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Sample records for aerobic ch4 oxidation

  1. Fractionation of the methane isotopologues 13CH4, 12CH3D, and 13CH3D during aerobic oxidation of methane by Methylococcus capsulatus (Bath)

    NASA Astrophysics Data System (ADS)

    Wang, David T.; Welander, Paula V.; Ono, Shuhei

    2016-11-01

    Aerobic oxidation of methane plays a major role in reducing the amount of methane emitted to the atmosphere from freshwater and marine settings. We cultured an aerobic methanotroph, Methylococcus capsulatus (Bath) at 30 and 37 °C, and determined the relative abundance of 12CH4, 13CH4, 12CH3D, and 13CH3D (a doubly-substituted, or "clumped" isotopologue of methane) to characterize the clumped isotopologue effect associated with aerobic methane oxidation. In batch culture, the residual methane became enriched in 13C and D relative to starting methane, with D/H fractionation a factor of 9.14 (Dε/13ε) larger than that of 13C/12C. As oxidation progressed, the Δ13CH3D value (a measure of the excess in abundance of 13CH3D relative to a random distribution of isotopes among isotopologues) of residual methane decreased. The isotopologue fractionation factor for 13CH3D/12CH4 was found to closely approximate the product of the measured fractionation factors for 13CH4/12CH4 and 12CH3D/12CH4 (i.e., 13C/12C and D/H). The results give insight into enzymatic reversibility in the aerobic methane oxidation pathway. Based on the experimental data, a mathematical model was developed to predict isotopologue signatures expected for methane in the environment that has been partially-oxidized by aerobic methanotrophy. Measurement of methane clumped isotopologue abundances can be used to distinguish between aerobic methane oxidation and alternative methane-cycling processes.

  2. Using carbon isotope fractionation for an improved quantification of CH4 oxidation efficiency in Arctic peatlands

    NASA Astrophysics Data System (ADS)

    Preuss, I.; Knoblauch, C.; Gebert, J.; Pfeiffer, E.-M.

    2012-04-01

    Much research effort is focused on identifying global CH4 sources and sinks to estimate their current and potential strength in response to land-use change and global warming. Aerobic CH4 oxidation is regarded as the key process reducing the strength of CH4 emissions in wetlands, but is hitherto difficult to quantify. Recent studies quantify the efficiency of CH4 oxidation based on CH4 stable isotope signatures. The approach utilizes the fact that a significant isotope fractionation occurs when CH4 is oxidized. Moreover, it also considers isotope fractionation by diffusion. For field applications the 'open-system equation' is applied to determine the CH4 oxidation efficiency: fox = (δE - δP)/ (αox - αtrans) where fox is the fraction of CH4 oxidized; δE is δ13C of emitted CH4; δP is δ13C of produced CH4; αox is the isotopic fractionation factor of oxidation; αtrans is the isotopic fractionation factor of transport. We quantified CH4 oxidation in polygonal tundra soils of Russia's Lena River Delta analyzing depth profiles of CH4 concentrations and stable isotope signatures. Therefore, both fractionation factors αox and αtrans were determined for three polygon centers with differing water table positions and a polygon rim. While most previous studies on landfill cover soils have assumed a gas transport dominated by advection (αtrans = 1), other CH4 transport mechanisms as diffusion have to be considered in peatlands and αtrans exceeds a value of 1. At our study we determined αtrans = 1.013 ± 0.003 for CH4 when diffusion is the predominant transport mechanism. Furthermore, results showed that αox differs widely between sites and horizons (αox = 1.013 ± 0.012) and has to be determined for each case. The impact of both fractionation factors on the quantification of CH4 oxidation was estimated by considering both the potential diffusion rate at different water contents and potential oxidation rates. Calculations for a water saturated tundra soil

  3. Improved quantification of microbial CH4 oxidation efficiency in arctic wetland soils using carbon isotope fractionation

    NASA Astrophysics Data System (ADS)

    Preuss, I.; Knoblauch, C.; Gebert, J.; Pfeiffer, E.-M.

    2013-04-01

    Permafrost-affected tundra soils are significant sources of the climate-relevant trace gas methane (CH4). The observed accelerated warming of the arctic will cause deeper permafrost thawing, followed by increased carbon mineralization and CH4 formation in water-saturated tundra soils, thus creating a positive feedback to climate change. Aerobic CH4 oxidation is regarded as the key process reducing CH4 emissions from wetlands, but quantification of turnover rates has remained difficult so far. The application of carbon stable isotope fractionation enables the in situ quantification of CH4 oxidation efficiency in arctic wetland soils. The aim of the current study is to quantify CH4 oxidation efficiency in permafrost-affected tundra soils in Russia's Lena River delta based on stable isotope signatures of CH4. Therefore, depth profiles of CH4 concentrations and δ13CH4 signatures were measured and the fractionation factors for the processes of oxidation (αox) and diffusion (αdiff) were determined. Most previous studies employing stable isotope fractionation for the quantification of CH4 oxidation in soils of other habitats (such as landfill cover soils) have assumed a gas transport dominated by advection (αtrans = 1). In tundra soils, however, diffusion is the main gas transport mechanism and diffusive stable isotope fractionation should be considered alongside oxidative fractionation. For the first time, the stable isotope fractionation of CH4 diffusion through water-saturated soils was determined with an αdiff = 1.001 ± 0.000 (n = 3). CH4 stable isotope fractionation during diffusion through air-filled pores of the investigated polygonal tundra soils was αdiff = 1.013 ± 0.003 (n = 18). Furthermore, it was found that αox differs widely between sites and horizons (mean αox = 1.017 ± 0.009) and needs to be determined on a case by case basis. The impact of both fractionation factors on the quantification of CH4 oxidation was analyzed by considering both the

  4. Improved quantification of microbial CH4 oxidation efficiency in Arctic wetland soils using carbon isotope fractionation

    NASA Astrophysics Data System (ADS)

    Preuss, I.; Knoblauch, C.; Gebert, J.; Pfeiffer, E.-M.

    2012-12-01

    Permafrost-affected tundra soils are significant sources of the climate-relevant trace gas methane (CH4). The observed accelerated warming of the Arctic will cause a deeper permafrost thawing followed by increased carbon mineralization and CH4 formation in water saturated tundra soils which might cause a positive feedback to climate change. Aerobic CH4 oxidation is regarded as the key process reducing CH4 emissions from wetlands, but quantification of turnover rates has remained difficult so far. The application of carbon stable isotope fractionation enables the in situ quantification of CH4 oxidation efficiency in arctic wetland soils. The aim of the current study is to quantify CH4 oxidation efficiency in permafrost-affected tundra soils in Russia's Lena River Delta based on stable isotope signatures of CH4. Therefore, depth profiles of CH4 concentrations and δ13CH4-signatures were measured and the fractionation factors for the processes of oxidation (αox) and diffusion (αdiff) were determined. Most previous studies employing stable isotope fractionation for the quantification of CH4 oxidation in soils of other habitats (e.g. landfill cover soils) have assumed a gas transport dominated by advection (αtrans = 1). In tundra soils, however, diffusion is the main gas transport mechanism, aside from ebullition. Hence, diffusive stable isotope fractionation has to be considered. For the first time, the stable isotope fractionation of CH4 diffusion through water-saturated soils was determined with an αdiff = 1.001 ± 0.000 (n = 3). CH4 stable isotope fractionation during diffusion through air-filled pores of the investigated polygonal tundra soils was αdiff = 1.013 ± 0.003 (n = 18). Furthermore, it was found that αox differs widely between sites and horizons (mean αox, = 1.017 ± 0.009) and needs to be determined individually. The impact of both fractionation factors on the quantification of CH4 oxidation was analyzed by considering both the potential diffusion

  5. [Advances in the research on sources and sinks of CH4 and CH4 oxidation (uptake) in soil].

    PubMed

    Wang, Chenrui; Huang, Guohong; Liang, Zhanbei; Wu, Jie; Xu, Guoqiang; Yue, Jin; Shi, Yi

    2002-12-01

    Methane (CH4) is one of the main greenhouse gases contributing greenhouse effect, and its potential greenhouse effect is 21 times of CO2. Therefore, to determine the sources and sinks of atmospheric CH4 and to assess and forecast their amounts become and important focus concerning the researches on global change and greenhouse effect. This paper summarized the researches on the sources and sinks of CH4, and amplified on the influential factors (e.g. land-use, ambient atmospheric CH4 concentration, soil temperature, soil moisture content, soil pH and soil porosity) on atmospheric and interior CH4 oxidation in soil. It is significant that studying CH4 oxidation in vertical zonation soil in forests of Changbai Mountain to evaluate the CH4 consumption in forest soil.

  6. A process-based inventory model for landfill CH4 emissions inclusive of seasonal soil microclimate and CH4 oxidation

    NASA Astrophysics Data System (ADS)

    Spokas, K.; Bogner, J.; Chanton, J.

    2011-12-01

    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 0.5° scale global climatic models. Based on 1-D diffusion, CALMIM (California Landfill Methane Inventory Model) is a freely available JAVA tool which models a typical annual cycle for CH4 emissions from site-specific daily, intermediate, and final landfill cover designs. Literature over the last decade has emphasized that the major factors controlling emissions in these highly managed soil systems are the presence or absence of engineered gas extraction, gaseous transport rates as affected by the thickness and physical properties of cover soils, and methanotrophic CH4 oxidation in cover materials as a function of seasonal soil microclimate. Moreover, current IPCC national inventory models for landfill CH4 emissions based on theoretical gas generation have high uncertainties and lack comprehensive field validation. This new approach, which is compliant with IPCC "Tier III" criteria, has been field-validated at two California sites (Monterey County; Los Angeles County), with limited field validation at three additional California sites. CALMIM accurately predicts soil temperature and moisture trends with emission predictions within the same order of magnitude as field measurements, indicating an acceptable initial model comparison in the context of published literature on measured CH4 emissions spanning 7 orders of magnitude. In addition to regional defaults for inventory purposes, CALMIM permits user-selectable parameters and boundary conditions for more rigorous site-specific applications where detailed CH4 emissions, meteorological, and soil microclimate data exist.

  7. The atmospheric CH4 increase since the Last Glacial Maximum. II - Interactions with oxidants

    NASA Astrophysics Data System (ADS)

    Thompson, Anne M.; Chappellaz, Jerome A.; Fung, Inez Y.; Kucsera, T. L.

    1993-07-01

    Results of two studies of the effect of changing CH4 fluxes on global tropospheric oxidant levels, O3, OH, and H2O2, performed with a multibox photochemical model, are presented. A sensitivity study is conducted by scaling back CH4, CO, and NO emissions relative to the present-day budget. When the CH4 ice core record is compared to calculated CH4 abundances, corresponding CH4 fluxes for the preindustrial Holocene (PIH) and Last Glacial Maximum (LGM) are fairly well-constrained: 175-225 Tg CH/4/yr for PIH and 100-130 Tg CH4/yr for LGM. Specific scenarios for CH4/CO/NO are selected to represent sources for the PIH and LGM. The CH4 budget is taken from an evaluation of wetlands and other natural sources.

  8. Differences in CH4 oxidation and pathways of production between rice cultivars deduced from measurements of CH4 flux and δ13C of CH4 and CO2

    NASA Astrophysics Data System (ADS)

    Bilek, Rebecca S.; Tyler, Stanley C.; Sass, Ronald L.; Fisher, Frank M.

    We report measurements of CH4 flux and δ13C and δD values of emitted CH4 and sediment CH4 and CO2 during the 1995 rice growing season in Beaumont, Texas. Four rice plant cultivars, Lemont, Mars, Cypress, and Della, and an unplanted plot were studied to provide possible explanations for the differences in CH4 emissions between cultivars. Using the measured isotope values, along with data of CH4 and CO2 concentrations and other ecosystem data, we determined differences between cultivars in the processes of oxidation and production throughout the growing season. For instance, rhizospheric CH4 oxidation increased as the season progressed in both Mars and Lemont cultivars. Late in the season, however, 71+/-10% of CH4 produced in the Mars plot was oxidized compared to only 39+/-10% in the Lemont plot. The contribution of acetate fermentation to methanogenesis at specific times during the season was calculated using measured isotopic values and assuming identical isotopic fractionation factors in methanogenic pathways for the cultivars. In these calculations a range of values for the contribution to CH4 production from acetate fermentation and CO2 reduction with H2 was estimated by considering different fractionation factors for the methanogenic CO2 reduction pathway and the possibility of a 10% contribution to CH4 production from acetate produced by homoacetogenesis. In general, a steady increase in the CH4 portion produced by acetate fermentation was noted in the Lemont cultivar, while an increase followed by a decrease near the end of the season was observed for the Mars cultivar.

  9. Methanogenic Pathway and Fraction of CH4 Oxidized in Paddy Fields: Seasonal Variation and Effect of Water Management in Winter Fallow Season

    PubMed Central

    Zhang, Guangbin; Liu, Gang; Zhang, Yi; Ma, Jing; Xu, Hua; Yagi, Kazuyuki

    2013-01-01

    A 2-year field and incubation experiment was conducted to investigate δ13C during the processes of CH4 emission from the fields subjected to two water managements (flooding and drainage) in the winter fallow season, and further to estimate relative contribution of acetate to total methanogenesis (Fac) and fraction of CH4 oxidized (Fox) based on the isotopic data. Compared with flooding, drainage generally caused CH4, either anaerobically or aerobically produced, depleted in 13C. There was no obvious difference between the two in transport fractionation factor (εtransport) and δ13C-value of emitted CH4. CH4 emission was negatively related to its δ13C-value in seasonal variation (P<0.01). Acetate-dependent methanogenesis in soil was dominant (60–70%) in the late season, while drainage decreased Fac-value by 5–10%. On roots however, CH4 was mostly produced through H2/CO2 reduction (60–100%) over the season. CH4 oxidation mainly occurred in the first half of the season and roughly 10–90% of the CH4 was oxidized in the rhizosphere. Drainage increased Fox-value by 5–15%, which is possibly attributed to a significant decrease in production while no simultaneous decrease in oxidation. Around 30–70% of the CH4 was oxidized at the soil-water interface when CH4 in pore water was released into floodwater, although the amount of CH4 oxidized therein might be negligible relative to that in the rhizosphere. CH4 oxidation was also more important in the first half of the season in lab conditions and about 5–50% of the CH4 was oxidized in soil while almost 100% on roots. Drainage decreased Fox-value on roots by 15% as their CH4 oxidation potential was highly reduced. The findings suggest that water management in the winter fallow season substantially affects Fac in the soil and Fox in the rhizosphere and roots rather than Fac on roots and Fox at the soil-water interface. PMID:24069259

  10. [Effects of Nitrate and CH4 on Anaerobic Oxidation of BETX in Landfill Cover Soils].

    PubMed

    Liu, Rong; Long, Yan; Wang, Li-li; He, Ting; Ye, Jin-shao

    2015-05-01

    BETX is one of the important components of stink organic gases in landfills, which simultaneously release much of greenhouse CH4. The microorganisms in landfill cover soils are able to degrade CH4 and BETX. Therefore, improving the capacity of biological oxidation of microorganisms in landfill cover soils can effectively reduce and control pollution caused by landfill gases. Some electron acceptors can couple to anaerobic oxidation of methane and some organic pollutants, thus eliminating methane and organic substances. Based on the above theory, this research investigated the effect of nitrate (NO3-) and CH4 on anaerobic degradation of benzene series (toluene, xylene and isopropyl benzene) with coexistence of SO4(2-) in landfill cover soils through static incubation experiment. The results showed that BTEX inhibited the degradation of CH4 without adding nitrate, however, BTEX instead improved the removal of CH4 after nitrate addition. Although single addition of nitrate or CH4 could improve the removal of BTEX in landfill cover soils, adding both of them could improve the removal of BTEX better as the removal efficiencies for benzene, toluene and isopropyl benzene were respectively reached 65%, 88% and 82%, much higher than those of 53%, 76% and 31% when not adding nitrate and CH4. The process of anaerobic methane oxidation coupled to nitrate reduction was able to synchronously improve anaerobic oxidation of BETX.

  11. A process-based inventory model for landfill CH4 emissions inclusive of seasonal soil microclimate and CH4 oxidation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  12. CH4/CO2 ratios indicate highly efficient methane oxidation by a pumice landfill cover-soil.

    PubMed

    Pratt, Chris; Walcroft, Adrian S; Deslippe, Julie; Tate, Kevin R

    2013-02-01

    Landfills that generate too little biogas for economic energy recovery can potentially offset methane (CH(4)) emissions through biological oxidation by methanotrophic bacteria in cover soils. This study reports on the CH(4) oxidation efficiency of a 10-year old landfill cap comprising a volcanic pumice soil. Surface CH(4) and CO(2) fluxes were measured using field chambers during three sampling intervals over winter and summer. Methane fluxes were temporally and spatially variable (-0.36 to 3044 mgCH(4)m(-2)h(-1)); but were at least 15 times lower than typical literature CH(4) fluxes reported for older landfills in 45 of the 46 chambers tested. Exposure of soil from this landfill cover to variable CH(4) fluxes in laboratory microcosms revealed a very strong correlation between CH(4) oxidation efficiency and CH(4)/CO(2) ratios, confirming the utility of this relationship for approximating CH(4) oxidation efficiency. CH(4)/CO(2) ratios were applied to gas concentrations from the surface flux chambers and indicated a mean CH(4) oxidation efficiency of 72%. To examine CH(4) oxidation with soil depth, we collected 10 soil depth profiles at random locations across the landfill. Seven profiles exhibited CH(4) removal rates of 70-100% at depths <60 cm, supporting the high oxidation rates observed in the chambers. Based on a conservative 70% CH(4) oxidation efficiency occurring at the site, this cover soil is clearly offsetting far greater CH(4) quantities than the 10% default value currently adopted by the IPCC.

  13. The incorporation of graphene oxide into polysulfone mixed matrix membrane for CO2/CH4 separation

    NASA Astrophysics Data System (ADS)

    Zahri, K.; Goh, P. S.; Ismail, A. F.

    2016-06-01

    Carbon dioxide (CO2) is often found as the main impurity in natural gas, where methane (CH4) is the major component. The presence of CO2 in natural gas leads to several problems such as reducing the energy content of natural gas and cause pipeline corrosion. Thus it must be removed to meet specifications (CO2 ≤ 2 mol%) before the gas can be delivered to the pipeline. In this work, hollow fiber mixed matrix membrane (MMM) were fabricated by embedding graphene oxide (GO) into a polysulfone (PSf) polymer matrix to improve membrane properties as well as its separation performance towards CO2/CH4 gas. The membrane properties were investigated for pristine membrane and mixed matrix membrane filled with filler loading of 0.25%. The synthesized GO and properties of fabricated membranes were characterized and studied using TEM, AFM, XRD, FTIR and SEM respectively. The permeance of pure gases and ideal selectivity of CO2/CH4 gas were determined using pure gas permeation experiment. GO has affinity towards CO2 gas. The nanosheet structure creates path for small molecule gas and restricted large molecule gas to pass through the membrane. The incorporation of GO in PSf polymer enhanced the permeance of CO 2 and CO2/CH4 separation from 64.47 to 86.80 GPU and from 19 to 25 respectively.

  14. 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.

  15. Geographic and seasonal variation of dissolved methane and aerobic methane oxidation in Alaskan lakes

    NASA Astrophysics Data System (ADS)

    Martinez-Cruz, K.; Sepulveda-Jauregui, A.; Anthony, K. Walter; Thalasso, F.

    2015-03-01

    Methanotrophic bacteria play an important role oxidizing a significant fraction of methane (CH4) produced in lakes. Aerobic CH4 oxidation depends on lake CH4 and oxygen (O2) concentrations, temperature, and organic carbon input to lakes, including from thawing permafrost in thermokarst (thaw)-affected lakes. Given the large variability in these environmental factors, CH4 oxidation is expected to be subject to large seasonal and geographic variations, which have been scarcely reported in the literature. In the present study, we measured CH4 oxidation rates in 30 Alaskan lakes along a north-south latitudinal transect during winter and summer with a new field laser spectroscopy method. Additionally, we measured dissolved CH4 and O2 concentrations. We found that in the winter, aerobic CH4 oxidation was mainly controlled by the dissolved O2 concentration, while in the summer it was controlled primarily by the CH4 concentration, which was in deficit compared to dissolved O2. The permafrost environment of the lakes was identified as another key factor. Thermokarst (thaw) lakes formed in yedoma-type permafrost had significantly higher CH4 oxidation rates compared to other thermokarst and non-thermokarst lakes formed in non-yedoma permafrost environments. These results confirm that landscape processes play an important role in lake CH4 cycling.

  16. Air-Independent Solid Oxide Fuel Cells for NASA's LOX-CH4 Landers

    NASA Technical Reports Server (NTRS)

    Ryan, Abigail C.; Araghi, Koorosh R.; Farmer, Serene C.

    2013-01-01

    Gemini, Apollo, and Space Shuttle used fuel cells as main power source for vehicle and water source for life support and thermal PEM (Gemini) and Alkaline (Apollo, Shuttle) fuel cells were used Ideal for short (less than 3 weeks) missions when the required O2 and H2 can be launched with the vehicle. New missions that might require long-duration stays in orbit or at a habitat, cannot rely on the availability of pure reactants but should also aim to be sun-independent - a problem for which Solid Oxide Fuel Cells might be the answer. Recently, NASA has investigated & developed LOX/CH4-propelled landers (Altair, MORPHEUS). In order to preserve mission flexibility, fuel cells are being studied as a potential power source. Much of NASA's fuel cell development has been focused on creating a dead-headed, non-flow through PEM fuel cells which would weigh less and be more reliable than the existing Alkaline and PEM technology; however, LOX/CH4 as a propellant introduces SOFCs as a power option due to their ability to accept those reactants without much reforming.

  17. Nitric Oxide Mediates Biofilm Formation and Symbiosis in Silicibacter sp. Strain TrichCH4B

    PubMed Central

    Rao, Minxi; Smith, Brian C.

    2015-01-01

    ABSTRACT Nitric oxide (NO) plays an important signaling role in all domains of life. Many bacteria contain a heme-nitric oxide/oxygen binding (H-NOX) protein that selectively binds NO. These H-NOX proteins often act as sensors that regulate histidine kinase (HK) activity, forming part of a bacterial two-component signaling system that also involves one or more response regulators. In several organisms, NO binding to the H-NOX protein governs bacterial biofilm formation; however, the source of NO exposure for these bacteria is unknown. In mammals, NO is generated by the enzyme nitric oxide synthase (NOS) and signals through binding the H-NOX domain of soluble guanylate cyclase. Recently, several bacterial NOS proteins have also been reported, but the corresponding bacteria do not also encode an H-NOX protein. Here, we report the first characterization of a bacterium that encodes both a NOS and H-NOX, thus resembling the mammalian system capable of both synthesizing and sensing NO. We characterized the NO signaling pathway of the marine alphaproteobacterium Silicibacter sp. strain TrichCH4B, determining that the NOS is activated by an algal symbiont, Trichodesmium erythraeum. NO signaling through a histidine kinase-response regulator two-component signaling pathway results in increased concentrations of cyclic diguanosine monophosphate, a key bacterial second messenger molecule that controls cellular adhesion and biofilm formation. Silicibacter sp. TrichCH4B biofilm formation, activated by T. erythraeum, may be an important mechanism for symbiosis between the two organisms, revealing that NO plays a previously unknown key role in bacterial communication and symbiosis. PMID:25944856

  18. Revisiting tropospheric yields of CO from CH4 oxidation using EMAC

    NASA Astrophysics Data System (ADS)

    Gromov, Sergey; Taraborrelli, Domenico

    2015-04-01

    Among various sources of tropospheric CO, methane oxidation (MO) is commonly assumed to be least uncertain term due to the fairly well studied kinetics of the reaction of CH4 with OH. Many studies on CO tropospheric budget (including forward and inverse modelling with CTMs and AC-GCMs) employ simplified treatment of MO source in their chemistry schemes, i.e. parameterising the photochemical production of CO using a 'net reaction' that can be written as CH4 + OH → λ CO + (products), where the yield λ approximates the effect of the chemistry regime and removal of intermediates from the CH4 oxidation chain, and is duly used as one of the fitting parameters. The estimates of λ, however, are hitherto inconsistent: Depending on the chemistry and dry/wet deposition schemes used, reckoned average tropospheric λ values vary within 0.6-1, whilst recent model parameterisations tend to favour almost complete conversion of CH4 to CO. The issue of such large uncertainty in CO yield from CH4 is especially important for the SH CO, where more than 50% of its inventory is typically attributed to the MO source in austral summer. In this study we scrutinise the MO source of CO using the ECHAM/MESSy Atmospheric Chemistry (EMAC) model employing elaborate chemistry mechanisms and tools to directly infer the value of λ, which is a diagnosed variable rather than an assumed parameter. Three chemical mechanisms differing in complexity of the MO cycle are used in simulations based on the EMAC evaluation study setup (detailed in Jöckel et al., 2010): (1) The reference (REF) mechanism which represents the 'standard' MO chemistry in EMAC including CH3O2, CH3OH, CH3OOH, HCHO and HCOOH, (2) The extension of REF that resolves CH3 and CH3O intermediates and reactions of CH3O2 with peroxy radicals, foremost HO2 (BASE mechanism), and (3) Further extension of BASE with pathways of MO involving formation and destruction of organic nitrates, plus reactions of CH3O2/CH3/HCHO with Ox and HOx from

  19. 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. PMID:20888749

  20. 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

  1. Geographic and seasonal variation of dissolved methane and aerobic methane oxidation in Alaskan lakes

    NASA Astrophysics Data System (ADS)

    Martinez-Cruz, K.; Sepulveda-Jauregui, A.; Anthony, K. Walter; Thalasso, F.

    2015-08-01

    Methanotrophic bacteria play an important role oxidizing a significant fraction of methane (CH4) produced in lakes. Aerobic CH4 oxidation depends mainly on lake CH4 and oxygen (O2) concentrations, in such a manner that higher MO rates are usually found at the oxic/anoxic interface, where both molecules are present. MO also depends on temperature, and via methanogenesis, on organic carbon input to lakes, including from thawing permafrost in thermokarst (thaw)-affected lakes. Given the large variability in these environmental factors, CH4 oxidation is expected to be subject to large seasonal and geographic variations, which have been scarcely reported in the literature. In the present study, we measured CH4 oxidation rates in 30 Alaskan lakes along a north-south latitudinal transect during winter and summer with a new field laser spectroscopy method. Additionally, we measured dissolved CH4 and O2 concentrations. We found that in the winter, aerobic CH4 oxidation was mainly controlled by the dissolved O2 concentration, while in the summer it was controlled primarily by the CH4 concentration, which was scarce compared to dissolved O2. The permafrost environment of the lakes was identified as another key factor. Thermokarst (thaw) lakes formed in yedoma-type permafrost had significantly higher CH4 oxidation rates compared to other thermokarst and non-thermokarst lakes formed in non-yedoma permafrost environments. As thermokarst lakes formed in yedoma-type permafrost have been identified to receive large quantities of terrestrial organic carbon from thaw and subsidence of the surrounding landscape into the lake, confirming the strong coupling between terrestrial and aquatic habitats and its influence on CH4 cycling.

  2. Effect of interannual variation in winter vertical mixing on CH4 dynamics in a subtropical reservoir

    NASA Astrophysics Data System (ADS)

    Itoh, Masayuki; Kobayashi, Yuki; Chen, Tzong-Yueh; Tokida, Takeshi; Fukui, Manabu; Kojima, Hisaya; Miki, Takeshi; Tayasu, Ichiro; Shiah, Fuh-Kwo; Okuda, Noboru

    2015-07-01

    Although freshwaters are considered to be substantial natural sources of atmospheric methane (CH4), in situ processes of CH4 production and consumption in freshwater ecosystems are poorly understood, especially in subtropical areas, leading to uncertainties in the estimation of global CH4 emissions. To improve our understanding of physical and biogeochemical factors affecting CH4 dynamics in subtropical lakes, we examined vertical and seasonal profiles of dissolved CH4 and its carbon isotope ratio (δ13C) and conducted incubation experiments to assess CH4 production and oxidation in the deep subtropical Fei-Tsui Reservoir (FTR; Taiwan). The mixing pattern of the FTR is essentially monomixis, but the intensity of winter vertical mixing changes with climatic conditions. In years with incomplete vertical mixing (does not reach the bottom) and subsequent strong thermal stratification resulting in profundal hypoxia, we observed increases in sedimentary CH4 production and thus profundal CH4 storage with the development of reducing conditions. In contrast, in years with strong winter vertical mixing to the bottom of the reservoir, CH4 production was suppressed under NO3--rich conditions, during which denitrifiers have the competitive advantage over methanogens. Diffusive emission from profundal CH4 storage appeared to be negligible due to the efficiency of CH4 oxidation during ascent through methane-oxidizing bacteria (MOB) activity. Most of the profundal CH4 was rapidly oxidized by MOB in both oxic and anoxic layers, as characterized by its carbon isotope signature. In contrast, aerobic CH4 production in the subsurface layer, which may be enhanced under high temperatures in summer, may account for a large portion of atmospheric CH4 emissions from this reservoir. Our CH4 profiling results provide valuable information for future studies predicting CH4 emissions from subtropical lakes with the progress of global warming.

  3. Environmental Controls on Aerobic Methane Oxidation in Coastal Waters

    NASA Astrophysics Data System (ADS)

    Steinle, L.; Maltby, J.; Engbersen, N.; Zopfi, J.; Bange, H. W.; Elvert, M.; Hinrichs, K. U.; Kock, A.; Lehmann, M. F.; Treude, T.; Niemann, H.

    2015-12-01

    Large quantities of the greenhouse gas CH4 are produced in anoxic sediments of continental margins and may be liberated to the overlying water column, and later into the atmosphere. Indeed, coastal seas account for more than 75% of global oceanic CH4 emissions. Yet, aerobic CH4 oxidizing bacteria (MOB) consume an important part of CH4 in the water column, thus mitigating CH4 release to the atmosphere. Coastal oceans are highly dynamic systems, in particular with regard to the variability of temperature, salinity and oxygen concentrations, all of which are potential key environmental factors controlling MOx. To determine the most important controlling factors, we conducted a two-year time-series study with measurements of CH4, MOx, the composition of the MOB community, and physicochemical water column parameters in a coastal inlet in the Baltic Sea (Eckernförde(E-) Bay, Boknis Eck Time Series Station). In addition, we investigated the influence of temperature and oxygen on MOx during controlled laboratory experiments. In E-Bay, seasonal stratification leads to hypoxia in bottom waters towards the end of the stratification period. Methane is produced year-round in the sediments, resulting in accumulation of methane in bottom waters, and supersaturation (with respect to the atmospheric equilibrium) in surface waters. Here, we will discuss the factors impacting MOx the most, which were a) perturbations of the water column caused by storm events, currents or seasonal mixing, b) temperature and c) oxygen concentration. a) Perturbations of the water column led to a sharp decrease in MOx within hours, probably caused by replacement of 'old' water with a high standing stock of MOB by 'new' waters with a lower abundance of MOB. b) An increase in temperature generally led to higher MOx rates. c) Even though CH4 was abundant at all depths, MOx was highest in bottom waters (1-5 nM/d), which usually contain the lowest O2 concentrations. Lab-based experiments with adjusted O2

  4. A Year in the Life: Annual Patterns of CO2 and CH4 from a Northern Finland Peatland, Including Anaerobic Methane Oxidation and Summer Ebullition Rates

    NASA Astrophysics Data System (ADS)

    Miller, K.; Lipson, D.; Biasi, C.; Dorodnikov, M.; Männistö, M.; Lai, C. T.

    2014-12-01

    The major ecological controls on methane (CH4) and carbon dioxide (CO2) fluxes in northern wetland systems are well known, yet estimates of source/sink magnitudes are often incongruous with measured rates. This mismatch persists because holistic flux datasets are rare, preventing 'whole picture' determinations of flux controls. To combat this, we measured net CO2 and CH4 fluxes from September 2012-2013 within a peatland in northern Lapland, Finland. In addition, we performed in situ manipulations and in vitro soil incubations to quantify anaerobic methane oxidation and methanogenic rates as they related to alternative electron acceptor availability. Average annual fluxes varied substantially between different depressions within the wetland, a pattern that persisted through all seasons. Season was a strong predictor of both CO2 and CH4 flux rates, yet CH4 rates were not related to melt-season 10cm or 30cm soil temperatures, and only poorly predicted with air temperatures. We found evidence for both autumnal and spring thaw CH4 bursts, collectively accounting for 26% of annual CH4 flux, although the autumnal burst was more than 5 fold larger than the spring burst. CH4 ebullition measured throughout the growing season augmented the CH4 source load by a factor of 1.5, and was linked with fine-scale spatial heterogeneity within the wetland. Surprisingly, CH4 flux rates were insensitive to Fe(III) and humic acid soil amendments, both of which amplified CO2 fluxes. Using in vitro incubations, we determined anaerobic methane oxidation and methanogenesis rates. Measured anaerobic oxidation rates showed potential consumption of between 6-39% of the methane produced, contributing approximately 1% of total carbon dioxide flux. Treatments of nitrate, sulfate and ferric iron showed that nitrate suppressed methanogenesis, but were not associated with anaerobic oxidation rates.

  5. WETTING STIMULATES ATMOSPHERIC CH4 OXIDATION BY ALPINE SOIL (R823442)

    EPA Science Inventory

    Studies were done to assess the effects of soil moisture manipulations on CH4 oxidation in soils from a dry alpine tundra site. When water was added to these soils there was a stimulation of CH4 oxidation. This stimulation of CH4 oxidation took ti...

  6. Effect of CH4 and O2 variations on rates of CH4 oxidation and stable isotope fractionation in tropical rain forest soils

    SciTech Connect

    Teh, Yit Arn; Conrad, Mark; Silver, Whendee L.; Carlson, Charlotte M.

    2003-10-01

    Methane-oxidizing bacteria are the primary sink for CH{sub 4} in reduced soils, and account for as much as 90 percent of all CH{sub 4} produced. Methanotrophic bacteria strongly discriminate against the heavy isotopes of carbon, resulting in CH{sub 4} emissions that are significantly more enriched in {sup 13}C than the original source material. Previous studies have used an isotope mass balance approach to quantify CH{sub 4} sources and sinks in the field, based on the assumption that the fractionation factor for CH{sub 4} oxidation is a constant. This study quantifies the effect of systematic variations in CH{sub 4} and O{sub 2} concentrations on rates of CH{sub 4} oxidation and stable isotope fractionation in tropical rain forest soils. Soils were collected from the 0-15 cm depth, and incubated with varying concentrations of CH{sub 4} (100 ppmv, 500 ppmv, 1000 ppmv, and 5000 ppmv) or O{sub 2} (3 percent, 5 percent, 10 percent, and 21 percent). The isotope fractionation factor for CH{sub 4} oxidation was calculated for each incubation using a Rayleigh fractionation model. Rates of CH{sub 4} oxidation varied significantly between CH{sub 4} treatments, with the 100 ppmv CH{sub 4} treatment showing the lowest rate of CH{sub 4} uptake, and the other 3 treatments showing similar rates of CH{sub 4} uptake. Rates of CH{sub 4} oxidation did not vary significantly between the different O{sub 2} treatments. The fractionation factor for CH{sub 4} oxidation varied significantly between the different CH{sub 4} treatments, with the 5000 ppmv CH{sub 4} treatment showing the largest {sup 13}C-enrichment of residual CH{sub 4}. In treatments where CH{sub 4} concentration was not rate-limiting (> 500 ppmv CH{sub 4}), the fractionation factor for CH{sub 4} oxidation was negatively correlated with CH{sub 4} oxidation rate (P < 0.003, r{sup 2} = 0.86). A multiple regression model that included initial CH{sub 4} concentration and CH{sub 4} oxidation rate as independent variables

  7. CO2 and CH4 Production and CH4 Oxidation in Low Temperature Soil Incubations from Flat- and High-Centered Polygons, Barrow, Alaska, 2012

    DOE Data Explorer

    David E. Graham; Jianqiu Zheng; Taniya RoyChowdhury

    2016-08-31

    The dataset consists of respiration and methane production rates and methane oxidation potential obtained from soil microcosm studies carried out under controlled temperature and incubation conditions. Soils cores collected in 2012 represent the flat- and high-centered polygon active layers and permafrost (when present) from the NGEE Arctic Intensive Study Site 1, Barrow, Alaska.

  8. CH4/Ar/H2/SF6 Plasma Etching for Surface Oxide Removal of Indium Bumps

    NASA Astrophysics Data System (ADS)

    Huang, Yue; Lin, Chun; Ye, Zhen-Hua; Liao, Qing-Jun; Ding, Rui-Jun

    2015-07-01

    Plasma etching for surface indium oxide removal by methane/argon/hydrogen/sulfur hexafluoride (CH4/Ar/H2/SF6) mixture has been implemented. The morphology of the indium bumps was not deteriorated after the plasma etching. High-resolution O 1 s x-ray photoelectron spectroscopy (XPS) proved that the In-O component decreased from 44.5% for the nonetched sample to 10.8% for the sample after plasma etching. The surface modification of the indium bumps might be in the form of doped fluorine according to the XPS results. The zero-bias resistance derived from current-voltage ( I- V) measurements for plasma-etched infrared detectors was comparable to that for nonetched ones, indicating that such plasma treatment is suitable for processing sensitive materials such as mercury cadmium telluride.

  9. 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

  10. 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.

  11. Consequences of metal-oxide interconversion for C-H bond activation during CH4 reactions on Pd catalysts.

    PubMed

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

    2013-10-16

    Mechanistic assessments based on kinetic and isotopic methods combined with density functional theory are used to probe the diverse pathways by which C-H bonds in CH4 react on bare Pd clusters, Pd cluster surfaces saturated with chemisorbed oxygen (O*), and PdO clusters. C-H activation routes change from oxidative addition to H-abstraction and then to σ-bond metathesis with increasing O-content, as active sites evolve from metal atom pairs (*-*) to oxygen atom (O*-O*) pairs and ultimately to Pd cation-lattice oxygen pairs (Pd(2+)-O(2-)) in PdO. The charges in the CH3 and H moieties along the reaction coordinate depend on the accessibility and chemical state of the Pd and O centers involved. Homolytic C-H dissociation prevails on bare (*-*) and O*-covered surfaces (O*-O*), while C-H bonds cleave heterolytically on Pd(2+)-O(2-) pairs at PdO surfaces. On bare surfaces, C-H bonds cleave via oxidative addition, involving Pd atom insertion into the C-H bond with electron backdonation from Pd to C-H antibonding states and the formation of tight three-center (H3C···Pd···H)(‡) transition states. On O*-saturated Pd surfaces, C-H bonds cleave homolytically on O*-O* pairs to form radical-like CH3 species and nearly formed O-H bonds at a transition state (O*···CH3(•)···*OH)(‡) that is looser and higher in enthalpy than on bare Pd surfaces. On PdO surfaces, site pairs consisting of exposed Pd(2+) and vicinal O(2-), Pd(ox)-O(ox), cleave C-H bonds heterolytically via σ-bond metathesis, with Pd(2+) adding to the C-H bond, while O(2-) abstracts the H-atom to form a four-center (H3C(δ-)···Pd(ox)···H(δ+)···O(ox))(‡) transition state without detectable Pd(ox) reduction. The latter is much more stable than transition states on *-* and O*-O* pairs and give rise to a large increase in CH4 oxidation turnover rates at oxygen chemical potentials leading to Pd to PdO transitions. These distinct mechanistic pathways for C-H bond activation, inferred from theory

  12. Evaluation of methyl fluoride and dimethyl ether as inhibitors of aerobic methane oxidation

    USGS Publications Warehouse

    Oremland, R.S.; Culbertson, C.W.

    1992-01-01

    Methyl fluoride (MF) and dimethyl ether (DME) were effective inhibitors of aerobic methanotrophy in a variety of soils. MF and DME blocked consumption of CH4 as well as the oxidation of 14CH4 to 14CO2, but neither MF nor DME affected the oxidation of [14C]methanol or [14C]formate to 14CO2. Cooxidation of ethane and propane by methane-oxidizing soils was also inhibited by MF. Nitrification (ammonia oxidation) in soils was inhibited by both MF and DME. Production of N2O via nitrification was inhibited by MF; however, MF did not affect N2O production associated with denitrification. Methanogenesis was partially inhibited by MF but not by DME. Methane oxidation was ~100-fold more sensitive to MF than was methanogenesis, indicating that an optimum concentration could be employed to selectively block methanotrophy. MF inhibited methane oxidation by cell suspensions of Methylococcus capsulatus; however, DME was a much less effective inhibitor.

  13. Effects of nitrogen conversion and environmental factors on landfill CH4 oxidation and N2O emissions in aged refuse.

    PubMed

    Zhang, Houhu; Zhao, Keqiang; Yan, Xiaofei; Sun, Qinfang; Li, Yi; Zhang, Yi; Zun, Zhao; Ke, Fan

    2013-09-15

    We determined the effects of nitrification capacity and environmental factors on landfill methane oxidation potential (MOP) using an aged refuse in laboratory batch assays and compared it with two different types of soils. The nitrogen conversion in the three experimental materials after 120 h incubation yielded first-order reaction kinetics at an initial concentration of 200 mg kg(-1) NH4(+)-N. The net nitrification rate for the aged refuse was 1.50 (p < 0.05) and 2.08 (p < 0.05) times that of the clay soil and the sandy soil, respectively. The net NO3(-)-N generation rate by the aged refuse was 1.93 (p < 0.05) and 2.57 (p < 0.05) times that of the clay soil and the sandy soil, respectively. When facilitated by ammonia-oxidizing bacteria during CH4 co-oxidation, the average value of the MOP in the aged refuse at a temperature range of 4-45 °C was 2.34 (p < 0.01) and 4.71 (p < 0.05) times greater than that of the clay soil and the sandy soil, respectively. When the moisture content ranged from 8 to 32% by mass, the average values for the MOP in the aged refuse were 2.08 (p < 0.01) and 3.15 (p < 0.01) times greater than that of the clay soil and the sandy soil, respectively. The N2O fluxes in the aged refuse at 32% moisture content were 5.33 (p < 0.05) and 12.00 (p < 0.05) times more than in the clay and the sandy soil, respectively. The increase in N2O emissions from a municipal solid waste landfill can be neglected after applying an aged refuse bio-cover because of the much higher MOP in the aged refuse. The calculated maximum MOP value in the aged refuse was 12.45 μmol g(-1) d.w. h(-1), which was much higher than the documented data.

  14. Microbial mechanisms to reduce the uncertainties in the CH4 emissions from global rice fields

    NASA Astrophysics Data System (ADS)

    Kamaljit, K.; Tian, H.; Ren, W.; Yang, J.

    2013-12-01

    In terrestrial ecosystems, methane (CH4) uptake or emission represents the net balance between activities of different microbial organisms including anaerobic Methanogens that produce CH4 and Methanotrophs which oxidize CH4 in the aerobic environments. In this way, anaerobic soil environments such as rice fields are major source of terrestrial CH4 emissions. However, large uncertainties in the CH4 emission estimates have been reported from rice fields. The bottom-up and top-down methods showed a wide range of CH4 emissions estimations ranging from 25 to 300 Tg yr-1 from rice fields. The major reason for uncertainties in the CH4 emissions includes the water management that alters the balance of Methanogens and Methanotrophs in the rice fields. Two kinds of water management practices are followed including continuous flooding (CF) which refers to the continuous submergence as well as alternate wetting and drying (AWD) in which the rice fields are drained for several days during the growing season. The AWD provides aeration stress on Methanogens resulting in lower CH4 emissions than CF water management followed in the rice fields. A single aeration during growing season may significantly reduce the CH4 emission from the rice fields. Currently, most of the models structures assume that Methanogens become active once the soil moisture content is raised to saturation. However, several laboratory scale studies have indicated that following aeration the Methanogens don't become fully functional immediately even if the soil moisture content is raised to saturation. In this study, we integrated the aeration stress mechanisms on the Methanogens in the Dynamic Land Ecosystem Model (DLEM). The improved version of DLEM was used to conduct uncertainty analysis on global CH4 emission estimation following CF and AWD water management in the rice fields. Results of this study have shown that inclusion of the aeration stress mechanism on Methanogens in the modeling framework has

  15. Controlling the catalytic aerobic oxidation of phenols.

    PubMed

    Esguerra, Kenneth Virgel N; Fall, Yacoub; Petitjean, Laurène; Lumb, Jean-Philip

    2014-05-28

    The oxidation of phenols is the subject of extensive investigation, but there are few catalytic aerobic examples that are chemo- and regioselective. Here we describe conditions for the ortho-oxygenation or oxidative coupling of phenols under copper (Cu)-catalyzed aerobic conditions that give rise to ortho-quinones, biphenols or benzoxepines. We demonstrate that each product class can be accessed selectively by the appropriate choice of Cu(I) salt, amine ligand, desiccant and reaction temperature. In addition, we evaluate the effects of substituents on the phenol and demonstrate their influence on selectivity between ortho-oxygenation and oxidative coupling pathways. These results create an important precedent of catalyst control in the catalytic aerobic oxidation of phenols and set the stage for future development of catalytic systems and mechanistic investigations. PMID:24784319

  16. High production of nitrous oxide (N2O), methane (CH4) and dimethylsulphoniopropionate (DMSP) in a massive marine phytoplankton culture

    NASA Astrophysics Data System (ADS)

    Florez-Leiva, L.; Tarifeño, E.; Cornejo, M.; Kiene, R.; Farías, L.

    2010-09-01

    The production of large amounts of algal biomass for different purposes such as aquaculture or biofuels, may cause impacts on the marine environment. One such impact is the production of radiatively active trace gases and aerosols with climate cooling (dimethyl sulfide DMS and its precursor DMSP) and warming (N2O and CH4) effects. Total and dissolved DMSP, N2O and CH4, together with other environmental variables were monitored daily for 46 days within a massive microalgae monoculture of Nannochloris (Chlorophyceae) in an open pond system. The growth of this green microalgae was stimulated by the addition of N- and P-rich salts, resulting in exponential growth (growth phase) during the first 17 days observed by cell abundance (1 × 106 to 4.4 × 106 cell mL-1) and Chl-a levels (from 1.4 to 96 mg Chl-a m-3) followed by a decrease in both Chl-a and cell abundance (senescence phase). Total DMSP (from 6.3 to 142 μmol m-3), dissolved DMSP i.e. 5.8 to 137 μmol m-3 and N2O (from 8 to 600 μmol m-3) abruptly peaked during the senescence phase, whereas CH4 steadily increased between 2 and 10 μmol m-3 during the growth phase. Different ratios between tracers and Chl-a during both phases reveal different biochemical processes involved in the cycling of these gases and tracers. Our results show that despite the consumption of large quantities of CO2 by the massive algal culture, a minor amount of DMS and huge amounts of greenhouse gases were produced, in particular N2O, which has a greater radiative effect per molecule than CO2. These findings have important implications for biogeochemical studies and for environmental management of aquaculture activities.

  17. 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

  18. High resolution and comprehensive techniques to analyze aerobic methane oxidation in mesocosm experiments

    NASA Astrophysics Data System (ADS)

    Chan, E. W.; Kessler, J. D.; Redmond, M. C.; Shiller, A. M.; Arrington, E. C.; Valentine, D. L.; Colombo, F.

    2015-12-01

    Many studies of microbially mediated aerobic methane oxidation in oceanic environments have examined the many different factors that control the rates of oxidation. However, there is debate on how quickly methane is oxidized once a microbial population is established and what factor(s) are limiting in these types of environments. These factors include the availability of CH4, O2, trace metals, nutrients, and the density of cell population. Limits to these factors can also control the temporal aspects of a methane oxidation event. In order to look at this process in its entirety and with higher temporal resolution, a mesocosm incubation system was developed with a Dissolved Gas Analyzer System (DGAS) coupled with a set of analytical tools to monitor aerobic methane oxidation in real time. With the addition of newer laser spectroscopy techniques (cavity ringdown spectroscopy), stable isotope fractionation caused by microbial processes can also be examined on a real time and automated basis. Cell counting, trace metal, nutrient, and DNA community analyses have also been carried out in conjunction with these mesocosm samples to provide a clear understanding of the biology in methane oxidation dynamics. This poster will detail the techniques involved to provide insights into the chemical and isotopic kinetics controlling aerobic methane oxidation. Proof of concept applications will be presented from seep sites in the Hudson Canyon and the Sleeping Dragon seep field, Mississippi Canyon 118 (MC 118). This system was used to conduct mesocosm experiments to examine methane consumption, O2 consumption, nutrient consumption, and biomass production.

  19. Effects of simulated spring thaw of permafrost from mineral cryosol on CO2 emissions and atmospheric CH4 uptake

    NASA Astrophysics Data System (ADS)

    Stackhouse, Brandon T.; Vishnivetskaya, Tatiana A.; Layton, Alice; Chauhan, Archana; Pfiffner, Susan; Mykytczuk, Nadia C.; Sanders, Rebecca; Whyte, Lyle G.; Hedin, Lars; Saad, Nabil; Myneni, Satish; Onstott, Tullis C.

    2015-09-01

    Previous studies investigating organic-rich tundra have reported that increasing biodegradation of Arctic tundra soil organic carbon (SOC) under warming climate regimes will cause increasing CO2 and CH4 emissions. Organic-poor, mineral cryosols, which comprise 87% of Arctic tundra, are not as well characterized. This study examined biogeochemical processes of 1 m long intact mineral cryosol cores (1-6% SOC) collected in the Canadian high Arctic. Vertical profiles of gaseous and aqueous chemistry and microbial composition were related to surface CO2 and CH4 fluxes during a simulated spring/summer thaw under light versus dark and in situ versus water saturated treatments. CO2 fluxes attained 0.8 ± 0.4 mmol CO2 m-2 h-1 for in situ treatments, of which 85 ± 11% was produced by aerobic SOC oxidation, consistent with field observations and metagenomic analyses indicating aerobic heterotrophs were the dominant phylotypes. The Q10 values of CO2 emissions ranged from 2 to 4 over the course of thawing. CH4 degassing occurred during initial thaw; however, all cores were CH4 sinks at atmospheric concentration CH4. Atmospheric CH4 uptake rates ranged from -126 ± 77 to -207 ± 7 nmol CH4 m-2 h-1 with CH4 consumed between 0 and 35 cm depth. Metagenomic and gas chemistry analyses revealed that high-affinity Type II methanotrophic sequence abundance and activity were highest between 0 and 35 cm depth. Microbial sulfate reduction dominated the anaerobic processes, outcompeting methanogenesis for H2 and acetate. Fluxes, microbial community composition, and biogeochemical rates indicate that mineral cryosols of Axel Heiberg Island act as net CO2 sources and atmospheric CH4 sinks during summertime thaw under both in situ and water saturated states.

  20. Surface Structure of Aerobically Oxidized Diamond Nanocrystals

    PubMed Central

    2015-01-01

    We investigate the aerobic oxidation of high-pressure, high-temperature nanodiamonds (5–50 nm dimensions) using a combination of carbon and oxygen K-edge X-ray absorption, wavelength-dependent X-ray photoelectron, and vibrational spectroscopies. Oxidation at 575 °C for 2 h eliminates graphitic carbon contamination (>98%) and produces nanocrystals with hydroxyl functionalized surfaces as well as a minor component (<5%) of carboxylic anhydrides. The low graphitic carbon content and the high crystallinity of HPHT are evident from Raman spectra acquired using visible wavelength excitation (λexcit = 633 nm) as well as carbon K-edge X-ray absorption spectra where the signature of a core–hole exciton is observed. Both spectroscopic features are similar to those of chemical vapor deposited (CVD) diamond but differ significantly from the spectra of detonation nanodiamond. The importance of these findings to the functionalization of nanodiamond surfaces for biological labeling applications is discussed. PMID:25436035

  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. Biogeochemical processes at the fringe of a landfill leachate pollution plume: potential for dissolved organic carbon, Fe(II), Mn(II), NH 4, and CH 4 oxidation

    NASA Astrophysics Data System (ADS)

    van Breukelen, Boris M.; Griffioen, Jasper

    2004-09-01

    Various redox reactions may occur at the fringe of a landfill leachate plume, involving oxidation of dissolved organic carbon (DOC), CH 4, Fe(II), Mn(II), and NH 4 from leachate and reduction of O 2, NO 3 and SO 4 from pristine groundwater. Knowledge on the relevance of these processes is essential for the simulation and evaluation of natural attenuation (NA) of pollution plumes. The occurrence of such biogeochemical processes was investigated at the top fringe of a landfill leachate plume (Banisveld, the Netherlands). Hydrochemical depth profiles of the top fringe were captured via installation of a series of multi-level samplers at 18, 39 and 58 m downstream from the landfill. Ten-centimeter vertical resolution was necessary to study NA within a fringe as thin as 0.5 m. Bromide appeared an equally well-conservative tracer as chloride to calculate dilution of landfill leachate, and its ratio to chloride was high compared to other possible sources of salt in groundwater. The plume fringe rose steadily from a depth of around 5 m towards the surface with a few meters in the period 1998-2003. The plume uplift may be caused by enhanced exfiltration to a brook downstream from the landfill, due to increased precipitation over this period and an artificial lowering of the water level of the brook. This rise invoked cation exchange including proton buffering, and triggered degassing of methane. The hydrochemical depth profile was simulated in a 1D vertical reactive transport model using PHREEQC-2. Optimization using the nonlinear optimization program PEST brought forward that solid organic carbon and not clay minerals controlled retardation of cations. Cation exchange resulted in spatial separation of Fe(II), Mn(II) and NH 4 fronts from the fringe, and thereby prevented possible oxidation of these secondary redox species. Degradation of DOC may happen in the fringe zone. Re-dissolution of methane escaped from the plume and subsequent oxidation is an explanation for absence

  3. Surface Structure of Aerobically Oxidized Diamond Nanocrystals

    SciTech Connect

    Wolcott, Abraham; Schiros, Theanne; Trusheim, Matthew E.; Chen, Edward H.; Nordlund, Dennis; Diaz, Rosa E.; Gaaton, Ophir; Englund, Dirk; Owen, Jonathan S.

    2014-10-27

    Here we investigate the aerobic oxidation of high-pressure, high-temperature nanodiamonds (5–50 nm dimensions) using a combination of carbon and oxygen K-edge X-ray absorption, wavelength-dependent X-ray photoelectron, and vibrational spectroscopies. Oxidation at 575 °C for 2 h eliminates graphitic carbon contamination (>98%) and produces nanocrystals with hydroxyl functionalized surfaces as well as a minor component (<5%) of carboxylic anhydrides. The low graphitic carbon content and the high crystallinity of HPHT are evident from Raman spectra acquired using visible wavelength excitation (λexcit = 633 nm) as well as carbon K-edge X-ray absorption spectra where the signature of a core–hole exciton is observed. Both spectroscopic features are similar to those of chemical vapor deposited (CVD) diamond but differ significantly from the spectra of detonation nanodiamond. Lastly, we discuss the importance of these findings to the functionalization of nanodiamond surfaces for biological labeling applications.

  4. Surface Structure of Aerobically Oxidized Diamond Nanocrystals

    DOE PAGES

    Wolcott, Abraham; Schiros, Theanne; Trusheim, Matthew E.; Chen, Edward H.; Nordlund, Dennis; Diaz, Rosa E.; Gaaton, Ophir; Englund, Dirk; Owen, Jonathan S.

    2014-10-27

    Here we investigate the aerobic oxidation of high-pressure, high-temperature nanodiamonds (5–50 nm dimensions) using a combination of carbon and oxygen K-edge X-ray absorption, wavelength-dependent X-ray photoelectron, and vibrational spectroscopies. Oxidation at 575 °C for 2 h eliminates graphitic carbon contamination (>98%) and produces nanocrystals with hydroxyl functionalized surfaces as well as a minor component (<5%) of carboxylic anhydrides. The low graphitic carbon content and the high crystallinity of HPHT are evident from Raman spectra acquired using visible wavelength excitation (λexcit = 633 nm) as well as carbon K-edge X-ray absorption spectra where the signature of a core–hole exciton is observed.more » Both spectroscopic features are similar to those of chemical vapor deposited (CVD) diamond but differ significantly from the spectra of detonation nanodiamond. Lastly, we discuss the importance of these findings to the functionalization of nanodiamond surfaces for biological labeling applications.« less

  5. Growth of nitrite-oxidizing bacteria by aerobic hydrogen oxidation.

    PubMed

    Koch, Hanna; Galushko, Alexander; Albertsen, Mads; Schintlmeister, Arno; Gruber-Dorninger, Christiane; Lücker, Sebastian; Pelletier, Eric; Le Paslier, Denis; Spieck, Eva; Richter, Andreas; Nielsen, Per H; Wagner, Michael; Daims, Holger

    2014-08-29

    The bacterial oxidation of nitrite to nitrate is a key process of the biogeochemical nitrogen cycle. Nitrite-oxidizing bacteria are considered a highly specialized functional group, which depends on the supply of nitrite from other microorganisms and whose distribution strictly correlates with nitrification in the environment and in wastewater treatment plants. On the basis of genomics, physiological experiments, and single-cell analyses, we show that Nitrospira moscoviensis, which represents a widely distributed lineage of nitrite-oxidizing bacteria, has the genetic inventory to utilize hydrogen (H2) as an alternative energy source for aerobic respiration and grows on H2 without nitrite. CO2 fixation occurred with H2 as the sole electron donor. Our results demonstrate a chemolithoautotrophic lifestyle of nitrite-oxidizing bacteria outside the nitrogen cycle, suggesting greater ecological flexibility than previously assumed.

  6. Methane oxidation in a crude oil contaminated aquifer: Delineation of aerobic reactions at the plume fringes

    NASA Astrophysics Data System (ADS)

    Amos, Richard T.; Bekins, Barbara A.; Delin, Geoffrey N.; Cozzarelli, Isabelle M.; Blowes, David W.; Kirshtein, Julie D.

    2011-07-01

    High resolution direct-push profiling over short vertical distances was used to investigate CH 4 attenuation in a petroleum contaminated aquifer near Bemidji, Minnesota. The contaminant plume was delineated using dissolved gases, redox sensitive components, major ions, carbon isotope ratios in CH 4 and CO 2, and the presence of methanotrophic bacteria. Sharp redox gradients were observed near the water table. Shifts in δ 13C CH4 from an average of - 57.6‰ (± 1.7‰) in the methanogenic zone to - 39.6‰ (± 8.7‰) at 105 m downgradient, strongly suggest CH 4 attenuation through microbially mediated degradation. In the downgradient zone the aerobic/anaerobic transition is up to 0.5 m below the water table suggesting that transport of O 2 across the water table is leading to aerobic degradation of CH 4 at this interface. Dissolved N 2 concentrations that exceeded those expected for water in equilibrium with the atmosphere indicated bubble entrapment followed by preferential stripping of O 2 through aerobic degradation of CH 4 or other hydrocarbons. Multivariate and cluster analysis were used to distinguish between areas of significant bubble entrapment and areas where other processes such as the infiltration of O 2 rich recharge water were important O 2 transport mechanisms.

  7. Methane oxidation in a crude oil contaminated aquifer: Delineation of aerobic reactions at the plume fringes

    USGS Publications Warehouse

    Amos, R.T.; Bekins, B.A.; Delin, G.N.; Cozzarelli, I.M.; Blowes, D.W.; Kirshtein, J.D.

    2011-01-01

    High resolution direct-push profiling over short vertical distances was used to investigate CH4 attenuation in a petroleum contaminated aquifer near Bemidji, Minnesota. The contaminant plume was delineated using dissolved gases, redox sensitive components, major ions, carbon isotope ratios in CH4 and CO2, and the presence of methanotrophic bacteria. Sharp redox gradients were observed near the water table. Shifts in ??13CCH4 from an average of - 57.6??? (?? 1.7???) in the methanogenic zone to - 39.6??? (?? 8.7???) at 105 m downgradient, strongly suggest CH4 attenuation through microbially mediated degradation. In the downgradient zone the aerobic/anaerobic transition is up to 0.5 m below the water table suggesting that transport of O2 across the water table is leading to aerobic degradation of CH4 at this interface. Dissolved N2 concentrations that exceeded those expected for water in equilibrium with the atmosphere indicated bubble entrapment followed by preferential stripping of O2 through aerobic degradation of CH4 or other hydrocarbons. Multivariate and cluster analysis were used to distinguish between areas of significant bubble entrapment and areas where other processes such as the infiltration of O 2 rich recharge water were important O2 transport mechanisms. ?? 2011 Elsevier B.V. All rights reserved.

  8. Dissociative recombination of CH4(+).

    PubMed

    Thomas, Richard D; Kashperka, Iryna; Vigren, E; Geppert, Wolf D; Hamberg, Mathias; Larsson, Mats; af Ugglas, Magnus; Zhaunerchyk, Vitali

    2013-10-01

    CH4(+) is an important molecular ion in the astrochemistry of diffuse clouds, dense clouds, cometary comae, and planetary ionospheres. However, the rate of one of the common destruction mechanisms for molecular ions in these regions, dissociative recombination (DR), is somewhat uncertain. Here, we present absolute measurements for the DR of CH4(+) made using the heavy ion storage ring CRYRING in Stockholm, Sweden. From our collision-energy dependent cross-sections, we infer a thermal rate constant of k(Te) = 1.71(±0.02) × 10(–6)(Te/300)(−0.66(±0.02)) cm3 s(–1) over the region of electron temperatures 10 ≤ Te ≤ 1000 K. At low collision energies, we have measured the branching fractions of the DR products to be CH4 (0.00 ± 0.00); CH3 + H (0.18 ± 0.03); CH2 + 2H (0.51 ± 0.03); CH2 + H2 (0.06 ± 0.01); CH + H2 + H (0.23 ± 0.01); and CH + 2H2 (0.02 ± 0.01), indicating that two or more C–H bonds are broken in 80% of all collisions.

  9. 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.

  10. Aerobic sulfur-oxidizing bacteria: Environmental selection and diversification

    NASA Technical Reports Server (NTRS)

    Caldwell, D.

    1985-01-01

    Sulfur-oxidizing bacteria oxidize reduced inorganic compounds to sulfuric acid. Lithotrophic sulfur oxidizer use the energy obtained from oxidation for microbial growth. Heterotrophic sulfur oxidizers obtain energy from the oxidation of organic compounds. In sulfur-oxidizing mixotrophs energy are derived either from the oxidation of inorganic or organic compounds. Sulfur-oxidizing bacteria are usually located within the sulfide/oxygen interfaces of springs, sediments, soil microenvironments, and the hypolimnion. Colonization of the interface is necessary since sulfide auto-oxidizes and because both oxygen and sulfide are needed for growth. The environmental stresses associated with the colonization of these interfaces resulted in the evolution of morphologically diverse and unique aerobic sulfur oxidizers.

  11. Landscape patterns of CH4 fluxes in an alpine tundra ecosystem

    USGS Publications Warehouse

    West, A.E.; Brooks, P.D.; Fisk, M.C.; Smith, L.K.; Holland, E.A.; Jaeger, C. H.; Babcock, S.; Lai, R.S.; Schmidt, S.K.

    1999-01-01

    We measured CH4 fluxes from three major plant communities characteristic of alpine tundra in the Colorado Front Range. Plant communities in this ecosystem are determined by soil moisture regimes induced by winter snowpack distribution. Spatial patterns of CH4 flux during the snow-free season corresponded roughly with these plant communities. In Carex-dominated meadows, which receive the most moisture from snowmelt, net CH4 production occurred. However, CH4 production in one Carex site (seasonal mean = +8.45 mg CH4 m-2 d-1) was significantly larger than in the other Carex sites (seasonal means = -0.06 and +0.05 mg CH4 m-2 d-1). This high CH4 flux may have resulted from shallower snowpack during the winter. In Acomastylis meadows, which have an intermediate moisture regime, CH4 oxidation dominated (seasonal mean = -0.43 mg CH4 m-2 d-1). In the windswept Kobresia meadow plant community, which receive the least amount of moisture from snowmelt, only CH4 oxidation was observed (seasonal mean = -0.77 mg CH4 m-2 d-1). Methane fluxes correlated with a different set of environmental factors within each plant community. In the Carex plant community, CH4 emission was limited by soil temperature. In the Acomastylis meadows, CH4 oxidation rates correlated positively with soil temperature and negatively with soil moisture. In the Kobresia community, CH4 oxidation was stimulated by precipitation. Thus, both snow-free season CH4 fluxes and the controls on those CH4 fluxes were related to the plant communities determined by winter snowpack.

  12. Aerobic cometabolic degradation of trichloroethene by methane and ammonia oxidizing microorganisms naturally associated with Carex comosa roots.

    PubMed

    Powell, C L; Nogaro, G; Agrawal, A

    2011-06-01

    The degradation potential of trichloroethene by the aerobic methane- and ammonia-oxidizing microorganisms naturally associated with wetland plant (Carex comosa) roots was examined in this study. In bench-scale microcosm experiments with washed (soil free) Carex comosa roots, the activity of root-associated methane- and ammonia-oxidizing microorganisms, which were naturally present on the root surface and/or embedded within the roots, was investigated. Significant methane and ammonia oxidation were observed reproducibly in batch reactors with washed roots incubated in growth media, where methane oxidation developed faster (2 weeks) compared to ammonia oxidation (4 weeks) in live microcosms. After enrichment, the methane oxidizers demonstrated their ability to degrade 150 μg l(-1) TCE effectively at 1.9 mg l(-1) of aqueous CH(4). In contrast, ammonia oxidizers showed a rapid and complete inhibition of ammonia oxidation with 150 μg l(-1) TCE at 20 mg l(-1) of NH(4)(+)-N, which may be attributed to greater sensitivity of ammonia oxidizers to TCE or its degradation product. No such inhibitory effect of TCE degradation was detected on methane oxidation at the above experimental conditions. The results presented here suggest that microorganisms associated with wetland plant roots can assist in the natural attenuation of TCE in contaminated aquatic environments.

  13. Low methane (CH4) emissions downstream of a monomictic subtropical hydroelectric reservoir (Nam Theun 2, Lao PDR)

    NASA Astrophysics Data System (ADS)

    Deshmukh, Chandrashekhar; Guérin, Frédéric; Labat, David; Pighini, Sylvie; Vongkhamsao, Axay; Guédant, Pierre; Rode, Wanidaporn; Godon, Arnaud; Chanudet, Vincent; Descloux, Stéphane; Serça, Dominique

    2016-03-01

    of the design of the water intake. A significant fraction of the CH4 that should have been transferred and emitted downstream of the powerhouse is emitted at the reservoir surface because of the artificial turbulence generated around the water intake. The positive counterpart of this artificial mixing is that it allows O2 diffusion down to the bottom of the water column, enhancing aerobic methane oxidation, and it subsequently lowered downstream emissions by at least 40 %.

  14. Low methane (CH4) emissions downstream of a monomictic subtropical hydroelectric reservoir (Nam Theun 2, Lao PDR)

    NASA Astrophysics Data System (ADS)

    Deshmukh, C.; Guérin, F.; Pighini, S.; Vongkhamsao, A.; Guédant, P.; Rode, W.; Godon, A.; Chanudet, V.; Descloux, S.; Serça, D.

    2015-07-01

    of the design of the water intake. A significant fraction of the CH4 that should have been transferred and emitted downstream of the powerhouse is emitted at the reservoir surface because of the artificial turbulence generated around the water intake. The positive counterpart of this artificial mixing is that it allows O2 diffusion down to the bottom of the water column enhancing aerobic methane oxidation and it subsequently lowering downstream emissions by at least 40 %.

