Gas adsorption and desorption effects on high pressure small volume cylinders and their relevance to atmospheric trace gas analysis

NASA Astrophysics Data System (ADS)

Satar, Ece; Nyfeler, Peter; Pascale, Céline; Niederhauser, Bernhard; Leuenberger, Markus

2017-04-01

Long term atmospheric monitoring of trace gases requires great attention to precision and accuracy of the measurement setups. For globally integrated and well established greenhouse gas observation networks, the World Meteorological Organization (WMO) has set recommended compatibility goals within the framework of its Global Atmosphere Watch (GAW) Programme [1]. To achieve these challenging limits, the measurement systems are regularly calibrated with standard gases of known composition. Therefore, the stability of the primary and secondary gas standards over time is an essential issue. Past studies have explained the small instabilities in high pressure standard gas cylinders through leakage, diffusion, regulator effects, gravimetric fractionation and surface processes [2, 3]. The latter include adsorption/desorption, which are functions of temperature, pressure and surface properties. For high pressure standard gas mixtures used in atmospheric trace gas analysis, there exists only a limited amount of data and few attempts to quantify the surface processes [4, 5]. Specifically, we have designed a high pressure measurement chamber to investigate trace gases and their affinity for adsorption on different surfaces over various temperature and pressure ranges. Here, we focus on measurements of CO2, CH4 and CO using a cavity ring down spectroscopy analyzer and quantify the concentration changes due to adsorption/desorption. In this study, the first results from these prototype cylinders of steel and aluminum will be presented. References [1] World Meteorological Organization (WMO), Global Atmosphere Watch.(GAW): Report No. 229, 18th WMO/IAEA Meeting on Carbon Dioxide, Other Greenhouse Gases and Related Tracers Measurement Techniques (GGMT-2015), 2016. [2] Keeling, R. F., Manning, A. C., Paplawsky, W. J., and Cox, A. C.: On the long-term stability of reference gases for atmospheric O2 /N2 and CO2 measurements, Tellus B, 59, 10.3402/tellusb.v59i1.16964, 2007. [3

Hot N2 in Titan's upper atmosphere

NASA Astrophysics Data System (ADS)

Lavvas, P.; Yelle, R. V.; Heays, A.; Campbell, L.; Brunger, M. J.; Galand, M.; Vuitton, V.

2015-10-01

We present a detailed model for the vibrational population of all non pre-dissociating excited electronic states of N2, as well as for the ground and ionic states,in Titan's atmosphere. Our model includes the detailed energy deposition calculations presented in the past [1] as well as the more recent developments in the high resolution N2 photo-absorption cross sections that allow us to calculate photo-excitation rates for different vibrational levels of singlet nitrogen states, and provide information for their pre-dissociation yields.In addition, we consider the effect of collisions and chemical reactions in the population of the different states. Our results demonstrate that a significant population of vibrationally excited ground state N2 survives in Titan's upper atmosphere. This hot N2population can improve the agreement between models and observations for the emission of the c'4 state that is significantly affected by resonant scattering. Moreover we discuss the potential implications of the vibrationally excited population on the ionospheric densities.

Sensitivity of terrestrial N2O emission to atmospheric nitrogen deposition

NASA Astrophysics Data System (ADS)

Ito, A.; Sudo, K.; Nishina, K.; Ishijima, K.; Inatomi, M. I.

2015-12-01

Terrestrial N2O emission is generated from several nitrogen sources including biological fixation, agricultural fertilizer, and atmospheric deposition. There remain large uncertainties how much N2O is produced from atmospheric deposition. This is a crosscutting issue between global warming and atmospheric pollution. In this study, we assessed the sensitivity of global terrestrial N2O emission to atmospheric deposition, using a process-based model VISIT. In the model, N2O emission is estimated separately for nitrification and denitrfication with the NGAS parameterization. The global simulations were conducted from 1901 to 2014 at spatial resolution of 0.5 degree. Atmospheric deposition of ammonium, NOy, and organic nitrogen simulated by the atmospheric chemistry model CHASER from the pre-industrial time to the present was used. Annual total nitrogen deposition was estimated to increase from 27 Tg N in 1901 to 77 Tg N in 2014. The total N2O emission was also estimated to increase in the period, but it was largely attributable to the increased emission from croplands. We need further investigations for the N2O emission from natural soils, which may be nitrogen-limited.

Nitrogen gas flushing can be bactericidal: the temperature-dependent destiny of Bacillus weihenstephanensis KBAB4 under a pure N2 atmosphere.

PubMed

Munsch-Alatossava, Patricia; Alatossava, Tapani

2014-01-01

Gram-negative Pseudomonas and Gram-positive Bacillus are the most common spoilage bacteria in raw and pasteurized milk, respectively. In previous studies, nitrogen (N2) gas flushing treatments of raw and pasteurized milk at cold chain-temperatures inhibited bacterial spoilage and highlighted different susceptibilities to the N2 treatment with the exclusion of certain bacterial types. Here, we investigated the effects of pure N2 gas flushing on representative strains of these genera grown in mono- or co-cultures at 15 and 25°C. Bacillus weihenstephanensis, a frequent inhabitant of fluid dairy products, is represented by the genome-sequenced KBAB4 strain. Among Pseudomonas, P. tolaasii LMG 2342(T) and strain C1, a raw milk psychrotroph, were selected. The N2 gas flushing treatment revealed: (1) temperature-dependent responses; (2) inhibition of the growth of both pseudomonads; (3) emergence of small colony variants (SCVs) for B. weihenstephanensis strain KBAB4 at 15°C induced by the N2 treatment or when grown in co-culture with Pseudomonas strains; (4) N2 gas flushing modulates (suppressed or stimulated) bacterial antagonistic reactions in co-cultures; (5) most importantly, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses revealed that at 25°C the majority of the KBAB4 cells were killed by pure N2 gas flushing. This observation constitutes the first evidence that N2 gas flushing has bactericidal effects.

The Effect of Thermal Convection on Earth-Atmosphere CO2 Gas Exchange in Aggregated Soil

NASA Astrophysics Data System (ADS)

Ganot, Y.; Weisbrod, N.; Dragila, M. I.

2011-12-01

Gas transport in soils and surface-atmosphere gas exchange are important processes that affect different aspects of soil science such as soil aeration, nutrient bio-availability, sorption kinetics, soil and groundwater pollution and soil remediation. Diffusion and convection are the two main mechanisms that affect gas transport, fate and emissions in the soils and in the upper vadose zone. In this work we studied CO2 soil-atmosphere gas exchange under both day-time and night-time conditions, focusing on the impact of thermal convection (TCV) during the night. Experiments were performed in a climate-controlled laboratory. One meter long columns were packed with matrix of different grain size (sand, gravel and soil aggregates). Air with 2000 ppm CO2 was injected into the bottom of the columns and CO2 concentration within the columns was continuously monitored by an Infra Red Gas Analyzer. Two scenarios were compared for each soil: (1) isothermal conditions, representing day time conditions; and (2) thermal gradient conditions, i.e., atmosphere colder than the soil, representing night time conditions. Our results show that under isothermal conditions, diffusion is the major mechanism for surface-atmosphere gas exchange for all grain sizes; while under night time conditions the prevailing mechanism is dependent on the air permeability of the matrix: for sand and gravel it is diffusion, and for soil aggregates it is TCV. Calculated CO2 flux for the soil aggregates column shows that the TCV flux was three orders of magnitude higher than the diffusive flux.

The natural greenhouse effect of atmospheric oxygen (O2) and nitrogen (N2)

NASA Astrophysics Data System (ADS)

Höpfner, M.; Milz, M.; Buehler, S.; Orphal, J.; Stiller, G.

2012-05-01

The effect of collision-induced absorption by molecular oxygen (O2) and nitrogen (N2) on the outgoing longwave radiation (OLR) of the Earth's atmosphere has been quantified. We have found that on global average under clear-sky conditions the OLR is reduced due to O2 by 0.11 Wm-2 and due to N2 by 0.17 Wm-2. Together this amounts to 15% of the OLR-reduction caused by CH4 at present atmospheric concentrations. Over Antarctica the combined effect of O2 and N2 increases on average to about 38% of CH4 with single values reaching up to 80%. This is explained by less interference of H2O spectral bands on the absorption features of O2 and N2 for dry atmospheric conditions.

Study of Eu{sup 3+} → Eu{sup 2+} reduction in BaAl{sub 2}O{sub 4}:Eu prepared in different gas atmospheres

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

Rezende, Marcos V. dos S., E-mail: mvsrezende@gmail.com; Valerio, Mário E.G.; Jackson, Robert A.

2015-01-15

Highlights: • The effect of different gas atmospheres on the Eu reduction process was studied. • The Eu reduction was monitored analyzing XANES region at the Eu L{sub III}-edge. • Hydrogen reducing agent are the most appropriate gas for Eu{sup 2+} stabilization. • Only a part of the Eu ions can be stabilized in the divalent state. • A model of Eu reduction process is proposed. - Abstract: The effect of different gas atmospheres such as H{sub 2}(g), synthetic air, carbon monoxide (CO) and nitrogen (N{sub 2}) on the Eu{sup 3+} → Eu{sup 2+} reduction process during the synthesis ofmore » Eu-doped BaAl{sub 2}O{sub 4} was studied using synchrotron radiation. The Eu{sup 3+} → Eu{sup 2+} reduction was monitored analyzing XANES region when the sample are excited at the Eu L{sub III}-edge. The results show that the hydrogen reducing agent are the most appropriate gas for Eu{sup 2+} stabilization in BaAl{sub 2}O{sub 4} and that only a part of the Eu ions can be stabilized in the divalent state. A model of Eu reduction process, based on the incorporation of charge compensation defects, is proposed.« less

Simulation of the impact of thunderstorm activity on atmospheric gas composition

NASA Astrophysics Data System (ADS)

Smyshlyaev, S. P.; Mareev, E. A.; Galin, V. Ya.

2010-08-01

A chemistry-climate model of the lower and middle atmosphere has been used to estimate the sensitivity of the atmospheric gas composition to the rate of thunderstorm production of nitrogen oxides at upper tropospheric and lower stratospheric altitudes. The impact that nitrogen oxides produced by lightning have on the atmospheric gas composition is treated as a subgrid-scale process and included in the model parametrically. The natural uncertainty in the global production rate of nitrogen oxides in lightning flashes was specified within limits from 2 to 20 Tg N/year. Results of the model experiments have shown that, due to the variability of thunderstorm-produced nitrogen oxides, their concentration in the upper troposphere and lower stratosphere can vary by a factor of 2 or 3, which, given the influence of nitrogen oxides on ozone and other gases, creates the potential for a strong perturbation of the atmospheric gas composition and thermal regime. Model calculations have shown the strong sensitivity of ozone and the OH hydroxyl to the amount of lightning nitrogen oxides at different atmospheric altitudes. These calculations demonstrate the importance of nitrogen oxides of thunderstorm origin for the balance of atmospheric odd ozone and gases linked to it, such as ozone and hydroxyl radicals. Our results demonstrate that one important task is to raise the accuracy of estimates of the rate of nitrogen oxide production by lightning discharges and to use physical parametrizations that take into account the local lightning effects and feedbacks arising in this case rather than climatological data in models of the gas composition and general circulation of the atmosphere.

Atmosphere-ocean gas exchange based on radiocarbon data

NASA Astrophysics Data System (ADS)

Byalko, Alexey

2014-05-01

In recent decades, the intensity of global atmospheric convection has accelerated faster than climate warming; it is possible to judge this process from indirect data. Increasing ocean salinity contrasts provide evidence that evaporation has intensified [1]; sea surface wind velocities and wave heights have increased [2]. The CO2 gas exchange between the atmosphere and ocean must also simultaneously increase. Monthly measurements of atmospheric CO2 concentration have been published since 1958 [3], but directly measuring its fluxes from the atmosphere to the ocean and back is hardly possible. We show they can be reconstructed from 14C isotope concentration data. In the past century, two processes influenced the atmospheric 14C concentration in opposite directions: burning fossil fuels and testing nuclear weapons in the atmosphere. We compare the gas exchange theory with measurements of radiocarbon content in the atmosphere [4—6], which allows assessing the gas exchange quantitatively for the ocean to atmosphere and atmosphere to ocean fluxes separately for period 1960—2010 [7]. References 1. Durack P. J. and Wijffels S. E., J. Climate 23, 4342 (2010). 2. Young I. R., Sieger S., and Babanin A.V., Science 332, 451 (2011). 3. NOAA Earth System Research Laboratory Data: ftp://ftp.cmdl.noaa.gov/ccg/co2/trends/co2_mm_mlo.txt. 4. Nydal R., Lövseth K. // J. Geophys. Res. 1983. V. 88. P. 3579. 5. Levin I., Kromer B. // Radiocarbon. 1997. V. 39. P. 205. 6. Miller J.B., Lehman S.J., Montzka S.A., et al. // J. Geophys. Res. 2012. V. 117. D08302. 7. Byalko A.V. Doklady Physics, 2013. V. 58, 267-271.

N2 state population in Titan's atmosphere

NASA Astrophysics Data System (ADS)

Lavvas, P.; Yelle, R. V.; Heays, A. N.; Campbell, L.; Brunger, M. J.; Galand, M.; Vuitton, V.

2015-11-01

We present a detailed model for the vibrational population of all non pre-dissociating excited electronic states of N2, as well as for the ground and ionic states, in Titan's atmosphere. Our model includes the detailed energy deposition calculations presented in the past (Lavvas, P. et al. [2011]. Icarus 213(1), 233-251) as well as the more recent developments in the high resolution N2 photo-absorption cross sections that allow us to calculate photo-excitation rates for different vibrational levels of singlet nitrogen states, and provide information for their pre-dissociation yields. In addition, we consider the effect of collisions and chemical reactions in the population of the different states. Our results demonstrate that above 600 km altitude, collisional processes are efficient only for a small sub-set of the excited states limited to the A and W(ν = 0) triplet states, and to a smaller degree to the a‧ singlet state. In addition, we find that a significant population of vibrationally excited ground state N2 survives in Titan's upper atmosphere. Our calculations demonstrate that this hot N2 population can improve the agreement between models and observations for the emission of the c4‧ state that is significantly affected by resonant scattering. Moreover we discuss the potential implications of the vibrationally excited population on the ionospheric densities.

[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.

Compact and portable open-path sensor for simultaneous measurements of atmospheric N2O and CO using a quantum cascade laser.

PubMed

Tao, Lei; Sun, Kang; Khan, M Amir; Miller, David J; Zondlo, Mark A

2012-12-17

A compact and portable open-path sensor for simultaneous detection of atmospheric N(2)O and CO has been developed with a 4.5 μm quantum cascade laser (QCL). An in-line acetylene (C(2)H(2)) gas reference cell allows for continuous monitoring of the sensor drift and calibration in rapidly changing field environments and thereby allows for open-path detection at high precision and stability. Wavelength modulation spectroscopy (WMS) is used to detect simultaneously both the second and fourth harmonic absorption spectra with an optimized dual modulation amplitude scheme. Multi-harmonic spectra containing atmospheric N(2)O, CO, and the reference C(2)H(2) signals are fit in real-time (10 Hz) by combining a software-based lock-in amplifier with a computationally fast numerical model for WMS. The sensor consumes ~50 W of power and has a mass of ~15 kg. Precision of 0.15 ppbv N(2)O and 0.36 ppbv CO at 10 Hz under laboratory conditions was demonstrated. The sensor has been deployed for extended periods in the field. Simultaneous N(2)O and CO measurements distinguished between natural and fossil fuel combustion sources of N(2)O, an important greenhouse gas with poorly quantified emissions in space and time.

Assessing Atmospheric CO2 Entrapped in Clay Nanotubes using Residual Gas Analyzer.

PubMed

Das, Sankar; Maity, Abhijit; Pradhan, Manik; Jana, Subhra

2016-02-16

A residual gas analyzer (RGA) coupled with a high-vacuum chamber has been explored to measure atmospheric CO2 entrapped in aminosilane-modified clay nanotubes. Ambient CO2 uptake efficacy together with stability of these novel adsorbents composed of both primary and/or secondary amine sites has been demonstrated at standard ambient temperature and pressure. The unprecedented sensitivity and accuracy of the RGA-based mass spectrometry technique toward atmospheric CO2 measurement has been substantiated with a laser-based optical cavity-enhanced integrated cavity output spectroscopy. The adsorption kinetics of atmospheric CO2 on amine-functionalized clay nanotubes followed the fractional-order kinetic model compared to that of the pseudo-first-order or pseudo-second-order rate equations. The efficiency along with stability of these novel adsorbents has also been demonstrated by their repetitive use for CO2 capture in the oxidative environment. Our findings thus point to a fundamental study on the atmospheric CO2 adsorption by amine-loaded adsorbents using an easy handling and low-cost benchtop RGA-based mass spectrometer, opening a new strategy for CO2 capture and sequestering study.

Biosequestration of atmospheric CO2 and flue gas-containing CO2 by microalgae.

PubMed

Cheah, Wai Yan; Show, Pau Loke; Chang, Jo-Shu; Ling, Tau Chuan; Juan, Joon Ching

2015-05-01

The unceasing rise of greenhouse gas emission has led to global warming and climate change. Global concern on this phenomenon has put forward the microalgal-based CO2 sequestration aiming to sequester carbon back to the biosphere, ultimately reducing greenhouse effects. Microalgae have recently gained enormous attention worldwide, to be the valuable feedstock for renewable energy production, due to their high growth rates, high lipid productivities and the ability to sequester carbon. The photosynthetic process of microalgae uses atmospheric CO2 and CO2 from flue gases, to synthesize nutrients for their growth. In this review article, we will primarily discuss the efficiency of CO2 biosequestration by microalgae species, factors influencing microalgal biomass productions, microalgal cultivation systems, the potential and limitations of using flue gas for microalgal cultivation as well as the bio-refinery approach of microalgal biomass. Copyright © 2014 Elsevier Ltd. All rights reserved.

Free energy study of H2O, N2O5, SO2, and O3 gas sorption by water droplets/slabs

NASA Astrophysics Data System (ADS)

Li, Wentao; Pak, Chi Yuen; Tse, Ying-Lung Steve

2018-04-01

Understanding gas sorption by water in the atmosphere is an active research area because the gases can significantly alter the radiation and chemical properties of the atmosphere. We attempt to elucidate the molecular details of the gas sorption of water and three common atmospheric gases (N2O5, SO2, and O3) by water droplets/slabs in molecular dynamics simulations. The system size effects are investigated, and we show that the calculated solvation free energy decreases linearly as a function of the reciprocal of the number of water molecules from 1/215 to 1/1000 in both the slab and the droplet systems. By analyzing the infinitely large system size limit by extrapolation, we find that all our droplet results are more accurate than the slab results when compared to the experimental values. We also show how the choice of restraints in umbrella sampling can affect the sampling efficiency for the droplet systems. The free energy changes were decomposed into the energetic ΔU and entropic -TΔS contributions to reveal the molecular details of the gas sorption processes. By further decomposing ΔU into Lennard-Jones and Coulombic interactions, we observe that the ΔU trends are primarily determined by local effects due to the size of the gas molecule, charge distribution, and solvation structure around the gas molecule. Moreover, we find that there is a strong correlation between the change in the entropic contribution and the mean residence time of water, which is spatially nonlocal and related to the mobility of water.

A 490 W transversely excited atmospheric CO2 spark gap laser with added H2

NASA Astrophysics Data System (ADS)

Zand, M.; Koushki, A. M.; Neshati, R.; Kia, B.; Khorasani, K.

2018-02-01

In this paper we present a new design for a high pulse repetition rate transversely excited atmospheric CO2 laser with ultraviolet pre-ionization. A new method of fast thyristor capacitor charging and discharging by a spark gap is used. The effect of H2 gas addition on the output and stability of a transversely excited atmospheric laser operating with a basic mixture of CO2, N2 and He is investigated. The output power was increased by adding H2 to the gas mixture ratio of CO2:N2:He:H2  =  1:1:8:0.5 at total pressure of 850 mbar. An average power of 490 W at 110 Hz with 4.5 J per pulse was obtained. The laser efficiency was 11.2% and oxygen gas was used in the spark gap for electron capture to reduce the recovery time and increase the repetition rate.

Mars Atmospheric Capture and Gas Separation

NASA Technical Reports Server (NTRS)

Muscatello, Anthony; Santiago-Maldonado, Edgardo; Gibson, Tracy; Devor, Robert; Captain, James

2011-01-01

The Mars atmospheric capture and gas separation project is selecting, developing, and demonstrating techniques to capture and purify Martian atmospheric gases for their utilization for the production of hydrocarbons, oxygen, and water in ISRU systems. Trace gases will be required to be separated from Martian atmospheric gases to provide pure C02 to processing elements. In addition, other Martian gases, such as nitrogen and argon, occur in concentrations high enough to be useful as buffer gas and should be captured as welL To achieve these goals, highly efficient gas separation processes will be required. These gas separation techniques are also required across various areas within the ISRU project to support various consumable production processes. The development of innovative gas separation techniques will evaluate the current state-of-the-art for the gas separation required, with the objective to demonstrate and develop light-weight, low-power methods for gas separation. Gas separation requirements include, but are not limited to the selective separation of: (1) methane and water from un-reacted carbon oxides (C02- CO) and hydrogen typical of a Sabatier-type process, (2) carbon oxides and water from unreacted hydrogen from a Reverse Water-Gas Shift process, (3) carbon oxides from oxygen from a trash/waste processing reaction, and (4) helium from hydrogen or oxygen from a propellant scavenging process. Potential technologies for the separations include freezers, selective membranes, selective solvents, polymeric sorbents, zeolites, and new technologies. This paper and presentation will summarize the results of an extensive literature review and laboratory evaluations of candidate technologies for the capture and separation of C02 and other relevant gases.

Production of simplex RNS and ROS by nanosecond pulse N2/O2 plasma jets with homogeneous shielding gas for inducing myeloma cell apoptosis

NASA Astrophysics Data System (ADS)

Liu, Zhijie; Xu, Dehui; Liu, Dingxin; Cui, Qingjie; Cai, Haifeng; Li, Qiaosong; Chen, Hailan; Kong, Michael G.

2017-05-01

In this paper, atmospheric pressure N2/O2 plasma jets with homogeneous shielding gas excited by nanosecond pulse are obtained to generate simplex reactive nitrogen species (RNS) and reactive oxygen species (ROS), respectively, for the purpose of studying the simplex RNS and ROS to induce the myeloma cell apoptosis with the same discharge power. The results reveal that the cell death rate by the N2 plasma jet with N2 shielding gas is about two times that of the O2 plasma jet with O2 shielding gas for the equivalent treatment time. By diagnosing the reactive species of ONOO-, H2O2, OH and \\text{O}2- in medium, our findings suggest the cell death rate after plasma jets treatment has a positive correlation with the concentration of ONOO-. Therefore, the ONOO- in medium is thought to play an important role in the process of inducing myeloma cell apoptosis.

Gas entrapment and microbial N2O reduction reduce N2O emissions from a biochar-amended sandy clay loam soil

PubMed Central

Harter, Johannes; Guzman-Bustamante, Ivan; Kuehfuss, Stefanie; Ruser, Reiner; Well, Reinhard; Spott, Oliver; Kappler, Andreas; Behrens, Sebastian

2016-01-01

Nitrous oxide (N2O) is a potent greenhouse gas that is produced during microbial nitrogen transformation processes such as nitrification and denitrification. Soils represent the largest sources of N2O emissions with nitrogen fertilizer application being the main driver of rising atmospheric N2O concentrations. Soil biochar amendment has been proposed as a promising tool to mitigate N2O emissions from soils. However, the underlying processes that cause N2O emission suppression in biochar-amended soils are still poorly understood. We set up microcosm experiments with fertilized, wet soil in which we used 15N tracing techniques and quantitative polymerase chain reaction (qPCR) to investigate the impact of biochar on mineral and gaseous nitrogen dynamics and denitrification-specific functional marker gene abundance and expression. In accordance with previous studies our results showed that biochar addition can lead to a significant decrease in N2O emissions. Furthermore, we determined significantly higher quantities of soil-entrapped N2O and N2 in biochar microcosms and a biochar-induced increase in typical and atypical nosZ transcript copy numbers. Our findings suggest that biochar-induced N2O emission mitigation is based on the entrapment of N2O in water-saturated pores of the soil matrix and concurrent stimulation of microbial N2O reduction resulting in an overall decrease of the N2O/(N2O + N2) ratio. PMID:28008997

N2O and CO production by electric discharge - Atmospheric implications. [Venus atmosphere simulation

NASA Technical Reports Server (NTRS)

Levine, J. S.; Howell, W. E.; Hughes, R. E.; Chameides, W. L.

1979-01-01

Enhanced levels of N2O and CO were measured in tropospheric air samples exposed to a 17,500-J laboratory discharge. These enhanced levels correspond to an N2O production rate of about 4 trillion molecules/J and a CO production rate of about 10 to the 14th molecules/J. The CO measurements suggest that the primary region of chemical production in the discharge is the shocked air surrounding the lightning channel, as opposed to the slower-cooling inner core. Additional experiments in a simulated Venus atmosphere (CO2 - 95%, N2 - 5%, at one atmosphere) indicate an enhancement of CO from less than 0.1 ppm prior to the laboratory discharge to more than 2000 ppm after the discharge. Comparison with theoretical calculations appears to confirm the ability of a shock-wave/thermochemical model to predict the rate of production of trace species by an electrical discharge.

The Nitrous Oxide (N2O) Budget: Constraints from Atmospheric Observations and Models

NASA Astrophysics Data System (ADS)

Tian, H.; Thompson, R.; Canadell, J.; Winiwarter, W.; Tian, H.; Thompson, R.; Prather, M. J.

2017-12-01

The increasing global abundance of N2O poses a threat to human health and society over this coming century through both climate change and ozone depletion. In the sense of greenhouse gases, N2O ranks third behind CO2 and CH4. In the sense of ozone depletion, N2O stands alone. In order to identify the cause of these increases and hopefully reverse them, we need to have a thorough understanding of the sources and sinks (a.k.a. the budget) of N2O and how they can be altered. A bottom-up approach to the budget evaluates individual biogeochemical sources of N2O from the land and ocean; whereas, a top-down approach uses atmospheric observations of the variability, combined with modeling of the atmospheric chemistry and transport, to infer the magnitude of sources and sinks throughout the Earth system. This paper reviews top-down approaches using atmospheric data; a similar top-down approach can be taken with oceanic measurements of N2O, but is not covered here. Stratospheric chemistry is the predominant loss of N2O, and here we review how a merging of new measurements with stratospheric chemistry models is able to provide a constrained budget for the global N2O sink. N2O surface sources are transported and mixed throughout the atmosphere, providing positive anomalies in the N2O abundance (mole fraction of N2O with respect to dry air); while N2O-depleted air from the stratosphere provides negative anomalies. With accurate atmospheric transport models, including for stratosphere-troposphere exchange, the observed tropospheric variability in N2O is effectively a fingerprint of the location and magnitude of sources. This inverse modeling of sources is part of the top-down constraints and is reviewed here.

N2O fluxes at the soil-atmosphere interface in various ecosystems and the global N2O budget

NASA Technical Reports Server (NTRS)

Banin, Amos

1987-01-01

The overall purpose of this research task is to study the effects of soil properties and ecosystem variables on N2O exchanges at the soil-atmosphere interface, and to assess their effects on the globle N2O budget. Experimental procedures are implemented in various sites to measure the source/sink relations of N2O at the soil-atmosphere interface over prolonged periods of time as part of the research of biogeochemical cycling in terrestrial ecosystems. A data-base for establishing quantitative correlations between N2O fluxes and soil and environmental parameters that are of potential use for remote sensing, is being developed.

Atmospheric trace gas analysis using matrix isolation-Fourier Transform Infrared Spectroscopy

NASA Astrophysics Data System (ADS)

Griffith, David W. T.; Schuster, Gerhard

1987-03-01

A novel cryogenic sampling method combining the matrix isolation technique with FTIR spectroscopy has been developed for atmospheric trace gas analysis. It is applicable to a wide range of molecules with detection limits typically in the 10-50 ppt range. The method is described along with some measurements of N2O, CFCl3, CF2Cl2, OCS, CS2, SO2 and PAN from samples collected at ground level and from an aircraft between 9 and 14 km.

Fighting global warming by greenhouse gas removal: destroying atmospheric nitrous oxide thanks to synergies between two breakthrough technologies.

PubMed

Ming, Tingzhen; de Richter, Renaud; Shen, Sheng; Caillol, Sylvain

2016-04-01

Even if humans stop discharging CO2 into the atmosphere, the average global temperature will still increase during this century. A lot of research has been devoted to prevent and reduce the amount of carbon dioxide (CO2) emissions in the atmosphere, in order to mitigate the effects of climate change. Carbon capture and sequestration (CCS) is one of the technologies that might help to limit emissions. In complement, direct CO2 removal from the atmosphere has been proposed after the emissions have occurred. But, the removal of all the excess anthropogenic atmospheric CO2 will not be enough, due to the fact that CO2 outgases from the ocean as its solubility is dependent of its atmospheric partial pressure. Bringing back the Earth average surface temperature to pre-industrial levels would require the removal of all previously emitted CO2. Thus, the atmospheric removal of other greenhouse gases is necessary. This article proposes a combination of disrupting techniques to transform nitrous oxide (N2O), the third most important greenhouse gas (GHG) in terms of current radiative forcing, which is harmful for the ozone layer and possesses quite high global warming potential. Although several scientific publications cite "greenhouse gas removal," to our knowledge, it is the first time innovative solutions are proposed to effectively remove N2O or other GHGs from the atmosphere other than CO2.

Modeling pN2 through Geological Time: Implications for Planetary Climates and Atmospheric Biosignatures.

PubMed

Stüeken, E E; Kipp, M A; Koehler, M C; Schwieterman, E W; Johnson, B; Buick, R

2016-12-01

Nitrogen is a major nutrient for all life on Earth and could plausibly play a similar role in extraterrestrial biospheres. The major reservoir of nitrogen at Earth's surface is atmospheric N 2 , but recent studies have proposed that the size of this reservoir may have fluctuated significantly over the course of Earth's history with particularly low levels in the Neoarchean-presumably as a result of biological activity. We used a biogeochemical box model to test which conditions are necessary to cause large swings in atmospheric N 2 pressure. Parameters for our model are constrained by observations of modern Earth and reconstructions of biomass burial and oxidative weathering in deep time. A 1-D climate model was used to model potential effects on atmospheric climate. In a second set of tests, we perturbed our box model to investigate which parameters have the greatest impact on the evolution of atmospheric pN 2 and consider possible implications for nitrogen cycling on other planets. Our results suggest that (a) a high rate of biomass burial would have been needed in the Archean to draw down atmospheric pN 2 to less than half modern levels, (b) the resulting effect on temperature could probably have been compensated by increasing solar luminosity and a mild increase in pCO 2 , and (c) atmospheric oxygenation could have initiated a stepwise pN 2 rebound through oxidative weathering. In general, life appears to be necessary for significant atmospheric pN 2 swings on Earth-like planets. Our results further support the idea that an exoplanetary atmosphere rich in both N 2 and O 2 is a signature of an oxygen-producing biosphere. Key Words: Biosignatures-Early Earth-Planetary atmospheres. Astrobiology 16, 949-963.

Estimating gas exchange of CO2 and CH4 between headwater systems and the atmosphere in Southwest Sweden

NASA Astrophysics Data System (ADS)

Somlai, Celia; Natchimuthu, Sivakiruthika; Bastviken, David; Lorke, Andreas

2015-04-01

Quantifying the role of inland water systems in terms of carbon sinks and sources and their connection to the terrestrial ecosystems and landscapes is fundamental for improving the balance approach of regional and global carbon budgets. Recent research showed that freshwater bodies emit significant amounts of CO2 and CH4 into the atmosphere. The extent of the emissions from small streams and headwaters, however, remains uncertain due to a limited availability of data. Studies have shown that headwater systems receive most of the terrestrial organic carbon, have the highest dissolved CO2 concentration and the highest gas exchange velocities and cover the largest fractional surface area within fluvial networks. The gas exchange between inland waters and the atmosphere is controlled by two factors: the difference between the dissolved gas concentration and its atmospheric equilibrium concentration, and the gas exchange velocity. The direct measurement of the dissolved gas concentration of greenhouse gases can be measured straightforwardly, for example, by gas chromatography from headspace extraction of water sample. In contrast, direct measurement of gas exchange velocity is more complex and time consuming, as simultaneous measurements with a volatile and nonvolatile inert tracer gas are needed. Here we analyze measurements of gas exchange velocities, concentrations and fluxes of dissolved CO2 and CH4, as well as loads of total organic and inorganic carbon in 10 reaches in headwater streams in Southwest Sweden. We compare the gas exchange velocities measured directly through tracer injections with those estimated through various empirical approaches, which are based on modelled and measured current velocity, stream depth and slope. Furthermore, we estimate the resulting uncertainties of the flux estimates. We also present different time series of dissolved CO2, CH4 and O2 concentration, water temperature, barometric pressure, electro conductivity, and pH values

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

CRITICAL REVIEW OF N, N{sup +}, N{sup +} {sub 2}, N{sup ++}, And N{sup ++} {sub 2} MAIN PRODUCTION PROCESSES AND REACTIONS OF RELEVANCE TO TITAN'S ATMOSPHERE

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

Dutuit, Odile; Thissen, Roland; Vuitton, Veronique

2013-02-15

This paper is a detailed critical review of the production processes and reactions of N, N{sup +}, N{sup +} {sub 2}, N{sup ++}, and N{sup ++} {sub 2} of relevance to Titan's atmosphere. The review includes neutral, ion-molecule, and recombination reactions. The review covers all possible active nitrogen species under Titan's atmospheric conditions, specifically N{sub 2} (A {sup 3}{Sigma}{sup +} {sub u}), N ({sup 4} S), N ({sup 2} D), N ({sup 2} P), N{sup +} {sub 2}, N{sup +} ({sup 3} P), N{sup +} ({sup 1} D), N{sup ++} {sub 2}, and N{sup ++} species, and includes a criticalmore » survey of the reactions of N, N{sup +}, N{sup +} {sub 2}, N{sup ++}, and N{sup ++} {sub 2} with N{sub 2}, H{sub 2}, D{sub 2}, CH{sub 4}, C{sub 2}H{sub 2}, C{sub 2}H{sub 4}, C{sub 2}H{sub 6}, C{sub 3}H{sub 8} and the deuterated hydrocarbon analogs, as well as the recombination reactions of N{sup +} {sub 2}, N{sup +}, N{sup ++} {sub 2}, and N{sup ++}. Production processes, lifetimes, and quenching by collisions with N{sub 2} of all reactant species are reviewed. The N ({sup 4} S) state is reactive with radicals and its reactions with CH{sub 2}, CH{sub 3}, C{sub 2}H{sub 3}, and C{sub 2}H{sub 5} are reviewed. Metastable states N{sub 2} (A {sup 3}{Sigma}{sup +} {sub u}), N ({sup 2} D), and N ({sup 2} P) are either reactive or quenched by collisions with the target molecules reviewed. The reactions of N{sup +} ({sup 1} D) have similar rate constants as N{sup +} ({sup 3} P), but the product branching ratios differ significantly. Temperature effects and the role of the kinetic energy content of reactants are investigated. In all cases, experimental uncertainties of laboratory data are reported or estimated. Recommended values with uncertainties, or estimated values when no data are available, are given for rate constants and product branching ratios at 300 K and at the atmospheric temperature range of Titan (150-200 K for neutral reactions and 150 K for ion reactions).« less

PRODUCTS OF THE GAS-PHASE REACTIONS OF THE OH RADICAL WITH N-BUTYL METHYL ETHER AND 2-ISOPROPOXYETHANOL: REACTIONS OF ROC(O)< RADICALS. (R825252)

EPA Science Inventory

The products of the gas-phase reactions of the OH radical with n-butyl methyl ether and 2-isopropoxyethanol in the presence of NO have been investigated at 298 ? 2 K and 740 Torr total pressure of air by gas chromatography and in situ atmospheric pressure ionization...

Influence of Gas Atmosphere Dew Point on the Galvannealing of CMnSi TRIP Steel

NASA Astrophysics Data System (ADS)

Cho, Lawrence; Kim, Myung Soo; Kim, Young Ha; De Cooman, Bruno C.

2013-11-01

The Fe-Zn reaction occurring during the galvannealing of a Si-bearing transformation-induced plasticity (TRIP) steel was investigated by field-emission electron probe microanalysis and field-emission transmission electron microscopy. The galvannealing was simulated after hot dipping in a Zn bath containing 0.13 mass pct Al at 733 K (460 °C). The galvannealing temperature was in the range of 813 K to 843 K (540 °C to 570 °C). The kinetics and mechanism of the galvannealing reaction were strongly influenced by the gas atmosphere dew point (DP). After the galvannealing of a panel annealed in a N2+10 pct H2 gas atmosphere with low DPs [213 K and 243 K (-60 °C and -30 °C)], the coating layer consisted of δ (FeZn10) and η (Zn) phase crystals. The Mn-Si compound oxides formed during intercritical annealing were present mostly at the steel/coating interface after the galvannealing. Galvannealing of a panel annealed in higher DP [263 K and 273 K, and 278 K (-10 °C, 0 °C, and +5 °C)] gas atmospheres resulted in a coating layer consisting of δ and Г (Fe3Zn10) phase crystals, and a thin layer of Г 1 (Fe11Zn40) phase crystals at the steel/coating interface. The Mn-Si oxides were distributed homogeneously throughout the galvannealed (GA) coating layer. When the surface oxide layer thickness on panels annealed in a high DP gas atmosphere was reduced, the Fe content at the GA coating surface increased. Annealing in a higher DP gas atmosphere improved the coating quality of the GA panels because a thinner layer of oxides was formed. A high DP atmosphere can therefore significantly contribute to the suppression of Zn-alloy coating defects on CMnSi TRIP steel processed in hot dip galvanizing lines.

Development of atmospheric N2O isotopomers model based on a chemistry-coupled atmospheric general circulation model

NASA Astrophysics Data System (ADS)

Ishijima, K.; Toyoda, S.; Sudo, K.; Yoshikawa, C.; Nanbu, S.; Aoki, S.; Nakazawa, T.; Yoshida, N.

2009-12-01

It is well known that isotopic information is useful to qualitatively understand cycles and constrain sources of some atmospheric species, but so far there has been no study to model N2O isotopomers throughout the atmosphere from the troposphere to the stratosphere, including realistic surface N2O isotopomers emissions. We have started to develop a model to simulate spatiotemporal variations of the atmospheric N2O isotopomers in both the troposphere and the stratosphere, based on a chemistry-coupled atmospheric general circulation model, in order to obtain more accurate quantitative understanding of the global N2O cycle. For surface emissions of the isotopomers, combination of EDGAR-based anthropogenic and soil fluxes and monthly varying GEIA oceanic fluxes are factored, using isotopic values of global total sources estimated from firn-air analyses based long-term trend of the atmospheric N2O isotopomers. Isotopic fractionations in chemical reactions are considered for photolysis and photo-oxidation of N2O in the stratosphere. The isotopic fractionation coefficients have been employed from studies based on laboratory experiments, but we also will test the coefficients determined by theoretical calculations. In terms of the global N2O isotopomer budgets, precise quantification of the sources is quite challenging, because even the spatiotemporal variabilities of N2O sources have never been adequately estimated. Therefore, we have firstly started validation of simulated isotopomer results in the stratosphere, by using the isotopomer profiles obtained by balloon observations. N2O concentration profiles are mostly well reproduced, partly because of realistic reproduction of dynamical processes by nudging with reanalysis meteorological data. However, the concentration in the polar vortex tends to be overestimated, probably due to relatively coarse wave-length resolution in photolysis calculation. Such model features also appear in the isotopomers results, which are

CO2 deficit in temperate forest soils receiving high atmospheric N-deposition.

