Measurement of greenhouse gas emissions from agricultural sites using open-path optical remote sensing method.

PubMed

Ro, Kyoung S; Johnson, Melvin H; Varma, Ravi M; Hashmonay, Ram A; Hunt, Patrick

2009-08-01

Improved characterization of distributed emission sources of greenhouse gases such as methane from concentrated animal feeding operations require more accurate methods. One promising method is recently used by the USEPA. It employs a vertical radial plume mapping (VRPM) algorithm using optical remote sensing techniques. We evaluated this method to estimate emission rates from simulated distributed methane sources. A scanning open-path tunable diode laser was used to collect path-integrated concentrations (PICs) along different optical paths on a vertical plane downwind of controlled methane releases. Each cycle consists of 3 ground-level PICs and 2 above ground PICs. Three- to 10-cycle moving averages were used to reconstruct mass equivalent concentration plum maps on the vertical plane. The VRPM algorithm estimated emission rates of methane along with meteorological and PIC data collected concomitantly under different atmospheric stability conditions. The derived emission rates compared well with actual released rates irrespective of atmospheric stability conditions. The maximum error was 22 percent when 3-cycle moving average PICs were used; however, it decreased to 11% when 10-cycle moving average PICs were used. Our validation results suggest that this new VRPM method may be used for improved estimations of greenhouse gas emission from a variety of agricultural sources.

Long open-path TDL based system for monitoring background concentration for deployment at Jungfraujoch High Altitude Research Station- Switzerland

NASA Astrophysics Data System (ADS)

Simeonov, Valentin; van den Bergh, Hubert; Parlange, Marc

2010-05-01

A new, long open-path instrument for monitoring of path-averaged methane and water vapor concentrations will be presented. The instrument is built on the monostatic scheme (transceiver - distant retroreflector). A VCSEL tunable diode laser (TDL) with a central wavelength of 1654 nm is used as a light source. A specially designed, single-cell, hollow-cube retroreflector with 150 mm aperture will be installed at 1200 m from the transceiver in the final deployment at Jungfraujjoch and 100 mm retroreflectors will be used in the other applications. The receiver is built around a 20 cm Newtonian telescope. To avoid distortions in the shape of a methane line, caused by atmospheric turbulences, the line is scanned within 1 µs. Fast InGaAs photodiodes and 200 MHz are used to achieve this scanning rate. The expected concentration resolution for the above mentioned path lengths is of the order of 2 ppb. The instrument is developed at the Swiss Federal Institute of Technology - Lausanne (EPFL) Switzerland and will be used within the GAW+ CH program for long-term monitoring of background methane concentration in the Swiss Alps. After completing the initial tests at EPFL the instrument will be installed in 2012 at the High Altitude Research Station Jungfraujoch (HARSJ) located at 3580 m ASL. The HARSJ is one of the 24 global GAW stations and carries on continuous observations of a number of trace gasses, including methane. One of the goals of the project is to compare path-averaged to ongoing point measurements of methane in order to identify possible influence of the station. Future deployments of a copy of the instrument include the Colombian part of Amazonia and Siberian wetlands.

INNOVATIVE APPROACH FOR MEASURING AMMONIA AND METHANE FLUXES FROM A HOG FARM USING OPEN-PATH FOURIER TRANSFORM INFRARED SPECTROSCOPY

EPA Science Inventory

The paper describes a new approach to quantify emissions from area air pollution sources. The approach combines path-integrated concentration data acquired with any path-integrated optical remote sensing (PI-ORS) technique and computed tomography (CT) technique. In this study, an...

Long-range open-path greenhouse gas monitoring using mid-infrared laser dispersion spectroscopy

NASA Astrophysics Data System (ADS)

Daghestani, Nart; Brownsword, Richard; Weidmann, Damien

2015-04-01

Accurate and sensitive methods of monitoring greenhouse gas (GHG) emission over large areas has become a pressing need to deliver improved estimates of both human-made and natural GHG budgets. These needs relate to a variety of sectors including environmental monitoring, energy, oil and gas industry, waste management, biogenic emission characterization, and leak detection. To address the needs, long-distance open-path laser spectroscopy methods offer significant advantages in terms of temporal resolution, sensitivity, compactness and cost effectiveness. Path-integrated mixing ratio measurements stemming from long open-path laser spectrometers can provide emission mapping when combined with meteorological data and/or through tomographic approaches. Laser absorption spectroscopy is the predominant method of detecting gasses over long integrated path lengths. The development of dispersion spectrometers measuring tiny refractive index changes, rather than optical power transmission, may offer a set of specific advantages1. These include greater immunity to laser power fluctuations, greater dynamic range due to the linearity of dispersion, and ideally a zero baseline signal easing quantitative retrievals of path integrated mixing ratios. Chirped laser dispersion spectrometers (CLaDS) developed for the monitoring of atmospheric methane and carbon dioxide will be presented. Using quantum cascade laser as the source, a minimalistic and compact system operating at 7.8 μm has been developed and demonstrated for the monitoring of atmospheric methane over a 90 meter open path2. Through full instrument modelling and error propagation analysis, precision of 3 ppm.m.Hz-0.5 has been established (one sigma precision for atmospheric methane normalized over a 1 m path and 1 s measurement duration). The system was fully functional in the rain, sleet, and moderate fog. The physical model and system concept of CLaDS can be adapted to any greenhouse gas species. Currently we are developing an in-lab instrument that can measure carbon dioxide using a quantum cascade laser operating in the 4 μm range. In this case, the dynamic range benefit of CLaDS is used to provide high precision even when peak absorbance in the CO2 spectrum gets greater than 2. Development for this deployable CO2 measurement system is still at an early stage. So far laboratory gas cell experiments have demonstrated a 9.3 ppm.m.Hz-0.5 for CO2 monitoring. This corresponds to about 0.02% relative precision in measuring CO2 atmospheric background over a 100 m open-path in one second. 1 G. Wysocki and D. Weidmann, "Molecular dispersion spectroscopy for chemical sensing using chirped mid-infrared quantum cascade laser," Opt. Express 18(25), 26123-26140 (2010). 2 N.S. Daghestani, R. Brownsword, D. Weidmann, 'Analysis and demonstration of atmospheric methane monitoring by mid-infrared open-path chirped dispersion spectroscopy' Opt. Express 22(25), A1731-A1743 (2014).

Long open-path TDL based system for monitoring the background concentration for deployment at Jungfraujoch High Altitude Research Station- Switzerland

NASA Astrophysics Data System (ADS)

Simeonov, V.; van den Bergh, H.; Parlange, M. B.

2009-12-01

A new long-open-path instrument developed at EPFL for methane and water vapor observation will be presented. The instrument is developed and will be used within the GAW+ CH program and aims at long-term monitoring of background methane concentration at the High Altitude Research Station Jungfraujoch (3580 mASL). The instrument is built on the monostatic scheme (transceiver -distant retroreflector) using a 1.65 nm tunable diode laser (TDL) and a retroreflector at 1200 m from the transceiver. The data will be compared with in-situ measurements to evaluate the effect of the station on the in-situ data.

SEASONAL EMISSIONS OF AMMONIA AND METHANE FROM A HOG WASTE LAGOON WITH BIOACTIVE COVER

EPA Science Inventory

The paper discusses the use of plane-integrated (PI) open-path Fourier transform infrared spectrometry (OP-FTIR) to measure the flux of ammonia and methane from a hog waste lagoon before and after the installation of a bioactive cover. A computed tomography algorithm using a smoo...

Spatial and temporal characterization of methane plumes from mobile platforms

NASA Astrophysics Data System (ADS)

O'Brien, A.; Wendt, L.; Miller, D. J.; Lary, D. J.; Zondlo, M. A.

2013-12-01

The spatial and temporal characterization of methane plumes from hydraulic fracturing well sites are presented. Methane measurements from the Marcellus shale region obtained using a commercial instrument on a motor vehicle are discussed. Over 100 well sites in the region were sampled and the methane signature in the vicinity of these wells is presented. Additionally, measurements of methane from our open-path instrument flown aboard the UT Dallas AMR Payload Master 100 remote-controlled, electric aircraft in the Barnett shale region are presented. Using our observations of aircraft surveys near well sites and a gaussian plume dispersion model emission estimates of fugitive methane are presented.

Eddy Correlation Flux Measurement System Handbook

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

Cook, D. R.

2016-01-01

The eddy correlation (ECOR) flux measurement system provides in situ, half-hour measurements of the surface turbulent fluxes of momentum, sensible heat, latent heat, and carbon dioxide (CO2) (and methane at one Southern Great Plains extended facility (SGP EF) and the North Slope of Alaska Central Facility (NSA CF). The fluxes are obtained with the eddy covariance technique, which involves correlation of the vertical wind component with the horizontal wind component, the air temperature, the water vapor density, and the CO2 concentration. The instruments used are: • a fast-response, three-dimensional (3D) wind sensor (sonic anemometer) to obtain the orthogonal wind componentsmore » and the speed of sound (SOS) (used to derive the air temperature) • an open-path infrared gas analyzer (IRGA) to obtain the water vapor density and the CO2 concentration, and • an open-path infrared gas analyzer (IRGA) to obtain methane density and methane flux at one SGP EF and at the NSA CF. The ECOR systems are deployed at the locations where other methods for surface flux measurements (e.g., energy balance Bowen ratio [EBBR] systems) are difficult to employ, primarily at the north edge of a field of crops. A Surface Energy Balance System (SEBS) has been installed collocated with each deployed ECOR system in SGP, NSA, Tropical Western Pacific (TWP), ARM Mobile Facility 1 (AMF1), and ARM Mobile Facility 2 (AMF2). The surface energy balance system consists of upwelling and downwelling solar and infrared radiometers within one net radiometer, a wetness sensor, and soil measurements. The SEBS measurements allow the comparison of ECOR sensible and latent heat fluxes with the energy balance determined from the SEBS and provide information on wetting of the sensors for data quality purposes. The SEBS at one SGP and one NSA site also support upwelling and downwelling PAR measurements to qualify those two locations as Ameriflux sites.« less

Effects of Environmental Conditions on an Urban Wetland's Methane Fluxes

NASA Astrophysics Data System (ADS)

Naor Azrieli, L.; Morin, T. H.; Bohrer, G.; Schafer, K. V.; Brooker, M.; Mitsch, W. J.

2013-12-01

Methane emissions from wetlands are the largest natural source of uncertainty in the global methane (CH4) budget. Wetlands are highly productive ecosystems with a large carbon sequestration potential. While wetlands are a net sink for carbon dioxide, they also release methane, a potent greenhouse gas. To effectively develop wetland management techniques, it is important to properly calculate the carbon budget of wetlands by understand the driving factors of methane fluxes. We constructed an eddy flux covariance system in the Olentangy River Wetland Research Park, a series of created and restored wetland in Columbus Ohio. Through the use of high frequency open path infrared gas analyzer (IRGA) sensors, we have continuously monitored the methane fluxes associated with the wetland since May 2011. To account for the heterogeneous landscape surrounding the tower, a footprint analysis was used to isolate data originating from within the wetland. Continuous measurements of the meteorological and environmental conditions at the wetlands coinciding with the flux measurements allow the interactions between methane fluxes and the climate and ecological forcing to be studied. The wintertime daily cycle of methane peaks around midday indicating a typical diurnal pattern in cold months. In the summer, the peak shifts to earlier in the day and also includes a daily peak occurring at approximately 10 AM. We believe this peak is associated with the onset of photosynthesis in Typha latifolia flushing methane from the plant's air filled tissue. Correlations with methane fluxes include latent heat flux, soil temperature, and incoming radiation. The connection to radiation may be further evidence of plant activity as a driver of methane fluxes. Higher methane fluxes corresponding with higher soil temperature indicates that warmer days stimulate the methanogenic consortium. Further analysis will focus on separating the methane fluxes into emissions from different terrain types within the wetland.

Ammonia and methane emissions from cattle and dairy feedlots in Colorado

NASA Astrophysics Data System (ADS)

Golston, L.; Pan, D.; Stanton, L. G.; Tao, L.; Sun, K.; Zondlo, M. A.

2014-12-01

Concentrated animal feeding operations (CAFOs) are recognized as a major contributor of both methane and ammonia to the atmosphere. Ammonia is released by volatilization of urea and nitrogen containing wastes from the feedlot surface and waste management systems, while methane is produced from enteric fermentation and primarily exhaled into the atmosphere. Our objective was to survey plumes downwind of open lot feedyards near Greeley, Colorado and surrounding areas, to quantify the spatial and temporal variability of agricultural emissions in this area. Research was conducted during the month-long NASA DISCOVER-AQ campaign in July-August 2014, with over 4000 km of on-road measurements. Methane and ammonia concentrations were measured using open-path laser spectroscopy, along with water vapor, carbon monoxide, and carbon dioxide on a roof-mounted, mobile platform. The open-path design enables high resolution measurements of ammonia with minimized sampling issues. Concurrent measurements during the campaign by other groups on stationary and aircraft platforms help characterize the meteorological conditions and atmospheric chemistry. We present measurements from 65 of the 67 registered CAFOs in Weld County, which contain up to 660,000 cattle-equivalent animals units. The ammonia to methane enhancement ratio, ΔNH3:ΔCH4, was positively skewed with a median of 0.14 ± 0.04 ppmv/ppmv, consistent with our previous measurements during DISCOVER-AQ California. Due to the much greater variability of ammonia compared to methane, the emissions ratio is used to provide an estimate of feedyard ammonia emissions, with results divided for cattle, dairy, and sheep. Using the most recent emissions estimates of methane, we calculated a total of ≈28.8 TgNH3/yr released globally from feedlots alone, nearly as large as the IPCC's estimate of 30.4 Tg/yr from all agriculture sources. This discrepancy suggests feedyard ammonia is underrepresented in current inventories and models, and its environmental effects on air quality and nitrogen deposition are not fully accounted for.

Near-Field Characterization of Methane Emission Variability from a Compressor Station Using a Model Aircraft.

PubMed

Nathan, Brian J; Golston, Levi M; O'Brien, Anthony S; Ross, Kevin; Harrison, William A; Tao, Lei; Lary, David J; Johnson, Derek R; Covington, April N; Clark, Nigel N; Zondlo, Mark A

2015-07-07

A model aircraft equipped with a custom laser-based, open-path methane sensor was deployed around a natural gas compressor station to quantify the methane leak rate and its variability at a compressor station in the Barnett Shale. The open-path, laser-based sensor provides fast (10 Hz) and precise (0.1 ppmv) measurements of methane in a compact package while the remote control aircraft provides nimble and safe operation around a local source. Emission rates were measured from 22 flights over a one-week period. Mean emission rates of 14 ± 8 g CH4 s(-1) (7.4 ± 4.2 g CH4 s(-1) median) from the station were observed or approximately 0.02% of the station throughput. Significant variability in emission rates (0.3-73 g CH4 s(-1) range) was observed on time scales of hours to days, and plumes showed high spatial variability in the horizontal and vertical dimensions. Given the high spatiotemporal variability of emissions, individual measurements taken over short durations and from ground-based platforms should be used with caution when examining compressor station emissions. More generally, our results demonstrate the unique advantages and challenges of platforms like small unmanned aerial vehicles for quantifying local emission sources to the atmosphere.

Methane distributions and transports in the nocturnal boundary layer at a rural station

NASA Astrophysics Data System (ADS)

Schäfer, Klaus; Zeeman, Matthias; Brosy, Caroline; Münkel, Christoph; Fersch, Benjamin; Mauder, Matthias; Emeis, Stefan

2016-10-01

To investigate the methane distributions and transports, the role of related atmospheric processes by determination of vertical profiles of wind, turbulence, temperature and humidity as well as nocturnal boundary layer (NBL) height and the quantification of methane emissions at local and plot scale the so-called ScaleX-campaign was performed in a pre-alpine observatory in Southern Germany from 01 June until 31 July 2015. The following measurements from the ground up to the free troposphere were performed: layering of the atmosphere by a ceilometer (Vaisala CL51); temperature, wind, turbulence profiles from 50 m up to 500 m by a Radio-Acoustic Sounding System (RASS, Metek GmbH); temperature, humidity profiles in situ by a hexacopter; methane farm emissions by two open-path laser spectrometers (Boreal GasFinder2); methane concentrations in situ (Los Gatos DLT-100) with tubes in 0.3 m agl and 5 sampling heads; and methane soil emissions by a big chamber (10 m length, 2.60 m width, up to 0.61 m height) with a plastic cover. The methane concentrations near the surface show a daily variation with a maximum and a frequent double-peak structure during night-time. Analysis of the variation of the nocturnal methane concentration together with the hexacopter and RASS data indicates that the first peak in the nocturnal methane concentration is probably due to local cooling and stabilization which keeps the methane emissions from the soil near the ground. The second peak seems to be due to advection of methane-enriched air which had formed in the environment of the nearby farm yards. These dairy farm emissions were determined by up-wind and down-wind open-path concentration measurements, turbulence data from an EC station nearby and Backward Lagrangian Simulation (WindTrax software). The methane fluxes at plot scale (big chamber) are characterized by emissions at water saturated grassland patches, by an exponential decrease of these emissions during grassland drying, and by an uptake of methane at dry grassland. Highest methane concentrations are found with lowest NBL heights which were determined from the ceilometer monitoring (correlation coefficient 0.56).

Management practices and controls on methane emissions from sub-tropical wetlands

NASA Astrophysics Data System (ADS)

DeLucia, Nicholas; Casa-Nova Gomez, Nuri; Bernacchi, Carl

2015-04-01

It is well documented that green house gas concentrations have risen at unequivocal rates since the industrial revolution but the disparity between anthropogenic sources and natural sources is uncertain. Wetlands are one example of a natural ecosystem that can be a substantial source or sink for methane (CH4) depending on any combination of climate conditions, natural and anthropogenic disturbances, or ecosystem perturbations. Due to strict anaerobic conditions required for CH4-generating microorganisms, natural wetlands are the main source for biogenic CH4. Although wetlands occupy less than 5% of total land surface area, they contribute approximately 20% of total CH4 emissions to the atmosphere. CH4 is one of the most damaging green house gases with current emission estimates ranging from 55 to 231 Tg CH4 yr-1. The processes regulating CH4 emissions are sensitive to land use and management practices of areas surrounding wetlands. Variation in adjacent vegetation or grazing intensity by livestock can, for example, alter CH4 fluxes from wetland soils by altering nutrient balance, carbon inputs and hydrology. Therefore, understanding how these changes will affect wetland source strength is essential to understand the impact of wetland management practices on the global climate system. In this study we quantify wetland methane fluxes from subtropical wetlands on a working cattle ranch in central Florida near Okeechobee Lake (27o10'52.04"N, 81o21'8.56"W). To determine differences in CH4 fluxes associated with land use and management, a replicated (n = 4) full factorial experiment was designed for wetlands where the surrounding vegetation was (1) grazed or un-grazed and (2) composed of native vegetation or improved pasture. Net exchange of CH4 and CO2 between the land surface and the atmosphere were sampled with a LICOR Li-7700 open path CH4 analyzer and Li-7500A open path CO2/H20 analyzer mounted in a 1-m3 static gas-exchange chamber. Our results showed and verified that CH4 emissions from subtropical wetlands were larger when high soil moisture was coupled with high temperatures. Grazing alone, does not appear to alter net ecosystem CH4 emissions from subtropical semi-native and improved wetlands. Pasture type is a stronger indicator of wetland methane potential. Wetlands embedded in improved pastures exhibited periods of increased methane emission that was particularly noticeable during the wet season (July- Nov). These results help quantify GHG emissions from subtropical wetlands under different management practices while demonstrating the differences in these fluxes based on the surrounding ecosystem.

Methane Fluxes from Subtropical Wetlands

NASA Astrophysics Data System (ADS)

DeLucia, N.; Gomez-Casanovas, N.; Bernacchi, C.

2013-12-01

It is well documented that green house gas concentrations have risen at unequivocal rates since the industrial revolution but the disparity between anthropogenic sources and natural sources is uncertain. Wetlands are one example of a natural ecosystem that can be a substantial source or sink for methane (CH4) depending on climate conditions. Due to strict anaerobic conditions required for CH4-generating microorganisms, natural wetlands are one of the main sources for biogenic CH4. Although wetlands occupy less than 5% of total land surface area, they contribute approximately 20% of total CH4 emissions to the atmosphere. The processes regulating CH4 emissions are sensitive to land use and management practices of areas surrounding wetlands. Variation in adjacent vegetation or grazing intensity by livestock can, for example, alter CH4 fluxes from wetland soils by altering nutrient balance, carbon inputs and hydrology. Therefore, understanding how these changes will affect wetland source strength is essential to understand the impact of wetland management practices on the global climate system. In this study we quantify wetland methane fluxes from subtropical wetlands on a working cattle ranch in central Florida near Okeechobee Lake (27o10'52.04'N, 81o21'8.56'W). To determine differences in CH4 fluxes associated with land use and management, a replicated (n = 4) full factorial experiment was designed for wetlands where the surrounding vegetation was (1) grazed or un-grazed and (2) composed of native vegetation or improved pasture. Net exchange of CH4 and CO2 between the land surface and the atmosphere were sampled with a LICOR Li-7700 open path CH4 analyzer and Li-7500A open path CO2/H20 analyzer mounted in a 1-m3 static gas-exchange chamber. Our results showed and verified that CH4 emissions from subtropical wetlands were larger when high soil moisture was coupled with high temperatures. The presence of cattle only amplified these results. These results help quantify GHG emissions from subtropical wetlands while demonstrating the differences in these fluxes based on the surrounding ecosystem.

Portable Dual-comb Spectrometer for Stable Detection of Methane Leaks over Kilometer Scale Paths at Oil and Natural Gas Production Site

NASA Astrophysics Data System (ADS)

Coburn, S.; Wright, R.; Cossel, K.; Truong, G. W.; Baumann, E.; Coddington, I.; Newbury, N.; Alden, C. B.; Ghosh, S.; Prasad, K.; Rieker, G. B.

2016-12-01

Newly proposed EPA regulations on volatile organic compound (VOC) emissions from oil and gas production facilities have been expanded to include methane, making the detection of this important trace gas a topic of growing interest to the oil and gas industry, regulators, and the scientific community in general. Reliable techniques that enable long-term monitoring of entire production facilities are needed in order to fully characterize the temporal and spatial trends of emissions from these sites. Recent advances in the development of compact and robust fiber frequency combs are enabling the use of this powerful spectroscopic tool outside of the laboratory, presenting opportunities for kilometer-scale open-path sensing of emissions at remote locations. Here we present the characterization and field deployment of a dual comb spectrometer (DCS) system with the potential to locate and size methane leaks from oil and gas production sites from long range. The DCS is a laser-based system that enables broad spectral absorption measurements (>50 nm) with high spectral resolution (<0.002 nm). Together these properties enable measurement of methane and other trace gas concentrations (e.g., H2O for deriving dry mole fractions) with high sensitivity and long-term stability from distances of 1 km or more. Field testing of this instrument has taken place at locations near Boulder, CO, demonstrating sensitivities of better than 2 ppb-km for methane. In addition, path integrated methane measurements from the DCS are coupled with an atmospheric inversion utilizing local meteorology and a high resolution fluid dynamics simulation to determine leak location and also derive a leak rate from simulated methane leaks

Evaluation of Density Corrections to Methane Fluxes Measured by Open-Path Eddy Covariance over Contrasting Landscapes

NASA Astrophysics Data System (ADS)

Chamberlain, Samuel D.; Verfaillie, Joseph; Eichelmann, Elke; Hemes, Kyle S.; Baldocchi, Dennis D.

2017-11-01

Corrections accounting for air density fluctuations due to heat and water vapour fluxes must be applied to the measurement of eddy-covariance fluxes when using open-path sensors. Experimental tests and ecosystem observations have demonstrated the important role density corrections play in accurately quantifying carbon dioxide (CO2) fluxes, but less attention has been paid to evaluating these corrections for methane (CH4) fluxes. We measured CH4 fluxes with open-path sensors over a suite of sites with contrasting CH4 emissions and energy partitioning, including a pavement airfield, two negligible-flux ecosystems (drained alfalfa and pasture), and two high-flux ecosystems (flooded wetland and rice). We found that density corrections successfully re-zeroed fluxes in negligible-flux sites; however, slight overcorrection was observed above pavement. The primary impact of density corrections varied over negligible- and high-flux ecosystems. For negligible-flux sites, corrections led to greater than 100% adjustment in daily budgets, while these adjustments were only 3-10% in high-flux ecosystems. The primary impact to high-flux ecosystems was a change in flux diel patterns, which may affect the evaluation of relationships between biophysical drivers and fluxes if correction bias exists. Additionally, accounting for density effects to high-frequency CH4 fluctuations led to large differences in observed CH4 flux cospectra above negligible-flux sites, demonstrating that similar adjustments should be made before interpreting CH4 cospectra for comparable ecosystems. These results give us confidence in CH4 fluxes measured by open-path sensors, and demonstrate that density corrections play an important role in adjusting flux budgets and diel patterns across a range of ecosystems.

Lightweight mid-infrared methane sensor for unmanned aerial systems

NASA Astrophysics Data System (ADS)

Golston, Levi M.; Tao, Lei; Brosy, Caroline; Schäfer, Klaus; Wolf, Benjamin; McSpiritt, James; Buchholz, Bernhard; Caulton, Dana R.; Pan, Da; Zondlo, Mark A.; Yoel, David; Kunstmann, Harald; McGregor, Marty

2017-06-01

The design and field performance of a compact diode laser-based instrument for measuring methane on unmanned aerial systems (UAS) is described. The system is based on open-path, wavelength modulation spectroscopy with a 3.27 µm GaSb laser. We design two versions of the sensor for a long-endurance fixed wing UAS and a rotary wing hexacopter, with instrument masses of 4.6 and 1.6 kg, respectively. The long-endurance platform was used to measure vertical profiles of methane up to 600 m in altitude and showed repeatability of 13 ppbv between multiple profiles. Additionally, the hexacopter system was used to evaluate the evolution of methane in the nocturnal boundary layer during the ScaleX field campaign in Germany, where measured data is consistent with supporting ground-based methane and meteorological measurements. Testing results on both platforms demonstrated our lightweight methane sensor had an in-flight precision of 5-10 ppbv Hz-1/2.

Eddy Covariance Measurements of Methane Flux at Remote Sites with New Low-Power Lightweight Fast Gas Analyzer

NASA Astrophysics Data System (ADS)

Xu, Liukang; Burba, George; Schedlbauer, Jessica; Zona, Donatella; McDermitt, Dayle K.; Anderson, Tyler; Oberbauer, Steven; Oechel, Walter; Komissarov, Anatoly; Riensche, Brad

2010-05-01

Majority of natural methane production happens at remote unpopulated areas in ecosystems with little or no infrastructure or easily available grid power, such as arctic and boreal wetlands, tropical mangroves, etc. Present approaches for direct measurements of CH4 fluxes rely on fast closed-path analyzers, which have to work under significantly reduced pressures, and require powerful pumps and grid power. Power and labor demands may be reasons why CH4 flux is often measured at locations with good infrastructure and grid power, and not with high CH4 production. An instrument was developed to allow Eddy Covariance measurements of CH4 flux with power consumption 30-150 times below presently available technologies. This instrument, LI-7700, uses <10W of power, and can easily be run on solar panel, or with small portable generator, while present technologies require 300-1500 Watts of the grid power. The proposed extremely low-power technology would allows placing methane Eddy Covariance stations in the middle of the source (wetland, rice paddy, forest, etc.) in the absence of the grid power. This could significantly expand the Eddy Covariance CH4 flux measurements coverage, and possibly, significantly improve the budget estimates of world CH4 emissions and budget. Various prototypes of the LI-7700 were field-tested for three seasons at the remote site in middle of Everglades National Park (Florida, USA) using solar panels, at three stationary and several mobile sites during three seasons at remote Arctic wetlands near Barrow (Alaska, USA), in the tropical mangroves near La Paz (Mexico) using portable generator, and in bare agricultural field near Mead (Nebraska, USA) during 2005 through 2010. Latest data on CH4 concentration, co-spectra and fluxes, and latest details of instrumental design are examined in this presentation. Overall, hourly methane fluxes ranged from near-zero at night to about 4 mg m-2 h-1 in midday in arctic tundra. Observed fluxes were within the ranges reported in the literature for a number of wetlands in North America, including the Everglades wetlands. Diurnal patterns were similar to those measured by closed-path sensors. The LI-7700 open-path analyzer is a valuable tool for measuring long-term eddy fluxes of methane due to the good frequency response and undisturbed in-situ sampling. It enables long-term deployment of permanent, portable or mobile CH4 flux stations at remote locations with high CH4 production, because it can be powered by a solar panels or a small generator. Authors appreciate help and support provided by the LI-COR Engineering Team, Barrow Arctic Science Consortium (BASC), and numerous colleagues involved in measurements, logistics, and maintenance of the experimental field sites. This project was supported by the Small Business Innovation Research (SBIR) and Small Business Technology Transfer Program (STTR) program of the Department of Energy (DOE), Grant Number DE-FG02-05ER84283.

Mobile Measurements of Methane Using High-Speed Open-Path Technology

NASA Astrophysics Data System (ADS)

Burba, G. G.; Anderson, T.; Ediger, K.; von Fischer, J.; Gioli, B.; Ham, J. M.; Hupp, J. R.; Kohnert, K.; Levy, P. E.; Polidori, A.; Pikelnaya, O.; Price, E.; Sachs, T.; Serafimovich, A.; Zondlo, M. A.; Zulueta, R. C.

2016-12-01

Methane plays a critical role in the radiation balance, chemistry of the atmosphere, and air quality. The major anthropogenic sources of CH4 include oil and gas development sites, natural gas distribution networks, landfill emissions, and agricultural production. The majority of oil and gas and urban CH4 emission occurs via variable-rate point sources or diffused spots in topographically challenging terrains (e.g., street tunnels, elevated locations at water treatment plants, vents, etc.). Locating and measuring such CH4 emissions is challenging when using traditional micrometeorological techniques, and requires development of novel approaches. Landfill CH4 emissions traditionally assessed at monthly or longer time intervals are subject to large uncertainties because of the snapshot nature of the measurements and the barometric pumping phenomenon. The majority of agricultural and natural CH4 production occurs in areas with little infrastructure or easily available grid power (e.g., rice fields, arctic and boreal wetlands, tropical mangroves, etc.). A lightweight, high-speed, high-resolution, open-path technology was recently developed for eddy covariance measurements of CH4 flux, with power consumption 30-150 times below other available technologies. It was designed to run on solar panels or a small generator and be placed in the middle of the methane-producing ecosystem without a need for grid power. Lately, this instrumentation has been utilized increasingly more frequently outside of the traditional use on stationary flux towers. These novel approaches include measurements from various moving platforms, such as cars, aircraft, and ships. Projects included mapping of concentrations and vertical profiles, leak detection and quantification, mobile emission detection from natural gas-powered cars, soil CH4 flux surveys, etc. This presentation will describe key projects utilizing the novel lightweight low-power high-resolution open-path technology, and will highlight several novel approaches where such instrumentation was used in mobile deployments in urban, agricultural and natural environments by academic institutions, regulatory agencies and industry.

Intercomparison of Open-Path Trace Gas Measurements with Two Dual Frequency Comb Spectrometers

PubMed Central

Waxman, Eleanor M.; Cossel, Kevin C.; Truong, Gar-Wing; Giorgetta, Fabrizio R.; Swann, William C.; Coburn, Sean; Wright, Robert J.; Rieker, Gregory B.; Coddington, Ian; Newbury, Nathan R.

2017-01-01

We present the first quantitative intercomparison between two open-path dual comb spectroscopy (DCS) instruments which were operated across adjacent 2-km open-air paths over a two-week period. We used DCS to measure the atmospheric absorption spectrum in the near infrared from 6021 to 6388 cm−1 (1565 to 1661 nm), corresponding to a 367 cm−1 bandwidth, at 0.0067 cm−1 sample spacing. The measured absorption spectra agree with each other to within 5×10−4 without any external calibration of either instrument. The absorption spectra are fit to retrieve concentrations for carbon dioxide (CO2), methane (CH4), water (H2O), and deuterated water (HDO). The retrieved dry mole fractions agree to 0.14% (0.57 ppm) for CO2, 0.35% (7 ppb) for CH4, and 0.40% (36 ppm) for H2O over the two-week measurement campaign, which included 23 °C outdoor temperature variations and periods of strong atmospheric turbulence. This agreement is at least an order of magnitude better than conventional active-source open-path instrument intercomparisons and is particularly relevant to future regional flux measurements as it allows accurate comparisons of open-path DCS data across locations and time. We additionally compare the open-path DCS retrievals to a WMO-calibrated cavity ringdown point sensor located along the path with good agreement. Short-term and long-term differences between the two systems are attributed, respectively, to spatial sampling discrepancies and to inaccuracies in the current spectral database used to fit the DCS data. Finally, the two-week measurement campaign yields diurnal cycles of CO2 and CH4 that are consistent with the presence of local sources of CO2 and absence of local sources of CH4. PMID:29276547

Intercomparison of open-path trace gas measurements with two dual-frequency-comb spectrometers

DOE PAGES

Waxman, Eleanor M.; Cossel, Kevin C.; Truong, Gar-Wing; ...

2017-09-11

We present the first quantitative intercomparison between two open-path dual-comb spectroscopy (DCS) instruments which were operated across adjacent 2 km open-air paths over a 2-week period. We used DCS to measure the atmospheric absorption spectrum in the near infrared from 6023 to 6376 cm −1 (1568 to 1660 nm), corresponding to a 355 cm −1 bandwidth, at 0.0067 cm −1 sample spacing. The measured absorption spectra agree with each other to within 5 × 10 −4 in absorbance without any external calibration of either instrument. The absorption spectra are fit to retrieve path-integrated concentrations for carbon dioxide (CO 2), methane (CH 4), water (H 2O), and deuteratedmore » water (HDO). The retrieved dry mole fractions agree to 0.14 % (0.57 ppm) for CO 2, 0.35 % (7 ppb) for CH 4, and 0.40 % (36 ppm) for H 2O at  ∼  30 s integration time over the 2-week measurement campaign, which included 24 °C outdoor temperature variations and periods of strong atmospheric turbulence. This agreement is at least an order of magnitude better than conventional active-source open-path instrument intercomparisons and is particularly relevant to future regional flux measurements as it allows accurate comparisons of open-path DCS data across locations and time. We additionally compare the open-path DCS retrievals to a World Meteorological Organization (WMO)-calibrated cavity ring-down point sensor located along the path with good agreement. Short-term and long-term differences between the open-path DCS and point sensor are attributed, respectively, to spatial sampling discrepancies and to inaccuracies in the current spectral database used to fit the DCS data. Finally, the 2-week measurement campaign yields diurnal cycles of CO 2 and CH 4 that are consistent with the presence of local sources of CO 2 and absence of local sources of CH 4.« less

Intercomparison of open-path trace gas measurements with two dual-frequency-comb spectrometers

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

Waxman, Eleanor M.; Cossel, Kevin C.; Truong, Gar-Wing

We present the first quantitative intercomparison between two open-path dual-comb spectroscopy (DCS) instruments which were operated across adjacent 2 km open-air paths over a 2-week period. We used DCS to measure the atmospheric absorption spectrum in the near infrared from 6023 to 6376 cm −1 (1568 to 1660 nm), corresponding to a 355 cm −1 bandwidth, at 0.0067 cm −1 sample spacing. The measured absorption spectra agree with each other to within 5 × 10 −4 in absorbance without any external calibration of either instrument. The absorption spectra are fit to retrieve path-integrated concentrations for carbon dioxide (CO 2), methane (CH 4), water (H 2O), and deuteratedmore » water (HDO). The retrieved dry mole fractions agree to 0.14 % (0.57 ppm) for CO 2, 0.35 % (7 ppb) for CH 4, and 0.40 % (36 ppm) for H 2O at  ∼  30 s integration time over the 2-week measurement campaign, which included 24 °C outdoor temperature variations and periods of strong atmospheric turbulence. This agreement is at least an order of magnitude better than conventional active-source open-path instrument intercomparisons and is particularly relevant to future regional flux measurements as it allows accurate comparisons of open-path DCS data across locations and time. We additionally compare the open-path DCS retrievals to a World Meteorological Organization (WMO)-calibrated cavity ring-down point sensor located along the path with good agreement. Short-term and long-term differences between the open-path DCS and point sensor are attributed, respectively, to spatial sampling discrepancies and to inaccuracies in the current spectral database used to fit the DCS data. Finally, the 2-week measurement campaign yields diurnal cycles of CO 2 and CH 4 that are consistent with the presence of local sources of CO 2 and absence of local sources of CH 4.« less

Methane and carbon dioxide emissions from Shan-Chu-Ku landfill site in northern Taiwan.

PubMed

Hegde, Ullas; Chang, Tsan-Chang; Yang, Shang-Shyng

2003-09-01

To investigate the methane and carbon dioxide emissions from landfill, samples were taken of material up to 5 years old from Shan-Chu-Ku landfill located in the northern part of Taiwan. Atmospheric concentrations of carbon dioxide, methane and nitrous oxide ranged from 310 to 530, 2.64 to 20.16 and 0.358 to 1.516 ppmv with the measurement of gas-type open-path Fourier transform infra-red (FTIR) spectroscopy during February 1998 to March 2000, respectively. Average methane emission rate was 13.17, 65.27 and 0.99 mgm(-2)h(-1) measured by the gas chromatography chamber method in 1-2, 2-3 and 5 year-old landfill, respectively. Similarly, average carbon dioxide emission rate was 93.70, 314.60 and 48.46 mgm(-2)h(-1), respectively. About 2-3 year-old landfill had the highest methane and carbon dioxide emission rates among the tested areas, while 5 year-old landfill was the least. Methane emission rate at night in most tested locations was higher than that in the daytime. Total amount of methane and carbon dioxide emission from this landfill was around 171 and 828 ton in 1999, respectively.

An anomalous CO2 uptake measured over asphalt surface by open-path eddy-covariance system

NASA Astrophysics Data System (ADS)

Bogoev, Ivan; Santos, Eduardo

2017-04-01

Measurements of net ecosystem exchange of CO2 in desert environments made by Wohlfahrt et al. (2008) and Ma (2014) indicate strong CO2 sink. The results of these studies have been challenged by Schlesinger (2016) because the rates of the CO2 uptake are incongruent with the increase of biomass in the vegetation and accumulation of organic and inorganic carbon in the soil. Consequently, the accuracy of the open-path eddy-covariance systems in arid and semi-arid ecosystems has been questioned. A new technology merging the sensing paths of the gas analyzer and the sonic anemometer has recently been developed. This integrated open-path system allows a direct measurement of CO2 mixing ratio in the open air and has the potential to improve the quality of the temperature related density and spectroscopic corrections by synchronously measuring the sensible heat flux in the optical path of the gas analyzer. We evaluate the performance and the accuracy of this new sensor over a large parking lot with an asphalt surface where the water vapor and CO2 fluxes are expected to be low and the interfering sensible heat fluxes are above 200 Wm-2. For independent CO2 flux reference measurements, we use a co-located closed-path analyzer with a short intake tube and a standalone sonic anemometer. We compare energy and carbon dioxide fluxes between the open- and the closed-path systems. During periods with sensible heat flux above 100 W m-2, the open-path system reports an apparent CO2 uptake of 0.02 mg m-2 s-1, while the closed-path system consistently measures a more acceptable upward flux of 0.015 mg m-2 s-1. We attribute this systematic bias to inadequate fast-response temperature compensation of absorption-line broadening effects. We demonstrate that this bias can be eliminated by using the humidity-corrected fast-response sonic temperature to compensate for the abovementioned spectroscopic effects in the open-path analyzer.

Near-Simultaneous Measurement of Ground Level Carbon Dioxide and Methane Concentrations with an Open-Path Tunable Diode Laser Sensor at the Bonanza Creek Long Term Ecological Research site near Fairbanks, Alaska

NASA Astrophysics Data System (ADS)

Bailey, D. M.; Miller, J. H. H.

2017-12-01

Beyond anthropogenic carbon emissions, the increase in atmospheric carbon from natural feedbacks such as thawing permafrost poses a risk to the global climate as global temperatures continue to increase. Permafrost is formally defined as soil that is continuously frozen for 24 consecutive months. These soils comprise nearly twenty-five percent of the Earth's terrestrial surface and possess twice the amount of carbon currently in the atmosphere. Continuous collection of carbon dioxide (CO2) and methane (CH4) concentrations is imperative in understanding seasonal and inter-annual variability of carbon feedbacks above thawing permafrost. A multi-year collaborative effort with the University of Alaska - Fairbanks, NASA Goddard Space Flight Center, and our group at George Washington University is underway to monitor these feedbacks near Fairbanks, Alaska. In June 2017, we deployed two open-path tunable diode laser sensors at the Bonanza Long Term Ecological Research Site for measurement of CO2 and CH4 concentrations. The open-path instrument (OPI) is an inexpensive, low-power sensor that collects spatially-integrated measurements of target molecules approximately 1.5 meters above ground level. With a total power burden of 18 W, the sensors ran exclusively on solar power for 15 days in a young thermokarst bog and 3.5 days at a rich fen site. Here we report on initial retrieval of diurnal cycles from each field site and compare our spatially-integrated measurements of CO2 and CH4. For CO2, the magnitude of the diurnal cycles show a strong dependence on daily weather at both field sites. These laser measurements are complemented by point measurements of CO2, temperature, pressure, and humidity made along the laser's optical path by non-dispersive infrared (NDIR) sensors.

A True Eddy Accumulation - Eddy Covariance hybrid for measurements of turbulent trace gas fluxes

NASA Astrophysics Data System (ADS)

Siebicke, Lukas

2016-04-01

Eddy covariance (EC) is state-of-the-art in directly and continuously measuring turbulent fluxes of carbon dioxide and water vapor. However, low signal-to-noise ratios, high flow rates and missing or complex gas analyzers limit it's application to few scalars. True eddy accumulation, based on conditional sampling ideas by Desjardins in 1972, requires no fast response analyzers and is therefore potentially applicable to a wider range of scalars. Recently we showed possibly the first successful implementation of True Eddy Accumulation (TEA) measuring net ecosystem exchange of carbon dioxide of a grassland. However, most accumulation systems share the complexity of having to store discrete air samples in physical containers representing entire flux averaging intervals. The current study investigates merging principles of eddy accumulation and eddy covariance, which we here refer to as "true eddy accumulation in transient mode" (TEA-TM). This direct flux method TEA-TM combines true eddy accumulation with continuous sampling. The TEA-TM setup is simpler than discrete accumulation methods while avoiding the need for fast response gas analyzers and high flow rates required for EC. We implemented the proposed TEA-TM method and measured fluxes of carbon dioxide (CO2), methane (CH4) and water vapor (H2O) above a mixed beech forest at the Hainich Fluxnet and ICOS site, Germany, using a G2301 laser spectrometer (Picarro Inc., USA). We further simulated a TEA-TM sampling system using measured high frequency CO2 time series from an open-path gas analyzer. We operated TEA-TM side-by-side with open-, enclosed- and closed-path EC flux systems for CO2, H2O and CH4 (LI-7500, LI-7200, LI-6262, LI-7700, Licor, USA, and FGGA LGR, USA). First results show that TEA-TM CO2 fluxes were similar to EC fluxes. Remaining differences were similar to those between the three eddy covariance setups (open-, enclosed- and closed-path gas analyzers). Measured TEA-TM CO2 fluxes from our physical sampling system closely reproduced dynamics of simulated TEA-TM fluxes. In conclusion this study introduces a new approach to trace gas flux measurements using transient-mode true eddy accumulation. First TEA-TM CO2 fluxes compared favorably with side-by-side EC fluxes, in agreement with our previous experiments comparing discrete TEA to EC. True eddy accumulation has thus potential for measuring turbulent fluxes of a range of atmospheric tracers using slow response analyzers.

Bootstrap inversion technique for atmospheric trace gas source detection and quantification using long open-path laser measurements

NASA Astrophysics Data System (ADS)

Alden, Caroline B.; Ghosh, Subhomoy; Coburn, Sean; Sweeney, Colm; Karion, Anna; Wright, Robert; Coddington, Ian; Rieker, Gregory B.; Prasad, Kuldeep

2018-03-01

Advances in natural gas extraction technology have led to increased activity in the production and transport sectors in the United States and, as a consequence, an increased need for reliable monitoring of methane leaks to the atmosphere. We present a statistical methodology in combination with an observing system for the detection and attribution of fugitive emissions of methane from distributed potential source location landscapes such as natural gas production sites. We measure long (> 500 m), integrated open-path concentrations of atmospheric methane using a dual frequency comb spectrometer and combine measurements with an atmospheric transport model to infer leak locations and strengths using a novel statistical method, the non-zero minimum bootstrap (NZMB). The new statistical method allows us to determine whether the empirical distribution of possible source strengths for a given location excludes zero. Using this information, we identify leaking source locations (i.e., natural gas wells) through rejection of the null hypothesis that the source is not leaking. The method is tested with a series of synthetic data inversions with varying measurement density and varying levels of model-data mismatch. It is also tested with field observations of (1) a non-leaking source location and (2) a source location where a controlled emission of 3.1 × 10-5 kg s-1 of methane gas is released over a period of several hours. This series of synthetic data tests and outdoor field observations using a controlled methane release demonstrates the viability of the approach for the detection and sizing of very small leaks of methane across large distances (4+ km2 in synthetic tests). The field tests demonstrate the ability to attribute small atmospheric enhancements of 17 ppb to the emitting source location against a background of combined atmospheric (e.g., background methane variability) and measurement uncertainty of 5 ppb (1σ), when measurements are averaged over 2 min. The results of the synthetic and field data testing show that the new observing system and statistical approach greatly decreases the incidence of false alarms (that is, wrongly identifying a well site to be leaking) compared with the same tests that do not use the NZMB approach and therefore offers increased leak detection and sizing capabilities.

Trace Gas Measurements on Mars and Earth Using Optical Parametric Generation

NASA Technical Reports Server (NTRS)

Numata, Kenji; Haris, Riris; Li, Steve; Sun, Xiaoli; Abshire, James Brice

2010-01-01

Trace gases and their isotopic ratios in planetary atmospheres offer important but subtle clues as to the origins of a planet's atmosphere, hydrology, geology, and potential for biology. An orbiting laser remote sensing instrument is capable of measuring trace gases on a global scale with unprecedented accuracy, and higher spatial resolution that can be obtained by passive instruments. We have developed an active sensing instrument for the remote measurement of trace gases in planetary atmospheres (including Earth). The technique uses widely tunable, seeded optical parametric generation (OPG) to measure methane, CO2, water vapor, and other trace gases in the near and mid-infrared spectral regions. Methane is a strong greenhouse gas on Earth and it is also a potential biogenic marker on Mars and other planets. Methane in the Earth's atmosphere survives for a shorter time than CO2 but its impact on climate change can be larger than CO2. Methane levels have remained relatively constant over the last decade around 1.78 parts per million (ppm) but recent observations indicate that methane levels may be on the rise. Increasing methane concentrations may trigger a positive feedback loop and a subsequent runaway greenhouse effect, where increasing temperatures result in increasing methane levels. The NRC Decadal Survey recognized the importance of global observations of greenhouse gases and called for simultaneous CH4, CO, and CO2 measurements but also underlined the technological limitations for these observations. For Mars, methane measurements are of great interest because of its potential as a strong biogenic marker. A remote sensing instrument that can measure day and night over all seasons and latitudes can identify and localize sources of biogenic gas plumes produced by subsurface chemistry or biology, and aid in the search for extra-terrestrial life. It can identify the dynamics of methane generation over time and latitude and identify future lander mission sites for more detailed in-situ analysis. In this paper we report on remote sensing measurements of methane using a high peak power, widely tunable optical parametric generator (OPG) operating at 3.3 micron and 1.65 micron. The OPG is pumped by a passively q-switched single frequency laser (3ns, 5KHz, 50uJ) and seeded by a diode laser. The spectral width of both signal and idler of seeded OPG is nearly Fourier transform limited. The output of seeded OPG is single frequency with high spectral purity and is widely tunable. Both 1650 nm and 3300 nm can be generated with a conversion efficiency of more than 30%. We have demonstrated detection of methane at 3274 nm and 1650 nm in a cell and also performed open path atmospheric measurements of methane at the same wavelengths. Finally, we were able to demonstrate simultaneous detection of methane at 3270.4 nm and CO2 at 1578.2 nm. In this paper we will discuss the OPG performance and atmospheric open path measurement results.

Inference of strata separation and gas emission paths in longwall overburden using continuous wavelet transform of well logs and geostatistical simulation

NASA Astrophysics Data System (ADS)

Karacan, C. Özgen; Olea, Ricardo A.

2014-06-01

Prediction of potential methane emission pathways from various sources into active mine workings or sealed gobs from longwall overburden is important for controlling methane and for improving mining safety. The aim of this paper is to infer strata separation intervals and thus gas emission pathways from standard well log data. The proposed technique was applied to well logs acquired through the Mary Lee/Blue Creek coal seam of the Upper Pottsville Formation in the Black Warrior Basin, Alabama, using well logs from a series of boreholes aligned along a nearly linear profile. For this purpose, continuous wavelet transform (CWT) of digitized gamma well logs was performed by using Mexican hat and Morlet, as the mother wavelets, to identify potential discontinuities in the signal. Pointwise Hölder exponents (PHE) of gamma logs were also computed using the generalized quadratic variations (GQV) method to identify the location and strength of singularities of well log signals as a complementary analysis. PHEs and wavelet coefficients were analyzed to find the locations of singularities along the logs. Using the well logs in this study, locations of predicted singularities were used as indicators in single normal equation simulation (SNESIM) to generate equi-probable realizations of potential strata separation intervals. Horizontal and vertical variograms of realizations were then analyzed and compared with those of indicator data and training image (TI) data using the Kruskal-Wallis test. A sum of squared differences was employed to select the most probable realization representing the locations of potential strata separations and methane flow paths. Results indicated that singularities located in well log signals reliably correlated with strata transitions or discontinuities within the strata. Geostatistical simulation of these discontinuities provided information about the location and extents of the continuous channels that may form during mining. If there is a gas source within their zone of influence, paths may develop and allow methane movement towards sealed or active gobs under pressure differentials. Knowledge gained from this research will better prepare mine operations for potential methane inflows, thus improving mine safety.

Mars methane analogue mission: Mission simulation and rover operations at Jeffrey Mine and Norbestos Mine Quebec, Canada

NASA Astrophysics Data System (ADS)

Qadi, A.; Cloutis, E.; Samson, C.; Whyte, L.; Ellery, A.; Bell, J. F.; Berard, G.; Boivin, A.; Haddad, E.; Lavoie, J.; Jamroz, W.; Kruzelecky, R.; Mack, A.; Mann, P.; Olsen, K.; Perrot, M.; Popa, D.; Rhind, T.; Sharma, R.; Stromberg, J.; Strong, K.; Tremblay, A.; Wilhelm, R.; Wing, B.; Wong, B.

2015-05-01

The Canadian Space Agency (CSA), through its Analogue Missions program, supported a microrover-based analogue mission designed to simulate a Mars rover mission geared toward identifying and characterizing methane emissions on Mars. The analogue mission included two, progressively more complex, deployments in open-pit asbestos mines where methane can be generated from the weathering of olivine into serpentine: the Jeffrey mine deployment (June 2011) and the Norbestos mine deployment (June 2012). At the Jeffrey Mine, testing was conducted over 4 days using a modified off-the-shelf Pioneer rover and scientific instruments including Raman spectrometer, Picarro methane detector, hyperspectral point spectrometer and electromagnetic induction sounder for testing rock and gas samples. At the Norbestos Mine, we used the research Kapvik microrover which features enhanced autonomous navigation capabilities and a wider array of scientific instruments. This paper describes the rover operations in terms of planning, deployment, communication and equipment setup, rover path parameters and instrument performance. Overall, the deployments suggest that a search strategy of “follow the methane” is not practical given the mechanisms of methane dispersion. Rather, identification of features related to methane sources based on image tone/color and texture from panoramic imagery is more profitable.

Variability of methane fluxes over high latitude permafrost wetlands

NASA Astrophysics Data System (ADS)

Serafimovich, Andrei; Hartmann, Jörg; Larmanou, Eric; Sachs, Torsten

2013-04-01

Atmospheric methane plays an important role in the global climate system. Due to significant amounts of organic material stored in the upper layers of high latitude permafrost wetlands and a strong Arctic warming trend, there is concern about potentially large methane emissions from Arctic and sub-Arctic areas. The quantification of methane fluxes and their variability from these regions therefore plays an important role in understanding the Arctic carbon cycle and changes in atmospheric methane concentrations. However, direct measurements of methane fluxes in permafrost regions are sparse, very localized, inhomogeneously distributed in space, and thus difficult to use for accurate model representation of regional to global methane contributions from the Arctic. We aim to contribute to reducing uncertainty and improve spatial coverage and spatial representativeness of flux estimates by using airborne eddy covariance measurements across large areas. The research aircraft POLAR 5 was equipped with a turbulence nose boom and a fast response methane analyzer and served as the platform for measurements of methane emissions. The measuring campaign was carried out from 28 June to 10 July 2012 across the entire North Slope of Alaska and the Mackenzie Delta in Canada. The supplemented simulations from the Weather Research and Forecasting (WRF) model exploring the dynamics of the atmospheric boundary layer were used to analyze high methane concentrations occasionally observed within the boundary layer with a distinct drop to background level above. Strong regional differences were detected over both investigated areas showing the non-uniform distribution of methane sources. In order to cover the whole turbulent spectrum and at the same time to resolve methane fluxes on a regional scale, different integration paths were analyzed and validated through spectral analysis. Methane emissions measured over the Mackenzie Delta were higher and generally more variable in space, especially in the outer Delta with known geogenic methane seepage. On the North Slope, methane fluxes were larger in the western part than in the central and eastern parts. The obtained results are essential for the advanced, scale dependent quantification of methane emissions. Our contribution will present an overview of the experiment as well as preliminary results from more than 52 flight hours over high latitude permafrost wetlands.

Eddy covariance measurements in complex terrain with a new fast response, closed-path analyzer: spectral characteristics and cross-system comparisons

EPA Science Inventory

In recent years, a new class of enclosed, closed-path gas analyzers suitable for eddy covariance applications has come to market, designed to combine the advantages of traditional closed-path systems (small density corrections, good performance in poor weather) and open-path syst...

Correlating Well-Pad Characteristics and Methane Emissions in the Marcellus Shale

NASA Astrophysics Data System (ADS)

Lu, J.; Caulton, D.; Lane, H.; Stanton, L. G.; Zondlo, M. A.

2015-12-01

Methane leaks from petrochemical activity are significant contributors to the total amount of methane in the atmosphere. While natural gas has been praised as a cleaner source of fuel than coal, methane's potent global-warming potential could pose barriers in reducing greenhouse gas footprints if significant leaks are observed from the natural gas supply chain. A field campaign spanning two and a half weeks was undertaken in July 2015 to quantify the levels of methane emitted from sites of petrochemical activity in the Marcellus Shale. Additional campaigns are expected in late 2015 and early 2016. Measurements of methane and carbon dioxide were taken downwind of known well sites using open-path laser spectroscopy mounted to the roof of the mobile platform. Approximately 250 well sites were visited, covering over 2000 miles on the road. The majority of the well pads were in southwestern Pennsylvania, but the compiled database includes wells in West Virginia and northeastern Pennsylvania. The data set consists of a variety of operators and equipment types spread over several counties. Correlating well pad characteristics with emission levels may provide useful insight into predicting which well pads are likely to be large emitters. Using the inverse Gaussian plume model and meteorology data from the NOAA Ready archive, the emissions from each transect were calculated. Preliminary results were examined with respect to two easily identifiable variables: the number of wells at each well pad and the operator. Higher emissions were not correlated with increased number of wells, despite the fact that additional infrastructure may provide additional leak pathways. In fact, the emission levels for pads with only a singular well, which accounted for nearly 70% of the wells analyzed thus far, had a range of 0 to 9 grams of methane per second. Sites with two or more wells tended to be concentrated on the lower end of the distribution. Higher emissions were also distributed roughtly equally among the 10 operators in the data subset. Continued analyses of methane emission rates will provide further insight into Marcellus Shale.

Unmanned aerial system laser based measurements of ammonia and methane emissions from animal feeding operations

NASA Astrophysics Data System (ADS)

Shadman, S.; McHale, L.; Miller, T.; Yalin, A.

2017-12-01

In the US, 40 Tg of ammonia is emitted every year into the atmosphere via agricultural activities. Ammonia is the third most abundant nitrogen containing species in the atmosphere and it has important impacts on atmospheric chemistry, health, and the environment. Since the atmospheric lifetime of ammonia is a few days, it typically deposits to the ground close to its source. In this study we are developing two laser-based sensors to measure ammonia and methane emissions from concentrated animal feeding operations (CAFOs) with the specific goal of quantifying the dry deposition of ammonia in the first few kilometers downwind of the CAFOs. Since methane is nonreactive and does not undergo dry deposition, its change in concentration with downwind distance is due to dispersion alone. We therefore plan to use methane as a conservative tracer, and will infer the ammonia deposition from the changing (deceasing) ratio of ammonia to methane as a function of downwind position. The laser sensors (ammonia and methane) developed in this study are relatively lightweight (<3.5 kg), low power (<40 W) and achieve part-per-billion level concentration sensitivity via sensitive open-path absorption spectroscopy methods. The sensors are designed for simultaneous airborne measurements of both species on a 12 foot Telemaster unmanned aerial system (UAS). The methane sensor employs cavity ring-down spectroscopy (CRDS) at 1.65 um with a distributed feedback laser and has effective cavity length of 20 km. The ammonia sensor employs wavelength modulation spectroscopy (WMS) with a quantum cascade laser at 10.33 um with a Herriot multipass cell (19 m effective length). In order to minimize the thermal expansion effects, most mounts and physical structures are made from carbon-fiber. For each sensor, a custom electronics module has been designed to control and power the electro-optic components, as well as to acquire, analyze, and save data (including concentration, temperature, pressure, and GPS time and position). The sensors have been characterized in the lab (Allan variance) and show sensitivities of 1.5 ppb (at 1 Hz) and 20 ppb (at 1 Hz), for ammonia and methane respectively.

Field evaluation of open and closed-path CO2 flux systems over asphalt surface

NASA Astrophysics Data System (ADS)

Bogoev, I.; Santos, E.

2016-12-01

Eddy covariance (EC) is a widely used method for quantifying surface fluxes of heat, water vapor and carbon dioxide between ecosystems and the atmosphere. A typical EC system consists of an ultrasonic anemometer measuring the 3D wind vector and a fast-response infrared gas analyzer for sensing the water vapor and CO2 density in the air. When using an open-path analyzer that detects the constituent's density in situ a correction for concurrent air temperature and humidity fluctuations must be applied, Webb et al. (1980). In environments with small magnitudes of CO2 flux (<5µmol m-2 s-1) and in the presence of high sensible heat flux, like wintertime over boreal forest, open-path flux measurements have been challenging since the magnitude of the density corrections are as large as the uncorrected CO2 flux itself. A new technology merging the sensing paths of the gas analyzer and the sonic anemometer has been recently developed. This new integrated instrument allows a direct measurement of CO2 mixing ratio in the open air and has the potential to improve the quality of the temperature related density corrections by synchronously measuring the sensible heat flux in the optical path of the gas analyzer. We evaluate the performance and the accuracy of this new sensor over a large parking lot with an asphalt surface where the CO2 fluxes are considered low and the interfering sensible heat fluxes are above 200 Wm-2. A co-located closed-path EC system is used as a reference measurement to examine any systematic biases and apparent CO2 uptake observed with open-path sensors under high sensible heat flux regimes. Half-hour mean and variance of CO2 and water vapor concentrations are evaluated. The relative spectral responses, covariances and corrected turbulent fluxes using a common sonic anemometer are analyzed. The influence of sensor separation and frequency response attenuation on the density corrections is discussed.

Eddy covariance measurements with a new fast-response, enclosed-path analyzer: Spectral characteristics and cross-system comparisons

Treesearch

K. Novick; J. Walker; W.S. Chan; A. Schmidt; C. Sobek; J.M. Vose

2013-01-01

A new class of enclosed path gas analyzers suitable for eddy covariance applications combines the advantages of traditional closed-path systems (small density corrections, good performance in poor weather) and open-path systems (good spectral response, low power requirements), and permits estimates of instantaneous gas mixing ratio. Here, the extent to which these...

Analyses of geological and hydrodynamic controls on methane emissions experienced in a Lower Kittanning coal mine

PubMed Central

Karacan, C. Özgen; Goodman, Gerrit V.R.

2015-01-01

This paper presents a study assessing potential factors and migration paths of methane emissions experienced in a room-and-pillar mine in Lower Kittanning coal, Indiana County, Pennsylvania. Methane emissions were not excessive at idle mining areas, but significant methane was measured during coal mining and loading. Although methane concentrations in the mine did not exceed 1% limit during operation due to the presence of adequate dilution airflow, the source of methane and its migration into the mine was still a concern. In the course of this study, structural and depositional properties of the area were evaluated to assess complexity and sealing capacity of roof rocks. Composition, gas content, and permeability of Lower Kittanning coal, results of flotation tests, and geochemistry of groundwater obtained from observation boreholes were studied to understand the properties of coal and potential effects of old abandoned mines within the same area. These data were combined with the data obtained from exploration boreholes, such as depths, elevations, thicknesses, ash content, and heat value of coal. Univariate statistical and principal component analyses (PCA), as well as geostatistical simulations and co-simulations, were performed on various spatial attributes to reveal interrelationships and to establish area-wide distributions. These studies helped in analyzing groundwater quality and determining gas-in-place (GIP) of the Lower Kittanning seam. Furthermore, groundwater level and head on the Lower Kittanning coal were modeled and flow gradients within the study area were examined. Modeling results were interpreted with the structural geology of the Allegheny Group of formations above the Lower Kittanning coal to understand the potential source of gas and its migration paths. Analyses suggested that the source of methane was likely the overlying seams such as the Middle and Upper Kittanning coals and Freeport seams of the Allegheny Group. Simulated ground-water water elevations, gradients of groundwater flow, and the presence of recharge and discharge locations at very close proximity to the mine indicated that methane likely was carried with groundwater towards the mine entries. Existing fractures within the overlying strata and their orientation due to the geologic conditions of the area, and activation of slickensides between shale and sandstones due to differential compaction during mining, were interpreted as the potential flow paths. PMID:26478644

Methane emission from flooded soils - from microorganisms to the atmosphere

NASA Astrophysics Data System (ADS)

Conrad, Ralf

2016-04-01

Methane is an important greenhouse gas that is affected by anthropogenic activity. The annual budget of atmospheric methane, which is about 600 million tons, is by more than 75% produced by methanogenic archaea. These archaea are the end-members of a microbial community that degrades organic matter under anaerobic conditions. Flooded rice fields constitute a major source (about 10%) of atmospheric methane. After flooding of soil, anaerobic processes are initiated, finally resulting in the disproportionation of organic matter to carbon dioxide and methane. This process occurs in the bulk soil, on decaying organic debris and in the rhizosphere. The produced methane is mostly ventilated through the plant vascular system into the atmosphere. This system also allows the diffusion of oxygen into the rizosphere, where part of the produced methane is oxidized by aerobic methanotrophic bacteria. More than 50% of the methane production is derived from plant photosynthetic products and is formed on the root surface. Methanocellales are an important group of methanogenic archaea colonizing rice roots. Soils lacking this group seem to result in reduced root colonization and methane production. In rice soil methane is produced by two major paths of methanogenesis, the hydrogenotrophic one reducing carbon dioxide to methane, and the aceticlastic one disproportionating acetate to methane and carbon dioxide. Theoretically, at least two third of the methane should be produced by aceticlastic and the rest by hydrogenotrophic methanogenesis. In nature, however, the exact contribution of the two paths can vary from zero to 100%. Several environmental factors, such as temperature and quality of organic matter affect the path of methane production. The impact of these factors on the composition and activity of the environmental methanogenic microbial community will be discussed.

Airborne monitoring of landfills CH_{4} emissions

NASA Astrophysics Data System (ADS)

Gasbarra, Daniele; Gioli, Beniamino; Carlucci, Pantaleone; Magliulo, Vincenzo; Toscano, Piero; Zaldei, Alessandro

2017-04-01

The disposal and treatment of waste produces emissions of greenhouse gases (GHGs), which contribute to global climate change. In particular, large quantities of Methane are released in the breakdown of organic matter in landfills. In this work we present a new payload of the Sky Arrow ERA aircraft and an original methodology to compute methane emissions, based on the atmospheric mass budget approach. The payload is presently being used for intensive measurements in the area known as "Terra dei fuochi". In this area, located between the provinces of Naples and Caserta (Southern Italy), urban waste combined with industrial toxic waste has been illegally dumped in old quarries or buried in the nearby countryside for decades. This led to patchy sources of methane, with several hot spots spread over a heterogeneous land. In this context, the use of aircraft allows for the investigation at the landscape as well as at the regional scale, taking into account all sources, including those of small dimensions. The Sky Arrow ERA is equipped with the Mobile Flux Platform, capable of deriving the 3D wind vector at 50 Hz, while CO2 and water vapor densities are measured by an infrared gas analyzer (Licor 7500). A new configuration of the Licor 7700 open path fast methane gas analyzer was developed, based on enclosing the sensor within a cylinder exposed to the external air in-flow. This set-up allows for fast response measurements, while avoiding external modifications, subjected to restrictions. Ambient methane mixing ratios in excess of 7 ppm were measured during landfills overpasses; performing grid flight plans at different heights, to describe a virtual box enclosing the study area, and applying interpolation procedures, it was possible to reconstruct wind components and scalar concentrations in a 5x5 kilometers domain containing 6 different landfills, with a resolution of 50 m horizontal and 20 m vertical. For each flight the methane mass flows along and across the wind direction have been computed as products of gas densities and wind speed, while contributions of each individual landfill to total flows were computed with a GLM (general linear model) approach. More than 15 flights were performed from October 2015 to December 2016. Results revealed high methane emissions ranging from 150 g s-1 to 400 g s-1for the entire domain with a mean value of 240 g s-1; no seasonal variation was observed over the whole measuring period.

High-quality eddy-covariance CO2 budgets under cold climate conditions

NASA Astrophysics Data System (ADS)

Kittler, Fanny; Eugster, Werner; Foken, Thomas; Heimann, Martin; Kolle, Olaf; Göckede, Mathias

2017-08-01

This study aimed at quantifying potential negative effects of instrument heating to improve eddy-covariance flux data quality in cold environments. Our overarching objective was to minimize heating-related bias in annual CO2 budgets from an Arctic permafrost system. We used continuous eddy-covariance measurements covering three full years within an Arctic permafrost ecosystem with parallel sonic anemometers operation with activated heating and without heating as well as parallel operation of open- and closed-path gas analyzers, the latter serving as a reference. Our results demonstrate that the sonic anemometer heating has a direct effect on temperature measurements while the turbulent wind field is not affected. As a consequence, fluxes of sensible heat are increased by an average 5 W m-2 with activated heating, while no direct effect on other scalar fluxes was observed. However, the biased measurements in sensible heat fluxes can have an indirect effect on the CO2 fluxes in case they are used as input for a density-flux WPL correction of an open-path gas analyzer. Evaluating the self-heating effect of the open-path gas analyzer by comparing CO2 flux measurements between open- and closed-path gas analyzers, we found systematically higher CO2 uptake recorded with the open-path sensor, leading to a cumulative annual offset of 96 gC m-2, which was not only the result of the cold winter season but also due to substantial self-heating effects during summer. With an inclined sensor mounting, only a fraction of the self-heating correction for vertically mounted instruments is required.

Solution for Minimizing Surface Heating Effect for Fast Open-Path CO2 Flux Measurements in Cold Environments

NASA Astrophysics Data System (ADS)

Hupp, J. R.; Burba, G. G.; McDermitt, D. K.; Anderson, D. J.; Eckles, R. D.

2010-12-01

Open-path design of the high speed gas analyzers is a well-established configuration widely used for measurements of CO2 fluxes and concentrations. This configuration has advantages and deficiencies. Advantages include excellent frequency response, long-term stability, low sensitivity to window contamination, low-power pump-free operation, and infrequent calibration requirements. Deficiencies include susceptibility to precipitation and icing, and a potential need for instrument surface heating correction in extremely cold environments. In spite of the deficiencies, open-path measurements often provide data coverage that would not have been possible using traditional closed-path approach. Data loss from precipitation and icing may not always be prevented for the open-path instruments, while heating effect does not pose a problem for CO2 flux in warm environments. Even in cold environments, the impact of heating on CO2 flux is much smaller than other well-known effects, such as Webb-Pearman-Leuning terms, or frequency response corrections for closed-path analyzers. Nonetheless, instrument surface heating effect in cold environments could be addressed scientifically, via developing the theoretical corrections, and instrumentally, via measuring fast integrated air temperature in the optical path, or via enclosing the open-path instrument into a low-power short-intake design. Here we provide an alternative way to minimize or eliminate open-path heating effect, achieved by minimizing or eliminating the temperature gradient between the instrument surface and ambient air. Open-path low temperature controlled design is discussed in comparison with two other approaches (e.g., traditional open-path design and closed-path design) in terms of their field performance for Eddy Covariance flux measurements in the cold. This study presents field data from a new open-path CO2/H2O gas analyzer, LI-7500A, based on the LI-7500 model modified to produce substantially less heat during extremely cold conditions. Two regiments of the temperature control for internal electronics were examined across a wide range of temperatures: (i) the traditional control temperature of about 30oC, and (ii) new regiment controlling parts of internal electronics at 5oC. When new 5oC regiment was activated, the following changes were observed: heat dissipation from the surface reduced several folds, surface-to-air temperature gradients reduced 2-50 times; and the number of false uptake hours were reduced by 3.5 times, to the same level as a closed-path standard. Significant advantage of the new regiment was also observed in the magnitude of CO2 fluxes, especially in cold weather below -10oC. At such cold temperatures, CO2 fluxes from a 30oC controlled LI-7500 were 19% below those of the closed-path standard, while fluxes from a 5oC controlled LI-7500A were, on average, within 1% of the standard. These are strong experimental evidence that open-path instrument heating can be substantially reduced or eliminated via such simple hardware based solution. This allows continued and expanded use of this ultimately lowest-power remote solution for fast gas measurements.

Ground and Airborne Methane Measurements Using Optical Parametric Amplifiers

NASA Technical Reports Server (NTRS)

Numata, Kenji; Riris, Haris; Li, Steve; Wu, Stewart; Kawa, Stephan R.; Abshire, James Brice; Dawsey, Martha; Ramanathan, Anand

2011-01-01

We report on ground and airborne methane measurements with an active sensing instrument using widely tunable, seeded optical parametric generation (OPG). The technique has been used to measure methane, CO2, water vapor, and other trace gases in the near and mid-infrared spectral regions. Methane is a strong greenhouse gas on Earth and it is also a potential biogenic marker on Mars and other planetary bodies. Methane in the Earth's atmosphere survives for a shorter time than CO2 but its impact on climate change can be larger than CO2. Carbon and methane emissions from land are expected to increase as permafrost melts exposing millennial-age carbon stocks to respiration (aerobic-CO2 and anaerobic-CH4) and fires. Methane emissions from c1athrates in the Arctic Ocean and on land are also likely to respond to climate warming. However, there is considerable uncertainty in present Arctic flux levels, as well as how fluxes will change with the changing environment. For Mars, methane measurements are of great interest because of its potential as a strong biogenic marker. A remote sensing instrument that can measure day and night over all seasons and latitudes can localize sources of biogenic gas plumes produced by subsurface chemistry or biology, and aid in the search for extra-terrestrial life. In this paper we report on remote sensing measurements of methane using a high peak power, widely tunable optical parametric generator (OPG) operating at 3.3 micrometers and 1.65 micrometers. We have demonstrated detection of methane at 3.3 micrometers and 1650 nanometers in an open path and compared them to accepted standards. We also report on preliminary airborne demonstration of methane measurements at 1.65 micrometers.

Current and emerging laser sensors for greenhouse gas sensing and leak detection

NASA Astrophysics Data System (ADS)

Frish, Michael B.

2014-05-01

To reduce atmospheric accumulation of the greenhouse gases methane and carbon dioxide, networks of continuously operating sensors that monitor and map their sources are desirable. In this paper, we discuss advances in laser-based open-path leak detectors, as well as technical and economic challenges inhibiting widespread sensor deployment for "ubiquitous monitoring". We describe permanently-installed, wireless, solar-powered sensors that overcome previous installation and maintenance difficulties while providing autonomous real-time leak reporting without false alarms.

OPEN PATH AMBIENT MEASUREMENTS OF POLLUTANTS WITH A DOAS SYSTEM

EPA Science Inventory

A differential optical absorption spectrometer (DOAS) has been in operation since August 1991 at the U.S. EPA in RTP, NC. he analyzer unit is located in an environmentally-controlled shelter in the EPA parking lot. our separate open optical paths have been established, ranging fr...

INVESTIGATION OF OPEN-PATH FTIR FOR FAST DEPLOYMENT EMERGENCY RESPONSE TO CHEMICAL THREATS AND ACCIDENTS.

EPA Science Inventory

We have performed a series of experiments to determine the tradeoff in detection sensitivity for implementing design features for an Open-Path Fourier Transform Infrared (OP-FTIR) chemical analyzer that would be quick to deploy under emergency response conditions. The fast-deplo...

Estimates of methane and ethane emissions from the Texas Barnett Shale

NASA Astrophysics Data System (ADS)

Karion, A.; Sweeney, C.; Yacovitch, T.; Petron, G.; Wolter, S.; Conley, S. A.; Hardesty, R. M.; Brewer, A.; Kofler, J.; Newberger, T.; Herndon, S.; Miller, B. R.; Montzka, S. A.; Rella, C.; Crosson, E.; Tsai, T.; Tans, P. P.

2013-12-01

The recent development of horizontal drilling technology by the oil and gas industry has dramatically increased onshore U.S. natural gas and oil production in the last several years. This production boom has led to wide-spread interest from the policy and scientific communities in quantifying the climate impact of the use of natural gas as a replacement for coal. Because the primary component of natural gas is methane, a powerful greenhouse gas, natural gas leakage into the atmosphere affects its climate impact. Several recent scientific field studies have focused on using atmospheric measurements to estimate this leakage in different producing basins. Methane can be measured precisely with commercial analyzers, and deployment of such analyzers on aircraft, coupled with meteorological measurements, can allow scientists to estimate emissions from regions of concentrated production. Ethane and other light hydrocarbons, also components of raw gas, can be used as tracers for differentiating natural gas emissions from those of other methane sources, such as agriculture or landfills, which do not contain any non-methane hydrocarbons such as ethane. Here we present results from one such field campaign in the Barnett Shale near Fort Worth, Texas, in March 2013. Several 4-hour flights were conducted over the natural gas and oil production region with a small single-engine aircraft instrumented with analyzers for measuring ambient methane, carbon monoxide, carbon dioxide, and ethane at high frequencies (0.3-1Hz). The aircraft also measured horizontal winds, temperature, humidity, and pressure, and collected whole air samples in flasks analyzed later for several light hydrocarbons. In addition to the aircraft, a ground-based High-Resolution Doppler Lidar was deployed in the basin to measure profiles of horizontal winds and estimate the boundary layer height 24 hours a day over the campaign period. The aircraft and lidar measurements are used together to estimate methane and ethane emissions in the region. Flight track colored by methane (CH4, left) and ethane (C2H6, right) mole fraction. A three-hour back trajectory (red line) constructed from lidar wind measurements passes over the Barnett natural gas well locations (gray points) prior to reaching the location on the flight path indicated by the red star.

Development of an Optical Gas Leak Sensor for Detecting Ethylene, Dimethyl Ether and Methane

PubMed Central

Tan, Qiulin; Pei, Xiangdong; Zhu, Simin; Sun, Dong; Liu, Jun; Xue, Chenyang; Liang, Ting; Zhang, Wendong; Xiong, Jijun

2013-01-01

In this paper, we present an approach to develop an optical gas leak sensor that can be used to measure ethylene, dimethyl ether, and methane. The sensor is designed based on the principles of IR absorption spectrum detection, and comprises two crossed elliptical surfaces with a folded reflection-type optical path. We first analyze the optical path and the use of this structure to design a miniature gas sensor. The proposed sensor includes two detectors (one to acquire the reference signal and the other for the response signal), the light source, and the filter, all of which are integrated in a miniature gold-plated chamber. We also designed a signal detection device to extract the sensor signal and a microprocessor to calculate and control the entire process. The produced sensor prototype had an accuracy of ±0.05%. Experiments which simulate the transportation of hazardous chemicals demonstrated that the developed sensor exhibited a good dynamic response and adequately met technical requirements. PMID:23539025

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

PubMed

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

2007-05-17

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

Production waters associated with the Ferron coalbed methane fields, central Utah: Chemical and isotopic composition and volumes

USGS Publications Warehouse

Rice, C.A.

2003-01-01

This study investigated the composition of water co-produced with coalbed methane (CBM) from the Upper Cretaceous Ferron Sandstone Member of the Mancos Shale in east-central Utah to better understand coalbed methane reservoirs. The Ferron coalbed methane play currently has more than 600 wells producing an average of 240 bbl/day/well water. Water samples collected from 28 wellheads in three fields (Buzzards Bench, Drunkards Wash, and Helper State) of the northeast-southwest trending play were analyzed for chemical and stable isotopic composition.Water produced from coalbed methane wells is a Na-Cl-HCO3 type. Water from the Drunkards Wash field has the lowest total dissolved solids (TDS) (6300 mg/l) increasing in value to the southeast and northeast. In the Helper State field, about 6 miles northeast, water has the highest total dissolved solids (43,000 mg/l), and major ion abundance indicates the possible influence of evaporite dissolution or mixing with a saline brine. In the southern Buzzards Bench field, water has variable total dissolved solids that are not correlated with depth or spatial distance. Significant differences in the relative compositions are present between the three fields implying varying origins of solutes and/or different water-rock interactions along multiple flow paths.Stable isotopic values of water from the Ferron range from +0.9??? to -11.4??? ?? 18O and -32??? to -90??? ?? 2H and plot below the global meteoric water line (GMWL) on a line near, but above values of present-day meteoric water. Isotopic values of Ferron water are consistent with modification of meteoric water along a flow path by mixing with an evolved seawater brine and/or interaction with carbonate minerals. Analysis of isotopic values versus chloride (conservative element) and total dissolved solids concentrations indicates that recharge water in the Buzzards Bench area is distinct from recharge water in Drunkards Wash and is about 3 ??C warmer. These variations in isotopes along with compositional variations imply that the Ferron reservoir is heterogeneous and compartmentalized, and that multiple flow paths may exist. ?? 2003 Published by Elsevier B.V. All rights reserved.

Assessment and mitigation of errors associated with a large-scale field investigation of methane emissions from the Marcellus Shale

NASA Astrophysics Data System (ADS)

Caulton, D.; Golston, L.; Li, Q.; Bou-Zeid, E.; Pan, D.; Lane, H.; Lu, J.; Fitts, J. P.; Zondlo, M. A.

2015-12-01

Recent work suggests the distribution of methane emissions from fracking operations is a skewed distributed with a small percentage of emitters contributing a large proportion of the total emissions. In order to provide a statistically robust distributions of emitters and determine the presence of super-emitters, errors in current techniques need to be constrained and mitigated. The Marcellus shale, the most productive natural gas shale field in the United States, has received less intense focus for well-level emissions and is here investigated to provide the distribution of methane emissions. In July of 2015 approximately 250 unique well pads were sampled using the Princeton Atmospheric Chemistry Mobile Acquisition Node (PAC-MAN). This mobile lab includes a Garmin GPS unit, Vaisala weather station (WTX520), LICOR 7700 CH4 open path sensor and LICOR 7500 CO2/H2O open path sensor. Sampling sites were preselected based on wind direction, sampling distance and elevation grade. All sites were sampled during low boundary layer conditions (600-1000 and 1800-2200 local time). The majority of sites were sampled 1-3 times while selected test sites were sampled multiple times or resampled several times during the day. For selected sites a sampling tower was constructed consisting of a Metek uSonic-3 Class A sonic anemometer, and an additional LICOR 7700 and 7500. Data were recorded for at least one hour at these sites. A robust study and inter-comparison of different methodologies will be presented. The Gaussian plume model will be used to calculate fluxes for all sites and compare results from test sites with multiple passes. Tower data is used to provide constraints on the Gaussian plume model. Additionally, Large Eddy Simulation (LES) modeling will be used to calculate emissions from the tower sites. Alternative techniques will also be discussed. Results from these techniques will be compared to identify best practices and provide robust error estimates.