  15. Effect of sporadic destratification, seasonal overturn, and artificial mixing on CH4 emissions from a subtropical hydroelectric reservoir

    NASA Astrophysics Data System (ADS)

    Guérin, Frédéric; Deshmukh, Chandrashekhar; Labat, David; Pighini, Sylvie; Vongkhamsao, Axay; Guédant, Pierre; Rode, Wanidaporn; Godon, Arnaud; Chanudet, Vincent; Descloux, Stéphane; Serça, Dominique

    2016-06-01

    Inland waters in general and freshwater reservoirs specifically are recognized as a source of CH4 into the atmosphere. Although the diffusion at the air-water interface is the most studied pathway, its spatial and temporal variations are poorly documented. We measured temperature and O2 and CH4 concentrations every 2 weeks for 3.5 years at nine stations in a subtropical monomictic reservoir which was flooded in 2008 (Nam Theun 2 Reservoir, Lao PDR). Based on these results, we quantified CH4 storage in the water column and diffusive fluxes from June 2009 to December 2012. We compared diffusive emissions with ebullition from Deshmukh et al. (2014) and aerobic methane oxidation and downstream emissions from Deshmukh et al. (2016). In this monomictic reservoir, the seasonal variations of CH4 concentration and storage were highly dependent on the thermal stratification. Hypolimnic CH4 concentration and CH4 storage reached their maximum in the warm dry season (WD) when the reservoir was stratified. Concentration and storage decreased during the warm wet (WW) season and reached its minimum after the reservoir overturned in the cool dry (CD) season. The sharp decreases in CH4 storage were concomitant with extreme diffusive fluxes (up to 200 mmol m-2 d-1). These sporadic emissions occurred mostly in the inflow region in the WW season and during overturn in the CD season in the area of the reservoir that has the highest CH4 storage. Although they corresponded to less than 10 % of the observations, these extreme CH4 emissions (> 5 mmol m-2 d-1) contributed up to 50 % of total annual emissions by diffusion. During the transition between the WD and WW seasons, a new emission hotspot was identified upstream of the water intake where diffusive fluxes peaked at 600 mmol m-2 d-1 in 2010 down to 200 mmol m-2 d-1 in 2012. The hotspot was attributed to the mixing induced by the water intakes (artificial mixing). Emissions from this area contributed 15-25 % to total annual emissions

  16. Aerobic Denitrifying Bacteria That Produce Low Levels of Nitrous Oxide

    PubMed Central

    Takaya, Naoki; Catalan-Sakairi, Maria Antonina B.; Sakaguchi, Yasushi; Kato, Isao; Zhou, Zhemin; Shoun, Hirofumi

    2003-01-01

    Most denitrifiers produce nitrous oxide (N2O) instead of dinitrogen (N2) under aerobic conditions. We isolated and characterized novel aerobic denitrifiers that produce low levels of N2O under aerobic conditions. We monitored the denitrification activities of two of the isolates, strains TR2 and K50, in batch and continuous cultures. Both strains reduced nitrate (NO3−) to N2 at rates of 0.9 and 0.03 μmol min−1 unit of optical density at 540 nm−1 at dissolved oxygen (O2) (DO) concentrations of 39 and 38 μmol liter−1, respectively. At the same DO level, the typical denitrifier Pseudomonas stutzeri and the previously described aerobic denitrifier Paracoccus denitrificans did not produce N2 but evolved more than 10-fold more N2O than strains TR2 and K50 evolved. The isolates denitrified NO3− with concomitant consumption of O2. These results indicated that strains TR2 and K50 are aerobic denitrifiers. These two isolates were taxonomically placed in the β subclass of the class Proteobacteria and were identified as P. stutzeri TR2 and Pseudomonas sp. strain K50. These strains should be useful for future investigations of the mechanisms of denitrifying bacteria that regulate N2O emission, the single-stage process for nitrogen removal, and microbial N2O emission into the ecosystem. PMID:12788710

  17. δ(13)C-CH4 reveals CH4 variations over oceans from mid-latitudes to the Arctic.

    PubMed

    Yu, Juan; Xie, Zhouqing; Sun, Liguang; Kang, Hui; He, Pengzhen; Xing, Guangxi

    2015-01-01

    The biogeochemical cycles of CH4 over oceans are poorly understood, especially over the Arctic Ocean. Here we report atmospheric CH4 levels together with δ(13)C-CH4 from offshore China (31°N) to the central Arctic Ocean (up to 87°N) from July to September 2012. CH4 concentrations and δ(13)C-CH4 displayed temporal and spatial variation ranging from 1.65 to 2.63 ppm, and from -50.34% to -44.94% (mean value: -48.55 ± 0.84%), respectively. Changes in CH4 with latitude were linked to the decreasing input of enriched δ(13)C and chemical oxidation by both OH and Cl radicals as indicated by variation of δ(13)C. There were complex mixing sources outside and inside the Arctic Ocean. A keeling plot showed the dominant influence by hydrate gas in the Nordic Sea region, while the long range transport of wetland emissions were one of potentially important sources in the central Arctic Ocean. Experiments comparing sunlight and darkness indicate that microbes may also play an important role in regional variations. PMID:26323236

  18. δ13C-CH4 reveals CH4 variations over oceans from mid-latitudes to the Arctic

    PubMed Central

    Yu, Juan; Xie, Zhouqing; Sun, Liguang; Kang, Hui; He, Pengzhen; Xing, Guangxi

    2015-01-01

    The biogeochemical cycles of CH4 over oceans are poorly understood, especially over the Arctic Ocean. Here we report atmospheric CH4 levels together with δ13C-CH4 from offshore China (31°N) to the central Arctic Ocean (up to 87°N) from July to September 2012. CH4 concentrations and δ13C-CH4 displayed temporal and spatial variation ranging from 1.65 to 2.63 ppm, and from −50.34% to −44.94% (mean value: −48.55 ± 0.84%), respectively. Changes in CH4 with latitude were linked to the decreasing input of enriched δ13C and chemical oxidation by both OH and Cl radicals as indicated by variation of δ13C. There were complex mixing sources outside and inside the Arctic Ocean. A keeling plot showed the dominant influence by hydrate gas in the Nordic Sea region, while the long range transport of wetland emissions were one of potentially important sources in the central Arctic Ocean. Experiments comparing sunlight and darkness indicate that microbes may also play an important role in regional variations. PMID:26323236

  19. Aerobic Oxidation of an Osmium(III) N-Hydroxyguanidine Complex To Give Nitric Oxide.

    PubMed

    Xiang, Jing; Wang, Qian; Yiu, Shek-Man; Man, Wai-Lun; Kwong, Hoi-Ki; Lau, Tai-Chu

    2016-05-16

    The aerobic oxidation of the N-hydroxyguanidinum moiety of N-hydroxyarginine to NO is a key step in the biosynthesis of NO by the enzyme nitric oxide synthase (NOS). So far, there is no chemical system that can efficiently carry out similar aerobic oxidation to give NO. We report here the synthesis and X-ray crystal structure of an osmium(III) N-hydroxyguanidine complex, mer-[Os(III){NH═C(NH2)(NHOH)}(L)(CN)3](-) (OsGOH, HL = 2-(2-hydroxyphenyl)benzoxazole), which to the best of our knowledge is the first example of a transition metal N-hydroxyguanidine complex. More significantly, this complex readily undergoes aerobic oxidation at ambient conditions to generate NO. The oxidation is pH-dependent; at pH 6.8, fac-[Os(NO)(L)(CN)3](-) is formed in which the NO produced is bound to the osmium center. On the other hand, at pH 12, aerobic oxidation of OsGOH results in the formation of the ureato complex [Os(III)(NHCONH2)(L)(CN)3](2-) and free NO. Mechanisms for this aerobic oxidation at different pH values are proposed. PMID:27135258

  20. Above- and belowground fluxes of CH4 from boreal shrubs and Scots pine

    NASA Astrophysics Data System (ADS)

    Halmeenmäki, Elisa; Heinonsalo, Jussi; Santalahti, Minna; Putkinen, Anuliina; Fritze, Hannu; Pihlatie, Mari

    2016-04-01

    Boreal upland forests are considered as an important sink for the greenhouse gas methane (CH4) due to CH4 oxidizing microbes in the soil. However, recent evidence suggests that vegetation can act as a significant source of CH4. Also, preliminary measurements indicate occasional emissions of CH4 above the tree canopies of a boreal forest. Nevertheless, the sources and the mechanisms of the observed CH4 emissions are still mostly unknown. Furthermore, the majority of CH4 flux studies have been conducted with the soil chamber method, thus not considering the role of the vegetation itself. We conducted a laboratory experiment to study separately the above- and belowground CH4 fluxes of bilberry (Vaccinium myrtillus), lingonberry (Vaccinium vitis-idaea), heather (Calluna vulgaris), and Scots pine (Pinus sylvestris), which were grown in microcosms. The above- and belowground fluxes of the plants were measured separately, and these fluxes were compared to fluxes of microcosms containing only humus soil. In addition to the flux measurements, we analysed the CH4 producing archaea (methanogens) and the CH4 consuming bacteria (methanotrophs) with the qPCR method to discover whether these microbes contribute to the CH4 exchange from the plant material and the soil. The results of the flux measurements indicate that the humus soil with roots of lingonberry, heather, and Scots pine consume CH4 compared to bare humus soil. Simultaneously, the shoots of heather and Scots pine emit small amounts of CH4. We did not find detectable amounts of methanogens from any of the samples, suggesting the produced CH4 could be of non-microbial origin, or produced by very small population of methanogens. Based on the first preliminary results, methanotrophs were present in all the studied plant species, and especially in high amounts in the rooted soils, thus implying that the methanotrophs could be responsible of the CH4 uptake in the root-soil systems.

  1. Early anthropogenic CH4 emissions and the variation of CH4 and 13CH4 over the last millennium

    NASA Astrophysics Data System (ADS)

    Houweling, S.; van der Werf, G. R.; Klein Goldewijk, K.; RöCkmann, T.; Aben, I.

    2008-03-01

    This study presents a new hypothesis to explain the observed variation of CH4 and δ13C-CH4 over the last millennium. It was originally proposed that the observed minimum of δ13C-CH4 prior to the start of industrialization is caused by a large shift in biomass burning emissions between 1400 and 1700 A.D. According to our new hypothesis, however, the δ13C-CH4 minimum is the first sign of the global rise of anthropogenic CH4 emissions. The main idea is that emissions of isotopically depleted CH4, from, for example, rice cultivation, domestic ruminants, and waste treatment started increasing earlier than the isotopically enriched emissions from fossil fuel, which started with the start of industrialization. However, because the observed increase of atmospheric methane only started around 1750 A.D., these preindustrial anthropogenic emissions must have been accompanied by a net reduction of natural CH4 sources during the Little Ice Age (LIA) compensating for the increase of anthropogenic emissions during that period. Results of transient box model simulations for the last millennium show that under the new hypothesis a close agreement can be obtained between model and measurements. Prior to 1400 A.D., low emissions from anthropogenic biomass burning require a sizable contribution of methane emissions from vegetation to explain the observed high level of δ13C-CH4. During the Little Ice Age, a larger than expected reduction of natural sources is needed, which calls for further verification using a more sophisticated modeling approach and additional constraints from ice core measurements.

  2. Mechanism of copper(I)/TEMPO-catalyzed aerobic alcohol oxidation.

    PubMed

    Hoover, Jessica M; Ryland, Bradford L; Stahl, Shannon S

    2013-02-13

    Homogeneous Cu/TEMPO catalyst systems (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) have emerged as some of the most versatile and practical catalysts for aerobic alcohol oxidation. Recently, we disclosed a (bpy)Cu(I)/TEMPO/NMI catalyst system (NMI = N-methylimidazole) that exhibits fast rates and high selectivities, even with unactivated aliphatic alcohols. Here, we present a mechanistic investigation of this catalyst system, in which we compare the reactivity of benzylic and aliphatic alcohols. This work includes analysis of catalytic rates by gas-uptake and in situ IR kinetic methods and characterization of the catalyst speciation during the reaction by EPR and UV-visible spectroscopic methods. The data support a two-stage catalytic mechanism consisting of (1) "catalyst oxidation" in which Cu(I) and TEMPO-H are oxidized by O(2) via a binuclear Cu(2)O(2) intermediate and (2) "substrate oxidation" mediated by Cu(II) and the nitroxyl radical of TEMPO via a Cu(II)-alkoxide intermediate. Catalytic rate laws, kinetic isotope effects, and spectroscopic data show that reactions of benzylic and aliphatic alcohols have different turnover-limiting steps. Catalyst oxidation by O(2) is turnover limiting with benzylic alcohols, while numerous steps contribute to the turnover rate in the oxidation of aliphatic alcohols.

  3. Mechanism of copper(I)/TEMPO-catalyzed aerobic alcohol oxidation.

    PubMed

    Hoover, Jessica M; Ryland, Bradford L; Stahl, Shannon S

    2013-02-13

    Homogeneous Cu/TEMPO catalyst systems (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) have emerged as some of the most versatile and practical catalysts for aerobic alcohol oxidation. Recently, we disclosed a (bpy)Cu(I)/TEMPO/NMI catalyst system (NMI = N-methylimidazole) that exhibits fast rates and high selectivities, even with unactivated aliphatic alcohols. Here, we present a mechanistic investigation of this catalyst system, in which we compare the reactivity of benzylic and aliphatic alcohols. This work includes analysis of catalytic rates by gas-uptake and in situ IR kinetic methods and characterization of the catalyst speciation during the reaction by EPR and UV-visible spectroscopic methods. The data support a two-stage catalytic mechanism consisting of (1) "catalyst oxidation" in which Cu(I) and TEMPO-H are oxidized by O(2) via a binuclear Cu(2)O(2) intermediate and (2) "substrate oxidation" mediated by Cu(II) and the nitroxyl radical of TEMPO via a Cu(II)-alkoxide intermediate. Catalytic rate laws, kinetic isotope effects, and spectroscopic data show that reactions of benzylic and aliphatic alcohols have different turnover-limiting steps. Catalyst oxidation by O(2) is turnover limiting with benzylic alcohols, while numerous steps contribute to the turnover rate in the oxidation of aliphatic alcohols. PMID:23317450

  4. Toxic effects of butyl elastomers on aerobic methane oxidation

    NASA Astrophysics Data System (ADS)

    Niemann, Helge; Steinle, Lea I.; Blees, Jan H.; Krause, Stefan; Bussmann, Ingeborg; Lehmann, Moritz F.; Treude, Tina

    2013-04-01

    Large quantities of the potent greenhouse gas methane are liberated into the water column of marine and lacustrine environments where it may be consumed by aerobic methane oxidising bacteria before reaching the atmosphere.The reliable quantification of aerobic methane oxidation (MOx) rates is consequently of paramount importance for estimating methane budgets and to understand the controls on water column methane cycling. A widely used set of methods for measuring MOx rates is based on the incubation of water samples during which the consumption of methane is monitored, for instance with radio-tracer assays. Typically, incubation vessels are sealed with butyl rubber stoppers because these elastomers are essentially impermeable for gases at the relevant time scales. We tested the effect of different stopper materials (unmodified- and halogenated butyl rubber) on MOx activity in environmental samples and in cultures of methane oxidising bacteria. MOx rates in samples sealed with unmodified butyl rubber were > 75% lower compared to parallel incubations with halogenated butyl rubber seals, suggesting inhibiting/toxic effects associated with the use of unmodified butyl elastomers. To further explore the cause of these effects, we analysed aqueous extracts of the different stoppers. Halogenated butyl rubber stoppers appeared to bleed off comparably little amounts of organics. In stark contrast, extracts of unmodified butyl rubber were contaminated with various organic compounds including potential bactericides such as benzyltoluenes, phenylalkanes and benzuothiazoles. We also found tetramethylthiourea, a scavenger of active oxygen species, which may inhibit the MOx pathway.

  5. Effect of sporadic destratification, seasonal overturn and artificial mixing on CH4 emissions at the surface of a subtropical hydroelectric reservoir (Nam Theun 2 Reservoir, Lao PDR)

    NASA Astrophysics Data System (ADS)

    Guérin, F.; Deshmukh, C.; Labat, D.; Pighini, S.; Vongkhamsao, A.; Guédant, P.; Rode, W.; Godon, A.; Chanudet, V.; Descloux, S.; Serça, D.

    2015-07-01

    Inland waters in general and specifically freshwater reservoirs are recognized as source of CH4 to the atmosphere. Although the diffusion at the air-water interface is the most studied pathway, its spatial and temporal variations are poorly documented. We measured fortnightly CH4 concentrations and physico-chemical parameters at nine stations in a subtropical monomictic reservoir which was flooded in 2008 (Nam Theun 2 Reservoir, Lao PDR). Based on these results, we quantified CH4 storage in the water column and diffusive fluxes from June 2009 to December 2012. We also compared emissions with aerobic methane oxidation calculated from Deshmukh et al. (2015). In this monomictic reservoir, the seasonal variations of CH4 concentration and storage were highly dependant of the thermal stratification. Hypolimnic CH4 concentration and CH4 storage reached their maximum in the warm dry season (WD) when the reservoir was stratified. They decreased during the warm wet (WW) season and reached its minimum after the reservoir overturned in the cool dry season (CD). The sharp decreases of the CH4 storage were concomitant with sporadic extreme diffusive fluxes (up to 200 mmol m-2 d-1). These hot moments of emissions occurred mostly in the inflow region in the WW season and during the overturn in the CD season in the area of the reservoir that has the highest CH4 storage. Although they corresponded to less than 10 % of the observations, these CH4 extreme emissions (> 5 mmol m-2 d-1) contributed up to 50 % of total annual emissions by diffusion. Based on our fortnightly monitoring, we determined that accurate estimation of the emissions can be determined from measurements made at least at a monthly frequency. During the transition between the WD and WW seasons, a new hotspot of emissions was identified upstream of the water intake where diffusive fluxes peaked at 600 mmol m-2 d-1 in 2010 down to 200 mmol m-2 d-1 in 2012. In the CD season, diffusive fluxes from this area were the

  6. CO2, CH4, and DOC Flux During Long Term Thaw of High Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Stackhouse, B. T.; Vishnivetskaya, T. A.; Layton, A.; Bennett, P.; Mykytczuk, N.; Lau, C. M.; Whyte, L.; Onstott, T. C.

    2013-12-01

    Arctic regions are expected to experience temperature increases of >4° C by the end of this century. This warming is projected to cause a drastic reduction in the extent of permafrost at high northern latitudes, affecting an estimated 1000 Pg of SOC in the top 3 m. Determining the effects of this temperature change on CO2 and CH4 emissions is critical for defining source constraints to global climate models. To investigate this problem, 18 cores of 1 m length were collected in late spring 2011 before the thawing of the seasonal active layer from an ice-wedge polygon near the McGill Arctic Research Station (MARS) on Axel Heiberg Island, Nunavut, Canada (N79°24, W90°45). Cores were collected from acidic soil (pH 5.5) with low SOC (~1%), summertime active layer depth between 40-70 cm (2010-2013), and sparse vegetation consisting primarily of small shrubs and sedges. Cores were progressively thawed from the surface over the course of 14 weeks to a final temperature of 4.5° C and held at that temperature for 15 months under the following conditions: in situ water saturation conditions versus fully water saturated conditions using artificial rain fall, surface light versus no surface light, cores from the polygon edge, and control cores with a permafrost table maintained at 70 cm depth. Core headspaces were measured weekly for CO2, CH4, H2, CO, and O2 flux during the 18 month thaw experiment. After ~20 weeks of thawing maximum, CO2 flux for the polygon edge and dark treatment cores were 3.0×0.7 and 1.7×0.4 mmol CO2 m-2 hr-1, respectively. The CO2 flux for the control, saturated, and in situ saturation cores reached maximums of 0.6×0.2, 0.9×0.5, and 0.9×0.1 mmol CO2 m-2 hr-1, respectively. Field measurements of CO2 flux from an adjacent polygon during the mid-summer of 2011 to 2013 ranged from 0.3 to 3.7 mmol CO2 m-2 hr-1. Cores from all treatments except water saturated were found to consistently oxidize CH4 at ~atmospheric concentrations (2 ppmv) with a maximum

  7. An Atmospheric CH4 Sink in the High Arctic and its Implication for Global Warming

    NASA Astrophysics Data System (ADS)

    Onstott, T. C.; Lau, C. M.; Stackhouse, B. T.; Medvigy, D.; Chen, Y.; Layton, A.; Vishnivetskaya, T. A.; Pfiffner, S. M.; Whyte, L.; Mykytczuk, N.; Ronholm, J.; Allan, J.; Bennett, P.; Chourey, K.; Hettich, R. L.

    2013-12-01

    Arctic permafrost underlies about 16% of the Earth's surface and contains ~500 Pg of C down to one meter. Organic-rich peatlands (averaging ~4 wt% SOC) comprise 19% of this area, whereas the remaining 81% is permafrost-affected mineral cryosols (0.5-1.5 wt% SOC). Temperatures in the Arctic are predicted to increase ~6°C over the next 100 years which increases the depth of the active layer, the seasonally thawed soil above the permafrost. Thawing permafrost peat deposits (e.g. Stordalen Mire, Sweden) are currently CH4 sources. Field measurements, intact core studies and microcosm experiments performed by us, however, over the past few years on mineral cryosols associated with ice wedge polygons from Axel Heiberg Island (AHI) in the Canadian High Arctic consistently indicate that they are sinks for atmospheric CH4 as well as the CH4 emitted from the underlying permafrost. After 1.5 years of thawing at 4°C, 1 m long intact cores of the active layer and underlying permafrost mineral cryosols collected from ice wedge polygons at AHI continue to exhibit uptake of atmospheric CH4 even for water saturated cores. The measured core fluxes are consistent with flux measurements performed in the field over the past two years, which range from 0.005 to 0.89 mg CH4-C/m2/hr and which have revealed significant differences in the atmospheric CH4 consumption fluxes between the polygon interiors and the polygon troughs. Metagenome and metaproteome analyses of these mineral cryosols indicates that the pmoA genes and proteins are most similar to an uncultured methanotroph type known as USC-α, which is recognized as a high affinity, atmospheric CH4 oxidizer. Our microcosm studies have yielded atmospheric CH4 uptake rates that are consistent with those of published results from high latitude organic-rich soils and temperate forest soils and indicate a temperature dependency for the cellular rate of CH4 oxidization that is approximately twice that reported for methanogenesis. This

  8. High-Frequency, Automated Measurements of CO2, N2O and CH4 from Forested Soils

    NASA Astrophysics Data System (ADS)

    Savage, K. E.; Davidson, E. A.; Phillips, R. L.

    2011-12-01

    Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are the most important anthropogenic greenhouse gases. Soils are the dominant natural source of N2O, and fertilized agricultural soils are a major source of increasing anthropogenic N2O. Anthropogenic sources of CH4 include rice cultivation, while wetlands are a significant natural source, and upland soils are a natural CH4 sink. While most anthropogenic CO2 is derived from fossil fuel combustion, a significant fraction is from land use change, including a portion from loss of soil carbon. Soils play a central role as sources and sinks of the three most important anthropogenic greenhouse gases of the 21st century, CO2, CH4, and N2O. Variation in soil moisture can be very dynamic, and it is one of the dominant factors controlling soil aeration, and hence the balance between aerobic (CO2 producing) and anaerobic (CH4 producing) respiration. The production and consumption of N2O is also highly dependent on spatial and temporal variation in soil moisture. Although technologies for high frequency, precise measurements of CO2 have been available for years, methods for measuring soil fluxes of CH4 and N2O at high temporal frequency have been hampered by lack of appropriate technology for in situ real-time measurements. We utilized a previously developed automated chamber system for measuring CO2 efflux (Licor 6252 IRGA) from soils, and configured it to run in-line with a new model quantum cascade laser (QCL) system which measures N2O and CH4 (Aerodyne model QC-TILDAS-CS). The QCL is thermoelectrically cooled and uses a 76-meter path length, 0.5 liter volume, and multiple pass absorption cell for sampling. The QCL sampling frequency is 10Hz, and its range is 0.3 to 3000 ppb for N2O with a sensitivity of 0.3 ppb, and 0.5 to 5000 ppb for CH4 with a sensitivity of 0.5 ppb. Six sampling chambers, with corresponding soil water content and soil temperature sensors, were deployed at the Howland Forest ME, in an upland

  9. Aerobic and anaerobic oxidation of hydrogen by acidophilic bacteria.

    PubMed

    Hedrich, Sabrina; Johnson, D Barrie

    2013-12-01

    While many prokaryotic species are known to use hydrogen as an electron donor to support their growth, this trait has only previously been reported for two acidophilic bacteria, Hydrogenobaculum acidophilum (in the presence of reduced sulfur) and Acidithiobacillus (At.) ferrooxidans. To test the hypothesis that hydrogen may be utilized more widely by acidophilic bacteria, 38 strains of acidophilic bacteria, including representatives of 20 designated and four proposed species, were screened for their abilities to grow via the dissimilatory oxidation of hydrogen. Growth was demonstrated in several species of acidophiles that also use other inorganic electron donors (ferrous iron and sulfur) but in none of the obligately heterotrophic species tested. Strains of At. ferrooxidans, At. ferridurans and At. caldus, grew chemolithotrophically on hydrogen, though those of At. thiooxidans and At. ferrivorans did not. Growth was also observed with Sulfobacillus acidophilus, Sb. benefaciens and Sb. thermosulfidooxidans, though not with other iron-oxidizing Firmicutes. Similarly, Acidimicrobium ferrooxidans grew on hydrogen, closely related acidophilic actinobacteria did not. Growth yields of At. ferrooxidans and At. ferridurans grown aerobically on hydrogen (c. 10(10)  cells mL(-1) ) were far greater than typically obtained using other electron donors. Several species also grew anaerobically by coupling hydrogen oxidation to the reduction of ferric iron.

  10. The Use of Biofilter to Reduce Atmospheric Global Warming Gas (CH4) Eemissions from Landfills

    NASA Astrophysics Data System (ADS)

    Park, S.; Thomas, J. C.; Brown, K. W.; Sung, K.

    2001-12-01

    The emission of greenhouse gasses resulting from anthropogenic activities is increasing the atmospheric concentration of these gases, which can influence the climatic system by changing the temperature, precipitation, wind and other climate factors. Methane (CH4) is a very potent greenhouse gas and CH4 emission from landfills in US has been reported as 37% of total anthropogenic source of CH4 emission. Properly designed soil biofilters may reduce atmospheric CH4 emissions from landfills and help reduce the accumulation of greenhouse gasses in the atmosphere. Biofilter performance was tested under a variety of environmental and design conditions. The results showed that biofilters have the potential to reduce CH4 emissions from landfills by as much as 83%. A quadratic equation was developed to describe the dependence of methane oxidation rate in a sandy loam textured soil as a function of soil temperature, soil moisture and ammonium nitrogen concentration. Using this equation and the averaged soil temperature and moisture contents, and census data for the largest cities of each of the 48 contiguous states, oxidation rates was calculated. A methane emission model was also developed to estimate the methane emission from municipal waste landfills with different covers. Older landfills with soil covers emitted an average of 83% of the generated CH4. Landfills with RCRA covers emitted 90% of the generated CH4 without biofilters and only 10% with biofilters. Thus, the installation of properly sized biofilters should significantly reduce atmospheric CH4 emissions from landfills.

  11. Catalytic Aerobic Dehydrogenation of Nitrogen Heterocycles Using Heterogeneous Cobalt Oxide Supported on Nitrogen-Doped Carbon.

    PubMed

    Iosub, Andrei V; Stahl, Shannon S

    2015-09-18

    Dehydrogenation of (partially) saturated heterocycles provides an important route to heteroaromatic compounds. A heterogeneous cobalt oxide catalyst, previously employed for aerobic oxidation of alcohols and amines, is shown to be effective for aerobic dehydrogenation of various 1,2,3,4-tetrahydroquinolines to the corresponding quinolines. The reactions proceed in good yields under mild conditions. Other N-heterocycles are also successfully oxidized to their aromatic counterparts.

  12. Isolation of an aerobic vinyl chloride oxidizer from anaerobic groundwater.

    PubMed

    Fullerton, Heather; Rogers, Rebecca; Freedman, David L; Zinder, Stephen H

    2014-11-01

    Vinyl chloride (VC) is a known human carcinogen and common groundwater contaminant. Reductive dechlorination of VC to non-toxic ethene under anaerobic conditions has been demonstrated at numerous hazardous waste sites. However, VC disappearance without stoichiometric production of ethene has also been observed at some sites and in microcosms. In this study we identify an organism responsible for this observation in presumably anaerobic microcosms and conclude that oxygen was not detectable based on a lack of color change from added resazurin. This organism, a Mycobacterium sp. closely related to known VC oxidizing strains, was present in high numbers in 16S rRNA gene clone libraries from a groundwater microcosm. Although the oxidation/reduction indicator resazurin remained in the clear reduced state in these studies, these results suggest inadvertent oxygen contamination occurred. This study helps to elucidate the dynamic behavior of chlorinated ethenes in contaminated groundwater, through the isolation of a strictly aerobic organism that may be responsible for at least some disappearance of VC without the concomitant production of ethene in groundwater considered anaerobic.

  13. Carbon isotope fractionation reveals distinct process of CH4 emission from different compartments of paddy ecosystem

    PubMed Central

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

    2016-01-01

    Carbon isotopic fractionations in the processes of CH4 emission from paddy field remain poorly understood. The δ13C-values of CH4 in association with production, oxidation and transport of CH4 in different pools of a paddy field were determined, and the stable carbon isotope fractionations were calibrated to assess relative contribution of acetate to CH4 production (fac) and fraction of CH4 oxidized (fox) by different pathways. The apparent isotope fractionation for CO2 conversion to CH4 (αapp) was 1.041–1.056 in the soil and 1.046–1.080 on the roots, indicating that fac was 10–60% and 0–50%, respectively. Isotope fractionation associated with CH4 oxidation (αox) was 1.021 ± 0.007 in the soil and 1.013 ± 0.005 on the roots, and the transport fractionation (εtransport) by rice plants was estimated to be −16.7‰ ~ −11.1‰. Rhizospheric fox was about 30–100%, and it was more important at the beginning but decreased fast towards the end of season. Large value of fox was also observed at the soil-water interface and soil and roots surfaces, respectively. The results demonstrate that carbon isotopic fractionations which might be different in different conditions were sensitive to the estimations of fac and fox in paddy field. PMID:27251886

  14. Carbon isotope fractionation reveals distinct process of CH4 emission from different compartments of paddy ecosystem

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    Carbon isotopic fractionations in the processes of CH4 emission from paddy field remain poorly understood. The δ13C-values of CH4 in association with production, oxidation and transport of CH4 in different pools of a paddy field were determined, and the stable carbon isotope fractionations were calibrated to assess relative contribution of acetate to CH4 production (fac) and fraction of CH4 oxidized (fox) by different pathways. The apparent isotope fractionation for CO2 conversion to CH4 (αapp) was 1.041–1.056 in the soil and 1.046–1.080 on the roots, indicating that fac was 10–60% and 0–50%, respectively. Isotope fractionation associated with CH4 oxidation (αox) was 1.021 ± 0.007 in the soil and 1.013 ± 0.005 on the roots, and the transport fractionation (εtransport) by rice plants was estimated to be ‑16.7‰ ~ ‑11.1‰. Rhizospheric fox was about 30–100%, and it was more important at the beginning but decreased fast towards the end of season. Large value of fox was also observed at the soil-water interface and soil and roots surfaces, respectively. The results demonstrate that carbon isotopic fractionations which might be different in different conditions were sensitive to the estimations of fac and fox in paddy field.

  15. Environmental control on aerobic methane oxidation in coastal waters

    NASA Astrophysics Data System (ADS)

    Steinle, Lea; Maltby, Johanna; Engbersen, Nadine; Zopfi, Jakob; Bange, Hermann; Elvert, Marcus; Hinrichs, Kai-Uwe; Kock, Annette; Lehmann, Moritz; Treude, Tina; Niemann, Helge

    2016-04-01

    Large quantities of methane are produced in anoxic sediments of continental margins and may be liberated to the overlying water column, where some of it is consumed by aerobic methane oxidizing bacteria (MOB). Aerobic methane oxidation (MOx) in the water column is consequently the final sink for methane before its release to the atmosphere, where it acts as a potent greenhouse gas. In the context of the ocean's contribution to atmospheric methane, coastal seas are particularly important accounting >75% of global methane emission from marine systems. Coastal oceans are highly dynamic, in particular with regard to the variability of methane and oxygen concentrations as well as temperature and salinity, all of which are potential key environmental factors controlling MOx. To determine important environmental controls on the activity of MOBs in coastal seas, we conducted a two-year time-series study with measurements of physicochemical water column parameters, MOx activity and the composition of the MOB community in a coastal inlet in the Baltic Sea (Boknis Eck Time Series Station, Eckernförde Bay - E-Bay). In addition, we investigated the influence of temperature and oxygen on MOx during controlled laboratory experiments. In E-Bay, hypoxia developed in bottom waters towards the end of the stratification period. Constant methane liberation from sediments resulted in bottom water methane accumulations and supersaturation (with respect to the atmospheric equilibrium) in surface waters. Here, we will discuss the factors impacting MOx the most, which were (i) perturbations of the water column (ii) temperature and (iii) oxygen concentration. (i) Perturbations of the water column caused by storm events or seasonal mixing led to a decrease in MOx, probably caused by replacement of stagnant water with a high standing stock of MOB by 'new' waters with a lower abundance of methanotrophs. b) An increase in temperature generally led to higher MOx rates. c) Even though methane was

  16. Role of plant-mediated gas transport in CH4 emissions from Phragmites-dominated peatlands

    NASA Astrophysics Data System (ADS)

    van den Berg, Merit; Ingwersen, Joachim; van den Elzen, Eva; Lamers, Leon P. M.; Streck, Thilo

    2016-04-01

    A large part of the methane (CH4) produced in peatlands is directly oxidized and the extent of its oxidation depends on the gas transport pathway. In wetland ecosystems, CH4 can be transported from the soil to the atmosphere via diffusion, ebullition and via aerenchyma of roots and stems of vascular plants. Compared to other wetland plants, the very common species Phragmites australis (Common reed) appears to have a high ability to transport gases between the soil and atmosphere. The gas exchange within Phragmites plants takes place via convective flow through the culm, which is believed to be achieved by a humidity-induced pressure gradient and is more than 5-times as efficient as diffusion. By this mechanism, CH4 surpasses the upper (oxic) soil layers and therefore oxidation of CH4 may well be reduced. On the other hand, transport of oxygen in Phragmites plants tends to enhance O2concentration in the rhizosphere, which will foster CH4oxidation in deeper soil layers. It is therefore unknown whether humidity-induced convection leads to higher or lower overall CH4 emission in Phragmites, which is essential to understand their role in the emissions from these very common peatland types. To investigate whether this internal gas transport mechanism of reed promotes or reduces CH4 fluxes to the atmosphere, we conducted manipulative field experiments in a large Phragmites peatland in South-West Germany in October 2014 and July 2015. Using large chambers, we compared CH4 fluxes from intact plots, plots with cut reed, and plots with cut + sealed reed to exclude gas transport through the plants. Additionally, pore water samples from the plots were analyzed for possible changes in soil chemistry due to the change of oxygen transport into the soil by the treatments. Based on our results, we will explain the potential role of rhizosphere oxygenation and convective flow on CH4 emissions from Phragmites-dominated peatlands in relation to other environmental condition.

  17. Warming Early Mars With CH4

    NASA Astrophysics Data System (ADS)

    Justh, H. L.; Kasting, J. F.

    2002-12-01

    The nature of the ancient climate of Mars remains one of the fundamental unresolved problems in martian research. While the present environment is hostile to life, images from the Mariner, Viking and Mars Global Surveyor missions, have shown geologic features on the martian surface that seem to indicate an earlier period of hydrologic activity. The fact that ancient valley networks and degraded craters have been seen on the martian surface indicates that the early martian climate may have been more Earth-like, with a warmer surface temperature. The presence of liquid water would require a greenhouse effect much larger than needed at present, as the solar constant, S0, was 25% lower 3.8 billion years ago when the channels are thought to have formed (1,2). Previous calculations have shown that gaseous CO2 and H2O alone could not have warmed the martian surface to the temperature needed to account for the presence of liquid water (3). It has been hypothesized that a CO2-H2O atmosphere could keep early Mars warm if it was filled with CO2 ice clouds in the upper martian troposphere (4). Obtaining mean martian surface temperatures above 273 K would require nearly 100% cloud cover, a condition that is unrealistic for condensation clouds on early Mars. Any reduction in cloud cover makes it difficult to achieve warm martian surface temperatures except at high pressures and CO2 clouds could cool the martian surface if they were low and optically thick (5). CO2 and CH4 have been suggested as important greenhouse gases on the early Earth. Our research focuses on the effects of increased concentrations of atmospheric greenhouse gases on the surface temperature of early Mars, with emphasis on the reduced greenhouse gas, CH4. To investigate the possible warming effect of CH4, we modified a one-dimensional, radiative-convective climate model used in previous studies of the early martian climate (5). New cloud-free temperature profiles for various surface pressures and CH4 mixing

  18. TES/Aura L2 Methane (CH4) Lite Nadir (TL2CH4LN)

    Atmospheric Science Data Center

    2015-08-31

    TES/Aura L2 Methane (CH4) Lite Nadir (TL2CH4LN) News:  TES News ... Level:  L2 Instrument:  TES/Aura L2 Methane Spatial Coverage:  5.3 km nadir Spatial ... OPeNDAP Access:  OPeNDAP Parameters:  Methane Order Data:  Reverb:   Order Data ...

  19. Reduced graphene oxide supported Au nanoparticles as an efficient catalyst for aerobic oxidation of benzyl alcohol

    NASA Astrophysics Data System (ADS)

    Yu, Xianqin; Huo, Yujia; Yang, Jing; Chang, Sujie; Ma, Yunsheng; Huang, Weixin

    2013-09-01

    Various Au/C catalysts were prepared by Au nanoparticels supported on different carbonaceous supports including reduced graphene oxide (RGO), activated carbon (AC) and graphite (GC) using sol-immobilization method. Au/RGO shows a much higher activity than Au/AC and Au/GC in the liquid phase aerobic oxidation of benzyl alcohol. The superior catalytic performance of Au/RGO may be related to the presence of surface O-containing functional groups and moderate graphite character of RGO supports.

  20. Inter-polar difference of CH4, δD(CH4) and δ13CH4 during the Holocene

    NASA Astrophysics Data System (ADS)

    Beck, Jonas; Bock, Michael; Schmitt, Jochen; Seth, Barbara; Blunier, Thomas; Fischer, Hubertus

    2014-05-01

    The past variation of the concentration of atmospheric methane (CH4), the third most important greenhouse gas after water vapour and carbon dioxide (CO2), is observed to be generally in phase with the northern summer insolation cycle driven by the precession of the rotation axis of the Earth. However, in the mid-Holocene this regularity breaks down, and atmospheric CH4 starts to rise again while the northern summer insolation continues to decline. Despite different attempts to explain this feature (e.g. contrasting hypotheses on early human influences and enhanced emissions in the southern tropics), a clear explanation for the evolution of the atmospheric methane concentration has not been found yet. One possibility to get more information about the highly under-determined system of the methane cycle is to measure the methane concentration in Greenland and Antarctica and to calculate the relative inter-polar difference (rIPD) of methane, allowing us to draw conclusions about the hemispherical imbalance of the source and sink distribution. More information on the involved production and sink processes of atmospheric CH4 can be gained from the isotopic composition (δD and δ13C) of CH4. Each source emits methane of a typical isotope signature, and each sink process leads to a certain isotopic fractionation and thus influences the isotopic composition of atmospheric methane. To exploit for the first time the full parameter set, we also measured the inter-polar difference of δD (IPDδD) and δ13C (IPDδ13C) of methane over the Holocene. The IPDδD record results from a high resolution δD record from the NGRIP (Greenland) ice core and a coarse resolution record of EDML (Antarctica) ice core samples. The NGRIP δD data show a clear covariation with the long-term CH4 concentrations changes during the Holocene. The δD variations of 8-10 o are significantly larger than our measurement error of 2.3 o which is of significantly better precision than previous data. To avoid

  1. Combustion of CH4/H2/air mixtures in catalytic microreactors.

    PubMed

    Specchia, Stefania; Vella, Luigi D; Burelli, Sara; Saracco, Guido; Specchia, Vito

    2009-03-23

    The combustion of CH(4)/H(2)/HC mixtures in a very small space represents an alternative, innovative way to produce thermal/electrical energy. Pd/NiCrO(4) catalysts are lined on SiC monoliths via in situ solution combustion synthesis (SCS), and the monoliths are then tested by feeding CH(4), H(2), and lean CH(4)/H(2) mixtures into a lab-scale test rig at an output thermal power of 7.6 MW(th) m(-3). In all cases, the combustion temperature shifts to values lower than those observed in non-catalytic combustion. When the power density is kept constant (by adding H(2) to the gas mixture), the value of CH(4)-T(50) (the half-conversion temperature of CH(4)) decreases relative to that of pure CH(4), and the slope of the conversion curve becomes steeper. The higher the H(2) concentration is, the higher the reactivity of the mixture towards CH(4) oxidation-probably due to a higher production of H(2) reactive radicals (OH).

  2. Recent variation of Siberian CH4 fluxes estimated from atmospheric observations of CH4

    NASA Astrophysics Data System (ADS)

    Kim, H.; Machida, T.; Sasakawa, M.; Belikov, D.; Saeki, T.; Ito, A.; Maksyutov, S.

    2012-12-01

    Siberia is an area of choice for observing the effects of global warming sooner than in other regions. Perceivable changes in ecosystem and cryosphere environment have been reported such as damage to the forest or frequent flood. In this study, we use atmospheric methane observations in Siberia to estimate Siberian CH4 fluxes during 2006-2010 using an inverse model of atmospheric transport and investigate the recent variation of the estimated fluxes. Interseasonally varying CH4 emissions developed in TransCom-CH4 project are used in forward CH4 tracer simulations with NIES transport model including chemical sink rates: wetland and rice paddy emissions simulated with a process-based biogeochemical model (VISIT), biomass burning emissions of GFED v3.1, aseasonal anthropogenic emissions of EDGAR v4.2, and interseasonally repeating termite emissions of GISS. We use flask sampling and continuous measurement data of atmospheric CH4 archived at WDCGG in flux estimates. In addition, atmospheric CH4 observed in Siberia by aircrafts and a tall tower network (JR-STATION: Japan-Russia Siberian Tall Tower Inland Observation Network) are used to optimize Siberian CH4 flux: 1) monthly vertical profiles at Surgut, Novosibirsk and Yakutsk, and 2) continuous measurements at the JR-STATION in Berezorechka, Demyanskoe, Karasevoe, Igrim, Noyabrsk, Savvushka, Vaganovo, and Yakutsk. Annual mean Siberian CH4 flux is estimated to be 21.63 ± 5.25 Tg/yr in 2006-2010, which is 4.3 % to the global total (505.40 Tg/yr). Our Siberian flux estimates present a positive flux anomaly since 2007 and the flux anomaly is defined as the departure from the 2006 flux estimates. In 2007, increased wetland flux is estimated in the north-western Siberia with large wetland area and high summer CH4 concentrations observed at Demyanskoe, Karasevoe and Igrim near extensive wetlands can be explained by the enhanced wetland flux under hot and wet summer. This result is consistent with other studies which

  3. Year-round measurements of CH4 exchange in a forested drained peatland using automated chambers

    NASA Astrophysics Data System (ADS)

    Korkiakoski, Mika; Koskinen, Markku; Penttilä, Timo; Arffman, Pentti; Ojanen, Paavo; Minkkinen, Kari; Laurila, Tuomas; Lohila, Annalea

    2016-04-01

    Pristine peatlands are usually carbon accumulating ecosystems and sources of methane (CH4). Draining peatlands for forestry increases the thickness of the oxic layer, thus enhancing CH4 oxidation which leads to decreased CH4 emissions. Closed chambers are commonly used in estimating the greenhouse gas exchange between the soil and the atmosphere. However, the closed chamber technique alters the gas concentration gradient making the concentration development against time non-linear. Selecting the correct fitting method is important as it can be the largest source of uncertainty in flux calculation. We measured CH4 exchange rates and their diurnal and seasonal variations in a nutrient-rich drained peatland located in southern Finland. The original fen was drained for forestry in 1970s and now the tree stand is a mixture of Scots pine, Norway spruce and Downy birch. Our system consisted of six transparent polycarbonate chambers and stainless steel frames, positioned on different types of field and moss layer. During winter, the frame was raised above the snowpack with extension collars and the height of the snowpack inside the chamber was measured regularly. The chambers were closed hourly and the sample gas was sucked into a cavity ring-down spectrometer and analysed for CH4, CO2 and H2O concentration with 5 second time resolution. The concentration change in time in the beginning of a closure was determined with linear and exponential fits. The results show that linear regression systematically underestimated the CH4 flux when compared to exponential regression by 20-50 %. On the other hand, the exponential regression seemed not to work reliably with small fluxes (< 3.5 μg CH4 m-2 h-1): using exponential regression in such cases typically resulted in anomalously large fluxes and high deviation. Due to these facts, we recommend first calculating the flux with the linear regression and, if the flux is high enough, calculate the flux again using the exponential

  4. Responses of methanotrophic activity, community and EPS production to CH4 and O2 concentrations in waste biocover soils.

    PubMed

    Wei, Xiao-Meng; Su, Yao; Zhang, Hong-Tao; Chen, Min; He, Ruo

    2015-08-01

    Biocover soils are known to be a good alternative material to mitigate CH4 emissions from landfills to the atmosphere. In this study, 16 treatments with four O2 concentrations (∼0%, 5%, 10% and 21%) and four CH4 concentrations (i.e. 1%, 10%, 20% and 50%) were conducted to estimate extracellular polymeric substances (EPS) production, methanotrophic activity and community in response to CH4 and O2 concentrations in waste biocover soil (WBS). When the CH4 concentration was saturated for CH4 oxidation in the WBS, the continuous exposure of CH4 above the saturated concentrations could not obviously enhance CH4 oxidation activity. In the WBS, extracellular protein (ECP) production was negatively related with the tested CH4 concentrations, while both ECP and extracellular polysaccharides (ECPS) productions were positively related with the tested O2 concentrations. Cloning and terminal restriction fragment length polymorphism analyses showed that type I methanotrophs (Methylocaldum, Methylococcaceae, Methylomicrobium and Methylobacter) and type II methanotrophs (Methylosinus) dominated in the WBS. Among them, Methylocaldum and/or Methylococcaceae were sensitive to low O2 concentrations of ∼0%. Methylobacter had propensity to grow at low O2 concentrations of ∼0% and 5%, while Methylosinus preferred environments with high concentrations of CH4 (⩾10%) and O2 (21%). In the tested five environmental variables of ECPS, O2, EPS, CH4 and ECP, only ECPS and O2 concentrations had significant effect on the methanotrophic communities. These results suggested that O2 concentration in landfill covers should be paid more attention to optimize and sustain CH4 oxidation for mitigating CH4 emission from landfills.

  5. On the mechanisms of degenerate ligand exchange in [M(CH(3))](+)/CH(4) Couples (M=Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt) as explored by mass spectrometric and computational studies: oxidative addition/reductive elimination versus sigma-complex-assisted metathesis.

    PubMed

    Armélin, Marc; Schlangen, Maria; Schwarz, Helmut

    2008-01-01

    The degenerate ligand exchange in [M(CH(3))](+)/CH(4) couples occurs in the gas phase at room temperature for M=Ni, Ru, Rh, Pd, and Pt, whereas the complexes containing Fe and Co are unreactive. Details of hydrogen-atom scrambling versus direct ligand switch have been uncovered by labeling experiments with CD(4) and (13)CH(4), respectively. The reactivity scale ranges from unreactive (M=Fe, Co) or inefficient (M=Ni, Pd) to moderately (M=Ru) and rather reactive (M=Rh, Pt). Quite extensive, but not complete, H/D exchange between the hydrogen atoms of the incoming and outgoing methyl groups is observed for M=Pt, whereas for M=Ni and Pd a predominantly direct ligand switch prevails. DFT calculations performed at the B3LYP level of theory account well for the thermal nonreactivity of the Fe and Co couples. For [Ni[CH(3))](+)/CH(4), a sigma-complex-assisted metathesis (sigma-CAM) is operative such that, in a two-state reactivity (TSR) scenario, two spin flips between the (3)A ground and (1)A excited states take place at the entrance and exit channels of the encounter complexes. For M=Ru and Rh, only oxidative addition/reductive elimination (OA/RE) is favored energetically, and the reaction is confined to the electronic ground states (3)A and (2)A. In contrast, for the [Pd(CH(3))](+)/CH(4) system, on the (1)A ground-state potential-energy surface both the OA/RE and sigma-CAM variants are energetically comparable, and the small reaction efficiency for the ligand switch is reflected in transition states located energetically close to the reactants. For the [M(CH(3))](+)/CH(4) complexes of the 5d elements, the sigma-CAM mechanism does not play a role. For M=Pt, the energetically most favored path proceeds in a spin-conserving manner on the (1)A potential-energy surface, which accounts for the extensive single and double hydrogen-atom exchange preceding ligand exchange. Although for M=Os and Ir the [M(CH(3))](+) complexes could not be generated experimentally, computational

  6. Base-catalyzed efficient tandem [3 + 3] and [3 + 2 + 1] annulation-aerobic oxidative benzannulations.

    PubMed

    Diallo, Aboubacar; Zhao, Yu-Long; Wang, He; Li, Sha-Sha; Ren, Chuan-Qing; Liu, Qun

    2012-11-16

    An efficient synthesis of substituted benzenes via a base-catalyzed [3 + 3] aerobic oxidative aromatization of α,β-unsaturated carbonyl compounds with dimethyl glutaconate was reported. All the reactions were carried out under mild, metal-free conditions to afford the products in high to excellent yields with molecular oxygen as the sole oxidant and water as the sole byproduct. Furthermore, a more convenient tandem [3 + 2 + 1] aerobic oxidative aromatization reaction was developed through the in situ generation of the α,β-unsaturated carbonyl compounds from aldehydes and ketones.

  7. Formation of Amides from Imines via Cyanide-Mediated Metal-Free Aerobic Oxidation.

    PubMed

    Seo, Hong-Ahn; Cho, Yeon-Ho; Lee, Ye-Sol; Cheon, Cheol-Hong

    2015-12-18

    A new protocol for the direct formation of amides from imines derived from aromatic aldehydes via metal-free aerobic oxidation in the presence of cyanide is described. This protocol was applicable to various aldimines, and the desired amides were obtained in moderate to good yields. Mechanistic studies suggested that this aerobic oxidative amidation might proceed via the addition of cyanide to imines followed by proton transfer from carbon to nitrogen in the original imines, leading to carbanions of α-amino nitriles, which undergo subsequent oxidation with molecular oxygen in air to provide the desired amide compounds.

  8. Copper N-Heterocyclic Carbene: A Catalyst for Aerobic Oxidation or Reduction Reactions.

    PubMed

    Zhan, Le-Wu; Han, Lei; Xing, Ping; Jiang, Biao

    2015-12-18

    Copper N-heterocyclic carbene complexes can be readily used as catalysts for both aerobic oxidation of alcohols to aldehydes and reduction of imines to amines. Our methodology is universal for aromatic substrates and shows versatile tolerance to potential cascade reactions. A one-pot tandem synthetic strategy could afford useful imines and secondary amines via an oxidation-reduction strategy.

  9. Catalytic Fehling's Reaction: An Efficient Aerobic Oxidation of Aldehyde Catalyzed by Copper in Water.

    PubMed

    Liu, Mingxin; Li, Chao-Jun

    2016-08-26

    The first example of homogeneous copper-catalyzed aerobic oxidation of aldehydes is reported. This method utilizes atmospheric oxygen as the sole oxidant, proceeds under extremely mild aqueous conditions, and covers a wide range of various functionalized aldehydes. Chromatography is generally not necessary for product purification. PMID:27505714

  10. Copper N-Heterocyclic Carbene: A Catalyst for Aerobic Oxidation or Reduction Reactions.

    PubMed

    Zhan, Le-Wu; Han, Lei; Xing, Ping; Jiang, Biao

    2015-12-18

    Copper N-heterocyclic carbene complexes can be readily used as catalysts for both aerobic oxidation of alcohols to aldehydes and reduction of imines to amines. Our methodology is universal for aromatic substrates and shows versatile tolerance to potential cascade reactions. A one-pot tandem synthetic strategy could afford useful imines and secondary amines via an oxidation-reduction strategy. PMID:26633757

  11. Quantifying (12/13)CH(4) migration and fate following sub-surface release to an agricultural soil.

    PubMed

    Shaw, G; Atkinson, B; Meredith, W; Snape, C; Steven, M; Hoch, A; Lever, D

    2014-07-01

    Following gas generation in a Geological Disposal Facility (GDF), (14)C-containing gases could migrate through the geosphere, eventually diffusing into soils at the Earth's surface. This paper reports summary results from laboratory and field experiments to obtain information on the probable rates of a) diffusive transport and b) oxidation of (12/13)CH(4) (as a surrogate for (14)CH4) in a typical agricultural soil in the UK. Rates of CH(4) oxidation were generally low in the field and undisturbed soil columns, though a re-packed column of homogenised topsoil oxidised ambient atmospheric CH(4) 20× faster than an undisturbed soil column. In contrast to low observed rates of CH(4) oxidation, the effective diffusion of CH(4) through the soil was rapid. Isotopically labelled CH(4) injected at a depth of 45 cm in the field diffused to the surface and exited the soil over a time period ranging from 8 to 24 h. The rate of CH(4) diffusion through the soil was increased by the presence of ryegrass roots which increased soil porosity and decreased water content. δ(13)C values for laboratory column soils after labelled CH(4) injection experiments showed no sign of residual (13)C, despite the extremely high δ(13)C values of the injected (12/13)CH(4). If laboratory observations are confirmed by measurements in field samples it can be concluded that the majority of (14)CH(4) from a GDF which enters a soil with low methanotrophic activity will be lost to the free atmosphere after diffusing rapidly through the soil column.

  12. Trimetallic Au/Pt/Rh Nanoparticles as Highly Active Catalysts for Aerobic Glucose Oxidation

    NASA Astrophysics Data System (ADS)

    Zhang, Haijun; Cao, Yingnan; Lu, Lilin; Cheng, Zhong; Zhang, Shaowei

    2015-02-01

    This paper reports the findings of an investigation of the correlations between the catalytic activity for aerobic glucose oxidation and the composition of Au/Pt/Rh trimetallic nanoparticles (TNPs) with average diameters of less than 2.0 nm prepared by rapid injection of NaBH4. The prepared TNPs were characterized by UV-Vis, TEM, and HR-TEM. The catalytic activity of the alloy-structured TNPs for aerobic glucose oxidation is several times higher than that of Au monometallic nanoparticles with nearly the same particle size. The catalytic activities of the TNP catalysts were dependent not only on the composition, but also on the electronic structure. The high catalytic activities of the Au/Pt/Rh TNPs can be ascribed to the formed negative-charged Au atoms due to electron donation of Rh neighboring atoms acting as catalytically active sites for aerobic glucose oxidation.

  13. Bioinspired aerobic oxidation of secondary amines and nitrogen heterocycles with a bifunctional quinone catalyst.

    PubMed

    Wendlandt, Alison E; Stahl, Shannon S

    2014-01-01

    Copper amine oxidases are a family of enzymes with quinone cofactors that oxidize primary amines to aldehydes. The native mechanism proceeds via an iminoquinone intermediate that promotes high selectivity for reactions with primary amines, thereby constraining the scope of potential biomimetic synthetic applications. Here we report a novel bioinspired quinone catalyst system consisting of 1,10-phenanthroline-5,6-dione/ZnI2 that bypasses these constraints via an abiological pathway involving a hemiaminal intermediate. Efficient aerobic dehydrogenation of non-native secondary amine substrates, including pharmaceutically relevant nitrogen heterocycles, is demonstrated. The ZnI2 cocatalyst activates the quinone toward amine oxidation and provides a source of iodide, which plays an important redox-mediator role to promote aerobic catalytic turnover. These findings provide a valuable foundation for broader development of aerobic oxidation reactions employing quinone-based catalysts. PMID:24328193

  14. Bioinspired Aerobic Oxidation of Secondary Amines and Nitrogen Heterocycles with a Bifunctional Quinone Catalyst

    PubMed Central

    Wendlandt, Alison E.; Stahl, Shannon S.

    2014-01-01

    Copper amine oxidases are a family of enzymes with quinone cofactors that oxidize primary amines to aldehydes. The native mechanism proceeds via an iminoquinone intermediate that promotes high selectivity for reactions with primary amines, thereby constraining the scope of potential biomimetic synthetic applications. Here, we report a novel bioinspired quinone catalyst system, consisting of 1,10-phenanthroline-5,6-dione/ZnI2, that bypasses these constraints via an abiological pathway involving a hemiaminal intermediate. Efficient aerobic dehydrogenation of non-native secondary amine substrates, including pharmaceutically relevant nitrogen heterocycles, is demonstrated. The ZnI2 cocatalyst activates the quinone toward amine oxidation and provides a source of iodide, which plays an important redox-mediator role to promote aerobic catalytic turnover. These findings provide a valuable foundation for broader development of aerobic oxidation reactions employing quinone-based catalysts. PMID:24328193

  15. Identification of functionally active aerobic methanotrophs in sediments from an arctic lake using stable isotope probing

    USGS Publications Warehouse

    He, Ruo; Wooller, Matthew J.; Pohlman, John W.; Catranis, Catharine; Quensen, John; Tiedje, James M.; Leigh, Mary Beth

    2012-01-01

    Arctic lakes are a significant source of the greenhouse gas methane (CH4), but the role that methane oxidizing bacteria (methanotrophs) play in limiting the overall CH4 flux is poorly understood. Here, we used stable isotope probing (SIP) techniques to identify the metabolically active aerobic methanotrophs in upper sediments (0–1 cm) from an arctic lake in northern Alaska sampled during ice-free summer conditions. The highest CH4 oxidation potential was observed in the upper sediment (0–1 cm depth) with 1.59 μmol g wet weight-1 day-1 compared with the deeper sediment samples (1–3 cm, 3–5 cm and 5–10 cm), which exhibited CH4 oxidation potentials below 0.4 μmol g wet weight-1 day-1. Both type I and type II methanotrophs were directly detected in the upper sediment total communities using targeted primer sets based on 16S rRNA genes. Sequencing of 16S rRNA genes and functional genes (pmoA and mxaF) in the 13C-DNA from the upper sediment indicated that type I methanotrophs, mainly Methylobacter, Methylosoma, Methylomonas and Methylovulum miyakonense, dominated the assimilation of CH4. Methylotrophs, including the genera Methylophilus and/or Methylotenera, were also abundant in the 13CDNA. Our results show that a diverse microbial consortium acquired carbon from CH4 in the sediments of this arctic lake.

  16. Contrasting wetland CH4 emission responses to simulated glacial atmospheric CO2 in temperate bogs and fens.

    PubMed

    Boardman, Carl P; Gauci, Vincent; Watson, Jonathan S; Blake, Stephen; Beerling, David J

    2011-12-01

    Wetlands were the largest source of atmospheric methane (CH(4) ) during the Last Glacial Maximum (LGM), but the sensitivity of this source to exceptionally low atmospheric CO(2) concentration ([CO(2) ]) at the time has not been examined experimentally. We tested the hypothesis that LGM atmospheric [CO(2) ] reduced CH(4) emissions as a consequence of decreased photosynthate allocation to the rhizosphere. We exposed minerotrophic fen and ombrotrophic bog peatland mesocosms to simulated LGM (c. 200 ppm) or ambient (c. 400 ppm) [CO(2) ] over 21 months (n = 8 per treatment) and measured gaseous CH(4) flux, pore water dissolved CH(4) and volatile fatty acid (VFA; an indicator of plant carbon supply to the rhizosphere) concentrations. Cumulative CH(4) flux from fen mesocosms was suppressed by 29% (P < 0.05) and rhizosphere pore water [CH(4) ] by c. 50% (P < 0.01) in the LGM [CO(2) ], variables that remained unaffected in bog mesocosms. VFA analysis indicated that changes in plant root exudates were not the driving mechanism behind these results. Our data suggest that the LGM [CO(2) ] suppression of wetland CH(4) emissions is contingent on trophic status. The heterogeneous response may be attributable to differences in species assemblage that influence the dominant CH(4) production pathway, rhizosphere supplemented photosynthesis and CH(4) oxidation.

  17. CH4 emission and conversion from A2O and SBR processes in full-scale wastewater treatment plants.

    PubMed

    Liu, Yan; Cheng, Xiang; Lun, Xiaoxiu; Sun, Dezhi

    2014-01-01

    Wastewater treatment systems are important anthropogenic sources of CH4 emission. A full-scale experiment was carried out to monitor the CH4 emission from anoxic/anaerobic/oxic process (A20) and sequencing batch reactor (SBR) wastewater treatment plants (WWTPs) for one year from May 2011 to April 2012. The main emission unit of the A2O process was an oxic tank, accounting for 76.2% of CH4 emissions; the main emission unit of the SBR process was the feeding and aeration phase, accounting for 99.5% of CH4 emissions. CH4 can be produced in the anaerobic condition, such as in the primary settling tank and anaerobic tank of the A2O process. While CH4 can be consumed in anoxic denitrification or the aeration condition, such as in the anoxic tank and oxic tank of the A2O process and the feeding and aeration phase of the SBR process. The CH4 emission flux and the dissolved CH4 concentration rapidly decreased in the oxic tank of the A2O process. These metrics increased during the first half of the phase and then decreased during the latter half of the phase in the feeding and aeration phase of the SBR process. The CH4 oxidation rate ranged from 32.47% to 89.52% (mean: 67.96%) in the A2O process and from 12.65% to 88.31% (mean: 47.62%) in the SBR process. The mean CH4 emission factors were 0.182 g/ton of wastewater and 24.75 g CH4/(person x year) for the A2O process, and 0.457 g/ton of wastewater and 36.55 g CH4/(person x year) for the SBR process. PMID:24649710

  18. Emission of N2O and CH4 from a constructed wetland in southeastern Norway.

    PubMed

    Søvik, A K; Kløve, B

    2007-07-15

    The Skjønhaug constructed wetland (CW) is a free surface water (FSW) wetland polishing chemically treated municipal wastewater in southeastern Norway and consists of three ponds as well as trickling, unsaturated filters with light weight aggregates (LWA). Fluxes of nitrous oxide (N(2)O) and methane (CH(4)) have been measured during the autumn, winter and summer from all three ponds as well as from the unsaturated filters. Physicochemical parameters of the water have been measured at the same localities. The large temporal and spatial variation of N(2)O fluxes was found to cover a range of -0.49 to 110 mg N(2)O-N m(-2) day(-1), while the fluxes of CH(4) was found to cover a range of -1.2 to 1900 mg m(-2) day(-1). Thus, both emission and consumption occurred. Regarding fluxes of N(2)O there was a significant difference between the summer, winter and autumn, with the highest emissions occurring during the autumn. The fluxes of CH(4) were, on the other hand, not significantly different with regard to seasons. Both the emissions of N(2)O and CH(4) were positively influenced by the amount of total organic carbon (TOC). The measured fluxes of N(2)O and CH(4) are in the same range as those reported from other CWs treating wastewater. There was an approximately equal contribution to the global warming potential from N(2)O and CH(4). PMID:17204306

  19. Asymmetric aerobic oxidative NHC-catalysed synthesis of dihydropyranones utilising a system of electron transfer mediators.

    PubMed

    Axelsson, A; Hammarvid, E; Ta, L; Sundén, H

    2016-10-01

    In the context of green chemistry, the replacement of high molecular weight stoichiometric oxidants with O2 is most desirable but difficult. Here, we report the asymmetric aerobic oxidative synthesis of dihydropyranones. The oxidation is aided by a system of electron transfer mediators and is selective toward the homoenolate. The dihydropyranones can be isolated in high to excellent yields, with high ee (up to 95%). PMID:27604573

  20. Response of Atmospheric-Methane Oxidation to Methane-Flux Manipulation in a Laboratory Soil-Column Experiment

    NASA Astrophysics Data System (ADS)

    Schroth, M. H.; Mignola, I.; Henneberger, R.

    2015-12-01

    Upland soils are an important sink for atmospheric methane (CH4). Uptake of atmospheric CH4 in soils is generally diffusion limited, and is mediated by aerobic CH4 oxidizing bacteria (MOB) that possess a high-affinity form of a key enzyme, allowing CH4 consumption at near-atmospheric concentrations (≤ 1.9 µL/L). As cultivation attempts for these high-affinity MOB have shown little success, there remains much speculation regarding their functioning in different environments. For example, it is frequently assumed that they are highly sensitive to physical disturbance, but their response in activity and abundance to changes in substrate availability remains largely unknown. We present results of a laboratory column experiment conducted to investigate the response in activity and abundance of high-affinity MOB to an increase in CH4 flux. Intact soil cores, collected at a field site where atmospheric CH4 oxidation activity is frequently quantified, were transferred into two 1-m-long, 12-cm-dia. columns. The columns were operated at constant temperature in the dark, their headspace being continuously flushed with air. Diffusive gas-transport conditions were maintained in the reference column, whereas CH4 flux was increased in several steps in the treatment column by inducing advective gas flow using a diaphragm pump. Soil-gas samples periodically collected from ports installed along the length of the columns were analyzed for CH4 content. Together with measurements of soil-water content, atmospheric CH4 oxidation was quantified using the soil-profile method. First results indicate that atmospheric CH4 oxidation activity comparable with the field was maintained in the reference column throughout the experiment. Moreover, high-affinity MOB quickly adjusted to an increase in CH4 flux in the treatment column, efficiently consuming CH4. Quantification of MOB abundance is currently ongoing. Our data provide new insights into controls on atmospheric CH4 oxidation in soils.

  1. Copper-catalyzed aerobic oxidative coupling: From ketone and diamine to pyrazine

    PubMed Central

    Wu, Kun; Huang, Zhiliang; Qi, Xiaotian; Li, Yingzi; Zhang, Guanghui; Liu, Chao; Yi, Hong; Meng, Lingkui; Bunel, Emilio E.; Miller, Jeffrey T.; Pao, Chih-Wen; Lee, Jyh-Fu; Lan, Yu; Lei, Aiwen

    2015-01-01

    Copper-catalyzed aerobic oxidative C–H/N–H coupling between simple ketones and diamines was developed toward the synthesis of a variety of pyrazines. Various substituted ketones were compatible for this transformation. Preliminary mechanistic investigations indicated that radical species were involved. X-ray absorption fine structure experiments elucidated that the Cu(II) species 5 coordinated by two N atoms at a distance of 2.04 Å and two O atoms at a shorter distance of 1.98 Å was a reactive one for this aerobic oxidative coupling reaction. Density functional theory calculations suggested that the intramolecular coupling of cationic radicals was favorable in this transformation. PMID:26601302

  2. Cu/Nitroxyl Catalyzed Aerobic Oxidation of Primary Amines into Nitriles at Room Temperature.

    PubMed

    Kim, Jinho; Stahl, Shannon S

    2013-07-01

    An efficient catalytic method has been developed for aerobic oxidation of primary amines to the corresponding nitriles. The reactions proceed at room temperature and employ a catalyst consisting of (4,4'- (t) Bu2bpy)CuI/ABNO (ABNO = 9-azabicyclo[3.3.1]nonan-3-one N-oxyl). The reactions exhibit excellent functional group compatibility and substrate scope, and are effective with benzylic, allylic and aliphatic amines. Preliminary mechanistic studies suggest that aerobic oxidation of the Cu catalyst is the turnover-limiting step of the reaction. PMID:24015373

  3. Aerobic bacterial pyrite oxidation and acid rock drainage during the Great Oxidation Event.

    PubMed

    Konhauser, Kurt O; Lalonde, Stefan V; Planavsky, Noah J; Pecoits, Ernesto; Lyons, Timothy W; Mojzsis, Stephen J; Rouxel, Olivier J; Barley, Mark E; Rosìere, Carlos; Fralick, Phillip W; Kump, Lee R; Bekker, Andrey

    2011-10-20

    The enrichment of redox-sensitive trace metals in ancient marine sedimentary rocks has been used to determine the timing of the oxidation of the Earth's land surface. Chromium (Cr) is among the emerging proxies for tracking the effects of atmospheric oxygenation on continental weathering; this is because its supply to the oceans is dominated by terrestrial processes that can be recorded in the Cr isotope composition of Precambrian iron formations. However, the factors controlling past and present seawater Cr isotope composition are poorly understood. Here we provide an independent and complementary record of marine Cr supply, in the form of Cr concentrations and authigenic enrichment in iron-rich sedimentary rocks. Our data suggest that Cr was largely immobile on land until around 2.48 Gyr ago, but within the 160 Myr that followed--and synchronous with independent evidence for oxygenation associated with the Great Oxidation Event (see, for example, refs 4-6)--marked excursions in Cr content and Cr/Ti ratios indicate that Cr was solubilized at a scale unrivalled in history. As Cr isotope fractionations at that time were muted, Cr must have been mobilized predominantly in reduced, Cr(III), form. We demonstrate that only the oxidation of an abundant and previously stable crustal pyrite reservoir by aerobic-respiring, chemolithoautotrophic bacteria could have generated the degree of acidity required to solubilize Cr(III) from ultramafic source rocks and residual soils. This profound shift in weathering regimes beginning at 2.48 Gyr ago constitutes the earliest known geochemical evidence for acidophilic aerobes and the resulting acid rock drainage, and accounts for independent evidence of an increased supply of dissolved sulphate and sulphide-hosted trace elements to the oceans around that time. Our model adds to amassing evidence that the Archaean-Palaeoproterozoic boundary was marked by a substantial shift in terrestrial geochemistry and biology. PMID:22012395

  4. Aerobic bacterial pyrite oxidation and acid rock drainage during the Great Oxidation Event.

    PubMed

    Konhauser, Kurt O; Lalonde, Stefan V; Planavsky, Noah J; Pecoits, Ernesto; Lyons, Timothy W; Mojzsis, Stephen J; Rouxel, Olivier J; Barley, Mark E; Rosìere, Carlos; Fralick, Phillip W; Kump, Lee R; Bekker, Andrey

    2011-10-19

    The enrichment of redox-sensitive trace metals in ancient marine sedimentary rocks has been used to determine the timing of the oxidation of the Earth's land surface. Chromium (Cr) is among the emerging proxies for tracking the effects of atmospheric oxygenation on continental weathering; this is because its supply to the oceans is dominated by terrestrial processes that can be recorded in the Cr isotope composition of Precambrian iron formations. However, the factors controlling past and present seawater Cr isotope composition are poorly understood. Here we provide an independent and complementary record of marine Cr supply, in the form of Cr concentrations and authigenic enrichment in iron-rich sedimentary rocks. Our data suggest that Cr was largely immobile on land until around 2.48 Gyr ago, but within the 160 Myr that followed--and synchronous with independent evidence for oxygenation associated with the Great Oxidation Event (see, for example, refs 4-6)--marked excursions in Cr content and Cr/Ti ratios indicate that Cr was solubilized at a scale unrivalled in history. As Cr isotope fractionations at that time were muted, Cr must have been mobilized predominantly in reduced, Cr(III), form. We demonstrate that only the oxidation of an abundant and previously stable crustal pyrite reservoir by aerobic-respiring, chemolithoautotrophic bacteria could have generated the degree of acidity required to solubilize Cr(III) from ultramafic source rocks and residual soils. This profound shift in weathering regimes beginning at 2.48 Gyr ago constitutes the earliest known geochemical evidence for acidophilic aerobes and the resulting acid rock drainage, and accounts for independent evidence of an increased supply of dissolved sulphate and sulphide-hosted trace elements to the oceans around that time. Our model adds to amassing evidence that the Archaean-Palaeoproterozoic boundary was marked by a substantial shift in terrestrial geochemistry and biology.

