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Sample records for abstract trace gas

  1. Trace gas effects on climate

    NASA Technical Reports Server (NTRS)

    Ramanathan, V.; Callis, L. B., Jr.; Cess, R. D.; Hansen, J. E.; Isaksen, I. S. A.; Kuhn, W. R.; Lacis, A.; Luther, F. M.; Mahlman, J. D.; Reck, R. A.

    1985-01-01

    The two primary objectives are to describe the new scientific challenges posed by the trace gas-climate problem and to summarize current strategies, and to make an assessment of the trace gas effects on troposphere-stratosphere temperature trends. Numerous reports on CO2-climate problems are examined with respect to climate modeling issues. The role of the oceans in governing the transient climate response to time varying CO2 concentrations is discussed.

  2. Trace Gas Analyzer (TGA) program

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The design, fabrication, and test of a breadboard trace gas analyzer (TGA) is documented. The TGA is a gas chromatograph/mass spectrometer system. The gas chromatograph subsystem employs a recirculating hydrogen carrier gas. The recirculation feature minimizes the requirement for transport and storage of large volumes of carrier gas during a mission. The silver-palladium hydrogen separator which permits the removal of the carrier gas and its reuse also decreases vacuum requirements for the mass spectrometer since the mass spectrometer vacuum system need handle only the very low sample pressure, not sample plus carrier. System performance was evaluated with a representative group of compounds.

  3. Space Shuttle Trace Gas Analyzer

    NASA Technical Reports Server (NTRS)

    Dencker, W.

    1975-01-01

    A Trace Gas Analyzer (TGA) with the ability to detect the presence of toxic contaminants in the Space Shuttle atmosphere within the subparts-per-million range is under development. The design is a modification of the miniaturized Gas Chromatograph-Mass Spectrometer (GCMS) developed for the Viking Mars Lander. An ambient air sample is injected onto the GC column from a constant volume sample loop and separated into individual compounds for identification by the MS. The GC-MS interface consists of an effluent divider and a silver-paladium separator, an electrochemical cell which removes more than 99.99% of the hydrogen carrier gas. The hydrogen is reclaimed and repressurized without affecting the separator efficiency, a feature which enables a considerable weight reduction in the carrier gas supply system.

  4. Trace gas emissions by plants

    SciTech Connect

    Sharkey, T.D.; Holland, E.A.

    1991-12-31

    The trace gases released or influenced by plants play a key role in atmospheric processes. In the troposphere, methane and carbon monoxide are key species that react with the hydroxyl radical (OH), an effective atmospheric detergent. Carbon monoxide is formed by the oxidation of the biogenic hydrocarbons discussed previously. In the presence of NO, the oxidation of CO, CH{sub 4} and NMHC can lead to the formation of ozone, a tropospheric pollutant. In the stratosphere, methane is an important source of water vapor. Volatile sulfur compounds released by plants may be an important source of cloud condensation nuclei. Collectively, these compounds may directly regulate the earth`s climate because they are radiatively active and influence the radiation balance at the earth`s surface or indirectly regulate the earth`s climate because they influence the concentration of radiatively active gases. The focus of the workshop was on naturally occurring gas fluxes. It is sometimes claimed that the gas fluxes from plants pollute the atmosphere. Our focus was on the natural chemistry occurring at the biosphere-atmosphere interface. Individual reports are processed separately for the data bases.

  5. Trace gas emissions by plants

    SciTech Connect

    Sharkey, T.D. . Dept. of Botany); Holland, E.A. ); Mooney, H.A. . Dept. of Biological Sciences)

    1991-01-01

    The trace gases released or influenced by plants play a key role in atmospheric processes. In the troposphere, methane and carbon monoxide are key species that react with the hydroxyl radical (OH), an effective atmospheric detergent. Carbon monoxide is formed by the oxidation of the biogenic hydrocarbons discussed previously. In the presence of NO, the oxidation of CO, CH[sub 4] and NMHC can lead to the formation of ozone, a tropospheric pollutant. In the stratosphere, methane is an important source of water vapor. Volatile sulfur compounds released by plants may be an important source of cloud condensation nuclei. Collectively, these compounds may directly regulate the earth's climate because they are radiatively active and influence the radiation balance at the earth's surface or indirectly regulate the earth's climate because they influence the concentration of radiatively active gases. The focus of the workshop was on naturally occurring gas fluxes. It is sometimes claimed that the gas fluxes from plants pollute the atmosphere. Our focus was on the natural chemistry occurring at the biosphere-atmosphere interface. Individual reports are processed separately for the data bases.

  6. Internal Versus External DSLs for Trace Analysis: Extended Abstract

    NASA Technical Reports Server (NTRS)

    Barringer, Howard; Havelund, Klaus

    2011-01-01

    This tutorial explores the design and implementation issues arising in the development of domain-specific languages for trace analysis. It introduces the audience to the general concepts underlying such special-purpose languages building upon the authors' own experiences in developing both external domain specific languages and systems, such as EAGLE, HAWK, RULER and LOGSCOPE, and the more recent internal domain-specific language and system TRACECONTRACT within the SCALA language.

  7. Clouds and trace gas distributions during TRACE-P

    NASA Astrophysics Data System (ADS)

    Crawford, J.; Olson, J.; Davis, D.; Chen, G.; Barrick, J.; Shetter, R.; Lefer, B.; Jordan, C.; Anderson, B.; Clarke, A.; Sachse, G.; Blake, D.; Singh, H.; Sandolm, S.; Tan, D.; Kondo, Y.; Avery, M.; Flocke, F.; Eisele, F.; Mauldin, L.; Zondlo, M.; Brune, W.; Harder, H.; Martinez, M.; Talbot, R.; Bandy, A.; Thornton, D.

    2003-11-01

    This paper addresses the question: To what extent do trace gas distributions correspond to cloudiness? Observations taken during NASA's TRACE-P experiment indicate that there can be statistically significant differences in trace gas concentrations between clear-sky and cloudy areas. During the TRACE-P mission, frontal outflow of Asian emissions from the Pacific Rim to the western, North Pacific was sampled by NASA's DC-8 and P-3B aircraft. On several occasions, enhanced CO mixing ratios were observed in and around frontal clouds. A more detailed analysis of trace gas distributions revealed CO enhancements of 30% in the lower free troposphere (1-5 km) for cloudy regions as compared to clear areas. These enhancements exist within clouds as well as above and below clouds. In the upper free troposphere (5-11 km), overall enhancement in CO of 15% was observed although enhancements are mainly restricted to observations within clouds. These in-cloud observations were enhanced by factors of 1.5 to 2 over clear air data. Similar enhancements were seen for many other anthropogenic tracers. By contrast, distributions for O3 revealed no clear differences between cloudy and clear regions suggesting that other influences (e.g., stratosphere-troposphere exchange) might complicate any correspondence with local cloudiness. Expected cloud influences on oxidation chemistry were evident in enhanced OH concentrations above clouds and depressed OH below clouds. These findings are particularly relevant to current and future satellite investigations of the troposphere. Understanding the potential biases created by the inability to probe cloudy regions will improve the interpretation of regional and globally averaged satellite observations.

  8. Trace gas concentrator FY 1995 summary report

    SciTech Connect

    Andriulli, J.B.; Szady, A.J. Jr.

    1996-05-01

    This report summarizes the accomplishments of the Trace Gas Concentrator Technology Demonstration Project during FY 1995 and through February 1996. The purpose of the activity was to demonstrate proof of principle of a system that concentrates airborne substances (e.g., chemical agents, explosives, narcotics and their precursors, and pollutants) to aid in their detection. A comprehensive computer model (initiated in FY 1994) was developed for the theoretical prediction of the fluid dynamics and mass concentration of the trace gas concentrator. The gas test stand has been installed and checked out. An automated computer data acquisition system has been installed and connected to the concentrator test stand. The data acquisition system is needed to record gas and mechanical operations.

  9. Trace gas assimilation of Mars satellite observations

    NASA Astrophysics Data System (ADS)

    Holmes, J. A. M.; Lewis, S. R.; Patel, M. R.

    2012-09-01

    Ozone, water vapour and argon are minor constituents in the Martian atmosphere, observations of which can be of use in constraining atmospheric dynamical and physical processes. This is especially true in the winter season of each hemisphere, when the bulk of the main constituent in the atmosphere (CO2) condenses in the polar regions shifting the balance of atmospheric composition to a more trace gas rich air mass. Current Mars Global Circulation Models (MGCMs) [5, 7, 9] are able to represent the photochemistry occuring in the atmosphere, with constraints being imposed by comparisons with observations. However, a long term comparison using data assimilation provides a more robust constraint on the model. We aim to provide a technique for trace gas data assimilation for the analysis of observations from current and future satellite missions (such as ExoMars) which observe the spatial and temporal distribution of trace gases on Mars.

  10. Low-background trace-gas detector

    NASA Technical Reports Server (NTRS)

    Rosengren, L.

    1978-01-01

    Spectrophone detects very small concentrations of trace gases. With gas in sample cell, laser is tuned to absorption line of interest. Molecular absorption in cell produces pulsed acoustical pressure at chopper frequency. Two optical paths with very different absorption lengths are used to pretune cell to balance out background absorption by cell windows.

  11. Gas chromatographic analysis of trace gas impurities in tungsten hexafluoride.

    PubMed

    Laurens, J B; de Coning, J P; Swinley, J M

    2001-03-01

    Highly reactive fluorinated gaseous matrices require special equipment and techniques for the gas chromatographic analysis of trace impurities in these gases. The impurities that were analysed at the low-microg/l levels included oxygen, nitrogen, carbon dioxide, carbon monoxide, sulfur hexafluoride and hydrogen. This paper describes the use of a system utilising backflush column switching to protect the columns and detectors in the analysis of trace gas impurities in tungsten hexafluoride. Two separate channels were used for the analysis of H2, O2, N2, CO, CO2 and SF6 impurities with pulsed discharge helium ionisation detection. PMID:11269587

  12. A photoacoustic spectrometer for trace gas detection

    NASA Astrophysics Data System (ADS)

    Telles, E. M.; Bezerra, E.; Scalabrin, A.

    2005-06-01

    A high-resolution external laser photoacoustic spectrometer has been developed for trace gas detection with absorption transitions in coincidence with CO2 laser emission lines (9,2-10,9 μm: 920-1086 cm-1). The CO2 laser operates in 90 CW lines with power of up to 15 W. A PC-controlled step motor can tune the laser lines. The resonance frequency of first longitudinal mode of the photoacoustic cell is at 1600 Hz. The cell Q-factor and cell constant are measured close to 50 and 28 mVcmW-1, respectively. The spectrometer has been tested in preliminary studies to analyze the absorption transitions of ozone (O_3). The ethylene (C_2H_4) from papaya fruit is also investigated using N2 as carrier gas at a constant flow rate.

  13. Infrared laser spectroscopic trace gas sensing

    NASA Astrophysics Data System (ADS)

    Sigrist, Markus

    2016-04-01

    -lived species like nitrous acid (HONO) with a QCL-based QEPAS system where the small gas sampling volume and hence short gas residence time are of particular importance [3]. A true analysis of gas mixtures has been performed with a widely tunable DFG system in a medical application that could also be adapted to atmospheric species [4]. It is demonstrated that a laser-based narrowband system with broad tunability combined with an appropriate detection scheme is feasible for the chemical analysis of multi-component gas mixtures even with an a priori unknown composition. Most recent examples will further confirm the great potential of infrared laser-based devices for trace species sensing. References 1. D. Marinov and M.W. Sigrist: "Monitoring of road-traffic emission with mobile photoacoustic system", Photochem. and Photobiol. Sciences 2, 774-778 (2003) 2. J.M. Rey, M. Fill, F. Felder and M.W. Sigrist: "Broadly tunable mid-infrared VECSEL for multiple components hydrocarbons gas sensing", Appl. Phys. B 117, 935-939 (2014) 3. H. Yi, R. Maamary, X. Gao, M.W. Sigrist, E. Fertein, and W. Chen: "Short-lived species detection of nitrous acid by external-cavity quantum cascade laser based quartz-enhanced photoacoustic absorption spectroscopy", Appl. Phys. Lett. 106, 101109 (2015) 4. M. Gianella and M.W. Sigrist: "Chemical Analysis of Surgical Smoke by Infrared Laser Spectroscopy", Appl. Phys. B 109, 485-496 (2012)

  14. The Colour and Stereo Surface Imaging System (CaSSIS) for ESA's Trace Gas Orbiter

    NASA Astrophysics Data System (ADS)

    Thomas, N.; Cremonese, G.; Banaszkiewicz, M.; Bridges, J.; Byrne, S.; da Deppo, V.; Debei, S.; El-Maarry, M. R.; Haubner, E.; Hansen, C. J.; Ivanov, A.; Kestay, L.; Kirk, R.; Kuzmini, R.; Mangold, N.; Marinangeli, L.; Markiewicz, W.; Massironi, M.; McEwen, A. S.; Okubo, C.; Orleanski, P.; Pommerol, A.; Wajer, P.; Wray, J.

    2014-04-01

    CaSSIS (Colour and Stereo Surface Imaging System) will be the main imaging system for the ExoMars 2016 Trace Gas Orbiter (TGO) mission. A viable and scientifically compelling instrument is now in the build phase with a target completion date of Sept. 2015 for a launch in Jan. 2016. This abstract describes CaSSIS and its capabilities.

  15. Trace Gas Exchange of Biofuel Crops

    NASA Astrophysics Data System (ADS)

    Graus, M.; Warneke, C.; Williams, E. J.; Lerner, B. M.; Gilman, J. B.; Li, R.; Eller, A. S.; Gray, C.; Fierer, N.; Fall, R.; Harley, P. C.; Roberts, J. M.; Yuan, B.; Qian, Y.; Westra, P.; Fryrear, C.; Collins, M.; Whitman, K.; De Gouw, J. A.

    2011-12-01

    In 2010 leaf level gas exchange and VOC fluxes from switchgrass and corn grown at the CSU horticultural farm in Ft Collins (CO) were measured using a PTR-MS coupled to a modified Li6400 cuvette system. Both species are C4 plants with corn currently being the dominant biofuel crop in the USA whilst switchgrass being a promising candidate for cellulosic fuel ethanol production. Amongst the strongest VOC emissions from both plants were methanol, acetic acid, acetaldehyde, acetone and toluene. The switchgrass VOC emissions compare reasonably well with the only published data measured from potted plants in a whole plant enclosure (Eller et al. 2011). VOC emission studies on corn are almost as scarce as those of switchgrass. Considering the acreage of corn grown in the USA every year, VOC flux measurements of this plant species are largely under-represented in the literature. The emission rates that do exist in the literature do not compare well with the numbers found in this study (e.g. Das et al. 2003; 35μg methanol per hour per gram biomass). To investigate the biosphere atmosphere exchange of corn fields in more detail the field campaign BioCORN 2011 was initiated. In summer 2011 an eddy covariance system was set up in a corn field at ARDEC (CSU, Ft Collins, CO) to investigate the energy flux and the trace gas exchange of the US' dominant biofuel crop. Besides energy flux, evapotranspiration and CO2 flux a comprehensive suite of volatile organic compounds and inorganic species (O3, NO, NO2, CO) are measured for virtual disjunct eddy covariance (vDEC) analysis and true eddy covariance (EC) fluxes, respectively. VOCs are monitored by PTR-MS and, for the first time, fluxes of formic acid are measured utilizing NI-CIMS data for vDEC analysis. Besides the EC approach leaf level flux measurements and soil flux measurements are performed using a GC-MS system (TACOH) coupled to a modified Li6400 system and to soil chambers, respectively. Ethanol and methanol are amongst the

  16. An Approach to Evaluate Scientist Support in Abstract Workflows and Provenance Traces

    SciTech Connect

    Salayandia, Leonardo; Gates, Ann Q.; Pinheiro da Silva, Paulo

    2012-11-02

    Abstract workflows are useful to bridge the gap between scientists and technologists towards using computer systems to carry out scientific processes. Provenance traces provide evidence required to validate results and support their reuse. Assuming both technologies are based on formal semantics, a knowledge-based system that consistently merges both technologies is useful for scientists that produce data to document their data collecting and transformation processes; it is also useful for scientists that reuse data to assess scientific processes and resulting datasets produced by others. While evaluation of each technology is necessary for a given application, this work discusses their combined evaluation. The claim is that both technologies should complement each other and align consistently to a scientist’s perspective in order to be effective for science. Evaluation criteria are proposed based on lessons learned and exemplified for discussion.

  17. Ethylene Trace-gas Techniques for High-speed Flows

    NASA Technical Reports Server (NTRS)

    Davis, David O.; Reichert, Bruce A.

    1994-01-01

    Three applications of the ethylene trace-gas technique to high-speed flows are described: flow-field tracking, air-to-air mixing, and bleed mass-flow measurement. The technique involves injecting a non-reacting gas (ethylene) into the flow field and measuring the concentration distribution in a downstream plane. From the distributions, information about flow development, mixing, and mass-flow rates can be dtermined. The trace-gas apparatus and special considerations for use in high-speed flow are discussed. A description of each application, including uncertainty estimates is followed by a demonstrative example.

  18. High Speed, Ultrasensitive Trace Gas Sensing

    NASA Astrophysics Data System (ADS)

    Long, David A.; Fleisher, Adam J.; Plusquellic, David F.; Hodges, Joseph

    2014-06-01

    I will describe a variety of cavity-enhanced spectroscopic techniques, including frequency-agile rapid scanning spectroscopy (FARS) and heterodyne-detected cavity ring-down spectroscopy (HD-CRDS), which we have recently developed for rapid, ultrasensitive absorption measurements. Scanning rates that are limited only by the cavity response time itself as well as noise-equivalent detection limits as low as 6×10-14 cm-1 Hz-1/2 have been achieved. I will discuss the application of these techniques to current problems in atmospheric science including recent infrared measurements of analytes which are present at ultra-trace concentrations.

  19. Ray tracing in nuclear-pumped flowing gas lasers

    SciTech Connect

    Mat'ev, V Yu

    2003-06-30

    The ray tracing in the resonators of a nuclear-pumped flowing gas lasers is considered. The refractive index profile of the medium in a direction perpendicular to the optical axis in such lasers can be considered parabolic, but the steepness of the parabola is quite nonuniform along the ray trace, and the resonator stability condition (the absolute value of the ray matrix trace for a single trip of the ray in the resonator is smaller than two) is not sufficient to confine the ray within the resonator after a large number of trips. (lasers)

  20. Cloud draft structure and trace gas transport

    NASA Technical Reports Server (NTRS)

    Scala, John R.; Tao, Wei-Kuo; Thompson, Anne M.; Simpson, Joanne; Garstang, Michael; Pickering, Kenneth E.; Browell, Edward V.; Sachse, Glen W.; Gregory, Gerald L.; Torres, Arnold L.

    1990-01-01

    During the second Amazon Boundary Layer Experiment (ABLE 2B), meteorological observations, chemical measurements, and model simulations are utilized in order to interpret convective cloud draft structure and to analyze its role in transport and vertical distribution of trace gases. One-dimensional photochemical model results suggest that the observed poststorm changes in ozone concentration can be attributed to convective transports rather than photochemical production and the results of a two-dimensional time-dependent cloud model simulation are presented for the May 6, 1987 squall system. The mesoscale convective system exhibited evidence of significant midlevel detrainment in addition to transports to anvil heights. Chemical measurements of O3 and CO obtained in the convective environment are used to predict photochemical production within the troposphere and to corroborate the cloud model results.

  1. Trace gas emissions from burning Florida wetlands

    NASA Technical Reports Server (NTRS)

    Cofer, Wesley R., III; Levine, Joel S.; Lebel, Peter J.; Winstead, Edward L.; Koller, Albert M., Jr.; Hinkle, C. Ross

    1990-01-01

    Measurements of biomass burn-produced trace gases were obtained using a helicopter at low altitudes above burning Florida wetlands on November 9, 1987, and from both helicopter and light-aircraft samplings on November 7, 1988. Carbon dioxide normalized emission ratios for carbon monoxide, hydrogen, methane, total nonmethane hydrocarbons, and nitrous oxide were obtained over burning graminoid wetlands consisting primarily of Spartina bakeri and Juncus roemerianus. Some interspersed scrub oak and saw palmetto were also burned. No significant differences were observed in the emission ratios determined for these gases from samples collected over flaming, mixed, and smoldering phases of combustion during the 1987 fire. Combustion-categorized differences in emission ratios were small for the 1988 fire. Combustion efficiency was relatively good (low emission ratios for reduced gases) for both fires. It is believed that the consistently low emission ratios were a unique result of graminoid wetlands fires, in which the grasses and rushes burned rapidly down to standing water and were quickly extinguished. Consequently, the efficiency of the combustion was good and the amount and duration of smoldering combustion was greatly deminished.

  2. Determining trace gas flux from container-grown woody ornamentals

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In recent years, anthropogenic climate change and its effects on the global environment has garnered significant attention from the scientific community. Increased trace gas emissions (CO2, CH4, and N2O) are widely believed to be the driving force behind global warming. Agriculture is a large contri...

  3. Trace Gas Emission from in-Situ Denitrifying Bioreactors

    NASA Astrophysics Data System (ADS)

    Pluer, W.; Walter, M. T.; Geohring, L.

    2014-12-01

    Despite decades of concerted effort to mitigate nonpoint source nitrate (NO3-) pollution from agricultural lands, these efforts have not been sufficient to arrest eutrophication. A primary process for removing excess NO3- from water is denitrification, where denitrifying bacteria use NO3- for respiration in the absence of oxygen. Denitrification results in reduced forms of nitrogen, often dinitrogen gas (N2) but also nitrous oxide (N2O), an aggressive greenhouse gas. A promising solution to NO3- pollution is to intercept agricultural discharges with denitrifying bioreactors (DNBRs). DNBRs provide conditions ideal for denitrifiers: an anaerobic environment, sufficient organic matter, and excess NO3-. These conditions are also ideal for methanogens, which produce methane (CH4), another harmful trace gas. While initial results from bioreactor studies show that they can cost-effectively remove NO3-, trace gas emissions are an unintended consequence. This study's goal was to determine how bioreactor design promotes denitrification while limiting trace gas production. Reactor inflow and outflow water samples were tested for nutrients, including NO3-, and dissolved inflow and outflow gas samples were tested for N2O and CH4. NO3- reduction and trace gas production were evaluated at various residence times, pHs, and inflow NO3- concentrations in field and lab-scale reactors. Low NO3- reduction indicated conditions that stressed denitrifying bacteria while high reductions indicated designs that optimized pollutant treatment for water quality. Several factors influenced high N2O, suggesting non-ideal conditions for the final step of complete denitrification. High CH4 emissions pointed to reactor media choice for discouraging methanogens, which may remove competition with denitrifiers. It is critical to understand all of potential impacts that DNBRs may have, which means identifying processes and design specifications that may affect them.

  4. Sampling and analysis of natural gas trace constituents

    SciTech Connect

    Attari, A.; Chao, S.

    1993-09-01

    Major and minor components of natural gas are routinely analyzed by gas chromatography (GC), using a thermal conductivity (TC). The best results obtained by these methods can report no better than 0.01 mole percent of each measured component. Even the extended method of analysis by flame ionization detector (FID) can only improve on the detection limit of hydrocarbons. The gas industry needs better information on all trace constituents of natural gas, whether native or inadvertently added during gas processing that may adversely influence the operation of equipment or the safety of the consumer. The presence of arsenic and mercury in some gas deposits have now been documented in international literature as causing not only human toxicity but also damaging to the field equipment. Yet, no standard methods of sampling and analysis exist to provide this much needed information. In this paper the authors report the results of a three-year program to develop an extensive array of sampling and analysis methods for speciation and measurement of trace constituents of natural gas. A cryogenic sampler operating at near 200 K ({minus}99 F) and at pipeline pressures up to 12.4 {times} 10{sup 6}Pa (1800 psig) has been developed to preconcentrate and recover all trace constituents with boiling points above butanes. Specific analytical methods have been developed for speciating and measurement of many trace components (corresponding to US EPA air toxics) by GC-AED and GC-MS, and for determining various target compounds by other techniques. Moisture, oxygen and sulfur contents are measured on site using dedicated field instruments. Arsenic, mercury and radon are sampled by specific solid sorbents for subsequent laboratory analysis.

  5. Tracing inflows and outflows with absorption lines in circumgalactic gas

    NASA Astrophysics Data System (ADS)

    Ford, Amanda Brady; Davé, Romeel; Oppenheimer, Benjamin D.; Katz, Neal; Kollmeier, Juna A.; Thompson, Robert; Weinberg, David H.

    2014-10-01

    We examine how H I and metal absorption lines within low-redshift galaxy haloes trace the dynamical state of circumgalactic gas, using cosmological hydrodynamic simulations that include a well-vetted heuristic model for galactic outflows. We categorize inflowing, outflowing, and ambient gas based on its history and fate as tracked in our simulation. Following our earlier work, showing that the ionization level of absorbers was a primary factor in determining the physical conditions of absorbing gas, we show here that it is also a governing factor for its dynamical state. Low-ionization metal absorbers (e.g. Mg II) tend to arise in gas that will fall on to galaxies within several Gyr, while high-ionization metal absorbers (e.g. O VI) generally trace material that was deposited by outflows many Gyr ago. Inflowing gas is dominated by enriched material that was previously ejected in an outflow; hence, accretion at low redshifts is typically substantially enriched. Recycling wind material is preferentially found closer to galaxies, and is more dominant in lower mass haloes since high-mass haloes have more hot gas that is able to support itself against infall. Low-mass haloes also tend to re-eject more of their accreted material, owing to our outflow prescription that employs higher mass loading factors for lower mass galaxies. Typical H I absorbers trace unenriched ambient material that is not participating in the baryon cycle, but stronger H I absorbers arise in cool, enriched inflowing gas. Instantaneous radial velocity measures of absorbers are generally poor at distinguishing between inflowing and outflowing gas, except in the case of very recent outflows. These results suggest that probing halo gas using a range of absorbers can provide detailed information about the amount and physical conditions of material that is participating in the baryon cycle.

  6. The role of trace gas flux networks in biogeosciences

    SciTech Connect

    Baldocch, Dennis; Reichstein, Markus; Papale, D.; Koteen, Laurie; Vargas, Rodrigo; Agarwal, D. A.; Cook, Robert B.

    2012-01-01

    Vast networks of meteorological sensors ring the globe, providing continuous measurements of an array of atmospheric state variables such as temperature, humidity, rainfall, and the concentration of carbon dioxide [New etal., 1999; Tans etal., 1996]. These measurements provide input to weather and climate models and are key to detecting trends in climate, greenhouse gases, and air pollution. Yet to understand how and why these atmospheric state variables vary in time and space, biogeoscientists need to know where, when, and at what rates important gases are flowing between the land and the atmosphere. Tracking trace gas fluxes provides information on plant or microbial metabolism and climate-ecosystem interactions. The existence of trace gas flux networks is a relatively new phenomenon, dating back to research in 1984. The first gas flux measurement networks were regional in scope and were designed to track pollutant gases such as sulfur dioxide, ozone, nitric acid, and nitrogen dioxide. Atmospheric observations and model simulations were used to infer the depositional rates of these hazardous chemicals [Fowler etal., 2009; Meyers etal., 1991]. In the late 1990s, two additional trace gas flux measurement networks emerged. One, the United States Trace Gas Network (TRAGNET), was a short-lived effort that measured trace gas emissions from the soil and plants with chambers distributed throughout the country [Ojima etal., 2000]. The other, FLUXNET, was an international endeavor that brought many regional networks together to measure the fluxes of carbon dioxide, water vapor, and sensible heat exchange with the eddy covariance technique [Baldocchi etal., 2001]. FLUXNET, which remains active today, currently includes more than 400 tower sites, dispersed across most of the world's climatic zones and biomes, with sites in North and South America, Europe, Asia, Africa, and Australia. More recently, several specialized networks have emerged, including networks dedicated to

  7. Trace gas emissions from chaparral and boreal forest fires

    NASA Technical Reports Server (NTRS)

    Cofer, Wesley R., III; Levine, Joel S.; Sebacher, Daniel I.; Winstead, Edward L.; Riggan, Philip J.; Stocks, Brian J.; Brass, James A.; Ambrosia, Vincent G.

    1989-01-01

    Using smoke samples collected during low-level helicopter flights, the mixing ratios of CO2, CO, CH4, total nonmethane hydrocarbons, H2, and N2O over burning chaparral in southern California and over a burning boreal forest site in northern Ontario, Canada, were determined. Carbon dioxide-normalized emission ratios were determined for each trace gas for conditions of flaming, mixed, and smoldering combustion. The emission ratios for these trace gases were found to be highest for the smoldering combustion, generally thought to be the least efficient combustion stage. However, high emission ratios for these gases could be also produced during very vigorous flaming combustion.

  8. Hyperspectral trace gas detection using the wavelet packet transform

    NASA Astrophysics Data System (ADS)

    Salvador, Mark Z.; Resmini, Ronald G.; Gomez, Richard B.

    2008-04-01

    A method for trace gas detection in hyperspectral data is demonstrated using the wavelet packet transform. This new method, the Wavelet Packet Subspace (WPS), applies the wavelet packet transform and selects a best basis for pattern matching. The wavelet packet transform is an extension of the wavelet transform, which fully decomposes a signal into a library of wavelet packet bases. Application of the wavelet packet transform to hyperspectral data for the detection of trace gases takes advantage of the ability of the wavelet transform to locate spectral features in both scale and location. By analyzing the wavelet packet tree of specific gas, nodes of the tree are selected which represent an orthogonal best basis. The best basis represents the significant spectral features of that gas. This is then used to identify pixels in the scene using existing matching algorithms such as spectral angle or matched filter. Using data from the Airborne Hyperspectral Imager (AHI), this method is compared to traditional matched filter detection methods. Initial results demonstrate a promising wavelet packet subspace technique for hyperspectral trace gas detection applications.

  9. Circular paraboloid reflection cell for laser spectroscopic trace gas analysis.

    PubMed

    Mangold, Markus; Tuzson, Béla; Hundt, Morten; Jágerská, Jana; Looser, Herbert; Emmenegger, Lukas

    2016-05-01

    Absorption cells with circular geometry are a class of multipass reflection cells consisting of a single, circular mirror. They can be particularly favorable for trace gas measurements because of their mechanical robustness, simplicity, and their optical versatility. In this article, we present detailed theoretical considerations and ray tracing simulations for the optimization of the optical design of circular multipass reflection cells. A parabolic mirror shape in a confocal arrangement is found to be most suitable for long optical paths in a small volume. We experimentally demonstrate more than 12 m optical path in a 14.5 cm diameter gas cell and NO2 concentration measurements in ambient air with a measurement precision better than 0.1 ppb. PMID:27140888

  10. Dual-wavelength quantum cascade laser for trace gas spectroscopy

    SciTech Connect

    Jágerská, J.; Tuzson, B.; Mangold, M.; Emmenegger, L.; Jouy, P.; Hugi, A.; Beck, M.; Faist, J.; Looser, H.

    2014-10-20

    We demonstrate a sequentially operating dual-wavelength quantum cascade laser with electrically separated laser sections, emitting single-mode at 5.25 and 6.25 μm. Based on a single waveguide ridge, this laser represents a considerable asset to optical sensing and trace gas spectroscopy, as it allows probing multiple gas species with spectrally distant absorption features using conventional optical setups without any beam combining optics. The laser capability was demonstrated in simultaneous NO and NO{sub 2} detection, reaching sub-ppb detection limits and selectivity comparable to conventional high-end spectroscopic systems.

  11. Anatomy of a cluster IDP. Part 2: Noble gas abundances, trace element geochemistry, isotopic abundances, and trace organic chemistry of several fragments from L2008#5

    NASA Technical Reports Server (NTRS)

    Thomas, K. L.; Clemett, S. J.; Flynn, G. J.; Keller, L. P.; Mckay, David S.; Messenger, S.; Nier, A. O.; Schlutter, D. J.; Sutton, S. R.; Walker, R. M.

    1994-01-01

    The topics discussed include the following: noble gas content and release temperatures; trace element abundances; heating summary of cluster fragments; isotopic measurements; and trace organic chemistry.

  12. Trace Elements in Hair from Tanzanian Children: Effect of Dietary Factor (abstract)

    NASA Astrophysics Data System (ADS)

    Mohammed, Najat K.; Spyrou, Nicholas M.

    2009-04-01

    Trace elements in certain amounts are essential for childrens' health, because they are present in tissues participating in metabolic reactions of organisms. Deficiency of the essential elements may result in malnutrition, impaired body immunity, and poor resistance to disease. These conditions might be enhanced against a background of additional adverse environmental factors such as toxic elements. The analysis of elements in childrens' hair will give information on the deficiency of essential elements and excess of toxic elements in relation to their diet. In this study, 141 hair samples from children (girls and boys) living in two regions of Tanzanian mainland (Dar es Salaam and Moshi) and the island of Zanzibar have been analysed for trace elements in relation to food consumption habits. The analysis was carried out using long and short irradiation instrumental neutron activation analysis (INAA) of the Nuclear Physics Institute at Rez, Czech Republic. Arithmetic and geometric means with their respective standard deviations are presented for 19 elements. Subgroups were formed according to age, gender, and geographic regions from which the samples were collected. Differences in concentrations for the groups and with other childhood populations were explored and discussed.

  13. Critical issues in trace gas biogeochemistry and global change.

    PubMed

    Beerling, David J; Nicholas Hewitt, C; Pyle, John A; Raven, John A

    2007-07-15

    The atmospheric composition of trace gases and aerosols is determined by the emission of compounds from the marine and terrestrial biospheres, anthropogenic sources and their chemistry and deposition processes. Biogenic emissions depend upon physiological processes and climate, and the atmospheric chemistry is governed by climate and feedbacks involving greenhouse gases themselves. Understanding and predicting the biogeochemistry of trace gases in past, present and future climates therefore demands an interdisciplinary approach integrating across physiology, atmospheric chemistry, physics and meteorology. Here, we highlight critical issues raised by recent findings in all of these key areas to provide a framework for better understanding the past and possible future evolution of the atmosphere. Incorporating recent experimental and observational findings, especially the influence of CO2 on trace gas emissions from marine algae and terrestrial plants, into earth system models remains a major research priority. As we move towards this goal, archives of the concentration and isotopes of N2O and CH4 from polar ice cores extending back over 650,000 years will provide a valuable benchmark for evaluating such models. In the Pre-Quaternary, synthesis of theoretical modelling with geochemical and palaeontological evidence is also uncovering the roles played by trace gases in episodes of abrupt climatic warming and ozone depletion. Finally, observations and palaeorecords across a range of timescales allow assessment of the Earth's climate sensitivity, a metric influencing our ability to decide what constitutes 'dangerous' climate change. PMID:17513267

  14. Trace Gas Retrievals from the GeoTASO Aircraft Instrument

    NASA Astrophysics Data System (ADS)

    Nowlan, C. R.; Liu, X.; Leitch, J. W.; Liu, C.; Gonzalez Abad, G.; Chance, K.; Cole, J.; Delker, T.; Good, W. S.; Murcray, F.; Ruppert, L.; Soo, D.; Loughner, C.; Follette-Cook, M. B.; Janz, S. J.; Kowalewski, M. G.; Pickering, K. E.; Zoogman, P.; Al-Saadi, J. A.

    2015-12-01

    The Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) instrument is a passive remote sensing instrument capable of making 2-D measurements of trace gases and aerosols from aircraft. The instrument measures backscattered UV and visible radiation, allowing the retrieval of trace gas amounts below the aircraft at horizontal resolutions on the order of 250 m x 250 m. GeoTASO was originally developed under NASA's Instrument Incubator Program as a test-bed instrument for the Geostationary Coastal and Air Pollution Events (GEO-CAPE) decadal survey mission, and is now also part of risk reduction for the upcoming Tropospheric Emissions: Monitoring of Pollution (TEMPO) and Geostationary Environment Monitoring Spectrometer (GEMS) geostationary satellite missions. We present spatially resolved observations of ozone, nitrogen dioxide, formaldehyde and sulfur dioxide over urban areas and power plants from flights during the DISCOVER-AQ field campaigns in Texas and Colorado, as well as comparisons with observations made by ground-based Pandora spectrometers, in situ monitoring instruments and other aircraft instruments deployed during these campaigns. These measurements at various times of day are providing a very useful data set for testing and improving TEMPO and GEMS retrieval algorithms, as well as demonstrating prototype validation strategies.

  15. Trace gas emissions from biomass burning in tropical Australian savannas

    SciTech Connect

    Hurst, D.F.; Griffith, D.W.T.; Cook, G.D.

    1994-08-20

    The trace gas emissions of biomass burning was measured during the 1991 and 1992 dry seasons (April through October) at the Kapalga Research Station in Kakadu National Park, Northern Territory, Australia. Over 100 smoke samples from savannah fires were collected, from the ground and from aircraft flying at 50 to 700 meters above the fires. The samples were analyzed for carbon dioxide, carbon monoxide, nitrous oxides, and other carbon and nitrogen compounds using gas phase Fourier transform infrared (FTIR) spectroscopy, matrix isolation FTIR spectroscopy, and chemiluminescence techniques. This paper describes the results of the gas analyses and discusses the potential impacts of these gases on regional atmospheric chemistry.49 refs., 4 figs., 7 tabs.

  16. Noble Gas Tracing of Fluid Transport in Shale Reservoirs

    NASA Astrophysics Data System (ADS)

    Heath, J. E.; Gardner, W. P.; Kuhlman, K. L.; Robinson, D. G.; Bauer, S. J.

    2014-12-01

    We investigate fluid transport mechanisms in a shale reservoir using natural noble gas tracers. Noble gas tracing is promising due to sensitivity of transport to: pore structure and sizes; phase partitioning between groundwater and liquid and gaseous hydrocarbons; and deformation from hydraulic fracturing and creation of surface area. A time-series of over thirty wellhead fluid samples were collected from two hydraulically-fractured wells with different oil-to-gas ratios, along with production data (i.e., flowrate and pressure). Tracer and production data sets can be combined to infer production flow regimes, to estimate reservoir transport parameters, and to improve forecasts of production decline. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  17. The Reanalysis for Stratospheric Trace-gas Studies

    NASA Technical Reports Server (NTRS)

    Pawson, Steven; Li, Shuhua

    2002-01-01

    In order to re-examine trace gas transport in the middle atmosphere for the period May 1991 until April 1995, a "reanalysis" is being performed using an up-to-date version of the DAO's "GEOS" assimilation system. The Reanalysis for Stratospheric Trace-gas Studies (ReSTS) is intended to provide state-of-the-art estimates of the atmosphere during a period when the Upper Atmospheric Research Satellite provided a high density of trace-gas observations, and when the aerosol loading from the eruption of Mount Pinatubo contaminated the lower stratosphere, at the same time performing a natural tracer transport experiment. This study will present the first results from ReSTS, focussing on the improvements over the meteorological analyses produced by the then-operational GEOS-1 data assimilation system; emphasis will be placed on the improved representations of physical processes between GEOS-1 and the current GEOS-4 systems, highlighting the transport properties of the datasets. Alongside the production of a comprehensive atmospheric dataset, important components of ReSTS include performing sensitivity studies to the formulation of the assimilation system (including the representation of physical processes in the GCM, such as feedbacks between ozone/aerosols and meteorology) and to the inclusion of additional data types (including limb-sounding temperature data alongside the TOVS observations). Impacts of some of these factors on the analyzed meteorology and transport will be discussed. Of particular interest are attempts to determine the relative importance of various steps in the assimilation process to the quality of the final analyses.

  18. Planar Laser-Based QEPAS Trace Gas Sensor

    PubMed Central

    Ma, Yufei; He, Ying; Chen, Cheng; Yu, Xin; Zhang, Jingbo; Peng, Jiangbo; Sun, Rui; Tittel, Frank K.

    2016-01-01

    A novel quartz enhanced photoacoustic spectroscopy (QEPAS) trace gas detection scheme is reported in this paper. A cylindrical lens was employed for near-infrared laser focusing. The laser beam was shaped as a planar line laser between the gap of the quartz tuning fork (QTF) prongs. Compared with a spherical lens-based QEPAS sensor, the cylindrical lens-based QEPAS sensor has the advantages of easier laser beam alignment and a reduction of stringent stability requirements. Therefore, the reported approach is useful in long-term and continuous sensor operation. PMID:27367686

  19. Planar Laser-Based QEPAS Trace Gas Sensor.

    PubMed

    Ma, Yufei; He, Ying; Chen, Cheng; Yu, Xin; Zhang, Jingbo; Peng, Jiangbo; Sun, Rui; Tittel, Frank K

    2016-01-01

    A novel quartz enhanced photoacoustic spectroscopy (QEPAS) trace gas detection scheme is reported in this paper. A cylindrical lens was employed for near-infrared laser focusing. The laser beam was shaped as a planar line laser between the gap of the quartz tuning fork (QTF) prongs. Compared with a spherical lens-based QEPAS sensor, the cylindrical lens-based QEPAS sensor has the advantages of easier laser beam alignment and a reduction of stringent stability requirements. Therefore, the reported approach is useful in long-term and continuous sensor operation. PMID:27367686

  20. Land use and ecosystem level controls of trace gas exchange

    NASA Astrophysics Data System (ADS)

    Mosier, A.; Ojima, D.; Parton, W.; Delgrosso, S.

    2003-04-01

    Significant changes in the way land areas are used have taken place over the past 50 years modifying critical biogeochemical cycles. These alterations in biogeochemical cycles have resulted in structural and functional changes within many ecosystems. Human activities are the primary agent of these changes. The conversion of forests to other uses, conversion of agricultural lands to urban development, conversion of range lands to crop lands and conversion from one type of agricultural system to another, have a significant impact on human society through changes in air quality, water quality and food production. One such concern is related to changes in agricultural field management and the impact on atmospheric trace gas concentrations. Water management in rice production can directly impact both methane (CH4) and nitrous oxide (N2O) fluxes and changes from animal waste based fertilization practices to synthetic fertilization can greatly influence N2O, NH3 and NOx emissions are. Regional analysis of these changes in land use and understanding of how these affect biogenic trace gas emissions are the focus of the collaborative research effort developed in the BATREX activity and the associated TRAGnet Data base development. Analysis of environmental and land management characteristics affecting the various process level controls on biogenic trace gas fluxes have been conducted and incorporated in modeling analysis for regional extrapolation. Results from these studies at site level and regional scale will be presented. The focus of these studies has been on agriculture since agricultural systems account for a large share of anthropogenic CH4 and N2O emissions as well as NH3 and NOx fluxes globally. Concurrently, the development of ecosystem level, process-based models such as the DNDC Model and DAYCENT are permitting the numerical evaluation of land management and conversion on trace gas fluxes. The development of the data bases and analyses of the data using such

  1. Estimation of Trace Gas Fluxes by Inverse Modelling

    NASA Astrophysics Data System (ADS)

    Prinn, R. G.; Chen, Y.; Huang, J.; Golombek, A.

    2003-12-01

    A wide range of scientific questions regarding chemically and/or radiatively important trace gases necessitate determinations of their sources and sinks at local to global scales. A powerful method for such determinations involves solution of an inverse problem in which the observed concentrations are effectively Lagrangian line integrals and the unknown sources or sinks are contained in the integrands. The inverse problem consists of calculating optimal estimates of the unknowns in the Bayesian sense using an atmospheric transport model and trace gas measurements gathered over space and time. Great care is necessary to include the effects of both measurement and transport model errors in calculating the uncertainty in the optimal estimates. We review the results of recent studies which use three-dimensional Eulerian (specifically MATCH) or Lagrangian transport models and Kalman filter and other optimization methods to compute emissions of methane, nitrous oxide, and selected halocarbons. These studies use high frequency trace gas observations from global networks (AGAGE, CMDL) to calibrate a priori emission maps for particular processes and geographic regions. The methods allow estimation of time varying emissions. For the hydrogen-containing gases these emission estimates require accurate specification of the concentrations of the hydroxyl radical which constitute their major sink. Hydroxyl radical levels can be optimally estimated in a separate problem using measurements of methyl chloroform whose global emissions are already very well known. The results show that the inverse approach is a powerful complement to traditional surface flux aggregation methods. At the same time, the inverse approach has its own limitations associated especially with transport model errors and/or inadequate atmospheric measurements.

  2. Miniature Trace Gas Detector Based on Microfabricated Optical Resonators

    NASA Technical Reports Server (NTRS)

    Aveline, David C.; Yu, Nan; Thompson, Robert J.; Strekalov, Dmitry V.

    2013-01-01

    While a variety of techniques exist to monitor trace gases, methods relying on absorption of laser light are the most commonly used in terrestrial applications. Cavity-enhanced absorption techniques typically use high-reflectivity mirrors to form a resonant cavity, inside of which a sample gas can be analyzed. The effective absorption length is augmented by the cavity's high quality factor, or Q, because the light reflects many times between the mirrors. The sensitivity of such mirror-based sensors scales with size, generally making them somewhat bulky in volume. Also, specialized coatings for the high-reflectivity mirrors have limited bandwidth (typically just a few nanometers), and the delicate mirror surfaces can easily be degraded by dust or chemical films. As a highly sensitive and compact alternative, JPL is developing a novel trace gas sensor based on a monolithic optical resonator structure that has been modified such that a gas sample can be directly injected into the cavity. This device concept combines ultra-high Q optical whispering gallery mode resonators (WGMR) with microfabrication technology used in the semiconductor industry. For direct access to the optical mode inside a resonator, material can be precisely milled from its perimeter, creating an open gap within the WGMR. Within this open notch, the full optical mode of the resonator can be accessed. While this modification may limit the obtainable Q, calculations show that the reduction is not significant enough to outweigh its utility for trace gas detection. The notch can be milled from the high- Q crystalline WGMR with a focused ion beam (FIB) instrument with resolution much finer than an optical wavelength, thereby minimizing scattering losses and preserving the optical quality. Initial experimental demonstrations have shown that these opened cavities still support high-Q whispering gallery modes. This technology could provide ultrasensitive detection of a variety of molecular species in an

  3. A Lagrangian view of stratospheric trace gas distributions

    NASA Astrophysics Data System (ADS)

    Schoeberl, M. R.; Sparling, L. C.; Jackman, C. H.; Fleming, E. L.

    2000-01-01

    As a result of photochemistry, some relationship between the stratospheric age of air or mean age and the amount of tracer contained within an air sample is expected. The existence of such a relationship allows inferences about transport history to be made from observations of chemical tracers. This paper lays down the conceptual foundations for the relationship between age and tracer amount for long-lived tracers, developed within a Lagrangian framework. Although the photochemical loss depends not only on the age of the parcel but also on its path, we show that under the "average path approximation" that the path variations are less important than parcel age. The average path approximation then allows us to develop a formal relationship between the age spectrum and the tracer distribution. Using this relationship, tracer-tracer correlations can be interpreted as the result of mixing which connects parts of the "single-path photochemistry curve," a universal path-independent curve that describes the photochemical loss in terms of the total photon exposure. This geometric interpretation of mixing gives rise to constraints on trace gas correlation curves as can be seen in the atmospheric trace molecule spectroscopy observations.

  4. Airborne Trace Gas Mapping During the GOSAT-COMEX Experiment

    NASA Astrophysics Data System (ADS)

    Tratt, D. M.; Leifer, I.; Buckland, K. N.; Johnson, P. D.; Van Damme, M.; Pierre-Francois, C.; Clarisse, L.

    2015-12-01

    The GOSAT-COMEX-IASI (Greenhouse gases Observing SATellite - CO2 and Methane EXperiment - Infrared Atmospheric Sounding Interferometer) experiment acquired data on 24-27 April 2015 with two aircraft, a mobile ground-based sampling suite, and the GOSAT and IASI platforms. Collections comprised the Kern Front and Kern River oil fields north of Bakersfield, Calif. and the Chino stockyard complex in the eastern Los Angeles Basin. The nested-grid experiment examined the convergence of multiple approaches to total trace gas flux estimation from the experimental area on multiple length-scales, which entailed the integrated analysis of ground-based, airborne, and space-based measurements. Airborne remote sensing was employed to map the spatial distribution of discrete emission sites - crucial information to understanding their relative aggregate contribution to the overall flux estimation. This contribution discusses the methodology in the context of the airborne GHG source mapping component of the GOSAT-COMEX experiment and its application to satellite validation.

  5. Trace gas measurements in the Kuwait oil fire smoke plume

    SciTech Connect

    Luke, W.T.; Kok, G.L.; Schillawski, R.D.; Zimmerman, P.R.; Greenberg, J.P.; Kadavanich, M.

    1992-09-20

    The authors report trace gas measurements made both inside and outside the Kuwait oil-fire smoke plume during a flight of an instrumented research aircraft on May 30, 1991. Concentrations of SO{sub 2}, CO, and NO{sub x} averaged vertically and horizontally throughout the plume 80 km downwind of Kuwait City were 106, 127, and 9.1 parts per billion by volume (ppbv), respectively, above background concentrations. With the exception of SO{sub 2}, trace gas concentrations were far below typical US urban levels and primary national ambient air quality standards. Ambient ozone was titrated by NO in the dark, dense core of the smoke plume close to the fires, and photochemical ozone production was limited to the diffuse edge of the plume. Photochemical O{sub 3} production was noted throughout the plume at a distance of 160 km downwind of Kuwait City, and averaged 2.3 ppbv per hour during the first 3 hours of transport. Little additional photochemical production was noted at a downwind range of 340 km. The fluxes of sulfur dioxide, carbon monoxide, and reactive nitrogen from the roughly 520 fires still burning on May 30, 1991 are estimated at 1.4 x 10{sup 7} kg SO{sub 2}/d, 6.9 x 10{sup 6} kg CO/d, and 2.7 x 10{sup 5} kg N/d, respectively. Generally low concentrations of CO and NO{sub x} indicate that the combustion was efficient and occurred at low temperatures. Low total nonmethane hydrocarbon concentrations suggest that the volatile components of the petroleum were burned efficiently. 37 refs., 4 figs., 4 tabs.

  6. Trace gas transport out of the Indian Summer Monsoon

    NASA Astrophysics Data System (ADS)

    Tomsche, Laura; Pozzer, Andrea; Zimmermann, Peter; Parchatka, Uwe; Fischer, Horst

    2016-04-01

    The trace gas transport out of the Indian summer monsoon was investigated during the aircraft campaign OMO (Oxidation Mechanism Observations) with the German research aircraft HALO (High Altitude and Long Range Research Aircraft) in July/August 2015. HALO was based at Paphos/Cyprus and also on Gan/Maledives. Flights took place over the Mediterranean Sea, the Arabian Peninsula and the Arabian Sea. In this work the focus is on the distribution of carbon monoxide (CO) and methane (CH4) in the upper troposphere. They were measured with the laser absorption spectrometer TRISTAR on board of HALO. During the Indian summer monsoon strong convection takes place over India and the Bay of Bengal. In this area the population is high accompanied by many emission sources e.g. wetlands and cultivation of rice. Consequently the boundary layer is polluted containing high concentrations of trace gases like methane and carbon monoxide. Due to vertical transport these polluted air masses are lifted to the upper troposphere. Here they circulate with the so called Asian monsoon anticyclone. In the upper troposphere polluted air masses lead to a change in the chemical composition thus influence the chemical processes. Furthermore the anticyclone spreads the polluted air masses over a larger area. Thus the outflow of the anticyclone in the upper troposphere leads to higher concentrations of trace gases over the Arabian Sea, the Arabian Peninsula and also over the eastern part of North Africa and the eastern part of the Mediterranean Sea. During OMO higher concentrations of methane and carbon monoxide were detected at altitudes between 11km and 15km. The highest measured concentrations of carbon monoxide and methane were observed over Oman. The CO concentration in the outflow of the monsoon exceeds background levels by 10-15ppb. However the enhancement in the concentration is not obviously connected to the monsoon due to the natural variability in the troposphere. The enhancement in the

  7. Development of a Miniaturized Hollow-Waveguide Gas Correlation Radiometer for Trace Gas Measurements in the Martian Atmosphere

    NASA Technical Reports Server (NTRS)

    Wilson, Emily L.; Georgieva, E. M.; Blalock, G. W.; Marx, C. T.; Heaps, W. S.

    2012-01-01

    We present preliminary results in the development of a miniaturized gas correlation radiometer (GCR) for column trace gas measurements in the Martian atmosphere. The GCR is designed as an orbiting instrument capable of mapping multiple trace gases and identifying active regions on the Mars surface.

  8. Trace Gas Trends in the Stratosphere: 1991-2005

    NASA Astrophysics Data System (ADS)

    Elkins, J. W.; Moore, F. L.; Dutton, G. S.; Hurst, D. F.; Ray, E. A.; Montzka, S. A.; Butler, J. H.; Fahey, D. W.; Hall, B. H.; Atlas, E.; Wofsy, S. C.; Romashkin, P. A.

    2005-05-01

    The first NOAA airborne gas chromatograph measured chlorofluorocarbon-11 (CFC-11) and CFC-113 during the Arctic Airborne Stratospheric Experiment in 1991-1992. In 1994, we added nitrous oxide (N2O), sulfur hexafluoride (SF6), CFC-12, halon-1211, methyl chloroform, carbon tetrachloride, methane, and hydrogen. NOAA scientists have since operated five airborne gas chromatographs on NASA airborne platforms, including the NASA Jet Propulsion Laboratory (JPL) balloon gondola and ER-2, WB-57F, DC-8, and NASA Altair Unmanned Air Vehicle (UAV) aircraft. Using these in situ measurements and tracer-tracer correlations from flask observations for the unmeasured halogen species (HCFCs and methyl halides including methyl chloride and bromide), we have estimated trends of total chlorine and bromine in the stratosphere. The determination of inorganic equivalent chlorine (Cl + 45*Br) requires the trend of tropospheric equivalent chlorine and the mean age of the parcel of stratospheric air. In general, there is good agreement between the mean age of the air mass calculations using carbon dioxide and SF6, except for regions of extreme down welling of mesospheric air where SF6 is consumed. Tropospheric trends of the methyl halides have been compiled against stable standards. We operated a airborne gas chromatograph on the Sage 3 Ozone Loss Validation Experiment (SOLVE-II) mission from Kiruna, Sweden during 2002. It measured the major HCFCs and methyl halides, so that these compounds do not have to be estimated from tracer-tracer correlations in the future. In 2005, we have added a new lightweight airborne instrument (<25 kg) that can measure CFC-11, CFC-12, halon-1211, SF6, N2O, and ozone. This instrument can operate on small or UAV aircraft and will be used for Aura satellite validation. This presentation will show trends for selected trace gases and our estimates of total equivalent chlorine stratospheric trends since 1991.

  9. Effects of fertilizer placement on trace gas emissions from container-grown plant production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increased trace gas emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are widely believed to be a primary cause of global warming. Agriculture is a large contributor to these emissions; however, its role in climate change is unique in that it can act as a source of trace gas ...

  10. Trace gas emissions from nursery crop production using different fertilizer methods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increased trace gas emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are widely believed to be a primary cause of global warming. Agriculture is a large contributor to these emissions; however, its role in climate change is unique in that it can act as a source of trace gas ...

  11. Effects of fertilizer placement on trace gas emissions from nursery container production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increased trace gas emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are widely believed to be a primary cause of global warming. Agriculture is a large contributor to these emissions; however, its role in climate change is unique in that it can act as a source of trace gas ...

  12. Trace gas absorption spectroscopy using laser difference-frequency spectrometer for environmental application

    NASA Technical Reports Server (NTRS)

    Chen, W.; Cazier, F.; Boucher, D.; Tittel, F. K.; Davies, P. B.

    2001-01-01

    A widely tunable infrared spectrometer based on difference frequency generation (DFG) has been developed for organic trace gas detection by laser absorption spectroscopy. On-line measurements of concentration of various hydrocarbons, such as acetylene, benzene, and ethylene, were investigated using high-resolution DFG trace gas spectroscopy for highly sensitive detection.

  13. Developing Tools to Assess European Trace Gas Trends

    NASA Astrophysics Data System (ADS)

    Wilson, Rebecca; Fleming, Zoe; Henne, Stephan; Monks, Paul

    2010-05-01

    The GEOmon (Global Earth Observation and MONitoring) project has produced a harmonised data set of trace gases from thirty ground-based measurement stations belonging to a number of regional, national and European air quality networks (e.g. EMEP, GAW). A variety of tools have been developed in R to evaluate European trace gas trends as a method to assess data quality and the effectiveness of European emission legislation. Long-term O3, NO2 and CO have been characterised at all sites using lowess regression. Additionally, O3 was deseasonalised and linear trends were fitted to and quantified for monthly means, 5th and 95th percentiles (to illustrate changes in mean, background and peak concentrations respectively). Twenty-four of these sites have data between 1996-2005 (Incl). Analysis of these sites for the time period provides an easily comparable characterisation of continental-scale O3 trends. However, few sites have statistically significant trends during this limited analysis period. The RETRO monthly NOx emissions fluxes at the GEOmon harmonised data sites were plotted from 1985-2000. The introduction of catalytic converters in Europe in 1985 and subsequent EU legislation in 1993 (requiring catalytic converters in all new petrol cars sold), corresponds to a decrease in NOx emissions throughout 1990's for the majority of sites. It is noted that the rate of reduction in NOx emissions decreases from the mid-1990's to 2000 for fifteen locations. This may account for the less pronounced, and reduced statistical significance of, O3 trends during the 1996-2005 period. Although the spatial distribution of European O3 trends 1996-2005 is inconclusive for the present GEOmon harmonised dataset, the expansion to more European sites may lead to a more detailed characterisation.

  14. A Lagrangian View of Stratospheric Trace Gas Distributions

    NASA Technical Reports Server (NTRS)

    Schoeberl, M. R.; Sparling, L.; Dessler, A.; Jackman, C. H.; Fleming, E. L.

    1998-01-01

    As a result of photochemistry, some relationship between the stratospheric age-of-air and the amount of tracer contained within an air sample is expected. The existence of such a relationship allows inferences about transport history to be made from observations of chemical tracers. This paper lays down the conceptual foundations for the relationship between age and tracer amount, developed within a Lagrangian framework. In general, the photochemical loss depends not only on the age of the parcel but also on its path. We show that under the "average path approximation" that the path variations are less important than parcel age. The average path approximation then allows us to develop a formal relationship between the age spectrum and the tracer spectrum. Using the relation between the tracer and age spectra, tracer-tracer correlations can be interpreted as resulting from mixing which connects parts of the single path photochemistry curve, which is formed purely from the action of photochemistry on an irreducible parcel. This geometric interpretation of mixing gives rise to constraints on trace gas correlations, and explains why some observations are do not fall on rapid mixing curves. This effect is seen in the ATMOS observations.

  15. Trace gas monitoring with infrared laser-based detection schemes

    NASA Astrophysics Data System (ADS)

    Sigrist, M. W.; Bartlome, R.; Marinov, D.; Rey, J. M.; Vogler, D. E.; Wächter, H.

    2008-02-01

    The success of laser-based trace gas sensing techniques crucially depends on the availability and performance of tunable laser sources combined with appropriate detection schemes. Besides near-infrared diode lasers, continuously tunable midinfrared quantum cascade lasers and nonlinear optical laser sources are preferentially employed today. Detection schemes are based on sensitive absorption measurements and comprise direct absorption in multi-pass cells as well as photoacoustic and cavity ringdown techniques in various configurations. We illustrate the performance of several systems implemented in our laboratory. These include time-resolved multicomponent traffic emission measurements with a mobile CO2-laser photoacoustic system, a diode-laser based cavity ringdown device for measurements of impurities in industrial process control, isotope ratio measurements with a difference frequency (DFG) laser source combined with balanced path length detection, detection of methylamines for breath analysis with both a near-IR diode laser and a DFG source, and finally, acetone measurements with a heatable multipass cell intended for vapor phase studies on doping agents in urine samples.

  16. Hollow Waveguide Gas Sensor for Mid-Infrared Trace Gas Analysis

    SciTech Connect

    Kim, S; Young, C; Chan, J; Carter, C; Mizaikoff, B

    2007-07-12

    A hollow waveguide mid-infrared gas sensor operating from 1000 cm{sup -1} to 4000 cm{sup -1} has been developed, optimized, and its performance characterized by combining a FT-IR spectrometer with Ag/Ag-halide hollow core optical fibers. The hollow core waveguide simultaneously serves as a light guide and miniature gas cell. CH{sub 4} was used as test analyte during exponential dilution experiments for accurate determination of the achievable limit of detection (LOD). It is shown that the optimized integration of an optical gas sensor module with FT-IR spectroscopy provides trace sensitivity at the few hundreds of parts-per-billion concentration range (ppb, v/v) for CH{sub 4}.

  17. Miniaturized Hollow-Waveguide Gas Correlation Radiometer (GCR) for Trace Gas Detection in the Martian Atmosphere

    NASA Technical Reports Server (NTRS)

    Wilson, Emily L.; Georgieva, E. M.; Melroy, H. R.

    2012-01-01

    Gas correlation radiometry (GCR) has been shown to be a sensitive and versatile method for detecting trace gases in Earth's atmosphere. Here, we present a miniaturized and simplified version of this instrument capable of mapping multiple trace gases and identifying active regions on the Mars surface. Reduction of the size and mass of the GCR instrument has been achieved by implementing a lightweight, 1 mm inner diameter hollow-core optical fiber (hollow waveguide) for the gas correlation cell. Based on a comparison with an Earth orbiting CO2 gas correlation instrument, replacement of the 10 meter mUltipass cell with hollow waveguide of equivalent pathlength reduces the cell mass from approx 150 kg to approx 0.5 kg, and reduces the volume from 1.9 m x 1.3 m x 0.86 m to a small bundle of fiber coils approximately I meter in diameter by 0.05 m in height (mass and volume reductions of >99%). This modular instrument technique can be expanded to include measurements of additional species of interest including nitrous oxide (N2O), hydrogen sulfide (H2S), methanol (CH3OH), and sulfur dioxide (SO2), as well as carbon dioxide (CO2) for a simultaneous measure of mass balance.

  18. Digital Architecture for a Trace Gas Sensor Platform

    NASA Technical Reports Server (NTRS)

    Gonzales, Paula; Casias, Miguel; Vakhtin, Andrei; Pilgrim, Jeffrey

    2012-01-01

    A digital architecture has been implemented for a trace gas sensor platform, as a companion to standard analog control electronics, which accommodates optical absorption whose fractional absorbance equivalent would result in excess error if assumed to be linear. In cases where the absorption (1-transmission) is not equivalent to the fractional absorbance within a few percent error, it is necessary to accommodate the actual measured absorption while reporting the measured concentration of a target analyte with reasonable accuracy. This requires incorporation of programmable intelligence into the sensor platform so that flexible interpretation of the acquired data may be accomplished. Several different digital component architectures were tested and implemented. Commercial off-the-shelf digital electronics including data acquisition cards (DAQs), complex programmable logic devices (CPLDs), field-programmable gate arrays (FPGAs), and microcontrollers have been used to achieve the desired outcome. The most completely integrated architecture achieved during the project used the CPLD along with a microcontroller. The CPLD provides the initial digital demodulation of the raw sensor signal, and then communicates over a parallel communications interface with a microcontroller. The microcontroller analyzes the digital signal from the CPLD, and applies a non-linear correction obtained through extensive data analysis at the various relevant EVA operating pressures. The microcontroller then presents the quantitatively accurate carbon dioxide partial pressure regardless of optical density. This technique could extend the linear dynamic range of typical absorption spectrometers, particularly those whose low end noise equivalent absorbance is below one-part-in-100,000. In the EVA application, it allows introduction of a path-length-enhancing architecture whose optical interference effects are well understood and quantified without sacrificing the dynamic range that allows

  19. Open Path Trace Gas Laser Sensors for UAV Deployment

    NASA Astrophysics Data System (ADS)

    Shadman, S.; Mchale, L.; Rose, C.; Yalin, A.

    2015-12-01

    Novel trace gas sensors based on open-path Cavity Ring-down Spectroscopy (CRDS) are being developed to enable remote and mobile deployments including on small unmanned aerial systems (UAS). Relative to established closed-path CRDS instruments, the use of open-path configurations allows removal of the bulky and power hungry vacuum and flow system, potentially enabling lightweight and low power instruments with high sensitivity. However, open path operation introduces new challenges including the need to maintain mirror cleanliness, mitigation of particle optical effects, and the need to measure spectral features that are relatively broad. The present submission details open-path CRDS instruments for ammonia and methane and their planned use in UAS studies. The ammonia sensor uses a quantum cascade laser at 10.3 mm in a configuration in which the laser frequency is continuously swept and a trigger circuit and acousto-optic modulator (AOM) extinguish the light when the laser is resonant with the cavity. Ring-down signals are measured with a two-stage thermoelectrically cooled MCT photodetector. The cavity mirrors have reflectivity of 0.9995 and a noise equivalent absorption of 1.5 ppb Hz-1/2 was demonstrated. A first version of the methane sensor operated at 1.7um with a telecom diode laser while the current version operates at 3.6 um with an interband cascade laser (stronger absorption). We have performed validation measurements against known standards for both sensors. Compact optical assemblies are being developed for UAS deployment. For example, the methane sensor head will have target mass of <4 kg and power draw <40 W. A compact single board computer and DAQ system is being designed for sensor control and signal processing with target mass <1 kg and power draw <10 W. The sensor size and power parameters are suitable for UAS deployment on both fixed wing and rotor style UAS. We plan to deploy the methane sensor to measure leakage and emission of methane from

  20. Detection of atmospheric trace gas species by DOAS gas-analyzer

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    A differential optical absorption spectroscopy (DOAS) gas-analyzer was successfully tested. A high pressure 150-W Xe arc lamp was employed as a light source This system consisted of a coaxial telescope, a spectrometer, an analyzer and retroreflector. In order to record the spectra, a monochrometer with a grating and photodiode array was adopted. Gas analyzer spectral data bank includes more than 30 moleculas absorbed in UV spectral region. The measured absorption spectra were evaluated by using a least-squares fit to determine the average mixing ratio of each species in the atmosphere. A number of air pollutants concentrations: SO2, NO2, O3, etc were trace measured. Minimally detected concentration on pathlength 400 m is the unit of ppb at the time of accumulation of 2 min. The results of the field test measurements of pollutants in Tomsk are presented.

  1. More than just CO2: Multiple trace gas exchange measurements at a temperate mountain grassland

    NASA Astrophysics Data System (ADS)

    Wohlfahrt, Georg; Hammerle, Albin; Hörtnagl, Lukas; Bamberger, Ines; Hansel, Armin

    2015-04-01

    Ecosystems exchange a large number of different trace gases to/from the atmosphere, however the vast majority of FLUXNET sites quantifies only the fluxes of carbon dioxide and when assessing the carbon or greenhouse gas balance neglect other carbon or greenhouse gas fluxes. This causes an overestimation of the role of carbon dioxid exchange for the ecosystem carbon and greenhouse gas balance, the magnitude of which is largely unconstrained Here we use the eddy covariance method (and variants thereof) with a large variety of analytical methods to quantify the exchange of multiple trace gases to/from a mountain grassland, partly for a time period of over a decade. The monitored trace gas fluxes cover: carbon dioxide, methane, nitrous oxide, carbon monoxide and several volatile organic compounds. The main result of our study is that carbon dioxide is the major contributor to the gaseous carbon and greenhouse gas budget at this temperate mountain grassland, which however may be significantly modulated by other trace gases may, at least during some years. Differences between source and sink periods for the different trace gases and the underlying drivers are discussed and annual budgets, for some compounds covering multiple years up to decades, are presented. We conclude that multiple trace gas flux measurements help to elucidate the importance of the exchange of carbon dioxide for the ecosystem carbon and greenhouse gas budget.

  2. Soil physiochemical controls on trace gas emissions for a North Dakota mollisol

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Quantification of trace gas emissions and an increased understanding of soil controls on emissions during freeze-thaw cycles are essential to refine climate change models. Six similar, intact soil cores were collected to a depth of 80 cm from an undisturbed prairie in central North Dakota. Trace g...

  3. Comparing two micrometeorological techniques for estimating trace gas emissions from distributed sources

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Measuring trace gas emission from distributed sources such as treatment lagoons, treatment wetlands, land spread of manure, and feedlots requires micrometeorological methods. In this study, we tested the accuracy of two relatively new micrometeorological techniques, vertical radial plume mapping (VR...

  4. The Pasamonte unequilibrated eucrite: Pyroxene REE systematic and major-, minor-, and trace-element zoning. [Abstract only

    NASA Technical Reports Server (NTRS)

    Pun, A.; Papike, J. J.

    1994-01-01

    We are evaluating the trace-element concentrations in the pyroxenes of Pasamonte. Pasamonte is a characteristic member of the main group eucrites, and has recently been redescribed as a polymict eucrite. Our Pasamonte sample contained eucritic clasts with textures ranging from subophitic to moderately coarse-grained. This study concentrates on pyroxenes from an unequilibrated, coarse-grained eucrite clast. Major-, minor-, and trace-element analyses were measured for zoned pyroxenes in the eucritic clast of Pasamonte. The major- and minor-element zoning traverses were measured using the JEOL 733 electron probe with an Oxford-Link imaging/analysis system. Complemenatry trace elements were then measured for the core and rim of each of the grains by SIMS. The trace elements analyzed consisted of eight REE, Sr, Y, and Zr. These analyses were performed on a Cameca 4f ion probe. The results of the CI chondrite normalized (average CI trace-element analyses for several grains and the major- and minor-element zoning patterns from a single pyroxene grain are given. The Eu abundance in the cores of the pyroxenes represents the detection limit and therefore the (-Eu) anomaly is a minimum. Major- and minor-element patterns are typical for igneous zoning. Pyroxene cores are Mg enriched, whereas the rims are enriched in Fe and Ca. Also, Ti and Mn are found to increase, while Cr and Al generally decrease in core-to-rim traverses. The cores of the pyroxenes are more depleted in the Rare Earth Elements (REE) than the rims. Using the minor- and trace-element concentrations of bulk Pasamonte and the minor- and trace-element concentrations from the cores of the pyroxenes in Pasamonte measured in this study, we calculated partition coefficients between pyroxene and melt. This calculation assumes that bulk Pasamonte is representative of a melt composition.

  5. TRACE GAS CONCENTRATIONS IN SMALL STREAMS OF THE GEORGIA PIEDMONT

    EPA Science Inventory

    Seventeen headwater watersheds within the SFBR watershed ranging from 0.5 to 3.4 km2 were selected. We have been monitoring concentrations of the trace gases nitrous oxide, methane, and carbon dioxide, and other parameters (T, conductivity, dissolved oxygen, pH, nutrients, flow r...

  6. Specific, trace gas induced phase transition in copper(II)oxide for highly selective gas sensing

    NASA Astrophysics Data System (ADS)

    Kneer, J.; Wöllenstein, J.; Palzer, S.

    2014-08-01

    Here, we present results on the investigation of the percolation phase transition in copper(II)oxide (CuO) and show how it may be used to determine trace gas concentrations. This approach provides a highly selective sensing mechanism for the detection of hydrogen sulfide even in oxygen depleted atmospheres. In real-world applications, this scenario is encountered in biogas plants and natural gas facilities, where reliable H2S sensing and filtering are important because of the destructive effects H2S has on machinery. As opposed to gas detection via standard metal-oxide reaction routes, the percolation dynamics are demonstrated to be independent of the surface morphology in accordance with the universality of phase transitions. The sensing behavior of ink-jet printed CuO layers was tested for a large set of parameters including layer temperature, hydrogen sulfide (H2S) and oxygen concentration, as well as the sensitivity towards other gas species. The electrical percolation of the sensing layer is heralded by a dramatic drop in the overall resistivity of the CuO layer for temperatures below 200 °C. The observed percolation phenomena in this temperature regime are unique to H2S even in comparison with related volatile thio-compounds making the sensing mechanism highly selective. At elevated temperatures above 300 °C, the phase transition does not occur. This enables two distinct operational modes which are tunable via the sensor temperature and also allows for resetting the sensing layer after an electrical breakthrough.

  7. Quantifying wind and pressure effects on trace gas fluxes across the soil-atmosphere interface

    NASA Astrophysics Data System (ADS)

    Redeker, K. R.; Baird, A. J.; Teh, Y. A.

    2015-12-01

    Large uncertainties persist in estimates of soil-atmosphere exchange of important trace gases. One significant source of uncertainty is the combined effect of wind and pressure on these fluxes. Wind and pressure effects are mediated by surface topography: few surfaces are uniform and over scales of tenths of a metre to tens of metres, air pressure and wind speed at the ground surface may be very variable. In this paper we consider how such spatial variability in air pressure and wind speed affects fluxes of trace gases. We used a novel nested wind tunnel design comprising a toroidial wind tunnel, in which wind speed and pressure may be controlled, set within a larger, linear wind tunnel. The effects of both wind speed and pressure differentials on fluxes of CO2 and CH4 within three different ecosystems (forest, grassland, peat bog) were quantified. We find that trace gas fluxes are positively correlated with both wind speed and pressure differential near the surface boundary. We argue that wind speed is the better proxy for trace gas fluxes because of its stronger correlation and because wind speed is more easily measured and wind speed measurement methodology more easily standardized. Trace gas fluxes, whether into or out of the soil, increase with wind speed within the toroidal tunnel (+55 % flux per m s-1), while faster, localized surface winds that are external to the toroidal wind tunnel reduce trace gas fluxes (-13 % flux per m s-1). These results are consistent for both trace gases over all ecosystem soil types studied. Our findings support the need for a revised conceptualization of soil-atmosphere gas exchange. We propose a conceptual model of the soil profile that has a "mixed layer", with fluxes controlled by wind speed, wind duration, porosity, water table, and gas production and consumption.

  8. Laboratory-scale measurement of trace gas fluxes from landfarm soils.

    PubMed

    Ausma, Sandra; Edwards, Grant C; Gillespie, Terry J

    2003-01-01

    Trace gas emissions from refinery and bioremediation landfarms were investigated in a mesocosm-scale simulator facility. Five simulators were constructed and integrated with a data acquisition system and trace gas analyzers, allowing automated real-time sampling and calculation of total hydrocarbon (THC), CO2, and water vapor fluxes. Experiments evaluating the influence of simulated cultivation and rainfall on trace gas fluxes from the soil surfaces were conducted. Results were compared with published field results. Results showed that cultivating dry or moderately wet soil resulted in brief enhancements of THC fluxes, up to a factor of 10, followed by a sharp decline. Cultivating dry soil did not enhance respiration. Cultivating wet soil did result in sustained elevated levels of respiration. Total hydrocarbon emissions were also briefly enhanced in wet soils, but to a lesser magnitude than in dry soil. Hydrocarbon fluxes from refinery landfarm soil were very low for the duration of the experiments. This lead to the conclusion that elevated THC fluxes would only be expected during waste application. An evaluation of the influence of simultaneous water vapor fluxes on other trace gas fluxes highlighted the importance in lab-scale experiments of correcting trace gas fluxes from soils. The results from this research can be used to guide management practices at landfarms and to provide data to aid in assessing the effect of landfarms. PMID:12549537

  9. Digital array gas radiometer (DAGR): a sensitive and reliable trace gas detection concept

    NASA Astrophysics Data System (ADS)

    Gordley, Larry L.; McHugh, Martin J.; Marshall, B. T.; Thompson, Earl

    2009-05-01

    The Digital Array Gas Radiometer (DAGR) concept is based on traditional and reliable Gas Filter Correlation Radiometry (GFCR) for remote trace gas detection and monitoring. GFCR sensors have been successful in many infrared remote sensing applications. Historically however, solar backscatter measurements have not been as successful because instrument designs have been susceptible to natural variations in surface albedo, which induce clutter and degrade the sensitivity. DAGR overcomes this limitation with several key innovations. First, a pupil imaging system scrambles the received light, removing nearly all spatial clutter and permitting a small calibration source to be easily inserted. Then, by using focal plane arrays rather than single detectors to collect the light, dramatic advances in dynamic range can be achieved. Finally, when used with the calibration source, data processing approaches can further mitigate detector non-uniformity effects. DAGR sensors can be made as small as digital cameras and are well suited for downlooking detection of gases in the boundary layer, where solar backscatter measurements are needed to overcome the lack of thermal contrast in the IR. Easily integrated into a satellite platform, a space-based DAGR would provide near-global sensing of climatically important species such as such as CO, CH4, and N2O. Aircraft and UAV measurements with a DAGR could be used to monitor agricultural and industrial emissions. Ground-based or portable DAGRs could augment early warning systems for chemical weapons or toxic materials. Finally, planetary science applications include detection and mapping of biomarkers such as CH4 in the Martian atmosphere.

  10. Trace Gas Emissions From Tropical North Australian Savanna Fires

    NASA Astrophysics Data System (ADS)

    Paton-Walsh, C.; Deutscher, N. M.; Griffith, D. W.; Wilson, S. R.; Jones, N. B.; Forgan, B.

    2008-12-01

    We present measurements of atmospheric trace gases within smoke plumes from tropical North Australian savanna fires. The remote sensing measurements are made from Darwin (12.4°S, 130.9°E) using Fourier Transform spectroscopy with the sun as the source. From these infrared spectra column amounts of carbon monoxide (CO), formaldehyde (H2CO), acetylene (C2H2), ethane (C2H6) and hydrogen cyanide (HCN) have been determined. Literature esimates of emission factors for CO are then used to infer emission factors for these other gases.

  11. Effects of trace gas components in carbon capture and storage: geochemical experiments and simulation of laboratory-scale brine-rock-CO2-trace gas interaction

    NASA Astrophysics Data System (ADS)

    Stadler, Susanne; Nowak, Thomas; Heeschen, Katja; Riße, Andreas; Ostertag-Henning, Christian

    2010-05-01

    In the research activities on geological storage of carbon dioxide many studies mainly focus on the impact of pure CO2 gas on the storage formations. However, flue gas streams of power plants not only contain CO2, but also number of trace gases such as O2, N2, Ar, NOX, SOX, CO, H2, H2S, COS and CH4. These trace gases may not only interact with pipeline material, but can also trigger short-term and long-term changes within the subsurface storage lithology. The chemical reactivity of each of these compounds has to be evaluated and their interactions with each other have to be understood, especially since some of them are far more reactive than CO2. Within the project COORAL (= CO2 Purity for Capture and Storage) we concentrate on geochemical investigations to determine reaction pathways and kinetics of different mineral phases typical for potential German storage formations as influenced by the presence of trace gases within the flue gas stream. Quantitative measurements of these reactions are relatively well described for pure CO2 systems but are so far not well described for multi-component mixtures. We combine laboratory experiments (batch and flow-through) with numerical simulations applying the geochemical simulators PHREEQC and ChemApp, which will be coupled to GeoSys/RockFlow for coupled thermo-hydro-mechanical-chemical (THMC) process simulations. Calculations and experiments are performed for temperatures up to 200°C and pressures up to 50 MPa. The aim of the study is to determine optimal maximum concentration levels of trace gases in flue gas streams to be used in geological CO2 storage.

  12. Development of trace gas detection instrumentation. [using the heterodyne principle

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Breadboard hardware was constructed to demonstrate detection of a gaseous species by the heterodyne principle. The characteristics of the component parts were investigated and preliminary measurements were made to establish the sensitivity and selectivity of the method for gas analysis of CO, CO2, and N2O. A prototype heterodyne gas analyzer was designed, built, and brought into operational condition. Performance parameters of the prototype analyzer were investigated and its sensitivity to CO2 measured. Further development was undertaken for both the optical bench and the electronic processor components. A three-gas prototype analyzer, capable of measuring the gases CO, CO2, and CH4 was also constructed and tested. Detailed descriptions of the work and results are presented.

  13. Trace-Gas Detection with Off-Beam Quartz Enhanced Photoacoustic Spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Kun; Wang, Lei; Tan, Tu; Zhang, Weijun; Chen, Weidong; Gao, Xiaoming

    2015-06-01

    Trace-gas sensors have a wide range of potential applications such as environmental monitoring, climate research, agriculture, workplace safety, medical diagnostics, and industrial process control. A recently introduced technique called quartz-enhanced photoacoustic spectroscopy (QEPAS) is described. QEPAS use a quartz tuning fork as an acoustic transducer for a photoacoustic signal induced in an absorbing gas by modulated optical radiation. Advantages of the QEPAS compared to conventional photoacoustic spectroscopy include immunity to environmental acoustic noise and ultra-small sample volume. Trace gases of , and were monitored with a novel off-beam QEPAS approach and are described in detail.

