exp 2)/sec at altitudes below 25 km; values were similar near the tropopause in winter, but increased markedly with altitude. The analysis suggests possibly longer residence times for exhaust from stratospheric aircraft, and more efficient transport from 20 km to the middle stratosphere, than predicted by many current models. Seasonally-resolved measurements of stratospheric CO2 and N2O provide significant new constraints on rates for global-scale vertical transport.

  5. Modeling of Isotope Fractionation in Stratospheric CO2, N2O, CH4, and O3: Investigations of Stratospheric Chemistry and Transport, Stratosphere-Troposphere Exchange, and Their Influence on Global Isotope Budgets

    NASA Technical Reports Server (NTRS)

    Boering, Kristie A.; Connell, Peter; Rotman, Douglas

    2005-01-01

    Until recently, the stable isotopic composition of chemically and datively important stratospheric species, such as ozone (O3), carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4), was largely unexplored, despite indications from the few measurements available and theoretical studies that global-scale isotopic variations will provide a unique tool for quantifying rates of global-scale mass transport into, within, and out of the stratosphere and for understanding the mechanisms of chemical reactions involved in ozone production. The number and geographical extent of observations are beginning to increase rapidly, however, as access to the stratosphere, both directly and by remote-sensing, has increased over the last 10 years and as new analytical techniques have been developed that make global-scale isotope measurements by whole-air sampling more feasible. The objective of this study, begun in April 1999, is to incorporate into the Livermore 2D model the likely photochemical fractionation processes that determine the isotopic compositions of stratospheric CO2, N2O, CH4, and O3, and to use the model results and new observations from NASA field campaigns in 1996 and 1997 to investigate stratospheric chemistry and mass transport. Additionally, since isotopic signatures from the stratosphere are transferred to the troposphere by downward transport at middle and high latitudes, the isotopic compositions may also serve as sensitive tracers of stratosphere-totroposphere transport. Comparisons of model results with stratospheric and upper tropospheric observations from these campaigns, as well as with ground-based observations from new NOAA and NSF-sponsored studies, will help determine whether the magnitudes of the stratospheric fractionation processes are large enough to use as global-scale tracers of transport into the troposphere and, if so, will be used to help constrain the degree of coupling between the troposphere and the stratosphere.

  6. Tests of stratospheric models - The reactions of atomic chlorine with O3 and CH4 at low temperature

    NASA Technical Reports Server (NTRS)

    Demore, W. B.

    1991-01-01

    The rate-constant ratio of the photochemical reactions of atomic chlorine with O3 and CH4 was determined using data from laboratory experiments on competitive chlorination of O3/CH4 mixtures at stratospheric temperatures (197-217 K). Two experimental approaches were used: (1) measuring the k1/k2 ratio for the reactions of atomic chlorine with ozone and methane and (2) testing for some of the ClO/CH3O2 chemistry. The chlorine and ozone concentrations were monitored by UV-Vis spectroscopy, and the CH3Cl concentration was measured by FTIR. The results on the k1/k2 ratio are in excellent agreement with the current NASA recommendation (DeMore et al., 1990), being only 12 percent higher. On the other hand, results on the ClO + CH3O2 reaction do not support the rate constant suggested by Simon et al. (1989).

  7. A high level computational study of the CH4/CF4 dimer: how does it compare with the CH4/CH4 and CF4/CF4 dimers?

    NASA Astrophysics Data System (ADS)

    Biller, Matthew J.; Mecozzi, Sandro

    2012-04-01

    The interaction within the methane-methane (CH4/CH4), perfluoromethane-perfluoromethane (CF4/CF4) methane-perfluoromethane dimers (CH4/CF4) was calculated using the Hartree-Fock (HF) method, multiple orders of Møller-Plesset perturbation theory [MP2, MP3, MP4(DQ), MP4(SDQ), MP4(SDTQ)], and coupled cluster theory [CCSD, CCSD(T)], as well as the PW91, B97D, and M06-2X density functional theory (DFT) functionals. The basis sets of Dunning and coworkers (aug-cc-pVxZ, x = D, T, Q), Krishnan and coworkers [6-311++G(d,p), 6-311++G(2d,2p)], and Tsuzuki and coworkers [aug(df, pd)-6-311G(d,p)] were used. Basis set superposition error (BSSE) was corrected via the counterpoise method in all cases. Interaction energies obtained with the MP2 method do not fit with the experimental finding that the methane-perfluoromethane system phase separates at 94.5 K. It was not until the CCSD(T) method was considered that the interaction energy of the methane-perfluoromethane dimer (-0.69 kcal mol-1) was found to be intermediate between the methane (-0.51 kcal mol-1) and perfluoromethane (-0.78 kcal mol-1) dimers. This suggests that a perfluoromethane molecule interacts preferentially with another perfluoromethane (by about 0.09 kcal mol-1) than with a methane molecule. At temperatures much lower than the CH4/CF4 critical solution temperature of 94.5 K, this energy difference becomes significant and leads perfluoromethane molecules to associate with themselves, forming a phase separation. The DFT functionals yielded erratic results for the three dimers. Further development of DFT is needed in order to model dispersion interactions in hydrocarbon/perfluorocarbon systems.

  8. Ro-vibrational Spectra of (para-H2 )N -CH4 in He Droplets.

    PubMed

    Hoshina, Hiromichi; Sliter, Russell; Ravi, Aakash; Kuma, Susumu; Momose, Takamasa; Vilesov, Andrey F

    2016-11-18

    In this work, we report on the infrared spectroscopic study of clusters of CH 4 molecules with up to N=80 para-hydrogen molecules assembled inside He droplets. Upon increase of the number of the added para-hydrogen molecules up to about N=12, both the rotational constant, B, and the origin frequency of the υ 3 band of CH 4 decrease gradually. In the range of 6 ≤N≤12, the spectra indicate some abrupt changes of B and υ 3 with both values being approximately constant at N≥12. The origin of this effect is discussed. Comparison of the spectra of methane molecules in para-hydrogen clusters to that in solid para-hydrogen is also presented. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Axial zero-field splitting in mononuclear Co(ii) 2-N substituted N-confused porphyrin: Co(2-NC3H5-21-Y-CH2C6H4CH3-NCTPP)Cl (Y = o, m, p) and Co(2-NC3H5-21-CH2C6H5-NCTPP)Cl.

    PubMed

    Lai, Ya-Yuan; Chang, Yu-Chang; Chen, Jyh-Horung; Wang, Shin-Shin; Tung, Jo-Yu

    2016-03-21

    The inner C-benzyl- and C-o-xylyl (or m-xylyl, p-xylyl)-substituted cobalt(ii) complexes of a 2-N-substituted N-confused porphyrin were synthesized from the reaction of 2-NC3H5NCTPPH (1) and CoCl2·6H2O in toluene (or o-xylene, m-xylene, p-xylene). The crystal structures of diamagnetic chloro(2-aza-2-allyl-5,10,15,20-tetraphenyl-21-hydrogen-21-carbaporphyrinato-N,N',N'')zinc(ii) [Zn(2-NC3H5-21-H-NCTPP)Cl; 3 ] and paramagnetic chloro(2-aza-2-allyl-5,10,15,20-tetraphenyl-21-benzyl-21-carbaporphyrinato-N,N',N'')cobalt(ii) [Co(2-NC3H5-21-CH2C6H5NCTPP)Cl; 7], and chloro(2-aza-2-allyl-5,10,15,20-tetraphenyl-21-Y-xylyl-21-carbaporphyrinato-N,N',N'')cobalt(ii) [Co(2-NC3H5-21-Y-CH2C6H4CH3NCTPP)Cl] [Y = o (8), m (9), p (10)] were determined. The coordination sphere around the Zn(2+) (or Co(2+)) ion in 3 (or 7-10) is a distorted tetrahedron (DT). The free energy of activation at the coalescence temperature Tc for the exchange of phenyl ortho protons o-H (26) with o-H (22) in 3 in a CDCl3 solvent is found to be ΔG = 61.4 kJ mol(-1) through (1)H NMR temperature-dependent measurements. The axial zero-field splitting parameter |D| was found to vary from 35.6 cm(-1) in 7 (or 30.7 cm(-1) in 8) to 42.0 cm(-1) in 9 and 46.9 cm(-1) in 10 through paramagnetic susceptibility measurements. The magnitude of |D| can be related to the coordination sphere at the cobalt sites.

  10. Effect of assessment scale on spatial and temporal variations in CH4, C02, and N20 fluxes in a forested wetland

    Treesearch

    Zhaohua Dai; Carl Trettin; Changsheng Li; Harbin Li; Ge Sun; Devendra Amatya

    2011-01-01

    Emissions of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) from a forested watershed (160 ha) in South Carolina, USA, were estimated with a spatially explicit watershed-scale modeling framework that utilizes the spatial variations in physical and biogeochemical characteristics across watersheds. The target watershed (WS80) consisting of wetland (23%) and...

  11. Stable isotope ratios of atmospheric CO_{2} and CH_{4} over Siberia measured at ZOTTO

    NASA Astrophysics Data System (ADS)

    Timokhina, Anastasiya; Prokushkin, Anatily; Lavric, Jost; Heimann, Martin

    2016-04-01

    The boreal and arctic zones of Siberia housing the large amounts of carbon stored in the living biomass of forests and wetlands, as well as in soils and specifically permafrost, play a crucial role in earth's global carbon cycle. The long-term studies of greenhouse gases (GHG) concentrations are important instruments to analyze the response of these systems to climate warming. In parallel to GHG observations, the measurements of their stable isotopic composition can provide useful information for distinguishing contribution of individual GHG source to their atmospheric variations, since each source has its own isotopic signature. In this study we report first results of laboratory analyses of the CO2 and CH4 concentrations, the stable isotope ratio of δ13C-CO2, δ18O-CO2, δ13C-CH4, δD-CH4 measured in one-liter glass flasks which were obtained from 301 height of ZOTTO (Zotino Tall Tower Observatory, near 60° N, 90° E, about 20 km west of the Yenisei River) during 2008 - 2013 and 2010 - 2013 for stable isotope composition of CO2 and CH4. The magnitudes of δ13C-CO2 and δ18O-CO2 in a seasonal cycle are -1.4±0.1‰ (-7.6 - -9.0‰) and -2.2±0.2‰ (-0.1 - -2.3‰), respectively. The δ13C-CO2 seasonal pattern opposes the CO2 concentrations, with a gradual enrichment in heavy isotope occurring during May - July, reflecting its discrimination in photosynthesis, and further depletion in August - September as photosynthetic activity decreases comparatively to ecosystem respiration. Relationship between the CO2 concentrations and respective δ13C-CO2 (Keeling plot) reveals isotopic source signature for growing season (May - September) -27.3±1.4‰ and -30.4±2.5‰ for winter (January - March). The behavior of δ18O-CO2 associated with both high photosynthetic rate in the June (enrichment of atmospheric CO2 by 18O as consequence of CO2 equilibrium with "heavy" leaf water) and respiratory activity of forest floor in June - October (depletion of respired CO2 by 18O

  12. 40 CFR Table C-2 to Subpart C of... - Default CH4 and N2O Emission Factors for Various Types of Fuel

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... for Various Types of Fuel C Table C-2 to Subpart C of Part 98 Protection of Environment ENVIRONMENTAL... Fuel Combustion Sources Pt. 98, Subpt. C, Table C-2 Table C-2 to Subpart C of Part 98—Default CH4 and...) Default N2O emission factor (kg N2O/mmBtu) Coal and Coke (All fuel types in Table C-1) 1.1 × 10−02 1.6...

  13. 40 CFR Table C-2 to Subpart C of... - Default CH4 and N2O Emission Factors for Various Types of Fuel

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... for Various Types of Fuel C Table C-2 to Subpart C of Part 98 Protection of Environment ENVIRONMENTAL... Fuel Combustion Sources Pt. 98, Subpt. C, Table C-2 Table C-2 to Subpart C of Part 98—Default CH4 and...) Default N2O emission factor (kg N2O/mmBtu) Coal and Coke (All fuel types in Table C-1) 1.1 × 10− 02 1.6...

  14. Impact of hydrochar on rice paddy CH4 and N2O emissions: A comparative study with pyrochar.

    PubMed

    Zhou, Beibei; Feng, Yanfang; Wang, Yueman; Yang, Linzhang; Xue, Lihong; Xing, Baoshan

    2018-08-01

    Hydrothermal carbonization (HTC) thermally converts wet biomasses to carbon materials, dramatically reducing energy use for drying and improving solid product yield compared to pyrolysis process. However, researches regarding agricultural usage of hydrochar (HC) are limited. In the present study, the influence of HC amendment on CH 4 and N 2 O emissions, as well as global warming potential (GWP) and greenhouse gas intensity (GHGI) were investigated. Additionally, pyrochar (PC) treatments as well as two char-free control treatments with (CKU) or without (CK) N fertilizer were also included for comparison. Chars were produced from wheat straw (WC) and saw dust (SC) and applied at different rates (0.5% and 3%, w/w). Both hydrochar and pyrochar decreased paddy CH 4 emissions when amended at a lower rate (0.5%) compared to CKU treatment, which was more obvious for pyrochar when applied at the rate of 3%. Contrarily, 3%-HC significantly stimulated CH 4 emissions, which were around 5 and 3 times higher than that of CKU for WC and SC, respectively. Furthermore, hydrochar showed the potential to decrease paddy N 2 O emissions (6.06-32.32%) at both application rates. However, N 2 O emissions with PC treatments varied depending on application rate (20.20-75.76%). GWP and GHGI values of 0.5%-HC and PC treatments were similar, 6.67-25.00% and 3.85-25.00% lower than those of CKU treatment, respectively. However, 3%-HC amendments led to significantly increased GWP and GHGI. This study suggested that application rate of hydrochar used in rice fields should be taken into serious consideration to fulfill its potential in GHGs mitigation and minimize environmental side effects. Copyright © 2018 Elsevier Ltd. All rights reserved.

  15. Coupled effects of straw and nitrogen management on N2O and CH4 emissions of rainfed agriculture in Northwest China

    NASA Astrophysics Data System (ADS)

    Htun, Yin Min; Tong, Yanan; Gao, Pengcheng; Xiaotang, Ju

    2017-05-01

    Straw incorporation is a common agricultural practice, but the additional carbon source may increase greenhouse gas emissions by stimulating microbial activity in soil, particularly when straw is applied at the same time as nitrogen (N) fertilizer. We investigated the coupled effects of straw and N fertilizer on greenhouse gas emissions in a rainfed winter wheat-summer fallow system in Northwest China. Simultaneous applications of straw and N fertilizer increased N2O emissions by up to 88%, net greenhouse gas (NGHG) emission and net greenhouse gas intensity (NGHGI) by over 90%, and the N2O emission factor by over 2-fold. When straw was applied before N fertilizer, the emission factor (0.22%) decreased by approximately one-half compared with that for simultaneous applications (0.45%). In addition, early straw incorporation decreased N2O emissions, NGHG, and NGHGI by 35% (0.62 kg N2O-N ha-1 yr-1), 40% (242 kg CO2-eq ha-1 yr-1), and 38% (42 kg CO2-eq t-1 grain), respectively. We identified the period 30-35 days after N fertilization as a crucial period for evaluating the effectiveness of management practices on N2O emissions. The time between straw and fertilizer applications was negatively related to N2O emission (R2 = 0.8031; p < 0.01) but positively related to soil CH4 uptake (R2 = 0.7662; p < 0.01). Therefore, early straw incorporation can effectively mitigate greenhouse gas emissions by reducing N2O flux and increasing soil CH4 uptake without significantly decreasing grain yield.

  16. Seasonal CH4 and N2O emissions and plant growth characteristics of several cultivars in direct seeded rice systems

    NASA Astrophysics Data System (ADS)

    Simmonds, M.; Anders, M. M.; Adviento-Borbe, M. A.; Van Kessel, C.; McClung, A.; Linquist, B.

    2014-12-01

    Understanding cultivar effects on field greenhouse gas (GHG) emissions in rice (Oryza sativa L.) systems is needed to improve the accuracy of predictive models used for estimating GHG emissions, and to determine to what extent choice of cultivar may have on GHG mitigation. We compared CH4 and N2O emissions, global warming potential (GWP = N2O + CH4), yield-scaled GWP (GWPY = GWP Mg-1 grain), and plant growth characteristics of 8 cultivars within 4 study sites in California and Arkansas. Seasonal CH4 emissions differed between cultivars by a factor of 2.1 and 1.3 at one California and one Arkansas site, respectively. Nitrous oxide emissions were negligible, comprised <10% of GWP, and were not different among cultivars. When sites and cultivars were pooled, and data were normalized to site averages, there was a positive correlation (r = 0.33) between root biomass at heading and seasonal CH4 emissions, but no correlation with shoot biomass at heading, or grain or straw biomass at maturity. Although differences in GWP and GWPY were observed, the consistency of some of the trends was variable across sites, indicating the importance of the genotype x environment interaction. While no high-yielding and low CH4-emitting cultivars were identified at the California sites, among the Southern varieties tested at the Arkansas site, the lowest emitting cultivar had the highest yield. This highlights the potential for breeding high-yielding varieties with low GWP, the ideal scenario to achieve low GWPY due to simultaneously mitigating GHG emissions and improving global food security.

  17. Hydrogen Migration and Vinylidene Pathway for Formation of Methane in the 193 nm Photodissociation of Propene: CH3CH=CH2 and CD3CD=CD2

    NASA Technical Reports Server (NTRS)

    Zhao, Yi-Lei; Laufer, Allan H.; Halpern, Joshua B.; Fahr, Askar

    2007-01-01

    Photodissociation channels and the final product yields from the 193 nm photolysis of propene-h6 (CH2=CHCH3) and propene-d6 (CD2=CDCD3) have been investigated, employing gas chromatography, mass spectroscopy, and flame ionization (GC/MS/FID) detection methods. The yields of methane as well as butadiene relative to ethane show considerable variations when propene-h6 or propene-d6 are photolyzed. This suggests significant variances in the relative importance of primary photolytic processes and/or secondary radical reactions, occurring subsequent to the photolysis. Theoretical calculations suggest the potential occurrence of an intramolecular dissociation through a mechanism involving vinylidene formation, accompanied by an ethylenic H-migration through the pi-orbitals. This process affects the final yields of methane-h4 versus methane-d4 with respect to other products. The product yields from previous studies of the 193 nm photolysis of methyl vinyl ketone-h6 and -d6 (CH2=CHCOCH3, CD2=CDCOCD3), alternative precursors for generating methyl and vinyl radicals, are compared with the current results for propene.

  18. Infrared photodissociation spectroscopy of H(+)(H2O)6·M(m) (M = Ne, Ar, Kr, Xe, H2, N2, and CH4): messenger-dependent balance between H3O(+) and H5O2(+) core isomers.

    PubMed

    Mizuse, Kenta; Fujii, Asuka

    2011-04-21

    Although messenger mediated spectroscopy is a widely-used technique to study gas phase ionic species, effects of messengers themselves are not necessarily clear. In this study, we report infrared photodissociation spectroscopy of H(+)(H(2)O)(6)·M(m) (M = Ne, Ar, Kr, Xe, H(2), N(2), and CH(4)) in the OH stretch region to investigate messenger(M)-dependent cluster structures of the H(+)(H(2)O)(6) moiety. The H(+)(H(2)O)(6), the protonated water hexamer, is the smallest system in which both the H(3)O(+) (Eigen) and H(5)O(2)(+) (Zundel) hydrated proton motifs coexist. All the spectra show narrower band widths reflecting reduced internal energy (lower vibrational temperature) in comparison with bare H(+)(H(2)O)(6). The Xe-, CH(4)-, and N(2)-mediated spectra show additional band features due to the relatively strong perturbation of the messenger. The observed band patterns in the Ar-, Kr-, Xe-, N(2)-, and CH(4)-mediated spectra are attributed mainly to the "Zundel" type isomer, which is more stable. On the other hand, the Ne- and H(2)-mediated spectra are accounted for by a mixture of the "Eigen" and "Zundel" types, like that of bare H(+)(H(2)O)(6). These results suggest that a messenger sometimes imposes unexpected isomer-selectivity even though it has been thought to be inert. Plausible origins of the isomer-selectivity are also discussed.

  19. Synthesis, structure, and properties of nickel complexes with nitrilotris(methylenephosphonic acid) [Ni(H{sub 2}O)3N(CH2PO{sub 3}H){sub 3}] and Na{sub 4}[Ni(H{sub 2}O)N(CH{sub 2}PO{sub 3}){sub 3}] ∙ 11H{sub 2}O

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Somov, N. V., E-mail: somov@phys.unn.ru; Chausov, F. F., E-mail: chaus@yandex.ru; Zakirova, R. M.

    2016-03-15

    Nitrilotris(methylenephosphonato)triaquanickel and tetrasodium nitrilotris(methylenephosphonato) aquanickelate undecahydrate were synthesized and characterized. The crystal of [Ni(H{sub 2}O){sub 3}N(CH{sub 2}PO{sub 3}H){sub 3}] is composed of linear coordination polymers and belongs to sp. gr. P2{sub 1}/c, Z = 4, a = 9.17120(10) Å, b = 16.05700(10) Å, c = 9.70890(10) Å, β = 115.830(2)°. The Ni atom is in an octahedral coordination formed by two oxygen atoms of one phosphonate ligand, one oxygen atom of another ligand molecule, and three water molecules in a meridional configuration. The crystal of Na{sub 4}[Ni(H{sub 2}O)N(CH{sub 2}PO{sub 3}){sub 3}] ∙ 11H{sub 2}O has an island dimeric chelate structuremore » and belongs to sp. gr. C2/c, Z = 8, a = 18.7152(2) Å, b = 12.05510(10) Å, c = 21.1266(2) Å, β = 104.4960(10)°. The Ni atom has a slightly distorted octahedral coordination involving one nitrogen atom and closes three five-membered N–C–P–O–Ni rings sharing the Ni–N bond.« less

  20. Crystal structure of mer-tris-{2,6-di-fluoro-3-[5-(2-fluoro-phen-yl)pyridin-2-yl-κN]pyridin-4-yl-κC4}iridium(III) di-chloro-methane hemisolvate n-hexane hemisolvate.

    PubMed

    Kang, Youngjin; Park, Ki-Min; Kim, Jinho

    2017-12-01

    The asymmetric unit of the title compound, [Ir(C 17 H 11 F 2 N 2 ) 3 ]·0.5CH 3 (CH 2 ) 4 CH 3 ·0.5CH 2 Cl 2 , comprises one Ir III atom, three 2,6-di-fluoro-3-[5-(2-fluoro-phen-yl)pyridin-2-yl]pyridin-4-yl ligands and half each of an n -hexane and a di-chloro-methane solvent mol-ecule located about crystallographic inversion centres. The Ir III atom displays a distorted octa-hedral coordination geometry, having three C , N -chelating 2,6-di-fluoro-3-[5-(2-fluoro-phen-yl)pyridin-2-yl]pyridin-4-yl ligands arranged in a meridional manner. The Ir III ion lies almost in the equatorial plane [deviation = 0.0069 (15) Å]. The average distance [2.041 (3) Å] of Ir-C bonds is slightly shorter than that [2.076 (3) Å] of Ir-N bonds. A variety of intra- and inter-molecular C-H⋯F and C-H⋯π hydrogen bonds, as well as inter-molecular C-F⋯π inter-actions, contribute to the stabilization of the mol-ecular and crystal structures, and result in the formation of a two-dimensional network parallel to the ab plane. No inter-actions between n -hexane solvent mol-ecules and the other components in the title compound are observed.

  1. Molecular Level Investigation of CH 4 and CO 2 Adsorption in Hydrated Calcium–Montmorillonite

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lee, Mal-Soon; McGrail, B. Peter; Rousseau, Roger

    2017-11-17

    We have studied the mechanism of intercalation and methane adsorption from a H2O/CH4/CO2 mixture on a prototypical shale component, Ca-montmorillonite. We employed ab initio molecular dynamics simulations at 323 K and 90 bar to obtain molecular level information of adsorption energetics, speciation, and structural and thermodynamic properties. Interaction of CH4 with surface Lewis acidic sites (Ca2+, surface OH) results in large induced dipoles (~1 D) that lead to relatively strong adsorption energies that level off once a full CH4 layer is formed. Intercalated CH4, also exhibits induced dipoles at low hydration levels, when the interaction with Ca2+ cations are lessmore » hindered. CO2 displaces CH4 in the coordination sphere of the cations (in the interlayer) or in the surface, thereby driving CH4 extraction. Our simulations indicate that there is a Goldilocks pressure range (~60-100 bar) where scCO2 –facilitated CH4 extraction will be maximized.« less

  2. Sensitivity of the boreal forest-mire ecotone CO2, CH4, and N2O global warming potential to rainy and dry weather

    NASA Astrophysics Data System (ADS)

    Ťupek, Boris; Minkkinen, Kari; Vesala, Timo; Nikinmaa, Eero

    2015-04-01

    In a mosaic of well drained forests and poorly drained mires of boreal landscape the weather events such as drought and rainy control greenhouse gas dynamics and ecosystem global warming potential (GWP). In forest-mire ecotone especially in ecosystems where CO2 sink is nearly balanced with CO2 source, it's fairly unknown whether the net warming effect of emissions of gases with strong radiative forcing (CH4 and N2O) could offset the net cooling effect of CO2 sequestration. We compared the net ecosystem CO2 exchange (NEE) estimated from the carbon sequestrations of forest stands and forest floor CO2 fluxes against CH4 and N2O fluxes of nine forest/mire site types along the soil moisture gradient in Finland. The ground water of nine sites changed between 10 m in upland forests and 0.1 m in mires, and weather during three years ranged between exceptionally wet and dry for the local climate. The NEE of upland forests was typically a sink of CO2, regardless the weather. Though, xeric pine forest was estimated to be a source of CO2 during wet and intermediate year and became a weak sink only in dry year. The NEE of forest-mire transitions ranged between a sink in dry year, while increased stand carbon sequestration could offset the reduced forest floor CO2 emission, and a source in wet year. The NEE of two sparsely forested mires strongly differed. The lawn type mire was balanced around zero and the hummock type mire was relatively strong NEE sink, regardless the weather. Generally, nearly zero N2O emission could not offset the cooling effect of net CH4 sink and net CO2 sink of upland forest and forest-mire transitions. However in sparsely forested mires, with N2O emission also nearly zero, the CH4 emission during wet and intermediate year played important role in turning the net cooling effect of NEE into a net warming. When evaluating GWP of boreal landscapes, undisturbed forest-mire transitions should be regarded as net cooling ecosystems instead of hotspots of net

  3. Methane to methanol conversion induced by thorium oxide through the CH3Th(O)H intermediate in solid argon.

    PubMed

    Gong, Yu; Andrews, Lester; Jackson, Virgil E; Dixon, David A

    2012-10-15

    Reactions of ThO molecules and CH(4) have been investigated in solid argon near 4 K. The CH(3)Th(O)H molecule is produced when the sample is exposed to UV irradiation. Identification of this new intermediate is substantiated by observation of the Th═O and Th-H stretching vibrational modes with isotopic substitution via matrix infrared spectroscopy, and the assignments are supported by electronic structure frequency calculations. Methanol absorptions increase together with formation of the CH(3)Th(O)H molecule, suggesting a methane to methanol conversion induced by thorium oxide proceeding through the CH(3)Th(O)H intermediate. The formation of CH(3)Th(O)H from ThO + CH(4) is exothermic (ΔH(rxn) = -11 kcal/mol) with an energy barrier of 30 kcal/mol at the CCSD(T)//B3LYP level. Decomposition of this intermediate to form methanol involves spin crossing, and the overall reaction from the intermediate is endothermic by 127 kcal/mol. There is no activation energy for the reaction of thorium atoms with methanol to give CH(3)Th(O)H, as observed in separate experiments with Th and CH(3)OH.

  4. Variations of atmospheric CH4, N2O and SF6 over Japan and the East China Sea

    NASA Astrophysics Data System (ADS)

    Ishijima, K.; Goto, D.; Ishidoya, S.; Yashiro, H.; Umezawa, T.; Sugawara, S.; Patra, P. K.; Muromachi, A.; Elkins, J. W.; Dutton, G. S.; Dlugokencky, E. J.; Morimoto, S.; Aoki, S.; Nakazawa, T.

    2013-12-01

    East Asia is one of the most important regions for anthropogenic sources of both short-lived air pollutants and long-lived greenhouse gases (GHGs). According to recent estimates from an emission database, China has become the largest emitter of long-lived GHGs. Since Japan and the East China Sea are located at the east end of Eurasia, atmospheric species emitted from the continent are transported over them throughout the year. Particularly in winter to spring, outflow of the emitted species is enhanced over the East China Sea due to the East Asian Monsoon. To monitor temporal and spatial variability of atmospheric GHGs in the East Asian region, we conducted systematic GHG observations during 2003-2012 from flask samples collected onboard four different commercial ferry boats, which connected between Wakkanai and Rishiri islands (WAK ; 45.4°N, 141.5°E), between Sakaiminato and Oki islands (OKI ; 35.8°N, 133.2°E), between Kagoshima and Okinawa islands (RYU ; 30.0°N, 130.0°E), and between Ishigaki and Hateruma islands (HTR ; 24.0°N, 124.0°E). Air samples were collected almost weekly, and they were sent to Tohoku University and analyzed for GHGs and related gases. In this study, we present analyses of observed CH4, N2O and SF6 concentrations in comparison with simulations by the Atmospheric general circulation model-based Chemistry Transport model (ACTM). The observed three species predictably show higher concentrations than those observed at Cape Kumukahi (KUM), which is a NOAA air sampling site located in the Central Pacific, reflecting strong outflow of the species from East Asia. Annual mean latitudinal gradients found from the four locations as well as decrease toward KUM are generally reproduced by the ACTM. This is mostly because of reasonable spatial distributions in GHG emissions given in the ACTM. The three species also show discernible seasonal cycles. ACTM simulates seasonal cycles of CH4 and SF6 relatively well, but not for N2O, suggesting

  5. Vertical distribution of CH4 and N2O over the tropical site Hyderabad

    NASA Technical Reports Server (NTRS)

    Lal, Shyam; Subbaraya, B. H.; Fabian, Peter; Borchers, R.

    1994-01-01

    Vertical distribution profiles of N2O and CH4 have been measured from Hyderabad, India using a balloon-borne cryogenic air sampler. The samples have been analyzed using gas chromatographic techniques. Results for two balloon flights made in 1987 and 1990 show effects of tropical characteristics like higher tropopause and upwelling motion due to Hadley circulation. These profiles also exhibit perturbations around 25 km height, which are likely to be due to dynamical effects. A comparison with the SAMS data show that the SAMS values for both these gases are higher by a factor of about 1.5 to 2 around 30 km height.

  6. [Effects of combined applications of pig manure and chemical fertilizers on CH4 and N2O emissions and their global warming potentials in paddy fields with double-rice cropping].

    PubMed

    Wang, Cong; Shen, Jian-Lin; Zheng, Liang; Liu, Jie-Yun; Qin, Hong-Ling; Li, Yong; Wu, Jin-Shui

    2014-08-01

    A field experiment was carried out to study the effects of combined applications of pig manure and chemical fertilizers on CH4 and N2O emissions, which were measured using the static chamber/gas chromatography method, and their global warming potentials in typical paddy fields with double-rice cropping in Hunan province. The results showed that the combined applications of pig manure and chemical fertilizers did not change the seasonal patterns of CH4 and N2O emissions from paddy soils, but significantly changed the magnitudes of CH4 and N2O fluxes in rice growing seasons as compared with sole application of chemical fertilizers. During the two rice growing seasons, the cumulative CH4 emissions for the pig manure and chemical nitrogen (N) fertilizer each contributing to 50% of the total applied N (1/2N + PM) treatment were higher than those for the treatments of no N fertilizer (ON), half amount of chemical N fertilizer (1/2N) and 100% chemical N fertilizer (N) by 54.83%, 33.85% and 43.30%, respectively (P < 0.05), whilst the cumulative N2O emissions for the 1/2N + PM treatment were decreased by 67.50% compared with N treatment, but increased by 129.43% and 119.23% compared with ON and 1/2N treatments, respectively (P < 0.05). CH4 was the dominant contributor to the global warming potential (GWP) in both rice growing seasons, which contributed more than 99% to the integrated GWP of CH4 and N2O emissions for all the four treatments. Both GWP and yield-scaled GWP for the treatment of 1/2N + PM were significantly higher than the other three treatments. The yield-scaled GWP for the treatment of 1/2N + PM was higher than those for the N, 1/2N and ON treatments by 58.21%, 26.82% and 20. 63%, respectively. Therefore, combined applications of pig manure and chemical fertilizers in paddy fields would increase the GWP of CH4 and N2O emissions during rice growing seasons and this effect should be considered in regional greenhouse gases emissions inventory.

  7. Permafrost collapse shifts alpine tundra to a carbon source but reduces N2O and CH4 release on the northern Qinghai-Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Mu, C. C.; Abbott, B. W.; Zhao, Q.; Su, H.; Wang, S. F.; Wu, Q. B.; Zhang, T. J.; Wu, X. D.

    2017-09-01

    Important unknowns remain about how abrupt permafrost collapse (thermokarst) affects carbon balance and greenhouse gas flux, limiting our ability to predict the magnitude and timing of the permafrost carbon feedback. We measured monthly, growing-season fluxes of CO2, CH4, and N2O at a large thermokarst feature in alpine tundra on the northern Qinghai-Tibetan Plateau (QTP). Thermokarst formation disrupted plant growth and soil hydrology, shifting the ecosystem from a growing-season carbon sink to a weak source but decreasing feature level CH4 and N2O flux. Temperature-corrected ecosystem respiration from decomposing permafrost soil was 2.7 to 9.5-fold higher than in similar features from Arctic and Boreal regions, suggesting that warmer and dryer conditions on the northern QTP could accelerate carbon decomposition following permafrost collapse. N2O flux was similar to the highest values reported for Arctic ecosystems and was 60% higher from exposed mineral soil on the feature floor, confirming Arctic observations of coupled nitrification and denitrification in collapsed soils. Q10 values for respiration were typically over 4, suggesting high-temperature sensitivity of thawed carbon. Taken together, these results suggest that QTP permafrost carbon in alpine tundra is highly vulnerable to mineralization following thaw, and that N2O production could be an important noncarbon permafrost climate feedback. Permafrost collapse altered soil hydrology, shifting the ecosystem from a carbon sink to carbon source but decreasing CH4 and N2O flux. Little to no vegetation recovery after stabilization suggests potentially large net carbon losses. High N2O flux compared to Arctic and Boreal systems suggests noncarbon permafrost climate feedback.

  8. Modeling methane emissions from Arctic lakes under warming conditions

    NASA Astrophysics Data System (ADS)

    Zhuang, Qianlai; Tan, Zeli

    2014-05-01

    To investigate the response of methane emissions from arctic lakes, a process-based climate-sensitive lake methane model is developed. The processes of methane production, oxidation and transport are modeled within a one-dimensional water and sediment column. Dynamics of point-source ebullition seeps are explicitly modeled. The model was calibrated and verified using observational data in the region. The model was further used to estimate the lake methane emissions from the Arctic from 2002 to 2004. We estimate that the total amount of methane emissions is 24.9 Tg CH4 yr-1, which is consistent with a recent estimation of 24±10 Tg CH4 yr-1 and two-fold of methane emissions from natural wetlands in the north of 60 oN. The methane emission rate of lakes spatially varies over high latitudes from 170.5 mg CH4 m-2 day-1 in northern Siberia to only 10.1 mg CH4 m-2 day-1 in northern Europe. A projection assuming 2-7.5oC warming and 15-25% expansion of lake coverage shows that the total amount of methane emitted from Arctic lakes will increase to 29.8-35.6 Tg CH4 yr-1.

  9. North American terrestrial CO 2 uptake largely offset by CH 4 and N 2O emissions: toward a full accounting of the greenhouse gas budget

    DOE PAGES

    Tian, Hanqin; Chen, Guangsheng; Lu, Chaoqun; ...

    2014-03-14

    The terrestrial ecosystems of North America have been identified as a sink of atmospheric CO 2 though there is no consensus on the magnitude. However, the emissions of non-CO 2 greenhouse gases (CH 4 and N 2O) may offset or even overturn the climate cooling effect induced by the CO 2 sink. Using a coupled biogeochemical model, in this study, we have estimated the combined global warming potentials (GWP) of CO 2, CH 4 and N 2O fluxes in North American terrestrial ecosystems and quantified the relative contributions of environmental factors to the GWP changes during 1979–2010. The uncertainty rangemore » for contemporary global warming potential has been quantified by synthesizing the existing estimates from inventory, forward modeling, and inverse modeling approaches. Our “best estimate” of net GWP for CO 2, CH 4 and N 2O fluxes was₋0.50 ± 0.27 Pg CO 2 eq/year (1 Pg=1015 g) in North American terrestrial ecosystems during 2001–2010. The emissions of CH 4 and N 2O from terrestrial ecosystems had offset about two thirds (73% ± 14%) of the land CO 2 sink in the North American continent, showing large differences across the three countries, with offset ratios of 57% ± 8% in US, 83% ± 17 % in Canada and 329% ± 119 % in Mexico. Climate change and elevated tropospheric ozone concentration have contributed the most to GWP increase, while elevated atmospheric CO 2 concentration have contributed the most to GWP reduction. Extreme drought events over certain periods could result in a positive GWP. By integrating the existing estimates, we have found a wide range of uncertainty for the combined GWP. In conclusion, from both climate change science and policy perspectives, it is necessary to integrate ground and satellite observations with models for a more accurate accounting of these three greenhouse gases in North America.« less

  10. Assessing methane oxidation under landfill covers and its contribution to the above atmospheric CO{sub 2} levels: The added value of the isotope ({delta}{sup 13}C and {delta}{sup 18}O CO{sub 2}; {delta}{sup 13}C and {delta}D CH{sub 4}) approach

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Widory, D., E-mail: d.widory@brgm.fr; Proust, E.; Bellenfant, G.

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer Comparison of the isotope and mass balance approaches to evaluate the level of methane oxidation within a landfill. Black-Right-Pointing-Pointer The level of methane oxidation is not homogenous under the landfill cover and is strongly correlated to the methane flux. Black-Right-Pointing-Pointer Isotope tracking of the contribution of the methane oxidation to the CO{sub 2} concentrations in the ambient air. - Abstract: We are presenting here a multi-isotope approach ({delta}{sup 13}C and {delta}{sup 18}O of CO{sub 2}; {delta}{sup 13}C and {delta}D of CH{sub 4}) to assess (i) the level(s) of methane oxidation during waste biodegradation and its migration through amore » landfill cover in Sonzay (France), and (ii) its contribution to the atmospheric CO{sub 2} levels above the surface. The isotope approach is compared to the more conventional mass balance approach. Results from the two techniques are comparable and show that the CH{sub 4} oxidation under the landfill cover is heterogenous, with low oxidation percentages in samples showing high biogas fluxes, which was expected in clay covers presenting fissures, through which CH{sub 4} is rapidly transported. At shallow depth, more immobile biogas pockets show a higher level of CH{sub 4} oxidation by the methanotrophic bacteria. {delta}{sup 13}C of CO{sub 2} samples taken at different heights (from below the cover up to 8 m above the ground level) were also used to identify and assess the relative contributions of its main sources both under the landfill cover and in the surrounding atmosphere.« less

  11. Drivers of small scale variability in soil-atmosphere fluxes of CH4, N2O and CO2 in a forest soil

    NASA Astrophysics Data System (ADS)

    Maier, Martin; Nicolai, Clara; Wheeler, Denis; Lang, Friedeike; Paulus, Sinikka

    2016-04-01

    Soil-atmosphere fluxes of CH4, N2O and CO2 can vary on different spatial scales, on large scales between ecosystems but also within apparently homogenous sites. While CO2 and CH4 consumption is rather evenly distibuted in well aerated soils, the production of N2O and CH4 seems to occur at hot spots that can be associated with anoxic or suboxic conditions. Small-scale variability in soil properties is well-known from field soil assesment, affecting also soil aeration and thus theoretically, greenhouse gas fluxes. In many cases different plant species are associated with different soil conditions and vegetation mapping should therefor combined with soil mapping. Our research objective was explaining the small scale variability of greenhouse gas fluxes in an apparently homogeneous 50 years old Scots Pine stand in a former riparian flood plain.We combined greenhouse gas measurements and soil physical lab measurments with field soil assessment and vegetation mapping. Measurements were conducted with at 60 points at a plot of 30 X 30 m at the Hartheim monitoring site (SW Germany). For greenhouse gas measurements a non-steady state chamber system and laser analyser, and a photoacoustic analyser were used. Our study shows that the well aerated site was a substantial sink for atmospheric CH4 (-2.4 nmol/m² s) and also a for N2O (-0.4 nmol/m² s), but less pronounced, whereas CO2 production was a magnitude larger (2.6 μmol/m² s). The spatial variability of the CH4 consumption of the soils could be explained by the variability of the soil gas diffusivity (measured in situ + using soil cores). Deviations of this clear trend were only observed at points where decomposing woody debris was directly under the litter layer. Soil texture ranged from gravel, coarse sand, fine sand to pure silt, with coarser texture having higher soil gas diffusivity. Changes in texture were rather abrupt at some positions or gradual at other positions, and were well reflected in the vegetation

  12. Differential retention and release of CO 2 and CH 4 in kerogen nanopores: Implications for gas extraction and carbon sequestration

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ho, Tuan Anh; Wang, Yifeng; Xiong, Yongliang

    Methane (CH 4) and carbon dioxide (CO 2), the two major components generated from kerogen maturation, are stored dominantly in nanometer-sized pores in shale matrix as (1) a compressed gas, (2) an adsorbed surface species and/or (3) a species dissolved in pore water (H 2O). In addition, supercritical CO 2 has been proposed as a fracturing fluid for simultaneous enhanced oil/gas recovery (EOR) and carbon sequestration. A mechanistic understanding of CH 4-CO 2-H 2O interactions in shale nanopores is critical for designing effective operational processes. Using molecular simulations, we show that kerogen preferentially retains CO 2 over CH 4 andmore » that the majority of CO 2 either generated during kerogen maturation or injected in EOR will remain trapped in the kerogen matrix. The trapped CO 2 may be released only if the reservoir pressure drops below the supercritical CO 2 pressure. When water is present in the kerogen matrix, it may block CH 4 release. Furthermore, the addition of CO 2 may enhance CH 4 release because CO 2 can diffuse through water and exchange for adsorbed methane in the kerogen nanopores.« less

  13. Differential retention and release of CO 2 and CH 4 in kerogen nanopores: Implications for gas extraction and carbon sequestration

    DOE PAGES

    Ho, Tuan Anh; Wang, Yifeng; Xiong, Yongliang; ...

    2018-02-06

    Methane (CH 4) and carbon dioxide (CO 2), the two major components generated from kerogen maturation, are stored dominantly in nanometer-sized pores in shale matrix as (1) a compressed gas, (2) an adsorbed surface species and/or (3) a species dissolved in pore water (H 2O). In addition, supercritical CO 2 has been proposed as a fracturing fluid for simultaneous enhanced oil/gas recovery (EOR) and carbon sequestration. A mechanistic understanding of CH 4-CO 2-H 2O interactions in shale nanopores is critical for designing effective operational processes. Using molecular simulations, we show that kerogen preferentially retains CO 2 over CH 4 andmore » that the majority of CO 2 either generated during kerogen maturation or injected in EOR will remain trapped in the kerogen matrix. The trapped CO 2 may be released only if the reservoir pressure drops below the supercritical CO 2 pressure. When water is present in the kerogen matrix, it may block CH 4 release. Furthermore, the addition of CO 2 may enhance CH 4 release because CO 2 can diffuse through water and exchange for adsorbed methane in the kerogen nanopores.« less

  14. The H2/CH4 ratio during serpentinization cannot reliably identify biological signatures

    NASA Astrophysics Data System (ADS)

    Huang, Ruifang; Sun, Weidong; Liu, Jinzhong; Ding, Xing; Peng, Shaobang; Zhan, Wenhuan

    2016-09-01

    Serpentinization potentially contributes to the origin and evolution of life during early history of the Earth. Serpentinization produces molecular hydrogen (H2) that can be utilized by microorganisms to gain metabolic energy. Methane can be formed through reactions between molecular hydrogen and oxidized carbon (e.g., carbon dioxide) or through biotic processes. A simple criterion, the H2/CH4 ratio, has been proposed to differentiate abiotic from biotic methane, with values approximately larger than 40 for abiotic methane and values of <40 for biotic methane. The definition of the criterion was based on two serpentinization experiments at 200 °C and 0.3 kbar. However, it is not clear whether the criterion is applicable at a wider range of temperatures. In this study, we performed sixteen experiments at 311-500 °C and 3.0 kbar using natural ground peridotite. Our results demonstrate that the H2/CH4 ratios strongly depend on temperature. At 311 °C and 3.0 kbar, the H2/CH4 ratios ranged from 58 to 2,120, much greater than the critical value of 40. By contrast, at 400-500 °C, the H2/CH4 ratios were much lower, ranging from 0.1 to 8.2. The results of this study suggest that the H2/CH4 ratios cannot reliably discriminate abiotic from biotic methane.

  15. The H2/CH4 ratio during serpentinization cannot reliably identify biological signatures

    PubMed Central

    Huang, Ruifang; Sun, Weidong; Liu, Jinzhong; Ding, Xing; Peng, Shaobang; Zhan, Wenhuan

    2016-01-01

    Serpentinization potentially contributes to the origin and evolution of life during early history of the Earth. Serpentinization produces molecular hydrogen (H2) that can be utilized by microorganisms to gain metabolic energy. Methane can be formed through reactions between molecular hydrogen and oxidized carbon (e.g., carbon dioxide) or through biotic processes. A simple criterion, the H2/CH4 ratio, has been proposed to differentiate abiotic from biotic methane, with values approximately larger than 40 for abiotic methane and values of <40 for biotic methane. The definition of the criterion was based on two serpentinization experiments at 200 °C and 0.3 kbar. However, it is not clear whether the criterion is applicable at a wider range of temperatures. In this study, we performed sixteen experiments at 311–500 °C and 3.0 kbar using natural ground peridotite. Our results demonstrate that the H2/CH4 ratios strongly depend on temperature. At 311 °C and 3.0 kbar, the H2/CH4 ratios ranged from 58 to 2,120, much greater than the critical value of 40. By contrast, at 400–500 °C, the H2/CH4 ratios were much lower, ranging from 0.1 to 8.2. The results of this study suggest that the H2/CH4 ratios cannot reliably discriminate abiotic from biotic methane. PMID:27666288

  16. The H2/CH4 ratio during serpentinization cannot reliably identify biological signatures.

    PubMed

    Huang, Ruifang; Sun, Weidong; Liu, Jinzhong; Ding, Xing; Peng, Shaobang; Zhan, Wenhuan

    2016-09-26

    Serpentinization potentially contributes to the origin and evolution of life during early history of the Earth. Serpentinization produces molecular hydrogen (H 2 ) that can be utilized by microorganisms to gain metabolic energy. Methane can be formed through reactions between molecular hydrogen and oxidized carbon (e.g., carbon dioxide) or through biotic processes. A simple criterion, the H 2 /CH 4 ratio, has been proposed to differentiate abiotic from biotic methane, with values approximately larger than 40 for abiotic methane and values of <40 for biotic methane. The definition of the criterion was based on two serpentinization experiments at 200 °C and 0.3 kbar. However, it is not clear whether the criterion is applicable at a wider range of temperatures. In this study, we performed sixteen experiments at 311-500 °C and 3.0 kbar using natural ground peridotite. Our results demonstrate that the H 2 /CH 4 ratios strongly depend on temperature. At 311 °C and 3.0 kbar, the H 2 /CH 4 ratios ranged from 58 to 2,120, much greater than the critical value of 40. By contrast, at 400-500 °C, the H 2 /CH 4 ratios were much lower, ranging from 0.1 to 8.2. The results of this study suggest that the H 2 /CH 4 ratios cannot reliably discriminate abiotic from biotic methane.

  17. Effects of N loading rate on CH4 and N2O emissions during cultivation and fallow periods from forage rice fields fertilized with liquid cattle waste.

    PubMed

    Riya, S; Zhou, S; Kobara, Y; Sagehashi, M; Terada, A; Hosomi, M

    2015-09-15

    The use of liquid cattle waste (LCW) as a fertilizer for forage rice is important for material recycling because it can promote biomass production, and reduce the use of chemical fertilizer. Meanwhile, increase in emission of greenhouse gases (GHGs), especially CH4 and N2O would be concerned. We conducted a field study to determine the optimum loading rate of LCW as N to promote forage rice growth with lower GHG emissions. The LCW was applied to forage rice fields, N100, N250, N500, and N750, at four different N loading rates of 107, 258, 522, and 786 kg N ha(-1), respectively, including 50 kg N ha(-1) of basal chemical fertilizer. The above-ground biomass yields increased 14.6-18.5 t ha(-1) with increases in N loading rates. During the cultivation period, both the CH4 and N2O fluxes increased with increases in LCW loading rates. In the treatments of N100, N250, N500, and N750, the cumulative CH4 emissions during the entire period, including cultivation and fallow period were 29.6, 18.1, 54.4, and 67.5 kg C ha(-1), respectively, whereas those of N2O were -0.15, -0.02, 1.49, and 5.82 kg N ha(-1), respectively. Considering the greenhouse gas emissions and above-ground biomass, the yield-scaled CO2-equivalents (CO2-eqs) were 66.3, 35.9, 161, and 272 kg CO2 t(-1) for N100, N250, N500, and N750, respectively. These results suggest that N250 is the most appropriate LCW loading rate for promoting forage rice production with lower GHG emissions. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. The Structure of Titan’s N2 and CH4 Coronae

    NASA Astrophysics Data System (ADS)

    Jiang, Fayu; Cui, Jun; Xu, Jiyao

    2017-12-01

    In this study, we analyze the structures of Titan’s N2 and CH4 coronae using a large data set acquired by the Ion Neutral Mass Spectrometer (INMS) instrument on board Cassini. The N2 and CH4 densities measured from the exobase up to 2000 km imply a mean exobase temperature of 146 K and 143 K, respectively, which is lower than the mean upper atmospheric temperature by 4 and 7 K. This indicates that on average, Titan possesses a subthermal rather than suprathermal corona. A careful examination reveals that the variability in corona structure is not very likely to be solar driven. Within the framework of the collisionless kinetic model, we investigate how the CH4 energy distribution near the exobase could be constrained if strong CH4 escape occurs on Titan. Several functional forms for the CH4 energy distribution are attempted, assuming two representative CH4 escape rates of 1.2× {10}25 s-1 and 2.2× {10}27 s-1. We find that the double Maxwellian and power-law distributions can reproduce the shape of the CH4 corona structure as well as the imposed CH4 escape rate. In both cases, the escape rate is contributed by a suprathermal CH4 population on the high-energy tail, with a number fraction below 5% and a characteristic energy of 0.1-0.6 eV per suprathermal CH4 molecule. The coexistence of the subthermal CH4 corona revealed by the INMS data and substantial CH4 escape suggested by some previous works could be reconciled by a significant departure in the exobase CH4 energy distribution from ideal Maxwellian that enhances escape and causes a noticeable redistribution of the corona structure.

  19. Highly Permeable AlPO-18 Membranes for N 2 /CH 4 Separation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zong, Zhaowang; Elsaidi, Sameh K.; Thallapally, Praveen K.

    Herein we demonstrate that AlPO-18 membranes can separate N2/CH4 gas mixtures at unprecedented N2 permeances. The best membranes separated N2/CH4 mixtures with N2 permeances as high as 3076 GPU and separation selectivities as high as 4.6. Gas mixture separation data, N2 and CH4 adsorption isotherms, ideal adsorbed solution theory (IAST), and breakthrough experiments were collected to understand the separation mechanisms. Competitive adsorption and differences in diffusivities were identified as the prevailing separation mechanisms. Differences in diffusivity played a more dominant role than the competitive adsorption, and led to nitrogen selective membranes.

  20. Synthesis, spectral and antifungal analysis of diaryldithiophosphates of mono- and dibutyltin(IV): x-ray structure of [{(3,5-CH3)2C6H3O)2PS2}2Sn(nBu)2].

    PubMed

    Syed, Atiya; Khajuria, Ruchi; Kumar, Sandeep; Jassal, Amanpreet Kaur; Hundal, Maninder S; Pandey, Sushil K

    2014-01-01

    Diaryldithiophosphate complexes of mono- and dibutyltin(IV) corresponding to [(ArO)(2)PS(2)(n)Sn(nBu)xCl(4-x-n)] (Ar = o-CH(3)C(6)H(4), m-CH(3)C(6)H(4), p-CH(3)C(6)H(4), 4-Cl-3-CH(3)C(6)H(3), (3,5-CH(3))(2)C(6)H(3); n = 1, 2 for x = 1 and n = 2 for x = 2) were successfully isolated and characterized by elemental analyses, IR, multinuclear NMR ((1)H, (13)C, (31)P and (119)Sn) spectroscopy and X-ray analysis. The thermal properties of the complex [(3,5-CH(3))(2)C(6)H(3)O(2)PS(2)](2)Sn(nBu)(2) (12) have been examined by combined DTA/ DTG thermal analyses. Single crystal X-ray analysis of [(3,5-CH(3))(2)C(6)H(3)O(2)PS(2)](2)S(n)(nBu)(2) (12) revealed that two diaryldithiophosphate ions are coordinated to tin atom in an anisobidentate fashion through the sulfur atoms of each dithiophosphate moiety leading to distorted skew-trapezoidal bipyramidal geometry. The antifungal activity depicts that these complexes are active against fungus Penicillium chrysogenium.

  1. Spatial variability of greenhouse gases emissions (CO2, CH4, N2O) in a tropical hydroelectric reservoir flooding primary forest (Petit Saut Reservoir, French Guiana)

    NASA Astrophysics Data System (ADS)

    Cailleaud, Emilie; Guérin, Frédéric; Bouillon, Steven; Sarrazin, Max; Serça, Dominique

    2014-05-01

    At the Petit Saut Reservoir (PSR, French Guiana, South America), vertical profiles were performed at 5 stations in the open waters (OW) and 6 stations in two shallow flooded forest (FF) areas between April 2012 and September 2013. Measurements included physico-chemical parameters, ammonium, nitrate and dissolved greenhouse gas (CO2, CH4, N2O) concentrations, dissolved and particulate organic carbon (DOC, POC) and nitrogen (PN), δ13C-POC and δ15N-PN . The diffusive fluxes were calculated from surface concentrations. The aim of this study was to estimate the spatial variations of greenhouse gas emissions at a dentrical hydroelectric reservoir located in the tropics and flooding primary forest. Twenty years after impoundment, the water column of the PSR is permanently and tightly stratified thermally in the FF whereas in the OW, the thermal gradients are not as stable. The different hydrodynamical behaviours between the two different zones have significant consequences on the biogeochemistry: oxygen barely diffuses down to the hypolimnion in the FF whereas destratification occurs sporadically during the rainy season in the OW. Although we found the same range of POC in the FF and the OW (2.5-29 μmol L-1) and 20% more DOC at the bottom of OW than in the FF (229-878 μmol L-1), CO2 and CH4 concentrations were always significantly higher in the FF (CO2: 11-1412 μmol L-1, CH4: 0.001-1015 μmol L-1) than in the OW. On average, the CO2 concentrations were 30-40% higher in the FF than in the OW and the CH4 concentrations were three times higher in the FF than in the OW. The δ13C-POC and C:N values did not suggest substantial differences in the sources of OM between the FF and OW. At all stations, POC at the bottom has an isotopic signature slightly lighter than the terrestrial OM in the surrounding forest whereas the isotopic signature of surface POM would result from phytoplankton and methanotrophs. The vertical profiles of nitrogen compounds reveal that the main

  2. Leachate treatment in landfills is a significant N2O source.

    PubMed

    Wang, Xiaojun; Jia, Mingsheng; Zhang, Chengliang; Chen, Shaohua; Cai, Zucong

    2017-10-15

    The importance of methane (CH 4 ) emissions from landfills has been extensively documented, while the nitrous oxide (N 2 O) emissions from landfills are considered negligible. In this study, three landfills were selected to measure CH 4 and N 2 O emissions using the static chamber method. Dongbu (DB) and Dongfu (DF) landfills, both located in Xiamen city, Fujian Province, were classified as sanitary. The former started to receive solid waste from Xiamen city in 2009, and the latter was closed in 2009. Nanjing (NJ) landfill, located in Nanjing county, Fujian Province, was classified as managed. Results showed that for the landfill reservoirs, CH 4 emissions were significant, while N 2 O emissions occurred mainly in operating areas (on average, 16.3 and 19.0mgN 2 Om -2 h -1 for DB and NJ landfills, respectively) and made a negligible contribution to the total greenhouse gas emissions in term of CO 2 equivalent. However, significant N 2 O emissions were observed in the leachate treatment systems of sanitary landfills and contributed 72.8% and 45.6% of total emissions in term of CO 2 equivalent in DB and DF landfills, respectively. The N 2 O emission factor (EF) of the leachate treatment systems was in the range of 8.9-11.9% of the removed nitrogen. The total N 2 O emissions from the leachate treatment systems of landfills in Xiamen city were estimated to be as high as 8.55gN 2 O-Ncapita -1 yr -1 . These results indicated that N 2 O emissions from leachate treatment systems of sanitary landfills were not negligible and should be included in national and/or local inventories of greenhouse gas emissions. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Is CH4 consumption by soils controlled by physics or biology? Results from a study of plot-scale variability of greenhouse gas fluxes

    NASA Astrophysics Data System (ADS)

    Maier, Martin; Paulus, Sinikka; Nicolai, Clara; Nauer, Philipp

    2017-04-01

    Soil-atmosphere fluxes of trace gases vary on different spatial scales, between landscapes and ecosystems down to the plot scale within apparently homogenous sites. The production and consumption of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) underlie different spatial and temporal changes, und thus, their interrelation is difficult to unravel. Small-scale variability in soil properties is well-known from soil surveys, affecting theoretically water availability for plants, soil aeration, vegetation, the local photosynthesis rate, and, eventually, greenhouse gas fluxes. We investigated the small scale variability of greenhouse gas fluxes in a homogenous Scots Pine stand in a former riparian flood plain. Soil-atmosphere fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) were carried out at 60 points on a 250 m2 plot with strata of diverse soil substrates and understory vegetation. Gas flux measurements were combined with soil physical lab measurements, and a soil vegetation survey. The soil was a source of CO2 and a sink for CH4 and N2O. No correlations between the fluxes and only weak correlations between the fluxes and soil physical factors were observed. CH4 and CO2 fluxes were significantly different for the soil-vegetation strata. Separating the dataset into the different soil-vegetation strata showed that CH4 consumption increased significantly with soil gas diffusivity and soil respiration. Methane consumption in the silt stratum was higher at a given soil gas diffusivity than in the sand stratum, indicating a higher methanotrophic microbe population and thus better habitats in silt. CH4 consumption increased with soil respiration in all strata, so that we speculate that the rhizosphere and decomposing organic litter (as origin of most of the soil respiration) facilitate a preferred habitat of methanotrophic microbes. The patterns of N2O consumption were more complex, but consumption seemed to be limited at locations with

  4. A two-dimensional model with coupled dynamics, radiative transfer, and photochemistry. 2: Assessment of the response of stratospheric ozone to increased levels of CO2, N2O, CH4, and CFC

    NASA Technical Reports Server (NTRS)

    Schneider, Hans R.; Ko, Malcolm K. W.; Shia, Run-Lie; Sze, Nien-Dak

    1993-01-01

    The impact of increased levels of carbon dioxide (CO2), chlorofluorocarbons (CFCs), and other trace gases on stratospheric ozone is investigated with an interactive, two-dimensional model of gas phase chemistry, dynamics, and radiation. The scenarios considered are (1) a doubling of the CO2 concentration, (2) increases of CFCs, (3) CFC increases combined with increases of nitrous oxide (N2O) and methane CH4, and (4) the simultaneous increase of CO2, CFCs, N2O, and CH4. The radiative feedback and the effect of temperature and circulation changes are studied for each scenario. For the double CO2 calculations the tropospheric warming was specified. The CO2 doubling leads to a 3.1% increase in the global ozone content. Doubling of the CO2 concentrations would lead to a maximum cooling of about 12 C at 45 km if the ozone concentration were held fixed. The cooling of the stratosphere leads to an ozone increase with an associated increase in solar heating, reducing the maximum temperature drop by about 3 C. The CFC increase from continuous emissions at 1985 rate causes a 4.5% loss of ozone. For the combined perturbations a net loss of 1.3% is calculated. The structure of the perturbations shows a north-south asymmetry. Ozone losses (when expressed in terms of percent changes) are generally larger in the high latitudes of the southern hemisphere as a result of the eddy mixing being smaller than in the northern hemisphere. Increase of chlorine leads to ozone losses above 30 km altitude where the radiative feedback results in a cooler temperature and an ozone recovery of about one quarter of the losses predicted with a noninteractive model. In all the cases, changes in circulation are small. In the chlorine case, circulation changes reduce the calculated column depletion by about one tenth compared to offline calculations.

  5. Reflected shock tube studies of high-temperature rate constants for OH + CH4 --> CH3 + H2O and CH3 + NO2 --> CH3O + NO.

    PubMed

    Srinivasan, N K; Su, M-C; Sutherland, J W; Michael, J V

    2005-03-10

    The reflected shock tube technique with multipass absorption spectrometric detection of OH radicals at 308 nm has been used to study the reactions OH + CH(4) --> CH(3) + H(2)O and CH(3) + NO(2) --> CH(3)O + NO. Over the temperature range 840-2025 K, the rate constants for the first reaction can be represented by the Arrhenius expression k = (9.52 +/- 1.62) x 10(-11) exp[(-4134 +/- 222 K)/T] cm(3) molecule(-1) s(-1). Since this reaction is important in both combustion and atmospheric chemistry, there have been many prior investigations with a variety of techniques. The present results extend the temperature range by 500 K and have been combined with the most accurate earlier studies to derive an evaluation over the extended temperature range 195-2025 K. A three-parameter expression describes the rate behavior over this temperature range, k = (1.66 x 10(-18))T(2.182) exp[(-1231 K)/T] cm(3) molecule(-1) s(-1). Previous theoretical studies are discussed, and the present evaluation is compared to earlier theoretical estimates. Since CH(3) radicals are a product of the reaction and could cause secondary perturbations in rate constant determinations, the second reaction was studied by OH radical production from the fast reactions CH(3)O --> CH(2)O + H and H + NO(2) --> OH + NO. The measured rate constant is 2.26 x 10(-11) cm(3) molecule(-1) s(-1) and is not dependent on temperature from 233 to 1700 K within experimental error.

