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Sample records for abstract trace gas

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Trace gas emissions from the marine biosphere.

    PubMed

    Liss, Peter S

    2007-07-15

    A wide variety of trace gases (e.g. dimethyl sulphide, organohalogens, ammonia, non-methane and oxygenated hydrocarbons, volatile oxygenated organics and nitrous oxide) are formed in marine waters by biological and photochemical processes. This leads in many, but not all, cases to supersaturation of the water relative to marine air concentrations and a net flux of trace gas to the atmosphere. Since the gases are often in their reduced forms in the water, once in the atmosphere they are subject to oxidation by photolysis or radical attack to form chemically reactive species that can affect the oxidizing capacity of the air. They can also lead to the formation of new particles or the growth of existing ones that can then contribute to both direct and indirect (via the formation of cloud condensation nuclei) aerosol effects on climate. These cycles are discussed with respect to their impacts on the chemistry of the atmosphere, climate and human health. This whole topic was the subject of an extensive review (Nightingale & Liss 2003 In Treatise in geochemistry (eds H. D. Holland & K. K. Turekian), pp. 49-81) and what will be attempted here is a brief update of the earlier paper. There is no attempt to be comprehensive either in terms of gases covered or to give a complete review of all the recent literature. It is a personal view of recent advances both from my own research group as well as significant work from others. Questions raised at the meeting 'Trace gas biogeochemistry and global change' are dealt with at appropriate places in the text (rather than at the end of the piece). Discussion of each of the gases or group of gases is given in the following separate sections.

  7. 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)

  8. 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.

  9. 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

  10. Trace gas measurements in Phoenix, Arizona (1998)

    SciTech Connect

    Nunnermacker, L.J.

    2000-01-09

    The DOE Atmospheric Chemistry Program, and the Arizona Department of Environmentel Quality (DEQ) conducted a field program in the Phoenix Metropolitan area in the late spring of 1998. The experiment was composed of a linked set of aircraft and surface measurements designed to characterize the chemical and meteorological processes leading to ozone episodes. The existing network of Arizona DEQ sites in Phoenix was utilized to document ground level concentrations of ozone and its precursors. West of the downtown area, a site (Usery Pass) was set up for the detailed characterization of the mature Phoenix urban plume. Detailed measurements in the source region were made at several sites in downtown Phoenix. The DOE G-1 aircraft, equipped wih a comprehensive array of instruments to characterize atmospheric trace gas and aerosol composition, flew over the region at various times during the day. All times in the following discussion are local standard time (LST). Morning flights were typically made between 08:00 and 12:00 upwind, to measure background concentrations, and over the Phoenix source region, to characterize the sources of ozone precursors. Afternoon flights over the Phoenix source region and downwind between 15:00 and 18:00 were made to examine the chemical properties and physical distribution of the photochemically aged urban plume. The aircraft flights typically included an atmospheric sounding to circa 3 km upwind and over Phoenix in the morning, and downwind in the afternoon. A total of 22 flights were made on 14 different days during the one month program. The motivation for conducting the program was to examine ozone formation rates and efficiencies in an environment where the pollutant mix is dominated by vehicle emissions, where the contribution of biogenic hydocarbons to ozone formation is thought to be low, and where processing conditions are different than they are in the Eastern US. The latter includes significant differences in atmospheric humidity

  11. TRACE GAS MEASUREMENTS IN PHOENIX, ARIZONA (1998).

    SciTech Connect

    NUNNERMACKER,L.J.

    2000-01-09

    The DOE Atmospheric Chemistry Program, and the Arizona Department of Environmental Quality (DEQ) conducted a field program in the Phoenix Metropolitan area in the late spring of 1998. The experiment was composed of a linked set of aircraft and surface measurements designed to characterize the chemical and meteorological processes leading to ozone episodes. The existing network of Arizona DEQ sites in Phoenix was utilized to document ground level concentrations of ozone and its precursors. West of the downtown area, a site (Usery Pass) was set up for the detailed characterization of the mature Phoenix urban plume. Detailed measurements in the source region were made at several sites in downtown Phoenix. The DOE G-1 aircraft, equipped with a comprehensive array of instruments to characterize atmospheric trace gas and aerosol composition, flew over the region at various times during the day. All times in the following discussion are local standard time (LST). Morning flights were typically made between 08:00 and 12:00 upwind, to measure background concentrations, and over the Phoenix source region, to characterize the sources of ozone precursors. Afternoon flights over the Phoenix source region and downwind between 15:00 and 18:00 were made to examine the chemical properties and physical distribution of the photochemically aged urban plume. The aircraft flights typically included an atmospheric sounding to circa 3 km upwind and over Phoenix in the morning, and downwind in the afternoon. A total of 22 flights were made on 14 different days during the one month program. The motivation for conducting the program was to examine ozone formation rates and efficiencies in an environment where the pollutant mix is dominated by vehicle emissions, where the contribution of biogenic hydrocarbons to ozone formation is thought to be low, and where processing conditions are different than they are in the Eastern US. The latter includes significant differences in atmospheric

  12. 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.

  13. 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.

  14. 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...

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. [Remote sensing of atmospheric trace gas by airborne passive FTIR].

    PubMed

    Gao, Min-quang; Liu, Wen-qing; Zhang, Tian-shu; Liu, Jian-guo; Lu, Yi-huai; Wang, Ya-ping; Xu, Liang; Zhu, Jun; Chen, Jun

    2006-12-01

    The present article describes the details of aviatic measurement for remote sensing trace gases in atmosphere under various surface backgrounds with airborne passive FTIR. The passive down viewing and remote sensing technique used in the experiment is discussed. The method of acquiring atmospheric trace gases infrared characteristic spectra in complicated background and the algorithm of concentration retrieval are discussed. The concentrations of CO and N2O of boundary-layer atmosphere in experimental region below 1000 m are analyzed quantitatively. This measurement technique and the data analysis method, which does not require a previously measured background spectrum, allow fast and mobile remote detection and identification of atmosphere trace gas in large area, and also can be used for urgent monitoring of pollution accidental breakout.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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

  13. The NOMAD Spectrometer Suite on ExoMars Trace Gas Orbiter

    NASA Astrophysics Data System (ADS)

    Thomas, I. R.; Vandaele, A. C.; Daerden, F.; Drummond, R.; Neefs, E.; Patel, M. R.; López-Moreno, J.-J.; Rodriguez Gomez, J.; Bellucci, G.; NOMAD Team

    2014-07-01

    NOMAD, due to launch in 2016 onboard ExoMars Trace Gas Orbiter, consists of one ultraviolet/visible and two infrared spectrometers. Through solar occultation, limb and nadir observations, it will measure a wide range of trace atmospheric gases.

  14. Reports published by the Gas Research Institute in the area of gas appliances: Bibliography and abstracts update through mid-1990

    SciTech Connect

    Murphy, M.J.; Locklin, D.W.; Johnson, O.D.; Brown, V.J.

    1990-11-08

    The updated bibliography contains citations of reports published by the Gas Research Institute pertaining to residential and commercial gas appliances and space conditioning equipment. It does not include heat pumps or cogeneration. The reports are listed in order of GRI number and are indexed by subject, author, and GRI report number. Report citations include abstracts taken from the NTIS database. The updated bibliography was compiled and indexed from the Gas Appliance Technology Center (GATC) InfoBase, an electronic database of evaluated references in the area of gas appliance technology.

  15. Two Decades of in situ Halocarbon Trace Gas Measurements

    NASA Astrophysics Data System (ADS)

    Dutton, G.; Nance, J. D.; Elkins, J. W.; Hall, B.; Thompson, T.

    2006-12-01

    Motivated by the signing of the Montreal Protocol in 1987 and interests in greenhouse gases, the NOAA Halocarbons and other Atmospheric Trace Species (HATS) group (now in the ESRL/GMD laboratory) focused on frequently measuring some of the regulated ozone depleting gases such as chlorofluorocarbons (CFC-11 and CFC-12), methyl chloroform (CH3CCl3), and carbon tetrachloride (CCl4). The original HATS in situ program, the Radiatively Important Trace Species (RITS) program, measured these four gases and nitrous oxide (N2O) using gas chromatographic (GC) techniques. The RITS GCs were deployed at the NOAA baseline observatories and a cooperative research station where they remained in operation for the next 13 years. Throughout the 1990s, the HATS in situ and flask programs documented the steady decline in global growth rates of the major chlorinated solvents and chlorofluorocarbons as a result of the Montreal Protocol. Widespread use of the replacement compounds to the now banned CFCs prompted improvements to the HATS in situ program. The RITS instruments were replaced from 1998-2000 by the four-channel Chromatograph for Atmospheric Trace Species (CATS) GCs. In addition to the gases measured by RITS, the CATS GCs added nine compounds including halon-1211, methyl chloride (CH3Cl) and CFC alternatives such as HFC-142b and HCFC-22. Since the RITS instruments have been taken offline, efforts have been focused on finalizing this important data set. A number of calibration scale changes from and improvements with the data reduction algorithms have facilitated comparing and combining the RITS and CATS data sets. In particular, the RITS calibration gas concentration tables were updated to reflect the most recent calibration scale changes. Ratios of calibration gas concentrations were fitted to ratios of RITS system responses to those gases in order to derive a detector response nonlinearity factor for each compound measured. The residuals of these fits were used to

  16. Quantum chemical studies of trace gas adsorption on ice nanoparticles

    NASA Astrophysics Data System (ADS)

    Schrems, Otto; Ignatov, Stanislav K.; Gadzhiev, Oleg B.; Masunov, Artem E.

    2013-04-01

    We have investigated the interaction of atmospheric trace gases with crystalline water ice particles of nanoscale size by modern quantum chemical methods. Small ice particles which can be formed in different altitudes play an important role in chemistry and physics of the Earth atmosphere. Knowledge about the uptake and incorporation of atmospheric trace gases in ice particles as well as their interactions with water molecules is very important for the understanding of processes at the air/ice interface. The interaction of the atmospheric trace gases with atmospheric ice nanoparticles is also an important issue for the development of modern physicochemical models. Usually, the interactions between trace gases and small particles considered theoretically apply small-size model complexes or the surface models representing only fragments of the ideal surface. Ice particles consisting of 48, 72, 216 and 270 water molecules with a distorted structure of hexagonal water ice Ih were studied using the new SCC-DFTBA method combining well the advantages of the DFT theory and semiempirical methods of quantum chemistry. The largest clusters correspond to the minimal nanoparticle size which are considered to be crystalline as determined experimentally. The clusters up to (H2O)72 were studied at the B3LYP/6-31++G(d,p) and B3LYP/6-311++G(2d,2p) levels. The larger clusters were studied using DFTBA and DFTB+ methods. Several adsorption complexes for the (H2O)270 water ice cluster were optimized at the RI-BLYP/6-31+G(d) theory level to verify the DFTB+ results. Trace gas molecules were coordinated on different sites of the nanoparticles corresponding to different ice Ih crystal planes: (0001), (10-10), (11-20). As atmospheric trace gases we have chosen CO, CO2, HCO*, HCOH*, HCHO, HCOOH and (HCO)2. which are the possible products and intermediates of the UV photolysis of organic molecules such as HCHCHO adsorbed on the ice surface. The structures of the corresponding coordination

  17. 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

  18. A Case Study of Trace Gas Transports at the Tropopause

    NASA Astrophysics Data System (ADS)

    Schaeler, B.; Offermann, D.; Hoffmann, L.; Riese, M.

    The CRISTA experiment provided global measurements of atmospheric trace gases in the stratosphere and upper troposphere during its second mission in August 1997. A new data product was recently developed, yielding water vapor mixing ratios in the upper troposphere and around the tropopause. The high data density of CRISTA enables an efficient assimilation of the water vapor field (by means of the NCAR ROSE CTM). From these data turbulent trace gas fluxes (v'') are derived. The global distribution of the H2 O fluxes is found highly structured at a given pressure level. Zonal means of fluxes indicate transport barriers at the equator and near the tropopause. This is compared to the effective diffusivities Kef f of Haynes and Shuckburgh (2000). General agreement is obtained. There is one important discrepancy, though: The effective diffusivities show a transequatorial "turbulent bridge" at about 12km. This "bridge" is also seen in the CRISTA H2 O data, but at considerably higher altitude. This finding is confirmed by CFC11 and O3 data from CRISTA, and by O3 data from UARS. Implication for the interhemispheric exchange of air pollutants is discussed.

  19. 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.

  20. 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.

  1. 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 ...

  2. 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 ...

  3. 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 ...

  4. 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.

  5. 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.

  6. 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.

  7. Trace gas observations over rural Virginia: Photochemistry and transport

    NASA Astrophysics Data System (ADS)

    Hallock-Waters, Kristen Anne

    Current understanding of photochemistry and acid deposition and the ability to model how species interact in the atmosphere and evaluate emissions inventories are limited by the availability of trace gas measurements. To address the deficiency in air quality data for the U.S. mid-Atlantic region, observations of O3, CO, SO2, NO, total nitrate (HNO3 vapor + particulate nitrate), and NOy (the sum of NO, NO2, HNO3, particulate nitrate, HONO, HO2NO2, N2O5, peroxyacetyl nitrate (PAN), and organic nitrates) were made at Shenandoah National Park-Big Meadows from 1995-1997. Diurnal, seasonal, and interannual variability in the trace gas species and correlations between pairs of pollutants are examined. A comparison of the 1995-1997 CO observations with measurements from the same site during 1988-1989 indicates a 5 ppbv yr-1 decreasing trend in CO concentration over the 9-year period. The observed decrease in CO is consistent with reported emissions reductions. Despite the observed decrease in CO and estimated reductions in anthropogenic hydrocarbon emissions, O3 concentrations indicate no statistically significant trend over 1987-1997, suggesting reductions in anthropogenic emissions of oxides of nitrogen are key to mitigating regional smog formation. From July-December 1997, measurements of NOx (NO + NO 2) were also made. Slopes of O3 versus NOy-NO x decrease from about 5 mol/mol during July through early September to 0.4 mol/mol in mid-September, indicating a rapid seasonal transition from NOx-limited to hydrocarbon-limited O3 production conditions. Total nitrate represented 20-50% of total NOy during most of this study. Deposition of HNO3 and particulate nitrate may contribute substantially to nitrogen loading to the Chesapeake Bay. Based on the average 1995-1997 total nitrate concentration, dry deposition of nitrate to the Chesapeake Bay is estimated at 118 × 109 g N yr-1, about 19% of the estimated total anthropogenic nitrogen loading to the Bay. As a rural and

  8. Trace-gas measurements with an infrared sun photometer

    SciTech Connect

    Allen, J.E. Jr.; Glenar, D.A.; Markham, B.L.

    1994-12-31

    Accurate assessment of the potential impact of greenhouse gases and aerosols on the Earth system can be enhanced by a global monitoring network and can be facilitated by the development of compact, portable optical instruments for field use. The more important of these gases, e.g., methane (CH{sub 4}), carbon dioxide (CO{sub 2}), and nitrous oxide (N{sub 2}O), have strong absorptions at wavelengths between 2 and 5 {micro}m; however, this spectral region is heavily dominated by absorption by water (H{sub 2}O) which is itself an important contributor to radiative transfer at these wavelengths. To achieve the desired reduction in instrument size, it is often necessary to relax wavelength resolution requirements which in turn affects the accuracy and precision of the retrieved column abundances. To address these measurement problems, an infrared sun photometer has been constructed for application to trace-gas detection and analysis techniques are being developed to extract column abundances from the spectrally congested data. The current instrument design is based on a circular variable filter (CVF) with wavelength coverage from 1.2 to 5 {micro}m. Preliminary measurements with this instrument will be presented and electro-optical alternatives to the CVF as the tuning element will be discussed.

  9. 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.

  10. 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}.

  11. 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.

  12. ANALYSIS AND SYNTHESIS OF TRACE GAS FLUXES. (R824993)

    EPA Science Inventory

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

  13. 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

  14. 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

  15. 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.

  16. Effect of Tropospheric Aerosols in Satellite-Based Trace Gas Retrieval

    NASA Technical Reports Server (NTRS)

    Krotkov, Nickolay; Torres, Omar; Yang, Kai; Vassilkov, Alexander

    2011-01-01

    Scattering and absorption by tropospheric aerosol particles have an effect on the airmass factor (AMF), a fundamental quantity for trace gas concentration retrieval by inversion of satellite measurements. The interference effect depends on the aerosols micro-physical and optical properties as well as the relative distribution of the tropospheric trace gas and aerosol load. Quantifying the aerosol impact on trace gas retrieval requires a sensitivity study using radiative transfer calculations. In this presentation we will describe a recently initiated effort to characterize the aerosol-related error in trace gas retrievals when the presence of aerosol particles is not accounted in the inversion procedure. A general description of the project will be presented and preliminary results on aerosol effects on SO2 retrieved concentrations will be discussed.

  17. Stratospheric Trace Gas Distributions from Far Infrared Thermal Emission Spectroscopy.

    NASA Astrophysics Data System (ADS)

    Guo, Jing

    1987-09-01

    An inversion algorithm has been developed to retrieve stratospheric trace gas distributions from high resolution far infrared limb thermal emission spectral data. The algorithm follows an onion peel approach and employs a non-linear least-square-fit spectral analysis technique. The infrared radiative transfer model used to compute the spectrum is based on full line-by-line and layer-by-layer calculations and includes curvature and refraction effects. Finite instrument field of view effects have been studied. An inversion algorithm has also been developed to correct observation angles. The spectral measurements were made in the Balloon Intercomparison Campaign (BIC), October, 1982, using a Fourier transform spectrometer. The observed spectra have an unapodized spectral resolution of 0.0033 cm ^{-1}, and cover the spectral region between 20-100 cm^{-1}. Spectral data for selected limb sequences have been calibrated. The instrument line shape function has been empirically determined. The observation angles of the spectra have been corrected from spectral lines of O_2 in the 23 -84 cm^{-1} region to have an accuracy within 4 arc minutes. The vertical profiles of O_3, H_2O, HDO, HCN, ^ {16}O^{16}O ^{18}O, and ^ {16}O^{18}O ^{16}O in the stratosphere have been retrieved with an altitude resolution of about 4-5 km in the 20-37 km range. The results are compared with available measurements in literature. The vertical profiles of O_3, H_2 O, and HDO are retrieved from spectral lines in the 20-100 cm^{-1} region. The variation of the D/H ratio of water vapor is derived. The vertical profile of HCN is retrieved from spectral lines in the 32-56 cm^{-1} region. The volume mixing ratio of HCN is found to be 139 pptv at 20 km, 127 pptv at 25 km, and increasing to 172 pptv at 37 km. The vertical profiles of stratospheric ^ {16}O^{16}O ^{18}O and ^ {16}O^{18}O ^{16}O are retrieved from spectral lines in the 39-76 cm^{-1 } region. The ratio of total heavy isotopic ozone ^{50}O_3 to

  18. 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.

  19. 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...

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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...

  6. 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

  7. 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.

  8. 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. ...

  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. Noble Gas Signatures in Athabasca Glacier - Tracing Glacial Meltwater Sources

    NASA Astrophysics Data System (ADS)

    Niu, Y.; Hall, C. M.; Castro, M. C.; Aciego, S.; Arendt, C. A.

    2015-12-01

    We present a noble gas study in glacial meltwater (GMW) from the Athabasca Glacier (AG) in the Columbia Icefield, Canada. It constrains the relative contributions of GMW sources, water residence times, and spatial locations where the GMW originates in the alpine glacier. This is possible due to the conservative nature of noble gases and temperature dependency of their concentrations in water in equilibrium with the atmosphere (ASW) which allows for estimation of the altitude at which GMW originated. In addition, crustal He accumulates in water over time, allowing for estimation of water residence times. Water samples were collected in the morning on selected dates in May and July 2011 at two locations about 200 m apart near the terminus area at altitudes between 2000 m and 2100 m. Eight samples were collected in six different days. Results show that the major source of subglacial meltwater is ASW rather than old, compressed glacial ice, which has a distinct noble gas signature not seen in our samples. Given that, GMW samples from the AG do deviate to a certain extent from the ASW values corresponding to measured water temperature and altitude at collection points. Two patterns are observed in the concentrations of the AG samples. The first one presents a relative Ar enrichment with respect to Ne, Kr, and Xe, first observed in high-altitude springs in the Galápagos Islands (Warrier et al., 2012). The second one displays a mass-dependent pattern, first observed in Michigan rainwater (Warrier et al., 2013). A preliminary Xe analysis indicates equilibration altitudes between 2500 m and 3400 m, values compatible with local topography. Samples present He excess of 4% to 91%, and suggest an average residence time of ~400 yrs. References:Warrier, R. B., Castro, M. C., and Hall, C. M. (2012), Recharge and source-water insights from the Galapagos Islands using noble gases and stable isotopes, Water Resour. Res., 48, W03508, doi:10.1029/2011WR010954. Warrier, R. B., Castro

  11. Natural gas: Marine transportation. (Latest citations from Oceanic Abstracts). Published Search

    SciTech Connect

    Not Available

    1994-04-01

    The bibliography contains citations concerning the design, construction, and operation of ships for the transport of liquified natural gas. Topics include safety devices, materials handling equipment for loading and unloading liquified natural gas, new hull and vessel designs, gas turbine propulsion systems, cargo tank designs and requirements, and liguid load dynamics. (Contains 250 citations and includes a subject term index and title list.)

  12. Natural gas: Marine transportation. (Latest citations from Oceanic Abstracts). Published Search

    SciTech Connect

    Not Available

    1992-11-01

    The bibliography contains citations concerning the design, construction, and operation of ships for the transport of liquified natural gas. Topics include safety devices, materials handling equipment for loading and unloading liquified natural gas, new hull and vessel designs, gas turbine propulsion systems, cargo tank designs and requirements, and liguid load dynamics. (Contains 250 citations and includes a subject term index and title list.)

  13. 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.

  14. CO-laser-based photoacoustic trace-gas detection: applications in postharvest physiology

    NASA Astrophysics Data System (ADS)

    Oomens, J.; Zuckermann, H.; Persijn, S.; Parker, D. H.; Harren, F. J. M.

    1998-10-01

    A sensitive CO-laser-based photoacoustic trace-gas detector has been applied to study physiological processes in biological samples. A continuous flow-through system at atmospheric pressure leads the released trace gases from the sample to the photoacoustic resonator cells at flow rates where these processes can be studied with high time resolution. We focus here on transient effects that were found during fermentation of red bell peppers and apples, yielding in particular ethanol and acetaldehyde. Results are discussed also in the light of simultaneous O2 measurements using polarographic oxygen sensors.

  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

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

    2014-07-25

    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.

  18. Adsorption equilibrium and kinetics for multiple trace impurities in various gas streams on activated carbon

    SciTech Connect

    Golden, T.C.; Kumar, R. )

    1993-01-01

    Equilibrium and kinetic adsorption data for seven trace impurities (propylene, Freon-12 (CF[sub 2]Cl[sub 2]), n-butane, methylene chloride, acetone, n-hexane, toluene, and Freon-22 (CHFCl[sub 2])) from various carrier gases (helium, nitrogen, methane, carbon dioxide, and a mixture of methane and carbon dioxide) are provided. Activated carbon at several temperatures and pressures is used as the adsorbent. Two empirical characteristic curves, one relating equilibrium isotherms of trace impurities with their physical properties and the other relating mass-transfer coefficients with equilibrium properties, are generated. These can be used to predict equilibrium capacities and mass-transfer zone lengths for multiple trace impurities from a carrier gas and design a thermal swing adsorption clean-up system.

  19. Quantitative detection of trace explosive vapors by programmed temperature desorption gas chromatography-electron capture detector.

    PubMed

    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

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

    SciTech Connect

    Wu, M.; Shi, J.; Hickey, 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. This work was designed to test how effectively hydrogen and CO could be to monitor high-rate anaerobic systems that has signficant 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.

  1. 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

  2. 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.

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

    PubMed

    Nikodem, Michal; Wysocki, Gerard

    2012-11-28

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

  4. 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.

  5. 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.

  6. Trace gas and particulate emissions from biomass burning in temperate ecosystems

    NASA Technical Reports Server (NTRS)

    Cofer, Wesley R., III; Levine, Joel S.; Winstead, Edward L.; Stocks, Brian J.

    1991-01-01

    Emissions measured from fires in graminoid wetlands, Mediterranean chaparrals, and boreal forests, suggest that such ecosystemic parameters as fuel size influence combustion emissions in ways that are broadly predictable. The degree of predictability is most noticeable when wetland fire-related results are compared with boreal forest emissions; the inorganic fraction of the particulate emissions is close in composition irrespective of the ecosystem. It is found that both aerosol and trace gas emissions are influenced by the phase of combustion.

  7. Study on the determination of trace methyl mercury in seawater by gas chromatography

    NASA Astrophysics Data System (ADS)

    Wang, Zhongzhu; Cui, Xianzhou

    1990-03-01

    Sample seawater containing trace methyl mercury was acidified and adsorbed on hydrosulfo-cotton, washed with hydrochloric acid, extracted by benzene and dried, and then determined by a gas chromatograph with electron capture detector. This method, which can detect a minimum concentration of 0.1×10-10%, can be used to monitor the 10-10% content of methyl mercury in seawater.

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

    NASA Astrophysics Data System (ADS)

    Phillips, Mark C.; Taubman, Matthew S.

    2013-05-01

    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 acetone 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. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Better Understanding Transport Related Differences Between CCMs and Trace Gas Measurements With an Idealized Stratospheric Model

    NASA Astrophysics Data System (ADS)

    Ray, E. A.; Moore, F. L.; Rosenlof, K. H.; Plummer, D. A.; Kolonjari, F.; Walker, K. A.

    2015-12-01

    We use a modified version of the tropical leaky pipe (TLP) model of the stratosphere to explore how well an idealized model can (1) reproduce global chemistry-climate model (CCM) output and (2) constrain transport characteristics necessary to replicate measurements of long-lived trace gases. The version of the TLP model we use includes the simulation of long-lived trace gases, such as SF6 and CO2, as well as photochemically active trace gases such as CFC-11, CFC-12 and N2O. The TLP model was found to accurately replicate trace gas output from the Canadian Middle Atmosphere Model (CMAM) for time-averaged profiles in the tropics and each extratropical region. With confidence that the TLP model could represent the basic transport features in CMAM we then used the TLP model to interpret differences between ACE satellite and balloon measurements and CMAM output. The TLP model is shown to uniquely determine mean circulation and recirculation (mixing between the extratropics and tropics) changes necessary for CMAM to more accurately simulate the measurements. This guidance on transport changes is novel, and cannot readily be obtained from direct comparison of CCM output with measurements. The TLP model can thus be used as a bridge between measurements and CCMs to allow more targeted modification of the CCMs than would otherwise be possible.