PubMed

Fleischer, Siegfried

2003-02-01

Evidence is provided for an internal CO2 sink in forest soils, that may have a potential impact on the global CO2-budget. Lowered CO2 fraction in the soil atmosphere, and thus lowered CO2 release to the aboveground atmosphere, is indicated in high N-deposition areas. Also at forest edges, especially of spruce forest, where additional N-deposition has occurred, the soil CO2 is lowered, and the gradient increases into the closed forest. Over the last three decades the capacity of the forest soil to maintain the internal sink process has been limited to a cumulative supply of approximately 1000 and 1500 kg N ha(-1). Beyond this limit the internal soil CO2 sink becomes an additional CO2 source, together with nitrogen leaching. This stage of "nitrogen saturation" is still uncommon in closed forests in southern Scandinavia, however, it occurs in exposed forest edges which receive high atmospheric N-deposition. The soil CO2 gradient, which originally increases from the edge towards the closed forest, becomes reversed.

Detection of the SO2 atmosphere on Io with the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Ballester, G. E.; Mcgrath, M. A.; Stobel, D. F.; Zhu, Xun; Feldman, P. D.; Moos, H. W.

1994-01-01

Observations of the trailing hemisphere of Io made with the Faint Object Spectrograph of the Hubble Space Telescope (HST) in March 1992 have resulted in the first detection of atmospheric SO2 absorption bands in the ultraviolet. These observations represent only the third positive means of detection of what is widely believed to be Io's primary atmospheric constituent. Below approximately 2130 A the geometric albedo of the satellite is dominated by SO2 gas absorption band signatures, which have been analyzed using models that include the effects of optical thickness, temperature, and spatial distribution. The disk-intergrated HST data cannot resolve the spatial distribution, but it is possible to define basic properties and set constraints on the atmosphere at the time of the observations. Hemispheric atmospheres with average column density N = 6 - 10 x 10(exp 15)/sq sm and T(gas) = 110 - 500 K fit the data, with preference for temperatures of approximately 200 - 250 K. Better fits are found as the atmosphere is spatially confined, with a limit of approximately 8% hemispheric areal coverage and N approximately equal to 3 x 10(exp 17)/sq cm with colder 110 - 250 K temepratures. A dense (N greater than or equal to 10(exp 16)/sq cm), localized component of SO2 gas, such as that possibly associated with active volcanoes, can generate the observed spectral constrast only when the atmosphere is cold (110 K) and an extended component such as Pele is included. The combination of a dense, localized atmosphere with a tenuous component (N less than 10(exp 16)/sq cm, either patchy or extended) also fits the data. In all cases the best fit models imply a disk-averaged column density larger than exospheric but approximately 10 - 30 times less than the previous upper limit from near-UV observations.

Time-dependent one-dimensional simulation of atmospheric dielectric barrier discharge in N2/O2/H2O using COMSOL Multiphysics

NASA Astrophysics Data System (ADS)

Sohbatzadeh, F.; Soltani, H.

2018-04-01

The results of time-dependent one-dimensional modelling of a dielectric barrier discharge (DBD) in a nitrogen-oxygen-water vapor mixture at atmospheric pressure are presented. The voltage-current characteristics curves and the production of active species are studied. The discharge is driven by a sinusoidal alternating high voltage-power supply at 30 kV with frequency of 27 kHz. The electrodes and the dielectric are assumed to be copper and quartz, respectively. The current discharge consists of an electrical breakdown that occurs in each half-period. A detailed description of the electron attachment and detachment processes, surface charge accumulation, charged species recombination, conversion of negative and positive ions, ion production and losses, excitations and dissociations of molecules are taken into account. Time-dependent one-dimensional electron density, electric field, electric potential, electron temperature, densities of reactive oxygen species (ROS) and reactive nitrogen species (RNS) such as: O, O-, O+, {O}2^{ - } , {O}2^{ + } , O3, {N}, {N}2^{ + } , N2s and {N}2^{ - } are simulated versus time across the gas gap. The results of this work could be used in plasma-based pollutant degradation devices.

CO2 Ice Formation and CO2 Gas Depletion in the Polar Winter Atmosphere of Mars from Mars Climate Sounder Measurements

NASA Astrophysics Data System (ADS)

Kleinboehl, A.; Patel, P. K.; Schofield, J. T.; Kass, D. M.; Hayne, P. O.; McCleese, D. J.

2016-12-01

Temperatures in the martian lower atmosphere commonly reach the frost point of CO2 in the polar winter vortices over an extended vertical range. New retrievals from the Mars Climate Sounder (MCS) instrument on Mars Reconnaissance Orbiter allow the characterization of the winter polar regions with improved accuracy. MCS is a passive infrared sounder with 5 mid-infrared, 3 far infrared, and one broadband visible/near-infrared channels. Each spectral channel uses a linear detector array consisting of 21 elements, which provides -10 to 90 km altitude coverage when pointed at the Mars limb. From the infrared measurements, vertical profiles of temperature and aerosols are retrieved with an altitude resolution of about 5 km. Due to their long optical path through the atmosphere, limb measurements are susceptible to horizontal gradients in temperature or absorber amount in their line-of-sight, an effect that is particularly important in polar winter regions due to strong latitudinal temperature gradients in the atmosphere. The new retrievals take horizontal gradients in temperature and aerosols into account by means of a two-dimensional radiative transfer scheme. The resulting temperature profiles reveal that temperatures in the south winter polar region repeatedly drop several degrees below the frost point of CO2. This behavior is consistent with the removal of CO2 from the atmosphere through condensation, resulting in an atmosphere that is depleted in gaseous CO2 and enhanced in non-condensable gases like N2 and Ar. In these regions emission features at 22 μm are often found in MCS limb measurements, consistent with the presence of CO2 ice in the polar vortex. We will map these depletions of CO2 gas and show correlations with the occurrence of CO2 ice. We will provide comparisons of these effects between the southern and the northern polar winter vortices.

Impact of nitrogen fertilization on soil-Atmosphere greenhouse gas exchanges in eucalypt plantations with different soil characteristics in southern China.

PubMed

Zhang, Kai; Zheng, Hua; Chen, Falin; Li, Ruida; Yang, Miao; Ouyang, Zhiyun; Lan, Jun; Xiang, Xuewu

2017-01-01

Nitrogen (N) fertilization is necessary to sustain productivity in eucalypt plantations, but it can increase the risk of greenhouse gas emissions. However, the response of soil greenhouse gas emissions to N fertilization might be influenced by soil characteristics, which is of great significance for accurately assessing greenhouse gas budgets and scientific fertilization in plantations. We conducted a two-year N fertilization experiment (control [CK], low N [LN], middle N [MN] and high N [HN] fertilization) in two eucalypt plantations with different soil characteristics (higher and lower soil organic carbon sites [HSOC and LSOC]) in Guangxi, China, and assessed soil-atmosphere greenhouse gas exchanges. The annual mean fluxes of soil CO2, CH4, and N2O were separately 153-266 mg m-2 h-1, -55 --40 μg m-2 h-1, and 11-95 μg m-2 h-1, with CO2 and N2O emissions showing significant seasonal variations. N fertilization significantly increased soil CO2 and N2O emissions and decreased CH4 uptake at both sites. There were significant interactions of N fertilization and SOC level on soil CO2 and N2O emissions. At the LSOC site, the annual mean flux of soil CO2 emission was only significantly higher than the CK treatment in the HN treatment, but, at the HSOC site, the annual mean flux of soil CO2 emission was significantly higher for both the LN (or MN) and HN treatments in comparison to the CK treatment. Under the CK and LN treatments, the annual mean flux of N2O emission was not significantly different between HSOC and LSOC sites, but under the HN treatment, it was significantly higher in the HSOC site than in the LSOC site. Correlation analysis showed that changes in soil CO2 and N2O emissions were significantly related to soil dissolved organic carbon, ammonia, nitrate and pH. Our results suggested significant interactions of N fertilization and soil characteristics existed in soil-atmosphere greenhouse gas exchanges, which should be considered in assessing greenhouse gas

Impact of nitrogen fertilization on soil–Atmosphere greenhouse gas exchanges in eucalypt plantations with different soil characteristics in southern China

PubMed Central

Zhang, Kai; Zheng, Hua; Chen, Falin; Li, Ruida; Yang, Miao; Ouyang, Zhiyun; Lan, Jun; Xiang, Xuewu

2017-01-01

Nitrogen (N) fertilization is necessary to sustain productivity in eucalypt plantations, but it can increase the risk of greenhouse gas emissions. However, the response of soil greenhouse gas emissions to N fertilization might be influenced by soil characteristics, which is of great significance for accurately assessing greenhouse gas budgets and scientific fertilization in plantations. We conducted a two-year N fertilization experiment (control [CK], low N [LN], middle N [MN] and high N [HN] fertilization) in two eucalypt plantations with different soil characteristics (higher and lower soil organic carbon sites [HSOC and LSOC]) in Guangxi, China, and assessed soil–atmosphere greenhouse gas exchanges. The annual mean fluxes of soil CO2, CH4, and N2O were separately 153–266 mg m-2 h-1, -55 –-40 μg m-2 h-1, and 11–95 μg m-2 h-1, with CO2 and N2O emissions showing significant seasonal variations. N fertilization significantly increased soil CO2 and N2O emissions and decreased CH4 uptake at both sites. There were significant interactions of N fertilization and SOC level on soil CO2 and N2O emissions. At the LSOC site, the annual mean flux of soil CO2 emission was only significantly higher than the CK treatment in the HN treatment, but, at the HSOC site, the annual mean flux of soil CO2 emission was significantly higher for both the LN (or MN) and HN treatments in comparison to the CK treatment. Under the CK and LN treatments, the annual mean flux of N2O emission was not significantly different between HSOC and LSOC sites, but under the HN treatment, it was significantly higher in the HSOC site than in the LSOC site. Correlation analysis showed that changes in soil CO2 and N2O emissions were significantly related to soil dissolved organic carbon, ammonia, nitrate and pH. Our results suggested significant interactions of N fertilization and soil characteristics existed in soil–atmosphere greenhouse gas exchanges, which should be considered in assessing

Solubility and diffusivity of N{sub 2}O and CO{sub 2} in (diethanolamine + N-methyldiethanolamine + water) and in (diethanolamine + 2-amino-2-methyl-1-propanol + water)

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

Li, M.H.; Lee, W.C.

1996-05-01

Acid gases such as CO{sub 2} and H{sub 2}S are frequently removed from natural gas, synthetic natural gas, and other process gas streams by means of absorption into aqueous alkanol-amine solutions. The solubility and diffusivity of N{sub 2}O in (diethanolamine + N-methyldiethanolamine + water) and in (diethanolamine + 2-amino-2-methyl-1-propanol + water) were measured at (30, 35, and 40)C and at atmospheric pressure. Five (diethanolamine + N-methyldiethanolamine + water) and four (diethanolamine + 2-amino-2-methyl-1-propanol + water) systems were studied. The total amine mass percent in all cases was 30. A solubility apparatus was used to measure the solubility of N{sub 2}Omore » in amine solutions. The diffusivity was measured by a wetted wall column absorber. The N{sub 2}O analogy was used to estimate the solubility and diffusivity of CO{sub 2} in (diethanolamine + N-methyldiethanolamine + water) and in (diethanolamine + 2-amino-2-methyl-1-propanol + water).« less

Atmospheric CO2: principal control knob governing Earth's temperature.

PubMed

Lacis, Andrew A; Schmidt, Gavin A; Rind, David; Ruedy, Reto A

2010-10-15

Ample physical evidence shows that carbon dioxide (CO(2)) is the single most important climate-relevant greenhouse gas in Earth's atmosphere. This is because CO(2), like ozone, N(2)O, CH(4), and chlorofluorocarbons, does not condense and precipitate from the atmosphere at current climate temperatures, whereas water vapor can and does. Noncondensing greenhouse gases, which account for 25% of the total terrestrial greenhouse effect, thus serve to provide the stable temperature structure that sustains the current levels of atmospheric water vapor and clouds via feedback processes that account for the remaining 75% of the greenhouse effect. Without the radiative forcing supplied by CO(2) and the other noncondensing greenhouse gases, the terrestrial greenhouse would collapse, plunging the global climate into an icebound Earth state.

CO2 Capture by Injection of Flue Gas or CO2-N2 Mixtures into Hydrate Reservoirs: Dependence of CO2 Capture Efficiency on Gas Hydrate Reservoir Conditions.

PubMed

Hassanpouryouzband, Aliakbar; Yang, Jinhai; Tohidi, Bahman; Chuvilin, Evgeny; Istomin, Vladimir; Bukhanov, Boris; Cheremisin, Alexey

2018-04-03

Injection of flue gas or CO 2 -N 2 mixtures into gas hydrate reservoirs has been considered as a promising option for geological storage of CO 2 . However, the thermodynamic process in which the CO 2 present in flue gas or a CO 2 -N 2 mixture is captured as hydrate has not been well understood. In this work, a series of experiments were conducted to investigate the dependence of CO 2 capture efficiency on reservoir conditions. The CO 2 capture efficiency was investigated at different injection pressures from 2.6 to 23.8 MPa and hydrate reservoir temperatures from 273.2 to 283.2 K in the presence of two different saturations of methane hydrate. The results showed that more than 60% of the CO 2 in the flue gas was captured and stored as CO 2 hydrate or CO 2 -mixed hydrates, while methane-rich gas was produced. The efficiency of CO 2 capture depends on the reservoir conditions including temperature, pressure, and hydrate saturation. For a certain reservoir temperature, there is an optimum reservoir pressure at which the maximum amount of CO 2 can be captured from the injected flue gas or CO 2 -N 2 mixtures. This finding suggests that it is essential to control the injection pressure to enhance CO 2 capture efficiency by flue gas or CO 2 -N 2 mixtures injection.

Efficient gas exchange between a boreal river and the atmosphere

NASA Astrophysics Data System (ADS)

Huotari, Jussi; Haapanala, Sami; Pumpanen, Jukka; Vesala, Timo; Ojala, Anne

2013-11-01

largest uncertainties in accurately resolving the role of rivers and streams in carbon cycling stem from difficulties in determining gas exchange between water and the atmosphere. So far, estimates for river-atmosphere gas exchange have lacked direct ecosystem-scale flux measurements not disturbing gas exchange across the air-water interface. We conducted the first direct riverine gas exchange measurements with eddy covariance in tandem with continuous surface water CO2 measurements in a large boreal river for 30 days. Our measured gas transfer velocity was, on average, 20.8 cm h-1, which is clearly higher than the model estimates based on river channel morphology and water velocity, whereas our floating chambers gave comparable values at 17.3 cm h-1. These results demonstrate that present estimates for riverine CO2 emissions are very likely too low. This result is also relevant to any other gases emitted, as their diffusive exchange rates are similarly proportional to gas transfer velocity.

Temperature dependence of surface tension of molten iron under reducing gas atmosphere

NASA Astrophysics Data System (ADS)

Ozawa, S.; Takahashi, S.; Fukuyama, H.; Watanabe, M.

2011-12-01

Surface tension of molten iron was measured under Ar-He-5vol.%H2 gas by oscillating droplet method using electromagnetic levitation furnace in consideration of the temperature dependence of oxygen partial pressure, Po2, of the gas. For comparison, the measurement was carried under Ar-He atmosphere to fix the Po2 of the inlet gas at 10-2Pa. The surface tension was successfully measured over a wide temperature range of about 780K including undercooling condition. When Po2 is fixed at 10-2 Pa, the surface tension increased and then decreased with increasing temperature like a boomerang shape. When the measurement was carried out under the H2-containing gas atmosphere, the temperature dependence of the surface tension shows unique kink at around 1810K instead of liner relationship due to competition between the temperature dependence of the Po2 and that of the equilibrium constant of oxygen adsorption reaction. The relationship between the calculated lnKad with respect to inverse temperature using Szyszkowski model was different between the atmospheric gases.

Spectroscopic study of bipolar nanosecond pulse gas-liquid discharge in atmospheric argon

NASA Astrophysics Data System (ADS)

Sen, WANG; Dezheng, YANG; Feng, LIU; Wenchun, WANG; Zhi, FANG

2018-07-01

Atmospheric gas-liquid discharge with argon as a working gas is presented by employed nanosecond pulse power. The discharge is presented in a glow-like mode. The discharge powers are determined to be less than 1 W, and remains almost constant when the discharge duration time increases. Bountiful active species are determined by capturing optical emission spectra, and their main generation processes are also discussed. The plasma gas temperature is calculated as 350 K by comparing the experimental spectra and the simulated ones of {{{N}}}2({{C}}{}3{{\\Pi }}{{g}}\\to {{B}}{}3{{\\Pi }}{{g}},{{Δ }}{{ν }}=-2). The time resolved vibrational and rotational temperature is researched to present the stability of discharge when pulse voltage and discharge duration vary. The electron density is determined to be 1016 cm‑3 according to the Stark broadening effect of the H α line.

Ammonia 15N/14N Isotope Ratio in the Jovian Atmosphere

NASA Technical Reports Server (NTRS)

Mahaffy, P.R.; Niemann, H. B.; Atreya, S. K.; Wong, M. H.; Owen, T. C; Einaudi, Franco (Technical Monitor)

2000-01-01

Data from the Galileo Probe Mass Spectrometer has been used to derive the N-15/N-14 isotope ratio in ammonia at Jupiter. Although the mass spectral interference from the water contribution to 18 amu makes an accurate derivation of the (N-15)H3/(N-14)H3 ratio difficult from measurements of the singly ionized signals at 18 and 17 amu, this interference is not present in the doubly charged 8.5 and 9.0 amu signals from (N-14)H3++ and (N-15)H3++ respectively. Although the count rate from the 9 amu signal is low during the direct sampling of the atmosphere, the ammonia signal was considerably enhanced during the first enrichment cell (EC1) experiment that measured gas sampled between 0.8 and 2.8 bar. Count rates at 9 amu in the EC1 experiment reach 60/second and measure ammonia sampled from 0.88 to 2.8 bar. In the EC1 measurements the 8.5 amu signal is not measured directly, but can be calculated from the ammonia contribution to 17 amu and the ratio of NH3 ions of a double to single charged observed during a high resolution mass scan taken near the end of the descent. The high resolution scan gives this ratio from ammonia sampled much deeper in the atmosphere. These results are described and compared with Infrared Space Observatory-Short Wavelength Spectrometer (ISO-SWS) observations that give this ratio at 400 mbar.

SO_2 Absorption Cross Sections and N_2 VUV Oscillator Strengths for Planetary Atmosphere Studies

NASA Astrophysics Data System (ADS)

Smith, Peter L.; Stark, G.; Rufus, J.; Pickering, J. C.; Cox, G.; Huber, K. P.

1998-09-01

The determination of the chemical composition of the atmosphere of Io from Hubble Space Telescope observations in the 190-220 nm wavelength region requires knowledge of the photoabsorption cross sections of SO_2 at temperatures ranging from about 110 K to 300 K. We are engaged in a laboratory program to measure SO_2 absorption cross sections with very high resolving power (lambda /delta lambda =~ 450,000) and at a range of temperatures appropriate to the Io atmosphere. Previous photoabsorption measurements, with lambda /delta lambda =~ 100,000, have been unable to resolve the very congested SO_2 spectrum, and, thus, to elucidate the temperature dependence of the cross sections. Our measurements are being performed at Imperial College, London, using an ultraviolet Fourier transform spectrometer. We will present our recently completed room temperature measurements of SO_2 cross sections in the 190-220 nm region and plans for extending these to ~ 195 K. Analyses of Voyager VUV occultation measurements of the N_2-rich atmospheres of Titan and Triton have been hampered by the lack of fundamental spectroscopic data for N_2, in particular, by the lack of reliable f-values and line widths for electronic bands of N_2 in the 80-100 nm wavelength region. We are continuing our program of measurements of band oscillator strengths for the many (approximately 100) N_2 bands between 80 and 100 nm. We report new f-values, derived from data obtained at the Photon Factory (Tsukuba, Japan) synchrotron radiation facility with lambda /delta lambda =~ 130,000, of 37 bands in the 80-86 nm region and 21 bands in the 90-95 nm region. We have also begun the compilation of a searchable archive of N_2 data on the World Wide Web; see http://cfa-www.harvard. edu/amp/data/n2/n2home.html. The archive, covering the spectroscopy of N_2 between 80 and 100 nm, will include published and unpublished (14) N_2, (14) N(15) N, and (15) N_2 line lists and spectroscopic identifications, excited state energy

An approach for verifying biogenic greenhouse gas emissions inventories with atmospheric CO 2 concentration data

DOE PAGES

Ogle, Stephen; Davis, Kenneth J.; Lauvaux, Thomas; ...

2015-03-10

Verifying national greenhouse gas (GHG) emissions inventories is a critical step to ensure that reported emissions data to the United Nations Framework Convention on Climate Change (UNFCCC) are accurate and representative of a country’s contribution to GHG concentrations in the atmosphere. Verification could include a variety of evidence, but arguably the most convincing verification would be confirmation of a change in GHG concentrations in the atmosphere that is consistent with reported emissions to the UNFCCC. We report here on a case study evaluating this option based on a prototype atmospheric CO2 measurement network deployed in the Mid-Continent Region of themore » conterminous United States. We found that the atmospheric CO2 measurement data did verify the accuracy of the emissions inventory within the confidence limits of the emissions estimates, suggesting that this technology could be further developed and deployed more widely in the future for verifying reported emissions.« less

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

USGS Publications Warehouse

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

2006-01-01

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

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

The Influence of CO2 Admixtures on the Product Composition in a Nitrogen-Methane Atmospheric Glow Discharge Used as a Prebiotic Atmosphere Mimic.

PubMed

Mazankova, V; Torokova, L; Krcma, F; Mason, N J; Matejcik, S

2016-11-01

This work extends our previous experimental studies of the chemistry of Titan's atmosphere by atmospheric glow discharge. The Titan's atmosphere seems to be similarly to early Earth atmospheric composition. The exploration of Titan atmosphere was initiated by the exciting results of the Cassini-Huygens mission and obtained results increased the interest about prebiotic atmospheres. Present work is devoted to the role of CO 2 in the prebiotic atmosphere chemistry. Most of the laboratory studies of such atmosphere were focused on the chemistry of N 2  + CH 4 mixtures. The present work is devoted to the study of the oxygenated volatile species in prebiotic atmosphere, specifically CO 2 reactivity. CO 2 was introduced to the standard N 2  + CH 4 mixture at different mixing ratio up to 5 % CH 4 and 3 % CO 2 . The reaction products were characterized by FTIR spectroscopy. This work shows that CO 2 modifies the composition of the gas phase with the detection of oxygenated compounds: CO and others oxides. There is a strong influence of CO 2 on increasing concentration other products as cyanide (HCN) and ammonia (NH 3 ).

Polyport atmospheric gas sampler

DOEpatents

Guggenheim, S. Frederic

1995-01-01

An atmospheric gas sampler with a multi-port valve which allows for multi, sequential sampling of air through a plurality of gas sampling tubes mounted in corresponding gas inlet ports. The gas sampler comprises a flow-through housing which defines a sampling chamber and includes a gas outlet port to accommodate a flow of gases through the housing. An apertured sample support plate defining the inlet ports extends across and encloses the sampling chamber and supports gas sampling tubes which depend into the sampling chamber and are secured across each of the inlet ports of the sample support plate in a flow-through relation to the flow of gases through the housing during sampling operations. A normally closed stopper means mounted on the sample support plate and operatively associated with each of the inlet ports blocks the flow of gases through the respective gas sampling tubes. A camming mechanism mounted on the sample support plate is adapted to rotate under and selectively lift open the stopper spring to accommodate a predetermined flow of gas through the respective gas sampling tubes when air is drawn from the housing through the outlet port.

Burning of CP Titanium (Grade 2) in Oxygen-Enriched Atmospheres

NASA Technical Reports Server (NTRS)

Stoltzfus, Joel M.; Jeffers, Nathan; Gallus, Timothy D.

2012-01-01

The flammability in oxygen-enriched atmospheres of commercially pure (CP) titanium rods as a function of diameter and test gas pressure was determined. Test samples of varying diameters were ignited at the bottom and burned upward in 70% O2/balance N2 and in 99.5+% O2 at various pressures. The burning rate of each ignited sample was determined by observing the apparent regression rate of the melting interface (RRMI) of the burning samples. The burning rate or RRMI increased with decreasing test sample diameter and with increasing test gas pressure and oxygen concentration

Why is gas phase 2-nitrophenol photolysis a potentially important source of OH radicals in the polluted atmosphere?

NASA Astrophysics Data System (ADS)

Zhu, L.

2017-12-01

2-Nitrophenol is an important component of "brown carbon" in the atmosphere. The concentration of 2-nitrophenol is higher in polluted urban areas where there are increased emissions of aromatic hydrocarbons. To assess the air quality impacts of pollutant emissions, it is important to understand the oxidant formation potential of the emitted species. Photolysis is the dominant atmospheric removal process for 2-nitrophenol. Although photodissociation dynamics studies of 2-nitrophenol have reported OH formation at photolysis wavelengths of 266 nm, 355 nm, and over the 361-390 nm range, and HONO has been observed as a product from 2-nitrophenol photolysis in an environmental chamber, the lack of quantitative absorption cross section and product quantum yield information has prevented quantitative assessment of the extent of oxidant formation from the photolysis of 2-nitrophenol in the atmosphere. My group determined the gas phase absorption cross sections of 2-nitrophenol in the 295-400 nm region by using cavity ring-down spectroscopy. The OH, HONO, and NO2 formation channels following the gas phase photolysis of 2-nitrophenol at 308 and 351 nm were investigated. Direct NO2 formation was not observed. OH and HONO were direct products from the 2-nitrophenol photolysis, and their quantum yields were obtained. The sum of the OH and the HONO quantum yields was about unity at both photolysis wavelengths. The estimated photolysis rate constant of 2-nitrophenol was about twice that of NO2. I will discuss the importance of 2-nitrophenol gas phase photolysis as a potential source of OH and HONO in regions of high anthropogenic emissions.

The persistent and pernicious myth of the early CO2-N2 atmospheres of terrestrial planets

NASA Astrophysics Data System (ADS)

Shaw, G. H.

2009-12-01

The accepted model for early atmospheres of terrestrial planets has settled on a CO2-N2 composition. Unfortunately, while it is largely based on a brilliant geological analysis by Rubey, there is no compelling evidence whatsoever for such a composition as the first “permanent” atmosphere for Earth or any other planet. In fact, geological discoveries of the past 50+ years reveal several problems with a CO2-N2 atmosphere, some of which Rubey recognized in his own analysis. He clearly addressed the problem of timing of degassing, concluding that early massive degassing of CO2 would produce readily observed and profound effects, which are not evident. Modeling and constraints on the timing of planetary accretion and core formation indicate massive early degassing. If early degassing emitted CO2-N2, the effects are concealed. Plate tectonic recycling is not a solution, as conditions would have persisted beyond the time of the earliest rocks, which do not show the effects. Attempts to return degassed CO2 to the mantle are not only ad hoc, but inconsistent with early thermal structure of the Earth. Second, production of prebiotic organic compounds from a CO2-N2 atmosphere has been a nagging problem. At best this has been addressed by invoking hydrogen production from the mantle to provide reducing capacity. While hydrogen may be emitted in volcanic eruptions, it is exceedingly difficult to imagine this process generating enough organics to yield high concentrations in a global ocean. The recent fashion of invoking organic synthesis at deep-sea vents suffers from the same problem: how to achieve sufficient concentrations of organics in a global ocean by abiotic synthesis when hydrothermal activity stirs the solution and carries the prebiotic products off to great dilution? Suggesting life began at deep-sea vents, and continues to carry on chemosynthesis there, begs the question. Unless you get high enough concentrations of prebiotics by abiotic processes, you simply

High-resolution modelling of atmospheric dispersion of dense gas using TWODEE-2.1: application to the 1986 Lake Nyos limnic eruption

NASA Astrophysics Data System (ADS)

Folch, Arnau; Barcons, Jordi; Kozono, Tomofumi; Costa, Antonio

2017-06-01

Atmospheric dispersal of a gas denser than air can threat the environment and surrounding communities if the terrain and meteorological conditions favour its accumulation in topographic depressions, thereby reaching toxic concentration levels. Numerical modelling of atmospheric gas dispersion constitutes a useful tool for gas hazard assessment studies, essential for planning risk mitigation actions. In complex terrains, microscale winds and local orographic features can have a strong influence on the gas cloud behaviour, potentially leading to inaccurate results if not captured by coarser-scale modelling. We introduce a methodology for microscale wind field characterisation based on transfer functions that couple a mesoscale numerical weather prediction model with a microscale computational fluid dynamics (CFD) model for the atmospheric boundary layer. The resulting time-dependent high-resolution microscale wind field is used as input for a shallow-layer gas dispersal model (TWODEE-2.1) to simulate the time evolution of CO2 gas concentration at different heights above the terrain. The strategy is applied to review simulations of the 1986 Lake Nyos event in Cameroon, where a huge CO2 cloud released by a limnic eruption spread downslopes from the lake, suffocating thousands of people and animals across the Nyos and adjacent secondary valleys. Besides several new features introduced in the new version of the gas dispersal code (TWODEE-2.1), we have also implemented a novel impact criterion based on the percentage of human fatalities depending on CO2 concentration and exposure time. New model results are quantitatively validated using the reported percentage of fatalities at several locations. The comparison with previous simulations that assumed coarser-scale steady winds and topography illustrates the importance of high-resolution modelling in complex terrains.

Novel microelectrode-based online system for monitoring N2O gas emissions during wastewater treatment.

PubMed

Marques, Ricardo; Oehmen, Adrian; Pijuan, Maite

2014-11-04

Clark-type nitrous oxide (N2O) microelectrodes are commonly used for measuring dissolved N2O levels, but have not previously been tested for gas-phase applications, where the N2O emitted from wastewater systems can be directly quantified. In this study, N2O microelectrodes were tested and validated for online gas measurements, and assessed with respect to their temperature, gas flow, composition dependence, gas pressure, and humidity. An exponential correlation between temperature and sensor signal was found, whereas gas flow, composition, pressure, and humidity did not have any influence on the signal. Two of the sensors were tested at different N2O concentration ranges (0-422.3, 0-50, 0-10, and 0-2 ppmv N2O) and exhibited a linear response over each range. The N2O emission dynamics from two laboratory scale sequencing batch reactors performing ammonia or nitrite oxidation were also monitored using one of the microsensors and results were compared with two other analytical methods. Results show that N2O emissions were accurately described with these microelectrodes and support their application for assessing gaseous N2O emissions from wastewater treatment systems. Advantages of the sensors as compared to conventional measurement techniques include a wider quantification range of N2O fluxes, and a single measurement system that can assess both liquid and gas-phase N2O dynamics.

Improved atmospheric density estimation for ANDE-2 satellites using drag coefficients obtained from gas-surface interaction equations

NASA Astrophysics Data System (ADS)

Flanagan, Harold Patrick

A major issue in the process of predicting the future position of satellites in low earth orbit (LEO) is that the drag coefficient of a satellite is generally not precisely known throughout the satellite's lifespan. One reason for this problem is that as a satellite travels through the Earth's thermosphere, variations in the composition of the thermosphere directly affect the drag coefficient of the satellite. The greatest amount of uncertainty in the drag coefficient from these variations in the thermosphere comes from the amount of atomic oxygen that covers the satellites surface as the satellite descends to lower altitudes. This percent surface coverage of atomic oxygen directly affects the interaction between the surface of the satellite and the gas through which it is passing. The work performed in this thesis determines the drag coefficients of the ANDE-2 satellites over their life spans by using satellite laser ranging (SLR) data of the ANDE-2 satellites in unison with gas-surface interaction equations. The fractional coverage of atomic oxygen is determined by using empirically determined data and semi-empirical models that attempt to predict the fractional coverage of oxygen relative to the composition of the atmosphere. These drag coefficients are then used to determine the atmospheric densities experienced by these satellites over various days, so that inaccuracies in the atmospheric models can be observed. The drag coefficients of the ANDE-2 satellites decrease throughout the satellites' life, and vary most due to changes in the temperature and density of the atmosphere. The greatest uncertainty in the atmosphere's composition occurs at lower altitudes at the end of ANDE-2's life.

Development of Diesel Engine Operated Forklift Truck for Explosive Gas Atmospheres

NASA Astrophysics Data System (ADS)

Vishwakarma, Rajendra Kumar; Singh, Arvind Kumar; Ahirwal, Bhagirath; Sinha, Amalendu

2018-02-01

For the present study, a prototype diesel engine operated Forklift truck of 2 t capacity is developed for explosive gas atmosphere. The parts of the Forklift truck are assessed against risk of ignition of the explosive gases, vapors or mist grouped in Gr. IIA and having ignition temperature more than 200°C. Identification of possible sources of ignition and their control or prevention is the main objective of this work. The design transformation of a standard Forklift truck into a special Forklift truck is made on prototype basis. The safety parameters of the improved Forklift truck are discussed in this paper. The specially designed Forklift truck is useful in industries where explosive atmospheres may present during normal working conditions and risk of explosion is a concern during handling or transportation of materials. This indigenous diesel engine based Forklift truck for explosive gas atmosphere classified as Zone 1 and Zone 2 area and gas group IIA is developed first time in India in association with the Industry.

Comparison of nitrous oxide (N2O) analyzers for high-precision measurements of atmospheric mole fractions

NASA Astrophysics Data System (ADS)

Lebegue, B.; Schmidt, M.; Ramonet, M.; Wastine, B.; Yver Kwok, C.; Laurent, O.; Belviso, S.; Guemri, A.; Philippon, C.; Smith, J.; Conil, S.; Jost, H. J.; Crosson, E. R.

2015-10-01

Over the last few decades, in-situ measurements of atmospheric N2O mole fractions have been performed using gas chromatographs (GCs) equipped with electron capture detectors (ECDs). When trying to meet the World Meteorological Organization's (WMO) quality goal, this technique becomes very challenging as the detectors are highly non-linear and the GCs at remote stations require a considerable amount of maintenance by qualified technicians to maintain good short-term and long-term repeatability. With more robust optical spectrometers being now available for N2O measurements, we aim to identify a robust and stable analyzer that can be integrated into atmospheric monitoring networks, such as the Integrated Carbon Observation System (ICOS). In this study, we tested seven analyzers that were developed and commercialized from five different companies and compared the results with established techniques. Each instrument was characterized during a time period of approximately eight weeks. The test protocols included the characterization of the short-term and long-term repeatability, drift, temperature dependence, linearity and sensitivity to water vapor. During the test period, ambient air measurements were compared under field conditions at the Gif-sur-Yvette station. All of the analyzers showed a standard deviation better than 0.1 ppb for the 10 min averages. Some analyzers would benefit from improvements in temperature stability to reduce the instrument drift, which could then help in reducing the frequency of calibrations. For most instruments, the water vapor correction algorithms applied by companies are not sufficient for high-precision atmospheric measurements, which results in the need to dry the ambient air prior to analysis.

Sugarcane vinasse CO2 gasification and release of ash-forming matters in CO2 and N2 atmospheres.

PubMed

Dirbeba, Meheretu Jaleta; Brink, Anders; DeMartini, Nikolai; Lindberg, Daniel; Hupa, Mikko

2016-10-01

Gasification of sugarcane vinasse in CO2 and the release of ash-forming matters in CO2 and N2 atmospheres were investigated using a differential scanning calorimetry and thermogravimetric analyzer (DSC-TGA) at temperatures between 600 and 800°C. The results showed that pyrolysis is the main mechanism for the release of the organics from vinasse. Release of ash-forming matters in the vinasse is the main cause for vinasse char weight losses in the TGA above 700°C. The losses are higher in N2 than in CO2, and increase considerably with temperature. CO2 gasification also consumes the carbon in the vinasse chars while suppressing alkali release. Alkali release was also significant due to volatilization of KCl and reduction of alkali sulfate and carbonate by carbon. The DSC measured thermal events during heating up in N2 atmosphere that correspond to predicted melting temperatures of alkali salts in the char. Copyright © 2016 Elsevier Ltd. All rights reserved.

Real-time N2O gas detection system for agricultural production using a 4.6-µm-band laser source based on a periodically poled LiNbO3 ridge waveguide.

PubMed

Tokura, Akio; Asobe, Masaki; Enbutsu, Koji; Yoshihara, Toshihiro; Hashida, Shin-nosuke; Takenouchi, Hirokazu

2013-08-05

This article describes a gas monitoring system for detecting nitrous oxide (N2O) gas using a compact mid-infrared laser source based on difference-frequency generation in a quasi-phase-matched LiNbO3 waveguide. We obtained a stable output power of 0.62 mW from a 4.6-μm-band continuous-wave laser source operating at room temperature. This laser source enabled us to detect atmospheric N2O gas at a concentration as low as 35 parts per billion. Using this laser source, we constructed a new real-time in-situ monitoring system for detecting N2O gas emitted from potted plants. A few weeks of monitoring with the developed detection system revealed a strong relationship between nitrogen fertilization and N2O emission. This system is promising for the in-situ long-term monitoring of N2O in agricultural production, and it is also applicable to the detection of other greenhouse gases.

Raman scattering by H2 and N2 in the atmospheres of exoplanets

NASA Astrophysics Data System (ADS)

Oklopcic, Antonija; Hirata, Christopher M.; Heng, Kevin

2016-06-01

Rayleigh scattering is an important source of opacity in the atmospheres of exoplanets at short optical and near-UV wavelengths. Raman scattering is an inelastic process related to Rayleigh scattering, but with a weaker cross section. We analyze the signatures of Raman scattering imprinted in the reflected light and the geometric albedo of exoplanets. Raman scattering causes filling-in of absorption lines in the incident spectrum, thus producing sharp enhancements in the geometric albedo. It also shifts the wavelengths of spectral features in the reflected light causing the Raman ghost lines. Observing the albedo enhancements could be used to measure the column density of the scattering molecule and provide constrains on the presence of clouds and hazes in the atmosphere. Observing the Raman ghost lines could be used to spectroscopically identify the main scatterer in the atmosphere -- molecules like H2 or N2 which do not show prominent spectral signatures in the optical wavelength range. If detected, ghost lines could also provide information about the temperature of the atmosphere. Here we present how these signatures of Raman scattering in hydrogen- and nitrogen-dominated atmospheres can be used as probes of atmospheric pressure, temperature and composition. We analyze the feasibility of detecting these features in the albedo spectra of nearby exoplanets with the existing and future observational facilities.