  5. Isolation of an aerobic sulfur oxidizer from the SUP05/Arctic96BD-19 clade.

    PubMed

    Marshall, Katharine T; Morris, Robert M

    2013-02-01

    Bacteria from the uncultured SUP05/Arctic96BD-19 clade of gamma proteobacterial sulfur oxidizers (GSOs) have the genetic potential to oxidize reduced sulfur and fix carbon in the tissues of clams and mussels, in oxygen minimum zones and throughout the deep ocean (>200 m). Here, we report isolation of the first cultured representative from this GSO clade. Closely related cultures were obtained from surface waters in Puget Sound and from the deep chlorophyll maximum in the North Pacific gyre. Pure cultures grow aerobically on natural seawater media, oxidize sulfur, and reach higher final cell densities when glucose and thiosulfate are added to the media. This suggests that aerobic sulfur oxidation enhances organic carbon utilization in the oceans. The first isolate from the SUP05/Arctic96BD-19 clade was given the provisional taxonomic assignment 'Candidatus: Thioglobus singularis', alluding to the clade's known role in sulfur oxidation and the isolate's planktonic lifestyle. PMID:22875135

  6. Highly practical copper(I)/TEMPO catalyst system for chemoselective aerobic oxidation of primary alcohols.

    PubMed

    Hoover, Jessica M; Stahl, Shannon S

    2011-10-26

    Aerobic oxidation reactions have been the focus of considerable attention, but their use in mainstream organic chemistry has been constrained by limitations in their synthetic scope and by practical factors, such as the use of pure O(2) as the oxidant or complex catalyst synthesis. Here, we report a new (bpy)Cu(I)/TEMPO catalyst system that enables efficient and selective aerobic oxidation of a broad range of primary alcohols, including allylic, benzylic, and aliphatic derivatives, to the corresponding aldehydes using readily available reagents, at room temperature with ambient air as the oxidant. The catalyst system is compatible with a wide range of functional groups and the high selectivity for 1° alcohols enables selective oxidation of diols that lack protecting groups. PMID:21861488

  7. Degraded Land Restoration in Reinstating CH4 Sink.

    PubMed

    Singh, Jay Shankar; Gupta, Vijai K

    2016-01-01

    Methane (CH4), a potent greenhouse gas, contributes about one third to the global green house gas emissions. CH4-assimilating microbes (mostly methanotrophs) in upland soils play very crucial role in mitigating the CH4 release into the atmosphere. Agricultural, environmental, and climatic shifts can alter CH4 sink profiles of soils, likely through shifts in CH4-assimilating microbial community structure and function. Landuse change, as forest and grassland ecosystems altered to agro-ecosystems, has already attenuated the soil CH4 sink potential, and are expected to be continued in the future. We hypothesized that variations in CH4 uptake rates in soils under different landuse practices could be an indicative of alterations in the abundance and/or type of methanotrophic communities in such soils. However, only a few studies have addressed to number and methanotrophs diversity and their correlation with the CH4 sink potential in soils of rehabilitated/restored lands. We focus on landuse practices that can potentially mitigate CH4 gas emissions, the most prominent of which are improved cropland, grazing land management, use of bio-fertilizers, and restoration of degraded lands. In this perspective paper, it is proposed that restoration of degraded lands can contribute considerably to improved soil CH4 sink strength by retrieving/conserving abundance and assortment of efficient methanotrophic communities. We believe that this report can assist in identifying future experimental directions to the relationships between landuse changes, methane-assimilating microbial communities and soil CH4 sinks. The exploitation of microbial communities other than methanotrophs can contribute significantly to the global CH4 sink potential and can add value in mitigating the CH4 problems.

  8. Degraded Land Restoration in Reinstating CH4 Sink.

    PubMed

    Singh, Jay Shankar; Gupta, Vijai K

    2016-01-01

    Methane (CH4), a potent greenhouse gas, contributes about one third to the global green house gas emissions. CH4-assimilating microbes (mostly methanotrophs) in upland soils play very crucial role in mitigating the CH4 release into the atmosphere. Agricultural, environmental, and climatic shifts can alter CH4 sink profiles of soils, likely through shifts in CH4-assimilating microbial community structure and function. Landuse change, as forest and grassland ecosystems altered to agro-ecosystems, has already attenuated the soil CH4 sink potential, and are expected to be continued in the future. We hypothesized that variations in CH4 uptake rates in soils under different landuse practices could be an indicative of alterations in the abundance and/or type of methanotrophic communities in such soils. However, only a few studies have addressed to number and methanotrophs diversity and their correlation with the CH4 sink potential in soils of rehabilitated/restored lands. We focus on landuse practices that can potentially mitigate CH4 gas emissions, the most prominent of which are improved cropland, grazing land management, use of bio-fertilizers, and restoration of degraded lands. In this perspective paper, it is proposed that restoration of degraded lands can contribute considerably to improved soil CH4 sink strength by retrieving/conserving abundance and assortment of efficient methanotrophic communities. We believe that this report can assist in identifying future experimental directions to the relationships between landuse changes, methane-assimilating microbial communities and soil CH4 sinks. The exploitation of microbial communities other than methanotrophs can contribute significantly to the global CH4 sink potential and can add value in mitigating the CH4 problems. PMID:27379053

  9. Degraded Land Restoration in Reinstating CH4 Sink

    PubMed Central

    Singh, Jay Shankar; Gupta, Vijai K.

    2016-01-01

    Methane (CH4), a potent greenhouse gas, contributes about one third to the global green house gas emissions. CH4-assimilating microbes (mostly methanotrophs) in upland soils play very crucial role in mitigating the CH4 release into the atmosphere. Agricultural, environmental, and climatic shifts can alter CH4 sink profiles of soils, likely through shifts in CH4-assimilating microbial community structure and function. Landuse change, as forest and grassland ecosystems altered to agro-ecosystems, has already attenuated the soil CH4 sink potential, and are expected to be continued in the future. We hypothesized that variations in CH4 uptake rates in soils under different landuse practices could be an indicative of alterations in the abundance and/or type of methanotrophic communities in such soils. However, only a few studies have addressed to number and methanotrophs diversity and their correlation with the CH4 sink potential in soils of rehabilitated/restored lands. We focus on landuse practices that can potentially mitigate CH4 gas emissions, the most prominent of which are improved cropland, grazing land management, use of bio-fertilizers, and restoration of degraded lands. In this perspective paper, it is proposed that restoration of degraded lands can contribute considerably to improved soil CH4 sink strength by retrieving/conserving abundance and assortment of efficient methanotrophic communities. We believe that this report can assist in identifying future experimental directions to the relationships between landuse changes, methane-assimilating microbial communities and soil CH4 sinks. The exploitation of microbial communities other than methanotrophs can contribute significantly to the global CH4 sink potential and can add value in mitigating the CH4 problems. PMID:27379053

  10. Aerobic and Anaerobic Oxidation of Organic Acids in Yellowstone Hot Spring Ecosystems

    NASA Astrophysics Data System (ADS)

    Windman, T. O.; Zolotova, N.; Shock, E.

    2007-12-01

    Thermodynamic analysis of energy supply based on samples collected from continental hot spring ecosystems at Yellowstone show that aerobic reactions yield the greatest energy. In terms of energy per mole of electrons transferred, aerobic oxidation of organic acids rivals or exceeds the energy supply from aerobic oxidation of hydrogen, CO, hydrogen sulfide, pyrite, sulfur or ammonia. This analysis is derived from samples collected where hot spring fluid are in contact with the atmosphere. It is likely that oxygen will be present at lower concentrations deeper in the system, which will place hard constraints on aerobic lifestyles. If so, which metabolisms could be supported deeper in the system? How will other oxidants be used to release energy? What characterizes the transition from aerobic to anaerobic oxidation? To answer these questions, pH, temperature, and alkalinity were measured in the field while measurements of dissolved oxygen and other redox-sensitive species (nitrate, ammonia, ferrous iron, and sulfide) were made with field-portable spectrophotometers and samples were taken for analysis of organic and inorganic ions by ion chromatography. Conditions in the subsurface can be predicted by starting from measured oxygen concentrations and calculating the effect of decreasing the concentration on the overall energetics of the system. Depending on hot spring composition, the amount of energy from aerobic oxidation of organic acid anions like succinate matches that from anaerobic oxidation (by nitrate or sulfate) once the log of the activity of dissolved oxygen drops to -6 to -8. These activities are 1 to 4 orders of magnitude lower that values determined for surface water in the hot springs. At lower oxygen activities aerobic oxidation gives way to anaerobic oxidation, and organic oxidation is more likely to involve nitrate and sulfate. Preliminary estimates indicate that these changes may occur at shallow depths in hot spring sediments (perhaps within the

  11. Reduced Atmospheric CH4 Consumption by Temperate Forest Soils Under Elevated CO2

    NASA Astrophysics Data System (ADS)

    Dubbs, L. E.; Whalen, S. C.; Fischer, E. N.

    2004-12-01

    Models project that atmospheric CO2 concentrations, by the end of the present century, will exceed the preindustrial concentration by up to 250%. The regional and global impact of this projected concentration increase on other biogeochemical cycles is uncertain. We recently reported in a two year study a 17 (year 2) to 30% (year 1) decrease in atmospheric CH4 consumption by soils in CO2-enriched plots in a temperate loblolly pine (Pinus taeda) forest, although the reason for the decline was unclear. Consumption by upland soils is the only terrestrial sink for atmospheric CH4, which is second only to CO2 in terms of radiative forcing. Forest ecosystems occupy about half of the Earth's terrestrial surface. A sustained CO2-induced negative feedback on forest soil CH4 consumption could lead to a 25% reduction (7.5 Tg CH4 yr-1) in the current upland soil sink of ˜30 Tg yr-1. However, CO2-enriched tundra ecosystems showed down regulation in at least the photosynthetic response after 3 yr of fertilization and it is uncertain whether decreased atmospheric CH4 consumption represents a transient or sustained response of forest-soil systems to elevated CO2. We report here the early results of our efforts to determine the duration and underlying causes for the decline in atmospheric CH4 consumption in a CO2-enriched forest. Reduced CH4 consumption persisted in elevated CO2 plots, which showed declines of 13% (year 3) and 34% (year 5, to date), relative to unenriched controls. This decline may be related to the rate of supply of CH4 to the subsurface zone of oxidation, as soil moisture was significantly higher in CO2-enriched plots. A single experiment to date showed that changes in the chemical composition of leachate from aboveground plant material had no impact on the CH4 oxidizing community, as rates of CH4 consumption by soil samples amended with throughfall from CO2-enriched and control plots were not significantly different.

  12. Light-Dependent Aerobic Methane Oxidation Reduces Methane Emissions from Seasonally Stratified Lakes

    PubMed Central

    Oswald, Kirsten; Milucka, Jana; Brand, Andreas; Littmann, Sten; Wehrli, Bernhard; Kuypers, Marcel M. M.; Schubert, Carsten J.

    2015-01-01

    Lakes are a natural source of methane to the atmosphere and contribute significantly to total emissions compared to the oceans. Controls on methane emissions from lake surfaces, particularly biotic processes within anoxic hypolimnia, are only partially understood. Here we investigated biological methane oxidation in the water column of the seasonally stratified Lake Rotsee. A zone of methane oxidation extending from the oxic/anoxic interface into anoxic waters was identified by chemical profiling of oxygen, methane and δ13C of methane. Incubation experiments with 13C-methane yielded highest oxidation rates within the oxycline, and comparable rates were measured in anoxic waters. Despite predominantly anoxic conditions within the zone of methane oxidation, known groups of anaerobic methanotrophic archaea were conspicuously absent. Instead, aerobic gammaproteobacterial methanotrophs were identified as the active methane oxidizers. In addition, continuous oxidation and maximum rates always occurred under light conditions. These findings, along with the detection of chlorophyll a, suggest that aerobic methane oxidation is tightly coupled to light-dependent photosynthetic oxygen production both at the oxycline and in the anoxic bottom layer. It is likely that this interaction between oxygenic phototrophs and aerobic methanotrophs represents a widespread mechanism by which methane is oxidized in lake water, thus diminishing its release into the atmosphere. PMID:26193458

  13. Tuning graphitic oxide for initiator- and metal-free aerobic epoxidation of linear alkenes

    NASA Astrophysics Data System (ADS)

    Pattisson, Samuel; Nowicka, Ewa; Gupta, Upendra N.; Shaw, Greg; Jenkins, Robert L.; Morgan, David J.; Knight, David W.; Hutchings, Graham J.

    2016-09-01

    Graphitic oxide has potential as a carbocatalyst for a wide range of reactions. Interest in this material has risen enormously due to it being a precursor to graphene via the chemical oxidation of graphite. Despite some studies suggesting that the chosen method of graphite oxidation can influence the physical properties of the graphitic oxide, the preparation method and extent of oxidation remain unresolved for catalytic applications. Here we show that tuning the graphitic oxide surface can be achieved by varying the amount and type of oxidant. The resulting materials differ in level of oxidation, surface oxygen content and functionality. Most importantly, we show that these graphitic oxide materials are active as unique carbocatalysts for low-temperature aerobic epoxidation of linear alkenes in the absence of initiator or metal. An optimum level of oxidation is necessary and materials produced via conventional permanganate-based methods are far from optimal.

  14. Tuning graphitic oxide for initiator- and metal-free aerobic epoxidation of linear alkenes

    PubMed Central

    Pattisson, Samuel; Nowicka, Ewa; Gupta, Upendra N.; Shaw, Greg; Jenkins, Robert L.; Morgan, David J.; Knight, David W.; Hutchings, Graham J.

    2016-01-01

    Graphitic oxide has potential as a carbocatalyst for a wide range of reactions. Interest in this material has risen enormously due to it being a precursor to graphene via the chemical oxidation of graphite. Despite some studies suggesting that the chosen method of graphite oxidation can influence the physical properties of the graphitic oxide, the preparation method and extent of oxidation remain unresolved for catalytic applications. Here we show that tuning the graphitic oxide surface can be achieved by varying the amount and type of oxidant. The resulting materials differ in level of oxidation, surface oxygen content and functionality. Most importantly, we show that these graphitic oxide materials are active as unique carbocatalysts for low-temperature aerobic epoxidation of linear alkenes in the absence of initiator or metal. An optimum level of oxidation is necessary and materials produced via conventional permanganate-based methods are far from optimal. PMID:27687877

  15. Treatment of real industrial wastewater using the combined approach of advanced oxidation followed by aerobic oxidation.

    PubMed

    Ramteke, Lokeshkumar P; Gogate, Parag R

    2016-05-01

    Fenton oxidation and ultrasound-based pretreatment have been applied to improve the treatment of real industrial wastewater based on the use of biological oxidation. The effect of operating parameters such as Fe(2+) loading, contact time, initial pH, and hydrogen peroxide loading on the extent of chemical oxygen demand (COD) reduction and change in biochemical oxygen demand (BOD5)/COD ratio has been investigated. The optimum operating conditions established for the pretreatment were initial pH of 3.0, Fe(2+) loading of 2.0, and 2.5 g L(-1) for the US/Fenton/stirring and Fenton approach, respectively, and temperature of 25 °C with initial H2O2 loading of 1.5 g L(-1). The use of pretreatment resulted in a significant increase in the BOD5/COD ratio confirming the production of easily digestible intermediates. The effect of the type of sludge in the aerobic biodegradation was also investigated based on the use of primary activated sludge (PAS), modified activated sludge (MAS), and activated sludge (AS). Enhanced removal of the pollutants as well as higher biomass yield was observed for MAS as compared to PAS and AS. The use of US/Fenton/stirring pretreatment under the optimized conditions followed by biological oxidation using MAS resulted in maximum COD removal at 97.9 %. The required hydraulic retention time for the combined oxidation system was also significantly lower as compared to only biological oxidation operation. Kinetic studies revealed that the reduction in the COD followed a first-order kinetic model for advanced oxidation and pseudo first-order model for biodegradation. The study clearly established the utility of the combined technology for the effective treatment of real industrial wastewater.

  16. The Arctic CH4 sink and its implications for the permafrost carbon feedbacks to the global climate system

    NASA Astrophysics Data System (ADS)

    Juncher Jørgensen, Christian; Christiansen, Jesper; Mariager, Tue; Hugelius, Gustaf

    2016-04-01

    Using atmospheric methane (CH4), certain soil microbes are able to sustain their metabolism, and in turn remove this powerful greenhouse gas from the atmosphere. While the process of CH4 oxidation is a common feature in most natural and unmanaged ecosystems in temperate and boreal ecosystems, the interactions between soil physical properties and abiotic process drivers, net landscape exchange and spatial patterns across Arctic drylands remains highly uncertain. Recent works show consistent CH4 comsumption in upland dry tundra soils in Arctic and High Arctic environments (Christiansen et al., 2014, Biogeochemistry 122; Jørgensen et al., 2015, Nature Geoscience 8; Lau et al., 2015, The ISME Journal 9). In these dominantly dry or barren soil ecosystems, CH4 consumption has been observed to significantly exceed the amounts of CH4 emitted from adjacent wetlands. These observations point to a potentially important but largely overlooked component of the global soil-climate system interaction and a counterperspective to the conceptual understanding of the Arctic being a only a source of CH4. However, due to our limited knowledge of spatiotemporal occurrence of CH4 consumption across a wider range of the Arctic landscape we are left with substantial uncertainites and an overall unconstrained range estimate of this terrestrial CH4 sink and its potential effects on permafrost carbon feedback to the atmospheric CH4 concentration. To address this important knowledge gap and identify the most relevant spatial scaling parameters, we studied in situ CH4 net exchange across a large landscape transect on West Greenland. The transect representated soils formed from the dominant geological parent materials of dry upland tundra soils found in the ice-free land areas of Western Greenland, i.e. 1) granitic/gneissic parent material, 2) basaltic parent material and 3) sedimentary deposits. Results show that the dynamic variations in soil physical properties and soil hydrology exerts an

  17. Incorporating the VSMOW and VPDB isotope scale into CH4 to produce isotope reference gases for CH4 in air

    NASA Astrophysics Data System (ADS)

    Sperlich, Peter; Richter, Jürgen M.; Brand, Willi A.

    2013-04-01

    Measurement accuracy offsets between laboratories and scale contraction effects are technical pitfalls that must be identified and corrected for when isotope data of atmospheric CH4 that were measured by multiple laboratories are merged for analysis. Measurement agreement can generally be assured by referencing the measurements to certified standard material. Unfortunately, international isotope reference material for CH4 does not exist, which challenges the compatibility prerequisite between laboratories measuring isotope ratios of CH4 in atmospheric samples. We are developing two methods to incorporate the hydrogen of VSMOW and the carbon of VPDB isotope scale material into CH4, so the CH4 is then itself representing the VSMOW and VPDB isotope reference scales for δ2H-CH4 and δ13C-CH4, respectively. This isotope scale holding CH4 is then diluted with CH4-free air to be used as an atmospheric isotope reference gas. We present our approach to produce isotope reference gas for δ2H-CH4 and show our first results.

  18. Effects of aerobic training on exercise-related oxidative stress in mitochondrial myopathies.

    PubMed

    Siciliano, Gabriele; Simoncini, Costanza; Lo Gerfo, Annalisa; Orsucci, Daniele; Ricci, Giulia; Mancuso, Michelangelo

    2012-12-01

    In mitochondrial myopathies with respiratory chain deficiency impairment of energy cell production may lead to in excess reactive oxygen species generation with consequent oxidative stress and cell damage. Aerobic training has been showed to increase muscle performance in patients with mitochondrial myopathies. Aim of this study has been to evaluate, in 7 patients (6 F e 1M, mean age 44.9 ± 12.1 years) affected by mitochondrial disease, concomitantly to lactate exercise curve, the occurrence of oxidative stress, as indicated by circulating levels of lipoperoxides, in rest condition and as effect of exercise, and also, to verify if an aerobic training program is able to modify, in these patients, ox-redox balance efficiency. At rest and before training blood level of lipoperoxides was 382.4 ± 37.8 AU, compared to controls (318.7 ± 63.8; P<0.05), this corresponding to a moderate oxidative stress degree according to the adopted scale. During incremental exercise blood level of lipoperoxides did not increase, but maintained significantly higher compared to controls. After an aerobic training of 10 weeks the blood level of lipoperoxides decreased by 13.7% at rest (P<0.01) and 10.4%, 8.6% and 8.5% respectively at the corresponding times during the exercise test (P=0.06). These data indicate that, in mitochondrial patients, oxidative stress occurs and that an aerobic training is useful in partially reverting this condition.

  19. A genomic view of methane oxidation by aerobic bacteria and anaerobic archaea

    PubMed Central

    Chistoserdova, Ludmila; Vorholt, Julia A; Lidstrom, Mary E

    2005-01-01

    Recent sequencing of the genome and proteomic analysis of a model aerobic methanotrophic bacterium, Methylococcus capsulatus (Bath) has revealed a highly versatile metabolic potential. In parallel, environmental genomics has provided glimpses into anaerobic methane oxidation by certain archaea, further supporting the hypothesis of reverse methanogenesis. PMID:15693955

  20. Cu-NHC-TEMPO catalyzed aerobic oxidation of primary alcohols to aldehydes.

    PubMed

    Liu, Xiaolong; Xia, Qinqin; Zhang, Yuejiao; Chen, Congyan; Chen, Wanzhi

    2013-09-01

    Imidazolium salts bearing TEMPO groups react with commercially available copper powder affording Cu-NHC complexes. The in situ generated Cu-NHC-TEMPO complexes are quite efficient catalysts for aerobic oxidation of primary alcohols into aldehydes. The catalyst is easily available, and various primary alcohols were selectively converted to aldehydes in excellent yields. PMID:23944937

  1. 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

  2. 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

  3. Phenazinium salt-catalyzed aerobic oxidative amidation of aromatic aldehydes.

    PubMed

    Leow, Dasheng

    2014-11-01

    Amides are prevalent in organic synthesis. Developing an efficient synthesis that avoids expensive oxidants and heating is highly desirable. Here the oxidative amidation of aromatic aldehydes is reported using an inexpensive metal-free visible light photocatalyst, phenazine ethosulfate, at low catalytic loading (1-2 mol %). The reaction proceeds at ambient temperature and uses air as the sole oxidant. The operationally easy procedure provides an economical, green, and mild alternative for the formation of amide bonds.

  4. The aerobic oxidation of alcohols with a ruthenium porphyrin catalyst in organic and fluorinated solvents.

    PubMed

    Korotchenko, Vasily N; Severin, Kay; Gagné, Michel R

    2008-06-01

    Carbonylruthenium tetrakis(pentafluorophenyl)porphyrin Ru(TPFPP)(CO) was utilized for the aerobic oxidation of alcohols. The in situ activation of the catalyst with mCPBA provided a species capable of catalyzing the oxidation of alcohols with molecular oxygen. The choice of solvent and additive was crucial to obtaining high activity and selectivity. Secondary aromatic alcohols were oxidized in the presence of the ruthenium porphyrin and tetrabutyl ammonium hydroxide in the solvent bromotrichloromethane, enabling high yields to be achieved (up to 99%). Alternatively, alcohols could be oxidized in perfluoro(methyldecalin) with the ruthenium porphyrin at higher temperatures (140 degrees C) and elevated oxygen pressures (50 psi).

  5. NHC-catalysed highly selective aerobic oxidation of nonactivated aldehydes

    PubMed Central

    Möhlmann, Lennart; Ludwig, Stefan

    2013-01-01

    Summary This publication describes a highly selective oxidation of aldehydes to the corresponding acids or esters. The reaction proceeds under metal-free conditions by using N-heterocyclic carbenes as organocatalysts in combination with environmentally friendly oxygen as the terminal oxidation agent. PMID:23616801

  6. Copper-catalyzed aerobic oxidative C-H functionalizations: trends and mechanistic insights.

    PubMed

    Wendlandt, Alison E; Suess, Alison M; Stahl, Shannon S

    2011-11-18

    The selective oxidation of C-H bonds and the use of O(2) as a stoichiometric oxidant represent two prominent challenges in organic chemistry. Copper(II) is a versatile oxidant, capable of promoting a wide range of oxidative coupling reactions initiated by single-electron transfer (SET) from electron-rich organic molecules. Many of these reactions can be rendered catalytic in Cu by employing molecular oxygen as a stoichiometric oxidant to regenerate the active copper(II) catalyst. Meanwhile, numerous other recently reported Cu-catalyzed C-H oxidation reactions feature substrates that are electron-deficient or appear unlikely to undergo single-electron transfer to copper(II). In some of these cases, evidence has been obtained for the involvement of organocopper(III) intermediates in the reaction mechanism. Organometallic C-H oxidation reactions of this type represent important new opportunities for the field of Cu-catalyzed aerobic oxidations. PMID:22034061

  7. Mechanism of Copper/Azodicarboxylate-Catalyzed Aerobic Alcohol Oxidation: Evidence for Uncooperative Catalysis.

    PubMed

    McCann, Scott D; Stahl, Shannon S

    2016-01-13

    Cooperative catalysis between Cu(II) and redox-active organic cocatalysts is a key feature of important chemical and enzymatic aerobic oxidation reactions, such as alcohol oxidation mediated by Cu/TEMPO and galactose oxidase. Nearly 20 years ago, Markó and co-workers reported that azodicarboxylates, such as di-tert-butyl azodicarboxylate (DBAD), are effective redox-active cocatalysts in Cu-catalyzed aerobic alcohol oxidation reactions [Markó, I. E., et al. Science 1996, 274, 2044], but the nature of the cooperativity between Cu and azodicarboxylates is not well understood. Here, we report a mechanistic study of Cu/DBAD-catalyzed aerobic alcohol oxidation. In situ infrared spectroscopic studies reveal a burst of product formation prior to steady-state catalysis, and gas-uptake measurements show that no O2 is consumed during the burst. Kinetic studies reveal that the anaerobic burst and steady-state turnover have different rate laws. The steady-state rate does not depend on [O2] or [DBAD]. These results, together with other EPR and in situ IR spectroscopic and kinetic isotope effect studies, reveal that the steady-state mechanism consists of two interdependent catalytic cycles that operate in sequence: a fast Cu(II)/DBAD pathway, in which DBAD serves as the oxidant, and a slow Cu(II)-only pathway, in which Cu(II) is the oxidant. This study provides significant insight into the redox cooperativity, or lack thereof, between Cu and redox-active organic cocatalysts in aerobic oxidation reactions. PMID:26694091

  8. Mechanism of Copper/Azodicarboxylate-Catalyzed Aerobic Alcohol Oxidation: Evidence for Uncooperative Catalysis.

    PubMed

    McCann, Scott D; Stahl, Shannon S

    2016-01-13

    Cooperative catalysis between Cu(II) and redox-active organic cocatalysts is a key feature of important chemical and enzymatic aerobic oxidation reactions, such as alcohol oxidation mediated by Cu/TEMPO and galactose oxidase. Nearly 20 years ago, Markó and co-workers reported that azodicarboxylates, such as di-tert-butyl azodicarboxylate (DBAD), are effective redox-active cocatalysts in Cu-catalyzed aerobic alcohol oxidation reactions [Markó, I. E., et al. Science 1996, 274, 2044], but the nature of the cooperativity between Cu and azodicarboxylates is not well understood. Here, we report a mechanistic study of Cu/DBAD-catalyzed aerobic alcohol oxidation. In situ infrared spectroscopic studies reveal a burst of product formation prior to steady-state catalysis, and gas-uptake measurements show that no O2 is consumed during the burst. Kinetic studies reveal that the anaerobic burst and steady-state turnover have different rate laws. The steady-state rate does not depend on [O2] or [DBAD]. These results, together with other EPR and in situ IR spectroscopic and kinetic isotope effect studies, reveal that the steady-state mechanism consists of two interdependent catalytic cycles that operate in sequence: a fast Cu(II)/DBAD pathway, in which DBAD serves as the oxidant, and a slow Cu(II)-only pathway, in which Cu(II) is the oxidant. This study provides significant insight into the redox cooperativity, or lack thereof, between Cu and redox-active organic cocatalysts in aerobic oxidation reactions.

  9. 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

  10. 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.

  11. Selective aerobic oxidation mediated by TiO(2) photocatalysis.

    PubMed

    Lang, Xianjun; Ma, Wanhong; Chen, Chuncheng; Ji, Hongwei; Zhao, Jincai

    2014-02-18

    TiO2 is one of the most studied metal oxide photocatalysts and has unparal-leled efficiency and stability. This cheap, abundant, and non-toxic material has the potential to address future environmental and energy concerns. Understanding about the photoinduced interfacial redox events on TiO2 could have profound effect on the degradation of organic pollutants, splitting of H2O into H2 and O2, and selective redox organic transformations. Scientists traditionally accept that for a semiconductor photocatalyst such as TiO2 under the illumination of light with energy larger than its band gap, two photocarriers will be created to carry out their independent reduction and oxidation processes. However, our recent discoveries indicate that it is the concerted rather than independent effect of both photocarriers of valence band hole (hvb(+)) and conduction band electron (ecb(-)) that dictate the product formation during interfacial oxidation event mediated by TiO2 photocatalysis. In this Account, we describe our recent findings on the selective oxidation of organic substrates with O2 mediated by TiO2 photocatalysis. The transfer of O-atoms from O2 to the corresponding products dominates the selective oxidation of alcohols, amines, and alkanes mediated by TiO2 photocatalysis. We ascribe this to the concerted effect of both hvb(+) and ecb(-) of TiO2 in contribution to the oxidation products. These findings imply that O2 plays a unique role in its transfer into the products rather than independent role of ecb(-) scavenger. More importantly, ecb(-) plays a crucial role to ensure the high selectivity for the oxygenation of organic substrates. We can also use the half reactions such as those of the conduction band electron of TiO2 for efficient oxidation reactions with O2. To this end, efficient selective oxidation of organic substrates such as alcohols, amines, and aromatic alkanes with O2 mediated by TiO2 photocatalysis under visible light irradiation has been achieved. In

  12. Selective aerobic oxidation mediated by TiO(2) photocatalysis.

    PubMed

    Lang, Xianjun; Ma, Wanhong; Chen, Chuncheng; Ji, Hongwei; Zhao, Jincai

    2014-02-18

    TiO2 is one of the most studied metal oxide photocatalysts and has unparal-leled efficiency and stability. This cheap, abundant, and non-toxic material has the potential to address future environmental and energy concerns. Understanding about the photoinduced interfacial redox events on TiO2 could have profound effect on the degradation of organic pollutants, splitting of H2O into H2 and O2, and selective redox organic transformations. Scientists traditionally accept that for a semiconductor photocatalyst such as TiO2 under the illumination of light with energy larger than its band gap, two photocarriers will be created to carry out their independent reduction and oxidation processes. However, our recent discoveries indicate that it is the concerted rather than independent effect of both photocarriers of valence band hole (hvb(+)) and conduction band electron (ecb(-)) that dictate the product formation during interfacial oxidation event mediated by TiO2 photocatalysis. In this Account, we describe our recent findings on the selective oxidation of organic substrates with O2 mediated by TiO2 photocatalysis. The transfer of O-atoms from O2 to the corresponding products dominates the selective oxidation of alcohols, amines, and alkanes mediated by TiO2 photocatalysis. We ascribe this to the concerted effect of both hvb(+) and ecb(-) of TiO2 in contribution to the oxidation products. These findings imply that O2 plays a unique role in its transfer into the products rather than independent role of ecb(-) scavenger. More importantly, ecb(-) plays a crucial role to ensure the high selectivity for the oxygenation of organic substrates. We can also use the half reactions such as those of the conduction band electron of TiO2 for efficient oxidation reactions with O2. To this end, efficient selective oxidation of organic substrates such as alcohols, amines, and aromatic alkanes with O2 mediated by TiO2 photocatalysis under visible light irradiation has been achieved. In

  13. High Resolution CH4 Emissions and Dissolved CH4 Measurements Elucidate Surface Gas Exchange Processes in Toolik Lake, Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Del Sontro, T.; Sollberger, S.; Kling, G. W.; Shaver, G. R.; Eugster, W.

    2013-12-01

    Approximately 14% of the Alaskan North Slope is covered in lakes of various sizes and depths. Diffusive carbon emissions (CH4 and CO2) from these lakes offset the tundra sink by ~20 %, but the offset would substantially increase if ebullitive CH4 emissions were also considered. Ultimately, arctic lake CH4 emissions are not insignificant in the global CH4 budget and their contribution is bound to increase due to impacts from climate change. Here we present high resolution CH4 emission data as measured via eddy covariance and a Los Gatos gas analyzer during the ice free period from Toolik Lake, a deep (20 m) Arctic lake located on the Alaskan North Slope, over the last few summers. Emissions are relatively low (< 25 mg CH4 m-2 d-1) with little variation over the summer. Diurnal variations regularly occur, however, with up to 3 times higher fluxes at night. Gas exchange is a relatively difficult process to estimate, but is normally done so as the product of the CH4 gradient across the air-water interface and the gas transfer velocity, k. Typically, k is determined based on the turbulence on the water side of the interface, which is most commonly approximated by wind speed; however, it has become increasingly apparent that this assumption does not remain valid across all water bodies. Dissolved CH4 profiles in Toolik revealed a subsurface peak in CH4 at the thermocline of up to 3 times as much CH4 as in the surface water. We hypothesize that convective mixing at night due to cooling surface waters brings the subsurface CH4 to the surface and causes the higher night fluxes. In addition to high resolution flux emission estimates, we also acquired high resolution data for dissolved CH4 in surface waters of Toolik Lake during the last two summers using a CH4 equilibrator system connected to a Los Gatos gas analyzer. Thus, having both the flux and the CH4 gradient across the air-water interface measured directly, we can calculate k and investigate the processes influencing

  14. Fe-Catalyzed Aerobic Oxidative C-CN Bond Cleavage of Arylacetonitriles Leading to Various Esters.

    PubMed

    Kong, Weiguang; Li, Bingnan; Xu, Xuezhao; Song, Qiuling

    2016-09-16

    Fe-catalyzed aerobic oxidative esterifications of arylacetonitriles with alcohols, tri alkoxsilanes, silicate esters, or borate esters have been developed. The acyl groups which were in situ generated via chemoselective C(CO)-CN bond cleavage were directly used as electrophiles, leading to corresponding aryl esters in good to excellent yields under molecular oxygen when attacked by alcohols or alcohol surrogates. Dioxygen serves as both oxidant and reactant in this protocol. The reaction has a very broad substrate scope. Cheap starting materials as well as environmentally benign and inexpensive iron catalyst and ideal oxidant O2 feature this transformation and make it a practical and sustainable protocol to afford esters. PMID:27555329

  15. Copper/TEMPO-Catalyzed Aerobic Alcohol Oxidation: Mechanistic Assessment of Different Catalyst Systems

    PubMed Central

    Hoover, Jessica M.; Ryland, Bradford L.; Stahl, Shannon S.

    2013-01-01

    Combinations of homogeneous Cu salts and TEMPO have emerged as practical and efficient catalysts for the aerobic oxidation of alcohols. Several closely related catalyst systems have been reported, which differ in the identity of the solvent, the presence of 2,2′-bipyridine as a ligand, the identity of basic additives, and the oxidation state of the Cu source. These changes have a significant influence on the reaction rates, yields, and substrate scope. In this report, we probe the mechanistic basis for differences among four different Cu/TEMPO catalyst systems and elucidate the features that contribute to efficient oxidation of aliphatic alcohols. PMID:24558634

  16. Iron/ABNO-Catalyzed Aerobic Oxidation of Alcohols to Aldehydes and Ketones under Ambient Atmosphere.

    PubMed

    Wang, Lianyue; Shang, SenSen; Li, Guosong; Ren, Lanhui; Lv, Ying; Gao, Shuang

    2016-03-01

    We report a new Fe(NO3)3·9H2O/9-azabicyclo[3.3.1]nonan-N-oxyl catalyst system that enables efficient aerobic oxidation of a broad range of primary and secondary alcohols to the corresponding aldehydes and ketones at room temperature with ambient air as the oxidant. The catalyst system exhibits excellent activity and selectivity for primary aliphatic alcohol oxidation. This procedure can also be scaled up. Kinetic analysis demonstrates that C-H bond cleavage is the rate-determining step and that cationic species are involved in the reaction. PMID:26859251

  17. Activated carbon for aerobic oxidation: Benign approach toward 2-benzoylbenzimidazoles and 2-benzoylbenzoxazoles synthesis

    PubMed Central

    Bao, Kai; Li, Fuqing; Liu, Hanjing; Wang, Zhiwei; Shen, Qirong; Wang, Jian; Zhang, Weige

    2015-01-01

    A general strategy involving a novel and highly efficient aerobic benzylic oxidation promoted by cheap, reusable activated carbon in water is developed. Application of this method has been demonstrated in the benign synthesis of bioactive 2-benzoylbenzimidazoles and 2-benzoylbenzoxazoles derivatives. Furthermore, the activated carbon catalyst could be recovered and reused at least three times without significantly losing its activity. Preliminary research suggests that the oxidation mechanism may involve intermediate hydroperoxidation and that a portion of the final carbonyl product is obtained through a secondary benzylic alcohol intermediate. Finally, theoretical calculations reveal that the oxidation yield is closely associated with the electric density at the benzylic position of the substrate. PMID:26041483

  18. Copper/TEMPO-Catalyzed Aerobic Alcohol Oxidation: Mechanistic Assessment of Different Catalyst Systems.

    PubMed

    Hoover, Jessica M; Ryland, Bradford L; Stahl, Shannon S

    2013-11-01

    Combinations of homogeneous Cu salts and TEMPO have emerged as practical and efficient catalysts for the aerobic oxidation of alcohols. Several closely related catalyst systems have been reported, which differ in the identity of the solvent, the presence of 2,2'-bipyridine as a ligand, the identity of basic additives, and the oxidation state of the Cu source. These changes have a significant influence on the reaction rates, yields, and substrate scope. In this report, we probe the mechanistic basis for differences among four different Cu/TEMPO catalyst systems and elucidate the features that contribute to efficient oxidation of aliphatic alcohols. PMID:24558634

  19. Uncertainties in modelling CH4 emissions from northern wetlands in glacial climates: the role of vegetation parameters

    NASA Astrophysics Data System (ADS)

    Berrittella, C.; van Huissteden, J.

    2011-10-01

    Marine Isotope Stage 3 (MIS 3) interstadials are marked by a sharp increase in the atmospheric methane (CH4) concentration, as recorded in ice cores. Wetlands are assumed to be the major source of this CH4, although several other hypotheses have been advanced. Modelling of CH4 emissions is crucial to quantify CH4 sources for past climates. Vegetation effects are generally highly generalized in modelling past and present-day CH4 fluxes, but should not be neglected. Plants strongly affect the soil-atmosphere exchange of CH4 and the net primary production of the vegetation supplies organic matter as substrate for methanogens. For modelling past CH4 fluxes from northern wetlands, assumptions on vegetation are highly relevant since paleobotanical data indicate large differences in Last Glacial (LG) wetland vegetation composition as compared to modern wetland vegetation. Besides more cold-adapted vegetation, Sphagnum mosses appear to be much less dominant during large parts of the LG than at present, which particularly affects CH4 oxidation and transport. To evaluate the effect of vegetation parameters, we used the PEATLAND-VU wetland CO2/CH4 model to simulate emissions from wetlands in continental Europe during LG and modern climates. We tested the effect of parameters influencing oxidation during plant transport (fox), vegetation net primary production (NPP, parameter symbol Pmax), plant transport rate (Vtransp), maximum rooting depth (Zroot) and root exudation rate (fex). Our model results show that modelled CH4 fluxes are sensitive to fox and Zroot in particular. The effects of Pmax, Vtransp and fex are of lesser relevance. Interactions with water table modelling are significant for Vtransp. We conducted experiments with different wetland vegetation types for Marine Isotope Stage 3 (MIS 3) stadial and interstadial climates and the present-day climate, by coupling PEATLAND-VU to high resolution climate model simulations for Europe. Experiments assuming dominance of

  20. Electrical Resistivity Measurements in Sandstone During CH4 Hydrate Formation and CH4-CO2 Exchange

    NASA Astrophysics Data System (ADS)

    Birkedal, K.; Hauge, L.; Ersland, G.; Graue, A.

    2012-12-01

    The electrical properties of hydrate bearing sediments change with mineralogy, porosity, hydrate saturation, brine salinity, and mobility of the formation brine. Reliable calibration data is therefore essential for correct interpretation. Electrical resistivity measurements have been conducted on homogeneous Bentheim sand during CH4 hydrate formation. Various initial conditions (salinity and Sw) were used to determine the robustness of resistivity as a measure of hydrate saturation. Two setups with different electrode-arrangements were used; the first setup was a four electrode core holder without imaging capabilities, the second a two-electrode core holder used in combination with MRI to calibrate saturation data. The agreement between the two setups was good and there was little variation in phase angle. An initial resistivity decrease was observed at the initiation of hydrate growth for all experiments. This effect was more pronounced with lower initial salinities. Further increase in hydrate saturation resulted in reduced pore connectivity and increased tortuosity which resulted in increased resistivity (45-2487 kΩ). Only CH4 and water were used to form hydrate. The brine NaCl concentration of the remaining brine solution therefore increased during hydrate growth. Dynamic Rw and R0 values were incorporated into Archie's equations to account for changes in brine composition during hydrate formation. Resistivity was also measured during exchange between CH4-hydrate and CO2. There was an immediate resistivity and pressure response as CO2 was introduced to the system. This may be explained by higher water activity and CO2-hydrate growth at the trans-axial core face as CO2 is the preferred guest molecule at the experimental conditions. A spontaneous exchange therefore occurs, where the change in enthalpy accelerates the exchange. The resistivity showed a continuous decreasing trend after CO2 was introduced. This is explained by local in-equilibrium where

  1. Marine hypoxia/anoxia as a source of CH4 and N2O

    NASA Astrophysics Data System (ADS)

    Naqvi, S. W. A.; Bange, H. W.; Farías, L.; Monteiro, P. M. S.; Scranton, M. I.; Zhang, J.

    2010-07-01

    We review here the available information on methane (CH4) and nitrous oxide (N2O) from major marine, mostly coastal, oxygen (O2)-deficient zones formed both naturally and as a result of human activities (mainly eutrophication). Concentrations of both gases in subsurface waters are affected by ambient O2 levels to varying degrees. Organic matter supply to seafloor appears to be the primary factor controlling CH4 production in sediments and its supply to (and concentration in) overlying waters, with bottom-water O2-deficiency exerting only a modulating effect. High (micromolar level) CH4 accumulation occurs in anoxic (sulphidic) waters of silled basins, such as the Black Sea and Cariaco Basin, and over the highly productive Namibian shelf. In other regions experiencing various degrees of O2-deficiency (hypoxia to anoxia), CH4 concentrations vary from a few to hundreds of nanomolar levels. Since coastal O2-deficient zones are generally very productive and are sometimes located close to river mouths and submarine hydrocarbon seeps, it is difficult to differentiate any O2-deficiency-induced enhancement from in situ production of CH4 in the water column and its inputs through freshwater runoff or seepage from sediments. While the role of bottom-water O2-deficiency in CH4 formation appears to be secondary, even when CH4 accumulates in O2-deficient subsurface waters, methanotrophic activity severely restricts its diffusive efflux to the atmosphere. As a result, an intensification or expansion of coastal O2-deficient zones will probably not drastically change the present status where emission from the ocean as a whole forms an insignificant term in the atmospheric CH4 budget. The situation is different for N2O, the production of which is greatly enhanced in low-O2 waters, and although it is lost through denitrification in most suboxic and anoxic environments, the peripheries of such environments offer most suitable conditions for its production, with the exception of

  2. Practical Synthesis of Amides via Copper/ABNO-Catalyzed Aerobic Oxidative Coupling of Alcohols and Amines.

    PubMed

    Zultanski, Susan L; Zhao, Jingyi; Stahl, Shannon S

    2016-05-25

    A modular Cu/ABNO catalyst system has been identified that enables efficient aerobic oxidative coupling of alcohols and amines to amides. All four permutations of benzylic/aliphatic alcohols and primary/secondary amines are viable in this reaction, enabling broad access to secondary and tertiary amides. The reactions exhibit excellent functional group compatibility and are complete within 30 min-3 h at rt. All components of the catalyst system are commercially available. PMID:27171973

  3. The Aerobic Oxidation of Bromide to Dibromine Catalyzed by Homogeneous Oxidation Catalysts and Initiated by Nitrate in Acetic Acid

    SciTech Connect

    Partenheimer, Walt; Fulton, John L.; Sorensen, Christina M.; Pham, Van Thai; Chen, Yongsheng

    2014-06-01

    A small amount of nitrate, ~0.002 molal, initiates the Co/Mn catalyzed aerobic oxidation of bromide compounds (HBr,NaBr,LiBr) to dibromine in acetic acid at room temperature. At temperatures 40oC or less , the reaction is autocatalytic. Co(II) and Mn(II) themselves and mixed with ionic bromide are known homogeneous oxidation catalysts. The reaction was discovered serendipitously when a Co/Br and Co/Mn/Br catalyst solution was prepared for the aerobic oxidation of methyaromatic compounds and the Co acetate contained a small amount of impurity i.e. nitrate. The reaction was characterized by IR, UV-VIS, MALDI and EXAFS spectroscopies and the coordination chemistry is described. The reaction is inhibited by water and its rate changed by pH. The change in these variables, as well as others, are identical to those observed during homogeneous, aerobic oxidation of akylaromatics. A mechanism is proposed. Accidental addition of a small amount of nitrate compound into a Co/Mn/Br/acetic acid mixture in a large, commercial feedtank is potentially dangerous.

  4. An insight into the mechanism of the aerobic oxidation of aldehydes catalyzed by N-heterocyclic carbenes.

    PubMed

    Bortolini, O; Chiappe, C; Fogagnolo, M; Giovannini, P P; Massi, A; Pomelli, C S; Ragno, D

    2014-02-25

    N-Heterocyclic carbene catalysis for the aerobic oxidation and esterification of aromatic aldehydes was monitored by ESI-MS (MS/MS) and the key intermediates were intercepted and characterized using the charge-tag strategy. PMID:24413829

  5. Interpreting the Shifted CH4 Spectra of Pluto and Triton

    NASA Astrophysics Data System (ADS)

    Trafton, Laurence M.

    2013-10-01

    It is known that the concentration of methane in Pluto’s atmosphere and surface ice is significantly greater than for Triton. The spectra of both bodies show methane lines shifted in wavelength relative to the laboratory spectrum by an amount that is characteristic of a solid solution of methane dissolved in nitrogen. In addition, Pluto shows an unshifted methane spectrum that is not seen for Triton. Moreover, the relative amounts of CH4, N2, and CO have been reported to vary with longitude for Pluto. The lack of a wavelength shift and the continent-sized variations have sometimes been interpreted to mean that the pure species exist and can relocate separately. This view simplifies the interpretation of the vapor pressure of each ice component because the vapor pressure is then assumed to be simply a function of the temperature. However, because the interaction between the atmosphere and volatile ice tends to move towards a dynamic equilibrium, it is likely that each pair of these species exits in both phases of a binary solid solution. At low temperature, the phase diagram of a solid solution of CH4 and N2 shows that saturation occurs at relatively dilute concentrations, about 3.5% and 5%, respectively, at 38 K. Therefore, N2 dissolved in CH4 should coexist with CH4 dissolved in N2 while exhibiting an essentially unshifted CH4 spectrum owing to the dominance of CH4 in this phase. Thus, the presence of both shifted and unshifted CH4 lines in Pluto’s spectrum suggests that there is more than enough CH4 to saturate N2 ice so that the leftover CH4 forms a saturated CH4-rich phase. In thermal equilibrium, both phases are saturated and no other phase exists. In Triton’s case, the ice CH4 inventory is not high enough to result in detectable unshifted CH4 lines in Triton’s spectrum. Raoult’s law does not apply near saturation, where activity matters. Laboratory experiments are needed for the vapor pressures in saturated solid solution mixtures to understand the

  6. Role of ammonia-oxidizing bacteria in micropollutant removal from wastewater with aerobic granular sludge.

    PubMed

    Margot, Jonas; Lochmatter, Samuel; Barry, D A; Holliger, Christof

    2016-01-01

    Nitrifying wastewater treatment plants (WWTPs) are more efficient than non-nitrifying WWTPs to remove several micropollutants such as pharmaceuticals and pesticides. This may be related to the activity of nitrifying organisms, such as ammonia-oxidizing bacteria (AOBs), which could possibly co-metabolically oxidize micropollutants with their ammonia monooxygenase (AMO). The role of AOBs in micropollutant removal was investigated with aerobic granular sludge (AGS), a promising technology for municipal WWTPs. Two identical laboratory-scale AGS sequencing batch reactors (AGS-SBRs) were operated with or without nitrification (inhibition of AMOs) to assess their potential for micropollutant removal. Of the 36 micropollutants studied at 1 μg l(-1) in synthetic wastewater, nine were over 80% removed, but 17 were eliminated by less than 20%. Five substances (bisphenol A, naproxen, irgarol, terbutryn and iohexol) were removed better in the reactor with nitrification, probably due to co-oxidation catalysed by AMOs. However, for the removal of all other micropollutants, AOBs did not seem to play a significant role. Many compounds were better removed in aerobic condition, suggesting that aerobic heterotrophic organisms were involved in the degradation. As the AGS-SBRs did not favour the growth of such organisms, their potential for micropollutant removal appeared to be lower than that of conventional nitrifying WWTPs. PMID:26877039

  7. Supplementation with vitamin A enhances oxidative stress in the lungs of rats submitted to aerobic exercise.

    PubMed

    Gasparotto, Juciano; Petiz, Lyvia Lintzmaier; Girardi, Carolina Saibro; Bortolin, Rafael Calixto; de Vargas, Amanda Rodrigues; Henkin, Bernardo Saldanha; Chaves, Paloma Rodrigues; Roncato, Sabrina; Matté, Cristiane; Zanotto-Filho, Alfeu; Moreira, José Cláudio Fonseca; Gelain, Daniel Pens

    2015-12-01

    Exercise training induces reactive oxygen species production and low levels of oxidative damage, which are required for induction of antioxidant defenses and tissue adaptation. This process is physiological and essential to improve physical conditioning and performance. During exercise, endogenous antioxidants are recruited to prevent excessive oxidative stress, demanding appropriate intake of antioxidants from diet or supplements; in this context, the search for vitamin supplements that enhance the antioxidant defenses and improve exercise performance has been continuously increasing. On the other hand, excess of antioxidants may hinder the pro-oxidant signals necessary for this process of adaptation. The aim of this study was to investigate the effects of vitamin A supplementation (2000 IU/kg, oral) upon oxidative stress and parameters of pro-inflammatory signaling in lungs of rats submitted to aerobic exercise (swimming protocol). When combined with exercise, vitamin A inhibited biochemical parameters of adaptation/conditioning by attenuating exercise-induced antioxidant enzymes (superoxide dismutase and glutathione peroxidase) and decreasing the content of the receptor for advanced glycation end-products. Increased oxidative damage to proteins (carbonylation) and lipids (lipoperoxidation) was also observed in these animals. In sedentary animals, vitamin A decreased superoxide dismutase and increased lipoperoxidation. Vitamin A also enhanced the levels of tumor necrosis factor alpha and decreased interleukin-10, effects partially reversed by aerobic training. Taken together, the results presented herein point to negative effects associated with vitamin A supplementation at the specific dose here used upon oxidative stress and pro-inflammatory cytokines in lung tissues of rats submitted to aerobic exercise.

  8. Dissolution of Fe(III)(hydr)oxides by an Aerobic Bacterium

    SciTech Connect

    Maurice, P.

    2004-12-13

    This project investigated the effects of an aerobic Pseudomonas mendocina bacterium on the dissolution of Fe(III)(hydr)oxides. The research is important because metals and radionuclides that adsorb to Fe(III)(hydr)oxides could potentially be remobilized by dissolving bacteria. We showed that P. mendocina is capable of dissolving Fe-bearing minerals by a variety of mechanisms, including production of siderophores, pH changes, and formation of reductants. The production of siderophores by P. mendocina was quantified under a variety of growth conditions. Finally, we demonstrated that microbial siderophores may adsorb to and enhance dissolution of clay minerals.

  9. Vibrational dynamics of the CH4·F- complex.

    PubMed

    Wodraszka, Robert; Palma, Juliana; Manthe, Uwe

    2012-11-26

    Motivated by recent photodetachment experiments studying resonance structures in the transition-state region of the F + CH(4) → HF + CH(3) reaction, the vibrational dynamics of the precursor complex CH(4)·F(-) is investigated. Delocalized vibrational eigenstates of CH(4)·F(-) are computed in full dimensionality employing the multiconfigurational time-dependent Hartree (MCTDH) approach and a recently developed iterative diagonalization approach for general multiwell systems. Different types of stereographic coordinates are used, and a corresponding general N-body kinetic energy operator is given. The calculated tunneling splittings of the ground and the lower vibrational excited states of the CH(4)·F(-) complex do not significantly exceed 1 cm(-1). Comparing the converged MCTDH results for localized vibrational excitations with existing results obtained by normal-mode-based (truncated) vibrational configuration interaction calculations, significantly lower frequencies are found for excitations in the intermolecular modes. PMID:22731911

  10. Long-term aerobic exercise increases redox-active iron through nitric oxide in rat hippocampus.

    PubMed

    Chen, Qian; Xiao, De-Sheng

    2014-01-30

    Adult hippocampus is highly vulnerable to iron-induced oxidative stress. Aerobic exercise has been proposed to reduce oxidative stress but the findings in the hippocampus are conflicting. This study aimed to observe the changes of redox-active iron and concomitant regulation of cellular iron homeostasis in the hippocampus by aerobic exercise, and possible regulatory effect of nitric oxide (NO). A randomized controlled study was designed in the rats with swimming exercise treatment (for 3 months) and/or an unselective inhibitor of NO synthase (NOS) (L-NAME) treatment. The results from the bleomycin-detectable iron assay showed additional redox-active iron in the hippocampus by exercise treatment. The results from nonheme iron content assay, combined with the redox-active iron content, showed increased storage iron content by exercise treatment. NOx (nitrate plus nitrite) assay showed increased NOx content by exercise treatment. The results from the Western blot assay showed decreased ferroportin expression, no changes of TfR1 and DMT1 expressions, increased IRP1 and IRP2 expression, increased expressions of eNOS and nNOS rather than iNOS. In these effects of exercise treatment, the increased redox-active iron content, storage iron content, IRP1 and IRP2 expressions were completely reversed by L-NAME treatment, and decreased ferroportin expression was in part reversed by L-NAME. L-NAME treatment completely inhibited increased NOx and both eNOS and nNOS expression in the hippocampus. Our findings suggest that aerobic exercise could increase the redox-active iron in the hippocampus, indicating an increase in the capacity to generate hydroxyl radicals through the Fenton reactions, and aerobic exercise-induced iron accumulation in the hippocampus might mainly result from the role of the endogenous NO.

  11. Effects of Methane Metabolism on Nitrification and Nitrous Oxide Production in Polluted Freshwater Sediment

    PubMed Central

    Roy, Réal; Knowles, Roger

    1994-01-01

    We report the effect of CH4 and of CH4 oxidation on nitrification in freshwater sediment from Hamilton Harbour, Ontario, Canada, a highly polluted ecosystem. Aerobic slurry experiments showed a high potential for aerobic N2O production in some sites. It was suppressed by C2H2, correlated to NO3- production, and stimulated by NH4+ concentration, supporting the hypothesis of a nitrification-dependent source for this N2O production. Diluted sediment slurries supplemented with CH4 (1 to 24 μM) showed earlier and enhanced nitrification and N2O production compared with unsupplemented slurries (≤1 μM CH4). This suggests that nitrification by methanotrophs may be significant in freshwater sediment under certain conditions. Suppression of nitrification was observed at CH4 concentrations of 84 μM and greater, possibly through competition for O2 between methanotrophs and NH4+ -oxidizing bacteria and/or competition for mineral N between these two groups of organisms. In Hamilton Harbour sediment, the very high CH4 concentrations (1.02 to 6.83 mM) which exist would probably suppress nitrification and favor NH4+ accumulation in the pore water. Indeed, NH4+ concentrations in Hamilton Harbour sediment are higher than those found in other lakes. We conclude that the impact of CH4 metabolism on N cycling processes in freshwater ecosystems should be given more attention. PMID:16349384

  12. Termite mound emissions of CH4 and CO2 are primarily determined by seasonal changes in termite biomass and behaviour.

    PubMed

    Jamali, Hizbullah; Livesley, Stephen J; Dawes, Tracy Z; Hutley, Lindsay B; Arndt, Stefan K

    2011-10-01

    Termites are a highly uncertain component in the global source budgets of CH(4) and CO(2). Large seasonal variations in termite mound fluxes of CH(4) and CO(2) have been reported in tropical savannas but the reason for this is largely unknown. This paper investigated the processes that govern these seasonal variations in CH(4) and CO(2) fluxes from the mounds of Microcerotermes nervosus Hill (Termitidae), a common termite species in Australian tropical savannas. Fluxes of CH(4) and CO(2) of termite mounds were 3.5-fold greater in the wet season as compared to the dry season and were a direct function of termite biomass. Termite biomass in mound samples was tenfold greater in the wet season compared to the dry season. When expressed per unit termite biomass, termite fluxes were only 1.2 (CH(4)) and 1.4 (CO(2))-fold greater in the wet season as compared to the dry season and could not explain the large seasonal variations in mound fluxes of CH(4) and CO(2). Seasonal variation in both gas diffusivity through mound walls and CH(4) oxidation by mound material was negligible. These results highlight for the first time that seasonal termite population dynamics are the main driver for the observed seasonal differences in mound fluxes of CH(4) and CO(2). These findings highlight the need to combine measurements of gas fluxes from termite mounds with detailed studies of termite population dynamics to reduce the uncertainty in quantifying seasonal variations in termite mound fluxes of CH(4) and CO(2).

  13. Aerobic and anaerobic methane oxidation in terrestrial mud volcanoes in the Northern Apennines

    NASA Astrophysics Data System (ADS)

    Wrede, C.; Brady, S.; Rockstroh, S.; Dreier, A.; Kokoschka, S.; Heinzelmann, S. M.; Heller, C.; Reitner, J.; Taviani, M.; Daniel, R.; Hoppert, M.

    2012-07-01

    Methane oxidizing prokaryotes are ubiquitous in oxic and anoxic habitats wherever C1-compounds are present. Thus, methane saturated mud volcano fluids should be a preferred habitat of methane consuming prokaryotes, using the readily available electron donors. In order to understand the relevance of methane as a carbon and energy source in mud volcano communities, we investigate the diversity of prokaryotic organisms involved in oxidation of methane in fluid samples from the Salse di Nirano mud volcano field situated in the Northern Apennines. Cell counts were at approximately 0.7 × 106 microbial cells/ml. A fraction of the microbial biomass was identified as ANME (anaerobic methanotroph) archaea by fluorescence in situ hybridization (FISH) analysis. They are associated in densely colonized flakes, of some tens of μm in diameter, embedded in a hyaline matrix. Diversity analysis based on the 16S rDNA genes, retrieved from amplified and cloned environmental DNA, revealed a high proportion of archaea, involved in anaerobic oxidation of methane (AOM). Aerobic methane-oxidizing proteobacteria could be highly enriched from mud volcano fluids, indicating the presence of aerobic methanotrophic bacteria, which may contribute to methane oxidation, whenever oxygen is readily available. The results imply that biofilms, dominated by ANME archaea, colonize parts of the mud volcano venting system.

  14. Coadsorption phase diagram for CH4/CCl4 on graphite

    NASA Astrophysics Data System (ADS)

    Weber, William J.; Goodstein, David L.

    2006-05-01

    We present an extensive thermodynamic study of methane coadsorbed on graphite precoated with a saturated monolayer of carbon tetrachloride. A combination of heat capacity and volumetric equation of state data permit construction of the multilayer coadsorption phase diagram between 70 and 115K . Displacement of the preadsorbed CCl4 by CH4 occurs by a continuous process across the temperature range studied. While the continuous nature of the transition implies a single phase mixed film during displacement, the observation of a commensurability transition characteristic of CH4 on bare graphite suggests the emergence of order in the coadsorbed CH4 in the early stages of displacement. At low temperatures and multilayer coverages, the coadsorption phase diagram shows small but measurable differences from the pure CH4 data, indicating that the multilayer film formed after displacement is not identical to that of CH4 in the absence of CCl4 . At higher temperatures, a new first order phase transition is observed to correspond with the completion of displacement. One interpretation is that the phase boundary represents the melting of a nearly pure CH4 monolayer solid into a mixed liquid film phase, with the size of the melting point depression indicating a concentration of nearly 1% CCl4 in the liquid phase.

  15. Temperature and peat type control CO2 and CH4 production in Alaskan permafrost peats.

    PubMed

    Treat, C C; Wollheim, W M; Varner, R K; Grandy, A S; Talbot, J; Frolking, S

    2014-08-01

    Controls on the fate of ~277 Pg of soil organic carbon (C) stored in permafrost peatland soils remain poorly understood despite the potential for a significant positive feedback to climate change. Our objective was to quantify the temperature, moisture, organic matter, and microbial controls on soil organic carbon (SOC) losses following permafrost thaw in peat soils across Alaska. We compared the carbon dioxide (CO2 ) and methane (CH4 ) emissions from peat samples collected at active layer and permafrost depths when incubated aerobically and anaerobically at -5, -0.5, +4, and +20 °C. Temperature had a strong, positive effect on C emissions; global warming potential (GWP) was >3× larger at 20 °C than at 4 °C. Anaerobic conditions significantly reduced CO2 emissions and GWP by 47% at 20 °C but did not have a significant effect at -0.5 °C. Net anaerobic CH4 production over 30 days was 7.1 ± 2.8 μg CH4 -C gC(-1) at 20 °C. Cumulative CO2 emissions were related to organic matter chemistry and best predicted by the relative abundance of polysaccharides and proteins (R(2) = 0.81) in SOC. Carbon emissions (CO2 -C + CH4 -C) from the active layer depth peat ranged from 77% larger to not significantly different than permafrost depths and varied depending on the peat type and peat decomposition stage rather than thermal state. Potential SOC losses with warming depend not only on the magnitude of temperature increase and hydrology but also organic matter quality, permafrost history, and vegetation dynamics, which will ultimately determine net radiative forcing due to permafrost thaw.

  16. Enrichment in 13C of atmospheric CH4 during the Younger Dryas termination

    NASA Astrophysics Data System (ADS)

    Melton, J. R.; Schaefer, H.; Whiticar, M. J.

    2012-07-01

    The abrupt warming across the Younger Dryas termination (~11 600 yr before present) was marked by a large increase in the global atmospheric methane mixing ratio. The debate over sources responsible for the rise in methane centers on the roles of global wetlands, marine gas hydrates, and thermokarst lakes. We present a new, higher-precision methane stable carbon isotope ratio (δ13CH4) dataset from ice sampled at Påkitsoq, Greenland that shows distinct 13C-enrichment associated with this rise. We investigate the validity of this finding in face of known anomalous methane concentrations that occur at Påkitsoq. Comparison with previously published datasets to determine the robustness of our results indicates a similar trend in ice from both an Antarctic ice core and previously published Påkitsoq data measured using four different extraction and analytical techniques. The δ13CH4 trend suggests that 13C-enriched CH4 sources played an important role in the concentration increase. In a first attempt at quantifying the various contributions from our data, we apply a methane triple mass balance of stable carbon and hydrogen isotope ratios and radiocarbon. The mass balance results suggest biomass burning (42-66% of total methane flux increase) and thermokarst lakes (27-59%) as the dominant contributing sources. Given the high uncertainty and low temporal resolution of the 14CH4 dataset used in the triple mass balance, we also performed a mass balance test using just δ13C and δD. These results further support biomass burning as a dominant source, but do not allow distinguishing of thermokarst lake contributions from boreal wetlands, aerobic plant methane, or termites. Our results in both mass balance tests do not suggest as large a role for tropical wetlands or marine gas hydrates as commonly proposed.

  17. Revealing the halide effect on the kinetics of the aerobic oxidation of Cu(I) to Cu(II)

    SciTech Connect

    Deng, Yi; Zhang, Guanghui; Qi, Xiaotian; Liu, Chao; Miller, Jeffrey T.; Kropf, A. Jeremy; Bunel, Emilio E.; Lan, Yu; Lei, Aiwen

    2015-01-01

    In situ infrared (IR) and X-ray absorption near-edge structure (XANES) spectroscopic investigations reveal that different halide ligands have distinct effects on the aerobic oxidation of Cu(I) to Cu(II) in the presence of TMEDA (tetramethylethylenediamine). The iodide ligand gives the lowest rate and thus leads to the lowest catalytic reaction rate of aerobic oxidation of hydroquinone to benzoquinone. Further DFT calculations suggest that oxidation of CuI–TMEDA involves a side-on transition state, while oxidation of CuCl–TMEDA involves an end-on transition state which has a lower activation energy.

  18. CH4 production via CO2 reduction in a temperate bog - A source of (C-13)-depleted CH4

    NASA Technical Reports Server (NTRS)

    Lansdown, J. M.; Quay, P. D.; King, S. L.

    1992-01-01

    The paper reports measurements, taken over two annual cycles, of the flux and delta(C-13) of CH4 released from an acidic peat bog located in the foothills of the Cascade Range in Washington state, U.S. Measurements of the rate of aceticlastic methanogenesis and CO2 reduction in peat soil, using (C-14)-labeled acetate and sodium bicarbonate, show that acetate was not an important CH4 precursor and that CO2 reduction could account for all of the CH4 production. The in situ kinetic isotope effect for CO2 reduction, calculated using the delta-(C-13) of soil water CO2 and CH4 flux, was 0.932 +/- 0.007.

  19. CH4 production via CO2 reduction in a temperate bog - A source of (C-13)-depleted CH4

    NASA Astrophysics Data System (ADS)

    Lansdown, J. M.; Quay, P. D.; King, S. L.

    1992-09-01

    The paper reports measurements, taken over two annual cycles, of the flux and delta(C-13) of CH4 released from an acidic peat bog located in the foothills of the Cascade Range in Washington state, U.S. Measurements of the rate of aceticlastic methanogenesis and CO2 reduction in peat soil, using (C-14)-labeled acetate and sodium bicarbonate, show that acetate was not an important CH4 precursor and that CO2 reduction could account for all of the CH4 production. The in situ kinetic isotope effect for CO2 reduction, calculated using the delta-(C-13) of soil water CO2 and CH4 flux, was 0.932 +/- 0.007.

  20. Denitrification and nitric oxide reduction in an aerobic toluene-treating biofilter

    SciTech Connect

    Plessis, C.A. du; Kinney, K.A.; Schroeder, E.D.; Chang, D.P.Y.; Scow, K.M.

    1998-05-20

    The presence of significant denitrification activity in an aerobic toluene-treating biofilter was demonstrated under batch and flow-through conditions. N{sub 2}O concentrations of 9.2 ppm{sub v} were produced by denitrifying bacteria in the presence of 15% acetylene, in a flow-through system with a bulk gas phase O{sub 2} concentration of >17%. The carbon source for denitrification was not toluene but a byproduct or metabolite of toluene catabolism. Denitrification conditions were successfully used for the reduction of 60 ppm{sub v} nitric oxide to 15 ppm{sub v} at a flow rate of 3 L/min (EBRT of 3 min) in a fully aerated, 17%/v/v O{sub 2} (superficially aerobic) biofilter. Higher NO removal efficiency (97%) was obtained by increasing the toluene supply to the biofilter.

  1. Observing the global distribution of atmospheric CH4 from space

    NASA Astrophysics Data System (ADS)

    Knappett, D.