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. [Research on detecting trace formaldehyde gas by the multi-wavelengths characteristics method].

    PubMed

    Li, Yang-jun; Wang, Gao

    2011-12-01

    In order to overcome the slow speed of detecting trace formaldehyde in the sample gas, material consumption by chemical reaction, and the limitations of the sampling area in the detection of trace formaldehyde, a multi-wavelength characteristics method for getting the exact concentration of formaldehyde quickly was designed. According to the spectrum characteristics of formaldehyde and the main interfering gases the system chose multiple wavelengths with the minimum degree of coherence (the number of characteristic wavelengths were selected to be 3, 4 and 5), in conjunction with the corresponding groups of narrow-band filters. With the infrared light of the light source through the chamber windows and narrow-band filters, the infrared light was collected by the PCI-2TE-13 infrared detectors, and the concentration of formaldehyde in the sample gas was calculated by the characteristics spectrum absorption algorithm. In the experiments, the system analyzed and calculated the concentration of formaldehyde in four gas samples collected in the newly renovated house, building materials market, supermarkets and outdoor parks. Experimental results of the system and test results of ARCSpectro-AMIR infrared spectrometer were compared, the results show that test data above 10 mg x m(-3) were close to true value by the multi-wavelengths characteristics method, and the average error is less than 5%. So the system meets the requirements of practical applications, and it has the advantages of real-time detection, not poisoning so on.

  4. Seasonal Trace Gas Dynamics on Minerotrophic Fen Peatlands in NE-Germany

    NASA Astrophysics Data System (ADS)

    Giebels, Michael; Beyer, Madlen; Augustin, Jürgen; Minke, Merten; Juszczak, Radoszlav; Serba, Tomasz

    2010-05-01

    In Germany more than 99 % of fens have lost their carbon and nutrient sink function due to heavy drainage and agricultural land use especially during the last decades and thus resulted in compression and heavy peat loss (CHARMAN 2002; JOOSTEN & CLARKE 2002; SUCCOW & JOOSTEN 2001; AUGUSTIN et al. 1996; KUNTZE 1993). Therefore fen peatlands play an important part (4-5 %) in the national anthropogenic trace gas budget. But only a small part of drained and agricultural used fens in NE Germany can be restored. Knowledge of the influence of land use to trace gas exchange is important for mitigation of the climate impact of the anthropogenic peatland use. We study carbon exchanges of several fen peatland use areas between soil and atmosphere at different sites in NE-Germany. Our research covers peatlands of supposed strongly climate forcing land use (cornfield and intensive pasture) and of probably less forcing, alternative types (meadow and extensive pasture) as well as rewetted (formerly drained) areas and near-natural sites like a low-degraded fen and a wetted alder woodland. We measured trace gas fluxes with manual and automatic chambers in periodic routines since spring 2007. The used chamber technique bases on DROESLER (2005). In total we now do research at 22 sites situated in 5 different locations covering agricultural, varying states of rewetted and near-natural treatments. We present results of at least 2 years of measurements and show significant differences in their annual trace gas balances depending on the genesis of the observed sites and the seasonal dynamics. Crosswise comparison of different site treatments combined with the seasonal environmental observations give good hints for the identification of main flux driving parameters. That is that a reduced intensity in land use as a supposed mitigating treatment did not show the expected effect, though a normal meadow treatment surprisingly resulted in the lowest balances in both years. For implementing a

  5. Trace gas evolution in the lowermost stratosphere from Aura Microwave Limb Sounder measurements

    NASA Astrophysics Data System (ADS)

    Santee, M. L.; Manney, G. L.; Livesey, N. J.; Froidevaux, L.; Schwartz, M. J.; Read, W. G.

    2011-09-01

    Daily global measurements from NASA's Aura Microwave Limb Sounder (MLS) allow comprehensive investigation of interhemispheric and interannual variations in chemical and transport processes throughout the lowermost stratosphere (LMS). We analyze nearly seven years of MLS O3, HNO3, HCl and ClO measurements along with meteorological analyses to place chemical processing in and dispersal of processed air from the winter polar lowermost vortex and subvortex in a global context. The MLS data, the first simultaneous observations of HCl and ClO covering much of the LMS, reveal that chlorine activation is widespread in the Antarctic subvortex and can occur to a significant degree in the Arctic subvortex. Unusually low temperatures and strong, prolonged chlorine activation in the lowermost vortex and subvortex promoted large ozone losses there in the 2006 (and 2008) Antarctic and 2004/2005 Arctic winters, consistent with reported record low column ozone. Processed air dispersing from the decaying vortex in spring induces rapid changes in extravortex trace gas abundances. After vortex breakdown, the subtropical jet/tropopause becomes the major transport barrier in the LMS. Quasi-isentropic transport of tropical tropospheric air into the LMS, associated with the summer monsoon circulations, leads to decreases in extratropical O3, HNO3, and HCl in both hemispheres. Strong mixing in the summertime LMS homogenizes extratropical trace gas fields. MLS measurements in the tropics show signatures of monsoon-related cross-equatorial stratosphere-to-troposphere transport. Observed seasonal and interannual variations in trace gas abundances in the LMS are consistent with variations in the strength of transport barriers diagnosed from meteorological analyses.

  6. 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

  7. 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

  8. 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

  9. 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.

  10. Microsecond fiber laser pumped, single-frequency optical parametric oscillator for trace gas detection.

    PubMed

    Barria, Jessica Barrientos; Roux, Sophie; Dherbecourt, Jean-Baptiste; Raybaut, Myriam; Melkonian, Jean-Michel; Godard, Antoine; Lefebvre, Michel

    2013-07-01

    We report on the first microsecond doubly resonant optical parametric oscillator (OPO). It is based on a nested cavity OPO architecture allowing single longitudinal mode operation and low oscillation threshold (few microjoule). The combination with a master oscillator-power amplifier fiber pump laser provides a versatile optical source widely tunable in the 3.3-3.5 μm range with an adjustable pulse repetition rate (from 40 to 100 kHz), high duty cycle (~10(-2)) and mean power (up to 25 mW in the idler beam). The potential for trace gas sensing applications is demonstrated through photoacoustic detection of atmospheric methane. PMID:23811865

  11. Sensitive in situ trace-gas detection by photothermal deflection spectroscopy

    SciTech Connect

    Fournier, D.; Boccara, A. C.; Amer, Nabil M.; Gerlach, Robert

    1980-03-01

    We present a sensitive (5ppb for ethylene, 10-7 cm-1) and simple photothermal scheme for the detection of trace gases and measuring weak absorption in gas-phase samples. We also demonstrate the feasibility of this scheme for performing i n s i t u measurements in the absence of sample cells or containers, thus eliminating the drawbacks of sampling and sampling techniques. Finally, factors limiting our detectivity are discussed, and a comparison to the thermal lens effect is made.

  12. 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.

  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. 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.

  15. The NOMAD Spectrometer Suite on ExoMars Trace Gas Orbiter: Calibration Results

    NASA Astrophysics Data System (ADS)

    Thomas, I. R.; Vandaele, A. C.; López-Moreno, J. J.; Patel, M. R.; Bellucci, G.; Drummond, R.; Neefs, E.; Rodriguez-Gómez, J.; Depiesse, C.; Mahieux, A.; Robert, S.; Daerden, F.

    2015-10-01

    NOMAD (Nadir and Occultation for MArs Discoveryis a suite of three high- resolution spectrometers on-board the ExoMars Trace Gas Orbiter. Observing in the ranges 200- 650nm and 2.2-4.3μm, the instrument will be able to detect and map a wide variety of Martian gases in unprecedented detail. The instrument was calibrated during March and April 2015; this presentation will describe the results of the tests performed and the expected performance when the instrument begins observing the planet in late 2017.

  16. [Determination of trace Hg element in gas by CVAAS with single optical path].

    PubMed

    Wang, Shuai; Wang, Peng; Wang, Xi-He; Gao, Ji-Hui; Zhang, Zhi-Guo; Wu, Shao-Hua

    2009-08-01

    Since the anthropogenic emissions of mercury into environment were mostly entering the atmosphere through flue gas, continuous monitoring of mercury in the flue gas was significant for mercury emission control. A bench scale test rig was set up for the measurement of mercury through both wet chemical method and CVAAS (cold vapor atomic absorption spectrometry) with single optical path. The concentration of Hg in absorbent solution was determined by Hydra AA mercury analyzer. The concentration of Hg in gas was calculated in terms of wet chemical testing results, which showed a stable rate of permeation device. Hg atom absorption signal intensity was detected and analyzed in comparison with the test results of wet chemical methods according to Beer-Lambert law. Experimental data well agreed with the theory analysis, which indicated that the single optical path was suitable for the determination of trace Hg element in pure gas. Further research work should aim at the improvement of system adaptability and anti-jamming ability. To reduce the intensity fluctuation of mercury lamp, another spectral line could be detected simultaneously. Interference from surroundings, e.g. dust in gas or spot on the quartz surface, could be eliminated by optoelectronic coupling. PMID:19839353

  17. SEASONAL CHANGES IN TITAN'S POLAR TRACE GAS ABUNDANCE OBSERVED BY CASSINI

    SciTech Connect

    Teanby, N. A.; Irwin, P. G. J.; De Kok, R.; Nixon, C. A.

    2010-11-20

    We use a six-year data set (2004-2010) of mid-infrared spectra measured by Cassini's Composite InfraRed Spectrometer to search for seasonal variations in Titan's atmospheric temperature and composition. During most of Cassini's mission Titan's northern hemisphere has been in winter, with an intense stratospheric polar vortex highly enriched in trace gases, and a single south-to-north circulation cell. Following northern spring equinox in mid-2009, dramatic changes in atmospheric temperature and composition were expected, but until now the temporal coverage of polar latitudes has been too sparse to discern trends. Here, we show that during equinox and post-equinox periods, abundances of trace gases at both poles have begun to increase. We propose that increases in north polar trace gases are due to a seasonal reduction in gas depletion by horizontal mixing across the vortex boundary. A simultaneous south polar abundance increase suggests that Titan is now entering, or is about to enter, a transitional circulation regime with two branches, rather than the single branch circulation pattern previously observed.

  18. Dual quantum cascade laser trace gas instrument with astigmatic Herriott cell at high pass number.

    PubMed

    McManus, J Barry; Zahniser, Mark S; Nelson, David D

    2011-02-01

    We have developed and demonstrated a high-sensitivity trace gas instrument employing two mid-infrared quantum cascade lasers and an astigmatic Herriott sample cell with up to a 240 m path length. Several aspects of astigmatic Herriott cell optics have been addressed to enable operation at a high pass number (up to 554), including aberrations and pattern selection to minimize interference fringes. The new instrument design, based on the 200 m cell, can measure various atmospheric trace gases, depending on the installed lasers, with multiple trace gases measured simultaneously. Demonstrated concentration noise levels (1 s average) are 40 parts per trillion [(ppt) 10(-12)] for formaldehyde, 10 ppt for carbonyl sulfide, 110 ppt for hydrogen peroxide (H2O2), and 180 ppt for nitrous acid (HONO). High-precision measurements of nitrous oxide and methane have been recorded at the same time as high-sensitivity measurements of HONO and H2O2.

  19. 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.

  20. 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.

  1. 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.

  2. Development of an In-Situ Data Logging System for Multiple Trace Gas Analyzers

    SciTech Connect

    Mioduszewski, John R.; Yu, Xiao-Ying

    2008-09-01

    A field deployable in-situ data logging system was developed at Pacific Northwest National Laboratory for trace gases including carbon monoxide (CO), ozone (O3), sulfur dioxide (SO2), and nitrogen oxides including nitric oxide, nitrogen dioxide, and odd nitrogens (NO/NO2/NOx). On-line data acquisition and calibration are essential to analysis of observables and data integrity. As such, a program was written to control the communication between the data logger and each analyzer in Logger Net, a program used to communicate with the data logger. Analog outputs were collected by a CR-23X Campbell data logger between July 2, 2007 and August 7, 2007 in Richland, Washington, with data being averaged every minute. A dynamic calibrator was used to calibrate the instruments using a gas standard with NIST-certified concentration. The National Oceanic and Atmospheric Administration’s HYSPLIT model was used to create a backward and forward trajectory of air during an episode of peak O3 to determine pollutant sources and sinks. Data collected through the duration of the sampling period revealed several observations. Concentrations of all trace gases were low, due in part to the scarcity of pollutant sources in the region. The average SO2 reading was less than 0.05 ppb over the period, whereas mixing ratios of 1-20 ppb are more common in rural-suburban environments. NO, NO2, and NOx averaged 0.3, 12.2, and 12.8 ppb, respectively, while the average CO was 228.5 ppb. Typical O3 in similar environments peaks at 80-150 ppb, but the highest mixing ratio of O3 observed was less than 45 ppb. HYSPLIT offered no apparent source for additional pollutants during the high O3 episode, but increased photochemistry due to high temperatures would explain the increase in O3. Both SO2 and NO readings registered near the detection limit of the instruments, and displayed a trend similar to background noise. The development of the data logging and display system for key trace gas species is an

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. External cavity tunable quantum cascade lasers and their applications to trace gas monitoring.

    PubMed

    Rao, Gottipaty N; Karpf, Andreas

    2011-02-01

    Since the first quantum cascade laser (QCL) was demonstrated approximately 16 years ago, we have witnessed an explosion of interesting developments in QCL technology and QCL-based trace gas sensors. QCLs operate in the mid-IR region (3-24 μm) and can directly access the rotational vibrational bands of most molecular species and, therefore, are ideally suited for trace gas detection with high specificity and sensitivity. These sensors have applications in a wide range of fields, including environmental monitoring, atmospheric chemistry, medical diagnostics, homeland security, detection of explosive compounds, and industrial process control, to name a few. Tunable external cavity (EC)-QCLs in particular offer narrow linewidths, wide ranges of tunability, and stable power outputs, which open up new possibilities for sensor development. These features allow for the simultaneous detection of multiple species and the study of large molecules, free radicals, ions, and reaction kinetics. In this article, we review the current status of EC-QCLs and sensor developments based on them and speculate on possible future developments.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

    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.

  11. 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.

  12. Expected trace gas and aerosol retrieval accuracy of the Geostationary Environment Monitoring Spectrometer

    NASA Astrophysics Data System (ADS)

    Jeong, U.; Kim, J.; Liu, X.; Lee, K. H.; Chance, K.; Song, C. H.

    2015-12-01

    The predicted accuracy of the trace gases and aerosol retrievals from the geostationary environment monitoring spectrometer (GEMS) was investigated. The GEMS is one of the first sensors to monitor NO2, SO2, HCHO, O3, and aerosols onboard geostationary earth orbit (GEO) over Asia. Since the GEMS is not launched yet, the simulated measurements and its precision were used in this study. The random and systematic component of the measurement error was estimated based on the instrument design. The atmospheric profiles were obtained from Model for Ozone And Related chemical Tracers (MOZART) simulations and surface reflectances were obtained from climatology of OMI Lambertian equivalent reflectance. The uncertainties of the GEMS trace gas and aerosol products were estimated based on the OE method using the atmospheric profile and surface reflectance. Most of the estimated uncertainties of NO2, HCHO, stratospheric and total O3 products satisfied the user's requirements with sufficient margin. However, about 26% of the estimated uncertainties of SO2 and about 30% of the estimated uncertainties of tropospheric O3 do not meet the required precision. Particularly the estimated uncertainty of SO2 is high in winter, when the emission is strong in East Asia. Further efforts are necessary in order to improve the retrieval accuracy of SO2 and tropospheric O3 in order to reach the scientific goal of GEMS. Random measurement error of GEMS was important for the NO2, SO2, and HCHO retrieval, while both the random and systematic measurement errors were important for the O3 retrievals. The degree of freedom for signal of tropospheric O3 was 0.8 ± 0.2 and that for stratospheric O3 was 2.9 ± 0.5. The estimated uncertainties of the aerosol retrieval from GEMS measurements were predicted to be lower than the required precision for the SZA range of the trace gas retrievals.

  13. Co-laser photoacoustic spectroscopy of gases and vapours for trace gas analysis

    NASA Astrophysics Data System (ADS)

    Bernegger, S.; Sigrist, M. W.

    This comprehensive study reviews the sensitive and selective detection of trace gases by laser photoacoustic spectroscopy. A computer controlled CO-laser photoacoustic system is presented. The wavelength range between 5.0 and 6.5 μm is of great interest because it coincides with specific absorption bands of various gases and vapours of environmental concern. However, since water-vapour, which is present in most samples, absorbs rather strongly in this wavelength region, its contribution to the total absorption has to be determined with high accuracy. For this purpose, we developed a dual-beam setup with sample- and reference cell. The novel design of these resonant photoacoustic cells is based on a new matrix formalism with distributed acoustic impedances and sources. Our photoacoustic system is calibrated with certified gas mixtures and vapours. In total, the absorption cross sections of 18 gases and vapours have been derived for all CO-laser lines. In addition to the absorption, the relaxation time of vibrationally excited nitric oxide (NO) could be deduced by measuring the phase shift of the photoacoustic signal for a sample of nitrogen containing traces of NO and water-vapour. The main application concerns the detection of multiple components in gas mixtures, particularly in exhaust gases. The high sensitivity achieved permits the detection of trace gases at ppbv concentrations. The problem of interfering absorptions occurring for multicomponent mixtures is studied in detail. We discuss measurements and results on exhausts of various vehicles. The photoacoustic spectra of the exhaust samples are analyzed on the basis of the calibration spectra with the aid of an iterative mathematical procedure. The individual concentrations of 12 of the most important components including nitric oxide, olefines, aromatic hydrocarbons and aldehydes could be derived. In particular, the selective detection of the different isomers of xylene is emphasized.

  14. Tracing gas and magnetic field with dust : lessons from Planck & Herschel

    NASA Astrophysics Data System (ADS)

    Guillet, Vincent

    2015-08-01

    Dust emission is a powerful tool to measure the gas mass. Its polarization also traces the magnetic field structure. With the Planck and Herschel multi-wavelength observations, we are now able to trace the gas and magnetic field over the full sky, with a large spectrum of scales, and up to high optical depths. But a question arises : is dust a reliable tracer ?I will present the statistical properties of the dust polarized emission as observed by Planck HFI over the full sky, and show how this compares to ancillary measures of starlight polarization in the optical, and to MHD simulations. I will distinguish between what is related to the 3D structure of the magnetic field, and what is related to dust (alignement efficiency, grain shape). I will show that the main features of dust polarization observed by Planck can be explained by the magnetic field structure on the line of sight, without any need for a variation of dust alignment efficiency up to an Av of 5 to 10. Dust polarization is therefore a good and reliable tracer of the magnetic field, at least at moderate extinction.I will also discuss the caveats in deriving the gas mass or dust extinction from a fit to the dust spectral energy distribution : 1) the dust far-infrared opacity is not uniform but varies accross the diffuse ISM, and increases inside star-forming regions; 2) Radiation transfer effects must be taken into account at high optical depths. I will present estimates for the systematic errors that are made when these effects are ignored.

  15. 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.

  16. 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

  17. 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

  18. Seasonal Patterns of Denitrification and Trace Gas Emissions in a Northern Hardwood Forest

    NASA Astrophysics Data System (ADS)

    Morse, J. L.; Durán, J.; Groffman, P. M.

    2012-12-01

    To determine denitrification rates and trace gas emissions in a northern hardwood forest (Hubbard Brook Experimental Forest, New Hampshire, USA), we conducted two years of seasonal chamber-based field gas flux measurements (carbon dioxide, methane, and nitrous oxide) and laboratory incubations to measure denitrification rates (nitrous oxide and dinitrogen) and carbon dioxide fluxes. We examined spatial and temporal dynamics of soil-atmosphere gas fluxes as well as relationships between environmental variables (soil moisture, soil temperature, and soil oxygen) and among the different gases. We found that denitrification in surface soils could be an important pathway for nitrogen loss in northern hardwood forest ecosystems, even if soils are rarely anoxic. While dinitrogen fluxes were particularly high during the snowmelt period, we did not see a pulse of nitrous oxide as a result of rapid soil warming as we had expected. Compared to cooler/wetter sites, we found that warmer/drier soils had higher soil respiration in early spring, but had stronger methane uptake and consistently lower nitrous oxide emissions throughout the year.

  19. 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.

  20. Trace gas and particle emissions from fires in large diameter and belowground biomass fuels

    NASA Astrophysics Data System (ADS)

    Bertschi, Isaac; Yokelson, Robert J.; Ward, Darold E.; Babbitt, Ron E.; Susott, Ronald A.; Goode, Jon G.; Hao, Wei Min

    2003-07-01

    We adopt a working definition of residual smoldering combustion (RSC) as biomass combustion that produces emissions that are not lofted by strong fire-induced convection. RSC emissions can be produced for up to several weeks after the passage of a flame front and they are mostly unaffected by flames. Fuels prone to RSC include downed logs, duff, and organic soils. Limited observations in the tropics and the boreal forest suggest that RSC is a globally significant source of emissions to the troposphere. This source was previously uncharacterized. We measured the first emission factors (EF) for RSC in a series of laboratory fires and in a wooded savanna in Zambia, Africa. We report EFRSC for both particles with diameter <2.5 μm (PM2.5) and the major trace gases as measured by open-path Fourier transform infrared (OP-FTIR) spectroscopy. The major trace gases include carbon dioxide, carbon monoxide, methane, ethane, ethene, acetylene, propene, formaldehyde, methanol, acetic acid, formic acid, glycolaldehyde, phenol, furan, ammonia, and hydrogen cyanide. We show that a model used to predict trace gas EF for fires in a wide variety of aboveground fine fuels fails to predict EF for RSC. For many compounds, our EF for RSC-prone fuels from the boreal forest and wooded savanna are very different from the EF for the same compounds measured in fire convection columns above these ecosystems. We couple our newly measured EFRSC with estimates of fuel consumption by RSC to refine emission estimates for fires in the boreal forest and wooded savanna. We find some large changes in estimates of biomass fire emissions with the inclusion of RSC. For instance, the wooded savanna methane EF increases by a factor of 2.5 even when RSC accounts for only 10% of fuel consumption. This shows that many more measurements of fuel consumption and EF for RSC are needed to improve estimates of biomass burning emissions.

  1. 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

  2. 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.

  3. Effects of an Experimental Drought on Trace Gas Emissions From a Humid Tropical Forest

    NASA Astrophysics Data System (ADS)

    Wood, T. E.; Silver, W. L.; Lugo, A. E.

    2008-12-01

    Tropical forest soils are a major source of radiatively-active trace gases, including carbon dioxide (CO2) and nitrous oxide (N2O). Climate change is likely to alter soil moisture availability in tropical forests, and consequently the magnitude and temporal pattern of trace gas emissions from these systems. In this study, we simulate one of the major future climate scenarios for tropical regions, drought, by excluding three months of wet season throughfall in a humid tropical forest in Puerto Rico. We paired five 1.24 m2 translucent roofs with five control plots of equal size in each of three forest types in the Bisley watershed (Palm, Ridge and Slope; 30 plots total). We measured weekly changes in CO2 and bi-weekly changes in N2O and methane (CH4) in response to the manipulation for each of the 30 plots. We additionally measured the physical and chemical changes associated with throughfall exclusion, including soil nutrient availability, pH and soil temperature. CO2 emissions decreased significantly in the exclusion plots in all three of the forest types. The exclusion effect on CO2 efflux was most pronounced in the sloped sites, followed by the Ridge and the Palm forest sites (32%, 30%, 15%, respectively). The strong negative effect of soil drying on CO2 efflux could mean reduced CO2 emissions from humid tropical forest soils during periods of drought.

  4. 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.

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

    PubMed

    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.

  6. [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.

  7. 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.

  8. Field comparison of disjunct and conventional eddy covariance techniques for trace gas flux measurements.

    PubMed

    Rinne, J; Douffet, T; Prigent, Y; Durand, P

    2008-04-01

    A field intercomparison experiment of the disjunct eddy covariance (DEC) and the conventional eddy covariance (EC) techniques was conducted over a grass field. The half-hourly water vapor fluxes measured by the DEC were within the estimated uncertainty from the fluxes measured by the EC. On the average there was a slight overestimation (<10%) of the fluxes measured by the DEC during the day and underestimation during the night as compared to the fluxes measured by the EC. As this bias does not appear in the simulated DEC measurements it is likely to be due to instrumental problems. The insensitivity of the quality of the fluxes measured by the DEC method to the deficiencies in the gas analysis shows the robustness of this new approach for measuring the surface-atmosphere exchange of trace gases.

  9. 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.

  10. 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.

  11. Trace gas variability within the Asian monsoon anticyclone on intraseasonal and interannual timescales

    NASA Astrophysics Data System (ADS)

    Nützel, Matthias; Dameris, Martin; Fierli, Federico; Stiller, Gabriele; Garny, Hella; Jöckel, Patrick

    2016-04-01

    The Asian monsoon and the associated monsoon anticyclone have the potential of substantially influencing the composition of the UTLS (upper troposphere/lower stratosphere) and hence global climate. Here we study the variability of the Asian summer monsoon anticyclone in the UTLS on intraseasonal and interannual timescales using results from long term simulations performed with the CCM EMAC (ECHAM5/MESSy Atmospheric Chemistry). In particular, we focus on specified dynamics simulations (Newtonian relaxation to ERA-Interim data) covering the period 1980-2013, which have been performed within the ESCiMo (Earth System Chemistry integrated Modelling) project (Jöckel et al., GMDD, 2015). Our main focus lies on variability of the anticyclone's strength (in terms of potential vorticity, geopotential and circulation) and variability in trace gas signatures (O3, H2O) within the anticyclone. To support our findings, we also include observations from satellites (MIPAS, MLS). Our work is linked to the EU StratoClim campaign in 2016.

  12. Mobile spectroscopic system for trace gas detection using a tunable mid-IR laser.

    PubMed

    Vaicikauskas, V; Kaucikas, M; Svedas, V; Kuprionis, Z

    2007-02-01

    We describe a mobile spectroscopic system for trace gas analysis based on the open path differential absorption spectrometer and the photoacoustic spectrometer. The first method allows long distance measurements (up to a few kilometers) while the second one provides local in situ detection of pollutants. The open path system is based on the nanosecond (f = 10 Hz, tau = 5 ns) lamp pumped Nd:YAG laser and a tunable two cascade optical parametric generator operating in the 5-12 microm spectral region. This source was mounted into the lidar setup based on the coaxial transmitter/receiver. The photoacoustic system was constructed using the same laser as well as a nonresonant photoacoustic cell. PMID:17578102

  13. 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

  14. Quartz enhanced photoacoustic spectroscopy based trace gas sensors using different quartz tuning forks.

    PubMed

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

    2015-03-27

    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.