Calibrating Laser Gas Measurements by Use of Natural CO2

NASA Technical Reports Server (NTRS)

Webster, Chris

2003-01-01

continuously as a calibration standard for every measurement point. Figure 1 depicts simulated spectral transmission measurements in a wavenumber range that contains two absorption lines of N2O and one of CO2. The simulations were performed for two different upper-atmospheric pressures for an airborne instrument that has a path length of 80 m. The relative abundance of CO2 in air was assumed to be 360 parts per million by volume (approximately its natural level in terrestrial air). In applying the present method to measurements like these, one could average the signals from the two N2O absorption lines and normalize their magnitudes to that of the CO2 absorption line. Other gases with which this calibration method can be used include H2O, CH4, CO, NO, NO2, HOCl, C2H2, NH3, O3, and HCN. One can also take advantage of this method to eliminate an atmospheric-pressure gauge and thereby reduce the mass of the instrument: The atmospheric pressure can be calculated from the temperature, the known relative abundance of CO2, and the concentration of CO2 as measured by spectral absorption. Natural CO2 levels on Mars provide an ideal calibration standard. Figure 2 shows a second example of the application of this method to Mars atmospheric gas measurements. For sticky gases like H2O, the method is particularly powerful, since water is notoriously difficult to handle at low concentrations in pre-flight calibration procedures.

Marine biological controls on atmospheric CO2 and climate

NASA Technical Reports Server (NTRS)

Mcelroy, M. B.

1983-01-01

It is argued that the ocean is losing N gas faster than N is being returned to the ocean, and that replenishment of the N supply in the ocean usually occurs during ice ages. Available N from river and estruarine transport and from rainfall after formation by lightning are shown to be at a rate too low to compensate for the 10,000 yr oceanic lifetime of N. Ice sheets advance and transfer moraine N to the ocean, lower the sea levels, erode the ocean beds, promote greater biological productivity, and reduce CO2. Ice core samples have indicated a variability in the atmospheric N content that could be attributed to the ice age scenario.

The contamination of commercial 15N2 gas stocks with 15N-labeled nitrate and ammonium and consequences for nitrogen fixation measurements.

PubMed

Dabundo, Richard; Lehmann, Moritz F; Treibergs, Lija; Tobias, Craig R; Altabet, Mark A; Moisander, Pia H; Granger, Julie

2014-01-01

We report on the contamination of commercial 15-nitrogen (15N) N2 gas stocks with 15N-enriched ammonium, nitrate and/or nitrite, and nitrous oxide. 15N2 gas is used to estimate N2 fixation rates from incubations of environmental samples by monitoring the incorporation of isotopically labeled 15N2 into organic matter. However, the microbial assimilation of bioavailable 15N-labeled N2 gas contaminants, nitrate, nitrite, and ammonium, is liable to lead to the inflation or false detection of N2 fixation rates. 15N2 gas procured from three major suppliers was analyzed for the presence of these 15N-contaminants. Substantial concentrations of 15N-contaminants were detected in four Sigma-Aldrich 15N2 lecture bottles from two discrete batch syntheses. Per mole of 15N2 gas, 34 to 1900 µmoles of 15N-ammonium, 1.8 to 420 µmoles of 15N-nitrate/nitrite, and ≥21 µmoles of 15N-nitrous oxide were detected. One 15N2 lecture bottle from Campro Scientific contained ≥11 µmoles of 15N-nitrous oxide per mole of 15N2 gas, and no detected 15N-nitrate/nitrite at the given experimental 15N2 tracer dilutions. Two Cambridge Isotopes lecture bottles from discrete batch syntheses contained ≥0.81 µmoles 15N-nitrous oxide per mole 15N2, and trace concentrations of 15N-ammonium and 15N-nitrate/nitrite. 15N2 gas equilibrated cultures of the green algae Dunaliella tertiolecta confirmed that the 15N-contaminants are assimilable. A finite-differencing model parameterized using oceanic field conditions typical of N2 fixation assays suggests that the degree of detected 15N-ammonium contamination could yield inferred N2 fixation rates ranging from undetectable, <0.01 nmoles N L(-1) d(-1), to 530 nmoles N L(-1) d(-1), contingent on experimental conditions. These rates are comparable to, or greater than, N2 fixation rates commonly detected in field assays. These results indicate that past reports of N2 fixation should be interpreted with caution, and demonstrate that the purity of commercial 15N2

Solubility and diffusivity of N{sub 2}O and CO{sub 2} in (monoethanolamine + N-methyldiethanolamine + water) and in (monoethanolamine + 2-amino-2-methyl-1-propanol + water)

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

Li, M.H.; Lai, M.D.

1995-03-01

Solutions of amines are frequently used in gas-treating processes to remove acid gases, such as CO{sub 2} and H{sub 2}S, from gas streams in the natural gas and synthetic ammonia industries and petroleum chemical plants. The solubility and diffusivity of N{sub 2}O in (monoethanolamine + N-methyldiethanolamine + water) and in (monoethanolamine + 2-amino-2-methyl-l-propanol + water) were measured at 30, 35, and 40 C and at atmospheric pressure. Six (monoethanolamine + N-methyldiethanolamine + water) and five (monoethanolamine + 2-amino-2-methyl-l-propanol + water) systems were studied. The total amine mass percent in all cases was 30. The solubilities were measured by a solubilitymore » apparatus similar to that of Haimour and Sandall (1984). A wetted wall column absorber was used to obtain the diffusivity of N{sub 2}O in amines. The N{sub 2}O solubilities in amine solutions have been correlated on the basis of the excess Henry constant correlation of Wang et al. (1992). The N{sub 2}O analogy was used to estimate the solubility and diffusivity of CO{sub 2} in (monoethanolamine + N-methyldiethanolamine + water) and in (monoethanolamine + 2-amino-2-methyl-l-propanol + water).« less

Development of an atmospheric N2O isotopocule model and optimization procedure, and application to source estimation

NASA Astrophysics Data System (ADS)

Ishijima, K.; Takigawa, M.; Sudo, K.; Toyoda, S.; Yoshida, N.; Röckmann, T.; Kaiser, J.; Aoki, S.; Morimoto, S.; Sugawara, S.; Nakazawa, T.

2015-07-01

This paper presents the development of an atmospheric N2O isotopocule model based on a chemistry-coupled atmospheric general circulation model (ACTM). We also describe a simple method to optimize the model and present its use in estimating the isotopic signatures of surface sources at the hemispheric scale. Data obtained from ground-based observations, measurements of firn air, and balloon and aircraft flights were used to optimize the long-term trends, interhemispheric gradients, and photolytic fractionation, respectively, in the model. This optimization successfully reproduced realistic spatial and temporal variations of atmospheric N2O isotopocules throughout the atmosphere from the surface to the stratosphere. The very small gradients associated with vertical profiles through the troposphere and the latitudinal and vertical distributions within each hemisphere were also reasonably simulated. The results of the isotopic characterization of the global total sources were generally consistent with previous one-box model estimates, indicating that the observed atmospheric trend is the dominant factor controlling the source isotopic signature. However, hemispheric estimates were different from those generated by a previous two-box model study, mainly due to the model accounting for the interhemispheric transport and latitudinal and vertical distributions of tropospheric N2O isotopocules. Comparisons of time series of atmospheric N2O isotopocule ratios between our model and observational data from several laboratories revealed the need for a more systematic and elaborate intercalibration of the standard scales used in N2O isotopic measurements in order to capture a more complete and precise picture of the temporal and spatial variations in atmospheric N2O isotopocule ratios. This study highlights the possibility that inverse estimation of surface N2O fluxes, including the isotopic information as additional constraints, could be realized.

Development of an atmospheric N2O isotopocule model and optimization procedure, and application to source estimation

NASA Astrophysics Data System (ADS)

Ishijima, K.; Takigawa, M.; Sudo, K.; Toyoda, S.; Yoshida, N.; Röckmann, T.; Kaiser, J.; Aoki, S.; Morimoto, S.; Sugawara, S.; Nakazawa, T.

2015-12-01

This work presents the development of an atmospheric N2O isotopocule model based on a chemistry-coupled atmospheric general circulation model (ACTM). We also describe a simple method to optimize the model and present its use in estimating the isotopic signatures of surface sources at the hemispheric scale. Data obtained from ground-based observations, measurements of firn air, and balloon and aircraft flights were used to optimize the long-term trends, interhemispheric gradients, and photolytic fractionation, respectively, in the model. This optimization successfully reproduced realistic spatial and temporal variations of atmospheric N2O isotopocules throughout the atmosphere from the surface to the stratosphere. The very small gradients associated with vertical profiles through the troposphere and the latitudinal and vertical distributions within each hemisphere were also reasonably simulated. The results of the isotopic characterization of the global total sources were generally consistent with previous one-box model estimates, indicating that the observed atmospheric trend is the dominant factor controlling the source isotopic signature. However, hemispheric estimates were different from those generated by a previous two-box model study, mainly due to the model accounting for the interhemispheric transport and latitudinal and vertical distributions of tropospheric N2O isotopocules. Comparisons of time series of atmospheric N2O isotopocule ratios between our model and observational data from several laboratories revealed the need for a more systematic and elaborate intercalibration of the standard scales used in N2O isotopic measurements in order to capture a more complete and precise picture of the temporal and spatial variations in atmospheric N2O isotopocule ratios. This study highlights the possibility that inverse estimation of surface N2O fluxes, including the isotopic information as additional constraints, could be realized.

N2O molecular tagging velocimetry

NASA Astrophysics Data System (ADS)

ElBaz, A. M.; Pitz, R. W.

2012-03-01

A new seeded velocity measurement technique, N2O molecular tagging velocimetry (MTV), is developed to measure velocity in wind tunnels by photochemically creating an NO tag line. Nitrous oxide "laughing gas" is seeded into the air flow. A 193 nm ArF excimer laser dissociates the N2O to O(1D) that subsequently reacts with N2O to form NO. O2 fluorescence induced by the ArF laser "writes" the original position of the NO line. After a time delay, the shifted NO line is "read" by a 226-nm laser sheet and the velocity is determined by time-of-flight. At standard atmospheric conditions with 4% N2O in air, ˜1000 ppm of NO is photochemically created in an air jet based on experiment and simulation. Chemical kinetic simulations predict 800-1200 ppm of NO for 190-750 K at 1 atm and 850-1000 ppm of NO for 0.25-1 atm at 190 K. Decreasing the gas pressure (or increasing the temperature) increases the NO ppm level. The presence of humid air has no significant effect on NO formation. The very short NO formation time (<10 ns) makes the N2O MTV method amenable to low- and high-speed air flow measurements. The N2O MTV technique is demonstrated in air jet to measure its velocity profile. The N2O MTV method should work in other gas flows as well (e.g., helium) since the NO tag line is created by chemical reaction of N2O with O(1D) from N2O photodissociation and thus does not depend on the bulk gas composition.

Hydrogen cyanide production due to mid-size impacts in a redox-neutral N2-rich atmosphere.

PubMed

Kurosawa, Kosuke; Sugita, Seiji; Ishibashi, Ko; Hasegawa, Sunao; Sekine, Yasuhito; Ogawa, Nanako O; Kadono, Toshihiko; Ohno, Sohsuke; Ohkouchi, Naohiko; Nagaoka, Yoichi; Matsui, Takafumi

2013-06-01

Cyanide compounds are amongst the most important molecules of the origin of life. Here, we demonstrate the importance of mid-size (0.1-1 km in diameter) hence frequent meteoritic impacts to the cyanide inventory on the early Earth. Subsequent aerodynamic ablation and chemical reactions with the ambient atmosphere after oblique impacts were investigated by both impact and laser experiments. A polycarbonate projectile and graphite were used as laboratory analogs of meteoritic organic matter. Spectroscopic observations of impact-generated ablation vapors show that laser irradiation to graphite within an N2-rich gas can produce a thermodynamic environment similar to that produced by oblique impacts. Thus, laser ablation was used to investigate the final chemical products after this aerodynamic process. We found that a significant fraction (>0.1 mol%) of the vaporized carbon is converted to HCN and cyanide condensates, even when the ambient gas contains as much as a few hundred mbar of CO2. As such, the column density of cyanides after carbon-rich meteoritic impacts with diameters of 600 m would reach ~10 mol/m(2) over ~10(2) km(2) under early Earth conditions. Such a temporally and spatially concentrated supply of cyanides may have played an important role in the origin of life.

Real-Time N2O Gas Detection System for Agricultural Production Using a 4.6-μm-Band Laser Source Based on a Periodically Poled LiNbO3 Ridge Waveguide

PubMed Central

Tokura, Akio; Asobe, Masaki; Enbutsu, Koji; Yoshihara, Toshihiro; Hashida, Shin-nosuke; Takenouchi, Hirokazu

2013-01-01

This article describes a gas monitoring system for detecting nitrous oxide (N2O) gas using a compact mid-infrared laser source based on difference-frequency generation in a quasi-phase-matched LiNbO3 waveguide. We obtained a stable output power of 0.62 mW from a 4.6-μm-band continuous-wave laser source operating at room temperature. This laser source enabled us to detect atmospheric N2O gas at a concentration as low as 35 parts per billion. Using this laser source, we constructed a new real-time in-situ monitoring system for detecting N2O gas emitted from potted plants. A few weeks of monitoring with the developed detection system revealed a strong relationship between nitrogen fertilization and N2O emission. This system is promising for the in-situ long-term monitoring of N2O in agricultural production, and it is also applicable to the detection of other greenhouse gases. PMID:23921829

Increased soil emissions of potent greenhouse gases under increased atmospheric CO2.

PubMed

van Groenigen, Kees Jan; Osenberg, Craig W; Hungate, Bruce A

2011-07-13

Increasing concentrations of atmospheric carbon dioxide (CO(2)) can affect biotic and abiotic conditions in soil, such as microbial activity and water content. In turn, these changes might be expected to alter the production and consumption of the important greenhouse gases nitrous oxide (N(2)O) and methane (CH(4)) (refs 2, 3). However, studies on fluxes of N(2)O and CH(4) from soil under increased atmospheric CO(2) have not been quantitatively synthesized. Here we show, using meta-analysis, that increased CO(2) (ranging from 463 to 780 parts per million by volume) stimulates both N(2)O emissions from upland soils and CH(4) emissions from rice paddies and natural wetlands. Because enhanced greenhouse-gas emissions add to the radiative forcing of terrestrial ecosystems, these emissions are expected to negate at least 16.6 per cent of the climate change mitigation potential previously predicted from an increase in the terrestrial carbon sink under increased atmospheric CO(2) concentrations. Our results therefore suggest that the capacity of land ecosystems to slow climate warming has been overestimated. ©2011 Macmillan Publishers Limited. All rights reserved

Effect of N{sub 2} and Ar gas on DC arc plasma generation and film composition from Ti-Al compound cathodes

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

Zhirkov, Igor, E-mail: igozh@ifm.liu.se; Rosen, Johanna; Oks, Efim

2015-06-07

DC arc plasma from Ti, Al, and Ti{sub 1−x}Al{sub x} (x = 0.16, 0.25, 0.50, and 0.70) compound cathodes has been characterized with respect to plasma chemistry (charged particles) and charge-state-resolved ion energy for Ar and N{sub 2} pressures in the range 10{sup −6} to 3 × 10{sup −2} Torr. Scanning electron microscopy was used for exploring the correlation between the cathode and film composition, which in turn was correlated with the plasma properties. In an Ar atmosphere, the plasma ion composition showed a reduction of Al of approximately 5 at. % compared to the cathode composition, while deposited films were in accordance with the cathodemore » stoichiometry. Introducing N{sub 2} above ∼5 × 10{sup −3} Torr, lead to a reduced Al content in the plasma as well as in the film, and hence a 1:1 correlation between the cathode and film composition cannot be expected in a reactive environment. This may be explained by an influence of the reactive gas on the arc mode and type of erosion of Ti and Al rich contaminations, as well as on the plasma transport. Throughout the investigated pressure range, a higher deposition rate was obtained from cathodes with higher Al content. The origin of generated gas ions was investigated through the velocity rule, stating that the most likely ion velocities of all cathode elements from a compound cathode are equal. The results suggest that the major part of the gas ions in Ar is generated from electron impact ionization, while gas ions in a N{sub 2} atmosphere primarily originate from a nitrogen contaminated layer on the cathode surface. The presented results provide a contribution to the understanding processes of plasma generation from compound cathodes. It also allows for a more reasonable approach to the selection of composite cathode and experimental conditions for thin film depositions.« less

Hybrid Global Model Simulations of He/N2 and He/H2O Atmospheric Pressure Capacitive Discharges

NASA Astrophysics Data System (ADS)

Lieberman, M. A.; Kawamura, E.; Ke, Ding; Lichtenberg, A. J.; Chabert, P.; Lazzaroni, C.

2014-10-01

We used 1D particle-in-cell (PIC) simulations of an atmospheric He/0.1%N2 discharge with simplified chemistry to guide the development of a hybrid analytical/numerical global model that includes electron multiplication and two classes of electrons: ``hot'' electrons associated with the sheaths, and ``warm'' electrons associated with the bulk. The model and PIC results show reasonable agreement and indicate a transition from a low power α-mode with a relatively high bulk electron temperature Te to a high power γ-mode with a low Te. The transition is accompanied by an increase in density and a decrease in sheath widths. Water is a trace gas of bio-medical interest since it may arise from contact with skin. We use the hybrid global model to simulate a chemically complex, bounded He/H2O atmospheric pressure discharge, including 148 volume reactions among 43 species, and including clusters up to H19O9+.For a planar discharge with a 1 cm electrode radius and a 0.5 mm gap driven at 13.56 MHz, we determine the depletion and diffusion effects and the α to γ transition for secondary emission γse = 0.25 over a range of rf currents and external H2O concentrations. Each simulation takes about 2 minutes on a moderate laptop. This work was partially supported by the Department of Energy Office of Fusion Energy Science Contract DE-SC000193 and by the Natural Science Foundation of China Contract 11375042.

BIOSIGNATURE GASES IN H{sub 2}-DOMINATED ATMOSPHERES ON ROCKY EXOPLANETS

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

Seager, S.; Bains, W.; Hu, R.

2013-11-10

Super-Earth exoplanets are being discovered with increasing frequency and some will be able to retain stable H{sub 2}-dominated atmospheres. We study biosignature gases on exoplanets with thin H{sub 2} atmospheres and habitable surface temperatures, using a model atmosphere with photochemistry and a biomass estimate framework for evaluating the plausibility of a range of biosignature gas candidates. We find that photochemically produced H atoms are the most abundant reactive species in H{sub 2} atmospheres. In atmospheres with high CO{sub 2} levels, atomic O is the major destructive species for some molecules. In Sun-Earth-like UV radiation environments, H (and in some casesmore » O) will rapidly destroy nearly all biosignature gases of interest. The lower UV fluxes from UV-quiet M stars would produce a lower concentration of H (or O) for the same scenario, enabling some biosignature gases to accumulate. The favorability of low-UV radiation environments to accumulate detectable biosignature gases in an H{sub 2} atmosphere is closely analogous to the case of oxidized atmospheres, where photochemically produced OH is the major destructive species. Most potential biosignature gases, such as dimethylsulfide and CH{sub 3}Cl, are therefore more favorable in low-UV, as compared with solar-like UV, environments. A few promising biosignature gas candidates, including NH{sub 3} and N{sub 2}O, are favorable even in solar-like UV environments, as these gases are destroyed directly by photolysis and not by H (or O). A more subtle finding is that most gases produced by life that are fully hydrogenated forms of an element, such as CH{sub 4} and H{sub 2}S, are not effective signs of life in an H{sub 2}-rich atmosphere because the dominant atmospheric chemistry will generate such gases abiologically, through photochemistry or geochemistry. Suitable biosignature gases in H{sub 2}-rich atmospheres for super-Earth exoplanets transiting M stars could potentially be detected in

Gas-analytic measurement complexes of Baikal atmospheric-limnological observatory

NASA Astrophysics Data System (ADS)

Pestunov, D. A.; Shamrin, A. M.; Shmargunov, V. P.; Panchenko, M. V.

2015-11-01

The paper presents the present-day structure of stationary and mobile hardware-software gas-analytical complexes of Baikal atmospheric-limnological observatory (BALO) Siberian Branch Russian Academy of Sciences (SB RAS), designed to study the processes of gas exchange of carbon-containing gases in the "atmosphere-water" system, which are constantly updated to include new measuring and auxiliary instrumentation.

High Resolution UV SO2 Absorption Cross Sections and VUV N2 Oscillator Strengths for Planetary Atmospheres Studies

NASA Astrophysics Data System (ADS)

Smith, P. L.; Stark, G.; Rufus, J.

2000-10-01

The determination of the chemical composition of the atmosphere of Io in the 190-220 nm wavelength region requires a knowledge of the photoabsorption cross section of SO2 at temperatures ranging from 110 to 300 K. We are continuing our laboratory program to measure SO2 absorption cross sections with very high resolving power (450,000) at a range of temperatures appropriate to the Io atmosphere. Previous photoabsorption measurements have been unable to resolve the very congested SO2 spectrum. Out measurements are being undertaken at Imperial College, London, using an ultraviolet Fourier transform spectrometer. We recently completed room temperature measurements of SO2 cross sections in the 190-220 nm region (Stark et al., JGR Planets 104, 16,585 (1999)). Current laboratory work is focusing on a complementary set of measurements at 160 K. Preliminary results will be presented. Analyses of Voyager VUV occultation measurements of the N2-rich atmospheres of Titan and Triton are hampered by the lack of fundamental spectroscopic data for N2, in particular, by the lack of reliable f-values and line widths for electronic bands of N2 in the 80-100 nm wavelength region. We are continuing our program to measure band oscillator strengths for about 100 N2 bands between 80-100 nm. We have begun an on-line molecular spectroscopic atlas [http://cfa-www.harvard.edu/amdata/ampdata/N2ARCHIVE/n2home.html]. The archive includes published and unpublished 14N2, 14N15N, and 15N2 line lists and spectroscopic identifications, excited state energy levels, band and line f-values, a summary of published band f-value and line width measurements, and a cross-referenced summary of the relevant N2 literature. The listings are searchable by wavelength interval or band identification and are suitable for down-loading in a convenient format. This work was supported in part by NASA Grant NAG5-6222 and the Smithsonian Institution Atherton Seidel Grant Program.

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

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

NASA Astrophysics Data System (ADS)

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

2012-12-01

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

Distribution of N2O in the atmosphere under global warming - a simulation study with the MPI Earth System Model

NASA Astrophysics Data System (ADS)

Kracher, Daniela; Manzini, Elisa; Reick, Christian H.; Schultz, Martin; Stein, Olaf

2014-05-01

Climate change is driven by an increasing release of anthropogenic greenhouse gases (GHGs) such as carbon dioxide and nitrous oxide (N2O). Besides fossil fuel burning, also land use change and land management are anthropogenic sources of GHGs. Especially inputs of reactive nitrogen via fertilizer and deposition lead to enhanced emissions of N2O. One effect of a drastic future increase in surface temperature is a modification of atmospheric circulation, e.g. an accelerated Brewer Dobson circulation affecting the exchange between troposphere and stratosphere. N2O is inert in the troposphere and decayed only in the stratosphere. Thus, changes in atmospheric circulation, especially changes in the exchange between troposphere and stratosphere, will affect the atmospheric transport, decay, and distribution of N2O. In our study we assess the impact of global warming on atmospheric circulation and implied effects on the distribution and lifetime of atmospheric N2O. As terrestrial N2O emissions are highly determined by inputs of reactive nitrogen - the location of which being determined by human choice - we examine in particular the importance of latitudinal source regions of N2O for its global distribution. For this purpose we apply the Max Planck Institute Earth System Model, MPI-ESM. MPI-ESM consists of the atmospheric general circulation model ECHAM, the land surface model JSBACH, and MPIOM/HAMOCC representing ocean circulation and ocean biogeochemistry. Prognostic atmospheric N2O concentrations in MPI-ESM are determined by land N2O emissions, ocean N2O exchange and atmospheric tracer transport. As stratospheric chemistry is not explicitly represented in MPI-ESM, stratospheric decay rates of N2O are prescribed from a MACC MOZART simulation.

Soil-atmosphere N2O and CH4 exchanges was suppressed by litter layer in a subtropical secondary forest

NASA Astrophysics Data System (ADS)

Cui, J. J.; Lai, D. Y. F.

2016-12-01

Forest soil has a great potential in affecting future climate change through biogeochemical cycling and exchanging greenhouse gases (GHGs) with the atmosphere. As a proxy of changing atmospheric CO2 concentration, enhanced litter production arising from CO2 fertilization can affect soil GHG fluxes and induce feedbacks to the climate system. However, these litter-soil- atmosphere interactions remain unclear, especially in subtropical forests. In this study, we carried out static chamber measurements and field manipulations in a subtropical secondary forest in Hong Kong over one year to investigate the temporal variations and controls, as well as the effects of changing litter amounts on soil-atmosphere GHG fluxes. Our results show distinct seasonal pattern of GHG fluxes and soil parameters over the study period. While CO2 flux did not respond significantly to litter manipulation, regression analysis indicates that CO2 flux was regulated by soil temperature and soil moisture. Litter reduction stimulated mean N2O emissions by 105%, and the positive effect was most pronounced during the hot-humid season from May to October. On the other hand, litter addition was found to reduce CH4 uptake by 32%. Our findings suggest that the presence of litter might serve a physical barrier for gas diffusion. It is suggested that the biogeochemical feedback arising from litterfall should be taken into account in simulating the response of forest GHG fluxes to future global change.

Diffusion Monte Carlo simulations of gas phase and adsorbed D2-(H2)n clusters

NASA Astrophysics Data System (ADS)

Curotto, E.; Mella, M.

2018-03-01

We have computed ground state energies and analyzed radial distributions for several gas phase and adsorbed D2(H2)n and HD(H2)n clusters. An external model potential designed to mimic ionic adsorption sites inside porous materials is used [M. Mella and E. Curotto, J. Phys. Chem. A 121, 5005 (2017)]. The isotopic substitution lowers the ground state energies by the expected amount based on the mass differences when these are compared with the energies of the pure clusters in the gas phase. A similar impact is found for adsorbed aggregates. The dissociation energy of D2 from the adsorbed clusters is always much higher than that of H2 from both pure and doped aggregates. Radial distributions of D2 and H2 are compared for both the gas phase and adsorbed species. For the gas phase clusters, two types of hydrogen-hydrogen interactions are considered: one based on the assumption that rotations and translations are adiabatically decoupled and the other based on nonisotropic four-dimensional potential. In the gas phase clusters of sufficiently large size, we find the heavier isotopomer more likely to be near the center of mass. However, there is a considerable overlap among the radial distributions of the two species. For the adsorbed clusters, we invariably find the heavy isotope located closer to the attractive interaction source than H2, and at the periphery of the aggregate, H2 molecules being substantially excluded from the interaction with the source. This finding rationalizes the dissociation energy results. For D2-(H2)n clusters with n ≥12 , such preference leads to the desorption of D2 from the aggregate, a phenomenon driven by the minimization of the total energy that can be obtained by reducing the confinement of (H2)12. The same happens for (H2)13, indicating that such an effect may be quite general and impact on the absorption of quantum species inside porous materials.

Microporous metal organic framework [M2(hfipbb)2(ted)] (M=Zn, Co; H2hfipbb=4,4-(hexafluoroisopropylidene)-bis(benzoic acid); ted=triethylenediamine): Synthesis, structure analysis, pore characterization, small gas adsorption and CO2/N2 separation properties

NASA Astrophysics Data System (ADS)

Xu, William W.; Pramanik, Sanhita; Zhang, Zhijuan; Emge, Thomas J.; Li, Jing

2013-04-01

Carbon dioxide is a greenhouse gas that is a major contributor to global warming. Developing methods that can effectively capture CO2 is the key to reduce its emission to the atmosphere. Recent research shows that microporous metal organic frameworks (MOFs) are emerging as a promising family of adsorbents that may be promising for use in adsorption based capture and separation of CO2 from power plant waste gases. In this work we report the synthesis, crystal structure analysis and pore characterization of two microporous MOF structures, [M2(hfipbb)2(ted)] (M=Zn (1), Co (2); H2hfipbb=4,4-(hexafluoroisopropylidene)-bis(benzoic acid); ted=triethylenediamine). The CO2 and N2 adsorption experiments and IAST calculations are carried out on [Zn2(hfipbb)2(ted)] under conditions that mimic post-combustion flue gas mixtures emitted from power plants. The results show that the framework interacts with CO2 strongly, giving rise to relatively high isosteric heats of adsorption (up to 28 kJ/mol), and high adsorption selectivity for CO2 over N2, making it promising for capturing and separating CO2 from CO2/N2 mixtures.

TA [2] Continuous, regional methane emissions estimates in northern Pennsylvania gas fields using atmospheric inversions

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

Lauvaux, Thomas

Natural Gas (NG) production activities in the northeastern Marcellus shale have significantly increased in the last decade, possibly releasing large amounts of methane (CH 4) into the atmosphere from the operations at the productions sites and during the processing and transmission steps of the natural gas chain. Based on an intensive aircraft survey, leakage rates from the NG production were quantified in May 2015 and found to be in the order of 0.5% of the total production, higher than reported by the Environmental Protection Agency (EPA) but below the usually observed leakage rates over the shale gases in the US.more » Thanks to the high production rates on average at each well, leakage rates normalized by production appeared to be low in the northeastern Marcellus shale. This result confirms that natural gas production using unconventional techniques in this region is emitting relatively less CH 4 into the atmosphere than other shale reservoirs. The low emissions rate can be explained in part by the high productivity of wells drilled across the northeastern Marcellus region. We demonstrated here that atmospheric monitoring techniques can provide an independent quantification of NG leakage rates using aircraft measurements. The CH 4 analyzers were successfully calibrated at four sites across the region, measuring continuously the atmospheric CH 4 mixing ratios and isotopic 13Ch 4. Our preliminary findings confirm the low leakage rates from tower data collected over September 2015 to November 2016 compared to the aircraft mass-balance estimates in may 2015. However, several episodes revealing large releases of natural gas over several weeks showed that temporal variations in the emissions of CH 4 may increase the actual leakage rate over longer time periods.« less

Modeling Io's Sublimation-Driven Atmosphere: Gas Dynamics and Radiation Emission

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

Walker, Andrew C.; Goldstein, David B.; Varghese, Philip L.

2008-12-31

Io's sublimation-driven atmosphere is modeled using the direct simulation Monte Carlo method. These rarefied gas dynamics simulations improve upon earlier models by using a three-dimensional domain encompassing the entire planet computed in parallel. The effects of plasma impact heating, planetary rotation, and inhomogeneous surface frost are investigated. Circumplanetary flow is predicted to develop from the warm subsolar region toward the colder night-side. The non-equilibrium thermal structure of the atmosphere, including vibrational and rotational temperatures, is also presented. Io's rotation leads to an asymmetric surface temperature distribution which is found to strengthen circumplanetary flow near the dusk terminator. Plasma heating ismore » found to significantly inflate the atmosphere on both day- and night-sides. The plasma energy flux also causes high temperatures at high altitudes but permits relatively cooler temperatures at low altitudes near the dense subsolar point due to plasma energy depletion. To validate the atmospheric model, a radiative transfer model was developed utilizing the backward Monte Carlo method. The model allows the calculation of the atmospheric radiation from emitting/absorbing and scattering gas using an arbitrary scattering law and an arbitrary surface reflectivity. The model calculates the spectra in the {nu}{sub 2} vibrational band of SO{sub 2} which are then compared to the observational data.« less

Gas-phase hydrolysis of triplet SO2: A possible direct route to atmospheric acid formation

NASA Astrophysics Data System (ADS)

Donaldson, D. James; Kroll, Jay A.; Vaida, Veronica

2016-07-01

Sulfur chemistry is of great interest to the atmospheric chemistry of several planets. In the presence of water, oxidized sulfur can lead to new particle formation, influencing climate in significant ways. Observations of sulfur compounds in planetary atmospheres when compared with model results suggest that there are missing chemical mechanisms. Here we propose a novel mechanism for the formation of sulfurous acid, which may act as a seed for new particle formation. In this proposed mechanism, the lowest triplet state of SO2 (3B1), which may be accessed by near-UV solar excitation of SO2 to its excited 1B1 state followed by rapid intersystem crossing, reacts directly with water to form H2SO3 in the gas phase. For ground state SO2, this reaction is endothermic and has a very high activation barrier; our quantum chemical calculations point to a facile reaction being possible in the triplet state of SO2. This hygroscopic H2SO3 molecule may act as a condensation nucleus for water, giving rise to facile new particle formation (NPF).

Emissions of nitrous acid (HONO), nitric oxide (NO) and nitrous oxide (N2O) from boreal agricultural soil - Effect of N fertilization

NASA Astrophysics Data System (ADS)

Bhattarai, Hem Raj; Virkajärvi, Perttu; -Yli Pirilä, Pasi; Maljanen, Marja

2017-04-01

There is no doubt that nitrogen (N) fertilization has crucial role in increasing food production. However, in parallel it can cause severe impact in environment such as eutrophication, surface/groundwater pollution via nitrate (NO3-) leaching and emissions of N trace gases. Fertilization increases the emissions of nitrous oxide (N2O) which is 260 stronger greenhouse gas than carbon dioxide (CO2). It also enhances the emissions of nitric oxide (NO); an oxidized and very reactive form of nitrogen which can fluctuate the ozone (O3) concentration in atmosphere and cause acidification. The effects of N- fertilization on the emission of N2O and NO from agricultural soil are well known. However, the effects of N fertilization on nitrous acid (HONO) emissions are unknown. Few studies have shown that HONO is emitted from soil but they lack to interlink fertilization and HONO emission. HONO accounts for 17-34 % of hydroxyl (OH-) radical production? in the atmosphere, OH- radicals have vital role in atmospheric chemistry; they can cause photochemical smog, form O3, oxidize volatile organic compounds and also atmospheric methane (CH4). We formulated hypothesis that N fertilization will increase the HONO emissions as it does for N2O and NO. To study this, we took soil samples from agricultural soil receiving different amount of N-fertilizer (0, 250 and 450 kg ha-1) in eastern Finland. HONO emissions were measured by dynamic chamber technique connected with LOPAP (Quma Elektronik & Analytik GmbH), NO by NOx analyzer (Thermo scientific) and static chamber technique and gas chromatograph was used for N2O gas sampling and analysis. Several soil parameters were also measured to establish the relationship between the soil properties, fertilization rate and HONO emission. This study is important because eventually it will open up more questions regarding the forms of N loss from soils and impact of fertilization on atmospheric chemistry.

Uniform rovibrational collisional N2 bin model for DSMC, with application to atmospheric entry flows

NASA Astrophysics Data System (ADS)

Torres, E.; Bondar, Ye. A.; Magin, T. E.

2016-11-01

A state-to-state model for internal energy exchange and molecular dissociation allows for high-fidelity DSMC simulations. Elementary reaction cross sections for the N2 (v, J)+ N system were previously extracted from a quantum-chemical database, originally compiled at NASA Ames Research Center. Due to the high computational cost of simulating the full range of inelastic collision processes (approx. 23 million reactions), a coarse-grain model, called the Uniform RoVibrational Collisional (URVC) bin model can be used instead. This allows to reduce the original 9390 rovibrational levels of N2 to 10 energy bins. In the present work, this reduced model is used to simulate a 2D flow configuration, which more closely reproduces the conditions of high-speed entry into Earth's atmosphere. For this purpose, the URVC bin model had to be adapted for integration into the "Rarefied Gas Dynamics Analysis System" (RGDAS), a separate high-performance DSMC code capable of handling complex geometries and parallel computations. RGDAS was developed at the Institute of Theoretical and Applied Mechanics in Novosibirsk, Russia for use by the European Space Agency (ESA) and shares many features with the well-known SMILE code developed by the same group. We show that the reduced mechanism developed previously can be implemented in RGDAS, and the results exhibit nonequilibrium effects consistent with those observed in previous 1D-simulations.

Effect of modified atmosphere and vacuum packaging on TVB-N production of rainbow trout (Oncorhynchus mykiss) and carp (Cyprinus carpio) cuts

NASA Astrophysics Data System (ADS)

Babić Milijašević, J.; Milijašević, M.; Đinović-Stojanović, J.; Vranić, D.

2017-09-01

The aim of our research was to examine the influence of packaging in modified atmosphere and vacuum on the total volatile basic nitrogen (TVB-N) content in muscle of rainbow trout (Oncorhynchus mykiss) and common carp (Cyprinus carpio), as well as to determine the most suitable gas mixtures for packing of these freshwater species. Three sample groups of trout and carp cuts were investigated. The two groups were packaged in modified atmosphere with different gas ratios: 90%CO2+10%N2 (MAP 1) and 60%CO2+40%N2 (MAP 2), whereas the third group of fish cuts were vacuum packaged. During trials, the trout and carp cuts were stored in refrigerator at 3°C±0.5°C. Determination of TVB-N was performed on 1, 4, 7, 9, 12 and 14 days of storage. The obtained results indicate that the investigated mixtures of gases and vacuum had a significant influence on the values of TVB-N in trout and carp cuts. The lowest increase in TVB-N was established in trout and carp cuts packaged in MAP 1, whereas the highest increase was established in vacuum packaged cuts. Based on the obtained results, it can be concluded that the gas mixture consisting of 90% CO2 and 10% N2 was the most suitable for packaging of fresh trout and carp cuts in terms of TVB-N value.

N2O emission from plant surfaces - light stimulated and a global phenomenon.

NASA Astrophysics Data System (ADS)

Mikkelsen, Teis; Bruhn, Dan; Ambus, Per

2017-04-01

Nitrous oxide (N2O) is an important long-lived greenhouse gas and precursor of stratospheric ozone depleting mono-nitrogen oxides. The atmospheric concentration of N2O is persistently increasing; however, large uncertainties are associated with the distinct source strengths. Here we investigate for the first time N2O emission from terrestrial vegetation in response to natural solar ultra violet radiation. We conducted field site measurements to investigate N2O atmosphere exchange from grass vegetation exposed to solar irradiance with and without UV-screening. Further laboratory tests were conducted with a range of species to study the controls and possible loci of UV-induced N2O emission from plants. Plants released N2O in response to natural sunlight at rates of c. 20-50 nmol m-2 h-1, mostly due to the UV component. The emission rate is temperature dependent with a rather high activation energy indicative for an abiotic process. The prevailing zone for the N2O formation appears to be at the very surface of leaves. However, only c. 26% of the UV-induced N2O appears to originate from plant-N. Further, the process is dependent on atmospheric oxygen concentration. Our work demonstrates that ecosystem emission of the important greenhouse gas, N2O, may be up to c. 30% higher than hitherto assumed. Literature: Mikkelsen TN, Bruhn D & Ambus P. (2016). Solar UV Irradiation-Induced Production of Greenhouse Gases from Plant Surfaces: From Leaf to Earth. Progress in Botany, DOI 10.1007/124_2016_10. Bruhn D, Albert KR, Mikkelsen TN & Ambus P. (2014). UV-induced N2O emission from plants. Atmospheric Environment 99, 206-214.

Gas chromatography vs. quantum cascade laser-based N2O flux measurements using a novel chamber design

NASA Astrophysics Data System (ADS)

Brümmer, Christian; Lyshede, Bjarne; Lempio, Dirk; Delorme, Jean-Pierre; Rüffer, Jeremy J.; Fuß, Roland; Moffat, Antje M.; Hurkuck, Miriam; Ibrom, Andreas; Ambus, Per; Flessa, Heinz; Kutsch, Werner L.