  14. Laser Raman sensor for measurement of trace-hydrogen gas

    NASA Technical Reports Server (NTRS)

    Adler-Golden, Steven M.; Goldstein, Neil; Bien, Fritz; Matthew, Michael W.; Gersh, Michael E.; Cheng, Wai K.; Adams, Frederick W.

    1992-01-01

    A new optical hydrogen sensor based on spontaneous Raman scattering of laser light has been designed and constructed for rugged field use. It provides good sensitivity, rapid response, and the inherent Raman characteristics of linearity and background gas independence of the signal. Efficient light collection and discrimination by using fast optics and a bandpass interference filter compensate for the inefficiency of the Raman-scattering process. A multipass optical cavity with a Herriott-type configuration provides intense illumination from an air-cooled CW gas laser. The observed performance is in good agreement with the theoretical signal and noise level predictions.

  15. Long term aerosol and trace gas measurements in Central Amazonia

    NASA Astrophysics Data System (ADS)

    Artaxo, Paulo; Barbosa, Henrique M. J.; Ferreira de Brito, Joel; Carbone, Samara; Rizzo, Luciana V.; Andreae, Meinrat O.; Martin, Scot T.

    2016-04-01

    The central region of the Amazonian forest is a pristine region in terms of aerosol and trace gases concentrations. In the wet season, Amazonia is actually one of the cleanest continental region we can observe on Earth. A long term observational program started 20 years ago, and show important features of this pristine region. Several sites were used, between then ATTO (Amazon Tall Tower Observatory) and ZF2 ecological research site, both 70-150 Km North of Manaus, receiving air masses that traveled over 1500 km of pristine tropical forests. The sites are GAW regional monitoring stations. Aerosol chemical composition (OC/EC and trace elements) is being analysed using filters for fine (PM2.5) and coarse mode aerosol as well as Aerodyne ACSM (Aerosol Chemical Speciation Monitors). VOCs are measured using PTR-MS, while CO, O3 and CO2 are routinely measured. Aerosol absorption is being studied with AE33 aethalometers and MAAP (Multi Angle Absorption Photometers). Aerosol light scattering are being measured at several wavelengths using TSI and Ecotech nephelometers. Aerosol size distribution is determined using scanning mobility particle sizer at each site. Lidars measure the aerosol column up to 12 Km providing the vertical profile of aerosol extinction. The aerosol column is measures using AERONET sun photometers. In the wet season, organic aerosol comprises 75-85% of fine aerosol, and sulfate and nitrate concentrations are very low (1-3 percent). Aerosols are dominated by biogenic primary particles as well as SOA from biogenic precursors. Black carbon in the wet season accounts for 5-9% of fine mode aerosol. Ozone in the wet season peaks at 10-12 ppb at the middle of the day, while carbon monoxide averages at 50-80 ppb. Aerosol optical thickness (AOT) is a low 0.05 to 0.1 at 550 nm in the wet season. Sahara dust transport events sporadically enhance the concentration of soil dust aerosols and black carbon. In the dry season (August-December), long range transported

  16. Hydrogen Attachment/Abstraction Dissociation (HAD) of Gas-Phase Peptide Ions for Tandem Mass Spectrometry.

    PubMed

    Takahashi, Hidenori; Sekiya, Sadanori; Nishikaze, Takashi; Kodera, Kei; Iwamoto, Shinichi; Wada, Motoi; Tanaka, Koichi

    2016-04-01

    Dissociation of gas-phase peptide ions through interaction with low-energy hydrogen (H) radical (∼0.15 eV) was observed with a quadrupole ion trap mass spectrometry. The H radical generated by thermal dissociation of H2 molecules passing through a heated tungsten capillary (∼2000 °C) was injected into the ion trap containing target peptide ions. The fragmentation spectrum showed abundant c-/z- and a-/x-type ions, attributable to H attachment/abstraction to/from peptide ion. Because the low-energy neutral H radical initiated the fragmentation, the charge state of the precursor ion was maintained during the dissociation. As a result, precursor ions of any charge state, including singly charged positive and negative ions, could be analyzed for amino acid sequence. The sequence coverage exceeding 90% was obtained for both singly protonated and singly deprotonated substance P peptide. This mass spectrometry also preserved labile post-translational modification bonds. The modification sites of triply phosphorylated peptide (kinase domain of insulin receptor) were identified with the sequence coverage exceeding 80%. PMID:27002918

  17. GAS CHROMATOGRAPHIC MICROMETHOD FOR TRACE DETERMINATIONS OF PHENOLS

    EPA Science Inventory

    A gas chromatographic procedure is described for the analysis of a variety of substituted phenols from water samples. The method was designed for situations when the sample size is very limited (0.5 to 1.0 ml), such as in laboratory microcosm experiments on transport and fate of ...

  18. Trace gas flux from container production of woody landscape plants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The agriculture industry is a large source of greenhouse gas (GHG) emissions which are widely believed to be causing increased global temperatures. Reduction of these emissions has been heavily researched, with most of the work focusing on row crop and animal production sectors. Little attention has...

  19. The penta-prism LTP: A long-trace-profiler with stationary optical head and moving penta prism (abstract)

    SciTech Connect

    Qian, S.; Jark, W. ); Takacs, P.Z. )

    1995-02-01

    Metrology requirements for optical components for third generation synchrotron sources are taxing the state-of-the-art in manufacturing technology. We have investigated a number of effect sources in a commercial figure measurement instrument, the Long Trace Profiler II (LTP II), and have demonstrated that, with some simple modifications, we can significantly reduce the effect of error sources and improve the accuracy and reliability of the measurement. By keeping the optical head stationary and moving a penta prism along the translation stage, the stability of the optical system is greatly improved, and the remaining error signals can be corrected by a simple reference beam subtraction. We illustrate the performance of the modified system by investigating the distortion produced by gravity on a typical synchrotron mirror and demonstrate the repeatability of the instrument despite relaxed tolerances on the translation stage.

  20. Advancement and application of gas chromatography isotope ratio mass spectrometry techniques for atmospheric trace gas analysis

    NASA Astrophysics Data System (ADS)

    Giebel, Brian M.

    2011-12-01

    The use of gas chromatography isotope ratio mass spectrometry (GC-IRMS) for compound specific stable isotope analysis is an underutilized technique because of the complexity of the instrumentation and high analytical costs. However stable isotopic data, when coupled with concentration measurements, can provide additional information on a compounds production, transformation, loss, and cycling within the biosphere and atmosphere. A GC-IRMS system was developed to accurately and precisely measure delta13C values for numerous oxygenated volatile organic compounds having natural and anthropogenic sources. The OVOCs include methanol, ethanol, acetone, methyl ethyl ketone, 2-pentanone, and 3-pentanone. Guided by the requirements for analysis of trace components in air, the GC-IRMS system was developed with the goals of increasing sensitivity, reducing dead-volume and peak band broadening, optimizing combustion and water removal, and decreasing the split ratio to the IRMS. The technique relied on a two-stage preconcentration system, a low-volume capillary reactor and water trap, and a balanced reference gas delivery system. Measurements were performed on samples collected from two distinct sources (i.e. biogenic and vehicle emissions) and ambient air collected from downtown Miami and Everglades National Park. However, the instrumentation and the method have the capability to analyze a variety of source and ambient samples. The measured isotopic signatures that were obtained from source and ambient samples provide a new isotopic constraint for atmospheric chemists and can serve as a new way to evaluate their models and budgets for many OVOCs. In almost all cases, OVOCs emitted from fuel combustion were enriched in 13C when compared to the natural emissions of plants. This was particularly true for ethanol gas emitted in vehicle exhaust, which was observed to have a uniquely enriched isotopic signature that was attributed to ethanol's corn origin and use as an alternative

  1. A mobile remote sensing laboratory for water vapor, trace gas, aerosol, and wind speed measurements

    SciTech Connect

    Slaughter, D.; White, W.; Tulloch, W.; DeSlover, D.

    1993-03-19

    The Lawrence Livermore National Laboratory has developed a mobile field laboratory for remote measurement of atmospheric processes and observables that are important in global climate change, dispersal of hazardous materials, and atmospheric pollution. Specific observables of interest are water vapor, trace gases, aerosol size and density, wind, and temperature. The goal is to study atmospheric processes continuously for extended periods in remote field locations. This laboratory has just reached field ready status with sensors for aerosol and trace gas measurement based on established techniques. A development program is underway to enhance the sensor suite with several new techniques and instruments that are expected to significantly extend the state of the art in remote trace gas analysis. The new sensors will be incorporated into the lab during the next two years.

  2. Synergistic effects in trace gas-aerosol interactions

    NASA Technical Reports Server (NTRS)

    Schryer, D. R.; Cofer, W. R., III; Rogowski, R. S.

    1980-01-01

    The reaction of SO2 and NO2 with soot has been studied experimentally by gravimetric determination of chemisorption with subsequent analysis of the chemisorbed species by various techniques. When samples of commercially available carbon black (used as soot surrogate) are exposed to SO2 or NO2 in dry air or N2 as carrier gas, no quantitative chemisorption (less than 5 micrograms per mg of substrate) is observed. However, exposure of the same grade of carbon to a combination of SO2 and NO2 in dry air of N2 results in significant chemisorption (180-200 micrograms/mg), a major fraction of which is analyzed as sulfate.

  3. Trace gas fluxes from a northern mixed-grass prairie interseeded with alfalfa

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The role of legumes in improving soil fertility, forage quantity and quality is well established, however what is less clear is the extent that the nitrogen fixed by legumes may drive increased trace gas emissions. A chronosequence study in native prairie that had been interseed with the legume alfa...

  4. Determining trace gas efflux from container production of woody nursery crops

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In recent years, climate change and its effects on the global environment has garnered significant attention from the scientific community. Increased trace gas emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are widely believed to be the driving force behind global warming. ...

  5. DIFFUSION THEORY IMPROVES CHAMBER-BASED MEASUREMENTS OF TRACE GAS EMISSIONS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Chambers temporarily sealed to the soil surface are an important and for many purposes the only means of measuring trace gas emissions to the atmosphere. However, past interpretations of chamber data systematically underestimated actual emission rates in most applications because they ignored or poo...

  6. VOC SURVEILLANCE USING EPA'S TRACE ATMOSPHERIC GAS ANALYZER (TAGA) AND ASPECT AERIAL PLATFORM FTIR

    EPA Science Inventory

    In a heavily industrialized area in Southeast Texas, EPA atmospheric scientists recently conducted an inter-comparison study of the EPA mobile Trace Atmospheric Gas Analyzer (TAGA) and the ASPECT Aerial Platform FTIR. The TAGA is a mobile air sampling device that is capable of d...

  7. TRACE GAS EMISSIONS IN CHAMBERS: A NON-STEADY-STATE DIFFUSION MODEL

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Non-steady-state (NSS) chambers are widely used to measure trace gas emissions from the Earth’s surface in the atmosphere. Unfortunately, traditional interpretations of time-dependent chamber concentrations often systematically underestimate predeployment exchange rates because they do not accuratel...

  8. The Colour and Stereo Surface Imaging System (CaSSIS) for ESA's Trace Gas Orbiter.

    NASA Astrophysics Data System (ADS)

    Thomas, N.; Cremonese, G.; Banaszkiewicz, M.; Bridges, J.; Byrne, S.; da Deppo, V.; Debei, S.; El-Maarry, M. R.; Hauber, E.; Hansen, C. J.; Ivanov, A.; Kestay, L.; Kirk, R.; Kuzmin, R.; Mangold, N.; Marinangeli, L.; Markiewicz, W.; Massironi, M.; McEwen, A. S.; Okubo, C.; Orleanski, P.; Pommerol, A.; Wajer, P.; Wray, J.

    2014-07-01

    The main imaging system (CaSSIS) for the ExoMars Trace Gas Orbiter will be described. The poster will illustrate what is to be expected from the instrument in terms of stereo and colour capability within the mass and volume available.

  9. Validity of using backward Lagrangian Stochastic technique in measuring trace gas emission from treatment lagoon

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study evaluates the accuracy of measuring trace gas emission from treatment lagoons using backward Lagrangian stochastic (bLs) technique. The bLs technique was originally developed for relatively homogeneous terrains without any obstacles causing significant windflow disturbance. The errors ass...

  10. Eddy covariance for quantifying trace gas fluxes from soils

    NASA Astrophysics Data System (ADS)

    Eugster, W.; Merbold, L.

    2015-02-01

    Soils are highly complex physical and biological systems, and hence measuring soil gas exchange fluxes with high accuracy and adequate spatial representativity remains a challenge. A technique which has become increasingly popular is the eddy covariance (EC) method. This method takes advantage of the fact that surface fluxes are mixed into the near-surface atmosphere via turbulence. As a consequence, measurements with an EC system can be done at some distance above the surface, providing accurate and spatially integrated flux density estimates. In this paper we provide a basic overview targeting scientists who are not familiar with the EC method. This review gives examples of successful deployments from a wide variety of ecosystems. The primary focus is on the three major greenhouse gases: carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Several limitations to the application of EC systems exist, requiring a careful experimental design, which we discuss in detail. Thereby we group these experiments into two main classes: (1) manipulative experiments, and (2) survey-type experiments. Recommendations and examples of successful studies using various approaches are given, including the combination of EC flux measurements with online measurements of stable isotopes. We conclude that EC should not be considered a substitute to traditional (e.g., chamber based) flux measurements but instead an addition to them. The greatest strength of EC measurements in soil science are (1) their uninterrupted continuous measurement of gas concentrations and fluxes that can also capture short-term bursts of fluxes that easily could be missed by other methods and (2) the spatial integration covering the ecosystem scale (several square meters to hectares), thereby integrating over small-scale heterogeneity in the soil.

  11. Eddy covariance for quantifying trace gas fluxes from soils

    NASA Astrophysics Data System (ADS)

    Eugster, W.; Merbold, L.

    2014-10-01

    Soils are highly complex physical and biological systems, and hence measuring soil gas exchange fluxes with high accuracy and adequate spatial representativity remains a challenge. A technique which has become increasingly popular is the eddy covariance (EC) method. This method takes advantage of the fact that surface fluxes are mixed into the near-surface atmosphere via turbulence. As a consequence, measurement with an EC system can be done at some distance above the surface, providing accurate and spatially integrated flux density estimates. In this paper we provide a basic overview targeting at scientists who are not familiar with the EC method. This reviews gives examples of successful deployments from a wide variety of ecosystems. The primary focus is on the three major greenhouse gases carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Several limitations to the application of EC systems exist, requiring a careful experimental design, which we discuss in detail. Thereby we group these experiments into two main classes: (1) manipulative experiments, and (2) survey-type experiments. Recommendations and examples of successful studies using various approaches, including the combination of EC flux measurements with online measurements of stable isotopes are given. We conclude that EC should not be considered a substitution of traditional flux measurements, but an addition to the latter. The greatest strength of EC measurements in soil science are (1) their uninterrupted continuous measurement of gas concentrations and fluxes that also can capture short-term bursts of fluxes that easily could be missed by other methods; and (2) the spatial integration covering the ecosystem scale (several m2 to ha), thereby integrating over small-scale heterogeneity in the soil.

  12. Trace Gas Retrievals from the GeoTASO Aircraft Instrument During the DISCOVER-AQ Campaigns

    NASA Astrophysics Data System (ADS)

    Nowlan, C. R.; Liu, X.; Leitch, J. W.; Liu, C.; Gonzalez Abad, G.; Chance, K.; Delker, T.; Good, W. S.; Murcray, F.; Ruppert, L.; Kaptchen, P. F.; Loughner, C.; Follette-Cook, M. B.; Pickering, K. E.

    2014-12-01

    The Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) instrument is a recently-developed passive remote sensing instrument capable of making 2-D measurements of trace gases from aircraft. GeoTASO was developed under NASA's Instrument Incubator program and is a test-bed instrument for the Geostationary Coastal and Air Pollution Events (GEO-CAPE) decadal survey and the upcoming Tropospheric Emissions: Monitoring of Pollution (TEMPO) satellite missions. The instrument collects spectra of backscattered UV-visible radiation for the detection of tropospheric trace gases such as NO2, ozone, formaldehyde and SO2. GeoTASO flew on the NASA HU-25C Falcon aircraft during the 2013 (Texas) and 2014 (Colorado) DISCOVER-AQ field campaigns, making satellite-analog measurements of trace gases at a spatial resolution of approximately 500x500 m over urban areas, power plants and other industrial sources of pollution. We present the GeoTASO retrieval algorithms, trace gas measurement results, and validation comparisons with ground-based observations and other aircraft instruments during these campaigns.

  13. African aerosol and trace-gas emissions from the Central-African Bujumbura station.

    NASA Astrophysics Data System (ADS)

    Gielen, Clio; Van Roozendael, Michel; Hendrick, Francois; Pinardi, Gaia; De Smet, Isabelle; Fayt, Caroline; Hermans, Christian; Ndenzako, Eugene; Nzohabonayo, Pierre; Akimana, Rachel

    2015-04-01

    We present aerosol and trace-gas retrievals from the new Central-African measurement site of Bujumbura, where a new MAX-DOAS instrument and cimel sun photometer have been operational since late 2013. This is the first time that MAX-DOAS measurements are performed in Central Africa, which are critical to resolve the large uncertainties of satellite observations of trace gases and aerosols over this area. The Bujumbura region is a source of strong biogenic compounds and biomass burning products, and invaluable to study the export of African emissions to the Indian ocean. Using the bePRO radiative transfer tool, we retrieve aerosol optical depths (AODs) and vertical extinction profiles for aerosols and trace gases such as NO2 and HCHO. The AOD retrievals are compared to the co-located AERONET sun photometer measurements and further analysed to investigate seasonal and diurnal cycles in the observed variability or to detect biomass-burning events.For the trace gases NO2 and HCHO, the ground-based MAX-DOAS vertical columns and profiles are used for tropospheric trace-gas validation of the GOME-2 and OMI satellites. We further discuss the representativity of the site regarding satelitte comparisons and modelling efforts, given its specific orography.

  14. Analysis of volatile organic compounds. [trace amounts of organic volatiles in gas samples

    NASA Technical Reports Server (NTRS)

    Zlatkis, A. (Inventor)

    1977-01-01

    An apparatus and method are described for reproducibly analyzing trace amounts of a large number of organic volatiles existing in a gas sample. Direct injection of the trapped volatiles into a cryogenic percolum provides a sharply defined plug. Applications of the method include: (1) analyzing the headspace gas of body fluids and comparing a profile of the organic volatiles with standard profiles for the detection and monitoring of disease; (2) analyzing the headspace gas of foods and beverages and comparing the profile with standard profiles to monitor and control flavor and aroma; and (3) analyses for determining the organic pollutants in air or water samples.

  15. Development of monitoring and control technology based on trace gas monitoring. Final report

    SciTech Connect

    Liebowitz, B.

    1997-07-01

    Trace gases are generated by many biological reactions. During anaerobic decomposition, trace levels of hydrogen (H{sub 2}) and carbon monoxide (CO) gases are produced. It was shown previously that these trace gases are intrinsically related to the biochemical reactions occurring and, therefore, offer promise for on-line process monitoring and control. This work was designed to test how effectively hydrogen and CO could be to monitor high-rate anaerobic systems that has significant mass transfer and complex hydraulics. An experimental program was designed to examine the behavior of an upflow anaerobic sludge blanket (UASB) reactor system under steady state and in response to organic loading perturbations. The responses of trace gases CO and H{sub 2} were tracked using an on-line, real-time gas-monitoring system linked to a computer-controlled data acquisition package. Data on conventional process parameters such as pH, chemical oxygen demand (COD), volatile fatty acids (VFAs) were concurrently collected. Monitoring of conventional process indicators (i.e., pH, VFA, gas production) and trace gas (H{sub 2} and CO) indicators was conducted using a matrix of nine different steady-state OLRs (4-23 kg COD/m{sup 3} -d) and system HRTs (0.5 to 2.5 days) was performed to determine any correlation among the indicators. Of OLR, HRT, and influent COD, only OLR had any significant influence on the process indicators examined. All parameters except methane increased with increases in OLR; methane decreased with increased OLR. The OLR and gas production rate (GP) were observed to be linearly correlated.

  16. [Research on trace gas spectral measurement on intra-cavity fiber optic laser].

    PubMed

    Zhang, Hong-Xia; Liu, Kun; Jia, Da-Gong; Liu, Tie-Gen; Peng, Gang-Ding; Wang, Yan; Zhang, Yi-Mo

    2011-08-01

    Due to the advantages of immunity of electrical/electronic, high performance cost ratio, remote detection and multiplexing capability, intra-cavity fiber optic gas measurement has aroused wide concern. The trace gas measurement system has been developed based on the elaborated gas cell and reflector. The wavelength sweeping technique (WST) is realized when the Fabry-Perot type tunable optical filter is applied by the sawtooth driver voltage. Multi absorption lines can be obtained and one scanning measurement with WST is equal to multiple independent detections, so the gas measurement sensitivity is improved remarkably. The experimental results show that the acetylene detection sensitivity is reduced to less than 100 ppm and the relative measurement error is less than 3% of practical gas concentration. PMID:22007380

  17. Quantitative Detection of Trace Explosive Vapors by Programmed Temperature Desorption Gas Chromatography-Electron Capture Detector

    PubMed Central

    Field, Christopher R.; Lubrano, Adam; Woytowitz, Morgan; Giordano, Braden C.; Rose-Pehrsson, Susan L.

    2014-01-01

    The direct liquid deposition of solution standards onto sorbent-filled thermal desorption tubes is used for the quantitative analysis of trace explosive vapor samples. The direct liquid deposition method yields a higher fidelity between the analysis of vapor samples and the analysis of solution standards than using separate injection methods for vapors and solutions, i.e., samples collected on vapor collection tubes and standards prepared in solution vials. Additionally, the method can account for instrumentation losses, which makes it ideal for minimizing variability and quantitative trace chemical detection. Gas chromatography with an electron capture detector is an instrumentation configuration sensitive to nitro-energetics, such as TNT and RDX, due to their relatively high electron affinity. However, vapor quantitation of these compounds is difficult without viable vapor standards. Thus, we eliminate the requirement for vapor standards by combining the sensitivity of the instrumentation with a direct liquid deposition protocol to analyze trace explosive vapor samples. PMID:25145416

  18. Understanding Biogenic and Anthropogenic Trace Gas Variations Measured Near Cool, CA in June 2010

    NASA Astrophysics Data System (ADS)

    Klein, B. Z.; Flowers, B. A.; Gorkowski, K.; Dubey, M. K.; Knighton, W. B.; Floerchinger, C.; Herndon, S. C.; Fast, J. D.; Zaveri, R. A.

    2011-12-01

    Trace gas signatures produced by forested and urban areas differ greatly. Forested areas are dominated by gases produced during photosynthesis and respiration: CO2 and volatile organic compounds (VOCs) including terpenes and isoprene. Urban areas are heavily influenced by vehicle exhaust emissions and have elevated levels of CO, NOx and aromatic hydrocarbons such as benzene. Ozone is produced as a byproduct of both of these sources; it is produced when NOx from urban areas reacts with either anthropogenic or biogenic hydrocarbons. The Carbonaceous Aerosol and Radiative Effects Study (CARES) campaign was conducted during June 2010, in part to observe the evolution of urban air masses as they mix into rural locations and to better understand anthropogenic-biogenic photochemical interactions. The campaign included two ground-based sampling sites, one in Sacramento, CA (T0) and one downwind, approximately 70km NE, rurally located near Cool, CA (T1). In situ measurements of CO2, CO, O3, NO and multiple different VOCs were performed at the T1 site during the study, and are analyzed here to gain insights into the chemistry and transport of these trace gases. Comparisons between these trace gases coupled with transport modeling is used to delineate biogenic and anthropogenic sources. Additionally, comparisons between trace gases produced predominately by biogenic sources provide valuable information on how meteorology affects their production. Two atmospheric models (HYSPLIT back-trajectories and WRF forecasts) are used to predict transport episodes, where polluted air masses from the Sacramento or more distant San Francisco areas are transported to Cool. The two models display significant overlap for eleven different transport episodes during the study period. Both models also agree on two transport-free multiple-day periods. By examining the periods during which the models are in agreement, we are able to characterize with high certainty the trace gas signatures of local

  19. The Science Operations Concept for the ExoMars 2016 Trace Gas Orbiter

    NASA Astrophysics Data System (ADS)

    Frew, D.

    2014-04-01

    The ExoMars 2016 Science Operations Centre (SOC) based at the European Space Astronomy Centre is responsible for coordinating the science planning activities for the Trace Gas Orbiter. Science planning will involve all members of the ExoMars 2016 science ground segment (SGS), namely the SOC at ESAC, the Russian SOC at IKI, the orbiter instrument teams and the science management of the 2016 mission represented by the science working team (SWT) that is chaired by the project scientist. The science operations concept for the mission builds on the legacy inherited from previous ESA planetary missions, in particular from Mars Express for the core plan validation aspects and from the Smart-1 lunar mission for the opportunity analysis and longterm planning approach. Further concept drivers have been derived from the ExoMars 2016 mission profile in the areas of orbit predictability, instrument design and the usage of TGO as a relay for surface assets including the ExoMars 2018 rover. This paper will give an over view of the entire uplink planning process as it is conducted over 3 distinct planning cycles. The Long Term Plan (LTP) establishes the baseline science plan and demonstrates the operational feasibility of meeting the mission science goals formulated by the science working team (SWT) at science management level. The LTP has a planning horizon of 6 months. Each month of the baseline science plan is refined with the instrument teams within the Medium Term Plan (MTP) to converge on a frozen attitude request and resource envelopes for all of the observations in the plan. During the Short Term Planning cycle the SOC will iterate with the teams to finalise the commanding for all of the observations in the plan for the coming week. The description of the uplink planning process will focus on two key areas that are common to all of the planning cycles mentioned above: • Science Plan Abstraction: Interacting with the science plan at the appropriate level of abstraction to

  20. Trace gas detection in hyperspectral imagery using the wavelet packet subspace

    NASA Astrophysics Data System (ADS)

    Salvador, Mark A. Z.

    This dissertation describes research into a new remote sensing method to detect trace gases in hyperspectral and ultra-spectral data. This new method is based on the wavelet packet transform. It attempts to improve both the computational tractability and the detection of trace gases in airborne and spaceborne spectral imagery. Atmospheric trace gas research supports various Earth science disciplines to include climatology, vulcanology, pollution monitoring, natural disasters, and intelligence and military applications. Hyperspectral and ultra-spectral data significantly increases the data glut of existing Earth science data sets. Spaceborne spectral data in particular significantly increases spectral resolution while performing daily global collections of the earth. Application of the wavelet packet transform to the spectral space of hyperspectral and ultra-spectral imagery data potentially improves remote sensing detection algorithms. It also facilities the parallelization of these methods for high performance computing. This research seeks two science goals, (1) developing a new spectral imagery detection algorithm, and (2) facilitating the parallelization of trace gas detection in spectral imagery data.

  1. Quantifying Aerosol Types and Their Impact on Trace Gas Retrievals From Satellite Measurements

    NASA Astrophysics Data System (ADS)

    Natraj, V.; Boesch, H.; Yung, Y. L.

    2005-12-01

    One of the major sources of uncertainty in the retrieval of trace gas abundances from space-borne measurements is the type, amount and vertical distribution of aerosols in the atmosphere. Optical properties were derived for the broad classification of aerosol types investigated by Kahn et al. (2001), taking polarization into account. Examination of the scattering matrix elements resulted in a smaller set of independent aerosol types whose radiative effects were different. Weighting functions were then calculated for each of these types, assuming exponentially tailing aerosol concentration in the troposphere and a Junge distribution for the stratosphere. The different shapes of the weighting functions indicate different amount and distribution of the information content. Implications for trace gas retrievals from satellite-based measurements made by polarization-sensitive instruments (such as those on OMI, GOME, SCIAMACHY and OCO) will be discussed.

  2. GT1_vgeers_1: Tracing Remnant Gas in Planet Forming Debris Disk Systems

    NASA Astrophysics Data System (ADS)

    Geers, V.

    2010-03-01

    Recent studies of gas emission lines with Spitzer and sub-millimeter telescopes have shown that 10-100 Myr old stars with debris disks have too little gas left to form Jupiter like gas giant planets. Whether enough gas remains in these systems to form ice giant planets is still unanswered. The [OI] emission line at 63 micron is one of the most sensitive tracers of gas mass in the ice-giant region of 10-50 AU in disks, and Herschel PACS is therefore uniquely suited to trace the remnant gas in planet-forming disks. We propose to obtain PACS line spectroscopy of [OI] (63 micron) for two nearby young stars, HR 8799 and HD 15115, which are two systems with detected giant planets or signs of planet formation, while still harbouring prominent debris disks that could be in the process of forming ice giants such as Neptune and Uranus. The proposed observations will probe down to gas masses of 0.01 Earth masses, and allow us to constrain prospects for ice giant formation, measure gas-to-dust ratios in evolved disks to compare with planet formation / disk evolution models, and put constraints on whether the dust dynamics in these systems is driven by the remnant gas or by the radiation. Note: this proposal is submitted under the Swiss part of the HIFI Guaranteed Time program; HIFI PI: Frank Helmich, HIFI Swiss Lead CoI: Arnold Benz.

  3. Satellite-derived Signatures of Trace Gases from US. Oil and Gas Operations

    NASA Astrophysics Data System (ADS)

    Kollonige, D. E.; Thompson, A. M.

    2013-12-01

    Since 2005, there has been an increase in shale gas production, which is expected to continue through 2035, leading to heightened environmental concerns regarding increased emissions of the greenhouse gas methane (CH4) and degradation of local air quality. Emissions of CH4 and VOCs may occur at any stage of exploration and production via venting, flashing, flaring, or fugitive/non-permitted emissions. The industrial equipment used to install and maintain a well is a potential emission source of CH4, VOCs, nitrogen oxides, and other gases. Emissions from these individual point sources can accumulate and represent a substantial area source of trace gases to the atmosphere. We have begun to characterize the trace gas signatures associated with oil and natural gas (O&NG) operations in the U.S. using satellite observations over two key regions: the Marcellus and Bakkan Shale Deposits. Current satellite products, including CH4 from the Tropospheric Emission Spectrometer (TES) and nitrogen dioxide (NO2) from the Ozone Monitoring Instrument (OMI) on Aura, are compared to aircraft and ground measurements. Preliminary analysis during June 2012 shows the potential for TES in the mid-troposphere to detect and track increases in CH4 due to a gas well leak in the Marcellus Shale Region. Trace gas trends from satellite observations are analyzed in the vicinity of O&NG sites. The TES CH4 representative tropospheric volume mixing ratio (RTVMR) product, particularly used for emission detection, displays evidence of increasing methane over PA from 2006 through 2012. This analysis begins to provide improved constraints on O&NG emissions and supply a template for future geo-missions, such as TEMPO, for continued observations of air quality.

  4. Spatial variations of nitrogen trace gas emissions from tropical mountain forests in Nyungwe, Rwanda

    NASA Astrophysics Data System (ADS)

    Gharahi Ghehi, N.; Werner, C.; Cizungu Ntaboba, L.; Mbonigaba Muhinda, J. J.; Van Ranst, E.; Butterbach-Bahl, K.; Kiese, R.; Boeckx, P.

    2012-04-01

    Globally, tropical forest soils represent the second largest source of N2O and NO. However, there is still considerable uncertainty on the spatial variability and soil properties controlling N trace gas emission. Therefore, we carried out an incubation experiment with soils from 31 locations in the Nyungwe tropical mountain forest in southwestern Rwanda. All soils were incubated at three different moisture levels (50, 70 and 90 % water filled pore space (WFPS)) at 17 °C. Nitrous oxide emission varied between 4.5 and 400 μg N m-2 h-1, while NO emission varied from 6.6 to 265 μg N m-2 h-1. Mean N2O emission at different moisture levels was 46.5 ± 11.1 (50 %WFPS), 71.7 ± 11.5 (70 %WFPS) and 98.8 ± 16.4 (90 %WFPS) μg N m-2 h-1, while mean NO emission was 69.3 ± 9.3 (50 %WFPS), 47.1 ± 5.8 (70 %WFPS) and 36.1 ± 4.2 (90 %WFPS) μg N m-2 h-1. The latter suggests that climate (i.e. dry vs. wet season) controls N2O and NO emissions. Positive correlations with soil carbon and nitrogen indicate a biological control over N2O and NO production. But interestingly N2O and NO emissions also showed a positive correlation with free iron and a negative correlation with soil pH (only N2O). The latter suggest that chemo-denitrification might, at least for N2O, be an important production pathway. In conclusion improved understanding and process based modeling of N trace gas emission from tropical forests will benefit from spatially explicit trace gas emission estimates linked to basic soil property data and differentiating between biological and chemical pathways for N trace gas formation.

  5. Hierarchical framework for coupling a biogeochemical trace gas model to a general circulation model

    SciTech Connect

    Miller, N.L.; Foster, I.T.

    1994-04-01

    A scheme is described for the computation of terrestrial biogeochemical trace gas fluxes in the context of a general circulation model. This hierarchical system flux scheme (HSFS) incorporates five major components: (1) a general circulation model (GCM), which provides a medium-resolution (i.e., 1{degrees} by 1{degrees}) simulation of the atmospheric circulation; (2) a procedure for identifying regions of defined homogeneity of surface type within GCM grid cells; (3) a set of surface process models, to be run within each homogeneous region, which include a biophysical model, the Biosphere Atmospheric Transfer Scheme (BATS), and a biogeochemical model (BGCM); (4) an interpolation/integration system that transfers information between the GCM and surface process models with finer resolution; and (5) an interactive data array based on a geographic information system (GIS), which provides land characteristic information via the interpolator. The goals of this detailed investigation are to compute the local and global sensitivities of trace gas fluxes to GCM and BATS variables, the effects of trace gas fluxes on global climate, and the effects of global climate on specific biomes.

  6. Analysis of trace impurities in semiconductor gas via cavity-enhanced direct frequency comb spectroscopy

    NASA Astrophysics Data System (ADS)

    Cossel, K. C.; Adler, F.; Bertness, K. A.; Thorpe, M. J.; Feng, J.; Raynor, M. W.; Ye, J.

    2010-09-01

    Cavity-enhanced direct frequency comb spectroscopy (CE-DFCS) has demonstrated powerful potential for trace-gas detection based on its unique combination of high bandwidth, rapid data acquisition, high sensitivity, and high resolution, which is unavailable with conventional systems. However, previous demonstrations have been limited to proof-of-principle experiments or studies of fundamental laboratory science. Here, we present the development of CE-DFCS towards an industrial application—measuring impurities in arsine, an important process gas used in III-V semiconductor compound manufacturing. A strongly absorbing background gas with an extremely complex, congested, and broadband spectrum renders trace detection exceptionally difficult, but the capabilities of CE-DFCS overcome this challenge and make it possible to identify and quantify multiple spectral lines associated with water impurities. Further, frequency combs allow easy access to new spectral regions via efficient nonlinear optical processes. Here, we demonstrate detection of multiple potential impurities across 1.75-1.95 μm (5710-5130 cm-1), with a single-channel detection sensitivity (simultaneously over 2000 channels) of ˜4×10-8 cm-1 Hz-1/2 in nitrogen and, specifically, an absorption sensitivity of ˜4×10-7 cm-1 Hz-1/2 for trace water doped in arsine.

  7. Ultrasensitive, self-calibrated cavity ring-down spectrometer for quantitative trace gas analysis.

    PubMed

    Chen, Bing; Sun, Yu R; Zhou, Ze-Yi; Chen, Jian; Liu, An-Wen; Hu, Shui-Ming

    2014-11-10

    A cavity ring-down spectrometer is built for trace gas detection using telecom distributed feedback (DFB) diode lasers. The longitudinal modes of the ring-down cavity are used as frequency markers without active-locking either the laser or the high-finesse cavity. A control scheme is applied to scan the DFB laser frequency, matching the cavity modes one by one in sequence and resulting in a correct index at each recorded spectral data point, which allows us to calibrate the spectrum with a relative frequency precision of 0.06 MHz. Besides the frequency precision of the spectrometer, a sensitivity (noise-equivalent absorption) of 4×10-11  cm-1  Hz-1/2 has also been demonstrated. A minimum detectable absorption coefficient of 5×10-12  cm-1 has been obtained by averaging about 100 spectra recorded in 2  h. The quantitative accuracy is tested by measuring the CO2 concentrations in N2 samples prepared by the gravimetric method, and the relative deviation is less than 0.3%. The trace detection capability is demonstrated by detecting CO2 of ppbv-level concentrations in a high-purity nitrogen gas sample. Simple structure, high sensitivity, and good accuracy make the instrument very suitable for quantitative trace gas analysis. PMID:25402995

  8. Trace-gas sensing using the compliance voltage of an external cavity quantum cascade laser

    SciTech Connect

    Phillips, Mark C.; Taubman, Matthew S.

    2013-06-04

    Quantum cascade lasers (QCLs) are increasingly being used to detect, identify, and measure levels of trace gases in the air. External cavity QCLs (ECQCLs) provide a broadly-tunable infrared source to measure absorption spectra of chemicals and provide high detection sensitivity and identification confidence. Applications include detecting chemical warfare agents and toxic industrial chemicals, monitoring building air quality, measuring greenhouse gases for atmospheric research, monitoring and controlling industrial processes, analyzing chemicals in exhaled breath for medical diagnostics, and many more. Compact, portable trace gas sensors enable in-field operation in a wide range of platforms, including handheld units for use by first responders, fixed installations for monitoring air quality, and lightweight sensors for deployment in unmanned aerial vehicles (UAVs). We present experimental demonstration of a new chemical sensing technique based on intracavity absorption in an external cavity quantum cascade laser (ECQCL). This new technique eliminates the need for an infrared photodetector and gas cell by detecting the intracavity absorption spectrum in the compliance voltage of the laser device itself. To demonstrate and characterize the technique, we measure infrared absorption spectra of chemicals including water vapor and Freon-134a. Sub-ppm detection limits in one second are achieved, with the potential for increased sensitivity after further optimization. The technique enables development of handheld, high-sensitivity, and high-accuracy trace gas sensors for in-field use.

  9. Photoacoustic spectrometry for trace gas analysis and leak detection using different cell geometries.

    PubMed

    Gondal, M A; Dastageer, A; Shwehdi, M H

    2004-01-01

    A photoacoustic (PA) spectrometer with high selectivity and sensitivity has been developed for trace gas analysis and for the detection of gas leak at part per trillion by volume (pptV) level. This PA system comprises of a resonant photoacoustic cell, a pulsed line tunable CO(2) laser as an excitation source and a sensitive electret microphone as a photoacoustic detector with an option to trigger the safety alarm system for early warning of gas leaks. In this work, three resonant PA cells with various geometries have been developed at our laboratory for the detection of photoacoustic signal using pulsed laser system and their comparative performance have been studied. As a special application of this PA system, the detection of sulfur hexa fluoride (SF(6)) gas using these three cells has been carried out for optimizing the sensitivity. Besides this, our PA system can very well be applied for pollution monitoring and detection of hazardous gases in a noisy environment. PMID:18969274

  10. Radon 222 tracing of soil and forest canopy trace gas exchange in an open canopy boreal forest

    NASA Technical Reports Server (NTRS)

    Ussler, William, III; Chanton, Jeffrey P.; Kelley, Cheryl A.; Martens, Christopher S.

    1994-01-01

    A set of continuous, high-resolution atmospheric radon (Rn-222) concentration time series and radon soil flux measurements were acquired during the summer of 1990 at a micrometeorological tower site 13 km northwest of Schefferville, Quebec, Canada. The tower was located in a dry upland, open-canopy lichen-spruce woodland. For the period July 23 to August 1, 1990, the mean radon soil flux was 41.1 +/- 4.8 Bq m(exp -2)/h. Radon surface flux from the two end-member forest floor cover types (lichen mat and bare soil) were 38.8 +/- 5.1 and 61.8 +/- 15.6 Bq m(exp -2)/h, respectively. Average total forest canopy resistances computed using a simple 'flux box' model for radon exchange between the forest canopy and the overlying atmosphere range from 0.47 +/- 0.24 s cm(exp -1) to 2.65 +/- 1.61 cm(exp -1) for daytime hours (0900-1700 LT) and from 3.44 +/- 0.91 s cm(exp -1) to 10.55 +/- 7.16 s cm(exp -1) for nighttime hours (2000-0600) for the period July 23 to August 6, 1990. Continuous radon profiling of canopy atmospheres is a suitable approach for determining rates of biosphere/atmosphere trace gas exchange for remote field sites where daily equipment maintenance is not possible. where daily equipment maintenance is not possible.

  11. Trace gas retrieval for limb DOAS under changing atmospheric conditions: The X-gas scaling method vs optimal estimation

    NASA Astrophysics Data System (ADS)

    Hueneke, Tilman; Grossmann, Katja; Knecht, Matthias; Raecke, Rasmus; Stutz, Jochen; Werner, Bodo; Pfeilsticker, Klaus

    2016-04-01

    Changing atmospheric conditions during DOAS measurements from fast moving aircraft platforms pose a challenge for trace gas retrievals. Traditional inversion techniques to retrieve trace gas concentrations from limb scattered UV/vis spectroscopy, like optimal estimation, require a-priori information on Mie extinction (e.g., aerosol concentration and cloud cover) and albedo, which determine the atmospheric radiative transfer. In contrast to satellite applications, cloud filters can not be applied because they would strongly reduce the usable amount of expensively gathered measurement data. In contrast to ground-based MAX-DOAS applications, an aerosol retrieval based on O4 is not able to constrain the radiative transfer in air-borne applications due to the rapidly decreasing amount of O4 with altitude. Furthermore, the assumption of a constant cloud cover is not valid for fast moving aircrafts, thus requiring 2D or even 3D treatment of the radiative transfer. Therefore, traditional techniques are not applicable for most of the data gathered by fast moving aircraft platforms. In order to circumvent these limitations, we have been developing the so-called X-gas scaling method. By utilising a proxy gas X (e.g. O3, O4, …), whose concentration is either a priori known or simultaneously in-situ measured as well as remotely measured, an effective absorption length for the target gas is inferred. In this presentation, we discuss the strengths and weaknesses of the novel approach along with some sample cases. A particular strength of the X-gas scaling method is its insensitivity towards the aerosol abundance and cloud cover as well as wavelength dependent effects, whereas its sensitivity towards the profiles of both gases requires a priori information on their shapes.

  12. The Role of Snow Cover on Surface Trace Gas Exchanges at Toolik Lake, AK

    NASA Astrophysics Data System (ADS)

    Helmig, D.; Obrist, D.; Moore, C.; Van Dam, B.; Jacques, H.; Molnar, T.; Williams, M. W.; Kramer, L. J.; Doskey, P. V.; Fain, X.

    2014-12-01

    Snow has a profound influence on the emission and deposition of atmospheric trace gases in the arctic environment. Processes that play a role in modulating gas exchanges include biological, soil biogeochemical, snow chemical, and snow physical processes. Environmental conditions underneath the snow are relatively stable throughout the winter period. Above the snow surface, variations in temperature, radiation, and wind exert a wide range of influences on snowpack gas chemistry, gas exchanges at the snow-air interface, and chemical interactions between the interstitial snowpack air and vegetation and soil below the snowpack. This presentation will present an overview of experimental approaches for continuous, all winter-long experiments conducted at a permafrost site at the Long-Term Ecological Research (LTER) station at Toolik Lake on the north slope of the Brooks Range, Alaska. These studies include observations of carbon dioxide and the reactive gases ozone, nitrogen oxides, and gaseous elemental mercury. Parameterizations developed from these measurements are used for improving descriptions of trace gas budgets and their feedbacks on climate and associated snow cover changes in the Arctic and seasonally snow-covered midlatitude environments.

  13. Aerosol and trace gas profile retrievals from MAX-DOAS observations using simple least squares methods

    NASA Astrophysics Data System (ADS)

    Wagner, Thomas; Beirles, Steffen; Shaiganfar, Reza

    2010-05-01

    Multi-AXis (MAX-) DOAS observations have become a widely used technique for the retrieval of atmospheric profiles of trace gases and aerosols. Since the information content of MAX-DOAS observations is limited, usually optimal estimation techniques are used for profile inversion, and a-priori assumptions are needed. In contrast, in our retrieval we limit the retrieved parameter to few basic profile parameters (e.g. profile shape and integrated column density), which are retrieved without further a-priori assumptions. The retrieval is instead based on simple least squares methods. Despite the simple retrieval scheme, our method has the advantage that it is very robust and stable. It also yields the most important parameters with good accuracy (e.g. total aerosol optical depth, total tropospheric trace gas column density, surface aerosol extinction, surface trace gas mixing ratio). Some of these parameters can even be retrieved for cloudy conditions. We present MAX-DOAS results from two measurement campaigns: The CINDI campaign in Cabauw, The Netherlands, in 2009 and the FORMAT campaign in Milano, Italy, in 2003. Results for aerosols, NO2, and HCHO, are presented and compared to independent measurements.

  14. Trace gas exchanges and convective transports over the Amazonian rain forest

    NASA Technical Reports Server (NTRS)

    Garstang, Michael; Harriss, Robert; Beck, Sherwin; Browell, Edward; Sachse, Glen; Gregory, Gerald; Hill, Gerald; Simpson, Joanne; Tao, Wei-Kuo; Torres, Arnold

    1988-01-01

    The NASA Amazon Boundary Layer Experiment (ABLE 2A) based in Manaus, Brazil, in July and August 1985, is used to examine meteorological processes responsible for the vertical and horizontal transport of biogenic and anthropogenic trace gases generated over the Amazon basin. Direct sampling of the surrounding environment of deep convective clouds shows marked changes in the vertical distribution of the lower and midtroposphere concentration of O3 and such surface-derived species as CO, CO2, and NO. Thermodynamic observations, together with two-dimensional cloud model simulations, confirm vertical transports within the convection and provide a basis for an estimation of the magnitude and efficiency of cloud upward and downward exchanges. A distinction is drawn between local changes due to convective updrafts and downdrafts and convective overturning as a net result of the storm processes. Marked variability is seen in trace gas concentrations along horizontal flight paths in the vicinity of the convection. Interpretation of simultaneously measured thermodynamic quantities and trace gas concentrations provide the information to infer the presence and direction of atmospheric transports and/or the presence of anthropogenic influences.

  15. Detection of trace gas emissions from point sources using shortwave infrared imaging spectrometry

    NASA Astrophysics Data System (ADS)

    Thorpe, A. K.; Roberts, D. A.; Dennison, P. E.; Bradley, E. S.; Funk, C. C.

    2011-12-01

    Existing spaceborne remote sensing provides an effective means of detecting continental-scale variation in trace gas concentrations, but does not permit mapping of local emissions from point sources. Point source emissions of methane (CH4), nitrous oxide (N2O) and particulates, often associated with combustion and carbon dioxide (CO2) emissions, have significant impacts on air quality. Using Airborne Visible InfraRed Imaging Spectrometer (AVIRIS) data and a cluster-tuned matched filter technique, we have mapped local CH4, N2O and CO2 emissions from terrestrial sources in the Los Angeles basin. CH4 anomalies were in close proximity to known and probable emission sources, including hydrocarbon storage tanks and gas flares. Multiple N2O and CH4 anomalies were detected at a wastewater treatment facility, while CH4 and CO2 anomalies were also identified at a large oil refinery. We discuss ongoing efforts to estimate CH4 concentrations using radiative transfer modeling and potential application of this technique to additional trace gasses with distinct absorption features. This method could be applied to data from existing airborne sensors and planned satellite missions like HyspIRI, thereby improving high resolution mapping of trace gasses and better constraining local sources.

  16. Improvement and validation of trace gas retrieval from ACAM aircraft observation

    NASA Astrophysics Data System (ADS)

    Liu, C.; Liu, X.; Kowalewski, M. G.; Janz, S. J.; Gonzalez Abad, G.; Pickering, K. E.; Chance, K.; Lamsal, L. N.

    2014-12-01

    The ACAM (Airborne Compact Atmospheric Mapper) instrument, flown on board the NASA UC-12 aircraft during the DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) campaigns, was designed to provide remote sensing observations of tropospheric and boundary layer pollutants and help understand some of the most important pollutants that directly affect the health of the population. In this study, slant column densities (SCD) of trace gases (O3, NO2, HCHO) are retrieved from ACAM measurements during the Baltimore-Washington D.C. 2011 campaign by the Basic Optical Absorption Spectroscopy (BOAS) trace gas fitting algorithm using a nonlinear least-squares (NLLS) inversion technique, and then are converted to vertical column densities (VCDs) using the Air Mass Factors (AMF) calculated with the VLIDORT (Vector Linearized Discrete Ordinate Radiative Transfer) model and CMAQ (Community Multi-scale Air Quality) model simulations of trace gas profiles. For surface treatment in the AMF, we use high-resolution MODIS climatological BRDF product (Bidirectional Reflectance Distribution Function) at 470 nm for NO2, and use high-resolution surface albedo derived by combining MODIS and OMI albedo databases for HCHO and O3. We validate ACAM results with coincident ground-based PANDORA, aircraft (P3B) spiral and satellite (OMI) measurements and find out generally good agreement especially for NO2 and O3

  17. Proton transfer reaction mass spectrometry: on-line trace gas analysis at the ppb level

    NASA Astrophysics Data System (ADS)

    Hansel, A.; Jordan, A.; Holzinger, R.; Prazeller, P.; Vogel, W.; Lindinger, W.

    1995-11-01

    A system for trace gas analysis using proton transfer reaction mass spectrometry (PTR-MS) has been developed which allows for on-line measurements of components with concentrations as low as 1 ppb. The method is based on reactions of H3O+ ions, which perform non-dissociative proton transfer to most of the common organic trace constituents but do not react with any of the components present in clean air. Examples of analysis of breath taken from smokers and non-smokers as well as from patients suffering from cirrhosis of the liver, and of air in buildings as well as of ambient air taken at a road crossing demonstrate the wide range of applicability of this method. An enhanced level of acetonitrile in the breath is a most suitable indicator that a person is a smoker. Enhanced levels of propanol strongly indicate that a person has a severe liver deficiency.

  18. Application of a broadly tunable SG-DBR QCL for multi-species trace gas spectroscopy.

    PubMed

    Diba, Abdou S; Xie, Feng; Gross, Barry; Hughes, Lawrence C; Zah, Chung-en; Moshary, Fred

    2015-10-19

    Feasibility of using a mid-Infrared tunable sampled-grating distributed Bragg reflectors quantum cascade laser for high resolution multicomponent trace gas spectroscopy is demonstrated. By controlling the driving currents to the front and back sections of the laser, we were able to tune a pulsed 4.55 µm laser over a frequency range a of 30 cm(-1) with high resolution, accuracy and repeatability. The laser was applied to absorption spectroscopy of ambient and reduced pressure (150 Torr) air in a 205 meters multi-pass Herriott cell, and by using standard LSQ fitting to a spectral database of these trace gases (HITRAN), the concentrations of nitrous oxide, carbon monoxide, and water vapor were retrieved. PMID:26480373

  19. Trace-Gas Mixing in Isolated Urban Boundary Layers: Results from the 2001 Phoenix Sunrise Experiment

    SciTech Connect

    Berkowitz, Carl M.; Doran, J C.; Shaw, William J.; Springston, Stephen R.; Spicer, Chet W.

    2006-01-01

    Measurements made from surface sites, from the 50-m and 140-m levels (the 16th and 39th floors) of a skyscraper and from an instrumented aircraft are used to characterize early morning profiles of CO, NOy and O3 within the mid-morning summertime convective atmospheric boundary layer (CABL) over Phoenix, Arizona. Although mixing was anticipated to produce uniform values of these species throughout the CABL, this was found not to be the case. Background air advected into the upper levels of the boundary layer and entrained air from above appears to be the most likely cause for the lack of well-mixed trace gases. The results show that surface measurements may provide only limited information on concentrations of trace gas species higher in the boundary layer.

  20. Rocket- and aircraft-borne trace gas measurements in the winter polar stratosphere

    NASA Technical Reports Server (NTRS)

    Arnold, F.; Moehler, O.; Pfeilsticker, K.; Ziereis, H.

    1988-01-01

    In January and February 1987 stratospheric rocket- and aircraft-borne trace gas measurements were done in the North Polar region using ACIMS (Active Chemical Ionization Mass Spectrometry) and PACIMS (PAssive Chemical Ionization Mass Spectrometry) instruments. The rocket was launched at ESRANGE (European Sounding Rocket Launching Range) (68 N, 21 E, Northern Sweden) and the twin-jet research aircraft operated by the DFVLR (Deutsche Forschungs- und Versuchs-anstalt fuer Luft- und Raumfahrt), and equipped with a mass spectrometer laboratory was stationed at Kiruna airport. Various stratospheric trace gases were measured including nitric acid, sulfuric acid, non-methane hydrocarbons (acetone, hydrogen cyanide, acetonitrile, methanol etc.), and ambient cluster ions. The experimental data is presented and possible implications for polar stratospheric ozone discussed.

  1. Detectability of trace gases in the Martian atmosphere using gas correlation filter radiometry

    NASA Astrophysics Data System (ADS)

    Sinclair, J.; Irwin, P. G. J.; Wilson, E.; Calcutt, S.

    2015-10-01

    We present the results of radiative transfer simulations of a gas correlation filter radiometer (GCFR) in the detection of trace species in the Martian atmosphere. We investigated two scenarios: 1) nadir and/or limb sounding from a Mars orbiter in the thermal infrared, 2) solar occultation measurements in the near-infrared from the Martian surface. In both scenarios, a GCFR would allow detection of trace gases at a lower concentration than that detectable by a conventional filter radiometer. In nadir/limb sounding, we find that CH4, SO2, N2O, C2H2 and CH3OH are detectable at concentrations lower than previously-derived upper limits. From solar occultation measurements, we find that CH4, SO2, C2H2, C2H6 are detectable at concentrations lower than previously-derived upper limits but only in low dust conditions.

  2. Obliquity-Controlled Water Vapor/Trace Gas Feedback in the Martian Greenhouse Cycle

    NASA Astrophysics Data System (ADS)

    Mischna, M. A.; Baker, V. R.; Milliken, R.; Richardson, M. I.; Lee, C.

    2013-12-01

    We have explored possible mechanisms for the generation of warm, wet climates on early Mars as a result of greenhouse warming by both water vapor and periodic volcanic trace gas emissions, using the Mars Weather Research and Forecasting (MarsWRF) general circulation model. The presence of both water vapor (a strong greenhouse gas) and other trace greenhouse gases (such as SO2) in a predominantly CO2 atmosphere may act, under certain conditions, to elevate surface temperatures above the freezing point of liquid water, at least episodically. The levels of warming obtained in our simulations do not reach the values seen in Johnson et al., (2008, JGR, 113, E08005), nor are they widespread for extended periods. Rather, warming above 273 K is found in more localized environments and for geologically brief periods of time. Such periodic episodes are controlled by two factors. First is the obliquity of the planet, which plays a significant role is ';activating' extant surface water ice reservoirs, allowing levels of atmospheric water vapor to rise when obliquity is high, and fall precipitously when the obliquity is low. During these low-obliquity periods, the atmosphere is all but incapable of supporting warm surface temperatures except for brief episodes localized wholly in the tropics; thus, there is a natural regulator in the obliquity cycle for maintaining periodic warming. Second is the presence of a secondary trace gas 'trigger', like volcanically released SO2, in the atmosphere. In the absence of such a trace gas, water vapor alone appears incapable of raising temperatures above the melting point; however, by temporarily raising the baseline global temperatures (in the absence of warming by water vapor) by 10-15 K, as with SO2, the trigger gas keeps atmospheric temperatures sufficiently warm, especially during nighttime, to maintain levels of water vapor in the atmosphere that provide the needed warming. Furthermore, we find that global warming can be achieved more

  3. Product energy deposition of CN + alkane H abstraction reactions in gas and solution phases

    NASA Astrophysics Data System (ADS)

    Glowacki, David R.; Orr-Ewing, Andrew J.; Harvey, Jeremy N.

    2011-06-01

    In this work, we report the first theoretical studies of post-transition state dynamics for reaction of CN with polyatomic organic species. Using electronic structure theory, a newly developed analytic reactive PES, a recently implemented rare-event acceleration algorithm, and a normal mode projection scheme, we carried out and analyzed quasi-classical and classical non-equilibrium molecular dynamics simulations of the reactions CN + propane (R1) and CN + cyclohexane (R2). For (R2), we carried out simulations in both the gas phase and in a CH2Cl2 solvent. Analysis of the results suggests that the solvent perturbations to the (R2) reactive free energy surface are small, leading to product energy partitioning in the solvent that is similar to the gas phase. The distribution of molecular geometries at the respective gas and solution phase variational association transition states is very similar, leading to nascent HCN which is vibrationally excited in both its CH stretching and HCN bending coordinates. This study highlights the fact that significant non-equilibrium energy distributions may follow in the wake of solution phase bimolecular reactions, and may persist for hundreds of picoseconds despite frictional damping. Consideration of non-thermal distributions is often neglected in descriptions of condensed-phase reactivity; the extent to which the present intriguing observations are widespread remains an interesting question.

  4. Formaldehyde in Absorption: Tracing Molecular Gas in Early-Type Galaxies

    NASA Astrophysics Data System (ADS)

    Dollhopf, Niklaus M.; Donovan Meyer, Jennifer

    2016-01-01

    Early-Type Galaxies (ETGs) have been long-classified as the red, ellipsoidal branch of the classic Hubble tuning fork diagram of galactic structure. In part with this classification, ETGs are thought to be molecular and atomic gas-poor with little to no recent star formation. However, recent efforts have questioned this ingrained classification. Most notably, the ATLAS3D survey of 260 ETGs within ~40 Mpc found 22% contain CO, a common tracer for molecular gas. The presence of cold molecular gas also implies the possibility for current star formation within these galaxies. Simulations do not accurately predict the recent observations and further studies are necessary to understand the mechanisms of ETGs.CO traces molecular gas starting at densities of ~102 cm-3, which makes it a good tracer of bulk molecular gas, but does little to constrain the possible locations of star formation within the cores of dense molecular gas clouds. Formaldehyde (H2CO) traces molecular gas on the order of ~104 cm-3, providing a further constraint on the location of star-forming gas, while being simple enough to possibly be abundant in gas-poor ETGs. In cold molecular clouds at or above ~104 cm-3 densities, the structure of formaldehyde enables a phenomenon in which rotational transitions have excitation temperatures driven below the temperature of the cosmic microwave background (CMB), ~2.7 K. Because the CMB radiates isotropically, formaldehyde can be observed in absorption, independent of distance, as a tracer of moderately-dense molecular clouds and star formation.This novel observation technique of formaldehyde was incorporated for observations of twelve CO-detected ETGs from the ATLAS3D sample, including NGC 4710 and PGC 8815, to investigate the presence of cold molecular gas, and possible star formation, in ETGs. We present images from the Very Large Array, used in its C-array configuration, of the J = 11,0 - 11,1 transition of formaldehyde towards these sources. We report our

  5. On the detectability of trace chemical species in the martian atmosphere using gas correlation filter radiometry

    NASA Astrophysics Data System (ADS)

    Sinclair, J. A.; Irwin, P. G. J.; Calcutt, S. B.; Wilson, E. L.

    2015-11-01

    The martian atmosphere is host to many trace gases including water (H2O) and its isotopologues, methane (CH4) and potentially sulphur dioxide (SO2), nitrous oxide (N2O) and further organic compounds, which would serve as indirect tracers of geological, chemical and biological processes on Mars. With exception of the recent detection of CH4 by Curiosity, previous detections of these species have been unsuccessful or considered tentative due to the low concentrations of these species in the atmosphere (∼10-9 partial pressures), limited spectral resolving power and/or signal-to-noise and the challenge of discriminating between telluric and martian features when observing from the Earth. In this study, we present radiative transfer simulations of an alternative method for detection of trace gas species - the gas correlation radiometry method. Two potential observing scenarios were explored where a gas correlation filter radiometer (GCFR) instrument: (1) performs nadir and/or limb sounding of the martian atmosphere in the thermal infrared (200-2000 cm-1 from an orbiting spacecraft or (2) performs solar occultation measurements in the near-infrared (2000-5000 cm-1) from a lander on the martian surface. In both scenarios, simulations of a narrowband filter radiometer (without gas correlation) were also generated to serve as a comparison. From a spacecraft, we find that a gas correlation filter radiometer, in comparison to a filter radiometer (FR), offers a greater discrimination between temperature and dust, a greater discrimination between H2O and HDO, and would allow detection of N2O and CH3OH at concentrations of ∼10 ppbv and ∼2 ppbv, respectively, which are lower than previously-derived upper limits. However, the lowest retrievable concentration of SO2 (approximately 2 ppbv) is comparable with previous upper limits and CH4 is only detectable at concentrations of approximately 10 ppbv, which is an order of magnitude higher than the concentration recently measured

  6. Downwind Trace Gas Vertical Profiles in SE Australia Associated with SAFARI 2000 Dry Season Campaign

    NASA Astrophysics Data System (ADS)

    Pak, B. C.; Langenfelds, R. L.; Young, S. A.; Francey, R. J.; Meyer, M.; Kivlighon, L. M.; Cooper, L. N.; Dunse, B. L.; Allison, C. E.; Steele, L. P.; Galbally, I. E.; Weeks, I. A.

    2001-12-01

    In association with the SAFARI 2000 Dry Season campaign in Africa, the Commonwealth Scientific and Industrial Research Organization (CSIRO) division of Atmospheric Research conducted aircraft measurements downwind, over Australia. Five missions were conducted using a Piper Navajo twin-engine aircraft to measure trace gas vertical profiles from near surface up to 7 km above Cape Grim (41oS, 144oE) and Melbourne (38oS, 145oE) regions. Air collected in glass flasks were analysed for CO2 and its stable isotopes (d13C and d18O of CO2), CH4, CO, H2 and N2O. Air collected in passivated canisters were analysed for C2 and C3 hydrocarbons. Ozone was monitored continuously in four of these missions and ground-based LIDAR was also employed in the Melbourne region in three occasions. Previous study on trace gas vertical profiles above Cape Grim between 1992 and 1997 had established using emission ratios that burning in Africa and S America are contributing to the enhanced mid-tropospheric content of various trace gases in SE Australia. Now the SAFARI 2000 in-situ data complemented with downwind observations in Australia provides the opportunity to more closely link the observed mid-tropospheric anomalies at Cape Grim to specific surface emissions and atmospheric processes. Combined with our previous data, this investigation of biomass burning impacts is extended for the whole period from 1992 to 2000. In this respect, we plan to collaborate with groups measuring the same trace gases in-situ during SAFARI 2000 (including ozone and VOCs) and compare the observations to simulated results from the UC Irvine chemistry transport model. Data requests for the vertical profile data could be addressed to B.C. Pak or R.L. Langenfelds via email: bpak@halo.ps.uci.edu, ray.langenfelds@dar.csiro.au

  7. Miniaturized Gas Correlation Radiometer for the Detection of Trace Gases in the Martian Atmosphere

    NASA Astrophysics Data System (ADS)

    Melroy, H.; Wilson, E. L.; Georgieva, E.

    2012-12-01

    We present a miniaturized and simplified version of a gas correlation radiometer (GCR) capable of simultaneously mapping multiple trace gases and identifying active regions on the Mars surface. Gas correlation radiometry (GCR) has been shown to be a sensitive and versatile method for detecting trace gases in Earth's atmosphere. Reduction of the size and mass of the GCR was achieved by implementing compact, light-weight 1 mm inner diameter hollow-core optical fibers (hollow waveguides) as the gas correlation cells. In a comparison with an Earth orbiting CO2 GCR instrument, exchanging the 10 m multipass cells with hollow waveguide gas correlation cells of equivalent pathlength reduces the mass from ~150 kg to ~0.5 kg, and reduces the volume from 1.9 m x 1.3 m x 0.86 m to a small bundle of fiber coils approximately 1 meter in diameter by 0.05 m in height (mass and volume reductions of >99%). A unique feature of this instrument is its stackable module design, with a single module for each trace gas. Each of the modules is self-contained, and fundamentally identical; differing by the bandpass filter wavelength range and gas mixtures inside the hollow-waveguide absorption cells. The current configuration contains four stacked modules for simultaneous measurements of methane (CH4), formaldehyde (H2CO), water vapor (H2O), and deuterated water vapor (HDO) but could easily be expanded to include measurements of additional species of interest including nitrous oxide (N2O), hydrogen sulfide (H2S), methanol (CH3OH), and sulfur dioxide (SO2), as well as carbon dioxide (CO2) for a simultaneous measure of mass balance. Preliminary results indicate that a 1 ppb detection limit is possible for both formaldehyde and methane with one second of averaging. Using non-optimized components, we have demonstrated an instrument sensitivity equivalent to ~30 ppb for formaldehyde, and ~500 ppb for methane. We expect custom bandpass filters and 6 m long waveguides to significantly improve these

  8. Miniaturized Gas Correlation Radiometer for the Detection of Trace Gases in the Martian Atmosphere

    NASA Technical Reports Server (NTRS)

    Melroy, Hilary R.; Wilson, Emily L.; Georgieva, Elena

    2012-01-01

    We present a miniaturized and simplified version of a gas correlation radiometer (GCR) capable of simultaneously mapping multiple trace gases and identifying active regions on the Mars surface. Gas correlation radiometry (GCR) has been shown to be a sensitive and versatile method for detecting trace gases in Earth's atmosphere. Reduction of the size and mass of the GCR was achieved by implementing compact, light-weight 1 mm inner diameter hollow-core optical fibers (hollow waveguides) as the gas correlation cells. In a comparison with an Earth orbiting CO2 GCR instrument, exchanging the 10 m multipass cells with hollow waveguide gas correlation cells of equivalent path length reduces the mass from approximately 150 kg to approximately 0.5 kg, and reduces the volume from 1.9 m x 1.3 m x 0.86 m to a small bundle of fiber coils approximately 1 meter in diameter by 0.05 m in height (mass and volume reductions of greater than 99%). A unique feature of this instrument is its stackable module design, with a single module for each trace gas. Each of the modules is self-contained, and fundamentally identical; differing by the bandpass filter wavelength range and gas mixtures inside the hollow-waveguide absorption cells. The current configuration contains four stacked modules for simultaneous measurements of methane (CH4), formaldehyde (H2CO), water vapor (H2O), and deuterated water vapor (HDO) but could easily be expanded to include measurements of additional species of interest including nitrous oxide (N2O), hydrogen sulfide (H2S), methanol (CH3OH), and sulfur dioxide (SO2), as well as carbon dioxide (CO2) for a simultaneous measure of mass balance. Preliminary results indicate that a 1 ppb detection limit is possible for both formaldehyde and methane with one second of averaging. Using non-optimized components, we have demonstrated an instrument sensitivity equivalent to approximately 30 ppb for formaldehyde, and approximately 500 ppb for methane. We expect custom

  9. A global aerosol classification algorithm incorporating multiple satellite data sets of aerosol and trace gas abundances

    NASA Astrophysics Data System (ADS)

    Penning de Vries, M. J. M.; Beirle, S.; Hörmann, C.; Kaiser, J. W.; Stammes, P.; Tilstra, L. G.; Tuinder, O. N. E.; Wagner, T.

    2015-09-01

    Detecting the optical properties of aerosols using passive satellite-borne measurements alone is a difficult task due to the broadband effect of aerosols on the measured spectra and the influences of surface and cloud reflection. We present another approach to determine aerosol type, namely by studying the relationship of aerosol optical depth (AOD) with trace gas abundance, aerosol absorption, and mean aerosol size. Our new Global Aerosol Classification Algorithm, GACA, examines relationships between aerosol properties (AOD and extinction Ångström exponent from the Moderate Resolution Imaging Spectroradiometer (MODIS), UV Aerosol Index from the second Global Ozone Monitoring Experiment, GOME-2) and trace gas column densities (NO2, HCHO, SO2 from GOME-2, and CO from MOPITT, the Measurements of Pollution in the Troposphere instrument) on a monthly mean basis. First, aerosol types are separated based on size (Ångström exponent) and absorption (UV Aerosol Index), then the dominating sources are identified based on mean trace gas columns and their correlation with AOD. In this way, global maps of dominant aerosol type and main source type are constructed for each season and compared with maps of aerosol composition from the global MACC (Monitoring Atmospheric Composition and Climate) model. Although GACA cannot correctly characterize transported or mixed aerosols, GACA and MACC show good agreement regarding the global seasonal cycle, particularly for urban/industrial aerosols. The seasonal cycles of both aerosol type and source are also studied in more detail for selected 5° × 5° regions. Again, good agreement between GACA and MACC is found for all regions, but some systematic differences become apparent: the variability of aerosol composition (yearly and/or seasonal) is often not well captured by MACC, the amount of mineral dust outside of the dust belt appears to be overestimated, and the abundance of secondary organic aerosols is underestimated in comparison

  10. Spatial variations of nitrogen trace gas emissions from tropical mountain forests in Nyungwe, Rwanda

    NASA Astrophysics Data System (ADS)

    Gharahi Ghehi, N.; Werner, C.; Cizungu Ntaboba, L.; Mbonigaba Muhinda, J. J.; van Ranst, E.; Butterbach-Bahl, K.; Kiese, R.; Boeckx, P.

    2011-12-01

    Globally, tropical forest soils represent the second largest source of N2O and NO. However, there is still considerable uncertainty on the spatial variability and soil properties controlling N trace gas emission. To investigate how soil properties affect N2O and NO emission, we carried out an incubation experiment with soils from 31 locations in the Nyungwe tropical mountain forest in southwestern Rwanda. All soils were incubated at three different moisture levels (50, 70 and 90% water filled pore space (WFPS)) at 17 °C. Nitrous oxide emission varied between 4.5 and 400 μg N m-2 h-1, while NO emission varied from 6.6 to 265 μg N m-2 h-1. Mean N2O emission at different moisture levels was 46.5 ± 11.1 (50% WFPS), 71.7 ± 11.5 (70% WFPS) and 98.8 ± 16.4 (90% WFPS) μg N m-2 h-1, while mean NO emission was 69.3 ± 9.3 (50% WFPS), 47.1 ± 5.8 (70% WFPS) and 36.1 ± 4.2 (90% WFPS) μg N m-2 h-1. The latter suggests that climate (i.e. dry vs. wet season) controls N2O and NO emissions. Positive correlations with soil carbon and nitrogen indicate a biological control over N2O and NO production. But interestingly N2O and NO emissions also showed a negative correlation (only N2O) with soil pH and a positive correlation with free iron. The latter suggest that chemo-denitrification might, at least for N2O, be an important production pathway. In conclusion improved understanding and process based modeling of N trace gas emission from tropical forests will not only benefit from better spatial explicit trace gas emission and basic soil property monitoring, but also by differentiating between biological and chemical pathways for N trace gas formation.

  11. Trace Gas Emissions Data from the Carbon Dioxide Information Analysis Center (CDIAC)

    DOE Data Explorer

    CDIAC products are indexed and searchable through a customized interface powered by ORNL's Mercury search engine. Products include numeric data packages, publications, trend data, atlases, and models and can be searched for by subject area, keywords, authors, product numbers, time periods, collection sites, spatial references, etc. Some of the collections may also be included in the CDIAC publication Trends Online: A Compendium of Global Change Data. Most data sets, many with numerous data files, are free to download from CDIAC's ftp area. Collections under the broad heading of Trace Gas Emissions are organized as Fossil-Fuel CO2 Emissions, Land-Use CO2 Emissions, Soil CO2 Emissions, and Methane.

  12. Derivatization in gas chromatographic determination of phenol and aniline traces in aqueous media

    NASA Astrophysics Data System (ADS)

    Gruzdev, I. V.; Zenkevich, I. G.; Kondratenok, B. M.

    2015-06-01

    Substituted anilines and phenols are the most common hydrophilic organic environmental toxicants. The principles of gas chromatographic determination of trace amounts of these compounds in aqueous media at concentrations <=0.1 μg litre-1 based on synthesis of their derivatives (derivatization) directly in the aqueous phase are considered. Conversion of relatively hydrophilic analytes into more hydrophobic derivatives makes it possible to achieve such low detection limits and optimize the protocols of extractive preconcentration and selective chromatographic detection. Among the known reactions, this condition is best met by electrophilic halogenation of compounds at the aromatic moiety. The bibliography includes 177 references.

  13. A ground-based trace gas observing system for detection of Arctic and Boreal change

    NASA Astrophysics Data System (ADS)

    Karion, A.; Miller, J. B.; Sweeney, C.; Bruhwiler, L.; Newberger, T.; Miller, C. E.; Dinardo, S. J.; Wolter, S.; Ledlow, L.

    2012-12-01

    The large reservoir of below-ground organic carbon in the Arctic and Boreal region (ABR) permafrost, combined with large observed and predicted temperature changes leads to the expectation of increasing surface emissions of CO2 and/or CH4 this century. However, the near-term response of northern ecosystems could be enhanced ecosystem productivity and carbon sequestration via, among other causes, longer growing seasons and encroachment of woody species into Arctic tundra. Regardless of the temporal evolution of carbon (both CO2 and CH4) sources and sinks in the ABR, monitoring these changes at regional (~10^5 - 10^6 km^2) scales using trace gas mixing and isotopic ratios will be a critical complement to detailed process-based studies at the plot scale and remote sensing of the land surface. Turbulent mixing in the lower few kilometers of the atmosphere naturally integrates emissions from all known and unknown processes and can provide a powerful bottom-line constraint on the net result of both sources and sinks. We will present the first year of results of a trace-gas measurement system capable of daily or more frequent observations of more than 50 trace gas species, including CO2, CH4 and their stable and radio isotope ratios. The measurements were initiated as part of the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) and come from a 30 m tower located on a ridge in central Alaska. Central Alaska is dominated by discontinuous permafrost, which is likely to undergo significant changes in the coming decades. Footprint analysis suggests that mixing ratios measured at the tower are influenced by large swaths of central Alaska, although in winter, anthropogenic emissions form the city of Fairbanks are evident. In summer, as expected, we observe a large drawdown of CO2. The seasonal cycle of CH4 is dominated by the large-scale destruction of methane by hydroxyl radical (OH). However, based on previous measurements from other ABR sites, we expect summer

  14. Gas chromatographic determination of trace amounts of vinyl chloride and dichloroethenes in landfill-gas.

    PubMed

    Wittsiepe, J; Selenka, F; Jackwerth, E

    1996-03-01

    A method for the determination of vinyl chloride (VC) and dichloroethenes (DCE) in gas samples is presented. The analytes are preconcentrated from a gas-volume of up to 20 l on an adsorption tube filled with 1.0 g of a carbon molecular sieve at a flow rate of 80 l/h and are subsequently desorbed with carbon disulfide. Vinyl bromide is added as internal standard to the extract. The analytes are determined as their 1,2-dibromo-derivatives by capillary gas chromatography with electron capture detection. The detection limits have been found to be 82 ng/m(3) = 32 ppt (VC), 190 ng/m(3) = 48 ppt (1,1-DCE) and 96 ng/m(3) = 24 ppt (cis-/trans-1,2-DCE). The method has been used for the quantification of the anaerobic microbial degradation of tetra- (PCE) and trichloroethene (TCE) to dichloroethenes and vinyl chloride in landfill sites. The substances have been analyzed in landfill-gas as well as in gaseous emissions from the landfill surface. The mean emission rates of tetrachloroethene, trichloroethene and vinyl chloride from the landfill surface into the ambient air are about 0.5 microg/(m(2) x h). PMID:15048415

  15. Applications of Kalman filtering to real-time trace gas concentration measurements

    NASA Technical Reports Server (NTRS)

    Leleux, D. P.; Claps, R.; Chen, W.; Tittel, F. K.; Harman, T. L.

    2002-01-01

    A Kalman filtering technique is applied to the simultaneous detection of NH3 and CO2 with a diode-laser-based sensor operating at 1.53 micrometers. This technique is developed for improving the sensitivity and precision of trace gas concentration levels based on direct overtone laser absorption spectroscopy in the presence of various sensor noise sources. Filter performance is demonstrated to be adaptive to real-time noise and data statistics. Additionally, filter operation is successfully performed with dynamic ranges differing by three orders of magnitude. Details of Kalman filter theory applied to the acquired spectroscopic data are discussed. The effectiveness of this technique is evaluated by performing NH3 and CO2 concentration measurements and utilizing it to monitor varying ammonia and carbon dioxide levels in a bioreactor for water reprocessing, located at the NASA-Johnson Space Center. Results indicate a sensitivity enhancement of six times, in terms of improved minimum detectable absorption by the gas sensor.

  16. Rn-222 tracing and stable isotope measurements of biogenic gas fluxes from methane saturated sediments

    NASA Technical Reports Server (NTRS)

    Martens, Christopher S.; Green, C. D.; Blair, Neal; Chanton, J. P.

    1985-01-01

    Transport of reduced biogenic gases from anoxic sediments and soils to the atmosphere can be quantitatively studied through measurement of radon-222/radium-226 disequilibrium. In previous work, seasonal variations in biogenic gas transport mechanisms, net fluxes and overall composition were documented. Now presented are direct field measurements of radon-222 activity in gases exiting organic rich sediments which show their usefulness for tracing of the stripping of dissolved biogenic gases from within the sediment column and transport via bubble ebullition. Methane is depleted in deuterium during the summer as compared with winter months and is in general lighter than in most marine sediments signaling the probable importance of acetate as an important precursor molecule. The significant seasonal isotopic variations observed illustrate the importance of understanding mechanisms and rates of biogenic gas production in order to interpret observed tropospheric isotopic data.

  17. An experimental trace gas investigation of fluid transport and mixing in a circular-to-rectangular transition duct

    NASA Technical Reports Server (NTRS)

    Reichert, B. A.; Hingst, W. R.; Okiishi, T. H.

    1991-01-01

    An ethylene trace gas technique was used to map out fluid transport and mixing within a circular-to-rectangular transition duct. Ethylene gas was injected at several points in a cross stream plane upstream of the transition duct. Ethylene concentration contours were determined at several cross stream measurement planes spaced axially within the duct. The flow involved a uniform inlet flow at a Mach number level of 0.5. Statistical analyses were used to quantitatively interpret the trace gas results. Also, trace gas data were considered along with aerodynamic and surface flow visualization results to ascertain transition duct flow phenomena. Convection of wall boundary layer fluid by vortices produced regions of high total pressure loss in the duct. The physical extent of these high loss regions is governed by turbulent diffusion.

  18. An experimental trace gas investigation of fluid transport and mixing in a circular-to-rectangular transition duct

    NASA Technical Reports Server (NTRS)

    Reichert, B. A.; Hingst, W. R.; Okiishi, T. H.

    1991-01-01

    An ethylene trace gas technique was used to map out fluid transport and mixing within a circular to rectangular transition duct. Ethylene gas was injected at several points in a cross stream plane upstream of the transition duct. Ethylene concentration contours were determined at several cross stream measurement planes spaced axially within the duct. The flow involved a uniform inlet flow at a Mach number level of 0.5. Statistical analyses were used to quantitatively interpret the trace gas results. Also, trace gas data were considered along with aerodynamic and surface flow visualization results to ascertain transition duct flow phenomena. Convection of wall boundary layer fluid by vortices produced regions of high total pressure loss in the duct. The physical extent of these high loss regions is governed by turbulent diffusion.