  15. 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.

  16. Trace gas and particulate emissions from the 2003 southern California wildfires

    NASA Astrophysics Data System (ADS)

    Mühle, J.; Lueker, T. J.; Su, Y.; Miller, B. R.; Prather, K. A.; Weiss, R. F.

    2007-02-01

    In October 2003, thirteen major wildfires in southern California burned more than 300,000 hectares of mainly chaparral biome. High-precision in situ trace gas and particle measurements of the wildfire plumes in La Jolla, California, showed a high degree of correlation among carbon dioxide (CO2), methane (CH4), nonmethane hydrocarbons, and methyl halide mixing ratios, as well as with particle number concentrations (10-300 nm and 500-2500 nm aerodynamic diameter). Aerosol time-of-flight mass spectrometry of individual aerosol particles (50-2500 nm range) showed that 70-85% had typical biomass burning signatures (levoglucosan coupled with potassium). Only 5-18% of particles in the 50-300 nm range had vehicle signatures. Molar trace gas enhancement ratios (ERs) versus ethane and CO2 were calculated and showed a narrow age distribution, consistent with the short distance from the wildfires. ERs for N2O and CH3CCl3 versus CO2 were determined, but correlations were poor. No significant CH2Cl2 or CHCl3 emissions were detected. CO2 emissions from the nearby Cedar fire were estimated both with a simple Lagrangian atmospheric transport model and a burned area approach and extrapolated to 11 Tg CO2 for the total burned area in southern California. Total CO2, CH4, C2-hydrocarbons, benzene, toluene, methyl chloride, methyl iodide, and PM2.5 emissions were ˜0.2-3.5% of yearly global extratropical forest fire emissions and more than 28% of CH4, C6H6, and PM2.5 2003 San Diego and South Coast Air Basins anthropogenic emissions. Particle distributions and single particle chemistry are discussed. PM2.5 considerably exceeded the EPA short-term exposure limit.

  17. 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

  18. 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).

  19. 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

  20. [Quartz-enhanced photoacoustic spectroscopy trace gas detection system based on the Fabry-Perot demodulation].

    PubMed

    Lin, Cheng; Zhu, Yong; Wei, Wei; Zhang, Jie; Tian, Li; Xu, Zu-Wen

    2013-05-01

    An all-optical quartz-enhanced photoacoustic spectroscopy system, based on the F-P demodulation, for trace gas detection in the open environment was proposed. In quartz-enhanced photoacoustic spectroscopy (QEPAS), an optical fiber Fabry-Perot method was used to replace the conventional electronic demodulation method. The photoacoustic signal was obtained by demodulating the variation of the Fabry-Perot cavity between the quartz tuning fork side and the fiber face. An experimental system was setup. The experiment for detection of water vapour in the open environment was carried on. A normalized noise equivalent absorption coefficient of 2.80 x 10(-7) cm(-1) x W x Hz(-1/2) was achieved. The result demonstrated that the sensitivity of the all-optical quartz-enhanced photoacoustic spectroscopy system is about 2.6 times higher than that of the conventional QEPAS system. The all-optical quartz-enhanced photoacoustic spectroscopy system is immune to electromagnetic interference, safe in flammable and explosive gas detection, suitable for high temperature and high humidity environments and realizable for long distance, multi-point and network sensing.

  1. 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.

  2. 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...

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. Predicting long-term carbon mineralization and trace gas production from thawing permafrost of Northeast Siberia.

    PubMed

    Knoblauch, Christian; Beer, Christian; Sosnin, Alexander; Wagner, Dirk; Pfeiffer, Eva-Maria

    2013-04-01

    trace gas fluxes from thawing permafrost landscapes. PMID:23504893

  9. 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

  10. 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.

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. Computer monitoring, capture and analysis of gas/liquid chromatograph traces.

    PubMed

    Bulleid, N; Schofield, J

    1986-12-01

    The work described here is effectively the computerization of a gas/liquid chromatograph of the pen recorder type using a BBC microcomputer. The output from the g.l.c. can be captured by the computer in accordance with a series of parameters. The sampling rate can be altered, as can an averaging facility to reduce noise, and a threshold level to eliminate the storage of irrelevant and space-consuming data. The unprocessed readings are initially stored on the computer's floppy disk, then later retrieved and cut into smaller sections to allow maximum resolution for on-screen analysis. In the main analysis stage of the system all processing is shown graphically on the computer monitor at all stages. The principal steps in analysis involve the mathematical modelling and elimination of the solvent peak, the fixing of the retention time for each subsequent peak and its disentangling from any following peaks, and finally the calculation of the area under each individual peak. Several alternative methods are made available for disentangling peaks, which can be tried successively on a single peak then each printed out with comments for comparison later. All readings and results in table form and screen dumps of all trace images are available via a dot matrix printer.

  16. 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.

  17. 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

  18. Identification and assessment of trace contaminants associated with oil and gas pipelines abandoned in place

    SciTech Connect

    Thorne, W.E.R.; Basso, A.C.; Dhol, S.K.

    1996-12-31

    As more Alberta oil and gas fields become depleted, attention is being given to development of economically and environmentally sound abandonment procedures. The objective of this study was to identify and assess residual internal and external contaminants associated with abandoned pipelines, particularly those to be abandoned in place. Circumstances which might increase the risk of contaminant release, and other issues relating to residual pipeline contaminants, were also identified. It was found that there are thousands of different substances which could potentially be associated with abandoned pipelines. A wide range in the potential quantities of residual contaminants was also found. Of the issues identified, the effectiveness of pipeline pigging and cleaning procedures prior to abandonment was the most critical determinant of the potential quantities of residual contaminants. However, a number of trace contaminants, such as PCBs (Polychlorinated Biphenyls) and NORMs (Naturally Occurring Radioactive Materials) may remain after thorough cleaning. A brief review of the legislation and regulations from a number of jurisdictions shows that pipeline abandonment has only recently become an issue of concern. Regulations specific to abandonment are lacking, and more general regulations and guidelines are being applied on a contaminant-specific basis, or in terms of waste disposal requirements.

  19. Responses of trace gas fluxes and N availability to experimentally elevated soil temperatures

    SciTech Connect

    Peterjohn, W.T.; Melillo, J.M.; Steudler, P.A.; Newkirk, K.M. ); Bowles, F.P. ); Aber, J.D. )

    1994-08-01

    A field study is being conducted to determine the long-term response of belowground processes to elevated soil temperatures in a mixed deciduous forest. Eighteen experimental plots were established and randomly assigned them to one of three treatments in six blocks. The treatments are: (1) heated plots in which the soil temperature is raised 5[degrees]C above ambient using buried heating cables; (2) disturbance control plots (cables but no heat); and (3) undisturbed control plots (no cables and no heat). In each plot indexes of N availability, the concentration of N in soil solutions leaching below the rooting zone, and trace gas emissions (CO[sub 2], N[sub 2]O, and CH[sub 4]) were measured. In this paper results are presented from the first 6 mo of this study. The daily average efflux of CO[sub 2] increased exponentially with increasing soil temperature and decreased linearly with increasing soil moisture. A linear regression of temperature and the natural logarithm of CO[sub 2] flux explained 92% of the variability. A linear regression of soil moisture and CO[sub 2] flux could explain only 44% of the variability. The relationship between soil temperature and CO[sub 2] flux is in good agreement with the Arrhenius equation. For these CO[sub 2] flux data, the activation energy was 63 kJ/mol and the Q[sub 10] was 2.5.

  20. Determination of trace benzene hydrocarbons in Jiaozhou Bay by enrichment and capillary column gas chromatography

    NASA Astrophysics Data System (ADS)

    Cui, Xian-Zhou; Cui, Hang

    1996-06-01

    Trace amounts of benzene hydrocarbons obtained in Jiaozhou Bay (Qingdao) were enriched by sorption on a GDX-102 column and eluted by carbon disulfide. The eluate was concentrated and then determined by capillary column gas chromatography. The contents of various kinds of benzene hydrocarbons in Jiaozhou Bay coastal water were benzene (22.3 141.6)×10-9 g/L; toluate (15.2 94.0)×10-9 g/L; ethyl benzene (11.8 85.1)×10-9 g/L; p—xylene (15.2 78.5)×10-9 g/L; m—xylene (10.9 79.4)×10-9 g/L; o—xylene (12.4 80.1)×10-9 g/L; iso—propyl (8.4 73.1)×10-9 g/L; n—propyl (6.9 76.4)×10-9 g/L; 1, 3, 5-trimethylbenzene (10.9 35.9)×10-9 g/L; 1, 2, 4-trimethybenzene (10.0 38.0)×10-9 g/L; n—butybenzene (8.1 34.6)×10-9 g/L. The recovery of benzene hydrocarbons was (85.1 95.6)%.

  1. 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.

  2. A compact high resolution ion mobility spectrometer for fast trace gas analysis.

    PubMed

    Kirk, Ansgar T; Allers, Maria; Cochems, Philipp; Langejuergen, Jens; Zimmermann, Stefan

    2013-09-21

    Drift tube ion mobility spectrometers (IMS) are widely used for fast trace gas detection in air, but portable compact systems are typically very limited in their resolving power. Decreasing the initial ion packet width improves the resolution, but is generally associated with a reduced signal-to-noise-ratio (SNR) due to the lower number of ions injected into the drift region. In this paper, we present a refined theory of IMS operation which employs a combined approach for the analysis of the ion drift and the subsequent amplification to predict both the resolution and the SNR of the measured ion current peak. This theoretical analysis shows that the SNR is not a function of the initial ion packet width, meaning that compact drift tube IMS with both very high resolution and extremely low limits of detection can be designed. Based on these implications, an optimized combination of a compact drift tube with a length of just 10 cm and a transimpedance amplifier has been constructed with a resolution of 183 measured for the positive reactant ion peak (RIP(+)), which is sufficient to e.g. separate the RIP(+) from the protonated acetone monomer, even though their drift times only differ by a factor of 1.007. Furthermore, the limits of detection (LODs) for acetone are 180 pptv within 1 s of averaging time and 580 pptv within only 100 ms.

  3. Fine Resolution Neutron Detector for ExoMars Trace Gas Orbiter. Instrument and science goals.

    NASA Astrophysics Data System (ADS)

    Malakhov, Alexey; Litvak, Maxim; Kozyrev, S. Alexander; Tretiyakov, Vladislav; Sanin, Anton; Mokrousov, Maxim; Vostrukhin, Andrey; Golovin, Dmitry; Semkova, Jordanka; Dachev, Tsvetan; Malchev, Stefan; Tomov, Borislav; Matviichuk, Yury; Dimitrov, Plamen; Koleva, Rositza; Mitrofanov, Igor; F

    Fine Resolution Neutron Detector (FREND) will measure neutrons of different energy ranges, charged particles and radiation environment onboard ExoMars 2016 Trace Gas Orbiter spacecraft. The instrument contains a set of (3) He detectors for epithermal neutrons and a scintillation crystal for high-energy neutrons and charged particles measurements. Dosimeter module will perform dose and particle flux monitoring. The instrument also contains a collimation module that narrows 3He counters’ and scintillator’s field of view to a narrow spot on the surface of Mars of about 40 km. FREND will be the first experiment to perform high resolution hydrogen mapping of the Martian surface. Current hydrogen maps obtained by HEND instrument onboard Mars Odyssey provide only 300km spatial resolution. Improved data from FREND will be very valuable for further exploration missions in terms of landing sites selection, as well as enable us to better understand Martian geology, seasonal CO _{2} cycles and planet’s history. Radiation environment data from dosimeter module on Martian orbit will provide improved knowledge for future human exploration as well as perform solar particle events monitoring.

  4. 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.

  5. 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.

  6. 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

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

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    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 NO2 (versus a laser broadband cavity ringdown spectrometer) and for H2O (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+δ 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 NO3 as a function of integration time are considered in detail using an Allan variance analysis. Experiments under laboratory conditions produce a 1σ detection limit of 0.25 pptv for a 10 s

  8. 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.

  9. 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)

  10. Estimation of trace gas fluxes with objectively determined basis functions using reversible-jump Markov chain Monte Carlo

    NASA Astrophysics Data System (ADS)

    Lunt, Mark F.; Rigby, Matt; Ganesan, Anita L.; Manning, Alistair J.

    2016-09-01

    Atmospheric trace gas inversions often attempt to attribute fluxes to a high-dimensional grid using observations. To make this problem computationally feasible, and to reduce the degree of under-determination, some form of dimension reduction is usually performed. Here, we present an objective method for reducing the spatial dimension of the parameter space in atmospheric trace gas inversions. In addition to solving for a set of unknowns that govern emissions of a trace gas, we set out a framework that considers the number of unknowns to itself be an unknown. We rely on the well-established reversible-jump Markov chain Monte Carlo algorithm to use the data to determine the dimension of the parameter space. This framework provides a single-step process that solves for both the resolution of the inversion grid, as well as the magnitude of fluxes from this grid. Therefore, the uncertainty that surrounds the choice of aggregation is accounted for in the posterior parameter distribution. The posterior distribution of this transdimensional Markov chain provides a naturally smoothed solution, formed from an ensemble of coarser partitions of the spatial domain. We describe the form of the reversible-jump algorithm and how it may be applied to trace gas inversions. We build the system into a hierarchical Bayesian framework in which other unknown factors, such as the magnitude of the model uncertainty, can also be explored. A pseudo-data example is used to show the usefulness of this approach when compared to a subjectively chosen partitioning of a spatial domain. An inversion using real data is also shown to illustrate the scales at which the data allow for methane emissions over north-west Europe to be resolved.

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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).

  17. Natural gas: marine transportation. January 1974-November 1988 (Citations from Oceanic Abstracts). Report for January 1974-November 1988

    SciTech Connect

    Not Available

    1988-12-01

    This bibliography contains citations concerning the design, construction, and operation of ships for the transport of liquified natural gas. Topics include safety devices, materials handling equipment for loading and unloading liquified natural gas, new hull and vessel designs, gas-turbine propulsion systems, cargo tank designs and requirements, and liguid load dynamics. (This updated bibliography contains 349 citations, 50 of which are new entries to the previous edition.)

  18. Method for detection of trace metal and metalloid contaminants in coal-generated fuel gas using gas chromatography/ion trap mass spectrometry.

    PubMed

    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 (AsH(3)), phosphine (PH(3)), and hydrogen selenide (H(2)Se), while qualitative detection was observed for mercury. Decreased accuracy and response caused by the primary components of fuel gas were observed.

  19. 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.

  20. 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

  1. Photoacoustic Techniques for Trace Gas Sensing Based on Semiconductor Laser Sources

    PubMed Central

    Elia, Angela; Lugarà, Pietro Mario; Di Franco, Cinzia; Spagnolo, Vincenzo

    2009-01-01

    The paper provides an overview on the use of photoacoustic sensors based on semiconductor laser sources for the detection of trace gases. We review the results obtained using standard, differential and quartz enhanced photoacoustic techniques. PMID:22303143

  2. [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

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. 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

  9. Fine Resolution Epithermal Neutron Detector (FREND) onboard ExoMars Trace Gas Orbiter

    NASA Astrophysics Data System (ADS)

    Malakhov, Alexey; Mitrofanov, Igor; Sanin, Anton; Litvak, Maxim; Kozyrev, Alexander; Tretiyakov, Vladislav; Mokrousov, Maxim; Vostrukhin, Andrey; Golovin, Dmitry; Fedosov, Fedor; Nikiforov, Sergey; Konovalov, Alexey; Tomilina, Tatiana; Bobrovnitsky, Yury; Grebennikov, Alexander; Bakhtin, Boris; Loktionova, Mariya

    2013-04-01

    ExoMars is a joint investigation of Mars carried out by Roscosmos and ESA that has 2 launches foreseen, in 2016 and 2018. Planned for launch in 2016, its first element, the Trace Gas Orbiter (TGO) will spend at least one Martian year orbiting the planet. Fine Resolution Neutron Detector (FREND) instrument was proposed by Roscosmos and 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 by HEND instrument since 2002 as part of the Mars Odyssey instrument suite. The important step in Martian exploration from FREND will be its high spatial resolution: FREND contains a collimator structure that narrows the instrument's field of view to a 40 km diameter spot at 400 km altitude. The collimation technology was previously confirmed by LEND, an instrument onboard NASA's Lunar Reconnaissance Orbiter (LRO) mission. FREND collimator is a structure with 2 layers, external polyethylene moderating neutrons and internal layer of 10B absorbing them. The instrument uses as much of LEND heritage (detection systems, electronics etc.) as possible. Like LEND, FREND will have a set of 3He proportional counters covering the thermal and epithermal neutrons range, plus the stilbene scintillator to cover the high energy neutrons range. FREND's dosimeter module is another important part of the system, providing charged particles measurements of dose and flux with time resolution of up to 1 minute and energy spectra covering the 100 keV to 80 MeV range. This will provide additional information for radiation environment on the orbit around Mars. When built, FREND will be the first collimated neutron detector to orbit Mars and will improve existing neutron maps by up to 10 times in the linear spatial resolution. This potentially will clarify our knowledge of water/hydrogen rich features and other

  10. 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

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. Quantum cascade semiconductor infrared and far-infrared lasers: from trace gas sensing to non-linear optics.

    PubMed

    Duxbury, Geoffrey; Langford, Nigel; McCulloch, Michael T; Wright, Stephen

    2005-11-01

    The Quantum cascade (QC) laser is an entirely new type of semiconductor device in which the laser wavelength depends on the band-gap engineering. It can be made to operate over a much larger range than lead salt lasers, covering significant parts of both the infrared and submillimetre regions, and with higher output power. In this tutorial review we survey some of the applications of these new lasers, which range from trace gas detection for atmospheric or medical purposes to sub-Doppler and time dependent non-linear spectroscopy.

  20. Natural gas: bulk carriers. January, 1974-July, 1981 (citations from Oceanic Abstracts). Report for January 1974-July 1981

    SciTech Connect

    Not Available

    1981-07-01

    The construction and operation of ships for the transport of liquefied natural gas are considered. Emphasis is on safety devices as well as the equipment used for loading and unloading. Insulation requirements for tanks are included. (Contains 75 citations fully indexed and including a title list.)

  1. 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.

  2. 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.

  3. Deep ALMA imaging of the merger NGC 1614. Is CO tracing a massive inflow of non-starforming gas?

    NASA Astrophysics Data System (ADS)

    König, S.; Aalto, S.; Muller, S.; Gallagher, J. S.; Beswick, R. J.; Xu, C. K.; Evans, A.

    2016-10-01

    Aims: Observations of the molecular gas over scales of ~0.5 to several kpc provide crucial information on how molecular gas moves through galaxies, especially in mergers and interacting systems, where it ultimately reaches the galaxy center, accumulates, and feeds nuclear activity. Studying the processes involved in the gas transport is one of the important steps forward to understand galaxy evolution. Methods: 12CO, 13CO, and C18O 1-0 high-sensitivity ALMA observations (~4'' × 2'') were used to assess the properties of the large-scale molecular gas reservoir and its connection to the circumnuclear molecular ring in the merger NGC 1614. Specifically, the role of excitation and abundances were studied in this context. We also observed the molecular gas high-density tracers CN and CS. Results: The spatial distributions of the detected 12CO 1-0 and 13CO 1-0 emission show significant differences. 12CO traces the large-scale molecular gas reservoir, which is associated with a dust lane that harbors infalling gas, and extends into the southern tidal tails. 13CO emission is for the first time detected in the large-scale dust lane. In contrast to 12CO, its line emission peaks between the dust lane and the circumnuclear molecular ring. A 12CO-to-13CO 1-0 intensity ratio map shows high values in the ring region (~30) that are typical for the centers of luminous galaxy mergers and even more extreme values in the dust lane (>45). Surprisingly, we do not detect C18O emission in NGC 1614, but we do observe gas emitting the high-density tracers CN and CS. Conclusions: We find that the 12CO-to-13CO 1-0 line ratio in NGC 1614 changes from >45 in the 2 kpc dust lane to ~30 in the starburst nucleus. This drop in ratio with decreasing radius is consistent with the molecular gas in the dust lane being kept in a diffuse, unbound state while it is being funneled toward the nucleus. This also explains why there are no (or very faint) signs of star formation in the dust lane, despite its

  4. 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.

  5. 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.

  6. 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.

  7. Research Abstracts.

    ERIC Educational Resources Information Center

    Plotnick, Eric

    2001-01-01

    Presents research abstracts from the ERIC Clearinghouse on Information and Technology. Topics include: classroom communication apprehension and distance education; outcomes of a distance-delivered science course; the NASA/Kennedy Space Center Virtual Science Mentor program; survey of traditional and distance learning higher education members;…

  8. 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)

  9. 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.

  10. Vertical level selection for temperature and trace gas profile retrievals using IASI

    NASA Astrophysics Data System (ADS)

    Vincent, R. A.; Dudhia, A.; Ventress, L. J.

    2015-06-01

    This work presents a new iterative method for optimally selecting a vertical retrieval grid based on the location of the information while accounting for inter-level correlations. Sample atmospheres initially created to parametrise the Radiative Transfer Model for the Television Infrared Observation Satellite Operational Vertical Sounder (RTTOV) forward model are used to compare the presented iterative selection method with two other common approaches, which are using levels of equal vertical spacing and selecting levels based on the cumulative trace of the averaging kernel matrix (AKM). This new method is shown to outperform compared methods for simulated profile retrievals of temperature, H2O, O3, CH4, and CO with the Infrared Atmospheric Sounding Interferometer (IASI). However, the benefits of using the more complicated iterative approach compared to the simpler cumulative trace method are slight and may not justify the added effort for the cases studied, but may be useful in other scenarios where temperature and trace gases have strong vertical gradients with significant estimate sensitivity. Furthermore, comparing retrievals using a globally optimised static grid vs. a locally adapted one shows that a static grid performs nearly as well for retrievals of O3, CH4, and CO. However, developers of temperature and H2O retrieval schemes may at least consider using adaptive or location specific vertical retrieval grids.

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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.

  16. Tracing kinematic (mis)alignments in CALIFA merging galaxies. Stellar and ionized gas kinematic orientations at every merger stage

    NASA Astrophysics Data System (ADS)

    Barrera-Ballesteros, J. K.; García-Lorenzo, B.; Falcón-Barroso, J.; van de Ven, G.; Lyubenova, M.; Wild, V.; Méndez-Abreu, J.; Sánchez, S. F.; Marquez, I.; Masegosa, J.; Monreal-Ibero, A.; Ziegler, B.; del Olmo, A.; Verdes-Montenegro, L.; García-Benito, R.; Husemann, B.; Mast, D.; Kehrig, C.; Iglesias-Paramo, J.; Marino, R. A.; Aguerri, J. A. L.; Walcher, C. J.; Vílchez, J. M.; Bomans, D. J.; Cortijo-Ferrero, C.; González Delgado, R. M.; Bland-Hawthorn, J.; McIntosh, D. H.; Bekeraitė, S.

    2015-10-01

    We present spatially resolved stellar and/or ionized gas kinematic properties for a sample of 103 interacting galaxies, tracing all merger stages: close companions, pairs with morphological signatures of interaction, and coalesced merger remnants. In order to distinguish kinematic properties caused by a merger event from those driven by internal processes, we compare our galaxies with a control sample of 80 non-interacting galaxies. We measure for both the stellar and the ionized gas components the major (projected) kinematic position angles (PAkin, approaching and receding) directly from the velocity distributions with no assumptions on the internal motions. This method also allow us to derive the deviations of the kinematic PAs from a straight line (δPAkin). We find that around half of the interacting objects show morpho-kinematic PA misalignments that cannot be found in the control sample. In particular, we observe those misalignments in galaxies with morphological signatures of interaction. On the other hand, thelevel of alignment between the approaching and receding sides for both samples is similar, with most of the galaxies displaying small misalignments. Radial deviations of the kinematic PA orientation from a straight line in the stellar component measured by δPAkin are large for both samples. However, for a large fraction of interacting galaxies the ionized gas δPAkin is larger than the typical values derived from isolated galaxies (48%), indicating that this parameter is a good indicator to trace the impact of interaction and mergers in the internal motions of galaxies. By comparing the stellar and ionized gas kinematic PA, we find that 42% (28/66) of the interacting galaxies have misalignments larger than 16°, compared to 10% from the control sample. Our results show the impact of interactions in the motion of stellar and ionized gas as well as the wide the variety of their spatially resolved kinematic distributions. This study also provides a local

  17. Constraining Gas Diffusivity-Soil Water Content Relationships in Forest Soils Using Surface Chamber Fluxes and Depth Profiles of Multiple Trace Gases

    NASA Astrophysics Data System (ADS)

    Dore, J. E.; Kaiser, K.; Seybold, E. C.; McGlynn, B. L.

    2012-12-01

    Forest soils are sources of carbon dioxide (CO2) to the atmosphere and can act as either sources or sinks of methane (CH4) and nitrous oxide (N2O), depending on redox conditions and other factors. Soil moisture is an important control on microbial activity, redox conditions and gas diffusivity. Direct chamber measurements of soil-air CO2 fluxes are facilitated by the availability of sensitive, portable infrared sensors; however, corresponding CH4 and N2O fluxes typically require the collection of time-course physical samples from the chamber with subsequent analyses by gas chromatography (GC). Vertical profiles of soil gas concentrations may also be used to derive CH4 and N2O fluxes by the gradient method; this method requires much less time and many fewer GC samples than the direct chamber method, but requires that effective soil gas diffusivities are known. In practice, soil gas diffusivity is often difficult to accurately estimate using a modeling approach. In our study, we apply both the chamber and gradient methods to estimate soil trace gas fluxes across a complex Rocky Mountain forested watershed in central Montana. We combine chamber flux measurements of CO2 (by infrared sensor) and CH4 and N2O (by GC) with co-located soil gas profiles to determine effective diffusivity in soil for each gas simultaneously, over-determining the diffusion equations and providing constraints on both the chamber and gradient methodologies. We then relate these soil gas diffusivities to soil type and volumetric water content in an effort to arrive at empirical parameterizations that may be used to estimate gas diffusivities across the watershed, thereby facilitating more accurate, frequent and widespread gradient-based measurements of trace gas fluxes across our study system. Our empirical approach to constraining soil gas diffusivity is well suited for trace gas flux studies over complex landscapes in general.

  18. 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.

  19. 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.

  20. 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.