    2009-04-01

    Atmospheric methane (CH4) plays a significant role in global warming despite being present in the atmosphere in smaller quantities than carbon dioxide (CO2) and has a radiative forcing efficiency or ‘global warming potential' of 21 times greater than that of CO2. The annual global source strength of CH4 is fairly well constrained to 550 (±50) Tg from the study of tropospheric OH which is the dominant sink for atmospheric CH4. However there is a distinct lack of knowledge surrounding the temporal and spatial variability of individual methane sources and sinks, leaving a number of scientific questions unanswered. For example, it is unclear why the atmospheric growth rate of CH4 has recently begun to rise again, following a 20 year decline, despite no obvious change in global emissions. It is clear that an accurate and comprehensive dataset of CH4 retrievals is required in order to properly quantify CH4 sources and sinks and hence allow problems such as this to be better understood. The Scanning Imaging Absorption Spectrometer for Atmospheric Chartography instrument (SCIAMACHY) is a nadir/limb viewing spectrometer of moderate resolution which observes in the UV, visible and NIR. SCIAMACHY detects sunlight reflected from the Earth's surface and as such has high sensitivity to the lowest atmospheric layers where anthropogenic trace gas emissions peak. Out of 8 spectral channels, CH4 is retrieved from channel 6 (971-1773nm) which has high spatial but low spectral resolution. The FSI WFM-DOAS retrieval algorithm, previously applied to CO2 data from SCIAMACHY (Barkley et al., 2006) has been adapted to perform retrievals of CH4. We will present results of a series of sensitivity tests that have been carried out to characterize the FSI algorithm for various aerosol, surface and temperature scenarios. Furthermore, first results and their validation will be shown. The next step will be to generate a global multi-year CH4 dataset to monitor CH4 variability on a global scale

  2. 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.

  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. The influence of methane oxidation on the stable isotopic composition of methane emitted from Florida swamp forests

    NASA Astrophysics Data System (ADS)

    Happell, James D.; Chanton, Jeffrey P.; Showers, William S.

    1994-10-01

    This study reports the first measurements of the δ 13C of CH 4 emitted from seasonally flooded swamp forests in the southeastern United States. The seasonally averaged δ 13C of CH 4 emitted from a north Florida swamp forest located in the St. Marks National Wildlife Refuge was -52.7 ± 6.11%. (error is ± one standard deviation throughout, n = 28), a value 13C-enriched, relative to typical wetland emissions. In an Everglades cypress dome, the average δ 13C of emitted CH 4 was -52.5 ± 6.7%.( n = 3). Consistent with attenuation of CH 4 emission by CH 4 oxidation in these environments, CH 4 emitted via diffusion from the St. Marks swamp forest was enriched in 13C by 6.4 ± 5.8%. ( n = 28) and D by 57 ± 36%. ( n = 6) relative to sedimentary CH 4. Methane emitted from the cypress dome had also been altered by oxidation, as it was enriched in 13C by 12.1 ± 4.3%. relative to sedimentary CH 4. Emission experiments, performed in situ with inhibitors of aerobic CH 4 oxidizing bacteria, were used to calculate the fractionation factors (α) for stable carbon and hydrogen isotopes of CH 4 undergoing transport and oxidation. Values ranged from 1.003 to 1.021 and 1.050 to 1.129, respectively. The best estimates for carbon and hydrogen α values were 1.020 and 1.068, respectively. The δ values of produced (sedimentary) CH 4 were relatively constant in the St. Marks subtropical swamp forest. Additionally, because the transport of CH 4 to the atmosphere was dominated by molecular diffusion, variations in the magnitude of CH 4 oxidation appeared to be the primary factor controlling the δ values of emitted CH 4. This contrasts with systems dominated by bubble ebullition, where variations in CH 4 production mechanisms have been hypothesized to be the primary factor controlling the δ values of emitted CH 4.

  5. Ammonium-oxidizing bacteria facilitate aerobic degradation of sulfanilic acid in activated sludge.

    PubMed

    Chen, Gang; Ginige, Maneesha P; Kaksonen, Anna H; Cheng, Ka Yu

    2014-01-01

    Sulfanilic acid (SA) is a toxic sulfonated aromatic amine commonly found in anaerobically treated azo dye contaminated effluents. Aerobic acclimatization of SA-degrading mixed microbial culture could lead to co-enrichment of ammonium-oxidizing bacteria (AOB) because of the concomitant release of ammonium from SA oxidation. To what extent the co-enriched AOB would affect SA oxidation at various ammonium concentrations was unclear. Here, a series of batch kinetic experiments were conducted to evaluate the effect of AOB on aerobic SA degradation in an acclimatized activated sludge culture capable of oxidizing SA and ammonium simultaneously. To account for the effect of AOB on SA degradation, allylthiourea was used to inhibit AOB activity in the culture. The results indicated that specific SA degradation rate of the mixed culture was negatively correlated with the initial ammonium concentration (0-93 mM, R²= 0.99). The presence of AOB accelerated SA degradation by reducing the inhibitory effect of ammonium (≥ 10 mM). The Haldane substrate inhibition model was used to correlate substrate concentration (SA and ammonium) and oxygen uptake rate. This study revealed, for the first time, that AOB could facilitate SA degradation at high concentration of ammonium (≥ 10 mM) in an enriched activated sludge culture.

  6. Seasonal variability of CH4 and N2O fluxes over a managed temperate mountain grassland

    NASA Astrophysics Data System (ADS)

    Hoertnagl, Lukas; Wohlfahrt, Georg

    2013-04-01

    The quantification of greenhouse gas (GHG) budgets on a global scale is an important step in assessing the effect of anthropogenic and biogenic controls on a future climate. In the past, measurements of CO2 fluxes were conducted over a wide array of ecosystems, leading to a better understanding of its exchange patterns on different time scales and more sophisticated models. However, only few studies quantified the fluxes of the other two major GHG, methane (CH4) and nitrous oxide (N2O), mainly due to expensive sensors and their time-consuming maintenance. In addition, early CH4 and N2O measurements mainly focused on ecosystems with presumably high emissions of CH4 (e.g. wetlands) or N2O (e.g. heavily fertilized crops). In recent years, devices for CH4 and N2O measurements became widely available and more studies are conducted over sites that exert small and often close-to-zero fluxes. Despite recent advances in sensor sensitivity and stability, the quantification of CH4 and N2O exchange rates remains challenging. Here we present measurements of CH4 and N2O exchange rates of a temperate mountain grassland managed as a hay meadow near the village Neustift in the Stubai Valley, Austria, that started in April 2010 by means of the eddy covariance method. The three wind components and the speed of sound were acquired at a time resolution of 20 Hz, while CH4 and N2O mixing ratios were recorded at 2 Hz by a quantum cascade laser absorption spectrometer (QCL-AS). Fluxes of both compounds were calculated using the virtual disjunct eddy covariance method (vDEC). For better comparability fluxes of N2O and CH4 were also converted to g CO2-equivalents and compared to the CO2 exchange at the same site. In addition to exchange rates, challenges regarding the calculation of GHG fluxes at the investigated grassland site will also be discussed. In 2011, deposition of CH4 was recorded on 9 days with average uptake rates of -0.6 nmol m-2 s-1. Peak emissions of up to 12.9 nmol m-2 s-1

  7. Diversity of active aerobic methanotrophs along depth profiles of arctic and subarctic lake water column and sediments

    PubMed Central

    He, Ruo; Wooller, Matthew J; Pohlman, John W; Quensen, John; Tiedje, James M; Leigh, Mary Beth

    2012-01-01

    Methane (CH4) emitted from high-latitude lakes accounts for 2–6% of the global atmospheric CH4 budget. Methanotrophs in lake sediments and water columns mitigate the amount of CH4 that enters the atmosphere, yet their identity and activity in arctic and subarctic lakes are poorly understood. We used stable isotope probing (SIP), quantitative PCR (Q-PCR), pyrosequencing and enrichment cultures to determine the identity and diversity of active aerobic methanotrophs in the water columns and sediments (0–25 cm) from an arctic tundra lake (Lake Qalluuraq) on the north slope of Alaska and a subarctic taiga lake (Lake Killarney) in Alaska's interior. The water column CH4 oxidation potential for these shallow (∼2 m deep) lakes was greatest in hypoxic bottom water from the subarctic lake. The type II methanotroph, Methylocystis, was prevalent in enrichment cultures of planktonic methanotrophs from the water columns. In the sediments, type I methanotrophs (Methylobacter, Methylosoma and Methylomonas) at the sediment-water interface (0–1 cm) were most active in assimilating CH4, whereas the type I methanotroph Methylobacter and/or type II methanotroph Methylocystis contributed substantially to carbon acquisition in the deeper (15–20 cm) sediments. In addition to methanotrophs, an unexpectedly high abundance of methylotrophs also actively utilized CH4-derived carbon. This study provides new insight into the identity and activity of methanotrophs in the sediments and water from high-latitude lakes. PMID:22592821

  8. Diversity of active aerobic methanotrophs along depth profiles of arctic and subarctic lake water column and sediments

    USGS Publications Warehouse

    He, Ruo; Wooller, Matthew J.; Pohlman, John W.; Quensen, John; Tiedje, James M.; Leigh, Mary Beth

    2012-01-01

    Methane (CH4) emitted from high-latitude lakes accounts for 2–6% of the global atmospheric CH4 budget. Methanotrophs in lake sediments and water columns mitigate the amount of CH4 that enters the atmosphere, yet their identity and activity in arctic and subarctic lakes are poorly understood. We used stable isotope probing (SIP), quantitative PCR (Q-PCR), pyrosequencing and enrichment cultures to determine the identity and diversity of active aerobic methanotrophs in the water columns and sediments (0–25 cm) from an arctic tundra lake (Lake Qalluuraq) on the north slope of Alaska and a subarctic taiga lake (Lake Killarney) in Alaska's interior. The water column CH4 oxidation potential for these shallow (~2m deep) lakes was greatest in hypoxic bottom water from the subarctic lake. The type II methanotroph, Methylocystis, was prevalent in enrichment cultures of planktonic methanotrophs from the water columns. In the sediments, type I methanotrophs (Methylobacter, Methylosoma and Methylomonas) at the sediment-water interface (0–1 cm) were most active in assimilating CH4, whereas the type I methanotroph Methylobacter and/or type II methanotroph Methylocystis contributed substantially to carbon acquisition in the deeper (15–20 cm) sediments. In addition to methanotrophs, an unexpectedly high abundance of methylotrophs also actively utilized CH4-derived carbon. This study provides new insight into the identity and activity of methanotrophs in the sediments and water from high-latitude lakes.

  9. Climatic thresholds for pedogenic iron oxides under aerobic conditions: Processes and their significance in paleoclimate reconstruction

    NASA Astrophysics Data System (ADS)

    Long, Xiaoyong; Ji, Junfeng; Barrón, Vidal; Torrent, José

    2016-10-01

    Iron oxides are widely distributed across the surface of the Earth as a result of the aerobic weathering of primary Fe-bearing minerals. Pedogenic iron oxides which consist mainly of hematite (Hm), goethite (Gt), maghemite (Mgh), are often concentrated synchronously in aerobic soils under low to moderate rainfall regimes. Magnetic susceptibility (χ) and redness, which respectively reflect the content of Mgh and Hm in soils, are considered reasonable pedogenic and climatic indicators in soil taxonomy and paleorainfall reconstruction. However, under high rainfall regimes, the grain growth of Mgh and transformation to Hm, combined with the prior formation of Gt under conditions of high relative humidity (RH), can result in magnetic reduction and dramatic yellowing of soils and sediments, which explains the existence of rainfall thresholds for Mgh and Hm at a large scale even before the pedogenic environment turns anaerobic. In order to capture the rainfall thresholds for Mgh and Hm occurring under aerobic conditions, we explored a tropical transect across a granitic region where the soil color turned from red to yellow under a wide rainfall range of 900-2200 mm/yr and a corresponding mean annual RH range of 77%-85%. We observed a lower rainfall threshold of ∼1500 mm/yr and a corresponding RH ∼80% for Mgh and Hm along this transect, as well as a higher rainfall threshold of ∼1700 mm/yr and a corresponding RH of ∼81% for Gt and total pedogenic iron oxides (citrate/bicarbonate/dithionite-extractable Fe, Fed). Cross-referencing with comparable studies in temperate and subtropical regions, we noted that the rainfall or RH thresholds for Fed and Hm or Mgh likewise increase with temperature. Moreover, the different thresholds for total and individual iron oxide phase indicates that a negative correlation between chemical weathering intensity and redness or χ in sediment sequences can occur under the prevalent climate regime just between their thresholds. Finally

  10. The Drivers of the CH4 Seasonal Cycle in the Arctic and What Long-Term Observations of CH4 Imply About Trends in Arctic CH4 Fluxes

    NASA Astrophysics Data System (ADS)

    Sweeney, C.; Karion, A.; Bruhwiler, L.; Miller, J. B.; Wofsy, S. C.; Miller, C. E.; Chang, R. Y.; Dlugokencky, E. J.; Daube, B.; Pittman, J. V.; Dinardo, S. J.

    2012-12-01

    The large seasonal change in the atmospheric column for CH4 in the Arctic is driven by two dominant processes: transport of CH4 from low latitudes and surface emissions throughout the Arctic region. The NOAA ESRL Carbon Cycle Group Aircraft Program along with the NASA funded Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) have initiated an effort to better understand the factors controlling the seasonal changes in the mole fraction of CH4 in the Arctic with a multi-scale aircraft observing network in Alaska. The backbone of this network is multi-species flask sampling from 500 to 8000 masl that has been conducted every two weeks for the last 10 years over Poker Flat, AK. In addition regular profiles at the interior Alaska site at Poker Flat, NOAA has teamed up with the United States Coast Guard to make profiling flights with continuous observations of CO2, CO, CH4 and Ozone between Kodiak and Barrow every 2 weeks. More recently, CARVE has significantly added to this observational network with targeted flights focused on exploring the variability of CO2, CH4 and CO in the boundary layer both in the interior and the North Slope regions of Alaska. Taken together with the profiling of HIAPER Pole-to-Pole Observations (HIPPO), ground sites at Barrow and a new CARVE interior Alaska surface site just north of Fairbanks, AK, we now have the ability to investigate the full evolution of the seasonal cycle in the Arctic using both the multi-scale sampling offered by the different aircraft platforms as well as the multi-species sampling offered by in-situ and flask sampling. The flasks also provide a valuable tie-point between different platforms so that spatial and temporal gradients can be properly interpreted. In the context of the seasonal cycle observed by the aircraft platforms we will look at long term ground observations over the last 20 years to assess changes in Arctic CH4 emissions which have occurred as a result of 0.6C/decade changes in mean surface

  11. BOREAS TF-1 SSA-OA Weekly Tower CH4 and N2O Flux

    NASA Technical Reports Server (NTRS)

    Thurtell, George; Edwards, Grant; Simpson, George; Hall, Forrest G. (Editor); Huemmrich, Karl (Editor)

    2000-01-01

    The BOREAS TF-1 team collected various trace gas and energy flux data in its efforts to characterize the temporal energy and gas exchanges that occurred over the SSA-OA site. This data set contains methane (CH4) and nitrous oxide (N2O) fluxes that were measured at the BOREAS SSA-OA site. These fluxes were measured from 16-Apr to 16-Sep-1994. The data were averaged to weekly values and are available in tabular ASCII files.

  12. Greenhouse impacts of anthropogenic CH4 and N2O emissions in Finland

    NASA Astrophysics Data System (ADS)

    Pipatti, Riitta; Savolainen, Ilkka; Sinisalo, Jukka

    1996-03-01

    The Finnish anthropogenic CH4 emissions in 1990 are estimated to be about 250 Gg, with an uncertainty range extending from 160 to 440 Gg. The most important sources are landfills and animal husbandry. The N2O emissions, which come mainly from agriculture and the nitric acid industry are about 20 Gg in 1990 (uncertainty range 10 30 Gg). The development of the emissions to the year 2010 is reviewed in two scenarios: the base and the reduction scenarios. According to the base scenario, the Finnish CH4 emissions will decrease in the near future. Emissions from landfills, energy production, and transportation will decrease because of already decided and partly realized volume and technical changes in these sectors. The average reduction potential of 50%, as assumed in the reduction scenario, is considered achievable. N2O emissions, on the other hand, are expected to increase as emissions from energy production and transportation will grow due to an increasing use of fluidized bed boilers and catalytic converters in cars. The average reduction potential of 50%, as assumed in the reduction scenario, is optimistic. Anthropogenic CH4 and N2O emissions presently cause about 30% of the direct radiative forcing due to Finnish anthropogenic greenhouse gas emissions. This share would be even larger if the indirect impacts of CH4 were included. The contribution of CH4 can be controlled due to its relatively short atmospheric lifetime and due to the existing emission reduction potential. Nitrous oxide has a long atmospheric lifetime and its emission control possiblities are limited consequently, the greenhouse impact of N2O seems to be increasing even if the emissions were limited somehow.

  13. The effect of widespread early aerobic marine ecosystems on methane cycling and the Great Oxidation

    NASA Astrophysics Data System (ADS)

    Daines, Stuart J.; Lenton, Timothy M.

    2016-01-01

    The balance of evidence suggests that oxygenic photosynthesis had evolved by 3.0-2.7 Ga, several hundred million years prior to the Great Oxidation ≈2.4 Ga. Previous work has shown that if oxygenic photosynthesis spread globally prior to the Great Oxidation, this could have supported widespread aerobic ecosystems in the surface ocean, without oxidising the atmosphere. Here we use a suite of models to explore the implications for carbon cycling and the Great Oxidation. We find that recycling of oxygen and carbon within early aerobic marine ecosystems would have restricted the balanced fluxes of methane and oxygen escaping from the ocean, lowering the atmospheric concentration of methane in the Great Oxidation transition and its aftermath. This in turn would have minimised any bi-stability of atmospheric oxygen, by weakening a stabilising feedback on oxygen from hydrogen escape to space. The result would have been a more reversible and probably episodic rise of oxygen at the Great Oxidation transition, consistent with existing geochemical evidence. The resulting drop in methane levels to ≈10 ppm is consistent with climate cooling at the time but adds to the puzzle of what kept the rest of the Proterozoic warm. A key test of the scenario of abundant methanotrophy in oxygen oases before the Great Oxidation is its predicted effects on the organic carbon isotope (δ13Corg) record. Our open ocean general circulation model predicts δC13org ≈ - 30 to -45‰ consistent with most data from 2.65 to 2.45 Ga. However, values of δC13org ≈ - 50 ‰ require an extreme scenario such as concentrated methanotroph production where shelf-slope upwelling of methane-rich water met oxic shelf water.

  14. Effect of CH4/O2 ratio on fatty acid profile and polyhydroxybutyrate content in a heterotrophic-methanotrophic consortium.

    PubMed

    Karthikeyan, Obulisamy P; Chidambarampadmavathy, Karthigeyan; Nadarajan, Saravanan; Lee, Patrick K H; Heimann, Kirsten

    2015-12-01

    Understanding the role of heterotrophic-methanotrophic (H-Meth) communities is important for improvement of methane (CH4) oxidation capacities (MOC) particularly in conjunction with bio-product development in industrial bio-filters. Initially, a H-Meth consortium was established and enriched from marine sediments and characterized by next generation sequencing of the 16s rDNA gene. The enriched consortium was subjected to 10-50% CH4 (i.e., 0.20-1.6 CH4/O2 ratios) to study the effects on MOCs, biomass growth, fatty acid profiles and biopolymer (e.g. polyhydroxybutyrate; PHB) content. Methylocystis, Methylophaga and Pseudoxanthomonas dominated the H-Meth consortium. Culture enrichment of the H-Meth consortium resulted in 15-20-folds higher MOC compared to seed sediments. Increasing CH4 concentration (and decreased O2 levels) yielded higher MOCs, but did not improve total fatty acid contents. PHB contents varied between 2.5% and 8.5% independently of CH4/O2 ratios. The results suggest that H-Meth consortia could potentially be used in industrial bio-filters for production of biopolymer/biofuel precursors from CH4. PMID:26247542

  15. Molecular Engineering of Trifunctional Supported Catalysts for the Aerobic Oxidation of Alcohols.

    PubMed

    Fernandes, Antony E; Riant, Olivier; Jensen, Klavs F; Jonas, Alain M

    2016-09-01

    We describe a simple and general method for the preparation and molecular engineering of supported trifunctional catalysts and their application in the representative Cu/TEMPO/NMI-catalyzed aerobic oxidation of benzyl alcohol. The methodology allows in one single step to immobilize, with precise control of surface composition, both pyta, Cu(I) , TEMPO, and NMI sites on azide-functionalized silica particles. To optimize the performance of the heterogeneous trifunctional catalysts, synergistic interactions are finely engineered through modulating the degree of freedom of the imidazole site as well as tuning the relative surface composition, leading to catalysts with an activity significantly superior to the corresponding homogeneous catalytic system.

  16. Molecular Engineering of Trifunctional Supported Catalysts for the Aerobic Oxidation of Alcohols.

    PubMed

    Fernandes, Antony E; Riant, Olivier; Jensen, Klavs F; Jonas, Alain M

    2016-09-01

    We describe a simple and general method for the preparation and molecular engineering of supported trifunctional catalysts and their application in the representative Cu/TEMPO/NMI-catalyzed aerobic oxidation of benzyl alcohol. The methodology allows in one single step to immobilize, with precise control of surface composition, both pyta, Cu(I) , TEMPO, and NMI sites on azide-functionalized silica particles. To optimize the performance of the heterogeneous trifunctional catalysts, synergistic interactions are finely engineered through modulating the degree of freedom of the imidazole site as well as tuning the relative surface composition, leading to catalysts with an activity significantly superior to the corresponding homogeneous catalytic system. PMID:27430481

  17. Pd/Cu-cocatalyzed aerobic oxidative carbonylative homocoupling of arylboronic acids and CO: a highly selective approach to diaryl ketones.

    PubMed

    Ren, Long; Jiao, Ning

    2014-09-01

    A highly selective Pd/Cu-cocatalyzed aerobic oxidative carbonylative homocoupling of arylboronic acids has been developed. This method employs a simple catalytic system, readily available boronic acids as the substrates, molecular oxygen as the oxidant, and 1 atm of CO/O2 , which makes this method practical for further applications. PMID:24990473

  18. Modeling of simultaneous denitrification--anaerobic digestion--organic matter aerobic oxidation and nitrification in an anoxic-anaerobic-aerobic compact filter reactor.

    PubMed

    Moya, Jaime; Huiliñir, César; Peredo, Karol; Aspé, Estrella; Roeckel, Marlene

    2012-08-31

    A mathematical model was developed for a compact anoxic-anaerobic-aerobic filter reactor with liquid recirculation for the treatment of fishing effluents. The model includes denitrification, anaerobic digestion, aerobic carbon oxidation and nitrification steps, as well as an evaluation of the liquid gas mass transfer and pH. The model was calibrated using one experimental condition at a recycling ratio (R)=10, and was validated with R equal to 2 and 0, with an organic concentration of 554±24 mg TOCL(-1), salinity of 24 g L(-1) and hydraulic retention time (HRT) of 2 d. Carbon total removal is higher than 98%, while maximum nitrogen removal is 62% using total nitrification in the aerobic zone, due to a higher quantity of NO(x) produced which were recirculated to the anoxic zone. In the aerobic zone, simultaneous nitrification and denitrification processes occur, because the diffusion limitations cause a low oxygen penetration in the biofilm. In the anoxic-anaerobic zone, denitrification or methanogenesis inhibition by DO (caused by the recycled oxygen) is not observed.

  19. 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

  20. Sensitivity of optimized high-resolution North American CH4 emissions to regional CH4 boundary conditions

    NASA Astrophysics Data System (ADS)

    Stanevich, Ilya; Strong, Kimberly; Jones, Dylan; Lin, John; Wecht, Kevin; Andrews, Arlyn; Worthy, Doug; Wennberg, Paul; Wunch, Debra; Roehl, Coleen

    2016-04-01

    Constraining CH4 emissions at subcontinental scales is of great value, especially for quantifying local anthropogenic emissions. However, high-resolution emission estimates are more uncertain, particularly due to their relatively weak signature in the atmosphere and the uncertainty of the CH4 measurements used to infer the emissions. In this work, we investigate the robustness of high-resolution North American emission estimates. We perform regional inversion analyses over North America using the Stochastic Time-Inverted Lagrangian Transport (STILT) model, with initial and boundary conditions imposed from the GEOS-Chem global chemical transport model, constrained by NOAA and Environment Canada CH4 flask measurements and CH4 columns measured using Fourier transform spectrometers at the University of Toronto Atmospheric Observatory and at the Total Carbon Column Observing Network (TCCON) Lamont station. We also perform STILT and GEOS-Chem inversions with pseudo in situ- and satellite-like measurements, respectively, to assess the seasonal sensitivity of optimized emissions to uncorrected biases in CH4 boundary conditions. We show that, depending on the season, the sensitivity of the emissions to the biases varies by up to 40%.

  1. Methane production and oxidation patterns along a hydrological gradient in Luther Bog, Ontario

    NASA Astrophysics Data System (ADS)

    Praetzel, Leandra; Berger, Sina; Blodau, Christian

    2016-04-01

    Methane emissions from natural peatlands contribute significantly to the global budget of atmospheric CH4. In the northern hemisphere, where climate models predict rising temperatures and precipitation rates, these emissions are likely to rise. So far, little is known about the change of processes of methane production and oxidation, which influence the total amount of methane emissions, in peatland soils under warmer and wetter climate conditions. Our work focuses on anaerobic CH4 production and aerobic CH4 oxidation processes along a hydrological gradient in an ombotrophic bog in Ontario, Canada that was induced by creation of a reservoir in 1952. Along this transect, four sites were established differing in hydrologic conditions and vegetation patterns. We examined depth profiles of CO2 and CH4 concentrations and delta 13C isotope ratios in the peat using silicon samplers, dialysis chambers and multi-level piezometers. Chamber flux measurements were used to determine carbon fluxes. Isotope mass balances were calculated based on 13C isotope ratios and concentration profiles. By this approach the contribution of anaerobic CH4 and CO2 production to the total ER flux and the amount of oxidised CH4 can be determined. In addition meteorological data, soil temperatures, moisture and water table levels were recorded. By raising data at different sites and dates and with the help of the additionally recorded parameters, we will be able to make predictions about changing CH4 production and oxidation processes due to changing climate conditions. Preliminary results show that CH4 concentrations in the soil profile are higher at the sites which are exposed to stronger water table fluctuations, whereas CO2 concentration levels are lower at these sites. At all sites, CO2 concentrations in the peat are increasing but CH4 profiles are fairly stable. Moreover, isotopic signatures of 13CH4 indicate that the importance of the production pathway changes with depth from acetoclastic

  2. 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. PMID:23505264

  3. Oxidation-reduction processes in ice swimmers after ice-cold water bath and aerobic exercise.

    PubMed

    Sutkowy, Paweł; Woźniak, Alina; Boraczyński, Tomasz; Boraczyński, Michał; Mila-Kierzenkowska, Celestyna

    2015-06-01

    The effect of an ice-cold water (ICW) bath as a recovery intervention from aerobic exercise on the oxidant-antioxidant balance in healthy ice swimmers was determined. Twenty ice swimmers aged 31.2 ± 6.3 years performed a 30-min cycloergometer exercise test at room temperature (20°C, RT), followed by recovery at RT or in a pool of ice-cold water (ICW bath, 3°C, 5 min). Blood for laboratory assays was collected from the basilic vein two times: before the exercise (baseline) and 40 min after the RT or ICW recovery. The concentrations of plasma and erythrocytic thiobarbituric acid reactive substances (plTBARS and erTBARS, respectively), serum concentrations of 8-iso-prostaglandin F2α, 4-hydroxynonenal and malondialdehyde, along with the erythrocytic activities of catalase (CAT) and superoxide dismutase (SOD), as well as the serum level of total antioxidant capacity, were assessed. No statistically significant changes were observed. However, a statistically significant negative linear correlation between the erTBARS concentration and the SOD activity was found 40 min after the combination of exercise/RT recovery (r=-0.571, P<0.01). The baseline CAT and SOD activities were also linearly correlated (r=0.469, P<0.05). Both the 5-min ICW bath and the 30-min aerobic exercise have practically no impact on the oxidant-antioxidant balance in healthy ice swimmers.

  4. Oxidation-reduction processes in ice swimmers after ice-cold water bath and aerobic exercise.

    PubMed

    Sutkowy, Paweł; Woźniak, Alina; Boraczyński, Tomasz; Boraczyński, Michał; Mila-Kierzenkowska, Celestyna

    2015-06-01

    The effect of an ice-cold water (ICW) bath as a recovery intervention from aerobic exercise on the oxidant-antioxidant balance in healthy ice swimmers was determined. Twenty ice swimmers aged 31.2 ± 6.3 years performed a 30-min cycloergometer exercise test at room temperature (20°C, RT), followed by recovery at RT or in a pool of ice-cold water (ICW bath, 3°C, 5 min). Blood for laboratory assays was collected from the basilic vein two times: before the exercise (baseline) and 40 min after the RT or ICW recovery. The concentrations of plasma and erythrocytic thiobarbituric acid reactive substances (plTBARS and erTBARS, respectively), serum concentrations of 8-iso-prostaglandin F2α, 4-hydroxynonenal and malondialdehyde, along with the erythrocytic activities of catalase (CAT) and superoxide dismutase (SOD), as well as the serum level of total antioxidant capacity, were assessed. No statistically significant changes were observed. However, a statistically significant negative linear correlation between the erTBARS concentration and the SOD activity was found 40 min after the combination of exercise/RT recovery (r=-0.571, P<0.01). The baseline CAT and SOD activities were also linearly correlated (r=0.469, P<0.05). Both the 5-min ICW bath and the 30-min aerobic exercise have practically no impact on the oxidant-antioxidant balance in healthy ice swimmers. PMID:25910677

  5. Greenhouse warming by CH4 in the atmosphere of early Earth.

    PubMed

    Pavlov, A A; Kasting, J F; Brown, L L; Rages, K A; Freedman, R

    2000-05-25

    Earth appears to have been warm during its early history despite the faintness of the young Sun. Greenhouse warming by gaseous CO2 and H2O by itself is in conflict with constraints on atmospheric CO2 levels derived from paleosols for early Earth. Here we explore whether greenhouse warming by methane could have been important. We find that a CH4 mixing ratio of 10(-4) (100 ppmv) or more in Earth's early atmosphere would provide agreement with the paleosol data from 2.8 Ga. Such a CH4 concentration could have been readily maintained by methanogenic bacteria, which are thought to have been an important component of the biota at that time. Elimination of the methane component of the greenhouse by oxidation of the atmosphere at about 2.3-2.4 Ga could have triggered the Earth's first widespread glaciation.

  6. Structural response of Ni/ZrO2 to feed modulations during CH4 reforming reactions

    NASA Astrophysics Data System (ADS)

    Steib, M.; Jentys, A.; Lercher, J. A.

    2016-05-01

    Time resolved oxidation and reduction cycles of ZrO2-supported Ni catalysts for dry reforming of CH4 (CO2 + CH4 ↔ 2 CO + 2 H2) during feed modulations have been studied. Under reaction conditions (1073 K) Ni remains fully reduced, whereas switching the feed gas to pure CO2 results in a slow (25 sec) formation of a stable NiO phase. When switching back to reaction conditions the NiO phase is rapidly reduced (∼ 1 sec) to metallic Ni. In the context of this study, a novel capillary cell has been built, allowing the parallel treatment of 5 catalyst samples with different gas compositions and different pressures. A comparison of the capillary cell to conventional systems regarding the spectral quality and the kinetic data shows that the capillary cell can be used to obtain identical kinetic data and high quality X-ray absorption spectra.

  7. Anaerobic Oxidation of Methane in Tropical and Boreal Soils: Ecological Significance

    NASA Astrophysics Data System (ADS)

    Blazewicz, S. J.; Petersen, D. G.; Waldrop, M. P.; Firestone, M. K.

    2011-12-01

    Anaerobic oxidation of methane (AOM) is a considerable sink for the greenhouse gas methane (CH4) in marine systems, but the importance of this process in terrestrial systems is less clear. Lowland boreal soils and wet tropical soils are two of the most dynamic terrestrial systems with regard to atmospheric CH4 cycles, yet little work has directly investigated AOM in these systems. We assessed the occurrence and potential importance of AOM in soils from Long Term Ecological Research sites in Alaska and Puerto Rico. Using in vitro techniques, isotope tracers were utilized to enable the simultaneous quantification of CH4 production and consumption without the use of biological inhibitors. Boreal peat soil and tropical mineral soil had the ability to oxidize significant quantities of CH4 to CO2 under anaerobic conditions (p < 0.001). Potential AOM rates were 21 ± 2 nmol gdw-1 d-1 and 2.9 ± 0.5 nmol gdw-1 d-1 for the boreal and tropical soils, respectively. The addition of terminal electron acceptors (NO3-, Fe3+, and SO42-) inhibited AOM and methanogenesis in both soils. In all incubations, CH4 production occurred simultaneously with AOM, and CH4 production rates were always greater than AOM rates. There was a strong correlation between the quantity of CH4 produced and the amount of CH4 oxidized under anaerobic conditions (Pearson's correlation coefficient: Alaska = 0.875, p < 0.0001; Puerto Rico = 0.817, p < 0.0001). Results indicate that CH4 oxidation under anaerobic conditions was biological and likely mediated by methanogenic archaea in both soils. For ecological perspective, we compared and contrasted rates of AOM in our two soils with AOM rates in marine systems and aerobic methane oxidation rates in our systems. While only a small percentage of the total methane produced in our soils was oxidized under anaerobic conditions, this process represents a previously unidentified sink in these soils that warrants further investigation.

  8. Impact of oxidative stress defense on bacterial survival and morphological change in Campylobacter jejuni under aerobic conditions.

    PubMed

    Oh, Euna; McMullen, Lynn; Jeon, Byeonghwa

    2015-01-01

    Campylobacter jejuni, a microaerophilic foodborne pathogen, inescapably faces high oxygen tension during its transmission to humans. Thus, the ability of C. jejuni to survive under oxygen-rich conditions may significantly impact C. jejuni viability in food and food safety as well. In this study, we investigated the impact of oxidative stress resistance on the survival of C. jejuni under aerobic conditions by examining three mutants defective in key antioxidant genes, including ahpC, katA, and sodB. All the three mutants exhibited growth reduction under aerobic conditions compared to the wild-type (WT), and the ahpC mutant showed the most significant growth defect. The CFU reduction in the mutants was recovered to the WT level by complementation. Higher levels of reactive oxygen species were accumulated in C. jejuni under aerobic conditions than microaerobic conditions, and supplementation of culture media with an antioxidant recovered the growth of C. jejuni. The levels of lipid peroxidation and protein oxidation were significantly increased in the mutants compared to WT. Additionally, the mutants exhibited different morphological changes under aerobic conditions. The ahpC and katA mutants developed coccoid morphology by aeration, whereas the sodB mutant established elongated cellular morphology. Compared to microaerobic conditions, interestingly, aerobic culture conditions substantially induced the formation of coccoidal cells, and antioxidant treatment reduced the emergence of coccoid forms under aerobic conditions. The ATP concentrations and PMA-qPCR analysis supported that oxidative stress is a factor that induces the development of a viable-but-non-culturable state in C. jejuni. The findings in this study clearly demonstrated that oxidative stress resistance plays an important role in the survival and morphological changes of C. jejuni under aerobic conditions. PMID:25914692

  9. Hot CH4 in the polar regions of Jupiter

    NASA Astrophysics Data System (ADS)

    Kim, Sang Joon; Sim, Chae Kyung; Ho, Jin; Geballe, Thomas R.; Yung, Yuk L.; Miller, Steve; Kim, Yong Ha

    2015-09-01

    We have obtained 3.3-3.4-μm spectro-images of Jupiter including CH4 and H3+ emission lines from both polar regions at the Gemini North telescope. We find that the peak of the 3-μm CH4 northern bright spot is located at ∼200° (SysIII) longitude, ∼20° west of the center of the 8-μm north-polar bright spot, and does not coincide with the 3-μm H3+ bright spot. We derive high temperatures (500-850 K) from CH4 rotational lines on the bright spots of both polar regions, above the 1-μbar pressure level, while we find cooler temperatures (<350 K) over the 8-μm spot. The intensity ratios of the various 3-μm vibrational bands of CH4 are roughly constant, indicating that the upper states of these bands are mostly populated by non-thermal excitation mechanisms, such as auroral particle precipitation and/or Joule heating, in contrast with the 8-μm thermal emission.

  10. Experimental simulations of CH4 evaporation on Titan

    NASA Astrophysics Data System (ADS)

    Luspay-Kuti, A.; Chevrier, V. F.; Wasiak, F. C.; Roe, L. A.; Welivitiya, W. D. D. P.; Cornet, T.; Singh, S.; Rivera-Valentin, E. G.

    2012-12-01

    We present the first experimental results on the evaporation of liquid CH4 under simulated Titan surface conditions similar to those observed at the Huygens landing site. An average evaporation rate of (3.1 ± 0.6) × 10-4 kg s-1 m-2 at 94 K and 1.5 bar was measured. While our results are generally higher than previous models based on energy balance, they show an excellent match with a theoretical mass transfer approach. Indeed, we find that evaporation in the Titan environmental chamber is predominantly diffusion driven and affected by the buoyancy of lighter CH4 in the heavier N2 atmosphere. After correcting for the difference in gravity of Earth and Titan, the resulting evaporation rate is (1.6 ± 0.3) × 10-4 kg s-1m-2 (or 1.13 ± 0.3 mm hr-1). Using our experimental evaporation rates, we determine that the low-latitude storm recently observed by Cassini ISS would have resulted in a maximum evaporated mass of (5.4 ± 1.2) × 1010 kg of CH4 equivalent to a 2.4 ± 0.5 m thick layer over 80 days. Based on our results, a sufficient amount of CH4 can accumulate in the otherwise arid equatorial regions to produce transient ponds and liquid flows.

  11. Effects of Long-Term CO2 Enrichment on Soil-Atmosphere CH4 Fluxes and the Spatial Micro-Distribution of Methanotrophic Bacteria

    PubMed Central

    Karbin, Saeed; Guillet, Cécile; Kammann, Claudia I.; Niklaus, Pascal A.

    2015-01-01

    Background Effects of elevated atmospheric CO2 concentrations on plant growth and associated C cycling have intensively been studied, but less is known about effects on the fluxes of radiatively active trace gases other than CO2. Net soil-atmosphere CH4 fluxes are determined by the balance of soil microbially-driven methane (CH4) oxidation and methanogenesis, and both might change under elevated CO2. Methods and Results Here, we studied CH4 dynamics in a permanent grassland exposed to elevated CO2 for 14 years. Soil-atmosphere fluxes of CH4 were measured using large static chambers, over a period of four years. The ecosystem was a net sink for atmospheric CH4 for most of the time except summer to fall when net CH4 emissions occurred. We did not detect any elevated CO2 effects on CH4 fluxes, but emissions were difficult to quantify due to their discontinuous nature, most likely because of ebullition from the saturated zone. Potential methanotrophic activity, determined by incubation of fresh sieved soil under standardized conditions, also did not reveal any effect of the CO2 treatment. Finally, we determined the spatial micro-distribution of methanotrophic activity at less than 5× atmospheric (10 ppm) and elevated (10000 ppm) CH4 concentrations, using a novel auto-radiographic technique. These analyses indicated that domains of net CH4 assimilation were distributed throughout the analyzed top 15 cm of soils, with no dependence on CH4 concentration or CO2 treatment. Conclusions Our investigations suggest that elevated CO2 exerts no or only minor effects on CH4 fluxes in the type of ecosystem we studied, at least as long as soil moisture differences are small or absent as was the case here. The autoradiographic analyses further indicate that the spatial niche of CH4 oxidation does not shift in response to CO2 enrichment or CH4 concentration, and that the same type of methanotrophs may oxidize CH4 from atmospheric and soil-internal sources. PMID:26147694

  12. Aerobic methane emissions from stinkweed (Thlaspi arvense) capsules

    PubMed Central

    Qaderi, Mirwais M; Reid, David M

    2014-01-01

    Aerobic methane (CH4) emission from plant vegetative parts has been confirmed by many studies. However, the origin of aerobic CH4 from plants and its emission from reproductive parts have not been well documented. We determined the effects of developmental stages (early, mid, late) and incubation conditions (darkness, dim light, bright light) on CH4 emissions from stinkweed (Thlaspi arvense) capsules. We found that CH4 emissions from capsules varied with developmental stage and incubation light. Methane emission was highest for the late harvested capsules and for those incubated under lower (dim) light condition. Our results also showed a significant negative correlation between CH4 emission and capsule moisture content. We conclude that CH4 emissions vary with capsule age and diurnal light environment. PMID:25482797

  13. Antibacterial Action of Nitric Oxide-Releasing Chitosan Oligosaccharides against Pseudomonas aeruginosa under Aerobic and Anaerobic Conditions

    PubMed Central

    Reighard, Katelyn P.

    2015-01-01

    Chitosan oligosaccharides were modified with N-diazeniumdiolates to yield biocompatible nitric oxide (NO) donor scaffolds. The minimum bactericidal concentrations and MICs of the NO donors against Pseudomonas aeruginosa were compared under aerobic and anaerobic conditions. Differential antibacterial activities were primarily the result of NO scavenging by oxygen under aerobic environments and not changes in bacterial physiology. Bacterial killing was also tested against nonmucoid and mucoid biofilms and compared to that of tobramycin. Smaller NO payloads were required to eradicate P. aeruginosa biofilms under anaerobic versus aerobic conditions. Under oxygen-free environments, the NO treatment was 10-fold more effective at killing biofilms than tobramycin. These results demonstrate the potential utility of NO-releasing chitosan oligosaccharides under both aerobic and anaerobic environments. PMID:26239983

  14. [Distribution of Aerobic Ammonia-Oxidizing Microorganisms in Sediments from Adjacent Waters of Rushan Bay].

    PubMed

    He, Hui; Zhen, Yu; Mi, Tie-zhu; Zhang, Yu; Fu, Lu-lu; Yu, Zhi-gang

    2015-11-01

    Nitrogen cycle is a key process in material circulation of marine ecosystem, which plays an important role in maintaining ecological balance. The ammonia oxidation process promoted by aerobic ammonia-oxidizing microorganism (AOM) is a rate-limiting step of nitrification. Real-time quantitative polymerase chain reaction (qPCR ), along with the determination of potential nitrification rates (PNR) was carried out in this study to understand the distribution of AOM in sediments of adjacent waters of Rushan Bay in August, 2014. The results indicated that the abundance of total ammonia-oxidizing bacteria (AOB) was always greater than that of total ammonia-oxidizing archaea (AOA) in the three sampling stations; the ratio of active AOB to total AOB was less than 1%, while no active AOA was detected in this study; the PNR significantly decreased after adding ampicillin which could inhibit the activity of AOB (P < 0.05). It was speculated that AOB might play a more important role in the ammonia oxidation in sediments of adjacent waters of Rushan Bay in August, 2014. Dissolved oxygen concentrations, temperature and ammonium concentrations played a significant role in distribution of AOM in sediments of adjacent waters of Rushan Bay.

  15. Osmium(ii) complexes for light-driven aerobic oxidation of amines to imines.

    PubMed

    Li, Yong-Hui; Liu, Xiao-Le; Yu, Zhen-Tao; Li, Zhao-Sheng; Yan, Shi-Cheng; Chen, Guang-Hui; Zou, Zhi-Gang

    2016-08-01

    Herein, we describe the synthesis and characterization of three Os(ii) complexes (i.e., [Os(fptz)2(PPhMe2)2] (1, fptzH = 3-trifluoromethyl-5-pyridyl-1,2,4-triazole), [Os(fptz)2(CO)(L1)] (2, L1 = PPh3; 3, L1 = pyridine)) that have been successfully utilized as good photocatalysts to promote aerobic oxidative coupling of amines to imines with molecular oxygen in air as a green oxidant. Complex 1 is the most effective catalyst for the oxidative coupling of benzylamine with molecular O2 (air) as the oxidant because of the complex's strong absorption of visible light and long-lived triplet state. The application of a low catalyst loading (0.06 mol%) of complex 1 to the oxidative coupling of a wide range of amines affords the corresponding imines efficiently and selectively in most cases. The reaction mechanism was investigated via relevant control and quenching experiments. The results indicated that the reaction occurs via an active (1)O2-involved pathway. The (1)O2-generating ability of complex 1 as a photosensitizer was evaluated using 9,10-dimethylanthracene (DMA) as a chemical trap for (1)O2. PMID:27431765

  16. Methanotrophic N2-Fixation in Boreal Peatlands: Master Regulation of Newly Fixed N and Moderation of CH4 Fluxes to the Atmosphere

    NASA Astrophysics Data System (ADS)

    Schlesinger, M.; Fillingim, H. M.; Wieder, R. K.; Vile, M. A.

    2015-12-01

    Boreal peatlands are important to global carbon (C) and nitrogen (N) cycling. While they cover only 3-4% of the terrestrial surface, they account for 25-30% and 9-15% of the world's soil C and N, respectively. Globally, peatlands function as a net sink for atmospheric CO2, but also act as a net source of CH4. In peatlands of Alberta, Canada, rates of atmospheric N deposition are low: ~1 kg·ha-1·yr-1, however, NPP of Sphagnum mosses is surprisingly high. Sphagnum mosses are able to maintain high levels of NPP due to their symbiotic relationship with N2-fixing methanotrophs. Annually, rates of N2-fixation typically provide between 10-30 kg of newly fixed N per ha, while also oxidizing CH4. CH4 fluxes from boreal peatlands in Canada are typically quite low, however, fluxes also can be high during rare episodic ebullition events. CH4 accumulation and storage is substantial, especially at depth as CH4 concentrations in peat pore water typically exceed 1000 μM at 1-m below the peat surface. Given that CH4 fluxes are typically low, we wanted to examine the importance of CH4 oxidation in these same peats. We hypothesized that methanotrophic N2-fixation may be important not only in providing inputs of newly fixed N, but also in regulating CH4 emissions from peatlands. We measured concentrations of CH4 in peat porewaters, CH4 flux rates, CH4 oxidation rates, biological N2-fixation rates. Porewater CH4 concentrations were highest at depth and decreased to negligible amounts closer to the surface of the water table. CH4 flux rates were low and ranged from -2.6 to +8.7 μmol·m-2·min-1 (negative values indicate net CH4 consumption). In Sphagnum incubations, rates of CH4 oxidation (0.6-10.2 mmol·m-2·min-1) were ~2-3 orders of magnitude higher than CH4 flux rates. Additionally, N2-fixation rates in paired cores ranged from 11.7-63.3 kg·ha-1·yr-1; CH4 oxidation rates in these same units ranged from ~3.1-622 kg·CH4 oxidized ha-1·yr-1. Additionally, we confirmed that N2

  17. Airborne measurements of CO2, CH4 and HCN in boreal biomass burning plumes

    NASA Astrophysics Data System (ADS)

    O'Shea, Sebastian J.; Bauguitte, Stephane; Muller, Jennifer B. A.; Le Breton, Michael; Archibald, Alex; Gallagher, Martin W.; Allen, Grant; Percival, Carl J.

    2013-04-01

    Biomass burning plays an important role in the budgets of a variety of atmospheric trace gases and particles. For example, fires in boreal Russia have been linked with large growths in the global concentrations of trace gases such as CO2, CH4 and CO (Langenfelds et al., 2002; Simpson et al., 2006). High resolution airborne measurements of CO2, CH4 and HCN were made over Eastern Canada onboard the UK Atmospheric Research Aircraft FAAM BAe-146 from 12 July to 4 August 2011. These observations were made as part of the BORTAS project (Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites). Flights were aimed at transecting and sampling the outflow from the commonly occurring North American boreal forest fires during the summer months and to investigate and identify the chemical composition and evolution of these plumes. CO2 and CH4 dry air mole fractions were determined using an adapted system based on a Fast Greenhouse Gas Analyser (FGGA, Model RMT-200) from Los Gatos Research Inc, which uses the cavity enhanced absorption spectroscopy technique. In-flight calibrations revealed a mean accuracy of 0.57 ppmv and 2.31 ppbv for 1 Hz observations of CO2 and CH4, respectively, during the BORTAS project. During these flights a number of fresh and photochemically-aged plumes were identified using simultaneous HCN measurements. HCN is a distinctive and useful marker for forest fire emissions and it was detected using chemical ionisation mass spectrometry (CIMS). In the freshest plumes, strong relationships were found between CH4, CO2 and other tracers for biomass burning. From this we were able to estimate that 8.5 ± 0.9 g of CH4 and 1512 ± 185 g of CO2 were released into the atmosphere per kg of dry matter burnt. These emission factors are in good agreement with estimates from previous studies and can be used to calculate budgets for the region. However for aged plumes the correlations between CH4 and other

  18. KetoABNO/NOx Cocatalytic Aerobic Oxidation of Aldehydes to Carboxylic Acids and Access to α-Chiral Carboxylic Acids via Sequential Asymmetric Hydroformylation/Oxidation.

    PubMed

    Miles, Kelsey C; Abrams, M Leigh; Landis, Clark R; Stahl, Shannon S

    2016-08-01

    A method for aerobic oxidation of aldehydes to carboxylic acids has been developed using organic nitroxyl and NOx cocatalysts. KetoABNO (9-azabicyclo[3.3.1]nonan-3-one N-oxyl) and NaNO2 were identified as the optimal nitroxyl and NOx sources, respectively. The mildness of the reaction conditions enables sequential asymmetric hydroformylation of alkenes/aerobic aldehyde oxidation to access α-chiral carboxylic acids without racemization. The scope, utility, and limitations of the oxidation method are further evaluated with a series of achiral aldehydes bearing diverse functional groups.

  19. CH4 and N2O from mechanically turned windrow and vermicomposting systems following in-vessel pre-treatment.

    PubMed

    Hobson, A M; Frederickson, J; Dise, N B

    2005-01-01

    Methane (CH4) and nitrous oxide (N2O) are included in the six greenhouse gases listed in the Kyoto protocol that require emission reduction. To meet reduced emission targets, governments need to first quantify their contribution to global warming. Composting has been identified as an important source of CH4 and N2O. With increasing divergence of biodegradable waste from landfill into the composting sector, it is important to quantify emissions of CH4 and N2O from all forms of composting and from all stages. This study focuses on the final phase of a two stage composting process and compares the generation and emission of CH4 and N2O associated with two differing composting methods: mechanically turned windrow and vermicomposting. The first stage was in-vessel pre-treatment. Source-segregated household waste was first pre-composted for seven days using an in-vessel system. The second stage of composting involved forming half of the pre-composted material into a windrow and applying half to vermicomposting beds. The duration of this stage was 85 days and CH4 and N2O emissions were monitored throughout for both systems. Waste samples were regularly subjected to respirometry analysis and both processes were found to be equally effective at stabilising the organic matter content. The mechanically turned windrow system was characterised by emissions of CH4 and to a much lesser extent N2O. However, the vermicomposting system emitted significant fluxes of N2O and only trace amounts of CH4. In-vessel pre-treatment removed considerable amounts of available C and N prior to the second stage of composting. This had the effect of reducing emissions of CH4 and N2O from the second stage compared to emissions from fresh waste found in other studies. The characteristics of each of the two composting processes are discussed in detail. Very different mechanisms for emission of CH4 and N2O are proposed for each system. For the windrow system, development of anaerobic zones were

  20. GENERAL CH4 OXIDATION MODEL AND COMPARISONS OF CH4 OXIDATION IN NATURAL AND MANAGED SYSTEMS. (R824993)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  1. Aerobic addition of secondary phosphine oxides to vinyl sulfides: a shortcut to 1-hydroxy-2-(organosulfanyl)ethyl(diorganyl)phosphine oxides

    PubMed Central

    Malysheva, Svetlana F; Artem’ev, Alexander V; Gusarova, Nina K; Belogorlova, Nataliya A; Albanov, Alexander I; Liu, C W

    2015-01-01

    Summary Secondary phosphine oxides react with vinyl sulfides (both alkyl- and aryl-substituted sulfides) under aerobic and solvent-free conditions (80 °C, air, 7–30 h) to afford 1-hydroxy-2-(organosulfanyl)ethyl(diorganyl)phosphine oxides in 70–93% yields. PMID:26664618

  2. Ammonia-oxidizing archaea use the most energy-efficient aerobic pathway for CO2 fixation.

    PubMed

    Könneke, Martin; Schubert, Daniel M; Brown, Philip C; Hügler, Michael; Standfest, Sonja; Schwander, Thomas; Schada von Borzyskowski, Lennart; Erb, Tobias J; Stahl, David A; Berg, Ivan A

    2014-06-01

    Archaea of the phylum Thaumarchaeota are among the most abundant prokaryotes on Earth and are widely distributed in marine, terrestrial, and geothermal environments. All studied Thaumarchaeota couple the oxidation of ammonia at extremely low concentrations with carbon fixation. As the predominant nitrifiers in the ocean and in various soils, ammonia-oxidizing archaea contribute significantly to the global nitrogen and carbon cycles. Here we provide biochemical evidence that thaumarchaeal ammonia oxidizers assimilate inorganic carbon via a modified version of the autotrophic hydroxypropionate/hydroxybutyrate cycle of Crenarchaeota that is far more energy efficient than any other aerobic autotrophic pathway. The identified genes of this cycle were found in the genomes of all sequenced representatives of the phylum Thaumarchaeota, indicating the environmental significance of this efficient CO2-fixation pathway. Comparative phylogenetic analysis of proteins of this pathway suggests that the hydroxypropionate/hydroxybutyrate cycle emerged independently in Crenarchaeota and Thaumarchaeota, thus supporting the hypothesis of an early evolutionary separation of both archaeal phyla. We conclude that high efficiency of anabolism exemplified by this autotrophic cycle perfectly suits the lifestyle of ammonia-oxidizing archaea, which thrive at a constantly low energy supply, thus offering a biochemical explanation for their ecological success in nutrient-limited environments.

  3. Ammonia-oxidizing archaea use the most energy-efficient aerobic pathway for CO2 fixation.

    PubMed

    Könneke, Martin; Schubert, Daniel M; Brown, Philip C; Hügler, Michael; Standfest, Sonja; Schwander, Thomas; Schada von Borzyskowski, Lennart; Erb, Tobias J; Stahl, David A; Berg, Ivan A

    2014-06-01

    Archaea of the phylum Thaumarchaeota are among the most abundant prokaryotes on Earth and are widely distributed in marine, terrestrial, and geothermal environments. All studied Thaumarchaeota couple the oxidation of ammonia at extremely low concentrations with carbon fixation. As the predominant nitrifiers in the ocean and in various soils, ammonia-oxidizing archaea contribute significantly to the global nitrogen and carbon cycles. Here we provide biochemical evidence that thaumarchaeal ammonia oxidizers assimilate inorganic carbon via a modified version of the autotrophic hydroxypropionate/hydroxybutyrate cycle of Crenarchaeota that is far more energy efficient than any other aerobic autotrophic pathway. The identified genes of this cycle were found in the genomes of all sequenced representatives of the phylum Thaumarchaeota, indicating the environmental significance of this efficient CO2-fixation pathway. Comparative phylogenetic analysis of proteins of this pathway suggests that the hydroxypropionate/hydroxybutyrate cycle emerged independently in Crenarchaeota and Thaumarchaeota, thus supporting the hypothesis of an early evolutionary separation of both archaeal phyla. We conclude that high efficiency of anabolism exemplified by this autotrophic cycle perfectly suits the lifestyle of ammonia-oxidizing archaea, which thrive at a constantly low energy supply, thus offering a biochemical explanation for their ecological success in nutrient-limited environments. PMID:24843170

  4. Aerobic exercise improves oxidant-antioxidant balance in patients with rheumatoid arthritis.

    PubMed

    Tuna, Zeynep; Duger, Tulin; Atalay-Guzel, Nevin; Aral, Arzu; Basturk, Bilkay; Haznedaroglu, Seminur; Goker, Berna

    2015-04-01

    [Purpose] Although oxidative stress is known to be present in rheumatoid arthritis (RA), the effects of exercise on oxidative parameters are unknown. The aim of this study was to investigate the effects of acute aerobic exercise on serum oxidant and antioxidant levels in patients with RA. [Subjects and Methods] Sixteen patients with RA and 10 age-matched healthy volunteers participated in this study. All participants wore polar telemeters and walked on a treadmill for 30 minutes at a speed eliciting 60-75% of maximal heart rates. Blood samples were obtained before, immediately and 24 hours after exercise and malondialdehyde (MDA) and total sulfhydrile group (RSH) levels were measured. [Results] Both groups had similar heart rates during the test but the treadmill speed of the RA patients was significantly lower than that of the healthy volunteers. Serum MDA levels were lower than in both groups immediately after exercise, with greater decrements in the RA patients than controls. MDA levels returned to baseline 24 hours after the exercise only in the controls; they remained low in the RA patients. There was a slight increase in serum RSH levels after exercise compared to baseline in both groups. [Conclusion] Moderate intensity treadmill exercise did not have any adverse effect on the oxidant-antioxidant balance. The results suggest that such an exercise may be safely added to the rehabilitation program of RA for additional antioxidant effects. Morever, this antioxidant environment is maintained longer in RA patients.

  5. Metabolic reprogramming during neuronal differentiation from aerobic glycolysis to neuronal oxidative phosphorylation

    PubMed Central

    Zheng, Xinde; Boyer, Leah; Jin, Mingji; Mertens, Jerome; Kim, Yongsung; Ma, Li; Ma, Li; Hamm, Michael; Gage, Fred H; Hunter, Tony

    2016-01-01

    How metabolism is reprogrammed during neuronal differentiation is unknown. We found that the loss of hexokinase (HK2) and lactate dehydrogenase (LDHA) expression, together with a switch in pyruvate kinase gene splicing from PKM2 to PKM1, marks the transition from aerobic glycolysis in neural progenitor cells (NPC) to neuronal oxidative phosphorylation. The protein levels of c-MYC and N-MYC, transcriptional activators of the HK2 and LDHA genes, decrease dramatically. Constitutive expression of HK2 and LDHA during differentiation leads to neuronal cell death, indicating that the shut-off aerobic glycolysis is essential for neuronal survival. The metabolic regulators PGC-1α and ERRγ increase significantly upon neuronal differentiation to sustain the transcription of metabolic and mitochondrial genes, whose levels are unchanged compared to NPCs, revealing distinct transcriptional regulation of metabolic genes in the proliferation and post-mitotic differentiation states. Mitochondrial mass increases proportionally with neuronal mass growth, indicating an unknown mechanism linking mitochondrial biogenesis to cell size. DOI: http://dx.doi.org/10.7554/eLife.13374.001 PMID:27282387

  6. Severe acute oxidant exposure: morphological damage and aerobic metabolism in the lung

    SciTech Connect

    Montgomery, M.R.; Teuscher, F.; LaSota, I.; Niewoehner, D.E.

    1986-09-01

    Groups of male rats were exposed to acute doses of oxygen, ozone, or paraquat which produced equivalent mortality (25-30%) over a 28 day post-exposure period. Quantitative evaluation of morphological changes indicated the primary response to be edema and inflammation with only slight fibrosis being apparent by the end of the observation period. Aerobic pulmonary metabolism was inhibited in lungs from animals exposed to oxygen and ozone as evidenced by decreased oxygen consumption; however, this was transient and O/sub 2/ consumption returned to normal within 24 hours after removal from the exposure chamber. Conversely, treatment with paraquat caused an immediate, transient stimulation of O/sub 2/ consumption. Glucose metabolism was unaltered by the gas exposures and, as previously reported, was initially stimulated by paraquat treatment. In vitro, only paraquat altered both O/sub 2/ consumption and glucose metabolism when added to lung slice preparations; ozone had no effect. Oxygen did not alter O/sub 2/ consumption but caused a slight biphasic response in glucose metabolism. Aerobic metabolism is relatively unchanged by these doses of oxygen and ozone which result in the death of 25-30% of all treated animals. Even though paraquat produces similar morphologic changes, it may represent a more severe metabolic insult than ''equivalent'' doses of oxygen or ozone. Also, if interstitial pulmonary fibrosis is a desired result of experimental exposure, rats may not be a suitable model for oxidant induced lung injury.

  7. Impact of aerobic and anaerobic exercise training on oxidative stress and antioxidant defense in athletes.

    PubMed

    Park, Song-Young; Kwak, Yi-Sub

    2016-04-01

    Exercise mediates an excessive free radical production leading to oxidative stress (OS). The body has natural antioxidant systems that help decrease OS, and these systems may be enhanced with exercise training. However, only a few studies have investigated the differences in resting OS and antioxidant capacity (AOC) between aerobically trained athletes (ET), anaerobically trained athletes (RT), and untrained individuals (UT). Therefore, this study sought to investigate the resting and postexercise OS and AOC in ET, RT, and UT. Sixty healthy young males (26.6±0.8 yr) participated in this study. Subjects were divided into three groups, ET, RT, and UT by distinct training background. Resting plasma malondialdehyde (MDA) and protein carbonyls (PC) were not significantly different in ET, RT, and UT. However, MDA and PC were significantly increased following a graded exercise test (GXT) in UT but not in ET and RT. Resting total antioxidant capacity (TAC) levels and TAC were not different in ET, RT, and UT. Interestingly, TAC levels significantly decreased after the GXT in all groups. Additionally, UT showed lower post-exercise TAC levels compared to ET and RT. These results showed that ET, RT, and UT have similar OS and AOC at rest. However, both ET and RT have greater AOC against exercise mediated OS compared to UT. These findings may explain, at least in part, why both aerobic and anaerobic types of exercise training improve redox balance. However, it appears there is no specific exercise type effect in terms of redox balance.

  8. Impact of aerobic and anaerobic exercise training on oxidative stress and antioxidant defense in athletes.

    PubMed

    Park, Song-Young; Kwak, Yi-Sub

    2016-04-01

    Exercise mediates an excessive free radical production leading to oxidative stress (OS). The body has natural antioxidant systems that help decrease OS, and these systems may be enhanced with exercise training. However, only a few studies have investigated the differences in resting OS and antioxidant capacity (AOC) between aerobically trained athletes (ET), anaerobically trained athletes (RT), and untrained individuals (UT). Therefore, this study sought to investigate the resting and postexercise OS and AOC in ET, RT, and UT. Sixty healthy young males (26.6±0.8 yr) participated in this study. Subjects were divided into three groups, ET, RT, and UT by distinct training background. Resting plasma malondialdehyde (MDA) and protein carbonyls (PC) were not significantly different in ET, RT, and UT. However, MDA and PC were significantly increased following a graded exercise test (GXT) in UT but not in ET and RT. Resting total antioxidant capacity (TAC) levels and TAC were not different in ET, RT, and UT. Interestingly, TAC levels significantly decreased after the GXT in all groups. Additionally, UT showed lower post-exercise TAC levels compared to ET and RT. These results showed that ET, RT, and UT have similar OS and AOC at rest. However, both ET and RT have greater AOC against exercise mediated OS compared to UT. These findings may explain, at least in part, why both aerobic and anaerobic types of exercise training improve redox balance. However, it appears there is no specific exercise type effect in terms of redox balance. PMID:27162773

  9. Soil CO2 constrain and distinction of root respiration and microbial activity by soil CO2 and CH4 profile

    NASA Astrophysics Data System (ADS)

    Ji, S.; Breecker, D.; Nie, J.

    2015-12-01

    Profiles of soil pore space CO2 and CH4 concentrations are rarely reported, especially from the same soils, yet are important for a number of applications. First, quantifying the component of respired CO2 in the soil pore spaces improves paleosol-based paleo-atmospheric CO2 estimates. Second, profiles can be used to estimate the average depth of biological activity (e.g. respiration and CH4 oxidation). Third, CH4 profiles, by identifying microbial activity, may help distinguish root/rhizosphere respiration from microbial decomposition. Here, we report soil CO2 and CH4 profiles measured at the Semi-Arid Climate Observatory and Laboratory (SACOL) on the Chinese Loess Plateau (CLP) at Lanzhou University, Gansu, China. Soil parent material on the site is mainly Quaternary aeolian loess and classifies as an Entisol. Soil respired CO2 (S(z) = soil CO2 - atmospheric CO2) is the most uncertain variable required to reconstruct ancient atmospheric CO2 concentrations from paleosol carbonates. Our direct soil pore space CO2 measurements show that S(z) values varied from ~100ppmV during the spring to ~2200ppmV during the summer. S(z) average 390 ± 30ppmV during May before the summer monsoon begins when soil temperature is increasing, soil water content is at a minimum and pedogenic carbonate may be forming. This value lies in the range of S(z) values previously estimated for surface Inceptisols (300 ± 100ppmV, Breecker 2013) and is lower than Pleistocene CLP paleosols (Da et al.,2015) in similar parent material. Our direct measurements of soil pore space CO2 thus support these previous independent S(z) estimates. We also investigate the average depth of CH4 oxidation and soil respiration, which range from 3-10cm and at least 20cm, respectively, using the shapes of soil gas profiles. Fitting observed soil CO2 and CH4 profiles with a production-diffusion model show that the average depth of CH4 oxidation was always at least 10 cm shallower than the average depth of respiration

  10. Soil microorganisms as controllers of atmospheric trace gases (H2, CO, CH4, OCS, N2O, and NO).

    PubMed Central

    Conrad, R

    1996-01-01

    Production and consumption processes in soils contribute to the global cycles of many trace gases (CH4, CO, OCS, H2, N2O, and NO) that are relevant for atmospheric chemistry and climate. Soil microbial processes contribute substantially to the budgets of atmospheric trace gases. The flux of trace gases between soil and atmosphere is usually the result of simultaneously operating production and consumption processes in soil: The relevant processes are not yet proven with absolute certainty, but the following are likely for trace gas consumption: H2 oxidation by abiontic soil enzymes; CO cooxidation by the ammonium monooxygenase of nitrifying bacteria; CH4 oxidation by unknown methanotrophic bacteria that utilize CH4 for growth; OCS hydrolysis by bacteria containing carbonic anhydrase; N2O reduction to N2 by denitrifying bacteria; NO consumption by either reduction to N2O in denitrifiers or oxidation to nitrate in heterotrophic bacteria. Wetland soils, in contrast to upland soils are generally anoxic and thus support the production of trace gases (H2, CO, CH4, N2O, and NO) by anaerobic bacteria such as fermenters, methanogens, acetogens, sulfate reducers, and denitrifiers. Methane is the dominant gaseous product of anaerobic degradation of organic matter and is released into the atmosphere, whereas the other trace gases are only intermediates, which are mostly cycled within the anoxic habitat. A significant percentage of the produced methane is oxidized by methanotrophic bacteria at anoxic-oxic interfaces such as the soil surface and the root surface of aquatic plants that serve as conduits for O2 transport into and CH4 transport out of the wetland soils. The dominant production processes in upland soils are different from those in wetland soils and include H2 production by biological N2 fixation, CO production by chemical decomposition of soil organic matter, and NO and N2O production by nitrification and denitrification. The processes responsible for CH4 production

  11. Soil microorganisms as controllers of atmospheric trace gases (H2, CO, CH4, OCS, N2O, and NO).

    PubMed

    Conrad, R

    1996-12-01

    Production and consumption processes in soils contribute to the global cycles of many trace gases (CH4, CO, OCS, H2, N2O, and NO) that are relevant for atmospheric chemistry and climate. Soil microbial processes contribute substantially to the budgets of atmospheric trace gases. The flux of trace gases between soil and atmosphere is usually the result of simultaneously operating production and consumption processes in soil: The relevant processes are not yet proven with absolute certainty, but the following are likely for trace gas consumption: H2 oxidation by abiontic soil enzymes; CO cooxidation by the ammonium monooxygenase of nitrifying bacteria; CH4 oxidation by unknown methanotrophic bacteria that utilize CH4 for growth; OCS hydrolysis by bacteria containing carbonic anhydrase; N2O reduction to N2 by denitrifying bacteria; NO consumption by either reduction to N2O in denitrifiers or oxidation to nitrate in heterotrophic bacteria. Wetland soils, in contrast to upland soils are generally anoxic and thus support the production of trace gases (H2, CO, CH4, N2O, and NO) by anaerobic bacteria such as fermenters, methanogens, acetogens, sulfate reducers, and denitrifiers. Methane is the dominant gaseous product of anaerobic degradation of organic matter and is released into the atmosphere, whereas the other trace gases are only intermediates, which are mostly cycled within the anoxic habitat. A significant percentage of the produced methane is oxidized by methanotrophic bacteria at anoxic-oxic interfaces such as the soil surface and the root surface of aquatic plants that serve as conduits for O2 transport into and CH4 transport out of the wetland soils. The dominant production processes in upland soils are different from those in wetland soils and include H2 production by biological N2 fixation, CO production by chemical decomposition of soil organic matter, and NO and N2O production by nitrification and denitrification. The processes responsible for CH4 production

  12. Aerobic and Anaerobic Thiosulfate Oxidation by a Cold-Adapted, Subglacial Chemoautotroph

    PubMed Central

    Harrold, Zoë R.; Skidmore, Mark L.; Hamilton, Trinity L.; Desch, Libby; Amada, Kirina; van Gelder, Will; Glover, Kevin; Roden, Eric E.