  19. Nanofiber-net-binary structured membranes for highly sensitive detection of trace HCl gas.

    PubMed

    Wang, Xianfeng; Wang, Jialin; Si, Yang; Ding, Bin; Yu, Jianyong; Sun, Gang; Luo, Wenjing; Zheng, Gang

    2012-12-01

    This work describes the detection of trace hydrogen chloride (HCl) gas through analyses of the resonance frequency signal from quartz crystal microbalance (QCM) sensors coated with polyaniline (PANI) functionalized polyamide 6 (PA 6) (PANI-PA 6) nanofiber-net-binary (NNB) structured membranes. The PA 6 NNB substrate comprising nanofibers and spider-web-like nano-nets fabricated by a versatile electro-spinning/netting (ESN) process offered an ideal interface for the uniform PANI functionalization and enhanced sensing performance. Benefiting from the large specific surface area, high porosity, and strong adhesive force to the QCM electrode of the PANI-PA 6 NNB membranes, the developed HCl-selective sensors exhibited a rapid response, good reproducibility and stability, and low detection limit (7 ppb) at room temperature. Additionally, the PANI-PA 6 NNB sensing membranes presented visible color changes upon cycled exposure to HCl and ammonia, suggesting their potential application in the development of colorimetric sensors. The PANI-PA 6 NNB coated QCM sensors are considered to be a promising candidate for trace HCl gas detection in practical applications. PMID:23108331

  20. The Impact of ENSO on Trace Gas Composition in the Upper Troposphere to Lower Stratosphere

    NASA Astrophysics Data System (ADS)

    Oman, Luke; Douglass, Anne; Ziemke, Jerald; Waugh, Darryn

    2016-04-01

    The El Nino-Southern Oscillation (ENSO) is the dominant mode of interannual variability in the tropical troposphere and its effects extend well into the stratosphere. Its impact on atmospheric dynamics and chemistry cause important changes to trace gas constituent distributions. A comprehensive suite of satellite observations, reanalyses, and chemistry climate model simulations are illuminating our understanding of processes like ENSO. Analyses of more than a decade of observations from NASA's Aura and Aqua satellites, combined with simulations from the Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM) and other Chemistry Climate Modeling Initiative (CCMI) models, and the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) reanalysis have provided key insights into the response of atmospheric composition to ENSO. While we will primarily focus on ozone and water vapor responses in the upper troposphere to lower stratosphere, the effects of ENSO ripple through many important trace gas species throughout the atmosphere. The very large 2015-2016 El Nino event provides an opportunity to closely examine these impacts with unprecedented observational breadth. An improved quantification of natural climate variations, like those from ENSO, is needed to detect and quantify anthropogenic climate changes.

  1. Trace Gas Emissions from Extensive Aquaculture Systems in the Red River Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Beman, J.; Seto, K. C.

    2002-12-01

    The Red River Delta of Vietnam is an area undergoing rapid land use change. Aquaculture development is among the most significant of these transformations, with important economic, social and environmental effects. We explored the potential for managed mangrove' and `converted paddy' aquaculture systems in the Delta to produce and/or consume greenhouse gasses. We measured dissolved concentrations of the radiatively-important trace gasses methane (CH4) and nitrous oxide (N2O), as well as associated parameters. All ponds were super-saturated with CH4, with concentrations ranging from 132-1203 nM, (mean 561 nM) in managed mangrove, and 28-521 nM (mean 110 nM) in converted paddy. Surprisingly, none of the ponds was measurably supersaturated with N2O. Methane fluxes were calculated for all ponds using five well-accepted models of gas flux based on wind speed. Mean flux values ranged from 1.04 to 17.09 mg CH4 m-2 d-1 for managed mangrove, falling somewhere between fluxes reported for natural systems and those receiving sewage inputs. Further measurements should be made in more intensive systems to better understand the potential for trace gas production-particularly N2O-in aquaculture systems.

  2. Diagnostics of nitrogen plasma by trace rare-gas-optical emission spectroscopy

    SciTech Connect

    Qayyum, A.; Zeb, Shaista; Naveed, M.A.; Ghauri, S.A.; Zakaullah, M.; Waheed, A.

    2005-11-15

    Trace rare-gas-optical emission spectroscopy is carried out to characterize the nitrogen plasma as a function of discharge parameters. The functional dependence of N{sub 2}(C {sup 3}{pi}{sub u}) and N{sub 2}{sup +}(B {sup 2}{sigma}{sub u}{sup +}) excited states is monitored by measuring the emission intensities of the bandheads of second positive and first negative systems. The excited-state population density of N atoms and N{sub 2} molecules, extracted from their optical emission, is related to the ground-state population density after normalizing the changes for excitation cross section and electron energy distribution function by optical actinometry. The electron temperature is determined from the plasma-induced optical emission of trace rare gas by the line-to-line method. The obtained data may help us to adjust the optimum discharge conditions for the production of active species, which are considered to be important for the desired treatment of the samples.

  3. Analysis of trace impurities in neon by a customized gas chromatography.

    PubMed

    Yin, Min Kyo; Lim, Jeong Sik; Moon, Dong Min; Lee, Gae Ho; Lee, Jeongsoon

    2016-09-01

    Excimer lasers, widely used in the semiconductor industry, are crucial for analyzing the purity of premix laser gases for the purpose of controlling stable laser output power. In this study, we designed a system for analyzing impurities in pure neon (Ne) base gas by customized GC. Impurities in pure neon (H2 and He), which cannot be analyzed at the sub-μmol/mol level using commercial GC detectors, were analyzed by a customized pulsed-discharge Ne ionization detector (PDNeD) and a pressurized injection thermal conductivity detector using Ne as the carrier gas (Pres. Inj. Ne-TCD). From the results, trace species in Ne were identified with the following detection limits: H2, 0.378μmol/mol; O2, 0.119μmol/mol; CH4, 0.880μmol/mol; CO, 0.263μmol/mol; CO2, 0.162μmol/mol (PDNeD); and He, 0.190μmol/mol (Pres. Inj. Ne-TCD). This PDNeD and pressurized injection Ne-TCD technique thus developed permit the quantification of trace impurities present in high-purity Ne. PMID:27527880

  4. Measurements of trace gas species and aerosols at three Siberian stations

    NASA Astrophysics Data System (ADS)

    Arshinov, Mikhail Yu.; Belan, Boris D.; Davydov, Denis K.; Kozlov, Artem V.; Ivlev, Georgii A.; Pestunov, Dmitrii A.; Tolmachev, Gennadii N.; Fofonov, Alexander V.

    2014-05-01

    Siberia is of great importance to understand the climate change due to it covers about 10% of Earth's land surface and it has the largest area to be studied under the Pan-Eurasian Experiment (PEEX). In the overview done by Kulmala et al. (2011) authors arrived at a conclusion that continuous and comprehensive measurements of GHGs and aerosols over Siberia are still lacking. Understanding the importance of this problem, in recent years the Institute of Atmospheric Optics SB RAS established several monitoring stations for continuous measurements of aerosol and trace gas species to fill up this gap. In this paper we present some results of continuous measurements of trace gas species and aerosols carried out at three stations located in West Siberia. The first one is a so-called TOR-station located in the scientific campus of Tomsk (56° 28'41"N, 85° 03'15"E), the second one is the Base Experimental Complex (BEC, 56° 28'49"N, 85° 06'08"E) - in the eastern suburbs of Tomsk, and the third one is Fonovaya Observatory (56° 25'07"N, 84° 04'27"E) - in a rural area 60 km west of Tomsk. All equipment of the stations is fully automated and can be monitored via Internet. Gas analyzers are hourly calibrated against standard gas mixtures, micro-flux gas sources, or gas generators, depending on the instrument type and the gas to be detected. Aerosol measurements carried out continuously from March 2010 enabled a frequency and seasonal dependency of the new particle formation (NPF) events to be revealed. NPF events in Siberia are more often observed during spring (from March to May) and early autumn (secondary frequency peak in September). On average, NPF evens took place on 23-28 % of all days. This work was funded by Presidium of RAS (Program No. 4), Brunch of Geology, Geophysics and Mining Sciences of RAS (Program No. 5), Interdisciplinary integration projects of Siberian Branch of RAS (No. 35, No. 70, No. 131), Russian Foundation for Basic Research (grants No 14

  5. Direct analysis of ultra-trace semiconductor gas by inductively coupled plasma mass spectrometry coupled with gas to particle conversion-gas exchange technique.

    PubMed

    Ohata, Masaki; Sakurai, Hiromu; Nishiguchi, Kohei; Utani, Keisuke; Günther, Detlef

    2015-09-01

    An inductively coupled plasma mass spectrometry (ICPMS) coupled with gas to particle conversion-gas exchange technique was applied to the direct analysis of ultra-trace semiconductor gas in ambient air. The ultra-trace semiconductor gases such as arsine (AsH3) and phosphine (PH3) were converted to particles by reaction with ozone (O3) and ammonia (NH3) gases within a gas to particle conversion device (GPD). The converted particles were directly introduced and measured by ICPMS through a gas exchange device (GED), which could penetrate the particles as well as exchange to Ar from either non-reacted gases such as an air or remaining gases of O3 and NH3. The particle size distribution of converted particles was measured by scanning mobility particle sizer (SMPS) and the results supported the elucidation of particle agglomeration between the particle converted from semiconductor gas and the particle of ammonium nitrate (NH4NO3) which was produced as major particle in GPD. Stable time-resolved signals from AsH3 and PH3 in air were obtained by GPD-GED-ICPMS with continuous gas introduction; however, the slightly larger fluctuation, which could be due to the ionization fluctuation of particles in ICP, was observed compared to that of metal carbonyl gas in Ar introduced directly into ICPMS. The linear regression lines were obtained and the limits of detection (LODs) of 1.5 pL L(-1) and 2.4 nL L(-1) for AsH3 and PH3, respectively, were estimated. Since these LODs revealed sufficiently lower values than the measurement concentrations required from semiconductor industry such as 0.5 nL L(-1) and 30 nL L(-1) for AsH3 and PH3, respectively, the GPD-GED-ICPMS could be useful for direct and high sensitive analysis of ultra-trace semiconductor gas in air. PMID:26388365

  6. Gas-Grain Simulation Facility: Fundamental studies of particle formation and interactions. Volume 2: Abstracts, candidate experiments and feasibility study

    NASA Technical Reports Server (NTRS)

    Fogleman, Guy (Editor); Huntington, Judith L. (Editor); Schwartz, Deborah E. (Editor); Fonda, Mark L. (Editor)

    1989-01-01

    An overview of the Gas-Grain Simulation Facility (GGSF) project and its current status is provided. The proceedings of the Gas-Grain Simulation Facility Experiments Workshop are recorded. The goal of the workshop was to define experiments for the GGSF--a small particle microgravity research facility. The workshop addressed the opportunity for performing, in Earth orbit, a wide variety of experiments that involve single small particles (grains) or clouds of particles. Twenty experiments from the fields of exobiology, planetary science, astrophysics, atmospheric science, biology, physics, and chemistry were described at the workshop and are outlined in Volume 2. Each experiment description included specific scientific objectives, an outline of the experimental procedure, and the anticipated GGSF performance requirements. Since these experiments represent the types of studies that will ultimately be proposed for the facility, they will be used to define the general science requirements of the GGSF. Also included in the second volume is a physics feasibility study and abstracts of example Gas-Grain Simulation Facility experiments and related experiments in progress.

  7. Analytical model of atmospheric pressure, helium/trace gas radio-frequency capacitive Penning discharges

    NASA Astrophysics Data System (ADS)

    Lieberman, M. A.

    2015-04-01

    Atmospheric and near-atmospheric pressure, helium/trace gas radio-frequency capacitive discharges have wide applications. An analytic equilibrium solution is developed based on a homogeneous, current-driven discharge model that includes sheath and electron multiplication effects and contains two electron populations. A simplified chemistry is used with four unknown densities: hot electrons, warm electrons, positive ions and metastables. The dominant electron-ion pair production is Penning ionization, and the dominant ion losses are to the walls. The equilibrium particle balances are used to determine a single ionization balance equation for the warm electron temperature, which is solved, both approximately within the α- and γ-modes, and exactly by conventional root-finding techniques. All other discharge parameters are found, the extinction and α-γ transitions are determined, and a similarity law is given, in which the equilibrium for a short gap at high pressure can be rescaled to a longer gap at lower pressure. Within the α-mode, we find the scaling of the discharge parameters with current density, frequency, gas density and gap width. The analytic results are compared to hybrid and particle-in-cell (PIC) results for He/0.1%N2, and to hybrid results for He/0.1%H2O. For nitrogen, a full reaction set is used for the hybrid calculations and a simplified reaction set for the PIC simulations. For the chemically complex water trace gas, a set of 209 reactions among 43 species is used. The analytic results are found to be in reasonably good agreement with the more elaborate hybrid and PIC calculations.

  8. Land use change effects on trace gas fluxes in the forest margins of Central Sulawesi, Indonesia

    NASA Astrophysics Data System (ADS)

    Veldkamp, Edzo; Purbopuspito, Joko; Corre, Marife D.; Brumme, Rainer; Murdiyarso, Daniel

    2008-06-01

    Land use changes and land use intensification are considered important processes contributing to the increasing concentrations of the greenhouse gases nitrous oxide (N2O) and methane (CH4) and of nitric oxide (NO), a precursor of ozone. Studies on the effects of land use changes and land use intensification on soil trace gas emissions were mostly conducted in Latin America and only very few in Asia. Here we present results from Central Sulawesi where profound changes in land use and cultivation practices take place: traditional agricultural practices like shifting cultivation and slash-and-burn agriculture are replaced by permanent cultivation systems and introduction of income-generating cash crops like cacao. Our results showed that N2O emissions were higher from cacao agroforestry (35 ± 10 μg N m-2 h-1) than maize (9 ± 2 μg N m-2 h-1), whereas intermediate rates were observed from secondary forests (25 ± 11 μg N m-2 h-1). NO emissions did not differ among land use systems, ranging from 12 ± 2 μg N m-2 h-1 for cacao agroforestry and secondary forest to 18 ± 2 μg N m-2 h-1 for maize. CH4 uptake was higher for maize (-30 ± 4 μg C m-2 h-1) than cacao agroforestry (-18 ± 2 μg C m-2 h-1) and intermediate rates were measured from secondary forests (-25 ± 4 μg C m-2 h-1). Combining these data with results from other studies in this area, we present chronosequence effects of land use change on trace gas emissions from natural forest, through maize cultivation, to cacao agroforestry (with or without fertilizer). Compared to the original forests, this typical land use change in the study area clearly led to higher N2O emissions and lower CH4 uptake with age of cacao agroforestry systems. We conclude that this common land use sequence in the area combined with the increasing use of fertilizer will strongly increase soil trace gas emissions. We suggest that the future hot spot regions of high N2O (and to a lesser extend NO) emissions in the tropics are those

  9. A hierarchical modeling approach to estimating soil trace gas fluxes from static chambers

    NASA Astrophysics Data System (ADS)

    Ogle, K.; Ryan, E.; Dijkstra, F. A.; Pendall, E.

    2014-12-01

    Static chambers are often employed to measure soil trace gas fluxes. Gas concentrations (C) in the headspace are sampled at different times (t), and for each group of chamber measurements, flux rates are frequently calculated as the slope of linear regressions of C versus t (ultimately, statistical analyses are performed with the flux rate "data"). While non-linear regressions are recognized to be more accurate than linear regressions, a trade-off with precision can arise due to variability in raw data leading to poor curve fits, and groups of data with too few observations or with poor regression fits (i.e., low R2) are often discarded. We solve these problems via a hierarchical Bayesian approach that fits a simple, dynamic non-linear model of C versus t based on Fick's law. Data are from the Prairie Heating and CO2 Enrichment (PHACE) study that involves manipulations of atmospheric CO2, temperature, soil moisture, and vegetation. CO2, CH4, and N2O gas samples were collected from static chambers bi-weekly during five growing seasons, resulting in >12,000 individual gas samples and >3100 groups of samples and associated fluxes. Using these data, we compare flux estimates from our non-linear model to those obtained from a linear model, and we evaluate the effect of conducting independent regressions for each group of samples versus simultaneously estimating the fluxes for all groups within a hierarchical framework motivated by the PHACE experimental design. The CO2 flux estimates from the hierarchical linear and non-linear models fit the observed CO2 data well (R2 = 0.97) and were highly correlated with each other (r = 0.99), but the linear model resulted in estimates that were ~10% lower than the non-linear model. The hierarchical versus non-hierarchical models also produced similar flux estimates (r = 0.94), but the non-hierarchical version yielded notably less precise estimates (the 95% CIs for its fluxes were 1-2 orders of magnitude wider that the hierarchical

  10. Large and small UAS for trace gas measurements in climate change studies

    NASA Astrophysics Data System (ADS)

    Elkins, J. W.; Moore, F. L.; Hintsa, E. J.; D'Amore, P.; Dutton, G. S.; Nance, J. D.; Hall, B. D.; Gao, R. S.

    2014-12-01

    NOAA and CIRES scientists have used Unmanned Aircraft Systems (UAS) for the measurement of trace gases involved in climate change since 2005, including both high altitude-long endurance (HALE UAS: NASA Altair & Global Hawk) and 1-m wingspan, small UAS (sUAS: SkyWisp, Aero). These gases include nitrous oxide (N2O), sulfur hexafluoride (SF6), methane (CH4), ozone (O3), carbon monoxide (CO), hydrogen (H2), and water vapor (H2O). In particular, atmospheric N2O is the third strongest greenhouse gas (326 parts-per-billion, ppb) and is the largest increasing stratospheric ozone depleting gas in terms of future emissions (~4 Tg N2O-N yr-1), primarily from fertilizer use. Atmospheric SF6, another potent greenhouse gas, is present globally at 8.2 parts-per-trillion (ppt) and growing at a rate of 0.25 ppt yr-1, and is used primarily in electrical power distribution. It is an excellent indicator of transport timescales (e.g., mean age) in the troposphere and stratosphere, because of its source distribution (~95% emitted in NH), long atmospheric lifetime (~600-3200 yr), and large relative atmospheric growth rate (~3%). We have developed atmospheric instrumentation for HALE platforms using a two-channel gas chromatograph with an ozone photometer and a water vapor tunable diode laser spectrometer. We are currently investigating a sUAS glider (SkyWisp) for balloon-assisted high altitude flights (30 km) and propeller driven sUAS (Aero) as a test bed for a new autopilot (Pixhawk, 3DRobotics). Our motivation for utilizing this autopilot is a low cost, open source autopilot alternative that can be used to return AirCore samples from high altitude balloons for quick laboratory analysis. The goal is a monitoring program to understand transport changes as a result of climate change during different seasons at many locations from a balloon-borne package (Moore et al., BAMS, pp. 147-155, Jan. 2014). The glider version of our open source autopilot system is also being considered for a

  11. Soil Trace Gas Flux for Wetland Vegetation Zones in North Dakota Prairie Pothole Basins

    NASA Astrophysics Data System (ADS)

    Phillips, R. L.; Beeri, O.; Dekaiser, E. S.

    2003-12-01

    Wetland ecosystems are considered a source for radiatively trace gases [methane (CH4), carbon dioxide (CO2), nitrous oxide (N2O)] but flux data for these greenhouse gases are lacking for depressional wetlands that comprise the Prairie Pothole Region. This region is characterized by thousands of small, closed basins that extend along the Missouri Coteau from north central Iowa to central Alberta. Surrounding each body of water are conspicuous zonation patterns given by specific vegetation life-forms and soil properties that are predominately formed by basin hydrology. Basin vegetation zones include deep marsh, shallow marsh, wet meadow, low prairie, and cropland (Stewart and Kantrud,1971). Our primary objective was to determine if net greenhouse gas flux for soils in these wetland basins [mg/m2/day CO2 equivalent (IPCC, 2000)] vary with vegetative zone for prairie pothole ecosystems. These data may then be used to map estimates for total basin greenhouse gas (GHG) flux. Additionally, we aimed to find the relative contribution of each of the 3 trace gases (CO2, CH4 and N2O) to net GHG flux. We hypothesized that flux would be greatest for marsh areas and lowest for upland areas. We selected a semi-permenant prairie pothole research site in Max, ND and mapped respective vegetative zones for 3 adjacent basins. Sample points were randomly selected for each basin and zone using aerial imagery. Samples of soil gases were collected using the static chamber method on August 3, 2003, and these were analyzed using gas chromatography for CO2, CH4 and N2O the following day. Soil moisture, clay content, organic matter, and temperature data were also collected. Net greenhouse gas flux for the cropped zone soils was significantly lower (p<0.01) than flux for the deep marsh, shallow marsh and wet meadow zone soils. Average flux measurement by zone (mg CO2 equivalent/m2/day) was 283 for cropland, 677 for low prairie, 1067 for wet meadow, 2572 for shallow marsh, and 6686 for deep

  12. The effect of temperature and moisture on trace gas emissions from deciduous and coniferous leaf litter

    NASA Astrophysics Data System (ADS)

    Gritsch, Christine; Egger, Florian; Zehetner, Franz; Zechmeister-Boltenstern, Sophie

    2016-05-01

    The forest litter layer lies at the boundary between soil and atmosphere and is a major factor in biogeochemical cycles. While there are several studies on how the litter layer controls soil trace gas emissions, litter emissions itself are less well understood, and it is still unclear how important gases respond to changing temperature and moisture. In order to assess leaf litter gas exchange, we conducted laboratory incubation experiments in which the full set of climate relevant gases, i.e., carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), and nitric oxide (NO) coming from deciduous and coniferous leaf litter were measured at five temperatures and seven moisture contents. In addition, we compared litter and soil from different origin in terms of temperature/moisture responses of gas fluxes and investigated possible interactions between the two climate factors. Deciduous litter emitted more CO2 (up to 335 mg CO2-C kg-1 h-1) than coniferous litter, whereas coniferous litter released maximum amounts of NO (207 µg NO-N kg-1 h-1). N2O was only emitted from litter under very moist and warm conditions (>70% wet weight, >10°C). CH4 emissions were close to zero. Temperature sensitivities of litter emissions were generally lower than for soil emissions. Nevertheless, wet and warm conditions always enhanced litter emissions, suggesting a strong feedback effect of the litter layer to predicted future climate change.

  13. Springtime Arctic Trace Gas Measurements and Comparisons With the Atmospheric Chemistry Experiment on SCISAT

    NASA Astrophysics Data System (ADS)

    Lindenmaier, R.; Batchelor, R.; Strong, K.; Walker, K.; Manney, G.; Daffer, W.

    2009-05-01

    The process of rapid stratospheric ozone loss in the polar regions begins during the polar winter, when dynamical and chemical conditions lead to the formation of reactive chlorine and bromine radicals. Arctic ozone loss varies significantly from year to year because of changing dynamical conditions. Therefore, long-term data sets of Arctic chemical composition measurements are needed to better understand the process of ozone loss, the links between ozone depletion and climate change, and the future evolution of ozone. Solar absorption spectra have been recorded at Eureka, Nunavut in the sunlit part of each year since July 2006, when a Bruker 125HR high-resolution Fourier transform infrared spectrometer was installed at the Polar Environment Atmospheric Research Laboratory (PEARL). Applying the optimal estimation technique, total columns and some vertical profile information are retrieved for a suite of trace gases that are involved in stratospheric ozone depletion. Total columns of O3, HCl, ClONO2, HNO3, and HF will be presented, with a focus on three Canadian Arctic ACE Validation spring campaigns that took place in 2007, 2008, and 2009. Very different dynamical situations were observed over Eureka during these three spring periods: the impact of these conditions on the trace gas measurements will be shown. SCISAT, also known as the Atmospheric Chemistry Experiment (ACE), is a Canadian satellite mission for remote sounding of the Earth's atmosphere and was launched on August 12, 2003. Its primary instrument is a high spectral resolution Fourier Transform Spectrometer (FTS) measuring sequences of atmospheric absorption spectra in solar occultation. From these spectra the vertical distribution of trace gases can be determined. Results of the Bruker 125HR comparisons with the ACE-FTS, made with the purpose of validating the satellite measurements, will be also shown.

  14. Pivotal roles of phyllosphere microorganisms at the interface between plant functioning and atmospheric trace gas dynamics

    PubMed Central

    Bringel, Françoise; Couée, Ivan

    2015-01-01

    The phyllosphere, which lato sensu consists of the aerial parts of plants, and therefore primarily, of the set of photosynthetic leaves, is one of the most prevalent microbial habitats on earth. Phyllosphere microbiota are related to original and specific processes at the interface between plants, microorganisms and the atmosphere. Recent –omics studies have opened fascinating opportunities for characterizing the spatio-temporal structure of phyllosphere microbial communities in relation with structural, functional, and ecological properties of host plants, and with physico-chemical properties of the environment, such as climate dynamics and trace gas composition of the surrounding atmosphere. This review will analyze recent advances, especially those resulting from environmental genomics, and how this novel knowledge has revealed the extent of the ecosystemic impact of the phyllosphere at the interface between plants and atmosphere. Highlights • The phyllosphere is one of the most prevalent microbial habitats on earth. • Phyllosphere microbiota colonize extreme, stressful, and changing environments. • Plants, phyllosphere microbiota and the atmosphere present a dynamic continuum. • Phyllosphere microbiota interact with the dynamics of volatile organic compounds and atmospheric trace gasses. PMID:26052316

  15. Airborne In-Situ Trace Gas Measurements of Multiple Wildfires in California (2013-2014)

    NASA Astrophysics Data System (ADS)

    Iraci, L. T.; Yates, E. L.; Tanaka, T.; Roby, M.; Gore, W.; Clements, C. B.; Lareau, N.; Ambrosia, V. G.; Quayle, B.; Schroeder, W.

    2014-12-01

    Biomass burning emissions are an important source of a wide range of trace gases and particles that can impact local, regional and global air quality, climate forcing, biogeochemical cycles and human health. In the western US, wildfires dominate over prescribed fires, contributing to atmospheric trace gas budgets and regional and local air pollution. Limited sampling of emissions from wildfires means western US emission estimates rely largely on data from prescribed fires, which may not be a suitable proxy for wildfire emissions. We report here in-situ measurements of carbon dioxide, methane, ozone and water vapor from the plumes of a variety of wildfires sampled in California in the fire seasons of 2013 and 2014. Included in the analysis are the Rim Fire (August - October 2013, near Yosemite National Park), the Morgan Fire (September 2013, near Clayton, CA), and the El Portal Fire (July - August 2014, in Yosemite National Park), among others. When possible, fires were sampled on multiple days. Emission ratios and estimated emission factors will be presented and discussed in the context of fuel composition, plume structure, and fire phase. Correlations of plume chemical composition to MODIS/VIIRS Fire Radiative Power (FRP) and other remote sensing information will be explored. Furthermore, the role of plumes in delivery of enhanced ozone concentrations to downwind municipalities will be discussed.

  16. Characterization of uncertainties in atmospheric trace gas inversions using hierarchical Bayesian methods

    NASA Astrophysics Data System (ADS)

    Ganesan, A. L.; Rigby, M.; Zammit-Mangion, A.; Manning, A. J.; Prinn, R. G.; Fraser, P. J.; Harth, C. M.; Kim, K.-R.; Krummel, P. B.; Li, S.; Mühle, J.; O'Doherty, S. J.; Park, S.; Salameh, P. K.; Steele, L. P.; Weiss, R. F.

    2014-04-01

    We present a hierarchical Bayesian method for atmospheric trace gas inversions. This method is used to estimate emissions of trace gases as well as "hyper-parameters" that characterize the probability density functions (PDFs) of the a priori emissions and model-measurement covariances. By exploring the space of "uncertainties in uncertainties", we show that the hierarchical method results in a more complete estimation of emissions and their uncertainties than traditional Bayesian inversions, which rely heavily on expert judgment. We present an analysis that shows the effect of including hyper-parameters, which are themselves informed by the data, and show that this method can serve to reduce the effect of errors in assumptions made about the a priori emissions and model-measurement uncertainties. We then apply this method to the estimation of sulfur hexafluoride (SF6) emissions over 2012 for the regions surrounding four Advanced Global Atmospheric Gases Experiment (AGAGE) stations. We find that improper accounting of model representation uncertainties, in particular, can lead to the derivation of emissions and associated uncertainties that are unrealistic and show that those derived using the hierarchical method are likely to be more representative of the true uncertainties in the system. We demonstrate through this SF6 case study that this method is less sensitive to outliers in the data and to subjective assumptions about a priori emissions and model-measurement uncertainties than traditional methods.

  17. The NOMAD Spectrometer Suite on ExoMars Trace Gas Orbiter

    NASA Astrophysics Data System (ADS)

    Carine Vandaele, Ann; Lopez-Moreno, Jose-Juan; Patel, Manish R.; Bellucci, Giancarlo; Neefs, Eddy; Thomas, Ian R.; Drummond, Rachel; Rodriguez-Gomez, Julio; Daerden, Frank

    2016-04-01

    NOMAD (Nadir and Occultation for MArs Discovery) is a suite of three high-resolution spectrometers on-board the ExoMars Trace Gas Orbiter. The instrument will be able to detect and map a wide variety of Martian gases in unprecedented detail. NOMAD's three spectrometers cover the UV-visible (UVIS channel - 200-650nm) and infrared ranges (SO and LNO channels - 2.2-4.3μm), operating in solar occultation, limb and nadir-viewing modes, generating a huge dataset of Martian atmospheric observations during the mission across a wide spectral range. NOMAD has the resolving power to identify many trace gases that exhibit absorption features within the spectral range of the three channels. The order-of-magnitude increase in spectral resolution over previous instruments will enable spatial and temporal mapping of several isotopologues of methane and water, providing important measurements of the Martian D/H and methane isotope ratios globally. Sensitivity studies have shown that, using expected SNR values, NOMAD should have the ability to measure methane concentrations <25 parts per trillion (ppt) in solar occultation mode, and 11 parts per billion in nadir mode. Occultation detections as low at 10 ppt could be made if spectra are averaged sufficiently. Using SO and LNO in combination with UVIS, aerosol properties such as optical depth, composition and size distribution can also be derived. NOMAD will also continue to monitor the major seasonal cycles on Mars, extending existing datasets made by successive space missions in the past decade.

  18. Measurement of gas/water uptake coefficients for trace gases active in the marine environment

    SciTech Connect

    Davidovits, P. . Dept. of Chemistry); Worsnop, D.W.; Zahniser, M.S.; Kolb, C.E. . Center for Chemical and Environmental Physics)

    1992-02-01

    Ocean produced reduced sulfur compounds including dimethylsulfide (DMS), hydrogen sulfide (H{sub 2}S), carbon disulfide (CS{sub 2}), methyl mercaptan (CH{sub 3}CH) and carbonyl sulfide (OCS) deliver a sulfur burden to the atmosphere which is roughly equal to sulfur oxides produced by fossil fuel combustion. These species and their oxidation products dimethyl sulfoxide (DMSO), dimethyl sulfone (DMSO{sub 2}) and methane sulfonic acid (MSA) dominate aerosol and CCN production in clean marine air. Furthermore, oxidation of reduced sulfur species will be strongly influenced by NO{sub x}/O{sub 3} chemistry in marine atmospheres. The multiphase chemical processes for these species must be understood in order to study the evolving role of combustion produced sulfur oxides over the oceans. We have measured the chemical and physical parameters affecting the uptake of reduced sulfur compounds, their oxidation products, ozone, and nitrogen oxides by the ocean's surface, and marine clouds, fogs, and aerosols. These parameters include: gas/surface mass accommodation coefficients; physical and chemically modified (effective) Henry's law constants; and surface and liquid phase reaction constants. These parameters are critical to understanding both the interaction of gaseous trace species with cloud and fog droplets and the deposition of trace gaseous species to dew covered, fresh water and marine surfaces.

  19. Characterizing sampling biases in the trace gas climatologies of the SPARC Data Initiative

    NASA Astrophysics Data System (ADS)

    Toohey, M.; Hegglin, M. I.; Tegtmeier, S.; Anderson, J.; Añel, J. A.; Bourassa, A.; Brohede, S.; Degenstein, D.; Froidevaux, L.; Fuller, R.; Funke, B.; Gille, J.; Jones, A.; Kasai, Y.; Krüger, K.; Kyrölä, E.; Neu, J. L.; Rozanov, A.; Smith, L.; Urban, J.; Clarmann, T.; Walker, K. A.; Wang, R. H. J.

    2013-10-01

    zonal mean climatologies of atmospheric measurements from satellite instruments can have biases due to the nonuniform sampling of the atmosphere by the instruments. We characterize potential sampling biases in stratospheric trace gas climatologies of the Stratospheric Processes and Their Role in Climate (SPARC) Data Initiative using chemical fields from a chemistry climate model simulation and sampling patterns from 16 satellite-borne instruments. The exercise is performed for the long-lived stratospheric trace gases O3 and H2O. Monthly sampling biases for O3 exceed 10% for many instruments in the high-latitude stratosphere and in the upper troposphere/lower stratosphere, while annual mean sampling biases reach values of up to 20% in the same regions for some instruments. Sampling biases for H2O are generally smaller than for O3, although still notable in the upper troposphere/lower stratosphere and Southern Hemisphere high latitudes. The most important mechanism leading to monthly sampling bias is nonuniform temporal sampling, i.e., the fact that for many instruments, monthly means are produced from measurements which span less than the full month in question. Similarly, annual mean sampling biases are well explained by nonuniformity in the month-to-month sampling by different instruments. Nonuniform sampling in latitude and longitude are shown to also lead to nonnegligible sampling biases, which are most relevant for climatologies which are otherwise free of biases due to nonuniform temporal sampling.

  20. Characterization of uncertainties in atmospheric trace gas inversions using hierarchical Bayesian methods

    NASA Astrophysics Data System (ADS)

    Ganesan, A. L.; Rigby, M.; Zammit-Mangion, A.; Manning, A. J.; Prinn, R. G.; Fraser, P. J.; Harth, C. M.; Kim, K.-R.; Krummel, P. B.; Li, S.; Mühle, J.; O'Doherty, S. J.; Park, S.; Salameh, P. K.; Steele, L. P.; Weiss, R. F.

    2013-12-01

    We present a hierarchical Bayesian method for atmospheric trace gas inversions. This method is used to estimate emissions of trace gases as well as "hyper-parameters" that characterize the probability density functions (PDF) of the a priori emissions and model-measurement covariances. By exploring the space of "uncertainties in uncertainties", we show that the hierarchical method results in a more complete estimation of emissions and their uncertainties than traditional Bayesian inversions, which rely heavily on expert judgement. We present an analysis that shows the effect of including hyper-parameters, which are themselves informed by the data, and show that this method can serve to reduce the effect of errors in assumptions made about the a priori emissions and model-measurement uncertainties. We then apply this method to the estimation of sulfur hexafluoride (SF6) emissions over 2012 for the regions surrounding four Advanced Global Atmospheric Gases Experiment (AGAGE) stations. We find that improper accounting of model representation uncertainties, in particular, can lead to the derivation of emissions and associated uncertainties that are unrealistic and show that those derived using the hierarchical method are likely to be more representative of the true uncertainties in the system. We demonstrate through this SF6 case study that this method is less sensitive to outliers in the data and to subjective assumptions about a priori emissions and model-measurement uncertainties, than traditional methods.

  1. [Determination of trace organochlorine pesticides in soil using isotope dilution-high resolution gas chromatography].

    PubMed

    Huang, Wenjun; Gao, Lirong; Gong, Aijun; Li, Cheng; Wang, Pu; Fu, Shan; Xiao, Ke; Zhang, Bing; Liu, Wenbin

    2010-05-01

    A method for the determination of trace organochlorine pesticides (OCPs) in soil using isotope dilution and high resolution gas chromatography-high resolution mass spectrometry (ID-HRGC-HRMS) was developed. The sample was extracted by accelerated solvent extractor (ASE) and cleaned-up by a Florisil solid phase extraction (SPE) cartridge. The analytes were separated by HRGC on a DB-5MS column (30 mx 0.25 mm x 0.25 microm) and determined by HRMS. The identifications of OCPs were based on the retention time of 13C-labelled standard and the abundance ratio of the two exact mass-to-charge ratios. The quantitative analysis was performed using the ratios of the integrated areas of the 13C-labelled standards. This method has the recoveries ranging from 77.3% to 114.5% and the relative standard deviations (RSD) less than 10.81% (n=5). The limits of detection (LODs) of this method for all OCPs were lower than 0.04 pg/g. The results indicated that the method is rapid, selective and sensitive for precise determination requirements of organochlorine pesticides at trace level in soil. PMID:20812621

  2. Warp of the ionized gas layer in the outer Galaxy, traced by recombination line observations

    NASA Astrophysics Data System (ADS)

    Azcárate, I. N.; Cersosimo, J. C.

    We report results of H166α recombination line observations from the outer Galaxy in both the Northern and Southern Galactic Plane. The Southern observations were made with the 30 m antenna of the Instituto Argentino de Radioastronomía in Villa Elisa, Buenos Aires, Argentina, and the Northern ones ( more sensitive, high quality observations, performed with an ``state of the art'' receiver) with the 43 m antenna of the National Radio Astronomy Observatory, in Green Bank, West Virginia, USA. >From the two sets of observations we obtain evidence of the warp of the low-density ionized gas layer, traced by the H166α emission in the outer Milky Way, towards positive galactic latitudes in the Northern and towards negative latitudes in the Southern Galaxy. The warp of this tracer qualitatively agrees with that of the HI.

  3. Quartz Enhanced Photoacoustic Spectroscopy Based Trace Gas Sensors Using Different Quartz Tuning Forks

    PubMed Central

    Ma, Yufei; Yu, Guang; Zhang, Jingbo; Yu, Xin; Sun, Rui; Tittel, Frank K.

    2015-01-01

    A sensitive trace gas sensor platform based on quartz-enhanced photoacoustic spectroscopy (QEPAS) is reported. A 1.395 μm continuous wave (CW), distributed feedback pigtailed diode laser was used as the excitation source and H2O was selected as the target analyte. Two kinds of quartz tuning forks (QTFs) with a resonant frequency (f0) of 30.72 kHz and 38 kHz were employed for the first time as an acoustic wave transducer, respectively for QEPAS instead of a standard QTF with a f0 of 32.768 kHz. The QEPAS sensor performance using the three different QTFs was experimentally investigated and theoretically analyzed. A minimum detection limit of 5.9 ppmv and 4.3 ppmv was achieved for f0 of 32.768 kHz and 30.72 kHz, respectively. PMID:25825977

  4. Land-Use Change, Soil Process and Trace Gas Fluxes in the Brazilian Amazon Basin

    NASA Technical Reports Server (NTRS)

    Melillo, Jerry M.; Steudler, Paul A.

    1997-01-01

    We measured changes in key soil processes and the fluxes of CO2, CH4 and N2O associated with the conversion of tropical rainforest to pasture in Rondonia, a state in the southwest Amazon that has experienced rapid deforestation, primarily for cattle ranching, since the late 1970s. These measurements provide a comprehensive quantitative picture of the nature of surface soil element stocks, C and nutrient dynamics, and trace gas fluxes between soils and the atmosphere during the entire sequence of land-use change from the initial cutting and burning of native forest, through planting and establishment of pasture grass and ending with very old continuously-pastured land. All of our work is done in cooperation with Brazilian scientists at the Centro de Energia Nuclear na Agricultura (CENA) through an extant official bi-lateral agreement between the Marine Biological Laboratory and the University of Sao Paulo, CENA's parent institution.

  5. Development of a powerful continuously tunable mid-infrared cw PPLN OPO for trace gas detection

    NASA Astrophysics Data System (ADS)

    van Herpen, Maarten; te Lintel Hekkert, Sacco; Bisson, Scott E.; Harren, Frans J. M.

    2002-08-01

    A new Optical Parametric Oscillator for the mid infrared wavelength region of 3-3.8 micrometer is developed with an idler output power of more than 1 Watt. The OPO is pumped with a 10 Watt, cw, Nd:YAG Laser and consists of a bowtie ring cavity (FSR 320 MHz) resonating at the signal wavelength. The wavelength is controlled with a fan-out PPLN crystal and a low finesse intracavity Fabry-Perot. The idler output could be tuned over more than 24 Ghz modehop-free, by tuning the pump laser and keep the OPO cavity fixed. Mode hop tuning over 100 Ghz could be obtained changing the length of the intracavity Fabry-Perot. This high power OPO is combined with photoacoustic spectroscopy in order to develop a sensitive trace gas detector for LifeScience applications.

  6. Nitrogen trace gas fluxes from a semiarid subtropical savanna under woody legume encroachment

    NASA Astrophysics Data System (ADS)

    Soper, Fiona M.; Boutton, Thomas W.; Groffman, Peter M.; Sparks, Jed P.

    2016-05-01

    Savanna ecosystems are a major source of nitrogen (N) trace gases that influence air quality and climate. These systems are experiencing widespread encroachment by woody plants, frequently associated with large increases in soil N, with no consensus on implications for trace gas emissions. We investigated the impact of encroachment by N-fixing tree Prosopis glandulosa on total reactive N gas flux (Nt = NO + N2O + NOy + NH3) from south Texas savanna soils over 2 years. Contrary to expectations, upland Prosopis groves did not have greater Nt fluxes than adjacent unencroached grasslands. However, abiotic conditions (temperature, rainfall, and topography) were strong drivers. Emissions from moist, low-lying Prosopis playas were up to 3 times higher than from Prosopis uplands. Though NO dominated emissions, NH3 and NOy (non-NO oxidized N) comprised 12-16% of the total summer N flux (up to 7.9 µg N m-2 h-1). Flux responses to soil wetting were temperature dependent for NO, NH3, and NOy: a 15 mm rainfall event increased flux 3-fold to 22-fold after 24 h in summer but had no effect in winter. Repeated soil wetting reduced N flux responses, indicating substrate depletion as a likely control. Rapid (<1 min) increases in NO emissions following wetting of dry soils suggested that abiotic chemodenitrification contributes to pulse emissions. We conclude that temperature and wetting dynamics, rather than encroachment, are primary drivers of N flux from these upland savannas, with implications for future emission patterns under altered precipitation regimes.

  7. Airborne Trace Gas and Aerosol Measurements in Several Shale Gas Basins during the SONGNEX (Shale Oil and Natural Gas Nexus) Campaign 2015

    NASA Astrophysics Data System (ADS)

    Warneke, C.; Trainer, M.; De Gouw, J. A.

    2015-12-01

    Oil and natural gas from tight sand and shale formations has increased strongly over the last decade. This increased production has been associated with emissions of methane, non-methane hydrocarbons and other trace gases to the atmosphere, which are concerns for air quality, climate and air toxics. The NOAA Shale Oil and Natural Gas Nexus (SONGNEX) aircraft campaign took place in 2015, when the NOAA WP-3 aircraft conducted 20 research flights between March 19 and April 27, 2015 in the following shale gas regions: Denver-Julesberg, Uintah, Upper Green River, San Juan, Bakken, Barnett, Eagle Ford, Haynesville, Woodford, and Permian. The NOAA P3 was equipped with an extensive set of gas phase measurements, including instruments for methane, ethane, CO, CO2, a new H3O+CIMS, canister and cartridge samples for VOCs, HCHO, glyoxal, HNO3, NH3, NOx, NOy, PANs, ozone, and SO2. Aerosol number and size distributions were also measured. This presentation will focus on an overview of all the measurements onboard the NOAA WP-3 aircraft and discuss the differences between the shale gas regions. Due to a drop in oil prices, drilling for oil decreased in the months prior to the mission, but nevertheless the production of oil and natural gas were near the all-time high. Many of the shale gas basins investigated during SONGNEX have quite different characteristics. For example, the Permian Basin is a well-established field, whereas the Eagle Ford and the Bakken saw an almost exponential increase in production over the last few years. The basins differ by the relative amounts of natural gas versus oil that is being produced. Previous work had shown a large variability in methane emissions relative to the production (leak rate) between different basins. By including more and qualitatively different basins during SONGNEX, the study has provided an extensive data set to address how emissions depend on raw gas composition, extraction techniques and regulation. The influence of these

  8. Dense gas tracing the collisional past of Andromeda. An atypical inner region?

    NASA Astrophysics Data System (ADS)

    Melchior, Anne-Laure; Combes, Françoise

    2016-01-01

    The central kiloparsec region of the Andromeda galaxy is relatively gas poor, while the interstellar medium appears to be concentrated in a ring-like structure at about 10 kpc radius. The central gas depletion has been attributed to a possible head-on collision 200 Myr ago, supported by the existence of an offset inner ring of warm dust. We present new IRAM 30 m radio telescope observations of the molecular gas in the central region, and the detection of CO and its isotopes 13CO(2-1) and C18O(2-1), together with the dense gas tracers, HCN(1-0) and HCO+(1-0). A systematic study of the observed peak temperatures with non-local thermal equilibrium simulations shows that the detected lines trace dense regions with nH2 in the range 2.5 × 104-5.6 × 105 cm-3, while the gas is very clumpy with a beam filling factor of 0.5-2 × 10-2. This is compatible with the dust mass derived from the far-infrared emission, assuming a dust-to-gas mass ratio of 0.01 with a typical clump size of 2 pc. We also show that the gas is optically thin in all lines except for 12CO(1-0) and 12CO(2-1), CO lines are close to their thermal equilibrium condition at 17-20 K, the molecular hydrogen density is larger than critical, and HCN and HCO+ lines have a subthermal excitation temperature of 9 K with a density smaller than critical. The average 12CO/13CO line ratio is high (~21), and close to the 12CO/C18O ratio (~30) that was measured in the north-western region and estimated in the south-east stacking. The fact that the optically thin 13CO and C18O lines have comparable intensities means that the secondary element 13C is depleted with respect to the primary 12C, as is expected just after a recent star formation. This suggests that there has been a recent starburst in the central region, supporting the head-on collision scenario. Based on observations carried out with the IRAM 30 m radio telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

  9. A novel method for measuring trace gas fluxes from tall vegetation

    NASA Astrophysics Data System (ADS)

    Keane, James; Phil, Ineson

    2014-05-01

    The nature of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) as greenhouse gases (GHGs) means that accurate measurement of their net ecosystem exchange (NEE) is extremely important to our ability to manage climate change. Manual static chambers are commonly used to measure soil fluxes of these trace gases, with landscape values extrapolated from point measurements of typically less than 1m2, at a weekly or monthly frequency. Moreover, due to the reliance upon manual sampling, data are typically biased towards day-time measurements, and use of opaque chambers halts photosynthesis. Automation of chambers, such as the Licor Li-8100 (Lincoln, NE) system, allows for measurement of soil respiration at a near-constant frequency, but does not solve the problem of measuring CH4 and N2O, neither does it allow measurements to be taken from over tall (more than 20 cm) vegetation. Eddy covariance (EC) techniques allow for high frequency measurements of CO2 and CH4 to be made at the landscape scale, and are increasingly available for N2O. However, the inability of EC to resolve to the plot scale hinders its use for manipulative experiments, and replication is rare. Additionally, stratification of the boundary layer creates difficulty in measuring night-time fluxes and it is common to discard large parts of data sets due to unsuitable wind direction or other meteorological conditions. Here we present a new technique for measuring trace gas fluxes from over tall vegetation. The system is capable of simultaneously delivering NEE of CO2, CH4 and N2O, automatically measuring at high temporal resolution (circa hourly) from replicated plots. We show the effect of green compost addition on trace gas fluxes from Miscanthus x giganteus, an important crop for bioenergy production. The ability to quantify NEE of GHGs from such crops forms an essential part of the lifecycle analysis of energy produced from biomass, which may play an important role in future mitigation of climate

  10. Behavior of trace gas mixing ratios on a very tall tower in North Carolina

    NASA Astrophysics Data System (ADS)

    Hurst, Dale F.; Bakwin, Peter S.; Myers, Richard C.; Elkins, James W.

    1997-04-01

    We present a 15-month record of mixing ratios of CO, CH4, N2O, and eight halogenated gases (CCl3F, CCl2F2, CCl2FCClF2, CH3CCl3, CCl4, CHCl3, C2Cl4, and SF6) at a rural site in eastern North Carolina. The data result from hourly gas Chromatographic analyses of air sampled at three heights on a 610-m-tall telecommunications tower during November 1994 through January 1996. At night, most of these gases were more abundant near the ground (51 m) than aloft (496 m) because of the buildup of local and regional surface emissions in the shallow nocturnal stable layer. The abundance and variability of trace gases at this continental site were generally higher than those at similar latitude remote locations. Mixing ratios of most gases were well correlated in polluted air masses occasionally advected to the tower. Frequent, strong enhancements in CHCl3 at the lower sampling level(s) indicate a local point source(s) of this gas that is not associated with combustion. Temporal trends of regional background mixing ratios at this continental site are, for the most part, in good agreement with recent trends of remote background mixing ratios in the northern hemisphere.

  11. ANALYSIS OF TRACE-LEVEL ORGANIC COMBUSTION PROCESS EMISSIONS USING NOVEL MULTIDIMENSIONAL GAS CHROMATOGRAPHY-MASS SPECTROMETRY PROCEDURES

    EPA Science Inventory

    The paper discusses the analysis of trace-level organic combustion process emissions using novel multidimensional gas chromatography-mass spectrometry (MDGC-MS) procedures. It outlines the application of the technique through the analyses of various incinerator effluent and produ...

  12. Use of external cavity quantum cascade laser compliance voltage in real-time trace gas sensing of multiple chemicals

    SciTech Connect

    Phillips, Mark C.; Taubman, Matthew S.; Kriesel, Jason M.

    2015-02-08

    We describe a prototype trace gas sensor designed for real-time detection of multiple chemicals. The sensor uses an external cavity quantum cascade laser (ECQCL) swept over its tuning range of 940-1075 cm-1 (9.30-10.7 µm) at a 10 Hz repetition rate.

  13. SIZE DISTRIBUTIONS OF TRACE METALS IN FLUE GAS PARTICULATE FROM A PILOT-SCALE ROTARY KILN INCINERATOR

    EPA Science Inventory

    The distributions of nine trace metals in flue gas particulate by particle size range were determined as part of a pilot-scale hazardous waste incineration test program. hese tests were conducted in the rotary kiln incinerator system at the U.S. EPA's Incineration Research Facili...

  14. Comparative Model Evaluation Studies of Biogenic Trace Gas Fluxes in Tropical Forests

    NASA Technical Reports Server (NTRS)

    Potter, C. S.; Peterson, David L. (Technical Monitor)

    1997-01-01

    Simulation modeling can play a number of important roles in large-scale ecosystem studies, including synthesis of patterns and changes in carbon and nutrient cycling dynamics, scaling up to regional estimates, and formulation of testable hypotheses for process studies. Recent comparative studies have shown that ecosystem models of soil trace gas exchange with the atmosphere are evolving into several distinct simulation approaches. Different levels of detail exist among process models in the treatment of physical controls on ecosystem nutrient fluxes and organic substrate transformations leading to gas emissions. These differences are is in part from distinct objectives of scaling and extrapolation. Parameter requirements for initialization scalings, boundary conditions, and time-series driven therefore vary among ecosystem simulation models, such that the design of field experiments for integration with modeling should consider a consolidated series of measurements that will satisfy most of the various model requirements. For example, variables that provide information on soil moisture holding capacity, moisture retention characteristics, potential evapotranspiration and drainage rates, and rooting depth appear to be of the first order in model evaluation trials for tropical moist forest ecosystems. The amount and nutrient content of labile organic matter in the soil, based on accurate plant production estimates, are also key parameters that determine emission model response. Based on comparative model results, it is possible to construct a preliminary evaluation matrix along categories of key diagnostic parameters and temporal domains. Nevertheless, as large-scale studied are planned, it is notable that few existing models age designed to simulate transient states of ecosystem change, a feature which will be essential for assessment of anthropogenic disturbance on regional gas budgets, and effects of long-term climate variability on biosphere-atmosphere exchange.

  15. Trace Gas Measurements on Mars and Earth using Optical Parametric Generation

    NASA Astrophysics Data System (ADS)

    Numata, K.; Riris, H.; Li, S.; Sun, X.; Abshire, J. B.

    2010-12-01

    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

  16. 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

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

    NASA Astrophysics Data System (ADS)

    Siebicke, Lukas

    2016-04-01

    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.

  18. Atmospheric trace gas measurements during SEEDS-II over the northwestern pacific

    NASA Astrophysics Data System (ADS)

    Kato, Shungo; Watari, Mayo; Nagao, Ippei; Uematsu, Mitsuo; Kajii, Yoshizumi

    2009-12-01

    Atmospheric trace gas measurements were conducted during SEEDS-II. Atmospheric dimethylsulfide (DMS) was continuously measured by GC-MS during the R/V Hakuho cruise. Further, ambient air was sampled into canisters (42 samples) and analyzed by GC-MS and GC-FID for various biogenic and anthropogenic volatile organic compounds (VOCs) after the cruise. CO, O 3, SO 2, and NO x were monitored continuously aboard the ship. A fertilization experiment was conducted in a high-nitrate, low-chlorophyll (HNLC) region (48°N, 165°E). The atmospheric concentrations inside a patch (fertilized area) were compared with those outside it (natural area); however, clear differences were not observed for biogenic trace gasses (DMS, CH 3Cl, CH 3I, isoprene, and alkenes) in the atmosphere. However, a high DMS concentration was observed over the northwestern Pacific Ocean. The fertilized area was also observed by R/V Kilo Moana, and DMS was measured by GC-FPD. A good agreement was observed between the results of the measurements made aboard the two independent ships by different measurement methods. The atmospheric SO 2 concentration was compared with the atmospheric DMS concentration. The SO 2 concentration was found to vary with the atmospheric DMS concentration. A diurnal variation of the atmospheric DMS concentration was observed around the fertilized region. The DMS content tends to increase during the night and decrease during the day. A box model calculation was conducted to explain the diurnal variation of the atmospheric DMS. Since there was no diurnal variation of the wind speed, a constant DMS flux from the ocean surface was assumed. Further, the atmospheric OH radical concentration was assumed to be dependent on sunlight. The box model can roughly reproduce the atmospheric DMS diurnal variation mainly caused by its removal reaction with OH radicals.

  19. Trace element chemistry of coal bed natural gas produced water in the Powder River Basin, Wyoming

    SciTech Connect

    Richard E. Jackson; K.J. Reddy

    2007-09-15

    Coal bed natural gas (CBNG) produced water is usually disposed into nearby constructed disposal ponds. Geochemistry of produced water, particularly trace elements interacting with a semiarid environment, is not clearly understood. The objective of this study was to collect produced water samples at outfalls and corresponding disposal ponds and monitor pH, iron (Fe), aluminum (Al), chromium (Cr), manganese (Mn), lead (Pb), copper (Cu), zinc (Zn), arsenic (As), boron (B), selenium (Se), molybdenum (Mo), cadmium (Cd), and barium (Ba). Outfalls and corresponding disposal ponds were sampled from five different watersheds including Cheyenne River (CHR), Belle Fourche River (BFR), Little Powder River (LPR), Powder River (PR), and Tongue River (TR) within the Powder River Basin (PRB), Wyoming from 2003 to 2005. Paired tests were conducted between CBNG outfalls and corresponding disposal ponds for each watershed. Results suggest that produced water from CBNG outfalls is chemically different from the produced water from corresponding disposal ponds. Most trace metal concentrations in the produced water increased from outfall to disposal pond except for Ba. In disposal ponds, Ba, As, and B concentrations increased from 2003 to 2005. Geochemical modeling predicted precipitation and dissolution reactions as controlling processes for Al, Cu, and Ba concentrations in CBNG produced water. Adsorption and desorption reactions appear to control As, Mo, and B concentrations in CBNG water in disposal ponds. Overall, results of this study will be important to determine beneficial uses (e.g., irrigation, livestock/wildlife water, and aquatic life) for CBNG produced water in the PRB, Wyoming. 18 refs., 4 figs., 3 tabs.

  20. Variability of trace gas concentrations over Asian region: satellite observations vs model

    NASA Astrophysics Data System (ADS)

    Sheel, Varun; Richter, Andreas; Srivastava, Shuchita; Lal, Shyam

    2012-07-01

    Nitrogen dioxide (NO_2) and Carbon Monoxide (CO) play a key role in the chemistry of the tropospheric ozone and are emitted mainly by anthropogenic processes. These emissions have been increasing over Asia over the past few years due to rapid economic growth and yet there are very few systematic ground based observations of these species over this region. We have analysed ten years of data from space borne instruments: Global Ozone Monitoring Experiment (GOME), SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) and Measurements of Pollution in the Troposphere (MOPITT), which have been measuring the tropospheric abundance of these trace gases. We have examined trends over the period 1996-2008 in NO_2 and CO over a few Indian regions where high economic growth in the present decade is likely to see increased emissions for these species. However, even the highest growth rate of these species seen in the present study, is less when compared with similar polluted regions of China, where a much more rapid increase has been observed. In order to understand the trends and variability in atmospheric trace gas concentrations, one must take into account changes in emissions and transport. Only by assessing the relevance of each of these factors will it be possible to predict future changes with reasonable confidence. To this effect we have used a global chemical transport model, MOZART, to simulate concentrations of NO_2 and CO using the POET (European) and REAS (Asian) emission inventories. These are compared with satellite measurements to study seasonal variations and the discrepancies are discussed. The combined uncertainties of the emission inventory and retrieval of the satellite data could be contributing factors to the discrepancies. It may be thus worthwhile to develop emission inventories for India at a higher resolution to include local level activity data.

  1. A New 2D-Advection-Diffusion Model Simulating Trace Gas Distributions in the Lowermost Stratosphere

    NASA Astrophysics Data System (ADS)

    Hegglin, M. I.; Brunner, D.; Peter, T.; Wirth, V.; Fischer, H.; Hoor, P.

    2004-12-01

    Tracer distributions in the lowermost stratosphere are affected by both, transport (advective and non-advective) and in situ sources and sinks. They influence ozone photochemistry, radiative forcing, and heating budgets. In-situ measurements of long-lived species during eight measurement campaigns revealed relatively simple behavior of the tracers in the lowermost stratosphere when represented in an equivalent-latitude versus potential temperature framework. We here present a new 2D-advection-diffusion model that simulates the main transport pathways influencing the tracer distributions in the lowermost stratosphere. The model includes slow diabatic descent of aged stratospheric air and vertical and/or horizontal diffusion across the tropopause and within the lowermost stratosphere. The diffusion coefficients used in the model represent the combined effects of different processes with the potential of mixing tropospheric air into the lowermost stratosphere such as breaking Rossby and gravity waves, deep convection penetrating the tropopause, turbulent diffusion, radiatively driven upwelling etc. They were specified by matching model simulations to observed distributions of long-lived trace gases such as CO and N2O obtained during the project SPURT. The seasonally conducted campaigns allow us to study the seasonal dependency of the diffusion coefficients. Despite its simplicity the model yields a surprisingly good description of the small scale features of the measurements and in particular of the observed tracer gradients at the tropopause. The correlation coefficients between modeled and measured trace gas distributions were up to 0.95. Moreover, mixing across isentropes appears to be more important than mixing across surfaces of constant equivalent latitude (or PV). With the aid of the model, the distribution of the fraction of tropospheric air in the lowermost stratosphere can be determined.

  2. Application of DOAS Instruments for Trace Gas Measurements on Unmanned Aerial Systems

    NASA Astrophysics Data System (ADS)

    Horbanski, M.; Pöhler, D.; Mahr, T.; Wagner, T.; Platt, U.

    2012-04-01

    Unmanned Aerial Systems (UAS) are a new powerful tool for observations in the atmospheric boundary layer. Recent developments in measuring technology allow the construction of compact and sensitive active and passive DOAS instruments which can fit the space and weight constraints on Unmanned Aircraft Systems. This opens new possibilities for trace gas measurements in the lower troposphere, especially in areas which are not accessible to manned aviation e.g. volcanic plumes or which should be monitored regularly (e.g. industrial emissions of a stack). Two DOAS instruments for the APAESO platform of the Energy, Environment and Water Research Centre (EEWRC) at the Cyprus Institute are presented. Our first system is a passive DOAS for remote sensing applications which measures scattered sunlight and light reflected by the surface. It is equipped with telescopes for observations in downward (nadir) and horizontal (limb) viewing direction. Thus it allows determining height profiles and the spatial distribution of trace gases. For this the light is analysed by a compact spectrometer which covers the UV-blue range allowing to measure a broad variety of atmospheric trace gases (e.g. NO2, SO2, BrO, IO, H2O ...) and aerosol properties via O4 absorption. Additionally, the nadir direction is equipped with a system for the observation of surface properties. It will be used to measure and analyse reflection of different types of vegetation. The spectra will serve as reference spectra for satellite measurements to create global maps. The instrumental setup and the results of first test flights are shown. The second instrument which is currently under development is a Cavity Enhanced (CE-) DOAS for in situ measurements of NO3. In contrast to the passive DOAS it is able to perform night time measurements as it uses an active LED light source. This is important for studies of NO3 since it plays an important role in night time chemistry while it is rapidly photolysed during daytime

  3. NOMAD, a spectrometer suite for Nadir and Solar Occultation observations on the ExoMars Trace Gas Orbiter

    NASA Astrophysics Data System (ADS)

    Drummond, Rachel; Robert, Severine; Vandaele, Ann-Carine; Willame, Yannick; Lopez-Moreno, Jose Juan; Patel, Manish; Belluci, Giancarlo; Daerden, Frank; Neefs, Eddy; Rodriguez-Gomez, Julio

    2013-04-01

    NOMAD, the "Nadir and Occultation for MArs Discovery" spectrometer suite was selected as part of the payload of the ExoMars Trace Gas Orbiter mission 2016. This instrument suite will conduct a spectroscopic survey of Mars' atmosphere in the UV, visible and IR regions covering the 0.2-0.65 and 2.2-4.3 µm spectral ranges. NOMAD's observation modes include solar occultation, nadir and limb observations. The NOMAD instrument is composed of 3 channels: a solar occultation only channel (SO) operating in the infrared wavelength domain, a second infrared channel capable of doing nadir, but also solar occultation and limb observations (LNO), and an ultraviolet/visible channel (UVIS) that can work in all observation modes. The spectral resolution of SO and LNO surpasses previous surveys in the infrared by more than one order of magnitude. NOMAD offers an integrated instrument combination of a flight-proven concept (SO is a copy of SOIR on Venus Express), and innovations based on existing and proven instrumentation (LNO is based on SOIR/VEX and UVIS has heritage from the ExoMars lander), that will provide mapping and vertical profile information at high spatio-temporal resolution. The three channels have each their own ILS and optical bench, but share the same single interface to the S/C. We will present the instrument and its capabilities in term of detection of a broad suite of species, its possibilities to improve our knowledge on vertical structure of the atmosphere as well as its mapping possibilities. Since last year's abstract, much progress has been made on the instrument design and prototypes have been tested, especially concerning the very challenging thermal needs of the instrument. This paper will concentrate on the developments in the last year that prove NOMAD will be a very powerful, sensitive instrument.

  4. Temperature Programmed Desorption of Quench-condensed Krypton and Acetone in Air; Selective Concentration of Ultra-trace Gas Components.

    PubMed

    Suzuki, Taku T; Sakaguchi, Isao

    2016-01-01

    Selective concentration of ultra-trace components in air-like gases has an important application in analyzing volatile organic compounds in the gas. In the present study, we examined quench-condensation of the sample gas on a ZnO substrate below 50 K followed by temperature programmed desorption (TPD) (low temperature TPD) as a selective gas concentration technique. We studied two specific gases in the normal air; krypton as an inert gas and acetone as a reactive gas. We evaluated the relationship between the operating condition of low temperature TPD and the lowest detection limit. In the case of krypton, we observed the selective concentration by exposing at 6 K followed by thermal desorption at about 60 K. On the other hand, no selectivity appeared for acetone although trace acetone was successfully concentrated. This is likely due to the solvent effect by a major component in the air, which is suggested to be water. We suggest that pre-condensation to remove the water component may improve the selectivity in the trace acetone analysis by low temperature TPD. PMID:27063719

  5. Release of trace metals, sulfate and complexed cyanide from soils contaminated with gas-purifier wastes: a microcosm study.

    PubMed

    Rennert, T; Mansfeldt, T

    2006-01-01

    Deposited gas-purifier wastes are commonly contaminated with trace metals, sulfate and cyanide (CN) compounds. We investigated their release from three soils contaminated with gas-purifier wastes into solution in microcosm experiments under varying redox conditions (E(H) 170-620 mV). The soils differed in pH (2.2; 4.9; 7.4) and featured low amounts of trace metals, but large amounts of total S and total CN. The pH governed trace metal release in the case of the acidic soil and CN release in the case of the slightly alkaline soil. The redox potential controlled trace metal and CN release in the case of the moderately acidic soil. Sources of dissolved SO(4)(2-) were dissolution of gypsum, desorption from Fe oxides and probably oxidation of elemental S. The geochemical behaviors of trace metals (soluble under acidic and reducing conditions) and CN (soluble under alkaline and oxidizing conditions) were diametrically opposed. PMID:16019115

  6. Regional trace gas monitoring simplified - A linear retrieval scheme for carbon monoxide from hyperspectral soundings

    NASA Astrophysics Data System (ADS)

    Smith, N.; Huang, A.; Weisz, E.; Annegarn, H. J.

    2011-12-01

    The Fast Linear Inversion Trace gas System (FLITS) is designed to retrieve tropospheric total column trace gas densities [molec.cm-2] from space-borne hyperspectral infrared soundings. The objective to develop a new retrieval scheme was motivated by the need for near real-time air quality monitoring at high spatial resolution. We present a case study of FLITS carbon monoxide (CO) retrievals from daytime (descending orbit) Infrared Atmospheric Sounding Interferometer (IASI) measurements that have a 0.5 cm-1 spectral resolution and 12 km footprint at nadir. The standard Level 2 IASI CO retrieval product (COL2) is available in near real-time but is spatially averaged over 2 x 2 pixels, or 50 x 50 km, and thus more suitable for global analysis. The study region is Southern Africa (south of the equator) for the period 28-31 August 2008. An atmospheric background estimate is obtained from a chemical transport model, emissivity from regional measurements and surface temperature (ST) from space-borne retrievals. The CO background error is set to 10%. FLITS retrieves CO by assuming a simple linear relationship between the IASI measurements and background estimate of the atmosphere and surface parameters. This differs from the COL2 algorithm that treats CO retrieval as a moderately non-linear problem. When compared to COL2, the FLITS retrievals display similar trends in distribution and transport of CO over time with the advantage of an improved spatial resolution (single-pixel). The value of the averaging kernel (A) is consistently above 0.5 and indicates that FLITS retrievals have a stable dependence on the measurement. This stability is achieved through careful channel selection in the strongest CO absorption lines (2050-2225 cm-1) and joint retrieval with skin temperature (IASI sensitivity to CO is highly correlated with ST), thus no spatial averaging is necessary. We conclude that the simplicity and stability of FLITS make it useful first as a research tool, i.e. the

  7. A wide field-of-view imaging DOAS instrument for continuous trace gas mapping from aircraft

    NASA Astrophysics Data System (ADS)

    Schönhardt, A.; Altube, P.; Gerilowski, K.; Krautwurst, S.; Hartmann, J.; Meier, A. C.; Richter, A.; Burrows, J. P.

    2014-04-01

    For the purpose of trace gas measurements and pollution mapping, the Airborne imaging DOAS instrument for Measurements of Atmospheric Pollution (AirMAP) has been developed, characterised and successfully operated from aircraft. From the observations with the AirMAP instrument nitrogen dioxide (NO2) columns were retrieved. A major benefit of the pushbroom imaging instrument is the spatially continuous, gap-free measurement sequence independent of flight altitude, a valuable characteristic for mapping purposes. This is made possible by the use of a frame-transfer detector. With a wide-angle entrance objective, a broad field-of-view across track of around 48° is achieved, leading to a swath width of about the same size as the flight altitude. The use of fibre coupled light intake optics with sorted light fibres allows flexible positioning within the aircraft and retains the very good imaging capabilities. The measurements yield ground spatial resolutions below 100 m. From a maximum of 35 individual viewing directions (lines of sight, LOS) represented by 35 single fibres, the number of viewing directions is adapted to each situation by averaging according to signal-to-noise or spatial resolution requirements. Exploitation of all the viewing directions yields observations at 30 m spatial resolution, making the instrument a suitable tool for mapping trace gas point sources and small scale variability. For accurate spatial mapping the position and aircraft attitude are taken into account using the Attitude and Heading Reference System of the aircraft. A first demonstration mission using AirMAP was undertaken. In June 2011, AirMAP has been operated on the AWI Polar-5 aircraft in the framework of the AIRMETH2011 campaign. During a flight above a medium sized coal-fired power plant in North-West Germany, AirMAP clearly detects the emission plume downwind from the exhaust stack, with NO2 vertical columns around 2 × 1016 molecules cm-2 in the plume center. The emission

  8. An Airborne Sensor and Retrieval Project for Geostationary Trace Gas and Aerosol Sensor Optimization for the GEO-CAPE Mission

    NASA Astrophysics Data System (ADS)

    Leitch, J. W.; Delker, T.; Chance, K.; Liu, X.; Janz, S. J.; Krotkov, N. A.; Pickering, K. E.; Wang, J.

    2012-12-01

    The Geostationary Trace gas and Aerosol Sensor Optimization (Geo-TASO) Instrument Incubator project involves spectrometer development, airborne data campaigns, and algorithm testing - all in support of mission risk reduction for the UV-Vis trace air quality measurements for the GEO-CAPE mission. A compact, two-channel spectrometer for spectral radiance measurements is being built and readied for use on NASA's DC-8. The goals of the project are to demonstrate the compact spectrometer concept, provide "satellite analog" measurements in support of air quality measurements and data campaigns, and to advance the retrieval algorithm readiness for the GEO-CAPE mission.

  9. A study of the trace gas columns of O3, NO2 and HCHO over Africa in September 1997.

    PubMed

    Meyer-Arnek, Julian; Ladstätter-Weissenmayer, Annette; Richter, Andreas; Wittrock, Folkard; Burrows, John P

    2005-01-01

    Retrievals of trace gas columns from the measurements of backscattered radiation by GOME (Global Ozone Monitoring Experiment) show that enhanced tropospheric columns of ozone (O3), nitrogen dioxide (NO2) and formaldehyde (HCHO), over the African continent occur frequently. This study focuses on the behaviour of trace gases over Africa in September 1997, a period impacted by the strongest known El Niño phase of the ENSO. It investigates our qualitative and quantitative understanding of the retrieved tropospheric trace gas column densities. The emissions of NOx and volatile organic compounds (VOC) from biomass burning, biogenic sources and lightning and their photochemical transformation have been investigated. By performing a trajectory analysis, the transport of air masses from the different emission regions was analysed and the potential atmospheric spatial distribution determined. BRemen's Atmospheric PHOtochemical model (BRAPHO) was applied to compute the chemistry along a large number of trajectories. From these results, tropospheric column amounts of O3, NO2 and HCHO were derived. Tropospheric trace gas columns retrieved from GOME measurements and those calculated are in reasonable agreement. Their general spatial extent was similar in the lower troposphere but the modeled trace gas columns in the upper troposphere were located south of the retrieved columns. We attribute this behaviour to uncertainties in the ERA-40 meteorological data in the upper troposphere. The significance of biomass burning and of biogenic emissions with respect to HCHO columns over Africa was investigated. The analysis reveals that the total amounts of HCHO generated over Africa during September 1997 as a result of biomass burning and biogenic emissions are similar. However the HCHO from biogenic sources has the highest specific columns and these are located close to their source. In comparison the HCHO from biomass burning is predicted to be produced and transported over a much wider

  10. Trace gas responses in a climate change experiment in northern peatlands

    SciTech Connect

    Bridgham, S.D.; Pastor, J.; Updegraff, K.

    1995-09-01

    We established 54 mesocosms of 2.2 m{sup 2} and approximately 0.6 m depth with intact vegetation communities, with half originating from a poor-intermediate fen and half from a bog in northern Minnesota. The mesocosms were subjected to a series of water-table (0,-10,-20 cm) and heating treatments, with the heating treatments from overhead infrared lamps (full on, half on, ambient). Heating began in late summer 1994, and gas flux measurements were taken until the onset of winter. The first year results indicate peatland type and water-table treatment had highly significant effects on CH{sub 4} emissions, while the effect of heating treatment was weaker (P=0.07). Overall CH{sub 4} fluxes were higher in bog than in fen mesocosms. Despite the significant treatment effects, a multiple regression with water-table depth and soil temperature as the independent variables only predicted 14% and 34% of the variation in CH{sub 4} flux in the bog and fen mesocosms, respectively. CO{sub 2} emissions (net ecosystem respiration) were significantly affected by peatland type (higher in bogs) and heat treatment, but not but by water-table treatment. Soil temperature predicted 34% and 48% of the CO{sub 2} flux in the bog and fen mesocosms, respectively. These preliminary results indicate that climate change will have a significant impact on trace gas emissions in northern peatlands, but that much of the variability in emission cannot be explained by environmental correlates, even under carefully controlled conditions.

  11. Development of a small unmanned aerial vehicle for thermodynamic and trace gas concentration measurement

    NASA Astrophysics Data System (ADS)

    Illingworth, Samuel; Allen, Grant; Percival, Carl; Gallagher, Martin; Ricketts, Hugo; Hollingsworth, Peter; Hayes, Harry; Roberts, Gareth; Ladosz, Pawel; Crawley, David

    2014-05-01

    This study will demonstrate novel measurements of in-situ trace gas concentrations and thermodynamics sampled on-board an instrumented Skywalker Unmanned Aerial Vehicle (UAV). Remotely piloted flights were conducted at in Manchester, UK, with the Skywalker equipped with an adapted Vaisala electrochemical cell ozonesonde measuring O3 concentrations at 0.5 Hz, and a RS92-KE radiosonde measuring pressure, temperature and humidity. Small local and temporal 3D gradients were observed corresponding to changes attributable to micrometeorology and local chemistry with changes to airmass background noted by back trajectory analysis. The ability to sample subtle variability over a localised 3D frame, such as enabled by the techniques demonstrated in this study, highlights the important and novel capabilities of UAVs to rapidly characterise local area micrometeorology and chemistry, as well as area-emissions, and fence-line inputs. By comparing to ground-based in situ measurement, and taking into account local meteorological conditions, it was found that the UAV measured concentrations were a reliable indicator of background concentrations at the urban scale whilst revealing additional local variability important for air quality monitoring and related policy obligations.

  12. Trace detection and discrimination of explosives using electrochemical potentiometric gas sensors.

    PubMed

    Sekhar, Praveen K; Brosha, Eric L; Mukundan, Rangachary; Linker, Kevin L; Brusseau, Charles; Garzon, Fernando H

    2011-06-15

    In this article, selective and sensitive detection of trace amounts of pentaerythritol tetranitrate (PETN), 2,4,6-trinitrotoluene (TNT) and cyclotrimethylenetrinitramine (RDX) is demonstrated. The screening system is based on a sampling/concentrator front end and electrochemical potentiometric gas sensors as the detector. Preferential hydrocarbon and nitrogen oxide(s) mixed potential sensors based on lanthanum strontium chromite and Pt electrodes with yttria stabilized zirconia (YSZ) solid electrolyte were used to capture the signature of the explosives. Quantitative measurements based on hydrocarbon and nitrogen oxide sensor responses indicated that the detector sensitivity scaled proportionally with the mass of the explosives (1-3 μg). Moreover, the results showed that PETN, TNT, and RDX samples could be discriminated from each other by calculating the ratio of nitrogen oxides to hydrocarbon integrated area under the peak. Further, the use of front-end technology to collect and concentrate the high explosive (HE) vapors make intrinsically low vapor pressure of the HE less of an obstacle for detection while ensuring higher sensitivity levels. In addition, the ability to use multiple sensors each tuned to basic chemical structures (e.g., nitro, amino, peroxide, and hydrocarbon groups) in HE materials will permit the construction of low-cost detector systems for screening a wide spectrum of explosives with lower false positives than present-day technologies. PMID:21435779

  13. Enhancement of a tunable diode laser tropospheric trace gas measurement system

    NASA Astrophysics Data System (ADS)

    Wert, Bryan P.; Fried, Alan; Henry, Bruce E.; Drummond, James R.

    1999-10-01

    Rapid and accurate ambient measurements of the tropospheric trace gas formaldehyde (CH2O) have been made by the NCAR low altitude tunable diode laser absorption spectrometer on both aircraft and ground based platforms. Field sensitivities of 80 - 120 pptv in 1 minute (40 - 60 pptv in 5 min) were typical of the first aircraft version of the instrument, providing good resolution for studying formaldehyde's role in the oxidative mechanisms of the troposphere. Recently the instrument has been modified to provide simultaneous detection of a second tropospherically interesting molecule, hydrogen peroxide (H2O2), as well as enhanced measurement precision and instrument stability. The optic assembly of the new Dual Channel Airborne Laser System (DCALS) has been designed to be more mechanically stable and better thermally conditioned. Other improvements include measures to mitigate optical noise, stabilize cell pressure, and minimize sample perturbation. Measurements of formaldehyde by DCALS at a ground site during the 1999 Southern Oxidants Study show improved sensitivities of 30 - 100 pptv in 1 minute, and much better long term instrument stability.

  14. Persistence of the dominant soil phylum Acidobacteria by trace gas scavenging

    PubMed Central

    Greening, Chris; Carere, Carlo R.; Rushton-Green, Rowena; Harold, Liam K.; Hards, Kiel; Taylor, Matthew C.; Morales, Sergio E.; Stott, Matthew B.; Cook, Gregory M.

    2015-01-01

    The majority of microbial cells in global soils exist in a spectrum of dormant states. However, the metabolic processes that enable them to survive environmental challenges, such as nutrient-limitation, remain to be elucidated. In this work, we demonstrate that energy-starved cultures of Pyrinomonas methylaliphatogenes, an aerobic heterotrophic acidobacterium isolated from New Zealand volcanic soils, persist by scavenging the picomolar concentrations of H2 distributed throughout the atmosphere. Following the transition from exponential to stationary phase due to glucose limitation, the bacterium up-regulates by fourfold the expression of an eight-gene operon encoding an actinobacteria-type H2-uptake [NiFe]-hydrogenase. Whole-cells of the organism consume atmospheric H2 in a first-order kinetic process. Hydrogen oxidation occurred most rapidly under oxic conditions and was weakly associated with the cell membrane. We propose that atmospheric H2 scavenging serves as a mechanism to sustain the respiratory chain of P. methylaliphatogenes when organic electron donors are scarce. As the first observation of H2 oxidation to our knowledge in the Acidobacteria, the second most dominant soil phylum, this work identifies new sinks in the biogeochemical H2 cycle and suggests that trace gas oxidation may be a general mechanism for microbial persistence. PMID:26240343

  15. A versatile integrating sphere based photoacoustic sensor for trace gas monitoring.

    PubMed

    Lassen, Mikael; Balslev-Clausen, David; Brusch, Anders; Petersen, Jan C

    2014-05-19

    A compact versatile photoacoustic (PA) sensor for trace gas detection is reported. The sensor is based on an integrating sphere as the PA absorption cell with an organ pipe tube attached to increase the sensitivity of the PA sensor. The versatility and enhancement of the sensitivity of the PA signal is investigated by monitoring specific ro-vibrational lines of CO(2) in the 2 μm wavelength region and of NO(2) in the 405 nm region. The measured enhancement factor of the PA signal exceeds 1200, which is due to the acoustic resonance of the tube and the absorption enhancement of the integrating sphere relatively to a non-resonant single pass cell. It is observed that the background absorption signals are highly attenuated due to the thermal conduction and diffusion effects in the polytetrafluoroethylene cell walls. This demonstrates that careful choice of cell wall materials can be highly beneficial to the sensitivity of the PA sensor. These properties makes the sensor suitable for various practical sensor applications in the ultraviolet (UV) to the near infrared (NIR) wavelength region, including climate, environmental and industrial monitoring. PMID:24921288

  16. Seasonality of trace gas emissions from soils in the eastern Amazon

    SciTech Connect

    Verchot, L.V.; Davidson, E.A.; Cattanio, J.H. |

    1995-09-01

    The eastern Amazon is becoming a mosaic of land use types, including primary forest, secondary forest, degraded pastures, and productive pastures. We are investigating how this land use change affects trace gas emissions from the soils of this region. Precipitation is highly seasonal, with less than 20% of the annual precipitation falling during the 6-month dry season. Despite this seasonality, soil fluxes of CO{sub 2} vary only about 20% between the wet and dry seasons in forests (0.30 v 0.24 g m{sup {minus}2} hr{sup {minus}1}) and degraded pastures (0.14 v 0.11 g m{sup {minus}2}hr{sup {minus}1}). Forest trees and woody plants of the degraded pastures are deep rooted and remain active during the dry season. In contrast, productive pastures from which woody weeds have been removed show larger seasonal variation in CO{sub 2} fluxes, from 0.09 g m{sup {minus}2}hr{sup {minus}1} when the grasses are dormant late in the dry season to 0.21 g m{sup {minus}2}hr{sup {minus}1} early in the wet season. Seasonal patterns of fluxes of NO, N{sub 2}O, and CH{sub 4} are currently being measured, and these preliminary results will also be presented.