2017-03-01

Recent advances in laser spectrometry offer new opportunities to investigate the soil-atmosphere exchange of nitrous oxide. During two field campaigns conducted at a grassland site and a willow field, we tested the performance of a quantum cascade laser (QCL) connected to a newly developed automated chamber system against a conventional gas chromatography (GC) approach using the same chambers plus an automated gas sampling unit with septum capped vials and subsequent laboratory GC analysis. Through its high precision and time resolution, data of the QCL system were used for quantifying the commonly observed nonlinearity in concentration changes during chamber deployment, making the calculation of exchange fluxes more accurate by the application of exponential models. As expected, the curvature values in the concentration increase was higher during long (60 min) chamber closure times and under high-flux conditions (FN2O > 150 µg N m-2 h-1) than those values that were found when chambers were closed for only 10 min and/or when fluxes were in a typical range of 2 to 50 µg N m-2 h-1. Extremely low standard errors of fluxes, i.e., from ˜ 0.2 to 1.7 % of the flux value, were observed regardless of linear or exponential flux calculation when using QCL data. Thus, we recommend reducing chamber closure times to a maximum of 10 min when a fast-response analyzer is available and this type of chamber system is used to keep soil disturbance low and conditions around the chamber plot as natural as possible. Further, applying linear regression to a 3 min data window with rejecting the first 2 min after closure and a sampling time of every 5 s proved to be sufficient for robust flux determination while ensuring that standard errors of N2O fluxes were still on a relatively low level. Despite low signal-to-noise ratios, GC was still found to be a useful method to determine the mean the soil-atmosphere exchange of N2O on longer timescales during specific campaigns. Intriguingly

Torrefaction of empty fruit bunches under biomass combustion gas atmosphere.

PubMed

Uemura, Yoshimitsu; Sellappah, Varsheta; Trinh, Thanh Hoai; Hassan, Suhaimi; Tanoue, Ken-Ichiro

2017-11-01

Torrefaction of oil palm empty fruit bunches (EFB) under combustion gas atmosphere was conducted in a batch reactor at 473, 523 and 573K in order to investigate the effect of real combustion gas on torrefaction behavior. The solid mass yield of torrefaction in combustion gas was smaller than that of torrefaction in nitrogen. This may be attributed to the decomposition enhancement effect by oxygen and carbon dioxide in combustion gas. Under combustion gas atmosphere, the solid yield for torrefaction of EFB became smaller as the temperature increased. The representative products of combustion gas torrefaction were carbon dioxide and carbon monoxide (gas phase) and water, phenol and acetic acid (liquid phase). By comparing torrefaction in combustion gas with torrefaction in nitrogen gas, it was found that combustion gas can be utilized as torrefaction gas to save energy and inert gas. Copyright © 2017 Elsevier Ltd. All rights reserved.

Implications of the (H2O)n + CO ↔ trans-HCOOH + (H2O)n-1 (n = 1, 2, and 3) reactions for primordial atmospheres of Venus and Earth

NASA Astrophysics Data System (ADS)

Vichietti, R. M.; Spada, R. F. K.; da Silva, A. B. F.; Machado, F. B. C.; Haiduke, R. L. A.

2018-04-01

The forward and backward (H2O)n + CO ↔ HCOOH + (H2O)n-1 (n = 1, 2, and 3) reactions were studied in order to furnish trustworthy thermochemical and kinetic data. Stationary point structures involved in these chemical processes were achieved at the B2PLYP/cc-pVTZ level so that the corresponding vibrational frequencies, zero-point energies, and thermal corrections were scaled to consider anharmonicity effects. A complete basis set extrapolation was also employed with the CCSD(T) method in order to improve electronic energy descriptions and providing therefore more accurate results for enthalpies, Gibbs energies, and rate constants. Forward and backward rate constants were encountered at the high-pressure limit between 200 and 4000 K. In turn, modified Arrhenius' equations were fitted from these rate constants (between 700 and 4000 K). Next, considering physical and chemical conditions that have supposedly prevailed on primitive atmospheres of Venus and Earth, our main results indicate that 85-88 per cent of all water forms on these atmospheres were monomers, whereas (H2O)2 and (H2O)3 complexes would represent 12-15 and ˜0 per cent, respectively. Besides, we estimate that Earth's and Venus' primitive atmospheres could have been composed by ˜0.001-0.003 per cent of HCOOH when their temperatures were around 1000-2000 K. Finally, the water loss process on Venus may have occurred by a mechanism that includes the formic acid as intermediate species.

Investigation of N2O Production from 266 and 532 nm Laser Flash Photolysis of O3/N2/O2 Mixtures

NASA Technical Reports Server (NTRS)

Estupinan, E. G.; Nicovich, J. M.; Li, J.; Cunnold, D. M.; Wine, P. H.

2002-01-01

Tunable diode laser absorption spectroscopy has been employed to measure the amount of N2O produced from laser flash photolysis of O3/N2/O2 mixtures at 266 and 532 nm. In the 532 nm photolysis experiments very little N2O is observed, thus allowing an upper limit yield of 7 x 10(exp -8) to be established for the process O3 + N2 yield N2O + O2, where O3 is nascent O3 that is newly formed via O(3P(sub J)) + O2 recombination (with vibrational excitation near the dissociation energy of O3). The measured upper limit yield is a factor of approx. 600 smaller than a previous literature value and is approximately a factor of 10 below the threshold for atmospheric importance. In the 266 nm photolysis experiments, significant N2O production is observed and the N2O quantum yield is found to increase linearly with pressure over the range 100 - 900 Torr in air bath gas. The source of N2O in the 266 nm photolysis experiments is believed to be the addition reaction O(1D(sub 2)) + N2 + M yields (k(sub sigma)) N2O + M, although reaction of (very short-lived) electronically excited O3 with N2 cannot be ruled out by the available data. Assuming that all observed N2O comes from the O(1D(sub 2)) + N2 + M reaction, the following expression describes the temperature dependence of k(sub sigma) (in its third-order low-pressure limit) that is consistent with the N2O yield data: k(sub sigma) = (2.8 +/- 0.1) x 10(exp -36)(T/300)(sup -(0-88+0.36)) cm(sup 6) molecule(sup -2)/s, where the uncertainties are 2(sigma) and represent precision only. The accuracy of the reported rate coefficients at the 95% confidence level is estimated to be 30 - 40% depending on the temperature. Model calculations suggest that gas phase processes initiated by ozone absorption of a UV photon represent about 1.4% of the currently estimated global source strength of atmospheric N2O. However, these processes could account for a significant fraction of the oxygen mass-independent enrichment observed in atmospheric N2O, and

Ignition and Combustion of Pulverized Coal and Biomass under Different Oxy-fuel O2/N2 and O2/CO2 Environments

NASA Astrophysics Data System (ADS)

Khatami Firoozabadi, Seyed Reza

This work studied the ignition and combustion of burning pulverized coals and biomasses particles under either conventional combustion in air or oxy-fuel combustion conditions. Oxy-fuel combustion is a 'clean-coal' process that takes place in O2/CO2 environments, which are achieved by removing nitrogen from the intake gases and recirculating large amounts of flue gases to the boiler. Removal of nitrogen from the combustion gases generates a high CO2-content, sequestration-ready gas at the boiler effluent. Flue gas recirculation moderates the high temperatures caused by the elevated oxygen partial pressure in the boiler. In this study, combustion of the fuels took place in a laboratory laminar-flow drop-tube furnace (DTF), electrically-heated to 1400 K, in environments containing various mole fractions of oxygen in either nitrogen or carbon-dioxide background gases. The experiments were conducted at two different gas conditions inside the furnace: (a) quiescent gas condition (i.e., no flow or inactive flow) and, (b) an active gas flow condition in both the injector and furnace. Eight coals from different ranks (anthracite, semi-snthracite, three bituminous, subbituminous and two lignites) and four biomasses from different sources were utilized in this work to study the ignition and combustion characteristics of solid fuels in O2/N2 or O2/CO2 environments. The main objective is to study the effect of replacing background N2 with CO2, increasing O2 mole fraction and fuel type and rank on a number of qualitative and quantitative parameters such as ignition/combustion mode, ignition temperature, ignition delay time, combustion temperatures, burnout times and envelope flame soot volume fractions. Regarding ignition, in the quiescent gas condition, bituminous and sub-bituminous coal particles experienced homogeneous ignition in both O2/N 2 and O2/CO2 atmospheres, while in the active gas flow condition, heterogeneous ignition was evident in O2/CO 2. Anthracite, semi

Atmospheric reactivity of hydroxyl radicals with guaiacol (2-methoxyphenol), a biomass burning emitted compound: Secondary organic aerosol formation and gas-phase oxidation products

NASA Astrophysics Data System (ADS)

Lauraguais, Amélie; Coeur-Tourneur, Cécile; Cassez, Andy; Deboudt, Karine; Fourmentin, Marc; Choël, Marie

2014-04-01

Methoxyphenols are low molecular weight semi-volatile polar aromatic compounds produced from the pyrolysis of wood lignin. The reaction of guaiacol (2-methoxyphenol) with hydroxyl radicals has been studied in the LPCA simulation chamber at (294 ± 2) K, atmospheric pressure, low relative humidity (RH < 1%) and under high-NOx conditions using CH3ONO as OH source. The aerosol production was monitored using a SMPS (Scanning Mobility Particle Sizer); the SOA yields were in the range from 0.003 to 0.87 and the organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model. Transmission (TEM) and Scanning (SEM) Electron Microscopy observations were performed to characterize the physical state of SOA produced from the OH reaction with guaiacol; they display both liquid and solid particles (in an amorphous state). GC-FID (Gas Chromatography - Flame Ionization Detection) and GC-MS (Gas Chromatography - Mass Spectrometry) analysis show the formation of nitroguaiacol isomers as main oxidation products in the gas- and aerosol-phases. In the gas-phase, the formation yields were (10 ± 2) % for 4-nitroguaiacol (1-hydroxy-2-methoxy-4-nitrobenzene; 4-NG) and (6 ± 2) % for 3- or 6-nitroguaiacol (1-hydroxy-2-methoxy-3-nitrobenzene or 1-hydroxy-2-methoxy-6-nitrobenzene; 3/6-NG; the standards are not commercially available so both isomers cannot be distinguished) whereas in SOA their yield were much lower (≤0.1%). To our knowledge, this work represents the first identification of nitroguaiacols as gaseous oxidation products of the OH reaction with guaiacol. As the reactivity of nitroguaiacols with atmospheric oxidants is probably low, we suggest using them as biomass burning emission gas tracers. The atmospheric implications of the guaiacol + OH reaction are also discussed.

The atmospheric emission method of calculating the neutral atmosphere and charged particle densities in the upper atmosphere

NASA Astrophysics Data System (ADS)

McElroy, Kenneth L., Jr.

1992-12-01

A method is presented for the determination of neutral gas densities in the ionosphere from rocket-borne measurements of UV atmospheric emissions. Computer models were used to calculate an initial guess for the neutral atmosphere. Using this neutral atmosphere, intensity profiles for the N2 (0,5) Vegard-Kaplan band, the N2 Lyman-Birge-Hopfield band system, and the OI2972 A line were calculated and compared with the March 1990 NPS MUSTANG data. The neutral atmospheric model was modified and the intensity profiles recalculated until a fit with the data was obtained. The neutral atmosphere corresponding to the intensity profile that fit the data was assumed to be the atmospheric composition prevailing at the time of the observation. The ion densities were then calculated from the neutral atmosphere using a photochemical model. The electron density profile calculated by this model was compared with the electron density profile measured by the U.S. Air Force Geophysics Laboratory at a nearby site.

Atmospheric emission characterization of Marcellus shale natural gas development sites.

PubMed

Goetz, J Douglas; Floerchinger, Cody; Fortner, Edward C; Wormhoudt, Joda; Massoli, Paola; Knighton, W Berk; Herndon, Scott C; Kolb, Charles E; Knipping, Eladio; Shaw, Stephanie L; DeCarlo, Peter F

2015-06-02

Limited direct measurements of criteria pollutants emissions and precursors, as well as natural gas constituents, from Marcellus shale gas development activities contribute to uncertainty about their atmospheric impact. Real-time measurements were made with the Aerodyne Research Inc. Mobile Laboratory to characterize emission rates of atmospheric pollutants. Sites investigated include production well pads, a well pad with a drill rig, a well completion, and compressor stations. Tracer release ratio methods were used to estimate emission rates. A first-order correction factor was developed to account for errors introduced by fenceline tracer release. In contrast to observations from other shale plays, elevated volatile organic compounds, other than CH4 and C2H6, were generally not observed at the investigated sites. Elevated submicrometer particle mass concentrations were also generally not observed. Emission rates from compressor stations ranged from 0.006 to 0.162 tons per day (tpd) for NOx, 0.029 to 0.426 tpd for CO, and 67.9 to 371 tpd for CO2. CH4 and C2H6 emission rates from compressor stations ranged from 0.411 to 4.936 tpd and 0.023 to 0.062 tpd, respectively. Although limited in sample size, this study provides emission rate estimates for some processes in a newly developed natural gas resource and contributes valuable comparisons to other shale gas studies.

Determination of nitrogen monoxide in high purity nitrogen gas with an atmospheric pressure ionization mass spectrometer

NASA Technical Reports Server (NTRS)

Kato, K.

1985-01-01

An atmospheric pressure ionization mass spectrometric (API-MS) method was studied for the determination of residual NO in high purity N2 gas. The API-MS is very sensitive to NO, but the presence of O2 interferes with the NO measurement. Nitrogen gas in cylinders as sample gas was mixed with NO standard gas and/or O2 standard gas, and then introduced into the API-MS. The calibration curves of NO and O2 has linearity in the region of 0 - 2 ppm, but the slopes changed with every cylinder. The effect of O2 on NO+ peak was additive and proportional to O2 concentration in the range of 0 - 0.5 ppm. The increase in NO+ intensity due to O2 was (0.07 - 0.13)%/O2, 1 ppm. Determination of NO and O2 was carried out by the standard addition method to eliminate the influence of variation of slopes. The interference due to O2 was estimated from the product of the O2 concentration and the ratio of slope A to Slope B. Slope A is the change in the NO+ intensity with the O2 concentration. Slope B is the intensity with O2 concentration.

Effects of gas temperature in the plasma layer on RONS generation in array-type dielectric barrier discharge at atmospheric pressure

NASA Astrophysics Data System (ADS)

Yoon, Sung-Young; Yi, Changho; Eom, Sangheum; Park, Seungil; Kim, Seong Bong; Ryu, Seungmin; Yoo, Suk Jae

2017-12-01

In this work, we studied the control of plasma-produced species under a fixed gas composition (i.e., ambient air) in a 10 kHz-driven array-type dielectric barrier atmospheric-pressure plasma discharge. Instead of the gas composition, only the gas velocity was controlled. Thus, the plasma-maintenance cost was considerably lower than methods such as external N2 or O2 injection. The plasma-produced species were monitored using Fourier transformed infrared spectroscopy. The discharge properties were measured using a voltage probe, current probe, infrared camera, and optical emission spectroscopy. The results showed that the major plasma products largely depend on the gas temperature in the plasma discharge layer. The gas temperature in the plasma discharge layer was significantly different to the temperature of the ceramic adjacent to the plasma discharge layer, even in the small discharge power density of ˜15 W/cm2 or ˜100 W/cm3. Because the vibrational excitation of N2 was suppressed by the higher gas flow, the major plasma-produced species shifted from NOx in low flow to O3 in high flow.

Annual mean mixing ratios of N2, Ar, O2, and CO in the martian atmosphere

NASA Astrophysics Data System (ADS)

Krasnopolsky, Vladimir A.

2017-09-01

The precise mixing ratios of N2, Ar, O2, and CO measured by the MSL Curiosity quadrupole mass spectrometer must be corrected for the seasonal variations of the atmospheric pressure to reproduce annual mean mixing ratios on Mars. The corrections are made using measurements for the first year of the Viking Landers 1 and 2 and the Mars Climate Database data. The mean correction factor is 0.899 ± 0.006 resulting in annual mean mixing ratios of (1.83 ± 0.03)% for N2, (1.86 ± 0.02)% for Ar, (1.56 ± 0.06) × 10-3 for O2, and 673 ± 2.6 ppm for CO. The O2 mixing ratio agrees with the Herschel value within its uncertainty, the ground-based observations corrected for the dust extinction, and photochemical models by Nair et al. (1994) and Krasnopolsky (2010). The CO mixing ratio is in excellent agreement with the MRO/CRISM value of 700 ppm and with 667, 693, and 684 ppm recently observed at LS = 60, 89, and 110° and corrected to the annual mean conditions. Lifetimes of N2 and Ar are very long in the martian atmosphere, and differences between the MSL and Viking data on these species cannot be attributed to their variations.

Sources and sinks of atmospheric N2O and the possible ozone reduction due to industrial fixed nitrogen fertilizers

NASA Technical Reports Server (NTRS)

Liu, S. C.; Cicerone, R. J.; Donahue, T. M.; Chameides, W. L.

1977-01-01

The terrestrial and marine nitrogen cycles are examined in an attempt to clarify how the atmospheric content of N2O is controlled. We review available data on the various reservoirs of fixed nitrogen, the transfer rates between the reservoirs, and estimate how the reservoir contents and transfer rates can change under man's influence. It is seen that sources, sinks and lifetime of atmospheric N2O are not understood well. Based on our limited knowledge of the stability of atmospheric N2O we conclude that future growth in the usage of industrial fixed nitrogen fertilizers could cause a 1% to 2% global ozone reduction in the next 50 years. However, centuries from now the ozone layer could be reduced by as much as 10% if soils are the major source of atmospheric N2O.

Annual mean mixing ratios of N2, Ar, O2, and CO in the martian atmosphere

NASA Astrophysics Data System (ADS)

Krasnopolsky, V.

2017-09-01

The precise mixing ratios of N2, Ar, O2, and CO measured by the MSL Curiosity quadrupole mass spectrometer must be corrected for the seasonal variations of the atmospheric pressure to reproduce annual mean mixing ratios on Mars. The corrections are made using measurements the Viking Landers and the Mars Climate Database data. The mean correction factor is 0.899 ± 0.006 resulting in annual mean mixing ratios of (1.83 ± 0.03)% for N2, (1.86 ± 0.02)% for Ar, (1.56 ± 0.06)×10-3 for O2, and 673 ± 2.6 ppm for CO. The O2 mixing ratio agrees with the Herschel value within its uncertainty, the ground-based observations corrected for the dust extinction, and photochemical models by Nair et al. (1994) and Krasnopolsky (2010). The CO mixing ratio is in excellent agreement with the MRO/CRISM value of 700 ppm and with 667, 693, and 684 ppm recently observed at LS = 60, 89, and 110° and corrected to the annual mean conditions. Lifetimes of N2 and Ar are very long in the martian atmosphere, and differences between the MSL and Viking data on these species cannot be attributed to their variations.

Multistage plasma initiation process by pulsed CO2 laser irradiation of a Ti sample in an ambient gas (He, Ar, or N2)

NASA Astrophysics Data System (ADS)

Hermann, J.; Boulmer-Leborgne, C.; Mihailescu, I. N.; Dubreuil, B.

1993-02-01

New experimental results are reported on plasma initiation in front of a titanium sample irradiated by ir (λ=10.6 μm) laser pulses in an ambient gas (He, Ar, and N2) at pressures ranging from several Torr up to the atmosphere. The plasma is studied by space- and time-resolved emission spectroscopy, while sample vaporization is probed by laser-induced fluorescence spectroscopy. Threshold laser intensities leading to the formation of a plasma in the vapor and in the ambient gases are determined. Experimental results support the model of a vaporization mechanism for the plasma initiation (vaporization-initiated plasma breakdown). The plasma initiation is described by simple numerical criteria based on a two-stage process. Theoretical predictions are found to be in a reasonable agreement with the experiment. This study provides also a clear explanation of the influence of the ambient gas on the laser beam-metal surface energy transfer. Laser irradiation always causes an important vaporization when performed in He, while in the case of Ar or N2, the interaction is reduced in heating and vaporization of some surface defects and impurities.

Aging behavior of near atmospheric N2 ambient sputtered/patterned Au IR absorber thin films

NASA Astrophysics Data System (ADS)

Gaur, Surender P.; Kothari, Prateek; Rangra, Kamaljit; Kumar, Dinesh

2018-03-01

Near atmospheric N2 ambient sputtered Au thin films exhibit significant spectral absorptivity over medium to long wave infrared radiations. Thin films were found adequately robust for micropatterning using conventional photolithography and metal lift off processes. Since long term spectral absorptivity is major practical concern for Au blacks, this paper reports on aging behavior of near atmospheric Ar and Ar + N2 (1:1) ambient sputtered infrared absorber Au thin films. Comparative analysis on electrical, morphological and spectral absorption behavior of twenty-five weeks room temperature/vacuum aged Au infrared absorber thin films is performed. The Ar and Ar + N2 ambient sputtered Au thing films have shown anticipated consistency in their physical, electrical and spectral properties regardless the long term aging in this work.

Fundamental Insulation Characteristics of Air, N2, CO2, N2/O2 and SF6/N2 Mixed Gases

NASA Astrophysics Data System (ADS)

Rokunohe, Toshiaki; Yagihashi, Yoshitaka; Endo, Fumihiro; Oomori, Takashi

SF6 gas has excellent dielectric strength and interruption performance. For these reasons, it has been widely used for gas insulated switchgear (GIS). However, use of SF6 gas has become regulated under agreements set at the 1997 COP3. Presently, development of a gas circuit breaker (GCB) using CO2 gas and development of a high voltage vacuum circuit breaker (VCB) are being pursued. GIS consists of disconnectors (DS), earthing switches (ES) and buses in addition to GCB. Since the interruption performance is not an important requirement for DS, ES and BUS, use of a gas with high dielectric strength is better than use of a gas with good interruption performance. Air and N2 are not greenhouse gases, and their dielectric strengths are higher than those of other SF6 alternative gases, but only about one-third of the dielectric strength of SF6 gas. This paper deals with a suitable insulation gas which has no greenhouse effect as an SF6 alternative gas. The N2/O2 mixed gas was investigated by changing the ratio of O2. Moreover, the effect of an insulation coating was investigated and compared with the dielectric strength of SF6/N2 mixed gas. The dielectric strength of air under the coating condition was equal to that of 10%SF6/N2 mixed gas.

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

Atmospheric contribution of gas emissions from Augustine volcano, Alaska during the 2006 eruption

USGS Publications Warehouse

McGee, K.A.; Doukas, M.P.; McGimsey, R.G.; Neal, C.A.; Wessels, R.L.

2008-01-01

Airborne surveillance of gas emissions from Augustine for SO2, CO2 and H2S showed no evidence of anomalous degassing from 1990 through May 2005. By December 20, 2005, Augustine was degassing 660 td-1 of SO2, and ten times that by January 4, 2006. The highest SO2 emission rate measured during the 2006 eruption was 8650 td-1 (March 1); for CO2, 13000 td-1 (March 9), and H2S, 8 td-1 (January 19). Thirty-four SO2 measurements were made from December 2005 through 2006, with 9 each for CO2 and H2S. Augustine released 1 ?? 106 tonnes of CO2 to the atmosphere during 2006, a level similar to the output of a medium-sized natural gas-fired power plant, and thus was not a significant contributor of greenhouse gas to the atmosphere compared to anthropogenic sources. Augustine released about 5 ?? 105 tonnes of SO2 during 2006, similar to that released in 1976 and 1986.

Mechanism of Runaway Electron Generation at Gas Pressures from a Few Atmospheres to Several Tens of Atmospheres

NASA Astrophysics Data System (ADS)

Zubarev, N. M.; Ivanov, S. N.

2018-04-01

The mechanism of runaway electron generation at gas pressures from a few atmospheres to several tens of atmospheres is proposed. According to this mechanism, the electrons pass into the runaway mode in the enhanced field zone that arises between a cathode micropoint—a source of field-emission electrons—and the region of the positive ion space charge accumulated near the cathode in the tails of the developing electron avalanches. As a result, volume gas ionization by runaway electrons begins with a time delay required for the formation of the enhanced field zone. This process determines the delay time of breakdown. The influence of the gas pressure on the formation dynamics of the space charge region is analyzed. At gas pressures of a few atmospheres, the space charge arises due to the avalanche multiplication of the very first field-emission electron, whereas at pressures of several tens of atmospheres, the space charge forms as a result of superposition of many electron avalanches with a relatively small number of charge carriers in each.

The effect of CO2 gas adsorption on the electrical properties of Fe doped TiO2 films

NASA Astrophysics Data System (ADS)

Mardare, Diana; Adomnitei, Catalin; Florea, Daniel; Luca, Dumitru; Yildiz, Abdullah

2017-11-01

CO2 has to be monitored for indoor air quality, being also an important greenhouse gas. The electrical and sensing gas properties of the undoped and Fe doped TiO2 thin films, obtained by RF sputtering, have been investigated in different CO2 atmospheres. It was observed that the response to CO2 increases by Fe doping for the lowest doped film, and then decreases, as the dopant concentration increases. An explanation was given based on multiphonon-assisted hopping model. By studying the films electrical conductivity in front of a certain CO2 atmosphere, we have qualitatively evidenced the semiconducting n-type nature of the films under study, except for the highest Fe doped film which has a p-type behavior. An important finding is that Fe doping determines the decrease of the optimum operating temperature, approaching the room temperature.

Infrared photodissociation spectroscopy of M(N2)n(+) (M = Y, La, Ce; n = 7-8) in the gas phase.

PubMed

Xie, Hua; Shi, Lei; Xing, Xiaopeng; Tang, Zichao

2016-02-14

M(N2)n(+) (M = Y, La, Ce; n = 7-8) complexes have been studied by infrared photodissociation (IRPD) spectroscopy and density functional theory (DFT) calculations. The experimental results indicate that the N-N stretching vibrational frequencies are red-shifted from the gas-phase N2 value. The π back-donation is found to be a main contributor in these systems. IRPD spectra and DFT calculations reveal the coexistence of two isomers in the seven-coordinate M(N2)7(+) and eight-coordinate M(N2)8(+) complexes, respectively. The present studies on these metal-nitrogen complexes shed light on the interactions and coordinations toward N2 with transition and lanthanide metals.

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

PubMed

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

2012-04-19

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

Soil Greenhouse Gas Fluxes, Environmental Controls, and the Partitioning of N2O Sources in UK Natural and Seminatural Land Use Types

NASA Astrophysics Data System (ADS)

Sgouridis, Fotis; Ullah, Sami

2017-10-01

Natural and seminatural terrestrial ecosystems (unmanaged peatlands and forests and extensive and intensive grasslands) have been under-represented in the UK greenhouse gas (GHG) inventory. Mechanistic studies of GHG fluxes and their controls can improve the prediction of the currently uncertain GHG annual emission estimates. The source apportionment of N2O emissions can further inform management plans for GHG mitigation. We have measured in situ GHG fluxes monthly in two replicated UK catchments and evaluated their environmental controlling factors. An adapted 15N-gas flux method with low addition of 15N tracer (0.03-0.5 kg 15N ha-1) was used to quantify the relative contribution of denitrification to net N2O production. Total N2O fluxes were 40 times higher in the intensive grasslands than in the peatlands (range: -1.32 to 312.3 μg N m-2 h-1). The contribution of denitrification to net N2O emission varied across the land use types and ranged from 9 to 60%. Soil moisture was the key parameter regulating the partitioning of N2O sources (r2 = 0.46). Total N2O fluxes were explained by a simple model (r2 = 0.83) including parameters such as total dissolved nitrogen, organic carbon, and water content. A parsimonious model with the soil moisture content as a single scalar parameter explained 84% of methane flux variability across land uses. The assumption that 1% of the atmospherically deposited N on natural ecosystems is emitted as N2O could be overestimated or underestimated (0.3-1.6%). The use of land use-specific N2O emission factors and further information on N2O source partitioning should help constrain this uncertainty.

A SIFT ion-molecule study of some reactions in Titan's atmosphere. reactions of N(+), N(2)(+), and HCN(+) with CH(4), C(2)H(2), and C(2)H(4)

NASA Technical Reports Server (NTRS)

Anicich, Vincent G.; Wilson, Paul; McEwan, Murray J.

2004-01-01

The results of a study of the ion-molecule reactions of N(+), N(2)(+), and HCN(+) with methane, acetylene, and ethylene are reported. These studies were performed using the FA-SIFT at the University of Canterbury. The reactions studied here are important to understanding the ion chemistry in Titan's atmosphere. N(+) and N(2)(+) are the primary ions formed by photo-ionization and electron impact in Titan's ionosphere and drive Titan's ion chemistry. It is therefore very important to know how these ions react with the principal trace neutral species in Titan's atmosphere: Methane, acetylene, and ethylene. While these reactions have been studied before the product channels have been difficult to define as several potential isobaric products make a definitive answer difficult. Mass overlap causes difficulties in making unambiguous species assignments in these systems. Two discriminators have been used in this study to resolve the mass overlap problem. They are deuterium labeling and also the differences in reactivities of each isobar with various neutral reactants. Several differences have been found from the products in previous work. The HCN(+) ion is important in both Titan's atmosphere and in the laboratory.

Fluid simulation of species concentrations in capacitively coupled N2/Ar plasmas: Effect of gas proportion

NASA Astrophysics Data System (ADS)

Liang, Ying-Shuang; Liu, Gang-Hu; Xue, Chan; Liu, Yong-Xin; Wang, You-Nian

2017-05-01

A two-dimensional self-consistent fluid model and the experimental diagnostic are employed to investigate the dependencies of species concentrations on the gas proportion in the capacitive N2/Ar discharges operated at 60 MHz, 50 Pa, and 140 W. The results indicate that the N2/Ar proportion has a considerable impact on the species densities. As the N2 fraction increases, the electron density, as well as the Ar+ and Arm densities, decreases remarkably. On the contrary, the N2 + density is demonstrated to increase monotonically with the N2 fraction. Moreover, the N density is observed to increase significantly with the N2 fraction at the N2 fractions below 40%, beyond which it decreases slightly. The electrons are primarily generated via the electron impact ionization of the feed gases. The electron impact ionization of Ar essentially determines the Ar+ density. For the N2 + production, the charge transition process between the Ar+ ions and the feed gas N2 dominates at low N2 fraction, while the electron impact ionization of N2 plays the more important role at high N2 fraction. At any gas mixtures, more than 60% Arm atoms are generated through the radiative decay process from Ar(4p). The dissociation of the feed gas N2 by the excited Ar atoms and by the electrons is responsible for the N formation at low N2 fraction and high N2 fraction, respectively. To validate the simulation results, the floating double probe and the optical emission spectroscopy are employed to measure the total positive ion density and the emission intensity originating from Ar(4p) transitions, respectively. The results from the simulation show a qualitative agreement with that from the experiment, which indicates the reliable model.

Soil-Atmosphere Greenhouse Gas Fluxes on the Margins of the Congo Forest: Effects of Forest Conversion towards Smallholder Agricultural Lands and Agricultural Intensification

NASA Astrophysics Data System (ADS)

kwatcho Kengdo, S.; Sonwa, D. J.; Njine-Bememba, C. B.; Djatsa, L. D.; Rufino, M. C.; Verchot, L. V.; Tejedor, J.; Dannenmann, M.

2016-12-01

The forests of the Congo Basin are subject to deforestation and land use change, which may severely influence the soil-atmosphere exchange of greenhouse gases (GHG). However, due to absence of analytical capacities in Central Africa, there is a lack of knowledge on fluxes of CO2, CH4 and N2O at the soil-atmosphere interface for natural and managed ecosystems, which introduces large uncertainties into regional and national GHG reporting. The objectives of this study were to quantify GHG emissions from typical land use on the margins of the Congo forests, to analyze seasonal variability and environmental controls of soil-atmosphere GHG fluxes across a land use gradient and explore options of sustainable intensification of maize cultivation. In Cameroon, we quantified fluxes of CO2, CH4, and N2O at the soil - atmosphere interface in secondary forests, cocoa agroforests, unfertilized mixed crop fields, and three different types of maize cultivation: unfertilized control, maize intercropped with N fixing beans, maize applied with mineral nitrogen fertilizer. We used manual static chamber techniques with approximately weekly temporal resolution over a full year and analyzed gas samples using a gas chromatograph. Soil temperature and moisture data were permanently recorded at main sites and soil sampling provided information on soil mineral N content. We found highest CO2 and N2O emissions, net CH4 uptake and soil mineral N concentrations in the secondary forest with lower values observed in cocoa agroforest and in particular in extensive mixed crop. Soil moisture changes were the dominant driver of seasonal changes of GHG fluxes at all study sites. Intercropping with N fixing beans did not alter soil N2O emissions from maize fields. In contrast, application of mineral N increased soil N2O emissions by more than a factor of five. Our work highlights the importance of soil moisture as the driver of GHG fluxes and in particular for N2O indicates a strong decrease in soil

Natural gas fugitive emissions rates constrained by global atmospheric methane and ethane.

PubMed

Schwietzke, Stefan; Griffin, W Michael; Matthews, H Scott; Bruhwiler, Lori M P

2014-07-15

The amount of methane emissions released by the natural gas (NG) industry is a critical and uncertain value for various industry and policy decisions, such as for determining the climate implications of using NG over coal. Previous studies have estimated fugitive emissions rates (FER)--the fraction of produced NG (mainly methane and ethane) escaped to the atmosphere--between 1 and 9%. Most of these studies rely on few and outdated measurements, and some may represent only temporal/regional NG industry snapshots. This study estimates NG industry representative FER using global atmospheric methane and ethane measurements over three decades, and literature ranges of (i) tracer gas atmospheric lifetimes, (ii) non-NG source estimates, and (iii) fossil fuel fugitive gas hydrocarbon compositions. The modeling suggests an upper bound global average FER of 5% during 2006-2011, and a most likely FER of 2-4% since 2000, trending downward. These results do not account for highly uncertain natural hydrocarbon seepage, which could lower the FER. Further emissions reductions by the NG industry may be needed to ensure climate benefits over coal during the next few decades.

Combustion gas properties. 2: Natural gas fuel and dry air

NASA Technical Reports Server (NTRS)

Wear, J. D.; Jones, R. E.; Trout, A. M.; Mcbride, B. J.

1985-01-01

A series of computations has been made to produce the equilibrium temperature and gas composition for natural gas fuel and dry air. The computed tables and figures provide combustion gas property data for pressures from 0.5 to 50 atmospheres and equivalence ratios from 0 to 2.0. Only samples tables and figures are provided in this report. The complete set of tables and figures is provided on four microfiche films supplied with this report.

Gas Leak Detection by Dilution of Atmospheric Oxygen

PubMed Central

Lambrecht, Armin; Maier, Eric; Strahl, Thomas; Herbst, Johannes

2017-01-01

Gas leak detection is an important issue in infrastructure monitoring and industrial production. In this context, infrared (IR) absorption spectroscopy is a major measurement method. It can be applied in an extractive or remote detection scheme. Tunable laser spectroscopy (TLS) instruments are able to detect CH4 leaks with column densities below 10 ppm·m from a distance of 30 m in less than a second. However, leak detection of non-IR absorbing gases such as N2 is not possible in this manner. Due to the fact that any leaking gas displaces or dilutes the surrounding background gas, an indirect detection is still possible. It is shown by sensitive TLS measurements of the ambient background concentration of O2 that N2 leaks can be localized with extractive and standoff methods for distances below 1 m. Minimum leak rates of 0.1 mbar·L/s were determined. Flow simulations confirm that the leakage gas typically effuses in a narrow jet. The sensitivity is mainly determined by ambient flow conditions. Compared to TLS detection of CH4 at 1651 nm, the indirect method using O2 at 761 nm is experimentally found to be less sensitive by a factor of 100. However, the well-established TLS of O2 may become a universal tool for rapid leakage screening of vessels that contain unknown or inexpensive gases, such as N2. PMID:29206133

The Composition of Titan's Lower Atmosphere and Simple Surface Volatiles as Measured by the Cassini-Huygens Probe Gas Chromatograph Mass Spectrometer Experiment

NASA Technical Reports Server (NTRS)

Niemann, H. B.; Atreya, S. K.; Demick, J. E.; Gautier, D.; Haberman, J. A.; Harpold, D. N.; Kasprzak, W. T.; Lunine, J. I.; Owen, T. C.; Raulin, F.

2010-01-01

The Cassini-Huygens Probe Gas Chromatograph Mass Spectrometer (GCMS) determined the composition of the Titan atmosphere from 140km altitude to the surface. After landing, it returned composition data of gases evaporated from the surface. Height profiles of molecular nitrogen (N2), methane (CH4) and molecular hydrogen (H2) were determined. Traces were detected on the surface of evaporating methane, ethane (C2H6), acetylene (C2H2), cyanogen (C2N2) and carbon dioxide (CO2). The methane data showed evidence that methane precipitation occurred recently. The methane mole fraction was (1.48+/-0.09) x 10(exp -2) in the lower stratosphere (139.8 km to 75.5 km) and (5.65+/-0.18) x 10(exp -2) near the surface (6.7 km to the surface). The molecular hydrogen mole fraction was (1.01+/-0.16) x 10(exp -3) in the atmosphere and (9.90+/-0.17) x 10(exp -4) on the surface. Isotope ratios were 167.7+/-0.6 for N-14/N-15 in molecular nitrogen, 91.1+/-1.4 for C-12/C-13 in methane and (1.35+/-0.30) x 10(exp -4) for D/H in molecular hydrogen. The mole fractions of Ar-36 and radiogenic Ar-40 are (2.1+/-0.8) x 10(exp -7) and (3.39 +/-0.12) x 10(exp -5) respectively. Ne-22 has been tentatively identified at a mole fraction of (2.8+/-2.1) x 10(exp -7) Krypton and xenon were below the detection threshold of 1 x 10(exp -8) mole fraction. Science data were not retrieved from the gas chromatograph subsystem as the abundance of the organic trace gases in the atmosphere and on the ground did not reach the detection threshold. Results previously published from the GCMS experiment are superseded by this publication.

Fabrication and characterization of a CNT forest integrated micromechanical resonator for a rarefied gas analyzer in a medium vacuum atmosphere

NASA Astrophysics Data System (ADS)

Sugano, Koji; Matsumoto, Ryu; Tsutsui, Ryota; Kishihara, Hiroyuki; Matsuzuka, Naoki; Yamashita, Ichiro; Uraoka, Yukiharu; Isono, Yoshitada

2016-07-01

This study focuses on the development of a multi-walled carbon nanotube (MWCNT) forest integrated micromechanical resonator working as a rarefied gas analyzer for nitrogen (N2) and hydrogen (H2) gases in a medium vacuum atmosphere. The resonant response is detected in the form of changes in the resonant frequency or damping effects, depending on the rarefied gas species. The carbon nanotube (CNT) forest on the resonator enhances the effective specific surface area of the resonator, such that the variation of the resonant frequency and the damping effect based on the gas species increase significantly. We developed the fabrication process for the proposed resonator, which consists of standard micro-electro-mechanical systems (MEMS) processes and high-density CNT synthesis on the resonator mass. The high-density CNT synthesis was realized using multistep alternate coating of two types of ferritin proteins that act as catalytic iron particles. Two devices with different CNT densities were fabricated and characterized to evaluate the effect of the surface area of the CNT forest on the resonant response as a function of gas pressures ranging from 0.011 to 1 Pa for N2 and H2. Considering the damping effect, we found that the device with higher density was able to distinguish N2 and H2 clearly, whereas the device with lower density showed no difference between N2 and H2. We confirmed that a larger surface area showed a higher damping effect. These results were explained based on the kinetic theory of gases. In the case of resonant frequency, the relative resonant frequency shift increased with gas pressure and surface area because of the adsorption of gas molecules on the resonator surfaces. Higher density CNT forest adsorbed more gas molecules on the surfaces. The developed CNT forest integrated micromechanical resonator could successfully detect N2 and H2 gases and distinguish between them under pressures of 1 Pa.