  1. Stratospheric response to trace gas perturbations: changes in ozone and temperature distributions.

    PubMed

    Brasseur, G; Hitchman, M H

    1988-04-29

    The stratospheric concentration of trace gases released in the atmosphere as a result of human activities is increasing at a rate of 5 to 8 percent per year in the case of the chlorofluorocarbons (CFCs), 1 percent per year in the case of methane (CH(4)), and 0.25 percent per year in the case of nitrous oxide (N(2)O). The amount of carbon dioxide (CO(2)) is expected to double before the end of the 21st century. Even if the production of the CFCs remains limited according to the protocol for the protection of the ozone layer signed in September 1987 in Montreal, the abundance of active chlorine (2 parts per billion by volume in the early 1980s) is expected to reach 6 to7 parts per billion by volume by 2050. The impact of these increases on stratospheric temperature and ozone was investigated with a two-dimensional numerical model. The model includes interactive radiation, wave and mean flow dynamics, and 40 trace species. An increase in CFCs caused ozone depletion in the model, with the largest losses near the stratopause and, in the vertical mean, at high latitudes. Increased CO(2) caused ozone amounts to increase through cooling, with the largest increases again near 45 kilometers and at high latitudes. This CO(2)-induced poleward increase reduced the CFC-induced poleward decrease. Poleward and downward ozone transport played a major role in determining the latitudinal variation in column ozone changes.

  2. Trace analysis of organic volatiles in water by gas chromatography-mass spectrometry with glass capillary columns.

    PubMed

    Bertsch, W; Anderson, E; Holzer, G

    1975-10-29

    Traces of volatile organic materials in water have been concentrated by gas phase stripping and adsorption onto a porous polymer. A simple all-glass sampling device is proposed which allows efficient concentration at elevated temperatures. Sample transfer from absorbent into a gas chromatographic column is effected by a simple one-step procedure involving heat desorption. The capacity of the absorbent has been determined for a number of model substances which are found in water. Under the sampling conditions used, compounds being less volatile than benzene are usually quantitatively retained, with some exceptions. Separations were effected with highly efficient glass capillary columns. Water samples, collected from a small number of locations, included both tap water and untreated waters. A number of volatiles have been determined by gas chromatography-mass spectrometry in drinking water and in a river which flows through an industrialized area. The drinking water examined contains a large number of chlorinated and brominated compounds whereas the river water is largely free from this class of substances. Derivatives of camphor and terpenes have been identified in this particular river.

  3. 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.}

  4. A passive DOAS instrument for trace gas measurements on medium sized UAS: Instrumental design and first measurements.

    NASA Astrophysics Data System (ADS)

    Horbanski, Martin; Pöhler, Denis; Mahr, Tobias; Wagner, Thomas; Keleshis, Christos; Ioannou, Stelios; Lange, Manfred A.; Lelieveld, Jos; Platt, Ulrich

    2013-04-01

    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 UAS. 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). We present a new developed passive DOAS instrument for the APAESO Platform of the Cyprus Institute, a medium size UAS. It is equipped with two telescopes for observations in downward (nadir) and horizontal (limb) viewing direction, respectively. Thus it allows determining height profiles and the horizontal distribution of trace gases. This is accomplished by analyzing the radiation collected by the telescopes with compact spectrometers, which cover the UV-blue spectral range allowing to measure a broad variety of atmospheric trace gases (e.g. NO2, SO2, BrO, IO, H2O ...) as well as aerosol properties via O4 absorption. Additionally, the nadir direction is equipped with a VIS-NIR spectrometer. It is used to measure reflection spectra of different types of vegetation. These will serve as references for satellite measurements to create global maps. First measurements on the APAESO platform were performed in October 2012 on Cyprus in a rural area south of Nicosia. The instrument is shown to work reliably and was able to detect NO2, H2O and O4 at atmospheric column densities. The instrumental design and first measurements will be presented and discussed.

  5. 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.

  6. 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

  7. 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.

  8. 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.

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

    PubMed

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

    2012-11-01

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

  10. [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.

  11. 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.

  12. Clouds and wet removal as causes of variability in the trace-gas composition of the marine troposphere

    NASA Technical Reports Server (NTRS)

    Thompson, A. M.; Cicerone, R. J.

    1982-01-01

    A modeling study of the effects of clouds and wet removal on the chemistry of the remote marine troposphere is described. Using a time-dependent model with parameterized vertical transport to calculate trace-gas concentrations, it is found that large variations in key species (e.g., HNO3, H2CO, and H2O2) result from simulations of sporadic rainfall, changes in cloud cover, and external inputs such as surface NO sources. Depending on the frequency and intensity of an event, the effects of these perturbations may persist for several days, thereby invalidating assumptions of photochemical equilibrium in the interpretation of measurements. Long-term integrations with fixed boundary conditions and regularly occurring cloud and rain episodes demonstrate a strong sensitivity of the mean concentration of longer-lived soluble gases to precipitation frequency but also confirm the validity of using properly chosen parameterizations of wet removal in steady state calculations.

  13. SALOMON: a new, light balloonborne UV-visible spectrometer for nighttime observations of stratospheric trace-gas species.

    PubMed

    Renard, J B; Chartier, M; Robert, C; Chalumeau, G; Berthet, G; Pirre, M; Pommereau, J P; Goutail, F

    2000-01-20

    A new, light balloonborne UV-visible spectrometer, called SALOMON, is designed to perform nighttime measurements of stratospheric trace-gas species by using the Moon as a light source. The first flight, performed on 31 October 1998 at mid-latitude with a float altitude of 26.7 km, allowed the performance of the pointing system to be checked and vertical profiles of ozone, NO(2), NO(3), and possibly OBrO to be obtained. First the instrument and then the performance of the pointing system and the detector are described. Finally the vertical profiles are compared with other profiles obtained at the same location five years before with the heavier balloonborne spectrometer AMON, which uses a star as the light source.

  14. 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.

  15. Seasonal variations in Titan's stratosphere observed with Cassini/CIRS: temperature, trace molecular gas and aerosol mixing ratio profiles

    NASA Astrophysics Data System (ADS)

    Vinatier, S.; Bézard, B.; Anderson, C.; Teanby, N.; Lebonnois, S.; Rannou, P.; de Kok, R.; T. CIRS Team

    2013-09-01

    Titan's northern spring equinox occurred in August 2009. General Circulation Models (e.g. [1]) 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., [2], [3], [4], [5]). 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 limbgeometry datasets acquired in 2010, 2011 and 2012 that we used to monitor the seasonal evolution of the vertical profiles of temperature, molecular (C2H2, C2H6, HCN, ...) and aerosol abundances.

  16. Characterization of fiber-laser-based sub-Doppler NICE-OHMS for quantitative trace gas detection.

    PubMed

    Foltynowicz, Aleksandra; Ma, Weiguang; Axner, Ove

    2008-09-15

    The potential of fiber-laser-based sub-Doppler noise-immune cavity-enhanced optical heterodyne molecular spectrometry for trace gas detection is scrutinized. The non-linear dependence of the on-resonance sub-Doppler dispersion signal on the intracavity pressure and power is investigated and the optimum conditions with respect to these are determined. The linearity of the signal strength with concentration is demonstrated and the dynamic range of the technique is discussed. Measurements were performed on C(2)H(2) at 1531 nm up to degrees of saturation of 100. The minimum detectable sub-Doppler optical phase shift was 5 x 10(-11) cm(-1) Hz(-1/2), corresponding to a partial pressure of C(2)H(2) of 1 x 10(-12) atm for an intracavity pressure of 20 mTorr, and a concentration of 10 ppb at 400 mTorr.

  17. 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.

  18. Manure and inorganic N affect trace gas emissions under semi-arid irrigated corn

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dairy manure is often applied to cropped soils as a substitute for inorganic N fertilizers, but the impacts of manure on soil greenhouse gas (GHG) fluxes, yields and soil N are uncertain in the semi-arid western U.S. Soil carbon dioxide (CO2-C), methane (CH4-C), and nitrous oxide (N2O-N) emissions ...

  19. Effect of trace metals on ethanol production from synthesis gas by the ethanologenic acetogen, Clostridium ragsdalei.

    PubMed

    Saxena, Jyotisna; Tanner, Ralph S

    2011-04-01

    The effect of trace metal ions (Co²+, Cu²+, Fe²+, Mn²+, Mo⁶+, Ni²+, Zn²+, SeO₄⁻ and WO₄⁻) on growth and ethanol production by an ethanologenic acetogen, Clostridium ragsdalei was investigated in CO:CO₂-grown cells. A standard acetogen medium (ATCC medium no. 1754) was manipulated by varying the concentrations of trace metals in the media. Increasing the individual concentrations of Ni²+, Zn²+, SeO₄⁻ and WO₄⁻ from 0.84, 6.96, 1.06, and 0.68 μM in the standard trace metals solution to 8.4, 34.8, 5.3, and 6.8 μM, respectively, increased ethanol production from 35.73 mM under standard metals concentration to 176.5, 187.8, 54.4, and 72.3 mM, respectively. Nickel was necessary for growth of C. ragsdalei. Growth rate (μ) of C. ragsdalei improved from 0.34 to 0.49 (day⁻¹), and carbon monoxide dehydrogenase (CODH) and hydrogenase (H₂ase)-specific activities improved from 38.45 and 0.35 to 48.5 and 1.66 U/mg protein, respectively, at optimum concentration of Ni²+. At optimum concentrations of WO₄⁻ and SeO₄⁻, formate dehydrogenase (FDH) activity improved from 32.3 to 42.6 and 45.4 U/mg protein, respectively. Ethanol production and the activity of FDH reduced from 35 mM and 32.3 U/mg protein to 1.14 mM and 8.79 U/mg protein, respectively, upon elimination of WO₄⁻ from the medium. Although increased concentration of Zn²+ enhanced growth and ethanol production, the activities of CODH, FDH, H₂ase and alcohol dehydrogenase (ADH) were not affected by varying the Zn²+ concentration. Omitting Fe²+ from the medium decreased ethanol production from 35.7 to 6.30 mM and decreased activities of CODH, FDH, H₂ase and ADH from 38.5, 32.3, 0.35, and 0.68 U/mg protein to 9.07, 7.01, 0.10, and 0.24 U/mg protein, respectively. Ethanol production improved from 35 to 54 mM when Cu²+ was removed from the medium. The optimization of trace metals concentration in the fermentation medium improved enzyme activities (CODH, FDH, and H

  20. 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.

  1. An Isotopic, Dissolved Gas, and Trace Organic Investigation of Nitrate Sources in Urbanized Groundwater Basins

    NASA Astrophysics Data System (ADS)

    Singleton, M. J.; Moran, J. E.; Esser, B. K.; Leif, R. N.; Beller, H. R.

    2006-12-01

    We combine the detection of trace organic compounds including pesticides, pharmaceuticals, and personal care products with 3H/3He apparent ages and isotopic compositions of nitrogen and oxygen in nitrate in order to distinguish between potential nitrate sources. Septic system-derived nitrate is formed by nitrification, and often cannot be differentiated from agricultural or background sources based on nitrate N and O isotopic compositions alone. Samples that lie within the overlapping fields of natural nitrate and septic discharge can sometimes be differentiated by the presence of trace organic compounds specific to septic discharge. Some target compounds are much more likely to come from septic system discharge than from agricultural irrigation return flow (caffeine; surfactants or surfactant breakdown products like LAS and alkylphenol carboxylic acids; carbamazepine and other pharmaceuticals and estrogenic compounds), whereas others are more likely to be present in irrigation return (herbicides and their breakdown products). Groundwater age dating using the 3H/3He method provides constraints on the nitrate inputs to groundwater. The occurrence of young 3H/3He apparent ages with high nitrate concentrations is indicative of a modern, nearby flux of nitrate. This relation is used to distinguish between modern sources of nitrate and legacy sources at formerly agricultural sites. Results are presented from a basin-wide study in Chico, CA and a study of instrumented septic system sites in Livermore, CA. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

  2. 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

  3. 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.

  4. Fourier transform microwave spectroscopy: A potential new analytical tool for trace gas species

    SciTech Connect

    Suenram, R.D.; Lovas, F.J.; Sams, R.L.

    1994-12-31

    A pulsed molecular beam Fabry-Perot microwave spectrometer has been developed that has demonstrated sensitivities to most polar gas-phase molecular species that are in the low parts-per-billion (ppb) range. The highest sensitivity is obtained using neon or argon carrier gas but nitrogen or air can also be used with some loss in sensitivity due to the less efficient cooling in the molecular beam with diatomic gases. The minimum detectable concentrations for several representative compounds has been determined. These include SO{sub 2}, propene, acrolein, and methyl t-butyl ether. Considerable attention has been given to making the instrument robust for use in industrial laboratories. The instrument is controlled using a standard Intel 486 based computer. A Graphical User Interface (Windows-type) operating system has been developed that makes the instrument extremely user-friendly allowing all instrument control functions to be carried out using a mouse.

  5. Laboratory Investigation of Trace Gas Emissions from Biomass Burning on DoD Bases

    NASA Astrophysics Data System (ADS)

    Burling, I. R.; Yokelson, R. J.; Griffith, D. W.; Roberts, J. M.; Veres, P. R.; Warneke, C.; Johnson, T. J.

    2009-12-01

    Vegetation representing fuels commonly managed with prescribed fires was collected from five DoD bases and burned under controlled conditions at the USFS Firelab in Missoula, MT. The smoke emissions were measured with a large suite of state-of-the-art instrumentation. Seventy-seven fires were conducted and the smoke composition data will improve DoD land managers’ ability to assess the impact of prescribed fires on local air quality. A key instrument used in the measurement of the gas phase species in smoke was an open-path FTIR (OP-FTIR) spectrometer, built and operated by the Universities of Montana and Wollongong. The OP-FTIR has to date detected and quantified 20 gas phase species - CO2, CO, H2O, N2O, NO2, NO, HONO, NH3, HCl, SO2, CH4, CH3OH, HCHO, HCOOH, C2H2, C2H4, CH3COOH, HCN, propylene and furan. The spectra were analyzed using a non-linear least squares fitting routine that included reference spectra recently acquired at the Pacific Northwest National Laboratories. Preliminary results from the OP-FTIR analysis are reported here. Of particular interest, gas-phase nitrous acid (HONO) was detected simultaneously by the OP-FTIR and negative-ion proton-transfer chemical ionization spectrometer (NI-PT-CIMS), with preliminary fire-integrated molar emission ratios (relative to NOx) ranging from approximately 0.03 to 0.20, depending on the vegetation type. HONO is an important precursor in the production of OH, the primary oxidizing species in the atmosphere. There existed little previous data documenting HONO emissions from either wild or prescribed fires. The non-methane organic emissions were dominated by oxygenated species, which can be further oxidized and thus involved in secondary aerosol formation. Elevated amounts of gas-phase HCl were also detected in the smoke, with the amounts varying depending on location and vegetation type.

  6. Pulsed quantum-cascade laser-based sensor for trace-gas detection of carbonyl sulfide.

    PubMed

    Wysocki, Gerard; McCurdy, Matt; So, Stephen; Weidmann, Damien; Roller, Chad; Curl, Robert F; Tittel, Frank K

    2004-11-10

    Simultaneous exhaled carbonyl sulfide (OCS) and carbon dioxide concentration measurements in human breath are demonstrated with a compact pulsed quantum-cascade laser-based gas sensor. We achieved a noise-equivalent sensitivity (1sigma) of 1.2 parts per billion by measuring a well-isolated OCS P(11) absorption line in the v3 band at 2057.6 cm(-1) using an astigmatic Herriott cell of 36-m optical path length and 0.4-s acquisition time.

  7. 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.

  8. Direct Measurement of Trace Elemental Mercury in Hydrocarbon Matrices by Gas Chromatography with Ultraviolet Photometric Detection.

    PubMed

    Gras, Ronda; Luong, Jim; Shellie, Robert A

    2015-11-17

    We introduce a technique for the direct measurement of elemental mercury in light hydrocarbons such as natural gas. We determined elemental mercury at the parts-per-trillion level with high precision [<3% RSD (n = 20 manual injection)] using gas chromatography with ultraviolet photometric detection (GC-UV) at 254 nm. Our approach requires a small sample volume (1 mL) and does not rely on any form of sample preconcentration. The GC-UV separation employs an inert divinylbenzene porous layer open tubular column set to separate mercury from other components in the sample matrix. We incorporated a 10-port gas-sampling valve in the GC-UV system, which enables automated sampling, as well as back flushing capability to enhance system cleanliness and sample throughput. Total analysis time is <2 min, and the procedure is linear over a range of 2-83 μg/m(3) [correlation coefficient of R(2) = 0.998] with a measured recovery of >98% over this range.

  9. Physical properties of CO-dark molecular gas traced by C+

    NASA Astrophysics Data System (ADS)

    Tang, Ningyu; Li, Di; Heiles, Carl; Wang, Shen; Pan, Zhichen; Wang, Jun-Jie

    2016-09-01

    Context. Neither Hi nor CO emission can reveal a significant quantity of so-called dark gas in the interstellar medium (ISM). It is considered that CO-dark molecular gas (DMG), the molecular gas with no or weak CO emission, dominates dark gas. Determination of physical properties of DMG is critical for understanding ISM evolution. Previous studies of DMG in the Galactic plane are based on assumptions of excitation temperature and volume density. Independent measurements of temperature and volume density are necessary. Aims: We intend to characterize physical properties of DMG in the Galactic plane based on C+ data from the Herschel open time key program, namely Galactic Observations of Terahertz C+ (GOT C+) and Hi narrow self-absorption (HINSA) data from international Hi 21 cm Galactic plane surveys. Methods: We identified DMG clouds with HINSA features by comparing Hi, C+, and CO spectra. We derived the Hi excitation temperature and Hi column density through spectral analysis of HINSA features. The Hi volume density was determined by utilizing the on-the-sky dimension of the cold foreground Hi cloud under the assumption of axial symmetry. The column and volume density of H2 were derived through excitation analysis of C+ emission. The derived parameters were then compared with a chemical evolutionary model. Results: We identified 36 DMG clouds with HINSA features. Based on uncertainty analysis, optical depth of HiτHi of 1 is a reasonable value for most clouds. With the assumption of τHi = 1, these clouds were characterized by excitation temperatures in a range of 20 K to 92 K with a median value of 55 K and volume densities in the range of 6.2 × 101 cm-3 to 1.2 × 103 cm-3 with a median value of 2.3 × 102 cm-3. The fraction of DMG column density in the cloud (fDMG) decreases with increasing excitation temperature following an empirical relation fDMG =-2.1 × 10-3Tex,(τHi = 1) + 1.0. The relation between fDMG and total hydrogen column density NH is given by f

  10. Determination of trace anions in liquefied petroleum gas using liquid absorption and electrokinetic migration for enrichment followed by ion chromatography.

    PubMed

    Li, Meilan; Yang, Jianmin; Li, Hai-Fang; Lin, Jin-Ming

    2012-06-01

    A simple sample enrichment technique, electrokinetic migration enrichment in single phase using a designed device, coupled with ion chromatography is presented for the determination of four anions (H(2)PO(4)(-), Cl(-), NO(3)(-), and SO(4)(2-)) in liquefied petroleum gas by liquid adsorption. The electrokinetic migration enrichment is based on the phenomenon of ion electrokinetic migration to the opposite electrode. When the anions migrated to the anode in a smaller volume chamber under the electric field, the concentration was realized. The main parameters affecting enrichment efficiency of applied voltage and enrichment time were investigated. The ion chromatography condition for anions separation was also studied. Under the optimal electrokinetic migration enrichment and ion chromatography conditions, the four anions were detected simultaneously with good linear relationship (r(2) = 0.9908-0.9968) and high precisions (less than 5% of the relative standard deviations of peak areas). The limits of detection of anions (S/N of 3) were in the range of 8-600 μg L(-1). The enrichment factors of the four anions ranged from 3.1 to 5.8. The established method was successfully applied to the analysis of the trace anions in liquefied petroleum gas by liquid adsorption with satisfactory results. The advantages of this method are simple operation and low cost.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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).

  17. Gas chromatography/trace analysis of derivatized azelaic acid as a stability marker.

    PubMed

    Alzweiri, Muhammed; Tarawneh, Ruba; Khanfar, Mohammad A

    2013-10-01

    Azelaic acid, a naturally occurring saturated dicarboxylic acid, is found in many topical formulations for its various medical benefits or as a byproduct of the oxidative decomposition of unsaturated fatty acids. The poor volatility of azelaic acid hinders its applicability in GC analysis. Therefore, azelaic acid was derivatized by methylation and silylation procedures to enhance its volatility for GC analysis. Accordingly, dimethyl azelate (DMA) and di(trimethylsilyl) azelate were synthesized and characterized by GC-MS. Subsequently, a GC with flame ionization detection method was developed and validated to analyze trace amounts of azelaic acid in some marketed skin creams. Unlike DMA, di(trimethylsilyl) azelate was chemically unstable and degraded within few hours. Nonane was used as a stable internal standard. Variability due to derivatization and extraction was controlled by a standard addition procedure. DMA analysis was linear in a wide concentration range (100 ng/mL to 100 mg/mL). Moreover, the method was accurate (96.4-103.4%) and precise with inter- and intraday variability <2.0% and LOQ and LOD of 100 and 10 ng/mL, respectively. PMID:23893928

  18. 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.

  19. 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...

  20. 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...

  1. 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

  2. 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.

  3. 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).

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Trace analysis of multi-class pesticide residues in Chinese medicinal health wines using gas chromatography with electron capture detection.

    PubMed

    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.

  10. 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

  11. 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.

  12. 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.

  13. The effect of mustard gas on salivary trace metals (Zn, Mn, Cu, Mg, Mo, Sr, Cd, Ca, Pb, Rb).

    PubMed

    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

  14. 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

  15. 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.

  16. 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

  17. Trace-gas metabolic versatility of the facultative methanotroph Methylocella silvestris.

    PubMed

    Crombie, Andrew T; Murrell, J Colin

    2014-06-01

    The climate-active gas methane is generated both by biological processes and by thermogenic decomposition of fossil organic material, which forms methane and short-chain alkanes, principally ethane, propane and butane. In addition to natural sources, environments are exposed to anthropogenic inputs of all these gases from oil and gas extraction and distribution. The gases provide carbon and/or energy for a diverse range of microorganisms that can metabolize them in both anoxic and oxic zones. Aerobic methanotrophs, which can assimilate methane, have been considered to be entirely distinct from utilizers of short-chain alkanes, and studies of environments exposed to mixtures of methane and multi-carbon alkanes have assumed that disparate groups of microorganisms are responsible for the metabolism of these gases. Here we describe the mechanism by which a single bacterial strain, Methylocella silvestris, can use methane or propane as a carbon and energy source, documenting a methanotroph that can utilize a short-chain alkane as an alternative to methane. Furthermore, during growth on a mixture of these gases, efficient consumption of both gases occurred at the same time. Two soluble di-iron centre monooxygenase (SDIMO) gene clusters were identified and were found to be differentially expressed during bacterial growth on these gases, although both were required for efficient propane utilization. This report of a methanotroph expressing an additional SDIMO that seems to be uniquely involved in short-chain alkane metabolism suggests that such metabolic flexibility may be important in many environments where methane and short-chain alkanes co-occur.

  18. Trace gas fluxes along soil carbon and drainage gradients at a peaty grassland

    NASA Astrophysics Data System (ADS)

    Leiber-Sauheitl, Katharina; Fuß, Roland; Freibauer, Annette

    2013-04-01

    The importance of organic soils for the greenhouse gas (GHG) balance and the beneficial effect of CO2 uptake by undisturbed peatlands are widely accepted. In contrast, it is known that after drainage peatlands become a large source of GHGs due to mineralization of organic material. Emissions decrease only when easily degradable substances are depleted and more stable substances accumulate. Therefore, subsequent to the first mineralization peak degraded peatlands are assumed to be a small source of GHGs. Based on GHG flux measurements along small-scale soil organic carbon and groundwater level gradients, we show that this assumption cannot be generalized. The study area "Grosses Moor" (Gifhorn, Germany) is located within a former peat bog, which has been altered by drainage and peat cutting and is currently grassland under extensive agricultural use. The peat is amorphous and highly degraded. The focus of our study is on the acquisition of CO2, CH4 and N2O fluxes at six measurement sites via manual closed chambers. The effects of small-scale soil organic carbon and groundwater level gradients on the GHG fluxes (CO2, CH4, and N2O) are quantified. In order to calculate the annual CO2 exchange rate, values are modeled on a 0.5 hour scale between measurement campaigns. The model is based on meteorological parameters, such as the photosynthetic active radiation and soil temperature. During the 2011/2012 campaign, CO2 was the most important greenhouse gas. Emissions were dependent on water table level but not on soil carbon content. Positive annual balances occurred on all sites demonstrating that even highly degraded peaty soils are an important source of greenhouse gases. This study gives valuable information on the GHG source function of degraded peaty soils. Thus, our study improves predictions of the reaction of peatland soils to changes of soil and climate conditions with respect to their GHG emissions.

  19. Trace-gas metabolic versatility of the facultative methanotroph Methylocella silvestris.

    PubMed

    Crombie, Andrew T; Murrell, J Colin

    2014-06-01

    The climate-active gas methane is generated both by biological processes and by thermogenic decomposition of fossil organic material, which forms methane and short-chain alkanes, principally ethane, propane and butane. In addition to natural sources, environments are exposed to anthropogenic inputs of all these gases from oil and gas extraction and distribution. The gases provide carbon and/or energy for a diverse range of microorganisms that can metabolize them in both anoxic and oxic zones. Aerobic methanotrophs, which can assimilate methane, have been considered to be entirely distinct from utilizers of short-chain alkanes, and studies of environments exposed to mixtures of methane and multi-carbon alkanes have assumed that disparate groups of microorganisms are responsible for the metabolism of these gases. Here we describe the mechanism by which a single bacterial strain, Methylocella silvestris, can use methane or propane as a carbon and energy source, documenting a methanotroph that can utilize a short-chain alkane as an alternative to methane. Furthermore, during growth on a mixture of these gases, efficient consumption of both gases occurred at the same time. Two soluble di-iron centre monooxygenase (SDIMO) gene clusters were identified and were found to be differentially expressed during bacterial growth on these gases, although both were required for efficient propane utilization. This report of a methanotroph expressing an additional SDIMO that seems to be uniquely involved in short-chain alkane metabolism suggests that such metabolic flexibility may be important in many environments where methane and short-chain alkanes co-occur. PMID:24776799

  20. Trace-gas metabolic versatility of the facultative methanotroph Methylocella silvestris

    NASA Astrophysics Data System (ADS)

    Crombie, Andrew T.; Murrell, J. Colin

    2014-06-01

    The climate-active gas methane is generated both by biological processes and by thermogenic decomposition of fossil organic material, which forms methane and short-chain alkanes, principally ethane, propane and butane. In addition to natural sources, environments are exposed to anthropogenic inputs of all these gases from oil and gas extraction and distribution. The gases provide carbon and/or energy for a diverse range of microorganisms that can metabolize them in both anoxic and oxic zones. Aerobic methanotrophs, which can assimilate methane, have been considered to be entirely distinct from utilizers of short-chain alkanes, and studies of environments exposed to mixtures of methane and multi-carbon alkanes have assumed that disparate groups of microorganisms are responsible for the metabolism of these gases. Here we describe the mechanism by which a single bacterial strain, Methylocella silvestris, can use methane or propane as a carbon and energy source, documenting a methanotroph that can utilize a short-chain alkane as an alternative to methane. Furthermore, during growth on a mixture of these gases, efficient consumption of both gases occurred at the same time. Two soluble di-iron centre monooxygenase (SDIMO) gene clusters were identified and were found to be differentially expressed during bacterial growth on these gases, although both were required for efficient propane utilization. This report of a methanotroph expressing an additional SDIMO that seems to be uniquely involved in short-chain alkane metabolism suggests that such metabolic flexibility may be important in many environments where methane and short-chain alkanes co-occur.