  17. An analysis of the Antarctic Halogen Occultation Experiment trace gas observations

    NASA Technical Reports Server (NTRS)

    Schoeberl, Mark R.; Luo, Mingzhao; Rosenfield, Joan E.

    1995-01-01

    Analysis of the version 16 Halogen Occultation Experiment (HALOE) CH4 data shows that this long-lived trace gas is well correlated with potential vorticity (PV) computed from National Meteorological Center balanced winds. Analyzing late September and October 1992 data, we show that very low CH4 values are confined to the interior of a vortex edge defined by the maximum gradient in PV. The CH4 and HF time tendency is used to estimate the descent rate in the Antarctic vortex. After removing a component of the trend correlated with the HALOE sampling pattern, we compute the lower stratosphere vertical descent rates and net heaing rates in the spring Antarctic vortex. Our computations of the spring Antarctic vortex heating rates give -0.5 to -0.1 K/day. Over the winter season, the overall lower stratospheric descent rate averages about 1.8-1.5 km/month. These computations are in line with radiative transfer estimates of the heating and descent rate. The HALOE data thus appear to be consistent with the picture of an isolated lower stratospheric Antarctic vortex.

  18. Numerical Analysis of a Multi-Physics Model for Trace Gas Sensors

    NASA Astrophysics Data System (ADS)

    Brennan, Brian

    Trace gas sensors are currently used in many applications from leak detection to national security and may some day help with disease diagnosis. These sensors are modelled by a coupled system of complex elliptic partial differential equations for pressure and temperature. Solutions are approximated using the finite element method which we will show admits a continuous and coercive variational problem with optimal H1 and L2 error estimates. Numerically, the finite element discretization yields a skew-Hermitian dominant matrix for which classical algebraic preconditioners quickly degrade. We develop a block preconditioner that requires scalar Helmholtz solutions to apply but gives a very low outer iteration count. To handle this, we explore three preconditoners for the resulting linear system. First we analyze the classical block Jacobi and block Gauss-Seidel preconditions before presenting a custom, physics based preconditioner. We also present analysis showing eigenvalues of the custom preconditioned system are mesh-dependent but with a small coefficient. Numerical experiments confirm our theoretical discussion.

  19. A software toolkit for processing and analyzing spectral and trace gas flux data collected via aircraft

    NASA Astrophysics Data System (ADS)

    Xu, Y.; Garrity, S. R.; Vierling, L. A.; Martins, D. K.; Shepson, P. B.; Stirm, B. H.

    2006-12-01

    In order to spatially extrapolate trace gas flux measurements made at the scale of individual flux towers to broader regions using spectral approaches, it is helpful to establish new methodologies for sampling and processing these data at scales coarser than one flux tower footprint. To this end, we mounted a dual-channel hyperspectral spectroradiometer capable of collecting spectra at ~3Hz to an experimental twin-engine Beechcraft Duchess instrumented to also measure eddy covariance fluxes of CO2. Experimental flights were conducted over a northern hardwood, deciduous forest between 21 July and 24 July 2006. To analyze these data in ecologically meaningful ways, it was necessary to first develop a software toolkit capable of marrying the spectral and flux data in appropriate spatial and spectral contexts. The toolkit is capable of merging the spectral and flux data streams with the GPS/Inertial Navigation System of the aircraft such that data can be interactively selected according to its timestamp or geographic location and queried to output a variety of preset and/or user defined spectral indices for comparison to collocated flux data. In addition, the toolkit enables the user to interactively plot the spectral target locations on any georectified image to facilitate comparisons among land cover type, topography, surface spectral characteristics, and CO2 fluxes. In this paper, we highlight the capabilities of the software toolkit as well as provide examples of ways in which it can be used to explore correlation among spectral and flux data collected via aircraft.

  20. Persistence of the dominant soil phylum Acidobacteria by trace gas scavenging.

    PubMed

    Greening, Chris; Carere, Carlo R; Rushton-Green, Rowena; Harold, Liam K; Hards, Kiel; Taylor, Matthew C; Morales, Sergio E; Stott, Matthew B; Cook, Gregory M

    2015-08-18

    The majority of microbial cells in global soils exist in a spectrum of dormant states. However, the metabolic processes that enable them to survive environmental challenges, such as nutrient-limitation, remain to be elucidated. In this work, we demonstrate that energy-starved cultures of Pyrinomonas methylaliphatogenes, an aerobic heterotrophic acidobacterium isolated from New Zealand volcanic soils, persist by scavenging the picomolar concentrations of H2 distributed throughout the atmosphere. Following the transition from exponential to stationary phase due to glucose limitation, the bacterium up-regulates by fourfold the expression of an eight-gene operon encoding an actinobacteria-type H2-uptake [NiFe]-hydrogenase. Whole-cells of the organism consume atmospheric H2 in a first-order kinetic process. Hydrogen oxidation occurred most rapidly under oxic conditions and was weakly associated with the cell membrane. We propose that atmospheric H2 scavenging serves as a mechanism to sustain the respiratory chain of P. methylaliphatogenes when organic electron donors are scarce. As the first observation of H2 oxidation to our knowledge in the Acidobacteria, the second most dominant soil phylum, this work identifies new sinks in the biogeochemical H2 cycle and suggests that trace gas oxidation may be a general mechanism for microbial persistence. PMID:26240343

  1. Orthopyroxene as a recorder of primitive achondrite petrogenesis: Major-, minor-, and trace-element systematics of orthopyroxene in Lodran. [Abstract only

    NASA Technical Reports Server (NTRS)

    Papike, J. J.; Spilde, M. N.; Fowler, G. W.; Shearer, C. K.

    1994-01-01

    Considerable attention has been paid recently to the primitive achondrites because they may form a link between chondrites and more differentiated achondrite meteorites. A recent paper by Miyamoto and Takeda addresses the thermal history of lodranites Yamato 74357 and MAC 88177 as inferred from chemical zoning of pyroxene and olivine determined by electron microprobe analyses. Their results suggested that interstitial melt was present and then extracted. We have taken the analysis of Lodran-type meteorites one step further by incorporating the techniques of Electromagnetic Pulse/Wavelength Dispersive Spectroscopy (EMP/WDS) compositional imaging and scanning ion mass spectroscopy (SIMS) analysis. Orthopyroxene in Lodran is strongly zoned in CaO, Al2O3, TiO2, and Cr2O3 within the last 10-30 microns from the grain boundaries. The rims are reversely zoned in Mg-Fe, exhibiting Mg enrichment, and compositions change from a fairly uniform Wo3En94 within the grains to Wo1En96 at the rims. CaO drops from 1.6 to 0.6 wt% and Al2O3, TiO2, and Cr2O3 exhibit similar depletions. MnO is fairly uniform throughout the grains at around 0.5 wt%. Olivine is also reversely zoned with respect to not only grain boundaries but also to fractures within the grains, giving many olivine grains a complex, patchy zoning pattern. Some of the core-rim trace-element systematics for orthopyroxene are illustrated. Because of the rather narrow zoned rims in Lodran orthopyroxene and the low trace-element abundances, it is difficult to clearly resolve the trace-element systematics. Nevertheless it is evident that the cores are enriched in the incompatible trace elements Ce, Nd, Dy, Er, Yb, Y, and Zr relative to the rims.

  2. Contribution of biomass and biofuel emissions to trace gas distributions in Asia during the TRACE-P experiment

    NASA Astrophysics Data System (ADS)

    Woo, Jung-Hun; Streets, David G.; Carmichael, Gregory R.; Tang, Youhua; Yoo, Bongin; Lee, Won-Chan; Thongboonchoo, Narisara; Pinnock, Simon; Kurata, Gakuji; Uno, Itsushi; Fu, Qingyan; Vay, Stephanie; Sachse, Glen W.; Blake, Donald R.; Fried, Alan; Thornton, Donald C.

    2003-11-01

    A comprehensive emission inventory with enhanced spatial and temporal resolution is used to help quantify the contribution from three source categories (fossil, biofuel, and biomass burning) during the NASA TRACE-P experiment. Daily biomass burning emissions are developed to support this analysis. Emissions of 27 species and their ratios, by sector, region, and source category are presented. The emission distributions and chemical composition are further analyzed using various statistical techniques. Using cluster analysis, the 27 chemical species are combined into 8 groups that have similar regional distribution, and 52 regions are assembled into 11 regional groups that have similar chemical composition. These groups are used in Chemical Mass Balance analysis to characterize air masses and to quantify the contribution of the three source categories to the observed species distributions. Five DC8 flights with 16 flight segments associated with outflow events are analyzed. In general, Asian outflow is a complex mixture of biofuel, biomass, and fossil sources. Flights in the post frontal regions at high latitudes and low altitudes have a high contribution of fossil fuel emissions. Flights in the warm sector of cold fronts are dominated by biomass burning contributions (about 70%). Biofuel contributions are high (about 70%) when air masses come from central China. The receptor model results are shown to be consistent with other 3-D chemical model sensitivity studies and analysis using ratios of indicator species (e.g., dK+/dSO42-, CH3CN/SOy, SOy/CO, and C2Cl4/CO).

  3. Selected Translated Abstracts of Chinese-Language Climate Change Publications

    SciTech Connect

    Cushman, R.M.; Burtis, M.D.

    1999-05-01

    This report contains English-translated abstracts of important Chinese-language literature concerning global climate change for the years 1995-1998. This body of literature includes the topics of adaptation, ancient climate change, climate variation, the East Asia monsoon, historical climate change, impacts, modeling, and radiation and trace-gas emissions. In addition to the biological citations and abstracts translated into English, this report presents the original citations and abstracts in Chinese. Author and title indexes are included to assist the reader in locating abstracts of particular interest.

  4. Effect of persistent trace compounds in landfill gas on engine performance during energy recovery: a case study.

    PubMed

    Sevimoğlu, Orhan; Tansel, Berrin

    2013-01-01

    Performances of gas engines operated with landfill gas (LFG) are affected by the impurities in the LFG, reducing the economic viability of energy recovery. The purpose of this study was to characterize the trace compounds in the LFG at the Odayeri Landfill, Istanbul, Turkey which is used for energy recovery. Composite gas samples were collected and analyzed for trace compounds (hydrocarbons, siloxanes, and volatile halogenated hydrocarbons) over a 3-year period. Trace compounds entering the gas engines, their impact on the engine performance were evaluated. The operational problems included deposit formation in the combustion chamber, turbocharger, and intercooler of engine before the scheduled maintenance times. High levels of hydrogen sulfide, as well as chlorinated and fluorinated compounds cause corrosion of the engine parts and decrease life of the engine oils. Persistence of siloxanes results in deposit formation, increasing engine maintenance costs. Pretreatment of LFG is necessary to protect the engines at the waste-to-energy facilities with persistence levels of siloxanes and volatile halogenated hydrocarbons. PMID:23063306

  5. Characterization and verification of ACAM slit functions for trace-gas retrievals during the 2011 DISCOVER-AQ flight campaign

    NASA Astrophysics Data System (ADS)

    Liu, C.; Liu, X.; Kowalewski, M. G.; Janz, S. J.; González Abad, G.; Pickering, K. E.; Chance, K.; Lamsal, L. N.

    2015-02-01

    The Airborne Compact Atmospheric Mapper (ACAM), an ultraviolet/visible/near-infrared spectrometer, has been flown on board the NASA UC-12 aircraft during the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) campaigns to provide remote sensing observations of tropospheric and boundary-layer pollutants from its radiance measurements. To assure the trace-gas retrieval from ACAM measurements we perform detailed characterization and verification of ACAM slit functions. The wavelengths and slit functions of ACAM measurements are characterized for the air-quality channel (~304-500 nm) through cross-correlation with a high-resolution solar irradiance reference spectrum after necessarily accounting for atmospheric gas absorption and the ring effect in the calibration process. The derived slit functions, assuming a hybrid combination of asymmetric Gaussian and top-hat slit functions, agree very well with the laboratory-measured slit functions. Comparisons of trace-gas retrievals between using derived and measured slit functions demonstrate that the cross-correlation technique can be reliably used to characterize slit functions for trace-gas retrievals.

  6. Characterization and verification of ACAM slit functions for trace gas retrievals during the 2011 DISCOVER-AQ flight campaign

    NASA Astrophysics Data System (ADS)

    Liu, C.; Liu, X.; Kowalewski, M. G.; Janz, S. J.; González Abad, G.; Pickering, K. E.; Chance, K.; Lamsal, L. N.

    2014-11-01

    The Airborne Compact Atmospheric Mapper (ACAM), an ultraviolet/visible/near-infrared spectrometer, has been flown on board the NASA UC-12 aircraft during the DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) campaigns to provide remote sensing observations of tropospheric and boundary layer pollutants from its radiance measurements. To improve the trace gas retrieval from ACAM measurements, we perform detailed characterization and verification of ACAM slit functions. The wavelengths and slit functions of ACAM measurements are characterized for the air quality channel (~304-500 nm) through cross-correlation with a high-resolution solar irradiance reference spectrum after necessarily accounting for atmospheric gas absorption and the Ring effect in the calibration process. The derived slit functions, assuming a hybrid combination of asymmetric Gaussian and top-hat slit functions, agree very well with the laboratory-measured slit functions. Comparisons of trace gas retrievals between using derived and measured slit functions demonstrate that the cross-correlation technique can be reliably used to characterize slit functions for trace gas retrievals.

  7. Polar vortex dynamics during spring and fall diagnosed using trace gas observations from the Atmospheric Trace Molecule Spectroscopy instrument

    NASA Astrophysics Data System (ADS)

    Manney, G. L.; Michelsen, H. A.; Santee, M. L.; Gunson, M. R.; Irion, F. W.; Roche, A. E.; Livesey, N. J.

    1999-08-01

    Trace gases measured by the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument during three Atmospheric Laboratory for Applications and Science (ATLAS) space-shuttle missions, in March/April 1992 (AT-1), April 1993 (AT-2), and November 1994 (AT-3) have been mapped into equivalent latitude/potential temperature (EqL/θ) coordinates. The asymmetry of the spring vortices results in coverage of subtropical to polar EqLs. EqL/θ fields of long-lived tracers in spring in both hemispheres show the net effects of descent at high EqL throughout the winter, reflecting strong descent in the upper stratosphere, decreasing descent at lower altitudes, and evidence of greater descent at the edge of the lower stratospheric vortex than in the vortex center; these results are consistent with trajectory calculations examining the history of the air measured by ATMOS in the month prior to each mission. EqL/θ tracer fields, the derived fields CH4-CH4* (CH4* is the expected CH4 calculated from a prescribed relationship with N2O for fall) and NOy-NOy* (analogous to CH4*), and parcel histories all indicate regions of strong mixing in the 1994 Southern Hemisphere (SH) spring vortex above 500 K, with the strongest mixing confined to the vortex edge region between 500 and 700 K, and mixing throughout the Northern Hemisphere (NH) spring vortex in 1993 below about 850 K. Parcel histories indicate mixing of extravortex air with air near the vortex edge below 500 K in the SH but not with air in the vortex core; they show extravortex air mixing well into the vortex above ˜450 K in the NH and into the vortex edge region below. The effects of severe denitrification are apparent in EqL/θ HNO3 in the SH lower stratospheric spring vortex. The morphology of HNO3 in the Arctic spring lower stratospheric vortex is consistent with the effects of descent. EqL/θ fields of ATMOS NOy-NOy* show decreases consistent with the effects of mixing throughout the NH lower stratospheric vortex. The Eq

  8. Fate of a few selected trace elements in pressurized fluidized-bed gasification and hot gas cleanup

    SciTech Connect

    Mojtahedi, W.; Salo, K.

    1996-12-31

    Increasingly more stringent environmental regulations have focused attention on the emissions of the so-called air toxics toxic trace elements (As, Be, Cd, Co, Cr, Hg, Mn, Ni, Pb, Sb, Se). In this paper, the results of an experimental program designed to measure the emissions of a few selected trace elements from a 15 MW{sub th} pressurized fluidized bed gasification pilot plant are reported and discussed. The pilot plant is equipped with an advanced hot gas cleanup train which includes a two fluidized-bed reactor system for high-temperature, high-pressure external sulfur removal and a filtration unit housing porous, rigid ceramic candle filters. The trace element concentrations in the fuel, bottom ash, and filter ash are determined and the results compared with EPA regulatory levels.

  9. A broadband absorption spectrometer using light emitting diodes for ultrasensitive, in situ trace gas detection

    SciTech Connect

    Langridge, Justin M.; Shillings, Alexander J. L.; Jones, Roderic L.; Ball, Stephen M.

    2008-12-15

    A broadband absorption spectrometer has been developed for highly sensitive and target-selective in situ trace gas measurements. The instrument employs two distinct modes of operation: (i) broadband cavity enhanced absorption spectroscopy (BBCEAS) is used to quantify the concentration of gases in sample mixtures from their characteristic absorption features, and (ii) periodic measurements of the cavity mirrors' reflectivity are made using step-scan phase shift cavity ringdown spectroscopy (PSCRDS). The latter PSCRDS method provides a stand-alone alternative to the more usual method of determining mirror reflectivities by measuring BBCEAS absorption spectra for calibration samples of known composition. Moreover, the instrument's two modes of operation use light from the same light emitting diode transmitted through the cavity in the same optical alignment, hence minimizing the potential for systematic errors between mirror reflectivity determinations and concentration measurements. The ability of the instrument to quantify absorber concentrations is tested in instrument intercomparison exercises for NO{sub 2} (versus a laser broadband cavity ringdown spectrometer) and for H{sub 2}O (versus a commercial hygrometer). A method is also proposed for calculating effective absorption cross sections for fitting the differential structure in BBCEAS spectra due to strong, narrow absorption lines that are under-resolved and hence exhibit non-Beer-Lambert law behavior at the resolution of the BBCEAS measurements. This approach is tested on BBCEAS spectra of water vapor's 4v+{delta} absorption bands around 650 nm. The most immediate analytical application of the present instrument is in quantifying the concentration of reactive trace gases in the ambient atmosphere. The instrument's detection limits for NO{sub 3} as a function of integration time are considered in detail using an Allan variance analysis. Experiments under laboratory conditions produce a 1{sigma} detection limit

  10. Atmospheric Trace Gas Abundances and Stable Isotope Ratios via IR-LIF

    NASA Technical Reports Server (NTRS)

    Blake, Geoffrey A.

    2004-01-01

    studies form the necessary precursors to the development of compact, lightweight stable isotope/trace gas sensors for future planetary missions.

  11. A Transdimensional, Hierarchical Bayesian Inversion Framework for Estimating Regional Trace Gas Emissions

    NASA Astrophysics Data System (ADS)

    Lunt, M. F.; Rigby, M. L.; Ganesan, A.; Grant, A.; Stavert, A.; Young, D.; O'Doherty, S.

    2015-12-01

    Bayesian inverse modelling is very widely used for estimating trace gas flux fields using atmospheric observations. For reasons of computational expense, and to avoid under-determination, these high-dimensional fields are usually partitioned into a set of basis functions, or are estimated subject to some choice of correlation between grid cells. This partitioning or smoothing of the space is typically based on some set of subjective decisions made by the investigator. However, both the derived flux estimates, and their uncertainties, can be strongly dependent on these choices. Furthermore, traditional approaches do not allow for the uncertainty surrounding these choices to be propagated through to the derived fluxes. We outline a method whereby the number of basis functions, and therefore resolution at which fluxes are estimated, are determined using the data. A priori, we consider the number of flux basis functions and their configuration in the inversion domain to be unknown. In such a framework, the dimensionality of the inverse problem can change, and is therefore referred to as a "transdimensional" inversion. Reversible-jump Markov Chain-Monte Carlo tools to perform such dimension changing were first devised over two decades ago, but their uptake within atmospheric science has been limited. We present a novel application of this method for regional emissions estimation, also incorporating hierarchical Bayesian methods for the quantification of model-related and prior uncertainties. We show that, since the arrangement and geometry of the flux basis functions is no longer fixed, a relatively sparse, and therefore computationally efficient, partitioning can achieve a high effective spatial resolution of fluxes, where permitted by the data. We present an example of this new system for estimating fluxes in the UK, using data from the Deriving Emissions Related to Climate Change (DECC) network. This transdimensional, hierarchical approach is of particular relevance

  12. Manure and Inorganic Nitrogen Affect Trace Gas Emissions under Semi-Arid Irrigated Corn.

    PubMed

    Halvorson, Ardell D; Del Grosso, Stephen J; Stewart, Catherine E

    2016-05-01

    Dairy manure is often applied to cropped soils as a substitute for inorganic N fertilizers, but the impacts of manure on soil trace gas fluxes, yields, and soil N are uncertain in the semiarid western United States. Soil carbon dioxide (CO-C), methane (CH-C), nitrous oxide (NO-N), and ammonia (NH-N) emissions were monitored using surface chambers from five N treatments: (i) partially composted solid dairy manure (DM) (412 kg N ha), (ii) DM + AgrotainPlus (DM+AP), (iii) enhanced efficiency N fertilizer (SuperU [SU]) (179 kg N ha), (iv) urea (179 kg N ha), and (v) check (no N applied), to determine their effect on growing season (GS) and nongrowing season emissions from a tilled clay loam soil under irrigated, continuous corn production for 3 yr. SuperU and AgrotainPlus contain urease and nitrification inhibitors. Averaged over years, GS soil CO-C emissions were greater for DM and DM+AP than for urea, SU, and check treatments due to the large amount of C added with the manure; CH-C emissions did not vary among N treatments; and NO-N emissions decreased in the order urea = DM = DM+AP > SU > check. AgrotainPlus added to the DM did not reduce NO-N emissions compared with DM. Cumulative NH-N emissions after manure application decreased in the order urea > SU > check, with no significant differences between SU, DM, and DM+AP. Dairy manure provided slow-release N with nitrate intensities lower than urea and NO-N emissions similar to urea. These results highlight the importance of best-management practices such as immediate irrigation after N application and use of urease and nitrification inhibitors to minimize N losses. PMID:27136157

  13. Time and Spatially Dependent Estimates of Pollutant Trace Gas Emissions and Their Effect on Tropospheric Ozone

    NASA Astrophysics Data System (ADS)

    Dignon, Jane Elizabeth

    Statistical models have been developed to relate the rate of pollutant emissions from fossil fuel combustion to the rate of fuel consumption. These models have been used to estimate global emissions of nitrogen and sulfur oxides in fossil fuel combustion since the year 1860. When averaged over the 1860 to 1980 period, global sulfur emissions increased at a rate of 2.9 percent per year, and the nitrogen emissions increased a rate of 3.4 percent per year. Using these statistical models along with population distribution estimates, high resolution geographical maps of emissions can be produced for each year which fuel consumption data are available. Global emissions of NO_ {x} and SO_{x} emissions for 1966 and 1980 are illustrated on a latitude-longitude grid appropriate for general circulation models of the atmosphere. Emissions of carbon monoxide from fossil fuel, wood and biomass fuel, and open burning of vegetation, as well as emissions of nitrogen and sulfur oxides from wood and biomass fuel burning, are estimated for 1980 using emission factor methods. These trace gas sources are also mapped globally. The impact of increasing emissions of NO _{x} on tropospheric ozone abundance is estimated by calculations with a one-dimensional (latitudinal) model which includes coupled tropospheric photo-chemistry and diffusive meridional transport. Steady-state photochemical calculations with the prescribed NO_{x } emissions appropriate for 1966 and 1980 indicate an ozone increase of 8 to 11 percent in the Northern Hemisphere, a result which is compatible with the rise of about 12 percent between 1970 and 1981 suggested by recent observations.

  14. TRACING COLD H I GAS IN NEARBY, LOW-MASS GALAXIES

    SciTech Connect

    Warren, Steven R.; Skillman, Evan D.; Stilp, Adrienne M.; Dalcanton, Julianne J.; Ott, Juergen; Walter, Fabian; Petersen, Eric A.; Koribalski, Baerbel; West, Andrew A. E-mail: skillman@astro.umn.edu E-mail: jd@astro.washington.edu E-mail: walter@mpia.de E-mail: Baerbel.Koribalski@csiro.au

    2012-09-20

    We analyze line-of-sight atomic hydrogen (H I) line profiles of 31 nearby, low-mass galaxies selected from the Very Large Array-ACS Nearby Galaxy Survey Treasury (VLA-ANGST) and The H I Nearby Galaxy Survey (THINGS) to trace regions containing cold (T {approx}< 1400 K) H I from observations with a uniform linear scale of 200 pc beam{sup -1}. Our galaxy sample spans four orders of magnitude in total H I mass and nine magnitudes in M{sub B} . We fit single and multiple component functions to each spectrum to isolate the cold, neutral medium given by a low-dispersion (<6 km s{sup -1}) component of the spectrum. Most H I spectra are adequately fit by a single Gaussian with a dispersion of 8-12 km s{sup -1}. Cold H I is found in 23 of 27 ({approx}85%) galaxies after a reduction of the sample size due to quality-control cuts. The cold H I contributes {approx}20% of the total line-of-sight flux when found with warm H I. Spectra best fit by a single Gaussian, but dominated by cold H I emission (i.e., have velocity dispersions of <6 km s{sup -1}), are found primarily beyond the optical radius of the host galaxy. The cold H I is typically found in localized regions and is generally not coincident with the very highest surface density peaks of the global H I distribution (which are usually areas of recent star formation). We find a lower limit for the mass fraction of cold-to-total H I gas of only a few percent in each galaxy.

  15. Interacting biochemical and diffusive controls on trace gas sources in unsaturated soils

    NASA Astrophysics Data System (ADS)

    Rubol, S.; Manzoni, S.; Bellin, A.; Porporato, A. M.

    2011-12-01

    Microbes react to environmental conditions on different timescales. When conditions improve (e.g., rewetting, substrate amendment), the residing population exits the dormant state, becomes active and starts synthesizing extra-cellular enzymes. If substrate availability, and hence energy, is sufficient, microbes may start to reproduce and increase the size of their population. These dynamics make it complicated to interpret measured relationships between microbial activity (e.g., respiration, denitrification, N mineralization) and environmental conditions. In particular, the relationship between bacterial activity and soil moisture, which is derived by incubating soil samples at constant soil moisture levels, seems to vary under dynamic hydrological conditions. This may be related to both soil physical properties and the resilience of bacteria to adapt to rapid changes in soil moisture. We present a process-based model that includes both the above effects and test the hypothesis that the ratio of the time scale of biological versus physical factors determines the shape describing the relationship between microbial activity and soil moisture. In particular, we focus on the role of oxygen dynamics, which regulate the prevalence of aerobic versus anaerobic conditions and thus the prevalence of nitrification versus denitrification. We identify and compare the time scale of the biological oxygen consumption with the time scale of physical diffusion. Starting from well-aerated conditions, as bacteria consume O2 in solution, more oxygen dissolves from the atmosphere - depending on gas-filled porosity. If water dynamics or tillage limits re-aeration, this can affect the equilibrium between the aqueous and the gaseous phase and thus alter the time scale of the reactions. This balance between consumption and re-aeration by diffusion ultimately controls the water quality as well the production of trace gases.

  16. Tracing coalbed natural gas-coproduced water using stable isotopes of carbon

    SciTech Connect

    Sharma, S.; Frost, C.D.

    2008-03-15

    Recovery of hydrocarbons commonly is associated with coproduction of water. This water may be put to beneficial use or may be reinjected into subsurface aquifers. In either case, it would be helpful to establish a fingerprint for that coproduced water so that it may be tracked following discharge on the surface or reintroduction to geologic reservoirs. This study explores the potential of using {delta}{sup 13}C of dissolved inorganic carbon (DIC) of coalbed natural gas (CBNG) - coproduced water as a fingerprint of its origin and to trace its fate once it is disposed on the surface. Our initial results for water samples coproduced with CBNG from the Powder River Basin show that this water has strongly positive {delta}{sup 13}C(DIC) (12 parts per thousand to 22 parts per thousand) that is readily distinguished from the negative {delta}{sup 13}C of most surface and ground water (-8 parts per thousand to -11 parts per thousand). Furthermore, the DIC concentrations in coproduced water samples are also high (more than 100 mg C/L) compared to the 20 to 50 mg C/L in ambient surface and ground water of the region. The distinctively high {delta}{sup 13}C and DIC concentrations allow us to identify surface and ground water that have incorporated CBNG-coproduced water. Accordingly, we suggest that the {delta}{sup 13}C(DIC) and DIC concentrations of water can be used for long-term monitoring of infiltration of CBNG-coproduced water into ground water and streams. Our results also show that the {delta} {sup 13}C (DIC) of CBNG-coproduced water from two different coal zones are distinct leading to the possibility of using {delta}{sup 13}C(DIC) to distinguish water produced from different coal zones.

  17. Ecological perspectives on biosphere-atmosphere trace gas exchange: Viewing gases in the context of ecosystem processes

    SciTech Connect

    Matson, P.A.

    1995-06-01

    Predictions and control of global climate change and regional changes in air chemistry depend on knowledge of sources and sinks of trace gases and their responses to the suite of global changes. In the past decade, major advances in the understanding of trace gas sources and sinks have been made through collaborations among ecologists and atmospheric scientists. Ecologists have brought to this topic a wholly new perspective -- one that emphasizes the need to view trace gas fluxes in terms of the ecosystem and microbial processes that produce them, and in terms of the environmental and edaphic factors that in turn control the processes. One consequence of this viewpoint is the transition from single gas measurement campaigns to the simultaneous measurement of fluxes of multiple gases and their often interacting controlling processes within ecosystems. Case studies illustrating the benefits of such an approach, in terms both of process-level understanding and of atmospheric dynamics, will be presented for the combinations of nitrous oxide and nitric oxide, nitrous oxide and methane, and non-methane hydrocarbons and nitric oxide.

  18. Multi-species trace gas analysis with dual-wavelength quantum cascade laser

    NASA Astrophysics Data System (ADS)

    Jágerská, Jana; Tuzson, Béla; Looser, Herbert; Jouy, Pierre; Hugi, Andreas; Mangold, Markus; Soltic, Patrik; Faist, Jérôme; Emmenegger, Lukas

    2015-04-01

    ). [2] J. Jágerská, P. Jouy, A. Hugi, B. Tuzson, H. Looser, M. Mangold, M. Beck, L. Emmenegger, and J. Faist, 'Dual-wavelength quantum cascade laser for trace gas spectroscopy,' Applied Physics Letters 105, 161109-161109-4 (2014).

  19. The Effect of Experimentally Induced Root Mortality on Trace Gas Exchange

    NASA Astrophysics Data System (ADS)

    Varner, R. K.; Keller, M.; Robertson, J. R.; Dias, J. D.; Silva, H.; Crill, P. M.; McGroddy, M.; Silver, W. L.

    2002-12-01

    Soil-atmosphere exchange of carbon dioxide (CO2), nitric oxide (NO), nitrous oxide (N2O) and methane (CH4) was measured following a root exclusion experiment in the Tapajos National Forest near Santarem, Para, Brazil. The sampling period (June 4 - August 14, 2000) coincided with the beginning of the dry season. The experiment was set up as a randomized complete block design with 5 pairs of 2.5 x 2.5 m plots in both sand and clay soils. Trenches were dug around one plot in each pair for screen installation. Trace gas fluxes were measured weekly for ten weeks following the trenching. Duplicate flux measurements were made for each of the trenched and non-trenched plots. Enclosures made of 0.25 m diameter PVC pipe were placed on a base imbedded in the soil. Dynamic measurements using a portable backpack system equipped with an NO2 chemiluminescent detector for NO and an infrared gas analyzer for CO2 were completed in the field. CH4 and N2O fluxes were measured through a static enclosure method. Syringe samples of the enclosure headspace were analyzed by GC-FID (CH4) and ECD (N2O) the following day. Daily average fluxes ranged between -0.01 and 60.3 ng-N cm-2 hr-1 for N2O. NO fluxes ranged between 0.58 and 8.74 ng-N cm-2 hr-1. CH4 fluxes varied between net consumption and production from -1.73 to 0.912 mg m-2 d-1. Soil respiration ranged from 1.34 to 5.12 umoles CO2 m-2 s-1. Significant differences were seen between trenched and non-trenched plots in both clay and sand soils for N2O emissions only. Hourly field standardization of the NO2 chemiluminescent analyzer resulted in lower variability than the traditional method of standardization which is completed at the beginning and end of the measurement day. Frequent field standardization of the analyzer is necessary to reduce measurement error due to intra-day variability.

  20. Abstract Painting

    ERIC Educational Resources Information Center

    Henkes, Robert

    1978-01-01

    Abstract art provokes numerous interpretations, and as many misunderstandings. The adolescent reaction is no exception. The procedure described here can help the student to understand the abstract from at least one direction. (Author/RK)

  1. Method for Detection of Trace Metal and Metalloid Contaminants in Coal-Generated Fuel Gas Using Gas Chromatography/Ion Trap Mass Spectrometry

    SciTech Connect

    Rupp, Erik C.; Granite, Evan J.; Stanko, Dennis C.

    2010-07-15

    There exists an increasing need to develop a reliable method to detect trace contaminants in fuel gas derived from coal gasification. While Hg is subject to current and future regulations, As, Se, and P emissions may eventually be regulated. Sorbents are the most promising technology for the removal of contaminants from coal-derived fuel gas, and it will be important to develop a rapid analytical detection method to ensure complete removal and determine the ideal time for sorbent replacement/regeneration in order to reduce costs. This technical note explores the use of a commercial gas chromatography/ion trap mass spectrometry system for the detection of four gaseous trace contaminants in a simulated fuel gas. Quantitative, repeatable detection with limits at ppbv to ppmv levels were obtained for arsine (AsH3), phosphine (PH3), and hydrogen selenide (H2Se), while qualitative detection was observed for mercury. Decreased accuracy and response caused by the primary components of fuel gas were observed.

  2. The Colour and Stereo Surface Imaging System for ESA's Trace Gas Orbiter

    NASA Astrophysics Data System (ADS)

    Thomas, Nicolas; Cremonese, Gabriele

    2016-04-01

    The Colour and Stereo Surface Imaging System (CaSSIS) is an 11 μrad/px imaging system ready to launch on the European Space Agency's (ESA) ExoMars Trace Gas Orbiter (TGO) on 14 March 2016 from Baikonur. CaSSIS is based around an 880 mm focal length carbon-fibre reinforced polymer (CFRP) telescope with a 135 mm primary mirror and a 2k x 2k CMOS hybrid detector with 10 micron pixel pitch providing 4.6 m/px imaging from the nominal 400 km circular orbit. The telescope is a slightly modified three mirror anastigmat optical configuration with no central obscuration. The instrument is designed to operate in "push-frame" mode where 2048 x 256 images are acquired at a repetition rate which matches the ground-track velocity (~3 km/s) allowing sufficient overlap for co-registration thereby building image strips along the surface. A filter strip assembly (FSA) is mounted directly above the detector providing images in 4 wavelength bands. Two of these (480.5nm and 676.5nm prior to convolution with the rest of the instrument) correspond closely to bands used by the HiRISE instrument on the Mars Reconnaissance Orbiter [4]. Two other filters split the NIR wavelengths with centres at 838 nm and close to 985 nm. Analyses show that the filters provide good differentiation between expected surface minerals, particularly Fe-bearing phases (Tornabene et al. LPSC, 2016). CaSSIS is designed to produce stereo from images acquired ~30 s apart by using a rotation drive. The telescope points 10 degrees off-nadir. The drive aligns the telescope with the ground-track direction so that the telescope is pointing forward. After image acquisition, the telescope is rapidly rotated by 180 degrees to point in the opposite direction and the second image of the stereo pair is acquired. CaSSIS will extend the monitoring of past missions to future years allowing the tracking of longer-term changes. It will also provide contemporaneous imaging of regions that may produce unique signatures detected by

  3. Long-term Operation of an External Cavity Quantum Cascade Laser-based Trace-gas Sensor for Building Air Monitoring

    SciTech Connect

    Phillips, Mark C.; Craig, Ian M.

    2013-11-03

    We analyze the long-term performance and stability of a trace-gas sensor based on an external cavity quantum cascade laser using data collected over a one-year period in a building air monitoring application.

  4. Analysis of Trace Gas Mixtures Using an External Cavity Quantum Cascade Laser Sensor

    SciTech Connect

    Phillips, Mark C.; Taubman, Matthew S.; Brumfield, Brian E.; Kriesel, Jason M.

    2015-07-01

    We measure and analyze mixtures of trace gases at ppb-ppm levels using an external cavity quantum cascade laser sensor with a 1-second response time. Accurate spectral fits are obtained in the presence of overlapping spectra.

  5. [Ring effect and correction studies while retrieving trace gas concentration with passive DOAS].

    PubMed

    Zhang, Ying-Hua; Xie, Pin-Hua; Si, Fu-Qi; Peng, Fu-Min; Dou, Ke; Li, Su-Wen

    2009-02-01

    The method of retrieving the concentration of trace gases using of the diagnostic absorption of trace gases based on the scattered sunlight is called passive DOAS. It has been developed so fast in recent years because it remains simple and is prone to being combined with different platform. While retrieving the column density of trace gases with the scattered sunlight as light source, it will be affected strongly by solar Fraunhofer lines, which is also called Ring effect. It makes it hard to retrieve trace gases concentration and affects measurement precision, especially for lower concentration. The influence of Ring effect and its relation with solar zenith angle in stable day will be introduced in the present paper, and the modification will be provided so that different Ring spectrum is selected according to different solar zenith angle. The slant column density (SCD) of NO2 for 3 stable days was retrieved with this modification. It was proved that the modification is possible. PMID:19445217

  6. Tidal controls on trace gas dynamics in a seagrass meadow of the Ria Formosa lagoon (southern Portugal)

    NASA Astrophysics Data System (ADS)

    Bahlmann, E.; Weinberg, I.; Lavrič, J. V.; Eckhard, T.; Michaelis, W.; Santos, R.; Seifert, R.

    2014-07-01

    Coastal zones are important source regions for a variety of trace gases including halocarbons and sulphur-bearing species. While salt-marshes, macroalgae and phytoplankton communities have been intensively studied, little is known about trace gas fluxes in seagrass meadows. Here we report results of a newly developed dynamic flux chamber system that can be deployed in intertidal areas over full tidal cycles allowing for high time resolved measurements. The trace gases measured in this study included carbon dioxide (CO2), methane (CH4) and a variety of hydrocarbons, halocarbons and sulphur-bearing compounds. The high time resolved CO2 and CH4 flux measurements revealed a complex dynamic mediated by tide and light. In contrast to most previous studies our data indicate significantly enhanced fluxes during tidal immersion relative to periods of air exposure. Short emission peaks occured with onset of the feeder current at the sampling site. We suggest an overall strong effect of advective transport processes to explain the elevated fluxes during tidal immersion. Many emission estimates from tidally influenced coastal areas still rely on measurements carried out during low tide only. Hence, our results may have significant implications for budgeting trace gases in coastal areas. This dynamic flux chamber system provides intensive time series data of community respiration (at night) and net community production (during the day) of shallow coastal systems.

  7. Design and Signature Analysis of Remote Trace-Gas Identification Methodology Based on Infrared-Terahertz Double-Resonance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Tanner, Elizabeth A.; Phillips, Dane J.; Persons, Christopher M.; De Lucia, Frank C.; Everitt, Henry O.

    2014-11-01

    The practicality of a newly proposed infrared-terahertz (IR-THz) double-resonance (DR) spectroscopic technique for remote trace-gas identification is explored. The strength of the DR signatures depends on known molecular parameters from which a combination of pump-probe transitions may be identified to recognize a specific analyte. Atmospheric pressure broadening of the IR and THz trace-gas spectra relaxes the stringent pump coincidence requirement, allowing many DR signatures to be excited, some of which occur in the favorable atmospheric transmission windows below 500 GHz. By designing the DR spectrometer and performing a detailed signal analysis, the pump-probe power requirements for detecting trace amounts of methyl fluoride, methyl chloride, or methyl bromide may be estimated for distances up to 1 km. The strength of the DR signature increases linearly with pump intensity but only as the square root of the probe power because the received signal is in the Townes noise limit. The concept of a specificity matrix is introduced and used to quantify the recognition specificity and calculate the probability of false positive detection of an interferent.

  8. Tracing of high latitude magnetopause by Interball, Polar and Geotail versus MHD and gas dynamic modelling

    NASA Astrophysics Data System (ADS)

    Savin, S.; Zelenyi, L.; Amata, E.; Berchem, J.; Buechner, J.; Song, P.; Fuselier, S.; Kawano, H.; Mukai, T.; Maynard, N.

    L. Zelenyi (1), E. Amata (6), J. Berchem (5), J. Buechner (7), P. Song (3), S. Fuselier (13), H. Kawano (4), V. Lutsenko (1), T. Mukai (8), K. Maezawa (8), N. Maynard (2), Z. Nemecek (14), R. Nakamura (15), M. Fujimoto (10), A. Pedersen (9), E. Panov (1), I. Sandahl (11), J. Safrankova (14), J.A. Sauvaud (16), V. Smirnov (1), K. Stasiewicz (12) (2) MRC, Nashua, USA, (3) U. Mass., Lowell, USA, (4) Kyushu U., Japan, (5) UCLA, USA, (6) IFSI, Roma, Italy, (7) MPAe, Lindau, Germany, (8) ISAS, Japan, (9) Oslo U., Norway, (10) Tokyo U., Japan, (11) IRF, Kiruna, Sweden, (12) IRF-U, Uppsala, Sweden, (13) LMATC, USA, (14) Charles U., Czech Rep., (15) IWF, Graz, Austria, (16) CESR, Toulouse, France, We present two case studies of magnetosheath (MSH) interaction with the high latitude magnetopause (MP) on the basis of Interball-1, Polar, Geotail and other ISTP spacecraft data. On April 23-24, 1998 Interball & Polar over cusp and Geotail at the tail flank (GSM Z =10 Re) traced boundary layers (BL). The time-depended MHD modeling serves to unite the 6-point data with the global reconnection pattern, driven by strong solar wind (SW) disturbances. At the smaller scales the BL perturbations display similar kinked magnetic spectra and 3-wave phase coupling, the correlation length is less than the distance between Interball-Polar (3 RE). Strong SW disturbances, decelerated over cusp, penetrate deep into tail. For quiet SW local perturbations dominate at frequencies over few mHz. Similar spectral features are seen on June 19, 1998 both in stagnant MSH (Polar) and upstream 'plasma ball' (PB, Interball-1) - demagnetized heated plasma (ion beta ~ 2-15) of MSH origin inside MP. Comparison with SW magnetic spectra and plasma moments from Geotail using Gas Dynamic Convection Field model indicates that the patchy reconnection pulses at Polar location are modulated by the upstream BL fluctuations. The fluctuations result from direct interaction of PB with MSH flow by means of reflected from

  9. Study of Atmospheric Trace Gas Amounts at the Stara Zagora Ground-Based Station

    NASA Astrophysics Data System (ADS)

    Werner, R.; Valev, D.; Kostadinov, I.; Atanassov, At.; Giovanelli, G.; Petritoli, A.; Bortoli, D.; Ravegnani, F.

    2006-03-01

    Since the end of August 1999 twilight daily measurements of scattered zenith sky radiation have been carried out at Stara Zagora for determination of trace gas amounts, deploying GASCOD instrument. It was developed at the Institute of Atmospheric Science and Climate, Bologna. Reference spectra are obtained at midday. The instrument, appearing a UV-VIS spectrometer, registers the zenith sky spectra automatically and 410 nm to 460 nm spectral interval is used to retrieve NO2 and O3 slant column amounts (SCA) by application of the DOAS methodology. The spectral analysis uses minimum least squares fitting of the cross sections at the expected absorbers to a logarithm of the twilight spectrum and a reference spectrum. The accumulated time series show the well-known typical seasonal variations, caused by the solar insulation. The residual time series of the removed semi-annual seasonal cycles from the measured original series show many different variations, with short periods up to inter-annual variations. Single spikes of SCA are detected and we consider them a result of over-passing weather fronts and/or lightning. Variations of SCA with time scale up to about 10 days are the consequence of weather cyclones. Some short-term variations of NO2 and O3 SCA are a result of intensive stratospheric-tropospheric exchange. Other residual time series periods are caused by Rossby waves, by over-passing of the polar vortex filaments. The inter-annual variations can be affected by QBO and NAO. Applying wavelet analysis of the obtained NO2 slant column amount data series, and the total O3 amount obtained by the GOME instrument, during the 23-rd solar cycle maximum, time intervals are found with periods of 27 days on the time scale. The applied cross-correlation analysis demonstrates a phase lag of some days of the NO2 and O3 response to the 27-days solar cycle. The calculated vertical column amounts of NO2 are used for validation of the satellite measurements, e.g. SCIAMACHY NO2

  10. Collimated neutron detector FREND for the ESA ExoMars Trace Gas Orbiter: objectives and modelling

    NASA Astrophysics Data System (ADS)

    Sanin, A.; Mitrofanov, I.; Malakhov, A.; Fedosov, F.; Golovin, D.; Kozyrev, A. S.; Litvak, M. L.; Lisov, D.; Mokrousov, M.; Nikiforov, S.; Shvetsov, V. N.; Tret'yakov, V. I.; Varenikov, A.; Vostrukhin, A.

    2013-09-01

    High Energy Neutron Detector (HEND) is continuously operating onboard the NASA Mars Odyssey spacecraft starting from Mars orbit insertion maneuver at October 24, 2001. It provides data about low, epithermal and fast neutrons fluxes and fluxes of charged particles on the spacecraft orbit. Significant amount of accumulated HEND data allows to study hydrogen distribution in top ~1 meter layer of the Martian regolith, seasonal variations of H2O permafrost, CO2 deposition and sublimation and radiation condition on Martian surface during Solar activity cycle. One of the most important results obtained from HEND data analysis is the evidence of presence of significant amount of H2O permafrost at high latitudes around both poles and enhanced hydrogen concentration at Arabia and Memnonia regions. The highest spatial resolution of HEND data is about 600*600 km, since the instrument measured neutron fluxes from all directions at the spacecraft orbit. Such resolution is much broader than sizes of most Martian relief features. Even 150-km diameter Gale crater is significantly smaller. It is obvious that such resolution makes difficult any studying of hydrogen distribution across small to medium size Martian relief features and, for example, landing sites of future robotic and/or manned missions. Fine Resolution Epithermal Neutron Detector (FREND) selected for flight as a part of scientific payload of the ESA ExoMars Trace Gas Orbiter (TGO) contains a neutron collimation module. It will provide a narrow field of view (FOV) for detectors of FREND instrument. LEND instrument onboard the NASA LRO mission is the heritage for FREND. The idea of neutron collimation has been successfully tested during the LRO mission. Mechanical design of the instrument is fixed and it is on manufacturing stage now. The ESA ExoMars TGO orbiter is scheduled to be launched at January 2016. After about 240 days of cruise the spacecraft will start Mars orbit insertion and aerobraking maneuvers. Science

  11. Environmental factors influencing trace house gas production in permafrost-affected soils

    NASA Astrophysics Data System (ADS)

    Walz, Josefine; Knoblauch, Christian; Böhme, Luisa; Pfeiffer, Eva-Maria

    2016-04-01

    The permafrost-carbon feedback has been identified as a major feedback mechanism to climate change. Soil organic matter (SOM) decomposition in the active layer and thawing permafrost is an important source of atmospheric carbon dioxide (CO2) and methane (CH4). Decomposability and potential CO2 and CH4 production are connected to the quality of SOM. SOM quality varies with vegetation composition, soil type, and soil depth. The regulating factors affecting SOM decomposition in permafrost landscapes are not well understood. Here, we incubated permafrost-affected soils from a polygonal tundra landscape in the Lena Delta, Northeast Siberia, to examine the influence of soil depth, oxygen availability, incubation temperature, and fresh organic matter addition on trace gas production. CO2 production was always highest in topsoil (0 - 10 cm). Subsoil (10 - 50 cm) and permafrost (50 - 90 cm) carbon did not differ significantly in their decomposability. Under anaerobic conditions, less SOM was decomposed than under aerobic conditions. However, in the absence of oxygen, CH4 can also be formed, which has a substantially higher warming potential than CO2. But, within the four-month incubation period (approximate period of thaw), methanogenesis played only a minor role with CH4 contributing 1-30% to the total anaerobic carbon release. Temperature and fresh organic matter addition had a positive effect on SOM decomposition. Across a temperature gradient (1, 4, 8°C) aerobic decomposition in topsoil was less sensitive to temperature than in subsoil or permafrost. The addition of labile plant organic matter (13C-labelled Carex aquatilis, a dominant species in the region) significantly increased overall CO2 production across different depths and temperatures. Partitioning the total amount of CO2 in samples amended with Carex material into SOM-derived CO2 and Carex-derived CO2, however, revealed that most of the additional CO2 could be assigned to the organic carbon from the amendment

  12. Fine Resolution Epithermal Neutron Detector (FREND) for ExoMarsTrace Gas Orbiter

    NASA Astrophysics Data System (ADS)

    Malakhov, A.; Mitrofanov, I.; Sanin, A.; Litvak, M.; Kozyrev, A.; Tretiyakov, V.; Mokrousov, M.; Vostrukhin, A.; Golovin, D.; Fedosov, F.

    2012-04-01

    ExoMars is now under considerations, as a joint mission of the three agencies, ESA,Roscosmos and NASA to explore the red planet. Planned for launch in 2016, its first element, the Trace Gas Orbiter (TGO) is going to spend one Martian year (687 Earth days) orbiting around the planet. Fine Resolution Epithermal Neutron Detector (FREND), once aboard TGO, will be measuring thermal, epithermal and high energy neutrons with energy ranges up to 10 MeV, which variations are an excellent signature of H bearing elements presence in the regolith at up to 1 meter depth. Neutron mapping of Mars is being performed since 2002 by HEND instrument on board of Mars Odyssey, but the significant step up in FREND design compared to this previous mission will be its ability to collimate neutrons and thus have a very narrow Field of View of 40 km at a 400 km altitude. Its collimator consists of layers of polyethylene to moderate neutrons and 10B to absorb them. The collimator's design is equal to one used in LEND instrument on board the Lunar Reconnaissance Orbiter and proved to be efficient. The instrument design and detectors will also be very similar to ones used in its both ancestors, LEND and HEND, benefitting from the best heritage there is. FREND will use a set of 3He proportional counters to cover the thermal and epithermal neutrons energy ranges, providing a set of several independent measurements for higher statistics, as well as a stilbene scintillation detector for high energy neutrons. FREND will be the first collimated neutron instrument to fly towards Mars and, like LEND on the Moon, FREND will be able to produce Martian neutron maps that could supersede previously created ones by about 10 times in the linear spatial resolution. This will potentially clarify the available global Mars neutron maps, but could also point out new, never before seen small water/hydrogen rich features and other places of interest on the surface of the planet. Without a doubt, this kind of

  13. Nutrient dynamics and nitrogen trace gas flux during ecosystem development in montane rain forest

    SciTech Connect

    Riley, R.H.; Vitousek, P.M.

    1995-01-01

    Patterns of nitrogen trace gas emissions, soil nitrogen flux, and nutrient availability were evaluated at five sites that form a chronosequence in Hawaiian montane rain forest. The estimated age of basaltic parent material from which soils developed at the Kilauea site was 200 yr, 6000 yr at the Puu Makaala site, 185000 yr at the Kohala site, 1.65 x 10{sup 6} yr at the Molokai site, and 4.5 x 10{sup 6} yr at the Kauai site. Peak net N mineralization and nitrification values were found in soils from the 185000-yr-old Kohala site. Nitrogen content of foliage and leaf litter was highest in the intermediate age sites (Puu Makaala and Kohala) and N and P retranslocation was lowest at the Puu Makaala site. Soil cores fertilized with nitrogen had significantly higher rates of root ingrowth than control cores at the two youngest sites (200 and 6000 yr old) but not in older sites (185000 and 4.5 x 10{sup 6}-yr-old sites) and total fine root growth into control cores was greatest at the Kohala site. The highest N{sub 2}O emissions were found at the 185000-yr-old Kohala site, while the highest combined flux of N{sub 2}O + NO was observed at the 4.5 x 10{sup 6}-yr-old Kauai site. While overall N{sub 2}O emission rates were correlated with rates of N transformations, soil water content appeared to influence the magnitude of emissions of N{sub 2}O and the ratios of emissions of NO vs. N{sub 2}O. N{sub 2}O emissions occurred when water-filled pore space (WFPS) values were >40%, with highest emissions in at least two sites observed at WFPS values of 75%. Among sites, high N{sub 2}O emissions were associated with high soil N transformation rates. Large NO fluxes were observed only at the Kauai site when WFPS values were <60%. 50 refs., 8 figs., 4 tabs.

  14. Measurements of methane emissions from landfills using mobile plume method with trace gas and cavity ring-down spectroscopy

    NASA Astrophysics Data System (ADS)

    Mønster, J.; Kjeldsen, P.; Scheutz, C.

    2012-04-01

    Methane is emitted to the atmosphere from both anthropogenic and natural sources. One of the major anthropogenic sources is methane produced by bacteria in anaerobic environments such as rice pads and landfills. Land filling has for many years been the preferred waste disposal method, resulting in a large methane production with a large contribution to the global increase in atmospheric green house gas concentration. Several steps have been taken to reduce the emission of methane from landfills. In order to validate the effect of these steps, a measurement method is needed to quantify methane emissions with a large spatial variation. One method is to use a highly sensitive and fast analytical method, capable of measuring the atmospheric concentration methane downwind from emission areas. Combined with down-wind measurements of a trace gas, emitted at a controlled mass flow rate, the methane emission can be calculated. This method is called the mobile plume method, as the whole plume is measured by doing several transects. In the current study a methane/acetylene analyzer with cavity ring-down spectroscopy detection (Picarro, G2203) was used to estimate methane from a number of Danish landfills. We measured at both active and closed landfills and investigated the difference in methane emission. At landfills where the emissions could have more than one origin, the source strength of the different emission areas was determined by accurate trace gas positioning and choosing appropriate wind speed and measurement distance. To choose these factors, we addressed the uncertainties and limitations of the method with respect to the configuration of the trace gas bottles and the distance between the emission area and the measurement points. Composting of organic material in large piles was done at several of the investigated landfills and where possible, the methane emission from this partly anaerobic digestion was measured as a separate emission.

  15. Russian contribution to ExoMars Trace Gas Orbiter: Atmospheric Chemistry Suite (ACS)

    NASA Astrophysics Data System (ADS)

    Shakun, Alexey; Korablev, Oleg; Trokhimovskiy, Alexander; Grigoriev, Alexey; Anufreychik, Konstantin; Fedorova, Anna; Ignatiev, Nikolay; Ivanov, Yuriy; Moshkin, Boris; Kalinnikov, Yuriy; Montmessin, Franck

    2016-04-01

    Atmospheric Chemistry Suite (ACS) is a part of science payload of Trace Gas Orbiter (TGO), ExoMars mission. This project developed by European Space Agency (ESA) in collaboration with Russian Space Agency (Roscosmos). Russian contribution to ExoMars TGO is the Proton rocket and two science instruments ACS (three infrared spectrometers) and FREND (neutron detector). ACS consists of three infrared spectrometers (ACS/NIR, ACS/MIR and ACS/TIRVIM) capable to take spectral measurements from near to thermal infrared range simultaneously or separately. Spectrometric channels of ACS share common mechanical, electrical, and thermal interfaces. Electronic box (ACS/BE) provides to spectrometric channels power and data transfer interfaces. SpaceWire link is used for science data transfer and MIL-1553 link - for commanding and housekeeping data transfer. The NIR channel is an echelle spectrometer with acousto-optic tunable filter (AOTF) for the selection of diffraction orders. ACS NIR is capable to perform nadir and occultation observations. NIR covers the spectral range of 0.7-1.7 μm with resolving power of ~25000. NIR will perform unique for TGO instruments nightglow science (searching for O2, OH, NO nightglow emissions on Mars). From the 1.38 μm band NIR will do water vapour mapping in nadir and H2O vertical profiling in solar occultations. High resolution NIR measurements of 1.27 μm O2(a1Δg) dayglow will supply indirect ozone observations on the dayside on nadir. In solar occultation mode, the O2 vertical profiles will be measured from the surface (in case of low dust activity) to the 40 km altitude based on 0.76 μm absorption band. Together with MIR channel in solar occultation NIR will support the measurements of CO2 density profiles (based on 1.43 μm band) and aerosols characterization from 0.7 to 4 μm. The wide spectral range will allow not just determine aerosol particle sizes and density at different altitudes, but also distinguish between dust and ice particles

  16. Soil-atmosphere trace gas exchange from tropical oil palm plantations on peat

    NASA Astrophysics Data System (ADS)

    Arn Teh, Yit; Manning, Frances; Zin Zawawi, Norliyana; Hill, Timothy; Chocholek, Melanie; Khoon Kho, Lip

    2015-04-01

    Oil palm is the largest agricultural crop in the tropics, accounting for 13 % of all tropical land cover. Due to its large areal extent, oil palm cultivation may have important implications not only for terrestrial stores of C and N, but may also impact regional and global exchanges of material and energy, including fluxes of trace gases and water vapor. In particular, recent expansion of oil palm into tropical peatlands has raised concerns over enhanced soil C emissions from degradation of peat, and elevated N-gas fluxes linked to N fertilizer application. Here we report our preliminary findings on soil carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes from a long-term, multi-scale project investigating the C, N and greenhouse gas (GHG) dynamics of oil palm ecosystems established on peat soils in Sarawak, Malaysian Borneo. Flux chamber measurements indicate that soil CO2, CH4 and N2O fluxes averaged 20.0 ± 16.0 Mg CO2-C ha-1 yr-1, 37.4 ± 29.9 kg CH4-C ha-1 yr-1 and 4.7 ± 4.2 g N2O-N ha-1 yr-1, respectively. Soil CO2 fluxes were on par with other drained tropical peatlands; whereas CH4 fluxes exceeded observations from similar study sites elsewhere. Nitrous oxide fluxes were in a similar range to fluxes from other drained tropical peatlands, but lower than emissions from mineral-soil plantations by up to three orders of magnitude. Fluxes of soil CO2 and N2O were spatially stratified, and contingent upon the distribution of plants, deposited harvest residues, and soil moisture. Soil CO2 fluxes were most heavily influenced by the distribution of palms and their roots. On average, autotrophic (root) respiration accounted for approximately 78 % of total soil CO2 flux, and total soil respiration declined steeply away from palms; e.g. soil CO2 fluxes in the immediate 1 m radius around palms were up to 6 times greater than fluxes in inter-palm spaces due to higher densities of roots. Placement of harvest residues played an important - but secondary

  17. Detection of trace concentrations of helium and argon in gas mixtures by laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    McNaghten, E. D.; Parkes, A. M.; Griffiths, B. C.; Whitehouse, A. I.; Palanco, S.

    2009-10-01

    We report what we believe to be the first demonstration of the detection of trace quantities of helium and argon in binary and ternary gas mixtures with nitrogen by laser-induced breakdown spectroscopy (LIBS). Although significant quenching of helium transitions due to collisional deactivation of excited species was observed, it was found that losses in analytical sensitivity could be minimized by increasing the laser irradiance and decreasing the pressure at which the analyses were performed. In consequence, limits of detection of parts-per-million and tens of parts-per-million and linear dynamic ranges of several orders of magnitude in analyte concentration were obtained. The results of this study suggest that LIBS may have potential applications in the detection of other noble gases at trace concentrations.

  18. Satellite Observations of Trace Gases and Their Application for Studying Air Quality Near Oil and Gas Operations

    NASA Astrophysics Data System (ADS)

    Kollonige, D. E.; Thompson, A. M.; Nichols, M.; Fasnacht, Z.; Martins, D. K.; Dickerson, R. R.

    2014-12-01

    The increase in the natural gas component of the energy sector has led many state and local municipalities to begin regulation of emissions from the oil and natural gas operators with air quality (AQ) as a concern. "Top-down" measurements of trace gases in the air above wells complement "bottom-up" inventories, used by EPA and AQ stakeholders, through a more accurate depiction of regional variability of methane and other species near and downwind of oil and gas operations. Satellite observations of methane, nitrogen dioxide, formaldehyde, ozone, and other carbon gases enhance the spatial and temporal coverage of the data needed to demonstrate any long-term impacts from shale gas development. As part of a NASA AQAST (Air Quality Applied Sciences Team) project, we are evaluating satellite measurements of trace gases in regions with oil and gas operations for their application as a "top-down" constraint. For validation of the satellite instruments' sensitivities to emitted gases, we focus on regions where the DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) campaign deployed with ground and aircraft measurements, including, Maryland (2011), California and Texas (2013), and Colorado (2014). We compare vertical distributions of methane and volatile organic compounds (VOCs) nearby and downwind of oil and gas wells to locate any regional differences during the campaign time periods. This allows for better characterization of the satellite observations and their limitations for application in air quality studies in similar environments. Taking advantage of current EOS-era satellites' data records, we also analyze methane anomalies and gas correlations in the free troposphere from 2005 to present to identify trends for basins with oil and gas extraction sites and their influence on background concentrations downwind of wells. In most regions with oil and gas activity, we see continually

  19. Tropospheric chemistry over the lower Great Plains of the United States. 2. Trace gas profiles and distributions

    SciTech Connect

    Luke, W.T.; Dickerson, R.R.; Ryan, W.F.; Pickering, K.E.; Nunnermacker, L.J. )

    1992-12-20

    Convective clouds and thunderstorms redistribute air pollutants vertically, and by altering the chemistry and radiative balance of the upper troposphere, these local actions can have global consequences. To study these effects, measurements of trace gases ozone, O[sub 3], carbon monoxide, CO, and odd nitrogen were made aboard the NCAR Sabreliner on 18 flights over the southern Great Plains during June 1985. To demonstrate chemical changes induced by vertical motions in the atmosphere and to facilitate comparison with computer model calculations, these data were categorized according to synoptic flow patterns. Part 1 of this two-part paper details the alternating pulses of polar and maritime air masses that dominate the vertical mixing in this region. In this paper, trace gas measurements are presented as altitude profiles (0-12 km) with statisitcal distributions of mixing ratios for each species in each flow pattern. The polar flow regime is characterized by northwesterly winds, subsiding air, and convective stability. The maritime regime is characterized by southerly surface winds, convective instability, and a deep planetary boundary layer PBL; uniformly high concentrations of trace gases were found up to 4 km on one flight. During frontal passage both stratiform and convective clouds mix pollutants more uniformly into the middle and upper levels; high mixing ratios of CO are found at all altitudes, and O[sub 3] levels are highest of any category, implicating photochemical production. These results illustrate the importance of convection in tropospheric chemistry. Use of average trace gas profiles or eddy diffusion parameterized vertical mixing can lead to errors of 30 to 50% in O[sub 3] and CO concentrations and an order of magnitude for odd nitrogen. 80 refs., 18 figs., 9 tabs.

  20. Oil and gas exploration system and method for detecting trace amounts of hydrocarbon gases in the atmosphere

    DOEpatents

    Wamsley, Paula R.; Weimer, Carl S.; Nelson, Loren D.; O'Brien, Martin J.

    2003-01-01

    An oil and gas exploration system and method for land and airborne operations, the system and method used for locating subsurface hydrocarbon deposits based upon a remote detection of trace amounts of gases in the atmosphere. The detection of one or more target gases in the atmosphere is used to indicate a possible subsurface oil and gas deposit. By mapping a plurality of gas targets over a selected survey area, the survey area can be analyzed for measurable concentration anomalies. The anomalies are interpreted along with other exploration data to evaluate the value of an underground deposit. The system includes a differential absorption lidar (DIAL) system with a spectroscopic grade laser light and a light detector. The laser light is continuously tunable in a mid-infrared range, 2 to 5 micrometers, for choosing appropriate wavelengths to measure different gases and avoid absorption bands of interference gases. The laser light has sufficient optical energy to measure atmospheric concentrations of a gas over a path as long as a mile and greater. The detection of the gas is based on optical absorption measurements at specific wavelengths in the open atmosphere. Light that is detected using the light detector contains an absorption signature acquired as the light travels through the atmosphere from the laser source and back to the light detector. The absorption signature of each gas is processed and then analyzed to determine if a potential anomaly exists.

  1. Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) data processing and atmospheric temperature and trace gas retrieval

    NASA Astrophysics Data System (ADS)

    Riese, M.; Spang, R.; Preusse, P.; Ern, M.; Jarisch, M.; Offermann, D.; Grossmann, K. U.

    1999-07-01

    The Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) experiment aboard the Shuttle Pallet Satellite (SPAS) was successfully flown in early November 1994 (STS 66) and in August 1997 (STS 85). This paper focuses on the first flight of the instrument, which was part of the Atmospheric Laboratory for Application and Science 3 (ATLAS 3) mission of NASA. During a free flying period of 7 days, limb scan measurements of atmospheric infrared emissions were performed in the 4 to 71 μm wavelength region. For improved horizontal resolution, three telescopes (viewing directions) were used that sensed the atmosphere simultaneously. Atmospheric pressures, temperatures, and volume mixing ratios of various trace gases were retrieved from the radiance data by using a fast onion-peeling retrieval technique. This paper gives an overview of the data system including the raw data processing and the temperature and trace gas profile retrieval. Examples of version 1 limb radiance data (level 1 product) and version 1 mixing ratios (level 2 product) of ozone, ClONO2, and CFC-11 are given. A number of important atmospheric transport processes can already be identified in the level 1 limb radiance data. Radiance data of the lower stratosphere (18 km) indicate strong upwelling in some equatorial regions, centered around the Amazon, Congo, and Indonesia. Respective data at the date line are consistent with convection patterns associated with El Niño. Very low CFC-11 mixing ratios occur inside the South Polar vortex and cause low radiance values in a spectral region sensitive to CFC-11 emissions. These low values are a result of considerable downward transport of CFC-11 poor air that occurred during the winter months. Limb radiance profiles and retrieved mixing ratio profiles of CFC-11 indicate downward transport over ˜5 km. The accuracy of the retrieved version 1 mixing ratios is rather different for the various trace gases. In the middle atmosphere the estimated

  2. Adsorption and reaction of trace gas-phase organic compounds on atmospheric water film surfaces: a critical review.

    PubMed

    Donaldson, D J; Valsaraj, Kalliat T

    2010-02-01

    The air-water interface in atmospheric water films of aerosols and hydrometeors (fog, mist, ice, rain, and snow) presents an important surface for the adsorption and reaction of many organic trace gases and gaseous reactive oxidants (hydroxyl radical (OH(.)), ozone (O(3)), singlet oxygen (O(2)((1)Delta(g))), nitrate radicals (NO(3)(.)), and peroxy radicals (RO(2)(.)). Knowledge of the air-water interface partition constant of hydrophobic organic species is necessary for elucidating the significance of the interface in atmospheric fate and transport. Various methods of assessing both experimental and theoretical values of the thermodynamic partition constant and adsorption isotherm are described in this review. Further, the reactivity of trace gases with gas-phase oxidants (ozone and singlet oxygen) at the interface is summarized. Oxidation products are likely to be more water-soluble and precursors for secondary organic aerosols in hydrometeors. Estimation of characteristic times shows that heterogeneous photooxidation in water films can compete effectively with homogeneous gas-phase reactions for molecules in the atmosphere. This provides further support to the existing thesis that reactions of organic compounds at the air-water interface should be considered in gas-phase tropospheric chemistry. PMID:20058916

  3. A portable automated system for trace gas sampling in the field and stable isotope analysis in the laboratory.

    PubMed

    Theis, Daniel E; Saurer, Matthias; Blum, Herbert; Frossard, Emmanuel; Siegwolf, Rolf T W

    2004-01-01

    A computer-controllable mobile system is presented which enables the automatic collection of 33 air samples in the field and the subsequent analysis for delta13C and delta18O stable isotope ratios of a carbon-containing trace gas in the laboratory, e.g. CO2, CO or CH4. The system includes a manifold gas source input for profile sampling and an infrared gas analyzer for in situ CO2 concentration measurements. Measurements of delta13C and delta18O of all 33 samples can run unattended and take less than six hours for CO2. Laboratory tests with three gases (compressed air with different pCO2 and stable isotope compositions) showed a measurement precision of 0.03 per thousand for delta13C and 0.02 per thousand for delta18O of CO2 (standard error (SE), n = 11). A field test of our system, in which 66 air samples were collected within a 24-hour period above grassland, showed a correlation of 0.99 (r2) between the inverse of pCO2 and delta13C of CO2. Storage of samples until analysis is possible for about 1 week; this can be an important factor for sampling in remote areas. A wider range of applications in the field is open with our system, since sampling and analysis of CO and CH4 for stable isotope composition is also possible. Samples of compressed air had a measurement precision (SE, n = 33) of 0.03 per thousand for delta13C and of 0.04 per thousand for delta18O on CO and of 0.07 per thousand for delta13C on CH4. Our system should therefore further facilitate research of trace gases in the context of the carbon cycle in the field, and opens many other possible applications with carbon- and possibly non-carbon-containing trace gases. PMID:15317047

  4. Batch methods for enriching trace impurities in hydrogen gas for their further analysis

    DOEpatents

    Ahmed, Shabbir; Lee, Sheldon H.D.; Kumar, Romesh; Papdias, Dionissios D.

    2014-07-15

    Provided herein are batch methods and devices for enriching trace quantities of impurities in gaseous mixtures, such as hydrogen fuel. The methods and devices rely on concentrating impurities using hydrogen transport membranes wherein the time period for concentrating the sample is calculated on the basis of optimized membrane characteristics, comprising its thickness and permeance, with optimization of temperature, and wherein the enrichment of trace impurities is proportional to the pressure ratio P.sub.hi/P.sub.lo and the volume ratio V.sub.1/V.sub.2, with following detection of the impurities using commonly-available detection methods.

  5. Coupled-Circulation-Chemistry Studies with the Finite-Volume CCM: Trace Gas Transport in the Tropopause Region

    NASA Technical Reports Server (NTRS)

    Pawson, Steven; Lin, Shian-Jiann; Rood, Richard B.; Nebuda, Sharon; Nielsen, J. Eric; Douglass, Anne R.

    2000-01-01

    A joint project between the Data Assimilation Office at NASA GSFC and NCAR involves linking the physical packages from the Community Climate Model (CCM) with the flux-form semi-Lagrangian dynamical core developed by Lin and Rood in the DAO. A further development of this model includes the implementation of a chemical package developed by Douglass and colleagues in the Atmospheric Chemistry and Dynamics Branch at NASA GSFC. Results from this coupled dynamics-radiation-chemistry model will be presented, focussing on trace gas transport in the tropopause region.

  6. A new multi-gas constrained model of trace gas non-homogeneous transport in firn: evaluation and behaviour at eleven polar sites

    NASA Astrophysics Data System (ADS)

    Witrant, E.; Martinerie, P.; Hogan, C.; Laube, J. C.; Kawamura, K.; Capron, E.; Montzka, S. A.; Dlugokencky, E. J.; Etheridge, D.; Blunier, T.; Sturges, W. T.

    2012-12-01

    Insoluble trace gases are trapped in polar ice at the firn-ice transition, at approximately 50 to 100 m below the surface, depending primarily on the site temperature and snow accumulation. Models of trace gas transport in polar firn are used to relate firn air and ice core records of trace gases to their atmospheric history. We propose a new model based on the following contributions. First, the firn air transport model is revised in a poromechanics framework with emphasis on the non-homogeneous properties and the treatment of gravitational settling. We then derive a nonlinear least square multi-gas optimisation scheme to calculate the effective firn diffusivity (automatic diffusivity tuning). The improvements gained by the multi-gas approach are investigated (up to ten gases for a single site are included in the optimisation process). We apply the model to four Arctic (Devon Island, NEEM, North GRIP, Summit) and seven Antarctic (DE08, Berkner Island, Siple Dome, Dronning Maud Land, South Pole, Dome C, Vostok) sites and calculate their respective depth-dependent diffusivity profiles. Among these different sites, a relationship is inferred between the snow accumulation rate and an increasing thickness of the lock-in zone defined from the isotopic composition of molecular nitrogen in firn air (denoted δ15N). It is associated with a reduced diffusivity value and an increased ratio of advective to diffusive flux in deep firn, which is particularly important at high accumulation rate sites. This has implications for the understanding of δ15N of N2 records in ice cores, in relation with past variations of the snow accumulation rate. As the snow accumulation rate is clearly a primary control on the thickness of the lock-in zone, our new approach that allows for the estimation of the lock-in zone width as a function of accumulation may lead to a better constraint on the age difference between the ice and entrapped gases.

  7. Tidal controls on trace gas dynamics in a seagrass meadow of the Ria Formosa lagoon (southern Portugal)

    NASA Astrophysics Data System (ADS)

    Bahlmann, E.; Weinberg, I.; Lavrič, J. V.; Eckhardt, T.; Michaelis, W.; Santos, R.; Seifert, R.

    2015-03-01

    Coastal zones are important source regions for a variety of trace gases, including halocarbons and sulfur-bearing species. While salt marshes, macroalgae and phytoplankton communities have been intensively studied, little is known about trace gas fluxes in seagrass meadows. Here we report results of a newly developed dynamic flux chamber system that can be deployed in intertidal areas over full tidal cycles allowing for highly time-resolved measurements. The fluxes of CO2, methane (CH4) and a range of volatile organic compounds (VOCs) showed a complex dynamic mediated by tide and light. In contrast to most previous studies, our data indicate significantly enhanced fluxes during tidal immersion relative to periods of air exposure. Short emission peaks occurred with onset of the feeder current at the sampling site. We suggest an overall strong effect of advective transport processes to explain the elevated fluxes during tidal immersion. Many emission estimates from tidally influenced coastal areas still rely on measurements carried out during low tide only. Hence, our results may have significant implications for budgeting trace gases in coastal areas. This dynamic flux chamber system provides intensive time series data of community respiration (at night) and net community production (during the day) of shallow coastal systems.

  8. Development of data processing, interpretation and analysis system for the remote sensing of trace atmospheric gas species

    NASA Technical Reports Server (NTRS)

    Casas, Joseph C.; Saylor, Mary S.; Kindle, Earl C.

    1987-01-01

    The major emphasis is on the advancement of remote sensing technology. In particular, the gas filter correlation radiometer (GFCR) technique was applied to the measurement of trace gas species, such as carbon monoxide (CO), from airborne and Earth orbiting platforms. Through a series of low altitude aircraft flights, high altitude aircraft flights, and orbiting space platform flights, data were collected and analyzed, culminating in the first global map of carbon monoxide concentration in the middle troposphere and stratosphere. The four major areas of this remote sensing program, known as the Measurement of Air Pollution from Satellites (MAPS) experiment, are: (1) data acquisition, (2) data processing, analysis, and interpretation algorithms, (3) data display techniques, and (4) information processing.

  9. Use of external cavity quantum cascade laser compliance voltage in real-time trace gas sensing of multiple chemicals

    NASA Astrophysics Data System (ADS)

    Phillips, Mark C.; Taubman, Matthew S.; Kriesel, Jason

    2015-01-01

    We describe a prototype trace gas sensor designed for real-time detection of multiple chemicals. The sensor uses an external cavity quantum cascade laser (ECQCL) swept over its tuning range of 940-1075 cm-1 (9.30-10.7 μm) at a 10 Hz repetition rate. The sensor was designed for operation in multiple modes, including gas sensing within a multi-pass Heriott cell and intracavity absorption sensing using the ECQCL compliance voltage. In addition, the ECQCL compliance voltage was used to reduce effects of long-term drifts in the ECQCL output power. The sensor was characterized for noise, drift, and detection of chemicals including ammonia, methanol, ethanol, isopropanol, Freon- 134a, Freon-152a, and diisopropyl methylphosphonate (DIMP). We also present use of the sensor for mobile detection of ammonia downwind of cattle facilities, in which concentrations were recorded at 1-s intervals.

  10. Tropospheric chemistry over the lower Great Plains of the United States. 2. Trace gas profiles and distributions

    NASA Astrophysics Data System (ADS)

    Luke, Winston T.; Dickerson, Russell R.; Ryan, William F.; Pickering, Kenneth E.; Nunnermacker, Linda J.

    1992-12-01

    Convective clouds and thunderstorms redistribute air pollutants vertically, and by altering the chemistry and radiative balance of the upper troposphere, these local actions can have global consequences. To study these effects, measurements of trace gases ozone, O3, carbon monoxide, CO, and odd nitrogen were made aboard the NCAR Sabreliner on 18 flights over the southern Great Plains during June 1985. To demonstrate chemical changes induced by vertical motions in the atmosphere and to facilitate comparison with computer model calculations, these data were categorized according to synoptic flow patterns. Part 1 of this two-part paper details the alternating pulses of polar and maritime air masses that dominate the vertical mixing in this region. In this paper, trace gas measurements are presented as altitude profiles (0-12 km) with statistical distributions of mixing ratios for each species in each flow pattern. The polar flow regime is characterized by northwesterly winds, subsiding air, and convective stability. Concentrations of CO and total odd nitrogen (NOy) are relatively high in the shallow planetary boundary layer (PBL) but decrease rapidly with altitude. Ozone, on the other hand, is uniformly distributed, suggesting limited photochemical production; in fact, nitric oxide, NO, mixing ratios fell below 10 ppt (parts per 1012 by volume) in the midtroposphere. The maritime regime is characterized by southerly surface winds, convective instability, and a deep PBL; uniformly high concentrations of trace gases were found up to 4 km on one flight. Severe storms occur in maritime flow, especially when capped by a dry layer, and they transport large amounts of CO, O3, and NOy into the upper troposphere. Median NO levels at high altitude exceeded 300 ppt. Lightning produces spikes of NO (but not CO) with mixing ratios sometimes exceeding 1000 ppt. This flow pattern tends to leave the midtroposphere relatively clean with concentrations of trace gases similar to those

  11. High Precision Soil and Atmospheric Trace Gas Stable Isotopic Measurements For Monitoring Sources and Fluxes of Co2

    NASA Astrophysics Data System (ADS)

    Mounier, L.; Davis, S.; Bilodeau, G.; Morrison, J.; Dudd, S. N.; Hillaire-Marcel, C.; Helie, J.-F.; Varfalvy, L.

    Reliable information relating to sources and sinks of CO2 is essential when moni- toring changes in atmospheric emissions, effects of emission reduction strategies and general carbon cycling within a given ecosystem. Studies of CO2 sampled from at- mospheric and soil gases often involve the analysis of large numbers of samples re- quiring high throughput, automated sample preparation and the ability to deal with trace amounts of analyte. The Micromass TraceGas (TM) inlet allows the analysis of CO2, N2O and CH4 in trace concentrations (ppb level and below). Volumes of less than 100 ml of ambient air can automatically be pre-concentrated, purified and ana- lyzed. We present the use of the TraceGas to investigate CO2 cycling in ecosystems, through the measurement of the isotopic signature of soil gases. Emissions of natural CO2 from an area of seasonal grassland in California are compared to a second plot where the majority of CO2 is derived from the addition of elevated quantities of bot- tled gas (manufactured from fossil fuel). Significant shifts in the isotopic signatures were observed between the two plots, thus demonstrating the ability of the technique to identify areas of pollution and anthropogenic influences. In addition, we present the outcome of a recent study monitoring 13CO2 in atmospheric low pCO2-samples over a hydro-electric reservoir in Quebec, Canada. In this case, the IsoPrime (TM) IRMS configured with the MultiFlow (TM) sample preparation system has been used to ob- tain 13C measurements in samples stored in 12cc Exetainer vials. The study assesses how various factors, such as climatic events, the proximity of riverine vegetation and inputs of dissolved organic carbon, influence the 13CUCO2 signature of the overlying air. Benefits of the system for the analysis of 13C in CO2 include full automation, and high sample throughput and capacity (~3 mins per sample; > 250 samples per day).