  6. CH4 emissions from European Major Population Centers: Results from aircraft-borne CH4 in-situ observations during EMeRGe-Europe campaign 2017

    NASA Astrophysics Data System (ADS)

    Roiger, A.; Klausner, T.; Schlager, H.; Ziereis, H.; Huntrieser, H.; Baumann, R.; Eirenschmalz, L.; Joeckel, P.; Mertens, M.; Fisher, R.; Bauguitte, S.; Young, S.; Andrés Hernández, M. D.

    2017-12-01

    Urban environments represent large and diffuse area sources of CH4 including emissions from pipeline leaks, industrial/sewage treatment plants, and landfills. However, there is little knowledge about the exact magnitude of these emissions and their contribution to total anthropogenic CH4. Especially in the context of an urbanizing world, a better understanding of the methane footprint of urban areas is crucial, both with respect to mitigation and projection of climate impacts. Aircraft-borne in-situ measurements are particularly useful to both quantify emissions from such area sources, as well as to study their impact on the regional distribution. However, airborne CH4 observations downstream of European cities are especially sparse.Here we report from aircraft-borne CH4 in-situ measurements as conducted during the HALO aircraft campaign EMeRGe (Effect of Megacities on the Transport and Transformation of Pollutants on the Regional to Global Scales) in July 2017, which was led by the University of Bremen, Germany. During seven research flights, emissions from a variety of European (Mega)-cities were probed at different altitudes from 3km down to 500m, including measurements in the outflows of London, Rome, Po Valley, Ruhr and Benelux. We will present and compare the CH4 distribution measured downstream of the various studied urban hot-spots. With the help of other trace gas measurements (including e.g. CO2, CO, O3, SO2), observed methane enhancements will be attributed to the different potential source types. Finally, by the combination of in-situ measurements and regional model simulations using the EMAC-MECO(n) model, the contribution of emissions from urban centers to the regional methane budget over Europe will be discussed.

  7. μ-Carbonato-κ(4) O,O':O',O''-bis-{[2'-(di-tert-butyl-phosphan-yl)biphenyl-2-yl-κ(2) P,C (1)]palladium(II)} dichloro-methane monosolvate.

    PubMed

    Muller, Alfred; Holzapfel, Cedric W

    2012-12-01

    The title compound, [(μ2-CO3){Pd(P(t-C4H9)2(C12H8)}2CH2Cl2, the first CO3-bridged palladium dimer complex reported to date, was obtained while preparing the Pd(0) complex with (2-biphen-yl)P( (t) Bu)2. In the crystal, each palladium dimer is accompanied by a dichloro-methane solvent mol-ecule. Coordination of the carbonate and chelated phosphane ligands gives distorted square-planar environments at the Pd atoms. Important geometrical parameters include Pd-P(av.) = 2.2135 (4) Å, Pd-C(av.) = 1.9648 (16) Å and P-Pd-C = 84.05 (5) and 87.98 (5)°, and O-Pd-O' = 60.56 (4) and 61.13 (4)°. Bonding with the carbonate O atoms shows values of 2.1616 (11) and 2.1452 (11) Å for the Pd-O-Pd bridge, whereas other Pd-O distances are slightly longer at 2.2136 (11) and 2.1946 (11) Å. One of the tert-butyl groups is disordered over two set of sites with an occupancy ratio of 0.723 (6):0.277 (6). Weak C-H⋯O interactions are observed propagating the molecules along the [100] direction.

  8. Effects of Boreal Lake Wetlands on Atmospheric 13CH3D and 12CH2D2

    NASA Astrophysics Data System (ADS)

    Haghnegahdar, M. A.; Kohl, I. E.; Schauble, E. A.; Walter Anthony, K. M.; Young, E. D.

    2017-12-01

    Recently, we developed a theoretical model to investigate the potential use of 13CH3D and 12CH2D2 as tools for tracking atmospheric methane budget. We used electronic structure methods to estimate kinetic isotope fractionations associated with the major sink reactions of CH4 in air (reactions with •OH and Cl•), and literature data with reconnaissance measurements of the relative abundances of 13CH3D and 12CH2D2 to estimate the compositions of the largest atmospheric sources. Here we present new methane rare isotopologue data from boreal wetlands, comprising one of the most important sources, in order to evaluate the robustness of the model. Boreal wetlands (>55° N) account for more than half of the wetland area in the Northern hemisphere. We analyzed methane samples from high latitude lakes representing different geographical regions, geological and ecological contexts, methane fluxes, and isotopic signatures. Using clumped isotopes of CH4 we are able to determine the likely production mechanism for natural CH4 samples. So far, all of our analyzed samples except one plot in the microbial pure-culture methanogenesis field (Young et al. 2017) with ranges of -0.2‰ to +1.2‰ for Δ13CH3D, and -29.6‰ to -18.2‰ for Δ12CH2D2. These compositions are far from equilibrium. The one exception, from Lake Doughnut, Alaska, exhibits Δ13CH3D and Δ12CH2D2 values of +5.2‰ and +18.7‰, respectively, which fall near ambient thermodynamic equilibrium values. This may be an effect of methanotrophy. Mean Δ13CH3D and Δ12CH2D2 for all lake samples are +1.7‰ and -15.4‰ respectively, compared to our original estimate of +6.1‰ and +21.2‰ for the wetland methane source based on an assumption of equilibrium. If we assume that these samples are representative of the overall wetland source, Δ13CH3D decreases by 0.8‰ and Δ12CH2D2 decreases by 0.6‰ in our model of bulk atmospheric methane. Δ13CH3D and Δ12CH2D2 values of air (including •OH and Cl• sink

  9. Bioelectrochemical methane (CH4) production in anaerobic digestion at different supplemental voltages.

    PubMed

    Choi, Kwang-Soon; Kondaveeti, Sanath; Min, Booki

    2017-12-01

    Microbial electrolysis cells (MECs) at various cell voltages (0.5, 0.7 1.0 and 1.5V) were operated in anaerobic fermentation. During the start-up period, the cathode potential decreased from -0.63 to -1.01V, and CH 4 generation increased from 168 to 199ml. At an applied voltage of 1.0V, the highest methane yields of 408.3ml CH 4 /g COD glucose was obtained, which was 30.3% higher than in the control tests (313.4ml CH 4 /g COD glucose). The average current of 5.1mA was generated at 1.0V at which the maximum methane yield was obtained. The other average currents were 1.42, 3.02, 0.53mA at 0.5, 0.7, and 1.5V, respectively. Cyclic voltammetry and EIS analysis revealed that enhanced reduction currents were present at all cell voltages with biocatalyzed cathode electrodes (no reduction without biofilm), and the highest value was obtained with 1V external voltage. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Endohedral complexes of fullerene-like silica molecules with H2O, CH4, and CH3NH2 molecules

    NASA Astrophysics Data System (ADS)

    Filonenko, O. V.; Lobanov, V. V.

    2013-07-01

    The possibility of formation of (SiO2)60@H2O, (SiO2)60@CH4, and (SiO2)60@CH3NH2 endohedral complexes was studied by the density functional (DFT) method (B3LYP exchange correlation functional, 6-31G** basis). The penetration of these molecules into the cavity of fullerene-like silica molecules is hindered by high activation barriers, which ensures the stability of the complexes formed during the synthesis of these molecules.

  11. Dual stable isotopes of CH 4 from Yellowstone hot-springs suggest hydrothermal processes involving magmatic CO 2

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Moran, James J.; Whitmore, Laura M.; Jay, Zackary J.

    Volcanism and post-magmatism contribute significant annual methane (CH 4) fluxes to the atmosphere (on par with other natural sources such as forest fire and wild animal emissions) and have been implicated in past climate-change events. The Yellowstone hot spot is one of the largest volcanic systems on Earth and is known to emit CH 4 (as well as carbon dioxide (CO 2) and other gases), but the ultimate sources of this CH 4 flux have not been elucidated. In this paper, we use dual stable isotope analysis (δ 2H and δ 13C) of CH 4 sampled from ten high-temperature geothermalmore » pools in Yellowstone National Park along with other isotopic and gas analyses to evaluate potential sources of methane. The average δ 13C and δ 2H values of CH 4 emitted from hot springs ( 26.7 (± 2.4) and - 236.9 (± 12.0) ‰, respectively) are inconsistent with microbial methanogenesis but do not allow distinction between thermogenic and abiotic sources. Correlation between δ 13C CH4 and δ 13C of dissolved inorganic C (DIC) is consistent with DIC as the parent C source for the observed CH 4, or with equilibration of CH 4 and DIC. Methane formation temperatures estimated by isotopic geothermometry based on δ 13C CH4 and δ 13C CO2 ranged from ~ 250–350 °C, which is just below previous temperature estimates for the hydrothermal reservoir. Further, the δ 2H H2O of the thermal springs and the measured δ 2H CH4 values are consistent with equilibration between the source water and the CH 4 at the formation temperatures. Though the ultimate origin of the CH 4 could be attributed to either abiotic of themorgenic processes with subsequent isotopic equilibration, the C 1/C 2+ composition of the gases is more consistent with abiotic origins for most of the samples. Finally, our data support the hypothesis that subsurface rock-water interactions are responsible for at least a significant fraction of the CH 4 flux from the Yellowstone National Park volcanic system.« less

  12. Dual stable isotopes of CH 4 from Yellowstone hot-springs suggest hydrothermal processes involving magmatic CO 2

    DOE PAGES

    Moran, James J.; Whitmore, Laura M.; Jay, Zackary J.; ...

    2017-05-16

    Volcanism and post-magmatism contribute significant annual methane (CH 4) fluxes to the atmosphere (on par with other natural sources such as forest fire and wild animal emissions) and have been implicated in past climate-change events. The Yellowstone hot spot is one of the largest volcanic systems on Earth and is known to emit CH 4 (as well as carbon dioxide (CO 2) and other gases), but the ultimate sources of this CH 4 flux have not been elucidated. In this paper, we use dual stable isotope analysis (δ 2H and δ 13C) of CH 4 sampled from ten high-temperature geothermalmore » pools in Yellowstone National Park along with other isotopic and gas analyses to evaluate potential sources of methane. The average δ 13C and δ 2H values of CH 4 emitted from hot springs ( 26.7 (± 2.4) and - 236.9 (± 12.0) ‰, respectively) are inconsistent with microbial methanogenesis but do not allow distinction between thermogenic and abiotic sources. Correlation between δ 13C CH4 and δ 13C of dissolved inorganic C (DIC) is consistent with DIC as the parent C source for the observed CH 4, or with equilibration of CH 4 and DIC. Methane formation temperatures estimated by isotopic geothermometry based on δ 13C CH4 and δ 13C CO2 ranged from ~ 250–350 °C, which is just below previous temperature estimates for the hydrothermal reservoir. Further, the δ 2H H2O of the thermal springs and the measured δ 2H CH4 values are consistent with equilibration between the source water and the CH 4 at the formation temperatures. Though the ultimate origin of the CH 4 could be attributed to either abiotic of themorgenic processes with subsequent isotopic equilibration, the C 1/C 2+ composition of the gases is more consistent with abiotic origins for most of the samples. Finally, our data support the hypothesis that subsurface rock-water interactions are responsible for at least a significant fraction of the CH 4 flux from the Yellowstone National Park volcanic system.« less

  13. Experimental and theoretical study of the gas phase reaction of ethynyl radical with methane (HCC+CH 4)

    NASA Astrophysics Data System (ADS)

    Ceursters, Benny; Thi Nguyen, Hue Minh; Peeters, Jozef; Tho Nguyen, Minh

    2000-10-01

    Absolute rate coefficients of the reaction of ethynyl radical with methane were measured for the first time at higher temperatures by a pulsed laser photolysis/chemiluminescence (PLP/CL) technique. Ethynyl radicals (HCC) radicals were generated pulsewise upon excimer laser photodissociation of acetylene at 193 nm and pseudo-first-order exponential decays of thermalized HCC were monitored in real-time by the CH( A2Δ → X2Π ) chemiluminescence produced by their reaction with O 2. The rate coefficients k(HCC+CH 4), over 295⩽T ( K)<800 , exhibit strong non-Arrhenius behaviour, being k(T)=1.39×10 -18T 2.34±0.40exp[(380±180) K/T] cm3 molecule-1 s-1. Calculations at the CCSD(T)/aug-cc-pvTZ level reveal that the direct H-abstraction yielding HCCH+CH 3 has the lowest energy barrier of about 10 kJ mol -1.

  14. The development and evaluation of airborne in situ N2O and CH4 sampling using a quantum cascade laser absorption spectrometer (QCLAS)

    NASA Astrophysics Data System (ADS)

    Pitt, J. R.; Le Breton, M.; Allen, G.; Percival, C. J.; Gallagher, M. W.; Bauguitte, S. J.-B.; O'Shea, S. J.; Muller, J. B. A.; Zahniser, M. S.; Pyle, J.; Palmer, P. I.

    2016-01-01

    Spectroscopic measurements of atmospheric N2O and CH4 mole fractions were made on board the FAAM (Facility for Airborne Atmospheric Measurements) large atmospheric research aircraft. We present details of the mid-infrared quantum cascade laser absorption spectrometer (QCLAS, Aerodyne Research Inc., USA) employed, including its configuration for airborne sampling, and evaluate its performance over 17 flights conducted during summer 2014. Two different methods of correcting for the influence of water vapour on the spectroscopic retrievals are compared and evaluated. A new in-flight calibration procedure to account for the observed sensitivity of the instrument to ambient pressure changes is described, and its impact on instrument performance is assessed. Test flight data linking this sensitivity to changes in cabin pressure are presented. Total 1σ uncertainties of 2.47 ppb for CH4 and 0.54 ppb for N2O are derived. We report a mean difference in 1 Hz CH4 mole fraction of 2.05 ppb (1σ = 5.85 ppb) between in-flight measurements made using the QCLAS and simultaneous measurements using a previously characterised Fast Greenhouse Gas Analyser (FGGA, Los Gatos Research, USA). Finally, a potential case study for the estimation of a regional N2O flux using a mass balance technique is identified, and the method for calculating such an estimate is outlined.

  15. Surface modification of layered perovskite Sr2TiO4 for improved CO2 photoreduction with H2O to CH4.

    PubMed

    Kwak, Byeong Sub; Do, Jeong Yeon; Park, No-Kuk; Kang, Misook

    2017-11-27

    Layered perovskite Sr 2 TiO 4 photocatalyst was synthesized by using sol-gel method with citric acid. In order to increase the surface area of layered perovskite Sr 2 TiO 4 , and thus to improve its photocatalytic activity for CO 2 reduction, its surface was modified via hydrogen treatment or exfoliation. The physical and chemical properties of the prepared catalysts were characterized by X-ray diffraction, high-resolution transmission electron microscopy, elemental mapping analysis, energy-dispersive X-ray spectroscopy, N 2 adsorption-desorption, UV-Vis spectroscopy, X-ray photoelectron spectroscopy, photoluminescence, and electrophoretic light scattering. CO 2 photoreduction was performed in a closed reactor under 6 W/cm 2 UV irradiation. The gaseous products were analyzed using a gas chromatograph equipped with flame ionization and thermal conductivity detectors. The exfoliated Sr 2 TiO 4 catalyst (E-Sr 2 TiO 4 ) exhibited a narrow band gap, a large surface area, and high dispersion. Owing to these advantageous properties, E-Sr 2 TiO 4 photocatalyst showed an excellent catalytic performance for CO 2 photoreduction reaction. The rate of CH 4 production from the photoreduction of CO 2 with H 2 O using E-Sr 2 TiO 4 was about 3431.77 μmol/g cat after 8 h.

  16. Photodissociation of the CH3Cl/+/ and N2O/+/ cations.

    NASA Technical Reports Server (NTRS)

    Dunbar, R. C.

    1971-01-01

    Use of the ion cyclotron resonance (icr) technique to observe the photodissociation of the cations CH3Cl(+) and N2O(+) in the gas phase. Ions were trapped in the icr cell for periods of the order of seconds, which permitted the photodissociation process to be observed with wavelength-selected light. A cyclotron resonance ejection technique was employed to show that CH3Cl(+) ions were being dissociated rather than the CH3ClH(+) ions which were also present. The photodissociation cross section for N2O(+) was found to be without strong wavelength dependence between 4000 and 6500 A. The cross section for CH3Cl(+) showed a large peak at 3150 A. Possible assignments of this peak are considered, and it is suggested that a photodissociation occurs through an ion excitation involving a change in occupation of the bonding or antibonding orbitals of the C-Cl bond.

  17. Geographic Distribution of N2, CH4, CO2, and H2O Ices on Triton from Near-IR Spectroscopic Monitoring

    NASA Astrophysics Data System (ADS)

    Grundy, W. M.; Young, L. A.; Young, E. F.; Buie, M. W.; Spencer, J. R.

    2004-11-01

    We present new 0.8 to 2.4 μ m spectral observations of Neptune's satellite Triton, obtained at IRTF\\slash SpeX between 2001 and 2004 as part of an ongoing search for time-variable phenomena associated with Triton's seasonal volatile transport processes, and also perhaps with reported shorter-term "reddening" events. The ability to detect spectral changes on these time scales depends critically on accurate characterization of any cyclic variations resulting from Triton's 5.877 day rotation period. We will report on our observations of periodic variations of Triton's near-IR absorption bands of N2, CH4, and H2O ices, but not of CO2 ice, in this initial stage of our Triton monitoring program. The observed variations (or lack thereof) give an indication of how these four ice species are distributed in longitude. The most heterogeneously distributed ice is N2, which shows nearly twice as much absorption on Triton's Neptune-facing hemisphere as on the anti-Neptune hemisphere. Comparison with Voyager-era, visual wavelength imaging of Triton's surface suggest that the observed N2 ice is concentrated on low-latitude regions of Triton's polar cap, which are predominantly located on the Neptune-facing hemisphere. Non-volatile H2O ice seems to be slightly concentrated on Triton's leading hemisphere. Despite being highly diluted in N2 ice, the longitudinal distribution of Triton's CH4 ice differs from that of Triton's N2 ice, being slightly concentrated on Triton's trailing hemisphere. Triton's CO2 ice shows the least longitudinal variation, suggesting that it is either very uniformly distributed or that it is confined to high latitudes. This work was supported by NASA's Planetary Astronomy and Planetary Geology &\\ Geophysics programs, and by NSF's Planetary Astronomy program. \\hangindent=0.3truein Grundy, W.M., and L.A. Young (2004) Near infrared spectral monitoring of Triton with IRTF\\slash SpeX I: Establishing a baseline. Icarus (in press).

  18. Using Mid-IR Cavity Ring-Down Spectrometry to Simultaneously Measure N2o, CO2, and CH4 Fluxes: Responses to Ammonium Nitrate Additions in Salt Marshes

    NASA Astrophysics Data System (ADS)

    Brannon, E.; Moseman-Valtierra, S.; Tang, J.; Chen, X.; Martin, R.; Garate, M.

    2014-12-01

    Greenhouse gas emissions from salt marshes, especially of nitrous oxide (N2O), are a central interest because anthropogenic nutrient loads may substantially alter net climatic forcing of these globally significant ecosystems. In a series of lab and field experiments, a new cavity ring down spectrometer (CRDS, Picarro G2508) that uses mid-infrared (mid-IR) frequencies to measure N2O was compared to a near-IR gas analyzer (LGR N2O/CO analyzer). The Picarro G2508 reports N2O as well as CO2 and CH4 concentrations roughly every second at the parts per billion level. Responses of N2O fluxes to experimental ammonium nitrate additions in marsh mesocosms and marsh plots in situ were compared among these analyzers, along with minimum detectable N2O fluxes. At fluxes above 150 μmol N2O m-2 d-1, the Picarro G2508 and LGR analyzers performed similarly in both mesocosm and field plots that had been enriched with ammonium nitrate, however there were significantly lower minimum detectable N2O fluxes (about 1 order of magnitude) for the LGR than for the Picarro. A gas chromatograph (Shimadzu GC 2014) was also used to test calibration of the G2508. These experiments suggest that mid-IR CRDS technology offers a new tool for simultaneous analyses of N2O along with CO2 and CH4, which fills an important need for quantifying the net climatic forcing of ecosystems. However based on relatively high minimum N2O detection levels of the CRDS, it may work best in highly eutrophic environments.

  19. MnTiO3-driven low-temperature oxidative coupling of methane over TiO2-doped Mn2O3-Na2WO4/SiO2 catalyst

    PubMed Central

    Wang, Pengwei; Zhao, Guofeng; Wang, Yu; Lu, Yong

    2017-01-01

    Oxidative coupling of methane (OCM) is a promising method for the direct conversion of methane to ethene and ethane (C2 products). Among the catalysts reported previously, Mn2O3-Na2WO4/SiO2 showed the highest conversion and selectivity, but only at 800° to 900°C, which represents a substantial challenge for commercialization. We report a TiO2-doped Mn2O3-Na2WO4/SiO2 catalyst by using Ti-MWW zeolite as TiO2 dopant as well as SiO2 support, enabling OCM with 26% conversion and 76% C2-C3 selectivity at 720°C because of MnTiO3 formation. MnTiO3 triggers the low-temperature Mn2+↔Mn3+ cycle for O2 activation while working synergistically with Na2WO4 to selectively convert methane to C2-C3. We also prepared a practical Mn2O3-TiO2-Na2WO4/SiO2 catalyst in a ball mill. This catalyst can be transformed in situ into MnTiO3-Na2WO4/SiO2, yielding 22% conversion and 62% selectivity at 650°C. Our results will stimulate attempts to understand more fully the chemistry of MnTiO3-governed low-temperature activity, which might lead to commercial exploitation of a low-temperature OCM process. PMID:28630917

  20. A laser flash photolysis-resonance fluorescence kinetics study of the reaction Cl/2P/ + CH4 yields CH3 + HCl

    NASA Technical Reports Server (NTRS)

    Ravishankara, A. R.; Wine, P. H.

    1980-01-01

    The technique of laser flash photolysis-resonance fluorescence is employed to study the kinetics of the reaction Cl(2P) + CH4 yields CH3 + HCl over the temperature range 221-375 K. At temperatures less than or equal to 241 K the apparent bimolecular rate constant is found to be dependent upon the identity of the chemically inert gases in the reaction mixture. For Cl2/CH4/He reaction mixtures (total pressure = 50 torr) different bimolecular rate constants are measured at low and high methane concentrations. For Cl2/CH4/CCl/He and Cl2/CH4/Ar reaction mixtures, the bimolecular rate constant is independent of methane concentration, being approximately equal to the rate constant measured at low methane concentrations for Cl2/CH4/He mixtures. These rate constants are in good agreement with previous results obtained using the discharge flow-resonance fluorescence and competitive chlorination techniques. At 298 K the measured bimolecular rate constant is independent of the identity of the chemically inert gases in the reaction mixture and in good agreement with all previous investigations. The low-temperature results obtained in this investigation and all previous investigations can be rationalized in terms of a model which assumes that the Cl(2P 1/2) state reacts with CH4 much faster than the Cl(2P 3/2) state. Extrapolation of this model to higher temperatures, however, is not straightforward.

  1. Electronic Effects on Room-Temperature, Gas-Phase C-H Bond Activations by Cluster Oxides and Metal Carbides: The Methane Challenge.

    PubMed

    Schwarz, Helmut; Shaik, Sason; Li, Jilai

    2017-12-06

    This Perspective discusses a story of one molecule (methane), a few metal-oxide cationic clusters (MOCCs), dopants, metal-carbide cations, oriented-electric fields (OEFs), and a dizzying mechanistic landscape of methane activation! One mechanism is hydrogen atom transfer (HAT), which occurs whenever the MOCC possesses a localized oxyl radical (M-O • ). Whenever the radical is delocalized, e.g., in [MgO] n •+ the HAT barrier increases due to the penalty of radical localization. Adding a dopant (Ga 2 O 3 ) to [MgO] 2 •+ localizes the radical and HAT transpires. Whenever the radical is located on the metal centers as in [Al 2 O 2 ] •+ the mechanism crosses over to proton-coupled electron transfer (PCET), wherein the positive Al center acts as a Lewis acid that coordinates the methane molecule, while one of the bridging oxygen atoms abstracts a proton, and the negatively charged CH 3 moiety relocates to the metal fragment. We provide a diagnostic plot of barriers vs reactants' distortion energies, which allows the chemist to distinguish HAT from PCET. Thus, doping of [MgO] 2 •+ by Al 2 O 3 enables HAT and PCET to compete. Similarly, [ZnO] •+ activates methane by PCET generating many products. Adding a CH 3 CN ligand to form [(CH 3 CN)ZnO] •+ leads to a single HAT product. The CH 3 CN dipole acts as an OEF that switches off PCET. [MC] + cations (M = Au, Cu) act by different mechanisms, dictated by the M + -C bond covalence. For example, Cu + , which bonds the carbon atom mostly electrostatically, performs coupling of C to methane to yield ethylene, in a single almost barrier-free step, with an unprecedented atomic choreography catalyzed by the OEF of Cu + .

  2. Measurements of CH4, N2O, CO, H2O and O3 in the middle atmosphere by the ATMOS experiment on Spacelab 3

    NASA Technical Reports Server (NTRS)

    Gunson, M. R.; Farmer, C. B.; Norton, R. H.; Zander, R.; Rinsland, C. P.; Shaw, J. H.; Gao, Bo-Cai

    1989-01-01

    The volume mixing ratios of five minor gases (CH4, N2O, CO, H2O, and O3) were retrieved through the middle atmosphere from the analysis of 0.01/cm resolution infrared solar occultation spectra recorded near 28 N and 48 S latitudes with the ATMOS (Atmospheric Trace Molecule Spectroscopy) instrument, flown on board Spacelab 3. The results, which constitute the first simultaneous observations of continuous profiles through the middle atmosphere for these gases, are in general agreement with reported measurements from ground, balloon and satellite-based instruments for the same seasons. In detail, the vertical profiles of these gases show the effects of the upper and middle atmospheric transport patterns dominant during the season of these observations. The profiles inferred at different longitudes around 28 N suggest a near-uniform zonal distribution of these gases. Although based on fewer observations, the sunrise occultation measurements point to a larger variability in the vertical distribution of these gases at 48 S.

  3. The development and evaluation of airborne in situ N2O and CH4 sampling using a Quantum Cascade Laser Absorption Spectrometer (QCLAS)

    NASA Astrophysics Data System (ADS)

    Pitt, Joseph; Le Breton, Michael; Allen, Grant; Percival, Carl; Gallagher, Martin; Bauguitte, Stephane; O'Shea, Sebastian; Muller, Jennifer; Zahniser, Mark; Pyle, John; Palmer, Paul

    2016-04-01

    Spectroscopic measurements of atmospheric N2O and CH4 mole fractions were made on board the FAAM (Facility for Airborne Atmospheric Measurements) large Atmospheric Research Aircraft. We evaluate the performance of the mid-IR continuous wave Aerodyne Research Inc. Quantum Cascade Laser Absorption Spectrometer (QCLAS) employed over 17 flights conducted during summer 2014. Two different methods of correcting for the influence of water vapour on the spectroscopic retrievals are compared and evaluated. Test flight data demonstrating the sensitivity of the instrument to changes in cabin pressure is presented, and a new in-flight calibration procedure to account for this issue is described and assessed. Total 1σ uncertainties of 1.81 ppb for CH4 and 0.35 ppb for N2O are derived. We report a mean difference in 1 Hz CH4 mole fraction of 2.05 ppb (1σ = 5.85 ppb) between in-flight measurements made using the QCLAS and simultaneous measurements using a previously characterised Los Gatos Research Fast Greenhouse Gas Analyser (FGGA).

  4. The development and evaluation of airborne in situ N2O and CH4 sampling using a Quantum Cascade Laser Absorption Spectrometer (QCLAS)

    NASA Astrophysics Data System (ADS)

    Pitt, J. R.; Le Breton, M. R.; Allen, G.; Percival, C.; Gallagher, M. W.; Bauguitte, S.; O'Shea, S.; Muller, J.; Zahniser, M. S.; Pyle, J. A.; Palmer, P. I.

    2015-12-01

    Spectroscopic measurements of atmospheric N2O and CH4 mole fractions were made on board the FAAM (Facility for Airborne Atmospheric Measurements) large Atmospheric Research Aircraft. We evaluate the performance of the mid-IR continuous wave Aerodyne Research Inc. Quantum Cascade Laser Absorption Spectrometer (QCLAS) employed over 17 flights conducted during summer 2014. Two different methods of correcting for the influence of water vapour on the spectroscopic retrievals are compared and evaluated. Test flight data demonstrating the sensitivity of the instrument to changes in cabin pressure is presented, and a new in-flight calibration procedure to account for this issue is described and assessed. Total 1σ uncertainties of 1.81 ppb for CH4 and 0.35 ppb for N2O are derived. We report a mean difference in 1 Hz CH4 mole fraction of 2.05 ppb (1σ = 5.85 ppb) between in-flight measurements made using the QCLAS and simultaneous measurements using a previously characterised Los Gatos Research Fast Greenhouse Gas Analyser (FGGA).

  5. The development and evaluation of airborne in situ N2O and CH4 sampling using a Quantum Cascade Laser Absorption Spectrometer (QCLAS)

    NASA Astrophysics Data System (ADS)

    Pitt, J. R.; Le Breton, M.; Allen, G.; Percival, C. J.; Gallagher, M. W.; Bauguitte, S. J.-B.; O'Shea, S. J.; Muller, J. B. A.; Zahniser, M. S.; Pyle, J.; Palmer, P. I.

    2015-08-01

    Spectroscopic measurements of atmospheric N2O and CH4 mole fractions were made on board the FAAM (Facility for Airborne Atmospheric Measurements) large Atmospheric Research Aircraft. We present details of the mid-IR Aerodyne Research Inc. Quantum Cascade Laser Absorption Spectrometer (QCLAS) employed, including its configuration for airborne sampling, and evaluate its performance over 17 flights conducted during summer 2014. Two different methods of correcting for the influence of water vapour on the spectroscopic retrievals are compared and evaluated. A new in-flight calibration procedure to account for the observed sensitivity of the instrument to ambient pressure changes is described, and its impact on instrument performance is assessed. Test flight data linking this sensitivity to changes in cabin pressure is presented. Total 1σ uncertainties of 1.81 ppb for CH4 and 0.35 ppb for N2O are derived. We report a mean difference in 1 Hz CH4 mole fraction of 2.05 ppb (1σ = 5.85 ppb) between in-flight measurements made using the QCLAS and simultaneous measurements using a previously characterised Los Gatos Research Fast Greenhouse Gas Analyser (FGGA). Finally, a potential case study for the estimation of a regional N2O flux using a mass balance technique is identified, and the method for calculating such an estimate is outlined.

  6. 40 CFR Table Aa-2 to Subpart Aa of... - Kraft Lime Kiln and Calciner Emissions Factors for CH4 and N2O

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Kraft Lime Kiln and Calciner Emissions Factors for CH4 and N2O AA Table AA-2 to Subpart AA of Part 98 Protection of Environment ENVIRONMENTAL... Manufacturing Pt. 98, Subpt. AA, Table AA -2 Table AA-2 to Subpart AA of Part 98—Kraft Lime Kiln and Calciner...

  7. Direct measurement of methane hydrate composition along the hydrate equilibrium boundary

    USGS Publications Warehouse

    Circone, S.; Kirby, S.H.; Stern, L.A.

    2005-01-01

    The composition of methane hydrate, namely nW for CH 4??nWH2O, was directly measured along the hydrate equilibrium boundary under conditions of excess methane gas. Pressure and temperature conditions ranged from 1.9 to 9.7 MPa and 263 to 285 K. Within experimental error, there is no change in hydrate composition with increasing pressure along the equilibrium boundary, but nW may show a slight systematic decrease away from this boundary. A hydrate stoichiometry of n W = 5.81-6.10 H2O describes the entire range of measured values, with an average composition of CH4??5.99(??0.07) H2O along the equilibrium boundary. These results, consistent with previously measured values, are discussed with respect to the widely ranging values obtained by thermodynamic analysis. The relatively constant composition of methane hydrate over the geologically relevant pressure and temperature range investigated suggests that in situ methane hydrate compositions may be estimated with some confidence. ?? 2005 American Chemical Society.

  8. In situ Investigation of Methane Dry Reforming on M-CeO 2(111) {M= Co, Ni, Cu} Surfaces: Metal-Support Interactions and the activation of C-H bonds at Low Temperature

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rodriguez, Jose A.; Liu, Zongyuan; Lustemberg, Pablo

    Studies with a series of M-CeO 2(111) {M= Co, Ni, Cu} surfaces indicate that metal-oxide interactions can play a very important role for the activation of methane and its reforming with CO 2 at relatively low temperatures (600-700 K). Among the systems examined, Co-CeO 2(111) exhibits the best performance and Cu-CeO 2(111) has negligible activity. Experiments using ambient pressure XPS indicate that methane dissociates on Co-CeO2(111), at temperatures as low as 300 K, generating CH x and CO x species on the catalyst surface. The results of density-functional calculations show a reduction in the methane activation barrier from 1.07 eVmore » on Co(0001) to 0.87 eV on Co 2+/CeO 2(111), and to only 0.05 eV on Co 0/CeO 2-x(111). At 700 K, under methane dry reforming conditions, CO 2 dissociates on the oxide surface and a catalytic cycle is established without coke deposition. In conclusion, a significant part of the CH x formed on the Co 0/CeO 2-x (111) catalyst recombines to yield ethane or ethylene.« less

  9. In situ Investigation of Methane Dry Reforming on M-CeO 2(111) {M= Co, Ni, Cu} Surfaces: Metal-Support Interactions and the activation of C-H bonds at Low Temperature

    DOE PAGES

    Rodriguez, Jose A.; Liu, Zongyuan; Lustemberg, Pablo; ...

    2017-08-16

    Studies with a series of M-CeO 2(111) {M= Co, Ni, Cu} surfaces indicate that metal-oxide interactions can play a very important role for the activation of methane and its reforming with CO 2 at relatively low temperatures (600-700 K). Among the systems examined, Co-CeO 2(111) exhibits the best performance and Cu-CeO 2(111) has negligible activity. Experiments using ambient pressure XPS indicate that methane dissociates on Co-CeO2(111), at temperatures as low as 300 K, generating CH x and CO x species on the catalyst surface. The results of density-functional calculations show a reduction in the methane activation barrier from 1.07 eVmore » on Co(0001) to 0.87 eV on Co 2+/CeO 2(111), and to only 0.05 eV on Co 0/CeO 2-x(111). At 700 K, under methane dry reforming conditions, CO 2 dissociates on the oxide surface and a catalytic cycle is established without coke deposition. In conclusion, a significant part of the CH x formed on the Co 0/CeO 2-x (111) catalyst recombines to yield ethane or ethylene.« less

  10. Evaluation of the airborne quantum cascade laser spectrometer (QCLS) measurements of the carbon and greenhouse gas suite - CO2, CH4, N2O, and CO - during the CalNex and HIPPO campaigns

    NASA Astrophysics Data System (ADS)

    Santoni, G. W.; Daube, B. C.; Kort, E. A.; Jiménez, R.; Park, S.; Pittman, J. V.; Gottlieb, E.; Xiang, B.; Zahniser, M. S.; Nelson, D. D.; McManus, J. B.; Peischl, J.; Ryerson, T. B.; Holloway, J. S.; Andrews, A. E.; Sweeney, C.; Hall, B.; Hintsa, E. J.; Moore, F. L.; Elkins, J. W.; Hurst, D. F.; Stephens, B. B.; Bent, J.; Wofsy, S. C.

    2014-06-01

    We present an evaluation of aircraft observations of the carbon and greenhouse gases CO2, CH4, N2O, and CO using a direct-absorption pulsed quantum cascade laser spectrometer (QCLS) operated during the HIPPO and CalNex airborne experiments. The QCLS made continuous 1 Hz measurements with 1σ Allan precisions of 20, 0.5, 0.09, and 0.15 ppb for CO2, CH4, N2O, and CO, respectively, over > 500 flight hours on 79 research flights. The QCLS measurements are compared to two vacuum ultraviolet (VUV) CO instruments (CalNex and HIPPO), a cavity ring-down spectrometer (CRDS) measuring CO2 and CH4 (CalNex), two broadband non-dispersive infrared (NDIR) spectrometers measuring CO2 (HIPPO), two onboard gas chromatographs measuring a variety of chemical species including CH4, N2O, and CO (HIPPO), and various flask-based measurements of all four species. QCLS measurements are tied to NOAA and WMO standards using an in-flight calibration system, and mean differences when compared to NOAA CCG flask data over the 59 HIPPO research flights were 100, 1, 1, and 2 ppb for CO2, CH4, N2O, and CO, respectively. The details of the end-to-end calibration procedures and the data quality assurance and quality control (QA/QC) are presented. Specifically, we discuss our practices for the traceability of standards given uncertainties in calibration cylinders, isotopic and surface effects for the long-lived greenhouse gas tracers, interpolation techniques for in-flight calibrations, and the effects of instrument linearity on retrieved mole fractions.

  11. Dual stable isotopes of CH4 from Yellowstone hot-springs suggest hydrothermal processes involving magmatic CO2

    NASA Astrophysics Data System (ADS)

    Moran, James J.; Whitmore, Laura M.; Jay, Zackary J.; Jennings, Ryan deM.; Beam, Jacob P.; Kreuzer, Helen W.; Inskeep, William P.

    2017-07-01

    Volcanism and post-magmatism contribute significant annual methane (CH4) fluxes to the atmosphere (on par with other natural sources such as forest fire and wild animal emissions) and have been implicated in past climate-change events. The Yellowstone hot spot is one of the largest volcanic systems on Earth and is known to emit CH4 (as well as carbon dioxide (CO2) and other gases), but the ultimate sources of this CH4 flux have not been elucidated. Here we use dual stable isotope analysis (δ2H and δ13C) of CH4 sampled from ten high-temperature geothermal pools in Yellowstone National Park along with other isotopic and gas analyses to evaluate potential sources of methane. The average δ13C and δ2H values of CH4 emitted from hot springs (26.7 (± 2.4) and - 236.9 (± 12.0) ‰, respectively) are inconsistent with microbial methanogenesis but do not allow distinction between thermogenic and abiotic sources. Correlation between δ13CCH4 and δ13C of dissolved inorganic C (DIC) is consistent with DIC as the parent C source for the observed CH4, or with equilibration of CH4 and DIC. Methane formation temperatures estimated by isotopic geothermometry based on δ13CCH4 and δ13CCO2 ranged from 250-350 °C, which is just below previous temperature estimates for the hydrothermal reservoir. Further, the δ2HH2O of the thermal springs and the measured δ2HCH4 values are consistent with equilibration between the source water and the CH4 at the formation temperatures. Though the ultimate origin of the CH4 could be attributed to either abiotic of themorgenic processes with subsequent isotopic equilibration, the C1/C2 + composition of the gases is more consistent with abiotic origins for most of the samples. Thus, our data support the hypothesis that subsurface rock-water interactions are responsible for at least a significant fraction of the CH4 flux from the Yellowstone National Park volcanic system.

  12. Bis[μ-N-(pyridin-2-yl)methane­sulfon­amido-κ2 N:N′]silver(I)

    PubMed Central

    Hu, Hui-Ling; Yeh, Chun-Wei

    2013-01-01

    In the title compound, [Ag2(C6H7N2O2S)2], the AgI atom is coordinated by two N atoms from two N-(pyridin-2-yl)methane­sulfonamidate anions in a slightly bent linear geometry [N—Ag—N = 166.03 (7)°]. The AgI atoms are bridged by the N-(pyridin-2-yl)methane­sulfonamidate anions, forming a centrosymmetric dinuclear mol­ecule, in which the Ag⋯Ag distance is 2.7072 (4) Å. PMID:24860285

  13. Glacial/interglacial wetland, biomass burning, and geologic methane emissions constrained by dual stable isotopic CH4 ice core records.

    PubMed

    Bock, Michael; Schmitt, Jochen; Beck, Jonas; Seth, Barbara; Chappellaz, Jérôme; Fischer, Hubertus

    2017-07-18

    Atmospheric methane (CH 4 ) records reconstructed from polar ice cores represent an integrated view on processes predominantly taking place in the terrestrial biogeosphere. Here, we present dual stable isotopic methane records [δ 13 CH 4 and δD(CH 4 )] from four Antarctic ice cores, which provide improved constraints on past changes in natural methane sources. Our isotope data show that tropical wetlands and seasonally inundated floodplains are most likely the controlling sources of atmospheric methane variations for the current and two older interglacials and their preceding glacial maxima. The changes in these sources are steered by variations in temperature, precipitation, and the water table as modulated by insolation, (local) sea level, and monsoon intensity. Based on our δD(CH 4 ) constraint, it seems that geologic emissions of methane may play a steady but only minor role in atmospheric CH 4 changes and that the glacial budget is not dominated by these sources. Superimposed on the glacial/interglacial variations is a marked difference in both isotope records, with systematically higher values during the last 25,000 y compared with older time periods. This shift cannot be explained by climatic changes. Rather, our isotopic methane budget points to a marked increase in fire activity, possibly caused by biome changes and accumulation of fuel related to the late Pleistocene megafauna extinction, which took place in the course of the last glacial.

  14. Glacial/interglacial wetland, biomass burning, and geologic methane emissions constrained by dual stable isotopic CH4 ice core records

    NASA Astrophysics Data System (ADS)

    Bock, Michael; Schmitt, Jochen; Beck, Jonas; Seth, Barbara; Chappellaz, Jérôme; Fischer, Hubertus

    2017-07-01

    Atmospheric methane (CH4) records reconstructed from polar ice cores represent an integrated view on processes predominantly taking place in the terrestrial biogeosphere. Here, we present dual stable isotopic methane records [δ13CH4 and δD(CH4)] from four Antarctic ice cores, which provide improved constraints on past changes in natural methane sources. Our isotope data show that tropical wetlands and seasonally inundated floodplains are most likely the controlling sources of atmospheric methane variations for the current and two older interglacials and their preceding glacial maxima. The changes in these sources are steered by variations in temperature, precipitation, and the water table as modulated by insolation, (local) sea level, and monsoon intensity. Based on our δD(CH4) constraint, it seems that geologic emissions of methane may play a steady but only minor role in atmospheric CH4 changes and that the glacial budget is not dominated by these sources. Superimposed on the glacial/interglacial variations is a marked difference in both isotope records, with systematically higher values during the last 25,000 y compared with older time periods. This shift cannot be explained by climatic changes. Rather, our isotopic methane budget points to a marked increase in fire activity, possibly caused by biome changes and accumulation of fuel related to the late Pleistocene megafauna extinction, which took place in the course of the last glacial.

  15. Soil CO2, CH4 and N2O effluxes and concentrations in soil profiles down to 15.5m depth in eucalypt plantations under contrasted rainfall regimes

    NASA Astrophysics Data System (ADS)

    Germon, A.; Nouvellon, Y.; Christophe, J.; Chapuis-Lardy, L.; Robin, A.; Rosolem, C. A.; Gonçalves, J. L. D. M.; Guerrini, I. A.; Laclau, J. P.

    2017-12-01

    Silvicultural practices in planted forests affect the fluxes of greenhouse gases at the soil surface and the major factors driving greenhouse gas production in forest soils (substrate supply, temperature, water content,…) vary with soil depth. Our study aimed to assess the consequences of drought on the temporal variability of CO2, CH4 and N2O fluxes throughout very deep soil profiles in Eucalyptus grandis plantations 3 months before the harvest then in coppice, the first 18 months after clear-cutting. Two treatments were compared: one with 37% of throughfall excluded by plastic sheets (TE), and one without rainfall exclusion (WE). Measurements of soil CO2 efflux were made every two weeks for 30 months using a closed-path Li8100 system in both treatment. Every two weeks for 21 months, CO2, CH4 and N2O surface effluxes were measured using the closed-chamber method and concentrations in the soil were measured at 7 depths down to 15.5 m in both TE and WE. At most measurement dates, soil CO2 efflux were significantly higher in TE than in WE. Across the two treatments and the measurement dates, CO2 concentrations increased from 4446 ± 2188 ppm at 10 cm deep to 15622 ± 3523 ppm at 15.5 m, CH4 concentrations increased from 0.41 ± 0.17 ppm at 10 cm deep to 0.77 ± 0.24 ppm at 15.5 m and N2O concentrations remained roughly constant and were on average 478 ± 55 ppb between soil surface and 15.5 m deep. CO2 and N2O concentrations were on average 20.7 and 7.6% lower in TE than in WE, respectively, across the sampling depths. However, CH4 concentrations in TE were on average 44.4% higher than in WE, throughout the soil profile. Those results suggest that extended drought periods might reduce the production of CO2 and N2O but increase the accumulation of CH4 in eucalypt plantations established in deep tropical soils. Very deep tropical soils cover huge areas worldwide and improving our understanding of the spatiotemporal dynamics of gas concentrations in deep soil layers

  16. Energetics of the O-H bond and of intramolecular hydrogen bonding in HOC6H4C(O)Y (Y = H, CH3, CH2CH=CH2, C[triple bond]CH, CH2F, NH2, NHCH3, NO2, OH, OCH3, OCN, CN, F, Cl, SH, and SCH3) compounds.

    PubMed

    Bernardes, Carlos E S; Minas da Piedade, Manuel E

    2008-10-09

    The energetics of the phenolic O-H bond in a series of 2- and 4-HOC 6H 4C(O)Y (Y = H, CH3, CH 2CH=CH2, C[triple bond]CH, CH2F, NH2, NHCH 3, NO2, OH, OCH3, OCN, CN, F, Cl, SH, and SCH3) compounds and of the intramolecular O...H hydrogen bond in 2-HOC 6H 4C(O)Y, was investigated by using a combination of experimental and theoretical methods. The standard molar enthalpies of formation of 2-hydroxybenzaldehyde (2HBA), 4-hydroxybenzaldehyde (4HBA), 2'-hydroxyacetophenone (2HAP), 2-hydroxybenzamide (2HBM), and 4-hydroxybenzamide (4HBM), at 298.15 K, were determined by micro- or macrocombustion calorimetry. The corresponding enthalpies of vaporization or sublimation were also measured by Calvet drop-calorimetry and Knudsen effusion measurements. The combination of the obtained experimental data led to Delta f H m (o)(2HBA, g) = -238.3 +/- 2.5 kJ.mol (-1), DeltafHm(o)(4HBA, g) = -220.3 +/- 2.0 kJ.mol(-1), Delta f H m (o)(2HAP, g) = -291.8 +/- 2.1 kJ.mol(-1), DeltafHm(o)(2HBM, g) = -304.8 +/- 1.5 kJ.mol (-1), and DeltafHm(o) (4HBM, g) = -278.4 +/- 2.4 kJ.mol (-1). These values, were used to assess the predictions of the B3LYP/6-31G(d,p), B3LYP/6-311+G(d,p), B3LYP/aug-cc-pVDZ, B3P86/6-31G(d,p), B3P86/6-311+G(d,p), B3P86/aug-cc-pVDZ, and CBS-QB3 methods, for the enthalpies of a series of isodesmic gas phase reactions. In general, the CBS-QB3 method was able to reproduce the experimental enthalpies of reaction within their uncertainties. The B3LYP/6-311+G(d,p) method, with a slightly poorer accuracy than the CBS-QB3 approach, achieved the best performance of the tested DFT models. It was further used to analyze the trends of the intramolecular O...H hydrogen bond in 2-HOC 6H 4C(O)Y evaluated by the ortho-para method and to compare the energetics of the phenolic O-H bond in 2- and 4-HOC 6H 4C(O)Y compounds. It was concluded that the O-H bond "strength" is systematically larger for 2-hydroxybenzoyl than for the corresponding 4-hydroxybenzoyl isomers mainly due to the presence of

  17. Dual stable isotopes of CH 4 from Yellowstone hot-springs suggest hydrothermal processes involving magmatic CO 2

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Moran, James J.; Whitmore, Laura M.; Jay, Zackary J.

    Volcanism and post-magmatism contribute both significant annual CH 4 fluxes to the atmosphere (on par with other natural sources such as forest fire and wild animal emissions) and have been implicated in past climate-change events. The Yellowstone hot spot is one of the largest volcanic systems on Earth and is known to emit methane in addition to other greenhouse gases (e.g. carbon dioxide) but the ultimate source of this methane flux has not been elucidated. Here we use dual stable isotope analysis (δ 2H and δ 13C) of CH 4(g) sampled from ten high-temperature geothermal pools in Yellowstone National Parkmore » to show that the predominant flux of CH4(g) is abiotic. The average δ 13C and δ 2H values of CH 4(g) emitted from hot springs (-26.7 (±2.4) and -236.9 (±12.0) ‰, respectively) are not consistent with biotic (microbial or thermogenic) methane sources, but are within previously reported ranges for abiotic methane production. Correlation between δ 13C CH4 and δ 13C-dissolved inorganic C (DIC) also suggests that CO 2 is a parent C source for the observed CH 4(g). Moreover, CH 4-CO 2 isotopic geothermometry was used to estimate CH 4(g) formation temperatures ranging from ~ 250 - 350°C, which is just below the temperature estimated for the hydrothermal reservoir and consistent with the hypothesis that subsurface, rock-water interactions are responsible for large methane fluxes from this volcanic system. An understanding of conditions leading to the abiotic production of methane and associated isotopic signatures are central to understanding the evolutionary history of deep carbon sources on Earth.« less

  18. Synthesis,and structural characterization of [(CH3(C5H4N))Ga(SCH2(CO)O)]-[(4-MepyH)]+, a novel Ga(III) five coordinate complex.

    NASA Technical Reports Server (NTRS)

    Banger, Kulbinder K.; Duraj, Stan A.; Fanwic, Phillp E.; Hepp, Aloysius F.; Martuch, Robert A.

    2003-01-01

    The synthesis and structural characterization of a novel ionic Ga(III) five coordinate complex [{CH3(C5H4N)}Ga(SCH2(CO)O)2]-[(4-MepyH)]+, (4-Mepy = CH3(C5H5N)) from the reaction between Ga2Cl4 with sodium mercapto-acetic acid in 4-methylpyridine is described. Under basic reaction conditions the mercapto ligand is found to behave as a 2e- bidentate ligand. Single crystal X-ray diffraction studies show the complex to have a distorted square pyramidal geometry with the [(-SCH2(CO)CO-)] ligands in a trans conformation. The compound crystallizes in the P2(sub 1)/c (No. 14) space group with a = 7.7413(6) A, b = 16.744(2) A, c = 14.459(2) A, V = 1987.1(6) A(sup 3), R(F) = 0.032 and R(sub w) = 0.038.

  19. Impacts of updated spectroscopy on thermal infrared retrievals of methane evaluated with HIPPO data

    NASA Astrophysics Data System (ADS)

    Alvarado, M. J.; Payne, V. H.; Cady-Pereira, K. E.; Hegarty, J. D.; Kulawik, S. S.; Wecht, K. J.; Worden, J. R.; Pittman, J. V.; Wofsy, S. C.

    2015-02-01

    Errors in the spectroscopic parameters used in the forward radiative transfer model can introduce spatially, temporally, and altitude-dependent biases in trace gas retrievals. For well-mixed trace gases such as methane, where the variability of tropospheric mixing ratios is relatively small, reducing such biases is particularly important. We use aircraft observations from all five missions of the HIAPER Pole-to-Pole Observations (HIPPO) of the Carbon Cycle and Greenhouse Gases Study to evaluate the impact of updates to spectroscopic parameters for methane (CH4), water vapor (H2O), and nitrous oxide (N2O) on thermal infrared retrievals of methane from the NASA Aura Tropospheric Emission Spectrometer (TES). We find that updates to the spectroscopic parameters for CH4 result in a substantially smaller mean bias in the retrieved CH4 when compared with HIPPO observations. After an N2O-based correction, the bias in TES methane upper tropospheric representative values for measurements between 50° S and 50° N decreases from 56.9 to 25.7 ppbv, while the bias in the lower tropospheric representative value increases only slightly (from 27.3 to 28.4 ppbv). For retrievals with less than 1.6 degrees of freedom for signal (DOFS), the bias is reduced from 26.8 to 4.8 ppbv. We also find that updates to the spectroscopic parameters for N2O reduce the errors in the retrieved N2O profile.

  20. Impacts of updated spectroscopy on thermal infrared retrievals of methane evaluated with HIPPO data

    NASA Astrophysics Data System (ADS)

    Alvarado, M. J.; Payne, V. H.; Cady-Pereira, K. E.; Hegarty, J. D.; Kulawik, S. S.; Wecht, K. J.; Worden, J. R.; Pittman, J. V.; Wofsy, S. C.

    2014-09-01

    Errors in the spectroscopic parameters used in the forward radiative transfer model can introduce altitude-, spatially-, and temporally-dependent biases in trace gas retrievals. For well-mixed trace gases such as methane, where the variability of tropospheric mixing ratios is relatively small, reducing such biases is particularly important. We use aircraft observations from all five missions of the HIAPER Pole-to-Pole Observations (HIPPO) of the Carbon Cycle and Greenhouse Gases Study to evaluate the impact of updates to spectroscopic parameters for methane (CH4), water vapor (H2O), and nitrous oxide (N2O) on thermal infrared retrievals of methane from the NASA Aura Tropospheric Emission Spectrometer (TES). We find that updates to the spectroscopic parameters for CH4 result in a substantially smaller mean bias in the retrieved CH4 when compared with HIPPO observations. After an N2O-based correction, the bias in TES methane upper tropospheric representative values for measurements between 50° S and 50° N decreases from 56.9 to 25.7 ppbv, while the bias in the lower tropospheric representative value increases only slightly (from 27.3 to 28.4 ppbv). For retrievals with less than 1.6 DOFS, the bias is reduced from 26.8 to 4.8 ppbv. We also find that updates to the spectroscopic parameters for N2O reduce the errors in the retrieved N2O profile.

  1. Conformational and spectroscopic study of xanthogen ethyl formates, ROC(S)SC(O)OCH2CH3. Isolation of CH3CH2OC(O)SH

    NASA Astrophysics Data System (ADS)

    Juncal, Luciana C.; Cozzarín, Melina V.; Romano, Rosana M.

    2015-03-01

    ROC(S)SC(O)OCH2CH3, with R = CH3sbnd , (CH3)2CHsbnd and CH3(CH2)2sbnd , were obtained through the reaction between potassium xanthate salts, ROC(S)SK, and ethyl chloroformate, ClC(O)OCH2CH3. The liquid compounds were identified and characterized by 1H and 13C NMR and mass spectrometry. The conformations adopted by the molecules were studied by DFT methods. 6 conformers were theoretically predicted for R = CH3sbnd and (CH3)2CHsbnd , while the conformational flexibility of the n-propyl substituent increases the total number of feasible rotamers to 21. For the three molecules, the conformers can be associated in 3 groups, being the most stable the AS forms - the Cdbnd S double bond anti (A) with respect to the Csbnd S single bond and the Ssbnd C single bond syn (S) with respect to the Cdbnd O double bond - followed by AA and SS conformers. The vibrational spectra were interpreted in terms of the predicted conformational equilibrium, presenting the ν(Cdbnd O) spectral region signals corresponding to the three groups of conformers. A moderated pre-resonance Raman enhancement of the ν(Cdbnd S) vibrational mode of CH3(CH2)2OC(S)SC(O)OCH2CH3 was detected, when the excitation radiation approaches the energy of a n → π∗ electronic transition associated with the Cdbnd S chromophore. UV-visible spectra in different solvents were measured and interpreted in terms of TD-DFT calculations. The unknown molecule CH3CH2OC(O)SH was isolated by the UV-visible photolysis of CH3OC(S)SC(O)OCH2CH3 isolated in Ar matrix, and also obtained as a side-product of the reaction between potassium xanthate salts, ROC(S)SK, and ethyl chloroformate, ClC(O)OCH2CH3.

  2. Glacial/interglacial wetland, biomass burning, and geologic methane emissions constrained by dual stable isotopic CH4 ice core records

    PubMed Central

    Beck, Jonas; Seth, Barbara; Chappellaz, Jérôme

    2017-01-01

    Atmospheric methane (CH4) records reconstructed from polar ice cores represent an integrated view on processes predominantly taking place in the terrestrial biogeosphere. Here, we present dual stable isotopic methane records [δ13CH4 and δD(CH4)] from four Antarctic ice cores, which provide improved constraints on past changes in natural methane sources. Our isotope data show that tropical wetlands and seasonally inundated floodplains are most likely the controlling sources of atmospheric methane variations for the current and two older interglacials and their preceding glacial maxima. The changes in these sources are steered by variations in temperature, precipitation, and the water table as modulated by insolation, (local) sea level, and monsoon intensity. Based on our δD(CH4) constraint, it seems that geologic emissions of methane may play a steady but only minor role in atmospheric CH4 changes and that the glacial budget is not dominated by these sources. Superimposed on the glacial/interglacial variations is a marked difference in both isotope records, with systematically higher values during the last 25,000 y compared with older time periods. This shift cannot be explained by climatic changes. Rather, our isotopic methane budget points to a marked increase in fire activity, possibly caused by biome changes and accumulation of fuel related to the late Pleistocene megafauna extinction, which took place in the course of the last glacial. PMID:28673973

  3. Formation and High-order Carboxylic Acids (RCOOH) in Interstellar Analogous Ices of Carbon Dioxide (CO2) and Methane(CH4)

    NASA Astrophysics Data System (ADS)

    Zhu, Cheng; Turner, Andrew M.; Abplanalp, Matthew J.; Kaiser, Ralf I.

    2018-01-01

    This laboratory study simulated the abiotic formation of carboxylic acids (RCOOH) in interstellar analogous ices of carbon dioxide (CO2) and methane (CH4) at 10 K upon exposure to energetic electrons. The chemical processing of the ices and the subsequent warm-up phase were monitored online and in situ, exploiting Fourier Transform Infrared Spectrometry and quadrupole mass spectrometry. Characteristic absorptions of functional groups of carboxylic acids (RCOOH) were observed in the infrared spectra of the irradiated ice. Two proposed reaction mechanisms replicated the kinetic profiles of the carboxylic acids along with the decay profile of the precursors during the irradiation via hydrocarbon formation, followed by carboxylation and/or through acetic acid along with mass growth processes of the alkyl chain. Mass spectra recorded during the warm-up phase demonstrated that these acids are distributed from acetic acid (CH3COOH) up to decanoic acid (C9H19COOH). High-dose irradiation studies (91 ± 14 eV) converted low-molecular-weight acids such as acetic acid (CH3COOH) and propionic acid (C2H5COOH) to higher-molecular-weight carboxylic acids, compared to low-dose irradiation studies (18 ± 3 eV). The traces of the {{{H}}}2{{C}}= {{C}}({OH}{)}2+ (m/z = 60) fragment—a link to linear carboxylic acids—implied that higher-order acids (C n H2n+1COOH, n ≥ 5) are likely branched, which correlates with the recent analysis of the structures of the monocarboxylic acids in the Murchison meteorite.

  4. Collision efficiency of water in the unimolecular reaction CH4 (+H2O) ⇆ CH3 + H (+H2O): one-dimensional and two-dimensional solutions of the low-pressure-limit master equation.

    PubMed

    Jasper, Ahren W; Miller, James A; Klippenstein, Stephen J

    2013-11-27

    The low-pressure-limit unimolecular decomposition of methane, CH4 (+M) ⇆ CH3 + H (+M), is characterized via low-order moments of the total energy, E, and angular momentum, J, transferred due to collisions. The low-order moments are calculated using ensembles of classical trajectories, with new direct dynamics results for M = H2O and new results for M = O2 compared with previous results for several typical atomic (M = He, Ne, Ar, Kr) and diatomic (M = H2 and N2) bath gases and one polyatomic bath gas, M = CH4. The calculated moments are used to parametrize three different models of the energy transfer function, from which low-pressure-limit rate coefficients for dissociation, k0, are calculated. Both one-dimensional and two-dimensional collisional energy transfer models are considered. The collision efficiency for M = H2O relative to the other bath gases (defined as the ratio of low-pressure limit rate coefficients) is found to depend on temperature, with, e.g., k0(H2O)/k0(Ar) = 7 at 2000 K but only 3 at 300 K. We also consider the rotational collision efficiency of the various baths. Water is the only bath gas found to fully equilibrate rotations, and only at temperatures below 1000 K. At elevated temperatures, the kinetic effect of "weak-collider-in-J" collisions is found to be small. At room temperature, however, the use of an explicitly two-dimensional master equation model that includes weak-collider-in-J effects predicts smaller rate coefficients by 50% relative to the use of a statistical model for rotations. The accuracies of several methods for predicting relative collision efficiencies that do not require solving the master equation and that are based on the calculated low-order moments are tested. Troe's weak collider efficiency, βc, includes the effect of saturation of collision outcomes above threshold and accurately predicts the relative collision efficiencies of the nine baths. Finally, a brief discussion is presented of mechanistic details of the

  5. Simultaneous measurement of stratospheric O3, H2O, CH4, and N2O profiles from infrared limb thermal emissions

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Glenn, M. J.; Kunde, V. G.; Brasunas, J.; Conrath, B. J.; Maguire, W. C.; Herman, J. R.

    1987-01-01

    Thermal emission measurements of the earth's stratospheric limb were made with a cryogenically cooled high-resolution Michelson interferometer on a balloon flight launched from Palestine, TX, on Nov. 6, 1984. Infrared spectra for complete limb sequences were obtained over portions of the 700-1940/cm range with an unapodized spectral resolution of 0.03/cm for tangent heights varying from 13 to 39 km. The observed data from 1125 to 1425/cm have been analyzed for simultaneous measurement of O3, H2O, CH4, and N2O profiles. The analysis employs line-by-line and layer-by-layer radiative-transfer calculations, including curvature and refraction effects. The optimum use of geometric and spectral effects is made to obtain sharply peaked weighting functions. Contributions from stratospheric aerosol are included by measuring the light extinction within the window regions of the observed spectra. The retrieved constituent profiles are compared with measurements made with a variety of techniques by other groups. The comparison shows good agreement with the published data for all gases, indicating the capability of retrieving trace gas profiles from high-resolution thermal emission limb measurements.