  1. Mercury emission and plant uptake of trace elements during early stage of soil amendment using flue gas desulfurization materials.

    PubMed

    Cheng, Chin-Min; Chang, Yung-Nan; Sistani, Karamat R; Wang, Yen-Wen; Lu, Wen-Chieh; Lin, Chia-Wei; Dong, Jing-Hong; Hu, Chih-Chung; Pan, Wei-Ping

    2012-02-01

    A pilot-scale field study was carried out to investigate the distribution of Hg and other selected elements (i.e., As, B, and Se), i.e., emission to ambient air, uptake by surface vegetation, and/or rainfall infiltration, after flue gas desulfurization (FGD) material is applied to soil. Three FGD materials collected from two power plants were used. Our results show Hg released into the air and uptake in grass from all FGD material-treated soils were all higher (P < 0.1) than the amounts observed from untreated soil. Hg in the soil amended with the FGD material collected from a natural oxidation wet scrubber (i.e., SNO) was more readily released to air compared to the other two FGD materials collected from the synthetic gypsum dewatering vacuum belt (i.e., AFO-gypsum) and the waste water treatment plant (i.e., AFO-CPS) of a forced oxidation FGD system. No Hg was detected in the leachates collected during the only 3-hour, 1-inch rainfall event that occurred throughout the 4-week testing period. For every kilogram of FGD material applied to soil, AFO-CPS released the highest amount of Hg, B, and Se, followed by SNO, and AFO gypsum. Based on the same energy production rate, the land application of SNO FGD material from Plant S released higher amounts of Hg and B into ambient air and/or grass than the amounts released when AFO-gypsum from Plant A was used. Using FGD material with lower concentration levels of Hg and other elements of concern does not necessary post a lower environmental risk. In addition, this study demonstrates that considering only the amounts of trace elements uptake in surface vegetation may under estimate the overall release of the trace elements from FGD material-amended soils. It also shows, under the same soil amendment conditions, the mobility of trace elements varies when FGD materials produced from different processes are used.

  2. 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.

  3. 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

  4. 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

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. THz quartz-enhanced photoacoustic sensor for H₂S trace gas detection.

    PubMed

    Spagnolo, Vincenzo; Patimisco, Pietro; Pennetta, Riccardo; Sampaolo, Angelo; Scamarcio, Gaetano; Vitiello, Miriam S; Tittel, Frank K

    2015-03-23

    We report on a quartz-enhanced photoacoustic (QEPAS) gas sensing system for hydrogen sulphide (H₂S) detection. The system architecture is based on a custom quartz tuning fork (QTF) optoacoustic transducer with a novel geometry and a quantum cascade laser (QCL) emitting 1.1 mW at a frequency of 2.913 THz. The QTF operated on the first flexion resonance frequency of 2871 Hz, with a quality factor Q = 17,900 at 20 Torr. The tuning range of the available QCL allowed the excitation of a H₂S rotational absorption line with a line-strength as small as S = 1.13·10⁻²² cm/mol. The measured detection sensitivity is 30 ppm in 3 seconds and 13 ppm for a 30 seconds integration time, which corresponds to a minimum detectable absorption coefficient α(min) = 2.3·10⁻⁷ cm⁻¹ and a normalized noise-equivalent absorption NNEA = 4.4·10⁻¹⁰ W·cm⁻¹·Hz(-1/2), several times lower than the values previously reported for near-IR and mid-IR H₂S QEPAS sensors.

  11. A simple inexpensive gas phase chemiluminescence analyzer for measuring trace levels of arsenic in drinking water.

    PubMed

    Sengupta, Mrinal K; Hossain, Zafreen A; Ohira, Shin-Ichi; Dasgupta, Purnendu K

    2010-01-01

    An inexpensive sensitive gas-phase chemiluminescence (GPCL) based analyzer for arsenic is described; this device utilizes manual fluid dispensing operations to reduce size, weight and cost. The analyzer in its present form has a limit of detection (LOD, S/N = 3) of 1.0 microg/L total inorganic As (peak heightbased, 3 mL sample). The system was used to measure low level arsenic in tap water samples from Texas and New Mexico and compared with results obtained by inductively coupled plasma-mass spectrometry (ICP-MS) as well as those from an automated GPCL analyzer. Good correlations were observed. Higher levels of As (50-500 microg/L, As(III), As(V) and mixtures thereof) were spiked into local tap water; the recoveries ranged from 95 +/- 2% to 101 +/- 1%. A single instrument weighs less than 3 kg, consumes <25 W in power, can be incorporated in a briefcase and constructed for <$US $1000. It is easily usable in the field.

  12. 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

  13. Determination of the origin of urinary norandrosterone traces by gas chromatography combustion isotope ratio mass spectrometry.

    PubMed

    Hebestreit, Moritz; Flenker, Ulrich; Fusshöller, Gregor; Geyer, Hans; Güntner, Ute; Mareck, Ute; Piper, Thomas; Thevis, Mario; Ayotte, Christiane; Schänzer, Wilhelm

    2006-09-01

    On the one hand, 19-norandrosterone (NA) is the most abundant metabolite of the synthetic anabolic steroid 19-nortestosterone and related prohormones. On the other hand, small amounts are biosynthesized by pregnant women and further evidence exists for physiological origin of this compound. The World Anti-Doping Agency (WADA) formerly introduced threshold concentrations of 2 or 5 ng of NA per ml of urine to discriminate 19-nortestosterone abuse from biosynthetic origin. Recent findings showed however, that formation of NA resulting in concentrations in the range of the threshold levels might be due to demethylation of androsterone in urine, and the WADA 2006 Prohibited List has defined NA as endogenous steroid. To elucidate the endogenous or exogenous origin of NA, (13)C/(12)C-analysis is the method of choice since synthetic 19-nortestosterone is derived from C(3)-plants by partial synthesis and shows delta(13)C(VPDB)-values of around -28 per thousand. Endogenous steroids are less depleted in (13)C due to a dietary mixture of C(3)- and C(4)-plants. An extensive cleanup based on two high performance liquid chromatography cleanup steps was applied to quality control and doping control samples, which contained NA in concentrations down to 2 ng per ml of urine. (13)C/(12)C-ratios of NA, androsterone and etiocholanolone were measured by gas chromatography/combustion/isotope ratio mass spectrometry. By comparing delta(13)C(VPDB)-values of androsterone as endogenous reference compound with NA, the origin of NA in doping control samples was determined as either endogenous or exogenous.

  14. 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.

  15. 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.

  16. Automated chamber technique for gaseous flux measurements: Evaluation of a photoacoustic infrared spectrometer-trace gas analyzer

    NASA Astrophysics Data System (ADS)

    Yamulki, S.; Jarvis, S. C.

    1999-03-01

    Experiments were made in order to evaluate the accuracy and sensitivity of a photoacoustic infrared trace gas analyzer (TGA) in conjunction with an automatic opening and closing chamber system developed for near-continuous (2 min intervals) soil gaseous flux measurements. Humidity interference tests on N2O, CH4, and CO2 concentrations measured by the TGA were carried out, and the results showed a linear interference, with correction factors of 3 × 10-5x, 1.9 × 10-3x and 4.4 × 10-3x(x = H2O vapor ppm), respectively. CO2 interference on N2O and CH4 signals were also linear, with average correction factors of 2.8 × 10-4x and 6 × 10-5 x (x = CO2 ppm), respectively. Laboratory intercomparisons between the TGA and GC measurements of N2O and CH4 standards showed good agreement (R2 > 0.993), indicating the accuracy of the TGA for measurement of these gases at concentrations up to 100 and 40 ppm N2O and CH4, respectively. The relatively rapid measurement time for up to five gases simultaneously in 2 min, linearity, and ease of operation of the TGA represent major advantages compared to gas chromatography (GC). The automated chamber system provides a continuous measurement of fluxes with minimum disturbance to the soil environment enclosed by the chamber and provides the means, for example, of quantifying diurnal variability. In situ measurements of N2O-N and CH4-C fluxes with a sensitivity <10 g ha-1 d-1 (11.6 ng m-2 s-1), as well as of CO2 and water vapor (H2O), can be measured by the TGA when used with the automated system, and fluxes at background levels (i.e., from unfertilized soils) can be determined.

  17. 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.

  18. 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.

  19. 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

  20. Impact of the Asian monsoon on the extratropical lower stratosphere: trace gas observations during TACTS over Europe 2012

    NASA Astrophysics Data System (ADS)

    Müller, Stefan; Hoor, Peter; Bozem, Heiko; Gute, Ellen; Vogel, Bärbel; Zahn, Andreas; Bönisch, Harald; Keber, Timo; Krämer, Martina; Rolf, Christian; Riese, Martin; Schlager, Hans; Engel, Andreas

    2016-08-01

    The transport of air masses originating from the Asian monsoon anticyclone into the extratropical upper troposphere and lower stratosphere (Ex-UTLS) above potential temperatures Θ = 380 K was identified during the HALO aircraft mission TACTS in August and September 2012. In situ measurements of CO, O3 and N2O during TACTS flight 2 on 30 August 2012 show the irreversible mixing of aged stratospheric air masses with younger (recently transported from the troposphere) ones within the Ex-UTLS. Backward trajectories calculated with the trajectory module of CLaMS indicate that these tropospherically affected air masses originate from the Asian monsoon anticyclone. These air masses are subsequently transported above potential temperatures Θ = 380 K from the monsoon circulation region into the Ex-UTLS, where they subsequently mix with stratospheric air masses. The overall trace gas distribution measured during TACTS shows that this transport pathway had affected the chemical composition of the Ex-UTLS during boreal summer and autumn 2012. This leads to an intensification of the tropospheric influence on the extratropical lower stratosphere with PV > 8 pvu within 3 weeks during the TACTS mission. During the same time period a weakening of the tropospheric influence on the lowermost stratosphere (LMS) is determined. The study shows that the transport of air masses originating from the Asian summer monsoon region within the lower stratosphere affects the change in the chemical composition of the Ex-UTLS over Europe and thus contributes to the flushing of the LMS during summer 2012.

  1. 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

  2. Trace gas constraints on vertical transport in models: a case study of Indonesian biomass burning emissions in 2006

    NASA Astrophysics Data System (ADS)

    Field, R. D.; Luo, M.; Worden, J.; Kim, D.; Del Genio, A. D.; Voulgarakis, A.

    2014-12-01

    We investigate the use of joint Aura TES and MLS CO retrievals in constraining vertical transport in the NASA GISS ModelE2 composition-climate model. We examine September to November 2006 over the tropics. El Nino-induced dry conditions over western Indonesia led to extensive biomass burning and persistent CO greater than 200 ppb in the upper troposphere. This was one of the highest CO episodes over the MLS period since 2004. We show how improvements in the vertical resolution of trace gas retrievals can help to distinguish between errors in parameterized vertical transport and biases in bottom-up emissions estimates. We simulate the episode using the NASA GISS ModelE2 coupled composition-climate model with different subgrid physics for small ensembles of experiments with perturbed initial conditions. The starting point is the CMIP5 version of the model, in which there was a pronounced vertical CO dipole over the Maritime Continent, but with a CO peak 100 ppb higher than Aura CO in the upper troposphere. With modified cumulus and boundary layer parameterizations, but the same prescribed biomass burning emissions estimates, the upper tropospheric CO bias is significantly reduced. Concurrently, precipitation over the emissions source region is reduced relative to observational estimates, leading to better consistency with the dry conditions under which the burning occurred. We discuss the effects of the physics changes on the roles of convective frequency and depth in reducing the bias.

  3. 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.

  4. Design and application of a mobile ground-based observatory for continuous measurements of atmospheric trace gas and criteria pollutant species

    NASA Astrophysics Data System (ADS)

    Bush, S. E.; Hopkins, F. M.; Randerson, J. T.; Lai, C.-T.; Ehleringer, J. R.

    2015-08-01

    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, 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.

  5. Design and application of a mobile ground-based observatory for continuous measurements of atmospheric trace-gas and criteria pollutant species

    NASA Astrophysics Data System (ADS)

    Bush, S. E.; Hopkins, F. M.; Randerson, J. T.; Lai, C.-T.; Ehleringer, J. R.

    2015-01-01

    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, 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.

  6. Design and application of a mobile ground-based observatory for continuous measurements of atmospheric trace-gas and criteria pollutant species

    DOE PAGES

    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

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. Study of solvent sublation for concentration of trace phthalate esters in plastic beverage packaging and analysis by gas chromatography-mass spectrometry.

    PubMed

    Chang, Lin; Bi, Pengyu; Li, Xiaochen; Wei, Yun

    2015-06-15

    A novel trace analytical method based on solvent sublation (SS) and gas chromatography-mass spectrometry (GC-MS) was developed for the trace determination of twenty-two phthalate esters (PAEs) from plastic beverage packaging. In the solvent sublation section, the effects of solution pH, NaCl concentration, nitrogen flow rate, and sublation time on the sublation efficiency were investigated in detail, and the optimal conditions were obtained. The trace PAEs migrated from plastic beverage packaging to food simulants were separated and concentrated by solvent sublation, and then the trace target compounds in the concentrated solution were analyzed by GC-MS. According to the European Union Regulation, the food simulants including distilled water for the normal beverages and acetic acid solution (3%) for the acetic beverage of yogurt were prepared for migration tests. The trace analysis method showed good linearity, low limits of detection (LODs) of 1.6-183.5 ng/L, and satisfied recoveries (67.3-113.7%). PMID:25660867

  15. Multicomponent Trace-Gas Analysis by Three Intracavity Photoacoustic Cells in a CO Laser: Observation of Anaerobic and Postanaerobic Emission of Acetaldehyde and Ethanol in Cherry Tomatoes

    NASA Astrophysics Data System (ADS)

    Bijnen, Frans G. C.; Zuckermann, Hanna; Harren, Frans J. M.; Reuss, Jörg

    1998-05-01

    Three serial photoacoustic cells are employed within the cavity of a liquid-nitrogen-cooled CO laser to monitor on-line trace-gas concentrations. Multicomponent gas analysis is performed on sequential repetitive measurements of ethylene, acetaldehyde, CO 2 , ethanol, and H 2 O. To demonstrate the high sensitivity of the laser photoacoustic detector for the biologically interesting gases, acetaldehyde (0.1-parts per billion in volume detection limit) and ethanol (10 parts per billion in volume), we follow the time-dependent release by cherry tomatoes during changing aerobic anaerobic conditions.

  16. 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.

  17. 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.

  18. NITROGEN OXIDE TRACE GAS TRANSPORT AND TRANSFORMATION: I. EVALUATION OF DATA FROM INTACT SOIL CORES. (R825433)

    EPA Science Inventory

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

  19. 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

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. Design and application of a mobile ground-based observatory for continuous measurements of atmospheric trace gas and criteria pollutant species

    DOE PAGES

    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

  6. 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

  7. 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

  8. Intercontinental transport of pollution from North America to Europe: Airborne trace gas measurements over Central and Northern Europe during CONTRACE

    NASA Astrophysics Data System (ADS)

    Huntrieser, H.; Schlager, H.; Heland, J.; Forster, C.; Stohl, A.; Lawrence, M.; Arnold, F.; Aufmhoff, H.; Cooper, O.

    2003-04-01

    The CONTRACE project investigates the uplift of pollution in frontal systems (warm conveyor belts) over North America and the transport of these air masses to Europe. The first airborne field experiment was carried out from Southern Germany in fall 2001. The DLR research aircraft Falcon was equipped with a complex instrumentation to measure NO, NOy, CO, CO2, O3, J(NO2), acetone, SO2, ions, H2O2, formaldehyde, NMHC, J(O1D) and particles. An extensive set of chemical and meteorological forecast products, including trajectory calculations, was developed and used in combination with satellite images to plan the flights. A passive tracer for surface emissions (CO) was included in the forecast models to separate the regional and intercontinental transport of polluted air masses. For the first time it succeeded to guide the Falcon aircraft into pollution plumes transported all the way from North America (NA). On 22nd November a complex chemical weather situation was predicted for Central Europe with lifting of European emissions into the lower troposphere ahead of an approaching cold front and simultaneously, the advection of a pollution plume from Eastern NA in mid tropospheric layers. Similar CO mixing ratios were observed in both plumes making it difficult to distinguish the two plumes without additional trace gas information. The European pollution plume was characterized by large enhancements in the CO (150 ppbv) and NOy (6 ppbv) mixing ratios. The NOy/CO ratio was 0.135 (typical value for fresh emissions). In comparison the estimated NOy/CO ratio for the NA pollution plume was 0.010 which indicate a tracer age of 4 days. The observed CO and NOy mixing ratios in this plume were 160 ppbv and 1 ppbv. The two plumes were also characterized by very different O3/CO relationships. In the plume from NA a positive O3/CO slope was observed indicating photochemical ozone production (O3 mixing ratios up to 50 ppbv were observed). Most likely O3 was produced photochemically in

  9. 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).

  10. Synthesis of Trace Gas and Aerosol Observations and Evaluation of Modelled Short-lived Climate Pollutants Across the Pan-Eurasian High Latitudes

    NASA Astrophysics Data System (ADS)

    Arnold, S.; Nieminen, T.

    2015-12-01

    Model calculations suggest that changes in short-lived climate pollutants (SLCPs) such as ozone and aerosol may have contributed significantly to rapid Arctic warming over the past century. Arctic tropospheric budgets of SLCPs are impacted by long-range transport of trace gases and aerosols from Europe, Asia and N. America, but also by local sources such as gas flaring, shipping and boreal fires. Recently, the POLARCAT Model Intercomparison Project (POLMIP) showed that significant model biases persist through the depth of the European and North American high latitude troposphere in modelled trace-gas abundances. Evaluation of models over the Siberian high latitudes is challenging due to a severe paucity of available observations, despite the potential importance of this region as a route for European pollution export to the Arctic. Despite the existence of a number of limited datasets, which could be used for model evaluation in this region, until now no effort has been made to synthesise and exploit these observations to evaluate modelled abundances of SLCPs such as tropospheric ozone & aerosol. In this presentation, we will show evaluation of simulated aerosol, tropospheric ozone, and precursor species in several global chemical transport models, using a synthesis of available surface, aircraft and satellite observations over the high latitude pan-Eurasian region. We use models and observations to investigate source regions contributing to remote Siberian SLCP abundances over the annual cycle, and show substantial biases in simulated aerosol and trace gas concentrations that are consistent across a suite of different models. These comparisons constitute the first multi-model evaluation of tropospheric composition in the pan-Eurasin region using observations from across the broad region. Finally, we use the model simulations to determine optimum locations for the development of future monitoring activities in high latitude Eurasia with an aim of better

  11. 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.

  12. SINBAD electronic models of the interface and control system for the NOMAD spectrometer on board of ESA ExoMars Trace Gas Orbiter mission

    NASA Astrophysics Data System (ADS)

    Jerónimo Zafra, José M.; Sanz Mesa, Rosario; Gómez López, Juan M.; Rodríguez Gómez, Julio F.; Aparicio del Moral, Beatriz; Morales Muñoz, Rafael; Candini, Gian Paolo; Pastor Morales, M. Carmen; Robles Muñoz, Nicolás.; López-Moreno, José Juan; Vandaele, Ann Carine; Neefs, Eddy; Drummond, Rachel; Delanoye, Sofie; Berkenbosch, Sophie; Clairquin, Roland; Ristic, Bojan; Maes, Jeroen; Bonnewijn, Sabrina; Patel, Manish R.; Leese, Mark

    2016-07-01

    NOMAD is a spectrometer suite: UV-visible-IR spectral ranges. NOMAD is part of the payload of ESA ExoMars Trace Gas Orbiter Mission. SINBAD boards are in charge of the communication and management of the power and control between the spacecraft and the instrument channels. SINBAD development took four years, while the entire development and test required five years, a very short time to develop an instrument devoted to a space mission. The hardware of SINBAD is shown in the attached poster: developed boards, prototype boards and final models. The models were delivered to the ESA in order to testing and integration with the spacecraft.

  13. 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.

  14. 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

  15. 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%.

  16. Improved atmospheric trace gas measurements with an aircraft-based tandem mass spectrometer: Ion identification by mass-selected fragmentation studies

    NASA Astrophysics Data System (ADS)

    Reiner, Thomas; MöHler, Ottmar; Arnold, Frank

    1998-12-01

    We have built and employed an aircraft-borne triple quadrupole mass spectrometer (TQMS) for fragmentation studies of mass-selected ions in the upper troposphere and lower stratosphere. The fragmentation studies included both ambient and artificially produced ions relevant for the measurement of atmospheric trace gases by ion molecule reaction mass spectrometry (IMRMS) and led to an unambiguous identification of the chemical composition of important ions used for IMRMS measurements. Among these are the product ions of ion molecule reactions of CO3-(H2O)n and H3O+(H2O)n ions with HNO3, SO2, acetone, HCN, and methyl cyanide. These reactions have been studied in the laboratory, and ions having the same masses as the expected product ions have been previously observed in atmospheric IMRMS spectra. The present fragmentation studies are the first to actually identify the chemical composition of these ions during aircraft measurements in the upper troposphere and lower stratosphere and demonstrate that these ions can reliably be used for atmospheric trace gas measurements. Furthermore, the fragmentation studies gave indications for the existence and the possible identification of previously unknown ions. Among these the tentative identification of CO3-H2O2 offers the possibility for sensitive measurements of H2O2 by IMRMS. The fragmentation studies were accompanied by IMRMS measurements of atmospheric trace gases using the TQMS. Altitude profiles of HNO3, SO2, and lower limits for H2O2 are shown.

  17. 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.

  18. 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)

  19. Aliphatic and polycyclic aromatic hydrocarbons and trace elements as indicators of contamination status near oil and gas platforms in the Sergipe-Alagoas Basin (Southwest Atlantic Ocean)

    NASA Astrophysics Data System (ADS)

    Lourenço, Rafael A.; Araujo Júnior, Marcus A. G.; Meireles Júnior, Ruy O.; Macena, Leandro F.; de A. Lima, Eleine Francioni; Carneiro, Maria Eulalia R.

    2013-12-01

    Oil and gas platforms from Sergipe-Alagoas Basin located in the northeastern region of Brazil do not discharge produced water. However, those platforms can be a potential source of contaminants to the marine environment due to their producing activities. In this study, sediment samples were collected in the vicinity of two offshore oil and gas platforms located in Sergipe-Alagoas Basin (PCM-9 and PGA-1) to evaluate the source and levels of hydrocarbons and trace elements (As, Fe, Al, Ti, Cu, Cd, Zn, Pb, Ni, Mn, Ba, V, Cr and Hg). Also, the potential impact of those platforms on the sediment quality was investigated. Polycyclic aromatic hydrocarbons diagnostic ratios observed in the sediment samples indicated hydrocarbons from pyrogenic source, specifically from biomass combustion. Trace elements As, Cd and Ba recorded concentrations higher than Threshold Effect Levels (TEL) in the sediment nearby the platforms. Also, there was evidence of some samples enriched by barium. Although As, Cd and Ba concentrations were higher than TEL, they most likely corresponded to background levels. The obtained results indicated that activities of the PCM-9 and PGA-1 platforms may not be affecting the quality of nearby sediment.

  20. Trace Gas Emissions and Soil C and N Transformations Following Moisture Pulses in Sagebrush: Effects of Invasive and Native Companion Plant Species

    NASA Astrophysics Data System (ADS)

    Norton, U.; Morgan, J. A.; Mosier, A. R.; Derner, J. D.

    2004-12-01

    Simulating water pulses is an important tool for understanding biogeochemical processes in semi arid environments. Global change triggered shifts in plant species composition exert significant control over belowground C and N transformations. They also affect the ecosystem resiliency and its ability to withstand exotic weed invasion. We monitored effects of water additions on trace gas emissions and soil C and N in sagebrush soils, both canopy and shrub interspace, on sites dominated by either native bunchgrass, western wheatgrass, or an exotic annual, cheatgrass. Our results indicate that long-term cheatgrass establishment affects not only soil under its own thatch, but also soil under shrubs within cheatgrass stand. Overall, soil total N and total organic C on cheatgrass sites were lower than these of western wheatgrass. Trace gas measurements of non-wetted soils showed greater N2O and smaller CH4 fluxes compared to western wheatgrass sites. Upon water pulse, cheatgrass soils demonstrated greater CO2 production rates, relative to pre-wet conditions, greater N2O flux per unit soil total N, and more rapid soil microbial biomass C and dissolved organic C response compared to western wheatgrass. Possible mechanisms include faster turnover of microbial biomass and greater nitrification potential of cheatgrass soils.

  1. Effects of Elevated CO2 on Soil Trace Gas (CH4, N2O and NO) Fluxes in a Scrub Oak Ecosystem at Kennedy Space Center, FL, USA

    NASA Astrophysics Data System (ADS)

    Hartley, A. E.; Bracho, R. G.; Stover, D.