  12. The Influence of Hydrogen Bonding on Hydrogen-Atom Abstraction Reactions of Dehydropyridinium Cations in the Gas Phase

    PubMed Central

    Adeuya, Anthony; Nash, John J.; Kenttämaa, Hilkka I.

    2010-01-01

    The reactions of several substituted, positively-charged dehydropyridinium cations with cyclohexane, methanol and tetrahydrofuran have been examined in a Fourier-transform ion cyclotron resonance mass spectrometer. All of the charged monoradicals react with the neutral reagents exclusively via hydrogen atom abstraction. For cyclohexane, there is a good correlation between the reaction efficiencies and the calculated electron affinities at the radical sites; that is, the greater the electron affinity of the charged monoradical at the radical site, the faster the reaction. The reaction efficiencies with methanol and tetrahydrofuran, however, do not correlate with the calculated electron affinities. Density functional theory (DFT) calculations indicate that for these reagents a stabilizing hydrogen bonding interaction exists in the hydrogen atom abstraction transition states for some of the charged monoradicals but not for others. At both the MPW1K and G3MP2B3 levels of theory, there is a good correlation between the calculated activation enthalpies and the observed reaction efficiencies although the G3MP2B3 method provides a slightly better correlation than the MPW1K method. The extent of enhancement in the reaction efficiencies caused by the hydrogen bonding interactions parallels the calculated hydrogen bond lengths in the transition states. PMID:21080694

  13. Simultaneous removal of SO2 and trace SeO2 from flue gas: effect of product layer on mass transfer.

    PubMed

    Li, Yuzhong; Tong, Huiling; Zhuo, Yuqun; Chen, Changhe; Xu, Xuchang

    2006-07-01

    Sulfur dioxide (SO2) and trace elements are all pollutants derived from coal combustion. This study relates to the simultaneous removal of sulfur and trace selenium dioxide (SeO2) by calcium oxide (CaO) adsorption in the medium temperature range, especially the mass transfer effect of sulfate product layer on trace elements. Through experiments on CaO adsorbing different concentrations of SO2 gases, conclusions can be drawn that although the product layer introduces extra mass transfer resistance into the sorbent-gas reaction process, the extent of CaO adsorption ability loss due to this factor decreases with decreasing SO2 concentration. When the gas concentration is at trace level, the loss of CaO adsorption ability can be neglected. Subsequent experiments on CaO adsorbing trace SeO2 gas suggest that the sulfate product layer, whether it is thick or thin, has no obvious effect on the CaO ability to adsorb trace SeO2 gas. PMID:16856751

  14. Seasonal variation of trace gas compounds and PM2.5 observed at an urban supersite in Beijing

    NASA Astrophysics Data System (ADS)

    Wu, Yusheng; Hu, Min; Zeng, Limin; Dong, Huabin; Li, Xin; Lu, Keding; Lu, Sihua; Yang, Yudong; Zhang, Yuanhang

    2016-04-01

    The air pollution in Beijing has been a growing concern in the last ten years. We have performed measurements on trace gas compounds (CO, NOx, NOy, O3, SO2), PM2.5, and meteorological parameters at Beijing urban Atmospheric Environmental Observation Station in the campus of Peking University for more than ten years. The measurement results provide us an opportunity to track the air quality change in downtown Beijing. Here, we present observations during year between 2011 and 2015. The annual averaged concentration of CO, NOx, NOy, O3, SO2, and PM2.5 is 1.2 ± 0.1 ppm, 49.9 ± 5.9 ppb, 54.6 ± 4.7 ppb, 26.1 ± 3.8 ppb, 10.6 ± 2.9 ppb, and 53.4 ± 9.8 μg ṡm‑3, respectively. A clear seasonal variation is identified for all the measured trace gas compounds and PM2.5, CO, NOx, NOy, SO2, and PM2.5 show their maximum in winter and minimum in summer. Whilst O3 shows an inverse pattern. This result indicates that the air pollution in Beijing is characterized by haze in winter but by photochemical smog in summer. The effects of meteorological conditions and emissions on the occurrence of pollution episode are discussed in details based on the long-term observation data set.

  15. Performance Evaluation of a New, Tunable-Diode Laser Trace-Gas Analyzer for Isotope Ratios of Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Sargent, S.

    2015-12-01

    Newly available interband cascade lasers (ICLs) have enabled the development of a family of tunable-diode laser trace-gas analyzers that do not require liquid nitrogen to cool the laser. The lasers are available in the 3000 to 6000 nm range, providing access to the strong mid-infrared absorption lines for important gases such as methane, nitrous oxide, and carbon dioxide. These ICLs are fabricated with distributed feedback to improve their stability and spectroscopic quality. A recently released trace-gas analyzer for carbon dioxide isotopes (TGA200A, Campbell Scientific, Inc.) was evaluated for short- and long-term precision using Allan variance. Accuracy and linearity of CO2 mole fraction was assessed with a set of seven NOAA standard reference gases ranging from 298.35 to 971.48 ppm. Dilution of high-concentration CO2 with CO2-free air demonstrated the linearity of isotope ratio measurements beyond 1000 ppm CO2. Two analyzer variants were tested: one for CO2, δ13C and δ18O; and the other for CO2 and δ13C at enhanced precision.

  16. Chemical studies of H chondrites. I - Mobile trace elements and gas retention ages

    NASA Technical Reports Server (NTRS)

    Lingner, David W.; Huston, Ted J.; Hutson, Melinda; Lipschutz, Michael E.

    1987-01-01

    Trends for 16 trace elements (Ag, As, Au, Bi, Cd, Co, Cs, Ga, In, K, Rb, Sb, Se, Te, Tl, and Zn), chosen to span a broad geochemical and thermal response range, in 44 H4-6 chondrites, differ widely from those in L4-6 chondrites. In particular, H chondrites classified as heavily shocked petrologically do not necessarily exhibit Ar-40 loss and vice versa. The clear-cut causal relationship between siderophile and mobile element loss with increasing late shock seen in L chondrites is not generally evident in the H group. H chondrite parent material experienced an early high temperature genetic episode that mobilized a substantial proportion of these trace elements so that later thermal episodes resulted in more subtle, collateral fractionations. Mildly shocked L chondrites escaped this early high temperature event, indicating that the two most numerous meteorite groups differ fundamentally in genetic history.

  17. Spatial contrasts of seasonal and intraflock broiler litter trace gas emissions, physical and chemical properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Comprehensive mitigation strategies for gaseous emissions from broiler operations require knowledge of litter physical and chemical properties, gas evolution, bird effects as well as broiler house management and type of structure. This research estimated broiler litter surface gas flux for ammonia ...

  18. An Ultra-Trace Analysis Technique for SF6 Using Gas Chromatography with Negative Ion Chemical Ionization Mass Spectrometry.

    PubMed

    Jong, Edmund C; Macek, Paul V; Perera, Inoka E; Luxbacher, Kray D; McNair, Harold M

    2015-07-01

    Sulfur hexafluoride (SF6) is widely used as a tracer gas because of its detectability at low concentrations. This attribute of SF6 allows the quantification of both small-scale flows, such as leakage, and large-scale flows, such as atmospheric currents. SF6's high detection sensitivity also facilitates greater usage efficiency and lower operating cost for tracer deployments by reducing quantity requirements. The detectability of SF6 is produced by its high molecular electronegativity. This property provides a high potential for negative ion formation through electron capture thus naturally translating to selective detection using negative ion chemical ionization mass spectrometry (NCI-MS). This paper investigates the potential of using gas chromatography (GC) with NCI-MS for the detection of SF6. The experimental parameters for an ultra-trace SF6 detection method utilizing minimal customizations of the analytical instrument are detailed. A method for the detection of parts per trillion (ppt) level concentrations of SF6 for the purpose of underground ventilation tracer gas analysis was successfully developed in this study. The method utilized a Shimadzu gas chromatography with negative ion chemical ionization mass spectrometry system equipped with an Agilent J&W HP-porous layer open tubular column coated with an alumina oxide (Al2O3) S column. The method detection limit (MDL) analysis as defined by the Environmental Protection Agency of the tracer data showed the method MDL to be 5.2 ppt. PMID:25452581

  19. Soil trace gas emissions (CH4 and N2O) offset the CO2 uptake in poplar short rotation coppice

    NASA Astrophysics Data System (ADS)

    Zenone, Terenzio; Zona, Donatella; Gelfand, Iya; Gielen, Bert; camino serrano, Marta; Ceulemans, Reinhart

    2015-04-01

    The need for renewable energy sources will lead to a considerable expansion in the planting of dedicated fast-growing biomass crops across Europe. Among them poplar (Populus spp) is the most widely planted as short rotation coppice (SRC) and an increase in the surface area of large-scale SRC poplar plantations might thus be expected. In this study we report the greenhouse gas fluxes (GHG) of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) measured using the eddy covariance technique in a SRC plantation for bioenergy production during the period 2010-2013. The plantation was established in April 2010 on 18.4 ha of former agricultural land with a density of 8000 plants ha-1; the above-ground biomass was harvested on February 2012 and 2014.The whole GHG balance of the four years of the study was 1.90 (± 1.37) Mg CO2eq ha-1; this indicated that soil trace gas emissions offset the CO2 uptake by the plantation. CH4 and N2O almost equally contributed to offset the CO2 uptake of -5.28 (±0.67) Mg CO2eq ha-1 with an overall emission of 3.56 (± 0.35) Mg CO2eq ha-1 of N2O and of 3.53 (± 0.85) Mg CO2eq ha-1 of CH4. N2O emissions mostly occurred during a single peak a few months after the site was converted into SRC and represented 44% of the entire N2O loss during the entire study. Accurately capturing these emission events proved to be critical for correct estimates of the GHG balance. The self-organizing map (SOM) technique graphically showed the relationship between the CO2 fluxes and the principal environmental variables but failed to explain the variability of the soil trace gas emissions. The nitrogen content in the soil and the water table depth were the two drivers that best explained the variability in N2O and CH4 respectively. This study underlines the importance of the "non-CO2 GHG" on the overall balance as well as the impact of the harvest on the CO2 uptake rate. Further long-term investigations of soil trace gas emissions should also monitor the N

  20. Analysis of trace contaminants in hot gas streams using time-weighted average solid-phase microextraction: proof of concept.

    PubMed

    Woolcock, Patrick J; Koziel, Jacek A; Cai, Lingshuang; Johnston, Patrick A; Brown, Robert C

    2013-03-15

    Time-weighted average (TWA) passive sampling using solid-phase microextraction (SPME) and gas chromatography was investigated as a new method of collecting, identifying and quantifying contaminants in process gas streams. Unlike previous TWA-SPME techniques using the retracted fiber configuration (fiber within needle) to monitor ambient conditions or relatively stagnant gases, this method was developed for fast-moving process gas streams at temperatures approaching 300 °C. The goal was to develop a consistent and reliable method of analyzing low concentrations of contaminants in hot gas streams without performing time-consuming exhaustive extraction with a slipstream. This work in particular aims to quantify trace tar compounds found in a syngas stream generated from biomass gasification. This paper evaluates the concept of retracted SPME at high temperatures by testing the three essential requirements for TWA passive sampling: (1) zero-sink assumption, (2) consistent and reliable response by the sampling device to changing concentrations, and (3) equal concentrations in the bulk gas stream relative to the face of the fiber syringe opening. Results indicated the method can accurately predict gas stream concentrations at elevated temperatures. Evidence was also discovered to validate the existence of a second boundary layer within the fiber during the adsorption/absorption process. This limits the technique to operating within reasonable mass loadings and loading rates, established by appropriate sampling depths and times for concentrations of interest. A limit of quantification for the benzene model tar system was estimated at 0.02 g m(-3) (8 ppm) with a limit of detection of 0.5 mg m(-3) (200 ppb). Using the appropriate conditions, the technique was applied to a pilot-scale fluidized-bed gasifier to verify its feasibility. Results from this test were in good agreement with literature and prior pilot plant operation, indicating the new method can measure low

  1. Abstract Constructions.

    ERIC Educational Resources Information Center

    Pietropola, Anne

    1998-01-01

    Describes a lesson designed to culminate a year of eighth-grade art classes in which students explore elements of design and space by creating 3-D abstract constructions. Outlines the process of using foam board and markers to create various shapes and optical effects. (DSK)

  2. Trace organic compounds in rain—II. Gas scavenging of neutral organic compounds

    NASA Astrophysics Data System (ADS)

    Ligocki, Mary P.; Leuenberger, Christian; Pankow, James F.

    Concurrent rain and air sampling was conducted for seven rain events in Portland, Oregon during February through to April of 1984. Concentration data are presented for a number of neutral organic compounds for both the rain-dissolved phase and the atmospheric gas phase. The ambient temperature averaged 8°C. Measured gas scavenging ratios ranged from 3 for tetrachloroethene to 10 5 for dibutylphthalate, and were generally 3-6 times higher than those calculated from Henry's Law constant ( H) values at 25°C taken from the literature. This discrepancy was due to the inappropriateness of applying 25°C H data at 5-10°C. Indeed, excellent agreement between the measured and predicted gas scavenging ratios was found for several polycyclic aromatic hydrocarbons for which temperature-dependent H data were available. These results demonstrate that equilibrium between rain and the atmospheric gas phase is attained for non-reactive neutral organic compounds.

  3. Stratospheric aerosol and gas experiment III (SAGE III) aerosol and trace gas measurements for Earth Observing System (EOS)

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Chu, W. P.; Zawodny, J. M.; Mauldin, L. E.; Mcmaster, L. R.

    1991-01-01

    The SAGE III instrument, the latest in a series of satellite-based instruments employing the self-calibrating solar occultation technique to monitor aerosols and trace gases in the atmosphere, and potential contributions to monitoring global change and other EOS objectives are described. Uses of these data are illustrated with SAGE I and II long-term ozone, aerosol, and water vapor data. The SAGE III instrument will improve the SAM II and SAGE data products with greater overall accuracy, and will provide the ability to extend these measurements over a greater height range. SAGE III will provide long-term self-calibrating global data sets from the midtroposphere to mesosphere, which will contribute greatly to the quantification and understanding of global change.

  4. A new multi-gas constrained model of trace gas non-homogeneous transport in firn: evaluation and behavior at eleven polar sites

    NASA Astrophysics Data System (ADS)

    Witrant, E.; Martinerie, P.; Hogan, C.; Laube, J. C.; Kawamura, K.; Capron, E.; Montzka, S. A.; Dlugokencky, E. J.; Etheridge, D.; Blunier, T.; Sturges, W. T.

    2011-08-01

    Insoluble trace gases are trapped in polar ice at the firn-ice transition, at approximately 50 to 100 m below the surface, depending primarily on the site temperature and snow accumulation. Due to the different time scales for snow accumulation versus diffusion of gases through the snowpack, age differences between gases and the ice in which they are "trapped" can be large; e.g. several thousand years in central Antarctica (a low snow accumulation area). Models of trace gas diffusion in polar firn are used to relate firn air and ice core records of trace gases to their atmospheric history. We propose a new diffusion model based on the following contributions. First, the airflow transport model is revised in a poromechanics framework with specific emphasis on the non-homogeneous properties (convective layer, depth-dependent diffusivity and lock-in zone) and an almost-stagnant behavior described by Darcy's law (gravity effect). We then derive a non-linear least square multi-gas optimization scheme to calculate the effective firn diffusivity (automatic diffusivity tuning). The improvements associated with the additional constraints gained by the multi-gas approach are investigated (up to eleven gases for a single site are included in the optimization process). The model is applied to measured data from four Arctic (Devon Island, NEEM, North GRIP, Summit) and seven Antarctic (DE08, Berkner Island, Siple Dome, Dronning Maud Land, South Pole, Dome C, Vostok) sites and the depth-dependent diffusivity profiles are calculated. Among these different sites, a relationship between an increasing thickness of the lock-in zone defined from the isotopic composition of molecular nitrogen in firn air (denoted δ15N) and the snow accumulation rate is obtained, in accordance with observations. It is associated with reduced diffusivity depth-gradients in deep firn, which decreases gas density depth-gradients, at high accumulation rate sites. This has implications for the understanding

  5. Trace gas emissions from biomass burning inferred from aerosol optical depth

    NASA Astrophysics Data System (ADS)

    Paton-Walsh, Clare; Jones, Nicholas; Wilson, Stephen; Meier, Arndt; Deutscher, Nicholas; Griffith, David; Mitchell, Ross; Campbell, Susan

    2004-03-01

    We have observed strong correlations between simultaneous and co-located measurements of aerosol optical depth and column amounts of carbon monoxide, hydrogen cyanide, formaldehyde and ammonia in bushfire smoke plumes over SE Australia during the Austral summers of 2001/2002 and 2002/2003. We show how satellite-derived aerosol optical depth maps may be used in conjunction with these correlations to determine the total amounts of these gases present in a fire-affected region. This provides the basis of a method for estimating total emissions of trace gases from biomass burning episodes using visible radiances measured by satellites.

  6. The missing link: Tracing molecular gas in the outer filament of Centaurus A

    NASA Astrophysics Data System (ADS)

    Morganti, Raffaella; Oosterloo, Tom; Oonk, J. B. Raymond; Santoro, Francesco; Tadhunter, Clive

    2016-08-01

    We report the detection, using observations of the CO(2-1) line performed with the Atacama Pathfinder EXperiment (APEX), of molecular gas in the region of the outer filament of Centaurus A, a complex region known to show various signatures of an interaction between the radio jet, an H i cloud, and ionised gas filaments. We detect CO(2-1) at all observed locations, which were selected to represent regions with very different physical conditions. The H2 masses of the detections range between 0.2 × 106 and 1.1 × 106M⊙, for conservative choices of the CO to H2 conversion factor. Surprisingly, the stronger detections are not coincident with the H i cloud, but instead are in the region of the ionised filaments. We also find variations in the widths of the CO(2-1) lines throughout the region, with broader lines in the region of the ionised gas, i.e. where the jet-cloud interaction is strongest, and with narrow profiles in the H i cloud. This may indicate that the molecular gas in the region of the ionised gas has the momentum of the jet-cloud interaction encoded in it, in the same way as the ionised gas does. These molecular clouds may therefore be the result of very efficient cooling of the down-stream gas photo- or shock-ionised by the interaction. On the other hand, the molecular clouds with narrower profiles, which are closer to or inside the H i cloud, could be pre-existing cold H2 cores which manage to survive the effects of the passing jet.

  7. Long-term trends in global trace gas emissions: CH4, ethane, propane, ethyne, C2Cl4, CHCl3

    NASA Astrophysics Data System (ADS)

    Simpson, I. J.; Meinardi, S.; Sulbaek Andersen, M.; Blake, N. J.; Rowland, F. S.; Blake, D. R.

    2011-12-01

    The University of California, Irvine (UC-Irvine) has monitored global atmospheric trace gas mixing ratios since 1978 using ground-based canister measurements in the remote Pacific basin (71N to 47S). The measured gases include methane (CH4), C2-C4 alkanes, ethyne, C1-C3 alkyl nitrates, CFCs, CH3CCl3, CCl4 and H-1211. Long-term records of several of these gases are unique to the UC-Irvine global monitoring network, and here we present our research highlights and inferred global trace gas emission trends. Despite a long-term decline in its global growth rate, the global CH4 mixing ratio has increased by 9% over the past 25 years, from 1647.7 ± 0.6 ppbv in 1985 to 1792.4 ± 0.7 ppbv in 2010, representing a global emission increase of ~48 Tg yr-1 assuming constant global OH levels. Over the same time, the global mixing ratio of ethane has declined by 21%, from 791 ± 19 pptv in 1986 to 625 ± 12 pptv in 2010, or a global emission decrease of ~3.4 Tg yr-1. The global trends of CH4 growth and ethane mixing ratio have shown a remarkably strong correlation in the past 25 years. The long-term global ethane decline has also been accompanied by simultaneous decreases in global levels of propane and the butanes since 1996. This is consistent with a long-term change in a source common to all four compounds, likely a decline in evaporative emissions from the oil and natural gas industry. The combustion tracer ethyne has also shown an 11% decline between 1996 and 2008, most likely related to improved controls on vehicle emissions despite an expanding global vehicle fleet. Global levels of the anthropogenic tracer and CFC-113 precursor tetrachloroethene (C2Cl4) have declined by 60% since 1989, to 2.5 ± 0.2 pptv (or 185 Gg yr-1) in 2009 (Fig. 1). In contrast, global levels of the industrial solvent chloroform (CHCl3) have increased by almost 20% since the late 1990s, from 9.0 ± 0.3 pptv in 1997 to 10.7 ± 0.4 pptv in 2008 (Fig. 1). These results highlight major temporal shifts

  8. Aerosol, Cloud and Trace Gas Observations Derived from Airborne Hyperspectral Radiance and Direct Beam Measurements in Recent Field Campaigns

    NASA Technical Reports Server (NTRS)

    Redemann, J.; Flynn, C. J.; Shinozuka, Y.; Kacenelenbogen, M.; Segal-Rosenheimer, M.; LeBlanc, S.; Russell, P. B.; Livingston, J. M.; Schmid, B.; Dunagan, S. E.; Johnson, R. R.

    2014-01-01

    The AERONET (AErosol RObotic NETwork) ground-based suite of sunphotometers provides measurements of spectral aerosol optical depth (AOD), precipitable water and spectral sky radiance, which can be inverted to retrieve aerosol microphysical properties that are critical to assessments of aerosol-climate interactions. Because of data quality criteria and sampling constraints, there are significant limitations to the temporal and spatial coverage of AERONET data and their representativeness for global aerosol conditions. The 4STAR (Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research) instrument, jointly developed by NASA Ames and PNNL with NASA Goddard collaboration, combines airborne sun tracking and AERONET-like sky scanning with spectroscopic detection. Being an airborne instrument, 4STAR has the potential to fill gaps in the AERONET data set. Dunagan et al. [2013] present results establishing the performance of the instrument, along with calibration, engineering flight test, and preliminary scientific field data. The 4STAR instrument operated successfully in the SEAC4RS [Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys] experiment in Aug./Sep. 2013 aboard the NASA DC-8 and in the DoE [Department of Energy]-sponsored TCAP [Two Column Aerosol Project, July 2012 & Feb. 2013] experiment aboard the DoE G-1 aircraft (Shinozuka et al., 2013), and acquired a wealth of data in support of mission objectives on all SEAC4RS and TCAP research flights. 4STAR provided direct beam measurements of hyperspectral AOD, columnar trace gas retrievals (H2O, O3, NO2; Segal-Rosenheimer et al., 2014), and the first ever airborne hyperspectral sky radiance scans, which can be inverted to yield the same products as AERONET ground-based observations. In addition, 4STAR measured zenith radiances underneath cloud decks for retrievals of cloud optical depth and effective diameter. In this presentation, we provide an overview of the new

  9. Interpretation of Trace Gas Data Using Inverse Methods and Global Chemical Transport Models

    NASA Technical Reports Server (NTRS)

    Prinn, Ronald G.

    1997-01-01

    This is a theoretical research project aimed at: (1) development, testing, and refining of inverse methods for determining regional and global transient source and sink strengths for long lived gases important in ozone depletion and climate forcing, (2) utilization of inverse methods to determine these source/sink strengths which use the NCAR/Boulder CCM2-T42 3-D model and a global 3-D Model for Atmospheric Transport and Chemistry (MATCH) which is based on analyzed observed wind fields (developed in collaboration by MIT and NCAR/Boulder), (3) determination of global (and perhaps regional) average hydroxyl radical concentrations using inverse methods with multiple titrating gases, and, (4) computation of the lifetimes and spatially resolved destruction rates of trace gases using 3-D models. Important goals include determination of regional source strengths of methane, nitrous oxide, and other climatically and chemically important biogenic trace gases and also of halocarbons restricted by the Montreal Protocol and its follow-on agreements and hydrohalocarbons used as alternatives to the restricted halocarbons.

  10. Studies of Trace Gas Chemical Cycles Using Inverse Methods and Global Chemical Transport Models

    NASA Technical Reports Server (NTRS)

    Prinn, Ronald G.

    2003-01-01

    We report progress in the first year, and summarize proposed work for the second year of the three-year dynamical-chemical modeling project devoted to: (a) development, testing, and refining of inverse methods for determining regional and global transient source and sink strengths for long lived gases important in ozone depletion and climate forcing, (b) utilization of inverse methods to determine these source/sink strengths using either MATCH (Model for Atmospheric Transport and Chemistry) which is based on analyzed observed wind fields or back-trajectories computed from these wind fields, (c) determination of global (and perhaps regional) average hydroxyl radical concentrations using inverse methods with multiple titrating gases, and (d) computation of the lifetimes and spatially resolved destruction rates of trace gases using 3D models. Important goals include determination of regional source strengths of methane, nitrous oxide, methyl bromide, and other climatically and chemically important biogenic/anthropogenic trace gases and also of halocarbons restricted by the Montreal protocol and its follow-on agreements and hydrohalocarbons now used as alternatives to the restricted halocarbons.

  11. Trace gas and particle emissions from open biomass burning in Mexico

    NASA Astrophysics Data System (ADS)

    Yokelson, R. J.; Burling, I. R.; Urbanski, S. P.; Atlas, E. L.; Adachi, K.; Buseck, P. R.; Wiedinmyer, C.; Akagi, S. K.; Toohey, D. W.; Wold, C. E.

    2011-03-01

    We report airborne measurements of emission factors (EF) for trace gases and PM2.5 made in southern Mexico in March of 2006 on 6 crop residue fires, 3 tropical dry forest fires, 8 savanna fires, 1 garbage fire, and 7 mountain pine-oak forest fires. The savanna fire EF were measured early in the local dry season and when compared to EF measured late in the African dry season they were at least 1.7 times larger for NOx, NH3, H2, and most non-methane organic compounds. Our measurements suggest that urban deposition and high windspeed may also be associated with significantly elevated NOx EF. When considering all fires sampled, the percentage of particles containing soot increased from 15 to 60% as the modified combustion efficiency increased from 0.88 to 0.98. We estimate that about 175 Tg of fuel was consumed by open burning of biomass and garbage and as biofuel (mainly wood cooking fires) in Mexico in 2006. Combining the fuel consumption estimates with our EF measurements suggests that the above combustion sources account for a large fraction of the reactive trace gases and more than 90% of the total primary, fine carbonaceous particles emitted by all combustion sources in Mexico.

  12. Trace gas and particle emissions from open biomass burning in Mexico

    NASA Astrophysics Data System (ADS)

    Yokelson, R. J.; Burling, I. R.; Urbanski, S. P.; Atlas, E. L.; Adachi, K.; Buseck, P. R.; Wiedinmyer, C.; Akagi, S. K.; Toohey, D. W.; Wold, C. E.

    2011-07-01

    We report airborne measurements of emission factors (EF) for trace gases and PM2.5 made in southern Mexico in March of 2006 on 6 crop residue fires, 3 tropical dry forest fires, 8 savanna fires, 1 garbage fire, and 7 mountain pine-oak forest fires. The savanna fire EF were measured early in the local dry season and when compared to EF measured late in the African dry season they were at least 1.7 times larger for NOx, NH3, H2, and most non-methane organic compounds. Our measurements suggest that urban deposition and high windspeed may also be associated with significantly elevated NOx EF. When considering all fires sampled, the percentage of particles containing soot increased from 15 to 60 % as the modified combustion efficiency increased from 0.88 to 0.98. We estimate that about 175 Tg of fuel was consumed by open burning of biomass and garbage and as biofuel (mainly wood cooking fires) in Mexico in 2006. Combining the fuel consumption estimates with our EF measurements suggests that the above combustion sources account for a large fraction of the reactive trace gases and more than 90 % of the total primary, fine carbonaceous particles emitted by all combustion sources in Mexico.

  13. Characterizing the gas phase ion chemistry of an ion trap mobility spectrometry based explosive trace detector using a tandem mass spectrometer.

    PubMed

    Kozole, Joseph; Tomlinson-Phillips, Jill; Stairs, Jason R; Harper, Jason D; Lukow, Stefan R; Lareau, Richard T; Boudries, Hacene; Lai, Hanh; Brauer, Carolyn S

    2012-09-15

    A commercial-off-the-shelf (COTS) ion trap mobility spectrometry (ITMS) based explosive trace detector (ETD) has been interfaced to a triple quadrupole mass spectrometer (MS/MS) for the purpose of characterizing the gas phase ion chemistry intrinsic to the ITMS instrument. The overall objective of the research is to develop a fundamental understanding of the gas phase ionization processes in the ITMS based ETD to facilitate the advancement of its operational effectiveness as well as guide the development of next generation ETDs. Product ion masses, daughter ion masses, and reduced mobility values measured by the ITMS/MS/MS configuration for a suite of nitro, nitrate, and peroxide containing explosives are reported. Molecular formulas, molecular structures, and ionization pathways for the various product ions are inferred using the mass and mobility data in conjunction with density functional theory. The predominant product ions are identified as follows: [TNT-H](-) for trinitrotoluene (TNT), [RDX+Cl](-) for cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), [NO(3)](-) for ethylene glycol dinitrate (EGDN), [NG+NO(3)](-) for nitroglycerine (NG), [PETN+NO(3)](-) for pentaerythritol tetranitrate (PETN), [HNO(3)+NO(3)](-) for ammonium nitrate (NH(4)NO(3)), [HMTD-NC(3)H(6)O(3)+H+Cl](-) for hexamethylene triperoxide diamine (HMTD), and [(CH(3))(2)CNH(2)](+) for triacetone triperoxide (TATP). The predominant ionization pathways for the formation of the various product ions are determined to include proton abstraction, ion-molecule attachment, autoionization, first-order and multi-order thermolysis, and nucleophilic substitution. The ion trapping scheme in the reaction region of the ITMS instrument is shown to increase predominant ion intensities relative to the secondary ion intensities when compared to non-ion trap operation. PMID:22967626

  14. Tracing Gas and Particle Phase Oxidation From Engine Sources as a Function of Fuel Type, Load, and Photochemical Age

    NASA Astrophysics Data System (ADS)

    Friedman, B.; Farmer, D.; Jathar, S.; Galang, A.; Fulgham, R.; Link, M.; Brophy, P.

    2015-12-01

    Motor vehicle emissions are an important source of anthropogenic gases and particles in the atmosphere. To study the gas and particle phase emissions, an HR-TOF-AMS and HR-TOF-CIMS were deployed at the CSU Engines Lab, along with an oxidative flow reactor, to measure emissions from a 4.5 L John Deere engine, which ran either diesel or biodiesel fuel. Concurrent gas-phase and particle-phase measurements allowed determination of the gas-phase and particle-phase oxidation properties as a function of fuel type, fuel load, and photochemical age. The impacts of particulate filers on composition and oxidation state were also assessed. While aerosol composition and associated oxidation properties for the biodiesel and diesel fuel types were similar, differences in photochemical production existed for the amount of load, or efficiency of the engine. The mean particulate oxygen to carbon ratios (O:C) and mean hydrogen to carbon ratios (H:C) moved from an initial 0.1 and 2 to a final 0.55 and 1.6, respectively, upon idle biodiesel and diesel engine exhaust exposure to approximately 7 days of OH exposure. The more efficient higher load biodiesel and diesel engine exhaust experienced less changes in the mean O:C and H:C values (an initial 0.1 and 2 to a final 0.3 and 1.7, respectively) with approximately the same amount of OH exposure. Despite largely scrubbing the majority of particles from the engine exhaust, experiments with engine particulate filters still showed photochemical production of oxidized particle-phase species at high photochemical ages, similar to that of idle engine exhaust without any particulate filters. Bulk gas-phase data was compared to bulk aerosol data in Van Krevelen space in order to understand how particle-phase oxidation traces gas-phase oxidation as a function of fuel type, engine load, and photochemical age.

  15. Development of a tunable mid-IR difference frequency laser source for highly sensitive airborne trace gas detection

    NASA Astrophysics Data System (ADS)

    Richter, D.; Fried, A.; Wert, B. P.; Walega, J. G.; Tittel, F. K.

    The development of a compact tunable mid-IR laser system at 3.5 μm for quantitative airborne spectroscopic trace gas absorption measurements is reported. The mid-IR laser system is based on difference frequency generation (DFG) in periodically poled LiNbO3 and utilizes optical fiber amplified near-IR diode and fiber lasers as pump sources operating at 1083 nm and 1562 nm, respectively. This paper describes the optical sensor architecture, performance characteristics of individual pump lasers and DFG, as well as its application to wavelength modulation spectroscopy employing an astigmatic Herriott multi-pass gas absorption cell. This compact system permits detection of formaldehyde with a minimal detectable concentration (1σ replicate precision) of 74 parts-per-trillion by volume (pptv) for 1 min of averaging time and was achieved using calibrated gas standards, zero air background and rapid dual-beam subtraction. This corresponds to a pathlength-normalized replicate fractional absorption sensitivity of 2.5×10-10 cm-1.

  16. 3C28 in Abell 115- A Radio Source With a Twist: Tracing Gas Vortices in a Merging Subcluster Core

    NASA Astrophysics Data System (ADS)

    Forman, William R.; Jones, Christine; Churazov, Eugene

    2014-08-01

    Abell 115 is one of the “bimodal” clusters, first identified from Einstein Observatory X-ray images. The X-ray image is dominated by emission from two subclusters, separated by about 900 kpc, that are in the process of merging. The northern subcluster (A115-N) contains a bright central galaxy that hosts the radio source 3C28. 3C28 has a remarkable morphology. Although there is no evidence of a presently active nucleus, there are two prominent jets connected to a pair of radio lobes, each of which exhibits a radio tail. A115-N shows a classic cold front, the remarkable phenomenon first studied from Chandra cluster observations. We describe the overall structure of the cluster from detailed Chandra observations. We review the gravitational lensing observations and radio observations of the relic and discuss the overall state of the cluster merger. In addition, we exploit the Chandra data and the cold front phenomenon to study the gas motions in and around A115-N that hosts 3C28. The subcluster motion of A115-N through the cluster induces counter-rotating vortices in the subcluster gas that give rise to the unique radio morphology of 3C28 with its two radio tails pointing in the direction of motion of A115-N. Thus, the radio emitting plasma acts as a dye in a fluid tracing the vortices in the X-ray emitting gas, resembling text book pictures of fluid motions.

  17. 3C28 in Abell 115- A Radio Source With a Twist: Tracing Gas Vortices in a Merging Subcluster Core

    NASA Astrophysics Data System (ADS)

    Forman, William R.; Churazov, Eugene; Heinz, Sebastian; Giacintucci, Simona; Jones, Christine; Bogdan, Akos; David, Laurence P; Kraft, Ralph P.; Murgia, Matteo; Markevitch, Maxim L.; Randall, Scott W.; Van Weeren, Reinout J.; Vikhlinin, Alexey

    2014-06-01

    Abell 115 is one of the “bimodal” clusters, first identified from Einstein Observatory X-ray images. The X-ray image is dominated by emission from two subclusters, separated by about 900 kpc, that are in the process of merging. The northern subcluster (A115-N) contains a bright central galaxy that hosts the radio source 3C28. 3C28 has a remarkable morphology. Although there is no evidence of a presently active nucleus, there are two prominent jets connected to a pair of radio lobes, each of which exhibits a radio tail. A115-N shows a classic cold front, the remarkable phenomenon first studied from Chandra cluster observations. We describe the overall structure of the cluster from detailed Chandra obserations. In addition, we exploit the Chandra data and the cold front phenomenon to study the gas motions in and around A115-N that hosts 3C28. The subcluster motion of A115-N through the cluster induces counter-rotating vortices in the subcluster gas that give rise to the unique radio morphology of 3C28 with its two radio tails pointing in the direction of motion of A115-N. Thus, the radio emitting plasma acts as a dye in a fluid tracing the vortices in the X-ray emitting gas, resembling text book pictures of fluid motions.

  18. Development of a tunable mid-IR difference frequency laser source for highly sensitive airborne trace gas detection.

    PubMed

    Richter, D; Fried, A; Wert, B P; Walega, J G; Tittel, F K

    2002-01-01

    The development of a compact tunable mid-IR laser system at 3.5 micrometers for quantitative airborne spectroscopic trace gas absorption measurements is reported. The mid-IR laser system is based on difference frequency generation (DFG) in periodically poled LiNbO3 and utilizes optical fiber amplified near-IR diode and fiber lasers as pump sources operating at 1083 nm and 1562 nm, respectively. This paper describes the optical sensor architecture, performance characteristics of individual pump lasers and DFG, as well as its application to wavelength modulation spectroscopy employing an astigmatic Herriott multi-pass gas absorption cell. This compact system permits detection of formaldehyde with a minimal detectable concentration (1 sigma replicate precision) of 74 parts-per-trillion by volume (pptv) for 1 min of averaging time and was achieved using calibrated gas standards, zero air background and rapid dual-beam subtraction. This corresponds to a pathlength-normalized replicate fractional absorption sensitivity of 2.5 x 10-(10 )cm-1. PMID:12599397

  19. A mass balance method for non-intrusive measurements of surface-air trace gas exchange

    NASA Astrophysics Data System (ADS)

    Denmead, O. T.; Harper, L. A.; Freney, J. R.; Griffith, D. W. T.; Leuning, R.; Sharpe, R. R.

    A mass balance method is described for calculating gas production from a surface or volume source in a small test plot from measurements of differences in the horizontal fluxes of the gas across upwind and downwind boundaries. It employs a square plot, 24 m×24 m, with measurements of gas concentration at four heights (up to 3.5 m) along each of the four boundaries. Gas concentrations are multiplied by the appropriate vector winds to yield the horizontal fluxes at each height on each boundary. The difference between these fluxes integrated over downwind and upwind boundaries represents production. Illustrations of the method, which involve exchanges of methane and carbon dioxide, are drawn from experiments with landfills, pastures and grazing animals. Tests included calculation of recovery rates from known gas releases and comparisons with a conventional micrometeorological approach and a backward dispersion model. The method performed satisfactorily in all cases. Its sensitivity for measuring exchanges of CO 2, CH 4 and N 2O in various scenarios was examined. As employed by us, the mass balance method can suffer from errors arising from the large number of gas analyses required for a flux determination, and becomes unreliable when there are light winds and variable wind directions. On the other hand, it is non-disturbing, has a simple theoretical basis, is independent of atmospheric stability or the shape of the wind profile, and is appropriate for flux measurement in situations where conventional micrometeorological methods can not be used, e.g. for small plots, elevated point sources, and heterogeneous surface sources.

  20. Compact TDLAS based sensor design using interband cascade lasers for mid-IR trace gas sensing.

    PubMed

    Dong, Lei; Tittel, Frank K; Li, Chunguang; Sanchez, Nancy P; Wu, Hongpeng; Zheng, Chuantao; Yu, Yajun; Sampaolo, Angelo; Griffin, Robert J

    2016-03-21

    Two compact TDLAS sensor systems based on different structural optical cores were developed. The two optical cores combine two recent developments, gallium antimonide (GaSb)-based ICL and a compact multipass gas cell (MPGC) with the goal to create compact TDLAS based sensors for the mid-IR gas detection with high detection sensitivity and low power consumption. The sensors achieved minimum detection limits of ~5 ppbv and ~8 ppbv, respectively, for CH4 and C2H6 concentration measurements with a 3.7-W power consumption. PMID:27136873

  1. [A trace gas sensor using mid-infrared quantum cascaded laser at 4.8 microm to detect carbon monoxide].

    PubMed

    Chen, Chen; Wang, Biao; Li, Chun-Guang; Li, Jian; Wang, Yi-Ding

    2014-03-01

    Presented in the present paper is a compact instrument developed for rapid, sensitive and continuous monitoring of trace gases in air, with results shown for carbon monoxide concentration. This instrument takes advantage of recent technology in mid-infrared quantum cascaded laser (QCL) operating at 4.8 microm and mercury cadmium telluride (HgCdTe) mid-infrared (MIR) detector, combing MIR multipass herriott cell with 76 m absorption path length to obtain low detection sensitivity down to 50 nmol x mol(-1) level in 4 s acquisition time. Meanwhile, in order to eliminate the instability induced by electrically modulated light source and effectively improve detection limit of the instrument, an optical structure with dual channel path was designed which is based on differential optical absorption spectroscopy method. The experimental results show that the instrument integrated with gas concentration inversion algorithm can be applied to in-situ measurements of trace gases without calibration. Additionally, operator could substitute a QCL operating at a different wavelength to measure other gases. PMID:25208424

  2. Measurement of gas/water uptake coefficients for trace gases active in the marine environment. [Annual report

    SciTech Connect

    Davidovits, P.; Worsnop, D.W.; Zahniser, M.S.; Kolb, C.E.

    1992-02-01

    Ocean produced reduced sulfur compounds including dimethylsulfide (DMS), hydrogen sulfide (H{sub 2}S), carbon disulfide (CS{sub 2}), methyl mercaptan (CH{sub 3}CH) and carbonyl sulfide (OCS) deliver a sulfur burden to the atmosphere which is roughly equal to sulfur oxides produced by fossil fuel combustion. These species and their oxidation products dimethyl sulfoxide (DMSO), dimethyl sulfone (DMSO{sub 2}) and methane sulfonic acid (MSA) dominate aerosol and CCN production in clean marine air. Furthermore, oxidation of reduced sulfur species will be strongly influenced by NO{sub x}/O{sub 3} chemistry in marine atmospheres. The multiphase chemical processes for these species must be understood in order to study the evolving role of combustion produced sulfur oxides over the oceans. We have measured the chemical and physical parameters affecting the uptake of reduced sulfur compounds, their oxidation products, ozone, and nitrogen oxides by the ocean`s surface, and marine clouds, fogs, and aerosols. These parameters include: gas/surface mass accommodation coefficients; physical and chemically modified (effective) Henry`s law constants; and surface and liquid phase reaction constants. These parameters are critical to understanding both the interaction of gaseous trace species with cloud and fog droplets and the deposition of trace gaseous species to dew covered, fresh water and marine surfaces.

  3. Trace analysis of explosives in seawater using solid-phase microextraction and gas chromatography/ion trap mass spectrometry

    SciTech Connect

    Barshick, S.A.; Griest, W.H.

    1998-07-15

    Complex matrices typically cannot be analyzed directly to obtain the selectivity and sensitivity required for most trace analysis applications. To circumvent this problem, solid-phase microextraction (SPME) techniques were used to preconcentrate analytes selectively prior to gas chromatographic/ion trap mass spectrometric analysis. This approach was applied to the trace analysis of explosives and their metabolites in seawater. The choice of SPME sorbent phase was shown to be important especially for the amino metabolites of trinitrotoluene (TNT) and RDX, which were extracted better on polar phases. Although equilibration times were quite lengthy, on the order of 30 min or greater, a sampling time of only 10 min was shown to be sufficient for achieving low part-per-billion (ppb) to part-per-trillion (ppt) detection limits for TNT and the amino metabolites in real seawater samples. While SPME was ideal for rapid screening of explosives in seawater samples, methods for improving the reproducibility and accuracy of quantification are still being investigated.

  4. Real-time trace gas sensor using a multimode diode laser and multiple-line integrated cavity enhanced absorption spectroscopy.

    PubMed

    Karpf, Andreas; Rao, Gottipaty N

    2015-07-01

    We describe and demonstrate a highly sensitive trace gas sensor based on a simplified design that is capable of measuring sub-ppb concentrations of NO2 in tens of milliseconds. The sensor makes use of a relatively inexpensive Fabry-Perot diode laser to conduct off-axis cavity enhanced spectroscopy. The broad frequency range of a multimode Fabry-Perot diode laser spans a large number of absorption lines, thereby removing the need for a single-frequency tunable laser source. The use of cavity enhanced absorption spectroscopy enhances the sensitivity of the sensor by providing a pathlength on the order of 1 km in a small volume. Off-axis alignment excites a large number of cavity modes simultaneously, thereby reducing the sensor's susceptibility to vibration. Multiple-line integrated absorption spectroscopy (where one integrates the absorption spectra over a large number of rovibronic transitions of the molecular species) further improves the sensitivity of detection. Relatively high laser power (∼400  mW) is used to compensate for the low coupling efficiency of a broad linewidth laser to the optical cavity. The approach was demonstrated using a 407 nm diode laser to detect trace quantities of NO2 in zero air. Sensitivities of 750 ppt, 110 ppt, and 65 ppt were achieved using integration times of 50 ms, 5 s, and 20 s respectively. PMID:26193156

  5. Trace-Rare-Gas Optical Emission Spectroscopy of Nitrogen Plasma Generated at a Frequency of 13.56 MHz

    NASA Astrophysics Data System (ADS)

    U. Rehman, N.; U. Khan, F.; Naseer, S.; Murtaza, G.; S. Hussain, S.; I., Ahmad; Zakaullah, M.

    2011-04-01

    Optical emission spectroscopic measurement of trace rare gas is carried out to determine the density of nitrogen (N) atom, in a nitrogen plasma, as a function of filling pressure and RF power applied. 2% of argon, used as an actinometer, is mixed with nitrogen. In order to normalize the changes in the excitation cross section and electron energy distribution function at different operational conditions, the Ar-I emission line at 419.83 nm is used, which is of nearly the same excitation efficiency coefficient as that of the nitrogen emission line at 493.51 nm. It is observed that the emission intensity of the selected argon and atomic nitrogen lines increases with both pressure and RF power, as does the nitrogen atomic density.

  6. Development, Application, and Transition of Aerosol and Trace Gas Products Derived from Next-Generation Satellite Observations to Operations

    NASA Technical Reports Server (NTRS)

    Berndt, Emily; Naeger, Aaron; Zavodsky, Bradley; McGrath, Kevin; LaFontaine, Frank

    2016-01-01

    NASA Short-term Prediction Research and Transition (SPoRT) Center has a history of successfully transitioning unique observations and research capabilities to the operational weather community to improve short-term forecasts. SPoRTstrives to bridge the gap between research and operations by maintaining interactive partnerships with end users to develop products that match specific forecast challenges, provide training, and assess the products in the operational environment. This presentation focuses on recent product development, application, and transition of aerosol and trace gas products to operations for specific forecasting applications. Recent activities relating to the SPoRT ozone products, aerosol optical depth composite product, sulfur dioxide, and aerosol index products are discussed.

  7. Operation of a cw rf driven ion source with hydrogen and deuterium gas (abstract){sup a}

    SciTech Connect

    Melnychuk, S.T.; Debiak, T.W.; Sredniawski, J.J.

    1996-03-01

    We will describe the operation of a cw rf driven multicusp ion source designed for extraction of high current hydrogen and deuterium beams. The source is driven at 2 MHz by a 2.5 turn induction antenna immersed in the plasma. Bare stainless-steel and porcelain-coated Cu antennas have been used. The plasma load is matched to the rf generator by a variable tap {ital N}:1 transformer isolated to 46 kV, and an LC network on the secondary. With H{sub 2} gas the source can be operated at pressures between 5 and 60 mT with power reflection coefficients {lt}0.01. The extracted ion current density with a porcelain-coated antenna is approximately given by 35 mA/cm{sup 2}/kW with an 80 G dipole filter field for input powers from 3.5 to 6.6 kW. The current density remained constant for operation with a 6 and an 8 mm aperture. The source has been operated for 260 h at 3.6 kW with a single-porcelain-coated antenna. Mass spectrometer measurements of the extracted beam at this power show a species mix for H{sup +}:H{sup +}{sub 2}:H{sup +}{sub 3}:OH{sup +} of 0.49: 0.04: 0.42: 0.04. The calculated beam divergence using the IGUN code is compared with the measured divergence from an electrostatic sweep emittance scanner designed for high-power cw beam diagnostics. Phase space measurements at 40 kV and 23 mA beam current result in a normalized rms emittance of 0.09 {pi}mmmrad. {copyright} {ital 1996 American Institute of Physics.}

  8. Investigation of 2D-Trace Gas Field Reconstruction Techniques From Tomographic AMAX-DOAS Measurements

    NASA Astrophysics Data System (ADS)

    Laepple, T.; Heue, K.; Friedeburg, C. V.; Wang, P.; Knab, V.; Pundt, I.

    2002-12-01

    Tomographic-Differential-Optical-Absorption-Spectroscopy (Tom-DOAS) is a new application of the DOAS method designed to measure 2-3-dimensional concentration fields of different trace gases (e.g. NO2, HCHO, Ozone) in the troposphere. Numerical reconstruction techniques are used to obtain spatially resolved data from the slant column densities provided by DOAS instruments. We discuss the detection of emission plumes by AMAX (Airborne Multi AXis) DOAS Systems which measure sunlight by telescopes pointing in different directions. 2D distributions are reconstructed from slant columns by using airmass factor matrices and inversion techniques. We discuss possibilities and limitations of this technique gained with the use of simulated test fields. Therefore the effect of the parameter choice (e.g. flight track, algorithm changes) and measurement errors is investigated. Further, first results from the Partenavia aircraft measurements over Milano (Italy) during the European FORMAT campaign will be presented.

  9. Trace Gas Transport in the Arctic Vortex Inferred from ATMOS ATLAS-2 Observations During April 1993

    NASA Technical Reports Server (NTRS)

    Abrams, M. C.; Manney, G. L.; Gunson, M. R.; Abbas, M. M.; Chang, A. Y.; Goldman, A.; Irion, F. W.; Michelsen, H. A.; Newchurch, M. J.; Rinsland, C, P,; Salawitch, R. J.; Stiller, G. P.; Zander, R.

    1996-01-01

    Measurements of the long-lived tracers CH4, N2O, and HF from the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument during the Atmospheric Laboratory for Science and Applications-2 (ATLAS-2) Space Shuttle mission in April 1993 are used to infer average winter descent rates ranging from 0.8 km/month at 20 km to 3.2 km/month at 40 km in the Arctic polar vortex during the 1992-93 winter. Descent rates in the mid-stratosphere are similar to those deduced for the Antarctic vortex using ATMOS/ATLAS-3 measurements in November 1994, but the shorter time period of descent in the Arctic leads to smaller total distances of descent. Strong horizontal gradients observed along the vortex edge indicate that the Arctic vortex remains a significant barrier to transport at least until mid-April in the lower to middle stratosphere.

  10. TRACING THE GAS TO THE VIRIAL RADIUS (R{sub 100}) IN A FOSSIL GROUP

    SciTech Connect

    Humphrey, Philip J.; Buote, David A.; Flohic, Helene M. L. G.; Gastaldello, Fabio; Brighenti, Fabrizio; Mathews, William G.

    2012-03-20

    We present a Chandra, Suzaku, and ROSAT study of the hot intragroup medium (IGrM) of the relaxed fossil group/poor cluster RX J1159+5531. This group exhibits an advantageous combination of flat surface brightness profile, high luminosity, and optimal distance, allowing the gas to be detected out to the virial radius (R{sub vir}{identical_to} R{sub 108} = 1100 kpc) in a single Suzaku pointing, while the complementary Chandra data reveal a round morphology and relaxed IGrM image down to kpc scales. We measure the IGrM entropy profile over {approx}3 orders of magnitude in radius, including three data bins beyond {approx}0.5R{sub 200} that have good azimuthal coverage (>30%). We find no evidence that the profile flattens at large scales (>R{sub 500}), and when corrected for the enclosed gas fraction, the entropy profile is very close to the predictions from self-similar structure formation simulations, as seen in massive clusters. Within R{sub vir}, we measure a baryon fraction of 0.17 {+-} 0.02, consistent with the cosmological value. These results are in sharp contrast to the gas behavior at large scales recently reported in the Virgo and Perseus clusters and indicate that substantial gas clumping cannot be ubiquitous near R{sub vir}, at least in highly evolved (fossil) groups.

  11. Can trace gas emission be modified by management scenarios in the northern Corn Belt?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Field plots were established in 2002 in west central Minnesota to compare tillage, rotation and fertilizer treatments and to identify and develop economically-viable and environmentally- sustainable farming systems. Greenhouse gas emission (nitrous oxide, methane and carbon dioxide) was monitored in...

  12. A trace gas sensor using near infrared distributed feedback laser at 1654 nm

    NASA Astrophysics Data System (ADS)

    Li, Bin; He, Qi-Xin; Liu, Hui-Fang; Wang, Yi-Ding

    2015-08-01

    A cost-effective compact instrument for high-stable and sensitive detection of methane (CH4) based on the tunable diode laser absorption spectroscopy technique was experimentally demonstrated. A distributed feedback laser modulated at 1654 nm and two InGaAs photodiodes were deployed in this instrument. The laser was driven by the self-developed temperature and current controller. Spectrum measurements show that the center wavelength of the laser is stable and linearly controlled. Meanwhile, a self-developed digital lock-in amplifier was developed for the extraction of harmonics (1f, 2f) of the gas absorption signal. Experiments of gas detection were carried out to investigate the sensor performance. Firstly, the relation between gas concentration and 1f and 2f harmonics was measured and the relation curve was plotted for calibration. Then, results of accuracy test in different concentrations show that the maximum relative detection error is less than 5.6% in the range 0%-100%. Keeping the other experimental parameters constant, gas samples of 5% concentration was detected during a period of 8 h. The maximum detection error is less than 2.8%, suggesting good detection stability. The sensor can also be applied to field measurement of other gases by adopting lasers at relative wavelength.

  13. INVENTORY ABSTRACTION

    SciTech Connect

    G. Ragan

    2001-12-19

    The purpose of the inventory abstraction, which has been prepared in accordance with a technical work plan (CRWMS M&O 2000e for ICN 02 of the present analysis, and BSC 2001e for ICN 03 of the present analysis), is to: (1) Interpret the results of a series of relative dose calculations (CRWMS M&O 2000c, 2000f). (2) Recommend, including a basis thereof, a set of radionuclides that should be modeled in the Total System Performance Assessment in Support of the Site Recommendation (TSPA-SR) and the Total System Performance Assessment in Support of the Final Environmental Impact Statement (TSPA-FEIS). (3) Provide initial radionuclide inventories for the TSPA-SR and TSPA-FEIS models. (4) Answer the U.S. Nuclear Regulatory Commission (NRC)'s Issue Resolution Status Report ''Key Technical Issue: Container Life and Source Term'' (CLST IRSR) key technical issue (KTI): ''The rate at which radionuclides in SNF [spent nuclear fuel] are released from the EBS [engineered barrier system] through the oxidation and dissolution of spent fuel'' (NRC 1999, Subissue 3). The scope of the radionuclide screening analysis encompasses the period from 100 years to 10,000 years after the potential repository at Yucca Mountain is sealed for scenarios involving the breach of a waste package and subsequent degradation of the waste form as required for the TSPA-SR calculations. By extending the time period considered to one million years after repository closure, recommendations are made for the TSPA-FEIS. The waste forms included in the inventory abstraction are Commercial Spent Nuclear Fuel (CSNF), DOE Spent Nuclear Fuel (DSNF), High-Level Waste (HLW), naval Spent Nuclear Fuel (SNF), and U.S. Department of Energy (DOE) plutonium waste. The intended use of this analysis is in TSPA-SR and TSPA-FEIS. Based on the recommendations made here, models for release, transport, and possibly exposure will be developed for the isotopes that would be the highest contributors to the dose given a release to the

  14. Interannual Variability in Soil Trace Gas (CO2, N2O, NO) Fluxes and Analysis of Controllers

    NASA Technical Reports Server (NTRS)

    Potter, C.; Klooster, S.; Peterson, David L. (Technical Monitor)

    1997-01-01

    Interannual variability in flux rates of biogenic trace gases must be quantified in order to understand the differences between short-term trends and actual long-term change in biosphere-atmosphere interactions. We simulated interannual patterns (1983-1988) of global trace gas fluxes from soils using the NASA Ames model version of CASA (Carnegie-Ames-Stanford Approach) in a transient simulation mode. This ecosystem model has been recalibrated for simulations driven by satellite vegetation index data from the NOAA Advanced Very High Resolution Radiometer (AVHRR) over the mid-1980s. The predicted interannual pattern of soil heterotropic CO2 emissions indicates that relatively large increases in global carbon flux from soils occurred about three years following the strong El Nino Southern Oscillation (ENSO) event of 1983. Results for the years 1986 and 1987 showed an annual increment of +1 Pg (1015 g) C-CO2 emitted from soils, which tended to dampen the estimated global increase in net ecosystem production with about a two year lag period relative to plant carbon fixation. Zonal discrimination of model results implies that 80-90 percent of the yearly positive increments in soil CO2 emission during 1986-87 were attributable to soil organic matter decomposition in the low-latitudes (between 30 N and 30 S). Soils of the northern middle-latitude zone (between 30 N and 60 N) accounted for the residual of these annual increments. Total annual emissions of nitrogen trace gases (N2O and NO) from soils were estimated to vary from 2-4 percent over the time period modeled, a level of variability which is consistent with predicted interannual fluctuations in global soil CO2 fluxes. Interannual variability of precipitation in tropical and subtropical zones (30 N to 20 S appeared to drive the dynamic inverse relationship between higher annual emissions of NO versus emissions of N2O. Global mean emission rates from natural (heterotrophic) soil sources over the period modeled (1983

  15. CW DFB RT diode laser-based sensor for trace-gas detection of ethane using a novel compact multipass gas absorption cell

    NASA Astrophysics Data System (ADS)

    Krzempek, Karol; Jahjah, Mohammad; Lewicki, Rafał; Stefański, Przemysław; So, Stephen; Thomazy, David; Tittel, Frank K.

    2013-09-01

    The development of a continuous wave, thermoelectrically cooled (TEC), distributed feedback diode laser-based spectroscopic trace-gas sensor for ultra-sensitive and selective ethane (C2H6) concentration measurements is reported. The sensor platform used tunable diode laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy as the detection technique. TDLAS was performed using an ultra-compact 57.6 m effective optical path length innovative spherical multipass cell capable of 459 passes between two mirrors separated by 12.5 cm and optimized for the 2.5-4 μm range TEC mercury-cadmium-telluride detector. For an interference-free C2H6 absorption line located at 2,976.8 cm-1, a 1 σ minimum detection limit of 740 pptv with a 1 s lock-in amplifier time constant was achieved.

  16. Tracing the flow of gas onto galaxies with the Green Bank Telescope

    NASA Astrophysics Data System (ADS)

    Pisano, Daniel J.; Rabidoux, K.; de Blok, W.; Leroy, A. K.; Walter, F.; Bigiel, F.; Brinks, E.; Keating, K. M.

    2014-01-01

    One of the key questions in astronomy today is how galaxies accrete their gas and then convert that gas into stars. The HI Nearby Galaxies Survey (THINGS), conducted with the VLA, has made great strides towards answering these questions, but it lacked sensitivity to the extended, diffuse HI in and around galaxies. To rectify this problem, my collaborators and I have recently completed a Green Bank Telescope (GBT) HI survey of the THINGS galaxies. The GBT's clean beam, low system temperature and good angular resolution make it the ideal single-dish telescope for observing low column density HI. Our survey was capable of detecting HI emission from analogs to Lyman limit systems, provided it fills the GBT beam. I will present the first results from our search for low column density tidal features and infall from the ``cosmic web", and I will detail my future plans.

  17. Control of Gas Tungsten Arc welding pool shape by trace element addition to the weld pool

    DOEpatents

    Heiple, C.R.; Burgardt, P.

    1984-03-13

    An improved process for Gas Tungsten Arc welding maximizes the depth/width ratio of the weld pool by adding a sufficient amount of a surface active element to insure inward fluid flow, resulting in deep, narrow welds. The process is especially useful to eliminate variable weld penetration and shape in GTA welding of steels and stainless steels, particularly by using a sulfur-doped weld wire in a cold wire feed technique.

  18. Gas analyzer for continuous monitoring of trace level methanethiol by microchannel collection and fluorescence detection.

    PubMed

    Toda, Kei; Kuwahara, Haruka; Kajiwara, Hidetaka; Hirota, Kazutoshi; Ohira, Shin-Ichi

    2014-09-01

    The highly odorous compound methanethiol, CH3SH, is commonly produced in biodegradation of biomass and industrial processes, and is classed as 2000 times more odorous than NH3. However, there is no simple analytical method for detecting low parts-per-billion in volume ratio (ppbv) levels of CH3SH. In this study, a micro gas analysis system (μGAS) was developed for continuous or near real time measurement of CH3SH at ppbv levels. In addition to a commercial fluorescence detector, a miniature high sensitivity fluorescence detector was developed using a novel micro-photomultiplier tube device. CH3SH was collected by absorption into an alkaline solution in a honeycomb-patterned microchannel scrubber and then mixed with the fluorescent reagent, 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F). Gaseous CH3SH was measured without serious interference from other sulfur compounds or amines. The limits of detection were 0.2ppbv with the commercial detector and 0.3ppbv with the miniature detector. CH3SH produced from a pulping process was monitored with the μGAS system and the data agreed well with those obtained by collection with a silica gel tube followed by thermal desorption-gas chromatography-mass spectrometry. The portable system with the miniature fluorescence detector was used to monitor CH3SH levels in near-real time in a stockyard and it was shown that the major odor component, CH3SH, presented and its concentration varied dynamically with time. PMID:25109855

  19. Tracing the conversion of gas into stars in Young Massive Cluster Progenitors

    NASA Astrophysics Data System (ADS)

    Walker, D. L.; Longmore, S. N.; Bastian, N.; Kruijssen, J. M. D.; Rathborne, J. M.; Jackson, J. M.; Foster, J. B.; Contreras, Y.

    2015-05-01

    Whilst young massive clusters (YMCs; M ≳ 104 M⊙, age ≲ 100 Myr) have been identified in significant numbers, their progenitor gas clouds have eluded detection. Recently, four extreme molecular clouds residing within 200 pc of the Galactic Centre have been identified as having the properties thought necessary to form YMCs. Here, we utilize far-IR continuum data from the Herschel infrared Galactic Plane Survey (HiGAL) and millimetre spectral line data from the Millimetre Astronomy Legacy Team 90 GHz Survey to determine their global physical and kinematic structure. We derive their masses, dust temperatures and radii and use virial analysis to conclude that they are all likely gravitationally bound - confirming that they are likely YMC progenitors. We then compare the density profiles of these clouds to those of the gas and stellar components of the Sagittarius B2 Main and North protoclusters and the stellar distribution of the Arches YMC. We find that even in these clouds - the most massive and dense quiescent clouds in the Galaxy - the gas is not compact enough to form an Arches-like (M = 2 × 104 M⊙, Reff = 0.4 pc) stellar distribution. Further dynamical processes would be required to condense the resultant population, indicating that the mass becomes more centrally concentrated as the (proto)cluster evolves. These results suggest that YMC formation may proceed hierarchically rather than through monolithic collapse.

  20. Aerosol and Trace Gas Processing by Clouds During the Cumulus Humilis Aerosol Processing Study (CHAPS)

    NASA Astrophysics Data System (ADS)

    Yu, X.; Berg, L.; Berkowitz, C.; Alexander, L.; Lee, Y.; Ogren, J.; Andrews, B.

    2008-12-01

    Clouds play an active role in the processing and cycling of atmospheric constituents. Gases and particles can partition to cloud droplets by absorption and condensation as well as activation and pact scavenging. The Cumulus Humilis Aerosol Processing Study (CHAPS) aimed at characterizing freshly emitted aerosols above, within and below fields of cumulus humilis (or fair-weather cumulus) in the vicinity of Oklahoma City. The experiment took place in June 2007. Evolution of aerosol and cloud properties downwind of the Oklahoma City is of particular interest in this project. These observations of a mid-size and mid-latitude city can be used in the development and evaluation of regional-scale and global climate model cumulus parameterizations that describes the transport and transformations of these aerosols by fair-weather cumulus. The Department of Energy (DOE) G-1 aircraft was one of the main platforms used in CHAPS. It carried a suite of instruments to measure properties of interstitial aerosols behind an isokinetic inlet and a set of duplicate instruments to determine properties of activated particles behind a counter-flow virtual impactor (CVI). The sampling line to the Aerodyne Aerosol Mass Spectrometer was switched between the isokinetic inlet and the CVI to allow characterization of interstitial particles out of clouds in contrast to particles activated in clouds. Trace gases including ozone, carbon monoxide, sulfur dioxide, and a series of volatile organic compounds (VOCs) were also measured as were key meteorological state parameters including liquid water content, cloud drop size, and dew point temperature were measured. This presentation will focus on results related to the transformation and transport of aerosols and trace gases observed in fair-weather cumulus and compare these results with concurrent observations made outside these clouds. Our interest will focus on the differences in particle size and composition under varying conditions. The role of

  1. Trace gas measurements over the northwest Pacific during the 2002 IOC cruise

    NASA Astrophysics Data System (ADS)

    Kato, Shungo; Ui, Takeshi; Uematsu, Mitsuo; Kajii, Yoshizumi

    2007-06-01

    The R/V Melville cruised from Osaka (Japan) on 1 May and reached Hawaii on 5 June on a project for the Intergovernmental Oceanographic Commission (IOC) in 2002. During this cruise, the concentrations of atmospheric trace gases (O3, CO, DMS, hydrocarbons, and halocarbons) were measured. Air at high latitudes and low latitudes exhibited starkly different characteristics regarding their chemical composition. The concentrations of anthropogenic species clearly decreased from high latitude to low latitude. On the other hand, biogenic species such as DMS and alkenes were highly abundant at lower latitudes. Backward air trajectories show that the northwestern continental air mass was dominant at higher latitudes and the eastern marine air mass was dominant at lower latitudes. However, the long-range transport of pollutants to clean regions near Hawaii was also observed. The ratios of ethane to CO decreased from high latitude to low latitude. On the basis of a VOC ratio analysis, the benzene concentration is relatively higher at low latitudes. DMS concentrations and wind speed at low latitudes have good correlation. This indicates that at low latitudes, the DMS concentration at the ocean surface is roughly uniform.

  2. Tracing the gas composition of Titan's atmosphere with Herschel : Advances and Discoveries

    NASA Astrophysics Data System (ADS)

    Rengel, Miriam; Moreno, Raphael; Courtin, Régis; Lellouch, Emmanuel; Sagawa, Hideo; Hartogh, Paul; Swinyard, Bruce; Lara, Luisa; Feuchtgruber, Helmut; Jarchow, Christopher; Fulton, Trevor; Cernicharo, José; Bockelée-Morvan, Dominique; Biver, Nicolás; Banaszkiewicz, Marek; González, Armando

    2014-11-01

    The nitrogen-dominated atmosphere of Titan exhibits a great diversity and complexity of molecules and high organic material abundances. The origin of Titan atmosphere is poorly understood and its chemistry is rather complicated. In the framework of the Herschel guaranteed time key programme "Water and Related Chemistry in the Solar System" (Hartogh et al 2009), we carried out observations of the atmosphere of Titan with HIFI, PACS and SPIRE onboard Herschel (Rengel et al. 2014; Courtin et al. 2011, Moreno et al. 2011, 2012). Here we will review key results and discoveries on the atmosphere of Titan obtained with Herschel:-an inventory of species detected including some isotopes from a new survey between 51 and 671 microns.-the determination of the abundance of trace constituents and comparisons with previous efforts.-the unexpected detection of hydrogen isocyanide (HNC), a specie not previously identified in Titan's atmosphere, and the measurement of 16O/18O ratio in CO in Titan for the first time published.-the determination of the vertical profile of water vapor over the 100-450 km altitude range, distribution which does not follow previous predictions and allows to strength an Enceladus' activity as the source for the current water on Titan.With the advent of Herschel, these advances and discoveries allow a further characterization of the complex atmosphere of Titan and help to advance the study of the abundance distribution and the investigation of a variety of processes in Titan atmosphere.

  3. Recent improvements in atmospheric trace gas monitoring using mid-infrared tunable diode lasers

    SciTech Connect

    Nelson, D.D.; Zahniser, M.S.; McManus, J.B.; Shorter, J.H.; Wormhoudt, J.C.; Kolb, C.E.

    1996-12-31

    This paper discusses recent advances in techniques for monitoring atmospheric trace gases using lead salt liquid nitrogen cooled diode lasers. The approach employs an optical system with all reflective optics. The closed path systems rely on a proprietary astigmatic multi pass cell to achieve long optical path lengths in a low volume sampling cell. The authors have also developed open path systems which they have used for remote sensing of automobile and aircraft engine exhaust. The data acquisition method uses rapid frequency sweeping ({approximately}3 kHz) followed by nonlinear least squares analysis of the retrieved spectrum. Recent advances include an emphasis on multi-laser multi-species detection systems, such as simultaneously monitoring the nitric oxide, carbon monoxide and carbon dioxide concentrations in automobile exhaust. Other advances are focused on achieving improved detection sensitivity. In support of this goal, the authors have demonstrated astigmatic multi pass cells with very long optical paths, they have improved the nonlinear least squares spectral fitting routines allowing them to fit complex multi-peak spectra (fingerprint fitting), and they have introduced photolytic modulation as a method to discriminate spectra of photolytically active species (HOCl, NO{sub 2}) from background absorption and optical interference fringes. These techniques are being applied to the monitoring of a wide variety of atmospheric molecules including CH{sub 4}, CO, CO{sub 2}, N{sub 2}O, NO, NO{sub 2}, HONO, HNO{sub 3}, O{sub 3} and HOCl.

  4. Three infrared spectrometers, an atmospheric chemistry suite for the ExoMars 2016 trace gas orbiter

    NASA Astrophysics Data System (ADS)

    Korablev, Oleg; Trokhimovsky, Alexander; Grigoriev, Alexei V.; Shakun, Alexei; Ivanov, Yuriy S.; Moshkin, Boris; Anufreychik, Konstantin; Timonin, Denis; Dziuban, Ilia; Kalinnikov, Yurii K.; Montmessin, Franck

    2014-01-01

    The atmospheric chemistry suite (ACS) package is a part of the Russian contribution to the ExoMars ESA-Roscosmos mission. ACS consists of three separate infrared spectrometers, sharing common mechanical, electrical, and thermal interfaces. The near-infrared (NIR) channel is a versatile spectrometer for the spectral range of 0.7-1.6 μm with a resolving power of ˜20,000. The instrument employs the principle of an echelle spectrometer with an acousto-optical tunable filter (AOTF) as a preselector. NIR will be operated in nadir, in solar occultations, and possibly on the limb. Scientific targets of NIR are the measurements of water vapor, aerosols, and dayside or nightside airglows. The mid-infrared (MIR) channel is a cross-dispersion echelle instrument dedicated to solar occultation measurements in the range of 2.2-4.4 μm targeting the resolving power of 50,000. MIR is dedicated to sensitive measurements of trace gases. The thermal infrared channel (TIRVIM) is a 2-inch double pendulum Fourier-transform spectrometer for the spectral range of 1.7-17 μm with apodized resolution varying from 0.2 to 1.6 cm-1. TIRVIM is primarily dedicated to the monitoring of atmospheric temperatures and aerosol states in nadir. The present paper describes the concept of the instrument, and in more detail, the optical design and the expected parameters of its three parts channel by channel.

  5. The potential impact on atmospheric ozone and temperature of increasing trace gas concentrations

    NASA Technical Reports Server (NTRS)

    Brasseur, G.; Derudder, A.

    1987-01-01

    The response of the atmosphere to emissions of chlorofluorocarbons (CFCs) and other chlorocarbons, and to increasing concentrations of other radiatively active trace gases such as CO2, CH4, and N2O is calculated by a coupled chemical-radiative transport one-dimensional model. It is shown that significant reductions in the ozone concentration and in the temperature are expected in the upper stratosphere as a result of increasing concentrations of active chlorine produced by photodecomposition of the CFCs. The ozone content is expected to increase in the troposphere, as a consequence of increasing concentrations of methane and nitrogen oxides. Due to enhanced greenhouse effects, the Earth's surface should warm up by several degrees. The amplitude and even the sign of future changes in the ozone column are difficult to predict as they are strongly scenario-dependent. An early detection system to prevent noticeable ozone changes as a result of increasing concentrations of source gases should thus be based on a continuous monitoring of the ozone amount in the upper stratosphere rather than on measurements of the ozone column only. Measurements of NOx, Clx, and HOx are also required for unambiguous trend detection and interpretation.

  6. Relationship between back trajectories and tropospheric trace gas concentrations in rural Virginia

    NASA Astrophysics Data System (ADS)

    Moy, Leslie A.; Dickerson, Russell R.; Ryan, William F.

    The day-to-day variations in mixing ratios of trace gases carbon monoxide (CO), ozone (O 3), and total reactive nitrogen (NO y) at rural Shenandoah National Park, VA, are explained to a large extent by the circulation of the air prior to arrival. Using 48 h back trajectories, we analyzed the variability of air quality. In one approach, we separated the highest 2% and lowest 32% of NO y mixing ratio, and compared composite sets of back trajectories for each group. In the "dirty" group, the air passed over the industrialized Midwest more frequently than in the "clean" group (51 vs 23%). When air from the industrialized Midwest was clean, its travel had often been interrupted by convective clouds that mix pollutants vertically and wash out soluble species. Radar summaries show that 80% of the clean trajectories from the northwest passed through areas of convection. In a second approach, we clustered daily trajectories into groups with similar circulation patterns. The cleanest air was associated with rapid westerly flow and strong subsidence, or with origins in the less-populated areas to the south and southeast of the Park. The highest levels of photochemical smog were not associated with stagnation and local emissions, or even transport from the nearby Washington metropolitan area. The dirtiest days resulted from slow air circulation and transport from the industrialized Midwest (as seen from the first approach).

  7. Quantifying Climate Feedbacks from Abrupt Changes in High-Latitude Trace-Gas Emissions

    SciTech Connect

    Schlosser, Courtney Adam; Walter-Anthony, Katey; Zhuang, Qianlai; Melillo, Jerry

    2013-04-26

    Our overall goal was to quantify the potential for threshold changes in natural emission rates of trace gases, particularly methane and carbon dioxide, from pan-arctic terrestrial systems under the spectrum of anthropogenically forced climate warming, and the extent to which these emissions provide a strong feedback mechanism to global climate warming. This goal is motivated under the premise that polar amplification of global climate warming will induce widespread thaw and degradation of the permafrost, and would thus cause substantial changes in the extent of wetlands and lakes, especially thermokarst (thaw) lakes, over the Arctic. Through a coordinated effort of field measurements, model development, and numerical experimentation with an integrated assessment model framework, we have investigated the following hypothesis: There exists a climate-warming threshold beyond which permafrost degradation becomes widespread and thus instigates strong and/or sharp increases in methane emissions (via thermokarst lakes and wetland expansion). These would outweigh any increased uptake of carbon (e.g. from peatlands) and would result in a strong, positive feedback to global climate warming.

  8. Optimisation of a gas chromatographic method for trace gaseous impurities in nitrogen trifluoride by column sequence reversal.

    PubMed

    de Coning, Johannes Petrus; Swinley, John McNeil

    2008-02-01

    Highly reactive fluorinated gaseous matrices require special equipment and techniques for the gas chromatographic analysis of trace impurities in these gases. The impurities that were analysed at the low mg/L levels included dioxygen (O2), dinitrogen (N2), carbon dioxide (CO2), carbon monoxide (CO), sulfur hexafluoride (SF6), methane (CH4) and nitrous oxide (N2O). Carbon tetrafluoride (CF4) is also present in the product at levels of 20-400mg/L and had to be analysed as well. This paper compares the use of a custom-built dual-channel gas chromatograph utilising single column back flush switching on one channel for the determination of O2, N2, CH4 and CO with column sequence reversal on a second channel for the determination of CO2, N2O, SF6 and CF4 to a similar system using a combination of dual-column back flush and heart-cut configurations. Pulsed discharge helium ionisation detectors were used on both channels in both configurations. PMID:18155712

  9. The Pillars of Creation revisited with MUSE: gas kinematics and high-mass stellar feedback traced by optical spectroscopy

    NASA Astrophysics Data System (ADS)

    McLeod, A. F.; Dale, J. E.; Ginsburg, A.; Ercolano, B.; Gritschneder, M.; Ramsay, S.; Testi, L.

    2015-06-01

    Integral field unit (IFU) data of the iconic Pillars of Creation in M16 are presented. The ionization structure of the pillars was studied in great detail over almost the entire visible wavelength range, and maps of the relevant physical parameters, e.g. extinction, electron density, electron temperature, line-of-sight velocity of the ionized and neutral gas are shown. In agreement with previous authors, we find that the pillar tips are being ionized and photoevaporated by the massive members of the nearby cluster NGC 6611. They display a stratified ionization structure where the emission lines peak in a descending order according to their ionization energies. The IFU data allowed us to analyse the kinematics of the photoevaporative flow in terms of the stratified ionization structure, and we find that, in agreement with simulations, the photoevaporative flow is traced by a blueshift in the position-velocity profile. The gas kinematics and ionization structure have allowed us to produce a sketch of the 3D geometry of the Pillars, positioning the pillars with respect to the ionizing cluster stars. We use a novel method to detect a previously unknown bipolar outflow at the tip of the middle pillar and suggest that it has an embedded protostar as its driving source. Furthermore we identify a candidate outflow in the leftmost pillar. With the derived physical parameters and ionic abundances, we estimate a mass-loss rate due to the photoevaporative flow of 70 M⊙ Myr-1 which yields an expected lifetime of approximately 3 Myr.

  10. Profiles of Trace Gas Concentrations in Undisturbed Forest in the Brazilian Amazon

    NASA Astrophysics Data System (ADS)

    Carmo, J.; Crill, P.; Dias, J.; Camargo, P.; Keller, M.

    2004-12-01

    Globally, upland tropical forests are the largest natural source of nitrous oxide (N2O). Soils of upland tropical forests generally consume methane (CH4) although this process has only a minor effect on the atmospheric CH4 budget. In this study, we investigate the concentrations of N2O, CH4, and carbon dioxide (CO2) measured in profiles on towers in undisturbed forest at three Amazon forest sites located in the municipalities of Manaus, Amazonas, Melgaço, Para (Caxiuana), and Sinop, Mato Grosso. We measured gas concentration profiles at six heights above the ground on during both wet and dry seasons in 2003 and 2004. Nylon tubes (0.95 cm OD) were installed on towers used for meteorological and flux measurements in LBA. Gas samples were drawn through teflon filters (1μ m pore size) to a manifold and directed either to an infra-red gas analyzer (LiCor IRGA Model 6262), to sampling canisters, or to exhaust. During sampling periods, we maintained a continuous flow of at least 1 L min-1 through all sampling tubes. CO2 concentration data from the IRGA were recorded continuously using a Datastick analog to digital converter and a palm top computer. We removed air samples in electro-polished stainless steel canisters for off-site analysis of N2O and CH4 by ECD and FID gas chromatography respectively. Sampling times were selected based upon real-time measurements of CO2 concentration. Relatively stable meteorological conditions at night led to consistent increases in CO2 concentrations. At times we also observed increases in the concentrations of CH4 and N2O concentrations correlated with increasing CO2. The source of the increasing CO2 is most likely respiration by soil and above-ground organisms. Correlated increases in CH4 and N2O concentrations also likely result from biological activity in the soil and the canopy layer of the studied forests. Concentrations of these gases increase at night because the rate of gas emission in the canopy layer exceeds the rates of

  11. Tracing the neutral gas environments of young radio AGN with ASKAP

    NASA Astrophysics Data System (ADS)

    Allison, J. R.; Sadler, E. M.; Moss, V. A.; Harvey-Smith, L.; Heywood, I.; Indermuehle, B. T.; McConnell, D.; Sault, R. J.; Whiting, M. T.