  6. Permafrost collapse shifts alpine tundra to a carbon source but reduces N2O and CH4 release on the northern Qinghai-Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Mu, C.

    2017-12-01

    Important unknowns remain about how abrupt permafrost collapse (thermokarst) affects carbon balance and greenhouse gas flux, limiting our ability to predict the magnitude and timing of the permafrost carbon feedback. We measured monthly, growing-season fluxes of CO2, CH4, and N2O at a large thermokarst feature in alpine tundra on the northern Qinghai-Tibetan Plateau (QTP). Thermokarst formation disrupted plant growth and soil hydrology, shifting the ecosystem from a growing-season carbon sink to a weak source, but decreasing feature-level CH4 and N2O flux. Temperature-corrected ecosystem respiration from decomposing permafrost soil was 2.7 to 9.5-fold higher than in similar features from Arctic and Boreal regions, suggesting that warmer and dryer conditions on the northern QTP could accelerate carbon decomposition following permafrost collapse. N2O flux was similar to the highest values reported for Arctic ecosystems, and was 60% higher from exposed mineral soil on the feature floor, confirming Arctic observations of coupled nitrification and denitrification in collapsed soils. Q10 values for respiration were typically over 4, suggesting high temperature sensitivity of thawed carbon. Taken together, these results suggest that QTP permafrost carbon in alpine tundra is highly vulnerable to mineralization following thaw, and that N2O production could be an important non-carbon permafrost climate feedback.

  7. Experimental binding energies for the metal complexes [Mg(CH3OH)n](2+), [Ca(CH3OH)n](2+), and [Sr(CH3OH)n](2+) for n in the range 4-20.

    PubMed

    Bruzzi, E; Stace, A J

    2014-10-09

    A supersonic source of clusters has been used to prepare neutral complexes of methanol in association with an alkaline earth metal atom. From these complexes the following metal-containing dications have been generated through electron ionization: [Mg(CH3OH)n](2+), [Ca(CH3OH)n](2+), and [Sr(CH3OH)n](2+), and for n in the range 4-20, kinetic energy release measurements following the evaporation of a single molecule have been undertaken using a high resolution mass spectrometer. Using finite heat bath theory, these data have been transformed into binding energies for individual methanol molecules attached to each of the three cluster systems. In the larger complexes (n > 6) the results exhibit a consistent trend, whereby the experimental binding energy data for all three metal ions are similar, suggesting that the magnitude of the charge rather than charge density influences the strength of the interaction. From a comparison with data recorded previously for (CH3OH)nH(+) it is found that the 2+ charge on a metal ion has an effect on the binding energy of molecules in complexes containing up to 20 solvent molecules. The results recorded for [Ca(CH3OH)n](2+) show evidence of a very marked transition between n = 6 and 7, which is thought to coincide with the completion of a primary solvation shell and the onset of molecules starting to occupy a second and most probably a third shell.

  8. Experimental measurements of vapor-liquid equilibria of the H2O + CO2 + CH4 ternary system

    USGS Publications Warehouse

    Qin, J.; Rosenbauer, R.J.; Duan, Zhenhao

    2008-01-01

    Reported are the experimental measurements on vapor-liquid equilibria in the H2O + CO2 + CH4 ternary system at temperatures from (324 to 375) K and pressures from (10 to 50) MPa. The results indicate that the CH4 solubility in the ternary mixture is about 10 % to 40 % more than that calculated by interpolation from the Henry's law constants of the binary system, H2O + CH4, and the solubility of CO2 is 6 % to 20 % more than what is calculated by the interpolation from the Henry's law constants of the binary mixture, H 2O + CO2. ?? 2008 American Chemical Society.

  9. In situ studies of surface of NiFe 2O 4 catalyst during complete oxidation of methane

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Shiran; Shan, Junjun; Nie, Longhui

    2015-12-21

    Here, NiFe 2O 4 with an inverse spinel structure exhibits high activity for a complete oxidation of methane at 400 °C–425 °C and a higher temperature. The surface of the catalyst and its adsorbates were well characterized with ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and in situ infrared spectroscopy (IR). In situ studies of the surface of NiFe 2O 4 using AP-XPS suggest the formation of methoxy-like and formate-like intermediates at a temperature lower than 200 °C, supported by the observed vibrational signatures in in situ IR studies. Evolutions of C1s photoemission features and the nominal atomic ratios of C/(Nimore » + Fe) of the catalyst surface suggest that the formate-like intermediate is transformed to product molecules CO 2 and H 2O in the temperature range of 250–300 °C. In situ studies suggest the formation of a spectator, – O lattice – CH 2O lattice –. It strongly bonds to surface through C–O bonds and cannot be activated even at 400 °C.« less

  10. Methane Clathrate Hydrate Prospecting

    NASA Technical Reports Server (NTRS)

    Duxbury, N.; Romanovsky, V.

    2003-01-01

    A method of prospecting for methane has been devised. The impetus for this method lies in the abundance of CH4 and the growing shortages of other fuels. The method is intended especially to enable identification of subpermafrost locations where significant amounts of methane are trapped in the form of methane gas hydrate (CH4(raised dot)6H2O). It has been estimated by the U.S. Geological Survey that the total CH4 resource in CH4(raised dot) 6H2O exceeds the energy content of all other fossil fuels (oil, coal, and natural gas from non-hydrate sources). Also, CH4(raised dot)6H2O is among the cleanest-burning fuels, and CH4 is the most efficient fuel because the carbon in CH4 is in its most reduced state. The method involves looking for a proxy for methane gas hydrate, by means of the combination of a thermal-analysis submethod and a field submethod that does not involve drilling. The absence of drilling makes this method easier and less expensive, in comparison with prior methods of prospecting for oil and natural gas. The proposed method would include thermoprospecting in combination with one more of the other non-drilling measurement techniques, which could include magneto-telluric sounding and/or a subsurface-electrical-resistivity technique. The method would exploit the fact that the electrical conductivity in the underlying thawed region is greater than that in the overlying permafrost.

  11. Nitrous oxide and methane in the Atlantic Ocean between 50°N and 52°S: Latitudinal distribution and sea-to-air flux

    NASA Astrophysics Data System (ADS)

    Forster, Grant; Upstill-Goddard, Rob C.; Gist, Niki; Robinson, Carol; Uher, Gunther; Woodward, E. Malcolm S.

    2009-07-01

    We discuss nitrous oxide (N 2O) and methane (CH 4) distributions in 49 vertical profiles covering the upper ˜300 m of the water column along two ˜13,500 km transects between ˜50°N and ˜52°S during the Atlantic Meridional Transect (AMT) programme (AMT cruises 12 and 13). Vertical N 2O profiles were amenable to analysis on the basis of common features coincident with Longhurst provinces. In contrast, CH 4 showed no such pattern. The most striking feature of the latitudinal depth distributions was a well-defined "plume" of exceptionally high N 2O concentrations coincident with very low levels of CH 4, located between ˜23.5°N and ˜23.5°S; this feature reflects the upwelling of deep waters containing N 2O derived from nitrification, as identified by an analysis of N 2O, apparent oxygen utilization (AOU) and NO 3-, and presumably depleted in CH 4 by bacterial oxidation. Sea-to-air emissions fluxes for a region equivalent to ˜42% of the Atlantic Ocean surface area were in the range 0.40-0.68 Tg N 2O yr -1 and 0.81-1.43 Tg CH 4 yr -1. Based on contemporary estimates of the global ocean source strengths of atmospheric N 2O and CH 4, the Atlantic Ocean could account for ˜6-15% and 4-13%, respectively, of these source totals. Given that the Atlantic Ocean accounts for around 20% of the global ocean surface, on unit area basis it appears that the Atlantic may be a slightly weaker source of atmospheric N 2O than other ocean regions but it could make a somewhat larger contribution to marine-derived atmospheric CH 4 than previously thought.

  12. The First Molybdenum(VI) and Tungsten(VI) Oxoazides MO2(N3)2, MO2(N3)22CH3CN, (bipy)MO2(N3)2, and [MO2(N3)4](2-) (M=Mo, W).

    PubMed

    Haiges, Ralf; Skotnitzki, Juri; Fang, Zongtang; Dixon, David A; Christe, Karl O

    2015-08-10

    Molybdenum(VI) and tungsten(VI) dioxodiazide, MO2(N3)2 (M=Mo, W), were prepared through fluoride-azide exchange reactions between MO2F2 and Me3SiN3 in SO2 solution. In acetonitrile solution, the fluoride-azide exchange resulted in the isolation of the adducts MO2(N3)22CH3CN. The subsequent reaction of MO2(N3)2 with 2,2'-bipyridine (bipy) gave the bipyridine adducts (bipy)MO2(N3)2. The hydrolysis of (bipy)MoO2(N3)2 resulted in the formation and isolation of [(bipy)MoO2N3]2O. The tetraazido anions [MO2(N3)4](2-) were obtained by the reaction of MO2(N3)2 with two equivalents of ionic azide. Most molybdenum(VI) and tungsten(VI) dioxoazides were fully characterized by their vibrational spectra, impact, friction, and thermal sensitivity data and, in the case of (bipy)MoO2(N3)2, (bipy)WO2(N3)2, [PPh4]2[MoO2(N3)4], [PPh4]2[WO2(N3)4], and [(bipy)MoO2N3]2O by their X-ray crystal structures. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Predicting Coupled Emissions of N2O, CO2 and CH4 from Arable Fields in Ireland Using the ECOSSE Model

    NASA Astrophysics Data System (ADS)

    Khalil, M. I.; Smith, J.; Abdalla, M.; O'Brien, P.; Smith, P.; Müller, C.

    2011-12-01

    Agriculture and associated land-use changes contribute a significant portion to global greenhouse gas (GHG) emissions; mainly as N2O, CO2 and CH4. Improved modelling of soil processes will greatly enhance the value of national inventories, both in terms of more accurate reporting and better mitigation policy options. In Ireland, Agriculture and Land Use, Land Use Change and Forestry, is currently a priority research focus, aimed at reducing uncertainty in estimates of GHG emissions and sinks. The ECOSSE model has several advantages, including limited meteorological and soil data requirements, compared to other models. It can simulate the impacts of land-use, management and climate change on C and N emissions and stocks for both mineral and organic soils at field and national scales. In this study, ECOSSE has been used to predict GHG emissions and SOC changes in arable lands cropped with spring barley receiving different rates of N application. The simulated outputs are evaluated against measured data available from a two-year field study. The modelled responses of N2O fluxes are found to be consistent with the measured values. The bias in the total difference between measured values and the corresponding modelled N2O fluxes was large due to the impact of a few unexpected measurements. In the fertilized fields, significant correlation between modelled and measured N2O fluxes was observed, with correlation coefficients of 0.54-0.60 and root mean square errors of 18.6-20.8 g N ha-1 d-1. The measured seasonal (crop growth period) N2O losses (integrated) were 0.41 and 0.50% of the N applied at rates of 70-79 and 140-159 kg ha-1, respectively. As a further comparison, the simulated values for the dates when measurements were taken were similarly integrated. The corresponding simulated seasonal N2O losses were 0.69 and 1.11% of the added N, suggesting an overestimation by 70-123% of the measured values. However, this could be due to missed emissions associated with the

  14. A synthetic precedent for the [FeIV2(μ-O)2] diamond core proposed for methane monooxygenase intermediate Q

    PubMed Central

    Xue, Genqiang; Wang, Dong; De Hont, Raymond; Fiedler, Adam T.; Shan, Xiaopeng; Münck, Eckard; Que, Lawrence

    2007-01-01

    Intermediate Q, the methane-oxidizing species of soluble methane monooxygenase, is proposed to have an [FeIV2(μ-O)2] diamond core. In an effort to obtain a synthetic precedent for such a core, bulk electrolysis at 900 mV (versus Fc+/0) has been performed in MeCN at −40°C on a valence-delocalized [FeIIIFeIV(μ-O)2(Lb)2]3+ complex (1b) (E1/2 = 760 mV versus Fc+/0). Oxidation of 1b results in the near-quantitative formation of a deep red complex, designated 2b, that exhibits a visible spectrum with λmax at 485 nm (9,800 M−1·cm−1) and 875 nm (2,200 M−1·cm−1). The 4.2 K Mössbauer spectrum of 2b exhibits a quadrupole doublet with δ = −0.04(1) mm·s−1 and ΔEQ = 2.09(2) mm·s−1, parameters typical of an iron(IV) center. The Mössbauer patterns observed in strong applied fields show that 2b is an antiferromagnetically coupled diiron(IV) center. Resonance Raman studies reveal the diagnostic vibration mode of the [Fe2(μ-O)2] core at 674 cm−1, downshifting 30 cm−1 upon 18O labeling. Extended x-ray absorption fine structure (EXAFS) analysis shows two O/N scatterers at 1.78 Å and an Fe scatterer at 2.73 Å. Based on the accumulated spectroscopic evidence, 2b thus can be formulated as [FeIV2(μ-O)2(Lb)2]4+, the first synthetic complex with an [FeIV2(μ-O)2] core. A comparison of 2b and its mononuclear analog [FeIV(O)(Lb)(NCMe)]2+ (4b) reveals that 4b is 100-fold more reactive than 2b in oxidizing weak CH bonds. This surprising observation may shed further light on how intermediate Q carries out the hydroxylation of methane. PMID:18093922

  15. Integral and differential cross section measurements at low collision energies for the N2++CH4/CD4 reactions

    NASA Astrophysics Data System (ADS)

    Nicolas, Christophe; Torrents, Raquel; Gerlich, Dieter

    2003-02-01

    Absolute integral cross sections are measured in the collision energy range between 0.1 to 3.5 eV for the N2++CH4 and N2++CD4 reactions using the universal guided ion beam apparatus. The reaction branching ratio, CX3+:CX2+:N2X+ (X=H or D), is found to be 0.86:0.09:0.05 and 0.88:0.07:0.05 for the N2++CH4 and N2++CD4 reactions, respectively. The CH3+/CH2+ ratio is constant over the whole collision energy range and very similar to the one obtained for the almost isoenergetic Ar++CH4 reaction. Axial velocity distributions of the product ions are measured by time of flight at collision energies between 0.1 and 3.5 eV. The results provide direct insight into the reaction dynamics. The dissociative charge transfer channels, leading to CH3+ and CH2+ product ions, occur via an electron jump combined with some exchange of momentum between the colliding partners. The H (D) transfer leading to N2H+ can be described as a direct process, similar to a spectator stripping mechanism. Various isotope effects are observed, the dominant being that the cross sections for reaction with CH4 are up to 20% bigger than the corresponding ones for CD4.

  16. Reactivity of chemisorbed oxygen atoms and their catalytic consequences during CH4-O2 catalysis on supported Pt clusters.

    PubMed

    Chin, Ya-Huei Cathy; Buda, Corneliu; Neurock, Matthew; Iglesia, Enrique

    2011-10-12

    Kinetic and isotopic data and density functional theory treatments provide evidence for the elementary steps and the active site requirements involved in the four distinct kinetic regimes observed during CH(4) oxidation reactions using O(2), H(2)O, or CO(2) as oxidants on Pt clusters. These four regimes exhibit distinct rate equations because of the involvement of different kinetically relevant steps, predominant adsorbed species, and rate and equilibrium constants for different elementary steps. Transitions among regimes occur as chemisorbed oxygen (O*) coverages change on Pt clusters. O* coverages are given, in turn, by a virtual O(2) pressure, which represents the pressure that would give the prevalent steady-state O* coverages if their adsorption-desorption equilibrium was maintained. The virtual O(2) pressure acts as a surrogate for oxygen chemical potentials at catalytic surfaces and reflects the kinetic coupling between C-H and O═O activation steps. O* coverages and virtual pressures depend on O(2) pressure when O(2) activation is equilibrated and on O(2)/CH(4) ratios when this step becomes irreversible as a result of fast scavenging of O* by CH(4)-derived intermediates. In three of these kinetic regimes, C-H bond activation is the sole kinetically relevant step, but occurs on different active sites, which evolve from oxygen-oxygen (O*-O*), to oxygen-oxygen vacancy (O*-*), and to vacancy-vacancy (*-*) site pairs as O* coverages decrease. On O*-saturated cluster surfaces, O*-O* site pairs activate C-H bonds in CH(4) via homolytic hydrogen abstraction steps that form CH(3) groups with significant radical character and weak interactions with the surface at the transition state. In this regime, rates depend linearly on CH(4) pressure but are independent of O(2) pressure. The observed normal CH(4)/CD(4) kinetic isotope effects are consistent with the kinetic-relevance of C-H bond activation; identical (16)O(2)-(18)O(2) isotopic exchange rates in the presence or

  17. Structure of complexes of nitrilo tris methylene phosphonic acid with copper, [CuN(CH{sub 2}PO{sub 3}){sub 3}(H{sub 2}O){sub 3}] and Na{sub 4}[CuN(CH{sub 2}PO{sub 3}){sub 3}]{sub 2} · 19H{sub 2}O, as bactericides and inhibitors of scaling and corrosion

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Somov, N. V., E-mail: somov@phys.unn.ru; Chausov, F. F., E-mail: chaus@uni.udm.ru

    2015-03-15

    Nitrilotris methylene phosphonate triaqua copper and octasodium bis(nitrilotris methylene phosphonate cuprate(II)) nonadecahydrate have been synthesized and investigated. [CuN(CH{sub 2}PO{sub 3}){sub 3}(H{sub 2}O){sub 3}] is crystallized in the sp. gr. P2{sub 1}/c, Z = 4, a = 9.2506(2) Å, b = 15.9815(2) Å, c = 9.5474(2) Å, β = 113.697(2)°. The copper atom is coordinated by oxygen atoms in the configuration of elongated octahedron; the ligand (of bridge type) links neighboring copper atoms. Na{sub 8}[CuN(CH{sub 2}PO{sub 3}){sub 3}]{sub 2} · 19H{sub 2}O is crystallized in the sp. gr. P2{sub 1}/c, Z = 2, a = 11.24550(10) Å, b = 17.38980(10) Å,more » c = 13.5852(2) Å, β = 127.8120(10)°. This complex is chelating; the copper atom closes three five-membered N-C-P-O-Cu cycles with a shared Cu-N bond. Copper is coordinated in a distorted trigonal-bipyramidal configuration.« less

  18. Influence of cattle wastes on nitrous oxide and methane fluxes in pasture land

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Flessa, H.; Doersch, P.; Beese, F.

    1996-11-01

    Agricultural practices are assumed to contribute significantly to the increase in atmospheric N{sub 2}O concentrations observed in the last decades, and they might influence the consumption of atmospheric CH{sub 4}. We report on measurements of N{sub 2}O and CH{sub 4} exchange of a pasture soil, as influenced by droppings of a grazing cattle (Bos taurus) herd. Nitrous oxide and methane fluxes in pasture soil were largely determined by the emission rates from cattle excrement with dung patches being hot spots of CH{sub 4} production and urine-affected areas showing extremely high N{sub 2}O release rates. Methane emissions from dung patches (0.778more » g CH{sub 4}-C per animal and day) were insignificant when compared with those from the rumen of the cattle. Total N{sub 2}O-N losses from the droppings were equivalent to 3.2% of the nitrogen excreted. Based on global data of total nitrogen excretion by dairy cattle, non-dairy cattle, buffalo (Syncerus caffer), and bison during grazing, we estimate the global N{sub 2}O emission from this source to be {approximately}1.18 teragrams N{sub 2}O-N per year, indicating that grazing cattle excretory products are one of the most important sources of atmospheric nitrous oxide. Our work suggests that these sources have been drastically underestimated. 27 refs., 2 figs., 2 tabs.« less

  19. Time-series measurements of methane (CH4) distribution during open water and ice-cover in lakes throughout the Mackenzie River Delta (Canada)

    NASA Astrophysics Data System (ADS)

    McIntosh, H.; Lapham, L.; Orcutt, B.; Wheat, C. G.; Lesack, L.; Bergstresser, M.; Dallimore, S. R.; MacLeod, R.; Cote, M.

    2016-12-01

    Arctic lakes are known to emit large amounts of methane to the atmosphere and their importance to the global methane (CH4) cycle has been recognized. It is well known CH4 builds up in Arctic lakes during ice-cover, but the amount of and when the CH4 is released to the atmosphere is not well known. Our preliminary results suggest the largest flux of CH4 from lakes to the atmosphere occurs slightly before complete ice-out; while others have shown the largest flux occurs when lakes overturn in the spring. During ice-out, CH4 can also be oxidized by methane oxidizing bacteria before it can efflux to the atmosphere from the surface water. In order to elucidate the processes contributing to Arctic lake CH4 emissions, continuous, long-term and large scale spatial sampling is required; however it is difficult to achieve in these remote locations. We address this problem using two sampling techniques. 1) We deployed osmotically powered pumps (OsmoSamplers), which were able to autonomously and continuously collect lake bottom water over the course of a year from multiple lakes in the Mackenzie River Delta. OsmoSamplers were placed in four lakes in the mid Delta near Inuvik, Northwest Territories, Canada, two lakes in the outer Delta, and two coastal lakes on Richard's Island in 2015. The dissolved CH4 concentration, stable isotope content of CH4 (δ13C-CH4), and dissolved sulfate concentrations in bottom water from these lakes will be presented to better understand methane dynamics under the ice and over time. 2) Along with the time-series data, we will also present data from discrete samples collected from 40 lakes in the mid Delta during key time periods, before and immediately after the spring ice-out. By determining the CH4 dynamics throughout the year we hope to improve predictions of how CH4 emissions may change in a warming Arctic environment.

  20. Pinus sylvestris as a missing source of nitrous oxide and methane in boreal forest.

    PubMed

    Machacova, Katerina; Bäck, Jaana; Vanhatalo, Anni; Halmeenmäki, Elisa; Kolari, Pasi; Mammarella, Ivan; Pumpanen, Jukka; Acosta, Manuel; Urban, Otmar; Pihlatie, Mari

    2016-03-21

    Boreal forests comprise 73% of the world's coniferous forests. Based on forest floor measurements, they have been considered a significant natural sink of methane (CH4) and a natural source of nitrous oxide (N2O), both of which are important greenhouse gases. However, the role of trees, especially conifers, in ecosystem N2O and CH4 exchange is only poorly understood. We show for the first time that mature Scots pine (Pinus sylvestris L.) trees consistently emit N2O and CH4 from both stems and shoots. The shoot fluxes of N2O and CH4 exceeded the stem flux rates by 16 and 41 times, respectively. Moreover, higher stem N2O and CH4 fluxes were observed from wet than from dry areas of the forest. The N2O release from boreal pine forests may thus be underestimated and the uptake of CH4 may be overestimated when ecosystem flux calculations are based solely on forest floor measurements. The contribution of pine trees to the N2O and CH4 exchange of the boreal pine forest seems to increase considerably under high soil water content, thus highlighting the urgent need to include tree-emissions in greenhouse gas emission inventories.

  1. Mercury-Bridged Cobaltacarborane Complexes Containing B-Hg-B Three-Center Bonds. Synthesis and Structure of mu, mu’-((n5-C5R5)Co(CH3)2C2B3H4)Hg, mu-(n(5)-C5R5)Co(CH3)2C2B3H4)HgCl, (R=H, CH3) and Related Compounds.

    DTIC Science & Technology

    1980-11-01

    MERCURY-BRIDGED COBALTACARBORANE COMPLEXES CONTAINING B-HG-B TH--ETC(U) NOV 80 D C FINSTER . R N GRIMES N0 0 0 1 4-75-0305 UNCLASSXFIED TR󈧨 NL ILn...C5R5) Co 3)2C2B3 4 2 5 .- -C5R5 )Co(CH3)2C2B3H4 ]HgCl, (R=H, CH3 ) and Related Compounds, David C./ Finster -- Russell N./Grimes ( Department of Chemistry...Compounds 1 \\David C. Finster And Russell N. Grimes* Abstract. Reactions of the nid~p-cobaltacarborane anions 01CR )(C 3 )C BH and [n (H 1oC ihH~5n 5

  2. Low-Temperature Collisional Broadening in the Far-Infrared Centrifugal Distortion Spectrum of CH_4

    NASA Astrophysics Data System (ADS)

    Boudon, Vincent; Vander Auwera, Jean; Manceron, Laurent; Kwabia Tchana, F.; Gabard, Tony; Amyay, Badr; Faye, Mbaye

    2015-06-01

    Previously, we could record on the AILES Beamline at the SOLEIL Synchrotron facility the first resolved centrifugal distorsion spectrum of methane (CH_4) in the THz region, which led to a precise determination of line intensities Later, we could measure collisional self- and N_2-broadening coefficients at room temperature. This time, we reinvestigated this topic by measuring these broadening coefficients at low temperature (between 120~K and 160~K) for J=5 to 12, thanks to a cryogenic multipass cell. We used a 93~m total optical path length. Five pure methane pressures (from 10 to 100 mbar) and four CH_4/N_2 mixtures (20~% of methane with a total pressure from 100 to 800 mbar) were used. These measurements allow us to obtain data for physical conditions approaching those of Titan's atmosphere and to estimate temperature exponents. V. Boudon, O. Pirali, P. Roy, J.-B. Brubach, L. Manceron and J. Vander Auwera, J. Quant. Spectrosc. Radiate. Transfer, 111, 1117--1129 (2010). M. Sanzharov, J. Vander Auwera, O. Pirali, P. Roy, J.-B. Brubach, L. Manceron, T. Gabard and V. Boudon, J. Quant. Spectrosc. Radiate. Transfer, 113, 1874--1886 (2012). F. Kwabia Tchana, F. Willaert, X. Landshere, J.-M. Flaud, L. Lago, M. Chapuis, C. Herbeaux, P. Roy and L. Manceron, Rev. Sci. Instrum., 84, 093101 (2013).

  3. Sunlight stimulates methane uptake and nitrous oxide emission from the High Arctic tundra.

    PubMed

    Li, Fangfang; Zhu, Renbin; Bao, Tao; Wang, Qing; Xu, Hua

    2016-12-01

    Many environmental factors affecting methane (CH 4 ) and nitrous oxide (N 2 O) fluxes have been investigated during the processes of carbon and nitrogen transformation in the boreal tundra. However, effects of sunlight on CH 4 and N 2 O fluxes and their budgets were neglected in the boreal tundra. Here, summertime CH 4 and N 2 O fluxes in the presence and total absence of sunlight were investigated at the six tundra sites (DM1-DM6) on Ny-Ålesund in the High Arctic. The mean CH 4 fluxes at the tundra sites ranged from -4.7 to -158.6μg CH 4 m -2 h -1 in the presence of light, indicating that a large CH 4 sink occurred in the tundra soils. However, enhanced CH 4 emission in total absence of light occurred at all the tundra sites. The mean N 2 O fluxes ranged from 7.4 to 14.6μg N 2 O m -2 h -1 in the presence of light, whereas in the absence of light all the tundra sites generally released less N 2 O, and even significant N 2 O uptake occurred there. Soil temperature, chamber temperature and soil moisture showed no significant correlations with tundra CH 4 and N 2 O flux. The presence of sunlight increased tundra CH 4 uptake by 114.2μg CH 4 m -2 h -1 and N 2 O emission by 10.9μg N 2 O m -2 h -1 compared with total absence of light. Overall our results showed that tundra ecosystem switched from CH 4 sink and N 2 O emission source in the presence of light to CH 4 emission source and N 2 O sink in the absence of light. Therefore sunlight had an important effect on CH 4 and N 2 O budgets in the High Arctic tundra. The exclusion of sunlight might overestimate CH 4 budgets, but underestimate N 2 O budgets in the Arctic tundra ecosystem. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. CH_{4} production in the deep soil as a source of stem CH_{4} emission in Fagus sylvatica}

    NASA Astrophysics Data System (ADS)

    Maier, Martin; Machacova, Katerina; Urban, Otmar; Lang, Friederike

    2017-04-01

    Predicting greenhouse gas (GHG) fluxes on a global scale requires understanding fluxes on the local scale. Understanding GHG processes in soil-plant-atmosphere systems is essential to understand and mitigate GHG fluxes on the local scale. Forests are known to act as carbon sink. Yet, trees at waterlogged sites are known to emit large amounts of CH4, what can offset the positive GHG balance due the CO2 that is sequestered as wood. Generally, upland trees like European beech (Fagus sylvatica L.) are assumed not to emit CH4, and the upland forest soils are regarded as CH4 sinks. Soil-atmosphere fluxes and stem-atmosphere fluxes of CH4 were studied together with soil gas profiles at two upland beech forest sites in Germany and Czech Republic. Soil was a net CH4 sink at both sites. While most trees showed no or low emissions, one beech tree had exorbitant CH4 emissions that were higher than the CH4 sink capacity of the soil. A soil survey showed strong redoximorphic color patterns in the soil adjacent to this tree. Although the soil around the tree was taking up CH4, the soil gas profiles around this tree showed CH4 production at a soil depth >0.3 m. We interpret the coincidence of the production of CH4 in the deep soil below the beech with the large stem emissions as strong hint that there is a transport link between the soil and stem. We think that the root system represents a preferential transport system for CH4 despite the fact that beech roots usually do not have a special gas transport tissue. The observed CH4 stem emissions represent an important CH4 flux in this ecosystem, and, thus, should be considered in future research. Acknowledgement This research was supported by the Czech Academy of Sciences and the German Academic Exchange Service within the project "Methane (CH4) and nitrous oxide (N2O) emissions from Fagus sylvatica trees" (DAAD-15-03), the Czech Science Foundation (17-18112Y), National Programme for Sustainability I (LO1415) and project DFG (MA 5826/2

  5. Estimates of methane emissions from India using CH4-CO-C2H6 relationships from CARIBIC observations in monsoon convective outflow

    NASA Astrophysics Data System (ADS)

    Baker, A. K.; Rauthe-Schöch, A.; Schuck, T. J.; van Velthoven, P. F.; Slemr, F.; Brenninkmeijer, C. A.

    2010-12-01

    A large fraction of methane sources are anthropogenic, and include fossil fuel use, biomass/biofuel burning, agriculture and waste treatment. Recently, much attention regarding emissions of greenhouse gases has focused on large, developing nations, as their emissions are expected to rise rapidly over the coming decades. As the second most populous country in the world, and one of the fastest growing economies, India has been of particular interest. Arguably the most important feature of meteorology in India is the Asian summer monsoon. During the monsoon period there exists persistent deep convection over Southern Asia, and the composition of convected air masses is strongly influenced by emissions from India. This ultimately results in a well-mixed air parcel containing air from India being transported to the upper troposphere. Over the course of the 2008 monsoon period the CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) passenger aircraft conducted monthly measurement flights which probed this outflow. Data collected during these flights provides a unique opportunity to examine sources of atmospheric species in India. Here we use measurements of methane (CH4), carbon monoxide (CO) and ethane (C2H6) from whole air samples collected during CARIBIC flights to estimate emissions of methane and to quantify those emissions related to flooding during the monsoon. Methane data from the monsoon period show enhancements inside the monsoon plume, which increase as the monsoon progresses. Using emission data for CO and ΔCH4/ΔCO derived from CARIBIC measurements, we estimate total methane emissions to be ~40 Tg yr-1. Relationships of methane to ethane, which shares the bulk of its sources with methane but lacks a biological component, are further used to estimate the fraction of “extra” emissions from biological activity related to increased monsoon rains. This additional methane is a considerable fraction of

  6. 40 CFR Table Aa-1 to Subpart Aa of... - Kraft Pulping Liquor Emissions Factors for Biomass-Based CO2, CH4, and N2O

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Kraft Pulping Liquor Emissions Factors for Biomass-Based CO2, CH4, and N2O AA Table AA-1 to Subpart AA of Part 98 Protection of Environment... Paper Manufacturing Pt. 98, Subpt. AA, Table AA-1 Table AA-1 to Subpart AA of Part 98—Kraft Pulping...

  7. 40 CFR Table Aa-1 to Subpart Aa of... - Kraft Pulping Liquor Emissions Factors for Biomass-Based CO2, CH4, and N2O

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Kraft Pulping Liquor Emissions Factors for Biomass-Based CO2, CH4, and N2O AA Table AA-1 to Subpart AA of Part 98 Protection of Environment... Paper Manufacturing Pt. 98, Subpt. AA, Table AA-1 Table AA-1 to Subpart AA of Part 98—Kraft Pulping...

  8. 40 CFR Table Aa-1 to Subpart Aa of... - Kraft Pulping Liquor Emissions Factors for Biomass-Based CO2, CH4, and N2O

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Kraft Pulping Liquor Emissions Factors for Biomass-Based CO2, CH4, and N2O AA Table AA-1 to Subpart AA of Part 98 Protection of Environment... Paper Manufacturing Pt. 98, Subpt. AA, Table AA-1 Table AA-1 to Subpart AA of Part 98—Kraft Pulping...

  9. 40 CFR Table Aa-1 to Subpart Aa of... - Kraft Pulping Liquor Emissions Factors for Biomass-Based CO2, CH4, and N2O

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Kraft Pulping Liquor Emissions Factors for Biomass-Based CO2, CH4, and N2O AA Table AA-1 to Subpart AA of Part 98 Protection of Environment... Paper Manufacturing Pt. 98, Subpt. AA, Table AA-1 Table AA-1 to Subpart AA of Part 98—Kraft Pulping...

  10. Synthesis and characterization of two novel inorganic/organic hybrid materials based on polyoxomolybdate clusters: (C5H5N5)2(C5H6N5)4[(HAsO4)2Mo6O18]·11H2O and Na2(Himi)3[SeMo6O21(CH3COO)3]·6H2O

    NASA Astrophysics Data System (ADS)

    Ayed, Meriem; Mestiri, Imen; Ayed, Brahim; Haddad, Amor

    2017-01-01

    Two new organic-inorganic hybrid compound, (C5H5N5)2(C5H6N5)4[(HAsO4)2Mo6O18]·11H2O (I) and Na2(Himi)3[SeMo6O21(CH3COO)3]·6H2O (II) were synthesized and structurally characterized by scanning electron microscopy (SEM), elemental analyses, FTIR, UV spectroscopy, thermal stability analysis, XRD and single crystal X-ray diffraction. Crystal data: (I) triclinic system, space group P-1, a = 11,217 (9) Å, b = 11,637 (8) Å, c = 14,919 (8) Å, α = 70,90 (5)°, β = 70,83 (2)°, γ = 62,00(1)° and Z = 1; (II) triclinic system, space group P-1, a = 10.6740(1) Å, b = 10.6740(1) Å, c = 20.0570(1) Å, α = 76.285(1)°, β = 82.198(2)°, γ = 87.075(1)°, Z = 1. The crystal structure of (I) can be described by infinite polyanions [(HAsO4)2Mo6O18]4- organized with water molecules in layers parallel to the c-direction; adjacent layers are further joined up by hydrogen bonding interactions with organic groups which were associated in chains spreading along the b-direction. The structure of (II) consists of functionalized selenomolybdate clusters [SeMo6O21(CH3COO)3]5-, protonated imidazole cations, sodium ions and lattice water molecules, which are held together to generate a three-dimensional supramolecular network via hydrogen-bonding interaction. Furthermore, the electrochemical properties of these compounds have been studied.

  11. Self-assembled 1D infinite inorganic [2]catenane and 2D sheet framework with calix[8]phenylazoimidazole and [4+4]metallomacrocyclic motifs based on silver and ditopic bis(imidazolyl)methane ligands

    NASA Astrophysics Data System (ADS)

    Jin, Tianqi; Zhou, Junqiang; Pan, Yangyang; Huang, Yu; Jin, Chuanming

    2018-05-01

    Three novel supramolecular complexes, [Ag4(2-mBIM)4](ClO4)4(H2O) (1), [Ag2(2-mBIM)2](PF6)2 (2) and [Ag2(PA-BIM)2](ClO4)2(CH2Cl2) (3) (2-mBIM = bis(2-methyl- imidazol-1-yl)methane; PA-BIM = 1,1-bis[(2-phenylazo)imidazol-1-yl]methane), have been prepared and structurally characterized. The reported complexes bear [4+4]metallomacrocyclic motifs comprising four silver atoms and four ditopic bis(imidazolyl)methane ligands. Complex 1 exhibits a rare 1D infinite inorganic [2]catenane structure, which was self-assembled by the interlocking action of [4+4]metallomacrocyclic units. Complex 2 is a 2D layered supramolecular motif containing [4+4]macrometallacycle units with π-π interaction between imidazole rings. Complex 3 has a 2D sheet supramolecular framework through Ag-Ag interactions in [4+4]macrometallacyclic calix [8]phenylazoimidazole with a nanocavity. The results suggest that the bisimidazolium ligands and anions play crucial roles in the formation of the different host structures. The thermal stability and photoluminescence spectra of the synthesized complexes have also been discussed.

  12. Treated domestic sewage irrigation significantly decreased the CH4, N2O and NH3 emissions from paddy fields with straw incorporation

    NASA Astrophysics Data System (ADS)

    Xu, Shanshan; Hou, Pengfu; Xue, Lihong; Wang, Shaohua; Yang, Linzhang

    2017-11-01

    Straw incorporation and domestic sewage irrigation have been recommended as an environmentally friendly agricultural practice and are widely used not only in China but also in other countries. The individual effects on yield and environmental impacts have been studied extensively, but the comprehensive effect when straw returning and domestic sewage irrigation are combined together has seldom been reported. This study was conducted to examine the effects of straw returning and domestic sewage irrigation on rice yields, greenhouse gas emissions (GHGs) and ammonia (NH3) volatilization from paddy fields from 2015 to 2016. The results showed that the rice yield was not affected by the irrigation water sources and straw returning under the same total N input, which was similar in both years. Due to the rich N in the domestic sewage, domestic sewage irrigation could reduce approximately 45.2% of chemical nitrogen fertilizer input without yield loss. Compared to straw removal treatments, straw returning significantly increased the CH4 emissions by approximately 7-9-fold under domestic sewage irrigation and 13-14-fold under tap water irrigation. Straw returning also increased the N2O emissions under the two irrigation water types. In addition, the seasonal NH3 volatilization loss was significantly increased by 88.8% and 61.2% under straw returning compared to straw removal in 2015 and 2016, respectively. However, domestic sewage irrigation could decrease CH4 emissions by 24.5-26.6%, N2O emissions by 37.0-39.0% and seasonal NH3 volatilization loss by 27.2-28.3% under straw returning compared to tap water irrigation treatments. Global warming potentials (GWP) and greenhouse gas intensities (GHGI) were significantly increased with straw returning compared with those of straw removal, while they were decreased by domestic sewage irrigation under straw returning compared to tap water irrigation. Significant interactions between straw returning and domestic sewage irrigation on

  13. Impact of agronomy practices on the effects of reduced tillage systems on CH4 and N2O emissions from agricultural fields: A global meta-analysis

    PubMed Central

    Zhou, Xiyue; Xu, Chunchun; Ji, Long; Chen, Zhongdu

    2018-01-01

    The effect of no- and reduced tillage (NT/RT) on greenhouse gas (GHG) emission was highly variable and may depend on other agronomy practices. However, how the other practices affect the effect of NT/RT on GHG emission remains elusive. Therefore, we conducted a global meta-analysis (including 49 papers with 196 comparisons) to assess the effect of five options (i.e. cropping system, crop residue management, split application of N fertilizer, irrigation, and tillage duration) on the effect of NT/RT on CH4 and N2O emissions from agricultural fields. The results showed that NT/RT significantly mitigated the overall global warming potential (GWP) of CH4 and N2O emissions by 6.6% as compared with conventional tillage (CT). Rotation cropping systems and crop straw remove facilitated no-tillage (NT) to reduce the CH4, N2O, or overall GWP both in upland and paddy field. NT significantly mitigated the overall GWP when the percentage of basal N fertilizer (PBN) >50%, when tillage duration > 10 years or rainfed in upland, while when PBN <50%, when duration between 5 and 10 years, or with continuous flooding in paddy field. RT significantly reduced the overall GWP under single crop monoculture system in upland. These results suggested that assessing the effectiveness of NT/RT on the mitigation of GHG emission should consider the interaction of NT/RT with other agronomy practices and land use type. PMID:29782525

  14. Impact of agronomy practices on the effects of reduced tillage systems on CH4 and N2O emissions from agricultural fields: A global meta-analysis.

    PubMed

    Feng, Jinfei; Li, Fengbo; Zhou, Xiyue; Xu, Chunchun; Ji, Long; Chen, Zhongdu; Fang, Fuping

    2018-01-01

    The effect of no- and reduced tillage (NT/RT) on greenhouse gas (GHG) emission was highly variable and may depend on other agronomy practices. However, how the other practices affect the effect of NT/RT on GHG emission remains elusive. Therefore, we conducted a global meta-analysis (including 49 papers with 196 comparisons) to assess the effect of five options (i.e. cropping system, crop residue management, split application of N fertilizer, irrigation, and tillage duration) on the effect of NT/RT on CH4 and N2O emissions from agricultural fields. The results showed that NT/RT significantly mitigated the overall global warming potential (GWP) of CH4 and N2O emissions by 6.6% as compared with conventional tillage (CT). Rotation cropping systems and crop straw remove facilitated no-tillage (NT) to reduce the CH4, N2O, or overall GWP both in upland and paddy field. NT significantly mitigated the overall GWP when the percentage of basal N fertilizer (PBN) >50%, when tillage duration > 10 years or rainfed in upland, while when PBN <50%, when duration between 5 and 10 years, or with continuous flooding in paddy field. RT significantly reduced the overall GWP under single crop monoculture system in upland. These results suggested that assessing the effectiveness of NT/RT on the mitigation of GHG emission should consider the interaction of NT/RT with other agronomy practices and land use type.

  15. Direct dynamics simulation of dioxetane formation and decomposition via the singlet .O-O-CH2-CH2. biradical: Non-RRKM dynamics

    NASA Astrophysics Data System (ADS)

    Sun, Rui; Park, Kyoyeon; de Jong, Wibe A.; Lischka, Hans; Windus, Theresa L.; Hase, William L.

    2012-07-01

    Electronic structure calculations and direct chemical dynamics simulations are used to study the formation and decomposition of dioxetane on its ground state singlet potential energy surface. The stationary points for 1O2 + C2H4, the singlet .O-O-CH2-CH2. biradical, the transition state (TS) connecting this biradical with dioxetane, and the two transition states and gauche .O-CH2-CH2-O. biradical connecting dioxetane with the formaldehyde product molecules are investigated at different levels of electronic structure theory including UB3LYP, UMP2, MRMP2, and CASSCF and a range of basis sets. The UB3LYP/6-31G* method was found to give representative energies for the reactive system and was used as a model for the simulations. UB3LYP/6-31G* direct dynamics trajectories were initiated at the TS connecting the .O-O-CH2-CH2. biradical and dioxetane by sampling the TS's vibrational energy levels, and rotational and reaction coordinate energies, with Boltzmann distributions at 300, 1000, and 1500 K. This corresponds to the transition state theory model for trajectories that pass the TS. The trajectories were directed randomly towards both the biradical and dioxetane. A small fraction of the trajectories directed towards the biradical recrossed the TS and formed dioxetane. The remainder formed 1O2 + C2H4 and of these ˜ 40% went directly from the TS to 1O2 + C2H4 without getting trapped and forming an intermediate in the .O-O-CH2-CH2. biradical potential energy minimum, a non-statistical result. The dioxetane molecules which are formed dissociate to two formaldehyde molecules with a rate constant two orders of magnitude smaller than that predicted by Rice-Ramsperger-Kassel-Marcus theory. The reaction dynamics from dioxetane to the formaldehyde molecules do not follow the intrinsic reaction coordinate or involve trapping in the gauche .O-CH2-CH2-O. biradical potential energy minimum. Important non-statistical dynamics are exhibited for this reactive system.

  16. Effect of drainage on CO2, CH4, and N2O fluxes from aquaculture ponds during winter in a subtropical estuary of China.

    PubMed

    Yang, Ping; Lai, Derrick Y F; Huang, Jia F; Tong, Chuan

    2018-03-01

    Aquaculture ponds are dominant features of the landscape in the coastal zone of China. Generally, aquaculture ponds are drained during the non-culture period in winter. However, the effects of such drainage on the production and flux of greenhouse gases (GHGs) from aquaculture ponds are largely unknown. In the present study, field-based research was performed to compare the GHG fluxes between one drained pond (DP, with a water depth of 0.05m) and one undrained pond (UDP, with a water depth of 1.16m) during one winter in the Min River estuary of southeast China. Over the entire study period, the mean CO 2 flux in the DP was (0.75±0.12) mmol/(m 2 ·hr), which was significantly higher than that in the UDP of (-0.49±0.09) mmol/(m 2 ·hr) (p<0.01). This indicates that drainage drastically transforms aquaculture ponds from a net sink to a net source of CO 2 in winter. Mean CH 4 and N 2 O emissions were significantly higher in the DP compared to those in the UDP (CH 4 =(0.66±0.31) vs. (0.07±0.06) mmol/(m 2 ·hr) and N 2 O=(19.54±2.08) vs. (0.01±0.04) µmol/(m 2 ·hr)) (p<0.01), suggesting that drainage would also significantly enhance CH 4 and N 2 O emissions. Changes in environmental variables (including sediment temperature, pH, salinity, redox status, and water depth) contributed significantly to the enhanced GHG emissions following pond drainage. Furthermore, analysis of the sustained-flux global warming and cooling potentials indicated that the combined global warming potentials of the GHG fluxes were significantly higher in the DP than in the UDP (p<0.01), with values of 739.18 and 26.46mgCO 2 -eq/(m 2 ·hr), respectively. Our findings suggested that drainage of aquaculture ponds can increase the emissions of potent GHGs from the coastal zone of China to the atmosphere during winter, further aggravating the problem of global warming. Copyright © 2017. Published by Elsevier B.V.

  17. Kinetic modeling and transient DRIFTS–MS studies of CO 2 methanation over Ru/Al 2O 3 catalysts

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Xiang; Hong, Yongchun; Shi, Hui

    CO 2 methanation was investigated on 5% and 0.5% Ru/Al 2O 3 catalysts (Ru dispersions: ~18% and ~40%, respectively) by steady-state kinetic measurements and transient DRIFTS–MS. Methanation rates were higher over 5% Ru/Al 2O 3 than over 0.5% Ru/Al 2O 3. The measured activation energies, however, were lower on 0.5% Ru/Al 2O 3 than on 5% Ru/Al 2O 3. Transient DRIFTS–MS results demonstrated that direct CO 2 dissociation was negligible over Ru. CO 2 has to first react with surface hydroxyls on Al 2O 3 to form bicarbonates, which, in turn, react with adsorbed H on Ru to produce adsorbed formate species. Formates, most likely at the metal/oxide interface, can react rapidly with adsorbed H forming adsorbed CO, only a portion of which is reactive toward adsorbed H, ultimately leading to CH4 formation. The measured kinetics are fully consistent with a Langmuir–Hinshelwood type mechanism in which the H-assisted dissociation of the reactive CO* is the rate-determining step (RDS). The similar empirical rate expressions (r CH4 = kPmore » $$0.1\\atop{CO2}$$P$$0.3-0.5\\atop{H2}$$) and DRIFTS–MS results on the two catalysts under both transient and steady-state conditions suggest that the mechanism for CO 2 methanation does not change with Ru particle size under the studied experimental conditions. Kinetic modeling results further indicate that the intrinsic activation barrier for the RDS is slightly lower on 0.5% Ru/Al 2O 3 than on 5% Ru/Al 2O 3. Due to the presence of unreactive adsorbed CO under reaction conditions, the larger fraction of such surface sites that bind CO too strongly on 0.5% Ru/Al 2O 3 than on 5% Ru/Al 2O 3, as revealed by FTIR measurements, is regarded as the main reason for the lower rates for CO 2 methanation on 0.5% Ru/Al 2O 3. The catalyst preparation and catalytic measurements were supported by a Laboratory Directed Research and Development (LDRD) project. The authors gratefully acknowledge the financial support of this work by the US Department

  18. HITRAN2016: Part I. Line lists for H_2O, CO_2, O_3, N_2O, CO, CH_4, and O_2

    NASA Astrophysics Data System (ADS)

    Gordon, Iouli E.; Rothman, Laurence S.; Tan, Yan; Kochanov, Roman V.; Hill, Christian

    2017-06-01

    The HITRAN2016 database is now officially released. Plethora of experimental and theoretical molecular spectroscopic data were collected, evaluated and vetted before compiling the new edition of the database. The database is now distributed through the dynamic user interface HITRANonline (available at www.hitran.org) which offers many flexible options for browsing and downloading the data. In addition HITRAN Application Programming Interface (HAPI) offers modern ways to download the HITRAN data and use it to carry out sophisticated calculations. The line-by-line lists for almost all of the 47 HITRAN molecules were updated in comparison with the previous compilation (HITRAN2012. Some of the most important updates for major atmospheric absorbers, such as H_2O, CO_2, O_3, N_2O, CO, CH_4, and O_2, will be presented in this talk, while the trace gases will be presented in the next talk by Y. Tan. The HITRAN2016 database now provides alternative line-shape representations for a number of molecules, as well as broadening by gases dominant in planetary atmospheres. In addition, substantial extension and improvement of cross-section data is featured, which will be described in a dedicated talk by R. V. Kochanov. The new edition of the database is a substantial step forward to improve retrievals of the planetary atmospheric constituents in comparison with previous editions, while offering new ways of working with the data. The HITRAN database is supported by the NASA AURA and PDART program grants NNX14AI55G and NNX16AG51G. I. E. Gordon, L. S. Rothman, C. Hill, R. V. Kochanov, Y. Tan, et al. The HITRAN2016 Molecular Spectroscopic Database. JQSRT 2017;submitted. Many spectroscopists and atmospheric scientists worldwide have contributed data to the database or provided invaluable validations. C. Hill, I. E. Gordon, R. V. Kochanov, L. Barrett, J.S. Wilzewski, L.S. Rothman, JQSRT. 177 (2016) 4-14 R.V. Kochanov, I. E. Gordon, L. S. Rothman, P. Wcislo, C. Hill, J. S. Wilzewski

  19. The rate of charge tunneling is insensitive to polar terminal groups in self-assembled monolayers in Ag(TS)S(CH2)(n)M(CH2)(m)T//Ga2O3/EGaIn junctions.

    PubMed

    Yoon, Hyo Jae; Bowers, Carleen M; Baghbanzadeh, Mostafa; Whitesides, George M

    2014-01-08

    This paper describes a physical-organic study of the effect of uncharged, polar, functional groups on the rate of charge transport by tunneling across self-assembled monolayer (SAM)-based large-area junctions of the form Ag(TS)S(CH2)(n)M(CH2)(m)T//Ga2O3/EGaIn. Here Ag(TS) is a template-stripped silver substrate, -M- and -T are "middle" and "terminal" functional groups, and EGaIn is eutectic gallium-indium alloy. Twelve uncharged polar groups (-T = CN, CO2CH3, CF3, OCH3, N(CH3)2, CON(CH3)2, SCH3, SO2CH3, Br, P(O)(OEt)2, NHCOCH3, OSi(OCH3)3), having permanent dipole moments in the range 0.5 < μ < 4.5, were incorporated into the SAM. A comparison of the electrical characteristics of these junctions with those of junctions formed from n-alkanethiolates led to the conclusion that the rates of charge tunneling are insensitive to the replacement of terminal alkyl groups with the terminal polar groups in this set. The current densities measured in this work suggest that the tunneling decay parameter and injection current for SAMs terminated in nonpolar n-alkyl groups, and polar groups selected from common polar organic groups, are statistically indistinguishable.

  20. Influence of bulking agents on CH4, N2O, and NH3 emissions during rapid composting of pig manure from the Chinese Ganqinfen system*

    PubMed Central

    Sun, Xiang-ping; Lu, Peng; Jiang, Tao; Schuchardt, Frank; Li, Guo-xue

    2014-01-01

    Mismanagement of the composting process can result in emissions of CH4, N2O, and NH3, which have caused severe environmental problems. This study was aimed at determining whether CH4, N2O, and NH3 emissions from composting are affected by bulking agents during rapid composting of pig manure from the Chinese Ganqinfen system. Three bulking agents, corn stalks, spent mushroom compost, and sawdust, were used in composting with pig manure in 60 L reactors with forced aeration for more than a month. Gas emissions were measured continuously, and detailed gas emission patterns were obtained. Concentrations of NH3 and N2O from the composting pig manure mixed with corn stalks or sawdust were higher than those from the spent mushroom compost treatment, especially the sawdust treatment, which had the highest total nitrogen loss among the three runs. Most of the nitrogen was lost in the form of NH3, which accounts for 11.16% to 35.69% of the initial nitrogen. One-way analysis of variance for NH3 emission showed no significant differences between the corn stalk and sawdust treatments, but a significant difference was noted between the spent mushroom compost and sawdust treatments. The introduction of sawdust reduced CH4 emission more than the corn stalks and spent mushroom compost. However, there were no significant differences among the three runs for total carbon loss. All treatments were matured after 30 d. PMID:24711356

  1. Urea deep placement reduces yield-scaled greenhouse gas (CH4 and N2O) and NO emissions from a ground cover rice production system.

    PubMed

    Yao, Zhisheng; Zheng, Xunhua; Zhang, Yanan; Liu, Chunyan; Wang, Rui; Lin, Shan; Zuo, Qiang; Butterbach-Bahl, Klaus

    2017-09-12

    Ground cover rice production system (GCRPS), i.e., paddy soils being covered by thin plastic films with soil moisture being maintained nearly saturated status, is a promising technology as increased yields are achieved with less irrigation water. However, increased soil aeration and temperature under GCRPS may cause pollution swapping in greenhouse gas (GHG) from CH 4 to N 2 O emissions. A 2-year experiment was performed, taking traditional rice cultivation as a reference, to assess the impacts of N-fertilizer placement methods on CH 4 , N 2 O and NO emissions and rice yields under GCRPS. Averaging across all rice seasons and N-fertilizer treatments, the GHG emissions for GCRPS were 1973 kg CO 2 -eq ha -1 (or 256 kg CO 2 -eq Mg -1 ), which is significantly lower than that of traditional cultivation (4186 kg CO 2 -eq ha -1 or 646 kg CO 2 -eq Mg -1 ). Furthermore, if urea was placed at a 10-15 cm soil depth instead of broadcasting, the yield-scaled GHG emissions from GCRPS were further reduced from 377 to 222 kg CO 2 -eq Mg -1 , as N 2 O emissions greatly decreased while yields increased. Urea deep placement also reduced yield-scaled NO emissions by 54%. Therefore, GCRPS with urea deep placement is a climate- and environment-smart management, which allows for maximal rice yields at minimal GHG and NO emissions.

  2. Contribution of Anthropogenic and Natural Emissions to Global CH4 Balances by Utilizing δ13C-CH4 Observations in CarbonTracker Data Assimilation System (CTDAS)

    NASA Astrophysics Data System (ADS)

    Kangasaho, V. E.; Tsuruta, A.; Aalto, T.; Backman, L. B.; Houweling, S.; Krol, M. C.; Peters, W.; van der Laan-Luijkx, I. T.; Lienert, S.; Joos, F.; Dlugokencky, E. J.; Michael, S.; White, J. W. C.

    2017-12-01

    The atmospheric burden of CH4 has more than doubled since preindustrial time. Evaluating the contribution from anthropogenic and natural emissions to the global methane budget is of great importance to better understand the significance of different sources at the global scale, and their contribution to changes in growth rate of atmospheric CH4 before and after 2006. In addition, observations of δ13C-CH4 suggest an increase in natural sources after 2006, which matches the observed increase and variation of CH4 abudance. Methane emission sources can be identified using δ13C-CH4, because different sources produce methane with process-specific isotopic signatures. This study focuses on inversion model based estimates of global anthropogenic and natural methane emission rates to evaluate the existing methane emission estimates with a new δ13C-CH4 inversion system. In situ measurements of atmospheric methane and δ13C-CH4 isotopic signature, provided by the NOAA Global Monitoring Division and the Institute of Arctic and Alpine Research, will be assimilated into the CTDAS-13C-CH4. The system uses the TM5 atmospheric transport model as an observation operator, constrained by ECMWF ERA Interim meteorological fields, and off-line TM5 chemistry fields to account for the atmospheric methane sink. LPX-Bern DYPTOP ecosystem model is used for prior natural methane emissions from wetlands, peatlands and mineral soils, GFED v4 for prior fire emissions and EDGAR v4.2 FT2010 inventory for prior anthropogenic emissions. The EDGAR antropogenic emissions are re-divided into enteric fermentation and manure management, landfills and waste water, rice, coal, oil and gas, and residential emissions, and the trend of total emissions is scaled to match optimized anthropogenic emissions from CTE-CH4. In addition to these categories, emissions from termites and oceans are included. Process specific δ13C-CH4 isotopic signatures are assigned to each emission source to estimate 13CH4 fraction

  3. Methane and nitrous oxide analyzer comparison and emissions from dairy freestall barns with manure flushing and scraping

    NASA Astrophysics Data System (ADS)

    Cortus, Erin L.; Jacobson, Larry D.; Hetchler, Brian P.; Heber, Albert J.; Bogan, Bill W.

    2015-01-01

    Continuous methane (CH4) and nitrous oxide (N2O) emission measurements were conducted at two crossflow-ventilated dairy freestall barns located in the state of Wisconsin, USA during a 19-month period from 2008 to 2010. The two cross-flow mechanically ventilated buildings (275 and 375 cow capacities) were evaluated in the National Air Emissions Monitoring Study. In September of 2008, the barns' manure collection systems were changed from flushing open gutter using manure basin effluent to a tractor scrape. A photoacoustic multi-gas analyzer (PAMGA) and a direct methane/non-methane hydrocarbon analyzer (GC-FID) provided side-by-side measurements of methane (CH4) for 13 months. The PAMGA also measured nitrous oxide (N2O), and a side-by-side comparison was performed with a gas-filter correlation analyzer (GFC) for six months. Barn ventilation rates were measured by recording run times of the 127-cm diameter exhaust fans. All 125 belt-driven exhaust fans were identical, and in situ airflow measurements using the Fan Assessment Numeration System (FANS) were conducted once at the beginning and twice during the test. Daily CH4 and N2O emission rates were calculated over approximately 19 and 6 month periods respectively, on per barn, head, animal unit, floor area space and barn capacity bases. The differences between the analyzers' concentration measurements were compared in conjunction with water vapor and other gases. The analyzer type had a significant impact on the average CH4 emission rate (p < 0.001) and the average N2O emission rate (p < 0.05). Based on the CH4 measurements with the GC-FID, average daily mean CH4 emissions were approximately 290 g AU-1 d-1 (390 g cow-1 d-1) with very limited seasonal effects. Little variation was observed in CH4 emission rates before and after the change in manure collection method, suggesting that most of the CH4 emissions were enteric losses directly from the cows. The average daily mean N2O emission rates based on the GFC were

  4. Shipboard measurements and modeling of the distribution of CH4 and 13CH4 in the western Pacific

    NASA Astrophysics Data System (ADS)

    Bromley, T.; Allan, W.; Martin, R.; Mikaloff Fletcher, S. E.; Lowe, D. C.; Struthers, H.; Moss, R.

    2012-02-01

    We present observations of methane (CH4) mixing ratio and 13C/12C isotopic ratios in CH4 (δ13C) data from a collaborative shipboard project using bulk carrier ships sailing between Nelson, New Zealand, and Osaka, Japan, in the western Pacific Ocean. Measurements of the CH4 mixing ratio and δ13C in CH4were obtained from large clean-air samples collected in each 2.5° to 5° of latitude between 30°S and 30°N on eight voyages from 2004 to 2007. The data show large variations in CH4 mixing ratio in the tropical western Pacific, and data analysis suggests that these large variations are related to the positions and strengths of the South Pacific Convergence Zone and the Intertropical Convergence Zone, with variability in the sources playing a much smaller role. These measurements are compared with results from a modified version of the Unified Model (UMeth) general circulation model along two transects, one similar to the ship transects and another 18.75° to the east. Although UMeth was run to a steady state with the same sources and sinks each year, the gradient structures varied considerably from year to year, supporting our conclusion that variability in transport is a major driver for the observed variations in CH4. Simulations forced with an idealized representation of the El Niño-Southern Oscillation (ENSO) suggest that a large component of the observed variability in latitudinal gradients of CH4 and its δ13C arises from intrinsic variability in the climate system that does not occur on ENSO time scales.

  5. Subsoil methanogenesis as source of stem CH4 emission in upland forest trees: preferential CH4 transport via the root system?

    NASA Astrophysics Data System (ADS)

    Maier, M.; Machacova, K.; Urban, O.; Friederike, L.

    2016-12-01

    Quantifying and understanding green house gas fluxes in natural soil-plant-atmosphere systems are crucial to predicting global climate change. Wetland species or trees at waterlogged sites are known to emit large amounts of CH4. Yet upland forest soils are regarded as CH4 sinks and tree species like upland European beech (Fagus sylvatica, L.) are assumed not to emit CH4. We studied the soil-atmosphere and stem-atmosphere fluxes of CH4, and soil gas profiles at two upland beech forest sites in Central Europe. Soil was a net CH4 sink at both. Unusually there was one beech tree with substantial CH4 emissions that were higher than the CH4 sink of the soil. The soil gas profile at this tree indicated CH4 production at a soil depth >0.3 m, despite the net uptake of CH4 observed at the soil surface adjacent to the tree. Field soil assessment showed strong redoximorphic color patterns in the adjacent soil. We think that there is a transport link between the soil and stem via the root system representing a preferential transport mechanism for CH4 despite the fact that beech roots usually do not bear aerenchyma. The gas transport process , either via dissolved CH4 in the xylem water or in the root gas phase, is not yet clear. The observed CH4 stem emissions represent an important CH4flux in this ecosystem, und thus should be considered in future research. AcknowledgementThis research was financially supported by the Czech Academy of Sciences and the German Academic Exchange Service within the project "Methane (CH4) and nitrous oxide (N2O) emissions from Fagus sylvatica trees" (DAAD-15-03), National Programme for Sustainability I (LO1415) and project DFG (MA 5826/2-1). We would like to thank Marek Jakubik, Katerina Svobodova, Sinikka Paulus, Ellen Halaburt and Sally Haddad for technical support.