Research on atmospheric CO2 remote sensing with open-path tunable diode laser absorption spectroscopy and comparison methods

NASA Astrophysics Data System (ADS)

Xin, Fengxin; Guo, Jinjia; Sun, Jiayun; Li, Jie; Zhao, Chaofang; Liu, Zhishen

2017-06-01

An open-path atmospheric CO2 measurement system was built based on tunable diode laser absorption spectroscopy (TDLAS). The CO2 absorption line near 2 μm was selected, measuring the atmospheric CO2 with direct absorption spectroscopy and carrying on the comparative experiment with multipoint measuring instruments of the open-path. The detection limit of the TDLAS system is 1.94×10-6. The calibration experiment of three AZ-7752 handheld CO2 measuring instruments was carried out with the Los Gatos Research gas analyzer. The consistency of the results was good, and the handheld instrument could be used in the TDLAS system after numerical calibration. With the contrast of three AZ-7752 and their averages, the correlation coefficients are 0.8828, 0.9004, 0.9079, and 0.9393 respectively, which shows that the open-path TDLAS has the best correlation with the average of three AZ-7752 and measures the concentration of atmospheric CO2 accurately. Multipoint measurement provides a convenient comparative method for open-path TDLAS.

Lidar Measurements of Methane and Applications for Aircraft and Spacecraft

NASA Technical Reports Server (NTRS)

Riris, Haris; Numata, Kenji; Abshire, James; Li, Steve; Wu, Stewart; Krainak, Michael; Sun, Xiaoli

2010-01-01

Atmospheric methane levels have remained relatively constant over the last decade around 1.78 parts per million (ppm) but observations since 2007 show that levels may be increasing. This trend may be caused by increased fossil fuel production, rice farming, livestock and landfills, but the underlying causes are quite uncertain. One hypothesis is that reservoirs of carbon trapped in the permafrost regions of northern Canada, Europe, and Siberia thaw as global temperatures rise and are releasing increasing amounts of methane. Another hypothesis points to increased production of methane by microbes as the permafrost warms. Currently most observations of greenhouse gases are limited to in-situ (surface and tower sites) and limited airborne in-situ measurements. Space column density measurements are starting to become available from the GOSAT mission. Although methane survives for a shorter time in the atmosphere than CO2, its impact on climate change per molecule is about 23 times than that of CO2. Accurate global observations of several greenhouse gases, including methane, are urgently needed in order to better understand climate change processes and to reduce the uncertainty in the carbon budget. Differential absorption lidar is a well-established technique to measure atmospheric gases, and methane has optical absorption bands near 1.65,2.2,3.4 and 7.8 micron. The near infrared overtones lines of CH4 near 1650 nm are relatively free of interference from other species. There are absorption lines near 1651 nm which are both temperature insensitive and have line strengths well suited for lidar measurements. We have developed a laser and demonstrated lidar measurements of CH4 using lines in this band. Our laser uses a narrow linewidth 1064 nm laser pulse passing through a nonlinear crystal. We generate the tunable laser signals near 1651 nm by using the optical parametric amplification (OPA) process. Inside the crystal the 1064 nm beam overlaps with an injection seed laser near 1651 nm from a wavelength tunable diode laser. Incident photons from the pump laser pulse are converted into two photons, with one at the wavelength of the injection seeder. The wavelength of the OPA output is tuned via the wavelength of diode laser. Our laser is tunable, operates near 1651 nm and generates approximately 4 uJ/pulse at 6 KHz. We vary the emission wavelengths within this band by tuning the diode laser's wavelength. We have used this OPA transmitter to make measurements of CH4 at various pressures in a gas cell and over open outdoor horizontal paths. We have measured the lineshape of methane in a 6 cm long cell at various energy levels with this transmitter, with excellent agreement with the lineshape calculated by HITRAN. We have also measured the absorption lineshape of atmospheric methane in an open 3 km outdoor path. The agreement between the measurements and HITRAN, for 1746 ppb and 760 Torr was quite good. We have also made pulsed two wavelength lidar measurements of methane line absorption in the column to a tower at 1.5 km range. These used on- and off-line wavelengths of 1650.957 nm, and 1651.072 nm, and a 20 cm diameter receiver telescope with an infrared PMT detector. The absorption of the on-line photons was 30%. The methane column absorption was estimated via HITRAN, and was in good agreement with the expected methane absorption for a concentration of 1750 ppm. Finally we have calculated the measurement performance of an airborne methane lidar using this transmitter, as well as the energy and telescope scaling needed for a lidar for space. These results, and more details of our experiments will be described in the presentation.

Lidar Measurements of Methane and Applications for Aircraft and Spacecraft

NASA Astrophysics Data System (ADS)

Riris, Haris; Numata, Kenji; Abshire, James; Li, Steve; Wu, Stewart; Krainak, Michael; Sun, Xiaoli

2010-05-01

Atmospheric methane levels have remained relatively constant over the last decade around 1.78 parts per million (ppm) but observations since 2007 show that levels may be increasing. This trend may be caused by increased fossil fuel production, rice farming, livestock and landfills, but the underlying causes are quite uncertain. One hypothesis is that reservoirs of carbon trapped in the permafrost regions of northern Canada, Europe, and Siberia thaw as global temperatures rise and are releasing increasing amounts of methane. Another hypothesis points to increased production of methane by microbes as the permafrost warms. Currently most observations of greenhouse gases are limited to in-situ (surface and tower sites) and limited airborne in-situ measurements. Space column density measurements are starting to become available from the GOSAT mission. Although methane survives for a shorter time in the atmosphere than CO2, its impact on climate change per molecule is about 23 times than that of CO2. Accurate global observations of several greenhouse gases, including methane, are urgently needed in order to better understand climate change processes and to reduce the uncertainty in the carbon budget. Differential absorption lidar is a well-established technique to measure atmospheric gases, and methane has optical absorption bands near 1.65, 2.2, 3.4 and 7.8 μm. The near infrared overtones lines of CH4 near 1650 nm are relatively free of interference from other species. There are absorption lines near 1651 nm which are both temperature insensitive and have line strengths well suited for lidar measurements. We have developed a laser and demonstrated lidar measurements of CH4 using lines in this band. Our laser uses a narrow linewidth 1064 nm laser pulse passing through a nonlinear crystal. We generate the tunable laser signals near 1651 nm by using the optical parametric amplification (OPA) process. Inside the crystal the 1064 nm beam overlaps with an injection seed laser near 1651 nm from a wavelength tunable diode laser. Incident photons from the pump laser pulse are converted into two photons, with one at the wavelength of the injection seeder. The wavelength of the OPA output is tuned via the wavelength of diode laser. Our laser is tunable, operates near 1651 nm and generates ~4 uJ/pulse at 6 KHz. We vary the emission wavelengths within this band by tuning the diode laser's wavelength. We have used this OPA transmitter to make measurements of CH4 at various pressures in a gas cell and over open outdoor horizontal paths. We have measured the lineshape of methane in a 6 cm long cell at various energy levels with this transmitter, with excellent agreement with the lineshape calculated by HITRAN. We have also measured the absorption lineshape of atmospheric methane in an open 3 km outdoor path. The agreement between the measurements and HITRAN, for 1746 ppb and 760 Torr was quite good. We have also made pulsed two wavelength lidar measurements of methane line absorption in the column to a tower at 1.5 km range. These used on- and off-line wavelengths of 1650.957 nm, and 1651.072 nm, and a 20 cm diameter receiver telescope with an infrared PMT detector. The absorption of the on-line photons was 30%. The methane column absorption was estimated via HITRAN, and was in good agreement with the expected methane absorption for a concentration of 1750 ppm. Finally we have calculated the measurement performance of an airborne methane lidar using this transmitter, as well as the energy and telescope scaling needed for a lidar for space. These results, and more details of our experiments will be described in the presentation.

Carbon fluxes in a heterogeneous estuarine wetland in Northern Ohio. Comparing eddy covariance and chamber measurements

NASA Astrophysics Data System (ADS)

Rey Sanchez, C.; Morin, T. H.; Stefanik, K. C.; Wrighton, K. C.; Bohrer, G.

2016-12-01

Wetlands are important carbon dioxide (CO2) sinks but also the largest source of methane (CH4), a powerful greenhouse gas. Wetlands are often heterogeneous landscapes with highly diverse land covers and different paths of CH4 release and CO2 uptake. Understanding the ecosystem level greenhouse gas budget of a wetland involves understanding several carbon fluxes associated with each of the different land cover patches. We studied CO2 and CH4 fluxes from different land cover types at the Old Woman Creek (OWC) National Estuarine Research Reserve, at the Lake Erie shore in Northern Ohio. OWC is composed of four main types of land cover: open water, emergent cattail vegetation (Typha spp), floating vegetation (Nelimbo spp), and mud flats. CH4 and CO2 gas exchange was measured in each patch type using enclosed chambers monthly during the growing seasons of 2015 and 2016. During the same period of time, an eddy covariance tower was deployed in a representative section of the wetland to measure continuous site-level CO2 and CH4 fluxes. A footprint model was used to account for the relative contributions of each patch type to the flux measured by the tower. The chamber measurements were used to constrain the contributions of each patch within the flux tower footprint, and to correct the flux measurements to the whole-wetland total flux. We analyzed the spatial and temporal variability of methane and carbon dioxide and related this variation to some of the most important environmental drivers at the site. We used these data to analyze the implications of different arrangements of land cover types on the carbon balance and greenhouse-gas budget in wetlands.

Fugitive methane leak detection using mid-infrared hollow-core photonic crystal fiber containing ultrafast laser drilled side-holes

NASA Astrophysics Data System (ADS)

Karp, Jason; Challener, William; Kasten, Matthias; Choudhury, Niloy; Palit, Sabarni; Pickrell, Gary; Homa, Daniel; Floyd, Adam; Cheng, Yujie; Yu, Fei; Knight, Jonathan

2016-05-01

The increase in domestic natural gas production has brought attention to the environmental impacts of persistent gas leakages. The desire to identify fugitive gas emission, specifically for methane, presents new sensing challenges within the production and distribution supply chain. A spectroscopic gas sensing solution would ideally combine a long optical path length for high sensitivity and distributed detection over large areas. Specialty micro-structured fiber with a hollow core can exhibit a relatively low attenuation at mid-infrared wavelengths where methane has strong absorption lines. Methane diffusion into the hollow core is enabled by machining side-holes along the fiber length through ultrafast laser drilling methods. The complete system provides hundreds of meters of optical path for routing along well pads and pipelines while being interrogated by a single laser and detector. This work will present transmission and methane detection capabilities of mid-infrared photonic crystal fibers. Side-hole drilling techniques for methane diffusion will be highlighted as a means to convert hollow-core fibers into applicable gas sensors.

Remote sensing of methane with OSAS-lidar on the 2ν3 band Q-branch: Experimental proof

NASA Astrophysics Data System (ADS)

Galtier, Sandrine; Anselmo, Christophe; Welschinger, Jean-Yves; Sivignon, J. F.; Cariou, Jean-Pierre; Miffre, Alain; Rairoux, Patrick

2018-06-01

Optical sensors based on absorption spectroscopy play a central role in the detection and monitoring of atmospheric trace gases. We here present for the first time the experimental demonstration of OSAS-Lidar on the remote sensing of CH4 in the atmosphere. This new methodology, the OSAS-Lidar, couples the Optical Similitude Absorption Spectroscopy (OSAS) methodology with a light detection and ranging device. It is based on the differential absorption of spectrally integrated signals following Beer Lambert-Bouguer law, which are range-resolved. Its novelty originates from the use of broadband laser spectroscopy and from the mathematical approach used to retrieve the trace gas concentration. We previously applied the OSAS methodology in laboratory on the 2ν3 methane absorption band, centered at the 1665 nm wavelength and demonstrated that the OSAS-methodology is almost independent from atmospheric temperature and pressure. In this paper, we achieve an OSAS-Lidar device capable of observing large concentrations of CH4 released from a methane source directly into the atmosphere. Comparison with a standard in-situ measurement device shows that the path-integrated concentrations retrieved from OSAS-Lidar methodology exhibit sufficient sensitivity (2 000 ppm m) and observational time resolution (1 s) to remotely sense methane leaks in the atmosphere. The coupling of OSAS-lidar with a wind measurement device opens the way to monitor time-resolved methane flux emissions, which is important in regards to future climate mitigation involving regional reduction of CH4 flux emissions.

Stream measurements locate thermogenic methane fluxes in groundwater discharge in an area of shale-gas development.

PubMed

Heilweil, Victor M; Grieve, Paul L; Hynek, Scott A; Brantley, Susan L; Solomon, D Kip; Risser, Dennis W

2015-04-07

The environmental impacts of shale-gas development on water resources, including methane migration to shallow groundwater, have been difficult to assess. Monitoring around gas wells is generally limited to domestic water-supply wells, which often are not situated along predominant groundwater flow paths. A new concept is tested here: combining stream hydrocarbon and noble-gas measurements with reach mass-balance modeling to estimate thermogenic methane concentrations and fluxes in groundwater discharging to streams and to constrain methane sources. In the Marcellus Formation shale-gas play of northern Pennsylvania (U.S.A.), we sampled methane in 15 streams as a reconnaissance tool to locate methane-laden groundwater discharge: concentrations up to 69 μg L(-1) were observed, with four streams ≥ 5 μg L(-1). Geochemical analyses of water from one stream with high methane (Sugar Run, Lycoming County) were consistent with Middle Devonian gases. After sampling was completed, we learned of a state regulator investigation of stray-gas migration from a nearby Marcellus Formation gas well. Modeling indicates a groundwater thermogenic methane flux of about 0.5 kg d(-1) discharging into Sugar Run, possibly from this fugitive gas source. Since flow paths often coalesce into gaining streams, stream methane monitoring provides the first watershed-scale method to assess groundwater contamination from shale-gas development.

Fugitive coke oven gas emission profile by continuous line averaged open-path Fourier transform infrared monitoring.

PubMed

Lin, Chitsan; Liou, Naiwei; Chang, Pao-Erh; Yang, Jen-Chin; Sun, Endy

2007-04-01

Although most coke oven research is focused on the emission of polycyclic aromatic hydrocarbons, well-known carcinogens, little has been done on the emission of volatile organic compounds, some of which are also thought to be hazardous to workers and the environment. To profile coke oven gas (COG) emissions, we set up an open-path Fourier transform infrared (OP-FTIR) system on top of a battery of coke ovens at a steel mill located in Southern Taiwan and monitored average emissions in a coke processing area for 16.5 hr. Nine COGs were identified, including ammonia, CO, methane, ethane, ethylene, acetylene, propylene, cyclohexane, and O-xylene. Time series plots indicated that the type of pollutants differed over time, suggesting that different emission sources (e.g., coke pushing, quench tower, etc.) were involved at different times over the study period. This observation was confirmed by the low cross-correlation coefficients of the COGs. It was also found that, with the help of meteorological analysis, the data collected by the OP-FTIR system could be analyzed effectively to characterize differences in the location of sources. Although the traditional single-point samplings of emissions involves sampling various sources in a coke processing area at several different times and is a credible profiling of emissions, our findings strongly suggest that they are not nearly as efficient or as cost-effective as the continuous line average method used in this study. This method would make it easier and cheaper for engineers and health risk assessors to identify and to control fugitive volatile organic compound emissions and to improve environmental health.

Optical fiber network sensor system for monitoring methane concentration

NASA Astrophysics Data System (ADS)

Zhang, Zhi-wei; Zhang, Ji-long

2011-08-01

With regard to the high accuracy optic-fiber sensor for monitoring methane concentration, the choice of light source depends on methane peak values. Besides, the environment of mine should be considered, that is to say other gas should be considered, such as vapor, CO and CO2 etc, without absorbent spectrum in the decided wavelength. It has been reported that vapor, CO and CO2 have no obvious absorption in 0.85μm, 1.3μm and 1.66μm area, CH4 has no obvious absorption in 0.85μm area. So diode laser with 1.3μm or 1.66μm peak wavelength is chosen as the optic-fiber sensor's light source for detecting methane concentration. On the basis of the principle of optic absorption varied with methane concentration at its characteristic absorbent wavelength, the advantage of optic-fiber sensor technology and the circumstance characteristic of the coal mine. An optic-fiber sensor system is presented for monitoring methane concentration. Space Division Multiple Access Technology (SDMAT) and long optical path absorbent pool technology are combined in the study. Considering the circumstance characteristic of the coal mine, the optic-fiber network sensors for detecting methane concentration from mix gas of vapor, CO, CH4 and CO2 are used. It introduces the principle of an optic-fiber sensor system for monitoring methane concentration in coal mine. It contains the structure block diagram of monitoring system, the system is mainly made up of diode laser for monitoring methane concentration, Y-shaped photo-coupler with coupled rate 50:50, optical switch 1×2, gas absorbent cell, the computer data process and control system and photoelectric transformer. In this study, in order to decrease to the influence of the dark-current of photodiode, intensity in light sources and temperature drifts of processing circuit on the system accuracy in measurement, a beam of light is broken down into two beams in the coupler of Y-shaped coupler, the one acts as the reference optical path, the other is known as the sensing optical path. The experimental result shows that diode laser with 1654.141nm in wavelength is taken as the optic source for detecting methane concentration, the detective limit of the sensor is below 4.274mg/m3 when the optical path of absorbent pool is 20 centimeters, and the prevision and stability could satisfy practical application. The whole instrument can also reach on-line measurement with multiple points on different spot.

Measurements of the global distribution of carbon monoxide in the troposphere

NASA Technical Reports Server (NTRS)

Hinton, R. R.

1982-01-01

Carbon monoxide and methane grab samples were obtained simultaneously with ozone, aerosol, nitric oxide and DACOM CO measurements. Eighty grab samples were collected at various altitudes up to 19,000 ft. along a north-south flight path from Wallops Flight Center, VA to 11 N. CO and CH were analyzed by flame ionization gas chromatography with cryogenic preconcentration. The relationship between CO and O3 concentrated is examined. A comparative analysis between trends in aerosol and CO concentration is performed.

Detecting Methane From Leaking Pipelines and as Greenhouse Gas in the Atmosphere

NASA Technical Reports Server (NTRS)

Riris, Haris; Numata, Kenji; Li, Steven; Wu, Stewart; Ramanathan, Anand; Dawsey, Martha

2012-01-01

Laser remote sensing measurements of trace gases from orbit can provide unprecedented information about important planetary science and answer critical questions about planetary atmospheres. Methane (CH4) is the second most important anthropogenically produced greenhouse gas. Though its atmospheric abundance is much less than that of CO2 (1.78 ppm vs. 380 ppm), it has much larger greenhouse heating potential. CH4 also contributes to pollution in the lower atmosphere through chemical reactions, leading to ozone production. Atmospheric CH4 concentrations have been increasing as a result of increased fossil fuel production, rice farming, livestock, and landfills. Natural sources of CH4 include wetlands, wild fires, and termites, and perhaps other unknown sources. Important sinks for CH4 include non-saturated soils and oxidation by hydroxyl radicals in the atmosphere. Remotely measuring CH4 and other biogenic molecules (such as ethane and formaldehyde) on Mars also has important implications on the existence of life on Mars. Measuring CH4 at very low (ppb) concentrations from orbit will dramatically improve the sensitivity and spatial resolution in the search for CH4 vents and sub-surface life on other planets. A capability has been developed using lasers and spectroscopic detection techniques for the remote measurements of trace gases in open paths. Detection of CH4, CO2, H2O, and CO in absorption cells and in open paths, both in the mid- IR and near-IR region, has been demonstrated using an Optical Parametric Amplifier laser transmitter developed at GSFC. With this transmitter, it would be possible to develop a remote sensing methane instrument. CH4 detection also has very important commercial applications. Pipeline leak detection from an aircraft or a helicopter can significantly reduce cost, response time, and pinpoint the location. The main advantage is the ability to rapidly detect CH4 leaks remotely. This is extremely important for the petrochemical industry. This capability can be used in manned or unmanned airborne platforms for the detection of leaks in pipelines and other areas of interest where a CH4 leak is suspected.

Sensitive detection of methane at 3.3 μm using an integrating sphere and interband cascade laser

NASA Astrophysics Data System (ADS)

Davis, N. M.; Hodgkinson, J.; Francis, D.; Tatam, R. P.

2016-04-01

Detection of methane at 3.3μm using a DFB Interband Cascade Laser and gold coated integrating sphere is performed. A 10cm diameter sphere with effective path length of 54.5cm was adapted for use as a gas cell. A comparison between this system and one using a 25cm path length single-pass gas cell is made using direct TDLS and methane concentrations between 0 and 1000 ppm. Initial investigations suggest a limit of detection of 1.0ppm for the integrating sphere and 2.2ppm for the single pass gas cell. The system has potential applications in challenging or industrial environments subject to high levels of vibration.

Consequences of incomplete surface energy balance closure for CO2 fluxes from open-path CO2/H2O infrared gas analyzers

Treesearch

Heping Liu; James T. Randerson; Jamie Lindfors; William J. Massman; Thomas Foken

2006-01-01

We present an approach for assessing the impact of systematic biases in measured energy fluxes on CO2 flux estimates obtained from open-path eddy-covariance systems. In our analysis, we present equations to analyse the propagation of errors through the Webb, Pearman, and Leuning (WPL) algorithm [Quart. J. Roy. Meteorol. Soc. 106, 85­100, 1980] that is widely used to...

Advances in data processing for open-path Fourier transform infrared spectrometry of greenhouse gases.

PubMed

Shao, Limin; Griffiths, Peter R; Leytem, April B

2010-10-01

The automated quantification of three greenhouse gases, ammonia, methane, and nitrous oxide, in the vicinity of a large dairy farm by open-path Fourier transform infrared (OP/FT-IR) spectrometry at intervals of 5 min is demonstrated. Spectral pretreatment, including the automated detection and correction of the effect of interrupting the infrared beam, is by a moving object, and the automated correction for the nonlinear detector response is applied to the measured interferograms. Two ways of obtaining quantitative data from OP/FT-IR data are described. The first, which is installed in a recently acquired commercial OP/FT-IR spectrometer, is based on classical least-squares (CLS) regression, and the second is based on partial least-squares (PLS) regression. It is shown that CLS regression only gives accurate results if the absorption features of the analytes are located in very short spectral intervals where lines due to atmospheric water vapor are absent or very weak; of the three analytes examined, only ammonia fell into this category. On the other hand, PLS regression works allowed what appeared to be accurate results to be obtained for all three analytes.

Merlin: an integrated path differential absorption (IPDA) lidar for global methane remote sensing

NASA Astrophysics Data System (ADS)

Bode, M.; Alpers, M.; Millet, B.; Ehret, G.; Flamant, P.

2017-11-01

The Methane Remote Sensing LIDAR Mission (MERLIN) is a joint French-German cooperation on the development, launch and operation of a climate monitoring satellite, executed by the French Space Agency CNES and the German Space Administration DLR.

Merlin: an integrated path differential absorption (IPDA) lidar for global methane remote sensing

NASA Astrophysics Data System (ADS)

Bode, M.; Wührer, C.; Alpers, M.; Millet, B.; Ehret, G.; Bousquet, P.

2017-09-01

The Methane Remote Sensing LIDAR Mission (MERLIN) is a joint French-German cooperation on the development, launch and operation of a climate monitoring satellite, executed by the French Space Agency CNES and the German Space Administration DLR.

Path integral Liouville dynamics: Applications to infrared spectra of OH, water, ammonia, and methane

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

Liu, Jian, E-mail: jianliupku@pku.edu.cn; State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871; Zhang, Zhijun

Path integral Liouville dynamics (PILD) is applied to vibrational dynamics of several simple but representative realistic molecular systems (OH, water, ammonia, and methane). The dipole-derivative autocorrelation function is employed to obtain the infrared spectrum as a function of temperature and isotopic substitution. Comparison to the exact vibrational frequency shows that PILD produces a reasonably accurate peak position with a relatively small full width at half maximum. PILD offers a potentially useful trajectory-based quantum dynamics approach to compute vibrational spectra of molecular systems.

New assignments in the 2 μm transparency window of the 12CH4 Octad band system

NASA Astrophysics Data System (ADS)

Daumont, L.; Nikitin, A. V.; Thomas, X.; Régalia, L.; Von der Heyden, P.; Tyuterev, Vl. G.; Rey, M.; Boudon, V.; Wenger, Ch.; Loëte, M.; Brown, L. R.

2013-02-01

This paper reports new assignments of rovibrational transitions of 12CH4 bands in the range 4600-4887 cm-1 which is usually referred to as a part of the 2 μm methane transparency window. Several experimental data sources for methane line positions and intensities were combined for this analysis. Three long path Fourier transform spectra newly recorded in Reims with 1603 m absorption path length and pressures of 1, 7 and 34 hPa for samples of natural abundance CH4 provided new measurements of 12CH4 lines. Older spectra for 13CH4 (90% purity) from JPL with 73 m absorption path length were used to identify the corresponding lines. Most of the lines in this region belong to the Octad system of 12CH4. The new spectra allowed us to assign 1014 new line positions and to measure 1095 line intensities in the cold bands of the Octad. These new line positions and intensities were added to the global fit of Hamiltonian and dipole moment parameters of the Ground State, Dyad, Pentad and Octad systems. This leads to a noticeable improvement of the theoretical description in this methane transparency window and a better global prediction of the methane spectrum.

Impact of different eddy covariance sensors and set-up on the annual balance of CO2 and fluxes of CH4 and latent heat in the Arctic

NASA Astrophysics Data System (ADS)

Goodrich, J. P.; Zona, D.; Gioli, B.; Murphy, P.; Burba, G. G.; Oechel, W. C.

2015-12-01

Expanding eddy covariance measurements of CO2 and CH4 fluxes in the Arctic is critical for refining the global C budget. Continuous measurements are particularly challenging because of the remote locations, low power availability, and extreme weather conditions. The necessity for tailoring instrumentation at different sites further complicates the interpretation of results and may add uncertainty to estimates of annual CO2 budgets. We investigated the influence of different sensor combinations on FCO2, latent heat (LE), and FCH4, and assessed the differences in annual FCO2 estimated with different instrumentation at the same sites. Using data from four sites across the North Slope of Alaska, we resolved FCO2 and FCH4 to within 5% using different combinations of open- and closed-path gas analyzers and within 10% using heated and non-heated anemometers. A continuously heated anemometer increased data coverage relative to non-heated anemometers while resulting in comparable annual FCO2, despite over-estimating sensible heat fluxes by 15%. We also implemented an intermittent heating strategy whereby activation only when ice or snow blockage of the transducers was detected. This resulted in comparable data coverage (~ 60%) to the continuously heated anemometer, while avoiding potential over-estimation of sensible heat and gas fluxes. We found good agreement in FCO2 and FCH4 from two closed-path and one open-path gas analyzer, despite the need for large spectral corrections of closed-path fluxes and density and temperature corrections to open-path sensors. However, data coverage was generally greater when using closed-path, especially during cold seasons (36-40% vs 10-14% for the open path), when fluxes from Arctic regions are particularly uncertain and potentially critical to annual C budgets. Measurement of Arctic LE remains a challenge due to strong attenuation along sample tubes, even when heated, that could not be accounted for with spectral corrections.

A theoretical study of three gas-phase reactions involving the production or loss of methane cations.

PubMed

Baptista, Leonardo; da Silveira, Enio F

2014-10-21

Hydrocarbon ions are important species in flames, spectroscopy and the interstellar medium. Their importance is reflected in the extensive body of literature on the structure and reactivity of carbocations. However, the geometry, electronic structure and reactivity of carbocations are difficult to assess. This study aims to contribute to the current knowledge of this subject by presenting a quantum mechanics description of methane cation dissociation using multiconfigurational methods. The geometric and electronic parameters of the minimum structure were determined for three main reaction paths: the dissociation CH4(+)→ CH2(+) + H2 and the dissociation-recombination processes CH4(+)↔ CH3(+) + H. The electronic and energetic effects of these reactions were analyzed, and it was found that each reaction path has a strong dependence on the methodology used as well as a strong multiconfigurational character during dissociation. The first doublet excited states are inner-shell excited states and may correspond to the ions that are expected to be formed after electron detachment. The rate coefficient for each reaction path was determined using variational transition state theory and RRKM/master equation calculations. The major dissociation paths, with their rate coefficients at the high-pressure limit, are CH4(+)(X(~)(2)B1) → CH3(+)(A(2)A1') + H((2)S) (k∞(T) = 1.42 × 10(+14) s(-1) exp(-37.12/RT)) and CH4(+)(X(~)(2)B1) → CH2(+)(A(2)A1) + H2((2)Σg(+)) (k∞(T) = 9.18 × 10(+14) s(-1) exp(-55.77/RT)). Our findings help to explain the abundance of ions formed from CH4 in the interstellar medium and to build models of chemical evolution.

Investigation of Natural Gas Fugitive Leak Detection Using an Unmanned Aerial Vehicle

NASA Astrophysics Data System (ADS)

Yang, S.; Talbot, R. W.; Frish, M. B.; Golston, L.; Aubut, N. F.; Zondlo, M. A.

2017-12-01

The U.S is now the world's largest natural gas producer, of which methane (CH4) is the main component. About 2% of the CH4 is lost through fugitive leaks. This research is under the DOE Methane Observation Networks with Innovative Technology to Obtain Reductions (MONITOR) program of ARPA-E. Our sentry measurement system is composed of four state-of-the-art technologies centered around the RMLDTM (Remote Methane Leak Detector). An open path RMLDTM measures column-integrated CH4 concentration that incorporates fluctuations in the vertical CH4 distribution. Based on Backscatter Tunable Diode Laser Absorption Spectroscopy and Small Unmanned Aerial Vehicles, the sentry system can autonomously, consistently and cost-effectively monitor and quantify CH4 leakage from sites associated with natural gas production. This system provides an advanced capability in detecting leaks at hard-to-access sites (e.g., wellheads) compared to traditional manual methods. Automated leak detecting and reporting algorithms combined with wireless data link implement real-time leak information reporting. Early data were gathered to set up and test the prototype system, and to optimize the leak localization and calculation strategies. The flight pattern is based on a raster scan which can generate interpolated CH4 concentration maps. The localization and quantification algorithms can be derived from the plume images combined with wind vectors. Currently, the accuracy of localization algorithm can reach 2 m and the calculation algorithm has a factor of 2 accuracy. This study places particular emphasis on flux quantification. The data collected at Colorado and Houston test fields were processed, and the correlation between flux and other parameters analyzed. Higher wind speeds and lower wind variation are preferred to optimize flux estimation. Eventually, this system will supply an enhanced detection capability to significantly reduce fugitive CH4 emissions in the natural gas industry.

Completely automated open-path FT-IR spectrometry.

PubMed

Griffiths, Peter R; Shao, Limin; Leytem, April B

2009-01-01

Atmospheric analysis by open-path Fourier-transform infrared (OP/FT-IR) spectrometry has been possible for over two decades but has not been widely used because of the limitations of the software of commercial instruments. In this paper, we describe the current state-of-the-art of the hardware and software that constitutes a contemporary OP/FT-IR spectrometer. We then describe advances that have been made in our laboratory that have enabled many of the limitations of this type of instrument to be overcome. These include not having to acquire a single-beam background spectrum that compensates for absorption features in the spectra of atmospheric water vapor and carbon dioxide. Instead, an easily measured "short path-length" background spectrum is used for calculation of each absorbance spectrum that is measured over a long path-length. To accomplish this goal, the algorithm used to calculate the concentrations of trace atmospheric molecules was changed from classical least-squares regression (CLS) to partial least-squares regression (PLS). For calibration, OP/FT-IR spectra are measured in pristine air over a wide variety of path-lengths, temperatures, and humidities, ratioed against a short-path background, and converted to absorbance; the reference spectrum of each analyte is then multiplied by randomly selected coefficients and added to these background spectra. Automatic baseline correction for small molecules with resolved rotational fine structure, such as ammonia and methane, is effected using wavelet transforms. A novel method of correcting for the effect of the nonlinear response of mercury cadmium telluride detectors is also incorporated. Finally, target factor analysis may be used to detect the onset of a given pollutant when its concentration exceeds a certain threshold. In this way, the concentration of atmospheric species has been obtained from OP/FT-IR spectra measured at intervals of 1 min over a period of many hours with no operator intervention.

Tracking the Career Paths of Marketing and Business Education Graduates

ERIC Educational Resources Information Center

Mooney, Carol; Haltinner, Urs; Stanislawski, Debbie

2006-01-01

Marketing and business education faculty at the University of Wisconsin-Stout (UW-Stout) recently conducted a longitudinal study, spanning the entire 35 years of the program's existence, describing and analyzing its graduates' career paths. Data was collected through a questionnaire that utilized a combination of Likert-type responses, open-ended…

[Remote system of natural gas leakage based on multi-wavelength characteristics spectrum analysis].

PubMed

Li, Jing; Lu, Xu-Tao; Yang, Ze-Hui

2014-05-01

In order to be able to quickly, to a wide range of natural gas pipeline leakage monitoring, the remote detection system for concentration of methane gas was designed based on static Fourier transform interferometer. The system used infrared light, which the center wavelength was calibrated to absorption peaks of methane molecules, to irradiated tested area, and then got the interference fringes by converging collimation system and interference module. Finally, the system calculated the concentration-path-length product in tested area by multi-wavelength characteristics spectrum analysis algorithm, furthermore the inversion of the corresponding concentration of methane. By HITRAN spectrum database, Selected wavelength position of 1. 65 microm as the main characteristic absorption peaks, thereby using 1. 65 pm DFB laser as the light source. In order to improve the detection accuracy and stability without increasing the hardware configuration of the system, solved absorbance ratio by the auxiliary wave-length, and then get concentration-path-length product of measured gas by the method of the calculation proportion of multi-wavelength characteristics. The measurement error from external disturbance is caused by this innovative approach, and it is more similar to a differential measurement. It will eliminate errors in the process of solving the ratio of multi-wavelength characteristics, and can improve accuracy and stability of the system. The infrared absorption spectrum of methane is constant, the ratio of absorbance of any two wavelengths by methane is also constant. The error coefficients produced by the system is the same when it received the same external interference, so the measured noise of the system can be effectively reduced by the ratio method. Experimental tested standards methane gas tank with leaking rate constant. Using the tested data of PN1000 type portable methane detector as the standard data, and were compared to the tested data of the system, while tested distance of the system were 100, 200 and 500 m. Experimental results show that the methane concentration detected value was stable after a certain time leakage, the concentration-path-length product value of the system was stable. For detection distance of 100 m, the detection error of the concentration-path-length product was less than 1. 0%. With increasing distance from tested area, the detection error is increased correspondingly. When the distance was 500 m, the detection error was less than 4. 5%. In short, the detected error of the system is less than 5. 0% after the gas leakage stable, to meet the requirements of the field of natural gas leakage remote sensing.

Exceptional summer warming leads to contrasting outcomes for methane cycling in small Arctic lakes of Greenland

NASA Astrophysics Data System (ADS)

Cadieux, Sarah B.; White, Jeffrey R.; Pratt, Lisa M.

2017-02-01

In thermally stratified lakes, the greatest annual methane emissions typically occur during thermal overturn events. In July of 2012, Greenland experienced significant warming that resulted in substantial melting of the Greenland Ice Sheet and enhanced runoff events. This unusual climate phenomenon provided an opportunity to examine the effects of short-term natural heating on lake thermal structure and methane dynamics and compare these observations with those from the following year, when temperatures were normal. Here, we focus on methane concentrations within the water column of five adjacent small lakes on the ice-free margin of southwestern Greenland under open-water and ice-covered conditions from 2012-2014. Enhanced warming of the epilimnion in the lakes under open-water conditions in 2012 led to strong thermal stability and the development of anoxic hypolimnia in each of the lakes. As a result, during open-water conditions, mean dissolved methane concentrations in the water column were significantly (p < 0.0001) greater in 2012 than in 2013. In all of the lakes, mean methane concentrations under ice-covered conditions were significantly (p < 0.0001) greater than under open-water conditions, suggesting spring overturn is currently the largest annual methane flux to the atmosphere. As the climate continues to warm, shorter ice cover durations are expected, which may reduce the winter inventory of methane and lead to a decrease in total methane flux during ice melt. Under open-water conditions, greater heat income and warming of lake surface waters will lead to increased thermal stratification and hypolimnetic anoxia, which will consequently result in increased water column inventories of methane. This stored methane will be susceptible to emissions during fall overturn, which may result in a shift in greatest annual efflux of methane from spring melt to fall overturn. The results of this study suggest that interannual variation in ground-level air temperatures may be the primary driver of changes in methane dynamics because it controls both the duration of ice cover and the strength of thermal stratification.

Sensitive Spectroscopic Analysis of Biomarkers in Exhaled Breath

NASA Astrophysics Data System (ADS)

Bicer, A.; Bounds, J.; Zhu, F.; Kolomenskii, A. A.; Kaya, N.; Aluauee, E.; Amani, M.; Schuessler, H. A.

2018-06-01

We have developed a novel optical setup which is based on a high finesse cavity and absorption laser spectroscopy in the near-IR spectral region. In pilot experiments, spectrally resolved absorption measurements of biomarkers in exhaled breath, such as methane and acetone, were carried out using cavity ring-down spectroscopy (CRDS). With a 172-cm-long cavity, an efficient optical path of 132 km was achieved. The CRDS technique is well suited for such measurements due to its high sensitivity and good spectral resolution. The detection limits for methane of 8 ppbv and acetone of 2.1 ppbv with spectral sampling of 0.005 cm-1 were achieved, which allowed to analyze multicomponent gas mixtures and to observe absorption peaks of 12CH4 and 13CH4. Further improvements of the technique have the potential to realize diagnostics of health conditions based on a multicomponent analysis of breath samples.

Experimental study on the flame behaviors of premixed methane/air mixture in horizontal rectangular ducts

NASA Astrophysics Data System (ADS)

Chen, Dongliang; Sun, Jinhua; Chen, Sining; Liu, Yi; Chu, Guanquan

2007-01-01

In order to explore the flame propagation characteristics and tulip flame formation mechanism of premixed methane/air mixture in horizontal rectangular ducts, the techniques of Schlieren and high-speed video camera are used to study the flame behaviors of the premixed gases in a closed duct and opened one respectively, and the propagation characteristics in both cases and the formation mechanism of the tulip flame are analyzed. The results show that, the propagation flame in a closed duct is prior to form a tulip flame structure than that in an opened duct, and the tulip flame structure formation in a closed duct is related to the flame propagation velocity decrease. The sharp decrease of the flame propagation velocity is one of the reasons to the tulip flame formation, and the decrease of the flame propagation velocity is due to the decrease of the burned product flow velocity mainly.

40 CFR 86.1325-94 - Methane analyzer calibration.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 19 2010-07-01 2010-07-01 false Methane analyzer calibration. 86.1325... Procedures § 86.1325-94 Methane analyzer calibration. Prior to introduction into service and monthly thereafter, the methane analyzer shall be calibrated: (a) Follow the manufacturer's instructions for...

40 CFR 86.1325-94 - Methane analyzer calibration.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 20 2012-07-01 2012-07-01 false Methane analyzer calibration. 86.1325... Procedures § 86.1325-94 Methane analyzer calibration. Prior to introduction into service and monthly thereafter, the methane analyzer shall be calibrated: (a) Follow the manufacturer's instructions for...

40 CFR 86.1325-94 - Methane analyzer calibration.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 20 2013-07-01 2013-07-01 false Methane analyzer calibration. 86.1325... Procedures § 86.1325-94 Methane analyzer calibration. Prior to introduction into service and monthly thereafter, the methane analyzer shall be calibrated: (a) Follow the manufacturer's instructions for...

40 CFR 86.1325-94 - Methane analyzer calibration.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 19 2011-07-01 2011-07-01 false Methane analyzer calibration. 86.1325... Procedures § 86.1325-94 Methane analyzer calibration. Prior to introduction into service and monthly thereafter, the methane analyzer shall be calibrated: (a) Follow the manufacturer's instructions for...

Open Path and Solar Sourced Atmospheric Spectra are Analyzed Yielding Concentration Profiles and Temporal Variation Results

NASA Astrophysics Data System (ADS)

Hager, John; Steill, Jeff; Compton, Robert

2004-11-01

A high-resolution FTIR Bomem DA8 spectrometer has been installed at the University of Tennessee and has been successfully coupled with a suntracker and open path optics. Solar absorption spectra were recorded on 75 days in the last 18 months over a large spectral range. The high-resolution spectra provide information on the vertical concentration profiles of trace gases in the atmosphere. The HITRAN data base was used along with SFIT2 in order to retrieve concentration profiles of different trace gases. Many atmospheric constituents are open to this analysis. Tropospheric Ozone in the Knoxville area is rated as the worst in the nation by the American Lung Association. Sunlight, pollutants and hot weather cause ground-level ozone to form in harmful concentrations in the air. Seasonal and daily trends of ozone show correlation with other sources such as the EPA, and recent efforts to correlate solar spectra with open-path spectra will be discussed.

77 FR 40032 - Methane Hydrate Advisory Committee

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-06

... DEPARTMENT OF ENERGY Methane Hydrate Advisory Committee AGENCY: Office of Fossil Energy, Department of Energy. ACTION: Notice of open meeting. SUMMARY: This notice announces a meeting of the Methane... of the Methane Hydrate Advisory Committee is to provide advice on potential applications of methane...

40 CFR 86.125-94 - Methane analyzer calibration.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 18 2010-07-01 2010-07-01 false Methane analyzer calibration. 86.125... Complete Heavy-Duty Vehicles; Test Procedures § 86.125-94 Methane analyzer calibration. Prior to introduction into service and monthly thereafter, the methane analyzer shall be calibrated: (a) Follow the...

40 CFR 86.125-94 - Methane analyzer calibration.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 18 2011-07-01 2011-07-01 false Methane analyzer calibration. 86.125... Complete Heavy-Duty Vehicles; Test Procedures § 86.125-94 Methane analyzer calibration. Prior to introduction into service and monthly thereafter, the methane analyzer shall be calibrated: (a) Follow the...

Quantifying the relative contribution of natural gas fugitive emissions to total methane emissions in Colorado and Utah using mobile stable isotope (13CH4) analysis

NASA Astrophysics Data System (ADS)

Rella, Chris; Jacobson, Gloria; Crosson, Eric; Karion, Anna; Petron, Gabrielle; Sweeney, Colm

2013-04-01

Fugitive emissions of methane into the atmosphere are a major concern facing the natural gas production industry. Because methane is more energy-rich than coal per kg of CO2 emitted into the atmosphere, it represents an attractive alternative to coal for electricity generation. However, given that the global warming potential of methane is many times greater than that of carbon dioxide (Solomon et al. 2007), the importance of quantifying the fugitive emissions of methane throughout the natural gas production and distribution process becomes clear (Howarth et al. 2011). A key step in the process of assessing the emissions arising from natural gas production activities is partitioning the observed methane emissions between natural gas fugitive emissions and other sources of methane, such as from landfills or agricultural activities. One effective method for assessing the contribution of these different sources is stable isotope analysis. In particular, the 13CH4 signature of natural gas (-35 to -40 permil) is significantly different that the signature of other significant sources of methane, such as landfills or ruminants (-45 to -70 permil). In this paper we present measurements of mobile field 13CH4 using a spectroscopic stable isotope analyzer based on cavity ringdown spectroscopy, in two intense natural gas producing regions of the United States: the Denver-Julesburg basin in Colorado, and the Uintah basin in Utah. Mobile isotope measurements in the nocturnal boundary layer have been made, over a total path of 100s of km throughout the regions, allowing spatially resolved measurements of the regional isotope signature. Secondly, this analyzer was used to quantify the isotopic signature of those individual sources (natural gas fugitive emissions, concentrated animal feeding operations, and landfills) that constitute the majority of methane emissions in these regions, by making measurements of the isotope ratio directly in the downwind plume from each source. These data are combined to establish the fraction of the observed methane emissions that can be attributed to natural gas activities in the regions. The fraction of total methane emissions in the Denver-Julesburg basin that can be attributed to natural gas fugitive emissions has been determined to be 71 +/- 9%. References: 1. S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.). IPCC, 2007: Climate Change 2007: The Physical Science Basis of the Fourth Assessment Report. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 2. R.W. Howarth, R. Santoro, and A. Ingraffea. "Methane and the greenhouse-gas footprint of natural gas from shale formations." Climate Change, 106, 679 (2011).

Integration of Ground-Based Solar FT-IR Absorption Spectroscopy and Open-Path Systems for Atmospheric Analysis

NASA Astrophysics Data System (ADS)

Steill, J. D.; Hager, J. S.; Compton, R. N.

2005-12-01

Air quality issues in the Knoxville and East Tennessee region are of great concern, particularly as regards the nearby Great Smoky Mountains National Park. Integration of a Bomem DA8 FT-IR spectrometer with rooftop sun-tracking optics and an open-path system provides a unique opportunity to analyze the local atmospheric chemical composition. Many trace atmospheric constituents are open to this analysis, such as O3, CO, CH4, and N2O. Boundary layer concentrations as well as total column abundances and vertical concentration profiles are derived. Vertical concentration profiles are determined by fitting solar absorbance lines with the SFIT2 algorithm. Improved fitting of solar spectra has been demonstrated by incorporating the tropospheric concentrations as determined by open-path measurements. In addition to providing a means to improve the analysis of solar spectra, the open-path data is useful for elucidation of diurnal trends in the trace gas concentrations. Anthropogenic influences are of special interest, and seasonal and daily trends in amounts of tropospheric pollutants such as ozone correlate with other sources such as the EPA. Although obviously limited by weather considerations, the technique is suited to the regional climate and a body of data of more than two years extent is available for analysis.

Single-site trinuclear copper oxygen clusters in mordenite for selective conversion of methane to methanol.

PubMed

Grundner, Sebastian; Markovits, Monica A C; Li, Guanna; Tromp, Moniek; Pidko, Evgeny A; Hensen, Emiel J M; Jentys, Andreas; Sanchez-Sanchez, Maricruz; Lercher, Johannes A

2015-06-25

Copper-exchanged zeolites with mordenite structure mimic the nuclearity and reactivity of active sites in particulate methane monooxygenase, which are enzymes able to selectively oxidize methane to methanol. Here we show that the mordenite micropores provide a perfect confined environment for the highly selective stabilization of trinuclear copper-oxo clusters that exhibit a high reactivity towards activation of carbon-hydrogen bonds in methane and its subsequent transformation to methanol. The similarity with the enzymatic systems is also implied from the similarity of the reversible rearrangements of the trinuclear clusters occurring during the selective transformations of methane along the reaction path towards methanol, in both the enzyme system and copper-exchanged mordenite.

Impact of methane flow through deformable lake sediments on atmospheric release

NASA Astrophysics Data System (ADS)

Scandella, B.; Juanes, R.

2010-12-01

Methane is a potent greenhouse gas that is generated geothermally and biologically in lake and ocean sediments. Free gas bubbles may escape oxidative traps and contribute more to the atmospheric source than dissolved methane, but the details of the methane release depend on the interactions between the multiple fluid phases and the deformable porous medium. We present a model and supporting laboratory experiments of methane release through “breathing” dynamic flow conduits that open in response to drops in the hydrostatic load on lake sediments, which has been validated against a high-resolution record of free gas flux and hydrostatic pressure in Upper Mystic Lake, MA. In contrast to previous linear elastic fracture mechanics analysis of gassy sediments, the evolution of gas transport in a deformable compliant sediment is presented within the framework of multiphase poroplasticity. Experiments address how strongly the mode and rate of gas flow, captured by our model, impacts the size of bubbles released into the water column. A bubble's size in turn determines how efficiently it transports methane to the atmosphere, and integrating this effect will be critical to improving estimates of the atmospheric methane source from lakes. Cross-sectional schematic of lake sediments showing two venting sites: one open at left and one closed at right. The vertical release of gas bubbles (red) at the open venting site creates a local pressure drop, which drives both bubble formation from the methane-rich pore water (higher concentrations shaded darker red) and lateral advection of dissolved methane (purple arrows). Even as bubbles in the open site escape, those at the closed site remain trapped.

New measurements of the 6190-A band of methane

NASA Technical Reports Server (NTRS)

Mickelson, M. E.; Larson, L. E.; Schubert, A.

1991-01-01

The present paper reports new laboratory measurements that were made of the absorption coefficient of the visible methane band at 6190 A. Data were obtained using a tunable dye laser system operating with a line width of 0.067/cm. Spectra were recorded at approximately 1-A intervals with the beam coupled to a 22-m base length White-type absorption cell adjusted for an optical path of 1584 km and filled to a density of 0.884 amagats. Errors in pressure, temperature, and path length amounted to an uncertainty in the abundance of no more than 0.4 percent. Fourteen data sets were recorded and coadded. The final signal-averaged methane data were divided by a similar set of signal-averaged empty cell scans to remove the transmittance of the White cell and system optics. The results are compared with previous low-resolution measurements in the spectral region from 6000 to 6400 A.

Identifying Methane Sources in Groundwater; Quantifying Changes in Compositional and Stable Isotope Values during Multiphase Transport

NASA Astrophysics Data System (ADS)

Larson, T.; Sathaye, K.

2014-12-01

A dramatic expansion of hydraulic fracturing and horizontal drilling for natural gas in unconventional reserves is underway. This expansion is fueling considerable public concern, however, that extracted natural gas, reservoir brines and associated fracking fluids may infiltrate to and contaminate shallower (< 500m depth) groundwater reservoirs, thereby posing a health threat. Attributing methane found in shallow groundwater to either deep thermogenic 'fracking' operations or locally-derived shallow microbial sources utilizes geochemical methods including alkane wetness and stable carbon and hydrogen isotope ratios of short chain (C1-C5) hydrocarbons. Compared to shallow microbial gas, thermogenic gas is wetter and falls within a different range of δ13C and δD values. What is not clear, however, is how the transport of natural gas through water saturated geological media may affect its compositional and stable isotope values. What is needed is a means to differentiate potential flow paths of natural gas including 'fast paths' along preexisting fractures and drill casings vs. 'slow paths' through low permeability rocks. In this study we attempt quantify transport-related effects using experimental 1-dimensional two-phase column experiments and analytical solutions to multi-phase gas injection equations. Two-phase experimental results for an injection of natural gas into a water saturated column packed with crushed illite show that the natural gas becomes enriched in methane compared to ethane and propane during transport. Carbon isotope measurements are ongoing. Results from the multi-phase gas injection equations that include methane isotopologue solubility and diffusion effects predict the development of a 'bank' of methane depleted in 13C relative to 12C at the front of a plume of fugitive natural gas. These results, therefore, suggest that transport of natural gas through water saturated geological media may complicate attribution methods needed to distinguish thermogenic and microbial methane.

A Mobile Sensing Approach for Regional Surveillance of Fugitive Methane Emissions in Oil and Gas Production.

PubMed

Albertson, John D; Harvey, Tierney; Foderaro, Greg; Zhu, Pingping; Zhou, Xiaochi; Ferrari, Silvia; Amin, M Shahrooz; Modrak, Mark; Brantley, Halley; Thoma, Eben D

2016-03-01

This paper addresses the need for surveillance of fugitive methane emissions over broad geographical regions. Most existing techniques suffer from being either extensive (but qualitative) or quantitative (but intensive with poor scalability). A total of two novel advancements are made here. First, a recursive Bayesian method is presented for probabilistically characterizing fugitive point-sources from mobile sensor data. This approach is made possible by a new cross-plume integrated dispersion formulation that overcomes much of the need for time-averaging concentration data. The method is tested here against a limited data set of controlled methane release and shown to perform well. We then present an information-theoretic approach to plan the paths of the sensor-equipped vehicle, where the path is chosen so as to maximize expected reduction in integrated target source rate uncertainty in the region, subject to given starting and ending positions and prevailing meteorological conditions. The information-driven sensor path planning algorithm is tested and shown to provide robust results across a wide range of conditions. An overall system concept is presented for optionally piggybacking of these techniques onto normal industry maintenance operations using sensor-equipped work trucks.

Evaluating the performance of commonly used gas analysers for methane eddy covariance flux measurements: the InGOS inter-comparison field experiment

NASA Astrophysics Data System (ADS)

Peltola, O.; Hensen, A.; Helfter, C.; Belelli Marchesini, L.; Bosveld, F. C.; van den Bulk, W. C. M.; Elbers, J. A.; Haapanala, S.; Holst, J.; Laurila, T.; Lindroth, A.; Nemitz, E.; Röckmann, T.; Vermeulen, A. T.; Mammarella, I.

2014-01-01

The performance of eight fast-response methane (CH4) gas analysers suitable for eddy covariance flux measurements were tested at a grassland site near the Cabauw tall tower (Netherlands) during June 2012. The instruments were positioned close to each other in order to minimize the effect of varying turbulent conditions. The moderate CH4 fluxes observed at the location, of the order of 25 nmol m-2 s-1, provided a suitable signal for testing the instruments' performance. Generally, all analysers tested were able to quantify the concentration fluctuations at the frequency range relevant for turbulent exchange and were able to deliver high-quality data. The tested cavity ring-down spectrometer (CRDS) instruments from Picarro, models G2311-f and G1301-f, were superior to other CH4 analysers with respect to instrumental noise. As an open-path instrument susceptible to the effects of rain, the LI-COR LI-7700 achieved lower data coverage and also required larger density corrections; however, the system is especially useful for remote sites that are restricted in power availability. In this study the open-path LI-7700 results were compromised due to a data acquisition problem in our data-logging setup. Some of the older closed-path analysers tested do not measure H2O vapour concentrations alongside CH4 (i.e. FMA1 and DLT-100 by Los Gatos Research) and this complicates data processing since the required corrections for dilution and spectroscopic interactions have to be based on external information. To overcome this issue, we used H2O mole fractions measured by other gas analysers, adjusted them with different methods and then applied them to correct the CH4 fluxes. Following this procedure we estimated a bias on the order of 0.1 g (CH4) m-2 (8% of the measured mean flux) in the processed and corrected CH4 fluxes on a monthly scale due to missing H2O concentration measurements. Finally, cumulative CH4 fluxes over 14 days from three closed-path gas analysers, G2311-f (Picarro Inc.), FGGA (Los Gatos Research) and FMA2 (Los Gatos Research), which were measuring H2O vapour concentrations in addition to CH4, agreed within 3% (355-367 mg (CH4) m-2) and were not clearly different from each other, whereas the other instruments derived total fluxes which showed small but distinct differences (±10%, 330-399 mg (CH4) m-2).

Evaluating the performance of commonly used gas analysers for methane eddy covariance flux measurements: the InGOS inter-comparison field experiment

NASA Astrophysics Data System (ADS)

Peltola, O.; Hensen, A.; Helfter, C.; Belelli Marchesini, L.; Bosveld, F. C.; van den Bulk, W. C. M.; Elbers, J. A.; Haapanala, S.; Holst, J.; Laurila, T.; Lindroth, A.; Nemitz, E.; Röckmann, T.; Vermeulen, A. T.; Mammarella, I.

2014-06-01

The performance of eight fast-response methane (CH4) gas analysers suitable for eddy covariance flux measurements were tested at a grassland site near the Cabauw tall tower (Netherlands) during June 2012. The instruments were positioned close to each other in order to minimise the effect of varying turbulent conditions. The moderate CH4 fluxes observed at the location, of the order of 25 nmol m-2 s-1, provided a suitable signal for testing the instruments' performance. Generally, all analysers tested were able to quantify the concentration fluctuations at the frequency range relevant for turbulent exchange and were able to deliver high-quality data. The tested cavity ringdown spectrometer (CRDS) instruments from Picarro, models G2311-f and G1301-f, were superior to other CH4 analysers with respect to instrumental noise. As an open-path instrument susceptible to the effects of rain, the LI-COR LI-7700 achieved lower data coverage and also required larger density corrections; however, the system is especially useful for remote sites that are restricted in power availability. In this study the open-path LI-7700 results were compromised due to a data acquisition problem in our data-logging setup. Some of the older closed-path analysers tested do not measure H2O concentrations alongside CH4 (i.e. FMA1 and DLT-100 by Los Gatos Research) and this complicates data processing since the required corrections for dilution and spectroscopic interactions have to be based on external information. To overcome this issue, we used H2O mole fractions measured by other gas analysers, adjusted them with different methods and then applied them to correct the CH4 fluxes. Following this procedure we estimated a bias of the order of 0.1 g (CH4) m-2 (8% of the measured mean flux) in the processed and corrected CH4 fluxes on a monthly scale due to missing H2O concentration measurements. Finally, cumulative CH4 fluxes over 14 days from three closed-path gas analysers, G2311-f (Picarro Inc.), FGGA (Los Gatos Research) and FMA2 (Los Gatos Research), which were measuring H2O concentrations in addition to CH4, agreed within 3% (355-367 mg (CH4) m-2) and were not clearly different from each other, whereas the other instruments derived total fluxes which showed small but distinct differences (±10%, 330-399 mg (CH4) m-2).

Bubble Shuttle: A newly discovered transport mechanism, which transfers microorganisms from the sediment into the water column

NASA Astrophysics Data System (ADS)

Schmale, O.; Stolle, C.; Leifer, I.; Schneider von Deimling, J.; Kiesslich, K.; Krause, S.; Frahm, A.; Treude, T.

2013-12-01

The diversity and abundance of methanotrophic microorganisms is well studied in the aquatic environment, indicating their importance in biogeochemical cycling of methane in the sediment and the water column. However, whether methanotrophs are distinct populations in these habitats or are exchanged between benthic and pelagic environments, remains an open question. Therefore, field studies were conducted at the 'Rostocker Seep' site (Coal Oil Point seep area, California, USA) to test our hypothesis that methane-oxidizing microorganisms can be transported by gas bubbles from the sediment into the water column. The natural methane emanating location 'Rostocker Seep' showed a strong surface water oversaturation in methane with respect to the atmospheric equilibrium. Catalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) analyzes were performed to determine the abundance of aerobic and anaerobic methanotrophic microorganisms. Aerobic methane oxidizing bacteria were detected in the sediment and the water column, whereas anaerobic methanotrophs were detected exclusively in the sediment. The key device of the project was the newly developed "Bubble Catcher" used to collect naturally emanating gas bubbles at the sea floor together with particles attached to the bubble surface rim. Bubble Catcher experiments were carried out directly above a natural bubble release spot and on a reference site at which artificially released gas bubbles were caught, which had no contact with the sediment. CARD-FISH analyzes showed that aerobic methane oxidizing bacteria were transported by gas bubbles from the sediment into the water column. In contrast anaerobic methanotrophs were not detected in the bubble catcher. Further results indicate that this newly discovered Bubble Shuttle transport mechanism might influence the distribution pattern of methanotrophic microorganisms in the water column and even at the air-sea interface. Methane seep areas are often characterized by an elevated abundance of methane-oxidizing microorganisms, which consume a considerable amount of methane before it escapes into the atmosphere. Based on our study we hypothesize that the Bubble Shuttle transport mechanism contributes to this pelagic methane sink by a sediment-water column transfer of methane oxidizing microorganisms. Furthermore, this Bubble Shuttle may influence the methanotrophic community in the water column after massive short-term submarine inputs of methane (e.g. release of methane from bore holes). Especially in deep-sea regions, where the abundance of methane oxidizing microorganisms in the water column is low in general, Bubble Shuttle may inject a relevant amount of methane oxidizing microorganisms into the water column during massive inputs, supporting indirectly the turnover of this greenhouse active trace gas in the submarine environment.

Measurement of the Temperature Dependence of Line Mixing and Pressure Broadening Parameters between 296 and 90 K in the v3 band of 12CH4 and their Influence on Atmospheric Methane Retrievals

NASA Technical Reports Server (NTRS)

Mondelain, Didier; Payan, Sebastien; Deng, Wenping; Camy-Peyret, Claude; Hurtmans, Daniel; Mantz, Arlan W.

2007-01-01

We measured the temperature dependence of the nitrogen broadening, narrowing and line-mixing coefficients of four lines of the P9 manifold in the v3 band of 12CH4 for atmospheric purposes. The data were collected using our tunable diode laser (TDL) spectrometer with active wavenumber control coupled to a newly developed cold Herriott cell with a path length of 5.37 m and a temperature uniformity of better than 0.01 K along the cell. We recorded and analyzed spectra recorded at sample temperature between 90 K and room temperature. We have investigate the influence of our new results in the inversion model used to retrieve methane profiles from atmospheric spectra; our new results make it possible to retrieve significantly more precise methane profiles. The atmospheric spectra we utilized were obtained by several of us with a balloon-born Fourier Transform infrared experiment in a limb configuration. Differences up to 7% on the retrieved volume mixing ratio were found compared to an inversion model using only HITRAN04 spectroscopic parameters.

Clumped isotope effects during OH and Cl oxidation of methane

NASA Astrophysics Data System (ADS)

Whitehill, Andrew R.; Joelsson, Lars Magnus T.; Schmidt, Johan A.; Wang, David T.; Johnson, Matthew S.; Ono, Shuhei

2017-01-01

A series of experiments were carried out to determine the clumped (13CH3D) methane kinetic isotope effects during oxidation of methane by OH and Cl radicals, the major sink reactions for atmospheric methane. Experiments were performed in a 100 L quartz photochemical reactor, in which OH was produced from the reaction of O(1D) (from O3 photolysis) with H2O, and Cl was from photolysis of Cl2. Samples were taken from the reaction cell and analyzed for methane (12CH4, 12CH3D, 13CH4, 13CH3D) isotopologue ratios using tunable infrared laser direct absorption spectroscopy. Measured kinetic isotope effects for singly substituted species were consistent with previous experimental studies. For doubly substituted methane, 13CH3D, the observed kinetic isotope effects closely follow the product of the kinetic isotope effects for the 13C and deuterium substituted species (i.e., 13,2KIE = 13KIE × 2KIE). The deviation from this relationship is 0.3‰ ± 1.2‰ and 3.5‰ ± 0.7‰ for OH and Cl oxidation, respectively. This is consistent with model calculations performed using quantum chemistry and transition state theory. The OH and Cl reactions enrich the residual methane in the clumped isotopologue in open system reactions. In a closed system, however, this effect is overtaken by the large D/H isotope effect, which causes the residual methane to become anti-clumped relative to the initial methane. Based on these results, we demonstrate that oxidation of methane by OH, the predominant oxidant for tropospheric methane, will only have a minor (∼0.3‰) impact on the clumped isotope signature (Δ13CH3D, measured as a deviation from a stochastic distribution of isotopes) of tropospheric methane. This paper shows that Δ13CH3D will provide constraints on methane source strengths, and predicts that Δ12CH2D2 can provide information on methane sink strengths.

30 CFR 57.22309 - Methane monitors (V-A mines).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Methane monitors (V-A mines). 57.22309 Section... Standards for Methane in Metal and Nonmetal Mines Equipment § 57.22309 Methane monitors (V-A mines). (a) Methane monitors shall be installed on continuous mining machines used in or beyond the last open crosscut...

30 CFR 57.22309 - Methane monitors (V-A mines).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Methane monitors (V-A mines). 57.22309 Section... Standards for Methane in Metal and Nonmetal Mines Equipment § 57.22309 Methane monitors (V-A mines). (a) Methane monitors shall be installed on continuous mining machines used in or beyond the last open crosscut...

Single-site trinuclear copper oxygen clusters in mordenite for selective conversion of methane to methanol

DOE PAGES

Grundner, Sebastian; Markovits, Monica A. C.; Li, Guanna; ...

2015-06-25

Copper-exchanged zeolites with mordenite structure mimic the nuclearity and reactivity of active sites in particulate methane monooxygenase, which are enzymes able to selectively oxidize methane to methanol. Here we show that the mordenite micropores provide a perfect confined environment for the highly selective stabilization of trinuclear copper-oxo clusters that exhibit a high reactivity towards activation of carbon–hydrogen bonds in methane and its subsequent transformation to methanol. In conclusion, the similarity with the enzymatic systems is also implied from the similarity of the reversible rearrangements of the trinuclear clusters occurring during the selective transformations of methane along the reaction path towardsmore » methanol, in both the enzyme system and copper-exchanged mordenite.« less

Single-site trinuclear copper oxygen clusters in mordenite for selective conversion of methane to methanol

PubMed Central

Grundner, Sebastian; Markovits, Monica A.C.; Li, Guanna; Tromp, Moniek; Pidko, Evgeny A.; Hensen, Emiel J.M.; Jentys, Andreas; Sanchez-Sanchez, Maricruz; Lercher, Johannes A.

2015-01-01

Copper-exchanged zeolites with mordenite structure mimic the nuclearity and reactivity of active sites in particulate methane monooxygenase, which are enzymes able to selectively oxidize methane to methanol. Here we show that the mordenite micropores provide a perfect confined environment for the highly selective stabilization of trinuclear copper-oxo clusters that exhibit a high reactivity towards activation of carbon–hydrogen bonds in methane and its subsequent transformation to methanol. The similarity with the enzymatic systems is also implied from the similarity of the reversible rearrangements of the trinuclear clusters occurring during the selective transformations of methane along the reaction path towards methanol, in both the enzyme system and copper-exchanged mordenite. PMID:26109507

Methane emissions from an alpine wetland on the Tibetan Plateau: Neglected but vital contribution of the nongrowing season

NASA Astrophysics Data System (ADS)

Song, Weimin; Wang, Hao; Wang, Guangshuai; Chen, Litong; Jin, Zhenong; Zhuang, Qianlai; He, Jin-Sheng

2015-08-01

The vast wetlands on the Tibetan Plateau are expected to be an important natural source of methane (CH4) to the atmosphere. The magnitude, patterns and environmental controls of CH4 emissions on different timescales, especially during the nongrowing season, remain poorly understood, because of technical limitations and the harsh environments. We conducted the first study on year-round CH4 fluxes in an alpine wetland using the newly developed LI-COR LI-7700 open-path gas analyzer. We found that the total annual CH4 emissions were 26.4 and 33.8 g CH4 m-2 in 2012 and 2013, respectively, and the nongrowing season CH4 emissions accounted for 43.2-46.1% of the annual emissions, highlighting an indispensable contribution that was often overlooked by previous studies. A two-peak seasonal variation in CH4 fluxes was observed, with a small peak in the spring thawing period and a large one in the peak growing season. We detected a significant difference in the diurnal variation of CH4 fluxes between the two seasons, with two peaks in the growing season and one peak in the nongrowing season. We found that the CH4 fluxes during the growing season were well correlated with soil temperature, water table depth and gross primary production, whereas the CH4 fluxes during the nongrowing season were highly correlated with soil temperature. Our results suggested that the CH4 emission during the nongrowing season cannot be ignored and the vast wetlands on the Tibetan plateau will have the potential to exert a positive feedback on climate considering the increasing warming, particularly in the nongrowing season in this region.

76 FR 59667 - Methane Hydrate Advisory Committee

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-27

... DEPARTMENT OF ENERGY Methane Hydrate Advisory Committee AGENCY: Office of Fossil Energy, Department of Energy. ACTION: Notice of Open Meeting. SUMMARY: This notice announces a meeting of the Methane...-5600. SUPPLEMENTARY INFORMATION: Purpose of the Committee: The purpose of the Methane Hydrate Advisory...

78 FR 37536 - Methane Hydrate Advisory Committee

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-21

... DEPARTMENT OF ENERGY Methane Hydrate Advisory Committee AGENCY: Office of Fossil Energy, Department of Energy. ACTION: Notice of open meeting. SUMMARY: This notice announces a meeting of the Methane... Committee: The purpose of the Methane Hydrate Advisory Committee is to provide advice on potential...

78 FR 26337 - Methane Hydrate Advisory Committee

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-06

... DEPARTMENT OF ENERGY Methane Hydrate Advisory Committee AGENCY: Office of Fossil Energy, Department of Energy. ACTION: Notice of Open Meeting. SUMMARY: This notice announces a meeting of the Methane.... SUPPLEMENTARY INFORMATION: Purpose of the Committee: The purpose of the Methane Hydrate Advisory Committee is to...

75 FR 9886 - Methane Hydrate Advisory Committee

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-04

... DEPARTMENT OF ENERGY Methane Hydrate Advisory Committee AGENCY: Department of Energy, Office of Fossil Energy. ACTION: Notice of open meeting. SUMMARY: This notice announces a meeting of the Methane... the Committee: The purpose of the Methane Hydrate Advisory Committee is to provide advice on potential...

Performance evaluation of a 1.6-µm methane DIAL system from ground, aircraft and UAV platforms.

PubMed

Refaat, Tamer F; Ismail, Syed; Nehrir, Amin R; Hair, John W; Crawford, James H; Leifer, Ira; Shuman, Timothy

2013-12-16

Methane is an efficient absorber of infrared radiation and a potent greenhouse gas with a warming potential 72 times greater than carbon dioxide on a per molecule basis. Development of methane active remote sensing capability using the differential absorption lidar (DIAL) technique enables scientific assessments of the gas emission and impacts on the climate. A performance evaluation of a pulsed DIAL system for monitoring atmospheric methane is presented. This system leverages a robust injection-seeded pulsed Nd:YAG pumped Optical Parametric Oscillator (OPO) laser technology operating in the 1.645 µm spectral band. The system also leverages an efficient low noise, commercially available, InGaAs avalanche photo-detector (APD). Lidar signals and error budget are analyzed for system operation on ground in the range-resolved DIAL mode and from airborne platforms in the integrated path DIAL (IPDA) mode. Results indicate system capability of measuring methane concentration profiles with <1.0% total error up to 4.5 km range with 5 minute averaging from ground. For airborne IPDA, the total error in the column dry mixing ratio is less than 0.3% with 0.1 sec average using ground returns. This system has a unique capability of combining signals from the atmospheric scattering from layers above the surface with ground return signals, which provides methane column measurement between the atmospheric scattering layer and the ground directly. In such case 0.5% and 1.2% total errors are achieved with 10 sec average from airborne platforms at 8 km and 15.24 km altitudes, respectively. Due to the pulsed nature of the transmitter, the system is relatively insensitive to aerosol and cloud interferences. Such DIAL system would be ideal for investigating high latitude methane releases over polar ice sheets, permafrost regions, wetlands, and over ocean during day and night. This system would have commercial potential for fossil fuel leaks detection and industrial monitoring applications.

Wide area methane emissions mapping with airborne IPDA lidar

NASA Astrophysics Data System (ADS)

Bartholomew, Jarett; Lyman, Philip; Weimer, Carl; Tandy, William

2017-08-01

Methane emissions from natural gas production, storage, and transportation are potential sources of greenhouse gas emissions. Methane leaks also constitute revenue loss potential from operations. Since 2013, Ball Aerospace has been developing advanced airborne sensors using integrated path differential absorption (IPDA) LIDAR instrumentation to identify methane, propane, and longer-chain alkanes in the lowest region of the atmosphere. Additional funding has come from the U.S. Department of Transportation, Pipeline and Hazardous Materials Administration (PHMSA) to upgrade instrumentation to a broader swath coverage of up to 400 meters while maintaining high spatial sampling resolution and geolocation accuracy. Wide area coverage allows efficient mapping of emissions from gathering and distribution networks, processing facilities, landfills, natural seeps, and other distributed methane sources. This paper summarizes the benefits of advanced instrumentation for aerial methane emission mapping, describes the operating characteristics and design of this upgraded IPDA instrumentation, and reviews technical challenges encountered during development and deployment.

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

PubMed

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

2014-06-01

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

Methane and nitrous oxide analyzer comparison and emissions from dairy freestall barns with manure flushing and scraping

NASA Astrophysics Data System (ADS)

Cortus, Erin L.; Jacobson, Larry D.; Hetchler, Brian P.; Heber, Albert J.; Bogan, Bill W.

2015-01-01

Continuous methane (CH4) and nitrous oxide (N2O) emission measurements were conducted at two crossflow-ventilated dairy freestall barns located in the state of Wisconsin, USA during a 19-month period from 2008 to 2010. The two cross-flow mechanically ventilated buildings (275 and 375 cow capacities) were evaluated in the National Air Emissions Monitoring Study. In September of 2008, the barns' manure collection systems were changed from flushing open gutter using manure basin effluent to a tractor scrape. A photoacoustic multi-gas analyzer (PAMGA) and a direct methane/non-methane hydrocarbon analyzer (GC-FID) provided side-by-side measurements of methane (CH4) for 13 months. The PAMGA also measured nitrous oxide (N2O), and a side-by-side comparison was performed with a gas-filter correlation analyzer (GFC) for six months. Barn ventilation rates were measured by recording run times of the 127-cm diameter exhaust fans. All 125 belt-driven exhaust fans were identical, and in situ airflow measurements using the Fan Assessment Numeration System (FANS) were conducted once at the beginning and twice during the test. Daily CH4 and N2O emission rates were calculated over approximately 19 and 6 month periods respectively, on per barn, head, animal unit, floor area space and barn capacity bases. The differences between the analyzers' concentration measurements were compared in conjunction with water vapor and other gases. The analyzer type had a significant impact on the average CH4 emission rate (p < 0.001) and the average N2O emission rate (p < 0.05). Based on the CH4 measurements with the GC-FID, average daily mean CH4 emissions were approximately 290 g AU-1 d-1 (390 g cow-1 d-1) with very limited seasonal effects. Little variation was observed in CH4 emission rates before and after the change in manure collection method, suggesting that most of the CH4 emissions were enteric losses directly from the cows. The average daily mean N2O emission rates based on the GFC were very low, with an approximate rate of only 690 mg AU-1 d-1 (970 mg cow-1 d-1). The change in manure collection had no apparent effect on N2O emission.

Methane seeps along boundaries of arctic permafrost thaw and melting glaciers

NASA Astrophysics Data System (ADS)

Anthony, P.; Walter Anthony, K. M.; Grosse, G.; Chanton, J.

2014-12-01

Methane, a potent greenhouse gas, accumulates in subsurface hydrocarbon reservoirs. In the Arctic, impermeable icy permafrost and glacial overburden form a 'cryosphere cap' that traps gas leaking from these reservoirs, restricting flow to the atmosphere. We document the release of geologic methane to the atmosphere from abundant gas seeps concentrated along boundaries of permafrost thaw and receding glaciers in Alaska. Through aerial and ground surveys we mapped >150,000 seeps identified as bubbling-induced open holes in lake ice. Subcap methane seeps had anomalously high fluxes, 14C-depletion, and stable isotope values matching known coalbed and thermogenic methane accumulations in Alaska. Additionally, we observed younger subcap methane seeps in Greenland that were associated with ice-sheet retreat since the Little Ice Age. These correlations suggest that in a warming climate, continued disintegration of permafrost, glaciers, and parts of the polar ice sheets will relax pressure on subsurface seals and further open conduits, allowing a transient expulsion of geologic methane currently trapped by the cryosphere cap.

Line intensities of methane in the 2700-2862-kayser region

NASA Technical Reports Server (NTRS)

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

1978-01-01

Individual strengths and wave numbers of 2080 methane absorption lines have been measured between 2700 and 2862 kaysers at an average resolution of 0.023 kayser using a grating spectrometer. The results include all lines with strengths greater than 0.00003 per sq cm/atm observable at 296 K with a maximum path of 32 m and a pressure of 4 torr.

Understanding and applying open-path optical sensing data

NASA Astrophysics Data System (ADS)

Virag, Peter; Kricks, Robert J.

1999-02-01

During the last 10 years, open-path air monitors have evolved to yield reliable and effective measurements of single and multiple compounds on a real-time basis. To many individuals within the optical remote sensing community, the attributes of open-path and its the potential uses seem unlimited. Then why has the market has been stagnant for the last few years? The reason may center on how open-path information is applied and how well the end user understands that information. We constantly try to compare open-path data to risk/health or safety levels that are based for use at a single point and for a specific averaging period often far longer than a typical open-path data point. Often this approach is perceived as putting a square peg in a round hole. This perception may be well founded, as open-path data at times may need to go through extensive data manipulation and assumptions before it can be applied. This paper will review pervious open-path monitoring programs and their success in applying the data collected. We will also look at how open-path data is being currently used, some previous pitfalls in data use, alternate methods of data interpretation, and how open-path data can be best practically applied to fit current needs.

Mars Methane Analogue Mission (M3): Analytical Techniques and Operations

NASA Astrophysics Data System (ADS)

Cloutis, E.; Vrionis, H.; Qadi, A.; Bell, J. F.; Berard, G.; Boivin, A.; Ellery, A.; Jamroz, W.; Kruzelecky, R.; Mann, P.; Samson, C.; Stromberg, J.; Strong, K.; Tremblay, A.; Whyte, L.; Wing, B.

2011-03-01

The Mars Methane Analogue Mission (M3) project is designed to simulate a rover-based search for, and analysis of, methane sources on Mars at a serpentinite open pit mine in Quebec, using a variety of instruments.

[A trace methane gas sensor using mid-infrared quantum cascaded laser at 7.5 microm].

PubMed

Chen, Chen; Dang, Jing-Min; Huang, Jian-Qiang; Yang, Yue; Wang, Yi-Ding

2012-11-01

Presented is a compact instrument developed for in situ high-stable and sensitive continuous measurement of trace gases in air, with results shown for ambient methane (CH4) concentration accurate, real-time and in-situ. This instrument takes advantage of recent technology in thermoelectrically cooling (TEC) pulsed Fabry-Perot (FP) quantum cascaded laser (QCL) driving in a pulse mode operating at 7.5 microm ambient temperature to cover a fundamental spectral absorption band near v4 of CH4. A high quality Liquid Nitrogen (LN) cooled Mercury Cadmium Telluride (HgCdTe) mid-infrared (MIR) detector is used along with a total reflection coated gold ellipsoid mirror offering 20 cm single pass optical absorption in an open-path cell to achieve stability of 5.2 x 10(-3) under experimental condition of 200 micromol x mol(-1) measured ambient CH4. The instrument integrated software via time discriminating electronics technology to control QCL provides continuous quantitative trace gas measurements without calibration. The results show that the instrument can be applied to field measurements of gases of environmental concern. Additional, operator could substitute a QCL operating at a different wavelength to measure other gases.

Localization and Quantification of Trace-gas Fugitive Emissions Using a Portable Optical Spectrometer

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

Zhang, Eric; Teng, Chu; van Kessel, Theodore

We present a portable optical spectrometer for fugitive emissions monitoring of methane (CH4). The sensor operation is based on tunable diode laser absorption spectroscopy (TDLAS), using a 5 cm open path design, and targets the 2ν3 R(4) CH4 transition at 6057.1 cm-1 (1651 nm) to avoid cross-talk with common interfering atmospheric constituents. Sensitivity analysis indicates a normalized precision of 2.0 ppmv∙Hz-1/2, corresponding to a noise-equivalent absorption (NEA) of 4.4×10-6 Hz-1/2 and minimum detectible absorption (MDA) coefficient of αmin = 8.8×10-7 cm-1∙Hz-1/2. Our TDLAS sensor is deployed at the Methane Emissions Technology Evaluation Center (METEC) at Colorado State University (CSU) formore » initial demonstration of single-sensor based source localization and quantification of CH4 fugitive emissions. The TDLAS sensor is concurrently deployed with a customized chemi-resistive metal-oxide (MOX) sensor for accuracy benchmarking, demonstrating good visual correlation of the concentration time-series. Initial angle-of-arrival (AOA) results will be shown, and development towards source magnitude estimation will be described.« less

Retrievals of atmospheric columnar carbon dioxide and methane from GOSAT observations with photon path-length probability density function (PPDF) method

NASA Astrophysics Data System (ADS)

Bril, A.; Oshchepkov, S.; Yokota, T.; Yoshida, Y.; Morino, I.; Uchino, O.; Belikov, D. A.; Maksyutov, S. S.

2014-12-01

We retrieved the column-averaged dry air mole fraction of atmospheric carbon dioxide (XCO2) and methane (XCH4) from the radiance spectra measured by Greenhouse gases Observing SATellite (GOSAT) for 48 months of the satellite operation from June 2009. Recent version of the Photon path-length Probability Density Function (PPDF)-based algorithm was used to estimate XCO2 and optical path modifications in terms of PPDF parameters. We also present results of numerical simulations for over-land observations and "sharp edge" tests for sun-glint mode to discuss the algorithm accuracy under conditions of strong optical path modification. For the methane abundance retrieved from 1.67-µm-absorption band we applied optical path correction based on PPDF parameters from 1.6-µm carbon dioxide (CO2) absorption band. Similarly to CO2-proxy technique, this correction assumes identical light path modifications in 1.67-µm and 1.6-µm bands. However, proxy approach needs pre-defined XCO2 values to compute XCH4, whilst the PPDF-based approach does not use prior assumptions on CO2 concentrations.Post-processing data correction for XCO2 and XCH4 over land observations was performed using regression matrix based on multivariate analysis of variance (MANOVA). The MANOVA statistics was applied to the GOSAT retrievals using reference collocated measurements of Total Carbon Column Observing Network (TCCON). The regression matrix was constructed using the parameters that were found to correlate with GOSAT-TCCON discrepancies: PPDF parameters α and ρ, that are mainly responsible for shortening and lengthening of the optical path due to atmospheric light scattering; solar and satellite zenith angles; surface pressure; surface albedo in three GOSAT short wave infrared (SWIR) bands. Application of the post-correction generally improves statistical characteristics of the GOSAT-TCCON correlation diagrams for individual stations as well as for aggregated data.In addition to the analysis of the observations over 12 TCCON stations we estimated temporal and spatial trends (interannual XCO2 and XCH4 variations, seasonal cycles, latitudinal gradients) and compared them with modeled results as well as with similar estimates from other GOSAT retrievals.