    2015-01-01

    Geochemical data indicate that protons released during pyrite (FeS2) oxidation are important drivers of mineral weathering in oxic and anoxic zones of many aquatic environments, including those beneath glaciers. Oxidation of FeS2 under oxic, circumneutral conditions proceeds through the metastable intermediate thiosulfate (S2O32−), which represents an electron donor capable of supporting microbial metabolism. Subglacial meltwaters sampled from Robertson Glacier (RG), Canada, over a seasonal melt cycle revealed concentrations of S2O32− that were typically below the limit of detection, despite the presence of available pyrite and concentrations of the FeS2 oxidation product sulfate (SO42−) several orders of magnitude higher than those of S2O32−. Here we report on the physiological and genomic characterization of the chemolithoautotrophic facultative anaerobe Thiobacillus sp. strain RG5 isolated from the subglacial environment at RG. The RG5 genome encodes genes involved with pathways for the complete oxidation of S2O32−, CO2 fixation, and aerobic and anaerobic respiration with nitrite or nitrate. Growth experiments indicated that the energy required to synthesize a cell under oxygen- or nitrate-reducing conditions with S2O32− as the electron donor was lower at 5.1°C than 14.4°C, indicating that this organism is cold adapted. RG sediment-associated transcripts of soxB, which encodes a component of the S2O32−-oxidizing complex, were closely affiliated with soxB from RG5. Collectively, these results suggest an active sulfur cycle in the subglacial environment at RG mediated in part by populations closely affiliated with RG5. The consumption of S2O32− by RG5-like populations may accelerate abiotic FeS2 oxidation, thereby enhancing mineral weathering in the subglacial environment. PMID:26712544

  13. Aerobic and Anaerobic Thiosulfate Oxidation by a Cold-Adapted, Subglacial Chemoautotroph.

    PubMed

    Harrold, Zoë R; Skidmore, Mark L; Hamilton, Trinity L; Desch, Libby; Amada, Kirina; van Gelder, Will; Glover, Kevin; Roden, Eric E; Boyd, Eric S

    2016-03-01

    Geochemical data indicate that protons released during pyrite (FeS2) oxidation are important drivers of mineral weathering in oxic and anoxic zones of many aquatic environments, including those beneath glaciers. Oxidation of FeS2 under oxic, circumneutral conditions proceeds through the metastable intermediate thiosulfate (S2O3 (2-)), which represents an electron donor capable of supporting microbial metabolism. Subglacial meltwaters sampled from Robertson Glacier (RG), Canada, over a seasonal melt cycle revealed concentrations of S2O3 (2-) that were typically below the limit of detection, despite the presence of available pyrite and concentrations of the FeS2 oxidation product sulfate (SO4 (2-)) several orders of magnitude higher than those of S2O3 (2-). Here we report on the physiological and genomic characterization of the chemolithoautotrophic facultative anaerobe Thiobacillus sp. strain RG5 isolated from the subglacial environment at RG. The RG5 genome encodes genes involved with pathways for the complete oxidation of S2O3 (2-), CO2 fixation, and aerobic and anaerobic respiration with nitrite or nitrate. Growth experiments indicated that the energy required to synthesize a cell under oxygen- or nitrate-reducing conditions with S2O3 (2-) as the electron donor was lower at 5.1°C than 14.4°C, indicating that this organism is cold adapted. RG sediment-associated transcripts of soxB, which encodes a component of the S2O3 (2-)-oxidizing complex, were closely affiliated with soxB from RG5. Collectively, these results suggest an active sulfur cycle in the subglacial environment at RG mediated in part by populations closely affiliated with RG5. The consumption of S2O3 (2-) by RG5-like populations may accelerate abiotic FeS2 oxidation, thereby enhancing mineral weathering in the subglacial environment. PMID:26712544

  14. Aerobic and Anaerobic Thiosulfate Oxidation by a Cold-Adapted, Subglacial Chemoautotroph.

    PubMed

    Harrold, Zoë R; Skidmore, Mark L; Hamilton, Trinity L; Desch, Libby; Amada, Kirina; van Gelder, Will; Glover, Kevin; Roden, Eric E; Boyd, Eric S

    2015-12-28

    Geochemical data indicate that protons released during pyrite (FeS2) oxidation are important drivers of mineral weathering in oxic and anoxic zones of many aquatic environments, including those beneath glaciers. Oxidation of FeS2 under oxic, circumneutral conditions proceeds through the metastable intermediate thiosulfate (S2O3 (2-)), which represents an electron donor capable of supporting microbial metabolism. Subglacial meltwaters sampled from Robertson Glacier (RG), Canada, over a seasonal melt cycle revealed concentrations of S2O3 (2-) that were typically below the limit of detection, despite the presence of available pyrite and concentrations of the FeS2 oxidation product sulfate (SO4 (2-)) several orders of magnitude higher than those of S2O3 (2-). Here we report on the physiological and genomic characterization of the chemolithoautotrophic facultative anaerobe Thiobacillus sp. strain RG5 isolated from the subglacial environment at RG. The RG5 genome encodes genes involved with pathways for the complete oxidation of S2O3 (2-), CO2 fixation, and aerobic and anaerobic respiration with nitrite or nitrate. Growth experiments indicated that the energy required to synthesize a cell under oxygen- or nitrate-reducing conditions with S2O3 (2-) as the electron donor was lower at 5.1°C than 14.4°C, indicating that this organism is cold adapted. RG sediment-associated transcripts of soxB, which encodes a component of the S2O3 (2-)-oxidizing complex, were closely affiliated with soxB from RG5. Collectively, these results suggest an active sulfur cycle in the subglacial environment at RG mediated in part by populations closely affiliated with RG5. The consumption of S2O3 (2-) by RG5-like populations may accelerate abiotic FeS2 oxidation, thereby enhancing mineral weathering in the subglacial environment.

  15. The possible role of heterogeneous aerosol processes in the chemistry of CH4 and CO in the troposphere

    NASA Technical Reports Server (NTRS)

    Luther, C. J.; Peters, L. K.

    1982-01-01

    The effect of particle-gas interactions on the CH4 to CO oxidation sequence in the troposphere is investigated by developing rate expressions for the heterogeneous removal of gaseous species based on the absorption of the species by aerosol particles. The results of this analysis indicate that the homogeneous models describe the tropospheric chemistry of CO and CH4 more accurately than heterogeneous models, which suggests that heterogeneous processes may not be significant in this sequence of chemical reactions. Estimates of the CO and CH4 emission rates are not found to provide a conclusive basis on which to compare the significance of the homogeneous and heterogeneous processes. In addition, the time period during which an aerosol particle is effective in removing a trace gaseous species from the troposphere is determined to vary according to the tropospheric concentration and solubility of the particular gaseous species.

  16. Carbonate control of H2 and CH4 production in serpentinization systems at elevated P-Ts

    USGS Publications Warehouse

    Jones, L. Camille; Rosenbauer, Robert; Goldsmith, Jonas I.; Oze, Christopher

    2010-01-01

    Serpentinization of forsteritic olivine results in the inorganic synthesis of molecular hydrogen (H2) in ultramafic hydrothermal systems (e.g., mid-ocean ridge and forearc environments). Inorganic carbon in those hydrothermal systems may react with H2 to produce methane (CH4) and other hydrocarbons or react with dissolved metal ions to form carbonate minerals. Here, we report serpentinization experiments at 200°C and 300 bar demonstrating Fe2+ being incorporated into carbonates more rapidly than Fe2+ oxidation (and concomitant H2 formation) leading to diminished yields of H2 and H2-dependent CH4. In addition, carbonate formation is temporally fast in carbonate oversaturated fluids. Our results demonstrate that carbonate chemistry ultimately modulates the abiotic synthesis of both H2 and CH4 in hydrothermal ultramafic systems and that ultramafic systems present great potential for CO2-mineral sequestration.

  17. Soluble porous coordination polymers by mechanochemistry: from metal-containing films/membranes to active catalysts for aerobic oxidation.

    PubMed

    Zhang, Pengfei; Li, Haiying; Veith, Gabriel M; Dai, Sheng

    2015-01-14

    Soluble porous coordination polymers from mechanochemical synthesis are presented through a coordination polymerization between highly contorted, rigid tetraphenol and a broad variety of transition metal ions. These polymers can be easily cast as metal-containing films or freestanding membranes. Importantly, as-made coordination polymers are highly active and stable in the aerobic oxidation of allylic C-H bonds. PMID:25389070

  18. Cu(II)-catalyzed esterification reaction via aerobic oxidative cleavage of C(CO)-C(alkyl) bonds.

    PubMed

    Ma, Ran; He, Liang-Nian; Liu, An-Hua; Song, Qing-Wen

    2016-02-01

    A novel Cu(II)-catalyzed aerobic oxidative esterification of simple ketones for the synthesis of esters has been developed with wide functional group tolerance. This process is assumed to go through a tandem sequence consisting of α-oxygenation/esterification/nucleophilic addition/C-C bond cleavage and carbon dioxide is released as the only byproduct.

  19. A template-free solvent-mediated synthesis of high surface area boron nitride nanosheets for aerobic oxidative desulfurization.

    PubMed

    Wu, Peiwen; Zhu, Wenshuai; Chao, Yanhong; Zhang, Jinshui; Zhang, Pengfei; Zhu, Huiyuan; Li, Changfeng; Chen, Zhigang; Li, Huaming; Dai, Sheng

    2016-01-01

    Hexagonal boron nitride nanosheets (h-BNNs) with rather high specific surface area (SSA) are important two-dimensional layer-structured materials. Here, a solvent-mediated synthesis of h-BNNs revealed a template-free lattice plane control strategy that induced high SSA nanoporous structured h-BNNs with outstanding aerobic oxidative desulfurization performance. PMID:26502800

  20. Oxidative stress in response to aerobic and anaerobic power testing: influence of exercise training and carnitine supplementation.

    PubMed

    Bloomer, Richard J; Smith, Webb A

    2009-01-01

    The purpose of this study is to compare the oxidative stress response to aerobic and anaerobic power testing, and to determine the impact of exercise training with or without glycine propionyl-L-carnitine (GPLC) in attenuating the oxidative stress response. Thirty-two subjects were assigned (double blind) to placebo, GPLC-1 (1g PLC/d), GPLC-3 (3g PLC/d) for 8 weeks, plus aerobic exercise. Aerobic (graded exercise test: GXT) and anaerobic (Wingate cycle) power tests were performed before and following the intervention. Blood was taken before and immediately following exercise tests and analyzed for malondialdehyde (MDA), hydrogen peroxide (H2O2), and xanthine oxidase activity (XO). No interaction effects were noted. MDA was minimally effected by exercise but lower at rest for both GPLC groups following the intervention (p = 0.044). A time main effect was noted for H2O2 (p = 0.05) and XO (p = 0.003), with values increasing from pre- to postexercise. Both aerobic and anaerobic power testing increase oxidative stress to a similar extent. Exercise training plus GPLC can decrease resting MDA, but it has little impact on exercise-induced oxidative stress biomarkers.

  1. The effect of aerobic exercise on hepatotoxicity induced by intratracheal instillation of iron oxide nanoparticles in Wistar rats.

    PubMed

    Vasili, Azadeh; Sharifi, Gholamreza; Faramarzi, Mohammad; Noori, Ali; Yazdanshenas, Shora

    2016-01-01

    Iron oxide nanoparticles (IONPs) can cause significant health problems due to their unique physicochemical properties and environmental characteristics. They are found as ultrafine particles in ambient air. After inhalation, these particles move from the lung to phagocytosis tissues, especially the liver. The aim of present study was to investigate the effect of concurrent aerobic exercise and IONPs on liver enzymes and histological hepatic appearance. 48 rats were divided into six groups: experimental 1 (aerobic exercise), experimental 2 (nanoparticle, anesthesia), experimental 3 (aerobic exercise, nanoparticles, anesthesia), placebo 4 (distilled water, anesthesia), placebo 5 (aerobic exercise, anesthesia), and control group. In groups 2 and 3, 40 mg/kg/b.w. of IONPs was injected via intratracheal installation every other day for 14 days. Groups 1, 3, and 5 [corrected] run on treadmill for 30 minutes with the intensity of 35-40% VO2max (maximal oxygen consumption) every day. ALT was increased in group 1 but decreased in groups 2 and 3. AST was not significant in any of the groups, while ALP was reduced significantly in groups 2 and 3 (p < 0.05). Histological examination of the liver showed that, in groups 2 and 3, hepatic cells were damaged and also the congestion, inflammation, mononuclear cell infiltration, and ballooning degeneration were occurred. Tissue injuries in group 3 were less than those of group 2. These findings indicated that hepatotoxicity was caused by iron oxide nanoparticles; however, low-intensity aerobic exercise could decrease the damage somewhat. PMID:26492071

  2. Oxidation of aquatic pollutants by ferrous-oxalate complexes under dark aerobic conditions.

    PubMed

    Lee, Jaesang; Kim, Jungwon; Choi, Wonyong

    2014-06-15

    This study evaluates the ability of Fe(II)-oxalate complexes for the generation of OH through oxygen reduction and the oxidative degradation of aquatic pollutants under dark aerobic conditions (i.e., with oxygen but without light). The degradation of 4-chlorophenol (4-CP) was rapid in the mixture of Fe(2+) and oxalate prepared using ultrapure water, but was absent without either Fe(2+) or oxalate. The formation of Fe(II)-oxalate complexes enables two-electron reduction of oxygen to generate H2O2 and subsequent production of OH. The significant inhibition of 4-CP degradation in the presence of H2O2 and OH scavenger confirms such mechanisms. The degradation experiments with varying [Fe(2+)], [oxalate], and initial pH demonstrated that the degradation rate depends on [Fe(II)(Ox)2(2-)], but the degree of degradation is primarily determined by [Fe(II)(Ox)2(2-)]+[Fe(II)(Ox)(0)]. Efficient degradation of diverse aquatic pollutants, especially phenolic pollutants, was observed in the Fe(II)-oxalate complexes system, wherein the oxidation efficacy was primarily correlated with the reaction rate constant between pollutant and OH. The effect of various organic ligands (oxalate, citrate, EDTA, malonate, and acetate) on the degradation kinetics of 4-CP was investigated. The highest efficiency of oxalate for the oxidative degradation is attributed to its high capability to enhance the reducing power and low reactivity with OH.

  3. Microsensor Measurements of Sulfate Reduction and Sulfide Oxidation in Compact Microbial Communities of Aerobic Biofilms

    PubMed Central

    Kühl, Michael; Jørgensen, Bo Barker

    1992-01-01

    The microzonation of O2 respiration, H2S oxidation, and SO42- reduction in aerobic trickling-filter biofilms was studied by measuring concentration profiles at high spatial resolution (25 to 100 μm) with microsensors for O2, S2-, and pH. Specific reaction rates were calculated from measured concentration profiles by using a simple one-dimensional diffusion reaction model. The importance of electron acceptor and electron donor availability for the microzonation of respiratory processes and their reaction rates was investigated. Oxygen respiration was found in the upper 0.2 to 0.4 mm of the biofilm, whereas sulfate reduction occurred in deeper, anoxic parts of the biofilm. Sulfate reduction accounted for up to 50% of the total mineralization of organic carbon in the biofilms. All H2S produced from sulfate reduction was reoxidized by O2 in a narrow reaction zone, and no H2S escaped to the overlying water. Turnover times of H2S and O2 in the reaction zone were only a few seconds owing to rapid bacterial H2S oxidation. Anaerobic H2S oxidation with NO3- could be induced by addition of nitrate to the medium. Total sulfate reduction rates increased when the availability of SO42- or organic substrate increased as a result of deepening of the sulfate reduction zone or an increase in the sulfate reduction intensity, respectively. PMID:16348687

  4. Oxidative stability of pork emulsion containing tomato products and pink guava pulp during refrigerated aerobic storage.

    PubMed

    Joseph, Serlene; Chatli, Manish K; Biswas, Ashim K; Sahoo, Jhari

    2014-11-01

    Lipid oxidation-induced quality problems can be minimized with the use of natural antioxidants. Antioxidant potential of tomato puree (10 %; T-1), tomato pulp (12.5 %; T-2), lyophilized tomato peel (6 %; T-3), and pink guava pulp (10 %; T-4) was evaluated in raw pork emulsion during refrigerated storage for 9 days under aerobic packaging. The lycopene and β-carotene content varied in pork emulsion as T-3 > T-1 > T-2 > T-4 and decreased (P < 0.05) during storage. The surface redness (a* value) increased (P < 0.05) with the incorporation of tomato products and pink guava pulp. Furthermore, metmyoglobin formation and lipid oxidation were lower (P < 0.05) in tomato- and guava-treated emulsions than in control. Overall, incorporation of tomato products and pink guava pulp improved the visual colour and odour scores of raw pork emulsion. These results indicated that tomato products and guava pulp can be utilized as sources of natural antioxidants in raw pork products to minimize lipid oxidation, off-odour development, and surface discolouration. PMID:26396313

  5. Spatial variability of CH 4 and N 2 O fluxes in alpine ecosystems on the Qinghai-Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Kato, Tomomichi; Hirota, Mitsuru; Tang, Yanhong; Wada, Eitaro

    2011-10-01

    The intra- and inter-site spatial variability of methane (CH 4) and nitrous oxide (N 2O) fluxes were investigated in three alpine ecosystems at Haibei station on the Qinghai-Tibetan Plateau (QTP) in summer 2005 and in sixteen alpine ecosystems with various vegetations across the QTP in summer 2006, respectively. The magnitude of average CH 4 emissions from wetlands was at least 100 times larger than average CH 4 uptake by grassland, suggesting that the entire QTP is likely to be a source of methane in summertime because of a significant fractional area of wetlands (˜ 2.2%) on the plateau. Intra-site investigation, with sixteen chambers, revealed a significant negative relationship of CH 4 emissions with the C/N ratio of aboveground biomass and soil pH in the alpine wetland when all chambers were considered. Moreover, soil oxidation-reduction potential (ORP) had a remarkably strong influence on CH 4 emissions for nine chambers above the water level, resulting in a negative exponential relationship. For N 2O flux in alpine meadows, a negative relationship with both soil pH and livestock dung biomass was observed. Aboveground plant biomass and soil pH were important variables overall in wetlands. Inter-site investigation found positive and negative relationships between CH 4 flux and soil biomass to 5 cm depth in nine grassland and seven wetland sites, respectively. N 2O flux showed a moderately strong negative exponential relationship with the C/N ratio of surface soil in the grassland sites. In the wetlands, soil pH was negatively correlated with N 2O flux, perhaps due to both reduced N 2O release from suppressed nitrification and denitrification.

  6. Long-term data on δ13C-CH4 emissions elucidate drivers of CH4 metabolism in temperate and northern wetlands

    NASA Astrophysics Data System (ADS)

    McCalley, C. K.; Shorter, J. H.; Crill, P. M.; Hodgkins, S. B.; Chanton, J.; Saleska, S. R.; Varner, R. K.

    2015-12-01

    Methane flux from wetlands is both a critical component of the global CH4 budget, and highly sensitive to global climate change. Gaps in our knowledge of the biological processes that underlie CH4 fluxes from natural ecosystems limit our ability to scale flux estimates as well as predict future emissions. To address these gaps, we used quantum cascade laser technology linked to automated chambers to quantify the isotopic composition of CH4 fluxes from a high latitude (68° N) wetland underlain by discontinuous permafrost (Stordalen Mire, Sweden) and a temperate wetland (43° N) undergoing shrub encroachment (Sallie's Fen, NH). Changes in plant communities and hydrology during permafrost thaw result in both large increases in CH4 emissions as well as shifts in the CH4 production pathway, from hydrogenotrophic to increasingly acetoclastic mechanisms. In contrast, shrub encroachment that replaces sedge species in the temperate wetland reduces CH4 emissions, but doesn't effect δ 13C-CH4, with predominantly acetoclastic production occurring across plant communities. Multi-year data sets identify temperature and hydrologic variability as key contributors to annual and interannual patterns in δ 13C-CH4. Fully-thawed fens at Stordalen had consistent δ13C-CH4 across years, with an annual pattern suggestive of more hydrogenotrophic production early and late in the growing season. In contrast, intermediate-thaw sites, where the water table was more dynamic, had large variations in δ13C-CH4 across years. At Sallie's Fen, patterns in δ13C-CH4 suggest an abrupt shift in CH4 transport and metabolism at the beginning of the growing season and then more stable δ13C-CH4 during the growing season. Together these results provide insights into how plant communities and variable environmental conditions interact to influence the microbial metabolisms that drive CH4 production and consumption in diverse wetland ecosystems.

  7. A Bioinspired Catalytic Aerobic Oxidative C–H Functionalization of Primary Aliphatic Amines: Synthesis of 1,2-Disubstituted Benzimidazoles

    PubMed Central

    Nguyen, Khac Minh Huy; Largeron, Martine

    2015-01-01

    Aerobic oxidative C–H functionalization of primary aliphatic amines has been accomplished with a biomimetic cooperative catalytic system to furnish 1,2-disubstituted benzimidazoles that play an important role as drug discovery targets. This one-pot atom-economical multistep process, which proceeds under mild conditions, with ambient air and equimolar amounts of each coupling partner, constitutes a convenient environmentally friendly strategy to functionalize non-activated aliphatic amines that remain challenging substrates for non-enzymatic catalytic aerobic systems. PMID:26206475

  8. Comparison of static chambers to measure N2O and CH4 fluxes from soils

    NASA Astrophysics Data System (ADS)

    Pihlatie, M.

    2009-04-01

    Soil fluxes of the greenhouse gases (GHG) nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) are often measured by closed static chambers. During a chamber enclosure the concentration of the target gas changes in the headspace of the chamber. This changes the concentration difference between the soil and the atmosphere and hence also the fluxes from the soil. We hypothesize that the magnitude how much a chamber affects the gas fluxes from the soil is chamber design specific. In addition, the use of inappropriate flux calculation methods can further lead to uncertainties in the flux estimates. To test different types of static chambers for N2O and CH4 flux measurements a chamber calibration campaign was organized at Hyytiälä Forestry Field Station in Southern Finland during August-October 2008. The overall aims of the campaign were to quantitatively assess the uncertainties and errors related to static chamber measurements. Overall 17 different static chambers were tested for five different N2O and CH4 flux levels with three different soil conditions (different moisture and porosity) in the chamber calibration system described by Pumpanen et al. (2004). Preliminary results show that most of the static chambers either over- or underestimated the N2O and CH4 fluxes. This chamber specific over- or underestimation remained near constant with different flux levels. However, the deviation varied greatly with different soil porosities. Here we will show the main results of the measurement campaign and give preliminary suggestions for ideal chamber designs, gas sampling protocol and flux calculation methods for N2O and CH4 flux measurements. References: Pumpanen, J., Kolari, P., Ilvesniemi, H., Minkkinen, K., Vesala, T., Niinistö, S., Lohila, A., Larmola, T., Morero, M., Pihlatie, M., Janssens, I., Curiel Yuste, J., Grünzweig, J. M., Reth, S., Subke, J.-A., Savage, K., Kutsch, W., Østreng, G., Ziegler, W., Anthoni, P., Lindroth, A. & Hari, P. 2004. Comparison

  9. Nitrous oxide emission and nutrient removal in aerobic granular sludge sequencing batch reactors.

    PubMed

    Quan, Xiangchun; Zhang, Mingchuan; Lawlor, Peadar G; Yang, Zhifeng; Zhan, Xinmin

    2012-10-15

    Application of aerobic granular sludge into wastewater treatment is promising due to its excellent settling ability and high microbial concentrations. However, its spatial structure could induce incomplete denitrification, leading to generation of nitrous oxide (N(2)O) - a potent greenhouse gas. Under the temperature of 14 ± 4 °C, three identical laboratory-scale aerobic granular sludge sequencing batch reactors (SBRs) were established to treat synthetic wastewater simulating a mixture of liquid pig manure digestate and municipal wastewater at three aeration rates (0.2, 0.6 and 1.0 L air/min) and three COD:N ratios (1:0.22, 1:0.15 and 1:0.11). The studies show the proportions of N(2)O emission to the influent nitrogen loading rate at the aeration rates of 0.2, 0.6 and 1.0 L air/min were 8.2%, 6.1% and 3.8% at a COD:N ratio of 1:0.22; 7.0%, 5.1% and 3.5% at a COD:N ratio of 1:0.15; and 4.4%, 2.9% and 2.2% at a COD:N ratio of 1:0.11, respectively. With NO(2)(-) as the only nitrogen source in the liquid phase, the specific N(2)O generation rates via denitrification were 1.7, 1.6 and 1.3 μg N(2)O/(g SS· min) at the aeration rates of 0.2, 0.6 and 1.0 L air/min, respectively, which were 40.9%, 44.8%, 39.9% higher than those with NO(3)(-) as the only nitrogen source, respectively. N(2)O generation by aerobic granular sludge due to NH(4)(+)-N nitrification was not sensitive to the aeration rate, and the average specific N(2)O generation rate was 0.8 ± 0.02 μg N(2)O/(g SS· min).

  10. [Effects of elevated CO2 on forest soil CH4 consumption in Changbai Mountains].

    PubMed

    Guan, Jian; Zhang, Ying; Shi, Rong-Jiu; Li, Hui; Han, Si-Qin; Xu, Hui

    2012-02-01

    Elevated atmospheric CO2 concentration may affect the oxidation rate of methane (CH4 ) in forest soil. In this study, the effects of a 6-year exposure to elevated CO2 concentration (500 micromol x mol(-1)) on the soil microbial process of CH4 oxidation under Quercus mongolica seedlings were investigated with open top chamber (OTC), and specific 16S rRNA and pmoA gene fragment primers were adopted to analyze the diversity and abundance of soil methanotrophs. Comparing with that under ambient CO2 and open-air, the soil methane consumption under elevated atmospheric CO2 during growth season was reduced by 4% and 22%, respectively. The specific 16S rRNA PCR-DGGE analysis showed that under elevated CO2, the community structure of methane-oxidizing bacteria (MOB) changed, and the diversity index decreased. Elevated CO2 concentration had no distinct effects on the abundance of Type I MOB, but decreased the amount of Type II MOB significantly. The pmoA gene copy number under elevated CO2 concentration decreased by 15% and 46%, respectively, as compared with that under ambient CO2 and open-air. Our results suggested that elevated atmospheric CO2 decreased the abundance and activity of soil methanotrophs, and the main cause could be the increase of soil moisture content.

  11. Continuous Flow Aerobic Alcohol Oxidation Reactions Using a Heterogeneous Ru(OH)x/Al2O3 Catalyst

    PubMed Central

    2015-01-01

    Ru(OH)x/Al2O3 is among the more versatile catalysts for aerobic alcohol oxidation and dehydrogenation of nitrogen heterocycles. Here, we describe the translation of batch reactions to a continuous-flow method that enables high steady-state conversion and single-pass yields in the oxidation of benzylic alcohols and dehydrogenation of indoline. A dilute source of O2 (8% in N2) was used to ensure that the reaction mixture, which employs toluene as the solvent, is nonflammable throughout the process. A packed bed reactor was operated isothermally in an up-flow orientation, allowing good liquid–solid contact. Deactivation of the catalyst during the reaction was modeled empirically, and this model was used to achieve high conversion and yield during extended operation in the aerobic oxidation of 2-thiophene methanol (99+% continuous yield over 72 h). PMID:25620869

  12. Copper(I)/ABNO-catalyzed aerobic alcohol oxidation: alleviating steric and electronic constraints of Cu/TEMPO catalyst systems.

    PubMed

    Steves, Janelle E; Stahl, Shannon S

    2013-10-23

    Cu/TEMPO catalyst systems promote efficient aerobic oxidation of sterically unhindered primary alcohols and electronically activated substrates, but they show reduced reactivity with aliphatic and secondary alcohols. Here, we report a catalyst system, consisting of ((MeO)bpy)Cu(I)(OTf) and ABNO ((MeO)bpy = 4,4'-dimethoxy-2,2'-bipyridine; ABNO = 9-azabicyclo[3.3.1]nonane N-oxyl), that mediates aerobic oxidation of all classes of alcohols, including primary and secondary allylic, benzylic, and aliphatic alcohols with nearly equal efficiency. The catalyst exhibits broad functional group compatibility, and most reactions are complete within 1 h at room temperature using ambient air as the source of oxidant. PMID:24128057

  13. Environmental detection of octahaem cytochrome c hydroxylamine/hydrazine oxidoreductase genes of aerobic and anaerobic ammonium-oxidizing bacteria.

    PubMed

    Schmid, Markus C; Hooper, Alan B; Klotz, Martin G; Woebken, Dagmar; Lam, Phyllis; Kuypers, Marcel M M; Pommerening-Roeser, Andreas; Op den Camp, Huub J M; Jetten, Mike S M

    2008-11-01

    Bacterial aerobic ammonium oxidation and anaerobic ammonium oxidation (anammox) are important processes in the global nitrogen cycle. Key enzymes in both processes are the octahaem cytochrome c (OCC) proteins, hydroxylamine oxidoreductase (HAO) of aerobic ammonium-oxidizing bacteria (AOB), which catalyses the oxidation of hydroxylamine to nitrite, and hydrazine oxidoreductase (HZO) of anammox bacteria, which converts hydrazine to N(2). While the genomes of AOB encode up to three nearly identical copies of hao operons, genome analysis of Candidatus'Kuenenia stuttgartiensis' showed eight highly divergent octahaem protein coding regions as possible candidates for the HZO. Based on their phylogenetic relationship and biochemical characteristics, the sequences of these eight gene products grouped in three clusters. Degenerate primers were designed on the basis of available gene sequences with the aim to detect hao and hzo genes in various ecosystems. The hao primer pairs amplified gene fragments from 738 to 1172 bp and the hzo primer pairs amplified gene fragments from 289 to 876 bp in length, when tested on genomic DNA isolated from a variety of AOB and anammox bacteria. A selection of these primer pairs was also used successfully to amplify and analyse the hao and hzo genes in community DNA isolated from different ecosystems harbouring both AOB and anammox bacteria. We propose that OCC protein-encoding genes are suitable targets for molecular ecological studies on both aerobic and anaerobic ammonium-oxidizing bacteria.

  14. Doped graphene as a metal-free carbocatalyst for the selective aerobic oxidation of benzylic hydrocarbons, cyclooctane and styrene.

    PubMed

    Dhakshinamoorthy, Amarajothi; Primo, Ana; Concepcion, Patricia; Alvaro, Mercedes; Garcia, Hermenegildo

    2013-06-01

    Nitrogen (N)-, boron (B)-, and boron,nitrogen (B,N)-doped graphene (G) act as carbocatalysts, promoting the aerobic oxidation of the benzylic positions of aromatic hydrocarbons and cyclooctane to the corresponding alcohol/ketone mixture with more than 90 % selectivity. The most active material was the co-doped (B,N)G, which, in the absence of solvent and with a substrate/(B,N)G ratio of 200, achieved 50 % tetralin conversion in 24 h with a alcohol/ketone selectivity of 80 %. An FT-Raman spectroscopic study of a sample of (B,N)G heated at 100 °C in the presence of oxygen revealed new bands that disappeared upon evacuation and that have been attributed to hydroperoxide-like species formed on the G sheet based on the isotopic shift of the peak from 819 to 779 cm(-1) when (18)O2 was used as the oxidizing reagent. Furthermore, (B)G and (N)G exhibited high catalytic activity in the aerobic oxidation of styrene to benzaldehyde (BA) in 4 h. However, the product distribution changed over time and after 10 h a significant percentage of styrene oxide (SO) was observed under the same conditions. The use of doped G as catalyst appears to offer broad scope for the aerobic oxidation of benzylic compounds and styrene, for which low catalyst loading, mild reaction temperatures, and no additional solvents are required.

  15. Release of ANP and fat oxidation in overweight persons during aerobic exercise in water.

    PubMed

    Fenzl, M; Schnizer, W; Aebli, N; Schlegel, C; Villiger, B; Disch, A; Gredig, J; Zaugg, T; Krebs, J

    2013-09-01

    Exercise in water compared to land-based exercise (LE) results in a higher release of natriuretic peptides, which are involved in the regulation of exercise-induced adipose tissue lipolysis. The present study was performed to compare the release of atrial natriuretic peptide (ANP) and free fatty acids (FFA) during prolonged aerobic water-based exercise (WE) with the release after an identical LE. 14 untrained overweight subjects performed 2 steady state workload tests on the same ergometer in water and on land. Before and after exercise, venous blood samples were collected for measuring ANP, FFA, epinephrine, norepinephrine, insulin and glucose. The respiratory exchange ratio (RER) was determined for fat oxidation.The exercises resulted in a significant increase in ANP in LE (61%) and in WE (177%), and FFA increased about 3-fold in LE and WE with no significant difference between the groups. Epinephrine increased, while insulin decreased similarly in both groups. The RER values decreased during the exercises, but there was no significant difference between LE and WE. In conclusion, the higher ANP concentrations in WE had no additional effect on lipid mobilization, FFA release and fat oxidation. Moderate-intensity exercises in water offer no benefit regarding adipose tissue lipolysis in comparison to LE.

  16. Mapping pan-Arctic CH4 emissions using an adjoint method by integrating process-based wetland and lake biogeochemical models and atmospheric CH4 concentrations

    NASA Astrophysics Data System (ADS)

    Tan, Z.; Zhuang, Q.; Henze, D. K.; Frankenberg, C.; Dlugokencky, E. J.; Sweeney, C.; Turner, A. J.

    2015-12-01

    Understanding CH4 emissions from wetlands and lakes are critical for the estimation of Arctic carbon balance under fast warming climatic conditions. To date, our knowledge about these two CH4 sources is almost solely built on the upscaling of discontinuous measurements in limited areas to the whole region. Many studies indicated that, the controls of CH4 emissions from wetlands and lakes including soil moisture, lake morphology and substrate content and quality are notoriously heterogeneous, thus the accuracy of those simple estimates could be questionable. Here we apply a high spatial resolution atmospheric inverse model (nested-grid GEOS-Chem Adjoint) over the Arctic by integrating SCIAMACHY and NOAA/ESRL CH4 measurements to constrain the CH4 emissions estimated with process-based wetland and lake biogeochemical models. Our modeling experiments using different wetland CH4 emission schemes and satellite and surface measurements show that the total amount of CH4 emitted from the Arctic wetlands is well constrained, but the spatial distribution of CH4 emissions is sensitive to priors. For CH4 emissions from lakes, our high-resolution inversion shows that the models overestimate CH4 emissions in Alaskan costal lowlands and East Siberian lowlands. Our study also indicates that the precision and coverage of measurements need to be improved to achieve more accurate high-resolution estimates.

  17. 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

  18. Methanogenic Conversion of CO2 Into CH4

    SciTech Connect

    Stevens, S.H., Ferry, J.G., Schoell, M.

    2012-05-06

    This SBIR project evaluated the potential to remediate geologic CO2 sequestration sites into useful methane gas fields by application of methanogenic bacteria. Such methanogens are present in a wide variety of natural environments, converting CO2 into CH4 under natural conditions. We conclude that the process is generally feasible to apply within many of the proposed CO2 storage reservoir settings. However, extensive further basic R&D still is needed to define the precise species, environments, nutrient growth accelerants, and economics of the methanogenic process. Consequently, the study team does not recommend Phase III commercial application of the technology at this early phase.

  19. Dynamics of atmospheric-methane oxidation in glacier-forefield soils

    NASA Astrophysics Data System (ADS)

    Chiri, Eleonora; Nauer, Philipp A.; Rainer, Edda-Marie; Henneberger, Ruth; Zeyer, Josef; Schroth, Martin H.

    2015-04-01

    Mature upland soils are currently considered the sole terrestrial sink for atmospheric methane (CH4). But little is known about CH4 dynamics in young, developing soil ecosystems such as glacier forefields formed by progressive glacial retreat. Glacier forefields are situated on diverse bedrock types, exhibit a continuum of soil age (chronosequence), and are comprised of various geomorphological landforms, which may differ in physicochemical properties. These features may affect activity and community structure of aerobic methane-oxidizing bacteria (MOB) catalyzing atmospheric CH4 oxidation. Moreover, MOB activity and community structure may be affected by environmental parameters subject to seasonal variability such as soil temperature, water content, and nutrient availability. The aim of this study was to assess spatial and seasonal variability in atmospheric CH4 oxidation in glacier-forefield soils derived from siliceous and calcareous bedrock. Specifically, we quantified soil-atmosphere CH4 flux and CH4 oxidation activity using the soil-gas-profile method and static flux chambers in soils of different age and belonging to different landforms. In these soils MOB abundance and variation in community structure were assessed by targeting the functional gene pmoA using quantitative PCR, TRFLP-based cluster analysis, and high-throughput DNA-sequencing technology. Seasonal variability in atmospheric CH4 oxidation was assessed based on the same attributes measured with high temporal resolution throughout one snow-free season. Most glacier-forefield soils acted as a sink for atmospheric CH4 regardless of bedrock type, and CH4 flux (-0.082 to -2.2 mg CH4 m-2 d-1) and MOB abundance (2.4×103 to 5.5×105 pmoA genecopies (g soil w.w.)-1) increased significantly with soil age. Cluster analysis revealed variations in MOB community composition related to bedrock type rather than soil age, suggesting that distinct MOB communities provided a similar ecosystem service in soils on

  20. Variability in aerobic methane oxidation over the past 1.2 Myrs recorded in microbial biomarker signatures from Congo fan sediments

    NASA Astrophysics Data System (ADS)

    Talbot, Helen M.; Handley, Luke; Spencer-Jones, Charlotte L.; Dinga, Bienvenu Jean; Schefuß, Enno; Mann, Paul J.; Poulsen, John R.; Spencer, Robert G. M.; Wabakanghanzi, Jose N.; Wagner, Thomas

    2014-05-01

    Methane (CH4) is a strong greenhouse gas known to have perturbed global climate in the past, especially when released in large quantities over short time periods from continental or marine sources. It is therefore crucial to understand and, if possible, quantify the individual and combined response of these variable methane sources to natural climate variability. However, past changes in the stability of greenhouse gas reservoirs remain uncertain and poorly constrained by geological evidence. Here, we present a record from the Congo fan of a highly specific bacteriohopanepolyol (BHP) biomarker for aerobic methane oxidation (AMO), 35-aminobacteriohopane-30,31,32,33,34-pentol (aminopentol), that identifies discrete periods of increased AMO as far back as 1.2 Ma. Fluctuations in the concentration of aminopentol, and other 35-aminoBHPs, follow a pattern that correlates with late Quaternary glacial-interglacial climate cycles, with highest concentrations during warm periods. We discuss possible sources of aminopentol, and the methane consumed by the precursor methanotrophs, within the context of the Congo River setting, including supply of methane oxidation markers from terrestrial watersheds and/or marine sources (gas hydrate and/or deep subsurface gas reservoir). Compound-specific carbon isotope values of -30‰ to -40‰ for BHPs in ODP 1075 and strong similarities between the BHP signature of the core and surface sediments from the Congo estuary and floodplain wetlands from the interior of the Congo River Basin, support a methanotrophic and likely terrigenous origin of the 35-aminoBHPs found in the fan sediments. This new evidence supports a causal connection between marine sediment BHP records of tropical deep sea fans and wetland settings in the feeding river catchments, and thus tropical continental hydrology. Further research is needed to better constrain the different sources and pathways of methane emission. However, this study identifies the large potential

  1. Microsensor measurements of sulfate reduction and sulfide oxidation in compact microbial communities of aerobic biofilms

    SciTech Connect

    Kuehl, M.; Joergensen, B.B. )

    1992-04-01

    The microzonation of O{sub 2} respiration, H{sub 2}S oxidation, and SO{sub 4}{sup 2{minus}} reduction in aerobic trickling-filter biofilms was studied by measuring concentration profiles at high spatial resolution (25 to 100 {mu}m) with microsensors for O{sub 2}, S{sup 2{minus}}, and pH. Specific reaction rates were calculated from measured concentration profiles by using a simple one-dimensional diffusion reaction model. The importance of electron acceptor and electron donor availability for the microzonation of respiratory processes and their reaction rates was investigated. Oxygen respiration was found in the upper 0.2 to 0.4 mm of the biofilm, whereas sulfate reduction occurred in deeper, anoxic parts of the biofilm. Sulfate reduction accounted for up to 50% of the total mineralization of organic carbon in the biofilms. All H{sub 2}S produced from sulfate reduction was reoxidized by O{sub 2} in a narrow reaction zone, and no H{sub 2}S escaped to the overlying water. Turnover times of H{sub 2}S and O{sub 2} in the reaction zone were only a few seconds owing to rapid bacterial H{sub 2}S oxidation. Anaerobic H{sub 2}S oxidation with NO{sub 3}{sup {minus}} could be induced by addition of nitrate to the medium. Total sulfate reduction rates increased when the availability of SO{sub 4}{sup 2{minus}} or organic substrate increased as a result of deepening of the sulfate reduction zone or an increase in the sulfate reduction intensity, respectively.

  2. Plutonium Oxidation State Distribution under Aerobic and Anaerobic Subsurface Conditions for Metal-Reducing Bacteria

    NASA Astrophysics Data System (ADS)

    Reed, D. T.; Swanson, J.; Khaing, H.; Deo, R.; Rittmann, B.

    2009-12-01

    The fate and potential mobility of plutonium in the subsurface is receiving increased attention as the DOE looks to cleanup the many legacy nuclear waste sites and associated subsurface contamination. Plutonium is the near-surface contaminant of concern at several DOE sites and continues to be the contaminant of concern for the permanent disposal of nuclear waste. The mobility of plutonium is highly dependent on its redox distribution at its contamination source and along its potential migration pathways. This redox distribution is often controlled, especially in the near-surface where organic/inorganic contaminants often coexist, by the direct and indirect effects of microbial activity. The redox distribution of plutonium in the presence of facultative metal reducing bacteria (specifically Shewanella and Geobacter species) was established in a concurrent experimental and modeling study under aerobic and anaerobic conditions. Pu(VI), although relatively soluble under oxidizing conditions at near-neutral pH, does not persist under a wide range of the oxic and anoxic conditions investigated in microbiologically active systems. Pu(V) complexes, which exhibit high chemical toxicity towards microorganisms, are relatively stable under oxic conditions but are reduced by metal reducing bacteria under anaerobic conditions. These facultative metal-reducing bacteria led to the rapid reduction of higher valent plutonium to form Pu(III/IV) species depending on nature of the starting plutonium species and chelating agents present in solution. Redox cycling of these lower oxidation states is likely a critical step in the formation of pseudo colloids that may lead to long-range subsurface transport. The CCBATCH biogeochemical model is used to explain the redox mechanisms and final speciation of the plutonium oxidation state distributions observed. These results for microbiologically active systems are interpreted in the context of their importance in defining the overall migration

  3. Origin and transport of CH4 in two maar lakes fed by mantle-derived volatiles (Mt. Vulture volcano, Italy)

    NASA Astrophysics Data System (ADS)

    Caracausi, Antonio; Cosenza, Paolo; Favara, Rocco; Foresta Martin, Luigi; Galli, Nunzio; Grassa, Fausto; Nuccio, Pasquale Mario; Paternoster, Michele; Riccobono, Giuseppe

    2014-05-01

    from previous limnological-geochemical investigations has been joined with isotope signature of gas (CH4 and CO2) collected from sediments at the bottom of LPM, by means of a specially designed robot called "Muddy". Muddy is also able to perform vertical profiles both of pH and of temperature in the water column and in the sediments as well. The obtained results lead us: 1) to assess the production ratio of CH4 through acetoclastic methanogenesis and CO2 reduction in the sediments; 2) to determinate CH4 oxidation; 3) to detect the origin of CO2 involved in methanogenic processes, evaluating the contribution organic-CO2 and the sink of mantle-derived CO2.;4) to discuss the differences in CH4 sources in the water and sediments; 5) to properly define gas hazards assessment. A. Caracausi, M. Nicolosi, P.M. Nuccio, R. Favara, M. Paternoster, A. Rosciglione (2013) Geochemical insight into differences in the physical structures and dynamics of two adjacent maar lakes at Mt. Vulture volcano (southern Italy), G. Cubed, doi: 10.1002/ggge.2011

  4. Rotational tunneling in CH4 II: Disorder effects

    NASA Astrophysics Data System (ADS)

    Press, Werner; Krasnow, Igor; Zamponi, Michaela; Prager, Michael

    2011-12-01

    Transitions within the tunneling multiplet of CH4 in phase II have been measured in an experiment at the backscattering instrument BASIS of the Neutron Source SNS. They all involve transitions from or to T-states. A statistical model is put forward which accounts for local departures from tetrahedral symmetry at the sites of ordered molecules. Different from previous work, in which discrete sets of overlap matrix elements have been studied, now large numbers of elements as well as the ensemble of T-states are considered. The observed neutron spectra can be explained rather well, all based on the pocket state formalism of A. Hüller [Phys. Rev. B 16, 1844 (1977)]. A completely new result is the observation and simulation of transitions between T-states, which give rise to a double peaked feature close to the elastic position and which reflect the disorder in the system. CH2D2 molecules in the CH4 matrix are largely responsible for the disorder and an interesting topic for their own sake. The simple model presented may lend itself to a broader application.

  5. Remediation of a winery wastewater combining aerobic biological oxidation and electrochemical advanced oxidation processes.

    PubMed

    Moreira, Francisca C; Boaventura, Rui A R; Brillas, Enric; Vilar, Vítor J P

    2015-05-15

    Apart from a high biodegradable fraction consisting of organic acids, sugars and alcohols, winery wastewaters exhibit a recalcitrant fraction containing high-molecular-weight compounds as polyphenols, tannins and lignins. In this context, a winery wastewater was firstly subjected to a biological oxidation to mineralize the biodegradable fraction and afterwards an electrochemical advanced oxidation process (EAOP) was applied in order to mineralize the refractory molecules or transform them into simpler ones that can be further biodegraded. The biological oxidation led to above 97% removals of dissolved organic carbon (DOC), chemical oxygen demand (COD) and 5-day biochemical oxygen demand (BOD5), but was inefficient on the degradation of a bioresistant fraction corresponding to 130 mg L(-1) of DOC, 380 mg O2 L(-1) of COD and 8.2 mg caffeic acid equivalent L(-1) of total dissolved polyphenols. Various EAOPs such as anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF), UVA photoelectro-Fenton (PEF) and solar PEF (SPEF) were then applied to the recalcitrant effluent fraction using a 2.2 L lab-scale flow plant containing an electrochemical cell equipped with a boron-doped diamond (BDD) anode and a carbon-PTFE air-diffusion cathode and coupled to a photoreactor with compound parabolic collectors (CPCs). The influence of initial Fe(2+) concentration and current density on the PEF process was evaluated. The relative oxidative ability of EAOPs increased in the order AO-H2O2 < EF < PEF ≤ SPEF. The SPEF process using an initial Fe(2+) concentration of 35 mg L(-1), current density of 25 mA cm(-2), pH of 2.8 and 25 °C reached removals of 86% on DOC and 68% on COD after 240 min, regarding the biologically treated effluent, along with energy consumptions of 45 kWh (kg DOC)(-1) and 5.1 kWh m(-3). After this coupled treatment, color, odor, COD, BOD5, NH4(+), NO3(-) and SO4(2-) parameters complied with the legislation targets and, in addition, a total

  6. Remediation of a winery wastewater combining aerobic biological oxidation and electrochemical advanced oxidation processes.

    PubMed

    Moreira, Francisca C; Boaventura, Rui A R; Brillas, Enric; Vilar, Vítor J P

    2015-05-15

    Apart from a high biodegradable fraction consisting of organic acids, sugars and alcohols, winery wastewaters exhibit a recalcitrant fraction containing high-molecular-weight compounds as polyphenols, tannins and lignins. In this context, a winery wastewater was firstly subjected to a biological oxidation to mineralize the biodegradable fraction and afterwards an electrochemical advanced oxidation process (EAOP) was applied in order to mineralize the refractory molecules or transform them into simpler ones that can be further biodegraded. The biological oxidation led to above 97% removals of dissolved organic carbon (DOC), chemical oxygen demand (COD) and 5-day biochemical oxygen demand (BOD5), but was inefficient on the degradation of a bioresistant fraction corresponding to 130 mg L(-1) of DOC, 380 mg O2 L(-1) of COD and 8.2 mg caffeic acid equivalent L(-1) of total dissolved polyphenols. Various EAOPs such as anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF), UVA photoelectro-Fenton (PEF) and solar PEF (SPEF) were then applied to the recalcitrant effluent fraction using a 2.2 L lab-scale flow plant containing an electrochemical cell equipped with a boron-doped diamond (BDD) anode and a carbon-PTFE air-diffusion cathode and coupled to a photoreactor with compound parabolic collectors (CPCs). The influence of initial Fe(2+) concentration and current density on the PEF process was evaluated. The relative oxidative ability of EAOPs increased in the order AO-H2O2 < EF < PEF ≤ SPEF. The SPEF process using an initial Fe(2+) concentration of 35 mg L(-1), current density of 25 mA cm(-2), pH of 2.8 and 25 °C reached removals of 86% on DOC and 68% on COD after 240 min, regarding the biologically treated effluent, along with energy consumptions of 45 kWh (kg DOC)(-1) and 5.1 kWh m(-3). After this coupled treatment, color, odor, COD, BOD5, NH4(+), NO3(-) and SO4(2-) parameters complied with the legislation targets and, in addition, a total

  7. Salinity-induced hydrate dissociation: A mechanism for recent CH4 release on Mars

    SciTech Connect

    Madden, Megan Elwood; Ulrich, Shannon M; Onstott, Tullis; Phelps, Tommy Joe

    2007-01-01

    Recent observations of CH4 in the Martian atmosphere suggest that CH4 has been added relatively recently. Several mechanisms for recent CH4 release have been proposed including subsurface biological methanogenesis, abiogenic hydrothermal and/or volcanic activity, dissociation of CH4 hydrates, atmospheric photolysis, or addition of organics via bolide impact. This study examines the effects of increasing salinity on gas hydrate stability and compares estimates of the Martian geothermal gradient to CH4 and CO2 hydrate stability fields in the presence of high salinity brines. The results demonstrate that salinity increases alone result in a significant decrease in the predicted hydrate stability zone within the Martian subsurface and may be a driving force in CH4 hydrate destabilization. Active thermal and/or pressure fluctuations are not required in order for CH4 hydrates to be the source of atmospheric CH4.

  8. 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.

  9. Effect of chemical functionalization groups on Zr6-AzoBDC to enhance H2, CH4 storage and CO2 capture: a theoretical investigation

    NASA Astrophysics Data System (ADS)

    Trang, Khung M.; Pham, Hung Q.; Pham-Tran, Nguyen-Nguyen

    2015-09-01

    Grand canonical Monte Carlo (GCMC) simulation combined with the ideal adsorbed solution theory (IAST) and a statistical method were utilized to investigate the effect of functional groups on zirconium oxide based metal-organic frameworks (MOFs) Zr6-AzoBDC (Zr6A) for the gases (H2, CH4) adsorption property and CO2/CH4 selectivity under low pressure. The results showed that phenyl groups containing nitrogen (pyridine, pyrimidine) and thiophene group enhance the gas affinity with MOFs, therefore increasing both gravimetric and volumetric uptake. In addition, this behavior can also cause significantly improved selective capture of CO2 from CO2/CH4 gas mixtures. Among functional groups studied, the sulfonic acid group can potentially improve CH4, CO2 uptake and H2 isosteric heat of adsorption. These findings would play a vital role in designing new materials toward gas adsorption properties.

  10. Aerobic oxidation of alkylaromatics using a lipophilic N-hydroxyphthalimide: overcoming the industrial limit of catalyst solubility.

    PubMed

    Petroselli, Manuel; Franchi, Paola; Lucarini, Marco; Punta, Carlo; Melone, Lucio

    2014-09-01

    4,4'-(4,4'-Isopropylidenediphenoxy)bis(N-hydroxyphthalimide), which is a new lipophilic analogue of N-hydroxyphthalimide, can act as an effective catalyst in the aerobic oxidation of alkylaromatics under reduced amounts of polar cosolvent. The catalyst was selected on the basis of an in-depth study of the influence that substituents on the aromatic ring of N-hydroxyphthalimide exert on determining the NO-H bond dissociation energy (BDE). BDE values for a range of model molecules are calculated by DFT and measured by EPR spectroscopy. The new catalyst can be successfully employed in the aerobic oxidation of cumene, ethylbenzene, and cyclohexylbenzene, affording, in all cases, good conversions and high selectivity for the corresponding hydroperoxide. The effect of solvent, catalyst, and temperature has also been investigated.

  11. [Enhanced Resistance of Pea Plants to Oxidative: Stress Caused by Paraquat during Colonization by Aerobic Methylobacteria].

    PubMed

    Agafonova, N V; Doronina, N Y; Trotsenko, Yu A

    2016-01-01

    The influence of colonization of the pea (Pisum sativum L.) by aerobic methylobacteria of five different species (Methylophilus flavus Ship, Methylobacterium extorquens G10, Methylobacillus arboreus Iva, Methylopila musalis MUSA, Methylopila turkiensis Sidel) on plant resistance to paraquat-induced stresses has been studied. The normal conditions of pea colonization by methylobacteria were characterized by a decrease in the activity of antioxidant enzymes (superoxide dismutase, catalase, and peroxidases) and in the concentrations of endogenous H2O2, proline, and malonic dialdehyde, which is a product of lipid peroxidation and indicator of damage to plant cell membranes, and an increase in the activity of the photosynthetic apparatus (the content of chlorophylls a, b and carotenoids). In the presence of paraquat, the colonized plants had higher activities of antioxidant enzymes, stable photosynthetic indices, and a less intensive accumulation of the products of lipid peroxidation as compared to noncolonized plants. Thus, colonization by methylobacteria considerably increased the adaptive protection of pea plants to the paraquat-induced oxidative stress.

  12. Praseodymium incorporated AIPO-5 molecular sieves for aerobic oxidation of ethylbenzene.

    PubMed

    Sundaravel, B; Babu, C M; Palanisamy, B; Palanichamy, M; Shanthi, K; Murugesan, V

    2013-04-01

    PrAlPO-5 with (Al + P)/Pr ratios of 25, 50, 75 and 100 molecular sieves were successfully synthesized by hydrothermal method. These molecular sieves were characterised using XPS, TPD-NH3, ex-situ pyridine adsorbed IR, TPR, TGA, 27Al and 31P MAS-NMR and ESR studies. The incorporation of praseodymium in the framework of AlPO-5 was confirmed by XRD, DRS UV-vis and 27Al and 31P MAS-NMR analysis. ESR spectrum showed the presence of adsorbed oxygen. The nature and strength of acid sites were identified by ex-situ pyridine adsorbed IR and TPD-NH3. The BET surface area was found to be in the range of 238-272 m2 g(-1). The catalytic activity of the molecular sieves was tested for the liquid phase aerobic oxidation of ethylbenzene. Acetophenone was found to be the major product with more than 90% ethylbenzene conversion. ICP-OES analysis revealed the presence of praseodymium intact in the framework of AlPO-5 up to five cycles.

  13. [Enhanced Resistance of Pea Plants to Oxidative: Stress Caused by Paraquat during Colonization by Aerobic Methylobacteria].

    PubMed

    Agafonova, N V; Doronina, N Y; Trotsenko, Yu A

    2016-01-01

    The influence of colonization of the pea (Pisum sativum L.) by aerobic methylobacteria of five different species (Methylophilus flavus Ship, Methylobacterium extorquens G10, Methylobacillus arboreus Iva, Methylopila musalis MUSA, Methylopila turkiensis Sidel) on plant resistance to paraquat-induced stresses has been studied. The normal conditions of pea colonization by methylobacteria were characterized by a decrease in the activity of antioxidant enzymes (superoxide dismutase, catalase, and peroxidases) and in the concentrations of endogenous H2O2, proline, and malonic dialdehyde, which is a product of lipid peroxidation and indicator of damage to plant cell membranes, and an increase in the activity of the photosynthetic apparatus (the content of chlorophylls a, b and carotenoids). In the presence of paraquat, the colonized plants had higher activities of antioxidant enzymes, stable photosynthetic indices, and a less intensive accumulation of the products of lipid peroxidation as compared to noncolonized plants. Thus, colonization by methylobacteria considerably increased the adaptive protection of pea plants to the paraquat-induced oxidative stress. PMID:27266250

  14. Premixed CH4/O2-enriched air combustion: Identification of thermal, chemical and aerodynamic effects

    NASA Astrophysics Data System (ADS)

    Most, J.-M.; Dahikar, S.; Pal, S.; Claverie, A.; Denis, D.; Pillier, L.; de Persis, S.

    2012-11-01

    This work contributes to the evaluation of a new innovative process focused on the reduction of the cost of a post-combustion capture of CO2 in a Carbon Capture and Storage system (CCS). The process based on the separation of dried fumes composed mainly by CO2 and N2 by using membranes, which should lead to a lower energetic separation cost than amines. But the membranes become efficient if the upstream CO2 concentration is higher than 30% at their entrance that requires enriching the oxidizer flow by O2. To maintain the exhaust temperature compatible with materials thermal resistance, the reactants are diluted by a recirculation of a part of the flue gases (like N2/O2/CO2). But, the chemical kinetic, the energetic efficiencies, the radiation transfer, the transport and thermal properties of the flow can be affected by CO2. The objective of this work will be to identify the behaviour of the combustion of premixed CH4/O2-enriched air, both diluted in N2 and CO2 and to determine the combustion parameters. This allows to recover the CH4/air conditions in terms of CO2 concentration in reactants, O2 excess, dilution rate, temperature of the reactants, etc. Experiments are performed on the laminar premixed flame using counterflow burner. To characterize the combustion behaviour, the flammability limits are determined and flame thickness and position are measured from PLIF-OH diagnostic. Further, CHEMKIN simulations are performed to check the validity of the GRI3.0 chemical kinetic mechanism for premixed CH4/air synthetic combustion and identify the leading phenomena.

  15. Methylmercury decomposition in sediments and bacterial cultures: Involvement of methanogens and sulfate reducers in oxidative demethylation

    USGS Publications Warehouse

    Oremland, R.S.; Culbertson, C.W.; Winfrey, M.R.

    1991-01-01

    Demethylation of monomethylmercury in freshwater and estuarine sediments and in bacterial cultures was investigated with 14CH3HgI. Under anaerobiosis, results with inhibitors indicated partial involvement of both sulfate reducers and methanogens, the former dominating estuarine sediments, while both were active in freshwaters. Aerobes were the most significant demethylators in estuarine sediments, but were unimportant in freshwater sediments. Products of anaerobic demethylation were mainly 14CO2 as well as lesser amounts of 14CH4. Acetogenic activity resulted in fixation of some 14CO2 produced from 14CH3HgI into acetate. Aerobic demethylation in estuarine sediments produced only 14CH4, while aerobic demethylation in freshwater sediments produced small amounts of both 14CH4 and 14CO2. Two species of Desulfovibrio produced only traces of 14CH4 from 14CH3HgI, while a culture of a methylotrophic methanogen formed traces of 14CO2 and 14CH4 when grown on trimethylamine in the presence of the 14CH3HgI. These results indicate that both aerobes and anaerobes demethylate mercury in sediments, but that either group may dominate in a particular sediment type. Aerobic demethylation in the estuarine sediments appeared to proceed by the previously characterized organomercurial-lyase pathway, because methane was the sole product. However, aerobic demethylation in freshwater sediments as well as anaerobic demethylation in all sediments studied produced primarily carbon dioxide. This indicates the presence of an oxidative pathway, possibly one in which methylmercury serves as an analog of one-carbon substrates.

  16. [Effects of temperature on CH4 emission from subtropical common tree species leaves].

    PubMed

    Yang, Yan-Hua; Yi, Li-Ming; Xie, Jin-Sheng; Yang, Zhi-Jie; Jiang, Jun; Xu, Chao; Yang, Yu-Sheng

    2013-06-01

    Laboratory incubation test was conducted to study the effects of temperature on the CH4 emission from the leaves of subtropical common tree species Castanopsis carlesii, Schima superb, Cinnamomum chekiangense, Castsanopsis fabri, Cunninghamia lanceolata, and Citrus reticulata. Among the six tree species, only S. superb, C. reticulate, and C. fabri emitted CH4 at 10 degrees C. At above 20 degrees C, all the six species emitted CH4, and the average CH4 emission rate at above 30 degrees C (1.010 ng CH4 x g(-1) DM x h(-1)) was 2.96 times higher than that at 10-30 degrees C (0.255 ng CH4 x g(-1) DM x h(-1)). Moreover, increasing temperature had much more effects on the CH4 emission rate of C. reticulata and C. lanceolata than on that of the other four tree species. Incubation time affected the CH4 emission rate of all test tree species significantly, suggesting that the effects of temperature stress on the CH4 emission could be controlled by plant activity. Dry leaves could not emit CH4 no matter the temperature was very high or low. It was suggested that high temperature stress had important effects on the CH4 emission from subtropical tree leaves, and global warming could increase the CH4 emission from plants. PMID:24066538

  17. Aerobic oxidation of diverse primary alcohols to methyl esters with a readily accessible heterogeneous Pd/Bi/Te catalyst.

    PubMed

    Powell, Adam B; Stahl, Shannon S

    2013-10-01

    Efficient aerobic oxidative methyl esterification of primary alcohols has been achieved with a heterogeneous catalyst consisting of 1 mol % Pd/charcoal (5 wt %) in combination with bismuth(III) nitrate and tellurium metal. The Bi and Te additives significantly increase the reaction rate, selectivity, and overall product yields. This readily accessible catalyst system exhibits a broad substrate scope and is effective with both activated (benzylic) and unactivated (aliphatic) alcohols bearing diverse functional groups. PMID:24050194

  18. 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.

  19. 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

  20. 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. PMID:27592518

  1. Investigating the chemical and isotopic kinetics of aerobic methane oxidation in the Northern US Atlantic Margin, Hudson Canyon

    NASA Astrophysics Data System (ADS)

    Chan, E. W.; Kessler, J. D.; Shiller, A. M.; Redmond, M. C.; Arrington, E. C.; Valentine, D. L.

    2015-12-01

    Recent discoveries of methane seepage along the US Atlantic margin have led to speculation on the fate of the released methane. Here we examine the kinetics of aerobic methane oxidation to gain a fundamental understanding of this methane sink. In order to look at this process in its entirety, a unique mesocosm incubation system was developed with a Dissolved Gas Analyzer System (DGAS) to monitor in real time the chemical and isotopic changes involved with aerobic methane oxidation. This system measures changes in methane, carbon dioxide, and oxygen concentrations as well as the stable carbon isotopes of methane and carbon dioxide with time. In addition samples are strategically removed to characterize trace metals, nutrients, cell counts, and microbial community genetics. This presentation will detail the results obtained from samples collected inside the Hudson Canyon at the edge of the methane clathrate stability zone and outside the Hudson Canyon, not influenced by the methane seepage. These results show that in both environments along the Atlantic margin, methane was consumed aggressively but the timing of consumption varied based on location. In addition, these results are leading to insights into the chemical requirements needed for aerobic methane oxidation and the resulting isotopic fractionation.

  2. Aerobic methane oxidation in a coastal environment with seasonal hypoxia - a time series study

    NASA Astrophysics Data System (ADS)

    Steinle, Lea; Bethke, Christina; Schweers, Johanna; Bange, Hermann; Kock, Annette; Lehmann, Moritz F.; Treude, Tina; Niemann, Helge

    2014-05-01

    In the coastal ocean, methane is generally produced in anoxic sediments from where it can migrate through the water column to the atmosphere. A significant amount of methane is consumed along this passage by a series of microbial filter systems. Over the last 15 years, researchers focused on the first filter in marine sediments, the anaerobic oxidation of methane (AOM). Comparably little is known about the second filter, the aerobic methane oxidation (MOx), which is mediated by bacteria and takes place in the oxic water column. MOx is particularly important in shallow coastal environments that account for more than 75 % of the global oceanic methane emissions. Key environmental factors possibly controlling MOx in these systems are subjected to strong temporal variations since coastal regions are highly dynamic systems. We will present results from a time-series study on methane cycling in the water column of a coastal inlet in the southwestern Baltic Sea (Eckernförde Bay, Boknis Eck Time Series Station, 54°31.823 N, 10°02.764 E, 28m water depth; www.bokniseck.de). Results from monthly samplings for the last 8 years revealed year-round methane seepage from the seafloor and methane supersaturation (with respect to the atmospheric equilibrium) of surface waters. Seasonal stratification during the summer months leads to intermittent oxygen depletion (hypoxic to anoxic) in bottom waters in late summer to early fall. The frequency of these low-oxygen events increased over the last 20 years. In addition to oxygen fluctuations, bottom water salinity can vary strongly (17-24 psu) due to regular inflows of salty North Sea water through the Kattegat. Over the course of one and a half years, we investigated MOx rates, the methanotrophic community, methane concentrations and physicochemical parameters of the water column on a quarterly basis. Albeit methane concentrations were high throughout the water column (20-120 nM), methane turnover showed a clear spatial pattern. That

  3. Stratospheric aerosols from CH4 photochemistry on Neptune

    NASA Astrophysics Data System (ADS)

    Romani, P. N.; Atreya, S. K.

    1989-08-01

    A combined photochemical-condensation model has been used to study hydrocarbon ices produced from CH4 photolysis in the stratosphere of Neptune. A total stratospheric haze production rate of 4.2 x 10 to the -15th g/sq cm/s. The total production rate is insensitive to within a factor of two to order of magnitude changes in the eddy diffusion coefficient and methane mixing ratio, which is within the present estimate of uncertainty for this number. The condensation temperatures are 97 K for C4H2, 71 K for C2H2, and 64 K for C2H6. Voyager 2 images of Neptune will be able to confirm the presence of stratospheric aerosols and provide constraints on their production rate and location.

  4. Stratospheric aerosols from CH4 photochemistry on Neptune

    NASA Technical Reports Server (NTRS)

    Romani, Paul N.; Atreya, Sushil K.

    1989-01-01

    A combined photochemical-condensation model has been used to study hydrocarbon ices produced from CH4 photolysis in the stratosphere of Neptune. A total stratospheric haze production rate of 4.2 x 10 to the -15th g/sq cm/s. The total production rate is insensitive to within a factor of two to order of magnitude changes in the eddy diffusion coefficient and methane mixing ratio, which is within the present estimate of uncertainty for this number. The condensation temperatures are 97 K for C4H2, 71 K for C2H2, and 64 K for C2H6. Voyager 2 images of Neptune will be able to confirm the presence of stratospheric aerosols and provide constraints on their production rate and location.

  5. Microbial Removal of Atmospheric Carbon Tetrachloride in Bulk Aerobic Soils▿

    PubMed Central

    Mendoza, Y.; Goodwin, K. D.; Happell, J. D.

    2011-01-01

    Atmospheric concentrations of carbon tetrachloride (CCl4) were removed by bulk aerobic soils from tropical, subtropical, and boreal environments. Removal was observed in all tested soil types, indicating that the process was widespread. The flux measured in field chamber experiments was 0.24 ± 0.10 nmol CCl4 (m2 day)−1 (average ± standard deviation [SD]; n = 282). Removal of CCl4 and removal of methane (CH4) were compared to explore whether the two processes were linked. Removal of both gases was halted in laboratory samples that were autoclaved, dry heated, or incubated in the presence of mercuric chloride (HgCl2). In marl soils, treatment with antibiotics such as tetracycline and streptomycin caused partial inhibition of CCl4 (50%) and CH4 (76%) removal, but removal was not affected in soils treated with nystatin or myxothiazol. These data indicated that bacteria contributed to the soil removal of CCl4 and that microeukaryotes may not have played a significant role. Amendments of methanol, acetate, and succinate to soil samples enhanced CCl4 removal by 59%, 293%, and 72%, respectively. Additions of a variety of inhibitors and substrates indicated that nitrification, methanogenesis, or biological reduction of nitrate, nitrous oxide, or sulfate (e.g., occurring in possible anoxic microzones) did not play a significant role in the removal of CCl4. Methyl fluoride inhibited removal of CH4 but not CCl4, indicating that CH4 and CCl4 removals were not directly linked. Furthermore, CCl4 removal was not affected in soils amended with copper sulfate or methane, supporting the results with MeF and suggesting that the observed CCl4 removal was not significantly mediated by methanotrophs. PMID:21724884

  6. Microbial removal of atmospheric carbon tetrachloride in bulk aerobic soils.

    PubMed

    Mendoza, Y; Goodwin, K D; Happell, J D

    2011-09-01

    Atmospheric concentrations of carbon tetrachloride (CCl(4)) were removed by bulk aerobic soils from tropical, subtropical, and boreal environments. Removal was observed in all tested soil types, indicating that the process was widespread. The flux measured in field chamber experiments was 0.24 ± 0.10 nmol CCl(4) (m(2) day)(-1) (average ± standard deviation [SD]; n = 282). Removal of CCl(4) and removal of methane (CH(4)) were compared to explore whether the two processes were linked. Removal of both gases was halted in laboratory samples that were autoclaved, dry heated, or incubated in the presence of mercuric chloride (HgCl(2)). In marl soils, treatment with antibiotics such as tetracycline and streptomycin caused partial inhibition of CCl(4) (50%) and CH(4) (76%) removal, but removal was not affected in soils treated with nystatin or myxothiazol. These data indicated that bacteria contributed to the soil removal of CCl(4) and that microeukaryotes may not have played a significant role. Amendments of methanol, acetate, and succinate to soil samples enhanced CCl(4) removal by 59%, 293%, and 72%, respectively. Additions of a variety of inhibitors and substrates indicated that nitrification, methanogenesis, or biological reduction of nitrate, nitrous oxide, or sulfate (e.g., occurring in possible anoxic microzones) did not play a significant role in the removal of CCl(4). Methyl fluoride inhibited removal of CH(4) but not CCl(4), indicating that CH(4) and CCl(4) removals were not directly linked. Furthermore, CCl(4) removal was not affected in soils amended with copper sulfate or methane, supporting the results with MeF and suggesting that the observed CCl(4) removal was not significantly mediated by methanotrophs.