  6. PEaCH4 v.2.0: A modelling platform to predict early diagenetic processes in marine sediments with a focus on biogenic methane - Case study: Offshore Namibia

    NASA Astrophysics Data System (ADS)

    Arning, Esther T.; Häußler, Steffen; van Berk, Wolfgang; Schulz, Hans-Martin

    2016-07-01

    The modelling of early diagenetic processes in marine sediments is of interest in marine science, and in the oil and gas industry, here, especially with respect to methane occurrence and gas hydrate formation as resources. Early diagenesis in marine sediments evolves from a complex web of intertwining (bio)geochemical reactions. It comprises microbially catalysed reactions and inorganic mineral-water-gas interactions. A model that will describe and consider all of these reactions has to be complex. However, it should be user-friendly, as well as to be applicable for a broad community and not only for experts in the field of marine chemistry. The presented modelling platform PeaCH4 v.2.0 combines both aspects, and is Microsoft Excel©-based. The modelling tool is PHREEQC (version 2), a computer programme for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations. The conceptual PEaCH4 model is based on the conversion of sediment-bound degradable organic matter. PEaCH4 v.2.0 was developed to quantify and predict early diagenetic processes in marine sediments with the focus on biogenic methane formation and its phase behaviour, and allows carbon mass balancing. In regard to the irreversible degradation of organic matter, it comprises a "reaction model" and a "kinetic model" to predict methane formation. Both approaches differ in their calculations and outputs as the "kinetic model" considers the modelling time to integrate temperature dependent biogenic methane formation in its calculations, whereas the "reaction model" simply relies on default organic matter degradation. With regard to the inorganic mineral-water-gas interactions, which are triggered by irreversible degradation of organic matter, PEaCH4 v.2.0 is based on chemical equilibrium thermodynamics, appropriate mass-action laws, and their temperature dependent equilibrium constants. The programme is exemplarily presented with the example of upwelling sediments off Namibia

  7. Hydrogen and carbon isotope systematics in hydrogenotrophic methanogenesis under H2-limited and H2-enriched conditions: implications for the origin of methane and its isotopic diagnosis

    NASA Astrophysics Data System (ADS)

    Okumura, Tomoyo; Kawagucci, Shinsuke; Saito, Yayoi; Matsui, Yohei; Takai, Ken; Imachi, Hiroyuki

    2016-12-01

    Hydrogen and carbon isotope systematics of H2O-H2-CO2-CH4 in hydrogenotrophic methanogenesis and their relation to H2 availability were investigated. Two H2-syntrophic cocultures of fermentatively hydrogenogenic bacteria and hydrogenotrophic methanogens under conditions of <102 Pa-H2 and two pure cultures of hydrogenotrophic methanogens under conditions of 105 Pa-H2 were tested. Carbon isotope fractionation between CH4 and CO2 during hydrogenotrophic methanogenesis was correlated with pH2, as indicated in previous studies. The hydrogen isotope ratio of CH4 produced during rapid growth of the thermophilic methanogen Methanothermococcus okinawensis under high pH2 conditions ( 105 Pa) was affected by the isotopic composition of H2, as concluded in a previous study of Methanothermobacter thermautotrophicus. This " {δ D}_{{H}_2} effect" is a possible cause of the diversity of previously reported values for hydrogen isotope fractionation between CH4 and H2O examined in H2-enriched culture experiments. Hydrogen isotope fractionation between CH4 and H2O, defined by (1000 + {δ D}_{{CH}_4} )/(1000 + {δ D}_{{H}_2O} ), during hydrogenotrophic methanogenesis of the H2-syntrophic cocultures was in the range 0.67-0.69. The hydrogen isotope fractionation of our H2-syntrophic dataset overlaps with those obtained not only from low- pH2 experiments reported so far but also from natural samples of "young" methane reservoirs (0.66-0.74). Conversely, such hydrogen isotope fractionation is not consistent with that of "aged" methane in geological samples (≥0.79), which has been regarded as methane produced via hydrogenotrophic methanogenesis from the carbon isotope fractionation. As a possible process inducing the inconsistency in hydrogen isotope signatures between experiments and geological samples, we hypothesize that the hydrogen isotope signature of CH4 imprinted at the time of methanogenesis, as in the experiments and natural young methane, may be altered by diagenetic hydrogen

  8. Modeling of Isotope Fractionation in Stratospheric CO2, N2O, CH4, and O3: Investigations of Stratospheric Chemistry and Transport, Stratosphere-Troposphere Exchange, and Their Influence on Global Isotope Budgets

    NASA Technical Reports Server (NTRS)

    Boering, Kristie A.; Connell, Peter; Rotman, Douglas

    2004-01-01

    We investigated the isotopic fractionation of CH4 and hydrogen (H2) in the stratosphere by incorporating isotope-specific rate coefficients into the Lawrence Livermore National Laboratory (LLNL) 2D model and comparing the model results with new observations from the NASA ER-2 aircraft (funded through a separate task under the Upper Atmosphere Research Program). The model results reveal that fractionation which occurs in the stratosphere has a significant influence on isotope compositions in the free troposphere, an important point which had previously been ignored, unrecognized or unquantified for many long-lived trace gases, including CH4 and H2 which we have focused our efforts on to date. Our analyses of the model results and new isotope observations have also been used to test how well the kinetic isotope effects are known, at least to within the uncertainties in model chemistry and transport. Overall, these results represent an important step forward in our understanding of isotope fractionation in the atmosphere and demonstrate that stratospheric isotope fractionation cannot be ignored in modeling studies which use isotope observations in the troposphere to infer the global budgets of CH4 (an important greenhouse gas) and of H2 (a gas whose atmospheric budget must be better quantified, particularly before a large human perturbation from fuel cell use is realized). Our analyses of model results and observations from the NASA ER-2 aircraft are briefly summarized separately below for CH4, H2, and H2O and for the contribution of these modeling studies to date to our understanding of isotope fractionation for N2O, CO2, and O3 as well.

  9. Isotopic signatures of anthropogenic CH4 sources in Alberta, Canada

    NASA Astrophysics Data System (ADS)

    Lopez, M.; Sherwood, O. A.; Dlugokencky, E. J.; Kessler, R.; Giroux, L.; Worthy, D. E. J.

    2017-09-01

    A mobile system was used for continuous ambient measurements of stable CH4 isotopes (12CH4 and 13CH4) and ethane (C2H6). This system was used during a winter mobile campaign to investigate the CH4 isotopic signatures and the C2H6/CH4 ratios of the main anthropogenic sources of CH4 in the Canadian province of Alberta. Individual signatures were derived from δ13CH4 and C2H6 measurements in plumes arriving from identifiable single sources. Methane emissions from beef cattle feedlots (n = 2) and landfill (n = 1) had δ13CH4 signatures of -66.7 ± 2.4‰ and -55.3 ± 0.2‰, respectively. The CH4 emissions associated with the oil or gas industry had distinct δ13CH4 signatures, depending on the formation process. Emissions from oil storage tanks (n = 5) had δ13CH4 signatures ranging from -54.9 ± 2.9‰ to -60.6 ± 0.6‰ and non-detectable C2H6, characteristic of secondary microbial methanogenesis in oil-bearing reservoirs. In contrast, CH4 emissions associated with natural gas facilities (n = 8) had δ13CH4 signatures ranging from -41.7 ± 0.7‰ to -49.7 ± 0.7‰ and C2H6/CH4 molar ratios of 0.10 for raw natural gas to 0.04 for processed/refined natural gas, consistent with thermogenic origins. These isotopic signatures and C2H6/CH4 ratios have been used for source discrimination in the weekly atmospheric measurements of stable CH4 isotopes over a two-month winter period at the Lac La Biche (LLB) measurement station, located in Alberta, approximately 200 km northeast of Edmonton. The average signature of -59.5 ± 1.4‰ observed at LLB is likely associated with transport of air after passing over oil industry sources located south of the station.

  10. Hg-sensitized photolysis of diethylamine in the absence and presence of O/sub 2/ or N/sub 2/O

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    DeStefano, G.; Heicklen, J.

    1986-09-11

    The Hg-sensitized photolysis of diethylamine (DEA) was studied in the absence and presence of O/sub 2/ or N/sub 2/O at room temperature. In the absence of foreign gases, the products were H/sub 2/, CH/sub 3/CH=NC/sub 2/H/sub 5/ and N,N'-diethylbutane-2,3-diamine (III), with respective quantum yields of 1.0, 1.0, and similarly ordered 0.02. Thus CH/sub 3/CHNHC/sub 2/H/sub 5/ radicals are produced exclusively and they are removed by self reaction: 2CH/sub 3/CHNHC/sub 2/H/sub 5/ ..-->.. DEA + CH/sub 3/CH=NC/sub 2/H/sub 5/ (4a) and 2CH/sub 3/CHNHC/sub 2/H/sub 5/ ..-->.. diamine III (4b), with k/sub 4a//k/sub 4b/ = 47.0 +/- 5.6. In the presence ofmore » O/sub 2/ the radicals are scavenged exclusively by abstraction of the H atom on the nitrogen to give the imine CH/sub 3/CH=NC/sub 2/H/sub 5/ as the exclusive product: (CH/sub 3/CHNHC/sub 2/H/sub 5/ + O/sub 2/ ..-->.. CH/sub 3/CH=NC/sub 2/H/sub 5/ + HO/sub 2/ (5). The Hg-sensitized photolysis of N/sub 2/O gives O(/sup 3/P) atoms, which in the presence of DEA react to give the imine and (C/sub 2/H/sub 5/)/sub 2/NOH (DEHA) as products in concerted parallel steps: O(/sup 3/P) + (C/sub 2/H/sub 5/)/sub 2/NH ..-->.. CH/sub 3/CH=NC/sub 2/H/sub 5/ + H/sub 2/O (9a) and O(/sup 3/P) + (C/sub 2/H/sub 5/)/sub 2/NH ..-->.. (C/sub 2/H/sub 5/)/sub 2/NOH (9b), with k/sub 9a//k/sub 9b/ similarly ordered 9.5 +/- 1.7.« less

  11. F -state quenching with CH 4 for buffer-gas cooled 171 Y b + frequency standard [Methane (CH4) for quenching the F-state in trapped Yb+ ions].

    DOE PAGES

    Jau, Y. -Y.; Hunker, J. D.; Schwindt, P. D. D.

    2015-11-01

    We report that methane, CH 4, can be used as an efficient F-state quenching gas for trapped ytterbium ions. The quenching rate coefficient is measured to be (2.8 ± 0.3) × 10 6 s -1 Torr -1. For applications that use microwave hyperfine transitions of the ground-state 171Y b ions, the CH4 induced frequency shift coefficient and the decoherence rate coefficient are measured as δν/ν = (-3.6 ± 0.1) × 10 -6 Torr -1 and 1/T2 = (1.5 ± 0.2) × 10 5 s -1 Torr -1. In our buffer-gas cooled 171Y b+ microwave clock system, we find that onlymore » ≤10 -8 Torr of CH 4 is required under normal operating conditions to efficiently clear the F-state and maintain ≥85% of trapped ions in the ground state with insignificant pressure shift and collisional decoherence of the clock resonance.« less

  12. [Research advances in control of N2O emission from municipal solid waste landfill sites].

    PubMed

    Cai, Chuan-Yu; Li, Bo; Lü, Hao-Hao; Wu, Wei-Xiang

    2012-05-01

    Landfill is one of the main approaches for municipal solid waste treatment, and landfill site is a main emission source of greenhouse gases nitrous oxide (N2O) and methane (CH4). As a high-efficient trace greenhouse gas, N2O has a very high warming potential, with a warming capacity 296 times of CO2, and has a long-term stability in atmosphere, giving greater damage to the ozone layer. Aiming at the researches in the control of N2O emission from municipal solid waste landfill sites, this paper summarized the characteristics and related affecting factors of the N2O emission from the landfill sites, and put forward a series of the measures adaptable to the N2O emission control of present municipal solid waste landfill sites in China. Some further research focuses on the control of N2O emission from the landfill sites were also presented.

  13. The effect of water regime and soil management on methane (CH4) emission of rice field

    NASA Astrophysics Data System (ADS)

    Naharia, O.; Setyanto, P.; Arsyad, M.; Burhan, H.; Aswad, M.

    2018-05-01

    Mitigation of CH4 emission of rice field is becoming a serious issue. The Agricultural Environment Preservation Research Station in Central Java conducted a field study to investigate the effect of water regime and soil tillage on CH4 emission from paddy fields. Treatments consisted of two factors. The first factor was water regime, e.g., 1) continuously flooded 5 cm, 2) intermittent irrigation and 3) saturated water condition at 0-1 cm water level. The second factor was soil management, e.g., 1) normal tillage, 2) zero tillage + 3 sulfosate ha-1 and 3) zero tillage + 3 L paraquat ha-1. Most of treatments gave a significant reduction of total CH4 emission between 34 – 85% during the wet season crop as compared to normal rice cropping practice, while in the dry season the CH4 reduction ranged between 16 – 92%. No-tillage with non-selective herbicides combined with intermittent/saturated irrigation system significantly reduced methane emission without significantly affecting rice productivity as compared to normal tillage with continuous flooding (farmers practice)

  14. Short-term nitrogen additions can shift a coastal wetland from a sink to a source of N2O

    USGS Publications Warehouse

    Moseman-Valtierra, Serena; Gonzalez, Rosalinda; Kroeger, Kevin D.; Tang, Jianwu; Chao, Wei Chun; Crusius, John; Bratton, John F.; Green, Adrian; Shelton, James

    2011-01-01

    Coastal salt marshes sequester carbon at high rates relative to other ecosystems and emit relatively little methane particularly compared to freshwater wetlands. However, fluxes of all major greenhouse gases (N2O, CH4, and CO2) need to be quantified for accurate assessment of the climatic roles of these ecosystems. Anthropogenic nitrogen inputs (via run-off, atmospheric deposition, and wastewater) impact coastal marshes. To test the hypothesis that a pulse of nitrogen loading may increase greenhouse gas emissions from salt marsh sediments, we compared N2O, CH4 and respiratory CO2fluxes from nitrate-enriched plots in a Spartina patens marsh (receiving single additions of NaNO3 equivalent to 1.4 g N m−2) to those from control plots (receiving only artificial seawater solutions) in three short-term experiments (July 2009, April 2010, and June 2010). In July 2009, we also compared N2O and CH4 fluxes in both opaque and transparent chambers to test the influence of light on gas flux measurements. Background fluxes of N2O in July 2009 averaged −33 μmol N2O m−2 day−1. However, within 1 h of nutrient additions, N2O fluxes were significantly greater in plots receiving nitrate additions relative to controls in July 2009. Respiratory rates and CH4 fluxes were not significantly affected. N2O fluxes were significantly higher in dark than in transparent chambers, averaging 108 and 42 μmol N2O m−2 day−1 respectively. After 2 days, when nutrient concentrations returned to background levels, none of the greenhouse gas fluxes differed from controls. In April 2010, N2O and CH4 fluxes were not significantly affected by nitrate, possibly due to higher nitrogen demands by growing S. patens plants, but in June 2010 trends of higher N2O fluxes were again found among nitrate-enriched plots, indicating that responses to nutrient pulses may be strongest during the summer. In terms of carbon equivalents, the highest average N2O and CH4 fluxes observed, exceeded half

  15. Fabrication of ZnO photonic crystals by nanosphere lithography using inductively coupled-plasma reactive ion etching with CH{sub 4}/H{sub 2}/Ar plasma on the ZnO/GaN heterojunction light emitting diodes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chen, Shr-Jia; Chang, Chun-Ming; Kao, Jiann-Shiun

    2010-07-15

    This article reports fabrication of n-ZnO photonic crystal/p-GaN light emitting diode (LED) by nanosphere lithography to further booster the light efficiency. In this article, the fabrication of ZnO photonic crystals is carried out by nanosphere lithography using inductively coupled plasma reactive ion etching with CH{sub 4}/H{sub 2}/Ar plasma on the n-ZnO/p-GaN heterojunction LEDs. The CH{sub 4}/H{sub 2}/Ar mixed gas gives high etching rate of n-ZnO film, which yields a better surface morphology and results less plasma-induced damages of the n-ZnO film. Optimal ZnO lattice parameters of 200 nm and air fill factor from 0.35 to 0.65 were obtained from fittingmore » the spectrum of n-ZnO/p-GaN LED using a MATLAB code. In this article, we will show our recent result that a ZnO photonic crystal cylinder has been fabricated using polystyrene nanosphere mask with lattice parameter of 200 nm and radius of hole around 70 nm. Surface morphology of ZnO photonic crystal was examined by scanning electron microscope.« less

  16. Enhanced photocatalytic CO2 reduction to CH4 over separated dual co-catalysts Au and RuO2

    NASA Astrophysics Data System (ADS)

    Dong, Chunyang; Hu, Songchang; Xing, Mingyang; Zhang, Jinlong

    2018-04-01

    A spatially separated, dual co-catalyst photocatalytic system was constructed by the stepwise introduction of RuO2 and Au nanoparticles (NPs) at the internal and external surfaces of a three dimensional, hierarchically ordered TiO2-SiO2 (HTSO) framework (the final photocatalyst was denoted as Au/HRTSO). Characterization by HR-TEM, EDS-mapping, XRD and XPS confirmed the existence and spatially separated locations of Au and RuO2. In CO2 photocatalytic reduction (CO2PR), Au/HRTSO (0.8%) shows the optimal performance in both the activity and selectivity towards CH4; the CH4 yield is almost twice that of the singular Au/HTSO or HRTSO (0.8%, weight percentage of RuO2) counterparts. Generally, Au NPs at the external surface act as electron trapping agents and RuO2 NPs at the inner surface act as hole collectors. This advanced spatial configuration could promote charge separation and transfer efficiency, leading to enhanced CO2PR performance in both the yield and selectivity toward CH4 under simulated solar light irradiation.

  17. Quantification of Methane and Nitrous Oxide Emissions from Wastewater Collection Systems (Cincinnati, Ohio, USA)

    NASA Astrophysics Data System (ADS)

    Fries, A. E.; Townsend-Small, A.; Shuster, W.; Schifman, L. A.

    2016-12-01

    Greenhouse gas emissions from urban areas is an emerging topic in environmental science, but source apportionment of these emissions, particularly for methane (CH4) and nitrous oxide (N2O), is still underway. Here we present an analysis of CH4 and N2O sources from urban pipelines in Cincinnati, Ohio, USA. Leaks from manholes and sewer grates in Cincinnati are found by using a Bascom Turner Gas Rover to indicate CH4 enhancements, along with spatial data for CH4 enhancements at street level from previously published work. When possible, the atmospheric flux of CH4 and N2O of these leaks are quantified by using a flux chamber method. Source apportionment is determined by using carbon and hydrogen stable isotope ratios (13C and D) and CH4 to N2O ratios. Biogenic CH4 has a δ13C of approximately -55‰ and δD of approximately -270‰, whereas thermogenic CH4 has a δ13C of approximately -45‰ and δD of approximately -150‰. Biogenic CH4 may also co-occur with N2O, whereas thermogenic natural gas does not contain N2O. Contrary to our expectations, we found a portion of CH4 enhancements that are biogenic CH4, presumably from sewer gas, whereas most studies have assumed them to be natural gas leaks. In the future we will be working on determining the exact proportion of biogenic and thermogenic CH4 in street leaks and further quantifying CH4 and N2O emissions throughout Cincinnati. Our work indicates that CH4 leaks in cities may be a mixture of sewer gas and natural gas, especially in cities like Cincinnati where natural gas pipelines have been replaced with less leak-prone pipe materials.

  18. Local- and regional-scale measurements of CH4, δ13CH4, and C2H6 in the Uintah Basin using a mobile stable isotope analyzer

    NASA Astrophysics Data System (ADS)

    Rella, C. W.; Hoffnagle, J.; He, Y.; Tajima, S.

    2015-10-01

    In this paper, we present an innovative CH4, δ13CH4, and C2H6 instrument based on cavity ring-down spectroscopy (CRDS). The design and performance of the analyzer is presented in detail. The instrument is capable of precision of less than 1 ‰ on δ13CH4 with 1 in. of averaging and about 0.1 ‰ in an hour. Using this instrument, we present a comprehensive approach to atmospheric methane emissions attribution. Field measurements were performed in the Uintah Basin (Utah, USA) in the winter of 2013, using a mobile lab equipped with the CRDS analyzer, a high-accuracy GPS, a sonic anemometer, and an onboard gas storage and playback system. With a small population and almost no other sources of methane and ethane other than oil and gas extraction activities, the Uintah Basin represents an ideal location to investigate and validate new measurement methods of atmospheric methane and ethane. We present the results of measurements of the individual fugitive emissions from 23 natural gas wells and six oil wells in the region. The δ13CH4 and C2H6 signatures that we observe are consistent with the signatures of the gases found in the wells. Furthermore, regional measurements of the atmospheric CH4, δ13CH4, and C2H6 signatures throughout the basin have been made, using continuous sampling into a 450 m long tube and laboratory reanalysis with the CRDS instrument. These measurements suggest that 85 ± 7 % of the total emissions in the basin are from natural gas production.

  19. Mean Ages of Stratospheric Air Derived From in Situ Observations of CO2, CH4, and N2O

    NASA Technical Reports Server (NTRS)

    Andrews, A. E.; Boering, K. A.; Daube, B. C.; Wofsy, S. C.; Loewenstein, M.; Jost, H.; Podolske, J. R.; Webster, C. R.; Herman, R. L.; Scott, D. C.; hide

    2001-01-01

    Accurate mean ages for stratospheric air have been derived from a spatially and temporally comprehensive set of in situ observations of CO2, CH4, and N2O obtained from 1992 to 1998 from the NASA ER-2 aircraft and balloon flights. Errors associated with the tropospheric CO2 seasonal cycle and interannual variations in the CO2 growth rate are less than 0.5 year throughout the stratosphere and less than 0.3 year for air older than 2 years (N2O less than 275 ppbv), indicating that the age spectra are broad enough to attenuate these influences over the time period covered by these observations. The distribution of mean age with latitude and altitude provides detailed, quantitative information about the general circulation of the stratosphere. At 20 km, sharp meridional gradients in the mean age are observed across the subtropics. Between 20 and 30 km, the average difference in mean age between the tropics and midlatitudes is approximately 2 years, with slightly smaller differences at higher and lower altitudes. The mean age in the midlatitude middle stratosphere (approx. 25-32 km) is relatively constant with respect to altitude at 5 plus or minus 0.5 years. Comparison with earlier balloon observations of CO2 dating back to the 1970s indicates that the mean age of air in this region has remained within 11 year of its current value over the last 25 years. A climatology of mean age is derived from the observed compact relationship between mean age and N2O. These characteristics of the distribution of mean age in the stratosphere will serve as critically needed diagnostics for models of stratospheric transport.

  20. Microwave Plasma-Activated Chemical Vapor Deposition of Nitrogen-Doped Diamond. II: CH4/N2/H2 Plasmas

    PubMed Central

    2016-01-01

    We report a combined experimental and modeling study of microwave-activated dilute CH4/N2/H2 plasmas, as used for chemical vapor deposition (CVD) of diamond, under very similar conditions to previous studies of CH4/H2, CH4/H2/Ar, and N2/H2 gas mixtures. Using cavity ring-down spectroscopy, absolute column densities of CH(X, v = 0), CN(X, v = 0), and NH(X, v = 0) radicals in the hot plasma have been determined as functions of height, z, source gas mixing ratio, total gas pressure, p, and input power, P. Optical emission spectroscopy has been used to investigate, with respect to the same variables, the relative number densities of electronically excited species, namely, H atoms, CH, C2, CN, and NH radicals and triplet N2 molecules. The measurements have been reproduced and rationalized from first-principles by 2-D (r, z) coupled kinetic and transport modeling, and comparison between experiment and simulation has afforded a detailed understanding of C/N/H plasma-chemical reactivity and variations with process conditions and with location within the reactor. The experimentally validated simulations have been extended to much lower N2 input fractions and higher microwave powers than were probed experimentally, providing predictions for the gas-phase chemistry adjacent to the diamond surface and its variation across a wide range of conditions employed in practical diamond-growing CVD processes. The strongly bound N2 molecule is very resistant to dissociation at the input MW powers and pressures prevailing in typical diamond CVD reactors, but its chemical reactivity is boosted through energy pooling in its lowest-lying (metastable) triplet state and subsequent reactions with H atoms. For a CH4 input mole fraction of 4%, with N2 present at 1–6000 ppm, at pressure p = 150 Torr, and with applied microwave power P = 1.5 kW, the near-substrate gas-phase N atom concentration, [N]ns, scales linearly with the N2 input mole fraction and exceeds the concentrations [NH]ns, [NH2]ns

  1. CH(X2∏, a4∑-) ... OH2 and CH2(X˜3B1, ã1A1) ... OH2 interactions. A first principles investigation

    NASA Astrophysics Data System (ADS)

    Tzeli, Demeter; Mavridis, Aristides

    We have investigated the interaction of the methylidene, CH(X2∏, a4∑-) and methylene, CH2(X˜3B1, ã1A1) with H2O, employing the (P)MPn (n = 2, 4) techniques in conjunction with the sequence of correlation consistent basis sets aug-cc-pVxZ, x = 2, 3, and 4. For the CH ... OH2 system, we have located four minima (m) and three transition states (ts) and for the CH2 ... OH2, five minima and four transition states. All our results have been corrected for zero-point energy (ZPE) and basis set superposition errors (BSSE), while for the most important m_ structures, we report complete basis set (CBS) interaction limits. We also report fully optimized geometries, harmonic frequencies, dipole moments, Mulliken charges, and potential energy curves. The highest CH(X2∏) ... OH2 (m1_2∏) and CH2(ã1A1) ... OH2 (m1_1A1) interactions are the result of electron transfer from the oxygen atom to the empty pπ orbitals of CH(X2∏) and CH2(ã1A1), respectively (ylide-like structures). At the (P)MP4/AQZ//MP2/ATZ level, including ZPE, BSSE, and CBS extrapolation, we obtain ΔE0(BSSE)+CBS = -9.36 kcal/mol at rC ... O = 1.752 Å, and -9.73 kcal/mol at rC ... O = 1.741 Å for the m1_2∏ and m1_1A1, respectively.

  2. Biomass fast pyrolysis in a fluidized bed reactor under N2, CO2, CO, CH4 and H2 atmospheres.

    PubMed

    Zhang, Huiyan; Xiao, Rui; Wang, Denghui; He, Guangying; Shao, Shanshan; Zhang, Jubing; Zhong, Zhaoping

    2011-03-01

    Biomass fast pyrolysis is one of the most promising technologies for biomass utilization. In order to increase its economic potential, pyrolysis gas is usually recycled to serve as carrier gas. In this study, biomass fast pyrolysis was carried out in a fluidized bed reactor using various main pyrolysis gas components, namely N(2), CO(2), CO, CH(4) and H(2), as carrier gases. The atmosphere effects on product yields and oil fraction compositions were investigated. Results show that CO atmosphere gave the lowest liquid yield (49.6%) compared to highest 58.7% obtained with CH(4). CO and H(2) atmospheres converted more oxygen into CO(2) and H(2)O, respectively. GC/MS analysis of the liquid products shows that CO and CO(2) atmospheres produced less methoxy-containing compounds and more monofunctional phenols. The higher heating value of the obtained bio-oil under N(2) atmosphere is only 17.8 MJ/kg, while that under CO and H(2) atmospheres increased to 23.7 and 24.4 MJ/kg, respectively. Copyright © 2010 Elsevier Ltd. All rights reserved.

  3. Effects of O 2 plasma and UV-O 3 assisted surface activation on high sensitivity metal oxide functionalized multiwalled carbon nanotube CH 4 sensors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Humayun, Md Tanim; Sainato, Michela; Divan, Ralu

    We present a comparative analysis of UV-O 3 (UVO) and O 2 plasma-based surface activation processes of multi-walled carbon nanotubes (MWCNTs) enabling highly effective functionalization with metal oxide nanocrystals (MONCs). Experimental results from transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy show that by forming COOH (carboxyl), C-OH (hydroxyl), and C=O (carbonyl) groups on the MWCNT surface that act as active nucleation sites, O 2 plasma and UVO-based dry pre-treatment techniques greatly enhance the affinity between MWCNT surface and the functionalizing MONCs. MONCs, such as ZnO and SnO 2, deposited by atomic layermore » deposition (ALD) technique, were implemented as the functionalizing material following UVO and O 2 plasma activation of MWCNTs. In conclusion, a comparative study on the relative resistance changes of O 2 plasma and UVO activated MWCNT functionalized with MONC in the presence of 10 ppm methane (CH 4) in air, is presented as well.« less

  4. Effects of O 2 plasma and UV-O 3 assisted surface activation on high sensitivity metal oxide functionalized multiwalled carbon nanotube CH 4 sensors

    DOE PAGES

    Humayun, Md Tanim; Sainato, Michela; Divan, Ralu; ...

    2017-07-28

    We present a comparative analysis of UV-O 3 (UVO) and O 2 plasma-based surface activation processes of multi-walled carbon nanotubes (MWCNTs) enabling highly effective functionalization with metal oxide nanocrystals (MONCs). Experimental results from transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy show that by forming COOH (carboxyl), C-OH (hydroxyl), and C=O (carbonyl) groups on the MWCNT surface that act as active nucleation sites, O 2 plasma and UVO-based dry pre-treatment techniques greatly enhance the affinity between MWCNT surface and the functionalizing MONCs. MONCs, such as ZnO and SnO 2, deposited by atomic layermore » deposition (ALD) technique, were implemented as the functionalizing material following UVO and O 2 plasma activation of MWCNTs. In conclusion, a comparative study on the relative resistance changes of O 2 plasma and UVO activated MWCNT functionalized with MONC in the presence of 10 ppm methane (CH 4) in air, is presented as well.« less

  5. Luminescence Spectroscopy and Crystal Field Simulations of Europium Propylenediphosphonate EuH[O 3P(CH 2) 3PO 3] and Europium Glutarate [Eu(H 2O)] 2[O 2C(CH 2) 3CO 2] 3·4H 2O

    NASA Astrophysics Data System (ADS)

    Serpaggi, F.; Férey, G.; Antic-Fidancev, E.

    1999-12-01

    The results of investigations on the photoluminescence of two europium hybrid compounds, EuH[O3P(CH2)3PO3] (Eu[diph]) and [Eu(H2O)]2[O2C(CH2)3CO2]3·4H2O (Eu[glut]), are presented. In both compounds one local environment is found for the rare earth (Re) ion and the symmetry of the Re polyhedron is low (Cs) as evidenced by the Eu3+ luminescence studies. The electrostatic crystal field (cf) parameters of the 7F multiplet are obtained by the application of the phenomenological cf theory. The simulations using C2v symmetry for the rare earth ion give good agreement between the calculated and the experimental 7F0-4 energy level schemes. The observed optical data are discussed in relation to the crystal structure of the compounds.

  6. Single Step Bi-reforming and Oxidative Bi-reforming of Methane (Natural Gas) with Steam and Carbon Dioxide to Metgas (CO-2H2) for Methanol Synthesis: Self-Sufficient Effective and Exclusive Oxygenation of Methane to Methanol with Oxygen.

    PubMed

    Olah, George A; Goeppert, Alain; Czaun, Miklos; Mathew, Thomas; May, Robert B; Prakash, G K Surya

    2015-07-15

    Catalysts based on suitable metal oxide supports, such as NiO/MgO and CoO/MgO, were shown to be active for single step bi-reforming, the combined steam and dry reforming of methane or natural gas with H2O and CO2 exclusively to metgas (CO-2H2) for efficient methanol synthesis. Reactions were carried out in a tubular flow reactor under pressures up to 42 bar at 830-910 °C. Using a CH4 to steam to CO2 ratio of ∼3:2:1 in the gas feed, the H2/CO ratio of 2:1 was achieved, which is desired for subsequent methanol synthesis. The needed 2/1 steam/CO2 feed ratio together with the reaction heat for the endothermic bi-reforming can be conveniently obtained by the complete combustion of a quarter part of the overall used methane (natural gas) with oxygen of the air (oxidative bi-reforming). Complete combustion of a part of methane followed by bi-reforming leads to the production of metgas (H2/CO in 2:1 mol ratio) for self-sufficient exclusive methanol synthesis. The long sought after but elusive efficient and selective oxygenation of methane to methanol is thus achieved in an effective and economic way without any oxidation byproduct formation according to CH4 + 1/2O2CH3OH.

  7. Interannual Variability and Trends of CH4, CO and OH Using the Computationally-Efficient CH4-CO-OH (ECCOH) Module

    NASA Technical Reports Server (NTRS)

    Elshorbany, Yasin F.; Duncan, Bryan N.; Strode, Sarah A.; Wang, James S.; Kouatchou, Jules

    2015-01-01

    Methane (CH4) is the second most important anthropogenic greenhouse gas (GHG). Its 100-year global warming potential (GWP) is 34 times larger than that for carbon dioxide. The 100-year integrated GWPof CH4 is sensitive to changes in hydroxyl radical (OH) levels.Oxidation of CH4 and carbon monoxide (CO) by OH is the main loss process, thus affecting the oxidizing capacity of the atmosphere and contributing to the global ozone background. Limitations of using archived, monthly OH fields for studies of methane's and COs evolution are that feedbacks of the CH4-CO-OH system on methane, CO and OH are not captured. In this study, we employ the computationally Efficient CH4-CO-OH (ECCOH) module (Elshorbany et al., 2015) to investigate the nonlinear feedbacks of the CH4-CO-OH system on the interannual variability and trends of the CH4, CO, OH system.

  8. Rate Coefficient Measurements of the Reaction CH3 + O2 = CH3O + O

    NASA Technical Reports Server (NTRS)

    Hwang, S. M.; Ryu, Si-Ok; DeWitt, K. J.; Rabinowitz, M. J.

    1999-01-01

    Rate coefficients for the reaction CH3 + O2 = CH3O + O were measured behind reflected shock waves in a series of lean CH4-O2-Ar mixtures using hydroxyl and methyl radical diagnostics. The rate coefficients are well represented by an Arrhenius expression given as k = (1.60(sup +0.67, sub -0.47 ) x 10(exp 13) e(-15813 +/- 587 K/T)/cubic cm.mol.s. This expression, which is valid in the temperature range 1575-1822 K, supports the downward trend in the rate coefficients that has been reported in recent determinations. All measurements to date, including the present study, have been to some extent affected by secondary reactions. The complications due to secondary reactions, choice of thermochemical data, and shock-boundary layer interactions that affect the determination of the rate coefficients are examined.

  9. Rate Coefficient Measurements of the Reaction CH3+O2+CH3O+O

    NASA Technical Reports Server (NTRS)

    Hwang, S. M.; Ryu, Si-Ok; DeWitt, K. J.; Rabinowitz, M. J.

    1999-01-01

    Rate coefficients for the reaction CH3 + O2 = CH3O + O were measured behind reflected shock waves in a series of lean CH4-O2-Ar mixtures using hydroxyl and methyl radical diagnostics. The rate coefficients are well represented by an Arrhenius expression given as k = (1.60(sup +0.67, -0.47)) X 10(exp 13) exp(- 15813 +/- 587 K/T)cc/mol s. This expression, which is valid in the temperature range 1575-1822 K, supports the downward trend in the rate coefficients that has been reported in recent determinations. All measurements to date, including the present study, have been to some extent affected by secondary reactions. The complications due to secondary reactions, choice of thermochemical data, and shock-boundary layer interactions that affect the determination of the rate coefficients are examined.

  10. Choice of precipitant and calcination temperature of precursor for synthesis of NiCo2O4 for control of CO-CH4 emissions from CNG vehicles.

    PubMed

    Trivedi, Suverna; Prasad, Ram

    2018-03-01

    Compressed natural gas (CNG) is most appropriate an alternative of conventional fuel for automobiles. However, emissions of carbon-monoxide and methane from such vehicles adversely affect human health and environment. Consequently, to abate emissions from CNG vehicles, development of highly efficient and inexpensive catalysts is necessary. Thus, the present work attempts to scan the effects of precipitants (Na 2 CO 3 , KOH and urea) for nickel cobaltite (NiCo 2 O 4 ) catalysts prepared by co-precipitation from nitrate solutions and calcined in a lean CO-air mixture at 400°C. The catalysts were used for oxidation of a mixture of CO and CH 4 (1:1). The catalysts were characterized by X-ray diffractometer, Brunauer-Emmett-Teller surface-area, X-ray photoelectron spectroscopy; temperature programmed reduction and Scanning electron microscopy coupled with Energy-Dispersive X-Ray Spectroscopy. The Na 2 CO 3 was adjudged as the best precipitant for production of catalyst, which completely oxidized CO-CH 4 mixture at the lowest temperature (T 100 =350°C). Whereas, for catalyst prepared using urea, T 100 =362°C. On the other hand the conversion of CO-CH 4 mixture over the catalyst synthesized by KOH limited to 97% even beyond 400°C. Further, the effect of higher calcination temperatures of 500 and 600°C was examined for the best catalyst. The total oxidation of the mixture was attained at higher temperatures of 375 and 410°C over catalysts calcined at 500 and 600°C respectively. Thus, the best precipitant established was Na 2 CO 3 and the optimum calcination temperature of 400°C was found to synthesize the NiCo 2 O 4 catalyst for the best performance in CO-CH 4 oxidation. Copyright © 2017. Published by Elsevier B.V.

  11. Aerial photography based census of Adélie Penguin and its application in CH4 and N2O budget estimation in Victoria Land, Antarctic.

    PubMed

    He, Hong; Cheng, Xiao; Li, Xianglan; Zhu, Renbin; Hui, Fengming; Wu, Wenhui; Zhao, Tiancheng; Kang, Jing; Tang, Jianwu

    2017-10-11

    Penguin guano provides favorable conditions for production and emission of greenhouse gases (GHGs). Many studies have been conducted to determine the GHG fluxes from penguin colonies, however, at regional scale, there is still no accurate estimation of total GHG emissions. We used object-based image analysis (OBIA) method to estimate the Adélie penguin (Pygoscelis adeliae) population based on aerial photography data. A model was developed to estimate total GHG emission potential from Adélie penguin colonies during breeding seasons in 1983 and 2012, respectively. Results indicated that OBIA method was effective for extracting penguin information from aerial photographs. There were 17,120 and 21,183 Adélie penguin breeding pairs on Inexpressible Island in 1983 and 2012, respectively, with overall accuracy of the estimation of 76.8%. The main reasons for the increase in Adélie penguin populations were attributed to increase in temperature, sea ice and phytoplankton. The average estimated CH 4 and N 2 O emissions tended to be increasing during the period from 1983 to 2012 and CH 4 was the main GHG emitted from penguin colonies. Total global warming potential (GWP) of CH 4 and N 2 O emissions was 5303 kg CO 2 -eq in 1983 and 6561 kg CO 2 -eq in 2012, respectively.

  12. SAFETY OF MANNITOL USE IN BOWEL PREPARATION: a prospective assessment of intestinal methane (CH4) levels during colonoscopy after mannitol and sodium phosphate (NaP) bowel cleansing.

    PubMed

    Paulo, Gustavo Andrade de; Martins, Fernanda Prata Borges; Macedo, Erika Pereira de; Gonçalves, Manoel Ernesto Peçanha; Ferrari, Angelo Paulo

    2016-01-01

    - Adequate bowel preparation is critical for the quality of colonoscopy. Despite reported occurrence of colonic explosion due to methane and hydrogen production by bacterial fermentation during colonoscopy, gas exchange during the procedure is believed to be effective in lowering existing methane concentration, allowing for safe utilization of mannitol for bowel preparation. Thus, mannitol is widely used for bowel cleansing prior to colonoscopy, considering its low cost and effectiveness for bowel preparation. - The aim of this study was to assess the safety of mannitol for bowel preparation, when compared to sodium phosphate (NaP). - We conducted a prospective observational study in which 250 patients undergoing colonoscopy at Universidade Federal de São Paulo and Hospital Albert Einstein (São Paulo, Brazil) were approached for inclusion in the study. Patients received either mannitol (n=50) or NaP (n=200) for bowel preparation, based on physician indication. Study was conducted from August 2009 to December 2009. The main outcome of interest was presence of detectable levels of methane (CH4) during colonoscopy and reduction in such levels after gas exchange during the procedure. Methane concentrations were measured in three intestinal segments during scope introduction and withdrawal. Safety was assessed as the absence of high levels of methane, defined as 5%. Measurements were made using a multi-gas monitor (X-am 7000, Dräger Safety AG & Co. KGaA, Lübeck, Germany) connected to a plastic catheter introduced into the working channel of the colonoscope. Additional outcomes of interest included levels of O2. Methane and O2 levels are reported as ppm. Mean, difference and standard deviation of levels of gas measured in both moments were calculated and compared in both groups. Proportions of patients with detectable or high levels of methane in both groups were compared. Continuous variables were analyzed using t test and categorical variables using qui

  13. Step Towards Modeling the Atmosphere of Titan: State-Selected Reactions of O+ with Methane.

    PubMed

    Hrušák, J; Paidarová, I

    2016-11-01

    Methane conversion and in particular the formation of the C-O bond is one of fundamental entries to organic chemistry and it appears to be essential for understanding parts of atmospheric chemistry of Titan, but, in broader terms it might be also relevant for Earth-like exoplanets. Theoretical study of the reactions of methane with atomic oxygen ion in its excited electronic states requires treating simultaneously at least 19 electronic states. Development of a computational strategy that would allow chemically reasonable and computationally feasible treatment of the CH 4 (X)/O + ( 2 D, 2 P) system is by far not trivial and it requires careful examination of all the complex features of the corresponding 19 potential energy surfaces. Before entering the discussion of the rich (photo) chemistry, inspection of the long range behavior of the system with focus on electric dipole transition moments is required. Our calculations show nonzero probability for the reactants to decay before entering the multiple avoided crossings region of the [CH 4  + O → products] + reaction. For the CH 4 /O + ( 2 P) system non-zero transition moment probabilities occur over the entire range of considered C-O distances (up to 15 Å), while for the CH 4 /O + ( 2 D) system these probabilities are lower by one order of magnitude and were found only at C-O distances smaller than 6 Å.

  14. Syntheses and multi-NMR study of fac- and mer-OsO(3)F(2)(NCCH(3)) and the X-ray crystal structure (n = 2) and Raman spectrum (n = 0) of fac-OsO(3)F(2)(NCCH(3)).nCH(3)CN.

    PubMed

    Hughes, Michael J; Gerken, Michael; Mercier, Hélène P A; Schrobilgen, Gary J

    2010-06-07

    Dissolution of the infinite chain polymer, (OsO(3)F(2))(infinity), in CH(3)CN solvent at -40 degrees C followed by solvent removal under vacuum at -40 degrees C yielded fac-OsO(3)F(2)(NCCH(3)).nCH(3)CN (n >/= 2). Continued pumping at -40 degrees C with removal of uncoordinated CH(3)CN yielded fac-OsO(3)F(2)(NCCH(3)). Both fac-OsO(3)F(2)(NCCH(3)).nCH(3)CN and fac-OsO(3)F(2)(NCCH(3)) are yellow-brown solids and were characterized by low-temperature (-150 degrees C) Raman spectroscopy. The crystal structure (-173 degrees C) of fac-OsO(3)F(2)(NCCH(3)).2CH(3)CN consists of two co-crystallized CH(3)CN molecules and a pseudo-octahedral OsO(3)F(2).NCCH(3) molecule in which three oxygen atoms are in a facial arrangement and CH(3)CN is coordinated trans to an oxygen atom in an end-on fashion. The Os---N bond length (2.205(3) A) is among the shortest M---N adduct bonds observed for a d(0) transition metal oxide fluoride. The (19)F NMR spectrum of (OsO(3)F(2))(infinity) in CH(3)CN solvent (-40 degrees C) is a singlet (-99.6 ppm) corresponding to fac-OsO(3)F(2)(NCCH(3)). The (1)H, (15)N, (13)C, and (19)F NMR spectra of (15)N-enriched OsO(3)F(2)(NCCH(3)) were recorded in SO(2)ClF solvent (-84 degrees C). Nitrogen-15 enrichment resulted in splitting of the (19)F resonance of fac-OsO(3)F(2)((15)NCCH(3)) into a doublet ((2)J((15)N-(19)F), 21 Hz). In addition, a doublet of doublets ((2)J((19)F(ax)-(19)F(eq)), 134 Hz; (2)J((15)N-(19)F(eq)), 18 Hz) and a doublet ((2)J((19)F(ax)-(19)F(eq)), 134 Hz) were observed in the (19)F NMR spectrum that have been assigned to mer-OsO(3)F(2)((15)NCCH(3)); however, coupling of (15)N to the axial fluorine-on-osmium environment could not be resolved. The nitrogen atom of CH(3)CN is coordinated trans to a fluorine ligand in the mer-isomer. Quantum-chemical calculations at the SVWN and B3LYP levels of theory were used to calculate the energy-minimized gas-phase geometries, vibrational frequencies of fac- and mer-OsO(3)F(2)(NCCH(3)) and of CH(3)CN. The

  15. Effect of frame size and season on enteric methane (CH4) and carbon dioxide (CO2)emissions in Angus brood cows grazing native tall-grass prairie in central Oklahoma USA

    USDA-ARS?s Scientific Manuscript database

    Effect of frame size and season on enteric methane (CH4) and carbon dioxide (CO2) emissions in Angus brood cows grazing native tall-grass prairie in central Oklahoma, USA J.P.S. Neel USDA ARS, El Reno, OK A reduction in enteric CH4 production in ruminants is associated with improved production effic...

  16. The global warming potential of methane reassessed with combined stratosphere and troposphere chemistry

    NASA Astrophysics Data System (ADS)

    Holmes, C. D.; Archibald, A. T.; Eastham, S. D.; Søvde, O. A.

    2017-12-01

    Methane is a direct and indirect greenhouse gas. The direct greenhouse effect comes from the radiation absorbed and emitted by methane itself. The indirect greenhouse effect comes from radiatively active gases that are produced during methane oxidation: principally O3, H2O, and CO2. Methane also suppresses tropospheric OH, which indirectly affects numerous greenhouses gases and aerosols. Traditionally, the methane global warming potential (GWP) has included the indirect effects on tropospheric O3 and OH and stratospheric H2O, with these effects estimated independently from unrelated tropospheric and stratospheric chemistry models and observations. Using this approach the CH4 is about 28 over 100 yr (without carbon cycle feedbacks, IPCC, 2013). Here we present a comprehensive analysis of the CH4 GWP in several 3-D global atmospheric models capable of simulating both tropospheric and stratospheric chemistry (GEOS-Chem, Oslo CTM3, UKCA). This enables us to include, for the first time, the indirect effects of CH4 on stratospheric O3 and stratosphere-troposphere coupling. We diagnose the GWP from paired simulations with and without a 5% perturbation to tropospheric CH4 concentrations. Including stratospheric chemistry nearly doubles the O3 contribution to CH4 GWP because of O3 production in the lower stratosphere and because CH4 inhibits Cl-catalyzed O3 loss in the upper stratosphere. In addition, stratosphere-troposphere coupling strengthens the chemical feedback on its own lifetime. In the stratosphere, this feedback operates by a CH4 perturbation thickening the stratospheric O3 layer, which impedes UV-driven OH production in the troposphere and prolongs the CH4 lifetime. We also quantify the impact of CH4-derived H2O on the stratospheric HOx cycles but these effects are small. Combining all of the above, these models suggest that the 100-yr GWP of CH4 is over 33.5, a 20% increase over the latest IPCC assessment.

  17. Relationships between the potential production of the greenhouse gases CO2, CH4 and N2O and soil concentrations of C, N and P across 26 paddy fields in southeastern China

    NASA Astrophysics Data System (ADS)

    Wang, Weiqi; Sardans, Jordi; Wang, Chun; Zeng, Congsheng; Tong, Chuan; Asensio, Dolores; Peñuelas, Josep

    2017-09-01

    Paddy fields are a major global anthropogenic source of greenhouse gases. China has the second largest area under rice cultivation, so determining the relationships between the emission of greenhouse gases and soil carbon content, nutrient availabilities and concentrations and physical properties is crucial for minimizing the climatic impacts of rice agriculture. We examined soil nutrients and other properties, greenhouse-gas production and their relationships in 26 paddy fields throughout the province of Fujian in China, one of the most important provinces for rice production. High P and K concentrations, contents and availabilities were correlated with low rates of CO2 production, whereas high C and N contents were correlated with high rates of CH4 production. Mean annual precipitation (MAP) and rates of gas production were not clearly correlated, at least partly due to the management of flooding that can mask the effect of precipitation. Higher mean annual temperatures and soil Fe contents favored the production of N2O. C, N, P and K concentrations and their ratios, especially the C:K and N:K ratios, and P availability were correlated with CO2 and CH4 production across the province, with higher C:K and N:K ratios correlated positively with increased CO2 production and available P correlated negatively with CH4 production. A management strategy to avoid excessive C accumulation in the soil and to increase P availability and decrease available Fe contents would likely decrease the production of greenhouse gases.

  18. Reduced gas seepages in ophiolitic complexes: Evidences for multiple origins of the H2-CH4-N2 gas mixtures

    NASA Astrophysics Data System (ADS)

    Vacquand, Christèle; Deville, Eric; Beaumont, Valérie; Guyot, François; Sissmann, Olivier; Pillot, Daniel; Arcilla, Carlo; Prinzhofer, Alain

    2018-02-01

    This paper proposes a comparative study of reduced gas seepages occurring in ultrabasic to basic rocks outcropping in ophiolitic complexes based on the study of seepages from Oman, the Philippines, Turkey and New Caledonia. This study is based on analyses of the gas chemical composition, noble gases contents, stable isotopes of carbon, hydrogen and nitrogen. These seepages are mostly made of mixtures of three main components which are H2, CH4 and N2 in various proportions. The relative contents of the three main gas components show 4 distinct types of gas mixtures (H2-rich, N2-rich, N2-H2-CH4 and H2-CH4). These types are interpreted as reflecting different zones of gas generation within or below the ophiolitic complexes. In the H2-rich type, associated noble gases display signatures close to the value of air. In addition to the atmospheric component, mantle and crustal contributions are present in the N2-rich, N2-H2-CH4 and H2-CH4 types. H2-bearing gases are either associated with ultra-basic (pH 10-12) spring waters or they seep directly in fracture systems from the ophiolitic rocks. In ophiolitic contexts, ultrabasic rocks provide an adequate environment with available Fe2+ and alkaline conditions that favor H2 production. CH4 is produced either directly by reaction of dissolved CO2 with basic-ultrabasic rocks during the serpentinization process or in a second step by H2-CO2 interaction. H2 is present in the gas when no more carbon is available in the system to generate CH4. The N2-rich type is notably associated with relatively high contents of crustal 4He and in this gas type N2 is interpreted as issued mainly from sediments located below the ophiolitic units.

  19. Stratospheric CH4 and CO2 profiles derived from SCIAMACHY solar occultation measurements

    NASA Astrophysics Data System (ADS)

    Noël, S.; Bramstedt, K.; Hilker, M.; Liebing, P.; Plieninger, J.; Reuter, M.; Rozanov, A.; Bovensmann, H.; Burrows, J. P.

    2015-11-01

    Stratospheric profiles of methane (CH4) and carbon dioxide (CO2) have been derived from solar occultation measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY). The retrieval is performed using a method called "Onion Peeling DOAS" (ONPD) which combines an onion peeling approach with a weighting function DOAS (Differential Optical Absorption Spectroscopy) fit. By use of updated pointing information and optimisation of the data selection and of the retrieval approach the altitude range for reasonable CH4 could be extended to about 17 to 45 km. Furthermore, the quality of the derived CO2 has been assessed such that now the first stratospheric profiles of CO2 from SCIAMACHY are available. Comparisons with independent data sets yield an estimated accuracy of the new SCIAMACHY stratospheric profiles of about 5-10 % for CH4 and 2-3 % for CO2. The accuracy of the products is currently mainly restricted by the appearance of unexpected vertical oscillations in the derived profiles which need further investigation. Using the improved ONPD retrieval, CH4 and CO2 stratospheric data sets covering the whole SCIAMACHY time series (August 2002-April 2012) and the latitudinal range between about 50 and 70° N have been derived. Based on these time series, CH4 and CO2 trends have been estimated, which are in reasonable agreement with total column trends for these gases. This shows that the new SCIAMACHY data sets can provide valuable information about the stratosphere.

  20. A process-based inventory model for landfill CH4 emissions inclusive of seasonal soil microclimate and CH4 oxidation

    USDA-ARS?s Scientific Manuscript database

    We have developed and field-validated an annual inventory model for California landfill CH4 emissions that incorporates both site-specific soil properties and soil microclimate modeling coupled to 0.5o scale global climatic models. Based on 1-D diffusion, CALMIM (California Landfill Methane Inventor...

  1. Biogeochemical controls on microbial CH4 and CO2 production in Arctic polygon tundra

    NASA Astrophysics Data System (ADS)

    Zheng, J.

    2016-12-01

    Accurately simulating methane (CH4) and carbon dioxide (CO2) emissions from high latitude soils is critically important for reducing uncertainties in soil carbon-climate feedback predictions. The signature polygonal ground of Arctic tundra generates high level of heterogeneity in soil thermal regime, hydrology and oxygen availability, which limits the application of current land surface models with simple moisture response functions. We synthesized CH4 and CO2 production measurements from soil microcosm experiments across a wet-to dry permafrost degradation gradient from low-centered (LCP) to flat-centered (FCP), and high-centered polygons (HCP) to evaluate the relative importance of biogeochemical processes and their response to warming. More degraded polygon (HCP) showed much less carbon loss as CO2 or CH4, while the total CO2 production from FCP is comparable to that from LCP. Maximum CH4 production from the active layer of LCP was nearly 10 times that of permafrost and FCP. Multivariate analyses identifies gravimetric water content and organic carbon content as key predictors for CH4 production, and iron reduction as a key regulator of pH. The synthesized data are used to validate the geochemical model PHREEQC with extended anaerobic organic substrate turnover, fermentation, iron reduction, and methanogenesis reactions. Sensitivity analyses demonstrate that better representations of anaerobic processes and their pH dependency could significantly improve estimates of CH4 and CO2 production. The synthesized data suggest local decreases in CH4 production along the polygon degradation gradient, which is consistent with previous surface flux measurements. Methane oxidation occurring through the soil column of degraded polygons contributes to their low CH4 emissions as well.

  2. Clumped isotope effects during OH and Cl oxidation of methane

    NASA Astrophysics Data System (ADS)

    Whitehill, Andrew R.; Joelsson, Lars Magnus T.; Schmidt, Johan A.; Wang, David T.; Johnson, Matthew S.; Ono, Shuhei

    2017-01-01

    A series of experiments were carried out to determine the clumped (13CH3D) methane kinetic isotope effects during oxidation of methane by OH and Cl radicals, the major sink reactions for atmospheric methane. Experiments were performed in a 100 L quartz photochemical reactor, in which OH was produced from the reaction of O(1D) (from O3 photolysis) with H2O, and Cl was from photolysis of Cl2. Samples were taken from the reaction cell and analyzed for methane (12CH4, 12CH3D, 13CH4, 13CH3D) isotopologue ratios using tunable infrared laser direct absorption spectroscopy. Measured kinetic isotope effects for singly substituted species were consistent with previous experimental studies. For doubly substituted methane, 13CH3D, the observed kinetic isotope effects closely follow the product of the kinetic isotope effects for the 13C and deuterium substituted species (i.e., 13,2KIE = 13KIE × 2KIE). The deviation from this relationship is 0.3‰ ± 1.2‰ and 3.5‰ ± 0.7‰ for OH and Cl oxidation, respectively. This is consistent with model calculations performed using quantum chemistry and transition state theory. The OH and Cl reactions enrich the residual methane in the clumped isotopologue in open system reactions. In a closed system, however, this effect is overtaken by the large D/H isotope effect, which causes the residual methane to become anti-clumped relative to the initial methane. Based on these results, we demonstrate that oxidation of methane by OH, the predominant oxidant for tropospheric methane, will only have a minor (∼0.3‰) impact on the clumped isotope signature (Δ13CH3D, measured as a deviation from a stochastic distribution of isotopes) of tropospheric methane. This paper shows that Δ13CH3D will provide constraints on methane source strengths, and predicts that Δ12CH2D2 can provide information on methane sink strengths.

  3. Real-time analysis of δ13C- and δD-CH4 by high precision laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Eyer, Simon; Emmenegger, Lukas; Tuzson, Béla; Fischer, Hubertus; Mohn, Joachim

    2014-05-01

    Methane (CH4) is the most important non-CO2 greenhouse gas (GHG) contributing 18% to total radiative forcing. Anthropogenic sources (e.g. ruminants, landfills) contribute 60% to total emissions and led to an increase in its atmospheric mixing ratio from 700 ppb in pre-industrial times to 1819 ± 1 ppb in 2012 [1]. Analysis of the most abundant methane isotopologues 12CH4, 13CH4 and 12CH3D can be used to disentangle the various source/sink processes [2] and to develop target oriented reduction strategies. High precision isotopic analysis of CH4 can be accomplished by isotope-ratio mass-spectrometry (IRMS) [2] and more recently by mid-infrared laser-based spectroscopic techniques. For high precision measurements in ambient air, however, both techniques rely on preconcentration of the target gas [3]. In an on-going project, we developed a fully-automated, field-deployable CH4 preconcentration unit coupled to a dual quantum cascade laser absorption spectrometer (QCLAS) for real-time analysis of CH4 isotopologues. The core part of the rack-mounted (19 inch) device is a highly-efficient adsorbent trap attached to a motorized linear drive system and enclosed in a vacuum chamber. Thereby, the adsorbent trap can be decoupled from the Stirling cooler during desorption for fast desorption and optimal heat management. A wide variety of adsorbents, including: HayeSep D, molecular sieves as well as the novel metal-organic frameworks and carbon nanotubes were characterized regarding their surface area, isosteric enthalpy of adsorption and selectivity for methane over nitrogen. The most promising candidates were tested on the preconcentration device and a preconcentration by a factor > 500 was obtained. Furthermore analytical interferants (e.g. N2O, CO2) are separated by step-wise desorption of trace gases. A QCL absorption spectrometer previously described by Tuzson et al. (2010) for CH4 flux measurements was modified to obtain a platform for high precision and simultaneous

  4. CO2 methanation on the catalyst of Ni/MCM-41 promoted with CeO2.

    PubMed

    Wang, Xiaoliu; Zhu, Lingjun; Liu, Yincong; Wang, Shurong

    2018-06-01

    CO 2 as a raw feed combined with renewable hydrogen for the production of useful chemicals and alternative energy products is one of the solutions to environmental and energy problems. In this study, a series of Ni-xCeO 2 /MCM-41 catalysts with a nickel content of 20wt% were prepared through deposition precipitation method for CO 2 methanation. Different characterization methods, including BET, XRD, TEM, SEM, H 2 -TPR and H 2 -TPD were applied to help explore the influence mechanism of CeO 2 on Ni/MCM-41 in CO 2 methanation. It was found that all CeO 2 -promoted catalysts exhibited enhanced catalytic activity when compared to Ni/MCM-41. The catalyst modified with 20wt% CeO 2 showed the best catalytic performance, with CO 2 conversion and CH 4 selectivity of 85.6% and 99.8%, respectively, at the temperature of 380°C under atmospheric pressure. The synergetic effects among Ni 0 active sites, the promoter and the support, including nickel dispersion improvement and increased CO 2 adsorption sites due to the addition of CeO 2 , were considered as important factors for high reactivity of the promoted catalysts. The stability test showed that the promoted catalyst maintained its high reactivity after 30h. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. CH3CO + O2 + M (M = He, N2) Reaction Rate Coefficient Measurements and Implications for the OH Radical Product Yield.