Batch anaerobic digestion of synthetic military base food waste and cardboard mixtures.

PubMed

Asato, Caitlin M; Gonzalez-Estrella, Jorge; Jerke, Amber C; Bang, Sookie S; Stone, James J; Gilcrease, Patrick C

2016-09-01

Austere US military bases typically dispose of solid wastes, including large fractions of food waste (FW) and corrugated cardboard (CCB), by open dumping, landfilling, or burning. Anaerobic digestion (AD) offers an opportunity to reduce pollution and recover useful energy. This study aimed to evaluate the rates and yields of AD for FW-CCB mixtures. Batch AD was analyzed at substrate concentrations of 1-50g total chemical oxygen demand (COD)L(-1) using response surface methodology. At low concentrations, higher proportions of FW were correlated with faster specific methanogenic activities and greater final methane yields; however, concentrations of FW ⩾18.75gCODL(-1) caused inhibition. Digestion of mixtures with ⩾75% CCB occurred slowly but achieved methane yields >70%. Greater shifts in microbial communities were observed at higher substrate concentrations. Statistical models of methane yield and specific methanogenic activity indicated that FW and CCB exhibited no considerable interactions as substrates for AD. Copyright © 2016 Elsevier Ltd. All rights reserved.

A laser application to nuclear astrophysics

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

Barbui, M.; Hagel, K.; Schmidt, K.

2014-05-09

In the last decade, the availability in high-intensity laser beams capable of producing plasmas with ion energies large enough to induce nuclear reactions has opened new research paths in nuclear physics. We studied the reactions {sup 3}He(d,p){sup 4}He and d(d,n){sup 3}He at temperatures of few keV in a plasma, generated by the interaction of intense ultrafast laser pulses with molecular deuterium or deuterated-methane clusters mixed with {sup 3}He atoms. The yield of 14.7 MeV protons from the {sup 3}He(d,p){sup 4}He reaction was used to extract the astrophysical S factor. Results of the experiment performed at the Center for High Energymore » Density Science at The University of Texas at Austin will be presented.« less

A Reactive-Transport Model Describing Methanogen Growth and Methane Production in Diffuse Flow Vents at Axial Seamount

NASA Astrophysics Data System (ADS)

Algar, C. K.

2015-12-01

Hydrogenotrophic methanogenesis is an important mode of metabolism in deep-sea hydrothermal vents. Diffuse vent fluids often show a depletion in hydrogen with a corresponding increase in methane relative to pure-mixing of end member fluid and seawater, and genomic surveys show an enrichment in genetic sequences associated with known methanogens. However, because we cannot directly sample the subseafloor habitat where these organisms are living, constraining the size and activity of these populations remains a challenge and limits our ability to quantify the role they play in vent biogeochemistry. Reactive-transport modeling may provide a useful tool for approaching this problem. Here we present a reactive-transport model describing methane production along the flow-path of hydrothermal fluid from its high temperature end-member to diffuse venting at the seafloor. The model is set up to reflect conditions at several diffuse vents in the Axial Seamount. The model describes the growth of the two dominant thermophilic methanogens, Methanothermococcus and Methanocaldococcus, observed at Axial seamount. Monod and Arrhenius constants for Methanothermococcus thermolithotrophicus and Methanocaldococcus jannaschii were obtained for the model using chemostat and bottle experiments at varying temperatures. The model is used to investigate the influence of different mixing regimes on the subseafloor populations of these methanogens. By varying the model flow path length and subseafloor cell concentrations, and fitting to observed hydrogen and methane concentrations in the venting fluid, the subseafloor biomass, fluid residence time, and methane production rate can be constrained.

Methane seeps along boundaries of receding glaciers in Alaska and Greenland

NASA Astrophysics Data System (ADS)

Walter Anthony, K. M.; Anthony, P. M.; Grosse, G.; Chanton, J.

2012-12-01

Glaciers, ice sheets, and permafrost form a 'cryosphere cap' that traps methane formed in the subsurface, restricting its flow to the Earth's surface and atmosphere. Despite model predictions that glacier melt and degradation of permafrost open conduits for methane's escape, there has been a paucity of field evidence for 'subcap' methane seepage to the atmosphere as a direct result of cryosphere disintegration in the terrestrial Arctic. Here, we document for the first time the release of sub-cryosphere methane to lakes, rivers, shallow marine fjords and the atmosphere from abundant gas seeps concentrated along boundaries of receding glaciers and permafrost thaw in Alaska and Greenland. Through aerial and ground surveys of 6,700 lakes and fjords in Alaska we mapped >150,000 gas seeps identified as bubbling-induced open holes in seasonal ice. Using gas flow rates, stable isotopes, and radiocarbon dating, we distinguished recent ecological methane from subcap, geologic methane. Subcap seeps had anomalously high bubbling rates, 14C-depletion, and stable isotope values matching microbial sources associated with sedimentary deposits and coal beds as well as thermogenic methane accumulations in Alaska. Since differential ice loading can overpressurize fluid reservoirs and cause sediment fracturing beneath ice sheets, and since the loss of glacial ice reduces normal stress on ground, opens joints, and activates faults and fissures, thereby increasing permeability of the crust to fluid flow, we hypothesized that in the previously glaciated region of Southcentral Alaska, where glacial wastage continues presently, subcap seeps should be disproportionately associated with neotectonic faults. Geospatial analysis confirmed that subcap seep sites were associated with faults within a 7 km belt from the modern glacial extent. The majority of seeps were located in areas affected by seismicity from isostatic rebound associated with deglaciation following the Little Ice Age (LIA; ca. 1650-1850 C.E.). Across Alaska, we found a relationship between methane stable isotopes, radiocarbon age, and distance to faults. Faults appear to allow the escape of deeper, more 14C-depleted methane to the atmosphere, whereas seeps away from faults entrained 14C-enriched methane formed in shallower sediments from microbial decomposition of younger organic matter. Additionally, we observed younger subcap methane seeps in lakes of Greenland's Sondrestrom Fjord that were associated with ice-sheet retreat since the LIA. These correlations suggest that in a warming climate, continued disintegration of glaciers, permafrost, and parts of the polar ice sheets will weaken subsurface seals and further open conduits, allowing a transient expulsion of methane currently trapped by the cryosphere cap.

ESTIMATE OF GLOBAL METHANE EMISSIONS FROM LANDFILLS AND OPEN DUMPS

EPA Science Inventory

The report presents an empirical model to estimate global methane (CH4) emissions from landfills and open dumps based on EPA data from landfill gas (LFG) recovery projects. The EPA CH4 estimates for 1990 range between 19 and 40 teragrams (10 to the 12th power) per year (Tg/yr), w...

Remote detection of methane with a 1.66-microm diode laser.

PubMed

Uehara, K; Tai, H

1992-02-20

High-sensitivity real-time remote detection of methane in air with a 1.66-microm distributed-feedback diode laser operating at room temperature is demonstrated by laboratory simulations. The laser current was modulated at a high frequency of ~5 MHz, and the laser-center frequency was locked onto a methane-absorption line. The laser light directed toward the probed region was received after one-way transmission or further reflection from a topographic target. The methane absorption was detected by the second-harmonic component in the optical-power variation. The minimum-detectable concentration-path-length product in the transmission scheme was 0.3 part in 10(6) m for a signal averaging time of 1.3 s. In the reflection scheme, the amount of methane could be measured from the ratio of the fundamental and second-harmonic signal intensities independently of the received power.

Aerodyne Research mobile infrared methane monitor

NASA Technical Reports Server (NTRS)

Mcmanus, J. B.; Kebabian, P. L.; Kolb, C. E.

1991-01-01

An improved real-time methane monitor based on infrared absorption of the 3.39 micron line of a HeNe laser is described. Real time in situ measurement of methane has important applications in stratospheric and tropospheric chemistry, especially when high accuracy measurements can be made rapidly, providing fine spatial-scale information. The methane instrument provides 5 ppb resolution in a 1 sec averaging time. A key feature in this instrument is the use of magnetic (Zeeman) broadening to achieve continuous tunability with constant output power over a range of 0.017/cm. The instruments optical absorption path length is 47 m through sampled air held at 50 torr in a multipass cell of the Herriott (off-axis resonator) type. A microprocessor controls laser frequency and amplitude and collects data with minimal operator attention. The instrument recently has been used to measure methane emissions from a variety of natural and artificial terrestrial sources.

Laser-based sensors on UAVs for quantifying local emissions of greenhouse gases

NASA Astrophysics Data System (ADS)

Zondlo, Mark; Tao, Lei; O'Brien, Anthony; Ross, Kevin; Khan, Amir; Pan, Da; Golston, Levi; Sun, Kang; DiGangi, Josh

2015-04-01

Small unmanned aerial systems (UAS) provide an ideal platform to sample both locally near an emission source as well as within the atmospheric boundary layer. However, small UAS (those with wingspans or rotors on the order of a meter) place severe constraints on sensor size (~ liter volume), mass (~ kg), and power (10s W). Laser-based sensors employing absorption techniques are ideally suited for such platforms due to their high sensitivity, high selectivity, and compact footprint. We have developed and flown compact sensors for water vapor, carbon dioxide and methane using new advances in open-path, laser-based spectroscopy on a variety of platforms ranging from remote control helicopters to long-duration UAS. Open-path spectroscopy allows for high frequency sampling (10-25 Hz) while avoiding the size/mass/power of sample delays, inlet lines, and pumps. To address the challenges of in-flight stability in changing environmental conditions and any associated flight artifacts on the measurement itself (e.g. vibrations), we use an in-line reference cell at a reduced pressure (10 hPa) to account for systematic drift continuously while in flight. Wavelength modulation spectroscopy is used at different harmonics to isolate the narrow linewidth of the in-line reference signal from the ambient, pressure-broadened absorption lineshape of the trace gas of interest. As a result, a metric of in-flight performance is achieved in real-time on the same optical pathlength as the ambient signal. To demonstrate the great potential of laser-based sensors on UAS, we deployed a 1.65 micron-based methane sensor (4 kg, 50 W, 100 ppbv precision at 10 Hz) on a UT-Dallas remote control aircraft for two weeks around gas/oil extraction activities as part of the EDF Barnett Coordinated Campaign in October 2013. We conducted thirty-four flights around a compressor station to examine the spatial and temporal characteristics of its emissions. Leaks of methane were typically lofted to altitudes well above the surface (up to 100 m). In addition, plumes were very narrow horizontally (10-30 m width) within 200 m of the emission origin. By using a mass balance approach of upwind versus downwind CH4 concentrations, coupled to meteorological wind data, the CH4 emission rate from the compressor station averaged 13 ± 5 g CH4 s-1, consistent with individual, leak surveys measured within the compressor station itself. More recently, we developed a mid-infrared version of the same sensor using an antimonide laser at 3.3 microns. This sensor has a precision of 2 ppbv CH4 at 10 Hz, a mass of 1.3 kg, and consumes 10 W of power. Flight tests show the improved precision is capable of detecting methane leaks from landfills and cattle feedlots at higher altitudes (500 m) and greater distances downwind (several km) than the near infrared CH4 sensor. Sampling strategy is particularly important for not only UAS-based flight patterns but also sensor design. Many tradeoffs exist between the sampling density of the flight pattern, sensor precision, accuracy of wind data, and geographic isolation of the source of interest, and these will be discussed in the context of airborne-based CH4 measurements in the field. The development of compact yet robust trace gas sensors to be deployed on small UAS opens new capabilities for atmospheric sensing such as quantifying local source emissions (e.g. farms, well pads), vertical profiling of trace gases in a forest canopy, and trace gas distributions in complex areas (mountains, urban canyons).

A computational study of CH 4 storage in porous framework materials with metalated linkers: connecting the atomistic character of CH 4 binding sites to usable capacity

DOE PAGES

Tsivion, Ehud; Mason, Jarad A.; Gonzalez, Miguel. I.; ...

2016-03-29

In order to store natural gas (NG) inexpensively at adequate densities for use as a fuel in the transportation sector, new porous materials are being developed. Our work uses computational methods to explore strategies for improving the usable methane storage capacity of adsorbents, including metal-organic frameworks (MOFs), that feature open-metal sites incorporated into their structure by postsynthetic modification. The adsorption of CH 4 on several open-metal sites is studied by calculating geometries and adsorption energies and analyzing the relevant interaction factors. Approximate site-specific adsorption isotherms are obtained, and the open-metal site contribution to the overall CH 4 usable capacity ismore » evaluated. It is found that sufficient ionic character is required, as exemplified by the strong CH 4 affinities of 2,2'-bipyridine-CaCl 2 and Mg, Ca-catecholate. In addition, it is found that the capacity of a single metal site depends not only on its affinity but also on its geometry, where trigonal or "bent" low-coordinate exposed sites can accommodate three or four methane molecules, as exemplified by Ca-decorated nitrilotriacetic acid. The effect of residual solvent molecules at the open-metal site is also explored, with some positive conclusions. Not only can residual solvent stabilize the open-metal site, surprisingly, solvent molecules do not necessarily reduce CH 4 affinity, but can contribute to increased usable capacity by modifying adsorption interactions.« less

Integration of Ground-Based Solar FT-IR Absorption Spectroscopy and Open-Path Systems for Atmospheric Analysis

NASA Astrophysics Data System (ADS)

Steill, J. D.; Hager, J. S.; Compton, R. N.

2006-05-01

Air quality issues in the Knoxville and East Tennessee region are of great concern, particularly as regards the nearby Great Smoky Mountains National Park. Infrared absorption spectroscopy of the atmosphere provides a unique opportunity to analyze the local chemical composition, since many trace atmospheric constituents are open to this analysis, such as O3, CO, CH4, and N2O. Integration of a Bomem DA8 FT-IR spectrometer with rooftop sun-tracking optics and an open-path system provide solar-sourced and boundary- layer atmospheric infrared spectra of these and other relevant atmospheric components. Boundary layer concentrations as well as total column abundances and vertical concentration profiles are derived. Vertical concentration profiles are determined by fitting solar-sourced absorbance lines with the SFIT2 algorithm. Improved fitting of solar spectra has been demonstrated by incorporating the tropospheric concentrations as determined by open-path measurements. A record of solar-sourced atmospheric spectra of greater than two years duration is under analysis to characterize experimental error and thus the limit of precision in the concentration determinations. Initial efforts using atmospheric O2 as a calibration indicate the solar- sourced spectra may not yet meet the precision required for accurate atmospheric CO2 quantification by such efforts as the OCO and NDSC. However, this variability is also indicative of local concentration fluxes pertinent to the regional atmospheric chemistry. In addition to providing a means to improve the analysis of solar spectra, the open-path data is useful for elucidation of seasonal and diurnal trends in the local trace gas concentrations.

Methane Measurements from Space: Technical Challenges and Solutions

NASA Technical Reports Server (NTRS)

Riris, Haris; Numata, Kenji; Wu, Stewart; Gonzalez, Brayler; Rodriguez, Michael; Kawa, Stephan; Mao, Jianping

2017-01-01

We report on an airborne demonstration of atmospheric methane (CH4) measurements with an Integrated Path Differential Absorption (IPDA) lidar using an optical parametric oscillator (OPO) and optical parametric amplifier (OPA) laser transmitter and a sensitive avalanche photo detector. The lidar measures the CH4 absorption at multiple, discrete wavelengths around 1650.9 nm. In September 2015, the instrument was deployed on NASAs DC-8 airborne laboratory and measured atmospheric methane over a wide range of topography and weather conditions from altitudes of 3 km to 13 km. In this paper, we will review the results from our flights, and identify areas of improvement.

Methane measurements from space: technical challenges and solutions

NASA Astrophysics Data System (ADS)

Riris, Haris; Numata, Kenji; Wu, Stewart; Gonzalez, Brayler; Rodriguez, Michael; Kawa, Stephan; Mao, Jianping

2017-05-01

We report on an airborne demonstration of atmospheric methane (CH4) measurements with an Integrated Path Differential Absorption (IPDA) lidar using an optical parametric oscillator (OPO) and optical parametric amplifier (OPA) laser transmitter and a sensitive avalanche photo detector. The lidar measures the CH4 absorption at multiple, discrete wavelengths around 1650.9 nm. In September 2015, the instrument was deployed on NASA's DC-8 airborne laboratory and measured atmospheric methane over a wide range of topography and weather conditions from altitudes of 3 km to 13 km. In this paper, we will review the results from our flights, and identify areas of improvement.

Genetic and environmental variation in methane emissions of sheep at pasture.

PubMed

Robinson, D L; Goopy, J P; Hegarty, R S; Oddy, V H; Thompson, A N; Toovey, A F; Macleay, C A; Briegal, J R; Woodgate, R T; Donaldson, A J; Vercoe, P E

2014-10-01

A total of 2,600 methane (CH4) and 1,847 CO2 measurements of sheep housed for 1 h in portable accumulation chambers (PAC) were recorded at 5 sites from the Australian Sheep CRC Information Nucleus, which was set up to test leading young industry sires for an extensive range of current and novel production traits. The final validated dataset had 2,455 methane records from 2,279 animals, which were the progeny of 187 sires and 1,653 dams with 7,690 animals in the pedigree file. The protocol involved rounding up animals from pasture into a holding paddock before the first measurement on each day and then measuring in groups of up to 16 sheep over the course of the day. Methane emissions declined linearly (with different slopes for each site) with time since the sheep were drafted into the holding area. After log transformation, estimated repeatability (rpt) and heritability (h(2)) of liveweight-adjusted CH4 emissions averaged 25% and 11.7%, respectively, for a single 1-h measurement. Sire × site interactions were small and nonsignificant. Correlations between EBV for methane emissions and Sheep Genetics Australia EBV for production traits were used as approximations to genetic correlations. Apart from small positive correlations with weaning and yearling weights (r = 0.21-0.25, P < 0.05), there were no significant relationships between production trait and methane EBV (calculated from a model adjusting for liveweight by fitting separate slopes for each site). To improve accuracy, future protocols should use the mean of 2 (rpt = 39%, h(2) = 18.6%) or 3 (rpt = 48%, h(2) = 23.2%) PAC measurements. Repeat tests under different pasture conditions and time of year should also be considered, as well as protocols measuring animals directly off pasture instead of rounding them up in the morning. Reducing the time in the PAC from 1 h to 40 min would have a relatively small effect on overall accuracy and partly offset the additional time needed for more tests per animal. Field testing in PAC has the potential to provide accurate comparisons of animal and site methane emissions, with potentially lower cost/increased accuracy compared to alternatives such as SF6 tracers or open path lasers. If similar results are obtained from tests with different protocols/seasonal conditions, use of PAC measurements in a multitrait selection index with production traits could potentially reduce methane emissions from Australian sheep for the same production level.

40 CFR 58.1 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... measurement data pairs. Administrator means the Administrator of the Environmental Protection Agency (EPA) or... storing and reporting of information relating to ambient air quality data. Approved regional method (ARM... of an open path analyzer in which a high-concentration test or audit standard gas contained in a...

Assessment of leachates from uncontrolled landfill: Tangier case study

NASA Astrophysics Data System (ADS)

Elmaghnougi, I.; Afilal Tribak, A.; Maatouk, M.

2018-05-01

Landfill site of Tangier City is non-engineered low lying open dump. It has neither bottom liner nor leachate collection and treatment system. Therefore, all the leachate generated finds its paths into the surrounding environment Leachate samples of landfill site were collected and analyzed to estimate its pollution potential. The analyzed samples contained a high concentration of organic and inorganic compounds, beyond the permissible limits.

Calculating CO2 and H2O eddy covariance fluxes from an enclosed gas analyzer using an instantaneous mixing ratio 2159

USDA-ARS?s Scientific Manuscript database

Eddy covariance flux research has relied on open- or closed-path gas analyzers for producing estimates of net ecosystem exchange of carbon dioxide (CO2) and water vapor (H2O). The two instruments have had different challenges that have led to development of an enclosed design that is intended to max...

A new method to study simultaneous methane oxidation and methane production in soils

NASA Astrophysics Data System (ADS)

Andersen, B. L.; Bidoglio, G.; Leip, A.; Rembges, D.

1998-12-01

Results of laboratory experiments show that 14C-labeled methane added to soil was consumed faster than atmospheric 12C methane. This implies a source of methane, presumably through methanogenesis, in a soil that is a net consumer of atmospheric methane. The soil was well-drained forest soil from Ispra, Italy. An undisturbed sample was taken with a steel corer and incubated under oxic conditions in a jar. Headspace samples were taken at time intervals and analyzed for total methane by gas chromatography and analyzed for 14C methane by liquid scintillation counting. Fluxes calculated from the decreasing headspace mixing ratios were, for example, -6.5 and -7.1 μmol m-2 hr-1 for 12C methane and 14C methane, respectively. A simple model is considered which reproduces reasonably well the observed mixing ratios as function of time.

In Situ Tropical Peatland Fire Emission Factors and Their Variability, as Determined by Field Measurements in Peninsula Malaysia

NASA Astrophysics Data System (ADS)

Smith, T. E. L.; Evers, S.; Yule, C. M.; Gan, J. Y.

2018-01-01

Fires in tropical peatlands account for >25% of estimated total greenhouse gas emissions from deforestation and degradation. Despite significant global and regional impacts, our understanding of specific gaseous fire emission factors (EFs) from tropical peat burning is limited to a handful of studies. Furthermore, there is substantial variability in EFs between sampled fires and/or studies. For example, methane EFs vary by 91% between studies. Here we present new fire EFs for the tropical peatland ecosystem; the first EFs measured for Malaysian peatlands, and only the second comprehensive study of EFs in this crucial environment. During August 2015 (under El Niño conditions) and July 2016, we embarked on field campaigns to measure gaseous emissions at multiple peatland fires burning on deforested land in Southeast Pahang (2015) and oil palm plantations in North Selangor (2016), Peninsula Malaysia. Gaseous emissions were measured using open-path Fourier transform infrared spectroscopy. The IR spectra were used to retrieve mole fractions of 12 different gases present within the smoke (including carbon dioxide and methane), and these measurements used to calculate EFs. Peat samples were taken at each burn site for physicochemical analysis and to explore possible relationships between specific physicochemical properties and fire EFs. Here we present the first evidence to indicate that substrate bulk density affects methane fire EFs reported here. This novel explanation of interplume, within-biome variability, should be considered by those undertaking greenhouse gas accounting and haze forecasting in this region and is of importance to peatland management, particularly with respect to artificial compaction.

Long open-path measurements of greenhouse gases in air using near-infrared Fourier transform spectroscopy

NASA Astrophysics Data System (ADS)

Griffith, David W. T.; Pöhler, Denis; Schmitt, Stefan; Hammer, Samuel; Vardag, Sanam N.; Platt, Ulrich

2018-03-01

In complex and urban environments, atmospheric trace gas composition is highly variable in time and space. Point measurement techniques for trace gases with in situ instruments are well established and accurate, but do not provide spatial averaging to compare against developing high-resolution atmospheric models of composition and meteorology with resolutions of the order of a kilometre. Open-path measurement techniques provide path average concentrations and spatial averaging which, if sufficiently accurate, may be better suited to assessment and interpretation with such models. Open-path Fourier transform spectroscopy (FTS) in the mid-infrared region, and differential optical absorption spectroscopy (DOAS) in the UV and visible, have been used for many years for open-path spectroscopic measurements of selected species in both clean air and in polluted environments. Near infrared instrumentation allows measurements over longer paths than mid-infrared FTS for species such as greenhouse gases which are not easily accessible to DOAS.In this pilot study we present the first open-path near-infrared (4000-10 000 cm-1, 1.0-2.5 µm) FTS measurements of CO2, CH4, O2, H2O and HDO over a 1.5 km path in urban Heidelberg, Germany. We describe the construction of the open-path FTS system, the analysis of the collected spectra, several measures of precision and accuracy of the measurements, and the results a four-month trial measurement period in July-November 2014. The open-path measurements are compared to calibrated in situ measurements made at one end of the open path. We observe significant differences of the order of a few ppm for CO2 and a few tens of ppb for CH4 between the open-path and point measurements which are 2 to 4 times the measurement repeatability, but we cannot unequivocally assign the differences to specific local sources or sinks. We conclude that open-path FTS may provide a valuable new tool for investigations of atmospheric trace gas composition in complex, small-scale environments such as cities.

Long - High Resolution Spectrum of Methane. Towards Titan's Atmosphere

NASA Astrophysics Data System (ADS)

Daumont, Ludovic; Tyuterev, Vladimir; Regalia, Laurence; Thomas, Xavier; von der Heyden, Pierre; Nikitin, Rei; Brown, Linda

2011-06-01

The precise knowledge of the methane absorption in the study of planetary systems, and especially of Titan (Saturn's largest satellite whose atmosphere is mainly composed of nitrogen and methane at temperatures ranging between 70 K and 200 K), is of great importance because it gives access to the determination of the physical properties of these objects. The full interpretation of the Titan data returned by the ground-based and space observations has been hindered by the lack of precise knowledge of the methane absorption which dominates Titan's near infrared spectra. We investigate the methane spectra in the closest conditions to existing Titan's spectra. We used the 50 m long cell from Reims university in front of the Home-made Fourier Transform Spectrometer to study the 12CH_4 spectra with 1603 m absorption path length, 1, 7 and 34 hPa pressures and at room temperature. The spectra was recorded in the all range from 3800 to 8100 Cm-1. The up-to-date measurements and assignments- mainly in the so called methane transparancy windows- will be presented and discussed.

Thermal control of low-pressure fractionation processes. [in basaltic magma solidification

NASA Technical Reports Server (NTRS)

Usselman, T. M.; Hodge, D. S.

1978-01-01

Thermal models detailing the solidification paths for shallow basaltic magma chambers (both open and closed systems) were calculated using finite-difference techniques. The total solidification time for closed chambers are comparable to previously published calculations; however, the temperature-time paths are not. These paths are dependent on the phase relations and the crystallinity of the system, because both affect the manner in which the latent heat of crystallization is distributed. In open systems, where a chamber would be periodically replenished with additional parental liquid, calculations indicate that the possibility is strong that a steady-state temperature interval is achieved near a major phase boundary. In these cases it is straightforward to analyze fractionation models of the basaltic liquid evolution and their corresponding cumulate sequences. This steady thermal fractionating state can be invoked to explain large amounts of erupted basalts of similar composition over long time periods from the same volcanic center and some rhythmically layered basic cumulate sequences.

[Measurements of stable isotopes in atmospheric CO2 and H2O by open-path Fourier transform infrared spectrometry].

PubMed

Wang, Wei; Liu, Wen-Qing; Zhang, Tian-Shu

2013-08-01

The development of spectroscopic techniques has offered continuous measurement of stable isotopes in the ambient air. The method of measuring environmental stable isotopes based on Fourier transform infrared spectrometry (FTIR) is described. In order to verify the feasibility of the method for continuous measurement of the stable isotopes, an open-path FTIR system was used to measure stable isotopes of CO2 and H2O in ambient air directly in a seven-day field experiment, including 12CO2, 3CO2, H2 16O and HD16 O. Also, the time course of carbon isotopic ratio delta13 C and deuterium isotope composition deltaD was calculated. The measurement precision is about 1.08 per thousand for delta13 C and 1.32 per thousand for deltaD. The measured stable isotopes of CO2 and H2O were analyzed on different time scales by Keeling plot methods, and the deuterium isotopic ratios of evapotranspiration were determined. The results of the field experiment demonstrate the potential of the open-path FTIR system for continuous measurement of stable isotopes in the air.

40 CFR 86.121-90 - Hydrocarbon analyzer calibration.

Code of Federal Regulations, 2013 CFR

2013-07-01

... used operating range with propane in air calibration gases (either methanol or methane in air as... response factor to methane. When the FID analyzer is to be used for the analysis of gasoline, diesel, methanol, ethanol, liquefied petroleum gas, and natural gas-fueled vehicle hydrocarbon samples, the methane...

40 CFR 86.121-90 - Hydrocarbon analyzer calibration.

Code of Federal Regulations, 2014 CFR

2014-07-01

... used operating range with propane in air calibration gases (either methanol or methane in air as... response factor to methane. When the FID analyzer is to be used for the analysis of gasoline, diesel, methanol, ethanol, liquefied petroleum gas, and natural gas-fueled vehicle hydrocarbon samples, the methane...

40 CFR 86.121-90 - Hydrocarbon analyzer calibration.

Code of Federal Regulations, 2012 CFR

2012-07-01

... used operating range with propane in air calibration gases (either methanol or methane in air as... response factor to methane. When the FID analyzer is to be used for the analysis of gasoline, diesel, methanol, ethanol, liquefied petroleum gas, and natural gas-fueled vehicle hydrocarbon samples, the methane...

Consumption of methane by soils.

PubMed

Dueñas, C; Fernández, M C; Carretero, J; Pérez, M; Liger, E

1994-05-01

Measurements of the methane flux and methane concentration profiles in soil air are presented. The flux of methane from the soil is calculated by two methods: a) Direct by placing a static open chamber at the soil surface. b) Indirect, using the (222)Rn concentrations profile and the (222)Rn flux in the soil surface in parallel with the methane concentration ((222)Rn calibrated fluxes). The methane flux has been determined in two kinds of soils (sandy and loamy) in the surroundings of Málaga (SPAIN). The directly measured methane fluxes at all investigated sites is higher than methane fluxes derived from "Rn calibrated fluxes". Atmospheric methane is consumed by soils, mean direct flux to the atmosphere were - 0.33 g m(-2)yr-1. The direct methane flux is the same within the measuring error in sandy and loamy soils. The influence of the soil parameters on the methane flux indicates that microbial decomposition of methane is primarily controlled by the transport of methane.

77 FR 77113 - Petitions for Modification of Application of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-31

... for methane immediately before and during the use of nonpermissible surveying equipment in or inby the last open crosscut. (e) Nonpermissible surveying equipment will not be used if methane is detected in concentrations at or above one percent for the area being surveyed. When methane is detected at such levels while...

77 FR 57157 - Petitions for Modification of Application of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-17

... for methane immediately before and during the use of nonpermissible surveying equipment in or inby the last open crosscut. (e) Nonpermissible surveying equipment will not be used if methane is detected in concentrations at or above one percent for the area being surveyed. When methane is detected at such levels while...

Spatial profiles of methane at the Swiss Plateau: A confrontation between measurements and emission inventories.

NASA Astrophysics Data System (ADS)

Bamberger, Ines; Eugster, Werner; Buchmann, Nina

2013-04-01

Methane and carbon dioxide are the two most prominent greenhouse gases in the atmosphere and a detailed knowledge about their sources is essential for climate predictions (Solomon et al., 2007). The knowledge about greenhouse gas fluxes is usually merged, albeit including considerable uncertainties, to emission inventories. To increase the quality of the inventories a comparison with measurements is necessary. We evaluate the values given by a Swiss emission inventory with regard to atmospheric measurements of methane in Switzerland. Spatial profiles of carbon dioxide and methane were investigated at the Swiss Plateau during two consecutive warm and sunny summer days in July 2012. For the mobile methane and carbon dioxide measurements a LGR methane analyser and a LI-COR closed-path infrared gas analyser (IRGA) were mounted on a car together with an AIRMAR WeatherStation to track geodetic-coordinates and meteorological parameters. First results of the measurements including aerial profiles of the greenhouse gases and bin-averaged elevation profiles of methane and temperature will be presented and a highly-resolved methane emission inventory will be evaluated in comparison with the spatial profiles of atmospheric methane at the Swiss Plateau. References: Solomon, S., Qin D., et al. (Eds.) (2007) Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 996 S. pp., Cambridge University Press, Cambridge.

Annual variability and regulation of methane and sulfate fluxes in Baltic Sea estuarine sediments

NASA Astrophysics Data System (ADS)

Sawicka, Joanna E.; Brüchert, Volker

2017-01-01

Marine methane emissions originate largely from near-shore coastal systems, but emission estimates are often not based on temporally well-resolved data or sufficient understanding of the variability of methane consumption and production processes in the underlying sediment. The objectives of our investigation were to explore the effects of seasonal temperature, changes in benthic oxygen concentration, and historical eutrophication on sediment methane concentrations and benthic fluxes at two type localities for open-water coastal versus eutrophic, estuarine sediment in the Baltic Sea. Benthic fluxes of methane and oxygen and sediment pore-water concentrations of dissolved sulfate, methane, and 35S-sulfate reduction rates were obtained over a 12-month period from April 2012 to April 2013. Benthic methane fluxes varied by factors of 5 and 12 at the offshore coastal site and the eutrophic estuarine station, respectively, ranging from 0.1 mmol m-2 d-1 in winter at an open coastal site to 2.6 mmol m-2 d-1 in late summer in the inner eutrophic estuary. Total oxygen uptake (TOU) and 35S-sulfate reduction rates (SRRs) correlated with methane fluxes showing low rates in the winter and high rates in the summer. The highest pore-water methane concentrations also varied by factors of 6 and 10 over the sampling period with the lowest values in the winter and highest values in late summer-early autumn. The highest pore-water methane concentrations were 5.7 mM a few centimeters below the sediment surface, but they never exceeded the in situ saturation concentration. Of the total sulfate reduction, 21-24 % was coupled to anaerobic methane oxidation, lowering methane concentrations below the sediment surface far below the saturation concentration. The data imply that bubble emission likely plays no or only a minor role in methane emissions in these sediments. The changes in pore-water methane concentrations over the observation period were too large to be explained by temporal changes in methane formation and methane oxidation rates due to temperature alone. Additional factors such as regional and local hydrostatic pressure changes and coastal submarine groundwater flow may also affect the vertical and lateral transport of methane.

Evidence and age estimation of mass wasting at the distal lobe of the Congo deep-sea fan

NASA Astrophysics Data System (ADS)

Croguennec, Claire; Ruffine, Livio; Dennielou, Bernard; Baudin, François; Caprais, Jean-Claude; Guyader, Vivien; Bayon, Germain; Brandily, Christophe; Le Bruchec, Julie; Bollinger, Claire; Germain, Yoan; Droz, Laurence; Babonneau, Nathalie; Rabouille, Christophe

2017-08-01

On continental margins, sulfate reduction occurs within the sedimentary column. It is coupled with the degradation of organic matter and the anaerobic oxidation of methane. These processes may be significantly disturbed by sedimentary events, leading to transient state profiles for the involved chemical species. Yet, little is known about the impact of turbidity currents and mass wasting on the migration of chemical species and the redox reactions in which they are involved. Due to its connection to the River, the Congo deep-sea fan continuously receives huge amount of organic matter-rich sediments primarily transported by turbidity currents, which impact on the development of the associated ecosystems (Rabouille et al., 2017). Thus, it is well suited to better understand causal relationships between sedimentary events and fluid flow path, with consequences on the zonation of early diagenesis sequences. Here, we combined sedimentological observations with geochemical analyses of pore-water and sediment samples to explore how sedimentary instabilities affected the migration of methane and the distribution of organic matter within the sedimentary column. The results unveiled mass wasting processes affecting recent turbiditic and pelagic deposits, and are interpreted as being slides/ slumps and debrites. Two slides were responsible for the exhumation of an organic matter-rich sedimentary block of more than 5 m thick and the movement of a methane-rich sedimentary block, while turbidity currents enable the intercalation of sandy intervals within a pelagic clay layer. The youngest slide promoted the development of two Sulfate Methane Transition Zones (SMTZ), and may have possibly triggered a lateral migration of methane. Numerical simulation of the sulfate profile indicates that the youngest sedimentary event has occurred around a century ago. Our study emphasizes that turbidity currents and sedimentary instabilities can significantly affect the transport paths and the distribution of both methane and organic matter in the terminal lobe complex, with consequences on geochemical zonation of the sequential early diagenetic processes within the sedimentary column.

Quantifying Fugitive Methane Emissions at an Underground Coal Fire Using Cavity Ring-Down Spectroscopy Technology

NASA Astrophysics Data System (ADS)

Fleck, D.; Gannon, L.; Kim-Hak, D.; Ide, T.

2016-12-01

Understanding methane emissions is of utmost importance due to its greenhouse warming potential. Methane emissions can occur from a variety of natural and anthropogenic sources which include wetlands, landfills, oil/gas/coal extraction activities, underground coal fires, and natural gas distribution systems. Locating and containing these emissions are critical to minimizing their environmental impacts and economically beneficial when retrieving large fugitive amounts. In order to design a way to mitigate these methane emissions, they must first be accurately quantified. One such quantification method is to measure methane fluxes, which is a measurement technique that is calculated based on rate of gas accumulation in a known chamber volume over methane seepages. This allows for quantification of greenhouse gas emissions at a localized level (sub one meter) that can complement remote sensing and other largescale modeling techniques to further paint the picture of emission points. High performance analyzers are required to provide both sufficient temporal resolution and precise concentration measurements in order to make these measurements over only minutes. A method of measuring methane fluxes was developed using the latest portable, battery-powered Cavity Ring-Down Spectroscopy analyzer from Picarro (G4301). In combination with a mobile accumulation chamber, the instrument allows for rapid measurement of methane and carbon dioxide fluxes over wide areas. For this study, methane fluxes that were measured at an underground coal fire near the Four Corners region using the Picarro analyzer are presented. The flux rates collected demonstrate the ability for the analyzer to detect methane fluxes across many orders of magnitude. Measurements were accompanied by simultaneously geotagging the measurements with GPS to georeferenced the data. Methane flux data were instrumental in our ability to characterize the extent and the migration of the underground fire. In the future, examining the tradeoffs and dynamics between methane and carbon dioxide emissions will allow us to further understand the propagation and evolution of these large greenhouse gas emitters.

On the importance of high-frequency air-temperature fluctuations for spectroscopic corrections of open-path carbon dioxide flux measurements

NASA Astrophysics Data System (ADS)

Bogoev, Ivan; Helbig, Manuel; Sonnentag, Oliver

2015-04-01

A growing number of studies report systematic differences in CO2 flux estimates obtained with the two main types of gas analyzers: compared to eddy-covariance systems based on closed-path (CP) gas analyzers, systems with open-path (OP) gas analyzers systematically overestimate CO2 uptake during daytime periods with high positive sensible heat fluxes, while patterns for differences in nighttime CO2 exchange are less obvious. These biases have been shown to correlate with the sign and the magnitude of the sensible heat flux and to introduce large uncertainties when calculating annual CO2 budgets. In general, CP and OP gas analyzers commonly used to measure the CO2 density in the atmosphere operate on the principle of infrared light absorption approximated by Beer-Lambert's law. Non-dispersive interference-based optical filter elements are used to select spectral bands with strong attenuation of light transmission, characteristic to the gas of interest. The intensity of the light passing through the optical sensing path depends primarily on the amount of absorber gas in the measurement volume. Besides the density of the gas, barometric pressure and air temperature are additional factors affecting the strength and the half-width of the absorption lines. These so-called spectroscopic effects are accounted for by measuring barometric pressure and air temperature in the sensing path and scaling the light-intensity measurements before applying the calibration equation. This approach works well for CP gas analyzers with an intake tube that acts as a low-pass filter on fast air-temperature fluctuations. Low-frequency response temperature sensors in the measurement cell are therefore sufficient to account for spectroscopic temperature effects. In contrast, OP gas analyzers are exposed to high-frequency air-temperature fluctuations associated with the atmospheric surface-layer turbulent heat exchange. If not corrected adequately, these fast air-temperature variations can cause systematic errors in the CO2 density measurements. Under conditions of high positive or negative sensible heat flux, air-temperature fluctuations are correlated with fluctuations of the vertical wind component and can lead to significant biases in the CO2 flux estimates. This study demonstrates that sonically derived fast-response air temperature in the optical sensing path of an OP gas analyzer can replace the slow-response measurements from the temperature sensor as a scaling parameter in the calibration model to correct for these air temperature-induced spectroscopic effects. Our approach is evaluated by comparison between different OP and CP gas analyzer-based eddy-covariance systems in ecosystems with low CO2 uptake under a range of sensible heat flux regimes and varying meteorological parameters. We show that ignoring high-frequency spectroscopic effects can lead to false interpretations of net ecosystem CO2 exchange for specific site and environmental conditions.

Does Dietary Mitigation of Enteric Methane Production Affect Rumen Function and Animal Productivity in Dairy Cows?

PubMed Central

Veneman, Jolien B.; Muetzel, Stefan; Hart, Kenton J.; Faulkner, Catherine L.; Moorby, Jon M.; Perdok, Hink B.; Newbold, Charles J.

2015-01-01

It has been suggested that the rumen microbiome and rumen function might be disrupted if methane production in the rumen is decreased. Furthermore concerns have been voiced that geography and management might influence the underlying microbial population and hence the response of the rumen to mitigation strategies. Here we report the effect of the dietary additives: linseed oil and nitrate on methane emissions, rumen fermentation, and the rumen microbiome in two experiments from New Zealand (Dairy 1) and the UK (Dairy 2). Dairy 1 was a randomized block design with 18 multiparous lactating cows. Dairy 2 was a complete replicated 3 x 3 Latin Square using 6 rumen cannulated, lactating dairy cows. Treatments consisted of a control total mixed ration (TMR), supplementation with linseed oil (4% of feed DM) and supplementation with nitrate (2% of feed DM) in both experiments. Methane emissions were measured in open circuit respiration chambers and rumen samples were analyzed for rumen fermentation parameters and microbial population structure using qPCR and next generation sequencing (NGS). Supplementation with nitrate, but not linseed oil, decreased methane yield (g/kg DMI; P<0.02) and increased hydrogen (P<0.03) emissions in both experiments. Furthermore, the effect of nitrate on gaseous emissions was accompanied by an increased rumen acetate to propionate ratio and consistent changes in the rumen microbial populations including a decreased abundance of the main genus Prevotella and a decrease in archaeal mcrA (log10 copies/ g rumen DM content). These results demonstrate that methane emissions can be significantly decreased with nitrate supplementation with only minor, but consistent, effects on the rumen microbial population and its function, with no evidence that the response to dietary additives differed due to geography and different underlying microbial populations. PMID:26509835

Does Dietary Mitigation of Enteric Methane Production Affect Rumen Function and Animal Productivity in Dairy Cows?

PubMed

Veneman, Jolien B; Muetzel, Stefan; Hart, Kenton J; Faulkner, Catherine L; Moorby, Jon M; Perdok, Hink B; Newbold, Charles J

2015-01-01

It has been suggested that the rumen microbiome and rumen function might be disrupted if methane production in the rumen is decreased. Furthermore concerns have been voiced that geography and management might influence the underlying microbial population and hence the response of the rumen to mitigation strategies. Here we report the effect of the dietary additives: linseed oil and nitrate on methane emissions, rumen fermentation, and the rumen microbiome in two experiments from New Zealand (Dairy 1) and the UK (Dairy 2). Dairy 1 was a randomized block design with 18 multiparous lactating cows. Dairy 2 was a complete replicated 3 x 3 Latin Square using 6 rumen cannulated, lactating dairy cows. Treatments consisted of a control total mixed ration (TMR), supplementation with linseed oil (4% of feed DM) and supplementation with nitrate (2% of feed DM) in both experiments. Methane emissions were measured in open circuit respiration chambers and rumen samples were analyzed for rumen fermentation parameters and microbial population structure using qPCR and next generation sequencing (NGS). Supplementation with nitrate, but not linseed oil, decreased methane yield (g/kg DMI; P<0.02) and increased hydrogen (P<0.03) emissions in both experiments. Furthermore, the effect of nitrate on gaseous emissions was accompanied by an increased rumen acetate to propionate ratio and consistent changes in the rumen microbial populations including a decreased abundance of the main genus Prevotella and a decrease in archaeal mcrA (log10 copies/g rumen DM content). These results demonstrate that methane emissions can be significantly decreased with nitrate supplementation with only minor, but consistent, effects on the rumen microbial population and its function, with no evidence that the response to dietary additives differed due to geography and different underlying microbial populations.

APPLYING OPEN-PATH OPTICAL SPECTROSCOPY TO HEAVY-DUTY DIESEL EMISSIONS

EPA Science Inventory

Non-dispersive infrared absorption has been used to measure gaseous emissions for both stationary and mobile sources. Fourier transform infrared spectroscopy has been used for stationary sources as both extractive and open-path methods. We have applied the open-path method for bo...

78 FR 13089 - Petitions for Modification of Application of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-26

... for methane immediately before and during the use of nonpermissible surveying equipment in or inby the last open crosscut. (e) Nonpermissible surveying equipment will not be used if methane [[Page 13090

Investigation into the effects of sulfur on syngas reforming inside a solid oxide fuel cell

NASA Astrophysics Data System (ADS)

Li, Ting Shuai; Xu, Min; Gao, Chongxin; Wang, Baoqing; Liu, Xiyun; Li, Baihai; Wang, Wei Guo

2014-07-01

The electrochemical performance and long-term durability of a solid oxide fuel cell have been evaluated with a simulated coal syngas containing 2 ppm H2S as fuel. The resulting impedance spectra indicate that no observable power loss is caused by the addition of 2 ppm H2S, and the cell shows stability of nearly 500 h at 0.625 A cm-2. The composition of mixed gas is analyzed both at a current load of 0.625 A cm-2 and open circuit state. Hydrogen and carbon monoxide are directly consumed as fuels at the anode side, whereas methane stays unchanged during the operation. It seems the internal carbohydrate reforming and impurity poisoning interacts and weakens the poisoning effects. The oxidation of H2 and the water gas shift reaction take advantages over methane reforming at the cell operational conditions.

Methane flux from the Central Amazonian Floodplain

NASA Technical Reports Server (NTRS)

Bartlett, Karen B.; Crill, Patrick M.; Sebacher, Daniel I.; Harriss, Robert C.; Wilson, John O.; Melack, John M.

1987-01-01

A total of 186 methane measurements from the three primary Amazon floodplain environments of open water lakes, flood forests, and floating grass mats were made over the period 18 July through 2 September 1985. These data indicate that emissions were lowest over open water lakes. Flux from flooded forests and grass mats was significantly higher. At least three transport processes contribute to tropospheric emissions: ebullition from sediments, diffusion along the concentration gradient from sediment to overlaying water to air, and transport through the roots and stems of aquatic plants. Measurements indicate that the first two of these processes are most significant. It was estimated that on the average bubbling makes up 49% of the flux from open water, 54% of that from flooded forests, and 64% of that from floating mats. If the measurements were applied to the entire Amazonian floodplain, it is calculated that the region could supply up to 12% of the estimated global natural sources of methane.

Tea saponin reduced methanogenesis in vitro but increased methane yield in lactating dairy cows.

PubMed

Guyader, J; Eugène, M; Doreau, M; Morgavi, D P; Gérard, C; Martin, C

2017-03-01

The effect of tea saponin supplementation in the ruminant diet on methane emissions, rumen fermentation, and digestive processes is still under debate. The objective of this study was to assess the effect of this plant extract on methanogenesis, total-tract digestibility, and lactating performances of dairy cows. The work included 2 independent and successive experiments. First, the effect of 7 tea saponin doses (from 0 to 0.50 g/L) on methane emissions and protozoa concentrations was tested in 2 repeated in vitro batch culture incubations using bovine rumen contents as inoculum and a cereal mixture as substrate. After 18 h of incubation, total gas production and composition as well as rumen fermentation parameters and protozoa concentration were analyzed. Increasing dosage of the plant extract reduced methane production and protozoa concentration, with a maximum reduction of 29% for CH 4 (mL/g of substrate) and 51% for protozoa (10 5 /mL). Tea saponin did not affect volatile fatty acids concentration, but marginally decreased total gas production by 5% at the highest dose. Second, a 2-period crossover design experiment was carried out with 8 lactating dairy cows fed a basal diet (54% corn silage, 6% hay, and 40% pelleted concentrates on a dry matter basis) without (control) or with 0.52% tea saponin (TSP). Each experimental period lasted 5 wk. Animals were fed ad libitum during the first 3 wk of the period (wk 1, 2, and 3) and restricted (95% of ad libitum intake) during the last 2 wk (wk 4 and 5). Intake and milk production were recorded daily. Methane emissions were quantified using open chambers (2 d, wk 4). Total-tract digestibility and nitrogen balance were determined from total feces and urine collected separately (5 d, wk 5). Rumen fermentation parameters and protozoa concentration were analyzed from samples taken after morning feeding (1 d, wk 5). Milk production, dry matter intake, and feed efficiency were reduced with TSP (-18, -12, and -8%, respectively). As daily methane production (g/d) was not affected, methane emissions (g/kg of dry matter intake) increased by 14% with TSP. Total-tract digestibility and nitrogen balance were similar between diets, except for acid detergent fiber digestibility, which tended to be improved with TSP (+4 percentage units). Rumen fermentation parameters and protozoa concentration were relatively unchanged by diets. Under the conditions of this experiment, tea saponin is not efficient to reduce methane emissions from dairy cows. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Aerosol and trace gas flux measurements from a mobile car platform on the highway

NASA Astrophysics Data System (ADS)

Gordon, M.; Miller, S. J.; Staebler, R. M.; Taylor, P.

2016-12-01

Mobile flux measurements of aerosols and trace gases at the surface can provide valuable information about the vertical transport of these compounds from near-surface sources. These measurements can be complimentary to stationary tower measurements or elevated mobile measurements from aircraft and unmanned aerial systems (UAS). In July, 2016 a mobile platform (Toyota Highlander), outfitted with a sonic anemometer (ATI), an open path CO2/H2O analyzer (Licor), and an ultrafine particle sizer (DMT), was driven on highways as part of a chasing study to investigate vehicle-induced turbulence and mixing. The open path analyzer and particle sizer inlet were co-located with the anemometer in order to investigate the feasibility of making flux measurements of heat, momentum, water vapour, CO2, and sub-micron aerosols on the highway. These highway flux measurements are compared to stationary platform measurements made upwind and downwind of the highway. Statistical and spectral analyses are used to demonstrate the validity of the mobile measurements. Uncertainties due to flow distortion around the vehicle, under-sampling, and heterogeneity of the vertical temperature and concentrations are investigated and discussed.

A Quantum Cascade Laser-Based Optical Sensor for Continuous Monitoring of Environmental Methane in Dunkirk (France).

PubMed

Maamary, Rabih; Cui, Xiaojuan; Fertein, Eric; Augustin, Patrick; Fourmentin, Marc; Dewaele, Dorothée; Cazier, Fabrice; Guinet, Laurence; Chen, Weidong

2016-02-08

A room-temperature continuous-wave (CW) quantum cascade laser (QCL)-based methane (CH4) sensor operating in the mid-infrared near 8 μm was developed for continuous measurement of CH4 concentrations in ambient air. The well-isolated absorption line (7F2,4 ← 8F1,2) of the ν4 fundamental band of CH4 located at 1255.0004 cm(-1) was used for optical measurement of CH4 concentration by direct absorption in a White-type multipass cell with an effective path-length of 175 m. A 1σ (SNR = 1) detection limit of 33.3 ppb in 218 s was achieved with a measurement precision of 1.13%. The developed sensor was deployed in a campaign of measurements of time series CH4 concentration on a site near a suburban traffic road in Dunkirk (France) from 9th to 22nd January 2013. An episode of high CH4 concentration of up to ~3 ppm has been observed and analyzed with the help of meteorological parameters combined with back trajectory calculation using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model of NOAA.

A Quantum Cascade Laser-Based Optical Sensor for Continuous Monitoring of Environmental Methane in Dunkirk (France)

PubMed Central

Maamary, Rabih; Cui, Xiaojuan; Fertein, Eric; Augustin, Patrick; Fourmentin, Marc; Dewaele, Dorothée; Cazier, Fabrice; Guinet, Laurence; Chen, Weidong

2016-01-01

A room-temperature continuous-wave (CW) quantum cascade laser (QCL)-based methane (CH4) sensor operating in the mid-infrared near 8 μm was developed for continuous measurement of CH4 concentrations in ambient air. The well-isolated absorption line (7F2,4 ← 8F1,2) of the ν4 fundamental band of CH4 located at 1255.0004 cm−1 was used for optical measurement of CH4 concentration by direct absorption in a White-type multipass cell with an effective path-length of 175 m. A 1σ (SNR = 1) detection limit of 33.3 ppb in 218 s was achieved with a measurement precision of 1.13%. The developed sensor was deployed in a campaign of measurements of time series CH4 concentration on a site near a suburban traffic road in Dunkirk (France) from 9 to 22 January 2013. An episode of high CH4 concentration of up to ~3 ppm has been observed and analyzed with the help of meteorological parameters combined with back trajectory calculation using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model of NOAA. PMID:26867196

CH4 IPDA Lidar mission data simulator and processor for MERLIN: prototype development at LMD/CNRS/Ecole Polytechnique

NASA Astrophysics Data System (ADS)

Olivier, Chomette; Armante, Raymond; Crevoisier, Cyril; Delahaye, Thibault; Edouart, Dimitri; Gibert, Fabien; Nahan, Frédéric; Tellier, Yoann

2018-04-01

The MEthane Remote sensing Lidar missioN (MERLIN), currently in phase C, is a joint cooperation between France and Germany on the development of a spatial Integrated Path Differential Absorption (IPDA) LIDAR (LIght Detecting And Ranging) to conduct global observations of atmospheric methane. This presentation will focus on the status of a LIDAR mission data simulator and processor developed at LMD (Laboratoire de Météorologie Dynamique), Ecole Polytechnique, France, for MERLIN to assess the performances in realistic observational situations.

A taxonomy of integral reaction path analysis

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

Grcar, Joseph F.; Day, Marcus S.; Bell, John B.

2004-12-23

W. C. Gardiner observed that achieving understanding through combustion modeling is limited by the ability to recognize the implications of what has been computed and to draw conclusions about the elementary steps underlying the reaction mechanism. This difficulty can be overcome in part by making better use of reaction path analysis in the context of multidimensional flame simulations. Following a survey of current practice, an integral reaction flux is formulated in terms of conserved scalars that can be calculated in a fully automated way. Conditional analyses are then introduced, and a taxonomy for bidirectional path analysis is explored. Many examplesmore » illustrate the resulting path analysis and uncover some new results about nonpremixed methane-air laminar jets.« less

Controls on Methane Occurrences in Aquifers Overlying the Eagle Ford Shale Play, South Texas.

PubMed

Nicot, Jean-Philippe; Larson, Toti; Darvari, Roxana; Mickler, Patrick; Uhlman, Kristine; Costley, Ruth

2017-07-01

Assessing natural vs. anthropogenic sources of methane in drinking water aquifers is a critical issue in areas of shale oil and gas production. The objective of this study was to determine controls on methane occurrences in aquifers in the Eagle Ford Shale play footprint. A total of 110 water wells were tested for dissolved light alkanes, isotopes of methane, and major ions, mostly in the eastern section of the play. Multiple aquifers were sampled with approximately 47 samples from the Carrizo-Wilcox Aquifer (250-1200 m depth range) and Queen City-Sparta Aquifer (150-900 m depth range) and 63 samples from other shallow aquifers but mostly from the Catahoula Formation (depth <150 m). Besides three shallow wells with unambiguously microbial methane, only deeper wells show significant dissolved methane (22 samples >1 mg/L, 10 samples >10 mg/L). No dissolved methane samples exhibit thermogenic characteristics that would link them unequivocally to oil and gas sourced from the Eagle Ford Shale. In particular, the well water samples contain very little or no ethane and propane (C1/C2+C3 molar ratio >453), unlike what would be expected in an oil province, but they also display relatively heavier δ 13 C methane (>-55‰) and δD methane (>-180‰). Samples from the deeper Carrizo and Queen City aquifers are consistent with microbial methane sourced from syndepositional organic matter mixed with thermogenic methane input, most likely originating from deeper oil reservoirs and migrating through fault zones. Active oxidation of methane pushes δ 13 C methane and δD methane toward heavier values, whereas the thermogenic gas component is enriched with methane owing to a long migration path resulting in a higher C1/C2+C3 ratio than in the local reservoirs. © 2017, National Ground Water Association.

Measuring H2O and CO2 Emissions in the Mud Volcano region of Yellowstone using Open Path FTIR

NASA Astrophysics Data System (ADS)

Moyer, D. K.; Sealing, C. R.; Carn, S. A.; Vanderkluysen, L.

2017-12-01

Magma degassing is an important factor in many aspects of monitoring active volcanic zones and mitigating associated hazards. The monitoring of these emissions in concentration, flux, and species ratios is important for detecting signs of unrest as well as understanding the natural cycle and budget of volatile species. However, standard gas measurement methods suffer from either low temporal resolution (e.g., direct sampling of fumaroles) or are limited to measuring a small range of species (e.g., MiniDOAS, MultiGAS). In order to establish a carbon budget of active gas sources at a volcano with a dynamic hydrothermal system, we carried out a survey of mud pots and fumaroles at Yellowstone National Park using Open-Path Fourier Transform Infrared Spectroscopy, or OP-FTIR, which allows for a temporal resolution as low as one measurement every 10 seconds. We placed an active infrared (IR) source behind the target gas plume and identified gas species from the presence of their absorption feature in measured spectra in the 2.5 to 25 µm range. From these, we derived pathlength concentrations for a wide range of gases, including: water vapor, carbon dioxide, and methane. During our September 2016 campaign in the Mud Volcano thermal area, we measured CO2 concentrations of 400 ppm in emissions from the Churning Cauldron acid-sulfate mud pot, with an H2O/CO2 ratio of 8; at Sulphur Cauldron and One Hundred Springs Plain, CO2 concentrations reached 200 ppm above background atmospheric values. We derived a CO2 flux of 8.15 T/d, 0.43 T/d and .00025 T/d, respectively, at these three acid-sulfate sources, within range of gas channeling-based estimates from the late 1990s. Previous accumulation chamber studies estimate the CO2 soil diffuse degassing in the Mud Volcano thermal region at 283.15 T/d, indicating that mud pots are minor contributors of CO2 emissions in this area, representing 3% of diffuse emissions. Due to the high acquisition rate and the abundance of water droplets in the plume, spectra were too noisy to reliably detect methane at these locations. Future work will focus on the measurement of trace gases at these same locations by increasing the acquisition time.

Emergence and stability of intermediate open vesicles in disk-to-vesicle transitions.

PubMed

Li, Jianfeng; Zhang, Hongdong; Qiu, Feng; Shi, An-Chang

2013-07-01

The transition between two basic structures, a disk and an enclosed vesicle, of a finite membrane is studied by examining the minimum energy path (MEP) connecting these two states. The MEP is constructed using the string method applied to continuum elastic membrane models. The results reveal that, besides the commonly observed disk and vesicle, open vesicles (bowl-shaped vesicles or vesicles with a pore) can become stable or metastable shapes. The emergence, stability, and probability distribution of these open vesicles are analyzed. It is demonstrated that open vesicles can be stabilized by higher-order elastic energies. The estimated probability distribution of the different structures is in good agreement with available experiments.

Geochemical study of groundwater at Sandia National Laboratories/New Mexico and Kirtland Air Force Base

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

NONE

The U.S. Department of Energy (DOE) Grand Junction Projects Office (GJPO) and its contractor, Rust Geotech, support the Kirtland Area Office by assisting Sandia National Laboratories/New Mexico (Sandia/NM) with remedial action, remedial design, and technical support of its Environmental Restoration Program. To aid in determining groundwater origins and flow paths, the GJPO was tasked to provide interpretation of groundwater geochemical data. The purpose of this investigation was to describe and analyze the groundwater geochemistry of the Sandia/NM Kirtland Air Force Base (KAFB). Interpretations of groundwater origins are made by using these data and the results of {open_quotes}mass balance{close_quotes} and {open_quotes}reactionmore » path{close_quote} modeling. Additional maps and plots were compiled to more fully comprehend the geochemical distributions. A more complete set of these data representations are provided in the appendices. Previous interpretations of groundwater-flow paths that were based on well-head, geologic, and geochemical data are presented in various reports and were used as the basis for developing the models presented in this investigation.« less

Hyperconnectivity, Attribute-Space Connectivity and Path Openings: Theoretical Relationships

NASA Astrophysics Data System (ADS)

Wilkinson, Michael H. F.

In this paper the relationship of hyperconnected filters with path openings and attribute-space connected filters is studied. Using a recently developed axiomatic framework based on hyperconnectivity operators, which are the hyperconnected equivalents of connectivity openings, it is shown that path openings are a special case of hyperconnected area openings. The new axiomatics also yield insight into the relationship between hyperconnectivity and attribute-space connectivity. It is shown any hyperconnectivity is an attribute-space connectivity, but that the reverse is not true.

A conduit dilation model of methane venting from lake sediments

USGS Publications Warehouse

Scandella, B.P.; Varadharajan, C.; Hemond, Harold F.; Ruppel, C.; Juanes, R.

2011-01-01

Methane is a potent greenhouse gas, but its effects on Earth's climate remain poorly constrained, in part due to uncertainties in global methane fluxes to the atmosphere. An important source of atmospheric methane is the methane generated in organic-rich sediments underlying surface water bodies, including lakes, wetlands, and the ocean. The fraction of the methane that reaches the atmosphere depends critically on the mode and spatiotemporal characteristics of free-gas venting from the underlying sediments. Here we propose that methane transport in lake sediments is controlled by dynamic conduits, which dilate and release gas as the falling hydrostatic pressure reduces the effective stress below the tensile strength of the sediments. We test our model against a four-month record of hydrostatic load and methane flux in Upper Mystic Lake, Mass., USA, and show that it captures the complex episodicity of methane ebullition. Our quantitative conceptualization opens the door to integrated modeling of methane transport to constrain global methane release from lakes and other shallow-water, organic-rich sediment systems, and to assess its climate feedbacks.

Development of a Miniaturized and Portable Methane Analyzer for Natural Gas Leak Walking Surveys

NASA Astrophysics Data System (ADS)

Huang, Y. W.; Leen, J. B.; Gupta, M.; Baer, D. S.

2016-12-01

Traditional natural gas leak walking surveys have been conducted with devices that are based on technologies such as flame ionization detector (FID), IR-based spectrometer and IR camera. The sensitivity is typically on the ppm level. The low sensitivity means the device cannot pick up leaks far from it, and more time is spent surveying the area before pinpointing the leak location. A miniaturized methane analyzer has been developed to significantly improve the sensitivity of the device used in walking surveys to detect natural gas leaks at greater distance. ABB/LGR's patented Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS) is utilized to offer rugged and highly sensitive methane detection in a portable package. The miniaturized package weighs 13.5 lb, with a 4-hour rechargeable battery inside. The precision of the analyzer for methane is 2 ppb at 1 second. The analyzer operates at 10 Hz and its flow response time is 3 seconds for measurements through a 1-meter long sampling wand to registering on the data stream. The data can be viewed in real-time on a tablet or a smartphone. The compact and simplified package of the methane analyzer allows for more efficient walking surveys. It also allows for other applications that require low-power, low-weight and a portable package. We present data from walking surveys to demonstrate its ability to detect methane leaks.

Interpretation of the Near-IR Spectra of the Kuiper Belt Object

NASA Technical Reports Server (NTRS)

Eluszkiewicz, Janusz; Cady-Pereira, Karen; Brown, Michael E.; Stansberry, John A.

2007-01-01

Visible and near-IR observations of the Kuiper Belt Object (136472) 2005 FY(9) have indicated the presence of unusually long (1 cm or more) optical path lengths in a layer of methane ice. Using microphysical and radiative transfer modeling, we show that even at the frigid temperatures in the outer reaches of the solar system, a slab of low porosity methane ice can indeed form by pressureless sintering of micron-sized grains, and it can qualitatively reproduce the salient features of the measured spectra. A good semiquantitative match with the near-IR spectra can be obtained with a realistic slab model, provided the spectra are scaled to a visible albedo of 0.6, at the low end of the values currently estimated from Spitzer thermal measurements. Consistent with previous modeling studies, matching spectra scaled to higher albedos requires the incorporation of strong backscattering effects. The albedo may become better constrained through an iterative application of the slab model to the analysis of the thermal measurements from Spitzer and the visible/near-IR reflectance spectra. The slab interpretation offers two falsifiable predictions (1) Absence of an opposition surge, which is commonly attributed to the fluffiness of the optical surface. This prediction is best testable with a spacecraft, as Earth-based observations at true opposition will not be possible until early next century. (2) Unlikelihood of the simultaneous occurrence of very long spectroscopic path lengths in both methane and nitrogen ice on the surface of any Kuiper Belt Object, as the more volatile nitrogen would hinder densification in methane ice.

Atmospheric Effects on Radio Frequency (RF) Wave Propagation in a Humid, Near-Surface Environment

DTIC Science & Technology

2010-03-01

additional IR temperature and Campbell water temperature probes, as well as a 3-D sonic anemometer, pyranometer , and LI-COR open path gas analyzer for...Zonen CNR-1 pyranometer . Lastly, the Campbell sonic anemometer (CSAT3) and LI- COR (CS7500) were extended 2.5 meters over the water from an

Methane Line Intensities: Near and Far IR

NASA Astrophysics Data System (ADS)

Brown, Linda R.; Devi, V. Malathy; Wishnow, Edward H.; Sung, Keeyoon; Crawford, Timothy J.; Mantz, Arlan W.; Smith, Mary Ann H.; Predoi-Cross, Adriana; Benner, D. Chris

2014-11-01

Accurate knowledge of line intensities is crucial input for radiance calculations to interpret atmospheric observations of planets and moons. We have therefore undertaken extensive laboratory studies to measure the methane spectrum line-by-line in order to improve theoretical quantum mechanical modeling for molecular spectroscopy databases (e. g. HITRAN and GEISA) used by planetary astronomers. Preliminary results will be presented for selected ro-vibrational transitions in both the near-IR (1.66 and 2.2 - 2.4 microns) and the far-IR (80 - 120 microns) regions. For this, we have recorded high-resolution spectra (instrumental resolving power: 1,300,000 (NIR) and 10,000 (FIR)) with the Bruker 125HR Fourier transform spectrometer at JPL using isotopically-enriched 12CH4 and 13CH4, as well as normal methane samples. For the NIR wavelengths, three different absorption cells have been employed to achieve sample temperatures ranging from 78 K to 299 K: 1) a White cell set to a path length of 13.09 m for room temperature data, 2) a single-pass 0.2038 m cold cell and 3) a new coolable Herriott cell with a fixed 20.941 m optical path and configured for the first time to a FT-IR spectrometer. For the Far-IR, another coolable absorption chamber set to a 52 m optical path has been used. These new experiments and intensity measurements will be presented and discussed.Part of the research described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology, the University of California, Berkeley, Connecticut College, and NASA Langley under contracts and grants with the National Aeronautics and Space Administration. A. Predoi-Cross and her research group have been supported by the National Science and Engineering Research Council of Canada.

40 CFR 86.1221-90 - Hydrocarbon analyzer calibration.

Code of Federal Regulations, 2012 CFR

2012-07-01

... methane. When the FID analyzer to be used for the analysis of natural gas-fueled vehicle hydrocarbon... and liquefied petroleum gas-fuel shall be optimized using propane. Analyzers used with natural gas... air (or methane in air as appropriate) calibration gases having nominal concentrations of 15, 30, 45...

40 CFR 86.1221-90 - Hydrocarbon analyzer calibration.

Code of Federal Regulations, 2013 CFR

2013-07-01

... methane. When the FID analyzer to be used for the analysis of natural gas-fueled vehicle hydrocarbon... and liquefied petroleum gas-fuel shall be optimized using propane. Analyzers used with natural gas... air (or methane in air as appropriate) calibration gases having nominal concentrations of 15, 30, 45...

Development of a Field-Deployable Methane Carbon Isotope Analyzer

NASA Astrophysics Data System (ADS)

Dong, Feng; Baer, Douglas

2010-05-01

Methane is a potent greenhouse gas, whose atmospheric surface mixing ratio has almost doubled compared with preindustrial values. Methane can be produced by biogenic processes, thermogenic processes or biomass, with different isotopic signatures. As a key molecule involved in the radiative forcing in the atmosphere, methane is thus one of the most important molecules linking the biosphere and atmosphere. Therefore precise measurements of mixing ratios and isotopic compositions will help scientists to better understand methane sources and sinks. To date, high precision isotope measurements have been exclusively performed with conventional isotope ratio mass spectrometry, which involves intensive labor and is not readily field deployable. Optical studies using infrared laser spectroscopy have also been reported to measure the isotopic ratios. However, the precision of optical-based analyses, to date, is typically unsatisfactory without pre-concentration procedures. We present characterization of the performance of a portable Methane Carbon Isotope Analyzer (MCIA), based on cavity enhanced laser absorption spectroscopy technique, that provides in-situ measurements of the carbon isotope ratio (13C/12C or del_13C) and methane mixing ratio (CH4). The sample is introduced to the analyzer directly without any requirement for pretreatment or preconcentration. A typical precision of less than 1 per mill (< 0.1%) with a 10-ppm methane sample can be achieved in a measurement time of less than 100 seconds. The MCIA can report carbon isotope ratio and concentration measurements over a very wide range of methane concentrations. Results of laboratory tests and field measurements will be presented.

Methane flux from the central Amazonian floodplain

NASA Technical Reports Server (NTRS)

Bartlett, Karen B.; Crill, Patrick M.; Sebacher, Daniel I.; Harriss, Robert C.; Wilson, John O.

1988-01-01

A total of 186 methane measurements from the three primary Amazon floodplain environments of open water lakes, flood forests, and floating grass mats were made over the period 18 July through 2 September 1985. These data indicate that emissions were lowest over open water lakes. Flux from flooded forests and grass mats was significantly higher. At least three transport processes contribute to tropospheric emissions: ebullition from sediments, diffusion along the concentration gradient from sediment to overlaying water to air, and transport through the roots and stems of aquatic plants. Measurements indicate that the first two of these processes are most significant. It was estimated that on the average bubbling makes up 49 percent of the flux from open water, 54 percent of that from flooded forests, and 64 percent of that from floating mats. If the measurements were applied to the entire Amazonian floodplain, it is calculated that the region could supply up to 12 percent of the estimated global natural sources of methane.

Project Morpheus Main Engine Development and Preliminary Flight Testing

NASA Technical Reports Server (NTRS)

Morehead, Robert L.

2011-01-01

A LOX/Methane rocket engine was developed for a prototype terrestrial lander and then used to fly the lander at Johnson Space Center. The development path of this engine is outlined, including unique items such as variable acoustic damping and variable film cooling.

Environmental control of methane fluxes over a Danish peatland

NASA Astrophysics Data System (ADS)

Herbst, M.; Ringgaard, R.; Friborg, T.; Soegaard, H.

2009-12-01

Reducing the greenhouse gas (GHG) emissions from natural and anthropogenic environments has become a key issue over the last decades. In Denmark the management of the wetlands is playing a key role in these attempts. The wetland area of Skjern Meadows in the western part of Denmark is one of the best known examples of peatland restauration in northern Europe. The valley of the Skjern river was restored in 2002, after it had been drained for about 35 years. A micrometeorological instrument mast was erected in the centre of the 2200 ha large area in the summer of 2008, in order to facilitate continuous eddy covariance measurements of the exchange of carbon dioxide and methane between the peatland and the atmosphere. A sonic anemometer (R3, Gill) was used together with a closed-path CO2 analyzer (LI-7000, Li-Cor) and a closed-path CH4 analyzer (DLT-100, Los Gatos). A measurement height of 7 m above the surface ensures that the observed eddy fluxes represent an average signal from the entire peatland. The first year of data collection confirmed the expectation that the area functions as a moderate CO2 sink, whilst it releases methane into the atmosphere. During a 12-months period starting in September 2008, the wetland removed 119 g CO2-C per m2 from the atmosphere and emitted 6 g CH4-C per m2. If the amount of the emitted CH4 is converted into CO2 equivalents, it remained lower than the annual CO2 uptake (188 versus 437 g CO2). This means that the restored peatland functions as a weak greenhouse gas sink, despite its methane production. Whilst the annual CO2 uptake at Skjern Meadows was similar to that reported by Friborg et al. (2003) for a Siberian wetland, the CH4 emission was much lower. The average CO2 and CH4 flux rates were both lower than those estimated for a Dutch wetland by Hendriks et al. (2007). The CH4 emission showed no particular diurnal pattern, but daily rates varied considerably throughout the year. This variability can be correlated to variations in the soil temperature, the water level and the carbon fixation rates of the vegetation. The highest CH4 emission rates with peak values around 160 mg m-2d-1 were observed in the late summer and early autumn of 2008, after the site had experienced a prolonged period of high rainfall while the temperature was still high. In contrast, CH4 emission rates never exceeded 20 mg m-2d-1 during the winter and the unusually dry spring of 2009. An exponential relationship was found between the soil temperature in 0.2 m depth and the methane flux into the atmosphere. A comparison of this relation with complementary observations from other studies indicates that a general temperature response function for the CH4 emission from northern peatlands can be developed. If such a response function can be validated for other sites as well, it would be a big step towards an improved predictability of the full greenhouse gas budget of northern peatlands in a changing climate. References: Friborg T, Søgaard H, Christensen TR, Lloyd CR, Panikov NS (2003) Siberian wetlands: Where a sink is a source. Geophys. Res. Letters, Vol. 30, No. 21, 2129. Hendriks DMD, van Huissteden J, Dolman AJ, van der Molen MK (2007) The full greenhouse gas balance of an abandoned peat meadow. Biogeosciences 4, 411-424.

Role of microorganisms for cycling of atmospheric constituents, emphasizing the greenhouse gas methane (Invited)

NASA Astrophysics Data System (ADS)

Conrad, R.

2013-12-01

Microorganisms have contributed significantly to the formation of the atmosphere and the habitability of Earth. Microbial methanogenesis probably helped overcoming the faint sun problem on young Earth. Later on, cyanobacterial photosynthesis produced oxygen and thus restricted the life zone of methanogenic microbial communities, which nowadays contribute only about 1% to total carbon cycle. Nevertheless, methanogenesis still dominates the budget of atmospheric methane and contributes significantly to the greenhouse effect. There are numerous habitats, which exchange methane with the atmosphere, and even more in which methane is intensively cycled albeit little emitted. Methane can be a byproduct of chemical reactions in plant leaves, or of aerobic methyl phosphonate consumption in ocean water. Most commonly, however, methane is a stoichiometric catabolic product in the degradation of organic matter by anaerobic microorganisms. The degradation is achieved by a complex microbial community consisting of various species of hydrolytic and fermentative Bacteria that produce hydrogen, carbon dioxide and acetate as major end products, and of methanogenic Archaea that eventually convert these compounds to methane and carbon dioxide. The composition of such methanogenic microbial communities, the rates and paths of methane formation, and the isotopic composition of the produced methane all exhibit quite some variability across the different habitats in which methane is produced from organic matter decomposition, such as flooded soils, lake sediments, peatlands, animal gut systems. The structure of the microbial communities often strongly affects their function. It is a challenging task to understand the environmental and biochemical basis of the interactions of abiotic factors and microorganisms shaping the structure and function of the microbial communities in the different methanogenic habitats.

In situ study of mass transfer in aqueous solutions under high pressures via Raman spectroscopy: A new method for the determination of diffusion coefficients of methane in water near hydrate formation conditions

USGS Publications Warehouse

Lu, W.J.; Chou, I.-Ming; Burruss, R.C.; Yang, M.Z.

2006-01-01

A new method was developed for in situ study of the diffusive transfer of methane in aqueous solution under high pressures near hydrate formation conditions within an optical capillary cell. Time-dependent Raman spectra of the solution at several different spots along the one-dimensional diffusion path were collected and thus the varying composition profile of the solution was monitored. Diffusion coefficients were estimated by the least squares method based on the variations in methane concentration data in space and time in the cell. The measured diffusion coefficients of methane in water at the liquid (L)-vapor (V) stable region and L-V metastable region are close to previously reported values determined at lower pressure and similar temperature. This in situ monitoring method was demonstrated to be suitable for the study of mass transfer in aqueous solution under high pressure and at various temperature conditions and will be applied to the study of nucleation and dissolution kinetics of methane hydrate in a hydrate-water system where the interaction of methane and water would be more complicated than that presented here for the L-V metastable condition. ?? 2006 Society for Applied Spectroscopy.

System and method for multi-stage bypass, low operating temperature suppressor for automatic weapons

DOEpatents

Moss, William C.; Anderson, Andrew T.

2015-06-09

The present disclosure relates to a suppressor for use with a weapon. The suppressor may be formed to have a body portion having a bore extending concentric with a bore axis of the weapon barrel. An opening in the bore extends at least substantially circumferentially around the bore. A flow path communicates with the opening and defines a channel for redirecting gasses flowing in the bore out from the bore, through the opening, into a rearward direction in the flow path. The flow path raises a pressure at the opening to generate a Mach disk within the bore at a location approximately coincident with the opening. The Mach disk forms as a virtual baffle to divert at least a portion of the gasses into the opening and into the flow path.

True eddy accumulation and eddy covariance methods and instruments intercomparison for fluxes of CO2, CH4 and H2O above the Hainich Forest

NASA Astrophysics Data System (ADS)

Siebicke, Lukas

2017-04-01

The eddy covariance (EC) method is state-of-the-art in directly measuring vegetation-atmosphere exchange of CO2 and H2O at ecosystem scale. However, the EC method is currently limited to a small number of atmospheric tracers by the lack of suitable fast-response analyzers or poor signal-to-noise ratios. High resource and power demands may further restrict the number of spatial sampling points. True eddy accumulation (TEA) is an alternative method for direct and continuous flux observations. Key advantages are the applicability to a wider range of air constituents such as greenhouse gases, isotopes, volatile organic compounds and aerosols using slow-response analyzers. In contrast to relaxed eddy accumulation (REA), true eddy accumulation (Desjardins, 1977) has the advantage of being a direct method which does not require proxies. True Eddy Accumulation has the potential to overcome above mentioned limitations of eddy covariance but has hardly ever been successfully demonstrated in practice in the past. This study presents flux measurements using an innovative approach to true eddy accumulation by directly, continuously and automatically measuring trace gas fluxes using a flow-through system. We merge high-frequency flux contributions from TEA with low-frequency covariances from the same sensors. We show flux measurements of CO2, CH4 and H2O by TEA and EC above an old-growth forest at the ICOS flux tower site "Hainich" (DE-Hai). We compare and evaluate the performance of the two direct turbulent flux measurement methods eddy covariance and true eddy accumulation using side-by-side trace gas flux observations. We further compare performance of seven instrument complexes, i.e. combinations of sonic anemometers and trace gas analyzers. We compare gas analyzers types of open-path, enclosed-path and closed-path design. We further differentiate data from two gas analysis technologies: infrared gas analysis (IRGA) and laser spectrometry (open path and CRDS closed-path laser spectrometers). We present results of CO2 and H2O fluxes from the following six instruments, i.e. combinations of sonic anemometers/gas analyzers (and methods): METEK-uSonic3/Picarro-G2301 (TEA), METEK-uSonic3/LI-7500 (EC), Gill-R3/LI-6262 (EC), Gill-R3/LI-7200 (EC), Gill-HS/LI-7200 (EC), Gill-R3/LGR-FGGA (EC). Further, we present results of much more difficult to measure CH4 fluxes from the following three instruments, i.e. combinations of sonic anemometers/gas analyzers (and methods): METEK-uSonic3/Picarro-G2301 (TEA), Gill-R3/LI-7700 (EC), Gill-R3/LGR-FGGA (EC). We observed that CO2, CH4 and H2O fluxes from the side-by-side measurements by true eddy accumulation and eddy covariance methods correlated well. Secondly, the difference between the TEA and EC methods using the same sonic anemometer but different gas analyzer was often smaller than the mismatch of the various side-by-side eddy covariance measurements using different sonic anemometers and gas analyzers. Signal-to-noise ratios of CH4 fluxes from the true eddy accumulation system system were superior to both eddy covariance sensors (open-path LI-7700 and closed-path CRDS LGR-FGGA sensors). We conclude that our novel implementation of the true eddy accumulation method demonstrated high signal-to-noise ratios, applicability to slow-response gas analyzers, small power consumption and direct proxy-free ecosystem-scale trace gas flux measurements of CO2, CH4 and H2O. The current results suggest that true eddy accumulation would be suitable and should be applied as the method-of-choice for direct flux measurements of a large number of atmospheric constituents beyond CO2 and H2O, including isotopes, aerosols, volatile organic compounds and other trace gases for which eddy covariance might not be a viable alternative. We will further develop true eddy accumulation as a novel approach using multiplexed systems for spatially distributed flux measurements.

The application of UV LEDs for differential optical absorption spectroscopy

NASA Astrophysics Data System (ADS)

Geiko, Pavel P.; Smirnov, Sergey S.; Samokhvalov, Ignatii V.