    2008-05-01

    Rising atmospheric CO2 concentrations increase the plant demand for soil nutrients, which in turn can impose a nitrogen limitation on unmanaged ecosystems. The microbial responses to CO2 enrichment are complex and difficult to predict. Some studies suggest that CO2 enrichment increases microbial mineralization of nitrogen, making nitrogen more available through a carbon priming effect. Alternatively, microbes may contribute to nitrogen limitation through accelerated soil nitrogen losses. In this study, we examined the effects of CO2 enrichment on trace gases that are released or taken up during soil microbial reactions: nitrification, denitrification and methane consumption. Ambient and approximately twice-ambient CO2 treatments were applied to a coastal scrub oak community at Kennedy Space Center, FL, via open-top chambers since May 1996. The CO2 treatments ended in July 2007 before an aboveground harvest took place inside the chambers. Nitrous oxide (N2O), nitric oxide (NO) and methane (CH4) fluxes were measured in the field from 2006-2008. Soil N2O losses from the study site were low (< 1 ng N2O-N cm-2 h-1) with no CO2 treatment effect. Soil NO losses were similarly low (< 1 ng N2O-N cm-2 h-1), but fluxes were consistently lower in elevated CO2 than in ambient CO2. NO production was higher for 3 months post-harvest in ambient CO2. Methane consumption was lower in elevated vs. ambient CO2 in 2006, although this trend was not significant. Over a decade of CO2 enrichment has reduced soil nitrogen availability, which could explain the low overall rates of nitrogen trace gas emission. Reduced soil carbon stores in elevated CO2 measured at this site could also explain the lower nitrification rates, measured as NO efflux. Trace gas emissions in this sandy, nutrient-poor scrub oak forest are comparable to published rates in desert ecosystems.

  2. 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.

  3. 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).

  4. Orthogonal array optimization of microwave-assisted derivatization for determination of trace amphetamine and methamphetamine using negative chemical ionization gas chromatography-mass spectrometry.

    PubMed

    Chung, Li-Wen; Lin, Keh-Liang; Yang, Thomas Ching-Cherng; Lee, Maw-Rong

    2009-05-01

    An orthogonal array design (OAD) was applied to optimize microwave-assisted derivatization (MAD) for analysis of trace amphetamine (AM) and methamphetamine (MA) by negative chemical ionization gas chromatography-mass spectrometry (NCI GC-MS). The 2,3,4,5,6-pentafluorobenzoyl chloride (PFBC) was used as a derivatization reagent. Experimental factors including solvent, microwave power, and irradiation time at four-levels were studied in 16 trials by OAD(16) (4(4)). The significance of these factors was investigated using analysis of variance (ANOVA) and percent contribution (PC). Solvent is statistically demonstrated a chief factor; microwave power and irradiation time are secondary factors. Under the optimum condition, calibration curve of AM is linear over a range from 0.01 to 100 ng mL(-1) with correlation coefficient 0.9988, and MA from 0.1 to 1000 ng mL(-1) with correlation coefficient 0.9951. The limit of detection (LOD) is 1.20 pg mL(-1) for AM and 13.04 pg mL(-1) for MA. An applicability of the method was tested by analyzing urine samples from amphetamine-type stimulants (ATS)-abusing suspects. Consequently, the OAD method not only optimizes the MAD condition for determination of trace AM and MA, but identifies the effects of factor solvent, microwave power and irradiation time on the MAD performance.

  5. Mobile system for open-path trace gas detection in the mid-infrared using a Raman-shifted Cr:LiSAF source

    NASA Astrophysics Data System (ADS)

    Wamsley, Paula R.; Weimer, Carl S.; Applegate, Jeffrey T.; Beaton, Stuart P.; Beyer, Brian S.

    1999-10-01

    Many trace atmospheric gas constituents have optical absorption bands in the 2 - 5 micrometers atmospheric transmission window. Remote sensing of these compounds is possible with an appropriate laser source. We use stimulated Raman scattering in hydrogen to shift pulsed, Cr:LiSAF laser emission from the near infrared to this mid-infrared band. Injection seeding the oscillator with a spectrally narrow, low-power diode laser produces a tunable, spectroscopic grade source. We have combined this laser source with transmitting and receiving optics in order to make double- ended, long-path DIAL measurements. For example, we are able to detect ambient levels of water and methane and trace levels of ethane over a two mile, round-trip path. Spectral control is critical for making these measurements for several reasons. First, the DIAL technique requires a spectrally narrow source to tune across the narrow absorption bands of molecules with absorption features in the 2 - 5 micrometers band. Second, good spectral control allows species-specific detection when there are target species with closely spaced absorption features. Third, strong water vapor and CO2 absorption bands are common throughout the 2 - 5 micrometers band causing large fluctuations in the background transmission. Good spectral control enables species specific detection within this highly variable transmission background.

  6. 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.

  7. Simple field-based automated dispersive liquid-liquid microextraction of trace level phthalate esters in natural waters with gas chromatography and mass spectrometric analysis.

    PubMed

    Leng, Geng; Chen, Wenjin; Wang, Yong

    2016-09-01

    A small, simple, and field-based automated dispersive liquid-liquid microextraction method followed by gas chromatography mass spectrometric analysis was developed for trace level phthalate esters analysis in natural waters. With a single syringe pump that is coupled with a multiposition valve, the whole extraction procedure including cleaning, sampling, mixing of extractant and disperser solvents, extraction, phase separation, and analytes collection was carried out in a totally automated way with a sample throughput of 21 h(-1) . Key factors, such as type and ratio of the extractant and disperser solvent, aspiration flow rate, extraction time, and matrix effect, were thoroughly investigated. Under the optimum conditions, linearity was found in the range from 0.03 to 60 μg/L. Limits of detection ranged from 0.0015 to 0.003 μg/L. Enrichment factors were in a range of 106-141. Reproducibility and recoveries were assessed by testing a series of three natural water samples that were spiked with different concentration levels. Finally, the proposed method was successfully applied in analysis of real surface waters. The developed system is inexpensive, light (2.6 kg), simple to use, applicable in the field, with high sample throughput, and sensitive enough for trace level phthalate esters analysis in natural waters. PMID:27377176

  8. Simple field-based automated dispersive liquid-liquid microextraction of trace level phthalate esters in natural waters with gas chromatography and mass spectrometric analysis.

    PubMed

    Leng, Geng; Chen, Wenjin; Wang, Yong

    2016-09-01

    A small, simple, and field-based automated dispersive liquid-liquid microextraction method followed by gas chromatography mass spectrometric analysis was developed for trace level phthalate esters analysis in natural waters. With a single syringe pump that is coupled with a multiposition valve, the whole extraction procedure including cleaning, sampling, mixing of extractant and disperser solvents, extraction, phase separation, and analytes collection was carried out in a totally automated way with a sample throughput of 21 h(-1) . Key factors, such as type and ratio of the extractant and disperser solvent, aspiration flow rate, extraction time, and matrix effect, were thoroughly investigated. Under the optimum conditions, linearity was found in the range from 0.03 to 60 μg/L. Limits of detection ranged from 0.0015 to 0.003 μg/L. Enrichment factors were in a range of 106-141. Reproducibility and recoveries were assessed by testing a series of three natural water samples that were spiked with different concentration levels. Finally, the proposed method was successfully applied in analysis of real surface waters. The developed system is inexpensive, light (2.6 kg), simple to use, applicable in the field, with high sample throughput, and sensitive enough for trace level phthalate esters analysis in natural waters.

  9. 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.

  10. Seasonal Variations In Titan’s Stratosphere Observed With Cassini/CIRS: Temperature, Trace Molecular Gas And Aerosol Mixing Ratio Profiles

    NASA Astrophysics Data System (ADS)

    Vinatier, Sandrine; Bézard, B.; Anderson, C.; Teanby, N.; de Kok, R.; Actherberg, R.; Coustenis, A.; CIRS Team

    2012-10-01

    Titan's northern spring equinox occurred in August 2009. General Circulation Models 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. 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, 2011 and 2012 that we used to monitor the seasonal evolution of the vertical profiles of temperature, molecular (C2H2, C2H6, HCN, ...) and aerosol abundances.

  11. 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.

  12. 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.

  13. 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.

  14. 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...

  15. 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 ...

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Psychological Abstracts/BRS.

    ERIC Educational Resources Information Center

    Dolan, Donna R.

    1978-01-01

    Discusses particular problems and possible solutions in searching the Psychological Abstracts database, with special reference to its loading on BRS. Included are examples of typical searches, citations (with or without abstract/annotation), a tabulated searchguide to Psychological Abstracts on BRS and specifications for the database. (Author/JD)

  2. 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…

  3. 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.

  4. 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

  5. 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.

  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. 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.

  8. 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.

  9. 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.

  10. 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).

  11. 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

  12. 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.

  13. Continental-Scale Trace Gas Measurements During COBRA and the Case for Airborne Flask Measurements in the NACP

    NASA Astrophysics Data System (ADS)

    Miller, J. B.; Stephens, B. B.; Bakwin, P.; Tans, P. P.; Gerbig, C.; Lin, J.; Wofsy, S.; Andrews, A.; Daube, B.

    2002-12-01

    Intensive airborne sampling of trace gases is envisioned as a major component of the planned North American Carbon Program (NACP). During August 2000 we sampled air between the surface and 10,000 m in the eastern two thirds of the conterminous United States as part of the CO2 Budget and Rectification-Airborne (COBRA) study. Our experience from COBRA can help inform our airborne sampling strategy for the NACP. In COBRA, CO2 and CO were measured in situ by continuous instrumentation, and CO2, CO, CH4, N2O, H2, SF6 and δ13CO2 were measured in the laboratory. Although the data density of the continuous measurements is much higher than that of the flask-based ones, flasks samples are an important complement to the in situ. Laboratory measurements of CO2 and CO provide quality control, while high precision measurements of CH4, δ13CO2 and other species cannot be made in situ. Significant vertical gradients were observed for all species as a result of emissions from biogenic, fossil-fuel related and biomass burning sources. Simultaneously measuring multiple species can help isolate the biogenic component from this mix. For example, if we know emission ratios, measurements of CO and SF6 can be used to identify the fossil fuel and biomass burning contributions to observed CO2. Measurements indicate substantial surface sources of both CH4 and N2O, and a surface sink for H2, in different parts of the United States. As is the case for CO2, the magnitudes and signs of the fluxes are geographically variable. When combined, the vertical gradients CO2 and δ13C can be related to the extent of isotopic discrimination that takes place during plant photosynthesis. This, in turn, is related to plant type and metabolism. Within the data assimilation context of the NACP, measurements of these biologically mediated trace gases will add information on the functioning of the biosphere and thus help to constrain estimates of CO2 fluxes. How much information is lost by taking flask samples

  14. Development and Validation of a Gas Chromatography Method for the Trace Level Determination of Allylamine in Sevelamer Hydrochloride and Sevelamer Carbonate Drug Substances

    PubMed Central

    Kadiyala, Raju V. S. N.; Kothapalli, Pavan Kumar S. R.; Peddolla, Madhava Reddy; Rajput, Pradeep; Sharma, Hemant Kumar; Budeti, Shankar Reddy; Gandham, Himabindu; Nowduri, Annapurna

    2014-01-01

    A capillary gas chromatography method using a flame ionization detector has been developed for the trace analysis of allylamine (AA) in sevelamer hydrochloride (SVH) and sevelamer carbonate (SVC) drug substances. The method utilized a mega bore capillary column DB-CAM (30 m × 0.53 mm × 1.0 μm) with a bonded and cross-linked, base-deactivated polyethylene glycol stationary phase and was validated for specificity, sensitivity, precision, linearity, and accuracy. The detection and quantitation limits obtained for allylamine were 2 μg/g and 6 μg/g, respectively. The method was found to be linear in the range between 6 μg/g and 148 μg/g with a correlation coefficient of 0.9990. The average recoveries obtained in SVH and SVC were 93.9% and 99.1%, respectively. The developed method was found to be robust for the determination of AA in sevelamer drug substances and also the specificity was demonstrated with a gas chromatograph coupled with a mass spectrometer. PMID:24634846

  15. On-line trace-level enrichment gas chromatography of triazine herbicides, organophosphorus pesticides, and organosulfur compounds from drinking and surface waters.

    PubMed

    Pico, Y; Louter, A J; Vreuls, J J; Brinkman, U A

    1994-09-01

    A simple, selective and precise procedure for the analysis of water samples by on-line solid phase extraction gas chromatography (SPE-GC) is presented. The determination of several triazines, organophosphorus pesticides, sulfur containing compounds in tap water was performed by SPE-GC using polymer-packed precolumns and flame ionization (FID), nitrogen-phosphorus (NPD) or flame photometric (FPD) detection. A cartridge packed with silica was inserted between the precolumn and the gas chromatograph in order to eliminate trace amounts of water present in the ethyl acetate used as desorption solvent. Incorporation of a drying step allowed the retention gap to be used for the analysis of ca. 100 samples without significant deterioration of the chromatographic peaks. Analyte recovery was at least 72% when 10 ml of tap-water sample were analysed. The detection limits for all analytes in tap water were lower than 0.1 microgram l-1, with all detectors used. Although with NPD and FPD, selectivity and sensitivity were markedly better. The SPE-GC-NPD system has also been used for the analysis of surface-water samples from different European rivers. PMID:7978329

  16. 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.

  17. 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

  18. 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.

  19. Biogeochemical trace gas and oxygen concentration signatures from the West African upwelling areas as observed at the Cape Verde Atmospheric Observatory (CVAO)

    NASA Astrophysics Data System (ADS)

    Kozlova, E.; Fiedler, B.; Leppert, R.; Seifert, T.; Neves, L.; Heimann, M.

    2011-12-01

    We present 3-year records of atmospheric concentrations of trace gases (CO2, CH4, CO, N2O, and SF6), and oxygen at the Cape Verde Atmospheric Observatory (CVAO). The Observatory is located on Sao Vicente Island in the north-eastern subtropical Atlantic (16.86° N, 24.87° W), and was first established within the frame of the Surface Ocean Lower Atmosphere project (SOLAS). The air is sampled from a 30-m tower. The analytical system is automated and samples air continuously (16 min for every O2 and CO2 measurement and 12 min for the rest of the species (Kozlova and Manning, 2009)). In addition, air flask samples are collected biweekly and subsequently analyzed at the Max-Planck Institute for Biogeochemistry. The Cape Verde Atmospheric Observatory is located in the North Atlantic trade wind system. We analyse the composition of marine boundary layer air masses that often have passed over the coastal upwelling areas off the coast of Western Sahara and Mauritania. These upwelling waters are supersaturated in CO2, CH4, and partly in N2O, and undersaturated in oxygen. Small shifts in the wind trajectories are reflected in synoptic variations of the atmospheric concentrations depending on the travel time of the air mass over the upwelling region. Using a footprint analysis with an atmospheric backtrajectory model, we analyse and quantify the integrated contribution of surface ocean gas exchange from these areas. We can place bounds on the gas exchange coefficient in the upwelling area by combining the flux estimates with in situ measurements of dissolved surface ocean oxygen from autonomous gliders (taken as part of the SOPRAN project) and remotely sensed ocean chlorophyll data (ocean color). The location of the Observatory provides a unique opportunity for monitoring long-term changes in spatially integrated marine productivity and oxygen depletion in the upwelling area of the West African Coast. Kozlova, E. A., and A. C. Manning, Methodology and calibration for

  20. 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

  1. 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.

  2. 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.

  3. TRACING THE PECULIAR DARK MATTER STRUCTURE IN THE GALAXY CLUSTER Cl 0024+17 WITH INTRACLUSTER STARS AND GAS

    SciTech Connect

    Jee, M. J.

    2010-07-01

    Intracluster light (ICL) is believed to originate from the stars stripped from cluster galaxies. They are no longer gravitationally bound to individual galaxies, but to the cluster, and their smooth distribution potentially makes them serve as much denser tracers of the cluster dark matter than the sparsely distributed cluster galaxies. We present our study of the ICL in the galaxy cluster Cl 0024+17 using both Advanced Camera for Surveys (ACS) and Subaru data, where we previously reported the discovery of a ring-like dark matter structure with gravitational lensing. The ACS images provide much lower sky levels than ground-based data, and enable us to measure relative variation of surface brightness reliably. This analysis is repeated with the Subaru images to examine if consistent features are recovered despite a different reduction scheme and different instrumental characteristics. We find that the ICL profile clearly resembles the peculiar mass profile, which stops decreasing at r {approx} 50'' ({approx}265 kpc) and slowly increases until it turns over at r {approx} 75'' ({approx}397 kpc). This feature is seen in both ACS and Subaru images for nearly all available passband images while the features are in general stronger in red filters. The consistency across different filters and instruments strongly rules out the possibility that the feature might come from any residual, uncorrected calibration errors. In addition, our re-analysis of the cluster X-ray data shows that the peculiar mass structure is also indicated by a non-negligible (3.7{sigma} in Chandra and 2.4{sigma} in XMM-Newton) bump in the intracluster gas profile when the geometric center of the dark matter ring, not the peak of the X-ray emission, is chosen as the center of the radial bin. The location of the gas ring is closer to the center by {approx}15'' ({approx}80 kpc), raising an interesting possibility that the ring-like structure is expanding and the gas ring is lagging behind perhaps because

  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. Comparison of GC/time-of-flight MS with GC/quadrupole MS for halocarbon trace gas analysis

    NASA Astrophysics Data System (ADS)

    Hoker, J.; Obersteiner, F.; Bonisch, H.; Engel, A.

    2015-05-01

    We present the application of time-of-flight mass spectrometry (TOF MS) for the analysis of halocarbons in the atmosphere after cryogenic sample preconcentration and gas chromatographic separation. For the described field of application, the quadrupole mass spectrometer (QP MS) is a state-of-the-art detector. This work aims at comparing two commercially available instruments, a QP MS and a TOF MS, with respect to mass resolution, mass accuracy, stability of the mass axis and instrument sensitivity, detector sensitivity, measurement precision and detector linearity. Both mass spectrometers are operated on the same gas chromatographic system by splitting the column effluent to both detectors. The QP MS had to be operated in optimised single ion monitoring (SIM) mode to achieve a sensitivity which could compete with the TOF MS. The TOF MS provided full mass range information in any acquired mass spectrum without losing sensitivity. Whilst the QP MS showed the performance already achieved in earlier tests, the sensitivity of the TOF MS was on average higher than that of the QP MS in the "operational" SIM mode by a factor of up to 3, reaching detection limits of less than 0.2 pg. Measurement precision determined for the whole analytical system was up to 0.2% depending on substance and sampled volume. The TOF MS instrument used for this study displayed significant non-linearities of up to 10% for two-thirds of all analysed substances.

  6. Noble Gas Tracing of Subsurface CO2 Origin and the Role of Groundwater as a CO2 Sink

    NASA Astrophysics Data System (ADS)

    Zhou, Z.; Ballentine, C. J.; Schoell, M.; Stevens, S. H.

    2003-12-01

    The source, generation, migration and accumulation of CO2 gas associated either alone or with hydrocarbons are unclear and therefore hard to predict. So far, noble gases provide one of the best tools to resolve this question, because they are conservative within the subsurface system. The atmosphere-derived noble gases dissolved in groundwater do not react with the rock system, while noble gases produced in the rock phase by radioactive decay or input from magmatic source are isotopically distinct and can be resolved from the dissolved air-derived noble gases. 10 samples were taken from a CO2-rich natural gas reservoir in Jackson Dome, Mississippi, USA to investigate its origin and extent of interaction with the groundwater system. The area lies within the Mississippi Interior Salt Basin. It is bounded on the north by the Pickens-Gilbertown fault system, the updip limit of the Jurassic Louann Salt unit, and on the south by basement highs of the Wiggins, South Mississippi, and Lasalle uplifts. We present compositional, stable isotope and noble gas results of Jackson Dome samples. Gas composition is 98.75-99.38% CO2, with small amounts of methane and nitrogen. CO2 content increases linearly with the decrease of CH4. d13C(CO2) in all samples ranges between -3.55 and -2.57 per mil, increasing with the increase of the CO2 content. Atmosphere-derived He contributions are negligible in all cases. 3He/4He ratios are between 4.27 and 5.01Ra, indicating a strong mantle signature. Crustal 4He in these samples therefore accounts for between 7.0% and 20.8%, the remainder being magmatic in origin. 40Ar/36Ar ratios are all above air ratio, ranging between 4071 and 6420. Air corrected 40Ar* vary between 92.7 and 95.4%, to give 4He/40Ar* ratios of between 1.26 and 2.52. This range is comparable with values estimated for the upper mantle. CO2/3He values are between 1.09E+9 and 4.62E+9, and also fall in the mantle range, indicating that the CO2 gas in Jackson Dome is also

  7. 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.

  8. 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.

  9. 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.

  10. [Mid-infrared distributed-feedback quantum cascade laser-based photoacoustic detection of trace methane gas].

    PubMed

    Tan, Song; Liu, Wan-feng; Wang, Li-jun; Zhang, Jin-chuan; Li, Lu; Liu, Jun-qi; Liu, Feng-qi; Wang, Zhan-guo

    2012-05-01

    There have been considerable interests in methane detection based on infrared absorption spectroscopy for industrial and environment monitoring. The authors report on the realization of photoacoustic detection of methane (CH4) using mid-infrared distributed-feedback quantum cascade laser (DFB-QCL). The absorption line at 1316.83 cm(-1) was selected for CH4 detection, which can be reached by the self-manufactured DFB-QCL source operating in pulsed mode near 7.6 microm at room-temperature. The CH4 gas is filled to a Helmholtz resonant photoacoustic cell, which was equipped with a commercial electret microphone. The DFB-QCL was operated at 234 Hz with an 80 mW optical peak power. A detection limit of 189 parts per billion in volume was derived when the signal-to-noise ratio equaled 1. PMID:22827065

  11. [Mid-infrared distributed-feedback quantum cascade laser-based photoacoustic detection of trace methane gas].

    PubMed

    Tan, Song; Liu, Wan-feng; Wang, Li-jun; Zhang, Jin-chuan; Li, Lu; Liu, Jun-qi; Liu, Feng-qi; Wang, Zhan-guo

    2012-05-01

    There have been considerable interests in methane detection based on infrared absorption spectroscopy for industrial and environment monitoring. The authors report on the realization of photoacoustic detection of methane (CH4) using mid-infrared distributed-feedback quantum cascade laser (DFB-QCL). The absorption line at 1316.83 cm(-1) was selected for CH4 detection, which can be reached by the self-manufactured DFB-QCL source operating in pulsed mode near 7.6 microm at room-temperature. The CH4 gas is filled to a Helmholtz resonant photoacoustic cell, which was equipped with a commercial electret microphone. The DFB-QCL was operated at 234 Hz with an 80 mW optical peak power. A detection limit of 189 parts per billion in volume was derived when the signal-to-noise ratio equaled 1.

  12. 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.

  13. 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.

  14. 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.

  15. Using the NAME Lagrangian Particle Dispersion model, and aircraft measurements to assess the accuracy of trace gas emission inventories from the U.K.

    NASA Astrophysics Data System (ADS)

    O'Sullivan, D. A.; Harrison, M.; Ploson, D.; Oram, D.; Reeves, C.

    2007-12-01

    A top-down approach using a combination of aircraft data and atmospheric dispersion modelling has been used to estimate emissions for 24 halogenated trace gases from the United Kingdom. This has been done using data collected during AMPEP/FLUXEX, a U.K based measurement campaign which took place between April and September 2005. The primary objective relating to this work was to make direct airborne measurements of concentration enhancements within the boundary layer arising from anthropogenic pollution events, and then to use mass balance methods to determine an emission flux. This was done by analysing Whole Air Samples (WAS) collected in the boundary layer upwind and downwind of the UK at frequent intervals around the coast using the technique of gas chromatography mass spectrometry (GCMS). Emissions were then calculated using a simple box-model approach and also using NAME (Numerical Atmospheric-dispersion Modelling Environment) which is a Lagrangian particle model using 3 hourly 3D meteorology fields from the Met Office Unified Model. By using such an approach it is also possible to identify the most likely main source regions in the UK for the compounds measured. Among the trace gases studied are many which through their effects on stratospheric ozone, and their large radiative forcing have a direct impact on global climate such as CFC's 11, 12, 113 and 114, HCFC's 21, 22, 141b and 142b, HFC's 134a and 152a, methyl chloroform, methyl bromide and carbon tetrachloride. Also the emissions of some short lived gases with have direct effects on human health, such as tetrachloroethene, and trichloroethene, have been derived. The UK emissions estimates calculated from this experimental and modelling work are compared with bottom-up and other top-down emission inventories for the UK and Europe. It was found that the estimates from this study were often higher than those in bottom-up emission inventories derived from industry. In addition for a number of trace gases

  16. 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

  17. 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…

  18. 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…

  19. 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…

  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. 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…

  2. Concept Formation and Abstraction.

    ERIC Educational Resources Information Center

    Lunzer, Eric A.

    1979-01-01

    This paper examines the nature of concepts and conceptual processes and the manner of their formation. It argues that a process of successive abstraction and systematization is central to the evolution of conceptual structures. Classificatory processes are discussed and three levels of abstraction outlined. (Author/SJL)

  3. Data Abstraction in GLISP.

    ERIC Educational Resources Information Center

    Novak, Gordon S., Jr.

    GLISP is a high-level computer language (based on Lisp and including Lisp as a sublanguage) which is compiled into Lisp. GLISP programs are compiled relative to a knowledge base of object descriptions, a form of abstract datatypes. A primary goal of the use of abstract datatypes in GLISP is to allow program code to be written in terms of objects,…

  4. 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…

  5. 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.

  6. 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

  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. 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.

  9. 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

  10. 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

  11. Trace analysis of trichlorobenzenes in fish by microwave-assisted extraction and gas chromatography-electron-capture detection.

    PubMed

    Wittmann, Gyula; Huybrechts, Tom; Van Langenhove, Herman; Dewulf, Jo; Nollet, Hendrik

    2003-04-18

    An analytical method consisting of extraction, clean-up, and analysis by gas chromatography-electron-capture detection (GC-ECD) was developed for the determination of trichlorobenzenes (TCBs) in fish samples. Two extraction methods, saponification and liquid-liquid extraction (S-LLE), and microwave-assisted extraction (MAE), were evaluated. In both cases, n-pentane was used as the extraction solvent. For S-LLE, the recoveries ranged from 66.6+/-9.1% for 1-bromo-4-chlorobenzene (4-BCB) to 93.5+/-4.9% for 1,2,4-trichlorobenzene (1,2,4-TCB). The recoveries were significantly lower, between 31.0+/-3.9% for 1,2,3-trichlorobenzene (1,2,3-TCB) and 52.3+/-3.0% for 1,3,5-trichlorobenzene (1,3,5-TCB), in the absence of fish. Proteins and glycerides of the fish tissue seemed to compete with TCBs for the base, and hence decreased their decomposition rate. In the case of MAE, the recoveries were highly dependent on the pressure applied during extraction. At 5 bar, much higher recoveries were obtained, from 66.7+/-15.6% for 4-BCB to 79.9+/-13.6% for 1,2,4-TCB, than at 1 bar. Sulfur formation was, however, observed at 5 bar, and interfered with the GC-ECD analysis of TCBs. Sulfur was adequately removed by copper powder treatment, which was shown not to affect the recovery of analytes. The recoveries of target analytes by S-LLE and MAE did not differ statistically (t-test, alpha = 0.01). Both methods were appropriate for the detection of TCBs at concentration levels typically observed in marine biota, i.e. approximately 1 ng/g. S-LLE was, however, more time consuming, and required larger volumes of high-purity organic solvents than MAE.