  7. Diffusion and separation of CH4/N2 in pillared graphene nanomaterials: A molecular dynamics investigation

    NASA Astrophysics Data System (ADS)

    Zhou, Sainan; Lu, Xiaoqing; Wu, Zhonghua; Jin, Dongliang; Guo, Chen; Wang, Maohuai; Wei, Shuxian

    2016-09-01

    Diffusion and separation of CH4/N2 in pillared graphene were investigated by molecular dynamics. The pillared graphene with (6, 6) carbon nanotube (CNT) exhibited the higher diffusion and selectivity of CH4 over N2 than that with (7, 7) CNT due to the cooperative effect of pore topological characteristics and interaction energy. The stronger interaction facilitated CH4 to enter CNT prior to N2, and higher pressure promoted CH4 to pass CNT more easily. The relative concentrations profiles showed that CH4 reached equilibrium state faster than N2 at low pressure. Our results highlight potential use of pillared graphene in gas purification and separation.

  8. Diversity and abundance of aerobic and anaerobic methane oxidizers at the Haakon Mosby Mud Volcano, Barents Sea.

    PubMed

    Lösekann, Tina; Knittel, Katrin; Nadalig, Thierry; Fuchs, Bernhard; Niemann, Helge; Boetius, Antje; Amann, Rudolf

    2007-05-01

    Submarine mud volcanoes are formed by expulsions of mud, fluids, and gases from deeply buried subsurface sources. They are highly reduced benthic habitats and often associated with intensive methane seepage. In this study, the microbial diversity and community structure in methane-rich sediments of the Haakon Mosby Mud Volcano (HMMV) were investigated by comparative sequence analysis of 16S rRNA genes and fluorescence in situ hybridization. In the active volcano center, which has a diameter of about 500 m, the main methane-consuming process was bacterial aerobic oxidation. In this zone, aerobic methanotrophs belonging to three bacterial clades closely affiliated with Methylobacter and Methylophaga species accounted for 56%+/-8% of total cells. In sediments below Beggiatoa mats encircling the center of the HMMV, methanotrophic archaea of the ANME-3 clade dominated the zone of anaerobic methane oxidation. ANME-3 archaea form cell aggregates mostly associated with sulfate-reducing bacteria of the Desulfobulbus (DBB) branch. These ANME-3/DBB aggregates were highly abundant and accounted for up to 94%+/-2% of total microbial biomass at 2 to 3 cm below the surface. ANME-3/DBB aggregates could be further enriched by flow cytometry to identify their phylogenetic relationships. At the outer rim of the mud volcano, the seafloor was colonized by tubeworms (Siboglinidae, formerly known as Pogonophora). Here, both aerobic and anaerobic methane oxidizers were found, however, in lower abundances. The level of microbial diversity at this site was higher than that at the central and Beggiatoa species-covered part of the HMMV. Analysis of methyl-coenzyme M-reductase alpha subunit (mcrA) genes showed a strong dominance of a novel lineage, mcrA group f, which could be assigned to ANME-3 archaea. Our results further support the hypothesis of Niemann et al. (54), that high methane availability and different fluid flow regimens at the HMMV provide distinct niches for aerobic and

  9. Diversity and Abundance of Aerobic and Anaerobic Methane Oxidizers at the Haakon Mosby Mud Volcano, Barents Sea▿

    PubMed Central

    Lösekann, Tina; Knittel, Katrin; Nadalig, Thierry; Fuchs, Bernhard; Niemann, Helge; Boetius, Antje; Amann, Rudolf

    2007-01-01

    Submarine mud volcanoes are formed by expulsions of mud, fluids, and gases from deeply buried subsurface sources. They are highly reduced benthic habitats and often associated with intensive methane seepage. In this study, the microbial diversity and community structure in methane-rich sediments of the Haakon Mosby Mud Volcano (HMMV) were investigated by comparative sequence analysis of 16S rRNA genes and fluorescence in situ hybridization. In the active volcano center, which has a diameter of about 500 m, the main methane-consuming process was bacterial aerobic oxidation. In this zone, aerobic methanotrophs belonging to three bacterial clades closely affiliated with Methylobacter and Methylophaga species accounted for 56% ± 8% of total cells. In sediments below Beggiatoa mats encircling the center of the HMMV, methanotrophic archaea of the ANME-3 clade dominated the zone of anaerobic methane oxidation. ANME-3 archaea form cell aggregates mostly associated with sulfate-reducing bacteria of the Desulfobulbus (DBB) branch. These ANME-3/DBB aggregates were highly abundant and accounted for up to 94% ± 2% of total microbial biomass at 2 to 3 cm below the surface. ANME-3/DBB aggregates could be further enriched by flow cytometry to identify their phylogenetic relationships. At the outer rim of the mud volcano, the seafloor was colonized by tubeworms (Siboglinidae, formerly known as Pogonophora). Here, both aerobic and anaerobic methane oxidizers were found, however, in lower abundances. The level of microbial diversity at this site was higher than that at the central and Beggiatoa species-covered part of the HMMV. Analysis of methyl-coenzyme M-reductase alpha subunit (mcrA) genes showed a strong dominance of a novel lineage, mcrA group f, which could be assigned to ANME-3 archaea. Our results further support the hypothesis of Niemann et al. (54), that high methane availability and different fluid flow regimens at the HMMV provide distinct niches for aerobic and

  10. Search of CH4 around the mud volcanism areas on Mars

    NASA Astrophysics Data System (ADS)

    Aoki, Shohei

    2012-06-01

    We propose the first measurement of CH4 specialized in the mud volcanism areas on Mars. Although the small amount of CH4 in the Martian atmosphere is remarkable because its source is potentially geological (or biological) activity, it is still open question. The high spectral and spatial resolution with high sensitivity and wide spectral coverage of IRCS/Subaru enable us the first mapping of CH4 on the localized mud volcanism areas. In the terrestrial case, mud volcanism vents about 25% of CH4 released from geological sources to the atmosphere. In such locations, CH4 can potentially combine with the infiltrated H2O and generate CH4-hydrate. While in the Martian case, the mud volcanism is expected the mounds in Acidalia Planitia and the Utopia/Isidis pitted cones. However, the releases of CH4 on these locations have not been discovered yet. Since the CH4-hydrate suggests the correlation of CH4 and H2O, high spatial resolution with simultaneous measurements of CH4 and H2O lines are essential. IRCS/Subaru can provide this opportunity. In addition, our observation will override the past one with CSHELL/IRTF in the following aspects, (1) less uncertainty by simultaneous measurement of multiple CH4 lines with wider spectral coverage, and (2) better spatial resolution.

  11. Implications of the large carbon kinetic isotope effect in the reaction CH4 + Cl for the 13C/12C ratio of stratospheric CH4

    NASA Astrophysics Data System (ADS)

    Bergamaschi, P.; Brühl, C.; Brenninkmeijer, C. A. M.; Saueressig, G.; Crowley, J. N.; Grooß, J. U.; Fischer, H.; Crutzen, P. J.

    Recent investigations of the carbon kinetic isotope effect (KIE) of the reaction CH4 + Cl yielded KIECl = 1.066±0.002 at 297 K (increasing to 1.075±0.005 at 223 K) [Saueressig et al., 1995]. In order to assess the effect of the exceptionally large KIEcl on δ13C of stratospheric CH4 we applied a two-dimensional, time dependent chemical transport model. The model results demonstrate the strong influence of the CH4 + Cl reaction on δ13CH4 in particular in the middle and upper stratosphere, where this reaction contributes several tens of percent to the total CH4 sink. The Cl sink helps to explain the relatively large overall isotope fractionation of 1.010-1.012 observed in the lower stratosphere [Brenninkmeijer et al., 1995; Brenninkmeijer et al., 1996], even though the model results predict a smaller effect than observed.

  12. High-Potential Electrocatalytic O2 Reduction with Nitroxyl / NOx Mediators: Implications for Fuel Cells and Aerobic Oxidation Catalysis

    SciTech Connect

    Gerken, James B.; Stahl, Shannon S.

    2015-07-15

    Efficient reduction of O2 to water is a central challenge in energy conversion and aerobic oxidation catalysis. In the present study, we investigate the electrochemical reduction of O2 with soluble organic nitroxyl and nitrogen oxide (NOx) mediators. When used alone, neither organic nitroxyls, such as TEMPO (2,2,6,6-tetramethyl-1-piperidinyl-N-oxyl), nor NOx species, such as sodium nitrite, are effective mediators of electrochemical O2 reduction. The combination of nitroxyl/NOx species, however, mediates sustained O2 reduction at electrochemical potentials of 0.19–0.33 V (vs. Fc/Fc+) in acetonitrile containing trifluoroacetic acid. Mechanistic analysis of the coupled redox reactions supports a process in which the nitrogen oxide catalyst drives aerobic oxidation of a nitroxyl mediator to an oxoammonium species, which then is reduced back to the nitroxyl at the cathode. The electrolysis potential is dictated by the oxoammonium/nitroxyl reduction potential. The high potentials observed with this ORR system benefit from the mechanism-based specificity for four-electron reduction of oxygen to water mediated by NOx species, together with kinetically efficient reduction of oxidized NOx species by TEMPO and other organic nitroxyls. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center, funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

  13. High-Potential Electrocatalytic O2 Reduction with Nitroxyl/NOx Mediators: Implications for Fuel Cells and Aerobic Oxidation Catalysis

    PubMed Central

    2015-01-01

    Efficient reduction of O2 to water is a central challenge in energy conversion and many aerobic oxidation reactions. Here, we show that the electrochemical oxygen reduction reaction (ORR) can be achieved at high potentials by using soluble organic nitroxyl and nitrogen oxide (NOx) mediators. When used alone, neither organic nitroxyls, such as 2,2,6,6-tetramethyl-1-piperidinyl-N-oxyl (TEMPO), nor NOx species, such as sodium nitrite, are effective ORR mediators. The combination of nitroxyl/NOx species, however, mediates sustained O2 reduction with overpotentials as low as 300 mV in acetonitrile containing trifluoroacetic acid. Mechanistic analysis of the coupled redox reactions supports a process in which the nitrogen oxide catalyst drives aerobic oxidation of a nitroxyl mediator to an oxoammonium species, which then is reduced back to the nitroxyl at the cathode. The electrolysis potential is dictated by the oxoammonium/nitroxyl reduction potential. The overpotentials accessible with this ORR system are significantly lower than widely studied molecular metal-macrocycle ORR catalysts and benefit from the mechanism-based specificity for four-electron reduction of oxygen to water mediated by NOx species, together with kinetically efficient reduction of oxidized NOx species by TEMPO and other organic nitroxyls. PMID:27162977

  14. 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.

  15. 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.

  16. Molecular characterization of a microbial consortium involved in methane oxidation coupled to denitrification under micro-aerobic conditions

    PubMed Central

    Liu, Jingjing; Sun, Faqian; Wang, Liang; Ju, Xi; Wu, Weixiang; Chen, Yingxu

    2014-01-01

    Methane can be used as an alternative carbon source in biological denitrification because it is nontoxic, widely available and relatively inexpensive. A microbial consortium involved in methane oxidation coupled to denitrification (MOD) was enriched with nitrite and nitrate as electron acceptors under micro-aerobic conditions. The 16S rRNA gene combined with pmoA phylogeny of methanotrophs and nirK phylogeny of denitrifiers were analysed to reveal the dominant microbial populations and functional microorganisms. Real-time quantitative polymerase chain reaction results showed high numbers of methanotrophs and denitrifiers in the enriched consortium. The 16S rRNA gene clone library revealed that Methylococcaceae and Methylophilaceae were the dominant populations in the MOD ecosystem. Phylogenetic analyses of pmoA gene clone libraries indicated that all methanotrophs belonged to Methylococcaceae, a type I methanotroph employing the ribulose monophosphate pathway for methane oxidation. Methylotrophic denitrifiers of the Methylophilaceae that can utilize organic intermediates (i.e. formaldehyde, citrate and acetate) released from the methanotrophs played a vital role in aerobic denitrification. This study is the first report to confirm micro-aerobic denitrification and to make phylogenetic and functional assignments for some members of the microbial assemblages involved in MOD. PMID:24245852

  17. Molecular characterization of a microbial consortium involved in methane oxidation coupled to denitrification under micro-aerobic conditions.

    PubMed

    Liu, Jingjing; Sun, Faqian; Wang, Liang; Ju, Xi; Wu, Weixiang; Chen, Yingxu

    2014-01-01

    Methane can be used as an alternative carbon source in biological denitrification because it is nontoxic, widely available and relatively inexpensive. A microbial consortium involved in methane oxidation coupled to denitrification (MOD) was enriched with nitrite and nitrate as electron acceptors under micro-aerobic conditions. The 16S rRNA gene combined with pmoA phylogeny of methanotrophs and nirK phylogeny of denitrifiers were analysed to reveal the dominant microbial populations and functional microorganisms. Real-time quantitative polymerase chain reaction results showed high numbers of methanotrophs and denitrifiers in the enriched consortium. The 16S rRNA gene clone library revealed that Methylococcaceae and Methylophilaceae were the dominant populations in the MOD ecosystem. Phylogenetic analyses of pmoA gene clone libraries indicated that all methanotrophs belonged to Methylococcaceae, a type I methanotroph employing the ribulose monophosphate pathway for methane oxidation. Methylotrophic denitrifiers of the Methylophilaceae that can utilize organic intermediates (i.e. formaldehyde, citrate and acetate) released from the methanotrophs played a vital role in aerobic denitrification. This study is the first report to confirm micro-aerobic denitrification and to make phylogenetic and functional assignments for some members of the microbial assemblages involved in MOD.

  18. The importance of biological oxidation of iron in the aerobic cells of the Wheal Jane pilot passive treatment system.

    PubMed

    Hall, G; Swash, P; Kotilainen, S

    2005-02-01

    The passive treatment system designed to treat the mine water discharge of the abandoned Wheal Jane tin mine in Cornwall consisted of a sequence of artificial wetland cells, an anaerobic cell and a final series of rock filters. Three systems were operated which differed only in the pre-treatment of the mine water before discharge to the aerobic wetland cells. The aerobic cells were designed to promote aerobic oxidation and precipitation of iron which could exceed a concentration of 100 mg/l in the raw mine water discharge. The largest investment of land area was to the artificial wetland cells and it was important to understand the processes of oxidation and precipitation of iron so that the performance of this aspect the pilot passive treatment plant (PPTP) could be managed as efficiently as possible. The generally low pH of the influent mine water and inevitable trend of decreasing pH due to hydrolysis of Fe(III) meant that distinguishing between biotic and abiotic mechanisms was fundamental for further design planning of passive treatment systems. This paper describes these observations. PMID:15680627

  19. Evaluation of performance in a combined UASB and aerobic contact oxidation process treating acrylic wastewater.

    PubMed

    Li, Anfeng; Dong, Na; He, Manni; Pan, Tao

    2015-01-01

    The lab-scale and full-scale performance of a combined mesophilic up-flow anaerobic sludge blanket (UASB) and aerobic contact oxidation (ACO) process for treating acrylic wastewater was studied. During lab-scale experiment, the overwhelmed volumetric load for UASB was above 6 kg chemical oxygen demand (COD) ·(m(-3)·d(-1)) since COD removal efficiency dropped dramatically from 73% at 6 kg COD·(m(-3)·d(-1)) to 61% at 7 kg COD·(m(-3)·d(-1)) and 53% at 8 kg COD·(m(-3)·d(-1)). Further results showed that an up-flow fluid velocity of 0.5 m h(-1) for UASB obtained a highest COD removal efficiency of 75%, and the optimum COD volumetric load for the corresponding ACO was 1.00 kg COD·(m(-3)·d(-1)). Based on the configuration of the lab-scale experiment, a full-scale application with an acrylic wastewater treatment capacity of 8 m3 h(-1) was constructed and operated at a volumetric load of 5.5 kg COD·(m(-3)·d(-1)), an up-flow fluid velocity of 0.5 m h(-1) for UASB and a volumetric load of 0.9 kg COD·(m(-3)·d(-1)) for ACO; and the final effluent COD was around 740 mg L(-1). The results suggest that a combined UASB-ACO process is promising for treating acrylic wastewater. PMID:25204720

  20. Simulated Nitrogen Deposition Reduces CH4 Uptake and Increases N2O Emission from a Subtropical Plantation Forest Soil in Southern China

    PubMed Central

    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. PMID:24714387

  1. 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.

  2. Impact of hydrology and vegetation community structure on CO2 and CH4 flux patterns in a permafrost ecosystem in Northeast Siberia

    NASA Astrophysics Data System (ADS)

    Kwon, M. J.; Goeckede, M.; Wildner, M.; Heimann, M.; Zimov, N.; Zimov, S. A.

    2014-12-01

    A large fraction of organic carbon stored in Arctic permafrost soil is to be decomposed and released to the atmosphere under climate change. Among many drivers that influence decomposition, changes in hydrology play a pivotal role: Shifts in water table depth (WTD) often trigger modifications on soil and vegetation (e.g. soil temperature and vegetation community structure), which in turn alter carbon cycle processes. The presented study is focused on CO2 and CH4 fluxes measured with chambers in a floodplain of the Kolyma River near Cherskii, Northeast Siberia. Our study site is separated into two areas, one that has been drained since 2004, and a nearby reference site. Carbon flux (NEE, ER, methane) was measured for ~16 weeks during summer and early winter of 2013, and summer of 2014. In addition, plant-mediated CH4 transport was measured in 2014 to separate different CH4 emission pathways. Vegetation community structure was investigated in 2013 and 2014. After a decade of drainage history that lowered WTD by about 20cm in the drained area, Eriophorum (cotton grass) that previously dominated have been much replaced by Carex (tussock-forming sedge) and shrub species. ANCOVA analysis revealed that NEE, ER, and methane flux rates were all influenced by vegetation in both summer and winter, leading to different flux patterns between two sites. WTD also influenced NEE and methane, showing little less CO2 uptake and much less CH4 emission in drained site. Plant-mediated CH4 transport through cotton grasses was correlated with diameter and length of green leaves, implying bigger plants transport more CH4 because their roots reach deeper soil layers where methanogenesis occurs. This correlation was strong at the drained site, where CH4 oxidation was dominant in shallow depths. Summarizing all effects of vegetation and WTD, the drainage results in a stronger net sink for carbon (CO2 and CH4 fluxes combined) in the growing season, but a stronger source in early winter.

  3. Silver(I) as a widely applicable, homogeneous catalyst for aerobic oxidation of aldehydes toward carboxylic acids in water—“silver mirror”: From stoichiometric to catalytic

    PubMed Central

    Liu, Mingxin; Wang, Haining; Zeng, Huiying; Li, Chao-Jun

    2015-01-01

    The first example of a homogeneous silver(I)-catalyzed aerobic oxidation of aldehydes in water is reported. More than 50 examples of different aliphatic and aromatic aldehydes, including natural products, were tested, and all of them successfully underwent aerobic oxidation to give the corresponding carboxylic acids in extremely high yields. The reaction conditions are very mild and greener, requiring only a very low silver(I) catalyst loading, using atmospheric oxygen as the oxidant and water as the solvent, and allowing gram-scale oxidation with only 2 mg of our catalyst. Chromatography is completely unnecessary for purification in most cases. PMID:26601150

  4. Combining Microbial Enzyme Kinetics Models with Light Use Efficiency Models to Predict CO2 and CH4 Ecosystem Exchange from Flooded and Drained Peatland Systems

    NASA Astrophysics Data System (ADS)

    Oikawa, P. Y.; Jenerette, D.; Knox, S. H.; Sturtevant, C. S.; Verfaillie, J. G.; Baldocchi, D. D.

    2014-12-01

    Under California's Cap-and-Trade program, companies are looking to invest in land-use practices that will reduce greenhouse gas (GHG) emissions. The Sacramento-San Joaquin River Delta is a drained cultivated peatland system and a large source of CO2. To slow soil subsidence and reduce CO2 emissions, there is growing interest in converting drained peatlands to wetlands. However, wetlands are large sources of CH4 that could offset CO2-based GHG reductions. The goal of our research is to provide accurate measurements and model predictions of the changes in GHG budgets that occur when drained peatlands are restored to wetland conditions. We have installed a network of eddy covariance towers across multiple land use types in the Delta and have been measuring CO2 and CH4 ecosystem exchange for multiple years. In order to upscale these measurements through space and time we are using these data to parameterize and validate a process-based biogeochemical model. To predict gross primary productivity (GPP), we are using a simple light use efficiency (LUE) model which requires estimates of light, leaf area index and air temperature and can explain 90% of the observed variation in GPP in a mature wetland. To predict ecosystem respiration we have adapted the Dual Arrhenius Michaelis-Menten (DAMM) model. The LUE-DAMM model allows accurate simulation of half-hourly net ecosystem exchange (NEE) in a mature wetland (r2=0.85). We are working to expand the model to pasture, rice and alfalfa systems in the Delta. To predict methanogenesis, we again apply a modified DAMM model, using simple enzyme kinetics. However CH4 exchange is complex and we have thus expanded the model to predict not only microbial CH4 production, but also CH4 oxidation, CH4 storage and the physical processes regulating the release of CH4 to the atmosphere. The CH4-DAMM model allows accurate simulation of daily CH4 ecosystem exchange in a mature wetland (r2=0.55) and robust estimates of annual CH4 budgets. The LUE

  5. Spatial patterns of methane oxidation and methanotrophic diversity in landfill cover soils of southern China.

    PubMed

    Chi, Zi-Fang; Lu, Wen-Jing; Wang, Hong-Tao

    2015-04-01

    Aerobic CH4 oxidation is an important CH4 sink in landfills. To investigate the distribution and community diversity of methanotrophs and link with soil characteristics and operational parameters (e.g., concentrations of O2, CH4), cover soil samples were collected at different locations and depths from the Mengzi semi-aerobic landfill (SAL) in Yunnan Province of southern China. Specific PCR followed by denaturing gradient gel electrophoresis and realtime PCR were used to examine methanotrophs in the landfill cover soils. The results showed that different locations did harbor distinct methanotroph communities. Methanotrophs were more abundant in areas near the venting pipes because of the higher O2 concentrations. The depth of 20-25 cm, where the ratio of the CH4 to O2 was within the range from 1.3 to 8.6, was more conducive to the growth of CH4-oxidizing bacteria. Type II methanotrophs dominated in all samples compared with Type I methanotrophs, as evidenced by the high ratio of Type II to Type I methanotrophic copy numbers (from 1.76 to 11.60). The total copy numbers of methanotrophs detected were similar to other ecosystems, although the CH4 concentration was much higher in SAL cover soil. Methylobacter and Methylocystis were the most abundant Type I and Type II methanotrophs genera, respectively, in the Mengzi SAL. The results suggested that SALs could provide a special environment with both high concentrations of CH4 and O2 for methanotrophs, especially around the vertical venting pipes.

  6. Spatial patterns of methane oxidation and methanotrophic diversity in landfill cover soils of southern China.

    PubMed

    Chi, Zi-Fang; Lu, Wen-Jing; Wang, Hong-Tao

    2015-04-01

    Aerobic CH4 oxidation is an important CH4 sink in landfills. To investigate the distribution and community diversity of methanotrophs and link with soil characteristics and operational parameters (e.g., concentrations of O2, CH4), cover soil samples were collected at different locations and depths from the Mengzi semi-aerobic landfill (SAL) in Yunnan Province of southern China. Specific PCR followed by denaturing gradient gel electrophoresis and realtime PCR were used to examine methanotrophs in the landfill cover soils. The results showed that different locations did harbor distinct methanotroph communities. Methanotrophs were more abundant in areas near the venting pipes because of the higher O2 concentrations. The depth of 20-25 cm, where the ratio of the CH4 to O2 was within the range from 1.3 to 8.6, was more conducive to the growth of CH4-oxidizing bacteria. Type II methanotrophs dominated in all samples compared with Type I methanotrophs, as evidenced by the high ratio of Type II to Type I methanotrophic copy numbers (from 1.76 to 11.60). The total copy numbers of methanotrophs detected were similar to other ecosystems, although the CH4 concentration was much higher in SAL cover soil. Methylobacter and Methylocystis were the most abundant Type I and Type II methanotrophs genera, respectively, in the Mengzi SAL. The results suggested that SALs could provide a special environment with both high concentrations of CH4 and O2 for methanotrophs, especially around the vertical venting pipes. PMID:25341468

  7. Whole-Genome Transcriptional Analysis of Chemolithoautotrophic Thiosulfate Oxidation by Thiobacillus denitrificans Under Aerobic vs. Denitrifying Conditions

    SciTech Connect

    Beller, H R; Letain, T E; Chakicherla, A; Kane, S R; Legler, T C; Coleman, M A

    2006-04-22

    Thiobacillus denitrificans is one of the few known obligate chemolithoautotrophic bacteria capable of energetically coupling thiosulfate oxidation to denitrification as well as aerobic respiration. As very little is known about the differential expression of genes associated with ke chemolithoautotrophic functions (such as sulfur-compound oxidation and CO2 fixation) under aerobic versus denitrifying conditions, we conducted whole-genome, cDNA microarray studies to explore this topic systematically. The microarrays identified 277 genes (approximately ten percent of the genome) as differentially expressed using Robust Multi-array Average statistical analysis and a 2-fold cutoff. Genes upregulated (ca. 6- to 150-fold) under aerobic conditions included a cluster of genes associated with iron acquisition (e.g., siderophore-related genes), a cluster of cytochrome cbb3 oxidase genes, cbbL and cbbS (encoding the large and small subunits of form I ribulose 1,5-bisphosphate carboxylase/oxygenase, or RubisCO), and multiple molecular chaperone genes. Genes upregulated (ca. 4- to 95-fold) under denitrifying conditions included nar, nir, and nor genes (associated respectively with nitrate reductase, nitrite reductase, and nitric oxide reductase, which catalyze successive steps of denitrification), cbbM (encoding form II RubisCO), and genes involved with sulfur-compound oxidation (including two physically separated but highly similar copies of sulfide:quinone oxidoreductase and of dsrC, associated with dissimilatory sulfite reductase). Among genes associated with denitrification, relative expression levels (i.e., degree of upregulation with nitrate) tended to decrease in the order nar > nir > nor > nos. Reverse transcription, quantitative PCR analysis was used to validate these trends.

  8. Characterization and validation of CH4 profiles derived from the GOSAT thermal infrared band

    NASA Astrophysics Data System (ADS)

    Tanaka, T.

    2015-12-01

    Methane (CH4) is one of most effective greenhouse gases which is responsible for global warming since pre-industrial time. CH4 emitted from anthropogenic and natural sources can be identified but poorly quantified in the local scale. Vertical profiles of CH4 are retrieved from the Greenhouse gases Observing SATellite (GOSAT) Thermal InfraRed (TIR) band, and the evaluation of the GOSAT TIR CH4 profile is being conducted. Here we show the results of the comparison of GOSAT TIR and the aircraft CH4 in-situ profiles measured by the National Oceanic and Atmospheric Administration (NOAA) and the Alpha Jet Atmospheric eXperiment (AJAX). We compare the TIR CH4 with the aircraft profiles from 15 NOAA sites and Railroad valley measured by AJAX. GOSAT TIR CH4 profiles are collected under conditions within 200 km and ±12 hours from the aircraft measurements at each observation site. The TIR CH4 profiles agree well with aircraft profiles and average differences have slightly negative biases (-3 to -6 ppb) in both the boundary layer and the free troposphere.Satellite based CH4 measurements can provide the large spatial and temporal that improve the understanding of CH4 transport, surface emissions and chemical loss.

  9. [CH4 absorption and its affecting factors in a wheat field with conservation tillage].

    PubMed

    Zhao, Jian-bo; Li, Zeng-jia; Chi, Shu-jun; Ning, Tang-yuan; Gu, Shu-bo; Qiu, Li-qun; Wang, Yun; Jiang, Xiao-dong

    2008-11-01

    In order to understand the relationships between CH4 fluxes and its affecting factors in a wheat field with conservation tillage, the CH4 fluxes in two wheat fields, one with conservation tillage and the another with conventional tillage, were measured in situ by static chamber-GC method, with soil temperature and soil moisture and inorganic nitrogen contents determined at the same time. The results showed that these two fields had an obvious and similar seasonal variation pattern of CH4 fluxes, but the average and seasonal CH4 absorption fluxes differed significantly. In the growth period of wheat, the fields were the sink of CH4, and the CH4 absorption fluxes was in the order of conventional tillage with no straw returning (CN) > conventional tillage with straw returning (CS) > subsoiling with straw returning (PS) > harrowing with straw returning (HS) > rotary tillage with straw returning (RS) > no tillage with straw covered (NS). Comparing with conventional tillage, conservation tillage reduced the CH4 absorption fluxes. In conservation tillage, the CH4 absorption fluxes was positively correlated with soil temperature but negatively correlated with soil moisture content; while in conventional tillage, the CH4 absorption fluxes had no significant correlations with the two factors. In all treatments, there was a significant negative correlation between CH4 absorption fluxes and soil NH4+ -N content.

  10. Thermodynamic and hydrochemical controls on CH4 in a coal seam gas and overlying alluvial aquifer: new insights into CH4 origins.

    PubMed

    Owen, D Des R; Shouakar-Stash, O; Morgenstern, U; Aravena, R

    2016-01-01

    Using a comprehensive data set (dissolved CH4, δ(13)C-CH4, δ(2)H-CH4, δ(13)C-DIC, δ(37)Cl, δ(2)H-H2O, δ(18)O-H2O, Na, K, Ca, Mg, HCO3, Cl, Br, SO4, NO3 and DO), in combination with a novel application of isometric log ratios, this study describes hydrochemical and thermodynamic controls on dissolved CH4 from a coal seam gas reservoir and an alluvial aquifer in the Condamine catchment, eastern Surat/north-western Clarence-Moreton basins, Australia. δ(13)C-CH4 data in the gas reservoir (-58‰ to -49‰) and shallow coal measures underlying the alluvium (-80‰ to -65‰) are distinct. CO2 reduction is the dominant methanogenic pathway in all aquifers, and it is controlled by SO4 concentrations and competition for reactants such as H2. At isolated, brackish sites in the shallow coal measures and alluvium, highly depleted δ(2)H-CH4 (<310‰) indicate acetoclastic methanogenesis where SO4 concentrations inhibit CO2 reduction. Evidence of CH4 migration from the deep gas reservoir (200-500 m) to the shallow coal measures (<200 m) or the alluvium was not observed. The study demonstrates the importance of understanding CH4 at different depth profiles within and between aquifers. Further research, including culturing studies of microbial consortia, will improve our understanding of the occurrence of CH4 within and between aquifers in these basins. PMID:27578542

  11. Recent trends in global methane emissions inferred from 30-years of surface CH4 and δ13C-CH4 measurements

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Methane (CH4) is the second most important greenhouse gas after carbon dioxide. Quantitative understanding of the global CH4 budget is important in order to predict future contributions of global warming and to develop effective strategies for its mitigation. After a decade-long period of decreasing growth rates, atmospheric CH4 concentrations have risen in recent years raising concerns about its long-term stability. Despite much study there is no clear consensus about the causes of this increase. Some bottom-up inventories suggest that fugitive emissions from the fossil fuel industry may be increasing though there are considerable uncertainties in these estimates due in part to the variable nature of this source. To better understand the changing budget of atmospheric CH4, we performed a time-dependent retrieval of CH4 fluxes spanning nearly 30 years using global surface and isotopic CH4 measurements. An earlier inversion from our group suggested that fugitive fossil fuel emissions increased from 2000-2008, contributing to the recent rise. Here we extend this study to year 2015 using the most recent NOAA Global Monitoring Division (GMD) CH4 measurements and available δ13C -CH4 data along with a higher resolution version of the chemical transport model GEOS-Chem (2ox2.5o). The higher resolution grid allowed us to extract more information from the observations due to the improved ability of the model to simulate CH4 at each station and the decreased need to aggregate neighboring stations. This in turn increased the error reduction between the a priori and posterior emissions leading to more accurate estimates of the retrieved fluxes and improved understanding of the drivers underlying the current atmospheric record.

  12. Thermodynamic and hydrochemical controls on CH4 in a coal seam gas and overlying alluvial aquifer: new insights into CH4 origins.

    PubMed

    Owen, D Des R; Shouakar-Stash, O; Morgenstern, U; Aravena, R

    2016-08-31

    Using a comprehensive data set (dissolved CH4, δ(13)C-CH4, δ(2)H-CH4, δ(13)C-DIC, δ(37)Cl, δ(2)H-H2O, δ(18)O-H2O, Na, K, Ca, Mg, HCO3, Cl, Br, SO4, NO3 and DO), in combination with a novel application of isometric log ratios, this study describes hydrochemical and thermodynamic controls on dissolved CH4 from a coal seam gas reservoir and an alluvial aquifer in the Condamine catchment, eastern Surat/north-western Clarence-Moreton basins, Australia. δ(13)C-CH4 data in the gas reservoir (-58‰ to -49‰) and shallow coal measures underlying the alluvium (-80‰ to -65‰) are distinct. CO2 reduction is the dominant methanogenic pathway in all aquifers, and it is controlled by SO4 concentrations and competition for reactants such as H2. At isolated, brackish sites in the shallow coal measures and alluvium, highly depleted δ(2)H-CH4 (<310‰) indicate acetoclastic methanogenesis where SO4 concentrations inhibit CO2 reduction. Evidence of CH4 migration from the deep gas reservoir (200-500 m) to the shallow coal measures (<200 m) or the alluvium was not observed. The study demonstrates the importance of understanding CH4 at different depth profiles within and between aquifers. Further research, including culturing studies of microbial consortia, will improve our understanding of the occurrence of CH4 within and between aquifers in these basins.

  13. Thermodynamic and hydrochemical controls on CH4 in a coal seam gas and overlying alluvial aquifer: new insights into CH4 origins

    NASA Astrophysics Data System (ADS)

    Owen, D. Des. R.; Shouakar-Stash, O.; Morgenstern, U.; Aravena, R.

    2016-08-01

    Using a comprehensive data set (dissolved CH4, δ13C-CH4, δ2H-CH4, δ13C-DIC, δ37Cl, δ2H-H2O, δ18O-H2O, Na, K, Ca, Mg, HCO3, Cl, Br, SO4, NO3 and DO), in combination with a novel application of isometric log ratios, this study describes hydrochemical and thermodynamic controls on dissolved CH4 from a coal seam gas reservoir and an alluvial aquifer in the Condamine catchment, eastern Surat/north-western Clarence-Moreton basins, Australia. δ13C-CH4 data in the gas reservoir (‑58‰ to ‑49‰) and shallow coal measures underlying the alluvium (‑80‰ to ‑65‰) are distinct. CO2 reduction is the dominant methanogenic pathway in all aquifers, and it is controlled by SO4 concentrations and competition for reactants such as H2. At isolated, brackish sites in the shallow coal measures and alluvium, highly depleted δ2H-CH4 (<310‰) indicate acetoclastic methanogenesis where SO4 concentrations inhibit CO2 reduction. Evidence of CH4 migration from the deep gas reservoir (200–500 m) to the shallow coal measures (<200 m) or the alluvium was not observed. The study demonstrates the importance of understanding CH4 at different depth profiles within and between aquifers. Further research, including culturing studies of microbial consortia, will improve our understanding of the occurrence of CH4 within and between aquifers in these basins.

  14. Thermodynamic and hydrochemical controls on CH4 in a coal seam gas and overlying alluvial aquifer: new insights into CH4 origins

    PubMed Central

    Owen, D. Des. R.; Shouakar-Stash, O.; Morgenstern, U.; Aravena, R.

    2016-01-01

    Using a comprehensive data set (dissolved CH4, δ13C-CH4, δ2H-CH4, δ13C-DIC, δ37Cl, δ2H-H2O, δ18O-H2O, Na, K, Ca, Mg, HCO3, Cl, Br, SO4, NO3 and DO), in combination with a novel application of isometric log ratios, this study describes hydrochemical and thermodynamic controls on dissolved CH4 from a coal seam gas reservoir and an alluvial aquifer in the Condamine catchment, eastern Surat/north-western Clarence-Moreton basins, Australia. δ13C-CH4 data in the gas reservoir (−58‰ to −49‰) and shallow coal measures underlying the alluvium (−80‰ to −65‰) are distinct. CO2 reduction is the dominant methanogenic pathway in all aquifers, and it is controlled by SO4 concentrations and competition for reactants such as H2. At isolated, brackish sites in the shallow coal measures and alluvium, highly depleted δ2H-CH4 (<310‰) indicate acetoclastic methanogenesis where SO4 concentrations inhibit CO2 reduction. Evidence of CH4 migration from the deep gas reservoir (200–500 m) to the shallow coal measures (<200 m) or the alluvium was not observed. The study demonstrates the importance of understanding CH4 at different depth profiles within and between aquifers. Further research, including culturing studies of microbial consortia, will improve our understanding of the occurrence of CH4 within and between aquifers in these basins. PMID:27578542

  15. A comparative study of silver-graphene oxide nanocomposites as a recyclable catalyst for the aerobic oxidation of benzyl alcohol: Support effect

    NASA Astrophysics Data System (ADS)

    Zahed, Bahareh; Hosseini-Monfared, Hassan

    2015-02-01

    Three different nanocomposites of silver and graphene oxide, namely silver nanoparticles (AgNPs) immobilized on reduced graphene oxide (AgNPs/rGO), partially reduced graphene oxide (AgNPs/GO) and thiolated partially reduced graphene oxide (AgNPs/GOSH), were synthesized in order to compare their properties. Characterizations were carried out by infrared and UV-Vis and Raman spectroscopy, ICP, X-ray diffraction, SEM and TEM, confirming both the targeted chemical modification and the composite formation. The nanocomposites were successfully employed in the aerobic oxidation of benzyl alcohol at atmospheric pressure. AgNPs/GOSH is stable and recyclable catalyst which showed the highest activity in the aerobic oxidation of benzyl alcohol in the presence of N-hydroxyphthalimide (NHPI) to give benzaldehyde with 58% selectivity in 24 h at 61% conversion. The favorite properties of AgNPs/GOSH are reasonably attributed to the stable and well distributed AgNPs over GOSH due to strong adhesion between AgNPs and GOSH.

  16. Basin scale controls on CO2 and CH4 emissions from the Upper Mississippi River

    NASA Astrophysics Data System (ADS)

    Crawford, John T.; Loken, Luke C.; Stanley, Emily H.; Stets, Edward G.; Dornblaser, Mark M.; Striegl, Robert G.

    2016-03-01

    The Upper Mississippi River, engineered for river navigation in the 1930s, includes a series of low-head dams and navigation pools receiving elevated sediment and nutrient loads from the mostly agricultural basin. Using high-resolution, spatially resolved water quality sensor measurements along 1385 river kilometers, we show that primary productivity and organic matter accumulation affect river carbon dioxide and methane emissions to the atmosphere. Phytoplankton drive CO2 to near or below atmospheric equilibrium during the growing season, while anaerobic carbon oxidation supports a large proportion of the CO2 and CH4 production. Reductions of suspended sediment load, absent of dramatic reductions in nutrients, will likely further reduce net CO2 emissions from the river. Large river pools, like Lake Pepin, which removes the majority of upstream sediments, and large agricultural tributaries downstream that deliver significant quantities of sediments and nutrients, are likely to persist as major geographical drivers of greenhouse gas emissions.

  17. Interannual and seasonal variability of CH4 and N2O exchange over a temperate mountain grassland

    NASA Astrophysics Data System (ADS)

    Hörtnagl, L. J.; Wohlfahrt, G.

    2012-12-01

    The quantification and understanding of the greenhouse gas (GHG) exchange between terrestrial ecosystems and the atmosphere is crucial when trying to assess the effect of anthropogenic and biogenic controls on a future climate. Using the eddy covariance method, fluxes of CO2 have been measured over a wide array of ecosystems, while measurements of the other two major GHG, methane (CH4) and nitrous oxide (N2O), were only conducted by few groups due to expensive scalar sensors and their time-consuming maintenance. These first measurments mainly focused on ecosystems that were believed to represent significant sources for CH4 (e.g. wetlands) or N2O (e.g. heavily fertilized crops). With CH4 and N2O measurement devices now being widely available, more measurements are made over sites that are characterized by relatively small and often close-to-zero fluxes, and despite recent advances in sensor sensitivity and stability, the quantification of these two GHG remains challenging. Here we report on the CO2, CH4 and N2O exchange measured over 2 years at a temperate mountain grassland managed as a hay meadow near the village Neustift in the Stubai Valley, Austria, by means of the eddy covariance method. The three wind components, the speed of sound and the CO2 mole densities were acquired at a time resolution of 20 Hz and used to calculate true eddy covariance CO2 fluxes. CH4 and N2O mixing ratios were recorded at 2 Hz by a quantum cascade laser absorption spectrometer (QCL-AS), resulting in a disjunct time series when compared to the 20 Hz wind data. Fluxes of both compounds were then calculated using the virtual disjunct eddy covariance method (vDEC). Mixing ratios of CH4 and N2O were then corrected for the cross-talk effect of water as described in earlier studies. The net ecosystem exchange of CO2 at the study site is monitored continously since 2001, while the measurement of CH4 and N2O fluxes started in April 2010. During the vegetation period, typical concentration

  18. Biogeochemical processes involving dissolved CO2 and CH4 at Albano, Averno, and Monticchio meromictic volcanic lakes (Central-Southern Italy)

    NASA Astrophysics Data System (ADS)

    Cabassi, Jacopo; Tassi, Franco; Vaselli, Orlando; Fiebig, Jens; Nocentini, Matteo; Capecchiacci, Francesco; Rouwet, Dmitri; Bicocchi, Gabriele

    2013-01-01

    measured δ13CTDIC values are not consistent, indicating that CO2 and the main carbon-bearing ion species (HCO3 -) are not in isotopic equilibrium, likely due to the fast kinetics of biochemical processes involving both CO2 and CH4. This study demonstrates that the vertical patterns of the CO2/CH4 ratio and of δ13C-CO2 and δ13C-CH4 are to be regarded as promising tools to detect perturbations, related to different causes, such as changes in the CO2 input from sublacustrine springs, that may affect aerobic and anaerobic layers of meromictic volcanic lakes.

  19. Shock tube measurements of specific reaction rates in the branched chain CH4-CO-O2 system

    NASA Technical Reports Server (NTRS)

    Brabbs, T. A.; Brokaw, R. S.

    1975-01-01

    Growth constants, obtained by measuring the blue CO flame band emission behind incident shock waves, were obtained for two elementary bimolecular reactions involved in the oxidation of methane. Gas mixtures containing small amounts of CH4 with varying amounts of CO, O2, and in one case CO2, diluted with argon, were investigated, and exponential growth constants were derived from plots of the logarithm of observed light intensity versus gas time. The rate constant for the reaction O + CH4 yields CH3 + OH was found to be 1.9 times 10 to the 14th exp(-5900/T) cu cm per mole per sec in the range 1300-2000 K; for the reaction CH3 + O2 yields CH3O + O, the rate constant was determined to be 2.4 times 10 to the 13th exp(-14,500/T) cu cm per mole per sec in the range 1200 to 1900 K.

  20. Spatial distribution of iron oxidation in the aerobic cells of the Wheal Jane Pilot Passive Treatment Plant.

    PubMed

    Hall, G H; Puhlmann, T

    2005-02-01

    The wetland cells of the Wheal Jane Pilot Passive Treatment Plant (PPTP) were designed to promote aerobic oxidation and precipitation of iron which could exceed a concentration of 100 mg l-1 in the raw mine water. The largest investment of land area was to the wetland (also called aerobic) cells and it was important to understand the processes of oxidation and precipitation of iron so that the performance of this part of the pilot passive treatment plant (PPTP) could be managed efficiently. The results of a high-resolution sampling programme on the distribution of Fe(II) within the first wetland cell of each treatment system are described. Comparison of inflow and outflow concentrations of iron adequately described the performance of the lime-dosed (LD) system. However, precipitation of iron in the anoxic limestone drain (ALD) and lime-free systems (LFS) was more efficient. On average, about 90% of the iron present in the inflow was removed using only 50% and 33% of the first aerobic cells of the ALD and LFS systems, respectively. As the concentration of iron approached 20 mg l-1, the rate of oxidation slowed considerably. This was probably due to be due to low pH levels caused by hydrolysis of Fe(III). With the introduction of passive pH control mechanisms, there was capacity to increase the volume of mine water treated by the ALD and LDS systems by 10 and 15 times, respectively, but it is uncertain as to whether or not other aspects of the passive treatment system would have sufficient capacity to deal with the increased volumes of mine water. PMID:15680628

  1. Effects of plant species on soil microbial processes and CH4 emission from constructed wetlands.

    PubMed

    Wang, Yanhua; Yang, Hao; Ye, Chun; Chen, Xia; Xie, Biao; Huang, Changchun; Zhang, Jixiang; Xu, Meina

    2013-03-01

    Methane (CH(4)) emission from constructed wetland has raised environmental concern. This study evaluated the influence of mono and polyculture constructed wetland and seasonal variation on CH(4) fluxes. Methane emission data showed large temporal variation ranging from 0 to 249.29 mg CH(4) m(-2) h(-1). Results indicated that the highest CH(4) flux was obtained in the polyculture system, planted with Phragmites australis, Zizania latifolia and Typha latifolia, reflecting polyculture system could stimulate CH(4) emission. FISH analysis showed the higher amount of methanotrophs in the profile of Z. latifolia in both mono and polyculture systems. The highest methanogens amount and relatively lower methanotrophs amount in the profile of polyculture system were obtained. The results support the characteristics of CH(4) fluxes. The polyculture constructed wetland has the higher potential of global warming. PMID:23291006

  2. Mechanistic Studies of Wacker-Type Intramolecular Aerobic Oxidative Amination of Alkenes Catalyzed by Pd(OAc)2/Pyridine

    PubMed Central

    Ye, Xuan; Liu, Guosheng; Popp, Brian V.; Stahl, Shannon S.

    2011-01-01

    Wacker-type oxidative cyclization reactions have been the subject of extensive research for several decades, but few systematic mechanistic studies of these reactions have been reported. The present study features experimental and DFT computational studies of Pd(OAc)2/pyridine-catalyzed intramolecular aerobic oxidative amination of alkenes. The data support a stepwise catalytic mechanism that consists of (1) steady-state formation of a PdII-amidate-alkene chelate with release of one equivalent of pyridine and AcOH from the catalyst center, (2) alkene insertion into a Pd–N bond, (3) reversible β-hydride elimination, (4) irreversible reductive elimination of AcOH, and (5) aerobic oxidation of palladium(0) to regenerate the active trans-Pd(OAc)2(py)2 catalyst. Evidence is obtained for two energetically viable pathways for the key C–N bond-forming step, featuring a pyridine-ligated and a pyridine-dissociated PdII species. Analysis of natural charges and bond lengths of the alkene-insertion transition state suggest that this reaction is best described as an intramolecular nucleophilic attack of the amidate ligand on the coordinated alkene. PMID:21250706

  3. How well can we assess impacts of agricultural land management changes on the total greenhouse gas balance (CO2, CH4 and N2O) of tropical rice-cropping systems with biogeochemical models?

    NASA Astrophysics Data System (ADS)

    Kraus, David; Weller, Sebastian; Janz, Baldur; Klatt, Steffen; Santabárbara, Ignacio; Haas, Edwin; Werner, Christian; Wassmann, Reiner; Kiese, Ralf; Butterbach-Bahl, Klaus

    2016-04-01

    Paddy rice cultivation is increasingly challenged by physical and economic irrigation water scarcity. This already results in the trend of converting paddy rice to upland crop cultivation (e.g., maize, aerobic rice) in large parts of South East Asia. Such land management change from flooded lowland systems to well-aerated upland systems drastically affects soil C and N cycling and related emissions of greenhouse gases. Emissions of methane (CH4) are expected to decrease, while emissions of nitrous oxide (N2O) will most likely increase. In addition to such fast evolving 'pollution swapping' it is expected that on longer time scales significant amounts of soil organic carbon (SOC) stocks will be lost in form of carbon dioxide (CO2). Within the DFG-funded research unit ICON (Introducing non-flooded crops in rice-dominated landscapes: Impact on carbon, nitrogen and water cycles), we investigated environmental impacts of land management change from historical paddy rice cultivation to the upland crops maize and aerobic rice at experimental sites at the International Rice Research Institute (IRRI), the Philippines. To present, more than three years of continuous measurement data of CH4 and N2O emissions under different fertilization regimes have been collected. In addition, measurements of SOC contents and bulk densities in different soil horizons allow for an overall very good characterization of the environmental impacts of mentioned land management change. In this contribution we will show how well mentioned land management change effects in tropical agricultural systems can be represented and thus better understood by the help of process-based biogeochemical models. Seasonal emissions of CH4 and N2O are simulated with r2 values of 0.85 and 0.78 and average underestimations of 15 and 14 %, respectively. These underestimations predominantly originate from treatments in which no fertilizer is applied (CH4) as well as uncertainties of soil hydrology (N2O). Long

  4. How well can we assess impacts of agricultural land management changes on the total greenhouse gas balance (CO2, CH4 and N2O) of tropical rice-cropping systems with biogeochemical models?

    NASA Astrophysics Data System (ADS)

    Kraus, David; Weller, Sebastian; Janz, Baldur; Klatt, Steffen; Santabárbara, Ignacio; Haas, Edwin; Werner, Christian; Wassmann, Reiner; Kiese, Ralf; Butterbach-Bahl, Klaus

    2016-04-01

    Paddy rice cultivation is increasingly challenged by physical and economic irrigation water scarcity. This already results in the trend of converting paddy rice to upland crop cultivation (e.g., maize, aerobic rice) in large parts of South East Asia. Such land management change from flooded lowland systems to well-aerated upland systems drastically affects soil C and N cycling and related emissions of greenhouse gases. Emissions of methane (CH4) are expected to decrease, while emissions of nitrous oxide (N2O) will most likely increase. In addition to such fast evolving 'pollution swapping' it is expected that on longer time scales significant amounts of soil organic carbon (SOC) stocks will be lost in form of carbon dioxide (CO2). Within the DFG-funded research unit ICON (Introducing non-flooded crops in rice-dominated landscapes: Impact on carbon, nitrogen and water cycles), we investigated environmental impacts of land management change from historical paddy rice cultivation to the upland crops maize and aerobic rice at experimental sites at the International Rice Research Institute (IRRI), the Philippines. To present, more than three years of continuous measurement data of CH4 and N2O emissions under different fertilization regimes have been collected. In addition, measurements of SOC contents and bulk densities in different soil horizons allow for an overall very good characterization of the environmental impacts of mentioned land management change. In this contribution we will show how well mentioned land management change effects in tropical agricultural systems can be represented and thus better understood by the help of process-based biogeochemical models. Seasonal emissions of CH4 and N2O are simulated with r2 values of 0.85 and 0.78 and average underestimations of 15 and 14 %, respectively. These underestimations predominantly originate from treatments in which no fertilizer is applied (CH4) as well as uncertainties of soil hydrology (N2O). Long

  5. Complete Genome Sequence of the Aerobic CO-Oxidizing Thermophile Thermomicrobium roseum

    PubMed Central

    Wu, Dongying; Raymond, Jason; Wu, Martin; Chatterji, Sourav; Ren, Qinghu; Graham, Joel E.; Bryant, Donald A.; Robb, Frank; Colman, Albert; Tallon, Luke J.; Badger, Jonathan H.; Madupu, Ramana; Ward, Naomi L.; Eisen, Jonathan A.

    2009-01-01

    In order to enrich the phylogenetic diversity represented in the available sequenced bacterial genomes and as part of an “Assembling the Tree of Life” project, we determined the genome sequence of Thermomicrobium roseum DSM 5159. T. roseum DSM 5159 is a red-pigmented, rod-shaped, Gram-negative extreme thermophile isolated from a hot spring that possesses both an atypical cell wall composition and an unusual cell membrane that is composed entirely of long-chain 1,2-diols. Its genome is composed of two circular DNA elements, one of 2,006,217 bp (referred to as the chromosome) and one of 919,596 bp (referred to as the megaplasmid). Strikingly, though few standard housekeeping genes are found on the megaplasmid, it does encode a complete system for chemotaxis including both chemosensory components and an entire flagellar apparatus. This is the first known example of a complete flagellar system being encoded on a plasmid and suggests a straightforward means for lateral transfer of flagellum-based motility. Phylogenomic analyses support the recent rRNA-based analyses that led to T. roseum being removed from the phylum Thermomicrobia and assigned to the phylum Chloroflexi. Because T. roseum is a deep-branching member of this phylum, analysis of its genome provides insights into the evolution of the Chloroflexi. In addition, even though this species is not photosynthetic, analysis of the genome provides some insight into the origins of photosynthesis in the Chloroflexi. Metabolic pathway reconstructions and experimental studies revealed new aspects of the biology of this species. For example, we present evidence that T. roseum oxidizes CO aerobically, making it the first thermophile known to do so. In addition, we propose that glycosylation of its carotenoids plays a crucial role in the adaptation of the cell membrane to this bacterium's thermophilic lifestyle. Analyses of published metagenomic sequences from two hot springs similar to the one from which this strain

  6. Stable TEMPO and ABNO Catalyst Solutions for User-Friendly (bpy)Cu/Nitroxyl-Catalyzed Aerobic Alcohol Oxidation.

    PubMed

    Steves, Janelle E; Stahl, Shannon S

    2015-11-01

    Two solutions, one consisting of bpy/TEMPO/NMI and the other bpy/ABNO/NMI (bpy =2,2'-bipyridyl; TEMPO = 2,2,6,6-tetramethylpiperidine N-oxyl, ABNO = 9-azabicyclo[3.3.1]nonane N-oxyl; NMI = N-methylimidazole), in acetonitrile are shown to have good long-term stability (≥1 year) under air at 5 °C. The solutions may be combined in appropriate quantities with commercially available [Cu(MeCN)4]OTf to provide a convenient catalyst system for the aerobic oxidation of primary and secondary alcohols.

  7. Experimental Limiting Oxygen Concentrations for Nine Organic Solvents at Temperatures and Pressures Relevant to Aerobic Oxidations in the Pharmaceutical Industry

    PubMed Central

    2015-01-01

    Applications of aerobic oxidation methods in pharmaceutical manufacturing are limited in part because mixtures of oxygen gas and organic solvents often create the potential for a flammable atmosphere. To address this issue, limiting oxygen concentration (LOC) values, which define the minimum partial pressure of oxygen that supports a combustible mixture, have been measured for nine commonly used organic solvents at elevated temperatures and pressures. The solvents include acetic acid, N-methylpyrrolidone, dimethyl sulfoxide, tert-amyl alcohol, ethyl acetate, 2-methyltetrahydrofuran, methanol, acetonitrile, and toluene. The data obtained from these studies help define safe operating conditions for the use of oxygen with organic solvents. PMID:26622165

  8. Stable TEMPO and ABNO Catalyst Solutions for User-Friendly (bpy)Cu/Nitroxyl-Catalyzed Aerobic Alcohol Oxidation.

    PubMed

    Steves, Janelle E; Stahl, Shannon S

    2015-11-01

    Two solutions, one consisting of bpy/TEMPO/NMI and the other bpy/ABNO/NMI (bpy =2,2'-bipyridyl; TEMPO = 2,2,6,6-tetramethylpiperidine N-oxyl, ABNO = 9-azabicyclo[3.3.1]nonane N-oxyl; NMI = N-methylimidazole), in acetonitrile are shown to have good long-term stability (≥1 year) under air at 5 °C. The solutions may be combined in appropriate quantities with commercially available [Cu(MeCN)4]OTf to provide a convenient catalyst system for the aerobic oxidation of primary and secondary alcohols. PMID:26457658

  9. Method for Indirect Quantification of CH4 Production via H2O Production Using Hydrogenotrophic Methanogens.

    PubMed

    Taubner, Ruth-Sophie; Rittmann, Simon K-M R

    2016-01-01

    Hydrogenotrophic methanogens are an intriguing group of microorganisms from the domain Archaea. Methanogens exhibit extraordinary ecological, biochemical, and physiological characteristics and possess a huge biotechnological potential. Yet, the only possibility to assess the methane (CH4) production potential of hydrogenotrophic methanogens is to apply gas chromatographic quantification of CH4. In order to be able to effectively screen pure cultures of hydrogenotrophic methanogens regarding their CH4 production potential we developed a novel method for indirect quantification of the volumetric CH4 production rate by measuring the volumetric water production rate. This method was established in serum bottles for cultivation of methanogens in closed batch cultivation mode. Water production was estimated by determining the difference in mass increase in a quasi-isobaric setting. This novel CH4 quantification method is an accurate and precise analytical technique, which can be used to rapidly screen pure cultures of methanogens regarding their volumetric CH4 evolution rate. It is a cost effective alternative determining CH4 production of methanogens over CH4 quantification by using gas chromatography, especially if applied as a high throughput quantification method. Eventually, the method can be universally applied for quantification of CH4 production from psychrophilic, thermophilic and hyperthermophilic hydrogenotrophic methanogens. PMID:27199898

  10. Method for Indirect Quantification of CH4 Production via H2O Production Using Hydrogenotrophic Methanogens

    PubMed Central

    Taubner, Ruth-Sophie; Rittmann, Simon K.-M. R.

    2016-01-01

    Hydrogenotrophic methanogens are an intriguing group of microorganisms from the domain Archaea. Methanogens exhibit extraordinary ecological, biochemical, and physiological characteristics and possess a huge biotechnological potential. Yet, the only possibility to assess the methane (CH4) production potential of hydrogenotrophic methanogens is to apply gas chromatographic quantification of CH4. In order to be able to effectively screen pure cultures of hydrogenotrophic methanogens regarding their CH4 production potential we developed a novel method for indirect quantification of the volumetric CH4 production rate by measuring the volumetric water production rate. This method was established in serum bottles for cultivation of methanogens in closed batch cultivation mode. Water production was estimated by determining the difference in mass increase in a quasi-isobaric setting. This novel CH4 quantification method is an accurate and precise analytical technique, which can be used to rapidly screen pure cultures of methanogens regarding their volumetric CH4 evolution rate. It is a cost effective alternative determining CH4 production of methanogens over CH4 quantification by using gas chromatography, especially if applied as a high throughput quantification method. Eventually, the method can be universally applied for quantification of CH4 production from psychrophilic, thermophilic and hyperthermophilic hydrogenotrophic methanogens. PMID:27199898

  11. The atmospheric CH4 increase since the Last Glacial Maximum. I - Source estimates

    NASA Astrophysics Data System (ADS)

    Chappellaz, Jerome A.; Fung, Inez Y.; Thompson, Anne M.

    1993-07-01

    An estimate of the distribution of wetland area and associated CH4 emission is presented for the Last Glacial Maximum (LGM, 18 kyr BP, kiloyear Before Present) and the Pre-Industrial Holocene (PIH, 9000-200 years BP). The wetland source, combined with estimates of the other biogenic sources and sink, yields total source strengths of 120 and 180 Tg CH4/yr for LGM and PIH respectively. These source strengths are shown to be consistent with source estimates inferred from a photochemical model, and point to changes in wetland CH4 source as a major factor driving the atmospheric CH4 increase from LGM to PIH.

  12. The atmospheric CH4 increase since the Last Glacial Maximum. I - Source estimates

    NASA Technical Reports Server (NTRS)

    Chappellaz, Jerome A.; Fung, Inez Y.; Thompson, Anne M.

    1993-01-01

    An estimate of the distribution of wetland area and associated CH4 emission is presented for the Last Glacial Maximum (LGM, 18 kyr BP, kiloyear Before Present) and the Pre-Industrial Holocene (PIH, 9000-200 years BP). The wetland source, combined with estimates of the other biogenic sources and sink, yields total source strengths of 120 and 180 Tg CH4/yr for LGM and PIH respectively. These source strengths are shown to be consistent with source estimates inferred from a photochemical model, and point to changes in wetland CH4 source as a major factor driving the atmospheric CH4 increase from LGM to PIH.

  13. Understanding effect of structure and stability on transformation of CH4 hydrate to CO2 hydrate

    NASA Astrophysics Data System (ADS)

    Liu, Jinxiang; Yan, Yujie; Liu, Haiying; Xu, Jiafang; Zhang, Jun; Chen, Gang

    2016-03-01

    Understanding the transformation process of CH4 hydrate to CO2 hydrate is crucial to develop the CH4sbnd CO2 replacement technique for CH4 production and CO2 sequestration. Ab initio calculations show that the transformation will slightly distort the host lattice and decrease the binding strength of guest molecules, but it is a thermodynamically spontaneous process dominated by the entropic contribution. Moreover, ab initio molecular dynamics simulations suggest that the dynamics of the host lattice is independent on the guest molecules, while CO2 in hydrate exhibits slower translational and rotational motion than CH4 in hydrate.

  14. Summertime N2O, CH4 and CO2 exchanges from a tundra marsh and an upland tundra in maritime Antarctica

    NASA Astrophysics Data System (ADS)

    Zhu, Renbin; Ma, Dawei; Xu, Hua

    2014-02-01

    This study provides the first concurrent measurements of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) fluxes from a tundra marsh and an upland tundra in maritime Antarctica over the summers of 2007/2008 and 2011/2012. Tundra N2O and CH4 fluxes showed large spatial variations depending on local hydrological regimes. N2O sinks generally occurred at waterlogged marsh sites (-3.0 to 27.5 μg N2O m-2 h-1) whereas relatively dry and mesic sites presented weak or strong N2O sources (2.2-41.6 μg N2O m-2 h-1). Upland tundra sites showed negligible N2O emissions due to low soil TN and NH4+-N contents. Dry/upland tundra sites showed weak to strong CH4 uptake (-4.5 to -85.8 μg CH4 m-2 h-1). The waterlogged sites showed weak to strong CH4 emissions (29.8 μg CH4 m-2 h-1-2.4 mg CH4 m-2 h-1). Both tundra marsh and upland tundra experienced a large net CO2 uptake with the greatest mean CO2 uptake rate (-92.1 mg CO2 m-2 h-1) at dry marsh sites. Mean ecosystem respiration (ER) ranged between 82.5 ± 13.2 and 174.9 ± 25.7 mg CO2 m-2 h-1 at all the sites, and showed a strong exponential correlation (P < 0.001) with 0-10 cm soil temperature. Gross photosynthesis (Pg) was more than two times higher in tundra marsh than in upland tundra due to the difference of vegetation coverage. N2O flux showed a strong negative correlation (P < 0.01) with 0-10 cm soil temperature at the marsh sites, and significant or weak positive correlations with total daily radiation (TDR) and sunlight time (ST). No significant correlation was obtained between CH4 fluxes and environmental variables at tundra marsh and upland tundra sites. There was a significant negative correlation (P < 0.01) between NEE and 0-10 cm mean soil temperature, total daily radiation. Our results indicated that the lowering of water table significantly increased N2O emissions and CH4 consumption, but decreased C loss from the tundra marsh. In the future, the combination of climate warming and frequent precipitation

  15. Rotational study of the CH4-CO complex: Millimeter-wave measurements and ab initio calculations.

    PubMed

    Surin, L A; Tarabukin, I V; Panfilov, V A; Schlemmer, S; Kalugina, Y N; Faure, A; Rist, C; van der Avoird, A

    2015-10-21

    The rotational spectrum of the van der Waals complex CH4-CO has been measured with the intracavity OROTRON jet spectrometer in the frequency range of 110-145 GHz. Newly observed and assigned transitions belong to the K = 2-1 subband correlating with the rotationless jCH4 = 0 ground state and the K = 2-1 and K = 0-1 subbands correlating with the jCH4 = 2 excited state of free methane. The (approximate) quantum number K is the projection of the total angular momentum J on the intermolecular axis. The new data were analyzed together with the known millimeter-wave and microwave transitions in order to determine the molecular parameters of the CH4-CO complex. Accompanying ab initio calculations of the intermolecular potential energy surface (PES) of CH4-CO have been carried out at the explicitly correlated coupled cluster level of theory with single, double, and perturbative triple excitations [CCSD(T)-F12a] and an augmented correlation-consistent triple zeta (aVTZ) basis set. The global minimum of the five-dimensional PES corresponds to an approximately T-shaped structure with the CH4 face closest to the CO subunit and binding energy De = 177.82 cm(-1). The bound rovibrational levels of the CH4-CO complex were calculated for total angular momentum J = 0-6 on this intermolecular potential surface and compared with the experimental results. The calculated dissociation energies D0 are 91.32, 94.46, and 104.21 cm(-1) for A (jCH4 = 0), F (jCH4 = 1), and E (jCH4 = 2) nuclear spin modifications of CH4-CO, respectively.

  16. Rotational study of the CH4-CO complex: Millimeter-wave measurements and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Surin, L. A.; Tarabukin, I. V.; Panfilov, V. A.; Schlemmer, S.; Kalugina, Y. N.; Faure, A.; Rist, C.; van der Avoird, A.

    2015-10-01

    The rotational spectrum of the van der Waals complex CH4-CO has been measured with the intracavity OROTRON jet spectrometer in the frequency range of 110-145 GHz. Newly observed and assigned transitions belong to the K = 2-1 subband correlating with the rotationless jCH4 = 0 ground state and the K = 2-1 and K = 0-1 subbands correlating with the jCH4 = 2 excited state of free methane. The (approximate) quantum number K is the projection of the total angular momentum J on the intermolecular axis. The new data were analyzed together with the known millimeter-wave and microwave transitions in order to determine the molecular parameters of the CH4-CO complex. Accompanying ab initio calculations of the intermolecular potential energy surface (PES) of CH4-CO have been carried out at the explicitly correlated coupled cluster level of theory with single, double, and perturbative triple excitations [CCSD(T)-F12a] and an augmented correlation-consistent triple zeta (aVTZ) basis set. The global minimum of the five-dimensional PES corresponds to an approximately T-shaped structure with the CH4 face closest to the CO subunit and binding energy De = 177.82 cm-1. The bound rovibrational levels of the CH4-CO complex were calculated for total angular momentum J = 0-6 on this intermolecular potential surface and compared with the experimental results. The calculated dissociation energies D0 are 91.32, 94.46, and 104.21 cm-1 for A (jCH4 = 0), F (jCH4 = 1), and E (jCH4 = 2) nuclear spin modifications of CH4-CO, respectively.

  17. Multi-regional input-output analysis for China's regional CH4 emissions

    NASA Astrophysics Data System (ADS)

    Zhang, Bo; Li, Jiashuo; Peng, Beihua

    2014-03-01

    China is the largest CH4 emitter in the world. Given the importance of CH4 in greenhouse gas emission inventories, the characteristics of China's CH4 emissions at different scales deserve to be fully understood. Presented in this paper is an interprovincial input-output embodiment analysis of China's regional CH4 emissions in 2007, based on the most recently available multi-regional input-output table, and relevant CH4 emissions data. The results show that the eastern, central and western areas contribute to 48.2%, 28.6%, and 23.3% of the national total embodied emissions, respectively. Guangdong has the highest level of embodied CH4 emissions among all of the 30 regions. The Agriculture sector produces the most embodied CH4 emissions in final demand, followed by the Construction, Food Production and Tobacco Processing, and Other Service Activities sectors. Significant net transfers of embodied CH4 emission flows are identified from the central and western areas to the eastern area via interregional trade. Shanxi is the largest interregional exporter of embodied CH4 emissions. In contrast, Guangdong is the largest interregional importer. Energy activities, agricultural activities, and waste management comprise 65.6%, 30.7%, and 3.7% of the total embodied CH4 emissions in interregional trade, respectively. By using consumption-based accounting principles, the emission magnitudes, per capita emissions, and emission intensities of most eastern regions increase remarkably, while those of some central and western regions decrease largely. To achieve regional CH4 emission mitigation, comprehensive mitigation measures should be designed under consideration of regional transfer of emission responsibility.

  18. Rotational study of the CH4-CO complex: Millimeter-wave measurements and ab initio calculations.

    PubMed

    Surin, L A; Tarabukin, I V; Panfilov, V A; Schlemmer, S; Kalugina, Y N; Faure, A; Rist, C; van der Avoird, A

    2015-10-21

    The rotational spectrum of the van der Waals complex CH4-CO has been measured with the intracavity OROTRON jet spectrometer in the frequency range of 110-145 GHz. Newly observed and assigned transitions belong to the K = 2-1 subband correlating with the rotationless jCH4 = 0 ground state and the K = 2-1 and K = 0-1 subbands correlating with the jCH4 = 2 excited state of free methane. The (approximate) quantum number K is the projection of the total angular momentum J on the intermolecular axis. The new data were analyzed together with the known millimeter-wave and microwave transitions in order to determine the molecular parameters of the CH4-CO complex. Accompanying ab initio calculations of the intermolecular potential energy surface (PES) of CH4-CO have been carried out at the explicitly correlated coupled cluster level of theory with single, double, and perturbative triple excitations [CCSD(T)-F12a] and an augmented correlation-consistent triple zeta (aVTZ) basis set. The global minimum of the five-dimensional PES corresponds to an approximately T-shaped structure with the CH4 face closest to the CO subunit and binding energy De = 177.82 cm(-1). The bound rovibrational levels of the CH4-CO complex were calculated for total angular momentum J = 0-6 on this intermolecular potential surface and compared with the experimental results. The calculated dissociation energies D0 are 91.32, 94.46, and 104.21 cm(-1) for A (jCH4 = 0), F (jCH4 = 1), and E (jCH4 = 2) nuclear spin modifications of CH4-CO, respectively. PMID:26493903

  19. Temperature Effects on Microbial CH4 and CO2 Production in Permafrost-Affected Soils From the Barrow Environmental Observatory

    NASA Astrophysics Data System (ADS)

    Graham, D. E.; Roy Chowdhury, T.; Zheng, J.; Moon, J. W.; Yang, Z.; Gu, B.; Wullschleger, S. D.