    2016-02-01

    At present neutral atomic hydrogen (H I) gas in galaxies at redshifts above {z ˜ 0.3} (the extent of 21 cm emission surveys in individual galaxies) and below {z ˜ 1.7} (where the Lyman-\\alpha line is not observable with ground-based telescopes) has remained largely unexplored. The advent of precursor telescopes to the Square Kilometre Array will allow us to conduct the first systematic radio-selected 21 cm absorption surveys for H I over these redshifts. While H I absorption is a tracer of the reservoir of cold neutral gas in galaxies available for star formation, it can also be used to reveal the extreme kinematics associated with jet-driven neutral outflows in radio-loud active galactic nuclei. Using the six-antenna Boolardy Engineering Test Array of the Australian Square Kilometre Array Pathfinder, we have demonstrated that in a single frequency tuning we can detect H I absorption over a broad range of redshifts between z = 0.4 and 1.0. As part of our early science and commissioning program, we are now carrying out a search for absorption towards a sample of the brightest GPS and CSS sources in the southern sky. These intrinsically compact sources present us with an opportunity to study the circumnuclear region of recently re-started radio galaxies, in some cases showing direct evidence of mechanical feedback through jet-driven outflows. With the sensitivity of the full ASKAP array we will be able to study the kinematics of atomic gas in a few thousand radio galaxies, testing models of radio jet feedback well beyond the nearby Universe.

  12. Miniature triaxial metastable ionization detector for gas chromatographic trace analysis of extraterrestrial volatiles

    NASA Technical Reports Server (NTRS)

    Woeller, F. H.; Kojiro, D. R.; Carle, G. C.

    1984-01-01

    The present investigation is concerned with a miniature metastable ionization detector featuring an unconventional electrode configuration, whose performance characteristics parallel those of traditional design. The ionization detector is to be incorporated in a flight gas chromatograph (GC) for use in the Space Shuttle. The design of the detector is discussed, taking into account studies which verified the sensitivity of the detector. The triaxial design of the detector is compared with a flat-plate style. The obtained results show that the principal goal of developing a miniature, highly sensitive ionization detector for flight applications was achieved. Improved fabrication techniques will utilize glass-to-metal seals and brazing procedures.

  13. Trace gas emissions from a mid-latitude prescribed chaparral fire

    NASA Technical Reports Server (NTRS)

    Cofer, Wesley R., III; Levine, Joel S.; Sebacher, Daniel I.; Riggan, Philip J.; Winstead, Edward L.; Shaw, Edwin F., Jr.; Brass, James A.; Ambrosia, Vincent G.

    1988-01-01

    Smoke-plume gas samples were collected at altitudes from 35-670 m above the ground over the San Dimas Experimental Forest during a 400-acre prescribed chaparral fire. Mean emission ratios relative to CO2 for CO, H2, CH4, and total nonmethane hydrocarbons were lower than previous values obtained for large biomass-burning field experiments. Comparison of samples from vigorously flaming and mixed stages of combustion revealed little differences in CO2 normalized emission ratios for these gases (except for N2O).

  14. Nitrogen dioxide observations from the Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) airborne instrument: Retrieval algorithm and measurements during DISCOVER-AQ Texas 2013

    EPA Science Inventory

    The Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) airborne instrument is a test bed for upcoming air quality satellite instruments that will measure backscattered ultraviolet, visible and near-infrared light from geostationary orbit. GeoTASO flew on the NASA F...

  15. Measuring trace gas emission from multi-distributed sources using vertical radial plume mapping (VRPM) and backward Lagrangian stochastic (bLS) techniques

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Two micrometeorological techniques for measuring trace gas emission rates from distributed area sources were evaluated using a variety of synthetic area sources. The accuracy of the vertical radial plume mapping (VRPM) and the backward Lagrangian (bLS) techniques with an open-path optical spectrosco...

  16. MODELING THE EFFECTS OF CLIMATE AND LAND USE CHANGE ON CARBON AND TRACE GAS BUDGETS OVER THE AMAZON REGION USING NASA SATELLITE PRODUCTS

    EPA Science Inventory

    As part of the LBA-ECO Phase III synthesis efforts for remote sensing and predictive modeling of Amazon carbon, water, and trace gas fluxes, we are evaluating results from the regional ecosystem model called NASA-CASA (Carnegie-Ames Stanford Approach). The NASA-CASA model has bee...

  17. Evaluating the Information from Minor Trace Gas Measurements by the Tropospheric Emission Spectrometer (TES)

    NASA Astrophysics Data System (ADS)

    Cady-Pereira, K. E.; Shephard, M. W.; Henze, D. K.; Zhu, L.; Pinder, R. W.; Bash, J. O.; Walker, J. T.; Millet, D. B.; Wells, K. C.; Jeong, G.; Luo, M.; Chaliyakunnel, S.

    2012-12-01

    The high spectral resolution and good SNR provided by the TES instrument allow for the detection and retrieval of numerous trace species. Advanced optimal estimation algorithms have been developed to retrieve three of these, ammonia, methanol and formic acid, from TES radiances. Ammonia is currently a standard TES operational product, while methanol and formic acid will be standard products in the next TES software update (V006). Given the highly reactive nature of ammonia, with its concurrent high spatial and temporal variability, the large uncertainty in global emissions of methanol, and the large biases between measured and modeled formic acid, the air quality community has a pressing need for global information on these species; there is great interest in using these new satellite derived products, but there is often no clear idea on the information they provide. Here we will provide a short summary of the characteristics of the retrieved products, then present results from comparisons with in situ measurements. We will discuss the distinct characteristics of point and satellite measurements and illustrate how information from the latter is related to the former. We will compare global TES ammonia and methanol measurements with outcome from the GEOS-CHEM model. These comparisons have led us to examine a potential sampling bias driven by TES insensitivity in regions with low concentrations (less than 1 ppbv) or with low thermal contrast or thick clouds. We will present results from the application of inverse methods using TES ammonia and methanol to constrain model emissions, an area of research that has showcased the value provided by satellite data. Finally, we will demonstrate the potential of a sensor with TES characteristics on a geostationary platform to provide high quality data sufficient to evaluate models of the ammonia bi-directional exchange at the surface.

  18. The Influence of Orographic Flows on PICO-NARE Trace-Gas Measurements

    NASA Astrophysics Data System (ADS)

    Kleissl, J.; Dziobak, M. P.; Honrath, R. E.

    2005-12-01

    The PICO-NARE station is located at a mountaintop on a remote island (Pico, Azores Islands, North Atlantic). Meteorological variables, atmospheric trace gases and aerosols are measured to study background concentrations and the frequency and impact of intercontinental transport of air pollution in the free troposphere (FT). This study evaluates the effects of upslope flows at this station. Orographic flows influence the origin of the airmasses sampled at the station. Mechanically forced lifting in strong winds or buoyant forced lifting in daytime and weak winds can cause upslope flow near the mountain which can potentially bring marine boundary layer (MBL) air to the station. To determine the origin of mechanically lifted air upstream of the mountain, a balance of upstream kinetic energy with potential energy as air flows over or around the mountain (Sheppard's model) was applied to upstream velocity and temperature profiles. The original height of an airmass was below the MBL height 25% of the time during July 2001 - December 2004, predominantly in the winter months (January through March). However, ozone mixing ratios at the summit during these periods were not significantly different than during FT episodes. Buoyant upslope flows were quantified through meteorological measurements on the mountain slope in summer 2004. Diurnal cycles consistent with daytime upslope and nighttime downslope flow on the mountain slope were found 28% of the time during July and August 2004. However, the water vapor mixing ratio was significantly smaller at the mountaintop than on the slope, indicating turbulent mixing during ascent or vertical decoupling of airmasses. Impacts of buoyant upslope flow on ozone or nitrogen oxides mixing ratios at the mountaintop station were rare or extremely small, and no clear diurnal cycle of ozone (expected if daytime upslope flow of MBL air occurred regularly) was present. The small size of Pico island, its high latitude, and the steep slope of the

  19. An airborne spectrometer with three infrared lasers for trace gas measurements applied to convection case studies

    NASA Astrophysics Data System (ADS)

    Catoire, V.; Krysztofiak, G.; Robert, C.; Chartier, M.

    2012-12-01

    An infrared absorption spectrometer named SPIRIT (SPectromètre InfraRouge In situ Toute altitude) has been built for airborne simultaneous online measurements of trace gases. SPIRIT is based on two recent technological advances, leading to optimal performances and miniaturization: continuous wave quantum cascade lasers (CW-QCL) operating near room temperature coupled to a new, patented, multipass optical cell (Robert, Appl. Optics, 2007). An essential electronic development allows the sequential use of three QCLs with the same single cell. With judicious selected spectral micro-windows, this potentially leads to the measurements of at least four species at 0.7 Hz frequency. The first deployment of SPIRIT was made onboard the DLR Falcon-20 aircraft during the campaign associated to the EU SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) project in Nov.-Dec. 2011 over Malaysia. In the present paper, the flight of 19 Nov. is presented in detail as an example of the SPIRIT performances, with CO, CO2, CH4 and N2O as measured species. The aircraft crossed four times the anvil of a severe thunderstorm from 11.3 km to 12.8 km altitude corresponding to a large convective system near Borneo island (6.0°N-115.5°E). During the crossing, carbon monoxide mixing ratios increase by 5 to 10 ppbv from the ambient cloud free environment to the anvil cloud correlated with an increase of CH4 mixing ratio. Using these observations, the fraction of boundary layer air contained in fresh convective outflow has been calculated. Other convection cases were detected, allowing for other fractions to be calculated, with results ranging between 0.15 and 0.55 and showing the variability of the mixing taking place during convective transport.

  20. FRESCO+: an improved O2 A-band cloud retrieval algorithm for tropospheric trace gas retrievals

    NASA Astrophysics Data System (ADS)

    Wang, P.; Stammes, P.; van der A, R.; Pinardi, G.; van Roozendael, M.

    2008-05-01

    The FRESCO (Fast Retrieval Scheme for Clouds from the Oxygen A-band) algorithm has been used to retrieve cloud information from measurements of the O2 A-band around 760 nm by GOME, SCIAMACHY and GOME-2. The cloud parameters retrieved by FRESCO are the effective cloud fraction and cloud pressure, which are used for cloud correction in the retrieval of trace gases like O3 and NO2. To improve the cloud pressure retrieval for partly cloudy scenes, single Rayleigh scattering has been included in an improved version of the algorithm, called FRESCO+. We compared FRESCO+ and FRESCO effective cloud fractions and cloud pressures using simulated spectra and one month of GOME measured spectra. As expected, FRESCO+ gives more reliable cloud pressures over partly cloudy pixels. Simulations and comparisons with ground-based radar/lidar measurements of clouds shows that the FRESCO+ cloud pressure is about the optical midlevel of the cloud. Globally averaged, the FRESCO+ cloud pressure is about 50 hPa higher than the FRESCO cloud pressure, while the FRESCO+ effective cloud fraction is about 0.01 larger. The effect of FRESCO+ cloud parameters on O3 and NO2 vertical column densities (VCD) is studied using SCIAMACHY data and ground-based DOAS measurements. We find that the FRESCO+ algorithm has a significant effect on tropospheric NO2 retrievals but a minor effect on total O3 retrievals. The retrieved SCIAMACHY tropospheric NO2 VCDs using FRESCO+ cloud parameters (v1.1) are lower than the tropospheric NO2 VCDs which used FRESCO cloud parameters (v1.04), in particular over heavily polluted areas with low clouds. The difference between SCIAMACHY tropospheric NO2 VCDs v1.1 and ground-based MAXDOAS measurements performed in Cabauw, The Netherlands, during the DANDELIONS campaign is about -2.12×1014 molec cm-2.

  1. FRESCO+: an improved O2 A-band cloud retrieval algorithm for tropospheric trace gas retrievals

    NASA Astrophysics Data System (ADS)

    Wang, P.; Stammes, P.; van der A, R.; Pinardi, G.; van Roozendael, M.

    2008-11-01

    The FRESCO (Fast Retrieval Scheme for Clouds from the Oxygen A-band) algorithm has been used to retrieve cloud information from measurements of the O2 A-band around 760 nm by GOME, SCIAMACHY and GOME-2. The cloud parameters retrieved by FRESCO are the effective cloud fraction and cloud pressure, which are used for cloud correction in the retrieval of trace gases like O3 and NO2. To improve the cloud pressure retrieval for partly cloudy scenes, single Rayleigh scattering has been included in an improved version of the algorithm, called FRESCO+. We compared FRESCO+ and FRESCO effective cloud fractions and cloud pressures using simulated spectra and one month of GOME measured spectra. As expected, FRESCO+ gives more reliable cloud pressures over partly cloudy pixels. Simulations and comparisons with ground-based radar/lidar measurements of clouds show that the FRESCO+ cloud pressure is about the optical midlevel of the cloud. Globally averaged, the FRESCO+ cloud pressure is about 50 hPa higher than the FRESCO cloud pressure, while the FRESCO+ effective cloud fraction is about 0.01 larger. The effect of FRESCO+ cloud parameters on O3 and NO2 vertical column density (VCD) retrievals is studied using SCIAMACHY data and ground-based DOAS measurements. We find that the FRESCO+ algorithm has a significant effect on tropospheric NO2 retrievals but a minor effect on total O3 retrievals. The retrieved SCIAMACHY tropospheric NO2 VCDs using FRESCO+ cloud parameters (v1.1) are lower than the tropospheric NO2VCDs which used FRESCO cloud parameters (v1.04), in particular over heavily polluted areas with low clouds. The difference between SCIAMACHY tropospheric NO2 VCDs v1.1 and ground-based MAXDOAS measurements performed in Cabauw, The Netherlands, during the DANDELIONS campaign is about -2.12×1014molec cm-2.

  2. Trace gas and aerosol sounding of the atmosphere using SAGE III

    NASA Astrophysics Data System (ADS)

    Polyakov, A. V.; Timofeyev, Y. M.; Steele, H. M.; Newchurch, M. J.

    2003-04-01

    We present here the results of a new inversion procedure for SAGE (Stratospheric Aerosol and Gas Experiment) III, in which vertical profiles of ozone, NO2, and aerosol extinction are retrieved using the solar occultation technique. Our algorithm employs a very extensive set of simulated aerosol models, used as a priori information, to derive a pseudoempirical orthogonal basis set. In the retrieval algorithm, the spectral dependence of the aerosol extinction coefficient is then parameterized as an expansion in this basis set. A modeled covariance matrix is used for the ozone and NO2 vertical profiles. Statistical regularization (optimal estimation) is employed to derive the aerosol and gas extinctions. Simultaneous inversion of spectral and spatial components is performed yielding a combined retrieval of all unknown parameters. This algorithm has been successful in the interpretation of solar occultation experiments using the Ozon-Mir device on board the Russian Space Station, “Mir”. Here, results of numerical experiments of the error budget of this algorithm are presented for SAGE III. We compare our retrievals of the atmospheric constituents from SAGE III data with those of independent measurements.

  3. Determination of trace sulfides in turbid waters by gas dialysis/ion chromatography

    SciTech Connect

    Goodwin, L.R.; Francom, D.; Urso, A.; Dieken, F.P.

    1988-02-01

    The accuracy of the methylene blue colorimetric procedure for the determination of sulfide in environmental waters and waste waters is influenced by turbidity interferences even after application of recommended pretreatment techniques. The direct analysis of sulfide by ion chromatography (IC), without sample pretreatment, is complicated by field preservation of samples with zinc ion (or equivalent). A continuous-flow procedure has been developed that converts the acid-extractable sulfide to H/sub 2/S, which is separated from the sample matrix by a gas dialysis membrane and then trapped in a dilute sodium hydroxide solution. A 200-..mu..L portion of this solution is injected into the ion chromatograph for analysis with an electrochemical detector. Detection limits as low as 1.9 ng/mL have been obtained. Good agreement was found between the gas dialysis/IC and methylene blue methods for nonturbid standards. The addition of ascorbic acid as an antioxidant is required to obtain adequate recoveries from spiked tap and well waters.

  4. Frequency Modulated Spectroscopy (FMS) - A Novel Method for Standoff Trace Gas Detection

    NASA Astrophysics Data System (ADS)

    Fessenden, J. E.; Clegg, S. M.; Nowak-Lovato, K.; Martinez, R.; Dobeck, L. M.; Spangler, L.

    2015-12-01

    Geologic storage of carbon rich gases captured from the emissions of fossil fuel combustion is a promising option to mitigate against greenhouse warming scenarios. Monitoring surface gas seepage is a strategy to create a successful geologic storage facility. At Los Alamos National Laboratory, new laser systems have been engineered which can measure concentration and isotope ratios of CO2, CH4, and H2S in real time and up to 1 km distances. These systems can work in closed and open path (LIght Detection And Ranging or LIDAR) settings where we use Frequency Modulated Spectroscopy (FMS) to measure the harmonics of the primary absorption peak for CO2, CH4, and H2S absorptions. This provides between 100-1000 times sensitivity to allow for small concentrations or low abundance isotopes to be observed at distance. We tested these systems at various locations around Los Alamos National Laboratory and at the ZERT Controlled Release site in Bozeman Montana. Results show pollution signatures, ecologically productive fluxes, and carbon storage signatures depending upon location monitored. We will present these results and share unique features of this novel system. Remote detection of concentration and isotope profiles of greenhouse and toxic gases can provide a new method for stand-off detection and mapping of gas in the environment. For geologic storage scenarios, this will allow for larger areas to be interrogated for subsurface CO2 leak detection and can accelerate the Monitoring Verification and Accounting (MVA) mission goals for the Carbon Sequestration and Storage (CCS) communities.

  5. An automated multidimensional preparative gas chromatographic system for isolation and enrichment of trace amounts of xenon from ambient air.

    PubMed

    Larson, Tuula; Östman, Conny; Colmsjö, Anders

    2011-04-01

    The monitoring of radioactive xenon isotopes is one of the principal methods for the detection of nuclear explosions in order to identify clandestine nuclear testing. In this work, a miniaturized, multiple-oven, six-column, preparative gas chromatograph was constructed in order to isolate trace quantities of radioactive xenon isotopes from ambient air, utilizing nitrogen as the carrier gas. The multidimensional chromatograph comprised preparative stainless steel columns packed with molecular sieves, activated carbon, and synthetic carbon adsorbents (e.g., Anasorb®-747 and Carbosphere®). A combination of purification techniques--ambient adsorption, thermal desorption, back-flushing, thermal focusing, and heart cutting--was selectively optimized to produce a well-defined xenon peak that facilitated reproducible heart cutting and accurate quantification. The chromatographic purification of a sample requires approximately 4 h and provides complete separation of xenon from potentially interfering components (such as water vapor, methane, carbon dioxide, and radon) with recovery and accuracy close to 100%. The preparative enrichment process isolates and concentrates a highly purified xenon gas fraction that is suitable for subsequent ultra-low-level γ-, ß/γ-spectroscopic or high-resolution mass spectrometric measurement (e.g., to monitor the gaseous fission products of nuclear explosions at remote locations). The Xenon Processing Unit is a free-standing, relatively lightweight, and transportable system that can be interfaced to a variety of sampling and detection systems. It has a relatively inexpensive, rugged, and compact modular (19-inch rack) design that provides easy access to all parts for maintenance and has a low power requirement. PMID:21347675

  6. Trace analysis of multi-class pesticide residues in Chinese medicinal health wines using gas chromatography with electron capture detection

    PubMed Central

    Kong, Wei-Jun; Liu, Qiu-Tao; Kong, Dan-Dan; Liu, Qian-Zhen; Ma, Xin-Ping; Yang, Mei-Hua

    2016-01-01

    A method is described for multi-residue, high-throughput determination of trace levels of 22 organochlorine pesticides (OCPs) and 5 pyrethroid pesticides (PYPs) in Chinese medicinal (CM) health wines using a QuEChERS (quick, easy, cheap, effective, rugged, and safe) based extraction method and gas chromatography-electron capture detection (GC-ECD). Several parameters were optimized to improve preparation and separation time while still maintaining high sensitivity. Validation tests of spiked samples showed good linearities for 27 pesticides (R = 0.9909–0.9996) over wide concentration ranges. Limits of detection (LODs) and quantification (LOQs) were measured at ng/L levels, 0.06–2 ng/L and 0.2–6 ng/L for OCPs and 0.02–3 ng/L and 0.06–7 ng/L for PYPs, respectively. Inter- and intra-day precision tests showed variations of 0.65–9.89% for OCPs and 0.98–13.99% for PYPs, respectively. Average recoveries were in the range of 47.74–120.31%, with relative standard deviations below 20%. The developed method was then applied to analyze 80 CM wine samples. Beta-BHC (Benzene hexachloride) was the most frequently detected pesticide at concentration levels of 5.67–31.55 mg/L, followed by delta-BHC, trans-chlordane, gamma-BHC, and alpha-BHC. The validated method is simple and economical, with adequate sensitivity for trace levels of multi-class pesticides. It could be adopted by laboratories for this and other types of complex matrices analysis. PMID:26883080

  7. The Effect of Mustard Gas on Salivary Trace Metals (Zn, Mn, Cu, Mg, Mo, Sr, Cd, Ca, Pb, Rb)

    PubMed Central

    Zamani Pozveh, Elham; Seif, Ahmad; Ghalayani, Parichehr; Maleki, Abbas; Mottaghi, Ahmad

    2015-01-01

    We have determined and compared trace metals concentration in saliva taken from chemical warfare injures who were under the exposure of mustard gas and healthy subjects by means of inductively coupled plasma optical emission spectroscopy (ICP-OES) for the first time. The influence of preliminary operations on the accuracy of ICP-OES analysis, blood contamination, the number of restored teeth in the mouth, salivary flow rate, and daily variations in trace metals concentration in saliva were also considered. Unstimulated saliva was collected at 10:00–11:00 a.m. from 45 subjects in three equal groups. The first group was composed of 15 healthy subjects (group 1); the second group consisted of 15 subjects who, upon chemical warfare injuries, did not use Salbutamol spray, which they would have normally used on a regular basis (group 2); and the third group contained the same number of patients as the second group, but they had taken their regular medicine (Salbutamol spray; group 3). Our results showed that the concentration of Cu in saliva was significantly increased in the chemical warfare injures compared to healthy subjects, as follows: healthy subjects 15.3± 5.45(p.p.b.), patients (group 2) 45.77±13.65, and patients (Salbutamol spray; group 3) 29 ±8.51 (P <0.02). In contrast, zinc was significantly decreased in the patients, as follows: healthy subjects 37 ± 9.03(p.p.b.), patients (group 2) 12.2 ± 3.56, and patients (Salbutamol spray; group 3) 20.6 ±10.01 (P < 0.01). It is important to note that direct dilution of saliva samples with ultrapure nitric acid showed the optimum ICP-OES outputs. PMID:25965704

  8. Trace analysis of multi-class pesticide residues in Chinese medicinal health wines using gas chromatography with electron capture detection

    NASA Astrophysics Data System (ADS)

    Kong, Wei-Jun; Liu, Qiu-Tao; Kong, Dan-Dan; Liu, Qian-Zhen; Ma, Xin-Ping; Yang, Mei-Hua

    2016-02-01

    A method is described for multi-residue, high-throughput determination of trace levels of 22 organochlorine pesticides (OCPs) and 5 pyrethroid pesticides (PYPs) in Chinese medicinal (CM) health wines using a QuEChERS (quick, easy, cheap, effective, rugged, and safe) based extraction method and gas chromatography-electron capture detection (GC-ECD). Several parameters were optimized to improve preparation and separation time while still maintaining high sensitivity. Validation tests of spiked samples showed good linearities for 27 pesticides (R = 0.9909-0.9996) over wide concentration ranges. Limits of detection (LODs) and quantification (LOQs) were measured at ng/L levels, 0.06-2 ng/L and 0.2-6 ng/L for OCPs and 0.02-3 ng/L and 0.06-7 ng/L for PYPs, respectively. Inter- and intra-day precision tests showed variations of 0.65-9.89% for OCPs and 0.98-13.99% for PYPs, respectively. Average recoveries were in the range of 47.74-120.31%, with relative standard deviations below 20%. The developed method was then applied to analyze 80 CM wine samples. Beta-BHC (Benzene hexachloride) was the most frequently detected pesticide at concentration levels of 5.67-31.55 mg/L, followed by delta-BHC, trans-chlordane, gamma-BHC, and alpha-BHC. The validated method is simple and economical, with adequate sensitivity for trace levels of multi-class pesticides. It could be adopted by laboratories for this and other types of complex matrices analysis.

  9. PCF-Based Cavity Enhanced Spectroscopic Sensors for Simultaneous Multicomponent Trace Gas Analysis

    PubMed Central

    Nakaema, Walter M.; Hao, Zuo-Qiang; Rohwetter, Philipp; Wöste, Ludger; Stelmaszczyk, Kamil

    2011-01-01

    A multiwavelength, multicomponent CRDS gas sensor operating on the basis of a compact photonic crystal fibre supercontinuum light source has been constructed. It features a simple design encompassing one radiation source, one cavity and one detection unit (a spectrograph with a fitted ICCD camera) that are common for all wavelengths. Multicomponent detection capability of the device is demonstrated by simultaneous measurements of the absorption spectra of molecular oxygen (spin-forbidden b-X branch) and water vapor (polyads 4v, 4v + δ) in ambient atmospheric air. Issues related to multimodal cavity excitation, as well as to obtaining the best signal-to-noise ratio are discussed together with methods for their practical resolution based on operating the cavity in a “quasi continuum” mode and setting long camera gate widths, respectively. A comprehensive review of multiwavelength CRDS techniques is also given. PMID:22319372

  10. Tunable photonic cavities for in-situ spectroscopic trace gas detection

    DOEpatents

    Bond, Tiziana; Cole, Garrett; Goddard, Lynford

    2012-11-13

    Compact tunable optical cavities are provided for in-situ NIR spectroscopy. MEMS-tunable VCSEL platforms represents a solid foundation for a new class of compact, sensitive and fiber compatible sensors for fieldable, real-time, multiplexed gas detection systems. Detection limits for gases with NIR cross-sections such as O.sub.2, CH.sub.4, CO.sub.x and NO.sub.x have been predicted to approximately span from 10.sup.ths to 10s of parts per million. Exemplary oxygen detection design and a process for 760 nm continuously tunable VCSELS is provided. This technology enables in-situ self-calibrating platforms with adaptive monitoring by exploiting Photonic FPGAs.

  11. Pencil-trace on printed silver interdigitated electrodes for paper-based NO2 gas sensors

    NASA Astrophysics Data System (ADS)

    Zhang, Jiankun; Huang, Lei; Lin, Youjie; Chen, Lu; Zeng, Ziyan; Shen, Leo; Chen, Qi; Shi, Wangzhou

    2015-04-01

    The pencil-drawn sensor is expected to enable a simple, low-cost, and reproducible paper-based sensor platform for widely deployed wireless environmental monitoring of NO2. Herein, we demonstrated a rapid prototyping of chemiresistor-type NO2 sensor by mechanical abrasion of an 8B pencil to form a stripe of uniform graphitic coating on printed silver interdigitated electrodes (IDEs). The Ag IDEs not only offer a low resistance but also provide the assembly of Ag nanoparticles into exfoliated graphene sheets for the paper-based NO2 gas sensors in order to realise much higher sensitivity and better reproducibility comparing with pencil-drawn sensors directly on weighing paper.

  12. The Use of Aerosol Optical Depth in Estimating Trace Gas Emissions from Biomass Burning Plumes

    NASA Astrophysics Data System (ADS)

    Jones, N.; Paton-Walsh, C.; Wilson, S.; Meier, A.; Deutscher, N.; Griffith, D.; Murcray, F.

    2003-12-01

    We have observed significant correlations between aerosol optical depth (AOD) at 500 nm and column amounts of a number of biomass burning indicators (carbon monoxide, hydrogen cyanide, formaldehyde and ammonia) in bushfire smoke plumes over SE Australia during the 2001/2002 and 2002/2003 fire seasons from remote sensing measurements. The Department of Chemistry, University of Wollongong, operates a high resolution Fourier Transform Spectrometer (FTS), in the city of Wollongong, approximately 80 km south of Sydney. During the recent bushfires we collected over 1500 solar FTIR spectra directly through the smoke over Wollongong. The total column amounts of the biomass burning indicators were calculated using the profile retrieval software package SFIT2. Using the same solar beam, a small grating spectrometer equipped with a 2048 pixel CCD detector array, was used to calculate simultaneous aerosol optical depths. This dataset is therefore unique in its temporal sampling, location to active fires, and range of simultaneously measured constituents. There are several important applications of the AOD to gas column correlation. The estimation of global emissions from biomass burning currently has very large associated uncertainties. The use of visible radiances measured by satellites, and hence AOD, could significantly reduce these uncertainties by giving a direct estimate of global emissions of gases from biomass burning through application of the AOD to gas correlation. On a more local level, satellite-derived aerosol optical depth maps could be inverted to infer approximate concentration levels of smoke-related pollutants at the ground and in the lower troposphere, and thus can be used to determine the nature of any significant health impacts.

  13. Seasonal variation of reactive trace gas profiles in an Amazonian rainforest

    NASA Astrophysics Data System (ADS)

    Wolff, Stefan; Tsokankunku, Anywhere; Pöhlker, Christopher; Saturno, Jorge; Walter, David; Ditas, Florian; Könemann, Tobias; Ganzeveld, Laurens; de Abreu Sá, Leonardo Deane; Yañez-Serrano, Ana Maria; Ocimar Manzi, Antonio; Souza, Rodrigo; Trebs, Ivonne; Sörgel, Matthias

    2016-04-01

    In 2011, an 80 m high walk up tower for atmospheric research was erected at the ATTO (Amazon Tall Tower Observatory) site (02°08'38.8''S, 58°59'59.5''W) in the remote Amazonian rainforest. The nearly pristine environment allows biosphere-atmosphere studies within an ecosystem far away from large anthropogenic emission sources. Since April 2012 vertical mixing ratio profiles of H2O, CO2 and O3 were measured at 8 different heights between 0.05 m and 79.3 m. During five intensive campaigns (Oct-Dec 2012, Oct-Nov 2013, Mar 2014, Aug-Sep 2014, Oct-Dec 2015) nitric oxide (NO) and nitrogen dioxide (NO2) were also measured. Ozone values exhibit a clear seasonal cycle with lower values in the wet season (Jan-Apr) and higher values the drier seasons (Aug-Nov). The last months of 2015 were strongly influenced by a strong El Niño signal in the Pacific region, leading to much drier conditions and enhanced biomass burning in the Amazon also resulting in an extended period of higher O3 mixing ratios. Back trajectories were used to identify the influence of biomass burning on the formation of O3 at the ATTO site. The burning events were additionally confirmed by aerosol and VOC measurements. By correlating these different measurements we could identify clear seasonal differences regarding sources and sinks of aerosols and trace gases, whereas different regimes of O3 production and destruction within and above the canopy could be detected. NO peaks above canopy in the morning were related to export of below-canopy air that was enriched in NOx and CO2 and depleted in O3. Additional to the detailed concentration measurements, there have also been, O3 flux measurements during this campaign allowing a more detailed analysis of the O3 exchange between atmosphere and the canopy as well as the role of various mechanisms involved in atmosphere-biosphere exchange at the ATTO site.

  14. The ExoMars Trace Gas Orbiter NOMAD Spectrometer Suite for Nadir and Solar Occultation Observations of Mars' Atmosphere

    NASA Astrophysics Data System (ADS)

    Thomas, Ian; Carine Vandaele, Ann; López-Moreno, José Juan; Patel, Manish; Bellucci, Giancarlo; Drummond, Rachel; Neefs, Eduard; Depiesse, Cedric; Daerden, Frank; Rodriguez-Gómez, Julio; Neary, Lori; Robert, Séverine; Willame, Yannick; Mahieux, Arnaud

    2015-04-01

    NOMAD (Nadir and Occultation for MArs Discovery) is one of four instruments on board the ExoMars Trace Gas Orbiter, scheduled for launch in January 2016 and to begin nominal science mission around Mars in late 2017. It consists of a suite of three high-resolution spectrometers - Solar Occultation (SO), LNO (Limb Nadir and Occultation) and UVIS (Ultraviolet-Visible) - which will generate a huge dataset of Martian atmospheric observations during the mission, across a wide spectral range. Specifically, the SO spectrometer channel will perform occultation measurements, operating between 2.2-4.3μm at a resolution of 0.15cm-1, with 180-1000m vertical spatial resolution and an SNR of 1500-3000. LNO will perform limb scanning, nadir and occultation measurements, operating between 2.2-3.8μm at a resolution of 0.3cm-1. In nadir, global coverage will extend between ±74O latitude with an IFOV of 0.5x17km on the surface. This channel can also make occultation measurements should the SO channel fail. UVIS will make limb, nadir and occultation measurements between 200-650nm, at a resolution of 1nm. It will have 300-1000m vertical resolution during occultation and 5x60km ground resolution during 15s nadir observations. An order-of-magnitude increase in spectral resolution over previous instruments will allow NOMAD to map previously unresolvable gas species, such as important trace gases and isotopes. CO, CO2, H2O, C2H2, C2H4, C2H6, H2CO, CH4, SO2, H2S, HCl, O3 and several isotopologues of methane and water will be detectable, providing crucial measurements of the Martian D/H and methane isotope ratios. It will also be possible to map the sources and sinks of these gases, such as regions of surface volcanism/outgassing and atmospheric production, over the course of an entire Martian year, to further constrain atmospheric dynamics and climatology. NOMAD will also continue to monitor the Martian water, carbon, ozone and dust cycles, extending existing datasets made by successive

  15. A wide field-of-view imaging DOAS instrument for two-dimensional trace gas mapping from aircraft

    NASA Astrophysics Data System (ADS)

    Schönhardt, A.; Altube, P.; Gerilowski, K.; Krautwurst, S.; Hartmann, J.; Meier, A. C.; Richter, A.; Burrows, J. P.

    2015-12-01

    The Airborne imaging differential optical absorption spectroscopy (DOAS) instrument for Measurements of Atmospheric Pollution (AirMAP) has been developed for the purpose of trace gas measurements and pollution mapping. The instrument has been characterized and successfully operated from aircraft. Nitrogen dioxide (NO2) columns were retrieved from the AirMAP observations. A major benefit of the push-broom imaging instrument is the spatially continuous, gap-free measurement sequence independent of flight altitude, a valuable characteristic for mapping purposes. This is made possible by the use of a charge coupled device (CCD) frame-transfer detector. A broad field of view across track of around 48° is achieved with wide-angle entrance optics. This leads to a swath width of about the same size as the flight altitude. The use of fibre coupled light intake optics with sorted light fibres allows flexible instrument positioning within the aircraft and retains the very good imaging capabilities. The measurements yield ground spatial resolutions below 100 m depending on flight altitude. The number of viewing directions is chosen from a maximum of 35 individual viewing directions (lines of sight, LOS) represented by 35 individual fibres. The selection is adapted to each situation by averaging according to signal-to-noise or spatial resolution requirements. Observations at 30 m spatial resolution are obtained when flying at 1000 m altitude and making use of all 35 viewing directions. This makes the instrument a suitable tool for mapping trace gas point sources and small-scale variability. The position and aircraft attitude are taken into account for accurate spatial mapping using the Attitude and Heading Reference System of the aircraft. A first demonstration mission using AirMAP was undertaken in June 2011. AirMAP was operated on the AWI Polar-5 aircraft in the framework of the AIRMETH-2011 campaign. During a flight above a medium-sized coal-fired power plant in north

  16. TRACING MOLECULAR GAS MASS IN EXTREME EXTRAGALACTIC ENVIRONMENTS: AN OBSERVATIONAL STUDY

    SciTech Connect

    Zhu Ming; Xilouris, Emmanuel M.; Kuno, Nario; Lisenfeld, Ute E-mail: padeli@astro.uni-bonn.d E-mail: kuno@nro.nao.ac.j

    2009-12-01

    We present a new observational study of the {sup 12}CO(1-0) line emission as an H{sub 2} gas mass tracer under extreme conditions in extragalactic environments. Our approach is to study the full neutral interstellar medium (H{sub 2}, H I, and dust) of two galaxies whose bulk interstellar medium (ISM) resides in environments that mark (and bracket) the excitation extremes of the ISM conditions found in infrared luminous galaxies, the starburst NGC 3310, and the quiescent spiral NGC 157. Our study maintains a robust statistical notion of the so-called X = N(H{sub 2})/I {sub CO} factor (i.e., a large ensemble of clouds is involved) while exploring its dependence on the very different average ISM conditions prevailing within these two systems. These are constrained by fully sampled {sup 12}CO(3-2) and {sup 12}CO(1-0) observations, at a matched beam resolution of half-power beam width approx15'', obtained with the James Clerk Maxwell Telescope (JCMT) on Mauna Kea (Hawaii) and the 45 m telescope of the Nobeyama Radio Observatory in Japan, combined with sensitive 850 mum and 450 mum dust emission and H I interferometric images which allow a complete view of all the neutral ISM components. Complementary {sup 12}CO(2-1) observations were obtained with the JCMT toward the center of the two galaxies. We found an X factor varying by a factor of 5 within the spiral galaxy NGC 157 and about two times lower than the Galactic value in NGC 3310. In addition, the dust emission spectrum in NGC 3310 shows a pronounced submillimeter 'excess'. We tried to fit this excess by a cold dust component but very low temperatures were required (T {sub C} approx 5-11 K) with a correspondingly low gas-to-dust mass ratio of approx5-43. We furthermore show that it is not possible to maintain the large quantities of dust required at these low temperatures in this starburst galaxy. Instead, we conclude that the dust properties need to be different from Galactic dust in order to fit the submillimeter

  17. Assessing changes in stratospheric mean age of air and fractional release using historical trace gas observations

    NASA Astrophysics Data System (ADS)

    Laube, Johannes; Bönisch, Harald; Engel, Andreas; Röckmann, Thomas; Sturges, William

    2014-05-01

    Large-scale stratospheric transport is pre-dominantly governed by the Brewer-Dobson circulation. Due to climatic change a long-term acceleration of this residual stratospheric circulation has been proposed (e.g. Austin et al.,2006). Observational evidence has revealed indications for temporary changes (e.g. Bönisch et al., 2011) but a confirmation of a significant long-term trend is missing so far (e.g. Engel et al., 2009). A different aspect is a possible long-term change in the break-down of chemically important species such as chlorofluorocarbons as proposed by Butchart et al. 2001. Recent studies show significant differences adding up to more than 20 % in the chlorine released from such compounds (Newman et al., 2007; Laube et al., 2013). We here use a data set of three long-lived trace gases, namely SF6, CF2Cl2, and N2O, as measured in whole-air samples collected during balloon and aircraft flights between 1975 and 2011, to assess changes in stratospheric transport and chemistry. For this purpose we utilise the mean stratospheric transit times (or mean ages of air) in combination with a measure of the chemical decomposition (i.e. fractional release factors). We also evaluate the influence of different trend correction methods on these quantities and explore their variability with latitude, altitude, and season. References Austin, J. & Li, F.: On the relationship between the strength of the Brewer-Dobson circulation and the age of stratospheric air, Geophys. Res. Lett., 33, L17807, 2006. Bönisch, H., Engel, A., Birner, Th., Hoor, P., Tarasick, D. W., and Ray, E. A.: On the structural changes in the Brewer-Dobson circulation after 2000, Atmos. Chem. Phys., 11, 3937-3948, 2011. Butchart, N. & Scaife, A. A. Removal of chlorofluorocarbons by increased mass exchange between the stratosphere and troposphere in a changing climate. Nature, 410, 799-802, 2001. Engel, A., Möbius, T., Bönisch, H., Schmidt, U., Heinz, R., Levin, I., Atlas, E., Aoki, S., Nakazawa, T

  18. Development of new method of δ(13)C measurement for trace hydrocarbons in natural gas using solid phase micro-extraction coupled to gas chromatography isotope ratio mass spectrometry.

    PubMed

    Li, Zhongping; Wang, Xibin; Li, Liwu; Zhang, Mingjie; Tao, Mingxin; Xing, Lantian; Cao, Chunhui; Xia, Yanqing

    2014-11-01

    Compound specific isotope analysis (CSIA) of normal-level hydrocarbons (C1-C4) in natural gas is often successfully used in natural gas origin identification and classification, but little progress so far has been made for trace level hydrocarbons (C5-C14) in natural gas. In this study, we developed a method for rapid analysis of carbon isotopic ratios for trace hydrocarbons in natural gas samples. This method can be described as a combined approach characterized by solid phase micro-extraction (SPME) technique coupled to gas chromatography isotope ratio mass spectrometry (GC/IRMS). In this study, the CAR-PDMS fiber was chosen as the SPME adsorptive material after comparative experiments with other four fibers, and the parameters, including equilibration time, extraction temperature and desorption time, for efficient extraction of trace hydrocarbons were systematically optimized. The results showed the carbon isotopic fractionation was not observed as a function of equilibration time and extraction temperature. And the δ(13)C signatures determined by SPME-GC/IRMS were in good agreement with the known δ(13)C values of C5-C14 measured by GC-IRMS, and the accuracy is generally within ±0.5‰. Five natural gas samples were analyzed using this method, and the δ(13)C values for C5-C14 components were obtained with satisfied repeatability. The SPME-GC/IRMS approach fitted with CAR-PDMS fiber is well suited for the preconcentration of trace hydrocarbons and provides so far the most reliable carbon isotopic analysis for trace compounds in natural gas. PMID:25465020

  19. Comparing Meteorite and Spacecraft Noble Gas Measurements to Trace Processes in the Martian Crust and Atmosphere

    NASA Astrophysics Data System (ADS)

    Swindle, T. D.

    2014-12-01

    Our knowledge of the noble gas abundances and isotopic compositions in the Martian crust and atmosphere come from two sources, measurements of meteorites from Mars and in situ measurements by spacecraft. Measurements by the Viking landers had large uncertainties, but were precise enough to tie the meteorites to Mars. Hence most of the questions we have are currently defined by meteorite measurements. Curiosity's SAM has confirmed that the Ar isotopic composition of the atmosphere is highly fractionated, presumably representing atmospheric loss that can now be modeled with more confidence. What turns out to be a more difficult trait to explain is the fact that the ratio of Kr/Xe in nakhlites, chassignites and ALH84001 is distinct from the atmospheric ratio, as defined by measurements from shergottites. This discrepancy has been suggested to be a result of atmosphere/groundwater/rock interaction, polar clathrate formation, or perhaps local temperature conditions. More detailed atmospheric measurements, along with targeted simulation experiments, will be needed to make full use of this anomaly.

  20. Optical fiber tip-based quartz-enhanced photoacoustic sensor for trace gas detection

    NASA Astrophysics Data System (ADS)

    Li, Zhili; Wang, Zhen; Wang, Chao; Ren, Wei

    2016-05-01

    We reported the development of an evanescent-wave quartz-enhanced photoacoustic sensor (EW-QEPAS) using a single-mode optical fiber tip for sensitive gas detection in the extended near-infrared region. It is a spectroscopic technique based on the combination of quartz-enhanced photoacoustic spectroscopy with fiber-optic evanescent-wave absorption to achieve low optical noise, easy optical alignment, and high compactness. Carbon monoxide (CO) detection at 2.3 μm using a fiber-coupled, continuous-wave, distributed-feedback laser was selected for the sensor demonstration. By tapering the optical fiber down to 2.5 μm diameter using the flame-brushing technique, an evanescent field of ~0.6 mW around the fiber tip was absorbed by CO molecules. Besides an excellent linear response ( R 2 = 0.9996) to CO concentrations, the EW-QEPAS sensor achieved a normalized noise-equivalent absorption (NNEA) coefficient of 8.6 × 10-8 cm-1W/√Hz for an incident optical power of 1.8 mW and integration time of 1 s. The sensor detection sensitivity can be further improved by enhancing the evanescent-wave power on the fiber tip.

  1. Trace analysis of sulfamethazine in animal feed, human urine, and wastewater by electron capture gas chromatography

    SciTech Connect

    Holder, C.L.; Thompson, H.C. Jr.; Bowman, M.C.

    1981-12-01

    Sulfamethazine, a widely used antibacterial drug additive in feeds for swine, chickens, and cattle, was scheduled for toxicological evaluation because of potential human health hazards associated with its residues in edible animal tissues. Analytical chemical procedures that would ensure proper concentration, homogeneity, and stability of the drug in dosed feed and its safe usage during the animal studies were prerequisites for such toxicological tests. Electron capture gas chromatographic (EC/GC) methods were therefore devised for the analysis of sulfamethazine residues in animal feed, human urine, and wastewater at levels as low as 100, 10, and 10 ppb, respectively. Sample extracts were cleaned up by using liquid/liquid partitioning, and the extracts were subjected to two derivatizations followed by cleanup on a silica gel column. The derivatizations of sulfamethazine consisted of methylation followed by trifluoroacetylation of the primary amine function. Ancillary data concerning stability of the compound in animal feed, water, and as a dry residue on glass, extraction efficiencies, partition values with various solvents, and the analysis of residues in feed by high pressure liquid chromatography (HPLC) at levels as low as 1.0 ppm are presented.

  2. Near-real-time measurement of trace volatile organic compounds from combustion processes using an on-line gas chromatography

    SciTech Connect

    Ryan, J.V.; Lemieux, P.M.; Preston, W.T.

    1998-12-31

    The US EPA`s current regulatory approach for combustion and incineration sources considers the use of real-time continuous emission monitors (CEMs) for particulate, metals, and organic compounds to monitor source emissions. Currently, the CEM technologies to support this approach have not been thoroughly developed and/or demonstrated. The EPA`s air Pollution Prevention and Control Division has developed a near-real-time volatile organic compound (VOC) CEM, using an on-line gas chromatograph (OLGC), capable of measuring over 20 VOCs at concentrations typically present in well-operated combustion systems. The OLGC system consists of a sample delivery system, a sample concentrator, and a GC equipped with both flame ionization and electron capture detectors. Application of the OLGC system was initially demonstrated through participation in the 1995 US EPA/DOE CEM demonstration program. Additional work has improved system performance, including increased automation and improved calibration technique. During pilot-scale incineration testing, measurement performance was examined in detail through comparisons to various CEM performance criteria. Specifically, calibration error, calibration drift error, and system bias were examined as a function of full scale and gas concentration. Although OLGC measurement performance was not able to meet standard EPA CEM measurement performance criteria, measurement performance was encouraging. The system demonstrated the ability to perform hourly trace level VOC measurements for as many as 23 different VOCs with boiling points ranging from {minus}23.7 to 180.5 C at a known level of measurement performance. This system is a suitable alternative to VOC reference method measurements which may be performed only intermittently.

  3. Application of mobile aerosol and trace gas measurements for the investigation of megacity air pollution emissions: the Paris metropolitan area

    NASA Astrophysics Data System (ADS)

    von der Weiden-Reinmüller, S.-L.; Drewnick, F.; Crippa, M.; Prévôt, A. S. H.; Meleux, F.; Baltensperger, U.; Beekmann, M.; Borrmann, S.

    2014-01-01

    For the investigation of megacity emission development and the impact outside the source region, mobile aerosol and trace gas measurements were carried out in the Paris metropolitan area between 1 July and 31 July 2009 (summer conditions) and 15 January and 15 February 2010 (winter conditions) in the framework of the European Union FP7 MEGAPOLI project. Two mobile laboratories, MoLa and MOSQUITA, were deployed, and here an overview of these measurements and an investigation of the applicability of such measurements for the analysis of megacity emissions are presented. Both laboratories measured physical and chemical properties of fine and ultrafine aerosol particles as well as gas phase constituents of relevance for urban pollution scenarios. The applied measurement strategies include cross-section measurements for the investigation of plume structure and quasi-Lagrangian measurements axially along the flow of the city's pollution plume to study plume aging processes. Results of intercomparison measurements between the two mobile laboratories represent the adopted data quality assurance procedures. Most of the compared measurement devices show sufficient agreement for combined data analysis. For the removal of data contaminated by local pollution emissions a video tape analysis method was applied. Analysis tools like positive matrix factorization and peak integration by key analysis applied to high-resolution time-of-flight aerosol mass spectrometer data are used for in-depth data analysis of the organic particulate matter. Several examples, including a combination of MoLa and MOSQUITA measurements on a cross section through the Paris emission plume, are provided to demonstrate how such mobile measurements can be used to investigate the emissions of a megacity. A critical discussion of advantages and limitations of mobile measurements for the investigation of megacity emissions completes this work.

  4. Application of mobile aerosol and trace gas measurements for the investigation of megacity air pollution emissions: the Paris metropolitan area

    NASA Astrophysics Data System (ADS)

    von der Weiden-Reinmüller, S.-L.; Drewnick, F.; Crippa, M.; Prévôt, A. S. H.; Meleux, F.; Baltensperger, U.; Beekmann, M.; Borrmann, S.

    2013-08-01

    For the investigation of megacity emission development and impact outside the source region mobile aerosol and trace gas measurements were carried out in the Paris metropolitan area between 1 July and 31 July 2009 (summer conditions) and 15 January and 15 February 2010 (winter conditions) in the framework of the European Union FP7 MEGAPOLI project. Two mobile laboratories, MoLa and MOSQUITA, were deployed, and here an overview of these measurements and an investigation of the applicability of such measurements for the analysis of megacity emissions are presented. Both laboratories measured physical and chemical properties of fine and ultrafine aerosol particles as well as gas phase constituents of relevance for urban pollution scenarios. The applied measurement strategies include cross section measurements for the investigation of plume structure and quasi-Lagrangian measurements radially away from the city center to study plume aging processes. Results of intercomparison measurements between the two mobile laboratories represent the adopted data quality assurance procedures. Most of the compared measurement devices show sufficient agreement for combined data analysis. For the removal of data contaminated by local pollution emissions a video tape analysis method was applied. Analysis tools like positive matrix factorization and peak integration by key analysis applied to high-resolution time-of-flight aerosol mass spectrometer data are used for in-depth data analysis of the organic particulate matter. Several examples, including a combination of MoLa and MOSQUITA measurements on a cross section through the Paris emission plume are provided to demonstrate how such mobile measurements can be used to investigate the emissions of a megacity. A critical discussion of advantages and limitations of mobile measurements for the investigation of megacity emissions completes this work.

  5. In Situ Trace Gas Measurements from the Unmanned Aerial System (UAS) Altair

    NASA Astrophysics Data System (ADS)

    Hurst, D. F.; Moore, F. L.; Dutton, G. S.; Vasel, B.; Elkins, J. W.; Oltmans, S. J.; Summers, S.; Fahey, D. W.; Jennison, C. D.

    2006-12-01

    It is anticipated that Unmanned Aerial Systems (UASs) will soon become an integral part of the effort to monitor global atmospheric composition because they provide a unique combination of payload capacity, altitude range, and especially endurance. The NOAA UAS Demonstration Project in 2005 was designed to test the flight endurance of the Altair UAS (General Atomics Aeronautical Systems Inc.) and its suitability as an airborne platform for atmospheric measurements. Instrumentation included an ozone photometer (OZ), a 2- channel gas chromatograph (GC), an ocean color sensor, and a passive microwave vertical sounder. Altair was interactively controlled by a ground-based pilot via line-of-sight or satellite-based communications which also allowed instrument data and commands to be telemetered between the aircraft and ground. The NOAA project demonstrated that Altair was able to fly continuously for at least 18 hours and reach an altitude of 14 km with an internal payload >300 kg. The GC obtained ~2500 in situ measurements each of CFC-11, CFC-12, Halon-1211, N2O, and SF6 during 65 flight hours (10 flights) of Altair. These gases and ozone were measured at 250 m vertical resolution during two ~7 km deep spiral dive/climb maneuvers performed over the Pacific Ocean as part of the 18.4 long-endurance flight. During a different flight, GC and OZ sampled a tongue of stratospheric air that had intruded into the upper troposphere through a tropopause fold. In September 2006, GC and OZ were operated aboard Altair as part of the NASA/USDA-Forest Service Fire Mission. One GC channel (CFCs and Halon-1211) was changed to instead measure H2, CH4, and CO every 140 s, and the combined GC and OZ instrument package was expanded to include in situ measurements of water vapor (laser hygrometer) along with temperature and relative humidity (external probe). Data obtained during these two missions of the UAS Altair, including comparisons of relative humidity and water vapor measurements

  6. Trace Level Determination of Mesityl Oxide and Diacetone Alcohol in Atazanavir Sulfate Drug Substance by a Gas Chromatography Method

    PubMed Central

    Raju, K. V. S. N.; Pavan Kumar, K. S. R.; Siva Krishna, N.; Madhava Reddy, P.; Sreenivas, N.; Kumar Sharma, Hemant; Himabindu, G.; Annapurna, N.

    2016-01-01

    A capillary gas chromatography method with a short run time, using a flame ionization detector, has been developed for the quantitative determination of trace level analysis of mesityl oxide and diacetone alcohol in the atazanavir sulfate drug substance. The chromatographic method was achieved on a fused silica capillary column coated with 5% diphenyl and 95% dimethyl polysiloxane stationary phase (Rtx-5, 30 m x 0.53 mm x 5.0 µm). The run time was 20 min employing programmed temperature with a split mode (1:5) and was validated for specificity, sensitivity, precision, linearity, and accuracy. The detection and quantitation limits obtained for mesityl oxide and diacetone alcohol were 5 µg/g and 10 µg/g, respectively, for both of the analytes. The method was found to be linear in the range between 10 µg/g and 150 µg/g with a correlation coefficient greater than 0.999, and the average recoveries obtained in atazanavir sulfate were between 102.0% and 103.7%, respectively, for mesityl oxide and diacetone alcohol. The developed method was found to be robust and rugged. The detailed experimental results are discussed in this research paper. PMID:27222607

  7. Near-infrared echelle-AOTF spectrometer ACS-NIR for the ExoMars Trace Gas Orbiter

    NASA Astrophysics Data System (ADS)

    Trokhimovskiy, Alexander; Korablev, Oleg; Kalinnikov, Yurii K.; Fedorova, Anna; Stepanov, Alexander V.; Titov, Andrei Y.; Dziuban, Ilia; Patrakeev, Andrei; Montmessin, Franck

    2015-09-01

    The near-Infrared echelle-AOTF spectrometer is one channel of the Atmospheric Chemistry Suite (ACS) package dedicated for the studies of the Martian atmosphere on board ExoMars Trace Gas Orbiter planned for launch in 2016. The near-infrared (NIR) channel of ACS is a versatile spectrometer for the spectral range of 0.7-1.6 μm with a resolving power of <20,000. The NIR channel is intended to measure the atmospheric water vapor, aerosols, airglows, in nadir, in solar occultation, and on the limb. The science goals of NIR are basically the same as for SPICAM IR channel presently in flight on board Mars Express ESA orbiter, but it offers significantly better spectral resolution. The instrument employs the principle of an echelle spectrometer with an acoustooptical tunable filter (AOTF) as a preselector. The same principle was employed in SOIR, operated on Venus Express ESA mission in 2006-2014, and in RUSALKA, operated onboard ISS in 2009-2012. The NIR channel of ACS consists of entry optics, the AOTF, a Littrow echelle spectrometer, and an electrically cooled InGaAs detector array. It is a complete block with power and data interfaces, and the overall mass of 3.2 kg. The protoflight model of NIR is completed, calibrated, integrated within the ACS suite, and is undergoing tests at the spacecraft.

  8. Upper Troposphere/Lower Stratosphere (UTLS) Trace Gas Evolution in Recent Satellite Datasets: Relationships to Stratospheric and Upper Tropospheric Jets

    NASA Astrophysics Data System (ADS)

    Manney, G. L.; Hegglin, M. I.; Daffer, W. H.; Santee, M. L.; Bernath, P. F.; Boone, C. D.; Gille, J. C.; Kinnison, D.; Krueger, K.; Livesey, N. J.; Minschwaner, K.; Nardi, B.; Pawson, S.; Walker, K. A.

    2008-12-01

    A method has been developed for categorizing the location and characteristics of upper tropospheric jets and of the lower reaches of the stratospheric polar night jet (PNJ) that extend into the upper troposphere/lower stratosphere (UTLS). This method is applied to define the position, width and dynamical characteristics (e.g., windspeed/direction, potential vorticity, temperature, static stability, etc) of the primary subtropical jet (STJ) core, as well as similar information on multiple jets in the extratropical (ET) UTLS. The PNJ in the UTLS is characterized at each level by its position, width, and dynamical characteristics. Jet characteristics during quasi-isentropic stratosphere-troposphere exchange (STE) events and seasonal evolution of jet structure are investigated in Goddard Earth Observing System Version 5 (GEOS-5) and other meteorological analyses. Satellite trace gas measurements from several current instruments, including the Aura Microwave Limb Sounder (MLS), Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) and the Aura High Resolution Dynamics Limb Sounder (HIRDLS), are studied to further our understanding of the seasonal evolution of the ET tropopause layer in relation to the STJ and the tropopause.

  9. Trace level determination of trichloroethylene from liver, lung and kidney tissues by gas chromatography - magnetic sector mass spectrometry

    SciTech Connect

    Stacy D. Brown; S. Muralidhara; James V. Bruckner, Michael G. Bartlett

    2002-07-30

    Trichloroethylene (TCE) is a common industrial chemical that has been heavily used as a metal degreaser and a solvent for the past 100 years. As a result of the extensive use and production of this compound, it has become prevalent in the environment, appearing at over 50% of the hazardous waste sites on the US EPA's National Priorities List (NPL). TCE exposure has been linked to neurological dysfunction as well as to several types of cancer in animals. This paper describes the development and validation of a gas chromatography-mass spectrometry (GC-MS) method for the quantitation of trace levels of TCE in its target tissues (i.e. liver, kidney and lungs). The limit of quantitation (5 ng/ml) is substantially lower than currently published methods for the analysis of TCE in tissues. The % RSD and % Error for the assay falls within the acceptable range (<15% for middle and high QC points and <20% for low QC points), and the recovery is high from all tissues (>79%).

  10. Trace level determination of trichloroethylene from liver, lung and kidney tissues by gas chromatography-magnetic sector mass spectrometry.

    PubMed

    Brown, Stacy D; Muralidhara, S; Bruckner, James V; Bartlett, Michael G

    2003-01-15

    Trichloroethylene (TCE) is a common industrial chemical that has been heavily used as a metal degreaser and a solvent for the past 100 years. As a result of the extensive use and production of this compound, it has become prevalent in the environment, appearing at over 50% of the hazardous waste sites on the US EPA's National Priorities List (NPL). TCE exposure has been linked to neurological dysfunction as well as to several types of cancer in animals. This paper describes the development and validation of a gas chromatography-mass spectrometry (GC-MS) method for the quantitation of trace levels of TCE in its target tissues (i.e. liver, kidney and lungs). The limit of quantitation (5 ng/ml) is substantially lower than currently published methods for the analysis of TCE in tissues. The % RSD and % Error for the assay falls within the acceptable range (<15% for middle and high QC points and <20% for low QC points), and the recovery is high from all tissues (>79%). PMID:12482474

  11. Trace gas and vegetation feedback responses of Alaskan tussock tundra to long-term snow depth manipulations

    NASA Astrophysics Data System (ADS)

    Ebbs, L. M.; Taneva, L.; Sullivan, P.; Welker, J. M.

    2009-12-01

    Changes in the precipitation and temperature regimes in Northern Alaska are manifesting themselves through shifts in sea ice, vegetation traits, animal migration timing and hydrologic dynamics. Changes in precipitation and soil temperature result in changes in plant mineral nutrition, soil nutrient availability, trace gas exchanges and differential nutrient acquisition strategies by arctic plants. In this study, we report on the extent to which long-term increases in snow depth, along with reductions in snow depth alter the magnitudes and pattern of CO2 exchange, soil properties and vegetation traits. A doubling of snow depth (from ~0.5 to ~1.0m) results in a delay of the growing season by ~ 2 weeks, however, by peak season, the rates of CO2 exchange are 50% higher in areas which had experienced deeper snow depth levels. To the contrary, long-term reductions in snow depth results in accelerated rates of plant phenology, however CO2 exchange rates at peak season are 30% less than those areas under ambient snow cover in the preceding winter. Reduced snow depth areas had the coldest winter soil temperatures while the deeper areas had the warmest winter soil temperatures, which may partially explain the summer CO2 fluxes indirectly via different rates of winter N mineralization and differences in leaf N properties. Our results indicate that shifting fall, winter and spring when snow is the primary form of precipitation, may have profound effects on tussock tundra systems.

  12. Trace Level Determination of Mesityl Oxide and Diacetone Alcohol in Atazanavir Sulfate Drug Substance by a Gas Chromatography Method.

    PubMed

    Raju, K V S N; Pavan Kumar, K S R; Siva Krishna, N; Madhava Reddy, P; Sreenivas, N; Kumar Sharma, Hemant; Himabindu, G; Annapurna, N

    2016-01-01

    A capillary gas chromatography method with a short run time, using a flame ionization detector, has been developed for the quantitative determination of trace level analysis of mesityl oxide and diacetone alcohol in the atazanavir sulfate drug substance. The chromatographic method was achieved on a fused silica capillary column coated with 5% diphenyl and 95% dimethyl polysiloxane stationary phase (Rtx-5, 30 m x 0.53 mm x 5.0 µm). The run time was 20 min employing programmed temperature with a split mode (1:5) and was validated for specificity, sensitivity, precision, linearity, and accuracy. The detection and quantitation limits obtained for mesityl oxide and diacetone alcohol were 5 µg/g and 10 µg/g, respectively, for both of the analytes. The method was found to be linear in the range between 10 µg/g and 150 µg/g with a correlation coefficient greater than 0.999, and the average recoveries obtained in atazanavir sulfate were between 102.0% and 103.7%, respectively, for mesityl oxide and diacetone alcohol. The developed method was found to be robust and rugged. The detailed experimental results are discussed in this research paper. PMID:27222607

  13. Seasonal Variations in Titan's Stratosphere Observed with Cassini/CIRS: Temperature, Trace Molecular Gas and Aerosol Mixing Ratio Profiles

    NASA Technical Reports Server (NTRS)

    Vinatier, S.; Bezard, B.; Anderson, C. M.; Coustenis, A.; Teanby, N.

    2012-01-01

    Titan's northern spring equinox occurred in August 2009. General Circulation Models (e.g. Lebonnois et al., 2012) predict strong modifications of the global circulation in this period, with formation of two circulation cells instead of the pole-to-pole cell that occurred during northern winter. This winter single cell, which had its descending branch at the north pole, was at the origin of the enrichment of molecular abundances and high stratopause temperatures observed by Cassini/CIRS at high northern latitudes (e.g. Achterberg et al., 2011, Coustenis et al., 2010, Teanby et al., 2008, Vinatier et al., 2010). The predicted dynamical seasonal variations after the equinox have strong impact on the spatial distributions of trace gas, temperature and aerosol abundances. We will present here an analysis of CIRS limb-geometry datasets acquired in 2010 and 2011 that we used to monitor the seasonal evolution of the vertical profiles of temperature, molecular (C2H2, C2H6, HCN, ..) and aerosol abundances.

  14. Design and application of a mobile ground-based observatory for continuous measurements of atmospheric trace-gas and criteria pollutant species

    DOE PAGESBeta

    Bush, S. E.; Hopkins, F. M.; Randerson, J. T.; Lai, C.-T.; Ehleringer, J. R.

    2015-01-06

    Ground-based measurements of atmospheric trace gas species and criteria pollutants are essential for understanding emissions dynamics across space and time. Gas composition in the surface 50 m has the greatest direct impacts on human health as well as ecosystem processes, hence data at this level is necessary for addressing carbon cycle and public health related questions. However, such surface data are generally associated with stationary measurement towers, where spatial representation is limited due to the high cost of establishing and maintaining an extensive network of measurement stations. We describe here a compact mobile laboratory equipped to provide high-precision, high-frequency, continuous,more » on-road synchronous measurements of CO2, CO, CH4, H2O, NOx, O3, aerosol, meteorological, and geospatial position data. The mobile laboratory has been deployed across the western USA. In addition to describing the vehicle and its capacity, we present data that illustrate the use of the laboratory as a powerful tool for investigating the spatial structure of urban trace gas emissions and criteria pollutants at spatial scales ranging from single streets to whole ecosystem and regional scales. We identify fugitive urban CH4 emissions and assess the magnitude of CH4 emissions from known point sources. We illustrate how such a mobile laboratory can be used to better understand emissions dynamics and quantify emissions ratios associated with trace gas emissions from wildfire incidents. Lastly, we discuss additional mobile laboratory applications in health and urban metabolism.« less

  15. Elevated gas flux and trace metal degassing from the 2014-2015 fissure eruption at the Bárðarbunga volcanic system, Iceland

    NASA Astrophysics Data System (ADS)

    Gauthier, Pierre-Jean; Sigmarsson, Olgeir; Gouhier, Mathieu; Haddadi, Baptiste; Moune, Séverine

    2016-03-01

    The 2014 Bárðarbunga rifting event in Iceland resulted in a 6-month long eruption at Holuhraun. This eruption was characterized by high lava discharge rate and significant gas emission. The SO2 flux for the first 3 months was measured with satellite sensors and the petrologic method. High-resolution time series of the satellite data give 1200 kg/s that concurs with 1050 kg/s obtained from melt inclusion minus degassed lava sulfur contents scaled to the mass of magma produced. A high-purity gas sample, with elevated S/Cl due to limited chlorine degassing, reveals a similar degassing pattern of trace metals as observed at Kīlauea (Hawai'i) and Erta Ale (Ethiopia). This suggests a common degassing mechanism at mantle plume-related volcanoes. The trace metal fluxes, calculated from trace element to sulfur ratios in the gas sample and scaled to the sulfur dioxide flux, are 1-2 orders of magnitude stronger at Holuhraun than Kīlauea and Erta Ale. In contrast, volcanoes at convergent margins (Etna and Stromboli, Italy) have 1-2 orders of magnitude higher trace element fluxes, most likely caused by abundant chlorine degassing. This emphasizes the importance of metal degassing as chlorine species. Short-lived disequilibria between radon daughters, 210Pb-210Bi-210Po measured in the gas, suggest degassing of a continuously replenished magma batch beneath the eruption site. Earlier and deep degassing phase of carbon dioxide and polonium is inferred from low (210Po/210Pb) in the gas, consistent with magma transfer rate of 0.75 m/s.

  16. Simultaneous removal of SO2 and trace SeO2 from flue gas: effect of SO2 on selenium capture and kinetics study.

    PubMed

    Li, Yuzhong; Tong, Huiling; Zhuo, Yuqun; Wang, Shujuan; Xu, Xuchang

    2006-12-15

    Sulfur dioxide (SO2) and trace elements are all pollutants derived from coal combustion. This study relates to the simultaneous removal of SO2 and trace selenium dioxide (SeO2) from flue gas by calcium oxide (CaO) adsorption in the moderate temperature range, especially the effect of SO2 presence on selenium capture. Experiments performed on a thermogravimetric analyzer (TGA) can reach the following conclusions. When the CaO conversion is relatively low and the reaction rate is controlled by chemical kinetics, the SO2 presence does not affect the selenium capture. When the CaO conversion is very high and the reaction rate is controlled by product layer diffusion, the SO2 presence and the product layer diffusion resistance jointly reduce the selenium capture. On the basis of the kinetics study, a method to estimate the trace selenium removal efficiency using kinetic parameters and the sulfur removal efficiency is developed. PMID:17256549

  17. Submicron aerosol and trace gas composition near Manaus as observed during GoAmazon2014/5

    NASA Astrophysics Data System (ADS)

    Ferreira De Brito, J.; Wurm, F.; Liu, Y.; de Sá, S. S.; Carbone, S.; Rizzo, L. V.; Cirino, G. G.; Barbosa, H. M.; Souza, R. A. F. D.; Martin, S. T.; Artaxo, P.

    2014-12-01

    The Amazon Basin, during the wet season, has one of the lowest aerosol concentrations worldwide, with air masses covering thousands of kilometers of pristine forest with negligible human impact. The atmosphere in such regions is strongly coupled with the biosphere through primary biological aerosols, biogenic salts and secondary aerosols from oxidation of biogenic VOCs. The natural environment is strongly modified nearby urbanized areas, in particular Manaus, a city of nearly two million people. The urban pollution plume has high concentrations of oxides of nitrogen and sulfur, carbon monoxide, particle concentrations, and soot, among other pollutants, strongly contrasting with the clean air masses reaching the city. Such unique location provides the ideal laboratory to study the isolated urban emission, as well the pristine environment by perturbing it in a relatively known fashion. The GoAmazon experiment was designed with these questions in mind, combining remote sensing, in situand airborne measurements. This manuscript describes the measurements currently taking place at the T2 site, near Manaus, frequently impacted by relatively fresh emissions from the city. This presentation focuses on aerosol properties and trace gas composition at the T2 site. PM1 mass concentration from March up to July 2014 has been observed to be dominated by organics (1.51 μg m-3), followed by BC (0.83 μg m-3), SO4 (0.17 μg m-3), NO3 (0.08 μg m-3) and NH4 (0.06 μg m-3). Mean aerosol number concentration was 3600 cm-3, with a mean geometric diameter of 70 nm. As for the trace gases, initial estimates of isoprene average ambient concentration is 0.95 ppb, whereas MVK+MACR has been estimated to be 0.76 ppb. Average mixing ratios of toluene, benzene and C8 aromatics were 0.31 ppb, 0.16 ppb and 0.15 ppb, respectively, correlating relatively well with markers of anthropogenic activities, such as BC. Such measurements will carry on throughout GoAmazon 2014/5, providing a unique dataset

  18. Atmospheric chemistry suite (ACS): a set of infrared spectrometers for atmospheric measurements on board ExoMars trace gas orbiter

    NASA Astrophysics Data System (ADS)

    Korablev, Oleg; Grigoriev, Alexei V.; Trokhimovsky, Alexander; Ivanov, Yurii S.; Moshkin, Boris; Shakun, Alexei; Dziuban, Ilia; Kalinnikov, Yurii K.; Montmessin, Franck

    2013-09-01

    The ACS package for ExoMars Trace Gas Orbiter is a part of Russian contribution to ExoMars ESA-Roscosmos mission. On the Orbiter it complements NOMAD investigation and is intended to recover in much extent the science lost with the cancellation of NASA MATMOS and EMCS infrared sounders. ACS includes three separate spectrometers, sharing common mechanical, electrical, and thermal interfaces. NIR is a versatile spectrometer for the spectral range of 0.7-1.6 μm with resolving power of ~20000. It is conceived on the principle of RUSALKA/ISS or SOIR/Venus Express experiments combining an echelle spectrometer and an AOTF (Acousto-Optical Tuneable Filter) for order selection. Up to 8 diffraction orders, each 10-20 nm wide can be measured in one sequence record. NIR will be operated principally in nadir, but also in solar occultations, and possibly on the limb. MIR is a high-resolution echelle instrument exclusively dedicated to solar occultation measurements in the range of 2.2-4.4 μm targeting the resolving power of 50000. The order separation is done by means of a steerable grating cross-disperser, allowing instantaneous coverage of up to 300-nm range of the spectrum for one or two records per second. MIR is dedicated to sensitive measurements of trace gases, approaching MATMOS detection thresholds for many species. TIRVIM is a 2- inch double pendulum Fourier-transform spectrometer for the spectral range of 1.7-17 μm with apodized resolution varying from 0.2 to 1.6 cm-1. TIRVIM is primarily dedicated to monitoring of atmospheric temperature and aerosol state in nadir, and would contribute in solar occultation to detection/reducing of upper limits of some components absorbing beyond 4 μm, complementing MIR and NOMAD. Additionally, TIRVIM targets the methane mapping in nadir, using separate detector optimized for 3.3-μm range. The concept of the instrument and in more detail the optical design and the expected parameters of its three parts, channel by channel are

  19. Gas phase ion chemistry of an ion mobility spectrometry based explosive trace detector elucidated by tandem mass spectrometry.

    PubMed

    Kozole, Joseph; Levine, Lauren A; Tomlinson-Phillips, Jill; Stairs, Jason R

    2015-08-01

    The gas phase ion chemistry for an ion mobility spectrometer (IMS) based explosive detector has been elucidated using tandem mass spectrometry. The IMS system, which is operated with hexachloroethane and isobutyramide reagent gases and an ion shutter type gating scheme, is connected to the atmospheric pressure interface of a triple quadrupole mass spectrometer (MS/MS). Product ion masses, daughter ion masses, and reduced mobility values for a collection of nitro, nitrate, and peroxide explosives measured with the IMS/MS/MS instrument are reported. The mass and mobility data together with targeted isotopic labeling experiments and information about sample composition and reaction environment are leveraged to propose molecular formulas, structures, and ionization pathways for the various product ions. The major product ions are identified as [DNT-H](-) for DNT, [TNT-H](-) for TNT, [RDX+Cl](-) and [RDX+NO2](-) for RDX, [HMX+Cl](-) and [HMX+NO2](-) for HMX, [NO3](-) for EGDN, [NG+Cl](-) and [NG+NO3](-) for NG, [PETN+Cl](-) and [PETN+NO3](-) for PETN, [HNO3+NO3](-) for NH4NO3, [NO2](-) for DMNB, [HMTD-NC3H6O3+H+Cl](-) and [HMTD+H-CH2O-H2O2](+) for HMTD, and [(CH3)3CO2](+) for TATP. In general, the product ions identified for the IMS system studied here are consistent with the product ions reported previously for an ion trap mobility spectrometer (ITMS) based explosive trace detector, which is operated with dichloromethane and ammonia reagent gases and an ion trap type gating scheme. Differences between the explosive trace detectors include the [NG+Cl](-) and [PETN+Cl](-) product ions being major ions in the IMS system compared to minor ions in the ITMS system as well as the major product ion for TATP being [(CH3)3CO2](+) for the IMS system and [(CH3)2CNH2](+) for the ITMS system. PMID:26048817

  20. Modelling Metamorphism by Abstract Interpretation

    NASA Astrophysics Data System (ADS)

    Dalla Preda, Mila; Giacobazzi, Roberto; Debray, Saumya; Coogan, Kevin; Townsend, Gregg M.

    Metamorphic malware apply semantics-preserving transformations to their own code in order to foil detection systems based on signature matching. In this paper we consider the problem of automatically extract metamorphic signatures from these malware. We introduce a semantics for self-modifying code, later called phase semantics, and prove its correctness by showing that it is an abstract interpretation of the standard trace semantics. Phase semantics precisely models the metamorphic code behavior by providing a set of traces of programs which correspond to the possible evolutions of the metamorphic code during execution. We show that metamorphic signatures can be automatically extracted by abstract interpretation of the phase semantics, and that regular metamorphism can be modelled as finite state automata abstraction of the phase semantics.

  1. Experimental determination of the retention time of reduced temperature of gas-vapor mixture in trace of water droplets moving in counterflow of combustion products

    NASA Astrophysics Data System (ADS)

    Volkov, R. S.; Kuznetsov, G. V.; Strizhak, P. A.

    2016-06-01

    We have experimentally studied temporal variation of the temperature of gas-vapor mixture in the trace of water droplets moving in the counterflow of high-temperature combustion products. The initial gas temperature was within 500-950 K. The water droplet radius in the aerosol flow varied from 40 to 400 μm. The motion of water droplets in the counterflow of combustion products in a 1-m-high hollow quartz cylinder with an internal diameter of 20 cm was visualized by optical flow imaging techniques (interferometric particle imaging, shadow photography, particle tracking velocimetry, and particle image velocimetry) with the aid of a cross-correlation complex setup. The scale of temperature decrease in the mixture of combustion products and water droplets was determined for a pulsed (within 1 s) and continuous supply of aerosol with various droplet sizes. Retention times of reduced temperature (relative to the initial level) in trace of water droplets (aerosol temperature trace) are determined. A hypothesis concerning factors responsible for the variation of temperature in the trace of droplets moving in the counterflow of combustion products is experimentally verified.

  2. Simultaneous Photoacoustic and Photopyroelectric Detection of Trace Gas Emissions from Some Plant Parts and Their Related Essential Oils in a Combined Detection Cell

    NASA Astrophysics Data System (ADS)

    Abu-Taha, M. I.; Abu-Teir, M. M.; Al-Jamal, A. J.; Eideh, H.

    The aim of this work was to establish the feasibility of the combined photoacoustic (PA) and photopyroelectric (PPE) detection of the vapours emitted from essential oils and their corresponding uncrushed leaves or flowers. Gas traces of jasmine (Jessamine (Jasminum)), mint (Mentha arvensis L.) and Damask rose (Rosa damascena Miller) and their essential oils were tested using a combined cell fitted with both a photopyroelectric film (PVDF) and a microphone in conjunction with a pulsed wideband infrared source (PWBS) source. Infrared PA and PPE absorbances were obtained simultaneously at room temperatures with excellent reproducibility and high signal-to-noise ratios. Significant similarities found between the PA and PPE spectra of the trace gas emissions of plant parts, i.e., flowers or leaves and their related essential oils show the good correlation of their emissions and that both effects are initiated by the same absorbing molecules.

  3. Evidence for in-situ metabolic activity in ice sheets based on anomalous trace gas records from the Vostok and other ice cores

    NASA Astrophysics Data System (ADS)

    Sowers, T.

    2003-04-01

    Measurements of trace gas species in ice cores are the primary means for reconstructing the composition of the atmosphere. The longest such record comes from the Vostok core taken from the central portion of the East Antarctic ice sheet [Petit et al., 1999]. In general, the trace gas records from Vostok are utilized as the reference signal when correlating trace gas measurements from other ice cores. The underlying assumption implicit in such endeavors is that the bubbles recovered from the ice cores record the composition of the atmosphere at the time the bubbles were formed. Another implicit assumption is that the composition of the bubbles has not been compromised by the extremely long storage periods within the ice sheet. While there is ample evidence that certain trace gas records (e.g. CO2 and CH4) have probably not been compromised, anomalous nitrous oxide (N2O) measurements from the penultimate glacial termination at Vostok are consistent with in-situ (N2O) production [Sowers, 2001]. In general, trace gas measurements from high altitude tropical/temperate glaciers are higher than expected based on contemporaneous measurements from polar cores. Measurements spanning the last 25kyr from the Sajama ice core from central Bolivia (18oS, 69oW, 6542masl), for example, were 1X-5X higher than contemporaneous values recorded in polar ice cores [Campen et al., 2003]. While other physical factors (like temperature/melting) may contribute to the elevated trace gas levels at these sites, the most likely explanation involves the accumulation of in-situ metabolic trace gas byproducts. Stable isotope measurements provide independent information for assessing the origin of the elevated trace gas levels in select samples. For the penultimate glacial termination at Vostok, the anomalous (N2O) values carry high δ15Nbulk and low δ18Obulk values that would be predicted if the added (N2O) was associated with in-situ nitrification. At Sajama, low δ13CH4 values observed during

  4. NOMAD, a spectrometer suite for Nadir and Solar Occultation observations on the ExoMars Trace Gas Orbiter

    NASA Astrophysics Data System (ADS)

    Vandaele, A. C.; López-Moreno, J.-J.; Patel, M. R.; Bellucci, G.; Daerden, F.; Drummond, R.; Neefs, E.; Robert, S.; Rodriguez Gomez, J.

    2012-04-01

    NOMAD, the "Nadir and Occultation for MArs Discovery" spectrometer suite has been selected by ESA and NASA to be part of the payload of the ExoMars Trace Gas Orbiter mission 2016. This instrument suite will conduct a spectroscopic survey of Mars' atmosphere in the UV, visible and IR regions covering the 0.2-0.65 and 2.2-4.3 μm spectral ranges. NOMAD's observation modes include solar occultation, nadir and limb observations. The NOMAD instrument is composed of 3 channels: a solar occultation only channel (SO) operating in the infrared wavelength domain, a second infrared channel capable of doing nadir, but also solar occultation and limb observations (LNO), and an ultraviolet/visible channel (UVIS) that can work in all observation modes. The spectral resolution of SO and LNO surpasses previous surveys in the infrared by more than one order of magnitude. NOMAD offers an integrated instrument combination of a flight-proven concept (SO is a copy of SOIR on Venus Express), and innovations based on existing and proven instrumentation (LNO is based on SOIR/VEX and UVIS has heritage from the ExoMars lander), that will provide mapping and vertical profile information at high spatio-temporal resolution. The three channels have each their own ILS and optical bench, but share the same single interface to the S/C. We will present the instrument and its capabilities in term of detection of a broad suite of species, its possibilities to improve our knowledge on vertical structure of the atmosphere as well as its mapping possibilities.

  5. Ultrasensitive, real-time trace gas detection using a high-power, multimode diode laser and cavity ringdown spectroscopy.