2018-04-01

Modern UV LEDs represent a potentially very advantageous alternative to thermal light sources, in particular xenon arc lamps, which are the most common light sources in trace gas-analyzers. So, the light-emitting diodes are very attractive for use of as light sources for Long Path Differential Optical Absorption Spectroscopy (DOAS) measurements of trace gases in the open atmosphere. Recent developments in fibre-coupling telescope technology and the availability of ultraviolet light emitting diodes have now allowed us to construct a portable, long path DOAS instrument for use at remote locations and specifically for measuring degassing from active volcanic systems. First of all, we are talking about the measurement of sulphur dioxide, carbon disulphide and, oxides of chlorine and bromine. The parallel measurements of sulfur dioxide using a certified gas analyzer, were conducted and showed good correlation.

New Remote Gas Sensor Using Rapid Electro-Optical Path Switching

NASA Technical Reports Server (NTRS)

Sachse, G. W.; Lebel, P. J.; Wallio, H. A.; Vay, S. A.; Wang, L. G.

1994-01-01

Innovative gas filter correlation radiometer (GFCR) features nonmechanical switching of internal optical paths. Incoming radiation switched electro-optically, by means of polarization, between two optical paths, one of which contains correlation gas cell while other does not. Advantages include switching speed, 2 to 3 orders of magnitude faster than mechanical techniques, and high reliability. Applications include regional studies of atmospheric chemistry from either manned or unmanned aircraft as well as satellite studies of global distributions, sources and sink mechanisms for key species involved in chemistry of troposphere. Commercial applications: ability to survey many miles of natural gas pipelines rapidly from aircraft, pinpointing gas leaks by measuring methane at 2.3 micrometers.

Methane clumped isotopes: Progress and potential for a new isotopic tracer

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

Douglas, Peter M. J.; Stolper, Daniel A.; Eiler, John M.

The isotopic composition of methane is of longstanding geochemical interest, with important implications for understanding hydrocarbon systems, atmospheric greenhouse gas concentrations, the global carbon cycle, and life in extreme environments. Recent analytical developments focusing on multiply substituted isotopologues (‘clumped isotopes’) are opening a potentially valuable new window into methane geochemistry. When methane forms in internal isotopic equilibrium, clumped isotopes can provide a direct record of formation temperature, making this property particularly valuable for identifying different methane origins. However, it has also become clear that in certain settings methane clumped isotope measurements record kinetic rather than equilibrium isotope effects. Here wemore » present a substantially expanded dataset of methane clumped isotope analyses, and provide a synthesis of the current interpretive framework for this parameter. We review different processes affecting methane clumped isotope compositions, describe the relationships between conventional isotope and clumped isotope data, and summarize the types of information that this measurement can provide in different Earth and planetary environments.« less

ARC-1986-AC86-7014

NASA Image and Video Library

1986-01-22

Range : 2.7 million miles (1.7 million miles) P-29497C Tis Voyager 2, false color composite of Uranus demonstrates the usefulness of special filters in the Voyager cameras for revealing the presence of high altitude hazes in Uranus' atmosphere. The picture is a composite of images obtained through the single orange and two methane filters of Voyager's wide angle camera. Orange, short wavelength and long wavelength methane images are displayed, retrospectively, as blue, green, and orange. The pink area centered on the pole is due to the presence of hazes high in the atmosphere that reflect the light before it has traversed a long enough path through the atmosphere to suffer absorbtion by methane gas. The bluest region at mid-latitude represent the most haze free regions on Uranus, thus, deeper cloud levels can be detected in these areas.

Expanding Education and Workforce Opportunities through Digital Badges

ERIC Educational Resources Information Center

Alliance for Excellent Education, 2013

2013-01-01

In the twenty-first century, learning takes place almost everywhere, at all times, on all kinds of paths and at all kinds of paces. With the click of a mouse or the touch of a screen, young people and adults can access a wealth of information, analyze it, and produce new knowledge at any time. These learning opportunities break wide open the…

Assessing the Accuracy of the Tracer Dilution Method with Atmospheric Dispersion Modeling

NASA Astrophysics Data System (ADS)

Taylor, D.; Delkash, M.; Chow, F. K.; Imhoff, P. T.

2015-12-01

Landfill methane emissions are difficult to estimate due to limited observations and data uncertainty. The mobile tracer dilution method is a widely used and cost-effective approach for predicting landfill methane emissions. The method uses a tracer gas released on the surface of the landfill and measures the concentrations of both methane and the tracer gas downwind. Mobile measurements are conducted with a gas analyzer mounted on a vehicle to capture transects of both gas plumes. The idea behind the method is that if the measurements are performed far enough downwind, the methane plume from the large area source of the landfill and the tracer plume from a small number of point sources will be sufficiently well-mixed to behave similarly, and the ratio between the concentrations will be a good estimate of the ratio between the two emissions rates. The mobile tracer dilution method is sensitive to different factors of the setup such as placement of the tracer release locations and distance from the landfill to the downwind measurements, which have not been thoroughly examined. In this study, numerical modeling is used as an alternative to field measurements to study the sensitivity of the tracer dilution method and provide estimates of measurement accuracy. Using topography and wind conditions for an actual landfill, a landfill emissions rate is prescribed in the model and compared against the emissions rate predicted by application of the tracer dilution method. Two different methane emissions scenarios are simulated: homogeneous emissions over the entire surface of the landfill, and heterogeneous emissions with a hot spot containing 80% of the total emissions where the daily cover area is located. Numerical modeling of the tracer dilution method is a useful tool for evaluating the method without having the expense and labor commitment of multiple field campaigns. Factors tested include number of tracers, distance between tracers, distance from landfill to transect path, and location of tracers with respect to the hot spot. Results show that location of the tracers relative to the hot spot of highest landfill emissions makes the largest difference in accuracy of the tracer dilution method.

Chirped Laser Dispersion Spectroscopy for Remote Open-Path Trace-Gas Sensing

PubMed Central

Nikodem, Michal; Wysocki, Gerard

2012-01-01

In this paper we present a prototype instrument for remote open-path detection of nitrous oxide. The sensor is based on a 4.53 μm quantum cascade laser and uses the chirped laser dispersion spectroscopy (CLaDS) technique for molecular concentration measurements. To the best of our knowledge this is the first demonstration of open-path laser-based trace-gas detection using a molecular dispersion measurement. The prototype sensor achieves a detection limit down to the single-ppbv level and exhibits excellent stability and robustness. The instrument characterization, field deployment performance, and the advantages of applying dispersion sensing to sensitive trace-gas detection in a remote open-path configuration are presented. PMID:23443389

Chirped laser dispersion spectroscopy for remote open-path trace-gas sensing.

PubMed

Nikodem, Michal; Wysocki, Gerard

2012-11-28

In this paper we present a prototype instrument for remote open-path detection of nitrous oxide. The sensor is based on a 4.53 μm quantum cascade laser and uses the chirped laser dispersion spectroscopy (CLaDS) technique for molecular concentration measurements. To the best of our knowledge this is the first demonstration of open-path laser-based trace-gas detection using a molecular dispersion measurement. The prototype sensor achieves a detection limit down to the single-ppbv level and exhibits excellent stability and robustness. The instrument characterization, field deployment performance, and the advantages of applying dispersion sensing to sensitive trace-gas detection in a remote open-path configuration are presented.

Electrical resistance tomography during in-situ trichloroethylene remediation at the Savannah River Site

NASA Astrophysics Data System (ADS)

Daily, W.; Ramirez, A.

1995-04-01

Electrical resistance tomography was used to monitor in-situ remediation processes for removal of volatile organic compounds from subsurface water and soil at the Savannah River Site near Aiken, South Carolina. This work was designed to test the feasibility of injecting a weak mixture of methane in air as a metabolic carbon source for natural microbial populations which are capable of trichloroethylene degradation. Electrical resistance tomograms were constructed of the subsurface during the test to provide detailed images of the process. These images were made using an iterative reconstruction algorithm based on a finite element forward model and Newton-type least-squares minimization. Changes in the subsurface resistivity distribution were imaged by a pixel-by-pixel subtraction of images taken before and during the process. This differential tomography removed all static features of formation resistivity but clearly delineated dynamic features induced by remediation processes. The air-methane mixture was injected into the saturated zone and the intrained air migration paths were tomographically imaged by the increased resistivity of the path as air displaced formation water. We found the flow paths to be confined to a complex three-dimensional network of channels, some of which extended as far as 30 m from the injection well. These channels were not entirely stable over a period of months since new channels appeared to form with time. Also, the resistivity of the air injection paths increased with time. In another series of tests, resistivity images of water infiltration from the surface support similar conclusions about the preferential permeability paths in the vadose zone. In this case, the water infiltration front is confined to narrow channels which have a three-dimensional structure. Here, similar to air injection in the saturated zone, the water flow is controlled by local variations in formation permeability. However, temporal changes in these channels are minor, indicating that the permeable paths do not seem to be modified by continued infiltration.

Observations of the release of non-methane hydrocarbons from fractured shale.

PubMed

Sommariva, Roberto; Blake, Robert S; Cuss, Robert J; Cordell, Rebecca L; Harrington, Jon F; White, Iain R; Monks, Paul S

2014-01-01

The organic content of shale has become of commercial interest as a source of hydrocarbons, owing to the development of hydraulic fracturing ("fracking"). While the main focus is on the extraction of methane, shale also contains significant amounts of non-methane hydrocarbons (NMHCs). We describe the first real-time observations of the release of NMHCs from a fractured shale. Samples from the Bowland-Hodder formation (England) were analyzed under different conditions using mass spectrometry, with the objective of understanding the dynamic process of gas release upon fracturing of the shale. A wide range of NMHCs (alkanes, cycloalkanes, aromatics, and bicyclic hydrocarbons) are released at parts per million or parts per billion level with temperature- and humidity-dependent release rates, which can be rationalized in terms of the physicochemical characteristics of different hydrocarbon classes. Our results indicate that higher energy inputs (i.e., temperatures) significantly increase the amount of NMHCs released from shale, while humidity tends to suppress it; additionally, a large fraction of the gas is released within the first hour after the shale has been fractured. These findings suggest that other hydrocarbons of commercial interest may be extracted from shale and open the possibility to optimize the "fracking" process, improving gas yields and reducing environmental impacts.

Seasonal dynamics of methane emissions from a subarctic fen in the Hudson Bay Lowlands

NASA Astrophysics Data System (ADS)

Hanis, K. L.; Tenuta, M.; Amiro, B. D.; Papakyriakou, T. N.

2013-03-01

Ecosystem-scale methane (CH4) flux (FCH4) over a subarctic fen at Churchill, Manitoba, Canada was measured to understand the magnitude of emissions during spring and fall shoulder seasons, and the growing season in relation to physical and biological conditions. FCH4 was measured using eddy covariance with a closed-path analyzer in four years (2008-2011). Cumulative measured annual FCH4 (shoulder plus growing seasons) ranged from 3.0 to 9.6 g CH4 m-2 yr-1 among the four study years, with a mean of 6.5 to 7.1 g CH4 m-2 yr-1 depending upon gap-filling method. Soil temperatures to depths of 50 cm and air temperature were highly correlated with FCH4, with near surface soil temperature at 5 cm most correlated across spring, fall, and the whole season. The response of FCH4 to soil temperature at the 5 cm depth and air temperature was more than double in spring to that of fall. Emission episodes were generally not observed during spring thaw. Growing season emissions also depended upon soil and air temperatures but water table also exerted influence with FCH4 highest when water was 2-13 cm below and least when it was at or above the mean peat surface.

Binding of methane to activated mineral surfaces - a methane sink on Mars?

NASA Astrophysics Data System (ADS)

Nørnberg, P.; Knak Jensen, S. J.; Skibsted, J.; Jakobsen, H. J.; ten Kate, I. L.; Gunnlaugsson, H. P.; Merrison, J. P.; Finster, K.; Bak, Ebbe; Iversen, J. J.; Kondrup, J. C.

2015-10-01

Tumbling experiments that simulate the wind erosion of quartz grains in an atmosphere of 13 C-enriched methane are reported. The eroded grains are analyzed by 13C and 29 Si solid-state NMR techniques after several months of tumbling. The analysis shows that methane has reacted with the eroded surface to form covalent Si-CH3 bonds, which stay intact for temperatures up to at least 250oC. These findings offer a model for a methane sink that might explain the fast disappearance of methane on Mars.

Comparison of two closed-path cavity-based spectrometers for measuring air-water CO2 and CH4 fluxes by eddy covariance

NASA Astrophysics Data System (ADS)

Yang, Mingxi; Prytherch, John; Kozlova, Elena; Yelland, Margaret J.; Parenkat Mony, Deepulal; Bell, Thomas G.

2016-11-01

In recent years several commercialised closed-path cavity-based spectroscopic instruments designed for eddy covariance flux measurements of carbon dioxide (CO2), methane (CH4), and water vapour (H2O) have become available. Here we compare the performance of two leading models - the Picarro G2311-f and the Los Gatos Research (LGR) Fast Greenhouse Gas Analyzer (FGGA) at a coastal site. Both instruments can compute dry mixing ratios of CO2 and CH4 based on concurrently measured H2O, temperature, and pressure. Additionally, we used a high throughput Nafion dryer to physically remove H2O from the Picarro airstream. Observed air-sea CO2 and CH4 fluxes from these two analysers, averaging about 12 and 0.12 mmol m-2 day-1 respectively, agree within the measurement uncertainties. For the purpose of quantifying dry CO2 and CH4 fluxes downstream of a long inlet, the numerical H2O corrections appear to be reasonably effective and lead to results that are comparable to physical removal of H2O with a Nafion dryer in the mean. We estimate the high-frequency attenuation of fluxes in our closed-path set-up, which was relatively small ( ≤ 10 %) for CO2 and CH4 but very large for the more polar H2O. The Picarro showed significantly lower noise and flux detection limits than the LGR. The hourly flux detection limit for the Picarro was about 2 mmol m-2 day-1 for CO2 and 0.02 mmol m-2 day-1 for CH4. For the LGR these detection limits were about 8 and 0.05 mmol m-2 day-1. Using global maps of monthly mean air-sea CO2 flux as reference, we estimate that the Picarro and LGR can resolve hourly CO2 fluxes from roughly 40 and 4 % of the world's oceans respectively. Averaging over longer timescales would be required in regions with smaller fluxes. Hourly flux detection limits of CH4 from both instruments are generally higher than the expected emissions from the open ocean, though the signal to noise of this measurement may improve closer to the coast.

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

Akagi, Sheryl; Burling, Ian R.; Mendoza, Albert

We report trace-gas emission factors from three pine-understory prescribed fires in South Carolina, U.S. measured during the fall of 2011. The fires were an attempt to simulate high-intensity burns and the fuels included mature pine stands not frequently subjected to prescribed fire that were lit following a sustained period of drought. In this work we focus on the emission factor measurements made using a fixed open-path gas analyzer Fourier transform infrared (FTIR) system. We compare these emission factors with those measured using a roving, point sampling, land-based FTIR and an airborne FTIR that were deployed on the same fires. Wemore » also compare to emission factors measured by a similar open-path FTIR system deployed on savanna fires in Africa. The data suggest that the method in which the smoke is sampled can strongly influence the relative abundance of the emissions that are observed. The airborne FTIR probed the bulk of the emissions, which were lofted in the convection column and the downwind chemistry while the roving ground-based point sampling FTIR measured the contribution of individual residual smoldering combustion fuel elements scattered throughout the burn site. The open-path FTIR provided a fixed path-integrated sample of emissions produced directly upwind mixed with emissions that were redirected by wind gusts, or right after ignition and before the adjacent plume achieved significant vertical development. It typically probed two distinct combustion regimes, “flaming-like” (immediately after adjacent ignition) and “smoldering-like”, denoted “early” and “late”, respectively. The calculated emission factors from open-path measurements were closer to the airborne than to the point measurements, but this could vary depending on the calculation method or from fire to fire given the changing MCE and dynamics over the duration of a typical burn. The emission factors for species whose emissions are not highly fuel dependent (e.g. CH4 and CH3OH) from all three systems can be plotted versus modified combustion efficiency and fit to a single consistent trend suggesting that differences between the systems for these species may be mainly due to the unique mix of flaming and smoldering that each system sampled. For other more fuel dependent species, the different fuels sampled also likely contributed to platform differences in emission factors. The path-integrated sample of the ground-level smoke layer adjacent to the fire provided by the open-path measurements is important for estimating fire-line exposure to smoke for wildland fire personnel. We provide a table of estimated fire-line exposures for numerous known air toxics based on synthesizing results from several studies. Our data suggest that peak exposures are more likely to challenge permissible exposure limits for wildland fire personnel than shift-average exposures.« less

Assessment of Hydrogen Sulfide Minimum Detection Limits of an Open Path Tunable Diode Laser

EPA Science Inventory

During June 2007, U.S. EPA conducted a feasibility study to determine whether the EPA OTM 10 measurement approach, also known as radial plume mapping (RPM), was feasible. A Boreal open-path tunable diode laser (OP-TDL) to collect path-integrated hydrogen sulfide measurements alon...

The anaerobic digestion process

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

Rivard, C.J.; Boone, D.R.

1996-01-01

The microbial process of converting organic matter into methane and carbon dioxide is so complex that anaerobic digesters have long been treated as {open_quotes}black boxes.{close_quotes} Research into this process during the past few decades has gradually unraveled this complexity, but many questions remain. The major biochemical reactions for forming methane by methanogens are largely understood, and evolutionary studies indicate that these microbes are as different from bacteria as they are from plants and animals. In anaerobic digesters, methanogens are at the terminus of a metabolic web, in which the reactions of myriads of other microbes produce a very limited rangemore » of compounds - mainly acetate, hydrogen, and formate - on which the methanogens grow and from which they form methane. {open_quotes}Interspecies hydrogen-transfer{close_quotes} and {open_quotes}interspecies formate-transfer{close_quotes} are major mechanisms by which methanogens obtain their substrates and by which volatile fatty acids are degraded. Present understanding of these reactions and other complex interactions among the bacteria involved in anaerobic digestion is only now to the point where anaerobic digesters need no longer be treated as black boxes.« less

Year-round methane emissions from permafrost in a North-east Siberian region

NASA Astrophysics Data System (ADS)

Castro-Morales, Karel; Kaiser, Sonja; Kleinen, Thomas; Kwon, Min Jung; Kittler, Fanny; Zaehle, Sönke; Beer, Christian; Göckede, Mathias

2017-04-01

In recent decades, permafrost regions in northern latitudes are thawing as a response of climate warming. Soils in permafrost areas contain vast amounts of organic material that is released into the environment after thaw, providing new labile material for bacterial decomposition. As a result, higher production of methane in the anoxic soil layers and within anaerobic wetlands is anticipated, and this will be further released to the atmosphere. In order to assess the current large-scale methane emissions from a wetland permafrost-thaw affected area, we present results of year-round simulated methane emissions at regional scale for a section at the Russian far Northeast in Siberia, located in the low Arctic tundra and characterized by continuous permafrost. For this we use a newly developed process-based methane model built in the framework of the land surface model JSBACH. The model contains explicit permafrost processes and an improved representation of the horizontal extent of wetlands with a hydrological model (TOPMODEL). Model simulated distribution and horizontal extent of wetlands is evaluated against high-resolution remote sensing data. Total and individual regional methane emissions by ebullition, molecular diffusion, plant-mediated and emissions through snow are presented for 2014 and 2015. The model shows a reasonable seasonal transition between the individual methane emission paths. Most of the methane emissions to the atmosphere occur in summer (July, August, September), with the peak of the emissions during August. In this month, plant-mediated transport is the dominant emission path with about 15 mg CH4 m-2 d-1 in 2014, followed by ebullition (7 mg CH4 m-2 d-1) accounting for about half of the emissions thorough plants. Molecular diffusion is a minor contributor with only 0.006 mg CH4 m-2 d-1 at the peak of the summer emissions. Methane emissions through snow occur only during spring, fall and winter months, with higher emissions in spring and autumn (max. 2 mg CH4 m-2 d-1) when the thickness of the snow layer starts to melt or accumulate, respectively. The performance of the model was evaluated by comparing the modeled total methane emissions from a section of the Kolyma river floodplain near Chersky, against methane fluxes obtained from eddy covariance (for 2014 and 2015) and chambers (for June - August 2014) measured in the same area. Model results agree well with observations, with the highest emissions during August each year with 92.3 mg CH4 m-2 d-1 from eddy fluxes, 72.5 mg CH4 m-2 d-1 from chambers and 79.0 mg CH4 m-2 d-1 from the model in 2014, while 64.4 mg CH4 m-2 d-1 from eddy and 66.3 mg CH4 m-2 d-1 from the model in August 2015. The model underestimates winter emissions by up to 15 mg CH4 m-2 d-1, however a better agreement is observed in April 2014. To understand the shortcomings of the model against observations, the heterogeneity between model grid cells will be discussed.

Fugitive Methane Emission Identification and Source Attribution: Ethane-to-Methane Analysis Using a Portable Cavity Ring-Down Spectroscopy Analyzer

NASA Astrophysics Data System (ADS)

Kim-Hak, D.; Fleck, D.

2017-12-01

Natural gas analysis and methane specifically have become increasingly important by virtue of methane's 28-36x greenhouse warming potential compared to CO2 and accounting for 10% of total greenhouse gas emissions in the US alone. Additionally, large uncontrolled leaks, such as the recent one from Aliso Canyon in Southern California, originating from uncapped wells, storage facilities and coal mines have increased the total global contribution of methane missions even further. Determining the specific fingerprint of methane sources by quantifying the ethane to methane (C2:C1) ratios provides us with means to understand processes yielding methane and allows for sources of methane to be mapped and classified through these processes; i.e. biogenic or thermogenic, oil vs. gas vs. coal gas-related. Here we present data obtained using a portable cavity ring-down spectrometry analyzer weighing less than 25 lbs and consuming less than 35W that simultaneously measures methane and ethane in real-time with a raw 1-σ precision of <30 ppb and <10 ppb, respectively at <1 Hz. These precisions allow for a C2:C1 ratio 1-σ measurement of <0.1% above 10 ppm in a single measurement. Furthermore, a high precision methane only mode is available for surveying and locating leakage with a 1-σ precision of <3 ppb. Source discrimination data of local leaks and methane sources using this analysis method are presented. Additionally, two-dimensional plume snapshots are constructed using an integrated onboard GPS in order to visualize horizontal plane gas propagation.

Conversion of (Meth)acrylic acids to methane granular sludge: Initiation by specific anerobic microflora

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

Shtarkman, N.B.; Obraztova, A.Y.; Laurinavichyus, K.S.

1995-03-01

The role of a specific anaerobic microflora in the initiation of degradation of (meth)acrylic acids to methane by granular sludge from a UASB reactor was investigated. Associations of anaerobic bacteria isolated from the anaerobic sludge, which was used for a long time for treatment of wastewater from (meth)acrylate production, were able to realize the initial stage of (meth)acrylic acid decomposition, i.e., a conversion of acrylic and methacrylic acids to propionic and isobutyric acids, respectively. When added to granules, these association played a role of an {open_quotes}initiator{close_quotes} of the degradation process, which was then continued by the granular sludge microflora utilizingmore » propionate and isobutyrate. Some characteristics of the granules adapted to propionate or isobutyrate are presented. The rates of propionate and isobutyrate consumption by adapted granules is, respectively, 21 and 53 times higher than the values obtained for nonadapted granules. A combined use of {open_quotes}initiating{close_quotes} bacteria and adapted granules provided degradation of (meth)acrylic acids with a maximum methane yield. The possibility is discussed of employing the granules, which are adapted to short-chain fatty acids, and the {open_quotes}initiating{close_quotes} bacteria, which accomplish the initial steps of the organic material decomposition to lower fatty acids, for the conversion of various chemical compounds to methane. 10 refs., 3 figs., 2 tabs.« less

Fugitive methane emissions from natural, urban, agricultural, and energy-production landscapes of eastern Australia

NASA Astrophysics Data System (ADS)

Kelly, Bryce F. J.; Iverach, Charlotte P.; Lowry, Dave; Fisher, Rebecca E.; France, James L.; Nisbet, Euan G.

2015-04-01

Modern cavity ringdown spectroscopy systems (CRDS) enable the continuous measurement of methane concentration. This allows for improved quantification of greenhouse gas emissions associated with various natural and human landscapes. We present a subset of over 4000 km of continuous methane surveying along the east coast of Australia, made using a Picarro G2301 CRDS, deployed in a utility vehicle with an air inlet above the roof at 2.2 mAGL. Measurements were made every 5 seconds to a precision of <0.5 ppb for CH4. These surveys were undertaken during dry daytime hours and all measurements were moisture corrected. We compare the concentration of methane in the near surface atmosphere adjacent to open-cut coal mines, unconventional gas developments (coal seam gas; CSG), and leaks detected in cities and country towns. In areas of dryland crops the median methane concentration was 1.78 ppm, while in the irrigation districts located on vertisol soils the concentration was as low as 1.76 ppm, which may indicate that these soils are a sink for methane. In the Hunter Valley, New South Wales, open-cut coal mining district we mapped a continuous 50 km interval where the concentration of methane exceeded 1.80 ppm. The median concentration in this interval was 2.02 ppm. Peak readings were beyond the range of the reliable measurement (in excess of 3.00 ppm). This extended plume is an amalgamation of plumes from 17 major pits 1 to 10 km in length. Adjacent to CSG developments in the Surat Basin, southeast Queensland, only small anomalies were detected near the well-heads. Throughout the vast majority of the gas fields the concentration of methane was below 1.80 ppm. The largest source of fugitive methane associated with CSG was off-gassing methane from the co-produced water holding ponds. At one location the down wind plume had a cross section of approximately 1 km where the concentration of methane was above 1.80 ppm. The median concentration within this section was 1.82 ppm, with a peak reading of 2.11 ppm. The ambient air methane concentration was always higher in urban environments compared to the surrounding countryside. Along one major road in Sydney we mapped an interval that extended for 6 km where the concentration was greater than 1.80 ppm. The median concentration in this interval was 1.90 ppm, with a peak reading of 1.97 ppm. This high reading in an urban setting is most likely due to leaks from the domestic gas distribution system. Methane leaks were detected in all country towns. Our measurements show that at the point of resource extraction the methane emission footprint of CSG is smaller than that of open-cut coal mining. However, leaking gas from urban centers must be added to the fugitive emissions of CSG to calculate the total fugitive emission footprint of CSG, which may therefore not be as low as claimed in the national greenhouse gas accounts. Our results highlight the need for additional continuous monitoring of methane emissions from all sectors, and for the full life-cycle of energy resources to be considered.

Characterization of C1-Metabolizing Prokaryotic Communities in Methane Seep Habitats at the Kuroshima Knoll, Southern Ryukyu Arc, by Analyzing pmoA, mmoX, mxaF, mcrA, and 16S rRNA Genes

PubMed Central

Inagaki, Fumio; Tsunogai, Urumu; Suzuki, Masae; Kosaka, Ayako; Machiyama, Hideaki; Takai, Ken; Nunoura, Takuro; Nealson, Kenneth H.; Horikoshi, Koki

2004-01-01

Samples from three submerged sites (MC, a core obtained in the methane seep area; MR, a reference core obtained at a distance from the methane seep; and HC, a gas-bubbling carbonate sample) at the Kuroshima Knoll in the southern Ryuku arc were analyzed to gain insight into the organisms present and the processes involved in this oxic-anoxic methane seep environment. 16S rRNA gene analyses by quantitative real-time PCR and clone library sequencing revealed that the MC core sediments contained abundant archaea (∼34% of the total prokaryotes), including both mesophilic methanogens related to the genus Methanolobus and ANME-2 members of the Methanosarcinales, as well as members of the δ-Proteobacteria, suggesting that both anaerobic methane oxidation and methanogenesis occurred at this site. In addition, several functional genes connected with methane metabolism were analyzed by quantitative competitive-PCR, including the genes encoding particulate methane monooxygenase (pmoA), soluble methane monooxygenase (mmoX), methanol dehydrogenese (mxaF), and methyl coenzyme M reductase (mcrA). In the MC core sediments, the most abundant gene was mcrA (2.5 × 106 copies/g [wet weight]), while the pmoA gene of the type I methanotrophs (5.9 × 106 copies/g [wet weight]) was most abundant at the surface of the MC core. These results indicate that there is a very complex environment in which methane production, anaerobic methane oxidation, and aerobic methane oxidation all occur in close proximity. The HC carbonate site was rich in γ-Proteobacteria and had a high copy number of mxaF (7.1 × 106 copies/g [wet weight]) and a much lower copy number of the pmoA gene (3.2 × 102 copies/g [wet weight]). The mmoX gene was never detected. In contrast, the reference core contained familiar sequences of marine sedimentary archaeal and bacterial groups but not groups specific to C1 metabolism. Geochemical characterization of the amounts and isotopic composition of pore water methane and sulfate strongly supported the notion that in this zone both aerobic methane oxidation and anaerobic methane oxidation, as well as methanogenesis, occur. PMID:15574947

40 CFR 89.324 - Calibration of other equipment.

Code of Federal Regulations, 2010 CFR

2010-07-01

... represent good engineering practice. For each range calibrated, if the deviation from a least-squares best... shall be calibrated as often as required by the instrument manufacturer or necessary according to good practice. (b) If a methane analyzer is used, the methane analyzer shall be calibrated prior to introduction...

High cleanliness globe valve with sine mechanism drive

NASA Astrophysics Data System (ADS)

Luo, Hu

2018-06-01

This paper gives a new type of quick-opening globe valve for life support pneumatic control system of the safety cabin at underground coal mine. The valve adopts the sine mechanism to transmit the rotating of the handle in the range of 90° to the reciprocating motion of the spool. The mechanism implements the quick-opening function of the valve through controlling the contact and separation between the O-ring and the end face of the valve. Since there is no relative sliding between the sealing interfaces, the valve solute uncontrollable disadvantage wear particles which produced by package ball valve, to ensure high cleanliness in flow path. Traditional transmission mechanism has a reinforcement effect and reduce handle open torque. By the finite element method, the relationship between the contact force and the compression of O-ring is analyzed to provide the boundary condition for the calculation of the rotational torque. Meanwhile the velocity field and pressure field along the flow path are simulated. The caliber size of the valve and the flow resistance coefficient are obtained. There is higher cleanliness, more reliable sealing, smaller handle open torque advantage compared with existing packing ball valve. The above work presents a new technical approach for the design of pneumatic control valve of the safety cabin.

30 CFR 57.22104 - Open flames (I-C mines).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Open flames (I-C mines). 57.22104 Section 57... Standards for Methane in Metal and Nonmetal Mines Fire Prevention and Control § 57.22104 Open flames (I-C mines). (a) Open flames, including cutting and welding, shall not be used underground. (b) Welding and...

30 CFR 57.22104 - Open flames (I-C mines).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Open flames (I-C mines). 57.22104 Section 57... Standards for Methane in Metal and Nonmetal Mines Fire Prevention and Control § 57.22104 Open flames (I-C mines). (a) Open flames, including cutting and welding, shall not be used underground. (b) Welding and...

30 CFR 57.22104 - Open flames (I-C mines).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Open flames (I-C mines). 57.22104 Section 57... Standards for Methane in Metal and Nonmetal Mines Fire Prevention and Control § 57.22104 Open flames (I-C mines). (a) Open flames, including cutting and welding, shall not be used underground. (b) Welding and...

30 CFR 57.22104 - Open flames (I-C mines).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Open flames (I-C mines). 57.22104 Section 57... Standards for Methane in Metal and Nonmetal Mines Fire Prevention and Control § 57.22104 Open flames (I-C mines). (a) Open flames, including cutting and welding, shall not be used underground. (b) Welding and...

30 CFR 57.22105 - Smoking and open flames (IV mines).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Smoking and open flames (IV mines). 57.22105... Standards for Methane in Metal and Nonmetal Mines Fire Prevention and Control § 57.22105 Smoking and open flames (IV mines). Smoking or open flames shall not be permitted in a face or raise, or during release of...

30 CFR 57.22105 - Smoking and open flames (IV mines).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Smoking and open flames (IV mines). 57.22105... Standards for Methane in Metal and Nonmetal Mines Fire Prevention and Control § 57.22105 Smoking and open flames (IV mines). Smoking or open flames shall not be permitted in a face or raise, or during release of...

30 CFR 57.22105 - Smoking and open flames (IV mines).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Smoking and open flames (IV mines). 57.22105... Standards for Methane in Metal and Nonmetal Mines Fire Prevention and Control § 57.22105 Smoking and open flames (IV mines). Smoking or open flames shall not be permitted in a face or raise, or during release of...

30 CFR 57.22105 - Smoking and open flames (IV mines).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Smoking and open flames (IV mines). 57.22105... Standards for Methane in Metal and Nonmetal Mines Fire Prevention and Control § 57.22105 Smoking and open flames (IV mines). Smoking or open flames shall not be permitted in a face or raise, or during release of...

Airborne Remote sensing of the OH tropospheric column with an Integrated Path Differential LIDAR.

NASA Astrophysics Data System (ADS)

Hanisco, T. F.; Liang, Q.; Nicely, J. M.; Brune, W. H.; Miller, D. O.; Thames, A. B.

2017-12-01

The Hydroxyl radical, OH, is central to the photochemistry that controls tropospheric oxidation including the removal of atmospheric methane. Measurements of this important species are thus critical to testing our understanding and for constraining model results. Until now, tropospheric measurements have been limited to airborne or ground-based in situ instruments best suited to test photochemical box models. However, because of the growing recognition of the importance of the global methane abundance, we have a growing need to better quantify OH at the regional to global scales that are best sampled with airborne or space-based remote sensing instruments. To address this need, we have developed an instrument concept and have begun work on a laser transmitter for an airborne integrated path differential absorption LIDAR for the detection of OH. We will describe the instrument and present the expected performance characteristics. As a demonstration, we will use measurements from the recent ATOM-1 NASA airborne campaign to show measured OH columns can be used to constrain regional and global models.

Identifying Methane Sources with an Airborne Pulsed IPDA Lidar System Operating near 1.65 µm

NASA Astrophysics Data System (ADS)

Yerasi, A.; Bartholomew, J.; Tandy, W., Jr.; Emery, W. J.

2016-12-01

Methane is a powerful greenhouse gas that is predicted to play an important role in future global climate trends. It would therefore be beneficial to locate areas that produce methane in significant amounts so that these trends can be better understood. In this investigation, some initial performance test results of a lidar system called the Advanced Leak Detector Lidar - Natural Gas (ALDL-NG) are discussed. The feasibility of applying its fundamental principle of operation to methane source identification is also explored. The ALDL-NG was originally created by the Ball Aerospace & Technologies Corp. to reveal leaks emanating from pipelines that transport natural gas, which is primarily composed of methane. It operates in a pulsed integrated path differential absorption (IPDA) configuration and it is carried by a piloted, single-engine aircraft. In order to detect the presence of natural gas leaks, the laser wavelengths of its online and offline channels operate in the 1.65 µm region. The functionality of the ALDL-NG was tested during a recent field campaign in Colorado. It was determined that the ambient concentration of methane in the troposphere ( 1.8 ppm) could indeed be retrieved from ALDL-NG data with a lower-than-expected uncertainty ( 0.2 ppm). Furthermore, when the ALDL-NG scanned over areas that were presumed to be methane sources (feedlots, landfills, etc.), significantly higher concentrations of methane were retrieved. These results are intriguing because the ALDL-NG was not specifically designed to observe anything beyond natural gas pipelines. Nevertheless, they strongly indicate that utilizing an airborne pulsed IPDA lidar system operating near 1.65 µm may very well be a viable technique for identifying methane sources. Perhaps future lidar systems could build upon the heritage of the ALDL-NG and measure methane concentration with even better precision for a variety of scientific applications.

New Insights into the Electroreduction of Ethylene Sulfite as Electrolyte Additive for Facilitating Solid Electrolyte Interphase of Lithium Ion Battery

PubMed Central

Sun, Youmin; Wang, Yixuan

2017-01-01

To help understand the solid electrolyte interphase (SEI) formation facilitated by electrolyte additives of lithium-ion batteries (LIB) the supermolecular clusters [(ES)Li+(PC)m](PC)n (m=1–2; n=0, 6, and 9) were used to investigate the electroreductive decompositions of the electrolyte additive, ethylene sulfite (ES), as well as the solvent, propylene carbonate (PC) with density functional theory. The results show that ES can be reduced prior to PC, resulting in a reduction precursor that will then undergo a ring opening decomposition to yield a radical anion. A new concerted pathway (path B) was located for the ring opening of the reduced ES, which has much lower energy barrier than the previously reported stepwise pathway (path A). The transition state for the ring opening of PC induced by the reduced ES (path C, indirect path) is closer to that of path A than path B in energy. The direct ring opening of the reduced PC (path D) has lower energy barrier than those of paths A, B and C, yet it is less favorable than the latter paths in terms of thermodynamics (vertical electron affinity or the reduction potential dissociation energy). The overall rate constant including the initial reduction and the subsequent ring opening for path B is the largest among the four paths, followed by paths A>C>D, which further signifies the importance of the concerted new path in facilitating the SEI. The hybrid models, the supermolecular cluster augmented by polarized continuum model, PCM-[(ES)Li+(PC)2](PC)n (n=0,6, and 9), were used to further estimate the reduction potential by taking into account both explicit and implicit solvent effects. The second solvation shell of Li+ in [(ES)Li+(PC)2](PC)n (n=6, and 9) partially compensates the overestimation of solvent effects arising from the PCM model for the naked (ES)Li+(PC)2, and the theoretical reduction potential with PCM-[(ES)Li+(PC)2](PC)6 (1.90–1.93V) agrees very well with the experimental one (1.8–2.0V). PMID:28220165

New insights into the electroreduction of ethylene sulfite as an electrolyte additive for facilitating solid electrolyte interphase formation in lithium ion batteries.

PubMed

Sun, Youmin; Wang, Yixuan

2017-03-01

To help understand the solid electrolyte interphase (SEI) formation facilitated by electrolyte additives of lithium-ion batteries (LIBs) the supermolecular clusters [(ES)Li + (PC) m ](PC) n (m = 1-2; n = 0, 6 and 9) were used to investigate the electroreductive decompositions of the electrolyte additive ethylene sulfite (ES) as well as the solvent propylene carbonate (PC) with density functional theory. The results show that ES can be reduced prior to PC, resulting in a reduction precursor that will then undergo a ring opening decomposition to yield a radical anion. A new concerted pathway (path B) was located for the ring opening of the reduced ES, which has a much lower energy barrier than the previously reported stepwise pathway (path A). The transition state for the ring opening of PC induced by the reduced ES (path C, indirect path) is closer to that of path A than path B in energy. The direct ring opening of the reduced PC (path D) has a lower energy barrier than paths A, B and C, yet it is less favorable than the latter paths in terms of thermodynamics (vertical electron affinity or reduction potential and dissociation energy). The overall rate constant including the initial reduction and the subsequent ring opening for path B is the largest among the four paths, followed by paths A > C > D, which further signifies the importance of the concerted new path in facilitating the SEI formation. The hybrid models, the supermolecular clusters augmented by a polarized continuum model, PCM-[(ES)Li + (PC) 2 ](PC) n (n = 0, 6 and 9), were used to further estimate the reduction potential by taking into account both explicit and implicit solvent effects. The second solvation shell of Li + in [(ES)Li + (PC) 2 ](PC) n (n = 6 and 9) partially compensates the overestimation of solvent effects arising from the PCM for the naked (ES)Li + (PC) 2 , and the theoretical reduction potential of PCM-[(ES)Li + (PC) 2 ](PC) 6 (1.90-1.93 V) agrees very well with the experimental one (1.8-2.0 V).

Portable open-path chemical sensor using a quantum cascade laser

NASA Astrophysics Data System (ADS)

Corrigan, Paul; Lwin, Maung; Huntley, Reuven; Chhabra, Amandeep; Moshary, Fred; Gross, Barry; Ahmed, Samir

2009-05-01

Remote sensing of enemy installations or their movements by trace gas detection is a critical but challenging military objective. Open path measurements over ranges of a few meters to many kilometers with sensitivity in the parts per million or billion regime are crucial in anticipating the presence of a threat. Previous approaches to detect ground level chemical plumes, explosive constituents, or combustion have relied on low-resolution, short range Fourier transform infrared spectrometer (FTIR), or low-sensitivity near-infrared differential optical absorption spectroscopy (DOAS). As mid-infrared quantum cascade laser (QCL) sources have improved in cost and performance, systems based on QCL's that can be tailored to monitor multiple chemical species in real time are becoming a viable alternative. We present the design of a portable, high-resolution, multi-kilometer open path trace gas sensor based on QCL technology. Using a tunable (1045-1047cm-1) QCL, a modeled atmosphere and link-budget analysis with commercial component specifications, we show that with this approach, accuracy in parts per billion ozone or ammonia can be obtained in seconds at path lengths up to 10 km. We have assembled an open-path QCL sensor based on this theoretical approach at City College of New York, and we present preliminary results demonstrating the potential of QCLs in open-path sensing applications.

MERLIN (Methane Remote Sensing Lidar Mission): an Overview

NASA Astrophysics Data System (ADS)

Pierangelo, C.; Millet, B.; Esteve, F.; Alpers, M.; Ehret, G.; Flamant, P.; Berthier, S.; Gibert, F.; Chomette, O.; Edouart, D.; Deniel, C.; Bousquet, P.; Chevallier, F.

2016-06-01

The Methane Remote Sensing Lidar Mission (MERLIN), currently in phase B, is a joint cooperation between France and Germany on the development, launch and operation of a methane (CH4) monitoring satellite. MERLIN is focused on global measurements of the spatial and temporal gradients of atmospheric CH4, the second most anthropogenic gas, with a precision and accuracy sufficient to constrain Methane fluxes significantly better than with the current observation network. For the first time, measurements of atmospheric composition will be performed from space thanks to an IPDA (Integrated Path Differential Absorption) LIDAR (Light Detecting And Ranging). This payload is under the responsibility of the German space agency (DLR), while the platform (MYRIADE Evolutions product line) is developed by the French space agency (CNES). The IPDA technique relies on DIAL (Differential Absorption LIDAR) measurements using a pulsed laser emitting at two wavelengths, one wavelength accurately locked on a spectral feature of the methane absorption line, and the other wavelength free from absorption to be used as reference. This technique enables measurements in all seasons, at all latitudes. It also guarantees almost no contamination by aerosols or water vapour cross-sensitivity, and thus has the advantage of an extremely low level of systematic error on the dry-air column mixing ratio of CH4.

Non-Detection of Methane in the Mars Atmosphere by the Curiosity Rover

NASA Technical Reports Server (NTRS)

Webster, Chris R.; Mahaffy, Paul R.; Atreya, Sushil K.; Flesch, Gregory J.; Farley, Kenneth A.

2014-01-01

By analogy with Earth, methane in the atmosphere of Mars is a potential signature of ongoing or past biological activity on the planet. During the last decade, Earth-based telescopic and Mars orbit remote sensing instruments have reported significant abundances of methane in the Martian atmosphere ranging from several to tens of parts-per-billion by volume (ppbv). Observations from Earth showed plumes of methane with variations on timescales much faster than expected and inconsistent with localized patches seen from orbit, prompting speculation of sources from sub-surface methanogen bacteria, geological water-rock reactions or infall from comets, micro-meteorites or interplanetary dust. From measurements on NASAs Curiosity Rover that landed near Gale Crater on 5th August 2012, we here report no definitive detection of methane in the near-surface Martian atmosphere. Our in situ measurements were made using the Tunable Laser Spectrometer (TLS) in the Sample Analysis at Mars (SAM) instrument suite6 that made three separate searches on Martian sols 79, 81 and 106 after landing. The measured mean value of 0.39 plus or minus 1.4 ppbv corresponds to an upper limit for methane abundance of 2.7 ppbv at the 95 confidence level. This result is in disagreement with both the remote sensing spacecraft observations taken at lower sensitivity and the telescopic observations that relied on subtraction of a very large contribution from terrestrial methane in the intervening observation path. Since the expected lifetime of methane in the Martian atmosphere is hundreds of years, our results question earlier observations and set a low upper limit on the present day abundance, reducing the probability of significant current methanogenic microbial activity on Mars.

Optimisation of frequency-modulated characteristics of output radiation in a lidar with Raman amplification

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

Grigorievsky, V I; Tezadov, Ya A

2016-03-31

The reported study is aimed at increasing the power in the transmission path of a lidar with Raman amplification for longpath sensing of methane by optimising the frequency-modulated characteristics of the output radiation. The pump current of the used distributed-feedback master laser was modulated by a linearfrequency signal with simultaneous application of a non-synchronous high-frequency signal. For such a modulation regime, the Raman amplifier provided the mean output power of 2.5 W at a wavelength of 1650 nm. The spectral broadening did not significantly decrease the lidar sensitivity at long paths. (lidars)

Implant-supported mandibular splinting affects temporomandibular joint biomechanics.

PubMed

Zaugg, Balthasar; Hämmerle, Christoph H F; Palla, Sandro; Gallo, Luigi M

2012-08-01

Mandibular functional movements lead to complex deformations of bony structures. The aim of this study was to test whether mandibular splinting influences condylar kinematics and temporomandibular joint (TMJ) loading patterns. Six subjects were analyzed by means of dynamic stereometry during jaw opening-closing with mandibles unconstrained as well as splinted transversally by a cast metal bar fixed bilaterally to two implant pairs in the (pre)molar region. Statistical analysis was performed by means of ANOVAs for repeated measurements (significance level α=0.05). Transversal splinting reduced mandibular deformation during jaw opening-closing as measured between two implants in the (pre)molar region on each side of the mandible significantly by 54%. Furthermore, splinting significantly reduced the distance between lateral condylar poles (average displacement vector magnitude of each pole: 0.84±0.36 mm; average mediolateral displacement component: 45±28% of the magnitude) and led to a medial displacement of their trajectories as well as a mediolateral displacement of stress-field paths. During jaw opening-closing, splinting of the mandible leads to a significant reduction of mandibular deformation and intercondylar distance and to altered stress-field paths, resulting in changed loading patterns of the TMJ structures. © 2011 John Wiley & Sons A/S.

Characterization of methane oxidation in a simulated landfill cover system by comparing molecular and stable isotope mass balances.

PubMed

Schulte, Marcel; Jochmann, Maik A; Gehrke, Tobias; Thom, Andrea; Ricken, Tim; Denecke, Martin; Schmidt, Torsten C

2017-11-01

Biological methane oxidation may be regarded as a method of aftercare treatment for landfills to reduce climate relevant methane emissions. It is of social and economic interest to estimate the behavior of bacterial methane oxidation in aged landfill covers due to an adequate long-term treatment of the gas emissions. Different approaches assessing methane oxidation in laboratory column studies have been investigated by other authors recently. However, this work represents the first study in which three independent approaches, ((i) mass balance, (ii) stable isotope analysis, and (iii) stoichiometric balance of product (CO 2 ) and reactant (CH 4 ) by CO 2 /CH 4 -ratio) have been compared for the estimation of the biodegradation by a robust statistical validation on a rectangular, wide soil column. Additionally, an evaluation by thermal imaging as a potential technique for the localization of the active zone of bacterial methane oxidation has been addressed in connection with stable isotope analysis and CO 2 /CH 4 -ratios. Although landfills can be considered as open systems the results for stable isotope analysis based on a closed system correlated better with the mass balance than calculations based on an open system. CO 2 /CH 4 -ratios were also in good agreement with mass balance. In general, highest values for biodegradation were determined from mass balance, followed by CO 2 /CH 4 -ratio, and stable isotope analysis. The investigated topsoil proved to be very suitable as a potential cover layer by removing up to 99% of methane for CH 4 loads of 35-65gm -2 d -1 that are typical in the aftercare phase of landfills. Finally, data from stable isotope analysis and the CO 2 /CH 4 -ratios were used to trace microbial activity within the reactor system. It was shown that methane consumption and temperature increase, as a cause of high microbial activity, correlated very well. Copyright © 2017 Elsevier Ltd. All rights reserved.

Landscape-level terrestrial methane flux observed from a very tall tower

USGS Publications Warehouse

Desai, Ankur R.; Xu, Ke; Tian, Hanqin; Weishampel, Peter; Thom, Jonthan; Baumann, Daniel D.; Andrews, Arlyn E.; Cook, Bruce D.; King, Jennifer Y.; Kolka, Randall

2015-01-01

Simulating the magnitude and variability of terrestrial methane sources and sinks poses a challenge to ecosystem models because the biophysical and biogeochemical processes that lead to methane emissions from terrestrial and freshwater ecosystems are, by their nature, episodic and spatially disjunct. As a consequence, model predictions of regional methane emissions based on field campaigns from short eddy covariance towers or static chambers have large uncertainties, because measurements focused on a particular known source of methane emission will be biased compared to regional estimates with regards to magnitude, spatial scale, or frequency of these emissions. Given the relatively large importance of predicting future terrestrial methane fluxes for constraining future atmospheric methane growth rates, a clear need exists to reduce spatiotemporal uncertainties. In 2010, an Ameriflux tower (US-PFa) near Park Falls, WI, USA, was instrumented with closed-path methane flux measurements at 122 m above ground in a mixed wetland–upland landscape representative of the Great Lakes region. Two years of flux observations revealed an average annual methane (CH4) efflux of 785 ± 75 mg CCH4 m−2 yr−1, compared to a mean CO2 sink of −80 g CCO2 m−2 yr−1, a ratio of 1% in magnitude on a mole basis. Interannual variability in methane flux was 30% of the mean flux and driven by suppression of methane emissions during dry conditions in late summer 2012. Though relatively small, the magnitude of the methane source from the very tall tower measurements was mostly within the range previously measured using static chambers at nearby wetlands, but larger than a simple scaling of those fluxes to the tower footprint. Seasonal patterns in methane fluxes were similar to those simulated in the Dynamic Land Ecosystem Model (DLEM), but magnitude depends on model parameterization and input data, especially regarding wetland extent. The model was unable to simulate short-term (sub-weekly) variability. Temperature was found to be a stronger driver of regional CH4flux than moisture availability or net ecosystem production at the daily to monthly scale. Taken together, these results emphasize the multi-timescale dependence of drivers of regional methane flux and the importance of long, continuous time series for their characterization.

Genetic and phenotypic variance and covariance components for methane emission and postweaning traits in Angus cattle.

PubMed

Donoghue, K A; Bird-Gardiner, T; Arthur, P F; Herd, R M; Hegarty, R F

2016-04-01

Ruminants contribute 80% of the global livestock greenhouse gas (GHG) emissions mainly through the production of methane, a byproduct of enteric microbial fermentation primarily in the rumen. Hence, reducing enteric methane production is essential in any GHG emissions reduction strategy in livestock. Data on 1,046 young bulls and heifers from 2 performance-recording research herds of Angus cattle were analyzed to provide genetic and phenotypic variance and covariance estimates for methane emissions and production traits and to examine the interrelationships among these traits. The cattle were fed a roughage diet at 1.2 times their estimated maintenance energy requirements and measured for methane production rate (MPR) in open circuit respiration chambers for 48 h. Traits studied included DMI during the methane measurement period, MPR, and methane yield (MY; MPR/DMI), with means of 6.1 kg/d (SD 1.3), 132 g/d (SD 25), and 22.0 g/kg (SD 2.3) DMI, respectively. Four forms of residual methane production (RMP), which is a measure of actual minus predicted MPR, were evaluated. For the first 3 forms, predicted MPR was calculated using published equations. For the fourth (RMP), predicted MPR was obtained by regression of MPR on DMI. Growth and body composition traits evaluated were birth weight (BWT), weaning weight (WWT), yearling weight (YWT), final weight (FWT), and ultrasound measures of eye muscle area, rump fat depth, rib fat depth, and intramuscular fat. Heritability estimates were moderate for MPR (0.27 [SE 0.07]), MY (0.22 [SE 0.06]), and the RMP traits (0.19 [SE 0.06] for each), indicating that genetic improvement to reduce methane emissions is possible. The RMP traits and MY were strongly genetically correlated with each other (0.99 ± 0.01). The genetic correlation of MPR with MY as well as with the RMP traits was moderate (0.32 to 0.63). The genetic correlation between MPR and the growth traits (except BWT) was strong (0.79 to 0.86). These results indicate that selection for lower MPR may have undesired effect on animal productivity. On the other hand, MY and the RMPR were either not genetically correlated or weakly correlated with BWT, YWT, and FWT (-0.06 to 0.23) and body composition traits (-0.18 to 0.18). Therefore, selection for lower MY or RMPR would lead to lower MPR without impacting animal productivity. Where the use of a ratio trait (e.g., MY) is not desirable, selection on any of the forms of RMP would be an alternative.

Template-Assisted Wet-Combustion Synthesis of Fibrous Nickel-Based Catalyst for Carbon Dioxide Methanation and Methane Steam Reforming.

PubMed

Aghayan, M; Potemkin, D I; Rubio-Marcos, F; Uskov, S I; Snytnikov, P V; Hussainova, I

2017-12-20

Efficient capture and recycling of CO 2 enable not only prevention of global warming but also the supply of useful low-carbon fuels. The catalytic conversion of CO 2 into an organic compound is a promising recycling approach which opens new concepts and opportunities for catalytic and industrial development. Here we report about template-assisted wet-combustion synthesis of a one-dimensional nickel-based catalyst for carbon dioxide methanation and methane steam reforming. Because of a high temperature achieved in a short time during reaction and a large amount of evolved gases, the wet-combustion synthesis yields homogeneously precipitated nanoparticles of NiO with average particle size of 4 nm on alumina nanofibers covered with a NiAl 2 O 4 nanolayer. The as-synthesized core-shell structured fibers exhibit outstanding activity in steam reforming of methane and sufficient activity in carbon dioxide methanation with 100% selectivity toward methane formation. The as-synthesized catalyst shows stable operation under the reaction conditions for at least 50 h.

QUANTIFICATION OF METHANE EMISSIONS AND DISCUSSON OF NITROUS OXIDE, AND AMMONIA EMISSIONS FROM SEPTIC TANKS, LATRINES, AND STAGNANT OPEN SEWERS OF THE WORLD

EPA Science Inventory

The report gives results of a first attempt to estimate global and country-specific methane (CH4) emissons from sewers and on-site wastewater treatment systems, including latrines and septic sewage tanks. It follows a report that includes CH4 and nitrous oxide (N2O) estimates fro...

Ice-sheet-driven methane storage and release in the Arctic

PubMed Central

Portnov, Alexey; Vadakkepuliyambatta, Sunil; Mienert, Jürgen; Hubbard, Alun

2016-01-01

It is established that late-twentieth and twenty-first century ocean warming has forced dissociation of gas hydrates with concomitant seabed methane release. However, recent dating of methane expulsion sites suggests that gas release has been ongoing over many millennia. Here we synthesize observations of ∼1,900 fluid escape features—pockmarks and active gas flares—across a previously glaciated Arctic margin with ice-sheet thermomechanical and gas hydrate stability zone modelling. Our results indicate that even under conservative estimates of ice thickness with temperate subglacial conditions, a 500-m thick gas hydrate stability zone—which could serve as a methane sink—existed beneath the ice sheet. Moreover, we reveal that in water depths 150–520 m methane release also persisted through a 20-km-wide window between the subsea and subglacial gas hydrate stability zone. This window expanded in response to post-glacial climate warming and deglaciation thereby opening the Arctic shelf for methane release. PMID:26739497

Methane drainage with horizontal boreholes in advance of longwall mining: an analysis. Final report

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

Gabello, D.P.; Felts, L.L.; Hayoz, F.P.

1981-05-01

The US Department of Energy (DOE) Morgantown Energy Technology Center has implemented a comprehensive program to demonstrate the technical and economic viability of coalbed methane as an energy resource. The program is directed toward solution of technical and institutional problems impeding the recovery and use of large quantities of methane contained in the nation's minable and unminable coalbeds. Conducted in direct support of the DOE Methane Recovery from Coalbeds Project, this study analyzes the economic aspects of a horizontal borehole methane recovery system integrated as part of a longwall mine operation. It establishes relationships between methane selling price and annualmore » mine production, methane production rate, and the methane drainage system capital investment. Results are encouraging, indicating that an annual coal production increase of approximately eight percent would offset all associated drainage costs over the range of methane production rates and capital investments considered.« less

Undersea Microbes Provide Path to Energy Storage | News | NREL

Science.gov Websites

microorganisms that will convert hydrogen and carbon dioxide into methane. Photo by Dennis Schroeder, NREL 47786 initially grew a small batch of the microorganisms. Photo by Dennis Schroeder, NREL 47789 A murky mixture of microorganisms. Photo by Dennis Schroeder, NREL 47789 California Utility Relying on NREL R&D NREL's pilot

Geology beneath and beside the notorious Payatas open dump, Metro Manila, Philippines

NASA Astrophysics Data System (ADS)

Tomarong, C.; Arcilla, C.; de Sales, L.; Chua, S.; Garcia, E.; Pamintuan, G.

2003-04-01

With a minimum of 6000 tonnes/day municipal waste output, and with NO existing operational sanitary landfill and with incineration illegal, Metro Manila has a very serious solid waste disposal problem. Unsorted municipal waste are being piled in open dumps, the most notorious of which is the Payatas open dump. A recent, tragic garbage-slide in this open dump caused dozens of deaths, news of which were broadcast internationally. Political expediency laced with a lot of corruption, rather than sound science, was the main basis for selecting this site as an open dump. As an example, this dump is situated < 1 km from the Novaliches Watershed Reservation, one of the main sources of drinking water for Metro Manila’s 12 million population! Yet, after dumping operations that have lasted more than 10 years, only recently were the preliminary geologic studies begun. Payatas is not a designed landfill and its untreated leachate is openly polluting the headwaters of the Marikina and Pasig Rivers. In addition, during the summer months, there is always the constant threat of fire due to methane induced burning from the dump, aside from the aerial pollution from dioxins and furans derived from incomplete combustion of municipal solid waste. With limited funding from the Quezon City government, a feasibility study was conducted to assess the methane generation potential of Payatas. This interdisciplinary study comprised bedrock geological studies, topographic mapping of the dump, drilling of the dump to obtain stratigraphic solid waste samples for waste characterization, laying of horizontal methane and dewatering pipes, and preliminary methane flow studies. The waste characterization has highlighted the unusually high organic (especially yard waste) component of the solid waste dumped at Payatas. Waste characterization shows that a significant portion of the waste is plastics. Several cross-sections cut across the dump show that the side slopes of the dump are on the average steeper than the pre-dump slopes. The “bedrock” of the Payatas dump are conglomerate members of the Pleistocene volcaniclastic Guadualupe Formation. Studies are still to be done on the extent of pollution on surface and groundwater in the Payatas environs.

Assessment of Shape Changes of Mistletoe Berries: A New Software Approach to Automatize the Parameterization of Path Curve Shaped Contours

PubMed Central

Derbidge, Renatus; Feiten, Linus; Conradt, Oliver; Heusser, Peter; Baumgartner, Stephan

2013-01-01

Photographs of mistletoe (Viscum album L.) berries taken by a permanently fixed camera during their development in autumn were subjected to an outline shape analysis by fitting path curves using a mathematical algorithm from projective geometry. During growth and maturation processes the shape of mistletoe berries can be described by a set of such path curves, making it possible to extract changes of shape using one parameter called Lambda. Lambda describes the outline shape of a path curve. Here we present methods and software to capture and measure these changes of form over time. The present paper describes the software used to automatize a number of tasks including contour recognition, optimization of fitting the contour via hill-climbing, derivation of the path curves, computation of Lambda and blinding the pictures for the operator. The validity of the program is demonstrated by results from three independent measurements showing circadian rhythm in mistletoe berries. The program is available as open source and will be applied in a project to analyze the chronobiology of shape in mistletoe berries and the buds of their host trees. PMID:23565255

A simple headspace equilibration method for measuring dissolved methane

USGS Publications Warehouse

Magen, C; Lapham, L.L.; Pohlman, John W.; Marshall, Kristin N.; Bosman, S.; Casso, Michael; Chanton, J.P.

2014-01-01

Dissolved methane concentrations in the ocean are close to equilibrium with the atmosphere. Because methane is only sparingly soluble in seawater, measuring it without contamination is challenging for samples collected and processed in the presence of air. Several methods for analyzing dissolved methane are described in the literature, yet none has conducted a thorough assessment of the method yield, contamination issues during collection, transport and storage, and the effect of temperature changes and preservative. Previous extraction methods transfer methane from water to gas by either a "sparge and trap" or a "headspace equilibration" technique. The gas is then analyzed for methane by gas chromatography. Here, we revisit the headspace equilibration technique and describe a simple, inexpensive, and reliable method to measure methane in fresh and seawater, regardless of concentration. Within the range of concentrations typically found in surface seawaters (2-1000 nmol L-1), the yield of the method nears 100% of what is expected from solubility calculation following the addition of known amount of methane. In addition to being sensitive (detection limit of 0.1 ppmv, or 0.74 nmol L-1), this method requires less than 10 min per sample, and does not use highly toxic chemicals. It can be conducted with minimum materials and does not require the use of a gas chromatograph at the collection site. It can therefore be used in various remote working environments and conditions.

Convergence of high order perturbative expansions in open system quantum dynamics.

PubMed

Xu, Meng; Song, Linze; Song, Kai; Shi, Qiang

2017-02-14

We propose a new method to directly calculate high order perturbative expansion terms in open system quantum dynamics. They are first written explicitly in path integral expressions. A set of differential equations are then derived by extending the hierarchical equation of motion (HEOM) approach. As two typical examples for the bosonic and fermionic baths, specific forms of the extended HEOM are obtained for the spin-boson model and the Anderson impurity model. Numerical results are then presented for these two models. General trends of the high order perturbation terms as well as the necessary orders for the perturbative expansions to converge are analyzed.

Toward estimation of origin of methane at ancient seeps — Carbon isotopes of seep carbonates, lipid biomarkers, and adsorbed gas

NASA Astrophysics Data System (ADS)

Miyajima, Yusuke; Watanabe, Yumiko; Ijiri, Akira; Goto, Akiko; Jenkins, Robert; Hasegawa, Takashi; Sakai, Saburo; Matsumoto, Ryo

2017-04-01

Methane is generated mainly by microbial or thermal degradation of organic matter, and the origin of methane can be estimated based on its stable carbon isotopic signature. Seafloor seepages of methane-charged fluids have been a major source of methane to the ocean, and knowing the origin of methane at the methane seeps can provide valuable insights into the subsurface fluid circulation and biogeochemical processes. Methane seeps in the geological past are archived as authigenic methane-derived carbonate rocks, which precipitate via an alkalinity increase facilitated by microbially mediated anaerobic oxidation of methane. Here we attempted to estimate origins of methane at ancient seeps, based on several proxies preserved within the seep carbonates. We examined methane-seep carbonate rocks in the Japan Sea region, collected from lower Miocene to middle Pleistocene sediments at 11 sites on land, and also carbonate nodules collected from the seafloor off Joetsu, where thermogenic methane is seeping. Carbon isotopic compositions of the carbonates and lipid biomarkers of methane-oxidizing archaea within them were analyzed. In order to directly know original isotopic signatures of methane, we also attempted to extract adsorbed methane through acid dissolution of the powdered carbonates. Early-diagenetic carbonate phases show various δ13C values between -64.7 and -4.7‰ vs. VPDB, suggesting either biogenic or thermogenic, or both origins of methane. A lipid biomarker pentamethylicosane (PMI) extracted from the ancient carbonates has δ13C values mostly lower than -100‰ , whereas that from the modern methane-derived carbonate nodule has a higher value (-80‰ ). The δ13C values of the seeping methane (-36‰ ) and PMI in the modern Joetsu seep carbonate shows an offset of -44‰ . If this carbon isotope offset was similar at the ancient seeps, the δ13C values of PMI indicate that methane at ancient seeps in the Japan Sea region was biogenic in origin, with δ13C values lower than -50‰ . Acid dissolution of the Miocene to Pliocene carbonates released methane with δ13C values mostly around or higher than -50‰ , which conflicts with the estimation based on biomarkers. Moreover, the Pleistocene and modern samples released only trace amounts of methane. It is thus highly possible that the extracted methane was mostly adsorbed on the carbonates within zones of thermogenic generation of hydrocarbons during burial. In conclusion, we can roughly estimate origins of methane at ancient seeps based on δ13C values of carbonates and biomarkers. However, in order to directly analyze methane contained in ancient seepage fluids, exploration of gas or fluid inclusions trapped within carbonate crystals is necessary.

Bioconversion of methane to lactate by an obligate methanotrophic bacterium

DOE PAGES

Henard, Calvin A.; Smith, Holly; Dowe, Nancy; ...

2016-02-23

Methane is the second most abundant greenhouse gas (GHG), with nearly 60% of emissions derived from anthropogenic sources. Microbial conversion of methane to fuels and value-added chemicals offers a means to reduce GHG emissions, while also valorizing this otherwise squandered high-volume, high-energy gas. However, to date, advances in methane biocatalysis have been constrained by the low-productivity and limited genetic tractability of natural methane-consuming microbes. Here, leveraging recent identification of a novel, tractable methanotrophic bacterium, Methylomicrobium buryatense, we demonstrate microbial biocatalysis of methane to lactate, an industrial platform chemical. Heterologous overexpression of a Lactobacillus helveticus L-lactate dehydrogenase in M. buryatense resultedmore » in an initial titer of 0.06 g lactate/L from methane. Cultivation in a 5 L continuously stirred tank bioreactor enabled production of 0.8 g lactate/L, representing a 13-fold improvement compared to the initial titer. The yields (0.05 g lactate/g methane) and productivity (0.008 g lactate/L/h) indicate the need and opportunity for future strain improvement. Additionally, real-time analysis of methane utilization implicated gas-to-liquid transfer and/or microbial methane consumption as process limitations. This work opens the door to develop an array of methanotrophic bacterial strain-engineering strategies currently employed for biocatalytic sugar upgrading to “green” chemicals and fuels.« less

Bioconversion of methane to lactate by an obligate methanotrophic bacterium

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

Henard, Calvin A.; Smith, Holly; Dowe, Nancy

Methane is the second most abundant greenhouse gas (GHG), with nearly 60% of emissions derived from anthropogenic sources. Microbial conversion of methane to fuels and value-added chemicals offers a means to reduce GHG emissions, while also valorizing this otherwise squandered high-volume, high-energy gas. However, to date, advances in methane biocatalysis have been constrained by the low-productivity and limited genetic tractability of natural methane-consuming microbes. Here, leveraging recent identification of a novel, tractable methanotrophic bacterium, Methylomicrobium buryatense, we demonstrate microbial biocatalysis of methane to lactate, an industrial platform chemical. Heterologous overexpression of a Lactobacillus helveticus L-lactate dehydrogenase in M. buryatense resultedmore » in an initial titer of 0.06 g lactate/L from methane. Cultivation in a 5 L continuously stirred tank bioreactor enabled production of 0.8 g lactate/L, representing a 13-fold improvement compared to the initial titer. The yields (0.05 g lactate/g methane) and productivity (0.008 g lactate/L/h) indicate the need and opportunity for future strain improvement. Additionally, real-time analysis of methane utilization implicated gas-to-liquid transfer and/or microbial methane consumption as process limitations. This work opens the door to develop an array of methanotrophic bacterial strain-engineering strategies currently employed for biocatalytic sugar upgrading to “green” chemicals and fuels.« less

Bioconversion of methane to lactate by an obligate methanotrophic bacterium

PubMed Central

Henard, Calvin A.; Smith, Holly; Dowe, Nancy; Kalyuzhnaya, Marina G.; Pienkos, Philip T.; Guarnieri, Michael T.

2016-01-01

Methane is the second most abundant greenhouse gas (GHG), with nearly 60% of emissions derived from anthropogenic sources. Microbial conversion of methane to fuels and value-added chemicals offers a means to reduce GHG emissions, while also valorizing this otherwise squandered high-volume, high-energy gas. However, to date, advances in methane biocatalysis have been constrained by the low-productivity and limited genetic tractability of natural methane-consuming microbes. Here, leveraging recent identification of a novel, tractable methanotrophic bacterium, Methylomicrobium buryatense, we demonstrate microbial biocatalysis of methane to lactate, an industrial platform chemical. Heterologous overexpression of a Lactobacillus helveticus L-lactate dehydrogenase in M. buryatense resulted in an initial titer of 0.06 g lactate/L from methane. Cultivation in a 5 L continuously stirred tank bioreactor enabled production of 0.8 g lactate/L, representing a 13-fold improvement compared to the initial titer. The yields (0.05 g lactate/g methane) and productivity (0.008 g lactate/L/h) indicate the need and opportunity for future strain improvement. Additionally, real-time analysis of methane utilization implicated gas-to-liquid transfer and/or microbial methane consumption as process limitations. This work opens the door to develop an array of methanotrophic bacterial strain-engineering strategies currently employed for biocatalytic sugar upgrading to “green” chemicals and fuels. PMID:26902345

Geologic methane seeps along boundaries of Arctic permafrost thaw and melting glaciers

NASA Astrophysics Data System (ADS)

Walter Anthony, Katey M.; Anthony, Peter; Grosse, Guido; Chanton, Jeffrey

2012-06-01

Methane, a potent greenhouse gas, accumulates in subsurface hydrocarbon reservoirs, such as coal beds and natural gas deposits. In the Arctic, permafrost and glaciers form a `cryosphere cap' that traps gas leaking from these reservoirs, restricting flow to the atmosphere. With a carbon store of over 1,200Pg, the Arctic geologic methane reservoir is large when compared with the global atmospheric methane pool of around 5Pg. As such, the Earth's climate is sensitive to the escape of even a small fraction of this methane. Here, we document the release of 14C-depleted methane to the atmosphere from abundant gas seeps concentrated along boundaries of permafrost thaw and receding glaciers in Alaska and Greenland, using aerial and ground surface survey data and in situ measurements of methane isotopes and flux. We mapped over 150,000 seeps, which we identified as bubble-induced open holes in lake ice. These seeps were characterized by anomalously high methane fluxes, and in Alaska by ancient radiocarbon ages and stable isotope values that matched those of coal bed and thermogenic methane accumulations. Younger seeps in Greenland were associated with zones of ice-sheet retreat since the Little Ice Age. Our findings imply that in a warming climate, disintegration of permafrost, glaciers and parts of the polar ice sheets could facilitate the transient expulsion of 14C-depleted methane trapped by the cryosphere cap.

Solubility of aqueous methane under metastable conditions: implications for gas hydrate nucleation.

PubMed

Guo, Guang-Jun; Rodger, P Mark

2013-05-30

To understand the prenucleation stage of methane hydrate formation, we measured methane solubility under metastable conditions using molecular dynamics simulations. Three factors that influence solubility are considered: temperature, pressure, and the strength of the modeled van der Waals attraction between methane and water. Moreover, the naturally formed water cages and methane clusters in the methane solutions are analyzed. We find that both lowering the temperature and increasing the pressure increase methane solubility, but lowering the temperature is more effective than increasing the pressure in promoting hydrate nucleation because the former induces more water cages to form while the latter makes them less prevalent. With an increase in methane solubility, the chance of forming large methane clusters increases, with the distribution of cluster sizes being exponential. The critical solubility, beyond which the metastable solutions spontaneously form hydrate, is estimated to be ~0.05 mole fraction in this work, corresponding to the concentration of 1.7 methane molecules/nm(3). This value agrees well with the cage adsorption hypothesis of hydrate nucleation.

Using multiple calibration sets to improve the quantitative accuracy of partial least squares (PLS) regression on open-path fourier transform infrared (OP/FT-IR) spectra of ammonia over wide concentration ranges

USDA-ARS?s Scientific Manuscript database

A technique of using multiple calibration sets in partial least squares regression (PLS) was proposed to improve the quantitative determination of ammonia from open-path Fourier transform infrared spectra. The spectra were measured near animal farms, and the path-integrated concentration of ammonia...

Airborne Measurements of Atmospheric Methane Using Pulsed Laser Transmitters

NASA Technical Reports Server (NTRS)

Numata, Kenji; Riris, Haris; Wu, Stewart; Gonzalez, Brayler; Rodriguez, Michael; Hasselbrack, William; Fahey, Molly; Yu, Anthony; Stephen, Mark; Mao, Jianping;

Nitrate but not tea saponin feed additives decreased enteric methane emissions in nonlactating cows.

PubMed

Guyader, J; Eugène, M; Doreau, M; Morgavi, D P; Gérard, C; Loncke, C; Martin, C

2015-11-01

Tea saponin is considered a promising natural compound for reducing enteric methane emissions in ruminants. A trial was conducted to study the effect of this plant extract fed alone or in combination with nitrate on methane emissions, total tract digestive processes, and ruminal characteristics in cattle. The experiment was conducted as a 2 × 2 factorial design with 4 ruminally cannulated nonlactating dairy cows. Feed offer was restricted to 90% of voluntary intake and diets consisted of (DM basis): 1) control (CON; 50% hay and 50% pelleted concentrates), 2) CON with 0.5% tea saponin (TEA), 3) CON with 2.3% nitrate (NIT), and 4) CON with 0.5% tea saponin and 2.3% nitrate (TEA+NIT). Tea saponin and nitrate were included in pelleted concentrates. Diets contained similar amounts of CP (12.2%), starch (26.0%), and NDF (40.1%). Experimental periods lasted 5 wk including 2 wk of measurement (wk 4 and 5), during which intake was measured daily. In wk 4, daily methane emissions were quantified for 4 d using open circuit respiratory chambers. In wk 5, total tract digestibility, N balance, and urinary excretion of purine derivatives were determined from total feces and urine collected separately for 6 d. Ruminal fermentation products and protozoa concentration were analyzed from samples taken after morning feeding for 2 nonconsecutive days in wk 5. Tea saponin and nitrate supplementation decreased feed intake ( < 0.05), with an additive effect when fed in combination. Compared with CON, tea saponin did not modify methane emissions (g/kg DMI; > 0.05), whereas nitrate-containing diets (NIT and TEA+NIT) decreased methanogenesis by 28%, on average ( < 0.001). Total tract digestibility, N balance, and urinary excretion of purine derivatives were similar among diets. Ruminal fermentation products were not affected by tea saponin, whereas nitrate-containing diets increased acetate proportion and decreased butyrate proportion and ammonia concentration ( < 0.05). Under the experimental conditions tested, we confirmed the antimethanogenic effect of nitrate, whereas tea saponin alone included in pelleted concentrates failed to decrease enteric methane emissions in nonlactating dairy cows.

ARPA-E: Guiding Technologies to Commercial Success

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

Tuttle, John; Aizenberg, Joanna; Madrone, Leila

ARPA-E’s Technology-to-Market Advisors work closely with each ARPA-E project team to develop and execute a commercialization strategy. ARPA-E requires our teams to focus on their commercial path forward, because we understand that to have an impact on our energy mission, technologies must have a viable path into the marketplace. ARPA-E Senior Commercialization Advisor Dr. John Tuttle discusses what this Tech-to-Market guidance in practice looks like with reference to two project teams. OPEN 2012 awardees from Harvard University and Sunfolding share their stories of how ARPA-E worked with their teams to analyze market conditions and identify commercial opportunities that ultimately convincedmore » them to pivot their technologies towards market applications with greater potential.« less

Methane hydrates in nature - Current knowledge and challenges

USGS Publications Warehouse

Collett, Timothy S.

2014-01-01

Recognizing the importance of methane hydrate research and the need for a coordinated effort, the United States Congress enacted the Methane Hydrate Research and Development Act of 2000. At the same time, the Ministry of International Trade and Industry in Japan launched a research program to develop plans for a methane hydrate exploratory drilling project in the Nankai Trough. India, China, the Republic of Korea, and other nations also have established large methane hydrate research and development programs. Government-funded scientific research drilling expeditions and production test studies have provided a wealth of information on the occurrence of methane hydrates in nature. Numerous studies have shown that the amount of gas stored as methane hydrates in the world may exceed the volume of known organic carbon sources. However, methane hydrates represent both a scientific and technical challenge, and much remains to be learned about their characteristics and occurrence in nature. Methane hydrate research in recent years has mostly focused on: (1) documenting the geologic parameters that control the occurrence and stability of methane hydrates in nature, (2) assessing the volume of natural gas stored within various methane hydrate accumulations, (3) analyzing the production response and characteristics of methane hydrates, (4) identifying and predicting natural and induced environmental and climate impacts of natural methane hydrates, (5) analyzing the methane hydrate role as a geohazard, (6) establishing the means to detect and characterize methane hydrate accumulations using geologic and geophysical data, and (7) establishing the thermodynamic phase equilibrium properties of methane hydrates as a function of temperature, pressure, and gas composition. The U.S. Department of Energy (DOE) and the Consortium for Ocean Leadership (COL) combined their efforts in 2012 to assess the contributions that scientific drilling has made and could continue to make to advance our understanding of methane hydrates in nature. COL assembled a Methane Hydrate Project Science Team with members from academia, industry, and government. This Science Team worked with COL and DOE to develop and host the Methane Hydrate Community Workshop, which surveyed a substantial cross section of the methane hydrate research community for input on the most important research developments in our understanding of methane hydrates in nature and their potential role as an energy resource, a geohazard, and/or as an agent of global climate change. Our understanding of how methane hydrates occur in nature is still growing and evolving, and it is known with certainty that field, laboratory, and modeling studies have contributed greatly to our understanding of hydrates in nature and will continue to be a critical source of the information needed to advance our understanding of methane hydrates.

Permafrost Thaw Induces Methane Oxidation in Transitional Thaw Stages in a Subarctic Peatland

NASA Astrophysics Data System (ADS)

Perryman, C. R.; Kashi, N. N.; Malhotra, A.; McCalley, C. K.; Varner, R. K.

2015-12-01

Rising temperatures in the subarctic are accelerating permafrost thaw and increasing methane (CH4) emissions from subarctic peatlands. Methanotrophs in these peatlands can consume/oxidize CH4, potentially mitigating CH4 emissions in these peatlands. Oxidation rates can exceed 90% of CH4 production in some settings, depending on O2 and CH4 availability and environmental conditions. Malhotra and Roulet identified 10 thaw stages in Stordalen Mire near Abisko, Sweden (68°21'N,18°49'E ) with variable vegetation, environmental conditions, and associated CH4 emissions. We investigated potential methane oxidation rates across these thaw stages. Peat cores were extracted from two depths at each stage and incubated in 350ml glass jars at in situ temperatures and CH4 concentrations. Headspace samples were collected from each incubation jar over a 48-hour period and analyzed for CH4 concentration using flame ionization detection gas chromatography (GC-FID). Oxidation rates ranged from <0.1 to 17 μg of CH4 per gram of dry biomass per day. Water table depth and pore water pH were the strongest environmental correlates of oxidation (sample size = 56, p < 0.001). The highest potential oxidation rates were observed in collapsing palsa sites and recently collapsed sedge-dominated open water sites near palsa mounds. Our results suggest that permafrost thaw induces high CH4 oxidation rates by creating conditions ideal for both methanogenic and methanotrophic microbial communities. Our results also reinforce the importance of incorporating transitional thaw stages in landscape level carbon budgets of thawing peatlands emphasized by Malhotra and Roulet. Forthcoming microbial analysis and stable isotope analysis will further elucidate the factors controlling methane oxidation rates at Stordalen Mire.

Influence from Surrounding Land on the Turbulence Measurements Above a Lake

NASA Astrophysics Data System (ADS)

Sahlée, Erik; Rutgersson, Anna; Podgrajsek, Eva; Bergström, Hans

2014-02-01

Turbulence measurements taken at a Swedish lake are analyzed. Although the measurements took place over a relatively large lake with several km of undisturbed fetch, the turbulence structure was found to be highly influenced by the surrounding land during daytime. Variance spectra of both horizontal velocity and scalars during both unstable and stable stratification displayed a low frequency peak. The energy at lower frequencies showed a daily variation, increasing in the morning and decreasing in the afternoon. This behaviour is explained by spectral lag, where the low frequency energy due to large eddies that originate from the convective boundary layer above the surrounding land. When the air is advected over the lake the small eddies rapidly equilibrate with the new surface forcing. However, the large eddies remain for an appreciable distance and influence the turbulence in the developing lake boundary layer. The variances of the horizontal velocity and scalars are increased by these large eddies, while the turbulent fluxes are mainly unaffected. The drag coefficient, Stanton number and Dalton number used to parametrize the momentum flux, heat flux and latent heat flux respectively all compare well with current parametrizations developed for open sea conditions. The diurnal cycle of the partial pressure of methane, pCH4, observed at this site is closely related to the diurnal cycle of the lake-air methane flux. An idealized two-dimensional model simulation of the boundary layer at a lake site indicates that the strong response of pCH4 to the surface methane flux is due to the shallow internal boundary layer that develops above the lake, allowing methane to accumulate in a relatively small volume.