  12. Ultra-trace level analysis of morpholine, cyclohexylamine, and diethylaminoethanol in steam condensate by gas chromatography with multi-mode inlet, and flame ionization detection.

    PubMed

    Luong, J; Shellie, R A; Cortes, H; Gras, R; Hayward, T

    2012-03-16

    Steam condensate water treatment is a vital and integral part of the overall cooling water treatment process. Steam condensate often contains varying levels of carbon dioxide and oxygen which acts as an oxidizer. Carbon dioxide forms corrosive carbonic acid when dissolved in condensed steam. To neutralize the harmful effect of the carbonic acid, volatile amine compounds such as morpholine, cyclohexylamine, and diethylaminoethanol are often employed as part of a strategy to control corrosion in the water treatment process. Due to the high stability of these compounds in a water matrix, the indirect addition of such chemicals into the process via steam condensate often results in their presence throughout the process and even into the final product. It is therefore important to understand the impact of these chemicals and their fate within a chemical plant. The ability to analyze such compounds by gas chromatography has historically been difficult due to the lack of chromatographic system inertness at the trace level concentrations especially in an aqueous matrix. Here a highly sensitive, practical, and reliable gas chromatographic approach is described for the determination of morpholine, cyclohexylamine, and diethylaminoethanol in steam condensate at the part-per-billion (ppb) levels. The approach does not require any sample enrichment or derivatization. The technique employs a multi-mode inlet operating in pulsed splitless mode with programmed inlet temperature for sample introduction, an inert base-deactivated capillary column for solute separation and flame ionization detection. Chromatographic performance was further enhanced by the incorporation of 2-propanol as a co-solvent. Detection limits for morpholine, cyclohexylamine, diethylaminoethanol were established to be 100 ppb (v/v), with relative standard deviations (RSD) of less than 6% at the 95% confidence level (n=20) and a percent recovery of 96% or higher for the solutes of interest over a range of 0

  13. Analysis of trace contamination of phthalate esters in ultrapure water using a modified solid-phase extraction procedure and automated thermal desorption-gas chromatography/mass spectrometry.

    PubMed

    Liu, Hsu-Chuan; Den, Walter; Chan, Shu-Fei; Kin, Kuan Tzu

    2008-04-25

    The present study was aimed to develop a procedure modified from the conventional solid-phase extraction (SPE) method for the analysis of trace concentration of phthalate esters in industrial ultrapure water (UPW). The proposed procedure allows UPW sample to be drawn through a sampling tube containing hydrophobic sorbent (Tenax TA) to concentrate the aqueous phthalate esters. The solid trap was then demoisturized by two-stage gas drying before subjecting to thermal desorption and analysis by gas chromatography-mass spectrometry. This process removes the solvent extraction procedure necessary for the conventional SPE method, and permits automation of the analytical procedure for high-volume analyses. Several important parameters, including desorption temperature and duration, packing quantity and demoisturizing procedure, were optimized in this study based on the analytical sensitivity for a standard mixture containing five different phthalate esters. The method detection limits for the five phthalate esters were between 36 ng l(-1) and 95 ng l(-1) and recovery rates between 15% and 101%. Dioctyl phthalate (DOP) was not recovered adequately because the compound was both poorly adsorbed and desorbed on and off Tenax TA sorbents. Furthermore, analyses of material leaching from poly(vinyl chloride) (PVC) tubes as well as the actual water samples showed that di-n-butyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) were the common contaminants detected from PVC contaminated UPW and the actual UPW, as well as in tap water. The reduction of DEHP in the production processes of actual UPW was clearly observed, however a DEHP concentration of 0.20 microg l(-1) at the point of use was still being quantified, suggesting that the contamination of phthalate esters could present a barrier to the future cleanliness requirement of UPW. The work demonstrated that the proposed modified SPE procedure provided an effective method for rapid analysis and contamination

  14. 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.

  15. 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

  16. 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.

  17. Warmer summers combined with increases in rain lead to major changes in trace gas feedbacks from high arctic polar semi-deserts in NW Greenland to the atmosphere

    NASA Astrophysics Data System (ADS)

    Sharp, E. D.; Sullivan, P.; Czimczik, C. I.; Welker, J. M.

    2010-12-01

    Greenland’s climate is changing at rates unprecedented across the Arctic and these are especially acute in the NW region of the island. For the past 9 years we have been examining how experimental low (~2030) and high (~2050) warming, with and without added summer water will alter trace gas exchanges and soil and vegetation traits as part of the Biocomplexity and International Tundra Experiment Programs. We have found that low levels of warming (T1) result in a 30% increase in net CO2 uptake, higher levels of warming (T2) result in a 20% increase in CO2 loss, and high levels of warming plus added summer water increase net CO2 sequestration by 200%. These differences are caused by the strong co-limitation of gross ecosystem photosynthesis by temperature and water. The higher rates of NEE is due to consistently higher rates of GEP as opposed to lower rates of RE. Our findings are consistent between 2009 and 2010 and indicate that the combination of warmer summers plus increases in rain will have the largest effect on CO2 exchange and thus C cycling in these extreme habitats which in turn may affect vegetation cover and surface albedo.

  18. 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

  19. 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.

  20. 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

  1. Abstracts--Citations

    ERIC Educational Resources Information Center

    Occupational Mental Health, 1971

    1971-01-01

    Provides abstracts and citations of journal articles and reports dealing with aspects of mental health. Topics include alcoholism, drug abuse, disadvantaged, mental health programs, rehabilitation, student mental health, and others. (SB)

  2. 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.

  3. Introducing Abstract Design

    ERIC Educational Resources Information Center

    Ciscell, Bob

    1973-01-01

    A functional approach involving collage, two-dimensional design, three-dimensional construction, and elements of Cubism, is used to teach abstract design in elementary and junior high school art classes. (DS)

  4. Abstracts of SIG Sessions.

    ERIC Educational Resources Information Center

    Proceedings of the ASIS Annual Meeting, 1991

    1991-01-01

    Presents abstracts of 36 special interest group (SIG) sessions. Highlights include the Chemistry Online Retrieval Experiment; organizing and retrieving images; intelligent information retrieval using natural language processing; interdisciplinarity; libraries as publishers; indexing hypermedia; cognitive aspects of classification; computer-aided…

  5. 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)

  6. Paradigms for Abstracting Systems.

    ERIC Educational Resources Information Center

    Pinto, Maria; Galvez, Carmen

    1999-01-01

    Discussion of abstracting systems focuses on the paradigm concept and identifies and explains four paradigms: communicational, or information theory; physical, including information retrieval; cognitive, including information processing and artificial intelligence; and systemic, including quality management. Emphasizes multidimensionality and…

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. Energy partitioning in polyatomic chemical reactions: Quantum state resolved studies of highly exothermic atom abstraction reactions from molecules in the gas phase and at the gas-liquid interface

    NASA Astrophysics Data System (ADS)

    Zolot, Alexander M.

    This thesis recounts a series of experiments that interrogate the dynamics of elementary chemical reactions using quantum state resolved measurements of gas-phase products. The gas-phase reactions F + HCl → HF + Cl and F + H2O → HF + OH are studied using crossed supersonic jets under single collision conditions. Infrared (IR) laser absorption probes HF product with near shot-noise limited sensitivity and high resolution, capable of resolving rovibrational states and Doppler lineshapes. Both reactions yield inverted vibrational populations. For the HCl reaction, strongly bimodal rotational distributions are observed, suggesting microscopic branching of the reaction mechanism. Alternatively, such structure may result from a quantum-resonance mediated reaction similar to those found in the well-characterized F + HD system. For the H2O reaction, a small, but significant, branching into v = 2 is particularly remarkable because this manifold is accessible only via the additional center of mass collision energy in the crossed jets. Rotationally hyperthermal HF is also observed. Ab initio calculations of the transition state geometry suggest mechanisms for both rotational and vibrational excitation. Exothermic chemical reaction dynamics at the gas-liquid interface have been investigated by colliding a supersonic jet of F atoms with liquid squalane (C30H62), a low vapor pressure hydrocarbon compatible with the high vacuum environment. IR spectroscopy provides absolute HF( v,J) product densities and Doppler resolved velocity component distributions perpendicular to the surface normal. Compared to analogous gas-phase F + hydrocarbon reactions, the liquid surface is a more effective "heat sink," yet vibrationally excited populations reveal incomplete thermal accommodation with the surface. Non-Boltzmann J-state populations and hot Doppler lineshapes that broaden with HF excitation indicate two competing scattering mechanisms: (i) a direct reactive scattering channel

  12. Abstracting and indexing guide

    USGS Publications Warehouse

    U.S. Department of the Interior; Office of Water Resources Research

    1974-01-01

    These instructions have been prepared for those who abstract and index scientific and technical documents for the Water Resources Scientific Information Center (WRSIC). With the recent publication growth in all fields, information centers have undertaken the task of keeping the various scientific communities aware of current and past developments. An abstract with carefully selected index terms offers the user of WRSIC services a more rapid means for deciding whether a document is pertinent to his needs and professional interests, thus saving him the time necessary to scan the complete work. These means also provide WRSIC with a document representation or surrogate which is more easily stored and manipulated to produce various services. Authors are asked to accept the responsibility for preparing abstracts of their own papers to facilitate quick evaluation, announcement, and dissemination to the scientific community.

  13. Thyra Abstract Interface Package

    2005-09-01

    Thrya primarily defines a set of abstract C++ class interfaces needed for the development of abstract numerical atgorithms (ANAs) such as iterative linear solvers, transient solvers all the way up to optimization. At the foundation of these interfaces are abstract C++ classes for vectors, vector spaces, linear operators and multi-vectors. Also included in the Thyra package is C++ code for creating concrete vector, vector space, linear operator, and multi-vector subclasses as well as other utilitiesmore » to aid in the development of ANAs. Currently, very general and efficient concrete subclass implementations exist for serial and SPMD in-core vectors and multi-vectors. Code also currently exists for testing objects and providing composite objects such as product vectors.« less

  14. 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 absorption, aerosol fluorescence, number and volume size distributions, chemical composition, cloud

  15. Determination of trace level genotoxic impurities in small molecule drug substances using conventional headspace gas chromatography with contemporary ionic liquid diluents and electron capture detection.

    PubMed

    Ho, Tien D; Yehl, Peter M; Chetwyn, Nik P; Wang, Jin; Anderson, Jared L; Zhong, Qiqing

    2014-09-26

    Ionic liquids (ILs) were used as a new class of diluents for the analysis of two classes of genotoxic impurities (GTIs), namely, alkyl/aryl halides and nitro-aromatics, in small molecule drug substances by headspace gas chromatography (HS-GC) coupled with electron capture detection (ECD). This novel approach using ILs as contemporary diluents greatly broadens the applicability of HS-GC for the determination of high boiling (≥ 130°C) analytes including GTIs with limits of detection (LOD) ranging from 5 to 500 parts-per-billion (ppb) of analytes in a drug substance. This represents up to tens of thousands-fold improvement compared to traditional HS-GC diluents such as dimethyl sulfoxide (DMSO) and dimethylacetamide (DMAC). Various ILs were screened to determine their suitability as diluents for the HS-GC/ECD analysis. Increasing the HS oven temperatures resulted in varying responses for alkyl/aryl halides and a significant increase in response for all nitroaromatic GTIs. Linear ranges of up to five orders of magnitude were found for a number of analytes. The technique was validated on two active pharmaceutical ingredients with excellent recovery. This simple and robust methodology offers a key advantage in the ease of method transfer from development laboratories to quality control environments since conventional validated chromatographic data systems and GC instruments can be used. For many analytes, it is a cost effective alternative to more complex trace analytical methodologies like LC/MS and GC/MS, and significantly reduces the training needed for operation.

  16. Spectrometers for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) Upgrade to Full Sun-Sky-Cloud-Trace Gas Spectrometry Capability for Airborne Science

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    The Spectrometers for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) instrument has been developed at NASA Ames in collaboration with Pacific Northwest National Laboratory (PNNL) and NASA Goddard, supported substantially since 2009 by NASA's Radiation Science Program and Earth Science Technology Office. It combines grating spectrometers with fiber optic links to a tracking, scanning head to enable sun tracking, sky scanning, and zenith viewing. 4STAR builds on the long and productive heritage of the NASA Ames Airborne Tracking Sunphotometers (AATS-6 and -14), which have yielded more than 100 peer-reviewed publications and extensive archived data sets in many NASA Airborne Science campaigns from 1986 to the present. The baseline 4STAR instrument has provided extensive data supporting the TCAP (Two Column Aerosol Project, July 2012 & Feb. 2013), SEAC4RS (Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys, 2013), and ARISE (Arctic Radiation - IceBridge Sea and Ice Experiment, 2014), field campaigns.This poster presents plans and progress for an upgrade to the 4STAR instrument to achieve full science capability, including (1) direct-beam sun tracking measurements to derive aerosol optical depth spectra, (2) sky radiance measurements to retrieve aerosol absorption and type (via complex refractive index and mode-resolved size distribution), (3) cloud properties via zenith radiance, and (4) trace gas spectrometry. Technical progress in context with the governing physics is reported on several upgrades directed at improved light collection and usage, particularly as related to spectrally and radiometrically stable propagation through the collection light path. In addition, improvements to field calibration and verification, and flight operability and reliability are addressed.

  17. 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

  18. 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.

  19. 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.

  20. Annual Conference Abstracts

    ERIC Educational Resources Information Center

    Engineering Education, 1976

    1976-01-01

    Presents the abstracts of 158 papers presented at the American Society for Engineering Education's annual conference at Knoxville, Tennessee, June 14-17, 1976. Included are engineering topics covering education, aerospace, agriculture, biomedicine, chemistry, computers, electricity, acoustics, environment, mechanics, and women. (SL)

  1. Seismic Consequence Abstraction

    SciTech Connect

    M. Gross

    2004-10-25

    The primary purpose of this model report is to develop abstractions for the response of engineered barrier system (EBS) components to seismic hazards at a geologic repository at Yucca Mountain, Nevada, and to define the methodology for using these abstractions in a seismic scenario class for the Total System Performance Assessment - License Application (TSPA-LA). A secondary purpose of this model report is to provide information for criticality studies related to seismic hazards. The seismic hazards addressed herein are vibratory ground motion, fault displacement, and rockfall due to ground motion. The EBS components are the drip shield, the waste package, and the fuel cladding. The requirements for development of the abstractions and the associated algorithms for the seismic scenario class are defined in ''Technical Work Plan For: Regulatory Integration Modeling of Drift Degradation, Waste Package and Drip Shield Vibratory Motion and Seismic Consequences'' (BSC 2004 [DIRS 171520]). The development of these abstractions will provide a more complete representation of flow into and transport from the EBS under disruptive events. The results from this development will also address portions of integrated subissue ENG2, Mechanical Disruption of Engineered Barriers, including the acceptance criteria for this subissue defined in Section 2.2.1.3.2.3 of the ''Yucca Mountain Review Plan, Final Report'' (NRC 2003 [DIRS 163274]).

  2. Abstraction through Game Play

    ERIC Educational Resources Information Center

    Avraamidou, Antri; Monaghan, John; Walker, Aisha

    2012-01-01

    This paper examines the computer game play of an 11-year-old boy. In the course of building a virtual house he developed and used, without assistance, an artefact and an accompanying strategy to ensure that his house was symmetric. We argue that the creation and use of this artefact-strategy is a mathematical abstraction. The discussion…

  3. Making the Abstract Concrete

    ERIC Educational Resources Information Center

    Potter, Lee Ann

    2005-01-01

    President Ronald Reagan nominated a woman to serve on the United States Supreme Court. He did so through a single-page form letter, completed in part by hand and in part by typewriter, announcing Sandra Day O'Connor as his nominee. While the document serves as evidence of a historic event, it is also a tangible illustration of abstract concepts…

  4. Annual Conference Abstracts

    ERIC Educational Resources Information Center

    Journal of Engineering Education, 1972

    1972-01-01

    Includes abstracts of papers presented at the 80th Annual Conference of the American Society for Engineering Education. The broad areas include aerospace, affiliate and associate member council, agricultural engineering, biomedical engineering, continuing engineering studies, chemical engineering, civil engineering, computers, cooperative…

  5. Computers in Abstract Algebra

    ERIC Educational Resources Information Center

    Nwabueze, Kenneth K.

    2004-01-01

    The current emphasis on flexible modes of mathematics delivery involving new information and communication technology (ICT) at the university level is perhaps a reaction to the recent change in the objectives of education. Abstract algebra seems to be one area of mathematics virtually crying out for computer instructional support because of the…

  6. 2002 NASPSA Conference Abstracts.

    ERIC Educational Resources Information Center

    Journal of Sport & Exercise Psychology, 2002

    2002-01-01

    Contains abstracts from the 2002 conference of the North American Society for the Psychology of Sport and Physical Activity. The publication is divided into three sections: the preconference workshop, "Effective Teaching Methods in the Classroom;" symposia (motor development, motor learning and control, and sport psychology); and free…

  7. Abstracts of SIG Sessions.

    ERIC Educational Resources Information Center

    Proceedings of the ASIS Annual Meeting, 1995

    1995-01-01

    Presents abstracts of 15 special interest group (SIG) sessions. Topics include navigation and information utilization in the Internet, natural language processing, automatic indexing, image indexing, classification, users' models of database searching, online public access catalogs, education for information professions, information services,…

  8. Abstraction and art.

    PubMed Central

    Gortais, Bernard

    2003-01-01

    In a given social context, artistic creation comprises a set of processes, which relate to the activity of the artist and the activity of the spectator. Through these processes we see and understand that the world is vaster than it is said to be. Artistic processes are mediated experiences that open up the world. A successful work of art expresses a reality beyond actual reality: it suggests an unknown world using the means and the signs of the known world. Artistic practices incorporate the means of creation developed by science and technology and change forms as they change. Artists and the public follow different processes of abstraction at different levels, in the definition of the means of creation, of representation and of perception of a work of art. This paper examines how the processes of abstraction are used within the framework of the visual arts and abstract painting, which appeared during a period of growing importance for the processes of abstraction in science and technology, at the beginning of the twentieth century. The development of digital platforms and new man-machine interfaces allow multimedia creations. This is performed under the constraint of phases of multidisciplinary conceptualization using generic representation languages, which tend to abolish traditional frontiers between the arts: visual arts, drama, dance and music. PMID:12903659

  9. Leadership Abstracts, 2002.

    ERIC Educational Resources Information Center

    Wilson, Cynthia, Ed.; Milliron, Mark David, Ed.

    2002-01-01

    This 2002 volume of Leadership Abstracts contains issue numbers 1-12. Articles include: (1) "Skills Certification and Workforce Development: Partnering with Industry and Ourselves," by Jeffrey A. Cantor; (2) "Starting Again: The Brookhaven Success College," by Alice W. Villadsen; (3) "From Digital Divide to Digital Democracy," by Gerardo E. de los…

  10. Water reuse. [Lead abstract

    SciTech Connect

    Middlebrooks, E.J.

    1982-01-01

    Separate abstracts were prepared for the 31 chapters of this book which deals with all aspects of wastewater reuse. Design data, case histories, performance data, monitoring information, health information, social implications, legal and organizational structures, and background information needed to analyze the desirability of water reuse are presented. (KRM)

  11. Abstract Film and Beyond.

    ERIC Educational Resources Information Center

    Le Grice, Malcolm

    A theoretical and historical account of the main preoccupations of makers of abstract films is presented in this book. The book's scope includes discussion of nonrepresentational forms as well as examination of experiments in the manipulation of time in films. The ten chapters discuss the following topics: art and cinematography, the first…

  12. Impacts of an African Green Revolution on Greenhouse Gases and Pollution Precursors: Nonlinear Trace N Gas Emission Responses to Incremental Increases in Fertilizer Inputs in a Western Kenyan Maize Field

    NASA Astrophysics Data System (ADS)

    Hickman, J. E.; Palm, C.

    2011-12-01

    Over the last several decades, agricultural soils in many parts of sub-Saharan Africa have become depleted of nitrogen (N) and other nutrients, creating challenges to achieving food security in many countries. At only 7 kg N ha-1 yr-1, average fertilizer application rates in the region are an order of magnitude lower than typical rates in the United States, and well below optimal levels. Increased use of nutrient inputs is a centerpiece of most African Green Revolution strategies, making it important to quantify the impacts of this change in practices as farmers begin moving towards 50-80 kg N ha-1 yr-1. Increased N inputs are invariably accompanied by losses of trace N gases to the atmosphere, including the greenhouse gas nitrous oxide (N2O), and nitric oxide (NO), a precursor to tropospheric ozone pollution. Several investigations of greenhouse gas emissions and one investigation of NO emissions from sub-Saharan agricultural systems have been conducted over the last 20 years, but they are few in number and were not designed to identify potentially important thresholds in the response of trace gas emissions to fertilization rate. Here we examine the response function of NO and N2O emissions to 6 different levels of inorganic fertilizer additions in a maize field in Yala, Kenya during the 2011 long rainy season. We used a randomized complete block design incorporating inorganic fertilizer treatments of 0, 50, 75, 100, 150, and 200 kg N ha-1 in 4 blocks. After each of 2 fertilizer applications, we measured trace gas fluxes daily, and conducted weekly measurements until trace gas emissions subsided to control levels. We fit the data to linear and exponential models relating N gas emissions to N input levels, and conducted a model comparison using AIC. Preliminary analysis suggests that NO emissions do respond in a non-linear fashion over the course of 67 days, as has been found in several commercial agroecosystems for N2O. Although N2O emissions responded linearly

  13. Finding Feasible Abstract Counter-Examples

    NASA Technical Reports Server (NTRS)

    Pasareanu, Corina S.; Dwyer, Matthew B.; Visser, Willem; Clancy, Daniel (Technical Monitor)

    2002-01-01

    A strength of model checking is its ability to automate the detection of subtle system errors and produce traces that exhibit those errors. Given the high computational cost of model checking most researchers advocate the use of aggressive property-preserving abstractions. Unfortunately, the more aggressively a system is abstracted the more infeasible behavior it will have. Thus, while abstraction enables efficient model checking it also threatens the usefulness of model checking as a defect detection tool, since it may be difficult to determine whether a counter-example is feasible and hence worth developer time to analyze. We have explored several strategies for addressing this problem by extending an explicit-state model checker, Java PathFinder (JPF), to search for and analyze counter-examples in the presence of abstractions. We demonstrate that these techniques effectively preserve the defect detection ability of model checking in the presence of aggressive abstraction by applying them to check properties of several abstracted multi-threaded Java programs. These new capabilities are not specific to JPF and can be easily adapted to other model checking frameworks; we describe how this was done for the Bandera toolset.

  14. An Abstract Data Interface

    NASA Astrophysics Data System (ADS)

    Allan, D. J.

    The Abstract Data Interface (ADI) is a system within which both abstract data models and their mappings on to file formats can be defined. The data model system is object-oriented and closely follows the Common Lisp Object System (CLOS) object model. Programming interfaces in both C and \\fortran are supplied, and are designed to be simple enough for use by users with limited software skills. The prototype system supports access to those FITS formats most commonly used in the X-ray community, as well as the Starlink NDF data format. New interfaces can be rapidly added to the system---these may communicate directly with the file system, other ADI objects or elsewhere (e.g., a network connection).

  15. Meeting Abstracts - Nexus 2015.

    PubMed

    2015-10-01

    The AMCP Abstracts program provides a forum through which authors can share their insights and outcomes of advanced managed care practice through publication in AMCP's Journal of Managed Care Specialty Pharmacy (JMCP). Of the abstracts accepted for publication, most are presented as posters, so interested AMCP meeting attendees can review findings and query authors. The main poster presentation is Tuesday, October 27, 2015; posters are also displayed on Wednesday, October 28, 2015. The AMCP Nexus 2015 in Orlando, Florida, is expected to attract more than 3,500 managed care pharmacists and other health care professionals who manage and evaluate drug therapies, develop and manage networks, and work with medical managers and information specialists to improve the care of all individuals enrolled in managed care programs.  Abstracts were submitted in the following categories:  Research Report: describe completed original research on managed care pharmacy services or health care interventions. Examples include (but are not limited to) observational studies using administrative claims, reports of the impact of unique benefit design strategies, and analyses of the effects of innovative administrative or clinical programs.Economic Model: describe models that predict the effect of various benefit design or clinical decisions on a population. For example, an economic model could be used to predict the budget impact of a new pharmaceutical product on a health care system. Solving Problems in Managed Care: describe the specific steps taken to introduce a needed change, develop and implement a new system or program, plan and organize an administrative function, or solve other types of problems in managed care settings. These abstracts describe a course of events; they do not test a hypothesis, but they may include data.

  16. Generalized Abstract Symbolic Summaries

    NASA Technical Reports Server (NTRS)

    Person, Suzette; Dwyer, Matthew B.

    2009-01-01

    Current techniques for validating and verifying program changes often consider the entire program, even for small changes, leading to enormous V&V costs over a program s lifetime. This is due, in large part, to the use of syntactic program techniques which are necessarily imprecise. Building on recent advances in symbolic execution of heap manipulating programs, in this paper, we develop techniques for performing abstract semantic differencing of program behaviors that offer the potential for improved precision.

  17. EBS Radionuclide Transport Abstraction

    SciTech Connect

    J. Prouty

    2006-07-14

    The purpose of this report is to develop and analyze the engineered barrier system (EBS) radionuclide transport abstraction model, consistent with Level I and Level II model validation, as identified in Technical Work Plan for: Near-Field Environment and Transport: Engineered Barrier System: Radionuclide Transport Abstraction Model Report Integration (BSC 2005 [DIRS 173617]). The EBS radionuclide transport abstraction (or EBS RT Abstraction) is the conceptual model used in the total system performance assessment (TSPA) to determine the rate of radionuclide releases from the EBS to the unsaturated zone (UZ). The EBS RT Abstraction conceptual model consists of two main components: a flow model and a transport model. Both models are developed mathematically from first principles in order to show explicitly what assumptions, simplifications, and approximations are incorporated into the models used in the TSPA. The flow model defines the pathways for water flow in the EBS and specifies how the flow rate is computed in each pathway. Input to this model includes the seepage flux into a drift. The seepage flux is potentially split by the drip shield, with some (or all) of the flux being diverted by the drip shield and some passing through breaches in the drip shield that might result from corrosion or seismic damage. The flux through drip shield breaches is potentially split by the waste package, with some (or all) of the flux being diverted by the waste package and some passing through waste package breaches that might result from corrosion or seismic damage. Neither the drip shield nor the waste package survives an igneous intrusion, so the flux splitting submodel is not used in the igneous scenario class. The flow model is validated in an independent model validation technical review. The drip shield and waste package flux splitting algorithms are developed and validated using experimental data. The transport model considers advective transport and diffusive transport

  18. Short term effects of clearfelling on soil trace gas fluxes in a Sitka spruce (picea sitchensis) forest on peaty gley soils

    NASA Astrophysics Data System (ADS)

    Zerva, A.; Mencuccini, M.; Smith, K. A.