    PubMed

    Karpf, Andreas; Qiao, Yuhao; Rao, Gottipaty N

    2016-06-01

    We present a simplified cavity ringdown (CRD) trace gas detection technique that is insensitive to vibration, and capable of extremely sensitive, real-time absorption measurements. A high-power, multimode Fabry-Perot (FP) diode laser with a broad wavelength range (Δλlaser∼0.6  nm) is used to excite a large number of cavity modes, thereby reducing the detector's susceptibility to vibration and making it well suited for field deployment. When detecting molecular species with broad absorption features (Δλabsorption≫Δλlaser), the laser's broad linewidth removes the need for precision wavelength stabilization. The laser's power and broad linewidth allow the use of on-axis cavity alignment, improving the signal-to-noise ratio while maintaining its vibration insensitivity. The use of an FP diode laser has the added advantages of being inexpensive, compact, and insensitive to vibration. The technique was demonstrated using a 1.1 W (λ=400  nm) diode laser to measure low concentrations of nitrogen dioxide (NO2) in zero air. A sensitivity of 38 parts in 1012 (ppt) was achieved using an integration time of 128 ms; for single-shot detection, 530 ppt sensitivity was demonstrated with a measurement time of 60 μs, which opens the door to sensitive measurements with extremely high temporal resolution; to the best of our knowledge, these are the highest speed measurements of NO2 concentration using CRD spectroscopy. The reduced susceptibility to vibration was demonstrated by introducing small vibrations into the apparatus and observing that there was no measurable effect on the sensitivity of detection. PMID:27411209

  6. Accurate analysis of trace earthy-musty odorants in water by headspace solid phase microextraction gas chromatography-mass spectrometry.

    PubMed

    Ma, Kang; Zhang, Jin Na; Zhao, Min; He, Ya Juan

    2012-06-01

    A simple and sensitive method was developed for the simultaneous separation and determination of trace earthy-musty compounds including geosmin, 2-methylisoborneol, 2-isobutyl-3-methoxypyrazine, 2-isopropyl-3-methoxypyrazine, 2,3,4-trichloroanisole, 2,4,6-trichloroanisole, and 2,3,6-trichloroanisole in water samples. This method combined headspace solid-phase microextraction (HS-SPME) with gas chromatography-mass spectrometry and used naphthalene-d(8) as internal standard. A divinylbenzene/carboxen/polydimethylsiloxane fiber exposing at 90°C for 30 min provided effective sample enrichment in HS-SPME. These compounds were separated by a DB-1701MS capillary column and detected in selected ion monitoring mode within 12 min. The method showed a good linearity from 1 to 100 ng L(-1) and detection limits within (0.25-0.61 ng L(-1)) for all compounds. Using naphthalene-d(8) as the internal standard, the intra-day relative standard deviation (RSD) was within (2.6-3.4%), while the inter-day RSD was (3.5-4.9%). Good recoveries were obtained for tap water (80.5-90.6%), river water (81.5-92.4%), and lake water (83.5-95.2%) spiked at 10 ng L(-1). Compared with other methods using HS-SPME for determination of odor compounds in water samples, this present method had more analytes, better precision, and recovery. This method was successfully applied for analysis of earthy-musty odors in water samples from different sources. PMID:22740259

  7. Quantitative analysis of trace-level benzene, toluene, ethylbenzene, and xylene in cellulose acetate tow using headspace heart-cutting multidimensional gas chromatography with mass spectrometry.

    PubMed

    Ji, Xiaorong; Zhang, Jing; Guo, Yinlong

    2016-06-01

    This study describes a method for the quantification of trace-level benzene, toluene, ethylbenzene, and xylene in cellulose acetate tow by heart-cutting multidimensional gas chromatography with mass spectrometry in selected ion monitoring mode. As the major volatile component in cellulose acetate tow samples, acetone would be overloaded when attempting to perform a high-resolution separation to analyze trace benzene, toluene, ethylbenzene, and xylene. With heart-cutting technology, a larger volume injection was achieved and acetone was easily cut off by employing a capillary column with inner diameter of 0.32 mm in the primary gas chromatography. Only benzene, toluene, ethylbenzene, and xylene were directed to the secondary column to result in an effective separation. The matrix interference was minimized and the peak shapes were greatly improved. Finally, quantitative analysis of benzene, toluene, ethylbenzene, and xylene was performed using an isotopically labeled internal standard. The headspace multidimensional gas chromatography mass spectrometry system was proved to be a powerful tool for analyzing trace volatile organic compounds in complex samples. PMID:27080077

  8. Intracavity CO laser photoacoustic trace gas detection: cyclic CH 4 , H 2 O and CO 2 emission by cockroaches and scarab beetles

    NASA Astrophysics Data System (ADS)

    Bijnen, F. G. C.; Harren, F. J. M.; Hackstein, J. H. P.; Reuss, J.

    1996-09-01

    A liquid-nitrogen-cooled CO laser and an intracavity resonant photoacoustic cell are employed to monitor trace gases. The setup was designed to monitor trace gas emissions of biological samples on line. The arrangement offers the possibility to measure gases at the 10 9 by volume (ppbv) level (e.g., CH 4 , H 2 O) and to detect rapid changes in trace gas emission. A detection limit of 1 ppbv for CH 4 in N 2 equivalent to a minimal detectable absorption of 3 10 9 cm 1 can be achieved. Because of the kinetic cooling effect we lowered the detection limit for CH 4 in air is decreased to 10 ppbv. We used the instrument in a first application to measure the CH 4 and H 2 O emission of individual cockroaches and scarab beetles. These emissions could be correlated with CO 2 emissions that were recorded simultaneously with an infrared gas analyzer. Characteristic breathing patterns of the insects could be observed; unexpectedly methane was also found to be released.

  9. Interaction of Trace gas Species of Atmospheric Interest With ice: Measurement of the Adsorption Enthalpy of Acetone on ice

    NASA Astrophysics Data System (ADS)

    Bartels-Rausch, T.; Guimbaud, C.; Gaggeler, H.; Ammann, M.

    2002-12-01

    Ice provides an important substrate for heterogeneous chemistry in the stratosphere, the upper troposphere, but also in the cold regions of the planetary boundary layer. Thus, we started to investigate the interaction of trace gases of atmospheric interest (acetone) with ice. In the upper troposphere, the photolysis of acetone is the main source of HOX, dominating the one from the reaction of O(1D) + H2O (Jaegle et al., 2001). Source and sinks of acetone need to be quantified to simulate the concentration of the main atmospheric oxidant (HOX). Ice cirrus clouds are suggested to be one of the acetone sinks. Thus, the adsorption enthalpy of acetone on ice needs to be investigated because it determines the mixing ratio of acetone between the gas and the particulate phase and the chemistry of the upper troposphere. In this paper, the chromatographic method applied for the measurement of the adsorption enthalpy of acetone on ice is described. This method uses a chromatographic ice-packed column similar to the one described by Bartels et al. (2002) and is combined with Proton Transfer Reaction Mass Spectrometry (PTR-MS) for the monitoring of the acetone concentration in the gas phase. Preliminary results show that the measured standard adsorption enthalpy obtained with a column packed with ice spheres, i.e. (-54+/-8) kJ mol-1, and with a column packed with a snow sample, i.e. (-56+/-3) kJ mol-1, are similar and in agreement with the ones derived by Winkler et al. (2002) and from Domine and Hanot (2002), using a low pressure ice coated wall flow tube reactor and a volumetric method, respectively. More investigations are scheduled in the near future using different ice surfaces (ice crystals, fresh snow). We briefly address the atmospheric implication of this study as well as the perspective of the chromatographic & APCI-MS system to investigate other processes of atmospheric interest. References Bartels, T., B. Eichler, P. Zimmermann, H. W. Gäggeler, and M. Ammann, The

  10. Megacity emission plume characteristics in summer and winter investigated by mobile aerosol and trace gas measurements: the Paris metropolitan area

    NASA Astrophysics Data System (ADS)

    von der Weiden-Reinmüller, S.-L.; Drewnick, F.; Zhang, Q. J.; Freutel, F.; Beekmann, M.; Borrmann, S.

    2014-05-01

    For the investigation of megacity emission plume characteristics mobile aerosol and trace gas measurements were carried out in the greater Paris region in July 2009 and January/February 2010 within the EU FP7 MEGAPOLI project. The deployed instruments measured physical and chemical properties of sub-micron aerosol particles, gas phase constituents of relevance for urban air pollution studies and meteorological parameters. The emission plume was identified based on fresh pollutant (e.g. particle-bound polycyclic aromatic hydrocarbons, black carbon, CO2 and NOx) concentration changes in combination with wind direction data. The classification into megacity influenced and background air masses allowed a characterization of the emission plume during summer and winter environmental conditions. On average, a clear increase of fresh pollutant concentrations in plume compared to background air masses was found for both seasons. For example, an average increase of 190% (+8.8 ng m-3) in summer and of 130% (+18.1 ng m-3) in winter was found for particle-bound polycyclic aromatic hydrocarbons in plume air masses. The aerosol particle size distribution in plume air masses was influenced by nucleation and growth due to coagulation and condensation in summer, while in winter only the second process seemed to be initiated by urban pollution. The observed distribution of fresh pollutants in the emission plume - its cross sectional Gaussian-like profile and the exponential decrease of pollutant concentrations with increasing distance to the megacity - are in agreement with model results. Differences between model and measurements were found for plume center location, plume width and axial plume extent. In general, dilution was identified as the dominant process determining the axial variations within the Paris emission plume. For in-depth analysis of transformation processes occurring in the advected plume, simultaneous measurements at a suburban measurement site and a stationary

  11. Megacity emission plume characteristics in summer and winter investigated by mobile aerosol and trace gas measurements: the Paris metropolitan area

    NASA Astrophysics Data System (ADS)

    von der Weiden-Reinmüller, S.-L.; Drewnick, F.; Zhang, Q. J.; Freutel, F.; Beekmann, M.; Borrmann, S.

    2014-12-01

    For the investigation of megacity emission plume characteristics mobile aerosol and trace gas measurements were carried out in the greater Paris region in July 2009 and January-February 2010 within the EU FP7 MEGAPOLI project (Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation). The deployed instruments measured physical and chemical properties of sub-micron aerosol particles, gas phase constituents of relevance for urban air pollution studies and meteorological parameters. The emission plume was identified based on fresh pollutant (e.g., particle-bound polycyclic aromatic hydrocarbons, black carbon, CO2 and NOx) concentration changes in combination with wind direction data. The classification into megacity influenced and background air masses allowed a characterization of the emission plume during summer and winter environmental conditions. On average, a clear increase of fresh pollutant concentrations in plume compared to background air masses was found for both seasons. For example, an average increase of 190% (+ 8.8 ng m-3) in summer and of 130% (+ 18.1 ng m-3) in winter was found for particle-bound polycyclic aromatic hydrocarbons in plume air masses. The aerosol particle size distribution in plume air masses was influenced by nucleation and growth due to coagulation and condensation in summer, while in winter only the latter process (i.e., particle growth) seemed to be initiated by urban pollution. The observed distribution of fresh pollutants in the emission plume - its cross sectional Gaussian-like profile and the exponential decrease of pollutant concentrations with increasing distance to the megacity - are in agreement with model results. Differences between model and measurements were found for plume center location, plume width and axial plume extent. In general, dilution was identified as the dominant process determining the axial variations within the Paris

  12. Trace Gas Monitoring

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Space technology is contributing to air pollution control primarily through improved detectors and analysis methods. Miniaturized mass spectrometer is under development to monitor vinyl chloride and other hydrocarbon contaminants in an airborne laboratory. Miniaturized mass spectrometer can be used to protect personnel in naval and medical operations as well as aboard aircraft.

  13. A general method for the calculation of absolute trace gas concentrations in air and breath from selected ion flow tube mass spectrometry data

    NASA Astrophysics Data System (ADS)

    Spanel, Patrik; Dryahina, Kseniya; Smith, David

    2006-03-01

    A complete description is presented of a numerical method that allows the calculation, in real time, of absolute concentrations of trace gases, including volatile organic compounds and water vapour, from selected ion flow tube mass spectrometry, SIFT-MS, data. No assumptions are made concerning the SIFT-MS instrument size or its configuration and thus the calculation can be applied to the currently available, relatively large instruments and the anticipated new generation of smaller SIFT-MS instruments. This numerical method clearly distinguishes those parameters that are obviously specific to a particular instrument, including flow tube geometry, degree of mass discrimination in the analytical mass spectrometer and flow tube reaction time, from general fundamental processes, in particular the differential diffusive loss of ions along the flow tube that is dependent on the properties of those ions involved in the determination of the concentrations of particular trace gases. The essential reaction and transport kinetics are outlined, which describe the formation and loss of the product ions formed in the chemical ionisation of the trace gases by the precursor ions. A generalised calculation of the required ionic diffusion coefficients is introduced with options either for their accurate determination from the molecular geometry of ions or for less accurate but simpler estimates obtained using just the ionic mass. Based on the above ideas, a straightforward calculation sequence is shown to determine trace gas concentrations by SIFT-MS, and its utility demonstrated by an example of the analysis of acetone in exhaled breath.

  14. Simultaneous removal of SO2 and trace As2O3 from flue gas: mechanism, kinetics study, and effect of main gases on arsenic capture.

    PubMed

    Li, Yuzhong; Tong, Huiling; Zhuo, Yuqun; Li, Yan; Xu, Xuchang

    2007-04-15

    Sulfur dioxide (SO2) and trace elements are pollutants derived from coal combustion. This study focuses on the simultaneous removal of S02 and trace arsenic oxide (As2O3) from flue gas by calcium oxide (CaO) adsorption in the moderate temperature range. Experiments have been performed on a thermogravimetric analyzer (TGA). The interaction mechanism between As2O3 and CaO is studied via XRD detection. Calcium arsenate [Ca3(AsO4)2] is found to be the reaction product in the range of 600-1000 degrees C. The ability of CaO to absorb As2O3 increases with the increasing temperature over the range of 400-1000 degrees C. Through kinetics analysis, it has been found that the rate constant of arsenate reaction is much higher than that of sulfate reaction. SO2 presence does not affect the trace arsenic capture either in the initial reaction stage when CaO conversion is relatively low or in the later stage when CaO conversion is very high. The product of sulfate reaction, CaS04, is proven to be able to absorb As2O3. The coexisting CO2 does not weaken the trace arsenic capture either. PMID:17533855

  15. Implementation of Cloud Retrievals for Tropospheric Emission Spectrometer (TES) Atmospheric Retrievals: Part 1. Description and Characterization of Errors on Trace Gas Retrievals

    NASA Technical Reports Server (NTRS)

    Kulawik, Susan S.; Worden, John; Eldering, Annmarie; Bowman, Kevin; Gunson, Michael; Osterman, Gregory B.; Zhang, Lin; Clough, Shepard A.; Shephard, Mark W.; Beer, Reinhard

    2006-01-01

    We develop an approach to estimate and characterize trace gas retrievals in the presence of clouds in high spectral measurements of upwelling radiance in the infrared spectral region (650-2260/cm). The radiance contribution of clouds is parameterized in terms of a set of frequency-dependent nonscattering optical depths and a cloud height. These cloud parameters are retrieved jointly with surface temperature, emissivity, atmospheric temperature, and trace gases such as ozone from spectral data. We demonstrate the application of this approach using data from the Tropospheric Emission Spectrometer (TES) and test data simulated with a scattering radiative transfer model. We show the value of this approach in that it results in accurate estimates of errors for trace gas retrievals, and the retrieved values improve over the initial guess for a wide range of cloud conditions. Comparisons are made between TES retrievals of ozone, temperature, and water to model fields from the Global Modeling and Assimilation Office (GMAO), temperature retrievals from the Atmospheric Infrared Sounder (AIRS), tropospheric ozone columns from the Goddard Earth Observing System (GEOS) GEOS-Chem, and ozone retrievals from the Total Ozone Mapping Spectrometer (TOMS). In each of these cases, this cloud retrieval approach does not introduce observable biases into TES retrievals.

  16. Effects of Particles on Trace-Gas Measurement Using Open-Path Cavity Ring-Down Spectroscopy

    NASA Astrophysics Data System (ADS)

    Mchale, L.; Shadman, S.; Yalin, A.

    2015-12-01

    Open-path Cavity Ring-down Spectroscopy offers many potential advantages over traditional closed-path configurations for the measurement of atmospheric trace gasses. Removal of the vacuum pump and flow system may enable more compact instruments suitable for remote and mobile deployments as well as real time measurement of 'sticky' gases. However, open path operation introduces new challenges including exposure of high reflectivity mirrors to ambient air and aerosols, the need to measure wider (pressure broadened) spectral peaks and possible signal interferences due to optical extinction by aerosol particles in the cavity laser beam. The present submission focuses on the effects of aerosol particles on open-path CRDS using a near-infrared (1742 nm) methane gas measurement system as a test bed. A simple purge enclosure system was developed to prevent aerosol deposition on the cavity high-reflectors. The purge uses ambient air pulled in with a micro-pump through a hepa filter and maintained mirror reflectivity R>0.99996 over 100 hours of use in the presence of high aerosol loading. Optical extinction due to ambient aerosols can change the cavity loss and influence the recorded ring-down times. We observed relatively large fluctuations due to supermicron particles and a near-constant baseline shift due to smaller submicron particles. The fluctuations correspond to absorption on the order of 10-8-10-7 cm-1, comparable to the amplitude of the targeted methane absorption features, causing significant interference. Simple software filter approaches were developed to counter these fluctuations without a priori knowledge of the ambient aerosols. The filters exploit the statistical distribution of signals as well as the expected absorption lineshape. Using these filters, noise-equivalent sensitivities within a factor of ~3 of closed-path systems were obtained (4x10-10cm-1Hz-1/2). Outdoor open-path measurements were validated with side-by-side measurements with a commercial

  17. A comparison of minor trace gas retrievals from the Tropospheric Emission Spectrometer (TES) and the Infrared Atmospheric Sounding Interferometer (IASI)

    NASA Astrophysics Data System (ADS)

    Cady-Pereira, K. E.; Shephard, M. W.; Henze, D. K.; Millet, D. B.; Gombos, D.; Van Damme, M.; Clarisse, L.; Coheur, P. F.; Pommier, M.; Clerbaux, C.

    2014-12-01

    The advent of hyperspectral infrared instruments orbiting the Earth has allowed for detecting and measuring numerous trace gas species that play important roles in atmospheric chemistry and impact air quality, but for which there is a dearth of information on their distribution and temporal variability. Here we will present global and regional comparisons of measurements from the NASA TES and the European MetOp IASI instruments of three of these gases: ammonia (NH3), formic acid (HCOOH) and methanol (CH3OH). Ammonia is highly reactive and thus very variable in space and time, while the sources and sinks of methanol and formic acid are poorly quantified: thus space-based measurements have the potential of significantly increasing our knowledge of the emissions and distributions of these gases. IASI and TES have many similarities but some significant differences. TES has significantly higher spectral resolution (0.06 cm-1), and its equator crossing times are ~1:30 am and 1:30 pm, local time, while IASI has lower resolution (0.5 cm-1) and an earlier equator crossing time (9:30 am and 9:30 pm), which leads to lower thermal contrast; however IASI provides much greater temporal and spatial coverage due to its cross-track scanning. Added to the instrumental differences are the differences in retrieval algorithms. The IASI team uses simple but efficient methods to estimate total column amounts of the species above, while the TES team performs full optimal estimation retrievals. We will compare IASI and TES total column measurements averaged on a 2.5x2.5 degree global grid for each month in 2009, and we will examine the seasonal cycle in some regions of interest, such as South America, eastern China, and the Midwest and the Central Valley in the US. In regions where both datasets are in agreement this analysis will provide confidence that the results are robust and reliable. In regions where there is disagreement we will look for the causes of the discrepancies, which will

  18. Spatial effects of aboveground biomass on soil ecological parameters and trace gas fluxes in a savannah ecosystem of Mount Kilimanjaro

    NASA Astrophysics Data System (ADS)

    Becker, Joscha; Gütlein, Adrian; Sierra Cornejo, Natalia; Kiese, Ralf; Hertel, Dietrich; Kuzyakov, Yakov

    2015-04-01

    The savannah biome is a hotspot for biodiversity and wildlife conservation in Africa and recently got in the focus of research on carbon sequestration. Savannah ecosystems are under strong pressure from climate and land-use change, especially around populous areas like the Mt. Kilimanjaro region. Savannah vegetation in this area consists of grassland with isolated trees and is therefore characterized by high spatial variation of canopy cover, aboveground biomass and root structure. Canopy structure is known to affect microclimate, throughfall and evapotranspiration and thereby controls soil moisture conditions. Consequently, the canopy structure is a major regulator for soil ecological parameters and soil-atmospheric trace gas exchange (CO2, N2O, CH4) in water limited environments. The spatial distribution of these parameters and the connection between above and belowground processes are important to understand and predict ecosystem changes and estimate its vulnerability. Our objective was to determine trends and changes of soil parameters and relate their spatial variability to the vegetation structure. We chose three trees from each of the two most dominant species (Acacia nilotica and Balanites aegyptiaca) in our research area. For each tree, we selected transects with nine sampling points of the same relative distances to the stem. Distances were calculated in relation to the crown radius. At these each sampling point a soil core was taken and separated in 0-10 cm and 10-30 cm depth. We measured soil carbon (C) and nitrogen (N) storage, microbial biomass carbon C and N, soil respiration as well as root biomass and -density, soil temperature and soil water content. Each tree was characterized by crown spread, leaf area index and basal area. Preliminary results show that C and N stocks decreased about 50% with depth independently of distance to the tree. Soil water content under the tree crown increased with depth while it decreased under grass cover. Microbial

  19. Design and application of a mobile ground-based observatory for continuous measurements of atmospheric trace gas and criteria pollutant species

    DOE PAGESBeta

    Bush, S. E.; Hopkins, F. M.; Randerson, J. T.; Lai, C.-T.; Ehleringer, J. R.

    2015-08-26

    Ground-based measurements of atmospheric trace gas species and criteria pollutants are essential for understanding emissions dynamics across space and time. Gas composition in the lower 50 m of the atmosphere has the greatest direct impacts on human health as well as ecosystem processes; hence data at this level are necessary for addressing carbon-cycle- and public-health-related questions. However, such surface data are generally associated with stationary measurement towers, where spatial representation is limited due to the high cost of establishing and maintaining an extensive network of measurement stations. We describe here a compact mobile laboratory equipped to provide high-precision, high-frequency, continuous,more » on-road synchronous measurements of CO2, CO, CH4, H2O, NOx, O3, aerosol, meteorological, and geospatial position data. The mobile laboratory has been deployed across the western USA. In addition to describing the vehicle and its capacity, we present data that illustrate the use of the laboratory as a powerful tool for investigating the spatial structure of urban trace gas emissions and criteria pollutants at spatial scales ranging from single streets to whole ecosystem and regional scales. We assess the magnitude of known point sources of CH4 and also identify fugitive urban CH4 emissions. We illustrate how such a mobile laboratory can be used to better understand emissions dynamics and quantify emissions ratios associated with trace gas emissions from wildfire incidents. Lastly, we discuss additional mobile laboratory applications in health and urban metabolism.« less

  20. Application of copper sulfate pentahydrate as an ammonia removal reagent for the determination of trace impurities in ammonia by gas chromatography.

    PubMed

    Aomura, Yoko; Kobayashi, Yoshihiko; Miyazawa, Yuzuru; Shimizu, Hideharu

    2010-03-12

    Rapid analysis of trace permanent gas impurities in high purity ammonia gas for the microelectronics industry is described, using a gas chromatograph equipped with a phtoionization detector. Our system incorporates a reactive precolumn in combination with the analytical column to remove the ammonia matrix peak that otherwise would complicate the measurements due to baseline fluctuations and loss of analytes. The performance of 21 precolumn candidate materials was evaluated. Copper sulfate pentahydrate (CuSO(4).5H(2)O) was shown to selectively react with ammonia at room temperature and atmospheric column pressures, without affecting the hydrogen, oxygen, nitrogen, methane or carbon monoxide peak areas. To prevent loss of trace carbon dioxide, an additional boron trioxide reactant layer was inserted above the copper sulfate pentahydrate bed in the reactive precolumn. Using the combined materials, calibration curves for carbon dioxide proved to be equivalent in both ammonia and helium matrix gases. These curves were equivalent in both matrix gases. The quantitative performance of the system was also evaluated. Peak repeatabilities, based on eight injections, were in the range of 4.1-8.2% relative standard deviation; and detection limits were 6.9 ppb for H(2), 1.8 ppb for O(2), 1.6 ppb for N(2), 6.4 ppb for CH(4), 13 ppb for CO, and 5.4 ppb for CO(2). PMID:20132934

  1. Analyzing Trace Gas Measurements to Understand Convective Dynamics: Results from SEAC4RS Field Campaign and Mozaic Project

    NASA Astrophysics Data System (ADS)

    Luo, Z. J.; Pyo, S.; Shah, N.

    2014-12-01

    Deep convective updrafts transport air parcels from near the PBL to the upper troposphere in about 20-30 min. At this time scale, most insoluble trace gases (e.g., ozone, some VOCs) can be treated as nearly conserved tracers. While the atmospheric chemistry community is most interested in the chemical consequences of the trace gases being lofted, these composition measurements, if sampled properly inside and near convection, can be utilized to study convective dynamics including lateral entrainment and mixing in the outflow. We will use measurements made from a recent NASA field campaign, SEAC4RS to illustrate how such studies can be conducted. Also, we analyzed long-term data from MOZAIC project to corroborate the findings from SEAC4RS. It will be shown that using trace gases to diagnose convective dynamics sometimes has certain advantages over the traditional meteorological approach using, e.g., equivalent potential temperature.

  2. Operational O3M-SAF trace gas column products: GOME-2 NO2, BrO, SO2 and CH2O

    NASA Astrophysics Data System (ADS)

    Hao, Nan; Valks, P.; de Smedt, I.; Emmadi, S.; Lambert, J.-C.; Loyola, D.; Pinardi, G.; Rix, M.; van Roozendael, M.; They, N.

    2010-05-01

    This contribution focuses on the operational GOME-2 trace gas column products developed at the German Aerospace Centre, in the framework of EUMETSAT's Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M-SAF). We present an overview of the retrieval algorithms and exemplary results for NO2, BrO, SO2 and CH2O. These trace gas column products are retrieved with the GOME Data Processor (GDP) version 4.4 using the Differential Optical Absorption Spectroscopy (DOAS) method in the UV and VIS wavelength regions. Total NO2 is retrieved in the 425-450 nm and an additional algorithm is applied to retrieve the tropospheric NO2 column for polluted conditions. The operational GOME-2 NO2 product is available for the users in near real time, i.e. within two hours after sensing. SO2 emissions from volcanic and anthropogenic sources can be measured by GOME-2 using the UV wavelength region around 320 nm. For BrO and CH2O, optimal DOAS fitting windows have been determined for GOME-2 in the UV wavelength region. The GOME-2 SO2, BrO and CH2O products have reached the operational O3M-SAF status, and are routinely available to the users. More than three years of operational trace gas column measurements are now available from GOME-2. We present initial validation results using ground-based measurements, as well as comparisons with other satellite products, such as those from SCIAMACHY and OMI. The use of tropospheric NO2, SO2 and CH2O columns for air quality applications will be presented, including temporal evolution analyses for China. Furthermore, we will show examples of BrO under polar winter conditions.

  3. Intercomparison of stratospheric water vapor observed by satellite experiments - Stratospheric Aerosol and Gas Experiment II versus Limb Infrared Monitor of the Stratosphere and Atmospheric Trace Molecule Spectroscopy

    NASA Technical Reports Server (NTRS)

    Chiou, E. W.; Mccormick, M. P.; Mcmaster, L. R.; Chu, W. P.; Larsen, J. C.; Rind, D.; Oltmans, S.

    1993-01-01

    A comparison is made of the stratospheric water vapor measurements made by the satellite sensors of the Stratospheric Aerosol and Gas Experiment II (SAGE II), the Nimbus-7 LIMS, and the Spacelab 3 Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment. It was found that, despite differences in the measurement techniques, sampling bias, and observational periods, the three experiments have disclosed a generally consistent pattern of stratospheric water vapor distribution. The only significant difference occurs at high southern altitudes in May below 18 km, where LIMS measurements were 2-3 ppmv greater than those of SAGE II and ATMOS.

  4. Scientific calibration and analysis of calibration data for the CaSSIS instrument of the ExoMars Trace Gas Orbiter

    NASA Astrophysics Data System (ADS)

    Roloff, V.; Gambicorti, L.; Pommerol, A.; Thomas, N.

    2015-10-01

    The Colour and Stereo Surface Imaging System (CaSSIS) is a camera, the development of which is led by the University of Bern (CH), with hardware contributions from the University of Padova (I) and the Space Research Center of Warsaw (Pl). It will take high resolution stereo images in 4 colours of the Martian surface, from on board the ExoMars Trace Gas Orbiter. Our calibration facility stands ready to perform the required measurements. We are currently testing the procedures on a dummy system and we will report on calibration results of the CaSSIS instrument.

  5. Compilation and evaluation of gas phase diffusion coefficients of reactive trace gases in the atmosphere: Volume 2. Diffusivities of organic compounds, pressure-normalised mean free paths, and average Knudsen numbers for gas uptake calculations

    NASA Astrophysics Data System (ADS)

    Tang, M. J.; Shiraiwa, M.; Poschl, U.; Cox, R. A.; Kalberer, M.

    2015-05-01

    Diffusion of organic vapours to the surface of aerosol or cloud particles is an important step for the formation and transformation of atmospheric particles. So far, however, a database of gas phase diffusion coefficients for organic compounds of atmospheric interest has not been available. In this work we have compiled and evaluated gas phase diffusivities (pressure-independent diffusion coefficients) of organic compounds reported by previous experimental studies, and we compare the measurement data to estimates obtained with Fuller's semi-empirical method. The difference between measured and estimated diffusivities are mostly < 10%. With regard to gas-particle interactions, different gas molecules, including both organic and inorganic compounds, exhibit similar Knudsen numbers (Kn) although their gas phase diffusivities may vary over a wide range. This is because different trace gas molecules have similar mean free paths in air at a given pressure. Thus, we introduce the pressure-normalised mean free path, λP ~ 100 nm atm, as a near-constant generic parameter that can be used for approximate calculation of Knudsen numbers as a simple function of gas pressure and particle diameter to characterise the influence of gas phase diffusion on the uptake of gases by aerosol or cloud particles. We use a kinetic multilayer model of gas-particle interaction to illustrate the effects of gas phase diffusion on the condensation of organic compounds with different volatilities. The results show that gas phase diffusion can play a major role in determining the growth of secondary organic aerosol particles by condensation of low-volatility organic vapours.

  6. Tracing natural gas transport into shallow groundwater using dissolved nitrogen and alkane chemistry in Parker County, Texas

    NASA Astrophysics Data System (ADS)

    Larson, T.; Nicot, J. P.; Mickler, P. J.; Darvari, R.

    2015-12-01

    Dissolved methane in shallow groundwater drives public concern about the safety of hydraulic fracturing. We report dissolved alkane and nitrogen gas concentrations and their stable isotope values (δ13C and δ15N, respectively) from 208 water wells in Parker county, Texas. These data are used to differentiate 'stray' natural gas and low temperature microbial methane, and (2) estimate the ratio of stray gas to groundwater. The ratio of (gas-phase) stray natural gas to groundwater is estimated by correlating dissolved methane and nitrogen concentrations and dissolved nitrogen δ15N values. Our hypothesis is groundwater exposed to high volumes of stray natural gas have high dissolved methane concentrations and low dissolved nitrogen concentrations and δ15N values. Alternatively, groundwater exposed to low volumes of stray gas-phase natural gas have elevated dissolved methane, but the concentration of dissolved nitrogen and its d15N value is atmospheric. A cluster of samples in Parker county have high concentrations of dissolved methane (>10mg/L) with d13Cmethane and alkane ratios (C1/C2+C3) typical of natural gas from the Barnett Shale and the Strawn Formation. Coupling dissolved nitrogen concentrations and δ15N values with these results, we suggest that few of the wells in this cluster preserve large gas to water ratios. Many samples with high dissolved methane concentrations have atmospheric dissolved nitrogen concentrations and δ15N values, providing evidence against high flux natural gas transport into shallow groundwater. These results demonstrate that dissolved nitrogen chemistry, in addition to dissolved alkane and noble gas measurements, may be useful to discern sources of dissolved methane and estimate ratios of stray natural gas-water ratios.

  7. Separation and analysis of trace volatile formaldehyde in aquatic products by a MoO₃/polypyrrole intercalative sampling adsorbent with thermal desorption gas chromatography and mass spectrometry.

    PubMed

    Ma, Yunjian; Zhao, Cheng; Zhan, Yisen; Li, Jianbin; Zhang, Zhuomin; Li, Gongke

    2015-05-01

    An in situ embedded synthesis strategy was developed for the preparation of a MoO3 /polypyrrole intercalative sampling adsorbent for the separation and analysis of trace volatile formaldehyde in aquatic products. Structural and morphological characteristics of the MoO3 /polypyrrole intercalative adsorbent were investigated by a series of characterization methods. The MoO3 /polypyrrole sampling adsorbent possessed a higher sampling capacity and selectivity for polar formaldehyde than commonly used commercial adsorbent Tenax TA. Finally, the MoO3 /polypyrrole adsorbent was packed in the thermal desorption tube that was directly coupled to gas chromatography with mass spectrometry for the analysis of trace volatile formaldehyde in aquatic products. Trace volatile formaldehyde from real aquatic products could be selectively sampled and quantified to be 0.43-6.6 mg/kg. The detection limit was achieved as 0.004 μg/L by this method. Good recoveries for spiked aquatic products were achieved in range of 75.0-108% with relative standard deviations of 1.2-9.0%. PMID:25677048

  8. From slant column densities to trace gas profiles: Post processing data from the new MAX-DOAS network in Mexico City

    NASA Astrophysics Data System (ADS)

    Friedrich, M. M.; Stremme, W.; Rivera, C. I.; Arellano, E. J.; Grutter, M.

    2014-12-01

    The new MAX-DOAS network in Mexico City provides results of O4, HCHO and NO2 slant column densities (SCD). Here, we present a new numerical code developed to retrieve gas profiles of NO2 and HCHO using radiative transfer simulations. We present first results of such profiles from the MAX-DOAS station located at UNAM campus. The code works in two steps: First, the O4 slant column density information is used to retrieve an aerosol profile. As an a-priori aerosol profile, we use averaged ceilometer data measured at UNAM and scaled to the total optical depth provided by the Aeronet data base. In the second step, the retrieved aerosol profile information is used together with the trace gas (HCHO or NO2) SCDs to retrieve the trace gas profiles. The inversion is based on a gauss-newton iteration scheme and uses constrained least square fitting with either optimal estimation or Tihkonov regularization. For the latter, the regulation matrix is currently constructed from the discrete first derivative operator. The forward model uses the radiative transfer code VLIDORT. The inputs to VLIDORT are calculated using temperature and pressure information from daily radiosounde measurements and aerosol single scattering optical depths and asymmetry factors from the Aeronet data base for Mexico City. For the gas absorption cross sections we use the same values as were used for the SCD calculation from the recorded spectra using QDOAS. Besides demonstrating the functionality of the algorithm showing profile retrievals of simulated SCDs with added random noise, we present HCHO and NO2 profiles retrieved from SCDs calculated from the MAX-DOAS measurements at UNAM campus at selected days.

  9. [Preparation technique of S2OF10 gas standard sample and determination method of the trace S2OF10 in SF6].

    PubMed

    Wang, L; Wang, J

    1999-09-01

    In this paper a series of methods and techniques for the S2OF10 standard sample preparation and quantitative determination are presented. They are, the preparation of S2OF10 by preparative chromatography with adsorption/thermal desorption, the standard sample of S2OF10 gas prepared by exponential dilution and the gas chromatography/flame photometric detector(GC/FPD) determination of trace S2OF10 from an SF6 sample with quantitative calibration factor. Especially, the S2OF10 gas from a used SF6 sample was directly separated and concentrated through a U-adsorbent-tube packed with 300 mg of Porasil A in a cold trap (-63 degrees C) with liquid-nitrogen and chloroform. Then it was purified by preparative-GC and to be injected into a preparative system of standard gas sample. In the meantime, the S2OF10 gas obtained was confirmed by the methods of GC/FPD, infrared spectrophotometer(IR) and gas chromatography/mass spectrometer(GC/MS) separately. The sub-ppm(by volume) level of the S2OF10 and SF6 mixture samples were prepared by use of the exponential dilution system. The GC/FPD experimental results showed that the detection linear range of S2OF10 gas concentration was 0.80 x 10(-6)-2.60 x 10(-4) (volume fraction) and the quantitative calibration factor of the S2OF10 was 0.197 based on SF6. The determination errors of quantitative calibration factor were 1.8%-20% and S2OF10 recovery of the adsorption/thermal desorption was 98.2% (n = 9) and its relative standard deviation was 6.2%. In addition, the results also showed that it is a simple and rapid method with good linearity and reproducibility. PMID:12552882

  10. Trace gas emissions from combustion of peat, crop residue, biofuels, grasses, and other fuels: configuration and FTIR component of the fourth Fire Lab at Missoula Experiment (FLAME-4)

    NASA Astrophysics Data System (ADS)

    Stockwell, C. E.; Yokelson, R. J.; Kreidenweis, S. M.; Robinson, A. L.; DeMott, P. J.; Sullivan, R. C.; Reardon, J.; Ryan, K. C.; Griffith, D. W. T.; Stevens, L.

    2014-04-01

    During the fourth Fire Lab at Missoula Experiment (FLAME-4, October-November~2012) a~large variety of regionally and globally significant biomass fuels was burned at the US Forest Service Fire Sciences Laboratory in Missoula, Montana. The particle emissions were characterized by an extensive suite of instrumentation that measured aerosol chemistry, size distribution, optical properties, and cloud-nucleating properties. The trace gas measurements included high resolution mass spectrometry, one- and two-dimensional gas chromatography, and open-path Fourier transform infrared (OP-FTIR) spectroscopy. This paper summarizes the overall experimental design for FLAME-4 including the fuel properties, the nature of the burn simulations, the instrumentation employed, and then focuses on the OP-FTIR results. The OP-FTIR was used to measure the initial emissions of 20 trace gases: CO2, CO, CH4, C2H2, C2H4, C3H6, HCHO, HCOOH, CH3OH, CH3COOH, glycolaldehyde, furan, H2O, NO, NO2, HONO, NH3, HCN, HCl, and SO2. These species include most of the major trace gases emitted by biomass burning and for several of these compounds it is the first time their emissions are reported for important fuel types. The main fuel types included: African grasses, Asian rice straw, cooking fires (open (3-stone), rocket, and gasifier stoves), Indonesian and extratropical peat, temperate and boreal coniferous canopy fuels, US crop residue, shredded tires, and trash. Comparisons of the OP-FTIR emission factors (EF) and emission ratios (ER) to field measurements of biomass burning verify that the large body of FLAME-4 results can be used to enhance the understanding of global biomass burning and its representation in atmospheric chemistry models.

  11. Laboratory scale studies of Pd/y-Al2O3 sorbents for the removal of trace contaminents from coal-derived fuel gas at elevated temperatures

    SciTech Connect

    Rupp, Erik C.; Granite, Evan J.; Stanko, Dennis C.

    2010-12-31

    The Integrated Gasification Combined Cycle (IGCC) is a promising technology for the use of coal in a clean and efficient manner. In order to maintain the overall efficiency of the IGCC process, it is necessary to clean the fuel gas of contaminants (sulfur, trace compounds) at warm (150-540 C) to hot (>540 C) temperatures. Current technologies for trace contaminant (such as mercury) removal, primarily activated carbon based sorbents, begin to lose effectiveness above 100 C, creating the need to develop sorbents effective at elevated temperatures. As trace elements are of particular environmental concern, previous work by this group has focused on the development of a Pd/{gamma}-Al{sub 2}O{sub 3} sorbent for Hg removal. This paper extends the research to Se (as hydrogen selenide, H{sub 2}Se), As (as arsine, AsH{sub 3}), and P (as phosphine, PH{sub 3}) which thermodynamic studies indicate are present as gaseous species under gasification conditions. Experiments performed under ambient conditions in He on 20 wt.% Pd/{gamma}-Al{sub 2}O{sub 3} indicate the sorbent can remove the target contaminants. Further work is performed using a 5 wt.% Pd/{gamma}-Al{sub 2}O{sub 3} sorbent in a simulated fuel gas (H{sub 2}, CO, CO{sub 2}, N{sub 2} and H{sub 2}S) in both single and multiple contaminant atmospheres to gauge sorbent performance characteristics. The impact of H{sub 2}O, Hg and temperature on sorbent performance is explored.

  12. Meteorological and trace gas factors affecting the number concentration of atmospheric Aitken (Dp = 50 nm) particles in the continental boundary layer: parameterization using a multivariate mixed effects model

    NASA Astrophysics Data System (ADS)

    Mikkonen, S.; Korhonen, H.; Romakkaniemi, S.; Smith, J. N.; Joutsensaari, J.; Lehtinen, K. E. J.; Hamed, A.; Breider, T. J.; Birmili, W.; Spindler, G.; Plass-Duelmer, C.; Facchini, M. C.; Laaksonen, A.

    2011-01-01

    Measurements of aerosol size distribution and different gas and meteorological parameters, made in three polluted sites in Central and Southern Europe: Po Valley, Italy, Melpitz and Hohenpeissenberg in Germany, were analysed for this study to examine which of the meteorological and trace gas variables affect the number concentration of Aitken (Dp= 50 nm) particles. The aim of our study was to predict the number concentration of 50 nm particles by a combination of in-situ meteorological and gas phase parameters. The statistical model needs to describe, amongst others, the factors affecting the growth of newly formed aerosol particles (below 10 nm) to 50 nm size, but also sources of direct particle emissions in that size range. As the analysis method we used multivariate nonlinear mixed effects model. Hourly averages of gas and meteorological parameters measured at the stations were used as predictor variables; the best predictive model was attained with a combination of relative humidity, new particle formation event probability, temperature, condensation sink and concentrations of SO2, NO2 and ozone. The seasonal variation was also taken into account in the mixed model structure. Model simulations with the Global Model of Aerosol Processes (GLOMAP) indicate that the parameterization can be used as a part of a larger atmospheric model to predict the concentration of climatically active particles. As an additional benefit, the introduced model framework is, in theory, applicable for any kind of measured aerosol parameter.

  13. Meteorological and trace gas factors affecting the number concentration of atmospheric Aitken (Dp=50 nm) particles in the continental boundary layer: parameterization using a multivariate mixed effects model

    NASA Astrophysics Data System (ADS)

    Mikkonen, S.; Korhonen, H.; Romakkaniemi, S.; Smith, J. N.; Joutsensaari, J.; Lehtinen, K. E. J.; Hamed, A.; Breider, T. J.; Birmili, W.; Spindler, G.; Plass-Duelmer, C.; Facchini, M. C.; Laaksonen, A.

    2010-08-01

    Measurements of aerosol size-distribution and different gas and meteorological parameters, made in three polluted sites in Central- and Southern Europe: Po Valley, Italy, Melpitz and Hohenpeissenberg in Germany, were analysed for this study to examine which of the meteorological and trace gas variables affect the number concentration of Aitken (Dp=50 nm) particles. The aim of our study was to predict the number concentration of 50 nm particles by a combination of in-situ meteorological and gas phase parameters. The statistical model needs to describe, amongst others, the factors affecting the growth of newly formed aerosol particles (below 10 nm) to 50 nm size, but also sources of direct particle emissions in that size range. As the analysis method we used multivariate nonlinear mixed effects model. Hourly averages of gas and meteorological parameters measured at the stations were used as predictor variables; the best predictive model was attained with a combination of relative humidity, new particle formation event probability, temperature, condensation sink and concentrations of SO2, NO2 and ozone. The seasonal variation was also taken into account in the mixed model structure. Model simulations with the Global Model of Aerosol Processes (GLOMAP) indicate that the parameterization can be used as a part of a larger atmospheric model to predict the concentration of climatically active particles. As an additional benefit, the introduced model framework is, in theory, applicable for any kind of measured aerosol parameter.

  14. Compilation and evaluation of gas-phase diffusion coefficients of reactive trace gases in the atmosphere: volume 2. Organic compounds and Knudsen numbers for gas uptake calculations

    NASA Astrophysics Data System (ADS)

    Tang, M. J.; Shiraiwa, M.; Pöschl, U.; Cox, R. A.; Kalberer, M.

    2015-02-01

    Diffusion of organic vapours to the surface of aerosol or cloud particles is an important step for the formation and transformation of atmospheric particles. So far, however, a database of gas phase diffusion coefficients for organic compounds of atmospheric interest has not been available. In this work we have compiled and evaluated gas phase diffusivities (pressure-independent diffusion coefficients) of organic compounds reported by previous experimental studies, and we compare the measurement data to estimates obtained with Fuller's semi-empirical method. The difference between measured and estimated diffusivities are mostly < 10%. With regard to gas-particle interactions, different gas molecules, including both organic and inorganic compounds, exhibit similar Knudsen numbers (Kn) although their gas phase diffusivities may vary over a wide range. Knudsen numbers of gases with unknown diffusivity can be approximated by a simple function of particle diameter and pressure and can be used to characterize the influence of diffusion on gas uptake by aerosol or cloud particles. We use a kinetic multi-layer model of gas-particle interaction to illustrate the effects of gas phase diffusion on the condensation of organic compounds with different volatilities. The results show that gas-phase diffusion can play a major role in determining the growth of secondary organic aerosol particles by condensation of low-volatility organic vapours.

  15. Piaget on Abstraction.

    ERIC Educational Resources Information Center

    Moessinger, Pierre; Poulin-Dubois, Diane

    1981-01-01

    Reviews and discusses Piaget's recent work on abstract reasoning. Piaget's distinction between empirical and reflective abstraction is presented; his hypotheses are considered to be metaphorical. (Author/DB)

  16. Design and Performance Assessment of a Stable Astigmatic Herriott Cell for Trace Gas Measurements on Airborne Platforms

    NASA Technical Reports Server (NTRS)

    Dyroff, Christoph; Fried, Alan; Richter, Dirk; Walega, James G.; Zahniser, Mark S.; McManus, J. Barry

    2005-01-01

    The present paper discusses a new, more stable, astigmatic Herriott cell employing carbon fiber stabilizing rods. Laboratory tests using a near-IR absorption feature of CO at 1564.168-nm revealed a factor of two improvement in measurement stability compared with the present commercial design when the sampling pressure was changed by +/-2 Torr around 50 Torr. This new cell should significantly enhance our efforts to measure trace gases employing pathlengths of 100 to 200-meters on airborne platforms with minimum detectable line center absorbances of less than 10(exp -6).

  17. Design, fabrication, and optimization of photo acoustic gas sensor for the trace level detection of NO2 in the atmosphere.

    PubMed

    Gondal, Mohammed A; Dastageer, Mohamed A

    2010-09-01

    Photoacoustic (PA) gas sensor for the detection of hazardous NO(2) with detection limit as low as few part per billion by volume (ppbV) has been designed and tested with pulsed UV laser. Some design optimization factors such as the optimum cell geometry, buffer gas etc has been proposed. It was found that a cylindrical cell with many acoustic filters considerably dampens the noise level and also argon as a buffer gas improves the photoacoustic signal level and this combination substantially improved the signal to noise ratio and the limit of detection. Ambiguous decline of photo acoustic signal at higher NO(2) concentration due to the adsorption of NO(2) on the walls of the photoacoustic cells and the dependence of this effect on the buffer gases are also discussed. The PA signal dependence on incident laser energy for three cells was also investigated. PMID:20665325

  18. A selected ion flow tube study of the reactions of NO + and O + 2 ions with some organic molecules: The potential for trace gas analysis of air

    NASA Astrophysics Data System (ADS)

    Španěl, Patrik; Smith, David

    1996-02-01

    A study has been carried out using our selected ion flow tube apparatus of the reactions of NO+ and O+2 ions in their vibronic ground states with ten organic species: the hydrocarbons, benzene, toluene, isoprene, cyclopropane, and n-pentane; the oxygen-containing organics, methanol, ethanol, acetaldehyde, acetone, and diethyl ether. The major objectives of this work are, on the one hand, to fully understand the processes involved in these reactions and, on the other hand, to explore the potential of NO+ and O+2 as chemical ionization agents for the analysis of trace gases in air and on human breath. Amongst the NO+ reactions, charge transfer, hydride-ion transfer, and termolecular association occur, and the measured rate coefficients, k, for the reactions vary from immeasurably small to the maximum value, collisional rate coefficient, kc. The O+2 reactions are all fast, in each case the k being equal to or an appreciable fraction of kc, and charge transfer producing the parent organic ion or dissociative charge transfer resulting in two or three fragments of the parent ion are the reaction processes that occur. We conclude from these studies, and from previous studies, that NO+ ions and O+2 ions can be used to great effect as chemical ionization agents for trace gas analysis, especially in combination with H3O+ ions which we now routinely use for this purpose.

  19. Trace gas detection from fermentation processes in apples; an intercomparison study between proton-transfer-reaction mass spectrometry and laser photoacoustics

    NASA Astrophysics Data System (ADS)

    Boamfa, E. I.; Steeghs, M. M. L.; Cristescu, S. M.; Harren, F. J. M.

    2004-12-01

    A custom-built proton-transfer-reaction mass spectrometry (PTR-MS) instrument was used to monitor the emission of various compounds (aldehydes, alcohols, acids, acetates and C-6 compounds) related to fermentation, aroma and flavour, released by four apple cultivars (Elstar, Jonaglod, Granny Smith and Pink Lady) under short anaerobic (24 h) and post-anaerobic conditions. The novel feature of our instrument is the new design of the collisional dissociation chamber, which separates the high pressure in the drift tube (2 mbar) from the high vacuum pressure in the detection region (10-6 mbar). The geometry of this chamber was changed and a second turbo pump was added to reduce the influence of collisional loss of ions, background signals and cluster ions, which facilitates the interpretation of the mass spectra and increases the signal intensity at the mass of the original protonated compound. With this system, detection limits of similar magnitude to the ones reported in literature are reached. An intercomparison study between PTR-MS and a CO laser-based photoacoustic trace gas detector is presented. The alcoholic fermentation products (acetaldehyde and ethanol) from young rice plants were simultaneously monitored by both methods. A very good agreement was observed for acetaldehyde production. The photoacoustic detector showed about two times lower ethanol concentration as compared to PTR-MS, caused by memory effects due to sticking of compounds to the walls of the nylon tube used to transport the trace gases to the detector.

  20. Warp of the ionized gas layer in the outer Galaxy, traced by Recombination Line Observations in both the First and Fourth Quadrants

    NASA Astrophysics Data System (ADS)

    Azcarate, I. N.; Cersosimo, J. C.

    2000-05-01

    Results of H166α recombination line observations from the Outer Galaxy in both the Northern and Southern Galactic Plane, are reported. The Southern observations were made with the 30m antenna of the Instituto Argentino de Radioastronomia in Villa Elisa, Buenos Aires, Argentina and the Northern ones ( more sensitive, high quality observations, performed with an "state of the art" receiver) with the 43m antenna of the National Radio Astronomy Observatory, in Green Bank, West Virginia, USA. From the two sets of observations, we obtain evidence of the warp of the low density ionized gas layer, traced by the H166α emission in the outer MIlky Way, towards positive galactic latitudes in the Northern and towards negative latitudes in the Southern Galaxy. The warp of this tracer qualitatively agrees with that of the HI.

  1. High power, widely tunable, mode-hop free, continuous wave external cavity quantum cascade laser for multi-species trace gas detection

    SciTech Connect

    Centeno, R.; Marchenko, D.; Mandon, J.; Cristescu, S. M.; Harren, F. J. M.; Wulterkens, G.

    2014-12-29

    We present a high power, widely tunable, continuous wave external cavity quantum cascade laser designed for infrared vibrational spectroscopy of molecules exhibiting broadband and single line absorption features. The laser source exhibits single mode operation with a tunability up to 303 cm{sup −1} (∼24% of the center wavelength) at 8 μm, with a maximum optical output power of 200 mW. In combination with off-axis integrated output spectroscopy, trace-gas detection of broadband absorption gases such as acetone was performed and a noise equivalent absorption sensitivity of 3.7 × 10{sup −8 }cm{sup −1 }Hz{sup −1/2} was obtained.

  2. Particulate and trace gas emissions from prescribed burns in southeastern U.S. fuel types: Summary of a 5-year project

    SciTech Connect

    Weise, David; Johnson, Timothy J.; Reardon, James

    2015-03-04

    Management of smoke from prescribed fires requires knowledge of fuel quantity and the amount and composition of the smoke produced by the fire to minimize adverse impacts on human health. A five-year study produced new emissions information for more than 100 trace gases and particulate matter in smoke for fuel types found in the southern United States of America using state-of-the-art instrumentation in both laboratory and field experiments. Emission factors for flaming, smoldering, and residual smoldering were developed. Agreement between laboratory and field-derived emission factors was generally good in most cases. Reference spectra of over 50 wildland fire gas-phase smoke components were added to a publicly-available database to support identification via infrared spectroscopy. Fuel loading for the field experiments was similar to previously measured fuels. This article summarizes the results of a five-year study to better understand the composition of smoke during all phases of burning for such forests.

  3. The impact of deep overshooting convection on the water vapour and trace gas distribution in the TTL and lower stratosphere

    NASA Astrophysics Data System (ADS)

    Frey, W.; Schofield, R.; Hoor, P. M.; Ravegnani, F.; Ulanovsky, A.; Viciani, S.; D'Amato, F.; Lane, T. P.

    2014-12-01

    Overshooting convection penetrating the tropical tropopause layer (TTL) and the lower stratosphere has a significant impact on the redistribution of water vapour and further trace gases. This is of importance for the stratospheric water vapour budget, which plays a central role in radiative and chemical processes. Modelling studies and in situ measurements show the hydration potential of convective overshooting partly by direct injection of ice particles into the stratosphere and subsequent sublimation. However, processes leading to dehydration of the TTL may also impact the stratospheric humidity by limiting the amount of water vapour carried aloft. While the large scale drives some of the dehydrating processes, others are of convective origin, for example gravity waves and cooling associated with overshooting turrets. Furthermore, downdrafts may transport dry and ozone rich air masses from the stratosphere into the TTL. Improving our understanding of overshooting convection and its influence on TTL water vapour will ultimately place better constraints on the budget of water vapour in the stratosphere.In this study we use three-dimensional cloud resolving (WRF-ARW) simulations of a deep convective thunderstorm (Hector) to study the redistribution of water vapour and trace gases in the upper TTL/lower stratosphere. Passive tracers are initialised to investigate the transport of air masses. The simulations focus on an Hector event that has been probed by aircraft during the SCOUT-O3 field campaign. Observations were performed in and around overshoots that even penetrated the stratosphere. These observations as well as the model simulations show downward transport and mixing of air masses from the stratosphere, though less strong and more localised in the simulation. Furthermore, the simulations shows a layering of hydrated and dehydrated air masses post-convection in the upper TTL and lower stratosphere. Here we use the model to explain the processes causing the

  4. TRACKING THE EMISSION OF CARBON DIOXIDE BY NATION, SECTOR, AND FUEL TYPE: A TRACE GAS ACCOUNTING SYSTEM (TGAS)

    EPA Science Inventory

    The paper describes a new way to estimate an efficient econometric model of global emissions of carbon dioxide (CO2) by nation, sector, and fuel type. Equations for fuel intensity are estimated for coal, oil, natural gas, electricity, and heat for six sectors: agricultural, indus...

  5. Fabrication and operation of a system for the PVA (polyvinyl alcohol) coating of polymer microshells with trace gas fill

    SciTech Connect

    King, K.J.

    1988-03-31

    Polymer microshells with a PVA (polyvinyl alcohol) coating are produced for the ICF Program by the Fusion Target Fabrication (FTF) Group at Lawrence Livermore National Laboratories. A PVA coating greatly reduces the permeation of gas through a polymer microshell. The equipment and procedures used in the production of PVA coated microshells are discussed. 6 figs.

  6. Mercury emission and plant uptake of trace elements during early stage of soil amendment using flue gas desulfurization materials.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A pilot-scale field study was carried out to investigate the distribution of Hg and other selected elements in the three potential mitigation pathways, i.e., emission to ambient air, uptake by surface vegetation (i.e., grass), and rainfall infiltration, after flue gas desulfurization (FGD) material ...

  7. Greenhouse Trace Gas Fluxes from an Irrigated Sweet Corn (Zea mays L.) - Potato (Solanum tuberosum L.) Rotation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is a critical need to develop management strategies that improve soil quality through adoption of suitable crop rotations and reduced tillage for carbon sequestration and control of greenhouse gas emissions. In this study emissions of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4...

  8. A Novel Low-Power, High-Performance, Zero-Maintenance Closed-Path Trace Gas Eddy Covariance System with No Water Vapor Dilution or Spectroscopic Corrections

    NASA Astrophysics Data System (ADS)

    Sargent, S.; Somers, J. M.

    2015-12-01

    Trace-gas eddy covariance flux measurement can be made with open-path or closed-path analyzers. Traditional closed-path trace-gas analyzers use multipass absorption cells that behave as mixing volumes, requiring high sample flow rates to achieve useful frequency response. The high sample flow rate and the need to keep the multipass cell extremely clean dictates the use of a fine-pore filter that may clog quickly. A large-capacity filter cannot be used because it would degrade the EC system frequency response. The high flow rate also requires a powerful vacuum pump, which will typically consume on the order of 1000 W. The analyzer must measure water vapor for spectroscopic and dilution corrections. Open-path analyzers are available for methane, but not for nitrous oxide. The currently available methane analyzers have low power consumption, but are very large. Their large size degrades frequency response and disturbs the air flow near the sonic anemometer. They require significant maintenance to keep the exposed multipass optical surfaces clean. Water vapor measurements for dilution and spectroscopic corrections require a separate water vapor analyzer. A new closed-path eddy covariance system for measuring nitrous oxide or methane fluxes provides an elegant solution. The analyzer (TGA200A, Campbell Scientific, Inc.) uses a thermoelectrically-cooled interband cascade laser. Its small sample-cell volume and unique sample-cell configuration (200 ml, 1.5 m single pass) provide excellent frequency response with a low-power scroll pump (240 W). A new single-tube Nafion® dryer removes most of the water vapor, and attenuates fluctuations in the residual water vapor. Finally, a vortex intake assembly eliminates the need for an intake filter without adding volume that would degrade system frequency response. Laboratory testing shows the system attenuates the water vapor dilution term by more than 99% and achieves a half-power band width of 3.5 Hz.

  9. Nitrogen dioxide observations from the Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) airborne instrument: retrieval algorithm and measurements during DISCOVER-AQ Texas 2013

    NASA Astrophysics Data System (ADS)

    Nowlan, C. R.; Liu, X.; Leitch, J. W.; Chance, K.; González Abad, G.; Liu, C.; Zoogman, P.; Cole, J.; Delker, T.; Good, W.; Murcray, F.; Ruppert, L.; Soo, D.; Follette-Cook, M. B.; Janz, S. J.; Kowalewski, M. G.; Loughner, C. P.; Pickering, K. E.; Herman, J. R.; Beaver, M. R.; Long, R. W.; Szykman, J. J.; Judd, L. M.; Kelley, P.; Luke, W. T.; Ren, X.; Al-Saadi, J. A.

    2015-12-01

    The Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) airborne instrument is a testbed for upcoming air quality satellite instruments that will measure backscattered ultraviolet, visible and near-infrared light from geostationary orbit. GeoTASO flew on the NASA Falcon aircraft in its first intensive field measurement campaign during the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) Earth Venture Mission over Houston, Texas in September 2013. Measurements of backscattered solar radiation between 420-465 nm collected on four days during the campaign are used to determine slant column amounts of NO2 at 250 m × 250 m spatial resolution with a fitting precision of 2.2 × 1015 molecules cm-2. These slant columns are converted to tropospheric NO2 vertical columns using a radiative transfer model and trace gas profiles from the Community Multiscale Air Quality (CMAQ) model. Total column NO2 from GeoTASO is well correlated with ground-based Pandora observations (r = 0.90 on the most polluted and cloud-free day of measurements), with GeoTASO NO2 slightly higher for the most polluted observations. Surface NO2 mixing ratios inferred from GeoTASO using the CMAQ model show good correlation with NO2 measured in situ at the surface during the campaign (r = 0.91 for the most polluted day). NO2 slant columns from GeoTASO also agree well with preliminary retrievals from the GEO-CAPE Airborne Simulator (GCAS) which flew on the NASA King Air B200 (r = 0.84, slope = 0.94). Enhanced NO2 is resolvable over areas of traffic NOx emissions and near individual petrochemical facilities.

  10. Nitrogen dioxide observations from the Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) airborne instrument: Retrieval algorithm and measurements during DISCOVER-AQ Texas 2013

    NASA Astrophysics Data System (ADS)

    Nowlan, Caroline R.; Liu, Xiong; Leitch, James W.; Chance, Kelly; González Abad, Gonzalo; Liu, Cheng; Zoogman, Peter; Cole, Joshua; Delker, Thomas; Good, William; Murcray, Frank; Ruppert, Lyle; Soo, Daniel; Follette-Cook, Melanie B.; Janz, Scott J.; Kowalewski, Matthew G.; Loughner, Christopher P.; Pickering, Kenneth E.; Herman, Jay R.; Beaver, Melinda R.; Long, Russell W.; Szykman, James J.; Judd, Laura M.; Kelley, Paul; Luke, Winston T.; Ren, Xinrong; Al-Saadi, Jassim A.

    2016-06-01

    The Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) airborne instrument is a test bed for upcoming air quality satellite instruments that will measure backscattered ultraviolet, visible and near-infrared light from geostationary orbit. GeoTASO flew on the NASA Falcon aircraft in its first intensive field measurement campaign during the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) Earth Venture Mission over Houston, Texas, in September 2013. Measurements of backscattered solar radiation between 420 and 465 nm collected on 4 days during the campaign are used to determine slant column amounts of NO2 at 250 m × 250 m spatial resolution with a fitting precision of 2.2 × 1015 moleculescm-2. These slant columns are converted to tropospheric NO2 vertical columns using a radiative transfer model and trace gas profiles from the Community Multiscale Air Quality (CMAQ) model. Total column NO2 from GeoTASO is well correlated with ground-based Pandora observations (r = 0.90 on the most polluted and cloud-free day of measurements and r = 0.74 overall), with GeoTASO NO2 slightly higher for the most polluted observations. Surface NO2 mixing ratios inferred from GeoTASO using the CMAQ model show good correlation with NO2 measured in situ at the surface during the campaign (r = 0.85). NO2 slant columns from GeoTASO also agree well with preliminary retrievals from the GEO-CAPE Airborne Simulator (GCAS) which flew on the NASA King Air B200 (r = 0.81, slope = 0.91). Enhanced NO2 is resolvable over areas of traffic NOx emissions and near individual petrochemical facilities.

  11. Operational O3M-SAF trace gas column products: GOME-2 ozone, NO2, BrO, SO2 and CH2O

    NASA Astrophysics Data System (ADS)

    Hao, Nan; Valks, Pieter; Loyola, Diego; de Smedt, Isabelle; van Roozendael, Michel; Theys, Nicolas; Rix, Meike; Koukouli, Mariliza; Balis, Dimitris; Lambert, Jean-Christopher; Pinardi, Gaia; Zimmer, Walter; Emmadi, Sunil

    This contribution focuses on the operational GOME-2 trace gas column products developed at the German Aerospace Centre, in the framework of EUMETSAT's Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M-SAF). We present an overview of the retrieval algorithms and exemplary results for ozone, NO2, BrO, SO2 and CH2O. These trace gas column products are retrieved with the GOME Data Processor (GDP) version 4.x algorithm and the UPAS system. Total ozone and NO2 are retrieved with the Differential Optical Absorption Spectroscopy (DOAS) method using the UV wavelength region around 330 nm and 435 nm respectively. An additional algorithm is applied to retrieve the tropospheric NO2 column for polluted con-ditions. The operational ozone and NO2 products are available for the users in near real time, i.e. within two hours after sensing. SO2 emissions from volcanic and anthropogenic sources can be measured by GOME-2 around 320 nm. For BrO and CH2O, optimal DOAS fitting windows have been determined for GOME-2 in the UV wavelength region. The GOME-2 ozone, total and tropospheric NO2, SO2, BrO, CH2O and cloud products from DLR have reached the operational EUMETSAT O3M-SAF status. All these products are routinely available to the users via EUMETCast, WMO/GTS and FTP in HDF5 and BUFR format. We present initial validation results for GOME-2 products using ground-based measurements, as well as comparisons with other satellite products, such as those from SCIAMACHY and OMI. The use of tropospheric NO2, SO2 and CH2O columns for air quality applications will be presented, including temporal evolution analyses for China. Furthermore, we will show examples of BrO under polar winter conditions.

  12. Level 2 processing for the imaging Fourier transform spectrometer GLORIA: derivation and validation of temperature and trace gas volume mixing ratios from calibrated dynamics mode spectra

    NASA Astrophysics Data System (ADS)

    Ungermann, J.; Blank, J.; Dick, M.; Ebersoldt, A.; Friedl-Vallon, F.; Giez, A.; Guggenmoser, T.; Höpfner, M.; Jurkat, T.; Kaufmann, M.; Kaufmann, S.; Kleinert, A.; Krämer, M.; Latzko, T.; Oelhaf, H.; Olchewski, F.; Preusse, P.; Rolf, C.; Schillings, J.; Suminska-Ebersoldt, O.; Tan, V.; Thomas, N.; Voigt, C.; Zahn, A.; Zöger, M.; Riese, M.

    2014-12-01

    The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an airborne infrared limb-imager combining a two-dimensional infrared detector with a Fourier transform spectrometer. It was operated aboard the new German Gulfstream G550 research aircraft HALO during the Transport And Composition in the upper Troposphere/lowermost Stratosphere (TACTS) and Earth System Model Validation (ESMVAL) campaigns in summer 2012. This paper describes the retrieval of temperature and trace gas (H2O, O3, HNO3) volume mixing ratios from GLORIA dynamics mode spectra. 26 integrated spectral windows are employed in a joint fit to retrieve seven targets using consecutively a fast and an accurate tabulated radiative transfer model. Typical diagnostic quantities are provided including effects of uncertainties in the calibration and horizontal resolution along the line-of-sight. Simultaneous in-situ observations by the BAsic HALO Measurement And Sensor System (BAHAMAS), the Fast In-Situ Stratospheric Hygrometer (FISH), FAIRO, and the Atmospheric chemical Ionization Mass Spectrometer (AIMS) allow a validation of retrieved values for three flights in the upper troposphere/lowermost stratosphere region spanning polar and sub-tropical latitudes. A high correlation is achieved between the remote sensing and the in-situ trace gas data, and discrepancies can to a large fraction be attributed to differences in the probed air masses caused by different sampling characteristics of the instruments. This 1-D processing of GLORIA dynamics mode spectra provides the basis for future tomographic inversions from circular and linear flight paths to better understand selected dynamical processes of the upper troposphere and lowermost stratosphere.

  13. Level 2 processing for the imaging Fourier transform spectrometer GLORIA: derivation and validation of temperature and trace gas volume mixing ratios from calibrated dynamics mode spectra

    NASA Astrophysics Data System (ADS)

    Ungermann, J.; Blank, J.; Dick, M.; Ebersoldt, A.; Friedl-Vallon, F.; Giez, A.; Guggenmoser, T.; Höpfner, M.; Jurkat, T.; Kaufmann, M.; Kaufmann, S.; Kleinert, A.; Krämer, M.; Latzko, T.; Oelhaf, H.; Olchewski, F.; Preusse, P.; Rolf, C.; Schillings, J.; Suminska-Ebersoldt, O.; Tan, V.; Thomas, N.; Voigt, C.; Zahn, A.; Zöger, M.; Riese, M.

    2015-06-01

    The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an airborne infrared limb imager combining a two-dimensional infrared detector with a Fourier transform spectrometer. It was operated aboard the new German Gulfstream G550 High Altitude LOng Range (HALO) research aircraft during the Transport And Composition in the upper Troposphere/lowermost Stratosphere (TACTS) and Earth System Model Validation (ESMVAL) campaigns in summer 2012. This paper describes the retrieval of temperature and trace gas (H2O, O3, HNO3) volume mixing ratios from GLORIA dynamics mode spectra that are spectrally sampled every 0.625 cm-1. A total of 26 integrated spectral windows are employed in a joint fit to retrieve seven targets using consecutively a fast and an accurate tabulated radiative transfer model. Typical diagnostic quantities are provided including effects of uncertainties in the calibration and horizontal resolution along the line of sight. Simultaneous in situ observations by the Basic Halo Measurement and Sensor System (BAHAMAS), the Fast In-situ Stratospheric Hygrometer (FISH), an ozone detector named Fairo, and the Atmospheric chemical Ionization Mass Spectrometer (AIMS) allow a validation of retrieved values for three flights in the upper troposphere/lowermost stratosphere region spanning polar and sub-tropical latitudes. A high correlation is achieved between the remote sensing and the in situ trace gas data, and discrepancies can to a large extent be attributed to differences in the probed air masses caused by different sampling characteristics of the instruments. This 1-D processing of GLORIA dynamics mode spectra provides the basis for future tomographic inversions from circular and linear flight paths to better understand selected dynamical processes of the upper troposphere and lowermost stratosphere.

  14. Tropospheric trace gases

    NASA Technical Reports Server (NTRS)

    Gammon, R.; Wofsy, S. C.; Cicerone, R. J.; Delany, A. C.; Harriss, R. T.; Khalil, M. A. K.; Logan, J. A.; Midgley, P.; Prather, M.

    1985-01-01

    Trace gas concentrations in the atmosphere reflect in part the overall metabolism of the biosphere, and in part the broad range of human activities such as agriculture, production of industrial chemicals, and combustion of fossil fuels and biomass. There is compelling evidence that the composition of the atmosphere is now changing. Observed trends in trace gas levels are reviewed and implications for the chemistry of the atmosphere are discussed. Throughout the discussion, particular emphasis is given to those species which are now increasing in the atmosphere.

  15. Quantification of trace O-containing compounds in GTL process samples via Fischer-Tropsch reaction by comprehensive two-dimensional gas chromatography/mass spectrometry.

    PubMed

    Fernandes, Daniella R; Pereira, Vinícius B; Stelzer, Karen T; Gomes, Alexandre O; Neto, Francisco R Aquino; Azevedo, Débora A

    2015-11-01

    Comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS) was successfully applied to eight real Brazilian Fischer-Tropsch (FT) product samples for the quantitative analysis of O-containing compounds. It not only allowed identifying and quantifying simultaneously a large number of O-containing compounds but also resolved many co-eluting components, such as carboxylic acids, which co-elute in one-dimensional gas chromatography. The homologous series of alcohols and carboxylic acids as trimethylsilyl derivatives were detected and identified at trace levels. The absolute quantification of each compound was accomplished with reliability using analytical curves. Linear alcohols (from C5 to C19), branched alcohols (C6-C13) and carboxylic acids (C4 to C12) were obtained in the range of 1.58 mg g(-1) to 14.75 mg g(-1), 0.51 mg g(-1) to 1.12 mg g(-1) and 0.21 mg g(-1) to 1.63 mg g(-1) of FT product samples, respectively. GC×GC-TOFMS provided a linear range (from 0.3 ng µL(-1) to 10 ng µL(-1)), good precision (<8%), and excellent accuracy (recovery range of 77% to 118%) for quantification of individual O-containing compounds in FT product samples. The results can benefit the development of gas-to-liquid technologies from natural gas and guide the choice of an FT conversion process that generates clean products with higher added value. PMID:26452870

  16. Annual Conference Abstracts

    ERIC Educational Resources Information Center

    Engineering Education, 1975

    1975-01-01

    Papers abstracted represent those submitted to the distribution center at the 83rd American Society for Engineering Education Convention. Abstracts are grouped under headings corresponding to the main topic of the paper. (Editor/CP)

  17. PROGRESSIVELY MORE PROLATE DARK MATTER HALO IN THE OUTER GALAXY AS TRACED BY FLARING H I GAS

    SciTech Connect

    Banerjee, Arunima; Jog, Chanda J. E-mail: cjjog@physics.iisc.ernet.in

    2011-05-01

    A galactic disk in a spiral galaxy is generally believed to be embedded in an extended dark matter halo, which dominates its dynamics in the outer parts. However, the shape of the halo is not clearly understood. Here we show that the dark matter halo in the Milky Way is prolate in shape. Further, it is increasingly more prolate at larger radii, with the vertical-to-planar axis ratio monotonically increasing to 2.0 at 24 kpc. This is obtained by modeling the observed steeply flaring atomic hydrogen gas layer in the outer Galactic disk, where the gas is supported by pressure against the net gravitational field of the disk and the halo. The resulting prolate-shaped halo can explain several long-standing puzzles in galactic dynamics, for example, it permits long-lived warps thus explaining their ubiquitous nature.

  18. Laboratory measurements of trace gas emissions from biomass burning of fuel types from the Southeastern and Southwestern United States

    NASA Astrophysics Data System (ADS)

    Burling, I. R.; Yokelson, R. J.; Griffith, D. W. T.; Johnson, T. J.; Veres, P.; Roberts, J. M.; Warneke, C.; Urbanski, S. P.; Reardon, J.; Weise, D. R.; Hao, W. M.; de Gouw, J.

    2010-07-01

    Vegetation commonly managed by prescribed burning was collected from five southeastern and southwestern US military bases and burned under controlled conditions at the US Forest Service Fire Sciences Laboratory in Missoula, Montana. The smoke emissions were measured with a large suite of state-of-the-art instrumentation including an open-path Fourier transform infrared (OP-FTIR) spectrometer for measurement of gas-phase species. The OP-FTIR detected and quantified 19 gas-phase species in these fires: CO2, CO, CH4, C2H2, C2H4, C3H6, HCHO, HCOOH, CH3OH, CH3COOH, furan, H2O, NO, NO2, HONO, NH3, HCN, HCl, and SO2. Emission factors for these species are presented for each vegetation type burned. Gas-phase nitrous acid (HONO), an important OH precursor, was detected in the smoke from all fires. The HONO emission factors ranged from 0.15 to 0.60 g kg-1 and were higher for the southeastern fuels. The fire-integrated molar emission ratios of HONO (relative to NOx) ranged from approximately 0.03 to 0.20, with higher values also observed for the southeastern fuels. The majority of non-methane organic compound (NMOC) emissions detected by OP-FTIR were oxygenated volatile organic compounds (OVOCs) with the total identified OVOC emissions constituting 61±12% of the total measured NMOC on a molar basis. These OVOC may undergo photolysis or further oxidation contributing to ozone formation. Elevated amounts of gas-phase HCl and SO2 were also detected during flaming combustion, with the amounts varying greatly depending on location and vegetation type. The fuels with the highest HCl emission factors were all located in the coastal regions, although HCl was also observed from fuels farther inland. Emission factors for HCl were generally higher for the southwestern fuels, particularly those found in the chaparral biome in the coastal regions of California.

  19. Laboratory measurements of trace gas emissions from biomass burning of fuel types from the southeastern and southwestern United States

    NASA Astrophysics Data System (ADS)

    Burling, I. R.; Yokelson, R. J.; Griffith, D. W. T.; Johnson, T. J.; Veres, P.; Roberts, J. M.; Warneke, C.; Urbanski, S. P.; Reardon, J.; Weise, D. R.; Hao, W. M.; de Gouw, J.

    2010-11-01

    Vegetation commonly managed by prescribed burning was collected from five southeastern and southwestern US military bases and burned under controlled conditions at the US Forest Service Fire Sciences Laboratory in Missoula, Montana. The smoke emissions were measured with a large suite of state-of-the-art instrumentation including an open-path Fourier transform infrared (OP-FTIR) spectrometer for measurement of gas-phase species. The OP-FTIR detected and quantified 19 gas-phase species in these fires: CO2, CO, CH4, C2H2, C2H4, C3H6, HCHO, HCOOH, CH3OH, CH3COOH, furan, H2O, NO, NO2, HONO, NH3, HCN, HCl, and SO2. Emission factors for these species are presented for each vegetation type burned. Gas-phase nitrous acid (HONO), an important OH precursor, was detected in the smoke from all fires. The HONO emission factors ranged from 0.15 to 0.60 g kg-1 and were higher for the southeastern fuels. The fire-integrated molar emission ratios of HONO (relative to NOx) ranged from approximately 0.03 to 0.20, with higher values also observed for the southeastern fuels. The majority of non-methane organic compound (NMOC) emissions detected by OP-FTIR were oxygenated volatile organic compounds (OVOCs) with the total identified OVOC emissions constituting 61 ± 12% of the total measured NMOC on a molar basis. These OVOC may undergo photolysis or further oxidation contributing to ozone formation. Elevated amounts of gas-phase HCl and SO2 were also detected during flaming combustion, with the amounts varying greatly depending on location and vegetation type. The fuels with the highest HCl emission factors were all located in the coastal regions, although HCl was also observed from fuels farther inland. Emission factors for HCl were generally higher for the southwestern fuels, particularly those found in the chaparral biome in the coastal regions of California.

  20. Thiourea-treated graphene aerogel as a highly selective gas sensor for sensing of trace level of ammonia.

    PubMed

    Alizadeh, Taher; Ahmadian, Farzaneh

    2015-10-15

    As a result of this study, a new and simple method was proposed for the fabrication of an ultra sensitive, robust and reversible ammonia gas sensor. The sensing mechanism was based upon the change in electrical resistance of a graphene aerogel as a result of sensor exposing to ammonia. Three-dimensional graphene hydrogel was first synthesized via hydrothermal method in the absence or presence of various amounts of thiourea. The obtained material was heated to obtain aerogel and then it was used as ammonia gas sensor. The materials obtained were characterized using different techniques such as Fourier transform infra red spectroscopy (FT-IR), thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The thiourea-treated graphene aerogel was more porous (389 m(2) g(-1)) and thermally unstable and exhibited higher sensitivity, shorter response time and better selectivity toward ammonia gas, compared to the aerogel produced in the absence of thiourea. Thiourea amount, involved in the hydrogel synthesis step, was found to be highly effective factor in the sensing properties of finally obtained aerogel. The sensor response time to ammonia was short (100 s) and completely reversible (recovery time of about 500 s) in ambient temperature. The sensor response to ammonia was linear between 0.02 and 85 ppm and its detection limit was found to be 10 ppb (3S/N). PMID:26515009

  1. Abstraction and Consolidation

    ERIC Educational Resources Information Center

    Monaghan, John; Ozmantar, Mehmet Fatih

    2006-01-01

    The framework for this paper is a recently developed theory of abstraction in context. The paper reports on data collected from one student working on tasks concerned with absolute value functions. It examines the relationship between mathematical constructions and abstractions. It argues that an abstraction is a consolidated construction that can…

  2. Cryogenic foam insulation: Abstracted publications

    NASA Technical Reports Server (NTRS)

    Williamson, F. R.

    1977-01-01

    A group of documents were chosen and abstracted which contain information on the properties of foam materials and on the use of foams as thermal insulation at cryogenic temperatures. The properties include thermal properties, mechanical properties, and compatibility properties with oxygen and other cryogenic fluids. Uses of foams include applications as thermal insulation for spacecraft propellant tanks, and for liquefied natural gas storage tanks and pipelines.

  3. Miniature Gas Chromatograph (GC): Penning Ionization Electron Spectroscopy (PIES) Instrument for the Trace Analyses of Extraterrestrial Environments

    NASA Technical Reports Server (NTRS)

    Kojiro, Daniel R.; Sheverev, Valery A.; Holland, Paul M.; Takeuchi, Norishige

    2006-01-01

    In situ exploration of the solar system to identify its early chemistry as preserved in icy bodies and to look for compelling evidence of astrobiology will require new technology for chemical analysis. Chemical measurements in space flight environments highlight the need for a high level of positive identification of chemical compounds, since re-measurement by alternative techniques for confirmation will not be feasible. It also may not be possible to anticipate all chemical species that are observed, and important species may be present only at trace levels where they can be masked by complex chemical backgrounds. Up to now, the only techniques providing independent sample identification of GC separated components across a wide range of chemical species have been Mass Spectrometry (MS) and Ion Mobility Spectrometry (IMS). We describe here the development of a versatile and robust miniature GC detector based on Penning Ionization Electron Spectroscopy (PIES), for use with miniature GC systems being developed for planetary missions. PIES identifies the sample molecule through spectra related to its ionization potential. The combination of miniature GC technology with the primary identification capabilities of PIES provides an analytical approach ideal for planetary analyses.