Quantifying the relative contribution of natural gas fugitive emissions to total methane emissions in Colorado, Utah, and Texas using mobile isotopic methane analysis based on Cavity Ringdown Spectroscopy

NASA Astrophysics Data System (ADS)

Rella, Chris; Winkler, Renato; Sweeney, Colm; Karion, Anna; Petron, Gabrielle; Crosson, Eric

2014-05-01

Fugitive emissions of methane into the atmosphere are a major concern facing the natural gas production industry. Because methane is more energy-rich than coal per kg of carbon dioxide emitted into the atmosphere, it represents an attractive alternative to coal for electricity generation, provided that the fugitive emissions of methane are kept under control. A key step in assessing these emissions in a given region is partitioning the observed methane emissions between natural gas fugitive emissions and other sources of methane, such as from landfills or agricultural activities. One effective method for assessing the contribution of these different sources is stable isotope analysis, using the isotopic carbon signature to distinguish between natural gas and landfills or ruminants. We present measurements of methane using a mobile spectroscopic stable isotope analyzer based on cavity ringdown spectroscopy, in three intense natural gas producing regions of the United States: the Denver-Julesburg basin in Colorado, the Uintah basin in Utah, and the Barnett Shale in Texas. Performance of the CRDS isotope analyzer is presented, including precision, calibration, stability, and the potential for measurement bias due to other atmospheric constituents. Mobile isotope measurements of individual sources and in the nocturnal boundary layer have been combined to establish the fraction of the observed methane emissions that can be attributed to natural gas activities. The fraction of total methane emissions in the Denver-Julesburg basin attributed to natural gas emissions is 78 +/- 13%. In the Uinta basin, which has no other significant sources of methane, the fraction is 96% +/- 15%. In addition, results from the Barnett shale are presented, which includes a major urban center (Dallas / Ft. Worth). Methane emissions in this region are spatially highly heterogeneous. Spatially-resolved isotope and concentration measurements are interpreted using a simple emissions model to arrive at an overall isotope ratio for the region.

Gas hydrates of outer continental margins

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

Kvenvolden, K.A.

1990-05-01

Gas hydrates are crystalline substances in which a rigid framework of water molecules traps molecules of gas, mainly methane. Gas-hydrate deposits are common in continental margin sediment in all major oceans at water depths greater than about 300 m. Thirty-three localities with evidence for gas-hydrate occurrence have been described worldwide. The presence of these gas hydrates has been inferred mainly from anomalous lacoustic reflectors seen on marine seismic records. Naturally occurring marine gas hydrates have been sampled and analyzed at about tensites in several regions including continental slope and rise sediment of the eastern Pacific Ocean and the Gulf ofmore » Mexico. Except for some Gulf of Mexico gas hydrate occurrences, the analyzed gas hydrates are composed almost exclusively of microbial methane. Evidence for the microbial origin of methane in gas hydrates includes (1) the inverse relation between methane occurence and sulfate concentration in the sediment, (2) the subparallel depth trends in carbon isotopic compositions of methane and bicarbonate in the interstitial water, and (3) the general range of {sup 13}C depletion ({delta}{sub PDB}{sup 13}C = {minus}90 to {minus}60 {per thousand}) in the methane. Analyses of gas hydrates from the Peruvian outer continental margin in particular illustrate this evidence for microbially generated methane. The total amount of methane in gas hydrates of continental margins is not known, but estimates of about 10{sup 16} m{sup 3} seem reasonable. Although this amount of methane is large, it is not yet clear whether methane hydrates of outer continental margins will ever be a significant energy resource; however, these gas hydrates will probably constitute a drilling hazard when outer continental margins are explored in the future.« less

Assessing Methane in Shallow Groundwater in Unconventional Oil and Gas Play Areas, Eastern Kentucky.

PubMed

Zhu, Junfeng; Parris, Thomas M; Taylor, Charles J; Webb, Steven E; Davidson, Bart; Smath, Richard; Richardson, Stephen D; Molofsky, Lisa J; Kromann, Jenna S; Smith, Ann P

2018-05-01

The expanding use of horizontal drilling and hydraulic fracturing technology to produce oil and gas from tight rock formations has increased public concern about potential impacts on the environment, especially on shallow drinking water aquifers. In eastern Kentucky, horizontal drilling and hydraulic fracturing have been used to develop the Berea Sandstone and the Rogersville Shale. To assess baseline groundwater chemistry and evaluate methane detected in groundwater overlying the Berea and Rogersville plays, we sampled 51 water wells and analyzed the samples for concentrations of major cations and anions, metals, dissolved methane, and other light hydrocarbon gases. In addition, the stable carbon and hydrogen isotopic composition of methane (δ 13 C-CH 4 and δ 2 H-CH 4 ) was analyzed for samples with methane concentration exceeding 1 mg/L. Our study indicates that methane is a relatively common constituent in shallow groundwater in eastern Kentucky, where methane was detected in 78% of the sampled wells (40 of 51 wells) with 51% of wells (26 of 51 wells) exhibiting methane concentrations above 1 mg/L. The δ 13 C-CH 4 and δ 2 H-CH 4 ranged from -84.0‰ to -58.3‰ and from -246.5‰ to -146.0‰, respectively. Isotopic analysis indicated that dissolved methane was primarily microbial in origin formed through CO 2 reduction pathway. Results from this study provide a first assessment of methane in the shallow aquifers in the Berea and Rogersville play areas and can be used as a reference to evaluate potential impacts of future horizontal drilling and hydraulic fracturing activities on groundwater quality in the region. © 2017, National Ground Water Association.

Quantifying the relative contribution of natural gas fugitive emissions to total methane emissions in Weld County Colorado using δ13CH4 analysis

NASA Astrophysics Data System (ADS)

Rella, C.; Jacobson, G. A.; Crosson, E.; Sweeney, C.; Karion, A.; Petron, G.

2012-12-01

Fugitive emissions of methane into the atmosphere are a major concern facing the natural gas production industry. Given that the global warming potential of methane is many times greater than that of carbon dioxide (Forster et al. 2007), the importance of quantifying methane emissions becomes clear. Companion presentations at this meeting describe efforts to quantify the overall methane emissions in two separate gas producing areas in Colorado and Utah during intensive field campaigns undertaken in 2012. A key step in the process of assessing the emissions arising from natural gas production activities is partitioning the observed methane emissions between natural gas fugitive emissions and other sources of methane, such as from landfills or agricultural activities. One method for assessing the contribution of these different sources is stable isotope analysis. In particular, the δ13CH4 signature of natural gas (-37 permil) is significantly different that the signature of other significant sources of methane, such as landfills or ruminants (-50 to -70 permil). In this paper we present measurements of δ13CH4 in Colorado in Weld County, a region of intense natural gas production, using a mobile δ13CH4¬ analyzer capable of high-precision measurements of the stable isotope ratio of methane at ambient levels. This analyzer was used to make stable isotope measurements at a fixed location near the center of the gas producing region, from which an overall isotope ratio for the regional emissions is determined. In addition, mobile measurements in the nocturnal boundary layer have been made, over a total distance of 150 km throughout Weld County, allowing spatially resolved measurements of this isotope signature. Finally, this analyzer was used to quantify the isotopic signature of those individual sources (natural gas fugitive emissions, concentrated animal feeding operations, and landfills) that constitute the majority of methane emissions in this region, by making measurements of the isotope ratio directly in the downwind plume from each source. These data are combined to establish the fraction of the observed methane emissions that can be attributed to natural gas activities in the region. The results are compared to inventories as well as other measurement techniques, and the uncertainty of the measurement is estimated.

Continuous time-resolved regional methane leak detection with on-line background estimation using a novel combination of dual frequency comb laser spectroscopy and atmospheric inversions

NASA Astrophysics Data System (ADS)

Alden, C. B.; Coburn, S.; Wright, R.; Baumann, E.; Cossel, K.; Sweeney, C.; Ghosh, S.; Newbury, N.; Prasad, K.; Coddington, I.; Rieker, G. B.

2017-12-01

Advances in natural gas extraction technology have led to increased US production and transport activity, and as a consequence, an increased need for monitoring of methane leaks. Current leak detection methods provide time snapshots, and not continuous, time-varying estimates of emissions. Most approaches also require specific atmospheric conditions, operators, or the use of a tracer gas, requiring site access. Given known intermittency in fugitive methane emissions, continuous monitoring is a critical need for emissions mitigation. We present a novel leak detection method that employs dual frequency comb spectrometry to offer continuous, autonomous, leak detection and quantification over square-km scale areas. The spectrometer is situated in a field of natural gas pads, and a series of retroreflectors around the field direct light back to a detector. The laser light spans 1620-1680 nm with 0.002 nm line spacing, measuring thousands of individual absorption features from multiple species. The result is high-stability trace gas (here CH4, CO2, and H2O) measurements over long (1 km+) open paths through the atmosphere. Measurements are used in an atmospheric inversion to estimate the time variability of emissions at each location of interest. Importantly, the measurement framework and inversion solve explicitly for background concentrations, which vary rapidly in fields of active oil and gas production. We present the results of controlled-leak field tests in rural Colorado. We demonstrate the ability to locate and size a leak located 1 km away from the spectrometer and varying in strength from 1.5 to 7.7 g/min, resulting in mean atmospheric enhancements of 20 ppb. The inversion correctly identifies when the leak turned on and off over a 24-hour period, and determines the mean leak strength to within 10% of the true controlled rate. We further demonstrate the ability of the system to correctly locate and size the start and end of simultaneous 2.7 to 4.8 g/min leaks from 2 sources in a field of 5 potential leak locations. Finally, we present the results of leak-detection tests in active oil and gas fields in the Denver Julesburg Basin, where background methane is complex.

Rapid Swept-Wavelength External Cavity Quantum Cascade Laser for Open Path Sensing

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

Brumfield, Brian E.; Phillips, Mark C.

2015-07-01

A rapidly tunable external cavity quantum cascade laser system is used for open path sensing. The system permits acquisition of transient absorption spectra over a 125 cm-1 tuning range in less than 0.01 s.

Using Support Vector Machines to Automatically Extract Open Water Signatures from POLDER Multi-Angle Data Over Boreal Regions

NASA Technical Reports Server (NTRS)

Pierce, J.; Diaz-Barrios, M.; Pinzon, J.; Ustin, S. L.; Shih, P.; Tournois, S.; Zarco-Tejada, P. J.; Vanderbilt, V. C.; Perry, G. L.; Brass, James A. (Technical Monitor)

2002-01-01

This study used Support Vector Machines to classify multiangle POLDER data. Boreal wetland ecosystems cover an estimated 90 x 10(exp 6) ha, about 36% of global wetlands, and are a major source of trace gases emissions to the atmosphere. Four to 20 percent of the global emission of methane to the atmosphere comes from wetlands north of 4 degrees N latitude. Large uncertainties in emissions exist because of large spatial and temporal variation in the production and consumption of methane. Accurate knowledge of the areal extent of open water and inundated vegetation is critical to estimating magnitudes of trace gas emissions. Improvements in land cover mapping have been sought using physical-modeling approaches, neural networks, and active microwave, examples that demonstrate the difficulties of separating open water, inundated vegetation and dry upland vegetation. Here we examine the feasibility of using a support vector machine to classify POLDER data representing open water, inundated vegetation and dry upland vegetation.

Baseline study of methane emission from anaerobic ponds of palm oil mill effluent treatment.

PubMed

Yacob, Shahrakbah; Ali Hassan, Mohd; Shirai, Yoshihito; Wakisaka, Minato; Subash, Sunderaj

2006-07-31

The world currently obtains its energy from the fossil fuels such as oil, natural gas and coal. However, the international crisis in the Middle East, rapid depletion of fossil fuel reserves as well as climate change have driven the world towards renewable energy sources which are abundant, untapped and environmentally friendly. Malaysia has abundant biomass resources generated from the agricultural industry particularly the large commodity, palm oil. This paper will focus on palm oil mill effluent (POME) as the source of renewable energy from the generation of methane and establish the current methane emission from the anaerobic treatment facility. The emission was measured from two anaerobic ponds in Felda Serting Palm Oil Mill for 52 weeks. The results showed that the methane content was between 35.0% and 70.0% and biogas flow rate ranged between 0.5 and 2.4 L/min/m(2). Total methane emission per anaerobic pond was 1043.1 kg/day. The total methane emission calculated from the two equations derived from relationships between methane emission and total carbon removal and POME discharged were comparable with field measurement. This study also revealed that anaerobic pond system is more efficient than open digesting tank system for POME treatment. Two main factors affecting the methane emission were mill activities and oil palm seasonal cropping.

Methane Emissions from Small Lakes: Dynamics and Distribution Patterns

NASA Astrophysics Data System (ADS)

Encinas Fernández, J. M.; Peeters, F.; Hofmann, H.

2014-12-01

The dynamics of dissolved methane were measured during three years in five small lakes with different surface areas and maximum water depth. We analyze and compare the horizontal and vertical distribution of dissolved methane within these lakes during different time periods: the stratified period in summer, the autumn overturn, the winter mixing period, and the period from spring to summer stratification. The horizontal distributions of dissolved methane within the lakes suggest that the relation between surface area and maximum water-depth is a key factor determining the heterogeneity of methane concentrations in the surface water. During most of the year littoral zones are the main source of the methane that is emitted to the atmosphere except for the overturn periods. The vertical distributions of temperature and dissolved oxygen within the different seasons affect the vertical distribution of dissolved methane and thus the methane budget within lakes. Anoxic conditions in the hypolimnion and the intense mixing during overturn periods are key factors for the overall annual methane emissions from lakes.

HAI, a new airborne, absolute, twin dual-channel, multi-phase TDLAS-hygrometer: background, design, setup, and first flight data

NASA Astrophysics Data System (ADS)

Buchholz, Bernhard; Afchine, Armin; Klein, Alexander; Schiller, Cornelius; Krämer, Martina; Ebert, Volker

2017-01-01

The novel Hygrometer for Atmospheric Investigation (HAI) realizes a unique concept for simultaneous gas-phase and total (gas-phase + evaporated cloud particles) water measurements. It has been developed and successfully deployed for the first time on the German HALO research aircraft. This new instrument combines direct tunable diode laser absorption spectroscopy (dTDLAS) with a first-principle evaluation method to allow absolute water vapor measurements without any initial or repetitive sensor calibration using a reference gas or a reference humidity generator. HAI contains two completely independent dual-channel (closed-path, open-path) spectrometers, one at 1.4 and one at 2.6 µm, which together allow us to cover the entire atmospheric H2O range from 1 to 40 000 ppmv with a single instrument. Both spectrometers each comprise a separate, wavelength-individual extractive, closed-path cell for total water (ice and gas-phase) measurements. Additionally, both spectrometers couple light into a common open-path cell outside of the aircraft fuselage for a direct, sampling-free, and contactless determination of the gas-phase water content. This novel twin dual-channel setup allows for the first time multiple self-validation functions, in particular a reliable, direct, in-flight validation of the open-path channels. During the first field campaigns, the in-flight deviations between the independent and calibration-free channels (i.e., closed-path to closed-path and open-path to closed-path) were on average in the 2 % range. Further, the fully autonomous HAI hygrometer allows measurements up to 240 Hz with a minimal integration time of 1.4 ms. The best precision is achieved by the 1.4 µm closed-path cell at 3.8 Hz (0.18 ppmv) and by the 2.6 µm closed-path cell at 13 Hz (0.055 ppmv). The requirements, design, operation principle, and first in-flight performance of the hygrometer are described and discussed in this work.

Evaluating host-associated sources of marine methane supersaturation

NASA Astrophysics Data System (ADS)

Blanton, J. M.; Pieper, L. M.; Allen, E. E.

2013-12-01

Methane can be found in surface ocean waters at levels from 5% to 75% greater than expected from exchange with the atmosphere. Because oceanic emissions account for up to 4% of the planet's annual methane inventory, understanding marine sources and sinks is relevant to global greenhouse gas budgets. These methane levels are presumed to result from the activity of microorganisms in the water column, yet this presents a paradox: how can biotic methanogensis, primarily understood as an anaerobic process, take place in oxic waters? One working theory is that methanogens find safe harbor in the gastrointestinal tracts of marine animals. We investigate the possibility that microbial communities within fish, and the fecal material they produce, contribute to in-situ methane production in the open ocean. Using genetic markers, we test the GI tracts of benthic and pelagic marine teleosts for the presence of methanogenic organisms and for components of the methanogenesis pathway. Our results indicate that methanogens may be present in fish, but in low numbers. This work sets the scene for measurement of methane production rates from these gut-associated communities in order to elucidate their contribution to oceanic methane supersaturation.

Isotopic constraints on global atmospheric methane sources and sinks: a critical assessment of recent findings and new data

NASA Astrophysics Data System (ADS)

Schwietzke, S.; Sherwood, O.; Michel, S. E.; Bruhwiler, L.; Dlugokencky, E. J.; Tans, P. P.

2017-12-01

Methane isotopic data have increasingly been used in recent studies to help constrain global atmospheric methane sources and sinks. The added scientific contributions to this field include (i) careful comparisons and merging of atmospheric isotope measurement datasets to increase spatial coverage, (ii) in-depth analyses of observed isotopic spatial gradients and seasonal patterns, and (iii) improved datasets of isotopic source signatures. Different interpretations have been made regarding the utility of the isotopic data on the diagnosis of methane sources and sinks. Some studies have found isotopic evidence of a largely microbial source causing the renewed growth in global atmospheric methane since 2007, and underestimated global fossil fuel methane emissions compared to most previous studies. However, other studies have challenged these conclusions by pointing out substantial spatial variability in isotopic source signatures as well as open questions in atmospheric sinks and biomass burning trends. This presentation will review and contrast the main arguments and evidence for the different conclusions. The analysis will distinguish among the different research objectives including (i) global methane budget source attribution in steady-state, (ii) source attribution of recent global methane trends, and (iii) identifying specific methane sources in individual plumes during field campaigns. Additional comparisons of model experiments with atmospheric measurements and updates on isotopic source signature data will complement the analysis.

Open-path TDL-Spectrometry for a Tomographic Reconstruction of 2D H2O-Concentration Fields in the Soil-Air-Boundary-Layer of Permafrost

NASA Astrophysics Data System (ADS)

Seidel, Anne; Wagner, Steven; Dreizler, Andreas; Ebert, Volker

2013-04-01

The melting of permafrost soils in arctic regions is one of the effects of climate change. It is recognized that climatically relevant gases are emitted during the thawing process, and that they may lead to a positive atmospheric feedback [1]. For a better understanding of these developments, a quantification of the gases emitted from the soil would be required. Extractive sensors with local point-wise gas sampling are currently used for this task, but are hampered due to the complex spatial structure of the soil surface, which complicates the situation due to the essential need for finding a representative gas sampling point. For this situation it would be much preferred if a sensor for detecting 2D-concentration fields of e.g. water vapor, (and in the mid-term also for methane or carbon dioxide) directly in the soil-atmosphere-boundary layer of permafrost soils would be available. However, it also has to be kept in mind that field measurements over long time periods in such a harsh environment require very sturdy instrumentation preferably without the need for sensor calibration. Therefore we are currently developing a new, robust TDLAS (tuneable diode laser absorption spectroscopy)-spectrometer based on cheap reflective foils [2]. The spectrometer is easily transportable, requires hardly any alignment and consists of industrially available, very stable components (e.g. diode lasers and glass fibers). Our measurement technique, open path TDLAS, allows for calibration-free measurements of absolute H2O concentrations. The static instrument for sampling open-path H2O concentrations consists of a joint sending and receiving optics at one side of the measurement path and a reflective element at the other side. The latter is very easy to align, since it is a foil usually applied for traffic purposes that retro-reflects the light to its origin even for large angles of misalignment (up to 60°). With this instrument, we achieved normalized detection limits of up to 0.9 ppmv?m??Hz. For absorption path lengths of up to 2 m and time resolution of 0.2 sec, we attained detection limits of 1 ppmv. Furthermore we realized a wide dynamic range covering concentrations between 200 ppmv and 12300 ppmv. The static spectrometer will now be extended to a spatially scanning TDL sensor using rapidly rotating polygon mirrors. In combination with tomographic reconstruction methods, spatially resolved 2D-fields will be measured and retrieved. The aim is to capture concentration fields with at least 1 m2 spatial coverage with concentration detection faster than 1 Hz rate. We simulated various measurements from typical concentration distributions ("phantoms") and used Algebraic Reconstruction Techniques (ART) to compute the according 2D-fields. The reconstructions look very promising and demonstrate the potential of the measurement method. In the presentation we will describe and discuss the optical setup of the stationary instrument and explain the concept of extending this instrument to a spatially scanning tomographic TDL instrument for soil studies. Further we present first results evaluating the capabilities of the selected ART reconstruction on tomographic phantoms. [1] E. Schuur, J. G. Vogel, K. G. Crummer, H. Lee, J. O. Sickman, and T. E. Osterkamp, "The effect of permafrost thaw on old carbon release and net carbon exchange from tundra.," Nature, vol. 459, no. 7246, pp. 556-9, May 2009. [2] A. Seidel, S. Wagner, and V. Ebert, "TDLAS-based open-path laser hygrometer using simple reflective foils as scattering targets," Applied Physics B, vol. 109, no. 3, pp. 497-504, Oct. 2012.

Performance Simulations for a Spaceborne Methane Lidar Mission

NASA Technical Reports Server (NTRS)

Kiemle, C.; Kawa, Stephan Randolph; Quatrevalet, Mathieu; Browell, Edward V.

2014-01-01

Future spaceborne lidar measurements of key anthropogenic greenhouse gases are expected to close current observational gaps particularly over remote, polar, and aerosol-contaminated regions, where actual in situ and passive remote sensing observation techniques have difficulties. For methane, a "Methane Remote Lidar Mission" was proposed by Deutsches Zentrum fuer Luft- und Raumfahrt and Centre National d'Etudes Spatiales in the frame of a German-French climate monitoring initiative. Simulations assess the performance of this mission with the help of Moderate Resolution Imaging Spectroradiometer and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations of the earth's surface albedo and atmospheric optical depth. These are key environmental parameters for integrated path differential absorption lidar which uses the surface backscatter to measure the total atmospheric methane column. Results showthat a lidar with an average optical power of 0.45W at 1.6 µm wavelength and a telescope diameter of 0.55 m, installed on a low Earth orbit platform(506 km), will measure methane columns at precisions of 1.2%, 1.7%, and 2.1% over land, water, and snow or ice surfaces, respectively, for monthly aggregated measurement samples within areas of 50 × 50 km2. Globally, the mean precision for the simulated year 2007 is 1.6%, with a standard deviation of 0.7%. At high latitudes, a lower reflectance due to snow and ice is compensated by denser measurements, owing to the orbital pattern. Over key methane source regions such as densely populated areas, boreal and tropical wetlands, or permafrost, our simulations show that the measurement precision will be between 1 and 2%.

High-coherence mid-infrared dual-comb spectroscopy spanning 2.6 to 5.2 μm

NASA Astrophysics Data System (ADS)

Ycas, Gabriel; Giorgetta, Fabrizio R.; Baumann, Esther; Coddington, Ian; Herman, Daniel; Diddams, Scott A.; Newbury, Nathan R.

2018-04-01

Mid-infrared dual-comb spectroscopy has the potential to supplant conventional Fourier-transform spectroscopy in applications requiring high resolution, accuracy, signal-to-noise ratio and speed. Until now, mid-infrared dual-comb spectroscopy has been limited to narrow optical bandwidths or low signal-to-noise ratios. Using digital signal processing and broadband frequency conversion in waveguides, we demonstrate a mid-infrared dual-comb spectrometer covering 2.6 to 5.2 µm with comb-tooth resolution, sub-MHz frequency precision and accuracy, and a spectral signal-to-noise ratio as high as 6,500. As a demonstration, we measure the highly structured, broadband cross-section of propane from 2,840 to 3,040 cm-1, the complex phase/amplitude spectra of carbonyl sulfide from 2,000 to 2,100 cm-1, and of a methane, acetylene and ethane mixture from 2,860 to 3,400 cm-1. The combination of broad bandwidth, comb-mode resolution and high brightness will enable accurate mid-infrared spectroscopy in precision laboratory experiments and non-laboratory applications including open-path atmospheric gas sensing, process monitoring and combustion.

Postural stability of preoperative acoustic neuroma patients assessed by sway magnetometry: are they unsteady?

PubMed

Collins, Melanie M; Johnson, Ian J M; Clifford, Elaine; Birchall, John P; O'Donoghue, Gerald M

2003-04-01

The objective was to evaluate the preoperative postural stability of acoustic neuroma patients using sway magnetometry. Prospective two-center study. Fifty-one patients (mean age, 53 years) diagnosed with unilateral acoustic neuroma on magnetic resonance imaging at two tertiary referral centers were studied. Preoperatively, each patient had sway patterns (with eyes open and with eyes closed, and standing on foam) recorded for 120 seconds by sway magnetometry. Path length for 30 seconds was calculated. The Romberg coefficient (path length with eyes open divided by path length with eyes closed) was calculated. Forty-four percent of patients had abnormal path lengths with eyes open, and 49% with eyes closed. The Romberg coefficients were significantly lower than normal (P <.001; 95% CI, 0.19-0.87). Mean Romberg coefficient was 0.59 (normal value = 0.73), and all patients had a coefficient of less than 1. Half of preoperative acoustic neuroma patients are unsteady, exhibiting abnormal sway patterns based on path length measurements. The increase in sway path length demonstrable in normal subjects with eyes closed was significantly exaggerated in patients with acoustic neuroma.

Effect of open metal sites on adsorption of polar and nonpolar molecules in metal-organic framework Cu-BTC.

PubMed

Karra, Jagadeswara R; Walton, Krista S

2008-08-19

Atomistic grand canonical Monte Carlo simulations were performed in this work to investigate the role of open copper sites of Cu-BTC in affecting the separation of carbon monoxide from binary mixtures containing methane, nitrogen, or hydrogen. Mixtures containing 5%, 50%, or 95% CO were examined. The simulations show that electrostatic interactions between the CO dipole and the partial charges on the metal-organic framework (MOF) atoms dominate the adsorption mechanism. The binary simulations show that Cu-BTC is quite selective for CO over hydrogen and nitrogen for all three mixture compositions at 298 K. The removal of CO from a 5% mixture with methane is slightly enhanced by the electrostatic interactions of CO with the copper sites. However, the pore space of Cu-BTC is large enough to accommodate both molecules at their pure-component loadings, and in general, Cu-BTC exhibits no significant selectivity for CO over methane for the equimolar and 95% mixtures. On the basis of the pure-component and low-concentration behavior of CO, the results indicate that MOFs with open metal sites have the potential for enhancing adsorption separations of molecules of differing polarities, but the pore size relative to the sorbate size will also play a significant role.

Determination of dissolved methane in natural waters using headspace analysis with cavity ring-down spectroscopy.

PubMed

Roberts, Hannah M; Shiller, Alan M

2015-01-26

Methane (CH4) is the third most abundant greenhouse gas (GHG) but is vastly understudied in comparison to carbon dioxide. Sources and sinks to the atmosphere vary considerably in estimation, including sources such as fresh and marine water systems. A new method to determine dissolved methane concentrations in discrete water samples has been evaluated. By analyzing an equilibrated headspace using laser cavity ring-down spectroscopy (CRDS), low nanomolar dissolved methane concentrations can be determined with high reproducibility (i.e., 0.13 nM detection limit and typical 4% RSD). While CRDS instruments cost roughly twice that of gas chromatographs (GC) usually used for methane determination, the process presented herein is substantially simpler, faster, and requires fewer materials than GC methods. Typically, 70-mL water samples are equilibrated with an equivalent amount of zero air in plastic syringes. The equilibrated headspace is transferred to a clean, dry syringe and then drawn into a Picarro G2301 CRDS analyzer via the instrument's pump. We demonstrate that this instrument holds a linear calibration into the sub-ppmv methane concentration range and holds a stable calibration for at least two years. Application of the method to shipboard dissolved methane determination in the northern Gulf of Mexico as well as river water is shown. Concentrations spanning nearly six orders of magnitude have been determined with this method. Copyright © 2014 Elsevier B.V. All rights reserved.

Identification, Attribution, and Quantification of Highly Heterogeneous Methane Sources Using a Mobile Stable Isotope Analyzer

NASA Astrophysics Data System (ADS)

Crosson, E.; Rella, C.; Cunningham, K.

2012-04-01

Despite methane's importance as a potent greenhouse gas second only to carbon dioxide in the magnitude of its contribution to global warming, natural contributions to the overall methane budget are only poorly understood. A big contributor to this gap in knowledge is the highly spatially and temporally heterogeneous nature of most natural (and for that matter anthropogenic) methane sources. This high degree of heterogeneity, where the methane emission rates can vary over many orders of magnitude on a spatial scale of meters or even centimeters, and over a temporal scale of minutes or even seconds, means that traditional methods of emissions flux estimation, such as flux chambers or eddy-covariance, are difficult or impossible to apply. In this paper we present new measurement methods that are capable of detecting, attributing, and quantifying emissions from highly heterogeneous sources. These methods take full advantage of the new class of methane concentration and stable isotope analyzers that are capable of laboratory-quality analysis from a mobile field platform in real time. In this paper we present field measurements demonstrating the real-time detection of methane 'hot spots,' attribution of the methane to a source process via real-time stable isotope analysis, and quantification of the emissions flux using mobile concentration measurements of the horizontal and vertical atmospheric dispersion, combined with atmospheric transport calculations. Although these techniques are applicable to both anthropogenic and natural methane sources, in this initial work we focus primarily on landfills and fugitive emissions from natural gas distribution, as these sources are better characterized, and because they provide a more reliable and stable source of methane for quantifying the measurement uncertainty inherent in the different methods. Implications of these new technologies and techniques are explored for the quantification of natural methane sources in a variety of environments, including wetlands, peatlands, and the arctic.

Openness to Experience and Night-Sky Watching Interest as Predictors of Reading for Pleasure: Path Analysis of a Mediation Model

ERIC Educational Resources Information Center

Kelly, William E.

2010-01-01

The relation between reading for pleasure, night-sky watching interest, and openness to experience were examined in a sample of 129 college students. Results of a path analysis examining a mediation model indicated that the influence of night-sky interest on reading for pleasure was not mediated by the broad personality domain openness to…

Open-Path Hydrocarbon Laser Sensor for Oil and Gas Facility Monitoring

EPA Science Inventory

This poster reports on an experimental prototype open-path laser absorption sensor for measurement of unspeciated hydrocarbons for oil and gas production facility fence-line monitoring. Such measurements may be useful to meet certain state regulations, and enable advanced leak d...

OPEN-PATH FTIR MEASUREMENTS OF NOX AND OTHER DIESEL EMISSIONS

EPA Science Inventory

The paper gives results of a demonstration of the feasibility of using an open-path Fourier transform infrared (OP-FTIR) monitoring technique to address the across-road characterization of diesel vehicle emissions of criteria pollutants and hazardous air pollutants. Four sets of ...

PARTICULATE MATTER MEASUREMENTS USING OPEN-PATH FOURIER TRANSFORM INFRARED SPECTROSCOPY

EPA Science Inventory

Open-path Fourier transform infrared (OP-FT1R) spectroscopy is an accepted technology for measuring gaseous air contaminants. OP-FT1R absorbance spectra acquired during changing aerosols conditions reveal related changes in very broad baseline features. Usually, this shearing of ...

Monitoring trace gases in downtown Toronto using open-path Fourier transform infrared spectroscopy

NASA Astrophysics Data System (ADS)

Byrne, B.; Strong, K.; Colebatch, O.; Fogal, P.; Mittermeier, R. L.; Wunch, D.; Jones, D. B. A.

2017-12-01

Emissions of greenhouse gases (GHGs) in urban environments can be highly heterogeneous. For example, vehicles produce point source emissions which can result in heterogeneous GHG concentrations on scales <10 m. The highly localized scale of these emissions can make it difficult to measure mean GHG concentrations on scales of 100-1000 m. Open-Path Fourier Transform Infrared Spectroscopy (OP-FTIR) measurements offer spatial averaging and continuous measurements of several trace gases simultaneously in the same airmass. We have set up an open-path system in downtown Toronto to monitor trace gases in the urban boundary layer. Concentrations of CO2, CO, CH4, and N2O are derived from atmospheric absorption spectra recorded over a two-way atmospheric open path of 320 m using non-linear least squares fitting. Using a simple box model and co-located boundary layer height measurements, we estimate surface fluxes of these gases in downtown Toronto from our OP-FTIR observations.

A sink for methane on Mars? The answer is blowing in the wind

NASA Astrophysics Data System (ADS)

Knak Jensen, Svend J.; Skibsted, Jørgen; Jakobsen, Hans J.; ten Kate, Inge L.; Gunnlaugsson, Haraldur P.; Merrison, Jonathan P.; Finster, Kai; Bak, Ebbe; Iversen, Jens J.; Kondrup, Jens C.; Nørnberg, Per

2014-07-01

Tumbling experiments that mimic the wind erosion of quartz grains in an atmosphere of 13C-enriched methane are reported. The eroded grains are analyzed by 13C and 29Si solid-state NMR techniques after several months of tumbling. The analysis shows that methane has reacted with the eroded surface to form covalent Si-CH3 bonds, which stay intact for temperatures up to at least 250 °C. The NMR findings offer an explanation for the fast disappearance of methane on Mars.

The Extent of CH4 Emission and Oxidation in Thermogenic and Biogenic Gas Hydrate Environments

NASA Astrophysics Data System (ADS)

Kastner, M.; Solem, C.; Bartlett, D.; MacDonald, I.; Valentine, D.

2003-12-01

The role of methane hydrate in the global methane budget is poorly understood, because relatively little is known about the transport of gaseous and dissolved methane through the seafloor into the ocean, from the water column into the atmosphere, and the extent of water-column methanotrophy that occurs en route. We characterize the transport and consumption of methane in three distinct gas hydrate environments, spanning the spectrum of thermogenic and biogenic methane occurrences: Bush Hill in the Gulf of Mexico, Eel River off the coast of Northern California, and the Noth and South Hydrate Ridges on the Cascadia Oregon margin. At all the sites studied a significant enrichment in δ 13CH4 with distance along isopycnals away from the methane source is observed, indicative of extensive aerobic bacterial methane oxidation in the water column. The effects of this process are principally pronounced in the mostly biogenic methane setting, with δ 13C-CH4 measured as high as -12 permil (PDB) between North and South Hydrate Ridge. The δ 13C-CH4 values ranged from -12 to -67 permil at Hydrate Ridge, -34 to -52 permil at Eel River, and -41 to -49 permil at Bush Hill. The large variation in methane carbon isotope ranges between the sites suggest that major differences exist in both the rates of aerobic methane oxidation and system openness at the studied locations. A mean kinetic isotope fractionation factor is being determined using a closed-system Rayleigh distillation model. An approximate regional methane flux from the ocean into the atmosphere is being estimated for the Gulf of Mexico, by extrapolation of the flux value from the Bush Hill methane plume over 390 plume locations having persistent oil slicks on the ocean surface, mapped by time series satellite data.

Long Open Path Fourier Transform Spectroscopy Measurements of Greenhouse Gases in the Near Infrared

NASA Astrophysics Data System (ADS)

Griffith, D. W. T.

2015-12-01

Atmospheric composition measurements are an important tool to quantify local and regional emissions and sinks of greenhouse gases. Most in situ measurements are made at a point, but how representative are such measurements in an inhomogeneous environment? Open path Fourier Transform Spectroscopy (FTS) measurements potentially offer spatial averaging and continuous measurements of several trace gases (including CO2, CH4, CO and N2O) simultaneously in the same airmass. Spatial averaging over kilometre scales is a better fit to the finest scale atmospheric models becoming available, and helps bridge the gap between models and in situ measurements. In this paper we assess the precision, accuracy and reliability of long open path measurements by Fourier Transform Spectroscopy in the near infrared from a 5-month continuous record of measurements over a 1.5 km pathlength. Direct open-atmosphere measurements of trace gases CO2, CH4, CO and N2O as well as O2 were retrieved from several absorption bands between 4000 and 8000 cm-1 (2.5 - 1.25 micron). At one end of the path an in situ FTIR analyser simultaneously collected well calibrated measurements of the same species for comparison with the open path-integrated measurements. The measurements ran continuously from June - November 2014. We introduce the open path FTS measurement system and present an analysis of the results, including assessment of precision, accuracy relative to co-incident in situ measurements, reliability. Short term precision of the open path measurement of CO2 was better than 1 ppm for 5 minute averages and thus sufficient for studies in urban and other non-background environments. Measurement bias relative to calibrated in situ measurements was stable across the measurement period. The system operated reliably with data losses mainly due to weather events such as rain and fog preventing transmission of the IR beam. In principle the system can be improved to provide longer pathlengths and higher precision, and we present recent progress in improving the original measurements.

Aqueous Mesocosm Techniques Enabling the Real-Time Measurement of the Chemical and Isotopic Kinetics of Dissolved Methane and Carbon Dioxide.

PubMed

Chan, Eric W; Kessler, John D; Shiller, Alan M; Joung, DongJoo; Colombo, Frank

2016-03-15

Previous studies of microbially mediated methane oxidation in oceanic environments have examined the many different factors that control the rates of oxidation. However, there is debate on what factor(s) are limiting in these types of environments. These factors include the availability of methane, O2, trace metals, nutrients, the density of cell population, and the influence that CO2 production may have on pH. To look at this process in its entirety, we developed an automated mesocosm incubation system with a Dissolved Gas Analysis System (DGAS) coupled to a myriad of analytical tools to monitor chemical changes during methane oxidation. Here, we present new high temporal resolution techniques for investigating dissolved methane and carbon dioxide concentrations and stable isotopic dynamics during aqueous mesocosm and pure culture incubations. These techniques enable us to analyze the gases dissolved in solution and are nondestructive to both the liquid media and the analyzed gases enabling the investigation of a mesocosm or pure culture experiment in a completely closed system, if so desired.

Space Subdivision in Indoor Mobile Laser Scanning Point Clouds Based on Scanline Analysis.

PubMed

Zheng, Yi; Peter, Michael; Zhong, Ruofei; Oude Elberink, Sander; Zhou, Quan

2018-06-05

Indoor space subdivision is an important aspect of scene analysis that provides essential information for many applications, such as indoor navigation and evacuation route planning. Until now, most proposed scene understanding algorithms have been based on whole point clouds, which has led to complicated operations, high computational loads and low processing speed. This paper presents novel methods to efficiently extract the location of openings (e.g., doors and windows) and to subdivide space by analyzing scanlines. An opening detection method is demonstrated that analyses the local geometric regularity in scanlines to refine the extracted opening. Moreover, a space subdivision method based on the extracted openings and the scanning system trajectory is described. Finally, the opening detection and space subdivision results are saved as point cloud labels which will be used for further investigations. The method has been tested on a real dataset collected by ZEB-REVO. The experimental results validate the completeness and correctness of the proposed method for different indoor environment and scanning paths.

Assessing Distribution and Origin of Methane in Shallow Groundwater in Horizontal Oil and Gas Play Areas, Eastern Kentucky

NASA Astrophysics Data System (ADS)

Zhu, J.; Parris, T. M.; Taylor, C. J.; Webb, S. E.; Davidson, B.; Smath, R.; Richardson, S. D.; Molofsky, L.; Kromann, J. S.

2016-12-01

Rapid implementation of horizontal drilling and hydraulic fracturing technology to produce oil and gas from tight rock formations across the country has increased public concern about possible impact on the environment, especially on shallow drinking-water aquifers. In eastern Kentucky, horizontal drilling and hydraulic fracturing have been used to develop the Upper Devonian Berea Sandstone in recent years. Although production in the Berea Sandstone is at a relatively small scale, the Rogersville Shale, a deeper, thicker, and more spatially extensive organic-rich shale, is projected to become a major shale play in eastern Kentucky. This has necessitated a better understanding of groundwater quality, especially the occurrence of dissolved methane, in aquifers overlying the Berea and Rogersville plays to help address the public's environmental concerns and protect groundwater resources. To assess baseline groundwater chemistry and evaluate distribution and origin of methane detected in the groundwater, 51 water wells in Greenup, Carter, Boyd, Lawrence, Johnson, and Elliott Counties were sampled and analyzed for major cations and anions, metals, and dissolved light hydrocarbon gases including methane. Twenty-six wells were identified as having methane concentrations greater than 1 mg/L and were further analyzed for carbon and hydrogen isotopes. The results indicate that methane is a relatively common constituent in shallow groundwater in eastern Kentucky. Correlation of methane distribution with water chemistry data shows that elevated methane concentrations were more common in sodium bicarbonate type water and in low-nitrate, low-sulfate redox conditions. Carbon and hydrogen isotope analysis suggests that the methane detected in groundwater is derived primarily from bacterial sources from the CO2 reduction pathway.

30 CFR 57.22105 - Smoking and open flames (IV mines).

Code of Federal Regulations, 2010 CFR

2010-07-01

... Section 57.22105 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Safety Standards for Methane in Metal and Nonmetal Mines Fire Prevention and Control § 57.22105 Smoking and open...

30 CFR 57.22104 - Open flames (I-C mines).

Code of Federal Regulations, 2010 CFR

2010-07-01

....22104 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Safety Standards for Methane in Metal and Nonmetal Mines Fire Prevention and Control § 57.22104 Open flames (I-C...

Formation of Methane Hydrate in the Presence of Natural and Synthetic Nanoparticles

PubMed Central

2018-01-01

Natural gas hydrates occur widely on the ocean-bed and in permafrost regions, and have potential as an untapped energy resource. Their formation and growth, however, poses major problems for the energy sector due to their tendency to block oil and gas pipelines, whereas their melting is viewed as a potential contributor to climate change. Although recent advances have been made in understanding bulk methane hydrate formation, the effect of impurity particles, which are always present under conditions relevant to industry and the environment, remains an open question. Here we present results from neutron scattering experiments and molecular dynamics simulations that show that the formation of methane hydrate is insensitive to the addition of a wide range of impurity particles. Our analysis shows that this is due to the different chemical natures of methane and water, with methane generally excluded from the volume surrounding the nanoparticles. This has important consequences for our understanding of the mechanism of hydrate nucleation and the design of new inhibitor molecules. PMID:29401390

Grid Visualization Tool

NASA Technical Reports Server (NTRS)

Chouinard, Caroline; Fisher, Forest; Estlin, Tara; Gaines, Daniel; Schaffer, Steven

2005-01-01

The Grid Visualization Tool (GVT) is a computer program for displaying the path of a mobile robotic explorer (rover) on a terrain map. The GVT reads a map-data file in either portable graymap (PGM) or portable pixmap (PPM) format, representing a gray-scale or color map image, respectively. The GVT also accepts input from path-planning and activity-planning software. From these inputs, the GVT generates a map overlaid with one or more rover path(s), waypoints, locations of targets to be explored, and/or target-status information (indicating success or failure in exploring each target). The display can also indicate different types of paths or path segments, such as the path actually traveled versus a planned path or the path traveled to the present position versus planned future movement along a path. The program provides for updating of the display in real time to facilitate visualization of progress. The size of the display and the map scale can be changed as desired by the user. The GVT was written in the C++ language using the Open Graphics Library (OpenGL) software. It has been compiled for both Sun Solaris and Linux operating systems.

Reusable Solid Rocket Motor Nozzle Joint-4 Thermal Analysis

NASA Technical Reports Server (NTRS)

Clayton, J. Louie

2001-01-01

This study provides for development and test verification of a thermal model used for prediction of joint heating environments, structural temperatures and seal erosions in the Space Shuttle Reusable Solid Rocket Motor (RSRM) Nozzle Joint-4. The heating environments are a result of rapid pressurization of the joint free volume assuming a leak path has occurred in the filler material used for assembly gap close out. Combustion gases flow along the leak path from nozzle environment to joint O-ring gland resulting in local heating to the metal housing and erosion of seal materials. Analysis of this condition was based on usage of the NASA Joint Pressurization Routine (JPR) for environment determination and the Systems Improved Numerical Differencing Analyzer (SINDA) for structural temperature prediction. Model generated temperatures, pressures and seal erosions are compared to hot fire test data for several different leak path situations. Investigated in the hot fire test program were nozzle joint-4 O-ring erosion sensitivities to leak path width in both open and confined joint geometries. Model predictions were in generally good agreement with the test data for the confined leak path cases. Worst case flight predictions are provided using the test-calibrated model. Analysis issues are discussed based on model calibration procedures.

OPEN PATH TUNABLE DIODE LASER ABSORPTION SPECTROSCOPY FOR ACQUISITION OF FUGITIVE EMISSION FLUX DATA

EPA Science Inventory

Air pollutant emission from unconfined sources is an increasingly important environmental issue. The U.S. EPA has developed a gorund-based optical remote sensing method that enables direct measurement of fugitive emission flux from large area sources. Open-path Fourier transfor...

Possible Peroxo State of the Dicopper Site of Particulate Methane Monooxygenase from Combined Quantum Mechanics and Molecular Mechanics Calculations.

PubMed

Itoyama, Shuhei; Doitomi, Kazuki; Kamachi, Takashi; Shiota, Yoshihito; Yoshizawa, Kazunari

2016-03-21

Enzymatic methane hydroxylation is proposed to efficiently occur at the dinuclear copper site of particulate methane monooxygenase (pMMO), which is an integral membrane metalloenzyme in methanotrophic bacteria. The resting state and a possible peroxo state of the dicopper active site of pMMO are discussed by using combined quantum mechanics and molecular mechanics calculations on the basis of reported X-ray crystal structures of the resting state of pMMO by Rosenzweig and co-workers. The dicopper site has a unique structure, in which one copper is coordinated by two histidine imidazoles and another is chelated by a histidine imidazole and primary amine of an N-terminal histidine. The resting state of the dicopper site is assignable to the mixed-valent Cu(I)Cu(II) state from a computed Cu-Cu distance of 2.62 Å from calculations at the B3LYP-D/TZVP level of theory. A μ-η(2):η(2)-peroxo-Cu(II)2 structure similar to those of hemocyanin and tyrosinase is reasonably obtained by using the resting state structure and dioxygen. Computed Cu-Cu and O-O distances are 3.63 and 1.46 Å, respectively, in the open-shell singlet state. Structural features of the dicopper peroxo species of pMMO are compared with those of hemocyanin and tyrosinase and synthetic dicopper model compounds. Optical features of the μ-η(2):η(2)-peroxo-Cu(II)2 state are calculated and analyzed with TD-DFT calculations.

Cleats and their relation to geologic lineaments and coalbed methane potential in Pennsylvanian coals in Indiana

USGS Publications Warehouse

Solano-Acosta, W.; Mastalerz, Maria; Schimmelmann, A.

2007-01-01

Cleats and fractures in Pennsylvanian coals in southwestern Indiana were described, statistically analyzed, and subsequently interpreted in terms of their origin, relation to geologic lineaments, and significance for coal permeability and coalbed gas generation and storage. These cleats can be interpreted as the result of superimposed endogenic and exogenic processes. Endogenic processes are associated with coalification (i.e., matrix dehydration and shrinkage), while exogenic processes are mainly associated with larger-scale phenomena, such as tectonic stress. At least two distinct generations of cleats were identified on the basis of field reconnaissance and microscopic study: a first generation of cleats that developed early on during coalification and a second generation that cuts through the previous one at an angle that mimics the orientation of the present-day stress field. The observed parallelism between early-formed cleats and mapped lineaments suggests a well-established tectonic control during early cleat formation. Authigenic minerals filling early cleats represent the vestiges of once open hydrologic regimes. The second generation of cleats is characterized by less prominent features (i.e., smaller apertures) with a much less pronounced occurrence of authigenic mineralization. Our findings suggest a multistage development of cleats that resulted from tectonic stress regimes that changed orientation during coalification and basin evolution. The coals studied are characterized by a macrocleat distribution similar to that of well-developed coalbed methane basins (e.g., Black Warrior Basin, Alabama). Scatter plots and regression analyses of meso- and microcleats reveal a power-law distribution between spacing and cleat aperture. The same distribution was observed for fractures at microscopic scale. Our observations suggest that microcleats enhance permeability by providing additional paths for migration of gas out of the coal matrix, in addition to providing access for methanogenic bacteria. The abundance, distribution, and orientation of cleats control coal fabric and are crucial features in all stages of coalbed gas operations (i.e., exploration and production). Understanding coal fabric is important for coal gas exploration as it may be related to groundwater migration and the occurrence of methanogenic bacteria, prerequisite to biogenic gas accumulations. Likewise, the distribution of cleats in coal also determines pathways for migration and accumulation of thermogenic gas generated during coalification. ?? 2007 Elsevier B.V. All rights reserved.

Observations and modeling of methane flux in northern wetlands

NASA Astrophysics Data System (ADS)

Futakuchi, Y.; Ueyama, M.; Matsumoto, Y.; Yazaki, T.; Hirano, T.; Kominami, Y.; Harazono, Y.; Igarashi, Y.

2016-12-01

Methane (CH4) budgets in northern wetlands vary greatly with high spatio-temporal heterogeneity. Owing to limited available data, yet, it is difficult to constrain the CH4 emission from northern wetlands. In this context, we continuously measured CH4 fluxes at two northern wetlands. Measured fluxes were used for constraining the new model that empirically partitioned net CH4 fluxes into the processes of production, oxidation, and transport associated with ebullition, diffusion, and plant, based on the optimization technique. This study reveal the important processes related to the seasonal variations in CH4 emission with the continuous observations and inverse model analysis. The measurements have been conducted at a Sphagnum-dominated cool temperate bog (BBY) since April 2015 using the open-path eddy covariance method and a sub-arctic forested bog on permafrost in University of Alaska Fairbanks (UAF) since May 2016 using three automated chambers by a laser-based gas analyzer (FGGA-24r-EP, Los Gatos Research Inc., USA). In BBY, daily CH4 fluxes ranged from 1.9 nmol m-2 s-1 in early spring to 97.9 nmol m-2 s-1 in mid-summer. Growing-season total CH4 flux was 13 g m-2 yr-1 in 2015. In contrast, CH4 flux at the UAF site was small (0.2 to 1.0 nmol m-2 s-1), and hardly increased since start of the observation. This difference could be caused by the difference in the climate and soil conditions; mean air and soil temperature, and presence of permafrost. For BBY, the seasonal variation of CH4 emission was mostly explained by soil temperature, suggesting that the production was the important controlling process. In mid-summer when soil temperature was high, however, decrease in atmospheric pressure and increase in vegetation greenness stimulated CH4 emission probably through plant-mediated transport and form of bubble, suggesting that the transport processes were important. Based on a preliminary results by the model optimization in BBY site, CH4 fluxes were strongly influenced by the processes associated with production, ebullition, and plant-mediated transports rather than the processes associated with oxidation and diffusion. In this presentation, we will show that the new data-model fusion that we developed is the effective tool for evaluating CH4 fluxes and controlling processes at northern wetlands.

Methane and Carbon Dioxide Emissions during the Seasonal Permafrost Thaw at the Bonanza Creek Research Forest: Results from the May 2016 Field Campaign

NASA Astrophysics Data System (ADS)

Wilson, E. L.; DiGregorio, A.; Carter, L. M.; Euskirchen, E. S.; Edgar, C.; Hoffman, C.; Ramanathan, A. K.; Mao, J.; Duncan, B. N.; Ott, L. E.; Liang, Q.; Melocik, K. A.; Tucker, C. J.

2016-12-01

We present field measurements from a May 2016 campaign funded under NASA's Interdisciplinary Science (IDS) program to track methane (CH4) and carbon dioxide (CO2) emissions above thawing permafrost at three sites near Fairbanks, AK. Each of the sites, located in the Bonanza Creek Research Forest, represent a different ecosystem including black spruce with cold soils and stable permafrost, collapse scar bog with thermokarst formation, and a site with moderately rich fen lacking near surface permafrost. Field experiments were carried out in May during the seasonal ground thaw of the active layer. Measurements included permafrost depth and subsurface structure using ground penetrating radar, meteorological variables (air and soil temperature, net radiation, albedo, precipitation, snow depth, vapor pressure, etc.), eddy covariance data from a 3-D sonic anemometer, and surface and column concentrations of CH4 and CO2 with an open-path infrared gas analyzer (LICOR) and Miniaturized Laser Heterodyne Radiometer (Mini-LHR) respectively. We have referred to this effort as a pilot study because our intent is to expand our observational network in the future to other sites in North America, which will aid in the monitoring of changes in GHG emissions in the Arctic as well as complement and help interpret data collected by space-borne instruments, such as GOSAT, IASI, and AIRS. This is the first time that these types of measurements have been combined to provide a holistic view of the evolution of, and the atmospheric response to permafrost thaw. The final year of this effort will focus on estimating a global source of GHG emissions from thawing permafrosts. We will use MODIS and Landsat-8 Operational Land Imager and Thermal Infrared Sensor data to "scale up" the data collected at the three sites on the basis of land surface type information. Based on the data collected at the three sites and a variety of existing satellite data sets, we will develop a computationally-efficient parameterization of emissions from thawing permafrosts for use in the NASA GEOS-5 Atmospheric General Circulation Model (AGCM), thus benefiting ongoing efforts in the NASA Global Modeling and Assimilation Office (GMAO) to build an Earth System Model which is used for both retrospective and predictive simulations of important GHGs.

Mobile Measurement of Methane and Ethane for the Detection and Attribution of Natural Gas Pipeline Leaks Using Off-Axis Integrated Output Spectroscopy

NASA Astrophysics Data System (ADS)

Leen, J. B.; Spillane, S.; Gardner, A.; Hansen, P. C.; Gupta, M.; Baer, D. S.

2015-12-01

Natural gas leaks pose a risk to public safety both because of potential explosions as well as from the greenhouse gas potential of fugitive methane. The rapid and cost effective detection of leaks in natural gas distribution is critical to providing a system that is safe for the public and the environment. Detection of methane from a mobile platform (vehicles, aircraft, etc.) is an accepted method of identifying leaks. A robust approach to differentiating pipeline gas (thermogenic) from other biogenic sources is the detection of ethane along with methane. Ethane is present in nearly all thermogenic gas but not in biogenic sources and its presence can be used to positively identify a gas sample. We present a mobile system for the simultaneous measurement of methane and ethane that is capable of detecting pipeline leaks and differentiating pipeline gas from other biogenic sources such as landfills, swamps, sewers, and enteric fermentation. The mobile system consists of a high precision GPS, sonic anemometer, and methane/ethane analyzer based on off-axis integrated cavity output spectroscopy (OA-ICOS). In order to minimize the system cost and facilitate the wide use of mobile leak detection, the analyzer operates in the near-infrared portion of the spectrum where lasers and optics are significantly less costly than in the mid-infrared. The analyzer is capable of detecting methane with a precision of <2 ppb (1σ in 1 sec) and detecting ethane with a precision of <30 ppb (1σ in 1 sec). Additionally, measurement rates of 5 Hz allow for detection of leaks at speeds up to 50 mph. The sonic anemometer, GPS and analyzer inlet are mounted to a generic roof rack for attachment to available fleet vehicles. The system can detect leaks having a downwind concentration of as little as 10 ppb of methane above ambient, while leaks 500 ppb above ambient can be identified as thermogenic with greater than 99% certainty (for gas with 6% ethane). Finally, analysis of wind data provides an estimate of leak direction and distance. The system presented provides a robust, cost effective solution to natural gas leak detection and attribution to maximize safety and minimize greenhouse gas impacts of distribution systems.

Marine biomass: New York state site and species study compositional analysis and systems studies. Final report Mar-Dec 81

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

Makinen, R.W.; Farley, K.M.; Kugler, W.R.

1982-02-26

The primary objective of the Marine Biomass Programs is to provide an optimized, integrated process for producing methane from seaweeds cultivated in the open ocean and to do so at a price which is competitive with that of methane from other sources. The New York State Site and Species Study represents the first evaluation of a site outside of Southern California.

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.

A Calibration-Capture-Recapture Model for Inferring Natual Gas Leak Population Characteristics Using Data from Google Street View Cars

NASA Astrophysics Data System (ADS)

Weller, Z.; Hoeting, J.; von Fischer, J.

2017-12-01

Pipeline systems that distribute natural gas (NG) within cities can leak, leading to safety hazards and wasted product. Moreover, these leaks are climate-altering because NG is primarily composed of methane, a potent greenhouse gas. Scientists have recently developed an innovative method for mapping NG leak locations by installing atmospheric methane analyzers on Google Street View cars. We develop new statistical methodology to answer key inferential questions using data collected by these mobile air monitors. The new calibration-capture-recapture (CCR) model utilizes data from controlled methane releases and data collected by GSV cars to provide inference for several desired quantities, including the number of undetected methane sources and the total methane output rate in a surveyed region. The CCR model addresses challenges associated with using a capture-recapture model to analyze data collected by a mobile detection system including variable sampling effort and lack of physically marking individuals. We develop a Markov chain Monte Carlo algorithm for parameter estimation and apply the CCR model to methane data collected in two U.S. cities. The CCR model provides a new framework for inferring the total number of leaks in NG distribution systems and offers critical insights for informing intelligent repair policy that is both cost-effective and environmentally friendly.

USING TUNABLE DIODE LASERS TO MEASURE EMISSIONS FROM ANIMAL HOUSING AND WASTE LAGOONS

EPA Science Inventory

Open-path optical spectroscopy has been applied to several fugitive sources by scientists at the EPA National Risk Management Research Laboratory for more than a decade. Open-path Fourier transform infrared (OP-FTIR) was used during the initial research phase because of the abil...

FEASIBILITY STUDY TO DEMONSTRATE APPLICABILITY OF TUNABLE INFRARED LASER EMISSION SPECTROSCOPY TECHNOLOGY TO MEASURE AIR POLLUTION

EPA Science Inventory

This project involves the real-time measurement of air quality using open-path IR spectroscopy. A prototype open-path tunable laser absorption spectroscopy instrument was designed, built, and successfully operated for several hundred hours between October and December 2000. The...

Comparative use of different emission measurement approaches to determine methane emissions from a biogas plant.

PubMed

Reinelt, Torsten; Delre, Antonio; Westerkamp, Tanja; Holmgren, Magnus A; Liebetrau, Jan; Scheutz, Charlotte

2017-10-01

A sustainable anaerobic biowaste treatment has to mitigate methane emissions from the entire biogas production chain, but the exact quantification of these emissions remains a challenge. This study presents a comparative measurement campaign carried out with on-site and ground-based remote sensing measurement approaches conducted by six measuring teams at a Swedish biowaste treatment plant. The measured emissions showed high variations, amongst others caused by different periods of measurement performance in connection with varying operational states of the plant. The overall methane emissions measured by ground-based remote sensing varied from 5 to 25kgh -1 (corresponding to a methane loss of 0.6-3.0% of upgraded methane produced), depending on operating conditions and the measurement method applied. Overall methane emissions measured by the on-site measuring approaches varied between 5 and 17kgh -1 (corresponding to a methane loss of 0.6 and 2.1%) from team to team, depending on the number of measured emission points, operational state during the measurements and the measurement method applied. Taking the operational conditions into account, the deviation between different approaches and teams could be explained, in that the two largest methane-emitting sources, contributing about 90% of the entire site's emissions, were found to be the open digestate storage tank and a pressure release valve on the compressor station. Copyright © 2017. Published by Elsevier Ltd.

Reduction of Non-CO2 Gas Emissions Through The In Situ Bioconversion of Methane

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

Scott, A R; Mukhopadhyay, B; Balin, D F

2012-09-06

The primary objectives of this research were to seek previously unidentified anaerobic methanotrophs and other microorganisms to be collected from methane seeps associated with coal outcrops. Subsurface application of these microbes into anaerobic environments has the potential to reduce methane seepage along coal outcrop belts and in coal mines, thereby preventing hazardous explosions. Depending upon the types and characteristics of the methanotrophs identified, it may be possible to apply the microbes to other sources of methane emissions, which include landfills, rice cultivation, and industrial sources where methane can accumulate under buildings. Finally, the microbes collected and identified during this researchmore » also had the potential for useful applications in the chemical industry, as well as in a variety of microbial processes. Sample collection focused on the South Fork of Texas Creek located approximately 15 miles east of Durango, Colorado. The creek is located near the subsurface contact between the coal-bearing Fruitland Formation and the underlying Pictured Cliffs Sandstone. The methane seeps occur within the creek and in areas adjacent to the creek where faulting may allow fluids and gases to migrate to the surface. These seeps appear to have been there prior to coalbed methane development as extensive microbial soils have developed. Our investigations screened more than 500 enrichments but were unable to convince us that anaerobic methane oxidation (AMO) was occurring and that anaerobic methanotrophs may not have been present in the samples collected. In all cases, visual and microscopic observations noted that the early stage enrichments contained viable microbial cells. However, as the levels of the readily substrates that were present in the environmental samples were progressively lowered through serial transfers, the numbers of cells in the enrichments sharply dropped and were eliminated. While the results were disappointing we acknowledge that anaerobic methane oxidizing (AOM) microorganisms are predominantly found in marine habitats and grow poorly under most laboratory conditions. One path for future research would be to use a small rotary rig to collect samples from deeper soil horizons, possibly adjacent to the coal-bearing horizons that may be more anaerobic.« less

MERLIN: a Franco-German LIDAR space mission for atmospheric methane

NASA Astrophysics Data System (ADS)

Bousquet, P.; Ehret, G.; Pierangelo, C.; Marshall, J.; Bacour, C.; Chevallier, F.; Gibert, F.; Armante, R.; Crevoisier, C. D.; Edouart, D.; Esteve, F.; Julien, E.; Kiemle, C.; Alpers, M.; Millet, B.

2017-12-01

The Methane Remote Sensing Lidar Mission (MERLIN), currently in phase C, is a joint cooperation between France and Germany on the development, launch and operation of a space LIDAR dedicated to the retrieval of total weighted methane (CH4) atmospheric columns. Atmospheric methane is the second most potent anthropogenic greenhouse gas, contributing 20% to climate radiative forcing but also plying an important role in atmospheric chemistry as a precursor of tropospheric ozone and low-stratosphere water vapour. Its short lifetime ( 9 years) and the nature and variety of its anthropogenic sources also offer interesting mitigation options in regards to the 2° objective of the Paris agreement. For the first time, measurements of atmospheric composition will be performed from space thanks to an IPDA (Integrated Path Differential Absorption) LIDAR (Light Detecting And Ranging), with a precision (target ±27 ppb for a 50km aggregation along the trace) and accuracy (target <3.7 ppb at 68%) sufficient to significantly reduce the uncertainties on methane emissions. The very low targeted systematic error target is particularly ambitious compared to current passive methane space mission. It is achievable because of the differential active measurements of MERLIN, which guarantees almost no contamination by aerosols or water vapour cross-sensitivity. As an active mission, MERLIN will deliver global methane weighted columns (XCH4) for all seasons and all latitudes, day and night Here, we recall the MERLIN objectives and mission characteristics. We also propose an end-to-end error analysis, from the causes of random and systematic errors of the instrument, of the platform and of the data treatment, to the error on methane emissions. To do so, we propose an OSSE analysis (observing system simulation experiment) to estimate the uncertainty reduction on methane emissions brought by MERLIN XCH4. The originality of our inversion system is to transfer both random and systematic errors from the observation space to the flux space, thus providing more realistic error reductions than usually provided in OSSE only using the random part of errors. Uncertainty reductions are presented using two different atmospheric transport models, TM3 and LMDZ, and compared with error reduction achieved with the GOSAT passive mission.

Leak localization and quantification with a small unmanned aerial system

NASA Astrophysics Data System (ADS)

Golston, L.; Zondlo, M. A.; Frish, M. B.; Aubut, N. F.; Yang, S.; Talbot, R. W.

2017-12-01

Methane emissions from oil and gas facilities are a recognized source of greenhouse gas emissions, requiring cost-effective and reliable monitoring systems to support leak detection and repair programs. We describe a set of methods for locating and quantifying natural gas leaks using a small unmanned aerial system (sUAS) equipped with a path-integrated methane sensor along with ground-based wind measurements. The algorithms are developed as part of a system for continuous well pad scale (100 m2 area) monitoring, supported by a series of over 200 methane release trials covering multiple release locations and flow rates. Test measurements include data obtained on a rotating boom platform as well as flight tests on a sUAS. The system is found throughout the trials to reliably distinguish between cases with and without a methane release down to 6 scfh (0.032 g/s). Among several methods evaluated for horizontal localization, the location corresponding to the maximum integrated methane reading have performed best with a median error of ± 1 m if two or more flights are averaged, or ± 1.2 m for individual flights. Additionally, a method of rotating the data around the estimated leak location is developed, with the leak magnitude calculated as the average crosswind integrated flux in the region near the source location. Validation of these methods will be presented, including blind test results. Sources of error, including GPS uncertainty, meteorological variables, and flight pattern coverage, will be discussed.

Intense methane ebullition from open water area of a shallow peatland lake on the eastern Tibetan Plateau.

PubMed

Zhu, Dan; Wu, Yan; Chen, Huai; He, Yixin; Wu, Ning

2016-01-15

Methane fluxes from a shallow peatland lake (3450 m a.s.l., 1.6 km(2) in area, maximum depth <1m) on eastern Tibetan Plateau were measured with floating chamber method during May to August, 2009. The overall average of methane emission rate during the study period was 34.71±29.15 mg CH4 m(-2) h(-1). The occurrence of ebullition among the overall methane flux from Lake Medo was about 74%. The average rate of ebullition was 32.45±28.31 mg CH4 m(-2) h(-1), which accounted for 93% of the overall average of methane emission. Significant seasonal variation was found for occurrence (P<0.05) and rate (P<0.01) of ebullition, both peaking synchronously in mid-summer. Both the occurrence and rate of ebullition were found positively related to sediment temperature but negatively related to lake water depth. The high methane production in the lake sediment was likely fueled by organic carbon loaded from surrounding peatlands to the lake. The shallowness of the water column could be another important favorable factor for methane-containing bubble formation in the sediment and their transportation to the atmosphere. The methane ebullition must have been enhanced by the low atmospheric pressure (ca. 672 hPa) in the high-altitude environment. For a better understanding on the mechanism of methane emission from alpine lakes, more lakes on the Tibetan Plateau should be studied in the future for their methane ebullition. Copyright © 2015 Elsevier B.V. All rights reserved.

Methane production and consumption in an active volcanic environment of Southern Italy.

PubMed

Castaldi, Simona; Tedesco, Dario

2005-01-01

Methane fluxes were measured, using closed chambers, in the Crater of Solfatara volcano, Campi Flegrei (Southern Italy), along eight transects covering areas of the crater presenting different landscape physiognomies. These included open bare areas, presenting high geothermal fluxes, and areas covered by vegetation, which developed along a gradient from the central open area outwards, in the form of maquis, grassland and woodland. Methane fluxes decreased logarithmically (from 150 to -4.5 mg CH4 m(-2)day(-1)) going from the central part of the crater (fangaia) to the forested edges, similarly to the CO2 fluxes (from 1500 g CO2 m(-2)day(-1) in the centre of the crater to almost zero flux in the woodlands). In areas characterized by high emissions, soil presented elevated temperature (up to 70 degrees C at 0-10 cm depth) and extremely low pH (down to 1.8). Conversely, in woodland areas pH was higher (between 3.7 and 5.1) and soil temperature close to air values. Soil (0-10 cm) was sampled, in two different occasions, along the eight transects, and was tested for methane oxidation capacity in laboratory. Areas covered by vegetation mostly consumed CH4 in the following order woodland>macchia>grassland. Methanotrophic activity was also measured in soil from the open bare area. Oxidation rates were comparable to those measured in the plant covered areas and were significantly correlated with field CH4 emissions. The biological mechanism of uptake was demonstrated by the absence of activity in autoclaved replicates. Thus results suggest the existence of a population of micro-organisms adapted to this extreme environment, which are able to oxidize CH4 and whose activity could be stimulated and supported by elevated concentrations of CH4.

Can cycling safety be improved by opening all unidirectional cycle paths for cycle traffic in both directions? A theoretical examination of available literature and data.

PubMed

Methorst, Rob; Schepers, Paul; Kamminga, Jaap; Zeegers, Theo; Fishman, Elliot

2017-08-01

Many studies have found bicycle-motor vehicle crashes to be more likely on bidirectional cycle paths than on unidirectional cycle paths because drivers do not expect cyclists riding at the right side of the road. In this paper we discuss the hypothesis that opening all unidirectional cycle paths for cycle traffic in both directions prevent this lack of expectancy and accordingly improves cycling safety. A new national standard requires careful consideration because a reversal is difficult once cyclists are used to their new freedom of route choice. We therefore explored the hypothesis using available data, research, and theories. The results show that of the length of cycle paths along distributor roads in the Netherlands, 72% is bidirectional. If drivers would become used to cyclists riding at the left side of the road, this result raises the question of why bidirectional cycle paths in the Netherlands still have a poor safety record compared to unidirectional cycle paths. Moreover, our exploration suggested that bidirectional cycle paths have additional safety problems. It increases the complexity of unsignalized intersections because drivers have to scan more directions in a short period of time. Moreover, there are some indications that the likelihood of frontal crashes between cyclists increases. We reject the hypothesis that opening all unidirectional cycle paths for cycle traffic in both directions will improve cycle safety. We recommend more attention for mitigating measures given the widespread application of bidirectional cycle paths in the Netherlands. Copyright © 2016 Elsevier Ltd. All rights reserved.

Expanding Spatial and Temporal Coverage of Arctic CH4 and CO2 Fluxes

NASA Astrophysics Data System (ADS)

Murphy, P.; Oechel, W. C.; Moreaux, V.; Losacco, S.; Zona, D.

2013-12-01

Carbon storage and exchange in Arctic ecosystems is the subject of intensive study focused on determining rates, controls, and mechanisms of CH4 and CO2 fluxes. The Arctic contains more than 1 Gt of Carbon in the upper meter of soil, both in the active layer and permafrost (Schuur et al., 2008; Tarnocai et al., 2009). However, the annual pattern and controls on the release of CH4 is inadequately understood in Arctic tundra ecosystems. Annual methane budgets are poorly understood, and very few studies measure fluxes through the freeze-up cycle during autumn months (Mastepanov et al., 2008; Mastepanov et al., 2010; Sturtevant et al., 2012). There is no known, relatively continuous, CH4 flux record for the Arctic. Clearly, the datasets that currently exist for budget calculations and model parameterization and verification are inadequate. This is likely due to the difficult nature of flux measurements in the Arctic. In September 2012, we initiated a research project towards continuous methane flux measurements along a latitudinal transect in Northern Alaska. The eddy-covariance (EC) technique is challenging in such extreme weather conditions due to the effects of ice formation and precipitation on instrumentation, including gas analyzers and sonic anemometers. The challenge is greater in remote areas of the Arctic, when low power availability and limited communication can lead to delays in data retrieval or data loss. For these reasons, a combination of open- and closed-path gas analyzers, and several sonic anemometers (including one with heating), have been installed on EC towers to allow for cross-comparison and cross-referencing of calculated fluxes. Newer instruments for fast CH4 flux determination include: the Los Gatos Research Fast Greenhouse Gas Analyzer and the Li-Cor LI-7700. We also included the self-heated Metek Class-A uSonic-3 Anemometer as a new instrument. Previously existing instruments used for comparison include the Li-Cor LI-7500; Li-Cor LI-7200; Gill WindmasterPro; Gill R3; Campbell Scientific CSAT-3, and METEK USA-1. To prevent gaps in data due to poor weather, we developed a temperature control system to allow de-icing of the sonic instrument based on data quality. Enclosures were also created to support equipment that was not designed for outdoor use. A similar temperature control system was implemented to maintain stable conditions in the enclosures. Five existing EC towers on the north slope of Alaska, in Barrow, Atqasuk, and Ivotuk, are used to obtain CH4 and CO2 fluxes, and allow a comparison of fluxes across sensor type and design. Here we present the instrument set-up and some of the preliminary eddy covariance CH4 and CO2 flux data, which might prove very useful as guidelines for further flux measurements in northern high latitudes.

Experimental investigation on variation of physical properties of coal samples subjected to microwave irradiation

NASA Astrophysics Data System (ADS)

Hu, Guozhong; Yang, Nan; Xu, Guang; Xu, Jialin

2018-03-01

The gas drainage rate of low-permeability coal seam is generally less than satisfactory. This leads to the gas disaster of coal mine, and largely restricts the extraction of coalbed methane (CBM), and increases the emission of greenhouse gases in the mining area. Consequently, enhancing the gas drainage rate is an urgent challenge. To solve this problem, a new approach of using microwave irradiation (MWR) as a non-contact physical field excitation method to enhance gas drainage has been attempted. In order to evaluate the feasibility of this method, the methane adsorption, diffusion and penetrability of coal subjected to MWR were experimentally investigated. The variation of methane adsorbed amount, methane diffusion speed and absorption loop for the coal sample before and after MWR were obtained. The findings show that the MWR can change the adsorption property and reduce the methane adsorption capacity of coal. Moreover, the methane diffusion characteristic curves for both the irradiated coal samples and theoriginal coal samples present the same trend. The irradiated coal samples have better methane diffusion ability than the original ones. As the adsorbed methane decreases, the methane diffusion speed increases or remain the same for the sample subjected to MWR. Furthermore, compared to the original coal samples, the area of the absorption loop for irradiated samples increases, especially for the micro-pore and medium-pore stage. This leads to the increase of open pores in the coal, thus improving the gas penetrability of coal. This study provides supports for positive MWR effects on changing the methane adsorption and improving the methane diffusion and the gas penetrability properties of coal samples.

Methane and Carbon Dioxide Concentrations and Fluxes in Amazon Floodplains

NASA Astrophysics Data System (ADS)

Melack, J. M.; MacIntyre, S.; Forsberg, B.; Barbosa, P.; Amaral, J. H.

2016-12-01

Field studies on the central Amazon floodplain in representative aquatic habitats (open water, flooded forests, floating macrophytes) combine measurements of methane and carbon dioxide concentrations and fluxes to the atmosphere over diel and seasonal times with deployment of meteorological sensors and high-resolution thermistors and dissolved oxygen sondes. A cavity ringdown spectrometer is used to determine gas concentrations, and floating chambers and bubble collectors are used to measure fluxes. To further understand fluxes, we measured turbulence as rate of dissipation of turbulent kinetic energy based on microstructure profiling. These results allow calculations of vertical mixing within the water column and of air-water exchanges using surface renewal models. Methane and carbon dioxide fluxes varied as a function of season, habitat and water depth. High CO2 fluxes at high water are related to high pCO2; low pCO2 levels at low water result from increased phytoplankton uptake. CO2 fluxes are highest at turbulent open water sites, and pCO2 is highest in macrophyte beds. Fluxes and pCH4 are high in macrophyte beds.

Seasonal dynamics in methane emissions from the Amazon River floodplain to the troposphere

NASA Technical Reports Server (NTRS)

Devol, Allan H.; Richey, Jeffrey E.; Forsberg, Bruce R.; Martinelli, Luiz A.

1990-01-01

Methane fluxes to the troposphere from the three principal habitats of the floodplain of the Amazon River main stem (open waters, emergent macrophyte beds, and flooded forests) were determined along a 1700-km reach of the river during the low-water period of the annual flood cycle (November-December 1988). Overall, emissions averaged 68 mg CH4/sq m per day and were significantly lower than similar emissions determined previously for the high-water period, 184 mg CH4/sq m per day (July-August 1986). This difference was due to significantly lower emissions from floating macrophyte environments. Low-water emissions from open waters and flooded forest areas were not significantly different than at high water. A monthly time series of methane emission from eight lakes located in the central Amazon basis showed similar results. The data were used to calculate a seasonally weighted annual emission to the troposphere from the Amazon River main stem floodplain of 5.1 Tg/yr, which indicates the importance of the area in global atmospheric chemistry.

Reducing Open Cell Landfill Methane Emissions with a Bioactive Alternative Daily

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

Helene Hilger; James Oliver; Jean Bogner

2009-03-31

Methane and carbon dioxide are formed in landfills as wastes degrade. Molecule-for-molecule, methane is about 20 times more potent than carbon dioxide at trapping heat in the earth's atmosphere, and thus, it is the methane emissions from landfills that are scrutinized. For example, if emissions composed of 60% methane and 40% carbon dioxide were changed to a mix that was 40% methane and 60% carbon dioxide, a 30% reduction in the landfill's global warming potential would result. A 10% methane, 90% carbon dioxide ratio will result in a 75% reduction in global warming potential compared to the baseline. Gas collectionmore » from a closed landfill can reduce emissions, and it is sometimes combined with a biocover, an engineered system where methane oxidizing bacteria living in a medium such as compost, convert landfill methane to carbon dioxide and water. Although methane oxidizing bacteria merely convert one greenhouse gas (methane) to another (carbon dioxide), this conversion can offer significant reductions in the overall greenhouse gas contribution, or global warming potential, associated with the landfill. What has not been addressed to date is the fact that methane can also escape from a landfill when the active cell is being filled with waste. Federal regulations require that newly deposited solid waste to be covered daily with a 6 in layer of soil or an alternative daily cover (ADC), such as a canvas tarp. The aim of this study was to assess the feasibility of immobilizing methane oxidizing bacteria into a tarp-like matrix that could be used for alternative daily cover at open landfill cells to prevent methane emissions. A unique method of isolating methanotrophs from landfill cover soil was used to create a liquid culture of mixed methanotrophs. A variety of prospective immobilization techniques were used to affix the bacteria in a tarp-like matrix. Both gel encapsulation of methanotrophs and gels with liquid cores containing methanotrophs were readily made but prone to rapid desiccation. Bacterial adsorption onto foam padding, natural sponge, and geotextile was successful. The most important factor for success appeared to be water holding capacity. Prototype biotarps made with geotextiles plus adsorbed methane oxidizing bacteria were tested for their responses to temperature, intermittent starvation, and washing (to simulate rainfall). The prototypes were mesophilic, and methane oxidation activity remained strong after one cycle of starvation but then declined with repeated cycles. Many of the cells detached with vigorous washing, but at least 30% appeared resistant to sloughing. While laboratory landfill simulations showed that four-layer composite biotarps made with two different types of geotextile could remove up to 50% of influent methane introduced at a flux rate of 22 g m{sup -2} d{sup -1}, field experiments did not yield high activity levels. Tests revealed that there were high hour-to-hour flux variations in the field, which, together with frequent rainfall events, confounded the field testing. Overall, the findings suggest that a methanotroph embedded biotarp appears to be a feasible strategy to mitigate methane emission from landfill cells, although the performance of field-tested biotarps was not robust here. Tarps will likely be best suited for spring and summer use, although the methane oxidizer population may be able to shift and adapt to lower temperatures. The starvation cycling of the tarp may require the capacity for intermittent reinoculation of the cells, although it is also possible that a subpopulation will adapt to the cycling and become dominant. Rainfall is not expected to be a major factor, because a baseline biofilm will be present to repopulate the tarp. If strong performance can be achieved and documented, the biotarp concept could be extended to include interception of other compounds beyond methane, such as volatile aromatic hydrocarbons and chlorinated solvents.« less

Methane Emissions from Leak and Loss Audits of Natural Gas Compressor Stations and Storage Facilities.

PubMed

Johnson, Derek R; Covington, April N; Clark, Nigel N

2015-07-07

As part of the Environmental Defense Fund's Barnett Coordinated Campaign, researchers completed leak and loss audits for methane emissions at three natural gas compressor stations and two natural gas storage facilities. Researchers employed microdilution high-volume sampling systems in conjunction with in situ methane analyzers, bag samples, and Fourier transform infrared analyzers for emissions rate quantification. All sites had a combined total methane emissions rate of 94.2 kg/h, yet only 12% of the emissions total resulted from leaks. Methane slip from exhausts represented 44% of the total emissions. Remaining methane emissions were attributed to losses from pneumatic actuators and controls, engine crankcases, compressor packing vents, wet seal vents, and slop tanks. Measured values were compared with those reported in literature. Exhaust methane emissions were lower than emissions factor estimates for engine exhausts, but when combined with crankcase emissions, measured values were 11.4% lower than predicted by AP-42 as applicable to emissions factors for four-stroke, lean-burn engines. Average measured wet seal emissions were 3.5 times higher than GRI values but 14 times lower than those reported by Allen et al. Reciprocating compressor packing vent emissions were 39 times higher than values reported by GRI, but about half of values reported by Allen et al. Though the data set was small, researchers have suggested a method to estimate site-wide emissions factors for those powered by four-stroke, lean-burn engines based on fuel consumption and site throughput.

Reactive transport model of growth and methane production by high-temperature methanogens in hydrothermal regions of the subseafloor

NASA Astrophysics Data System (ADS)

Stewart, L. C.; Algar, C. K.; Topçuoğlu, B. D.; Fortunato, C. S.; Larson, B. I.; Proskurowski, G. K.; Butterfield, D. A.; Vallino, J. J.; Huber, J. A.; Holden, J. F.