    PubMed

    Papadimitriou, Vassileios C; Karafas, Emmanuel S; Gierczak, Tomasz; Burkholder, James B

    2015-07-16

    The gas-phase CH3CO + O2 reaction is known to proceed via a chemical activation mechanism leading to the formation of OH and CH3C(O)OO radicals via bimolecular and termolecular reactive channels, respectively. In this work, rate coefficients, k, for the CH3CO + O2 reaction were measured over a range of temperature (241-373 K) and pressure (0.009-600 Torr) with He and N2 as the bath gas and used to characterize the bi- and ter-molecular reaction channels. Three independent experimental methods (pulsed laser photolysis-laser-induced fluorescence (PLP-LIF), pulsed laser photolysis-cavity ring-down spectroscopy (PLP-CRDS), and a very low-pressure reactor (VLPR)) were used to characterize k(T,M). PLP-LIF was the primary method used to measure k(T,M) in the high-pressure regime under pseudo-first-order conditions. CH3CO was produced by PLP, and LIF was used to monitor the OH radical bimolecular channel reaction product. CRDS, a complementary high-pressure method, measured k(295 K,M) over the pressure range 25-600 Torr (He) by monitoring the temporal CH3CO radical absorption following its production via PLP in the presence of excess O2. The VLPR technique was used in a relative rate mode to measure k(296 K,M) in the low-pressure regime (9-32 mTorr) with CH3CO + Cl2 used as the reference reaction. A kinetic mechanism analysis of the combined kinetic data set yielded a zero pressure limit rate coefficient, kint(T), of (6.4 ± 4) × 10(-14) exp((820 ± 150)/T) cm(3) molecule(-1) s(-1) (with kint(296 K) measured to be (9.94 ± 1.3) × 10(-13) cm(3) molecule(-1) s(-1)), k0(T) = (7.39 ± 0.3) × 10(-30) (T/300)(-2.2±0.3) cm(6) molecule(-2) s(-1), and k∞(T) = (4.88 ± 0.05) × 10(-12) (T/300)(-0.85±0.07) cm(3) molecule(-1) s(-1) with Fc = 0.8 and M = N2. A He/N2 collision efficiency ratio of 0.60 ± 0.05 was determined. The phenomenological kinetic results were used to define the pressure and temperature dependence of the OH radical yield in the CH3CO + O2 reaction. The

  6. Microbial Abundances Predict Methane and Nitrous Oxide Fluxes from a Windrow Composting System

    PubMed Central

    Li, Shuqing; Song, Lina; Gao, Xiang; Jin, Yaguo; Liu, Shuwei; Shen, Qirong; Zou, Jianwen

    2017-01-01

    Manure composting is a significant source of atmospheric methane (CH4) and nitrous oxide (N2O) that are two potent greenhouse gases. The CH4 and N2O fluxes are mediated by methanogens and methanotrophs, nitrifying and denitrifying bacteria in composting manure, respectively, while these specific bacterial functional groups may interplay in CH4 and N2O emissions during manure composting. To test the hypothesis that bacterial functional gene abundances regulate greenhouse gas fluxes in windrow composting systems, CH4 and N2O fluxes were simultaneously measured using the chamber method, and molecular techniques were used to quantify the abundances of CH4-related functional genes (mcrA and pmoA genes) and N2O-related functional genes (amoA, narG, nirK, nirS, norB, and nosZ genes). The results indicate that changes in interacting physicochemical parameters in the pile shaped the dynamics of bacterial functional gene abundances. The CH4 and N2O fluxes were correlated with abundances of specific compositional genes in bacterial community. The stepwise regression statistics selected pile temperature, mcrA and NH4+ together as the best predictors for CH4 fluxes, and the model integrating nirK, nosZ with pmoA gene abundances can almost fully explain the dynamics of N2O fluxes over windrow composting. The simulated models were tested against measurements in paddy rice cropping systems, indicating that the models can also be applicable to predicting the response of CH4 and N2O fluxes to elevated atmospheric CO2 concentration and rising temperature. Microbial abundances could be included as indicators in the current carbon and nitrogen biogeochemical models. PMID:28373862

  7. Annual methane and nitrous oxide emissions from rice paddies and inland fish aquaculture wetlands in southeast China

    NASA Astrophysics Data System (ADS)

    Wu, Shuang; Hu, Zhiqiang; Hu, Tao; Chen, Jie; Yu, Kai; Zou, Jianwen; Liu, Shuwei

    2018-02-01

    Inland aquaculture ponds have been documented as important sources of atmospheric methane (CH4) and nitrous oxide (N2O), while their regional or global source strength remains unclear due to lack of direct flux measurements by covering more typical habitat-specific aquaculture environments. In this study, we compared the CH4 and N2O fluxes from rice paddies and nearby inland fish aquaculture wetlands that were converted from rice paddies in southeast China. Both CH4 and N2O fluxes were positively related to water temperature and sediment dissolved organic carbon, but negatively related to water dissolved oxygen concentration. More robust response of N2O fluxes to water mineral N was observed than to sediment mineral N. Annual CH4 and N2O fluxes from inland fish aquaculture averaged 0.51 mg m-2 h-1 and 54.78 μg m-2 h-1, amounting to 42.31 kg CH4 ha-1 and 2.99 kg N2O-N ha-1, respectively. The conversion of rice paddies to conventional fish aquaculture significantly reduced CH4 and N2O emissions by 23% and 66%, respectively. The emission factor for N2O was estimated to be 0.46% of total N input in the feed or 1.23 g N2O-N kg-1 aquaculture production. The estimate of sustained-flux global warming potential of annual CH4 and N2O emissions and the net economic profit suggested that such conversion of rice paddies to inland fish aquaculture would help to reconcile the dilemma for simultaneously achieving both low climatic impacts and high economic benefits in China. More solid direct field measurements from inland aquaculture are in urgent need to direct the overall budget of national or global CH4 and N2O fluxes.

  8. Coupled potential energy surface for the F(2P)+CH4→HF+CH3 entrance channel and quantum dynamics of the CH4·F- photodetachment.

    PubMed

    Westermann, Till; Eisfeld, Wolfgang; Manthe, Uwe

    2013-07-07

    An approach to construct vibronically and spin-orbit coupled diabatic potential energy surfaces (PESs) which describe all three relevant electronic states in the entrance channels of the X(P) + CH4 →HX + CH3 reactions (with X=F((2)P), Cl((2)P), or O((3)P)) is introduced. The diabatization relies on the permutational symmetry present in the methane molecule and results in diabatic states which transform as the three p orbitals of the X atom. Spin-orbit coupling is easily and accurately included using the atomic spin-orbit coupling matrix of the isolated X atom. The method is applied to the F + CH4 system obtaining an accurate PES for the entrance channel based on ab initio multi-reference configuration interaction (MRCI) calculations. Comparing the resulting PESs with spin-orbit MRCI calculations, excellent agreement is found for the excited electronic states at all relevant geometries. The photodetachment spectrum of CH4·F(-) is investigated via full-dimensional (12D) quantum dynamics calculations on the coupled PESs using the multi-layer multi-configurational time-dependent Hartree approach. Extending previous work [J. Palma and U. Manthe, J. Chem. Phys. 137, 044306 (2012)], which was restricted to the dynamics on a single adiabatic PES, the contributions of the electronically excited states to the photodetachment spectrum are calculated and compared to experiment. Considering different experimental setups, good agreement between experiment and theory is found. Addressing questions raised in the previous work, the present dynamical calculations show that the main contribution to the second peak in the photodetachment spectrum results from electron detachment into the electronically excited states of the CH4F complex.

  9. Methane and nitrous oxide exchange over a managed hay meadow

    PubMed Central

    Hörtnagl, L.; Wohlfahrt, G.

    2015-01-01

    The methane (CH4) and nitrous oxide (N2O) exchange of a temperate mountain grassland near Neustift, Austria, was measured during 2010–2012 over a time period of 22 months using the eddy covariance method. Exchange rates of both compounds at the site were low, with 97% of all half-hourly CH4 and N2O fluxes ranging between ±200 and ±50 ng m−2 s−1, respectively. The meadow acted as a sink for both compounds during certain time periods, but was a clear source of CH4 and N2O on an annual timescale. Therefore, both gases contributed to an increase of the global warming potential (GWP), effectively reducing the sink strength in terms of CO2 equivalents of the investigated grassland site. In 2011, our best guess estimate showed a net greenhouse gas (GHG) sink of −32 g CO2 equ. m−2 yr−1 for the meadow, whereby 55% of the CO2 sink strength of −71 g CO2m−2 yr−1 was offset by CH4 (N2O) emissions of 7 (32) g CO2 equ. m−2 yr−1. When all data were pooled, the ancillary parameters explained 27 (42)% of observed CH4 (N2O) flux variability, and up to 62 (76)% on shorter timescales in-between management dates. In the case of N2O fluxes, we found the highest emissions at intermediate soil water contents and at soil temperatures close to 0 or above 14 °C. In comparison to CO2, H2O and energy fluxes, the interpretation of CH4 and N2O exchange was challenging due to footprint heterogeneity regarding their sources and sinks, uncertainties regarding post-processing and quality control. Our results emphasize that CH4 and N2O fluxes over supposedly well-aerated and moderately fertilized soils cannot be neglected when evaluating the GHG impact of temperate managed grasslands. PMID:25821473

  10. New assignments in the 2 μm transparency window of the 12CH4 Octad band system

    NASA Astrophysics Data System (ADS)

    Daumont, L.; Nikitin, A. V.; Thomas, X.; Régalia, L.; Von der Heyden, P.; Tyuterev, Vl. G.; Rey, M.; Boudon, V.; Wenger, Ch.; Loëte, M.; Brown, L. R.

    2013-02-01

    This paper reports new assignments of rovibrational transitions of 12CH4 bands in the range 4600-4887 cm-1 which is usually referred to as a part of the 2 μm methane transparency window. Several experimental data sources for methane line positions and intensities were combined for this analysis. Three long path Fourier transform spectra newly recorded in Reims with 1603 m absorption path length and pressures of 1, 7 and 34 hPa for samples of natural abundance CH4 provided new measurements of 12CH4 lines. Older spectra for 13CH4 (90% purity) from JPL with 73 m absorption path length were used to identify the corresponding lines. Most of the lines in this region belong to the Octad system of 12CH4. The new spectra allowed us to assign 1014 new line positions and to measure 1095 line intensities in the cold bands of the Octad. These new line positions and intensities were added to the global fit of Hamiltonian and dipole moment parameters of the Ground State, Dyad, Pentad and Octad systems. This leads to a noticeable improvement of the theoretical description in this methane transparency window and a better global prediction of the methane spectrum.

  11. CO2 CH4 and N20 fluxes during land conversion in early bioenergy systems

    NASA Astrophysics Data System (ADS)

    Zenone, T.

    2012-04-01

    CO2 CH4 and N20 fluxes during land conversion in early bioenergy systems Terenzio Zenone1-2, Jiquan Chen1-2, Ilya Gelfand3-4, G. Philip Robertson3-4 1 Department of Environmental Sciences, University of Toledo, Toledo, OH USA 2 Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI USA 3 W.K. Kellogg Biological Station, Michigan State University, Hickory Corners, MI USA 4Department of Crop and Soil Sciences, Michigan State University, East Lansing, MI USA Environmental sustainability of bioenergy crop cultivation represents an important challenge and is a topic of intensive scientific and political debate worldwide due to increasing societal needs for renewable energy. Despite the increasing knowledge related to potential bioenergy systems, the effect of land use change (LUC) on GHG fluxes during the conversion remains poorly understood but is likely to be substantial. In order to tackle this issue the Great lake Bioenergy Research Center (GLBRC) of the US Department of Energy (DOE) has established a field experiment and deployed a cluster of eddy-covariance towers to quantify the magnitude and changes of ecosystem carbon assimilation, loss, and balance during the conversion and establishment years in a permanent prairie and four types of candidate biofuel systems [Conservation Reserve Program (CRP) grassland, switchgrass, mixed-species restored prairie and corn]. Six sites were converted to soybean in 2009 before establishing the bioenergy systems in 2010 while one site was kept grassland as reference. Soil N2O and CH4 fluxes were measured biweekly with static chambers in four replicate locations in each fields, within the footprint of the eddy covariance tower using static chamber GHG flux protocols of the KBS LTER site. Our field observations, made between January 2009 through December 2010, showed that conversion of CRP to soybean induced net C emissions during the conversion year that ranging from 288 g C m-2, to 173 g C m-2 . while

  12. Enhanced selective photocatalytic reduction of CO2 to CH4 over plasmonic Au modified g-C3N4 photocatalyst under UV-vis light irradiation

    NASA Astrophysics Data System (ADS)

    Li, Hailong; Gao, Yan; Xiong, Zhuo; Liao, Chen; Shih, Kaimin

    2018-05-01

    A series of Au-g-C3N4 (Au-CN) catalysts were prepared through a NaBH4-reduction method using g-C3N4 (CN) from pyrolysis of urea as precursor. The catalysts' surface area, crystal structure, surface morphology, chemical state, functional group composition and optical properties were characterized by X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy, ultraviolet visible (UV-vis) diffuse reflectance spectra, fourier transform infrared, photoluminescence and transient photocurrent analysis. The carbon dioxide (CO2) photoreduction activities under ultraviolet visible (UV-vis) light irradiation were significantly enhanced when gold (Au) was loaded on the surface of CN. 2Au-CN catalyst with Au to CN mole ratio of 2% showed the best catalytic activity. After 2 h UV-vis light irradiation, the methane (CH4) yield over the 2Au-CN catalyst was 9.1 times higher than that over the pure CN. The CH4 selectivity also greatly improved for the 2Au-CN compared to the CN. The deposited Au nanoparticles facilitated the separation of electron-hole pairs on the CN surface. Moreover, the surface plasmon resonance effect of Au further promoted the generation of hot electrons and visible light absorption. Therefore, Au loading significantly improved CO2 photoreduction performance of CN under UV-vis light irradiation.

  13. Soil fluxes of methane, nitrous oxide, and nitric oxide from aggrading forests in coastal Oregon

    USGS Publications Warehouse

    Erickson, Heather E.; Perakis, Steven S.

    2014-01-01

    Soil exchanges of greenhouse and other gases are poorly known for Pacific Northwest forests where gradients in nutrient availability and soil moisture may contribute to large variations in fluxes. Here we report fluxes of methane (CH4), nitrous oxide (N2O), and nitric oxide (NO) over multiple seasons from three naturally N-rich, aggrading forests of coastal Oregon, USA. Mean methane uptake rates (3.2 mg CH4 m−2 d−1) were high compared with forests globally, negatively related to water-filled pore space (WFPS), but unrelated to N availability or temperature. Emissions of NO (6.0 μg NO–N m−2 h−1) exceeded N2O (1.4 μg N2O–N m−2 h−1), except when WFPS surpassed 55%. Spatial variation in NO fluxes correlated positively with soil nitrate concentrations (which generally exceeded ammonium concentrations, indicating the overall high N status for the sites) and negatively with soil pH, and at one site increased with basal area of N2-fixing red alder. Combined NO and N2O emissions were greatest from the site with highest annual net N mineralization and lowest needle litterfall C/N. Our findings of high CH4 uptake and NO/N2O ratios generally >1 most likely reflect the high porosity of the andic soils underlying the widespread regenerating forests in this seasonally wet region.

  14. Luminescent Copper(I) Halide Butterfly Dimers Coordinated to [Au(CH3imCH2py)2]BF4 and [Au(CH3imCH2quin)2]BF4

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Catalano, V.; Moore, A; Shearer, J

    2009-01-01

    The coordination chemistry of copper(I) halides to the homoleptic, N-heterocyclic carbene Au(I) complexes [Au(CH{sub 3}imCH{sub 2}quin){sub 2}]BF{sub 4} and [Au(CH{sub 3}imCH{sub 2}py){sub 2}]BF{sub 4} was explored. The reaction of CuX (X = Cl, Br, I) with either [Au(CH{sub 3}imCH{sub 2}quin){sub 2}]BF{sub 4} or [Au(CH{sub 3}imCH{sub 2}py){sub 2}]BF{sub 4} produces trimetallic complexes containing Cu{sub 2}X{sub 2}-butterfly copper clusters coordinated to the two imine moieties. The triangular arrangement of the metals places the gold(I) center in close proximity ({approx}2.5-2.6 {angstrom}) to the centroid of the Cu-Cu vector. The Cu-Cu separations vary as a function of bridging halide with the shortest Cu-Cu separationsmore » of {approx}2.5 {angstrom} found in the iodo-complexes and the longest separations of 2.9 {angstrom} found in the bridging chloride complexes. In all six complexes the Au-Cu separations range from {approx}2.8 to 3.0 {angstrom}. In the absence of halides, the dimetallic complex [AuCu(CH{sub 3}imCH{sub 2}py){sub 2}(NCCH{sub 3}){sub 2}](BF{sub 4}){sub 2}, containing a long Au-Cu distance of {approx}4.72 {angstrom} is formed. Additionally, as the byproduct of the reaction of CuBr with [Au(CH{sub 3}imCH{sub 2}quin){sub 2}]BF{sub 4} the deep-red, dimetallic compound, AuCuBr{sub 2}(CH{sub 3}imCH{sub 2}quin){sub 2}, was isolated in very low yield. All of these complexes were studied by NMR spectroscopy, mass spectrometry, and the copper containing species were additionally characterized by X-ray crystallography. In solution the copper centers dissociate from the gold complexes, but as shown by XANES and EXAFS spectroscopy, at low temperature the Cu-Cu linkage is broken, and the individual copper(I) halides reposition themselves to opposite sides of the gold complex while remaining coordinated to one imine moiety. In the solid state all of the complexes are photoluminescent, though the nature of the excited state was not determined.« less

  15. Dissimilatory perchlorate reduction linked to aerobic methane oxidation via chlorite dismutase

    NASA Astrophysics Data System (ADS)

    Oremland, R. S.; Baesman, S. M.; Miller, L. G.

    2013-12-01

    The presence of methane (CH4) in the atmosphere of Mars is controversial yet the evidence has aroused scientific interest, as CH4 could be a harbinger of extant or extinct microbial life. There are various oxidized compounds present on the surface of Mars that could serve as electron acceptors for the anaerobic oxidation of CH4, including perchlorate (ClO4-). We examined the role of perchlorate, chlorate (ClO3-) and chlorite (ClO2-) as oxidants linked to CH4 oxidation. Dissimilatory perchlorate reduction begins with reduction of ClO4- to ClO2- and ends with dismutation of chlorite to yield chloride (Cl-) and molecular oxygen (O2). We explored the potential for aerobic CH4 oxidizing bacteria to couple with oxygen derived from chlorite dismutation during dissimilatory perchlorate reduction. Methane (0.2 kPa) was completely removed within several days from the N2-flushed headspace above cell suspensions of methanotrophs (Methylobacter albus strain BG8) and perchlorate reducing bacteria (Dechloromonas agitata strain CKB) in the presence of 5 mM ClO2-. Similar rates of CH4 consumption were observed for these mixed cultures whether they were co-mingled or segregated under a common headspace, indicating that direct contact of cells was not required for methane consumption to occur. We also observed complete removal of 0.2 kPa CH4 in bottles containing dried soil (enriched in methanotrophs by CH4 additions over several weeks) and D. agitata CKB and in the presence of 10 mM ClO2-. This soil (seasonally exposed sediment) collected from the shoreline of a freshwater lake (Searsville Lake, CA) demonstrated endogenous CH4 uptake as well as perchlorate, chlorate and chlorite reduction/dismutation. However, these experiments required physical separation of soil from the aqueous bacterial culture to allow for the partitioning of O2 liberated from chlorite dismutation into the shared headspace. Although dissimilatory reduction of ClO4- and ClO3- could be inferred from the

  16. Suppression of peatland methane emission by cumulative sulfate deposition in simulated acid rain

    Treesearch

    Nancy B. Dise; Elon S. Verry

    2001-01-01

    This field manipulation study tested the effect of weekly pulses of solutions of NH4NO3 and (NH4)2SO4 salts on the evolution of CH4 and N2O from peatland soils. Methane and nitrous oxide emission from a...

  17. Microsolvation effects on the reactivity of oxy-nucleophiles: the case of gas-phase SN2 reactions of YO-(CH3OH) n=1,2 towards CH3Cl.

    PubMed

    Yun-Yun, Liu; Fang-Zhou, Qiu; Jun, Zhu; Yi, Ren; Kai-Chung, Lau

    2017-06-01

    The modified G4(MP2) method was applied to explore microsolvation effects on the reactivity of four solvated normal oxy-nucleophiles YO - (CH 3 OH) n=1,2 (Y = CH 3 , C 2 H 5 , FC 2 H 4 , ClC 2 H 4 ), and five α-oxy-nucleophiles YO - (CH 3 OH) n=1,2 (Y = HO, CH 3 O, F, Cl, Br), in gas-phase S N 2 reactions towards the substrate CH 3 Cl. Based on a Brønsted-type plot, our calculations reveal that the overall activation barriers of five microsolvated α-oxy-nucleophiles are obviously smaller than the prediction from the correlation line constructed by four normal microsolvated ones to different degrees, and clearly demonstrate the existence of an α-effect in the presence of one or two methanol molecule(s). Moreover, it was found that the α-effect of the mono-methanol microsolvated α-nucleophile is stronger than that of the monohydrated α-nucleophile. However, the α-effect of YO - (CH 3 OH) 2 becomes weaker for Y = HO and CH 3 O, whereas it becomes stronger for Y = F, Cl, Br than that of YO - (H 2 O) 2 , which can be explained by analyses of the activation strain model in the two cases. It was also found that the rationale about the low ionization energy of α-nucleophile inducing the α-effect was not widely significant. Graphical abstract Variation of alpha-effect in the gas-phase S N 2 reaction with the microsolvation.

  18. UV radiation and CH4 gas detection with a single ZnO:Pd nanowire

    NASA Astrophysics Data System (ADS)

    Lupan, O.; Adelung, R.; Postica, V.; Ababii, N.; Chow, L.; Viana, B.; Pauporté, T.

    2017-02-01

    There is an increasing demand for sensors to monitor environmental levels of ultraviolet (UV) radiation and pollutant gases. In this work, an individual nanowire of Pd modified ZnO nanowire (ZnO:Pd NW) was integrated in a nanosensor device for efficient and fast detection of UV light and CH4 gas at room temperature. Crystalline ZnO:Pd nanowire/nanorod arrays were synthesized onto fluorine doped tin oxide (FTO) substrates by electrochemical deposition (ECD) at relative low-temperatures (90 °C) with different concentrations of PdCl2 in electrolyte solution and investigated by SEM and EDX. Nanodevices were fabricated using dual beam focused electron/ion beam (FIB/SEM) system and showed improved UV radiation response compared to pristine ZnO NW, reported previously by our group. The UV response was increased by one order in magnitude (≈ 11) for ZnO:Pd NW. Gas sensing measurements demonstrated a higher gas response and rapidity to methane (CH4 gas, 100 ppm) at room temperature, showing promising results for multifunctional applications. Also, due to miniature size and ultra-low power consumption of these sensors, it is possible to integrate them into portable devices easily, such as smartphones, digital clock, flame detection, missile lunching and other smart devices.

  19. CO2 adsorption-assisted CH4 desorption on carbon models of coal surface: A DFT study

    NASA Astrophysics Data System (ADS)

    Xu, He; Chu, Wei; Huang, Xia; Sun, Wenjing; Jiang, Chengfa; Liu, Zhongqing

    2016-07-01

    Injection of CO2 into coal is known to improve the yields of coal-bed methane gas. However, the technology of CO2 injection-enhanced coal-bed methane (CO2-ECBM) recovery is still in its infancy with an unclear mechanism. Density functional theory (DFT) calculations were performed to elucidate the mechanism of CO2 adsorption-assisted CH4 desorption (AAD). To simulate coal surfaces, different six-ring aromatic clusters (2 × 2, 3 × 3, 4 × 4, 5 × 5, 6 × 6, and 7 × 7) were used as simplified graphene (Gr) carbon models. The adsorption and desorption of CH4 and/or CO2 on these carbon models were assessed. The results showed that a six-ring aromatic cluster model (4 × 4) can simulate the coal surface with limited approximation. The adsorption of CO2 onto these carbon models was more stable than that in the case of CH4. Further, the adsorption energies of single CH4 and CO2 in the more stable site were -15.58 and -18.16 kJ/mol, respectively. When two molecules (CO2 and CH4) interact with the surface, CO2 compels CH4 to adsorb onto the less stable site, with a resulting significant decrease in the adsorption energy of CH4 onto the surface of the carbon model with pre-adsorbed CO2. The Mulliken charges and electrostatic potentials of CH4 and CO2 adsorbed onto the surface of the carbon model were compared to determine their respective adsorption activities and changes. At the molecular level, our results showed that the adsorption of the injected CO2 promoted the desorption of CH4, the underlying mechanism of CO2-ECBM.

  20. Methane on Titan: Photochemical-Meteorological-Hydrogeochemical Cycle

    NASA Astrophysics Data System (ADS)

    Atreya, S. K.; Niemann, H. B.; Owen, T. C.; Adams, E. Y.; Demick, J. E.; GCMS Team

    2005-08-01

    Photochemically driven destruction of methane in Titan's stratosphere leads to irreversible conversion to heavier hydrocarbons (1). The latter would largely condense out of the atmosphere (2). In the absence of recycling, Titan's methane would thus be destroyed in 10-100 million years (1). However, methane is key to the maintenance of Titan's nitrogen atmosphere. Without warming provided by CH4-generated hydrocarbon hazes in the stratosphere and pressure induced opacity in the infrared, particularly by H2-N2 and CH4-N2 collisions in the troposphere, the atmosphere would gradually diminish to tens of millibar pressure (3). Thus, the source-sink cycle of methane is crucial to the evolutionary history of Titan and its atmosphere. The GCMS measurements show that a ``methalogical" cycle with surface evaporation, cloud formation, followed by precipitation (rain) of methane exists. However, this ``closed" cycle does not recycle methane lost to heavy hydrocarbons. A source is required. Unlike the deep, hot, H2-rich interiors of the giant planets, Titan's interior is ill suited for thermochemical conversion of hydrocarbons back to methane. Instead we propose that serpentinization is an effective process for producing methane in Titan's interior (4). Hydration of ultramafic silicates, followed by reaction between the released H2 gas and CO2 or carbon grains can produce large quantities of CH4 at relatively mild (40-90oC) temperatures. Such thermal conditions are believed to exist below the purported water-ammonia ocean (5). Storage of methane produced via serpentinization can occur in form of clathrates. Evidence of outgassing from Titan's interior is provided by GCMS (6) and VIMS (7) data. (1) Wilson, Atreya, JGR 109, E06002, doi:10.1029/2003JE002181, 2004. (2) Wilson, Atreya, PSS 51, 1017, 2003. (3) Lorenz etal. Science 275, 642, 1997. (4) Owen etal. Phys. Uspekhi, in press. (5) Grasset, Pargamin, PSS 53, 371, 2005. (6) Niemann etal., Submitted to Nature, 2005. (7) Sotin

  1. Aircraft emissions of methane and nitrous oxide during the alternative aviation fuel experiment.

    PubMed

    Santoni, Gregory W; Lee, Ben H; Wood, Ezra C; Herndon, Scott C; Miake-Lye, Richard C; Wofsy, Steven C; McManus, J Barry; Nelson, David D; Zahniser, Mark S

    2011-08-15

    Given the predicted growth of aviation and the recent developments of alternative aviation fuels, quantifying methane (CH(4)) and nitrous oxide (N(2)O) emission ratios for various aircraft engines and fuels can help constrain projected impacts of aviation on the Earth's radiative balance. Fuel-based emission indices for CH(4) and N(2)O were quantified from CFM56-2C1 engines aboard the NASA DC-8 aircraft during the first Alternative Aviation Fuel Experiment (AAFEX-I) in 2009. The measurements of JP-8 fuel combustion products indicate that at low thrust engine states (idle and taxi, or 4% and 7% maximum rated thrusts, respectively) the engines emit both CH(4) and N(2)O at a mean ± 1σ rate of 170 ± 160 mg CH(4) (kg Fuel)(-1) and 110 ± 50 mg N(2)O (kg Fuel)(-1), respectively. At higher thrust levels corresponding to greater fuel flow and higher engine temperatures, CH(4) concentrations in engine exhaust were lower than ambient concentrations. Average emission indices for JP-8 fuel combusted at engine thrusts between 30% and 100% of maximum rating were -54 ± 33 mg CH(4) (kg Fuel)(-1) and 32 ± 18 mg N(2)O (kg Fuel)(-1), where the negative sign indicates consumption of atmospheric CH(4) in the engine. Emission factors for the synthetic Fischer-Tropsch fuels were statistically indistinguishable from those for JP-8.

  2. Methane Fingerprinting: Isotopic Methane and Ethane-to-Methane Ratio Analysis Using a Cavity Ring-Down Spectrometer

    NASA Astrophysics Data System (ADS)

    Saad, Nabil; Fleck, Derek; Hoffnagle, John

    2016-04-01

    Emissions of Natural gas, and methane (CH4) specifically, have come under increased scrutiny by virtue of methane's 28-36x greenhouse warming potential compared to carbon dioxide (CO2) while accounting for 10% of the total greenhouse gas emissions in the US. Large uncontrolled leaks, such as the recent Aliso Canyon leak, originating from uncapped wells, coal mines and storage facilities have increased the total global contribution of methane missions even further. Determining the specific fingerprint of methane sources, by quantifying δ13C values and C2:C1 ratios, provides the means to understand methane producing processes and allows for sources of methane to be mapped and classified through these processes; i.e. biogenic vs. thermogenic, wet vs dry. In this study we present a fully developed Cavity Ring-Down Spectrometer (CRDS) that precisely measures 12CH4 concentration and its 13CH4 isotope concentration, yielding δ13C measurements, C2H6 concentration, along with CO2 and H2O. This provides real-time continuous measurements without an upfront separation requirement or multiple analyses to derive the origin of the gas samples. The highly sensitive analyzer allows for measurements of scarce molecules down to sub-ppb 1-σ precision in 5 minutes of measurement: with CH4 <0.1ppb, δ13C <1‰ C2H6 <1ppb and CO2 <1ppm. To complement this work, we provide the analysis of different methane sources providing a 2-dimensional mapping of methane sources as functions of δ13C and C2:C1 ratios, which can be thought of as a modified Bernard Plot. This dual ratio mapping can be used to discriminate between naturally occurring biogenic methane sources, naturally occurring enriched thermogenic sources, and natural gas distribution sources. This also shows future promise in aiding gas and oil exploration, in distinguishing oil vs coal gases, as well as a valuable tool in the development of methane sequestration.

  3. Ice core δD(CH4) record precludes marine hydrate CH4 emissions at the onset of Dansgaard-Oeschger events

    NASA Astrophysics Data System (ADS)

    Bock, M.; Schmitt, J.; Möller, L.; Spahni, R.; Blunier, T.; Fischer, H.

    2010-12-01

    Air enclosures in polar ice cores represent the only direct paleoatmospheric archive (besides firn air) and show that atmospheric CH4 concentrations changed in concert with northern hemisphere temperature during both glacial/interglacial transitions as well as rapid climate changes (Dansgaard-Oeschger events). For stadials and interstadials during Marine Isotope Stage 3 concentration jumps of 100 - 200 ppbv within a few decades are observed. A concentration gradient with higher values in the northern versus the southern hemisphere during warm stages was reconstructed from ice core methane data from Greenland and Antarctica. This gradient indicates additional methane emissions during warm periods located in the northern hemisphere. However, the underlying processes for these changes are still not well understood. With tropical and boreal wetlands, biomass burning, thermokarst lakes, ruminants, termites, UV-induced emissions from organic matter and marine gas hydrates all contributing to the natural atmospheric CH4 level, an unambiguous source attribution remains difficult. Also changes in the methane sinks can modify the tropospheric CH4 budget, as trace gases like volatile organic compounds are competing for the major reactant - the OH radical. Additionally, the changing global atmospheric methane concentration itself feeds back on its lifetime. Together with the CH4 interhemispheric gradient, stable hydrogen and carbon isotopic studies on methane (δD(CH4) and δ13CH4) in ice cores allow to constrain individual CH4 source/sink changes. Here we present clear evidence from the North Greenland Ice Core Project ice core based on the hydrogen isotopic composition of methane δD(CH4) that clathrates did not cause atmospheric methane concentration to rise at the onset of Dansgaard-Oeschger (DO) events 7 and 8 (34 - 41 kilo years before present), however, we can not exclude that they played a minor role during and at the end of an interstadial. Box modeling supports

  4. Development and characterization of polyethersulfone/TiO2 mixed matrix membranes for CO2/CH4 separation

    NASA Astrophysics Data System (ADS)

    Galaleldin, S.; Mannan, H. A.; Mukhtar, H.

    2017-12-01

    In this study, mixed matrix membranes comprised of polyethersulfone as the bulk polymer phase and titanium dioxide (TiO2) nanoparticles as the inorganic discontinuous phase were prepared for CO2/CH4 separation. Membranes were synthesized at filler loading of 0, 5, 10 and 15 wt % via dry phase inversion method. Morphology, chemical bonding and thermal characteristics of membranes were scrutinized utilizing different techniques, namely: Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform InfraRed (FTIR) spectra and Thermogravimetric analysis (TGA) respectively. Membranes gas separation performance was evaluated for CO2 and CH4 gases at 4 bar feed pressure. The highest separation performance was achieved by mixed matrix membrane (MMM) at 5 % loading of TiO2.

  5. Reduced gas seepages in serpentinized peridotite complexes: Evidences for multiple origins of the H2-CH4-N2 gas mixtures

    NASA Astrophysics Data System (ADS)

    Deville, E.; Vacquand, C.; Beaumont, V.; Francois, G.; Sissmann, O.; Pillot, D.; Arcilla, C. A.; Prinzhofer, A.

    2017-12-01

    A comparative study of reduced gas seepages associated to serpentinized ultrabasic rocks was conducted in the ophiolitic complexes of Oman, the Philippines, Turkey and New Caledonia. This study is based on analyzes of the gas chemical composition, noble gases contents, and stable isotopes of carbon, hydrogen and nitrogen. These gas seepages are mostly made of mixtures of three main components which are H2, CH4 and N2 in various proportions. The relative contents of the three main gas components show 4 distinct families of gas mixtures (H2-rich, N2-rich, N2-H2-CH4 and H2-CH4). These families are interpreted as reflecting different zones of gas generation within or below the ophiolitic complexes. In the H2-rich family associated noble gases display signatures close to the value of air. In addition to the atmospheric component, mantle and crustal contributions are present in the N2-rich, N2-H2-CH4 and H2-CH4 families. H2-bearing gases are either associated to ultra-basic (pH 10-12) spring waters or they seep directly in fracture systems from the ophiolitic rocks. In ophiolitic contexts, ultrabasic rocks provide an adequate environment with available Fe2+ and high pH conditions that favor H2 production. CH4 is produced either directly by reaction of dissolved CO2 with basic-ultrabasic rocks during the serpentinization process or in a second step by H2-CO2 interaction. H2 is present in the gas when no more carbon is available in the system to generate CH4 (conditions of strong carbon restriction). The N2-rich family is associated with relatively high contents of crustal 4He. In this family N2 is interpreted as issued mainly from sediments located below the ophiolitic units.

  6. Selenium carboxylic acids betaine; 3,3‧,3″-selenotris(propanoic acid) betaine, Se(CH2CH2COOH)2(CH2CH2COO)

    NASA Astrophysics Data System (ADS)

    Doudin, Khalid; Törnroos, Karl W.

    2017-06-01

    Attempts to prepare [Se(CH2CH2COOH)3]+Cl- from Se(CH2CH2COOH)2 and H2Cdbnd CHCOOH in concentrated hydrochloric acid, for the corresponding sulfonium salt, led exclusively to the Se-betaine, Se(CH2CH2COOH)2(CH2CH2COO). The Se-betaine crystallises in the space group P2l/c with the cell dimensions at 223 K, a = 5.5717(1), b = 24.6358(4), c = 8.4361(1) Å, β = 104.762(1)°, V = 1119.74(3) Å3, Z = 4, Dcalc = 1.763 Mgm- 3, μ = 3.364 Mm-1. The structure refined to RI = 0.0223 for 2801 reflections with Fo > 4σ(Fo). In the crystalline state the molecule is intermolecularly linked to neighbouring molecules by a number of hydrogen bonds; a very strong carboxylic-carboxylate bond with an O⋯O distance of 2.4435(16) Å, a medium strong carboxylic-carboxylate bond with an O⋯O distance of 2.6431(16) Å and several weak O⋯H(CH2) with O⋯C distances between 3.2 and 3.3 Å. In the carboxylic group involved in the very strong hydrogen bond the O⋯H bond is antiperiplanar to the Cdbnd O bond while the Osbnd H bond is periplanar to the Cdbnd O bond in the second carboxylic group. Based upon the Csbnd O bond lengths and the elongation of the Osbnd H bond involved in the strong hydrogen bond one may describe the compound as strongly linked units of Se(CH2CH2COOH)(CH2CH2COO)2 rather than Se(CH2CH2COOH)2(CH2CH2COO). The selenium atom forms two strong intramolecular 1,5-Se⋯O contacts, with a carboxylate oxygen atom, 2.9385(12) Å, and with a carboxylic oxygen atom, 2.8979(11) Å. To allow for these contacts the two organic fragments have been forced into the periplanar conformation. The molecule is only slightly asymmetric with regard to the Csbnd Sesbnd C bond angles but is very asymmetric with regard to the torsion angles.

  7. Methane and Nitrous Oxide Emissions Reduced Following Conversion of Rice Paddies to Inland Crab-Fish Aquaculture in Southeast China.

    PubMed

    Liu, Shuwei; Hu, Zhiqiang; Wu, Shuang; Li, Shuqing; Li, Zhaofu; Zou, Jianwen

    2016-01-19

    Aquaculture is an important source of atmospheric methane (CH4) and nitrous oxide (N2O), while few direct flux measurements are available for their regional and global source strength estimates. A parallel field experiment was performed to measure annual CH4 and N2O fluxes from rice paddies and rice paddy-converted inland crab-fish aquaculture wetlands in southeast China. Besides N2O fluxes dependent on water/sediment mineral N and CH4 fluxes related to water chemical oxygen demand, both CH4 and N2O fluxes from aquaculture were related to water/sediment temperature, sediment dissolved organic carbon, and water dissolved oxygen concentration. Annual CH4 and N2O fluxes from inland aquaculture averaged 0.37 mg m(-2) h(-1) and 48.1 μg m(-2) h(-1), yielding 32.57 kg ha(-1) and 2.69 kg N2O-N ha(-1), respectively. The conversion of rice paddies to aquaculture significantly reduced CH4 and N2O emissions by 48% and 56%, respectively. The emission factor for N2O was estimated to be 0.66% of total N input in the feed or 1.64 g N2O-N kg(-1) aquaculture production in aquaculture. The conversion of rice paddies to inland aquaculture would benefit for reconciling greenhouse gas mitigation and agricultural income increase as far as global warming potentials and net ecosystem economic profits are of concomitant concern. Some agricultural practices such as better aeration and feeding, and fallow season dredging would help to lower CH4 and N2O emissions from inland aquaculture. More field measurements from inland aquaculture are highly needed to gain an insight into national and global accounting of CH4 and N2O emissions.

  8. Carbon isotope exchange in the system CO 2-CH 4 at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Horita, Juske

    2001-06-01

    Carbon isotope exchange was investigated for the system CO 2-CH 4 at 150 to 600°C in the presence of several potential catalysts by use of isotopically normal or 13C-enriched gases. Silica gel, graphite, molecular sieve Linde 4A, magnetite, and hematite oxidized small amounts of CH 4 in starting CO 2-CH 4 mixtures to CO and CO 2 but failed to enhance the net rate of carbon isotope exchange between CO 2 and CH 4, even after 169 to 1833 h at 400 to 500°C. In contrast, several commercial transition-metal catalysts (Ni, Pd, Rh, and Pt) promoted reactions significantly toward chemical and isotopic equilibrium. With the Ni catalyst, the attainment of carbon isotopic equilibrium between CO 2 and CH 4 was demonstrated for the first time at temperatures from 200 to 600°C by complete isotopic reversal from opposite directions. The experimentally determined carbon isotope fractionation factors between CO 2 and CH 4 (10 3lnα) were similar to, but slightly greater than (0.7-1.1‰, 0.89‰ on average), those of statistical-mechanical calculations by Richet et al. (1977). The experimental results can be described by the following equation between 200 and 600°C only: 10 3lnα(CO 2-CH 4) = 26.70 - 49.137(10 3/T) + 40.828(10 6/T 2) - 7.512(10 9/T 3) (T = 473.15-873.15 K, 1σ = ±0.14‰, n = 44). Alternatively, an equation generated by fitting Richet et al. (1977) data in the temperature range from 0 to 1300°C can be modified by adding +0.89‰ to its constant; 10 3lnα(CO 2-CH 4) = 0.16 + 11.754(10 6/T 2) - 2.3655(10 9/T 3) + 0.2054(10 12/T 4) (T = 273-1573 K, 1σ = ±0.21‰, n = 44). This and other recent experimental studies in the literature demonstrate that transition metals, which are widespread in many natural materials, can catalyze reactions among natural gases at relatively low temperatures (≤200°C). The role of natural catalysts, "geocatalysts," in the abiogenic formation of methane, hydrocarbons, and simple organic compounds has important implications, ranging

  9. BOREAS TGB-1 Soil CH4 and CO2 Profile Data from NSA Tower Sites

    NASA Technical Reports Server (NTRS)

    Crill, Patrick; Varner, Ruth K.; Hall, Forrest G. (Editor); Conrad, Sara K. (Editor)

    2000-01-01

    The BOREAS TGB-1 team made numerous measurements of trace gas concentrations and fluxes at various NSA sites. This data set contains methane (CH4) and carbon dioxide (CO2) concentrations in soil profiles from the NSA-OJP, NSA-OBS, NSA-YJP, and NSA-BP sites during the period of 23-May to 20-Sep-1994. The soil gas sampling profiles of CH 4 and CO 2 were completed to quantify controls on CO2 and CH4 fluxes in the boreal forest. The data are provided in tabular ASCII files.

  10. Experimental Equipment Validation for Methane (CH4) and Carbon Dioxide (CO2) Hydrates

    NASA Astrophysics Data System (ADS)

    Saad Khan, Muhammad; Yaqub, Sana; Manner, Naathiya; Ani Karthwathi, Nur; Qasim, Ali; Mellon, Nurhayati Binti; Lal, Bhajan

    2018-04-01

    Clathrate hydrates are eminent structures regard as a threat to the gas and oil industry in light of their irritating propensity to subsea pipelines. For natural gas transmission and processing, the formation of gas hydrate is one of the main flow assurance delinquent has led researchers toward conducting fresh and meticulous studies on various aspects of gas hydrates. This paper highlighted the thermodynamic analysis on pure CH4 and CO2 gas hydrates on the custom fabricated equipment (Sapphire cell hydrate reactor) for experimental validation. CO2 gas hydrate formed at lower pressure (41 bar) as compared to CH4 gas hydrate (70 bar) while comparison of thermodynamic properties between CH4 and CO2 also presented in this study. This preliminary study could provide pathways for the quest of potent hydrate inhibitors.

  11. A compact QCL based methane and nitrous oxide sensor for environmental and medical applications.

    PubMed

    Jahjah, Mohammad; Ren, Wei; Stefański, Przemysław; Lewicki, Rafał; Zhang, Jiawei; Jiang, Wenzhe; Tarka, Jan; Tittel, Frank K

    2014-05-07

    A methane (CH4) and nitrous oxide (N2O) sensor based on a sensitive, selective and well established technique of quartz enhanced photoacoustic spectroscopy (QEPAS) was developed for environmental and biomedical measurements. A thermoelectrically cooled (TEC) distributed feedback quantum cascade laser (DFB-QCL), capable of continuous wave (CW) mode hop free emission in the 7.83 μm wavelength range, was used as an excitation source. For the targeted CH4 and N2O absorption lines located at 1275.04 cm(-1) and 1275.49 cm(-1) detection limits (1σ) of 13 ppbv and 6 ppbv were achieved with a 1 second data acquisition time, respectively. Environmental data of CH4 and N2O mixing ratios acquired using the QEPAS sensor system are also reported.

  12. Early Mars serpentinization-derived CH4 reservoirs, H2 induced warming and paleopressure evolution

    NASA Astrophysics Data System (ADS)

    Lasue, J.; Chassefiere, E.; Langlais, B.; Quesnel, Y.

    2016-12-01

    CH4 has been observed on Mars both by remote sensing and in situ during the past 15 years. Early Mars serpentinization is one possible abiotic mechanism that could not only produce methane, but also explain the observed Martian remanent magnetic field. Assuming a cold early Mars, a cryosphere could trap such CH4 as clathrates in stable form at depth. We recently estimated the maximum storage capacity of such clathrate layer to be about 2x1019 to 2x1020 moles of methane. Such reservoirs may be stable or unstable, depending on many factors that are poorly constrained: major and sudden geological events such as the Tharsis bulge formation, the Hellas impact or the martian polar wander, could have destabilized the clathrates early in the history of the planet and released large quantities of gas in the atmosphere. Here we estimate the associated amounts of serpentinization-derived CH4 stored in the cryosphere that have been released to the atmosphere at the end of the Noachian and the beginning of the Hesperian. Due to rapid clathrate dissociation and photochemical conversion of CH4 to H2, these episodes of massive CH4 release may have resulted in transient H2-rich atmospheres, at typical levels of 10-20% in a background 1-2 bar CO2 atmosphere. We propose that the early Mars cryosphere had a sufficient CH4 storage capacity to have maintained H2-rich transient atmospheres during a total time period up to several Myr or tens of Myr, having potentially contributed - by collision-induced heating effect of atmospheric H2 - to the formation of valley networks during the late Noachian and early Hesperian.

  13. Optical sensor system for time-resolved quantification of methane densities in CH4-fueled spark ignition engines.

    PubMed

    Golibrzuch, Kai; Digulla, Finn-Erik; Bauke, Stephan; Wackerbarth, Hainer; Thiele, Olaf; Berg, Thomas

    2017-08-01

    We present the development and the first application of an optical sensor system that allows single-cycle determination of methane (CH 4 ) concentration inside internal combustion (IC) engines. We use non-dispersive infrared absorption spectroscopy to detect the CH 4 density with a time resolution up to 33 μs at acquisition rates of 30 kHz. The measurement scheme takes advantage of the strong temperature dependence of the absorption band applying two detection channels for CH 4 that detect different spectral regions of the ν 3 anti-symmetric C-H-stretch absorption. The strategy allows the simultaneous determination of fuel concentration as well as gas temperature. We show the proof-of-concept by validation of the measurement strategy in static pressure cell experiments as well as its application to a methane-fueled IC engine using a modified spark plug probe. Our results clearly demonstrate that it is crucial to determine the CH 4 temperature in the probe volume. Due to thermal influences of the sensor probe, the temperature needed to calculate the desired quantities (fuel density, fuel concentration) significantly differs from the gas phase temperature in the rest of the combustion chamber and estimations from standard thermodynamic models, e.g., polytropic compression, will fail.

  14. Mitigating global warming potentials of methane and nitrous oxide gases from rice paddies under different irrigation regimes.

    PubMed

    Ali, Muhammad Aslam; Hoque, M Anamul; Kim, Pil Joo

    2013-04-01

    A field experiment was conducted in Bangladesh Agricultural University Farm to investigate the mitigating effects of soil amendments such as calcium carbide, calcium silicate, phosphogypsum, and biochar with urea fertilizer on global warming potentials (GWPs) of methane (CH4) and nitrous oxide (N2O) gases during rice cultivation under continuous and intermittent irrigations. Among the amendments phosphogypsum and silicate fertilizer, being potential source of electron acceptors, decreased maximum level of seasonal CH4 flux by 25-27 % and 32-38 % in continuous and intermittent irrigations, respectively. Biochar and calcium carbide amendments, acting as nitrification inhibitors, decreased N2O emissions by 36-40 % and 26-30 % under continuous and intermittent irrigations, respectively. The total GWP of CH4 and N2O gases were decreased by 7-27 % and 6-34 % with calcium carbide, phosphogypsum, and silicate fertilizer amendments under continuous and intermittent irrigations, respectively. However, biochar amendments increased overall GWP of CH4 and N2O gases.

  15. In situ Low-temperature Pair Distribution Function (PDF) Analysis of CH4 and CO2 Hydrates

    NASA Astrophysics Data System (ADS)

    Cladek, B.; Everett, M.; McDonnell, M.; Tucker, M.; Keffer, D.; Rawn, C.

    2017-12-01

    Gas hydrates occur in ocean floor and sub-surface permafrost deposits and are stable at moderate to high pressures and low temperatures. They are a clathrate structure composed of hydrogen bonded water cages that accommodate a wide variety of guest molecules. CO2 and CH4 hydrates both crystallize as the cubic sI hydrate and can form a solid solution. Natural gas hydrates are interesting as a potential methane source and for CO2 sequestration. Long-range diffraction studies on gas hydrates give valuable structural information but do not provide a detailed understanding of the disordered gas molecule interactions with the host lattice. In-situ low temperature total scattering experiments combined with pair distribution function (PDF) analysis are used to investigate the gas molecule motions and guest-cage interactions. CO2 and methane hydrates exhibit different decomposition behavior, and CO2 hydrate has a smaller lattice parameter despite it being a relatively larger molecule. Total scattering studies characterizing both the short- and long-range order simultaneously help to elucidate the structural source of these phenomena. Low temperature neutron total scattering data were collected using the Nanoscale Ordered MAterials Diffractometer (NOMAD) beamline at the Spallation Neutron Source (SNS) on CO2 and CH4 hydrates synthesized with D2O. Guest molecule motion within cages and interactions between gases and cages are investigated through the hydrate stability and decomposition regions. Data were collected from 2-80 K at a pressure of 55 mbar on CO2 and CH4 hydrates, and from 80-270 K at 25 bar on CH4 hydrate. The hydrate systems were modeled with classical molecular dynamic (MD) simulations to provide an analysis of the total energy into guest-guest, guest-host and host-host contributions. Combined Reitveld and Reverse Monte Carlo (RMC) structure refinement were used to fit models of the data. This combined modeling and simulation characterizes the effects of CO2 and

  16. In situ measurements of H2O, CH4 and CO2 in the upper troposphere and the lower stratosphere (UT-LS) with the baloonborne picoSDLA and AMULSE tunable diode laser spectrometers during the 2014 and 2015 "Stratoscience" campaigns

    NASA Astrophysics Data System (ADS)

    Miftah-El-Khair, Zineb; Joly, Lilian; Decarpenterie, Thomas; Cousin, Julien; Dumelié, Nicolas; Grouiez, Bruno; Albo, Grégory; Chauvin, Nicolas; Maamary, Rabih; Amarouche, Nadir; Durry, Georges

    2016-04-01

    H2O, CH4 and CO2 are major greenhouse gases with a strong impact on climate. The concentrations of CO2 and CH4 have dramatically increased since the beginning of the industrialization era due to anthropogenic activities, contributing thereby to the global warming. Anthropogenic activities as fossil fuels, ruminant, and biomass burning constitute the major sources of carbon dioxide and methane. The increase of H2O concentration in the stratosphere could cause a cooling of this atmospheric region, impacting the recovery of the ozone layer. Therefore, having information and data about the vertical distribution of H2O, CO2 and CH4 is very useful to improve our knowledge of the future of our climate. We have developed, with the help of French space agency (CNES) and CNRS, two laser diode sensors PicoSDLA and AMULSE devoted to the in situ measurements of H2O, CH4 and CO2 from balloon platforms. These instruments were operated from open stratospheric balloons in Timmins, CA, in August 2014 and 2015. We report and discuss the instrumental achievements of both sensors during these flights in the UT-LS. Aknowledgments: The authors acknowledge financial supports from CNES, CNRS and the region Champagne-Ardenne.

  17. Identifying sources of methane sampled in the Arctic using δ13C in CH4 and Lagrangian particle dispersion modelling.

    NASA Astrophysics Data System (ADS)

    Cain, Michelle; France, James; Pyle, John; Warwick, Nicola; Fisher, Rebecca; Lowry, Dave; Allen, Grant; O'Shea, Sebastian; Illingworth, Samuel; Jones, Ben; Gallagher, Martin; Welpott, Axel; Muller, Jennifer; Bauguitte, Stephane; George, Charles; Hayman, Garry; Manning, Alistair; Myhre, Catherine Lund; Lanoisellé, Mathias; Nisbet, Euan

    2016-04-01

    An airmass of enhanced methane was sampled during a research flight at ~600 m to ~2000 m altitude between the North coast of Norway and Svalbard on 21 July 2012. The largest source of methane in the summertime Arctic is wetland emissions. Did this enhancement in methane come from wetland emissions? The airmass was identified through continuous methane measurements using a Los Gatos fast greenhouse gas analyser on board the UK's BAe-146 Atmospheric Research Aircraft (ARA) as part of the MAMM (Methane in the Arctic: Measurements and Modelling) campaign. A Lagrangian particle dispersion model (the UK Met Office's NAME model) was run backwards to identify potential methane source regions. This was combined with a methane emission inventory to create "pseudo observations" to compare with the aircraft observations. This modelling was used to constrain the δ13C CH4 wetland source signature (where δ13C CH4 is the ratio of 13C to 12C in methane), resulting in a most likely signature of -73‰ (±4‰7‰). The NAME back trajectories suggest a methane source region of north-western Russian wetlands, and -73‰ is consistent with in situ measurements of wetland methane at similar latitudes in Scandinavia. This analysis has allowed us to study emissions from remote regions for which we do not have in situ observations, giving us an extra tool in the determination of the isotopic source variation of global methane emissions.

  18. Crystal structure of aqua-1κO-{μ-2-[(2-hydroxy-ethyl)methylamino]ethanolato-2:1κ(4) O (1),N,O (2):O (1)}[μ-2,2'-(methylimino)diethanolato-1:2κ(4) O,N,O':O]dithiocyanato-1κN,2κN-chromium(III)copper(II).

    PubMed

    Rusanova, Julia A; Semenaka, Valentina V; Dyakonenko, Viktoriya V; Shishkin, Oleg V

    2015-09-01

    The title compound, [CrCu(C5H11NO2)(C5H12NO2)(NCS)2(H2O)] or [Cr(μ-mdea)Cu(μ-Hmdea)(NCS)2H2O], (where mdeaH2 is N-methylethanolamine, C5H13NO2) is formed as a neutral heterometal Cu(II)/Cr(III) complex. The mol-ecular structure of the complex is based on a binuclear {CuCr(μ-O)2} core. The coordination environment of each metal atom involves the N,O,O atoms of the tridentate ligand, one bridging O atom of the ligand and the N atom of the thio-cyanato ligands. The Cu(II) ion adopts a distorted square-pyramidal coordination while the Cr(III) ion has a distorted octa-hedral coordination geometry completed by the aqua ligand. In the crystal, the binuclear complexes are linked via two pairs of O-H⋯O hydrogen bonds to form inversion dimers, which are arranged in columns parallel to the a axis. In the μ-mdea ligand two -CH2 groups and the methyl group were refined as disordered over two sets of sites with equal occupancies. The structure was refined as a two-component twin with a twin scale factor of 0.242 (1).

  19. A novel Zn-based heterocycle metal-organic framework for high C2H2/C2H4, CO2/CH4 and CO2/N2 separations

    NASA Astrophysics Data System (ADS)

    Zhang, Ling; Jiang, Ke; Yang, Yu; Cui, Yuanjing; Chen, Banglin; Qian, Guodong

    2017-11-01

    Efficient separation of the small gas molecules especially the hydrocarbons is essential to social economy. The microporous metal-organic frameworks (MOFs) are taking precedence in this respect by virtue of their irreplaceable advantages. Herein, the new organic linker 5-(5-carboxypyridin-3-yl)isophthalic acid simplified as H3L-N has been excavated to construct successfully the novel Zn-based heterocycle metal-organic framework ZnL·(DMF)1.5·(H2O)6.0 (ZJU-197, ZJU = Zhejiang University, DMF = N,N-dimethylformamide). ZJU-197 has been structurally characterized and explored in details for gas separation. It is commendable that the activated ZJU-197a has exhibited excellent C2H2/C2H4, CO2/CH4 and CO2/N2 separations simultaneously with IAST selectivity of 137.8, 53.0 and 514.1 respectively at ambient conditions.

  20. Synthesis of ultrasmooth nanostructured diamond films by microwave plasma chemical vapor deposition using a He/H(2)/CH(4)/N(2) gas mixture.

    PubMed

    Chowdhury, S; Hillman, Damon A; Catledge, Shane A; Konovalov, Valery V; Vohra, Yogesh K

    2006-10-01

    Ultrasmooth nanostructured diamond (USND) films were synthesized on Ti-6Al-4V medical grade substrates by adding helium in H(2)/CH(4)/N(2) plasma and changing the N(2)/CH(4) gas flow from 0 to 0.6. We were able to deposit diamond films as smooth as 6 nm (root-mean-square), as measured by an atomic force microscopy (AFM) scan area of 2 μm(2). Grain size was 4-5 nm at 71% He in (H(2) + He) and N(2)/CH(4) gas flow ratio of 0.4 without deteriorating the hardness (~50-60 GPa). The characterization of the films was performed with AFM, scanning electron microscopy, x-ray diffraction (XRD), Raman spectroscopy, and nanoindentation techniques. XRD and Raman results showed the nanocrystalline nature of the diamond films. The plasma species during deposition were monitored by optical emission spectroscopy. With increasing N(2)/CH(4) feedgas ratio (CH(4) was fixed) in He/H(2)/CH(4)/N(2) plasma, a substantial increase of CN radical (normalized by Balmer H(α) line) was observed along with a drop in surface roughness up to a critical N(2)/CH(4) ratio of 0.4. The CN radical concentration in the plasma was thus correlated to the formation of ultrasmooth nanostructured diamond films.

  1. Methane Fluxes from Subtropical Wetlands

    NASA Astrophysics Data System (ADS)

    DeLucia, N.; Gomez-Casanovas, N.; Bernacchi, C.

    2013-12-01

    It is well documented that green house gas concentrations have risen at unequivocal rates since the industrial revolution but the disparity between anthropogenic sources and natural sources is uncertain. Wetlands are one example of a natural ecosystem that can be a substantial source or sink for methane (CH4) depending on climate conditions. Due to strict anaerobic conditions required for CH4-generating microorganisms, natural wetlands are one of the main sources for biogenic CH4. Although wetlands occupy less than 5% of total land surface area, they contribute approximately 20% of total CH4 emissions to the atmosphere. The processes regulating CH4 emissions are sensitive to land use and management practices of areas surrounding wetlands. Variation in adjacent vegetation or grazing intensity by livestock can, for example, alter CH4 fluxes from wetland soils by altering nutrient balance, carbon inputs and hydrology. Therefore, understanding how these changes will affect wetland source strength is essential to understand the impact of wetland management practices on the global climate system. In this study we quantify wetland methane fluxes from subtropical wetlands on a working cattle ranch in central Florida near Okeechobee Lake (27o10'52.04'N, 81o21'8.56'W). To determine differences in CH4 fluxes associated with land use and management, a replicated (n = 4) full factorial experiment was designed for wetlands where the surrounding vegetation was (1) grazed or un-grazed and (2) composed of native vegetation or improved pasture. Net exchange of CH4 and CO2 between the land surface and the atmosphere were sampled with a LICOR Li-7700 open path CH4 analyzer and Li-7500A open path CO2/H20 analyzer mounted in a 1-m3 static gas-exchange chamber. Our results showed and verified that CH4 emissions from subtropical wetlands were larger when high soil moisture was coupled with high temperatures. The presence of cattle only amplified these results. These results help quantify

  2. Syntheses and structures of [UO2( L)5](ClO4)2 and [U( L')4(H2O)4](ClO4)4 ( L is dimethylformamide, L' is N,N-dimethylcarbamide)

    NASA Astrophysics Data System (ADS)

    Serezhkin, V. N.; Vologzhanina, A. V.; Pushkin, D. V.; Astashkina, D. A.; Savchenkov, A. V.; Serezhkina, L. B.

    2017-09-01

    The reaction of aqueous solutions of uranyl perchlorate with selected organic amides was studied in the dark and under the sunlight. The complexes [UVIO2(C3H7NO)5](ClO4)2 ( I) and [UIV(C3H8N2O)4(H2O)4](ClO4)4 ( II), where C3H7NO is N,N-dimethylformamide ( Dmfa) and C3H8N2O is N,N-dimethylcarbamide ( a-Dmur), were studied by X-ray diffraction. Complex II and the complex UIV( s-Dmur)4(H2O)4(ClO4)4 ( III), where s-Dmur is N,N'-dimethylcarbamide, were studied by IR spectroscopy. Crystals I and II are composed of mononuclear [UO2( Dmfa)5]2+ and [U( Dmur)4(H2O)4]4+ groups as uranium-containing structural units belonging to the crystal-chemical groups AM 7 1 ( A = UVI, M 1 = O2- and Dmfa) and AM 8 1 ( A = UIV, M 1 = Dmur and H2O) of uranium complexes, respectively. The mononuclear uranium- containing complexes in the crystals of U(IV) and U(VI) perchlorates were found to obey the 14 neighbors rule.

  3. The spectroscopic observation of the CH radical in its a4Sigma(-) state

    NASA Technical Reports Server (NTRS)

    Nelis, Thomas; Brown, John M.; Evenson, Kenneth M.

    1988-01-01

    The first spectroscopic observation of CH in the a 4Sigma(0-) state are reported. The molecule was generated in a discharge-flow system in the reaction betweeen fluorine atoms and methane or between oxygen atoms and acetylene at a total pressure of about 1 Torr. Several resonances associated with the N = 1 - 0 transitions of 4Sigma(-) CH were observed at three separate laser wavelengths, while those for the N = 2 - 1 transition were observed at two wavelengths. Each observed Zeeman component consists of a well-split doublet arising from proton hyperfine structure. The reasons for assigning the observations to CH in its a 4Sigma(-) state are discussed.

  4. Thermochemistry and kinetics for 2-butanone-1-yl radical (CH2·C(═O)CH2CH3) reactions with O2.

    PubMed

    Sebbar, N; Bozzelli, J W; Bockhorn, H

    2014-01-09

    Thermochemistry of reactants, intermediates, transition state structures, and products along with kinetics on the association of CH2·C(═O)CH2CH3 (2-butanone-1-yl) with O2 and dissociation of the peroxy adduct isomers are studied. Thermochemical properties are determined using ab initio (G3MP2B3 and G3) composite methods along with density functional theory (B3LYP/6-311g(d,p)). Entropy and heat capacity contributions versus temperature are determined from structures, vibration frequencies, and internal rotor potentials. The CH2·C(═O)CH2CH3 radical + O2 association results in a chemically activated peroxy radical with 27 kcal mol(-1) excess of energy. The chemically activated adduct can react to stabilized peroxy or hydroperoxide alkyl radical adducts, further react to lactones plus hydroxyl radical, or form olefinic ketones and a hydroperoxy radical. Kinetic parameters are determined from the G3 composite methods derived thermochemical parameters, and quantum Rice-Ramsperger-Kassel (QRRK) analysis to calculate k(E) with master equation analysis to evaluate falloff in the chemically activated and dissociation reactions. One new, not previously reported, peroxy chemistry reaction is presented. It has a low barrier path and involves a concerted reaction resulting in olefin formation, H2O elimination, and an alkoxy radical.