  4. Retrieval and monitoring of atmospheric trace gas concentrations in nadir and limb geometry using the space-borne SCIAMACHY instrument.

    PubMed

    Sierk, B; Richter, A; Rozanov, A; Von Savigny, Ch; Schmoltner, A M; Buchwitz, M; Bovensmann, H; Burrows, J P

    2006-09-01

    The Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) onboard the European Envisat spacecraft performs continuous spectral observations of reflected, scattered and transmitted sunlight in various observation geometries. A unique feature of SCIAMACHY is the capability of probing the atmosphere in three different observation geometries:The nadir, limb, and occultation measurement modes. In nadir mode, column densities of trace gases are retrieved with a spatial resolution of typically 30 x 60 km using the Differential Optical Absorption Spectroscopy (DOAS) technique (Platt and Perner, 1983). Alternating with the nadir measurement, vertical profiles of absorber concentration in the stratosphere are derived in limb and occultation. In this paper we present an overview over some applications of SCIAMACHY data in space-based monitoring of atmospheric pollution. The DOAS algorithms for the retrieval of total column amounts from nadir spectra are briefly described and case studies of pollution events are presented. We also illustrate the technique used to derive stratospheric concentration profiles from limb observations and show comparisons with other remote sensing systems. Special emphasis will be given to techniques, which take advantage of SCIAMACHY's different viewing geometries. In particular, we will discuss the potential and limits of strategies to infer tropospheric abundances of O3 and NO2. PMID:16715354

  5. Highly regioselective hydride transfer, oxidative dehydrogenation, and hydrogen-atom abstraction in the thermal gas-phase chemistry of [Zn(OH)](+)/C3H8.

    PubMed

    Wu, Xiao-Nan; Zhao, Hai-Tao; Li, Jilai; Schlangen, Maria; Schwarz, Helmut

    2014-12-28

    The thermal reactions of [Zn(OH)](+) with C3H8 have been studied by means of gas-phase experiments and computational investigation. Two types of C-H bond activation are observed in the experiment, and pertinent mechanistic features include inter alia: (i) the metal center of [Zn(OH)](+) serves as active site in the hydride transfer to generate [i-C3H7](+) as major product, (ii) generally, a high regioselectivity is accompanied by remarkable chemoselectivity: for example, the activation of a methyl C-H bond results mainly in the formation of water and [Zn(C3,H7)](+). According to computational work, this ionic product corresponds to [HZn(CH3CH=CH2)](+). Attack of the zinc center at a secondary C-H bond leads preferentially to hydride transfer, thus giving rise to the generation of [i-C3H7](+); (iii) upon oxidative dehydrogenation (ODH), liberation of CH3CH2=CH2 occurs to produce [HZn(H2O)](+). Both, ODH as well as H2O loss proceed through the same intermediate which is characterized by the fact that a methylene hydrogen atom from the substrate is transferred to the zinc and one hydrogen atom from the methyl group to the OH group of [Zn(OH)](+). The combined experimental/computational gas-phase study of C-H bond activation by zinc hydroxide provides mechanistic insight into related zinc-catalyzed large-scale processes and identifies the crucial role that the Lewis-acid character of zinc plays. PMID:25230924

  6. Abstraction and Problem Reformulation

    NASA Technical Reports Server (NTRS)

    Giunchiglia, Fausto

    1992-01-01

    In work done jointly with Toby Walsh, the author has provided a sound theoretical foundation to the process of reasoning with abstraction (GW90c, GWS9, GW9Ob, GW90a). The notion of abstraction formalized in this work can be informally described as: (property 1), the process of mapping a representation of a problem, called (following historical convention (Sac74)) the 'ground' representation, onto a new representation, called the 'abstract' representation, which, (property 2) helps deal with the problem in the original search space by preserving certain desirable properties and (property 3) is simpler to handle as it is constructed from the ground representation by "throwing away details". One desirable property preserved by an abstraction is provability; often there is a relationship between provability in the ground representation and provability in the abstract representation. Another can be deduction or, possibly inconsistency. By 'throwing away details' we usually mean that the problem is described in a language with a smaller search space (for instance a propositional language or a language without variables) in which formulae of the abstract representation are obtained from the formulae of the ground representation by the use of some terminating rewriting technique. Often we require that the use of abstraction results in more efficient .reasoning. However, it might simply increase the number of facts asserted (eg. by allowing, in practice, the exploration of deeper search spaces or by implementing some form of learning). Among all abstractions, three very important classes have been identified. They relate the set of facts provable in the ground space to those provable in the abstract space. We call: TI abstractions all those abstractions where the abstractions of all the provable facts of the ground space are provable in the abstract space; TD abstractions all those abstractions wllere the 'unabstractions' of all the provable facts of the abstract space are

  7. Automated trace determination of earthy-musty odorous compounds in water samples by on-line purge-and-trap-gas chromatography-mass spectrometry.

    PubMed

    Salemi, Amir; Lacorte, Sílvia; Bagheri, Habib; Barceló, Damià

    2006-12-15

    An automated technique based on purge-and-trap coupled to gas chromatography with mass spectrometric detection has been developed and optimized for the trace determination of five of the most important water odorants; 2-isopropyl-3-methoxypyrazine, 2-isobutyl-3-methoxypyrazine, 2-methylisoborneol, 2,4,6-trichloroanisole and geosmin. The extraction method was absolutely solvent-free. Analytes were purged from 20 ml of water sample containing sodium chloride at room temperature by a flow of He and trapped on a Tenax sorbent. The desorption step was performed with helium and temperature programming and desorbed analytes were directly transferred to a gas chromatograph coupled to a mass spectrometer for separation and determination. The method was reproducible (RSD<8%) and linear over the calibration range (10-200 ngl(-1)). The relative recoveries of the analytes from ground water sample were calculated and were between 80 and 103% and limits of detection (LOD) below odor thresholds were achieved for most of the compounds. PMID:17055519

  8. Abstraction in mathematics.

    PubMed

    Ferrari, Pier Luigi

    2003-07-29

    Some current interpretations of abstraction in mathematical settings are examined from different perspectives, including history and learning. It is argued that abstraction is a complex concept and that it cannot be reduced to generalization or decontextualization only. In particular, the links between abstraction processes and the emergence of new objects are shown. The role that representations have in abstraction is discussed, taking into account both the historical and the educational perspectives. As languages play a major role in mathematics, some ideas from functional linguistics are applied to explain to what extent mathematical notations are to be considered abstract. Finally, abstraction is examined from the perspective of mathematics education, to show that the teaching ideas resulting from one-dimensional interpretations of abstraction have proved utterly unsuccessful. PMID:12903658

  9. Tracing groundwater input into Lake Vanda, Wright Valley, Antarctica using major ions, stable isotopes and noble gas

    NASA Astrophysics Data System (ADS)

    Dowling, C. B.; Poreda, R. J.; Snyder, G. T.

    2008-12-01

    The McMurdo Dry Valleys (MDV), Antarctica, is the largest ice-free region on Antarctica. Lake Vanda, located in central Wright Valley, is the deepest lake among the MDV lakes. It has a relatively fresh water layer above 50 m with a hypersaline calcium-chloride brine below (50-72 m). The Onyx River is the only stream input into Lake Vanda. It flows westward from the coastal Lower Wright Glacier and discharges into Lake Vanda. Suggested by the published literature and this study, there has been and may still be groundwater input into Lake Vanda. Stable isotopes, major ions, and noble gas data from this study coupled with previously published data indicate that the bottom waters of Lake Vanda have had significant contributions from a deep groundwater system. The dissolved gas of the bottom waters of Lake Vanda display solubility concentrations rather than the Ar-enriched dissolved gas seen in the Taylor Valley lakes (such as Lake Bonney). The isotopic data indicate that the bottom calcium-chloride-brine of Lake Vanda has undergone very little evaporation. The calcium-chloride chemistry of the groundwater that discharges into Lake Vanda most likely results from the chemical weathering and dissolution of cryogenic evaporites (antarcticite and gypsum) within the glacial sediments of Wright Valley. The high calcium concentrations of the brine have caused gypsum to precipitate on the lake bottom. Our work also supports previous physical and chemical observations suggesting that the upper portion actively circulates and the hypersaline bottom layer does not. The helium and calcium chloride values are concentrated at the bottom, with a very narrow transition layer between it and the above fresh water. If the freshwater layer did not actively circulate, then diffusion over time would have caused the helium and calcium chloride to slowly permeate upwards through the water column.

  10. Impact of wildfire emissions on trace gas and aerosol concentration measured at the Zotino Tall Tower Observatory (ZOTTO) in Central Siberia

    NASA Astrophysics Data System (ADS)

    Panov, A.; Chi, X.; Winderlich, J.; Birmili, W.; Lavrič, J. V.; Andreae, M. O.

    2012-04-01

    Boreal wildfires are large sources of reactive trace gases and aerosols to the atmosphere, accounting for 20% of carbon emissions from global biomass burning. Siberian wildfires are a major extratropical source of carbon monoxide (CO), as well as a significant source of black carbon, smoke aerosols, and other climate-relevant atmospheric gas/particle species. Smoke particles released by Siberian wildfires could be tracked thousands of kilometers downwind in the entire Northern Hemisphere, perturbing regional to global radiation budgets by influencing light scattering and cloud microphysical processes. The boreal regions of the Northern Hemisphere are expected to experience the largest temperature increases, which will likely increase the severity and frequency of fires. Consequently, long-term continuous trace gas and aerosol measurements in central Siberia are vital for assessing the atmospheric impact of Siberian boreal fires on regional to global air quality and climate. Since 2006, the Zotino Tall Tower Facility (ZOTTO; www.zottoproject.org), a unique international research platform for large-scale climatic observations, is operational about 20 km west of the Yenisei river (60.8°N; 89.35°E). A 300 m-tall tower allows regular probing of the mixed part of the boundary layer, which is only moderately influenced by diurnal variations of local surface fluxes and thus, in comparison with surface layer, representative for a larger region. Our investigation of the wildfires' impact on surface air composition in Central Siberia is based on four years of CO/CO2/CH4 and aerosol particle mass data measured at 300 m a.g.l.. Episodes of atmospheric transport from wildfires upwind of the measurements site are identified based on ensembles of HYSPLIT backward trajectories and MODIS active fire products. The emission factors are calculated using the Carbon Mass Balance method. In an effort to simplify combustion to its most fundamental principles, the combustion efficiency

  11. Laboratory measurements of trace gas emissions from biomass burning of fuel types from the southeastern and southwestern United States

    SciTech Connect

    Burling, Ian; Yokelson, Robert J.; Griffith, David WT; Johnson, Timothy J.; Veres, Patrick; Roberts, J.; Warneke, Carsten; Urbanski, Shawn; Reardon, James; Weise, David; Hao, WeiMin; Gouw, Joost de

    2010-11-25

    Fuels commonly managed by prescribed burning were collected from five Department of Defense (DoD) bases in the southeast and southwest U.S. 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. A key instrument used in the measurement of the gas-phase species in smoke was an open-path Fourier transform infrared (OP FTIR) spectrometer. The OP FTIR detected and quantified 19 gas-phase species in these fires - CO2, CO, H2O, NO2, NO, HONO, NH3, HCl, SO2, CH4, CH3OH, HCHO, HCOOH, C2H2, C2H4, CH3COOH, HCN, C3H6 and C4H4O. Of particular interest, gas-phase nitrous acid (HONO) was detected in the smoke from all fires. The HONO emission factor ranged from 0.15 to 0.60 g kg 1 and was higher for the southeast fuels. Similarly, the fire-integrated molar emission ratios (relative to NOx) ranged from approximately 0.03 to 0.20, with higher values observed for the southeast fuels. HONO is an important precursor in the production of OH, the primary oxidizing species in the atmosphere but there exists little previous data documenting HONO emissions from either wild or prescribed fires. The detected non-methane organic compound (NMOC) emissions were dominated by oxygenated volatile organic compounds (OVOCs) with total identified molar OVOC emissions ranging from 39 to 79% of the total identified molar non-methane organic compounds (NMOC). Emitted NMOC can undergo further oxidation and photolysis in the case of OVOC and thus involved in secondary aerosol formation. Elevated amounts of gas-phase HCl and SO2 were also detected in the smoke, with the amounts varying depending on location and vegetation type. Emission factors for HCl were typically much higher for the southwest fuels, particularly those found in the chaparral biome in the coastal regions of California.

  12. Detection of trace levels of triclopyr using capillary gas chromatography-electron-capture negative-ion chemical ionization mass spectrometry.

    PubMed

    Begley, P; Foulger, B E

    1988-04-01

    Triclopyr, after esterification, is shown to be a suitable candidate for detection by gas chromatography-electron-capture negative-ion chemical ionization mass spectrometry forming a characteristic carboxylate anion which offers a high detection sensitivity. A detection limit of 70 fg reaching the ionizer is indicated. Low backgrounds and an absence of chemical interferences are shown for vegetation extracts, using a simple method of extraction and derivatisation. A similar behaviour is demonstrated for 2,4-D and 2,4,5-T. PMID:3379116

  13. Estimating trace gas and aerosol emissions over South America: Relationship between fire radiative energy released and aerosol optical depth observations

    NASA Astrophysics Data System (ADS)

    Pereira, Gabriel; Freitas, Saulo R.; Moraes, Elisabete Caria; Ferreira, Nelson Jesus; Shimabukuro, Yosio Edemir; Rao, Vadlamudi Brahmananda; Longo, Karla M.

    2009-12-01

    Contemporary human activities such as tropical deforestation, land clearing for agriculture, pest control and grassland management lead to biomass burning, which in turn leads to land-cover changes. However, biomass burning emissions are not correctly measured and the methods to assess these emissions form a part of current research area. The traditional methods for estimating aerosols and trace gases released into the atmosphere generally use emission factors associated with fuel loading and moisture characteristics and other parameters that are hard to estimate in near real-time applications. In this paper, fire radiative power (FRP) products were extracted from Moderate Resolution Imaging Spectroradiometer (MODIS) and from the Geostationary Operational Environmental Satellites (GOES) fire products and new South America generic biomes FRE-based smoke aerosol emission coefficients were derived and applied in 2002 South America fire season. The inventory estimated by MODIS and GOES FRP measurements were included in Coupled Aerosol-Tracer Transport model coupled to the Brazilian developments on the Regional Atmospheric Modeling System (CATT-BRAMS) and evaluated with ground truth collected in Large Scale Biosphere-Atmosphere Smoke, Aerosols, Clouds, rainfall, and Climate (SMOCC) and Radiation, Cloud, and Climate Interactions (RaCCI). Although the linear regression showed that GOES FRP overestimates MODIS FRP observations, the use of a common external parameter such as MODIS aerosol optical depth product could minimize the difference between sensors. The relationship between the PM 2.5μm (Particulate Matter with diameter less than 2.5 μm) and CO (Carbon Monoxide) model shows a good agreement with SMOCC/RaCCI data in the general pattern of temporal evolution. The results showed high correlations, with values between 0.80 and 0.95 (significant at 0.5 level by student t test), for the CATT-BRAMS simulations with PM 2.5μm and CO.

  14. Comparison of measured reactive trace gas profiles with a multi-layer canopy chemical exchange model in an Amazonian rainforest

    NASA Astrophysics Data System (ADS)

    Wolff, Stefan; Ganzeveld, Laurens; Tsokankunku, Anywhere; Pöhlker, Christopher; de Abreu Sá, Leonardo Deane; Ocimar Manzi, Antonio; Souza, Rodrigo; Trebs, Ivonne; Sörgel, Matthias

    2016-04-01

    In 2011, an 80 m high walk up tower for atmospheric research was erected at the ATTO (Amazon Tall Tower Observatory) site (02°08'38.8''S, 58°59'59.5''W) in the remote Amazonian rainforest. The nearly pristine environment allows biosphere-atmosphere studies within an ecosystem far away from large anthropogenic emission sources. Since April 2012 vertical mixing ratio profiles of H2O, CO2 and O3 were measured at 8 different heights between 0.05 m and 79.3 m. During five intensive campaigns (Oct-Dec 2012, Oct-Nov 2013, Mar 2014, Aug-Sep 2014, Oct-Dec 2015) nitric oxide (NO) and nitrogen dioxide (NO2) were also measured. We applied the Multi-layer Canopy Chemical Exchange Model - MLC-CHEM to support the analysis of the observed profiles of NOx and O3. This includes inferring bi-directional surface-atmosphere exchange fluxes as well as the role of the canopy interactions between the emissions, dry deposition, chemistry and turbulent transport of trace gases. During our investigation of diurnal and seasonal differences between model and measurements, we conducted a set of sensitivity studies to analyse the effects of changes in NOx-soil emissions, in-canopy turbulence and resistances for O3 and NO2 uptake on wet surfaces. These analyses suggest some modification in the representation of some of the poorly constrained canopy processes resulting in a significantly better comparison between the simulated and measured exchange fluxes and concentrations.

  15. Trace element incorporation into quartz: A combined study by ICP-MS, electron spin resonance, cathodoluminescence, capillary ion analysis, and gas chromatography

    NASA Astrophysics Data System (ADS)

    Götze, Jens; Plötze, Michael; Graupner, Torsten; Hallbauer, Dieter Klaus; Bray, Colin J.

    2004-09-01

    Pegmatite quartz from different occurrences in Norway and Namibia was investigated by a combination of ICP-MS, Electron Spin Resonance (ESR), Capillary Ion Analysis (CIA) and Gas Chromatography (GC) to quantify trace elements in very low concentrations and to determine their position in the quartz structure. The studied quartz samples show similar geochemical characteristics with low contents of most trace elements. Remarkable are the elevated concentrations of Al (36-636 ppm), Ti (1.6-25.2 ppm), Ge (1.0-7.1 ppm), Na (5.2 to >50 ppm), K (1.6 to >100 ppm) and Li (2.1-165.6 ppm). These elements are preferentially incorporated into the quartz lattice on substitutional (Al, Ti, Ge) and interstitial (Li, Na, K) positions. Li + was found to be the main charge compensating ion for Al, Ge and Ti, whereas some ppm of Na and K may also be hosted by fluid inclusions. Ti may be incorporated as substitutional ion for Si or bound on mineral microinclusions (rutile). The results of the ESR measurements show that there may be a redistribution of alkali ions during irradiation. The diamagnetic [AlO 4/M +] 0 center transforms into the paramagnetic [AlO 4] 0 center, whilst the compensating ions diffuse away and may be captured by the diamagnetic precursor centers of [GeO 4] 0 and [TiO 4] 0 to form paramagnetic centers ([TiO 4/Li +] 0, [GeO 4/Li +] 0). In general, fluid inclusions in pegmatite quartz can be classified as H 2O-CO 2-NaCl type inclusions with water as the predominant volatile. Among the main elements hosted by fluid inclusions in quartz are Na, K, NH 4, Ca, Mg and the anionic complexes Cl -, NO 3-, HCO 3- and SO 42-. Gas analysis of trapped fluids shows volatile components in the following order of abundance: H 2O > CO 2 > N 2(+) ≥ CH 4 > COS > C 2 and C 3 hydrocarbons. Additionally, traces of Co, Ni, Zn, Pb, and Cu were detected by CIA in fluid inclusions of some samples. There are indications that the REE and Rb are also bound in fluid inclusions, however, the

  16. Third LDEF Post-Retrieval Symposium Abstracts

    NASA Technical Reports Server (NTRS)

    Levine, Arlene S. (Compiler)

    1993-01-01

    This volume is a compilation of abstracts submitted to the Third Long Duration Exposure Facility (LDEF) Post-Retrieval Symposium. The abstracts represent the data analysis of the 57 experiments flown on the LDEF. The experiments include materials, coatings, thermal systems, power and propulsion, science (cosmic ray, interstellar gas, heavy ions, micrometeoroid, etc.), electronics, optics, and life science.

  17. Trace gas measurements in nascent, aged, and cloud-processed smoke from African savanna fires by airborne Fourier transform infrared spectroscopy (AFTIR)

    NASA Astrophysics Data System (ADS)

    Yokelson, Robert J.; Bertschi, Isaac T.; Christian, Ted J.; Hobbs, Peter V.; Ward, Darold E.; Hao, Wei Min

    2003-07-01

    We measured stable and reactive trace gases with an airborne Fourier transform infrared spectrometer (AFTIR) on the University of Washington Convair-580 research aircraft in August/September 2000 during the SAFARI 2000 dry season campaign in Southern Africa. The measurements included vertical profiles of CO2, CO, H2O, and CH4 up to 5.5 km on six occasions above instrumented ground sites and below the TERRA satellite and ER-2 high-flying research aircraft. We also measured the trace gas emissions from 10 African savanna fires. Five of these fires featured extensive ground-based fuel characterization, and two were in the humid savanna ecosystem that accounts for most African biomass burning. The major constituents that we detected in nascent smoke were (in order of excess molar abundance) H2O, CO2, CO, CH4, NO2, NO, C2H4, CH3COOH, HCHO, CH3OH, HCN, NH3, HCOOH, and C2H2. These are the first quantitative measurements of the initial emissions of oxygenated volatile organic compounds (OVOC), NH3, and HCN from African savanna fires. On average, we measured 5.3 g/kg of OVOC and 3.6 g/kg of hydrocarbons (including CH4) in the initial emissions from the fires. Thus, the OVOC will have profound, largely unexplored effects on tropical tropospheric chemistry. The HCN emission factor was only weakly dependent on fire type; the average value (0.53 g/kg) is about 20 times that of a previous recommendation. HCN may be useful as a tracer for savanna fires. ΔO3/ΔCO and ΔCH3COOH/ΔCO increased to as much as 9% in <1 h of photochemical processing downwind of fires. Direct measurements showed that cloud processing of smoke greatly reduced CH3OH, NH3, CH3COOH, SO2, and NO2 levels, but significantly increased HCHO and NO.

  18. Trace gas composition in the free and upper troposphere over Asia: Examining the influence of long-range transport and convection of local pollution

    NASA Astrophysics Data System (ADS)

    Baker, A. K.; Traud, S.; Brenninkmeijer, C. A.; Hoor, P. M.; Neumaier, M.; Oram, D.; Rauthe-Schöch, A.; Schloegl, S.; Sprung, D.; Slemr, F.; van Velthoven, P.; Wernli, H.; Zahn, A.; Ziereis, H.

    2013-12-01

    Between May 2005 and March 2008 the CARIBIC observatory (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) was deployed to make atmospheric observations during 21 round-trip flights between Frankfurt, Germany and Manila, the Philippines with a stopover in Guangzhou, China. This nearly 3 year flight series provides us with information about atmospheric composition in the free and upper troposphere over Asia during all seasons and was used to investigate seasonal and regional differences in trace gas distributions and the relative influences of long range transport and convected local air masses on composition. The flight route was separated into three different regions having unique characteristics in transport and composition; these were Western Asia (5°E to 70°E), Central Asia (70°E to 100°E) and East Asia (100°E to 125°E). The region over Western Asia was heavily influenced by long range transport of air masses from North America and had elevated levels of NOy and acetone, while the region over East Asia was mostly influenced by convected local (South East Asian) pollution, particularly from biomass/biofuel burning as indicated by high levels of acetonitrile and carbon monoxide. Air masses over Central Asia were found to be influenced by both recently convected air masses from the Indian subcontinent and mid-range transport from Eastern Europe and the Middle East. Elevated levels of propane and other non-methane hydrocarbons, both with and without concommitant elevations in other trace gases (i.e. carbon monoxide, acetonitrile) were a persisent feature of this region in all seasons except summer, and were particularly prominent in fall. Influences on composition over Central Asia were investigated more thoroughly in a case study from a series of flights in October 2006, and elevated levels of pollutants were found to be the result of convective transport of both biomass/biofuel burning and urban emissions from

  19. Trace Gas Measurements in Nascent, Aged and Cloud-processed Smoke from Africa Savanna Fires by Airborne Fourier Transform Infrared Spectroscopy (AFTIR)

    NASA Technical Reports Server (NTRS)

    Yokelson, Robert J.; Bertschi, Isaac T.; Christian, Ted J.; Hobbs, Peter V.; Ward, Darold E.; Hao, Wei Min

    2003-01-01

    We measured stable and reactive trace gases with an airborne Fourier transform infrared spectrometer (AFTIR) on the University of Washington Convair-580 research aircraft in August/September 2000 during the SAFARI 2000 dry season campaign in Southern Africa. The measurements included vertical profiles of C02, CO, H20, and CH4 up to 5.5 km on six occasions above instrumented ground sites and below the TERRA satellite and ER-2 high-flying research aircraft. We also measured the trace gas emissions from 10 African savanna fires. Five of these fires featured extensive ground-based fuel characterization, and two were in the humid savanna ecosystem that accounts for most African biomass burning. The major constituents we detected in nascent CH3OOH, HCHO, CH30H, HCN, NH3, HCOOH, and C2H2. These are the first quantitative measurements of the initial emissions of oxygenated volatile organic compounds (OVOC), NH3, and HCN from African savanna fires. On average, we measured 5.3 g/kg of OVOC and 3.6 g/kg of hydrocarbons (including CH4) in the initial emissions from the fires. Thus, the OVOC will have profound, largely unexplored effects on tropical tropospheric chemistry. The HCN emission factor was only weakly dependent on fire type; the average value (0.53 g/kg) is about 20 times that of a previous recommendation. HCN may be useful as a tracer for savanna fires. Delta O3/Delta CO and Delta CH3COO/Delta CO increased to as much as 9% in <1 h of photochemical processing downwind of fires. Direct measurements showed that cloud processing of smoke greatly reduced CH30H, NH3, CH3COOH, SO2, and NO2 levels, but significantly increased HCHO and NO.

  20. An overview of the flight campaign for the GAUGE project: airborne greenhouse gas (and other complementary trace gas) measurements around and over the UK between April 2014 and May 2015

    NASA Astrophysics Data System (ADS)

    Allen, Grant; Pitt, Joseph; Le Breton, Michael; Percival, Carl; Bannan, Thomas; O'Doherty, Simon; Manning, Alistair; Rigby, Matt; Gannesan, Anita; Mead, Mohammed; Bauguitte, Stephane; Lee, James; Wenger, Angelina; Palmer, Paul

    2016-04-01

    This work highlights data measured during flights by the UK Facility for Airborne Atmospheric Measurement (FAAM) as part of the Greenhouse gAs UK and Global Emissions (GAUGE) campaign. A total of 17 flights (85 flight-hours) have been conducted so far around the UK mainland and Ireland to sample precision in situ CH4, CO2, N2O (and other trace gas) concentrations and meteorological parameters at altitudes up to 9500m throughout the period April 2014 to May 2015. Airborne remote sensing retrievals of greenhouse gas total columns have also been calculated using the Manchester Airborne Retrieval Scheme for the UK Met Office ARIES high resolution FTIR instrument. This airborne dataset represents a mapped climatology and a series of case studies from which to assess top-down bulk-net-flux snapshots for regions of the UK, and provides for evaluation of inverse modelling approaches that challenge bottom-up inventories, satellite remote sensing measurements, and assessment of model transport uncertainty. In this paper, we shall describe the instrumentation on the FAAM aircraft and provide a diary of GAUGE FAAM flights (and data highlights) to date; and discuss selected flights of interest to studies such as those above with a focus of net mass flux evaluation.

  1. Potential for Measurement of Trace Volatile Organic Compounds in Closed Environments Using Gas Chromatograph/Differential Mobility Spectrometer

    NASA Technical Reports Server (NTRS)

    Limero, Thomas; Cheng, Patti

    2007-01-01

    For nearly 3.5 years, the Volatile Organic Analyzer (VOA) has routinely analyzed the International Space Station (ISS) atmosphere for a target list of approximately 20 volatile organic compounds (VOCs). Additionally, an early prototype of the VOA collected data aboard submarines in two separate trials. Comparison of the data collected on ISS and submarines showed a surprising similarity in the atmospheres of the two environments. Furthermore, in both cases it was demonstrated that the VOA data can detect hardware issues unrelated to crew health. Finally, it was also clear in both operations that the VOA s size and resource consumption were major disadvantages that would restrict its use in the future. The VOA showed the value of measuring VOCs in closed environments, but it had to be shrunk if it was to be considered for future operations in these environments that are characterized by cramped spaces and limited resources. The Sionex Microanalyzer is a fraction of the VOA s size and this instrument seems capable of maintaining or improving upon the analytical performance of the VOA. The two design improvements that led to a smaller, less complex instrument are the Microanalyzer s use of recirculated air as the gas chromatograph s carrier gas and a micromachined detector. Although the VOA s ion mobility spectrometer and the Microanalyzer s differential mobility spectrometer (DMS) are related detector technologies, the DMS was more amenable to micromachining. This paper will present data from the initial assessment of the Microanalyzer. The instrument was challenged with mixtures that simulated the VOCs typically detected in closed-environment atmospheres.

  2. The Ionized Gas in Nearby Galaxies as Traced by the [N II] 122 and 205 μm Transitions

    NASA Astrophysics Data System (ADS)

    Herrera-Camus, R.; Bolatto, A.; Smith, J. D.; Draine, B.; Pellegrini, E.; Wolfire, M.; Croxall, K.; de Looze, I.; Calzetti, D.; Kennicutt, R.; Crocker, A.; Armus, L.; van der Werf, P.; Sandstrom, K.; Galametz, M.; Brandl, B.; Groves, B.; Rigopoulou, D.; Walter, F.; Leroy, A.; Boquien, M.; Tabatabaei, F. S.; Beirao, P.

    2016-08-01

    The [N ii] 122 and 205 μm transitions are powerful tracers of the ionized gas in the interstellar medium. By combining data from 21 galaxies selected from the Herschel KINGFISH and Beyond the Peak surveys, we have compiled 141 spatially resolved regions with a typical size of ˜1 kpc, with observations of both [N ii] far-infrared lines. We measure [N ii] 122/205 line ratios in the ˜0.6–6 range, which corresponds to electron gas densities of n e ˜ 1–300 cm‑3, with a median value of n e = 30 cm‑3. Variations in the electron density within individual galaxies can be as high as a factor of ˜50, frequently with strong radial gradients. We find that n e increases as a function of infrared color, dust-weighted mean starlight intensity, and star-formation rate (SFR) surface density (ΣSFR). As the intensity of the [N ii] transitions is related to the ionizing photon flux, we investigate their reliability as tracers of the SFR. We derive relations between the [N ii] emission and SFR in the low-density limit and in the case of a log-normal distribution of densities. The scatter in the correlation between [N ii] surface brightness and ΣSFR can be understood as a property of the n e distribution. For regions with n e close to or higher than the [N ii] line critical densities, the low-density limit [N ii]-based SFR calibration systematically underestimates the SFR because the [N ii] emission is collisionally quenched. Finally, we investigate the relation between [N ii] emission, SFR, and n e by comparing our observations to predictions from the MAPPINGS-III code.

  3. An airborne infrared laser spectrometer for in-situ trace gas measurements: application to tropical convection case studies

    NASA Astrophysics Data System (ADS)

    Catoire, V.; Krysztofiak, G.; Robert, C.; Chartier, M.; Jacquet, P.; Guimbaud, C.; Hamer, P. D.; Marécal, V.

    2015-09-01

    A three-channel laser absorption spectrometer called SPIRIT (SPectromètre InfraRouge In situ Toute altitude) has been developed for airborne measurements of trace gases in the troposphere and lower stratosphere. More than three different species can be measured simultaneously with high time resolution (each 1.6 s) using three individual CW-DFB-QCLs (Continuous Wave Distributed FeedBack Quantum Cascade Lasers) coupled to a single Robert multipass optical cell. The lasers are operated in a time-multiplexed mode. Absorption of the mid-infrared radiations occur in the cell (2.8 L with effective path lengths of 134 to 151 m) at reduced pressure, with detection achieved using a HgCdTe detector cooled by Stirling cycle. The performances of the instrument are described, in particular precisions of 1, 1 and 3 %, and volume mixing ratio (vmr) sensitivities of 0.4, 6 and 2.4 ppbv are determined at 1.6 s for CO, CH4 and N2O, respectively (at 1σ confidence level). Estimated accuracies without calibration are about 6 %. Dynamic measuring ranges of about four decades are established. The first deployment of SPIRIT was realized aboard the Falcon-20 research aircraft operated by DLR (Deutsches Zentrum für Luft- und Raumfahrt) within the frame of the SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) European project in November-December 2011 over Malaysia. The convective outflows from two large convective systems near Borneo Island (6.0° N-115.5° E and 5.5° N-118.5° E) were sampled above 11 km in altitude on 19 November and 9 December, respectively. Correlated enhancements in CO and CH4 vmr were detected when the aircraft crossed the outflow anvil of both systems. These enhancements were interpreted as the fingerprint of transport from the boundary layer up through the convective system and then horizontal advection in the outflow. Using these observations, the fraction of boundary layer air contained in fresh convective outflow was calculated to range

  4. Loving Those Abstracts

    ERIC Educational Resources Information Center

    Stevens, Lori

    2004-01-01

    The author describes a lesson she did on abstract art with her high school art classes. She passed out a required step-by-step outline of the project process. She asked each of them to look at abstract art. They were to list five or six abstract artists they thought were interesting, narrow their list down to the one most personally intriguing,…

  5. Trace level determination of organochlorine, organophosphorus and pyrethroid pesticides in lanolin using gel permeation chromatography followed by dual gas chromatography and gas chromatography-negative chemical ionization mass spectrometric confirmation.

    PubMed

    Jover, Eric; Bayona, Josep Maria

    2002-03-15

    A methodology for multi-class pesticide determination at trace level in lanolin is presented. Gel permeation chromatography on a Bio-Beads SX-3 column followed by a dual GC chromatographic determination has been developed. The effluent of the analytical column (50% diphenyl-methyl- or 14% cyanopropyl-phenylpolysiloxane) was split into an electron-capture and a nitrogen-phosphorus detection system. The chromatographic system was optimised for 28 pesticides commonly used to control sheep pests and corresponding to organochlorine, organophosphorus and pyretroid classes. Identification has been carried out by gas chromatography coupled to negative chemical ionization mass spectrometry. Recoveries ranged from 72 to 94% and the detection limits from 20 to 97 ng/g depending on the pesticide class, the RSDs were below 10%. Finally, the developed analytical methodology has been successfully applied to the determination of pesticides in several lanolin samples. PMID:11990995

  6. Operational O3M-SAF trace-gas column products: GOME-2 tropospheric NO2, SO2 and BrO

    NASA Astrophysics Data System (ADS)

    Valks, P.; Hao, N.; Rix, M.; Lambert, J.-C.; Pinardi, G.; van Roozendael, M.; Theys, N.; Loyola, D.

    2009-04-01

    This contribution focuses on the operational GOME-2 trace-gas column products developed at the German Aerospace Centre, in the framework of EUMETSAT's Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M-SAF). We present the algorithms and exemplary results of tropospheric NO2, total BrO and SO2. These trace-gas column products are retrieved from GOME-2 solar backscattered measurements in the UV/VIS wavelength region, using the Differential Optical Absorption Spectroscopy (DOAS) method. Total NO2 is routinely retrieved with the GOME Data Processor (GDP) version 4.2 using the 425-450 nm wavelength region. An additional algorithm is applied to derive the tropospheric NO2 column for polluted conditions: after subtracting the estimated stratospheric component from the total column, the tropospheric NO2 column is determined using an air mass factor based on monthly climatological NO2 profiles from the MOZART-2 model. SO2 emissions from volcanic and anthropogenic sources can be measured by GOME-2 using the UV wavelength region around 320 nm. With GOME-2, it is possible to detect and track volcanic SO2 in near-real time and on a global scale, which is of particular importance for volcanic early warning services. For the GOME-2 retrieval of the total BrO column, current research focuses on the optimisation of the DOAS fitting window in the UV wavelength region. BrO columns retrieved from the baseline GOME fitting window (344.6-359 nm) show relatively large noise levels. Therefore, the use of an alternative fitting window has been analysed. More than two years of tropospheric NO2, total BrO and SO2 measurements are now available from GOME-2. We present initial validation results using ground-based measurements, as well as comparisons with other satellite products, such as those from SCIAMACHY and OMI. The use of tropospheric NO2 columns for air quality applications will be presented. We will show examples of BrO from volcanic eruptions and under

  7. Trace gas emissions from a chronosequence of bark beetle-infested lodgepole pine (Pinus contorta) forest stands

    NASA Astrophysics Data System (ADS)

    Norton, U.; Pendall, E.; Ewers, B. E.; Borkhuu, B.

    2011-12-01

    Severe outbreak of mountain pine beetle (MPB) and associated blue stain fungi have killed millions of hectares of coniferous forests in Western North America. This unprecedented disturbance has critically impacted ecosystem biogeochemistry and net carbon (C) and nitrogen (N) fluxes. However, the effects on greenhouse gas (GHG) emissions and drivers of biogeochemical processes that trigger GHG emissions following MPB infestations are not well understood. Such information can help assess regional-level changes in ecosystem C and N budgets and large-scale disturbance impacts on gas exchange between the atmosphere and terrestrial ecosystem. The overall objective of this research was to assess the immediate responses of GHG fluxes and soil C and N mineralization rates along a chronosequence of recently infested (1-yr, 3-yr and 4-yr ago) and uninfested (150-yr, 20-yr and 15-yr old) lodgepole pine stands in Medicine Bow National Forest in southeastern Wyoming. We hypothesize that MPB-induced tree mortality significantly changes stand-level hydrology, soil organic matter quality and chemistry of aboveground and belowground plant inputs. Consequently, these modifications influence nitrous oxide (N2O) emissions and methane (CH4) assimilation. Biweekly GHG measurements using static chambers were carried out during three consecutive snow-free growing seasons. Our results suggest that a stand infested within a year already shows a 20% increase in spring N2O production and a small decline in summer CH4 assimilation when compared to uninfested stands. Stands infested three and four years prior to our measurements produce over three times more N2O and assimilate three to five times less CH4 when compared to uninfested stands. In addition, a notable increase in soil moisture content and soil mineral N concentrations following early onset of the MPB infestation was also observed. An overall increase in N2O production and decline in CH4 assimilation following MPB infestation may

  8. Closed-loop 15N measurement of N2O and its isotopomers for real-time greenhouse gas tracing

    NASA Astrophysics Data System (ADS)

    Slaets, Johanna; Mayr, Leopold; Heiling, Maria; Zaman, Mohammad; Resch, Christian; Weltin, Georg; Gruber, Roman; Dercon, Gerd

    2016-04-01

    Quantifying sources of nitrous oxide is essential to improve understanding of the global N cycle and to develop climate-smart agriculture, as N2O has a global warming potential 300 times higher than CO2. The isotopic signature and the intramolecular distribution (site preference) of 15N are powerful tools to trace N2O, but the application of these methods is limited as conventional methods cannot provide continuous and in situ data. Here we present a method for closed-loop, real time monitoring of the N2O flux, the isotopic signature and the intramolecular distribution of 15N by using off-axis integrated cavity output spectroscopy (ICOS, Los Gatos Research). The developed method was applied to a fertilizer inhibitor experiment, in which N2O emissions were measured on undisturbed soil cores for three weeks. The treatments consisted of enriched urea-N (100 kg urea-N/ha), the same fertilizer combined with the nitrification inhibitor nitrapyrin (375 g/100 kg urea), and control cores. Monitoring the isotopic signature makes it possible to distinguish emissions from soil and fertilizer. Characterization of site preference could additionally provide a tool to identify different microbial processes leading to N2O emissions. Furthermore, the closed-loop approach enables direct measurement on site and does not require removal of CO2 and H2O. Results showed that 75% of total N2O emissions (total=11 346 μg N2O-N/m2) in the fertilized cores originated from fertilizer, while only 55% of total emissions (total=2 450 μg N2ON/m2) stemmed from fertilizer for the cores treated with nitrapyrin. In the controls, N2O derived from soil was only 40% of the size of the corresponding pool from the fertilized cores, pointing towards a priming effect on the microbial community from the fertilizer and demonstrating the bias that could be introduced by relying on non-treated cores to estimate soil emission rates, rather than using the isotopic signature. The site preference increased linearly

  9. Trace Gas and Carbon Sequestration Dynamics in Temperate Croplands and Successional Ecosystems: A Full-Cost Accounting

    NASA Astrophysics Data System (ADS)

    Robertson, G. P.; McSwiney, C. P.

    2003-12-01

    Agriculture is responsible for 21-25% of the global anthropic CO2 flux, 55-60% of the anthropic CH4 flux, and 65-80% of the anthopic flux of N2O. A number of CO2 stabilization strategies target agricultural production practices, and the potential for simultaneously abating fluxes of the non-CO2 greenhouse gases is substantial. But so is the potential for creating greenhouse gas (GHG) liabilities, the unintentional increase in one or more GHGs by activities that mitigate another. Whole-system accounting provides a means for including all GHG-contributing processes in the same cropping system analysis in order to illuminate major liabilities and synergies. We contrast a field crop system in the upper U.S. midwest with unmanaged successional ecosystems in the same landscape, and provide evidence that N2O flux - the major contributor to radiative forcing in row-crop systems - can be abated with little loss of crop productivity.

  10. Trace analysis of explosives in soil: pressurized fluid extraction and gas and liquid chromatography-mass spectrometry.

    PubMed

    Campbell, Sonia; Ogoshi, Richard; Uehara, Goro; Li, Qing X

    2003-07-01

    Soil samples are collected from the former Open Burn/Open Detonation Unit, Makua Military Reservation, on the island of Oahu, Hawaii. The soil is the Helemano series. The soil samples are fortified with eight explosives for development of the analytical method. These analytes are 2-amino-4,6-dinitrotoluene; 1,3-dinitrobenzene; 2,4-dinitrotoluene (DNT); hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX); nitrobenzene (NB); octogen; 1,3,5-trinitrobenzene; and 2,4,6-trinitrotoluene. The analytes are recovered with pressurized fluid extraction and measured with liquid chromatography (LC), LC-mass spectrometry (MS), and gas chromatography-MS. Average recoveries of the seven analytes, except for NB, range from 67% to 110% from freshly fortified samples. The procedure fails to extract NB in soil. The average recoveries decrease from 67-110% to 41-81% as the soil is aged for 1 day to 6 months after fortification of the soil with the seven explosives. The field samples are analyzed for the presence of explosives, of which DNT and RDX are indeed detected. The results obtained with this procedure agree well with those obtained by an independent laboratory following the standard U.S. Environmental Protection Agency (EPA) method SW-846 8330. Compared with the EPA method, this new method provides MS confirmation of the analytes, and the extraction requires approximately 15 min, rather than 18 h by the EPA method. PMID:12935298

  11. Analysis of Trace Quaternary Ammonium Compounds (QACs) in Vegetables Using Ultrasonic-Assisted Extraction and Gas Chromatography-Mass Spectrometry.

    PubMed

    Xiang, Lei; Wang, Xiong-Ke; Li, Yan-Wen; Huang, Xian-Pei; Wu, Xiao-Lian; Zhao, Hai-Ming; Li, Hui; Cai, Quan-Ying; Mo, Ce-Hui

    2015-08-01

    A reliable, sensitive, and cost-effective method was developed for determining three quaternary ammonium compounds (QACs) including dodecyltrimethylammonium chloride, cetyltrimethylammonium chloride, and didodecyldimethylammonium chloride in various vegetables using ultrasonic-assisted extraction and gas chromatography-mass spectrometry. The variety and acidity of extraction solvents, extraction times, and cleanup efficiency of sorbents were estimated to obtain an optimized procedure for extraction of the QACs in nine vegetable matrices. Excellent linearities (R(2) > 0.992) were obtained for the analytes in the nine matrices. The limits of detection and quantitation were 0.7-6.0 and 2.3-20.0 μg/kg (dry weight, dw) in various matrices, respectively. The recoveries in the nine matrices ranged from 70.5% to 108.0% with relative standard deviations below 18.0%. The developed method was applied to determine the QACs in 27 vegetable samples collected from Guangzhou in southern China, showing very high detection frequency with a concentration of 23-180 μg/kg (dw). PMID:26165915

  12. Evaluation of a hybrid sampling train for measuring trace elements and identifying mercury species in combustion flue gas

    SciTech Connect

    Miller, S.F.; Wincek, R.T.; Miller, B.G.; Scaroni, A.W.

    1999-07-01

    The Environmental Protection Agency (EPA) initiated an information collection request (ICR) on January 1, 1999 for coal-fired electric utility steam generating units (>25 MW) to document mercury levels in their fuels and emissions. The issuance of an ICR generally precedes the implementation of regulatory action by the EPA. The EPA has designated the Modified Ontario Hydro Method for stack gas sampling to measure total, elemental and oxidized mercury. This recommendation is based on extensive work by the University of North Dakota Energy and Environmental Research Center (UNDEERC) in evaluating a series of methodologies for determining mercury speciation. EPA has also designed the Method 29 sampling train for the sampling and measurement of the other elements identified as HAP's, i.e. As, Be, Cd, Co, Mn, Ni, Pb, Sb, Se, and Hg. Extensive testing has shown that EPA Method 29 may not speciate mercury correctly; however, it may still be used to measure total mercury. Currently there are no emission restrictions on these elements from power plants, however studies are being conducted as to their health risk and environmental impact. The objective of the study is to evaluate a hybrid train consisting of components of both the Modified Ontario Hydro Method and Method 29 sampling trains. Both sampling procedures are very labor intensive and require time to develop sampling expertise. The various sample trains are being tested in a 20 million Btu/hr demonstration boiler and a 2 million Btu/hr research boiler using a variety of fuels and combustion conditions.

  13. Multi-Component Profiling of Trace Volatiles in Blood by Gas Chromatography/Mass Spectrometry with Dynamic Headspace Extraction

    PubMed Central

    Kakuta, Shoji; Yamashita, Toshiyuki; Nishiumi, Shin; Yoshida, Masaru; Fukusaki, Eiichiro; Bamba, Takeshi

    2015-01-01

    A dynamic headspace extraction method (DHS) with high-pressure injection is described. This dynamic extraction method has superior sensitivity to solid phase micro extraction, SPME and is capable of extracting the entire gas phase by purging the headspace of a vial. Optimization of the DHS parameters resulted in a highly sensitive volatile profiling system with the ability to detect various volatile components including alcohols at nanogram levels. The average LOD for a standard volatile mixture was 0.50 ng mL−1, and the average LOD for alcohols was 0.66 ng mL−1. This method was used for the analysis of volatile components from biological samples and compared with acute and chronic inflammation models. The method permitted the identification of volatiles with the same profile pattern as in vitro oxidized lipid-derived volatiles. In addition, the concentration of alcohols and aldehydes from the acute inflammation model samples were significantly higher than that for the chronic inflammation model samples. The different profiles between these samples could also be identified by this method. Finally, it was possible to analyze alcohols and low-molecular-weight volatiles that are difficult to analyze by SPME in high sensitivity and to show volatile profiling based on multi-volatile simultaneous analysis. PMID:26819905

  14. Community Development Abstracts.

    ERIC Educational Resources Information Center

    Agency for International Development (Dept. of State), Washington, DC.

    This volume of 1,108 abstracts summarizes the majority of important works on community development during the last ten years. Part I contains abstracts of periodical literature and is classified into 19 sections, including general history, communications, community and area studies, decision-making, leadership, migration and settlement, social…

  15. Leadership Abstracts, Volume 10.

    ERIC Educational Resources Information Center

    Milliron, Mark D., Ed.

    1997-01-01

    The abstracts in this series provide brief discussions of issues related to leadership, administration, professional development, technology, and education in community colleges. Volume 10 for 1997 contains the following 12 abstracts: (1) "On Community College Renewal" (Nathan L. Hodges and Mark D. Milliron); (2) "The Community College Niche in a…

  16. Has Abstractness Been Resolved?

    ERIC Educational Resources Information Center

    Al-Omoush, Ahmad

    1989-01-01

    A discussion focusing on the abstractness of analysis in phonology, debated since the 1960s, describes the issue, reviews the literature on the subject, cites specific natural language examples, and examines the extent to which the issue has been resolved. An underlying representation is said to be abstract if it is different from the derived one,…

  17. Designing for Mathematical Abstraction

    ERIC Educational Resources Information Center

    Pratt, Dave; Noss, Richard

    2010-01-01

    Our focus is on the design of systems (pedagogical, technical, social) that encourage mathematical abstraction, a process we refer to as "designing for abstraction." In this paper, we draw on detailed design experiments from our research on children's understanding about chance and distribution to re-present this work as a case study in designing…

  18. Knowledge-Based Abstracting.

    ERIC Educational Resources Information Center

    Black, William J.

    1990-01-01

    Discussion of automatic abstracting of technical papers focuses on a knowledge-based method that uses two sets of rules. Topics discussed include anaphora; text structure and discourse; abstracting techniques, including the keyword method and the indicator phrase method; and tools for text skimming. (27 references) (LRW)

  19. Leadership Abstracts, 1995.

    ERIC Educational Resources Information Center

    Johnson, Larry, Ed.

    1995-01-01

    The abstracts in this series provide two-page discussions of issues related to leadership, administration, and teaching in community colleges. The 12 abstracts for Volume 8, 1995, are: (1) "Redesigning the System To Meet the Workforce Training Needs of the Nation," by Larry Warford; (2) "The College President, the Board, and the Board Chair: A…

  20. Paper Abstract Animals

    ERIC Educational Resources Information Center

    Sutley, Jane

    2010-01-01

    Abstraction is, in effect, a simplification and reduction of shapes with an absence of detail designed to comprise the essence of the more naturalistic images being depicted. Without even intending to, young children consistently create interesting, and sometimes beautiful, abstract compositions. A child's creations, moreover, will always seem to…

  1. Is It Really Abstract?

    ERIC Educational Resources Information Center

    Kernan, Christine

    2011-01-01

    For this author, one of the most enjoyable aspects of teaching elementary art is the willingness of students to embrace the different styles of art introduced to them. In this article, she describes a project that allows upper-elementary students to learn about abstract art and the lives of some of the master abstract artists, implement the idea…

  2. Journalism Abstracts. Vol. 15.

    ERIC Educational Resources Information Center

    Popovich, Mark N., Ed.

    This book, the fifteenth volume of an annual publication, contains 373 abstracts of 52 doctoral and 321 master's theses from 50 colleges and universities. The abstracts are arranged alphabetically by author, with the doctoral dissertations appearing first. These cover such topics as advertising, audience analysis, content analysis of news issues…

  3. Leadership Abstracts, 1996.

    ERIC Educational Resources Information Center

    Johnson, Larry, Ed.

    1996-01-01

    The abstracts in this series provide two-page discussions of issues related to leadership, administration, professional development, technology, and education in community colleges. Volume 9 for 1996 includes the following 12 abstracts: (1) "Tech-Prep + School-To-Work: Working Together To Foster Educational Reform," (Roderick F. Beaumont); (2)…

  4. Mathematical Abstraction through Scaffolding

    ERIC Educational Resources Information Center

    Ozmantar, Mehmet Fatih; Roper, Tom

    2004-01-01

    This paper examines the role of scaffolding in the process of abstraction. An activity-theoretic approach to abstraction in context is taken. This examination is carried out with reference to verbal protocols of two 17 year-old students working together on a task connected to sketching the graph of |f|x|)|. Examination of the data suggests that…

  5. Abstract coherent categories.

    PubMed

    Rehder, B; Ross, B H

    2001-09-01

    Many studies have demonstrated the importance of the knowledge that interrelates features in people's mental representation of categories and that makes our conception of categories coherent. This article focuses on abstract coherent categories, coherent categories that are also abstract because they are defined by relations independently of any features. Four experiments demonstrate that abstract coherent categories are learned more easily than control categories with identical features and statistical structure, and also that participants induced an abstract representation of the category by granting category membership to exemplars with completely novel features. The authors argue that the human conceptual system is heavily populated with abstract coherent concepts, including conceptions of social groups, societal institutions, legal, political, and military scenarios, and many superordinate categories, such as classes of natural kinds. PMID:11550753

  6. Abstract Datatypes in PVS

    NASA Technical Reports Server (NTRS)

    Owre, Sam; Shankar, Natarajan

    1997-01-01

    PVS (Prototype Verification System) is a general-purpose environment for developing specifications and proofs. This document deals primarily with the abstract datatype mechanism in PVS which generates theories containing axioms and definitions for a class of recursive datatypes. The concepts underlying the abstract datatype mechanism are illustrated using ordered binary trees as an example. Binary trees are described by a PVS abstract datatype that is parametric in its value type. The type of ordered binary trees is then presented as a subtype of binary trees where the ordering relation is also taken as a parameter. We define the operations of inserting an element into, and searching for an element in an ordered binary tree; the bulk of the report is devoted to PVS proofs of some useful properties of these operations. These proofs illustrate various approaches to proving properties of abstract datatype operations. They also describe the built-in capabilities of the PVS proof checker for simplifying abstract datatype expressions.

  7. Tracing partial melting and subduction-related metasomatism in the Kamchatkan mantle wedge using noble gas compositions

    NASA Astrophysics Data System (ADS)

    Hopp, Jens; Ionov, Dmitri A.

    2011-02-01

    We determined noble gas composition of minerals separated from mantle-derived xenoliths hosted by andesites in the active Avacha volcano, Kamchatka peninsula, Russia in order to better constrain the provenance and nature of fluids involved in partial melting and metasomatism in the mantle wedge. The lithospheric mantle beneath Avacha mainly consists of spinel harzburgites produced by high degrees of melt extraction. Data on coarse olivine separated from seven harzburgite xenoliths constrain fluid regime during flux melting in arc settings. Pyroxenes from two websterite veins cross-cutting the harzburgites characterize post-melting metasomatism by subduction-related melts or fluids. 3He/4He-ratios of 5.2 ± 0.6 to 8.1 ± 0.3 RA obtained on both olivines and pyroxenes overlap the highest values reported for volcanic rocks from Kamchatka and fall into the typical range of continental lithospheric mantle worldwide. This rules out significant contributions of slab-derived radiogenic 4He*. The highest 40Ar/36Ar ratios are 400; Ne and Xe isotope ratios are indistinguishable from those in the air. We consider the slab as the initial source of a major portion of these ‘atmospheric’ gases. Element composition of noble gases in olivine differs markedly from that in vein pyroxene indicating that the composition of the fluid phase involved in partial melting was distinct from that during metasomatism. In particular, the harzburgites and veins define distinct linear trends on plots of 3He/36Ar vs. 40Ar/36Ar and of 132Xe/36Ar vs. 40Ar/36Ar. Estimates of ‘mantle’ 132Xe/36Ar values by extrapolating 40Ar/36Ar to 40 000 yield unrealistically high values of 0.5-0.8 (olivine) and 4-5 (vein pyroxene) ruling out a simple two-component mixing of mantle and atmospheric noble gases. Rather a two-stage mixing process applies: (1) Changes in relative proportions of slab-derived element-fractionated atmospheric gases and ‘mantle’ produce two hybrid mixtures dominated by atmospheric

  8. Quantification of trace fatty acid methyl esters in diesel fuel by using multidimensional gas chromatography with electron and chemical ionization mass spectrometry.

    PubMed

    Webster, R L; Rawson, P M; Evans, D J; Marriott, P J

    2016-07-01

    Measurement of contamination of marine and naval diesel fuels (arising from product mixing or adulteration) with biodiesel or fatty acid methyl esters can be problematic, especially at very low levels. A suitable solution for this task for trace amounts of individual fatty acid methyl esters with resolution and quantification can be achieved by using a multidimensional gas chromatographic approach with electron and chemical ionization mass spectrometric detection. A unique column set comprising a 100 m methyl-siloxane nonpolar first dimension column and high-temperature ionic liquid column in the second dimension enabled identification of individual fatty acid methyl esters at below the lowest concentrations required to be reported in a diesel fuel matrix. Detection limits for individual fatty acid methyl esters compounds ranged from 0.5 to 5.0 mg/L, with excellent linearity up to 5000 mg/L and repeatability of the method from 1.3 to 3.2%. The method was applied to the analysis of diesel fuel samples with suspected biodiesel contamination. Contamination at 568 mg/L was calculated for an unknown sample and interpretation of the results permitted the determination of a likely source of the contamination. PMID:27159197

  9. Trace analysis of impurities in bulk gases by gas chromatography-pulsed discharge helium ionization detection with "heart-cutting" technique.

    PubMed

    Weijun, Yao

    2007-10-12

    A method has been developed for the detection of low-nL/L-level impurities in bulk gases such as H(2), O(2), Ar, N(2), He, methane, ethylene and propylene, respectively. The solution presented here is based upon gas chromatography-pulsed discharge helium ionization detection (GC-PDHID) coupled with three two-position valves, one two-way solenoid valve and four packed columns. During the operation, the moisture and heavy compounds are first back-flushed via a pre-column. Then the trace impurities (except CO(2) which is diverted to a separate analytical column for separation and detection) together with the matrix enter onto a main column, followed by the heart-cut of the impurities onto a longer analytical column for complete separation. Finally the detection is performed by PDHID. This method has been applied to different bulk gases and the applicability of detecting impurities in H(2), Ar, and N(2) are herewith demonstrated. As an example, the resulting detection limit of 100 nL/L and a dynamic range of 100-1000 nL/L have been obtained using an Ar sample containing methane. PMID:17850804

  10. Thermal desorption - comprehensive two-dimensional gas chromatography coupled with tandem mass spectrometry for determination of trace polycyclic aromatic hydrocarbons and their derivatives.

    PubMed

    Fushimi, Akihiro; Hashimoto, Shunji; Ieda, Teruyo; Ochiai, Nobuo; Takazawa, Yoshikatsu; Fujitani, Yuji; Tanabe, Kiyoshi

    2012-08-24

    We developed a highly sensitive method for determination of polycyclic aromatic hydrocarbons (PAHs) and their derivatives (oxygenated, nitrated, and methylated PAHs) in trace particulate samples by using thermal desorption followed by comprehensive two-dimensional gas chromatography coupled with tandem mass spectrometry (TD-GC×GC-MS/MS) with a selected reaction monitoring mode. The sensitivity of TD-GC×GC-MS/MS was greater than that of TD-GC-HRMS and TD-GC×GC-QMS by one or two orders of magnitude. The instrumental detection limits were 0.03-0.3pg (PAHs), 0.04-0.2pg (oxygenated PAHs), 0.03-0.1pg (nitrated PAHs), and 0.01-0.08pg (methylated PAHs). For small amounts (10-20μg) of standard reference materials (SRMs 1649a and 1650b, urban dust and diesel exhaust particles, respectively), the values measured by using TD-GC×GC-MS/MS agreed with the certified or reference values within a factor of two. Major analytes were quantified successfully by TD-GC×GC-MS/MS from diesel exhaust nanoparticles (18-32nm) and accumulation-mode particles (100-180nm) from an 8-L diesel engine with no exhaust after-treatment system. The PAH profiles differed among driving conditions but they did not differ markedly among the particle sizes. PMID:22795936

  11. Trace-level determination of polar flavour compounds in butter by solid-phase extraction and gas chromatography-mass spectrometry.

    PubMed

    Adahchour, M; Vreuls, R J; van der Heijden, A; Brinkman, U A

    1999-06-01

    Volatile compounds are responsible for the aromas of butter. A simple technique for the determination of these components is described which is based on solid-phase extraction (SPE) after melting of the butter and separation of the aqueous phase from the fat. Volatile flavours present in the water fraction are collected by off-line SPE on cartidges packed with a copolymer sorbent. After desorption with 500 microliters of methyl acetate, 1-microliter aliquots are quantified and/or identified by gas chromatography-mass spectrometry. The procedure was tested with respect to recovery, linearity and limit of detection in real-life samples using five polar model analytes. It allows the characterisation of polar flavour compounds in butter prior to and after heat treatment at 170 degrees C. From the five model compounds, vanillin, traces of diacetyl and maltol were found to be present in the butter samples. After heat treatment 500-1000-fold increased concentration of maltol, and substantial amounts of furaneol were detected. PMID:10399332

  12. Development of heart-cutting multidimensional gas chromatography coupled to time of flight mass spectrometry for silicon speciation at trace levels in gasoline samples.

    PubMed

    Chainet, Fabien; Lienemann, Charles-Philippe; Ponthus, Jérémie; Courtiade, Marion; Donard, Olivier François Xavier

    2012-11-16

    To improve the understanding of hydrotreatment (HDT) catalyst poisoning by silicon species, these molecules must be characterized in petroleum products using powerful analytical systems. Heart-cutting gas chromatography coupled to time of flight mass spectrometry (GC-GC/TOFMS) method equipped with a Deans switch (DS) system was developed for the direct characterization of target silicon compounds at trace level (μg kg(-1)) in gasoline samples. This method was performed to identify silicon compounds never characterized before. After the selection of the second dimension column using GC-GC-FID, GC-GC/TOFMS was performed. The calibration curves obtained by the GC-GC/TOFMS method were linear up to 1,000 μg kg(-1). Limits of detection (LOD) were ranging from 5 to 33 μg kg(-1) in spiked gasoline. The method provided sufficient selectivity and sensitivity to characterize known silicon compounds thanks to their specific ions and their retention times. The analysis of a naphtha sample by GC-GC/TOFMS has shown the presence of cyclic siloxanes (D(n)) as major compounds of PDMS thermal degradation with the occurrence of linear siloxanes, especially hexamethyldisiloxane (L(2)), which was never characterized in petroleum products but already known as severe poison for catalyst. PMID:23063792

  13. Spatiotemporal inhomogeneity in atmospheric trace-gas over Fukuoka, an urban area in Japan, observed by ground-based MAX-DOAS

    NASA Astrophysics Data System (ADS)

    Takashima, H.; Kanaya, Y.; Irie, H.

    2015-12-01

    Continuous trace-gas observations have been made using ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) at Fukuoka (33.55N, 130.36E), an urban area in Japan. The maximum of the NOx emissions at Fukuoka is estimated to be at the city center, and the monitoring site is located ~5 km southwest of the city center, outside of the central area. To clarify the inhomogeneity as well as the transport/mixing processes of the polluted air in the urban area, continuous profile measurements have been conducted in two azimuth directions: towards and away from the city center. From NO2 observations, we sometimes observed spatial inhomogeneity associated with vertical/horizontal transport of high concentrations of NO2 from the city center, and horizontal transport of low concentrations from the ocean via a land-sea breeze. On the other hand, we observed spatial inhomogeneity in HONO and HCHO during summer, which was probably due to photochemical production over the city center.

  14. Potential Enhancements to the Cross-track Infrared Sounder (CrIS) Ground Test, Data Downlink and Processing for Climate Monitoring including Trace Gas Retrievals

    NASA Astrophysics Data System (ADS)

    Farrow, S. V.; Christensen, T.; Hagan, D. E.

    2009-12-01

    Together with ATMS, the Cross-track Infrared Sounder (CrIS) sensor is a critical payload for National Polar-orbiting Operational Environmental Satellite System (NPOESS) and will first fly on the NPOESS Preparatory Project (NPP) mission, the risk reduction flight for NPOESS. NPOESS is the next generation weather and climate monitoring system for the Department of Defense and National Oceanic and Atmospheric Administration (NOAA), being developed under contract by Northrop Grumman Aerospace Systems. The paper describes potential changes to the program baseline to make CrIS data useful for climate monitoring, including trace gas retrievals such as CO2. Specifically, these are changes to ground calibration tests, changes to the Sensor Data Record (SDR) algorithm, and changes in the spacecraft interface to downlink all of the spectral channels the sensor produces. These changes are presented to promote discussion in the science community of an alternative to achieving some of the key requirements of NASA's OCO mission, which was to monitor CO2, but was destroyed during launch.

  15. Abstract Interpreters for Free

    NASA Astrophysics Data System (ADS)

    Might, Matthew

    In small-step abstract interpretations, the concrete and abstract semantics bear an uncanny resemblance. In this work, we present an analysis-design methodology that both explains and exploits that resemblance. Specifically, we present a two-step method to convert a small-step concrete semantics into a family of sound, computable abstract interpretations. The first step re-factors the concrete state-space to eliminate recursive structure; this refactoring of the state-space simultaneously determines a store-passing-style transformation on the underlying concrete semantics. The second step uses inference rules to generate an abstract state-space and a Galois connection simultaneously. The Galois connection allows the calculation of the "optimal" abstract interpretation. The two-step process is unambiguous, but nondeterministic: at each step, analysis designers face choices. Some of these choices ultimately influence properties such as flow-, field- and context-sensitivity. Thus, under the method, we can give the emergence of these properties a graph-theoretic characterization. To illustrate the method, we systematically abstract the continuation-passing style lambda calculus to arrive at two distinct families of analyses. The first is the well-known k-CFA family of analyses. The second consists of novel "environment-centric" abstract interpretations, none of which appear in the literature on static analysis of higher-order programs.

  16. Polar Ozone Workshop. Abstracts

    NASA Technical Reports Server (NTRS)

    Aikin, Arthur C.

    1988-01-01

    Results of the proceedings of the Polar Ozone Workshop held in Snowmass, CO, on May 9 to 13, 1988 are given. Topics covered include ozone depletion, ozonometry, polar meteorology, polar stratospheric clouds, remote sensing of trace gases, atmospheric chemistry and dynamical simulations.

  17. IEEE conference record--Abstracts

    SciTech Connect

    Not Available

    1992-01-01

    The following topics were covered in this meeting: basic plasma phenomena and plasma waves; plasma diagnostics; space plasma diagnostics; magnetic fusion; electron, ion and plasma sources; intense electron and ion beams; intense beam microwaves; fast wave M/W devices; microwave plasma interactions; plasma focus; ultrafast Z-pinches; plasma processing; electrical gas discharges; fast opening switches; magnetohydrodynamics; electromagnetic and electrothermal launchers; x-ray lasers; computational plasma science; solid state plasmas and switches; environmental/energy issues in plasma science; vacuum electronics; plasmas for lighting; gaseous electronics; and ball lightning and other spherical plasmas. Separate abstracts were prepared for 278 papers of this conference.

  18. Abstracts of SIG Sessions.

    ERIC Educational Resources Information Center

    Proceedings of the ASIS Annual Meeting, 1997

    1997-01-01

    Presents abstracts of SIG Sessions. Highlights include digital collections; information retrieval methods; public interest/fair use; classification and indexing; electronic publication; funding; globalization; information technology projects; interface design; networking in developing countries; metadata; multilingual databases; networked…

  19. Automatic Abstraction in Planning

    NASA Technical Reports Server (NTRS)

    Christensen, J.

    1991-01-01

    Traditionally, abstraction in planning has been accomplished by either state abstraction or operator abstraction, neither of which has been fully automatic. We present a new method, predicate relaxation, for automatically performing state abstraction. PABLO, a nonlinear hierarchical planner, implements predicate relaxation. Theoretical, as well as empirical results are presented which demonstrate the potential advantages of using predicate relaxation in planning. We also present a new definition of hierarchical operators that allows us to guarantee a limited form of completeness. This new definition is shown to be, in some ways, more flexible than previous definitions of hierarchical operators. Finally, a Classical Truth Criterion is presented that is proven to be sound and complete for a planning formalism that is general enough to include most classical planning formalisms that are based on the STRIPS assumption.

  20. 1971 Annual Conference Abstracts

    ERIC Educational Resources Information Center

    Journal of Engineering Education, 1971

    1971-01-01

    Included are 112 abstracts listed under headings such as: acoustics, continuing engineering studies, educational research and methods, engineering design, libraries, liberal studies, and materials. Other areas include agricultural, electrical, mechanical, mineral, and ocean engineering. (TS)

  1. 2016 ACPA MEETING ABSTRACTS.

    PubMed

    2016-07-01

    The peer-reviewed abstracts presented at the 73rd Annual Meeting of the ACPA are published as submitted by the authors. For financial conflict of interest disclosure, please visit http://meeting.acpa-cpf.org/disclosures.html. PMID:27447885

  2. Abstracts of contributed papers

    SciTech Connect

    Not Available

    1994-08-01

    This volume contains 571 abstracts of contributed papers to be presented during the Twelfth US National Congress of Applied Mechanics. Abstracts are arranged in the order in which they fall in the program -- the main sessions are listed chronologically in the Table of Contents. The Author Index is in alphabetical order and lists each paper number (matching the schedule in the Final Program) with its corresponding page number in the book.

  3. Aerosol particle and trace gas emissions from earthworks, road construction, and asphalt paving in Germany: Emission factors and influence on local air quality

    NASA Astrophysics Data System (ADS)

    Faber, Peter; Drewnick, Frank; Borrmann, Stephan

    2015-12-01

    Aerosol emissions from construction sites have a strong impact on local air quality. The chemical and physical characteristics of particles and trace gases emitted by earthworks (excavation and loading of soil as well as traffic on unpaved roads) and road works (asphalt sawing, smashing, soil compacting, asphalt paving) have therefore been addressed in this study by using a mobile set-up of numerous modern online aerosol and trace gas instruments including a high-resolution aerosol mass spectrometer. Fuel-based emission factors for several variables have been determined, showing that earthwork activities and compacting by use of a plate compactor revealed the highest median emission factors for PM10 (up to 54 g l-1). Construction activities were assigned to contribute about 17% (36 000 t a-1) to total PM10 emissions and 3% (13 500 t a-1) to total traffic-related NOx emissions in Germany. In particular, calculated PM10 emissions by earthworks are about 15 800 t a-1 corresponding to 44% of total PM10 emissions by construction activities in Germany. Mechanical processes such as asphalt sawing (PM1/PM10 = 18 ± 31%), soil compacting by a plate compactor (PM1/PM10 = 5 ± 6%) and earthworks (PM1/PM10 = 2 ± 5%) emit predominantly coarse mineral dust particles. Contrary to that, particle emissions by thermal construction processes (asphalt paving: PM1/PM10 = 62 ± 14%) and by the internal combustion engines of heavy machinery (e.g. road roller PM1/PM10 = 94 ± 9%) are mostly in the submicron range. These particles were mainly composed of organics containing non-polar saturated and unsaturated hydrocarbons (e.g. asphalting: O:C < 0.01, H:C = 2.01). Besides construction activities, mineral dust is also emitted over cleared land by wind-driven resuspension depending on wind speed. PM10 emissions by construction activities often result in local concentrations > 100 μg m-3 and can easily breach the European limit level of PM10. This study also shows that particulate mineral

  4. Metacognition and abstract reasoning.

    PubMed

    Markovits, Henry; Thompson, Valerie A; Brisson, Janie

    2015-05-01

    The nature of people's meta-representations of deductive reasoning is critical to understanding how people control their own reasoning processes. We conducted two studies to examine whether people have a metacognitive representation of abstract validity and whether familiarity alone acts as a separate metacognitive cue. In Study 1, participants were asked to make a series of (1) abstract conditional inferences, (2) concrete conditional inferences with premises having many potential alternative antecedents and thus specifically conducive to the production of responses consistent with conditional logic, or (3) concrete problems with premises having relatively few potential alternative antecedents. Participants gave confidence ratings after each inference. Results show that confidence ratings were positively correlated with logical performance on abstract problems and concrete problems with many potential alternatives, but not with concrete problems with content less conducive to normative responses. Confidence ratings were higher with few alternatives than for abstract content. Study 2 used a generation of contrary-to-fact alternatives task to improve levels of abstract logical performance. The resulting increase in logical performance was mirrored by increases in mean confidence ratings. Results provide evidence for a metacognitive representation based on logical validity, and show that familiarity acts as a separate metacognitive cue. PMID:25416026

  5. Application of gas chromatography-triple quadrupole mass spectrometry in the quantification-confirmation of pesticides and polychlorinated biphenyls in eggs at trace levels.

    PubMed

    Bolaños, P Plaza; Frenich, A Garrido; Vidal, J L Martínez

    2007-10-01

    A new multiresidue method has been developed and validated for the simultaneous analysis of 57 compounds, including organochlorine and organophosphorus pesticide residues (OCPs and OPPs) and polychlorinated biphenyls (PCBs), in eggs at trace levels by gas chromatography coupled to triple quadrupole mass spectrometry (GC-QqQ-MS/MS). Egg samples were extracted by a simple and fast matrix solid phase dispersion (MSPD) procedure using C18 as sorbent, and ethyl acetate and acetonitrile saturated in n-hexane (85:15, v/v) as elution solvent with a simultaneous clean up with Florisil in-line. The QqQ analyzer acquired data in selected reaction monitoring (SRM) mode, permitting both quantification and confirmation in a single injection with a running time reduced up to 17.70 min. Recovery was in the range of 70-110% and 70-106% at 15 and 50 microg/kg, respectively. Precision values expressed as relative standard deviation (RSD) were lower than 20%. Linearity in the range of 10-150 microg/kg provided determination coefficients (R(2)) higher than 0.98 for all compounds. Limits of detection (LODs) for pesticides were < or =2.25 microg/kg and limits of quantification (LOQs) ranged from 0.02 to 7.78 microg/kg. LODs for PCBs were < or =0.41 microg/kg and LOQ were < or =0.71 microg/kg. The method was applied to real samples. Endosulfan sulphate and p,p'-DDE were found in two samples at concentrations below the first calibration level. PMID:17764679

  6. Characterization of a low-pressure chlorine plasma column sustained by propagating surface waves using phase-sensitive microwave interferometry and trace-rare-gas optical emission spectroscopy

    SciTech Connect

    Mattei, S.; Boudreault, O.; Stafford, L.; Khare, R.; Donnelly, V. M.

    2011-06-01

    Phase-sensitive microwave interferometry and trace-rare-gas optical emission spectroscopy were used to measure the line-integrated electron density, n{sub e}, and electron temperature, T{sub e}, in a high-density chlorine plasma sustained in a quartz discharge tube (inner diameter = 6 mm) by an electromagnetic surface wave at 2.45 GHz. For pressures in the 0.1-1 Torr range, n{sub e} decreased nearly linearly along the tube's z-axis down to the critical density for surface wave propagation, where the plasma decayed abruptly. At lower pressures (< 50 mTorr), however, the plasma extended well beyond this critical point, after which n{sub e} decreased quasiexponentially toward the end of the plasma column. The length of this expansion region increased with decreasing pressure, going from {approx}8 cm at 5 mTorr to {approx}1 cm at 50 mTorr. T{sub e} was nearly independent of the axial position in the main plasma region and strongly decreased in the expansion region at lower pressures. The Cl{sub 2} percent dissociation, {tau}{sub D}, obtained from the calibrated Cl{sub 2} (306 nm)-to-Xe (828 nm) emission ratio, displayed behavior similar to that of n{sub e} and T{sub e}. For example, at 5 mTorr, {tau}{sub D} was close to 100% near the wave launcher and {approx}70% at 0.5 cm from the end of the plasma column.

  7. Intercomparison of stratospheric water vapor observed by satellite experiments: Stratospheric Aerosol and Gas Experiment II versus Limb Infrared Monitor of the Stratosphere and Atmospheric Trace Molecule Spectroscopy

    SciTech Connect

    Chiou, E.W.; Larsen, J.C. ); McCormick, M.P.; McMaster, L.R.; Chu, W.P. ); Rind, D. ); Oltmans, S. )

    1993-03-20

    This paper presents a comparison of the stratospheric water vapor measurements made by the satellite-borne sensors the Stratospheric Aerosol and Gas Experiment II (SAGE II), the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS), and the Spacelab 3 Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment. LIMS obtained data for 7 months between November 1978 and May 1979; ATMOS was carried on Shuttle and observed eight profiles from April 30 to May 6, 1985 at approximately 30[degrees]N and 50[degrees]S; and, SAGE II continues to make measurements since its launch in October 1984. For both 30[degrees]N and 50[degrees]S in May, the comparisons between SAGE II and ATMOS show agreement within the estimated combined uncertainty of the two experiments. Several important features identified by LIMS observations have been confirmed by SAGE II: a well-developed hygropause in the lower stratosphere at low- to mid-latitudes, a poleward latitudinal gradient, increasing water vapor mixing ratios with altitude in the tropics, and the transport of dry lower stratospheric water vapor upward and southward in May, and upward and northward in November. A detailed comparative study also indicates that the two previously suggested corrections for LIMS, a correction in tropical lower stratosphere due to a positive temperature bias and the correction above 28 km based on improved emissivities will bring LIMS measurements much closer to those of SAGE II. The only significant difference occurs at high southern latitudes in May below 18 km, where LIMS measurements are 2-3 ppmv greater. It should be noted that LIMS observations are from 16 to 50 km, ATMOS from 14 to 86 km, and SAGE II from mid-troposphere to 40 km. With multiyear coverage, SAGE II observations should be useful for studying tropospheric-stratospheric exchange, for stratospheric transport, and for preparing water vapor climatologies for the stratosphere and the upper troposphere. 32 refs., 14 figs., 2 tabs.

  8. The Amazon Tall Tower Observatory (ATTO) in the remote Amazon Basin: overview of first results from ecosystem ecology, meteorology, trace gas, and aerosol measurements

    NASA Astrophysics Data System (ADS)

    Andreae, M. O.; Acevedo, O. C.; Araùjo, A.; Artaxo, P.; Barbosa, C. G. G.; Barbosa, H. M. J.; Brito, J.; Carbone, S.; Chi, X.; Cintra, B. B. L.; da Silva, N. F.; Dias, N. L.; Dias-Júnior, C. Q.; Ditas, F.; Ditz, R.; Godoi, A. F. L.; Godoi, R. H. M.; Heimann, M.; Hoffmann, T.; Kesselmeier, J.; Könemann, T.; Krüger, M. L.; Lavric, J. V.; Manzi, A. O.; Moran-Zuloaga, D.; Nölscher, A. C.; Santos Nogueira, D.; Piedade, M. T. F.; Pöhlker, C.; Pöschl, U.; Rizzo, L. V.; Ro, C.-U.; Ruckteschler, N.; Sá, L. D. A.; Sá, M. D. O.; Sales, C. B.; Santos, R. M. N. D.; Saturno, J.; Schöngart, J.; Sörgel, M.; de Souza, C. M.; de Souza, R. A. F.; Su, H.; Targhetta, N.; Tóta, J.; Trebs, I.; Trumbore, S.; van Eijck, A.; Walter, D.; Wang, Z.; Weber, B.; Williams, J.; Winderlich, J.; Wittmann, F.; Wolff, S.; Yáñez-Serrano, A. M.

    2015-04-01

    The Amazon Basin plays key roles in the carbon and water cycles, climate change, atmospheric chemistry, and biodiversity. It already has been changed significantly by human activities, and more pervasive change is expected to occur in the next decades. It is therefore essential to establish long-term measurement sites that provide a baseline record of present-day climatic, biogeochemical, and atmospheric conditions and that will be operated over coming decades to monitor change in the Amazon region as human perturbations increase in the future. The Amazon Tall Tower Observatory (ATTO) has been set up in a pristine rain forest region in the central Amazon Basin, about 150 km northeast of the city of Manaus. An ecological survey including a biodiversity assessment has been conducted in the forest region surrounding the site. Two 80 m towers have been operated at the site since 2012, and a 325 m tower is nearing completion in mid-2015. Measurements of micrometeorological and atmospheric chemical variables were initiated in 2012, and their range has continued to broaden over the last few years. The meteorological and micrometeorological measurements include temperature and wind profiles, precipitation, water and energy fluxes, turbulence components, soil temperature profiles and soil heat fluxes, radiation fluxes, and visibility. A tree has been instrumented to measure stem profiles of temperature, light intensity, and water content in cryptogamic covers. The trace gas measurements comprise continuous monitoring of carbon dioxide, carbon monoxide, methane, and ozone at 5 to 8 different heights, complemented by a variety of additional species measured during intensive campaigns (e.g., VOC, NO, NO2, and OH reactivity). Aerosol optical, microphysical, and chemical measurements are made above the canopy as well as in the canopy space. They include light scattering and absorpt