2014-12-01

Hydrogenotrophic methanogens are keystone high-temperature autotrophs in deep-sea hydrothermal vents and tracers of habitability and biogeochemical activity in the hydrothermally active subseafloor. At Axial Seamount, nearly all thermophilic methanogens are Methanothermococcus and Methanocaldococcus species, making this site amenable to modeling through pure culture laboratory experiments coupled with field studies. Based on field microcosm incubations with 1.2 mM, 20 μM, or no hydrogen, the growth of methanogens at 55°C and 80°C is limited primarily by temperature and hydrogen availability, with ammonium amendment showing no consistent effect on total methane output. The Arrhenius constants for methane production by Methanocaldococcus jannaschii (optimum 82°C) and Methanothermococcus thermolithotrophicus (optimum 65°C) were determined in pure culture bottle experiments. The Monod constants for hydrogen concentration were measured by growing both organisms in a 2-liter chemostat at two dilution rates; 55°C, 65°C and 82°C; and variable hydrogen concentrations. M. jannaschii showed higher ks and Vmax constants than M. thermolithotrophicus. In the field, hydrogen and methane concentrations in hydrothermal end-member and low-temperature diffuse fluids were measured, and the concentrations of methanogens that grow at 55°C and 80°C in diffuse fluids were determined using most-probable-number estimates. Methane concentration anomalies in diffuse fluids relative to end-member hydrothermal concentrations and methanogen cell concentrations are being used to constrain a 1-D reactive transport model using the laboratory-determined Arrhenius and Monod constants for methane production by these organisms. By varying flow path length and subseafloor cell concentrations in the model, our goal is to determine solutions for the potential depth of the subseafloor biosphere coupled with the amount of methanogenic biomass it contains.

30 CFR 57.22213 - Air flow (III mines).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Air flow (III mines). 57.22213 Section 57.22213... Methane in Metal and Nonmetal Mines Ventilation § 57.22213 Air flow (III mines). The quantity of air coursed through the last open crosscut in pairs or sets of entries, or through other ventilation openings...

Micrometeorological Mass Balance Measurements of Greenhouse Gas Emissions from Composting Green-waste

NASA Astrophysics Data System (ADS)

Kent, E. R.; Bailey, S.; Stephens, J.; Horwath, W. R.; Paw U, K.

2013-12-01

Managed decomposition of organic materials is increasingly being used as an alternative waste management option and the resulting compost can be used as a fertilizer and soil amendment in home gardens and agriculture. An additional benefit is the avoidance of methane emissions associated with anaerobic decomposition in landfills. Greenhouse gases are still emitted during the composting process, but few studies have measured emissions from a full-scale windrow of composting green-waste. This study uses a micrometeorological mass balance technique (upwind and downwind vertical profile measurements of trace gas concentrations and wind velocity) to calculate emissions of carbon dioxide, methane, and nitrous oxide from a pile of composting green-waste during the dry season in Northern California. The expected source pattern was observed in measured upwind-downwind concentration differences of all three gases averaged over the study period despite substantial noise seen in the half-hourly emission calculations. Sources of uncertainty are investigated and temporal patterns analyzed. An in-situ zero-source test was conducted to examine the mass balance technique when the source of emissions was removed. Results from the micrometeorological mass balance measurements are compared with measurements taken using the more common open chamber technique.

Methane for Power Generation in Muaro Jambi: A Green Prosperity Model Project

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

Moriarty, K.; Elchinger, M.; Hill, G.

2014-07-01

NREL conducted eight model projects for Millennium Challenge Corporation's (MCC) Compact with Indonesia. Green Prosperity, the largest project of the Compact, seeks to address critical constraints to economic growth while supporting the Government of Indonesia's commitment to a more sustainable, less carbon-intensive future. This study evaluates electricity generation from the organic content of wastewater at a palm oil mill in Muaro Jambi, Sumatra. Palm mills use vast amounts of water in the production process resulting in problematic waste water called palm oil mill effluent (POME). The POME releases methane to the atmosphere in open ponds which could be covered tomore » capture the methane to produce renewable electricity for rural villages. The study uses average Indonesia data to determine the economic viability of methane capture at a palm oil mill and also evaluates technology as well as social and environmental impacts of the project.« less

VALIDATION OF A METHOD FOR ESTIMATING POLLUTION EMISSION RATES FROM AREA SOURCES USING OPEN-PATH FTIR SEPCTROSCOPY AND DISPERSION MODELING TECHNIQUES

EPA Science Inventory

The paper describes a methodology developed to estimate emissions factors for a variety of different area sources in a rapid, accurate, and cost effective manner. he methodology involves using an open-path Fourier transform infrared (FTIR) spectrometer to measure concentrations o...

Additional Term in the Webb-Pearman-Leuning Correction due to Surface Heating From an Open-Path Gas Analyzer

NASA Astrophysics Data System (ADS)

Burba, G. G.; Anderson, D. J.; Xu, L.; McDermitt, D. K.

2006-12-01

One laboratory and two field experiments were conducted between September 2005 and September 2006 to investigate the impact of an added heat flux in the sample path of the LI-7500 CO2/H2O gas analyzer caused by the difference in temperatures between the ambient air and the surface of the instrument. Contribution of heat dissipated from the internal instrument electronics toward the instrument surface was substantial, especially in cold conditions. In the environmental chamber, surface heating ranged from about 0 °C above ambient, at air temperatures above +40 °C, to about 7 °C, at an air temperature of -25 °C. In the field, daytime temperature differences were overall smaller than in the chamber due to convective cooling by the wind and some long-wave cooling, despite the added sunlight contribution. However, considerable temperature gradients (up to 2 °C per 1mm) were still observed over the lower window of the LI-7500, suggesting strong sensible heat fluxes above the instrument surface. The nighttime situation was different due to strong long-wave cooling of some parts of the instrument, partially (and sometimes, fully) offsetting effects of the electronics heating in the other parts. The concept of an added heat flux term in the Web-Pearman-Leuning correction is revisited, and effect of the instrument surface heating on the CO2 flux measurements is examined. The proposed concept is presented in detail, along with resulted corrections to the originally computed flux. Field data are examined separately for daytime and nighttime cases, and on hourly and seasonal time scales. Significant reduction in the apparent CO2 uptake during off-season periods was observed as a result of applying correction due to the added heat, while fluxes during the growing season have not been noticeably affected. The correction also resulted in the elimination of most of the wrong signs from the off-season open- path CO2 fluxes, in considerable reduction in variability of the data, elimination of the difference between measurements made with the LI-6262 and the LI-7500, and in a significant improvement in off-season integrations of CO2 exchange. A framework was created to develop a site-specific practical correction due to instrument surface heating. The concept may provide a basis for further research in the area of instrument temperature affecting the measurement of the open-path fluxes. Proposed correction may be useful for future CO2 flux research, and it can also be applied to pre-existing data today.

Methane fluxes and inventories in the accretionary prism of southwestern Taiwan

NASA Astrophysics Data System (ADS)

Lin, L. H.; Chen, N. C.; Yang, T. F.; Hong, W. L.; Chen, H. W.; Chen, H. C.; Hu, C. Y.; Huang, Y. C.; Lin, S.; Su, C. C.; Liao, W. Z.; Sun, C. H.; Wang, P. L.; Yang, T.; Jiang, S. Y.; Liu, C. S.; Wang, Y.; Chung, S. H.

2017-12-01

Sediments distributed across marine and terrestrial realms represent the largest methane reservoir on Earth. The degassing of methane facilitated through either geological structures or perturbation would contribute significantly to global climatic fluctuation and elemental cycling. The exact fluxes and processes governing methane production, consumption and transport in a geological system remain largely unknown in part due to the limited coverage and access of samples. In this study, more than 200 sediment cores were collected from offshore and onshore southwestern Taiwan and analyzed for their gas and aqueous geochemistry. These data combined with published data and existing parameters of subduction system were used to calculate methane fluxes across different geochemical transitions and to develop scenarios of mass balance to constrain deep microbial and thermogenic methane production rates within the Taiwanese accretionary prism. The results showed that high methane fluxes tend to be associated with structural features, suggesting a strong structural control on methane transport. A significant portion of ascending methane (>50%) was consumed by anaerobic oxidation of methane at most sites. Gas compositions and isotopes revealed a transition from the predominance of microbial methane in the passive margin to thermogenic methane at the upper slope of the active margin and onshore mud volcanoes. Methane production and consumption at shallow depths were nearly offset with a small fraction of residual methane discharged into seawater or the atmosphere. The flux imbalance arose primarily from the deep microbial and thermogenic production and could be likely accounted for by the sequestration of methane into hydrate forms, and clay absorption.

Sensitivity studies for a space-based methane lidar mission

NASA Astrophysics Data System (ADS)

Kiemle, C.; Quatrevalet, M.; Ehret, G.; Amediek, A.; Fix, A.; Wirth, M.

2011-10-01

Methane is the third most important greenhouse gas in the atmosphere after water vapour and carbon dioxide. A major handicap to quantify the emissions at the Earth's surface in order to better understand biosphere-atmosphere exchange processes and potential climate feedbacks is the lack of accurate and global observations of methane. Space-based integrated path differential absorption (IPDA) lidar has potential to fill this gap, and a Methane Remote Lidar Mission (MERLIN) on a small satellite in polar orbit was proposed by DLR and CNES in the frame of a German-French climate monitoring initiative. System simulations are used to identify key performance parameters and to find an advantageous instrument configuration, given the environmental, technological, and budget constraints. The sensitivity studies use representative averages of the atmospheric and surface state to estimate the measurement precision, i.e. the random uncertainty due to instrument noise. Key performance parameters for MERLIN are average laser power, telescope size, orbit height, surface reflectance, and detector noise. A modest-size lidar instrument with 0.45 W average laser power and 0.55 m telescope diameter on a 506 km orbit could provide 50-km averaged methane column measurement along the sub-satellite track with a precision of about 1% over vegetation. The use of a methane absorption trough at 1.65 μm improves the near-surface measurement sensitivity and vastly relaxes the wavelength stability requirement that was identified as one of the major technological risks in the pre-phase A studies for A-SCOPE, a space-based IPDA lidar for carbon dioxide at the European Space Agency. Minimal humidity and temperature sensitivity at this wavelength position will enable accurate measurements in tropical wetlands, key regions with largely uncertain methane emissions. In contrast to actual passive remote sensors, measurements in Polar Regions will be possible and biases due to aerosol layers and thin ice clouds will be minimised.

Sensitivity studies for a space-based methane lidar mission

NASA Astrophysics Data System (ADS)

Kiemle, C.; Quatrevalet, M.; Ehret, G.; Amediek, A.; Fix, A.; Wirth, M.

2011-06-01

Methane is the third most important greenhouse gas in the atmosphere after water vapour and carbon dioxide. A major handicap to quantify the emissions at the Earth's surface in order to better understand biosphere-atmosphere exchange processes and potential climate feedbacks is the lack of accurate and global observations of methane. Space-based integrated path differential absorption (IPDA) lidar has potential to fill this gap, and a Methane Remote Lidar Mission (MERLIN) on a small satellite in Polar orbit was proposed by DLR and CNES in the frame of a German-French climate monitoring initiative. System simulations are used to identify key performance parameters and to find an advantageous instrument configuration, given the environmental, technological, and budget constraints. The sensitivity studies use representative averages of the atmospheric and surface state to estimate the measurement precision, i.e. the random uncertainty due to instrument noise. Key performance parameters for MERLIN are average laser power, telescope size, orbit height, surface reflectance, and detector noise. A modest-size lidar instrument with 0.45 W average laser power and 0.55 m telescope diameter on a 506 km orbit could provide 50-km averaged methane column measurement along the sub-satellite track with a precision of about 1 % over vegetation. The use of a methane absorption trough at 1.65 μm improves the near-surface measurement sensitivity and vastly relaxes the wavelength stability requirement that was identified as one of the major technological risks in the pre-phase A studies for A-SCOPE, a space-based IPDA lidar for carbon dioxide at the European Space Agency. Minimal humidity and temperature sensitivity at this wavelength position will enable accurate measurements in tropical wetlands, key regions with largely uncertain methane emissions. In contrast to actual passive remote sensors, measurements in Polar Regions will be possible and biases due to aerosol layers and thin ice clouds will be minimised.

Coalbed methane: from hazard to resource

USGS Publications Warehouse

Flores, R.M.

1998-01-01

Coalbed gas, which mainly consists of methane, has remained a major hazard affecting safety and productivity in underground coal mines for more than 100 yr. Coalbed gas emissions have resulted in outbursts and explosions where ignited by open lights, smoking or improper use of black blasting powder, and machinery operations. Investigations of coal gas outbursts and explosions during the past century were aimed at predicting and preventing this mine hazard. During this time, gas emissions were diluted with ventilation by airways (eg, tunnels, vertical and horizontal drillholes, shsfts) and by drainage boreholes. The 1970s 'energy crisis' led to studies of the feasibility of producing the gas for commercial use. Subsequent research on the origin, accumulation, distribution, availability, and recoverability has been pursued vigorously during the past two decades. Since the 1970s research investigations on the causes and effects of coal mine outbursts and gas emissions have led to major advances towards the recovery and development of coalbed methane for commercial use. Thus, coalbed methane as a mining hazard was harnessed as a conventional gas resource.Coalbed gas, which mainly consists of methane, has remained a major hazard affecting safety and productivity in underground coal mines for more than 100 years. Coalbed gas emissions have resulted in outbursts and explosions where ignited by open lights, smoking or improper use of black blasting powder, and machinery operations. Investigations of coal gas outbursts and explosions during the past century were aimed at predicting and preventing this mine hazard. During this time, gas emissions were diluted with ventilation by airways (e.g., tunnels, vertical and horizontal drillholes, shafts) and by drainage boreholes. The 1970's `energy crisis' led to studies of the feasibility of producing the gas for commercial use. Subsequent research on the origin, accumulation, distribution, availability, and recoverability has been pursued vigorously during the past two decades. Since the 1970's research investigations on the causes and effects of coal mine outbursts and gas emissions have led to major advances towards the recovery and development of coalbed methane for commercial use. Thus, coalbed methane as a mining hazard was harnessed as a conventional gas resource.

Patterns of in-soil methane production and atmospheric emission among different land covers of a Lake Erie estuarine wetland

NASA Astrophysics Data System (ADS)

Rey Sanchez, C.; Morin, T. H.; Stefanik, K. C.; Angle, J.; Wrighton, K. C.; Bohrer, G.

2017-12-01

Wetland soils store a great amount of carbon, but also accumulate and emit methane (CH4), a powerful greenhouse gas. To better understand the vertical and horizontal spatial variability of CH4 emissions, we monitored production and fluxes of CH4 in Old Woman Creek, an estuarine wetland of Lake Erie, Ohio, during the growing seasons of 2015 and 2016. Our combined observation methods targeted three different scales: 1) the eddy covariance technique provided continuous high frequency observations integrated over a large spatial footprint; 2) monthly chamber measurements provided sparse point measurements of fluxes in four distinct land-cover types in the wetland: open water, emergent vegetation (Typha spp.), floating vegetation (Nelumbo spp.) and mud flats; and 3) in-situ porewater dialysis samplers, "peepers", provided vertical CH4 concentration data in the soil at the same locations and temporal time steps as the chambers. In addition, we studied gene transcripts to quantify methanogenesis activity along the vertical soil profile. Using integrated chamber and EC measurements, we found an average surface emission rate from Typha, the most abundant vegetated land cover, of 219.4 g CH4-C m-2 y-1, which was much higher than rates reported in similar emergent vegetation types in other wetlands. There was large spatial variation of flux rates, with mud flats having the highest rates of CH4 emission, followed by Nelumbo and Typha patches, and with open water having the lowest emissions. Within the soil column, we applied a numerical model to convert soil methane concentrations to emissions rates. We found that, contrary to current ideas of methane production, most methane was being produced in the well-oxygenated surface soils, probably in anoxic microsites within the oxic layer. Our metatranscriptomic data supported these findings, clearly showing nine times greater methanogenic activity in oxic surface soils relative to deeper anoxic soils. Combined, our results provide important insights for the representation of processes of methane production and consumption in models, which can largely affect the estimates of methane emission from wetlands.

Frequency specific patterns of resting-state networks development from childhood to adolescence: A magnetoencephalography study.

PubMed

Meng, Lu; Xiang, Jing

2016-11-01

The present study investigated frequency dependent developmental patterns of the brain resting-state networks from childhood to adolescence. Magnetoencephalography (MEG) data were recorded from 20 healthy subjects at resting-state with eyes-open. The resting-state networks (RSNs) was analyzed at source-level. Brain network organization was characterized by mean clustering coefficient and average path length. The correlations between brain network measures and subjects' age during development from childhood to adolescence were statistically analyzed in delta (1-4Hz), theta (4-8Hz), alpha (8-12Hz), and beta (12-30Hz) frequency bands. A significant positive correlation between functional connectivity with age was found in alpha and beta frequency bands. A significant negative correlation between average path lengths with age was found in beta frequency band. The results suggest that there are significant developmental changes of resting-state networks from childhood to adolescence, which matures from a lattice network to a small-world network. Copyright © 2016 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

Assessment of anaerobic biodegradability of five different solid organic wastes

NASA Astrophysics Data System (ADS)

Kristanto, Gabriel Andari; Asaloei, Huinny

2017-03-01

The concept of waste to energy emerges as an alternative solution to increasing waste generation and energy crisis. In the waste to energy concept, waste will be used to produce renewable energy through thermochemical, biochemical, and physiochemical processes. In an anaerobic digester, organic matter brake-down due to anaerobic bacteria produces methane gas as energy source. The organic waste break-down is affected by various characteristics of waste components, such as organic matter content (C, N, O, H, P), solid contents (TS and VS), nutrients ratio (C/N), and pH. This research aims to analyze biodegradability and potential methane production (CH4) from organic waste largely available in Indonesia. Five solid wastes comprised of fecal sludge, cow rumen, goat farm waste, traditional market waste, and tofu dregs were analyzed which showed tofu dregs as waste with the highest rate of biodegradability compared to others since the tofu dregs do not contain any inhibitor which is lignin, have 2.7%VS, 14 C/N ratios and 97.3% organic matter. The highest cumulative methane production known as Biochemical Methane Potential was achieved by tofu dregs with volume of 77 ml during 30-day experiment which then followed by cow rumen, goat farm waste, and traditional market waste. Subsequently, methane productions were calculated through percentage of COD reduction, which showed the efficiency of 99.1% that indicates complete conversion of the high organic matter into methane.

Investigation of the applicability of using the triple redundant hydrogen sensor for methane sensing

NASA Technical Reports Server (NTRS)

Lantz, J. B.; Wynveen, R. A.

1983-01-01

Application specifications for the methane sensor were assembled and design guidelines, development goals and evaluation criteria were formulated. This was done to provide a framework to evaluate sensor performance and any design adjustments to the preprototype sensor that could be required to provide methane sensitivity. Good response to hydrogen was experimentally established for four hydrogen sensor elements to be later evaluated for methane response. Prior results were assembled and analyzed for other prototype hydrogen sensor performance parameters to form a comparison base. The four sensor elements previously shown to have good hydrogen response were experimentally evaluated for methane response in 2.5% methane-in-air. No response was obtained for any of the elements, despite the high methane concentration used (50% of the Lower Flammability Limit). It was concluded that the preprototype sensing elements were insensitive to methane and were hydrogen specific. Alternative sensor operating conditions and hardware design changes were considered to provide methane sensitivity to the preprototype sensor, including a variety of different methane sensing techniques. Minor changes to the existing sensor elements, sensor geometry and operating conditions will not make the preprototype hydrogen sensor respond to methane. New sensor elements that will provide methane and hydrogen sensitivity require replacement of the existing thermistor type elements. Some hydrogen sensing characteristics of the modified sensor will be compromised (larger in situ calibration gas volume and H2 nonspecificity). The preprototype hydrogen sensor should be retained for hydrogen monitoring and a separate methane sensor should be developed.

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

NASA Astrophysics Data System (ADS)

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

2013-04-01

Studying the emission and uptake of greenhouse gases from soil is essential for understanding, adapting to and ultimately mitigating the effects of climate change. To-date, majority of such studies have been focused on carbon dioxide (CO2 ) , however, in 2006 the EPA estimated that "Agricultural activities currently generate the largest share, 63 percent, of the world's anthropogenic non-carbon dioxide (non-CO2) emissions (84 percent of nitrous oxide [N2O] and 52 percent of methane[CH4]), and make up roughly 15 percent of all anthropogenic greenhouse gas emissions" (Prentice et al., 2001). Therefore, enabling accurate N2O and CH4 flux measurements in the field are clearly critical to our ability to better constrain carbon and nitrogen budgets, characterize soil sensitivities, agricultural practices, and microbial processes like denitrification and nitrification. To aide in these studies, Picarro has developed a new analyzer based on its proven, NIR technology platform, which is capable of measuring both N2O and CH4 down to ppb levels in a single, field-deployable analyzer. This analyzer measures N2O with a 1-sigma, precision of 3.5 ppb and CH4 with a 1-sigma precision of 3ppb on a 5 minute average. The instrument also has extremely low drift to enable accurate measurements with infrequent calibrations. The data rate of the analyzer is on the order of 5 seconds in order to capture fast, episodic emission events. One of the keys to making accurate CRDS measurements is to thoroughly characterize and correct for spectral interfering species. This is especially important for closed system soil chambers used on agricultural soils where a variety of soil amendments may be applied and gases not usually present in ambient air could concentrate to high levels. In this work, we present the results of analyzer interference testing and corrections completed for the interference of carbon dioxide, methane, ammonia, ethane, ethylene, acetylene, and water on N2O. In addition, we will present the results of testing done with the analyzer attached to both closed and open chamber systems to quantify fluxes of N2O and CH4 from active soil samples. The soil samples were collected by the University of Iowa from soil test sites used for studying the application of biochar as a soil amendment. Results will compare the two chamber methodologies and results from several soil sample types, garden, agricultural and natural. Preliminary results from laboratory measurements of soil core samples taken from a garden soil sample using the closed-system chamber method show N2O emission to be on the order of 5.67 x 10-2 μg/cm3*hr, which is in good agreement with the open-system chamber method tested on the same soil sample, which yielded fluxes of 6.01 x 10-2 μg/cm3*hr . Additional work presented will verify these initial results and will be compared to literature such as Hutchinsion and Livingston 1993 assessment of the bias of different chamber flux methodologies.

Critical Factors Driving the High Volumetric Uptake of Methane in Cu₃(btc)₂.

PubMed

Hulvey, Zeric; Vlaisavljevich, Bess; Mason, Jarad A; Tsivion, Ehud; Dougherty, Timothy P; Bloch, Eric D; Head-Gordon, Martin; Smit, Berend; Long, Jeffrey R; Brown, Craig M

2015-08-26

A thorough experimental and computational study has been carried out to elucidate the mechanistic reasons for the high volumetric uptake of methane in the metal-organic framework Cu3(btc)2 (btc(3-) = 1,3,5-benzenetricarboxylate; HKUST-1). Methane adsorption data measured at several temperatures for Cu3(btc)2, and its isostructural analogue Cr3(btc)2, show that there is little difference in volumetric adsorption capacity when the metal center is changed. In situ neutron powder diffraction data obtained for both materials were used to locate four CD4 adsorption sites that fill sequentially. This data unequivocally shows that primary adsorption sites around, and within, the small octahedral cage in the structure are favored over the exposed Cu(2+) or Cr(2+) cations. These results are supported by an exhaustive parallel computational study, and contradict results recently reported using a time-resolved diffraction structure envelope (TRDSE) method. Moreover, the computational study reveals that strong methane binding at the open metal sites is largely due to methane-methane interactions with adjacent molecules adsorbed at the primary sites instead of an electronic interaction with the metal center. Simulated methane adsorption isotherms for Cu3(btc)2 are shown to exhibit excellent agreement with experimental isotherms, allowing for additional simulations that show that modifications to the metal center, ligand, or even tuning the overall binding enthalpy would not improve the working capacity for methane storage over that measured for Cu3(btc)2 itself.

Application of a rotating impeller anode in a bioelectrochemical anaerobic digestion reactor for methane production from high-strength food waste.

PubMed

Park, Jungyu; Lee, Beom; Shin, Wonbeom; Jo, Sangyeol; Jun, Hangbae

2018-07-01

In this study, a practical bioelectrochemical anaerobic digestion (BEAD) reactor equipped with a rotating STS304 impeller was tested to verify its methane production performance. Methane production in the BEAD reactor was possible without accumulation of volatile fatty acids (VFAs) and decreases in pH at high organic loading rates (OLRs) up to 6 kg-COD/m 3 ·d (COD: chemical oxygen demand). Methane production in a BEAD-O (open circuit) reactor was inhibited at OLRs above 4 kg-COD/m 3 ·d; however, the performance could be recovered bioelectrochemically by supplying voltage. The population density of hydrogenotrophic methanogens increased to 73.3% in the BEAD-C (closed circuit) reactor, even at high OLRs, through the removal of VFAs and conversion of hydrogen to methane. The energy efficiency in the BEAD-C reactor was 85.6%, indicating that the commercialization of BEAD reactors equipped with rotating STS304 impeller electrodes is possible. Copyright © 2018 Elsevier Ltd. All rights reserved.

Vehicle-based Methane Mapping Helps Find Natural Gas Leaks and Prioritize Leak Repairs

NASA Astrophysics Data System (ADS)

von Fischer, J. C.; Weller, Z.; Roscioli, J. R.; Lamb, B. K.; Ferrara, T.

2017-12-01

Recently, mobile methane sensing platforms have been developed to detect and locate natural gas (NG) leaks in urban distribution systems and to estimate their size. Although this technology has already been used in targeted deployment for prioritization of NG pipeline infrastructure repair and replacement, one open question regarding this technology is how effective the resulting data are for prioritizing infrastructure repair and replacement. To answer this question we explore the accuracy and precision of the natural gas leak location and emission estimates provided by methane sensors placed on Google Street View (GSV) vehicles. We find that the vast majority (75%) of methane emitting sources detected by these mobile platforms are NG leaks and that the location estimates are effective at identifying the general location of leaks. We also show that the emission rate estimates from mobile detection platforms are able to effectively rank NG leaks for prioritizing leak repair. Our findings establish that mobile sensing platforms are an efficient and effective tool for improving the safety and reducing the environmental impacts of low-pressure NG distribution systems by reducing atmospheric methane emissions.

Methane flux from Minnesota Peatlands

NASA Astrophysics Data System (ADS)

Crill, P. M.; Bartlett, K. B.; Harriss, R. C.; Gorham, E.; Verry, E. S.; Sebacher, D. I.; Madzar, L.; Sanner, W.

1988-12-01

Northern (>40°N) wetlands have been suggested as the largest natural source of methane (CH4) to the troposphere. To refine our estimates of source strengths from this region and to investigate climatic controls on the process, fluxes were measured from a variety of Minnesota peatlands during May, June, and August 1986. Sites included forested and unforested ombrotrophic bogs and minerotrophic fens in and near the U.S. Department of Agriculture Marcell Experimental Forest and the Red Lake peatlands. Late spring and summer fluxes ranged from 11 to 866 mg CH4 m-2 d-1, averaging 207 mg CH4 m-2 d-1 overall. At Marcell Forest, forested bogs and fen sites had lower fluxes (averages of 77 ± 21 mg CH4 m-2 d-1 and 142 ± 19 mg CH4 m-2 d-1) than open bogs (average of 294 ± 30 mg CH4 m-2 d-1). In the Red Lake peatland, circumneutral fens, with standing water above the peat surface, produced more methane than acid bog sites in which the water table was beneath the moss surface (325 ± 31 and 102 ± 13 mg CH4 m-2 d-1, respectively). Peat temperature was an important control. Methane flux increased in response to increasing soil temperature. For example, the open bog in the Marcell Forest with the highest CH4 flux exhibited a 74-fold increase in flux over a three-fold increase in temperature. We estimate that the methane flux from all peatlands north of 40° may be on the order of 70 to 90 Tg/yr though estimates of this sort are plagued by uncertainties in the areal extent of peatlands, length of the CH4 producing season, and the spatial and temporal variability of the flux.

Increasing the quantitative credibility of open-path FT-IR spectroscopic data with focus on several properties of the background spectrum

USDA-ARS?s Scientific Manuscript database

The choice of the type of background spectrum affects the credibility of open-path Fourier transform infrared (OP/FT-IR) spectroscopic data, and consequently the quality of data analysis. We systematically investigated several properties of the background spectrum. The results show that a short-pa...

Open-path atmospheric transmission for a diode-pumped cesium laser.

PubMed

Rice, Christopher A; Lott, Gordon E; Perram, Glen P

2012-12-01

A tunable diode laser absorption spectroscopy device was developed to study atmospheric propagation for emerging high-energy laser weapons. The cesium diode-pumped alkali laser operates near 895 nm in the vicinity of several water-vapor absorption lines. Temperature, pressure, and water vapor concentration were determined for 150 m and 1 km open paths with statistical errors of ∼0.2%. Comparison with meteorological instruments yields agreement for the 1 km path to within 0.6% for temperature, 3.7% for pressure, and 2.4% for concentration.

Systems and methods of manufacturing microchannel arrays

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

Paul, Brian K.; Brannon, Samuel T.

The present application relates to apparatus and methods of reducing the cost of microchannel array production and operation. In a representative embodiment, a microchannel array can comprise a first lamina having one or more flanges and a plurality of elongated bosses. The one or more flanges can extend along a perimeter of the first lamina, the plurality of elongated bosses can at least partially define a plurality of first flow paths, and the first lamina can define at least one opening. The microchannel array can also comprise a second lamina having a plurality of second flow paths, and can definemore » at least one opening. The second lamina can be disposed above the first lamina such that the second lamina encloses the first flow paths of the first lamina and the at least one opening of the first lamina is coaxial with the at least one opening of the second lamina.« less

Application of harmonic detection technology in methane telemetry

NASA Astrophysics Data System (ADS)

Huo, Yuehua; Fan, Weiqiang

2017-08-01

Methane telemetry plays a vital role in ensuring the safe production of coal mines and monitoring the leakage of natural gas pipelines. Harmonic detection is the key technology of methane telemetry accuracy and sensitivity, but the current telemetry distance is short, the relationship between different modulation parameters is complex, and the harmonic signal is affected by noise interference. These factors seriously affect the development of harmonic detection technology. In this paper, the principle of methane telemetry based on harmonic detection technology is introduced. The present situation and characteristics of harmonic detection technology are expounded. The problems existing in harmonic detection are analyzed. Finally, the future development trend is discussed.

Light-induced diurnal pattern of methane exchange in a boreal forest

NASA Astrophysics Data System (ADS)

Sundqvist, Elin; Crill, Patrick; Mölder, Meelis; Vestin, Patrik; Lindroth, Anders

2013-04-01

Boreal forests represents one third of the Earth's forested land surface area and is a net sink of methane and an important component of the atmospheric methane budget. Methane is oxidized in well-aerated forest soils whereas ponds and bog soils are sources of methane. Besides the microbial processes in the soil also forest vegetation might contribute to methane exchange. Due to a recent finding of methane consumption by boreal plants that correlated with photosynthetic active radiation (PAR), we investigate the impact of PAR on soil methane exchange at vegetated plots on the forest floor. The study site, Norunda in central Sweden, is a 120 years old boreal forest stand, dominated by Scots pine and Norway spruce. We used continuous chamber measurements in combination with a high precision laser gas analyzer (Los Gatos Research), to measure the methane exchange at four different plots in July-November 2009, and April-June 2010. The ground vegetation consisted almost entirely of mosses and blueberry-shrubs. Two of the plots acted as stable sinks of methane whereas the other two plots shifted from sinks to sources during very wet periods. The preliminary results show a clear diurnal pattern of the methane exchange during the growing season, which cannot be explained by temperature. The highest consumption occurs at high PAR levels. The amplitude of the diurnal methane exchange during the growing season is in the order of 10 μmol m-2 h-1. This indicates that besides methane oxidation by methanotrophs in the soil there is an additional removal of methane at soil level by a process related to ground vegetation.

Phase and flow behavior of mixed gas hydrate systems during gas injection

NASA Astrophysics Data System (ADS)

Darnell, K.; Flemings, P. B.; DiCarlo, D. A.

2017-12-01

We present one-dimensional, multi-phase flow model results for injections of carbon dioxide and nitrogen mixtures, or flue gas, into methane hydrate bearing reservoirs. Our flow model is coupled to a thermodynamic simulator that predicts phase stabilities as a function of composition, so multiple phases can appear, disappear, or change composition as the injection invades the reservoir. We show that the coupling of multi-phase fluid flow with phase behavior causes preferential phase fractionation in which each component flows through the system at different speeds and in different phases. We further demonstrate that phase and flow behavior within the reservoir are driven by hydrate stability of each individual component in addition to the hydrate stability of the injection composition. For example, if carbon dioxide and nitrogen are both individually hydrate stable at the reservoir P-T conditions, then any injection composition will convert all available water into hydrate and plug the reservoir. In contrast, if only carbon dioxide is hydrate stable at the reservoir P-T conditions, then nitrogen preferentially stays in the gaseous phase, while the carbon dioxide partitions into the hydrate and liquid water phases. For all injections of this type, methane originally held in hydrate is released by dissociation into the nitrogen-rich gaseous phase. The net consequence is that a gas phase composed of nitrogen and methane propagates through the reservoir in a fast-moving front. A slower-moving front lags behind where carbon dioxide and nitrogen form a mixed hydrate, but methane is absent due to dissociation-induced methane stripping from the first, fast-moving front. The entire composition path traces through the phase space as the flow develops with each front moving at different, constant velocities. This behavior is qualitatively similar to the dynamics present in enhanced oil recovery or enhanced coalbed methane recovery. These results explain why the inclusion of nitrogen in mixed gas injection into methane hydrate reservoirs has been far more successful at producing methane than pure carbon dioxide injections. These results also provide a test for the validity of equilibrium thermodynamics in transport-dominated mixed hydrate systems that can be validated by laboratory-scale flow-through experiments.

Baseline groundwater quality from 20 domestic wells in Sullivan County, Pennsylvania, 2012

USGS Publications Warehouse

Sloto, Ronald A.

2013-01-01

Concentrations of dissolved methane ranged from less than 0.001 to 51.1 mg/L. Methane was not detected in water samples from 13 wells, and the methane concentration was less than 0.07 mg/L in samples from five wells. The highest dissolved methane concentrations were 4.1 and 51.1 mg/L, and the pH of the water from both wells was greater than 8. Water samples from these wells were analyzed for isotopes of carbon and hydrogen in the methane. The isotopic ratio values fell in the range for a thermogenic (natural gas) source. The water samples from these two wells had the highest concentrations of arsenic, boron, bromide, chloride, fluoride, lithium, molybdenum, and sodium of the 20 wells sampled.

Applications of open-path Fourier transform infrared for identification of volatile organic compound pollution sources and characterization of source emission behaviors.

PubMed

Lin, Chitsan; Liou, Naiwei; Sun, Endy

2008-06-01

An open-path Fourier transform infrared spectroscopy (OP-FTIR) system was set up for 3-day continuous line-averaged volatile organic compound (VOC) monitoring in a paint manufacturing plant. Seven VOCs (toluene, m-xylene, p-xylene, styrene, methanol, acetone, and 2-butanone) were identified in the ambient environment. Daytime-only batch operation mode was well explained by the time-series concentration plots. Major sources of methanol, m-xylene, acetone, and 2-butanone were identified in the southeast direction where paint solvent manufacturing processes are located. However, an attempt to uncover sources of styrene was not successful because the method detection limit (MDL) of the OP-FTIR system was not sensitive enough to produce conclusive data. In the second scenario, the OP-FTIR system was set up in an industrial complex to distinguish the origins of several VOCs. Eight major VOCs were identified in the ambient environment. The pollutant detected wind-rose percentage plots that clearly showed that ethylene, propylene, 2-butanone, and toluene mainly originated from the tank storage area, whereas the source of n-butane was mainly from the butadiene manufacturing processes of the refinery plant, and ammonia was identified as an accompanying reduction product in the gasoline desulfuration process. Advantages of OP-FTIR include its ability to simultaneously and continuously analyze many compounds, and its long path length monitoring has also shown advantages in obtaining more comprehensive data than the traditional multiple, single-point monitoring methods.

Radio-anatomical Study of the Greater Palatine Canal and the Pterygopalatine Fossa in a Lebanese Population: A Consideration for Maxillary Nerve Block

PubMed Central

Aoun, Georges; Nasseh, Ibrahim; Sokhn, Sayde

2016-01-01

Aim: The aim of this study was to describe the morphology of the component, greater palatine canal-pterygopalatine fossa (GPC-PPF), in a Lebanese population using cone-beam computed tomography (CBCT) technology. Materials and Methods: CBCT images of 79 Lebanese adult patients (38 females and 41 males) were included in this study, and a total of 158 cases were evaluated bilaterally. The length and path of the GPCs-PPFs were determined, and the data obtained analyzed statistically. Results: In the sagittal plane, of all the GPCs-PPFs assessed, the average length was 35.02 mm on the right and 35.01 mm on the left. The most common anatomic path consisted in the presence of a curvature resulting in an internal narrowing whose average diameter was 2.4 mm on the right and 2.45 mm on the left. The mean diameter of the upper opening was 5.85 mm on the right and 5.82 mm on the left. As for the lower opening corresponding to the greater palatine foramen, the right and left average diameters were 6.39 mm and 6.42 mm, respectively. Conclusion: Within the limits of this study, we concluded that throughout the Lebanese population, the GPC-PPF path is variable with a predominance of curved one (77.21% [122/158] in both the right and left sides); however, the GPC-PPF length does not significantly vary according to gender and side. PMID:27833777

Robust Flight Path Determination for Mars Precision Landing Using Genetic Algorithms

NASA Technical Reports Server (NTRS)

Bayard, David S.; Kohen, Hamid

1997-01-01

This paper documents the application of genetic algorithms (GAs) to the problem of robust flight path determination for Mars precision landing. The robust flight path problem is defined here as the determination of the flight path which delivers a low-lift open-loop controlled vehicle to its desired final landing location while minimizing the effect of perturbations due to uncertainty in the atmospheric model and entry conditions. The genetic algorithm was capable of finding solutions which reduced the landing error from 111 km RMS radial (open-loop optimal) to 43 km RMS radial (optimized with respect to perturbations) using 200 hours of computation on an Ultra-SPARC workstation. Further reduction in the landing error is possible by going to closed-loop control which can utilize the GA optimized paths as nominal trajectories for linearization.

Identification of adsorption sites in Cu-BTC by experimentation and molecular simulation.

PubMed

García-Pérez, Elena; Gascón, Jorge; Morales-Flórez, Víctor; Castillo, Juan Manuel; Kapteijn, Freek; Calero, Sofía

2009-02-03

The adsorption of several quadrupolar and nonpolar gases on the Metal Organic Framework Cu-BTC has been studied by combining experimental measurements and Monte Carlo simulations. Four main adsorption sites for this structure have been identified: site I close to the copper atoms, site I' in the bigger cavities, site II located in the small octahedral cages, and site III at the windows of the four open faces of the octahedral cage. Our simulations identify the octahedral cages (sites II and III) and the big cages (site I') as the preferred positions for adsorption, while site I, near the copper atoms, remains empty over the entire range of pressures analyzed due to its reduced accessibility. The occupation of the different sites for ethane and propane in Cu-BTC proceeds similarly as for methane, and shows small differences for O2 and N2 that can be attributed to the quadrupole moment of these molecules. Site II is filled predominantly for methane (the nonpolar molecule), whereas for N2, the occupation of II and I' can be considered almost equivalent. The molecular sitting for O2 shows an intermediate behavior between those observed for methane and for N2. The differences between simulated and experimental data at elevated temperatures for propane are tentatively attributed to a reversible change in the lattice parameters of Cu-BTC by dehydration and by temperature, blocking the accessibility to site III and reducing that to site I'. Adsorption parameters of the investigated molecules have been determined from the simulations.

Methane concentration and isotopic composition measurements with a mid-infrared quantum-cascade laser

NASA Technical Reports Server (NTRS)

Kosterev, A. A.; Curl, R. F.; Tittel, F. K.; Gmachl, C.; Capasso, F.; Sivco, D. L.; Baillargeon, J. N.; Hutchinson, A. L.; Cho, A. Y.

1999-01-01

A quantum-cascade laser operating at a wavelength of 8.1 micrometers was used for high-sensitivity absorption spectroscopy of methane (CH4). The laser frequency was continuously scanned with current over more than 3 cm-1, and absorption spectra of the CH4 nu 4 P branch were recorded. The measured laser linewidth was 50 MHz. A CH4 concentration of 15.6 parts in 10(6) ( ppm) in 50 Torr of air was measured in a 43-cm path length with +/- 0.5-ppm accuracy when the signal was averaged over 400 scans. The minimum detectable absorption in such direct absorption measurements is estimated to be 1.1 x 10(-4). The content of 13CH4 and CH3D species in a CH4 sample was determined.

Bacterial Degradation of Phosphonates Bound to High-Molecular-Weight Dissolved Organic Matter Produces Methane and Other Hydrocarbons

NASA Astrophysics Data System (ADS)

Sosa, O.; Ferron Smith, S.; Karl, D. M.; DeLong, E.; Repeta, D.

2016-02-01

The biological degradation of dissolved organic matter (DOM) plays important roles in the carbon cycle and energy balance of the ocean. Yet, the biochemical pathways that drive DOM turnover remain to be fully characterized. In this study, we tested the ability of two open ocean bacterial isolates (a Pseudomonas stutzeri strain (Gammaproteobacteria) and a Sulfitobacter isolate (Alphaproteobacteria)) to degrade DOM phosphonates. Each isolate encoded a complete phosphonate degradation pathway in its genome, and each was able to degrade simple alkyl-phosphonates like methyl phosphonate, releasing methane (or other short chain hydrocarbon gases) as a result. We found that cultures incubated in the presence of HMW DOM polysaccharides also produced methane and other trace gases under aerobic conditions. To demonstrate that phosphonates were the source of these gases, we constructed a P. stutzeri mutant disabled in the phosphonate degradation pathway. Unlike the wild type, the mutant strain was deficient in the production of methane and other gases from HMW DOM-associated phosphonates. These observations support the hypothesis that DOM-bound methyl phosphonates may be a significant source of methane in the water column, and that bacterial degradation of these compounds likely contribute to the subsurface methane maxima observed throughout the world's oceans.

Illuminating Geochemical Controls of Methane Oxidation Along a Gradient of Permafrost Thaw

NASA Astrophysics Data System (ADS)

Perryman, C. R.; Kashi, N.; McCalley, C. K.; Malhotra, A.; Giesler, R.; Varner, R.

2017-12-01

Increases in annual mean temperature in the subarctic have accelerated the thaw of organic-rich permafrost peatlands, exacerbating methane (CH4) production from microbial decomposition of peat deposits and subsequent CH4 emissions. Methanotrophic bacteria may oxidize/consume upwards of 90% of produced CH4 in some settings, pending substrate availability and environmental conditions. Redox chemistry may also control the rate of CH4 oxidation in thawing permafrost areas, particularly redox potential (Eh) and the availability of oxygen (O2) and other terminal electron receptors. We investigated potential CH4 oxidation rates across a permafrost thaw gradient in Stordalen Mire (68°21'N,18°49'E) near Abisko, Sweden. Methane oxidation rates for sites from thawing and collapsed palsa, semi-wet Sphagnum, and open-water sedge sites were determined through laboratory incubations. Peat cores were extracted from two depths at each site and incubated at in situ temperatures and CH4 concentrations. Headspace samples were collected over a 48-hour period and analyzed for CH4 concentration using flame ionization detection gas chromatography (GC-FID). Dissolved O2, Eh, and dissolved CH4 were measured in sites with porewater. Oxidation rates ranged from <0.1 to 19 μg of CH4 per gram of dry biomass per day. Eh remained positive (41.6 to 316.8 mV) with available dissolved O2 (0.3 - 5.2 mg/L) in all measurement locations down to 20cm, indicating in situ aerobic CH4 oxidation is viable across these environments. Potential CH4 oxidation rates increased with increasing dissolved CH4 concentration. Highest potential CH4 oxidation rates were found in open-water sedge sites. Eh and dissolved O2 were lowest at these sites, suggesting that methanotrophs with low-O2 demand may populate sedge areas. Furthermore, potential CH4 oxidation rates were higher at depth than at the surface in thawing palsa, suggesting CH4 oxidation may mitigate CH4 production triggered by warming in these actively thawing environments. Forthcoming elemental analyses of peat and pore water will further elucidate trends and geochemical controls of CH4 oxidation rates in thawing permafrost areas.

Bovine Host Genetic Variation Influences Rumen Microbial Methane Production with Best Selection Criterion for Low Methane Emitting and Efficiently Feed Converting Hosts Based on Metagenomic Gene Abundance

PubMed Central

Roehe, Rainer; Dewhurst, Richard J.; Duthie, Carol-Anne; Rooke, John A.; McKain, Nest; Ross, Dave W.; Hyslop, Jimmy J.; Waterhouse, Anthony; Freeman, Tom C.

2016-01-01

Methane produced by methanogenic archaea in ruminants contributes significantly to anthropogenic greenhouse gas emissions. The host genetic link controlling microbial methane production is unknown and appropriate genetic selection strategies are not developed. We used sire progeny group differences to estimate the host genetic influence on rumen microbial methane production in a factorial experiment consisting of crossbred breed types and diets. Rumen metagenomic profiling was undertaken to investigate links between microbial genes and methane emissions or feed conversion efficiency. Sire progeny groups differed significantly in their methane emissions measured in respiration chambers. Ranking of the sire progeny groups based on methane emissions or relative archaeal abundance was consistent overall and within diet, suggesting that archaeal abundance in ruminal digesta is under host genetic control and can be used to genetically select animals without measuring methane directly. In the metagenomic analysis of rumen contents, we identified 3970 microbial genes of which 20 and 49 genes were significantly associated with methane emissions and feed conversion efficiency respectively. These explained 81% and 86% of the respective variation and were clustered in distinct functional gene networks. Methanogenesis genes (e.g. mcrA and fmdB) were associated with methane emissions, whilst host-microbiome cross talk genes (e.g. TSTA3 and FucI) were associated with feed conversion efficiency. These results strengthen the idea that the host animal controls its own microbiota to a significant extent and open up the implementation of effective breeding strategies using rumen microbial gene abundance as a predictor for difficult-to-measure traits on a large number of hosts. Generally, the results provide a proof of principle to use the relative abundance of microbial genes in the gastrointestinal tract of different species to predict their influence on traits e.g. human metabolism, health and behaviour, as well as to understand the genetic link between host and microbiome. PMID:26891056

Bovine Host Genetic Variation Influences Rumen Microbial Methane Production with Best Selection Criterion for Low Methane Emitting and Efficiently Feed Converting Hosts Based on Metagenomic Gene Abundance.

PubMed

Roehe, Rainer; Dewhurst, Richard J; Duthie, Carol-Anne; Rooke, John A; McKain, Nest; Ross, Dave W; Hyslop, Jimmy J; Waterhouse, Anthony; Freeman, Tom C; Watson, Mick; Wallace, R John

2016-02-01

Methane produced by methanogenic archaea in ruminants contributes significantly to anthropogenic greenhouse gas emissions. The host genetic link controlling microbial methane production is unknown and appropriate genetic selection strategies are not developed. We used sire progeny group differences to estimate the host genetic influence on rumen microbial methane production in a factorial experiment consisting of crossbred breed types and diets. Rumen metagenomic profiling was undertaken to investigate links between microbial genes and methane emissions or feed conversion efficiency. Sire progeny groups differed significantly in their methane emissions measured in respiration chambers. Ranking of the sire progeny groups based on methane emissions or relative archaeal abundance was consistent overall and within diet, suggesting that archaeal abundance in ruminal digesta is under host genetic control and can be used to genetically select animals without measuring methane directly. In the metagenomic analysis of rumen contents, we identified 3970 microbial genes of which 20 and 49 genes were significantly associated with methane emissions and feed conversion efficiency respectively. These explained 81% and 86% of the respective variation and were clustered in distinct functional gene networks. Methanogenesis genes (e.g. mcrA and fmdB) were associated with methane emissions, whilst host-microbiome cross talk genes (e.g. TSTA3 and FucI) were associated with feed conversion efficiency. These results strengthen the idea that the host animal controls its own microbiota to a significant extent and open up the implementation of effective breeding strategies using rumen microbial gene abundance as a predictor for difficult-to-measure traits on a large number of hosts. Generally, the results provide a proof of principle to use the relative abundance of microbial genes in the gastrointestinal tract of different species to predict their influence on traits e.g. human metabolism, health and behaviour, as well as to understand the genetic link between host and microbiome.

Masticatory path pattern during mastication of chewing gum with regard to gender difference.

PubMed

Kobayashi, Yoshinori; Shiga, Hiroshi; Arakawa, Ichiro; Yokoyama, Masaoki; Nakajima, Kunihisa

2009-01-01

To clarify the masticatory path patterns of the mandibular incisal point during mastication of softened chewing gum with regard to gender difference. One hundred healthy subjects (50 males and 50 females) were asked to chew softened chewing gum on one side at a time (right side and left side) and the movement of the mandibular incisal point was recorded using MKG K6I. After a catalog of path patterns was made, the movement path was classified into one of the pattern groups, and then the frequency of each pattern was investigated. A catalog of path patterns consisting of the three types of opening path (op1, linear or concave path; op2, path toward the chewing side after toward the non-working side; op3, convex path) and two types of closing path (cl1, convex path; cl2, concave path) was made. The movement path was classified into one of seven patterns, with six patterns being from the catalog and a final extra pattern in which the opening and closing paths crossed. The most common pattern among the subjects was Pattern I, followed by Patterns III, II, IV, V, VII, and VI, in that order. The majority of cases, 149 (74.5%) of 200 cases, showed either Pattern I (op1 and cl1) or Pattern III (op2 and cl1). There was no significant difference between the two genders in the frequency of each pattern. The movement path could be classified into seven patterns and no gender-related difference was found in the frequency of each pattern.

Comparison of Lyman-alpha and LI-COR infrared hygrometers for airborne measurement of turbulent fluctuations of water vapour

NASA Astrophysics Data System (ADS)

Lampert, Astrid; Hartmann, Jörg; Pätzold, Falk; Lobitz, Lennart; Hecker, Peter; Kohnert, Katrin; Larmanou, Eric; Serafimovich, Andrei; Sachs, Torsten

2018-05-01

To investigate if the LI-COR humidity sensor can be used as a replacement of the Lyman-alpha sensor for airborne applications, the measurement data of the Lyman-alpha and several LI-COR sensors are analysed in direct intercomparison flights on different airborne platforms. One vibration isolated closed-path and two non-isolated open-path LI-COR sensors were installed on a Dornier 128 twin engine turbo-prop aircraft. The closed-path sensor provided absolute values and fluctuations of the water vapour mixing ratio in good agreement with the Lyman-alpha. The signals of the two open-path sensors showed considerable high-frequency noise, and the absolute value of the mixing ratio was observed to drift with time in this vibrational environment. On the helicopter-towed sensor system Helipod, with very low vibration levels, the open-path LI-COR sensor agreed very well with the Lyman-alpha sensor over the entire frequency range up to 3 Hz. The results show that the LI-COR sensors are well suited for airborne measurements of humidity fluctuations, provided that a vibrationless environment is given, and this turns out to be more important than close sensor spacing.

Boiler using combustible fluid

DOEpatents

Baumgartner, H.; Meier, J.G.

1974-07-03

A fluid fuel boiler is described comprising a combustion chamber, a cover on the combustion chamber having an opening for introducing a combustion-supporting gaseous fluid through said openings, means to impart rotation to the gaseous fluid about an axis of the combustion chamber, a burner for introducing a fluid fuel into the chamber mixed with the gaseous fluid for combustion thereof, the cover having a generally frustro-conical configuration diverging from the opening toward the interior of the chamber at an angle of between 15/sup 0/ and 55/sup 0/; means defining said combustion chamber having means defining a plurality of axial hot gas flow paths from a downstream portion of the combustion chamber to flow hot gases into an upstream portion of the combustion chamber, and means for diverting some of the hot gas flow along paths in a direction circumferentially of the combustion chamber, with the latter paths being immersed in the water flow path thereby to improve heat transfer and terminating in a gas outlet, the combustion chamber comprising at least one modular element, joined axially to the frustro-conical cover and coaxial therewith. The modular element comprises an inner ring and means of defining the circumferential, radial, and spiral flow paths of the hot gases.

Mobile sensing of point-source fugitive methane emissions using Bayesian inference: the determination of the likelihood function

NASA Astrophysics Data System (ADS)

Zhou, X.; Albertson, J. D.

2016-12-01

Natural gas is considered as a bridge fuel towards clean energy due to its potential lower greenhouse gas emission comparing with other fossil fuels. Despite numerous efforts, an efficient and cost-effective approach to monitor fugitive methane emissions along the natural gas production-supply chain has not been developed yet. Recently, mobile methane measurement has been introduced which applies a Bayesian approach to probabilistically infer methane emission rates and update estimates recursively when new measurements become available. However, the likelihood function, especially the error term which determines the shape of the estimate uncertainty, is not rigorously defined and evaluated with field data. To address this issue, we performed a series of near-source (< 30 m) controlled methane release experiments using a specialized vehicle mounted with fast response methane analyzers and a GPS unit. Methane concentrations were measured at two different heights along mobile traversals downwind of the sources, and concurrent wind and temperature data are recorded by nearby 3-D sonic anemometers. With known methane release rates, the measurements were used to determine the functional form and the parameterization of the likelihood function in the Bayesian inference scheme under different meteorological conditions.

Origin of methane and sources of high concentrations in Los Angeles groundwater

USGS Publications Warehouse

Kulongoski, Justin; McMahon, Peter B.; Land, Michael; Wright, Michael; Johnson, Theodore; Landon, Matthew K.

2018-01-01

In 2014, samples from 37 monitoring wells at 17 locations, within or near oil fields, and one site >5 km from oil fields, in the Los Angeles Basin, California, were analyzed for dissolved hydrocarbon gas isotopes and abundances. The wells sample a variety of depths of an aquifer system composed of unconsolidated and semiconsolidated sediments under various conditions of confinement. Concentrations of methane in groundwater samples ranged from 0.002 to 150 mg/L—some of the highest concentrations reported in a densely populated urban area. The δ13C and δ2H of the methane ranged from −80.8 to −45.5 per mil (‰) and −249.8 to −134.9‰, respectively, and, along with oxidation‐reduction processes, helped to identify the origin of methane as microbial methanogenesis and CO2 reduction as its main formation pathway. The distribution of methane concentrations and isotopes is consistent with the high concentrations of methane in Los Angeles Basin groundwater originating from relatively shallow microbial production in anoxic or suboxic conditions. Source of the methane is the aquifer sediments rather than the upward migration or leakage of thermogenic methane associated with oil fields in the basin.

Origin of Methane and Sources of High Concentrations in Los Angeles Groundwater

NASA Astrophysics Data System (ADS)

Kulongoski, J. T.; McMahon, P. B.; Land, M.; Wright, M. T.; Johnson, T. A.; Landon, M. K.

2018-03-01

In 2014, samples from 37 monitoring wells at 17 locations, within or near oil fields, and one site >5 km from oil fields, in the Los Angeles Basin, California, were analyzed for dissolved hydrocarbon gas isotopes and abundances. The wells sample a variety of depths of an aquifer system composed of unconsolidated and semiconsolidated sediments under various conditions of confinement. Concentrations of methane in groundwater samples ranged from 0.002 to 150 mg/L—some of the highest concentrations reported in a densely populated urban area. The δ13C and δ2H of the methane ranged from -80.8 to -45.5 per mil (‰) and -249.8 to -134.9‰, respectively, and, along with oxidation-reduction processes, helped to identify the origin of methane as microbial methanogenesis and CO2 reduction as its main formation pathway. The distribution of methane concentrations and isotopes is consistent with the high concentrations of methane in Los Angeles Basin groundwater originating from relatively shallow microbial production in anoxic or suboxic conditions. Source of the methane is the aquifer sediments rather than the upward migration or leakage of thermogenic methane associated with oil fields in the basin.

Geochemical evidences of methane hydrate dissociation in Alaskan Beaufort Margin during Holocene

NASA Astrophysics Data System (ADS)

Uchida, M.; Rella, S.; Kubota, Y.; Kumata, H.; Mantoku, K.; Nishino, S.; Itoh, M.

2017-12-01

Alaskan Beaufort margin bear large abundances of sub-sea and permafrost methane hydrate[Ruppel, 2016]. During the Last Glacial, previous reported direct and indirect evidences accumulated from geochemical data from marginal sea sediment suggests that methane episodically released from hydrate trapped in the seafloor sediments[Kennett et al., 2000; Uchida et al., 2006, 2008; Cook et al, 2011]. Here we analyzed stable isotopes of foraminifera and molecular marker derived from the activity of methanotrophic bacteria from piston cores collected by the 2010 R/V Mirai cruise in Alaskan Beaufort Margin. Our data showed highly depleted 13C compositions of benthic foraminifera, suggesting indirect records of enhanced incorporation of 13C-depleted CO2 formed by methanotrophic process that use 12C-enriched methane as their main source of carbon. This is the first evidence of methane hydrate dissociation in Alaskan margin. Here we discussed timing of signals of methane dissociation with variability of sea ice and intermediate Atlantic water temperature. The dissociation of methane hydrate in the Alaskan Margin may be modulated by Atlantic warm intermediate water warming. Our results suggest that Arctic marginal regions bearing large amount methane hydrate may be a profound effect on future warming climate changes.

Anaerobic methanotrophic communities thrive in deep submarine permafrost.

PubMed

Winkel, Matthias; Mitzscherling, Julia; Overduin, Pier P; Horn, Fabian; Winterfeld, Maria; Rijkers, Ruud; Grigoriev, Mikhail N; Knoblauch, Christian; Mangelsdorf, Kai; Wagner, Dirk; Liebner, Susanne

2018-01-22

Thawing submarine permafrost is a source of methane to the subsurface biosphere. Methane oxidation in submarine permafrost sediments has been proposed, but the responsible microorganisms remain uncharacterized. We analyzed archaeal communities and identified distinct anaerobic methanotrophic assemblages of marine and terrestrial origin (ANME-2a/b, ANME-2d) both in frozen and completely thawed submarine permafrost sediments. Besides archaea potentially involved in anaerobic oxidation of methane (AOM) we found a large diversity of archaea mainly belonging to Bathyarchaeota, Thaumarchaeota, and Euryarchaeota. Methane concentrations and δ 13 C-methane signatures distinguish horizons of potential AOM coupled either to sulfate reduction in a sulfate-methane transition zone (SMTZ) or to the reduction of other electron acceptors, such as iron, manganese or nitrate. Analysis of functional marker genes (mcrA) and fluorescence in situ hybridization (FISH) corroborate potential activity of AOM communities in submarine permafrost sediments at low temperatures. Modeled potential AOM consumes 72-100% of submarine permafrost methane and up to 1.2 Tg of carbon per year for the total expected area of submarine permafrost. This is comparable with AOM habitats such as cold seeps. We thus propose that AOM is active where submarine permafrost thaws, which should be included in global methane budgets.

Geochemical and geological factors controlling the spatial distribution of sulfate-methane transition zone in the Ría de Vigo (NW Spain)

NASA Astrophysics Data System (ADS)

Martínez-Carreño, N.; García-Gil, S.; Cartelle, V.; de Blas, E.; Ramírez-Pérez, A. M.; Insua, T. L.

2017-05-01

High-resolution seismic profiles, gravity core analysis and radiocarbon data have been used to identify the factors behind the methane production and free gas accumulation in the Ría de Vigo. Lithological and geochemical parameters (sulfate and methane concentration) from seventeen gravity cores were analyzed to characterize the sediment of the ria. The distribution of methane-charged sediments is mainly controlled by the quantity and quality of organic matter. Geochemical analyses reveal minimum methane concentrations ranging between 1 μM and 1 mM in sediments located outside the acoustic gas field, while gas-bearing sediments, show methane concentrations up to 5 mM. A shallowing of the sulfate-methane transition zone (SMTZ) is observed from the outer to the inner area of the ria. The presence of methane in the sulfate reduction zone (SRZ) likely to reflect the existence of methylotropic methanogenesis and/or migration processes of deeper methane gas in the sediments of the Ría de Vigo. The presence of an 'anomalous' high-sulfate concentration layer below the SMTZ in the inner and middle area of the ria, is attributed to the intrusion of sulfate-rich waters from adjacent areas that could be transported laterally through more porous layers.

New insights into the transport processes controlling the sulfate-methane-transition-zone near methane vents.

PubMed

Sultan, Nabil; Garziglia, Sébastien; Ruffine, Livio

2016-05-27

Over the past years, several studies have raised concerns about the possible interactions between methane hydrate decomposition and external change. To carry out such an investigation, it is essential to characterize the baseline dynamics of gas hydrate systems related to natural geological and sedimentary processes. This is usually treated through the analysis of sulfate-reduction coupled to anaerobic oxidation of methane (AOM). Here, we model sulfate reduction coupled with AOM as a two-dimensional (2D) problem including, advective and diffusive transport. This is applied to a case study from a deep-water site off Nigeria's coast where lateral methane advection through turbidite layers was suspected. We show by analyzing the acquired data in combination with computational modeling that a two-dimensional approach is able to accurately describe the recent past dynamics of such a complex natural system. Our results show that the sulfate-methane-transition-zone (SMTZ) is not a vertical barrier for dissolved sulfate and methane. We also show that such a modeling is able to assess short timescale variations in the order of decades to centuries.

Effects of Nitrogen Load on the Function and Diversity of Methanotrophs in the Littoral Wetland of a Boreal Lake

PubMed Central

Siljanen, Henri M. P.; Saari, Anne; Bodrossy, Levente; Martikainen, Pertti J.

2012-01-01

Methane is the second most abundant greenhouse gas in the atmosphere. A major part of the total methane emissions from lake ecosystems is emitted from littoral wetlands. Methane emissions are significantly reduced by methanotrophs, as they use methane as their sole energy and carbon source. Methanotrophic activity can be either activated or inhibited by nitrogen. However, the effects of nitrogen on methanotrophs in littoral wetlands are unknown. Here we report how nitrogen loading in situ affected the function and diversity of methanotrophs in a boreal littoral wetland. Methanotrophic community composition and functional diversity were analyzed with a particulate methane monooxygenase (pmoA) gene targeted microarray. Nitrogen load had no effects on methane oxidation potential and methane fluxes. Nitrogen load activated pmoA gene transcription of type I (Methylobacter, Methylomonas, and LW21-freshwater phylotypes) methanotrophs, but decreased the relative abundance of type II (Methylocystis, Methylosinus trichosporium, and Methylosinus phylotypes) methanotrophs. Hence, the overall activity of a methanotroph community in littoral wetlands is not affected by nitrogen leached from the catchment area. PMID:22363324

Hydrogen and methane gases are frequently detected in the stomach.

PubMed

Urita, Yoshihisa; Ishihara, Susumu; Akimoto, Tatsuo; Kato, Hiroto; Hara, Noriko; Honda, Yoshiko; Nagai, Yoko; Nakanishi, Kazushige; Shimada, Nagato; Sugimoto, Motonobu; Miki, Kazumasa

2006-05-21

To investigate the incidence of bacterial overgrowth in the stomach by using a new endoscopic method in which intragastric hydrogen and methane gases are collected and analyzed. Studies were performed in 490 consecutive patients undergoing esophagogastroscopy. At endoscopy, we intubated the stomach without inflation by air, and 20 mL of intragastric gas was collected through the biopsy channel using a 30 mL syringe. Intragastric hydrogen and methane concentrations were immediately measured by gaschromatography. H pylori infection was also determined by serology. Most of intragastric hydrogen and methane levels were less than 15 ppm (parts per million). The median hydrogen and methane values (interquartile range) were 3 (1-8) ppm and 2 (1-5) ppm, respectively. The high hydrogen and methane levels for indication of fermentation were decided if the patient had the values more than 90 percentile range in each sample. When a patient had a high level of hydrogen or methane in one or more samples, the patient was considered to have fermentation. The overall incidence of intragastric fermentation was 15.4% (73/473). Intragastric methane levels were higher in the postoperative group than in other groups. None of the mean hydrogen or methane values was related to H pylori infection. Hydrogen and methane gases are more frequently detected in the stomach than expected, regardless of the presence of abdominal symptoms. Previous gastric surgery influences on the growth of methane-producing bacteria in the fasting stomach.

Pulmonary hypoxic vasoconstriction: how strong? How fast?

NASA Technical Reports Server (NTRS)

Sheehan, D. W.; Klocke, R. A.; Farhi, L. E.

1992-01-01

We have developed a minimally invasive technique for studying regional blood flow in conscious sheep, bypassing the complications of open-chest surgery, flow probes and tracer infusion. We quantitate regional perfusion continuously on the basis of regional clearance of methane (methane is produced in the sheep rumen, enters the circulation and is eliminated nearly completely (greater than 95%) in the lung). Tracheal intubation with a dual-lumen catheter isolates the gas exchange of the right apical lobe (RAL; less than 15% of the lung) from that of the remainder of the lung, which serves as a control (CL). We measure RAL and CL methane elimination by entraining expirates in constant flows, sampled continuously for methane. Results obtained with this technique and from regional oxygen uptake are in excellent agreement. We have found that hypoxic vasoconstriction is far more potent and stable during eucapnic hypoxia than during hypocapnic hypoxia. The time course of the vasoconstriction suggests that many of the data in the literature may have been obtained prior to steady state.

Development of vanadium-phosphate catalysts for methanol production by selective oxidation of methane

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

McCormick, R.L.

1995-12-31

The United States has vast natural gas reserves which could contribute significantly to our energy security if economical technologies for conversion to liquid fuels and chemicals were developed. Many of these reserves are small scale or in remote locations and of little value unless they can be transported to consumers. Transportation is economically performed via pipeline, but this route is usually unavailable in remote locations. Another option is to convert the methane in the gas to liquid hydrocarbons, such as methanol, which can easily and economically be transported by truck. Therefore, the conversion of methane to liquid hydrocarbons has themore » potential to decrease our dependence upon oil imports by opening new markets for natural gas and increasing its use in the transportation and chemical sectors of the economy. In this project, we are attempting to develop, and explore new catalysts capable of direct oxidation of methane to methanol. The specific objectives of this work are discussed.« less

Forest ecosystem changes from annual methane source to sink depending on late summer water balance

Treesearch

Julie K. Shoemaker; Trevor F. Keenan; David Y. Hollinger; Andrew D. Richardson

2014-01-01

Forests dominate the global carbon cycle, but their role in methane (CH4) biogeochemistry remains uncertain. We analyzed whole-ecosystem CH4 fluxes from 2 years, obtained over a lowland evergreen forest in Maine, USA. Gross primary productivity provided the strongest correlation with the CH4 flux in...

Liquid hydrogen production via hydrogen sulfide methane reformation

NASA Astrophysics Data System (ADS)

Huang, Cunping; T-Raissi, Ali

Hydrogen sulfide (H 2S) methane (CH 4) reformation (H 2SMR) (2H 2S + CH 4 = CS 2 + 4H 2) is a potentially viable process for the removal of H 2S from sour natural gas resources or other methane containing gases. Unlike steam methane reformation that generates carbon dioxide as a by-product, H 2SMR produces carbon disulfide (CS 2), a liquid under ambient temperature and pressure-a commodity chemical that is also a feedstock for the synthesis of sulfuric acid. Pinch point analyses for H 2SMR were conducted to determine the reaction conditions necessary for no carbon lay down to occur. Calculations showed that to prevent solid carbon formation, low inlet CH 4 to H 2S ratios are needed. In this paper, we analyze H 2SMR with either a cryogenic process or a membrane separation operation for production of either liquid or gaseous hydrogen. Of the three H 2SMR hydrogen production flowsheets analyzed, direct liquid hydrogen generation has higher first and second law efficiencies of exceeding 80% and 50%, respectively.

Sub-micrometer epsilon-near-zero electroabsorption modulators enabled by high-mobility cadmium oxide

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

Campione, Salvatore; Wood, Michael; Serkland, Darwin K.

Here, epsilon-near-zero materials provide a new path for tailoring light-matter interactions at the nanoscale. In this paper, we analyze a compact electroabsorption modulator based on epsilon-near-zero confinement in transparent conducting oxide films. The non-resonant modulator operates through field-effect carrier density tuning. We compare the performance of modulators composed of two different conducting oxides, namely indium oxide (In2O3) and cadmium oxide (CdO), and show that better modulation performance is achieved when using high-mobility (i.e. low-loss) epsilon-near-zero materials such as CdO. In particular, we show that non-resonant electroabsorption modulators with sub-micron lengths and greater than 5 dB extinction ratios may be achievedmore » through the proper selection of high-mobility transparent conducting oxides, opening a path for device miniaturization and increased modulation depth.« less

Sub-micrometer epsilon-near-zero electroabsorption modulators enabled by high-mobility cadmium oxide

DOE PAGES

Campione, Salvatore; Wood, Michael; Serkland, Darwin K.; ...

2017-07-06

Here, epsilon-near-zero materials provide a new path for tailoring light-matter interactions at the nanoscale. In this paper, we analyze a compact electroabsorption modulator based on epsilon-near-zero confinement in transparent conducting oxide films. The non-resonant modulator operates through field-effect carrier density tuning. We compare the performance of modulators composed of two different conducting oxides, namely indium oxide (In2O3) and cadmium oxide (CdO), and show that better modulation performance is achieved when using high-mobility (i.e. low-loss) epsilon-near-zero materials such as CdO. In particular, we show that non-resonant electroabsorption modulators with sub-micron lengths and greater than 5 dB extinction ratios may be achievedmore » through the proper selection of high-mobility transparent conducting oxides, opening a path for device miniaturization and increased modulation depth.« less

Mapping chemicals in air using an environmental CAT scanning system: evaluation of algorithms

NASA Astrophysics Data System (ADS)

Samanta, A.; Todd, L. A.

A new technique is being developed which creates near real-time maps of chemical concentrations in air for environmental and occupational environmental applications. This technique, we call Environmental CAT Scanning, combines the real-time measuring technique of open-path Fourier transform infrared spectroscopy with the mapping capabilitites of computed tomography to produce two-dimensional concentration maps. With this system, a network of open-path measurements is obtained over an area; measurements are then processed using a tomographic algorithm to reconstruct the concentrations. This research focussed on the process of evaluating and selecting appropriate reconstruction algorithms, for use in the field, by using test concentration data from both computer simultation and laboratory chamber studies. Four algorithms were tested using three types of data: (1) experimental open-path data from studies that used a prototype opne-path Fourier transform/computed tomography system in an exposure chamber; (2) synthetic open-path data generated from maps created by kriging point samples taken in the chamber studies (in 1), and; (3) synthetic open-path data generated using a chemical dispersion model to create time seires maps. The iterative algorithms used to reconstruct the concentration data were: Algebraic Reconstruction Technique without Weights (ART1), Algebraic Reconstruction Technique with Weights (ARTW), Maximum Likelihood with Expectation Maximization (MLEM) and Multiplicative Algebraic Reconstruction Technique (MART). Maps were evaluated quantitatively and qualitatively. In general, MART and MLEM performed best, followed by ARTW and ART1. However, algorithm performance varied under different contaminant scenarios. This study showed the importance of using a variety of maps, particulary those generated using dispersion models. The time series maps provided a more rigorous test of the algorithms and allowed distinctions to be made among the algorithms. A comprehensive evaluation of algorithms, for the environmental application of tomography, requires the use of a battery of test concentration data before field implementation, which models reality and tests the limits of the algorithms.

Methane occurrence in groundwater of south-central New York State, 2012: summary of findings

USGS Publications Warehouse

Heisig, Paul M.; Scott, Tia-Marie

2013-01-01

A survey of methane in groundwater was undertaken to document methane occurrence on the basis of hydrogeologic setting within a glaciated 1,810-square-mile area of south-central New York that has not seen shale-gas resource development. The adjacent region in northeastern Pennsylvania has undergone shale-gas resource development from the Marcellus Shale. Well construction and subsurface data were required for each well sampled so that the local hydrogeologic setting could be classified. All wells were also at least 1 mile from any known gas well (active, exploratory, or abandoned). Sixty-six domestic wells and similar purposed supply wells were sampled during summer 2012. Field water-quality characteristics (pH, specific conductance, dissolved oxygen, and temperature) were measured at each well, and samples were collected and analyzed for dissolved gases, including methane and short-chain hydrocarbons. Carbon and hydrogen isotopic ratios of methane were measured in 21 samples that had at least 0.3 milligram per liter (mg/L) methane.

Rising methane emissions from northern wetlands associated with sea ice decline

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

Parmentier, Frans-Jan W.; Zhang, Wenxin; Mi, Yanjiao

The Arctic is rapidly transitioning toward a seasonal sea ice-free state, perhaps one of the most apparent examples of climate change in the world. This dramatic change has numerous consequences, including a large increase in air temperatures, which in turn may affect terrestrial methane emissions. Nonetheless, terrestrial and marine environments are seldom jointly analyzed. By comparing satellite observations of Arctic sea ice concentrations to methane emissions simulated by three process-based biogeochemical models, this study shows that rising wetland methane emissions are associated with sea ice retreat. Our analyses indicate that simulated high-latitude emissions for 2005-2010 were, on average, 1.7 Tgmore » CH4 yr(-1) higher compared to 1981-1990 due to a sea ice-induced, autumn-focused, warming. Since these results suggest a continued rise in methane emissions with future sea ice decline, observation programs need to include measurements during the autumn to further investigate the impact of this spatial connection on terrestrial methane emissions.« less

Rising methane emissions from northern wetlands associated with sea ice decline.

PubMed

Parmentier, Frans-Jan W; Zhang, Wenxin; Mi, Yanjiao; Zhu, Xudong; van Huissteden, Jacobus; Hayes, Daniel J; Zhuang, Qianlai; Christensen, Torben R; McGuire, A David

2015-09-16

The Arctic is rapidly transitioning toward a seasonal sea ice-free state, perhaps one of the most apparent examples of climate change in the world. This dramatic change has numerous consequences, including a large increase in air temperatures, which in turn may affect terrestrial methane emissions. Nonetheless, terrestrial and marine environments are seldom jointly analyzed. By comparing satellite observations of Arctic sea ice concentrations to methane emissions simulated by three process-based biogeochemical models, this study shows that rising wetland methane emissions are associated with sea ice retreat. Our analyses indicate that simulated high-latitude emissions for 2005-2010 were, on average, 1.7 Tg CH 4  yr -1 higher compared to 1981-1990 due to a sea ice-induced, autumn-focused, warming. Since these results suggest a continued rise in methane emissions with future sea ice decline, observation programs need to include measurements during the autumn to further investigate the impact of this spatial connection on terrestrial methane emissions.

Rising methane emissions from northern wetlands associated with sea ice decline

DOE PAGES

Parmentier, Frans-Jan W.; Zhang, Wenxin; Mi, Yanjiao; ...

2015-09-10

The Arctic is rapidly transitioning toward a seasonal sea ice-free state, perhaps one of the most apparent examples of climate change in the world. This dramatic change has numerous consequences, including a large increase in air temperatures, which in turn may affect terrestrial methane emissions. Nonetheless, terrestrial and marine environments are seldom jointly analyzed. By comparing satellite observations of Arctic sea ice concentrations to methane emissions simulated by three process-based biogeochemical models, this study shows that rising wetland methane emissions are associated with sea ice retreat. Our analyses indicate that simulated high-latitude emissions for 2005-2010 were, on average, 1.7 Tgmore » CH4 yr(-1) higher compared to 1981-1990 due to a sea ice-induced, autumn-focused, warming. Since these results suggest a continued rise in methane emissions with future sea ice decline, observation programs need to include measurements during the autumn to further investigate the impact of this spatial connection on terrestrial methane emissions.« less

Rising methane emissions from northern wetlands associated with sea ice decline

USGS Publications Warehouse

Parmentier, Frans-Jan W.; Zhang, Wenxin; Zhu, Xudong; van Huissteden, Jacobus; Hayes, Daniel J.; Zhuang, Qianlai; Christensen, Torben R.; McGuire, A. David

2015-01-01

The Arctic is rapidly transitioning toward a seasonal sea ice-free state, perhaps one of the most apparent examples of climate change in the world. This dramatic change has numerous consequences, including a large increase in air temperatures, which in turn may affect terrestrial methane emissions. Nonetheless, terrestrial and marine environments are seldom jointly analyzed. By comparing satellite observations of Arctic sea ice concentrations to methane emissions simulated by three process-based biogeochemical models, this study shows that rising wetland methane emissions are associated with sea ice retreat. Our analyses indicate that simulated high-latitude emissions for 2005–2010 were, on average, 1.7 Tg CH4 yr−1 higher compared to 1981–1990 due to a sea ice-induced, autumn-focused, warming. Since these results suggest a continued rise in methane emissions with future sea ice decline, observation programs need to include measurements during the autumn to further investigate the impact of this spatial connection on terrestrial methane emissions.

Rising methane emissions from northern wetlands associated with sea ice decline

PubMed Central

Zhang, Wenxin; Mi, Yanjiao; Zhu, Xudong; van Huissteden, Jacobus; Hayes, Daniel J.; Zhuang, Qianlai; Christensen, Torben R.; McGuire, A. David

2015-01-01

Abstract The Arctic is rapidly transitioning toward a seasonal sea ice‐free state, perhaps one of the most apparent examples of climate change in the world. This dramatic change has numerous consequences, including a large increase in air temperatures, which in turn may affect terrestrial methane emissions. Nonetheless, terrestrial and marine environments are seldom jointly analyzed. By comparing satellite observations of Arctic sea ice concentrations to methane emissions simulated by three process‐based biogeochemical models, this study shows that rising wetland methane emissions are associated with sea ice retreat. Our analyses indicate that simulated high‐latitude emissions for 2005–2010 were, on average, 1.7 Tg CH4 yr−1 higher compared to 1981–1990 due to a sea ice‐induced, autumn‐focused, warming. Since these results suggest a continued rise in methane emissions with future sea ice decline, observation programs need to include measurements during the autumn to further investigate the impact of this spatial connection on terrestrial methane emissions. PMID:27667870

A Novel Airborne Carbon Isotope Analyzer for Methane and Carbon Dioxide Source Fingerprinting

NASA Astrophysics Data System (ADS)

Berman, E. S.; Huang, Y. W.; Owano, T. G.; Leifer, I.

2014-12-01

Recent field studies on major sources of the important greenhouse gas methane (CH4) indicate significant underestimation of methane release from fossil fuel industrial (FFI) and animal husbandry sources, among others. In addition, uncertainties still exist with respect to carbon dioxide (CO2) measurements, especially source fingerprinting. CO2 isotopic analysis provides a valuable in situ measurement approach to fingerprint CH4 and CO2as associated with combustion sources, leakage from geologic reservoirs, or biogenic sources. As a result, these measurements can characterize strong combustion source plumes, such as power plant emissions, and discriminate these emissions from other sources. As part of the COMEX (CO2 and MEthane eXperiment) campaign, a novel CO2 isotopic analyzer was installed and collected data aboard the CIRPAS Twin Otter aircraft. Developing methods to derive CH4 and CO2 budgets from remote sensing data is the goal of the summer 2014 COMEX campaign, which combines hyperspectral imaging (HSI) and non-imaging spectroscopy (NIS) with in situ airborne and surface data. COMEX leverages the synergy between high spatial resolution HSI and moderate spatial resolution NIS. The carbon dioxide isotope analyzer developed by Los Gatos Research (LGR) uses LGR's patented Off-Axis ICOS (Integrated Cavity Output Spectroscopy) technology and incorporates proprietary internal thermal control for high sensitivity and optimal instrument stability. This analyzer measures CO2 concentration as well as δ13C, δ18O, and δ17O from CO2 at natural abundance (100-3000 ppm). The laboratory accuracy is ±1.2 ppm (1σ) in CO2 from 370-1000 ppm, with a long-term (1000 s) precision of ±0.012 ppm. The long-term precision for both δ13C and δ18O is 0.04 ‰, and for δ17O is 0.06 ‰. The analyzer was field-tested as part of the COWGAS campaign, a pre-cursor campaign to COMEX in March 2014, where it successfully discriminated plumes related to combustion processes associated with dairy activities (tractor exhaust) from plumes and sources in air enriched in methane and ammonia from bovine activities including waste maintenance. Methodology, laboratory data, field data from COWGAS, and field data from the COMEX campaign acquired by LGR's carbon isotope analyzer as well as other COMEX analyzers are presented.

Biogeochemical Carbon Cycling in Ultrabasic Reducing Springs in Sonoma County, CA

NASA Astrophysics Data System (ADS)

Cotton, J. M.; Morrill, P.; Johnson, O.; Nealson, K. H.; Sherwood Lollar, B.; Eigenbrode, J.; Fogel, M.