Water relations and gas exchange in poplar and willow under water stress and elevated atmospheric CO2.

PubMed

Johnson, Jon D; Tognetti, Roberto; Paris, Piero

2002-05-01

Predictions of shifts in rainfall patterns as atmospheric [CO2] increases could impact the growth of fast growing trees such as Populus spp. and Salix spp. and the interaction between elevated CO2 and water stress in these species is unknown. The objectives of this study were to characterize the responses to elevated CO2 and water stress in these two species, and to determine if elevated CO2 mitigated drought stress effects. Gas exchange, water potential components, whole plant transpiration and growth response to soil drying and recovery were assessed in hybrid poplar (clone 53-246) and willow (Salix sagitta) rooted cuttings growing in either ambient (350 &mgr;mol mol-1) or elevated (700 &mgr;mol mol-1) atmospheric CO2 concentration ([CO2]). Predawn water potential decreased with increasing water stress while midday water potentials remained unchanged (isohydric response). Turgor potentials at both predawn and midday increased in elevated [CO2], indicative of osmotic adjustment. Gas exchange was reduced by water stress while elevated [CO2] increased photosynthetic rates, reduced leaf conductance and nearly doubled instantaneous transpiration efficiency in both species. Dark respiration decreased in elevated [CO2] and water stress reduced Rd in the trees growing in ambient [CO2]. Willow had 56% lower whole plant hydraulic conductivity than poplar, and showed a 14% increase in elevated [CO2] while poplar was unresponsive. The physiological responses exhibited by poplar and willow to elevated [CO2] and water stress, singly, suggest that these species respond like other tree species. The interaction of [CO2] and water stress suggests that elevated [CO2] did mitigate the effects of water stress in willow, but not in poplar.

The effect of modified atmospheres and packaging on patulin production in apples.

PubMed

Moodley, R S; Govinden, R; Odhav, B

2002-05-01

This study was undertaken to determine the effectiveness of modified atmospheres and packaging materials on the growth of Penicillium expansum and patulin production in apples. Granny Smith apples were surface sterilized with 76% ethanol and inoculated with 0.1 ml of a 1.1 x 10(7) spore/ml P. expansum spore suspension. The apples were packaged either in polyethylene (PE) or polypropylene (PP) and treated with three different gas combinations, viz., 58% CO2/42% N2, 48% CO2/52% N2, and 88% CO2/12% N2, and were then incubated for 14 days at 25 degrees C. Fungal growth was monitored every 2 to 4 days by measuring radial growth from the point of inoculation. After the 14th day, apples were pulped, and patulin was extracted, purified, and quantified by high-performance liquid chromatography. PP did not inhibit fungal growth in any of the atmospheres tested, and it only inhibited patulin production in atmospheric gas and 58% CO2/42% N2. PE was very effective and inhibited fungal growth by four- or fivefold, depending on the modified atmosphere. Patulin production in PE-packaged apples was almost completely inhibited by all three gas combinations. Gas chromatographic analysis of the PE-packaged samples before and after the incubation period showed that CO2 levels dropped and N2 levels increased for all of the atmospheres tested. Our studies showed conclusively that PE is an excellent packaging material for the storage of apples since it inhibited the growth of P. expansum, thereby allowing <3.2 microg/ml of patulin to be produced, regardless of gaseous environment.

Pt-decorated GaN nanowires with significant improvement in H2 gas-sensing performance at room temperature.

PubMed

Abdullah, Q N; Yam, F K; Hassan, Z; Bououdina, M

2015-12-15

Superior sensitivity towards H2 gas was successfully achieved with Pt-decorated GaN nanowires (NWs) gas sensor. GaN NWs were fabricated via chemical vapor deposition (CVD) route. Morphology (field emission scanning electron microscopy and transmission electron microscopy) and crystal structure (high resolution X-ray diffraction) characterizations of the as-synthesized nanostructures demonstrated the formation of GaN NWs having a wurtzite structure, zigzaged shape and an average diameter of 30-166nm. The Pt-decorated GaN NWs sensor shows a high response of 250-2650% upon exposure to H2 gas concentration from 7 to 1000ppm respectively at room temperature (RT), and then increases to about 650-4100% when increasing the operating temperature up to 75°C. The gas-sensing measurements indicated that the Pt-decorated GaN NWs based sensor exhibited efficient detection of H2 at low concentration with excellent sensitivity, repeatability, and free hysteresis phenomena over a period of time of 100min. The large surface-to-volume ratio of GaN NWs and the catalytic activity of Pt metal are the most influential factors leading to the enhancement of H2 gas-sensing performances through the improvement of the interaction between the target molecules (H2) and the sensing NWs surface. The attractive low-cost, low power consumption and high-performance of the resultant decorated GaN NWs gas sensor assure their uppermost potential for H2 gas sensor working at low operating temperature. Copyright © 2015 Elsevier Inc. All rights reserved.

Gas-phase hydration of glyoxylic acid: Kinetics and atmospheric implications.

PubMed

Liu, Ling; Zhang, Xiuhui; Li, Zesheng; Zhang, Yunhong; Ge, Maofa

2017-11-01

Oxocarboxylic acids are one of the most important organic species found in secondary organic aerosols and can be detected in diverse environments. But the hydration of oxocarboxylic acids in the atmosphere has still not been fully understood. Neglecting the hydration of oxocarboxylic acids in atmospheric models may be one of the most important reasons for the significant discrepancies between field measurements and abundance predictions of atmospheric models for oxocarboxylic acids. In the present paper, glyoxylic acid, as the most abundant oxocarboxylic acids in the atmosphere, has been selected as an example to study whether the hydration process can occur in the atmosphere and what the kinetic process of hydration is. The gas-phase hydration of glyoxylic acid to form the corresponding geminal diol and those catalyzed by atmospheric common substances (water, sulfuric acid and ammonia) have been investigated at the CCSD(T)-F12/cc-pVDZ-F12//M06-2X/6-311++G(3df,3pd) level of theory. The contour map of electron density difference of transition states have been further analyzed. It is indicated that these atmospheric common substances can all catalyze on the hydration to some extent and sulfuric acid is the most effective reducing the Gibbs free energy of activation to 9.48 kcal/mol. The effective rate constants combining the overall rate constants and concentrations of the corresponding catalysts have shown that water and sulfuric acid are both important catalysts and the catalysis of sulfuric acid is the most effective for the gas-phase hydration of glyoxylic acid. This catalyzed processes are potentially effective in coastal regions and polluted regions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Oceanic nitrogen cycling and N2O flux perturbations in the Anthropocene

NASA Astrophysics Data System (ADS)

Landolfi, A.; Somes, C. J.; Koeve, W.; Zamora, L. M.; Oschlies, A.

2017-08-01

There is currently no consensus on how humans are affecting the marine nitrogen (N) cycle, which limits marine biological production and CO2 uptake. Anthropogenic changes in ocean warming, deoxygenation, and atmospheric N deposition can all individually affect the marine N cycle and the oceanic production of the greenhouse gas nitrous oxide (N2O). However, the combined effect of these perturbations on marine N cycling, ocean productivity, and marine N2O production is poorly understood. Here we use an Earth system model of intermediate complexity to investigate the combined effects of estimated 21st century CO2 atmospheric forcing and atmospheric N deposition. Our simulations suggest that anthropogenic perturbations cause only a small imbalance to the N cycle relative to preindustrial conditions (˜+5 Tg N y-1 in 2100). More N loss from water column denitrification in expanded oxygen minimum zones (OMZs) is counteracted by less benthic denitrification, due to the stratification-induced reduction in organic matter export. The larger atmospheric N load is offset by reduced N inputs by marine N2 fixation. Our model predicts a decline in oceanic N2O emissions by 2100. This is induced by the decrease in organic matter export and associated N2O production and by the anthropogenically driven changes in ocean circulation and atmospheric N2O concentrations. After comprehensively accounting for a series of complex physical-biogeochemical interactions, this study suggests that N flux imbalances are limited by biogeochemical feedbacks that help stabilize the marine N inventory against anthropogenic changes. These findings support the hypothesis that strong negative feedbacks regulate the marine N inventory on centennial time scales.

Modeling a 15-min extravehicular activity prebreathe protocol using NASA's exploration atmosphere (56.5 kPa/34% O2)

NASA Astrophysics Data System (ADS)

Abercromby, Andrew F. J.; Conkin, Johnny; Gernhardt, Michael L.

2015-04-01

NASA's plans for future human exploration missions utilize a new atmosphere of 56.5 kPa (8.2 psia), 34% O2, 66% N2 to enable rapid extravehicular activity (EVA) capability with minimal gas losses; however, existing EVA prebreathe protocols to mitigate risk of decompression sickness (DCS) are not applicable to the new exploration atmosphere. We provide preliminary analysis of a 15-min prebreathe protocol and examine the potential benefits of intermittent recompression (IR) and an abbreviated N2 purge on crew time and gas consumables usage. A probabilistic model of decompression stress based on an established biophysical model of DCS risk was developed, providing significant (p<0.0001) prediction and goodness-of-fit with 84 cases of DCS in 668 human altitude exposures including a variety of pressure profiles. DCS risk for a 15-min prebreathe protocol was then estimated under different exploration EVA scenarios. Estimated DCS risk for all EVA scenarios modeled using the 15-min prebreathe protocol ranged between 6.1% and 12.1%. Supersaturation in neurological tissues (5- and 10-min half-time compartments) is prevented and tissue tensions in faster half-time compartments (≤40 min), where the majority of whole-body N2 is located, are reduced to about the levels (30.0 vs. 27.6 kPa) achieved during a standard Shuttle prebreathe protocol. IR reduced estimated DCS risk from 9.7% to 7.9% (1.8% reduction) and from 8.4% to 6.1% (2.3% reduction) for the scenarios modeled; the penalty of N2 reuptake during IR may be outweighed by the benefit of decreased bubble size. Savings of 75% of purge gas and time (0.22 kg gas and 6 min of crew time per person per EVA) are achievable by abbreviating the EVA suit purge to 20% N2 vs. 5% N2 at the expense of an increase in estimated DCS risk from 9.7% to 12.1% (2.4% increase). A 15-min prebreathe protocol appears feasible using the new exploration atmosphere. IR between EVAs may enable reductions in suit purge and prebreathe requirements

Quantifying N2O reduction to N2 based on N2O isotopocules - validation with independent methods (helium incubation and 15N gas flux method)

NASA Astrophysics Data System (ADS)

Lewicka-Szczebak, Dominika; Augustin, Jürgen; Giesemann, Anette; Well, Reinhard

2017-02-01

Stable isotopic analyses of soil-emitted N2O (δ15Nbulk, δ18O and δ15Nsp = 15N site preference within the linear N2O molecule) may help to quantify N2O reduction to N2, an important but rarely quantified process in the soil nitrogen cycle. The N2O residual fraction (remaining unreduced N2O, rN2O) can be theoretically calculated from the measured isotopic enrichment of the residual N2O. However, various N2O-producing pathways may also influence the N2O isotopic signatures, and hence complicate the application of this isotopic fractionation approach. Here this approach was tested based on laboratory soil incubations with two different soil types, applying two reference methods for quantification of rN2O: helium incubation with direct measurement of N2 flux and the 15N gas flux method. This allowed a comparison of the measured rN2O values with the ones calculated based on isotopic enrichment of residual N2O. The results indicate that the performance of the N2O isotopic fractionation approach is related to the accompanying N2O and N2 source processes and the most critical is the determination of the initial isotopic signature of N2O before reduction (δ0). We show that δ0 can be well determined experimentally if stable in time and then successfully applied for determination of rN2O based on δ15Nsp values. Much more problematic to deal with are temporal changes of δ0 values leading to failure of the approach based on δ15Nsp values only. For this case, we propose here a dual N2O isotopocule mapping approach, where calculations are based on the relation between δ18O and δ15Nsp values. This allows for the simultaneous estimation of the N2O-producing pathways' contribution and the rN2O value.

Relaxation of heavy species and gas temperature in the afterglow of a N2 microwave discharge

NASA Astrophysics Data System (ADS)

Pintassilgo, Carlos D.; Guerra, Vasco

2017-10-01

In this paper we present a self-consistent kinetic model to study the temporal variation of the gas temperature in the afterglow of a 440 Pa microwave nitrogen discharge operating at 433 MHz in a 3.8 cm diameter tube. The initial conditions in the afterglow are determined by a kinetic model that solves the electron Boltzmann equation coupled to the gas thermal balance equation and a system of rate-balance equations for N2(X 1∑g+, v) molecules, electronically excited states of N2, ground and excited states of atomic nitrogen and the main positive ions. Once the initial concentrations of the heavy species and gas temperature are known, their relaxation in the afterglow is obtained from the solutions to the corresponding time-dependent equations. Modelling predictions are found to be in good agreement with previously measured values for the concentrations of N(4S) atoms and N2(A 3∑u+) molecules, and the radially averaged gas temperature Tg along the afterglow of a microwave discharge in N2 under the same working conditions. It is shown that gas heating in the afterglow comes essentially from the energy transfer involving non-resonant vibration-vibration (V-V) collisions between vibrationally excited nitrogen molecules, as well as from energy exchanges in vibration-translation (V-T) on N2-N collisions. Contribution to the topical issue "Plasma Sources and Plasma Processes (PSPP)", edited by Luis Lemos Alves, Thierry Belmonte and Tiberiu Minea

A Controlled Environment System For Measuring Plant-Atmosphere Gas Exchange

Treesearch

James M. Brown

1975-01-01

Describes an inexpensive, efficient system for measuring plant-atmosphere gas exchange. Designed to measure transpiration from potted tree seedlings, it is readily adaptable for measuring other gas exchanges or gas exchange by plant parts. Light level, air and root temperature can be precisely controlled at minimum cost.

Atmospheric chemistry of cyc-CF2CF2CF2CH=CH-: Kinetics, products, and mechanism of gas-phase reaction with OH radicals, and atmospheric implications

NASA Astrophysics Data System (ADS)

Guo, Qin; Zhang, Ni; Uchimaru, Tadafumi; Chen, Liang; Quan, Hengdao; Mizukado, Junji

2018-04-01

The rate constants for the gas-phase reactions of cyc-CF2CF2CF2CH=CH- with OH radicals were determined by a relative rate method between 253 and 328 K. The rate constant k1 at 298 K was measured to be (1.08 ± 0.04) × 10-13 cm3 molecule-1 s-1, and the Arrhenius expression was k1 = (3.72 ± 0.14) × 10-13 exp [(-370 ± 12)/T]. The atmospheric lifetime of cyc-CF2CF2CF2CH=CH- was calculated to be 107 d. The products and mechanism for the reaction of cyc-CF2CF2CF2CH=CH- with OH radicals were also investigated. CO, CO2, and COF2 were identified as the main carbon-containing products following the OH-initiated reaction. Moreover, the radiative efficiency (RE) was determined to be 0.143 W m-2 ppb-1, and the global warming potentials (GWPs) for 20, 100, and 500 yr were 54, 15, and 4, respectively. The photochemical ozone creation potential of the title compound was estimated to be 1.3.

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

PubMed

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

2014-06-01

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

Atmospheric and soil-gas monitoring for surface leakage at the San Juan Basin CO{sub 2} pilot test site at Pump Canyon New Mexico, using perfluorocarbon tracers, CO{sub 2} soil-gas flux and soil-gas hydrocarbons

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

Wells, Arthur W; Diehl, J Rodney; Strazisar, Brian R

2012-05-01

Near-surface monitoring and subsurface characterization activities were undertaken in collaboration with the Southwest Regional Carbon Sequestration Partnership on their San Juan Basin coal-bed methane pilot test site near Navajo City, New Mexico. Nearly 18,407 short tons (1.670 × 107 kg) of CO{sub 2} were injected into 3 seams of the Fruitland coal between July 2008 and April 2009. Between September 18 and October 30, 2008, two additions of approximately 20 L each of perfluorocarbon (PFC) tracers were mixed with the CO{sub 2} at the injection wellhead. PFC tracers in soil-gas and in the atmosphere were monitored over a period ofmore » 2 years using a rectangular array of permanent installations. Additional monitors were placed near existing well bores and at other locations of potential leakage identified during the pre-injection site survey. Monitoring was conducted using sorbent containing tubes to collect any released PFC tracer from soil-gas or the atmosphere. Near-surface monitoring activities also included CO{sub 2} surface flux and carbon isotopes, soil-gas hydrocarbon levels, and electrical conductivity in the soil. The value of the PFC tracers was demonstrated when a significant leakage event was detected near an offset production well. Subsurface characterization activities, including 3D seismic interpretation and attribute analysis, were conducted to evaluate reservoir integrity and the potential that leakage of injected CO{sub 2} might occur. Leakage from the injection reservoir was not detected. PFC tracers made breakthroughs at 2 of 3 offset wells which were not otherwise directly observable in produced gases containing 20–30% CO{sub 2}. These results have aided reservoir geophysical and simulation investigations to track the underground movement of CO{sub 2}. 3D seismic analysis provided a possible interpretation for the order of appearance of tracers at production wells.« less

Simultaneous gas chromatographic determination of four toxic gases generally present in combustion atmospheres.

PubMed

Endecott, B R; Sanders, D C; Chaturvedi, A K

1996-01-01

The measurement of combustion gases produced by burning aircraft cabin materials poses a continuing limitation for smoke toxicity research. Because toxic effects of gases depend on both their concentrations and the duration of exposure, frequent atmosphere sampling is necessary to define the gas concentration-exposure time curve. A gas chromatographic (GC) method was developed for the simultaneous analyses of carbon monoxide (CO), hydrogen sulfide (H2S), sulfur dioxide (SO2), and hydrogen cyanide (HCN). The method used an MTI M200 dual-column gas chromatograph equipped with 4-m molecular sieve-5A and 8-m PoraPlot-U wall-coated capillary columns and two low-volume, high-sensitivity thermal conductivity detectors. Detectability (in parts per million [ppm]) and retention times (in seconds) for the gases were as follows: CO, 100 ppm, 28 s; H2S, 50 ppm, 26 s; SO2, 125 ppm, 76 s; and HCN, 60 ppm, 108 s. The method was effective for determining these gases in mixtures and in the combustion atmospheres generated by burning wool (CO, HCN, and H2S) and modacrylic fabrics (CO and HCN). Common atmospheric gaseous or combustion products (oxygen, carbon dioxide, nitrogen, water vapor, and other volatiles) did not interfere with the analyses. However, filtration of the combustion atmospheres was necessary to prevent restriction of the GC sampling inlet by smoke particulates. The speed, sensitivity, and selectivity of this method make it suitable for smoke toxicity research and for evaluating performance of passenger protective breathing equipment. Also, this method can potentially be modified to analyze these gases when they are liberated from biosamples.

A CRDS approach to gas phase equilibrium constants: the case of N 2O 4 ↔ 2NO 2 at 283 K

NASA Astrophysics Data System (ADS)

Tuchler, Matthew F.; Schmidt, Kierstin L.; Morgan, Mackenzie

2005-01-01

We report a general technique for determining the gas phase equilibrium constant, KP, of the A ↔ 2C system using cavity ringdown spectroscopy (CRDS). Working at a constant temperature, the absorption of one of the equilibrium species is measured at two different total pressures. KP is determined from the total pressures of the equilibrium mixture and the ratio of the absorptions. Theoretical limits on sensitivity of this technique are described as a function of experimental conditions. We present results from the reaction N 2O 4 ↔ 2NO 2 measured at T = 283 K. KP measured in this experiment, 21 (±5) Torr, is found to be lower than that recommended by the NASA Panel for Data Evaluation, 32 Torr. [S.P. Sander, A.R. Ravishankara, D.M. Golden, C.E. Kolb, M.J. Kurylo, R.E. Huie, V.L. Orkin, M.J. Molina, G.K. Moortgat, B.J. Finlayson-Pitts, Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies. Evaluation No. 14; Jet Propulsion Laboratory, Pasadena, CA, 2003].

Gas and particle size distributions of polychlorinated naphthalenes in the atmosphere of Beijing, China.

PubMed

Zhu, Qingqing; Zhang, Xian; Dong, Shujun; Gao, Lirong; Liu, Guorui; Zheng, Minghui

2016-05-01

Polychlorinated naphthalenes (PCNs) were listed as persistent organic pollutants in the Stockholm Convention in 2015. Despite numerous studies on PCNs, little is known about their occurrence in atmospheric particulate matter of different sizes. In this study, 49 PCN congeners were investigated for their concentrations and size-specific distributions in an urban atmosphere, and preliminary exposure assessments were conducted. Ambient air samples were collected using a high-volume cascade impactor for division into a gas fraction and four particle size fractions. Samples were collected from October 2013 to June 2014 at an urban site in Beijing, China. The concentration range for PCNs in the atmosphere (gas + particle fractions) was 6.77-25.90 pg/m(3) (average 16.28 pg/m(3)). The particle-bound concentration range was 0.17-2.78 pg/m(3) (average 1.73 pg/m(3)). Therefore, PCNs were mainly found in the gas phase. The concentrations of PCNs in a fraction increased as the particle size decreased (dae > 10 μm, 10 μm ≥ dae > 2.5 μm, 2.5 μm ≥ dae > 1.0 μm and dae ≤ 1.0 μm). Consequently, PCNs were ubiquitous in inhalable fine particles, and the ΣPCNs associated with PM1.0 and PM2.5 reached 68.4% and 84.3%, respectively. Tetra-CNs and penta-CNs (the lower chlorinated homologues) predominated in the atmosphere. The homologue profiles in different size particles were almost similar, but the particulate profiles were different from those in the gas phase. Among the individual PCNs identified, CN38/40, CN52/60 and CN75 were the dominant compounds in the atmosphere. CN66/67 and CN73 collectively accounted for most of the total dioxin-like TEQ concentrations of the PCNs. Exposure to toxic compounds, such as PCNs present in PM1.0 or PM2.5, may affect human health. This work presents the first data on size-specific distributions of PCNs in the atmosphere. Copyright © 2016 Elsevier Ltd. All rights reserved.

Characteristics of surface-wave plasma with air-simulated N2 O2 gas mixture for low-temperature sterilization

NASA Astrophysics Data System (ADS)

Xu, L.; Nonaka, H.; Zhou, H. Y.; Ogino, A.; Nagata, T.; Koide, Y.; Nanko, S.; Kurawaki, I.; Nagatsu, M.

2007-02-01

Sterilization experiments using low-pressure air discharge plasma sustained by the 2.45 GHz surface-wave have been carried out. Geobacillus stearothermoplilus spores having a population of 3.0 × 106 were sterilized for only 3 min using air-simulated N2-O2 mixture gas discharge plasma, faster than the cases of pure O2 or pure N2 discharge plasmas. From the SEM analysis of plasma-irradiated spores and optical emission spectroscopy measurements of the plasmas, it has been found that the possible sterilization mechanisms of air-simulated plasma are the chemical etching effect due to the oxygen radicals and UV emission from the N2 molecules and NO radicals in the wavelength range 200-400 nm. Experiment suggested that UV emission in the wavelength range less than 200 nm might not be significant in the sterilization. The UV intensity at 237.0 nm originated from the NO γ system (A 2Σ+ → X 2Π) in N2-O2 plasma as a function of the O2 percentage added to N2-O2 mixture gas has been investigated. It achieved its maximum value when the O2 percentage was roughly 10-20%. This result suggests that air can be used as a discharge gas for sterilization, and indeed we have confirmed a rapid sterilization with the actual air discharge at a sample temperature of less than 65 °C.

Multiplex gas chromatography: an alternative concept for gas chromatographic analysis of planetary atmospheres

NASA Technical Reports Server (NTRS)

Valentin, J. R.

1989-01-01

Gas chromatography (GC) is a powerful technique for analyzing gaseous mixtures. Applied to the earth's atmosphere, GC can be used to determine the permanent gases--such as carbon dioxide, nitrogen, and oxygen--and to analyze organic pollutants in air. The U.S. National Aeronautics and Space Administration (NASA) has used GC in spacecraft missions to Mars (the Viking Biology Gas Exchange Experiment [GEX] and the Viking Gas Chromatograph-Mass Spectrometer [GC-MS]) and to Venus (the Pioneer Venus Gas Chromatograph [PVGC] on board the Pioneer Venus sounder probe) for determining the atmospheric constituents of these two planets. Even though conventional GC was very useful in the Viking and Pioneer missions, spacecraft constraints and limitations intrinsic to the technique prevented the collection of more samples. With the Venus probe, for instance, each measurement took a relatively long time to complete (10 min), and successive samples could not be introduced until the previous samples had left the column. Therefore, while the probe descended through the Venusian atmosphere, only three samples were acquired at widely separated altitudes. With the Viking mission, the sampling rate was not a serious problem because samples were acquired over a period of one year. However, the detection limit was a major disadvantage. The GC-MS could not detect simple hydrocarbons and simple alcohols below 0.1 ppm, and the GEX could not detect them below 1 ppm. For more complex molecules, the detection limits were at the parts-per-billion level for both instruments. Finally, in both the Viking and Pioneer missions, the relatively slow rate of data acquisition limited the number of analyses, and consequently, the amount of information returned. Similar constraints are expected in future NASA missions. For instance, gas chromatographic instrumentation is being developed to collect and analyze organic gases and aerosols in the atmosphere of Titan (one of Saturn's satellites). The Titan

From biota to chemistry and climate: towards a comprehensive description of trace gas exchange between the biosphere and atmosphere

NASA Astrophysics Data System (ADS)

Arneth, A.; Sitch, S.; Bondeau, A.; Butterbach-Bahl, K.; Foster, P.; Gedney, N.; de Noblet-Ducoudré, N.; Prentice, I. C.; Sanderson, M.; Thonicke, K.; Wania, R.; Zaehle, S.

2010-01-01

Exchange of non-CO2 trace gases between the land surface and the atmosphere plays an important role in atmospheric chemistry and climate. Recent studies have highlighted its importance for interpretation of glacial-interglacial ice-core records, the simulation of the pre-industrial and present atmosphere, and the potential for large climate-chemistry and climate-aerosol feedbacks in the coming century. However, spatial and temporal variations in trace gas emissions and the magnitude of future feedbacks are a major source of uncertainty in atmospheric chemistry, air quality and climate science. To reduce such uncertainties Dynamic Global Vegetation Models (DGVMs) are currently being expanded to mechanistically represent processes relevant to non-CO2 trace gas exchange between land biota and the atmosphere. In this paper we present a review of important non-CO2 trace gas emissions, the state-of-the-art in DGVM modelling of processes regulating these emissions, identify key uncertainties for global scale model applications, and discuss a methodology for model integration and evaluation.

From biota to chemistry and climate: towards a comprehensive description of trace gas exchange between the biosphere and atmosphere

NASA Astrophysics Data System (ADS)

Arneth, A.; Sitch, S.; Bondeau, A.; Butterbach-Bahl, K.; Foster, P.; Gedney, N.; de Noblet-Ducoudré, N.; Prentice, I. C.; Sanderson, M.; Thonicke, K.; Wania, R.; Zaehle, S.

2009-07-01

Exchange of non-CO2 trace gases between the land surface and the atmosphere plays an important role in atmospheric chemistry and climate. Recent studies have highlighted its importance for interpretation of glacial-interglacial ice-core records, the simulation of the pre-industrial and present atmosphere, and the potential for large climate-chemistry and climate-aerosol feedbacks in the coming century. However, spatial and temporal variations in trace gas emissions and the magnitude of future feedbacks are a major source of uncertainty in atmospheric chemistry, air quality and climate science. To reduce such uncertainties Dynamic Global Vegetation Models (DGVMs) are currently being expanded to mechanistically represent processes relevant to non-CO2 trace gas exchange between land biota and the atmosphere. In this paper we present a review of important non-CO2 trace gas emissions, the state-of-the-art in DGVM modelling of processes regulating these emissions, identify key uncertainties for global scale model applications, and discuss a methodology for model integration and evaluation.

Dissolved atmospheric gas in xylem sap measured with membrane inlet mass spectrometry.

PubMed

Schenk, H Jochen; Espino, Susana; Visser, Ate; Esser, Bradley K

2016-04-01

A new method is described for measuring dissolved gas concentrations in small volumes of xylem sap using membrane inlet mass spectrometry. The technique can be used to determine concentrations of atmospheric gases, such as argon, as reported here, or for any dissolved gases and their isotopes for a variety of applications, such as rapid detection of trace gases from groundwater only hours after they were taken up by trees and rooting depth estimation. Atmospheric gas content in xylem sap directly affects the conditions and mechanisms that allow for gas removal from xylem embolisms, because gas can dissolve into saturated or supersaturated sap only under gas pressure that is above atmospheric pressure. The method was tested for red trumpet vine, Distictis buccinatoria (Bignoniaceae), by measuring atmospheric gas concentrations in sap collected at times of minimum and maximum daily temperature and during temperature increase and decline. Mean argon concentration in xylem sap did not differ significantly from saturation levels for the temperature and pressure conditions at any time of collection, but more than 40% of all samples were supersaturated, especially during the warm parts of day. There was no significant diurnal pattern, due to high variability between samples. © 2015 John Wiley & Sons Ltd.

Measurements of N2O and SF6 mole fraction between 1977 and 1998 in archived air samples from Cape Meares, Oregon

NASA Astrophysics Data System (ADS)

Rolfe, T.; Rice, A. L.; Radda, J.

2015-12-01

The quantification of greenhouse gas concentrations in the atmosphere is important for monitoring imbalances in their global budgets between sources and sinks and their changes in time. Nitrous oxide (N2O) is a strong radiative trace gas with a GWP of ~300 times CO2 over a 100 year period and an atmospheric lifetime of ~100 years. The preindustrial revolution background concentration of N2O was ~270 ppb. Today, the concentration is ~330 ppb. Sulfur hexafluoride (SF6) is another potent greenhouse gas with a long lifetime (800 to 3200 years) and very large GWP (~23000 times CO2 over a 100 year period). Its current atmospheric concentration is low (~8 ppt today). Direct measurements of N2O and SF6 in air prior to the mid-1990s are few. Over 200 archived atmospheric gas samples collected at Cape Meares, Oregon between 1977 and 1998 were analyzed for their N2O and SF6 concentrations using an Agilent (model 6890 N) gas chromatograph fitted with an electron capture detector using a two column "heart-cut" technique. Precision of measurement of N2O and SF6 is calculated at 0.13% (1σ) and 1.35% (1σ) respectively. N2O concentrations in the late 1970s and early 1980s average around 303 ppb, rising to 309 ppb in the early 1990s. Between 1980 and 1990, the increase in N2O concentrations is found to be ~0.5 ppb/yr. SF6 concentrations during the late 1970s and early 1980s average around 0.9 ppt and rise slowly, reaching 1.6 ppt in the 1990s. We find that the increase in SF6 between 1980 and 1990 to be ~0.07 ppt/yr. We also discuss sample integrity in storage and observed temporal trends of N2O and SF6.

Recuperated atmospheric SOFC/gas turbine hybrid cycle

DOEpatents

Lundberg, Wayne

2010-05-04

A method of operating an atmospheric-pressure solid oxide fuel cell generator (6) in combination with a gas turbine comprising a compressor (1) and expander (2) where an inlet oxidant (20) is passed through the compressor (1) and exits as a first stream (60) and a second stream (62) the first stream passing through a flow control valve (56) to control flow and then through a heat exchanger (54) followed by mixing with the second stream (62) where the mixed streams are passed through a combustor (8) and expander (2) and the first heat exchanger for temperature control before entry into the solid oxide fuel cell generator (6), which generator (6) is also supplied with fuel (40).

Recuperated atmosphere SOFC/gas turbine hybrid cycle

DOEpatents

Lundberg, Wayne

2010-08-24

A method of operating an atmospheric-pressure solid oxide fuel cell generator (6) in combination with a gas turbine comprising a compressor (1) and expander (2) where an inlet oxidant (20) is passed through the compressor (1) and exits as a first stream (60) and a second stream (62) the first stream passing through a flow control valve (56) to control flow and then through a heat exchanger (54) followed by mixing with the second stream (62) where the mixed streams are passed through a combustor (8) and expander (2) and the first heat exchanger for temperature control before entry into the solid oxide fuel cell generator (6), which generator (6) is also supplied with fuel (40).

Rich soil carbon and nitrogen but low atmospheric greenhouse gas fluxes from North Sulawesi mangrove swamps in Indonesia.

PubMed

Chen, Guang C; Ulumuddin, Yaya I; Pramudji, Sastro; Chen, Shun Y; Chen, Bin; Ye, Yong; Ou, Dan Y; Ma, Zhi Y; Huang, Hao; Wang, Jing K

2014-07-15

The soil to atmosphere fluxes of greenhouse gases N2O, CH4 and CO2 and their relationships with soil characteristics were investigated in three tropical oceanic mangrove swamps (Teremaal, Likupang and Kema) in North Sulawesi, Indonesia. Mangrove soils in North Sulawesi were rich in organic carbon and nitrogen, but the greenhouse gas fluxes were low in these mangroves. The fluxes ranged -6.05-13.14 μmol m(-2)h(-1), -0.35-0.61 μmol m(-2)h(-1) and -1.34-3.88 mmol m(-2)h(-1) for N2O, CH4 and CO2, respectively. The differences in both N2O and CH4 fluxes among different mangrove swamps and among tidal positions in each mangrove swamp were insignificant. CO2 flux was influenced only by mangrove swamps and the value was higher in Kema mangrove. None of the measured soil parameters could explain the variation of CH4 fluxes among the sampling plots. N2O flux was negatively related to porewater salinity, while CO2 flux was negatively correlated with water content and organic carbon. This study suggested that the low gas emissions due to slow metabolisms would lead to the accumulations of organic matters in North Sulawesi mangrove swamps. Copyright © 2014 Elsevier B.V. All rights reserved.

An approach for verifying biogenic greenhouse gas emissions inventories with atmospheric CO2 concentration data

Treesearch

Stephen M Ogle; Kenneth Davis; Thomas Lauvaux; Andrew Schuh; Dan Cooley; Tristram O West; Linda S Heath; Natasha L Miles; Scott Richardson; F Jay Breidt; James E Smith; Jessica L McCarty; Kevin R Gurney; Pieter Tans; A Scott Denning

2015-01-01

Verifying national greenhouse gas (GHG) emissions inventories is a critical step to ensure that reported emissions data to the United Nations Framework Convention on Climate Change (UNFCCC) are accurate and representative of a country's contribution to GHG concentrations in the atmosphere. Furthermore, verifying biogenic fluxes provides a check on estimated...

N2O, NO, N2 and CO2 emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores

NASA Astrophysics Data System (ADS)

Werner, C.; Reiser, K.; Dannenmann, M.; Hutley, L. B.; Jacobeit, J.; Butterbach-Bahl, K.

2014-11-01

Strong seasonal variability of hygric and thermal soil conditions are a defining environmental feature in northern Australia. However, how such changes affect the soil-atmosphere exchange of nitrous oxide (N2O), nitric oxide (NO) and dinitrogen (N2) is still not well explored. By incubating intact soil cores from four sites (three savanna, one pasture) under controlled soil temperatures (ST) and soil moisture (SM) we investigated the release of the trace gas fluxes of N2O, NO and carbon dioxide (CO2). Furthermore, the release of N2 due to denitrification was measured using the helium gas flow soil core technique. Under dry pre-incubation conditions NO and N2O emissions were very low (<7.0 ± 5.0 μg NO-N m-2 h-1; <0.0 ± 1.4 μg N2O-N m-2 h-1) or in the case of N2O, even a net soil uptake was observed. Substantial NO (max: 306.5 μg N m-2 h-1) and relatively small N2O pulse emissions (max: 5.8 ± 5.0 μg N m-2 h-1) were recorded following soil wetting, but these pulses were short lived, lasting only up to 3 days. The total atmospheric loss of nitrogen was generally dominated by N2 emissions (82.4-99.3% of total N lost), although NO emissions contributed almost 43.2% to the total atmospheric nitrogen loss at 50% SM and 30 °C ST incubation settings (the contribution of N2 at these soil conditions was only 53.2%). N2O emissions were systematically higher for 3 of 12 sample locations, which indicates substantial spatial variability at site level, but on average soils acted as weak N2O sources or even sinks. By using a conservative upscale approach we estimate total annual emissions from savanna soils to average 0.12 kg N ha-1 yr-1 (N2O), 0.68 kg N ha-1 yr-1 (NO) and 6.65 kg N ha-1 yr-1 (N2). The analysis of long-term SM and ST records makes it clear that extreme soil saturation that can lead to high N2O and N2 emissions only occurs a few days per year and thus has little impact on the annual total. The potential contribution of nitrogen released due to pulse events

Broadening of spectral lines of CO2, N2O , H2CO, HCN, and H2S by pressure of gases dominant in planetary atmospheres (H2, He and CO2)

NASA Astrophysics Data System (ADS)

Samuels, Shanelle; Gordon, Iouli; Tan, Yan

2018-01-01

HITRAN1,2 is a compilation of spectroscopic parameters that a variety of computer codes use to predict and simulate the transmission and emission of light in planetary atmospheres. The goal of this project is to add to the potential of the HITRAN database towards the exploration of the planetary atmospheres by including parameters describing broadening of spectral lines by H2, CO2, and He. These spectroscopic data are very important for the study of the hydrogen and helium-rich atmospheres of gas giants as well as rocky planets with volcanic activities, including Venus and Mars, since their atmospheres are dominated by CO2. First step in this direction was accomplished by Wilzewski et al.3 where this was done for SO2, NH3, HF, HCl, OCS and C2H2. The molecules investigated in this work were CO2, N2O, H2CO, HCN and H2S. Line-broadening coefficients, line shifts and temperature-dependence exponents for transitions of these molecules perturbed by H2, CO2 and He have been assembled from available peer-reviewed experimental and theoretical sources. The data was evaluated and the database was populated with these data and their extrapolations/interpolations using semi-empirical models that were developed to this end.Acknowledgements: Financial support from NASA PDART grant NNX16AG51G and the Smithsonian Astrophysical Observatory Latino Initiative Program from the Latino Initiatives Pool, administered by the Smithsonian Latino Center is gratefully acknowledged.References: 1. HITRAN online http://hitran.org/2. Gordon, I.E., Rothman, L.S., Hill, C., Kochanov, R.V., Tan, Y., et al., 2017. The HITRAN2016 Molecular Spectroscopic Database. J. Quant. Spectrosc. Radiat. Transf. doi:10.1016/j.jqsrt.2017.06.0383. Wilzewski, J.S., Gordon, I.E., Kochanov, R. V., Hill, C., Rothman, L.S., 2016. H2, He, and CO2 line-broadening coefficients, pressure shifts and temperature-dependence exponents for the HITRAN database. Part 1: SO2, NH3, HF, HCl, OCS and C2H2. J. Quant. Spectrosc. Radiat

Thermal decomposition of sewage sludge under N2, CO2 and air: Gas characterization and kinetic analysis.