  5. Characterisation of methane isotope composition over the Silesian Coal Basin, Poland.

    NASA Astrophysics Data System (ADS)

    Necki, Jaroslaw; Zimnoch, Miroslaw; Jasek, Alina; Chmura, Lukasz; Galkowski, Michal; Wolkowicz, Wojciech

    2017-04-01

    Methane emissions from Silesian Coal Basin (SCB), one of European regions associated with coal excavation industry constitute an important component of the continental anthropogenic flux of this gas into the atmosphere. It is estimated by different methodology that SCB is responsible for between 450 - 1350 Gg CH4 of atmospheric methane releases annually, making it one of the most significant sources of this gas in Europe. In this region, active or restructuring coal mining methane emissions may lead to elevated concentrations of this gas in near-ground atmosphere. Observed methane mixing ratio in pbl during nighttime over the specific areas of SCB is elevated by up to 50ppm with carbon isotope source ratio -46‰ to -52‰ with occasionally lighter methane (-58) form particular coal beds. Numbers were derived from direct measurement of samples taken from ventilation shafts (concentration 1.5% to 4% of CH4, subsequently diluted to 2ppm with zero air and measured by Picarro CRDS analyzer). Measurements of CH4 mixing ratios and isotopic composition were performed along latitudinal transects (ca. 50oN), typically extending from ca. 15oE to 20oE, covering the Upper Silesia and bordering regions on the public roads in vicinity of the mine ventilation shafts. Apart from CH4 emissions associated with coal production, other sources of anthropogenic methane are also active over SCB. These include city gas networks leakages that enrich the air by up to 5ppm (in the city centers, carbon isotope ratio on average -52). Most of the numerous landfills, not yet equipped with appropriate CH4 uptake installations, also contribute to substantial anthropogenic flux of this gas to the atmosphere. Values of methane mixing ratio recorded during the in-situ measurements close to the landfill sites reached 15ppm (with carbon isotope ratio -56‰ to -60). The transects of methane concentration over Silesian area, assisted by analysis of its stable isotopic composition has been performed in

  6. (Phosphinoalkyl)silanes. 4.(1) Hydrozirconation as a Non-Photochemical Route to (Phosphinopropyl)silanes: Facile Assembly of the Bis(3-(diphenylphosphino)propyl)silyl ("biPSi") Ligand Framework. Access to the Related Poly(3-(dimethylsilyl)propyl)phosphines R(n)()P(CH(2)CH(2)CH(2)SiMe(2)H)(3)(-)(n)() (n = 1, R = Ph; n = 0).

    PubMed

    Zhou, Xiaobing; Stobart, Stephen R.; Gossage, Robert A.

    1997-08-13

    Treatment of SiEt(3)(CH=CH(2)) with ZrCp(2)HCl (Schwartz's reagent) followed by reaction with PPh(2)Cl provides a high-yield (75%) route to Ph(2)PCH(2)CH(2)SiEt(3), and accordingly hydrozirconation of CH(2)=CHCH(2)SiHMe(2) affords the intermediate ZrCp(2)(CH(2)CH(2)CH(2)SiHMe(2))Cl (2). The latter, which is very sensitive to hydrolysis and reacts with HCl forming SiHMe(2)Pr(n)() and with NBS or I(2) affording SiHMe(2)CH(2)CH(2)CH(2)X (X = Br (3), I (4)), behaves similarly with PPh(2)Cl, PPhCl(2), or PBr(3) undergoing cleavage to the known Ph(2)PCH(2)CH(2)CH(2)SiMe(2)H (i.e. chelH, A) and the novel bis- and tris(silylpropyl)phosphines PhP(CH(2)CH(2)CH(2)SiMe(2)H)(2) (5) and P(CH(2)CH(2)CH(2)SiMe(2)H)(3) (6), respectively, with concomitant formation of ZrCp(2)Cl(2). Corresponding hydroboration of allylsilanes is facile, but subsequent phosphine halide cleavage yields (phosphinoalkyl)silanes only as constituents of intractable mixtures. Hydrozirconation followed by phosphination with PPh(2)Cl also converts SiHMe(CH(2)CH=CH(2))(2) to SiHMe(CH(2)CH(2)CH(2)PPh(2))(2) (i.e. biPSiH, B) together with a propyl analogue Ph(2)PCH(2)CH(2)CH(2)SiMe(Pr(n)())H (7) of A (ca. 2:1 ratio), as well as SiH(CH(2)CH=CH(2))(3) to a mixture (ca. 5:2:1 ratio) of SiH(CH(2)CH(2)CH(2)PPh(2))(3) (i.e. triPSiH, C), a new analogue SiH(Pr(n)())(CH(2)CH(2)CH(2)PPh(2))(2) (8) of B, and a further analogue Ph(2)PCH(2)CH(2)CH(2)SiHPr(n)()(2) (9) of A. A further analogue SiH(2)(CH(2)CH(2)CH(2)PPh(2))(2) (10) of biPSiH (B) is obtained similarly starting from SiH(2)(CH(2)CH=CH(2))(2). Steric control of silylalkyl cleavage from 2 is indicated by the fact that, like PPh(2)Cl (which forms B), two further biPSiH analogues SiH(Me)[CH(2)CH(2)CH(2)P(n-hex)(2)](2) (11) and SiH(Me)(CH(2)CH(2)CH(2)PPhBz)(2) (12) were obtained using P(n-hex)(2)Cl (i.e. n-hex = CH(3)(CH(2))(4)CH(2)-) or PPhBzCl (i.e. Bz = -CH(2)C(6)H(5)), respectively, whereas neither PPr(i)(2)Cl nor PBu(t)(2)Cl led to (phosphinoalkyl)silane formation

  7. Net emissions of CH4 and CO2 in Alaska: Implications for the region's greenhouse gas budget

    USGS Publications Warehouse

    Zhuang, Q.; Melillo, J.M.; McGuire, A.D.; Kicklighter, D.W.; Prinn, R.G.; Steudler, P.A.; Felzer, B.S.; Hu, S.

    2007-01-01

    We used a biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to study the net methane (CH4) fluxes between Alaskan ecosystems and the atmosphere. We estimated that the current net emissions of CH4 (emissions minus consumption) from Alaskan soils are ???3 Tg CH 4/yr. Wet tundra ecosystems are responsible for 75% of the region's net emissions, while dry tundra and upland boreal forests are responsible for 50% and 45% of total consumption over the region, respectively. In response to climate change over the 21st century, our simulations indicated that CH 4 emissions from wet soils would be enhanced more than consumption by dry soils of tundra and boreal forests. As a consequence, we projected that net CH4 emissions will almost double by the end of the century in response to high-latitude warming and associated climate changes. When we placed these CH4 emissions in the context of the projected carbon budget (carbon dioxide [CO2] and CH4) for Alaska at the end of the 21st century, we estimated that Alaska will be a net source of greenhouse gases to the atmosphere of 69 Tg CO2 equivalents/yr, that is, a balance between net methane emissions of 131 Tg CO2 equivalents/yr and carbon sequestration of 17 Tg C/yr (62 Tg CO2 equivalents/yr). ?? 2007 by the Ecological Society of America.

  8. Tropical rainforest methane consumption during the El Niño of 2015-16

    NASA Astrophysics Data System (ADS)

    Aronson, E. L.; Dierick, D.; Botthoff, J.; Swanson, A. C.; Allen, M. F.

    2016-12-01

    Tropical forests sequester up to 40% of the anthropogenic and natural carbon exchanged with the atmosphere. Even though soils are the largest pool of terrestrial carbon, relatively little is known about the methane consumption capacity of tropical forest soils. Under high water, low oxygen (anaerobic) conditions, carbon decomposed is respired as methane (CH4) by methanogen microorganisms. During dry seasons, deeper rainforest soils remain wet, but dry at the surface. Since molecule for molecule the global warming potential of CH4 is two orders of magnitude greater than CO2, the relative production and sequestration of CO2 versus CH4 in tropical rainforests has a large impact on global climate trends. In 2015-16, the globe experienced an unusually strong ENSO event, which impacted the tropics. Atypical ENSO climatic events such as this include drought in tropical forests of Central America. We hypothesized that ENSO controls much of the year-to-year variability in the global CH4 cycle, primarily by turning the tropical forest from a strong annual source for CH4 during the La Niña or normal rainy season, to a year-round sink for CH4 during El Niño events. Further, we hypothesized that during a strong El Niño event, the unusually dry conditions of the tropical rainy season lead to the methanotrophs in these soils consuming large amounts of CH4. In order to investigate these predictions, CH4 flux was measured in three campaigns in March, during peak ENSO impact, as well as May and July 2016, at the La Selva Biological Station, Costa Rica. Fluxes were measured in eight paired plots, each with four collars. The collars measure 20 cm diameter by 12 cm in length, inserted into the soil, with a collar height of around 8 cm, in February 2016, a month before the first field campaign. Air samples were injected into pre-evacuated exetainers, and analyzed by gas chromatograph within 72 h. We found an average CH4 sink of -0.018 mg m-2 h-1. This flux is roughly four times lower

  9. Megafauna and frozen soil: the drivers of atmospheric CH4 dynamics

    NASA Astrophysics Data System (ADS)

    Zimov, N.; Zimov, S. A.

    2010-12-01

    During the last deglaciation (LD) a strong increase in atmospheric methane (CH4) concentrations occurred simultaneously with a rise in Greenland temperatures indicating that in the north, during this time period, strong CH4 sources “awakened”, as additionally documented by the appearance of a strong gradient between northern (Greenland) and southern (Antarctica) hemisphere atmospheric CH4 concentrations. This rise could not be caused by wetland expansion. A reconstruction of peatland formation dynamics has indicated that wetlands on Earth were few in LD and only actively expanded 10,000 yr BP, after atmospheric CH4 concentrations began to decline. Destabilization of methane clathrates also could not be the source for atmospheric CH4 increase. Geological CH4 (including methane clathrates) has the highest deuterium content (δD) among all of the known sources of CH4 while atmospheric CH4 δD values determined for the LD were record low. To explain recorded atmospheric CH4 and its isotopic dynamics required a strong northern source, which was active only during the LD and that provided very low δD CH4 values. Such a source is permafrost thawing under anaerobic conditions (or better stated soils of mammoth steppe-tundra ecosystems). Permafrost thawing is the strongest, among known, wetland sources (usually over 100g CH4/m2yr) and has a unique isotopic signature (δD = -400 per mil (-338 to -479 per mil), δ13C = -73 per mil (-58 to -99 per mil)). The main sources of atmospheric CH4 have different isotopic signatures (δ13C, δD). The isotopic content of atmospheric CH4 is a simple function of the weight average for all of the sources. Inclusion of permafrost source into a budget model of the atmospheric methane and its isotopes allowed us to reconstruct the dynamics of methane’s main sources. Model indicated geological source to be negligible as in LGM so and in LD and Holocene. During the glaciation, the largest methane source was megafauna, whose 1.4

  10. Hybrid quantum chemical studies for the methanol formation reaction assisted by the proton transfer mechanism in supercritical water: CH3Cl+nH2O-->CH3OH+HCl+(n-1)H2O

    NASA Astrophysics Data System (ADS)

    Hori, T.; Takahashi, H.; Nitta, T.

    2003-10-01

    The proton transfer along the chain of hydrogen bonds is involved in many chemical reactions in aqueous solution and known to play a decisive role. We have performed the hybrid quantum chemical simulations for the methanol formation reaction catalyzed by the proton transfer mechanism [CH3Cl+nH2O→CH3OH+HCl+(n-1)H2O, n=3] in supercritical water (SCW) to investigate the role of water solvent on the reaction. In the simulation, the electronic state of the chemically active solutes (CH3Cl+3H2O) has been determined quantum mechanically, while the static water solvent has been represented by a classical model. The activation free energy for the water-catalytic reaction in SCW has been found to be 9.6 kcal/mol, which is much lower than that in the gas phase (29.2 kcal/mol). The fractional charge analysis has revealed that the notable charge separation in the solute complex takes place at the transition state (TS) and the resulting huge dipole gives rise to the considerable stabilization of the TS as compared to the reactant. It has been shown that the reaction assisted by the proton transfer mechanism is energetically much favored than the ionic SN2 reaction (CH3Cl+OH-→CH3OH+Cl-, 18.8 kcal/mol). The present calculations suggest that the proton migrations through the chain of hydrogen bonds can be regarded as a probable candidate responsible for the anomalous reactivities observed in SCW.

  11. Assessment of errors and biases in retrievals of X CO2, X CH4, X CO, and X N2O from a 0.5 cm –1 resolution solar-viewing spectrometer

    DOE PAGES

    Hedelius, Jacob K.; Viatte, Camille; Wunch, Debra; ...

    2016-08-03

    Bruker™ EM27/SUN instruments are commercial mobile solar-viewing near-IR spectrometers. They show promise for expanding the global density of atmospheric column measurements of greenhouse gases and are being marketed for such applications. They have been shown to measure the same variations of atmospheric gases within a day as the high-resolution spectrometers of the Total Carbon Column Observing Network (TCCON). However, there is little known about the long-term precision and uncertainty budgets of EM27/SUN measurements. In this study, which includes a comparison of 186 measurement days spanning 11 months, we note that atmospheric variations of X gas within a single day aremore » well captured by these low-resolution instruments, but over several months, the measurements drift noticeably. We present comparisons between EM27/SUN instruments and the TCCON using GGG as the retrieval algorithm. In addition, we perform several tests to evaluate the robustness of the performance and determine the largest sources of errors from these spectrometers. We include comparisons of X CO2, X CH4, X CO, and X N2O. Specifically we note EM27/SUN biases for January 2015 of 0.03, 0.75, –0.12, and 2.43 % for X CO2, X CH4, X CO, and X N2O respectively, with 1 σ running precisions of 0.08 and 0.06 % for X CO2 and X CH4 from measurements in Pasadena. We also identify significant error caused by nonlinear sensitivity when using an extended spectral range detector used to measure CO and N 2O.« less

  12. Laser-based measurements of δ13 C and δ2 H methane isotope signatures: precisions competitive with mass spectrometry methods

    NASA Astrophysics Data System (ADS)

    Yacovitch, Tara; Shorter, Joanne; Nelson, David; Herndon, Scott; Agnese, Mike; McManus, Barry; Zahniser, Mark

    2017-04-01

    In order to understand how and why methane (CH4 ) concentrations change over time, it is necessary to understand their sources and sinks. Stable isotope measurements of 13 CH4 :12 CH4 and CH3 D:12 CH4 ratios constrain the inventory of these sinks and sources. Current measurements often depend on Isotope Ratio Mass Spectrometry (IRMS), which requires extensive sample preparation including cryogenic separation of methane from air and subsequent conversion to either CO2 or H2 . Here, we detail improvements to a direct-absorption laser spectrometer that enable fast and precise measurements of methane isotope ratios (δ13 C and δ2 H ) of ambient air samples, without such sample preparation. The measurement system consists of a laser-based direct absorption spectrometer configured with a sample manifold for measurement of discrete samples (as opposed to flow-through measurements). Samples are trapped in the instrument using a rapid sample switching technique that compares each flask sample against a monitor tank sample. This approach reduces instrument drift and results in excellent precision. Precisions of 0.054 o/oo for δ13 C and 1.4 o/oo for δ2 H have been achieved (Allan-Werle deviations). These results are obtained in 20 minutes using 4 replicate comparisons to a monitor tank.

  13. Methane, carbon dioxide, and nitrous oxide emissions from septic tank systems.

    PubMed

    Diaz-Valbuena, Libia R; Leverenz, Harold L; Cappa, Christopher D; Tchobanoglous, George; Horwath, William R; Darby, Jeannie L

    2011-04-01

    Emissions of CH4, CO2, and N2O from conventional septic tank systems are known to occur, but there is a dearth of information as to the extent. Mass emission rates of CH4, CO2, and N2O, as measured with a modified flux chamber approach in eight septic tank systems, were determined to be 11, 33.3, and 0.005 g capita(-1) day(-1), respectively, in this research. Existing greenhouse gas (GHG) emission models based on BOD (biochemical oxygen demand) loading have estimated methane emissions to be as high as 27.1 g CH4 capita(-1) day(-1), more than twice the value measured in our study, and concluded that septic tanks are potentially significant sources of GHGs due to the large number of systems currently in use. Based on the measured CH4 emission value, a revised CH4 conversion factor of 0.22 (compared to 0.5) for use in the emissions models is suggested. Emission rates of CH4, CO2, and N2O were also determined from measurements of gas concentrations and flow rates in the septic vent system and were found to be 10.7, 335, and 0.2 g capita(-1)day(-1), respectively. The excellent agreement in the CH4 emission rates between the flux chamber and the vent values indicates the dominant CH4 source is the septic tank.

  14. Ab Initio Chemical Kinetics for the CH3 + O((3)P) Reaction and Related Isomerization-Decomposition of CH3O and CH2OH Radicals.

    PubMed

    Xu, Z F; Raghunath, P; Lin, M C

    2015-07-16

    The kinetics and mechanism of the CH3 + O reaction and related isomerization-decomposition of CH3O and CH2OH radicals have been studied by ab initio molecular orbital theory based on the CCSD(T)/aug-cc-pVTZ//CCSD/aug-cc-pVTZ, CCSD/aug-cc-pVDZ, and G2M//B3LYP/6-311+G(3df,2p) levels of theory. The predicted potential energy surface of the CH3 + O reaction shows that the CHO + H2 products can be directly generated from CH3O by the TS3 → LM1 → TS7 → LM2 → TS4 path, in which both LM1 and LM2 are very loose and TS7 is roaming-like. The result for the CH2O + H reaction shows that there are three low-energy barrier processes including CH2O + H → CHO + H2 via H-abstraction and CH2O + H → CH2OH and CH2O + H → CH3O by addition reactions. The predicted enthalpies of formation of the CH2OH and CH3O radicals at 0 K are in good agreement with available experimental data. Furthermore, the rate constants for the forward and some key reverse reactions have been predicted at 200-3000 K under various pressures. Based on the new reaction pathway for CH3 + O, the rate constants for the CH2O + H and CHO + H2 reactions were predicted with the microcanonical variational transition-state/Rice-Ramsperger-Kassel-Marcus (VTST/RRKM) theory. The predicted total and individual product branching ratios (i.e., CO versus CH2O) are in good agreement with experimental data. The rate constant for the hydrogen abstraction reaction of CH2O + H has been calculated by the canonical variational transition-state theory with quantum tunneling and small-curvature corrections to be k(CH2O + H → CHO + H2) = 2.28 × 10(-19) T(2.65) exp(-766.5/T) cm(3) molecule(-1) s(-1) for the 200-3000 K temperature range. The rate constants for the addition giving CH3O and CH2OH and the decomposition of the two radicals have been calculated by the microcanonical RRKM theory with the time-dependent master equation solution of the multiple quantum well system in the 200-3000 K temperature range at 1 Torr to

  15. Oxidative condensation reactions of (diethylenetriamine)cobalt(III) complexes with substituted bis(pyridin-2-yl)methane ligands

    NASA Astrophysics Data System (ADS)

    Zhou, Xiangting; Hockless, David C. R.; Willis, Anthony C.; Jackson, W. Gregory

    2005-04-01

    The synthesis and characterisation of Co(III) complexes derived from a condensation reaction with a central or terminal nitrogen of a dien ligand and the α-carbon of a range of substituted bis(pyridin-2-yl)methane ligands are described. Aerial oxidation of bpm {bis(pyridin-2-yl)methane with Co(II)/dien or direct reaction with Co(dien)Cl 3 provided in low yield a single C-N condensation product 1 (at the primary terminal NH 2) after the pyridyl -CH 2- is formally oxidised to -CH +-. The methyl substituted ligand bpe {1,1-bis(pyridin-2-yl)ethane} behaves likewise, except both terminal (prim) and central (sec) amines condense to yield isomeric products 2 and 3. Two of these three materials have been characterised by single crystal X-ray crystallography. The corresponding reactions for the bis(pyridyl) ligand bpk {bis(pyridin-2-yl)ketone} provided C-N condensation products without the requirement for oxidation at the α-C center; two carbinolamine complexes in different geometrical configurations resulted, mer-anti-[Co(dienbpc)Cl]ZnCl 4, 5, and unsym- fac-[Co(dienbpc)Cl]ZnCl 4, 6, {dienbpc=[2-(2-aminoethylamino)-ethylamino]-di-pyridin-2-yl-methanol}. In addition, a novel complex, [Co(bpk)(bpd-OH)Cl]ZnCl 4, 4, in which one bidentate N, N-bonded bpk ligand and one tridentate N, O, N-bonded bpd (the diol from bpk+OH -) were coordinated, was obtained via the Co(II)/O 2 synthetic route. When the bpc ligand (bpc=bis(pyridin-2-yl)methanol) was employed directly as a reagent along with dien, no condensation reactions were observed, but rather a single isomeric complex [Co(dien)(bpc)]Cl.ZnCl 4, 7, in which the ligand bpc acted as a N,N,O-bonded tridentate ligand rather than as a N,N-bidentate ligand was isolated. 13C, 1D and 2D 1H NMR studies are reported for all the complexes; they establish the structures unambiguously.

  16. Nitrous Oxide and Methane Fluxes Following Ammonium Sulfate and Vinasse Application on Sugar Cane Soil.

    PubMed

    Paredes, Debora da S; Alves, Bruno J R; dos Santos, Marco A; Bolonhezi, Denizart; Sant'Anna, Selenobaldo A C; Urquiaga, Segundo; Lima, Magda A; Boddey, Robert M

    2015-09-15

    This study aimed to quantify nitrous oxide (N2O) and methane (CH4) emission/sink response from sugar cane soil treated with fertilizer nitrogen (N) and vinasse applied separately or in sequence, the latter being investigated with regard to the time interval between applications for a possible effect on emissions. The study was carried out in a traditional area of unburned sugar cane in São Paulo state, Brazil. Two levels of N fertilization (0 and 100 kg N ha(-1)) with no added vinasse and combined with vinasse additions at different times (100 m(-3) ha(-1) at 3 and 15 days after N fertilization) were evaluated. Methane and N2O fluxes were monitored for 211 days. On average, the soil was a sink for CH4, which was not affected by the treatments. Emissions of N2O were induced by N fertilizer and vinasse applications. For ammonium sulfate, 0.6% of the added N was emitted as N2O, while for vinasse, this ranged from 1.0 to 2.2%. Changes in N2O fluxes were detected the day after application of vinasse on the N fertilized areas, but although the emission factor (EF) was 34% greater, the EF was not significantly different from fertilizer N alone. Nevertheless, we recommend to not apply vinasse after N fertilization to avoid boosting N2O emissions.

  17. Joint CO2 and CH4 accountability for global warming.

    PubMed

    Smith, Kirk R; Desai, Manish A; Rogers, Jamesine V; Houghton, Richard A

    2013-07-30

    We propose a transparent climate debt index incorporating both methane (CH4) and carbon dioxide (CO2) emissions. We develop national historic emissions databases for both greenhouse gases to 2005, justifying 1950 as the starting point for global perspectives. We include CO2 emissions from fossil sources [CO2(f)], as well as, in a separate analysis, land use change and forestry. We calculate the CO2(f) and CH4 remaining in the atmosphere in 2005 from 205 countries using the Intergovernmental Panel on Climate Change's Fourth Assessment Report impulse response functions. We use these calculations to estimate the fraction of remaining global emissions due to each country, which is applied to total radiative forcing in 2005 to determine the combined climate debt from both greenhouse gases in units of milliwatts per square meter per country or microwatts per square meter per person, a metric we term international natural debt (IND). Australia becomes the most indebted large country per capita because of high CH4 emissions, overtaking the United States, which is highest for CO2(f). The differences between the INDs of developing and developed countries decline but remain large. We use IND to assess the relative reduction in IND from choosing between CO2(f) and CH4`control measures and to contrast the imposed versus experienced health impacts from climate change. Based on 2005 emissions, the same hypothetical impact on world 2050 IND could be achieved by decreasing CH4 emissions by 46% as stopping CO2 emissions entirely, but with substantial differences among countries, implying differential optimal strategies. Adding CH4 shifts the basic narrative about differential international accountability for climate change.

  18. Dry reforming of methane on a highly-active Ni-CeO 2 catalyst: Effects of metal-support interactions on C–H bond breaking

    DOE PAGES

    Liu, Zongyuan; Grinter, David C.; Lustemberg, Pablo G.; ...

    2016-05-04

    Ni-CeO 2 is a highly efficient, stable and non-expensive catalyst for methane dry reforming at relative low temperatures (700 K). The active phase of the catalyst consists of small nanoparticles of nickel dispersed on partially reduced ceria. Experiments of ambient pressure XPS indicate that methane dissociates on Ni/CeO 2 at temperatures as low as 300 K, generating CH x and CO x species on the surface of the catalyst. Strong metal–support interactions activate Ni for the dissociation of methane. The results of density-functional calculations show a drop in the effective barrier for methane activation from 0.9 eV on Ni(111) tomore » only 0.15 eV on Ni/CeO 2–x(111). At 700 K, under methane dry reforming conditions, no signals for adsorbed CH x or C species are detected in the C1s XPS region. As a result, the reforming of methane proceeds in a clean and efficient way.« less

  19. Hydrothermal Syntheses and Structures of Three-Dimensional Oxo-fluorovanadium Phosphates: [H 2N(C 2H 4) 2NH 2] 0.5[(VO) 4V(HPO 4) 2(PO 4) 2F 2(H 2O) 4] · 2H 2O and K 2[(VO) 3(PO 4) 2F 2(H 2O)] · H 2O

    NASA Astrophysics Data System (ADS)

    Bonavia, Grant; Haushalter, R. C.; Zubieta, Jon

    1996-11-01

    The hydrothermal reactions of FPO3H2with vanadium oxides result in the incorporation of fluoride into V-P-O frameworks as a consequence of metal-mediated hydrolysis of the fluorophosphoric acid to produce F-and PO3-4. By exploiting this convenient source of F-, two 3-dimensional oxo-fluorovanadium phosphate phases were isolated, [H2N(C2H4)2NH2]0.5[(VO)4V(HOP4)2(PO4)2F2(H2O)4) · 2H2O (1 · 2H2O) and K2[(VO)3(PO4)2F2(H2O)] · H2O (2 · H2O). Both anionic frameworks contain (VIVO)-F--phosphate layers, with confacial bioctahedral {(VIVO)2FO6} units as the fundamental motif. In the case of 1, the layers are linked through {VIIIO6} octahedra, while for 2 the interlayer connectivity is provided by edge-sharing {(VIVO)2F2O6} units. Crystal data are 1 · 2H2O, CH10FN0.5O13P2V2.5, monoclinicC2/m,a= 18.425(4) Å,c= 8.954(2) Å, β = 93.69(2)0,V= 1221.1(4) Å3,Z= 4,Dcalc= 2.423 g cm-3; 2 · H2O, H4F2K2O13P2V3, triclinicPoverline1,a= 7.298(1) Å,b= 8.929(2) Å,c = 10.090(2) Å, α = 104.50(2)0, β = 100.39(2)0, δ = 92.13(2)0,V= 623.8(3) Å3,Z= 2,Dcalc= 2.891 g cm-3.

  20. CH4 and N2O Emissions from Rice Paddy Soils in Vietnam - Identifying Regional Hotspots and Quantifying the Total Emission Strength using a Biogeochemical Model

    NASA Astrophysics Data System (ADS)

    Werner, C.; Kraus, D.; Mai, T. V.; Butterbach-Bahl, K.

    2016-12-01

    Agriculture is the economic backbone for over two thirds of Vietnam's population, providing food security, employment and income. However, agriculture in Vietnam is challenged by climate change and climate extremes and at the same time, agriculture remains a key source of greenhouse gas (GHG) emissions. The first bi-annual update report (BUR1), published in 2014 indicated that while the proportion of GHG emissions from agriculture had fallen from 43.1% to 33.2% from 2000 to 2010, the emission total increased from 65.1 mio to 88.4 mio t CO2e. Reducing GHG emissions from agriculture has thus become a key issue within the national strategy of GHG emission management. Here we present first data using IPCC Tier 3 modeling for quantifying the source strength of rice based crop systems for CH4 and N2O. We used LandscapeDNDC and linked it to a newly developed spatial landuse and land management database (climate, soil properties, and detailed field management data). Site application showed good agreement of simulated biomass, yield and GHG emissions with field observations, providing confidence for model use at national scale. Our results also show good agreement with national yield data and total annual emissions of the simulated period (2006-2015) ranged from 1060 - 1502 kt CH4 and 6.2 - 7.7 kt N2O, respectively. The dominating emission hotspot for CH4 is the Mekong Delta region with its double and triple rice cropping systems (819 kt CH4/yr, Fig. 1). With regard to N2O, emission hotspots have been identified to be closely related to regions with high fertilizer use and single to double rice cropping systems (Fig. 1). Though, our emission estimates are likely representing the best of current knowledge on national GHG emissions from rice based systems in Vietnam, the uncertainty is significant as information on rice system management remains vague. Sensitivity studies show that changes in field management affecting the soil organic carbon dynamics (duration of flooding

  1. The catalytic effects of H2CO3, CH3COOH, HCOOH and H2O on the addition reaction of CH2OO + H2OCH2(OH)OOH

    NASA Astrophysics Data System (ADS)

    Zhang, Tianlei; Lan, Xinguang; Wang, Rui; Roy, Soumendra; Qiao, Zhangyu; Lu, Yousong; Wang, Zhuqing

    2018-07-01

    The addition reaction of CH2OO + H2OCH2(OH)OOH without and with X (X = H2CO3, CH3COOH and HCOOH) and H2O was studied at CCSD(T)/6-311+ G(3df,2dp)//B3LYP/6-311+G(2d,2p) level of theory. Our results show that X can catalyse CH2OO + H2OCH2(OH)OOH reaction both by increasing the number of rings, and by adding the size of the ring in which ring enlargement by COOH moiety of X inserting into CH2OO...H2O is favourable one. Water-assisted CH2OO + H2OCH2(OH)OOH can occur by H2O moiety of (H2O)2 or the whole (H2O)2 forming cyclic structure with CH2OO, where the latter form is more favourable. Because the concentration of H2CO3 is unknown, the influence of CH3COOH, HCOOH and H2O were calculated within 0-30 km altitude of the Earth's atmosphere. The results calculated within 0-5 km altitude show that H2O and HCOOH have obvious effect on enhancing the rate with the enhancement factors are, respectively, 62.47%-77.26% and 0.04%-1.76%. Within 5-30 km altitude, HCOOH has obvious effect on enhancing the title rate with the enhancement factor of 2.69%-98.28%. However, compared with the reaction of CH2OO + HCOOH, the rate of CH2OO...H2O + HCOOH is much slower.

  2. Illuminating Geochemical Controls of Methane Oxidation Along a Gradient of Permafrost Thaw

    NASA Astrophysics Data System (ADS)

    Perryman, C. R.; Kashi, N.; McCalley, C. K.; Malhotra, A.; Giesler, R.; Varner, R.

    2017-12-01

    Increases in annual mean temperature in the subarctic have accelerated the thaw of organic-rich permafrost peatlands, exacerbating methane (CH4) production from microbial decomposition of peat deposits and subsequent CH4 emissions. Methanotrophic bacteria may oxidize/consume upwards of 90% of produced CH4 in some settings, pending substrate availability and environmental conditions. Redox chemistry may also control the rate of CH4 oxidation in thawing permafrost areas, particularly redox potential (Eh) and the availability of oxygen (O2) and other terminal electron receptors. We investigated potential CH4 oxidation rates across a permafrost thaw gradient in Stordalen Mire (68°21'N,18°49'E) near Abisko, Sweden. Methane oxidation rates for sites from thawing and collapsed palsa, semi-wet Sphagnum, and open-water sedge sites were determined through laboratory incubations. Peat cores were extracted from two depths at each site and incubated at in situ temperatures and CH4 concentrations. Headspace samples were collected over a 48-hour period and analyzed for CH4 concentration using flame ionization detection gas chromatography (GC-FID). Dissolved O2, Eh, and dissolved CH4 were measured in sites with porewater. Oxidation rates ranged from <0.1 to 19 μg of CH4 per gram of dry biomass per day. Eh remained positive (41.6 to 316.8 mV) with available dissolved O2 (0.3 - 5.2 mg/L) in all measurement locations down to 20cm, indicating in situ aerobic CH4 oxidation is viable across these environments. Potential CH4 oxidation rates increased with increasing dissolved CH4 concentration. Highest potential CH4 oxidation rates were found in open-water sedge sites. Eh and dissolved O2 were lowest at these sites, suggesting that methanotrophs with low-O2 demand may populate sedge areas. Furthermore, potential CH4 oxidation rates were higher at depth than at the surface in thawing palsa, suggesting CH4 oxidation may mitigate CH4 production triggered by warming in these actively

  3. Serpentinization and the Formation of H2 and CH4 on Celestial Bodies (Planets, Moons, Comets)

    PubMed Central

    Oze, C.; Mousis, O.; Waite, J.H.; Guilbert-Lepoutre, A.

    2015-01-01

    Abstract Serpentinization involves the hydrolysis and transformation of primary ferromagnesian minerals such as olivine ((Mg,Fe)2SiO4) and pyroxenes ((Mg,Fe)SiO3) to produce H2-rich fluids and a variety of secondary minerals over a wide range of environmental conditions. The continual and elevated production of H2 is capable of reducing carbon, thus initiating an inorganic pathway to produce organic compounds. The production of H2 and H2-dependent CH4 in serpentinization systems has received significant interdisciplinary interest, especially with regard to the abiotic synthesis of organic compounds and the origins and maintenance of life in Earth's lithosphere and elsewhere in the Universe. Here, serpentinization with an emphasis on the formation of H2 and CH4 are reviewed within the context of the mineralogy, temperature/pressure, and fluid/gas chemistry present in planetary environments. Whether deep in Earth's interior or in Kuiper Belt Objects in space, serpentinization is a feasible process to invoke as a means of producing astrobiologically indispensable H2 capable of reducing carbon to organic compounds. Key Words: Serpentinization—Fischer-Tropsch-type synthesis—Hydrogen formation—Methane formation—Ultramafic rocks. Astrobiology 15, 587–600. PMID:26154779

  4. Co-processing CH4 and oxygenates on Mo/H-ZSM-5: 2. CH4-CO2 and CH4-HCOOH mixtures.

    PubMed

    Bedard, Jeremy; Hong, Do-Young; Bhan, Aditya

    2013-08-07

    Co-processing of formic acid or carbon dioxide with CH4 (FA/CH4 = 0.01-0.03 and CO2/CH4 = 0.01-0.03) on Mo/H-ZSM-5 catalysts at 950 K with the prospect of kinetically coupling dehydrogenation and deoxygenation cycles results instead in a two-zone, staged bed reactor configuration consisting of upstream oxygenate/CH4 reforming and downstream CH4 dehydroaromatization. The addition of an oxygenate co-feed (oxygenate/CH4 = 0.01-0.03) causes oxidation of the active molybdenum carbide catalyst while producing CO and H2 until completely converted. Forward rates of C6H6 synthesis are unaffected by the introduction of an oxygenate co-feed after rigorously accounting for the thermodynamic reversibility caused by the H2 produced in oxygenate reforming reactions and the fraction of the active catalyst deemed unavailable for CH4 DHA. All effects of co-processing oxygenates with CH4 can be construed in terms of an approach to equilibrium.

  5. Global methane emission estimates for 2000-2012 from CarbonTracker Europe-CH4 v1.0

    NASA Astrophysics Data System (ADS)

    Tsuruta, Aki; Aalto, Tuula; Backman, Leif; Hakkarainen, Janne; van der Laan-Luijkx, Ingrid T.; Krol, Maarten C.; Spahni, Renato; Houweling, Sander; Laine, Marko; Dlugokencky, Ed; Gomez-Pelaez, Angel J.; van der Schoot, Marcel; Langenfelds, Ray; Ellul, Raymond; Arduini, Jgor; Apadula, Francesco; Gerbig, Christoph; Feist, Dietrich G.; Kivi, Rigel; Yoshida, Yukio; Peters, Wouter

    2017-03-01

    We present a global distribution of surface methane (CH4) emission estimates for 2000-2012 derived using the CarbonTracker Europe-CH4 (CTE-CH4) data assimilation system. In CTE-CH4, anthropogenic and biospheric CH4 emissions are simultaneously estimated based on constraints of global atmospheric in situ CH4 observations. The system was configured to either estimate only anthropogenic or biospheric sources per region, or to estimate both categories simultaneously. The latter increased the number of optimizable parameters from 62 to 78. In addition, the differences between two numerical schemes available to perform turbulent vertical mixing in the atmospheric transport model TM5 were examined. Together, the system configurations encompass important axes of uncertainty in inversions and allow us to examine the robustness of the flux estimates. The posterior emission estimates are further evaluated by comparing simulated atmospheric CH4 to surface in situ observations, vertical profiles of CH4 made by aircraft, remotely sensed dry-air total column-averaged mole fraction (XCH4) from the Total Carbon Column Observing Network (TCCON), and XCH4 from the Greenhouse gases Observing Satellite (GOSAT). The evaluation with non-assimilated observations shows that posterior XCH4 is better matched with the retrievals when the vertical mixing scheme with faster interhemispheric exchange is used. Estimated posterior mean total global emissions during 2000-2012 are 516 ± 51 Tg CH4 yr-1, with an increase of 18 Tg CH4 yr-1 from 2000-2006 to 2007-2012. The increase is mainly driven by an increase in emissions from South American temperate, Asian temperate and Asian tropical TransCom regions. In addition, the increase is hardly sensitive to different model configurations ( < 2 Tg CH4 yr-1 difference), and much smaller than suggested by EDGAR v4.2 FT2010 inventory (33 Tg CH4 yr-1), which was used for prior anthropogenic emission estimates. The result is in good agreement with other

  6. Historical Pattern and Future Trajectories of Terrestrial N2O Emission driven by Multi-factor Global Changes

    NASA Astrophysics Data System (ADS)

    Lu, C.; Tian, H.; Yang, J.; Zhang, B.; Xu, R.

    2015-12-01

    Nitrous oxide (N2O) is among the most important greenhouse gases only next to carbon dioxide (CO2) and methane (CH4) due to its long life time and high radiative forcing (with a global warming potential 265 times as much as CO2 at 100-year time horizon). The Atmospheric concentration of N2O has increased by 20% since pre-industrial era, and this increase plays a significant role in shaping anthropogenic climate change. However, compared to CO2- and CH4-related research, fewer studies have been performed in assessing and predicting the spatiotemporal patterns of N2O emission from natural and agricultural soils. Here we used a coupled biogeochemical model, DLEM, to quantify the historical and future changes in global terrestrial N2O emissions resulting from natural and anthropogenic perturbations including climate variability, atmospheric CO2 concentration, nitrogen deposition, land use and land cover changes, and agricultural land management practices (i.e., synthetic nitrogen fertilizer use, manure application, and irrigation etc.) over the period 1900-2099. We focused on inter-annual variation and long-term trend of terrestrial N2O emission driven by individual and combined environmental changes during historical and future periods. The sensitivity of N2O emission to climate, atmospheric composition, and human activities has been examined at biome-, latitudinal, continental and global scales. Future projections were conducted to identify the hot spots and hot time periods of global N2O emission under two emission scenarios (RCP2.6 and RCP8.5). It provides a modeling perspective for understanding human-induced N2O emission growth and developing potential management strategies to mitigate further atmospheric N2O increase and climate warming.

  7. CO2 hydrate: Synthesis, composition, structure, dissociation behavior, and a comparison to structure I CH4 hydrate

    USGS Publications Warehouse

    Circone, S.; Stern, L.A.; Kirby, S.H.; Durham, W.B.; Chakoumakos, B.C.; Rawn, C.J.; Rondinone, A.J.; Ishii, Y.

    2003-01-01

    Structure I (sI) carbon dioxide (CO2) hydrate exhibits markedly different dissociation behavior from sI methane (CH4) hydrate in experiments in which equilibrated samples at 0.1 MPa are heated isobarically at 13 K/h from 210 K through the H2O melting point (273.15 K). The CO2 hydrate samples release only about 3% of their gas content up to temperatures of 240 K, which is 22 K above the hydrate phase boundary. Up to 20% is released by 270 K, and the remaining CO2 is released at 271.0 plusmn; 0.5 K, where the sample temperature is buffered until hydrate dissociation ceases. This reproducible buffering temperature for the dissociation reaction CO2??nH2O = CO2(g) + nH2O(1 to s) is measurably distinct from the pure H2O melting point at 273.15 K, which is reached as gas evolution ceases. In contrast, when si CH4 hydrate is heated at the same rate at 0.1 MPa, >95% of the gas is released within 25 K of the equilibrium temperature (193 K at 0.1 MPa). In conjunction with the dissociation study, a method for efficient and reproducible synthesis of pure polycrystalline CO2 hydrate with suitable characteristics for material properties testing was developed, and the material was characterized. CO2 hydrate was synthesized from CO2 liquid and H2O solid and liquid reactants at pressures between 5 and 25 MPa and temperatures between 250 and 281 K. Scanning electron microscopy (SEM) examination indicates that the samples consist of dense crystalline hydrate and 50-300 ??m diameter pores that are lined with euhedral cubic hydrate crystals. Deuterated hydrate samples made by this same procedure were analyzed by neutron diffraction at temperatures between 4 and 215 K; results confirm that complete conversion of water to hydrate has occurred and that the measured unit cell parameter and thermal expansion are consistent with previously reported values. On the basis of measured weight gain after synthesis and gas yields from the dissociation experiments, approximately all cages in the

  8. Aerobic Methane Oxidation in Alaskan Lakes Along a Latitudinal Transect

    NASA Astrophysics Data System (ADS)

    Martinez-Cruz, K. C.; Sepulveda-Jauregui, A.; Walter Anthony, K. M.; Anthony, P.; Thalasso, F.

    2013-12-01

    Karla Martinez-Cruz* **, Armando Sepulveda-Jauregui*, Katey M. Walter Anthony*, Peter Anthony*, and Frederic Thalasso**. * Water and Environmental Research Center, Institute of Northern Engineering, University of Alaska Fairbanks, Fairbanks, Alaska. ** Biotechnology and Bioengineering Department, Cinvestav, Mexico city, D. F., Mexico. Methane (CH4) is the third most important greenhouse gas in the atmosphere, after carbon dioxide and water vapor. Boreal lakes play an important role in the current global warming by contributing as much as 6% of global atmospheric CH4 sources annually. On the other hand, aerobic methane oxidation (methanotrophy) in lake water is a fundamental process in global methane cycling that reduces the amount of CH4 emissions to the atmosphere. Several environmental factors affect aerobic methane oxidation in the water column both directly and indirectly, including concentration of CH4 and O2, temperature and carbon budgets of lakes. We analyzed the potential of aerobic methane oxidation (PMO) rates in incubations of water collected from 30 Alaskan lakes along a north-south transect during winter and summer 2011. Our findings showed an effect of CH4 and O2 concentrations, temperature and yedoma thawing permafrost on PMO activity in the lake water. The highest PMO rates were observed in summer by lakes situated on thawing yedoma permafrost, most of them located in the interior of Alaska. We also estimated that 60-80% of all CH4 produced in Alaskan lakes could be taken up by methanotrophs in the lake water column, showing the significant influence of aerobic methane oxidation of boreal lakes to the global CH4 budget.

  9. Methane oxidation and abundance of methane oxidizers in tropical agricultural soil (vertisol) in response to CuO and ZnO nanoparticles contamination.

    PubMed

    Mohanty, Santosh Ranjan; Rajput, Parul; Kollah, Bharati; Chourasiya, Dipanti; Tiwari, Archana; Singh, Muneshwar; Rao, A Subba

    2014-06-01

    There is worldwide concern over the increase use of nanoparticles (NPs) and their ecotoxicological effect. It is not known if the annual production of tons of industrial nanoparticles (NPs) has the potential to impact terrestrial microbial communities, which are so necessary for ecosystem functioning. Here, we have examined the consequences of adding the NPs particularly the metal oxide (CuO, ZnO) on CH4 oxidation activity in vertisol and the abundance of heterotrophs, methane oxidizers, and ammonium oxidizers. Soil samples collected from the agricultural field located at Madhya Pradesh, India, were incubated with either CuO and ZnO NPs or ionic heavy metals (CuCl2, ZnCl2) separately at 0, 10, and 20 μg g(-1) soil. CH4 oxidation activity in the soil samples was estimated at 60 and 100 % moisture holding capacity (MHC) in order to link soil moisture regime with impact of NPs. NPs amended to soil were highly toxic for the microbial-mediated CH4 oxidation, compared with the ionic form. The trend of inhibition was Zn 20 > Zn 10 > Cu 20 > Cu 10. NPs delayed the lag phase of CH4 oxidation to a maximum of 4-fold and also decreased the apparent rate constant k up to 50 % over control. ANOVA and Pearson correlation analysis (α = 0.01) revealed significant impact of NPs on the CH4 oxidation activity and microbial abundance (p < 0.0001, and high F statistics). Principal component analysis (PCA) revealed that PC1 (metal concentration) rendered 76.06 % of the total variance, while 18.17 % of variance accounted by second component (MHC). Biplot indicated negative impact of NPs on CH4 oxidation and microbial abundance. Our result also confirmed that higher soil moisture regime alleviates toxicity of NPs and opens new avenues of research to manage ecotoxicity and environmental hazard of NPs.

  10. Nitrous oxide and methane emissions from different treatment processes in full-scale municipal wastewater treatment plants.

    PubMed

    Rena, Y G; Wang, J H; Li, H F; Zhang, J; Qi, P Y; Hu, Z

    2013-01-01

    Nitrous oxide (N2O) and methane (CH4) are two important greenhouse gases (GHG) emitted from biological nutrient removal (BNR) processes in municipal wastewater treatment plants (WWTP). In this study, three typical biological wastewater treatment processes were studied in WWTP of Northern China: pre-anaerobic carrousel oxidation ditch (A+OD) process, pre-anoxic anaerobic-anoxic-oxic (A-A/ A/O) process and reverse anaerobic-anoxic-oxic (r-A/ A/O) process. The N2O and CH4 emissions from these three different processes were measured in every processing unit of each WWTP. Results showed that N2O and CH4 were mainly discharged during the nitrification/denitrification process and the anaerobic/anoxic treatment process, respectively and the amounts of their formation and release were significantly influenced by different BNR processes implemented in these WWTP. The N2O conversion ratio of r-A/ A/O process was the lowest among the three WWTP, which were 10.9% and 18.6% lower than that of A-A/A/O process and A+OD process, respectively. Similarly, the CH4 conversion ratio of r-A/ A/O process was the lowest among the three WWTP, which were 89. I% and 80.8% lower than that of A-A/ A/O process and A+OD process, respectively. The factors influencing N2O and CH4 formation and emission in the three WWTP were investigated to explain the difference between these processes. The nitrite concentration and oxidation-reduction potential (ORP) value were found to be the dominant influencing factors affecting N2O and CH4 production, respectively. The flow-based emission factors of N2O and CH4 of the WWTP were figured out for better quantification of GHG emissions and further technical assessments of mitigation options.

  11. High temporal resolution ecosystem CH4, CO2 and H2O flux data measured with a novel chamber technique

    NASA Astrophysics Data System (ADS)

    Steenberg Larsen, Klaus; Riis Christiansen, Jesper

    2016-04-01

    Soil-atmosphere exchange of greenhouse gases (GHGs) is commonly measured with closed static chambers (Pihlatie et al., 2013) with off-site gas chromatographic (GC) analysis for CH4 and N2O. Static chambers are widely used to observe in detail the effect of experimental manipulations, like climate change experiments, on GHG exchange (e.g. Carter et al., 2012). However, the low sensitivity of GC systems necessitates long measurement times and manual sampling, which increases the disturbance of the exchange of GHGs and leads to potential underestimation of fluxes (Christiansen et al., 2011; Creelman et al., 2013). The recent emergence of field proof infrared lasers using cavity ring-down spectroscopy (CRDS) have increased frequency and precision of concentration measurements and enabled better estimates of GHG fluxes (Christiansen et al., 2015) due to shorter chamber enclosure times. This minimizes the negative impact of the chamber enclosure on the soil-atmosphere gas exchange rate. Secondly, an integral aspect of understanding GHG exchange in terrestrial ecosystem is to achieve high temporal coverage. This is needed to capture the often dynamic behavior where fluxes can change rapidly over the course of days or even a few hours in response to e.g. rain events. Consequently, low temporal coverage in measurements of GHG exchange have in many past investigations led to highly uncertain annual budgets which severely limits our understanding of the ecosystem processes interacting with the climate system through GHG exchange. Real-time field measurements at high temporal resolution are needed to obtain a much more detailed understanding of the processes governing ecosystem CH4 exchange as well as for better predicting the effects of climate and environmental changes. We combined a state-of-the-art field applicable CH4 sensor (Los Gatos UGGA) with a newly developed ecosystem-level automatic chamber controlled by a LI-COR 8100/8150 system. The chamber is capable of

  12. Interplay of Electronic Cooperativity and Exchange Coupling in Regulating the Reactivity of Diiron(IV)-oxo Complexes towards C-H and O-H Bond Activation.

    PubMed

    Ansari, Azaj; Ansari, Mursaleem; Singha, Asmita; Rajaraman, Gopalan

    2017-07-26

    Activation of inert C-H bonds such as those of methane are extremely challenging for chemists but in nature, the soluble methane monooxygenase (sMMO) enzyme readily oxidizes methane to methanol by using a diiron(IV) species. This has prompted chemists to look for similar model systems. Recently, a (μ-oxo)bis(μ-carboxamido)diiron(IV) ([Fe IV 2 O(L) 2 ] 2+ L=N,N-bis-(3',5'-dimethyl-4'-methoxypyridyl-2'-methyl)-N'-acetyl-1,2-diaminoethane) complex has been generated by bulk electrolysis and this species activates inert C-H bonds almost 1000 times faster than mononuclear Fe IV =O species and at the same time selectively activates O-H bonds of alcohols. The very high reactivity and selectivity of this species is puzzling and herein we use extensive DFT calculations to shed light on this aspect. We have studied the electronic and spectral features of diiron {Fe III -μ(O)-Fe III } +2 (complex I), {Fe III -μ(O)-Fe IV } +3 (II), and {Fe IV -μ(O)-Fe IV } +4 (III) complexes. Strong antiferromagnetic coupling between the Fe centers leads to spin-coupled S=0, S=3/2, and S=0 ground state for species I-III respectively. The mechanistic study of the C-H and O-H bond activation reveals a multistate reactivity scenario where C-H bond activation is found to occur through the S=4 spin-coupled state corresponding to the high-spin state of individual Fe IV centers. The O-H bond activation on the other hand, occurs through the S=2 spin-coupled state corresponding to an intermediate state of individual Fe IV centers. Molecular orbital analysis reveals σ-π/π-π channels for the reactivity. The nature of the magnetic exchange interaction is found to be switched during the course of the reaction and this offers lower energy pathways. Significant electronic cooperativity between two metal centers during the course of the reaction has been witnessed and this uncovers the reason behind the efficiency and selectivity observed. The catalyst is found to prudently choose the desired spin

  13. Valorization of CH4 emissions into high-added-value products: Assessing the production of ectoine coupled with CH4 abatement.

    PubMed

    Cantera, Sara; Lebrero, Raquel; Sadornil, Lidia; García-Encina, Pedro A; Muñoz, Raúl

    2016-11-01

    This study assessed an innovative strategy for the valorization of dilute methane emissions based on the bio-conversion of CH4 (the second most important greenhouse gas (GHG)) into ectoine by the methanotrophic ectoine-producing strain Methylomicrobium alcaliphilum 20 Z. The influence of CH4 (2-20%), Cu(2+) (0.05-50 μM) and NaCl (0-9%) concentration as well as temperature (25-35 °C) on ectoine synthesis and specific CH4 biodegradation rate was evaluated for the first time. Concentrations of 20% CH4 (at 3% NaCl, 0.05 μM Cu(2+), 25 °C) and 6% NaCl (at 4% CH4, 0.05 μM Cu(2+), 25 °C) supported the maximum intra-cellular ectoine production yield (31.0 ±1.7 and 66.9 ±4.2 mg g biomass(-1), respectively). On the other hand, extra-cellular ectoine concentrations of up to 4.7 ± 0.1 mg L(-1) were detected at high Cu(2+)concentrations (50 μM), despite this methanotroph has not been previously classified as an ectoine-excreting strain. This research demonstrated the feasibility of the bio-conversion of dilute emissions of methane into high-added value products in an attempt to develop a sustainable GHG bioeconomy. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Methane production in ruminants: Its effect on the doubly labeled water method

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Midwood, A.J.; Haggarty, P.; McGaw, B.A.

    1989-12-01

    The doubly labeled water (DLW) technique for measuring CO2 production (rCO2) in free-living animals requires an assessment of the elimination of both 2H and 18O from the body over a long period of time. To calculate rCO2, it is necessary to calculate water turnover (rH2O) from the 2H flux rate. In ruminant animals, the accuracy of this calculation is affected by the loss of 2H in methane. We have quantified the effect of methane production (rCH4) on the 2H flux rate, determined in four sheep given 2H2O. The methane produced was depleted in 2H relative to the urine. A relationshipmore » between the enrichment of the methane and urine was established. The ratio of urine to methane enrichment was found on average to be 0.6536, and this value was unaffected by the level of rCH4 but showed some dependence on the absolute concentration of 2H in urine. For this reason, the ratio value obtained from four sheep not given 2H2O was different, a mean of 0.6886 was measured, this ratio was unaffected by changes in the diet supplied to the animals. Computer modeling was used to illustrate the dependence of the isotopically derived value for rCO2 on not only rCH4 but also the magnitude of rCO2 itself. The effect of rCH4 on the DLW method can be predicted from the observed ratio of rCO2 to rCH4 and the value of 0.6536 obtained for the ratio of methane to urine enrichment. With the use of data from several studies at this Institute, a limited range of 10 to 20 was found for rCO2/rCH4 in animals fed at or above maintenance.« less

  15. Comparison of two closed-path cavity-based spectrometers for measuring air-water CO2 and CH4 fluxes by eddy covariance

    NASA Astrophysics Data System (ADS)

    Yang, Mingxi; Prytherch, John; Kozlova, Elena; Yelland, Margaret J.; Parenkat Mony, Deepulal; Bell, Thomas G.

    2016-11-01

    In recent years several commercialised closed-path cavity-based spectroscopic instruments designed for eddy covariance flux measurements of carbon dioxide (CO2), methane (CH4), and water vapour (H2O) have become available. Here we compare the performance of two leading models - the Picarro G2311-f and the Los Gatos Research (LGR) Fast Greenhouse Gas Analyzer (FGGA) at a coastal site. Both instruments can compute dry mixing ratios of CO2 and CH4 based on concurrently measured H2O, temperature, and pressure. Additionally, we used a high throughput Nafion dryer to physically remove H2O from the Picarro airstream. Observed air-sea CO2 and CH4 fluxes from these two analysers, averaging about 12 and 0.12 mmol m-2 day-1 respectively, agree within the measurement uncertainties. For the purpose of quantifying dry CO2 and CH4 fluxes downstream of a long inlet, the numerical H2O corrections appear to be reasonably effective and lead to results that are comparable to physical removal of H2O with a Nafion dryer in the mean. We estimate the high-frequency attenuation of fluxes in our closed-path set-up, which was relatively small ( ≤ 10 %) for CO2 and CH4 but very large for the more polar H2O. The Picarro showed significantly lower noise and flux detection limits than the LGR. The hourly flux detection limit for the Picarro was about 2 mmol m-2 day-1 for CO2 and 0.02 mmol m-2 day-1 for CH4. For the LGR these detection limits were about 8 and 0.05 mmol m-2 day-1. Using global maps of monthly mean air-sea CO2 flux as reference, we estimate that the Picarro and LGR can resolve hourly CO2 fluxes from roughly 40 and 4 % of the world's oceans respectively. Averaging over longer timescales would be required in regions with smaller fluxes. Hourly flux detection limits of CH4 from both instruments are generally higher than the expected emissions from the open ocean, though the signal to noise of this measurement may improve closer to the coast.

  16. The natural greenhouse effect of atmospheric oxygen (O2) and nitrogen (N2)

    NASA Astrophysics Data System (ADS)

    Höpfner, M.; Milz, M.; Buehler, S.; Orphal, J.; Stiller, G.

    2012-05-01

    The effect of collision-induced absorption by molecular oxygen (O2) and nitrogen (N2) on the outgoing longwave radiation (OLR) of the Earth's atmosphere has been quantified. We have found that on global average under clear-sky conditions the OLR is reduced due to O2 by 0.11 Wm-2 and due to N2 by 0.17 Wm-2. Together this amounts to 15% of the OLR-reduction caused by CH4 at present atmospheric concentrations. Over Antarctica the combined effect of O2 and N2 increases on average to about 38% of CH4 with single values reaching up to 80%. This is explained by less interference of H2O spectral bands on the absorption features of O2 and N2 for dry atmospheric conditions.

  17. Adsorption of CH4 on nitrogen- and boron-containing carbon models of coal predicted by density-functional theory

    NASA Astrophysics Data System (ADS)

    Liu, Xiao-Qiang; Xue, Ying; Tian, Zhi-Yue; Mo, Jing-Jing; Qiu, Nian-Xiang; Chu, Wei; Xie, He-Ping

    2013-11-01

    Graphene doped by nitrogen (N) and/or boron (B) is used to represent the surface models of coal with the structural heterogeneity. Through the density functional theory (DFT) calculations, the interactions between coalbed methane (CBM) and coal surfaces have been investigated. Several adsorption sites and orientations of methane (CH4) on graphenes were systematically considered. Our calculations predicted adsorption energies of CH4 on graphenes of up to -0.179 eV, with the strongest binding mode in which three hydrogen atoms of CH4 direct to graphene surface, observed for N-doped graphene, compared to the perfect (-0.154 eV), B-doped (-0.150 eV), and NB-doped graphenes (-0.170 eV). Doping N in graphene increases the adsorption energies of CH4, but slightly reduced binding is found when graphene is doped by B. Our results indicate that all of graphenes act as the role of a weak electron acceptor with respect to CH4. The interactions between CH4 and graphenes are the physical adsorption and slightly depend upon the adsorption sites on graphenes and the orientations of methane as well as the electronegativity of dopant atoms in graphene.

  18. Adsorption of methane and CO2 onto olivine surfaces in Martian dust conditions

    NASA Astrophysics Data System (ADS)

    Escamilla-Roa, Elizabeth; Martin-Torres, Javier; Sainz-Díaz, C. Ignacio

    2018-04-01

    Methane has been detected on all planets of our Solar System, and most of the larger moons, as well as in dwarf-planets like Pluto and Eric. The presence of this molecule in rocky planets is very interesting because its presence in the Earth's atmosphere is mainly related to biotic processes. Space instrumentation in orbiters around Mars has detected olivine on the Martian soil and dust. On the other hand the measurements of methane from the Curiosity rover report detection of background levels of atmospheric methane with abundance that is lower than model estimates of ultraviolet degradation of accreted interplanetary dust particles or carbonaceous chondrite material. Additionally, elevated levels of methane about this background have been observed implying that Mars is episodically producing methane from an additional unknown source, making the reasons of these temporal fluctuations of methane a hot topic in planetary research. The goal of this study is to investigate at atomic level the interactions during the adsorption processes of methane and other Mars atmospheric species (CO2, H2O) on forsterite surfaces, through electronic structure calculations based on the Density Functional Theory (DFT). We propose two models to simulate the interaction of adsorbates with the surface of dust mineral, such as binary mixtures (5CH4+5H2O/5CH4+5CO2) and as a semi-clathrate adsorption. We have obtained interesting results of the adsorption process in the mixture 5CH4+5CO2. Associative and dissociative adsorptions were observed for water and CO2 molecules. The methane molecules were only trapped and held by water or CO2 molecules. In the dipolar surface, the adsorption of CO2 molecules produced new species: one CO from a CO2 dissociation, and, two CO2 molecules chemisorbed to mineral surface forming in one case a carbonate group. Our results suggest that CO2 has a strong interaction with the mineral surface when methane is present. These results could be confirmed after the

  19. Dissolved greenhouse gases (nitrous oxide and methane) associated with the natural iron-fertilized Kerguelen region (KEOPS 2 cruise) in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Farías, L.; Florez-Leiva, L.; Besoain, V.; Fernández, C.

    2014-08-01

    The concentrations of greenhouse gases (GHGs) like nitrous oxide (N2O) and methane (CH4) were measured in the Kerguelen Plateau Region (KPR), an area with annual microalgal bloom caused by natural Fe fertilization, which may stimulate microbes involved in GHG cycling. This study was carried out during the KEOPS 2 cruise during the austral spring of 2011. Two transects were sampled along and across the KRP, the north-south (N-S) transect (46-51° S, 72° E meridian) and the west-east (W-E) transect (66-75° E, 48.3° S latitude), both associated with the presence of a plateau, polar fronts and other mesoscale features. The W-E transect had N2O levels ranging from equilibrium (105%) to light supersaturation (120%) with respect to the atmosphere. CH4 levels fluctuated dramatically, with intense supersaturations (120-970%) in areas close to the coastal waters of Kerguelen Island and in the polar front (PF). There, Fe and nutrient fertilization seem to promote high total chlorophyll a (TChl a) levels. The distribution of both gases was more homogenous in the N-S transect, but CH4 peaked at southeastern stations of the KPR (A3 stations), where phytoplankton bloom was observed. Both gases responded significantly to the patchy distribution of particulate matter as Chl a, stimulated by Fe supply by complex mesoscale circulation. While CH4 appears to be produced mainly at the pycnoclines, N2O seems to be consumed superficially. Air-sea fluxes for N2O (from -10.5 to 8.65, mean 1.71 μmol m-2d-1), and for CH4 (from 0.32 to 38.1, mean 10.07 μmol m-2d-1) reflected sink and source behavior for N2O and source behavior for CH4, with considerable variability associated with a highly fluctuating wind regime and, in the case of CH4, due to its high superficial levels that had not been reported before in the Southern Ocean and may be caused by an intense microbial CH4 cycling.

  20. Phosphinodi(benzylsilane) PhP{(o-C6H4CH2)SiMe2H}2: a versatile "PSi2Hx" pincer-type ligand at ruthenium.

    PubMed

    Montiel-Palma, Virginia; Muñoz-Hernández, Miguel A; Cuevas-Chávez, Cynthia A; Vendier, Laure; Grellier, Mary; Sabo-Etienne, Sylviane

    2013-09-03

    The synthesis of the new phosphinodi(benzylsilane) compound PhP{(o-C6H4CH2)SiMe2H}2 (1) is achieved in a one-pot reaction from the corresponding phenylbis(o-tolylphosphine). Compound 1 acts as a pincer-type ligand capable of adopting different coordination modes at Ru through different extents of Si-H bond activation as demonstrated by a combination of X-ray diffraction analysis, density functional theory calculations, and multinuclear NMR spectroscopy. Reaction of 1 with RuH2(H2)2(PCy3)2 (2) yields quantitatively [RuH2{[η(2)-(HSiMe2)-CH2-o-C6H4]2PPh}(PCy3)] (3), a complex stabilized by two rare high order ε-agostic Si-H bonds and involved in terminal hydride/η(2)-Si-H exchange processes. A small free energy of reaction (ΔrG298 = +16.9 kJ mol(-1)) was computed for dihydrogen loss from 3 with concomitant formation of the 16-electron species [RuH{[η(2)-(HSiMe2)-CH2-o-C6H4]PPh[CH2-o-C6H4SiMe2]}(PCy3)] (4). Complex 4 features an unprecedented (29)Si NMR decoalescence process. The dehydrogenation process is fully reversible under standard conditions (1 bar, 298 K).