    2003-04-01

    We have investigated how the clearfelling of forests can affect soil trace gas emissions and the contribution of forest soils to the greenhouse effect. Emissions of CO_2, CH_4 and N_2O were measured using a closed static chamber technique and GC and IRGA analysis, in two Sitka spruce stands (40 years old) growing on peaty gley soils. One stand was kept intact for two growing seasons; the other was clearfelled after one season of preliminary monitoring. Soil temperature, soil moisture content and depth to the water table were also recorded. Clearfelling did not increase soil respiration above the levels of the control stand during the first ten months after clearfelling (March-December 2002), with respiration in the clearfelled site being significantly lower than in the mature stand (6.42±1.18 and 10.42±0.63 t CO_2 ha-1 in the clearfelled and 40 yrs respectively). Soil CO_2 efflux was strongly correlated with soil temperature in both mature stands, but after clear felling no significant correlation with temperature was detected, while the relationship with soil moisture became significant. This indicated that factors other than temperature drive the soil respiration after clear felling. Clearfelling increased the CH4 emissions (6.63±4.67 and 0.41± 0.21 kg CH_4 ha-1 in the clearfelled and 40 yrs respectively for the same period), but had no significant effect on N_2O emissions (1.34±0.28 and 1.10±0.12 kg N_2O ha-1 in the clearfelled and 40 yrs respectively for the same period), although a peak was apparent during the warmest months (August, September) at the clearfelled site. Fluxes of CH_4 and N_2O after clearfelling were significantly dependent on soil temperature but there was no consistent relationship with soil moisture or depth to the water table. Clearfelling, in the early stages, causes a decrease in the soil CO_2 emissions probably because of the rise of the water table and the disappearance of autotrophic respiration, while the CH_4 emissions increase

  19. Trace gas exchange in a high-Arctic valley: 3. Integrating and scaling CO2 fluxes from canopy to landscape using flux data, footprint modeling, and remote sensing

    NASA Astrophysics Data System (ADS)

    Soegaard, Henrik; Nordstroem, Claus; Friborg, Thomas; Hansen, Birger U.; Christensen, Torben R.; Bay, Christian

    2000-09-01

    Within the framework of the European Land Arctic Physical Processes project and as part of the Danish Research Council's Polar Program, a study on trace gas exchange in a high-arctic ecosystem was conducted in NE Greenland, May-August 1997. On the basis of carbon dioxide flux measurements from three dominant surface types, this paper reports on the upscaling of such measurements from canopy to landscape level. Over a three-week period starting in mid-July, the different surfaces revealed large differences in the CO2 flux with uptake rates ranging from 0.7 g C m-2 d-1 over the dwarf shrub heath to 3.0 g Cm-2 d-1 over denser parts of the fen, while willow snowbed revealed intermediate uptake rates. The carbon dioxide exchange could be simulated by a CO2 model, combining photosynthesis and soil respiration routines, for which the parametrization depended on the vegetation type. Results from the simulation were supported by a sensitivity analysis based on a three-dimensional footprint model where it was shown that the CO2 uptake was strongly related to the measured leaf area index. The CO2 model was used to calculate the spatial distribution in Net Ecosystem Exchange (NEE) on the basis of Landsat satellite data acquired at the peak of the growing season and stratified according to vegetation type. It was found that there was a reasonable agreement between the satellite-based flux estimate (-0.77 g C m-2 d-1) and the CO2 flux found by areal weighting of the eddy correlation measurements (-0.88 g C m-2 d-1) for the specific study day. Finally, the summer season NEE was calculated for the whole Zackenberg Valley bottom. In June, there was a valley-wide carbon loss of 8.4±2.6 g C m-2 month-1, whereas the valley system accumulated 18.8±6.7 g C m-2 season-1 during the growing season (July-August).

  20. Efficacy of head space solid-phase microextraction coupled to gas chromatography-mass spectrometry method for determination of the trace extracellular hydrocarbons of cyanobacteria.

    PubMed

    Guan, Wenna; Zhu, Tao; Wang, Yuejie; Zhang, Zhongyi; Jin, Zhao; Wang, Cong; Bai, Fali

    2016-09-01

    Hydrocarbons are widespread in cyanobacteria, and the biochemical synthetic pathways were recently identified. Intracellular fatty alka(e)nes of cyanobacteria have been detected by liquid-liquid extraction (LLE) coupled to gas chromatography-mass spectrometry (GC/MS). However, whether fatty alka(e)nes can be released to cyanobacterial culture media remains to be clarified. This work develops a sensitive method for analyzing the trace level of extracellular hydrocarbons in cyanobacterial culture media by head space solid-phase microextraction (HS-SPME) coupled to GC/MS. Headspace (HS) extraction mode using polydimethylsiloxane fiber to extract for 30min at 50°C was employed as the optimal extraction conditions. Five cyanobacterial fatty alka(e)nes analogs including pentadecene (C15:1), pentadecane (C15:0), heptadecene (C17:1), heptadecane (C17:0), nonadecane (C19:0) were analyzed, and the data obtained from HS-SPME-GC/MS method were quantified using internal standard peak area comparisons. Limits of detection (LOD), limits of quantitation (LOQ), linear dynamic range, precisions (RSD) and recovery for the analysis of extracellular fatty alka(e)nes of cyanobacteria by HS-SPME-GC/MS were evaluated. The LODs limits of detection (S/N = 3) varied from 10 to 21 ng L-1. The correlation coefficients (r) of the calibration curves ranged from 0.9873 to 0.9977 with a linearity from 0.1 to 50 μg L-1. The RSD values were ranging from 7.8 to 14.0% and from 4.0 to 8.8% at 1.0 μg L-1 and 10.0 μg L-1 standard solutions, respectively. Comparative analysis of extracellular fatty alka(e)nes in the culture media of model cyanobacteria Synechocystis sp. PCC 6803 demonstrated that sensitivity of HS-SPME-GC/MS method was significantly higher than LLE method. Finally, we found that heptadecane can be released into the culture media of Synechocystis sp. PCC 6803 at the later growth period. PMID:27428454

  1. The Alaskan Fire Emissions Database (AKFED): analysis of environmental controls on daily fire emissions and comparison with atmospheric trace gas measurements

    NASA Astrophysics Data System (ADS)

    Veraverbeke, S.; Rogers, B. M.; Wiggins, E. B.; Randerson, J. T.

    2014-12-01

    impacts on atmospheric trace gas composition and in characterizing environmental controls on fire growth. Emission estimates of the 2013 fire season were input into an aerosol transport model and modeled CO2 concentrations were compared with measurements from NASA's CARVE mission during fire-affected days.

  2. Efficacy of head space solid-phase microextraction coupled to gas chromatography-mass spectrometry method for determination of the trace extracellular hydrocarbons of cyanobacteria.

    PubMed

    Guan, Wenna; Zhu, Tao; Wang, Yuejie; Zhang, Zhongyi; Jin, Zhao; Wang, Cong; Bai, Fali

    2016-09-01

    Hydrocarbons are widespread in cyanobacteria, and the biochemical synthetic pathways were recently identified. Intracellular fatty alka(e)nes of cyanobacteria have been detected by liquid-liquid extraction (LLE) coupled to gas chromatography-mass spectrometry (GC/MS). However, whether fatty alka(e)nes can be released to cyanobacterial culture media remains to be clarified. This work develops a sensitive method for analyzing the trace level of extracellular hydrocarbons in cyanobacterial culture media by head space solid-phase microextraction (HS-SPME) coupled to GC/MS. Headspace (HS) extraction mode using polydimethylsiloxane fiber to extract for 30min at 50°C was employed as the optimal extraction conditions. Five cyanobacterial fatty alka(e)nes analogs including pentadecene (C15:1), pentadecane (C15:0), heptadecene (C17:1), heptadecane (C17:0), nonadecane (C19:0) were analyzed, and the data obtained from HS-SPME-GC/MS method were quantified using internal standard peak area comparisons. Limits of detection (LOD), limits of quantitation (LOQ), linear dynamic range, precisions (RSD) and recovery for the analysis of extracellular fatty alka(e)nes of cyanobacteria by HS-SPME-GC/MS were evaluated. The LODs limits of detection (S/N = 3) varied from 10 to 21 ng L-1. The correlation coefficients (r) of the calibration curves ranged from 0.9873 to 0.9977 with a linearity from 0.1 to 50 μg L-1. The RSD values were ranging from 7.8 to 14.0% and from 4.0 to 8.8% at 1.0 μg L-1 and 10.0 μg L-1 standard solutions, respectively. Comparative analysis of extracellular fatty alka(e)nes in the culture media of model cyanobacteria Synechocystis sp. PCC 6803 demonstrated that sensitivity of HS-SPME-GC/MS method was significantly higher than LLE method. Finally, we found that heptadecane can be released into the culture media of Synechocystis sp. PCC 6803 at the later growth period.

  3. EBS Radionuclide Transport Abstraction

    SciTech Connect

    J.D. Schreiber

    2005-08-25

    The purpose of this report is to develop and analyze the engineered barrier system (EBS) radionuclide transport abstraction model, consistent with Level I and Level II model validation, as identified in ''Technical Work Plan for: Near-Field Environment and Transport: Engineered Barrier System: Radionuclide Transport Abstraction Model Report Integration'' (BSC 2005 [DIRS 173617]). The EBS radionuclide transport abstraction (or EBS RT Abstraction) is the conceptual model used in the total system performance assessment for the license application (TSPA-LA) to determine the rate of radionuclide releases from the EBS to the unsaturated zone (UZ). The EBS RT Abstraction conceptual model consists of two main components: a flow model and a transport model. Both models are developed mathematically from first principles in order to show explicitly what assumptions, simplifications, and approximations are incorporated into the models used in the TSPA-LA. The flow model defines the pathways for water flow in the EBS and specifies how the flow rate is computed in each pathway. Input to this model includes the seepage flux into a drift. The seepage flux is potentially split by the drip shield, with some (or all) of the flux being diverted by the drip shield and some passing through breaches in the drip shield that might result from corrosion or seismic damage. The flux through drip shield breaches is potentially split by the waste package, with some (or all) of the flux being diverted by the waste package and some passing through waste package breaches that might result from corrosion or seismic damage. Neither the drip shield nor the waste package survives an igneous intrusion, so the flux splitting submodel is not used in the igneous scenario class. The flow model is validated in an independent model validation technical review. The drip shield and waste package flux splitting algorithms are developed and validated using experimental data. The transport model considers

  4. A LARI Experience (Abstract)

    NASA Astrophysics Data System (ADS)

    Cook, M.

    2015-12-01

    (Abstract only) In 2012, Lowell Observatory launched The Lowell Amateur Research Initiative (LARI) to formally involve amateur astronomers in scientific research by bringing them to the attention of and helping professional astronomers with their astronomical research. One of the LARI projects is the BVRI photometric monitoring of Young Stellar Objects (YSOs), wherein amateurs obtain observations to search for new outburst events and characterize the colour evolution of previously identified outbursters. A summary of the scientific and organizational aspects of this LARI project, including its goals and science motivation, the process for getting involved with the project, a description of the team members, their equipment and methods of collaboration, and an overview of the programme stars, preliminary findings, and lessons learned is presented.

  5. IEEE conference record -- Abstracts

    SciTech Connect

    Not Available

    1994-01-01

    This conference covers the following areas: computational plasma physics; vacuum electronic; basic phenomena in fully ionized plasmas; plasma, electron, and ion sources; environmental/energy issues in plasma science; space plasmas; plasma processing; ball lightning/spherical plasma configurations; plasma processing; fast wave devices; magnetic fusion; basic phenomena in partially ionized plasma; dense plasma focus; plasma diagnostics; basic phenomena in weakly ionized gases; fast opening switches; MHD; fast z-pinches and x-ray lasers; intense ion and electron beams; laser-produced plasmas; microwave plasma interactions; EM and ETH launchers; solid state plasmas and switches; intense beam microwaves; and plasmas for lighting. Separate abstracts were prepared for 416 papers in this conference.

  6. Writing a successful research abstract.

    PubMed

    Bliss, Donna Z

    2012-01-01

    Writing and submitting a research abstract provides timely dissemination of the findings of a study and offers peer input for the subsequent development of a quality manuscript. Acceptance of abstracts is competitive. Understanding the expected content of an abstract, the abstract review process and tips for skillful writing will improve the chance of acceptance.

  7. Trace Chemistry

    NASA Technical Reports Server (NTRS)

    Radhakrishnan, Krishnan; Whitefield, Philip

    1999-01-01

    The goals of the trace chemistry group were to identify the processes relevant to aerosol and aerosol precursor formation occurring within aircraft gas turbine engines; that is, within the combustor, turbine, and nozzle. The topics of discussion focused on whether the chemistry of aerosol formation is homogeneous or heterogeneous; what species are important for aerosol and aerosol precursor formation; what modeling/theoretical activities to pursue; what experiments to carry out that both support modeling activities and elucidate fundamental processes; and the role of particulates in aerosol and aerosol precursor formation. The consensus of the group was that attention should be focused on SO2, SO3, and aerosols. Of immediate concern is the measurement of the concentration of the species SO3, SO2, H2SO4 OH, HO2, H2O2, O, NO, NO2, HONO, HNO3, CO, and CO2 and particulates in various engines, both those currently in use and those in development. The recommendation was that concentration measurements should be made at both the combustor exit and the engine exit. At each location the above species were classified into one of four categories of decreasing importance, Priority I through IV, as follows: Combustor exit: Priority I species - SO3:SO2 ratio, SO3, SO2, and particulates; Priority II species: OH and O; Priority III species - NO and NO2; and Priority IV species - CO and CO2. For the Engine exit: Priority I species - SO3:SO2 ratio, SO3, SO2,H2SO4, and particulates; Priority II species: OH,HO2, H2O2, and O; Priority III species - NO, NO2, HONO, and HNO3; and Priority IV species - CO and CO2. Table I summarizes the anticipated concentration range of each of these species. For particulate matter, the quantities of interest are the number density, size distribution, and composition. In order to provide data for validating multidimensional reacting flow models, it would be desirable to make 2-D, time-resolved measurements of the concentrations of the above species and

  8. Some problems associated with trace contaminant removal systems for spacecabins

    NASA Technical Reports Server (NTRS)

    Wydeven, T.

    1985-01-01

    Potential problems associated with acid gas sorbents, activated charcoal beds and the catalytic oxidizer proposed for spacecabin trace contaminant control are discussed. The need for further research on atmospheric trace contaminant control methods is noted.

  9. Program and abstracts

    SciTech Connect

    Not Available

    1994-10-01

    The increasing scale-up of fast pyrolysis in North America and Europe, as well as the exploration and expansion of markets for the energy use of biocrude oils that now needs to take place, suggested that it was timely to convene an international meeting on the properties and combustion behavior of these oils. A common understanding of the state-of-the-art and technical and other challenges which need to be met during the commercialization of biocrude fuel use, can be achieved. The technical issues and understanding of combustion of these oils are rapidly being advanced through R&D in the United States, Canada, Europe and Scandinavia. It is obvious that for the maximum economic impact of biocrude, it will be necessary to have a common set of specifications so that oils can be used interchangeably with engines and combustors which require minimal modification to use these renewable fuels. Fundamental and applied studies being pursued in several countries are brought together in this workshop so that we can arrive at common strategies. In this way, both the science and the commercialization are advanced to the benefit of all, without detracting from the competitive development of both the technology and its applications. This United States-Canada-Finland collaboration has led to the two and one half day specialists meeting at which the technical basis for advances in biocrude development is discussed. The goal is to arrive at a common agenda on issues that cross national boundaries in this area. Examples of agenda items are combustion phenomena, the behavior of trace components . of the oil (N, alkali metals), the formation of NO{sub x}, in combustion, the need for common standards and environmental safety and health issues in the handling, storage and transportation of biocrudes.

  10. Stellar Presentations (Abstract)

    NASA Astrophysics Data System (ADS)

    Young, D.

    2015-12-01

    (Abstract only) The AAVSO is in the process of expanding its education, outreach and speakers bureau program. powerpoint presentations prepared for specific target audiences such as AAVSO members, educators, students, the general public, and Science Olympiad teams, coaches, event supervisors, and state directors will be available online for members to use. The presentations range from specific and general content relating to stellar evolution and variable stars to specific activities for a workshop environment. A presentation—even with a general topic—that works for high school students will not work for educators, Science Olympiad teams, or the general public. Each audience is unique and requires a different approach. The current environment necessitates presentations that are captivating for a younger generation that is embedded in a highly visual and sound-bite world of social media, twitter and U-Tube, and mobile devices. For educators, presentations and workshops for themselves and their students must support the Next Generation Science Standards (NGSS), the Common Core Content Standards, and the Science Technology, Engineering and Mathematics (STEM) initiative. Current best practices for developing relevant and engaging powerpoint presentations to deliver information to a variety of targeted audiences will be presented along with several examples.

  11. Automated Supernova Discovery (Abstract)

    NASA Astrophysics Data System (ADS)

    Post, R. S.

    2015-12-01

    (Abstract only) We are developing a system of robotic telescopes for automatic recognition of Supernovas as well as other transient events in collaboration with the Puckett Supernova Search Team. At the SAS2014 meeting, the discovery program, SNARE, was first described. Since then, it has been continuously improved to handle searches under a wide variety of atmospheric conditions. Currently, two telescopes are used to build a reference library while searching for PSN with a partial library. Since data is taken every night without clouds, we must deal with varying atmospheric and high background illumination from the moon. Software is configured to identify a PSN, reshoot for verification with options to change the run plan to acquire photometric or spectrographic data. The telescopes are 24-inch CDK24, with Alta U230 cameras, one in CA and one in NM. Images and run plans are sent between sites so the CA telescope can search while photometry is done in NM. Our goal is to find bright PSNs with magnitude 17.5 or less which is the limit of our planned spectroscopy. We present results from our first automated PSN discoveries and plans for PSN data acquisition.

  12. Long-term aerosol and trace gas measurements in Eastern Lapland, Finland: the impact of Kola air pollution to new particle formation and potential CCN

    NASA Astrophysics Data System (ADS)

    Kyrö, Ella-Maria; Väänänen, Riikka; Kerminen, Veli-Matti; Virkkula, Aki; Asmi, Ari; Nieminen, Tuomo; Dal Maso, Miikka; Petäjä, Tuukka; Keronen, Petri; Aalto, Pasi; Riipinen, Ilona; Lehtipalo, Katrianne; Hari, Pertti; Kulmala, Markku

    2014-05-01

    Sulphur and primary emissions have been decreasing largely all over Europe, resulting in improved air quality and decreased direct radiation forcing by aerosols. The smelter industry in Kola Peninsula is one of largest sources of anthropogenic SO2 within the Arctic domain and since late 1990s the sulphur emissions have been decreasing rapidly (Paatero et al., 2008; Prank et al., 2010). New particle formation (NPF) is tightly linked with the oxidizing product of SO2, namely sulphuric acid (H2SO4), since it is known to be the key component in atmospheric nucleation (Sipilä et al., 2010). Thus, decreasing sulphur pollution may lead to less NPF. However, low values of condensation sink (CS), which is determined by the amount of pre-existing particles, favours NPF. We used 14 years (1998-2011) of aerosol number size distribution and trace gas data from SMEAR I station in Eastern Lapland, Finland, to investigate these relationships between SO2, NPF and CS. The station is a clean background station with occasional sulphur pollution episodes when the air masses arrive over Kola Peninsula. We found that while SO2 decreased by 11.3 % / year, the number of clear NPF event days was also decreasing by 9.9 % / year. At the same time, CS was decreasing also (-8.0 % / year) leading to formation of more particles per single NPF event (J3 increased by 29.7 % / year in 2006-2011) but the low vapour concentrations of H2SO4 (proxy decreased by 6.2 % / year) did not allow them to grow into climatically relevant sizes. Over the time, concentrations of potential CCN (cloud condensing nuclei) were also decreasing with more moderate pace, -4.0 % / year. The events started on average earlier after sunrise when the SO2 concentration during the start of the event was higher and NPF occurred more frequently in air masses which were travelling over Kola. Despite the total decrease in sulphur pollution originating from Kola there is currently no evidence of cleaning of the emissions, rather the

  13. Effect of ocean acidification and elevated fCO2 on trace gas production by a Baltic Sea summer phytoplankton community

    NASA Astrophysics Data System (ADS)

    Webb, Alison L.; Leedham-Elvidge, Emma; Hughes, Claire; Hopkins, Frances E.; Malin, Gill; Bach, Lennart T.; Schulz, Kai; Crawfurd, Kate; Brussaard, Corina P. D.; Stuhr, Annegret; Riebesell, Ulf; Liss, Peter S.

    2016-08-01

    The Baltic Sea is a unique environment as the largest body of brackish water in the world. Acidification of the surface oceans due to absorption of anthropogenic CO2 emissions is an additional stressor facing the pelagic community of the already challenging Baltic Sea. To investigate its impact on trace gas biogeochemistry, a large-scale mesocosm experiment was performed off Tvärminne Research Station, Finland, in summer 2012. During the second half of the experiment, dimethylsulfide (DMS) concentrations in the highest-fCO2 mesocosms (1075-1333 µatm) were 34 % lower than at ambient CO2 (350 µatm). However, the net production (as measured by concentration change) of seven halocarbons analysed was not significantly affected by even the highest CO2 levels after 5 weeks' exposure. Methyl iodide (CH3I) and diiodomethane (CH2I2) showed 15 and 57 % increases in mean mesocosm concentration (3.8 ± 0.6 increasing to 4.3 ± 0.4 pmol L-1 and 87.4 ± 14.9 increasing to 134.4 ± 24.1 pmol L-1 respectively) during Phase II of the experiment, which were unrelated to CO2 and corresponded to 30 % lower Chl a concentrations compared to Phase I. No other iodocarbons increased or showed a peak, with mean chloroiodomethane (CH2ClI) concentrations measured at 5.3 (±0.9) pmol L-1 and iodoethane (C2H5I) at 0.5 (±0.1) pmol L-1. Of the concentrations of bromoform (CHBr3; mean 88.1 ± 13.2 pmol L-1), dibromomethane (CH2Br2; mean 5.3 ± 0.8 pmol L-1), and dibromochloromethane (CHBr2Cl, mean 3.0 ± 0.5 pmol L-1), only CH2Br2 showed a decrease of 17 % between Phases I and II, with CHBr3 and CHBr2Cl showing similar mean concentrations in both phases. Outside the mesocosms, an upwelling event was responsible for bringing colder, high-CO2, low-pH water to the surface starting on day t16 of the experiment; this variable CO2 system with frequent upwelling events implies that the community of the Baltic Sea is acclimated to regular significant declines in pH caused by up to 800 µatm fCO2. After

  14. Assessment of atmospheric trace element concentrations by lichen-bag near an oil/gas pre-treatment plant in the Agri Valley (southern Italy)

    NASA Astrophysics Data System (ADS)

    Caggiano, R.; Trippetta, S.; Sabia, S.

    2015-02-01

    The atmospheric concentrations of 17 trace elements (Al, Ca, Cd, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, Pb, S, Ti and Zn) were measured by means of the "lichen-bag" technique in the Agri Valley (southern Italy). The lichen samples were collected from an unpolluted site located in Rifreddo forest (southern Italy), about 30 km away from the study area along the north direction. The bags were exposed to ambient air for 6 and 12 months. The exposed-to-control (EC) ratio values highlighted that the used lichen species were suitable for biomonitoring investigations. The results showed that the concentrations of almost all the examined trace elements increased with respect to the control after 6-12-month exposures. Furthermore, Ca, Al, Fe, K, Mg and S were the most abundant trace elements both in the 6-month and 12-month-exposed samples. Moreover, principal component analysis (PCA) results highlighted that the major sources of the measured atmospheric trace elements were related both to anthropogenic contributions due to traffic, combustion processes agricultural practices, construction and quarrying activities, and to natural contributions mainly represented by the re-suspension of local soil and road dusts. In addition, the contribution both of secondary atmospheric reactions involving Centro Olio Val d'Agri (COVA) plant emissions and the African dust long-range transport were also identified.

  15. Assessment of atmospheric trace element concentrations by lichen-bag near an oil/gas pre-treatment plant in the Agri Valley (southern Italy)

    NASA Astrophysics Data System (ADS)

    Caggiano, R.; Trippetta, S.; Sabia, S.

    2014-10-01

    The atmospheric concentrations of 17 trace elements (Al, Ca, Cd, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, Pb, S, Ti and Zn) were measured by means of the "lichen-bag" technique in the Agri Valley (southern Italy). The lichen samples were collected from an unpolluted site located in Rifreddo forest (southern Italy). The bags were exposed to ambient air for 6 and 12 months. The exposed-to-control (EC) ratio values highlighted that the used lichen species were suitable for biomonitoring investigations. The results showed that the concentrations of almost all the examined trace elements increased with respect to the control after 6-12 month exposures. Furthermore, Ca, Al, Fe, K, Mg and S were the most abundant trace elements both in the 6 and 12 month-exposed samples. Moreover, principal component analysis (PCA) results highlighted that the major sources of the measured atmospheric trace elements were related both to anthropogenic contributions due to traffic, combustion processes, agricultural practices, construction and quarrying activities, and to natural contributions mainly represented by the re-suspension of local soil and road dusts. In addition, the contribution both of secondary atmospheric reactions involving Centro Olio Val d'Agri (COVA) plant emissions and the African dust long-range transport were also identified.

  16. Study on the decomposition of trace benzene over V2O5–WO3/TiO2-based catalysts in simulated flue gas

    EPA Science Inventory

    Trace levels (1 and 10 ppm) of gaseous benzene were catalytically decomposed in a fixed-bed catalytic reactor with monolithic oxides of vanadium and tungsten supported on titanium oxide (V2O5–WO3/TiO2) catalysts under conditions simulating the cooling of waste incineration flue g...