PubMed

Hernández, Ana Belén; Okonta, Felix; Freeman, Ntuli

2017-07-01

Thermochemical valorisation processes that allow energy to be recovered from sewage sludge, such as pyrolysis and gasification, have demonstrated great potential as convenient alternatives to conventional sewage sludge disposal technologies. Moreover, these processes may benefit from CO 2 recycling. Today, the scaling up of these technologies requires an advanced knowledge of the reactivity of sewage sludge and the characteristics of the products, specific to the thermochemical process. In this study the behaviour of sewage sludge during thermochemical conversion, under different atmospheres (N 2 , CO 2 and air), was studied, using TGA-FTIR, in order to understand the effects of different atmospheric gases on the kinetics of degradation and on the gaseous products. The different steps observed during the solid degradation were related with the production of different gaseous compounds. A higher oxidative degree of the atmosphere surrounding the sample resulted in higher reaction rates and a shift of the degradation mechanisms to lower temperatures, especially for the mechanisms taking place at temperatures above 400 °C. Finally, a multiple first-order reaction model was proposed to compare the kinetic parameters obtained under different atmospheres. Overall, the highest activation energies were obtained for combustion. This work proves that CO 2 , an intermediate oxidative atmosphere between N 2 and air, results in an intermediate behaviour (intermediate peaks in the derivative thermogravimetric curves and intermediate activation energies) during the thermochemical decomposition of sewage sludge. Overall, it can be concluded that the kinetics of these different processes require a different approach for their scaling up and specific consideration of their characteristic reaction temperatures and rates should be evaluated. Copyright © 2017 Elsevier Ltd. All rights reserved.

Study of DC Circuit Breaker of H2-N2 Mixture Gas for High Voltage

NASA Astrophysics Data System (ADS)

Shiba, Yuji; Morishita, Yukinaga; Kaneko, Shuhei; Okabe, Shigemitsu; Mizoguchi, Hitoshi; Yanabu, Satoru

Global warming caused by CO2 etc. is a field where the concern is very high. Especially, automobile emissions are problem for it. Therefore, the hybrid car is widely development and used recently. Hybrid car used electric power and gasoline. So, the car reduces CO2. Hybrid car has engine and motor. To rotate the motor, hybrid car has battery. This battery is large capacity. Therefore, the relay should interrupt high DC current for the switch of the motor and the engine. So, hybrid car used hydrogen gas filling relay We studied interruption test for the research of a basic characteristic of hydrogen gas. DC current has not current zero point. So, it is necessary to make the current zero by high arc voltage and forcible current zero point. The loss coefficient and arc voltage of hydrogen is high. Therefore, we studied interruption test for used high arc voltage. We studied interruption test and dielectric breakdown test of air, pure Hydrogen, and Hydrogen- nitrogen mixture gas. As a result, we realized H2-N2(80%-20%) is the best gas.

Gas chromatographic concepts for the analysis of planetary atmospheres

NASA Technical Reports Server (NTRS)

Valentin, J. R.; Cullers, D. K.; Hall, K. W.; Krekorian, R. L.; Phillips, J. B.

1991-01-01

Over the last few years, new gas chromatographic (GC) concepts were developed for use on board spacecraft or any other restricted environments for determining the chemical composition of the atmosphere and surface material of various planetary bodies. Future NASA Missions include an entry probe that will be sent to Titan and various spacecraft that will land on Mars. In order to be able to properly respond to the mission science requirements and physical restrictions imposed on the instruments by these missions, GC analytical techniques are being developed. Some of these techniques include hardware and mathematical techniques that will improve GC sensitivity and increase the sampling rate of a GC descending through a planetary atmosphere. The technique of Multiplex Gas Chromatography (MGC) is an example of a technique that was studied in a simulated Titan atmosphere. In such an environment, the atmospheric pressure at instrument deployment is estimated to be a few torr. Thus, at such pressures, the small amount of sample that is acquired might not be enough to satisfy the detection requirements of the gas chromatograph. In MGC, many samples are pseudo-randomly introduced to the chromatograph without regard to elution of preceding components. The resulting data is then reduced using mathematical techniques such as cross-correlation of Fourier Transforms. Advantages realized from this technique include: improvement in detection limits of several orders of magnitude and increase in the number of analyses that can be conducted in a given period of time. Results proving the application of MGC at very low pressures emulating the same atmospheric pressures that a Titan Probe will encounter when the instruments are deployed are presented. The sample used contained hydrocarbons that are expected to be found in Titan's atmosphere. In addition, a new selective modulator was developed to monitor water under Martian atmospheric conditions. Since this modulator is selective only

Modelling of N2 Vegard-Kaplan and LBH emissions in the planetary atmospheres

NASA Astrophysics Data System (ADS)

Jain, Sonal Kumar; Bhardwaj, Anil

The N_{2} triplet band emissions are common features in the dayglow of Earth. Recent discoveries of N _{2} Vegard-Kaplan (VK) band emissions on Mars by SPICAM/Mars-Express and N _{2} VK and LBH band emissions on Titan by Cassini's UVIS have led planetary scientists to look for the processes governing the N _{2} triplet and singlet band emissions in different planetary atmospheres. We have developed a model to calculate N _{2} triplet and Lyman-Birge-Hopefield (LBH) band emissions in the dayglow of Venus, Mars, Titan, and Pluto. The Steady state photoelectron fluxes and volume excitation rates have been calculated using the Analytical Yield Spectra (AYS) technique. Since interstate cascading is important for triplet and singlet states of N _{2}, the population of any given level of N _{2} triplet and singlet states is calculated under statistical equilibrium considering direct excitation, cascading, and quenching effects. Relative population of all vibrational levels of each triplet and singlet states is calculated in the model. Line of sight intensities and height-integrated overhead intensities have been calculated for VK ( A(3Sigma_u^+) - X(1Sigma^+_g) ), first positive ( B(3Pi_g) - A(3Sigma^+_u) ), second positive ( C(3Pi_u) - B(3Pi_g) ), Wu-Benesch (W(3Delta_u) - B(3Pi_g) ), B '-> B, E -> B, E-> C, E-> A, and LBH (a(1Pi_g) - X(1Sigma^+_g) ) bands of N _{2}. The N _{2} VK band span wavelength range from far ultraviolet to visible, and some transitions even originate at wavelength more than 1000 nm. Our calculations show that the overhead intensity of VK bands in the wavelength range 400-800, 300-190, 200-300, and 150-200 nm are 22%, 39%, 35%, and 4% of the total VK band emission. On Titan, the calculated intensities of N _{2} VK and LBH bands in 150-190 and 120-190 nm wavelength range, respectively, are in good agreement with the Cassini-UVIS observation. On Mars, calculated intensities of N _{2} VK bands are in agreement with the SPICAM observed limb profile of

Catalytic and atmospheric effects on microwave pyrolysis of corn stover.

PubMed

Huang, Yu-Fong; Kuan, Wen-Hui; Chang, Chi-Cheng; Tzou, Yu-Min

2013-03-01

Corn stover, which is one of the most abundant agricultural residues around the world, could be converted into valuable biofuels and bio based products by means of microwave pyrolysis. After the reaction at the microwave power level of 500W for the processing time of 30min, the reaction performance under N2 atmosphere was generally better than under CO2 atmosphere. This may be due to the better heat absorbability of CO2 molecules to reduce the heat for stover pyrolysis. Most of the metal-oxide catalysts effectively increased the maximum temperature and mass reduction ratio but lowered the calorific values of solid residues. The gas most produced was CO under N2 atmosphere but CO2 under CO2 atmosphere. Catalyst addition lowered the formation of PAHs and thus made liquid products less toxic. More liquid products and less gas products were generated when using the catalysts possibly due to the existence of the Fischer-Tropsch synthesis. Copyright © 2013 Elsevier Ltd. All rights reserved.

Role of Exposure Atmospheres on Particle Coarsening and Phase Transformation of LiAlO 2

DOE PAGES

Heo, Su Jeong; Hu, Boxun; Uddin, Md Aman; ...

2017-05-05

The phase transformation and particle coarsening of lithium aluminate (α-LiAlO 2) in electrolyte are the major causes of degradation affecting the performance and the lifetime of the molten carbonate fuel cell (MCFC). The stability of LiAlO 2 has been studied in Li 2CO 3-Na 2CO 3 electrolyte under accelerated conditions in reducing and oxidizing gas atmospheres at temperatures of 650 and 750 for up to 500 hours. X-ray diffraction analyses show that the progressive transformation of α-LiAlO 2 to γ-LiAlO 2 phase proceeds with increasing temperature in lower P CO2 and lower P O2 environments. Spherical LiAlO 2 particles weremore » transformed to coarsened pyramid-shape particles in 4% H 2-3% H 2O-N 2 and 100% N 2 (~10 ppm P O2 ) atmospheres. Under CO 2-rich atmospheres (4% H 2-30% CO 2-N 2 and 70% air-30% CO 2), both phase and particle size remained unchanged at 650 and 750ºC. The selected area electron diffraction (SAED) pattern analysis indicated that the large pyramidal shape particles (~30 μm) were γ-LiAlO 2 phase. Experimental observations and related simulation results pertaining to particle coarsening and phase transformation behavior of LiAlO 2 are presented.« less

The quenching effect of hydrogen on the nitrogen in metastable state in atmospheric-pressure N{sub 2}-H{sub 2} microwave plasma torch

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

Li, Shou-Zhe, E-mail: lisz@dlut.edu.cn; Zhang, Xin; Chen, Chuan-Jie

2014-07-15

The atmospheric-pressure microwave N{sub 2}-H{sub 2} plasma torch is generated and diagnosed by optical emission spectroscopy. It is found that a large amount of N atoms and NH radicals are generated in the plasma torch and the emission intensity of N{sub 2}{sup +} first negative band is the strongest over the spectra. The mixture of hydrogen in nitrogen plasma torch causes the morphology of the plasma discharge to change with appearance that the afterglow shrinks greatly and the emission intensity of N{sub 2}{sup +} first negative band decreases with more hydrogen mixed into nitrogen plasma. In atmospheric-pressure microwave-induced plasma torch,more » the hydrogen imposes a great influence on the characteristics of nitrogen plasma through the quenching effect of the hydrogen on the metastable state of N{sub 2}.« less

Gas Diffusion Barriers Prepared by Spatial Atmospheric Pressure Plasma Enhanced ALD.

PubMed

Hoffmann, Lukas; Theirich, Detlef; Pack, Sven; Kocak, Firat; Schlamm, Daniel; Hasselmann, Tim; Fahl, Henry; Räupke, André; Gargouri, Hassan; Riedl, Thomas

2017-02-01

In this work, we report on aluminum oxide (Al 2 O 3 ) gas permeation barriers prepared by spatial ALD (SALD) at atmospheric pressure. We compare the growth characteristics and layer properties using trimethylaluminum (TMA) in combination with an Ar/O 2 remote atmospheric pressure plasma for different substrate velocities and different temperatures. The resulting Al 2 O 3 films show ultralow water vapor transmission rates (WVTR) on the order of 10 -6 gm -2 d -1 . In notable contrast, plasma based layers already show good barrier properties at low deposition temperatures (75 °C), while water based processes require a growth temperature above 100 °C to achieve equally low WVTRs. The activation energy for the water permeation mechanism was determined to be 62 kJ/mol.

Formation of nitrogenated organic aerosols in the Titan upper atmosphere.

PubMed

Imanaka, Hiroshi; Smith, Mark A

2010-07-13

Many aspects of the nitrogen fixation process by photochemistry in the Titan atmosphere are not fully understood. The recent Cassini mission revealed organic aerosol formation in the upper atmosphere of Titan. It is not clear, however, how much and by what mechanism nitrogen is incorporated in Titan's organic aerosols. Using tunable synchrotron radiation at the Advanced Light Source, we demonstrate the first evidence of nitrogenated organic aerosol production by extreme ultraviolet-vacuum ultraviolet irradiation of a N(2)/CH(4) gas mixture. The ultrahigh-mass-resolution study with laser desorption ionization-Fourier transform-ion cyclotron resonance mass spectrometry of N(2)/CH(4) photolytic solid products at 60 and 82.5 nm indicates the predominance of highly nitrogenated compounds. The distinct nitrogen incorporations at the elemental abundances of H(2)C(2)N and HCN, respectively, are suggestive of important roles of H(2)C(2)N/HCCN and HCN/CN in their formation. The efficient formation of unsaturated hydrocarbons is observed in the gas phase without abundant nitrogenated neutrals at 60 nm, and this is confirmed by separately using (13)C and (15)N isotopically labeled initial gas mixtures. These observations strongly suggest a heterogeneous incorporation mechanism via short lived nitrogenated reactive species, such as HCCN radical, for nitrogenated organic aerosol formation, and imply that substantial amounts of nitrogen is fixed as organic macromolecular aerosols in Titan's atmosphere.

Carbon Disulfide (CS2) Mechanisms in Formation of Atmospheric Carbon Dioxide (CO2) Formation from Unconventional Shale Gas Extraction and Processing Operations and Global Climate Change.

PubMed

Rich, Alisa L; Patel, Jay T

2015-01-01

Carbon disulfide (CS2) has been historically associated with the production of rayon, cellophane, and carbon tetrachloride. This study identifies multiple mechanisms by which CS2 contributes to the formation of CO2 in the atmosphere. CS2 and other associated sulfide compounds were found by this study to be present in emissions from unconventional shale gas extraction and processing (E&P) operations. The breakdown products of CS2; carbonyl sulfide (COS), carbon monoxide (CO), and sulfur dioxide (SO2) are indirect greenhouse gases (GHGs) that contribute to CO2 levels in the atmosphere. The heat-trapping nature of CO2 has been found to increase the surface temperature, resulting in regional and global climate change. The purpose of this study is to identify five mechanisms by which CS2 and the breakdown products of CS2 contribute to atmospheric concentrations of CO2. The five mechanisms of CO2 formation are as follows: Chemical Interaction of CS2 and hydrogen sulfide (H2S) present in natural gas at high temperatures, resulting in CO2 formation;Combustion of CS2 in the presence of oxygen producing SO2 and CO2;Photolysis of CS2 leading to the formation of COS, CO, and SO2, which are indirect contributors to CO2 formation;One-step hydrolysis of CS2, producing reactive intermediates and ultimately forming H2S and CO2;Two-step hydrolysis of CS2 forming the reactive COS intermediate that reacts with an additional water molecule, ultimately forming H2S and CO2. CS2 and COS additionally are implicated in the formation of SO2 in the stratosphere and/or troposphere. SO2 is an indirect contributor to CO2 formation and is implicated in global climate change.

Compound Specific Concentration and Stable Isotope Ratio Measurements of Atmospheric Particulate Organic Matter and Gas Phase Nitrophenols

NASA Astrophysics Data System (ADS)

Busca, R.; Saccon, M.; Moukhtar, S.; Rudolph, J.

2009-05-01

Atmospheric particulate organic matter (POM) adversely affects health and climate. One of the still poorly understood sources of secondary organic matter (SOM) is the formation of secondary POM from the photo- oxidation of atmospheric volatile organic compounds (VOC). Nitrophenols, which are toxic semi-volatile compounds, are formed in the atmosphere by OH-radical initiated photo-oxidation of aromatic hydrocarbons, such as toluene. A method was developed to determine concentrations and stable carbon isotope ratios of particulate methyl nitrophenols in the atmosphere. This method has been used to quantify methyl nitrophenols, specifically 2-methyl-4-nitrophenol and 4-methyl-2-nitrophenol, found in atmospheric PM samples in trace quantities. Using this method, we conducted measurements of methyl nitrophenols in atmospheric PM in rural and suburban areas in Southern Ontario. The results of these measurements showed that the concentration of methyl nitrophenols in atmospheric PM is much lower than expected from the extrapolation of laboratory experiments and measured atmospheric toluene concentrations. In order to better understand the reasons for these findings, an analytical method for the analysis of nitrophenols in the gas phase is currently being developed. Similarly, the measurement technique is modified to allow analysis of other phenolic products of the oxidation of aromatic hydrocarbons in PM as well as in the gas phase. In this poster, sampling techniques for collection and GC-MS analysis of nitrophenols in gas phase and PM will be presented along with preliminary results from summer 2008 and spring 2009 studies.

Diagnostic of N2(A) concentration in high velocity nitrogen afterglow at atmospheric pressure

NASA Astrophysics Data System (ADS)

Pointu, Anne-Marie; Mintusov, Evgeny

2009-10-01

An optical emission diagnostic was used to measure N2(A) concentration in a high velocity (1000 cm/s) N2 flowing afterglow of corona discharge at atmospheric pressure, used for biological decontamination. Introducing impurities of NO (<1e-5) we used two well separated and relatively intense lines of NO gamma and beta bands (248nm and 321 nm), easily studied with a low resolution spectrometer. Based on a simplified transport kinetics, the technique is validated using a variation of lines intensity ratios used as coordinates, for numerous experimental points, measured at different axial distances and for different values of NO injected flow. Moreover, it has been demonstrated that N2(A) creation comes from N+N+N2 atom recombination with a global rate around 2e-33 cm^6/s, a result which agrees with literature, as well as N2(A) loss mechanisms were confirmed to go via quenching with O and N atoms. The order of magnitude of obtained N2(A) concentration, about 1e11 cm-3, coincides with the results of direct measurement (by Vegard-Kaplan band), using a spectrometer of better resolution.

Estimating lake-atmosphere CO2 exchange

USGS Publications Warehouse

Anderson, D.E.; Striegl, Robert G.; Stannard, D.I.; Michmerhuizen, C.M.; McConnaughey, T.A.; LaBaugh, J.W.

1999-01-01

Lake-atmosphere CO2 flux was directly measured above a small, woodland lake using the eddy covariance technique and compared with fluxes deduced from changes in measured lake-water CO2 storage and with flux predictions from boundary-layer and surface-renewal models. Over a 3-yr period, lake-atmosphere exchanges of CO2 were measured over 5 weeks in spring, summer, and fall. Observed springtime CO2 efflux was large (2.3-2.7 ??mol m-2 s-1) immediately after lake-thaw. That efflux decreased exponentially with time to less than 0.2 ??mol m-2 s-1 within 2 weeks. Substantial interannual variability was found in the magnitudes of springtime efflux, surface water CO2 concentrations, lake CO2 storage, and meteorological conditions. Summertime measurements show a weak diurnal trend with a small average downward flux (-0.17 ??mol m-2 s-1) to the lake's surface, while late fall flux was trendless and smaller (-0.0021 ??mol m-2 s-1). Large springtime efflux afforded an opportunity to make direct measurement of lake-atmosphere fluxes well above the detection limits of eddy covariance instruments, facilitating the testing of different gas flux methodologies and air-water gas-transfer models. Although there was an overall agreement in fluxes determined by eddy covariance and those calculated from lake-water storage change in CO2, agreement was inconsistent between eddy covariance flux measurements and fluxes predicted by boundary-layer and surface-renewal models. Comparison of measured and modeled transfer velocities for CO2, along with measured and modeled cumulative CO2 flux, indicates that in most instances the surface-renewal model underpredicts actual flux. Greater underestimates were found with comparisons involving homogeneous boundary-layer models. No physical mechanism responsible for the inconsistencies was identified by analyzing coincidentally measured environmental variables.

Titan Atmospheric Entry Radiative Heating

NASA Technical Reports Server (NTRS)

Brandis, A. M; Cruden, B. A.

2017-01-01

Detailed spectrally and spatially resolved radiance has been measured in the Electric Arc Shock Tube for conditions relevant to Titan entry, varying atmospheric composition, free-stream density (equivalent to altitude) and shock velocity. Permutations in atmospheric composition include 1.1, 2, 5 and 8.6 CH4 by mole with a balance of N2 and 1.5 CH4 0.5 Ar 98 N2 by mole, which is consistent with the current understanding of Titan's atmosphere. The effect of gas impurities identified in previous shock tube studies were also examined by testing in pure N2 and deliberate addition of air to the CH4N2 mixtures. The test campaign measured radiation at velocities from 4.7 kms to 8 kms and free-stream pressures from 0.1 to 0.47 Torr. These conditions cover a range of potential trajectories for flight missions, including a direct ballistic trajectory, a fly by or an extremely high speed entry. Radiances measured in this work are substantially larger compared to that reported both in past EAST test campaigns and other shock tube facilities. Depending on the metric used for comparison, the discrepancy can be as high as an order of magnitude. Potential causes for the discrepancy, such as the effect of oxygen due to Air leakage, gas composition and purity are discussed. The present work provides a new benchmark set of data to replace those published in previous studies.

The Contamination of Commercial 15N2 Gas Stocks with 15N–Labeled Nitrate and Ammonium and Consequences for Nitrogen Fixation Measurements

PubMed Central

Dabundo, Richard; Lehmann, Moritz F.; Treibergs, Lija; Tobias, Craig R.; Altabet, Mark A.; Moisander, Pia H.; Granger, Julie

2014-01-01

We report on the contamination of commercial 15-nitrogen (15N) N2 gas stocks with 15N-enriched ammonium, nitrate and/or nitrite, and nitrous oxide. 15N2 gas is used to estimate N2 fixation rates from incubations of environmental samples by monitoring the incorporation of isotopically labeled 15N2 into organic matter. However, the microbial assimilation of bioavailable 15N-labeled N2 gas contaminants, nitrate, nitrite, and ammonium, is liable to lead to the inflation or false detection of N2 fixation rates. 15N2 gas procured from three major suppliers was analyzed for the presence of these 15N-contaminants. Substantial concentrations of 15N-contaminants were detected in four Sigma-Aldrich 15N2 lecture bottles from two discrete batch syntheses. Per mole of 15N2 gas, 34 to 1900 µmoles of 15N-ammonium, 1.8 to 420 µmoles of 15N-nitrate/nitrite, and ≥21 µmoles of 15N-nitrous oxide were detected. One 15N2 lecture bottle from Campro Scientific contained ≥11 µmoles of 15N-nitrous oxide per mole of 15N2 gas, and no detected 15N-nitrate/nitrite at the given experimental 15N2 tracer dilutions. Two Cambridge Isotopes lecture bottles from discrete batch syntheses contained ≥0.81 µmoles 15N-nitrous oxide per mole 15N2, and trace concentrations of 15N-ammonium and 15N-nitrate/nitrite. 15N2 gas equilibrated cultures of the green algae Dunaliella tertiolecta confirmed that the 15N-contaminants are assimilable. A finite-differencing model parameterized using oceanic field conditions typical of N2 fixation assays suggests that the degree of detected 15N-ammonium contamination could yield inferred N2 fixation rates ranging from undetectable, <0.01 nmoles N L−1 d−1, to 530 nmoles N L−1 d−1, contingent on experimental conditions. These rates are comparable to, or greater than, N2 fixation rates commonly detected in field assays. These results indicate that past reports of N2 fixation should be interpreted with caution, and demonstrate that the purity of commercial 15N2

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.

Atmospheric aerosol and gas sensing using Scheimpflug lidar

NASA Astrophysics Data System (ADS)

Mei, Liang; Brydegaard, Mikkel

2015-04-01

This work presents a new lidar technique for atmospheric remote sensing based on Scheimpflug principle, which describes the relationship between nonparallel image- and object-planes[1]. When a laser beam is transmitted into the atmosphere, the implication is that the backscattering echo of the entire illuminated probe volume can be in focus simultaneously without diminishing the aperture. The range-resolved backscattering echo can be retrieved by using a tilted line scan or two-dimensional CCD/CMOS camera. Rather than employing nanosecond-pulsed lasers, cascade detectors, and MHz signal sampling, all of high cost and complexity, we have developed a robust and inexpensive atmospheric lidar system based on compact laser diodes and array detectors. We present initial applications of the Scheimpflug lidar for atmospheric aerosol monitoring in bright sunlight, with a 3 W, 808 nm CW laser diode. Kilohertz sampling rates are also achieved with applications for wind speed and entomology [2]. Further, a proof-of-principle demonstration of differential absorption lidar (DIAL) based on the Scheimpflug lidar technique is presented [3]. By utilizing a 30 mW narrow band CW laser diode emitting at around 760 nm, the detailed shape of an oxygen absorption line can be resolved remotely with an integration time of 6 s and measurement cycle of 1 minute during night time. The promising results demonstrated in this work show potential for the Scheimpflug lidar technique for remote atmospheric aerosol and gas sensing, and renews hope for robust and realistic instrumentation for atmospheric lidar sensing. [1] F. Blais, "Review of 20 years of range sensor development," Journal of Electronic Imaging, vol. 13, pp. 231-243, Jan 2004. [2] M. Brydegaard, A. Gebru, and S. Svanberg, "Super resolution laser radar with blinking atmospheric particles - application to interacting flying insects " Progress In Electromagnetics Research, vol. 147, pp. 141-151, 2014. [3] L. Mei and M. Brydegaard

Flux to the atmosphere of CH4 and CO2 from wetland ponds on the Hudson Bay lowlands (HBLs)

NASA Technical Reports Server (NTRS)

Hamilton, J. David; Kelly, Carol A.; Rudd, John W. M.; Hesslein, Raymond H.; Roulet, Nigel T.

1994-01-01

Ponds on peatlands of the Hudson Bay lowlands (HBLs) are complex ecosystems in which the fluxes to the atmosphere of CH4 and CO2 were controlled by interacting physical and biological factors. This resulted in strong diel variations of both dissolved gas concentrations and gas fluxes to the atmosphere, necessitating frequent sampling on a 24-hour schedule to enable accurate estimates of daily fluxes. Ponds at three sites on the HBL were constant net sources of CH4 and CO2 to the atmosphere at mean rates of 110-180 mg CH4 m(exp -2)/d and 3700-11,000 mg CO2 m(exp -2)/d. Rates peaked in August and September. For CH4 the pond fluxes were 3-30 times higher than adjacent vegetated surfaces. For CO2 the net pond fluxes were similar in magnitude to the vegetated fluxes but the direction of the flux was opposite, toward atmosphere. Even though ponds cover only 8-12% of the HBL area, they accounted for 30% of its total CH4 flux to the atmosphere. There is some circumstantial evidence that the ponds are being formed by decomposition of the underlying peat and that this decomposition is being stimulated by the activity of N2 fixing cyanobacteria that grow in mats at the peat-water interface. The fact that the gas fluxes from the ponds were so different from the surrounding vegetated surfaces means that any change in the ratio of pond to vegetated area, as may occur in response to climate change, would affect the total HBL fluxes.

Analysis of reaction products formed in the gas phase reaction of E,E-2,4-hexadienal with atmospheric oxidants: Reaction mechanisms and atmospheric implications

NASA Astrophysics Data System (ADS)

Colmenar, I.; Martin, P.; Cabañas, B.; Salgado, S.; Martinez, E.

2018-03-01

An analysis of reaction products for the reaction of E,E-2,4-hexadienal with chlorine atoms (Cl) and OH and NO3 radicals has been carried out at the first time with the aim of obtaining a better understanding of the tropospheric reactivity of α,β-unsaturated carbonyl compounds. Fourier Transform Infrared (FTIR) spectroscopy and Gas Chromatography-Mass Spectrometry with a Time of Flight detector (GC-TOFMS) were used to carry out the qualitative and/or quantitative analyses. Reaction products in gas and particulate phase were observed from the reactions of E,E-2,4- hexadienal with all oxidants. E/Z-Butenedial and maleic anhydride were the main products identified in gas phase. E-butenedial calculated molar yield ranging from 4 to 10%. A significant amount of multifunctional compounds (chloro and hydroxy carbonyls) was identified. These compounds could be formed in particulate phase explaining the ∼90% of unaccounted carbon in gas phase. The reaction with Cl atoms in the presence of NOx with a long reaction time gave Peroxy Acetyl Nitrate (PAN) as an additional product, which is known for being an important specie in the generation of the photochemical smog. Nitrated compounds were the major organic products from the reaction with the NO3 radical. Based on the identified products, the reaction mechanisms have been proposed. In these mechanisms a double bond addition of the atmospheric oxidant at C4/C5 of E,E-2,4-hexadienal is the first step for tropospheric degradation.

Solar UV irradiation-induced production of N2O from plant surfaces - low emissions rates but all over the world.

NASA Astrophysics Data System (ADS)

Mikkelsen, T. N.; Bruhn, D.; Ambus, P.

2016-12-01

Nitrous oxide (N2O) is an important long-lived greenhouse gas and precursor of stratospheric ozone depleting mono-nitrogen oxides. The atmospheric concentration of N2O is persistently increasing; however, large uncertainties are associated with the distinct source strengths. Here we investigate for the first time N2O emission from terrestrial vegetation in response to natural solar ultra violet radiation. We conducted field site measurements to investigate N2O atmosphere exchange from grass vegetation exposed to solar irradiance with and without UV-screening. Further laboratory tests were conducted with a range of species to study the controls and possible loci of UV-induced N2O emission from plants. Plants released N2O in response to natural sunlight at rates of c. 20-50 nmol m-2 h-1, mostly due to the UV component. The emission rate is temperature dependent with a rather high activation energy indicative for an abiotic process. The prevailing zone for the N2O formation appears to be at the very surface of leaves. However, only c. 26% of the UV-induced N2O appears to originate from plant-N. Further, the process is dependent on atmospheric oxygen concentration. Our work demonstrates that ecosystem emission of the important greenhouse gas, N2O, may be up to c. 30% higher than hitherto assumed.

Assessing Greenhouse Gas emissions in the Greater Toronto Area using atmospheric observations (Invited)

NASA Astrophysics Data System (ADS)

Vogel, F. R.; Chan, E.; Huang, L.; Levin, I.; Worthy, D.

2013-12-01

Urban areas are said to be responsible for approximately 75% of anthropogenic Greenhouse Gases (GHGs) emissions while comprising only two percent of the land area [1]. This limited spatial expansion should facilitate a monitoring of anthropogenic GHGs from atmospheric observations. As major sources of emissions, cities also have a huge potential to drive emissions reductions. To effectively manage emissions, cities must however, first measure and report these publicly [2]. Modelling studies and measurements of CO2 from fossil fuel burning (FFCO2) in densely populated areas does, however, pose several challenges: Besides continuous in-situ observations, i.e. finding an adequate atmospheric transport model, a sufficiently fine-grained FFCO2 emission model and the proper background reference observations to distinguish the large-scale from the local/urban contributions to the observed FFCO2 concentration offsets ( ΔFFCO2) are required. Pilot studies which include the data from two 'sister sites*' in the vicinity of Toronto, Canada helped to derive flux estimates for Non-CO2 GHGs [3] and improve our understanding of urban FFCO2 emissions. Our 13CO2 observations reveal that the contribution of natural gas burning (mostly due to domestic heating) account for 80%×7% of FFCO2 emissions in the Greater Toronto Area (GTA) during winter. Our 14CO2 observations in the GTA, furthermore, show that the local offset of CO2 (ΔCO2) between our two sister sites can be largely attributed to urban FFCO2 emissions. The seasonal cycle of the observed ΔFFCO2 in Toronto, combined with high-resolution atmospheric modeling, helps to independently assess the contribution from different emission sectors (transportation, primary energy and industry, domestic heating) as predicted by a dedicated city-scale emission inventory, which deviates from a UNFCCC-based inventory. [1] D. Dodman. 2009. Blaming cities for climate change? An analysis of urban greenhouse gas emissions inventories

Ionization and current growth in N/sub 2/ at very high electric field to gas density ratios

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

Gylys, V.T.; Jelenkovic, B.M.; Phelps, A.V.

1989-05-01

Measurements and analyses have been made of electron impact ionization and of current growth in pulsed, low-current, prebreakdown discharges in parallel-plane geometry in N/sub 2/ at very high electric field to gas density ratios E/n and low products of the gas density n and electrode separation d. The E/n range and nd ranges were 1

A whiff of nebular gas in Titan's atmosphere - Potential implications for the conditions and timing of Titan's formation

NASA Astrophysics Data System (ADS)

Glein, Christopher R.

2017-09-01

In situ data from the GCMS instrument on the Huygens probe indicate that Titan's atmosphere contains small amounts of the primordial noble gases 36Ar and 22Ne (tentative detection), but it is unknown how they were obtained by the satellite. Based on the apparent similarity in the 22Ne/36Ar (atom) ratio between Titan's atmosphere and the solar composition, a previously neglected hypothesis for the origin of primordial noble gases in Titan's atmosphere is suggested - these species may have been acquired near the end of Titan's formation, when the moon could have gravitationally captured some nebular gas that would have been present in its formation environment (the Saturnian subnebula). These noble gases may be remnants of a primary atmosphere. This could be considered the simplest hypothesis to explain the 22Ne/36Ar ratio observed at Titan. However, the 22Ne/36Ar ratio may not be exactly solar if these species can be fractionated by external photoevaporation in the solar nebula, atmospheric escape from Titan, or sequestration on the surface of Titan. While the GCMS data are consistent with a 22Ne/36Ar ratio of 0.05 to 2.5 times solar (1σ range), simple estimates that attempt to account for some of the effects of these evolutionary processes suggest a sub-solar ratio, which may be depleted by approximately one order of magnitude. Models based on capture of nebular gas can explain why the GCMS did not detect any other primordial noble gas isotopes, as their predicted abundances are below the detection limits (especially for 84Kr and 132Xe). It is also predicted that atmospheric Xe on Titan should be dominated by radiogenic 129Xe if the source of primordial Xe is nebular gas. Of order 10-2-10-1 bar of primordial H2 may have been captured along with the noble gases from a gas-starved disk, but this H2 would have quickly escaped from the initial atmosphere. To have the opportunity to capture nebular gas, Titan should have formed within ∼10 Myr of the formation of the

Influence of Gas Atmosphere Dew Point on the Selective Oxidation and the Reactive Wetting During Hot Dip Galvanizing of CMnSi TRIP Steel

NASA Astrophysics Data System (ADS)

Cho, Lawrence; Lee, Seok Jae; Kim, Myung Soo; Kim, Young Ha; De Cooman, Bruno C.

2013-01-01

The selective oxidation and reactive wetting of intercritically annealed Si-bearing CMnSi transformation-induced plasticity steels were investigated by high-resolution transmission electron microscopy. In a N2 + 10 pct H2 gas atmosphere with a dew point (DP) ranging from 213 K to 278 K (-60 °C to 5 °C), a continuous layer of selective oxides was formed on the surface. Annealing in a higher DP gas atmosphere resulted in a thinner layer of external oxidation and a greater depth of internal oxidation. The hot dipping was carried out in a Zn bath containing 0.22 mass pct Al, and the bath temperature was 733 K (460 °C). Coarse and discontinuous Fe2Al5- x Zn x grains and Fe-Zn intermetallics (ζ and δ) were observed at the steel/coating interface after the hot dip galvanizing (HDG) of panels were annealed in a low DP atmosphere 213 K (-60 °C). The Fe-Zn intermetallics were formed both in areas where the Fe2Al5- x Zn x inhibition layer had not been formed and on top of non-stoichiometric Fe-Al-Zn crystals. Poor wetting was observed on panels annealed in a low DP atmosphere because of the formation of thick film-type oxides on the surface. After annealing in higher DP gas atmospheres, i.e., 263 K and 278 K (-10 °C and 5 °C), a continuous and fine-grained Fe2Al5- x Zn x layer was formed. No Fe-Zn intermetallics were formed. The small grain size of the inhibition layer was attributed to the nucleation of the Fe2Al5- x Zn x grains on small ferrite sub-surface grains and the presence of granular surface oxides. A high DP atmosphere can therefore significantly contribute to the decrease of Zn-coating defects on CMnSi TRIP steels processed in HDG lines.

Emissions of N2O, CH4 and CO2 from tropical forest soils

NASA Technical Reports Server (NTRS)

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

1986-01-01

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

Graphene Membranes for Atmospheric Pressure Photoelectron Spectroscopy.

PubMed

Weatherup, Robert S; Eren, Baran; Hao, Yibo; Bluhm, Hendrik; Salmeron, Miquel B

2016-05-05

Atmospheric pressure X-ray photoelectron spectroscopy (XPS) is demonstrated using single-layer graphene membranes as photoelectron-transparent barriers that sustain pressure differences in excess of 6 orders of magnitude. The graphene serves as a support for catalyst nanoparticles under atmospheric pressure reaction conditions (up to 1.5 bar), where XPS allows the oxidation state of Cu nanoparticles and gas phase species to be simultaneously probed. We thereby observe that the Cu(2+) oxidation state is stable in O2 (1 bar) but is spontaneously reduced under vacuum. We further demonstrate the detection of various gas-phase species (Ar, CO, CO2, N2, O2) in the pressure range 10-1500 mbar including species with low photoionization cross sections (He, H2). Pressure-dependent changes in the apparent binding energies of gas-phase species are observed, attributable to changes in work function of the metal-coated grids supporting the graphene. We expect atmospheric pressure XPS based on this graphene membrane approach to be a valuable tool for studying nanoparticle catalysis.

Atmosphere Behavior in Gas-Closed Mouse-Algal Systems: An Experimental and Modelling Study

NASA Technical Reports Server (NTRS)

Averner, M. M.; Moore, B., III; Bartholomew, I.; Wharton, R.

1985-01-01

A dual approach of mathematical modelling and laboratory experimentation aimed at examining the gas exchange characteristics of artificial animal/plant systems closed to the ambient atmosphere was initiated. The development of control techniques and management strategies for maintaining the atmospheric levels of carbon dioxide and oxygen at physiological levels is examined. A mathematical model simulating the atmospheric behavior in these systems was developed and an experimental gas closed system was constructed. These systems are described and preliminary results are presented.

Greenhouse gas emissions and N turnover along an altitudinal gradient at Mt. Kilimanjaro, Tanzania.

NASA Astrophysics Data System (ADS)

Gütlein, Adrian; Gerschlauer, Friederike; Zistl-Schlingmann, Marcus; Dannenmann, Michael; Meier, Rudolf; Kolar, Alison; Butterbach-Bahl, Klaus; Kiese, Ralf

2016-04-01

Worldwide climate and land-use change force alterations in various ecosystem properties and functions such as diversity and activity of soil microbial communities which are responsible for biogeochemical processes like soil nitrogen (N) turnover and associated greenhouse gas (GHG) exchange. Tropical deforestation is highest in Africa and despite the importance of those ecosystems to global climate and biogeochemical cycles, data for greenhouse gas exchange is still rare (Serca et al., 1994, Werner et al., 2007) and no study regarding N turnover processes has been published yet. For that reason, we focused on seven different land-use types extending along an altitudinal gradient (950 -- 3880m) at Mt. Kilimanjaro, East Africa, covering (semi-) natural savanna, two montane forests and one afro alpine ecosystem, an extensive agroforest (homegarden) and an intensively managed coffee plantation. On all ecosystems we measured CO_2, CH4 and N_2O fluxes and gross rates of ammonification, nitrification, N immobilization, and dissimilatory nitrate reduction to ammonium (DNRA). GHG results reveal pronounced N_2O fluxes depending mainly on soil moisture and to a lesser extent on soil temperature. Emissions are highest during the rainy seasons while lowest at dry season conditions. The largest N_2O emissions are recognizable at Ocotea forest, most likely due to the generally higher SOC/ totN and wetter conditions favoring formation and emission of N_2O via denitrification. Soils of the studied ecosystems were a sink of atmospheric CH

Emission Spectroscopy of the 4X Source Discharge With and Without N 2 Gas

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

Smith, Horace Vernon

2016-01-14

This tech note summarizes the December, 1988 emission spectroscopy measurements made on the 4X source discharge with and without N₂ gas added to the H + Cs discharge. This study is motivated by the desire to understand why small amounts of N₂ gas added to the source discharge results in a reduction in the H⁻ beam noise. The beneficial effect of N₂ gas on H⁻ beam noise was first discovered by Bill Ingalls and Stu Orbesen on the ATS SAS source. For the 4X source the observed effect is that when N2 gas is added to the discharge the H⁻more » beam noise is reduced about a factor of 2.« less

Formation of nitrogenated organic aerosols in the Titan upper atmosphere

PubMed Central

Imanaka, Hiroshi; Smith, Mark A.