2006-12-01

Dissolved gases in the ultrabasic spring waters from The Cedars in Sonoma County, CA were analyzed for concentrations and carbon and hydrogen isotopic ratios in order to determine the geobiological processes occurring in this extreme environment of unknown biological activity. The ultrabasic, highly reducing conditions unique to these springs result from local serpentinization. Gases bubbling from the springs are mainly composed of methane, hydrogen, and nitrogen. Serpentinization is a process characteristic of early Earth, Mars and Titan that is thought to produce abiogenic hydrocarbons as well as provide geochemical energy for chemolithotrophic life. Methane, CO2, hydrogen and nitrogen were detected in the aqueous phases. Earlier work indicated that the primary source of the methane in the free gases bubbling from the springs was associated with microbial fermentation a suspected source of the dissolved methane. Here we report, a negative, linear correlation between concentrations of CO2 and methane that is an indicator of microbial anaerobic methane oxidation taking place in the ultrabasic waters. Furthermore, as the concentrations of methane decrease, the concentration of CO2 increases and both reactant and product become 13C-enriched. These observations are consistent with microbial oxidation of methane, suggesting a biogeochemical carbon cycle exists in these springs. We hypothesize that one group of microbes is breaking down organic matter by a process of fermentation to produce methane and CO2. The CO2 dissolves in the basic springs, while most of the methane escapes solution. The residual dissolved methane undergoes a conversion to CO2 by anaerobic methane oxidation.

X-ray Fluorescence Measurements of Turbulent Methane-Oxygen Shear Coaxial Flames (Briefing Charts)

DTIC Science & Technology

2015-03-01

Radiography- Radial EPL Profiles • Near-injector EPL profiles have elliptical shape expected from a solid liquid jet • Closest measurements were...turbulent flames relevant to liquid rocket engines – Explore the use of two different tracers, Argon & Krypton – Identify a path forward to apply these...made 0.02 mm downstream • EPL decreases axially as liquid core is atomized and droplets are accelerated – EPL is a function of local mass flux

Reactions of O/1D/ with methane and ethane.

NASA Technical Reports Server (NTRS)

Lin, C.-L.; Demore, W. B.

1973-01-01

Mixtures of nitrous oxide and methane and mixtures of nitrous oxide and ethane were photolyzed with 1849-A light. The reaction products were analyzed chromatographically. It was found that the reaction of the excited atomic oxygen with methane gives mainly CH3 and OH radicals as initial products, along with about 9% of formaldehyde and molecular hydrogen. The reaction of the excited atomic oxygen with ethane gives C2H5, OH, CH3 and CH2OH as major initial products, with only a few per cent of molecular hydrogen.

FIELD EVALUATION OF A METHOD FOR ESTIMATING GASEOUS FLUXES FROM AREA SOURCES USING OPEN-PATH FTIR

EPA Science Inventory

The paper gives preliminary results from a field evaluation of a new approach for quantifying gaseous fugitive emissions of area air pollution sources. The approach combines path-integrated concentration data acquired with any path-integrated optical remote sensing (PI-ORS) ...

FIELD EVALUATION OF A METHOD FOR ESTIMATING GASEOUS FLUXES FROM AREA SOURCES USING OPEN-PATH FOURIER TRANSFORM INFRARED

EPA Science Inventory

The paper describes preliminary results from a field experiment designed to evaluate a new approach to quantifying gaseous fugitive emissions from area air pollution sources. The new approach combines path-integrated concentration data acquired with any path-integrated optical re...

Dry (CO2) reforming of methane over Pt catalysts studied by DFT and kinetic modeling

NASA Astrophysics Data System (ADS)

Niu, Juntian; Du, Xuesen; Ran, Jingyu; Wang, Ruirui

2016-07-01

Dry reforming of methane (DRM) is a well-studied reaction that is of both scientific and industrial importance. In order to design catalysts that minimize the deactivation and improve the selectivity and activity for a high H2/CO yield, it is necessary to understand the elementary reaction steps involved in activation and conversion of CO2 and CH4. In our present work, a microkinetic model based on density functional theory (DFT) calculations is applied to explore the reaction mechanism for methane dry reforming on Pt catalysts. The adsorption energies of the reactants, intermediates and products, and the activation barriers for the elementary reactions involved in the DRM process are calculated over the Pt(1 1 1) surface. In the process of CH4 direct dissociation, the kinetic results show that CH dissociative adsorption on Pt(1 1 1) surface is the rate-determining step. CH appears to be the most abundant species on the Pt(1 1 1) surface, suggesting that carbon deposition is not easy to form in CH4 dehydrogenation on Pt(1 1 1) surface. In the process of CO2 activation, three possible reaction pathways are considered to contribute to the CO2 decomposition: (I) CO2* + * → CO* + O*; (II) CO2* + H* → COOH* + * → CO* + OH*; (III) CO2* + H* → mono-HCOO* + * → bi-HCOO* + * [CO2* + H* → bi-HCOO* + *] → CHO* + O*. Path I requires process to overcome the activation barrier of 1.809 eV and the forward reaction is calculated to be strongly endothermic by 1.430 eV. In addition, the kinetic results also indicate this process is not easy to proceed on Pt(1 1 1) surface. While the CO2 activation by H adsorbed over the catalyst surface to form COOH intermediate (Path II) is much easier to be carried out with the lower activation barrier of 0.746 eV. The Csbnd O bond scission is the rate-determining step along this pathway and the process needs to overcome the activation barrier of 1.522 eV. Path III reveals the CO2 activation through H adsorbed over the catalyst surface to form HCOO intermediate firstly. This reaction requires a quite high activation barrier and is a strongly endothermic process leading to a very low forward rate constant. In conclusion, Path II is the dominant reaction pathway in CO2 activation. Additionally, there are two pathways of CH oxidation by O: (A) CH* + O* → CHO* + * → CO* + H*; (B) CH* + O* → COH* + * → CO* + H*. Both the activation barriers and kinetic results demonstrate that Path A is the prior reaction pathway. Furthermore, in the two pathways of CH oxidation by OH: (C) CH* + OH* → CHOH* + * → CHO* + H*; (D) CH* + OH* → CHOH* + * → COH* + H*. Path C is easier to proceed. In conclusion, the main reaction pathway in CH oxidation according to the mechanism: CH* + OH* → CHOH* + * → CHO* + H* → CO* + 2H*. These results could provide some useful information for the operation of DRM over Pt catalysts, and are helpful to understand the mechanisms of DRM from the atomic scale.

A low-volume cavity ring-down spectrometer for sample-limited applications

NASA Astrophysics Data System (ADS)

Stowasser, C.; Farinas, A. D.; Ware, J.; Wistisen, D. W.; Rella, C.; Wahl, E.; Crosson, E.; Blunier, T.

2014-08-01

In atmospheric and environmental sciences, optical spectrometers are used for the measurements of greenhouse gas mole fractions and the isotopic composition of water vapor or greenhouse gases. The large sample cell volumes (tens of milliliters to several liters) in commercially available spectrometers constrain the usefulness of such instruments for applications that are limited in sample size and/or need to track fast variations in the sample stream. In an effort to make spectrometers more suitable for sample-limited applications, we developed a low-volume analyzer capable of measuring mole fractions of methane and carbon monoxide based on a commercial cavity ring-down spectrometer. The instrument has a small sample cell (9.6 ml) and can selectively be operated at a sample cell pressure of 140, 45, or 20 Torr (effective internal volume of 1.8, 0.57, and 0.25 ml). We present the new sample cell design and the flow path configuration, which are optimized for small sample sizes. To quantify the spectrometer's usefulness for sample-limited applications, we determine the renewal rate of sample molecules within the low-volume spectrometer. Furthermore, we show that the performance of the low-volume spectrometer matches the performance of the standard commercial analyzers by investigating linearity, precision, and instrumental drift.

Seasonal and Latitudinal Variations in Dissolved Methane from 42 Lakes along a North-South Transect in Alaska

NASA Astrophysics Data System (ADS)

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

2013-12-01

Armando Sepulveda-Jauregui,* Katey M. Walter Anthony,* Karla Martinez-Cruz,* ** 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. Northern lakes are important reservoirs and sources to the atmosphere of methane (CH4), a potent greenhouse gas. It is estimated that northern lakes (> 55 °N) contribute about 20% of the total global lake methane emissions, and that emissions from these lakes will increase with climate warming. Temperature rise enhances methane production directly by providing the kinetic energy to methanogenesis, and indirectly by supplying organic matter from thawing permafrost. Warmer lakes also store less methane since methane's solubility is inversely related to temperature. Alaskan lakes are located in three well-differentiated permafrost classes: yedoma permafrost with high labile carbon stocks, non-yedoma permafrost with lower carbon stocks, and areas without permafrost, also with generally lower carbon stocks. We sampled dissolved methane from 42 Alaskan lakes located in these permafrost cover classes along a north-south Alaska transect from Prudhoe Bay to the Kenai Peninsula during open-water conditions in summer 2011. We sampled 26 of these lakes in April, toward the end of the winter ice-covered period. Our results indicated that the largest dissolved methane concentrations occurred in interior Alaska thermokarst lakes formed in yedoma-type permafrost during winter and summer, with maximal concentrations of 17.19 and 12.76 mg L-1 respectively. In these lakes, emission of dissolved gases as diffusion during summer and storage release in spring were 18.4% and 17.4% of the annual emission budget, while ebullition (64.2 %) comprised the rest. Dissolved oxygen was inversely correlated with dissolved methane concentrations in both seasons; the absence of O2 enhances methane production, while high concentration of O2 could favor methane oxidation. These relationships suggest that permafrost type, and specifically the availability of permafrost organic matter, influences methane cycling in Alaskan lakes.

The phase transition of methane caused by pressure change during its seeping up from seepage, revealed by video observation and acoustic reflection data

NASA Astrophysics Data System (ADS)

Aoyama, C.

2017-12-01

Methane plumes often exist in the vicinity sea area where shallow type methane hydrates are extracted and they are observed as images displayed on monitors of multi-beam sonar and echo sounder onboard, where methane hydrates are expected at sea bottom on ROV observation data. The hydrates are generally considered to be generated in shallow depths below the sea floor. In this study, author examined annual amount of methane dissolving into seawater by measuring the amount of plume in order to make a quantification of dissolving methane from seafloor. Measurement procedure is plume exploration using multi-beam and quantitative echo sounder , submerge ROV to gushing point at seafloor , calculate the rising speed of methane plumes and examine the phases by monitoring seeping plumes from seafloor with high-definition camera. Components of seeping plumes were defined as methane hydrate particles based on the result by measuring water temperature. From this procedure, it can be concluded that the minimum rising speed of methane hydrate particles from gushing point is 1.6×10-1(m/s) and the maximum of 2.0×10-1(m/s) indicating a difference of more than ten times the gaseous theoretical value of 2.74(m/s). This speed is theoretically closer to the solid speed of the material with physical property similar to hydrates, which is 3.05×10-1 (m/s). Therefore, it can be determined that those particles are in the solid state, immediately above seafloor. To measure the amount of plumes seeping from gushing points funnel-shaped instruments with 20cm diameter opening were used to collect methane plumes in this sea area. This was performed in three different gushing points. As a result, 300ml of methane plume was collected in 643 seconds. Assuming that gushing points exist evenly in the sea area, the annual amount of methane gas seeping from these points will be 7.7×105m3 /per m2. Result shows a large quantity of methane seeping from seafloor into the water. This data is an important factor when considering carbon cycle and future development the shallow methane hydrate resources.

Open Quantum Random Walks on the Half-Line: The Karlin-McGregor Formula, Path Counting and Foster's Theorem

NASA Astrophysics Data System (ADS)

Jacq, Thomas S.; Lardizabal, Carlos F.

2017-11-01

In this work we consider open quantum random walks on the non-negative integers. By considering orthogonal matrix polynomials we are able to describe transition probability expressions for classes of walks via a matrix version of the Karlin-McGregor formula. We focus on absorbing boundary conditions and, for simpler classes of examples, we consider path counting and the corresponding combinatorial tools. A non-commutative version of the gambler's ruin is studied by obtaining the probability of reaching a certain fortune and the mean time to reach a fortune or ruin in terms of generating functions. In the case of the Hadamard coin, a counting technique for boundary restricted paths in a lattice is also presented. We discuss an open quantum version of Foster's Theorem for the expected return time together with applications.

Remote sensing measurements of atmospheric methane at 2.3 microns with a nonmechanical GFCR

NASA Technical Reports Server (NTRS)

Wang, Liang-guo; Sachse, Glen; Wallio, Andrew; LeBel, Peter; Vay, Stephanie

1995-01-01

Gas filter correlation radiometer (GFCR) is a passive remote sensing technique used in a variety of atmospheric measurements. In recent years, a nonmechanical optical switching GFCR has been invented and developed at NASA Langley Research Center. The use of a polarization modulator, in conjunction with a polarization beamsplitter, enables rapid optical switching without mechanically moving parts. In comparison with the conventional GFCR, which involves mechanical chopping or switching between two optical paths, the nonmechanical GFCR possesses some very attractive advantages such as fast sampling rate, high reliability, low weight, and long operational life time. In a recent study, we have developed a new GFCR configuration and have fabricated a compact, nonmechanical breadboard instrument. Using this instrument, we have carried out atmospheric methane measurements in the 2.3 micron region. Measurement results are compared with theoretical predictions using the HITRAN database.

Phosphoketolase overexpression increases biomass and lipid yield from methane in an obligate methanotrophic biocatalyst

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

Henard, Calvin A.; Smith, Holly K.; Guarnieri, Michael T.

Microbial conversion of methane to high-value bio-based chemicals and materials offers a path to mitigate GHG emissions and valorize this abundant-yet -underutilized carbon source. In addition to fermentation optimization strategies, rational methanotrophic bacterial strain engineering offers a means to reach industrially relevant titers, carbon yields, and productivities of target products. The phosphoketolase pathway functions in heterofermentative bacteria where carbon flux through two sugar catabolic pathways to mixed acids (lactic acid and acetic acid) increases cellular ATP production. Importantly, this pathway also serves as an alternative route to produce acetyl-CoA that bypasses the CO 2 lost through pyruvate decarboxylation in themore » Embden-Meyerhof-Parnas pathway. Thus, the phosphoketolase pathway can be leveraged for carbon efficient biocatalysis to acetyl-CoA-derived intermediates and products. Here, we show that the industrially promising methane biocatalyst, Methylomicrobium buryatense, encodes two phosphoketolase isoforms that are expressed in methanol- and methane-grown cells. Overexpression of the PktB isoform led to a 2-fold increase in intracellular acetyl-CoA concentration, and a 2.6-fold yield enhancement from methane to microbial biomass and lipids compared to wild-type, increasing the potential for methanotroph lipid-based fuel production. Off-gas analysis and metabolite profiling indicated that global metabolic rearrangements, including significant increases in post-translational protein acetylation and gene expression of the tetrahydromethanopterin-linked pathway, along with decreases in several excreted products, coincided with the superior biomass and lipid yield observed in the engineered strain. Further, these data suggest that phosphoketolase may play a key regulatory role in methanotrophic bacterial metabolism. As a result, given that acetyl-CoA is a key intermediate in several biosynthetic pathways, phosphoketolase overexpression offers a viable strategy to enhance the economics of an array of biological methane conversion processes.« less

Phosphoketolase overexpression increases biomass and lipid yield from methane in an obligate methanotrophic biocatalyst.

PubMed

Henard, Calvin A; Smith, Holly K; Guarnieri, Michael T

2017-05-01

Microbial conversion of methane to high-value bio-based fuels, chemicals, and materials offers a path to mitigate GHG emissions and valorize this abundant-yet -underutilized carbon source. In addition to fermentation optimization strategies, rational methanotrophic bacterial strain engineering offers a means to reach industrially relevant titers, carbon yields, and productivities of target products. The phosphoketolase pathway functions in heterofermentative bacteria where carbon flux through two sugar catabolic pathways to mixed acids (lactic acid and acetic acid) increases cellular ATP production. Importantly, this pathway also serves as an alternative route to produce acetyl-CoA that bypasses the CO 2 lost through pyruvate decarboxylation in the Embden-Meyerhof-Parnas pathway. Thus, the phosphoketolase pathway can be leveraged for carbon efficient biocatalysis to acetyl-CoA-derived intermediates and products. Here, we show that the industrially promising methane biocatalyst, Methylomicrobium buryatense, encodes two phosphoketolase isoforms that are expressed in methanol- and methane-grown cells. Overexpression of the PktB isoform led to a 2-fold increase in intracellular acetyl-CoA concentration, and a 2.6-fold yield enhancement from methane to microbial biomass and lipids compared to wild-type, increasing the potential for methanotroph lipid-based fuel production. Off-gas analysis and metabolite profiling indicated that global metabolic rearrangements, including significant increases in post-translational protein acetylation and gene expression of the tetrahydromethanopterin-linked pathway, along with decreases in several excreted products, coincided with the superior biomass and lipid yield observed in the engineered strain. Further, these data suggest that phosphoketolase may play a key regulatory role in methanotrophic bacterial metabolism. Given that acetyl-CoA is a key intermediate in several biosynthetic pathways, phosphoketolase overexpression offers a viable strategy to enhance the economics of an array of biological methane conversion processes. Copyright © 2017. Published by Elsevier Inc.

Phosphoketolase overexpression increases biomass and lipid yield from methane in an obligate methanotrophic biocatalyst

DOE PAGES

Henard, Calvin A.; Smith, Holly K.; Guarnieri, Michael T.

2017-04-02

Microbial conversion of methane to high-value bio-based chemicals and materials offers a path to mitigate GHG emissions and valorize this abundant-yet -underutilized carbon source. In addition to fermentation optimization strategies, rational methanotrophic bacterial strain engineering offers a means to reach industrially relevant titers, carbon yields, and productivities of target products. The phosphoketolase pathway functions in heterofermentative bacteria where carbon flux through two sugar catabolic pathways to mixed acids (lactic acid and acetic acid) increases cellular ATP production. Importantly, this pathway also serves as an alternative route to produce acetyl-CoA that bypasses the CO 2 lost through pyruvate decarboxylation in themore » Embden-Meyerhof-Parnas pathway. Thus, the phosphoketolase pathway can be leveraged for carbon efficient biocatalysis to acetyl-CoA-derived intermediates and products. Here, we show that the industrially promising methane biocatalyst, Methylomicrobium buryatense, encodes two phosphoketolase isoforms that are expressed in methanol- and methane-grown cells. Overexpression of the PktB isoform led to a 2-fold increase in intracellular acetyl-CoA concentration, and a 2.6-fold yield enhancement from methane to microbial biomass and lipids compared to wild-type, increasing the potential for methanotroph lipid-based fuel production. Off-gas analysis and metabolite profiling indicated that global metabolic rearrangements, including significant increases in post-translational protein acetylation and gene expression of the tetrahydromethanopterin-linked pathway, along with decreases in several excreted products, coincided with the superior biomass and lipid yield observed in the engineered strain. Further, these data suggest that phosphoketolase may play a key regulatory role in methanotrophic bacterial metabolism. As a result, given that acetyl-CoA is a key intermediate in several biosynthetic pathways, phosphoketolase overexpression offers a viable strategy to enhance the economics of an array of biological methane conversion processes.« less

Fugitive greenhouse gas emissions from shale gas activities - a case study of Dish, TX

NASA Astrophysics Data System (ADS)

Khan, A.; Roscoe, B.; Lary, D.; Schaefer, D.; Tao, L.; Sun, K.; Brian, A.; DiGangi, J.; Miller, D. J.; Zondlo, M. A.

2012-12-01

We evaluate new findings on aerial (horizontal and vertical) mapping of methane emissions in the atmospheric boundary layer region to help study fugitive methane emissions from extraction, transmission, and storage of natural gas and oil in Dish, Texas. Dish is located in the Barnett Shale which has seen explosive development of hydraulic fracking activities in recent years. The aerial measurements were performed with a new laser-based methane sensor developed specifically for an unmanned aerial vehicle (UAV). The vertical cavity surface emitting laser (VCSEL) methane sensor, with a mass of 2.5 kg and a precision of < 20 ppbv methane at 1 Hz, was flown on the UT-Dallas ARC Payload Master electronic aircraft at two sites in Texas: one representative of urban emissions of the Dallas-Fort Worth area in Richardson, Texas and another in Dish, Texas, closer to gas and oil activities. Methane mixing ratios at Dish were ubiquitously in the 3.5 - 4 ppmv range which was 1.5 - 2 ppmv higher than methane levels immediately downwind of Dallas. During the flight measurements at Dish, narrow methane plumes exceeding 20 ppmv were frequently observed at altitudes from the surface to 130 m above the ground. Based on the wind speed at the sampling location, the horizontal widths of large methane plumes were of the order of 100 m. The locations of the large methane plumes were variable in space and time over a ~ 1 km2 area sampled from the UAV. Spatial mapping over larger scales (10 km) by ground-based measurements showed similar methane levels as the UAV measurements. To corroborate our measurements, alkane and other hydrocarbon mixing ratios from an on-site TCEQ environmental monitoring station were analyzed and correlated with methane measurements to fingerprint the methane source. We show that fugitive methane emissions at Dish are a significant cause of the large and ubiquitous methane levels on the 1-10 km scale.

Bats coordinate sonar and flight behavior as they forage in open and cluttered environments.

PubMed

Falk, Benjamin; Jakobsen, Lasse; Surlykke, Annemarie; Moss, Cynthia F

2014-12-15

Echolocating bats use active sensing as they emit sounds and listen to the returning echoes to probe their environment for navigation, obstacle avoidance and pursuit of prey. The sensing behavior of bats includes the planning of 3D spatial trajectory paths, which are guided by echo information. In this study, we examined the relationship between active sonar sampling and flight motor output as bats changed environments from open space to an artificial forest in a laboratory flight room. Using high-speed video and audio recordings, we reconstructed and analyzed 3D flight trajectories, sonar beam aim and acoustic sonar emission patterns as the bats captured prey. We found that big brown bats adjusted their sonar call structure, temporal patterning and flight speed in response to environmental change. The sonar beam aim of the bats predicted the flight turn rate in both the open room and the forest. However, the relationship between sonar beam aim and turn rate changed in the forest during the final stage of prey pursuit, during which the bat made shallower turns. We found flight stereotypy developed over multiple days in the forest, but did not find evidence for a reduction in active sonar sampling with experience. The temporal patterning of sonar sound groups was related to path planning around obstacles in the forest. Together, these results contribute to our understanding of how bats coordinate echolocation and flight behavior to represent and navigate their environment. © 2014. Published by The Company of Biologists Ltd.

Bats coordinate sonar and flight behavior as they forage in open and cluttered environments

PubMed Central

Falk, Benjamin; Jakobsen, Lasse; Surlykke, Annemarie; Moss, Cynthia F.

2014-01-01

Echolocating bats use active sensing as they emit sounds and listen to the returning echoes to probe their environment for navigation, obstacle avoidance and pursuit of prey. The sensing behavior of bats includes the planning of 3D spatial trajectory paths, which are guided by echo information. In this study, we examined the relationship between active sonar sampling and flight motor output as bats changed environments from open space to an artificial forest in a laboratory flight room. Using high-speed video and audio recordings, we reconstructed and analyzed 3D flight trajectories, sonar beam aim and acoustic sonar emission patterns as the bats captured prey. We found that big brown bats adjusted their sonar call structure, temporal patterning and flight speed in response to environmental change. The sonar beam aim of the bats predicted the flight turn rate in both the open room and the forest. However, the relationship between sonar beam aim and turn rate changed in the forest during the final stage of prey pursuit, during which the bat made shallower turns. We found flight stereotypy developed over multiple days in the forest, but did not find evidence for a reduction in active sonar sampling with experience. The temporal patterning of sonar sound groups was related to path planning around obstacles in the forest. Together, these results contribute to our understanding of how bats coordinate echolocation and flight behavior to represent and navigate their environment. PMID:25394632

Characteristics of molecular hydrogen and CH* radicals in a methane plasma in a magnetically enhanced capacitive RF discharge

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

Avtaeva, S. V.; Lapochkina, T. M.

2007-09-15

The parameters of a methane-containing plasma in an asymmetric RF capacitive discharge in an external magnetic field were studied using optical emission spectroscopy. The power deposited in the discharge was 90 W and the gas pressure and magnetic field were varied in the ranges 1-5 Pa and 50-200 G, respectively. The vibrational and rotational temperatures of hydrogen molecules and CH* radicals were measured as functions of the magnetic field and methane pressure. The ratio between the densities of atomic and molecular hydrogen was estimated. The processes responsible for the excitation of molecular hydrogen and CH* radicals in a methane-containing plasmamore » in an RF capacitive discharge are analyzed.« less

Expansion of Phragmites australis alters methane dynamics and methanogen, methanotroph, and sulfate reducing bacteria communities in tidal marsh in Korea

NASA Astrophysics Data System (ADS)

Kim, J.; Lee, J.; Kim, H.; Gauhar, M.; Kang, H.

2016-12-01

Plant invasion is known to change substantially methane dynamics in tidal marshes. However, the exact mechanisms related to methane dynamics change due to plant invasion have not been fully understood. In Suncheon Bay, South Korea, Phragmites australis has invaded the habitat of native species, Suaeda japonica, and becomes dominant vegetation in this area. We measured methane fluxes, soil biogeochemistry, and microbial communities from both vegetation sites throughout a growing season and conducted a chronosequence analysis in order to illustrate the effect of plant invasion on methane dynamics and microbial communities. For analyzing microbial communities, we collected 1m intact soil cores and conducted functional gene-targeted real-time qPCR, T-RFLP, and PLFA. P. australis invasion significantly increased methane emission in a summer season, accompanied by greater dissolved organic carbon and soil water content. Methanogen, methanotroph, and sulfate reducing bacterial communities were gradually changed along with the invasion periods. In particular, abundances ratio of mcrA/pmoA and mcrA/dsrA had a positive correlation with methane emission, which indicates that P. australis invasion reduces methane oxidation by methanotroph, and competitive inhibition between methanogen and sulfate reducing bacteria. In conclusion, P. australis invasion on S. japonica significantly increased methane emission in tidal marsh by altering the microbial communities in a way that C decomposition would be dominated by methanogenesis.

Quantification of Methane and VOC Emissions from Natural Gas Production in Two Basins with High Ozone Events

NASA Astrophysics Data System (ADS)

Edie, R.; Robertson, A.; Snare, D.; Soltis, J.; Field, R. A.; Murphy, S. M.

2015-12-01

Since 2005, the Uintah Basin of Utah and the Upper Green River Basin of Wyoming frequently exceeded the EPA 8-hour allowable ozone level of 75 ppb, spurring interest in volatile organic compounds (VOCs) emitted during oil and gas production. Debate continues over which stage of production (drilling, flowback, normal production, transmission, etc.) is the most prevalent VOC source. In this study, we quantify emissions from normal production on well pads by using the EPA-developed Other Test Method 33a. This methodology combines ground-based measurements of fugitive emissions with 3-D wind data to calculate the methane and VOC emission fluxes from a point source. VOC fluxes are traditionally estimated by gathering a canister of air during a methane flux measurement. The methane:VOC ratio of this canister is determined at a later time in the laboratory, and applied to the known methane flux. The University of Wyoming Mobile Laboratory platform is equipped with a Picarro methane analyzer and an Ionicon Proton Transfer Reaction-Time of Flight-Mass Spectrometer, which provide real-time methane and VOC data for each well pad. This independent measurement of methane and VOCs in situ reveals multiple emission sources on one well pad, with varying methane:VOC ratios. Well pad emission estimates of methane, benzene, toluene and xylene for the two basins will be presented. The different emission source VOC profiles and the limitations of real-time and traditional VOC measurement methods will also be discussed.

Carbon nanotubes accelerate methane production in pure cultures of methanogens and in a syntrophic coculture.

PubMed

Salvador, Andreia F; Martins, Gilberto; Melle-Franco, Manuel; Serpa, Ricardo; Stams, Alfons J M; Cavaleiro, Ana J; Pereira, M Alcina; Alves, M Madalena

2017-07-01

Carbon materials have been reported to facilitate direct interspecies electron transfer (DIET) between bacteria and methanogens improving methane production in anaerobic processes. In this work, the effect of increasing concentrations of carbon nanotubes (CNT) on the activity of pure cultures of methanogens and on typical fatty acid-degrading syntrophic methanogenic coculture was evaluated. CNT affected methane production by methanogenic cultures, although acceleration was higher for hydrogenotrophic methanogens than for acetoclastic methanogens or syntrophic coculture. Interestingly, the initial methane production rate (IMPR) by Methanobacterium formicicum cultures increased 17 times with 5 g·L -1 CNT. Butyrate conversion to methane by Syntrophomonas wolfei and Methanospirillum hungatei was enhanced (∼1.5 times) in the presence of CNT (5 g·L -1 ), but indications of DIET were not obtained. Increasing CNT concentrations resulted in more negative redox potentials in the anaerobic microcosms. Remarkably, without a reducing agent but in the presence of CNT, the IMPR was higher than in incubations with reducing agent. No growth was observed without reducing agent and without CNT. This finding is important to re-frame discussions and re-interpret data on the role of conductive materials as mediators of DIET in anaerobic communities. It also opens new challenges to improve methane production in engineered methanogenic processes. © 2017 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.

Chemical Evolution of Groundwater Near a Sinkhole Lake, Northern Florida: 2. Chemical Patterns, Mass Transfer Modeling, and Rates of Mass Transfer Reactions

NASA Astrophysics Data System (ADS)

Katz, Brian G.; Plummer, L. Niel; Busenberg, Eurybiades; Revesz, Kinga M.; Jones, Blair F.; Lee, Terrie M.

1995-06-01

Chemical patterns along evolutionary groundwater flow paths in silicate and carbonate aquifers were interpreted using solute tracers, carbon and sulfur isotopes, and mass balance reaction modeling for a complex hydrologic system involving groundwater inflow to and outflow from a sinkhole lake in northern Florida. Rates of dominant reactions along defined flow paths were estimated from modeled mass transfer and ages obtained from CFC-modeled recharge dates. Groundwater upgradient from Lake Barco remains oxic as it moves downward, reacting with silicate minerals in a system open to carbon dioxide (CO2), producing only small increases in dissolved species. Beneath and downgradient of Lake Barco the oxic groundwater mixes with lake water leakage in a highly reducing, silicate-carbonate mineral environment. A mixing model, developed for anoxic groundwater downgradient from the lake, accounted for the observed chemical and isotopic composition by combining different proportions of lake water leakage and infiltrating meteoric water. The evolution of major ion chemistry and the 13C isotopic composition of dissolved carbon species in groundwater downgradient from the lake can be explained by the aerobic oxidation of organic matter in the lake, anaerobic microbial oxidation of organic carbon, and incongruent dissolution of smectite minerals to kaolinite. The dominant process for the generation of methane was by the CO2 reduction pathway based on the isotopic composition of hydrogen (δ2H(CH4) = -186 to -234‰) and carbon (δ13C(CH4) = -65.7 to -72.3‰). Rates of microbial metabolism of organic matter, estimated from the mass transfer reaction models, ranged from 0.0047 to 0.039 mmol L-1 yr-1 for groundwater downgradient from the lake.

Modeling Modern Methane Emissions from Natural Wetlands. 2; Interannual Variations 1982-1993

NASA Technical Reports Server (NTRS)

Walter, Bernadette P.; Heimann, Martin; Mattews, Elaine; Hansen, James E. (Technical Monitor)

2001-01-01

A global run of a process-based methane model [Walter et al., this issue] is performed using high-frequency atmospheric forcing fields from ECMWF reanalyses of the period from 1982 to 1993. We calculate global annual methane emissions to be 260 Tg/ yr. 25% of methane emissions originate from wetlands north of 30 deg. N. Only 60% of the produced methane is emitted, while the rest is re-oxidized. A comparison of zonal integrals of simulated global wetland emissions and results obtained by an inverse modeling approach shows good agreement. In a test with data from two wetlands, the seasonality of simulated and observed methane emissions agrees well. The effects of sub-grid scale variations in model parameters and input data are examined. Modeled methane emissions show high regional, seasonal and interannual variability. Seasonal cycles of methane emissions are dominated by temperature in high latitude wetlands, and by changes in the water table in tropical wetlands. Sensitivity tests show that +/- 1 C changes in temperature lead to +/- 20 % changes in methane emissions from wetlands. Uniform changes of +/- 20% in precipitation alter methane emissions by about +/- 18%. Limitations in the model are analyzed. Simulated interannual variations in methane emissions from wetlands are compared to observed atmospheric growth rate anomalies. Our model simulation results suggest that contributions from other sources than wetlands and/or the sinks are more important in the tropics than north-of 30 deg. N. In higher northern latitudes, it seems that a large part, of the observed interannual variations can be explained by variations in wetland emissions. Our results also suggest that reduced wetland emissions played an important role in the observed negative methane growth rate anomaly in 1992.

Effect of methane partial pressure on the performance of a membrane biofilm reactor coupling methane-dependent denitrification and anammox.

PubMed

Cai, Chen; Hu, Shihu; Chen, Xueming; Ni, Bing-Jie; Pu, Jiaoyang; Yuan, Zhiguo

2018-10-15

Complete nitrogen removal has recently been demonstrated by integrating anaerobic ammonium oxidation (anammox) and denitrifying anaerobic methane oxidation (DAMO) processes. In this work, the effect of methane partial pressure on the performance of a membrane biofilm reactor (MBfR) consisting of DAMO and anammox microorganisms was evaluated. The activities of DAMO archaea and DAMO bacteria in the biofilm increased significantly with increased methane partial pressure, from 367 ± 9 and 58 ± 22 mg-N L -1 d -1 to 580 ± 12 and 222 ± 22 mg-N L -1 d -1 , respectively, while the activity of anammox bacteria only increased slightly, when the methane partial pressure was elevated from 0.24 to 1.39 atm in the short-term batch tests. The results were supported by a long-term (seven weeks) continuous test, when the methane partial pressure was dropped from 1.39 to 0.78 atm. The methane utilization efficiency was always above 96% during both short-term and long-term tests. Taken together, nitrogen removal rate (especially the nitrate reduction rate by DAMO archaea) and methane utilization efficiency could be maintained at high levels in a broad range of methane partial pressure (0.24-1.39 atm in this study). In addition, a previously established DAMO/anammox biofilm model was used to analyze the experimental data. The observed impacts of methane partial pressure on biofilm activity were well explained by the modeling results. These results suggest that methane partial pressure can potentially be used as a manipulated variable to control reaction rates, ultimately to maintain high nitrogen removal efficiency, according to nitrogen loading rate. Copyright © 2018 Elsevier B.V. All rights reserved.

Microbial communities in methane seep sediments along US Atlantic Margin are structured by organic matter and seepage dynamics

NASA Astrophysics Data System (ADS)

Graw, M. F.; Pohlman, J.; Treude, T.; Ruppel, C. D.; Colwell, F. S.

2016-12-01

Methane seeps are dynamic environments on continental margins where subsurface methane reaches the ocean. Microbial communities play a critical role in carbon cycling within seep sediments via organic carbon degradation, methane production, and anaerobic oxidation of methane (AOM), which consumes 20-80% of methane in seep sediments. However, biogeochemical controls on microbial community structure at seeps on a margin-wide scale remain unclear. The passive US Atlantic Margin (USAM) has been identified as a region of active methane seepage. Passive margin seeps have traditionally been understudied relative to seeps on active margins. Passive margins exhibit large cross-margin variability in organic carbon deposition and are anticipated to have divergent seep dynamics from active margins. Thus, the USAM offers a unique opportunity to investigate controls on microbial communities in seep sediments. We undertook analysis of microbial communities inhabiting seep sediments at 6 biogeochemically distinct sites along the USAM. Microbiological samples were co-located with measurements of sediment geochemistry and AOM and sulfate reduction rates. Illumina sequencing of the 16S rRNA gene, using both universal (83 samples) and archaeal-specific (64 samples) primers, and the mcrA gene (18 samples) identified 44 bacterial phyla and 7 archaeal phyla. Seeps in canyons and on open slope, likely representing high and low organic content sediments, hosted distinct communities; the former was dominated by ammonia-oxidizing Marine Group I Thaumarchaeota and the latter by mixotrophic Hadesarchaeota. Seep stability also impacted microbial community structure, and in particular the establishment of an AOM community rather than a Bathyarchaeota-dominated community. These findings contribute to understanding how microbial communities are structured within methane seep sediments and pave the way for investigating broad differences in carbon cycling between seeps on passive and active margins.

Electrical properties of methane hydrate + sediment mixtures

USGS Publications Warehouse

Du Frane, Wyatt L.; Stern, Laura A.; Constable, Steven; Weitemeyer, Karen A.; Smith, Megan M; Roberts, Jeffery J.

2015-01-01

Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. Toward this goal, we built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EM field surveys. Here we report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. These results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.

Methane emission from Minnesota peatlands: Spatial and seasonal variability

NASA Astrophysics Data System (ADS)

Dise, Nancy. B.

1993-03-01

The variability of methane flux with season, year, and habitat type was investigated in northern Minnesota peatlands from September 1988 through September 1990. Average daily fluxes calculated by integration of annual data for an open poor fen, an open bog, a forested bog hollow, a fen lagg in the forested bog and a forested bog hummock were 180,118, 38, 35, and 10 mg CH4 m-2 d-1, respectively. Fluxes among the five ecosystems were significantly different from one another, although emission from all sites was highest in July and lowest in March. Winter fluxes occurred in all sites but the fen lagg. There was no difference in fluxes measured from the same sites in the spring of 1986, 1989, or 1990, but summer fluxes were significantly higher in the wetter year of 1989 than in 1990, and a summer pulse in methane emission occurred in 1989 that was not seen the next year. Concentrations of methane in pore water, reflecting the seasonal balance of production, oxidation, and release, declined during the month of peak flux, then increased to levels of about 500 μM in December. Consistent spatial and temporal differences in flux could be ascribed to differences in water table, temperature, and peat nutrient status, although additional variability remained. Integration gave an annual average flux of 20 g CH4, m-2 ot; for the three bog ecosystems and 39 g CH4, m-2 for the two fen ecosystems. This gives an estimate of 1-2 Tg CH4, yr-1 from peatlands in the Great Lake states of Minnesota, Wisconsin, and Michigan.

Effect of magnetite powder on anaerobic co-digestion of pig manure and wheat straw.

PubMed

Wang, Yanzi; Ren, Guangxin; Zhang, Tong; Zou, Shuzhen; Mao, Chunlan; Wang, Xiaojiao

2017-08-01

This study investigated the effects of different amounts of magnetite powder (i.e., 0g, 1.5g, 3g, 4.5g, 6g) on the anaerobic co-digestion of pig manure (PM) and wheat straw (WS). The variations in pH, alkalinity, cellulase activity (CEA), dehydrogenase activity (DHA) and methane production, were analyzed by phases. Correlation of the activities of the two enzymes with methane production was also analyzed, and the Gompertz model was used to evaluate the efficiency of anaerobic digestion (AD) with the addition of magnetite powder. The results showed that magnetite powder had significant effects on the anaerobic co-digestion of PM and WS. The maximum total methane production with the addition of 3g of magnetite powder was 195mL/g total solids (TS), an increase of 72.1%. The CEA and DHA increased with magnetite powder in the ranges of 1.5-4.5g, 1.5-6g, respectively, while the methane production showed a better correlation with DHA than with CEA. Using the Gompertz model, the efficiency of AD was optimal when adding 3g magnetite powder, with higher methane production potential (206mL/g TS), shorter lag-phase time (14.9d) and shorter AD period (44d). Copyright © 2017 Elsevier Ltd. All rights reserved.

Shallow borehole array for measuring fluxes of reduced trace gases in Greenland as an analogue for volatile emission on Mars

NASA Astrophysics Data System (ADS)

Pratt, L. M.

2011-12-01

Planetary exploration of Mars is rapidly advancing with high-resolution data from orbiting and landed instruments upending the image of a monotonously arid red planet and raising interest in the search for evidence of past or present Martian life. The plausibility of biotic influences on release and sequestration of water and other volatile molecules on Mars remains a highly contentious topic. Despite this uncertainty, treating volatile emissions as potential atmospheric biomarkers is prudent for planetary protection and is critical for refinement of exploration strategies aimed at life detection on Mars. Using deeply eroded Paleoproterozoic bedrock in southwestern Greenland as an analogue for Mars, a team of scientists from Indiana University, Princeton University, Goddard Space Flight Center, the Jet Propulsion Laboratory, and Honey Bee Robotics is participating in a three-year field campaign to analyze seasonal and diurnal variation in concentration and isotopic composition of methane, ethane, and hydrogen sulfide in bedrock boreholes (0.5 to 2 m depth) and soil pipe wells (1 to 1.5 m depth) intersecting permafrost environments across a study site of about 1 km2. Open-path laser spectroscopy (OPLS) will be used from a fixed platform coupled to a roving reflector in order to map out gas emissions from a variety of bedrock and vegetated terrains in periglacial settings. OPLS mapping will be used to target sites for seasonal and diurnal monitoring surface fluxes of reduced gases. Bedrock boreholes will be drilled percussively and soil pipe-wells will be inserted by hand. Each borehole or well will have one fiber optic line and two capillary lines installed by hand through an inert screw-compression seal. The capillary lines will be used to transfer gas into detection instruments at the surface and the fiber optic line will allow transfer of data from temperature and pressure sensors to data loggers. The field campaign will culminate with an integrated drill-packer-optic-capillary system as a technology demonstration of semi-autonomous drilling for planetary exploration. Carbon and hydrogen isotopic compositions for methane and ethane will be determined in the field using Integrated Cavity Output Spectroscopy and Cavity Ring Down Spectroscopy. Continuous permafrost is present at the study site down to 300 m depth with temperatures dropping to -3 degrees C at a depth of about 4 meters, providing a relatively shallow and pristine setting for an instrumented study of reduced trace gases in soil, fractured bedrock, and groundwater constituting the active layer.

Effects of gas reservoir configuration and pore radius on shale gas nanoflow: A molecular dynamics study.

PubMed

Tian, Huiquan; Guo, Guang-Jun; Geng, Ming; Zhang, Zhengcai; Zhang, Mingmin; Gao, Kai

2018-05-28

We calculated methane transport through cylindrical graphite nanopores in cyclical steady-state flows using non-equilibrium molecular dynamics simulations. First, two typical gas reservoir configurations were evaluated: open (OS) and closed (CS) systems in which pores connect to the gas reservoir without/with a graphite wall parallel to the gas flow. We found that the OS configuration, which is commonly used to study nanoflows, exhibited obvious size effects. Smaller gas reservoir cross-sectional areas were associated with faster gas flows. Because Knudsen diffusion and slip flow in pores are interrupted in a gas reservoir that does not have walls as constraints, OSs cannot be relied upon in cyclical nanoflow simulations. Although CSs eliminated size effects, they introduced surface roughness effects that stem from the junction surface between the gas reservoir and the pore. To obtain a convergent nanoflow, the length of a side of the gas reservoir cross-section should be at least 2 nm larger than the pore diameter. Second, we obtained methane flux data for various pore radii (0.5-2.5 nm) in CSs and found that they could be described accurately using the Javadpour formula. This is the first direct molecular simulation evidence to validate this formula. Finally, the radial density and flow-velocity distributions of methane in CS pores were analyzed in detail. We tested pores with a radius between 0.5 nm and 2.5 nm and determined that the maximum ratio (∼34%) of slip flow to overall flow occurred in the pore with a radius of 1.25 nm. This study will aid in the design of gas reservoir configurations for nanoflow simulations and is helpful in understanding shale gas nanoflows.

Effects of gas reservoir configuration and pore radius on shale gas nanoflow: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Tian, Huiquan; Guo, Guang-Jun; Geng, Ming; Zhang, Zhengcai; Zhang, Mingmin; Gao, Kai

2018-05-01

We calculated methane transport through cylindrical graphite nanopores in cyclical steady-state flows using non-equilibrium molecular dynamics simulations. First, two typical gas reservoir configurations were evaluated: open (OS) and closed (CS) systems in which pores connect to the gas reservoir without/with a graphite wall parallel to the gas flow. We found that the OS configuration, which is commonly used to study nanoflows, exhibited obvious size effects. Smaller gas reservoir cross-sectional areas were associated with faster gas flows. Because Knudsen diffusion and slip flow in pores are interrupted in a gas reservoir that does not have walls as constraints, OSs cannot be relied upon in cyclical nanoflow simulations. Although CSs eliminated size effects, they introduced surface roughness effects that stem from the junction surface between the gas reservoir and the pore. To obtain a convergent nanoflow, the length of a side of the gas reservoir cross-section should be at least 2 nm larger than the pore diameter. Second, we obtained methane flux data for various pore radii (0.5-2.5 nm) in CSs and found that they could be described accurately using the Javadpour formula. This is the first direct molecular simulation evidence to validate this formula. Finally, the radial density and flow-velocity distributions of methane in CS pores were analyzed in detail. We tested pores with a radius between 0.5 nm and 2.5 nm and determined that the maximum ratio (˜34%) of slip flow to overall flow occurred in the pore with a radius of 1.25 nm. This study will aid in the design of gas reservoir configurations for nanoflow simulations and is helpful in understanding shale gas nanoflows.

Direct Conversion of Methane to Value-Added Chemicals over Heterogeneous Catalysts: Challenges and Prospects.

PubMed

Schwach, Pierre; Pan, Xiulian; Bao, Xinhe

2017-07-12

The quest for an efficient process to convert methane efficiently to fuels and high value-added chemicals such as olefins and aromatics is motivated by their increasing demands and recently discovered large reserves and resources of methane. Direct conversion to these chemicals can be realized either oxidatively via oxidative coupling of methane (OCM) or nonoxidatively via methane dehydroaromatization (MDA), which have been under intensive investigation for decades. While industrial applications are still limited by their low yield (selectivity) and stability issues, innovations in new catalysts and concepts are needed. The newly emerging strategy using iron single sites to catalyze methane conversion to olefins, aromatics, and hydrogen (MTOAH) attracted much attention when it was reported. Because the challenge lies in controlled dehydrogenation of the highly stable CH 4 and selective C-C coupling, we focus mainly on the fundamentals of C-H activation and analyze the reaction pathways toward selective routes of OCM, MDA, and MTOAH. With this, we intend to provide some insights into their reaction mechanisms and implications for future development of highly selective catalysts for direct conversion of methane to high value-added chemicals.

Open-path FTIR ozone measurements in Korea

NASA Astrophysics Data System (ADS)

Walter, William T.; Perry, Stephen H.; Han, Jin-Seok; Park, Chul-Jin

1999-02-01

In July 1997 the Republic of Korea became the 15th country to exceed 10-million registered motor vehicles. The number of cars has been increasing exponentially in Korea for the past 12 years opening an era of one car per household in this nation with a population of 44 million. The air quality effects of the growth of increasingly congested motor vehicle traffic in Seoul, home to more than one-fourth of the entire population, is of great concern to Korea's National Institute of Environmental Research (NIER). AIL's Open-Path FTIR air quality monitor, RAM 2000TM, has been used to quantify the ozone increase over the course of a warm summer day. The RAM 2000 instrument was setup on the roof of the 6-story NIER headquarters. The retroreflector was sited 180-m away across a major highway where it was tripod-mounted on top of the 6- story Korean National Institute of Health facility. During the Open-Path FTIR data taking, NIER Air Physics Division research team periodically tethered an airborne balloon containing pump and a potassium iodide solution to obtain absolute ozone concentration results which indicated that the ambient ozone level was 50 ppb when the Open-Path FTIR measurements began. Total ozone concentrations exceeded 120 ppb for five hours between 11:30 AM and 4:30 PM. The peak ozone concentration measured was 199 ppb at 12:56 PM. The averaged concentration for five and a half hours of data collection was 145 ppb. Ammonia concentrations were also measured.

Seasonal and inter-annual variation in ecosystem scale methane emission from a boreal fen

NASA Astrophysics Data System (ADS)

Rinne, Janne; Li, Xuefei; Raivonen, Maarit; Peltola, Olli; Sallantaus, Tapani; Haapanala, Sami; Smolander, Sampo; Alekseychik, Pavel; Aurela, Mika; Korrensalo, Aino; Mammarella, Ivan; Tuittila, Eeva-Stiina; Vesala, Timo

2016-04-01

Northern wetlands are one of the major sources of atmospheric methane. We have measured ecosystem scale methane emissions from a boreal fen continuously since 2005. The site is an oligotrophic fen in boreal vegetation zone situated in Siikaneva wetland complex in Southern Finland. The mean annual temperature in the area is 3.3°C and total annual precipitation 710 mm. We have conducted the methane emission measurements by the eddy covariance method. Additionally we have measured fluxes of carbon dioxide, water vapor, and sensible heat together with a suite of other environmental parameters. We have analyzed this data alongside with a model run with University of Helsinki methane model. The measured fluxes show generally highest methane emission in late summers coinciding with the highest temperatures in saturated peat zone. During winters the fluxes show small but detectable emission despite the snow and ice cover on the fen. More than 90% of the annual methane emission occurs in snow-free period. The methane emission and peat temperature are connected in exponential manner in seasonal scales, but methane emission does not show the expected behavior with water table. The lack of water table position dependence also contrasts with the spatial variation across microtopography. There is no systematic variation in sub-diurnal time scale. The general seasonal cycle in methane emission is captured well with the methane model. We will show how well the model reproduces the temperature and water table position dependencies observed. The annual methane emission is typically around 10 gC m-2. This is a significant part of the total carbon exchange between the fen and the atmosphere and about twice the estimated carbon loss by leaching from the fen area. The inter-annual variability in the methane emission is modest. The June-September methane emissions from different years, comprising most of the annual emission, correlates positively with peat temperature, but not with water table position.

Performance of Charm-F - the airborne demonstrator for Merlin

NASA Astrophysics Data System (ADS)

Amediek, Axel; Ehret, Gerhard; Fix, Andreas; Wirth, Martin; Büdenbender, Christian; Quatrevalet, Mathieu; Kiemle, Christoph

2018-04-01

In 2015, the new airborne lidar CHARM-F for the measurement of the greenhouse gases carbon dioxide and methane was set into operation. It is an integrated path differential absorption (IPDA) lidar designed for the use onboard the German research aircraft HALO. Due to its high technological similarity to the MERLIN space lidar, it is also a demonstrator for the space system. Here, we report on CHARM-F's technology, the experiences with the IPDA lidar method and the achieved performance.

A Deterministic and Random Propagation Study with the Design of an Open Path 320 GHz to 340 GHz Transmissometer

NASA Astrophysics Data System (ADS)

Scally, Lawrence J.

This program was implemented by Lawrence J. Scally for a Ph.D. under the EECE department at the University of Colorado at Boulder with most funding provided by the U.S. Army. Professor Gasiewski is the advisor and guider for the entire program; he has a strong history decades ago in this type of program. This program is developing a more advanced than previous years transmissometer, called Terahertz Atmospheric and Ionospheric Propagation, Absorption and Scattering System (TAIPAS), on an open path between the University of Colorado EE building roof and the mesa on owned by National Institute of Standards and Technology (NIST); NIST has invested money, location and support for the program. Besides designing and building the transmissometer, that has never be accomplished at this level, the system also analyzes the atmospheric propagation of frequencies by scanning between 320 GHz and 340 GHz, which includes the peak absorption frequency at 325.1529 GHz due to water absorption. The processing and characterization of the deterministic and random propagation characteristics of the atmosphere in the real world was significantly started; this will be executed with varies aerosols for decades on the permanently mounted system that is accessible 24/7 via a network over the CU Virtual Private Network (VPN).

cPath: open source software for collecting, storing, and querying biological pathways.

PubMed

Cerami, Ethan G; Bader, Gary D; Gross, Benjamin E; Sander, Chris

2006-11-13

Biological pathways, including metabolic pathways, protein interaction networks, signal transduction pathways, and gene regulatory networks, are currently represented in over 220 diverse databases. These data are crucial for the study of specific biological processes, including human diseases. Standard exchange formats for pathway information, such as BioPAX, CellML, SBML and PSI-MI, enable convenient collection of this data for biological research, but mechanisms for common storage and communication are required. We have developed cPath, an open source database and web application for collecting, storing, and querying biological pathway data. cPath makes it easy to aggregate custom pathway data sets available in standard exchange formats from multiple databases, present pathway data to biologists via a customizable web interface, and export pathway data via a web service to third-party software, such as Cytoscape, for visualization and analysis. cPath is software only, and does not include new pathway information. Key features include: a built-in identifier mapping service for linking identical interactors and linking to external resources; built-in support for PSI-MI and BioPAX standard pathway exchange formats; a web service interface for searching and retrieving pathway data sets; and thorough documentation. The cPath software is freely available under the LGPL open source license for academic and commercial use. cPath is a robust, scalable, modular, professional-grade software platform for collecting, storing, and querying biological pathways. It can serve as the core data handling component in information systems for pathway visualization, analysis and modeling.

Evanescent-wave photoacoustic spectroscopy with optical micro/nano fibers.

PubMed

Cao, Yingchun; Jin, Wei; Ho, Lut Hoi; Liu, Zhibo

2012-01-15

We demonstrate gas detection based on evanescent-wave photoacoustic (PA) spectroscopy with tapered optical fibers. Evanescent-field instead of open-path absorption is exploited for PA generation, and a quartz tuning fork is used for PA detection. A tapered optical fiber with a diameter down to the wavelength scale demonstrates detection sensitivity similar to an open-path system but with the advantages of easier optical alignment, smaller insertion loss, and multiplexing capability.

Open-path in situ measurement of the nitrate radical concentrations during the CAREBeijing-NCP 2014 summer campaign

NASA Astrophysics Data System (ADS)

George, Midhun; Suhail, Suhail; Chandran, Satheesh; Chen, Jun; Lu, Keding; Ruth, Albert; Venables, Dean; Varma, Ravi

2016-04-01

We describe the application of an incoherent broadband cavity-enhanced absorption spectrometer in an open path configuration (OP-IBBCEAS) for in situ detection of nitrate radical (NO3) and aerosol extinction. The optical cavity was 3.35 m long with separate transmitter and receiver units, and the instrument was installed on top of a residential complex (elevation of 17 m) near the CAREBEIJING-NCP 2014 supersite in Wangdu, 200 km southwest of Beijing. Despite high aerosol loading, NO3 was detected on all nights when the instrument was operational (28-30 June, 2014). The maximum concentration measured was 170 pptv with a detection limit of 40 pptv for measurements. Preliminary quantification of the aerosol extinction is also described. The results presented here demonstrate the sensitivity and specificity that can be achieved from open path measurements and its application to polluted environments.

New Zealand's 70 million sheep create 350 million methane gallons daily

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

Not Available

If you could hook up a sheep to the carburetor of a car, you could run it for several kilometers a day. To power the same vehicle by people, you'd need a whole football team and a couple of kegs of beer. That observation is made by David Lowe, a geophysicist with the New Zealand Institute of Nuclear Sciences in Wellington. Scientists are studying the methane output because of its potential serious threat by contributing to global warming via the greenhouse effect. According to a report in the Wall Street Journal, analysis of ancient air bubbles trapped in Antarctic icemore » shows that 30,000 years ago methane concentration in the Earth's atmosphere was only a third as much as it is today. Radioactive dating can distinguish ages of different types of methane in the air, and researchers hope to quantify sources from sheep, swamps, people or industry. Sheep methane is collected at a local agricultural university from sheep with tubes protruding from their intestines. Sample collector Lowe alternates specimens from the university and the digester tank at the sewage treatment plant. The cleanest air samples, by contrast, are collected by Lowe at Baring Head, the first outcrop of land Antarctic winds hit after crossing thousands of miles of open sea. So far, Lowe and his colleagues have found that 75% of methane in the atmosphere is biological and of very recent origin. While the research goes on, New Zealand's sheep population continue to churn out 2.5 billion gallons of methane every week.« less

Towards Understanding the Impact of Production Techniques and Regulations on Widely Varying Methane Emission Rates in Western Basins

NASA Astrophysics Data System (ADS)

Robertson, A.; Edie, R.; Soltis, J.; Field, R. A.; Murphy, S. M.

2017-12-01

Recent airborne and mobile lab-based studies by our group and others have demonstrated that production-normalized emission rates of methane can vary dramatically between different Western basins. Three oil and gas basins that are geographically near one another and have relatively similar production characteristics (all three basins produce a mix of natural gas and condensate) have starkly different production-normalized methane emission rates at both the facility and basin-wide levels. This presentation will review previously published data on methane emissions from these basins (Denver Julesburg, Uintah, and Upper Green River) and present new measurement work supporting and expanding upon previous estimates. Beyond this, we use facility level data emissions data combined with information about the date of last upgrade to determine what impact regulations have had on methane emission rates from facilities within the basins. We also investigate what impact different approaches to production may have, in particular the role of having many individual wells processed at a central facility with high throughput is analyzed in terms of its impact on methane emissions.

Towards Understanding the Impact of Production Techniques and Regulations on Widely Varying Methane Emission Rates in Western Basins

NASA Astrophysics Data System (ADS)

Regayre, L. A.; Johnson, J. S.; Yoshioka, M.; Pringle, K.; Sexton, D.; Booth, B.; Mann, G.; Lee, L.; Bellouin, N.; Lister, G. M. S.; Johnson, C.; Johnson, B. T.; Mollard, J.; Carslaw, K. S.

2016-12-01

Recent airborne and mobile lab-based studies by our group and others have demonstrated that production-normalized emission rates of methane can vary dramatically between different Western basins. Three oil and gas basins that are geographically near one another and have relatively similar production characteristics (all three basins produce a mix of natural gas and condensate) have starkly different production-normalized methane emission rates at both the facility and basin-wide levels. This presentation will review previously published data on methane emissions from these basins (Denver Julesburg, Uintah, and Upper Green River) and present new measurement work supporting and expanding upon previous estimates. Beyond this, we use facility level data emissions data combined with information about the date of last upgrade to determine what impact regulations have had on methane emission rates from facilities within the basins. We also investigate what impact different approaches to production may have, in particular the role of having many individual wells processed at a central facility with high throughput is analyzed in terms of its impact on methane emissions.

[Technical Gap of Chinese Medical Accelerator and Its Development Path].

PubMed

Tian, Xinzhi

2017-11-30

With the reform and opening up the tide through nearly four decades of development, our medical accelerator business isfacing new era demands now, in this new historical opportunity in front of the younger generation of medical accelerator staff must assume the older generation of scientific research personnel are different of the historical responsibility. Based on the development of the predecessors, we try to analyze the current situation of the domestic accelerator, establish the new development ideas of the domestic medical accelerator, and directly face and solve the dilemma facing the development of the domestic accelerator.

Sensitivity of the Arctic Ocean gas hydrate to climate changes in the period of 1948-2015

NASA Astrophysics Data System (ADS)

Malakhova, Valentina V.; Golubeva, Elena N.; Iakshina, Dina F.

2017-11-01

The objective of the present study is to analyze the interactions between a methane hydrates stability zone and the ocean temperature variations and to define the hydrate sensitivity to the contemporary warming in the Arctic Ocean. To obtain the spatial-temporary variability of the ocean bottom temperature we employ the ICMMG regional Arctic-North Atlantic ocean model that has been developed in the Institute of Computational Mathematics and Mathematical Geophysics. With the ice-ocean model the Arctic bottom water temperatures were analyzed. The resulting warming ocean bottom water is spatially inhomogeneous, with a strong impact by the Atlantic inflow on shallow regions of 200-500 m depth. Results of the mathematical modeling of the dynamics of methane hydrate stability zone in the Arctic Ocean sediment are reported. We find that the reduction of the methane hydrate stability zone occurs in the Arctic Ocean between 250 and 400 m water depths within the upper 100 m of sediment in the area influenced by the Atlantic inflow. We have identified the areas of the Arctic Ocean where an increase in methane release is probable to occur at the present time.

An afterburner-powered methane/steam reformer for a solid oxide fuel cells application

NASA Astrophysics Data System (ADS)

Mozdzierz, Marcin; Chalusiak, Maciej; Kimijima, Shinji; Szmyd, Janusz S.; Brus, Grzegorz

2018-04-01

Solid oxide fuel cell (SOFC) systems can be fueled by natural gas when the reforming reaction is conducted in a stack. Due to its maturity and safety, indirect internal reforming is usually used. A strong endothermic methane/steam reforming process needs a large amount of heat, and it is convenient to provide thermal energy by burning the remainders of fuel from a cell. In this work, the mathematical model of afterburner-powered methane/steam reformer is proposed. To analyze the effect of a fuel composition on SOFC performance, the zero-dimensional model of a fuel cell connected with a reformer is formulated. It is shown that the highest efficiency of a solid oxide fuel cell is achieved when the steam-to-methane ratio at the reforming reactor inlet is high.

Quantification of methane emissions from 15 Danish landfills using the mobile tracer dispersion method

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

Mønster, Jacob; Samuelsson, Jerker, E-mail: jerker.samuelsson@fluxsense.se; Kjeldsen, Peter

2015-01-15

Highlights: • Quantification of whole landfill site methane emission at 15 landfills. • Multiple on-site source identification and quantification. • Quantified methane emission from shredder waste and composting. • Large difference between measured and reported methane emissions. - Abstract: Whole-site methane emissions from 15 Danish landfills were assessed using a mobile tracer dispersion method with either Fourier transform infrared spectroscopy (FTIR), using nitrous oxide as a tracer gas, or cavity ring-down spectrometry (CRDS), using acetylene as a tracer gas. The landfills were chosen to represent the different stages of the lifetime of a landfill, including open, active, and closed coveredmore » landfills, as well as those with and without gas extraction for utilisation or flaring. Measurements also included landfills with biocover for oxidizing any fugitive methane. Methane emission rates ranged from 2.6 to 60.8 kg h{sup −1}, corresponding to 0.7–13.2 g m{sup −2} d{sup −1}, with the largest emission rates per area coming from landfills with malfunctioning gas extraction systems installed, and the smallest emission rates from landfills closed decades ago and landfills with an engineered biocover installed. Landfills with gas collection and recovery systems had a recovery efficiency of 41–81%. Landfills where shredder waste was deposited showed significant methane emissions, with the largest emission from newly deposited shredder waste. The average methane emission from the landfills was 154 tons y{sup −1}. This average was obtained from a few measurement campaigns conducted at each of the 15 landfills and extrapolating to annual emissions requires more measurements. Assuming that these landfills are representative of the average Danish landfill, the total emission from Danish landfills were calculated at 20,600 tons y{sup −1}, which is significantly lower than the 33,300 tons y{sup −1} estimated for the national greenhouse gas inventory for 2011.« less

Anaerobic oxidation of methane associated with sulfate reduction in a natural freshwater gas source

PubMed Central

Timmers, Peer HA; Suarez-Zuluaga, Diego A; van Rossem, Minke; Diender, Martijn; Stams, Alfons JM; Plugge, Caroline M

2016-01-01

The occurrence of anaerobic oxidation of methane (AOM) and trace methane oxidation (TMO) was investigated in a freshwater natural gas source. Sediment samples were taken and analyzed for potential electron acceptors coupled to AOM. Long-term incubations with 13C-labeled CH4 (13CH4) and different electron acceptors showed that both AOM and TMO occurred. In most conditions, 13C-labeled CO2 (13CO2) simultaneously increased with methane formation, which is typical for TMO. In the presence of nitrate, neither methane formation nor methane oxidation occurred. Net AOM was measured only with sulfate as electron acceptor. Here, sulfide production occurred simultaneously with 13CO2 production and no methanogenesis occurred, excluding TMO as a possible source for 13CO2 production from 13CH4. Archaeal 16S rRNA gene analysis showed the highest presence of ANME-2a/b (ANaerobic MEthane oxidizing archaea) and AAA (AOM Associated Archaea) sequences in the incubations with methane and sulfate as compared with only methane addition. Higher abundance of ANME-2a/b in incubations with methane and sulfate as compared with only sulfate addition was shown by qPCR analysis. Bacterial 16S rRNA gene analysis showed the presence of sulfate-reducing bacteria belonging to SEEP-SRB1. This is the first report that explicitly shows that AOM is associated with sulfate reduction in an enrichment culture of ANME-2a/b and AAA methanotrophs and SEEP-SRB1 sulfate reducers from a low-saline environment. PMID:26636551

Distribution and origin of groundwater methane in the Wattenberg oil and gas field of northern Colorado.

PubMed

Li, Huishu; Carlson, Kenneth H

2014-01-01

Public concerns over potential environmental contamination associated with oil and gas well drilling and fracturing in the Wattenberg field in northeast Colorado are increasing. One of the issues of concern is the migration of oil, gas, or produced water to a groundwater aquifer resulting in contamination of drinking water. Since methane is the major component of natural gas and it can be dissolved and transported with groundwater, stray gas in aquifers has elicited attention. The initial step toward understanding the environmental impacts of oil and gas activities, such as well drilling and fracturing, is to determine the occurrence, where it is and where it came from. In this study, groundwater methane data that has been collected in response to a relatively new regulation in Colorado is analyzed. Dissolved methane was detected in 78% of groundwater wells with an average concentration of 4.0 mg/L and a range of 0-37.1 mg/L. Greater than 95% of the methane found in groundwater wells was classified as having a microbial origin, and there was minimal overlap between the C and H isotopic characterization of the produced gas and dissolved methane measured in the aquifer. Neither density of oil/gas wells nor distance to oil/gas wells had a significant impact on methane concentration suggesting other important factors were influencing methane generation and distribution. Thermogenic methane was detected in two aquifer wells indicating a potential contamination pathway from the producing formation, but microbial-origin gas was by far the predominant source of dissolved methane in the Wattenberg field.

Evidence of Sulfate-Dependent Anaerobic Methane Oxidation within an Area Impacted by Coalbed Methane-Related Gas Migration

NASA Astrophysics Data System (ADS)

Wolfe, A. L.; Wikin, R. T.

2017-12-01

We evaluated water quality characteristics in the northern Raton Basin of Colorado and documented the response of the Poison Canyon aquifer system several years after upward migration of methane gas occurred from the deeper Vermejo Formation coalbed production zone. Over a 17-month study period, water samples were obtained from domestic water wells and monitoring wells located within the impacted area, and analyzed for 245 constituents, including organic compounds, nutrients, major and trace elements, dissolved gases, and isotopic tracers for carbon, sulfur, oxygen, and hydrogen. Multiple lines of evidence suggest that sulfate-dependent methane biodegradation, which involves the oxidation of methane (CH4) to carbon dioxide (CO2) using sulfate (SO42-) as the terminal electron acceptor, is occurring: (i) consumption of methane and sulfate and production of sulfide and bicarbonate, (ii) methane loss coupled to production of higher molecular weight (C2+) gaseous hydrocarbons, (iii) patterns of 13C enrichment and depletion in methane and dissolved inorganic carbon, and (iv) a systematic shift in sulfur and oxygen isotope ratios of sulfate, indicative of microbial sulfate reduction. Groundwater-methane attenuation is linked to the production of dissolved sulfide, and elevated dissolved sulfide concentrations represent an undesirable secondary water quality impact. The biogeochemical response of the aquifer system has not mobilized naturally occurring trace metals, including arsenic, chromium, cobalt, nickel, and lead, likely due to the microbial production of hydrogen sulfide, which favors stabilization of metals in aquifer solids.

Short-Path Statistics and the Diffusion Approximation

NASA Astrophysics Data System (ADS)

Blanco, Stéphane; Fournier, Richard

2006-12-01

In the field of first return time statistics in bounded domains, short paths may be defined as those paths for which the diffusion approximation is inappropriate. This is at the origin of numerous open questions concerning the characterization of residence time distributions. We show here how general integral constraints can be derived that make it possible to address short-path statistics indirectly by application of the diffusion approximation to long paths. Application to the moments of the distribution at the low-Knudsen limit leads to simple practical results and novel physical pictures.

Methane Fluxes in a Composite Landscape in the Sacramento-San Joaquin Delta

NASA Astrophysics Data System (ADS)

Guha, A.; Detto, M.; Baldocchi, D. D.; Goldstein, A. H.

2009-12-01

Much of the Sacramento-San Joaquin Delta region post the Gold Rush era was reclaimed and drained for agriculture by building a network of ‘islands’ surrounded by levees. The exposure of organic peat soil to air has caused the peat soil to oxidize and soil to subside. Today, a combination of oxidation, subsidence, erosion, and compaction has caused many ‘islands’ to be 10 m below sea level. The continued oxidation/subsidence of the Delta peatlands is threatening long-term agricultural use of these lands by pushing the soil level further and further below sea-level. In an attempt to protect the Delta, State and Federal governmental institutions (e.g. CalFed) and local water districts are converting some of these agricultural lands back to wetlands. This is being accomplished by breaching levees, with the intent of sequestering carbon and building up the soils, by introducing flooded crops, like rice, or carbon farming by converting farm land to native tules and cattails. Knowing what the environmental trade-offs of such land conversion are on coupled carbon and water exchange is critical for proper environmental management, as there can be many unintended consequences such as the emission of greenhouse gases that promote global warming. Large greenhouse gas fluxes specially that of methane are expected from wetlands in the Sacramento-San Joaquin Delta for a variety of reasons. This campaign aimed at measuring the methane fluxes over the complex and fragmented landscapes of the Delta where a piece of land can vary from being a slight sink of methane to a vast source depending upon land use, land cover and degree of saturation of soil. Los Gatos Research (LGR) designed and fabricated a mobile trailer which housed their latest closed-path infrared laser based absorption spectrometers for fast response in-situ measurements of methane at a frequency which permits eddy covariance technique to be applied to measure flux. The trailer was taken to selected landscapes across the Delta which were expected to be hotspots for production of methane. These included a drained peatland at Sherman Islands, wet irrigated pastures, rice paddy fields at Twitchell Islands, marshy, tidal floodplains, and flooded water fowl habitat. In this way, methane fluxes were measured across a spectrum of time and space scales in the Delta. The measurements address how fluxes of methane vary diurnally, seasonally, and annually over Delta peatlands. We focus on how methane fluxes vary with space in the vertical and horizontal and how this is affected by land use (e.g. agriculture, restored and native wetlands) and water management (e.g. water table and flooding)? Our findings address the issue of whether management decisions to sequester carbon, by flooding and ecological restoration, will be offset by enhanced emissions of methane.

Anaerobic digestion of grape pomace: Biochemical characterization of the fractions and methane production in batch and continuous digesters.

PubMed

El Achkar, Jean H; Lendormi, Thomas; Hobaika, Zeina; Salameh, Dominique; Louka, Nicolas; Maroun, Richard G; Lanoisellé, Jean-Louis

2016-04-01

In this study, we have estimated the biogas and methane production from grape pomace (variety Cabernet Franc). The physical and chemical characteristics of the raw material were determined, and the structural polysaccharides were identified and analyzed by the Van Soest method. Batch anaerobic digestions were carried out to assess the methane production of the grape pomace, pulp and seeds. The obtained cumulative methane productions are 0.125, 0.165 and 0.052 Nm(3) kg COD(-1) for grape pomace, pulps and seeds, respectively. The effect of grinding on the methane potential of the substrates, as a mechanical pretreatment, was evaluated. We found that it increased the anaerobic biodegradability for grape pomace, pulp and seeds by 13.1%, 4.8% and 22.2%, respectively. On the other hand, the methane potential of the grape pomace was determined in a laboratory pilot plant (12L) continuously mixed with an organic loading rate of 2.5 kg COD m(3) d(-1) and a hydraulic retention time of 30 days. The corresponding biogas production was 6.43 × 10(-3) Nm(3) d(-1), with a methane content of 62.3%. Thus, the pilot plant's efficiency compared to that achieved in the batch process was 81.2%. Finally, a significant correlation was found between the biochemical content and methane production. Copyright © 2016 Elsevier Ltd. All rights reserved.

Methane turnover and methanotrophic communities in arctic aquatic ecosystems of the Lena Delta, Northeast Siberia.

PubMed

Osudar, Roman; Liebner, Susanne; Alawi, Mashal; Yang, Sizhong; Bussmann, Ingeborg; Wagner, Dirk

2016-08-01

Large amounts of organic carbon are stored in Arctic permafrost environments, and microbial activity can potentially mineralize this carbon into methane, a potent greenhouse gas. In this study, we assessed the methane budget, the bacterial methane oxidation (MOX) and the underlying environmental controls of arctic lake systems, which represent substantial sources of methane. Five lake systems located on Samoylov Island (Lena Delta, Siberia) and the connected river sites were analyzed using radiotracers to estimate the MOX rates, and molecular biology methods to characterize the abundance and the community composition of methane-oxidizing bacteria (MOB). In contrast to the river, the lake systems had high variation in the methane concentrations, the abundance and composition of the MOB communities, and consequently, the MOX rates. The highest methane concentrations and the highest MOX rates were detected in the lake outlets and in a lake complex in a flood plain area. Though, in all aquatic systems, we detected both, Type I and II MOB, in lake systems, we observed a higher diversity including MOB, typical of the soil environments. The inoculation of soil MOB into the aquatic systems, resulting from permafrost thawing, might be an additional factor controlling the MOB community composition and potentially methanotrophic capacity. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Vertical structure and horizontal variations in the cycling of methane in the sediment of Lake Onego, Russia

NASA Astrophysics Data System (ADS)

Thomas, Camille; Perga, Marie-Elodie; Frossard, Victor; Pasche, Natacha; Hofmann, Hilmar; Ariztegui, Daniel; Dubois, Nathalie; Belkina, Natalya; Lyautey, Emilie

2017-04-01

Lake Onego, the second largest lake in Europe, is a dystrophic, seasonally ice-covered lake in Karelia, Russia. Like most winter-covered lakes, its study has largely been limited to the summer period. However, it is well known that methane production is still ongoing in lake sediments during winter, potentially resulting in accumulation and major release upon thawing. Within the "Life Under The Ice" research project, our objectives were to assess winter contribution to the annual methane flux in Lake Onego, and to understand conditions and factors influencing methane cycling. During two on-ice field campaigns in March 2015 and 2016, sediment cores were retrieved at different sites of Petrozavodsk Bay, located in the north-western part of the lake. DNA and RNA were extracted from these cores to investigate the functional structure of microbial communities. Genes involved in methanogenesis, anaerobic and aerobic methane oxidations were quantified along with the concentrations and isotopic ratio of methane in the sediment pore water. Incubations, fingerprinting and sequencing of mcrA genes were also realized. Vertically, the sediment is structured in a deep anoxic zone (below 10 cm) where mcrA gene and transcript copies increased implying methanogenesis, a transitional zone (5-8 cm) hosting methanotrophic organisms (Cand. Methanoperedens) able to oxidize the diffusing methane anaerobically by coupling nitrate reduction (Haroon et al., 2013), and a shallower oxic zone where methanotrophs were detected (pmoA gene and transcripts) and where methane concentrations drop below detection limit. Sediment cores were also collected at three sites along a transect from the mouth of the river Shuya (the major inflow to the bay) to the open lake. Functional assemblage close to the river mouth had higher diversity and higher potential production rates and consumption of methane than further in the lake. However, the methane produced was almost completely consumed regardless of the sites, suggesting that this heterogeneity does not convey significant methane inputs to Lake Onego's water column during ice cover in winter. Haroon, M. F., Hu, S., Shi, Y., Imelfort, M., Keller, J., Hugenholtz, P., … Tyson, G. W. (2013). Anaerobic oxidation of methane coupled to nitrate reduction in a novel archaeal lineage. Nature, 500(7464), 567-70.

Preliminary assignments of 2 ν 3 - ν 4 hot band of 12 CH 4 in the 2 μm transparency window from long-path FTS spectra

NASA Astrophysics Data System (ADS)

Nikitin, A. V.; Daumont, L.; Thomas, X.; Régalia, L.; Rey, M.; Tyuterev, Vl. G.; Brown, L. R.

2011-07-01

New measurements and assignments for the rovibrational transitions of the hot band 2 v3- v4 of 12CH 4 are reported from 4600 to 4880 cm -1 and refer to lower part of the 2 μm methane transparency window. Three long-path spectra were recorded with a Fourier transform spectrometer (FTS) in Reims using an L = 1603 m absorption path length at 1, 7, 34 h Pa for the natural samples of CH 4; a spectrum of enriched 13CH 4 was also used. Assignments were made for 196 lines of 2 v3(F 2,E)- v4. These transitions had an integrated intensity of 5 × 10 -24 cm/molecule at 296 K and improved the overall description of absorption in the 2.1 μm region. The empirical upper state levels of these assignments belong to Tetradecad (4800-6200 cm -1). The new analysis provided much better accuracies of badly blended positions of 2 v3(F 2)-ground state manifolds at 1.66 μm.

The very homogeneous surface of the dwarf planet Makemake

NASA Astrophysics Data System (ADS)

Perna, D.; Hromakina, T.; Merlin, F.; Ieva, S.; Fornasier, S.; Belskaya, I.; Mazzotta Epifani, E.

2017-04-01

The dwarf planet (136472) Makemake is one of the largest trans-Neptunian objects discovered to date. Noteworthy, the size and surface temperature of this celestial body put it in a transition region where nitrogen is preferentially lost, while the less volatile methane is retained. Indeed, literature spectra clearly show that the surface of Makemake is dominated by methane ice, though the presence of nitrogen and of irradiation products of methane has been inferred by several authors and a debate is still open about the eventual rotational variability of the surface composition. In this work, we present new visible and near-infrared spectra of Makemake obtained with the TNG telescope (La Palma, Spain) in the time span 2006-2013. Our data sample different rotational phases, covering about 80 per cent of the surface. All of the obtained spectra look very similar, suggesting an overall homogeneous composition. No secular variations appear when comparing our data to literature results (as expected, considering the quite short orbital arc travelled by Makemake since its discovery in 2005). The presence of methane diluted in nitrogen is evidenced by the shift of the observed absorption bands with respect to those of pure methane, with a dilution state looking homogeneous over the surface. We modelled a complete visible and near-infrared spectrum of Makemake using the Shkuratov formalism, and found that adding irradiation products of methane like ethane and ethylene seems indeed improving the fit of the synthetic spectrum to our data. We found no hints of a localized/temporary atmosphere.

Ethanol prefermentation of food waste in sequencing batch methane fermentation for improved buffering capacity and microbial community analysis.

PubMed

Yu, Miao; Wu, Chuanfu; Wang, Qunhui; Sun, Xiaohong; Ren, Yuanyuan; Li, Yu-You

2018-01-01

This study investigates the effects of ethanol prefermentation (EP) on methane fermentation. Yeast was added to the substrate for EP in the sequencing batch methane fermentation of food waste. An Illumina MiSeq high-throughput sequencing system was used to analyze changes in the microbial community. Methane production in the EP group (254mL/g VS) was higher than in the control group (35mL/g VS) because EP not only increased the buffering capacity of the system, but also increased hydrolytic acidification. More carbon source was converted to ethanol in the EP group than in the control group, and neutral ethanol could be converted continuously to acetic acid, which promoted the growth of Methanobacterium and Methanosarcina. As a result, the relative abundance of methane-producing bacteria was significantly higher than that of the control group. Kinetic modeling indicated that the EP group had a higher hydrolysis efficiency and shorter lag phase. Copyright © 2017 Elsevier Ltd. All rights reserved.

Impacts of initial temperature and cylindrical obstacles on the dispersing flammable limits of accidental methane releases in an LNG bunkering terminal.

PubMed

Choi, Byung Chul; Park, Kweon-Ha; Doh, Deog-Hee

2018-05-16

This paper presents a numerical study on the dispersing flammable limits with respect to the initial methane releases at T CH4,0  = -50 and -150 °C in the crosswind of ambient air according to the arrangement of (a) No Tank, (b) Tank I, (c) Tank II, and (d) Tank I and II on the ground. To provide a better physical insight on the dispersion behaviors of the methane releases, the spatial distributions of the quasi-averaged methane concentration and flow fields were mainly analyzed using 3-D large eddy simulations. Consequently, the results of both the parameters can be summarized in that the vortex characteristics of the rotating direction and vorticity generated by the interactions not only between the crosswind and cylindrical obstacles but also between the crosswind and releasing methane flows played important roles in determining the dispersing flammable limits depending on the mixing characteristics. Copyright © 2018 Elsevier B.V. All rights reserved.

COMET: a planned airborne mission to simultaneously measure CO2 and CH4 columns using airborne remote sensing and in-situ techniques

NASA Astrophysics Data System (ADS)

Fix, A.; Amediek, A.; Büdenbender, C.; Ehret, G.; Wirth, M.; Quatrevalet, M.; Rapp, M.; Gerilowski, K.; Bovensmann, H.; Gerbig, C.; Pfeilsticker, K.; Zöger, M.; Giez, A.