  1. A 156 kyr smoothed history of the atmospheric greenhouse gases CO2, CH4, and N2O and their radiative forcing

    NASA Astrophysics Data System (ADS)

    Köhler, Peter; Nehrbass-Ahles, Christoph; Schmitt, Jochen; Stocker, Thomas F.; Fischer, Hubertus

    2017-06-01

    Continuous records of the atmospheric greenhouse gases (GHGs) CO2, CH4, and N2O are necessary input data for transient climate simulations, and their associated radiative forcing represents important components in analyses of climate sensitivity and feedbacks. Since the available data from ice cores are discontinuous and partly ambiguous, a well-documented decision process during data compilation followed by some interpolating post-processing is necessary to obtain those desired time series. Here, we document our best possible data compilation of published ice core records and recent measurements on firn air and atmospheric samples spanning the interval from the penultimate glacial maximum ( ˜ 156 kyr BP) to the beginning of the year 2016 CE. We use the most recent age scales for the ice core data and apply a smoothing spline method to translate the discrete and irregularly spaced data points into continuous time series. These splines are then used to compute the radiative forcing for each GHG using well-established, simple formulations. We compile only a Southern Hemisphere record of CH4 and discuss how much larger a Northern Hemisphere or global CH4 record might have been due to its interpolar difference. The uncertainties of the individual data points are considered in the spline procedure. Based on the given data resolution, time-dependent cutoff periods of the spline, defining the degree of smoothing, are prescribed, ranging from 5000 years for the less resolved older parts of the records to 4 years for the densely sampled recent years. The computed splines seamlessly describe the GHG evolution on orbital and millennial timescales for glacial and glacial-interglacial variations and on centennial and decadal timescales for anthropogenic times. Data connected with this paper, including raw data and final splines, are available at doi:10.1594/PANGAEA.871273.

  2. Management practices and controls on methane emissions from sub-tropical wetlands

    NASA Astrophysics Data System (ADS)

    DeLucia, Nicholas; Casa-Nova Gomez, Nuri; Bernacchi, Carl

    2015-04-01

    It is well documented that green house gas concentrations have risen at unequivocal rates since the industrial revolution but the disparity between anthropogenic sources and natural sources is uncertain. Wetlands are one example of a natural ecosystem that can be a substantial source or sink for methane (CH4) depending on any combination of climate conditions, natural and anthropogenic disturbances, or ecosystem perturbations. Due to strict anaerobic conditions required for CH4-generating microorganisms, natural wetlands are the main source for biogenic CH4. Although wetlands occupy less than 5% of total land surface area, they contribute approximately 20% of total CH4 emissions to the atmosphere. CH4 is one of the most damaging green house gases with current emission estimates ranging from 55 to 231 Tg CH4 yr-1. The processes regulating CH4 emissions are sensitive to land use and management practices of areas surrounding wetlands. Variation in adjacent vegetation or grazing intensity by livestock can, for example, alter CH4 fluxes from wetland soils by altering nutrient balance, carbon inputs and hydrology. Therefore, understanding how these changes will affect wetland source strength is essential to understand the impact of wetland management practices on the global climate system. In this study we quantify wetland methane fluxes from subtropical wetlands on a working cattle ranch in central Florida near Okeechobee Lake (27o10'52.04"N, 81o21'8.56"W). To determine differences in CH4 fluxes associated with land use and management, a replicated (n = 4) full factorial experiment was designed for wetlands where the surrounding vegetation was (1) grazed or un-grazed and (2) composed of native vegetation or improved pasture. Net exchange of CH4 and CO2 between the land surface and the atmosphere were sampled with a LICOR Li-7700 open path CH4 analyzer and Li-7500A open path CO2/H20 analyzer mounted in a 1-m3 static gas-exchange chamber. Our results showed and verified

  3. Potential of Svalbard reindeer winter droppings for emission/absorption of methane and nitrous oxide during summer

    NASA Astrophysics Data System (ADS)

    Hayashi, Kentaro; Cooper, Elisabeth J.; Loonen, Maarten J. J. E.; Kishimoto-Mo, Ayaka W.; Motohka, Takeshi; Uchida, Masaki; Nakatsubo, Takayuki

    2014-06-01

    Droppings of Svalbard reindeer (Rangifer tarandus platyrhynchus) could affect the carbon and nitrogen cycles in tundra ecosystems. The aim of this study was to evaluate the potential of reindeer droppings originating from the winter diet for emission and/or absorption of methane (CH4) and nitrous oxide (N2O) in summer. An incubation experiment was conducted over 14 days using reindeer droppings and mineral subsoil collected from a mound near Ny-Ålesund, Svalbard, to determine the potential exchanges of CH4 and N2O for combinations of two factors, reindeer droppings (presence or absence) and soil moisture (dry, moderate, or wet). A line transect survey was conducted to determine the distribution density of winter droppings at the study site. The incubation experiment showed a weak absorption of CH4 and a weak emission of N2O. Reindeer droppings originating from the winter diet had a negligible effect on the exchange fluxes of both CH4 and N2O. Although the presence of droppings resulted in a short-lasting increase in N2O emissions on day 1 (24 h from the start) for moderate and wet conditions, the emission rates were still very small, up to 3 μg N2O m-2 h-1.

  4. A Mechanistical Study on the Formation of Dimethyl Ether (CH3OCH3) and Ethanol (CH3CH2OH) in Methanol-containing Ices and Implications for the Chemistry of Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Bergantini, Alexandre; Góbi, Sándor; Abplanalp, Matthew J.; Kaiser, Ralf I.

    2018-01-01

    The underlying formation mechanisms of complex organic molecules (COMs)—in particular, structural isomers—in the interstellar medium (ISM) are largely elusive. Here, we report new experimental findings on the role of methanol (CH3OH) and methane (CH4) ices in the synthesis of two C2H6O isomers upon interaction with ionizing radiation: ethanol (CH3CH2OH) and dimethyl ether (CH3OCH3). The present study reproduces the interstellar abundance ratios of both species with ethanol to dimethyl ether branching ratios of (2.33 ± 0.14):1 suggesting that methanol and methane represents the key precursor to both isomers within interstellar ices. Exploiting isotopic labeling combined with reflectron time-of-flight mass spectrometry (Re-TOF-MS) after isomer selective vacuum ultra-violet (VUV) photoionization of the neutral molecules, we also determine the formation mechanisms of both isomers via radical–radical recombination versus carbene (CH2) insertion with the former pathway being predominant. Formation routes to higher molecular weight reaction products such as ethylene glycol (HOCH2CH2OH), dimethyl peroxide (CH3OOCH3), and methoxymethanol (CH3OCH2OH) are discussed briefly as well.

  5. Synthesis and structure of cesium complexes of nitrilotris(methylenephosphonic) acid [Cs-μ6-NH(CH2PO3)3H4] and [Cs2-μ10-NH(CH2PO3H)3] · H2O

    NASA Astrophysics Data System (ADS)

    Somov, N. V.; Chausov, F. F.; Zakirov, R. M.

    2017-07-01

    3D coordination polymers cesium nitrilotris(methylenephosphonate) and dicesium nitrilotris( methylenephosphonate) are synthesized and their crystal structure is determined. In the crystal of [Cs-μ6-NH(CH2PO3)3H4] (space group P, Z = 2), cesium atoms occupy two crystallographically inequivalent positions with c.n. = 10 and c.n. = 14. The phosphonate ligand plays the bridging function; its denticity is nine. The crystal packing consists of alternating layers of Cs atoms in different environments with layers of ligand molecules between them. A ligand is bound to three Cs atoms of one layer and three Cs atoms of another layer. In the crystal of [Cs2-μ10-NH(CH2PO3H)3] · H2O (space group P, Z = 2), the complex has a dimeric structure: the bridging phosphonate ligand coordinates Cs to form a three-dimensional Cs4O6 cluster. The denticity of the ligand is equal to nine; the coordination numbers of cesium atoms are seven and nine. Two-dimensional corrugated layers of Cs4O6 clusters lie in the (002) plane, and layers of ligand molecules are located between them. Each ligand molecule coordinates eight Cs atoms of one layer and two Cs atoms of the neighboring layer.

  6. Infrared absorption of methanol-water clusters (CH3OH)n(H2O), n = 1-4, recorded with the VUV-ionization/IR-depletion technique.

    PubMed

    Lee, Yu-Fang; Kelterer, Anne-Marie; Matisz, Gergely; Kunsági-Máté, Sándor; Chung, Chao-Yu; Lee, Yuan-Pern

    2017-04-14

    We recorded infrared (IR) spectra in the CH- and OH-stretching regions of size-selected clusters of methanol (M) with one water molecule (W), represented as M n W, n = 1-4, in a pulsed supersonic jet using the photoionization/IR-depletion technique. Vacuum ultraviolet emission at 118 nm served as the source of ionization in a time-of-flight mass spectrometer to detect clusters M n W as protonated forms M n-1 WH + . The variations in intensities of M n-1 WH + were monitored as the wavelength of the IR laser light was tuned across the range 2700-3800 cm -1 . IR spectra of size-selected clusters were obtained on processing of the observed action spectra of the related cluster-ions according to a mechanism that takes into account the production and loss of each cluster due to IR photodissociation. Spectra of methanol-water clusters in the OH region show significant variations as the number of methanol molecules increases, whereas those in the CH region are similar for all clusters. Scaled harmonic vibrational wavenumbers and relative IR intensities predicted with the M06-2X/aug-cc-pVTZ method for the methanol-water clusters are consistent with our experimental results. For dimers, absorption bands of a structure WM with H 2 O as a hydrogen-bond donor were observed at 3570, 3682, and 3722 cm -1 , whereas weak bands of MW with methanol as a hydrogen-bond donor were observed at 3611 and 3753 cm -1 . For M 2 W, the free OH band of H 2 O was observed at 3721 cm -1 , whereas a broad feature was deconvoluted to three bands near 3425, 3472, and 3536 cm -1 , corresponding to the three hydrogen-bonded OH-stretching modes in a cyclic structure. For M 3 W, the free OH shifted to 3715 cm -1 , and the hydrogen-bonded OH-stretching bands became much broader, with a weak feature near 3179 cm -1 corresponding to the symmetric OH-stretching mode of a cyclic structure. For M 4 W, the observed spectrum agrees unsatisfactorily with predictions for the most stable cyclic structure

  7. Ion imaging study of dissociative charge transfer in the N{sub 2}{sup +}+ CH{sub 4} system

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pei Linsen; Farrar, James M.

    The velocity map ion imaging method is applied to the dissociative charge transfer reactions of N{sub 2}{sup +} with CH{sub 4} studied in crossed beams. The velocity space images are collected at four collision energies between 0.5 and 1.5 eV, providing both product kinetic energy and angular distributions for the reaction products CH{sub 3}{sup +} and CH{sub 2}{sup +}. The general shapes of the images are consistent with long range electron transfer from CH{sub 4} to N{sub 2}{sup +} preceding dissociation, and product kinetic energy distributions are consistent with energy resonance in the initial electron transfer step. The branching ratiomore » for CH{sub 3}{sup +}:CH{sub 2}{sup +} is 85:15 over the full collision energy range, consistent with literature reports.« less

  8. A Single-Culture Bioprocess of Methanothermobacter thermautotrophicus to Upgrade Digester Biogas by CO2-to-CH4 Conversion with H2

    PubMed Central

    Martin, Matthew R.; Fornero, Jeffrey J.; Angenent, Largus T.

    2013-01-01

    We optimized and tested a postbioprocessing step with a single-culture archaeon to upgrade biogas (i.e., increase methane content) from anaerobic digesters via conversion of CO2 into CH4 by feeding H2 gas. We optimized a culture of the thermophilic methanogen Methanothermobacter thermautotrophicus using: (1) a synthetic H2/CO2 mixture; (2) the same mixture with pressurization; (3) a synthetic biogas with different CH4 contents and H2; and (4) an industrial, untreated biogas and H2. A laboratory culture with a robust growth (dry weight of 6.4–7.4 g/L; OD600 of 13.6–15.4), a volumetric methane production rate of 21 L/L culture-day, and a H2 conversion efficiency of 89% was moved to an industrial anaerobic digester facility, where it was restarted and fed untreated biogas with a methane content of ~70% at a rate such that CO2 was in excess of the stoichiometric requirements in relation to H2. Over an 8-day operating period, the dry weight of the culture initially decreased slightly before stabilizing at an elevated level of ~8 g/L to achieve a volumetric methane production rate of 21 L/L culture-day and a H2 conversion efficiency of 62%. While some microbial contamination of the culture was observed via microscopy, it did not affect the methane production rate of the culture. PMID:24194675

  9. Joint CO2 and CH4 accountability for global warming

    PubMed Central

    Smith, Kirk R.; Desai, Manish A.; Rogers, Jamesine V.; Houghton, Richard A.

    2013-01-01

    We propose a transparent climate debt index incorporating both methane (CH4) and carbon dioxide (CO2) emissions. We develop national historic emissions databases for both greenhouse gases to 2005, justifying 1950 as the starting point for global perspectives. We include CO2 emissions from fossil sources [CO2(f)], as well as, in a separate analysis, land use change and forestry. We calculate the CO2(f) and CH4 remaining in the atmosphere in 2005 from 205 countries using the Intergovernmental Panel on Climate Change’s Fourth Assessment Report impulse response functions. We use these calculations to estimate the fraction of remaining global emissions due to each country, which is applied to total radiative forcing in 2005 to determine the combined climate debt from both greenhouse gases in units of milliwatts per square meter per country or microwatts per square meter per person, a metric we term international natural debt (IND). Australia becomes the most indebted large country per capita because of high CH4 emissions, overtaking the United States, which is highest for CO2(f). The differences between the INDs of developing and developed countries decline but remain large. We use IND to assess the relative reduction in IND from choosing between CO2(f) and CH4`control measures and to contrast the imposed versus experienced health impacts from climate change. Based on 2005 emissions, the same hypothetical impact on world 2050 IND could be achieved by decreasing CH4 emissions by 46% as stopping CO2 emissions entirely, but with substantial differences among countries, implying differential optimal strategies. Adding CH4 shifts the basic narrative about differential international accountability for climate change. PMID:23847202

  10. Computation provides chemical insight into the diverse hydride NMR chemical shifts of [Ru(NHC)4(L)H]0/+ species (NHC = N-heterocyclic carbene; L = vacant, H2, N2, CO, MeCN, O2, P4, SO2, H-, F- and Cl-) and their [Ru(R2PCH2CH2PR2)2(L)H]+ congeners.

    PubMed

    Häller, L Jonas L; Mas-Marzá, Elena; Cybulski, Mateusz K; Sanguramath, Rajashekharayya A; Macgregor, Stuart A; Mahon, Mary F; Raynaud, Christophe; Russell, Christopher A; Whittlesey, Michael K

    2017-02-28

    Relativistic density functional theory calculations, both with and without the effects of spin-orbit coupling, have been employed to model hydride NMR chemical shifts for a series of [Ru(NHC) 4 (L)H] 0/+ species (NHC = N-heterocyclic carbene; L = vacant, H 2 , N 2 , CO, MeCN, O 2 , P 4 , SO 2 , H - , F - and Cl - ), as well as selected phosphine analogues [Ru(R 2 PCH 2 CH 2 PR 2 ) 2 (L)H] + (R = i Pr, Cy; L = vacant, O 2 ). Inclusion of spin-orbit coupling provides good agreement with the experimental data. For the NHC systems large variations in hydride chemical shift are shown to arise from the paramagnetic term, with high net shielding (L = vacant, Cl - , F - ) being reinforced by the contribution from spin-orbit coupling. Natural chemical shift analysis highlights the major orbital contributions to the paramagnetic term and rationalizes trends via changes in the energies of the occupied Ru d π orbitals and the unoccupied σ* Ru-H orbital. In [Ru(NHC) 42 -O 2 )H] + a δ-interaction with the O 2 ligand results in a low-lying LUMO of d π character. As a result this orbital can no longer contribute to the paramagnetic shielding, but instead provides additional deshielding via overlap with the remaining (occupied) d π orbital under the L z angular momentum operator. These two effects account for the unusual hydride chemical shift of +4.8 ppm observed experimentally for this species. Calculations reproduce hydride chemical shift data observed for [Ru( i Pr 2 PCH 2 CH 2 P i Pr 2 ) 22 -O 2 )H] + (δ = -6.2 ppm) and [Ru(R 2 PCH 2 CH 2 PR 2 ) 2 H] + (ca. -32 ppm, R = i Pr, Cy). For the latter, the presence of a weak agostic interaction trans to the hydride ligand is significant, as in its absence (R = Me) calculations predict a chemical shift of -41 ppm, similar to the [Ru(NHC) 4 H] + analogues. Depending on the strength of the agostic interaction a variation of up to 18 ppm in hydride chemical shift is possible and this factor (that is not necessarily

  11. Origin of the Excellent Performance of Ru on Nitrogen-Doped Carbon Nanofibers for CO2 Hydrogenation to CH4.

    PubMed

    Roldán, Laura; Marco, Yanila; García-Bordejé, Enrique

    2017-03-22

    Carbon materials have rarely been used as support for CO 2 methanation, which is usually carried out using catalysts supported on metal oxides. Here, it is shown that Ru nanoparticles supported on nitrogen-doped carbon nanofibers (NCNF) provide competitive CH 4 production rate and stability compared to Al 2 O 3 -supported catalysts. Contrary to the general belief about the inert nature of carbon supports, it is demonstrated that NCNF is a non-innocent spectator in CO 2 methanation due to its ability to store a high amount of CO ad reaction intermediates. This explains the excellent catalytic behaviour afforded by this unconventional catalyst support. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Thermal decomposition of ethanol. 4. Ab initio chemical kinetics for reactions of H atoms with CH3CH2O and CH3CHOH radicals.

    PubMed

    Xu, Z F; Xu, Kun; Lin, M C

    2011-04-21

    The potential energy surfaces of H-atom reactions with CH(3)CH(2)O and CH(3)CHOH, two major radicals in the decomposition and oxidation of ethanol, have been studied at the CCSD(T)/6-311+G(3df,2p) level of theory with geometric optimization carried out at the BH&HLYP/6-311+G(3df,2p) level. The direct hydrogen abstraction channels and the indirect association/decomposition channels from the chemically activated ethanol molecule have been considered for both reactions. The rate constants for both reactions have been calculated at 100-3000 K and 10(-4) Torr to 10(3) atm Ar pressure by microcanonical VTST/RRKM theory with master equation solution for all accessible product channels. The results show that the major product channel of the CH(3)CH(2)O + H reaction is CH(3) + CH(2)OH under atmospheric pressure conditions. Only at high pressure and low temperature, the rate constant for CH(3)CH(2)OH formation by collisonal deactivation becomes dominant. For CH(3)CHOH + H, there are three major product channels; at high temperatures, CH(3)+CH(2)OH production predominates at low pressures (P < 100 Torr), while the formation of CH(3)CH(2)OH by collisional deactivation becomes competitive at high pressures and low temperatures (T < 500 K). At high temperatures, the direct hydrogen abstraction reaction producing CH(2)CHOH + H(2) becomes dominant. Rate constants for all accessible product channels in both systems have been predicted and tabulated for modeling applications. The predicted value for CH(3)CHOH + H at 295 K and 1 Torr pressure agrees closely with available experimental data. For practical modeling applications, the rate constants for the thermal unimolecular decomposition of ethanol giving key accessible products have been predicted; those for the two major product channels taking place by dehydration and C-C breaking agree closely with available literature data.

  13. Real-time analysis of δ13C- and δD-CH4 in ambient air with laser spectroscopy: Method development and intercomparison

    NASA Astrophysics Data System (ADS)

    Harris, E. J.; Eyer, S.; Mohn, J.; Röckmann, T.; Popa, E.; Lowry, D.; Nisbet, E. G.; Fisher, R. E.; Brennwald, M. S.; Fischer, H.; Emmenegger, L.; Tuzson, B.; Zellweger, C.

    2015-12-01

    Methane (CH4) is the second most important anthropogenically emitted greenhouse gas after carbon dioxide (CO2). Its mole fraction has increased from around 722 ppb in pre-industrial times to 1824 ppb in 2013 and the anthropogenic fraction is estimated to be 60 % of the total emissions. A promising approach to improve the understanding of the CH4 budget is the use of isotopologues to distinguish between various CH4 source processes. In the presented study in situ and simultaneous measurement of the three most abundant isotopologues of methane using mid-infrared laser absorption spectroscopy is demonstrated. A field-deployable, autonomous platform is realized by coupling a compact quantum cascade laser absorption spectrometer (QCLAS) to a preconcentration unit, called TRace gas EXtractor (TREX). This unit enhances CH4 mole fractions by a factor of up to 500 above ambient levels and quantitatively separates interfering trace gases such as N2O and CO2. The analytical precision of the QCLAS isotope measurement on the preconcentrated (750 ppm, parts-per-million, mmole/mole) methane is 0.1‰ and 0.5 ‰ for δ13C- and δD-CH4 at 10 min averaging time. [1] Based on replicate measurements of compressed air during a two-week intercomparison campaign, the repeatability of the TREX-QCLAS was determined to be 0.19 ‰ and 1.9 ‰ for δ13C and δD-CH4, respectively. In this intercomparison campaign the new in situ technique is compared to IRMS based on glass flask and bag sampling and real time CH4 isotope analysis by two commercially available laser spectrometers (Figure). Both laser-based analyzers were limited to methane mole fraction and δ13C-CH4 analysis, and only one of them, a cavity ring down spectrometer, was capable to deliver meaningful data for the isotopic composition. After correcting for scale offsets, the average difference between TREX-QCLAS data and bag/flask sampling-IRMS values are within the extended WMO compatibility goals of 0.2 and 5 ‰ for δ13C- and

  14. Assessment of nitrous oxide and methane emissions for California agriculture

    NASA Astrophysics Data System (ADS)

    Horwath, W. R.; Burger, M.; Assa, Y.; Wilson, T. J.

    2012-12-01

    The California Global Warming Solutions Act of 2006 (AB 32) mandates comprehensive strategies to reduce nitrous oxide (N2O) and methane (CH4) emissions. In agriculture crop production, sources of N2O are related to nitrogen fertilization while CH4 emission is associated with rice production. More than half the GHG emissions from agriculture are attributed to N2O production. Currently, baseline N2O emission data for most cropping systems in the State is lacking. Estimates of CH4 emission in rice have been established from previous studies, but a lack of information exists for its expansion into the San Joaquin Delta to address subsidence issues. The paucity of N2O emission data has hampered biogeochemical modeling efforts. The objectives of this assessment are to (1) measure annual N2O and CH4 emissions for major California crops (vineyards, almonds, tomato, wheat, alfalfa, lettuce, and rice) under typical management practices, (2) characterize the effects of environmental factors on the temporal profile of N2O and CH4 emissions, and (3) determine N2O emission factors. The growth of rice in Delta peat soils produced highly variable CH4 emissions depending on tillage intensity. In 2010, standard tillage produced 184 kg CH4-C/ha while in 2011 after deep plowing placing rice residue deeper into the soil, only 26 kg CH4-C/ha was observed. In processing tomato systems, an average 2.5 kg N2O-N/ha was emitted with standard fertilization (160 kg N / ha), similar to background emissions and those from a drip irrigated system, while 4.0 to 5.8 kg N2O-N /ha y-1 was emitted at fertilizer rates of 225 and 300 kg N /ha (see Fig. 1 for example of temporal sources of emissions). About half the annual emissions were emitted within 3 d after the first seasonal rainfall event. In other tomato studies, estimated losses of fertilizer N as N2O were 0.38 ± 0.03 kg/ha y-1 in a drip irrigated system and 1.79 ± 0.21 kg/ha y-1 in furrow irrigated system, which was equivalent to 0.19% and 0

  15. Biochar effects on gaseous losses of N2O and CH4

    USDA-ARS?s Scientific Manuscript database

    The flux of N2O from soil is controlled by both biological and abiotic processes resulting in production and consumption. In a recent review by Butterbach-Bahl et al., (2013), key processes that contribute to N2O formation in soils included: 1) chemical decomposition of hydroxylamine during autotrop...

  16. Land-use change effects on fluxes and isotopic composition of CO2 and CH4 in Panama, and possible insights into the atmospheric H2 cycle

    NASA Astrophysics Data System (ADS)

    Pendall, E.; Schwendenmann, L.; Potvin, C.

    2003-12-01

    Land-use changes in tropical regions are believed to release a quantity of C to the atmosphere which is similar in magnitude to the entire "missing" sink for anthropogenic CO2. Our research attempts to evaluate carbon cycling in three land-cover systems in central Panama: cow pasture, native tree plantation, and undisturbed moist forest. In this ongoing project, we are collecting samples of air from profiles in the stable, nocturnal boundary layer, which is dominated by ecosystem respiration. Samples are analyzed for CO2 and its isotopes, CH4 and its C isotopic composition, N2O, H2, CO, and SF6. We use a flux-gradient method to estimate ecosystem-scale fluxes of trace gases from soil to the atmosphere. Keeling plot intercepts reflect the respiratory contribution of C3 and C4 biomass under contrasting land cover systems, and how this varies with pronounced wet-dry seasonal cycles. C isotopes of methane and gradients of molecular hydrogen provide insight into the source of methane production from pasture and plantation soils. Rainforest soils, in contrast, are sinks for both atmospheric methane and hydrogen. The process oriented nature of this field experiment will contribute to parameterization of carbon cycle models at a variety of spatial scales.

  17. Methane flux from Minnesota Peatlands

    NASA Astrophysics Data System (ADS)

    Crill, P. M.; Bartlett, K. B.; Harriss, R. C.; Gorham, E.; Verry, E. S.; Sebacher, D. I.; Madzar, L.; Sanner, W.

    1988-12-01

    Northern (>40°N) wetlands have been suggested as the largest natural source of methane (CH4) to the troposphere. To refine our estimates of source strengths from this region and to investigate climatic controls on the process, fluxes were measured from a variety of Minnesota peatlands during May, June, and August 1986. Sites included forested and unforested ombrotrophic bogs and minerotrophic fens in and near the U.S. Department of Agriculture Marcell Experimental Forest and the Red Lake peatlands. Late spring and summer fluxes ranged from 11 to 866 mg CH4 m-2 d-1, averaging 207 mg CH4 m-2 d-1 overall. At Marcell Forest, forested bogs and fen sites had lower fluxes (averages of 77 ± 21 mg CH4 m-2 d-1 and 142 ± 19 mg CH4 m-2 d-1) than open bogs (average of 294 ± 30 mg CH4 m-2 d-1). In the Red Lake peatland, circumneutral fens, with standing water above the peat surface, produced more methane than acid bog sites in which the water table was beneath the moss surface (325 ± 31 and 102 ± 13 mg CH4 m-2 d-1, respectively). Peat temperature was an important control. Methane flux increased in response to increasing soil temperature. For example, the open bog in the Marcell Forest with the highest CH4 flux exhibited a 74-fold increase in flux over a three-fold increase in temperature. We estimate that the methane flux from all peatlands north of 40° may be on the order of 70 to 90 Tg/yr though estimates of this sort are plagued by uncertainties in the areal extent of peatlands, length of the CH4 producing season, and the spatial and temporal variability of the flux.

  18. Global Methane Biogeochemistry

    NASA Astrophysics Data System (ADS)

    Reeburgh, W. S.

    2003-12-01

    . Methane absorbs infrared radiation in the troposphere, as do CO2 and H2O, and is an important greenhouse gas (Lacis et al., 1981; Ramanathan et al., 1985).A number of review articles on atmospheric CH4 have appeared during the last 15 years. Cicerone and Oremland (1988) reviewed evidence for the temporal atmospheric increase, updated source estimates in the global CH4 budget, and placed constraints on the global budget, emphasizing that the total is well constrained, but that the constituent sources may be uncertain by a factor of 2 or more. This paper was part of a special section in Global Biogeochemical Cycles that resulted from a 1987 American Chemical Society Symposium, "Atmospheric Methane: Formation and Fluxes form the Biosphere and Geosphere." Tyler (1991) and Wahlen (1993) emphasized new information on stable isotopes of CH4 and 14CH4, respectively. Several reviews deal with the microbially mediated CH4 oxidation. King (1992) reviewed the ecology of microbial CH4 oxidation, emphasizing the important role of this process in global CH4 dynamics. R. S. Hanson and T. E. Hanson (1996) reviewed the physiology and taxonomy of methylotrophic bacteria, their role in the global carbon cycle, and the ecology of methanotrophic bacteria. Conrad (1996) reviewed the role of soils and soil microbial communities as controllers of CH4 fluxes, as well as those of H2, CO, OCS, N2O, and NO. Two meetings focusing on CH4 biogeochemistry were held in 1991: an NATO Advanced Science Workshop held at Mt. Hood, OR, and the Tenth International Symposium on Environmental Biogeochemistry (ISEB). A dedicated issue of Chemosphere (26(1-4), 1993) contains contributions from the NATO workshop; two additional volumes (Khalil, 1993 and Khalil, 2000) contain a report of the workshop and updates of important topics. Contributions to the ISEB meeting are presented in Oremland (1993). Wuebbles and Hayhoe (2002) reviewed the effects of CH4 on atmospheric chemistry and examined the direct and indirect

  19. Spectroscopic properties of morin in various CH3OH-H2O and CH3CN-H2O mixed solvents.

    PubMed

    Park, Hyoung-Ryun; Im, Seo-Eun; Seo, Jung-Ja; Kim, Bong-Gon; Yoon, Jin Ah; Bark, Ki-Min

    2015-01-01

    The specific fluorescence properties of morin (3,2',4',5,7-pentahydroxyflavone) were studied in various CH3OH-H2O and CH3CN-H2O mixed solvents. Although the dihedral angle is large in the S0 state, morin has an almost planar molecular structure in the S1 state owing to the very low rotational energy barrier around the interring bond between B and the A, C ring. The excited state intramolecular proton transfer (ESIPT) at the S1 state cannot occur immediately after excitation, S1 → S0 fluorescence can be observed. Two conformers, Morin A and B have been known. At the CH3OH-H2O, Morin B will be the principal species but at the CH3CN-H2O, Morin A is the principal species. At the CH3OH-H2O, owing to the large Franck-Condon (FC) factor for S2 → S1 internal convernal (IC) and flexible molecular structure, only S1 → S0 fluorescence was exhibited. At the CH3CN-H2O, as the FC factor for S2 → S1 IC is small and molecular structure is rigid, S2 → S0 and S1 → S0 dual fluorescence was observed. This abnormal fluorescence property was further supported by the small pK1 value, effective delocalization of the lone pair electrons of C(2')-OH to the A, C ring, and a theoretical calculation. © 2014 The American Society of Photobiology.

  20. Stratospheric CH4 and CO2 profiles derived from SCIAMACHY solar occultation measurements

    NASA Astrophysics Data System (ADS)

    Noël, Stefan; Bramstedt, Klaus; Hilker, Michael; Liebing, Patricia; Plieninger, Johannes; Reuter, Max; Rozanov, Alexei; Sioris, Christopher E.; Bovensmann, Heinrich; Burrows, John P.

    2016-04-01

    Stratospheric profiles of methane (CH4) and carbon dioxide (CO2) have been derived from solar occultation measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY). The retrieval is performed using a method called onion peeling DOAS (ONPD), which combines an onion peeling approach with a weighting function DOAS (differential optical absorption spectroscopy) fit in the spectral region between 1559 and 1671 nm. By use of updated pointing information and optimisation of the data selection as well as of the retrieval approach, the altitude range for reasonable CH4 could be broadened from 20 to 40 km to about 17 to 45 km. Furthermore, the quality of the derived CO2 has been assessed such that now the first stratospheric profiles (17-45 km) of CO2 from SCIAMACHY are available. Comparisons with independent data sets yield an estimated accuracy of the new SCIAMACHY stratospheric profiles of about 5-10 % for CH4 and 2-3 % for CO2. The accuracy of the products is currently mainly restricted by the appearance of unexpected vertical oscillations in the derived profiles which need further investigation. Using the improved ONPD retrieval, CH4 and CO2 stratospheric data sets covering the whole SCIAMACHY time series (August 2002-April 2012) and the latitudinal range between about 50 and 70° N have been derived. Based on these time series, CH4 and CO2 trends have been estimated. CH4 trends above about 20 km are not significantly different from zero and the trend at 17 km is about 3 ppbv year-1. The derived CO2 trends show a general decrease with altitude with values of about 1.9 ppmv year-1 at 21 km and about 1.3 ppmv year-1 at 39 km. These results are in reasonable agreement with total column trends for these gases. This shows that the new SCIAMACHY data sets can provide valuable information about the stratosphere.

  1. Predicting CH4 adsorption capacity of microporous carbon using N2 isotherm and a new analytical model

    USGS Publications Warehouse

    Sun, Jielun; Chen, S.; Rostam-Abadi, M.; Rood, M.J.

    1998-01-01

    A new analytical pore size distribution (PSD) model was developed to predict CH4 adsorption (storage) capacity of microporous adsorbent carbon. The model is based on a 3-D adsorption isotherm equation, derived from statistical mechanical principles. Least squares error minimization is used to solve the PSD without any pre-assumed distribution function. In comparison with several well-accepted analytical methods from the literature, this 3-D model offers relatively realistic PSD description for select reference materials, including activated carbon fibers. N2 and CH4 adsorption data were correlated using the 3-D model for commercial carbons BPL and AX-21. Predicted CH4 adsorption isotherms, based on N2 adsorption at 77 K, were in reasonable agreement with the experimental CH4 isotherms. Modeling results indicate that not all the pores contribute the same percentage Vm/Vs for CH4 storage due to different adsorbed CH4 densities. Pores near 8-9 A?? shows higher Vm/Vs on the equivalent volume basis than does larger pores.

  2. A new method for speciated CH3O2 radical detection and HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry) studies of the CH3O2 self-reaction

    NASA Astrophysics Data System (ADS)

    Onel, Lavinia; Brennan, Alexander; Seakins, Paul W.; Whalley, Lisa; Heard, Dwayne

    2016-04-01

    A new method has been developed for the speciated detection of CH3O2 radicals by FAGE (Fluorescence Assay by Gas Expansion) by titrating CH3O2 to CH3O by reaction with added NO and then detecting the resultant CH3O by LIF (laser induced fluorescence). The limit of detection of the technique is ˜108 cm-3 CH3O2 for a unity signal-to-noise ratio and 5 min averaging time. The method has been used for time monitoring of CH3O2 during its self-reaction within HIRAC at 1 bar and room temperature to determine a preliminary value of the rate coefficient of 4.2 × 10-13 cm3 s-1, which lies in the range of the previous results, (2.7 - 5.2) × 10-13 cm3 s-1.1 In addition to detection of CH3O2, products of the CH3O2 self-reaction were also observed for the two reaction channels over a range of temperatures from 260 - 320 K: (a) 2CH3O2CH2O + CH3OH; (b) 2CH3O22CH3O + O2, namely HO2 radicals (from reaction of CH3O + O2) and formaldehyde monitored by FAGE and formaldehyde and methanol observed by FTIR. A good agreement has been obtained between the FTIR and FAGE measurements of CH2O which increased to ˜ 2 ppmv over the experiments. Using the concentrations of CH3OH and CH2O, the branching ratio for channel (a) at room temperature has been determined as ra = 0.66 ± 0.06. The result is in very good agreement with the value recommended in the review of Tyndall et al.2 of ra = 0.63 ± 0.06. No temperature dependence of ra has been observed from 296 K to 321 K. 1. http://iupac.pole-ether.fr/ 2. G. S. Tyndall et al., J. Geophys. Res. 106, 12157 (2001).

  3. A search for interstellar CH3D: Limits to the methane abundance in Orion-KL

    NASA Technical Reports Server (NTRS)

    Womack, Maria; Ziurys, L. M.; Apponi, A. J.

    1995-01-01

    A search has been performed for interstellar CH3D via its J(K) = 1(0) - 0(0) transition at 230 GHz and its J(K) = 2(0) - l(0) and J(K) = 2(1) - 1(1) lines at 465 GHz using the NRAO 12 m and CSO 10 m telescopes towards Orion-KL. This search was done in conjunction with laboratory measurements of all three transitions of CH3D using mm/sub-mm direct absorption spectroscopy. The molecule was not detected down to a 3 sigma level of T(A) less than 0.05 K towards Orion, which suggests an upper limit to the CH3D column density of N less than 6 x 10(exp 18)/sq cm in the hot core region and a fractional abundance (with respect to H2) of less than 6 x 10(exp -6). These measurements suggest that the methane abundance in the Orion hot core is f less than 6 x 10-4, assuming D/H approximately 0.01. Such findings are in agreement with recent hot core chemical models, which suggest CH4/H2 approximately 10(exp -4).

  4. Molecular dynamic simulations of N2-broadened methane line shapes and comparison with experiments

    NASA Astrophysics Data System (ADS)

    Le, Tuong; Doménech, José-Luis; Lepère, Muriel; Tran, Ha

    2017-03-01

    Absorption spectra of methane transitions broadened by nitrogen have been calculated for the first time using classical molecular dynamic simulations. For that, the time evolution of the auto-correlation function of the dipole moment vector, assumed along a C-H axis, was computed using an accurate site-site intermolecular potential for CH4-N2. Quaternion coordinates were used to treat the rotation of the molecules. A requantization procedure was applied to the classical rotation and spectra were then derived as the Fourier-Laplace transform of the auto-correlation function. These computed spectra were compared with experimental ones recorded with a tunable diode laser and a difference-frequency laser spectrometer. Specifically, nine isolated methane lines broadened by nitrogen, belonging to various vibrational bands and having rotational quantum numbers J from 0 to 9, were measured at room temperature and at several pressures from 20 to 945 mbar. Comparisons between measured and calculated spectra were made through their fits using the Voigt profile. The results show that ab initio calculated spectra reproduce with very high fidelity non-Voigt effects on the measurements and that classical molecular dynamic simulations can be used to predict spectral shapes of isolated lines of methane perturbed by nitrogen.

  5. Real-time analysis of δ13C- and δD-CH4 in ambient air with laser spectroscopy: method development and first intercomparison results

    NASA Astrophysics Data System (ADS)

    Eyer, S.; Tuzson, B.; Popa, M. E.; van der Veen, C.; Röckmann, T.; Rothe, M.; Brand, W. A.; Fisher, R.; Lowry, D.; Nisbet, E. G.; Brennwald, M. S.; Harris, E.; Zellweger, C.; Emmenegger, L.; Fischer, H.; Mohn, J.

    2015-08-01

    In situ and simultaneous measurement of the three most abundant isotopologues of methane using mid-infrared laser absorption spectroscopy is demonstrated. A field-deployable, autonomous platform is realized by coupling a compact quantum cascade laser absorption spectrometer (QCLAS) to a preconcentration unit, called TRace gas EXtractor (TREX). This unit enhances CH4 mole fractions by a factor of up to 500 above ambient levels and quantitatively separates interfering trace gases such as N2O and CO2. The analytical precision of the QCLAS isotope measurement on the preconcentrated (750 ppm, parts-per-million, μmole/mole) methane is 0.1 and 0.5 ‰ for δ13C- and δD-CH4 at 10 min averaging time. Based on replicate measurements of compressed air during a two-week intercomparison campaign, the repeatability of the TREX-QCLAS was determined to be 0.19 and 1.9 ‰ for δ13C and δD-CH4, respectively. In this intercomparison campaign the new in situ technique is compared to isotope-ratio mass-spectrometry (IRMS) based on glass flask and bag sampling and real time CH4 isotope analysis by two commercially available laser spectrometers. Both laser-based analyzers were limited to methane mole fraction and δ13C-CH4 analysis, and only one of them, a cavity ring down spectrometer, was capable to deliver meaningful data for the isotopic composition. After correcting for scale offsets, the average difference between TREX-QCLAS data and bag/flask sampling-IRMS values are within the extended WMO compatibility goals of 0.2 and 5 ‰ for δ13C- and δD-CH4, respectively. Thus, the intercomparison also reveals the need for reference air samples with accurately determined isotopic composition of CH4 to further improve the interlaboratory compatibility.

  6. Unusual structural phase transition in [N(C2H5)4][N(CH3)4][ZnBr4

    NASA Astrophysics Data System (ADS)

    Krawczyk, Monika K.; Ingram, Adam; Cach, Ryszard; Czapla, Zbigniew; Czupiński, Olaf; Dacko, Sławomir; Staniorowski, Piotr

    2018-04-01

    The new hybrid organic-inorganic crystal [N(C2H5)4][N(CH3)4][ZnBr4] was grown and its physical properties and structural phase transition are presented. On the basis of thermal analysis (DSC (differential scanning calorimetry), DTA (differential thermal analysis), DTG), X-ray structural, dilatometric and dielectric studies as well as optical observation, the reversible first-order phase transition at 490/488 K on heating and cooling run, respectively, has been found. An appearance of domain structure of ferroelastic type gives evidence for an untypical lowering of crystal symmetry during the phase transition. At room temperature, the satisfying crystal structure solution was found in the tetragonal system, in the P?21m space group.

  7. Estimating the potential for methane clathrate instability in the 1%-CO2 IPCC AR-4 simulations

    NASA Astrophysics Data System (ADS)

    Lamarque, Jean-François

    2008-10-01

    The recent work of Reagan and Moridis (2007) has shown that even a limited warming of 1 K over 100 years can lead to clathrate destabilization, leading to a significant flux of methane into the ocean water, at least for shallow deposits. Here we study the potential for methane clathrate destabilization by identifying the 100-year temperature increase in the available IPCC (Intergovernmental Panel on Climate Change) AR-4 1%-CO2 increase per year (up to doubling over pre-industrial conditions, which occurs after 70 years) simulations. Depending on assumptions made on the possible locations (in this case, only depth) of methane clathrates and on temperature dependence, our calculation leads to an estimated model-mean release of methane at the bottom of the ocean of approximately 560-2140 Tg(CH4)/year; as no actual geographical distribution of methane clathrates is considered here, these flux estimates must be viewed as upper bound estimates. Using an observed 1% ratio to estimate the amount of methane reaching the atmosphere, our analysis leads to a relatively small methane flux of approximately 5-21 Tg(CH4)/year, with an estimated inter-model standard deviation of approximately 30%. The role of sea-level rise by 2100 will be to further stabilize methane clathrates, albeit to a small amount as the sea-level rise is expected to be less than a few meters.

  8. Structure, phase transitions, and isotope effects in [(CH3)4N]2PuCl6

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wilson, Richard E.

    2015-11-02

    The single crystal X-ray diffraction structure of [(CH3)4N]2PuCl6 is presented for the first time, resolving long standing confusion and speculation regarding the structure of this compound in the literature. A temperature dependent study of this compound shows that the structure of [(CH3)4N]2PuCl6 undergoes no fewer than two phase transitions between 100 and 360 K. The phase of [(CH3)4N]2PuCl6 at room temperature is Fd-3c a = 26.012(3) Å. At 360 K, the structure is in space group Fm-3m with a = 13.088(1) Å. The plutonium octahedra and tetramethylammonium cations undergo a rotative displacement and the degree of rotation varies with temperature,more » giving rise to the phase transition from Fm-3m to Fd-3c as the crystal is cooled. Synthesis and structural studies of the deuterated salt [(CD3)4N]2PuCl6 suggest that there is an isotopic effect associated with this phase transition as revealed by a changing transition temperature in the deuterated versus protonated compound indicating that the donor-acceptor interactions between the tetramethylammonium cations and the hexachloroplutonate anions are driving the phase transformation.« less

  9. Radical routes to interstellar glycolaldehyde. The possibility of stereoselectivity in gas-phase polymerization reactions involving CH(2)O and ˙CH(2)OH.

    PubMed

    Wang, Tianfang; Bowie, John H

    2010-10-21

    A previous report that the interstellar molecule glycolaldehyde (HOCH(2)CHO) can be made from hydroxymethylene (HOCH:) and formaldehyde has been revisited at the CCSD(T)/6-311++G(3df,2p)//MP2/6-311++G(3df,2p) level of theory. This reaction competes with the formation of acetic acid and methylformate, molecules which have also been detected in interstellar clouds. Other possible modes of formation of glycolaldehyde by radical/radical reactions have been shown to be viable theoretically as follows: HO˙+˙CH2CHO -->HOCH2CHO [ΔG(Γ)(298K)=-303kJ mol⁻¹] HOCH2˙+˙CHO-->HOCH2CHO (-259kJ mol⁻¹). The species in these two processes are known interstellar molecules. Key radicals ˙CH(2)CHO and ˙CH(2)OH in these sequences have been shown to be stable for the microsecond duration of neutralization/reionization experiments in the dual collision cells of a VG ZAB 2HF mass spectrometer. The polymerization reaction HOCH(2)CH˙OH + nCH(2)O → HOCH(2)[CH(OH)](n)˙CHOH (n = 1 to 3) has been studied theoretically and shown to be energetically feasible, as is the cyclization reaction of HOCH(2)[(CH(2)OH)(4)]˙CHOH (in the presence of one molecule of water at the reacting centre) to form glucose. The probability of such a reaction sequence is small even if polymerization were to occur in interstellar ice containing a significant concentration of CH(2)O. The large number of stereoisomers produced by such a reaction sequence makes the formation of a particular sugar, again for example glucose, an inefficient synthesis. The possibility of stereoselectivity occurring during the polymerization was investigated for two diastereoisomers of HOCH(2)[(CHOH)](2)˙CHOH. No significant difference was found in the transition state energies for addition of CH(2)O to these two diastereoisomers, but a barrier difference of 12 kJ mol(-1) was found for the H transfer reactions ˙OCH(2)[(CHOH)](2)CH(2)OH → HOCH(2)[(CHOH)(2)˙CHOH of the two diastereoisomers.

  10. Active standoff detection of CH4 and N2O leaks using hard-target backscattered light using an open-path quantum cascade laser sensor

    NASA Astrophysics Data System (ADS)

    Diaz, Adrian; Thomas, Benjamin; Castillo, Paulo; Gross, Barry; Moshary, Fred

    2016-05-01

    Fugitive gas emissions from agricultural or industrial plants and gas pipelines are an important environmental concern as they contribute to the global increase of greenhouse gas concentrations. Moreover, they are also a security and safety concern because of possible risk of fire/explosion or toxicity. This study presents standoff detection of CH4 and N2O leaks using a quantum cascade laser open-path system that retrieves path-averaged concentrations by collecting the backscattered light from a remote hard target. It is a true standoff system and differs from other open-path systems that are deployed as point samplers or long-path transmission systems that use retroreflectors. The measured absorption spectra are obtained using a thermal intra-pulse frequency chirped DFB quantum cascade laser at ~7.7 µm wavelength range with ~200 ns pulse width. Making fast time resolved observations, the system simultaneously realizes high spectral resolution and range to the target, resulting in path-averaged concentration retrieval. The system performs measurements at high speed ~15 Hz and sufficient range (up to 45 m, ~148 feet) achieving an uncertainty of 3.1 % and normalized sensitivity of 3.3 ppm m Hz-1/2 for N2O and 9.3 % and normalized sensitivity of 30 ppm m Hz-1/2 for CH4 with a 0.31 mW average power QCL. Given these characteristics, this system is promising for mobile or multidirectional search and remote detection of gas leaks.

  11. Gas Hydrates as a CH4 Source and a CO2 Sink: New Approaches Based on Fundamental Research

    NASA Astrophysics Data System (ADS)

    Schicks, J. M.; Spangenberg, E.; Erzinger, J.

    2007-12-01

    The huge amount of methane, stored in the gas hydrate reservoirs of the world suggests that natural gas hydrates may be used in the future as a source of energy. A first production test was performed during the Mallik 2002 Gas Hydrate Production Research Well Program, showing that the thermal stimulation of natural gas hydrates successfully results in methane production (Dallimore et al. 2005). However, regarding the energy balance, the most efficient method for methane production from hydrates still needs to be developed. From another point of view, the sequestration of CO2 in form of gas hydrates in (marine) sediments is an interesting idea. A combination of methane production from natural gas hydrates on the one hand and CO2 - sequestration on the other hand seems to be an obvious and ideal solution. Different studies on possible methods - e.g. the exchange of CH4 with CO2 in gas hydrates (Lee et al, 2003, Graue and Kvamme, 2006) - have been published recently and demonstrated that this could be a possible way, in principle. Our own investigations on the exchange of CH4 with gaseous CO2 showed that this reaction is much too slow and inefficient to be a reasonable approach. The exchange of only 20 percent CH4 with CO2 could be detected in stable structure I hydrate crystals after 120 hours. In addition, multicomponent hydrates containing higher hydrocarbons beside methane tend to be more stable than pure methane hydrates (Schicks et al, 2006). Therefore, the application of an additional and controlled method for CH4 -hydrate destabilization seems to be necessary and might lead to an efficient release of CH4 from and CO2 inclusion into hydrates. In any case, the question of process optimization still remains. In this contribution the chances and challenges of a combination of these two processes based on experimental data will be examined. Different kinds of experiments have been performed on natural marine and permafrost gas hydrates and synthesized clathrate

  12. Methane and nitrous oxide emissions from three paddy rice based cultivation systems in Southwest China

    NASA Astrophysics Data System (ADS)

    Jiang, Changsheng; Wang, Yuesi; Zheng, Xunhua; Zhu, Bo; Huang, Yao; Hao, Qingju

    2006-05-01

    To understand methane (CH4) and nitrous oxide (N2O) emissions from permanently flooded rice paddy fields and to develop mitigation options, a field experiment was conducted in situ for two years (from late 2002 to early 2005) in three rice-based cultivation systems, which are a permanently flooded rice field cultivated with a single time and followed by a non-rice season (PF), a rice-wheat rotation system (RW) and a rice-rapeseed rotation system (RR) in a hilly area in Southwest China. The results showed that the total CH4 emissions from PF were 646.3±52.1 and 215.0±45.4 kg CH4 hm-2 during the rice-growing period and non-rice period, respectively. Both values were much lower than many previous reports from similar regions in Southwest China. The CH4 emissions in the rice-growing season were more intensive in PF, as compared to RW and RR. Only 33% of the total annual CH4 emission in PF occurred in the non-rice season, though the duration of this season is two times longer than the rice season. The annual mean N2O flux in PF was 4.5±0.6 kg N2O hm-2 yr-1. The N2O emission in the rice-growing season was also more intensive than in the non-rice season, with only 16% of the total annual emission occurring in the non-rice season. The amounts of N2O emission in PF were ignorable compared to the CH4 emission in terms of the global warming potential (GWP). Changing PF to RW or RR not only eliminated CH4 emissions in the non-rice season, but also substantially reduced the CH4 emission during the following rice-growing period (ca. 58%, P<0.05). However, this change in cultivation system substantially increased N2O emissions, especially in the non-rice season, by a factor of 3.7 to 4.5. On the 100-year horizon, the integrated GWP of total annual CH4 and N2O emissions satisfies PF≫RR≈RW. The GWP of PF is higher than that of RW and RR by a factor of 2.6 and 2.7, respectively. Of the total GWP of CH4 and N2O emissions, CH4 emission contributed to 93%, 65% and 59% in PF, RW

  13. Silicon nitride and silicon etching by CH{sub 3}F/O{sub 2} and CH{sub 3}F/CO{sub 2} plasma beams

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kaler, Sanbir S.; Lou, Qiaowei; Donnelly, Vincent M., E-mail: vmdonnelly@uh.edu

    2016-07-15

    Silicon nitride (SiN, where Si:N ≠ 1:1) films low pressure-chemical vapor deposited on Si substrates, Si films on Ge on Si substrates, and p-Si samples were exposed to plasma beams emanating from CH{sub 3}F/O{sub 2} or CH{sub 3}F/CO{sub 2} inductively coupled plasmas. Conditions within the plasma beam source were maintained at power of 300 W (1.9 W/cm{sup 3}), pressure of 10 mTorr, and total gas flow rate of 10 sccm. X-ray photoelectron spectroscopy was used to determine the thicknesses of Si/Ge in addition to hydrofluorocarbon polymer films formed at low %O{sub 2} or %CO{sub 2} addition on p-Si and SiN. Polymer film thickness decreasedmore » sharply as a function of increasing %O{sub 2} or %CO{sub 2} addition and dropped to monolayer thickness above the transition point (∼48% O{sub 2} or ∼75% CO{sub 2}) at which the polymer etchants (O and F) number densities in the plasma increased abruptly. The C(1s) spectra for the polymer films deposited on p-Si substrates appeared similar to those on SiN. Spectroscopic ellipsometry was used to measure the thickness of SiN films etched using the CH{sub 3}F/O{sub 2} and CH{sub 3}F/CO{sub 2} plasma beams. SiN etching rates peaked near 50% O{sub 2} addition and 73% CO{sub 2} addition. Faster etching rates were measured in CH{sub 3}F/CO{sub 2} than CH{sub 3}F/O{sub 2} plasmas above 70% O{sub 2} or CO{sub 2} addition. The etching of Si stopped after a loss of ∼3 nm, regardless of beam exposure time and %O{sub 2} or %CO{sub 2} addition, apparently due to plasma assisted oxidation of Si. An additional GeO{sub x}F{sub y} peak was observed at 32.5 eV in the Ge(3d) region, suggesting deep penetration of F into Si, under the conditions investigated.« less

  14. Methane and nitrous oxide emissions from livestock agriculture in 16 local administrative districts of Korea.

    PubMed

    Ji, Eun Sook; Park, Kyu-Hyun

    2012-12-01

    This study was conducted to evaluate methane (CH4) and nitrous oxide (N2O) emissions from livestock agriculture in 16 local administrative districts of Korea from 1990 to 2030. National Inventory Report used 3 yr averaged livestock population but this study used 1 yr livestock population to find yearly emission fluctuations. Extrapolation of the livestock population from 1990 to 2009 was used to forecast future livestock population from 2010 to 2030. Past (yr 1990 to 2009) and forecasted (yr 2010 to 2030) averaged enteric CH4 emissions and CH4 and N2O emissions from manure treatment were estimated. In the section of enteric fermentation, forecasted average CH4 emissions from 16 local administrative districts were estimated to increase by 4%-114% compared to that of the past except for Daejeon (-63%), Seoul (-36%) and Gyeonggi (-7%). As for manure treatment, forecasted average CH4 emissions from the 16 local administrative districts were estimated to increase by 3%-124% compared to past average except for Daejeon (-77%), Busan (-60%), Gwangju (-48%) and Seoul (-8%). For manure treatment, forecasted average N2O emissions from the 16 local administrative districts were estimated to increase by 10%-153% compared to past average CH4 emissions except for Daejeon (-60%), Seoul (-4.0%), and Gwangju (-0.2%). With the carbon dioxide equivalent emissions (CO2-Eq), forecasted average CO2-Eq from the 16 local administrative districts were estimated to increase by 31%-120% compared to past average CH4 emissions except Daejeon (-65%), Seoul (-24%), Busan (-18%), Gwangju (-8%) and Gyeonggi (-1%). The decreased CO2-Eq from 5 local administrative districts was only 34 kt, which was insignificantly small compared to increase of 2,809 kt from other 11 local administrative districts. Annual growth rates of enteric CH4 emissions, CH4 and N2O emissions from manure management in Korea from 1990 to 2009 were 1.7%, 2.6%, and 3.2%, respectively. The annual growth rate of total CO2-Eq was 2.2

  15. Development of methane and nitrous oxide emission factors for the biomass fired circulating fluidized bed combustion power plant.

    PubMed

    Cho, Chang-Sang; Sa, Jae-Hwan; Lim, Ki-Kyo; Youk, Tae-Mi; Kim, Seung-Jin; Lee, Seul-Ki; Jeon, Eui-Chan

    2012-01-01

    This study makes use of this distinction to analyze the exhaust gas concentration and fuel of the circulating fluidized bed (CFB) boiler that mainly uses wood biomass, and to develop the emission factors of Methane (CH(4)), Nitrous oxide (N(2)O). The fuels used as energy sources in the subject working sites are Wood Chip Fuel (WCF), RDF and Refused Plastic Fuel (RPF) of which heating values are 11.9 TJ/Gg, 17.1 TJ/Gg, and 31.2 TJ/Gg, respectively. The average concentrations of CH(4) and N(2)O were measured to be 2.78 ppm and 7.68 ppm, respectively. The analyzed values and data collected from the field survey were used to calculate the emission factor of CH(4) and N(2)O exhausted from the CFB boiler. As a result, the emission factors of CH(4) and N(2)O are 1.4 kg/TJ (0.9-1.9 kg/TJ) and 4.0 kg/TJ (2.9-5.3 kg/TJ) within a 95% confidence interval. Biomass combined with the combustion technology for the CFB boiler proved to be more effective in reducing the N(2)O emission, compared to the emission factor of the CFB boiler using fossil fuel.

  16. QUANTIFICATION OF METHANE EMISSIONS AND DISCUSSON OF NITROUS OXIDE, AND AMMONIA EMISSIONS FROM SEPTIC TANKS, LATRINES, AND STAGNANT OPEN SEWERS OF THE WORLD

    EPA Science Inventory

    The report gives results of a first attempt to estimate global and country-specific methane (CH4) emissons from sewers and on-site wastewater treatment systems, including latrines and septic sewage tanks. It follows a report that includes CH4 and nitrous oxide (N2O) estimates fro...

  17. Nitrous oxide and methane emissions following application of animal manures to grassland

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chadwick, D.R.; Pain, B.F.; Brookman, S.K.E.

    2000-02-01

    Nitrous oxide (N{sub 2}O) and methane (CH{sub 4}) emissions were measured from grassland following manure applications at three times of the year. Pig (Sus scrofa) slurry and dairy cow (Bos taurus) slurry were applied in April, at equal rates of ammoniacal-N (NH{sub 4}{sup +}-N), and in July, at equal volumetric rates (50 m{sup 3}ha{sup {minus}1}). In October, five manure types were applied to grassland plots at typical application rates: pig slurry, dilute diary cow effluent, pig farm yard manure (FYM), beef FYM and layer manure. Emissions were measured for 20, 22, and 24 d, respectively. In April, greater cumulative emissionsmore » of N{sub 2}O-N were measured following application of dairy cow slurry (1.51 kg ha{sup {minus}1}) than pig slurry (90.77 kg ha{sup {minus}1}). Cumulative CH{sub 4} emissions following application in April were significantly greater from the dairy cow slurry treatment (0.58 kg ha{sup {minus}1}) than the pig slurry treatment (0.13 kg ha{sup {minus}1}) (P < 0.05). In July, significantly greater N{sub 2}O-N emissions resulted from pig slurry-treated plots (0.57 kg ha{sup {minus}1}) than dairy cow slurry-treated plots (0.34 kg ha{sup {minus}1}). Cumulative net CH{sub 4} emissions were very low following July applications (<10 g ha{sup {minus}1}). In October, the lowest N{sub 2}O-N emission resulted from application of dilute dairy effluent, 0.15 kg ha{sup {minus}1}, with the greatest net emission from the application of pig slurry, 0.74 kg ha{sup {minus}1}. Methane emissions were greatest from the plots that received pig FYM, resulting in a mean cumulative net emission of 2.39 kg ha{sup {minus}1}.« less

  18. Physiology, biochemistry, and specific inhibitors of CH4, NH4+, and CO oxidation by methanotrophs and nitrifiers.

    PubMed Central

    Bédard, C; Knowles, R

    1989-01-01

    Ammonia oxidizers (family Nitrobacteraceae) and methanotrophs (family Methylococcaceae) oxidize CO and CH4 to CO2 and NH4+ to NO2-. However, the relative contributions of the two groups of organisms to the metabolism of CO, CH4, and NH4+ in various environments are not known. In the ammonia oxidizers, ammonia monooxygenase, the enzyme responsible for the conversion of NH4+ to NH2OH, also catalyzes the oxidation of CH4 to CH3OH. Ammonia monooxygenase also mediates the transformation of CH3OH to CO2 and cell carbon, but the pathway by which this is done is not known. At least one species of ammonia oxidizer, Nitrosococcus oceanus, exhibits a Km for CH4 oxidation similar to that of methanotrophs. However, the highest rate of CH4 oxidation recorded in an ammonia oxidizer is still five times lower than rates in methanotrophs, and ammonia oxidizers are apparently unable to grow on CH4. Methanotrophs oxidize NH4+ to NH2OH via methane monooxygenase and NH4+ to NH2OH via methane monooxygenase and NH2OH to NO2- via an NH2OH oxidase which may resemble the enzyme found in ammonia oxidizers. Maximum rates of NH4+ oxidation are considerably lower than in ammonia oxidizers, and the affinity for NH4+ is generally lower than in ammonia oxidizers. NH4+ does not apparently support growth in methanotrophs. Both ammonia monooxygenase and methane monooxygenase oxidize CO to CO2, but CO cannot support growth in either ammonia oxidizers or methanotrophs. These organisms have affinities for CO which are comparable to those for their growth substrates and often higher than those in carboxydobacteria. The methane monooxygenases of methanotrophs exist in two forms: a soluble form and a particulate form. The soluble form is well characterized and appears unrelated to the particulate. Ammonia monooxygenase and the particulate methane monooxygenase share a number of similarities. Both enzymes contain copper and are membrane bound. They oxidize a variety of inorganic and organic compounds, and

  19. Radial Microchannel Reactor (RMR) used in Steam Reforming CH4

    DTIC Science & Technology

    2013-05-13

    process on land and at sea will reduce CO2 emission and enable cost reductions in the generation of energy in many small market economies. Peter R...size of GTL process on land and at sea will reduce CO2 emission and enable cost reductions in the generation of energy in many small market ...distribution of a 3.3:1 steam-methane mixture at 750 °C and 11 bar is: H2 45.8%, H2O 36.99%, CO 6.365%, CO2 6.681% and CH4 4.14% Barring any coking , this

  20. Electric conductivity analysis and dielectric relaxation behavior of the hybrid polyvanadate (H{sub 3}N(CH{sub 2}){sub 3}NH{sub 3})[V{sub 4}O{sub 10}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nefzi, H.; Sediri, F., E-mail: faouzi.sediri@ipeit.rnu.tn; Faculté des Sciences de Tunis, Université Tunis El Manar, 2092 El Manar, Tunis

    2013-05-15

    Highlights: ► Plate-like crystals (H{sub 3}N(CH{sub 2}){sub 3}NH{sub 3})[V{sub 4}O{sub 10}] were synthesized. ► Frequency and temperature dependence of AC conductivity indicate CBH model. ► The temperature dependence of DC conductivity exhibits two conduction mechanisms. - Abstract: Layered hybrid compound (H{sub 3}N(CH{sub 2}){sub 3}NH{sub 3})[V{sub 4}O{sub 10}] has been synthesized via hydrothermal method. Techniques X-ray powder diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and impedance spectroscopy have been used to characterize the hybrid material. Electrical and dielectric properties dependence on both temperature and frequency of the compound have been reported. The direct current conductivity process is thermally activated andmore » it is found to be 12.67 × 10{sup −4} Ω{sup −1} m{sup −1} at 523 K. The spectra follow the Arrhenius law with two activation energy 0.25 eV for T < 455 K and 0.5 eV for T > 455 K.« less

  1. Hydrogen bonding in microsolvation: photoelectron imaging and theoretical studies on Au(x)(-)-(H2O)(n) and Au(x)(-)-(CH3OH)(n) (x = 1, 2; n = 1, 2) complexes.