2010-01-01

Many aspects of the nitrogen fixation process by photochemistry in the Titan atmosphere are not fully understood. The recent Cassini mission revealed organic aerosol formation in the upper atmosphere of Titan. It is not clear, however, how much and by what mechanism nitrogen is incorporated in Titan’s organic aerosols. Using tunable synchrotron radiation at the Advanced Light Source, we demonstrate the first evidence of nitrogenated organic aerosol production by extreme ultraviolet–vacuum ultraviolet irradiation of a N2/CH4 gas mixture. The ultrahigh-mass-resolution study with laser desorption ionization-Fourier transform-ion cyclotron resonance mass spectrometry of N2/CH4 photolytic solid products at 60 and 82.5 nm indicates the predominance of highly nitrogenated compounds. The distinct nitrogen incorporations at the elemental abundances of H2C2N and HCN, respectively, are suggestive of important roles of H2C2N/HCCN and HCN/CN in their formation. The efficient formation of unsaturated hydrocarbons is observed in the gas phase without abundant nitrogenated neutrals at 60 nm, and this is confirmed by separately using 13C and 15N isotopically labeled initial gas mixtures. These observations strongly suggest a heterogeneous incorporation mechanism via short lived nitrogenated reactive species, such as HCCN radical, for nitrogenated organic aerosol formation, and imply that substantial amounts of nitrogen is fixed as organic macromolecular aerosols in Titan’s atmosphere. PMID:20616074

Flared natural gas-based onsite atmospheric water harvesting (AWH) for oilfield operations

NASA Astrophysics Data System (ADS)

Wikramanayake, Enakshi D.; Bahadur, Vaibhav

2016-03-01

Natural gas worth tens of billions of dollars is flared annually, which leads to resource waste and environmental issues. This work introduces and analyzes a novel concept for flared gas utilization, wherein the gas that would have been flared is instead used to condense atmospheric moisture. Natural gas, which is currently being flared, can alternatively power refrigeration systems to generate the cooling capacity for large scale atmospheric water harvesting (AWH). This approach solves two pressing issues faced by the oil-gas industry, namely gas flaring, and sourcing water for oilfield operations like hydraulic fracturing, drilling and water flooding. Multiple technical pathways to harvest atmospheric moisture by using the energy of natural gas are analyzed. A modeling framework is developed to quantify the dependence of water harvest rates on flared gas volumes and ambient weather. Flaring patterns in the Eagle Ford Shale in Texas and the Bakken Shale in North Dakota are analyzed to quantify the benefits of AWH. Overall, the gas currently flared annually in Texas and North Dakota can harvest enough water to meet 11% and 65% of the water consumption in the Eagle Ford and the Bakken, respectively. Daily harvests of upto 30 000 and 18 000 gallons water can be achieved using the gas currently flared per well in Texas and North Dakota, respectively. In fifty Bakken sites, the water required for fracturing or drilling a new well can be met via onsite flared gas-based AWH in only 3 weeks, and 3 days, respectively. The benefits of this concept are quantified for the Eagle Ford and Bakken Shales. Assessments of the global potential of this concept are presented using data from countries with high flaring activity. It is seen that this waste-to-value conversion concept offers significant economic benefits while addressing critical environmental issues pertaining to oil-gas production.

Integrated capture of fossil fuel gas pollutants including CO.sub.2 with energy recovery

DOEpatents

Ochs, Thomas L [Albany, OR; Summers, Cathy A [Albany, OR; Gerdemann, Steve [Albany, OR; Oryshchyn, Danylo B [Philomath, OR; Turner, Paul [Independence, OR; Patrick, Brian R [Chicago, IL

2011-10-18

A method of reducing pollutants exhausted into the atmosphere from the combustion of fossil fuels. The disclosed process removes nitrogen from air for combustion, separates the solid combustion products from the gases and vapors and can capture the entire vapor/gas stream for sequestration leaving near-zero emissions. The invention produces up to three captured material streams. The first stream is contaminant-laden water containing SO.sub.x, residual NO.sub.x particulates and particulate-bound Hg and other trace contaminants. The second stream can be a low-volume flue gas stream containing N.sub.2 and O.sub.2 if CO2 purification is needed. The final product stream is a mixture comprising predominantly CO.sub.2 with smaller amounts of H.sub.2O, Ar, N.sub.2, O.sub.2, SO.sub.X, NO.sub.X, Hg, and other trace gases.

Fast gas heating and radial distribution of active species in nanosecond capillary discharge in pure nitrogen and N2:O2 mixtures

NASA Astrophysics Data System (ADS)

Lepikhin, N. D.; Popov, N. A.; Starikovskaia, S. M.

2018-05-01

Fast gas heating is studied experimentally and numerically using pulsed nanosecond capillary discharge in pure nitrogen and N2:O2 mixtures under the conditions of high specific deposited energy (up to 1 eV/molecule) and high reduced electric fields (100–300 Td). Deposited energy, electric field and gas temperature are measured as functions of time. The radial distribution of active species is analyzed experimentally. The roles of processes involving {{{N}}}2({{B}}) ={{{N}}}2({{{B}}}3{{{\\Pi }}}{{g}},{{{W}}}3{{{Δ }}}{{u}},{{B}}{{\\prime} }3{{{Σ }}}{{u}}-), {{{N}}}2({{{A}}}3{{{Σ }}}{{u}}+) and N(2D) excited nitrogen species leading to heat release are analyzed using numerical modeling in the framework of 1D axial approximation.

FirefOx Design Reference fO2 Sensor for Hot, Deep Atmospheres

NASA Astrophysics Data System (ADS)

Izenberg, N.; Papadakis, S.; Deglau, D.; Francomacaro, A. S.

2016-12-01

Understanding the composition of the lowest portion of Venus' atmosphere is critical to knowing the stable mineralogy of the rocks there. Oxygen gas is a critical trace component, with fugacity, or partial pressure, estimated in the range of 10-19 to 10-22 from early probe measurements down to 22km altitude (Pioneer Venus, Venera), chemical equilibrium measurements, and other modeling. "FirefOx" is a simple oxygen fugacity sensor with the express purpose of determining the partial pressure of oxygen in the lowest scale heights of the Venus atmosphere, and especially the lowest hundreds of meters; the surface atmosphere interface, where the atmosphere and surface move to thermodynamic equilibrium. Knowledge of the fO2 at the surface atmosphere interface is crucial to determining the stable mineralogy of surface materials (e.g. magnetite vs. hematite) and gas chemistry in the near-surface atmosphere FirefOx is a Metal/Metal Oxide oxygen fugacity sensor intended to be mounted on the outside of a Venus descent probe, with electronics housed inside a thermally controlled environment. The sole sensor capability is the precise, accurate detection of the partial pressure of oxygen gas (fO2) in the near-surface environment of Venus, at up to 95-bar pressure (predominantly CO2. Surface temperatures at mean planetary elevation are near 735 K, thus a required operational temperature range of 710-740 K covers a range of near-surface elevations. FirefOx system requirements are low ( 100-200 grams, mass, milliwatt power, several kilobytes total science data). A design reference sensor, composed of custom, Yittria-ZrO ceramic electrolyte, with an encapsulated Pd/PdO standard and patterned Pt electrodes has demonstrated scientifically useful signal-to-noise millivolt level potential at temperatures as low as 620 K, relatable to fO2 by a Nernst equation E = RT/4F ln(PO2/PrefO2) where E = open circuit potential across the sensor electrolyte, R = universal gas constant, T

Efficacy of passive sampler collection for atmospheric NO2 isotopes under simulated environmental conditions.

PubMed

Coughlin, Justin G; Yu, Zhongjie; Elliott, Emily M

2017-07-30

Nitrogen oxides or NO x (NO x = NO + NO 2 ) play an important role in air quality, atmospheric chemistry, and climate. The isotopic compositions of anthropogenic and natural NO 2 sources are wide-ranging, and they can be used to constrain sources of ambient NO 2 and associated atmospheric deposition of nitrogen compounds. While passive sample collection of NO 2 isotopes has been used in field studies to determine NO x source influences on atmospheric deposition, this approach has not been evaluated for accuracy or precision under different environmental conditions. The efficacy of NO 2 passive sampler collection for NO 2 isotopes was evaluated under varied temperature and relative humidity (RH) conditions in a dynamic flux chamber. The precision and accuracy of the filter NO 2 collection as nitrite (NO 2 - ) for isotopic analysis were determined using a reference NO 2 gas tank and through inter-calibration with a modified EPA Method 7. The bacterial denitrifer method was used to convert 20 μM of collected NO 2 - or nitrate (NO 3 - ) into N 2 O and was carried out on an Isoprime continuous flow isotope ratio mass spectrometer. δ 15 N-NO 2 values determined from passive NO 2 collection, in conditions of 11-34 °C, 1-78% RH, have an overall accuracy and precision of ±2.1 ‰, and individual run precision of ±0.6 ‰. δ 18 O-NO 2 values obtained from passive NO 2 sampler collection, under the same conditions, have an overall precision of ± 1.3 ‰. Suitable conditions for passive sampler collection of NO 2 isotopes are in environments ranging from 11 to 34 °C and 1 to 78% RH. The passive NO 2 isotope measurement technique provides an accurate method to determine variations in atmospheric δ 15 N-NO 2 values and a precise method for determining atmospheric δ 18 O-NO 2 values. The ability to measure NO 2 isotopes over spatial gradients at the same temporal resolution provides a unique perspective on the extent and seasonality of fluctuations in atmospheric NO 2

Effect of modified atmosphere packaging on the shelf life of rainbow trout (Oncorhynchus mykiss, Walbaum 1792) mince.

PubMed

Kocatepe, Demet; Turan, Hülya; Altan, Can Okan; Keskin, Irfan; Ceylan, Asuman

2016-06-01

This paper reports the effect of different concentrations of CO2/N2 gases on chemical/sensorial stability, color properties (L*, a*, and b* values), and microbiological properties of trout mince stored at 3 ± 1℃. The gas mixtures were used as follows; 60%CO2 + 40%N2 (B), 75%CO2 + 25%N2 (C), 40%CO2 + 60%N2 (D). Control samples (A) were packed under atmospheric air. Analyses were carried out on the 1st, 4th, 8th, 12th, 16th, 20th, 24th and 28th days of storage. Among three modified atmosphere gas compositions, the best preservation method and most suitable gas concentration for trout mince were found in group C including 75% CO2 The inconsumable day of trout mince packed with air (control) and MAPs (Modified Atmosphere Packaging) (group B, C, and D) were 12th, 16th, 24th, and 16th days, respectively. © The Author(s) 2015.

Characterization of organic matter of plants from lakes by thermal analysis in a N2 atmosphere

NASA Astrophysics Data System (ADS)

Guo, Fei; Wu, Fengchang; Mu, Yunsong; Hu, Yan; Zhao, Xiaoli; Meng, Wei; Giesy, John P.; Lin, Ying

2016-03-01

Organic matter (OM) has been characterized using thermal analysis in O2 atmospheres, but it is not clear if OM can be characterized using slow thermal degradation in N2 atmospheres (STDN). This article presents a new method to estimate the behavior of OM in anaerobic environment. Seventeen different plants from Tai Lake (Ch: Taihu), China were heated to 600 °C at a rate of 10 °C min-1 in a N2 atmosphere and characterized by use of differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). DSC chromatograms were compared with 9 standard compounds. Seven peaks were observed in DSC chromatograms, 2 main peaks strongly correlated with biochemical indices, and one main peak was a transitional stage. Energy absorbed by a peak at approximately 200 °C and total organic carbon were well correlated, while energy absorbed at approximately 460 °C was negatively correlated with lignin content. Presence of peaks at approximately 350 and 420 °C varied among plant biomass sources, providing potential evidence for biomass identification. Methods of STDN reported here were rapid and accurate ways to quantitatively characterize OM, which may provide useful information for understanding anaerobic behaviors of natural organic matters.

Theoretical study on atmospheric reactions of fluoranthene and pyrene with N2O5/NO3/NO2

NASA Astrophysics Data System (ADS)

Wang, Youfeng; Yang, Bo; Shu, Jinian; Li, Nana; Zhang, Peng; Sun, Wanqi

2015-08-01

It is complex to assign the products obtained from the gas-phase reactions of PAHs with NO3/NO2 and N2O5. For this purpose, theoretical calculations are performed. Results show that 2-nitrofluoranthene and 2-nitropyrene are the dominant products for reactions of fluoranthene and pyrene with NO3/NO2, while 3-nitrofluoranthene and 1-nitropyrene are the major nitration products of N2O5. SN2 reaction mechanisms are elucidated and homolytic mechanisms are calculated for the first time. Rate constants for reactions of fluoranthene and pyrene with N2O5 are deduced for the first time, which are 2.50 × 10-27 and 2.16 × 10-24 cm3 molecule-1 s-1, respectively at 298 K.

Effect of feed-gas humidity on nitrogen atmospheric-pressure plasma jet for biological applications.

PubMed

Stephan, Karl D; McLean, Robert J C; DeLeon, Gian; Melnikov, Vadim

2016-11-14

We investigate the effect of feed-gas humidity on the oxidative properties of an atmospheric-pressure plasma jet using nitrogen gas. Plasma jets operating at atmospheric pressure are finding uses in medical and biological settings for sterilization and other applications involving oxidative stress applied to organisms. Most jets use noble gases, but some researchers use less expensive nitrogen gas. The feed-gas water content (humidity) has been found to influence the performance of noble-gas plasma jets, but has not yet been systematically investigated for jets using nitrogen gas. Low-humidity and high-humidity feed gases were used in a nitrogen plasma jet, and the oxidation effect of the jet was measured quantitatively using a chemical dosimeter known as FBX (ferrous sulfate-benzoic acid-xylenol orange). The plasma jet using high humidity was found to have about ten times the oxidation effect of the low-humidity jet, as measured by comparison with the addition of measured amounts of hydrogen peroxide to the FBX dosimeter. Atmospheric-pressure plasma jets using nitrogen as a feed gas have a greater oxidizing effect with a high level of humidity added to the feed gas.

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

NASA Technical Reports Server (NTRS)

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

1989-01-01

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

Atmosphere behavior in gas-closed mouse-algal systems: An experimental and modelling study

NASA Astrophysics Data System (ADS)

Averner, Maurice M.; Moore, Berrien; Bartholomew, Irene; Wharton, Robert

Concepts of biologically-based regenerative life support systems anticipate the use of photosynthetic organisms for air revitalization. However, mismatches in the rates of production and uptake of oxygen or carbon dioxide between the crew and the plants will lead to an accumulation or depletion of these gases beyond tolerable limits. One method for correcting these atmospheric changes is to use physicochemical devices. This would conflict with the constraint of minimal size and weight imposed upon the successful development of a competitive bioregenerative system. An alternate control strategy is based upon reducing the gas exchange mismatch by manipulation of those environmental parameters known to affect plant or algae gas exchange ratios. We have initiated a research program using a dual approach of mathematical modelling and laboratory experimentation aimed at examining the gas exchange characteristics of artificial animal/plant systems closed to the ambient atmosphere. Our goal is to develop control techniques and management strategies for maintaining the atmospheric levels of carbon dioxide and oxygen at physiological levels. A mathematical model simulating the atmospheric behavior in these systems has been developed and an experimental gas-closed system has been constructed. These will be described and preliminary results will be presented.

Gas Nonideality at One Atmosphere Revealed through Speed of Sound Measurements and Heat Capacity Determinations

ERIC Educational Resources Information Center

Halpern, Arthur M.; Liu, Allen

2008-01-01

Using an easy-to-make cylindrical resonator, students can measure the speed of sound in a gas, u, with sufficiently high precision (by locating standing-wave Lissajous patterns on an oscilloscope) to observe real gas properties at one atmosphere and 300 K. For CO[subscript 2] and SF[subscript 6], u is found to be 268.83 and 135.25 m s[superscript…

Real Time Mud Gas Logging During Drilling of DFDP-2B

NASA Astrophysics Data System (ADS)

Mathewson, L. A.; Toy, V.; Menzies, C. D.; Zimmer, M.; Erzinger, J.; Niedermann, S.; Cox, S.

2015-12-01

The Deep Fault Drilling Project (DFDP) aims to improve our understanding of the Alpine Fault Zone, a tectonically active mature fault system in New Zealand known to rupture in large events, by deep scientific drilling. The borehole DFDP-2B approached the Alpine Fault at depth, reaching a final depth of 892 m (820 m true vertical depth). Online gas analysis (OLGA) while drilling tracked changes in the composition of gases extracted from the circulating drill mud. The composition of fluids from fault zones can provide information about their origins, flow rates and -paths, fluid-rock interactions along these paths, and the permeability structure of the faulted rock mass. Apart from an atmospheric input, the gases in drilling mud derive from the pore space of rock, crushed at the drill bit, and from permeable layers intersected by the borehole. The rapid formation of mud wall cake seals the borehole from further fluid inflow, hence formation-derived gases enter mostly at the depth of the drill bit. OLGA analyses N2, O2, Ar, CO2, CH4, He, and H2 on a mass spectrometer, hydrocarbons CH4, C2H6, C3H8, i-C4H10, and n-C4H10 on a gas chromatograph, and Rn using a lucas-cell detector. Gas was sampled for offline analyses on noble gas and stable isotopes to complement the OLGA dataset. The principle formation-derived gases found in drilling mud during drilling of DFDP-2 were CO2 and CH4, with smaller component of H2 and He2. High radon activity is interpreted to reflect intervals of active fluid flow through highly fractured and faulted rock. 3He/4He values in many samples were extremely air-contaminated, i.e. there was almost no excess of non-atmospheric He. The 3He/4He values measured at 236 m and 610 m, which are the only analyses with uncertainties <100%, are very similar to those measured in hot springs along the Alpine Fault, e.g. Fox River (0.64 Ra), Copland (0.42 Ra), Lower Wanganui (0.81 Ra). We will compare these data to those gathered using OLGA and discuss the

Atmospheric pulsed laser deposition of plasmonic nanoparticle films of silver with flowing gas and flowing atmospheric plasma

NASA Astrophysics Data System (ADS)

Khan, T. M.; Pokle, A.; Lunney, J. G.

2018-04-01

Two methods of atmospheric pulsed laser deposition of plasmonic nanoparticle films of silver are described. In both methods the ablation plume, produced by a 248 nm, 20 ns excimer laser in gas, is strongly confined near the target and forms a nanoparticle aerosol. For both the flowing gas, and the atmospheric plasma from a dielectric barrier discharge plasma source, the aerosol is entrained in the flow and carried to a substrate for deposition. The nanoparticle films produced by both methods were examined by electron microscopy and optical absorption spectroscopy. With plasma assistance, the deposition rate was significantly enhanced and the film morphology altered. With argon gas, isolated nanoparticles of 20 nm size were obtained, whereas in argon plasma, the nanoparticles are aggregated in clusters of 90 nm size. Helium gas also leads to the deposition of isolated nanoparticles, but with helium plasma, two populations of nanoparticles are observed: one of rounded particles with a mean size of 26 nm and the other of faceted particles with a mean size 165 nm.

Investigating Titan's Atmospheric Chemistry at Low Temperature in Support of the NASA Cassini Mission

NASA Technical Reports Server (NTRS)

Sciamma-O'Brien, Ella; Salama, Farid

2013-01-01

Titan's atmosphere, composed mainly of N2 and CH4, is the siege of a complex chemistry induced by solar UV radiation and electron bombardment from Saturn's magnetosphere. This organic chemistry occurs at temperatures lower than 200 K and leads to the production of heavy molecules and subsequently solid aerosols that form the orange haze surrounding Titan. The Titan Haze Simulation (THS) experiment has been developed on the COSMIC simulation chamber at NASA Ames in order to study the different steps of Titan's atmospheric chemistry at low temperature and to provide laboratory data in support for Cassini data analysis. The chemistry is simulated by plasma in the stream of a supersonic expansion. With this unique design, the gas mixture is adiabatically cooled to Titan-like temperature (approx. 150 K) before inducing the chemistry by plasma discharge. Different gas mixtures containing N2, CH4, and the first products of the N2,-CH4 chemistry (C2H2, C2H4, C6H6...) but also heavier molecules such as PAHs or nitrogen containing PAHs can be injected. Both the gas phase and solid phase products resulting from the plasma-induced chemistry can be monitored and analyzed. Here we present the results of recent gas phase and solid phase studies that highlight the chemical growth evolution when injecting heavier hydrocarbon trace elements in the initial N2-CH4 mixture. Due to the short residence time of the gas in the plasma discharge, only the first steps of the chemistry have time to occur in a N2-CH4 discharge. However by adding acetylene and benzene to the initial N2-CH4 mixture, we can study the intermediate steps of Titan's atmospheric chemistry as well as specific chemical pathways. These results show the uniqueness of the THS experiment to help understand the first and intermediate steps of Titan fs atmospheric chemistry as well as specific chemical pathways leading to Titan fs haze formation.

Fifteen-minute Extravehicular Activity Prebreathe Protocol Using NASA's Exploration Atmosphere (8.2 psia/ 34% 02)

NASA Technical Reports Server (NTRS)

Abercromby, Andrew F. J.; Gernhardt, Michael L.; Conkin, Johnny

2013-01-01

A TBDM DCS probability model based on an existing biophysical model of inert gas bubble growth provides significant prediction and goodness-of-fit with 84 cases of DCS in 668 human altitude exposures. 2. Model predictions suggest that 15-minute O2 prebreathe protocols used in conjunction with suit ports and an 8.2 psi, 34% O2, 66% N2 atmosphere may enable rapid EVA capability for future exploration missions with the risk of DCS = 12%. ? EVA could begin immediately at 6.0 psi, with crewmembers decreasing suit pressure to 4.3 psi after completing the 15-minute in-suit prebreathe. 3. Model predictions suggest that intermittent recompression during exploration EVA may reduce decompression stress by 1.8% to 2.3% for 6 hours of total EVA time. Savings in gas consumables and crew time may be accumulated by abbreviating the EVA suit N2 purge to 2 minutes (20% N2) compared with 8 minutes (5% N2) at the expense of an increase in estimated decompression risk of up to 2.4% for an 8-hour EVA. ? Increased DCS risk could be offset by IR or by spending additional time at 6 psi at the beginning of the EVA. ? Savings of 0.48 lb of gas and 6 minutes per person per EVA corresponds to more than 31 hours of crew time and 1800 lb of gas and tankage under the Constellation lunar architecture. 6. Further research is needed to characterize and optimize breathing mixtures and intermittent recompression across the range of environments and operational conditions in which astronauts will live and work during future exploration missions. 7. Development of exploration prebreathe protocols will begin with definition of acceptable risk, followed by development of protocols based on models such as ours, and, ultimately, validation of protocols through ground trials before operational implementation.

Effect of nitrogen gas packaging on the quality and microbial growth of fresh-cut vegetables under low temperatures.

PubMed

Koseki, Shigenobu; Itoh, Kazuhiko

2002-02-01

Nitrogen (N2) gas packaging for fresh-cut vegetables (lettuce and cabbage) has been examined as a means of modified atmosphere packaging (MAP) for extending the shelf life of cut vegetables. Gas composition in enclosed packages that contained cut vegetables and were filled with 100% N2 had an oxygen (O2) concentration of 1.2 to 5.0% and a carbon dioxide (CO2) concentration of 0.5 to 3.5% after 5 days of storage. An atmosphere of low concentrations of O2 and high CO2 conditions occurred naturally in the package filled with N2 gas. Degradation of cut vegetables in terms of appearance was delayed by N2 gas packaging. Because of this effect, the appearance of fresh-cut vegetables packaged with N2 gas remained acceptable at temperatures below 5 degrees C after 5 days. Treatment with acidic electrolyzed water (AcEW) contributed to the acceptability of the vegetables' appearance at 5 and 10 degrees C in the air-packaging system. N2 gas packaging did not significantly affect the growth of microbial populations (total aerobic bacteria, coliform bacteria, Bacillus cereus, and psychrotrophic bacteria) in or on cut vegetables at 1, 5, and 10 degrees C for 5 days. Microbial growth in or on the cut vegetables was inhibited at 1 degrees C for 5 days regardless of atmospheric conditions.

CO2 greenhouse in the early martian atmosphere: SO2 inhibits condensation

NASA Technical Reports Server (NTRS)

Yung, Y. L.; Nair, H.; Gerstell, M. F.

1997-01-01

Many investigators of the early martian climate have suggested that a dense carbon dioxide atmosphere was present and warmed the surface above the melting point of water (J.B. Pollack, J.F. Kasting, S.M. Richardson, and K. Poliakoff 1987. Icarus 71, 203-224). However, J.F. Kasting (1991. Icarus 94, 1-13) pointed out that previous thermal models of the primitive martian atmosphere had not considered the condensation of CO2. When this effect was incorporated, Kasting found that CO2 by itself is inadequate to warm the surface. SO2 absorbs strongly in the near UV region of the solar spectrum. While a small amount of SO2 may have a negligible effect by itself on the surface temperature, it may have significantly warmed the middle atmosphere of early Mars, much as ozone warms the terrestrial stratosphere today. If this region is kept warm enough to inhibit the condensation of CO2, then CO2 remains a viable greenhouse gas. Our preliminary radiative modeling shows that the addition of 0.1 ppmv of SO2 in a 2 bar CO2 atmosphere raises the temperature of the middle atmosphere by approximately 10 degrees, so that the upper atmosphere in a 1 D model remains above the condensation temperature of CO2. In addition, this amount of SO2 in the atmosphere provides an effective UV shield for a hypothetical biosphere on the martian surface.

New technique for the direct analysis of food powders confined in a small hole using transversely excited atmospheric CO(2) laser-induced gas plasma.

PubMed

Khumaeni, Ali; Ramli, Muliadi; Deguchi, Yoji; Lee, Yong Inn; Idris, Nasrullah; Kurniawan, Koo Hendrik; Lie, Tjung Jie; Kagawa, Kiichiro

2008-12-01

Taking advantage of the differences between the interactions of transversely excited atmospheric (TEA) CO(2) lasers with metal and with organic powder, a new technique for the direct analysis of food powder samples has been developed. In this technique, the powder samples were placed into a small hole with a diameter of 2 mm and a depth of 3 mm and covered by a metal mesh. The TEA CO(2) laser (1500 mJ, 200 ns) was focused on the powder sample surfaces, passing through the metal mesh, at atmospheric pressure in nitrogen gas. It is hypothesized that the small hole functions to confine the powder particles and suppresses the blowing-off of sample, while the metal mesh works as the source of electrons to initiate the strong gas breakdown plasma. The confined powder particles are then ablated by laser irradiation and the ablated particles move into the strong gas breakdown plasma region to be atomized and excited; this method cannot be applied for the case of Nd:YAG lasers because in such case the metal mesh itself was ablated by the laser irradiation. A quantitative analysis of a milk powder sample containing different concentrations of Ca was successfully demonstrated, resulting in a good linear calibration curve with high precision.

Imagining CO2: development and assessment of interactive visualizations for high resolution greenhouse gas observations collected by BEACO2N

NASA Astrophysics Data System (ADS)

Raheja, G.; Shusterman, A.; Martin, S.; Shahar, E.; Laughner, J.; Turner, A. J.; Miller, M. K.; Cohen, R. C.

2016-12-01

The Berkeley Atmospheric CO2 Observation Network (BEACO2N) is a high-density network of 28 carbon dioxide sensors distributed around the San Francisco Bay Area that serve to enhance understanding of intra-city variations in CO2 concentrations that are not necessarily captured by sparser networks maintained by local and national air quality management agencies. We partner with designers at the San Francisco Exploratorium to create a suite of interactive exhibits and hands-on activities that creatively visualize data from BEACO2N for general audiences. Museum goers can manipulate a light-up "bar graph" of live CO2 concentrations by exhaling on an in-room sensor, query the current readings of rooftop sensors using a scale model of the Wired Pier observation system, scroll through the data from other BEACO2N sites projected on a 3-D "topographic table" of the Bay Area, and view interpolated CO2 fields driven by research-grade weather models on a nine-screen LCD display. We present lessons learned from these initial installations, from layperson audience feedback to details of the Stochastic Time-Inverted Lagrangian Transport (STILT) model coupled to Weather Research and Forecasting (WRF) weather fields used to generate intuitive concentration maps. We propose that compelling visual demonstrations of elevated CO2 concentrations due to routine small-scale high-emission anthropogenic activities (e.g. rush hour) and/or special events (such as fireworks or factory fires) generate deeper engagement in local environmental issues and interest in undertaking personal actions that can become part of the broader climate solution. While global means and other large-scale aggregate climate metrics can lead to feelings of disconnect and subsequent ambivalence, via such exhibitions, distributed network instruments like BEACO2N can provide the local sensitivity needed to "personalize" greenhouse gas concentrations to a given individual or community and incite the drive toward

Atmospheric Methane Enhancements Related with Natural Gas Usage in the Greater Houston Area

NASA Astrophysics Data System (ADS)

Sanchez, N. P.; Zheng, C.; Ye, W.; Czader, B.; Cohan, D. S.; Tittel, F. K.; Griffin, R. J.

2017-12-01

Natural gas (NG) usage as a replacement of oil and coal has increased significantly in the U.S in recent years. Despite the benefits associated with this fuel, leakage from NG distribution systems and in-use uncombusted NG (e.g., compressed natural gas vehicles) can be relevant sources of methane (CH4) emissions in urban centers. Methane, the main constituent of NG, is a potent greenhouse gas impacting the chemistry of the atmosphere, whose emission might outweigh the potential environmental advantages of NG use. Although the Greater Houston area (GHA) is the fifth-largest metropolitan area in the U.S, no studies on the potential impact of NG usage on atmospheric CH4 levels have been published in the scientific literature to date. In this work, a mobile-based study of CH4 and ethane (C2H6) concentration levels in eight residential zones with different expected probability of NG leakage in the GHA was conducted in the summer of 2016. A novel laser-based sensor system for simultaneous detection of CH4 and C2H6 was developed and deployed in a mid-sized vehicle, and monitoring of these gas species was conducted for over 14 days covering 250 road miles. Both linear discriminant and cluster analyses were performed to assess the spatial variability of atmospheric CH4 concentrations in the GHA. These analyses showed clear differences in the CH4 mixing ratios in an inter- and intra-neighborhood level and indicated the presence of high CH4 concentration clusters mainly located in the central and west central parts of the GHA. Source discrimination analyses based on orthogonal regression analysis and a Keeling-like plot method were conducted to establish the predominant origin of CH4 in the identified high concentration clusters and in over 30 CH4 concentration peaks observed during the field campaign. Results of these analyses indicate that thermogenic sources of CH4 (e.g., NG) were predominant in short-duration concentration spikes (lasting less than 10 minutes), while CH4

Nitrous Oxide: A Greenhouse Gas That is Also an Ozone Layer Depleting Gas

NASA Astrophysics Data System (ADS)

Reed, S.; Uriarte, M.; Wood, T. E.; Cavaleri, M. A.; Lugo, A. E.

2014-12-01

Nitrous oxide, N2O, is the major source of nitrogen oxides in the stratosphere, where these oxides playa critical roles in ozone layer depletion by itself and moderating ozone layer depletion by chlorinated chemicals. Thus N2O plays a complex role in the stratosphere. Nitrous oxide is also a greenhouse gas and it contributes to the radiative forcing of climate. Indeed, it is considered the third most important greenhouse gas next to carbon dioxide and methane. This dual role of nitrous oxide makes it an interesting gas for the atmosphere- it bridges the issue of ozone layer depletion and climate change. Nitrous oxide has both natural and anthropogenic sources. Therefore, one needs to consider this important distinction between natural and anthropogenic sources as well as its role in two related but separate environmental issues. Further, the sources of nitrous oxide are varied and diffuse, which makes it difficult to quantify different sources. However, it is clear that a majority of anthropogenic nitrous oxide comes from food production (including agricultural and animal growth practices), an activity that is at the heart of human existence. Thus, limiting N2O emissions is not a simple task! I will briefly summarize our understanding of these roles of nitrous oxide in the earth's atmosphere and touch on the possible ways to limit N2O emissions.

Nitrous Oxide: A Greenhouse Gas That is Also an Ozone Layer Depleting Gas

NASA Astrophysics Data System (ADS)

Ravishankara, A. R.

2015-12-01

Nitrous oxide, N2O, is the major source of nitrogen oxides in the stratosphere, where these oxides playa critical roles in ozone layer depletion by itself and moderating ozone layer depletion by chlorinated chemicals. Thus N2O plays a complex role in the stratosphere. Nitrous oxide is also a greenhouse gas and it contributes to the radiative forcing of climate. Indeed, it is considered the third most important greenhouse gas next to carbon dioxide and methane. This dual role of nitrous oxide makes it an interesting gas for the atmosphere- it bridges the issue of ozone layer depletion and climate change. Nitrous oxide has both natural and anthropogenic sources. Therefore, one needs to consider this important distinction between natural and anthropogenic sources as well as its role in two related but separate environmental issues. Further, the sources of nitrous oxide are varied and diffuse, which makes it difficult to quantify different sources. However, it is clear that a majority of anthropogenic nitrous oxide comes from food production (including agricultural and animal growth practices), an activity that is at the heart of human existence. Thus, limiting N2O emissions is not a simple task! I will briefly summarize our understanding of these roles of nitrous oxide in the earth's atmosphere and touch on the possible ways to limit N2O emissions.

Images reveal that atmospheric particles can undergo liquid–liquid phase separations

PubMed Central

You, Yuan; Renbaum-Wolff, Lindsay; Carreras-Sospedra, Marc; Hanna, Sarah J.; Hiranuma, Naruki; Kamal, Saeid; Smith, Mackenzie L.; Zhang, Xiaolu; Weber, Rodney J.; Shilling, John E.; Dabdub, Donald; Martin, Scot T.; Bertram, Allan K.

2012-01-01

A large fraction of submicron atmospheric aerosol particles contains both organic material and inorganic salts. As the relative humidity cycles in the atmosphere and the water content of the particles correspondingly changes, these mixed particles can undergo a range of phase transitions, possibly including liquid–liquid phase separation. If liquid–liquid phase separation occurs, the gas-particle partitioning of atmospheric semivolatile organic compounds, the scattering and absorption of solar radiation, and the reactive uptake of gas species on atmospheric particles may be affected, with important implications for climate predictions. The actual occurrence of liquid–liquid phase separation within individual atmospheric particles has been considered uncertain, in large part because of the absence of observations for real-world samples. Here, using optical and fluorescence microscopy, we present images that show the coexistence of two noncrystalline phases for real-world samples collected on multiple days in Atlanta, GA as well as for laboratory-generated samples under simulated atmospheric conditions. These results reveal that atmospheric particles can undergo liquid–liquid phase separations. To explore the implications of these findings, we carried out simulations of the Atlanta urban environment and found that liquid–liquid phase separation can result in increased concentrations of gas-phase NO3 and N2O5 due to decreased particle uptake of N2O5. PMID:22847443

Images reveal that atmospheric particles can undergo liquid-liquid phase separations.

PubMed

You, Yuan; Renbaum-Wolff, Lindsay; Carreras-Sospedra, Marc; Hanna, Sarah J; Hiranuma, Naruki; Kamal, Saeid; Smith, Mackenzie L; Zhang, Xiaolu; Weber, Rodney J; Shilling, John E; Dabdub, Donald; Martin, Scot T; Bertram, Allan K

2012-08-14

A large fraction of submicron atmospheric aerosol particles contains both organic material and inorganic salts. As the relative humidity cycles in the atmosphere and the water content of the particles correspondingly changes, these mixed particles can undergo a range of phase transitions, possibly including liquid-liquid phase separation. If liquid-liquid phase separation occurs, the gas-particle partitioning of atmospheric semivolatile organic compounds, the scattering and absorption of solar radiation, and the reactive uptake of gas species on atmospheric particles may be affected, with important implications for climate predictions. The actual occurrence of liquid-liquid phase separation within individual atmospheric particles has been considered uncertain, in large part because of the absence of observations for real-world samples. Here, using optical and fluorescence microscopy, we present images that show the coexistence of two noncrystalline phases for real-world samples collected on multiple days in Atlanta, GA as well as for laboratory-generated samples under simulated atmospheric conditions. These results reveal that atmospheric particles can undergo liquid-liquid phase separations. To explore the implications of these findings, we carried out simulations of the Atlanta urban environment and found that liquid-liquid phase separation can result in increased concentrations of gas-phase NO(3) and N(2)O(5) due to decreased particle uptake of N(2)O(5).

Atmospheric Implications of Light Alkane Emissions From the U.S. Oil and Natural Gas Sector

NASA Astrophysics Data System (ADS)

Fischer, E. V.; Tzompa Sosa, Z. A.; Henderson, B.; Travis, K.; Keller, C.; Sive, B. C.; Helmig, D.; Fried, A.; Herndon, S. C.; Yacovitch, T. I.; Mahieu, E.; Franco, B.

2017-12-01

New efficient drilling techniques triggered a massive growth of unconventional oil and natural gas production in North America starting in 2005. Emissions of a variety of volatile organic compounds (VOCs) from the oil and gas sector occur during well development and production phases, and emissions to the atmosphere also continue when wells are abandoned. Determining VOC emission fluxes in the context of rapid growth of the oil and natural gas industry presents a big challenge for emission inventories. In the U.S., the latest version of the 2011 National Emission Inventory (NEI2011v6.3) includes updates over important oil and natural gas basins and speciation profiles based on the Western Regional Air Partnership. We incorporated the NEI2011v6.3 into the GEOS-Chem chemical transport model to simulate the atmospheric abundances of C2-C5 alkanes over the U.S. attributed to emissions from the oil and gas sector. We present results from a nested high-resolution (0.5 degree x 0.667 degree) simulation over North America. C2-C5 alkane emissions from NEI 2011v6.3 increase across the U.S. compared to the previous NEI 2011 v2 incorporated as default in GEOS-Chem. Ethane (C2H6) and propane (C3H8) emission fluxes increased over important oil and natural gas basins. We compare our simulation to a suite of surface observations, column measurements, and aircraft profiles. Finally, we estimate the contribution that C2-C5 alkanes make to the abundance and production of important secondary species including ozone, peroxy acetyl nitrate, and several ketones.

Photochemical removal of NO(2) by using 172-nm Xe(2) excimer lamp in N(2) or air at atmospheric pressure.