2013-12-01

To better predict future trends in the cycles of the most important anthropogenic greenhouse gases, CO2 and CH4, there is a need to measure and understand their distribution and variation on various scales. To address these requirements it is envisaged to deploy a suite of state-of-the-art airborne instruments that will be capable to simultaneously measure the column averaged dry-air mixing ratios (XGHG) of both greenhouse gases along the flight path. As the measurement platform serves the research aircraft HALO, a modified Gulfstream G550, operated by DLR. This activity is dubbed CoMet (CO2 and Methane Mission). The instrument package of CoMet will consist of active and passive remote sensors as well as in-situ instruments to complement the column measurements by highly-resolved profile information. As an active remote sensing instrument CHARM-F, the integrated-path differential absorption lidar currently under development at DLR, will provide both, XCO2 and XCH4, below flight altitude. The lidar instrument will be complemented by MAMAP which is a NIR/SWIR absorption spectrometer developed by University of Bremen and which is also capable to derive XCH4 and XCO2. As an additional passive instrument, mini-DOAS operated by University of Heidelberg will contribute with additional context information about the investigated air masses. In order to compare the remote sensing instruments with integrated profile information, in-situ instrumentation is indispensable. The in-situ package will therefore comprise wavelength-scanned Cavity-Ring-Down Spectroscopy (CRDS) for the detection of CO2, CH4, CO and H2O and a flask sampler for collection of atmospheric samples and subsequent laboratory analysis. Furthermore, the BAsic HALO Measurement And Sensor System (BAHAMAS) will provide an accurate set of meteorological and aircraft state parameters for each scientific flight. Within the frame of the first CoMet mission scheduled for the 2015 timeframe it is planned to concentrate on small to sub-continental scale variations of the greenhouse gases. This does not only allow to identify local emission sources of GHGs, but also opens up the opportunity to use important remote sensing and in-situ data information for the inverse modeling approach for regional budgeting. CoMet is also targeting at providing a validation platform of future spaceborne GHG missions in particular the upcoming French-German methane mission MERLIN. CHARM-F was devised as an airborne demonstrator for MERLIN, and, as such will be a key instrument for MERLIN validation.

The Yearly Variation in Fall-Winter Arctic Winter Vortex Descent

NASA Technical Reports Server (NTRS)

Schoeberl, Mark R.; Newman, Paul A.

1999-01-01

Using the change in HALOE methane profiles from early September to late March, we have estimated the minimum amount of diabatic descent within the polar which takes place during Arctic winter. The year to year variations are a result in the year to year variations in stratospheric wave activity which (1) modify the temperature of the vortex and thus the cooling rate; (2) reduce the apparent descent by mixing high amounts of methane into the vortex. The peak descent amounts from HALOE methane vary from l0km -14km near the arrival altitude of 25 km. Using a diabatic trajectory calculation, we compare forward and backward trajectories over the course of the winter using UKMO assimilated stratospheric data. The forward calculation agrees fairly well with the observed descent. The backward calculation appears to be unable to produce the observed amount of descent, but this is only an apparent effect due to the density decrease in parcels with altitude. Finally we show the results for unmixed descent experiments - where the parcels are fixed in latitude and longitude and allowed to descend based on the local cooling rate. Unmixed descent is found to always exceed mixed descent, because when normal parcel motion is included, the path average cooling is always less than the cooling at a fixed polar point.

Integrated solar thermochemical reaction system for steam methane reforming

DOE PAGES

Zheng, Feng; Diver, Rich; Caldwell, Dustin D.; ...

2015-06-05

Solar-aided upgrade of the energy content of fossil fuels, such as natural gas, can provide a near-term transition path towards a future solar-fuel economy and reduce carbon dioxide emission from fossil fuel consumption. Both steam and dry reforming a methane-containing fuel stream have been studied with concentrated solar power as the energy input to drive the highly endothermic reactions but the concept has not been demonstrated at a commercial scale. Under a current project with the U.S. Department of Energy, PNNL is developing an integrated solar thermochemical reaction system that combines solar concentrators with micro- and meso-channel reactors and heatmore » exchangers to accomplish more than 20% solar augment of methane higher heating value. The objective of our three-year project is to develop and prepare for commercialization such solar reforming system with a high enough efficiency to serve as the frontend of a conventional natural gas (or biogas) combined cycle power plant, producing power with a levelized cost of electricity less than 6¢/kWh, without subsidies, by the year 2020. In this paper, we present results from the first year of our project that demonstrated a solar-to-chemical energy conversion efficiency as high as 69% with a prototype reaction system.« less

Kinematics of the human mandible for different head postures.

PubMed

Visscher, C M; Huddleston Slater, J J; Lobbezoo, F; Naeije, M

2000-04-01

The influence of head posture on movement paths of the incisal point (IP) and of the mandibular condyles during free open-close movements was studied. Ten persons, without craniomandibular or cervical spine disorders, participated in the study. Open close mandibular movements were recorded with the head in five postures, viz., natural head posture, forward head posture, military posture, and lateroflexion to the right and to the left side, using the Oral Kinesiologic Analysis System (OKAS-3D). This study showed that in a military head posture, the opening movement path of the incisal point is shifted anteriorly relative to the path in a natural head posture. In a forward head posture, the movement path is shifted posteriorly whereas during lateroflexion, it deviates to the side the head has moved to. Moreover, the intra-articular distance in the temporomandibular joint during closing is smaller with the head in military posture and greater in forward head posture, as compared to the natural head posture. During lateroflexion, the intra-articular distance on the ipsilateral side is smaller. The influence of head posture upon the kinematics of the mandible is probably a manifestation of differences in mandibular loading in the different head postures.

Temperature dependence of bioelectrochemical CO2 conversion and methane production with a mixed-culture biocathode.

PubMed

Yang, Hou-Yun; Bao, Bai-Ling; Liu, Jing; Qin, Yuan; Wang, Yi-Ran; Su, Kui-Zu; Han, Jun-Cheng; Mu, Yang

2018-02-01

This study evaluated the effect of temperature on methane production by CO 2 reduction during microbial electrosynthesis (MES) with a mixed-culture biocathode. Reactor performance, in terms of the amount and rate of methane production, current density, and coulombic efficiency, was compared at different temperatures. The microbial properties of the biocathode at each temperature were also analyzed by 16S rRNA gene sequencing. The results showed that the optimum temperature for methane production from CO 2 reduction in MES with a mixed-culture cathode was 50°C, with the highest amount and rate of methane production of 2.06±0.13mmol and 0.094±0.01mmolh -1 , respectively. In the mixed-culture biocathode MES, the coulombic efficiency of methane formation was within a range of 19.15±2.31% to 73.94±2.18% due to by-product formation at the cathode, including volatile fatty acids and hydrogen. Microbial analysis demonstrated that temperature had an impact on the diversity of microbial communities in the biofilm that formed on the MES cathode. Specifically, the hydrogenotrophic methanogen Methanobacterium became the predominant archaea for methane production from CO 2 reduction, while the abundance of the aceticlastic methanogen Methanosaeta decreased with increased temperature. Copyright © 2017. Published by Elsevier B.V.

Constraining the 2012-2014 growing season Alaskan methane budget using CARVE aircraft measurements

NASA Astrophysics Data System (ADS)

Hartery, S.; Chang, R. Y. W.; Commane, R.; Lindaas, J.; Miller, S. M.; Wofsy, S. C.; Karion, A.; Sweeney, C.; Miller, C. E.; Dinardo, S. J.; Steiner, N.; McDonald, K. C.; Watts, J. D.; Zona, D.; Oechel, W. C.; Kimball, J. S.; Henderson, J.; Mountain, M. E.

2015-12-01

Soil in northen latitudes contains rich carbon stores which have been historically preserved via permafrost within the soil bed; however, recent surface warming in these regions is allowing deeper soil layers to thaw, influencing the net carbon exchange from these areas. Due to the extreme nature of its climate, these eco-regions remain poorly understood by most global models. In this study we analyze methane fluxes from Alaska using in situ aircraft observations from the 2012-2014 Carbon in Arctic Reservoir Vulnerability Experiment (CARVE). These observations are coupled with an atmospheric particle transport model which quantitatively links surface emissions to atmospheric observations to make regional methane emission estimates. The results of this study are two-fold. First, the inter-annual variability of the methane emissions was found to be <1 Tg over the area of interest and is largely influenced by the length of time the deep soil remains unfrozen. Second, the resulting methane flux estimates and mean soil parameters were used to develop an empirical emissions model to help spatially and temporally constrain the methane exchange at the Alaskan soil surface. The empirical emissions model will provide a basis for exploring the sensitivity of methane emissions to subsurface soil temperature, soil moisture, organic carbon content, and other parameters commonly used in process-based models.

Direct Quantification of Methane Emissions Across the Supply Chain: Identification of Mitigation Targets

NASA Astrophysics Data System (ADS)

Darzi, M.; Johnson, D.; Heltzel, R.; Clark, N.

2017-12-01

Researchers at West Virginia University's Center for Alternative Fuels, Engines, and Emissions have recently participated in a variety of studies targeted at direction quantification of methane emissions from across the natural gas supply chain. These studies included assessing methane emissions from heavy-duty vehicles and their fuel stations, active unconventional well sites - during both development and production, natural gas compression and storage facilities, natural gas engines - both large and small, two- and four-stroke, and low-throughput equipment associated with coal bed methane wells. Engine emissions were sampled using conventional instruments such as Fourier transform infrared spectrometers and heated flame ionization detection analyzers. However, to accurately quantify a wide range of other sources beyond the tailpipe (both leaks and losses), a full flow sampling system was developed, which included an integrated cavity-enhanced absorption spectrometer. Through these direct quantification efforts and analysis major sources of methane emissions were identified. Technological solutions and best practices exist or could be developed to reduce methane emissions by focusing on the "lowest-hanging fruit." For example, engine crankcases from across the supply chain should employ vent mitigation systems to reduce methane and other emissions. An overview of the direct quantification system and various campaign measurements results will be presented along with the identification of other targets for additional mitigation.

Analysis of Atmospheric Composition and Tropospheric Variability With Integrated Open- Path and Ground-Based Solar Infrared Absorption Spectroscopy

NASA Astrophysics Data System (ADS)

Steill, J. D.; Compton, R. N.; Hager, J. S.

2006-12-01

Ground-based solar infrared absorption spectroscopy coupled with open-path spectroscopy provides a means for analysis of the highly variable contribution of the boundary layer to problems of radiative transfer and atmospheric chemistry. This is of particular importance in geographic regions of significant local anthropogenic influence and large tropospheric fluctuations in general. A Bomem DA8 FT-IR integrated with a sun-tracking and open-path system (~0.5 km) is located at The University of Tennessee, in downtown Knoxville and near The Great Smoky Mountains National Park, an area known for problematic air quality. From atmospheric absorption spectra, boundary layer concentrations as well as total column abundances and vertical concentration profiles are derived. A record of more than 1000 solar-sourced atmospheric spectra covering a period greater than three years in duration is under analysis to characterize the limit of precision in total column abundance determinations for many gases such as O3, CO, CH4, N2O, HF and CO2. Initial efforts using atmospheric O2 as a calibration indicate the solar-sourced spectra may not meet the precision required for the highly accurate atmospheric CO2 quantification by such global efforts as the OCO and NDSC. However, the determined variability of CO2 and other gas concentrations is statistically significant and is indicative of local concentration fluxes pertinent to the regional atmospheric chemistry. This is therefore an important data record in the southeastern United States, a somewhat under- sampled geographic region. In addition to providing a means to improve the analysis of solar spectra, the open-path data is useful for elucidation of seasonal and diurnal trends in the trace gas concentrations. This provides an urban air quality monitor in addition to improving the description of the total atmospheric composition, as the open-path system is stable and permanent.

Emission sources of non-methane volatile organic compounds (NMVOCs) and their contribution to photochemical ozone (O3) formation at an urban atmosphere in western India.

NASA Astrophysics Data System (ADS)

Yadav, R.; Sahu, L. K.; Tripathi, N.; Pal, D.

2017-12-01

Atmospheric non-methane volatile organic compounds (NMVOCs) were measured at a sampling site in Udaipur city of western India during 2015 to recognize their pollution levels, variation characteristics, sources and photochemical reactivity. The samples were analyzed for NMVOCs using a Gas Chromatograph equipped with Flame Ionization Detector (GC/FID) and Thermal Desorption (TD) system. The main focus on understand the sources responsible for NMVOC emissions, and evaluating the role of the identified sources towards ozone formation. Hourly variations of various NMVOC species indicate that VOCs mixing ratios were influenced by photochemical removal with OH radicals for reactive species, secondary formation for oxygenated VOCs. In general, higher mixing ratios were observed during winter/pre-monsoon and lower levels during the monsoon season due to the seasonal change in meteorological, transport path of air parcel and boundary layer conditions. The high levels of propane (C3H8) and butane (C4H10) show the dominance of LPG over the study location. The correlation coefficients of typical NMVOC pairs (ethylene/propylene, propylene/isoprene, and ethane/propane) depicted that vehicular emission and natural gas leakages were important sources for atmospheric hydrocarbons in Udaipur. Based on the annual data, PMF analysis suggest the source factors namely biomass burning/ bio-fuel, automobile exhaust, Industrial/ natural gas/power plant emissions, petrol/Diesel, gasoline evaporation, and use of liquid petroleum gas (LPG) contribute to NMVOCs loading. The propylene-equivalent and ozone formation potential of NMVOCs have also been calculated in order to find out their OH reactivity and contribution to the photochemical ozone formation.

Dynamical characterization of inactivation path in voltage-gated Na+ ion channel by non-equilibrium response spectroscopy

PubMed Central

Pal, Krishnendu; Gangopadhyay, Gautam

2016-01-01

ABSTRACT Inactivation path of voltage gated sodium channel has been studied here under various voltage protocols as it is the main governing factor for the periodic occurrence and shape of the action potential. These voltage protocols actually serve as non-equilibrium response spectroscopic tools to study the ion channel in non-equilibrium environment. In contrast to a lot of effort in finding the crystal structure based molecular mechanism of closed-state(CSI) and open-state inactivation(OSI); here our approach is to understand the dynamical characterization of inactivation. The kinetic flux as well as energetic contribution of the closed and open- state inactivation path is compared here for voltage protocols, namely constant, pulsed and oscillating. The non-equilibrium thermodynamic quantities used in response to these voltage protocols serve as improved characterization tools for theoretical understanding which not only agrees with the previously known kinetic measurements but also predict the energetically optimum processes to sustain the auto-regulatory mechanism of action potential and the consequent inactivation steps needed. The time dependent voltage pattern governs the population of the conformational states which when couple with characteristic rate parameters, the CSI and OSI selectivity arise dynamically to control the inactivation path. Using constant, pulsed and continuous oscillating voltage protocols we have shown that during depolarization the OSI path is more favored path of inactivation however, in the hyper-polarized situation the CSI is favored. It is also shown that the re-factorisation of inactivated sodium channel to resting state occurs via CSI path. Here we have shown how the subtle energetic and entropic cost due to the change in the depolarization magnitude determines the optimum path of inactivation. It is shown that an efficient CSI and OSI dynamical profile in principle can characterize the open-state drug blocking phenomena. PMID:27367642

Influence of environmental parameters on the concentration of subsurface dissolved methane in two hydroelectric power plants in Brazil

NASA Astrophysics Data System (ADS)

Silva, M. G.; Marani, L.; Alvala, P. C.

2013-12-01

Methane (CH4) is a trace gas in the atmosphere of great importance for atmospheric chemistry as one of the main greenhouse gases. There are different sources with the largest individual production associated with the degradation of organic matter submerged in flooded areas. The amount of dissolved methane that reaches the surface depends on the production in the sediments and consumption in the water column. Both processes are associated with microbial activity and consequently dependent on the physico-chemical environmental conditions. The construction of hydroelectric dams cause flooding of areas near the river that can change the characteristics of the environment and cause changes in subsurface methane concentration. In this work, we studied two hydroelectric plants located in Brazil: Batalha (17°20'39.52"S, 47°29'34.29"W), under construction when the samples were take, and Itaipu (25°24'45.00"S, 54°35'39.00"W) which has been floated over 30 years ago. The water samples to determine dissolved methane were collected approximately 5 cm near the surface. In each collection point was measured depth, water temperature, pH and redox potential. The range of dissolved methane between the two dams was similar: 0.07-10.33 μg/l (Batalha) and 0.15-10.93 μg/l (Itaipu). However, the Batalha's average (4.04 × 3.43 μg/l; median = 3.66 μg/l) was higher than that observed in Itaipu (2.15 × 1.59 μg/l; median = 2.53 μg/l). The influence of environmental parameters on the concentration of dissolved methane was evaluated by multivariate statistical techniques (Principal Component Analysis - PCA). All of the parameters had some correlation with dissolved methane, however, the greatest contribution in Batalha was associated with pH while in Itaipu was the depth. The pH variation of the various points studied in Batalha may be associated with periods of drought and flooding of the river and hence the incorporation of organic matter in the environment. The organisms responsible for the production and oxidation of methane in water are very susceptible to changes in pH, resulting in variations in the amount of gas that is transported to the surface. In Itaipu, depth variation was shown to have more influence than the other parameters. The increase of the water column results in a longer path through which methane is transported, increasing the oxidation potencial by bacteria in the water, decreasing the amount of CH4 can be emitted to the atmosphere. The comparison between the two dams showed that the environmental parameters influences the the production and consumption of methane in water and the importance of each parameter can vary according to the characteristics of each reservoir.

cPath: open source software for collecting, storing, and querying biological pathways

PubMed Central

Cerami, Ethan G; Bader, Gary D; Gross, Benjamin E; Sander, Chris

2006-01-01

Background Biological pathways, including metabolic pathways, protein interaction networks, signal transduction pathways, and gene regulatory networks, are currently represented in over 220 diverse databases. These data are crucial for the study of specific biological processes, including human diseases. Standard exchange formats for pathway information, such as BioPAX, CellML, SBML and PSI-MI, enable convenient collection of this data for biological research, but mechanisms for common storage and communication are required. Results We have developed cPath, an open source database and web application for collecting, storing, and querying biological pathway data. cPath makes it easy to aggregate custom pathway data sets available in standard exchange formats from multiple databases, present pathway data to biologists via a customizable web interface, and export pathway data via a web service to third-party software, such as Cytoscape, for visualization and analysis. cPath is software only, and does not include new pathway information. Key features include: a built-in identifier mapping service for linking identical interactors and linking to external resources; built-in support for PSI-MI and BioPAX standard pathway exchange formats; a web service interface for searching and retrieving pathway data sets; and thorough documentation. The cPath software is freely available under the LGPL open source license for academic and commercial use. Conclusion cPath is a robust, scalable, modular, professional-grade software platform for collecting, storing, and querying biological pathways. It can serve as the core data handling component in information systems for pathway visualization, analysis and modeling. PMID:17101041

Active standoff detection of CH4 and N2O leaks using hard-target backscattered light using an open-path quantum cascade laser sensor

NASA Astrophysics Data System (ADS)

Diaz, Adrian; Thomas, Benjamin; Castillo, Paulo; Gross, Barry; Moshary, Fred

2016-05-01

Fugitive gas emissions from agricultural or industrial plants and gas pipelines are an important environmental concern as they contribute to the global increase of greenhouse gas concentrations. Moreover, they are also a security and safety concern because of possible risk of fire/explosion or toxicity. This study presents standoff detection of CH4 and N2O leaks using a quantum cascade laser open-path system that retrieves path-averaged concentrations by collecting the backscattered light from a remote hard target. It is a true standoff system and differs from other open-path systems that are deployed as point samplers or long-path transmission systems that use retroreflectors. The measured absorption spectra are obtained using a thermal intra-pulse frequency chirped DFB quantum cascade laser at ~7.7 µm wavelength range with ~200 ns pulse width. Making fast time resolved observations, the system simultaneously realizes high spectral resolution and range to the target, resulting in path-averaged concentration retrieval. The system performs measurements at high speed ~15 Hz and sufficient range (up to 45 m, ~148 feet) achieving an uncertainty of 3.1 % and normalized sensitivity of 3.3 ppm m Hz-1/2 for N2O and 9.3 % and normalized sensitivity of 30 ppm m Hz-1/2 for CH4 with a 0.31 mW average power QCL. Given these characteristics, this system is promising for mobile or multidirectional search and remote detection of gas leaks.

Accelerated path integral methods for atomistic simulations at ultra-low temperatures

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

Uhl, Felix, E-mail: felix.uhl@rub.de; Marx, Dominik; Ceriotti, Michele

2016-08-07

Path integral methods provide a rigorous and systematically convergent framework to include the quantum mechanical nature of atomic nuclei in the evaluation of the equilibrium properties of molecules, liquids, or solids at finite temperature. Such nuclear quantum effects are often significant for light nuclei already at room temperature, but become crucial at cryogenic temperatures such as those provided by superfluid helium as a solvent. Unfortunately, the cost of converged path integral simulations increases significantly upon lowering the temperature so that the computational burden of simulating matter at the typical superfluid helium temperatures becomes prohibitive. Here we investigate how accelerated pathmore » integral techniques based on colored noise generalized Langevin equations, in particular the so-called path integral generalized Langevin equation thermostat (PIGLET) variant, perform in this extreme quantum regime using as an example the quasi-rigid methane molecule and its highly fluxional protonated cousin, CH{sub 5}{sup +}. We show that the PIGLET technique gives a speedup of two orders of magnitude in the evaluation of structural observables and quantum kinetic energy at ultralow temperatures. Moreover, we computed the spatial spread of the quantum nuclei in CH{sub 4} to illustrate the limits of using such colored noise thermostats close to the many body quantum ground state.« less

Novel techniques for characterization of hydrocarbon emission sources in the Barnett Shale

NASA Astrophysics Data System (ADS)

Nathan, Brian Joseph

Changes in ambient atmospheric hydrocarbon concentrations can have both short-term and long-term effects on the atmosphere and on human health. Thus, accurate characterization of emissions sources is critically important. The recent boom in shale gas production has led to an increase in hydrocarbon emissions from associated processes, though the exact extent is uncertain. As an original quantification technique, a model airplane equipped with a specially-designed, open-path methane sensor was flown multiple times over a natural gas compressor station in the Barnett Shale in October 2013. A linear optimization was introduced to a standard Gaussian plume model in an effort to determine the most probable emission rate coming from the station. This is shown to be a suitable approach given an ideal source with a single, central plume. Separately, an analysis was performed to characterize the nonmethane hydrocarbons in the Barnett during the same period. Starting with ambient hourly concentration measurements of forty-six hydrocarbon species, Lagrangian air parcel trajectories were implemented in a meteorological model to extend the resolution of these measurements and achieve domain-fillings of the region for the period of interest. A self-organizing map (a type of unsupervised classification) was then utilized to reduce the dimensionality of the total multivariate set of grids into characteristic one-dimensional signatures. By also introducing a self-organizing map classification of the contemporary wind measurements, the spatial hydrocarbon characterizations are analyzed for periods with similar wind conditions. The accuracy of the classification is verified through assessment of observed spatial mixing ratio enhancements of key species, through site-comparisons with a related long-term study, and through a random forest analysis (an ensemble learning method of supervised classification) to determine the most important species for defining key classes. The hydrocarbon classification is shown to have performed very well in identifying expected signatures near and downwind-of oil and gas facilities with active permits, which showcases this method's usefulness for future regional hydrocarbon source-apportionment analyses.

Laboratory Investigation of Trace Gas Emissions from Biomass Burning on DoD Bases

NASA Astrophysics Data System (ADS)

Burling, I. R.; Yokelson, R. J.; Griffith, D. W.; Roberts, J. M.; Veres, P. R.; Warneke, C.; Johnson, T. J.

2009-12-01

Vegetation representing fuels commonly managed with prescribed fires was collected from five DoD bases and burned under controlled conditions at the USFS Firelab in Missoula, MT. The smoke emissions were measured with a large suite of state-of-the-art instrumentation. Seventy-seven fires were conducted and the smoke composition data will improve DoD land managers’ ability to assess the impact of prescribed fires on local air quality. A key instrument used in the measurement of the gas phase species in smoke was an open-path FTIR (OP-FTIR) spectrometer, built and operated by the Universities of Montana and Wollongong. The OP-FTIR has to date detected and quantified 20 gas phase species - CO2, CO, H2O, N2O, NO2, NO, HONO, NH3, HCl, SO2, CH4, CH3OH, HCHO, HCOOH, C2H2, C2H4, CH3COOH, HCN, propylene and furan. The spectra were analyzed using a non-linear least squares fitting routine that included reference spectra recently acquired at the Pacific Northwest National Laboratories. Preliminary results from the OP-FTIR analysis are reported here. Of particular interest, gas-phase nitrous acid (HONO) was detected simultaneously by the OP-FTIR and negative-ion proton-transfer chemical ionization spectrometer (NI-PT-CIMS), with preliminary fire-integrated molar emission ratios (relative to NOx) ranging from approximately 0.03 to 0.20, depending on the vegetation type. HONO is an important precursor in the production of OH, the primary oxidizing species in the atmosphere. There existed little previous data documenting HONO emissions from either wild or prescribed fires. The non-methane organic emissions were dominated by oxygenated species, which can be further oxidized and thus involved in secondary aerosol formation. Elevated amounts of gas-phase HCl were also detected in the smoke, with the amounts varying depending on location and vegetation type.

HAI: A new TDLAS hygrometer for the HALO research aircraft

NASA Astrophysics Data System (ADS)

Klostermann, Tim; Afchine, Armin; Barthel, Jochen; Höh, Matthias; Wagner, Steven; Witzel, Oliver; Saathoff, Harald; Schiller, Cornelius; Ebert, Volker

2010-05-01

Water vapor is the most important greenhouse gas in the Earth's atmosphere and a key component for several physical and chemical processes. Therefore it is a key parameter to be measured during most research campaigns. The Hygrometer for Atmospheric Investigations (HAI) is especially designed for operations on the research aircraft HALO (High Altitude and LOng range research aircraft). HAI permits both, the in-situ measurement of water vapor with an open-path cell and the measurement of total water with an extractive close-path absorption cell. We are using TDLAS (Tunable Diode Laser Absorption Spectroscopy) in two water absorption bands with different line strength to increase the dynamical range. With this concept it is possible to measure from the middle troposphere up to the stratosphere. The open-path cell outside of the fuselage consists of a robust, aerodynamically designed aluminum structure with a single integrated White-cell for both laser beams. Although the mirror separation is only 15cm the cell allows an open absorption path of 4.8m. The detection of higher H2O concentrations is realized with a fiber coupled 1.4µm DFB diode laser. Inside the UTLS layer were small concentrations in the low ppm range are common, we employ up to 20 times stronger fundamental ro-vibration lines of the water molecule near 2.6µm. To supply this, the fiber coupled 2.6µm laser setup was developed and is a part of the HAI. Both detection wavelengths are introduced in the same open path cell via glass fibers which provide water measurements with a minimum of parasitic absorption. We will present the spectrometer design for high-quality airborne water measurements. Furthermore, first laboratory measurements will be shown.

Relative permeability of hydrate-bearing sediments from percolation theory and critical path analysis: theoretical and experimental results

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

Daigle, Hugh; Rice, Mary Anna; Daigle, Hugh

Relative permeabilities to water and gas are important parameters for accurate modeling of the formation of methane hydrate deposits and production of methane from hydrate reservoirs. Experimental measurements of gas and water permeability in the presence of hydrate are difficult to obtain. The few datasets that do exist suggest that relative permeability obeys a power law relationship with water or gas saturation with exponents ranging from around 2 to greater than 10. Critical path analysis and percolation theory provide a framework for interpreting the saturation-dependence of relative permeability based on percolation thresholds and the breadth of pore size distributions, whichmore » may be determined easily from 3-D images or gas adsorption-desorption hysteresis. We show that the exponent of the permeability-saturation relationship for relative permeability to water is related to the breadth of the pore size distribution, with broader pore size distributions corresponding to larger exponents. Relative permeability to water in well-sorted sediments with narrow pore size distributions, such as Berea sandstone or Toyoura sand, follows percolation scaling with an exponent of 2. On the other hand, pore-size distributions determined from argon adsorption measurements we performed on clays from the Nankai Trough suggest that relative permeability to water in fine-grained intervals may be characterized by exponents as large as 10 as determined from critical path analysis. We also show that relative permeability to the gas phase follows percolation scaling with a quadratic dependence on gas saturation, but the threshold gas saturation for percolation changes with hydrate saturation, which is an important consideration in systems in which both hydrate and gas are present, such as during production from a hydrate reservoir. Our work shows how measurements of pore size distributions from 3-D imaging or gas adsorption may be used to determine relative permeabilities.« less

"I CAMMINI DELLA REGINA" - Open Source based tools for preserving and culturally exploring historical traffic routes.

NASA Astrophysics Data System (ADS)

Cannata, Massimiliano; Colombo, Massimo; Antonovic, Milan; Cardoso, Mirko; Delucchi, Andrea; Gianocca, Giancarlo; Brovelli, Maria Antonia

2015-04-01

"I CAMMINI DELLA REGINA" (The Via Regina Paths) is an Interreg project funded within the transnational cooperation program between Italy and Switzerland 2007-2013. The aim of this project is the preservation and valorization of the cultural heritage linked to the walking historically paths crossing, connecting and serving the local territories. With the approach of leveraging the already existing tools, which generally consist of technical descriptions of the paths, the project uses the open source geospatial technologies to deploy innovative solutions which can fill some of the gaps in historical-cultural tourism offers. The Swiss part, and particularly the IST-SUPSI team, has been focusing its activities in the realization of two innovative solutions: a mobile application for the survey of historical paths and a storytelling system for immersive cultural exploration of the historical paths. The former, based on Android, allows to apply in a revised manner a consolidated and already successfully used methodology of survey focused on the conservation of the historical paths (Inventory of historical traffic routes in Switzerland). Up to now operators could rely only on hand work based on a combination of notes, pictures and GPS devices synthesized in manually drawn maps; this procedure is error prone and shows many problems both in data updating and extracting for elaborations. Thus it has been created an easy to use interface which allows to map, according to a newly developed spatially enabled data model, paths, morphological elements, and multimedia notes. When connected to the internet the application can send the data to a web service which, after applying linear referencing and further elaborating the data, makes them available using open standards. The storytelling system has been designed to provide users with cultural insights embedded in a multimedial and immersive geospatial portal. Whether the tourist is exploring physically or virtually the desired historical path, the system will provide notifications and immersive multimedia information that foster a new sight of the territory: award of the culture and history of the place thanks to attractive description of the geological, land use, historical and ethnographic contexts. The technologies used for these developments are: mongoDB, tornado, Android SDK, geoserver, bootstrap, OpenLayers, HTML5, CSS3, JQuery. The approach, methodologies and technical implementations will be discussed and presented.

Trace-gas Spectroscopy of Methane on a Silicon Photonic Chip

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

Zhang, Eric; Xiong, Chi; Martin, Yves

Recent advances in hybrid integrated silicon photonic (SiPh) technologies are enabling the migration of conventional free-space optical spectroscopic sensors onto a compact on-chip platform [1-3]. In addition to the small spatial footprint and power efficiency, we envision such sensors to be scalably manufactured using existing CMOS-compatible foundry processes, thus providing disruptive SWaP-C (size, weight, power, and cost) benefits in contrast to commercially available optical sensors. Initial demonstration of evanescent TDLAS (tunable diode laser absorption spectroscopy) of methane (CH4) on a passive SiPh waveguide has indicated minimum fractional absorption of (αL)min = 3.3×10-5 Hz-1/2, which is on-par with state-of-art open-path TDLASmore » sensor systems [4]. Given the general recent movement toward cleaner fuels, CH4 fugitive emissions monitoring is of significant interest given the extremely high radiative forcing potential [5]. For a nominal waveguide length of 30 cm with Γ = 25 % evanescent exposure, this corresponds to ~ 10 ppmv detection sensitivity at 1 s integration time, and further sensitivity enhancement is expected with even longer waveguides, as the laser RIN typically dominates our measurements at nominal waveguide lengths. Despite the excellent sensitivities for short-term integration periods, long-term measurements (> 10 s) are potentially limited on a silicon platform due to the high material thermo-optic coefficient, resulting in significant susceptibility of Fabry-Perot etalons to drift in the presence of even small (~ 1 mK) thermal fluctuations. To this end, customized spectral fitting algorithms have played a significant role in both fringe drift mitigation and peak detection fidelity (e.g. in the presence of a passing CH4 plume), which are crucial for enhancing long-term stability without the need for frequent sensor recalibration. A variety of spectral algorithms have been designed for this purpose, and details will be presented at the meeting.« less

Identification of Acetylene on Titan's Surface

NASA Astrophysics Data System (ADS)

Singh, S.; McCord, T. B.; Rodriguez, S.; Combe, J. P.; Cornet, T.; Le Mouelic, S.; Maltagliati, L.; Chevrier, V.; Clark, R. N.

2015-12-01

Titan's atmosphere is opaque in the near infrared due to gaseous absorptions, mainly by methane, and scattering by aerosols, except in a few "transparency windows" (e.g., Sotin et al., 2005). Thus, the composition of Titan surface remains difficult to access from space and is still poorly constrained, limited to ethane in the polar lakes (Brown et al., 2008) and a few possible organic molecules on the surface (Clark et al., 2010). Photochemical models suggest that most of the organic compounds formed in the atmosphere are heavy enough to condense and build up at the surface in liquid and solid states over geological timescale (Cordier et al., 2009, 2011). Acetylene (C2H2) is one of the most abundant organic molecules in the atmosphere and thus thought to present on the surface as well. Here we report direct evidence of solid C2H2 on Titan's surface using Cassini Visual and Infrared Mapping Spectrometer (VIMS) data. By comparing VIMS observations and laboratory measurements of solid and liquid C2H2, we identify a specific absorption at 1.55 µm that is widespread over Titan but is particularly strong in the brightest terrains. This surface variability suggests that C2H2 is mobilized by surface processes, such as surface weathering, topography, and dissolution/evaporation. The detection of C2H2 on the surface of Titan opens new paths to understand and constrain Titan's surface activity. Since C2H2 is highly soluble in Titan liquids (Singh et al. 2015), it can easily dissolve in methane/ethane and may play an important role in carving of fluvial channels and existence of karstic lakes at higher latitudes on Titan. These processes imply the existence of a dynamic surface with a continued history of erosion and deposition of C2H2 on Titan.

Non-methane organic gas emissions from biomass burning: identification, quantification, and emission factors from PTR-ToF during the FIREX 2016 laboratory experiment

NASA Astrophysics Data System (ADS)

Koss, Abigail R.; Sekimoto, Kanako; Gilman, Jessica B.; Selimovic, Vanessa; Coggon, Matthew M.; Zarzana, Kyle J.; Yuan, Bin; Lerner, Brian M.; Brown, Steven S.; Jimenez, Jose L.; Krechmer, Jordan; Roberts, James M.; Warneke, Carsten; Yokelson, Robert J.; de Gouw, Joost

2018-03-01

Volatile and intermediate-volatility non-methane organic gases (NMOGs) released from biomass burning were measured during laboratory-simulated wildfires by proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF). We identified NMOG contributors to more than 150 PTR ion masses using gas chromatography (GC) pre-separation with electron ionization, H3O+ chemical ionization, and NO+ chemical ionization, an extensive literature review, and time series correlation, providing higher certainty for ion identifications than has been previously available. Our interpretation of the PTR-ToF mass spectrum accounts for nearly 90 % of NMOG mass detected by PTR-ToF across all fuel types. The relative contributions of different NMOGs to individual exact ion masses are mostly similar across many fires and fuel types. The PTR-ToF measurements are compared to corresponding measurements from open-path Fourier transform infrared spectroscopy (OP-FTIR), broadband cavity-enhanced spectroscopy (ACES), and iodide ion chemical ionization mass spectrometry (I- CIMS) where possible. The majority of comparisons have slopes near 1 and values of the linear correlation coefficient, R2, of > 0.8, including compounds that are not frequently reported by PTR-MS such as ammonia, hydrogen cyanide (HCN), nitrous acid (HONO), and propene. The exceptions include methylglyoxal and compounds that are known to be difficult to measure with one or more of the deployed instruments. The fire-integrated emission ratios to CO and emission factors of NMOGs from 18 fuel types are provided. Finally, we provide an overview of the chemical characteristics of detected species. Non-aromatic oxygenated compounds are the most abundant. Furans and aromatics, while less abundant, comprise a large portion of the OH reactivity. The OH reactivity, its major contributors, and the volatility distribution of emissions can change considerably over the course of a fire.

Can we reconcile our understanding of the atmospheric methane budget over the past decades with atmospheric observations?

NASA Astrophysics Data System (ADS)

Bruhwiler, L. M.; Matthews, E.

2007-12-01

The balance of methane in the atmosphere is determined by surface emission, and losses due to uptake in soils and reaction with the hydroxyl radical. The atmospheric abundance of methane has risen by about a factor of three since pre-industrial times, but the growth rate has decreased substantially since the 1990's. Thus, global atmospheric methane appears to have equilibrated to around 1780 ppb subject to considerable interannual variability, the causes of which are not well-understood. Methane emissions are expected to increase in the future due to increases in fossil fuel use and possible changes in wetlands at high-latitudes, and it is therefore important to test our understanding of the methane budget over the last two decades against network observations of atmospheric methane. Issues of interest are whether we can match the rise in methane over the 1980's, whether we can explain the decrease in growth rate during the 1990's, and whether we are able to simulate the observed interannual variability in the observations. We will show results from a multi-decade model simulation using analyzed meteorology from the ERA-40 reanalysis over this period. New times series of methane sources for 1980 through the early 2000's are used in the simulation. Anthropogenic sources include fossil fuels with a total of 7 fuel-process emission combinations associated with mining, processing, transport and distribution of coal, natural gas and oil; ruminant animals and manure based on regionally-representative profiles of bovine populations ; landfills including the impact of on- site methane capture; and irrigated rice cultivation based on seasonal rice-cropping calendars. Natural sources we include are biomass burning from the GFED emission data base, oceans, termites, and natural wetlands using a multiple-regression model derived from a process-based model. If time permits, we will also show preliminary results of a methane data assimilation using the Cooperative Air-Sampling and GMD network observations, and our new estimates of methane sources.

Biogenic Methane Generation Potential in the Eastern Nankai Trough, Japan: Effect of Reaction Temperature and Total Organic Carbon

NASA Astrophysics Data System (ADS)

Aung, T. T.; Fujii, T.; Amo, M.; Suzuki, K.

2017-12-01

Understanding potential of methane flux from the Pleistocene fore-arc basin filled turbiditic sedimentary formation along the eastern Nankai Trough is important in the quantitative assessment of gas hydrate resources. We considered generated methane could exist in sedimentary basin in the forms of three major components, and those are methane in methane hydrate, free gas and methane dissolved in water. Generation of biomethane strongly depends on microbe activity and microbes in turn survive in diverse range of temperature, salinity and pH. This study aims to understand effect of reaction temperature and total organic carbon on generation of biomethane and its components. Biomarker analysis and cultural experiment results of the core samples from the eastern Nankai Trough reveal that methane generation rate gets peak at various temperature ranging12.5°to 35°. Simulation study of biomethane generation was made using commercial basin scale simulator, PetroMod, with different reaction temperature and total organic carbon to predict how these effect on generation of biomethane. Reaction model is set by Gaussian distribution with constant hydrogen index and standard deviation of 1. Series of simulation cases with peak reaction temperature ranging 12.5°to 35° and total organic carbon of 0.6% to 3% were conducted and analyzed. Simulation results show that linear decrease in generation potential while increasing reaction temperature. But decreasing amount becomes larger in the model with higher total organic carbon. At higher reaction temperatures, >30°, extremely low generation potential was found. This is due to the fact that the source formation modeled is less than 1 km in thickness and most of formation do not reach temperature more than 30°. In terms of the components, methane in methane hydrate and free methane increase with increasing TOC. Drastic increase in free methane was observed in the model with 3% of TOC. Methane amount dissolved in water shows almost same for all models.

Temporal variation of ecosystem scale methane emission from a boreal fen in relation to common model drivers

NASA Astrophysics Data System (ADS)

Rinne, J.; Tuittila, E. S.; Peltola, O.; Li, X.; Raivonen, M.; Alekseychik, P.; Haapanala, S.; Pihlatie, M.; Aurela, M.; Mammarella, I.; Vesala, T.

2017-12-01

Models for calculating methane emission from wetland ecosystems typically relate the methane emission to carbon dioxide assimilation. Other parameters that control emission in these models are e.g. peat temperature and water table position. Many of these relations are derived from spatial variation between chamber measurements by space-for-time approach. Continuous longer term ecosystem scale methane emission measurements by eddy covariance method provide us independent data to assess the validity of the relations derived by space-for-time approach.We have analyzed eleven-year methane flux data-set, measured at a boreal fen, together with data on environmental parameters and carbon dioxide exchange to assess the relations to typical model drivers. The data was obtained by the eddy covariance method at Siikaneva mire complex, Southern Finland, during 2005-2015. The methane flux showed seasonal cycles in methane emission, with strongest correlation with peat temperature at 35 cm depth. The temperature relation was exponential throughout the whole peat temperature range of 0-16°C. The methane emission normalized to remove temperature dependence showed a non-monotonous relation on water table and positive correlation with gross primary production (GPP). However, inclusion of these as explaining variables improved algorithm-measurement correlation only slightly, with r2=0.74 for exponential temperature dependent algorithm, r2=0.76 for temperature - water table algorithm, and r2=0.79 for temperature - GPP algorithm. The methane emission lagged behind net ecosystem exchange (NEE) and GPP by two to three weeks. Annual methane emission ranged from 8.3 to 14 gC m-2, and was 20 % of NEE and 2.8 % of GPP. The inter-annual variation of methane emission was of similar magnitude as that of GPP and ecosystem respiration (Reco), but much smaller than that of NEE. The interannual variability of June-September average methane emission correlated significantly with that of GPP indicating a close link between these two processes in boreal fen ecosystems.

Episodic methane release events from Last Glacial marginal sediments in the western North Pacific

NASA Astrophysics Data System (ADS)

Uchida, Masao; Shibata, Yasuyuki; Ohkushi, Ken'ichi; Ahagon, Naokazu; Hoshiba, Mayumi

2004-08-01

According to recent observations of anomalous bottom-simulating reflections (BSR), the northwest Pacific marginal sediments around Japan main islands bear large abundances of methane hydrate [, 2002]. During the Last Glacial, direct and indirect evidence accumulated from geochemical data suggests that methane episodically released from hydrate trapped in the seafloor sediments [, 1995; , 2003; , 2000]. Here we show that marginal sediments from the western North Pacific contain a hopanoid 17α(H), 21β(H)-hop-22(29)-ene (diploptene) derived from the activity of methanotrophic bacteria in water column and/or surface sediment during a warming period (Interstadial 3) in the Last Glacial. The carbon isotopic compositions of diploptene range between -41.0‰ and -27.9‰ (relative to PDB). In the horizon indicative of a contribution of methanotrophic bacteria, foraminiferal isotope signals were also found with highly depleted 13C compositions of planktonic foraminifera (˜-1.9‰, PDB) and benthic foraminifera (˜-0.8‰, PDB), suggesting indirect records of enhanced incorporation of 13C-depleted CO2 formed by methanotrophic process that use 12C-enriched methane as their main source of carbon. From combined isotopic data of molecular (diploptene) and foraminifera, the most prominent signal of methane release was detected in the sediments deposited around 25.4 cal. kyr BP (˜100 year time span), corresponding to the Interstadial 3. This is the first evidence of methane hydrate instability in the open western North Pacific during the Last Glacial. Considering the glacial-interglacial hydrographic conditions in this region, the instability of methane hydrate may be modulated by intermediate water warming and/or the lowering of sea level. Our results suggest that the western North Pacific marginal regions may be a profound effect on rapid global warming climate changes during the Last Glacial.

Thermodynamic and structural signatures of water-driven methane-methane attraction in coarse-grained mW water.

PubMed

Song, Bin; Molinero, Valeria

2013-08-07

Hydrophobic interactions are responsible for water-driven processes such as protein folding and self-assembly of biomolecules. Microscopic theories and molecular simulations have been used to study association of a pair of methanes in water, the paradigmatic example of hydrophobic attraction, and determined that entropy is the driving force for the association of the methane pair, while the enthalpy disfavors it. An open question is to which extent coarse-grained water models can still produce correct thermodynamic and structural signatures of hydrophobic interaction. In this work, we investigate the hydrophobic interaction between a methane pair in water at temperatures from 260 to 340 K through molecular dynamics simulations with the coarse-grained monatomic water model mW. We find that the coarse-grained model correctly represents the free energy of association of the methane pair, the temperature dependence of free energy, and the positive change in entropy and enthalpy upon association. We investigate the relationship between thermodynamic signatures and structural order of water through the analysis of the spatial distribution of the density, energy, and tetrahedral order parameter Qt of water. The simulations reveal an enhancement of tetrahedral order in the region between the first and second hydration shells of the methane molecules. The increase in tetrahedral order, however, is far from what would be expected for a clathrate-like or ice-like shell around the solutes. This work shows that the mW water model reproduces the key signatures of hydrophobic interaction without long ranged electrostatics or the need to be re-parameterized for different thermodynamic states. These characteristics, and its hundred-fold increase in efficiency with respect to atomistic models, make mW a promising water model for studying water-driven hydrophobic processes in more complex systems.

Electrical properties of methane hydrate + sediment mixtures: The σ of CH 4 Hydrate + Sediment

DOE PAGES

Du Frane, Wyatt L.; Stern, Laura A.; Constable, Steven; ...

2015-07-30

Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. We built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EMmore » field surveys. We report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. Finally, these results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.« less

Scanning, standoff TDLAS leak imaging and quantification

NASA Astrophysics Data System (ADS)

Wainner, Richard T.; Aubut, Nicholas F.; Laderer, Matthew C.; Frish, Michael B.

2017-05-01

This paper reports a novel quantitative gas plume imaging tool, based on active near-infrared Backscatter Tunable Diode Laser Absorption Spectroscopy (b-TDLAS) technology, designed for upstream natural gas leak applications. The new tool integrates low-cost laser sensors with video cameras to create a highly sensitive gas plume imager that also quantifies emission rate, all in a lightweight handheld ergonomic package. It is intended to serve as a lower-cost, higherperformance, enhanced functionality replacement for traditional passive non-quantitative mid-infrared Optical Gas Imagers (OGI) which are utilized by industry to comply with natural gas infrastructure Leak Detection and Repair (LDAR) requirements. It addresses the need for reliable, robust, low-cost sensors to detect and image methane leaks, and to quantify leak emission rates, focusing on inspections of upstream oil and gas operations, such as well pads, compressors, and gas plants. It provides: 1) Colorized quantified images of path-integrated methane concentration. The images depict methane plumes (otherwise invisible to the eye) actively interrogated by the laser beam overlaid on a visible camera image of the background. The detection sensitivity exceeds passive OGI, thus simplifying the manual task of leak detection and location; and 2) Data and algorithms for using the quantitative information gathered by the active detection technique to deduce plume flux (i.e. methane emission rate). This key capability will enable operators to prioritize leak repairs and thereby minimize the value of lost product, as well as to quantify and minimize greenhouse gas emissions, using a tool that meets EPA LDAR imaging equipment requirements.

Electrical properties of methane hydrate + sediment mixtures: The σ of CH 4 Hydrate + Sediment

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

Du Frane, Wyatt L.; Stern, Laura A.; Constable, Steven

Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. We built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EMmore » field surveys. We report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. Finally, these results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.« less

Determination of the Zone Endangered by Methane Explosion in Goaf with Caving of Longwalls Ventilated on "Y" System

NASA Astrophysics Data System (ADS)

Brodny, Jarosław; Tutak, Magdalena

2016-12-01

One of the most dangerous and most commonly present risks in hard coal mines is methane hazard. During exploitation by longwall system with caving, methane is emitted to mine heading from the mined coal and coal left in a pile. A large amount of methane also flows from neighboring seams through cracks and fissures formed in rock mass. In a case of accumulation of explosive methane concentration in goaf zone and with appropriate oxygen concentration and occurrence of initials (e.g. spark or endogenous fire), it may come to the explosion of this gas. In the paper there are presented results of numerical analysis of mixture of air and methane streams flow through the real heading system of a mine, characterized by high methane hazard. The aim of the studies was to analyze the ventilation system of considered heading system and determination of braking zones in goaf zone, in which dangerous and explosive concertation of methane can occur with sufficient oxygen concentration equal to at least 12%. Determination of position of these zones is necessary for the selection of appropriate parameters of the ventilation system to ensure safety of the crew. Analysis of the scale of methane hazard allows to select such a ventilation system of exploitation and neighboring headings that ensures chemical composition of mining atmosphere required by regulation, and required efficiency of methane drainage. The obtained results clearly show that numerical methods, combined with the results of tests in real conditions can be successfully used for the analysis of variants of processes related to ventilation of underground mining, and also in the analysis of emergency states.

Differentiation of pre-existing trapped methane from thermogenic methane in an igneous-intruded coal by hydrous pyrolysis

USGS Publications Warehouse

Dias, Robert F.; Lewan, Michael D.; Birdwell, Justin E.; Kotarba, Maciej J.

2014-01-01

So as to better understand how the gas generation potential of coal changes with increasing rank, same-seam samples of bituminous coal from the Illinois Basin that were naturally matured to varying degrees by the intrusion of an igneous dike were subjected to hydrous pyrolysis (HP) conditions of 360 °C for 72 h. The accumulated methane in the reactor headspace was analyzed for δ13C and δ2H, and mol percent composition. Maximum methane production (9.7 mg/g TOC) occurred in the most immature samples (0.5 %Ro), waning to minimal methane values at 2.44 %Ro (0.67 mg/g TOC), and rebounding to 3.6 mg/g TOC methane in the most mature sample (6.76 %Ro). Methane from coal with the highest initial thermal maturity (6.76 %Ro) shows no isotopic dependence on the reactor water and has a microbial δ13C value of −61‰. However, methane from coal of minimal initial thermal maturity (0.5 %Ro) shows hydrogen isotopic dependence on the reaction water and has a δ13C value of −37‰. The gas released from coals under hydrous pyrolysis conditions represents a quantifiable mixture of ancient (270 Ma) methane (likely microbial) that was generated in situ and trapped within the rock during the rapid heating by the dike, and modern (laboratory) thermogenic methane that was generated from the indigenous organic matter due to thermal maturation induced by hydrous pyrolysis conditions. These findings provide an analytical framework for better assessment of natural gas sources and for differentiating generated gas from pre-existing trapped gas in coals of various ranks.

Ground based mobile isotopic methane measurements in the Front Range, Colorado

NASA Astrophysics Data System (ADS)

Vaughn, B. H.; Rella, C.; Petron, G.; Sherwood, O.; Mielke-Maday, I.; Schwietzke, S.

2014-12-01

Increased development of unconventional oil and gas resources in North America has given rise to attempts to monitor and quantify fugitive emissions of methane from the industry. Emission estimates of methane from oil and gas basins can vary significantly from one study to another as well as from EPA or State estimates. New efforts are aimed at reconciling bottom-up, or inventory-based, emission estimates of methane with top-down estimates based on atmospheric measurements from aircraft, towers, mobile ground-based vehicles, and atmospheric models. Attributing airborne measurements of regional methane fluxes to specific sources is informed by ground-based measurements of methane. Stable isotopic measurements (δ13C) of methane help distinguish between emissions from the O&G industry, Confined Animal Feed Operations (CAFO), and landfills, but analytical challenges typically limit meaningful isotopic measurements to individual point sampling. We are developing a toolbox to use δ13CH4 measurements to assess the partitioning of methane emissions for regions with multiple methane sources. The method was applied to the Denver-Julesberg Basin. Here we present data from continuous isotopic measurements obtained over a wide geographic area by using MegaCore, a 1500 ft. tube that is constantly filled with sample air while driving, then subsequently analyzed at slower rates using cavity ring down spectroscopy (CRDS). Pressure, flow and calibration are tightly controlled allowing precise attribution of methane enhancements to their point of collection. Comparisons with point measurements are needed to confirm regional values and further constrain flux estimates and models. This effort was made in conjunction with several major field campaigns in the Colorado Front Range in July-August 2014, including FRAPPÉ (Front Range Air Pollution and Photochemistry Experiment), DISCOVER-AQ, and the Air Water Gas NSF Sustainability Research Network at the University of Colorado.

Fine-Scale Community Structure Analysis of ANME in Nyegga Sediments with High and Low Methane Flux

PubMed Central

Roalkvam, Irene; Dahle, Håkon; Chen, Yifeng; Jørgensen, Steffen Leth; Haflidason, Haflidi; Steen, Ida Helene

2012-01-01

To obtain knowledge on how regional variations in methane seepage rates influence the stratification, abundance, and diversity of anaerobic methanotrophs (ANME), we analyzed the vertical microbial stratification in a gravity core from a methane micro-seeping area at Nyegga by using 454-pyrosequencing of 16S rRNA gene tagged amplicons and quantitative PCR. These data were compared with previously obtained data from the more active G11 pockmark, characterized by higher methane flux. A down core stratification and high relative abundance of ANME were observed in both cores, with transition from an ANME-2a/b dominated community in low-sulfide and low methane horizons to ANME-1 dominance in horizons near the sulfate-methane transition zone. The stratification was over a wider spatial region and at greater depth in the core with lower methane flux, and the total 16S rRNA copy numbers were two orders of magnitude lower than in the sediments at G11 pockmark. A fine-scale view into the ANME communities at each location was achieved through operational taxonomical units (OTU) clustering of ANME-affiliated sequences. The majority of ANME-1 sequences from both sampling sites clustered within one OTU, while ANME-2a/b sequences were represented in unique OTUs. We suggest that free-living ANME-1 is the most abundant taxon in Nyegga cold seeps, and also the main consumer of methane. The observation of specific ANME-2a/b OTUs at each location could reflect that organisms within this clade are adapted to different geochemical settings, perhaps due to differences in methane affinity. Given that the ANME-2a/b population could be sustained in less active seepage areas, this subgroup could be potential seed populations in newly developed methane-enriched environments. PMID:22715336

Comparative Analysis of the Methane Data Products from the Tropospheric Emission Spectrometer and the Atmospheric Infrared Sounder.

NASA Astrophysics Data System (ADS)

Pagano, T. J.; Worden, J. R.

2016-12-01

Methane is the second most powerful greenhouse gas with a highly positive radiative forcing of 0.48 W/m2 (IPCC 2013). Global concentrations of methane have been steadily increasing since 2007 (Bruhwiler 2014), raising concerns about methane's impact on the future global climate. For about the last decade, the Tropospheric Emission Spectrometer (TES) on the Earth Observing System (EOS) Aura spacecraft has been detecting several trace gas species in the troposphere including methane. The goal of this study is to compare TES methane products to that of the Atmospheric Infrared Sounder (AIRS) on the EOS Aqua spacecraft so that scientific investigations may be transferred from TES to AIRS. The two instruments fly in the afternoon constellations (A-Train), providing numerous coincident measurements for comparison. In addition, they also have a similar spectral range, (3.3 to 15.4 µm) for TES (Beer, 2006) and (3.7 to 15.4 µm) for AIRS (Chahine, 2006), making both satellites sensitive to the mid and upper troposphere. This makes them ideal candidates to compare methane data products. In a previous study, total column methane was mapped and global zonal averages were compared. It was found that bias of the total column measurements between the two sounders was about constant over tropical and subtropical regions. However, because AIRS spectral resolution is lower than that of the TES, it is important to analyze the difference in vertical sensitivity. In this study, we will construct vertical profiles of methane concentration and compare them statistically through RMS difference and bias to better understand these differences. In addition, we will compare the error profile and total column errors of the TES and AIRS methane from the data to better understand error characteristics of the products.

Using Unmanned Air Systems to Monitor Methane in the Atmosphere

NASA Technical Reports Server (NTRS)

Clow, Jacqueline; Smith, Jeremy Christopher

2016-01-01

Methane is likely to be an important contributor to global warming, and our current knowledge of its sources, distributions, and transport is insufficient. It is estimated that there could be from 7.5 to 400 billion tons carbon-equivalent of methane in the arctic region, a broad range that is indicative of the uncertainty within the Earth Science community. Unmanned Air Systems (UASs) are often used for combat or surveillance by the military, but they also have been used for Earth Science field missions. In this study, we will analyze the utility of the NASA Global Hawk and the Aurora Flight Sciences Orion UASs compared to the manned DC-8 aircraft for conducting a methane monitoring mission. The mission will focus on the measurement of methane along the boundaries of Arctic permafrost thaw and melting glaciers. The use of Long Endurance UAS brings a new range of possibilities including the ability to obtain long- term and persistent observations and to significantly augment methane measurements/retrievals collected by satellite. Furthermore, we discuss the future of long endurance UAS and their potential for science applications in the next twenty to twenty-five years.

Analysis on Operating Parameter Design to Steam Methane Reforming in Heat Application RDE

NASA Astrophysics Data System (ADS)

Dibyo, Sukmanto; Sunaryo, Geni Rina; Bakhri, Syaiful; Zuhair; Irianto, Ign. Djoko

2018-02-01

The high temperature reactor has been developed with various power capacities and can produce electricity and heat application. One of heat application is used for hydrogen production. Most hydrogen production occurs by steam reforming that operated at high temperature. This study aims to analyze the feasibility of heat application design of RDE reactor in the steam methane reforming for hydrogen production using the ChemCAD software. The outlet temperature of cogeneration heat exchanger is analyzed to be applied as a feed of steam reformer. Furthermore, the additional heater and calculating amount of fuel usage are described. Results show that at a low mass flow rate of feed, its can produce a temperature up to 480°C. To achieve the temperature of steam methane reforming of 850°C the additional fired heater was required. By the fired heater, an amount of fuel usage is required depending on the Reformer feed temperature produced from the heat exchanger of the cogeneration system.

In-situ study of the gas-phase composition and temperature of an intermediate-temperature solid oxide fuel cell anode surface fed by reformate natural gas

NASA Astrophysics Data System (ADS)

Santoni, F.; Silva Mosqueda, D. M.; Pumiglia, D.; Viceconti, E.; Conti, B.; Boigues Muñoz, C.; Bosio, B.; Ulgiati, S.; McPhail, S. J.

2017-12-01

An innovative experimental setup is used for in-depth and in-operando characterization of solid oxide fuel cell anodic processes. This work focuses on the heterogeneous reactions taking place on a 121 cm2 anode-supported cell (ASC) running with a H2, CH4, CO2, CO and steam gas mixture as a fuel, using an operating temperature of 923 K. The results have been obtained by analyzing the gas composition and temperature profiles along the anode surface in different conditions: open circuit voltage (OCV) and under two different current densities, 165 mA cm-2 and 330 mA cm-2, corresponding to 27% and 54% of fuel utilization, respectively. The gas composition and temperature analysis results are consistent, allowing to monitor the evolution of the principal chemical and electrochemical reactions along the anode surface. A possible competition between CO2 and H2O in methane internal reforming is shown under OCV condition and low current density values, leading to two different types of methane reforming: Steam Reforming and Dry Reforming. Under a current load of 40 A, the dominance of exothermic reactions leads to a more marked increase of temperature in the portion of the cell close to the inlet revealing that current density is not uniform along the anode surface.

Structural control of coalbed methane production in Alabama

USGS Publications Warehouse

Pashin, J.C.; Groshong, R.H.

1998-01-01

Thin-skinned structures are distributed throughout the Alabama coalbed methane fields, and these structures affect the production of gas and water from coal-bearing strata. Extensional structures in Deerlick Creek and Cedar Cove fields include normal faults and hanging-wall rollovers, and area balancing indicates that these structures are detached in the Pottsville Formation. Compressional folds in Gurnee and Oak Grove fields, by comparison, are interpreted to be detachment folds formed above decollements at different stratigraphic levels. Patterns of gas and water production reflect the structural style of each field and further indicate that folding and faulting have affected the distribution of permeability and the overall success of coalbed methane operations. Area balancing can be an effective way to characterize coalbed methane reservoirs in structurally complex regions because it constrains structural geometry and can be used to determine the distribution of layer-parallel strain. Comparison of calculated requisite strain and borehole expansion data from calliper logs suggests that strain in coalbed methane reservoirs is predictable and can be expressed as fracturing and small-scale faulting. However, refined methodology is needed to analyze heterogeneous strain distributions in discrete bed segments. Understanding temporal variation of production patterns in areas where gas and water production are influenced by map-scale structure will further facilitate effective management of coalbed methane fields.Thin-skinned structures are distributed throughout the Alabama coalbed methane fields, and these structures affect the production of gas and water from coal-bearing strata. Extensional structures in Deerlick Creek and Cedar Cove fields include normal faults and hanging-wall rollovers, and area balancing indicates that these structures are detached in the Pottsville Formation. Compressional folds in Gurnee and Oak Grove fields, by comparison, are interpreted to be detachment folds formed above decollements at different stratigraphic levels. Patterns of gas and water production reflect the structural style of each field and further indicate that folding and faulting have affected the distribution of permeability and the overall success of coalbed methane operations. Area balancing can be an effective way to characterize coalbed methane reservoirs in structurally complex regions because it constrains structural geometry and can be used to determine the distribution of layer-parallel strain. Comparison of calculated requisite strain and borehole expansion data from calliper logs suggests that strain in coalbed methane reservoirs is predictable and can be expressed as fracturing and small-scale faulting. However, refined methodology is needed to analyze heterogeneous strain distributions in discrete bed segments. Understanding temporal variation of production patterns in areas where gas and water production are influenced by map-scale structure will further facilitate effective management of coalbed methane fields.

Methane Concentrations and Biogeochemistry in Lake Sediments from Stordalen Mire, Sub-Arctic Sweden

NASA Astrophysics Data System (ADS)

Halloran, M.; DeStasio, J.; Erickson, L.; Johnson, J. E.; Varner, R. K.; Setera, J.; Prado, M. F.; Wik, M.; Crill, P. M.

2013-12-01

Lake sediments are an important global carbon sink of both allochthonous and autochthonous inputs. However, lakes are also known to emit carbon in gaseous form, most often as methane (CH4) or carbon dioxide (CO2), which are potent greenhouse gases. As northern latitudes warm, it is increasingly important to understand these gases and the sediments that store them. In July of 2013 we took 48 cores at 16 sites throughout three lakes surrounding a mire underlain by degrading permafrost in sub-arctic Sweden. The goal was to characterize the sedimentology and geochemistry of the lake sediments to better understand the production, distribution, and flux of CO2 and CH4 from these lakes. Villasjön is a shallow lake less than 1.5 meters deep, Mellan Harrsjön has a maximum depth of 7 meters and is stream-fed, and Inre Harrsjön has a maximum depth of 5 meters and is connected to Mellan Harrsjön. Published radiocarbon dates suggest that all three lakes formed approximately 3400 years ago. At each sample site, we retrieved 2 to 4 cores from the lake bottom, approximately 40-80 cm in length. The cores were sub-sampled for measurements of bulk TOC, TC, TN, TS, and CaCO3 (by difference) using a CHNS Elemental Analyzer, and grain size using a laser particle size analyzer. Headspace CO2 and CH4 by gas chromatography and infrared gas analysis (IRGA) yielded production rates and CH4 sediment concentrations. Dissolved inorganic carbon (DIC) from porewater extractions were analyzed using IRGA and stable carbon isotopes of DIC were analyzed via a Quantum Cascade Laser. The recovered sediments in the cores from all three lakes were composed of three layers: an upper layer of organic rich sediment (30-40 cm thick), a middle transition layer of mixed organic and lithogenic materials (5-10 cm thick), and a deep layer of grey lithogenic clay with less organic carbon (of variable thickness). Preliminary results from the 12 Villasjön sites indicate that CH4 is present and produced from the organic-rich layer in the upper 20-40 cm of the sediment. TOC values in this lake range from <1 to 44 wt. %. The TOC maximum (approximately 20-40 wt. %) consistently occurred at the same depth as the methane maximum, centered at ~20 cm. A TOC minimum zone (approximately 0-5 wt. %) occurs from 35-80 cm. Particle size distributions in this lake are dominated by silt and sand size fractions (>4 um). Calcium carbonate (CaCO3) concentrations varied, but the maximum always occurred in the upper 20 cm of the core. Core sites with known high lake surface methane fluxes from bubble trap measurements also show high methane concentrations in the sediment, high DIC concentrations in the pore fluids, and δ 13C signatures of CO2 ranging from 0 to 10, consistent with methanogenesis. Similar results are expected from the integration of pending sediment methane profiles with these data from the other two lakes: Mellan Harrsjön and Inre Harrsjön. Future work, including 14C dating, microbial community profiling, and δ13C signatures of CH4 will yield more insight into the biogeochemical mechanisms that regulate sediment methane distributions. 13C isotopes of methane and DIC should indicate if methane consumption through AOM or diffusion is controlling its distribution.

The exposure history of the Apollo 16 site: An assessment based on methane and hydrolysable carbon

NASA Technical Reports Server (NTRS)

Pillinger, C. T.; Eglinton, G.; Gowar, A. P.; Jull, A. J. T.; Maxwell, J. R.

1977-01-01

Nineteen soils from eight stations at the Apollo 16 landing site have been analyzed for methane and hydrolysable carbon. These results, in conjunction with published data from photogeology, bulk chemistry, rare gases, primordial and cosmogenic radionuclides, and agglutinate abundances have been interpreted in terms of differing contributions from three components-North and South Ray Crater ejecta and Cayley Plains material.

The exposure history of the Apollo 16 sites. An assessment based on methane and carbide measurements. [in lunar soils

NASA Technical Reports Server (NTRS)

Pillinger, C. T.; Eglinton, C.; Gowar, A. P.; Jull, A. J. T.; Maxwell, J. R.

1974-01-01

Soils from eight stations at the Apollo 16 landing site have been analyzed for methane and carbide. These results, in conjunction with published data from photogeology, bulk chemistry, rare gases, primordial and radionuclides, and agglutinate abundances have been interpreted in terms of differing contributions from three components, North and South Ray crater ejecta and Cayley Plains material.

40 CFR 86.521-90 - Hydrocarbon analyzer calibration.

Code of Federal Regulations, 2014 CFR

2014-07-01

.... Analyzers used with petroleum fuels and liquefied petroleum gas-fuel shall be optimized using propane. Analyzers used with natural gas-fuel for measurement of hydrocarbons shall be optimized using methane. If a... gas-fuel. Alternate methods yielding equivalent results may be used, if approved in advance by the...

40 CFR 86.521-90 - Hydrocarbon analyzer calibration.

Code of Federal Regulations, 2012 CFR

2012-07-01

.... Analyzers used with petroleum fuels and liquefied petroleum gas-fuel shall be optimized using propane. Analyzers used with natural gas-fuel for measurement of hydrocarbons shall be optimized using methane. If a... gas-fuel. Alternate methods yielding equivalent results may be used, if approved in advance by the...

40 CFR 86.521-90 - Hydrocarbon analyzer calibration.

Code of Federal Regulations, 2013 CFR

2013-07-01

.... Analyzers used with petroleum fuels and liquefied petroleum gas-fuel shall be optimized using propane. Analyzers used with natural gas-fuel for measurement of hydrocarbons shall be optimized using methane. If a... gas-fuel. Alternate methods yielding equivalent results may be used, if approved in advance by the...

Methane-Oxidizing Bacteria Shunt Carbon to Microbial Mats at a Marine Hydrocarbon Seep

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

Paul, Blair G.; Ding, Haibing; Bagby, Sarah C.

The marine subsurface is a reservoir of the greenhouse gas methane. While microorganisms living in water column and seafloor ecosystems are known to be a major sink limiting net methane transport from the marine subsurface to the atmosphere, few studies have assessed the flow of methane-derived carbon through the benthic mat communities that line the seafloor on the continental shelf where methane is emitted. We analyzed the abundance and isotope composition of fatty acids in microbial mats grown in the shallow Coal Oil Point seep field off Santa Barbara, CA, USA, where seep gas is a mixture of methane andmore » CO 2. We further used stable isotope probing (SIP) to track methane incorporation into mat biomass. We found evidence that multiple allochthonous substrates supported the rich growth of these mats, with notable contributions from bacterial methanotrophs and sulfur-oxidizers as well as eukaryotic phototrophs. Fatty acids characteristic of methanotrophs were shown to be abundant and 13C-enriched in SIP samples, and DNA-SIP identified members of the methanotrophic family Methylococcaceae as major 13CH 4 consumers. Members of Sulfuricurvaceae, Sulfurospirillaceae, and Sulfurovumaceae are implicated in fixation of seep CO 2. The mats’ autotrophs support a diverse assemblage of co-occurring bacteria and protozoa, with Methylophaga as key consumers of methane-derived organic matter. This study identifies the taxa contributing to the flow of seep-derived carbon through microbial mat biomass, revealing the bacterial and eukaryotic diversity of these remarkable ecosystems.« less

Methane-Oxidizing Bacteria Shunt Carbon to Microbial Mats at a Marine Hydrocarbon Seep

DOE PAGES

Paul, Blair G.; Ding, Haibing; Bagby, Sarah C.; ...

2017-02-27

The marine subsurface is a reservoir of the greenhouse gas methane. While microorganisms living in water column and seafloor ecosystems are known to be a major sink limiting net methane transport from the marine subsurface to the atmosphere, few studies have assessed the flow of methane-derived carbon through the benthic mat communities that line the seafloor on the continental shelf where methane is emitted. We analyzed the abundance and isotope composition of fatty acids in microbial mats grown in the shallow Coal Oil Point seep field off Santa Barbara, CA, USA, where seep gas is a mixture of methane andmore » CO 2. We further used stable isotope probing (SIP) to track methane incorporation into mat biomass. We found evidence that multiple allochthonous substrates supported the rich growth of these mats, with notable contributions from bacterial methanotrophs and sulfur-oxidizers as well as eukaryotic phototrophs. Fatty acids characteristic of methanotrophs were shown to be abundant and 13C-enriched in SIP samples, and DNA-SIP identified members of the methanotrophic family Methylococcaceae as major 13CH 4 consumers. Members of Sulfuricurvaceae, Sulfurospirillaceae, and Sulfurovumaceae are implicated in fixation of seep CO 2. The mats’ autotrophs support a diverse assemblage of co-occurring bacteria and protozoa, with Methylophaga as key consumers of methane-derived organic matter. This study identifies the taxa contributing to the flow of seep-derived carbon through microbial mat biomass, revealing the bacterial and eukaryotic diversity of these remarkable ecosystems.« less

Methane-Oxidizing Bacteria Shunt Carbon to Microbial Mats at a Marine Hydrocarbon Seep

PubMed Central

Paul, Blair G.; Ding, Haibing; Bagby, Sarah C.; Kellermann, Matthias Y.; Redmond, Molly C.; Andersen, Gary L.; Valentine, David L.

2017-01-01

The marine subsurface is a reservoir of the greenhouse gas methane. While microorganisms living in water column and seafloor ecosystems are known to be a major sink limiting net methane transport from the marine subsurface to the atmosphere, few studies have assessed the flow of methane-derived carbon through the benthic mat communities that line the seafloor on the continental shelf where methane is emitted. We analyzed the abundance and isotope composition of fatty acids in microbial mats grown in the shallow Coal Oil Point seep field off Santa Barbara, CA, USA, where seep gas is a mixture of methane and CO2. We further used stable isotope probing (SIP) to track methane incorporation into mat biomass. We found evidence that multiple allochthonous substrates supported the rich growth of these mats, with notable contributions from bacterial methanotrophs and sulfur-oxidizers as well as eukaryotic phototrophs. Fatty acids characteristic of methanotrophs were shown to be abundant and 13C-enriched in SIP samples, and DNA-SIP identified members of the methanotrophic family Methylococcaceae as major 13CH4 consumers. Members of Sulfuricurvaceae, Sulfurospirillaceae, and Sulfurovumaceae are implicated in fixation of seep CO2. The mats’ autotrophs support a diverse assemblage of co-occurring bacteria and protozoa, with Methylophaga as key consumers of methane-derived organic matter. This study identifies the taxa contributing to the flow of seep-derived carbon through microbial mat biomass, revealing the bacterial and eukaryotic diversity of these remarkable ecosystems. PMID:28289403

OH and CH luminescence in opposed flow methane oxy-flames

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

De Leo, Maurizio; Saveliev, Alexei; Kennedy, Lawrence A.

Emission spectroscopy is a 2-D nonintrusive diagnostic technique that offers spatially resolved data for combustion optimization and control. The UV and visible chemiluminescence of the excited radicals CH(A{sup 2}{delta},B{sup 2}{sigma}{sup -}) and OH(A{sup 2}{sigma}{sup +}) is studied experimentally and numerically in opposed-flow diffusion flames of methane and oxygen-enriched air. The oxidized oxygen content is varied from 21 to 100% while the range of the studied strain rates spans from 20 to 40 s{sup -1}. The spectrally resolved imaging is obtained by two different methods: scattering through a grating monochromator and interposition of interference filters along the optical path. Absolute measuredmore » chemiluminescence intensities, coupled with a numerical model based on the opposed flow flame code, are used to evaluate the chemical kinetics of the excited species. The predictions of the selected model are in good agreement with the experimental data over the range of the studied flame conditions. (author)« less

Temperature structure and emergent flux of the Jovian planets

NASA Technical Reports Server (NTRS)

Silvaggio, P.; Sagan, C.

1978-01-01

Long path, low temperature, moderate resolution spectra of methane and ammonia, broadened by hydrogen and helium, are used to calculate non-gray model atmospheres for the four Jovian planets. The fundamental and first overtone of hydrogen contributes enough absorption to create a thermal inversion for each of the planets. The suite of emergent spectral fluxes and representative limb darkenings and brightenings are calculated for comparison with the Voyager infrared spectra. The temperature differences between Jovian belts and zones corresponds to a difference in the ammonia cirrus particle radii (1 to 3 micron in zones; 10 micron in belts). The Jovian tropopause is approximately at the 0.1 bar level. A thin ammonia cirrus haze should be distributed throughout the Saturnian troposphere; and NH3 gas must be slightly supersaturated or ammonia ice particles are carried upwards convectively in the upper troposphere of Saturn. Substantial methane clouds exist on both Uranus and Neptune. There is some evidence for almost isothermal structures in the deep atmospheres of these two planets.

Accuracy of noninvasive breath methane measurements using Fourier transform infrared methods on individual cows.

PubMed

Lassen, J; Løvendahl, P; Madsen, J

2012-02-01

Individual methane (CH(4)) production was recorded repeatedly on 93 dairy cows during milking in an automatic milking system (AMS), with the aim of estimating individual cow differences in CH(4) production. Methane and CO(2) were measured with a portable air sampler and analyzer unit based on Fourier transform infrared (FTIR) detection. The cows were 50 Holsteins and 43 Jerseys from mixed parities and at all stages of lactation (mean=156 d in milk). Breath was captured by the FTIR unit inlet nozzle, which was placed in front of the cow's head in each of the 2 AMS as an admixture to normal barn air. The FTIR unit was running continuously for 3 d in each of 2 AMS units, 1 with Holstein and another with Jersey cows. Air was analyzed every 20 s. From each visit of a cow to the AMS, CH(4) and CO(2) records were summarized into the mean, median, 75, and 90% quantiles. Furthermore, the ratio between CH(4) and CO(2) was used as a derived measure with the idea of using CO(2) in breath as a tracer gas to quantify the production of methane. Methane production records were analyzed with a mixed model, containing cow as random effect. Fixed effects of milk yield and daily intake of the total mixed ration and concentrates were also estimated. The repeatability of the CH(4)-to-CO(2) ratio was 0.39 for Holsteins and 0.34 for Jerseys. Both concentrate intake and total mixed ration intake were positively related to CH(4) production, whereas milk production level was not correlated with CH(4) production. In conclusion, the results from this study suggest that the CH(4)-to-CO(2) ratio measured using the noninvasive method is an asset of the individual cow and may be useful in both management and genetic evaluations. Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Lambs Fed Fresh Winter Forage Rape (Brassica napus L.) Emit Less Methane than Those Fed Perennial Ryegrass (Lolium perenne L.), and Possible Mechanisms behind the Difference

PubMed Central

Sun, Xuezhao; Henderson, Gemma; Cox, Faith; Molano, German; Harrison, Scott J.; Luo, Dongwen; Janssen, Peter H.; Pacheco, David

2015-01-01

The objectives of this study were to examine long-term effects of feeding forage rape (Brassica napus L.) on methane yields (g methane per kg of feed dry matter intake), and to propose mechanisms that may be responsible for lower emissions from lambs fed forage rape compared to perennial ryegrass (Lolium perenne L.). The lambs were fed fresh winter forage rape or ryegrass as their sole diet for 15 weeks. Methane yields were measured using open circuit respiration chambers, and were 22-30% smaller from forage rape than from ryegrass (averages of 13.6 g versus 19.5 g after 7 weeks, and 17.8 g versus 22.9 g after 15 weeks). The difference therefore persisted consistently for at least 3 months. The smaller methane yields from forage rape were not related to nitrate or sulfate in the feed, which might act as alternative electron acceptors, or to the levels of the potential inhibitors glucosinolates and S-methyl L-cysteine sulfoxide. Ruminal microbial communities in forage rape-fed lambs were different from those in ryegrass-fed lambs, with greater proportions of potentially propionate-forming bacteria, and were consistent with less hydrogen and hence less methane being produced during fermentation. The molar proportions of ruminal acetate were smaller and those of propionate were greater in forage rape-fed lambs, consistent with the larger propionate-forming populations and less hydrogen production. Forage rape contained more readily fermentable carbohydrates and less structural carbohydrates than ryegrass, and was more rapidly degraded in the rumen, which might favour this fermentation profile. The ruminal pH was lower in forage rape-fed lambs, which might inhibit methanogenic activity, shifting the rumen fermentation to more propionate and less hydrogen and methane. The significance of these two mechanisms remains to be investigated. The results suggest that forage rape is a potential methane mitigation tool in pastoral-based sheep production systems. PMID:25803688

MASS SPECTROMETRY

DOEpatents

Friedman, L.

1962-01-01

method is described for operating a mass spectrometer to improve its resolution qualities and to extend its period of use substantially between cleanings. In this method, a small amount of a beta emitting gas such as hydrogen titride or carbon-14 methane is added to the sample being supplied to the spectrometer for investigation. The additive establishes leakage paths on the surface of the non-conducting film accumulating within the vacuum chamber of the spectrometer, thereby reducing the effect of an accumulated static charge on the electrostatic and magnetic fields established within the instrument. (AEC)

Open-path FTIR data reduction algorithm with atmospheric absorption corrections: the NONLIN code

NASA Astrophysics Data System (ADS)

Phillips, William; Russwurm, George M.

1999-02-01

This paper describes the progress made to date in developing, testing, and refining a data reduction computer code, NONLIN, that alleviates many of the difficulties experienced in the analysis of open path FTIR data. Among the problems that currently effect FTIR open path data quality are: the inability to obtain a true I degree or background, spectral interferences of atmospheric gases such as water vapor and carbon dioxide, and matching the spectral resolution and shift of the reference spectra to a particular field instrument. This algorithm is based on a non-linear fitting scheme and is therefore not constrained by many of the assumptions required for the application of linear methods such as classical least squares (CLS). As a result, a more realistic mathematical model of the spectral absorption measurement process can be employed in the curve fitting process. Applications of the algorithm have proven successful in circumventing open path data reduction problems. However, recent studies, by one of the authors, of the temperature and pressure effects on atmospheric absorption indicate there exist temperature and water partial pressure effects that should be incorporated into the NONLIN algorithm for accurate quantification of gas concentrations. This paper investigates the sources of these phenomena. As a result of this study a partial pressure correction has been employed in NONLIN computer code. Two typical field spectra are examined to determine what effect the partial pressure correction has on gas quantification.

Path Similarity Analysis: A Method for Quantifying Macromolecular Pathways

PubMed Central

Seyler, Sean L.; Kumar, Avishek; Thorpe, M. F.; Beckstein, Oliver

2015-01-01

Diverse classes of proteins function through large-scale conformational changes and various sophisticated computational algorithms have been proposed to enhance sampling of these macromolecular transition paths. Because such paths are curves in a high-dimensional space, it has been difficult to quantitatively compare multiple paths, a necessary prerequisite to, for instance, assess the quality of different algorithms. We introduce a method named Path Similarity Analysis (PSA) that enables us to quantify the similarity between two arbitrary paths and extract the atomic-scale determinants responsible for their differences. PSA utilizes the full information available in 3N-dimensional configuration space trajectories by employing the Hausdorff or Fréchet metrics (adopted from computational geometry) to quantify the degree of similarity between piecewise-linear curves. It thus completely avoids relying on projections into low dimensional spaces, as used in traditional approaches. To elucidate the principles of PSA, we quantified the effect of path roughness induced by thermal fluctuations using a toy model system. Using, as an example, the closed-to-open transitions of the enzyme adenylate kinase (AdK) in its substrate-free form, we compared a range of protein transition path-generating algorithms. Molecular dynamics-based dynamic importance sampling (DIMS) MD and targeted MD (TMD) and the purely geometric FRODA (Framework Rigidity Optimized Dynamics Algorithm) were tested along with seven other methods publicly available on servers, including several based on the popular elastic network model (ENM). PSA with clustering revealed that paths produced by a given method are more similar to each other than to those from another method and, for instance, that the ENM-based methods produced relatively similar paths. PSA applied to ensembles of DIMS MD and FRODA trajectories of the conformational transition of diphtheria toxin, a particularly challenging example, showed that the geometry-based FRODA occasionally sampled the pathway space of force field-based DIMS MD. For the AdK transition, the new concept of a Hausdorff-pair map enabled us to extract the molecular structural determinants responsible for differences in pathways, namely a set of conserved salt bridges whose charge-charge interactions are fully modelled in DIMS MD but not in FRODA. PSA has the potential to enhance our understanding of transition path sampling methods, validate them, and to provide a new approach to analyzing conformational transitions. PMID:26488417