    PubMed

    Wu, Xia; Tan, Kai; Tang, Zichao; Lu, Xin

    2014-03-14

    We have combined photoelectron velocity-map imaging (VMI) spectroscopy and theoretical calculations to elucidate the geometry and energy properties of Aux(-)(Solv)n clusters with x = 1, 2; n = 1, 2; and Solv = H2O and CH3OH. Besides the blue-shifted vertical electron detachment energies (VDEs) of the complexes Au1,2(-)(Solv)n with the increase of the solvation number (n), we independently probed two distinct Au(-)(CH3OH)2 isomers, which combined with MP2/aug-cc-pVTZ(pp) calculations represent a competition between O···H-O hydrogen bonds (HBs) and Au···H-O nonconventional hydrogen bonds (NHBs). Complementary calculations provide the total binding energies of the low-energy isomers. Moreover, the relationship between the total binding energies and total VDEshift is discussed. We found that the Au1,2(-) anions exhibit halide-analogous behavior in microsolvation. These findings also demonstrate that photoelectron velocity map imaging spectroscopy with the aid of the ab initio calculations is an effective tool for investigating weak-interaction complexes.

  2. Atmospheric CH 4 and H 2 O Monitoring With Near-Infrared InGaAs Laser Diodes by the SDLA, a Balloonborne Spectrometer for Tropospheric and Stratospheric In Situ Measurements

    NASA Astrophysics Data System (ADS)

    Durry, Georges; Megie, Gerard

    1999-12-01

    The Spectrom tre Diodes Laser Accordables (SDLA), a balloonborne spectrometer devoted to the in situ measurement of CH 4 and H 2 O in the atmosphere that uses commercial distributed-feedback InGaAs laser diodes in combination with differential absorption spectroscopy, is described. Absorption spectra of CH 4 (in the 1.653- m region) and H 2 O (in the 1.393- m region) are simultaneously sampled at 1-s intervals by coupling with optical fibers of two near-infrared laser diodes to a Herriott multipass cell open to the atmosphere. Spectra of methane and water vapor in an altitude range of 1 to 31 km recorded during the recent balloon flights of the SDLA are presented. Mixing ratios with a precision error ranging from 5% to 10% are retrieved from the atmospheric spectra by a nonlinear least-squares fit to the spectral line shape in conjunction with in situ simultaneous pressure and temperature measurements.

  3. Remote sensing of methane and nitrous oxide fluxes from waste incineration.

    PubMed

    Gålfalk, Magnus; Bastviken, David

    2018-05-01

    Incomplete combustion processes lead to the formation of many gaseous byproducts that can be challenging to monitor in flue gas released via chimneys. This study presents ground-based remote sensing approaches to make greenhouse gas (GHG) flux measurements of methane (CH 4 ) and nitrous oxide (N 2 O) from a waste incineration chimney at distances of 150-200 m. The study found emission of N 2 O (corresponding to 30-40 t yr -1 ), which is a consequence of adding the reduction agent urea to decrease NO X emissions due to NO X regulation; a procedure that instead increases N 2 O emissions (which is approximately 300 times more potent as a GHG than CO 2 on a 100-year time scale). CH 4 emissions of 7-11 t yr -1 was also detected from the studied chimney despite the usage of a high incineration temperature. For this particular plant, local knowledge is high and emission estimates at corresponding levels have been reported previously. However, emissions of CH 4 are often not included in GHG emission inventories for waste incineration. This study highlights the importance of monitoring combustion processes, and shows the possibility of surveying CH 4 and N 2 O emissions from waste incineration at distances of several hundred meters. Copyright © 2018 Elsevier Ltd. All rights reserved.

  4. An empirical equation with tables of smoothed solubilities of methane in water and aqueous sodium chloride solutions up to 25 weight percent, 360 degrees C, and 138 MPa

    USGS Publications Warehouse

    Haas, John L.

    1978-01-01

    The total pressure for the system H2O-CH 4 is given by p(total) = P(H2O,t) + exp10[log x(CH 4) - a - b x(CH4)], where P(H2O,t) is the vapor pressure of H2O liquid at the temperature t (?C) and x(CH 4) is the molal concentration of methane in the solution. The terms a and b are functions of temperature only. Where the total pressure and temperature are known, the concentration of methane, x(CH4), is found by iteration. The concentration of methane in a sodium chloride brine, y(CH4), is estimated using the function log y(CH4) = log x(CH4) - A I, where A is the salting out constant and I is the ionic strength. For sodium chloride solutions, the ionic strength is equal to the molality of the salt. The equations are valid to 360?C, 138 MPa, and 25 weight percent sodium chloride.

  5. The variability of methane, nitrous oxide and sulfur hexafluoride in Northeast India

    NASA Astrophysics Data System (ADS)

    Ganesan, A. L.; Chatterjee, A.; Prinn, R. G.; Harth, C. M.; Salameh, P. K.; Manning, A. J.; Hall, B. D.; Mühle, J.; Meredith, L. K.; Weiss, R. F.; O'Doherty, S.; Young, D.

    2013-06-01

    High-frequency atmospheric measurements of methane (CH4), nitrous oxide (N2O) and sulfur hexafluoride (SF6) from Darjeeling, India are presented from December 2011 (CH4)/March 2012 (N2O and SF6) through February 2013. These measurements were made on a gas chromatograph equipped with a flame ionization detector and electron capture detector and were calibrated on the Tohoku University, the Scripps Institution of Oceanography (SIO)-98 and SIO-2005 scales for CH4, N2O and SF6, respectively. The observations show large variability and frequent pollution events in CH4 and N2O mole fractions, suggesting significant sources in the regions sampled by Darjeeling throughout the year. In contrast, SF6 mole fractions show little variability and only occasional pollution episodes, likely due to weak sources in the region. Simulations using the Numerical Atmospheric dispersion Modelling Environment (NAME) particle dispersion model suggest that many of the enhancements in the three gases result from the transport of pollutants from the densely populated Indo-Gangetic plains of India to Darjeeling. The meteorology of the region varies considerably throughout the year from Himalayan flows in the winter to the strong South Asian summer monsoon. The model is consistent in simulating a diurnal cycle in CH4 and N2O mole fractions that is present during the winter but absent in the summer and suggests that the signals measured at Darjeeling are dominated by large scale (~100 km) flows rather than local (<10 km) flows.

  6. The variability of methane, nitrous oxide and sulfur hexafluoride in Northeast India

    NASA Astrophysics Data System (ADS)

    Ganesan, A. L.; Chatterjee, A.; Prinn, R. G.; Harth, C. M.; Salameh, P. K.; Manning, A. J.; Hall, B. D.; Mühle, J.; Meredith, L. K.; Weiss, R. F.; O'Doherty, S.; Young, D.

    2013-11-01

    High-frequency atmospheric measurements of methane (CH4), nitrous oxide (N2O) and sulfur hexafluoride (SF6) from Darjeeling, India are presented from December 2011 (CH4)/March 2012 (N2O and SF6) through February 2013. These measurements were made on a gas chromatograph equipped with a flame ionization detector and electron capture detector, and were calibrated on the Tohoku University, the Scripps Institution of Oceanography (SIO)-98 and SIO-2005 scales for CH4, N2O and SF6, respectively. The observations show large variability and frequent pollution events in CH4 and N2O mole fractions, suggesting significant sources in the regions sampled by Darjeeling throughout the year. By contrast, SF6 mole fractions show little variability and only occasional pollution episodes, likely due to weak sources in the region. Simulations using the Numerical Atmospheric dispersion Modelling Environment (NAME) particle dispersion model suggest that many of the enhancements in the three gases result from the transport of pollutants from the densely populated Indo-Gangetic Plains of India to Darjeeling. The meteorology of the region varies considerably throughout the year from Himalayan flows in the winter to the strong south Asian summer monsoon. The model is consistent in simulating a diurnal cycle in CH4 and N2O mole fractions that is present during the winter but absent in the summer and suggests that the signals measured at Darjeeling are dominated by large-scale (~100 km) flows rather than local (<10 km) flows.

  7. Strong intramolecular Si-N interactions in the chlorosilanes Cl3-nHnSiOCH2CH2NMe2 (n = 1-3).

    PubMed

    Hagemann, Michael; Mix, Andreas; Berger, Raphael J F; Pape, Tania; Mitzel, Norbert W

    2008-11-17

    The compounds Cl 3SiOCH 2CH 2NMe 2 ( 1) and Cl 2HSiOCH 2CH 2NMe 2 ( 2) were prepared by reactions of lithium 2-(dimethylamino)ethanolate with SiCl 4 and HSiCl 3. The analogous reaction with H 2SiCl 2 gave ClH 2SiOCH 2CH 2NMe 2 ( 3), but only in a mixture with Cl 2HSiOCH 2CH 2NMe 2 ( 2), from which it could not be separated. All compounds were characterized by IR and NMR ( (1)H, (13)C, (29)Si) spectroscopy, 1 and 2 by elemental analyses and by determination of their crystal structures. Cl 3SiOCH 2CH 2NMe 2 ( 1) and Cl 2HSiOCH 2CH 2NMe 2 ( 2) crystallize as monomeric ring compounds with pentacoordinate silicon atoms participating in intramolecular Si-N bonds [2.060(2) A ( 1), 2.037(2) A ( 2)]. The dative bonds in 1 and 2 between the silicon and nitrogen atoms could also be proven to exist at low temperatures in solution in (1)H, (29)Si-HMBC-NMR experiments by detection of the scalar coupling between the (29)Si and the protons of the NCH 2 and NCH 3 groups. A function describing the chemical shift delta exp (29)Si dependent on the chemical shifts of the individual equilibrium components, the temperature, and the free enthalpy of reaction was worked out and fitted to the experimental VT-NMR data of 1 and 2. This provided values of the free reaction enthalpies of Delta G = -28.8 +/- 3.9 kJ x mol (-1) for 1 and Delta G = -22.3 +/- 0.4 kJ x mol (-1) for 2 and estimates for the chemical shifts of open-chain (index o) and ring conformers (index r) for 1 of delta r = -94 +/- 2 ppm and delta o = -36 +/- 5 ppm and for 2 of delta r = -82 +/- 1 ppm and delta o = -33 +/- 4 ppm. The value of delta r for 1 is very close to that obtained from a solid-state (29)Si MAS NMR spectrum. Quantumchemical calculations (up to MP2/TZVPP) gave largely differing geometries for 1 (with a Si...N distance of 3.072 A), but well reproduced the geometry of 2. These differences are due to Cl...H and Cl...C repulsions and solid state effects, which can be modeled by conductor-like screening model

  8. Ultra-Smooth Nanostructured Diamond Films Deposited from He/H2/CH4/N2 Microwave Plasmas

    PubMed Central

    Konovalov, Valery V.; Melo, Andrew; Catledge, Shane A.; Chowdhury, Shafiul

    2008-01-01

    Addition of He to a high CH4 content (10.7 vol%) H2/CH4/N2 feedgas mixture for microwave plasma chemical vapor deposition produced hard (56–72 GPa), ultra-smooth nanostructured diamond films on Ti-6Al-4V alloy substrates. Upon increase in He content up to 71 vol%, root mean squared (RMS) surface roughness of the film decreased to 9–10 nm and average diamond grain size to 5–6 nm. Our studies show that increased nanocrystallinity with He addition in plasma is related to plasma dilution, enhanced fragmentation of carbon containing species, and enhanced formation of CN radical. PMID:16573106

  9. Nitrous oxide and methane dynamics in a coral reef lagoon driven by pore water exchange: Insights from automated high-frequency observations

    NASA Astrophysics Data System (ADS)

    O'Reilly, Chiara; Santos, Isaac R.; Cyronak, Tyler; McMahon, Ashly; Maher, Damien T.

    2015-04-01

    Automated cavity ring down spectroscopy was used to make continuous measurements of dissolved methane, nitrous oxide, and carbon dioxide in a coral reef lagoon for 2 weeks (Heron Island, Great Barrier Reef). Radon (222Rn) was used to trace the influence of tidally driven pore water exchange on greenhouse gas dynamics. Clear tidal variation was observed for CH4, which correlated to 222Rn in lagoon waters. N2O correlated to 222Rn during the day only, which appears to be a response to coupled nitrification-denitrification in oxic sediments, fueled by nitrate derived from bird guano. The lagoon was a net source of CH4 and N2O to the atmosphere and a sink for atmospheric CO2. The estimated pore water-derived CH4 and N2O fluxes were 3.2-fold and 24.0-fold greater than the fluxes to the atmosphere. Overall, pore water and/or groundwater exchange were the only important sources of CH4 and major controls of N2O in the coral reef lagoon.

  10. Infrared spectroscopy of water clusters isolated in methane matrices: Effects of isotope substitution and annealing

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yamakawa, Koichiro, E-mail: koichiro.yamakawa@gakushuin.ac.jp; Ehara, Namika; Ozawa, Nozomi

    2016-07-15

    Using infrared-active solvents of CH{sub 4} and CD{sub 4} for matrix isolation, we measured infrared spectra of H{sub 2}O and D{sub 2}O clusters at 7 K. The solute-concentration dependence of the spectrum of H{sub 2}O clusters in a CH{sub 4} matrix was investigated and was used for the peak assignment. Annealing procedures were found to promote the size growth of water clusters in methane matrices for all the combinations of (H{sub 2}O, CH{sub 4}), (H{sub 2}O, CD{sub 4}), (D{sub 2}O, CH{sub 4}), and (D{sub 2}O, CD{sub 4}). We also monitored the ν{sub 3} absorption due to methane to find themore » annealing-induced structural change only of solid CH{sub 4}. The matrix effects on the vibrations of the clusters are discussed on the basis of “T{sub c} plots”, where their frequencies are plotted as a function of the square root of the matrix critical temperature, T{sub c}. The obtained plots assure the validity of the assignment of the cluster peaks.« less

  11. A new method for CH3O2 and C2H5O2 radical detection and kinetic studies of the CH3O2 self-reaction in HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry)

    NASA Astrophysics Data System (ADS)

    Onel, L. C.; Brennan, A.; Ingham, T.; Kirk, D.; Leggott, A.; Seakins, P. W.; Whalley, L.; Heard, D. E.

    2016-12-01

    Peroxy (RO2) radicals such as methylperoxy (CH3O2) and ethylperoxy (C2H5O2) are significant atmospheric species in the ozone formation in the presence of NO. At low concentrations of NO, the self-reaction of RO2 and RO2 + HO2 are important radical termination reactions. Despite their importance, at present typically only the sum of RO2 is measured in the atmosphere, making no distinction between different RO2 species.A new method has been developed for the direct detection of CH3O2 and C2H5O2 by FAGE (Fluorescence Assay by Gas Expansion) by titrating the peroxy radicals to RO (R = CH3 and C2H5) by reaction with NO and then detecting the resultant RO by laser induced fluorescence. The method has the potential to directly measure atmospheric levels of CH3O2 and potentially other RO2 species. The limit of detection is 3.8 × 108 molecule cm-3 for CH3O2 and 4.9 × 109 molecule cm-3 for C2H5O2 for a signal-to-noise ratio of 2 and a 4 min averaging time. The method has been used for time-resolved monitoring of CH3O2 during its self-reaction within HIRAC at 1 bar and at room temperature to determine a rate coefficient that is lower than the range of the previous results obtained by UV absorption measurements (http://iupac.pole-ether.fr/). A range of products of the CH3O2 self-reaction were also observed for the two reaction channels, (a) leading to formaldehyde and methanol and (b) forming methoxy (CH3O) radicals, over a range of temperatures from 296 - 340 K: CH3O and HO2 radicals (from reaction of CH3O + O2) were monitored by FAGE, formaldehyde was measured by FAGE and FTIR, and methanol was observed by FTIR. Good agreement was observed between the FTIR and FAGE measurements of formaldehyde. Using the concentrations of methanol and formaldehyde, the branching ratios at room temperature have been determined and are in very good agreement with the values recommended by IUPAC. Little temperature dependence of the branching ratios has been observed from 296 K to 340 K.

  12. Fluid inclusion volatile analysis by gas chromatography with photoionization micro-thermal conductivity detectors: Applications to magmatic MoS 2 and other H 2O-CO 2 and H 2O-CH 4 fluids

    NASA Astrophysics Data System (ADS)

    Bray, C. J.; Spooner, E. T. C.

    1992-01-01

    Eighteen fluid inclusion volatile peaks have been detected and identified from 1-2 g samples (quartz) by gas chromatography using heated (~105°C) on-line crushing, helium carrier gas, a single porous polymer column (HayeSep R; 10' × 1/8″: 100/120#; Ni alloy tubing), two temperature programme conditions for separate sample aliquots, micro-thermal conductivity (TCD) and photoionization detectors (PID; 11.7 eV lamp), and off-line digital peak processing. In order of retention time these volatile peaks are: N 2, Ar, CO, CH 4, CO 2, C 2H 4, C 2H 6, C 2H 2, COS, C 3H 6, C 3H 8, C 3H 4 (propyne), H 2O (22.7 min at 80°C), SO 2, ± iso- C4H10 ± C4H8 (1-butene) ± CH3SH, C 4H 8 (iso-butylene), (?) C 4H 6 (1,3 butadiene) and ± n- C4H10 ± C4H8 (trans-2-butene) (80 and -70°C temperature programme conditions combined). H 2O is analysed directly. O 2 can be analysed cryogenically between N 2 and Ar, but has not been detected in natural samples to date in this study. H 2S, SO 2, NH 3, HCl, HCN, and H 2 ca nnot be analysed at present. Blanks determined by crushing heat-treated Brazilian quartz (800-900°C/4 h) are zero for 80°C temperature programme conditions, except for a large, unidentified peak at ~64 min, but contain H 2O, CO 2, and some low molecular weight hydrocarbons at -70°C temperature conditions due to cryogenic accumulation from the carrier gas and subsequent elution. TCD detection limits are ~30 ppm molar in inclusions; PID detection limits are ~ 1 ppm molar in inclusions and lower for unsaturated hydrocarbons (e.g., ~0.2 ppm for C 2H 4; ~ 1 ppb for C 2H 2; ~0.3 ppb for C 3H 6). Precisions (1σ) are ~ ±1-2% and ~ ± 13% for H 2O in terms of total moles detected; the latter value is equivalent to ±0.6 mol% at the 95 mol% H 2O level. Major fluid inclusion volatile species have been successfully analysed on a ~50 mg fluid inclusion section chip (~7 mm × ~10 mm × ~100 μm). Initial inclusion volatile analyses of fluids of interpreted magmatic origin from

  13. A comparative DFT study of interactions of Au and small gold clusters Aun (n = 2-4) with CH3S and CH2 radicals

    NASA Astrophysics Data System (ADS)

    Blaško, Martin; Rajský, Tomáš; Urban, Miroslav

    2017-03-01

    We compare DFT binding energies (BEs) of Au and small gold clusters interacting with CH3S and CH2 ligands (Aun-L complexes, n = 1-4). The spin state and the binding mechanism in Aun-L varies with the participation of singly occupied non-bonding orbitals or doubly occupied lone-pair orbitals of a ligand and on the number of atoms (even or odd) of Aun. The highest BE, 354 kJ/mol, exhibits the Au3-CH2 complex with the covalent bond in which participate two singly occupied orbitals of the triplet state of CH2. With CH3S the highest BE (277 kJ/mol) is calculated for Au3-SCH3 with the single Au-S bond.

  14. A flux-gradient system for simultaneous measurement of the CH4, CO2, and H2O fluxes at a lake-air interface.

    PubMed

    Xiao, Wei; Liu, Shoudong; Li, Hanchao; Xiao, Qitao; Wang, Wei; Hu, Zhenghua; Hu, Cheng; Gao, Yunqiu; Shen, Jing; Zhao, Xiaoyan; Zhang, Mi; Lee, Xuhui

    2014-12-16

    Inland lakes play important roles in water and greenhouse gas cycling in the environment. This study aims to test the performance of a flux-gradient system for simultaneous measurement of the fluxes of water vapor, CO2, and CH4 at a lake-air interface. The concentration gradients over the water surface were measured with an analyzer based on the wavelength-scanned cavity ring-down spectroscopy technology, and the eddy diffusivity was measured with a sonic anemometer. Results of a zero-gradient test indicate a flux measurement precision of 4.8 W m(-2) for water vapor, 0.010 mg m(-2) s(-1) for CO2, and 0.029 μg m(-2) s(-1) for CH4. During the 620 day measurement period, 97%, 69%, and 67% of H2O, CO2, and CH4 hourly fluxes were higher in magnitude than the measurement precision, which confirms that the flux-gradient system had adequate precision for the measurement of the lake-air exchanges. This study illustrates four strengths of the flux-gradient method: (1) the ability to simultaneously measure the flux of H2O, CO2, and CH4; (2) negligibly small density corrections; (3) the ability to resolve small CH4 gradient and flux; and (4) continuous and noninvasive operation. The annual mean CH4 flux (1.8 g CH4 m(-2) year(-1)) at this hypereutrophic lake was close to the median value for inland lakes in the world (1.6 g CH4 m(-2) year(-1)). The system has adequate precision for CH4 flux for broad applications but requires further improvement to resolve small CO2 flux in many lakes.

  15. Photocatalytic reduction of CO2 with H2O to CH4 on Cu(I) supported TiO2 nanosheets with defective {001} facets.

    PubMed

    Zhu, Shuying; Liang, Shijing; Tong, Yuecong; An, Xiaohan; Long, Jinlin; Fu, Xianzhi; Wang, Xuxu

    2015-04-21

    Highly dispersed Cu2O clusters loaded on TiO2 nanosheets with dominant exposed {001} facets are prepared by a hydrothermal treatment followed by photodeposition. The physicochemical properties of the as-prepared samples are characterized carefully. The deposition position and chemical state of the Cu2O clusters are characterized by X-ray diffraction, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, EPR spectroscopy, and in situ CO-adsorbed FTIR spectroscopy, respectively. The results show that in situ Cu deposition leads to in situ formation of abundant oxygen vacancies (Vo) on the surface of the TiO2 nanosheets. Interestingly, the co-existence of Vo and Cu2O clusters could promote the photoactivity of CO2 reduction efficiently. The surface Vo play a significant role in the reduction of CO2. Meanwhile, the deposited Cu(I) species serve also as active sites for the formation of CH4, and then protect CH4 from degradation by generated oxidation species. For the photoreduction of CO2 to CH4, it is found that the content level of Cu2O has a significant influence on the activity. Cu-TiO2-1.0 shows the highest photocatalytic activity, which is over 30 times higher than that of the parent TiO2. This great enhancement of photocatalytic activity may be contributed by high CO2 adsorption capacity, high electron mobility, and high concentration of Vo. However, the effect of the surface area of the samples on the activity is negligible. All of this evidence is obtained by CO2-sorption, electrochemistry, in situ FTIR spectroscopy, in situ ERP techniques, etc. The reaction intermediates are detected by in situ FTIR spectroscopy. Finally, a probable mechanism is proposed based on the experimental results. It is hoped that our work could render one of the most effective strategies to achieve advanced properties over photofunctional materials for solar energy conversion of CO2.

  16. Crystal structure of aqua-1κO-{μ-2-[(2-hydroxy­ethyl)methylamino]ethanolato-2:1κ4 O 1,N,O 2:O 1}[μ-2,2′-(methylimino)diethanolato-1:2κ4 O,N,O′:O]dithiocyanato-1κN,2κN-chromium(III)copper(II)

    PubMed Central

    Rusanova, Julia A.; Semenaka, Valentina V.; Dyakonenko, Viktoriya V.; Shishkin, Oleg V.

    2015-01-01

    The title compound, [CrCu(C5H11NO2)(C5H12NO2)(NCS)2(H2O)] or [Cr(μ-mdea)Cu(μ-Hmdea)(NCS)2H2O], (where mdeaH2 is N-methylethanolamine, C5H13NO2) is formed as a neutral heterometal CuII/CrIII complex. The mol­ecular structure of the complex is based on a binuclear {CuCr(μ-O)2} core. The coordination environment of each metal atom involves the N,O,O atoms of the tridentate ligand, one bridging O atom of the ligand and the N atom of the thio­cyanato ligands. The CuII ion adopts a distorted square-pyramidal coordination while the CrIII ion has a distorted octa­hedral coordination geometry completed by the aqua ligand. In the crystal, the binuclear complexes are linked via two pairs of O—H⋯O hydrogen bonds to form inversion dimers, which are arranged in columns parallel to the a axis. In the μ-mdea ligand two –CH2 groups and the methyl group were refined as disordered over two sets of sites with equal occupancies. The structure was refined as a two-component twin with a twin scale factor of 0.242 (1). PMID:26396853

  17. A post-new horizons global climate model of Pluto including the N2, CH4 and CO cycles

    NASA Astrophysics Data System (ADS)

    Forget, F.; Bertrand, T.; Vangvichith, M.; Leconte, J.; Millour, E.; Lellouch, E.

    2017-05-01

    We have built a new 3D Global Climate Model (GCM) to simulate Pluto as observed by New Horizons in 2015. All key processes are parametrized on the basis of theoretical equations, including atmospheric dynamics and transport, turbulence, radiative transfer, molecular conduction, as well as phases changes for N2, CH2 and CO. Pluto's climate and ice cycles are found to be very sensitive to model parameters and initial states. Nevertheless, a reference simulation is designed by running a fast, reduced version of the GCM with simplified atmospheric transport for 40,000 Earth years to initialize the surface ice distribution and sub-surface temperatures, from which a 28-Earth-year full GCM simulation is performed. Assuming a topographic depression in a Sputnik-planum (SP)-like crater on the anti-Charon hemisphere, a realistic Pluto is obtained, with most N2 and CO ices accumulated in the crater, methane frost covering both hemispheres except for the equatorial regions, and a surface pressure near 1.1 Pa in 2015 with an increase between 1988 and 2015, as reported from stellar occultations. Temperature profiles are in qualitative agreement with the observations. In particular, a cold atmospheric layer is obtained in the lowest kilometers above Sputnik Planum, as observed by New Horizons's REX experiment. It is shown to result from the combined effect of the topographic depression and N2 daytime sublimation. In the reference simulation with surface N2 ice exclusively present in Sputnik Planum, the global circulation is only forced by radiative heating gradients and remains relatively weak. Surface winds are locally induced by topography slopes and by N2 condensation and sublimation around Sputnik Planum. However, the circulation can be more intense depending on the exact distribution of surface N2 frost. This is illustrated in an alternative simulation with N2 condensing in the South Polar regions and N2 frost covering latitudes between 35°N and 48°N. A global condensation

  18. Nitrogen Incorporation in CH4-N2 Photochemical Aerosol Produced by Far UV Irradiation

    NASA Technical Reports Server (NTRS)

    Trainer, Melissa G.; Jimenez, Jose L.; Yung, Yuk L.; Toon, Owen B.; Tolbert, Margaret A.

    2012-01-01

    Nitrile incorporation into Titan aerosol accompanying hydrocarbon chemistry is thought to be driven by extreme UV wavelengths (lambda < 120 nm) or magnetospheric electrons in the outer reaches of the atmosphere. Far UV radiation (120 - 200 nm), which is transmitted down to the stratosphere of Titan, is expected to affect hydrocarbon chemistry only and not initiate the formation of nitrogenated species. We have examined the chemical properties of photochemical aerosol produced at far UV wavelengths using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS), which allows for elemental analysis of particle-phase products. Our results show that aerosol formed from CH4/N2 photochemistry contains a surprising amount of nitrogen, up to 16% by mass, a result of photolysis in the far UV. The proportion of nitrogenated organics to hydrocarbon species is shown to be correlated with that of N2 in the irradiated gas. The aerosol mass greatly decreases when N2 is removed, indicating that N2 plays a major role in aerosol production. Because direct dissociation of N2 is highly improbable given the immeasurably low cross-section at the wavelengths studied, the chemical activation of N2 must occur via another pathway. Any chemical activation of N2 at wavelengths > 120 nm is presently unaccounted for in atmospheric photochemical models. We suggest that reaction with CH radicals produced from CH4 photolysis may provide a mechanism for incorporating N into the molecular structure of the aerosol. Further work is needed to understand the chemistry involved, as these processes may have significant implications for prebiotic chemistry on the early Earth and similar planets.

  19. Species and temperature measurements of methane oxidation in a nanosecond repetitively pulsed discharge

    PubMed Central

    Lefkowitz, Joseph K; Guo, Peng; Rousso, Aric; Ju, Yiguang

    2015-01-01

    Speciation and temperature measurements of methane oxidation during a nanosecond repetitively pulsed discharge in a low-temperature flow reactor have been performed. Measurements of temperature and formaldehyde during a burst of pulses were made on a time-dependent basis using tunable diode laser absorption spectroscopy, and measurements of all other major stable species were made downstream of a continuously pulsed discharge using gas chromatography. The major species for a stoichiometric methane/oxygen/helium mixture with 75% dilution are H2O, CO, CO2, H2, CH2O, CH3OH, C2H6, C2H4 and C2H2. A modelling tool to simulate homogeneous plasma combustion kinetics is assembled by combining the ZDPlasKin and CHEMKIN codes. In addition, a kinetic model for plasma-assisted combustion (HP-Mech/plasma) of methane, oxygen and helium mixtures has been assembled to simulate the measurements. Predictions can accurately capture reactant consumption as well as production of the major product species. However, significant disagreement is found for minor species, particularly CH2O and CH3OH. Further analysis revealed that the plasma-activated low-temperature oxidation pathways, particularly those involving CH3O2 radical reactions and methane reactions with O(1D), are responsible for this disagreement. PMID:26170433

  20. Dynamic Oxygen on Surface: Catalytic Intermediate and Coking Barrier in the Modeled CO 2 Reforming of CH 4 on Ni (111)

    DOE PAGES

    Yuan, Kaidi; Zhong, Jian-Qiang; Zhou, Xiong; ...

    2016-06-08

    We identify Ni-O phases as important intermediates in a model dry (CO 2) reforming of methane catalyzed by Ni (111), based on results from in operando near ambient X-ray photoelectron spectroscopy (NAP-XPS), low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). We find that under a CO 2 or CO 2-CH 4 atmosphere, the Ni-O phases exist as p(2×2) structured chemisorbed oxygen (Chem-O), epitaxial NiO (111), or oxygen-rich Ni xO y (x2O 3), depending on the chemical potential. The growth rates of the Ni-O phases have a negative correlation with temperature from 600 K to 900 K, proving thatmore » their dynamic concentrations in the reaction are not limited by CO 2 activation, but by their thermal stability. Between 300 K and 800 K (1:1 CH 4 and CO 2 mixture), oxidation by CO 2is dominant, resulting in a fully Ni-O covered surface. Between 800 K and 900 K, a partially oxidized Ni (111) exists which could greatly facilitate the effective conversion of CH 4. As CH 4 is activation-limited and dissociates mainly on metallic nickel, the released carbon species can quickly react with the adjacent oxygen (Ni-O phases) to form CO. After combining with carbon and releasing CO molecules, the Ni-O phases can be further regenerated through oxidation by CO 2. In this way, the Ni-O phases participate in the catalytic process, acting as an intermediate in addition to the previously reported Ni-C phases. We also reveal the carbon phobic property of the Ni-O phases, which links to the intrinsic coking resistance of the catalysts. The low dynamic coverage of surface oxygen at higher temperatures (>900 K) is inferred to be an underlying factor causing carbon aggregation. Therefore solutions based on Ni-O stabilization are proposed in developing coking resisting catalysts.« less

  1. Simultaneous atmospheric nitrous oxide, methane and water vapor detection with a single continuous wave quantum cascade laser.

    PubMed

    Cao, Yingchun; Sanchez, Nancy P; Jiang, Wenzhe; Griffin, Robert J; Xie, Feng; Hughes, Lawrence C; Zah, Chung-en; Tittel, Frank K

    2015-02-09

    A continuous wave (CW) quantum cascade laser (QCL) based absorption sensor system was demonstrated and developed for simultaneous detection of atmospheric nitrous oxide (N(2)O), methane (CH(4)), and water vapor (H(2)O). A 7.73-µm CW QCL with its wavelength scanned over a spectral range of 1296.9-1297.6 cm(-1) was used to simultaneously target three neighboring strong absorption lines, N(2)O at 1297.05 cm(-1), CH(4) at 1297.486 cm(-1), and H(2)O at 1297.184 cm(-1). An astigmatic multipass Herriott cell with a 76-m path length was utilized for laser based gas absorption spectroscopy at an optimum pressure of 100 Torr. Wavelength modulation and second harmonic detection was employed for data processing. Minimum detection limits (MDLs) of 1.7 ppb for N(2)O, 8.5 ppb for CH(4), and 11 ppm for H(2)O were achieved with a 2-s integration time for individual gas detection. This single QCL based multi-gas detection system possesses applications in environmental monitoring and breath analysis.

  2. Simultaneous in situ measurements and diurnal variations of NO, NO2, O3, jNO2, CH4, H2O, and CO2 in the 40- to 26-km region using an open path tunable diode laser spectrometer

    NASA Technical Reports Server (NTRS)

    Webster, Christopher R.; May, Randy D.

    1987-01-01

    Simultaneous in situ measurements of temperature, pressure, and the NO, NO2, O3, jNO2, CH4, H2O, and CO2 concentrations were conducted in the 40- to 26-km region of the stratosphere using the JPL Balloon-borne Laser In Situ Sensor, a tunable diode laser absorption spectrometer. The NO, NO2, CH4, H2O, and CO2 concentration measurements generally show good agreement with previous observations, with a tendency for somewhat lower NO2 amounts. Measured O3 concentrations at 38 km agree well with comparable measurements from in situ UV photometers, but at 28 km they are lower by about 10 percent and agree more closely with the solar backscattered UV data. A decline was found in NO2 during the night over a 5-km altitude range, which implies either lower NO2 postsunset profiles, or an NO2 decay rate that is significantly higher than current model predictions that use N2O5 chemistry.

  3. Thermal regulation of methane hydrate dissociation: Implications for gas production models

    USGS Publications Warehouse

    Circone, S.; Kirby, S.H.; Stern, L.A.

    2005-01-01

    Thermal self-regulation of methane hydrate dissociation at pressure, temperature conditions along phase boundaries, illustrated by experiment in this report, is a significant effect with potential relevance to gas production from gas hydrate. In surroundings maintained at temperatures above the ice melting point, the temperature in the vicinity of dissociating methane hydrate will decrease because heat flow is insufficient to balance the heat absorbed by the endothermic reaction: CH4??nH2O (s) = CH4 (g) + nH2O (l). Temperature decreases until either all of the hydrate dissociates or a phase boundary is reached. At pressures above the quadruple point, the temperature-limiting phase boundary is that of the dissociation reaction itself. At lower pressures, the minimum temperature is limited by the H2O solid/liquid boundary. This change in the temperature-limiting phase boundary constrains the pressure, temperature conditions of the quadruple point for the CH4-H2O system to 2.55 ?? 0.02 MPa and 272.85 ?? 0.03 K. At pressures below the quadruple point, hydrate dissociation proceeds as the liquid H2O produced by dissociation freezes. In the laboratory experiments, dissociation is not impeded by the formation of ice byproduct per se; instead rates are proportional to the heat flow from the surroundings. This is in contrast to the extremely slow dissociation rates observed when surrounding temperatures are below the H2O solid/liquid boundary, where no liquid water is present. This "anomalous" or "self" preservation behavior, most pronounced near 268 K, cannot be accessed when surrounding temperatures are above the H2O solid/liquid boundary. ?? 2005 American Chemical Society.

  4. Mechanism of the reaction, CH4+O(1D2)→CH3+OH, studied by ultrafast and state-resolved photolysis/probe spectroscopy of the CH4O3 van der Waals complex

    NASA Astrophysics Data System (ADS)

    Miller, C. Cameron; van Zee, Roger D.; Stephenson, John C.

    2001-01-01

    The mechanism of the reaction CH4+O(1D2)→CH3+OH was investigated by ultrafast, time-resolved and state-resolved experiments. In the ultrafast experiments, short ultraviolet pulses photolyzed ozone in the CH4O3 van der Waals complex to produce O(1D2). The ensuing reaction with CH4 was monitored by measuring the appearance rate of OH(v=0,1;J,Ω,Λ) by laser-induced fluorescence, through the OH A←X transition, using short probe pulses. These spectrally broad pulses, centered between 307 and 316 nm, probe many different OH rovibrational states simultaneously. At each probe wavelength, both a fast and a slow rise time were evident in the fluorescence signal, and the ratio of the fast-to-slow signal varied with probe wavelength. The distribution of OH(v,J,Ω,Λ) states, Pobs(v,J,Ω,Λ), was determined by laser-induced fluorescence using a high-resolution, tunable dye laser. The Pobs(v,J,Ω,Λ) data and the time-resolved data were analyzed under the assumption that different formation times represent different reaction mechanisms and that each mechanism produces a characteristic rovibrational distribution. The state-resolved and the time-resolved data can be fit independently using a two-mechanism model: Pobs(v,J,Ω,Λ) can be decomposed into two components, and the appearance of OH can be fit by two exponential rise times. However, these independent analyses are not mutually consistent. The time-resolved and state-resolved data can be consistently fit using a three-mechanism model. The OH appearance signals, at all probe wavelengths, were fit with times τfast≈0.2 ps, τinter≈0.5 ps and τslow≈5.4 ps. The slowest of these three is the rate for dissociation of a vibrationally excited methanol intermediate (CH3OH*) predicted by statistical theory after complete intramolecular energy redistribution following insertion of O(1D2) into CH4. The Pobs(v,J,Ω,Λ) was decomposed into three components, each with a linear surprisal, under the assumption that the

  5. Bis[1-meth­oxy-2,2,2-tris­(pyrazol-1-yl-κN 2)ethane]­nickel(II) bis­(tri­fluoro­methane­sulfonate) methanol disolvate

    PubMed Central

    Lyubartseva, Ganna; Parkin, Sean; Mallik, Uma Prasad

    2013-01-01

    In the title salt, [Ni(C12H14N6O)2](CF3SO3)2·2CH3OH, the NiII ion is coordinated by six N atoms from two tridentate 1-meth­oxy-2,2,2-tris­(pyrazol-1-yl)ethane ligands in a distorted octa­hedral geometry. The NiII ion is situated on an inversion centre. The Ni—N distances range from 2.0589 (19) to 2.0757 (19) Å, intra-ligand N—Ni—N angles range from 84.50 (8) to 85.15 (8)°, and adjacent inter-ligand N—Ni—N angles range between 94.85 (8) and 95.50 (8)°. In the crystal, O—H⋯O hydrogen bonds between methanol solvent mol­ecules and tri­fluoro­methane­sulfonate anions are observed. PMID:24098170

  6. CH4 emission estimates from an active landfill site inferred from a combined approach of CFD modelling and in situ FTIR measurements

    NASA Astrophysics Data System (ADS)

    Sonderfeld, Hannah; Boesch, Hartmut; Jeanjean, Antoine P. R.; Riddick, Stuart N.; Allen, Grant; Ars, Sebastien; Davies, Stewart; Harris, Neil; Humpage, Neil; Leigh, Roland; Pitt, Joseph

    2017-04-01

    Globally, the waste sector contributes to nearly a fifth of anthropogenic methane (CH4) emitted to the atmosphere and is the second largest source of methane in the UK. In recent years great improvements to reduce those emissions have been achieved by installation of methane recovery systems at landfill sites and subsequently methane emissions reported in national emission inventories have been reduced. Nevertheless, methane emissions of landfills remain uncertain and quantification of emission fluxes is essential to verify reported emission inventories and to monitor changes in emissions. We are presenting data from the deployment of an in situ FTIR (Fourier Transform Infrared Spectrometer, Ecotech) for continuous and simultaneous sampling of CO2, CH4, N2O and CO with high time resolution of the order of minutes. During a two week field campaign at an operational landfill site in Eastern England in August 2014, measurements were taken within a radius of 320 m of the uncovered and active area of the landfill, which was still filled with new incoming waste. We have applied a computation fluid dynamics (CFD) model, constrained with local wind measurements and a detailed topographic map of the landfill site, to the in situ concentration data to calculate CH4 fluxes of the active site. A mean daytime flux of 0.83 mg m-2 s-1 (53.26 kg h-1) was calculated for the area of the active site. An additional source area was identified and incorporated into the CFD model, which resulted in higher total methane emissions of 75.97 kg h-1 for the combined emission areas. Our method of combining a CFD model to in situ data, in medium proximity of the source area, allows to distinguish between different emission areas and thereby provide more detailed information compared to bulk emission approaches.

  7. Vertical structure of the upper troposphere-low stratosphere in the tropics, at mid-latitude and in polar region based on recent N2O and CH4 measured by SPIRALE in situ balloon borne instrument.

    NASA Astrophysics Data System (ADS)

    Huret, N.; Catoire, V.; Pirre, M.; Hauchecornes, A.; Robert, C.

    2006-12-01

    In the framework of ENVISAT validation campaign, three flights of the SPIRALE balloon borne instrument took place in the tropics on 22 June 2005, at mid-latitude on 02 October 2002 and in the polar region on 21 January 2003. SPIRALE utilises a direct absorption technique using tunable diodes laser operating in the mid-infrared. For the three flights N2O and CH4 profiles allow us to highlight detailed vertical structures of the atmosphere from the upper troposphere to the stratosphere with small vertical extents layers of less than 1 km. In addition to the previous study of Huret et al. (JGR 2006), we present and discuss the recent tropical measurements of N2O and CH4 from the upper troposphere to the TTL and to the stratosphere. N2O-CH4 correlation points measured by SPIRALE are compared with correlation curves derived from ATMOS space shuttle measurements. The high vertical resolution (5m) and high precision of the measurements allow us to discuss in detail the origin of the air masses sampled and the occurrence of mixing processes. To help with the interpretation the potential vorticity maps calculated using the contour advection model MIMOSA have been used.

  8. Global methane and nitrous oxide emissions from terrestrial ecosystems due to multiple environmental changes

    DOE PAGES

    Tian, Hanqin; Chen, Guangsheng; Lu, Chaoqun; ...

    2015-03-16

    Greenhouse gas (GHG)-induced climate change is among the most pressing sustainability challenges facing humanity today, posing serious risks for ecosystem health. Methane (CH 4) and nitrous oxide (N 2O) are the two most important GHGs after carbon dioxide (CO 2), but their regional and global budgets are not well known. In this paper, we applied a process-based coupled biogeochemical model to concurrently estimate the magnitude and spatial and temporal patterns of CH 4 and N 2O fluxes as driven by multiple environmental changes, including climate variability, rising atmospheric CO 2, increasing nitrogen deposition, tropospheric ozone pollution, land use change, andmore » nitrogen fertilizer use.« less

  9. Methane oxidation and attenuation of sulphur compounds in landfill top cover systems: Lab-scale tests.

    PubMed

    Raga, Roberto; Pivato, Alberto; Lavagnolo, Maria Cristina; Megido, Laura; Cossu, Raffaello

    2018-03-01

    In this study, a top cover system is investigated as a control for emissions during the aftercare of new landfills and for old landfills where biogas energy production might not be profitable. Different materials were studied as landfill cover system in lab-scale columns: mechanical-biological pretreated municipal solid waste (MBP); mechanical-biological pretreated biowaste (PB); fine (PBS f ) and coarse (PBS c ) mechanical-biological pretreated mixtures of biowaste and sewage sludge, and natural soil (NS). The effectiveness of these materials in removing methane and sulphur compounds from a gas stream was tested, even coupled with activated carbon membranes. Concentrations of CO 2 , CH 4 , O 2 , N 2 , H 2 S and mercaptans were analysed at different depths along the columns. Methane degradation was assessed using mass balance and the results were expressed in terms of methane oxidation rate (MOR). The highest maximum and mean MOR were observed for MBP (17.2gCH 4 /m 2 /hr and 10.3gCH 4 /m 2 /hr, respectively). Similar values were obtained with PB and PBS c . The lowest values of MOR were obtained for NS (6.7gCH 4 /m 2 /hr) and PBS f (3.6gCH 4 /m 2 /hr), which may be due to their low organic content and void index, respectively. Activated membranes with high load capacity did not seem to have an influence on the methane oxidation process: MBP coupled with 220g/m 2 and 360g/m 2 membranes gave maximum MOR of 16.5gCH 4 /m 2 /hr and 17.4gCH 4 /m 2 /hr, respectively. Activated carbon membranes proved to be very effective on H 2 S adsorption. Furthermore, carbonyl sulphide, ethyl mercaptan and isopropyl mercaptan seemed to be easily absorbed by the filling materials. Copyright © 2017. Published by Elsevier B.V.

  10. Photo reduction of CO2 to CH4 on g-C3N4: The effect of concentrating light and pretreatment

    NASA Astrophysics Data System (ADS)

    Li, Dong; Fang, Xiaoxiang; Liu, Huayan; Lu, Hanfeng; Zhang, Zekai

    2018-06-01

    The behavior of CO2 photoreduction to CH4 on the g-C3N4 catalyst was studied in a concentrating light reactor. The g-C3N4 catalysts before and after pretreatment were characterized by FE-SEM, XRD and photoilluminance. It is found that concentrating light increases the CH4 yield on the g-C3N4 by heightening the incident light intensity, and light pretreatment has an excessive effect on the performance. Pretreated by suitable light intensity, air atmosphere and time, the CH4 yield on the g-C3N4 under concentrating light irradiation reached about 3.39 μmol.g-1.h-1, which is about 16 times of that g-C3N4 reacted at nature incident light without pretreatment. The mechanism of pretreatment is considered to be from the surface oxidation state change of the catalyst either from the oxidation of the catalyst surface or the activation of surface oxygen.

  11. Stability of methane in reduced C-O-H fluid at 6.3 GPa and 1300-1400°C

    NASA Astrophysics Data System (ADS)

    Sokol, A. G.; Tomilenko, A. A.; Bul'bak, T. A.; Palyanova, G. A.; Palyanov, Yu. N.; Sobolev, N. V.

    2017-06-01

    The composition of a reduced C-O-H fluid was studied by the method of chromatography-mass spectrometry under the conditions of 6.3 GPa, 1300-1400°C, and fO2 typical of the base of the subcratonic lithosphere. Fluids containing water (4.4-96.3 rel. %), methane (37.6-0.06 rel. %), and variable concentrations of ethane, propane, and butane were obtained in experiments. With increasing fO2, the proportion of the CH4/C2H6 peak areas on chromatograms first increases and then decreases, whereas the CH4/C3H8 and CH4/C4H10 ratios continually decrease. The new data show that ethane and heavier HCs may be more stable to oxidation, than previously thought. Therefore, when reduced fluids pass the "redox-front," carbon is not completely released from the fluid and may be involved in diamond formation.

  12. Oxidative coupling of methane over a Sr-promoted La{sub 2}O{sub 3} catalyst supported on a low surface area porous catalyst carrier

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Choudhary, V.R.; Uphade, B.S.; Mulla, S.A.R.

    1997-09-01

    Oxidative coupling of methane (OCM) to higher hydrocarbons over Sr-promoted La{sub 2}O{sub 3} supported on commercial low surface area porous catalyst carriers at 800 and 850 C and a space velocity of 102,000 cm{sup 3}/g{center_dot}h has been thoroughly investigated. Effects of support, catalyst particle size, linear gas velocity, Sr/La ratio, CH{sub 4}/O{sub 2} ratio in the feed, and catalyst dilution by inert solid particles on the conversion, yield, or selectivity and product ratios (C{sub 2}H{sub 4}/C{sub 2}H{sub 6} and CO/CO{sub 2}) in the OCM process have been studied. The catalysts have been characterized for their basicity, acidity, and oxygen chemisorptionmore » by the TPD of CO{sub 2}, ammonia, and oxygen, respectively, from 50 to 950 C and also characterized for their surface area. The supported catalysts showed better performance than the unsupported one. The best OCM results (obtained over Sr-La{sub 2}O{sub 3}/SA-5205 with a Sr/La ratio of 0.3 at a space velocity of 102,000 cm{sup 3}/g{center_dot}h) are 30.1% CH{sub 4} conversion with 65.6% selectivity for C{sub 2+} (or 19.7% C{sub 2+}-yield) at 850 C (CH{sub 4}/O{sub 2} = 16.0). The basicity is strongly influenced by the Sr/La ratio; the supported catalysts showed the best performance for their Sr/La ratio of about 0.3. The methane/O{sub 2} ratio also showed a strong influence for their Sr/La ratio of about 0.3. The methane/O{sub 2} ratio also showed a strong influence on the OCM process. However, the influence of linear gas velocity and particle size is found to be small; it results mainly from the temperature gradient in the catalyst. The catalyst dilution has beneficial effects for achieving a higher C{sub 2}H{sub 4}/C{sub 2}H{sub 6} ratio and also for reducing the hazardous nature of the OCM process because of the coupling of the exothermic oxidative conversion reactions and the endothermic thermal cracking reactions and also due to the increased heat transfer area.« less

  13. Diurnal variability of CO2 and CH4 emissions from tropical reservoirs

    NASA Astrophysics Data System (ADS)

    Linkhorst, Annika; Reinaldo Paranaíba, José; Barros, Nathan; DelSontro, Tonya; Isidorova, Anastasija; Mendonça, Raquel; Sobek, Sebastian

    2017-04-01

    Reservoirs are important atmospheric sources of carbon dioxide (CO2) and methane (CH4) with CH4 being a greenhouse gas (GHG) at least 28 times more potent than CO2. Reservoir GHG emissions tend to be heterogeneous, however, and thus current emission estimates are likely conservative since they often overlook emission hot spots and hot moments, especially for CH4 ebullition. For CO2, diffusion is the dominant flux pathway, and diurnal patterns in CO2 emissions can largely be linked to photosynthesis. In contrast, ebullition, the release of gases through bubbles that are formed in the sediments and travel through the water column, is a major emission pathway for CH4 in shallow waters. We visually observed a change in quantity and size of bubbles at different times of the day, and therefore conducted a diurnal study in four different Brazilian reservoirs of different size, age, climatic and geographic characteristics. We hypothesized that sub-daily trends in CH4 ebullition occur in Brazilian reservoirs as bubble release depends on physical factors such as turbulence and hydrostatic pressure, which can exhibit sub-daily patterns in large, managed reservoirs. In each reservoir, we performed measurements of CO2 and CH4 fluxes at one location over 24 hours. CH4 ebullition was tracked continuously by an echosounder, and 13 anchored bubble traps per reservoir were sampled every three hours. Further, a custom-built equilibrator monitored dissolved CH4 and CO2 concentrations, and diffusive and total fluxes of CO2 and CH4 were measured using floating chambers in triplicates every 30 minutes during the same period. We observed that CH4 ebullition as well as CH4 and CO2 diffusion peaked during the day, with peak fluxes being up to four times higher than low fluxes. However, the exact timing and magnitude varied for the different sampling events, and could in part be linked to biological and physical properties of the respective reservoir. This study combined different state

  14. Microstructural evolution of diamond films from CH{sub 4}/H{sub 2}/N{sub 2} plasma and their enhanced electrical properties

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sankaran, K. J.; Tai, N. H., E-mail: nhtai@mx.nthu.edu.tw; Lin, I. N., E-mail: inanlin@mail.tku.edu.tw

    2015-02-21

    The influence of N{sub 2} concentration in CH{sub 4}/H{sub 2}/N{sub 2} plasma on microstructural evolution and electrical properties of diamond films is systematically investigated. While the diamond films grown in CH{sub 4}/H{sub 2} plasma contain large diamond grains, for the diamond films grown using CH{sub 4}/H{sub 2}/(4%)N{sub 2} plasma, the microstructure drastically changed, resulting in ultra-nanosized diamond grains with Fd3m structure and a{sub 0} = 0.356 nm, along with the formation of n-diamond (n-D), a metastable form of diamond with space group Fm3m and a{sub 0} = 0.356 nm, and i-carbon (i-C) clusters, the bcc structured carbon with a{sub 0} = 0.432 nm. In addition, these films contain widemore » grain boundaries containing amorphous carbon (a-C). The electron field emission (EFE) studies show the best EFE behavior for 4% N{sub 2} films among the CH{sub 4}/H{sub 2}/N{sub 2} grown diamond films. They possess the lowest turn-on field value of 14.3 V/μm and the highest EFE current density value of 0.37 mA/cm{sup 2} at an applied field of 25.4 V/μm. The optical emission spectroscopy studies confirm that CN species are the major criterion to judge the changes in the microstructure of the films. It seems that the grain boundaries can provide electron conduction networks to transport efficiently the electrons to emission sites for field emission, as long as they have sufficient thickness. Whether the matrix nano-sized grains are 3C-diamond, n-D or i-C is immaterial.« less

  15. Introducing ionic and/or hydrogen bonds into the SAM//Ga2O3 top-interface of Ag(TS)/S(CH2)nT//Ga2O3/EGaIn junctions.

    PubMed

    Bowers, Carleen M; Liao, Kung-Ching; Yoon, Hyo Jae; Rappoport, Dmitrij; Baghbanzadeh, Mostafa; Simeone, Felice C; Whitesides, George M

    2014-06-11

    Junctions with the structure Ag(TS)/S(CH2)nT//Ga2O3/EGaIn (where S(CH2)nT is a self-assembled monolayer, SAM, of n-alkanethiolate bearing a terminal functional group T) make it possible to examine the response of rates of charge transport by tunneling to changes in the strength of the interaction between T and Ga2O3. Introducing a series of Lewis acidic/basic functional groups (T = -OH, -SH, -CO2H, -CONH2, and -PO3H) at the terminus of the SAM gave values for the tunneling current density, J(V) in A/cm(2), that were indistinguishable (i.e., differed by less than a factor of 3) from the values observed with n-alkanethiolates of equivalent length. The insensitivity of the rate of tunneling to changes in the terminal functional group implies that replacing weak van der Waals contact interactions with stronger hydrogen- or ionic bonds at the T//Ga2O3 interface does not change the shape (i.e., the height or width) of the tunneling barrier enough to affect rates of charge transport. A comparison of the injection current, J0, for T = -CO2H, and T = -CH2CH3--two groups having similar extended lengths (in Å, or in numbers of non-hydrogen atoms)--suggests that both groups make indistinguishable contributions to the height of the tunneling barrier.

  16. Radiative forcing of carbon dioxide, methane, and nitrous oxide: A significant revision of the methane radiative forcing

    NASA Astrophysics Data System (ADS)

    Etminan, M.; Myhre, G.; Highwood, E. J.; Shine, K. P.

    2016-12-01

    New calculations of the radiative forcing (RF) are presented for the three main well-mixed greenhouse gases, methane, nitrous oxide, and carbon dioxide. Methane's RF is particularly impacted because of the inclusion of the shortwave forcing; the 1750-2011 RF is about 25% higher (increasing from 0.48 W m-2 to 0.61 W m-2) compared to the value in the Intergovernmental Panel on Climate Change (IPCC) 2013 assessment; the 100 year global warming potential is 14% higher than the IPCC value. We present new simplified expressions to calculate RF. Unlike previous expressions used by IPCC, the new ones include the overlap between CO2 and N2O; for N2O forcing, the CO2 overlap can be as important as the CH4 overlap. The 1750-2011 CO2 RF is within 1% of IPCC's value but is about 10% higher when CO2 amounts reach 2000 ppm, a value projected to be possible under the extended RCP8.5 scenario.

  17. Photocatalytic decomposition of N2O over TiO2/g-C3N4 photocatalysts heterojunction

    NASA Astrophysics Data System (ADS)

    Kočí, K.; Reli, M.; Troppová, I.; Šihor, M.; Kupková, J.; Kustrowski, P.; Praus, P.

    2017-02-01

    TiO2/g-C3N4 photocatalysts with the various TiO2/g-C3N4 weight ratios from 1:2 to 1:6 were fabricated by mechanical mixing in water suspension followed by calcination. Pure TiO2 was prepared by thermal hydrolysis and pure g-C3N4 was prepared from commercial melamine by thermal annealing at 620 °C. All the nanocomposites were characterized by X-ray powder diffraction, UV-vis diffuse reflectance spectroscopy, Raman spectroscopy, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, photoelectrochemical measurements and nitrogen physisorption. The prepared mixtures along with pure TiO2 and g-C3N4 were tested for the photocatalytic decomposition of nitrous oxide under UVC (λ = 254 nm), UVA (λ = 365 nm) and Vis (λ > 400 nm) irradiation. The TiO2/g-C3N4 nanocomposites showed moderate improvement compared to pure g-C3N4 but pure TiO2 proved to be a better photocatalyst under UVC irradiation. However, under UVA irradiation conditions, the photocatalytic activity of TiO2/g-C3N4 (1:2) nanocomposite exhibited an increase compared to pure TiO2. Nevertheless, further increase of g-C3N4 amount leads/led to a decrease in reactivity. These results are suggesting the nanocomposite with the optimal weight ratio of TiO2 and g-C3N4 have shifted absorption edge energy towards longer wavelengths and decreased the recombination rate of charge carriers compared to pure g-C3N4. This is probably due to the generation of heterojunction on the TiO2/g-C3N4 interface.

  18. Changing concentrations of CO, CH(4), C(5)H(8), CH(3)Br, CH(3)I, and dimethyl sulfide during the Southern Ocean Iron Enrichment Experiments.

    PubMed

    Wingenter, Oliver W; Haase, Karl B; Strutton, Peter; Friederich, Gernot; Meinardi, Simone; Blake, Donald R; Rowland, F Sherwood

    2004-06-08

    Oceanic iron (Fe) fertilization experiments have advanced the understanding of how Fe regulates biological productivity and air-sea carbon dioxide (CO(2)) exchange. However, little is known about the production and consumption of halocarbons and other gases as a result of Fe addition. Besides metabolizing inorganic carbon, marine microorganisms produce and consume many other trace gases. Several of these gases, which individually impact global climate, stratospheric ozone concentration, or local photochemistry, have not been previously quantified during an Fe-enrichment experiment. We describe results for selected dissolved trace gases including methane (CH(4)), isoprene (C(5)H(8)), methyl bromide (CH(3)Br), dimethyl sulfide, and oxygen (O(2)), which increased subsequent to Fe fertilization, and the associated decreases in concentrations of carbon monoxide (CO), methyl iodide (CH(3)I), and CO(2) observed during the Southern Ocean Iron Enrichment Experiments.

  19. On the methane paradox: Transport from shallow water zones rather than in situ methanogenesis is the major source of CH4 in the open surface water of lakes

    NASA Astrophysics Data System (ADS)

    Encinas Fernández, Jorge; Peeters, Frank; Hofmann, Hilmar

    2016-10-01

    Estimates of global methane (CH4) emissions from lakes and the contributions of different pathways are currently under debate. In situ methanogenesis linked to algae growth was recently suggested to be the major source of CH4 fluxes from aquatic systems. However, based on our very large data set on CH4 distributions within lakes, we demonstrate here that methane-enriched water from shallow water zones is the most likely source of the basin-wide mean CH4 concentrations in the surface water of lakes. Consistently, the mean surface CH4 concentrations are significantly correlated with the ratio between the surface area of the shallow water zone and the entire lake, fA,s/t, but not with the total surface area. The categorization of CH4 fluxes according to fA,s/t may therefore improve global estimates of CH4 emissions from lakes. Furthermore, CH4 concentrations increase substantially with water temperature, indicating that seasonally resolved data are required to accurately estimate annual CH4 emissions.

  20. Development of Methane and Nitrous Oxide Emission Factors for the Biomass Fired Circulating Fluidized Bed Combustion Power Plant

    PubMed Central

    Cho, Chang-Sang; Sa, Jae-Hwan; Lim, Ki-Kyo; Youk, Tae-Mi; Kim, Seung-Jin; Lee, Seul-Ki; Jeon, Eui-Chan

    2012-01-01

    This study makes use of this distinction to analyze the exhaust gas concentration and fuel of the circulating fluidized bed (CFB) boiler that mainly uses wood biomass, and to develop the emission factors of Methane (CH4), Nitrous oxide (N2O). The fuels used as energy sources in the subject working sites are Wood Chip Fuel (WCF), RDF and Refused Plastic Fuel (RPF) of which heating values are 11.9 TJ/Gg, 17.1 TJ/Gg, and 31.2 TJ/Gg, respectively. The average concentrations of CH4 and N2O were measured to be 2.78 ppm and 7.68 ppm, respectively. The analyzed values and data collected from the field survey were used to calculate the emission factor of CH4 and N2O exhausted from the CFB boiler. As a result, the emission factors of CH4 and N2O are 1.4 kg/TJ (0.9–1.9 kg/TJ) and 4.0 kg/TJ (2.9–5.3 kg/TJ) within a 95% confidence interval. Biomass combined with the combustion technology for the CFB boiler proved to be more effective in reducing the N2O emission, compared to the emission factor of the CFB boiler using fossil fuel. PMID:23365540