PubMed

Tsuji, Masaharu; Kawahara, Masashi; Noda, Kenji; Senda, Makoto; Sako, Hiroshi; Kamo, Naohiro; Kawahara, Takashi; Kamarudin, Khairul Sozana Nor

2009-03-15

Photochemical removal of NO(2) in N(2) or air (5-20% O(2)) mixtures was studied by using 172-nm Xe(2) excimer lamps to develop a new simple photochemical aftertreatment technique of NO(2) in air at atmospheric pressure without using any catalysts. When a high power lamp (300 mW/cm(2)) was used, the conversion of NO(2) (200-1000 ppm) to N(2) and O(2) in N(2) was >93% after 1 min irradiation, whereas that to N(2)O(5), HNO(3), N(2), and O(2) in air (10% O(2)) was 100% after 5s irradiation in a batch system. In a flow system, about 92% of NO(2) (200 ppm) in N(2) was converted to N(2) and O(2), whereas NO(2) (200-400 ppm) in air (20% O(2)) could be completely converted to N(2)O(5), HNO(3), N(2), and O(2) at a flow rate of 1l/min. It was found that NO could also be decomposed to N(2) and O(2) under 172-nm irradiation, though the removal rate is slower than that of NO(2) by a factor of 3.8. A simple model analysis assuming a consecutive reaction NO(2)-->NO-->N+O indicated that 86% of NO(2) is decomposed directly into N+O(2) and the rest is dissociated into NO+O under 172-nm irradiation. These results led us to conclude that the present technique is a new promising catalyst-free photochemical aftertreatment method of NO(2) in N(2) and air in a flow system.

Experimental Investigation of Gas/Slag/Matte/Tridymite Equilibria in the Cu-Fe-O-S-Si System in Controlled Gas Atmospheres: Experimental Results at 1473 K (1200 °C) and P(SO2) = 0.25 atm

NASA Astrophysics Data System (ADS)

Fallah-Mehrjardi, Ata; Hidayat, Taufiq; Hayes, Peter C.; Jak, Evgueni

2017-12-01

Experimental studies were undertaken to determine the gas/slag/matte/tridymite equilibria in the Cu-Fe-O-S-Si system at 1473 K (1200 °C), P(SO2) = 0.25 atm, and a range of P(O2)'s. The experimental methodology involved high-temperature equilibration using a substrate support technique in controlled gas atmospheres (CO/CO2/SO2/Ar), rapid quenching of equilibrium phases, followed by direct measurement of the chemical compositions of the phases with Electron Probe X-ray Microanalysis (EPMA). The experimental data for slag and matte were presented as a function of copper concentration in matte (matte grade). The data provided are essential for the evaluation of the effect of oxygen potential under controlled atmosphere on the matte grade, liquidus composition of slag and chemically dissolved copper in slag. The new data provide important accurate and reliable quantitative foundation for improvement of the thermodynamic databases for copper-containing systems.

The structure of liquid UO2-x in reducing gas atmospheres

NASA Astrophysics Data System (ADS)

Alderman, O. L. G.; Benmore, C. J.; Weber, J. K. R.; Skinner, L. B.; Tamalonis, A. J.; Sendelbach, S.; Hebden, A.; Williamson, M. A.

2017-02-01

High energy X-ray diffraction experiments performed on hypostoichiometric UO2-x liquids in reducing gas mixtures of 95%Ar:5%CO and 95%Ar:5%H2 are compared to that conducted in a pure Ar atmosphere [Skinner et al., Science 346, 984 (2014)]. The measurements are pertinent to severe accident scenarios at nuclear reactors, where core melts can encounter reducing conditions and further shed light on the oxide chemistry of the low valence states of uranium, particularly U(III), which become stable only at very high temperatures and low oxygen potentials. The radioactive samples were melted by floating small spheres of material using an aerodynamic levitator and heating with a laser beam. In the more reducing environments, a 1.7% shift to lower Q-values is observed in the position of the principal peak of the measured X-ray structure factors, compared to the more oxidizing Ar environment. This corresponds to an equivalent elongation in the U-U nearest neighbor distances and the U-U periodicity. The U-O peak (modal) bond-length, as measured from the real-space total correlation functions, is also observed to expand by 0.9-1.6% under reducing conditions, consistent with the presence of 15-27% U3+ cations, assuming constant U-O coordination number. The slightly larger U-U elongation, as compared to the U-O elongation, is interpreted as a slight increase in U-O-U bond angles. Difficulties concerning the determination of the hypostoichiometry, x, are discussed, along with the future directions for related research.

The structure of liquid UO 2-x in reducing gas atmospheres

DOE PAGES

Alderman, O. L. G.; Benmore, C. J.; Weber, J. K. R.; ...

2017-02-22

High energy X-ray diffraction experiments performed on hypostoichiometric UO 2-x liquids in reducing gas mixtures of 95%Ar:5%CO and 95%Ar:5%H 2 are compared to that conducted in a pure Ar atmosphere [Skinner et al., Science 346, 984 (2014)]. The measurements are pertinent to severe accident scenarios at nuclear reactors, where core melts can encounter reducing conditions and further shed light on the oxide chemistry of the low valence states of uranium, particularly U(III), which become stable only at very high temperatures and low oxygen potentials. The radioactive samples were melted by floating small spheres of material using an aerodynamic levitator andmore » heating with a laser beam. In the more reducing environments, a 1.7% shift to lower Q-values is observed in the position of the principal peak of the measured X-ray structure factors, compared to the more oxidizing Ar environment. This corresponds to an equivalent elongation in the U-U nearest neighbor distances and the U-U periodicity. The U-O peak (modal) bond-length, as measured from the real-space total correlation functions, is also observed to expand by 0.9–1.6% under reducing conditions, consistent with the presence of 15–27% U 3+ cations, assuming constant U-O coordination number. The slightly larger U-U elongation, as compared to the U-O elongation, is interpreted as a slight increase in U-O-U bond angles. Difficulties concerning the determination of the hypostoichiometry, x, are discussed, along with the future directions for related research.« less

Atmospheric Detection of Perfluorotributyl Amine, an Uncharacterized Long-Lived Greenhouse Gas

NASA Astrophysics Data System (ADS)

Hong, A. C.; Young, C. J.; Mabury, S. A.

2012-12-01

Poly- and perfluoroalkyl substances (PFASs) are trace atmospheric constituents of radiative significance. In the atmosphere, PFASs may represent a class of potent long-lived greenhouse gases (LLGHGs) because they possess long lifetimes and exceptionally strong absorption bands in the infrared (IR) spectral region where other naturally occurring greenhouse gases (GHGs) do not absorb. The Intergovernmental Panel on Climate Change determined the radiative forcing (RF) of halocarbons to be +0.337 [± 0.03] W m-2, accounting for 13 % of the total RF attributed to LLGHGs. Although this value claims high certainty, it does not represent the actual perturbation from all environmentally relevant PFASs. Here we present the radiative efficiency (RE) and atmospheric concentration of a previously uncharacterized and unreported PFAS, perfluorotributyl amine (PFBAm). To assess the radiative properties of PFBAm, IR spectra were acquired by Fourier transform spectroscopy at 0.25 cm-1 resolution over the spectral range 0-2500 cm-1 at 296 K. The total integrated band strength, 7.08 x 10-16 cm2 molec-1 cm-1, was used to derive the cloudy-sky, instantaneous RE assuming a 0 to 1 ppbv change in concentration.The RE of PFBAm is calculated to be 0.86 W m-2 ppb-1, exceeding the RE of SF5CF3, the most effective GHG on a per molecule basis as reported in the literature to date. To evaluate the RF of PFBAm, a highly sensitive and selective method for detection was developed and validated. PFBAm was cryogenically extracted and pre-concentrated from bulk air samples for the offline detection by a custom-designed manifold coupled to a gas chromatograph-mass spectrometer. Quantitation was achieved by external calibration with a gravimetrically prepared, matrix-matched, authentic gaseous standard. Validation of the sampling method was performed by simultaneous measurement of several legacy chlorofluorocarbons and hydrochlorofluorocarbons. Preliminary results indicate that PFBAm is present in the

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

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

Dingyi Ye; Bethany Kurz; Marc Kurz

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

Experimental study of NO2 reduction in N2/Ar and O2/Ar mixtures by pulsed corona discharge.

PubMed

Zhu, Xinbo; Zheng, Chenghang; Gao, Xiang; Shen, Xu; Wang, Zhihua; Luo, Zhongyang; Cen, Kefa

2014-11-01

Non-thermal plasma technology has been regarded as a promising alternative technology for NOx removal. The understanding of NO2 reduction characteristics is extremely important since NO2 reduction could lower the total NO oxidation rate in the plasma atmosphere. In this study, NO2 reduction was experimentally investigated using a non-thermal plasma reactor driven by a pulsed power supply for different simulated gas compositions and operating parameters. The NO2 reduction was promoted by increasing the specific energy density (SED), and the highest conversion rates were 33.7%, 42.1% and 25.7% for Ar, N2/Ar and O2/Ar, respectively. For a given SED, the NO2 conversion rate had the order N2/Ar>Ar>O2/Ar. The highest energy yield of 3.31g/kWh was obtained in N2/Ar plasma and decreased with increasing SED; the same trends were also found in the other two gas compositions. The conversion rate decreased with increasing initial NO2 concentration. Furthermore, the presence of N2 or O2 led to different reaction pathways for NO2 conversion due to the formation of different dominating reactive radicals. Copyright © 2014. Published by Elsevier B.V.

Kinetic and mechanistic study of the gas-phase reaction of CxF2x+1CHCH2 (x=1, 2, 3, 4 and 6) with O3 under atmospheric conditions.

PubMed

Soto, A; Ballesteros, B; Jiménez, E; Antiñolo, M; Martínez, E; Albaladejo, J

2018-06-01

The relative-rate technique has been used to determine the rate coefficient for the reaction of C x F 2x+1 CHCH 2 (x = 1, 2, 3, 4 and 6) with ozone at (298 ± 2) K and (720 ± 5) Torr of air by FTIR (Fourier Transform Infrared Spectroscopy) and by GC-MS/SPME (Gas Chromatography-Mass Spectroscopy with Solid Phase Micro Extraction) in two different atmospheric simulation chambers. The following rate coefficients, in units of 10 -19  cm 3 molecule -1 s -1 , were obtained: (3.01 ± 0.10) for CF 3 CHCH 2 , (2.11 ± 0.35) for C 2 F 5 CHCH 2 , (2.34 ± 0.42) for C 3 F 7 CHCH 2 , (2.05 ± 0.31) for C 4 F 9 CHCH 2 and (2.07 ± 0.39) for C 6 F 13 CHCH 2 , where uncertainties represent ±2σ statistical error. The atmospheric lifetime of C x F 2x+1 CHCH 2 due to reaction with ozone was estimated from the reported rate coefficients. Additionally, the gaseous products formed in these reactions were investigated in the presence of synthetic air simulating a clean atmosphere. Perfluoroaldehydes, C x F 2x+1 C(O)H (PFALs), formaldehyde, formic acid and CF 2 O were identified as reaction products in the investigated reactions. The identified products made possible to propose a reaction mechanism that justifies the observed products. The atmospheric implications of these results are discussed in terms of the potential contribution of the atmospheric degradation of these species to PFAL and PFCA burden. Copyright © 2018 Elsevier Ltd. All rights reserved.

Validation of a predictive model coupling gas transfer and microbial growth in fresh food packed under modified atmosphere.

PubMed

Guillard, V; Couvert, O; Stahl, V; Hanin, A; Denis, C; Huchet, V; Chaix, E; Loriot, C; Vincelot, T; Thuault, D

2016-09-01

Predicting microbial safety of fresh products in modified atmosphere packaging implies to take into account the dynamic of O2, CO2 and N2 exchanges in the system and its effect on microbial growth. In this paper a mechanistic model coupling gas transfer and predictive microbiology was validated using dedicated challenge-tests performed on poultry meat, fresh salmon and processed cheese, inoculated with either Listeria monocytogenes or Pseudomonas fluorescens and packed in commercially used packaging materials (tray + lid films). The model succeeded in predicting the relative variation of O2, CO2 and N2 partial pressure in headspace and the growth of the studied microorganisms without any parameter identification. This work highlighted that the respiration of the targeted microorganism itself and/or that of the naturally present microflora could not be neglected in most of the cases, and could, in the particular case of aerobic microbes contribute to limit the growth by removing all residual O2 in the package. This work also confirmed the low sensitivity of L. monocytogenes toward CO2 while that of P. fluorescens permitted to efficiently prevent its growth by choosing the right combination of packaging gas permeability value and initial % of CO2 initially flushed in the pack. Copyright © 2016 Elsevier Ltd. All rights reserved.

Gas solubility in hydrophobic confinement.

PubMed

Luzar, Alenka; Bratko, Dusan

2005-12-01

Measured forces between apolar surfaces in water have often been found to be sensitive to exposure to atmospheric gases despite low gas solubilities in bulk water. This raises questions as to how significant gas adsorption is in hydrophobic confinement, whether it is conducive to water depletion at such surfaces, and ultimately if it can facilitate the liquid-to-gas phase transition in the confinement. Open Ensemble molecular simulations have been used here to determine saturated concentrations of atmospheric gases in water-filled apolar confinements as a function of pore width at varied gas fugacities. For paraffin-like confinements of widths barely exceeding the mechanical instability threshold (spinodal) of the liquid-to-vapor transition of confined water (aqueous film thickness between three and four molecular diameters), mean gas concentrations in the pore were found to exceed the bulk values by a factor of approximately 30 or approximately 15 in cases of N2 and CO2, respectively. At ambient conditions, this does not result in visible changes in the water density profile next to the surfaces. Whereas the barrier to capillary evaporation has been found to decrease in the presence of dissolved gas (Leung, K.; Luzar, A.; and Bratko, D. Phys. Rev. Lett. 2003, 90, 065502), gas concentrations much higher than those observed at normal atmospheric conditions would be needed to produce noticeable changes in the kinetics of capillary evaporation. In simulations, dissolved gas concentrations corresponding to fugacities above approximately 40 bar for N2, or approximately 2 bar for CO2, were required to trigger expulsion of water from a hydrocarbon slit as narrow as 1.4 nm. For nanosized pore widths corresponding to the mechanical instability threshold or above, no significant coupling between adsorption layers at opposing confinement walls was observed. This finding explains the approximately linear increase in gas solubility with inverse confinement width and the

A process for capturing CO 2 from the atmosphere

DOE PAGES

Keith, David W.; Holmes, Geoffrey; St. Angelo, David; ...

2018-06-07

Here, we describe a process for capturing CO 2 from the atmosphere in an industrial plant. The design captures ~1 Mt-CO 2/year in a continuous process using an aqueous KOH sorbent coupled to a calcium caustic recovery loop. We describe the design rationale, summarize performance of the major unit operations, and provide a capital cost breakdown developed with an independent consulting engineering firm. We report results from a pilot plant which provides data on performance of the major unit operations. We summarize the energy and material balance computed using an Aspen process simulation. When CO 2 is delivered at 15more » MPa the design requires either 8.81 GJ of natural gas, or 5.25 GJ of gas and 366 kWhr of electricity, per ton of CO 2 captured. Depending on financial assumptions, energy costs, and the specific choice of inputs and outputs, the levelized cost per ton CO 2 captured from the atmosphere ranges from 94 to 232 $/t-CO 2.« less

A process for capturing CO 2 from the atmosphere

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

Keith, David W.; Holmes, Geoffrey; St. Angelo, David

Here, we describe a process for capturing CO 2 from the atmosphere in an industrial plant. The design captures ~1 Mt-CO 2/year in a continuous process using an aqueous KOH sorbent coupled to a calcium caustic recovery loop. We describe the design rationale, summarize performance of the major unit operations, and provide a capital cost breakdown developed with an independent consulting engineering firm. We report results from a pilot plant which provides data on performance of the major unit operations. We summarize the energy and material balance computed using an Aspen process simulation. When CO 2 is delivered at 15more » MPa the design requires either 8.81 GJ of natural gas, or 5.25 GJ of gas and 366 kWhr of electricity, per ton of CO 2 captured. Depending on financial assumptions, energy costs, and the specific choice of inputs and outputs, the levelized cost per ton CO 2 captured from the atmosphere ranges from 94 to 232 $/t-CO 2.« less

Sub-atmospheric pressure gas sources for bulk storage and delivery of arsine and phosphine to MOCVD tools

NASA Astrophysics Data System (ADS)

Raynor, M. W.; Houlding, V. H.; Funke, H. H.; Frye, R.; Dietz, J. A.

2003-02-01

A sub-atmospheric (SA) pressure gas source, based on the reversible adsorption of hydride gas onto a high surface area substrate within a cylinder, has been developed for the safe storage and delivery of high-purity arsine and phosphine for MOCVD processes. SA pressure and high-pressure sources are compared with respect to gas delivery and purity, risk reduction, and cost benefits. Gas analysis and performance of epi-structures grown with SA pressure cylinders confirm that the hydride gas delivered meets the purity requirements of MOCVD processes. Further, the low gas release rates measured from 2.2 and 49 l SA pressure cylinders indicate that the technology can be scaled up without additional safety risk.

X-ray diffraction analysis of hydroxyapatite-coated in different plasma gas atmosphere on Ti and Ti-6Al-4V

PubMed Central

Kotian, Ravindra; Rao, P. Prasad; Madhyastha, Prashanthi

2017-01-01

Objective: The aim is to study the effect of plasma working gas on composition, crystallinity, and microstructure of hydroxyapatite (HA) coated on Ti and Ti-6Al-4V metal substrates. Materials and Methods: Ti and Ti-6Al-4V metal substrates were coated with HA by plasma spray using four plasma gas atmospheres of argon, argon/hydrogen, nitrogen, and nitrogen/hydrogen. The degree of crystallinity, the phases present, and microstructure of HA coating were characterized using X-ray diffraction and scanning electron microscopy. Results: Variation in crystallinity and the microstructure of HA coating on plasma gas atmosphere was observed. Micro-cracks due to thermal stresses and shift in the 2θ angle of HA compared to feedstock was seen. Conclusion: Plasma gas atmosphere has a significant influence on composition, crystallinity, and micro-cracks of HA-coated dental implants. PMID:29279668

Technical Note: A minimally invasive experimental system for pCO2 manipulation in plankton cultures using passive gas exchange (atmospheric carbon control simulator)

NASA Astrophysics Data System (ADS)

Love, Brooke A.; Olson, M. Brady; Wuori, Tristen

2017-05-01

As research into the biotic effects of ocean acidification has increased, the methods for simulating these environmental changes in the laboratory have multiplied. Here we describe the atmospheric carbon control simulator (ACCS) for the maintenance of plankton under controlled pCO2 conditions, designed for species sensitive to the physical disturbance introduced by the bubbling of cultures and for studies involving trophic interaction. The system consists of gas mixing and equilibration components coupled with large-volume atmospheric simulation chambers. These chambers allow gas exchange to counteract the changes in carbonate chemistry induced by the metabolic activity of the organisms. The system is relatively low cost, very flexible, and when used in conjunction with semi-continuous culture methods, it increases the density of organisms kept under realistic conditions, increases the allowable time interval between dilutions, and/or decreases the metabolically driven change in carbonate chemistry during these intervals. It accommodates a large number of culture vessels, which facilitate multi-trophic level studies and allow the tracking of variable responses within and across plankton populations to ocean acidification. It also includes components that increase the reliability of gas mixing systems using mass flow controllers.

Electron energy deposition in N2 gas

NASA Technical Reports Server (NTRS)

Fox, J. L.; Victor, G. A.

1988-01-01

The processes by which energetic electrons lose energy in a weakly ionized gas of molecular nitrogen are analyzed and calculations are carried out taking into account the discrete nature of the excitation processes. The excitation, ionization, dissociation and heating efficiencies are computed for energies up to 200 eV absorbed in a gas with fractional ionizations varying from 10(-6) to 10(-2). Individual vibrational excitations up to the seventh vibrational level are presented.

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.

Formation of nitro-PAHs from the heterogeneous reaction of ambient particle-bound PAHs with N2O5/NO3/NO2

PubMed Central

Zimmermann, Kathryn; Jariyasopit, Narumol; Massey Simonich, Staci L.; Tao, Shu; Atkinson, Roger; Arey, Janet

2014-01-01

Reactions of ambient particles collected from four sites within the Los Angeles, CA air basin and Beijing, China with a mixture of N2O5, NO2, and NO3 radicals were studied in an environmental chamber at ambient pressure and temperature. Exposures in the chamber system resulted in the degradation of particle-bound PAHs and formation of molecular weight (mw) 247 nitropyrenes (NPYs) and nitrofluoranthenes (NFLs), mw 273 nitrotriphenylenes (NTPs), nitrobenz[a]anthracenes (NBaAs), and nitrochrysene (NCHR), and mw 297 nitrobenzo[a]pyrene (NBaP). The distinct isomer distributions resulting from exposure of filter-adsorbed deuterated fluoranthene to N2O5/NO3/NO2 and that collected from the chamber gas-phase suggest that formation of NFLs in ambient particles did not occur by NO3 radical-initiated reaction, but from reaction of N2O5, presumably subsequent to its surface adsorption. Accordingly, isomers known to result from gas-phase radical-initiated reactions of parent PAHs, such as 2-NFL and 2- and 4-NPY, were not enhanced from the exposure of ambient particulate matter to N2O5/NO3/NO2. The reactivity of ambient particles toward nitration by N2O5/NO3/NO2, defined by relative 1-NPY formation, varied significantly, with the relative amounts of freshly emitted particles versus aged particles (particles that had undergone atmospheric chemical processing) affecting the reactivity of particle-bound PAHs toward heterogeneous nitration. Analyses of unexposed ambient samples suggested that, in nighttime samples where NO3 radical-initiated chemistry had occurred, heterogeneous formation of 1-NPY on ambient particles may have contributed to the ambient 1-NPY concentrations at downwind receptor sites. These results, together with observations that 2-NFL is consistently the dominant particle-bound nitro-PAH measured in ambient atmospheres, suggest that for PAHs that exist in both the gas- and particle-phase, the heterogeneous formation of particle-bound nitro-PAHs is a minor formation

Atmosphere behavior in gas-closed mouse-algal systems - An experimental and modelling study

NASA Technical Reports Server (NTRS)

Averner, M. M.; Moore, B., III; Bartholomew, I.; Wharton, R.

1984-01-01

A NASA-sponsored research program initiated using mathematical modelling and laboratory experimentation aimed at examining the gas-exchange characteristics of artificial animal/plant systems closed to the ambient atmosphere is studied. The development of control techniques and management strategies for maintaining the atmospheric levels of carbon dioxide and oxygen at physiological levels is considered. A mathematical model simulating the behavior of a gas-closed mouse-algal system under varying environmental conditions is described. To verify and validate the model simulations, an analytical system with which algal growth and gas exchange characteristics can be manipulated and measured is designed, fabricated, and tested. The preliminary results are presented.

Atmospheric measurement of point source fossil CO2 emissions

NASA Astrophysics Data System (ADS)

Turnbull, J. C.; Keller, E. D.; Baisden, T.; Brailsford, G.; Bromley, T.; Norris, M.; Zondervan, A.

2014-05-01

We use the Kapuni Gas Treatment Plant to examine methodologies for atmospheric monitoring of point source fossil fuel CO2 (CO2ff) emissions. The Kapuni plant, located in rural New Zealand, removes CO2 from locally extracted natural gas and vents that CO2 to the atmosphere, at a rate of ~0.1 Tg carbon per year. The plant is located in a rural dairy farming area, with no other significant CO2ff sources nearby, but large, diurnally varying, biospheric CO2 fluxes from the surrounding highly productive agricultural grassland. We made flask measurements of CO2 and 14CO2 (from which we derive the CO2ff component) and in situ measurements of CO2 downwind of the Kapuni plant, using a Helikite to sample transects across the emission plume from the surface up to 100 m above ground level. We also determined the surface CO2ff content averaged over several weeks from the 14C content of grass samples collected from the surrounding area. We use the WindTrax plume dispersion model to compare the atmospheric observations with the emissions reported by the Kapuni plant, and to determine how well atmospheric measurements can constrain the emissions. The model has difficulty accurately capturing the fluctuations and short-term variability in the Helikite samples, but does quite well in representing the observed CO2ff in 15 min averaged surface flask samples and in ~ one week integrated CO2ff averages from grass samples. In this pilot study, we found that using grass samples, the modeled and observed CO2ff emissions averaged over one week agreed to within 30%. The results imply that greater verification accuracy may be achieved by including more detailed meteorological observations and refining 14C sampling strategies.

[Gas chromatography with a Pulsed discharge helium ionization detector for measurement of molecular hydrogen(H2) in the atmosphere].

PubMed

Luan, Tian; Fang, Shuang-xi; Zhou, Ling-xi; Wang, Hong-yang; Zhang, Gen

2015-01-01

A high precision GC system with a pulsed discharge helium ionization detector was set up based on the commercial Agilent 7890A gas chromatography. The gas is identified by retention time and the concentration is calculated through the peak height. Detection limit of the system is about 1 x 10(-9) (mole fraction, the same as below). The standard deviation of 140 continuous injections with a standard cylinder( concentration is roughly 600 x 10(-9)) is better than 0.3 x 10(-9). Between 409.30 x 10(-9) and 867.74 x 10(-9) molecular hydrogen mole fractions and peak height have good linear response. By using two standards to quantify the air sample, the precision meets the background molecular hydrogen compatibility goal within the World Meteorological Organization/Global Atmosphere Watch (WMO/GAW) program. Atmospheric molecular hydrogen concentration at Guangzhou urban area was preliminarily measured by this method from January to November 2013. The results show that the atmospheric molecular hydrogen mole fraction varies from 450 x 10(-9) to 700 x 10(-9) during the observation period, with the lowest value at 14:00 (Beijing time, the same as below) and the peak value at 20:00. The seasonal variation of atmospheric hydrogen at Guangzhou area was similar with that of the same latitude stations in northern hemisphere.

Chemical and biochemical study of industrially produced San Simón da Costa smoked semi-hard cow's milk cheeses: Effects of storage under vacuum and different modified atmospheres.

PubMed

Garabal, J I; Rodríguez-Alonso, P; Franco, D; Centeno, J A

2010-05-01

Two batches of smoked, semi-hard (ripened for 45 d) San Simón da Costa cow's milk cheeses with Protected Designation of Origin were used to investigate the chemical, biochemical, and sensorial parameters that may be affected by modified-atmosphere packaging. Cheeses were packaged for 45 d as follows: vacuum packaging, packaging in 100% N(2), packaging in a gas mixture of 20% CO(2)/80% N(2), and packaging in a gas mixture of 50% CO(2)/50% N(2). The San Simón da Costa cheeses were characterized by high contents of lactic, oxalic, and citric organic acids. The main free amino acids found were isoleucine, phenylalanine, serine, valine, lysine, and glutamic acid, and the most abundant volatile compounds included ethanol, diacetyl, 2-butanol, isopropyl alcohol, furfural, acetaldehyde, 2-butanone, acetone, and 2-methylfuran. Modified atmospheres appeared to alter the ripening processes by affecting lipolysis, as indicated by the lower concentrations of butyric and propionic acids compared with control cheeses. In addition, modified-atmosphere packaging altered the proteolysis processes, yielding higher amounts of branched-chain alcohols. The results revealed that storage under modified atmosphere contributes to the accumulation of several compounds probably derived from smoke, including aldehydes such as 2-furancarboxaldehyde (furfural), alcohols such as 2-methoxyphenol (guaiacol), ketones such as 2-cyclopenten-1-one, and esters such as methyl furancarboxylate, which were negatively correlated with flavor. Vacuum packaging was the most useful technique in terms of preserving the sensory quality of San Simón da Costa Protected Designation of Origin cheeses. Considering the current demands for packaged portions of food at the distribution and retail levels and the potential health risks associated with some smoke-derived compounds usually present in some smoked foods, the results obtained in this study may be of special interest to the cheese industry. Copyright 2010

Evaluation of Mars CO2 Capture and Gas Separation Technologies

NASA Technical Reports Server (NTRS)

Muscatello, Anthony C.; Santiago-Maldonado, Edgardo; Gibson, Tracy; Devor, Robert; Captain, James

2011-01-01

Recent national policy statements have established that the ultimate destination of NASA's human exploration program is Mars. In Situ Resource Utilization (ISRU) is a key technology required to ,enable such missions and it is appropriate to review progress in this area and continue to advance the systems required to produce rocket propellant, oxygen, and other consumables on Mars using the carbon dioxide atmosphere and other potential resources. The Mars Atmospheric Capture and Gas separation project is selecting, developing, and demonstrating techniques to capture and purify Martian atmospheric gases for their utilization for the production of hydrocarbons, oxygen, and water in ISRU systems. Trace gases will be required to be separated from Martian atmospheric gases to provide pure CO2 to processing elements. In addition, other Martian gases, such as nitrogen and argon, occur in concentrations high enough to be useful as buffer gas and should be captured as well. To achieve these goals, highly efficient gas separation processes will be required. These gas separation techniques are also required across various areas within the ISRU project to support various consumable production processes. The development of innovative gas separation techniques will evaluate the current state-of-the-art for the gas separation required, with the objective to demonstrate and develop light-weight, low-power methods for gas separation. Gas separation requirements include, but are not limited to the selective separation of: (1) methane and water from unreacted carbon oxides (C02-CO) and hydrogen typical of a Sabatier-type process, (2) carbon oxides and water from unreacted hydrogen from a Reverse Water-Gas Shift process, (3)/carbon oxides from oxygen from a trash/waste processing reaction, and (4) helium from hydrogen or oxygen from a propellant scavenging process. Potential technologies for the separations include' freezers, selective membranes, selective solvents, polymeric sorbents

When the Sun's Away, N2O5 Comes Out to Play: An Updated Analysis of Ambient N2O5 Heterogeneous Chemistry

NASA Astrophysics Data System (ADS)

McDuffie, E. E.; Brown, S. S.

2017-12-01

The heterogeneous chemistry of N2O5 impacts the budget of tropospheric oxidants, which directly controls air quality at Earth's surface. The reaction between gas-phase N2O5 and aerosol particles occurs largely at night, and is therefore more important during the less-intensively-studied winter season. Though N2O5-aerosol interactions are vital for the accurate understanding and simulation of tropospheric chemistry and air quality, many uncertainties persist in our understanding of how various environmental factors influence the reaction rate and probability. Quantitative and accurate evaluation of these factors directly improves the predictive capabilities of atmospheric models, used to inform mitigation strategies for wintertime air pollution. In an update to last year's presentation, The Wintertime Fate of N2O5: Observations and Box Model Analysis for the 2015 WINTER Aircraft Campaign, this presentation will focus on recent field results regarding new information about N2O5 heterogeneous chemistry and future research directions.

Upper limits to the fractionation of isotopes due to atmospheric escape: Implications for potential 14N/15N in Pluto's atmosphere

NASA Astrophysics Data System (ADS)

Mandt, K.; Mousis, O.

2014-12-01

Formation and evolution of the solar system is studied in part using stable isotope ratios that are presumed to be primordial, or representative of conditions in the protosolar Nebula. Comets, meteorites and giant planet atmospheres provide measurements that can reasonably be presumed to represent primordial conditions while the terrestrial planets, Pluto and Saturn's moon Titan have atmospheres that have evolved over the history of the solar system. The stable isotope ratios measured in these atmospheres are, therefore, first a valuable tool for evaluating the history of atmospheric escape and once escape is constrained can provide indications of conditions of formation. D/H ratios in the atmosphere of Venus provide indications of the amount of water lost from Venus over the history of the solar system, while several isotope ratios in the atmosphere of Mars provide evidence for long-term erosion of the atmosphere. We have recently demonstrated that the nitrogen ratios, 14N/15N, in Titan's atmosphere cannot evolve significantly over the history of the solar system and that the primordial ratio for Titan must have been similar to the value recently measured for NH3 in comets. This implies that the building blocks for Titan formed in the protosolar nebula rather than in the warmer subnebula surrounding Saturn at the end of its formation. Our result strongly contrasts with works showing that 14N/15N in the atmosphere of Mars can easily fractionate from the terrestrial value to its current value due to escape processes within the lifetime of the solar system. The difference between how nitrogen fractionates in Mars and Titan's atmospheres presents a puzzle for the fractionation of isotopes in an atmosphere due to atmospheric escape. Here, we present a method aiming at determining an upper limit to the amount of fractionation allowed to occur due to escape, which is a function of the escape flux and the column density of the atmospheric constituent. Through this

Formation of amino acids and nucleotide bases in a Titan atmosphere simulation experiment.

PubMed

Hörst, S M; Yelle, R V; Buch, A; Carrasco, N; Cernogora, G; Dutuit, O; Quirico, E; Sciamma-O'Brien, E; Smith, M A; Somogyi, A; Szopa, C; Thissen, R; Vuitton, V

2012-09-01

The discovery of large (>100 u) molecules in Titan's upper atmosphere has heightened astrobiological interest in this unique satellite. In particular, complex organic aerosols produced in atmospheres containing C, N, O, and H, like that of Titan, could be a source of prebiotic molecules. In this work, aerosols produced in a Titan atmosphere simulation experiment with enhanced CO (N(2)/CH(4)/CO gas mixtures of 96.2%/2.0%/1.8% and 93.2%/5.0%/1.8%) were found to contain 18 molecules with molecular formulae that correspond to biological amino acids and nucleotide bases. Very high-resolution mass spectrometry of isotopically labeled samples confirmed that C(4)H(5)N(3)O, C(4)H(4)N(2)O(2), C(5)H(6)N(2)O(2), C(5)H(5)N(5), and C(6)H(9)N(3)O(2) are produced by chemistry in the simulation chamber. Gas chromatography-mass spectrometry (GC-MS) analyses of the non-isotopic samples confirmed the presence of cytosine (C(4)H(5)N(3)O), uracil (C(5)H(4)N(2)O(2)), thymine (C(5)H(6)N(2)O(2)), guanine (C(5)H(5)N(5)O), glycine (C(2)H(5)NO(2)), and alanine (C(3)H(7)NO(2)). Adenine (C(5)H(5)N(5)) was detected by GC-MS in isotopically labeled samples. The remaining prebiotic molecules were detected in unlabeled samples only and may have been affected by contamination in the chamber. These results demonstrate that prebiotic molecules can be formed by the high-energy chemistry similar to that which occurs in planetary upper atmospheres and therefore identifies a new source of prebiotic material, potentially increasing the range of planets where life could begin.

Development of a mobile and high-precision atmospheric CO2 monitoring station

NASA Astrophysics Data System (ADS)

Molnár, M.; Haszpra, L.; Major, I.; Svingor, É.; Veres, M.

2009-04-01

Nowadays one of the most burning questions for the science is the rate and the reasons of the recent climate change. Greenhouse gases (GHG), mainly CO2 and CH4 in the atmosphere could affect the climate of our planet. However, the relation between the amount of atmospheric GHG and the climate is complex, full with interactions and feedbacks partly poorly known even by now. The only way to understand the processes, to trace the changes, to develop and validate mathematical models for forecasts is the extensive, high precision, continuous monitoring of the atmosphere. Fossil fuel CO2 emissions are a major component of the European carbon budget. Separation of the fossil fuel signal from the natural biogenic one in the atmosphere is, therefore, a crucial task for quantifying exchange flux of the continental biosphere through atmospheric observations and inverse modelling. An independent method to estimate trace gas emissions is the top-down approach, using atmospheric CO2 concentration measurements combined with simultaneous radiocarbon (14C) observations. As adding fossil fuel CO2 to the atmosphere, therefore, leads not only to an increase in the CO2 content of the atmosphere but also to a decrease in the 14C/12C ratio in atmospheric CO2. The ATOMKI has more than two decade long experience in atmospheric 14CO2 monitoring. As a part of an ongoing research project being carried out in Hungary to investigate the amount and temporal and spatial variations of fossil fuel CO2 in the near surface atmosphere we developed a mobile and high-precision atmospheric CO2 monitoring station. We describe the layout and the operation of the measuring system which is designed for the continuous, unattended monitoring of CO2 mixing ratio in the near surface atmosphere based on an Ultramat 6F (Siemens) infrared gas analyser. In the station one atmospheric 14CO2 sampling unit is also installed which is developed and widely used since more than one decade by ATOMKI. Mixing ratio of CO2 is

The effect of ethanol gas impurity on the discharge mode and discharge products of argon plasma jet at atmospheric pressure

NASA Astrophysics Data System (ADS)

Xia, Wenjie; Liu, Dingxin; Xu, Han; Wang, Xiaohua; Liu, Zhijie; Rong, Mingzhe; Kong, Michael G.

2018-05-01

Argon is a widely used working gas of plasmas, which is much cheaper than helium but on the other hand much more difficult to generate diffuse discharge at atmospheric pressure. In order to meet the application requirements, plenty of researches have been reported to facilitate the diffuse discharge happening for argon plasmas, and in this paper an approach of using ethanol gas (EtOH) impurity is investigated. The discharge characteristics of Ar + EtOH plasma jet are studied as a function of the applied voltage and the concentration of EtOH, from which the concentration of EtOH between ∼200 and ∼3300 parts per million (ppm) is determined necessary for the generation of diffuse discharge. Compared with the helium plasma jet in literature, it is deduced that the diffuse discharge is probably caused by the Penning ionization happening between the metastable argon and EtOH. The discharge products of Ar + EtOH (672 ppm) plasma jet are measured and the corresponding chemistry pathways are analyzed. About 20% of EtOH is decomposed via complex chemical reactions to form more than a dozen of neutral species, such as CH3CHO, CH3COOH, CO, H2O, and C n H2n+2 (n ≥ 3), and various kinds of ionic species, including C+, CH+, ArH+, {{{{O}}}2}-, CH3CH2O‑, etc.

A novel 15N tracer approach for the quantification of N2 and N2O emissions from soil incubations in a completely automated laboratory set up

NASA Astrophysics Data System (ADS)

Scheer, Clemens; Dannenmann, Michael; Meier, Rudolf

2015-04-01

The microbial mediated production of nitrous oxide (N2O) and its reduction to dinitrogen (N2) via denitrification represents a loss of nitrogen (N) from fertilised agro-ecosystems to the atmosphere. Although denitrification has received great interest by biogeochemists in the last decades, the magnitude of N2lossesand related N2:N2O ratios from soils still are largely unknown due to methodical constraints. We present a novel 15N tracer approach, based on a previous developed tracer method to study denitrification in pure bacterial cultures which was modified for the use on soil incubations in a completely automated laboratory set up. The method uses a background air in the incubation vessels that is replaced with a helium-oxygen gas mixture with a 50-fold reduced N2 background (2 % v/v). This method allows for a direct and sensitive quantification of the N2 and N2O emissions from the soil with isotope-ratio mass spectrometry after 15N labelling of denitrification N substrates and minimises the sensitivity to the intrusion of atmospheric N2 at the same time. The incubation set up was used to determine the influence of different soil moisture levels on N2 and N2O emissions from a sub-tropical pasture soil in Queensland/Australia. The soil was labelled with an equivalent of 50 μg-N per gram dry soil by broadcast application of KNO3solution (4 at.% 15N) and incubated for 3 days at 80% and 100% water filled pore space (WFPS), respectively. The headspace of the incubation vessel was sampled automatically over 12hrs each day and 3 samples (0, 6, and 12 hrs after incubation start) of headspace gas analysed for N2 and N2O with an isotope-ratio mass spectrometer (DELTA V Plus, Thermo Fisher Scientific, Bremen, Germany(. In addition, the soil was analysed for 15N NO3- and NH4+ using the 15N diffusion method, which enabled us to obtain a complete N balance. The method proved to be highly sensitive for N2 and N2O emissions detecting N2O emissions ranging from 20 to 627 μN kg