    2015-12-01

    Warmer Arctic temperatures are increasing the annual soil thaw depth and prolonging the thaw season in Alaskan permafrost zones. This change exposes organic matter buried in the soils and permafrost to microbial degradation and mineralization to form CO2 and CH4. The proportion and fluxes of these greenhouse gases released into the atmosphere control the global feedback on warming. To improve representations of these biogeochemical processes in terrestrial ecosystem models we compared soil properties and microbial activities in core samples of polygonal tundra from the Barrow Environmental Observatory. Measurements of soil water potential through the soil column characterized water binding to the organic and mineral components. This suction combines with temperature to control freezing, gas diffusion and microbial activity. The temperature-dependence of CO2 and CH4 production from anoxic soil incubations at -2, +4 or +8 °C identified a significant lag in methanogenesis relative to CO2 production by anaerobic respiration and fermentation. Changes in the abundance of methanogen signature genes during incubations indicate that microbial population shifts caused by thawing and warmer temperatures drive changes in the mixtures of soil carbon degradation products. Comparisons of samples collected across the microtopographic features of ice-wedge polygons address the impacts of water saturation, iron reduction and organic matter content on CH4 production and oxidation. These combined measurements build process understanding that can be applied across scales to constrain key response factors in models that address Arctic soil warming.

  20. Attributing changes in atmospheric methane 1850-2000 to changes in CH4, NOx, CO, and NMVOC emissions (Invited)

    NASA Astrophysics Data System (ADS)

    Stevenson, D. S.

    2013-12-01

    Global atmospheric methane concentrations rose from 791 ppb in 1850 to 1751 ppb in 2000, with an associated radiative forcing (RF) of 427 mW m-2. This growth can be attributed to several factors - here we focus on changes in anthropogenic emissions of methane itself, but also on emissions of nitrogen oxides (NOx), carbon monoxide (CO) and non-methane hydrocarbons (NMVOC). Within the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP), six models conducted sensitivity experiments and found that CH4 emissions alone produced a CH4 RF of 533 mW m-2; other contributions (mW m-2) were: NOx, -312; CO, 58; and NMVOC, 35. These four numbers sum to 300, not 427, indicating that the RFs cannot be simply added, and that important interactions between emitted species have occurred. A further suite of sensitivity experiments were carried out with one of the ACCMIP models (STOC-HadAM3), changing combinations of emissions, to investigate these interactions in more detail. The largest sources of non-linearity are from interactions between emitted NOx and the other emitted species. These results indicate that a simple, individual species attribution of CH4 RF to emitted species is only approximately correct, and hides important interactions. These interactions will probably depend on individual model's chemical schemes, and they present a further difficulty in communicating robust results on short-lived climate forcing agents to policymakers.

  1. The emissions and soil concentrations of N2O and CH4 from natural soil temperature gradients in a volcanic area in southwest Iceland

    NASA Astrophysics Data System (ADS)

    Maljanen, Marja; Yli-Moijala, Heli; Leblans, Niki I. W.; De Boeck, Hans J.; Bjarnadóttir, Brynhildur; Sigurdsson, Bjarni D.

    2016-04-01

    We studied nitrous oxide (N2O) and methane (CH4) emissions along three natural geothermal soil temperature (Ts) gradients in a volcanic area in southwest Iceland. Two of the gradients (on a grassland and a forest site, respectively) were recently formed (in May 2008). The third gradient, a grassland site, had been subjected to long-term soil warming (over 30 years, and probably centuries). Nitrous oxide and methane emissions were measured along the temperature gradients using the static chamber method and also soil gas concentrations were studied. With a moderate soil temperature increase (up to +5 °C) there were no significant increase in gas flux rates in any of the sites but an increase of 20 to 45 °C induced an increase in both N2O and CH4 emissions. The measured N2O emissions (up to 2600 μg N2O m-2 h-1) from the warmest plots were about two magnitudes higher compared with the coolest plots (less than 20 μg N2O m-2 h-1). While a net uptake of CH4 was measured in the coolest plots (up to -0.15 mg CH4 m-2 h-1), a net emission of CH4 was measured from the warmest plots (up to 1.3 mg CH4 m-2 h-1). Soil CH4 concentrations decreased first with a moderate (up to +5 °C) increase in Ts, but above that threshold increased significantly. The soil N2O concentration at depths from 5 to 20 cm increased with increasing Ts, indicating enhanced N-turnover. Further, there was a clear decrease in soil organic matter (SOM), C- and N concentration with increasing Ts at all sites. One should note, however, that a part of the N2O emitted from the warmest plots may be partly geothermally derived, as was revealed by 15N2O isotope studies. These natural Ts gradients show that the emission of N2O and CH4 can increase significantly when Ts increases considerably. This implies that these geothermally active sites can act as local hot spots for CH4 and N2O emissions.

  2. P-Doped Porous Carbon as Metal Free Catalysts for Selective Aerobic Oxidation with an Unexpected Mechanism.

    PubMed

    Patel, Mehulkumar A; Luo, Feixiang; Khoshi, M Reza; Rabie, Emann; Zhang, Qing; Flach, Carol R; Mendelsohn, Richard; Garfunkel, Eric; Szostak, Michal; He, Huixin

    2016-02-23

    An extremely simple and rapid (seconds) approach is reported to directly synthesize gram quantities of P-doped graphitic porous carbon materials with controlled P bond configuration. For the first time, it is demonstrated that the P-doped carbon materials can be used as a selective metal free catalyst for aerobic oxidation reactions. The work function of P-doped carbon materials, its connectivity to the P bond configuration, and the correlation with its catalytic efficiency are studied and established. In direct contrast to N-doped graphene, the P-doped carbon materials with higher work function show high activity in catalytic aerobic oxidation. The selectivity trend for the electron donating and withdrawing properties of the functional groups attached to the aromatic ring of benzyl alcohols is also different from other metal free carbon based catalysts. A unique catalytic mechanism is demonstrated, which differs from both GO and N-doped graphene obtained by high temperature nitrification. The unique and unexpected catalytic pathway endows the P-doped materials with not only good catalytic efficiency but also recyclability. This, combined with a rapid, energy saving approach that permits fabrication on a large scale, suggests that the P-doped porous materials are promising materials for "green catalysis" due to their higher theoretical surface area, sustainability, environmental friendliness, and low cost.

  3. The synthesis of a bifunctional copper metal organic framework and its application in the aerobic oxidation/Knoevenagel condensation sequential reaction.

    PubMed

    Miao, Zongcheng; Luan, Yi; Qi, Chao; Ramella, Daniele

    2016-09-21

    A novel one-pot aerobic oxidation/Knoevenagel condensation reaction system was developed employing a Cu(ii)/amine bifunctional, basic metal-organic framework (MOF) as the catalyst. The sequential aerobic alcohol oxidation/Knoevenagel condensation reaction was efficiently promoted by the Cu3TATAT MOF catalyst in the absence of basic additives. The benzylidenemalononitrile product was produced in high yield and selectivity from an inexpensive benzyl alcohol starting material under an oxygen atmosphere. The role of the basic functionality was studied to demonstrate its role in the aerobic oxidation and Knoevenagel condensation reactions. The reaction progress was monitored in order to identify the reaction intermediate and follow the accumulation of the desired product. Lastly, results showed that the yield was not significantly compromised by the reuse of a batch of catalyst, even after more than five cycles.

  4. The synthesis of a bifunctional copper metal organic framework and its application in the aerobic oxidation/Knoevenagel condensation sequential reaction.

    PubMed

    Miao, Zongcheng; Luan, Yi; Qi, Chao; Ramella, Daniele

    2016-09-21

    A novel one-pot aerobic oxidation/Knoevenagel condensation reaction system was developed employing a Cu(ii)/amine bifunctional, basic metal-organic framework (MOF) as the catalyst. The sequential aerobic alcohol oxidation/Knoevenagel condensation reaction was efficiently promoted by the Cu3TATAT MOF catalyst in the absence of basic additives. The benzylidenemalononitrile product was produced in high yield and selectivity from an inexpensive benzyl alcohol starting material under an oxygen atmosphere. The role of the basic functionality was studied to demonstrate its role in the aerobic oxidation and Knoevenagel condensation reactions. The reaction progress was monitored in order to identify the reaction intermediate and follow the accumulation of the desired product. Lastly, results showed that the yield was not significantly compromised by the reuse of a batch of catalyst, even after more than five cycles. PMID:27523776

  5. N 2O emissions at municipal solid waste landfill sites: Effects of CH 4 emissions and cover soil

    NASA Astrophysics Data System (ADS)

    Zhang, Houhu; He, Pinjing; Shao, Liming

    Municipal solid waste landfills are the significant anthropogenic sources of N 2O due to the cooxidation of ammonia by methane-oxidizing bacteria in cover soils. Such bacteria could be developed through CH 4 fumigation, as evidenced by both laboratory incubation and field measurement. During a 10-day incubation with leachate addition, the average N 2O fluxes in the soil samples, collected from the three selected landfill covers, were multiplied by 1.75 ( p < 0.01), 3.56 ( p < 0.01), and 2.12 ( p < 0.01) from the soil samples preincubated with 5% CH 4 for three months when compared with the control, respectively. Among the three selected landfill sites, N 2O fluxes in two landfill sites were significantly correlated with the variations of the CH 4 emissions without landfill gas recovery ( p < 0.001). N 2O fluxes were also elevated by the increase of the CH 4 emissions with landfill gas recovery in another landfill site ( p > 0.05). The annual average N 2O flux was 176 ± 566 μg N 2O-N m -2 h -1 ( p < 0.01) from sandy soil-covered landfill site, which was 72% ( p < 0.05) and 173% ( p < 0.01) lower than the other two clay soil covered landfill sites, respectively. The magnitude order of N 2O emissions in three landfill sites was also coincident by the results of laboratory incubation, suggesting the sandy soil cover could mitigate landfill N 2O emissions.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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 to 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. 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 to background fluxes measured during periods without management (< 5nmol 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.

  7. Design of Highly Selective Platinum Nanoparticle Catalysts for the Aerobic Oxidation of KA-Oil using Continuous-Flow Chemistry.

    PubMed

    Gill, Arran M; Hinde, Christopher S; Leary, Rowan K; Potter, Matthew E; Jouve, Andrea; Wells, Peter P; Midgley, Paul A; Thomas, John M; Raja, Robert

    2016-03-01

    Highly active and selective aerobic oxidation of KA-oil to cyclohexanone (precursor for adipic acid and ɛ-caprolactam) has been achieved in high yields using continuous-flow chemistry by utilizing uncapped noble-metal (Au, Pt & Pd) nanoparticle catalysts. These are prepared using a one-step in situ methodology, within three-dimensional porous molecular architectures, to afford robust heterogeneous catalysts. Detailed spectroscopic characterization of the nature of the active sites at the molecular level, coupled with aberration-corrected scanning transmission electron microscopy, reveals that the synthetic methodology and associated activation procedures play a vital role in regulating the morphology, shape and size of the metal nanoparticles. These active centers have a profound influence on the activation of molecular oxygen for selective catalytic oxidations.

  8. The Unique Gas-Phase Chemistry of the [AuO](+) /CH4 Couple: Selective Oxygen-Atom Transfer to, Rather than Hydrogen-Atom Abstraction from, Methane.

    PubMed

    Zhou, Shaodong; Li, Jilai; Schlangen, Maria; Schwarz, Helmut

    2016-08-26

    The thermal reaction of [AuO](+) with methane has been explored using FT-ICR mass spectrometry complemented by high-level quantum chemical calculations. In contrast to the previously studied congener [CuO](+) , and to [AgO](+) , [AuO](+) reacts with CH4 exclusively via oxygen-atom transfer to form CH3 OH, and a novel mechanistic scenario for this selective oxidation process has been revealed. Also, the origin of the inertness of the [AgO](+) /CH4 couple has been addressed computationally. PMID:27390885

  9. 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

  10. Sequential chemical oxidation and aerobic biodegradation of equivalent carbon number-based hydrocarbon fractions in jet fuel.

    PubMed

    Xie, Guibo; Barcelona, Michael J

    2003-10-15

    Remediation of petroleum mixtures is complicated by the differing environmental degradabilities of hundreds of individual hydrocarbons in the mixtures. By grouping the individual hydrocarbons into a few fractions based on equivalent carbon number (EC), the present study examined the chemical and biological degradation of the fractions. With or without prechemical oxidation (25 days) by three oxidants (KMnO4, H202, MgO2), sterile and live microcosms were constituted with aquifer samples for aerobic biodegradation (134 days) of JP-4 jet fuel. Eighty-seven hydrocarbons were recovered and grouped into nine EC fractions. The apparent removal and actual transformation rate constants were estimated for both chemical and biological degradations. The data show that prechemical oxidations facilitated removal of total petroleum hydrocarbons (TPH) (up to 80%) within shorter times (<50 days) than biological alone. KMnO4 and H202 were better oxidants in terms of mass reduction in shorter times yet to some extent inhibited the subsequent microbial activity. MgO2 was a moderate oxidant with less inhibition of microbial activity. Selective degradation of the EC fractions was observed for both chemical and biological processes. The biological processes were much less effective than the prechemical oxidations in transforming aromatic fractions, the more toxic fractions. The favorable substrates (i.e., aliphatic EC approximately 10) for microbial growth were also those most subject to chemical oxidation. The results suggest that for remediation of petroleum contaminants, sequential chemical and biological technologies may surpass biological alone and more moderate oxidants such as MgO2 may be better candidates. More work is needed on the optimal dose and residence time for applied oxidants and on the application to engineering design and formulation of cleanup standards.

  11. The description and validation of the computationally Efficient CH4-CO-OH (ECCOHv1.01) chemistry module for 3-D model applications

    NASA Astrophysics Data System (ADS)

    Elshorbany, Yasin F.; Duncan, Bryan N.; Strode, Sarah A.; Wang, James S.; Kouatchou, Jules

    2016-02-01

    We present the Efficient CH4-CO-OH (ECCOH) chemistry module that allows for the simulation of the methane, carbon monoxide, and hydroxyl radical (CH4-CO-OH) system, within a chemistry climate model, carbon cycle model, or Earth system model. The computational efficiency of the module allows many multi-decadal sensitivity simulations of the CH4-CO-OH system, which primarily determines the global atmospheric oxidizing capacity. This capability is important for capturing the nonlinear feedbacks of the CH4-CO-OH system and understanding the perturbations to methane, CO, and OH, and the concomitant impacts on climate. We implemented the ECCOH chemistry module in the NASA GEOS-5 atmospheric global circulation model (AGCM), performed multiple sensitivity simulations of the CH4-CO-OH system over 2 decades, and evaluated the model output with surface and satellite data sets of methane and CO. The favorable comparison of output from the ECCOH chemistry module (as configured in the GEOS-5 AGCM) with observations demonstrates the fidelity of the module for use in scientific research.

  12. Kinetics of the CI(2PJ) + CH4 Reaction: Effects of Secondary Chemistry Below 300k

    NASA Technical Reports Server (NTRS)

    Keyser, L.; Wang, J.

    1999-01-01

    Because of the relatively large disagreement among earlier measurements at low temperatures, the results were examined for possible effects of non-Boltzmann spin distribution and vibrational excitation of CH4, secondary chemistry of CH3 radicals,and impuities in the CH4 source.

  13. From California dreaming to California data: Challenging historic models for landfill CH4 emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Improved quantification of diverse CH4 sources at the urban scale is needed to guide local greenhouse gas (GHG) mitigation strategies in the Anthropocene. Herein, we focus on landfill CH4 emissions in California, challenging the current IPCC methodology which focuses on a climate dependency for land...

  14. Contribution of winter to the annual CH4 emission from a eutrophied boreal lake.

    PubMed

    Huttunen, Jari T; Alm, Jukka; Saarijärvi, Erkki; Lappalainen, K Matti; Silvola, Jouko; Martikainen, Pertti J

    2003-01-01

    The springtime methane (CH4) emission from a small, eutrophied boreal lake was assessed during the winter ice-cover by measurement of gas ebullition and CH4 accumulation in the water column in association with the development of oxygen depletion after ice formation. The winter CH4 production was estimated to result in a loss of 3.6-7.9 g CH4 m(-2) from the lake to the atmosphere during the short period of ice melt. This could account for 22-48% of the annual CH4 emission from the pelagic zone of the lake. The contribution of winter to the annual CH4 release can be similar or even higher in seasonally ice-covered northern aquatic ecosystems than in northern terrestrial wetlands, thus winter must be considered in any studies into the aquatic CH4 emissions. The trophic state and wintertime oxygen conditions, linked to the changes in land-use in the catchments and climate, are important factors controlling the springtime lake CH4 emissions. PMID:12653296

  15. Early Mars Serpentinization Derived CH4 Reservoirs and H2 Induced Warming

    NASA Astrophysics Data System (ADS)

    Chassefiere, E.; Lasue, J.; Langlais, B.; Quesnel, Y.

    2014-11-01

    The early martian cryosphere has potentiality trapped all the CH4 released by early serpentinization, which could explain sporadic release of CH4 today. The H2 released may have increased surface temperature above 0°C during 2 107 yr.

  16. Palladium-Catalyzed Aerobic Oxidative Dehydrogenation of Cyclohexenes to Substituted Arene Derivatives

    PubMed Central

    Iosub, Andrei V.; Stahl, Shannon S.

    2015-01-01

    A palladium(II) catalyst system has been identified for aerobic dehydrogenation of substituted cyclohexenes to the corresponding arene derivatives. Use of sodium anthraquinone-2-sulfonate (AMS) as a co-catalyst enhances the product yields. A wide range of functional groups are tolerated in the reactions, and the scope and limitations of the method are described. The catalytic dehydrogenation of cyclohexenes is showcased in an efficient route to a phthalimide-based TRPA1 activity modulator. PMID:25734414

  17. 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

  18. Responses of aerobic and anaerobic ammonia/ammonium-oxidizing microorganisms to anthropogenic pollution in coastal marine environments.

    PubMed

    Cao, Huiluo; Li, Meng; Dang, Hongyue; Gu, Ji-Dong

    2011-01-01

    Up to date, numerous studies have shown that the community structure of aerobic ammonia oxidizers including ammonia-oxidizing Betaproteobacteria (Beta-AOB) and ammonia-oxidizing archaea (AOA) and, more recently, the anaerobic ammonium-oxidizing (anammox) bacteria is responsive to environmental conditions including salinity, pH, selected metal ions, concentrations of inorganic nitrogen, total phosphorus, the ratio of organic carbon and nitrogen, and sedimentological factors such as the sediment median grain size. Identification of these responses to known anthropogenic pollution is of particular interest to better understand the growth dynamics and activities of nitrogen transforming microorganisms in marine environments. This chapter discusses currently available methods including molecular ecological analysis using clone library constructions with specific molecular genetic markers for delineating community changes of Beta-AOB, AOA, and anammox bacteria. Using data on ammonia-oxidizing microbial community structures from Jiaozhou Bay in North China and three marine environments with anthropogenic pollution gradients in South China from coastal Mai Po Nature Reserve of Hong Kong to the South China Sea as examples, statistical analyses packages (DOTUR, UniFrac, and Canoco) are presented as useful tools to illustrate the relationship between changes in nitrogen metabolizing microbial communities and established environmental variables. PMID:21514459

  19. Responses of aerobic and anaerobic ammonia/ammonium-oxidizing microorganisms to anthropogenic pollution in coastal marine environments.

    PubMed

    Cao, Huiluo; Li, Meng; Dang, Hongyue; Gu, Ji-Dong

    2011-01-01

    Up to date, numerous studies have shown that the community structure of aerobic ammonia oxidizers including ammonia-oxidizing Betaproteobacteria (Beta-AOB) and ammonia-oxidizing archaea (AOA) and, more recently, the anaerobic ammonium-oxidizing (anammox) bacteria is responsive to environmental conditions including salinity, pH, selected metal ions, concentrations of inorganic nitrogen, total phosphorus, the ratio of organic carbon and nitrogen, and sedimentological factors such as the sediment median grain size. Identification of these responses to known anthropogenic pollution is of particular interest to better understand the growth dynamics and activities of nitrogen transforming microorganisms in marine environments. This chapter discusses currently available methods including molecular ecological analysis using clone library constructions with specific molecular genetic markers for delineating community changes of Beta-AOB, AOA, and anammox bacteria. Using data on ammonia-oxidizing microbial community structures from Jiaozhou Bay in North China and three marine environments with anthropogenic pollution gradients in South China from coastal Mai Po Nature Reserve of Hong Kong to the South China Sea as examples, statistical analyses packages (DOTUR, UniFrac, and Canoco) are presented as useful tools to illustrate the relationship between changes in nitrogen metabolizing microbial communities and established environmental variables.

  20. Ultrafine MnO2 nanoparticles decorated on graphene oxide as a highly efficient and recyclable catalyst for aerobic oxidation of benzyl alcohol.

    PubMed

    Hu, Zonggao; Zhao, Yafei; Liu, Jindun; Wang, Jingtao; Zhang, Bing; Xiang, Xu

    2016-12-01

    The highly active and selective aerobic oxidation of aromatic alcohols over earth-abundant, inexpensive and recyclable catalysts is highly desirable. We fabricated herein MnO2/graphene oxide (GO) composites by a facile in-situ growth approach at room temperature and used them in selective aerobic oxidation of benzyl alcohol to benzaldehyde. TEM, XRD, FTIR, XPS and N2 adsorption/desorption analysis were employed to systematically investigate the morphology, particle size, structure and surface properties of the catalysts. The 96.8% benzyl alcohol conversion and 100% benzaldehyde selectivity over the MnO2/GO (10/100) catalyst with well dispersive ultrafine MnO2 nanoparticles (ca. 3nm) can be obtained within 3h under 383K. Simultaneously, no appreciable loss of activity and selectivity occurred after recycling use up to six times. Due to their significant low cost, excellent catalytic performance, the MnO2/GO composites have huge application prospect in organic synthesis. PMID:27544446

  1. Characteristics of atmospheric CO2 and CH4 at the Shangdianzi regional background station in China

    NASA Astrophysics Data System (ADS)

    Fang, Shuang-xi; Tans, Pieter P.; Dong, Fan; Zhou, Huaigang; Luan, Tian

    2016-04-01

    Atmospheric CO2 and CH4 have been continuously measured at the Shangdianzi regional background station (SDZ) in China from 2009 to 2013. Based on the influences of local surface wind and long-distance transport, the observed records were flagged into locally influenced, Beijing-Tianjin-Hebei (BTH) influenced, and Russia, Mongolia, and Inner Mongolia autonomous region influenced (RMI). ∼ 81.4% of CO2 and ∼75.6% of CH4 mole fractions were flagged as locally representative, indicating that the atmospheric CO2 and CH4 at SDZ were strongly influenced by local sources and sinks. Cluster analysis of back trajectories proved that the atmospheric CO2 and CH4 were influenced by air masses from northwest (RMI) or from south and southeast (BTH). The CO2 and CH4 mole fractions in BTH are always higher than in RMI, with the largest difference of 11.5 ± 0.3 ppm for CO2 and 102 ± 1 ppb for CH4 in July. The annual growth rates of CO2 and CH4 in BTH are 3.8 ± 0.01 ppm yr-1 and 10 ± 0.1 ppb yr-1, respectively, which are apparently higher than those of the RMI and the global means. The long-term trends of CO2 and CH4 in BTH are deviating from those in RMI, with ratios of ∼1.0 ppm yr-1 for CO2 and ∼2 ppb yr-1 for CH4, indicating the strengths of CO2 and CH4 emission in Beijing-Tianjin-Hebei plain increased more than 20% every year.

  2. Noble gases in CH 4-rich gas fields, Alberta, Canada

    NASA Astrophysics Data System (ADS)

    Hiyagon, H.; Kennedy, B. M.

    1992-04-01

    The elemental and isotopic compositions of helium, neon, argon, and xenon in twenty-one CH 4-rich natural gas samples from Cretaceous and Devonian reservoirs in the Alberta, Canada, sedimentary basin were measured. In all but a few cases, radiogenic ( 4He, 40Ar, and 131-136Xe) and nucleogenic ( 21,22Ne) isotopes dominated. Based solely on the noble gas composition, two types of natural gas reservoirs are identified. One (Group B) is highly enriched in radiogenic-nucleogenic noble gases and varies little in composition: 3He /4He = 1.5 ± 0.5 × 10 -8, 40Ar /36Ar = 5000-6500 , 40∗Ar /4He = 0.10 , 136∗Xe /4He ~ 0.7 × 10 -9, and 21∗Ne /22∗Ne = 0.452 ± 0.041 (∗ denotes radiogenic or nucleogenic origin; all 4He is radiogenic). High nitrogen content with 4He /N 2 ~ 0.06 is also characteristic of Group B samples. The remaining samples (Group A) contain a radiogenic-nucleogenic component with a different composition and, relative to Group B samples, the extent of enrichment in this component is less and more variable: 3He /4He = 10-70 × 10 -8, 40Ar /36Ar < 1550 , and 40∗Ar /4He ~ 0.25 . The composition of Group B radiogenic-nucleogenic noble gases is consistent with production in crust of average composition. Enrichment in Group B noble gases and nitrogen increases with proximity to the underlying Precambrian basement, consistent with a present-day mass flux into the overlying sedimentary basin. Inferred 40∗Ar /136∗Xe 4He ratios imply a basement source enriched in thorium relative to uranium and potassium (Th/U > 20). Combined, the overall lower total radiogenic-nucleogenic content of Group A reservoirs, the greater variability in composition, and the appearance of Group A noble gases in reservoirs higher in the sedimentary sequence relative to the underlying basement implies that the Group A radiogenic-nucleogenic noble gases are indigenous to the sediments. The most interesting aspect of the Group A noble gases are the very high 3He /4He ratios; ~ 10

  3. Dynamics of Gross Methane Production and Oxidation in a Peatland Soil

    NASA Astrophysics Data System (ADS)

    McNicol, G.; Yang, W. H.; Teh, Y.; Silver, W. L.

    2012-12-01

    Globally, peatlands are major sources of the potent greenhouse gas methane (CH4) that is implicated in 20% of the post-industrial increase in radiative forcing. Many temperate peatlands have been drained for alternative land-use and are characterized by a layer of unsaturated soil overlying the remnant organic histosol. Drained soil layers may attenuate surface CH4 emissions from deeper, flooded peat layers via microbial CH4 consumption. We measured gross rates of CH4 production and oxidation seasonally across a range of topographic landforms in a partially drained peatland on Sherman Island, California. Net CH4 fluxes across the soil-atmosphere interface ranged from -7.4 to 1096 mg-C m-2 d-1 across all landforms. Fluxes were highest in May and in irrigation ditches (date, p < 0.001; landform, p < 0.001; n = 55). Gross CH4 production rates ranged from 0-1461 mg-C m-2 d-1 and oxidation rates ranged from 0-40 mg-C m-2 d-1. Excluding the irrigation ditches, gross fluxes did not vary seasonally. Gross CH4 fluxes were significantly higher in the hollow/hummock than in the slope. We subsequently selected the hollow/hummock based upon the observation of a strong redox gradient with depth and characterized gross fluxes of CH4 both in the field and in laboratory incubations of four soil depth increments (0-10 cm, 10-30 cm, 30-60 cm, 60-80 cm). The laboratory incubation consisted of 3 separate gross flux experiments: the first using fresh soil under ambient headspace, the second after incubation in an N2 headspace, and the third after incubation in an ambient headspace. Gross CH4 fluxes in the field varied from a slight sink (-0.11 mg-C m-2 d-1) to a large source (23.9 mg-C m-2 d-1). In 3 plots net fluxes were reduced by competing CH4 oxidation. In the depth profile experiment, production and consumption were observed in the fresh soil, but without a clear depth trend. In contrast, we found that consumption rates increased with depth following the aerobic incubation and

  4. Large-scale synthesis of ultrathin tungsten oxide nanowire networks: an efficient catalyst for aerobic oxidation of toluene to benzaldehyde under visible light.

    PubMed

    Bai, Hua; Yi, Wencai; Liu, Jingyao; Lv, Qing; Zhang, Qing; Ma, Qiang; Yang, Haifeng; Xi, Guangcheng

    2016-07-14

    As a very important chemical raw material, the selective formation of benzaldehyde from toluene at preparative or industrial levels requires the use of highly corrosive chlorine and high reaction temperatures, which severely corrodes equipment, pollutes the environment, and consumes a lot of energy. Herein, we report a robust and highly active catalyst for the benzaldehyde evolution reaction that is constructed by the surfactant-free growth of oxygen vacancy-rich W18O49 ultrathin nanowire networks. Under atmospheric pressure and visible-light irradiation, the new catalyst can selectively (92% selectivity) catalyze the aerobic oxidation of toluene to benzaldehyde with yields of above 95%.

  5. Reducing Uncertainty in Life Cycle CH4 Emissions from Natural Gas using Atmospheric Inversions

    NASA Astrophysics Data System (ADS)

    Schwietzke, S.; Griffin, W.; Matthews, H.; Bruhwiler, L.

    2013-12-01

    Rising interest in natural gas (NG) as a potentially cleaner alternative to coal and successful tapping of unconventional resources in North America, particularly shale gas, have led to numerous life cycle assessment (LCA) studies revisiting NG leakage rates, i.e., the fraction of produced NG, mostly methane, emitted to the atmosphere, intentionally or unintentionally. Accurately quantifying leakage rates of the full NG life cycle - extraction, processing, transport, and distribution - is challenging due to the size and complexity of the NG industry. Recent U.S. LCA estimates suggest that current NG leakage could be as high as 8% and 6%, from shale and conventional NG, respectively, compared to less than 2% in the latest EPA GHG emission inventory. Reducing uncertainty in the NG leakage rate is important for assessing potential climate benefits of NG over coal, and for understanding the global CH4 budget. The objective of this research is to analyze which ranges of the global average NG leakage rate are reasonable given existing atmospheric observations. We establish detailed prior global CH4 and C2H6 emission inventory scenarios for NG, oil, and coal using emissions data from the LCA literature including uncertainty estimates. Global CH4 and C2H6 inverse box-modeling is used to test the above hypotheses of various global NG leakage rates over the period 1984-2011. Forward simulations with NOAA's CarbonTracker-CH4 (CT-CH4) model provide additional spatial and seasonal information about CH4 atmospheric distribution. Box model inversion results indicate worst-case scenarios of current (2010) global average NG leakage rates of 7% (128 Tg CH4/yr) and 5% (92 Tg CH4/yr) based on CH4 isotope and C2H6 observations, respectively, as well as available raw gas composition data. Worst-case assumptions include upper bound estimates of the global CH4 and C2H6 budget, lower bound literature estimates of all CH4 and C2H6 sources other than NG simultaneously, and absence of a

  6. Metallic Sn spheres and SnO2@C core-shells by anaerobic and aerobic catalytic ethanol and CO oxidation reactions over SnO2 nanoparticles

    PubMed Central

    Kim, Won Joo; Lee, Sung Woo; Sohn, Youngku

    2015-01-01

    SnO2 has been studied intensely for applications to sensors, Li-ion batteries and solar cells. Despite this, comparatively little attention has been paid to the changes in morphology and crystal phase that occur on the metal oxide surface during chemical reactions. This paper reports anaerobic and aerobic ethanol and CO oxidation reactions over SnO2 nanoparticles (NPs), as well as the subsequent changes in the nature of the NPs. Uniform SnO2@C core-shells (10 nm) were formed by an aerobic ethanol oxidation reaction over SnO2 NPs. On the other hand, metallic Sn spheres were produced by an anaerobic ethanol oxidation reaction at 450 °C, which is significantly lower than that (1200 °C) used in industrial Sn production. Anaerobic and aerobic CO oxidation reactions were also examined. The novelty of the methods for the production of metallic Sn and SnO2@C core-shells including other anaerobic and aerobic reactions will contribute significantly to Sn and SnO2-based applications. PMID:26300041

  7. Metallic Sn spheres and SnO2@C core-shells by anaerobic and aerobic catalytic ethanol and CO oxidation reactions over SnO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Kim, Won Joo; Lee, Sung Woo; Sohn, Youngku

    2015-08-01

    SnO2 has been studied intensely for applications to sensors, Li-ion batteries and solar cells. Despite this, comparatively little attention has been paid to the changes in morphology and crystal phase that occur on the metal oxide surface during chemical reactions. This paper reports anaerobic and aerobic ethanol and CO oxidation reactions over SnO2 nanoparticles (NPs), as well as the subsequent changes in the nature of the NPs. Uniform SnO2@C core-shells (10 nm) were formed by an aerobic ethanol oxidation reaction over SnO2 NPs. On the other hand, metallic Sn spheres were produced by an anaerobic ethanol oxidation reaction at 450 °C, which is significantly lower than that (1200 °C) used in industrial Sn production. Anaerobic and aerobic CO oxidation reactions were also examined. The novelty of the methods for the production of metallic Sn and SnO2@C core-shells including other anaerobic and aerobic reactions will contribute significantly to Sn and SnO2-based applications.

  8. Organization of the Escherichia coli aerobic enzyme complexes of oxidative phosphorylation in dynamic domains within the cytoplasmic membrane

    PubMed Central

    Erhardt, Heiko; Dempwolff, Felix; Pfreundschuh, Moritz; Riehle, Marc; Schäfer, Caspar; Pohl, Thomas; Graumann, Peter; Friedrich, Thorsten

    2014-01-01

    The Escherichia coli cytoplasmic membrane contains the enzyme complexes of oxidative phosphorylation (OXPHOS). Not much is known about their supramolecular organization and their dynamics within the membrane in this model organism. In mitochondria and other bacteria, it was demonstrated by nondenaturing electrophoretic methods and electron microscopy that the OXPHOS complexes are organized in so-called supercomplexes, stable assemblies with a defined number of the individual enzyme complexes. To investigate the organization of the E. coli enzyme complexes of aerobic OXPHOS in vivo, we established fluorescent protein fusions of the NADH:ubiquinone oxidoreductase, the succinate:ubiquinone oxidoreductase, the cytochrome bd-I, and the cytochrome bo3 terminal oxidases, and the FoF1 ATP-synthase. The fusions were integrated in the chromosome to prevent artifacts caused by protein overproduction. Biochemical analysis revealed that all modified complexes were fully assembled, active, and stable. The distribution of the OXPHOS complexes in living cells was determined using total internal reflection fluorescence microscopy. The dynamics within the membrane were detected by fluorescence recovery after photobleaching. All aerobic OXPHOS complexes showed an uneven distribution in large mobile patches within the E. coli cytoplasmic membrane. It is discussed whether the individual OXPHOS complexes are organized as clustered individual complexes, here called “segrazones.” PMID:24729508

  9. Organization of the Escherichia coli aerobic enzyme complexes of oxidative phosphorylation in dynamic domains within the cytoplasmic membrane.

    PubMed

    Erhardt, Heiko; Dempwolff, Felix; Pfreundschuh, Moritz; Riehle, Marc; Schäfer, Caspar; Pohl, Thomas; Graumann, Peter; Friedrich, Thorsten

    2014-06-01

    The Escherichia coli cytoplasmic membrane contains the enzyme complexes of oxidative phosphorylation (OXPHOS). Not much is known about their supramolecular organization and their dynamics within the membrane in this model organism. In mitochondria and other bacteria, it was demonstrated by nondenaturing electrophoretic methods and electron microscopy that the OXPHOS complexes are organized in so-called supercomplexes, stable assemblies with a defined number of the individual enzyme complexes. To investigate the organization of the E. coli enzyme complexes of aerobic OXPHOS in vivo, we established fluorescent protein fusions of the NADH:ubiquinone oxidoreductase, the succinate:ubiquinone oxidoreductase, the cytochrome bd-I, and the cytochrome bo3 terminal oxidases, and the FoF1 ATP-synthase. The fusions were integrated in the chromosome to prevent artifacts caused by protein overproduction. Biochemical analysis revealed that all modified complexes were fully assembled, active, and stable. The distribution of the OXPHOS complexes in living cells was determined using total internal reflection fluorescence microscopy. The dynamics within the membrane were detected by fluorescence recovery after photobleaching. All aerobic OXPHOS complexes showed an uneven distribution in large mobile patches within the E. coli cytoplasmic membrane. It is discussed whether the individual OXPHOS complexes are organized as clustered individual complexes, here called "segrazones."

  10. Field-Scale Inhibition and Recovery of Atmospheric-Methane Oxidation in Soil

    NASA Astrophysics Data System (ADS)

    Schroth, M. H.; Dax, A.; Genter, F.; Henneberger, R.

    2015-12-01

    Aerobic methane (CH4) oxidation in upland soils is the only known terrestrial sink for atmospheric CH4. It is mediated by methane-oxidizing bacteria (MOB) that possess a high-affinity form of the enzyme methane monooxygenase (MMO), allowing utilization of CH4 at near-atmospheric, low concentrations (≤ 1.9 µL/L). As cultivation attempts for high-affinity MOB have shown little success to date, there remains much speculation regarding their functioning in different environmental systems. For quantification of microbial functions at the field scale, inhibition experiments are often used as a control and to verify that observed substrate turnover is microbially mediated. Targeting MMO, several compounds have been proposed as inhibitors of CH4 oxidation. However, previous inhibition experiments were mostly conducted in systems dominated by low-affinity MOB, which mediate CH4 oxidation at elevated CH4 concentrations. On the contrary, inhibition experiments targeting high-affinity MOB are scare, particularly at the field scale. We present results of field-scale experiments to investigate effectiveness of and recovery from inhibition of atmospheric CH4 oxidation using the competitive inhibitors CH3F and CH2F2, as well as the non-competitive inhibitor C2H2. The latter is of particular interest, because C2H2 irreversibly binds to MMO, requiring de-novo synthesis of MMO for recovery of CH4 oxidation activity. Experiments were conducted during both winter and summer seasons in a sandy soil. Atmospheric CH4 oxidation was quantified in regular intervals at reference and treatment locations using the soil-profile method with concurrent measurements of soil-water contents and -temperature. Whereas C2H2 inhibition was highly effective in both seasons, the time required for recovery to the level of the reference location was much shorter during the summer experiment (~1 mo compared with 4 mo during winter). Our data provide new insights into the physiology of high-affinity MOB.

  11. 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.

  12. A convenient and selective palladium-catalyzed aerobic oxidation of alcohols.

    PubMed

    Gowrisankar, Saravanan; Neumann, Helfried; Gördes, Dirk; Thurow, Kerstin; Jiao, Haijun; Beller, Matthias

    2013-11-18

    An efficient procedure for the oxidation of primary and secondary alcohols to aldehydes and ketones, respectively, with molecular oxygen under ambient conditions has been achieved. By applying catalytic amounts of Pd(OAc)2 in the presence of tertiary phosphine oxides (O=PR3) as ligands, a variety of substrates are selectively oxidized without formation of ester byproducts. Spectroscopic investigations and DFT calculations suggest stabilization of the active palladium(II) catalyst by phosphine oxide ligands.

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

    SciTech Connect

    Li, SG; Zong, ZW; Zhou, SJ; Huang, Y; Song, ZN; Feng, XH; Zhou, RF; Meyer, HS; Yu, M; Carreon, MA

    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 and 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,

  14. Outgassing from the Congo River Basin: a Major Source of Atmospheric CH4

    NASA Astrophysics Data System (ADS)

    Salter, M. E.; Mann, P. J.; Dinga, B.; Poulsen, J.; Barnes, J.; Fiske, G.; Upstill-Goddard, R. C.; Holmes, R. M.

    2011-12-01

    Methane (CH4) is a major greenhouse gas and although its production by human activities now exceeds that by natural sources, the single largest source in the global CH4 budget is natural production in wetlands. Recent studies have highlighted the potential importance of tropical regions as a significant source of tropospheric CH4 although large uncertainties remain. A major part of the uncertainty is that many important source regions remain at best only poorly investigated. One such region is the Congo River basin. Although recent satellite-derived measurements have highlighted the potentially large contribution of the Congo basin (25.7 ± 1.7 Tg CH4 y-1) to overall wetland emissions, political instability and limited infrastructure have severely inhibited in situ sampling of this region. Here we report surface water measurements of dissolved methane from a range of streams and rivers throughout a ˜ 260,600 km2 quadrant of the low-gradient central Congo basin collected in November 2010 and August 2011. We estimated regional CH4 emissions by partitioning the basin into distinct landcover types using satellite-derived estimates of seasonal water coverage and land-cover type. Scaling-up these estimates, we demonstrate that the Congo River basin, and in particular its wetland regions, are a globally significant atmospheric source of CH4. These wetland regions are now under threat from deforestation and degradation, highlighting the critical need for improved regional CH4 budgets to inform future policy decisions within the region.

  15. Long-term Variations of Atmospheric CH4 Concentration over Siberia Derived from Aircraft Observation.

    NASA Astrophysics Data System (ADS)

    Sasakawa, M.; Machida, T.; Ito, A.; Tsuda, N.; Arshinov, M.; Davydov, D.; Fofonov, A.; Krasnov, O.; Patra, P. K.; Ishijima, K.

    2015-12-01

    We have been carrying out monthly flask sampling over 3 Siberian sites (Surgut, Novosibirsk, and Yakutsk) using aircraft and obtained the vertical profile of CH4 concentration up to 7 km since 1993. Temporal variation at each altitude exhibited increasing trend as observed globally (Figure). Seasonal variation at Yakutsk in East Siberia showed expected summer minimum, as seen at remote sites in northern mid to high latitudes, although no clear seasonality was observed at West Siberian sites (Surgut and Novosibirsk). Large CH4 emissions from West Siberian Lowlands (WSL) might compensate CH4 loss by reaction with OH radical during summer. The vertical gradient in CH4 concentration was larger in Surgut and Novosibirsk than in Yakutsk, which suggests a strong CH4 emission from WSL as well. However, the vertical gradient at Surgut was obviously decreasing; the annual mean difference between 5.5 km and 1.0 km decreased from 62-76 ppb during 1994-1996 to 33-49 ppb during 2012-2014. Chemical transport model reproduced this decrease tendency and suggested that global CH4 emissions have increased, but the contribution from WSL and Europe have decreased in this decade. Figure. Temporal variations in CH4 concentration observed at 1000 and 5500 km altitude over Surgut in West Siberia. Dot color and error bar indicates the number of samples in the same altitude and the range of measured concentration, respectively. The curved line shows fitting line.

  16. Seismic characteristics and strain of coal during the sorption of CO2 and CH4

    NASA Astrophysics Data System (ADS)

    Iyengar, Padmavathi

    Coal has been studied for its extensive capability of adsorbing CO2 in exchange for coalbed CH4. Various sorption models have been developed and enhanced in order to precisely understand the implications of carbon sequestration and enhanced coalbed CH4 recovery processes. Our study aims at analyzing the characteristic behavior of a bituminous coal in various CO2 and CH4 pressure environments through seismic waveform and strain analyses. Laboratory-scale geophysical investigation of a coal specimen was performed under pressures of up to 1000 psi for CH 4 and up to 700 psi for CO2. The results show that the coal specimen has a significantly higher rate of swelling from CO2 injection than CH4. The coal specimen shows instability to reach equilibrium at higher CO2 pressure level; micro-bedding layers of the coal specimen exhibit high seismic impedance at atmospheric pressure, which decreases concurrently as CO2/CH4 pressure increases. The results also show that the coal experiences different rates of swelling and shrinkage for CO2 and CH4 in a confined pressure environment, after a given time interval.

  17. Hydrothermal plumes in the Gulf of Aden, as characterized by light transmission, Mn, Fe, CH4 and δ13C-CH4 anomalies

    NASA Astrophysics Data System (ADS)

    Gamo, Toshitaka; Okamura, Kei; Hatanaka, Hiroshi; Hasumoto, Hiroshi; Komatsu, Daisuke; Chinen, Masakazu; Mori, Mutsumi; Tanaka, Junya; Hirota, Akinari; Tsunogai, Urumu; Tamaki, Kensaku

    2015-11-01

    We conducted water column surveys to search for hydrothermal plumes over the spreading axes in the Gulf of Aden between 45°35‧E and 52°42‧E. We measured light transmission and chemical tracers Mn, Fe, CH4 and δ13C of CH4 in seawater taken using a CTD-Carrousel multi-sampling system at 12 locations including a control station in the Arabian Sea. We recognized three types of hydrothermal plumes at depths of ~650 to ~900 m (shallow plumes), ~1000 to ~1200 m (intermediate plumes), and >1500 m (deep plumes). The shallow plumes were apparently originated from newly discovered twin seamounts (12°03-06‧N and 45°35-41‧E) at the westernmost survey area, where two-dimensional distributions of light transmission and Mn were mapped by tow-yo observations of the CTD-sampling system with an in situ auto-analyzer GAMOS. The maximum concentrations of Mn, Fe, and CH4 of 46 nM, 251 nM, and 15 nM, respectively, were observed for collected seawater within the shallow plumes. The intermediate plumes were characterized by anomalies of light transmission, Mn, Fe, and δ13C of CH4, but by little CH4 anomalies, suggesting that CH4 had been consumed down to the background level during the aging of the plumes. Anomalies of δ3He already reported by the World Ocean Circulation Experiment (WOCE) program exhibited a hydrothermal plume-like peak at ~2000 m depth in the Gulf of Aden, which seems to coincide with the deep plumes observed in this study. The endmember δ13C-CH4 values for the shallow and the deep plumes were estimated to be in a range between -10‰ and -15‰, demonstrating that the sources of CH4 are not biogenic but magmatic as similarly observed at sediment-starved mid-oceanic ridges.

  18. Large-scale synthesis of ultrathin tungsten oxide nanowire networks: an efficient catalyst for aerobic oxidation of toluene to benzaldehyde under visible light

    NASA Astrophysics Data System (ADS)

    Bai, Hua; Yi, Wencai; Liu, Jingyao; Lv, Qing; Zhang, Qing; Ma, Qiang; Yang, Haifeng; Xi, Guangcheng

    2016-07-01

    As a very important chemical raw material, the selective formation of benzaldehyde from toluene at preparative or industrial levels requires the use of highly corrosive chlorine and high reaction temperatures, which severely corrodes equipment, pollutes the environment, and consumes a lot of energy. Herein, we report a robust and highly active catalyst for the benzaldehyde evolution reaction that is constructed by the surfactant-free growth of oxygen vacancy-rich W18O49 ultrathin nanowire networks. Under atmospheric pressure and visible-light irradiation, the new catalyst can selectively (92% selectivity) catalyze the aerobic oxidation of toluene to benzaldehyde with yields of above 95%.As a very important chemical raw material, the selective formation of benzaldehyde from toluene at preparative or industrial levels requires the use of highly corrosive chlorine and high reaction temperatures, which severely corrodes equipment, pollutes the environment, and consumes a lot of energy. Herein, we report a robust and highly active catalyst for the benzaldehyde evolution reaction that is constructed by the surfactant-free growth of oxygen vacancy-rich W18O49 ultrathin nanowire networks. Under atmospheric pressure and visible-light irradiation, the new catalyst can selectively (92% selectivity) catalyze the aerobic oxidation of toluene to benzaldehyde with yields of above 95%. Electronic supplementary information (ESI) available: Experimental procedure, XRD patterns, TEM and HRTEM images, energy-dispersive X-ray spectra, UV-vis spectra, X-ray photoelectron spectroscopy (XPS), and EDS. See DOI: 10.1039/c6nr02949c

  19. BOREAS TGB-1 CH4 Concentration and Flux Data from NSA Tower Sites

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Conrad, Sara K. (Editor); Crill, Patrick; Varner, Ruth K.

    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 half-hourly averages of ambient methane (CH4) measurements and calculated fluxes for the NSA-Fen in 1996 and the NSA-BP and NSA-OJP tower sites in 1994. The purpose of this study was to determine the CH4 flux from the study area by measuring ambient CH 4 concentrations. This flux can then be compared to the chamber flux measurements taken at the same sites. The data are provided in tabular ASCII files.

  20. [Effect of butachlor on CH4 emission and anaerobes in paddy soil].

    PubMed

    Zhao, Y; Mei, Q; Chen, M; Min, H

    1997-12-01

    Effects of butachlor on CH4 emission and the count of anaerobes in paddy soil or in the media were studied. The results obtained showed that CH4 emission and growth of methanogens would be greatly affected at field rates of butachlor within 2 weeks, but this adverse effects would disappear as time went on. CH4 emission and methanogenic activities would be retarded by butachlor in media for longer time. The amount of butachlor available to act upon anaerobes depended on application rate and method of application.

  1. Dissociation of CH4 at high pressures and temperatures: diamond formation in giant planet interiors?

    PubMed

    Benedetti, L R; Nguyen, J H; Caldwell, W A; Liu, H; Kruger, M; Jeanloz, R

    1999-10-01

    Experiments using laser-heated diamond anvil cells show that methane (CH4) breaks down to form diamond at pressures between 10 and 50 gigapascals and temperatures of about 2000 to 3000 kelvin. Infrared absorption and Raman spectroscopy, along with x-ray diffraction, indicate the presence of polymeric hydrocarbons in addition to the diamond, which is in agreement with theoretical predictions. Dissociation of CH4 at high pressures and temperatures can influence the energy budgets of planets containing substantial amounts of CH4, water, and ammonia, such as Uranus and Neptune. PMID:10506552

  2. Dissociation of CH4 at high pressures and temperatures: diamond formation in giant planet interiors?

    PubMed

    Benedetti, L R; Nguyen, J H; Caldwell, W A; Liu, H; Kruger, M; Jeanloz, R

    1999-10-01

    Experiments using laser-heated diamond anvil cells show that methane (CH4) breaks down to form diamond at pressures between 10 and 50 gigapascals and temperatures of about 2000 to 3000 kelvin. Infrared absorption and Raman spectroscopy, along with x-ray diffraction, indicate the presence of polymeric hydrocarbons in addition to the diamond, which is in agreement with theoretical predictions. Dissociation of CH4 at high pressures and temperatures can influence the energy budgets of planets containing substantial amounts of CH4, water, and ammonia, such as Uranus and Neptune.

  3. 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.

  4. Aqueous aerobic oxidation of alkyl arenes and alcohols catalyzed by copper(II) phthalocyanine supported on three-dimensional nitrogen-doped graphene at room temperature.

    PubMed

    Mahyari, Mojtaba; Laeini, Mohammad Sadegh; Shaabani, Ahmad

    2014-07-25

    Copper(ii) tetrasulfophthalocyanine supported on three-dimensional nitrogen-doped graphene-based frameworks was synthesized and introduced as a bifunctional catalyst for selective aerobic oxidation of alkyl arenes and alcohols to the corresponding carbonyl compounds. The ease of catalyst separation, high turnover, low catalyst loading and recyclability could potentially render it applicable in industrial setting. PMID:24912023

  5. 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

  6. Airborne measurements of CO2 and CH4 onboard the UK FAAM research aircraft using a, Los Gatos Research Inc, cavity enhanced absorption spectrometer

    NASA Astrophysics Data System (ADS)

    O'Shea, S.; Bauguitte, S.; Muller, J. B.; Le Breton, M.; Gallagher, M. W.; Allen, G.; Percival, C. J.

    2012-12-01

    Airborne measurements of CO2 and CH4 have been made using the UK Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 research aircraft since spring 2011.The measurement system uses a commercially available analyser, based on the off-axis integrated cavity output spectroscopy technique, from Los Gatos Research Inc (FGGA, Model RMT-200). During the first year of operation (29 flights), 1 Hz measurements were found to be accurate to 0.07 ± 2.48ppbv for CH4 and -0.06± 0.66ppmv for CO2. In summer 2011, as part of the BORTAS project (Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites), outflow from boreal forest fires was measured in Eastern Canada. A number of fresh and photochemically-aged plumes were identified using simultaneous HCN measurements, a widely used tracer for biomass burning. In the freshest plumes, strong relationships were found between CH4, CO2 and other tracers for biomass burning. From this we were able to estimate that 6.9±0.8 g of CH4 and 1551±213 g of CO2 were released into the atmosphere per kg of dry matter burnt. These emission factors are in good agreement with estimates from previous studies in boreal regions. However for aged plumes the correlations between CH4 and other biomass burning tracers were not as robust, most likely due to mixing from other CH4 emission sources, such as the wetland regions. The role of additional emission sources will be investigated using the UK Met Office NAME atmospheric dispersion model and the HYSPLIT trajectory model. Using tailored back trajectory analysis, we will present an interpretation of this new dataset in the context of air mass/fire origin, relating this to MODIS fire maps and source strength.

  7. 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.

  8. 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

  9. New evidence for Cu-decorated binary-oxides mediating bacterial inactivation/mineralization in aerobic media.

    PubMed

    Rtimi, S; Pulgarin, C; Bensimon, M; Kiwi, J

    2016-08-01

    Binary oxide semiconductors TiO2-ZrO2 and Cu-decorated TiO2-ZrO2 (TiO2-ZrO2-Cu) uniform films were sputtered on polyester (PES). These films were irradiated under low intensity solar simulated light and led to bacterial inactivation in aerobic and anaerobic media as evaluated by CFU-plate counting. But bacterial mineralization was only induced by TiO2-ZrO2-Cu in aerobic media. The highly oxidative radicals generated on the films surface under light were identified by the use of appropriate scavengers. The hole generated on the TiO2-ZrO2 films is shown to be the main specie leading to bacterial inactivation. TiO2-ZrO2 and Cu-decorated TiO2-ZrO2 films release Zr and Ti <1ppb and Cu 4.6ppb/cm(2) as determined by inductively coupled plasma mass spectrometry (ICP-MS) This level is far below the citotoxicity permitted level allowed for mammalian cells suggesting that bacterial disinfection proceeds through an oligodynamic effect. By Fourier transform attenuated infrared spectroscopy (ATR-FTIR) the systematic shift of the predominating νs(CH2) vibrational-rotational peak making up most of the bacterial cell-wall content in C was monitored. Based on this evidence a mechanism suggested leading to CH bond stretching followed by cell lysis and cell death. Bacterial inactivation cycling was observed on TiO2-ZrO2-Cu showing the stability of these films leading to bacterial inactivation. PMID:27088192

  10. Investigation of oxidative phosphorylation in continuous cultures. A non-equilibrium thermodynamic approach to energy transduction for Escherichia coli in aerobic condition

    NASA Astrophysics Data System (ADS)

    Ghafuri, Mohazabeh; Nosrati, Mohsen; Hosseinkhani, Saman

    2015-03-01

    Adenosine triphosphate (ATP) production in living cells is very important. Different researches have shown that in terms of mathematical modeling, the domain of these investigations is essentially restricted. Recently the thermodynamic models have been suggested for calculation of the efficiency of oxidative phosphorylation process and rate of energy loss in animal cells using chemiosmotic theory and non-equilibrium thermodynamics equations. In our previous work, we developed a mathematical model for mitochondria of animal cells. In this research, according to similarities between oxidative phosphorylation process in microorganisms and animal cells, Golfar's model was developed to predict the non-equilibrium thermodynamic behavior of the oxidative phosphorylation process for bacteria in aerobic condition. With this model the rate of energy loss, P/O ratio, and efficiency of oxidative phosphorylation were calculated for Escherichia coli in aerobic condition. The results then were compared with experimental data given by other authors. The thermodynamic model had an acceptable agreement with the experimental data.

  11. Highly efficient aerobic oxidation of alcohols by using less-hindered nitroxyl-radical/copper catalysis: optimum catalyst combinations and their substrate scope.

    PubMed

    Sasano, Yusuke; Kogure, Naoki; Nishiyama, Tomohiro; Nagasawa, Shota; Iwabuchi, Yoshiharu

    2015-04-01

    The oxidation of alcohols into their corresponding carbonyl compounds is one of the most fundamental transformations in organic chemistry. In our recent report, 2-azaadamantane N-oxyl (AZADO)/copper catalysis promoted the highly chemoselective aerobic oxidation of unprotected amino alcohols into amino carbonyl compounds. Herein, we investigated the extension of the promising AZADO/copper-catalyzed aerobic oxidation of alcohols to other types of alcohol. During close optimization of the reaction conditions by using various alcohols, we found that the optimum combination of nitroxyl radical, copper salt, and solution concentration was dependent on the type of substrate. Various alcohols, including highly hindered and heteroatom-rich ones, were efficiently oxidized into their corresponding carbonyl compounds under mild conditions with lower amounts of the catalysts.

  12. Depth profiles of methane oxidation potentials and methanotrophic community in a lab-scale biocover.

    PubMed

    Lee, Eun-Hee; Moon, Kyung-Eun; Kim, Tae Gwan; Cho, Kyung-Suk

    2014-08-20

    The depth profiles of the CH4 oxidation potentials and the methanotrophic community were characterized in a lab-scale soil mixture biocover. The soil mixture samples were collected from the top (0-10cm), middle (10-40cm), and bottom (40-50cm) layers of the biocover where most of methane was oxidized at the top layer due to consumption of O2. Batch tests using serum bottles showed that the middle and bottom samples displayed CH4 oxidation activity under aerobic conditions, and their CH4 oxidation rates were 85 and 71% of the rate of top sample (8.40μmolgdry sample(-1)h(-1)), respectively. The numbers of methanotrophs in the middle and bottom were not significantly different from those in the top sample. There was no statistical difference in the community stability indices (diversity and evenness) among the methanotrophic communities of the three layer samples, even though the community structures were distinguished from each other. Based on microarray analysis, type I and type II methanotrophs were equally present in the top sample, while type I was more dominant than type II in the middle and bottom samples. We suggested that the qualitative difference in the community structures was probably caused by the difference in the depth profiles of the CH4 and O2 concentrations. The results for the CH4 oxidation potential, methanotrophic biomass, and community stability indices in the middle and bottom layer samples indicated that the deeper layer in the methanotrophic biocover serves as a bioresource reservoir for sustainable CH4 mitigation.

  13. Biofilter for removal of nitrogen oxides from contaminated gases under aerobic conditions

    DOEpatents

    Apel, William A.

    1998-01-01

    A biofilter for reducing concentrations of gaseous nitrogen oxides in a polluted gas comprises a porous organic filter bed medium disposed in a housing, the filter bed medium including a mixed culture of naturally occurring denitrifying bacteria for converting the nitrogen oxides to nitrogen gas, carbon dioxide, and water. A method of reducing concentrations of nitrogen oxides in polluted gas comprises conducting the polluted gas through the biofilter so that the denitrifying bacteria can degrade the nitrogen oxides. A preferred filter medium is wood compost, however composts of other organic materials are functional. Regulation of pH, moisture content, exogenous carbon sources, and temperature are described.

  14. Biofilter for removal of nitrogen oxides from contaminated gases under aerobic conditions

    DOEpatents

    Apel, W.A.

    1998-08-18

    A biofilter is described for reducing concentrations of gaseous nitrogen oxides in a polluted gas comprises a porous organic filter bed medium disposed in a housing, the filter bed medium including a mixed culture of naturally occurring denitrifying bacteria for converting the nitrogen oxides to nitrogen gas, carbon dioxide, and water. A method is described of reducing concentrations of nitrogen oxides in polluted gas comprises conducting the polluted gas through the biofilter so that the denitrifying bacteria can degrade the nitrogen oxides. A preferred filter medium is wood compost, however composts of other organic materials are functional. Regulation of pH, moisture content, exogenous carbon sources, and temperature are described. 6 figs.

  15. 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.

  16. 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

  17. Surface Forcing from CH4 at the North Slope of Alaska and Southern Great Plains Sites

    NASA Astrophysics Data System (ADS)

    Collins, W.; Feldman, D.; Turner, D. D.

    2014-12-01

    Recent increases in atmospheric CH4 have been spatially heterogeneous as indicated by in situ flask measurements and space-borne remote-sensing retrievals from the AIRS instrument, potentially leading to increased radiative forcing. We present detailed, specialized measurements at the DOE ARM North Slope of Alaska (NSA) and Southern Great Plains (SGP) sites to derive the time-series of both CH4 atmospheric concentrations and associated radiative implications at highly-contrasting natural and anthropogenic sources. Using a combination of spectroscopic measurements, in situ observations, and ancillary data for the atmospheric thermodynamic state from radiosondes and cloud-clearing from active sounders, we can separate out the contribution of CH4 to clear-sky downwelling radiance spectra and its infrared surface forcing. The time-series indicates year-to-year variation in shoulder season increases of CH4 concentration and forcing at NSA and large signals from anthropogenic activity at SGP.

  18. Space-based remote imaging spectroscopy of the Aliso Canyon CH4 superemitter

    NASA Astrophysics Data System (ADS)

    Thompson, D. R.; Thorpe, A. K.; Frankenberg, C.; Green, R. O.; Duren, R.; Guanter, L.; Hollstein, A.; Middleton, E.; Ong, L.; Ungar, S.

    2016-06-01

    The Aliso Canyon gas storage facility near Porter Ranch, California, produced a large accidental CH4 release from October 2015 to February 2016. The Hyperion imaging spectrometer on board the EO-1 satellite successfully detected this event, achieving the first orbital attribution of CH4 to a single anthropogenic superemitter. Hyperion measured shortwave infrared signatures of CH4 near 2.3 μm at 0.01 μm spectral resolution and 30 m spatial resolution. It detected the plume on three overpasses, mapping its magnitude and morphology. These orbital observations were consistent with measurements by airborne instruments. We evaluate Hyperion instrument performance, draw implications for future orbital instruments, and extrapolate the potential for a global survey of CH4 superemitters.

  19. Emissions of N2O and CH4 during the composting of liquid swine manure.

    PubMed

    Thompson, A G; Wagner-Riddle, C; Fleming, R

    2004-02-01

    Composted organic wastes have been shown to reduce emissions of N2O and CH4, but little is known about the release of these gases during the composting process. This research examined the emissions of N2O and CH4 during the composting of liquid swine manure and wheat straw at two operations, one with forced aeration and the other without. The lack of aeration increased CH4 emissions to 24 times that of composting with aeration, but had no significant effect on N2O production. When total N2O and CH4 emissions from composting were compared with liquid swine manure emissions, aerated composting was found to reduce emissions to as low as 30% of those from liquid manure storage, while non-aerated composting elevated emissions up to an estimated 330% of liquid manure storage.

  20. A pan-Arctic synthesis of CH4 and CO2 production from anoxic soil incubations

    USGS Publications Warehouse

    Treat, C.C.; Natali, S.M.; Ernakovich, Jessica; Iverson, Colleen M.; Lupasco, Massimo; McGuire, Anthony; Norby, Richard J.; Roy Chowdhury, Taniya; Richter, Andreas; Šantrůčková, Hana; Schädel, C.; Schuur, Edward A.G.; Sloan, Victoria L.; Turetsky, Merritt R.; Waldrop, Mark P.

    2015-01-01

    Permafrost thaw can alter the soil environment through changes in soil moisture, frequently resulting in soil saturation, a shift to anaerobic decomposition, and changes in the plant community. These changes, along with thawing of previously frozen organic material, can alter the form and magnitude of greenhouse gas production from permafrost ecosystems. We synthesized existing methane (CH4) and carbon dioxide (CO2) production measurements from anaerobic incubations of boreal and tundra soils from the geographic permafrost region to evaluate large-scale controls of anaerobic CO2 and CH4 production and compare the relative importance of landscape-level factors (e.g., vegetation type and landscape position), soil properties (e.g., pH, depth, and soil type), and soil environmental conditions (e.g., temperature and relative water table position). We found fivefold higher maximum CH4 production per gram soil carbon from organic soils than mineral soils. Maximum CH4 production from soils in the active layer (ground that thaws and refreezes annually) was nearly four times that of permafrost per gram soil carbon, and CH4 production per gram soil carbon was two times greater from sites without permafrost than sites with permafrost. Maximum CH4 and median anaerobic CO2 production decreased with depth, while CO2:CH4 production increased with depth. Maximum CH4 production was highest in soils with herbaceous vegetation and soils that were either consistently or periodically inundated. This synthesis identifies the need to consider biome, landscape position, and vascular/moss vegetation types when modeling CH4 production in permafrost ecosystems and suggests the need for longer-term anaerobic incubations to fully capture CH4 dynamics. Our results demonstrate that as climate warms in arctic and boreal regions, rates of anaerobic CO2 and CH4 production will increase, not only as a result of increased temperature, but also from shifts in vegetation and increased

  1. Hydrosilane and bismuth-accelerated palladium catalyzed aerobic oxidative esterification of benzylic alcohols with air.

    PubMed

    Bai, Xing-Feng; Ye, Fei; Zheng, Long-Sheng; Lai, Guo-Qiao; Xia, Chun-Gu; Xu, Li-Wen

    2012-09-01

    In a palladium-catalyzed oxidative esterification, hydrosilane can serve as an activator of palladium catalyst with bismuth, thus leading to a novel ligand- and silver-free palladium catalyst system for facile oxidative esterification of a variety of benzylic alcohols in good yields.

  2. Hydrosilane and bismuth-accelerated palladium catalyzed aerobic oxidative esterification of benzylic alcohols with air.

    PubMed

    Bai, Xing-Feng; Ye, Fei; Zheng, Long-Sheng; Lai, Guo-Qiao; Xia, Chun-Gu; Xu, Li-Wen

    2012-09-01

    In a palladium-catalyzed oxidative esterification, hydrosilane can serve as an activator of palladium catalyst with bismuth, thus leading to a novel ligand- and silver-free palladium catalyst system for facile oxidative esterification of a variety of benzylic alcohols in good yields. PMID:22814568

  3. N2O and CH4 emissions from a Chinese wheat-rice cropping system under different tillage practices during the wheat-growing season

    NASA Astrophysics Data System (ADS)

    Zhang, Y.

    2015-12-01

    The annual wheat (Triticum aestivum L.)-rice (Oryza sativa L.) cropping system is the most important cereal production system in the Yangtze River Valley of China, in which various tillage systems are currently implemented during the wheat-growing season. The emissions of nitrous oxide (N2O) and methane (CH4) from the different tillage systems in this system remain unclear. We conducted a 3-year field experiment in a wheat-rice cropping system in a silt clay loam soil to investigate the effects of the type of tillage employed during the wheat-growing season (no-tillage (NT), reduced tillage (RT) or conventional tillage (CT)) on the emissions of N2O and CH4 using the static chamber method over three annual rotation cycles from the 2008 wheat season to the 2011 rice season. The results revealed that the adoption of an NT system during the wheat-growing season significantly increased CH4 emissions during both the wheat-growing season and the following rice-growing season. Over the three annual rotation cycles studied, the annual N2O emissions from the NT (2.24 kg N2O-N ha-1) and CT (2.01 kg N2O-N ha-1) treatments were similar to each other and significantly higher than those from the RT treatment (1.73 kg N2O-N ha-1); the annual CH4 emissions were significantly higher from the NT (100.1 kg CH4-C ha-1) than the CT (83.7 kg CH4-C ha-1) and RT (73.9 kg CH4-C ha-1) systems. The overall results regarding the net global warming potential associated with annual N2O and CH4 emissions indicate that the conversion of conventional tillage to no-tillage systems during the wheat-growing season would intensify the radiative forcing in wheat-rice cropping systems in China.

  4. The history of aerobic ammonia oxidizers: from the first discoveries to today.

    PubMed

    Monteiro, Maria; Séneca, Joana; Magalhães, Catarina

    2014-07-01

    Nitrification, the oxidation of ammonia to nitrite and nitrate, has long been considered a central biological process in the global nitrogen cycle, with its first description dated 133 years ago. Until 2005, bacteria were considered the only organisms capable of nitrification. However, the recent discovery of a chemoautotrophic ammonia-oxidizing archaeon, Nitrosopumilus maritimus, changed our concept of the range of organisms involved in nitrification, highlighting the importance of ammonia-oxidizing archaea (AOA) as potential players in global biogeochemical nitrogen transformations. The uniqueness of these archaea justified the creation of a novel archaeal phylum, Thaumarchaeota. These recent discoveries increased the global scientific interest within the microbial ecology society and have triggered an analysis of the importance of bacterial vs archaeal ammonia oxidation in a wide range of natural ecosystems. In this mini review we provide a chronological perspective of the current knowledge on the ammonia oxidation pathway of nitrification, based on the main physiological, ecological and genomic discoveries.

  5. BOREAS TF-4 CO2 and CH4 Chamber Flux Data from the SSA

    NASA Technical Reports Server (NTRS)

    Anderson, Dean; Striegl, Robert; Wickland, Kimberly; Hall, Forrest G. (Editor); Conrad, Sara (Editor)

    2000-01-01

    The BOREAS TF-4 team measured fluxes of CO2 and CH4 across the soil-air interface in four ages of jack pine forest at the BOREAS SSA during August 1993 to March 1995. Gross and net flux of CO2 and flux of CH4 between soil and air are presented for 24 chamber sites in mature jack pine forest, 20-year-old, 4-year-old, and clear cut areas. The data are stored in tabular ASCII files.

  6. Total Electron Scattering and Electronic State Excitations Cross Sections for O_2, CO, and CH_4

    NASA Technical Reports Server (NTRS)

    Kanik, I.; Trajmar, S.; Nickel, J. C.

    1993-01-01

    Available electron collision cross section data concerning total and elastic scattering, vibrationalexcitation, and ionization for O_2, CO, and CH_4 have been critically reviewed, and a set of crosssections for modeling of planetary atmospheric behavior is recommended. Utilizing theserecommended cross sections, we derived total electronic state excitation cross sections and upperlimits for dissociation cross sections, which in the case of CH_4 should very closely equal the actualdissociation cross section.

  7. Total electron scattering and electronic state excitations cross sections for O2, CO, and CH4

    NASA Technical Reports Server (NTRS)

    Kanik, I.; Trajmar, S.; Nickel, J. C.

    1993-01-01

    Available electron collision cross section data concerning total and elastic scattering, vibrational excitation, and ionization for O2, CO, and CH4 have been critically reviewed, and a set of cross sections for modeling of planetary atmospheric behavior is recommended. Utilizing these recommended cross sections, we derived total electronic state excitation cross sections and upper limits for dissociation cross sections, which in the case of CH4 should very closely equal the actual dissociation cross section.

  8. Influence of Vegetation on Peatland CH4 Flux at a New Hampshire Fen

    NASA Astrophysics Data System (ADS)

    Varner, R. K.; Goodrich, J. P.; Steele, K.; Noyce, G. L.; Crill, P. M.

    2012-12-01

    Uncertainties in wetland methane (CH4) flux characteristics stem from complex spatial and temporal heterogeneity driven, in part, by climate, vegetation and hydrology. Reducing the magnitude of these uncertainties requires analysis of in situ measurements at high temporal resolution. Automated chamber measurements from a New Hampshire fen provide semi-continuous observations of CH4 and carbon dioxide (CO2) flux and environmental data. The autochamber system at Sallies's Fen was equipped with an integrated cavity output spectroscopy analyzer allowing for 2 s CH4 and CO2 concentration data from which 2.5 minute fluxes were calculated every 12 - 18 minutes for the period April, 2009 - May, 2012. The 10 transparent chambers in this measurement system cover several dominant vegetation functional groups including sedge and shrub sites in order to assess the influence of vegetation cover on CH4 flux dynamics. Chambers with high percent cover of Carex spp. were associated with highest overall CH4 flux, which may be attributed to aerenchymous transport. However, results from simultaneous CO2 flux observations are presented to investigate the contribution of root exudation of labile substrate to methanogens, using GPP as an indicator of potential root exudation activity. A distinct diel pattern in CH4 ebullition flux suggests a short lag between plant carbon uptake and exudation of labile substrate and the subsequent CH4 production. However, lack of a diel cycle in diffusive flux pathways suggests a more complex relationship between methanogen substrate availability and transport mechanisms that result in the observed net flux. Chamber CH4 flux data were also grouped based on species composition to investigate the impact of vegetation on flux response to environmental drivers. Implications of these results are related to potential long term changes in vegetation structure and phenology.

  9. 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.

  10. 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. PMID:27472052

  11. 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.

  12. [Effect of NO3(-)-N on CH4 emission during denitrification in subtropical soils].

    PubMed

    Xu, Yong-bo; Cai, Zu-cong; Lei, Bao-kun

    2008-12-01

    Methane production and emission were investigated in 45 subtropical soil samples, collected from different land use and derived from different soil parent materials in Jiangxi province, by incubating flooded soil slurries in a closed system under N2 gas in the headspace after treatment with or without NO3(-)-N (200 mg x kg(-1)) for 28 days at 30 degrees C. The results indicated that the content and availability of soil organic C were the dominant factors influencing CH4 production and emission whether NO3(-)-N was added or not under this anaerobic incubation condition. Methane emission was higher in the soils derived from granite in the unamended soils and used for rice cultivation in the amended soils. During the anaerobic incubation, the NO3(-)-N added significantly inhibited the production and emission of CH4. The inhibitory effect of NO3(-)-N on CH4 emission might be stronger than that of N2O. The amount and rate of NO3(-)-N denitrified in the first 7 days of incubation determined the CH4 emission amount in the soils with NO3(-)-N. The Fe2+ content increased exponentially with the CH4 emission in 73% of the control soils without NO3(-)-N, which indicated that Fe3+ reduction processed simultaneously with CO2 reduction. Nitrate nitrogen inhibits not only the production and emission of CH4 but also the reduction of Fe3+.

  13. Atmospheric radon, CO2 and CH4 dynamics in an Australian coal seam gas field

    NASA Astrophysics Data System (ADS)

    Tait, D. R.; Santos, I. R.; Maher, D. T.

    2013-12-01

    Atmospheric radon (222Rn), carbon dioxide (CO2), and methane concentrations (CH4) as well as carbon stable isotope ratios (δ13C) were used to gain insight into atmospheric chemistry within an Australian coal seam gas (CSG) field (Surat Basin, Tara region, Queensland). A˜3 fold increase in maximum 222Rn concentration was observed inside the gas field compared to outside of it. There was a significant relationship between maximum and average 222Rn concentrations and the number of gas wells within a 2 km to 4 km radius of the sampling sites (n = 5 stations; p < 0.05). We hypothesize that the radon relationship was a response to enhanced emissions within the gas field related to point sources (well heads, pipelines, etc.) and diffse soil sources due to changes in the soil structural and hydrological characteristics. A rapid qualitative assessment of CH4 and CO2 concentration, and carbon isotopes using a mobile cavity ring-down spectrometer system showed a widespread enrichment of both CH4 and CO2 within the production gas field. Concentrations of CH4 and CO2 were as high as 6.89 ppm and 541 ppm respectively compared average concentrations of 1.78 ppm (CH4) and 388 ppm (CO2) outside the gas field. The δ13C values showed distinct differences between areas inside and outside the production field with the δ13C value of the CH4 source within the field matching that of the methane in the CSG.

  14. Relationship between environmental variables and CH4 fluxes in sub-Boreal peatlands

    NASA Astrophysics Data System (ADS)

    Pypker, T. G.; Moore, P. A.; Waddington, J. M.; Chimner, R. A.; Hribljan, J. A.

    2012-12-01

    Peatlands are a critical component in the global carbon (C) cycle because they have been slowly sequestering atmospheric greenhouse gases as peat since the last glaciation. Today, soil C stocks in peatlands are estimated to represent 224 to 455 Pg, equal to 12-30% of the global soil C pool. At present, peatlands are estimated to sequester 76 Tg C yr-1. The flux of C from peatlands is likely to respond to climate change, thereby influencing atmospheric C concentrations. We explored the relationship between ecosystem CO2 exchange, CH4 emissions and weather from May to November 2011 using the eddy covariance method. The peatland was located in the Seney National Wildlife Refuge in the Upper Peninsula of Michigan. During the study period, CO2 and CH4 fluxes ranged between -7.7 to 3.44 g CO2 m-2 d-1 and 0.01 to 0.21 nmol CH4 m-2 d-1, respectively. Both CO2 uptake and CH4 losses peaked in early July and were lowest in early May and late September. To better understand the environmental mechanisms controlling CH4 emissions, changes in CH4 fluxes were related to changes in temperature, precipitation, water table height and CO2 uptake.

  15. [Spatiotemporal variations of natural wetland CH4 emissions over China under future climate change].

    PubMed

    Liu, Jian-gong; Zhu, Qiu-an; Shen, Yan; Yang, Yan-zheng; Luo, Yun-peng; Peng, Chang-hui

    2015-11-01

    Based on a new process-based model, TRIPLEX-GHG, this paper analyzed the spatio-temporal variations of natural wetland CH4 emissions over China under different future climate change scenarios. When natural wetland distributions were fixed, the amount of CH4 emissions from natural wetland ecosystem over China would increase by 32.0%, 55.3% and 90.8% by the end of 21st century under three representative concentration pathways (RCPs) scenarios, RCP2. 6, RCP4.5 and RCP8.5, respectively, compared with the current level. Southern China would have higher CH4 emissions compared to that from central and northern China. Besides, there would be relatively low emission fluxes in western China while relatively high emission fluxes in eastern China. Spatially, the areas with relatively high CH4 emission fluxes would be concentrated in the middle-lower reaches of the Yangtze River, the Northeast and the coasts of the Pearl River. In the future, most natural wetlands would emit more CH4 for RCP4.5 and RCP8.5 than that of 2005. However, under RCP2.6 scenario, the increasing trend would be curbed and CH4 emissions (especially from the Qinghai-Tibet Plateau) begin to decrease in the late 21st century.

  16. Aerobic oxidation of lignin models using a base metal vanadium catalyst.

    PubMed

    Hanson, Susan K; Baker, R Tom; Gordon, John C; Scott, Brian L; Thorn, David L

    2010-06-21

    Dipicolinate vanadium(V) complexes oxidize lignin model complexes pinacol monomethyl ether (A), 2-phenoxyethanol (B), 1-phenyl-2-phenoxyethanol (C), and 1,2-diphenyl-2-methoxyethanol (D). With substrates having C-H bonds adjacent to the alcohol moiety (B-D), the C-H bond is broken in pyridine-d(5) solvent, yielding 2-phenoxyacetaldehyde from B, 2-phenoxyacetophenone from C, and benzoin methyl ether from D. In DMSO-d(6) solvent the reaction is slower, and both C-H and C-C bond cleavage products are observed for D. The vanadium(IV) products of these reactions have been identified and characterized. Catalytic oxidation of C and D has been demonstrated using air and (dipic)V(O)O(i)Pr. For both substrates, the C-C bond between the alcohol and ether groups is broken in the catalytic oxidation. 1-Phenyl-2-phenoxyethanol is oxidized to a mixture of phenol, formic acid, benzoic acid, and 2-methoxyacetophenone. The products of oxidation of 1,2-diphenyl-2-methoxyethanol depend on the solvent; in DMSO benzaldehyde and methanol are the major products, while benzoic acid and methyl benzoate are the major products obtained in pyridine solvent. Phenyl substituents on the model complex facilitate the oxidation, with relative rates of oxidation D > C > B.

  17. Metal-free aerobic alcohol oxidation: intensification under three-phase flow conditions.

    PubMed

    Aellig, Christof; Scholz, David; Hermans, Ive

    2012-09-01

    The selective oxidation of alcohols is a pivotal transformation within industrial and synthetic chemistry. In this contribution we use O₂ as terminal oxidant and (H)NO(x) species as oxygen shuttle in order to mediate the oxidation of primary and secondary alcohols under the influence of a solid acid catalyst. Process optimization and intensification through the use of a continuous three-phase flow reactor is demonstrated. Space-time yields were found to increase by two orders of magnitude with respect to batch experiments, along with additional gains in selectivity and a decrease of N₂O formation.

  18. Selective aerobic alcohol oxidation method for conversion of lignin into simple aromatic compounds

    DOEpatents

    Stahl, Shannon S; Rahimi, Alireza

    2015-03-03

    Described is a method to oxidize lignin or lignin sub-units. The method includes oxidation of secondary benzylic alcohol in the lignin or lignin sub-unit to a corresponding ketone in the presence of unprotected primarily aliphatic alcohol in the lignin or lignin sub-unit. The optimal catalyst system consists of HNO.sub.3 in combination with another Bronsted acid, in the absence of a metal-containing catalyst, thereby yielding a selectively oxidized lignin or lignin sub-unit. The method may be carried out in the presence or absence of additional reagents including TEMPO and TEMPO derivatives.

  19. Systemic Oxidative Stress Is Associated With Lower Aerobic Capacity and Impaired Skeletal Muscle Energy Metabolism in Patients With Metabolic Syndrome

    PubMed Central

    Yokota, Takashi; Kinugawa, Shintaro; Yamato, Mayumi; Hirabayashi, Kagami; Suga, Tadashi; Takada, Shingo; Harada, Kuniaki; Morita, Noriteru; Oyama-Manabe, Noriko; Kikuchi, Yasuka; Okita, Koichi; Tsutsui, Hiroyuki

    2013-01-01

    OBJECTIVE Systemic oxidative stress is associated with insulin resistance and obesity. We tested the hypothesis that systemic oxidative stress is linked to lower aerobic capacity and skeletal muscle dysfunction in metabolic syndrome (MetS). RESEARCH DESIGN AND METHODS The incremental exercise testing with cycle ergometer was performed in 14 male patients with MetS and 13 age-, sex-, and activity-matched healthy subjects. Systemic lipid peroxidation was assessed by serum thiobarbituric acid reactive substances (TBARS), and systemic antioxidant defense capacity was assessed by serum total thiols and enzymatic activity of superoxide dismutase (SOD). To assess skeletal muscle energy metabolism, we measured high-energy phosphates in the calf muscle during plantar flexion exercise and intramyocellular lipid (IMCL) in the resting leg muscle, using 31P- and 1proton-magnetic resonance spectroscopy, respectively. RESULTS Serum TBARS were elevated (12.4 ± 7.1 vs. 3.7 ± 1.1 μmol/L; P < 0.01), and serum total thiols and SOD activity were decreased (290.8 ± 51.2 vs. 398.7 ± 105.2 μmol/L, P < 0.01; and 22.2 ± 8.4 vs. 31.5 ± 8.5 units/L, P < 0.05, respectively) in patients with MetS compared with healthy subjects. Peak VO2 and anaerobic threshold normalized to body weight were significantly lower in MetS patients by 25 and 31%, respectively, and inversely correlated with serum TBARS (r = −0.49 and r = −0.50, respectively). Moreover, muscle phosphocreatine loss during exercise was 1.4-fold greater in patients with MetS (P < 0.05), and IMCL content was 2.9-fold higher in patients with MetS (P < 0.01), indicating impaired skeletal muscle energy metabolism, and these indices positively correlated with serum TBARS (r = 0.45 and r = 0.63, respectively). CONCLUSIONS Systemic oxidative stress was associated with lower aerobic capacity and impaired skeletal muscle energy metabolism in patients with MetS. PMID:23393211

  20. Long Path Quantum Cascade Laser Based Sensor for Environment Sensing/Ambient Detection of CH4 and N2O

    NASA Astrophysics Data System (ADS)

    Castillo, P. C.; Sydoryk, I.; Gross, B.; Moshary, F.

    2013-12-01

    Methane (CH4) and Nitrous Oxide (N2O) are long-lived greenhouse gases in the atmosphere with significant global warming effects. These gases also are known to be produced in a number of anthropogenic settings such as manure management systems, which releases substantial GHGs and is mandated by the EPA to provide continuous monitoring. In addition, natural gas leaks in urban areas is another source of strong spatially inhomogeneous methane emissions Most open path methods for quantitative detection of trace gases utilize either Fourier Transform Spectrometer (FTIR) or near-IR differential optical absorption spectroscopy (DOAS). Although, FTIR is suitable for ambient air monitoring measurement of more abundant gases such as CO2 and H20 etc., the lack of spectral resolution makes the retrieval of weaker absorbing features such as N20 more difficult. On the other hand, conventional DOAS systems can be large and impractical. As an alternative, we illustrate a robust portable quantum cascade laser (QCL) approach for simultaneous detection of CH4 and N2O. In particular, gas spectra were recorded by ultrafast pulse intensity (thermal) chirp tuning over the 1299 - 1300cm-1 spectral window. Etalon measurements insure stable tuning was obtained. To deal with multiple species, a LSQ spectral fitting approach was used which accounted for both the overlapping trace gases , background water vapor as well as detector drift and calibration. In summary, ambient concentrations of CH4 with and N2O with accuracy < 1% was obtained on the order of 5ms using optical paths of 500 m path length. In addition, unattended long term operation was demonstrated and validations using other sensors when possible were shown to be consistent. The system accuracy is limited by systemic errors, which are still being explored.

  1. Iron Catalysis for Room-Temperature Aerobic Oxidation of Alcohols to Carboxylic Acids.

    PubMed

    Jiang, Xingguo; Zhang, Jiasheng; Ma, Shengming

    2016-07-13

    Oxidation from alcohols to carboxylic acids, a class of essential chemicals in daily life, academic laboratories, and industry, is a fundamental reaction, usually using at least a stoichiometric amount of an expensive and toxic oxidant. Here, an efficient and practical sustainable oxidation technology of alcohols to carboxylic acids using pure O2 or even O2 in air as the oxidant has been developed: utilizing a catalytic amount each of Fe(NO3)3·9H2O/TEMPO/MCl, a series of carboxylic acids were obtained from alcohols (also aldehydes) in high yields at room temperature. A 55 g-scale reaction was demonstrated using air. As a synthetic application, the first total synthesis of a naturally occurring allene, i.e., phlomic acid, was accomplished.

  2. Sustainable synthesis of diverse privileged heterocycles by palladium-catalyzed aerobic oxidative isocyanide insertion.

    PubMed

    Vlaar, Tjøstil; Cioc, Razvan C; Mampuys, Pieter; Maes, Bert U W; Orru, Romano V A; Ruijter, Eelco

    2012-12-21

    O(2) in, H(2)O out: Various diamines and related bisnucleophiles readily undergo oxidative isocyanide insertion with Pd(OAc)(2) (1 mol %) as the catalyst and O(2) as the terminal oxidant to give a diverse array of medicinally relevant N heterocycles. The utility of this highly sustainable method is demonstrated by a formal synthesis of the antihistamines astemizole and norastemizole. PMID:23161862

  3. Potential application of aerobic denitrifying bacterium Pseudomonas aeruginosa PCN-2 in nitrogen oxides (NOx) removal from flue gas.

    PubMed

    Zheng, Maosheng; Li, Can; Liu, Shufeng; Gui, Mengyao; Ni, Jinren

    2016-11-15

    Conventional biological removal of nitrogen oxides (NOx) from flue gas has been severely restricted by the presence of oxygen. This paper presents an efficient alternative for NOx removal at varying oxygen levels using the newly isolated bacterial strain Pseudomonas aeruginosa PCN-2 which was capable of aerobic and anoxic denitrification. Interestingly, nitric oxide (NO), as the obligatory intermediate, was negligibly accumulated during nitrate and nitrite reduction. Moreover, normal nitrate reduction with decreasing NO accumulation was realized under O2 concentration ranging from 0 to 100%. Reverse transcription and real-time quantitative polymerase chain reaction (RT-qPCR) analysis revealed that high efficient NO removal was attributed to the coordinate regulation of gene expressions including napA (for periplasmic nitrate reductase), nirS (for cytochrome cd1 nitrite reductase) and cnorB (for NO reductase). Further batch experiments demonstrated the immobilized strain PCN-2 possessed high capability of removing NO and nitrogen dioxide (NO2) at O2 concentration of 0-10%. A biotrickling filter established with present strain achieved high NOx removal efficiencies of 91.94-96.74% at inlet NO concentration of 100-500ppm and O2 concentration of 0-10%, which implied promising potential applications in purifying NOx contaminated flue gas.

  4. Potential application of aerobic denitrifying bacterium Pseudomonas aeruginosa PCN-2 in nitrogen oxides (NOx) removal from flue gas.

    PubMed

    Zheng, Maosheng; Li, Can; Liu, Shufeng; Gui, Mengyao; Ni, Jinren

    2016-11-15

    Conventional biological removal of nitrogen oxides (NOx) from flue gas has been severely restricted by the presence of oxygen. This paper presents an efficient alternative for NOx removal at varying oxygen levels using the newly isolated bacterial strain Pseudomonas aeruginosa PCN-2 which was capable of aerobic and anoxic denitrification. Interestingly, nitric oxide (NO), as the obligatory intermediate, was negligibly accumulated during nitrate and nitrite reduction. Moreover, normal nitrate reduction with decreasing NO accumulation was realized under O2 concentration ranging from 0 to 100%. Reverse transcription and real-time quantitative polymerase chain reaction (RT-qPCR) analysis revealed that high efficient NO removal was attributed to the coordinate regulation of gene expressions including napA (for periplasmic nitrate reductase), nirS (for cytochrome cd1 nitrite reductase) and cnorB (for NO reductase). Further batch experiments demonstrated the immobilized strain PCN-2 possessed high capability of removing NO and nitrogen dioxide (NO2) at O2 concentration of 0-10%. A biotrickling filter established with present strain achieved high NOx removal efficiencies of 91.94-96.74% at inlet NO concentration of 100-500ppm and O2 concentration of 0-10%, which implied promising potential applications in purifying NOx contaminated flue gas. PMID:27469045

  5. Effect of Aloe barbadensis Miller juice on oxidative stress biomarkers in aerobic cells using Artemia franciscana as a model.

    PubMed

    Sirdaarta, J; Cock, I E

    2010-03-01

    This study reports on the induction of oxidative stress in aerobic cell systems by Aloe barbadensis Miller (Aloe vera) juice using the salt water crustacean Artemia franciscana as a model. A consistent pattern was observed in which Artemia franciscana nauplii responded to Aloe vera juice exposure with a decrease in the overall activity of redox related enzymes. Exposure of Artemia franciscana to sub-lethal levels of Aloe vera juice resulted in a decreased activity of thioredoxin reductase, glutathione reductase and glutathione peroxidase by 34% (66% enzymatic activity), 79% (21% enzymatic activity) and 90% (10% enzymatic activity), respectively. Similarly apparent was the trend whereby the co-exposure of the nauplii to vitamin E counteracted this effect. For each of the biomarker enzymes tested, vitamin E co-exposure resulted in enzyme activities closer to the control value (78%, 56% and 32% of control enzymatic activities for thioredoxin reductase, glutathione reductase and glutathione peroxidase activity, respectively). These results indicate that exposure to sub-lethal doses of Aloe vera juice induces alterations in the cellular redox status of Artemia franciscana and that the addition of vitamin E helps the Artemia franciscana nauplii to overcome/block the juice induced oxidative stress.

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

    PubMed

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

    2016-02-16

    Climatic warming is expected to particularly alter greenhouse gas (GHG) emissions from soils in cold ecosystems such as tundra. We used 1 m(2) 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(-2)h(-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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

  8. 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

  9. What can we learn about an early human influence on the global methane cycle from bipolar atmospheric CH4, δD(CH4) and δ13CH4 measurements during the Holocene

    NASA Astrophysics Data System (ADS)

    Beck, Jonas; Bock, Michael; Schmitt, Jochen; Seth, Barbara; Blunier, Thomas; Fischer, Hubertus

    2015-04-01

    The past variation of the concentration of atmospheric methane (CH4) is observed to be generally in phase with the northern summer insolation cycle driven by the precession of the rotation axis of the Earth. However, in the mid-Holocene this regularity breaks down, and atmospheric CH4 starts to rise while the northern summer insolation continues to decline. Despite different attempts to explain this feature (e.g. contrasting hypotheses on early human influences or enhanced natural emissions in the southern tropics), an unambiguous explanation of the evolution of the atmospheric methane concentration has not yet been found. In addition to the inter-polar difference (IPD) of methane, allowing us to draw conclusions about the hemispheric imbalance of the source and sink distribution, the isotopic composition (δD and δ13C) of atmospheric CH4 provides further information about the methane cycle. Each source emits methane of a typical isotope signature, and each sink process leads to a certain isotopic fractionation and, thus, influences the isotopic composition of atmospheric methane. To exploit the full parameter set, we measured the methane isotopes on ice cores from both polar regions (NGRIP from Greenland; EDML and Talos Dome from Antarctica) and are able to calculate the inter-polar difference of δD (IPDδD) and δ13C (IPDδ13C) of methane over the Holocene. To avoid systematic errors, the samples from both hemispheres have been measured on the same system and during the same measurement campaign for each parameter. The NGRIP δD data show a clear covariation with the long-term changes in CH4 concentrations during the Holocene. The δD variations of 8-10 o are significantly larger than our measurement error of 2.3 o. However, the resulting IPDδD is constant within the measurement error at approximately -16.5 o (north-south) during the entire Holocene. The δ13C records (with a measurement precision of 0.13 o) show a clear decrease in δ13C of about 1.9 o and an

  10. 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

  11. Non-equilibrium simulation of CH4 production through the depressurization method from gas hydrate reservoirs

    NASA Astrophysics Data System (ADS)

    Qorbani, Khadijeh; Kvamme, Bjørn

    2016-04-01

    Natural gas hydrates (NGHs) in nature are formed from various hydrate formers (i.e. aqueous, gas, and adsorbed phases). As a result, due to Gibbs phase rule and the combined first and second laws of thermodynamics CH4-hydrate cannot reach thermodynamic equilibrium in real reservoir conditions. CH4 is the dominant component in NGH reservoirs. It is formed as a result of biogenic degradation of biological material in the upper few hundred meters of subsurface. It has been estimated that the amount of fuel-gas reserve in NGHs exceed the total amount of fossil fuel explored until today. Thus, these reservoirs have the potential to satisfy the energy requirements of the future. However, released CH4 from dissociated NGHs could find its way to the atmosphere and it is a far more aggressive greenhouse gas than CO2, even though its life-time is shorter. Lack of reliable field data makes it difficult to predict the production potential, as well as safety of CH4 production from NGHs. Computer simulations can be used as a tool to investigate CH4 production through different scenarios. Most hydrate simulators within academia and industry treat hydrate phase transitions as an equilibrium process and those which employ the kinetic approach utilize simple laboratory data in their models. Furthermore, it is typical to utilize a limited thermodynamic description where only temperature and pressure projections are considered. Another widely used simplification is to assume only a single route for the hydrate phase transitions. The non-equilibrium nature of hydrate indicates a need for proper kinetic models to describe hydrate dissociation and reformation in the reservoir with respect to thermodynamics variables, CH4 mole-fraction, pressure and temperature. The RetrasoCodeBright (RCB) hydrate simulator has previously been extended to model CH4-hydrate dissociation towards CH4 gas and water. CH4-hydrate is added to the RCB data-base as a pseudo mineral. Phase transitions are treated

  12. Aerobic fitness determines whole-body fat oxidation rate during exercise in the heat.

    PubMed

    Del Coso, Juan; Hamouti, Nassim; Ortega, Juan Fernando; Mora-Rodriguez, Ricardo

    2010-12-01

    The purpose of this study was to determine whole-body fat oxidation in endurance-trained (TR) and untrained (UNTR) subjects exercising at different intensities in the heat. On 3 occasions, 10 TR cyclists and 10 UNTR healthy subjects (peak oxygen uptake = 60 ± 6 vs. 44 ± 3 mL·kg-1·min-1; p < 0.05) exercised at 40%, 60%, and 80% peak oxygen uptake in a hot, dry environment (36 °C; 25% relative humidity). To complete the same amount of work in all 3 trials, exercise duration varied (107 ± 4, 63 ± 1, and 45 ± 0 min for 40%, 60%, and 80% peak oxygen uptake, respectively). Substrate oxidation was calculated using indirect calorimetry. Blood samples were collected at the end of exercise to determine plasma epinephrine ([EPI]plasma) and norepinephrine ([NEPI]plasma) concentrations. The maximal rate of fat oxidation was achieved at 60% peak oxygen uptake for the TR group (0.41 ± 0.01 g·min-1) and at 40% peak oxygen uptake for the UNTR group (0.28 ± 0.01 g·min-1). TR subjects oxidized absolutely (g·min-1) and relatively (% of total energy expenditure) more fat than UNTR subjects at 60% and 80% peak oxygen uptake (p < 0.05). At these exercise intensities, TR subjects also had higher [NEPI]plasma concentrations than UNTR subjects (p < 0.05). In the heat, whole-body peak fat oxidation occurs at higher relative exercise intensities in TR than in UNTR subjects (60% vs. 40% peak oxygen uptake). Moreover, TR subjects oxidize more fat than UNTR subjects when exercising at moderate to high intensities (>60% peak oxygen uptake).

  13. Soil trace gas emissions (CH4 and N2O) offset the CO2 uptake in poplar short rotation coppice

    NASA Astrophysics Data System (ADS)

    Zenone, Terenzio; Zona, Donatella; Gelfand, Iya; Gielen, Bert; camino serrano, Marta; Ceulemans, Reinhart

    2015-04-01

    The need for renewable energy sources will lead to a considerable expansion in the planting of dedicated fast-growing biomass crops across Europe. Among them poplar (Populus spp) is the most widely planted as short rotation coppice (SRC) and an increase in the surface area of large-scale SRC poplar plantations might thus be expected. In this study we report the greenhouse gas fluxes (GHG) of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) measured using the eddy covariance technique in a SRC plantation for bioenergy production during the period 2010-2013. The plantation was established in April 2010 on 18.4 ha of former agricultural land with a density of 8000 plants ha-1; the above-ground biomass was harvested on February 2012 and 2014.The whole GHG balance of the four years of the study was 1.90 (± 1.37) Mg CO2eq ha-1; this indicated that soil trace gas emissions offset the CO2 uptake by the plantation. CH4 and N2O almost equally contributed to offset the CO2 uptake of -5.28 (±0.67) Mg CO2eq ha-1 with an overall emission of 3.56 (± 0.35) Mg CO2eq ha-1 of N2O and of 3.53 (± 0.85) Mg CO2eq ha-1 of CH4. N2O emissions mostly occurred during a single peak a few months after the site was converted into SRC and represented 44% of the entire N2O loss during the entire study. Accurately capturing these emission events proved to be critical for correct estimates of the GHG balance. The self-organizing map (SOM) technique graphically showed the relationship between the CO2 fluxes and the principal environmental variables but failed to explain the variability of the soil trace gas emissions. The nitrogen content in the soil and the water table depth were the two drivers that best explained the variability in N2O and CH4 respectively. This study underlines the importance of the "non-CO2 GHG" on the overall balance as well as the impact of the harvest on the CO2 uptake rate. Further long-term investigations of soil trace gas emissions should also monitor the N

  14. Uniform distributions of glucose oxidation and oxygen extraction in gray matter of normal human brain: No evidence of regional differences of aerobic glycolysis.

    PubMed

    Hyder, Fahmeed; Herman, Peter; Bailey, Christopher J; Møller, Arne; Globinsky, Ronen; Fulbright, Robert K; Rothman, Douglas L; Gjedde, Albert

    2016-05-01

    Regionally variable rates of aerobic glycolysis in brain networks identified by resting-state functional magnetic resonance imaging (R-fMRI) imply regionally variable adenosine triphosphate (ATP) regeneration. When regional glucose utilization is not matched to oxygen delivery, affected regions have correspondingly variable rates of ATP and lactate production. We tested the extent to which aerobic glycolysis and oxidative phosphorylation power R-fMRI networks by measuring quantitative differences between the oxygen to glucose index (OGI) and the oxygen extraction fraction (OEF) as measured by positron emission tomography (PET) in normal human brain (resting awake, eyes closed). Regionally uniform and correlated OEF and OGI estimates prevailed, with network values that matched the gray matter means, regardless of size, location, and origin. The spatial agreement between oxygen delivery (OEF≈0.4) and glucose oxidation (OGI ≈ 5.3) suggests that no specific regions have preferentially high aerobic glycolysis and low oxidative phosphorylation rates, with globally optimal maximum ATP turnover rates (VATP ≈ 9.4 µmol/g/min), in good agreement with (31)P and (13)C magnetic resonance spectroscopy measurements. These results imply that the intrinsic network activity in healthy human brain powers the entire gray matter with ubiquitously high rates of glucose oxidation. Reports of departures from normal brain-wide homogeny of oxygen extraction fraction and oxygen to glucose index may be due to normalization artefacts from relative PET measurements. PMID:26755443

  15. Physical Training Status Determines Oxidative Stress and Redox Changes in Response to an Acute Aerobic Exercise.

    PubMed

    Seifi-Skishahr, Farnaz; Damirchi, Arsalan; Farjaminezhad, Manoochehr; Babaei, Parvin

    2016-01-01

    Objective. To assess the influence of different physical training status on exercise-induced oxidative stress and changes in cellular redox state. Methods. Thirty male subjects participated in this study and were assigned as well-trained (WT), moderately trained (MT), and untrained (UT) groups. The levels of cortisol, creatine kinase, plasma reduced glutathione to oxidized glutathione (GSH/GSSG), cysteine/cystine (Cys/CySS), and GSH/GSSG ratio in red blood cells (RBCs) were measured immediately and 10 and 30 min after exercise. Results. Following the exercise, plasma GSH/GSSG (p = 0.001) and Cys/CySS (p = 0.005) were significantly reduced in all groups. Reduction in plasma GSH/GSSG ratio in all groups induced a transient shift in redox balance towards a more oxidizing environment without difference between groups (p = 0.860), while RBCs GSH/GSSG showed significant reduction (p = 0.003) and elevation (p = 0.007) in UT and MT groups, respectively. The highest level of RBCs GSH/GSSG ratio was recorded in MT group, and the lowest one was recorded in the WT group. Conclusion. Long term regular exercise training with moderate intensity shifts redox balance towards more reducing environment, versus intensive exercise training leads to more oxidizing environment and consequently development of related diseases. PMID:27064342

  16. Nitrite-Driven Nitrous Oxide Production Under Aerobic Soil Conditions: Kinetics and Biochemical Controls

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nitrite (NO2-) can accumulate during nitrification in soil following fertilizer application. While the role of NO2- as a substrate regulating nitrous oxide (N2O) production is recognized, kinetic data are not available that allow for estimating N2O production or soil-to-atmosphere fluxes as a functi...

  17. Physical Training Status Determines Oxidative Stress and Redox Changes in Response to an Acute Aerobic Exercise

    PubMed Central

    Damirchi, Arsalan; Farjaminezhad, Manoochehr

    2016-01-01

    Objective. To assess the influence of different physical training status on exercise-induced oxidative stress and changes in cellular redox state. Methods. Thirty male subjects participated in this study and were assigned as well-trained (WT), moderately trained (MT), and untrained (UT) groups. The levels of cortisol, creatine kinase, plasma reduced glutathione to oxidized glutathione (GSH/GSSG), cysteine/cystine (Cys/CySS), and GSH/GSSG ratio in red blood cells (RBCs) were measured immediately and 10 and 30 min after exercise. Results. Following the exercise, plasma GSH/GSSG (p = 0.001) and Cys/CySS (p = 0.005) were significantly reduced in all groups. Reduction in plasma GSH/GSSG ratio in all groups induced a transient shift in redox balance towards a more oxidizing environment without difference between groups (p = 0.860), while RBCs GSH/GSSG showed significant reduction (p = 0.003) and elevation (p = 0.007) in UT and MT groups, respectively. The highest level of RBCs GSH/GSSG ratio was recorded in MT group, and the lowest one was recorded in the WT group. Conclusion. Long term regular exercise training with moderate intensity shifts redox balance towards more reducing environment, versus intensive exercise training leads to more oxidizing environment and consequently development of related diseases. PMID:27064342

  18. Selective Aerobic Oxidation of 5-(Hydroxymethyl)furfural to 5-Formyl-2-furancarboxylic Acid in Water.

    PubMed

    Ventura, Maria; Aresta, Michele; Dibenedetto, Angela

    2016-05-23

    A simple, cheap, and selective catalyst based on copper/cerium oxides is described for the oxidation of 5-(hydroxymethyl)furfural (5-HMF) in water. An almost quantitative conversion (99 %) with excellent (90 %) selectivity towards the formation of 5-formyl-2-furancarboxylic acid, a platform molecule for other high value chemicals, is observed. The catalyst does not require any pretreatment or additives, such as bases, to obtain high yield and selectivity in water as solvent and using oxygen as oxidant. When a physical mixture of the oxides is used, low conversion and selectivity are observed. Air can be used instead of oxygen, but a lower conversion rate is observed if the same overall pressure is used, and the selectivity remains high. The catalyst can be recovered almost quantitatively and reused. Deactivation of the catalyst, observed in repeated runs, is due to the deposition of humins on its surface. Upon calcination the catalyst almost completely recovers its activity and selectivity, proving that the catalyst is robust. PMID:27101568

  19. Confined iron nanowires enhance the catalytic activity of carbon nanotubes in the aerobic oxidation of cyclohexane.

    PubMed

    Yang, Xixian; Yu, Hao; Peng, Feng; Wang, Hongjuan

    2012-07-01

    Inside job: New applications of carbon materials pave the way towards greener chemical syntheses. The encapsulation of metallic Fe within CNTs improves electron transfer between the metal and the CNTs. The resulting material offers a high catalytic activity and easy magnetic separation of catalyst in the heterogeneous selective oxidation of cyclohexane. PMID:22488987

  20. Zoom in new insights of potential microbial control of N and CH4 gaseous losses induced by different agricultural practices in temperate paddy soils

    NASA Astrophysics Data System (ADS)

    Cucu, Maria Alexandra; Bardi, Laura; Said-Pullicino, Daniel; Sacco, Dario; Celi, Luisella; Gorra, Roberta

    2016-04-01

    that the assimilation of N contributes to the last step of archaeal denitrification. In a field experiment a high abundance of aerobic ammonia oxidizers suggested nitrification as proxy for complete denitrification, highlighting the importance of the latter in mitigating N2O emission from rice ecosystem. As a new insight for temperate rice paddies, our data indicated a high abundance of Anammox bacteria, suggesting this process to be very important in controlling N losses independently of water and rice straw management. Characteristic treatment interactions and cooperation were shown between aerobic and anaerobic ammonia oxidizers. Rice straw incorporation and the increased rice biomass due to N fertilization supported the methanogenesis. In this regard, a high abundance of mcrA gene was shown in situ level. Our findings highlighted the possibility of microorganisms niche differentiation not only driven by differential responses to NH4+ concentration, but also through different organic C substrates derived from more or less labile pools, and the contrasting straw C/N ratios in different treatments. The results provide novel insights into the influence of paddy soil management on microbial communities dynamics, with important implications on their potential functionality. These studies are a step forward in understanding the overall microbial control in N and CH4 gaseous losses mitigation from rice fields.

  1. Porous Au-embedded WO3 Nanowire Structure for Efficient Detection of CH4 and H2S

    PubMed Central

    Minh Vuong, Nguyen; Kim, Dojin; Kim, Hyojin

    2015-01-01

    We developed a facile method to fabricate highly porous Au-embedded WO3 nanowire structures for efficient sensing of CH4 and H2S gases. Highly porous single-wall carbon nanotubes were used as template to fabricate WO3 nanowire structures with high porosity. Gold nanoparticles were decorated on the tungsten nanowires by dipping in HAuCl4 solution, followed by oxidation. The surface morphology, structure, and electrical properties of the fabricated WO3 and Au-embedded WO3 nanowire structures were examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and current–voltage measurements. Formation of a nanowire structure resulted in significant enhancement in sensing response to H2S and CH4 gases. Furthermore, Au embedment into the WO3 nanowire structures remarkably improved the performance of the sensors. The increase in response performance of sensors and adsorption–desorption kinetic processes on the sensing layers were discussed in relation with the role of Au embedment. PMID:26087355

  2. 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

  3. Monitoring CO2 and CH4 concentrations along an urban-rural transect in London, UK

    NASA Astrophysics Data System (ADS)

    Boon, Alex; Broquet, Gregoire; Clifford, Debbie; Chevallier, Frederic; Butterfield, David

    2013-04-01

    Cities are important sources of carbon dioxide (CO2) and methane (CH4). Anthropogenic CO2 is released in the combustion of fossil fuels for heating, electricity and transport. The major sources of CH4 in city environments are natural gas leakage, landfill sites and transport emissions. Monitoring of urban greenhouse gas concentrations is crucial for cities aiming to reduce emissions through measures such as changes to the transport infrastructure and green planning. We present measurements of CO2 and CH4 concentrations using Cavity Ring-Down Spectroscopy (CRDS) at four sites located in and around London, UK. Two sites were located in the inner city, one in the suburban fringe and the fourth in a rural location close to the city. This study was funded by Astrium Services Ltd as part of a pilot scheme to monitor city-scale GHG emissions and presented a unique opportunity to study changes in greenhouse gas concentrations across an urban to rural 'transect'. The CHIMERE chemistry-transport model is used to estimate CO2 and CH4 concentrations throughout the four month measurement period during the summer of 2012. Comparisons are made between the measured and modelled CO2 and CH4 concentrations and the representativity of the study sites for future urban greenhouse gas monitoring is considered. This study also examines the ability of a variety of measurement and modelling techniques to partition anthropogenic and biogenic CO2 sources.

  4. 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.

  5. Lake Physical and Geochemical Traits Impact CH4 and CO2 Concentrations

    NASA Astrophysics Data System (ADS)

    Perry, A. L.; Logozzo, L. A.; Wik, M.; Thornton, B. F.; Crill, P. M.; Johnson, J. E.; Varner, R. K.

    2014-12-01

    Spatiotemporal variability combined with few lake measurements have resulted in a large amount of uncertainty regarding the emission potential of lakes. Both the amount of methane (CH4) emitted and controls on this emission vary spatially and temporally. A positive correlation has been shown between lake water/sediment temperature and the amount of CH4 emitted from lakes. Lack of data available on how other lake characteristics affect the emission of greenhouse gasses, specifically CH4 and carbon dioxide (CO2), indicate the need for measurements across a diversity of lake types to be able to accurately predict emissions in the future. This study focused on answering the question of how lake physical and geochemical traits impact emission potential in lake waters. Twenty subarctic lakes located in the Stordalen area, Abisko, Sweden (68°21'N, 18°49'E) were sampled for dissolved CH4, CO2 (as dissolved inorganic carbon (DIC)), DOC, particulate organic carbon (POC), water temperature, dissolved oxygen (DO), conductivity, and pH. Qualitative characteristics of shoreline vegetation and lake bottom structure were also noted. Data analysis included analysis of variance (ANOVA) and multiple linear regression analysis to determine the differences and predictability of emission potential based on the observed lake characteristics. The strongest correlation between CH4 concentrations and temperature occurred in lakes with algae and sediment bottom types with the lowest occurrences in rock and peat bottom types. Methane concentrations were highest in lakes with shore types composed of Carex spp., peat/ Carex spp. and rock/ Carex spp..

  6. Estimating CH4 Emissions in California Using Measurements from a Tower Network

    NASA Astrophysics Data System (ADS)

    Jeong, S.; Hsu, Y.; Andrews, A. E.; Bianco, L.; Vaca, P.; Wilczak, J. M.; Fischer, M. L.

    2012-12-01

    We estimate regionally resolved methane (CH4) emissions for California using a Bayesian inverse model driven by CH4 mixing ratios measured at a network of five towers across the Central Valley during 2010 - 2011. The method estimates emissions by comparing measurements with transport model predictions of CH4 signals obtained from two 0.1 degree prior emission maps: 1) seasonally varying "California-specific" emission maps, calibrated to State emission totals, and 2) the EDGAR4.2 static global emission map. Atmospheric transport is calculated from particle trajectories and surface footprints using the Weather Research and Forecasting (WRF) and Stochastic Time-Inverted Lagrangian Transport (STILT) models. Results for the 5-tower CARB-CEC-LBNL-NOAA network show that significant reductions in posterior emissions uncertainty are obtained for regions comprising ~ 90% of California's known CH4 emissions, with annually averaged emissions totaling 1.6+/-0.1 and 2.5+/-0.3 times California's inventory for the California-specific and EDGAR4.2 emissions maps, respectively. Assuming these results apply across California, total CH4 emissions account for approximately 8% - 14% of current state total greenhouse gas emissions. The magnitude and uncertainty of emissions from specific regions and source sectors (e.g., crop agriculture, waste management, livestock, and energy activities) are estimated by comparing region and source sector results obtained with the CA-specific and EDGAR4.2 emission maps.

  7. Insights into the structure of mixed CO2/CH4 in gas hydrates

    DOE PAGES

    Everett, S. Michelle; Rawn, Claudia J.; Chakoumakos, Bryan C.; Keffer, David J.; Huq, Ashfia; Phelps, Tommy J.

    2015-05-12

    The exchange of carbon dioxide for methane in natural gas hydrates is an attractive approach to harvesting CH4 for energy production while simultaneously sequestering CO2. In addition to the energy and environmental implications, the solid solution of clathrate hydrate (CH4)1-x(CO2)x·5.75H2O provides a model system to study how the distinct bonding and shapes of CH4 and CO2 influence the structure and properties of the compound. In this paper, high-resolution neutron diffraction was used to examine mixed CO2/CH4 gas hydrates. CO2-rich hydrates had smaller lattice parameters, which were attributed to the higher affinity of the CO2 molecule interacting with H2O molecules thatmore » 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 CH4/CO2 gas hydrate.« less

  8. Spectroscopic characterization of rovibrational temperatures in atmospheric pressure He /CH4 plasmas

    NASA Astrophysics Data System (ADS)

    Moon, Se Youn; Kim, D. B.; Gweon, B.; Choe, W.

    2008-10-01

    Atmospheric pressure of helium (He) and methane (CH4) mixture discharge characteristics are investigated using emission spectroscopic methods. Plasmas are produced in a radio frequency capacitively coupled device at atmospheric pressure in the ambient air. Without the CH4 gas introduced in the plasma, the emission spectrum exhibits typical helium discharge characteristics showing helium atomic lines with nitrogen molecular bands and oxygen atomic lines resulting from air impurities. Addition of a small amount (<1%) of CH4 to the supplied He results in the emission of CN (B2∑+-X2∑+: violet system) and CH (A2Δ-X2∏: 430nm system) molecular bands. Analyzing the CN and CH diatomic molecular emission spectra, the vibrational temperature (Tvib) and rotational temperature (Trot) are simultaneously obtained. As input power levels are raised from 20Wto200W, Tvib and Trot are increased from 4230Kto6310K and from 340K to500K, respectively. On the contrary, increasing the CH4 amount brings about the decrease of both temperatures because CH4 is harder to ionize than He. The emission intensities of CN and CH radicals, which are important in plasma processing, are also changed along with the temperature variation. From the results, the atmospheric pressure plasma shows strong nonequilibrium discharge properties, which may be effectively utilized for thermal damage free material treatments.

  9. Oxidation of ammonia and methane in an alkaline, saline lake

    USGS Publications Warehouse

    Joye, S.B.; Connell, T.L.; Miller, L.G.; Oremland, R.S.; Jellison, R.S.

    1999-01-01

    The oxidation of ammonia (NH3) and methane (CH4) was investigated in an alkaline saline lake, Mono Lake, California (U.S.A.). Ammonia oxidation was examined in April and July 1995 by comparing dark 14CO2 fixation rates in the presence or absence of methyl fluoride (MeF), an inhibitor of NH3 oxidation. Ammonia oxidizer-mediated dark 14CO2 fixation rates were similar in surface (5-7 m) and oxycline (11-15 m) waters, ranging between 70-340 and 89-186 nM d-1, respectively, or 1-7% of primary production by phytoplankton. Ammonia oxidation rates ranged between 580-2,830 nM d-1 in surface waters and 732-1,548 nM d-1 in oxycline waters. Methane oxidation was examined using a 14CH4 tracer technique in July 1994, April 1995, and July 1995. Methane oxidation rates were consistently higher in July, and rates in oxycline and anaerobic bottom waters (0.5-37 and 7-48 nM d-1, respectively) were 10-fold higher than those in aerobic surface waters (0.04-3.8 nM d-1). The majority of CH4 oxidation, in terms of integrated activity, occurred within anoxic bottom waters. Water column oxidation reduced the potential lake-atmosphere CH4 flux by a factor of two to three. Measured oxidation rates and water column concentrations were used to estimate the biological turnover times of NH3 and CH4. The NH3 pool turns over rapidly, on time scales of 0.8 d in surface waters and 10 d within the oxycline, while CH4 is cycled on 103-d time scales in surface waters and 102-d time scales within oxycline and bottom waters. Our data suggest an important role for NH3 oxidation in alkaline, saline lakes since the process converts volatile NH3 to soluble NO2-, thereby reducing loss via lake-atmosphere exchange and maintaining nitrogen in a form that is readily available to phytoplankton.

  10. Aerobic oxidation of hydroxymethylfurfural and furfural by using heterogeneous Cox Oy -N@C catalysts.

    PubMed

    Deng, Jin; Song, Hai-Jie; Cui, Min-Shu; Du, Yi-Ping; Fu, Yao

    2014-12-01

    2,5-Furandicarboxylic acid (FDCA) is considered to be a promising replacement for terephthalic acid since they share similar structures and properties. In contrast to FDCA, 2,5-furandicarboxylic acid methyl (FDCAM) has properties that allow it to be easily purified. In this work, we reported an oxidative esterification of 5-hydroxymethylfurfural (HMF) and furfural to prepare corresponding esters over Cox Oy -N@C catalysts using O2 as benign oxidant. High yield and selectivity of FDCAM and methyl 2-furoate were obtained under optimized conditions. Factors which influenced the product distribution were examined thoroughly. The Cox Oy -N@C catalysts were recycled five times and no significant loss of activity was detected. Characterization of the catalysts could explain such phenomena. Using XPS and TGA, we made a thorough investigation of the effects of ligand and pyrolysis temperature on catalyst activity.

  11. Factors Contributing to High CH4 and CO2 Efflux Rates from Thermokarst Lakes in the Rapidly Warming Hudson Bay Region

    NASA Astrophysics Data System (ADS)

    Matveev, A.; Vincent, W. F.; Laurion, I.

    2014-12-01

    Thermokarst lakes and ponds that form on thawing permafrost landscapes have long been recognized as biogeochemical reactors that emit significant amounts of CH4 and CO2. However, there is considerable uncertainty in the exact contribution of these water bodies to the global carbon cycle, in large part because of the paucity of observations from different ecosystem types across the circumpolar North, and the incomplete understanding of factors that control the balance between methane production (methanogenesis) and loss (methanotrophy). The aim of our research was to address these gaps by focusing on thermokarst lakes in subarctic Canada (eastern Hudson Bay), primarily at the southern limit of permafrost that is experiencing rapid warming, but where limnological changes have received little attention to date. Thermokarst lakes were sampled at five geographical locations that differed in their degree of permafrost degradation, as well as in carbon content and lability. All sampled lakes were supersaturated with CH4, with epilimnetic concentrations varying from CO2 undersaturation in turbid mineral (lithalsa) lakes of the continuous and discontinuous permafrost landscapes, to oversaturation by several orders of magnitude of both CO2 and CH4 in the organic-rich (palsa) lakes, especially in the areas of highly degraded permafrost at its southern limit. Concentrations and fluxes of CH4 and CO2 in these palsa lakes were at or above the highest values reported for thermokarst waters elsewhere. In addition, methane oxidation experiments showed high rates of methanotrophy that substantially reduced the net emission of CH4 from both lithalsa and palsa lake types. Our results imply that subarctic thermokarst lakes, especially those at the northward migrating permafrost margin, may be a major source of greenhouse gases as the circumpolar North continues to warm.

  12. A mild copper-catalyzed aerobic oxidative thiocyanation of arylboronic acids with TMSNCS.

    PubMed

    Sun, Nan; Che, Liusheng; Mo, Weimin; Hu, Baoxiang; Shen, Zhenlu; Hu, Xinquan

    2015-01-21

    A facile and efficient transformation of arylboronic acids to their corresponding aryl thiocyanates has been successfully developed. Based on the CuCl-catalyzed oxidative cross-coupling reaction between arylboronic acids and trimethylsilylisothiocyanate (TMSNCS) under oxygen atmosphere, the transformation can be readily conducted at ambient temperature. The newly-developed protocol provided a competitive synthetic approach to aryl thiocyanates that can tolerate a broad range of reactive functional groups and/or strong electron-withdrawing groups. PMID:25514847

  13. Hydrogen isotope systematics among H2-H2O-CH4 during the growth of the hydrogenotrophic methanogen Methanothermobacter thermautotrophicus strain ΔH

    NASA Astrophysics Data System (ADS)

    Kawagucci, Shinsuke; Kobayashi, Mariko; Hattori, Shohei; Yamada, Keita; Ueno, Yuichiro; Takai, Ken; Yoshida, Naohiro

    2014-10-01

    Stable hydrogen isotope systematics among H2, H2O, and CH4 during hydrogenotrophic methanogenesis were investigated by growing a thermophilic methanogen, Methanothermobacter thermautotrophicus strain ΔH, in batch cultures spiked with deuterium-labeled H2 and/or H2O. The hydrogen isotope ratio of the product, CH4, reflected not only the isotope ratio of the H2O in the medium but also that of the substrate, H2. The D/H ratios of the CH4 were highest during the early phase of growth, and the growth-phase-dependent changes were greatest in the deuterium-enriched H2 cultures. The hydrogen isotope systematics among H2, H2O, and CH4 during growth of the methanogen could be described with the following equations: δDCH4=a×δDH2O+b×δDH2-c a=0.71-0.55×b 0.17⩽b⩽0.38 c=1000×(a+b-1) The greatest effect of δDH2 on δDCH4 (b = 0.38) was observed during the earliest phase of growth. In contrast to this study, the possible disappearance of the effect (b = 0) has been suggested in a previous study (Valentine et al., 2004a) in which Methanothermobacter marburgensis was cultured and hydrogen isotope systematics during growth was monitored, as was the case in this study. The close phylogenetic relationship between M. thermautotrophicus and M. marburgensis, which likely have similar biochemical pathways, suggests a possibly broad range of the b value, 0-0.38. To explain the observed hydrogen isotope systematics, two cellular mechanisms were proposed. One is that the hydrogen atoms of both H2 and H2O are directly incorporated into the product, CH4. The other is that all four hydrogen atoms in the product, CH4, are derived from intracellular H2O, which consists of a mixture of medium-derived pristine H2O and isotopically distinct H2O derived from methanogenic H2 oxidation. Although we attempted to evaluate the feasibility of these mechanisms, both cellular mechanisms remain hypothetical. The hydrogen isotope systematics shown here contribute to put forward utility of δDCH4

  14. Contribution of grazing to soil atmosphere CH4 exchange during the growing season in a continental steppe

    NASA Astrophysics Data System (ADS)

    Tang, Shiming; Wang, Chengjie; Wilkes, Andreas; Zhou, Pei; Jiang, Yuanyuan; Han, Guodong; Zhao, Mengli; Huang, Ding; Schönbach, Philipp

    2013-03-01

    Degradation of steppes induced by overgrazing may affect the uptake of atmospheric methane (CH4) by soil sinks. However, uncertainty is associated with the very limited knowledge of gas fluxes in rapidly degrading steppe. In this study, we investigated the effects of grazing on CH4 uptake during the growing season in three types of steppe (meadow steppe, typical steppe and desert steppe and) in Inner Mongolia, China, to quantify and compare CH4 uptake in steppe ecosystems under different grazing management conditions. The CH4 fluxes were measured using an automatic cavity ring-down spectrophotometer at three steppe locations that differed primarily in grazing intensity. The results indicated that steppe soils were CH4 sinks throughout the growing season. CH4 uptake at all sites averaged 7.98 kg CH4-C ha-1 yr-1 (ranging from 1.53 to 18.74 kg CH4-C ha-1 yr-1), of which approximately 43.8% occurred in the desert steppe. CH4 uptake in the desert steppe increased 20.4% and 51.2% compared with the typical steppe and meadow steppe, respectively. Light grazing (LG) of steppe did not significantly change CH4 uptake compared with un-grazed (UG) steppe, but moderate and heavy grazing (MG, HG) reduced CH4 uptake significantly (by 6.8-37.9%, P < 0.05). These findings imply that reducing the grazing pressure on steppe would help increase the atmospheric CH4 sinks in steppe soils. Our results suggest that HG exerts a considerable negative impact on CH4 uptake in a continental steppe. Further studies involving year-round, intensive measurements of CH4 uptake are needed.

  15. Nanoscaled copper metal-organic framework (MOF) based on carboxylate ligands as an efficient heterogeneous catalyst for aerobic epoxidation of olefins and oxidation of benzylic and allylic alcohols.

    PubMed

    Qi, Yue; Luan, Yi; Yu, Jie; Peng, Xiong; Wang, Ge

    2015-01-19

    Aerobic epoxidation of olefins at a mild reaction temperature has been carried out by using nanomorphology of [Cu3(BTC)2] (BTC = 1,3,5-benzenetricarboxylate) as a high-performance catalyst through a simple synthetic strategy. An aromatic carboxylate ligand was employed to furnish a heterogeneous copper catalyst and also serves as the ligand for enhanced catalytic activities in the catalytic reaction. The utilization of a copper metal-organic framework catalyst was further extended to the aerobic oxidation of aromatic alcohols. The shape and size selectivity of the catalyst in olefin epoxidation and alcohol oxidation was investigated. Furthermore, the as-synthesized copper catalyst can be easily recovered and reused several times without leaching of active species or significant loss of activity. PMID:25430789

  16. Emissions of methane and nitrous oxide from outdoor-stored broiler litter using tunable-diode laser spectroscopy

    NASA Astrophysics Data System (ADS)

    de Wit, William Harrison

    Handling and storage of a variety of types of agricultural wastes results in the formation and release of nitrous oxide (N2O) and methane (CH4) gases to the atmosphere. These gases contribute to climate change through the greenhouse effect. Few studies have examined evolution of these gases from stored poultry litter in North America. Although N 2O is a by-product of nitrification, it is largely produced as an intermediate product of denitrification and is produced most intensely when both aerobic and anaerobic conditions are present. CH4 emissions, however, are typically associated with anaerobic reactions. Outdoor storage of broiler litter provides an excellent media for which both aerobic and anaerobic zones can coexist, particularly when the litter is of varying ages from multiple broiler flocks (cycles). It provides a large amount of nitrogen for bacterial nitrification/denitrification processes as well as Carbon to support anaerobic bacterial fermentation. The objective of the study was to quantify N 2O and CH4 emissions for broiler litter stored in an uncovered, outdoor bunker by conducting small-scale dynamic flux chamber studies and full-scale field experiments. The field experiments used a modified micrometeorological mass balance approach to monitor emissions from stored broiler litter in a three-walled concrete bunker. Atmospheric concentrations of N2O and CH4 were measured using tunable-diode laser spectroscopy. Field experiments over the course of approximately four months yielded average emission rates of 14+/-17mug m-2 s -1 and 84+/-61 mug m-2 s-1 for N2O and CH4 respectively that agreed well with the trends of emission rates observed in the dynamic flux chamber experiments. The primary drivers of emissions of both CH4 and N2O appeared to be temperature and moisture content while organic carbon and organic nitrogen (loss on ignition, nitrate concentrations) contents were also important factors.

  17. A combustion setup to precisely reference δ13C and δ2H isotope ratios of pure CH4 to produce isotope reference gases of δ13C-CH4 in synthetic air

    NASA Astrophysics Data System (ADS)

    Sperlich, P.; Guillevic, M.; Buizert, C.; Jenk, T. M.; Sapart, C. J.; Schaefer, H.; Blunier, T.

    2012-05-01

    Isotope records of atmospheric CH4 can be used to infer changes in the biochemistry of CH4. One factor limiting quantitative estimates of changes in the biogeochemistry of CH4 are the uncertainties of the isotope measurements due to the lack of a unique isotope reference gas, certified for δ13C-CH4 or δ2H-CH4. We present a method to produce isotope reference gases for CH4 in synthetic airs that are precisely anchored to the VPDB and VSMOW scale and contain δ13C-CH4 values typical for the modern and glacial atmosphere. We quantitatively combusted two pure CH4 gases from fossil and biogenic sources and determined the δ13C and δ2H values of the produced CO2 and H2O relative to the VPDB and VSMOW scale within a very small analytical uncertainty of 0.04‰ and 0.7‰, respectively. We found isotope ratios of -39.56‰ and -56.37‰ for δ13C and -170.1‰ and -317.4‰ for δ2H in the fossil and biogenic CH4, respectively. We used both CH4 types as parental gases from which we mixed two filial CH4 gases. Their δ13C was determined to be -42.21‰ and -47.25‰, representing glacial and present atmospheric δ13C-CH4. The δ2H isotope ratios of the filial CH4 gases were found with -193.1‰ and -237.1‰, respectively. Next, we mixed aliquots of the filial CH4 gases with ultrapure N2/O2 (CH4 ≤ 2 ppb) producing two isotope reference gases of synthetic air with CH4 mixing ratios near atmospheric values. We show that our method is reproducible and does not introduce isotopic fractionation for δ13C within the uncertainties of our detection limit (we cannot conclude this for δ2H because our system is currently not prepared for δ2H-CH4 measurements in air samples). The general principle of our method can be applied to produce synthetic isotope reference gases targeting δ2H-CH4 or other gas species.

  18. Biogeochemical modeling of CO2 and CH4 production in anoxic Arctic soil microcosms

    DOE PAGES

    Tang, Guoping; Zheng, Jianqiu; Xu, Xiaofeng; Yang, Ziming; Graham, David E.; Gu, Baohua; Painter, Scott L.; Thornton, Peter E.

    2016-09-12

    Soil organic carbon turnover to CO2 and CH4 is sensitive to soil redox potential and pH conditions. But, land surface models do not consider redox and pH in the aqueous phase explicitly, thereby limiting their use for making predictions in anoxic environments. Using recent data from incubations of Arctic soils, we extend the Community Land Model with coupled carbon and nitrogen (CLM-CN) decomposition cascade to include simple organic substrate turnover, fermentation, Fe(III) reduction, and methanogenesis reactions, and assess the efficacy of various temperature and pH response functions. Incorporating the Windermere Humic Aqueous Model (WHAM) enables us to approximately describe themore » observed pH evolution without additional parameterization. Though Fe(III) reduction is normally assumed to compete with methanogenesis, the model predicts that Fe(III) reduction raises the pH from acidic to neutral, thereby reducing environmental stress to methanogens and accelerating methane production when substrates are not limiting. Furthermore, the equilibrium speciation predicts a substantial increase in CO2 solubility as pH increases, and taking into account CO2 adsorption to surface sites of metal oxides further decreases the predicted headspace gas-phase fraction at low pH. Without adequate representation of these speciation reactions, as well as the impacts of pH, temperature, and pressure, the CO2 production from closed microcosms can be substantially underestimated based on headspace CO2 measurements only. Our results demonstrate the efficacy of geochemical models for simulating soil biogeochemistry and provide predictive understanding and mechanistic representations that can be incorporated into land surface models to improve climate predictions.« less

  19. 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.

  20. Biogeochemical modeling of CO2 and CH4 production in anoxic Arctic soil microcosms

    NASA Astrophysics Data System (ADS)

    Tang, Guoping; Zheng, Jianqiu; Xu, Xiaofeng; Yang, Ziming; Graham, David E.; Gu, Baohua; Painter, Scott L.; Thornton, Peter E.

    2016-09-01

    Soil organic carbon turnover to CO2 and CH4 is sensitive to soil redox potential and pH conditions. However, land surface models do not consider redox and pH in the aqueous phase explicitly, thereby limiting their use for making predictions in anoxic environments. Using recent data from incubations of Arctic soils, we extend the Community Land Model with coupled carbon and nitrogen (CLM-CN) decomposition cascade to include simple organic substrate turnover, fermentation, Fe(III) reduction, and methanogenesis reactions, and assess the efficacy of various temperature and pH response functions. Incorporating the Windermere Humic Aqueous Model (WHAM) enables us to approximately describe the observed pH evolution without additional parameterization. Although Fe(III) reduction is normally assumed to compete with methanogenesis, the model predicts that Fe(III) reduction raises the pH from acidic to neutral, thereby reducing environmental stress to methanogens and accelerating methane production when substrates are not limiting. The equilibrium speciation predicts a substantial increase in CO2 solubility as pH increases, and taking into account CO2 adsorption to surface sites of metal oxides further decreases the predicted headspace gas-phase fraction at low pH. Without adequate representation of these speciation reactions, as well as the impacts of pH, temperature, and pressure, the CO2 production from closed microcosms can be substantially underestimated based on headspace CO2 measurements only. Our results demonstrate the efficacy of geochemical models for simulating soil biogeochemistry and provide predictive understanding and mechanistic representations that can be incorporated into land surface models to improve climate predictions.

  1. Special role of corn flour as an ideal carbon source for aerobic denitrification with minimized nitrous oxide emission.

    PubMed

    Zhu, Shuangyue; Zheng, Maosheng; Li, Can; Gui, Mengyao; Chen, Qian; Ni, Jinren

    2015-06-01

    Much effort has been made for reducing nitrous oxide (N2O) emission in wastewater treatment processes. This paper presents an interesting way to minimize N2O in aerobic denitrification by strain Pseudomonas stutzeri PCN-1 with help of corn flour as cheaper additional carbon source. Experimental results showed that maximal N2O accumulation by strain PCN-1 was only 0.02% of removed nitrogen if corn flour was used as sole carbon source, which was significantly reduced by 52.07-99.81% comparing with others such as succinate, glucose, acetate and citrate. Sustained release of reducing sugar from starch and continuous expression of nosZ coding for N2O reductase contributed to the special role of corn flour as the ideal carbon source for strain PCN-1. Further experiments in sequencing batch reactors (SBRs) demonstrated similarly efficient nitrogen removal with much less N2O emission due to synergy of the novel strain and activated sludge, which was then confirmed by quantitative PCR analysis. PMID:25802047

  2. Preparation and Catalytic Activity for Aerobic Glucose Oxidation of Crown Jewel Structured Pt/Au Bimetallic Nanoclusters

    NASA Astrophysics Data System (ADS)

    Zhang, Haijun; Wang, Liqiong; Lu, Lilin; Toshima, Naoki

    2016-08-01

    Understanding of the “structure-activity” relations for catalysts at an atomic level has been regarded as one of the most important objectives in catalysis studies. Bimetallic nanoclusters (NCs) in its many types, such as core/shell, random alloy, cluster-in-cluster, bi-hemisphere, and crown jewel (one kind of atom locating at the top position of another kind of NC), attract significant attention owing to their excellent optical, electronic, and catalytic properties. PVP-protected crown jewel-structured Pt/Au (CJ-Pt/Au) bimetallic nanoclusters (BNCs) with Au atoms located at active top sites were synthesized via a replacement reaction using 1.4-nm Pt NCs as mother clusters even considering the fact that the replacement reaction between Pt and Au3+ ions is difficult to be occurred. The prepared CJ-Pt/Au colloidal catalysts characterized by UV-Vis, TEM, HR-TEM and HAADF-STEM-EELS showed a high catalytic activity for aerobic glucose oxidation, and the top Au atoms decorating the Pt NCs were about 15 times more active than the Au atoms of Au NCs with similar particle size.

  3. Preparation and Catalytic Activity for Aerobic Glucose Oxidation of Crown Jewel Structured Pt/Au Bimetallic Nanoclusters.

    PubMed

    Zhang, Haijun; Wang, Liqiong; Lu, Lilin; Toshima, Naoki

    2016-01-01

    Understanding of the "structure-activity" relations for catalysts at an atomic level has been regarded as one of the most important objectives in catalysis studies. Bimetallic nanoclusters (NCs) in its many types, such as core/shell, random alloy, cluster-in-cluster, bi-hemisphere, and crown jewel (one kind of atom locating at the top position of another kind of NC), attract significant attention owing to their excellent optical, electronic, and catalytic properties. PVP-protected crown jewel-structured Pt/Au (CJ-Pt/Au) bimetallic nanoclusters (BNCs) with Au atoms located at active top sites were synthesized via a replacement reaction using 1.4-nm Pt NCs as mother clusters even considering the fact that the replacement reaction between Pt and Au(3+) ions is difficult to be occurred. The prepared CJ-Pt/Au colloidal catalysts characterized by UV-Vis, TEM, HR-TEM and HAADF-STEM-EELS showed a high catalytic activity for aerobic glucose oxidation, and the top Au atoms decorating the Pt NCs were about 15 times more active than the Au atoms of Au NCs with similar particle size. PMID:27476577

  4. Preparation and Catalytic Activity for Aerobic Glucose Oxidation of Crown Jewel Structured Pt/Au Bimetallic Nanoclusters

    PubMed Central

    Zhang, Haijun; Wang, Liqiong; Lu, Lilin; Toshima, Naoki

    2016-01-01

    Understanding of the “structure-activity” relations for catalysts at an atomic level has been regarded as one of the most important objectives in catalysis studies. Bimetallic nanoclusters (NCs) in its many types, such as core/shell, random alloy, cluster-in-cluster, bi-hemisphere, and crown jewel (one kind of atom locating at the top position of another kind of NC), attract significant attention owing to their excellent optical, electronic, and catalytic properties. PVP-protected crown jewel-structured Pt/Au (CJ-Pt/Au) bimetallic nanoclusters (BNCs) with Au atoms located at active top sites were synthesized via a replacement reaction using 1.4-nm Pt NCs as mother clusters even considering the fact that the replacement reaction between Pt and Au3+ ions is difficult to be occurred. The prepared CJ-Pt/Au colloidal catalysts characterized by UV-Vis, TEM, HR-TEM and HAADF-STEM-EELS showed a high catalytic activity for aerobic glucose oxidation, and the top Au atoms decorating the Pt NCs were about 15 times more active than the Au atoms of Au NCs with similar particle size. PMID:27476577

  5. Integrated thermophilic submerged aerobic membrane bioreactor and electrochemical oxidation for pulp and paper effluent treatment--towards system closure.

    PubMed

    Qu, X; Gao, W J; Han, M N; Chen, A; Liao, B Q

    2012-07-01

    A novel integrated thermophilic submerged aerobic membrane bioreactor (TSAMBR) and electrochemical oxidation (EO) technology was developed for thermomechanical pulping pressate treatment with the aim of system closure. The TSAMBR was able to achieve a chemical oxygen demand (COD) removal efficiency of 88.6 ± 1.9-92.3 ± 0.7% under the organic loading rate of 2.76 ± 0.13-3.98 ± 0.23 kg COD/(m(3) d). An optimal hydraulic retention time (HRT) of 1.1 ± 0.1d was identified for COD removal. Cake formation was identified as the dominant mechanism of membrane fouling. The EO of the TSAMBR permeate was performed using a Ti/SnO(2)-Sb(2)O(5)-IrO(2) electrode. After 6-h EO, a complete decolourization was achieved and the COD removal efficiency was increased to 96.2